Sintered soft magnetic Fe-Al,Fe-Si,and Fe-Si-Al alloys

Summary The results are presented of an investigation of soft magnetic iron-aluminum, iron-silicon, and iron-silicon-aluminum alloys produced by powder metallurgy methods. A study was made of the effect of preparation conditions on the magnetic and electrical properties of these alloys. It was found that powder metallurgy permits the preparation of one-piece magnetic cores which in many cases can be used in 50 cps alternating fields.     

Spontaneous Emission and Lasing of a Two-Wavelength Quantum-Cascade Laser

Semiconductors - The results of experiments on the fabrication (by molecular-beam epitaxy) and investigation of the heterostructures of a two-frequency quantum-cascade laser produced on the basis...     

Spectral Shift of Quantum-Cascade Laser Emission under the Action of Control Voltage

Technical Physics Letters - Spectral redistribution of the intensity of short- and long-wavelength emission components within gain bandwidth of a 7- to 8-μm quantum-cascade laser under the...     

Secondary Production of Highly Unsaturated Fatty Acids by Zoobenthos Across Rivers Contrasting in Temperature

Highly unsaturated fatty acids (HUFA), namely eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA), which are essential for many animals, including humans, are mainly produced in aquatic trophic webs. In fast‐flowing rivers, macrozoobenthos is the main source of HUFA for fish and may be particularly vulnerable to thermal alterations associated with climate change. We studied benthic communities in a unique natural ecosystem: the Yenisei River downstream of the dam of Krasnoyarsk Hydroelectric Power Station with very low temperature in summer because of discharge of cold water from deep in the reservoir and its tributaries with high summer temperature. This ‘natural experiment’ allowed to get rid of confounding factors, such as differences in light, seasonality, geology (biogeochemistry) and biogeography (regional species pools). As found, in spite of an increase of biodiversity and rates of daily production in warm rivers compared with cold sites, DHA and partly EPA production of zoobenthos decreased with the increase of temperature because of changes in species composition. Thus, in a climate warming context, we can predict a decrease of production of these HUFA by river zoobenthos and thereby a diminishing of their supply for fish and next to humans. Copyright © 2015 John Wiley & Sons, Ltd.     

Lasing wavelength of quantum dot heterostructures controlled within the 1.3–0.85 μm range by means of high-temperature annealing

We have studied the effect of high-temperature annealing on the properties of a laser heterostructure with InAs quantum dots in AlAs/GaAs superlattice. By increasing the time of annealing at 700°C, it is possible to provide for a smooth variation of the lasing wavelength from 1290 to 916 nm at a constant threshold current density (250 A/cm² at T ₀=110 K). By annealing the structure at 750°C, the lasing wavelength can be reduced to 845 nm.     

Formate dehydrogenase in a reversed micelle system: regulation of catalytic activity and oligomeric composition of the enzyme

Formate dehydrogenases from the methylotrophic bacteria Pseudomonas sp. 101 and Mycobacterium vaccae N10 were studied in a system of Aerosol OT reversed micelles in octane. Three peaks of the catalytic activity were found on the plot of activity versus surfactant hydration degree (the size of the micellar inner cavity) which corresponded to functions of the enzyme in various oligomeric forms: monomeric, dimeric, and octameric. Kinetic data were confirmed by results of sedimentation analysis. The enzyme was chemically modified by a bifunctional reagent (dimethyl suberimidate) to obtain a catalytically active non-dissociating dimeric molecule of formate dehydrogenase. In the case of the covalently-linked non-dissociating dimeric enzyme, the peak which corresponded to the monomeric form of the enzyme was found to disappear from the catalytic activity curve.     

Effect of way of cooking on content of essential polyunsaturated fatty acids in muscle tissue of humpback salmon (Oncorhynchus gorbuscha)

Contents of fatty acids in filets of unfrozen (control), boiled, fried, roasted and boiled in a small amount of water humpback salmon, collected from a wholesale market in Krasnoyarsk city (Siberia, Russia) were analyzed. Special attention was paid to essential polyunsaturated fatty acids of ω3 family: eicosapentaenoic, 20:5ω3 (EPA) and docosahexaenoic, 22:6ω3 (DHA). Heat treatment in general did not decrease content of EPA and DHA in humpback, except a modest reduction during frying. Cooked humpback appeared to be the valuable source of essential ω3 PUFAs, namely EPA and DHA. It was hypothesized that the absence of significant reduction of PUFAs’ contents in red flesh of fishes of Salmonidae family during heat treatment may be due to a high level of natural antioxidants which formed in the course of evolution as adaptation to their ecological niche.