Morphology dependent field emission of acid-spun carbon nanotube fibers.

Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber's electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of <1 V µm(-1). This stable high current operation makes these CNT fibers excellent candidates for use as low voltage electron sources for vacuum electronic devices.

Synthesis and Quasi-Static Compressive Properties of Mg-AZ91D-Al2O3 Syntactic Foams.

Magnesium alloys have considerably lower density than the aluminum alloy matrices that are typically used in syntactic foams, allowing for greater specific energy absorption. Despite the potential advantages, few studies have reported the properties of magnesium alloy matrix syntactic foams. In this work, Al2O3 hollow particles of three different size ranges, 0.106-0.212 mm, 0.212-0.425 mm, and 0.425-0.500 mm were encapsulated in Mg-AZ91D by a sub-atmospheric pressure infiltration technique. It is shown that the peak strength, plateau strength and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance-specifically, higher energy absorption per unit weight. These foams show better performance than other metallic foams on a specific property basis.

Retinal venous beading with recurrent preretinal hemorrhage.

PURPOSE: To report a patient with idiopathic retinal venous beading and recurrent preretinal hemorrhage. METHOD: Case report of a 17-year-old girl with bilateral retinal venous beading, greater in the left eye than in the right eye, and recurrent preretinal hemorrhage in the left eye. RESULTS: Complete blood cell count, platelet count, blood glucose level, and hemoglobin electrophoresis were normal. Fluorescein angiography showed normal retinal arterial and venous filling with no evidence of retinal capillary nonperfusion or neovascularization. CONCLUSION: Idiopathic retinal venous beading may be associated with recurrent preretinal hemorrhage, even in the absence of retinal ischemia or neovascularization.

Speech training aids for hearing-impaired individuals: II. Configuration of the Johns Hopkins aids.

Two interrelated personal computer (PC) based speech training aids have been developed: one for use in a school or clinic, the Speech Training Station (STS); and the other for the deaf child's home, the Speech Practice Station (SPS). The STS monitors speech production by microphone, electroglottograph, and pneumotachograph. The SPS system uses only the microphone input. Both systems utilize commercially available board-level hardware and a custom analog preprocessor board for the analysis of the acoustic and/or physiologic inputs. The school system has been used by speech therapists for diagnosis, training by game playing, and specification of exercises for the SPS. The home system provides directed speech practice between therapy sessions.

Surgical decision making.

The decision-making process in a general surgical outpatient clinic has been studied by following the course of 2000 consecutive newly referred patients of whom 1045 were put on surgical waiting lists. Surgeons were asked to record their reasons for selection for each of four levels of care: main ward, 5-day ward, day bed unit or minor outpatient surgery. Selections were influenced by social and psychological factors in 12 per cent of patients, the remaining 88 per cent were determined by the medical history or physical condition. The decision was assessed by monitoring the progress in hospital and the outcome at a follow-up clinic. In 84 per cent of patients arrangements had gone according to plan. Eleven (1.75 per cent) of 5-day or day care patients were transferred to a higher level of care and 13 (1.4 per cent) of the total series were re-admitted. Surgeons were asked to forecast the duration of postoperative stay. Thirty-six per cent were discharged on the day forecast, 63 per cent within 24 h and 75 per cent within 48 h. Forecasts of length of stay for hernias and varicose veins were accurate but were usually underestimated for major surgery. It is concluded that for the majority of general surgical patients the selection of the level of care and the forecast of postoperative stay were sufficiently reliable to allow confident and definite advice to be given to the patient and to allow resources to be efficiently used.

A five-day ward as part of a comprehensive surgical service.

The role of a five-day ward was examined as part of an audit of the work of a general surgical unit. The four levels of care for elective operations were main ward, five-day ward, major day care, and minor day care. In a prospective study 2000 consecutive patients were followed through their hospital courses from the first referral to the surgical clinic to the postoperative follow-up visit. The aim was to measure the surgical needs of this population and to determine the rates of success or failure in carrying through the planned care. One thousand and forty-five (52%) of the referred patients were put on waiting lists, and of these, 975 (93%) completed their hospital course within the two years of the study. The surgeons chose five-day ward care for 28% of the patients, major and minor day care for 8% and 33% respectively, leaving only 30% who were judged to require care in the main ward. Selections were validated by postoperative interview, which showed that 82% had followed the expected hospital course, and by monitoring deviations from planned care. Four per cent of the five-day ward patients required transfer to the main ward and 3.3% required readmission. Patients managed in the five-day ward were on average younger and the conditions less urgent than those in the main ward. We conclude that a five-day ward can fulfil a large and important part of a general surgical service provided that its function is closely integrated with other parts of the service and that patients are accurately assessed in the outpatient clinic.

Effects of chronic lithium administration on concanavalin A binding to plasma membranes from the corpus striatum of rat brain.

The effects of chronic in vivo lithium administration on mannose-containing components of plasma membranes from rat corpus striatum were examined by a 3H-concanavalin A binding displacement method. No difference on Con A binding was observed between sodium or lithium-treated rats during a 1-month period.

Single-mode collapse in 6328-A He-Ne lasers.

Internal-mirror 6328-A He-Ne lasers have an intramode frequency difference when placed in a transverse magnetic field. When the magnetic field strength is increased until the Zeeman frequency shift approaches the mode spacing, mode coupling is nduced. In some multimode lasers, this mode coupling results in a collapse into single-mode operation with no loss of over-all laser power in the output. The intramode frequency difference can be exploited to produce a simple frequency stabilization system whose frequency variation is less than 1 part in 10(10). Plots of beat frequency variation and single-mode tuning range are included.

Purification and properties of a soluble protein activator of rat liver squalene epoxidase.

A soluble rat liver protein, termed "supernatant protein factor" (SPF), that stimulates microsomal squalene epoxidase has been purified approximately 11,000-fold. The most highly purified preparation obtained by isoelectric focusing shows a single coincident peak for activity and protein (the isoelectric point, pI, was 6.74). SPF is about 95% pure, judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and it migrates to a position corresponding to an apparent molecular weight of 47,000. An amino acid analysis of SPF is presented, and the properties of SPF and of the various soluble protein activators of microsomal sterol biosynthesis described by other laboratories are compared.

Bifunctional inhibitors of pepsin.

Two bifunctional reagents designed to probe the active site of pepsin and other acid proteinases are described. One of these, the bisdiazoketone 1,1-bis(diazoacetyl)-2-phenylethane inactivates pepsin at pH 5.0 much more rapidly than the corresponding monodiazoketon 1-diazoacetyl-2-phenylethane, whereas the other, the bromodiazoketone dl-1-diazoacetyl-1-bromo-2-phenylethane is less effective in this regard. The inactivation is greatly accelerated by the presence of Cu(II), and the pH dependence of the process is consistent with the interaction of the enzyme with the metal complex of the carbene derived from the reagent. The bisdiazoketone appears to react stoichiometrically with pepsin in a 1:1 ratio to form a product whose apparent molecular size is the same as that of untreated pepsin. The inactivation of pepsin by the bromodiazoketone is accompanied by the release of stoichiometric amounts of bromide ions and the formation of a major product whose apparent size is similar to that of pepsin, and a minor component larger than the untreated enzyme.