22,981 research outputs found
Communication Platform Payload Definition (CPPD) study. Volume 3: Addendum
This is Volume 3 (Addendum) of the Ford Aerospace & Communications Corporation Final Report for the Communication Platform Payload Definition (CPPD) Study Program conducted for NASA Lewis Research Center under contract No. NAS3-24235. This report presents the results of the study effort leading to five potential platform payloads to service CONUS and WARC Region 2 traffic demand as projected to the year 2008. The report addresses establishing the data bases, developing service aggregation scenarios, selecting and developing 5 payload concepts, performing detailed definition of the 5 payloads, costing them, identifying critical technology, and finally comparing the payloads with each other and also with non-aggregated equivalent services
Cluster phases of membrane proteins
A physical scenario accounting for the existence of size-limited
submicrometric domains in cell membranes is proposed. It is based on the
numerical investigation of the counterpart, in lipidic membranes where proteins
are diffusing, of the recently discovered cluster phases in colloidal
suspensions. I demonstrate that the interactions between proteins, namely
short-range attraction and longer-range repulsion, make possible the existence
of stable small clusters. The consequences are explored in terms of membrane
organization and diffusion properties. The connection with lipid rafts is
discussed and the apparent protein diffusion coefficient as a function of their
concentration is analyzed.Comment: 5 pages - enhanced versio
New Limits on Local Lorentz Invariance in Mercury and Cesium
We report new bounds on Local Lorentz Invariance (LLI) violation in Cs and
Hg. The limits are obtained through the observation of the the spin- precession
frequencies of 199Hg and 133Cs atoms in their ground states as a function of
the orientation of an applied magnetic field with respect to the fixed stars.
We measure the amplitudes of the dipole couplings to a preferred direction in
the equatorial plane to be 19(11) nHz for Hg and 9(5) microHz for Cs. The upper
bounds established here improve upon previous bounds by about a factor of four.
The improvement is primarily due to mounting the apparatus on a rotating table.
New bounds are established on several terms in the standard model extension
including the first bounds on the spin-couplings of the neutron and proton to
the z direction, <7e-30 GeV and <7e-29 GeV, respectively.Comment: 17 pages, 6 figure
Portable dynamic fundus instrument
A portable diagnostic image analysis instrument is disclosed for retinal funduscopy in which an eye fundus image is optically processed by a lens system to a charge coupled device (CCD) which produces recordable and viewable output data and is simultaneously viewable on an electronic view finder. The fundus image is processed to develop a representation of the vessel or vessels from the output data
Subarcsecond Imaging of the NGC 6334 I(N) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate
Using the SMA and VLA, we have imaged the massive protocluster NGC6334I(N) at
high angular resolution (0.5"~650AU) from 6cm to 0.87mm, detecting 18 new
compact continuum sources. Three of the new sources are coincident with
previously-identified water masers. Together with the previously-known sources,
these data bring the number of likely protocluster members to 25 for a
protostellar density of ~700 pc^-3. Our preliminary measurement of the
Q-parameter of the minimum spanning tree is 0.82 -- close to the value for a
uniform volume distribution. All of the (nine) sources with detections at
multiple frequencies have SEDs consistent with dust emission, and two (SMA1b
and SMA4) also have long wavelength emission consistent with a central
hypercompact HII region. Thermal spectral line emission, including CH3CN, is
detected in six sources: LTE model fitting of CH3CN(J=12-11) yields
temperatures of 72-373K, confirming the presence of multiple hot cores. The
fitted LSR velocities range from -3.3 to -7.0 km/s, with an unbiased mean
square deviation of 2.05 km/s, implying a dynamical mass of 410+-260 Msun for
the protocluster. From analysis of a wide range of hot core molecules, the
kinematics of SMA1b are consistent with a rotating, infalling Keplerian disk of
diameter 800AU and enclosed mass of 10-30 Msun that is perpendicular (within 1
degree) to the large-scale bipolar outflow axis. A companion to SMA1b at a
projected separation of 0.45" (590AU; SMA1d), which shows no evidence of
spectral line emission, is also confirmed. Finally, we detect one 218.440GHz
and several 229.7588GHz Class-I methanol masers.Comment: 54 pages, 11 figures. Accepted for publication in The Astrophysical
Journal. Version 2: Keywords updated, and three "in press" citations updated
to journal reference. Version 3: corrected the error in the quantum numbers
of the 218 GHz methanol transition in the text and in Table 8. For a PDF
version with full-resolution figures, see
http://www.cv.nrao.edu/~thunter/papers/ngc6334in2014.pd
First Results from a 1.3 cm EVLA Survey of Massive Protostellar Objects: G35.03+0.35
We have performed a 1.3 centimeter survey of 24 massive young stellar objects
(MYSOs) using the Expanded Very Large Array (EVLA). The sources in the sample
exhibit a broad range of massive star formation signposts including Infrared
Dark Clouds (IRDCs), UCHII regions, and extended 4.5 micron emission in the
form of Extended Green Objects (EGOs). In this work, we present results for
G35.03+0.35 which exhibits all of these phenomena. We simultaneously image the
1.3 cm ammonia (1,1) through (6,6) inversion lines, four methanol transitions,
two H recombination lines, plus continuum at 0.05 pc resolution. We find three
areas of thermal ammonia emission, two within the EGO (designated the NE and SW
cores) and one toward an adjacent IRDC. The NE core contains an UCHII region
(CM1) and a candidate HCHII region (CM2). A region of non-thermal, likely
masing ammonia (3,3) and (6,6) emission is coincident with an arc of 44 GHz
methanol masers. We also detect two new 25 GHz Class I methanol masers. A
complementary Submillimeter Array 1.3 mm continuum image shows that the
distribution of dust emission is similar to the lower-lying ammonia lines, all
peaking to the NW of CM2, indicating the likely presence of an additional MYSO
in this protocluster. By modeling the ammonia and 1.3 mm continuum data, we
obtain gas temperatures of 20-220 K and masses of 20-130 solar. The diversity
of continuum emission properties and gas temperatures suggest that objects in a
range of evolutionary states exist concurrently in this protocluster.Comment: To appear in Astrophysical Journal Letters Special Issue on the EVLA.
16 pages, 3 figures. Includes the complete version of Figure 3, which was
unable to fit into the journal article due to the number of panel
Study of an engine flow diverter system for a large scale ejector powered aircraft model
Requirements were established for a conceptual design study to analyze and design an engine flow diverter system and to include accommodations for an ejector system in an existing 3/4 scale fighter model equipped with YJ-79 engines. Model constraints were identified and cost-effective limited modification was proposed to accept the ejectors, ducting and flow diverter valves. Complete system performance was calculated and a versatile computer program capable of analyzing any ejector system was developed
The Protocluster G18.67+0.03: A Test Case for Class I Methanol Masers as Evolutionary Indicators for Massive Star Formation
We present high angular resolution Submillimeter Array (SMA) and Karl G.
Jansky Very Large Array (VLA) observations of the massive protocluster
G18.67+0.03. Previously targeted in maser surveys of GLIMPSE Extended Green
Objects (EGOs), this cluster contains three Class I methanol maser sources,
providing a unique opportunity to test the proposed role of Class I masers as
evolutionary indicators for massive star formation. The millimeter observations
reveal bipolar molecular outflows, traced by 13CO(2-1) emission, associated
with all three Class I maser sources. Two of these sources (including the EGO)
are also associated with 6.7 GHz Class II methanol masers; the Class II masers
are coincident with millimeter continuum cores that exhibit hot core line
emission and drive active outflows, as indicated by the detection of SiO(5-4).
In these cases, the Class I masers are coincident with outflow lobes, and
appear as clear cases of excitation by active outflows. In contrast, the third
Class I source is associated with an ultracompact HII region, and not with
Class II masers. The lack of SiO emission suggests the 13CO outflow is a relic,
consistent with its longer dynamical timescale. Our data show that massive
young stellar objects associated only with Class I masers are not necessarily
young, and provide the first unambiguous evidence that Class I masers may be
excited by both young (hot core) and older (UC HII) MYSOs within the same
protocluster.Comment: Astrophysical Journal Letters, accepted. emulateapj, 7 pages
including 4 figures and 1 table. Figures compressed. v2: coauthor affiliation
updated, emulateapj versio
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