Development and evaluation of AGNI : a distributed netgraph data collection and analysis tool

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (leaves 46-47).AGNI is a tool developed to facilitate the analysis of communication networks between people in large organizations. Determining patterns of communication within organiza­tions is critical to the analysis of the effectiveness of their structure. Until recently, large organizations presented a special problem. The copious amounts of data that had to be analyzed made the process slow and tedious. AGNI makes the job easier by automating many of the tasks involved in this process. It provides a user friendly graphical environ­ment in which data can be collected and analyzed. It also provides an easy way to display the data in a graphical format so that it is easy to visualize.by Ian J.C. Duggan.M.Eng

Modeling the near-ultraviolet band of GK stars. III. dependence on abundance pattern

Publisher's Version/PDFWe extend the grid of non-LTE (NLTE) models presented in Paper II to explore variations in abundance pattern in two ways: (1) the adoption of the Asplund et al. (GASS10) abundances, (2) for stars of metallicity, [M/H], of −0.5, the adoption of a non-solar enhancement of [alpha]-elements by +0.3 dex. Moreover, our grid of synthetic spectral energy distributions (SEDs) is interpolated to a finer numerical resolution in both T[subscript eff] ([delta]T[subscript eff] = 25 K) and log g ([delta] log g = 0.25). We compare the values of T[subscript eff] and log g inferred from fitting LTE and NLTE SEDs to observed SEDs throughout the entire visible band, and in an ad hoc “blue” band. We compare our spectrophotometrically derived T[subscript eff] values to a variety of T[subscript eff] calibrations, including more empirical ones, drawn from the literature. For stars of solar metallicity, we find that the adoption of the GASS10 abundances lowers the inferred T[subscript eff] value by 25–50 K for late-type giants, and NLTE models computed with the GASS10 abundances give T[subscript eff] results that are marginally in better agreement with other T[subscript eff] calibrations. For stars of [M/H] = −0.5 there is marginal evidence that adoption of [alpha]-enhancement further lowers the derived T[subscript eff] value by 50 K. Stellar parameters inferred from fitting NLTE models to SEDs are more dependent than LTE models on the wavelength region being fitted, and we find that the effect depends on how heavily line blanketed the fitting region is, whether the fitting region is to the blue of the Wien peak of the star’s SED, or both

Next-Generation Evaporative Cooling Systems for the Advanced Extravehicular Mobility Unit Portable Life Support System

The development of the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support System (PLSS) is currently underway at NASA Johnson Space Center. The AEMU PLSS features two new evaporative cooling systems, the Reduced Volume Prototype Spacesuit Water Membrane Evaporator (RVP SWME), and the Auxiliary Cooling Loop (ACL). The RVP SWME is the third generation of hollow fiber SWME hardware, and like its predecessors, RVP SWME provides nominal crewmember and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crewmember and PLSS electronics. Major design improvements, including a 36% reduction in volume, reduced weight, and more flight like back-pressure valve, facilitate the packaging of RVP SWME in the AEMU PLSS envelope. In addition to the RVP SWME, the Auxiliary Cooling Loop (ACL), was developed for contingency crewmember cooling. The ACL is a completely redundant, independent cooling system that consists of a small evaporative cooler--the Mini Membrane Evaporator (Mini-ME), independent pump, independent feed-water assembly and independent Liquid Cooling Garment (LCG). The Mini-ME utilizes the same hollow fiber technology featured in the RVP SWME, but is only 25% of the size of RVP SWME, providing only the necessary crewmember cooling in a contingency situation. The ACL provides a number of benefits when compared with the current EMU PLSS contingency cooling technology; contingency crewmember cooling can be provided for a longer period of time, more contingency situations can be accounted for, no reliance on a Secondary Oxygen Vessel (SOV) for contingency cooling--thereby allowing a SOV reduction in size and pressure, and the ACL can be recharged-allowing the AEMU PLSS to be reused, even after a contingency event. The development of these evaporative cooling systems will contribute to a more robust and comprehensive AEMU PLSS

Reduced Volume Prototype Spacesuit Water Membrane Evaporator; A Next-Generation Evaporative Cooling System for the Advanced Extravehicular Mobility Unit Portable Life Support System

Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the reduced volume prototype (RVP) spacesuit water membrane evaporator (SWME). The RVP SWME is the third generation of hollow fiber SWME hardware. Like its predecessors, RVP SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Major design improvements, including a 36% reduction in volume, reduced weight, and a more flight-like backpressure valve, facilitate the packaging of RVP SWME in the AEMU PLSS envelope. The development of these evaporative cooling systems will contribute to a more robust and comprehensive AEMU PLSS

Modeling the near-UV band of GK stars, Paper II: NLTE models

We present a grid of atmospheric models and synthetic spectral energy distributions (SEDs) for late-type dwarfs and giants of solar and 1/3 solar metallicity with many opacity sources computed in self-consistent Non-Local Thermodynamic Equilibrium (NLTE), and compare them to the LTE grid of Short & Hauschildt (2010) (Paper I). We describe, for the first time, how the NLTE treatment affects the thermal equilibrium of the atmospheric structure (T(tau) relation) and the SED as a finely sampled function of Teff, log g, and [A/H] among solar metallicity and mildly metal poor red giants. We compare the computed SEDs to the library of observed spectrophotometry described in Paper I across the entire visible band, and in the blue and red regions of the spectrum separately. We find that for the giants of both metallicities, the NLTE models yield best fit Teff values that are ~30 to 90 K lower than those provided by LTE models, while providing greater consistency between \log g values, and, for Arcturus, Teff values, fitted separately to the blue and red spectral regions. There is marginal evidence that NLTE models give more consistent best fit Teff values between the red and blue bands for earlier spectral classes among the solar metallicity GK giants than they do for the later classes, but no model fits the blue band spectrum well for any class. For the two dwarf spectral classes that we are able to study, the effect of NLTE on derived parameters is less significant.Comment: Submitted to The Astrophysical Journal. Observed spectrophotometric library, and grids of NLTE and LTE) synthetic spectra for GK stars available at http://www.ap.smu.ca/~ishort/PHOENI

Palliative care needs in patients hospitalized with heart failure (PCHF) study: rationale and design

Abstract Aims The primary aim of this study is to provide data to inform the design of a randomized controlled clinical trial (RCT) of a palliative care (PC) intervention in heart failure (HF). We will identify an appropriate study population with a high prevalence of PC needs defined using quantifiable measures. We will also identify which components a specific and targeted PC intervention in HF should include and attempt to define the most relevant trial outcomes. Methods An unselected, prospective, near-consecutive, cohort of patients admitted to hospital with acute decompensated HF will be enrolled over a 2-year period. All potential participants will be screened using B-type natriuretic peptide and echocardiography, and all those enrolled will be extensively characterized in terms of their HF status, comorbidity, and PC needs. Quantitative assessment of PC needs will include evaluation of general and disease-specific quality of life, mood, symptom burden, caregiver burden, and end of life care. Inpatient assessments will be performed and after discharge outpatient assessments will be carried out every 4 months for up to 2.5 years. Participants will be followed up for a minimum of 1 year for hospital admissions, and place and cause of death. Methods for identifying patients with HF with PC needs will be evaluated, and estimates of healthcare utilisation performed. Conclusion By assessing the prevalence of these needs, describing how these needs change over time, and evaluating how best PC needs can be identified, we will provide the foundation for designing an RCT of a PC intervention in HF

Clinical stakeholders' opinions on the use of selective decontamination of the digestive tract in critically ill patients in intensive care units : an international Delphi study

Peer reviewedPublisher PD

Stretched exponential behavior and random walks on diluted hypercubic lattices

Diffusion on a diluted hypercube has been proposed as a model for glassy relaxation and is an example of the more general class of stochastic processes on graphs. In this article we determine numerically through large scale simulations the eigenvalue spectra for this stochastic process and calculate explicitly the time evolution for the autocorrelation function and for the return probability, all at criticality, with hypercube dimensions $N$ up to N=28. We show that at long times both relaxation functions can be described by stretched exponentials with exponent 1/3 and a characteristic relaxation time which grows exponentially with dimension $N$. The numerical eigenvalue spectra are consistent with analytic predictions for a generic sparse network model.Comment: 16 pages, 7 figure

OB Stars & Stellar Bowshocks in Cygnus-X: A Novel Laboratory Estimating Stellar Mass Loss Rates

We use mid-IR images from the Spitzer Cygnus~X Legacy Survey to search for stellar bowshocks, a signature of early type "runaway" stars with high space velocities. We identify ten arc-shaped nebulae containing centrally located stars as candidate bowshocks. New spectroscopic observations of five stars show that all are late O to early B dwarfs. Our morphologically selected sample of bowshock candidates encompasses diverse physical phenomena. Three of the stars appear to be pre-main-sequence objects on the basis of rising SEDs in the mid-IR, and their nebulae may be photon-dominated regions (PDRs). Four objects have ambiguous classification. These may be partial dust shells or bubbles. We conclude that three of the objects are probable bowshocks, based on their morphological similarity to analytic prescriptions. Their nebular morphologies reveal no systematic pattern of orientations that might indicate either a population of stars ejected from or large-scale hydrodynamic outflows from Cyg OB2. The fraction of runaways among OB stars near Cyg OB2 identified either by radial velocity or bowshock techniques is ~0.5%, much smaller than the 8% estimated among field OB stars. We also obtained a heliocentric radial velocity for the previously known bowshock star, BD+43\degr3654, of -66.2+/-9.4 km/s, solidifying its runaway status and implying a space velocity of 77+/-10 km/s. We use the principles of momentum-driven bowshocks to arrive at a novel method for estimating stellar mass loss rates. Derived mass loss rates range between 10^-7 and few x10^-6 solar masses/yr for the three O5V -- ~B2V stars identified as generating bowshocks. These values are at the upper range of, but broadly consistent with, estimates from other methods. (Abridged)Comment: 49 pages, 19 figures; Accepted for publication in ApJ; full-resolution color figure version available at http://physics.uwyo.edu/~chip/Papers/CygXBowshocks; comments invite

The Hornless Australian Burrowing Mayfly Ulmerophlebia (Ephemeroptera: Leptophlebiidae)

The hornless Australian burrowing mayfly genus Ulmerophlebia Demoulin (Leptophlebiidae) is revised based on comprehensive examinations of adult and larval material collected throughout Australia. Two new species [Ulmerophlebia deani n. sp. and U. minuta n. sp.] and three named species [U. annulata (Harker), U. mjobergi (Ulmer) and U. pipinna Suter] are included. The larva of U. deani can be distinguished by the moderately developed apicomedial expansion of gills and W-shaped markings on the abdominal terga. The male adult of U. minuta can be easily distinguished by the greatly reduced penes. Descriptions, diagnoses, line-drawings of key characters, material and distributional data, taxonomic remarks and adult and larval keys are provided