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[Article]物理化学学报(Wuli Huaxue Xuebao )Acta Phys.鄄Chim.Sin .,2006,22(11)：1347~1352Received:May 11,2006;Revised:June 29,2006.∗Correspondent,E ⁃mail:efly_snow@;Tel/Fax:+8621⁃65686049.国家自然科学基金(50206013)和上海市重点学科建设项目(T0503)资助ⒸEditorial office of Acta Physico ⁃Chimica SinicaNovember 用DSC 测量葡萄糖溶液部分玻璃化转变温度的新方法叶秀东周国燕∗华泽钊(上海理工大学低温医学与食品冷冻研究所,上海200093)摘要用差示扫描量热仪,采用经过退火处理的连续扫描法,以不同浓度(20%、45%)的葡萄糖溶液为研究对象,研究了退火温度对T gf (部分结晶的玻璃化转变温度)的影响,给出了确定T g ′(部分玻璃化转变温度)的新方法.研究发现,不同退火温度下的T gf 不同.在-50℃以上退火,T gf 随着退火温度的增大而减小;在-50℃以下退火,T gf 随着退火温度的增大而增大,都有很好的线性关系.不同浓度的溶液具有相似的规律.提出从T gf 确定T g ′的方法:T gf 在-50℃上下随退火温度变化线的交点所对应的部分结晶玻璃化转变温度即为T g ′.使用该方法测得葡萄糖的T g ′为-55℃.关键词：部分玻璃化转变温度,葡萄糖,差示量热扫描,退火,部分结晶玻璃化转变温度中图分类号:O642A New Method for Measuring the Glass Transition Temperature of theMaximally Freeze 鄄Concentrated Glucose Solution by DSCYE,Xiu ⁃DongZHOU,Guo ⁃Yan ∗HUA,Ze ⁃Zhao(Institute of Cryomedicine and Food Refrigeration,Shanghai University of Science and Technology,Shanghai200093,P.R.China )AbstractThe new concept of the glass ⁃transition temperature of the partially freeze ⁃concentrated solution (T gf )isbrought forward and a new method is given for measuring T gf of 20%and 45%glucose solution using differential scanning calorimetry (DSC),which is based on annealing samples for long periods of time at different temperatures.The influence of annealing temperature on T gf is studied.It is found that the T gf increases initially with annealing temperature up to -50℃,and decreases as the temperature continues to increase,and exhibiting a good linear relation in both cases.The same phenomenon was observed for glucose solutions of different concentrations.It is concluded that the T g ′(glass transition temperature of the maximally freeze ⁃concentrated solution)can be determined from the intersection of the two curves reflecting the T gf change with annealing temperature.The optimal annealing temperature (-50℃)and accurate glass transition temperature(T g ′,-55℃）of glucose solution are obtained.Keywords ：Glass transition temperature of the maximally freeze ⁃concentrated solution,Glucose,DSC,Annealing,Glass transition temperature of the partially freeze ⁃concentrated solution随着温度的升高,聚合物一般会发生由玻璃态向橡胶态的转变,即玻璃化转变,这一转变点对应的温度通常称之为玻璃化转变温度(T g ).食品中由于含水量的不同,会出现完全玻璃化和部分玻璃化两种变化,一般含水量低于20%的食品出现完全玻璃化,对应温度T g ,而含水量高于20%的食品和浓度比较低的溶液中往往形成部分结晶的玻璃化,对应转变温度为部分玻璃化转变温度T g ′.富含水体系在冻结过程中,溶液中的水先开始结晶,未冻溶液浓度逐渐增大,黏度逐渐增大.继续进行降温,到达某一温度,1347Acta Phys.鄄Chim.Sin.(Wuli Huaxue Xuebao),2006Vol.22溶液中的水分不再结晶,而是与溶质分子一起形成类似玻璃的物质,即实现了玻璃化转变.开始出现玻璃化转变那一点对应的溶液为最大冻结浓缩溶液,发生玻璃化时的温度即为最大冻结浓缩溶液的玻璃化转变温度,在玻璃体中包含着很多冰晶,而不是全部玻璃体,所以也称之为部分玻璃化转变温度(T g′).由于T g′是对应于溶液最大冻结浓缩状态下的玻璃化转变温度,但实际上,在溶液冻结过程中,随着温度的降低,溶液黏度增加,水分结晶变得越来越困难,是不可能形成最大冻结浓缩溶液的,所以T g′是一个理想值,在实际测量过程中,我们往往测得的是部分结晶玻璃化转变温度(T gf),需要采用一定的方法和手段,获得溶液最大结晶状态下的T gf,即T g′.目前用DSC的三种方法可测量食品的T g′,即经过退火处理的连续扫描法[1⁃2]、不经过退火处理的连续扫描法[3]和分布扫描法[4].对于不经过退火处理的连续扫描法和分布扫描法,是不能测出最大冻结浓缩溶液状态下的玻璃化转变温度的,实际上测得的是部分结晶玻璃化转变温度.经过我们前期对这些方法进行的比较,发现经过退火处理的连续扫描法是最佳的测量T g′的方法.在研究中发现,随着等温温度的不同,T gf的值不同.针对如何从T gf值确定出T g′的研究比较少. Liesebach等人[1]用经过退火的连续扫描法对32%、43%、53%、54%、59%的葡萄糖溶液进行了玻璃化转变温度的测量,他们认为葡萄糖溶液的部分结晶玻璃化转变温度是随着退火温度的变化呈线性变化的,并且对浓度与部分结晶玻璃化转变温度(T gf)关系进行线性外推交至葡萄糖的完全玻璃化转变温度(T g)线,获得T g′的值,约为-53℃.Ablett等人[5]用经过退火处理的连续扫描法对40%的蔗糖溶液进行了部分玻璃化转变温度的测量,他们认为蔗糖溶液的部分结晶玻璃化转变温度随着退火温度的变化而变化,并且具有一个最大的峰值,不是简单的线性关系,曲线的峰值即为T g′的最大值,约为-41℃.上述两篇文献中,退火温度所取的范围都非常窄,并且都是在二次转变温度以上的温度进行退火研究,不能完全体现出T gf随退火温度变化的规律,两篇文章中T g′的实验结果也相差很大,需要进一步研究.本文选择20%、45%葡萄糖溶液作为研究对象,采用经过退火处理的连续扫描方法对T g′进行了测量,以确定测量T g′的最佳方法.1材料与方法1.1仪器与材料差示扫描量热仪为DSC⁃Pyris Diamond(美国Perkin⁃Elmer公司).温度标定采用环戊烷降温过程中的-135.06℃相转变以及纯净水的熔融(均采用外推起始温度)进行两点标定;热焓标定采用纯净水的熔融焓(333.88J·g-1)标定[6⁃7].标定速率为10℃·min-1.液氮冷却采用Cryofill TM,Perkin⁃Elmer公司的液氮容器控制.样品冲洗气体为高纯度氦气(纯度> 99.999%),流量30mL·min-1保持不变.样品皿为PE 标准液体铝皿(美国Perkin⁃Elmer公司),样品量为10~ 20mg,精确到±0.01mg.天平采用赛多利斯的BP系列,精确到0.01mg.液体铝皿用压片机密封.葡萄糖(分析纯,中国新兴华工试剂研究所).样品为20%、45%葡糖糖溶液.1.2扫描程序以220℃·min-1的速率快速降温到-100℃,维持1min;再以220℃·min-1的速率升温到某一退火温度,并维持60min;以220℃·min-1的降温速率快速降到-85℃,维持1min;从-85℃以10℃·min-1进行连续扫描过程,直至达到10℃,同样维持1 min.2实验结果图1是45%葡萄糖溶液未经过退火的连续扫描热流曲线图,从图中可以看出,在冰晶熔融峰之前出现两个转变峰,取第一个峰为玻璃化转变温度读取峰.得到45%葡萄糖溶液不经过退火连续扫描的T gf为-60.19℃.图2和图3是45%葡萄糖溶液在-30℃图145%葡萄糖溶液DSC曲线(未经退火)Fig.1DSC themogram of45%glucose solutionwithout annealing1348No.11周国燕等：用DSC 测量葡萄糖溶液部分玻璃化转变温度的新方法条件下退火的热流曲线图中的玻璃化转变峰和冰晶熔融峰,从中利用onset 点读取方法可以读取T gf 、T m 和驻H 值.图4是45%葡萄糖溶液在不同等温温度(等温60min)得出的所有系列热流曲线图.同样得到其他退火温度下的数据(见表1).3分析与讨论3.1部分结晶玻璃化转变峰确定45%的葡萄糖溶液在冻结过程中出现两个转变峰(图1),普遍观点认为第一个峰为玻璃化转变峰,然而对第二个转变峰的争议越来越多[8⁃13],我们认为第二个峰为冰晶初融峰,主要因为:(1)在-45、-40、-35及-30℃几个温度点退火时,部分结晶玻璃化转变温度急剧降低(表1),说明在这几个温度点附近,其中的一些冰晶已经开始融化,从而稀释了浓缩溶液,导致T gf 的急剧下降;(2)冰晶熔融要比玻璃化转变剧烈(图1),开始阶段,第一个峰比第二个峰变化要缓慢得多;(3)表1表明在-50℃退火时,得到的部分结晶玻璃化转变温度是最大的,这说明在此温度下退火,形成的冻结浓缩溶液的浓度最大,未冻水份额最小,大部分水分已经结晶,所以在升温过程中,冰晶的熔融焓值应该是最大的,但由表1可以看出,在-50℃退火时,并没有得到最大的焓值,这说明在冰晶熔融之前,一部分冰晶已经完成了熔融,则必然在玻璃化转变峰和冰晶熔融峰之间存在一个冰晶初融峰,由此推测,第二个转变峰为冰晶的初融峰,而不是玻璃化转变峰.3.2退火温度对T gf 的影响45%葡萄糖溶液在连续扫描下测得的T gf 仅为-60.19℃,这是因为在溶液冻结的过程中,随着温度的降低,溶液的黏度越来越大,溶液中水分子运动缓慢,结晶受阻,以至于不能达到最大冻结浓缩溶液的浓度,测得的T gf 不是T g ′,为了让水分有足够的时间结晶,真正地形成最大冻结浓缩溶液,就必须采用经过退火处理的连续扫描法.先用不经过退火连续扫描法测得溶液的T gf ,然后在T gf 附近的一些温度点等温足够长的时间,测得不同等温温度下的T gf .虽然退火方法确实可以减少未冻水份额,增加水的结晶量.但因为不能事先确定最佳退火温度,还是不能完全达到最大冻结浓缩溶液,测出的值仍然是部分结晶玻璃化转变温度(T gf ),而不是最大冻结浓缩溶液的玻璃化转变温度(T g ′).图245%葡萄糖溶液在-30℃退火的DSC 曲线中的玻璃化转变峰Fig.2Glass transition of 45%glucose solutionannealed at -30℃for 60min图345%葡萄糖溶液在-30℃退火的DSC 曲线中的熔融峰Fig.3Melting transition of 45%glucose solutionannealed at -30℃for 60min图445%葡萄糖溶液在不同等温温度(等温60min)的系列热流-温度曲线图Fig.4DSC thermograms for a series of 45%glucosesolutions annealed for 60min at different temperaturesthe annealing temperature(℃)from the bottom up:-30,-35,-40,-45,-50,-55,-60,-65,-70,-751349Acta Phys.鄄Chim.Sin.(Wuli Huaxue Xuebao ),2006Vol.22从表1和图4中葡萄糖的T gf 可以看出,在-50℃以上退火,部分结晶玻璃化转变温度随着退火温度的增大而减小,在-50℃以下退火,部分结晶玻璃化转变温度随着退火温度的增大而增大,两边基本呈线形关系.这是因为在-50℃以下退火时,随着退火温度的增加,冻结溶液中反玻璃化现象越来越严重,未冻水分额越来越少,导致部分结晶玻璃化转变温度越来越高,而在-50℃以上退火时,由于在此温度下,冰晶已经开始熔融,溶液被稀释,浓度降低,导致部分结晶玻璃化转变温度降低.对于20%的葡萄糖溶液也有相同的影响趋势.3.3浓度对T gf 的影响从表1可以看出,对于两种浓度而言,在同一退火温度下,45%葡萄糖的T gf 要稍大于20%葡萄糖溶液的T gf .在退火的情况下,20%葡萄糖溶液的水分含量比45%葡萄糖溶液要大,降温过程中形成冰晶需要的时间比较长,在相同退火时间的条件下,20%葡萄糖溶液结晶不够完全,未冻水份额较大,未冻溶液的浓度相对低一些,测量得到T gf 也就低一些,而对于45%的葡萄糖溶液的T gf 就相对高一些.3.4T g 忆的确定从表1中葡萄糖的T gf 可以看出,在-50℃以上退火,部分结晶玻璃化转变温度随着退火温度的增大而减小,在-50℃以下退火,部分结晶玻璃化转变温度随着退火温度的增大而增大,两边基本呈线形关系.那么中间一定存在一个点,在这个点达到最佳结晶效果,达到最大冻结浓缩溶液浓度.这个点为最佳等温点,对应的T gf 为真正的T g ′的值.对上表中的数据进行线形拟合(图5),得到20%葡萄糖溶液的交点(退火温度为-50.48℃,T gf 为-55.32℃),45%葡萄糖溶液的交点(退火温度为-49.55℃,T gf 为-55.36℃).说明对于葡萄糖溶液存在一个最佳的退火温度,约为-50℃,得到最大的玻璃化转变温度,约为-55℃.这与20%葡萄糖溶液在-50℃退火得到的结果相吻合.这个结果与最大冻结浓缩溶液的玻璃化转变温度与溶液初始浓度大小无关相吻合.并且葡萄糖溶液最佳退火温度在-50℃左右,T g ′约为-55℃,比未经退火时测得的值要大5℃左右.从表1可以看出,在-55、-50℃退火时,20%葡萄糖溶液玻璃化现象不明显,45%葡萄糖溶液玻璃化现象消失.而-55、-50℃两个退火温度恰好在一次转变温度以上、二次转变温度以下这个温度范围内,溶液冻结中形成的冰晶的融化与溶液中未冻水的再结晶同时进行,第一个转变峰有向第二个转变峰推近的趋势.对于20%的葡萄糖溶液,含水量高,溶液中冰晶量较多,前者占主要地位,虽然第一个峰有向第二个峰推近的趋势,但还没出现重合现象;表120%、45%葡萄糖溶液的T gf 、T m 和ΔH Table 1T gf ,T m ,and ΔH of 20%and 45%glucose solutionsC (%)Annealing temperature (℃)-30-35-40-45-50-55-60-65-70-7520T gf /℃-65.98-64.88-62.99-58.54-54.64-58.22-63.95-66.93-70.58-74.84not clear not clear T m /℃-7.83-7.75-7.60-7.86-7.35-6.77-6.45-7.31-7.43-7.56ΔH /(J ·g -1)200.56209.10202.81207.19203.65196.00195.43196.40195.67194.8745T gf /℃-65.92-63.26-60.66-57.75---58.60-59.97-62.12-63.06T m /℃-14.83-15.15-14.79-15.24-15.32-16.16-15.78-15.82-14.68-15.69ΔH /(J ·g -1)82.2488.6583.3393.1696.57118.55107.23108.04107.56105.43图520%、45%葡萄糖溶液的T gf 随退火温度的变化关系Fig.5T gf values of the annealed samples of 20%and 45%glucose solutions with annealing temperature1350No.11周国燕等：用DSC 测量葡萄糖溶液部分玻璃化转变温度的新方法而对于45%葡萄糖溶液,溶液中冰晶量较少,溶液中未冻水含量较多,后者占主要地位,第一个转变峰与第二个转变峰已经基本重合在一起了,因此出现玻璃化转变不明显,甚至玻璃化现象消失的情况.如图6所示,对于45%的葡萄糖溶液,在-45℃退火时,依然有两个转变峰,在-50、-55℃退火时,只有一个转变峰.从图中可以看出,在-45℃退火和在-50、-55℃退火时,转变峰的形状存在明显的区别,在-45℃退火时,初融峰的跨度较小,初融温度较高,初融发生得较晚,而在-50、-55℃退火时,峰的跨度较大,转变峰发生得较早,峰开始的起始温度较低,说明在-50、-55℃退火时,已经不单纯是冰晶的初融,还伴随着其他转变过程,说明此时玻璃化转变和冰晶初融同时发生了,是一个较复杂的过程,无法用单一的过程来表征.3.5本文方法与其他方法比较采用本文的方法测得葡萄糖溶液的T g ′为-55℃,而Liesebach 等人[1]测得的结果是-53℃,Ablett 等人[5]测得的结果为-41℃.在Liesebach 等人的方法中,他们取了-41、-42、-43、-44、-45、-46、-47℃几个等温点进行退火实验,得到T gf 随退火温度呈线性的规律,然后用得到的T gf 与浓度的关系得到T g ′.虽然测得的结果相对比较接近,但这种方法是存在很大问题的.首先,等温温度范围取得太窄,并且退火温度基本都是在葡萄糖二次转变温度(-46.77℃)以上.由上面的分析可知,二次转变是冰晶的初融,一次转变才是真正的玻璃化转变.其次,在这个比较窄的温度范围内退火时,得出的规律不能反应出整体的规律,只是局部的规律,虽然文献中给出T gf 与退火温度呈线性变化规律,但这只是在二次转变温度以上退火得出的结果.如果在一次转变温度以上,二次转变温度以下退火,或者在一次转变温度以下退火时,得出的规律是否还是线性的,文中并没有给出相应的实验结果,所以单单用这么窄的几个退火温度点来得出规律,再得到T g ′值,是非常没有说服力的.在Ablett 等人的方法中,他们取了-30、-35、-40、-45、-50℃几个温度点进行退火,也基本上处于蔗糖溶液的二次转变温度以上,也存在与Liesebach 等人的方法同样的问题.3.6退火对T m 和驻H 的影响为了便于区别,本文把二次转变温度称之为冰晶初融温度,把二次转变后面的转变峰称之为冰晶熔融峰,对应的温度为T m .从表1可以看出,对于20%和45%的葡萄糖溶液,在不同的退火温度下,冰晶的熔融温度相差不大,这主要是因为溶液在冻结过程中的结晶温度主要取决于溶液的初始浓度,其它因素影响不大.对于45%的葡萄糖溶液,初始浓度较大,溶质与水形成氢键能力较强,溶液黏度较大,水分不易结晶,导致溶液在冻结过程中形成较大的过冷度,从而冰晶的熔融温度较低,而20%的葡萄糖溶液的熔融温度较高.从表1中还可以看出,20%葡萄糖溶液在每个退火温度下的熔融焓都比45%的葡萄糖溶液要高得多,这主要是因为两者浓度相差太大,水分含量存在明显的差异,虽然退火会改变一些未冻水的含量,但只是非常小的一部分,对焓值影响不大,也不会影响20%葡萄糖溶液比45%葡萄糖溶液焓值大很多的趋势.4结论本文用Pyris Diamond DSC,以不同浓度(20%、45%)的葡萄糖溶液为研究对象,研究了退火温度(-30、-35、-40、-45、-50、-55、-60、-65、-70、-75℃)对T gf 的影响,提出T gf 的概念,给出了确定T g ′的新方法.在不能完全实现玻璃化的情况下,无论是否退火,因为不能到达溶液的最大冻结浓缩状态,直接测量得到的往往是部分结晶玻璃化转变温度(T gf ),而不是部分玻璃化转变温度(T g ′).研究发现,葡萄糖溶液在冻结时,在冰晶熔融之前,会出现两个转变峰.低温度峰为T gf ,高温度峰为初融峰.在同一退火温度下,高浓度的葡萄糖溶液的T gf 比低浓度的要高.测量发现,不同退火温度下的T gf 不同,在-50图645%葡萄糖溶液分别在-45、-50、-55℃的热流曲线图Fig.6DSC thermograms of 45%glucose solutionsannealed for 60min at -45,-50,and -55℃1351Acta Phys.⁃Chim.Sin.(Wuli Huaxue Xuebao),2006Vol.22℃以上退火,玻璃化转变温度随着退火温度的增大而减小,在-50℃以下退火,玻璃化转变温度随着退火温度的增大而增大,并有很好的线性关系.提出从T gf确定T g′的新方法是两侧T gf的交点对应的温度为T g′.本文中得到葡萄糖的T g′为-55℃,最佳退火温度为-50℃.References1Liesebach,J.;Rades,T.;Lim,M.Thermochimica Acta,2003,401: 1592Liu,B.L.Ph.D.Dissertation.Shanghai:The University ofShanghai for Science and Technology,1996[刘宝林.博士学位论文.上海:上海理工大学,1996]3Levine,H.;Slade,L.Food Chem.,1989,1:3154Kerr,W.L.;Reid,D.S.Thermochimica Acta,1994,246:2995Ablett,S.;Lzzard,M.J.;Lillford,P.J.J.Chem.Soc.FayadayTrans.,1992,88:7896Gao,C.;Zhou,G.Y.;Xu,Y.;Hua,Z.Z.Acta Phys.⁃Chim.Sin.,2004,20(2):123[高才,周国燕,胥义,华泽钊.物理化学学报(Wuli Huaxue Xuebao),2004,20(2):123]7Gao,C.;Wang,W.H.;Hu,T.J.;Xu,Y.;Zhou,G.Y.;Hua,Z.Z.Acta Phys.⁃Chim.Sin.,2004,20(7):701[高才,王文华,胡桐记,胥义,周国燕,华泽钊.物理化学学报(Wuli HuaxueXuebao),2004,20(7):701]8Goff,H.D.;Verespej,E.;Jermann,D.Thermochimica Acta,2003, 399:439Shalaev,E.Y.;Franks,F.J.Chem.Soc.Faraday Trans.,1995,91: 151110Sun,W.Q.Cryoletters,1997,18:9911Blond,G.Cryoletters,1989,10:29912Roos,Y.;Karel,M.Food Science,1991,56:2661352。
HY-8 Version 7.3 Quick Start Guide Introduction to the HY-8 Quick Start GuideThis Quick Start Guide is intended to provide basic information for downloading and running version 7.3 of the HY-8 Culvert Hydraulic Analysis Program (HY-8 7.3). HY-8 is a computerized implementation of FHWA-endorsed culvert hydraulic analysis approaches and protocols. The HY-8 program is available free of charge.The FHWA has been sponsoring development of computerized culvert hydraulic software since the early 1960’s (beginning with the HY-1 program). The FHWA released the initial DOS version of the HY-8 program in the early 1980’s and released a Windows version (7.0) in March 2007. The HY-8 program has successfully operated on all current “flavors” of the Windows operating system.HY-8 7.3 represents the third phase of the FHWA’s multi-phase culvert hydraulic software upgrade plan. The plan calls for incremental upgrades and additions of features, based on available time, budget, and adoption of new hydraulic research and techniques. The following state Departments of Transportation have contributed to the pooled-fund project, which made the development of version 7.3 possible: Alabama, Iowa, Minnesota, Nebraska, Ohio, South Dakota, Texas, and Wisconsin. The FHWA offers these Departments its sincere thanks. The software development work was completed by Aquaveo, LLC.What’s in this Quick Start DocumentThis document includes information about:•technical methods,•downloading the software,•file management,•new features in version 7.3, and•getting help.Technical MethodsThe technical methods incorporated in the updated HY-8 program are based on the following research efforts and FHWA publications:•"Hydraulic Design Series 5: Hydraulic Design of Highway Culverts" (HDS 5), Third Edition, February 2012•"Hydraulic Engineering Circular 14: Hydraulic Design of Energy Dissipators for Culverts and Channels" (HEC-14), Third Edition, July 2006•“Effects of Inlet Geometry on Hydraulic Performance of Box Culverts,” December, 2006 •NCHRP Project 15-24, Hydraulic Loss Coefficients for Culverts, 2011HDS 5 and HEC-14 are the primary technical references for the software, and PDF versions can be downloaded from the FHWA Hydraulic Engineering website:http s:///engineering/hydraulics/library_listing.cfm.FHWA certifies that HY-8 7.3 continues to represent reviewed, tested, and accepted software for the purposes of performing FHWA culvert analyses regulated under 23 CFR 650 Subpart A and meeting 44 CFR 65.6(a)(6) in the FEMA NFIP regulations.DownloadingThe installation package executable file can be obtained by downloading from the FHWA Hydraulic website at: http s:///engineering/hydraulics/software/hy8.As stated in the FHWA Hydraulics website, by downloading the software, the user is agreeing to and accepting the following conditions and limitations:•FHWA does not provide user assistance or support for this software.•The application of this software is the responsibility of the user. It is imperative that the responsible engineer understands the potential accuracy limitations of the program results, independently cross checks those results with other methods, and examines thereasonableness of the results with engineering knowledge and experience.•There are no expressed or implied warranties.•The installation package can be downloaded to any location (for example, folder “C:\Temp”) on the user’s computer.Prior to InstallationThe development team modified this release so that older versions of HY-8 can remain on the user’s system. In doing so, users may end up with multiple versions (version 7.1, version 7.2 etc.) on their computers.If users wish to remove older Windows versions, they can go to the Windows Control Panel and use the “Add/Remove Programs” command. When doing so, user-created project files will not be deleted, but will remain in the program folder.Installation Location and FilesThe default location for program installation is folder: “C:\Program Files\HY-8 7.30”. As well as installing program files, the setup program also adds a tutorial (“HY-8 7.3 QuickTutorial.pdf”), sample input files, and PDF versions of HDS 5 and HEC-14 to the system. The user also has the option to change the file location to any directory without affecting the performance of the program.File ManagementThe Project File ApproachHY-8 versions 7.0 and newer adopt a Project File approach. These project files are implemented into the Project Explorer – allowing quick selection and application of a specific culvert system1. HY-8 saves these project files using a “.hy8” extension and allows any file name format and length permitted by Windows.As described below, the addition of this approach adds utility in: (1) organizing and applying culvert systems within multiple drainage crossings, and (2) analyzing different design configurations and materials.Multiple Drainage CrossingsIn HY-8 version 7.0 and newer, any number of crossings can be defined within the project file. Users now have the option of performing an analysis on several crossings and grouping them together. Of course, the Windows version retains the older version’s ability to consider only a single drainage crossing. This single crossing can also still consist of multiple culvert systems (e.g., three circular barrels at one invert [system 1] and a box culvert at another invert [system 2] at the same roadway crossing).Design AlternativesHY-8 versions 7.0 and newer provide a means to consider separate design alternatives of the same crossing within the same project file.HY-8 provides the user the option of “copying” a culvert and associated crossing information. With this “duplicate crossing” the user can make any change(s) they wish to evaluate. The project explorer then makes it easy to toggle back and forth between the alternative crossing designs.Order of InputIn the Windows version of HY-8, a single input screen presents all of the input necessary to analyze a single crossing.However, there are some important subtleties - the grouping of the information has been organized into “crossing” information and the “culvert” information. The discharge, tailwater, and roadway data are unique to the crossing while the culvert shape, inlet conditions, and site data define a culvert within the crossing.1 As in prior versions of HY-8, a culvert system is considered as a collection of culverts, having the same type, material, inlet, dimension, and layout (invert elevations, length) characteristics. So a single barrel corrugated metal pipe or a box culvert with cell barrels (cells) would be considered a system, whereas, if a crossing had both a circular HDPE AND a pipe arch, these would be considered two systems. A potential reason for multiple culvert systems at a crossing would be to allow “critter crossings” in one system and normal discharge through the other system.Report GenerationHY-8 includes report generation tools that are customizable, allow many options for plots, and are saved in rich text format (RTF) or portable document format (PDF). The primary target for the report is an MS-Word document; however, an rtf format is readable by many word processing programs.A few issues related to Report Generation remain in this version. Each time a table or graph is written to the report, the report starts a new page. This can make reports longer (wasting paper). The HY-8 7.3 QuickTutorial document describes how to edit a RTF formatted HY-8 report in Word to condense the number of pages and make the document more concise. HY-8 also has the capability to write energy dissipation reports from the energy dissipation dialog.What’s New in Version 7.3Notable new features completed for version 7.3 include analysis of:•Discharge values, which can now be entered in three ways•Hydraulic jumps that form within the culvert barrel•Broken back culvert profiles for all HY-8 barrel shapes•Horizontal and adversely sloped barrels•Additional culvert shapesSummaries of the new features follow, and additional detail may be found in the HY-8 User Manual for version 7.3, available from the Help menu within HY-8.User Selection of Method for Entering Discharge ValuesHY-8 7.3 now has three options to enter discharge data into HY-8: "Minimum, Design, and Maximum", "User-Defined", and "Recurrence". The "Minimum, Design, and Maximum" is the default option and historically was the only option available.Hydraulic JumpsWhen hydraulic jumps are calculated to occur, they are reflected in both the water surface profile plot and summary table. To determine if a hydraulic jump exists, HY-8 calculates the supercritical and subcritical water surface profiles that form within the culvert using a direct step profile computation. At each location along the two profiles, HY-8 computes the sequent depths of the supercritical profile and compares these sequent depths to the subcritical profile’s computed depth.Broken-Back CulvertsBroken-back culverts have one or more changes in slope along the length of the culvert barrel. HY-8 7.3 supports single and double broken-back culverts, meaning one or two changes in slope.Horizontal and Adversely Sloped BarrelsHY-8 7.3 has the ability to analyze culverts with horizontal and adverse (inlet invert elevation less than the outlet invert elevation) slopes.Additional Culvert ShapesHY-8 has a shape/coefficient database. This database allows FHWA2 to add new or update older shapes or materials to the HY-8 interface. The database also allows FHWA to modify the analysis coefficients used to compute inlet control depths. New shapes/coefficients added to version 7.3 of HY-8 are for concrete open-bottom arches, circular embedded culverts, and South Dakota prefabricated reinforced concrete box (RCB) shapes. Details about the research resulting in the coefficients for these shapes is discussed in the HY-8 7.3 user manual.HY-8 Version 7.3 has coefficients for computing inlet control depths for concrete open-bottom arch (commonly called Con/Span) culverts. Concrete open-bottom arches have unique geometric configurations, and multiple sizes and shapes are available. The exact coordinates used in HY-8 to compute areas and other geometric cross section parameters for these structures are available in the HY-8 7.3 user manual.In HY-8 version 7.3 for embedded circular culverts, HY-8 uses the 5th-degree polynomial to determine the inlet control depth. The coefficients used are derived from the NCHRP 15-24 report. This report gives coefficients for a circular culvert that is embedded 20%, 40%, and 50%. HY-8 will linearly interpolate between the coefficients for the level of embedment specified; however, if the embedment is outside the range of data, the closest set of coefficients is used. The document "Effects of Inlet Geometry on Hydraulic Performance of Box Culverts" (FHWA Publication No. FHWA-HRT-06-138, October 2006) describes a series of tests that were performed to obtain design coefficients for various inlet configurations of reinforced concrete box culverts commonly used by the South Dakota DOT. The following variations in inlet configurations were tested: wingwall and top edge bevels and corner fillets, multiple barrels, different culvert span-to-rise ratios, and skewed headwalls. These test results were modified and incorporated into HY-8 as 10 sets of inlet configurations under the label "South Dakota Concrete Box Culvert.”Getting HelpBeyond this Quick Start Guide, HDS 5, and HEC-14, the majority of the HY-8 documentation is self-contained within the program. The functional use of the program is documented in the2 To ensure adherence to FHWA HDS-5 approaches, only FHWA will have the ability to access this file. The fileand the contents are still considered to be under development and remain proprietary.hyper-linked help file available from the Help menu or by selecting help buttons or icons () from the graphical user interface. The help file is formatted as a user manual and can be printed as a hard copy.Additionally, the National Highway Institute has a design course, 135056 – “Culvert Design,” which heavily features application of the HY-8 software to complete in-class design problems. (135056 – “Culvert Design”). For more detail on this and other courses, please visit the NHI website: http s:///default.aspx.While FHWA does not offer any user support (as described in the Terms and Conditions for downloading and using the program), comments and bug reports may be sent to:*********************.。
PCR常见问题分析及对策PCR常见问题分析及对策(无扩增产物、非特异性扩增、拖尾、假阳性) 问题1：无扩增产物现象：正对照有条带，而样品则无原因:1.模板:含有抑制物，含量低2.Buffer对样品不合适3.引物设计不当或者发生降解4.反应条件：退火温度太高，延伸时间太短对策:1.纯化模板或者使用试剂盒提取模板DNA或加大模板的用量2.更换Buffer或调整浓度3.重新设计引物（避免链间二聚体和链内二级结构）或者换一管新引物4.降低退火温度、延长延伸时间问题2：非特异性扩增现象：条带与预计的大小不一致或者非特异性扩增带原因：1.引物特异性差2.模板或引物浓度过高3.酶量过多4.Mg2+浓度偏高5.退火温度偏低现非特异条带而另一来源的酶则不出现，酶量过多有时也会出现非特异性扩增。
其对策有：①必要时重新设计引物。
②减低酶量或调换另一来源的酶。
③降低引物量，适当增加模板量，减少循环次数。
④适当提高退火温度或采用二温度点法(93℃变性，65℃左右退火与延伸)。
出现片状拖带或涂抹带PCR扩增有时出现涂抹带或片状带或地毯样带。
其原因往往由于酶量过多或酶的质量差，dNTP浓度过高，Mg2+浓度过高，退火温度过低，循环次数过多引起。
其对策有：①减少酶量，或调换另一来源的酶。
②减少dNTP的浓度。
③适当降低Mg2+浓度。
④增加模板量，减少循环次数。
克隆PCR产物的最优条件是什么？最佳插入片段：载体比需实验确定。
1：1（插入片段：载体）常为最佳比，摩尔数比1：8或8：1也行。
应测定比值范围。
连接用5ul 2X连接液, 50ng质粒DNA,1Weiss单位的T4连接酶，插入片段共10ul。
室温保温1小时，或4oC过夜。
在这2种温度下，缺T-凸出端的载体会自连，产生蓝斑。
室温保温1小时能满足大多数克隆要求，为提高连接效率，需4oC过夜。
PCR产物是否需要用凝胶纯化？如凝胶分析扩增产物只有一条带，不需要用凝胶纯化。
如可见其他杂带，可能是积累了大量引物的二聚体。
八年级科技前沿英语阅读理解25题1<背景文章>Artificial intelligence (AI) has been making remarkable strides in the medical field in recent years. AI - powered systems are being increasingly utilized in various aspects of healthcare, bringing about significant improvements and new possibilities.One of the most prominent applications of AI in medicine is in disease diagnosis. AI algorithms can analyze vast amounts of medical data, such as patient symptoms, medical histories, and test results. For example, deep - learning algorithms can scan X - rays, CT scans, and MRIs to detect early signs of diseases like cancer, pneumonia, or heart diseases. These algorithms can often spot minute details that might be overlooked by human doctors, thus enabling earlier and more accurate diagnoses.In the realm of drug development, AI also plays a crucial role. It can accelerate the process by predicting how different molecules will interact with the human body. AI - based models can sift through thousands of potential drug candidates in a short time, identifying those with the highest probability of success. This not only saves time but also reduces the cost associated with traditional trial - and - error methods in drug research.Medical robots are another area where AI is making an impact.Surgical robots, for instance, can be guided by AI systems to perform complex surgeries with greater precision. These robots can filter out the natural tremors of a surgeon's hand, allowing for more delicate and accurate incisions. Additionally, there are robots designed to assist in patient care, such as those that can help patients with limited mobility to move around or perform simple tasks.However, the application of AI in medicine also faces some challenges. Issues like data privacy, algorithmic bias, and the need for regulatory approval are important considerations. But overall, the potential of AI to transform the medical field is vast and holds great promise for the future of healthcare.1. What is one of the main applications of AI in the medical field according to the article?A. Designing hospital buildings.B. Disease diagnosis.C. Training medical students.D. Managing hospital finances.答案：B。
0前言Al-Mg系合金因具有中等强度、良好的耐蚀性和可焊性，在航空、航天、舰船、电子等行业中得到广泛应用[1]。
近年来的研究表明，Sc是目前为止所发现的对铝合金最为有效的合金化元素，微量Sc 加入到铝合金中，可显著提高合金的强度、塑性、焊接性能及耐蚀性能等，而复合添加Sc、Zr两种微量元素是一条既节约成本又大幅提高强塑性的有效途径[2-3]。
Al-Mg-Sc合金是一种具备优异综合性能的新型结构材料，属于热处理不可强化合金，其薄板一般在冷轧后退火状态下使用。
退火处理的目的，一是消除冷加工过程中形成的内应力，二是调整合金的强度和塑性，稳定合金组织使之保持较好的耐蚀性能[4]。
本文主要研究不同退火温度对铝镁钪合金板材力学性能、腐蚀性能的影响规律，为铝镁钪合金板材的工业化应用提供理论和实验依据。
1样品来源和实验方法以Al99.95、Al-Sc、Al-Zr、Al-4Ti块、Al-Cr、Zn锭、铝基Mn剂、Mg锭为原材料，铸造成规格为400mm×1320mm的方铸锭，表1为所制备的铝镁钪合金的化学成分。
铸锭经350℃/20h均匀化退火处理后铣面至380mm，然后在450℃下保温3h后热轧至8.0mm，最后冷轧至规格为2.0mm厚的薄板。
冷轧板分别在100℃、150℃、200℃、250℃、300℃、350℃、400℃、500℃下进行退火试验，保温时间2h。
退火完成后，通过常温拉伸力学性能、腐蚀性能测试及显微组织分析来综合评价不同退火温度对合金显微组织及性能的影响。
同时取板材的纵向和横向样品进行拉伸试验。
所用设备为AG-IS10KN电子拉力试验机。
剥落腐蚀试验依据ASTMG66进行；晶间腐蚀试验依据ASTMG67进行。
金相试样受检面为板材的纵向截面，经机械抛光、凯勒试剂浸蚀后观察显微组织，经阳极覆膜后在偏振光下观察显微晶粒组织。
金相组织观察在LEICA DM4M金相显微镜上进行。
表1铝镁钪合金化学成分（质量分数/%）Si0.03Fe0.06Cu0.03Mn0.66Mg4.68Cr0.10Zn0.10Ti0.08Zr0.10Sc0.21Al余量2实验结果2.1不同退火温度对冷轧板力学性能的影响图1为Al-Mg-Sc合金2.0mm厚冷轧板经不同退火温度处理后纵向、横向力学性能变化曲线。
Low Temperature Crystallization of Indium-tin-oxide Kuo-Lung Fang, Han-Tu Lin, Feng-Yuan Gan, and Hsin-Chih Chiu Array Technology Division. AUO Technology CenterAU Optronics CorporationNo. 1 Li-Hsin Rd. 2, HsinChu Science Park HsinChu 300, TaiwanHardy.Fang@Abstract:Indium-tin-oxide (ITO) thin films were deposited at different temperatures via physical vapor deposition. Amorphous ITO annealing process was proceeded to study the crystallization under low temperature of 180 ºC. Effects of both sputtering temperature and post-annealing temperature on the resistivity and optical transparency were investigated. It is observed that sputter-deposited ITO films at 110 ºC requires lower crystallization temperature to reduce bulk ITO resistivity. Meanwhile, room temperature sputter-deposited ITO films need higher anneal temperature to achieve lower resistivity and increase transparency. It is believed that as-deposited ITO films 110 ºC were inherently formed with very small nucleus grain, and hence requiring lower post-anneal temperature than the room-temperature deposited one to have better crystalline structures.Keywords: low temperature; ITO; crystallization; resistivityIntroductionThin film of indium-tin-oxide (ITO) has been widely used for transparent conducting layer in various optoelectronic devices, such as liquid crystal displays (LCD), plasma display, and solar cells. Within the flat panel display applications, ITO thin films were typically deposited with DC sputtering at low substrate temperature in order to be in amorphous structure state. Though non-crystallized ITO is with higher resistivity and lower transparency, it could be easily patterned via oxalic acid wet-etching. Thus patterned ITO thin films with high transparency and low resistivity after post-crystallization annealing are suitable for flat panel display (FPD) applications such as, mobile phones and personal digital assistants. ITO films were normally crystallized by annealing at about 250ºC to gain low resistivity and high transparency [1-2]. Nowadays, FPD devices were typically processed on plastic substrate that does not support high temperatures. Therefore low temperature process technology has drawn more and more attention recently.In this work, we focus on the low temperature annealing process (below 200ºC) of sputter-deposited ITO films. ITO thin films were firstly deposited at different substrate temperature and followed with different anneal temperature blow 200 ºC.ExperimentalITO thin films were deposited on glass substrate by physical vapor sputtering using an ITO ceramic target. Two glass substrate temperatures were chosen for ITO deposition. Sample-A was deposited of 42nm at 110 ºC, and Sample-B was deposited of 70nm at room temperature 23 ºC. The total gas pressure was kept at 0.67Pa. The Ar gas flow was kept constant with 1 sccm H2O introduction with power density of 15KW/m2. Post annealing of the films at temperature 130 ºC, 150 ºC and 180 ºC for different period of time were carried out in N2 gas ambient to clarify the relationships between the microstructure and the various properties of the ITO films. X-ray diffraction (XRD) analysis was carried out in 2θ scan mode by using Cu radiation to study ITO structure. Transmission spectra in the visible 400-800 nm were measured with a UV-VIS spectrophotometer (Lamda-800). Resistivity of the ITO films was analyzed by four-point probe method.Results and DiscussionFig. 1 reveals the resistivity measurements of Sample-A after post-annealing in nitrogen gas (N2). It was observed that Sample-A’s resistance can be reduced apparently after long time annealing at 150 ºC and its resistance tends to saturate after 4 hours annealing. Nevertheless, annealing at 130 ºC did not have any strong effect on Sample-A’s bulk resistivity until reaching 4 hours annealing. The slightly reduction of resistance after first hour annealing at both conditions results from the condensation effect ITO film structure instead of ITO crystallization.0.20.40.60.81.0NormalizedResistivity(a.u.)Anneal Tim e (H our)Figure 1. Resistance measurement of sample-A with different anneal temperature and time.Fig. 2(a) and 2(b) are the measured results of tranmittance in Sample-A after oven annealing. There is no obvious improvement in transmittance at 130 ºC condition; meanwhile, annealing at 150 ºC can have higher transparency. As for Sample-B, the N2-annealing at 150 ºC had little influence on ITO resistivity. Fig. 3 exhibits the annealing results of resistance and transmittance corresponding to Sample-B under different temperatures. It is noted that annealing at 180℃ help to reduce sample-B’s resistivity but the trend can not beProc. of ASID ’06, 8-12 Oct, New Delhi 302Proc. of ASID ’06, 8-12 Oct, New Delhi303found for annealing at 150 ºC. Besides, there was little impact of Sample-B’s transparency measurement after 150 ºC 4 hours annealing. Only longer time N 2-annealing with 180 ºC could improve Sample-B’s transparency. Both transmittance results of annealed Sample-B were shown in Fig. 4(a) and 4(b).400500600700800020*********(a)T r a n s m i t t a n c e (%)W avelength (nm )as-deposited130oC 1H r130oC 2H r130oC 3H r130oC 4H r400500600700800020*********(b)T r a n s m i t t a n c e (%)Wavelength (nm)as-deposited.150oC 1Hr150oC 2Hr150oC 3Hr150oC 4HrFigure 2. Transmittance measure of Sample-A after (a) 130 ºC annealing and (b) 150 ºC annealing.0.20.40.60.81.0N o r m a l i z e d R e s i s t i v i t y (a .u .)Anneal Time (Hour)Figure 3. Resistance change of Sample-B withdifferent anneal temperature and time.To understand the difference between both samples in the above discussion, XRD measurement results were analyzed. The results were displayed in Fig. 5(a) and 5(b). All samples have one broaden amorphous peak profile at 2θ angle about 23 º, this might result from glass substrate. There was one (2,2,2) orientation peak at 2θ angle 30.5 º of Sample-A after 150 ºC 4 hours annealing. It is understood that 150 ºC long time annealing help400500600700800010********60708090100(a)T r a n s m i t t a n c e (%)Wavelength (nm)as deposited 150-1hr 150-2hr 150-3hr 150-4hr 400500600700800010********60708090100(b)T r a n s m i t t a n c e (%)Wavelength (nm)as-deposited 180C-1hr 180C-2hr 180C-3hr 180C-4hrFigure 4. Transmittance measure of Sample-B after (a) 150 ºC annealing and (b) 180 ºC annealing.Sample - A crystallize into poly-type with grain growth (Fig. 5(a)). But there were not any change of Sample-B after the same annealing condition (Fig. 5(b)). Sample-B kept amorphous without any growth of orientation peak. Slightly (2,2,2) orientation peak can be found at 2θ angle 30.5 º after 2 hours annealing at 180 ºC and became even stronger after 4 hours annealing. It is now understood that the reduction of resistance for both Sample-A and Sample-B were contributed by annealing the amorphous ITO phase into polycrystalline structure.There is one unclarified question about the difference on the magnitude of ITO crystallization temperature between two samples. Thus the TEM measurement and transmission electron diffraction (TED) of both ITO films were analyzed. Fig. 6(a) and Fig. 6(b) show the thickness of both samples, in which Sample-A is with thickness of 42.2 nm, while Sample-B is with thickness of 70 nm. From the TED results of Sample-A (Fig. 7(a)), we could understand that as-deposited ITO film at 110 ºC can show stronger diffraction pattern, which can explain that as-deposited Sample-A was in slightly crystalline state. Small nucleus grains may be formed during ITO sputtering under 110 ºC with power density 15KW/m 2. The following 150 ºC annealing could help Sample-A nucleus grains to grow larger and thus reducing its resistivity.Proc. of ASID ’06, 8-12 Oct, New Delhi304203040506070(a)I n t e n s i t y (a . u .)2θ angle (degree)Sample-Aafter 150oC 2Hrafter 150oC 4Hr203040506070(b)(a)I n t e n s i t y (a . u .)2θ angle (degree)Sample-Bafter 180oC 2Hrafter 180oC 4Hrafter 150oC 2Hrafter 150oC 2HrFigure 5. XRD measurements of (a) Sample-A and(b) Sample-B after thermal annealingFigure 6. TEM thickness measurement of (a)sample-A and (b) sample-BFigure 7. Transmission electron diffraction pattern of as-deposited (a) Sample-A and (b) Sample-BBut as shown in Fig. 7(b), as-deposited Sample-B did not have any diffraction pattern. It means that ITO deposited at room temperature with power density 15KW/m 2 could not help amorphous ITO to form nucleus grains. And Sample-B need more higher temperature, 180 ºC, to form initial nucleus grains and then grow into larger grains by heat energy.ConclusionsWe have investigated the kinetics of the crystallization of amorphous ITO by using sputtering system at room temperature and 110 ºC temperature and its effect to the electrical behavior of the material during and after low temperature annealing. It was found that the resistivity of ITO is changed via two different thermally activated temperatures. ITO deposited at 110 ºC was formed intrinsically with nucleus grains under power density 15KW/m 2. Thus lower temperature annealing at 150 ºC could help to decrease its resistivity. ITO deposited at room temperature was fully amorphous structure, and needed higher temperature annealing to form nucleus grains to migrate into crystalline state. This provides us one alternative way to fit the demands of low temperature and short thermal annealing process between sputter deposition temperature and post annealing temperature. References1. David C. Paine, T. Whitson, D. Janiac, R. Beresford,and Cleva Ow Yang, Journal of Applied Physics , vol. 85, no. 12, pp. 8445-8450, 1999 2. C. M. Hsu, J. W. Lee, J. S. Chen, C. Y. Huang, andJ. C. Lin, Proceedings of SPIE, vol. 4918, pp. 135-142, 2002(a)(b)(a)(b)。
