121 research outputs found

    Raman scattering reveals strong LO-phonon-hole-plasmon coupling in nominally undoped GaAsBi: optical determination of carrier concentration

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    We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1−xBix epitaxial layers exhibiting Biinduced (p-type) longitudinal-optical-plasmon coupled (LOPC) modes for 0.018≤x≤0.048. Redshifts in the GaAs-like optical modes due to alloying are evaluated and are paralleled by strong damping of the LOPC. The relative integrated Raman intensities of LO(Γ) and LOPC ALO/ALOPC are characteristic of heavily doped p-GaAs, with a remarkable near total screening of the LO(Γ) phonon (ALO/ALOPC →0) for larger Bi concentrations. A method of spectral analysis is set out which yields estimates of hole concentrations in excess of 5 × 1017 cm−3 and correlates with the Bi molar fraction. These findings are in general agreement with recent electrical transport measurements performed on the alloy, and while the absolute size of the hole concentrations differ, likely origins for the discrepancy are discussed. We conclude that the damped LO-phonon-hole-plasmon coupling phenomena plays a dominant role in Raman scattering from unpassivated nominally undoped GaAsBi

    Summation of two illusions of extent

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    Oppel-Kundt illusion balance

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    A phase I dose-escalation study of LRP5/6 antagonist BI 905677 in patients with advanced solid tumors

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    Background: Aberrant Wnt pathway signaling has been implicated in the development of many cancers. Targeting of low-density lipoprotein receptor-related protein 5/6 (LRP5/6) co-receptors inhibits Wnt signaling and may be a novel therapy. BI 905677 is an LRP5/6 antagonist that has demonstrated preclinical antitumor activity. Patients and methods: This (NCT03604445) was a phase I, dose-escalation study evaluating BI 905677 for patients with advanced solid tumors over two dosing schedules (A: i.v. infusion every 3 weeks, 3-week cycles; B: i.v. infusion every 2 weeks, 4-week cycles). Adult patients were eligible if they had exhausted treatment options and had an Eastern Cooperative Oncology Group performance status of 0-1. The primary endpoints were the maximum tolerated dose (MTD) and safety. Other endpoints were pharmacokinetics, pharmacodynamics, and efficacy. Results:In total, 37 patients received BI 905677 over nine dose cohorts (0.05-3.6 mg/kg/every 3 weeks). Dose-limiting toxicities were only reported during cycle 1 in the 3.6 mg/kg cohort and the MTD was established at 2.8 mg/kg every 3 weeks. Enrollment for schedule B was not pursued. The most frequently reported adverse events were diarrhea (35.1%), vomiting (21.6%), and C-telopeptide increase (18.9%). All patients in the 3.6 mg/kg cohort experienced a dose-limiting toxicity, suggesting a narrow therapeutic index. Paired pre-treatment and on-treatment biopsies, where available, showed decreased Axin2 expression by reverse transcriptase polymerase chain reaction with treatment, suggesting target inhibition. Best response observed was stable disease in 14 (38%) patients. Conclusion: The MTD of BI 905677 was set at 2.8 mg/kg every 3 weeks. BI 905677 was well tolerated but a narrow therapeutic range and minimal efficacy led to early termination of the trial.</p

    Enhancement of terahertz photoconductive antenna operation by optical nanoantennas

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    Photoconductive antennas are promising sources of terahertz radiation that is widely used for spectroscopy, characterization, and imaging of biological objects, deep space studies, scanning of surfaces, and detection of potentially hazardous substances. These antennas are compact and allow for generation of both ultrabroadband pulses and tunable continuous wave terahertz signals at room temperatures, with no need for high-power optical sources. However, such antennas have relatively low energy conversion efficiency of femtosecond laser pulses or two close pump wavelengths (photomixers) into the pulsed and continuous terahertz radiation, correspondingly. Recently, an approach to solving this problem that involves known methods of nanophotonics applied to terahertz photoconductive antennas and photomixers has been proposed. This approach comprises the use of optical nanoantennas for enhancing the absorption of pump laser radiation in the antenna gap, reducing the lifetime of photoexcited carriers, and improving the antenna thermal efficiency. This Review is intended to systematize the main results obtained by researchers in this promising field of hybrid optical-to-terahertz photoconductive antennas and photomixers. We summarize the main results on hybrid THz antennas, compare the approaches to their implementation, and offer further perspectives of their development including an application of all-dielectric nanoantennas instead of plasmonic ones

    Interim Brigade Combat Team (IBCT) Munitions Distribution Study

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    This research sought to describe an alternative way for calculating expected back order (EBO) for reparable inventory systems. The high costs associated with reparable items management, together with its importance for system\u27s availability, make the assessment of back orders of great importance in supporting decisions of what-to-buy and where-to-locate those items. Starting at the point that existing models (METRIC, MOD-METRIC, and VARIMETRIC) rely on some assumptions that often cannot be met in real life, the proposed method (called P-METRIC), which is a mix of simulation and mathematical analytical model, relaxes assumptions about Demand, Time to Repair (TTR), and Ordering & Ship Time (OST) distributions looking for potential differences that may cause on the EBO calculation. The study consists of 10 conceptual examples where the parameters of Demand, TTR, and OST vary according to probability distributions recognized by the related literature. It also presents a case study of 20 reparable items of the T-27 Tucano, an advanced-training, light-attack deployed by the Brazilian Air Force. EBO numbers of the existing and proposed models are compared with results gathered from simulation (conceptual examples) and a field research (T-27 Tucano) in order to allow conclusions about the accuracy and suitability of the proposed method
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