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教学楼外观颜色形状英语作文英文回答：The exterior of the newly built teaching building stands out on campus with its modern yet timeless design. The façade's bold color scheme, geometric shapes, and dynamic textures create a striking visual appeal that complements the historic architectural surroundings.The dominant color of the building is a deep, earthy brown, providing a stable and grounded foundation. The brown hue evokes a sense of strength and reliability, echoing the university's long-standing legacy of academic excellence. Contrasting with the brown background are vibrant accents of blue and orange, reminiscent of the university's official colors. These hues add a touch of energy and dynamism to the building's exterior, symbolizing the university's forward-thinking spirit and commitment to innovation.The geometric shapes that define the building's structure further enhance its contemporary appearance. The main entrance features a sharp, angular canopy that extends over the doorway, creating a sense of shelter and inviting visitors into the building. The windows, arranged in irregular patterns, break up the monotony of the façade and provide glimpses into the vibrant interior spaces.Textural variations add depth and interest to the building's exterior. Smooth, polished surfaces contrast with rough, textured stone panels, creating a tactile interplay that engages the senses. The stone panels, reminiscent of the university's historic buildings, pay homage to the institution's past while simultaneously blending seamlessly with the modern design.Overall, the exterior of the teaching building is a harmonious fusion of bold colors, geometric shapes, and dynamic textures that reflects the university's commitment to tradition while embracing modernity. Its striking visual presence establishes a strong identity for the building and becomes a landmark on campus, inspiring students, faculty,and visitors alike.中文回答：教学楼的外观以其现代而又不失时代感的建筑设计在校园中脱颖而出。
语⾔学教程课后答案定义归纳胡壮麟《语⾔学教程》（第三版）---------课后习题单词定义归纳Chapter I Invitation to Linguistics1. Define the following terms:定义特征design feature:the distinctive features of human language that essentially make human language distinguishable from languages of animals.功能function:the role language plays in communication . to express ideas, attitudes) or in particular social situations . religious, legal).共时的synchronic:said of an approach that studies language at a theoretical ‘point’ in time.历时的diachronic:said of the study of development of language and languages over time.规定式prescriptive:to make authoritarian statement about the correctness of a particular use of language.描写式descriptive:to make an objective and systematic account of the patterns and use of a language or variety.任意式arbitrariness:the absence of any physical correspondence between linguistic signals and the entities to which they refer.⼆层式duality: the structural organization of language into two abstract levels: meaningful units . words) and meaningless segments . sounds, letters).移位式displacement:the ability of language to refer to contexts removed from the speaker’s immediate situation.寒暄phatic communion:said of talk used to establish atmosphere or maintain social contact.元语⾔metalanguage:a language used for talking about language.宏观语⾔学macrolinguistics:a broad conception of linguistic enquiry, including psychological, cultural, etc.语⾔能⼒competence:unconscious knowledge of the system of grammatical rules in a language.语⾔运⽤performance:the language actually used by people in speaking or writing.语⾔langue:the language system shared by a “speech community”.⾔语parole:the concrete utterances of a speaker.Chapter 2 Speech sounds1. Define the following terms:语⾳学phonetics:the study of how speech sounds are produced, transmitted, and perceived. It can be divided into three main areas of study—articulatory phonetics, acoustic phonetics and perceptual/auditory phonetics.发⾳语⾳学articulatory phonetics:the study of the production of speech sounds, or the study of how speech sounds are produced/made.⾳系学phonology:the study of the sound patterns and sound systems of languages. It aims to discover the principles that govern the way sounds are organized in languages, and to explain the variations that occur.发⾳器官speech organs:those parts of the human body involved in the production of speech, also known as ‘vocal organs’.带声器官voicing:the vibration of the vocal folds. When the vocal folds are close together, the airstream causes them to vibrate again st each other and the resultant sound is said to be ‘voiced’. When the vocal folds are apart and the air can pass through easily, the sound produced is said to be ‘voiceless’.国际⾳标International Phonetic Alphabet:a set of standard phonetic symbols in the form of a chart (the IPA chart), designed by the International Phonetic Association since 1888. It has been revised from time to time to include new discoveries and changes in phonetic theory and practice. The latest version has been revised in 1993 and updated in 1996.辅⾳consonant:a major category of sound segments, produced by a closure in the vocal tract, or by a narrowing which is so marked that air cannot escape without producing audible friction.元⾳vowel:a major category of sound segments, produced without obstruction of the vocal tract so that air escapes in a relatively unimpeded way through the mouth or the nose.发⾳⽅式manner of articulation:ways in which articulation of consonants can be accomplished—(a) the articulators may close off the oral tract for an instant or a relatively long period; (b) they may narrow the space considerably; or (c) they may simply modify the shape of the tract by approaching each other.发⾳部位place of articulation:the point where an obstruction to the flow of air is made in producing a consonant.基本元⾳Cardinal Vowels:a set of vowel qualities arbitrarily defined, fixed and unchanging, intended to provide a frame of reference for the description of the actual vowels of existing languages.半元⾳semi-vowel:segments that are neither consonants nor vowels, . [j] and [w].滑元⾳vowel glide:vowels that involve a change of quality, including diphthongs, when a single movement of the tongue is made, and triphthongs, where a double movement is perceived.协同发⾳coarticulation:simultaneous or overlapping articulations, as when the nasal quality of a nasal sound affects the preceding or following sound so that the latter becomes nasalized. If the affected sound becomes more like the followingsound, it is known as ‘anticipatory coarticulation’; if the sound shows the influence of the preceding sound, it is ‘perseverative coarticution’.⾳位phoneme:a unit of explicit sound contrast. If two sounds in a language make a contrast ,between two different words, they are said to be different phonemes.⾳位变体allophone:variants of the same phoneme. If two or more phonetically different sounds do not make a contrast in meaning, they are said to be allophones of the same phoneme. To be allophones, they must be in complementary distribution and bear phonetic similarity.同化现象assimilation:a process by which one sound takes on some or all the characteristics of a neighboring sound, a term often used synonymously with ‘coarticulation’. If a following sound is influencing a preceding sound, it is called ‘regressive assimilation’; the converse process, in which a preceding sound is influencing a following sound, is known as ‘progressive assimilation’.剩余位置条件Elsewhere Condition:The more specific rule applied first. It is applied when two or more rules are involved in deriving the surface form from the underlying form.区别特征distinctive features:a means of working out a set of phonological contrasts or oppositions to capture particular aspects of language sounds, first suggested by Roman Jacobson in the 1940s and then developed by numerous other people.⾳节syllable:an important unit in the study of suprasegmentals. A syllable must have a nucleus or peak, which is often the task of a vowel or possibly that of a syllabic consonant, and often involves an optional set of consonants before and/or after the nucleus.最⼤节⾸原则Maximal Onset Principle:a principle for dividing the syllables when there is a cluster of consonants between two vowels, which states that when there is a choice as to where to place a consonant, it is put into the onset rather than the coda.重⾳stress:the degree of force used in producing a syllable. When a syllable is produced with more force and is therefore more‘prominent’, it is a ‘stressed’ syllable in contrast to a less prominent, ‘unstressed’ syllable.语调intonation:the occurrence of recurring fall-rise patterns, each of which is used with a set of relatively consistent meanings, either on single words or on groups of words of varying length.声调tone:a set of fall-rise patterns affecting the meanings of individual words.Chapter 3 Lexicon1.Define the following terms语素morpheme:the smallest unit of language in terms of the relationship between expression and content, a unit that can not be divided into further smaller units without destroying or drastically altering the meaning, whether it is lexically or grammatically. Take forexample, the word tourists contains three morphemes. There is one minimal unit of meaning, tour, another minimal unit of meaning –ist (meaning “person who does someth ing), and a minimal unit of grammatical function –s (indicating plural). Meanwhile, from the above example, we can further classify morphemes into different types on different dimensions: (a) free morphemes, which can stand by themselves as single words, . tour in tourist, and bound morphemes, which cannot normally stand alone, but which are typically attached to another form, . –ist, -s. (b) lexical morphemes and functional morphemes. Both of these two types of morphemes fall into the “free” category. The first category is that set of ordinary nouns, adjectives and verbs that carry the “content” of message we convey, . house, long and follow. The second category consists largely of the functional words in the language such as conjunctions, prepositions, articles and pronouns, . but, above, the and it. (c) derivational morphemes and inflectional morphemes. These two types of morphemes fall into the “bound” category. The derivational morphemes are used to make new words in the language and are often employed to produce words of a different grammatical category from the stem. For example, the addition of the derivational morpheme –ness changes the adjective good to the noun goodness. In contrast, inflectional morphemes never change the grammatical category ofa word, but indicate aspects of the grammatical function of a word. For example, both old and older are adjectives. The –er inflection simply creates a different version of the adjective, indicating a comparative degree. As a useful way to remember the different categories of morphemes, the following chart can be used: It should be pointed out, morphemes may also be divided into roots and affixes, the root being that partof a word structure which is left when all the affixes have been removed. Root morphemes may be bound or free, and are potentially unlimited in number in a language; Affixes are bound morphemes and limited in number. For instance, in try, tries, trying, tried, the root is try, and –s, -ing, -ed are affixes.复合词compound:refers to the words that consist of more than on lexical morpheme or the way to join two separate wordsto produce a single form, such as classroom, mailbox, fingerprint, sunburn. In terms of the word class of compounds, there are Noun compounds . daybreak), Verb compounds . brainwash), Adjective compounds . dutyfree) and Preposition compounds . throughout). Meanwhile compounds can be further divided into endocentric compound and exocentric compound in terms of its structural organization. The head of a nominal or adjectival endocentric compound is d is derived from a Verb, and it is usually the case that the first member is a participant of the process verb. Consider the following two examples: self-control and virus-sensitive. The exocentric nominal compounds are formed by V+N, V+A, and V+P, whereas the exocentric adjectives come from V+N and V+A. Here are some examples: Nouns scarecrow playboy cutthroat Adjectives take home Lackluster breakneck屈折变化inflection:is the manifestation of grammatical relationship through the addition of inflectional affixes such as number, person, finiteness, aspect and cases to which they are attached.词缀affix:the collective term for the type of formative that can be used when added to another morpheme. Affixes ina language are limited in number, and are generally classified into three subtypes, namely, prefix, suffix, and infix, depending on their position around the root or stem of a word. Prefixes are these affixes that have be added to the beginning of a word . un- in unhappy); suffixes are those added to the end of a word . –ish in foolish); infixes, as a third type of affix, is not normally found in English but fairly common。
专八语言学考点语言学概论一.语言的甄别特征（Design Features）：语言的甄别特征（Design Features）包括：1. 任意性（Arbitrariness）2. 能产性（Productivity）3. 双层性（Duality）4. 移位性（Replacement）5. 文化传承（Cultural transmission）二．语言学的主要分支（the Main Branches of Linguistics）：1. 语音学（phonetics）：用以研究语音的特点，并提供语音描写、分类和标记方法的学科。
2. 音系学（phonology）：研究语言中出现的区别语音及其模式是如何形成语音系统来表达意义的学科。
3. 形态学（morphology）：研究词的内部结构和构词规则。
4. 句法学（syntax）：用以研究词是被如何组成句子，以及支配句子构成的学科。
5. 语义学（semantics）：研究语言意义的学科。
6. 语用学（pragmatics）：研究语言的意义在语境中如何被理解、传递和产出的学科。
7. 宏观语言学（Macrolinguistics）：主要包括社会语言学（Sociolinguistics）、心理语言学（Psycholinguistics）、人类语言学（Anthropological Linguistics）、计算机语言学（Computational Linguistics）。
三．语言学的流派（Different Approaches of Linguistics）：1. 结构主义语言学（Structural Lingustics）：1.1 布拉格学派（The Prague School）1.2 哥本哈根学派（The Copenhagen School）1.3 美国结构主义学派（American Structuralism）以上三个学派都受到索绪尔（Saussure）的影响，例如都区分语言和言语（Langue vs. Parole），共时和历时（Synchronic vs. Diachronic）。
高三英语学术成果单选题50题1. In the scientific research paper, the new discovery was described as "a ______ breakthrough that could change the future of medicine."A. crucialB. criticalC. acuteD. severe答案：A。
本题考查词汇辨析。
crucial表示至关重要的，在描述突破对医学未来的影响时，表达其关键重要性；critical也有批判的、关键的意思，但更多用于批判性的情况或危机时刻，在这里不如crucial合适；acute主要指尖锐的、敏锐的或者急性的（疾病等），与语境不符；severe表示严重的，多形容程度恶劣，不适用于描述突破的重要性。
2. The history article mentioned that during the war, the city faced a ______ shortage of food.A. severeB. strictC. rigidD. stern答案：A。
解析：severe表示严重的，用来形容食物短缺的程度非常严重，符合语境；strict侧重于严格的，常指规定、纪律等严格；rigid表示僵硬的、死板的，多形容物体或者规则缺乏灵活性；stern主要指严厉的，多形容人的态度，这三个选项均不符合食物短缺的语境。
3. In the literary analysis, the author's use of symbolism was very ______, adding deep meaning to the story.A. subtleB. delicateC. faintD. weak答案：A。
答案解析：subtle表示微妙的、隐晦的，在文学分析中，作者对象征手法的使用很微妙，给故事增添深意，是合适的表达；delicate指精致的、娇弱的，更多形容物体的外观或者人的身体状况等；faint表示微弱的、模糊的，多形容声音、光线等；weak表示虚弱的、薄弱的，不适合形容象征手法的运用。
贵州家乡菜辣子鸡特点介绍二年级作文示例回答如下1:Introduction:Spicy chicken with peanuts, also known as "辣子鸡" (làz ǐ jī) in Chinese, is a popular dish in my hometown of Guizhou, China. It is a flavorful and spicy dish that combines tender chicken pieces with crunchy peanuts and aromatic spices. In this article, I will introduce the unique characteristics of this dish.Characteristics of Spicy Chicken with Peanuts:1. Spicy Flavor: One of the key features of 辣子鸡 is its spicy flavor. The dish is made with a generous amount of dried red chili peppers, which give it a fiery kick. The spiciness of the dish can be adjusted according to personal preference, making it suitable for those who enjoy a mild to intense heat.2. Tender Chicken: The chicken used in 辣子鸡 is typically cut into small bite-sized pieces and marinated in a flavorful mixture of soy sauce, ginger, and garlic. The chicken is thenstir-fried until tender and juicy, creating a delicious contrast to the spicy peppers.3. Crunchy Peanuts: Another distinctive feature of this dish is the addition of crunchy peanuts. The peanuts add a nutty flavor and textural contrast to the dish, making each bite a delightful combination of spicy, savory, and crunchy elements.4. Aromatic Spices: In addition to dried red chili peppers, 辣子鸡 is seasoned with a blend of aromatic spices such as Sichuan peppercorns, star anise, and cinnamon. These spices contribute to the complex flavor profile of the dish and give it a unique and unforgettable taste.5. Quick and Easy to Prepare: Despite its bold flavors, 辣子鸡 is a relatively simple dish to prepare. With just a few key ingredients and some basic cooking techniques, you can recreate this delicious dish at home and impress your family and friends with your culinary skills.Conclusion:Spicy chicken with peanuts is a beloved dish in Guizhou cuisine, known for its bold flavors and satisfying combination of spicy, savory, and crunchy elements. Whether you enjoy the fiery heat of dried red chili peppers or the nutty crunch of peanuts, this dish has something to offer for everyone. Next time you visit Guizhou, be sure to try this iconic dish and experience the unique flavors of my hometown.中文回答：介绍：辣子鸡是我家乡贵州的一道受欢迎的菜肴，也被称为“辣子鸡”。
2017年英语专八参考答案来了！2017-03-22久等啦！2017年英语专八参考答案来也！你看或不看，它就在这里。
PartⅠ LISTENING COMPREHENSIONSECTION A MINI-LECTURE1. signing2. primary3. literacy4. different but complementary5. avoiding6. many other contexts7. characteristics/features8. reaction9. distance10. emotion11. deliberate12. intimacy and immediacy13. continuum14. types of language15. the usageSECTION B INTERVIEW1. What is international leaders’ assessment of the current battle against Ebola?答案：B. Disheartening.2.How many people are now working in the treatment unit in Liberia?答案：A. 200.3.According to Mary, what is the challenge in the battle against Ebola?答案：D. Insufficient operational efforts on the ground.4.Why do health workers need case management protocol training?答案：B. They can open up more treatment units.5.What does this interview mainly talk about?答案：C. Ebola outpacing operational efforts.6.What is Tom’s main role in his new position?答案：C. Using media information to inspire new ideas.7.According to T om, what does innovation require of people?答案：B. Being brave and willing to take a risk8.What does Tom see as game-changing chances in the future?答案：B. Aiming at a consumer level.9.What does Tom do first to deal with the toughest part of his work?答案：D. Examining the future carefully.10.Which of the following might Tom work for?答案：A. A media agency.PartⅡ READING COMPREHENSIONSECTION A MULTIPLE CHOICE QUESTIONSPASSAGE ONE11. The first part of Para. 4 refers to the fact that .答案：[A] life there is quiet and slow12. “The lack of awareness” in Para. 5 refers to .答案：［C］little knowledge of the beauty of the beach13. The author uses “gloriously” in Para. 6 to .答案：［C］contrast greenery with isolation14. The sentence “We never ate the same thing twice” in Para. 10 reflects the of the seafood there.答案：［D］variety15. Which of the following themes is repeated in both Paras.1 and 11?答案：［A］Publicity.PASSAGE TWO16. It can be inferred from Paras.1 and 2 that teachers used to .答案：［D］teach extended reading in a perfunctory way17. The sentence “we all understand and instinctively feel narrative structure” in Para.4 indicates that .答案：［C］we are born story-tellers18. Samuel Johnson regards the relationship between a writer and a reader as (Para.5).答案：［B］collaborative19. In Para.7, the author sees “pre-reading” as the most important part of reading because .答案：［C］it can attract students’ attention20. “Textual Intervention” suggested by Rob Pope (in Para.8) is expected to fulfill all the following functions EXCEPT .答案：［C］stretching the imaginationPASSAGE THREE21. According to the author, “national service” is comparable to “military training” because they both cultivate youngsters’答案：［B］self discipline22. The author cites the example of his father in order to show .答案：［A］the importance of discipline23. According to the author, a national service program can bring the following benefits to America’s youngsters EXCEPT .答案：［A］increase in income24. According to the context, what does “the fire” refer to (Para. 14)?答案：［B］Anger.SECTION B SHORT ANSWER QUESTIONS(说明：简答题答案不唯一，意思对即可。
土壤学部分专业名词1 土壤soil。
2 土壤学soil science3 发生土壤学pedology4 耕作土壤学edaphology5 土壤地理[学] soil geography6 土壤物理[学] soil physics7 土壤化学soil chemistry8 土壤生物化学soil biochemistry9 土壤矿物学soil mineralogy10 农业化学agrochemistry11 土壤分析化学soil analytical chemistry12 土壤生物学soil biology13 土壤微生物学soil microbiology14 土壤生态学soil ecology15 土壤微形态[学] soil micromor-phology16 土壤资源soil resources17 土壤区划soil regionalization18 土壤肥力soil fertility19 土壤管理soil management20 土壤利用soil utilizaion21 土壤改良soil amelioration, soil improvement22 土壤侵蚀[学] soil erosion23 水土保持soil and water conservation24 农业化学分析agrochemistry analysis25 土壤信息系统soil information system, SIS26 土壤遥感soil remote sensing27 土壤圈pedosphere28 土壤景观soil landscape29自然土壤natural soil30人为土壤anthropogenic soil31 耕作土壤cultivated soil32 森林土壤forest soil33 草原土壤steppe soil34 荒漠土壤desert soil 35 水田土壤paddy field soil 36 旱地土壤upland soil37低地土壤lowland soil38湿地土壤wetland soil39 盐渍土壤salt-affected soil40 山地土壤mountain soil41高山土壤slpine soil42 风化作用weathering43物理风化physical weathering44化学风化chemical weathering45 生物风化biological weathering46 风化产物weathering product47 风化残余物weathering residue48 风化强度weathering intensity49 风化指数weathering index50 风化淋溶系数ba value51 半风化体saprolite52 风化壳weathering crust53 碎屑风化壳clastic weathering crust54 含盐风化壳salic weathering crust55 碳酸盐风化壳carbonated weathering crust56 硅铝风化壳siallitic weathering crust57 铁铝风化壳ferrallitic weathering crust58[成土]母质parent material59 土壤发育soil development60 土壤发育序列soil development sequence61 年代序列chronosequence62 地形系列toposequence63 原始土壤primitive soil, initial soil64 幼年土壤young soil65 成熟土壤mature soil66 顶极土壤climax soil67 古土壤学paleopedology68 古土壤paleosol69 埋藏土buried soil70 裸露埋藏土exhumed soil71 残遗土relict soil72土壤年龄soil age73 土壤绝对年龄absolute age of soil 74土壤相对年龄relative age of soil75 放射[性]碳定年radiocarbon dating76 [表观]平均停留时间[aparent] mean residence time, AMRT77 土壤地球化学soil geochemistry78 土壤生物地球化学soil biogeochemistry79 土壤发生soil genesis80 土壤形成soil formation81 土壤形成因素soil-forming factor82 土壤形成过程soil-forming process83 淋溶作用eluviation84 淋洗作用leaching85 螯合淋溶作用cheluviation86 [机械]淋移作用mechanical eluviation, lessivage87 淀积作用illuviation88 淋淀作用eluviation-illuviation89生物积累作用biological accumulation90 腐殖质积累作用humus accumulation91 泥炭形成[作用] peat formation92 盐化[作用] salinization93碱化[作用] solonization94 次生盐化[作用] secondary salinization95脱盐作用desalinization。
广东省2025届普通高中毕业班第一次调研考试英语本试卷共8页，考试用时120分钟，满分120分。
注意事项：1．答卷前，考生务必将自己所在的市（县、区）、学校、班级、姓名、考场号和座位号填写在答题卡上，将条形码横贴在每张答题卡左上角“条形码粘贴处”。
2．作答选择题时，选出每小题答案后，用2B铅笔在答题卡上将对应题目选项的答案信息点涂黑；如需改动，用橡皮擦干净后，再选涂其他答案。
答案不能答在试卷上。
3．非选择题必须用黑色字迹的钢笔或签字笔作答，答案必须写在答题卡各题目指定区域内相应位置上；如需改动，先画掉原来的答案，然后再写上新答案；不准使用铅笔和涂改液。
不按以上要求作答无效。
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考试结束后，将试卷和答题卡一并交回。
第二部分阅读（共两节，满分50分）第一节（共15小题；每小题2.5分，满分37.5分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。
ATICKJETS FOR KENSINGTON PALACJE AND UNTOJLJD JLIVESKensington Palace TicketsAn admission ticket includes access to all public areas of the palace and gardens including: Untold Lives exhibition, Victoria:A Royal Childhood, The King's State Apartments and The Queen’s State Apartments.（续表）How to Get Tickets You've Bought OnlineDownload your PDF ticket to your mobile for scanning(扫描) at the entrance or click the link in the email that we’ll send you and print out all your tickets.If you are not able to download your e-tickets using the link in your confirmation email, please show your reference number which begins 42xxxxxxxxx to the ticket desk when you arrive and staff on site will be able to print your tickets for you.21. What can a Kensington Palace ticket be used to do?A. Serve as an identification card.B. Provide discounts for kid tickets.C. Offer free visit to several places.D. Show how to print online tickets.22. How much should a class of 20 pupils and a teacher pay for the entry?A. About ￡21.B. About￡264.C. About ￡404.D. About￡464.23. What is needed when you have your tickets printed on site?A. The cellphone screen.B. The reference number.C. The ticket price table.D. The confirmation email.BAs a college professor, I am required to hold an office hour before my lecture. These office hours are optional and tend to be busier at the beginning and end of a semester(学期).In the middle, they can become quiet. A few years ago I was given a flute(长笛) as a gift, so I decided that I would use my quiet office hours to practice this new instrument. The experience brought unexpected insights into performance anxiety.I held my office hour in the near-empty lecture hall, one hour before the class began. The hall was open to any student who wished to talk with me about coursework or to take a seat and quietly read before the lecture began. I would assemble (组装) my flute, open my lesson book, and begin working on the instrument I had never played before. I also followed online video lesson s－a ll done in front of a few students who would come early to class.I would begin playing l ong tones, closing my eyes and “forgetting” that anyone was in the room with me. I was surprised to find that I felt no anxiety while learning a new instrument in front of others. Had I been playing my main instrument, I would have had more concern about the level of my playing and how my playing was being received. However, in this setting, it was clear that I was an absolute beginner with no expectations of impressing anyone with my mastery. My attention was set on figuring the instrument out. I had no expectations of how I would sound and had little expectations of sounding like anything more than a beginner.There have been many things I have learned from my experiment of learning an instrument in public. Whenever musicians talk with me about their stage fright, I offer them this story.24. What is “an office hour” for?A. The professors to show talents.B. The students to appreciate music.C. The teachers to offer consultation.D. The lecturers to make preparations.25. Why did the author play a flute?A. To pass the time.B. To give a lecture.C. To do a research.D. To attract students.26. What made the author at ease when playing the flute?A. The technique from the video.B. His impressive performance.C. The audience’s active response.D. His concentration on playing.27. Which of the following is a suitable title for the text?A. My Joy of Learning a New ThingB. My Tip on Performing in the PublicC. My Discovery to Ease Stage FrightD. My Office Hour Before Every LessonCAs AI develops, it becomes challenging to distinguish between its content and human-created work. Before compar ing both, it’s good to know about the Perplexity & Burstiness of a text.Perplexity is a measurement used to evaluate the performance of language models in predicting the next word in a group of words. It measures how well the model can estimate the probability of a word occurring based on the previous context. A lower perplexity score indicates better predictability and understanding of the language, while a higher perplexity score suggests a higher degree of uncertainty and less accurate predictions. The human mind is so complex compared to current AI models that human-written text has high perplexity compared to AI-generated text.Examples :High Perplexity: “The teapot sang an opera of hot, wheeling tea, every steamy note a symphony of flavor. ”Low Perplexity: “I poured hot water into the teapot, and a fresh smell filled the room. ”Burstiness refers to the variation in the length and structure of sentences within a piece of content. It measures the degree of diversity and unpredictability in the arrangement of sentences. Human writing often exhibits bursts and lulls (间歇) , with a mix of long and short sentences, while AI-generated content tends to have a more uniform and regular pattern. Higher burstiness indicates greater creativity, spontaneity (自发性) , and engagement in writing, while lower burstiness reflects a more robotic and monotonous (单调的) style. Just like the perplexity score, human-written content usually has a high burstiness score.Examples :High Burstiness: “The alarm screamed. Feet hit the floor. The tea kettle whistled. Steam streamed. Heart pounded. The world, awake. ”Low Burstiness: “In the peaceful morning, the alarm clock’s soft ring greeted a new day. I walked to the kitchen, my steps light and unhurried. The tea kettle whistled its gentle song, a comforting tune that harmonized with the steam’s soft whisper. ”Here, I wrote a passage on the “Importance of l ifelong learning”myself and also asked ChatGPT to do the same to compare better AI-generated and human-written text.28. What do Perplexity & Burstiness probably serve as?A. Complexities of a language.B. Criteria on features of a text.C. Phenomena of language varieties.D. References in generating a text.29. What are the characteristics of an Al-generated text?A. Low perplexity and low burstiness.B. High perplexity and low burstiness.C. Low perplexity and high burstiness.D. High perplexity and high burstiness.30. Which of the writing ways below does the author skip when developing the article?A. Quoting sayings.B. Showing examples.C. Giving definitions.D. Making comparisons.31. What will be probably talked about next?A. Some essays from ChatGPT.B. An illustration for differences.C. An example of the writer’s own.D. Analyses of lifelong learning.DWhen stressed out, many of us turn to junk food like deep-fried food for comfort. But a new research suggests this strategy may backfire. The study found that in animals, a high-fat diet disrupts resident gut bacteria (肠道细菌) , changes behavior and, through a complex pathway connecting the gut to the brain, influences brain chemicals in ways chat fuel anxiety.“Everyone knows that these are not healthy foods, but we tend to think about them strictly in terms of a little weight gain,”said lead author Christopher Lowry, a professor of integrative physiology at CU Boulder. “If you understand that they also impact your brain in a way that can promote anxiety, that makes the risk even higher.”Lowry’s team divided mice into two groups: Half got a standard diet of about 11% fat for nine weeks; the others got a high-fat diet of 45% fat, consisting mostly of fat from animal products. The typical American diet is about 36% fat, according to the Centers for Disease Control and Prevention.When compared to the control group, the group eating a high-fat diet, not surprisingly, gained weight. But the animals also showed significantly less diversity of gut bacteria. Generally speaking, more bacterial diversity is associated with better health, Lowry explained. The high-fat diet group also showed higher expression of three genes（基因）（tph2, htrla, and slc6a4) involved in production and signaling of the brain chemical called serotoni n－particularly in a region of the central part of the brain known as the dorsal raphe nucleus cDRD, which is associated with stress and anxiety. While serotonin is often billed as a “feel-good brain chemical”, Lowry notes that certain subsets of serotonin neurons（神经元）can, when activated, touch off anxiety-like responses in animals. Especially, heightened expression of tph2 in the cDRD has been associated with mood disorders in humans.“To think that just a high-fat diet could change expression of these genes in the brain is extraordinary,” said Lowry.“The high-fat group essentially had a high anxiety state in their brain. ” However, L owry stresses that not all fats are bad, and that healthy fats like those found in fish, nuts and seeds can be good for the brain.32. What is山e new finding?A. Junk food leads to overweight.B. High-fat food brings bad moods.C. Brain chemicals cause anxiety.D. Gut bacteria benefit brain health.33. What does the underlined word “disrupts” in paragraph l mean?A. Upsets.B. Facilitates.C. Loosens.D. Generates.34. How were the mice eating a high-fat diet by contrast with the control group?A. They looked more anxious.B. They lost much more weight.C. They suffered mood disorders.D. They lacked gut bacteria variety.35. What does Lowry agree with?A. Every fat is harmful.B. Fish fat is harmless.C. Stress comes from fat.D. Some fats are good.第二节（共5小题；每小题2.5分，满分12.5分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。
高三英语写作风格与文体判断单选题30题1. The story is told in a vivid and detailed way. What kind of writing style is it?A. NarrativeB. DescriptiveC. ExpositoryD. Persuasive答案：A。
本题考查写作风格的判断。
选项A“Narrative”即记叙文风格，题干中提到故事以生动详细的方式讲述，符合记叙文的特点。
选项B“Descriptive”是描写文风格，主要侧重于对事物的描述。
选项C“Expository”是说明文风格，用于解释说明事物。
选项D“Persuasive”是议论文风格，目的是说服读者。
2. A story that focuses on the development of a character is mainly what kind of writing style?A. Narrative with character focusB. Plot-driven narrativeC. Descriptive narrativeD. Argumentative narrative答案：A。
题干中强调故事聚焦于人物的发展，这是带有人物焦点的记叙文风格。
选项B“Plot-driven narrative”是以情节推动的记叙文风格。
选项C“Descriptive narrative”是带有描写的记叙文风格。
选项D“Argumentative narrative”是议论文风格的记叙文，不存在这种说法。
3. A text that tells a story from the first-person perspective is likely to be what kind of writing style?A. First-person narrativeB. Third-person omniscient narrativeC. Third-person limited narrativeD. Objective narrative答案：A。
Irregular textural features of dried alginate–filler beadsC.Zohar-Perez a ,I.Chet b ,A.Nussinovitch a,*aFaculty of Agricultural,Food and Environmental Quality Sciences,Institute of Biochemistry,Food Science and Nutrition,The Hebrew University of Jerusalem,P.O.Box 12,Rehovot 76100,IsraelbDepartment of Biological Chemistry,Weizmann Institute of Science,P.O.Box 26,Rehovot 76100,IsraelReceived 27January 2003;accepted 12May 2003AbstractFreeze-dried hydrocolloid beads can be used as carriers for many food,non-food and biotechnological rmation on their shape and surface properties,how different features are produced on their outer surface as a result of technological procedures,and the influence of fillers and other ingredients on external and internal shape and texture have never been investigated in detail.These parameters are very important since the surface of the bead is the first part to come into contact with its fluid,solid or gaseous environment and together with its internal structure,will influence,if not determine,its suitability to a predetermined task.In our study,projections formed on the surface of the bead during freezing.Smaller-sized fillers (such as kaolin)gave a smoother surface;a rougher surface was achieved with a bigger-diameter filler,such as bentonite.The presence of filler and/or glycerol in the bead increased the number of mid-area ‘craters’and reduced the number of the smaller ‘craters’formed on the bead’s dried surface.Moreover,the inclusion of glycerol had a large influence on the distribution of pores within the beads.Filler inclusion in the dried product reduced its collapse and roundness distortion during the drying process.In conclusion,the components and the method by which the dried bead was formed completely determined its weight,volume,shape and surface features.Taking these parameters into consideration provides the researcher with a useful tool for creating tailor-made dried beads for a predetermined operation,thereby increasing the probability of success.This was proven by the improved antifungal activity of entrapped Pantoae agglomerans (biocontrol agent)within alginate–glycerol–chitin beads.q 2003Elsevier Ltd.All rights reserved.Keywords:Alginate beads;Freeze-drying;Fillers;Surface characteristics;Roundness;Biocontrol1.IntroductionDried hydrocolloid beads can be used for many biotechnological purposes,such as water denitrification (Iza,1991;Power &Schepers,1989;Tatsuo,Hiroki,&Naomichi,1991;Tchobanoglous &Burton,1991),matrices for the immobilization of denitrifying isolates (Tal,van Rijn,&Nussinovitch,1997),carriers of bacteria or spores for biological control of soil-borne root diseases (Zohar-Perez,Ritte,Chernin,Chet,&Nussinovitch,2002),and as UVC protectants of spores and bacteria (Zohar-Perez,Nussinovitch,&Chet,2003),and carriers of Gram-positive lactic acid bacteria starter cultures involved in dairy and food fermentation (Champagne,Gardner,Soulignac,&Innocent,2000;Champagne,Mondou,Raymond,&Brochu,1996).Starch can be incorporated into freeze-dried alginate beads,serving as a carbon source and filler (Tal,van Rijn,&Nussinovitch,1999).In general,dried hydrocolloid beads are stronger than non-dried gel beads,their porosity can be controlled such that produced gases can be liberated from their matrix without interfering with its structure,and they are important as carriers for food and biotechnological operations (Nussinovitch,2003).Dried agar gel beads have served as a study model for drying (Kubota,Kobatake,Suzuki,&Hosaka,1977;Suzuki,Onishi,Esaka,Kubota,&Hosaka,1989).In addition to their many described applications and uses as models for drying studies,dried gel beads can be used for the separation of enzymes (Jun,Chang,&Ruan,1995).Information on the shape and surface of dried hydro-colloid beads is limited.Muyima and Cloete (1995)described freeze-dried alginate beads after immobilization of Acinetobacter johnsonii to have some grooves on their surface.The authors hypothesized that the ‘intensity’of0268-005X/$-see front matter q 2003Elsevier Ltd.All rights reserved.doi:10.1016/S0268-005X(03)00081-XFood Hydrocolloids 18(2004)249–258/locate/foodhyd*Corresponding author.Tel.:þ972-8-948-9016;fax:þ972-8-936-3208.E-mail address:nussi@agri.huji.ac.il (A.Nussinovitch).those structures may vary according to the dehydration process used.Another manuscript describes lyophilized alginate beads used as carriers for the slow release of bacteria that affect plant growth,to have concentric layers of dried solidified matrix(Bashan,1986).Freeze-dried algi-nate beads were used to entrap probiotic bacteria for survival purposes in frozen,fermented dairy desserts;based on SEM micrographs the beads were described only as ‘spherical’(Shah&Ravula,2000).Alginate gel beads that were coated with chitosan at a constant concentration and vacuum-dried for the release of brilliant blue presented a spherical shape when the alginate concentration was$3% (Shu&Zhu,2002).While many applications of dried hydrocolloid beads have been reviewed(Nussinovitch,1997,2003),only very limited usually incomplete information can be found on their regular or irregular shapes and surface features. Therefore,the objectives of this study were to document these irregular surface textural features as well as the beads’internal structure and to investigate when and how the production process influences them and howfillers affect their appearance and their biological performance.These questions are of utmost importance because of the many options for the use of dried beads in future food and non-food applications.2.Materials and methods2.1.Bacterial and fungal growthFor entrapment,the biocontrol agent Pantoae agglom-erans IC1270was used(Chernin,Ismailov,Haran,&Chet, 1995).The bacteria were grown on liquid or solid(1.5%w/v agar)nutrient broth(NB)and agar(NA)for24h at288C. The pathogenic fungus Rhizoctonia solani was grown on solid potato dextrose agar(PDA)for7days at288C.2.2.Bead preparationAlginate,with a molecular mass of60–70kDa and containing61%mannuronic acid and39%guluronic acid (Sigma,LV,St Louis,MO),was dissolved in distilled water (2%w/w).Glycerol(30%w/w,final concentration)was added to the alginate(2%w/w,final concentration)solution. For the alginate–filler bead preparation,a colloidal chitin suspension(C8H13NO5),bentonite[Sigma,hydrated alumi-num silicate(clay),consisting principally of montmorillo-nite Al2O3·4SiO2·H2O,average particle size9.7m m,density 2.3–2.7g/cm3]or kaolin[Sigma,aluminum silicate hydroxide H2Al2Si2O8·H2O(clay),average particle size 0.5m m,density2.3–2.7g/cm3]was added to the alginate–glycerol solution to afinal concentration of0.5%(w/w).The colloidal chitin suspension was prepared by dissolving ground crustacean chitin in a concentrated HCl solution according to the method of Rodriguez-Kabana,Godoy,Morgan-Jones,and Shelby(1983).When beads containing bacteria were required for the biocontrol assay, P.agglomerans cells(,109cells/ml)were added at a1:9 volumetric ratio to alginate–glycerol or alginate–glycerol–chitin solutions(after their sterilization).Thefinal mixtures were dripped into a1%(w/w)solution of calcium chloride and stirred for30min(the volumetric ratio between the alginate mixture and the calcium chloride solution was 1:50).A spontaneous cross-linking reaction produced spherical beads with an average diameter of about4mm. The beads were frozen at2808C for1h before freeze-drying,which was carried out at2508C at a pressure of 1.1Pa(Martin Christ model ALFA I-5;Osterode am Harz, Germany)(Tal et al.,1999).2.3.Physical properties of alginate solutionsThe surface tension of alginate,alginate–glycerol, alginate–glycerol–chitin,alginate–glycerol–bentonite and alginate–glycerol–kaolin solutions was measured by computerized tensiometer(Sigma70,KSV,Helsinki,Fin-land)equipped with a platinum/iridium DuNouy ring.The probe was dipped at a rate of10mm/min and raised at 5mm/min.Each solution was testedfive times with three repetitions at25^28C and an ambient relative humidity of about55%.Solution density was measured with a calibrated10-ml pycnometer at25^28C.Solution viscosity was measured by viscometer(Brook-field Engineering Labs Inc.,Stoughton,MA)at25^28C.2.4.Temperature measurements in the beadsThe temperature decrease inside the beads during freezing at2808C was determined by data-logging K/J thermometer and appropriate thermocouples(TES Elec-trical Electronic Corp.,Taipei,Taiwan).2.5.Electron micrographs and image analysisTo study bead structure,a Jeol JSM35C SEM(Tokyo, Japan)at25kV was used in two different modes:low-vacuum SEM(at0.2Torr)for gel beads and beads after freezing in2808C,and high-vacuum SEM(at1023Torr) for beads after freeze-drying.The freeze-dried beads were glued to a polypropylene stub and gold-coated(150–200A˚) in a Polaron5150sputter coater(Polaron Equipment Ltd, Holywall Industrial Estate Watford,Hertfordshire,England) (Forini,Tel-Or,Bar,&Grilli-Caiola,1991).Electron micrographs were scanned(Hewlett Packard scanner,version3.02,model5300C)and analyzed using Image Pro Plus(version 3.0.01.00,Media Cybernetics, L.P.).This program determines the thickness of a marked protuberance wall,and the number of sections bordered by such walls and their area,measured in pixels,and translates this data into metric units.Freeze-dried beads that wereC.Zohar-Perez et al./Food Hydrocolloids18(2004)249–258 250made from alginate,alginate–glycerol,alginate–glycerol–chitin,alginate–glycerol–bentonite and alginate–gly-cerol–kaolin solutions were examined for these characteristics.2.6.Estimation of bead weight,diameter,volume and roundnessTo estimate the roundness and diameter of the beads at different stages of their creation,gel beads,beads after freezing and freeze-dried beads were photographed from three different angles using a digital camera(COOL-PIX5000,Nikon,Japan)in a manner similar to that proposed by Nussinovitch and Gershon(1996).The resultant photographs were analyzed using Image Pro Plus (version3.0.01.00,Media Cybernetics,L.P.).This program determines the maximalðD maxÞ;minimalðD minÞand average diameter,area and perimeter of the bead,and calculates its aspect ratio and roundness using the following equations:(1)aspect ratio¼D max=D min(2)roundness¼perimeter2/(4p£area)The roundness of the freeze-dried beads was estimated by these two equations;values closer to1indicated rounder beads(a values of1indicating a perfect sphere).Beads were approximated as spheres in order to calculate their volume,using their average diameter.The diameter of the beads during cross-linking(1min after dropping into the CaCl2solution)was measured by digital caliper(Mitutoyo,Tokyo,Japan).Weight(^0.001g)was measured with an analytical balance,model262MSA-FR(Precisa,Bern,Switzerland).2.7.Bead water-content estimationWater content in the different beads was evaluated by taking into account the amount of ingredients(alginate and filler)included in the initial formulation;glycerol concen-tration in the beads was determined in accordance with a previously described method(Zohar-Perez et al.,2002). Briefly,samples offive beads were dissolved in a2%citrate solution and analyzed for glycerol using the Sigma triglyceride reagent A kit.2.8.In vitro antifungal activityAlginate–glycerol beads,with or without chitin,and before and after freeze-dehydration,entrapping P.agglom-erans(107cells/bead),were seeded at two corners of a PDA plate(9cm)and incubated at288C for5days.A5-mm-diameter agar disk from the actively growing pathogenic fungal culture R.solani was then placed at the center of the PDA plate and the plates were incubated at288C until mycelium growing on a control plate(containing beads without bacteria in the corners)covered the whole plate area.The extent of mycelial growth on plates containing beads with bacteria was then estimated.2.9.Statistical analysisResults represent the average of three independent experiments.In every test,10beads were evaluated(unless otherwise noted).Statistical analyses were conducted with JMP software(SAS Institute,1995),including ANOVA and the Tukey-Kramer Honestly Significant Difference Method for comparisons of means.P#0:05was considered significant.3.Results and discussionSpherical hydrocolloid beads can be produced by using molds(for example with gums such as agar,cold-set alginate,gellan or k-carrageenan),or by dropping a gum solution into a cross-linking solution and allowing them to react.In the case of alginate without any additional constituent,immediately after the spontaneous cross-linking reaction the beads had an average weight of63.4^7.0mg and a diameter of5.04^0.21mm.With time and as a result of the diffusion of calcium ions and further cross-linking, the bead contracted to an average weight of43.6^1.6mg and diameter of4.35^0.08mm.Whenfillers and glycerol were included in the alginate solution,dripping and drop size changed.Threefillers were used:bentonite and kaolin have average particle sizes of9.7 and0.5m m,respectively;the average particle size of the treated chitin has been evaluated to vary from fractions of microns to aggregates of tens or even hundreds of microns in produced pasta(Nitoda,Kurumatani,Kanzaki,& Kawazu,1999).The surface tension,density and viscosity of alginate–glycerol and alginate–glycerol–filler solutions were higher than those of alginate solution alone(Table1). Increases in viscosity and surface tension of the dropped solution increased the drop size and volume(Haq,Akesson, Table1Measured surface tension,density and viscosity values for different alginate solutionsSolution type Surface tension*(mN/m)Density*(kg/m3)Viscosity*(Pa.s)Alginate56.0a(0.7)997a(0)0.104a(0.009) Alginate with glycerol62.1b(1.3)1069b(0)0.287b(0.024) Alginate with glyceroland chitin58.3c(1.0)1075c(1)0.350c(0.020)Alginate with glyceroland kaolin63.3b(0.8)1077d(1)0.310b(0.026) Alginate with glyceroland bentonite64.1b(1.0)1078d(1)0.360c(0.027)*Values followed by the same letter are not significantly differentðP# 0:05Þ:Data are the average of three experiments^SD in parentheses.C.Zohar-Perez et al./Food Hydrocolloids18(2004)249–258251Yates,Kaneko,&Akesson,1983;Lagerfelt,1986).These changes,although expected,were not great,and were only pronounced at the start of the cross-linking reaction (,1min after submerging in the calcium solution), resulting in increases in drop size and volume of,5and 12%,respectively,for all alginate–filler and/or glycerol combinations in comparison to alginate solution droplets. After30min of calcium diffusion and cross-linking, differences decreased(Table2),perhaps due to the stronger influence of the contraction stage.After freezing,theaverage diameter of the bead increased by,5–10%.The volume of ice is9%greater than that of pure water and bead expansion after freezing(before dehydration)is expected.In most cases,the degree of expansion varies considerably owing to many factors,among them moisture content (Fennema,1975).In general,the higher the moisture content,the higher the volume of the frozen bead,calculated from the measured average diameter(with bentonite this effect is less pronounced,see Tables2and3).After freeze-dehydration,the beads’diameter contracted by,18–45% in comparison to their non-dried counterparts,depending on filler inclusion.A reduction as a result of freeze-dehydration has also been reported for foods that regularly contain almost the same percentage of inherent water(Karel,1975), for similar alginate beads(van Neerven,Wijffels,& Zehnder,1990)and cylindrical gels(Rassis,Saguy,& Nussinovitch,2002).Even though the viscosity and surface tension of the dropping solution had little effect on gel-bead size,the roundness of those beads was significantly affected, resulting in rounder alginate–glycerol and alginate–gly-cerol–filler gel beads in comparison to those withoutfiller and/or glycerol.This is not surprising because as it is dropped and enters the cross-linking solution,the drop is rounder and therefore so is the formed bead.After freezing, a reduction in bead roundness was observed in beads containingfiller.In accordance to Fennema(1975),during freezing there are localized areas of expansion(ice crystals) and localized areas of contraction(most other constituents), and thus the volume change is not uniform throughout the system.A frozen multicomponent product is therefore expected to have a high aspect ratio.On the contrary,the drying process decreased bead roundness the most for regular(without any addition)and glycerol beads;less influenced were those beads withfillers,maybe because these particles present resistance to some phenomenological collapse(Rassis et al.,2002;Tal et al.,1999).Since our interest is in extending the shelf life of preparations based on gel beads,freeze-dehydration seems to be the natural way of preserving the product with only minimally disturbing its dimensions(especially whenfiller is present), whereas regular drying could cause catastrophic collapse of the gel(van Neerven et al.,1990;Rassis et al.,2002;Shu& Zhu,2002).Moreover,as far as we could tell,depolymer-ization of the alginate did not occur during freeze-dehydration;the addition of glycerol to the alginate solution reduces such phenomena during sterilization due to its contribution to increasing the viscosity(Daigle&Cotty, 1997).In addition to bead volume and roundness,other alterations occurred during freezing and drying:surface morphology differences were observed after freezing;these changes intensified after the drying,partially as a result of bead shrinkage.To the naked eye the gel beads had a smooth surface (Fig.1).This is in fact true,but in the process of freeze-dehydration,alterations occurred in accordance to the content and type offiller included within the formulation. Fig.2A–D demonstrates the influence of thefiller on the surface of the frozen bead(before drying).Withoutfiller (Fig.2A)the surface is rugged and looks like it is composed of craters bordered by prominent walls.With includedfillersTable2Final diameter and roundness parameters of alginate beadsBead content and state Diameter(mm)Roundness Aspect ratio ControlGel beads A4.35a(0.08)A1.33a(0.15)A1.20a(0.15) Beads after freezing AB4.94b(0.20)A1.32a(0.10)A1.24a(0.07) Freeze-dried beads A2.37c(0.08)A1.46b(0.11)A1.61b(0.17) Beads with glycerolGel beads AB4.41a(0.09)AB1.26a(0.00)B1.12a(0.06) Beads after freezing B4.64a(0.38)A1.34ab(0.10)A1.22ab(0.07) Freeze-dried beads B2.95b(0.04)A1.46b(0.18)B1.27b(0.06) Beads with glycerol and chitinGel beads A4.34a(0.06)B1.14a(0.02)B1.09a(0.02) Beads after freezing B4.65b(0.16)A1.42b(0.16)A1.32b(0.16) Freeze-dried beads C3.56c(0.08)B1.23a(0.02)B1.18a(0.08) Beads with glycerol and kaolinGel beads A4.33a(0.14)B1.13a(0.02)B1.11a(0.04) Beads after freezing B4.60a(0.32)A1.30b(0.15)A1.21b(0.07) Freeze-dried beads C3.44b(0.03)B1.21b(0.02)B1.25b(0.03) Beads with glycerol and bentoniteGel beads B4.49a(0.05)B1.16a(0.01)B1.13a(0.00) Beads after freezing A5.00a(0.16)A1.36b(0.14)A1.21ab(0.10) Freeze-dried beads C3.39b(0.03)B1.20a(0.02)B1.17b(0.03) Values followed by the same letter are not significantly differentðP# 0:05Þ;a–c represent statistical difference between beads in a different state (i.e.gel/after freezing/freeze-dried beads)in the same content group;A–C represent statistical difference between beads with a different content in the same state.Data are the average of10beads^SD in parentheses.Table3Calculated water content of alginate gel beadsBead content Approximate water content(%) Gel bead98.0Gel bead with glycerol a90.7Gel bead with glycerol a andfiller90.2a Glycerol amount inside the beads(7.3^0.4%)differed from its inclusion in the alginate solution(30%)due to leakage during cross-linking (Zohar-Perez et al.,2002).C.Zohar-Perez et al./Food Hydrocolloids18(2004)249–258 252(Fig.2B–D ),the height and thickness of the protuberances appear to lessen,being smallest for beads containing kaolin.This observation was verified by measuring those protuber-ances on freeze-dried bead surfaces (Fig.3A–D ).The thickness of the protuberances on the outer surface of the freeze-dried alginate beads (control)was 14^7m m;addition of fillers and or glycerol to the beads significantly reduced the thickness to 8–10m m.Thus it appears that smooth or rough surface features can be selectively produced by varying filler inclusion and size.If a smooth surface is required,inclusion of a smaller-size filler such as kaolin is recommended;if a rougher surface is required,then a filler with a bigger diameter can be used.Rougher surfaces can also be achieved with no inclusion of filler,but bead ‘collapse’will be considerable.Kaolin has a smaller average particle size than bentonite (0.5versus 9.7m m,respectively).However a smaller diametermeansFig.1.Electron micrograph of an alginate gelbead.Fig.2.Electron micrographs of alginate (A),alginate–glycerol–bentonite (B),alginate–glycerol–chitin (C)and alginate–glycerol–kaolin (D)gel beads after freezing at 2808C.Bar,500m m.C.Zohar-Perez et al./Food Hydrocolloids 18(2004)249–258253more particles (per same weight)per bead.In fact,about ,106bentonite particles are present within one bead versus ,5£109kaolin particles/bead.The higher number of kaolin particles per bead and their small size may be contributing to matrix ‘resistance’against collapse,result-ing in a smoother surface.For treated chitin,it is not possible to state average particle size due to the aforemen-tioned substantial variations (Nitoda et al.,1999).The projections on the bead surface seem to form during the freezing stage.Fig.4demonstrates the behavior of the beads with or without glycerol and fillers during freezing.The beads were first cooled to below their freezingpoint.Fig.3.Influence of initial bead formulation on protuberance formation on the outer surface of the freeze-dried beads.(A/a)alginate beads,(B/b)alginate beads with glycerol,(C/c)alginate beads with glycerol and bentonite,(D/d)alginate beads with glycerol and chitin.(A–D)£150,(a–d)£750.C.Zohar-Perez et al./Food Hydrocolloids 18(2004)249–258254At point S,the water remains liquid,although the temperature is below the freezing point.This phenomenon is known as supercooling(Fennema,1975)and is most pronounced for alginate–glycerol beads,due to glycerol’s well-known properties(Madigan,1997).From S to B the temperature rises rapidly to the freezing point as ice crystals begin to form and latent heat of crystallization is released.Values of20.75^0.21,21.65^0.07, 21.50^0.08,21.47^0.15and21.25^0.078C were detected for freezing points of alginate,alginate–glycerol, alginate–glycerol–chitin,alginate–glycerol–kaolin and alginate–glycerol–bentonite beads,respectively.The effect of particle size and concentration on the temperature of ice nucleation has been evidenced by many experimen-tal studies in variousfields of interest(Diehl,Matthias-Maser,Jaenicke,&Mitra,2002;Evans&Lane,1973; Gobinathan,Palanisamy,&Ramasamy,1985;Prodi, Santachiara,&Prodi,1982;Tabazadeh,Martin,&Lin,2000).Different particles in the size range of0.05–100m m in general,and bentonite and kaolin particles in particular (Prodi et al.,1982),have been found to have ice-nucleating ability.Moreover,larger particles and higher particle concentrations have been found to better correlate with ice nuclei.A higher freezing point was observed for beads with bentonite than for beads with kaolin,probably since overall,the size effect had more impact on ice nucleation than particle concentration.The freezing points and water contents of the alginate beads mimicked those of different foods.For example water content in vegetables is78–92%and their freezing point is 20.8to22.88C;for fruits water content is87–95%and their freezing point is20.9to22.78C.Therefore,the alginate beads can serve as models for food freezing and drying as was previously suggested for different gel beads (Kubota et al.,1977;Suzuki et al.,1989).From points B to C in Fig.4,the latent heat is removed as ice formsandthe temperature therefore remains almost constant;the total time taken is determined by the rate at which heat is removed (Fennema,1975).For gel beads without any additions this time was estimated to be 4.5min.For all other beads with filler and/or glycerol,this time ranged between 3.0and 3.5min.No differences were observed between the different fillers,probably because the main contribution is that resulting from the bead’s water content (Table 3).Image-processing software was used to evaluate the presence of craters on the dried beads’outer surface (Fig.5).For dried alginate beads (no glycerol or filler included),the smallest craters (those with areas up to 104m m 2)were dominant.The presence of the filler and/or glycerol appears to have increased the number of mid-area craters and reduced the number of smaller craters.A parallel phenom-enon was observed in the inner structure of the dried beads.In beads based solely on alginate,the proportion of pores with minimal surface area was greatest,while the presence of glycerol (with or without filler)in the dried products resulted in changes in the pore distribution function of these moieties,i.e.the proportion of pores with increased area shifted to a population with both very small and very large pores (Zohar-Perez et al.,2002,see Fig.6).As described,we worked with three different fillers.Only one of them,chitin,had proven biological control activity (Chet,1987).Therefore,we decided to continue our experiments with dried alginate beads (in comparison to gel beads)including chitin and to examine the antifungal activity of the immobilized biocontrol agent P.agglomerans .This bacterium,entrapped in the dried beads,suppressed the growth of the phytopathogenic fungus R.solani more strongly than the same bacterium entrapped in the gel beads (Fig.7).This improved antifungal activity is probably a result of the different external (surface features)and internal structures of the dried vs.non-dried gel beads.Freeze-drying of a gel bead results in a low-density dried cellular product that is composed of many fused open and closedcellsFig.6.Electron micrographs of halved alginate (A)and alginate–glycerol (B)freeze-dried beads.C.Zohar-Perez et al./Food Hydrocolloids 18(2004)249–258256(Nussinovitch,Velez-Silvestre,&Peleg,1993).This cellular structure enables the controlled release of microbial cells or their products from the matrix (Zohar-Perez et al.,2002)and thus exhibits enhanced antagonistic activity.It is not surprising that addition of chitin to the beads’formulation resulted in improved antifungal effect in both gel and dried beads.Chitinolytic bacteria such as P.agglomerans can utilize chitin as the sole carbon and nitrogen source.It is also well known that chitin is an inducer of chitinolytic enzyme production by P.agglomerans (Chernin et al.,1995).The latter is of particular interest in cases where immobilized chitinolytic microorganism preparations are used as biocontrol agents of plant-pathogenic fungi carrying chitin as the major structural component of their cell walls.4.ConclusionsThe composition of the bead and the inclusion and type of filler are responsible for the irregular textural features of the freeze-dried bead.If a smoother surface is required then a filler with a smaller particle size is needed.Pore-size distribution within the dried bead is also influenced by its content.Moreover,filler inclusion in the dried product reduces its collapse and roundness distortion during the drying process.The inclusion of a filler such as chitin contributes not only to improving cellular bead structure but also to biological activity.Such multipurpose ingredients could be ben-eficial for the up-and-coming biological control industry or for those fields in which tailor-made matrices are either of interest or a necessity.AcknowledgementsThis work was supported in part by Grant no.823-0126-98,Israeli Ministry of Agriculture.ReferencesBashan,Y.(1986).Alginate beads as synthetic inoculant carriers for slowrelease of bacteria that affect plant growth.Applied and Environmental Microbiology ,51,1089–1098.Champagne,C.P.,Gardner,N.J.,Soulignac,L.,&Innocent,J.P.(2000).The production of freeze-dried immobilized cultures of Streptococcus thermophilus and their acidification properties in milk.Journal of Applied Microbiology ,88,124–131.Champagne,C.P.,Mondou,F.,Raymond,Y.,&Brochu,E.(1996).Effectof immobilization in alginate on the stability of freeze-dried Bifidobacterium longum .Bioscience and Microflora ,15,9–15.Chernin,L.,Ismailov,Z.,Haran,S.,&Chet,I.(1995).ChitinolyticEnterobacter agglomerans antagonistic to fungal plant pathogens.Applied and Environmental Microbiology 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