Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol

Electrochemical deposition (ECD), a versatile and widely employed surface modification technique, offers unparalleled precision and control in the creation of functional coatings, thin films, and nanostructured materials. This method involves the controlled reduction or oxidation of ions at an electrode surface under the influence of an applied electric field, resulting in the formation of a deposit with desired properties. To achieve high-quality and high-standard ECD processes, it is crucial to consider multiple factors, including the selection of appropriate electrolyte systems, electrode design, process parameters, and post-deposition treatments. This comprehensive analysis delves into these aspects, highlighting their significance and interplay in ensuring the successful execution of electrochemical deposition.1. **Electrolyte Systems: The Foundation of Electrochemical Deposition**The choice of electrolyte system plays a pivotal role in determining the quality and standard of the deposited material. An ideal electrolyte should:a. **Contain the desired metal ions**: The electrolyte must contain soluble salts or complexes of the metal to be deposited. The chemical stability, solubility, and redox potential of these ions directly influence the deposition rate, morphology, and composition of the film.b. **Provide suitable supporting electrolytes**: Supporting electrolytes, such as inorganic salts or organic additives, enhance ionic conductivity, stabilize the double layer, and minimize side reactions. They also influence the nucleation and growth kinetics of the deposit, affecting its microstructure and adhesion.c. **Include functional additives**: To tailor the properties of the deposited material, various functional additives can be incorporated into the electrolyte. These may include surfactants for modifying surface energy and controlling particle size, complexing agents for adjusting ion speciation, or inhibitors for suppressing unwanted reactions or impurity incorporation.2. **Electrode Design: The Interface of Electrochemistry and Deposition**The design and preparation of the substrate electrode significantly impactthe quality and standard of the deposited film. Key considerations include:a. **Substrate material**: The substrate material should possess adequate electrical conductivity, chemical compatibility with the electrolyte, and mechanical stability during the deposition process. Moreover, its surface chemistry and roughness can influence nucleation and adhesion of the deposited layer.b. **Surface pre-treatment**: Prior to deposition, the substrate surface may require cleaning, polishing, or activation treatments to remove contaminants, create a defined surface topography, or induce specific surface chemistries that promote nucleation and adhesion.c. **Electrode geometry**: The electrode geometry, including shape, size, and arrangement, can affect mass transport, current distribution, and the development of local electric fields, which in turn influence deposition uniformity, thickness control, and defect formation.3. **Process Parameters: The Fine-Tuning Elements**Optimizing process parameters is crucial for achieving high-quality and high-standard electrochemical deposition. Key parameters include:a. **Applied voltage or current**: The magnitude and mode (direct current, pulsed current, alternating current) of the applied electrical field govern the kinetics of ion reduction/oxidation, deposition rate, and energy input into the system. Careful control is essential for achieving desired film thickness, composition, and microstructure.b. **Temperature**: Temperature influences electrolyte conductivity, reaction kinetics, and mass transport. It can be used to modulate deposition rate, phase formation, and stress development in the deposited film.c. **Deposition time**: The duration of the deposition process determines the overall thickness of the film and can influence the evolution of microstructure and properties. Balancing deposition time with other parameters ensures efficient use of resources while maintaining desired film characteristics.4. **Post-Deposition Treatments: Enhancing and Preserving Deposit Quality**Post-deposition treatments are often employed to further refine the properties of the electrochemically deposited material or to ensure its long-term stability. Some common treatments include:a. **Annealing**: Thermal annealing can be used to homogenize the microstructure, relieve residual stresses, improve crystallinity, or induce phase transformations, thereby enhancing the mechanical, electrical, or optical properties of the deposited film.b. **Chemical or electrochemical passivation**: Surface passivation treatments can be applied to increase corrosion resistance, reduce surface roughness, or modify surface chemistry for improved adhesion or functionality in subsequent processing steps.c. **Mechanical or chemical polishing**: Polishing techniques can be employed to achieve a desired surface finish, remove defects, or control the thickness of the deposited layer with high precision.In conclusion, achieving high-quality and high-standard electrochemical deposition requires a holistic approach that encompasses careful selection of electrolyte systems, meticulous design of electrode substrates, optimization of process parameters, and strategic implementation of post-deposition treatments. Each of these aspects is interconnected and contributes uniquely to the overall performance and reliability of the deposited material. By systematically considering and fine-tuning these factors, researchers and engineers can harness the full potential of electrochemical deposition for the synthesis of advanced functional coatings, thin films, and nanostructured materials with tailored properties and exceptional performance.。

硫磺制酸工艺流程参数英文回答：Sulfuric acid production process parameters can vary depending on the specific technology being used. However, there are some common parameters that are typically considered in sulfuric acid production.1. Feedstock: The quality and composition of the feedstock, which is usually sulfur or sulfur-containing compounds, can significantly impact the process parameters. The sulfur content, impurities, and moisture content of the feedstock need to be carefully controlled.2. Reaction temperature: The temperature at which the sulfur dioxide (SO2) is reacted with oxygen (O2) in the presence of a catalyst is a critical parameter. Higher temperatures generally lead to faster reaction rates, but excessively high temperatures can also result in catalyst deactivation or thermal degradation of the product. Theoptimal reaction temperature depends on the specific catalyst and technology being used.3. Reaction pressure: The pressure at which the reaction takes place can affect the equilibrium of the reaction and the overall reaction rate. Higher pressures can favor the formation of sulfur trioxide (SO3), which is necessary for the production of sulfuric acid. However, operating at high pressures can also increase the risks associated with equipment and safety.4. Catalyst: The choice of catalyst and its concentration can significantly impact the reactionkinetics and selectivity. Vanadium pentoxide (V2O5) is a commonly used catalyst in sulfuric acid production, but other catalysts such as platinum or palladium-based catalysts can also be employed. The concentration of the catalyst needs to be optimized to achieve the desired reaction rate and product quality.5. Gas composition: The composition of the gas mixture, which includes sulfur dioxide, oxygen, and other gases,needs to be carefully controlled. The stoichiometric ratioof SO2 to O2 is critical for the formation of sulfur trioxide. Impurities in the gas mixture, such as nitrogen oxides, can also affect the reaction kinetics and thequality of the final product.6. Absorption parameters: After the sulfur trioxide is formed, it needs to be absorbed in water to producesulfuric acid. The parameters such as temperature, pressure, and the concentration of the absorbing solution need to be optimized to achieve high absorption efficiency andminimize the formation of by-products.中文回答：硫磺制酸的工艺流程参数可以根据具体的技术方案而有所不同。

两种不同的加料方式对铝钛硼中间合金成分的影响陈越;卢育;汤皓元;杨钢;方树铭【摘要】the different charging methods of potassium fluotitanate and potassium fluoborate in preparation of Al-Ti-B master alloy directly influence the whole chemical reaction process, thereby it has a certain effect on the chemical composition of Al-Ti-B master alloy, i. e. the absorptivity of Ti, B elements; under the same condition of other process parameters (reaction temperature, reaction time) , the comparison of Al-Ti-B master alloy's composition with different raw material charging method shows the different charging methods can make bigger difference of Al-Ti-B master alloy's composition, and then influence the particle distribution, morphology and size dimension of TiB2 and TiAl3. The effect of charging methods on the composition of Al-Ti-B master alloy is the emphasis of this paper.%在熔制Al-Ti-B中间合金时,氟钛酸钾、氟硼酸钾的不同的加料方式直接影响整个化学反应过程,从而对Al-Ti-B中间合金的化学成分即Ti,B元素的吸收率有一定影响；在其它(反应温度、反应时间)相同的工艺参数条件下,通过不同的原料添加方式得到的Al-Ti-B中间合金成分的对比,结果表明,不同的加料方式使得Al-Ti-B 中间合金成分存在较大的差异,进而影响中间合金TiB2和TiAl3颗粒的分布,形貌及其尺寸大小.本文重点讨论加料方式对铝钛硼中间合金细化剂成分的影响.【期刊名称】《云南冶金》【年(卷),期】2013(042)002【总页数】5页(P81-84,95)【关键词】铝钛硼;合金成份;晶粒细化【作者】陈越;卢育;汤皓元;杨钢;方树铭【作者单位】昆明冶金研究院,云南昆明650031【正文语种】中文【中图分类】TG146.21铝钛硼合金是铝及铝合金最常用的晶粒细化剂，添加到铝和铝合金中对基材细化，在全球铝铸轧行业中应用极其广泛，由于其一般以成卷的线材方式供货，通常也被称呼为铝钛硼丝。

大学英语阅读三级PassageThe secret of being born lucky is a summer birthday, with May babies most likely to enjoy a lifetime’s good fortune, according to a study of more than 40,000 people. The time of year at which you are born has an enduring influence on levels of optimism and self-reported luck, according to research by British and Swedish scientists. May was the luckiest month in which to be born, with 50 per cent of those born then considering themselves lucky, while October was the least lucky month, with just 43 percent claiming good fortune.The findings add to growing evidence that the phenomenon of luck is not all down to chance, but is affected by a person’ s general disposition.Other research has shown that whether people think themselves fortunate depends less on objective success than on having a “glass half-full” or “half-empty” approach to life. “What we are seeing suggests that something is influencing how people perceive their luckiness. My hypothesis is that people create their own luck by traits such as optimism, that luck is a psychological phenomenon rather than a matter of blind chance,” said Professor Richard Wise man, who led the research.The pattern of the results, with those born in spring and summer reporting themselves luckier than those born in autumn or winter, could have two potential explanations, Professor Wiseman said.1. According to the passage, whether people think themselves lucky not depends on the following factors EXCEPT ______A) one’s objective success B) one’s general dispositionC) one’s attitude to life D) one’s place of birth2. According to the passage, those who were born in _______ regard themselves as the most fortunate.A) March B) April C) May D) October3. Which of the following statements is TRUE according to the passage?A) Optimistic people tend to be luckier.B) Devoted people tend to be luckier.C) Objective success is more important than one’s general disposition in feeling lucky.D) People drinking more water tend to be luckier.4. Which of the following words can best replace the word “trait”(Line 8, Para.2)?A) quality. B) expectation. C) belief. D) idea.is the best title for the passage?A) Luck is Something Born.B) Luck is Not All Down to Chance.C) Luck is A Matter of Blind Chance.D) Luck and Age.Passage 2Researchers say most of us make instant judgement about a person on the basis of how they look. They say facial features can determine whether we like or trust someone. It may even influence how we vote.“Over the years, we have found that facial features affect the way many of us perceive others,” says Elisabeth Cornwell, a psychology researcher at the university’s Perception Laboratory. Studies suggest that people are less likely to trust those with particularly masculine features, such as a square jaw, small eyesor big nose. “They are perceived as dominant and less trustworthy,” says Ms Cornwell. “It doesn’t mean that men who look more masculine are less trustworthy—It’s just our first impressions. “ Those with less masculine features—larger eyes, a smaller nose and thinner lips—are deemed to be more trustworthy. “We are very good at processing these features quickly,” says Ms Cornwell.The researchers are putting their science to the test at the Royal society’s annual summer exhibition in London. They have subtly manipulated the faces of Prime Minister T ony Blair, Conservative leader Michael Howard and Liberal Democrat leader Charles Kennedy accentuating their dominant and tru stworthy features respectively. “We have u sed a computer programme to change the shape of their face and features. We hope it will help people to understand our work.” So should we expect to see Tony Blair, Michael Howard and Charles Kennedy at the exhibi tion getting tips? “I don’t think it’s something they will want to try,” says Ms Cornwell. “It’s not really possible with television. We all know what they look like. I think they would be naive to try it.”1. Why are people less likely to trust those with particularly masculine features?A) Because they are bad-tempered.B) Because they are perceived as dominant and less trustworthy.C) Because they are perceived as tricky.D) Because they are more stubborn.2. According to the passage, which of the following is perceived as a g masculine feature?A) Larger eyes. B) A square jaw.C) A smaller nose. D) Thinner lips.3. What can be inferred from the passage?A) Most of us tend to judge people by how they look.B) Some studies show that people with particular masculine features are more dominant.C) A candidate with less masculine features is more likely to win a vote.D) Most of us are with masculine features.4. Why will Tony Blair not want to change his facial features according to the passage?A) Because he is so popular that everyone knows what he looks like.B) Because he does not want to get tips.C) Because he has great confidence in his looks.D) Because he is very naive.5.. What is the best title for the passage?A) Facial Features.B) How People Perceive Others.C) Facial Features Are Everything.D) How Facial Features Affect One’s First Impression.Passage 3British university entrants expect to be provided with washing machines and dryers in their rooms, and even car parking spaces, a survey has found. Students are also less prepared to tolerate poor quality living conditions than their predecessors, says the survey by British polling organization Mori.More than 1,000 full-time undergraduates and postgraduates from 21 universities across the UK were surveyed for the research. It shows that location is the key factor in choosing accommodation for students—nearly half of thoseinterviewed said that being close to their place of study was the most important factor in their choice. Cost came second, with evidence that many parents foot the bills for their children’s rent. The survey also shows that students are no longer prepared to carry bags of washing to the nearest launderette. These newcomers expect washers and dryers to be provided with their ac commodation. The study also highlights those things today’s students expect as standard—communal areas to be cleaned regularly, utility bills to be included, even private car parking space to be included.Separate findings from the UK’s National Union of S tudents published earlier this year show more than half of students in private rented accommodation are living in unsatisfactory conditions.1. Who are the subjects of the survey?A) Some oversea students in U. K.B) Some undergraduates and postgraduates in U. K. universities.C) Some graduates in U. K. universities.D) Some British students in other countries.2. What kind of accommodation is the most attractive to students according to the survey by British polling organization Mori?A) An apartment near their universities.B) A cheap house far way from their universities.C) An apartment with car parking space.D) An apartment with washing machines.3. Which of the following statements is TRUE according to the passage?A) The survey described in the passage is conducted by UK‘ s National Union ofStudents.B) Most of the subjects are from universities in London.C) Most college students pay the rent by themselves.D) Students think that communal areas should be cleaned regularly by cleaners rather than themselves.4. According to the passage, the choice of accommodation is influenced by the following factors EXCEPT ______.A) convenience B) comfortC) low rents D) weather5. What does the survey indicate?A) U. K. university students are increasingly satisfied with their living conditions.B) U. K. university students are less and less energetic.C) U. K. university students demand higher qualities of their living conditions.D) U. K. university students pay less and less attention to their studies. Passage 4The former first lady and now New York Senator, Hillary Rodham Clinton, has written a book about her eight years in the White House. It is being released with a great deal of public fanfare. The book reveals details about the notorious Monica Lewinsky scandal involving her husband, President Clinton.In Living History, the wife of former President Clinton recounts the moment when Mr. Clinton informed her that he had, fact, had what he called “a relationship that was not appropriate” with Miss Lewins ky, then a White House intern. She writes, “I’ could hardly breathe. Gulping for air, I started crying and yelling at him. What do you mean? What are you saying? Why did you lie to me? I was furious and getting more so by the second. Hejust stood th ere s aying over and over again, I’m sorry. I’m so sorry. I was trying to protect you and Chelsea, referring to their daughter.”Mrs. Clinton says she hopes that people will read the book for more than intimate details of her troubled marriage. “It’ s a pretty lo ng book, and it’s about my life, and it’s about all of the issues that I’ve worked on, particularly on behalf of women and children, and things that I’ ye cared about literally since I was a little girl,” she said. “I think it will give people more insight and, perhaps, answer questions. It’s also my story.”Publisher Simon & Schuster paid Senator Clinton $ 8 million for the 560-page book, and has ordered an unusually large first printing of one-million copies. Publishing rights to the book already have been sold in 16 countries.1. What appeals to the readers most in the book Living History according to the passage?A) Hilary’s eight years in the White House.B) Hilary’s troubled marriage.C) The issues that Hilary have worked on.D) Hilary’s life as a sena tor.2. The word “notorious” (Line 4, Para. 1) is closest in meaning to______.A) well-known B) unheard-ofC) surprising D) amusing3. Which of the following can best describe Hilary’s reaction when Mr. Clinton told her his inappropriate relationship with Miss Lewinsky?A) Indifferent. B) Calm.C) Angry. D) Astonished.4. What is Hilary’s comment on her own book?A) It is more than interesting.B) It can meet the need of people to know about other’ s intim acy.C) It is an academic bookD) The language of the book is beautiful.5. What CANNOT be inferred from the passage?A) Living History is expected to sell well.B) Living History will be published beyond America.C) Mrs. Clinton is well paid for the book Living History.D) Mr. Clinton is a responsible husband.passage 5The human form of mad cow disease, an incurable, brain-wasting illness that’s killed more than 100 people in Britain, has claimed its first Canadian victim. Canadian health officials confirmed Thursday that the unidentified man died sometime this summer. The man, who lived in the western province of Saskatchewan, contracted the disease from eating contaminated meat while traveling in Britain.Dr. Antonio Giulivi, an official with the government agency Health Canada, quickly moved to calm fears by assuring the public the disease had not entered the Canadian food supply.The variant of the cow-killing illness, known as Creutzfeldt-Jakob disease, is believed to be caused when ground parts of diseased cattle are mixed into cattle feed and those cows are turned into processed meats for human consumption. Though the disease cannot be confirmed until an autopsy is performed on the dead brain, symptoms of human infection include uncontrolled shaking, dementia and finally paralysis.But while government officials insisted safeguards are in place to keep the disease out of Canadian meat, warnings were issued to 71 patients at the hospital where the infected man wastreated before his illness was identified. Those patients had been treated with the same medical instruments used on the diseased man. Though the instruments were cleaned and disinfected, officials said a theoretical possibility remains that those people could have been infected.News of the death initially sent Canadian restaurant stocks into a tailspin, but most of them recovered by the end of the trading session.1. Where is the Canadian supposed to contact mad cow disease?A) In Saskatchewan. B) In Britain.C) In Canada. D) Not mentioned.2. Which part of the body does the mad cow disease mainly affect?A) Hands. B) Legs.C) Brain. D) Liver.3. Why did the Canadian government issue warnings to 71 patients?A) They ever used the same medical instruments with the first Canadian victim.B) They were intimate relatives of the first Canadian victim.C) They had ever traveled to Britain.D) They were supposed to have contacted mad cow disease.4. What did Health Canada do after the mad cow disease infected a Canadian?A) Health Canada concealed the truth by all means.B) Health Canada tried to remove public fear.C) Health Canada succeeded in curing the victim.D) Health Canada tried to find ways to cure the disease.5. What can be inferred from the passage?A) The news of the mad cow disease death has no effect on Canadian economy.B) We can decide whether a person contract mad cow disease by the symptoms of uncontrolled shaking, dementia and paralysis.C) Some cows in Canada contracted mad cow disease.D) The mad cow disease is not completely known to the scientists yet.Passage 6A United Nations report is sounding an alarm on the state of the earth’s natural resources, in advance of this month’ s U. N. -sponsored sustainable development summit in Johannesburg.The report says sea levels rose and forests were destroyed at unprecedented rates during the last decade. It notes that more than 40 percent of the world’s population—two billion people now face water shortages. And it predicts that with the global population expected to increase from six billion to eight billion people over the next 25 years, further environmental stress is expected. . Undersecretary General Nitin Desai says the most important message in the report is that the world’s environmental crises are interrelated. As an example, he cites the “Asian Brown Cloud,” a “poisonous cocktail” of particulate matter, chemicals, and various aerosols currently hanging over a vast area of southeast Asia.“Here you have a situation which arises because of the unsustainable way energy is used in this region, which is leading to these problems which impact on agriculture, on water, on health,” said Mr. Desai. “If you really want to address water, agriculture and health, you have to address energy. You can’t reduce poverty unless you also address land and water. Youcan’t improve children’s hea lth without addressing water and sanitation and air quality.”Mr. Desai, who will lead the Earth Summit, says that governments must form specific partnerships to reduce threats in five areas: water, energy, agriculture, biodiversity and health.1. When is the . report mentioned in the passage released?A) At the sustainable development summit.B) Before the Earth Summit.C) After the sustainable development summit.D) Last year.2. “Asian Brown Cloud” is used as an example to show that ______A) environmental protection needs cooperation.B) Asia is the most polluted area in the world.C) air pollution in Asia is very serious.D) travelers are warned not to visit Asia.3. What results in the problems concerning agriculture, water and health according to the passage?A) The rising sea level.B) The conflicts around the world.C) The improved living standard.D) The unsustainable way energy is used.4. What doe s the word “address” (Line 4, Para. 3) mean?A) Speak to. B) Make a formal speech to.C) Deal with. D) Make use of.5. What can be inferred from the passage?A) Natural resource shortage will be a great problem in the future.B) Poverty can be reduced by increasing production.C) Sustainable development is impossible.D) Southeast Asia is the most polluted area in the world.Passage 7The University of Chicago is a private, nondenominational, coeducational institution of higher learning and research. It is located in the community of Hyde Park—South Ken-wood, a culturally rich and ethnically diverse neighborhood, seven miles south of downtown Chicago.The University was founded by John D. Rockefeller. William Rainey Harper was its first president. Classes began on October 1, 1892, with an enrollment of 594 students and a faculty of 103, including eight former college presidents. In 1930 the undergraduate College and the graduate divisions were created. Such cross-fertilization continues to characterize the University.Candidates for admission to graduate programs in the divisions at the University of Chicago should address their inquiries, including requests for application forms, to the dean of students of the graduate division to which application is being made.An applicant who holds a degree from an accredited institution is considered for admission on the basis of (1) an undergraduate record, (2) a well-organized plan for graduate study, (3) Graduate Record Examination (GRE) and TOEFL scores, where required, and (4) recommendations from three college faculty members acquainted with the character, ability, potential, qualifications, and motivation of he applicant. Persons who have been away from school for several years may submit recommendationsfrom employers, professional associates, or supervisors. Transcripts of all academic work should be submitted with the application if at all possible; the applicant should request eachinstitution attended to provide an official transcript in a settled envelope.I. What can be concluded from the first paragraph?A) Only boys were admitted when the University of Chicago was founded.B) The University of Chicago is mainly financed by the government.C) The University of Chicago is located in the suburb of a city.D) The people of South Kenwood have similar cultural tradition.2. The University of Chicago has long been characterized by _____A) its cross-fertilization B) its long historyC) its excellent teaching staff D) its beautiful campus3. Which of the following statements is TRUE according to the passage?A) The founder of the University of Chicago is also its first president.B) The University of Chicago began to enroll graduates since its foundation.C) Some of its first graduates or teachers became the presidents of its several colleges.D) The University of Chicago has always been reluctant to enroll students from other universities in its graduate programs.4. To whom should the application form for the admission to the graduate programs of the University of Chicago be addressed?A) The dean of students of its graduate division.B) The president of the university.C) The concerning professor.D) Any teachers in the university5. What is NOT a requirement for a graduate who wants to be admitted in the graduate programs in the University of Chicago?A) An undergraduate record. B) GRE scores.C) A detailed plan for graduate study. D) A national examination.Passage 8Internet use appears to cause a decline in psychological well-being, according to research at Carnegie Mellon University. Even people who spent just a few hours a week on the Internet experienced more depression and loneliness than those who logged on less frequently, the two- year study showed. And it wasn’t that people who were already feeling bad spent more time on the Internet, but that using the Net actually appeared to cause the bad feelings.Researchers are puzzling over the results, which were complete contrary to their expectations. They expected that the Net would prove socially healthier than television, since the Net allows users to choose their information and to communicate with others. The fact that Internet use reduces time available for family and friends may account for the drop in well-being, researchers hypothesized. Faceless, bodiless“virtual”communication may be less psychologically satisfying than actual conversation, and the relationships formed through it may be shallower. Another possibility is that exposure the wider world via the Net makes users less satisfied with their lives.“But it’s important to remember this is not about the technology per se ; it’s about how it is used,” says psychologist Christine Riley of Intel, one of the study’s sponsors. “It reallypo ints he need for considering social factors in terms of how you design applications and services for technology.”1. The word “well-being” (Line 1, Para. 1) is c losest in meaning toA) trouble B) health C) depression D) excitement2. What is the intended conclusion of the research conducted by Carnegie?A) Internet use may lead to mental dissatisfaction.B) Internet use is sure to cause a decline in mental well-being.C) People who spend just a few hours on the Internet will be happier.D) People who use TV are less socially healthier than those who use the Internet.3. Which of the following CANNOT explain the result of the research according to the passage?A) Internet users may spend less time with their family and friends.B) The “virtual” communication may be less psychologically satisfying.C) Internet users may be less satisfied with their lives.D) Internet users make too many friends through the Internet.4. What lessons may be drawn from the result of the research?A) We should not have developed the Internet technology.B) We should change the way we use the Internet.C) We need Internet technology very much.D) TV is more useful than the Internet.5. What is the best title for the passage?A) The Popularity of Internet Use.B) The History of Internet Use.C) The Harm of Internet Use.D) The Fast Development of Internet Use.Passage 9The computer virus is an outcome of the computer overgrowth in the 1980s. The cause of the term “computer virus” is the likeness between the biolo gical virus and the evil program infected with computers. The origin of this term came from an American science fiction The Adolescence of P-1written by Thomas J. Ryan, published in 1977. Human viruses invade a living cell and turn it into a factory for manufacturing viruses. However, computer viruses are small programs. They replicate by attaching a copy of themselves to another program.Once attached to me host Program, the viruses then look for other programs to“infect”. In this way, the virus can spre ad quickly throughout a hard disk or an entire organization when it infects a LAN or a multi-user system. At some point, determined by how the virus was programmed the virus attacks. The timing of the attack can be linked to a number of situations, including a certain time or date, the presence of a particular file, the security privilege level of the user, and the number of times a file is used. Likewise, the mode of attack varies. So-called “benign”viruses might simply display a message, like the one tha t infected IBM’s main computer system last Christmas with a season’s greeting. Malignant viruses are designed to damage the system. The attack is to wipe out data, to delete files, or to format the hard disk.1. What results in the wide spread of computer viruses according to the passage?A) The overgrowth of computer.B) The likeness between the biological virus and evil program.C) The American science fiction The Adolescence of P-ID) The weak management of the government.2. What is computer virus in fact?A) A kind of biological virus.B) A kind of evil program.C) A kind of biological worm.D) Something that only exists in the fictions.3. What usually determines the variety of the virus attacks?A) The time the attack is made.B) The presence of a particular file.C) The security privilege level of the user.D) The different ways the virus was programmed.4. What is the harm of “benign” viruses according to the passage?A) “Benign” virus might wipe out data from the computer.B) “Benign” virus might de lete files.C) “Benign” virus might display a message.D) “Benign” virus might format the hard disk.5. Where does the term “computer virus” come from?A) It comes from a play.B ) It comes from a computer game.C) It comes from a science fiction.D) It comes from a news report.Passage 10Fast food, a mainstay of American eating for decades, may have reached a high in the United States as the maturing baby-boom generation looks for a more varied menu. Fast food still represents a $ 102 billion a year industry, but growth has turned sluggish recently amid tough competition from retail food stores and a more affluent population willing to try new things andspend more, analysts say.Signs of trouble in fast food include price-cutting by industry leaders, including efforts by McDonald’s to attract customers with a 55cent hamburger, and major players pulling out or selling. 0’ Pepsico, for example, is selling its fast-food restaurant divi sion that includes Taco Bell, Pizza Hut and KFC. “It’s becoming harder a nd harder for these firms to grow,” said Jim Brown, a professor of marketing at Virginia Tech University. “I think in the United States fast food has reached a saturation point becaus e of the number of competitors and the number of outlets.”Fast-food restaurant revenues grew 2. 5 per cent in 1996, according to industry figures, the slowest since the recession of 1991. That is a far cry from the levels of the 1970s and1980s. According to the Food Marketing Institute, consumers are using supermarkets for 21 per cent of take-home food, nearly double the level of a year ago. While fast-food restaurants still lead, their share slipped significantly, from 48 per cent in 1996 to 41 percent in 1997.1. According to the passage, the following factors EXCEPT _____ lead to the slower growth of fast food industry.A) the tough competitionB) a richer populationC) the saturation of marketD) the lower quality of fast food2. Which of the following signs does NOT show that fast food industry is experiencinga hard time?A) Price-cutting by industry leaders.B) The leading role of fast food in the market of take-home foodC) The selling of KFC.D) The pulling out of some fast food restaurant.3. Who is a strong competitor to fast-food restaurants in the market take-home food according to the passage?A) Supermarkets. B) Chinese restaurants. C) Hotels. D) Groceries.4. What can be inferred from the passage?A) Fast-food restaurant revenues are declining.B) Fast food is very popular in the 1970s and the 1980s.C) The baby boom generation has never liked fast food.D) Rich people like fast food more.5. What is the passage mainly concerned about?A) The popularity of fast food.B) The disadvantage of fast food.C) The troubles of fast food.D) The advantages of fast food.。

电镀翻译ElectroplatingElectroplating refers to the process of depositing a thin layer of metal onto the surface of an object using electricity. It is a common method used to enhance the appearance, protect against corrosion, and improve the conductivity of various metallic and non-metallic materials.The electroplating process involves several steps. First, the object to be electroplated, known as the substrate, is thoroughly cleaned to remove any dirt, grease, or oxide layers. This ensures proper adhesion of the metal coating. Then, the substrate is immersed in a solution known as an electrolyte, which contains metal ions of the desired coating material.The electrolyte is usually made by dissolving a salt of the metal in water. For example, to electroplate with copper, copper sulfate may be used. The substrate is connected to the negative terminal of a power supply, while a metal electrode of the same material is connected to the positive terminal. When an electric current is applied, metal cations from the electrolyte are reduced at the substrate, forming a layer of metal on its surface.The thickness of the electroplated coating can be controlled by adjusting the parameters of the electroplating process, such as the current density, plating time, and temperature. A higher current density or longer plating time results in a thicker coating. Temperature affects the rate of the electroplating reaction and can also influence the quality of the coating.Various metals can be used for electroplating, depending on the desired properties of the coated object. Commonly electroplated metals include gold, silver, nickel, chromium, and tin. Each metal has its own unique appearance, corrosion resistance, and conductivity characteristics. For example, gold plating is often used in jewelry-making to give a luxurious and aesthetically pleasing appearance, while nickel plating is commonly used for automotive parts due to its corrosion resistance.Electroplating is widely utilized in many industries. In addition to decorative applications, it is also used for functional purposes. For example, electrical connectors and components are often electroplated with a thin layer of gold or silver to improve their conductivity and prevent oxidation. Printed circuit boards are electroplated with copper to create conductive traces.However, electroplating can also have negative environmental impacts. The electrolyte used in the process may contain toxic substances, such as cyanide or heavy metals, which can be harmful if improperly handled or disposed of. Efforts are being made to develop more environmentally friendly electroplating processes, such as using alternative electrolytes or implementing waste treatment systems.In conclusion, electroplating is a versatile process that offers many benefits. It can enhance the appearance, protect against corrosion, and improve the functionality of various objects. However, it is important to consider the environmental impact and ensure proper handling and disposal of the electroplating materials.。

Investigation on the rate of reaction between gas (CO2) and liquor (NaOH) phases1 CHEN Bin(陈滨)，LI Xiao-bin（李小斌）*，LIU Gui-hua（刘桂华），PENG Zhi-hong（彭志宏），ZHOU Qiu-sheng（周秋生），XU Xiao-hui（徐晓辉），LIU Xiang-min（刘祥民）( School of Metallurgical Science and Engineering ,Central South University, Changsha 410083, P.R.China)Abstract：The neutralization of sodium hydroxide by carbon dioxide occurring during the process of carbonization precipitation of sodium aluminate solution was investigated. Firstly, the effects of those main factors such as CO2 concentration、temperature、initial concentration of NaOH were investigated. Then the kinetics equation concerning this reaction was obtained after proper data treatment. The results showed that it assumes an apparent activation energy of 8.06 kJ/mol which indicated a diffusion-controlled process. Furthermore, based on the principles governing diffusion-controlled process, the dependence of neutralization rate on gas flow was deduced theoretically with a form as: r d=KD K C A(Q/V L)2/3 whose plausibility was validated by those experimental research thereafter.Key words：reaction between gas & liquor phase；sodium hydroxide；carbon dioxide；diffusion control；kineticsCLC number: TF801 Document code: A1．INTRODUCTIONPresently in China, about 40% of alumina was produced by sintering process, where carbonization decomposition, that is, CO2 is ventilated into desilicated sodium aluminate solution to obtain Al(OH)3, holds a crucial procedure during alumina production[1]. Hitherto the mechanism of carbonization decomposition remains ambiguous for it’s a multiphase reaction involving series of complicated physicochemical processes such as crystallization, heat and mass transport, etc[2]. Thermodynamic and kinetic research[3,4] indicated that the essential of this process lies in the precipitation of Al(OH)3 resulting from the elevation of supersaturation with OH- being neutralized by CO2. So the ventilation profile of CO2 exerts a remarkable influence on the rate of the reaction and quality of the product. Generally speaking, it includes following steps: 1) transport of CO2 towards the gas-liquor phase interface; 2) chemical reaction between NaOH and CO2 at the interface; 3) removal of product from and transport of fresh reagents to the interface; 4) Mass transport relating to the production and growth of crystalline embryos on the seed surface[5].As described above, the neutralization of NaOH by CO2 holds a vital step during carbonization process. For the sake of controlling the process effectively, there’s every necessity to obtain the quantitative relationship between reaction rate and gas flow rate. However, related researches on this issue haven’t been reported so far. Though recently in consideration of the environmental protection which requires enterprises to reduce the emission of industrial gas resulting in greenhouse effect, the reaction behavior of CO2 in alkaline solution has been particularly studied[6-11], some influential factors such as air column height, configuration, gas pressure and interface area etc have been discussed at length and corresponding mathematical models established, yet the effect of gas flow rate was not singled out and what’s more, those systems were quite different from that of carbonization process.So a systematical study on the reaction process between CO2(g) and NaOH(L) was performed in this1Foundation item: Project (50274076) supported by the National Natural Science Foundation of China.* Correspondence: LI Xiao-bin, professor;. Tel: +86-731-8830454; E-mail: X.B.Li@.paper in the hope of realizing an effective control on carbonization and other similar processes.2．EXPERIMENTALDevices used in the experiments include a carbonizer as illustrated in Fig.1, a CYSE-II type O2/CO2 aerometer (XueLian meter company of Jia Ding, Shanghai), a thermostat with stirrer (Nanjing Timing electromotor Co., Ltd)and a LZB-6 type vitreous rotor flowmeter (Yuyao meter factory, Zhejiang).NaOH solution was prepared by dissolving chemical pure NaOH in distilled water and feeding gas by blending air and pure CO2. The carbonizer served as a cylindrical reactor with a diameter of 16.5cm and a height of 20cm where certain amount of solution was poured and feeding gas (air and CO2) continuously ventilated through the orbicular porous vent-pipe located in its bottom. CO2 concentration was measured with the CYSE-II type O2/CO2 aerometer and gas flow rate with the LZB-6 type vitreous rotor flowmeter. At controlled temperature and stirring speed, small amount of solution samples were taken at specified intervals for measuring the NaOH concentration with chemical titration method.1. Lift Tank;2.Electromotor;3. Pulleys;4. Reactor;5.Thermostatic oil bathFig.1 Schematic diagram of carbonizer3．RESULTS AND DISCUSSION3.1Establishment of the kinetics equation concerning CO2(g)—NaOH(L) reaction3.1.1 Influence of main factors on the reaction rateThe variation of NaOH concentration with reaction time at different experimental conditions was plotted in Fig.2～Fig.4, which shows the influence of CO2 concentration, temperature and initial NaOH concentration on the reaction rate respectively. Under all circumstances, the liquor’s volume is 2 liter. As shown in Fig.2 there’s a linear relationship between NaOH concentration and reaction time; that is, the time that NaOH is completely neutralized decreases with the raise of CO2 concentration, or to say, the reaction rate climbs up rapidly with the increase of CO2 concentration. While the influence of temperature is not remarkable as the four curves in Fig.3 are nearly overlapped within the temperature range of 75～95℃, the initial NaOH concentration either exerts little influence on the reaction rate as the three curves in Fig.4 are almost parallel. All these results are consistent well with those from literatures[12,13].Fig.2 Variation of NaOH concentration Fig.3 Variation of NaOH concentration with reaction time at different CO 2 concentrations with reaction time at different temperatures(temperature 85℃, flow rate 0.22Nm 3.h -1,(concentration of carbon dioxide 31%, flow rate stirring speed 250r.min -1)0.22Nm 3.h -1,stirring speed 250r.min -1)Fig.4 Variation of NaOH concentration with timeat different initial NaOH concentrations(temperature 85℃, flow rate 0.22 Nm 3.h -1, stirring speed 250 r.min -1, concentration of carbon dioxide 30%)3.1.2 Establishment of the kinetics equationThe reaction that NaOH solution is neutralized by CO 2 can be expressed as an equation as follows:2NaOH+CO 2=Na 2CO 3+H 2O (1)According to the principles of chemical kinetics [14], the kinetics equation of reaction (1) can be defined as:r=－τd NaOH dc )(=A )(RT Ea e − 221)()(n n CO c NaOH c (2)As discussed above, the influence of NaOH concentration on the reaction rate can be neglected in Eq.(2); Since the pressure of the system is 105 Pa as the feeding gas is ventilated into the unsealed reactor, the volume percent of CO 2 equals to its partial pressure according to Henry’s law on the premise that feeding gas meets the behavior characteristics of those idea ones at given temperature ；The ratio of CO 2 which participated in reaction to whole CO 2 can be calculated using the data in Fig.2～Fig.4, its value is in the range of 70～100% (The highest approached 98.7%). So we can consider that most of CO 2 was absorbed. Thus comes following equation:r=A )(RT Ea e −n CO )(2ϕ (3)Taking natural logarithm at both sides of Eq. (3) yields :)(ln ln ln 2CO n A r RT Eaϕ+−= (4)Where: r ―reaction rate ,mol.L -1.min -1； A ―preexponential factor ； Ea ―activationenergy ,J.mol -1；)(2CO ϕ―CO concentration ,%；τ―reaction time ,min ；R ―gas constant ,8.314 J.mol 2 -1.K -1；T ―temperature ，K 。

化学专业英语实验设计方案范文Experimental Design Proposal for a Chemical Process.Introduction.In the field of chemical engineering, the optimization of processes is crucial for achieving desired outcomes while minimizing resource waste and environmental impact. The proposed experiment aims to investigate the efficiency of a specific chemical reaction under varying conditions. The objective is to identify the optimal conditions that maximize the reaction yield while minimizing by-product formation and energy consumption. This experiment will provide valuable insights into the kinetics and mechanisms of the reaction, leading to improved process design and operation.Experimental Objectives.1. To study the effect of temperature on the rate andyield of the chemical reaction.2. To investigate the impact of catalyst concentration on the reaction kinetics.3. To evaluate the influence of reactant concentration on product selectivity and by-product formation.4. To determine the optimal reaction conditions that maximize the desired product yield.Materials and Methods.Materials.1. Reactants A and B (purified to ≥99% purity)。

小学上册英语第五单元测验试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.Which of these is a vegetable?A. AppleB. BananaC. CarrotD. Strawberry答案:C2.The puppy is _____ (cute/ugly).3.I love exploring new places. Every summer, my family goes on a trip to __________. We visit museums, parks, and try local foods.4.What is the name of the process plants use to make food?A. RespirationB. PhotosynthesisC. DigestionD. Transpiration答案:B5. A solid has a definite shape and ______.6.Which animal is known for its ability to change colors?A. ChameleonB. LizardC. GeckoD. Turtle答案:A7. A _______ is a substance that can neutralize acids. (碱)8.What is the main ingredient in chocolate?A. CocoaB. SugarC. MilkD. Butter答案:A9.What is the hardest natural substance on Earth?A. GoldB. DiamondC. IronD. Silver答案:B10.The _______ (Human Rights Declaration) was adopted by the UN in 1948.11.I can ______ (解决) puzzles quickly.12.The garden is _______ (full) of bees.13.My sister is a ______. She loves to explore new places.14.What is the term for an animal that hunts other animals for food?A. PredatorB. PreyC. ScavengerD. Herbivore答案:A15.What is the color of an apple?A. BlackB. WhiteC. RedD. Purple16. A lion is a majestic _______ that roams its territory with pride.17.I pretend my dolls are having a _________ (派对).18.What do we call the person who tells stories?A. AuthorB. ChefC. TeacherD. Doctor答案:A19.How many colors are in the American flag?A. TwoB. ThreeC. FourD. Five答案:B20.The ______ (植物遗传学) studies traits passed through generations.21. A ______ (植物的分类系统) helps in identification.22.I like to take ________ (照片) of nature.23.What is the name of the famous American actor known for his role in "The Godfather"?A. Robert De NiroB. Al PacinoC. Marlon BrandoD. Jack Nicholson答案:B24.What do we call the machine that makes copies of documents?A. PrinterB. ScannerC. CopierD. Fax答案:C25.What do we call a large body of freshwater?A. OceanB. LakeC. RiverD. Sea26.What is the name of the main character in "The Great Gatsby"?A. Jay GatsbyB. Nick CarrawayC. Tom BuchananD. Daisy Buchanan答案:A27.My uncle works as a __________. (医生)28.The ____ is a friendly animal that loves to be petted.29.Which of these is a dessert?A. SaladB. CakeC. SoupD. Rice30.My favorite game is ______.31.My mom is a ______. She enjoys baking cakes.32.We have fun playing with ________ (玩具名称).33.What is the capital of the Dominican Republic?A. Santo DomingoB. SantiagoC. La RomanaD. San Pedro deMacorís答案:A34.We have ______ (许多) different cultures in our city.35. A ______ (猴子) is playful and loves to climb.36.I want to _______ (学习) how to drive.37. A whale is a type of ______ that lives in the ocean.38.My ______ loves to share her knowledge.39.What is the shape of a basketball?A. SquareB. TriangleC. RectangleD. Circle答案:D40.The dog is _____ by the tree. (sitting)41.She has a _____ (funny) face.42., I feel _______ (情感) when I study. But I know that I can always ask for _______ (帮助). Sometime43.Which fruit is red and often eaten in pies?A. BananaB. GrapeC. AppleD. Orange44.The ________ (forest) is full of wildlife.45. A non-renewable resource is one that cannot be _______ quickly.46.What is 8 3?A. 4B. 5C. 6D. 7答案:B47.The milk is in the ________.48.My sister enjoys writing ____.49.What is the capital of Tanzania?A. DodomaB. Dar es SalaamC. ArushaD. Mwanza50.I love watching _______ (海豚) at the aquarium.51.What is the opposite of hot?A. WarmB. ColdC. CoolD. Lukewarm答案:B52.The symbol for cadmium is _____.53.The first man to walk on the moon was _______ Armstrong.54.The __________ (山区) offers great hiking trails.55.I have a toy _______ that can climb stairs.56. A base turns red litmus paper _____.57.We have a ______ (快乐的) family tradition for holidays.58. A ____ is a small mammal that is very curious and loves to explore.59.The concept of biodiversity loss highlights the decline of ______ species.60.________ (植物适应性改善) benefits agriculture.61.What is the term for a small rocky body that orbits the sun?A. CometB. AsteroidC. MeteorD. Planet62.The ______ helps with the growth of plants.63.We have _____ (homework/fun) this weekend.64.What do we call the process of capturing and storing carbon dioxide?A. Carbon sequestrationB. Greenhouse effectC. Carbon footprintD. Emission reduction答案:A Carbon sequestration65.The _____ (花卉装饰) can brighten up any space.66.The sun is ______ (bright) in the sky.67. A __________ is a reaction that produces new substances with different properties.68.The Rockies are a well-known _______ range.69.I saw a _______ (鸭子) in the pond.70.is important for the ______ (光合作用) process. Sunsets71.Which of these is a flying mammal?A. BatB. DogC. CatD. Elephant72.There are many ______ (花) in the garden. They are very ______ (美丽).73.What is the name of the liquid that falls from clouds?A. RainB. SnowC. HailD. Drizzle答案:A74.My favorite animal is a ________ that loves to eat.75.The flowers are ___ (in bloom).76.I love to _______ (参与)公益活动。

Research ReportsO. Henegariu, N.A. Heerema, S.R. Dlouhy, G.H. Vance and P.H. Vogt1Indiana University, Indianapo-lis, IN, USA and 1Heidelberg University, Heidelberg, GermanyABSTRACTBy simultaneously amplifying more than one locus in the same reaction, multiplex PCR is becoming a rapid and convenient screening assay in both the clinical and the research laboratory. While numerous pa-pers and manuals discuss in detail condi-tions influencing the quality of PCR in gen-eral, relatively little has been published about the important experimental factors and the common difficulties frequently en-countered with multiplex PCR. We have ex-amined various conditions of the multiplex PCR, using a large number of primer pairs. Especially important for a successful multi-plex PCR assay are the relative concentra-tions of the primers at the various loci, the concentration of the PCR buffer, the cycling temperatures and the balance between the magnesium chloride and deoxynucleotide concentrations. Based on our experience, we propose a protocol for developing a mul-tiplex PCR assay and suggest ways to over-come commonly encountered problems. INTRODUCTIONMultiplex polymerase chain reac-tion (PCR) is a variant of PCR in whichtwo or more loci are simultaneouslyamplified in the same reaction. Sinceits first description in 1988 (6), thismethod has been successfully appliedin many areas of DNA testing, includ-ing analyses of deletions (2,8), muta-tions (14) and polymorphisms (11), orquantitative assays (10) and reverse-transcription PCR (7).The role of various reagents in PCRhas been discussed (3,9,12,13), andprotocols for multiplex PCR have beendescribed by a number of groups. How-ever, few studies (5,15) have presentedan extensive discussion of some of thefactors (e.g., primer concentration, cy-cling profile) that can influence the re-sults of multiplex analysis. In thisstudy, over 50 loci were amplified invarious combinations in multiplexPCRs using a common, KCl-containingPCR buffer. Because of specific prob-lems associated with multiplex PCR,including uneven or lack of amplifica-tion of some loci and difficulties in re-producing some results, a study of theparameters influencing the amplifica-tion was initiated. Based on this experi-ence, a step-by-step multiplex PCRprotocol was designed (Figure 1), withpractical solutions to many of the prob-lems encountered. This protocol shouldbe useful to those using PCR technolo-gy in both the research and the clinicallaboratories.MATERIALS AND METHODSStandard Solutions and Reagents forthe PCRNucleotides (dNTP) (PharmaciaBiotech [Piscataway, NJ, USA] orBoehringer Mannheim [Indianapolis,IN, USA]) were stored as a 100 mMstock solution (25 mM each dA TP,dCTP, dGTP and dTTP). The standard10×PCR buffer was made as described(Perkin-Elmer, Norwalk, CT, USA) andcontained: 500 mM KCl, 100 mM Tris-HCl, pH 8.3 (at 24°C) and 15 mMMgCl2. Taq DNA Polymerase was pur-chased from Life Technologies(Gaithersburg, MD, USA) or fromPerkin-Elmer. Dimethyl sulfoxide(DMSO), bovine serum albumin (BSA)and glycerol were purchased from Sig-ma Chemical (St. Louis, MO, USA).Primers were either commercially ob-tained (Genosys [The Woodlands, TX,USA] or Research Genetics [Hunts-ville, AL, USA]) or synthesized locallyand were used in a final concentrationof 10–25 pmol/µL each. One set ofprimer pairs (sY) was used to map dele-tions on the human Y chromosome(8,16). Another 10–15 primer pairswere for the Duchenne muscular dys-trophy (DMD) gene on human chromo-some X (4). Other primers representvarious polymorphic loci (microsatel-lites) on human chromosome 12 (Re-search Genetics). Primers were com-bined in multiplex mixtures asdescribed in Table 1 and Figures 2b, 3bMultiplex PCR: Critical Parameters and Step-by-Step ProtocolBioTechniques 23:504-511 (September 1997)and 5e. Genomic DNA was preparedusing a standard sodium dodecyl sul-fate (SDS)/proteinase K protocol(Boehringer Mannheim).Basic PCR ProtocolThe basic PCR (25 µL vol) includ-ed: autoclaved ultra-filtered water; PCR buffer (1×); dNTP mixture (200µM each); primer(s) (0.04–0.6 µM each); DMSO, glycerol or BSA (5% - if used); Taq DNA polymerase (1–2 U/25µL) and genomic DNA template (150 ng/25 µL). The components of the re-action can be added in any order, pro-vided that water is added first. Pipetting was done on ice, and the vials were placed from ice directly into the pre-heated metal block or water bath (94°C) of the thermal cycler. For ra-dioactive labeling, 1 µCi [32P]dCTP (Amersham, Arlington Heights, IL,USA) was added to a 100 µL mastermixture immediately before setting upthe reaction. Results of PCR were thesame when 100- or 25- or 6.2-µL reac-tion volumes were used. With smallervolumes, pipetting is critical, especial-ly for dNTP. Various thermal cyclerswere used during these studies and,with minor cycling adjustments, allperformed well.Gel Analysis of PCR ProductsThe PCR products of non-polymor-phic loci (chromosomes X and Y) wereseparated by electrophoresis on 3%SeaKem®LE or NuSieve®(3:1)Agarose Gels (FMC BioProducts,Rockland, ME, USA) in 1×TAE [0.04M Tris-acetate; 0.001 M EDTA (pH8.0)] or 1×TBE [0.09 M Tris-borate;0.002 M EDTA (pH 8.0)] buffer, re-spectively, at room temperature usingvoltage gradients of 7–10 V/cm. Forany given gel analysis, the same vol-ume of PCR products was loaded ineach gel slot. Results were visualizedafter staining the gels in 0.5–1 µg/mLethidium bromide. Sequencing gels(6% polyacrylamide [PAA]/7 M urea)were used for separation of the PCRproducts when the loci tested werepolymorphic or a higher resolution wasrequired. The equivalent of about 0.2µL radioactively labeled PCR productwas loaded in each gel lane, after mix-ing it in loading buffer. These gels wererun in 0.6×TBE at 1800–2000 V (60A) for about 2 h. Autoradiographs wereobtained after overnight exposure.RESULTS AND DISCUSSIONBased on many experiments, a pro-tocol for establishing a multiplex PCRhas been designed (Figure 1), includinga number of practical solutions to someof the most commonly encounteredproblems. For convenience and ease ofuse, the words in italic characters linkthe scheme with various points present-ed in Materials and Methods and thefollowing subsections.Basic Principles of the MultiplexPCRDNA primers (Steps 1 and 2).Primer selection followed simple rules:primer length of 18–24 bp or higherand a GC content of 35%–60%, thushaving an annealing temperature of55°-58°C or higher. Longer primers(DMD primers, 28-30 bp) allowed thereaction to be performed at a higher an-nealing temperature and yielded lessunspecific products. To calculate themelting point and test for possibleprimer-primer interactions, “Primers1.2” (a freeware that can be down-loaded from ) wasused. To test for possible repetitive se-quences, many of the primers usedwere aligned with the sequence data-bases at the National Center forBiotechnology Information (NCBI) us-ing the Basic Local Alignment SearchTool (BLAST) family of programs.Single locus PCR (Step 3).A PCRFigure 1. Step-by-step protocol for the multiplex PCR.Research Reports program to amplify all loci individuallywas designed. Reaction mixture includ-ed 1×PCR buffer, 0.4 µM each primer,5% DMSO and 1 U Taq DNA poly-merase/25 µL reaction volume. Resultsof PCR were compared when the reac-tions were done consecutively in thesame thermal cycler, or in parallel, inmachines of the same model and in ma-chines of different models or manufac-turers. Results were very reproduciblewhen the same machine or same ma-chine model was used but couldmarkedly differ when the same exactPCR program was used on thermal cy-clers from different manufacturers.However, with adjustments in only thecycling conditions, results became re-producible even in different types ofmachines. We have observed that forthe loci tested (100–300-bp long), yieldof some products was increased by de-creasing the extension temperature. Forindividually amplified loci, the anneal-ing time (from 30–120 s) and the exten-sion time (from 30–150 s) did not visi-bly influence the results, but thespecificity and yield of PCR productwere increased or decreased bychanges in annealing temperature. Toamplify the 22 Y-specific loci (Figure2a), PCR program A gave best results(Table 2).Multiplex PCR: equimolar primermixture (Step 4).Combining the pri-mers in various mixtures and amplify-ing many loci simultaneously (Table 1and Figure 2b), required alteration/opti-mization of some of the parameters ofthe reaction. When the multiplex reac-tion is performed for the first time, it isuseful to add the primers in equimolaramounts. The results will suggest howthe individual primer concentration andother parameters need to be changed.Examples of some useful changes areillustrated and discussed below; howev-er, these examples do not necessarilyfollow the exact order as listed in theprotocol (Figure 1) since a number of parameters (e.g., extension tempera-ture) are referred to more than once.Optimization of Multiplex PCR Cycling ConditionsExtension temperature (Step 5, A–C).Figure 2c illustrates the results obtained when four different amplifica-tion mixtures containing equal amounts(0.4 µM each) of different Y-chromo-some primers were subjected to multi-plex PCR with program A and programB (Table 2); the latter program had ahigher extension temperature (72°C)and longer annealing and extensiontimes. In general, there was a visiblyhigher yield of PCR products for mix-tures Y-1, Y-3* and Y-4 with programA. In addition, with program B, someproducts are missing (in Y-1 and Y-2)and some unspecific products appear(in Y-1 and Y-3*). The results withprogram B were considered less desir-able overall and suggested that thehigher extension temperature in pro-gram B decreased the amplification of Name Size Name Size Name Size Name Size (locus)(bp)(locus)(bp)(locus)(bp)(locus)(bp) Y-1Y-2Y-3Y-4sY84 326sY143311sY86320sY14472 DYS273DYS231DYS148SRYsY134 301sY157285sY105301sY95303 DYS224DYS240DYS201DYS280sY117262sY81209sY82264sY127274DS209DYS271DYS272DYS218sY102 218sY182125Y6HP35226sY109233 DYS198KAL Y DYS274DYF43S1sY151 183sY147100Y6PHc54166sY149132 KAL Y DYS232n.a.DYS1sY94 150sY153139DYS279DYS237sY88 123sY97104DYS276DYS281DMD exon Size DMD exon Size Name Size No.(bp)No. (bp)(locus)(bp) X-1X-312-1 No. 45547PM535AFM263zd1 317-341D12S332PM535No. 3410AFM205ve5 271-291D12S93No. 19459No. 50271AFM205xg3 243-253D12S310No. 17416No. 6202AFM211wb6 228-238D12S98No. 51388No. 60139AFM206ze5 183-201D12S94No. 8360AFM299zd5 165-181D12S349No. 12331AFM135xe3 142-168D12S87No. 44268AFM122xf6 105-125D12S85No. 4196n.a. = locus not assigned.PM = promoter regionTable 1. List of Primers Used in the Multiplex Mixturessome loci, even though we tried to compensate using a longer annealing time and slightly longer extension time.Extension time (Step 5, A, B and D).In multiplex PCR, as more loci are simultaneously amplified, the pool of enzyme and nucleotides becomes a limiting factor and more time is neces-sary for the polymerase molecules to complete synthesis of all the products.Two experiments illustrated the influ-ence of the extension time. In one ex-periment, a Y -chromosome primer pair (Y6BaH34pr, 910bp) was added to a X-chromosome primer mixture (X-3).The results (Figure 3b) showed that in-creasing the extension time in the mul-tiplex PCR (program A vs. program D)increased the amount of longer prod-ucts. In another experiment, four Y multiplex mixtures were amplified us-ing PCR programs C and A (Figure 3a and Table 2). Visibly higher yields of PCR products were obtained for all Y mixtures when a longer extension time was used.Annealing time and temperature (Step 5, A–D; Figure 1).Modification of the annealing time from 20 s to 2min did not alter the amplification effi-ciency (not shown), but the annealing temperature was one of the most im-portant parameters. Although many in-dividual loci could be specifically am-plified at 56°–60°C, our experience showed that lowering the annealing temperature by 4°–6°C was required for the same loci to be co-amplified in multiplex mixtures. This is demonstrat-ed in Figure 3, d–f, which depict an op-timal multiplex annealing temperature of 54°C for primers individually usable at 60°C. At 54°C, although unspecific amplification probably occurs (e.g.,Figure 3c), it is overcome by the con-current amplification of an increased number of specific loci in the multiplex reaction and thus remains invisible.Similarly, when many specific loci are simultaneously amplified, the more ef-ficiently amplified loci will negatively influence the yield of product from the less efficient loci. This is due to the fact that PCR has a limited supply of en-zyme and nucleotides, and all products compete for the same pool of supplies. Number of PCR cycles. Primer mixture Y -3* was used to amplify two different genomic DNA samples, stop-Figure 2.(a) Single-locus PCR. Amplification of the sY loci using 1×PCR buffer and program A. On the gel, the products are arranged in increasing order of sY number (1=sY14, 2=sY81, 3=sY82, 4=sY84,5=sY86, 6=sY88, 7=sY94, 8=sY95, 9=sY97, 10=sY102, 11=sY105, 12=sY109, 13=sY117, 14=sY127,15=sY134, 16=sY143, 17=sY147, 18=sY149, 19=sY151, 20=sY153, 21=sY157 and 22=sY182). All products had the expected length, and there was no visible unspecific amplification. In all gels, lanes without a label show the size marker (1-kb ladder; Life Technologies). (b) Optimized multiplex reactions.Multiplex PCR with primer mixtures Y-1 (sY84, sY134, sY117, sY102, sY151, sY94 and sY88), Y-2(sY143, sY157, sY81, sY182 and sY147), Y-3 (sY86, sY105, sY82, Y6HP35, Y6Phc54, sY153 and sY97) and Y-4 (sY14, sY95, sY127, sY109 and sY149) in 1.6×PCR buffer (PCR program E). Mix Y-3*is mixture Y-3 without primers Y6HP35 and Y6Phc54. Arrows indicate the expected amplification prod-ucts. (c) Extension temperature. Multiplex PCR with mixtures Y-1 to Y-4 with PCR programs A and B (Table 2). All amplification products are visible in the first four lanes (extension at 65°C). In the last four lanes (extension at 72°C), bands are missing in Y-1 and Y-2, and unspecific products appear in Y-1 and Y-3*. Length marker in all figures = 1-kb ladder. In all images, electrophoresis was conducted from top to bottom. Program AProgram B Program C First Denaturing 94°C, 4 min 94°C, 4 min 94°C, 4 min Denature 94°C, 30 s 94°C, 30 s 94°C, 30 s Anneal 54°-56°C, 30 s*54°C, 1 min54°C, 45 sExtend 65°C, 1 min72°C, 1 min, 20 s 65°C, 2 min 32 cycles 32 cycles 32 cycles Final Extension65°C, 3 min 72°C, 3 min 65°C, 3 min Program DProgram E Program F First Denaturing 94°C, 4 min 94°C, 4 min none Denature 94°C, 30 s 94°C, 30 s 94°C, 30-45 s Anneal 55°C, 30 s 54°C, 45 s 56°-58°C, 45 s Extend 65°C, 4 min 65°C, 2 min 68°C, 2 min, 30 s 32 cycles 45 cycles 35 cycles Final Extension65°C, 3 min65°C, 5 minnoneBold characters show most important modifications when programs are com-pared.*Program A was used with two different annealing temperatures, according to the type of PCR amplification (see Results and Discussion).Table 2. Cycling Conditions/PCR ProgramsResearch Reportsping the reaction after increasing num-bers of cycles (Figure 4a). One of the two genomic DNAs was a better tem-plate, possibly due to the higher quality and/or amount of DNA. Both of them,however, show a gradual increase in the yield of all bands with the number of cycles. The most obvious variation in the amount of products was around 25cycles (for ethidium bromide-stained gels). Twenty-eight to thirty cycles are usually sufficient for a reaction; little is gained by increasing cycle number up to 60.Optimization of Multiplex Reaction ComponentsInitially, there was some variation from test to test when the same PCR program was used (e.g., Figures 2c and 3a). Solving this reproducibility prob-lem required adjustments of PCR com-ponents.Amount of primer (Step 5, B and C). Initially, equimolar primer concen-trations of 0.2–0.4µM each were used in the multiplex PCR (Figure 3c), but there was uneven amplification, with some of the products barely visible even after the reaction was optimized for the cycling conditions. Overcoming this problem required changing the pro-portions of various primers in the reac-tion, with an increase in the amount of primers for the “weak” loci and a de-crease in the amount for the “strong”loci. The final concentration of theprimers (0.04–0.6µM) varied consider-ably among the loci and was estab-lished empirically.dNTP and MgCl 2concentrations (Step 5D).dNTP .The significance of the dNTP concentration was tested in a multiplex PCR test with primer mixture Y-4.Magnesium chloride concentration was kept constant (3 mM), while the dNTP concentration was increased stepwisefrom 50–1200µM each (Figure 4b).The best results were at 200 and 400µM each dNTP, values above which the amplification was rapidly inhibited.Lower dNTP concentration (50µM) al-lowed PCR amplification but with visi-bly lower amounts of products. dNTP stocks are sensitive to thawing/freezing cycles. After 3–5 such cycles, multi-plex PCRs often did not work well;products became almost completely in-visible. To avoid such problems, small aliquots (2–4 µL, 10–20 reactions) of dNTP (25 mM each) can be made and kept frozen at -20°C and centrifuged before use. This “low stability” of dNTP is not so obvious when single loci are amplified.MgCl 2. A recommended magne-sium chloride concentration in a stan-dard PCR is 1.5 mM at dNTP con-centrations of around 200µM each. To test the influence of magnesium chlo-ride, a multiplex PCR (mixture Y -3)was performed, keeping dNTP concen-tration at 200 µM and gradually in-creasing magnesium chloride from 1.8–10.8 mM (Figure 4c). Amplifica-tion became more specific (unspecific bands disappeared), and the products acquired comparable intensities (at 10.8 mM). In PCRs with up to 20 mM MgCl 2, products became barely visible,as if the reactions were inhibited (not shown).dNTP/MgCl 2balance.To work properly, Taq DNA polymerase re-quires free magnesium (besides theFigure 3.(a) Extension time. Multiplex PCR of mixtures Y-1 to Y-4, comparing PCR programs C (2-minextension time) and A (1-min extension time, 54°C annealing temperature). Comparison of equivalent lanes shows an improvement in yield when extension time is 2 min. Some faint unspecific bands appear,possibly due to the low buffer concentration (1×). (b) Extension time. Multiplex PCR with mixture X-3(primers for DMD gene exons Nos. PM, 3, 50, 6, 60) and primer pair Y6BaH34 (910-bp product, upper arrow). Primers giving shorter amplification products are preferentially amplified with short extension times (1-min, program A). (c) Equimolar primer mixture. PCR with individual primer pairs of mixture 12–1 (separate and multiplex), using program F. Products are arranged on the gel according to their de-creasing length. Individual products have comparable intensities. When equimolar amounts of primers were mixed for the multiplex reaction (first lane), some products were not efficiently amplified but un-specific products disappeared. (d–f) Annealing temperature, buffer concentration and number of primers.Multiplex amplification of mixture Y-3* (first three lanes in each gel), primer pair sY 153 (lanes 4–6)and mixture Y-3 (lanes 7–12 in 1×or 2×PCR buffer) on three different template DNAs using three PCR programs differing in annealing temperature (48°, 54°or 59°C). Lanes 1–9 on each gel show reactions in 1×PCR buffer. Lanes 10–12 on each gel show reactions in 2×PCR buffer. Lanes 7–12 on each gel (under 1×PCR and 2×PCR) were with primer set Y-3. The very last lane in Figure 3, d and f is the marker (1-kb ladder). Small horizontal arrows indicate the expected products of mixture Y-3* (five products) including the longest specific product on the gel. Oblique arrow (3e) indicates a strong unspecific product. Solid arrowheads indicate the two extra products expected in mixture Y-3 (total of seven products) compared with Y-3*. Arrowhead outlines show positions of some missing products (e.g., 3e, first lane). With mul-tiplex amplification at 48°C, many unspecific bands appear. In 1×PCR buffer, the sY153 product is stronger when amplified in mixture Y-3* (5 primer pairs) than in mixture Y-3 (7 primer pairs), which shows that at least for some products, an increased number of simultaneously amplified loci can influ-ence the yield at some specific loci. Raising the PCR buffer concentration from 1×to 2×allows a more even amplification of all specific products and helps to decrease the intensity of many longer unspecific products (compare lanes 7–9 vs. 10–12). The strong 470–480-bp unspecific band (oblique arrow) seen with 2×buffer was eliminated by varying the proportion of different primers in the reaction (compare with Y-3, Figure 2b). At 59°C the sY153 product can be seen only when 2×buffer is used or when the lo-cus is amplified alone.magnesium bound by the dNTP and theDNA) (9). This is probably why in-creases in the dNTP concentrations(Figure 4b) can rapidly inhibit the PCR,whereas increases in magnesium con-centration often have positive effects (Figure 4c). By combining various amounts of dNTP and MgCl2, it was found that 200 µM each dNTP work well in 1.5–2 mM MgCl2, whereas 800µM dNTP require at least 6–7 mM MgCl2. The threshold for the reaction was roughly 1 mM MgCl2when 200µM dNTP was used, with reduced PCR amplification below this MgCl2con-centration.PCR buffer (KCl) concentration.Comparison of PCR buffers (Step 5, B–D).KCl or PCR buffer concentration.Raising the buffer concentration to 2×(or only the KCl concentration to 100mM) improved the efficiency of the multiplex reaction (Figure 4d and alsoFigure 3, d–f), this effect being moreimportant than using any of the adju-vants tested (DMSO, glycerol or BSA). Generally, primer pairs with longer am-plification products worked better at lower salt concentrations, whereas primer pairs with short amplification products worked better at higher salt concentrations, where longer products become harder to denature (compare 0.4×with 2.8×in Figure 4d). For exam-ple, pair sY94 (melting point ca. 58°C) is favored over both sY88 (melting point ca. 58°C) and sY151 (melting point ca. 52°C) at 0.8×buffer but not at higher salt concentrations. The proper buffer concentration may help over-come other factors (product size, GCFigure 4.(a) Number of cycles. Amplification with two different DNA templates using primer mixture Y-3* in 1.4×PCR buffer, with increasing numbers of cycles by units of three. (b) dNTP concentration. PCR amplification using mixture Y-4 in 2×PCR buffer (3 mM MgCl2) and increasing concentrations of dNTP (50, 100, 200, 400, 600 and 1200 µM). Most efficient amplification is seen at concentrations of 200–400 µM dNTP. Further increase in the dNTP concentration inhibits the reaction when MgCl2 concentration is kept constant. (c) MgCl2concentration. Multiplex PCR was performed with mixture Y-3 in 1.4×PCR buffer, using PCR program E and gradually raising the concentration of MgCl2. (d) PCR buffer concentration. Amplification products of mixture X-1 (DMD gene exons Nos. 45, PM, 19, 17, 51, 8, 12, 44 and 4) using increasing concentrations of PCR buffer and program E. As the stringency in the reaction mixture decreases, shorter products are amplified more efficiently, whereas the intensity of longer products gradually decreases. For this particular primer mixture, the optimal buffer concentration was 1.2×–1.6×. (e) Comparison of PCR buffers. Comparison of multiplex PCR of mixture X-1 in the DMD buffer and the 1.6×KCl-based PCR buffer, using the same proportion of ingredients (DNA, Taq DNA polymerase, primer amount) and PCR program E. For every DNA sample tested, the amounts of products were increased when 1.6×PCR buffer was used. Only four lanes are shown, although the gel had more samples loaded, and identical results were observed. (f) Amount of template DNA. Various amounts of template DNA were amplified with primer sY153 and mixture Y-3* in 2×PCR buffer with program E. Reaction volumes were 25 µL. There were no major differences using 500 or 30 ng DNA; however, some bands became weaker as the DNA amount was further decreased to 0.5 ng/25 µL reac-tion. No major differences due to the DNA template concentration were seen when primer pair sY153 was used alone.Research Reportscontent, etc).Comparison of PCR buffers.We have compared a previously described multiplex PCR buffer (6), called “DMD” for the purpose of this paper,with the less complex, KCl-based buffer in the multiplex reaction. The 5דDMD” buffer contains 83 mM (NH 4)2SO 4, 335 mM Tris-HCl (pH8.8), 33.5 mM MgCl 2, 50 mMβ-mer-captoethanol, 850µg/mL BSA, and it is used at 1×final concentration together with 10% DMSO and 1.5 mM each dNTP (1,2,4). When tested with the DMD gene primers (mixture X-1) the regular KCl-based PCR buffer at 1.6×worked better than the “DMD” buffer (visibly higher yield of products) (Fig-ure 4e). Results were reproducible indozens of patient DNA samples tested.The KCl-based buffer is less complex and easier to adjust and optimize. Also,since the fidelity of the Taq DNA poly-merase is higher at lower dNTP con-centrations (9), using the KCl-based buffer (which requires much less dNTP) can be beneficial when the PCR products need to be further analyzed for mutations.Amount of template DNA and Taq DNA polymerase (Step 5, A and D).At DNA template quantities between 30 and 500 ng/25 µL reaction, mixture Y-3* showed no significant differences (Figure 4f); however, below 30 ng the amount of some of the products de-creased. When the amount of template DNA is very low (pg of DNA), efficientand specific amplification can be ob-tained by further lowering the anneal-ing temperature, sometimes by as much as 10°–12°C (data not shown).Different concentrations of Taq DNA Polymerase (Perkin-Elmer) were tested using primer mixture Y -3 (Figure 5a). The most efficient enzyme concen-tration seemed to be around 0.4µL or 2U/25µL reaction volume. Too much enzyme, possibly because of the high glycerol concentration in the stock so-lution, resulted in an unbalanced ampli-fication of various loci and a slight in-crease in the background. Five native Taq DNA polymerases, from five dif-ferent sources, performed similarly on mixture Y -4 in 1.6×PCR buffer using 2U/25µL (Figure 5b).Use of adjuvants: DMSO, glyc-erol, BSA (Step 5E). Various authors recommend DMSO and glycerol to im-prove amplification efficiency (higher amount of product) and specificity (no unspecific products) of PCR, when used in concentrations varying between 5%–10% (vol/vol) (9). However, in the multiplex reaction, these adjuvants gave conflicting results. For example,5% DMSO improved the amplification of some products and decreased the amount of others, whereas some loci were not influenced at all (Figure 5c).Similar results were obtained with 5%glycerol (data not shown). Therefore,the usefulness of these adjuvants needs to be tested in each case. BSA, in con-centrations up to 0.8µg/µL (higher than previously described) increased the efficiency of the PCR much more than either DMSO or glycerol. BSA did not have an inhibitory effect on any of the loci amplified (data not shown).Agarose vs. Polyacrylamide Gels Agarose.Multiplex PCR products,differing from each other by 30–40 bp in length could be conveniently sepa-rated on 3% gels of commonly used agaroses, such as SeaKem or NuSieve (FMC BioProducts). Overnight separa-tion of products at lower voltage gradi-ents notably decreased the sharpness of individual PCR bands, especially when the products were smaller than 400–500 bp.Polyacrylamide (PAA) gels.To separate PCR products differing in onlyFigure 5.(a) Amount of enzyme. Amplification products of mixture Y-3, after using 0.5, 1, 2, 4 and 8U/25µL reaction volume are shown. Arrows indicate the expected positions of the amplification prod-ucts. The most appropriate enzyme concentration was between 1–2 U/25µL. (b) Source of enzyme. Mul-tiplex PCR of mixture Y-4 in 1.6×PCR buffer usesTaq DNA polymerases from five sources. Lane 4*shows the products obtained when the enzyme from lane 4 was used in the buffer provided by the vendor.An unspecific product appeared. (c) Use of adjuvants. Comparative multiplex PCR using the Y-specific mixtures with 5% DMSO (superscript D) and without DMSO, in 1×buffer. Loci sY151 and sY88 from mixture Y-1D (oblique arrows) are stronger when no DMSO is used. However, DMSO helps amplify (vertical arrows) locus sY81 in mixture Y-2 and locus sY95 in mixture Y-4. (d) Nondenaturing PAA gel separation. Simultaneous PCR amplification of loci D12S93 and D12S349 performed on genomic DNA from two human-rodent cell lines, GM 10868 (A) and GM 12072 (B), each containing a different copy of human chromosome 12, and their combination (A+B). Although in lanes A and B each locus should have yielded only one allele (i.e., one band), on a nondenaturing polyacrylamide gel, each of the two expected products (arrows) was accompanied by another one running slower on the gel (oblique lines). A similar aspect persisted in lane A+B. Lanes labeled 1 and 2 show separation of amplification products of mixture 12-1 (including eight D12S polymorphic loci, the numbers of which are indicated to the left side of Pan-el e) on two different genomic template DNAs. (e) Denaturing PAA gels. Sequencing gel separation of the same multiplex products as in Figure 4e, after “hot” PCR. Lanes A and B show mono-allelic amplifi-cation of the respective polymorphic loci (D12S93 and D12S349). Lane A+B shows simultaneous am-plification of both alleles at each locus. Lanes 1 and 2 show results using primer mixture 12-1 on two dif-ferent human genomic DNAs, with polymorphisms detected at some loci. Lane 3 shows results after multiplex PCR with mixture 12-1 on DNA from hybridoma cell line GM 10868 yielding homozygous amplification of all loci tested. Numbers to the left of the figure indicate the D12S loci tested.。

小学上册英语第四单元测验试卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The Earth's surface is constantly undergoing ______.2.Astronomers can determine a star's temperature by studying its _______.3.I have a _________ (魔法玩具) that changes colors when you touch it.4. A ________ (森林) is vital for the ecosystem.5.What is the chemical symbol for gold?A. AgB. AuC. PbD. Fe答案:B6.The teacher is ______ the lesson on math. (explaining)7.She has ___ (two) brothers.8.The Earth's surface is shaped by both human and ______ influences.9.My neighbor has a _______ (动物). 它的名字是 _______ (名字).10.The invention of the printing press allowed for the mass production of _______.11.What is the name of the famous fictional detective created by Sir Arthur Conan Doyle?A. Hercule PoirotB. Sherlock HolmesC. Sam SpadeD. Philip Marlowe答案: B12.Alkaline substances feel _______ to the touch.13.The ant can lift objects many times its _________ (重量).14.What do we call a place where animals are kept and displayed?A. ZooB. AquariumC. ParkD. Farm答案: A. Zooing organic methods in gardening promotes a healthier ______. (在园艺中使用有机方法可以促进更健康的环境。