A distributed scheduler for air traffic flow management

A system was developed to efficiently schedule aircraft into congested resources over long ranges and present that schedule as a decision support system. The scheduling system consists of a distributed network of independent schedulers, loosely coupled by sharing capacity information. This loose coupling insulates the schedules from uncertainty in long-distance estimations of arrival times, while allowing precise short-term schedules to be constructed. This ??rate profile?? mechanism allows feasible schedules to be produced over long ranges, essentially constructing precise short-range schedules that also ensure that future scheduling problems are solvable while meeting operational constraints. The system was tested operationally and demonstrated reduced airborne delay and improved coordination.     

Electrodeposition of aluminium and aluminium/platinum alloys from AlCl3/benzyltrimethylammonium chloride room temperature ionic liquids

This paper shows that aluminium and aluminium/platinum alloys can be deposited from room temperature ionic liquids formed from an adduct of aluminium trichloride with benzyltrimethyl ammonium chloride. The advantages of this ionic liquid over the majority of those previously investigated is that it is less water sensitive, easier to purify and form and significantly more cost effective. Voltammetry and chronoamperometry were used to investigate the deposition and stripping of aluminium on Pt, Al and Fe electrodes. Hull cell tests were performed to obtain the optimum deposition conditions and bulk electrolysis showed that uniform, adherent, crack-free aluminium deposits could be obtained from such ionic liquids. Co-electrodeposition of Al with Pt was also studied and the nucleation mechanism was found to change significantly when Pt complexes were added to the ionic solution. The platinum ligands were found to change the solubility of the complex, but had little effect on the morphology of the deposited film.     

An Interlaboratory Comparison of Relative Humidity and Temperature Probes Using Diverse Generation Techniques

An interlaboratory comparison using relative-humidity (RH) and temperature probes at three national measurement institutes and two accredited laboratories has been carried out. The work had three purposes: firstly, to establish the instruments’ level of reproducibility and suitability for use as transfer standards within their specified range of operation; secondly, to show the agreement of a method of RH generation utilizing certified non-saturated salt RH standards when compared with a method of RH calibration using a chilled-mirror reference and platinum-resistance thermometers; and finally, from the results obtained it is possible to establish the equivalence between the participating laboratories, to the level of uncertainty achievable with the transfer standards used. A total of six RH probes were tested in two groups. The instruments of the first group were calibrated in the range from 10 %rh to 90 %rh at a temperature of 23 °C. The second group of instruments was measured in the same RH range, but at the temperatures of 5 °C, 23 °C, and 50 °C. The objective of the tests on the second group of instruments was to determine the effect of a wider operating temperature range on performance. This article presents and discusses the results of the comparison in the context of an international collaboration that provides confidence in the measurements performed by the participants within their respective accredited scopes and the ILAC or the CIPM mutual recognition arrangements.     

Hyperplastic gastric polyp causing progressive gastric outlet obstruction

Hyperplastic polyps represent 75 to 90% of gastric polypoid lesions. The manifestations of these unique gastric neoplasms vary, including abdominal pain, nausea, and vomiting or gastrointestinal bleeding. The vast majority of these lesions are small, asymptomatic, and found incidentally on radiologic evaluation or endoscopic examination of the upper gastrointestinal tract. Herein we describe a large, benign, pedunculated hyperplastic polyp that led to progressive gastric outlet obstruction. In addition, we provide an overview of gastric polyps and a review of the literature. Excision of gastric polyps by endoscopic or surgical means is recommended as prudent treatment to eliminate occurrence of malignant foci.     

Running in the real world: adjusting leg stiffness for different surfaces

A running animal coordinates the actions of many muscles, tendons, and ligaments in its leg so that the overall leg behaves like a single mechanical spring during ground contact. Experimental observations have revealed that an animal's leg stiffness is independent of both speed and gravity level, suggesting that it is dictated by inherent musculoskeletal properties. However, if leg stiffness was invariant, the biomechanics of running (e.g. peak ground reaction force and ground contact time) would change when an animal encountered different surfaces in the natural world. We found that human runners adjust their leg stiffness to accommodate changes in surface stiffness, allowing them to maintain similar running mechanics on different surfaces. These results provide important insight into mechanics and control of animal locomotion and suggest that incorporating an adjustable leg stiffness in the design of hopping and running robots is important if they are to match the agility and speed of animals on varied terrain.     

Survival of infectious Cryptosporidium parvum oocysts in seawater and eastern oysters (Crassostrea virginica) in the Chesapeake Bay

Oocysts of Cryptosporidium parvum placed in artificial seawater at salinities of 10, 20, and 30 ppt at 10 degrees C and at 10 ppt at 20 degrees C were infectious after 12 weeks. Those placed in seawater at 20 ppt and 30 ppt at 20 degrees C were infectious for 8 and 4 weeks, respectively. These findings suggested that oocysts could survive in estuarine waters long enough to be removed by filter feeders such as oysters. Thereafter, 30 Eastern oysters, Crassostrea virginica, were collected with a dredge or with hand tongs at each of six sites within Maryland tributaries of the Chesapeake Bay in May and June and in August and September of 1997. Hemocytes and gill washings from all oysters were examined for the presence of Cryptosporidium oocysts and Giardia cysts by immunofluorescence microscopy utilizing a commercially available kit containing fluorescein isothiocyanate-conjugated monoclonal antibodies. Giardia was not detected by this method from any of the 360 oysters examined. Presumptive identification of Cryptosporidium oocysts was made in either hemocytes or gill washings of oysters from all six sites both times that surveys were conducted. In addition, during August and September, for each of the six sites, hemocytes from the 30 oysters were pooled and gill washings from the oysters were pooled. Each pool was delivered by gastric intubation to a litter of neonatal mice to produce a bioassay for oocyst infectivity. Intestinal tissue from two of three mice that received gill washings from oysters collected at a site near a large cattle farm and shoreline homes with septic tanks was positive for developmental stages of C. parvum. These findings demonstrate for the first time that oysters in natural waters harbor infectious C. parvum oocysts and can serve as mechanical vectors of this pathogen.     

Bacterial meningitis in the United States in 1995. Active Surveillance Team

BACKGROUND: Before the introduction of the conjugate vaccines, Haemophilus influenzae type b was the major cause of bacterial meningitis in the United States, and meningitis was primarily a disease of infants and young children. We describe the epidemiologic features of bacterial meningitis five years after the H. influenzae type b conjugate vaccines were licensed for routine immunization of infants. METHODS: Data were collected from active, population-based surveillance for culture-confirmed meningitis and other invasive bacterial disease during 1995 in laboratories serving all the acute care hospitals in 22 counties of four states (total population, more than 10 million). The rates were compared with those for 1986 obtained by similar surveillance. RESULTS: On the basis of 248 cases of bacterial meningitis in the surveillance areas, the rates of meningitis (per 100,000) for the major pathogens in 1995 were Streptococcus pneumoniae, 1.1; Neisseria meningitidis, 0.6; group B streptococcus, 0.3; Listeria monocytogenes, 0.2; and H. influenzae, 0.2. Group B streptococcus was the predominant pathogen among newborns, N. meningitidis among children 2 to 18 years old, and S. pneumoniae among adults. Pneumococcal meningitis had the highest case fatality rate (21 percent) and in 36 percent of cases was caused by organisms that were not susceptible to penicillin. From these data, we estimate that 5755 cases of bacterial meningitis were caused by these five pathogens in the United States in 1995, as compared with 12,920 cases in 1986, a reduction of 55 percent. The median age of persons with bacterial meningitis increased greatly, from 15 months in 1986 to 25 years in 1995, largely as a result of a 94 percent reduction in the number of cases of H. influenzae meningitis. CONCLUSIONS: Because of the vaccine-related decline in meningitis due to H. influenzae type b, bacterial meningitis in the United States is now a disease predominantly of adults rather than of infants and young children.     

Reduction in the bioelectric properties of swine tracheal submucosal gland cells in culture after daily short-term exposure to cocaine

Chronic use of cocaine has been associated with respiratory complications. In this study, we investigated the effects of daily short-term cocaine exposure on epithelial bioelectric properties and chloride secretion in response to secretagogues in primary culture of swine tracheal submucosal gland cells grown on microporous inserts. Cell cultures exposed continuously to cocaine for 24 h or intermittently for 30 min daily for up to 3 consecutive days, resulted in a concentration-dependent reduction in transwell voltage and transepithelial resistance. Cocaine (300 microM) treatment for 24 h decreased the voltage and resistance by 87 and 75%, respectively. The voltage and resistance were also substantially decreased after 3 days of intermittent cocaine (10-30 microM) exposure. Cocaine exposure protocols used here did not enhance lactate dehydrogenase (LDH) release. Chloride secretion was measured as short-circuit current utilizing Ussing chamber methodology. Cocaine exposure did not change the decreases in short-circuit current caused by amiloride (10 microM), but reduced the increases in short-circuit current induced by acetylcholine and isoproterenol. After 3 days of intermittent cocaine (30 microM) exposure, the maximal acetylcholine and isoproterenol responses were reduced by 67 and 71%, respectively. Therefore, cocaine exposure continuously for 24 h or intermittently for 30 min daily for up to 3 days decreased basal transepithelial voltage as well as resistance and reduced the responses to cholinergic and beta-adrenoceptor agonists. These results suggest that alterations in epithelial function can occur even after daily transient cocaine exposure.     

The role of defects in the diffusion and activation of impurities in ion implanted semiconductors

Ion implantation is an extremely attractive method of selectively doping semiconductors, in part because the as-implanted distribution of impurities can be accurately predicted. However, electrical activation of implanted dopants generally requires high temperature annealing which allows these impurities to redistribute by various mechanisms. This paper reviews the role of defects in redistribution during the annealing of ion-implanted semiconductors. Some problems are inherent in the annealing process and are commonly observed in various materials. These include enhanced diffusion, gettering, and redistribution during recrystallization. Some problems are peculiar to compounds and include the effects of encapsulation, imbalances in crystal stoichiometry, and unequal recoil of host atoms of different masses. Dual implants and various implant temperatures have been employed in an effort to avoid some of these problems. Pulse annealing methods have also been investigated which reduce redistribution by considerably shortening the anneal time. However, problems associated with redistribution of dopants during annealing still limit the effectiveness of implantations in compound semiconductors.