Structural, Magnetic and Magneto-caloric studies of Ni50Mn30Sn20Shape Memory Alloy

We have synthesized a nominal composition of Ni50Mn30Sn20 alloy using arc melting technique. Rietveld refinement confirms the austenite L21 structure in Fm-3m space group. Electrical resistivity has been found to clearly exhibiting two different phenomena viz. a magnetic transition from paramagnetic to ferromagnetic and a structural transition from austenite to martensitic phase. Thermo-magnetization measurements M(T) confirms ferromagnetic transition temperature TC at 222 K and martensitic transition starting at 127 K(MS). Magnetization measurement M(H) at 10 K confirms the ferromagnetic state. Frequency dependence of ac susceptibility \c{hi}' at low temperature suggests spin glass behavior in the system. The isothermal magnetic entropy change values have been found to be 1.14 J/Kg.K, 2.69 J/Kg.K and 3.9 J/Kg.K, with refrigeration capacities of 19.6 J/kg, 37.8 J/kg and 54.6 J/kg for the field change of 1, 2 and 3 Tesla respectively at 227 K.Comment: 16 pages text + Figs. Ni50Mn30Sn20 alloy: reasonable refrigeration capacity tunable to Room

Spectrum of the three dimensional fuzzy well

We develop the formalism of quantum mechanics on three dimensional fuzzy space and solve the Schr\"odinger equation for a free particle, finite and infinite fuzzy wells. We show that all results reduce to the appropriate commutative limits. A high energy cut-off is found for the free particle spectrum, which also results in the modification of the high energy dispersion relation. An ultra-violet/infra-red duality is manifest in the free particle spectrum. The finite well also has an upper bound on the possible energy eigenvalues. The phase shifts due to scattering around the finite fuzzy potential well have been calculated

Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37

We present a multiwavelength study of the filamentary infrared dark cloud (IRDC) G333.73+0.37. The region contains two distinct mid-infrared sources S1 and S2 connected by dark lanes of gas and dust. Cold dust emission from the IRDC is detected at seven wavelength bands and we have identified 10 high density clumps in the region. The physical properties of the clumps such as temperature: 14.3-22.3 K and mass: 87-1530 M_sun are determined by fitting a modified blackbody to the spectral energy distribution of each clump between 160 micron and 1.2 mm. The total mass of the IRDC is estimated to be $~4700 M_sun. The molecular line emission towards S1 reveals signatures of protostellar activity. Low frequency radio emission at 1300 and 610 MHz is detected towards S1 (shell-like) and S2 (compact morphology), confirming the presence of newly formed massive stars in the IRDC. Photometric analysis of near and mid-infrared point sources unveil the young stellar object population associated with the cloud. Fragmentation analysis indicates that the filament is supercritical. We observe a velocity gradient along the filament, that is likely to be associated with accretion flows within the filament rather than rotation. Based on various age estimates obtained for objects in different evolutionary stages, we attempt to set a limit to the current age of this cloud.Comment: 26 pages, 20 figures, accepted by Ap

Enhanced Critical parameters of nano-Carbon doped MgB2 Superconductor

The high field magnetization and magneto transport measurements are carried out to determine the critical superconducting parameters of MgB2-xCx system. The synthesized samples are pure phase and the lattice parameters evaluation is carried out using the Rietveld refinement. The R-T(H) measurements are done up to a field of 140 kOe. The upper critical field values, Hc2 are obtained from this data based upon the criterion of 90% of normal resistivity i.e. Hc2=H at which Rho=90%Rho; where RhoN is the normal resistivity i.e., resistivity at about 40 K in our case. The Werthamer-Helfand-Hohenberg (WHH) prediction of Hc(0) underestimates the critical field value even below than the field up to which measurement is carried out. After this the model, the Ginzburg Landau theory (GL equation) is applied to the R-T(H) data which not only calculates the Hc2(0) value but also determines the dependence of Hc2 on temperature in the low temperature high field region. The estimated Hc(0)=157.2 kOe for pure MgB2 is profoundly enhanced to 297.5 kOe for the x=0.15 sample in MgB2-xCx series. Magnetization measurements are done up to 120 kOe at different temperatures and the other parameters like irreversibility field, Hirr and critical current density Jc(H) are also calculated. The nano carbon doping results in substantial enhancement of critical parameters like Hc2, Hirr and Jc(H) in comparison to the pure MgB2 sample.Comment: 25 pages with 9 Figs: comments/suggestions([email protected]

Why Defining the Construct Matters: An Examination of Teacher Knowledge Using Different Lenses on One Assessment

What does it mean to align an assessment to the domain of interest? In this paper, we analyze teachers’ performance on the Learning Mathematics for Teaching assessment of Proportional Reasoning. Using a mixture Rasch model, we analyze their performance on the entire assessment, then on two different subsets of items from the original assessment. We consider the affordances of different conceptualizations of the domain and consider the implications of the domain definition on the claims we can make about teacher performance. We use a single assessment to illustrate the differences in results that can arise based on the ways in which the domain of interest is conceptualized. Suggestions for test development are provided