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In this work, we study the absorption properties of AlN in the range of 1.5–5.5 eV, as well as the metastable change in absorption induced by ultraviolet (UV) irradiation (photochromism). We also study the restoration of the initial state under the action of the irradiation of 2–4 eV or elevated temperatures. UV irradiation results in a decrease of the absorption coefficient from 110 to 55 cm−1 at 4.7 eV, while in the visible range, the absorption coefficient increases from values below 5 to ∼35 cm−1. Measurements with two linear polarizations, E ∥ c and E ⊥ c, provide the determination of several different absorption bands at 2.6, 2.8, 3.4, 4.0, 4.5, and 4.8 eV. The bands at 2.6 and 3.4 eV identify the defect levels near the valence band, while the band peaking at 2.8 eV is related to the conduction band. Photochromism allows for controlling the absorption of light in two related spectral ranges, because the decrease of UV absorption and increase of visible absorption are related to switching the charge state of the same defects. [ABSTRACT FROM AUTHOR]

Aims: Develop a robust and user‐friendly software tool for the prediction of dopamine D2 receptor occupancy (RO) in patients with schizophrenia treated with either olanzapine or risperidone, in order to facilitate clinician exploration of the impact of treatment strategies on RO using sparse plasma concentration measurements. Methods: Previously developed population pharmacokinetic models for olanzapine and risperidone were combined with a pharmacodynamic model for D2 RO and implemented in the R programming language. Maximum a posteriori Bayesian estimation was used to provide predictions of plasma concentration and RO based on sparse concentration sampling. These predictions were then compared to observed plasma concentration and RO. Results: The average (standard deviation) response times of the tools, defined as the time required for the application to predict parameter values and display the output, were 2.8 (3.1) and 5.3 (4.3) seconds for olanzapine and risperidone, respectively. The mean error (95% confidence interval) and root mean squared error (95% confidence interval) of predicted vs. observed concentrations were 3.73 ng/mL (−2.42–9.87) and 10.816 ng/mL (6.71–14.93) for olanzapine, and 0.46 ng/mL (−4.56–5.47) and 6.68 ng/mL (3.57–9.78) for risperidone and its active metabolite (9‐OH risperidone). Mean error and root mean squared error of RO were −1.47% (−4.65–1.69) and 5.80% (3.89–7.72) for olanzapine and −0.91% (−7.68–5.85) and 8.87% (4.56–13.17) for risperidone. Conclusion: Our monitoring software predicts concentration–time profiles and the corresponding D2 RO from sparsely sampled concentration measurements in an accessible and accurate form. [ABSTRACT FROM AUTHOR]

Two inch diameter, highly conducting (Si-doped) bulk β-Ga2O3 single crystals with the cylinder length up to one inch were grown by the Czochralski method. The obtained crystals revealed high structural quality characterized by narrow x-ray rocking curves (FWHM ≤ 25 arc sec) and high surface smoothness (RMS < 200 pm) of the epi-ready wafers. The free electron concentration and Hall mobility at room temperature were in the range of 1.6–9 × 1018 cm−3 and 118 – 52 cm2 V−1 s−1, respectively, which are not affected by a heat treatment at temperatures up to 1000 °C in an oxidizing atmosphere. Temperature-dependent electrical properties of the crystals revealed a degenerated semiconducting state. Both high structural quality and electrical properties make the crystals well suited as substrates for homoepitaxy and electronic device fabrication in the vertical configuration. [ABSTRACT FROM AUTHOR]

In this article, the suitability of the etchants NaOH/KOH and Ba(OH)2 for defect etching of metalorganic vapour‐phase epitaxy (MOVPE) grown AlN layers with a MgO‐assisted "drop method" is compared. Defect selectivity for the new etchant Ba(OH)2 is confirmed by the local TEM analysis. Temperature dependence (420–500 °C) of etch pit sizes of a‐, mixed‐, and c‐type dislocations for both etchants are investigated by statistical evaluation of scanning electron microscopy (SEM) images. Additionally, the etch pit shape is analyzed for samples etched at 460 °C by atomic force microscopy (AFM) measurements. While a‐ and mixed‐type dislocations result in pits of comparable size and shape for both etchants, c‐type dislocations are already strongly etched with NaOH/KOH at low temperatures leading to over‐etching and MgO precipitation. Ba(OH)2, in contrast, generates smaller c‐type etch pits at low and medium etching temperatures and no MgO precipitates and is therefore preferable for drop etching. [ABSTRACT FROM AUTHOR]

The article focuses on the U.S. Food and Drug Administration (FDA) is to address the high cost of medicines by promoting market competition. Topics include the FDA has announced the Drug Competition Action Plan which aims to remove barriers to generic drug development and encourage timely entry of generic competition, and the FDA has focused its efforts under this plan to improve the efficiency and transparency to the regulatory review process for generic drug applications.

Pre-exposure prophylaxis (PrEP) has emerged as a promising strategy for preventing the transmission of HIV. Although only one formulation is currently approved for PrEP, research into both new compounds and new delivery systems for PrEP regimens offer intriguing challenges from the perspective of pharmacokinetic and pharmacodynamic modeling. This review aims to provide an overview the current modeling landscape for HIV PrEP, focused on PK/PD and QSP models relating to antiretroviral agents. Both current PrEP treatments and new compounds that show promise as PrEP agents are highlighted, as well as models of uncommon administration routes, predictions based on models of mechanism of action and viral dynamics, and issues related to adherence to therapy. The spread of human immunodeficiency virus (HIV) remains one of the foremost global health concerns. In the absence of a vaccine, other prophylactic strategies have been developed to prevent HIV transmission. One approach, known as pre-exposure prophylaxis (PrEP), allows HIV-negative individuals who are at high risk of exposure to the virus, be it through an HIV-positive sexual partner or through the shared use of drug injection equipment, to substantially reduce the risk of developing an HIV infection. PrEP is a relatively recent approach to combating the HIV epidemic, with the only currently approved treatment being Truvada, a daily oral antiretroviral (ARV) therapy initially indicated in the treatment of active HIV-1 infections, but approved for HIV PrEP in 2012. Although PrEP therapy has consistently demonstrated high efficacy in preventing HIV infection, this efficacy is dependent on patient adherence to the prescribed treatment regimen. This can present a significant problem in low- and middle-income countries, which may lack the infrastructure to provide sufficient access to PrEP medication to maintain daily dosing regimens. Furthermore, while the conventional approach has generally been to advocate for continuous administration akin to regimens used for viral suppression in infected patients, there has been some discussion of whether a better treatment paradigm might be to push for PrEP therapy primarily during those known periods of heightened exposure risk, while relying on post-exposure prophylaxis regimens to prevent infection after unanticipated exposures during low-risk periods. These considerations have led to a push for the development of long-duration and on-demand PrEP formulations, including subdermal and subcutaneous implants, slow-release intramuscular depot injections, vaginal and rectal antimicrobial gels, and intravaginal rings and dissolving films. PrEP therapy is a quickly evolving field, with a variety of antiretroviral compounds and formulations under investigation. This review aims to report on notable drugs and formulations from a pharmacokinetic/pharmacodynamic (PK/PD) modeling perspective. Given the nature of PrEP as a preventive therapy designed for long-term use, clinical trials for PrEP therapies can last for months or even years, particularly in the case of long-duration formulations. Furthermore, in contrast to antiretroviral trials in infected patients, pharmacodynamic endpoints in PrEP therapies are difficult to quantify, as the primary endpoint for efficacy is generally the rate of seroconversion. Computational modeling approaches offer flexible and powerful tools to provide insight into drug behavior in clinical settings, and can ultimately reduce the time, expense, and patient burden incurred in the development of PrEP therapies. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe in order to control the gas phase composition of the conventional physical vapor transport (PVT) configuration. We discuss the experimental implementation of the extra gas pipe by comparing crystal growth runs under various gas flow conditions with numerical simulations. The potential of the M-PVT growth method will be demonstrated by showing the improved doping characteristics when performing nitrogen, phosphorus and aluminum doping of SiC using the additional gas pipe for dopant supply. [Copyright &y& Elsevier]