How much laser power can propagate through fusion plasma?

Propagation of intense laser beams is crucial for inertial confinement fusion, which requires precise beam control to achieve the compression and heating necessary to ignite the fusion reaction. The National Ignition Facility (NIF), where fusion will be attempted, is now under construction. Control of intense beam propagation may be ruined by laser beam self-focusing. We have identified the maximum laser beam power that can propagate through fusion plasma without significant self-focusing and have found excellent agreement with recent experimental data, and suggest a way to increase that maximum by appropriate choice of plasma composition with implication for NIF designs. Our theory also leads to the prediction of anti-correlation between beam spray and backscatter and suggests the indirect control of backscatter through manipulation of plasma ionization state or acoustic damping.Comment: 15 pages, 4 figures, submitted to Plasma Physics and Controlled Fusio

Carbon and nitrogen pools in thermokarst-affected permafrost landscapes in Arctic Siberia

Ice rich Yedoma-dominated landscapes store considerable amounts of organic carbon (C) and nitrogen (N) and are vulnerable to degradation under climate warming. We investigate the C and N pools in two thermokarst-affected Yedoma landscapes – on Sobo-Sise Island and on Bykovsky Peninsula in the North of East Siberia. Soil cores up to three meters depth were collected along geomorphic gradients and analysed for organic C and N contents. A high vertical sampling density in the profiles allowed the calculation of C and N stocks for short soil column intervals and enhanced understanding of within-core parameter variability. Profile-level C and N stocks were scaled to the landscape level based on landform classifications from five-meter resolution, multispectral RapidEye satellite imagery. Mean landscape C and N storage in the first meter of soil for Sobo-Sise Island is estimated to be 20.2 kg C m−2 and 1.8 kg N m−2 and for Bykovsky Peninsula 25.9 kg C m−2 and 2.2 kg N m−2. Radiocarbon dating demonstrates the Holocene age of thermokarst basin deposits but also suggests the presence of thick Holocene aged cover layers which can reach up to two meters on top of intact Yedoma landforms. Reconstructed sedimentation rates of 0.10 mm yr−1–0.57 mm yr−1 suggest sustained mineral soil accumulation across all investigated landforms. Both Yedoma and thermokarst landforms are characterized by limited accumulation of organic soil layers (peat). We further estimate that an active layer deepening by about 100 cm will increase organic C availability in a seasonally thawed state in the two study areas by ~ 5.8 Tg (13.2 kg C m−2). Our study demonstrates the importance of increasing the number of C and N storage inventories in ice-rich Yedoma and thermokarst environments in order to account for high variability of permafrost and thermokarst environments in pan-permafrost soil C and N pool estimates

Critical Strain Region Evaluation of Self-Assembled Semiconductor Quantum Dots

A novel peak finding method to map the strain from high resolution transmission electron micrographs, known as the Peak Pairs method, has been applied to In(Ga) As/AlGaAs quantum dot (QD) samples, which present stacking faults emerging from the QD edges. Moreover, strain distribution has been simulated by the finite element method applying the elastic theory on a 3D QD model. The agreement existing between determined and simulated strain values reveals that these techniques are consistent enough to qualitatively characterize the strain distribution of nanostructured materials. The correct application of both methods allows the localization of critical strain zones in semiconductor QDs, predicting the nucleation of defects, and being a very useful tool for the design of semiconductor device

Dielectric properties of BiB3O6 crystal in the sub-THz range

We present the thorough studies of dielectric properties of BiB3O6 (BIBO) crystal in the sub-THz range. We observe a large birefringence Δn = nZ −nX = 1.5 and the values of absorption coefficients of all three axes to be less than 0.5 cm−1. The difference from visible range in angle ϕ between the axes z and X is found to be more than 6°. The simulated phase-matching curves show the optimal value of the angle θ to be around 25.5°±1° for an efficient millimeter-wave generation under the pump of 1064 nm laser radiation

Monolithic and hybrid integration of InAs/GaAs quantum dot microdisk lasers on silicon

A method of hybrid integration of quantum dot microdisk lasers with silicon wafer is proposed and realized. In addition to the possibility of combining microlasers with various silicon-based electronic and photonic devices, this makes it possible to significantly improve heat removal from the active region of the microlaser. The thermal resistance normalized to the mesa area reaches the level of about 0.002 (K/W)*cm2, which is significantly lower than the corresponding values of QD microlasers on GaAs substrate and monolithically grown on Si. As a result, the threshold current as well as current-induced shift of emission wavelength are reduced in continuous-wave regime

Physiological and biochemical mechanisms of the hen’s body recovery from dermanyssosis associated with deacarization

The purpose of the research is to study the efficacy of the insectoacaricide "5% D-cyphenotrine emulsion" against infestation of birds with Dermanyssus gallinae (dermanyssosis) after the deacarization of the poultry building and to characterize physiological and biochemical mechanisms of the recovery of Hy-Line hens after removed parasites.Materials and methods. A parasitological examination of the poultry farm found D. gallinae in one of the poultry buildings. Given positive results of the drug efficacy against the poultry red mite, we analyzed the morpho-physiological and physiological and biochemical parameters of the hen’s blood before and 10 and 20 days after the treatments. Changes in the ethological status of birds were recorded. We used 0.005% aqueous emulsion of "5% D-cyphenothrin emulsion" for treatment. To obtain it, the drug was diluted with water at a ratio of 1:1000 immediately before use.Results and discussion. After double treatment with "5% D-cyphenotrine emulsion" of the shop with hens from the test group, no live poultry red mite was found. Within 20 days after the disease reduction, representatives of this group showed high concentrations of cortisol which were 2.3–2.4 times (p < 0.001) higher than those of healthy hens. This indicates that the stress state of hens still remains after the parasitizing of D. gallinae. In addition, the recovery process takes a long time and with great stress for all systems of their body. This is also confirmed by a high level of lipid peroxidation. At the same time, high intensity of gluconeogenesis and, as a result, deterioration of lipid and protein metabolism were recorded in the hens in question. The positive results indicate an increasing need for additional energy expenditures which are paramount for the effective and well-timed implementation of adaptation mechanisms. It should be noted here that the values of all the above-mentioned indicators tend to normalize by the end of the study period. The changes noted in the blood of birds indicate the restoration of a number of body systems. The poultry red mite as an emergency factor affects the morphophysiology of the blood, in particular, the level of white blood cells, which is restored by the 10th day after deacarization, which triggers regenerative and reparative processes. There were also changes in the number of cells of the immune system, an increase in hemoglobin concentration to control values and optimization of behavior in representatives of the test group which are largely related to the normalized physiological activity of the thyroid gland after the poultry building deacarization. We found a partial recovery of the hen’s body systems after the poultry building deacarization with the drug "5% D-cyphenotrine emulsion", which is due to the long-term parasitizing of D. gallinae, a stressor of extreme strength

Investigation of Transformations of Model Petroleum Raw Materials on a Spent Hydrotreating Catalyst

Experiments were carried out to investigate the physicochemical properties and catalytic activity of the regenerated spent catalyst on model mixtures and conclusions were drawn about the prospects of using catalysts of this type in the process of thermal cracking in the presence of a catalyst

Deep Insights into the Past: Terrestrial Permafrost Drilling Campaigns

Permafrost thaw is associated with impacts on climate, land surface and coastal and river bank structures. Thermokarst and thermoerosion, for example, are thaw processes that lead to ground subsidence. Two main factors of surface subsidence vulnerability are the sedimentological composition, including ground ice content, and the temperature state of permafrost. This surface destabilization is getting relevant because of a potential positive feedback of deep thaw to the global climate system through the release of greenhouse gases trapped beneath or in the permafrost, as well as through the release of so far freeze-locked old carbon by microbial decomposition. With these facts in mind the overarching aims of our drilling campaigns were to retrieve deep (> 50m) frozen and unfrozen sediment cores including sediments, ice, and organic components

Terrestrische Permafrost-Bohrkampagnen: Tiefe Einblicke in die Vergangenheit

Permafrosttauen hat Auswirkungen auf Klima, Landoberflächen, Küsten- und Flussuferstrukturen. Die eisreichen Permafrostböden im Lenadelta laufen Gefahr sich durch das Tauen abzusenken. Zwei Hauptfaktoren der möglichen Oberflächensenkung sind die sedimentologische Zusammensetzung einschließlich des Eisgehalts und der Temperaturzustand des Permafrosts. Diese Oberflächendestabilisierung wird klimarelevant, weil eine mögliche sich selbst verstärkende Rückkopplung durch tiefes Permafrost-Tauen möglich ist. Diese Rückkoppelung funktioniert über die Freisetzung von im Permafrost eingeschlossenen Treibhausgasen, sowie durch die Freisetzung von bisher eingefrorenem altem Kohlenstoff durch mikrobielle Zersetzung. Vor diesem Hintergrund waren die Ziele unserer Bohrkampagnen tiefe (>5m) gefrorene und ungefrorene Sedimentkerne einschließlich Sedimente, Eis und organische Bestandteile zu erbohren