Aerospace applications of SINDA/FLUINT at the Johnson Space Center

SINDA/FLUINT has been found to be a versatile code for modeling aerospace systems involving single or two-phase fluid flow and all modes of heat transfer. Several applications of SINDA/FLUINT are described in this paper. SINDA/FLUINT is being used extensively to model the single phase water loops and the two-phase ammonia loops of the Space Station Freedom active thermal control system (ATCS). These models range from large integrated system models with multiple submodels to very detailed subsystem models. An integrated Space Station ATCS model has been created with ten submodels representing five water loops, three ammonia loops, a Freon loop and a thermal submodel representing the air loop. The model, which has approximately 800 FLUINT lumps and 300 thermal nodes, is used to determine the interaction between the multiple fluid loops which comprise the Space Station ATCS. Several detailed models of the flow-through radiator subsystem of the Space Station ATCS have been developed. One model, which has approximately 70 FLUINT lumps and 340 thermal nodes, provides a representation of the ATCS low temperature radiator array with two fluid loops connected only by conduction through the radiator face sheet. The detailed models are used to determine parameters such as radiator fluid return temperature, fin efficiency, flow distribution and total heat rejection for the baseline design as well as proposed alternate designs. SINDA/FLUINT has also been used as a design tool for several systems using pressurized gasses. One model examined the pressurization and depressurization of the Space Station airlock under a variety of operating conditions including convection with the side walls and internal cooling. Another model predicted the performance of a new generation of manned maneuvering units. This model included high pressure gas depressurization, internal heat transfer and supersonic thruster equations. The results of both models were used to size components, such as the heaters and gas bottles and also to point to areas where hardware testing was needed

Career Choice With the Serious Game Like2be

Choosing a career is an important biographical event for adolescents. Toward the end of compulsory education, they must decide which career path they want to pursue. The serious game like2be was developed to support adolescents in this individual career choice process. In a quasi-experimental intervention study with 809 adolescents, like2be was evaluated for its effectiveness in career choice classes at the lower secondary level. In addition, a teaching concept for the application of the serious game which included additional teaching materials was analyzed. The data show that like2be is an effective medium for broadening personal career choice horizons, especially when it is pedagogically well-founded and integrated into career choice classes. Although the effectiveness of like2be in stimulating intensive reflection on one's own vocational aptitude or a gender-sensitive attitude towards occupations is limited, the present study shows that like2be has major potential for supporting the process of career choice among adolescents

Stellar Associations and their Field East of LMC 4 in the Large Magellanic Cloud

We report about the stellar content and the luminosity and mass functions of three stellar associations and their field located on the north-east edge of the super-bubble LMC 4 in the Large Magellanic Cloud.Comment: To be appeared in the meeting Proceedings of ``Modes of Star Formation and the Origin of Field Populations'', Heidelberg, Germany, October 2000; to be published in the ASP Conference Series, edited by E. K. Grebel and W. Brandne

Polymorphism of the tumor necrosis factor beta gene in systemic lupus erythematosus

We investigated the Nco I restriction fragment length polymorphism (RFLP) of the tumor necrosis factor beta (TNFB) gene in 173 patients with systemic lupus erythematosus (SLE), 192 unrelated healthy controls, and eleven panel families, all of German origin. The phenotype frequency of the TNFB*I allele was significantly increased in patients compared to controls (63.6% vs 47.1%, RR = 1.96, p <0.002). The results of a two-point haplotype statistical analysis between TNFB and HLA alleles show that there is linkage disequilibrium between TNFB*I and HLA-A1, Cw7, B8, DR3, DQ2, and C4A DE. The frequency of TNFB*I was compared in SLE patients and controls in the presence or absence of each of these alleles. TNFB*I is increased in patients over controls only in the presence of the mentioned alleles. Therefore, the whole haplotypeA1, Cw7, B8, TNFB* I, C4A DE, DR3, DQ2 is increased in patients and it cannot be determined which of the genes carried by this haplotype is responsible for the susceptibility to SLE. In addition, two-locus associations were analyzed in 192 unrelated healthy controls for TNFB and class I alleles typed by serology, and for TNFB and class II alleles typed by polymerase chain reaction/oligonucleotide probes. We found positive linkage disequilibrium between TNFB*I and the following alleles: HLA-A24, HLA-B8, DRBI*0301, DRBI*ll04, DRBI*1302, DQAI*0501, DQBI*0201, DQBI*0604, and DPBI*OIO1. TNFB*2 is associated with HLA-B7, DRBI*1501, and DQB I *0602

Negative Oxygen Isotope Effect on the Static Spin Stripe Order in La_(2-x)Ba_xCuO_4 (x = 1/8)

Large negative oxygen-isotope (16O/18O) effects (OIE's) on the static spin-stripe ordering temperature T_so and the magnetic volume fraction V_m were observed in La_(2-x)Ba_xCuO_4 (x = 1/8) by means of muon spin rotation experiments. The corresponding OIE exponents were found to be alpha_(T_so) = -0.57(6) and alpha_(V_m) = -0.71(9), which are sign reversed to alpha_(T_c) = 0.46(6) measured for the superconducting transition temperature T_c. This indicates that the electron-lattice interaction is involved in the stripe formation and plays an important role in the competition between bulk superconductivity and static stripe order in the cuprates.Comment: 5 pages, 4 figure

Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}

The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature superconducting energy gap \Delta_0 was studied for a series of Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on \Delta_0 was found to scale with the one on the superconducting transition temperature. These experimental results are in quantitative agreement with predictions from a polaronic model for cuprate high-temperature superconductors and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure

A cluster mode-coupling approach to weak gelation in attractive colloids

Mode-coupling theory (MCT) predicts arrest of colloids in terms of their volume fraction, and the range and depth of the interparticle attraction. We discuss how effective values of these parameters evolve under cluster aggregation. We argue that weak gelation in colloids can be idealized as a two-stage ergodicity breaking: first at short scales (approximated by the bare MCT) and then at larger scales (governed by MCT applied to clusters). The competition between arrest and phase separation is considered in relation to recent experiments. We predict a long-lived `semi-ergodic' phase of mobile clusters, showing logarithmic relaxation close to the gel line.Comment: 4 pages, 3 figure

Correlation between oxygen isotope effects on the transition temperature and the magnetic penetration depth in high-temperature superconductors close to optimal doping

The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the in-plane magnetic penetration depth \lambda_{ab}(0) in optimally-doped YBa_2Cu_3O_{7-\delta} and La_{1.85}Sr_{0.15}CuO_4, and in slightly underdoped YBa_2Cu_4O_8 and Y_{0.8}Pr_{0.2}Ba_2Cu_3O_{7-\delta} was studied by means of muon-spin rotation. A substantial OIE on \lambda_{ab}(0) with an OIE exponent \beta_O=-d\ln\lambda_{ab}(0)/d\ln M_O\approx - 0.2 (M_O is the mass of the oxygen isotope), and a small OIE on the transition temperature T_c with an OIE exponent \alpha_O=-d\ln T_{c}/d \ln M_O\simeq0.02 to 0.1 were observed. The observation of a substantial isotope effect on \lambda_{ab}(0), even in cuprates where the OIE on T_c is small, indicates that lattice effects play an important role in cuprate HTS.Comment: 6 pages, 4 figure