Interplay of spin,lattice, vibration,and charge degrees of freedom: Magneto-dielectricity in Ca3Mn2O7

From low-temperature Synchrotron X-ray diffraction, a precise thermal characterization of octahedral distortions in single-phase Ruddlesden-Popper Ca₃Mn₂O₇ is performed. Highly sensitive close-steps temperature dependences of Mn-O-Mn bond angles connecting MnO₆ octahedra clearly reveal the signature of spin ordering in the system. Spin-lattice coupling is thus revealed via the structural distortions, responsible for the evolution of the magnetic state. Further, benchmark temperature anomalies observed in the unit cell volume and its polarization-measure highlight the interplay between spin, lattice, and charge degrees of freedom. Strong spin-lattice coupling is supported by the Raman spectroscopy results across the magnetic ordering. Dielectric study on Ca₃Mn₂O₇ features relaxor-like segmented dynamics below the antiferromagnetic ordering. Dipolar relaxations of different origins are spectrally resolved, exhibiting distinct H-field alterations which identify their allegiance to different magnetic subphases. Dipole-relaxation characteristics examined under applied magnetic field and the ensuing magneto-dielectricity consistently correlate with the concurrent magnetic, structural, and vibrational features.     

New clinical issues in celiac disease

The present study examined, in rats with N-methyl-D-aspartate-induced lesions of the basolateral amygdala, the effects of long-term adrenalectomy (i.e. 12-13 weeks) on memory for spatial and cued learning in a water maze. In sham amygdala-lesioned rats, adrenalectomy induced impairments in acquisition and retention performance for the spatial, but not the cued water-maze task. The adrenalectomized rats sustained selective degeneration and death of granule cells in the dentate gyrus dorsal blade. Continuous supplementation of the animals' drinking water with an extremely low dose of corticosterone (20 microg/ml) did not block the retention deficit, but blocked the acquisition deficit and the dentate gyrus neurodegenerative changes. The finding that the memory impairments and dentate gyrus neurodegeneration are dissociable supports the view that the adrenalectomy-induced memory effects are due to the loss of activational effects of circulating adrenal hormones at the time of learning. In adrenalectomized rats which received corticosterone as well as those which did not, lesions of the basolateral amygdala blocked the impairing effects of adrenalectomy on spatial learning and memory. However, the basolateral amygdala lesions did not affect the neurodegenerative changes in the dentate gyrus. In conclusion, the present findings provide further evidence that the basolateral amygdala is involved in regulating stress hormone effects on learning and memory.     

Influence of Hydrogenation on Electronic and Magnetic Properties of PrNi: A First Principles Study

Electronic and magnetic properties of PrNi and PrNi–H have been investigated by using first principles approach. Calculations are performed using full potential linearized augmented plane wave plus local orbitals method including spin-polarization within the frame work of density functional theory. The electronic exchange–correlation energy is described by generalized gradient approximation. The ground state of both the compounds is base-centered orthorhombic CrB structure. The hydrogen stored in PrNi, i.e., PrNi–H has been studied to analyze the effective changes in magnetic moments and electronic structures in comparison with PrNi. The total cell energy of the hydrogenated PrNi compound has been found to be lower than in PrNi compound. The decrease in the cell energy shows more stability of the hydrogenated PrNi at ambient conditions. The values for total and local magnetic moments decrease on hydrogen insertion in PrNi. A comparative study of the projected density of states in both the compounds has also been presented. Both the compounds are found metallic in nature.     

High-responsivity (Ga2Ge)100−x(Ga3Sb2)x (x = 15, 30, 45, 60) photodetection sensor for optoelectronic applications

Journal of Materials Science: Materials in Electronics - Electromagnetic signal detection for applications such as astronomy, product quality monitoring, health, and necessitates systems that are...     

The Effect of Heat Treatment of TiO2 Nanoparticles on Photovoltaic Performance of Fabricated DSSCs

The present work focuses on the synthesis of mixed phase TiO₂ nanoparticles with reduced band gaps without even being doped. The synthesis was carried out by chemical route followed by heat treatments at different temperatures to favor rutile incorporation in anatase network. The significance of different heat treatment temperatures on the phase composition of TiO₂ nanoparticles and its effect on optical band gap and the photovoltaic performance are analyzed. The thermal analysis, phases, morphology, and energy band gap of as-synthesized TiO₂ nanoparticles have been characterized by DTA/TG, x-ray diffraction, field-emission scanning electron microscope, transmission electron microscope, and UV-Vis-NIR, respectively. The results show the presence of rutile (~15 nm) and anatase phases (~17 nm) in “as-synthesized” TiO₂ nanoparticles. TiO₂ nanoparticles are heat treated for 2 h at 200, 400, and 600 °C in air. It is observed that heat treatment results in higher photoactivity in visible region of the solar radiation and the material demonstrated high photovoltaic performance in conjunction with N-719. The optical band gap values are found to be in the range of 2.59-2.88 eV. The dye-sensitized solar cells (DSSCs) fabricated by TiO₂ nanoparticles, heat treated at 600 ºC show the energy conversion efficiency (η) of 6.08% with high photo current density (J _sc) of 11.76 mA/cm². The work highlighted in this paper represents the realization of simple method of achieving low band gap semiconductors without being doped, for DSSCs applications.     

Optimization of carboxylate-terminated poly(amidoamine) dendrimer-mediated cisplatin formulation

Cisplatin is mainly used in the treatment of ovarian, head and neck and testicular cancer. Poor solubility and non-specific interactions causes hurdles in the development of successful cisplatin formulation. There were few reports on poly(amidoamine) (PAMAM) dendrimer–cisplatin complexes for anticancer treatment. But the earlier research was mainly focused on therapeutic effect of PAMAM dendrimer–cisplatin complex, with less attention paid on the formulation development of these complexes. Objective of the present study is to optimize and validate the carboxylate-terminated, EDA core PAMAM dendrimer-based cisplatin formulation with respect to various variables such as dendrimer core, generation, drug entrapment, purification, yield, reproducibility, stability, storage and in-vitro release. Dendrimer–cisplatin complex was prepared by an efficient method which significantly increases the % platinum (Pt) content along with the product yield. Dendrimers showed reproducible (～27%) platinum loading by weight. Variation in core and generations does not produce significant change in the % Pt content. Percentage Pt content of dendrimeric formulation increases with increase in drug/dendrimer mole ratio. Formulation with low drug/dendrimer mole ratio showed delayed release compared to the higher drug/dendrimer mole ratio; these dendrimer formulations are stable in room temperature. In vitro release profiles of the stored dendrimer–cisplatin samples showed comparatively slow release of cisplatin, which may be due to formation of strong bond between cisplatin and dendrimer. This study will contribute to create a fine print for the formulation development of PAMAM dendrimer–cisplatin complexes.     

Test-enhanced learning in a middle school science classroom: The effects of quiz frequency and placement.

Typically, teachers use tests to evaluate students' knowledge acquisition. In a novel experimental study, we examined whether low-stakes testing (quizzing) can be used to foster students' learning of course content in 8th grade science classes. Students received multiple-choice quizzes (with feedback); in the quizzes, some target content that would be included on the class summative assessments was tested, and some of the target content was not tested. In Experiment 1, three quizzes on the content were spaced across the coverage of a unit. Quizzing produced significant learning benefits, with between 13% and 25% gains in performance on summative unit examinations. In Experiments 2a and 2b, we manipulated the placement of the quizzing, with students being quizzed on some content prior to the lecture, quizzed on some immediately after the lecture, and quizzed on some as a review prior to the unit exam. Review quizzing produced the greatest increases in exam performance, and these increases were only slightly augmented when the items had appeared on previous quizzes. The benefits of quizzing (relative to not quizzing) persisted on cumulative semester and end-of-year exams. We suggest that the present effects reflect benefits accruing to retrieval practice, benefits that are well established in the basic literature. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Fe3+-substitution effect on the thermal variation of J–E characteristics and DC resistivity of quadruple perovskite CaCu3Ti4O12

The electrical properties of cubic perovskite series, CaCu_3–xTi_4–xFe_2xO₁₂ with x = 0.0, 0.1, 0.3, 0.5, and 0.7, have been studied by employing current density as a function of electric field characteristics registered at different temperatures and thermal variations of direct current electrical resistivity measurements. All of the compositions exhibit strong non-ohmic behavior. The concentration dependence of breakdown field, the temperature at which switching action takes place, and maximum value of current density (J_max) has been explained on account of structural, microstructural, and positron lifetime parameters. The highest ever reported value of J_max = 327 mA/cm² has been observed for pristine composition. The values of the nonlinear coefficient advise the suitability of ceramics for low-voltage varistor applications. The Arrhenius plots show typical semiconducting nature. The activation energy values indicate that electric conduction proceeds through electrons with deformation in the system.