Wideband infrared heterodyne receiver front-end

A 10.6 micron infrared heterodyne receiver front end was developed for use in a wideband CO2 laser communications link. The infrared receiver employs an 850 MHz response PV HgCdTe photomixer which is mounted in a space quality housing, a low-noise 5 to 1500 MHz IF preamplifier, and a remote control panel. The receiver was designed to handle + or - 750 MHz of Doppler shift while providing an instantaneous information bandwidth of 400 MHz. The measured receiver sensitivity NEP was 1.0 x 10 to the 19th power W/Hz for a photomixer temperature of T sub m = 77 K and an IF beat frequency of 20 MHz and degraded to 1.75 x 10 to the 19th power W/Hz for T sub m = 130 K

A network-based approach for predicting key enzymes explaining metabolite abundance alterations in a disease phenotype

<p>Background The study of metabolism has attracted much attention during the last years due to its relevance in various diseases. The advance in metabolomics platforms allows us to detect an increasing number of metabolites in abnormal high/low concentration in a disease phenotype. Finding a mechanistic interpretation for these alterations is important to understand pathophysiological processes, however it is not an easy task. The availability of genome scale metabolic networks and Systems Biology techniques open new avenues to address this question.</p> <p>Results In this article we present a novel mathematical framework to find enzymes whose malfunction explains the accumulation/depletion of a given metabolite in a disease phenotype. Our approach is based on a recently introduced pathway concept termed Carbon Flux Paths (CFPs), which extends classical topological definition by including network stoichiometry. Using CFPs, we determine the Connectivity Curve of an altered metabolite, which allows us to quantify changes in its pathway structure when a certain enzyme is removed. The influence of enzyme removal is then ranked and used to explain the accumulation/depletion of such metabolite. For illustration, we center our study in the accumulation of two metabolites (L-Cystine and Homocysteine) found in high concentration in the brain of patients with mental disorders. Our results were discussed based on literature and found a good agreement with previously reported mechanisms. In addition, we hypothesize a novel role of several enzymes for the accumulation of these metabolites, which opens new strategies to understand the metabolic processes underlying these diseases.</p> <p>Conclusions With personalized medicine on the horizon, metabolomic platforms are providing us with a vast amount of experimental data for a number of complex diseases. Our approach provides a novel apparatus to rationally investigate and understand metabolite alterations under disease phenotypes. This work contributes to the development of Systems Medicine, whose objective is to answer clinical questions based on theoretical methods and high-throughput “omics” data.</p&gt

Ballistic Flash Characterization of Entry-Side Flash

Aircraft survivability is a broad subject that encompasses many fields and subjects. An important part of aircraft survivability is fire prevention. Flashes created by ballistic impacts are a very real threat to aircraft because they can start fires or cause explosions. In an effort to better protect against these flashes, this study seeks to further the understanding and characterization of them. Recent research on this subject has been greatly helped by the use of high-speed video footage of flash events. This footage has led to new algorithms and methodologies for how to characterize a flash. A preliminary predictive model of a flash event has already been made, but needs to be refined before implementation. This research effort is dedicated to further refining and developing this predictive model by finding a new time series model that more aptly describes the shape of the analyzed data. To this end, new data have been created and analyzed, and a new predictive flash model has been created. This model has been validated and proven to be adequate. Even though there is some amount of work that can still be done to enhance it, it is recommended that this model be implemented into the current flash prediction tools

Feasibility And Characterization Of Leak-Tight Single-Track Thin Walls Produced By Laser Powder Bed Fusion In 316L Stainless Steel

This thesis explores the optimization of process parameters for producing single-track thin walls using Laser Powder Bed Fusion (LPBF) additive manufacturing. Using two different coupon designs, the study assesses the feasibility of creating the thinnest possible leak-tight structures within LPBF and evaluating their mechanical properties, including burst pressure and modulus of elasticity under pressure loads. A series of experimental iterations were conducted, varying laser power and laser speed to identify optimal conditions. The findings indicate that a narrow range of process parameters can produce consistently leak-tight thin walls. The results contribute to understanding how to achieve high quality, reliable thin wall structures in the LPBF process, with implications for industrial applications requiring thin, precise, leak tight, and durable walls

Developments in electromagnetic tomography instrumentation.

A new EMT sensor and instrumentation is described which combines the best features of previous systems and has a modular structure to allow for future system expansion and development

Application of tunable diode lasers as local oscillators in an Infrared Heterodyne Radiometer (IHR)

The utility of diode lasers as local oscillators (LOs) in a heterodyne receiver application was investigated. The CW power, spectral tunability, spectral stability, and spatial intensity distribution of the TDL outputs were measured. A tunable diode laser LO was incorporated into a laboratory Dicke-switched infrared heterodyne setup and used to measure radiometer sensitivity as well as spectroscopic characteristics of selected absorption lines of ammonia. The test results on one of the two tunable diode lasers are emphasized in an attempt to provide a comprehensive data package which may be useful for future planning purposes. The second tunable diode laser exhibits characteristics similar to the fully tested TDL with the exception that some changes in its performance characteristics as it was temperature cycled between room temperature and the operating temperature of approximately 50K occurred

Optical constants of uranium plasma Final report

Thermodynamic and optical properties of uranium plasma in proposed gaseous core nuclear rocket

The Cost of Stability in Coalitional Games

A key question in cooperative game theory is that of coalitional stability, usually captured by the notion of the \emph{core}--the set of outcomes such that no subgroup of players has an incentive to deviate. However, some coalitional games have empty cores, and any outcome in such a game is unstable. In this paper, we investigate the possibility of stabilizing a coalitional game by using external payments. We consider a scenario where an external party, which is interested in having the players work together, offers a supplemental payment to the grand coalition (or, more generally, a particular coalition structure). This payment is conditional on players not deviating from their coalition(s). The sum of this payment plus the actual gains of the coalition(s) may then be divided among the agents so as to promote stability. We define the \emph{cost of stability (CoS)} as the minimal external payment that stabilizes the game. We provide general bounds on the cost of stability in several classes of games, and explore its algorithmic properties. To develop a better intuition for the concepts we introduce, we provide a detailed algorithmic study of the cost of stability in weighted voting games, a simple but expressive class of games which can model decision-making in political bodies, and cooperation in multiagent settings. Finally, we extend our model and results to games with coalition structures.Comment: 20 pages; will be presented at SAGT'0