Effect of cation distribution on the properties of Mn0.2ZnxNi0.8−xFe2O4

Mn_0.2Zn_xNi_0.8−xFe₂O₄ (x=0.2, 0.3, 0.4, 0.5, 0.6) are synthesized by the citrate precursor method. Effects of zinc substitution on DC resistivity, dielectric relaxation intensity, initial permeability, saturation magnetization and Curie temperature have been investigated. It is observed that resistivity increases with increase in zinc concentration up to x=0.5 and then decreases. The observed behaviour is explained in terms of hopping and site preference of ions in the lattice. The main contribution to dielectric relaxation intensity is observed to be due to space charge polarization. Initial permeability is observed to increase with increase in zinc concentration. Saturation magnetization increases up to x=0.4 and then starts decreasing. Canting effect is observed for higher zinc concentrations.     

Metal derivatives of amidoximes : II. Synthesis of 2-(tributylstannoxy)-, 2-(triphenylstannoxy)- and 2-(trimethylsiloxy)-3-hydro-4-alkyl or -4-phenyl-1,3,5,2- oxadiazaboroles

2-(Tributylstannoxy)-, 2(triphenylstannoxy)- and 2-(trimethylsiloxy)-3- hydro-4-alkyl- or -4-phenyl-1,3,5,2-oxadiazaboroles have been synthesized, and their properties examined.     

Current Scenario of Poly (2,5-Benzimidazole) (ABPBI) as Prospective PEM for Application in HT-PEMFC

Abstract

In last two decades, acid doped polybenzimidazole as polymer electrolyte membrane (PEM) has been widely recognized and envisioned as “ideal” proton conducting materials for application in high temperature PEM fuel cell (HT-PEMFC). The majority of research and developmental work is mainly focused on poly (2,2´-m-phenylene-5,5´-bibenzimidazole), However, it is neither easy-processed nor inexpensive component of the respective family. On the other hand, among the various members belonging to benzimidazole family, poly (2,5-benzimidazole) is unique because it possesses a cost-attractive, single-step synthesis process, high extent of doping as well as good chemical and thermal stability. In the recent years this material has proved its potency in the earlier research. Thus this review puts special emphasis on poly (2,5-benzimidazole) and epitomizes the on-going breath-taking progress and achievements on the fabrication of poly (2,5-benzimidazole) based membranes. The write-up describes the effect of blending, cross-linking, ionic liquids and incorporation organic/inorganic nano-fillers. In addition, incorporating other protonic dopants such as heteropoly acids into the chain of poly (2,5-benzimidazole) molecular skeleton is also overviewed. Moreover, the critical interpretation of different causes responsible for earlier degradation and their effect towards the fabrication of high temperature membrane electrode assembly are visualized herein.

• Highlights

• Current developments and existing challenges of ABPBI in PEMFC have been reviewed.

• PEM Modification and addition of protonic dopants has been discussed.

• Proton migration, permeability, stability and reliability are thoroughly illustrated.

• Different ABPBI-based membranes and their performance are comparatively analyzed.

     

Chemistry of platinum hydrides : XXV. Preparation and characterization of platinum(II) hydridotin complexes containing bulky phosphines

Platinum(II) hydridotin complexes containing bulky phosphine ligands, trans-Pt(H)L₂(SnR₃) have been prepared from: (i) the equimolar reaction between corresponding platinum(II) dihydride complexes and HSnR₃ (Cy = cyclohexyl), P-i-Pr₃, P-t-BuPh₂, P-t-Bu₂Me; R = Ph), (ii) the oxidative addition of the corresponding zerovalent complexes, Pt⁰L₂, with HSnR₃ (L = P-i-Pr₃, P-t-BuPh₂; R = Ph), (iii) the reaction of the corresponding platinum(II) dihydride complexes with ClSnR₃ in the presence of pyridine in benzene (L = P-i-Pr₃, P-t-BuPh₂; R = CH₃, n-Bu), (iv) the sodium borohydride reduction of the corresponding hydridochloride complexes Pt(H)Cl(PR₃)₂ with ClSnR₃ in THF (L = PCy₃; R = Ph), these compounds have been characterized by their elemental analysis, infrared, ¹H and ³¹P NMR spectral data.     

Development of Light‐Activated CRISPR Using Guide RNAs with Photocleavable Protectors

The ability to remotely trigger CRISPR/Cas9 activity would enable new strategies to study cellular events with greater precision and complexity. In this work, we have developed a method to photocage the activity of the guide RNA called “CRISPR‐plus” (CRISPR‐precise light‐mediated unveiling of sgRNAs). The photoactivation capability of our CRISPR‐plus method is compatible with the simultaneous targeting of multiple DNA sequences and supports numerous modifications that can enable guide RNA labeling for use in imaging and mechanistic investigations.     

Attractions, water structure, and thermodynamics of hydrophobic polymer collapse

We explore the prospects of a perturbation approach for predicting how weak attractive interactions affect collapse thermodynamics of hydrophobic polymers in water. Specifically, using molecular dynamics simulations of model polymers in explicit water, we show that the hydration structure is sensitive to the strength of the van der Waals attractions but that the hydration contribution to the potential of mean force for collapse is not. We discuss how perturbation theory ideas developed for small spherical apolar solutes need to be modified in order to account for the effect of attractions on the conformational equilibria of polymers.     

Fluoroaryl-substituted aminoalane dimers: syntheses and structures

Six dimeric aminoalanes of formula [Me(2)Al-mu-N(H)Ar(F)](2)(Ar(F)= 4-C(6)H(4)F (1), 2-C(6)H(4)F (2), 3,5-C(6)H(3)F(2)(3), 2,3,4,5-C(6)HF(4)(4), 2,3,5,6-C(6)HF(4)(5) and C(6)F(5)(6)) have been prepared by treatment of the appropriate fluoroaniline with AlMe(3) in toluene solution at 25 degrees C. The structures of 1-6 were determined by X-ray crystallography.     

Lattice dynamics of ND4I and NH4I crystals

The phonon dispersion curves and one phonon density of states for ND₄I and NH₄I crystals in the sodium chloride structure have been calculated by making use of the deformation dipole model of Hardy incorporating general short range forces out to second neighbours. Since the electronic configuration of both the compounds is identical, we have used the input data of NH₄I to calculate the model parameters for both the crystals. The results have been compared in the three principal symmetry directions with the neutron scattering measurements available only in case of ND₄I. The theoretical results show a reasonably good agreement with the experimental data.     

Development of a highly sensitive and selective hyphenated technique (molecularly imprinted micro-solid phase extraction fiber-molecularly imprinted polymer fiber sensor) for ultratrace analysis of folic acid

A simple polymerization strategy is reported in this work which allows molecularly imprinted polymeric fiber (monolith) fabrication for direct use in sensing devices. This is advantageous for achieving higher degree of enrichment of target analyte (folic acid) from the complex matrices of real samples, without any surface fouling, cross-reactivity, and non-specific (false-positive) contributions. In order to measure serum folic acid at ultratrace level to detect spina bifida, a neural tube defect in mother, and other acute cases of proteomic diseases, the hyphenation between molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer-carbon composite fiber sensor has been found quite efficient. The primitive diagnosis of many chronic diseases is feasible by estimating folic acid as biomarker, with the detection limit as low as 0.0036 ng mL⁻¹ (relative standard deviation = 0.13%, signal/noise = 3) in human blood serum.     

Retailer’s optimal replenishment decisions with credit-linked demand under permissible delay in payments

Usually it is assumed that the supplier would offer a fixed credit period to the retailer but the retailer in turn would not offer any credit period to its customers, which is unrealistic, because in real practice retailer might offer a credit period to its customers in order to stimulate his own demand. Moreover, it is observed that credit period offered by the retailer to its customers has a positive impact on demand of an item but the impact of credit period on demand has received a very little attention by the researchers. To incorporate this phenomenon, we assume that demand is linked to credit period offered by the retailer to the customers.