Tunable Thermoelectric Performance in Porous Armchair Graphene Nanoribbons as a Function of Strain,Pore Morphology and Temperature

In this paper, the thermoelectric performance of porous armchair graphene nanoribbons under tensile and compressive strain is investigated as a function of pore morphology and temperature. For all the porous structures irrespective of their pore size, the performance improves at a compressive strain of 10%, while for tensile nature, the minimum cut-off strain required for improved thermoelectric figure of merit (ZT) shows an inverse relation with the pore size. In addition, optimal pore shape geometry can yield better performance, even at lower values of strain. Further analysis reveals that tensile strain is not able to improve the performance at low and intermediate temperatures of around 300 K, whereas tensile/compressive strain is effective in enhancing the performance of porous armchair graphene nanoribbons at higher temperatures. Furthermore, the structures are found to be more sensitive to compressive strain than the tensile one since the effect of compressive strain is found to improve ZT more significantly. Our analysis based on Non-Equilibrium Green’s function calculations suggests a possible route for tailoring the functionality of nanomaterials so as to achieve great potentials for thermoelectric applications at various temperatures.     

Metabolic and endocrine aspects of the ventromedial hypothalamic syndrome in the rat.

Subjected 8 male Long-Evans hooded rats to parasagittal knife cuts that separated the medial from the lateral hypothalamic areas; following surgery, some Ss were given free access to food while others were restricted to normal quantities. Compared with 6 sham-operated controls, the restricted-food Ss exhibited hyperinsulinemia as early as 36 hr after surgery without any change in plasma glucose levels. The blood samples of free-food Ss which had become obese, showed hyperinsulinemia, mild hyperglycemia, and elevated levels of free fatty acids. These results suggest that the interruption of mediolateral hypothalamic connections produces hyperinsulinemia directly, and that further increases in insulin, glucose, and free fatty acid levels are caused by overeating. The surgical cuts produced an increase in aggressive behavior but no change in the circulating levels of testosterone. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypothalamic and midbrain neural pathways involved in eating, drinking, irritability, aggression, and copulation in rats.

Investigated in 3 experiments with male hooded rats (N = 61) the effects of parasagittal cuts placed at 3 anterior-posterior positions. Cuts that separated portions of the medial from the lateral hypothalamus produced severe hyposexuality if they lay lateral to the medial preoptic-anterior hypothalamic continuum. Hyperphagia, irritability, and modest sexual impairment were produced if the cuts lay lateral to the anterior tips of the ventromedial hypothalamic nuclei and slightly invaded the anterior hypothalamus. Posterior, but not anterior, medial-forebrain-bundle (MFB) cuts disrupted copulation. Central gray cuts resulted in slight hyperphagia, and reticular formation cuts resulted in hyposexuality. It is concluded that the medial hypothalamic nuclei exert their effects on eating, irritability, and copulation through their lateral connections with the lateral hypothalamus and those components of the MFB that descend on (or ascend from) the lower brainstem. (40 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capacitive gas and vapor sensors using nanomaterials

An immense number of sensors has been reported in the literature employing various methods for the detection of different gases and vapors. This article summarizes those sensors whose sensing layer is made up of nanostructured materials and a change in capacitance value of device is the key parameter for detecting a gas or vapor. Now-a-days, capacitive sensors are emerging as they consume less power, operate well at room temperature and show decent response and recovery time. The sensing principles, configurations, mechanisms and performances of capacitive sensors based on different nanostructures are summarized and discussed in the current article. Emerging carbon based nanomaterials like carbon nanotube and graphene are also highlighted for capacitive mode detection of gases and vapors. Finally, an outlook of primary challenges in this field are identified and discussed at the end of the review.     

Tailoring of Electromagnetic Absorption in Substituted Hexaferrites from 8.2 GHz to 12.4 GHz

Journal of Electronic Materials - Microwave absorbers are an important topic of interest to mitigate electromagnetic interference. Here, we have investigated electromagnetic absorption properties...     

Microwave Absorption Properties of Cobalt-Zirconium Doped Strontium Hexaferrites in Ku-Frequency Band

In this article, microwave electromagnetic properties of doped strontium hexaferrites have been investigated in Ku microwave frequency band (12.4–18 GHz), along with their performance as microwave absorbing materials. Vector network analyzer has been used for characterization of cobalt-zirconium substituted strontium hexaferrites Sr(CoZr)_xFe_(12?2x)O₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0), synthesized using sol-gel method. Real parts of permittivity and permeability have shown very small variations up to 16 GHz. There has been a dip in spectrum of real part of permittivity and a peak in spectrum of real part of permeability at the same frequency in 16–18 GHz range for every composition. Regarding the electromagnetic wave absorption, all the six prepared compositions have potential (≥90% absorption) for usage in suppressing electromagnetic pollution. The composition with x = 1.0 has achieved the highest ?10 dB absorption bandwidth from 15 to 18 GHz frequency. The realization of absorbing materials with maximum absorption is related to the phenomenon of impedance matching and high electromagnetic losses. The correlation of absorption peaks with attenuation constant, wave impedance and complex thickness has also been studied.     

Effect of temperature on dielectric and electrical properties of Co–Zr doped barium hexaferrites prepared by sol–gel method

In the present research, temperature dependence of dielectric properties of cobalt–zirconium substituted barium hexaferrites, fabricated using citric acid sol gel method, has been reported. The dielectric constant, loss tangent and A.C. conductivity were investigated on the circular pellets in temperature range 30–350 °C and frequency range 10 kHz–1 MHz using impedance analyzer. This paper also presents impedance (Z*) and electric modulus (M*) analysis of all the samples. The single semi-circular arcs, observed in impedance Nyquist plots, suggest the dominance of grain boundaries in the conduction process. Dielectric constant and dielectric loss tangent show very small variation up to 200–250 °C temperature and abrupt increase afterwards up to 350 °C. Thus, these ferrites can be successfully implemented in the practical applications like capacitors, microwave devices etc. up to 250 °C, without any significant change in properties.     

Performance Analysis of Combined Space Time Block Coding with Generalized Selection Combining in Underlay Cognitive Radio

Wireless Personal Communications - In this paper, we demonstrate the performance analysis of an underlay MIMO cognitive radios employing space time block coding at secondary’s user...