Modeling, Analysis, and Optimization Issues for Large Space Structures

Topics concerning the modeling, analysis, and optimization of large space structures are discussed including structure-control interaction, structural and structural dynamics modeling, thermal analysis, testing, and design

Comparison of optical model results from a microscopic Schr\"odinger approach to nucleon-nucleus elastic scattering with those from a global Dirac phenomenology

Comparisons are made between results of calculations for intermediate energy nucleon-nucleus scattering for 12C, 16O, 40Ca, 90Zr, and 208Pb, using optical potentials obtained from global Dirac phenomenology and from a microscopic Schr\"odinger model. Differential cross sections and spin observables for scattering from the set of five nuclei at 65 MeV and 200 MeV have been studied to assess the relative merits of each approach. Total reaction cross sections from proton-nucleus and total cross sections from neutron-nucleus scattering have been evaluated and compared with data for those five targets in the energy range 20 MeV to 800 MeV. The methods of analyses give results that compare well with experimental data in those energy regimes for which the procedures are suited.Comment: 22 pages, 12 figure

Tin Concentrations and Human Health Risk Assessment for Children and Adults in Seafood and Canned Fish commonly consumed in Bayelsa State, Nigeria

Tin is a naturally occurring element in the environment, and the most important dietary intake is from tin-plates steel cans used for food packaging. The objective of this paper is to evaluate the tin concentrations and human health risk assessment of children and adults in seafood and canned fish (Sardine and Mackerel) obtained from Bayelsa State, Nigeria using the Thermo-Elemental Atomic Absorption Spectrometer (S4-71096 model) after mixed-acid digestion. Data obtained reveal tin concentrations (mean ± SD, mg/kg) in seafood in the order of fresh water fish (0.99 ± 0.07)  salt water fish (0.98 ± 0.16)  salt water–Blood Clam (0.75  0.022)  fresh water- Clam (0.17 ± 0.12)  fresh water-Prawn (0.06 ± 0.01)  salt water shrimp (0.02 ± 0.01) respectively, tin concentrations in the brands of canned fish were significantly higher than the concentration in seafood (p < 0.05). However, the mean concentrations of tin in the seafood and brands of canned fish were lower than the standard guideline limits set by regulatory bodies (200 mg/kg - 250 mg/kg). The health risk exposure assessment revealed that the values of all the samples were lower than the provisional maximum tolerable daily intake (PMTDI) of tin. The target hazard quotient (THQ) values of tin for both children and adults in all the samples were also lower than the reference dose (RfD). The health risk index (HRI) values of the seafood and the brands of canned fish for both children and adults were less than 1.0, which indicates that there are no adverse effects at the moment. However, the HRI values of the brands of canned fish were higher than the seafood for children and adults. Hence, assessment of tin in seafood and canned food could be periodically assessed by Nigerian food and drug regulatory organizations for efficient policy regulations

Reconfigurable and non-volatile vertical magnetic logic gates

In this paper, we discuss the concept and prototype fabrication of reconfigurable and non-volatile vertical magnetic logic gates. These gates consist of two input layers and a RESET layer. The RESET layer allows the structure to be used as either an and or an or gate, depending on its magnetization state. To prove this concept, the gates were fabricated using a multi-layered patterned magnetic media, in which three magnetic layers are stacked and exchange-decoupled via non-magnetic interlayers. We demonstrate the functionality of these logic gates by conducting atomic force microscopy and magnetic force microscopy (MFM) analysis of the multi-layered patterned magnetic media. The logic gates operation mechanism and fabrication feasibility are both validated by the MFM imaging results

A z=5.34 Galaxy Pair in the Hubble Deep Field

We present spectrograms of the faint V-drop (V(606) = 28.1, I(814) = 25.6) galaxy pair HDF3-951.1 and HDF3-951.2 obtained at the Keck II Telescope. Fernandez-Soto, Lanzetta, & Yahil (1998) derive a photometric redshift of z(ph) = 5.28 (+0.34,-0.41; 2 sigma) for these galaxies; our integrated spectrograms show a large and abrupt discontinuity near 7710 (+- 5) Angstroms. This break is almost certainly due to the Lyman alpha forest as its amplitude (1 - fnu(short) / fnu(long) > 0.87; 95% confidence limit) exceeds any discontinuities observed in stellar or galaxian rest-frame optical spectra. The resulting absorption-break redshift is z=5.34 (+- 0.01). Optical/near-IR photometry from the HDF yields an exceptionally red (V(606)-I(814)) color, consistent with this large break. A more accurate measure of the continuum depression blueward of Lyman alpha utilizing the imaging photometry yields D(A) = 0.88. The system as a whole is slightly brighter than L*(1500) relative to the z~3 Lyman break population and the total star formation rate inferred from the UV continuum is ~22 h(50)^-2 M(sun) yr^-1 (q(0) = 0.5) assuming the absence of dust extinction. The two individual galaxies are quite small (size scales < 1 h(50)^-1 kpc). Thus these galaxies superficially resemble the Pascarelle etal (1996) ``building blocks''; if they comprise a gravitationally bound system, the pair will likely merge in a time scale ~100 Myr.Comment: 18 pages, 4 figures; accepted to A