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51.
Pelegrina J. L. Sade M. Auguet C. Torra V. Torralba A. 《Journal of Thermal Analysis and Calorimetry》1999,56(1):247-259
A non-differential calorimetric analyzer was developed for an INSTRON 1123 machine (a stress-strain-temperature analyzer)
with a temperature chamber INSTRON 1110. The study was performed using the Joule effect and pseudoelastic martensitic transformations
in single crystals of Cu-Zn-Al alloys. The analysis of the system establishes that: the sensitivity of calorimetric measurements
after a filter of two poles and two zeros is 166 mV W-1 (at 297 K), the noise is near 1.5 μV and the drift is close to 30 μV in 6 h. The reproducibility of the sensitivity working
with one sample is better than ±0.3%, and the change to a new sample keeps the value below ±0.5%. The uncertainty in reproducibility
in the martensitic transformation (including repositioning) does not overcome ±1.6%. The used calorimetric sensors limit the
temperature to 373 K. The furnace control originated fluctuations on the base line (near ±20 μV), which by means of an auxiliary
signal processing were reduced to 50% (less than ±10 μV).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
52.
Dr. Rosa María Tejedor Dr. Santiago Uriel Sara Graus Dr. Teresa Sierra Dr. José Luis Serrano Dr. Rosa M. Claramunt Dr. Concepción López Dr. Marta Pérez‐Torralba Dr. Ibon Alkorta Dr. José Elguero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):6044-6051
Achiral compounds 4‐methoxy‐4‐(p‐methoxyphenyl)cyclohexanoneethylene ketal ( 2 ), 4‐hydroxy‐4‐(p‐methoxy phenyl)cyclohexanoneethylene ketal ( 3 ), and 3,5‐dimethyl‐4‐nitropyrazole ( 4 ) crystallized in chiral structures and the samples showed an enantiomeric excess. We have determined the absolute structures of these compounds by using X‐ray diffraction with copper radiation at low temperatures. Moreover, we have also established the prevalent absolute structures in these samples, by comparing their calculated and solid‐state vibrational circular dichroism (VCD) spectra. The consistency of this method was confirmed by using (R,R)‐2,8‐diiodo‐4,10‐dimethyl‐6 H,12H‐5,11‐methano‐dibenzo[b,f][1,5]diazocine, Tröger′s base, (R,R)‐ 1 , as a chiral compound of known absolute configuration. 相似文献
53.
An in-depth study of the ion transfer facilitated by complexation in the organic phase (TOC mechanism) in liquid membrane systems of one and two polarized interfaces is carried out by taking into account the kinetic effects associated with the complexation reaction. Explicit analytical equations for the normal pulse voltammetric (I/E) and chronoamperometric (I/t) responses with an explicit dependence on the kinetic parameters of the chemical complexation are presented for both kinds of membrane system, which could be useful for modeling artificial and biological membranes. The equations are compared with those obtained by using the widely used approximation of total equilibrium conditions that leads to the transfer by interfacial complexation mechanism (TIC), which only depends on thermodynamic parameters. Simple methods are proposed that allow quantitative determination of the equilibrium and kinetic constants of the complexation reaction in the organic phase for both kinds of membrane system. 相似文献
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Using two similar high resolution computer controlled stress-strain-temperature set-up of equivalent resolution (1 mN, 0.1 μm, 5 mK) the detailed study of the martensitic transformation in single crystals of the Cu?Zn?Al shape memory alloys is realized. The devices can obtain 20 or 150 N in applied force, 2 or 4 mm in length and can be operated near room temperature (between 280 and 360 K). The analysis of the hysteresis domain in single crystals clearly visualises the intrinsic characteristics of the material (pseudoelasticity, nucleation, interface friction) and enables the obtenton of parameters for physical models of the hysteretic behaviour in force—lengthening—temperature and, eventually, time-dependent processes. The observation of time evolution shows the ‘recoverable martensite creep’ associated to a microstabilization process. 相似文献
56.
It is shown that the potassium iodide to the samples to reduce As(V) to AS(III) is not essential when total inorganic arsenic is determined by molecular spectrophotometry (trapping AsH(3) in Ag-DDTC) or by atomic-absorption spectrometry (if Ar flow-rate and NaBH(4) addition rate are controlled in 6M hydrochloric acid medium). Furthermore, in the presence of low concentration of organic arsenic, a method is reported for the selective determination of inorganic As(III) and As(V), based on the use of citrate/citric acid medium to determine As(III) and hydrochloric acid to determine total inorganic As. As(V) is determined by the difference between total inorganic As and As(III). The interference level of organic arsenic species (monomethylarsenic acid and dimethylarsenic acid) in the determination of total inorganic arsenic and AS(III) in 6M hydrochloric acid and citrate/citric acid medium respectively, is reported in the text. The developed method is applied to determine As(III) and As(V) in spiked, tap and waste waters and in lake sediments. 相似文献
57.
van Tiggelen BA Lagendijk A van Albada MP Tip A 《Physical review. B, Condensed matter》1992,45(21):12233-12243
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