Bias and Geometrical Effects on Optically Controlled MESFETs

A detailed characterization of the optical response of illuminated MESFETs due to several operating and geometrical conditions is presented. The characterization targets important optical performance factors including terminal photocurrent peak value and discharge time. A figure-of-merit is defined to quantify the overall response to these effects. The simulation results should be very useful in device operation and optimization

Bias and Geometrical Effects on Optically Controlled MESFETs

A detailed characterization of the optical response of illuminated MESFETs due to several operating and geometrical conditions is presented. The characterization targets important optical performance factors including terminal photocurrent peak value and discharge time. A figure-of-merit is defined to quantify the overall response to these effects. The simulation results should be very useful in device operation and optimization

Exercise protects against obesity induced semen abnormalities via downregulating stem cell factor, upregulating Ghrelin and normalizing oxidative stress

Increased oxidative stress and hormonal imbalance have been hypothesized to underlie infertility in obese animals. However, recent evidence suggests that Ghrelin and Stem Cell Factor (SCF) play an important role in fertility, in lean individuals. Therefore, this study aimed at investigating whether changes in the levels of Ghrelin and SCF in rat testes underlie semen abnormal parameters observed in obese rats, and secondly, whether endurance exercise or Orlistat can protect against changes in Ghrelin, SCF, and/or semen parameters in diet induced obese rats. Obesity was modelled in male Wistar rats using High Fat Diet (HFD) 12-week protocol. Eight week-old rats (n=40) were divided into four groups, namely, Group I: fed with a standard diet (12 % of calories as fat); Group II: fed HFD (40 % of calories as fat); Group III: fed the HFD with a concomitant dose of Orlistat (200 mg/kg); and Group IV: fed the HFD and underwent 30 min daily swimming exercise. The model was validated by measuring the levels of testosterone, FSH, LH, estradiol, leptin, triglycerides, total, HDL, and LDL cholesterol, and final change in body weight. Levels were consistent with published obesity models (see Results). As predicted, the HFD group had a 76.8 % decrease in sperm count, 44.72 % decrease in sperm motility, as well as 47.09 % increase in abnormal sperm morphology. Unlike the control group, in the HFD group (i.e. obese rats) Ghrelin mRNA and protein were elevated, while SCF mRNA and protein were diminished in the testes. Furthermore, in the HFD group, SOD and GPx activities were significantly reduced, 48.5±5.8 % (P=0.0012) and 45.6±4.6 % (P=0.0019), respectively, while TBARS levels were significantly increased (112.7±8.9 %, P≤0.0001). Finally, endurance exercise training and Orlistat administration individually and differentially protected semen parameters in obese rats. The mechanism includes, but is not limited to, normalizing the levels of Ghrelin, SCF, SOD, GPx and TBARS. In rat testes, diet induced obesity down regulates SCF expression, upregulates Ghrelin expression, and deteriorate oxidative stress levels, which are collectively detrimental to semen parameters. Exercise, and to a lesse r extent Orlistat administration, protected effectively against this detrimental effect

Plasmonic Nanostructured Cellular Automata

In this work, we have investigated the scattering plasmonic resonance characteristics of silver nanospheres with a geometrical distribution that is modelled by Cellular Automata using time-domain numerical analysis. Cellular Automata are discrete mathematical structures that model different natural phenomena. Two binary one-dimensional Cellular Automata rules are considered to model the nanostructure, namely rule 30 and rule 33. The analysis produces three-dimensional scattering profiles of the entire plasmonic nanostructure. For the Cellular Automaton rule 33, the introduction of more Cellular Automata generations resulted only in slight red and blue shifts in the plasmonic modes with respect to the first generation. On the other hand, while rule 30 introduced significant red shifts in the resonance peaks at early generations, at later generations however, a peculiar effect is witnessed in the scattering profile as new peaks emerge as a feature of the overall Cellular Automata structure rather than the sum of the smaller parts that compose it. We strongly believe that these features that emerge as a result adopting the different 256 Cellular Automata rules as configuration models of nanostructures in different applications and systems might possess a great potential in enhancing their capability, sensitivity, efficiency, and power utilization

Acute presentation of a heterotopic pregnancy following spontaneous conception: a case report

Spontaneous heterotopic pregnancy is a rare clinical condition in which intrauterine and extra uterine pregnancies occur at the same time. It can be a life threatening condition and can be easily missed with the diagnosis being overlooked. We present the case of a 40 year old patient who was treated for a heterotopic pregnancy. She had a transvaginal ultrasound because of a previous ectopic pregnancy and an intrauterine gestational sac was seen with false reassurances. The patient presented acutely with a ruptured tubal pregnancy and this was managed laparoscopically. The ectopic pregnancy was not suspected at her initial presentation. A high index of suspicion is needed in women with risk factors for an ectopic pregnancy and in low risk women who have free fluid with or without an adnexal mass with an intrauterine gestation

Effects of Electrode Spacing on the Response of Optically Controlled MESFETs

In microwave GaAs MESFETs, carrier transport is a strong function of carrier energy. When illuminated, the carrier energy and carrier distribution inside the device are substantially affected by the incident optical energy. To account for these effects an accurate model based on the energy formulation of the transport equation coupled with optical energy conversion equations is used [1-2]. This model is used to investigate the optimum design of optically controlled MESFET structures considering the trade -off between the degradation in electric characteristics and the improvement in photoelectric conversion efficiency. Time domain simulations show the significant effect of electrode spacing, specifically, the drain-gate separation

Effects of Electrode Spacing on the Response of Optically Controlled MESFETs

In microwave GaAs MESFETs, carrier transport is a strong function of carrier energy. When illuminated, the carrier energy and carrier distribution inside the device are substantially affected by the incident optical energy. To account for these effects an accurate model based on the energy formulation of the transport equation coupled with optical energy conversion equations is used [1-2]. This model is used to investigate the optimum design of optically controlled MESFET structures considering the trade -off between the degradation in electric characteristics and the improvement in photoelectric conversion efficiency. Time domain simulations show the significant effect of electrode spacing, specifically, the drain-gate separation

A Higher-order Accurate FDTD Solution to Scalar SHG Problems

A higher-order accurate FDTD simulation algorithm for the solution of the phase-dependent SHG problem is presented. This algorithm approximates the spatial derivatives in the propagation direction using 4th order FD schemes. It has been shown that this scheme guarantees the convergence of the solution using significantly less computation time and less memory requirement as compared to 2nd order scheme

Microwave Performance of Optically Controlled MESFETs

This paper presents the characterization of illuminated high-frequency active devices using a time -domain physical simulation model. The model is based on Boltztnann’s Transport Equation (BTE), which accurately accounts for carrier transport in microwave and millimeter wave devices with sub-micrometer gate lengths. Illumination effects are accommodated in the model to represent camer density changes inside the illuminated device. The simulation results are compared to available experimental records for a typical MESFET for validation purposes. The calculated y-parameters of the device show the profound effect of illumination on the microwave characteristics. These findmgs make the model an important tool for the design of active devices under illumination control