Room temperature magnetocaloric effect in Pr1.75Sr1.25Mn2O7 double-layered perovskite manganite system

Abstract

In this work, we have studied on double-layered perovskite (Ruddlesden–Popper) manganite structure in Pr_1.75Sr_1.25Mn₂O₇ synthesised by sol–gel method. The crystal structure of the double-layered perovskite is found as tetragonal from the X-ray diffraction analysis with I4/mmm space group. A high Curie temperature, T_C = 305 K is observed from the temperature dependence of magnetisation measurement. The isothermal magnetisation curves showed that magnetic phase transition is second order due to the positive slope of the Arrott plots. Maximum magnetic entropy change (ΔS_M) and adiabatic temperature change (ΔT_ad) values are calculated as 3.99 J kg^?1 K^?1 and 2.1 K under external magnetic field of 70 kOe, respectively. Since our double-layered perovskite manganite sample has desired T_C value and relatively high ΔS_M, it can be a potential candidate as a magnetocaloric material for room temperature magnetic cooling systems.     

A novel amperometric glucose biosensor based on reconstitution of glucose oxidase on thiophene-3-boronic acid polymer layer

The biosensor was constructed for determination of glucose by using glucose oxidase enzyme immobilized on poly(thiophene-3-boronic acid) (PTBA). Boronic acid functionalized polythiophene layer was obtained by electrochemical polymerization of Thiophene (Th) and thiophene-3-boronic acid (TBA) with different monomer rations. The reconstitution of the apo-glucose oxidase (apo-GOx) on a complexed flavin adenine dinucleotide (FAD) linked to polythiophene boronic acid (PTBA) monolayer yields an electrically contacted enzyme monolayer. The GOx-reconstituted enzyme electrode exhibited excellent electrocatalytic activities toward the reduction and oxidation of hydrogen peroxide as well. The PTBA/FAD/GOx biosensor shows an excellent performance for glucose at +0.4 V with a high sensitivity (2.14 μA/mM) and lower response time (～5 s) in a wide concentration range of 0.5–18 mM (correlation coefficient of 0.9952). Furthermore, the effects of applied potential, pH, temperature, electroactive interference, stability and reusability of the biosensors were discussed.     

Semiperfect Modules with Respect to a Preradical

In an earlier paper [8] the authors introduced strongly and properly semiprime modules. Here properly semiprime modules M are investigated under the condition that every cyclic submodule is M-projective (self-pp-modules). We study the idempotent closure of M using the techniques of Pierce stalks related to the central idempotents of the self-injective hull of M. As an application of our theory we obtain several results on (not necessarily associative) biregular, properly semiprime, reduced and Firings. An example is given of an associative semiprime PSP ring with polynomial identity which coincides with its central closure and is not biregular (see 3.6). Another example shows that a semiprime left and right FP-injective Pl-ring need not be regular (see 4.8). Some of the results were already announced in [7].     

A One-Time Excess Inventory Disposal Decision Under a Stationary Base-Stock Policy

We consider a stochastic inventory system that has been operated under a policy different from the one that will be implemented in the future. Such a situation may arise as a result of changes in model assumptions leading to the implementation of a different policy. Before the new policy is implemented, there may be some units on hand which may exceed the optimal order-up-to level. Hence, one needs to evaluate a one-time inventory disposal decision immediately before the new policy replaces the policy in use. For this purpose, we develop three models under different assumptions that describe the demand during the disposal period and present analytical results characterizing their optimal solutions.     

A Vulnerability Parameter of Networks

Mathematical Notes - The vulnerability in a communication network is the measurement of the strength of the network against damage that occurs in nodes or communication links. It is important that...     

A Modular Peel Fixture for Tape Peel Tests on Immovable Substrates

Background

Peel tests are frequently used to perform measurements of adhesive strength for pressure sensitive adhesive (PSA) tapes. Current lab methodologies for 90° peel tests translate the model substrate orthogonally to the peel direction in order to maintain the peel angle, precluding testing from immovable substrates.

Objective

It was our objective to develop a peel fixture capable of testing temporary pavement marking (TPM) tapes and other PSA tapes from immovable substrates such as roadways surfaces.

Methods

We present a modular peel fixture for conducting peel experiments directly on immovable substrates. The fixture was validated through a series of peel tests on consumer tapes to reproduce the linear width dependence and viscoelastic rate dependence found in traditional peeling setups. To test the capabilities of the fixture, a series of peel tests were conducted with various tapes on controlled surfaces, and a commercial tape on various immovable substrates.

Results

We demonstrate the ability of our fixture to reproduce results reported for traditional peel tests from literature. In addition, we were able to conduct peel tests directly on immovable substrates such as the benchtop.

Conclusions

This fixture shows potential for both traditional peeling tests, and for use in in-situ peel experiments from substrates relevant to the end application of the PSA tape.

     

Palladium(II)‐N‐heterocyclic carbene complexes: synthesis,characterization and catalytic application

N‐Heterocyclic carbenes (NHCs) are of great importance and are powerful ligands for transition metals. A new series of sterically hindered benzimidazole‐based NHC ligands (LHX) ( 2a , 2b , 2c , 2d , 2e , 2f ), silver–NHC complexes ( 3a , 3b , 3c , 3d , 3e , 3f ) and palladium–NHC complexes ( 4a , 4b , 4c , 4d , 4e , 4f ) have been synthesized and characterized using appropriate spectroscopic techniques. Studies have focused on the development of a more efficient catalytic system for the Suzuki coupling reaction of aryl chlorides. Catalytic performance of Pd–NHC complexes and in situ prepared Pd(OAc)₂/LHX catalysts has been investigated for the Suzuki cross‐coupling reaction under mild reaction conditions in aqueous N,N‐dimethylformamide (DMF). These complexes smoothly catalyzed the Suzuki–Miyaura reactions of electron‐rich and electron‐poor aryl chlorides. Copyright © 2014 John Wiley & Sons, Ltd.     

Computational estimates of thermochemistry and pKa values of cyclopropenyl imine superbases

The thermochemical properties of superbase species derived from cyclopropeneimine are estimated by computations on systems of isodesmic reactions. Proton affinities, gas phase basicities, and pK_a values are well represented by computations incorporating G4 and CBS‐QB3 schemes augmented for large systems by DFT calculations with functionals M06‐2X and ωB97DX in the cc‐pVTZ Dunning basis. Our calculations show that relative base strengths in gas are enhanced by alkyl substitution, either by methyl groups or larger species. For acetonitrile solution, alkyl substitution seems to weaken the base. © 2013 Wiley Periodicals, Inc.