Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor

The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25–310 °C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor ( I ds > 1 A mm −1 ) to be defined (0.5 A mm −1 at 300 °C). The vertical breakdown voltage has been determined to be ∼850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current

Geological controls on the dynamics of riverbank retreat in the western Podhale region

The western part of Podhale region is drained by the Czarny Dunajec and the Biały Dunajec rivers, flowing from the Tatra Mts., and streams originating in the region (Cichy Stream, Bystry Stream, Czerwony Stream, Wielki Rogoźnik). River banks are cut in the Podhale Flysch or in the alluvium of these rivers overlain with loam deposits of varied origin. This paper investigates the combined effect of weathering, frost processes and mass movements on the banks of the Czarny Dunajec River and its tributaries typified by different substrate material. Bank retreat due to frost processes was measured during multigelation periods using erosion pins. Grain size distribution and cohesion of the substrate were also determined for alluvial and loam deposits. On flysch cutbanks, we determined joint spacing and the density and direction of fractures, and other structural and textural characteristics of the rocks. The results indicate that the rate of bank retreat decreases from the banks cut in sandy loam deposits, through alluvial loam banks (with high clay content), the banks composed of poorly cemented gravels and shaly flysch, to the banks cut in sandstones and highly cemented Neogene gravels. Bank retreat due to frost processes and mass-wasting was more efficient in the cold half-year

The efficiency of pollutant elimination in the Dobra treatment plant

This study was aimed to conduct an analysis of the efficiency of pollutant elimination in the Dobra treatment plant, which operates based on the SBR reactor. The object purifies domestic sewage and pre-treated industrial sewage from a slaughterhouse within the Dobra municipality. The source material for the analysis comprised the values of pollution indicators: BOD5 , CODCr, total suspended solids (TTS) in raw sewage (19 samples) and treated sewage (34 samples). The results of chemical analyses were obtained in the period 2007-2014. The results were compared with the limit values imposed by the Regulation (2014). The coefficient of reliability of the treatment plant was also calculated in this study. The average efficiency of pollutant elimination in the treatment plant was: BOD5 - 98.6%, CODCr - 94.9%, total suspended solids - 97.6%. These results demonstrate that the studied facility operates flawlessly and the treatment efficiency is high. On the other hand, the reliability coefficient values indicate that the operation of this object is unstable

Electron microscopy and spectroscopy investigations of CuOx–CeO2−δ/Si thin films

International audienceCuO x-CeO 2-δ /Si thin films were elaborated by pulsed laser deposition. At the surface of all CuO x-CeO 2-δ thin films, Ce 4+ and Cu +1 ions were present. Depth profiles indicated that a Cu 2 O rich layer, roughly 40 nm thick, covered the CuO x-CeO 2−δ thin films. Apart from the copper enriched surface, the copper repartition in the thin films is highly inhomogeneous and two types of copper oxides, CuO and Cu 2 O, in form of rounded grains 20 nm were identified in the thin films. At least 10 at. % Cu seems to be inserted in the ceria lattice. Pure CeO 2 grains result from the deposition of tetrahedron-like nanoclusters followed by coalescence of (111) faces, and CuO x-CeO 2-δ grains from the deposition of cube-like nanoclusters followed by coalescence of (110) faces. The good catalytic performances of the CuO x-CeO 2-δ /Si thin films are due to active {100} ceria exposed facets covered by a Cu 2 O nanoparticles

Products of lipid, protein and RNA oxidation as signals and regulators of gene expression in plants

Reactive oxygen species (ROS) are engaged in several processes essential for normal cell functioning, such as differentiation, anti-microbial defense, stimulus sensing and signaling. Interestingly, recent studies imply that cellular signal transduction and gene regulation are mediated not only directly by ROS but also by the molecules derived from ROS-mediated oxidation. Lipid peroxidation leads to non-enzymatic formation of oxylipins. These molecules were shown to modulate expression of signaling associated genes including genes encoding phosphatases, kinases and transcription factors. Oxidized peptides derived from protein oxidation might be engaged in organelle-specific ROS signaling. In turn, oxidation of particular mRNAs leads to decrease in the level of encoded proteins and thus, contributes to the post-transcriptional regulation of gene expression. Present mini review summarizes latest findings concerning involvement of products of lipid, protein and RNA oxidation in signal transduction and gene regulation

Effect of cobalt chloride on soybean seedlings subjected to cadmium stress

Contamination of the environment with heavy metals such as Cd is a serious problem of modern world. Exposure of plants to Cd leads to oxidative stress, inhibition of respiration and photosynthesis, increased rate of mutation and, as a consequence, stunted growth and yield decrease. One of the common reactions of plants to cadmium stress is over-production of ethylene, however the exact role of this hormone in plants response to Cd is still unrecognized. The aim of the present study is evaluation of the impact of an ethylene synthesis inhibitor, Co, on the response of soybean seedlings to cadmium stress. The experiments included measurements of growth, cell viability, ethylene production and expression of genes associated with cellular signaling in soybean seedlings exposed to CdCl2 (with Cd in a concentration of 223 μM) and/or CoCl2 (with Co in concentration of 4.6 μM). Surprisingly, the results show that Co has no effect on ethylene biosynthesis, however, it affects cell viability and expression of Cd-induced genes associated with plant signaling pathways. The affected genes encode mitogen-activated protein kinase kinase2 (MAPKK2), nitrate reductase and DOF1 and bZIP2 transcription factors. The role of Co in plants response to cadmium stress and its potential use as an ethylene inhibitor is discussed

Damage to the forest environment as a result of tourism and recreation

The purpose of the paper was to determine the impact of the most popular form of recreation and tourism (i.e. walking) on the environment in selected forests that were made available by the means of educational trails. The research was carried out in south−eastern Poland, in the forest reserves Bór (RB) and Polanki (RP) as well as in the economic forests of the Kołaczyce (NK) and Brzozów (NB) forest districts. A 1−km−long transect was established on both sides along each educational trail with control points determined every 10 m. In total 200 points were distinguished and data on the degree of soil damage was collected at research plots with an area of 1 m2 each. Based on these 200 plots, damage of young trees and soil were measured. The studies indicate that the damage to the soil and trees in the immediate vicinity of the routes available for recreation and tourism are very large. In all objects, 53−99% of the soil surface and 28−56% of trees were damaged. Slightly damaged soil earned the highest fraction on all studied trails (for NK it was 62%, RB – 49%, RP – 35.5% and NB – 26.5%). The most severe soil damage (packed soil) was recorded in as many as 37% of the measurement points in RB, 9.5% in RP and NB and 7% in NK. The most common form of damage to the trees was bark rub without damaging the pulp or partial damage to the needles or leaves. In case of NK, such damage was observed in 41% of trees, while 30.4% of RB, NB in 20.9% and RP in 13.9%. Trees ranked as the 2 most severe degrees of damage accounted for as much as 9.2% in NK, while 7.2% of RP, 6.4% in RB and 5.6% in NB. The damage level of the examined components of the forest environment determined in the study as a result of tourist and recreational use should be considered as high