Point defects and p-type conductivity in Zn1-xMnxGeAs2

Positron annihilation spectroscopy is used to study point defects in Zn1–xMnxGeAs2 crystals with low Mn content 0≤x≤0.042 with disordered zincblende and chalcopyrite structure. The role of negatively charged vacancies and non-open-volume defects is discussed with respect to the high p-type conductivity with carrier concentration 10exp19≤p≤10exp21cm−3 in our samples. Neutral As vacancies, together with negatively charged Zn vacancies and non-open-volume defects with concentrations around 10exp16−10exp18 cm−3, are observed to increase with increasing Mn content in the alloy. The observed concentrations of defects are not sufficient to be responsible for the strong p-type conductivity of our crystals. Therefore, we suggest that other types of defects, such as extended defects, have a strong influence on the conductivity of Zn1–xMnxGeAs2 crystals.Peer reviewe

Study of ultrathin Pt/Co/Pt trilayers modified by nanosecond XUV pulses from laser-driven plasma source

We have studied the structural mechanisms responsible for the magnetic reorientation between in-plane and out-of-plane magnetization in the (25 nm Pt)/(3 and 10 nm Co)/(3 nm Pt) trilayer systems irradiated with nanosecond XUV pulses generated with laser-driven gas-puff target plasma source of a narrow continuous spectrum peaked at wavelength of 11 nm. The thickness of individual layers, their density, chemical composition and irradiation-induced lateral strain were deduced from symmetric and asymmetric X-ray diffraction (XRD) patterns, grazing-incidence X-ray reflectometry (GIXR), grazing incidence X-ray fluorescence (GIXRF), extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) measurements. In the as grown samples we found, that the Pt buffer layers are relaxed and that the layer interfaces are sharp. As a result of a quasi-uniform irradiation of the samples, the XRD, EXAFS, GIXR and GIXRF data reveal the formation of two distinct layers composed of Pt1-xCox alloys with different Co concentrations, dependent on the thickness of the as grown magnetic Co film but with similar ∼1% lateral tensile residual strain. For smaller exposure dose (lower number of accumulated pulses) only partial interdiffusion at the interfaces takes place with the formation of a tri-layer composed of Co-Pt alloy sandwiched between thinned Pt layers, as revealed by TEM. The structural modifications are accompanied by magnetization changes, evidenced by means of magneto-optical microscopy. The difference in magnetic properties of the irradiated samples can be related to their modification in Pt1-xCox alloy composition, as the other parameters (lateral strain and alloy thickness) remain almost unchanged. The out-of-plane magnetization observed for the sample with initially 3 nm Co layer can be due to a significant reduction of demagnetization factor resulting from a lower Co concentration

Saccharomyces cerevisiae w układzie pokarmowym, oddechowym i na skórze człowieka

The results of observations on the occurrence of S. cerevisiaein the respiratory and digestive systems and on the skin in hospitalised individuals, mostly belonging to so-called risk groups of fungal infections, conducted over a period of five years (1999-2004), are described and discussed. The participation of S. cerevisiaein the mycocoenoses studied was 11.04% of all the recorded fungi. A significant increase in its prevalence, especially on the skin, was noticed. The fungus was mostly isolated with fungi of the genera Candidaand Trichosporon, as well as separately in the last two years of the study.Przeanalizowano (1999-2004) udział S. cerevisiaew dodatnich wynikach mikologicznych (2880 prób) Pracowni Bakteriologii SPZG i ChP w Olsztynie. Grzyby pochodziły z różnych odcinków ontocenozy układu oddechowego, pokarmowego oraz ze skóry pacjentów onkologicznych i z przewlekłymi chorobami układu oddechowego, w tym podejrzanych o gruźlicę. Ogólnie uzyskano 317 izolatów S. cerevisiae, co stanowi 11,04% wszystkich stwierdzonych grzybów – gatunek ten najczęściej towarzyszył licznym grzybom drożdżopodobnym (Candida, Trichosporon). Ontocenozą najczęściej zasiedlaną przez S. cerevisiaebył układ pokarmowy, a następnie oddechowy. Na skórze notowano go głównie w ostatnich dwóch latach badań. O ile w układzie oddechowym i pokarmowym drożdże pojawiały się z podobną częstością u kobiet i mężczyzn (z niewielkim przesunięciem w kierunku kobiet), to na skórze kobiet notowano je prawie dwukrotnie częściej. Z reguły izolowano je latem i jesienią, rzadko wiosną i zimą. We wszystkich ontocenozach zauważono wyraźny wzrost prewalencji badanego gatunku, co może świadczyć o wzroście jego ekspansywności w stosunku do organizmu człowieka

Tempo wzrostu Candida albicans [Robin, 1853] i Candida stellatoidea [Martin et Jones, 1938] izolowanych z ukladu oddechowego czlowieka

The study comprises an analysis of the growth rate of C. albicans and C. stellatoidea strains isolated from the respiratory system and incubated on Nickerson's and Sabouraud's agar in the dark and by light. The property to form hyphae and pseudohyphae by both species was used to evaluate the growth rate. The increase in their growth allowed to isolate the stages characteristic for growth and development of most fungi. Disturbances appeared with the fungi exposed to light which is the factor definitely setting back the growth. Faster growth and development was observed with C. stellatoidea