Electrical, magnetoresistance and magnetotransport properties of Nd1−xSrxMnO3

The effects of Sr substitution on the electrical, magnetoresistance and magnetotransport properties of Nd1−xSrxMnO3 were studied. Nd1−xSrxMnO3 samples were prepared using the solid-state reaction method with x=0.12, 0.152, 0.22, 0.252 and 0.32. All samples showed an orthorhombic structure, and no impurities were detected when the samples were examined using the X-ray diffraction method. The grain size was between 10 μm and 16 μm for all samples. The sample with x=0.32 showed the smallest grain size and the lowest To value, where To reflects the MnOMn bond angle. As the Sr concentration increased, the grains grew into more pentagonal and hexagonal shapes, and the insulator–metal transition temperature, Tim, also increased from 131 K to 180 K. The exceptions were the samples with x=0.152 and 0.252, where charge ordering was found at 120 K. The samples with the most pentagonal and hexagonal shaped grains (x=0.32) had the highest Tim. The magnetoresistance (MR) values were found to increase with increasing magnetic field. The sample with x=0.32 showed the highest MR value (31.5%), the highest Tim, the smallest grain size (∼10 μm) and the least bending of the MnOMn bonding angle

MODEL COMPUTATION WITH SECOND-ORDER RADIATIVE TRANSFER EQUATION FOR SNOW MEDIUM USING COUPLED FINITE ELEMENT METHOD AND METHOD OF MOMENT AND RELAXED HIERARCHICAL EQUIVALENT SOURCE ALGORITHM

Active microwave remote sensing is essential to monitor the conditions of the environment by analyzing the microwave returns from the earth terrain. Various Computational Electromagnetics (CEM) techniques are implemented to study the backscattering coefficient of numerous earth terrains such as vegetation and snow medium. In this paper, a theoretical model based on second order radiative transfer equation is investigated by incorporating two computational methods which are known as coupled Finite Element Method (FEM) and Method of Moment (MoM), and Relaxed Hierarchical Equivalent Source Algorithm (RHESA). These theoretical models consider three shapes of scatterers which can be used to represent the ice particles of snow medium. These mentioned shapes are sphere, droxtal and hexagonal column. These methods are used to investigate the effect of various incident angles and frequencies on the backscattering mechanism. These results are compared with analytical Mie solution and ground truth measurement to analyze and verify the model

Magnetotransport properties of La0.67Ca0.33MnO3 with different grain sizes

The magnetotransport and magnetoresistive (MR)properties of manganese-based La0.67Ca0.33MnO3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature in magnetic fields of 0.5 and 1 T. The insulator–metal transition temperature, TIM, shifted to a higher temperature with the application of the magnetic field. In zero field, TIM is almost constant (∼271 K) for all samples except for the sample with the largest grain size, where TIM = 265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region and the insulating (paramagnetic) region. The density of states at the Fermi level, N(EF), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The ρ–T 2 curves are nearly linear in the metallic regime, but the ρ–T 2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data well in the high-temperature region,indicating the existence of the Jahn–Teller distortion that localizes the charge carriers. MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling effect

Sound velocity in perovskite manganites La0.67Ca0.33MnO3 with different grain sizes

The longitudinal and shear sound velocities in colossal magnetoresistive material La0.67Ca0.33MnO3 sintered at 1100, 1250 and 1350 1C with average grain size 1, 3 and 5 mm, respectively, have been measured from 80 to 300K using the pulse-echo-overlap method.A pronounced increase in the longitudinal sound velocity was observed in all samples around the insulator–metal transition temperature (TIM272 K). XRD patterns showed the orthorhombic structure for all samples. The longitudinal and shear velocities showed the largest hysteresis for the sample with 3 mm grain size. A step-like shear sound velocity anomaly near 120K during cooling or warming was observed to be dependent on the grain size

RNomic identification and evaluation of npcTB_6715, a nonprotein- coding RNA gene as a potential biomarker for the detection of Mycobacterium tuberculosis

Technological advances in RNA biology greatly improved transcriptome profiling during the last two decades. Besides the discovery of many small RNAs (sRNA) that are involved in the physiological and pathophysiological regulation of various cellular circuits, it becomes evident that the corresponding RNA genes might also serve as potential biomarkers to monitor the progression of disease and treatment. sRNA gene candidate npcTB_6715 was previously identified via experimental RNomic (unpublished data), and we report its application as potential biomarker for the detection of Mycobacterium tuberculosis (MTB) in patient samples. For proof of principle, we developed a multiplex PCR assay and report its validation with 500 clinical cultures, positive for Mycobacteria. The analysis revealed 98.9% sensitivity, 96.1% specificity, positive and negative predictive values of 98.6% and 96.8%, respectively. These results underscore the diagnostic value of the sRNA gene as diagnostic marker for the specific detection of MTB in clinical samples. Its successful application and the general ease of PCR-based detection compared to standard bacterial culture techniques might be the first step towards ‘point-of-care’ diagnostics of Mycobacteria. To the best of our knowledge, this is the first time for the design of diagnostic applications based on sRNA genes, in Mycobacteria

Performance of solar air collector-thermoelectric hybrid system

Solar collectors are technologies which using sunlight to collect heat energy. In this study, solar air collector-thermoelectric hybrid systemis designed and constructed. Performance testing is conducted in the lab. The size of this hybrid system is 97.5 × 59 × 12 cm. The manipulating factor is the mass flow rate which is fixed at 0.033, 0.0385, 0.044, 0.0495 and0.055 kg/s. The intensity of solar radiation is set at 700 W/m2. Maximum temperature change (To -Ti) reaches 7.5 °C while maximum temperature change (Tback - Thollow) reaches 16.7 °C. Maximum thermal efficiency of this hybrid system reaches 79.0% at the highest mass flow rate of 0.055 kg/s. The maximum electrical efficiency reaches 5.3% at the lowest mass flow rate of 0.033 kg/s. Maximum overall efficiency reaches 79% at the highest mass flow rate. The hybrid system has better thermal efficiency than a stand-alone solar air collector. Due to the increased overall efficiency, the proposed hybrid system is anticipated to promote wider application of thermoelectric hybrid system

The effect of a reversed circular jet impingement on a bifacial module PVT collector energy performance

Photovoltaic thermal (PVT) technologies have a significant downside in addition to their numerous advantages. PVT technologies are constrained by the fact that its photovoltaic module gains heat due to exposure to solar irradiance, which reduces the photovoltaic efficiency. Jet impingement is one of the most effective methods to cool a photovoltaic module. An indoor experiment using a solar simulator was conducted on a bifacial PVT solar collector cooled by a reversed circular flow jet impingement (RCFJI) to evaluate the energy performance of the PVT collector. The study was conducted under a constant solar irradiance of 900W/m2 and flowrate (mass) ranging from 0.01 to 0.14 kg/s. Three bifacial modules with 0.22, 0.33, and 0.66 packing factors were mounted 25 mm above the RCFJI for cooling. The 0.66 packing factor module recorded the highest photovoltaic efficiency of 10.91 % at 0.14 kg/s flowrate (mass). Meanwhile, the 0.22 and 0.33 packing factors recorded a photovoltaic efficiency of 4.50 % and 6.45 %, respectively. The highest thermal efficiency recorded under the same operating condition was 61.43 %, using a 0.66 packing factor. Overall, the highest combined photovoltaic thermal (PVT) efficiency for 0.22, 0.33, and 0.66 was 56.62 %, 61.88 %, and 72.35 %, respectively

Surface plasmon modes of a single silver nanorod: an electron energy loss study

We present an electron energy loss study using energy filtered TEM of spatially resolved surface plasmon excitations on a silver nanorod of aspect ratio 14.2 resting on a 30 nm thick silicon nitride membrane. Our results show that the excitation is quantized as resonant modes whose intensity maxima vary along the nanorod's length and whose wavelength becomes compressed towards the ends of the nanorod. Theoretical calculations modelling the surface plasmon response of the silver nanorod-silicon nitride system show the importance of including retardation and substrate effects in order to describe accurately the energy dispersion of the resonant modes.Comment: 9 pages, 6 figure

Performance enhancement of photovoltaic modules with passive cooling multidirectional tapered fin heat sinks (MTFHS)

The electrical output of photovoltaic (PV) modules degrades with continued exposure to extreme temperatures caused by solar radiation. The uniqueness of this research lies in the utilization of multidirectional fins with varying heights, which effectively accelerate heat transfer in PV cooling systems by inducing a transition in the boundary layer within the confined zone of the fins. The research aims to investigate the effect of using Multidirectional Tapered Fin Heat Sinks (MTFHS) to improve the efficiency of PV modules by utilizing aluminum alloy material as heatsinks. The proposed multidirectional design aims to facilitate enhanced heat transfer by promoting airflow in the central area of the PV module. The experimental procedures in our study differ from previous research as we utilized the latest generation of PV modules (405 Wp, PERC Half-cut cells) to fill the discrepancy between laboratory-based investigations and practical applications. Two PV modules were tested for an outdoor parametric analysis under outdoor operating conditions, with solar irradiance recorded from 200 to 1000 W/m2 and ambient temperatures ranging from 26° to 38 °C. Findings indicated that the proposed MTFHS could lower PV module temperatures by 12 ⁰C. Reduced temperature boosts PV module efficiency by 1.53%. Cooling advancements proved vital in contributing to sustainability in PV system installations

Clostridium perfringens epsilon toxin increases the small intestinal permeability in mice and rats

Epsilon toxin is a potent neurotoxin produced by Clostridium perfringens types B and D, an anaerobic bacterium that causes enterotoxaemia in ruminants. In the affected animal, it causes oedema of the lungs and brain by damaging the endothelial cells, inducing physiological and morphological changes. Although it is believed to compromise the intestinal barrier, thus entering the gut vasculature, little is known about the mechanism underlying this process. This study characterizes the effects of epsilon toxin on fluid transport and bioelectrical parameters in the small intestine of mice and rats. The enteropooling and the intestinal loop tests, together with the single-pass perfusion assay and in vitro and ex vivo analysis in Ussing's chamber, were all used in combination with histological and ultrastructural analysis of mice and rat small intestine, challenged with or without C. perfringens epsilon toxin. Luminal epsilon toxin induced a time and concentration dependent intestinal fluid accumulation and fall of the transepithelial resistance. Although no evident histological changes were observed, opening of the mucosa tight junction in combination with apoptotic changes in the lamina propria were seen with transmission electron microscopy. These results indicate that C. perfringens epsilon toxin alters the intestinal permeability, predominantly by opening the mucosa tight junction, increasing its permeability to macromolecules, and inducing further degenerative changes in the lamina propria of the bowel. © 2009 Goldstein et al