M. M. Uddin

Slow arsenic poisoning of the contaminated groundwater users

This paper gives impact of Arsenic contaminated water on human health as well as overview of the extent and severity of groundwater arsenic contamination in Bangladesh. Scalp hair is the most important part of the human body to monitor the accumulation of this type of poison. Therefore, an experiment has been carried out by Neutron Activation Analysis (NAA) at Atomic Energy Research Establishment (AERE), Savar, Dhaka, Bangladesh on human hair of corresponding tube well water users of these areas to determine the total accumulation of arsenic to their body. Hair samples collected from the region where the groundwater was found highly contaminated with arsenic. The obtained results of arsenic concentration in the lower age (Hb) categories of users (below 12 years of age users) is in the range of 0.33 to 3.29 /gmg/g (ppm) and that in the Hu categories (upper 12 years of age users) is 0.47 to 6.64 μg/g (ppm). Where as maximum permissible range is 1 ppm certified from WHO. Results show that the peoples are highly affected where the groundwater is highly contaminated with arsenic and acts as the primary source of arsenic poisoning among the peoples of those areas. The results indicate that human population is affected with arsenic locally using the contaminated water for a long time.

Gate depletion of an InSb two-dimensional electron gas

We investigated the gate control of a two-dimensional electron gas (2DEG) confined to InSb quantum wells with an Al2O3 gate dielectric formed by atomic layer deposition on a surface layer of Al0.1In0.9Sb or InSb. The wider bandgap of Al0.1In0.9Sb compared to InSb resulted in a linear, sharp, and non-hysteretic response of the 2DEG density to gate bias in the structure with an Al0.1In0.9Sb surface layer. In contrast, a nonlinear, slow, and hysteretic (nonvolatile-memory-like) response was observed in the structure with an InSb surface layer. The 2DEG with the Al0.1In0.9Sb surface layer was completely depleted by application of a small gate voltage (∼ −0.9 V).

Characterization of InSb quantum wells with atomic layer deposited gate dielectrics

We report magnetotransport measurements of a gated InSb quantum well (QW) with high quality Al2O3 dielectrics (40 nm thick) grown by atomic layer deposition. The magnetoresistance data demonstrate a parallel conduction channel in the sample at zero gate voltage (Vg). A good interface between Al2O3 and the top InSb layer ensures that the parallel channel is depleted at negative Vg and the density of two-dimensional electrons in the QW is tuned by Vg with a large ratio of 6.5 × 1014 m−2 V−1 but saturates at large negative Vg. These findings are closely related to layer structures of the QW as suggested by self-consistent Schrodinger-Poisson simulation and two-carrier model.

First‐Principles Study of Superconducting ScRhP and ScIrP Pnictides

For the first time, we have reported in this study an ab initio investigation on elastic properties, Debye temperature, Mulliken population, Vickers hardness, and charge density of the two recently synthesized superconducting ScRhP and ScIrP pnictides. The optimized cell parameters show fair agreement with the experimental results. The mechanical stability of both ternary phosphides is confirmed via the calculated elastic constants. Both compounds are ductile in nature and damage tolerant. ScIrP is expected to be elastically more anisotropic than ScRhP. The estimated value of Debye temperature predicts that ScRhP is thermally more conductive than ScIrP and the phonon frequency in ScRhP is higher than that in ScIrP. Both pnictides are soft and easily machinable due to their low Vickers hardness. Moreover, the hardness of ScRhP is lower due to the presence of antibonding Rh-Rh in ScRhP. The metallic conductivity of ScRhP reduces significantly when Rh is replaced with Ir. The main contribution to the total density of states (TDOS) at Fermi-level (EF) comes from d-electrons of Sc and Rh/Ir in both pnictides. These two ternary compounds are characterized mainly by metallic and covalent bonding with little ionic contribution. The calculated superconducting transition temperatures fairly coincide with the reported measured values.

Predicted MAX Phase Sc 2 InC: Dynamical Stability, Vibrational and Optical Properties

The calculations of phonon dispersion, thermodynamic and optical properties including charge density, Fermi surface, Mulliken population analysis, theoretical Vickers hardness of predicted Sc 2 InC have been performed for the first time. The Sc 2 InC is mechanically as well as dynamically stable. It is promising for optoelectronic devices in the visible and ultraviolet energy regions and as a coating material to avoid solar heating.

Effects of transition metals on physical properties of M2BC (M = V, Nb, Mo and Ta): A DFT calculation

Abstract In the present study, the effects of transition metals on structural, electronic, elastic, optical and thermodynamic properties of M2BC (M = V, Nb, Mo and Ta) have been investigated using the density functional theory (DFT) based first-principles method. The electronic band structures along with Fermi surface, elastic anisotropy, Vickers hardness, analysis of Mulliken populations, optical and thermodynamic properties are studied for the first time. The optimized unit cell parameters are compared with available theoretical and experimental results and a reasonable agreement is recorded. The mechanical stability of these compounds is confirmed by the calculations of single crystal elastic constants using the Born criteria. The compounds herein exhibit metallic conductivity where major contribution comes from the d-orbital electrons. The total density of states at EF are found to be 9.15, 6.77, 6.37 and 5.83 states/eV/unit cells for M2BC (M = V, Nb, Mo and Ta) compounds, respectively. The hardness values of 10.71, 12.44, 8.52 and 16.80 GPa are noted for the M2BC (M = V, Nb, Mo and Ta) compounds, respectively. The value of bulk modulus, B is found to increase in the sequence of B (V2BC)