Pressure induced magnetic and magnetocaloric properties in NiCoMnSb Heusler alloy

The effect of pressure on the magnetic and the magnetocaloric properties around the martensitic transformation temperature in NiCoMnSb Heusler alloy has been studied. The martensitic transition temperature has significantly shifted to higher temperatures with pressure, whereas the trend is opposite with the application of applied magnetic field. The maximum magnetic entropy change around the martensitic transition temperature for Ni45Co5Mn38Sb12 is 41.4 J/kg K at the ambient pressure, whereas it is 33 J/kg K at 8.5 kbar. We find that by adjusting the Co concentration and applying suitable pressure, NiCoMnSb system can be tuned to achieve giant magnetocaloric effect spread over a large temperature span around the room temperature, thereby making it a potential magnetic refrigerant material for applications.Comment: 16 pages, 5 figure

Heusler 4.0: Tunable Materials

Heusler compounds are a large family of binary, ternary and quaternary compounds that exhibit a wide range of properties of both fundamental and potential technological interest. The extensive tunability of the Heusler compounds through chemical substitutions and structural motifs makes the family especially interesting. In this article we highlight recent major developments in the field of Heusler compounds and put these in the historical context. The evolution of the Heusler compounds can be described by four major periods of research. In the latest period, Heusler 4.0 has led to the observation of a variety of properties derived from topology that includes: topological metals with Weyl and Dirac points; a variety of non-collinear spin textures including the very recent observation of skyrmions at room temperature; and giant anomalous Hall effects in antiferromagnetic Heuslers with triangular magnetic structures. Here we give a comprehensive overview of these major achievements and set research into Heusler materials within the context of recent emerging trends in condensed matter physics

The admissible tsunamigenic source region of 24 September 2013 land-based earthquake application of backward ray tracing technique

A minor tsunami of about 50 cm was generated along the coast of Qurayat near Makran subduction zone in the Arabian Sea due to the 24 September 2013 Pakistan earthquake of magnitude 7.6 Mw(mB),although its source was ~200 km far inland of the Makran trench. The real time sea level observation network in the Arabian Sea recorded minor tsunami arrivals. In an attempt to explain the mechanism of this unusual tsunami, we use backward ray tracing technique to map the admissible region of tsunamigenic source. Basically, in this technique the ray equations are integrated starting from the specific locations of tsunami observations, in all possible directions. The known travel time of the initial waves to the respective tide gauges and tsunami buoys is used in this method. Backward wave front is constructed by joining all endpoints of the rays from each of the locations. The region where the envelope of all backward wave fronts converges is considered as the source of the tsunami, which is ~470 km from the earthquake epicentre with the location at 24.8 N and 61.5E. The admissible region identified is an undersea section between Chabahar and Gwadar, where a mud island had appeared subsequent to this earthquake. Convergence of the tsunami source zone and location of the mud island suggest that the sudden uplift must have caused the tsunam

Potential predictability of the Asian summer monsoon on monthly and seasonal time scales

The potential predictability of the monthly and seasonal means during the Northern Hemisphere summer and winter is studied by estimating the signal-to-noise ratio. Based on 33 years of daily low-level wind observations and 24 years of satellite observations of outgoing long wave radiation, the predictability of the Asian summer monsoon region is contrasted with that over other tropical regions. A method of separating the contributions from slowly varying boundary forcing and internal dynamics (e.g., intraseasonal oscillations) that determine the predictability of the monthly mean tropical climate is proposed. We show that the Indian monsoon climate is only marginally predictable in monthly time scales as the contribution of the boundary forcing in this region is relatively low and that of the internal dynamics is relatively large. It is shown that excluding the Indian monsoon region, the predictable region is larger and predictability is higher in the tropics during northern summer. Even though the boundary forced variance is large during northern winter, the predictable region is smaller as the internal variance is larger and covers a larger region during northern winter (due to stronger intraseasonal activity). Consistent with the estimates of predictability of monthly means, estimates of potential predictability on seasonal time scales also indicate that predictability of seasonal mean Indian monsoon is limited

A common spatial mode for intra-seasonal and inter-annual variation and predictability of the Indian summer monsoon

How and to what extent the intra-seasonal oscillations (ISOs) of the Indian summer monsoon influence the seasonal mean and its inter-annual variability is investigated using long records of daily circulation data (1956-1997) and outgoing long wave radiation (OLR) data (1974-1997). The underlying spatial structure of a typical ISO cycle that is invariant from event to event and year to year is brought out. It is shown that the intra-seasonal and interannual variations are governed by a common mode of spatial variability. A higher frequency of occurrence of 'active' ('break') conditions within a monsoon season, therefore, could result in a 'strong' ('weak') summer monsoon. Two-dimensional probability density function estimates of the ISOs show that 'strong' ('weak') monsoon years are indeed associated with higher probability of occurrence of 'active' ('break') conditions. For the first time, these results show that the frequency of chaotic ISO regimes determine the seasonal mean monsoon, thereby setting a limit on monsoon predictability

Studies in Sulphonamides Part X

The present paper describes the synthesis of four differently substituted dibenzoylmethanes, viz., 1(m-nitropheny1)-3-(p-chloropheny1)-, 1-(m-notropheny1)-3-(p-bromopheny1)-, 1,3-di(p-methoxypheny1) and 1-(p-ethoxypheny1)-3-pheny1 propane-1,3-diones and study of their coupling reactions with different diazotised sulphonamide bases. The resulting 2-sulphonamidobenzeneazo derivatives were subjected to biological assay in vitro against S. aureus and E. coli and some of these found to posses considerable activity

Studies in Sulphonamides Part VII: Synthesis of 1,3 diary1 2 (substituted sulphonamidobenzeneazo) propane 1, 3 diones and evaluation of their antibacterial properties

Different 1, 3-diarylpropane-1, 3-diones, 1-(P-nitropheny1) 3-phenyI-, p-nitropheny1) 3-(p-methyI-pheny1)- 1,)p-nitropheny1-3-(p-methoxypheny1)-, and 1-(m-nitropheny)-3- (p-methyIpheny1) propane 1, 3-diones have synthesised and coupled with a number a diazotised sulphonamide bases to yield the respective 1,3-diaryI-2-(substituted sulphonamidozeneazo) propane. All these substituted sulphonamidobenzence propane-1,3- diones have been screened in vitro for their antibacterial properties using cup plate agar diffusion method and some of these have been found active

Studies in Heterocyclic Compounds -Part VIII

Different azo compounds, 1-(m-nitrophenyl)-3-(p-bromophenyl)-and 1-(m-nitrophenyl) 3-(p-chlorophenyl)-2-(substituted sulphonamidobenzeneazo) propane-1,3-dinoes on condensation with hydrazine hydrate (100%), phenylhydrazine, p-nitrophenyllhydrazine and benzoylhydrazine yield the corresponding 1-simple/substituted-3-(m-nitrophenyl)-5-(p-bromo chlorophenyl)-4-(substituted sulphonamidobenzeneazo) pyrazoles. The homogeneity and purity of these was confirmed by TLC and these on screening in vitro against S. aureus and E. coli were found to exhibit antibacterial activity