72 research outputs found
Hydraulic drive system prevents backlash
Hydraulic drive system uses a second drive motor operating at reduced torque. This exerts a relative braking action which eliminates the normal gear train backlash that is intolerable when driving certain heavy loads
Anti-backlash circuit for hydraulic drive system Patent
Antibacklash circuit for hydraulic drive syste
Solar vane actuator Patent
Design and characteristics of device for sensing solar radiation and providing spacecraft attitude control to maintain direction with respect to incident radiatio
Attitude control for spacecraft Patent
Attitude control system for spacecraft based on conversion of incident solar radiation on movable control surfaces into mechanical torque
Calixarene Assisted Rapid Synthesis of Silver-Graphene Nanocomposites with Enhanced Antibacterial Activity
Demonstrated herein is a single rapid approach employed for synthesis of Agâgraphene nanocomposites, with excellent antibacterial properties and low cytotoxicity, by utilizing a continuous hydrothermal flow synthesis (CHFS) process in combination with p-hexasulfonic acid calix[6]arene (SCX6) as an effective particle stabilizer. The nanocomposites showed high activity against E. coli (Gram-negative) and S. aureus (Gram-positive) bacteria. The materials were characterized using a range of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UVâvis spectrophotometry, FT-IR, and X-ray powder diffraction (XRD). This rapid, single step synthetic approach not only provides a facile means of enabling and controlling graphene reduction (under alkaline conditions) but also offers an optimal route for homogeneously producing and depositing highly crystalline Ag nanostructures into reduced graphene oxide substrate
Vaccination with novel low-molecular weight proteins secreted from Trichinella spiralis inhibits establishment of infection
Trichinella spiralis muscle stage larvae (mL1) produce excretory-secreted products (ESPs), a complex mixture of protein, which are believed to be important for establishing or maintaining an infection niche within skeletal muscle and the intestine. Studies of both whole ESPs and individual cloned proteins have shown that some ESPs are potent immunogens capable of eliciting protective immune responses. Here we describe two novel proteins, Secreted from Muscle stage Larvae SML-4 and SML-5 which are 15 kDa and 12 kDa respectively. The genes encoding these proteins are highly conserved within the Trichinellids, are constituents of mL1 ESP and localized in the parasite stichosome. While SML-5 is only expressed in mL1 and early stages of adult nematode development, SML-4 is a tyvosylated glycoprotein also produced by adult nematodes, indicating it may have a function in the enteral phase of the infection. Vaccination with these proteins resulted in an impaired establishment of adult stages and consequently a reduction in the burden of mL1 in BALB/c mice. This suggests that both proteins may be important for establishment of parasite infection of the intestine and are prophylactic vaccine candidates
A survey of SiO 5-4 emission towards outflows from massive young stellar objects
Results are presented of a survey of SiO 5-4 emission observed with the James
Clerk Maxwell Telescope (JCMT) towards a sample of outflows from massive young
stellar objects. The sample is drawn from a single-distance study by Ridge &
Moore. In a sample of 12 sources, the 5-4 line was detected in 5, a detection
rate of 42 per cent. This detection rate is higher than that found for a sample
of low-luminosity outflow sources, although for sources of comparable
luminosity, it is in good agreement with the results of a previous survey of
high luminosity sources. For most of the detected sources, the 5-4 emission is
compact or slightly extended along the direction of the outflow. NGC6334I shows
a clear bipolar flow in the 5-4 line. Additional data were obtained for
W3-IRS5, AFGL5142 and W75N for the 2-1 transition of SiO using the
Berkeley-Illinois-Maryland Association (BIMA) millimetre interferometer. There
is broad agreement between the appearance of the SiO emission in both lines,
though there are some minor differences. The 2-1 emission in AFGL5142 is
resolved into two outflow lobes which are spatially coincident on the sky, in
good agreement with previous observations. In general the SiO emission is
clearly associated with the outflow. The primary indicator of SiO 5-4
detectability is the outflow velocity, i.e. the presence of SiO is an indicator
of a high velocity outflow. This result is consistent with the existence of a
critical shock velocity required to disrupt dust grains and subsequent SiO
formation in post-shock gas. There is also weak evidence that higher luminosity
sources and denser outflows are more likely to be detected.Comment: Accepted for publication in MNRA
A Multi-Epoch Study of the Radio Continuum Emission of Orion Source I: Constraints on the Disk Evolution of a Massive YSO and the Dynamical History of Orion BN/KL
We present new 7mm continuum observations of Orion BN/KL with the VLA. We
resolve the emission from the protostar radio Source I and BN at several
epochs. Source I is highly elongated NW-SE, and remarkably stable in flux
density, position angle, and overall morphology over nearly a decade. This
favors the extended emission component arising from an ionized disk rather than
a jet. We have measured the proper motions of Source I and BN for the first
time at 43 GHz. We confirm that both sources are moving at high speed (12 and
26 km/s, respectively) approximately in opposite directions, as previously
inferred from measurements at lower frequencies. We discuss dynamical scenarios
that can explain the large motions of both BN and Source I and the presence of
disks around both. Our new measurements support the hypothesis that a close
(~50 AU) dynamical interaction occurred around 500 years ago between Source I
and BN as proposed by Gomez et al. From the dynamics of encounter we argue that
Source I today is likely to be a binary with a total mass on the order of 20
Msun, and that it probably existed as a softer binary before the close
encounter. This enables preservation of the original accretion disk, though
truncated to its present radius of ~50 AU. N-body numerical simulations show
that the dynamical interaction between a binary of 20 Msun total mass (I) and a
single star of 10 Msun mass (BN) may lead to the ejection of both and binary
hardening. The gravitational energy released in the process would be large
enough to power the wide-angle flow traced by H2 and CO emission in the BN/KL
nebula. Assuming the proposed dynamical history is correct, the smaller mass
for Source I recently estimated from SiO maser dynamics (>7 Msun) by Matthews
et al., suggests that non-gravitational forces (e.g. magnetic) must play an
important role in the circumstellar gas dynamics.Comment: 17 pages, 7 figures, 4 tables, accepted by Ap
Massive Star Formation
This chapter reviews progress in the field of massive star formation. It
focuses on evidence for accretion and current models that invoke high accretion
rates. In particular it is noted that high accretion rates will cause the
massive young stellar object to have a radius much larger than its eventual
main sequence radius throughout much of the accretion phase. This results in
low effective temperatures which may provide the explanation as to why luminous
young stellar objects do not ionized their surroundings to form ultra-compact H
II regions. The transition to the ultra-compact H II region phase would then be
associated with the termination of the high accretion rate phase. Objects
thought to be in a transition phase are discussed and diagnostic diagrams to
distinguish between massive young stellar objects and ultra-compact H II
regions in terms of line widths and radio luminosity are presented.Comment: 21 pages, 6 figures, chapter in Diffuse Matter from Star Forming
Regions to Active Galaxies - A Volume Honouring John Dyson, Edited by T.W.
Hartquist, J. M. Pittard, and S. A. E. G. Falle. Series: Astrophysics and
Space Science Proceedings. Springer Dordrecht, 2007, p.6
Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W28 (G6.4-0.1) field
We observed the W28 field (for ~40 h) at Very High Energy (VHE) gamma-ray
energies (E>0.1 TeV) with the H.E.S.S. Cherenkov telescopes. A reanalysis of
EGRET E>100 MeV data was also undertaken. Results from the NANTEN 4m telescope
Galactic plane survey and other CO observations have been used to study
molecular clouds. We have discovered VHE gamma-ray emission (HESSJ1801-233)
coincident with the northeastern boundary of W28, and a complex of sources
(HESSJ1800-240A, B and C) ~0.5 deg south of W28, in the Galactic disc. The VHE
differential photon spectra are well fit by pure power laws with indices
Gamma~2.3 to 2.7. The NANTEN ^{12}CO(J=1-0) data reveal molecular clouds
positionally associating with the VHE emission, spanning a ~15 km s^{-1} range
in local standard of rest velocity. The VHE/molecular cloud association could
indicate a hadronic origin for HESSJ1801-233 and HESSJ1800-240, and several
cloud components in projection may contribute to the VHE emission. The clouds
have components covering a broad velocity range encompassing the distance
estimates for W28 (~2 kpc), and extending up to ~4 kpc. Assuming a hadronic
origin, and distances of 2 and 4 kpc for cloud components, the required cosmic
ray density enhancement factors (with respect to the solar value) are in the
range ~10 to ~30. If situated at 2 kpc distance, such cosmic ray densities may
be supplied by a SNR like W28. Additionally and/or alternatively, particle
acceleration may come from several catalogued SNRs and SNR candidates, the
energetic ultra compact HII region W28A2, and the HII regions M8 and M20 along
with their associated open clusters. Further sub-mm observations would be
recommended to probe in detail the dynamics of the molecular clouds at
velocites >10 km s^{-1}, and their possible connection to W28.Comment: 10 pages, 4 figures. Accepted for publication in Astronomy &
Astrophysics. (Abstract shortened
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