Web team overview

Analytical and experimental work were combined to develop a stress model to determine the temperature profile which will yield a satisfactory web. A thermal model of the web will be used to determine the thermal configuration which will yield the desired temperature profile. Thermal analysis of growth interface and the susceptor melt will be developed to determine a thermal configuration which will improve stability of growth process. The thermal configurations will be designed, fabricated, and tested and the results fed back into the models

Mean field convergence of a model of multiple TCP connections through a buffer implementing RED

RED (Random Early Detection) has been suggested when multiple TCP sessions are multiplexed through a bottleneck buffer. The idea is to detect congestion before the buffer overflows by dropping or marking packets with a probability that increases with the queue length. The objectives are reduced packet loss, higher throughput, reduced delay and reduced delay variation achieved through an equitable distribution of packet loss and reduced synchronization. Baccelli, McDonald and Reynier [Performance Evaluation 11 (2002) 77--97] have proposed a fluid model for multiple TCP connections in the congestion avoidance regime multiplexed through a bottleneck buffer implementing RED. The window sizes of each TCP session evolve like independent dynamical systems coupled by the queue length at the buffer. The key idea in [Performance Evaluation 11 (2002) 77--97] is to consider the histogram of window sizes as a random measure coupled with the queue. Here we prove the conjecture made in [Performance Evaluation 11 (2002) 77--97] that, as the number of connections tends to infinity, this system converges to a deterministic mean-field limit comprising the window size density coupled with a deterministic queue.Comment: Published at http://dx.doi.org/10.1214/105051605000000700 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Examination of a culturable microbial population from the gastrointestinal tract of the wood-eating loricariid catfish Panaque nigrolineatus

Fish play a critical role in nutrient cycling and organic matter flow in aquatic environments. However, little is known about the microbial diversity within the gastrointestinal tracts that may be essential in these degradation activities. Panaque nigrolineatus is a loricariid catfish found in the Neotropics that have a rare dietary strategy of consuming large amounts of woody material in its natural environment. As a consequence, the gastrointestinal (GI) tract of P. nigrolineatus is continually exposed to high levels of cellulose and other recalcitrant wood compounds and is, therefore, an attractive, uncharacterized system to study microbial community diversity. Our previous 16S rRNA gene surveys demonstrated that the GI tract microbial community includes phylotypes having the capacity to degrade cellulose and fix molecular nitrogen. In the present study we verify the presence of a resident microbial community by fluorescence microscopy and focus on the cellulose-degrading members by culture-based and 13C-labeled cellulose DNA stable-isotope probing (SIP) approaches. Analysis of GI tract communities generated from anaerobic microcrystalline cellulose enrichment cultures by 16S rRNA gene analysis revealed phylotypes sharing high sequence similarity to known cellulolytic bacteria including Clostridium, Cellulomonas, Bacteroides, Eubacterium and Aeromonas spp. Related bacteria were identified in the SIP community, which also included nitrogen-fixing Azospirillum spp. Our ability to enrich for specialized cellulose-degrading communities suggests that the P. nigrolineatus GI tract provides a favorable environment for this activity and these communities may be involved in providing assimilable carbon under challenging dietary conditions

Negative Group Velocity

The group velocity for pulses in an optical medium can be negative at frequencies between those of a pair of laser-pumped spectral lines. The gain medium then can amplify the leading edge of a pulse resulting in a time advance of the pulse when it exits the medium, as has been recently demonstrated in the laboratory. This effect has been called superluminal, but, as a classical analysis shows, it cannot result in signal propgation at speeds greater than that of light in vacuum.Comment: v3 adds discussion of "rephasing", and adds a figure. v4 adds references to the early history of negative group velocity, and adds a figure; thanks to Alex Grani

Large deviations of a modified Jackson network: stability and rough asymptotics

Consider a modified, stable, two node Jackson network where server 2 helps server 1 when server 2 is idle. The probability of a large deviation of the number of customers at node one can be calculated using the flat boundary theory of Schwartz and Weiss [Large Deviations Performance Analysis (1994), Chapman and Hall, New York]. Surprisingly, however, these calculations show that the proportion of time spent on the boundary, where server 2 is idle, may be zero. This is in sharp contrast to the unmodified Jackson network which spends a nonzero proportion of time on this boundary.Comment: Published at http://dx.doi.org/10.1214/105051604000000666 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Flat-plate solar array project. Volume 1: Executive summary

In 1975, the U.S. Government contracted the Jet Propulsion Lab. to develop, by 1985, in conjunction with industry, the photovoltaics (PV) module and array technology required for widespread use of photovoltaics as a significant terrestrial energy source. As a result, a project that eventually became known as the Flat Plate Solar Array (FSA) Project was formed to manage an industry, university, and Government team to perform the necessary research and development. The original goals were to achieve widespread commercial use of PV modules and arrays through the development of technology that would allow them to be profitably sold for $1.07/peak watts (1985 dollars). A 10% module conversion efficiency and a 20 year lifetime were also goals. It is intended that the executive summary provide the means by which one can gain a perspective on 11 years of terrestrial photovoltaic research and development conducted by the FSA Project

Evaluation of the onset time and intubation conditions of rocuronium bromide in children

Publisher's copy made available with the permission of the publisher © 1997 Australian Society of AnaesthetistsWe have assessed, in children aged three to eight years, the intubating conditions after administration of rocuronium 0.6 mg/kg at 50 or 60 seconds, in groups of 15 patients. Intubating conditions were excellent in 11, good in 3 and fair in 1 patient at 50 seconds and excellent in 12 and good in 3 patients at 60 seconds. The mean onset time, for all patients, to when the first twitch of the train of four (T1), measured at the adductor pollicis, was depressed to less than 30% and 5% of control was 50 (SD 11.4) seconds and 94 (SD 31.7) seconds respectively. Depression of T1 to less than 30% of control, measured at the adductor pollicis in children, appears to indicate that intubating conditions will be clinically acceptable when using rocuronium.P.F. McDonald, D.A. Sainsbury, R.J. Lain