100分求：计算化学类文献，要求，英文原文，部分翻译成汉语且翻译字数不少于3000字
作者&投稿：裔雅 （若有异议请与网页底部的电邮联系）
Computational chemistry that can predict the spectra of a variety of compounds that cannot be obtained as
pure compounds was used to study the highly sensitive detection of bromate in ion chromatography. Several
possible ions, molecules, and their complexes were constructed by a molecular editor, and optimized by
molecular mechanics (MM2) and MOPAC (PM3) calculations. The possible electronic spectra of these
ions, molecules, and complexes were then obtained by the ZINDO (INDO)-Vizualyzer in the CAChe program.
The lambda maximum (ìmax) of the spectra and the transition dipole were calculated using the ProjectLeader
program. The comparison of the experimental and predicted results indicated that Br3
- was the probable
reaction product, and that NO2
- and ClO- accelerated the reaction.
1. INTRODUCTION
Bromate is considered a carcinogen and the World Health
Organization (WHO) has recommended the provisional
bromate guideline value of 25 mg/L, which is associated with
an excess lifetime cancer risk of 7 10-5, because of the
limitations in the available analytical and treatment methods.1
A highly sensitive analytical method was therefore developed.
Bromate in ozonized water was detected with very
high sensitivity by ion chromatography with a postcolumn
reaction detection using ultraviolet absorption. With the
addition of nitrite for the postcolumn reaction, the sensitivity
was improved 738-fold. The detection limit was 0.35 mg/
L, and the linear range was >4 orders of magnitude, from
0.5 to 10 mg/L.2 The addition of ClO- improved the
sensitivity 327-fold.2
Chiu and Eubanks3 examined bromide spectrophotometrically;
they proposed a reaction mechanism and suggested
that the end product is tribromide.3 The proposed reactions
are as follows:
In addition, bromate and chlorate were determined by
potentiometric titration after reduction with sodium nitrite.4
Sodium nitrite was added in sodium bromide for the on-line
hydrobromic acid generator in this system, and highly
sensitive detection was achieved.2 However, the reaction
mechanism and the final product have not been determined.
Tuchler et al.5 studied bimolecular interactions and directly
detected the internal conversion involving Br(2P1/2) + I2
initiated from a van der Waals dimer. The reaction complex
was formed from a van der Waals dimer precursor, HBrâI2.
The resulting product, highly vibrationally excited molecular
I2, was monitored by resonance-enhanced multiphoton
ionization combined with time-of-flight mass spectroscopy.
The HBr constituent of the precursor HBrâI2 was photodissociated
at 220 nm. The H atom departed instantaneously,
allowing the remaining electronically excited Br(2P1/2) to
form a collision complex, (BrI2)*, in a restricted region along
with the Br + I2 reaction coordinate determined by precursor
geometry. Sims et al.6 reported the fentosecond real-time
probing of bimolecular reaction Br + I2, and summarized a
number of trihalogen intermediates observed in matrix
isolation studies.
Computational chemistry can predict the electronic spectra
of a variety of compounds that cannot be obtained as pure
compounds. This tool was applied to study the highly
sensitive detection of bromate in ion chromatography.
Several possible ions and molecules and their complexes
were constructed by a molecular editor, and optimized by
molecular mechanics (MM2) and MOPAC (PM3 and AM1)
calculations. Their possible electronic spectra were then
obtained with the ZINDO (INDO/1)-Vizualyzer in the
CAChe program. The lambda maximum (ìmax) of the spectra
of the transition dipole were calculated using the ProjectLeader
program. The properties used for the calculation of
the molecular mechanics were bond stretch, bond angle,
dihedral angle, improper torsion, van der Waals, electrostatic
(MM2 bond dipole), hydrogen bond, and cut-off distance
for van der Waals interactions (9.00 Å). (van der Waals
interactions were updated every 50 interactions.) The
parameters for the MOPAC calculation were geometry search
* Author to whom correspondence should be sent.
† Health Research Foundation.
‡ Yokogawa Analytical Systems.
Br- + 3ClO- f BrO3
- + 3Cl- (1)
BrO3
- + 5Br- + 6H+ f 3Br2 + 3H2O (2)
Br2 + Br- f Br3
- (3)
J. Chem. Inf. Comput. Sci. 1998, 38, 885-888 885
S0095-2338(98)00084-5 CCC: $15.00 © 1998 American Chemical Society
Published on Web 08/14/1998
options (precise, minimized by NLLSQ, optimized geometry
by BFGS), and properties [Mulliken population, energy
partitioning, polarizabilities, localize, thermo, rotational
symmetry (C1)] in the CAChe program. The predicted data
were compared with those obtained experimentally.
2. THEORY
According to the Lambert-Beer law, the ratio of the
intensity of the light of the inlet site (Io(î)) and the outlet
site (I(î)) is given by the following equation:
That is, absorbance A ) log10I/Io ) k(î)Dx, where the molar
extinction coefficient (molar absorption coefficient) I ) Io
10k(î)Dx, and k(î): molar extinction coefficient is the molar
absorptivity.
The following equation is given as the relation between
absorption intensity as measured experimentally and that
estimated theoretically:7
The intensity of the spectrum is given by the following
equation:
where jájjköâerjiñj2 is the transition dipole.
That is, molar absorptivity, k(î), is related to the transition
dipole. The following parameters are found in eqs 4-7: D,
concentration of analyte; x, pass length of light; c, light speed;
N, Avogadro’s constant; h, Planck’s constant; V, frequency;
j, excited state; i, ground state; k, Boltzmann’s constant; er,
transition dipole moment; and kö, polarized light vector.
3. RESULTS AND DISCUSSION
The computational chemical calculation was performed
by the CAChe program from Sony-Tektronix (Tokyo) using
a Macintosh 8100/100 personal computer. The molar
absorptivity of several ions, molecules, and complexes were
directly measured on spectra obtained by ZINDO-Visualization
after their conformations were optimized by MM2 and
MOPAC (PM3 and AM1). Their transition dipoles were
calculated by the ProjectLeader program using MM2
and MOPAC (PM3 and AM1). The values of molar
absorptivity and the transition dipoles are summarized in
Table 1. The values of their complexes with nitrite and
chlorite are included. The energy values of angle and van
der Waals obtained by the MM2 calculation are also given
in Table 1.
The relation between the transition dipole and the molar
absorptivity was:
where Y is molar absorptivity (I/mol-cm) and X is the
transition dipole (debye). The chromatographic sensitivity
is directly related to the molar absorptivity of the analytes.
The molar absorptivity of Br3
- and the Br2 + Br- complex
was very high, 190 000. The measurements of molar
absorptivity and the ìmax wavelength were not easily
obtained, but these values can be automatically calculated
using the ProjectLeader program. The Br3
- and the Br2 +
Br- complex have similar structures, as shown in Figure 1.
The complex between Br2 and Br- was automatically formed
after the optimization of the structure, and the heat of
formation energy value was the lowest among the analytes
listed in Table 1; the values were about -106 kcal/mol. The
value of the complex was the same as that of Br3
-. This
Table 1. Properties of Analytesa
analyte HOF, kcal/mol ìmax, nm td debye ma, L/mol-cm angle, kcal/mol vwv, kcal/mol
Br- -56.00 - - * 0.00 0.00
Br2 4.92 602 0.277 81 0.00 0.00
Br3
- -105.69 258 12.300 188200 0.00 0.00
BrO3
- -39.59 462 0.927 595 3.28 0.00
NO2
- -42.93 208 4.005 24660 0.00 0.00
ClO- -32.97 234 0.409 458 0.00 0.00
Br2 + NO2
-/1 -98.49 224 7.227 74550 0.00 -0.26
Br2 + NO2
-/2 -104.80 239 8.183 91440 0.03 -0.05
Br2 + NO2
-/3 -99.93 230 5.550 43370 0.00 -0.22
Br2 + Br- -105.69 258 12.327 188250 0.00 -0.36
Br2 + ClO-/1 -113.02 228 4.758 30670 0.00 -0.33
Br2 + ClO-/2 -74.52 228 10.385 148400 0.00 -0.46
Cl- -51.22 - - * 0.00 0.00
Cl2 -11.57 410 0.464 336 0.00 0.00
Cl3
- -91.06 214 10.615 168200 0.00 0.00
Cl2Br- -95.30 247 10.727 148760 0.00 -0.32
Cl2 + OCl- -87.51 243 5.220 34 0.00 -0.36
BrO3
- + NO2
- -51.11 209 4.117 30166 0.00 -0.75
I3 -85.58 221 12.738 236800 0.00 0.00
I2Br -87.59 229 12.276 209360 0.00 0.00
a HOF: heat of formation (PM3); td: transition dipole; ma: molar absorptivity; angle: dihedral angle (MM2); vwv: van der Waals energy
(MM2); *: molecule lacks electronic state information.
Y ) 1057.422X2 + 3017.582X - 2368.256
r2 ) 0.993 (n ) 14) (8)
[I(î) Io(î)] ) 10-k(î)Dx ) e-ln10âk(î)Dx (4)
103âln 10âc
Nh
s k(î)
î
dî ) 8ð3
h2
jájjköâerjiñj2 (5)
f(theoretical) ) 8ð2mî
3h
jájjköâerjiñj2 (6)
k(î) ) 1
Dx
log10 I/Io µ jájjköâerjiñj2 (7)
886 J. Chem. Inf. Comput. Sci., Vol. 38, No. 5, 1998 HANAI ET AL.
result indicated that Br3
- can be formed where Br2 and Brco-
exist as the BrI2 complex.5,6
The question arises as to how NO2
- and ClO- acted in
the reaction: did these ions form different compounds or
complexes with bromide or bromine for the highly sensitive
detection of bromate? The Br2 + NO2
- complex was
thusconstructed, and we optimized the structure by MM2
and PM3 calculations. The Br2 and NO2
- formed three types
of conformations, as shown in Figure 2. The structures A
and B were obtained as molecules and the structure C was
obtained as a transition state. Their energy values of heat
of formation are given in Table 1 as Br2 + NO2
-/1, Br2 +
NO2
-/2, and Br2 + NO2
-/3, respectively. Their heat of
formation energy values were low; the lowest energy value
was -105 kcal/mol, about the same as that of the Br2 +
Br- complex. The structure with the lowest energy value
is structure B in Figure 2. However, its molar absorptivity
was less than half of that of the Br2 + Br- complex. This
result suggested that NO2
- may form a complex with Br2;
however, such a complex may not be the final product
because of the low sensitivity. The ìmax wavelengths of
structures A, B, and C in Figure 2 were 224, 230, and 240
nm, respectively, and were different from that of the Br2 +
Br- complex and Br3
-, whose ìmax was 258 nm. The ìmax
of 258 nm was the closest wavelength to that observed
experimentally (265 nm). This result also suggested that
such a complex may not be the final product. The formation
of these complexes was supported by the negative values of
their van der Waals energy calculated by MM2 (Table 1).
Bromide did not form a complex with NO2
-. Bromide,
bromine, bromate, and nitrite were not highly sensitive
analytes, due to their low transition dipole values and ìmax
wavelength.
Another question was why the sensitivity measured in the
existence of ClO- was about the half of that measured in
the existence of NO2
-. The reaction processes were estimated
according to the proposal of Chiu and Eubanks.3
The value of molecular absorptivity of Cl2Br- (148 760) was
lower than that of Br3
- (188 200), and the ìmax wavelength
of Cl2Br- (247 nm) was also lower than that of Br3
- (258
nm). Therefore, the final sensitivity using ClO- as the
reaction reagent was less than that using NO2
-.
Bromate formed a complex with nitrite; however, the
complex may be unstable due to the high energy value of
the heat of formation. This complex is not a candidate for
the highly sensitive detection of bromate because of the low
transition dipole value and ìmax wavelength. Bromine can
form a complex with ClO-; however, the energy value of
heat of formation was high for a complex with a higher
transition dipole. This means that the Br2 + ClO- complex
may be not a candidate for the highly sensitive detection of
bromate. The results just presented indicate that the highly
sensitive detection of chlorate and iodinate can be achieved
by using the techniques employed for the bromate analysis.
The sensitivity of chlorate and iodinate will be 90 and 111%
of bromate; however, the ìmax wavelengths of Cl2Br- and
I2Br- are 10 and 30 nm lower, respectively, than that of
Br2Br-. IfCl3
- and I3
- are the final products, the specific
ion generator should be constructed; however, the detection
wavelengths of Cl3
- and I3
- are further lower than those of
Cl2Br- and I2Br-, and the selective detection may not be
easy. The computational chemical analysis of fluorate could
not performed due to the lack of stable electron stable
information for fluorate.
An AM1 calculation can be used to optimize these
structures; however, the present AM1 calculation did not give
complex forms because of the fixed atomic distances. The
ìmax wavelengths were usually shorter than that obtained
by PM3, and the values of molar absorptivity were smaller.
For example, the maximum atomic distances of Br3
-
calculated by PM3 and AM1 were 5.065 and 4.575 Å,
respectively. Their ìmax wavelengths and their values of
Figure 1. Electron density of the optimized structures of Br2 +
Br- complex and Br3
-.
Figure 2. Possible conformations of Br2 + NO2
-.
2BrO3
- + 4NO2
- + 4H+ f Br2 + 4HNO3 + 2H2O (9)
Br2 + Br- f Br3
- (10)
2BrO3
- + 4ClO- + 6H+ f
Br2 + Cl2 + 2HClO3 + 3H2O (11)
Br2 + Br- f Br3
- and Cl2 + Br- f Cl2Br- (12)可以预测有机混合物中一系列有机物色谱的计算化学能在离子色谱中进行溴离子的高灵敏度色谱分析。一些能测的离子，分子和他们的复合物分子结构能通过一个分子编辑器得到。再通过分子力学进一步优化和用MOPAC进一步计算来完善它,这些离子，分子和配和物的电子光谱就会在高度缓存程序中通过ZINDO (INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。通过实验结果和预测结果的比较表明Br3-是可能的反应产物，而且其中的NO2-和CLO-加快了反应。
1. 前言
溴酸盐被认为是一种致癌物子和世界卫生组织已建议它的含量准则为25mg/L，这与人一生超过7*10-5 的癌症发病率有关，这是由于以前溴酸盐在有效分析和处理方法上受到限制。因此，一种高灵敏度的分析方法就发展起来了。溴酸盐在溴氧水中通过离子色谱能被精确的检测到，而离子色谱是使用紫外吸收进行柱后反应测定的。随着亚硝酸盐在柱后反应中的加入，灵敏度提高了738倍。检测线0.35mg/L，并且从0.5-10mg/L的线性范围大于四个数量级，CLO-的加入也使灵敏度提高了327倍。
Chiu和Eubanks审查了甲基溴光度法，他们提出了一种反应机制，并认为那最终的产物是三溴化物。
此外，溴和氯在减少硝酸钠加入量后可通过电位滴定法测得，溴化钠中加入硝酸钠是为了溶液中出现氢溴酸，从而获得精确的测定结果。但是，反应的机制和最终产物仍然是没有确定。图兹勒等人研究双分子的相互作用和发现内部转换Br(2P1/2) + I2开始于范德华二聚体。那反应产物形成范德华二聚体，HBr.I2。那最后产物是高聚物分子，他是通过共振性强的多光子电离法和质谱法相结合而测到的。那HBr.I2的反应产物溴化氢的键长是220nm。氢原子的瞬间离开，使得其余的电子激发Br(2P1/2)，彼此发生复杂的碰撞，形成(BrI2)*。在一个限制的区域伴随着Br- + I2同样取决于反应初始条件。Sims et al，他报告了双分子反应Br- + I2方面的探究结果，总结出了反应中间体在进行分离实验研究时能被观察到。
计算化学可以预测混合有机物中一系列有机物的电子色谱，计算化学还应用于精确检测离子色谱中的溴。一些可测的离子，分子和配合物的分子结构通过分子编辑器能被构造出来，再通过分子力学进一步优化和用MOPAC进一步计算。那么他们的电子色谱就会在高度缓存程序中通过ZINDO(INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。计算化学中的程序还可以计算分子的键长，键角，二面角，扭转力，范德华力，静电力，氢键和由范德华力分离的距离（9.00 Å）。用MOPAC 计算方法计算的参数在下表1，并且各种特性都通过那CAChe程序显现出来了。然后，我们预测的数据就可以和这些实验得出的数据进行比较。
文献第三部分：
2. 结果与讨论
计算化学的计算是由CAChe程序来完成的，这个程序是由东京的索尼泰克公司开发的，更适用于个人电脑。一些离子，分子和配合物的摩尔吸收率能在光谱中直接测量得到，而它们各自的光谱是离子，分子，配合物分子在经过进一步优化和计算后通过ZINDO-Visualization方法而得到的。那ProjectLeader程序用MM2和MOPAC方法可以计算它们的过渡偶极子。摩尔吸收率和过渡偶极子的测试值总结在表1中。它们的复合物如亚硝酸盐和亚氯酸盐的测试值也列在表1中。角度和范德华力的测试值通过MM2计算也被列在表1中。
摩尔吸收率和过渡偶极子的关系是：
Y = 1057.422X2 + 3017.582X - 2368.256
r2=0.993(n=14)(8)
其中Y是摩尔吸收率(I/mol-cm)，X是过渡偶极子(debye)。那色谱的灵敏度直接关系到样品的摩尔吸收率。Br3-的摩尔吸收率和Br2 + Br-配合物的摩尔吸收率都很高，大约是190000。摩尔吸收率和最大波长的大小是不容易测得的，但是这些值可以通过ProjectLeader程序自动计算出来。Br3和-Br2 + Br-配合物有类似的结构，如图1所示。
在Br3-和Br2 + Br-之间的复合物是在结构的优化中自动形成的，它能量中的热量值是上述表1样品中最低的。那测量值大约是-106kcal/mol.那复合物的测量值是和Br3-的值一样的。这结果表明Br3-能形成诸如BrI2之类的复合物。
那么问题就归于了解亚硝酸根和亚氯酸根是怎样参与反应的：这些离子之间可以形成不同的化合物吗？或者由于溴的高灵敏度能与溴化物和溴酸盐形成复合物吗？Br2 + NO2-形成的配合物被构造出来，并且我们通过MM2和PM3计算来优化那结构。那溴与亚硝酸盐就可能有三种不同的构造，这些构造都列在表2中。
那A和B是获得的分子，而C是过渡态。它们的热量值分别列在表1中。它们的热量值都很低，其中最低的能量值是-105kcal/mol,这能量值是和Br+Br-的能量值一样的。在表2中可以知道最低能量值的构造是B化合物的结构。然而，它的摩尔吸收率比Br2 + Br-复合物的一半还少。这结果表明亚硝酸根能和溴形成复合物；然而，由于那低的灵敏度得知这种复合物不是最终产物，A,B,C的最大波长列在表2中，一次是224，230和240nm。显然，这是和Br+Br复合物不同的。那最大波长258nm最靠近那理论波长265nm。这结果也表明了那产物不是那最终产物。这些复合物的范德华力通过MM2和PM3计算得知是负值列在表1中。溴化物不能和亚硝酸根形成复合物。溴化物，溴酸盐，溴离子和亚硝酸盐都不是高灵敏度样品，这是由于他们的最长波长和过渡偶极子决定的。
高中英语整体性教学复述法的实践和体会
为了使高中英语教学达到新大纲的要求，我在教学实践中作了些尝试，把课 堂教学由注重语言知识的讲授 课转变成注重语言能力的训练课，把培养和训练 学生的语感、语言习惯当作英语教学的中心任务。我在教学中 利用现行高中精 读课文，采用整体性教学复述法，努力把传授新知识和训练运用语言能力结合起 来，使课文教 学成为教师、教材、学生相互作用的积极过程，在培养学生语言 能力方面收到了良好的效果。在此谨从实践的 角度谈谈我的具体做法。
复述是口头表达课文内容的言语过程，是给学生提供施展运用语言能力的机 会。这一训练不仅能提高学生 的听力、语感、改进语音语调，还能促进学生的 记忆、思维和自学能力。在实际教学中它已成为语言知识转化 为言语能力，培 养听、说、读、写能力的重要途径。为了获得有效的复述效果，我始终遵循记忆 规律，重视各 教学环节的密切配合，利用行之有效的方法，使学生积极参与到 这个有纲可循，有词可用，有话可说的四步教 学活动中来。
第一步：（不要求预习课文）由教师将课文复述一遍，在复述过程中出现部 分生词短语，并用简明英语释 义。（可用板书、幻灯、投影等伴随教师复述。）
第二步：根据教师复述的内容要求学生回答问题，目的在于检查学生是否理 解课文大概内容。在提问题时 要简略、清楚、易懂，注意调动所有学生的积极 性，可多用些"yes"、"No"questions。
第三步：学生在阅读课文后回答一些比第二步复杂些的问题。（在回答问题 的过程中学生会自然地使用第 一步中所出现的生词短语。）然后再引导他们将这 些问题的答案串成复述内容。
下面是高中英语第二册《体育运动》一课复述法三步的具体设计。
Step1.Teacher Presentation Retell the text with the following words and expressions onthe blackboard:
joyful and relaxing;have a game of;be of great value;popularform of relaxation;amusement;go all about;build our bodies.
Step2.Learner Presentation According to what the teacher says answer the following:
(1)Is it joyful and relaxing to have sports and games?
(2)Do many people take part in different kinds of sports?
(3)Some people seem to think that sports and games are unimportant things,don't they?
(4)Do people have different ideas about sports and games?
Step3,Learner Presentation Read the text again and try to pick out a topic sentence foreach paragraph.
Retell the text paragraph by paragraph.
The first paragraph:
Sports and games are perhaps the most popular forms of relaxation.We can learn that from. Swimming in a river in summer Having a game of table tennis almost all can enjoy Watching a close game of … … …
The second paragraph:
They should not be treated only as amusements.(We can learnthatfrom the third and the fourth paragraph.)
The third:
Sports and games build our bodies(We can learn that fromplaying table tennis).
The fourth:
Sports and games are also very useful for character-training.(We can compare the lessons at school with activities on thesports fields.) 以上三步如下简示：teacher retelling→students answering"yes"or"NO" reading the passage questions→students answering further questions retelling it paragraph by paragraph
它以递进的方式给学生提供了从内容到语言材料理解和掌握的渐进过程，为 第四步复述全篇课文创造了条 件。
第四步：复述全篇课文，这一环节是对前三步所做大量训练工作效果的检测， 也是对学生大面积进行能力 训练的时机。利用板书、表格、表演以及主题画来 组织学生复述课文，周密组织好这一环节才能最后达到预期 教学目的。
我在《体育运动》一课在第四步的板书是这样设计的：（以正中sports and games为中心，先由上至下， 再从左至右进行复述）。
板书必须做到重点突出，具有概括性和条理性，并且简明生动，这样诱导学 生复述全篇课文不仅能达到对 课文内容及语言特点的理解，还能培养学生口头 造句和作文的能力。
复述法的实施过程也就是利用内容设置情景引导学生进行交际的过程。针对 不同的教材，不同的教学对象 和不同的时机灵活利用各种行之有效的方法，使 复述发挥更大的效用，以提高实际运用语言的能力，这是我在 课程设计中的首 要原则。
去中国知网去找吧，网址是http://www.cnki.com.cn，里面有很多相关东西，论文什么都都能找到。
+100我想找一篇关于习语翻译（中英文）的外文文献，出处要求是国外。字数要够因为要求翻译出来得3000字~
pure compounds was used to study the highly sensitive detection of bromate in ion chromatography. Several
possible ions, molecules, and their complexes were constructed by a molecular editor, and optimized by
molecular mechanics (MM2) and MOPAC (PM3) calculations. The possible electronic spectra of these
ions, molecules, and complexes were then obtained by the ZINDO (INDO)-Vizualyzer in the CAChe program.
The lambda maximum (ìmax) of the spectra and the transition dipole were calculated using the ProjectLeader
program. The comparison of the experimental and predicted results indicated that Br3
- was the probable
reaction product, and that NO2
- and ClO- accelerated the reaction.
1. INTRODUCTION
Bromate is considered a carcinogen and the World Health
Organization (WHO) has recommended the provisional
bromate guideline value of 25 mg/L, which is associated with
an excess lifetime cancer risk of 7 10-5, because of the
limitations in the available analytical and treatment methods.1
A highly sensitive analytical method was therefore developed.
Bromate in ozonized water was detected with very
high sensitivity by ion chromatography with a postcolumn
reaction detection using ultraviolet absorption. With the
addition of nitrite for the postcolumn reaction, the sensitivity
was improved 738-fold. The detection limit was 0.35 mg/
L, and the linear range was >4 orders of magnitude, from
0.5 to 10 mg/L.2 The addition of ClO- improved the
sensitivity 327-fold.2
Chiu and Eubanks3 examined bromide spectrophotometrically;
they proposed a reaction mechanism and suggested
that the end product is tribromide.3 The proposed reactions
are as follows:
In addition, bromate and chlorate were determined by
potentiometric titration after reduction with sodium nitrite.4
Sodium nitrite was added in sodium bromide for the on-line
hydrobromic acid generator in this system, and highly
sensitive detection was achieved.2 However, the reaction
mechanism and the final product have not been determined.
Tuchler et al.5 studied bimolecular interactions and directly
detected the internal conversion involving Br(2P1/2) + I2
initiated from a van der Waals dimer. The reaction complex
was formed from a van der Waals dimer precursor, HBrâI2.
The resulting product, highly vibrationally excited molecular
I2, was monitored by resonance-enhanced multiphoton
ionization combined with time-of-flight mass spectroscopy.
The HBr constituent of the precursor HBrâI2 was photodissociated
at 220 nm. The H atom departed instantaneously,
allowing the remaining electronically excited Br(2P1/2) to
form a collision complex, (BrI2)*, in a restricted region along
with the Br + I2 reaction coordinate determined by precursor
geometry. Sims et al.6 reported the fentosecond real-time
probing of bimolecular reaction Br + I2, and summarized a
number of trihalogen intermediates observed in matrix
isolation studies.
Computational chemistry can predict the electronic spectra
of a variety of compounds that cannot be obtained as pure
compounds. This tool was applied to study the highly
sensitive detection of bromate in ion chromatography.
Several possible ions and molecules and their complexes
were constructed by a molecular editor, and optimized by
molecular mechanics (MM2) and MOPAC (PM3 and AM1)
calculations. Their possible electronic spectra were then
obtained with the ZINDO (INDO/1)-Vizualyzer in the
CAChe program. The lambda maximum (ìmax) of the spectra
of the transition dipole were calculated using the ProjectLeader
program. The properties used for the calculation of
the molecular mechanics were bond stretch, bond angle,
dihedral angle, improper torsion, van der Waals, electrostatic
(MM2 bond dipole), hydrogen bond, and cut-off distance
for van der Waals interactions (9.00 Å). (van der Waals
interactions were updated every 50 interactions.) The
parameters for the MOPAC calculation were geometry search
* Author to whom correspondence should be sent.
† Health Research Foundation.
‡ Yokogawa Analytical Systems.
Br- + 3ClO- f BrO3
- + 3Cl- (1)
BrO3
- + 5Br- + 6H+ f 3Br2 + 3H2O (2)
Br2 + Br- f Br3
- (3)
J. Chem. Inf. Comput. Sci. 1998, 38, 885-888 885
S0095-2338(98)00084-5 CCC: $15.00 © 1998 American Chemical Society
Published on Web 08/14/1998
options (precise, minimized by NLLSQ, optimized geometry
by BFGS), and properties [Mulliken population, energy
partitioning, polarizabilities, localize, thermo, rotational
symmetry (C1)] in the CAChe program. The predicted data
were compared with those obtained experimentally.
2. THEORY
According to the Lambert-Beer law, the ratio of the
intensity of the light of the inlet site (Io(î)) and the outlet
site (I(î)) is given by the following equation:
That is, absorbance A ) log10I/Io ) k(î)Dx, where the molar
extinction coefficient (molar absorption coefficient) I ) Io
10k(î)Dx, and k(î): molar extinction coefficient is the molar
absorptivity.
The following equation is given as the relation between
absorption intensity as measured experimentally and that
estimated theoretically:7
The intensity of the spectrum is given by the following
equation:
where jájjköâerjiñj2 is the transition dipole.
That is, molar absorptivity, k(î), is related to the transition
dipole. The following parameters are found in eqs 4-7: D,
concentration of analyte; x, pass length of light; c, light speed;
N, Avogadro’s constant; h, Planck’s constant; V, frequency;
j, excited state; i, ground state; k, Boltzmann’s constant; er,
transition dipole moment; and kö, polarized light vector.
3. RESULTS AND DISCUSSION
The computational chemical calculation was performed
by the CAChe program from Sony-Tektronix (Tokyo) using
a Macintosh 8100/100 personal computer. The molar
absorptivity of several ions, molecules, and complexes were
directly measured on spectra obtained by ZINDO-Visualization
after their conformations were optimized by MM2 and
MOPAC (PM3 and AM1). Their transition dipoles were
calculated by the ProjectLeader program using MM2
and MOPAC (PM3 and AM1). The values of molar
absorptivity and the transition dipoles are summarized in
Table 1. The values of their complexes with nitrite and
chlorite are included. The energy values of angle and van
der Waals obtained by the MM2 calculation are also given
in Table 1.
The relation between the transition dipole and the molar
absorptivity was:
where Y is molar absorptivity (I/mol-cm) and X is the
transition dipole (debye). The chromatographic sensitivity
is directly related to the molar absorptivity of the analytes.
The molar absorptivity of Br3
- and the Br2 + Br- complex
was very high, 190 000. The measurements of molar
absorptivity and the ìmax wavelength were not easily
obtained, but these values can be automatically calculated
using the ProjectLeader program. The Br3
- and the Br2 +
Br- complex have similar structures, as shown in Figure 1.
The complex between Br2 and Br- was automatically formed
after the optimization of the structure, and the heat of
formation energy value was the lowest among the analytes
listed in Table 1; the values were about -106 kcal/mol. The
value of the complex was the same as that of Br3
-. This
Table 1. Properties of Analytesa
analyte HOF, kcal/mol ìmax, nm td debye ma, L/mol-cm angle, kcal/mol vwv, kcal/mol
Br- -56.00 - - * 0.00 0.00
Br2 4.92 602 0.277 81 0.00 0.00
Br3
- -105.69 258 12.300 188200 0.00 0.00
BrO3
- -39.59 462 0.927 595 3.28 0.00
NO2
- -42.93 208 4.005 24660 0.00 0.00
ClO- -32.97 234 0.409 458 0.00 0.00
Br2 + NO2
-/1 -98.49 224 7.227 74550 0.00 -0.26
Br2 + NO2
-/2 -104.80 239 8.183 91440 0.03 -0.05
Br2 + NO2
-/3 -99.93 230 5.550 43370 0.00 -0.22
Br2 + Br- -105.69 258 12.327 188250 0.00 -0.36
Br2 + ClO-/1 -113.02 228 4.758 30670 0.00 -0.33
Br2 + ClO-/2 -74.52 228 10.385 148400 0.00 -0.46
Cl- -51.22 - - * 0.00 0.00
Cl2 -11.57 410 0.464 336 0.00 0.00
Cl3
- -91.06 214 10.615 168200 0.00 0.00
Cl2Br- -95.30 247 10.727 148760 0.00 -0.32
Cl2 + OCl- -87.51 243 5.220 34 0.00 -0.36
BrO3
- + NO2
- -51.11 209 4.117 30166 0.00 -0.75
I3 -85.58 221 12.738 236800 0.00 0.00
I2Br -87.59 229 12.276 209360 0.00 0.00
a HOF: heat of formation (PM3); td: transition dipole; ma: molar absorptivity; angle: dihedral angle (MM2); vwv: van der Waals energy
(MM2); *: molecule lacks electronic state information.
Y ) 1057.422X2 + 3017.582X - 2368.256
r2 ) 0.993 (n ) 14) (8)
[I(î) Io(î)] ) 10-k(î)Dx ) e-ln10âk(î)Dx (4)
103âln 10âc
Nh
s k(î)
î
dî ) 8ð3
h2
jájjköâerjiñj2 (5)
f(theoretical) ) 8ð2mî
3h
jájjköâerjiñj2 (6)
k(î) ) 1
Dx
log10 I/Io µ jájjköâerjiñj2 (7)
886 J. Chem. Inf. Comput. Sci., Vol. 38, No. 5, 1998 HANAI ET AL.
result indicated that Br3
- can be formed where Br2 and Brco-
exist as the BrI2 complex.5,6
The question arises as to how NO2
- and ClO- acted in
the reaction: did these ions form different compounds or
complexes with bromide or bromine for the highly sensitive
detection of bromate? The Br2 + NO2
- complex was
thusconstructed, and we optimized the structure by MM2
and PM3 calculations. The Br2 and NO2
- formed three types
of conformations, as shown in Figure 2. The structures A
and B were obtained as molecules and the structure C was
obtained as a transition state. Their energy values of heat
of formation are given in Table 1 as Br2 + NO2
-/1, Br2 +
NO2
-/2, and Br2 + NO2
-/3, respectively. Their heat of
formation energy values were low; the lowest energy value
was -105 kcal/mol, about the same as that of the Br2 +
Br- complex. The structure with the lowest energy value
is structure B in Figure 2. However, its molar absorptivity
was less than half of that of the Br2 + Br- complex. This
result suggested that NO2
- may form a complex with Br2;
however, such a complex may not be the final product
because of the low sensitivity. The ìmax wavelengths of
structures A, B, and C in Figure 2 were 224, 230, and 240
nm, respectively, and were different from that of the Br2 +
Br- complex and Br3
-, whose ìmax was 258 nm. The ìmax
of 258 nm was the closest wavelength to that observed
experimentally (265 nm). This result also suggested that
such a complex may not be the final product. The formation
of these complexes was supported by the negative values of
their van der Waals energy calculated by MM2 (Table 1).
Bromide did not form a complex with NO2
-. Bromide,
bromine, bromate, and nitrite were not highly sensitive
analytes, due to their low transition dipole values and ìmax
wavelength.
Another question was why the sensitivity measured in the
existence of ClO- was about the half of that measured in
the existence of NO2
-. The reaction processes were estimated
according to the proposal of Chiu and Eubanks.3
The value of molecular absorptivity of Cl2Br- (148 760) was
lower than that of Br3
- (188 200), and the ìmax wavelength
of Cl2Br- (247 nm) was also lower than that of Br3
- (258
nm). Therefore, the final sensitivity using ClO- as the
reaction reagent was less than that using NO2
-.
Bromate formed a complex with nitrite; however, the
complex may be unstable due to the high energy value of
the heat of formation. This complex is not a candidate for
the highly sensitive detection of bromate because of the low
transition dipole value and ìmax wavelength. Bromine can
form a complex with ClO-; however, the energy value of
heat of formation was high for a complex with a higher
transition dipole. This means that the Br2 + ClO- complex
may be not a candidate for the highly sensitive detection of
bromate. The results just presented indicate that the highly
sensitive detection of chlorate and iodinate can be achieved
by using the techniques employed for the bromate analysis.
The sensitivity of chlorate and iodinate will be 90 and 111%
of bromate; however, the ìmax wavelengths of Cl2Br- and
I2Br- are 10 and 30 nm lower, respectively, than that of
Br2Br-. IfCl3
- and I3
- are the final products, the specific
ion generator should be constructed; however, the detection
wavelengths of Cl3
- and I3
- are further lower than those of
Cl2Br- and I2Br-, and the selective detection may not be
easy. The computational chemical analysis of fluorate could
not performed due to the lack of stable electron stable
information for fluorate.
An AM1 calculation can be used to optimize these
structures; however, the present AM1 calculation did not give
complex forms because of the fixed atomic distances. The
ìmax wavelengths were usually shorter than that obtained
by PM3, and the values of molar absorptivity were smaller.
For example, the maximum atomic distances of Br3
-
calculated by PM3 and AM1 were 5.065 and 4.575 Å,
respectively. Their ìmax wavelengths and their values of
Figure 1. Electron density of the optimized structures of Br2 +
Br- complex and Br3
-.
Figure 2. Possible conformations of Br2 + NO2
-.
2BrO3
- + 4NO2
- + 4H+ f Br2 + 4HNO3 + 2H2O (9)
Br2 + Br- f Br3
- (10)
2BrO3
- + 4ClO- + 6H+ f
Br2 + Cl2 + 2HClO3 + 3H2O (11)
Br2 + Br- f Br3
- and Cl2 + Br- f Cl2Br- (12)可以预测有机混合物中一系列有机物色谱的计算化学能在离子色谱中进行溴离子的高灵敏度色谱分析。一些能测的离子，分子和他们的复合物分子结构能通过一个分子编辑器得到。再通过分子力学进一步优化和用MOPAC进一步计算来完善它,这些离子，分子和配和物的电子光谱就会在高度缓存程序中通过ZINDO (INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。通过实验结果和预测结果的比较表明Br3-是可能的反应产物，而且其中的NO2-和CLO-加快了反应。
1. 前言
溴酸盐被认为是一种致癌物子和世界卫生组织已建议它的含量准则为25mg/L，这与人一生超过7*10-5 的癌症发病率有关，这是由于以前溴酸盐在有效分析和处理方法上受到限制。因此，一种高灵敏度的分析方法就发展起来了。溴酸盐在溴氧水中通过离子色谱能被精确的检测到，而离子色谱是使用紫外吸收进行柱后反应测定的。随着亚硝酸盐在柱后反应中的加入，灵敏度提高了738倍。检测线0.35mg/L，并且从0.5-10mg/L的线性范围大于四个数量级，CLO-的加入也使灵敏度提高了327倍。
Chiu和Eubanks审查了甲基溴光度法，他们提出了一种反应机制，并认为那最终的产物是三溴化物。
此外，溴和氯在减少硝酸钠加入量后可通过电位滴定法测得，溴化钠中加入硝酸钠是为了溶液中出现氢溴酸，从而获得精确的测定结果。但是，反应的机制和最终产物仍然是没有确定。图兹勒等人研究双分子的相互作用和发现内部转换Br(2P1/2) + I2开始于范德华二聚体。那反应产物形成范德华二聚体，HBr.I2。那最后产物是高聚物分子，他是通过共振性强的多光子电离法和质谱法相结合而测到的。那HBr.I2的反应产物溴化氢的键长是220nm。氢原子的瞬间离开，使得其余的电子激发Br(2P1/2)，彼此发生复杂的碰撞，形成(BrI2)*。在一个限制的区域伴随着Br- + I2同样取决于反应初始条件。Sims et al，他报告了双分子反应Br- + I2方面的探究结果，总结出了反应中间体在进行分离实验研究时能被观察到。
计算化学可以预测混合有机物中一系列有机物的电子色谱，计算化学还应用于精确检测离子色谱中的溴。一些可测的离子，分子和配合物的分子结构通过分子编辑器能被构造出来，再通过分子力学进一步优化和用MOPAC进一步计算。那么他们的电子色谱就会在高度缓存程序中通过ZINDO(INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。计算化学中的程序还可以计算分子的键长，键角，二面角，扭转力，范德华力，静电力，氢键和由范德华力分离的距离（9.00 Å）。用MOPAC 计算方法计算的参数在下表1，并且各种特性都通过那CAChe程序显现出来了。然后，我们预测的数据就可以和这些实验得出的数据进行比较。
文献第三部分：
2. 结果与讨论
计算化学的计算是由CAChe程序来完成的，这个程序是由东京的索尼泰克公司开发的，更适用于个人电脑。一些离子，分子和配合物的摩尔吸收率能在光谱中直接测量得到，而它们各自的光谱是离子，分子，配合物分子在经过进一步优化和计算后通过ZINDO-Visualization方法而得到的。那ProjectLeader程序用MM2和MOPAC方法可以计算它们的过渡偶极子。摩尔吸收率和过渡偶极子的测试值总结在表1中。它们的复合物如亚硝酸盐和亚氯酸盐的测试值也列在表1中。角度和范德华力的测试值通过MM2计算也被列在表1中。
摩尔吸收率和过渡偶极子的关系是：
Y = 1057.422X2 + 3017.582X - 2368.256
r2=0.993(n=14)(8)
其中Y是摩尔吸收率(I/mol-cm)，X是过渡偶极子(debye)。那色谱的灵敏度直接关系到样品的摩尔吸收率。Br3-的摩尔吸收率和Br2 + Br-配合物的摩尔吸收率都很高，大约是190000。摩尔吸收率和最大波长的大小是不容易测得的，但是这些值可以通过ProjectLeader程序自动计算出来。Br3和-Br2 + Br-配合物有类似的结构，如图1所示。
在Br3-和Br2 + Br-之间的复合物是在结构的优化中自动形成的，它能量中的热量值是上述表1样品中最低的。那测量值大约是-106kcal/mol.那复合物的测量值是和Br3-的值一样的。这结果表明Br3-能形成诸如BrI2之类的复合物。
那么问题就归于了解亚硝酸根和亚氯酸根是怎样参与反应的：这些离子之间可以形成不同的化合物吗？或者由于溴的高灵敏度能与溴化物和溴酸盐形成复合物吗？Br2 + NO2-形成的配合物被构造出来，并且我们通过MM2和PM3计算来优化那结构。那溴与亚硝酸盐就可能有三种不同的构造，这些构造都列在表2中。
那A和B是获得的分子，而C是过渡态。它们的热量值分别列在表1中。它们的热量值都很低，其中最低的能量值是-105kcal/mol,这能量值是和Br+Br-的能量值一样的。在表2中可以知道最低能量值的构造是B化合物的结构。然而，它的摩尔吸收率比Br2 + Br-复合物的一半还少。这结果表明亚硝酸根能和溴形成复合物；然而，由于那低的灵敏度得知这种复合物不是最终产物，A,B,C的最大波长列在表2中，一次是224，230和240nm。显然，这是和Br+Br复合物不同的。那最大波长258nm最靠近那理论波长265nm。这结果也表明了那产物不是那最终产物。这些复合物的范德华力通过MM2和PM3计算得知是负值列在表1中。溴化物不能和亚硝酸根形成复合物。溴化物，溴酸盐，溴离子和亚硝酸盐都不是高灵敏度样品，这是由于他们的最长波长和过渡偶极子决定的。
高中英语整体性教学复述法的实践和体会
为了使高中英语教学达到新大纲的要求，我在教学实践中作了些尝试，把课 堂教学由注重语言知识的讲授 课转变成注重语言能力的训练课，把培养和训练 学生的语感、语言习惯当作英语教学的中心任务。我在教学中 利用现行高中精 读课文，采用整体性教学复述法，努力把传授新知识和训练运用语言能力结合起 来，使课文教 学成为教师、教材、学生相互作用的积极过程，在培养学生语言 能力方面收到了良好的效果。在此谨从实践的 角度谈谈我的具体做法。
复述是口头表达课文内容的言语过程，是给学生提供施展运用语言能力的机 会。这一训练不仅能提高学生 的听力、语感、改进语音语调，还能促进学生的 记忆、思维和自学能力。在实际教学中它已成为语言知识转化 为言语能力，培 养听、说、读、写能力的重要途径。为了获得有效的复述效果，我始终遵循记忆 规律，重视各 教学环节的密切配合，利用行之有效的方法，使学生积极参与到 这个有纲可循，有词可用，有话可说的四步教 学活动中来。
第一步：（不要求预习课文）由教师将课文复述一遍，在复述过程中出现部 分生词短语，并用简明英语释 义。（可用板书、幻灯、投影等伴随教师复述。）
第二步：根据教师复述的内容要求学生回答问题，目的在于检查学生是否理 解课文大概内容。在提问题时 要简略、清楚、易懂，注意调动所有学生的积极 性，可多用些"yes"、"No"questions。
第三步：学生在阅读课文后回答一些比第二步复杂些的问题。（在回答问题 的过程中学生会自然地使用第 一步中所出现的生词短语。）然后再引导他们将这 些问题的答案串成复述内容。
下面是高中英语第二册《体育运动》一课复述法三步的具体设计。
Step1.Teacher Presentation Retell the text with the following words and expressions onthe blackboard:
joyful and relaxing;have a game of;be of great value;popularform of relaxation;amusement;go all about;build our bodies.
Step2.Learner Presentation According to what the teacher says answer the following:
(1)Is it joyful and relaxing to have sports and games?
(2)Do many people take part in different kinds of sports?
(3)Some people seem to think that sports and games are unimportant things,don't they?
(4)Do people have different ideas about sports and games?
Step3,Learner Presentation Read the text again and try to pick out a topic sentence foreach paragraph.
Retell the text paragraph by paragraph.
The first paragraph:
Sports and games are perhaps the most popular forms of relaxation.We can learn that from. Swimming in a river in summer Having a game of table tennis almost all can enjoy Watching a close game of … … …
The second paragraph:
They should not be treated only as amusements.(We can learnthatfrom the third and the fourth paragraph.)
The third:
Sports and games build our bodies(We can learn that fromplaying table tennis).
The fourth:
Sports and games are also very useful for character-training.(We can compare the lessons at school with activities on thesports fields.) 以上三步如下简示：teacher retelling→students answering"yes"or"NO" reading the passage questions→students answering further questions retelling it paragraph by paragraph
它以递进的方式给学生提供了从内容到语言材料理解和掌握的渐进过程，为 第四步复述全篇课文创造了条 件。
第四步：复述全篇课文，这一环节是对前三步所做大量训练工作效果的检测， 也是对学生大面积进行能力 训练的时机。利用板书、表格、表演以及主题画来 组织学生复述课文，周密组织好这一环节才能最后达到预期 教学目的。
我在《体育运动》一课在第四步的板书是这样设计的：（以正中sports and games为中心，先由上至下， 再从左至右进行复述）。
板书必须做到重点突出，具有概括性和条理性，并且简明生动，这样诱导学 生复述全篇课文不仅能达到对 课文内容及语言特点的理解，还能培养学生口头 造句和作文的能力。
复述法的实施过程也就是利用内容设置情景引导学生进行交际的过程。针对 不同的教材，不同的教学对象 和不同的时机灵活利用各种行之有效的方法，使 复述发挥更大的效用，以提高实际运用语言的能力，这是我在 课程设计中的首 要原则。
去中国知网去找吧，网址是http://www.cnki.com.cn，里面有很多相关东西，论文什么都都能找到。
+100我想找一篇关于习语翻译（中英文）的外文文献，出处要求是国外。字数要够因为要求翻译出来得3000字~
在大学里用中国知网下载，不仅免费，还很权威~
沿着柱体轴线的堆积周期性和沿着分子盘法线（molecular disc normal）的堆积周期性(分别为h0和h)表明，分子几乎垂直于柱体轴线而堆积（参见支持信息中的表S1）[16]。而且，为了填满邻近分子之间可得的空间，分子很可能以交替的形式堆积。这也被分子动力学（MD）仿真所表明，在此仿真中，遵照实验的X射线数据，由一个高度为13.3-Å(4×3.33 Å相当于4个堆积分子）的周期性的圆柱细胞建立了一个柱体模型。这些计算表明，可得的体积有良好的空间填充，以及在整个仿真实验时间内微偏析的增强，从而对柱状结构的内聚性做出了贡献。而且，该模型表明，柱体的内聚由于Pt－Pt和Pt－炔烃的互作用而进一步得到增强，就如也被尖锐的宽角度信号（h0）所揭示的那样。BF4－阴离子位于络合物之间。MD实验的快照解释了2c在六边形柱体（Colh）相中优异的分子包装，如图4所示的那样。
中心的刚性富电子核心的大小大约为2nm，这是一个非常接近于如2b在稀释凝胶下用TEM确定的一根纤维的最小宽度的值。
最后还研究了在定义良好的结晶学表面（例如云母和高度有序的热解石墨（HOPG）上的这些纤丝状超结构的组织（注意，分子沉积在无定形碳薄膜上用于TEM研究）。2b的稀释凝胶（0.08m mol L－1）用滴铸（drop casting）法沉积在云母基体上。如图5a中所示的那样，没有表观取向次序和平均高度为2nm的纤维清晰可见（参见图5b的横截面）
令人感兴趣的是，用旋转涂覆沉积在新鲜劈开的HOPG上的化合物2b的稀释的十二烷凝胶导致了分子纤维的自组合，它主要遵循着下面HOPG基体的优先结晶学方向（图5c）。片段图形三倍的对称性在纤维相互形成60°和120°角度的截距处特别可以看出。这些横截面表明了存在两种纤维，它们相应于两种不同的分子高度，即（2.0±0.1）nm和（4.0±0.3nm）（图5d）。此2nm高的纤维可以认为是由平坦处于表面上的单一的分子层构成的（支持信息中的图S1）。4nm高的纤维由两层这样堆积起来的层构成，它们的烷烃链仍与表面处于平行。
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