Effect of temperature — Time factors on the yield point of crystalline polymers in the flat stressed state (high-density polyethylene)

Conclusions 1. Experiments have been performed on biaxial stretching of HDPE over a wide range in ratios of the principal stress components, strain rates, and temperature. The character of change in the limiting characteristics of HDPE are different in different temperature regions.2. The limiting resistance of HDPE in the flat stressed state for T=const and v_i=const is described satisfactorily by the Malmeister and Gol'denblat-Kopnov criteria.3. Prediction of the limiting resistance of HDPE should be carried out within limited temperature ranges, in which similarity of strain diagrams, a similar character of structural changes in the material (accumulation of damage), and identical character of change in its limiting characteristics are observed.Okhtinsk "Plastpolimer" Scientific and Production Union, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 247–254, March–April, 1977,     

Raman effect of light on argon atoms

Scalar scattering of light on the 3p and 3s subshells of the argon atom (Stokes scattering) and anti-Stokes scattering on the excited 4p and 4s states of argon are examined in the Hartree-Fock approximation. The calculation is made in a velocity form and in a length form. It is shown that the value in the r form is 1.5–2 times greater than in the form.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 36–42, January, 1977.     

聚L-苏氨酸修饰电极对多巴胺和肾上腺素的电催化氧化

利用循环伏安法将L-苏氨酸聚合修饰在玻碳电极表面, 制成聚L-苏氨酸修饰电极. 实验表明, 该电极对多巴胺和肾上腺素都有较好的催化氧化效果. 运用循环伏安法详细研究了修饰电极的电化学性质. 在pH 2.5的磷酸盐缓冲溶液(PBS)中, 肾上腺素的电子传递系数为0.51, 表观反应速率常数为1.33 s-1; 在pH 7.5的PBS中, 多巴胺在电极上产生一对氧化还原峰, 多巴胺在电极上的电子传递系数为0.60, 表观反应速率常数为0.92 s-1. 该修饰电极对多巴胺和肾上腺素能够进行同时测定, 还原峰电流与多巴胺和肾上腺素浓度分别在1.0×10-6-5.0×10-4 mol·L-1和3.0×10-6-1.0×10-4 mol·L-1范围内呈现良好的线性关系.     

SiHCl3-H2气相外延生长Si单晶反应机理的理论研究

采用密度泛函理论计算方法, 在B3LYP/6-311G*水平下, 计算并得到了SiHCl3与H2反应各反应通道上各驻点的构型、振动频率和能量. 结果表明, 在气相中SiHCl3分解的通道d和SiHCl3与H2反应的通道c为竞争反应, 但其均未还原出Si原子, 只有衬底Si参与SiHCl3-H2的反应, Si原子才淀积在Si衬底上.     

α-乙酰氧基-N-亚硝基吡咯烷的解离及其致癌代谢机理的理论研究

用ab initio方法, 在MP2/6-31G**水平下讨论了α-乙酰氧基-亚硝基吡咯烷(α-Acetoxy-NPYR)在各种条件下的解离反应机理, 并对形成终致癌物B, C, D的代谢机理进行研究. 发现在OH^－和H₂O作用下的解离都遵循羟基进攻羰基机理, OH^－作用下是一个经四面体中间体阴离子的无位垒过程, H₂O作用下有相对高的活化能(165.36 kJ/mol). H₃O^＋作用下是先形成阳离子产物的S_N1过程, 并没有发现遵循两种综合的解离情形. 同时, 羟基化产物异构化为终致癌物B, C, D是一个相对容易进行的过程.     

Itosides A – I,New Phenolic Glycosides from Itoa orientalis

Eight new benzoylated gentisyl alcohol (=2‐(hydroxymethyl)benzene‐1,4‐diol) glucosides, itosides A–H ( 1 – 8 ), together with the new pyrocatechol (=benzene‐1,2‐diol) glycoside itoside I ( 9 ) were isolated from the bark and twigs of Itoa orientalis (Flacourtiaceae). In itosides B–D ( 2 – 4 ), the gentisyl alcohol moiety was esterified by 1‐hydroxy‐6‐oxocyclohex‐2‐ene‐1‐carboxylic acid, while itosides E–H ( 5 – 8 ) contained instead an additional 2‐hydroxybenzoic acid moiety. The compounds were accompanied by the known derivatives 4‐hydroxytremulacin ( 10 ), poliothyrsoside ( 11 ), poliothyrsin ( 12 ), homaloside D ( 13 ), tremulacin, and pyrocatechol β‐D ‐glucopyranoside. The structures of the new compounds were elucidated by spectral and chemical methods.     

Synthesis and properties of the copper(Ⅱ) complexes with stable radical

Four novel copper(Ⅱ) complexes have been synthesized,namely Cu(hfac)2NITPhNO2 (1),Cu(hfac)2NITPhCH3 (2),Cu(pfpr)2NITPhNO2,(3) and Cu(Pfpr)2NITPhCH3 (4),where hfac= hexafluoro-acetylacetonate,pfpr=pentafluoropropionate,NITR.=2-R-4,4,5,5-tetraniethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide.(R=4-nitrophenyl,4-methylphenyl).These complexes were rharicter-ized by elemental analyses,IR,electronic spectra and molar conductance.The temperature-dependent magnetic susceptibility of complexes 1 and 3 have been studied in the 4 300 K range,giving I he exchange integral J=10.56 cm-1 for complex 1 and J =-30.9 cm-1 for complex 3.     

Azaindole derivatives

It is shown that it is possible to synthesize 1-acyl-4-methyl-7-azatryptamines from ethyl (4-methyl-7-aza-3-indolyl)acetate through 3-(-chloroethyl)-4-methyl-7-azaindole with subsequent acylation by replacement of halogen by a nitro group and reduction. The N-acetyl group is cleaved in the reaction of 1-acetyl-3-(-chloroethyl)-4-methyl-7-azaindole with ammonia, bis (dimethylmethoxysilyl)amide potassium salt, and potassium phthalimide (with subsequent removal of the phthalimide protective group).See [1] for communication XLII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1370–1373, October, 1973.     

Synthesis of 4-trifluoromethyl-7-hydroxycoumarin derivatives. Structure of 3-cyano-4-trifluoromethyl-7-acetoxycoumarin

A method was developed for the production of derivatives of 4-trifluoromethyl-7-hydroxycoumarin with electron-withdrawing groups (CN, CF₃CO) at position 3. The structure of 3-cyano-4-trifluoromethyl-7-acetoxycoumarin was proved by x-ray crystallographic investigation. The effect of the substituents on the geometry of the molecule is discussed.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Institute of Biochemistry, Academy of Sciences of Armenia, 375044 Erevan. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1371–1375, June, 1992.     

Structure and phase transitions in poly(diethylsiloxane)

The structure changes accompanying phase transitions in poly(diethylsiloxane) (PDES) have been studied by WAXS and SAXS techniques using oriented and isotropic samples. PDES may exist in two low-temperature modifications (the monoclinic α₁-form and presumably the “tetragonal” β₁-form) and two high-temperature modifications (the monoclinic α₂-form and the “tetragonal” β₂-form). In linear PDES the crystal - crystal transitions α₁–α₂ and β₁–β₂ occur near 214 and 206 K, respectively. At higher temperatures α₂ (280 K) and β₂ (290 K) forms transform into the mesomorphic phase α_m that gradually melts at 280–300 K giving an amorphous phase. According to x-ray and density data, α_m phase is also characterized by monoclinic structure slightly different from hexagonal packing.