Effect of Site-disorder, Off-stoichiometry and Epitaxial Strain on the Optical Properties of Magnetoelectric Gallium Ferrite

We present a combined experimental-theoretical study demonstrating the role of site disorder, off-stoichiometry and strain on the optical behavior of magnetoelectric gallium ferrite. Optical properties such as band-gap, refractive indices and dielectric constants were experimentally obtained by performing ellipsometric studies over the energy range 0.8 eV to 4.2 eV on pulsed laser deposited epitaxial thin films of stoichiometric gallium ferrite with b-axis orientation and the data was compared with theoretical results. Calculations on the ground state structure show that the optical activity in GaFeO3 arises primarily from O2p-Fe3d transitions. Further, inclusion of site disorder and epitaxial strain in the ground state structure significantly improves the agreement between the theory and the room temperature experimental data substantiating the presence of site-disorder in the experimentally derived strained GaFeO3 films at room temperature. We attribute the modification of the ground state optical behavior upon inclusion of site disorder to the corresponding changes in the electronic band structure, especially in Fe3d states leading to a lowered band-gap of the material.Comment: 18 Pages, 6 figure

PENGARUH GAYA KEPEMIMPINAN SITUASIONAL DAN MOTIVASI KERJA TERHADAP KEPUASAN KERJA PEGAWAI SEKRETARIAT DPRD DI KABUPATEN TOJO UNA-UNA

Tujuan penelitian ini adalah mengetahui dan menganalisa pengaruh gaya kepemimpinan situasional dan motivasi kerja terhadap kepuasan kerja Pegawai Sekretariat DPRD di Kabupaten Tojo Una-Una. Responden penelitian berjumlah 35 yang dipilih dengan metode sensus. Pengolahan data menggunakan Program Statiscal Product and Service Solution (SPSS 18.0), dengan metode analisis Regresi Linier Berganda.  Hasil penelitian menyimpulkan  sebagai berikut: (1) Gaya Kepemimpinan Situasional dan Motivasi Kerja  secara bersama-sama berpengaruh signifikan terhadap kepuasan kerja  Pegawai Sekretariat DPRD di Kabupaten Tojo Una-Una (2)  Gaya Kepemimpinan Situasional berpengaruh signifikan terhadap kepuasan kerja  Pegawai Sekretariat DPRD di Kabupaten Tojo Una-Una (3)  Motivasi kerja berpengaruh signifikan terhadap kepuasan kerja  Pegawai Sekretariat DPRD di Kabupaten Tojo Una-Una

Electronic Structures, Born Effective Charges and Spontaneous Polarization in Magnetoelectric Gallium Ferrite

We present a theoretical study of the structure-property correlation in gallium ferrite, based on the first principles calculations followed by a subsequent comparison with the experiments. Local spin density approximation (LSDA+U) of the density functional theory has been used to calculate the ground state structure, electronic band structure, density of states and Born effective charges. Calculations reveal that the ground state structure is orthorhombic Pc21n having A-type antiferromagnetic spin configuration, with lattice parameters matching well with those obtained experimentally. Plots of partial density of states of constituent ions exhibit noticeable hybridization of Fe 3d, Ga 4s, Ga 4p and O 2p states. However, the calculated charge density and electron localization function show largely ionic character of the Ga/Fe-O bonds which is also supported by lack of any significant anomaly in the calculated Born effective charges with respect to the corresponding nominal ionic charges. The calculations show a spontaneous polarization of ~ 59 microC/cm^2 along b-axis which is largely due to asymmetrically placed Ga1, Fe1, O1, O2 and O6 ions.Comment: Total 21 pages including 3 tables and 6 figure

Influence of anti-site disorder and electron-electron correlations on the electronic structure of CeMnNi4_4

CeMnNi$_4$ exhibits an unusually large spin polarization, but its origin has baffled researchers for more than a decade. We use bulk sensitive hard x-ray photoelectron spectroscopy (HAXPES) and density functional theory based on the Green's function technique to demonstrate the importance of electron-electron correlations of both the Ni 3$d$ ($U_{Ni}$) and Mn 3$d$ ($U_{Mn}$) electrons in explaining the valence band of this multiply correlated material. We show that Mn-Ni anti-site disorder as well as $U_{Ni}$ play crucial role in enhancing its spin polarization: anti-site disorder broadens a Ni 3$d$ minority-spin peak close to the Fermi level ($E_F$), while an increase in $U_{Ni}$ shifts it towards $E_F$, both leading to a significant increase of minority-spin states at $E_F$. Furthermore, rare occurrence of a valence state transition between the bulk and the surface is demonstrated highlighting the importance of HAXPES in resolving the electronic structure of materials unhindered by surface effects.Comment: Manuscript and Supplementary material, 13 pages, 17 figure

B cell responses to a peptide epitope. V. Kinetic regulation of repertoire discrimination and antibody optimization for epitope

The influence of imposing various conformational constraints on immune responses to a model epitope within a synthetic peptide immunogen was examined in mice. Although overall immunogenicity was affected, the model epitope (sequence DPAF) remained the predominant recognition site regardless of the conformation in which it was presented. A comparison of anti-DPAF mAbs obtained in response to two analogue peptides, PS1CT3 and CysCT3, in which the DPAF segment was either unconstrained or held within a cyclic loop, respectively, revealed a significant homology in the paratope composition. At one level a subset of anti-PS1CT3 and anti-CysCT3 mAbs was found to share a common heavy chain variable region. In addition, nucleotide sequence homology comparisons of both heavy and light chain variable regions identified the presence of anti-PS1CT3 and anti-CysCT3 mAbs that collectively appeared to derive from a common progenitor, but with nonidentical somatic mutations. Interestingly, however, no bias toward homologous Ag could be discerned on measurement of relative affinities of the mAbs for the two peptides. In contrast, mAb binding on-rates clearly discriminated between peptides representing the homologous vs the heterologous confomer of the DPAF epitope. Thus, it would appear that the kinetics of Ag recognition dominate over equilibrium binding criteria both in epitope-driven repertoire selection and Ab maturation in a humoral response

Plant-microbe community dynamics in rhizosphere: Reviewing the grassroots ecology towards sustainable agriculture

The interaction between microbes and plants in rhizospheric environment is evident regarding sustainable development in agriculture. Microbes are involved in various metabolic activities in plant systems, which in turn help in plant health improvement. Eventually, plant-microbe interactions are connected with biogeochemical cycles. In this context, metagenomic study helps us to survey the microbial diversity in their natural niches, especially in rhizospheric regions. Noticeably, a diverse group of bacteria, fungi, and archaea are likely to be involved in plant growth promoting (PGP) activities. Variation in microbial communities in the rhizosphere depends on various parameters, such as soil organic matter, plant genotype, plant exudates, crop rotation, soil pH, nutrient cycling, etc. Some abiotic factors and chemical fertilizers have negative impact on crop productivity, influencing sustainable development of environment. Despite having negative impacts from climate change, microbes cope with this altered scenario and try to adjust themselves successfully and consequently promote plant growth by nutrient acquisition and stress tolerance approaches. Therefore, climate change has appeared as a big threat to the agricultural sector in recent past and this might be persistent in near future. However, the conservation of microbial diversity in the rhizospheric regions appears as one of the most promising options for long-term environmental sustainability