Medium power hydrogen arcjet performance

An experimental investigation was performed to evaluate hydrogen arcjet operating characteristics in the range of 1 to 4 kW. A series of nozzles were operated in modular laboratory thrusters to examine the effects of geometric parameters such as constrictor diameter and nozzle divergence angle. Each nozzle was tested over a range of current and mass flow rates to explore stability and performance. In the range of mass flow rates and power levels tested, specific impulse values between 650 and 1250 sec were obtained at efficiencies between 30 and 40 percent. The performance of the two larger half angle (20, 15 deg) nozzles was similar for each of the two constrictor diameters tested. The nozzles with the smallest half angle (10 deg) were difiicult to operate. A restrike mode of operation was identified and described. Damage in the form of melting was observed in the constrictor region of all the nozzle inserts tested. Arcjet ignition was also difficult in many tests and a glow discharge mode that prevents starting was identified

Efficient decomposition of quantum gates

Optimal implementation of quantum gates is crucial for designing a quantum computer. We consider the matrix representation of an arbitrary multiqubit gate. By ordering the basis vectors using the Gray code, we construct the quantum circuit which is optimal in the sense of fully controlled single-qubit gates and yet is equivalent with the multiqubit gate. In the second step of the optimization, superfluous control bits are eliminated, which eventually results in a smaller total number of the elementary gates. In our scheme the number of controlled NOT gates is $O(4^n)$ which coincides with the theoretical lower bound.Comment: 4 pages, 2 figure

Triton's surface age and impactor population revisited in light of Kuiper Belt fluxes: Evidence for small Kuiper Belt objects and recent geological activity

Neptune's largest satellite, Triton, is one of the most fascinating and enigmatic bodies in the solar system. Among its numerous interesting traits, Triton appears to have far fewer craters than would be expected if its surface was primordial. Here we combine the best available crater count data for Triton with improved estimates of impact rates by including the Kuiper Belt as a source of impactors. We find that the population of impactors creating the smallest observed craters on Triton must be sub-km in scale, and that this small-impactor population can be best fit by a differential power-law size index near -3. Such results provide interesting, indirect probes of the unseen small body population of the Kuiper Belt. Based on the modern, Kuiper Belt and Oort Cloud impactor flux estimates, we also recalculate estimated ages for several regions of Triton's surface imaged by Voyager 2, and find that Triton was probably active on a time scale no greater than 0.1-0.3 Gyr ago (indicating Triton was still active after some 90% to 98% of the age of the solar system), and perhaps even more recently. The time-averaged volumetric resurfacing rate on Triton implied by these results, 0.01 km$^3$ yr$^{-1}$ or more, is likely second only to Io and Europa in the outer solar system, and is within an order of magnitude of estimates for Venus and for the Earth's intraplate zones. This finding indicates that Triton likely remains a highly geologically active world at present, some 4.5 Gyr after its formation. We briefly speculate on how such a situation might obtain.Comment: 14 pages (TeX), plus 2 postscript figures Stern & McKinnon, 2000, AJ, in pres

Crisis management during anaesthesia: problems associated with drug administration during anaesthesia

© 2005 BMJ Publishing Group Ltd.BACKGROUND: Modern anaesthetic practice relies upon the administration of a wide range of potent drugs given by a variety of routes, at times in haste or under conditions of stress. Problems associated with drug administration make up the largest group of incidents reported during anaesthesia, with outcomes including major morbidity and death. It was decided to examine the role of a structured approach to the diagnosis and management of drug problems under anaesthesia. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD–A SWIFT CHECK", supplemented by a specific sub-algorithm for drug problems, in the detection and management of drug problems occurring in association with anaesthesia. METHODS: The potential performance of this structured approach for the relevant incidents among the first 4000 incidents reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual performances as reported by the anaesthetists involved. RESULTS: Among the first 4000 reports received by AIMS there were 1199 reports which detailed 1361 incidents involving the use of drugs. Contributing factors named included errors of judgement (20%), lack of attention (17%), and drugs deemed to have been given in haste. Major morbidity or prolonged stay ensued in over one quarter of reports and 15 patients (1.25%) died. Drug overdose, side effects, and allergic reactions accounted for the majority of serious outcomes. CONCLUSION: It was judged that the use of the COVER–ABCD algorithm during the course of an anaesthetic, properly applied, would prevent many drug related incidents from occurring. The sub-algorithm presented here provides a systematic framework for detecting the causes of drug related incidents.A D Paix, M F Bullock, W B Runciman and J A Williamso

PURIFIED PROTEIN DERIVATIVE OF TUBERCULIN INDUCES IMMUNOGLOBULIN PRODUCTION IN NORMAL MOUSE SPLEEN CELLS

Purified protein derivative (PPD) tuberculin induced immunoglobulin production in cultures of nonimmune mouse spleen cells, as measured by plaque-forming cells (PFC) against sheep erythrocytes (SRBC), horse erythrocytes, and 4-hydroxy-3,5-dinitrophenacetyl-SRBC. The increase started between 15 and 20 h of culture and reached a peak at 48–72 h. Higher PPD concentrations resulted in earlier peak responses than low concentrations. The Ig produced was mainly 19S and of very low avidity. The response elicited by PPD was of the same type as that caused by lipopolysaccharide of bacterial origin. Mitomycin treatment of cells before culture did not change the numbers of PFC/106 recovered cells but the cell recovery was considerably lower. Also injection of PPD in vivo resulted in increased numbers of PFC. On the basis of these results it is suggested that PPD nonspecifically activates a majority of the B cell population to proliferation and immunoglobulin synthesis

Hybrid Reactions to Phytotoxic Effects of The Corn Herbicide, Eradicane Extra

Although corn hybrids are primarily evaluated only for yield performance in the Kentucky Hybrid Corn Performance Test, the 1984 test (Poneleit and Evans, 1985) provided a unique opportunity to evaluate hybrid reactions to an unusual hybrid-herbicide interacting Of seven non-virus test locations, four were treated with Eradicane Extra or Eradicane for weed control. At the Princeton location Eradicane Extra, at 8 pints/acre, was used for johnsongrass rhizome suppression and seedling control. In late July, a routine check revealed that numerous plants had unusual appearances that were similar to abnormalities reported earlier as caused by Eptam and Eradicane (Poneleit et aI, 1975). Subsequent observations confirmed the severity of damage at the Princeton test site and reports of similar hybrid reactions from farmer fields prompted the collection of apparent herbicide damage data from the replicated Princeton test. The other performance test sites where Eradicane Extra or Eradicane was applied did not show significant plant abnormalities. Apparently the appearance of phytotoxic effects owing to Eradicane Extra are sporadic and strongly influenced by specific interaction of environmental factors. It was postulated that this injury occurrence in 1984 was the result of excessive rainfall four to six weeks after planting. Dichlormid (safener) is very water soluble and could have been leached away from the corn roots, and thus not available to protect the corn from EPTC

Polyethylene Oxide Nanofiber Production by Electrospinning

Electrospinning is an inexpensive technique that is used to produce nanofibers for a variety of applications. In electrospinning, a polymer solution is dispensed from a hypodermic-like syringe where an intense electric field attracts the solution to a collector while drawing the polymer into a very thin fiber. The diameter of the fiber can be controlled by tuning the process parameters such as the applied electric field, solution flow rate, distance between syringe tip and collector, and the collector geometry. In this paper we describe results from electrospinning poly(ethylene oxide) (PEO), a likely candidate for applications involving scaffolding for tissue engineering. The PEO nanofibers were fabricated from different polymer solution concentrations ranging from 14% - 22% (by weight). Each sample was then imaged using a scanning electron microscope. The morphology of the fibers produced from varying solution concentrations is discussed