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At least 325 records · Page 18

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DOE OSTI2023

Kullback–Leibler Divergence of an Open-Queuing Network of a Cell-Signal-Transduction Cascade

Queuing networks (QNs) are essential models in operations research, with applications in cloud computing and healthcare systems. However, few studies have analyzed the cell’s biological signal transduction using QN theory. This study entailed the modeling of signal transduction as an open Jackson’s QN (JQN) to theoretically determine cell signal transduction, under the assumption that the signal mediator queues in the cytoplasm, and the mediator is exchanged from one signaling molecule to another through interactions between the signaling molecules. Each signaling molecule was regarded as a network node in the JQN. The JQN Kullback–Leibler divergence (KLD) was defined using the ratio of the queuing time (λ) to the exchange time (μ), λ/μ. The mitogen-activated protein kinase (MAPK) signal-cascade model was applied, and the KLD rate per signal-transduction-period was shown to be conserved when the KLD was maximized. Our experimental study on MAPK cascade supported this conclusion. This result is similar to the entropy-rate conservation of chemical kinetics and entropy coding reported in our previous studies. Thus, JQN can be used as a novel framework to analyze signal transduction.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2024

All-sky Search for Transient Astrophysical Neutrino Emission with 10 Years of IceCube Cascade Events

Abstract Neutrino flares in the sky are searched for in data collected by IceCube between 2011 and 2021 May. This data set contains cascade-like events originating from charged-current electron neutrino and tau neutrino interactions and all-flavor neutral-current interactions. IceCube’s previous all-sky searches for neutrino flares used data sets consisting of track-like events originating from charged-current muon neutrino interactions. The cascade data set is statistically independent of the track data sets, and while inferior in angular resolution, the low-background nature makes it competitive and complementary to previous searches. No statistically significant flare of neutrino emission was observed in an all-sky scan. Upper limits are calculated on neutrino flares of varying duration from 1 hr to 100 days. Furthermore, constraints on the contribution of these flares to the diffuse astrophysical neutrino flux are presented, showing that multiple unresolved transient sources may contribute to the diffuse astrophysical neutrino flux.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Pair Cascades in Magnetar Magnetospheres

Resonant inverse Compton scattering (RICS) of soft thermal photons by relativistic particles on closed magnetic field loops has been proposed to explain the hard emission observed up to and beyond 200 keV from magnetars. If particles injected at the base of the loops have Lorentz factors ≳10 2 , the RICS spectra will be attenuated by both one-photon pair production and photon splitting in the ultrastrong magnetar fields, producing additional spectral components from pair synchrotron radiation and split photons that produce further generations of pairs and split photons. We investigate such cascades initiated by the primary injected electrons through a Monte Carlo simulation, and study the cascade spectra and pair distributions. For most observer angles, the pair synchrotron and split-photon spectra dominate the RICS primary spectra and produce complex polarization signals. In particular, the synchrotron spectra are highly polarized with degree 40%–80%, are softer than the RICS spectra, and may account for the high polarization of some magnetar spectra observed by the Imaging X-ray Polarimetry Explorer above 3 keV.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Optimal Membrane Cascade Design for Critical Mineral Recovery Through Logic-based Superstructure Optimization

Critical minerals and rare earth elements play an important role in our climate change initiatives, particularly in applications related with energy storage. Here, we use discrete optimization approaches to design a process for the recovery of Lithium and Cobalt from battery recycling, through membrane separation. Our contribution involves proposing a Generalized Disjunctive Programming (GDP) model for the optimal design of a multistage diafiltration cascade for Li-Co separation. By solving the resulting nonconvex mixed-integer nonlinear program model to global optimality, we investigated scalability and solution quality variations with changes in the number of stages and elements per stage. Results demonstrate the computational tractability of the nonlinear GDP formulation for design of membrane separation processes while opening the door for decom-position strategies for multicomponent separation cascades. Future work aims to extend the GDP formulation to account for stage installation and explore various decomposition techniques to enhance solution efficiency.

Ovalle, Daniel↗

NASA NTRS1969

A cascade theory of turbulence

Cascade theory of turbulence, applying cascade decomposition resulting from Navier-Stokes application to hydrodynamic turbulence to Riemann equation for atmospheric and plasma turbulence

Tchen, C. M.↗

NASA NTRS1971

Nuclear electromagnetic cascades from alpha particles incident on an iron absorber

Mean values and fluctuations of the nuclear-electromagnetic cascade development resulting from alpha particles incident on an iron absorber was determined for the primary energy range 10 to 300 GeV/nucleon. This has been accomplished by using a three-dimensional Monte Carlo simulation of the cascade process. The model used was first adjusted until it gave predictions for a small ionization spectrometer which agreed with measurements obtained by exposing the same spectrometer to 10, 20.5, and 28 GeV/c protons at an accelerator. The calcuations were then modified to apply to high energy alpha particles. The results show that measurements of the energies of alpha particles incident on an iron spectrometer with six interaction lengths total depth can be made with accuracies ranging from approximately 5% at 300 GeV/nucleon to approximately 16% at 10 GeV/nucleon.

Jones, W. V.↗

NASA NTRS1972

Monte Carlo calculations of high energy nucleon meson cascades and applications to galactic cosmic ray transport

Results obtained using a recently developed calculational method for determining the nucleon-meson cascade induced in thick materials by high-energy nucleons and charged pions are presented. The calculational method uses the intranuclear-cascade-evaporation model to treat nonelastic collisions by particles with energies approximately or smaller than GeV and an extrapolation model at higher energies. The following configurations are considered: (1) 19.2-GeV/c protons incident on iron; (2) 30.3-GeV/c protons incident on iron; (3) solar and galactic protons incident on the moon, and (4) galactic protons incident on tissue. For the first three configurations, experimental results are available and comparisons between the experimental and calculated results are given.

Armstrong, T. W.↗

NASA NTRS1972

Quantum beats in transitions from levels subject to optical cascades.

Discussion of the g values of weakly aligned O II and O III multiplet levels subject to strong optical cascades, obtained by means of a beam-foil quantum beat method. Within the measurement precision limits of nearly plus or minus 1%, the effects of the optical cascades on the measured g values are shown to be negligible.

Liu, C. J.↗

NASA NTRS1972

Laser-induced gas breakdown - Electron cascade.

Development of a theory of electron cascade which takes explicitly into account the electron energy distribution. For the particular case of a Boltzmann distribution, it is shown that the monoenergetic approximation is valid, except for low flux densities (less than 20 MW per sq cm) of the laser beam. It is emphasized that the equilibrium temperature can be calculated easily. When electron-ion inverse bremsstrahlung comes into play, this approximation becomes invalid; there is a pressure below which the cascade cannot develop. Numerical results are presented for model calculations of helium and argon.

De Montgolfier, P.↗

NASA NTRS1973

Highly loaded multi-stage fan drive turbine-cascade test program

Test results are presented for 19 cascades involving five plain and two tandem blade sections. High camber and/or negative reaction is associated with six of the sections. Exit Mach numbers range up to slightly above sonic. Cascade efficiency, exit flow angle and static pressure, and blade surface pressure data are reported with incidence angle, Mach number, solidity, and relative position of the tandem blades as independent variables.

Cherry, D. G.↗

NASA NTRS1973

Thermal surveillance of volcanoes of the Cascade Range and Iceland utilizing ERTS DCP systems and imagery

The author has identified the following significant results. Significant results of the thermal surveillance of volcanoes experiment during 1972 included the design, construction, emplacement, and successful operation at volcanic sites in the Cascade Range, North America and on Surtsey, Iceland, of automated thermistor arrays which transmit ground and fumarole temperatures via the ERTS-1 data communication system to Goddard Space Flight Center. Temperature, radiance, and anomalous heat flow variations are being plotted by a U.S. Geological Survey IBM 360/65 computer program to show daily fluctuations at each of the sites. Results are being compiled in conjunction with NASA and USGS aircraft infrared survey data to provide thermal energy yield estimates during the current repose period of several Cascade Range volcanic systems. ERTS-1 MSS images have provided new information on the extent of structural elements controlling thermal emission at Lassen Volcanic National Park.

Friedman, J. D.↗

NASA NTRS1973

Aerodynamic performance of a core-engine turbine stator vane tested in a two-dimensional cascade of 10 vanes and in a single vane tunnel

A turbine stator vane was tested in a two-dimensional cascade of 10 vanes and in a single-vane tunnel. The single-vane tunnel was a cold air version of a tunnel which will be used for high temperature heat transfer testing of cooled turbine vanes. The purpose of the investigation was to determine if the flow conditions in the single-vane tunnel were sufficiently similar to those of a 10-vane cascade to permit meaningful heat transfer testing. The vane was tested over a range of ideal exit critical velocity ratios. The principal measurements were vane surface static pressure and cross-channel surveys of exit static pressure, total pressure, and flow angle. A brief description of the test vane and tunnels is included. The results of the exit surveys, the vane surface pressure distributions, and overall performance in terms of flow and loss for the two test configurations are compared.

Stabe, R. G.↗

NASA NTRS1973

Thermal surveillance of volcanoes of the Cascade Range utilizing ERTS DCP systems and imagery

The author has identified the following significant results. Successful installation of DCP sets at Mt. Baker volcano and at Mt. St. Helens volcano, Washington, completed the installation phase of experiment SR 251. Aerial IR scanner missions over the Cascade volcanoes were completed with a mission April 29th which provided thermographic IR images of Glacier Peak, Mt. Baker, Mt. St. Helens, Mt. Rainier, and Mt. Adams. Earlier repetitive coverage had obtained IR images depicting thermal anomalies of Lassen Volcanic National Park, Shasta, Crater Lake, and the northern Cascades. The April 29th mission and subsequent ground reconnaissance yielded new information on 48 heretofore unreported pinpoint radiation anomalies, of possible fumarolic origin, on the flanks of Mt. Rainier and several new thermal points on Mt. Baker. Cartographic plots of these anomalies, in conjunction with surface temperature and other data obtained as a result of experiment SR 251 will permit estimation of radiation heat loss during the repose periods of the host volcanoes.

Friedman, J. D.↗

NASA NTRS1974

Incidence loss for a core turbine rotor blade in a two-dimensional cascade

The effect of incidence angle on the aerodynamic performance of an uncooled core turbine rotor blade was investigated experimentally in a two-dimensional cascade. The cascade test covered a range of incidence angles from minus 15 deg to 15 deg in 5-degree increments and a range of pressure ratios corresponding to ideal exit critical velocity ratios of 0.6 to 0.95. The principal measurements were blade-surface static pressures and cross-channel surveys of exit total pressure, static pressure, and flow angle. The results of the investigation include blade-surface velocity distribution and overall performance in terms of weight flow and loss for the range of incidence angles and exit velocity ratios investigated. The measured losses are also compared with two common methods of predicting incidence loss.

Stabe, R. G.↗

NASA NTRS1974

On first cycle slip time of phase-locked loops in cascade

Precise measurement and spacecraft tracking are obtained by using phase-locked loops in cascade in two-way communications links. Statistics on cycle slip time are of vital importance in system planning and design. This paper presents: (1) results of a computer simulation study of the mean time to first cycle slip of cascade phase-locked loops preceded by bandpass limiters, and (2) the determination of probability distributions of cycle slip. Numerical results are obtained for a typical coherent communication system.

Yuen, J. H.↗

NASA NTRS1974

Matrix methods for the design of cascades to prescribed surface velocity distributions and for fully compressible flow

This paper describes matrix methods that have been developed for calculating compressible flow on a blade-to-blade surface of revolution. The methods have been fully tested to date only for the design of plane cascades to prescribed blade surface distributions; the methods will be illustrated here for that problem only. Similar methods are presently being applied to both the direct and indirect problems and for flow on arbitrary surfaces of revolution in annular cascades with stream sheet thickness variations. It is believed that by such methods, both the direct and indirect calculations can be reduced to about 60 to 90 seconds of computing.

Silvester, M. E.↗

NASA NTRS1974

A note on the influence of axial velocity ratio on cascade performance

A thin airfoil quasi-two-dimensional potential flow theory has been used to analyze cascades with axial-flow contraction. Attention is centered on the flow turning of a lattice of foils as measured by the deviation angle. The influence of both axial-flow acceleration and foil thickness on the deviation angle is summarized in plots that should be useful for design purposes. It is shown that the effect of axial-flow contraction is larger when the foils are relatively far apart than when they are close together. The influence of axial velocity ratio across the cascade changes markedly with the stagger angle. These effects are essentially unaltered due to foil thickness.

Wilson, M. B.↗

NASA NTRS1975

Cold-air annular-cascade investigation of aerodynamic performance of cooled turbine vanes. 2: Trailing-edge ejection, film cooling, and transpiration cooling

The aerodynamic performance of four different cooled vane configurations was experimentally determined in a full-annular cascade at a primary- to coolant-total-temperature ratio of 1.0. The vanes were tested over a range of coolant flow rates and pressure ratios. Overall vane efficiencies were obtained and compared, where possible, with the results obtained in a four-vane, annular-sector cascade. The vane efficiency and exit flow conditions as functions of radial position were also determined and compared with solid (uncooled) vane results.

Goldman, L. J.↗