Advanced heat receiver conceptual design study

Solar Dynamic space power systems are candidate electrical power generating systems for future NASA missions. One of the key components of the solar dynamic power system is the solar receiver/thermal energy storage (TES) subsystem. Receiver development was conducted by NASA in the late 1960's and since then a very limited amount of work has been done in this area. Consequently the state of the art (SOA) receivers designed for the IOC space station are large and massive. The objective of the Advanced Heat Receiver Conceptual Design Study is to conceive and analyze advanced high temperature solar dynamic Brayton and Stirling receivers. The goal is to generate innovative receiver concepts that are half of the mass, smaller, and more efficient than the SOA. It is also necessary that these innovative receivers offer ease of manufacturing, less structural complexity and fewer thermal stress problems. Advanced Brayton and Stirling receiver storage units are proposed and analyzed in this study which can potentially meet these goals

In-Line Photoresist Thickness Monitor

An in-line photoresist thickness measuring device wherein a plurality of projection optical fibers are disposed over a wafer processing track for illuminating portions of a wafer as the wafer proceeds along the track. The light scattered back from each illuminated portion is detected by a corresponding plurality of pickup optical fibers and communicated to an optical fiber multiplexer. The multiplexer sequentially selects the optical signal from each pickup optical fiber and communicates the light from the selected pickup optical fiber to a spectrometer. The spectrometer simultaneously diffuses the scattered light into a plurality of light bands, each light band having a different wavelength. The plurality of light bands are projected in parallel onto a pin diode array which acts as a photodeteeter. The electrical signals generated by each pin diode in response to the incident light bands are communicated to a processor which calculates resist thickness for each illuminated portion of the wafer. The average and standard deviation values for the thickness data may be calculated as well

Transplacental xylose transfer in bovine pregnancy

A substantial portion of placental function is committed to the regulation of nutrient transfer from the dam to the fetus, with glucose being the major substrate for conceptus metabolism. Due to its homomorphism with glucose, xylose can be used as tracer for the assessment of placental nutrient transfer capacity. This study was designed to evaluate transplacental permeability to xylose in bovine pregnancies on Days 90 and 180 of gestation. In Experiment 1, pregnant and nonpregnant females were infused into the jugular vein or into the allantoic sac with a 10% xylose solution to evaluate the maternal plasma xylose disappearance and the existence of feto-maternal xylose transfer, respectively. Glucose and xylose concentrations were determined in venous blood samples collected at 0, 15, 30, 60, 90, 120, 150, and 180 min. A materno-fetal but not a feto-maternal xylose transport was observed in both gestational periods. In Experiment 2, pregnant animals were slaughtered on Days 90 or 180 of gestation. A 10% xylose solution was infused intravenously into each female 60 min before slaughter to measure the materno-fetal transfer of xylose. Fetal and maternal blood samples and amniotic and allantoic fluids were collected for the determination of glucose and xylose concentrations. An increase in xylose accumulation in the uterine subcompartments was observed toward the end of the second trimester of pregnancy, demonstrating an increase in materno-fetal placental sugar transport as pregnancy advances. In conclusion, xylose can be a valid tracer for studies on transplacental transport with potential implications to conceptus growth in cattle

Solid-State NMR Studies of a Diverged Microsomal Amino-Proximate Δ12 Desaturase Peptide Reveal Causes of Stability in Bilayer: Tyrosine Anchoring and Arginine Snorkeling

This study reports the solid-state NMR spectroscopic characterization of the amino-proximate transmembrane domain (TM-A) of a diverged microsomal Δ12-desaturase (CREP-1) in a phospholipid bilayer. A series of TM-A peptides were synthesized with (2)H-labeled side chains (Ala-53, -56, and -63, Leu-62, Val-50), and their dynamic properties were studied in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) bilayers at various temperatures. At 6 mol % peptide to lipid, (31)P NMR spectra indicated that the peptides did not significantly disrupt the phospholipid bilayer in the L(α) phase. The (2)H NMR spectra from Ala-53 and Ala-56 samples revealed broad Pake patterns with quadrupolar splittings of 16.9 kHz and 13.3 kHz, respectively, indicating restricted motion confined within the hydrocarbon core of the phospholipid bilayer. Conversely, the deuterated Ala-63 sample revealed a peak centered at 0 kHz with a linewidth of 1.9 kHz, indicating increased side-chain motion and solvent exposure relative to the spectra of the other Ala residues. Val-50 and Leu-62 showed Pake patterns, with quadrupolar splittings of 3.5 kHz and 3.7 kHz, respectively, intermediate to Ala-53/Ala-56 and Ala-63. This indicates partial motional averaging and supports a model with the Val and Leu residues embedded inside the lipid bilayer. Solid-state NMR spectroscopy performed on the (2)H-labeled Ala-56 TM-A peptide incorporated into magnetically aligned phospholipid bilayers indicated that the peptide is tilted 8° with respect to the membrane normal of the lipid bilayer. Snorkeling and anchoring interactions of Arg-44 and Tyr-60, respectively, with the polar region or polar hydrophobic interface of the lipid bilayer are suggested as control elements for insertional depth and orientation of the helix in the lipid matrix. Thus, this study defines the location of key residues in TM-A with respect to the lipid bilayer, describes the conformation of TM-A in a biomembrane mimic, presents a peptide-bilayer model useful in the consideration of local protein folding in the microsomal desaturases, and presents a model of arginine and tyrosine control of transmembrane protein stability and insertion