Effect of electron-phonon interaction on the shift and attenuation of optical phonons

Using the Boltzmann equation for electrons in metals, we show that the optical phonons soften and have a dispersion due to screening in agreement with the results reported recently [M. Reizer, Phys. Rev. B {\bf 61}, 40 (2000)]. Additional phonon damping and frequency shift arise when the electron--phonon interaction is properly included.Comment: 4 pages, late

AlGaInN Laser Diode Technology for Systems Applications

Gallium Nitride (GaN) laser diodes fabricated from the AlGaInN material system is an emerging technology that allows laser diodes to be fabricated over a very wide wavelength range from u.v. to the visible, and is a key enabler for the development of new system applications such as (underwater and terrestrial) telecommunications, quantum technologies, display sources and medical instrumentation

Free-space and underwater GHz data transmission using AlGaInN laser diode technology

Laser diodes fabricated from the AlGaInN material system is an emerging technology for defence and security applications; in particular for free space laser communication. Conventional underwater communication is done acoustically with very slow data rates, short reach, and vulnurable for interception. AlGaInN blue-green laser diode technology allows the possibility of both airbourne links and underwater telecom that operate at very fast data rates (GHz), long reach (100’s of metres underwater) and can also be quantum encrypted. The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of <100mW. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported in free-space and underwate

Перспективы использования современных средств фото- и видеосъемки при расследовании преступлений

Розглянуто перспективи використання сучасних засобів фото- та відеозйомки під час розслідування злочинів. Проаналізовано технічні характеристики таких сучасних технічних засобів, як action-камери та ендоскопи. Розглянуто аction-камери як цифрові пристрої, що можуть значно розширити можливості фото- та відеофіксації перебігу і результатів слідчих (розшукових) дій. Для пошуку та фіксації доказової інформації в ускладнених умовах запропоновано використання ендоскопів. Надано пропозиції щодо упровадження зазначених засобів у криміналістичну діяльність для пошуку і фіксації доказової та орієнтуючої інформації під час проведення слідчих (розшукових) дій.Perspectives for the use of modern means of photography and video recording within forensic activities have been studied. It has been indicated that photo and video equipment is rapidly becoming obsolete and losing its relevance, so we should use the latest tools based on digital technologies for more effective recording of investigative (search) actions. The technical characteristics of such modern technical means as action cameras and endoscopes have been analyzed. Action cameras have been studied as digital devices that can significantly expand the possibilities of photo and video recording of the course of investigative (search) actions, as well as some types of forensic research. Extensive possibilities of using action cameras within investigative practice during investigative (search) actions allow to reproduce the movements, facial expressions, gestures of persons (during interrogation and simultaneous interrogation of two or more persons) with high accuracy; allow to display not only static, but also dynamic situation (crime scene search, search, presentation for identification, investigative experiment), and also provide many other advantages.The use of endoscopes in forensic activities will solve the problem not only of fixation, but also the search for evidence in difficult conditions (in ventilation ducts, pipes, hidden places of bathrooms, built-in furniture). The waterproofness of the endoscope allows us to use it for underwater inspection (in a well, pond, aquarium). The effectiveness of the endoscope is unquestionable in studying internal structure of the weapon, the overlap of the walls and in many other cases, when penetration into hard-to-reach places is required during the expert examination.Рассмотрены перспективы использования современных средств фото-, видеосъемки при расследовании преступлений. Проанализированы технические характеристики таких современных технических средств, как action-камеры и эндоскопы. Рассмотрены аction-камеры как цифровые устройства, которые могут значительно расширить возможности фото- и видеофиксации хода и результатов следственных (розыскных) действий. Для поиска и фиксации доказательственной информации в затрудненных условиях предложено использование эндоскопов. Изложены предложения по внедрению таких средств в криминалистическую деятельность для поиска и фиксации доказательственной и ориентирующей информации при проведении следственных (розыскных) действий

Lateral grating DFB AlGaInN laser diodes for optical communications and atomic clocks

AlGaInN laser diode technology is of considerable interest for telecom applications and next generation atomic optical clocks based on Sr (by using 422nm & 461nm) and Rb at 420.2nm.Very narrow linewidths (<1MHz) are required for such applications. We report lateral gratings on AlGaInN ridge waveguide laser diodes to achieve a single wavelength device with a good side mode suppression ratio (SMSR) that is suitable for atomic clock and telecom applications

High Speed Visible Light Communication Using Blue GaN Laser Diodes

GaN-based laser diodes have been developed over the last 20 years making them desirable for many security and defence applications, in particular, free space laser communications. Unlike their LED counterparts, laser diodes are not limited by their carrier lifetime which makes them attractive for high speed communication, whether in free space, through fiber or underwater. Gigabit data transmission can be achieved in free space by modulating the visible light from the laser with a pseudo-random bit sequence (PRBS), with recent results approaching 5 Gbit/s error free data transmission. By exploiting the low-loss in the blue part of the spectrum through water, data transmission experiments have also been conducted to show rates of 2.5 Gbit/s underwater. Different water types have been tested to monitor the effect of scattering and to see how this affects the overall transmission rate and distance. This is of great interest for communication with unmanned underwater vehicles (UUV) as the current method using acoustics is much slower and vulnerable to interception. These types of laser diodes can typically reach 50-100 mW of power which increases the length at which the data can be transmitted. This distance could be further improved by making use of high power laser arrays. Highly uniform GaN substrates with low defectivity allow individually addressable laser bars to be fabricated. This could ultimately increase optical power levels to 4 W for a 20-emitter array. Overall, the development of GaN laser diodes will play an important part in free space optical communications and will be vital in the advancement of security and defence applications

COVID-19-Associated Candidiasis (CAC): An Underestimated Complication in the Absence of Immunological Predispositions?

The recent global pandemic of COVID-19 has predisposed a relatively high number of patients to acute respiratory distress syndrome (ARDS), which carries a risk of developing super-infections. Candida species are major constituents of the human mycobiome and the main cause of invasive fungal infections, with a high mortality rate. Invasive yeast infections (IYIs) are increasingly recognized as s complication of severe COVID-19. Despite the marked immune dysregulation in COVID-19, no prominent defects have been reported in immune cells that are critically required for immunity to Candida. This suggests that relevant clinical factors, including prolonged ICU stays, central venous catheters, and broad-spectrum antibiotic use, may be key factors causing COVID-19 patients to develop IYIs. Although data on the comparative performance of diagnostic tools are often lacking in COVID-19 patients, a combination of serological and molecular techniques may present a promising option for the identification of IYIs. Clinical awareness and screening are needed, as IYIs are difficult to diagnose, particularly in the setting of severe COVID-19. Echinocandins and azoles are the primary antifungal used to treat IYIs, yet the therapeutic failures exerted by multidrug-resistant Candida spp. such as C. auris and C. glabrata call for the development of new antifungal drugs with novel mechanisms of action.M.H. received research funding by Gilead and Pfizer. D.S.P. receives research support and/or serves on advisory boards for Amplyx, Cidara, Scynexis, N8 Medical, Merck, Regeneron, and Pfizer. He also has a patent covering the detection of fungal species and drug resistance, as well as a pending patent on COVID-19 detection licensed to T2 Biosystems. A.C. was supported by the Fundação para a Ciência e a Tecnologia (FCT) (CEECIND/03628/2017 and PTDC/MED-GEN/28778/2017). Additional support was provided by FCT (UIDB/50026/2020 and UIDP/50026/2020), the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement through the European Regional Development Fund (ERDF) (NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000023), the European Union’s Horizon 2020 research and innovation program under grant agreement no. 847507, and the “la Caixa” Foundation (ID 100010434) and FCT under the agreement LCF/PR/HP17/52190003

Surface and electronic structure of MOCVD-grown Ga(0.92)In(0.08)N investigated by UV and X-ray photoelectron spectroscopies

The surface and electronic structure of MOCVD-grown layers of Ga(0.92)In(0.08)N have been investigated by means of photoemission. An additional feature at the valence band edge, which can be ascribed to the presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface was prepared by argon ion sputtering and annealing. Stability of chemical composition of the investigated surface subjected to similar ion etching was proven by means of X-ray photoemission spectroscopy.Comment: 13 pages, 6 figure

A multicentre study to optimize echinocandin susceptibility testing of Aspergillus species with the EUCAST methodology and a broth microdilution colorimetric method

BACKGROUND: The determination of the minimal effective concentration (MEC) of echinocandins against Aspergillus species is subjective, time consuming and has been associated with very major errors. METHODS: The MECs/MICs of 40 WT [10 each of Aspergillus fumigatus species complex (SC), Aspergillus flavus SC, Aspergillus terreus SC and Aspergillus niger SC] and 4 non-WT A. fumigatus isolates were determined with EUCAST E.Def 9.3.1 read microscopically, macroscopically, spectrophotometrically and colorimetrically in three centres. The optimal conditions for spectrophotometric (single- versus multi-point readings) and colorimetric (XTT/menadione concentration and stability, incubation time) methods were evaluated in preliminary studies using different cut-offs for the determination of macroscopic, spectrophotometric and colorimetric MIC endpoints compared with the microscopically determined MEC. Inter-centre and inter-method essential (within one 2-fold dilution) agreement (EA) and categorical agreement (CA) were determined. RESULTS: Both macroscopic and spectr