The energies of dissociation of the N—O bonds in pyridine 1-oxide derivatives

The enthalpies of combustion of some pyridine derivatives in the solid state have been measured by precision bomb calorimetry, and their enthalpies of formation have been calculated. The enthalpies of sublimation of these compounds have been determined from the experimental temperature dependences of saturated vapor pressure using the Clausius-Clapeyron equation. The enthalpies of combustion, formation, and sublimation are the following (kJ mol^–1): -3360.9±2.1, -0.5±2.1, and 79.1±1.3, respectively, for 4-methylpyridine 1-oxide; -2551.0±1.7, 11.7±1.7, and 89.1±2.5, respectively, for 4-nitropyridine 1-oxide;-2355.6±1.3, 102.1±1.3, and 106.3±2.9 for 2,4,6-trinitropyridine 1-oxide; and -2287.6±1.3, 34.3±1.3, and 101.7±2.9 for 2,4,6-trinitropyridine. The enthalpies of formation in the solid state and the enthalpies of sublimation of pyridine derivatives obtained together with the literature data allowed the energies of dissociation of the donor-acceptor N—O bonds in pyridine 1-oxides to be calculated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 660–662, April, 1995.     

Shape analysis based critical Eotvos numbers for buoyancy induced partial detachment of oil drops from hydrophilic surfaces

Removal of oil drops from solid surfaces immersed in an aqueous medium is of interest in many applications. It has been shown that drop shape analysis can be used to predict conditions at which the stability limit of a lighter than water oil drop on a solid surface immersed in an aqueous bath is reached (Adv. Colloid Interface Sci. 98 (2002) 265). However the above analysis is restricted to cases where the contact angle made by the drop is below 90degrees and when the surface conditions result in a 'pinned' contact line. In this paper, it is shown that drop shape analysis can be used to predict the critical conditions at which drop stability limit is reached for drop contact angles of 90degrees and above, which is encountered with 'hydrophilic' surfaces. This critical condition can predict the occurrence of partial oil drop detachment, before complete removal due to 'roll-up', which occurs when the hydrophilic surface is adequately smooth which prevents 'pinning' of the contact line. The critical conditions at which partial drop detachment occurs can also be approximately predicted from simple force balances. It has been shown (Adv. Colloid Interface Sci. 98 (2002) 265) that for contact angles less than 90degrees, the critical limit based on shape analysis appears to resolve the differences that arise due to alternate expressions for capillary retention force. This paper shows that even for contact angles above 90degrees, the critical conditions predicted from the shape analysis resolves the differences in the predictions from the alternate force balances. Drop shape analysis used in this paper is based on the 'Arc-length' form of Young-Laplace or 'drop shape' equation, which is different from the 'Y vs X' form of the above equation that is used in Adv. Colloid Interface Sci. 98 (2002) 265. The above drop shape equation is solved by a fourth order Runge-Kutta technique and it is shown that for angles less than 90degrees, the two forms of the drop shape equation, predict almost identical values of the critical Eotvos number. This paper highlights the competing effects of interfacial tension lowering induced drop instability and 'roll-up', a term that is used to describe the retraction of the contact line of an oil drop on a surface, in being the primary c ause for drop detachment.     

Mass shifting roles of negative kernel mass in density estimation

f(x) is a univariate density in C ⁴ with bounded support. For any n and sufficiently small kernel bandwidths, the symmetric appendage of any negative mass, –U, to any smooth unimodal symmetric kernel of order p=2 shifts expected estimator mass from regions where f(x)>0 to regions where f(x)<0. For large n, the mean automatic kernel adaptation induced by –U is analyzed in the simplest MISE reduction scenario: The symmetric appendage of –U to the uniform kernel K(x, X) over MISE-optimal bandwidths reduces MISE by shifting K(x, X) mass asymmetrically across the observation X in the direction of decreasing |f(x)|.     

微波等离子体光谱法测定碲的研究

微波等离子体原子发射光谱法(MIPAES)测定碲,前人已作过一些工作。本文利用我们建立的微量进样系统与MIPAES联用,对碲的测定进行了研究。实验中发现,加入适量的SnCl_2可降低检出限约一个数量级,Te_(214.3nm)的检出限为5 ng/mL,同时还研究了碱金属卤化物对碲的测定的影响。     

Measurements of HO2 uptake coefficient on aqueous (NH4)2SO4 aerosol using aerosol flow tube with LIF system

The γ(HO₂) was elevated with increase of Cu(II) concentrations in aqueous (NH₄)₂SO₄ aerosol. The threshold of Cu(II) concentration was 10^-3 mol/L for the dramatic increase of γ(HO₂) to 0.1, suggesting sensitive γ(HO₂) value to concentration of transition metal ions in aerosol.     

固定pH滴定法测定弱酸弱碱性药物

报道一种水溶液吕测定弱酸弱碱性药物的新型滴定分析方法－固定ｐＨ滴定法，其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在ｐＨ值固定时为常数，对甲硝唑，盐酸美西律等离散常数在１０＾－８至１０＾－１１范围内的７种弱酸弱碱性药物进行测定。结果与药典法吻合，回收率在９９．４％～１００．６％，方法简便，快速，准确，制剂中的赋形剂及色物不影响测定。     

A sequence of electrophile induced cyclisation and concomitant N-deprotection of alkenylsulfinimines and alkenylsulfinamides as a direct route to cyclic or spirocyclic imines, pyrrolidines and piperidines

Alkenylsulfinimines and alkenylsulfinamides underwent electrophile induced cyclisation reactions with phenylselenyl bromide, iodine and bromine to cyclic and spirocyclic imines, pyrrolidines and piperidines with spontaneous cleavage of the protective group at nitrogen in good to excellent yield.     

硅酸及其盐的研究 ⅩⅩⅠ.三甲基硅烷化-气相色谱法测定单硅酸的离解常数

单硅酸的离解常数是表征其基本性质的重要数据,前人已有不少工作,但由于测定的方法和实验条件不同,所得数据很不一致。     

粉煤灰空心微珠沸石化制备复合空心球

采用晶种静电吸附-诱导转化技术，成功地将选自工业废弃物粉煤灰的空心微 球转化为具有沸石/莫来石双层复合球壳结构的空心球，用XRD和SEM等手段对产物 进行了表征，并对球壳的转化机理进行了讨论。