Study of resin-bonded calcia investment: Part 1. Setting time and compressive strength. (9/368)

This study was carried out to develop a new titanium casting investment consisting of calcia as the refractory material and a cold-curing resin system as the binder. The setting time of the investment was investigated under different N,N-dimethyl-p-toluidine (DMPT) contents in methyl methacrylate monomer (MMA) and benzoyl peroxide (BPO) contents in calcia without any sintering agent. The effects of the sintering agents, which were calcium fluoride (CaF2) and calcium chloride (CaCl2), on the compressive strength of the investments were investigated at room temperature before and after heating to two different temperatures. The shortest setting time (68 minutes) of the investment was obtained at 0.37 DMPT/BPO (1.5 vol% /1.0 mass%) ratio by mass. The highest strength (16.5 MPa) was obtained from the investment which contained 2 mass% CaF2 and was heated to 1,100 degrees C. It was found that the developed calcia investment containing 2 mass% CaF2 has a possibility for use in titanium castings.  (+info)

Lack of degradation of sevoflurane by a new carbon dioxide absorbent in humans. (10/368)

BACKGROUND: Potent inhaled anesthetics degrade in the presence of the strong bases (sodium hydroxide or potassium hydroxide) in carbon dioxide (CO2) absorbents. A new absorbent, Amsorb (Armstrong Medical Ltd., Coleraine, Northern Ireland), does not employ these strong bases. This study compared the scavenging efficacy and compound A production of two commercially available absorbents (soda lime and barium hydroxide lime) with Amsorb in humans undergoing general anesthesia. METHODS: Four healthy volunteers were anesthetized on different days with desflurane, sevoflurane, enflurane, and isoflurane. End-tidal carbon dioxide (ETCO2) and anesthetic concentrations were measured with infrared spectroscopy; blood pressure and arterial blood gases were obtained from a radial artery catheter. Each anesthetic exposure lasted 3 h, during which the three fresh (normally hydrated) CO2 absorbents were used for a period of 1 h each. Anesthesia was administered with a fresh gas flow rate of 2 l/min of air:oxygen (50:50). Tidal volume was 10 ml/kg; respiratory rate was 8 breaths/min. Arterial blood gases were obtained at baseline and after each hour. Inspired concentrations of compound A were measured after 15, 30, and 60 min of anesthetic administration for each CO2 absorbent. RESULTS: Arterial blood gases and ETCO2 were not different among three CO2 absorbents. During sevoflurane, compound A formed with barium hydroxide lime and soda lime, but not with Amsorb. CONCLUSIONS: This new CO2 absorbent effectively scavenged CO2 and was not associated with compound A production.  (+info)

A comparative study of the adsorption of amino acids on to calcium minerals found in renal calculi. (11/368)

To assess the binding of individual amino acids to the principal calcium minerals found in human kidney stones, the adsorption of 20 amino acids on to calcium oxalate monohydrate, CaHPO4*2H2O, Ca3(PO4)2 and Ca5(PO4)3OH crystals was determined over the physiological urinary pH range (pH 5-8) in aqueous solutions. All amino acids adsorbed most strongly at pH 5, and this decreased in all cases as the pH was increased. The amino acids which adsorbed most strongly were aspartic acid, glutamic acid and gamma-carboxyglutamic acid, with the last displaying the strongest affinity. All amino acids bound more avidly to calcium oxalate monohydrate than to any of the phosphate minerals. Adsorption on to CaHPO4*2H2O was generally higher than for Ca3(PO4)2 and Ca5(PO4)3OH, for which all amino acids, with the exception of gamma-carboxyglutamic acid, had only a weak affinity. The binding affinity of these acids is thought to be due to their zwitterions being able to adopt conformations in which two carboxyl groups, and possibly the amino group, can interact with the mineral surface without further rotation. The strong binding affinity of di-and tri-carboxylic acids for calcium stone minerals indicates that proteins rich in these amino acids are more likely to play a functional role in stone pathogenesis than those possessing only a few such residues. These findings, as well as the preferential adsorption of the amino acids for calcium oxalate monohydrate rather than calcium phosphate minerals, have ramifications for research aimed at discovering the true role of proteins in stone formation and for potential application in the design of synthetic peptides for use in stone therapy.  (+info)

Rapid improvement of osteomalacia by treatment in a case with Sjogren's syndrome, rheumatoid arthritis and renal tubular acidosis type 1. (12/368)

We present here a case of Sjogren's syndrome (SjS) with osteomalacia based on renal tubular acidosis type 1 (RTA-1). A 53-year-old woman, diagnosed as having rheumatoid arthritis (RA) at the age of 33, was admitted to our hospital because of sicca complex, fatigability and worsening general aching. The activity of RA had been low, but it was complicated by SjS, RTA-1 and remarkable osteomalacia. Acidosis was corrected by alkali supplement therapy. By treatment with a regimen consisting of alfacalcidol, calcium L-aspartate, elcatonin and ipriflavone, her bone mineral density (BMD) was remarkably improved within months and the generalized aching gradually diminished.  (+info)

Compound A production from sevoflurane is not less when KOH-free absorbent is used in a closed-circuit lung model system. (13/368)

In an in vitro study, less compound A was formed when a KOH-free carbon dioxide absorbent was used. To confirm this observation we used a lung model in which carbon dioxide was fed in at 160 ml min(-1) and sampling gas was taken out for analysis at 200 ml min(-1); ventilation aimed for a PE'CO2 of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow ports (Tin and Tout) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH-free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflurane was injected using a syringe pump to obtain 2.1% E'. Compound A was measured by capillary gas chromatography combined with mass spectrometry. Median (range) compound Ainsp increased to a maximum of 22.7 (7.9) ppm for Sodasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and increased to approximately 40 degrees C at 240 min. Contrary to expectation, compound A concentrations were greater with the KOH-free absorbent despite similar canister temperatures with both absorbents.  (+info)

Multistate outbreak of Salmonella serovar Muenchen infections associated with alfalfa sprouts grown from seeds pretreated with calcium hypochlorite. (14/368)

During September 1999, a multistate outbreak of Salmonella serovar Muenchen infection associated with eating raw alfalfa sprouts was identified in Wisconsin. Despite use of a calcium hypochlorite sanitizing procedure to pretreat seeds before sprouting, at least 157 outbreak-related illnesses were identified in seven states having sprouters who received alfalfa seed from a specific lot. The continued occurrence of sprout-related outbreaks despite presprouting disinfection supports the concern that no available treatment will eliminate pathogens from seeds before sprouting and reinforces the need for additional safeguards to protect the public. A lack of consumer knowledge regarding exposure to sprouts documented in this investigation suggests that more-targeted outreach to high-risk individuals may be needed to reduce their risk.  (+info)

Carbon monoxide production from desflurane, enflurane, halothane, isoflurane, and sevoflurane with dry soda lime. (15/368)

BACKGROUND: Previous studies in which volatile anesthetics were exposed to small amounts of dry soda lime, generally controlled at or close to ambient temperatures, have demonstrated a large carbon monoxide (CO) production from desflurane and enflurane, less from isoflurane, and none from halothane and sevoflurane. However, there is a report of increased CO hemoglobin in children who had been induced with sevoflurane that had passed through dry soda lime. Because this clinical report appears to be inconsistent with existing laboratory work, the authors investigated CO production from volatile anesthetics more realistically simulating conditions in clinical absorbers. METHODS: Each agent, 2.5 or 5% in 2 l/min oxygen, were passed for 2 h through a Drager absorber canister (bottom to top) filled with dried soda lime (Dragersorb 800). CO concentrations were continuously measured at the absorber outlet. CO production was calculated. Experiments were performed in ambient air (19-20 degrees C). The absorbent temperature was not controlled. RESULTS: Carbon monoxide production peaked initially and was highest with desflurane (507 +/- 70, 656 +/- 59 ml CO), followed by enflurane (460 +/- 41, 475 +/- 99 ml CO), isoflurane (176 +/- 2.8, 227 +/- 21 ml CO), sevoflurane (34 +/- 1, 104 +/- 4 ml CO), and halothane (22 +/- 3, 20 +/- 1 ml CO) (mean +/- SD at 2.5 and 5%, respectively). CONCLUSIONS: The absorbent temperature increased with all anesthetics but was highest for sevoflurane. The reported magnitude of CO formation from desflurane, enflurane, and isoflurane was confirmed. In contrast, a smaller but significant CO formation from sevoflurane was found, which may account for the CO hemoglobin concentrations reported in infants. With all agents, CO formation appears to be self-limited.  (+info)

Salmonella Typhimurium infections transmitted by chlorine-pretreated clover sprout seeds. (16/368)

Raw seed sprouts have caused numerous outbreaks of enteric infections. Presoaking seeds in a 20,000 mg/liter (ppm) calcium hypochlorite solution before sprouting is recommended to reduce bacterial contamination and infection risk. In 1999, the authors investigated an outbreak of Salmonella serotype Typhimurium infections in Colorado. In a case-control study, they matched 20 cases with 58 controls by age, sex, and telephone prefix; 10 (52%) of 19 cases and no controls recalled eating raw alfalfa-style sprouts in the 5 days before the patient's illness (p < 0.00001). Traceback implicated clover sprouts grown from seeds shared by two sprouters. The time period and region over which these sprouts were sold matched the occurrences of 112 culture-confirmed illnesses. Only one of the sprouters presoaked seeds as recommended, and fewer infections were attributable to this sprouter (0.29 vs. 1.13 culture-confirmed infections/50-pound (110.1-kg) bag of seed). After recall of the implicated sprouts and seed, S. Typhimurium illnesses declined. Contaminated raw clover sprouts can cause outbreaks of enteric illness. Presoaking contaminated seeds in a 20,000 mg/liter calcium hypochlorite solution reduces, but does not eliminate, the risk of infection. Until safer production methods are developed, persons eating raw sprouts continue to risk developing potentially serious gastrointestinal illness.  (+info)