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  • 1
    Publication Date: 1993-11-05
    Description: B7 delivers a costimulatory signal through CD28, resulting in interleukin-2 secretion and T cell proliferation. Blockade of this pathway results in T cell anergy. The in vivo role of B7 was evaluated with B7-deficient mice. These mice had a 70 percent decrease in costimulation of the response to alloantigen. Despite lacking B7 expression, activated B cells from these mice bound CTLA-4 and GL1 monoclonal antibody, demonstrating that alternative CTLA-4 ligand or ligands exist. These receptors are functionally important because the residual allogenic mixed lymphocyte responses were blocked by CTLA4Ig. Characterization of these CTLA-4 ligands should lead to strategies for manipulating the immune response.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Freeman, G J -- Borriello, F -- Hodes, R J -- Reiser, H -- Hathcock, K S -- Laszlo, G -- McKnight, A J -- Kim, J -- Du, L -- Lombard, D B -- CA 40216/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1993 Nov 5;262(5135):907-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Hematologic Malignancies, Dana-Farber Cancer Institute, Boston, MA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7694362" target="_blank"〉PubMed〈/a〉
    Keywords: Abatacept ; Animals ; Antigens, CD ; Antigens, CD80/genetics/*immunology/metabolism ; Antigens, Differentiation/immunology/*metabolism ; B-Lymphocytes/*immunology ; Base Sequence ; CTLA-4 Antigen ; Cell Line ; *Immunoconjugates ; Interleukin-2/secretion ; Isoantigens/immunology ; Lymphocyte Activation ; Lymphocyte Culture Test, Mixed ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Mice, Knockout ; Molecular Sequence Data ; Mutation ; T-Lymphocytes/*immunology ; Transfection
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1993-11-05
    Description: A system for stable transformation of Toxoplasma gondii tachyzoites was developed that exploited the susceptibility of Toxoplasma to chloramphenicol. Introduction of the chloramphenicol acetyltransferase (CAT) gene fused to Toxoplasma flanking sequences followed by chloramphenicol selection resulted in parasites stably expressing CAT. A construct incorporating the tandemly repeated gene, B1, targeted efficiently to its homologous chromosomal locus. Knockout of the single-copy gene, ROP1, was also successful. Stable transformation should permit the identification and analysis of Toxoplasma genes important in the interaction of this opportunistic parasite with its host.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kim, K -- Soldati, D -- Boothroyd, J C -- New York, N.Y. -- Science. 1993 Nov 5;262(5135):911-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, Stanford University School of Medicine 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8235614" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chloramphenicol/pharmacology ; Chloramphenicol O-Acetyltransferase/*genetics ; Drug Resistance ; *Genes, Protozoan ; Genetic Markers ; Multigene Family ; Plasmids ; Recombination, Genetic ; Toxoplasma/drug effects/*genetics ; Transfection ; *Transformation, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1993-09-03
    Description: Cyclic adenosine diphosphoribose (cADPR), a recently discovered metabolite of nicotinamide adenine dinucleotide (NAD), is a potent calcium-releasing agent postulated to be a new second messenger. An enzyme that catalyzes the synthesis of cADPR from NAD and the hydrolysis of cADPR to ADP-ribose (ADPR) was purified to homogeneity from canine spleen microsomes. The net conversion of NAD to ADPR categorizes this enzyme as an NAD glycohydrolase. NAD glycohydrolases are ubiquitous membrane-bound enzymes that have been known for many years but whose function has not been identified. The results presented here suggest that these enzymes may function in the regulation of calcium homeostasis by the ability to synthesize and degrade cADPR.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kim, H -- Jacobson, E L -- Jacobson, M K -- CA43894/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1993 Sep 3;261(5126):1330-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biology, University of North Texas Health Science Center at Fort Worth 76107.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8395705" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Diphosphate Ribose/*analogs & derivatives/biosynthesis/metabolism ; Animals ; Calcium/metabolism ; Cyclic ADP-Ribose ; Dogs ; Hydrolysis ; Kinetics ; NAD/metabolism ; NAD+ Nucleosidase/isolation & purification/*metabolism ; Spleen/enzymology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2019-07-13
    Description: The flowfields and performance of nuclear thermal rockets, which utilize radiation and film-cooling to cool the nozzle extension, are studied by solving the Navier-Stokes equations and species equations. The thrust level of the rocket for the present study is about 75,000 lb(f) for a chamber pressure of 68 atm(l,000 psi) and a chamber temperature of 2700 K. The throat radius of the nozzle is 0.0936 m and the area ratios of the nozzles are 300 and 500. It is assumed that the flow is chemically frozen and the turbulence is simulated by the modified Baldwin-Lomax turbulence model. The calculated results for various area ratios and film mass-flow rates are presented as Mach number contours, variations of nozzle wall temperature, exit profiles, and vacuum specific impulses. The present study shows that by selecting the flow rate of the film-cooling hydrogen and area ratio of the nozzle correctly, high area ratio nozzle extensions can be cooled effectively with radiation and film-cooling without significant penalty in performance.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-2498 , ; 12 p.|AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
    Format: text
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  • 5
    Publication Date: 2019-07-13
    Description: The structure of the flow around a nuclear thermal rocket nozzle lip has been investigated using the direct simulation Monte Carlo method. Special attention has been paid to the behavior of a small amount of harmful particles that may be present in the rocket exhaust gas. The harmful fission product particles are modeled by four inert gases whose molecular weights are in a range of 4 131. Atomic hydrogen, which exists in the flow due to the extremely high nuclear fuel temperature in the reactor, is also included. It is shown that the plume backflow is primarily determined by the thin subsonic fluid layer adjacent to the surface of the nozzle lip, and that the inflow boundary in the plume region has negligible effect on the backflow. It is also shown that a relatively large amount of the lighter species is scattered into the backflow region while the amount of the heavier species becomes negligible in this region due to extreme separation between the species. Results indicate that the backscattered molecules are very energetic and are fast-moving along the surface in the backflow region near the nozzle lip.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-2497 , AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States|; 10 p.
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  • 6
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: A gas generator which can be ignited reliably during the initial start-up period and offers fairly uniform gas temperature at the exit was studied numerically. Various sizes and shapes of the mixing enhancement devices and their positions were examined to evaluate the uniformity of the exit gas temperature and the change of internal pressure drop incurred by introducing the mixing enhancement devices. By introducing a turbulence ring and a splash plate with an appropriate size and position, it was possible to obtain fairly uniform gas temperature distributions and a maximum gas temperature that is within the design limit temperature of 1600 R at the generator exit. However, with the geometry studied, the pressure drop across the generator was great, approximately 1150 psi, to satisfy the assigned design limit temperature. If the design limit temperature is increased to 1650 R, the pressure drop across the generator could be lowered by as much as 350 psi.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-2158 , ; 9 p.|AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
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  • 7
    Publication Date: 2019-07-13
    Description: Following the consensus of a workshop in Turbulence Modelling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows, and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data to account for the non-isotropic turbulence effects.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-192466 , NAS 1.26:192466 , UAH-5-32688
    Format: application/pdf
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  • 8
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: The performance of low-thrust rocket nozzles was studied with a full Navier-Stokes code. The effect of the reduction of the nozzle length on the viscous loss and on the two-dimensional loss due to the increase in the nozzle exit angle was examined by calculating the flowfield and performance values of hydrogen resistojet nozzle with various lengths and shapes (such as 20-deg or 30-deg conical nozzles and a nozzle whose wall contour is given by the Rao nozzle optimization code). It was found that the vacuum specific impulse value of the 30-deg conical nozzle was the highest and that of the contoured nozzle was the lowest among the three nozzles, whose throat Reynolds number and area ratio were 1150 and 82, respectively.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-0888 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 11 p.
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