Ignition of boron-containing high-energy materials based on an oxidizer and polymer binder

The use of aluminum borides is a promising direction in the development of modern propellant compositions and aerial vehicles. We present experimental data on the kinetics of oxidation of microscale powders of aluminum, amorphous boron, and the aluminum borides AlB2 and AlB12 in air upon heating at a constant rate of 10°C/min and the results of laser-assisted ignition of high-energy materials that contain these metal powders and are based on ammonium perchlorate, ammonium nitrate, and an inert binder or an energetic combustible binder. We show that the use of the boron-containing powders enables us to lower the onset temperature of oxidation and the temperature of intense oxidation, while increasing their oxidation effectiveness, compared to pure aluminum. The dependences of ignition delay time on the heat flux show that the AlB2 and AlB12 powders are the most effective metal fuel components for solid propellants based on ammonium perchlorate, ammonium nitrate, and an energetic binder: they display the shortest ignition delay time and require the lowest heat input for ignition

The theoretical DFT study of electronic structure of thin Si/SiO2 quantum nanodots and nanowires

The atomic and electronic structure of a set of proposed thin (1.6 nm in diameter) silicon/silica quantum nanodots and nanowires with narrow interface, as well as parent metastable silicon structures (1.2 nm in diameter), was studied in cluster and PBC approaches using B3LYP/6-31G* and PW PP LDA approximations. The total density of states (TDOS) of the smallest quasispherical silicon quantum dot (Si85) corresponds well to the TDOS of the bulk silicon. The elongated silicon nanodots and 1D nanowires demonstrate the metallic nature of the electronic structure. The surface oxidized layer opens the bandgap in the TDOS of the Si/SiO2 species. The top of the valence band and the bottom of conductivity band of the particles are formed by the silicon core derived states. The energy width of the bandgap is determined by the length of the Si/SiO2 clusters and demonstrates inverse dependence upon the size of the nanostructures. The theoretical data describes the size confinement effect in photoluminescence spectra of the silica embedded nanocrystalline silicon with high accuracy.Comment: 22 pages, 5 figures, 1 tabl

Система экологического менеджмента как средство снижения вероятности техногенных аварий и загрязнения окружающей природной среды на предприятиях авиакосмического комплекса

Due to the costs caused by environmental pollution, Russia loses about 10% of the gross domestic product (GDP) annually. The negative impact on the environment is exacerbated by industrial accidents. Enterprises from the category of hazardous industrial facilities must carry out preparations for emergency situations and industrial accidents. Accidents occurring at machine-building enterprises can also cause significant damage to the environment. Creation of environmental management systems at the enterprises will allow providing effective response to accidents at all types of enterprises, because one of the stages of the system implementation is preparation for emergency situations. At this stage, we consider the features of production and technological processes, the properties of hazardous substances used in production, we carry out the identification of possible emergency situations and environmental pollution arising from this, we select the most probable and large-scale emergency situations, and we develop a system of measures that impede their occurrence and contribute to reducing their negative consequences.Los costos causados por la contaminación ambiental generan a Rusia unas pérdidas anuales de alrededor del 10% de su producto interno bruto. El impacto negativo sobre el medio ambiente se ve agravado por los accidentes industriales. Las empresas que pertenecen a la categoría de instalaciones industriales peligrosas deben estar debidamente preparadas para situaciones de emergencia y accidentes industriales. Aquellos accidentes que ocurren en empresas de construcción de maquinaria también pueden causar daños significativos al medio ambiente. La creación de sistemas de gestión ambiental permite proporcionar una respuesta efectiva a las emergencias en todo tipo de empresas, ya que una de las etapas de la implementación del sistema es la preparación para situaciones de accidente. En esta etapa, se toman en consideración las características de los procesos tecnológicos y de producción, las propiedades de las sustancias peligrosas utilizadas, la identificación de posibles situaciones de emergencia y la contaminación ambiental derivada de la actividad industrial. Tras ello, se desarrolla un sistema de medidas que reducen significativamente tanto el riesgo de que dichos accidentes se produzcan como las consecuencias negativas de los mismos en caso de que sucedan.Из-за расходов, вызванных загрязнением окружающей среды, Россия ежегодно теряет около 10% валового внутреннего продукта. Негативное воздействие на окружающую среду усугубляется при возникновении промышленных аварий. Предприятия, относящиеся к категории опасных промышленных объектов, должны в обязательном порядке проводить работы по подготовке к чрезвычайным ситуациям и авариям на производстве. Аварии, возникающие на машиностроительных предприятиях, также могут наносить значительный ущерб окружающей природной среде. Создание на предприятиях систем экологического менеджмента позволит обеспечить эффективное противодействие авариям на всех типах предприятий, так как одним из этапов внедрения системы является подготовка к чрезвычайным ситуациям. На этом этапе рассматриваются особенности производства и технологических процессов, свойства используемых в производстве и производимых опасных веществ, проводится идентификация возможных аварийных ситуаций и возникающих при этом загрязнений окружающей среды, выбираются наиболее вероятные и масштабные аварийные ситуации, разрабатывается система мероприятий, препятствующих их возникновению и способствующих уменьшению их негативных последствий

Clusters of orthologous genes for 41 archaeal genomes and implications for evolutionary genomics of archaea

<p>Abstract</p> <p>Background</p> <p>An evolutionary classification of genes from sequenced genomes that distinguishes between orthologs and paralogs is indispensable for genome annotation and evolutionary reconstruction. Shortly after multiple genome sequences of bacteria, archaea, and unicellular eukaryotes became available, an attempt on such a classification was implemented in Clusters of Orthologous Groups of proteins (COGs). Rapid accumulation of genome sequences creates opportunities for refining COGs but also represents a challenge because of error amplification. One of the practical strategies involves construction of refined COGs for phylogenetically compact subsets of genomes.</p> <p>Results</p> <p>New Archaeal Clusters of Orthologous Genes (arCOGs) were constructed for 41 archaeal genomes (13 Crenarchaeota, 27 Euryarchaeota and one Nanoarchaeon) using an improved procedure that employs a similarity tree between smaller, group-specific clusters, semi-automatically partitions orthology domains in multidomain proteins, and uses profile searches for identification of remote orthologs. The annotation of arCOGs is a consensus between three assignments based on the COGs, the CDD database, and the annotations of homologs in the NR database. The 7538 arCOGs, on average, cover ~88% of the genes in a genome compared to a ~76% coverage in COGs. The finer granularity of ortholog identification in the arCOGs is apparent from the fact that 4538 arCOGs correspond to 2362 COGs; ~40% of the arCOGs are new. The archaeal gene core (protein-coding genes found in all 41 genome) consists of 166 arCOGs. The arCOGs were used to reconstruct gene loss and gene gain events during archaeal evolution and gene sets of ancestral forms. The Last Archaeal Common Ancestor (LACA) is conservatively estimated to possess 996 genes compared to 1245 and 1335 genes for the last common ancestors of Crenarchaeota and Euryarchaeota, respectively. It is inferred that LACA was a chemoautotrophic hyperthermophile that, in addition to the core archaeal functions, encoded more idiosyncratic systems, e.g., the CASS systems of antivirus defense and some toxin-antitoxin systems.</p> <p>Conclusion</p> <p>The arCOGs provide a convenient, flexible framework for functional annotation of archaeal genomes, comparative genomics and evolutionary reconstructions. Genomic reconstructions suggest that the last common ancestor of archaea might have been (nearly) as advanced as the modern archaeal hyperthermophiles. ArCOGs and related information are available at: <url>ftp://ftp.ncbi.nih.gov/pub/koonin/arCOGs/</url>.</p> <p>Reviewers</p> <p>This article was reviewed by Peer Bork, Patrick Forterre, and Purificacion Lopez-Garcia.</p

Influence of nanoparticles and metal vapors on the color of laboratory and atmospheric discharges

Currently, electrical discharges occurring at altitudes of tens to hundreds of kilometers from the Earth’s surface attract considerable attention from researchers from all over the world. A significant number of (nano)particles coming from outer space burn up at these altitudes. As a result, vapors of various substances, including metals, are formed at different altitudes. This paper deals with the influence of vapors and particles released from metal electrodes on the color and shape of pulse-periodic discharge in air, nitrogen, argon, and hydrogen. It presents the results of experimental studies. The discharge was implemented under an inhomogeneous electric field and was accompanied by the generation of runaway electrons and the formation of mini-jets. It was established that regardless of the voltage pulse polarity, the electrode material significantly affects the color of spherical- and cylindrical-shaped mini jets formed when bright spots appear on electrodes. Similar jets are observed when the discharge is transformed into a spark. It was shown that the color of the plasma of mini-jets is similar to that of atmospheric discharges (red sprites, blue jets, and ghosts) at altitudes of dozens of kilometers and differs from the color of plasma of pulsed diffuse discharges in air and nitrogen at the same pressure. It was revealed that to observe the red, blue and green mini-jets, it is necessary to use aluminum, iron, and copper electrodes, respectivel

From pre-attentive processes to durable representation : An ERP index of visual distraction

Visual search and oddball paradigms were combined to investigate memory for to-be-ignored color changes in a group of 12 healthy participants. The onset of unexpected color change of an irrelevant stimulus evoked two reliable ERP effects: a component of the event-related potential (ERP), similar to the visual mismatch negativity response (vMMN), with a latency of 120-160 ms and a posterior distribution over the left hemisphere and Late Fronto-Central Negativity (LFCN) with a latency of 320-400 ms, apparent at fronto-central electrodes and some posterior sites. Color change of that irrelevant stimulus also slowed identification of a visual target, indicating distraction. The amplitude of this color-change vMMN, but not LFCN, indexed this distraction effect. That is, electrophysiological and behavioral measures were correlated. The interval between visual scenes approximated 1 s (611-1629 ms), indicating that the brain's sensory memory for the color of the preceding visual scenes must persist for at least 600 ms. Therefore, in the case of the neural code for color, durable memory representations are formed in an obligatory manner. (C) 2014 Elsevier B.V. All rights reserved.Peer reviewe