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41.
In the present study, the influence of aluminium (Al) addition on the martensite-austenite phase transformation and exchange bias of Ni–Mn–Sb films have been investigated. Ni–Mn–Sb–Al films with different Al concentration (∼0–5.6%) were deposited by co-sputtering of Ni–Mn–Sb and Al targets. Experimental results revealed the decrease in martensitic transformation temperature with increasing Al content upto a certain extent (3.3%) beyond which martensitic transformation was suppressed. Paramagnetic to ferromagnetic transition temperature (TC) also decreased with increasing Al concentration. Ni50Mn36.3Sb10.4Al3.3 thin film showed significant improvement in exchange bias field as compared to pure Ni50.3Mn36.9Sb12.8 thin film. This enhancement in the exchange bias field HEB = 611 Oe at 10 K is attributed to the increase of AFM-FM interactions that result from the decrease of Mn–Mn distance due to the incorporation of Al atoms. This behaviour is an additional property of the FSMA thin films apart from various other multifunctional properties and therefore, is of technological importance for their applications in magnetic storage devices. 相似文献
42.
One-pot, catalyst-free, facile, and efficient sulfenylations of resorcinol, 1,3-diaminobenzene, 2-naphthol, 2-aminonaphthalene, indole, pentane-2,4-dione, etc., in aqueous and ethanolic solution by a mild sulfenium carrier azobenzene-2-sulfenyl bromide are described. Efficient sulfenylating reagent, mild reaction conditions, and excellent yields make this method quite simple, convenient, and practical. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
43.
Zufang Huang Soumik Siddhanta Gang Zheng Thomas Kickler Ishan Barman 《Angewandte Chemie (International ed. in English)》2020,59(15):5972-5978
The use of surface‐enhanced Raman spectroscopy (SERS) to determine spectral markers for the diagnosis of heparin‐induced thrombocytopenia (HIT), a difficult‐to‐diagnose immune‐related complication that often leads to limb ischemia and thromboembolism, is proposed. The ability to produce distinct molecular signatures without the addition of labels enables unbiased inquiry and makes SERS an attractive complementary diagnostic tool. A capillary‐tube‐derived SERS platform offers ultrasensitive, label‐free measurement as well as efficient handling of blood serum samples. This shows excellent reproducibility, long‐term stability and provides an alternative diagnostic rubric for the determination of HIT by leveraging machine‐learning‐based classification of the spectroscopic data. We envision that a portable Raman instrument could be combined with the capillary‐tube‐based SERS analytical tool for diagnosis of HIT in the clinical laboratory, without perturbing the existing diagnostic workflow. 相似文献
44.
Cumene is a commercially important product in the petrochemical industries. In isopropylation of benzene, 1,4-diisopropyl benzene (1,4-DIPB) is produced as low value by-product. This low value by-product DIPB is used to maximize the production of commercially important product cumene by transalkylation reaction. Reduction of crystal size in zeolite can increase surface area of the external surface and in this way bring about substantial changes in catalytic activity. Moreover modification with rare-earth metal enhances the acidity of zeolite. In this work, nanocrystalline and microcrystalline zeolite X were modified with cerium to study the combine effect of crystal size and ion modification of zeolite on selectivity of cumene in commercially important transalkylation reaction. Benzene and 1,4-diisopropylbenzene in a molar ratio of 1 to 12.5 were subjected to vapour-phase reaction in the temperature range of 498 to 593 K at atmospheric pressure with space time of 5.27–10.54 kg h/kmol. Nanosized crystalline zeolite gives much higher conversions of 1,4-DIPB than microcrystalline zeolite. Over cerium modified nanosized zeolite CeXN 81.85% conversion of 1,4-DIPB and 97% cumene selectivity were achieved. It was found that stability and activity of CeXN for cumene synthesis was much higher than that of CeXM zeolite. Kinetic constants for the reactions were estimated and the activation energies for various reactions over CeXM were determined. The activation enegy for transalkylation reaction was found to be 78.54 kJ/mol. 相似文献
45.
Umme Solaem Akond Koushik Barman Abhinandan Mahanta Sk. Jasimuddin 《Electroanalysis》2021,33(4):900-908
p-Nitrophenol (p−NP) is a high priority toxic pollutant and that has harmful effects on human, animals and plants. Thus, the detection and determination of p−NP present in the environment is an urgent as well as highly important requisite. The present article, therefore focused on the construction of a novel electrochemical sensor based on NiO nanoparticles/α-cyclodextrin functionalized reduced graphene oxide modified glassy carbon electrode (NiO−NPs-α-CD-rGO-GCE) for the selective and sensitive detection of p−NP. UV-vis, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction pattern (SAED) and X-ray diffraction (XRD) analysis confirms the formation of highly pure NiO nanoparticles. Field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and cyclic voltammetry (CV) were used to characterize the step-wise electrode modification process. DPV was carried out to quantify p−NP within the concentration range of 1−10 μM and found the detection limit of 0.12 nM on the basis of the signal-to-noise ratio S/N=3. The electrode can able to detect different isomers of nitrophenols. Interferences of other pollutants such as phenol, p-aminophenol, o- and m- nitrophenol, 4-chlorophenol, 2,6-dichlorophenol and ions like K+, Cd2+, Cl−, SO42− did not affect the sensing of p−NP. The newly developed sensor exhibited diffusion controlled kinetics and had excellent sensitivity, selectivity and reproducibility for the detection of p−NP. The electrode showed good recoveries in real sample analysis. 相似文献
46.
Mixed saturated-unsaturated alkyl-chain assemblies: solid solutions of zinc stearate and zinc oleate
The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions. 相似文献
47.
Dr. Jessica L. Klockow Dr. Kenneth S. Hettie Dr. Kristen E. Secor Dr. Dipti N. Barman Dr. Timothy E. Glass 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11446-11451
Tunable dual‐analyte fluorescent molecular logic gates (ExoSensors) were designed for the purpose of imaging select vesicular primary‐amine neurotransmitters that are released from secretory vesicles upon exocytosis. ExoSensors are based on the coumarin‐3‐aldehyde scaffold and rely on both neurotransmitter binding and the change in environmental pH associated with exocytosis to afford a unique turn‐on fluorescence output. A pH‐functionality was directly integrated into the fluorophore π‐system of the scaffold, thereby allowing for an enhanced fluorescence output upon the release of labeled neurotransmitters. By altering the pH‐sensitive unit with various electron‐donating and ‐withdrawing sulfonamide substituents, we identified a correlation between the pKa of the pH‐sensitive group and the fluorescence output from the activated fluorophore. In doing so, we achieved a twelvefold fluorescence enhancement upon evaluating the ExoSensors under conditions that mimic exocytosis. ExoSensors are aptly suited to serve as molecular imaging tools that allow for the direct visualization of only the neurotransmitters that are released from secretory vesicles upon exocytosis. 相似文献
48.
H. Chaudhuri C. Barman A. N. S. Iyengar D. Ghose P. Sen B. Sinha 《The European physical journal. Special topics》2013,222(3-4):827-838
Research on earthquake prediction has drawn serious attention of the geophysicist, geologist and investigators in different fields of science across the globe for many decades. Researchers around the world are actively working on recording pre-earthquake changes in non-seismic parameters through a variety of methods that include anomalous changes in geochemical parameters of the Earth’s crust, geophysical properties of the lithosphere as well as ionosphere etc. Several works also have been done in India to detect earthquake precursor signals using geochemical and geophysical methods. However, very few works have been done so far in India in this field through the application of nonlinear techniques to the recorded geophysical and geochemical precursory signals for earthquakes. The present paper deals with a short review of the early works on geochemical precursors that have been carried out in India as yet. With a view to detect earthquake precursory signals by means of gas-geochemical method we developed a network of seismo-geochemical monitoring observatories in India in hot springs and mud volcano crater. In the last few years we detected several geochemical anomalies and those were observed prior to some major earthquakes that occurred within a radius of 1500?km from the test sites. In the present paper we have applied nonlinear techniques to the long term, real-time and natural data sets of radon-222 and associated gamma originated out of the terrestrial degassing process of the earth. The results reveal a clear signature of the long range correlation present in the geochemical time series. This approach appears to be a potential tool to explore intrinsic information hidden within the earthquake precursory signals. 相似文献
49.
50.
A.K. Bhosale N.L. Tarwal P.S. Shinde P.M. Kadam R.S. Patil S.R. Barman P.S. Patil 《Solid State Ionics》2009,180(23-25):1324-1331
Nanocrystalline cerium oxide (CeO2) thin films were deposited onto the fluorine doped tin oxide coated glass substrates using methanolic solution of cerium nitrate hexahydrate precursor by a simple spray pyrolysis technique. Thermal analysis of the precursor salt showed the onset of crystallization of CeO2 at 300 °C. Therefore, cerium dioxide thin films were prepared at different deposition temperatures from 300 to 450 °C. Films were transparent (T ~ 80%), polycrystalline with cubic fluorite crystal structure and having band gap energy (Eg) in the range of 3.04–3.6 eV. The different morphological features of the film obtained at various deposition temperatures had pronounced effect on the ion storage capacity (ISC) and electrochemical stability. The larger film thickness coupled with adequate degree of porosity of CeO2 films prepared at 400 °C showed higher ion storage capacity of 20.6 mC cm? 2 in 0.5 M LiClO4 + PC electrolyte. Such films were also electrochemically more stable than the other studied samples. The Ce4+/Ce3+ intervalancy charge transfer mechanism during the bleaching–lithiation of CeO2 film was directly evidenced from X-ray photoelectron spectroscopy. The optically passive behavior of the CeO2 film (prepared at 400 °C) is affirmed by its negligible transmission modulation upon Li+ ion insertion/extraction, irrespective of the extent of Li+ ion intercalation. The coloration efficiency of spray deposited tungsten oxide (WO3) thin film is found to enhance from 47 to 53 cm2 C? 1 when CeO2 is coupled with WO3 as a counter electrode in electrochromic device. Hence, CeO2 can be a good candidate for optically passive counter electrode as an ion storage layer. 相似文献