Room temperature mid-infrared InAsSbN multi-quantum well photodiodes grown by MBE

Room temperature photoresponse in the mid-infrared spectral region is demonstrated from InAsSbN/InAs multi-quantum well photodiodes grown by nitrogen plasma assisted molecular beam epitaxy. The structural quality of the InAsSbN MQWs was ascertained in situ by reflection high energy electron diffraction and ex situ by high resolution x-ray diffraction and photoluminescence measurements. The extended long wavelength photoresponse is identified to originate from the electron–heavy hole (e1–hh1) and electron–light hole (e1–lh1) transitions in the InAsSbN MQW, with a cut off wavelength ~4.20 µm and peak detectivity D *  =  1.25  ×  109 cm Hz1/2 W−1

Lichens facilitate seedling recruitment in alpine heath

Abstract Questions How do mat thickness, physical structure and allelopathic properties of terricolous mat-forming lichens affect recruitment of vascular plants in dwarf-shrub and lichen heath vegetation?. Location The mountains of Dovrefjell, central Norway. Methods In autumn, seeds of ten vascular plant species were collected and sown in a common garden experiment with mats of six lichen species and bare-soil controls as experimental treatments. We recorded growing season soil temperature and moisture, and seedling recruitment and growth after one year. The effect of lichen secondary compounds on germination was tested in a growth chamber experiment and compared to the lichen-plant interactions detected under field conditions. Results The lichen mats buffered extreme soil temperatures and soil drying in dry weather, with soils below the thickest mats (Cladonia stellaris and C. rangiferina) experiencing the lowest temperature fluctuations. Seedling recruitment and seedling growth in the field and seed germination in the lab were species-specific. Seedling recruitment rates were overall higher within lichen mats than on bare soil, but the c. 6.5 cm thick mats of C. stellaris reduced recruitment of many species. The lab experiment suggested no overall strong effect of lichen allelopathy on seed germination, and effects on seed germination were only moderately correlated with the lichen-plant interactions observed for seedling recruitment in the field. Conclusions In harsh environments like alpine dwarf-shrub and lichen heaths, the presence of lichens and the resulting amelioration of the microclimate seems more important for vascular plant recruitment than are allelopathic effects often reported in lab experiments. We might therefore expect most terricolous lichens, depending on the plant species in focus, to facilitate rather than hamper the early stages of plant recruitment into lichen-dominated arctic-alpine heath vegetation. This article is protected by copyright. All rights reserved.Peer reviewe

Analytical solutions for semiconductor luminescence including Coulomb correlations with applications to dilute bismides

In this paper we introduce analytical solutions of interband polarization, which is the self-energy of the Dyson equation for the photon Green’s functions, and apply them to studying photoluminescence of Coulomb-correlated semiconductor materials. The accuracy of the easily programmable solutions is proven by consistently demonstrating the low-temperature s-shape of the luminescence peak of dilute bismide semiconductors. The different roles of homogeneous versus inhomogeneous broadening at low and high temperatures are described, as well as the importance of many body effects, which are in very good agreement with experiments

Efektywność rozmnażania in vitro zwartnicy chmiela (Hippeastrum x chmielii CHM.) z eksplantatów pędowych i łuskowych

Material inicjalny umieszczono na pożywce MS bez regulatorów wzrostu; z dodatkiem 2,0 mg BA·dm⁻³ + 0,2 mg NAA·dm⁻³ lub 2,0 mg 2iP·dm⁻³ + 0,2 mg NAA·dm⁻³. Tylko 12-24% eksplantatów pędowych formowało cebulki bez egzogennych regulatorów wzrostu, a w ich obecności cebulki różnicowały się na prawie wszystkich eksplantatach (92-100%). Na eksplantatach łuskowych cebulki formowały się w 100%, niezależnie od obecności regulatorów wzrostu w pożywce. Średnio uzyskano 0,6-0,9 małych cebulek (o średnicy poniżej 2 mm) z eksplantatu pędowego na pożywce bez regulatorów wzrostu i aż 14-16 cebulek średniej wielkości (o średnicy 2,1-4 mm) w obecności obydwu kombinacji regulatorów wzrostu. Z eksplantatów dwułuskowych uzyskiwano około 2 dużych cebulek (o średnicy 4,1-6,0 mm), niezależnie od obecności regulatorów wzrostu.Initial plant material was cultured on MS medium without growth regulators, supplemented with 2.0 mg BA·dm⁻³ + 0.2 mg NAA·dm⁻³ or 2.0 mg 2iP·dm⁻³ + 0.2 mg NAA·dm⁻³. Only 12-24% of shoot explants formed bulblets in the absence of exogenous growth regulators, whereas in their presence almost all explants produced bulblets (92-100%). Scale explants regenerated bulblets in 100%, regardless of the presence of growth regulators in the medium. On the average, 0.6-0.9 small bulblets (diameter: less than 2 mm) were obtained from a shoot explant in the medium without growth regulators and 14-16 bulblets medium sized (diameter: 2.1-4 mm) in the presence of both growth regulator combinations. Approximately 2 big bulblets (diameter: 4.1-6.0 mm) were obtained from twin scale explants in all medium types

Hopping Excitons in GaInNAs - Simulation οf Micro- and Macrophotoluminescence Spectra

Model of hopping excitons has been applied to explain the origin of sharp lines observed in microphotoluminescence spectra of GaInNAs layers. It has been shown that shape of the micro- and macrophotoluminescence spectra results from the exciton hopping between localizing centers and this phenomenon is responsible for the observation of sharp lines in microphotoluminescence experiment. In addition, the influence of different model parameters on photoluminescence spectra and their characteristic parameters such as the Stokes shift and full width at half maximum has been investigated

Monte Carlo Simulations of the Influence of Localization Centres on Carrier Dynamics in GaInNAs Quantum Wells

Model of hopping excitons is applied to study the carrier dynamics in GaInNAs/GaAs quantum well system. Impact of parameters describing localizing states (i.e., an average energy and density) on carrier dynamics in GaInNAs material is investigated theoretically. It is shown how those parameters affect the quantities that can be extracted from time resolved photoluminescence experiments. It is shown that obtained simulations can be very helpful in the interpretation of the experimental data

Wpływ różnych metod modyfikacji skrobi ziemniaczanej, pszennej i kukurydzianej na ich cechy fizykochemiczne

The physico-chemical properties of potato, wheat and maize starch, native and modified according to three methods, were studied. It was found that mild acid or enzymatic hydrolysis resulted in an increased temperature of starch pasting, a reduction of paste viscosity, and an increase of gel syneresis after defreezing. The physico-chemical changes brought about by phosphate modification were opposite to those induced by the acid and enzymatic modification. Studies of three fractions of potato starch differing in granule size showed that the changes due to modification increase with the decrease of average granule size.Przeprowadzono badania fizykochemiczne skrobi ziemniaczanej, pszennej i kukurydzianej naturalnej i modyfikowanej metodami: kwasową, enzymatyczną i fosforanową. Skrobia ziemniaczana przed modyfikacją była rozdzielana na trzy frakcje różnicą się średnią wielkością ziarn (tab. 2). Stwierdzono (tab. 1), że w wyniku łagodnej hydrolizy kwasowej lub enzymatycznej nastąpiło - w stosunku do skrobi niemodyfikowanej - podwyższenie temperatury kleikowania skrobi, obniżenie lepkości kleiku i zwiększenie synerezy żelu po jego rozmrożeniu. Modyfikacja fosforanowa spowodowała zmiany badanych cech fizykochemicznych, ale w przeciwnym kierunku niż modyfikacja kwasowa i enzymatyczna. Stosunkowo najbardziej podatna skrobia kukurydziana i najmniej - skrobia pszenna. Badania frakcji skrobi ziemniaczanej różniących się wielkością ziarn ujawniły (tab. 3), że im drobniejsza była frakcja, tym łatwiej zachodziła hydroliza kwasowa lub enzymatyczna oraz silniej wzrastała lepkość kleików otrzymanych ze skrobi modyfikowanej metodą fosforanową. Natomiast wchłanianie wody było tym większe, im większe były ziarna skrobi

Profile of volatile compounds in European dry-cured hams as indicator of their quality and authenticity

W pracy przedstawiono analizę profili związków lotnych szynek surowo dojrzewających przy zastosowaniu techniki SPME (mikroekstrakcja do fazy stałej) w połączeniu z GC-MS (chromatografia gazowa sprzężona ze spektrometrią mas) oraz technikami chemometrycznymi PCA (analiza składowych głównych) i CA (analiza skupień). Przebadano szynki pochodzące: z Hiszpanii – Serrano, z Włoch – Parma, Crudo, Mantovelle, z Polski – kumpiak podlaski i z Niemiec – Schinkenspeck. W przebadanych szynkach zidentyfikowano 61 związków lotnych, które zakwalifikowano do następujących grup: aldehydy (14), ketony (3), alkohole (7), estry (9), alkany (6), węglowodory aromatyczne (2), kwasy (4), związki heterocykliczne (1), terpeny (11), fenole (1), inne (3). Dominującymi grupami były aldehydy i alkohole. Stwierdzono obecność alifatycznych aldehydów nasyconych (2-metylobutanalu i 3-metylobutanalu), które stanowią dobry wskaźnik procesu oksydacji, zachodzącego w szynkach surowo dojrzewających oraz produktów utleniania kwasów tłuszczowych (heksanal, oktanal). Obróbka chemometryczna umożliwiła zróżnicowanie badanego materiału oraz rozróżnienie szynek między innymi ze względu na technologię produkcji. Po zastosowaniu analizy składowych głównych oraz analizy skupień wyodrębniono 4 grupy szynek: włoskie i hiszpańskie, szynkę polską i szynkę niemiecką. Połączenie analizy instrumentalnej z metodami chemometrycznymi może być użyteczne do określania pochodzenia produktu i jego autentyczności.In the research study, the analysis is presented of profiles of volatile compounds in dry-cured hams using SPME (solid phase microextraction) together with GC-MS and chemometric techniques of PCA (principal component analysis) and CA (cluster analysis). Seven dry-cured hams from different European countries were analyzed: Serrano ham from Spain, Parma, Crudo, and Mantovelle hams from Italy, kumpiak podlaski ham from Poland, and Schinkenspeck ham from Germany. In the hams analyzed, 61 volatile compounds were identified and classified in the following groups: aldehydes (14), ketones (3), alcohols (7), esters (9), alkanes (6), aromatic hydrocarbons (2), acids (4), heterocyclic compounds (1), terpenes (11), phenols (1) and others (3). The prevailing groups were aldehydes and alcohols. It was found that the saturated aliphatic aldehydes (2-metylobutanal and 3-metylobutanal) were present in the hams; they are a good indicator of the oxidation process ongoing in the dry-cued hams; moreover, there were found products of fatty acid oxidation (hexanal, octanal). The chemometric treatment made it possible to diversify the material under analysis and to identify hams based, among other things, on the production technology. On the basis of the analysis of principal components and cluster analysis, 4 groups of hams were defined: Italian and Spanish, Polish ham, and German ham. The combination of instrumental analysis and chemometric methods can be useful for determining the origin of product and its authenticity

Fine Structure of the Localized Emission from GaInNAs Layers Studied by Micro-Photoluminescence

GaInNAs bulk-like layers ( ≈ 20% In and ≈ 3% N) grown on GaAs substrate with various crystallographic orientations have been studied by micro-photoluminescence at low temperatures for a broad range of excitation conditions. In addition to photoluminescence peaks, which are associated with heavy- and light-hole free exciton recombination, a band of sharp lines was observed below the fundamental free exciton transition at low excitation. It shows that the localized emission which is typical of this alloy at low temperatures is composed of individual narrow photoluminescence lines which are associated with the recombination of single excitons. They can be localized on various local potential minima including those originating from the alloy content fluctuations and/or deep acceptor(donor)-like complexes