From adapted and computerized thermomechanical equipments to modelling and the time-evolution behaviour in Cu−Zn−Al shape memory alloys

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.     

A Facile Method to Determine the Absolute Structure of Achiral Molecules: Supramolecular‐Tilt Structures

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.     

New class of multibit sigma-delta modulators using multiratearchitecture

A new multibit sigma-delta modulator is presented where the analogue-to-digital converter in the forward path is replaced by an increase in the clock rate of the integrators in the final stages. Theoretical and simulation results are presented for second- and third-order modulators     

Simple technique for op amp continuous-time 1 V supply operation

A simple scheme for achieving continuous-time low-voltage operation of op amps is discussed. The scheme involves placing a floating battery in series with one of the op amp input terminals. Simulations and experimental results are presented that verify the proposed scheme with the example of a CMOS op amp that operates from a single 1 V supply and with 0.8 V signal swing     

Ion transfer through solvent polymeric membranes driven by an exponential current flux

General analytical equations which govern ion transfer through liquid membranes with one and two polarized interfaces driven by an exponential current flux are derived. Expressions for the transient and stationary E-t, dt/dE-E and dI/dE-E curves are obtained, and the evolution from transient to steady behaviour has been analyzed in depth. We have also shown mathematically that the voltammetric and stationary chronopotentiometric I(N)-E curves are identical (with E being the applied potential for voltammetric techniques and the measured potential for chronopotentiometric techniques), and hence, their derivatives provide identical information.     

The structure of azines derived from C‐formyl‐1H‐imidazoles in solution and in the solid state: tautomerism,configurational and conformational studies

The structures of three azines derived from 2‐formylimidazole, 4(5)‐formylimidazole, and 4(5)‐formyl‐5(4)‐methylimidazole have been determined in solution and in the solid state. Density Functional Theory (DFT) Polarizable Continuum Model (PCM) calculations (geometries, energies, and chemical shifts), NMR [solution and cross polarization magic‐angle spinning (CPMAS)], and X‐ray crystallography [azine of 4(5)‐formylimidazole] have been used. The configuration around the central C = N bonds has been determined and some insights about prototropic tautomerism and conformation have been gained. Copyright © 2013 John Wiley & Sons, Ltd.     

Generation of AsH(3) from As(V) in the absence of KI as prereducing agent: Speciation of inorganic arsenic

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.