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201.
A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal
thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by
the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary
estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced
amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more
accurate techniques for vapor pressure assessment. 相似文献
202.
203.
A new kinetic-catalytic method by the initial rate procedure for the determination of nanogram level of iron(III) is developed, which is based on its catalytic effect on the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with N,N-dimethylaniline (DMA) to form an indamine dye (λmax=590 nm) in the presence of hydrogen peroxide. Iron(II) is also determined, being oxidized to iron(III) by hydrogen peroxide. Calibration graphs obtained by the initial rate method are linear in the range 1–1000 ng ml−1 Fe and as low as 10−8 M Fe(II, III) can easily be determined. The relative standard deviations are 6.6, 2.5 and 1.5% for ten determinations of 1, 20 and 60 ng ml−1 of Fe(III), respectively. The method is applicable to the determination of iron in natural waters without preconcentration and separation. 相似文献
204.
A new fertilizer of cocrystal type,known as durably efficacious ammonium bicarbonate (DEAB),has been developed by adding a certain amount of dicyandiamide (DCD) as an ammonia-stabilizing agent to ammonium bearbenate(AB)during the process of its production.As compared with AB,DEAB was found to have a reduction of direct volatilization loss by 53%,a fertilizer availability period prolonged from 35-45 to 90-110 d,and an increase in the rate of nitrogen in fertilizer being utilized by 5.9%-10.2%,and a saving of the amount of fertilizer to be ap-phed by 20%-30% for the same level of yield,or an increase of the crop yield by over 10% for the same level of ni-tregen fertilization;in addition,it was found to show usually a function of promoting the crop to early mature.It can be apptied as basal dressing all in one time to soil and thus also used as a labour-saving and crop yield-increasing fertil-izer for is non-mtertillage,plastics film covering and water-saving agriculture 相似文献
205.
The reaction of fluorobenzene with urotropine in trifluoroacetic acid (TFAA) at high pressures and temperatures affords predominantly fluorobenzaldehydes andN-(fluorophenylmethyl)trifluoroacetamides. The yields of these products depend considerably on the reaction conditions. The rates of their formation have the maximum values at the momemt of the phase transition (PT) of TFAA. A new efficient cyclic (dynamic) regime is proposed for the synthesis at high pressures. The regime involves periodically occurring PT of the solvent. The change in the relative rate of product formation with the degree of fluorobenzene conversion is wave-like.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 319–323, February, 1995. 相似文献
206.
钴(II)-联吡啶-α-氨基酸的热力学和动力学研究 总被引:3,自引:0,他引:3
关于联吡啶为第一配体的二元、三元配合物的热力学和动力学性质的研究,以铜(Ⅱ)作为中心离子最为多见,而以钴(Ⅱ)作为中心离子的报导较少.实验表明,过渡金属钻(Ⅱ)能与大多数的生物配体、大π共轭体系形成相当稳定的二元、三元配合物,是生物功能模拟的一个具有应用价值的中心离子·钴(Ⅱ)卟啉可以代替铁(Ⅱ)卟啉,模拟血红蛋白、肌红蛋白[1],在生物体内起到输送氧的作用.为了充分了解钴(Ⅱ)与生物配体的配伍能力、配位方式以及其配位过程的动态行为,为推动钴(Ⅱ)配合物及其生物功能的模拟研究,本文分别采用PH电位法… 相似文献
207.
在束-气条件下,通过检测产物的化学发光,研究了亚稳电子激发态He(23S)原子与CH3Cl、CH3I传能反应.采用参比反应的方法,测得了由上述反应产生的主要碎片CH(A2△)、CH(B2∑-)、CH(C2∑+)和H*形成速率常数.通过对测得的CH(A2△-X2∏r)和CH(B2∑--X2∏r)色散谱进行计算机模拟,获得了初生态的CH(A2△,v=0-2)和CH(B2∑-,v=0态)的振动-转动布居,实验结果表明,CH(A2△,v=0)态的转动布居是呈双Boltzman分布的,并且反应的可资用能大部分将转变成产物的平动能.根据实验结果和反应阈能的分析,本文对He(23S)与CH3Cl/CH3I传能反应机理进行了探讨。 相似文献
208.
Historically, due to the size and nature of the instrumentation, highly skilled laboratory professionals performed clinical
testing in centralized laboratories. Today’s clinicians demand realtime test data at the point of care. This has led to a
new generation of compact, portable instruments permitting ”laboratory” testing to be performed at or near the patient’s bedside
by nonlaboratory workers who are unfamiliar with testing practices. Poorly controlled testing processes leading to poor quality
test results are an insidious problem facing point of care testing today. Manufacturers are addressing this issue through
instrument design. Providers of clinical test results, regardless of location, working with manufacturers and regulators must
create and manage complete test systems that eliminate or minimize sources of error. The National Committee for Clinical Laboratory
Standards (NCCLS) in its EP18 guideline, ”Quality management for unit-use testing,” has developed a quality management system
approach specifically for test devices used for point of care testing (POCT). Simply stated, EP18 utilizes a ”sources of error”
matrix to identify and address potential errors that can impact the test result. The key is the quality systems approach where
all stakeholders – professionals, manufacturers and regulators – collaboratively seek ways to manage errors and ensure quality. We illustrate the use of one quality systems approach, EP18, as a means to advance the quality of test results at point of
care.
Received: 26 June, 2002 Accepted: 17 July 2002
Presented at the European Conference on Quality in the Spotlight in Medical Laboratories, 7–9 October 2001, Antwerp, Belgium
Abbreviations NCCLS National Committee for Clinical Laboratory Standards (formerly) · POCT point of care testing · QC quality control ·
HACCP hazard analysis critical control points · CLIA clinical laboratory improvement amendments (of 1988)
Correspondence to S. S. Ehrmeyer 相似文献
209.
Nikos G. Tsierkezos 《Journal of solution chemistry》2007,36(10):1301-1310
The reduction of benzophenone (Bzph) in 3-pentanone (PEN), acetone (ACE), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), acetonitrile (ACN) and dimethyl sulfoxide (DMSO) with n-tetrabutylammonium hexafluorophosphate (TBAPF6) as background electrolyte was studied using the technique of cyclic voltammetry at the temperature of 263.15 K. The half-wave
potentials (E
1/2) were extracted. The reduction of Bzph occurs in two successive one-electron steps to produce first the free radical anion
Bzph− and then the dianion Bzph2−. The results indicated that the radical anion Bzph− is reoxidized to Bzph in all investigated solvent media whereas the dianion Bzph2− is reoxidized to Bzph− only in THF. The heterogeneous electron-transfer rate constants (k
s
) were evaluated by employing the electrochemical rate equation proposed by Nicholson. The rate of electron transfer for the
Bzph/Bzph− couple was found to be relatively slow in all investigated solvent media. Consequently, the electron-transfer processes can
be recognized as quasi-reversible. The diffusion coefficients (D) of Bzph in the investigated solvent media have been calculated using the modified Randles-Sevcik equation. The effect of
the physical and chemical properties of the solvent medium on the electrochemical behavior of Bzph has been examined. 相似文献
210.
The pretreatment of waste-activated sludge (WAS) by electron beam irradiation was studied in order to improve anaerobic sludge
digestion. The irradiation dose of the electron beam was varied from 0.5 to 10 kGy. Batch and continuous-flow stirred tank
reactors (CFSTRs) were operated to evaluate the effect of the electron beam pretreatment on anaerobic sludge digestion. Approximately
30–52% of the total chemical oxygen demand (COD) content of the WAS was solubilized within 24 h after electron beam irradiation.
A large quantity of soluble COD, protein, and carbohydrates leached out from cell ruptures caused by the electron beam irradiation.
Volatile fatty acids production from the irradiated sludge was approx 90% higher than that of the unirradiated sludge. The
degradation of irradiated sewage sludge was described by two distinct first-order decay rates (k
1 and k
2). Most initial decay reaction accelerated within 10 d, with an average k
1 of 0.06/d for sewage sludge irradiated at all dosages. The mean values for the long-term batch first-order decay coefficient
(k
2) were 0.025/d for irradiated sewage sludge and 0.007/d for unirradiated sludge. Volatile solids removal efficiency of the
control reactor fed with unirradiated sewage sludge at a hydraulic retention time (HRT) of 20 d was almost the same as that
of the CFSTRs fed with irradiated sludge at an HRT of 10 d. Therefore, disintegration of sewage sludge cells using electron
beam pretreatment could reduce the reactor solid retention time by half. 相似文献