北京宏剑讯科软件技术有限公司常用化学软件

Gaussian03——业界应用最广泛的量子化学软件,是作半经验计算和从头计算使用最广泛的量子化学软件。可以研究：分子能量和结构,过渡态的能量和结构化学键以及反应能量,分子轨道,偶极矩和多极矩,原子电荷和电势,振动频率,红外和拉曼光谱,NMR,极化率和超极化率,热力学性质,反应路径。计算可以模拟在气相和溶液中的体系,模拟基态和激发态,还可以对周期边界体系进行计算。公司每月一期G03软件培训。     

关于状态性质的加和性

本文提出将状态性质的加和性分为三种:部分加和性、组分加和性和基因加和性。这样分类后,容量性质和强度性质的区别与联系更加清晰。凡容量性质必定具有部分加和性,而强度性质必定没有部分加和性。因此,用有无部分加和性来区分状态性质为容量性质和强度性质是最确切的,不易引起误解。部分加和性就是通常说“容量性质在一定条件下有加和性”的那种加和性。     

医用生物陶瓷及临床应用

生物陶瓷是用于修复和重建外伤和疾病患者骨骼的陶瓷。它们可以是惰性, 可吸收和生物活性的。临床应用于髋、膝、牙、腱和韧带, 治疗牙周病和颌面重建, 牙嵴增高与加固颌骨, 脊柱融合及肿瘤切除后骨的填充, 碳涂层用作心脏瓣膜。新开发的模拟生物过程和离子注入的新技术, 在聚合物表面形成类骨磷灰石层, 具有良好的生物活性和延展性, 不仅可替代硬组织, 而且可替代软组织。生物活性铁磁微晶玻璃和耐化学腐蚀的放射性玻璃可用于癌症治疗。     

生物质水热液化和炭化产物特性研究

分别选取稻杆,水葫芦,纤维素和木聚糖（生物质模型化合物）为原料,在反应釜中进行水热液化（300℃,30min）和水热炭化（220℃,4h）实验,对液化产物和炭化产物进行分析。结果表明,稻杆获得重油产率达最大值21.62%。纤维素,木聚糖和水葫芦的重油产率分别为15.00%,11.61%和12.19%。生物质化学组分对其重油产率和组分有着一定的影响。液态产物分别利用总有机碳分析仪（TOC）和气质联用仪（GC-MS）进行测定。表明重质油中主要含有酮类,酚类,醛类,醇类和少量的酸类化合物。利用扫描电镜（SEM）和透射电镜（TEM）对水热炭化固态产物进行了形貌与结构表征,得到具有核壳结构的纳米微球。纤维素,水葫芦和稻杆有着较高的焦炭产率,最后对木聚糖的碳微球形成机理进行初探。     

水热炭化生物质与煤共热解和共气化特性研究

煤和生物质共热化学转化有助于当前化石能源系统的低碳化发展。本研究以烟煤和木质生物质为原料,研究煤和生物质共热解和共气化特性,并考察了不同水热炭化温度和生物质掺混比的影响。利用热重分析仪和在线质谱分析共热解和共气化的协同作用和氢气释放特性。采用Model-fitting方法,单独分析热解和气化阶段的整体反应动力学。结果表明,煤和生物质共气化阶段的协同作用显著强于共热解阶段。生物质比例越高,共气化协同作用越明显,水热炭化会削弱共气化的协同作用。共热解过程,H₂的产生受抑制。共气化过程可采用一级模型描述,而共热解过程需遵循n级反应模型。未处理的或轻度水热炭化的生物质与煤的混合物,共热解整体活化能和反应级数大于加权平均值,而其共气化的活化能变化趋势相反。重度水热炭化生物质与煤的混合物,共热解和共气化的活化能均接近加权平均值。     

高效液相色谱法测定饲料用灌木中的淀粉和果胶

1 引言。发展多年生饲料用灌木不仅可获得充足的饲料源,还可防止水土流失,保护生态环境。淀粉和果胶是饲料用灌木中的重要营养成分,其含量测定对饲料用灌木营养评价具有重要意义。为了快速准确地测定饲料用灌木中的淀粉和果胶,研究了用高效液相色谱法同时测定淀粉和果胶的方法;样品中淀粉和果胶在盐酸介质中被水解为葡萄糖和半乳糖醛酸,然后用高效液相色谱分离测定葡萄糖和半乳糖醛酸含量,再换算成淀粉和果胶含量。由于淀粉和果胶可同时测定,和常规方法相比,该方法更为简便快速。     

基于空间组学-临床影像技术的肿瘤精准诊断

作为全球公共卫生事件,恶性肿瘤严重影响人类健康、寿命和生活质量。肿瘤的发生发展经历了极其复杂的过程,表现出高度的时空异质性,影响其转移和耐药。为探寻这种异质性,多种临床影像技术和空间组学技术得以飞速发展。其中,临床影像技术准确率高但无法提供高通量的生物分子信息。空间组学技术可以获得标本的多种生物学特征,包括基因、蛋白和代谢等,但无法提供在体信息。将临床影像和空间组学技术相结合,可以优势互补,在临床和基础科学研究中具有较大应用前景,对于精确解析肿瘤的时空异质性和鉴别肿瘤分子分型、开展肿瘤精准诊断和发展进程预测等研究具有重要的推进作用。本文对该技术方法和特征进行了评述并展望了其发展趋势。     

单硝基甲苯和多硝基甲苯偶极矩的理论计算和实验测定

用 MINDO/3和 CNDO/2法对单硝基甲苯和多硝基甲苯的平衡几何构型进行了全优化和 SCF 计算,求得了o,m,p-MNT,2,3-,2,4-,2,5-,2,6-,3,4-,3,5-DNT 和2,3,4-,2,3,5-,2,3,6-,2,4,5-,2,4,6-以及3,4,5-TNT 的“气相”偶极矩。用折射法实测了 MNT 和 DNT 共9种化合物在 CCl_4溶液中的偶极矩。计算值和实测值之间存在良好的线性关系。以甲苯和硝基苯的计算值通过“向量加和”近似地估算了 MNT,DNT 和 TNT的偶极矩,估算值与上述实验值和量子化学计算值之间也线性相关。     

北京宏剑讯科软件技术有限公司常用化学软件

Gaussian0 3———业界应用最广泛的量子化学软件 ,是作半经验计算和从头计算使用最广泛的量子化学软件。可以研究 :分子能量和结构 ,过渡态的能量和结构化学键以及反应能量 ,分子轨道 ,偶极矩和多极矩 ,原子电荷和电势 ,振动频率 ,红外和拉曼光谱 ,NMR ,极化率和超极化率 ,热力学性质 ,反应路径。计算可以模拟在气相和溶液中的体系 ,模拟基态和激发态 ,还可以对周期边界体系进行计算。公司每月一期G0 3软件培训ADF———化学家的通用密度泛函程序 ,专门作密度泛函计算的软件。ADF基于密度泛函理论 (DFT) ,主要应用于量子化学计算。广…     

金属合金化学

门捷列夫元素周期系有七十以上的元素属於金属,它们位於周期表的左部和下部。周期系第一和第八族的许多元素,都属於金属。金属和非金属不同的地方,是它们的物理性、化学性和机械性。所有金属都有结晶的构造,其中许多具有高度的坚固性,电和热的传导性,以及可塑性。这些在技术上重要的性质,决定着金属在实践中的广泛应用。固态金属所固有的物理性和机械性质,决定於内部构造和原子间键的性质。和离子键或共价键不     

Syntheses of vinyl polymers with pendant porphyrin dimers and their catalytic effects on photoreductions

Vinyl copolymers with pendant porphyrin dimers were synthesized first by the dimerizations of chlorophyll-α and protoporphyrin IX via the ethylenebisamide linkage, then by copolymerization of the vinylbenzyl esters of the resulting dimers with N-vinylpyrrolidone or the esterification reaction of the dimers with chloromethylstyrene copolymers. Dimer-pendant copolymers with vinyl pyrrolidone catalyzed photoredox systems in aqueous solutions more efficiently than the corresponding monomer analogs, presumably because of the interactions exerted between the two combined porphyrin rings, which are manifested in the hypochromic effect in absorption spectra. The effect of the central Mg atom in the protoporphyrin IX ring was also considerable.     

Click synthesis of ubiquitin dimer analogs to interrogate linkage-specific UBA domain binding

A new route to the synthesis of triazole-linked ubiquitin dimers (diUbs) as structural analogs of the seven diUbs is reported. Binding studies with the Lys48-specific UBA domain of the Mud1 protein suggest that they represent functionally suitable surrogates of their native counterparts linked by an isopeptide bond.     

Carbocyclic Analogs of Nucleosides. Part 4. Preparation of enantiomerically pure analogs of purine nucleosides for the synthesis of sulfone-linked oligonucleotide analogs

Cyclopentane derivatives bearing a 3-(hydroxymethyl) group, a 4-(2-hydroxyethyl) functionality, and a nucleoside base are carbocyclic variants of nucleoside analogs previously described as building blocks for the preparation of oligonucleotide analogs having dimethylene sulfone (= methanosulfonylmethano) linking groups replacing the phosphodiester linking units found in natural oligonucleotides. These carbocyclic nucleoside analogs (e.g. 17 and 20 ) are stable to both acid-catalyzed depurination and base-catalyzed hydrolysis, in contrast with most non-ionic analogs of oligonucleotides. Furthermore, they can be prepared with complete control over the stereochemistry at the ‘anomeric’ center. A procedure is given for preparing these purine-nucleoside analogs via the construction of an enantiomerically pure carbocyclic skeleton (Schemes 1–3), followed by a Mitsunobu-type reaction to introduce the purine-base derivatives (Scheme 4). Furthermore, preliminary results for the coupling of these analogs to yield nucleoside dimers (e.g. 26 ) are also reported (Scheme 5).     

Proton-bound homodimers involving second-row atoms

High-level ab initio quantum chemical calculations (G4(MP2)//MP2/6-311+G(2df,p)) have been used to examine homodimers of second-row bases, and to compare the results with those obtained previously for the first-row analogs. The relationship between the binding energies of the dimers and the proton affinities (PAs) of the bases follows the same pattern as that for the first-row systems, with the binding energies initially increasing with increasing proton affinity but subsequently decreasing. This may be attributed to the opposing effects of increased PA on the hydrogen-bond donor and hydrogen-bond acceptor. The binding energies are generally smaller for the second-row dimers than for the corresponding first-row dimers. There is an increased tendency for asymmetrical hydrogen bonds in homodimers of the second-row compared with first-row dimers. This may be attributed to the lower electronegativities of second-row atoms relative to their first-row counterparts, and to the longer internuclear separation between the hydrogen-bonded second-row atoms.     

Amphiphilic Dipyrrinones

Summary. Replacing the typical lactam β-alkyl substituents of xanthobilirubinic acid and kryptopyrromethenone, two bilirubin analogs long used as model compounds in studies of its photochemistry and metabolism, leads to increased amphiphilicity. Synthesized by base-catalyzed condensation of 3,4-dimethoxypyrrolin-2-one with the appropriate pyrrole α-aldehyde, the 2,3-dimethoxyl analogs of xanthobilirubinic acid and kryptopyrromethenone are yellow-colored dipyrrinones that form intermolecular hydrogen-bonded dimers in the solid, as determined by X-ray crystallography, and in CHCl₃, as revealed by ¹H NMR and vapor pressure osmometry. These two new dipyrrinones are approximately ten times more soluble in water than their parent dipyrrinones.     

Syntheses and reactions of some 4,5-dihaloimidazole-2-carboxylic acid derivatives

The preparation of 5H,10H-diimidazo[1,2-a:1′,2′-d]pyrazine-5,10-dione ( 2a ) and its 2,3,7,8-tetrabromo- and 2,3,7,8-tetrachloro- analogs ( 2b and 2c , respectively) is reported. These dimers, when allowed to react with various anilines, afford imidazole-2-carboxamides ( 3a-c ).     

The ground-state tunneling splitting of various carboxylic acid dimers

Carboxylic acid dimers in gas phase reveal ground-state tunneling splittings due to a double proton transfer between the two subunits. In this study we apply a recently developed accurate semiclassical method to determine the ground-state tunneling splittings of eight different carboxylic acid derivative dimers (formic acid, benzoic acid, carbamic acid, fluoro formic acid, carbonic acid, glyoxylic acid, acrylic acid, and N,N-dimethyl carbamic acid) and their fully deuterated analogs. The calculated splittings range from 5.3e-4 to 0.13 cm(-1) (for the deuterated species from 2.8e-7 to 3.3e-4 cm(-1)), thus indicating a strong substituent dependence of the splitting, which varies by more than two orders of magnitude. One reason for differences in the splittings could be addressed to different barriers heights, which vary from 6.3 to 8.8 kcal/mol, due to different mesomeric stabilization of the various transition states. The calculated splittings were compared to available experimental data and good agreement was found. A correlation could be found between the tunneling splitting and the energy barrier of the double proton transfer, as the splitting increases with increased strength of the hydrogen bonds. From this correlation an empirical formula was derived, which allows the prediction of the ground-state tunneling splitting of carboxylic acid dimers at a very low cost and the tunneling splittings for parahalogen substituted benzoic acid dimers is predicted.     

Novel tetrahydrofuran structures derived from beta-beta-coupling reactions involving sinapyl acetate in Kenaf lignins

Free radical coupling of sinapyl gamma-acetate or cross-coupling between sinapyl acetate and sinapyl alcohol yields novel tetrahydrofuran beta-beta-(cross-)coupled dehydrodimers. Such substructures are therefore anticipated in naturally acetylated lignins, e.g. in Kenaf, if sinapyl acetate is a component of the lignin monomer pool. The DFRC (derivatization followed by reductive cleavage) method, modified by replacing all acetyl reagents and solvents with their propionyl analogs (DFRC'), allows the analysis of naturally acetylated lignins. DFRC' treatment of the sinapyl acetate-derived dimers or crossed dimers gave diagnostic products that retain at least one acetate group on a sidechain gamma-position; the products have been authenticated by comparison of their mass spectra and GC retention times with those of synthesized compounds. DFRC' of Kenaf lignins produces the same diagnostic products as from the dimers, implicating the presence of the various tetrahydrofuran units in Kenaf lignins. With data from the model compounds in hand, NMR analysis of Kenaf lignins elegantly confirms the presence of such substructures in the polymer, establishing that acetates on Kenaf lignins arise through incorporation of sinapyl acetate, as a lignin precursor, via enzyme-mediated radical coupling mechanisms.     

Explaining the structure of the OH stretching band in the IR spectra of strongly hydrogen-bonded dimers of phosphinic acid and their deuterated analogs in the gas phase: a computational study

We present a simulation of the OH stretching band in the gas-phase IR spectra of strongly hydrogen-bonded dimers of phosphinic acid and their deuterated analogs [(R(2)POOH(D), with R = CH(2)Cl, CH(3)], which is based on a model for a centrosymmetric hydrogen-bonded dimer that treats the high-frequency OH stretches harmonically and the low-frequency intermonomer (i.e., O···O) stretches anharmonically. This model takes into account the following effects: anharmonic coupling between the OH and O···O stretching modes; Davydov coupling between the two hydrogen bonds in the dimer; promotion of symmetry-forbidden OH stretching transitions; Fermi resonances between the fundamental of the OH stretches and the overtones of the in- and out-of-plane bending modes involving the OH groups; direct relaxation of the OH stretches; and indirect relaxation of the OH stretches via the O···O stretches. Using a set of physically sound parameters as input into this model, we have captured the main features in the experimental OH(D) bands of these dimers. The effects of key parameters on the spectra are also elucidated. By increasing the number and strength of the Fermi resonances and by promoting symmetry-forbidden OH stretching transitions in our simulations, we directly see the emergence of the ABC structure, which is a characteristic feature in the spectra of very strongly hydrogen-bonded dimers. However, in the case of the deuterated dimers, which do not exhibit the ABC structure, the Fermi resonances are found to be much weaker. The results of this model therefore shed light on the origin of the ABC structure in the IR spectra of strongly hydrogen-bonded dimers, which has been a subject of debate for decades.