Dielectric properties of polymer-derived ceramic reinforced with boron nitride nanotubes

The electrical and dielectric properties of boron nitride nanotubes (BNNTs) reinforced ceramic composites using the polymer-derived ceramic (PDC) processing route were investigated in this work. The electrical resistivity of the pristine PDC increases from 10⁶ to 10⁸ Ω m after the addition of BNNTs. When the BNNT loading was increased to 5 wt%, the average real relative permittivity of the PDC decreased from 2.94 to 2.80, while the quality factor (Q) of the PDC increased from 134.40 to 176.77. The BNNTs can increase the Q factor of the PDC due to the reduction in the porosity cause by the introduction of the BNNTs. Further increasing the BNNT content decreases the real relative permittivity of the nanocomposites and increases the Q factor at high frequency. The average real relative permittivity decreases to 2.29, while the average Q factor increases to 208.60 when the BNNT content is increased to 30 wt%. The dielectric loss after the addition of high fraction of BNNTs can be explained by the Lorentz resonance relaxation process. Results of this work showed that PDC-BNNT nanocomposites are satisfactory electromagnetic transparent materials when the BNNT fraction is less than 10 wt%.     

Effect of physico-chemical factors and semi-synthetic media on vegetative growth of Lentinus subnudus (Berk.), an edible mushroom from Nigeria

Attempts were made to investigate the effect of different semi-synthetic growth media, pH, temperature, carbon and nitrogen compounds, as well as additives, on vegetative growth of L. subnudus (Berk.), an edible mushroom from Nigeria. The best mycelial extensions (92.7 and 92. mm) were obtained on potato dextrose agar (PDA) and yellow corn agar (YCA), respectively. Moderate growths (87.0, 85.0 and 80.0 mm) were observed on white corn agar (WCA), yeast extract agar (YEA) and malt extract agar (MEA), respectively, but least growth (38.6 mm) was recorded on ‘Ife brown’ beans agar (IBBA). This fungus grew within a temperature range of 15–40 °C (optimum 30 °C) and, pH range of 5.0–8.0 (optimum 5.5).     

Sodium nitrite alone protects the brain microsomal Ca(2+)-ATPase against potassium cyanide-induced neurotoxicity in rats

The effect of a short-term oral administration of potassium cyanide (KCN) (200 ppm in diet) with or without sodium nitrite (NaNO2) pretreatment on rat brain microsomal Ca2 +/- ATPase was investigated. The specific activity value of the enzyme significantly decreased (p < 0.05) by 50% compared with control and by 63% for KCN-treated rats compared with KCN-treated rats pretreated with NaNO2. There was no significant difference at the h = 0.05 level between the values obtained for the control and KCN-treated rats pretreated with NaNO2. These results show both that feeding lowers brain microsomal Ca(2+)-ATPase activity and that NaNO2 has a protective role (antidote function) in that respect.     

Collagen induces cytokine release by fetal platelets: implications in scarless healing

In previous studies the authors demonstrated that unlike adult platelets, fetal platelets respond poorly to collagen. When platelets make contact with the exposed collagen at the site of injury, the result is activation, aggregation, and degranulation with the release of cytokines and growth factors. This sequence of events is well characterized in adult wounds, which heal with an acute inflammatory response and dense scar formation. In sharp contrast, fetal dermal wounds heal without an acute inflammatory response and minimal scar formation. Therefore, the aim of this study was to test the hypothesis that collagen, abundant at the site of dermal injury, is a poor inducer of cytokine release by fetal platelets. This could explain, in part, the minimal inflammation accompanying fetal dermal wound healing. Platelet suspensions from six fetal Yorkshire swine at day 80 of gestation (term, 114 days) were exposed to either arachidonic acid, 0.5 mg/mL, collagen, 0.19 mg/mL, or saline. The release into plasma of transforming growth factor-beta (TGF-beta 1), and platelet-derived growth factor (PDGF)-AB effected by these agents was determined by enzyme-linked immunosorbent assays. Transmission electron microscopy (TEM) was used to correlate the biochemical findings with ultrastructural changes and showed that arachidonate-treated platelets were aggregated and devoid of granules. In contrast, collagen-treated platelets had undergone conformational changes but showed only a moderate change in the quantity and homogeneity of their secretory granules compared with saline-treated controls. There was a significant increase in TGF-beta 1 release into plasma after treatment with collagen (6.64 +/- 0.36 ng/mL) and arachidonate (7.64 +/- 0.77 ng/mL) compared with saline (4.74 +/- 0.36 ng/mL), P < .05. Likewise, PDGF-AB release was significantly higher after collagen (0.22 +/- 0.02 ng/mL) and arachidonate treatment (0.44 +/- 0.04 ng/mL) compared with saline (0.09 +/- 0.02 ng/ mL), P < .05. The authors conclude that fetal platelets actually do release cytokines in response to contact with collagen despite poor aggregation. Therefore, impaired aggregation to collagen cannot solely explain the minimal inflammation after fetal wounding.     

A study of weight loss of stored yam (Dioscorea cayenensis) as affected by the ventilation of the storage locations

Investigation of the effect of ventilation on the storage losses of yam (Dioscorea cayenensis L) was carried out. The tubers were stored in three ventilation locations (1.4%, 3.8% and exposed ventilation) in two storage environments. It was found that the higher the ventilation level, the greater the weight loss. Exposed tubers that were subjected to direct heating and cooling of the sun and rain, respectively, rotted away; the high temperature involved preventing the sprouting of the tubers. Tubers in the 1.4% and 3.8% ventilation levels outside took a longer time to sprout than those stored inside.     

Hygienic evaluation of acetone cyanohydrin transformation in water

The study of acetone cyanohydrin (ACH) showed that it is an unstable substance. Its stability in water depends on pH of water and less so on its initial concentration; water temperature and biota are insignificant. Acetone and cyanid-ion, forming from ACH, after 20 days are transformed into a complex of cyan compounds.     

Ectopic pregnancy involving the rectum

A case of advanced extrauterine pregnancy involving the rectum and with passage of fetal limb through the anus is presented. The patient probably had a heterotopic gestation.     

Degradation of commercial detergent products by microbial populations of the Lagos lagoon

We herein report the case of a 53-year-old man with a nonspecific acute colonic ulcer whose liver function deteriorated after he had undergone hepatectomy. He was referred to our hospital for a hepatoma caused by hepatitis B virus and a right hemihepatectomy was performed. His liver function was poor after the operation, and minor complications such as pleural effusion and biliary fistula developed. A large amount of melena was seen 29 days after the hepatectomy and he developed hemorrhagic shock. Superior mesenteric arteriography revealed pooling of blood in both the hepatic flexure of the ascending colon and the cecum. An emergency right hemicolectomy was performed. There was a 5 x 1-mm ulcer 18 cm distal to the ileocecal valve. Numerous erosions were observed to be scattered throughout the colonic mucosa. The patient recovered slowly and was discharged 6 months after the hepatectomy. This is the first report of an acute colonic ulcer that could have been caused by liver dysfunction.     

Evidence of scuffing initiation by adiabatic shear instability

A mechanism for the initiation of scuffing based on adiabatic shear instability was assessed experimentally through the measurement of dislocation densities by X-ray diffraction. Scuffing was predicted to occur when the rate of local thermal softening exceeded that of work hardening in the tribological contact. Since these rates were dependent on microstructure, the theory was tested by performing scuffing tests on SAE 4340 steel subjected to five different heat treatments. The scuffing resistances were consistent with the theory, and thermal events during the tests and the resulting microstructural morphologies were consistent with a locally adiabatic environment. The dislocation densities measured in samples from tests stopped before, during, and after scuffing were consistent with the theory. Use of the Advanced Photon Source (APS) at Argonne National Laboratory was supported by the U.S. Department of Energy under Contract W-31-109-ENG-38.     

Unilateral brain lesions and performance on Russell's version of the Wechsler Memory Scale in an African American population

Studies of patients with unilateral lesions report hemisphere-specific and locus-specific impairments on Russell's (1975) Revision of the Wechsler Memory Scale (RWMS). In the current investigation "race-homogeneous" and "race-comparative" paradigms provide the context in which the generalizability of RWMS findings are examined in a population of African Americans with unilateral lesions. The performances of brain-damaged patients were impaired relative to normal controls on five of the six RWMS measures. However, patients with left and right hemisphere damage in our sample did not differ systematically on RWMS subtests. Likewise, among patients with lesions confined to one of the quadrants in the brain, there were no quadrant group differences in performance on RWMS subtests. But, right posteriors were impaired relative to controls on immediate and delayed VR subtests. The relative merits of the race-comparative and race-homogeneous paradigms are considered in the context of these findings.