Adhesion of Epoxy Resin with Hexagonal Boron Nitride and Graphite.

Adhesion interaction of epoxy resin with the basal surfaces of h-BN and graphite is investigated with the first-principles density functional theory calculations in conjunction with the dispersion correction. The h-BN/epoxy and graphite/epoxy interfaces play an important role in producing nanocomposite materials with excellent thermal dissipation properties. The epoxy resin structure is simulated by using four kinds of fragmentary models. Their structures are optimized on the h-BN and graphite surfaces after an annealing simulation. The distance between the epoxy fragment and the surface is about 3 Å. At the interface between h-BN and epoxy resin, no H-bonding formation is observed, though one could expect that the active functional groups of epoxy resin, such as hydroxyl (-OH) group, would be involved in a hydrogen-bonding interaction with nitrogen atoms of the h-BN surface. The adhesion energies for the two interfaces are calculated, showing that these two interfaces are characterized by almost the same strength of adhesion interaction. To obtain the adhesion force-separation curve for the two interfaces, the potential energy surface associated with the detachment of the epoxy fragment from the surface is calculated with the help of the nudged elastic band method and then the adhesion force is obtained by using either the Morse-potential approximation or the Hellmann-Feynman force calculation. The results from both methods agree with each other. The maximum adhesion force for the h-BN/epoxy interface is as high as that for the graphite/epoxy interface. To better understand this result, a force-decomposition analysis is carried out, and it has been disclosed that the adhesion forces working at both interfaces mainly come from the dispersion force. The trend of increase in the C 6 parameters used for the dispersion correction for the atoms included in the h-BN or graphite surface is in the order: N < C < B, which reasonably explains why the strengths of the dispersion forces operating at the two interfaces are similar. Also, the electron localization function analysis can explain why the h-BN surface cannot form an H bond with the hydroxyl group in epoxy resin.

Urinary monitoring of exposure to yttrium, scandium, and europium in male Wistar rats.

On the assumption that rare earth elements (REEs) are nontoxic, they are being utilized as replacements of toxic heavy metals in novel technological applications. However, REEs are not entirely innocuous, and their impact on health is still uncertain. In the past decade, our laboratory has studied the urinary excretion of REEs in male Wistar rats given chlorides of europium, scandium, and yttrium solutions by one-shot intraperitoneal injection or oral dose. The present paper describes three experiments for the suitability and appropriateness of a method to use urine for biological monitoring of exposure to these REEs. The concentrations of REEs were determined in cumulative urine samples taken at 0-24 h by inductively coupled plasma atomic emission spectroscopy, showing that the urinary excretion of REEs is <2 %. Rare earth elements form colloidal conjugates in the bloodstream, which make high REEs accumulation in the reticuloendothelial system and glomeruli and low urinary excretion. The high sensitivity of inductively coupled plasma-argon emission spectrometry analytical methods, with detection limits of <2 µg/L, makes urine a comprehensive assessment tool that reflects REE exposure. The analytical method and animal experimental model described in this study will be of great importance and encourage further discussion for future studies.

Distribution, elimination, and renal effects of single oral doses of europium in rats.

Single doses of europium (III) chloride hexahydrate were orally administered to several groups of rats. Cumulative urine samples were taken at 0-24 h, and blood samples were drawn after 24-h administration. The europium concentration was determined in these samples by inductively coupled plasma atomic emission spectroscopy. The volume, creatinine, ß-2-microglobulin, and N-acetyl-ß-D-glucosaminidase were measured in the urine samples to evaluate possible europium-induced renal effects. The blood samples showed low europium distribution, with an average of 77.5 µg/L for all groups. Although the urinary concentration and excretion showed dose-dependent increases, the percentage of europium excreted showed a dose-dependent decrease, with an average of 0.31% in all groups. The administration of europium resulted in a significant decrease of creatinine and a significant increase of urinary volume, N-acetyl-ß-D-glucosaminidase, and ß-2-microglobulin. Rare earth elements, including europium, are believed to form colloidal conjugates that deposit in the reticuloendothelial system and glomeruli. This specific reaction may contribute to low europium bioavailability and renal function disturbances. Despite low bioavailability, the high performance of the analytical method for determination of europium makes the blood and urine sampling suitable tools for monitoring of exposure to this element. The results presented in this study will be of great importance in future studies on the health impacts of rare earth elements.

Toxicological aspects of cadmium and occupational health activities to prevent workplace exposure in Japan: A narrative review.

Chemicals are an essential part of modern manufacture processes. Their use must be managed with great attention in occupational settings to avoid serious detrimental effects to the health of employees. For example, cadmium compounds are indispensable for the production of nickel-cadmium rechargeable batteries or as chemical stabilizer in plastics. It is an exceptionally toxic heavy metal and personnel exposed to cadmium in the workplace meet with potential health risks that can lead to the development of kidney, skeletal and respiratory disorders. In consequence, proactive and systematical development of occupational hygiene and health activities are necessary to reduce chemical exposure to cadmium in the workplace. This review describes the known facts of cadmium toxicity, the biological effects of cadmium exposure, possible regulation measures to prevent occupational cadmium exposure in three industrial health management systems and discusses future cooperation programs in these systems, proactive safety activities and occupational safety and health management strategies.

Thoracoscopic ethanol injection and radiofrequency ablation for the treatment of hepatocellular carcinoma located immediately under the diaphragm.

We previously reported that the combination therapy of percutaneous ethanol injection and radiofrequency ablation (PEI-RFA) was more effective than RFA alone in inducing wider coagulated necrosis for the treatment of hepatocellular carcinoma (HCC). In the present study, we thoracoscopically applied the combination therapy to the treatment of HCC located immediately under the diaphragm. RFA electrode and ethanol injection needle were inserted into the tumor through the right side of the diaphragm in 6 patients with HCC close to the diaphragm. In all cases, the tumor was completely ablated with enough safety margin around the tumor. No local tumor recurrence has been observed in a relatively short-time follow-up period. The volume of coagulated necrosis and the energy requirement for coagulation in thoracoscopic ethanol injection and RFA (T-EI-RFA) were comparable to those of PEI-RFA. Although HCC located immediately under the diaphragm is difficult to treat with a percutaneous approach due to the poor visualization by ultrasonography, T-EI-RFA is considered to be an effective treatment modality.

Surgical-site infection surveillance at a small-scale community hospital.

Surveillance of surgical-site infection (SSI) is becoming more important given the current situation of increasing antibiotic resistance by microorganisms. It may be difficult to carry out SSI surveillance at small-scale community hospitals because of small staff numbers. We examined whether SSI surveillance could be carried out with a system we devised. Furthermore, we investigated the SSI rateat our small-scale community hospital (179 beds) in a Japanese city (populations, 330 000). Between June and December 2003, operations were performed on 210 patients. Procedures were identified as clean (n = 85),clean-contaminated (n = 108), contaminated (n = 14), or dirty-infected (n = 3). A 7-month prospective survey of SSI was conducted. SSIs were classified according to the Centers for Disease Control and Prevention criteria and identified using bedside surveillance and post-discharge follow-up. SSI developed following 16 procedures (7.6%). All patients who developed SSI had received antibiotic prophylaxis. Among the 16 patients with SSI, operations were clean (n = 1), clean-contaminated (n = 8), contaminated(n = 5), or dirty-infected (n = 2). Enterobacteriaceae were the most frequently isolated microorganisms, followed by Pseudomonas aeruginosa. SSI surveillance is just as important at small community hospitals as it is at larger hospitals, and SSI surveillance is relatively simple to institute at small-scale community hospitals with the selective use of investigation items.

Allowable warm ischemic time to tracheal extraction for allotransplantation of cryopreserved trachea.

OBJECTIVE: The allowable warm ischemic time from circulatory arrest to tracheal extraction for allotransplantation of cryopreserved tracheal grafts from cadaveric donors was examined in adult mongrel dogs. SUBJECTS AND METHODS: The animals were divided into 4 groups (n = 28) according to the warm ischemic time of less than 1 hour, 3 hours, 6 hours, and 12 hours, after transplantation, and comparisons were made. The grafts were cryopreserved for at least 2 months and were evaluated by extraction from the recipients generally 2 months after transplantation. RESULTS: All the grafts with a warm ischemic time of less than 1 hour were viable and did not show stenosis. This group did not differ significantly from the groups with a warm ischemic time of 3 and 6 hours in terms of viability. However, all of the grafts with a warm ischemic time of 12 hours showed stenosis, and there was a significantly lower viability rate. Histological examination of the grafts showed that warm ischemia caused necrosis of the tracheal cartilage. CONCLUSION: Based on these results, it was concluded that 6 hours was the maximum allowable warm ischemic time for cryopreserved tracheal transplantation, and that necrosis of the tracheal cartilage due to warm ischemia reduced the viability of the grafts.