Influence of Slurry Flocculation on the Character and Compaction of Spray-Dried Silicon Nitride Granules

The effect of slurry flocculation on the characteristics of silicon nitride granules prepared by the spray drying process is investigated. The flocculation state of an aqueous silicon nitride slurry is controlled by adding nitric acid and evaluated as a function of pH. Dense and hard silicon nitride granules result from a well-dispersed slurry having a high pH (e.g., 10.8). These hard granules retain their shape in green compacts and form detrimental defects. Lowering the pH of the slurry to a certain value (e.g., pH 7.9) results in slurry flocculation. Granules prepared from this flocculated slurry have low density and low diametral compression strength and contribute to the elimination of large pores in green compacts.     

Stellate ganglion block does not change the tympanic membrane temperatures of either block or unblock sides in male volunteers

STUDY OBJECTIVES: To test the effect of stellate ganglion block on tympanic membrane temperatures. DESIGN: Prospective, observational study. SETTING: Department of Anesthesia, Yamanashi Medical University, Yamanashi, Japan. SUBJECTS: 7 healthy male volunteers. INTERVENTIONS: Stellate ganglion block, 6 ml of 1% mepivacaine hydrochloride, was administered. MEASUREMENTS AND MAIN RESULTS: Application of temperature probes (right and left tympanic membranes, eight adhesive right skin-surface temperatures at the chest, upper arm, digital fingertip, lateral calf, thigh, and great toe) was followed by a 30-minute control period. Temperatures were recorded every 15 minutes for 30 minutes before stellate ganglion block and every 5 minutes for 40 minutes after the block. The right tympanic membrane temperature increased slightly but not significantly compared with the left tympanic membrane temperature 10 minutes after stellate ganglion block and subsequently. Right skin-surface temperature gradients at the upper limb decreased slightly but not significantly after stellate ganglion block. Similarly, right skin-surface temperature gradients at the lower limb decreased slightly but not significantly after stellate ganglion block. CONCLUSIONS: Stellate ganglion block does not change the tympanic membrane temperatures of either block or unblock sides.     

Simultaneous absorption with reaction in a slurry containing fine particles

The simultaneous absorption of two gases accompanied by chemical reaction into a slurry of fine suspended particles was numerically analysed using the model obtained with some extension of the corresponding single gas absorption.Experiments were performed for the simultaneous absorption of sulfur dioxide and carbon dioxide with a plane gas—liquid type stirred tank absorber. The experimental results were satisfactorily elucidated by the proposed model and it is suggested that when accompanied by sulfur dioxide absorption, carbon dioxide may almost be regarded as an inert gas.     

Interfacial turbulence accompanying chemical absorption

Absorption rates for carbon dioxide into aqueous solutions of EDA and MEA with and without adding surface active agent were measured in a laminar liquid-jet apparatus to check and verify the Marangoni effect. In addition, experiments were conducted for the tracer desorption of ethylene from aqueous EDA and MEA solutions into carbon dioxide or nitrogen stream. It has been concluded that the Marangoni effect cannot be neglected for such short contact times as in a laminar liquid-jet. The Marangoni instability accompanying the present chemical absorptions is attributed to combinated effects of the presence of ionic products, the depletion of the reactant liquid near the interface and an increase in interfacial temperature.     

Toxicity following methoxyflurane anaesthesia. IV. The role of obesity and the effect of low dose anaesthesia on fluoride metabolism and renal function

Seven obese and five normal weight patients were studied before, during and after one hour of methoxyflurane-nitrous oxide anaesthesia during peripheral surgical operations and compared with eight patients of normal weight anaesthetized with nitrous oxide-meperidine and d-tubocurare. Estimates were made of renal function, including serum and urinary electrolytes, osmolarity, uric acid, urea and creatinine. Renal clearances for the latter three substances were also calculated. Serum and urinary inorganic and organic fluoride concentrations were measured, as were renal clearances. This low dose methoxyflurane anaesthesia resulted only in a decrease in uric acid clearance among all the measures, when compared to the meperidine-nitrous oxide controls. The clearance of uric acid remained depressed for longer in the obese patients, but otherwise they did not differ from the normal weight patients. It is possible but not proven that depressed uric acid clearance may be related to the organic fluoride metabolite and an early indicator of methoxyflurane renal toxicity. The previously documented biotransformation of methoxyflurane was seen in this study. A double peak in serum inorganic fluoride was shown in all patients but one. Rather large differences in peak levels of serum inorganic fluoride occurred. The only significant difference between the obese and normal weight patients as far as fluoride metabolism was concerned was a greater variability in the serum inorganic fluoride levels in the obese patients. It would appear that the obese patient metabolizes methoxyflurane in a quantitatively if not qualitatively different fashion than the normal weight patient, perhaps because of fatty infiltration of the liver. Caution is advised in the use of methoxyflurane for more than 90 minutes of low concentration administration in view of the unpredictability of the biotransformation.     

Gas absorption with consecutive chemical reaction: Absorption of carbon dioxide into aqueous amine solutions

Experiments were carried out over a wide range of contact time for the absorption of carbon dioxide into aqueous amine solutions. It was suggested from the experimental results with a laminar liquid-jet, a wetted wall column and a quiescent liquid absorber that the present absorption processes should be analyzed by a gas absorption with the consecutive reaction of the form of A + 2B →k_I R and A + R →k_II Products. The values of rate constants for the second-order first reaction step (k₁) for the diethanolamine and triethanolamine were estimated as 1340 and 16.8 1/mol-sec, respectively. The value of rate constant for the second reaction step was found to be constant irrespective of the liquid reactant.     

Clinical features of transurethral anterior sphincterotomy and urological management of patients with cervical spinal cord injury

BACKGROUND: The ideal urological management for the patients with cervical spinal cord injury (CSCI) is to obtain catheter free urination and to prevent urinary tract complications. We have evaluated cases that had undergone transurethral anterior sphincterotomy from the view-point of the operative indications and the efficacy. METHODS: We carried out sphincterotomy 166 times on 133 male patients with CSCI in our Center. Before the operations were performed, all patients suffered from urinary incontinence, and they were unable to catheterize themselves for low level activity of daily life. Before and after the operation, their detrusor functions with sphincter reactions were assessed by urodynamic study. In principle we have followed up these cases by cystogram combined with cystometry, cystogram and excretory-pyelography or abdominal ultrasonography. RESULTS: In post-operative evaluations, more than 80% of cases attained hypotonic detrusor contractions and residual urine was significantly decreased. In long term follow-up, 96% of patients had obtained catheter free urination and about 85% of patients had no urinary tract complications, such as bladder deformity, vesicoureteral reflux, or hydronephrosis, with the exception of common unavoidable urinary infections. About 20% of cases had to be re-operated upon, and some cases showed hypertonic detrusor contractions or detrusor-sphincter-dyssynnergia during follow-up. CONCLUSION: The operative indications of sphincterotomy should be decided when the CSCI patients is unable to perform self-catheterization, and when due to the dysfunction of the urethral sphincter, these patients suffered from voiding difficulties or autonomic dysreflexia, or when the urinary tract complications might occur. In the majority of cases the aims of the sphincterotomy were achieved but some cases underwent another operation or had recurrent dysfunction of the urethral sphincter, indicating the need for careful follow-up.     

Determination of cyanide in whole blood by capillary gas chromatography with cryogenic oven trapping

Cyanide, one of the most important toxic substances, has been found measurable with high sensitivity by capillary gas chromatography (GC) with cryogenic oven trapping upon injection of headspace (HS) vapor samples. The entire amount of cyanide in the HS sample could be cryogenically trapped prior to on-line GC analysis. A 0.5-mL volume of blood in the presence or absence of cyanide and propionitrile (internal standard, IS) was added to a vial containing 0.25 mL of distilled water, 0.3 g of Na2-SO4, 0.2 mL of 50% H3PO4, and 0.1 g of ascorbic acid (when needed), and the mixture was heated at 70 degrees C for 15 min. A 5-mL volume of the HS vapor was introduced into a GC capillary column in the splitless mode at -30 degrees C oven temperature that was programmed up to 160 degrees C for GC analysis with nitrogen-phosphorus detection. A sharp peak was obtained for cyanide under the present conditions, and backgrounds were very clean. The extraction efficiencies of cyanide and IS were 2.89-3.22 (100 or 500 ng/mL) and 2.42%, respectively. The calibration curve showed good linearity in the range of 25-1000 ng/mL and the detection limit was approximately 2 ng/mL. The coefficients of intraday and interday variations were 2.9 and 11.8%, respectively. The mean blood cyanide level measured for actual fire victims was 687 +/- 597 ng/mL (mean +/- SD, n = 9). Endogenous blood cyanide concentration for healthy subjects was 8.41 +/- 3.09 ng/mL (mean +/- SD, n = 6).     

Evaluation and control of the adhesiveness of cohesive calcium carbonate particles at high temperatures

Understanding the adhesiveness of fine particulate materials at high temperatures is important to achieving the stable, economical operation of various industrial systems. In the present research, two types of calcium carbonate (CaCO₃) particles having different mean particle sizes (often used as heat carriers in energy systems) were evaluated. The tensile strengths of beds of these materials were determined at various temperatures by tensile strength measurement tester. The adhesiveness was found to increase greatly at 500 °C even without chemical reactions or sintering, and X-ray diffraction analyses showed thermal expansion of the CaCO₃ crystals at 500 °C. Pure alumina (Al₂O₃) and silica (SiO₂) microparticles did not exhibit the same pronounced increases in tensile strength or crystal expansion at this same temperature. Because the surface distances between these primary particles were presumably small, it is proposed that van der Waals forces between the particles greatly increased at high temperatures. The addition of Al₂O₃ nanoparticles to the CaCO₃ decreased the tensile strengths of the powder beds both at ambient temperature and at 500 °C. The experimental data confirm that the surface distances between primary particles were increased upon incorporating the nanoparticles, such that the tensile strength decreased during heat treatment.