Content addressable memory project

A parameterized version of the tree processor was designed and tested (by simulation). The leaf processor design is 90 percent complete. We expect to complete and test a combination of tree and leaf cell designs in the next period. Work is proceeding on algorithms for the computer aided manufacturing (CAM), and once the design is complete we will begin simulating algorithms for large problems. The following topics are covered: (1) the practical implementation of content addressable memory; (2) design of a LEAF cell for the Rutgers CAM architecture; (3) a circuit design tool user's manual; and (4) design and analysis of efficient hierarchical interconnection networks

Substituent Effects on the Electronic Spectroscopy of Tryptophan Derivatives in Jet Expansions

Electronic excitation spectra of seven tryptophan derivatives entrained in a supersonic expansion have been recorded using both resonantly enhanced two-photon ionization and laser induced fluorescence. Two derivatives, tryptophan amide and tryptophan methyl amide, were found to have substantial low frequency vibrational progressions in their excitation spectra, yet in both compounds this behavior was apparent in only one conformer. Other derivatives did not display as much vibronic activity. Conformers which had vibrational progressions were found to emit in a broad band far to the red of excitation. All other conformers were found to fluoresce most strongly in resonance with excitation. The presence of low frequency vibrational activity and red shifted fluorescence correlates well with the ability of the derivative to form an intramolecular hydrogen bond between the amine and the carboxylic acid. Backbone conformers that contain an intramolecular hydrogen bond are expected to have large dipole moments, which may strongly perturb the electronic structure of the indole chromophore. © 1990 American Institute of Physics

United States and Western Europe cooperation in planetary exploration

A framework was sought for U.S.-European cooperation in planetary exploration. Specific issues addressed include: types and levels of possible cooperative activities in the planetary sciences; specific or general scientific areas that seem most promising as the main focus of cooperative efforts; potential mission candidates for cooperative ventures; identification of special issues or problems for resolution by negotiation between the agencies, and possible suggestions for their resolutions; and identification of coordinated technological and instrumental developments for planetary missions

Free-Body Modeling of the Stability and Control of Submarines. Volume I - Text. Volume II - Figures

An experimental study of the dynamic control and stability of submarines has been made by means of small-scale, free-running, powered and controlled models at the California Institute of Technology, Hydrodynamics Laboratory. The experimental and theoretical basis of the modeling of the behavior of fully submerged submarines is discussed. The design and construction of the models are described, and development of experimental techniques is outlined. The experimental program was conducted with models of two full-scale submarines -- the U.S.S. Odax and the U.S.S. Albacore -- to (1) evaluate the efficacy of small-scale modeling, and (2) to predict control characteristics of a boat of radically new design. Satisfactory agreement between the dynamic behavior in free flight of the small-scale (120:1) model and the Guppy-type submarine Odax is demonstrated for one type of maneuver. Zig-zag maneuvers in the vertical plane were chosen for this purpose because of their simplicity and suitability for comparison with available full-scale data. The model's diving planes were made to reproduce the time-sequence of the diving plane motions of the full-scale submarine and the resulting depth and inclination responses compared to those of the full size vessel. The consistency of the model's behavior was evaluated from repeated tests with each of four selected control programs for which only a single full-scale test was run. Predictions of the dynamic control and maneuverability characteristics of the U.S.S. Albacore (AGSS 569) Scheme IV submarine, which marks a radical departure in hull design, were made with a 100 to 1 scale model. This model was built at about the same time that the keel was laid for the prototype ship. The studies made with this model were divided into three parts: (1) Control characteristics in the vertical plane. (2) Turning characteristics with rudder control alone. (3) Turning characteristics with depth control, and with combination depth-and-roll control. The tests under item (1) were made with two sets of appendages (tail structure, bow planes, and bridge fairwater), for which only minor differences in control response were found and no measurable difference noted in directional stability. Items (Z) and (3) were made with one set of appendages (corresponding to those first used on the prototype) and with Froude-scaled model velocity. Specific maneuvering problems, such as the determination of control plane programs required to execute optimum dives or horizontal turns without changing depth, are solved by successive approximation with the model. The tests show that a high degree of prescience is required and that precise execution of the control program is necessary to successfully accomplish an optimum maneuver. Comparison of the behavior of the two models shows that the Albacore has a greater degree of directional stability and a faster response to its controls than the Odax. This is certainly due to its better hydrodynamic design. The Albacore model also demonstrated much better consistency in it- own behavior than did the Odax model. This is due in part to better design and in part to the improvements made in the techniques of building and operating the models and in processing the model test data. At the time of this writing, no detailed comparisons have been made between results obtained with the Albacore model and those of the sea trials of the prototype which were made in the fall of 1955. The few spot comparisons which were made (but not included in this report) show good agreement. Detailed comparisons of these two sets of tests will be made at the David Taylor Model Basin (under whose supervision the sea trials were conducted) and will be the subject of a separate report

Free-Body Modeling of the Stability and Control of Submarines. Volume I - Text. Volume II - Figures

An experimental study of the dynamic control and stability of submarines has been made by means of small-scale, free-running, powered and controlled models at the California Institute of Technology, Hydrodynamics Laboratory. The experimental and theoretical basis of the modeling of the behavior of fully submerged submarines is discussed. The design and construction of the models are described, and development of experimental techniques is outlined. The experimental program was conducted with models of two full-scale submarines -- the U.S.S. Odax and the U.S.S. Albacore -- to (1) evaluate the efficacy of small-scale modeling, and (2) to predict control characteristics of a boat of radically new design. Satisfactory agreement between the dynamic behavior in free flight of the small-scale (120:1) model and the Guppy-type submarine Odax is demonstrated for one type of maneuver. Zig-zag maneuvers in the vertical plane were chosen for this purpose because of their simplicity and suitability for comparison with available full-scale data. The model's diving planes were made to reproduce the time-sequence of the diving plane motions of the full-scale submarine and the resulting depth and inclination responses compared to those of the full size vessel. The consistency of the model's behavior was evaluated from repeated tests with each of four selected control programs for which only a single full-scale test was run. Predictions of the dynamic control and maneuverability characteristics of the U.S.S. Albacore (AGSS 569) Scheme IV submarine, which marks a radical departure in hull design, were made with a 100 to 1 scale model. This model was built at about the same time that the keel was laid for the prototype ship. The studies made with this model were divided into three parts: (1) Control characteristics in the vertical plane. (2) Turning characteristics with rudder control alone. (3) Turning characteristics with depth control, and with combination depth-and-roll control. The tests under item (1) were made with two sets of appendages (tail structure, bow planes, and bridge fairwater), for which only minor differences in control response were found and no measurable difference noted in directional stability. Items (Z) and (3) were made with one set of appendages (corresponding to those first used on the prototype) and with Froude-scaled model velocity. Specific maneuvering problems, such as the determination of control plane programs required to execute optimum dives or horizontal turns without changing depth, are solved by successive approximation with the model. The tests show that a high degree of prescience is required and that precise execution of the control program is necessary to successfully accomplish an optimum maneuver. Comparison of the behavior of the two models shows that the Albacore has a greater degree of directional stability and a faster response to its controls than the Odax. This is certainly due to its better hydrodynamic design. The Albacore model also demonstrated much better consistency in it- own behavior than did the Odax model. This is due in part to better design and in part to the improvements made in the techniques of building and operating the models and in processing the model test data. At the time of this writing, no detailed comparisons have been made between results obtained with the Albacore model and those of the sea trials of the prototype which were made in the fall of 1955. The few spot comparisons which were made (but not included in this report) show good agreement. Detailed comparisons of these two sets of tests will be made at the David Taylor Model Basin (under whose supervision the sea trials were conducted) and will be the subject of a separate report

Severity scoring of manganese health effects for categorical regression

Characterizing the U-shaped exposure response relationship for manganese (Mn) is necessary for estimating the risk of adverse health from Mn toxicity due to excess or deficiency. Categorical regression has emerged as a powerful tool for exposure-response analysis because of its ability to synthesize relevant information across multiple studies and species into a single integrated analysis of all relevant data. This paper documents the development of a database on Mn toxicity designed to support the application of categorical regression techniques. Specifically, we describe (i) the conduct of a systematic search of the literature on Mn toxicity to gather data appropriate for dose-response assessment; (ii) the establishment of inclusion/exclusion criteria for data to be included in the categorical regression modeling database; (iii) the development of a categorical severity scoring matrix for Mn health effects to permit the inclusion of diverse health outcomes in a single categorical regression analysis using the severity score as the outcome variable; and (iv) the convening of an international expert panel to both review the severity scoring matrix and assign severity scores to health outcomes observed in studies (including case reports, epidemiological investigations, and in vivo experimental studies) selected for inclusion in the categorical regression database. Exposure information including route, concentration, duration, health endpoint(s), and characteristics of the exposed population was abstracted from included studies and stored in a computerized manganese database (MnDB), providing a comprehensive repository of exposure-response information with the ability to support categorical regression modeling of oral exposure data

Fiber Optic Temperature Sensors in TPS: Arc Jet Model Design & Testing

Techniques for using fiber optics with Fiber Bragg Gratings (FBGs) have been developed by IFOS Corp. for use in thermal protection systems (TPS) on spacecraft heat shield materials through NASA Phase 1 and 2 SBIR efforts and have been further improved in a recent collaboration between IFOS and NASA that will be described here. Fiber optic temperature sensors offer several potential advantages over traditional thermocouple sensors including a) multiplexing many sensors in a single fiber to increase sensor density in a given array or to provide spatial resolution, b) improved thermal property match between sensor and TPS to reduce heat flow disruption, c) lack of electrical conductivity

Climatic Drivers for Multi-Decadal Shifts in Solute Transport and Methane Production Zones within a Large Peat Basin

Northern peatlands are an important source for greenhouse gases but their capacity to produce methane remains uncertain under changing climatic conditions. We therefore analyzed a 43-year time series of pore-water chemistry to determine if long-term shifts in precipitation altered the vertical transport of solutes within a large peat basin in northern Minnesota. These data suggest that rates of methane production can be finely tuned to multi-decadal shifts in precipitation that drive the vertical penetration of labile carbon substrates within the Glacial Lake Agassiz Peatlands. Tritium and cation profiles demonstrate that only the upper meter of these peat deposits was flushed by downwardly moving recharge from 1965 through 1983 during a Transitional Dry-to-Moist Period. However, a shift to a moister climate after 1984 drove surface waters much deeper, largely flushing the pore waters of all bogs and fens to depths of 2 m. Labile carbon compounds were transported downward from the rhizosphere to the basal peat at this time producing a substantial enrichment of methane in Delta C-14 with respect to the solid-phase peat from 1991 to 2008. These data indicate that labile carbon substrates can fuel deep production zones of methanogenesis that more than doubled in thickness across this large peat basin after 1984. Moreover, the entire peat profile apparently has the capacity to produce methane from labile carbon substrates depending on climate-driven modes of solute transport. Future changes in precipitation may therefore play a central role in determining the source strength of peatlands in the global methane cycle

Energy efficiency of information transmission by electrically coupled neurons

The generation of spikes by neurons is energetically a costly process. This paper studies the consumption of energy and the information entropy in the signalling activity of a model neuron both when it is supposed isolated and when it is coupled to another neuron by an electrical synapse. The neuron has been modelled by a four dimensional Hindmarsh-Rose type kinetic model for which an energy function has been deduced. For the isolated neuron values of energy consumption and information entropy at different signalling regimes have been computed. For two neurons coupled by a gap junction we have analyzed the roles of the membrane and synapse in the contribution of the energy that is required for their organized signalling. Computational results are provided for cases of identical and nonidentical neurons coupled by unidirectional and bidirectional gap junctions. One relevant result is that there are values of the coupling strength at which the organized signalling of two neurons induced by the gap junction takes place at relatively low values of energy consumption and the ratio of mutual information to energy consumption is relatively high. Therefore, communicating at these coupling values could be energetically the most efficient option

The effect of the systemic inflammatory response on plasma vitamin 25 (OH) D concentrations adjusted for albumin

<b>Aim</b><p></p> To examine the relationship between plasma 25(OH)D, CRP and albumin concentrations in two patient cohorts.<p></p> <b>Methods</b><p></p> 5327 patients referred for nutritional assessment and 117 patients with critical illness were examined. Plasma 25 (OH) D concentrations were measured using standard methods. Intra and between assay imprecision was <10%.<p></p> <b>Result</b><p></p> In the large cohort, plasma 25 (OH) D was significantly associated with CRP (rs = −0.113, p<0.001) and albumin (rs = 0.192, p<0.001). 3711 patients had CRP concentrations ≤10 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were significantly lower from 35 to 28 to 14 nmol/l (p<0.001). This decrease was significant when albumin concentrations were reduced between 25–34 g/L (p<0.001) and when albumin <25 g/L (p<0.001). 1271 patients had CRP concentrations between 11–80 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were significantly lower from 31 to 24 to 19 nmol/l (p<0.001). This decrease was significant when albumin concentration were 25–34 g/L (p<0.001) and when albumin <25 g/L (p<0.001). 345 patients had CRP concentrations >80 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were not significantly altered varying from 19 to 23 to 23 nmol/l. Similar relationships were also obtained in the cohort of patients with critical illness.<p></p> <b>Conclusion</b><p></p> Plasma concentrations of 25(OH) D were independently associated with both CRP and albumin and consistent with the systemic inflammatory response as a major confounding factor in determining vitamin D status.<p></p&gt