Cooxidation of anilides and oxalic acid by chromic acid: A one‐step,three‐electron oxidation

The chromic acid oxidation of a mixture of oxalic acid and anilides proceeds much faster than that of either of the two substrates alone. The oxidation kinetics of acetanilide, p‐methyl‐, p‐chloro‐, and p‐nitroacetanilides by Cr(VI) in the presence of oxalic acid in aqueous acetic acid medium follows first‐order, zero‐order, and second‐order dependence in [oxidant], [substrate], and in [oxalic acid], respectively, while the oxidation kinetics of benzanilide, p‐methyl‐, p‐chloro‐, and p‐nitrobenzanilides follow first order in [oxidant] and fractional order each in [substrate] and [oxalic acid] and yields corresponding azobenzenes and benzaldehydes in the case of benzanilide and substituted benzanilides as the main products of oxidation. Aluminium ions suppress the reaction. The intermediate is believed to be formed from the anilide and a chromic acid‐oxalic acid complex. In the proposed mechanism, the rate‐limiting step involves the direct reduction of Cr(VI) to Cr(III). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 21–28, 2001     

具临界位势和权函数的非线性双调和问题

本文考虑具有临界位势和临界权函数的四维非线性重调和问题,证明非平凡解的存在性.     

Functionalized guanidinium chloride based colourimetric sensors for fluoride and acetate: single crystal X-ray structural evidence of -NH deprotonation and complexation

A series of new symmetrically functionalized guanidinium chlorides (S1-S10) are synthesized in good yields and their sensing ability toward anions is studied in MeCN-DMF (24?:?1) (v/v). The absorption bands of these molecules in the presence of anions are tuned by varying the functional groups attached to the guanidinium moiety (which resembles urea) with respect to (i) aromaticity (S1-S4), (ii) electron induction effect (S1, S5-S9), (iii) positional isomeric effect (S7-S9), (iv) indole functionality (S10) of the conjugated aryl units. Anions that are above Cl(-) in the Hofmeister series (F(-), AcO(-), H(2)PO(4)(-)) are eligible as an analyte in this series of molecules whereas less basic anions than Cl(-) do not cause any interference. Thus, this series of molecules are suitable for the detection of anions in the narrow window of the Hofmeister series. Out of all the anions, only fluoride causes vivid colour changes from yellow to red to reddish orange and finally to blue, irrespective of the increasing aromaticity, induction and positional isomeric effect of the substituent that is attached to the guanidinium moiety. Interestingly, S9 has shown the ability to sense distinctly both F(-) and AcO(-) colourimetrically. Further S10, a sensor attached with indole functionality shows selective sensing of F(-) colourimetrically with a NIR signature at ～930 nm though both these outputs are very unstable in nature. Stability constants for complex formation of S1-S10 (except S5) with F(-), AcO(-) are calculated by UV-vis titration experiments. Finally single crystal X-ray structural studies on the species 1 formed upon treating S6 with sodium fluoride confirms -NH deprotonation, whereas the reaction of S6 and S2 with sodium benzoate shows 1:1 host:guest binding that results in complexes 2 and 3 respectively.     

A chelation enhanced selective fluorescence sensing of Hg2+ by a simple quinoline substituted tripodal amide receptor

Two tris(2-aminoethyl)amine (tren) based tripodal amide fluoroionophores, 1 and 2, functionalized with quinoline (chelating fluorophore) and naphthalene (non-chelating fluorophore) respectively, are synthesized in good yields. Fluoroionophore 1 shows a selective UV-Vis spectral shift in the case of Hg(2+) in acetonitrile among different metal ions like Li(+), Na(+), Ca(2+), Mg(2+), Cr(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+). On the other hand, fluoroionophore 2 shows no selectivity towards any of the above metal ions in the UV-Vis study. Furthermore, 1 shows a selective chelation induced fluorescence enhancement in the presence of Hg(2+) whereas 2 shows the enhancement of fluorescence with most of the metal ions via a photoinduced charge transfer mechanism. The naked eye detection of Hg(2+) in an acetonitrile solution of 1 shows a greenish fluorescence upon UV light irradiation. The isolated Hg(2+) complex of 1, 3, shows a similar UV-Vis and fluorescence spectral output as observed from in situ spectroscopic studies of 1 in the presence of Hg(2+). Infra-red (IR) and (1)H- NMR studies also reveal the interaction of Hg(2+) with the quinoline nitrogen atoms as well as with the amide functionality.     

Electropatterning—Contemporary developments for selective particle arrangements employing electrokinetics

The selective positioning and arrangement of distinct types of multiscale particles can be used in numerous applications in microfluidics, including integrated circuits, sensors and biochips. Electrokinetic (EK) techniques offer an extensive range of options for label-free manipulation and patterning of colloidal particles by exploiting the intrinsic electrical properties of the target of interest. EK-based techniques have been widely implemented in many recent studies, and various methodologies and microfluidic device designs have been developed to achieve patterning two- and three-dimensional (3D) patterned structures. This review provides an overview of the progress in electropatterning research during the last 5 years in the microfluidics arena. This article discusses the advances in the electropatterning of colloids, droplets, synthetic particles, cells, and gels. Each subsection analyzes the manipulation of the particles of interest via EK techniques such as electrophoresis and dielectrophoresis. The conclusions summarize recent advances and provide an outlook on the future of electropatterning in various fields of application, especially those with 3D arrangements as their end goal.     

A Machine Learning Model for the Prognosis of Pulseless Electrical Activity during Out-of-Hospital Cardiac Arrest

Pulseless electrical activity (PEA) is characterized by the disassociation of the mechanical and electrical activity of the heart and appears as the initial rhythm in 20–30% of out-of-hospital cardiac arrest (OHCA) cases. Predicting whether a patient in PEA will convert to return of spontaneous circulation (ROSC) is important because different therapeutic strategies are needed depending on the type of PEA. The aim of this study was to develop a machine learning model to differentiate PEA with unfavorable (unPEA) and favorable (faPEA) evolution to ROSC. An OHCA dataset of 1921 5s PEA signal segments from defibrillator files was used, 703 faPEA segments from 107 patients with ROSC and 1218 unPEA segments from 153 patients with no ROSC. The solution consisted of a signal-processing stage of the ECG and the thoracic impedance (TI) and the extraction of the TI circulation component (ICC), which is associated with ventricular wall movement. Then, a set of 17 features was obtained from the ECG and ICC signals, and a random forest classifier was used to differentiate faPEA from unPEA. All models were trained and tested using patientwise and stratified 10-fold cross-validation partitions. The best model showed a median (interquartile range) area under the curve (AUC) of 85.7(9.8)% and a balance accuracy of 78.8(9.8)%, improving the previously available solutions at more than four points in the AUC and three points in balanced accuracy. It was demonstrated that the evolution of PEA can be predicted using the ECG and TI signals, opening the possibility of targeted PEA treatment in OHCA.     

Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD

This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface.     

Resonance Energy Transfer Studies from Derivatives of Thiophene Substituted 1,3,4-Oxadiazoles to Coumarin-334 Dye in Liquid and Dye-Doped Polymer Media

In the present work, we have carried out energy transfer studies using newly synthesised derivatives of thiophene substituted 1,3,4-oxadiazoles namely, 2-(-4-(thiophene-3-yl)phenyl)-5-(5-(thiophene-3-yl)thiophene-2-yl)-1,3,4-oxadiazole [TTO], 2-(-4-(benzo[b]thiophene-2-yl)phenyl)-5-(5-(benzo[b]thiophene-2-yl)-1,3,4-oxadiozole [TBO] and 2-(4-(4-(trifluoromethyl)phenyl)phenyl)-5-(5-(4-(trifluoromethyl)phenyl)thiophen-2-yl)-1,3,4-oxadiazole [TMO] as donors and laser dye coumarin-334 as acceptor in ethanol and dye-doped polymer (poly(methyl methacrylate) (PMMA)) media following steady-state and time-resolved fluorescence methods. Bimolecular quenching constant (k _q), translation diffusion rate parameter (k _d), diffusion length (D _l), critical transfer distance (R ₀), donor- acceptor distance (r) and energy transfer efficiency (E _T) are calculated. It is observed that, critical transfer distance is more than the diffusion length for all the pairs. Further, bimolecular quenching constant is also more than the translation diffusion rate parameter. Hence, our experimental findings suggest that overall energy transfer is due to Förster resonance energy transfer (FRET) between donor and acceptor in both the media and for all the pairs. In addition, considerable increase in fluorescence intensity and energy transfer efficiency is observed in dye-doped polymer matrix systems as compared to liquid media. This suggests that, these donor-acceptor pairs doped in PMMA matrix may be used for applications such as energy transfer dye lasers (ETDL) to improve the efficiency and photostability, to enhance tunability and for plastic scintillation detectors.     

Structural,optical, and electrical properties of electron beam evaporated CdSe thin films

CdSe films have been deposited on glass substrates at different substrate temperatures between room temperature and 300 °C. The films exhibited hexagonal structure with preferential orientation in the (002) direction. The crystallinity improved and the grain size increased with temperature. Band gap values are found decreasing from about 1.92 eV to 1.77 eV with increase of the substrate temperature. It is observed that the resistivity decreases continuously with temperature. Laser Raman studies show the presence of 2 LO and 3 LO peaks at 416 cm^‐1 and 625 cm^‐1respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)