Niobium oxide as support material for the oxidative dehydrogenation of propane

The ability of using niobium oxide (Nb₂O₅) as a support for preparing surface metal oxide species and testing the catalyst for the ODH of propane was done in the present study. Chromium oxide was used as the representative surface metal oxide species. To test the objective several loadings of Cr₂O₃/Nb₂O₅ were prepared by the incipient wetness impregnation technique. Surface area analysis, Raman, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectroscopy and TPR studies were used to characterize the sample. It was observed that surface chromium oxide species are formed similar to those on other oxide supports and similar monolayer coverages were achieved. However, the reduction characteristic (T_max temperature) was different due to the change in the Cr–O–support bond. The ODH of propane over the Cr₂O₃/Nb₂O₅ catalysts revealed that the activity increased up to monolayer coverage and then decreased due to the presence of Cr₂O₃ crystals. Similar observations were seen for the V₂O₅/Nb₂O₅ and MoO₃/Nb₂O₅ catalysts. The turnover frequency (TOF) was independent of coverage for the surface chromium, vanadium and molybdenum oxide species on Nb₂O₅. The constant TOF suggests the structure insensitivity of this type of reaction. The propene selectivities were high and relatively constant for the Cr₂O₃/Nb₂O₅ catalysts revealing the higher yields that can be obtained on this series of catalysts compared to the Cr₂O₃/Al₂O₃ and Cr₂O₃/TiO₂ catalysts. Additional studies involving tungsten and molybdenum oxide additives on 1% Cr₂O₃/Nb₂O₅ reveal the effect of exposed support surface on the propene selectivities.     

Hyperglycemia increases neurological damage and behavioral deficits from post-traumatic secondary ischemic insults

The effects of post-traumatic administration of glucose 2.0 g/kg was compared to saline infusion with and without control of brain temperature at 37 degrees C on behavioral and histological measures of brain injury after controlled cortical impact injury complicated by a secondary ischemic insult. The glucose infusion increased blood glucose concentration from 114 +/- 4 to 341 +/- 76 mg/dl prior to the secondary ischemic insult. The resulting outcome measures were significantly worse in the glucose infusion group than in either control group. Mortality rate was significantly increased by the glucose administration, from 0% to 55% (p < 0.001). The median contusion volume was increased from 7.9 to 64.2 by glucose administration (p < 0.001) and the neuronal loss in the CA1 and CA3 areas of the hippocampus were greater in the glucose infusion group. In the animals that survived for the 2 weeks of behavioral studies, the duration of beam balance was shorter; the percent of animals that could balance on the beam for at least 60 s was less, the percent of animals that could perform the beam-walking task was less, and the length of time required to find the platform in the Morris water maze task was longer in the glucose infusion group. These studies demonstrate that the infusion of glucose after the cortical impact injury significantly increases the damage caused by post-traumatic ischemic insults. The adverse effect on neurological outcome could not be explained by the temperature effects of glucose infusion.     

Parameter estimation in stochastic mammogram model by heuristic optimization techniques.

The appearance of disproportionately large amounts of high-density breast parenchyma in mammograms has been found to be a strong indicator of the risk of developing breast cancer. Hence, the breast density model is popular for risk estimation or for monitoring breast density change in prevention or intervention programs. However, the efficiency of such a stochastic model depends on the accuracy of estimation of the model's parameter set. We propose a new approach-heuristic optimization-to estimate more accurately the model parameter set as compared to the conventional and popular expectation-maximization (EM) algorithm. After initial segmentation of a given mammogram, the finite generalized Gaussian mixture (FGGM) model is constructed by computing the statistics associated with different image regions. The model parameter set thus obtained is estimated by particle swarm optimization (PSO) and evolutionary programming (EP) techniques, where the objective function to be minimized is the relative entropy between the image histogram and the estimated density distributions. When our heuristic approach was applied to different categories of mammograms from the Mini-MIAS database, it yielded lower floor of estimation error in 109 out of 112 cases (97.3 %), and 101 out of 102 cases (99.0%), for the number of image regions being five and eight, respectively, with the added advantage of faster convergence rate, when compared to the EM approach. Besides, the estimated density model preserves the number of regions specified by the information-theoretic criteria in all the test cases, and the assessment of the segmentation results by radiologists is promising.     

Microwell device for targeting single cells to electrochemical microelectrodes for high-throughput amperometric detection of quantal exocytosis

Electrochemical microelectrodes are commonly used to detect spikes of amperometric current that correspond to exocytosis of oxidizable transmitter from individual vesicles, i.e., quantal exocytosis. We are developing transparent multielectrochemical electrode arrays on microchips in order to automate measurement of quantal exocytosis. Here, we report development of an improved device to target individual cells to each microelectrode in an array. Efficient targeting (~75%) is achieved using cell-sized microwell traps fabricated in SU-8 photoresist together with patterning of poly(l-lysine) in register with electrodes to promote cell adhesion. The surface between electrodes is made resistant to cell adhesion using poly(ethylene glycol) in order to facilitate movement of cells to electrode "docking sites". We demonstrate the activity of the electrodes using the test analyte ferricyanide and perform recordings of quantal exocytosis from bovine adrenal chromaffin cells on the device. Multiple cell recordings on a single device demonstrate the consistency of spike measurements, and multiple recordings from the same electrodes demonstrate that the device can be cleaned and reused without degradation of performance. The new device will enable high-throughput studies of quantal exocytosis and may also find application in rapidly screening drugs or toxins for effects on exocytosis.     

Metallothionein and apoptosis in primary human hepatocellular carcinoma and metastatic adenocarcinoma

AIMS: Differences in expression of metallothionein (MT) have been reported in various human tumours. MT is mainly expressed in proliferating epithelial tumour cells but in human hepatocellular carcinoma (HCC) there is only a minimal expression of MT. Since MT is a zinc binding protein and certain inducers of MT including zinc play a role in apoptosis, studies were undertaken to compare the expression of MT and the presence of apoptotic cells (APPC) in both primary HCC and metastatic adenocarcinoma. METHODS AND RESULTS: Histological sections of 13 cases of primary HCC and eight cases of metastatic adenocarcinoma were obtained from archival samples. They were stained for MT using a polyclonal antibody which crossreacts readily with human MT and for APPC by the TUNEL technique. Normal human liver had consistent MT staining with no detectable APPC. The primary HCC showed moderate MT staining with a small number of APPC while metastatic adenocarcinoma showed no MT staining with a large number of APPC. CONCLUSIONS: These results suggest a relationship between absence of MT and appearance of APPC in human liver tumours, especially in metastatic adenocarcinomas.     

Effect of glucose administration on contusion volume after moderate cortical impact injury in rats

Previous studies had shown that pre- and postinjury glucose administration increased brain injury caused by a mild cortical impact injury only when the traumatic injury was complicated by a secondary ischemic insult. The purpose of this study was to examine the effect of pre- and postinjury glucose administration on a more severe cortical impact injury, where primary ischemia occurs at the site of the impact. Long Evans rats who were fasted overnight and anesthetized with isoflurane were subjected to a 5-m/sec, 2.5-mm impact injury. The animals were randomly assigned one of the following treatments: (1) 2.2 g/kg glucose in 4 ml of saline, 20 min prior to injury; (2) 2.0 g/kg glucose in 4 ml of saline, 20 min after injury; or (3) 4 ml of saline either 20 min before injury or 20 min after the injury. At 2 weeks, the animals were sacrificed and the brains were examined for contusion volume and for neuronal loss in CA1 and CA3 regions of the hippocampus. Contusion volume was increased from a median value of 23 mm3 in the saline-infused animals to 34 mm3 in the preimpact glucose infusion animals (p=0.005). Postimpact glucose infusion had no effect on contusion volume. Neuron density in CA1 and CA3 regions of the hippocampus was similar in all three treatment groups. These studies support the hypothesis that glucose administration adversely affects experimental traumatic brain injury in those circumstances where the trauma is complicated by primary cerebral ischemia, such as around cortical contusions.     

A regulatory role of sulfhydryl groups in modulation of sperm membrane conformation by heavy metals: sulfhydryl groups as markers for infertility assessment

Sperm membrane sulfhydryl groups, when masked by heavy metals like cobalt and copper at very low concentration (10(-9)) shows inhibition of lipid peroxidation and superoxide dismutase activity. Inhibition of lipid peroxidation is suggested to lead to reduction in membrane fluidity, a prerequisite for normal sperm function. Augmentation of lipid peroxidation by pentoxifylline in oligospermia provides evidence to this hypothesis that membrane sulfhydryls play a regulatory role in membrane modulation. It is therefore suggested that these sulfhydryl groups can be used as a tool for infertility assessment in unexplained male infertility.     

Frequency and quality of parental communication as antecedents of adolescent smoking cognitions and smoking onset.

The present study examines whether aspects of parental communication about smoking function as antecedents of adolescent smoking cognitions. In this longitudinal full-family study (428 families), parent and adolescent reports were used to assess parental communication. Concepts of the Theory of Planned Behavior were measured among adolescents. Differences between older and younger siblings within the family were examined. Cross-sectionally, frequency and quality of communication were associated with smoking cognitions. Longitudinally, only quality of communication preceded smoking cognitions. This effect was mainly found for younger siblings. The results of this study emphasize the importance of quality of parental communication rather than frequency. Communication patterns based on mutual respect and equality help to prevent adolescent smoking onset. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Precipitation of diamond from MexCyHz solutions at 1 ATM

 We describe herein a new process for the synthesis of diamond in the presence of various metals and atomic H in a microwave plasma. Along with the traditional high pressure high temperature (HPHT) process and the chemical vapor deposition (CVD) process, for diamonds synthesis this makes it a third route for this purpose. Starting materials used are intimate mixtures of various forms of carbon with one of many metals. These are exposed to a pure H₂ microwave-assisted plasma at temperatures in the range 600–1100o C. Novel amorphous alloys are formed containing 40 to 70 atomic percent of carbon. From these liquid alloys diamonds are precipitated with temperature change and/or with possible evaporation of complex, hydrogen-rich Me−C−H species. The carbon content of the metallic liquid drops sequentially down to 5–6%C as more and more diamonds are precipitated therefrom. Au, Ag, Fe, Cu, Ni, and many other metals are used in most runs. Others e.g. La, Mn, Sn, each give distinctive habits or morphology to the diamonds grown. Single crystals have been grown from these Me_xC_yH_z metallic liquids on natural diamond substrates, using the same low pressure solid state source (LPSSS) technique. They show high perfection. A mechanism is proposed quite analogous to the HPHT process, to explain this precipitation from metallic solutions, with atomic hydrogen ”substituting” for high pressure. Received: 8 April 1997 / Accepted: 8 June 1997     

An analytical investigation of an energy flow divider to attenuate hand-transmitted vibration

A five-degrees-of-freedom (DOF) bio-mechanical model of the hand-arm system is developed to study the vibration transmissibility characteristics of the human hand-arm. The model parameters are identified from the characteristics of vibration transmitted to the hand, forearm and upper arm, measured in the 10–200 Hz frequency range under a constant 25.0 N grip force. A concept of an energy flow divider is proposed to reduce the flow of vibration energy into the hand. The coupled hand-arm-divider is modeled as a six-DOF dynamical system and the response characteristics are evaluated for handle excitations caused by a palm-grip orbital sander. The response characteristics of the coupled hand-arm-divider model are compared to those of the hand-arm model to demonstrate the potential performance benefits of the proposed energy flow divider. The hand-transmitted vibration is further assessed using the overall weighted acceleration response, and it is concluded that the proposed energy flow divider can reduce the magnitude of hand-transmitted vibration considerably.