Microstructure and densification of ZrB2–SiC composites prepared by spark plasma sintering

ZrB₂–SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1800–2100 °C for 180–300 s under a pressure of 20 MPa and at higher temperatures of above 2100 °C without a holding time under 10 MPa. Densification, microstructure and mechanical properties of ZrB₂–SiC composites were investigated. Fully dense ZrB₂–SiC composites containing 20–60 mass% SiC with a relative density of more than 99% were obtained at 2000 and 2100 °C for 180 s. Below 2120 °C, microstructures consisted of equiaxed ZrB₂ grains with a size of 2–5 μm and α-SiC grains with a size of 2–4 μm. Morphological change from equiaxed to elongated α-SiC grains was observed at higher temperatures. Vickers hardness of ZrB₂–SiC composites increased with increasing sintering temperature and SiC content up to 60 mass%, and ZrB₂–SiC composite containing 60 mass% SiC sintered at 2100 °C for 180 s had the highest value of 26.8 GPa. The highest fracture toughness was observed for ZrB₂–SiC composites containing 50 mass% SiC independent of sintering temperatures.     

Characterization of cryogenic heat treated Vanadis 4 PM cold work tool steel

The amount of retained austenite in the quenched cold work tool steel sample is 17.7%, in the condition of sub-zero heat treated and double tempered samples following by quenching is 1.9% determined by XRD analysis. The types of carbides (MC, M₇C₃, M₂₃C₆) present in the structure was determined by XRD and SEM-EDS analysis. The hardness of test samples were 865 HV(0.1) for quenched sample and 785 HV(0.1) forth sample subjected to sub-zero treatment and double tempered after the quenching.     

The effect of granulocyte colony-stimulating factor (G-CSF) on bacterial translocation in the splenectomized rat

BACKGROUND/AIMS: We created a study group in order to investigate the effects of splenectomy and filgrastim. Filgrastim is an immunomodulator granulocyte colony-stimulating factor (G-CSF), that affects bacterial translocation. MATERIALS AND METHODS: We created 3 study groups with 30 male Sprague-Dawley rats; the first group included sham splenectomy, the second group was splenectomy, and the third group was splenectomy+ filgrastim group. RESULTS: The mean bacterial colony count of the cecum were 2.5 x 10(9) in group 1, 1.2 x 10(10) in group 2 and 3.5 x 10(9) in group 3. The differences between these groups were accepted as statistically significant. The mean counts of the terminal ileum were 1.1 x 10(9) in group 1, 5.5 x 10(10) in group 2 and 2.5 x 10(10) in group 3. The p values of group 1-2 were 0.036 (statistically significant) and 0.123 in groups 2-3) were not statistically significant. The mean counts of the liver were 0.2 x 10(4), 1 x 10(10) and 3.4 x 10(5), respectively. In comparison of the groups the p values of the first and last 2 groups were found to be 0.047 (statistically significant). The mean counts of the mesenteric lymph node were 0.7 x 10(3), 1 x 10(10) and 0.9 x 10(6) respectively. The p values were 0.343 for the first and the last 2 groups both. As they were above 0.05, they were not statistically significant. The degrees of liver Kupffer cell hyperplasia were (+) 40%, (+2) 50% and (+3) 10% (group 1), (+) 10%, (+2) 40% and (+3) 50% (group 2), (+2) 60% and (+3) 40% (group 3) (p = 0.0039). The rates of the absence of pathology in mesenteric lymph nodes were 70% (group 1), 90% (group 2) and 100% (group 3) (p = 0.049). These findings were statistically significant. CONCLUSIONS: We found that splenectomy has activated the whole predisposing factors of bacterial translocation and created the latter itself. In addition, we showed that filgrastim, a recently widespread used G-CSF, decreases bacterial translocation significantly.     

Sources and dechlorination of polychlorinated biphenyl congeners in the sediments of Fox River, Wisconsin

Polychlorinated biphenyl (PCB) congeners were analyzed in eight deep, dated sediment cores collected from the immediate upstream and downstream of DePere dam in Fox River, Wisconsin. The average time span of the cores is about 100 yr, except for one core (FR-9) which is influenced by mixing or covers a short time period (2 yr). The total PCB concentrations have a range of 0.2-6.8 ppm for the upstream and 0.3-17.6 ppm for the downstream cores. The PCB data obtained from the sampling were analyzed as upstream and downstream data, using a factor analysis (FA) model with nonnegative constraints to identify PCB sources and congener patterns. The factor loadings obtained from the FA model were interpreted in terms of the presence of possible environmental degradation mechanisms. In addition, a recently developed model, which is used to identify and quantify possible pathways of anaerobic dechlorination of PCBs in the sediments, was validated on the basis of in situ data from the literature, and then applied to the congener patterns obtained from the FA model. The major PCB source to the Fox River sediments is identified as Aroclor 1242, for both the upstream and the downstream sediments. Loss of di- and trichlorobiphenyls (e.g., 2-4, 25-2) from the sediments suggests desorption from the sediments. On the other hand, observation of elevated amounts of certain congeners such as 24-3 and 25-3 indicates the presence of anaerobic dechlorination activity. The anaerobic dechlorination model demonstrates significant similarities between the Aroclor 1242 profile altered according to dechlorination processes Q (upstream) and H' (downstream) and the dominant congener patterns obtained from the FA model.     

Physiological response to firefighting activities of various work cycles using extended duration and prototype SCBA

Firefighters’ self-contained breathing apparatus (SCBA) protects the respiratory system during firefighting but increases the physiological burden. Extended duration SCBA (>30 min) have increased air supply, potentially increasing the duration of firefighting work cycles. To examine the effects of SCBA configuration and work cycle (length and rest), 30 firefighters completed seven trials using different SCBA and one or two bouts of simulated firefighting following work cycles common in the United States. Heart rate, core temperature, oxygen consumption, work output and self-reported perceptions were recorded during all activities. Varying SCBA resulted in few differences in these parameters. However, during a second bout, work output significantly declined while heart rates and core temperatures were elevated relative to a single bout. Thirty seven per cent of the subjects were unable to complete the second bout in at least one of the two-bout conditions. These firefighters had lower fitness and higher body mass than those who completed all assigned tasks.

Practitioner Summary: The effects of extended duration SCBA and work/rest cycles on physiological parameters and work output have not been examined. Cylinder size had minimal effects, but extended work cycles with no rest resulted in increased physiological strain and decreased work output. This effect was more pronounced in firefighters with lower fitness.     

Modeling and visualization of lifecycle building performance assessment

Lifecycle building performance assessment (LBPA) ensures that buildings perform and operate as intended during building lifecycle. Such assessment activities are typically multi-phase and multi-disciplinary, and generate large amounts of information that need efficient management. During the lifecycle of one building, multiple assessment methods are employed semi-concurrently and with a great deal of information overlap between successive phases. This information is semantically rich and context-dependent, reflecting the local perspective that it exists within. Usage of separate and disconnected tools for each method results in information fragmentation and redundancy, posing problems for well-informed decision making. The objective of this research is to develop an integral reference model, CLIP (Computational support for Lifecycle Integral Performance assessment), that aims to improve the efficiency and quality of existing performance assessment practices. The model provides flexible, modular, and extensible data structures and algorithms for the representation, transformation, integration, and visualization of performance information. The initial results support the CLIP model’s ability to deal with the local volatility and variation in the processes and information content that is being managed, while requiring further refinement and extension work to achieve a customized solution to fit in different contextual settings.     

Multiple bulk-reaction asymptotics and the electrochemical pickling of steel

Asymptotic methods are used to explore the role of multiple homogeneous chemical reactions, water protolysis, and the disassociation of sulfuric acid in a recent numerical model for the industrial electrochemical pickling of steel. The analysis demonstrates the surprising result that, even though the asymptotic structure of the solution differs from that found when either one or both of the chemical reactions are neglected, the overall current density remains unchanged. Most importantly from an industrial perspective, the asymptotic model provides results of practical value for process design at a fraction of the computational cost of the earlier numerical model.     

Shaping single-walled metal oxide nanotubes from precursors of controlled curvature

We demonstrate new molecular-level concepts for constructing nanoscopic metal oxide objects. First, the diameters of metal oxide nanotubes are shaped with angstrom-level precision by controlling the shape of nanometer-scale precursors. Second, we measure (at the molecular level) the subtle relationships between precursor shape and structure and final nanotube curvature. Anionic ligands are used to exert fine control over precursor shapes, allowing assembly into nanotubes whose diameters relate directly to the curvatures of the 'shaped' precursors.     

Understanding the Potential In Vitro Modes of Action of Bis(β-diketonato) Oxovanadium(IV) Complexes

To understand the potential in vitro modes of action of bis(β-diketonato) oxovanadium(IV) complexes, nine compounds of varying functionality have been screened using a range of biological techniques. The antiproliferative activity against a range of cancerous and normal cell lines has been determined, and show these complexes are particularly sensitive against the lung carcinoma cell line, A549. Annexin V (apoptosis) and Caspase-3/7 assays were studied to confirm these complexes induce programmed cell death. While gel electrophoresis was used to determine DNA cleavage activity and production of reactive oxygen species (ROS), the Comet assay was used to determine induced genomic DNA damage. Additionally, Förster resonance energy transfer (FRET)-based DNA melting and fluorescent intercalation displacement assays have been used to determine the interaction of the complexes with double strand (DS) DNA and to establish preferential DNA base-pair binding (AT versus GC).     

Effect of pre-setting pressure applied to mechanical behaviours of reactive powder concrete during setting phase

In this study, mixing rates, fiber content and pre-setting pressure of reactive powder concrete (RPC) were examined. Mixing ratios were determined by different mixing techniques in literature using material characteristics via computer software. The samples were prepared according to these mixing ratios. The fresh (plastic) concrete samples were filled in a specified mould. Six different (0, 5, 10, 15, 20, 25 MPa) pre-setting pressure were applied. It is observed that application of pre-setting pressure increased compressive strength of the samples about twice.