Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by STM, RHEED and HRTEM

Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470--650C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH_4F aqueous solutions. It has been shown that smooth surfaces composed by wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures > 600C, whereas clean surfaces obtained at the temperatures < 600C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.Comment: 8 pages, 8 figures; version accepted to J. Appl. Phy

Petro fabric characteristics of olivine from xenoliths, peridotites, and basalts (from Canary Islands, Kuznetsk Alatau and Yoko-Dovyren Massif)

This paper presents results of study of petro fabric specific characteristics of olivine from xenoliths, peridotites, and basalts (from Canary Islands, Kuznetsk Alatau and Yoko-Dovyren Massif

Sedimentary deposits and petrography of the basalts of the island of Tenerife of the Canary archipelago (Spain)

The article is devoted to the study of sedimentary deposits on the slopes of the Teide volcano and petrography of the volcanic rocks of the island of Tenerife of the Canary archipelago (Spain). A description of the sediments, which are presented on the island's territory, and an analysis of the features of the material composition of rocks are given

Experience of universities in practice-oriented training personnel for high-tech enterprises

Different options have been considered of work-based learning (WBL) in Russian and foreign universities. Special attention is given to the variant of PBL - project learning (PL) on training bachelors. Basic concepts and principles have been discussed dealing with the organization of PL developed by Aalborg University - one of the founders of this teaching technique. Тhe advisability is shown of organizing special courses of introduction to project learning in the first two semesters.peer-reviewe

Regulation of flavonoid biosynthesis in representatives of the tribe Phaseoleae DC.

Flavonoids play a crucial role in plant metabolism. Many of them have antioxidant activity, and they are also pigments that render a variety of colors to plant tissues. Foods rich in flavonoid compounds are considered as functional components of a healthy diet. Currently, there is an increased interest in studying genetic mechanisms underlying the coloration of plants. Flavonoid biosynthesis pathways are controlled by two groups of genes. Structural genes encode enzymes, while regulatory genes are responsible for transcription factors that activate the expression of structural genes. Transcription factors that belong to R2R3-Myb, bHLH-Myc and WDR families form the ternary MBW complex, which is involved in regulating the expression of structural genes of flavonoid biosynthesis. The mechanisms of regulation of the anthocyanins and proanthocyanidin biosynthesis by the MBW complex are described in detail for the model plant Arabidopsis thaliana L. This review summarizes data on the regulation of phenolic pigment biosynthesis and the features of phenolic pigment accumulation in plant tissues in the main representatives of the Phaseoleae tribe: soybean Glycine max (L.) Merr., common bean Phaseolus vulgaris L., adzuki bean Vigna angularis (Willd.) Ohwi &amp; Ohashi, and cowpea V. unguiculata (L.) Walp. The species discussed in this review are the most important food legumes in many countries of the world and they comprise the staple food in diets of millions of people. Identification and characterization of the genes controlling the flavonoid biosynthesis pathways are necessary for successful breeding of modern varieties with an increased dietary value. Identification of the flavonoid accumulation patterns is essential for solving the problem of broadening the diversity of plant products

Prospects for obtaining low-alkaloid and adaptive forms of narrow-leafed lupinе based on the genome and transcriptome resources of the species

The narrow-leafed lupinе (Lupinus angustifolius L.) is considered as a crop of untapped opportunities. The food and forage potential of the species is not fully exploited due to the presence of quinolizidine alkaloids (QA) in plants, which are secondary metabolites that make the seeds bitter and toxic to humans and animals. Varieties with a low content of QA (“sweet” varieties) created over the last 50-60 years turned out to be more susceptible to damage by sucking insects and insect-transmitted viruses than high alkaloid ones (“bitter” varieties). Based on the rapidly developing genomic, transcriptomic and metabolomic profiling of the species, some molecular determinants and features of alkaloid biosynthesis in narrow-leafed lupinе plants have been identified: alkaloids are formed in the vegetative organs of the plant and then transported to the seeds. This information substantiated the creation of “bitter-sweet” forms with a high content of alkaloids in the vegetative parts of the plant, which would make it possible to reduce the attack of pathogens, and a minimal content of alkaloids in the seeds. This review summarizes the existing prerequisites for obtaining such forms of narrow-leafed lupinе on the basis of the available scientific developments. Information on the creation of saturated genetic maps of the species, in which the iucundus (iuc) locus determining the overall low alkaloid content in seeds is integrated and is used in breeding programs. The use of the new generation sequencing allowed the identification of the RAP2-7 gene, encoding the transcription factor APETALA2/ETHYLENE RESPONSE FACTOR, which is coupled to the iuc locus and located in the area with the main QTLs that affect the composition of the QA. It is a likely candidate gene for regulating alkaloid content in narrow-leafed lupinе seeds. The initial stages of QA biosynthesis and its regulatory factors have been revealed. Two reference assemblies of the genome of narrow-leafed lupinе have been carried out. All these achievements constitute a valuable resource for the creation of forms of narrow-leafed lupinе with a high content of alkaloids in the vegetative mass and low in the seeds, which are absent in nature

Impact of High-Temperature, High-Pressure Synthesis Conditions on the Formation of the Grain Structure and Strength Properties of Intermetallic Ni[3]Al

The impact of the preliminary load on 3Ni+Al powder mixture and the impact of the duration of the delay in application of compacting pressure to synthesis product under the conditions of continuous heating of the mixture up to its self-ignition on the grain size and strength properties of the synthesized Ni[3]Al intermetallide material have been studied. The grain structure of the intermetallide synthesized under pressure was studied by means of metallography, transmission electron microscopy and EBSD analysis, with the dependence of ultimate tensile strength on the grain size in the synthesized intermetallide having been investigated at room temperature and at temperatures up to 1000°С. It is shown that an increase in the pressure preliminarily applied to the initial mixture compact results in reduced grain size of the final intermetallide, whereas an increase in pre-compaction time makes the grain size increased. A decrease in the grain size increases the ultimate tensile strength of the intermetallide. The maximum value of the ultimate tensile strength in the observed anomalous temperature dependence of this strength exhibits a shift by 200°С toward higher temperatures, and the ultimate strength of the synthesized intermetallide at 1000°С increases roughly two-fold