Investigation of high frequency performance limit of graphene field effect transistors

Cataloged from PDF version of article.Extremely high field effect mobility together with the high surface coverage makes graphene a promising material for high frequency electronics application. We investigate the intrinsic high frequency performance limit of graphene field effect transistors limited by the charge impurity scattering. The output and transfer characteristics of graphene field effect transistors together with the high frequency performance are characterized as a function of impurity concentration and dielectric constant of the gate insulator. Our results reveal that graphene transistors could provide power gain at radio frequency band. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506506

A Continuous Review Replenishment-Disposal Policy for an Inventory System with autonomous supply and fixed disposal costs

Cataloged from PDF version of article.In this study, we analyze an inventory system facing stochastic external demands and an autonomous supply (independent return flow) in the presence of fixed disposal costs and positive lead times under a continuous review replenishment-disposal policy. We derive the analytical expressions of the operating characteristics of the system; and, construct the objective function to minimize the total expected costs of ordering, holding, purchasing and disposal per unit time subject to a fill rate constraint. An extensive numerical analysis is conducted to study the sensitivity of the policy parameters and the benefit of employing a policy which allows for disposal of excess stock in this setting. We model the net demand process as the superposition of normally distributed external demand and inflows, which is expressed as a Brownian motion process. Our findings indicate that the disposal option results in considerable savings even (i) in the presence of non-zero fixed disposal costs, (ii) large actual demand rates with high return ratios (resulting in small net demands) and (iii) for moderate return ratios with high demand variability. (C) 2007 Elsevier B.V. All rights reserved

Femtosecond pulse generation from an extended cavity Cr4+: Forsterite laser using graphene on YAG

A room temperature, multipass-cavity, femtosecond Cr4+:forsterite laser was modelocked with a single-layer graphene saturable absorber on a YAG substrate. The resonator produced nearly transform-limited 92 fs pulses near 1250 nm with 53 kW of peak power. © OSA 2013

Is the mycobacteria-derived purified protein response in atopic asthmatic children different? A case study from Istanbul, Turkey

Background: The response to mycobacteria-derived purified protein (PPD) is mediated primarily by T-helper-1 response and is expected to be inhibited in atopic diseases. The aim of this study was to investigate whether the PPD response is different in atopic asthmatic children. Methods: 40 atopic asthmatic children (mean age 8.3 +/- 4.9 years) and 40 healthy age- and sex-matched children who had received bacillus Calmette-Guerin (BCG) vaccination were included in the study. Five PPD units were administered intradermally to all children and were interpreted after 48 h. Results: There was no correlation between serum total IgE level and PPD induration (p = 0.054). The PPD induration was not statistically different between the children who used inhaled corticosteroid and those who did not. Although the PPD positivity (induration 6 5 mm) rate was higher in atopic asthmatic children (50%) than in healthy children (32.5%), the difference was not found to be statistically significant. The PPD induration in atopic asthmatic children (7.41 8 5.58 mm) was found to be greater than the one in healthy children (5.21 +/- 3.39) (p < 0.039). The induration in atopic asthmatic children (5.21 +/- 3.77) and healthy children (4.43 +/- 2.32) did not show a difference in children who where vaccinated only once with BCG, but it was found to be statistically significantly greater in atopic asthmatic children (12.50 +/- 5.90) than healthy children (7.08 +/- 4.70) who were vaccinated with BCG twice (p < 0.012). The proportion of having a PPD induration of 6 10 mm was found to be higher in atopic asthmatic children than in the healthy ones (32.5 vs. 12.5%) (p < 0.032). Conclusion: Our data showed that the PPD response was stronger in BCG-vaccinated atopic asthmatic children than in healthy BCG-vaccinated ones. Copyright (C) 2004 S. Karger AG, Basel

Femtosecond pulse generation from an extended cavity Cr⁴⁺: Forsterite laser using graphene on YAG

A room temperature, multipass-cavity, femtosecond Cr4+:forsterite laser was modelocked with a single-layer graphene saturable absorber on a YAG substrate. The resonator produced nearly transform-limited 92 fs pulses near 1250 nm with 53 kW of peak power. © OSA 2013

Graphene mode-locked multipass-cavity femtosecond Cr4+: Forsterite laser

We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr4+ : forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr4+ : forsterite laser mode locked with a graphene saturable absorber. The corresponding pulse energy was 5.3 nJ with only 24 mW of average output power. The saturation fluence and modulation depth of the GSA were measured to be 25 μJ/cm2 and 0.74%, respectively. The nonlinear effects in the Cr4+ : forsterite medium that limit further power scaling were also investigated by using different output couplers. © 2013 Optical Society of America

Graphene mode-locked multipass-cavity femtosecond Cr⁴⁺: Forsterite laser

We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr4+ : forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr4+ : forsterite laser mode locked with a graphene saturable absorber. The corresponding pulse energy was 5.3 nJ with only 24 mW of average output power. The saturation fluence and modulation depth of the GSA were measured to be 25 μJ/cm2 and 0.74%, respectively. The nonlinear effects in the Cr4+ : forsterite medium that limit further power scaling were also investigated by using different output couplers. © 2013 Optical Society of America

Active Matter Alters the Growth Dynamics of Coffee Rings

We show that bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets, as the droplet evaporation rate slows down

Initial Pharmacological Characterization of a Major Hydroxy Metabolite of PF-5190457: Inverse Agonist Activity of PF-6870961 at the Ghrelin Receptor

Preclinical and clinical studies have identified the ghrelin receptor [growth hormone secretagogue receptor (GHSR)1a] as a potential target for treating alcohol use disorder. A recent phase 1a clinical trial of a GHSR1a antagonist/inverse agonist, PF-5190457, in individuals with heavy alcohol drinking identified a previously undetected major hydroxy metabolite of PF-5190457, namely PF-6870961. Here, we further characterized PF-6870961 by screening for off-target interactions in a high-throughput screen and determined its in vitro pharmacodynamic profile at GHSR1a through binding and concentration-response assays. Moreover, we determined whether the metabolite demonstrated an in vivo effect by assessing effects on food intake in male and female rats. We found that PF-6870961 had no off-target interactions and demonstrated both binding affinity and inverse agonist activity at GHSR1a. In comparison with its parent compound, PF-5190457, the metabolite PF-6870961 had lower binding affinity and potency at inhibiting GHSR1a-induced inositol phosphate accumulation. However, PF-6870961 had increased inhibitory potency at GHSR1a-induced β-arrestin recruitment relative to its parent compound. Intraperitoneal injection of PF-6870961 suppressed food intake under conditions of both food restriction and with ad libitum access to food in male and female rats, demonstrating in vivo activity. The effects of PF-6870961 on food intake were abolished in male and female rats knockout for GHSR, thus demonstrating that its effects on food intake are in fact mediated by the GHSR receptor. Our findings indicate that the newly discovered major hydroxy metabolite of PF-5190457 may contribute to the overall activity of PF-5190457 by demonstrating inhibitory activity at GHSR1a. SIGNIFICANCE STATEMENT: Antagonists or inverse agonists of the growth hormone secretagogue receptor (GHSR)1a have demonstrated substantial potential as therapeutics for alcohol use disorder. We here expand understanding of the pharmacology of one such GHSR1a inverse agonist, PF-5190457, by studying the safety and pharmacodynamics of its major hydroxy metabolite, PF-6870961. Our data demonstrate biased inverse agonism of PF-6870961 at GHSR1a and provide new structure-activity relationship insight into GHSR1a inverse agonism