Relationship between the rock mass deformation and places of occurrence of seismological events

Static effort of rock mass very rarely causes of rock burst in polish coal mines. Rock bursts with source in the seismic tremor within the roof rock layers are prevailing. A seismic tremor is an effect of rupture or sliding in roof layers above the exploited panel in coal seam, sometime in a distance from actual exploitation. Sliding, as a rule occurs in fault zone and tremors in it are expected, but monolithic layer rupture is very hard to predict. In a past few years a practice of analyzing state of deformation in high energy seismic tremors zones has been employed. It let gathering experience thanks to witch determination of dangerous shape of reformatted roof is possible. In the paper some typical forms of roof rocks deformations leading to seismic tremor occurrence will be presented. In general these are various types of multidirectional rock layers bending. Real examples of seismic events and rock bursts will be shown.     

Modification of Triclosan Scaffold in Search of Improved Inhibitors for Enoyl‐Acyl Carrier Protein (ACP) Reductase in Toxoplasma gondii

Through our focused effort to discover new and effective agents against toxoplasmosis, a structure‐based drug design approach was used to develop a series of potent inhibitors of the enoyl‐acyl carrier protein (ACP) reductase (ENR) enzyme in Toxoplasma gondii (TgENR). Modifications to positions 5 and 4′ of the well‐known ENR inhibitor triclosan afforded a series of 29 new analogues. Among the resulting compounds, many showed high potency and improved physicochemical properties in comparison with the lead. The most potent compounds 16 a and 16 c have IC₅₀ values of 250 nM against Toxoplasma gondii tachyzoites without apparent toxicity to the host cells. Their IC₅₀ values against recombinant TgENR were found to be 43 and 26 nM , respectively. Additionally, 11 other analogues in this series had IC₅₀ values ranging from 17 to 130 nM in the enzyme‐based assay. With respect to their excellent in vitro activity as well as improved drug‐like properties, the lead compounds 16 a and 16 c are deemed to be excellent starting points for the development of new medicines to effectively treat Toxoplasma gondii infections.     

Synthesis of curing agent for epoxy resin based on halogenophosphazene

Epoxy resins are, due to their excellent properties (such as chemical resistance, dimensional stability, and heat resistence), widely used in practice. The basic principle of curing epoxy resins with a hardener containing multiple amino groups is the crosslinking reaction between active hydrogen atoms in the hardener and the oxirane groups in the epoxy resin. This study deals with the synthesis and characterization of hexachloro‐cyclo‐triphosphazene derivative and its subsequent use for curing epoxy resins. The new hardener was prepared from hexachloro‐cyclo‐triphosphazene by nucleophilic substitution with isophorone diamine and its curing capability was compared with original isophorone diamine. The prepared derivative hexaisophorone diamino‐cyclo‐triphosphazene (HICTP) provided advantages over conventional curing system, as it improved mechanical properties as well as the flame resistance. Testing of the cured epoxy resin during burning was carried out using dual cone calorimeter, which enables more extensive monitoring of parameters in comparison with testing using oxygen index that has been used in many publications. The epoxy resin cured with the prepared phosphorus containing HICTP exhibits lower values for total heat release, amount of smoke released and oxygen consumed, which may cause a slower flame spread. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42917.     

Isolation and expression of the gene encoding mitochondrial ADP/ATP carrier (AAC) from the pathogenic yeast Candida parapsilosis

A gene homologous to Saccharomyces cerevisiae AAC genes coding for mitochondrial ADP/ATP carriers has been cloned from the pathogenic yeast Candida parapsilosis. A probe obtained by PCR amplification from C. parapsilosis DNA, using primers derived from the conserved transmembrane region of yeast ADP/ATP carriers, was used for screening of the C. parapsilosis genomic library. The cloned gene was sequenced and found to encode a polypeptide of 303 amino acids that shows homology with other yeast and fungal mitochondrial ADP/ATP carriers. The gene was designated CpAAC1 and was able to complement the growth phenotypes of S. cerevisiae double deletion mutant (Δaac2; Δaac3). The expression of the CpAAC1 gene was reduced under semi‐anaerobic conditions and it was affected at normal aerobic conditions by the nature of carbon sources used for growth. Hybridization experiments indicate that C. parapsilosis possesses a single gene encoding a mitochondrial ADP/ATP carrier. The GenBank Accession No. for the C. parapsilosis CpAAC1 gene is AF085429. Copyright © 1999 John Wiley & Sons, Ltd.     

On the fast BSS transition algorithms in the IEEE 802.11r local area wireless networks

Handover performance is critical to support multimedia services that are becoming increasingly available over the wireless devices. The high transition delay can be unaccepted for such services or can be a source of disruption on the session. On the other side, IEEE 802.11 standard is being extended with new functionalities. Security and QoS features, included in recent IEEE 802.11-2007 standard, add management frames that are exchanged during the transition process. In consequence the handover delay is increased. IEEE 802.11r-2008 amendment introduces Fast BSS Transition (FT) that simplifies the handover process. The authors propose the new handover algorithms based on FT protocol and compare them with existing solution. Additionally, simulation experiments are conducted to answer the question if multimedia services can be properly supported in IEEE 802.11r networks. The authors prove that handover delay can be reduced to 13 ms in the average case.     

Thermal analysis and phase transformation behaviour during additive manufacturing of Ti–6Al–4V alloy

Despite the fact that the additive manufacturing (AM) technique has been established for almost two decades, its optimisation is still performed by trial and error experimentation. In the present work, a finite element modelling approach was used to study both the temperature distribution and heat flux vector characteristics during multi-layer deposition of a Ti–6Al–4V alloy that take place in the AM process. The results revealed the difference between different powder deposition time intervals on thermal cycles, heat flux vectors and the resulting microstructures. Good agreement between the numerical and experimental results was found. The results obtained can be used for process optimisation.     

Synthesis,microstructure and mechanical properties of Yttria Stabilized Zirconia (3YTZP) – Multi-Walled Nanotube (MWNTs) nanocomposite by direct in-situ growth of MWNTs on Zirconia particles

In this research, Yttria Stabilized Zirconia (3YTZP) – carbon nanotube (CNT) composites are fabricated by direct in-situ growth of CNTs on the Zirconia particles, followed by densification via the Spark Plasma Sintering (SPS) technique. Scanning electron microscopy analysis of the 3YTZP-CNT powders shows uniform distribution of CNTs without the formation of agglomerates frequently seen with the traditional ex-situ mixing of CNTs in ceramic compositions. The samples were sintered to nearly 100% theoretical density and with a finer grain size microstructure. High Resolution Transmission Electron Microscopy (HRTEM) and Raman Spectroscopy confirm CNT retention in the sintered nanocomposites up to 1600 °C. The flexural strength increases from ∼260 MPa for samples without CNTs sintered at 1600 °C to ∼312 MPa for samples with ∼4 wt.% CNTs sintered at the same temperature. A corresponding increase in the indentation fracture toughness is also observed for samples with ∼4 wt.% CNTs sintered at 1600 °C as compared to samples sintered at the same temperature without CNTs.     

Opportunities in nanometer sized Si wires for PV applications

Quantum-confined silicon material has been a very active field of research in the years 1990–2000 with the rapid development of opto-electronics. The main application targeted by this research was a light-emitting device (either LED, or laser). In the years 2000–2010, with the emerging need for efficient and cheap photovoltaic devices, new materials, and in particular new silicon-based materials trigger again a special interest. In particular, all-crystalline-Si tandem solar cells where the high-bandgap material is provided by the 2D confinement of excitons in nm-sized nanowires could provide the high-efficiency potential of a tandem device, while taking benefit of the decade-long buildup of knowhow of crystalline silicon material technology (both science and processing). In a first part of this review, we summarize the features described in the relevant literature for the functioning of a photovoltaic device based on Si NWs. This literature shows that from the conceptual point of view such an all-crystalline-Si-tandem solar cell using quantum confined nanowires should be feasible to produce in order to achieve the goal of inexpensive high efficiency (>30%) Si-based solar cells. Keeping the fabrication of efficient photovoltaic devices as driving theme, we review the dense literature of Si nanowires. The literature on the fabrication of nanometer-sized Si nanowires is reviewed in the second part.     

Functional Derivatives of Sterically Hindered Amines: Piperazine diesters

Several diesters of dicarboxylic acids with pendant sterically hindered amines of the piperazine type were prepared from α-bromo- and α,α′-dibromosubstituted dicarboxylic acid esters by reactions with 14,16-dioxo-7,15-diaza-dispiro[5,1,5,3]hexadecane and 7,15-diazadispiro [5,1,5,3] hexadecane.