Standard spacecraft economic analysis. Volume 1: Executive summary

A study of the comparative program costs associated with use of various standardized spacecraft for Air Force space test program missions to be flown on the space shuttle during the 1980-1990 time period is reviewed. The first phase of the study considered a variety of procurement mixes composed of existing or programmed NASA standard spacecraft designs and a Air Force standard spacecraft design. The results were briefed to a joint NASA/Air Force audience on July 11, 1976. The second phase considered additional procurement options using an upgraded version of an existing NASA design. The results of both phases are summarized

Perfect quantum state transfer of hard-core bosons on weighted path graphs

The ability to accurately transfer quantum information through networks is an important primitive in distributed quantum systems. While perfect quantum state transfer (PST) can be effected by a single particle undergoing continuous-time quantum walks on a variety of graphs, it is not known if PST persists for many particles in the presence of interactions. We show that if single-particle PST occurs on one-dimensional weighted path graphs, then systems of hard-core bosons undergoing quantum walks on these paths also undergo PST. The analysis extends the Tonks-Girardeau ansatz to weighted graphs using techniques in algebraic graph theory. The results suggest that hard-core bosons do not generically undergo PST, even on graphs which exhibit single-particle PST.Comment: 19 page

Insights into Activation Mechanisms of Store-Operated TRPC1 Channels in Vascular Smooth Muscle.

In vascular smooth muscle cells (VMSCs), the stimulation of store-operated channels (SOCs) mediate Ca2+ influx pathways which regulate important cellular functions including contraction, proliferation, migration, and growth that are associated with the development of vascular diseases. It is therefore important that we understand the biophysical, molecular composition, activation pathways, and physiological significance of SOCs in VSMCs as these maybe future therapeutic targets for conditions such as hypertension and atherosclerosis. Archetypal SOCs called calcium release-activated channels (CRACs) are composed of Orai1 proteins and are stimulated by the endo/sarcoplasmic reticulum Ca2+ sensor stromal interaction molecule 1 (STIM1) following store depletion. In contrast, this review focuses on proposals that canonical transient receptor potential (TRPC) channels composed of a heteromeric TRPC1/C5 molecular template, with TRPC1 conferring activation by store depletion, mediate SOCs in native contractile VSMCs. In particular, it summarizes our recent findings which describe a novel activation pathway of these TRPC1-based SOCs, in which protein kinase C (PKC)-dependent TRPC1 phosphorylation and phosphatidylinositol 4,5-bisphosphate (PIP2) are obligatory for channel opening. This PKC- and PIP2-mediated gating mechanism is regulated by the PIP2-binding protein myristoylated alanine-rich C kinase (MARCKS) and is coupled to store depletion by TRPC1-STIM1 interactions which induce Gq/PLCβ1 activity. Interestingly, the biophysical properties and activation mechanisms of TRPC1-based SOCs in native contractile VSMCs are unlikely to involve Orai1

SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation

The Molonglo Observatory Synthesis Telescope, operating at 843 MHz with a 5 square degree field of view, is carrying out a radio imaging survey of the sky south of declination -30 deg. This survey (the Sydney University Molonglo Sky Survey, or SUMSS) produces images with a resolution of 43" x 43" cosec(Dec.) and an rms noise level of about 1 mJy/beam. SUMSS is therefore similar in sensitivity and resolution to the northern NRAO VLA Sky Survey (NVSS; Condon et al. 1998). The survey is progressing at a rate of about 1000 square degrees per year, yielding individual and statistical data for many thousands of weak radio sources. This paper describes the main characteristics of the survey, and presents sample images from the first year of observation.Comment: 27 pages, 12 figures (figures 2, 8, 10 in jpg format); AJ, in pres

Standard spacecraft economic analysis. Volume 2: Findings and conclusions

The comparative program costs associated with use of various standardized spacecraft for Air Force space test program missions to be flown on the space shuttle were studied in two phases. In the first phase, a variety of procurement mixes composed of existing or programmed NASA standard spacecraft designs and an Air Force standard spacecraft design were considered. The second phase dealt with additional procurement options using an upgraded version of an existing NASA design. The results of both phases are discussed

The Distribution of H2O Maser Emission in the Nucleus of NGC 4945

We present the first interferometer map of the water maser emission in the active nucleus of NGC 4945. Although the declination of the galaxy is about -49 degrees, we were able to make the observations with the southernmost antennas of the Very Long Baseline Array. Strong maser emission is present in three velocity ranges, one near the systemic velocity and two shifted roughly symmetrically by +/-(100-150) km/s. This is the first detection of highly blue-shifted water emission in NGC 4945. We determined the position of the maser to be RA(B1950)= 13 02 32.28 +/- 0.02 ; Dec(B1950)= -49 12 01.9 +/- 0.1. The uncertainties in earlier estimates are at least several arcseconds. The maser lies within 2'' (36 pc at a distance of 3.7 Mpc) of the peaks in 1.4 GHz continuum and 1.6 micron emission from the nucleus. The mappable maser emission is distributed roughly linearly over about 40 milliarcseconds (0.7 pc) at a position angle of about 45 degrees, which is close to the 43 +/- 2 degree position angle of the galactic disk. The red and blue-shifted emission symmetrically stradle the systemic emission on the sky, which suggests material in edge-on circular motion around a central object. The position-velocity structure indicates a binding mass of about one million Suns, within a volume of radius about 0.3 pc. This implies that the central engine radiates on the order of 10% of its Eddington luminosity.Comment: 18 pages, including 5 Postscript figures. Accepted for publication in ApJ Letter

Store-operated interactions between plasmalemmal STIM1 and TRPC1 proteins stimulate PLCβ1 to induce TRPC1 channel activation in vascular smooth muscle cells.

KEY POINTS: Depletion of Ca(2+) stores activates store-operated channels (SOCs), which mediate Ca(2+) entry pathways that regulate cellular processes such as contraction, proliferation and gene expression. In vascular smooth muscle cells (VSMCs), stimulation of SOCs composed of canonical transient receptor potential channel 1 (TRPC1) proteins requires G protein α q subunit (Gαq)/phospholipase C (PLC)β1/protein kinase C (PKC) activity. We studied the role of stromal interaction molecule 1 (STIM1) in coupling store depletion to this activation pathway using patch clamp recording, GFP-PLCδ1-PH imaging and co-localization techniques. Store-operated TRPC1 channel and PLCβ1 activities were inhibited by STIM1 short hairpin RNA (shRNA) and absent in TRPC1(-/-) cells, and store-operated PKC phosphorylation of TRPC1 was inhibited by STIM1 shRNA. Store depletion induced interactions between STIM1 and TRPC1, Gαq and PLCβ1, which required STIM1 and TRPC1. Similar effects were produced with noradrenaline. These findings identify a new activation mechanism of TRPC1-based SOCs in VSMCs, and a novel role for STIM1, where store-operated STIM1-TRPC1 interactions stimulate Gαq/PLCβ1/PKC activity to induce channel gating. ABSTRACT: In vascular smooth muscle cells (VSMCs), stimulation of canonical transient receptor potential channel 1 (TRPC1) protein-based store-operated channels (SOCs) mediates Ca(2+) entry pathways that regulate contractility, proliferation and migration. It is therefore important to understand how these channels are activated. Studies have shown that stimulation of TRPC1-based SOCs requires G protein α q subunit (Gαq)/phospholipase C (PLC)β1 activities and protein kinase C (PKC) phosphorylation, although it is unclear how store depletion stimulates this gating pathway. The present study examines this issue by focusing on the role of stromal interaction molecule 1 (STIM1), an endo/sarcoplasmic reticulum Ca(2+) sensor. Store-operated TRPC1 channel activity was inhibited by TRPC1 and STIM1 antibodies and STIM1 short hairpin RNA (shRNA) in wild-type VSMCs, and was absent in TRPC1(-/-) VSMCs. Store-operated PKC phosphorylation of TRPC1 was reduced by knockdown of STIM1. Moreover, store-operated PLCβ1 activity measured with the fluorescent phosphatidylinositol 4,5-bisphosphate/inositol 1,4,5-trisphosphate biosensor GFP-PLCδ1-PH was reduced by STIM1 shRNA and absent in TRPC1(-/-) cells. Immunocytochemistry, co-immunoprecipitation and proximity ligation assays revealed that store depletion activated STIM1 translocation from within the cell to the plasma membrane (PM) where it formed STIM1-TRPC1 complexes, which then associated with Gαq and PLCβ1. Noradrenaline also evoked TRPC1 channel activity and associations between TRPC1, STIM1, Gαq and PLCβ1, which were inhibited by STIM1 knockdown. Effects of N-terminal and C-terminal STIM1 antibodies on TRPC1-based SOCs and STIM1 staining suggest that channel activation may involve insertion of STIM1 into the PM. The findings of the present study identify a new activation mechanism of TRPC1-based SOCs in VSMCs, and a novel role for STIM1, in which store-operated STIM1-TRPC1 interactions stimulate PLCβ1 activity to induce PKC phosphorylation of TRPC1 and channel gating

Evidence that Orai1 does not contribute to store-operated TRPC1 channels in vascular smooth muscle cells.

Ca(2+)-permeable store-operated channels (SOCs) mediate Ca(2+) entry pathways which are involved in many cellular functions such as contraction, growth, and proliferation. Prototypical SOCs are formed of Orai1 proteins and are activated by the endo/sarcoplasmic reticulum Ca(2+) sensor stromal interaction molecule 1 (STIM1). There is considerable debate about whether canonical transient receptor potential 1 (TRPC1) proteins also form store-operated channels (SOCs), and if they do, is Orai1 involved. We recently showed that stimulation of TRPC1-based SOCs involves store depletion inducing STIM1-evoked Gαq/PLCβ1 activity in contractile vascular smooth muscle cells (VSMCs). Therefore the present work investigates the role of Orai1 in activation of TRPC1-based SOCs in freshly isolated mesenteric artery VSMCs from wild-type (WT) and Orai1(-/-) mice. Store-operated whole-cell and single channel currents recorded from WT and Orai1(-/-) VSMCs had similar properties, with relatively linear current-voltage relationships, reversal potentials of about +20mV, unitary conductances of about 2pS, and inhibition by anti-TRPC1 and anti-STIM1 antibodies. In Orai1(-/-) VSMCs, store depletion induced PLCβ1 activity measured with the fluorescent phosphatidylinositol 4,5-bisphosphate/inositol 1,4,5-trisphosphate biosensor GFP-PLCδ1-PH, which was prevented by knockdown of STIM1. In addition, in Orai1(-/-) VSMCs, store depletion induced translocation of STIM1 from within the cell to the plasma membrane where it formed STIM1-TRPC1 interactions at discrete puncta-like sites. These findings indicate that activation of TRPC1-based SOCs through a STIM1-activated PLCβ1 pathway are likely to occur independently of Orai1 proteins, providing evidence that TRPC1 channels form genuine SOCs in VSMCs with a contractile phenotype