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At least 163 records · Page 9

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NASA NTRS2002

Ozone Correction for AM0 Calibrated Solar Cells for the Aircraft Method

The aircraft solar cell calibration method has provided cells calibrated to space conditions for 37 years. However, it is susceptible to systematic errors due to ozone concentration in the stratosphere. The present correction procedure applies a 1% increase to the measured Isc values. High band-gap cells are more sensitive to ozone adsorbed wavelengths so it has become important to reassess the correction technique. This paper evaluates the ozone correction to be 1+{O3}sup Fo, where Fo is 29.5x10(exp-6)/d.u. for a Silicon solar cell and 42.2xl0(exp -6)/d.u. for a GaAs cell. Results will be presented for high band-gap cells. A comparison with flight data indicates that this method of correcting for the ozone density improves the uncertainty of AM0 Isc to 0.5%.

Snyder, David B.↗

NASA NTRS1972

Biological effects of radiation, metabolic and replication kinetics alterations

The biological effects of radiation upon normal and cancerous tissues were studied. A macromolecular precursor of DNA, 3ETdR, was incorporated into the cell nucleus during synthesis and provided intranuclear beta radiation. Tritium labeled cells were studied with autoradiographic methods; cell cycle kinetics were determined and cell functions modified by radiation dosage or by drugs were also evaluated. The long term program has included; (1) effects of radiation on cell replication and the correlation with incorporated dose levels, (2) radiation induced changes in cell function, viz., the response of beta irradiated spleen lymphocytes to antigenic stimulation by sheep red blood cells (SRBC), (3) kinetics of tumor and normal cell replication; and (4) megakaryocyte formation and modification by radiomimetic drugs.

Post, J.↗

NASA NTRS2002

Ozone Correction for AM0 Calibrated Solar Cells for the Aircraft Method

The aircraft solar cell calibration method has provided cells calibrated to space conditions for 37 years. However, it is susceptible to systematic errors due to ozone concentrations in the stratosphere. The present correction procedure applies a 1 percent increase to the measured I(sub SC) values. High band-gap cells are more sensitive to ozone absorbed wavelengths (0.4 to 0.8 microns) so it becomes important to reassess the correction technique. This paper evaluates the ozone correction to be 1+O3xFo, where O3 is the total ozone along the optical path, and Fo is 29.8 x 10(exp -6)/du for a Silicon solar cell, 42.6 x 10(exp -6)/du for a GaAs cell and 57.2 x 10(exp -6)/du for an InGaP cell. These correction factors work best to correct data points obtained during the flight rather than as a correction to the final result.

Snyder, David B.↗

NASA NTRS2017

Comparison of Multiscale Method of Cells-Based Models for Predicting Elastic Properties of Filament Wound C/C-SiC

Three different multiscale models, based on the method of cells (generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the following multiscale modeling strategies were employed: Concurrent multiscale modeling of all phases using the generalized method of cells, synergistic (two-way coupling in space) multiscale modeling with the generalized method of cells, and hierarchical (one-way coupling in space) multiscale modeling with the high fidelity generalized method of cells. The three models are validated against data from a hierarchical multiscale finite element model in the literature for a repeating unit cell of C/C-SiC. Furthermore, the multiscale models are used in conjunction with classical lamination theory to predict the stiffness of C/C-SiC plates manufactured via a wet filament winding and liquid silicon infiltration process recently developed by the German Aerospace Institute.

multiscale modeling↗

DOE OSTI2024

Hybrid particle-spectral method for kinetic plasma simulations

A hybrid model for numerical solutions of the Vlasov–Poisson equations is presented, which blends spectral and particle approaches. The model splits the distribution function for plasma species into both spectral and particle representations in the velocity space to combine the advantages of each approach. The spectral representation leverages asymmetrically weighted Hermite basis, whereas the particle representation leverages the particle-in-cell method. Configuration phase space is decomposed with the Fourier method, which is well suited for periodic problems. We derive conservation equations for mass, momentum, and energy for the proposed combined method. It is shown that the coupling error between the two methods is absent in the semi-discrete setting (not taking into account time discretization). Finally, numerical test cases are presented simulating a weak electron beam interaction with plasma, leading to beam–plasma instability. The initially localized electron beam evolved into a highly non-equilibrium distribution function in the velocity space. A small growth rate and the resonance nature of instability make it difficult to obtain accurate solutions for purely particle methods due to noise, which falls as ∼1/Np with a number of particles. At the same time, purely spectral methods may require a large number of modes to capture the highly non-equilibrium state of the evolved beam. We show that the hybrid method is well suited for such problems: it reproduces the linear stage as well as nonlinear dynamics with sufficient accuracy using a highly non-equilibrium distribution function.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2021

Devices for cell culture and methods of making and using the same

Devices and systems for cell culture that include one or more hollow fibers or channels integrated into a chamber are provided. The hollow fibers or channels and/or the chamber are seeded with one or more cell types. Methods of co-culturing two or more cell types in the devices are also provided.

Nath, Pulak↗

NASA NTRS1986

Electrophoretic separation and analysis of living cells from solid tissues by several methods - Human embryonic kidney cell cultures as a model

The use of free-fluid electrophoresis methods to separate tissue cells having a specific function is discussed. It is shown that cells suspended by trypsinization from cultures of human embryonic kidney are electrophoretically heterogeneous and tolerate a wide range of electrophoresis buffers and conditions without significant attenuation of function. Moreover, these cells do not separate electrophoretically on the basis of size or cell position alone and can be separated according to their ability to give rise to progeny that produce specific plasminogen activators.

Todd, Paul↗

DOE OSTI2025

Particle Acceleration in Collisionless Magnetically Arrested Disks

We present the first collisionless realization of two-dimensional axisymmetric black hole accretion consistent with a persistent magnetically arrested disk state. The accretion flow, consisting of an ion-electron disk plasma combined with magnetospheric pair creation effects, is simulated using first-principles general-relativistic particle-in-cell methods. The simulation is evolved over significant dynamical timescales during which a quasisteady accretion state is reached with several magnetic flux eruption cycles. We include a realistic treatment of inverse Compton scattering and pair production, which allows for studying the interaction between the collisionless accretion flow and pair-loaded jet. Our findings indicate that magnetic flux eruptions associated with equatorial magnetic reconnection within the black hole magnetosphere and the formation of spark gaps are locations of maximal particle acceleration. Flux eruptions, starting near the central black hole, can trigger Kelvin-Helmholtz-like vortices at the jet-disk interface that facilitate efficient mixing between disk and jet plasma in this region. Transient periods of increased pair production following magnetic flux eruptions and reconnection events are responsible for most of the highly accelerated particles.

Accretion disk & black-hole plasma↗

NASA NTRS2001

Routine detection of Epstein-Barr virus specific T-cells in the peripheral blood by flow cytometry

The ability to detect cytomegalovirus-specific T-cells (CD4(+)) in the peripheral blood by flow cytometry has been recently described by Picker et al. In this method, cells are incubated with viral antigen and responding (cytokine producing) T-cells are then identified by flow cytometry. To date, this technique has not been reliably used to detect Epstein-Barr virus (EBV)-specific T-cells primarily due to the superantigen/mitogenic properties of the virus which non-specifically activate T-cells. By modifying culture conditions under which the antigens are presented, we have overcome this limitation and developed an assay to detect and quantitate EBV-specific T-cells. The detection of cytokine producing T-cells by flow cytometry requires an extremely strong signal (such as culture in the presence of PMA and ionomycin). Our data indicate that in modified culture conditions (early removal of viral antigen) the non-specific activation of T-cells by EBV is reduced, but antigen presentation will continue uninhibited. Using this method, EBV-specific T-cells may be legitimately detected using flow cytometry. No reduction in the numbers of antigen-specific T-cells was observed by the early removal of target antigen when verified using cytomegalovirus antigen (a virus with no non-specific T-cell activation properties). In EBV-seropositive individuals, the phenotype of the EBV-specific cytokine producing T-cells was evaluated using four-color flow cytometry and found to be CD45(+), CD3(+), CD4(+), CD45RA(-), CD69(+), CD25(-). This phenotype indicates the stimulation of circulating previously unactivated memory T-cells. No cytokine production was observed in CD4(+) T-cells from EBV-seronegative individuals, confirming the specificity of this assay. In addition, the use of four color cytometry (CD45, CD3, CD69, IFNgamma/IL-2) allows the total quantitative assessment of EBV-specific T-cells while monitoring the interference of EBV non-specific mitogenic activity. This method may have significant utility for the monitoring of the immune response to latent virus infection/reactivation.

Non-NASA Center↗

NASA NTRS1974

Methods for improved resolution of flow electrophoresis cells

First method involves remote adjusting of zeta potential. Second approach sandwiches two conducting metal plates between opposite cell walls and thin insulating layer. Third method forces buffer to flow in direction opposite particle streams.

Mccreight, L. R.↗

NASA NTRS1983

N-Butyl acrylate polymer composition for solar cell encapsulation and method

A polymer syrup for encapsulating solar cell assemblies. The syrup includes uncrosslinked poly(n-butyl)acrylate dissolved in n-butyl acrylate monomer. Preparation of the poly(n-butyl)acrylate and preparation of the polymer syrup is disclosed. Methods for applying the polymer syrup to solar cell assemblies as an encapsulating pottant are described. Also included is a method for solar cell construction utilizing the polymer syrup as a dual purpose adhesive and encapsulating material.

Gupta, Amitava↗

DOE OSTI2019

Battery cell and n situ battery electrode analysis method

Battery cells are provided that can include: a housing defining a chamber having a fluid inlet and outlet; an anode at one side of the housing; a cathode at another side of the housing opposing and spaced apart from the anode a sufficient amount to allow for electrolyte between the anode and cathode; and the other side of the chamber defined by an ion permeable member. Methods for in situ battery electrode analysis are provided and these methods can include: providing a battery cell having an anode and a cathode; exposing the battery cell to an ion beam while the battery cell is operational to form secondary ions; and detecting the secondary ions to analyze the battery.

25 ENERGY STORAGE↗

NASA NTRS2005

Bioreactor and methods for producing synchronous cells

Apparatus and methods are directed to a perfusion culture system in which a rotating bioreactor is used to grow cells in a liquid culture medium, while these cells are attached to an adhesive-treated porous surface. As a result of this arrangement and its rotation, the attached cells divide, with one cell remaining attached to the substrate, while the other cell, a newborn cell is released. These newborn cells are of approximately the same age, that are collected upon leaving the bioreactor. The populations of newborn cells collected are of synchronous and are minimally, if at all, disturbed metabolically.

Helmstetter, Charles E.↗

NASA NTRS2015

Methods for Stem Cell Production and Therapy

The present invention relates to methods for rapidly expanding a stem cell population with or without culture supplements in simulated microgravity conditions. The present invention relates to methods for rapidly increasing the life span of stem cell populations without culture supplements in simulated microgravity conditions. The present invention also relates to methods for increasing the sensitivity of cancer stem cells to chemotherapeutic agents by culturing the cancer stem cells under microgravity conditions and in the presence of omega-3 fatty acids. The methods of the present invention can also be used to proliferate cancer cells by culturing them in the presence of omega-3 fatty acids. The present invention also relates to methods for testing the sensitivity of cancer cells and cancer stem cells to chemotherapeutic agents by culturing the cancer cells and cancer stem cells under microgravity conditions. The methods of the present invention can also be used to produce tissue for use in transplantation by culturing stem cells or cancer stem cells under microgravity conditions. The methods of the present invention can also be used to produce cellular factors and growth factors by culturing stem cells or cancer stem cells under microgravity conditions. The methods of the present invention can also be used to produce cellular factors and growth factors to promote differentiation of cancer stem cells under microgravity conditions.

Claudio, Pier Paolo↗

NASA NTRS2014

Battery Cell Balancing System and Method

A battery cell balancing system is operable to utilize a relatively small number of transformers interconnected with a battery having a plurality of battery cells to selectively charge the battery cells. Windings of the transformers are simultaneously driven with a plurality of waveforms whereupon selected battery cells or groups of cells are selected and charged. A transformer drive circuit is operable to selectively vary the waveforms to thereby vary a weighted voltage associated with each of the battery cells.

Davies, Francis J.↗

NASA NTRS1985

Measuring The Contact Resistances Of Photovoltaic Cells

Simple method devised to measure contact resistances of photovoltaic solar cells. Method uses readily available equipment and applicable at any time during life of cell. Enables evaluation of cell contact resistance, contact-end resistance, contact resistivity, sheet resistivity, and sheet resistivity under contact.

Burger, D. R.↗

NASA NTRS1991

Cloned Hemoglobin Genes Enhance Growth Of Cells

Experiments show that portable deoxyribonucleic acid (DNA) sequences incorporated into host cells make them produce hemoglobins - oxygen-binding proteins essential to function of red blood cells. Method useful in several biotechnological applications. One, enhancement of growth of cells at higher densities. Another, production of hemoglobin to enhance supplies of oxygen in cells, for use in chemical reactions requiring oxygen, as additive to serum to increase transport of oxygen, and for binding and separating oxygen from mixtures of gases.

Khosla, Chaitan↗

NASA NTRS2000

Ball tonometry: a rapid, nondestructive method for measuring cell turgor pressure in thin-walled plant cells

In this article we describe a new method for the determination of turgor pressures in living plant cells. Based on the treatment of growing plant cells as thin-walled pressure vessels, we find that pressures can be accurately determined by observing and measuring the area of the contact patch formed when a spherical glass probe is lowered onto the cell surface with a known force. Within the limits we have described, we can show that the load (determined by precalibration of the device) divided by the projected area of the contact patch (determined by video microscopy) provides a direct, rapid, and accurate measure of the internal turgor pressure of the cell. We demonstrate, by parallel measurements with the pressure probe, that our method yields pressure data that are consistent with those from the pressure probe. Also, by incubating target tissues in stepped concentrations of mannitol to incrementally reduce the turgor pressure, we show that the pressures measured by tonometry accurately reflect the predicted changes from the osmotic potential of the bathing medium. The advantages of this new method over the pressure probe are considerable, however, in that we can move rapidly from cell to cell, taking measurements every 20 s. In addition, the nondestructive nature of the method means that we can return to the same cell repeatedly for periodic pressure measurements. The limitations of the method lie in the fact that it is suitable only for superficial cells that are directly accessible to the probe and to cells that are relatively thin walled and not heavily decorated with surface features. It is also not suitable for measuring pressures in flaccid cells.

NASA Discipline Plant Biology↗