35,893 research outputs found
Frequency domain laser velocimeter signal processor
A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a signal processor capable of operating in the frequency domain maximizing the information obtainable from each signal burst. This allows a sophisticated approach to signal detection and processing, with a more accurate measurement of the chirp frequency resulting in an eight-fold increase in measurable signals over the present high-speed burst counter technology. Further, the required signal-to-noise ratio is reduced by a factor of 32, allowing measurements within boundary layers of wind tunnel models. Measurement accuracy is also increased up to a factor of five
Effect of Waste Discharges into a Silt-laden Estuary: A Case Study of Cook Inlet, Alaska
Cook Inlet is not well known. Although its thirty-foot tidal range is widely appreciated,
its other characteristics, such as turbulence, horizontal velocities of flow, suspended sediment
loads, natural biological productivity, the effects of fresh water inflows, temperature,
and wind stresses, are seldom acknowledged. The fact that the Inlet has not been used for
recreation nor for significant commercial activity explains why the average person is not
more aware of these characteristics. Because of the gray cast created by the suspended
sediments in the summer and the ice floes in the winter, the Inlet does not have the aura of
a beautiful bay or fjord. The shoreline is inhospitable for parks and development, the currents
too strong for recreational activities, and, because of the high silt concentration, there
is little fishing. Yet, Cook Inlet, for all its negative attributes, can in no way be considered
an unlimited dumping ground for the wastes of man. It may be better suited for this purpose
than many bays in North America, but it does have a finite capacity for receiving
wastes without unduly disturbing natural conditions.
This report was written for the interested layman by engineers and scientists who tried
to present some highly technical information in such a manner that it could be understood
by environmentalists, concerned citizens, students, decision makers, and lawmakers alike.
In attempting to address such a diverse audience, we risked failing to be completely understood
by any one group. However, all too often research results are written solely for other
researchers, a practice which leads to the advancement of knowledge but not necessarily to
its immediate use by practicing engineers nor to its inclusion in social, economic, and
political decision-making processes. We hope this report will shorten the usual time lag between
the acquisition of new information and its use. Several additional reports will be
available for a limited distribution. These will be directed to technicians who wish to know
the mathematical derivations, assumptions, and other scientific details used in the study.
Technical papers by the individual authors, published in national and international scientific
and engineering journals, are also anticipated.The work upon which this report is based was supported in part by funds (Proj. B-015-ALAS)
provided by the United States Department of the Interior, Office of Water Resources
Research, as authorized under the Water Resources Act of 1964, as amended
Antioxidants that protect mitochondria reduce interleukin-6 and oxidative stress, improve mitochondrial function, and reduce biochemical markers of organ dysfunction in a rat model of acute sepsis
Funding This study was funded by the Medical Research Council (Grant number G0800149). Research material from this study is not available. Acknowledgement We are very grateful to Dr Robin A.J. Smith, Department of Chemistry, University of Otago, Dunedin, New Zealand, for the generous gifts of MitoE and MitoQ, without which this work would not have been possible.Peer reviewedPublisher PD
Timing by Stellar Pulsations as an Exoplanet Discovery Method
The stable oscillations of pulsating stars can serve as accurate timepieces,
which may be monitored for the influence of exoplanets. An external companion
gravitationally tugs the host star, causing periodic changes in pulsation
arrival times. This method is most sensitive to detecting substellar companions
around the hottest pulsating stars, especially compact remnants like white
dwarfs and hot subdwarfs, as well as delta Scuti variables (A stars). However,
it is applicable to any pulsating star with sufficiently stable oscillations.
Care must be taken to ensure that the changes in pulsation arrival times are
not caused by intrinsic stellar variability; an external, light-travel-time
effect from an exoplanet identically affects all pulsation modes. With more
long-baseline photometric campaigns coming online, this method is yielding new
detections of substellar companions.Comment: 9 pages, 2 figures: Invited review to appear in 'Handbook of
Exoplanets,' Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
The Local Radio-IR Relation in M51
We observed M51 at three frequencies, 1.4 GHz (20 cm), 4.9 GHz (6 cm), and 8.4 GHz (3.6 cm), with the Very Large Array and the Effelsberg 100 m telescope to obtain the highest quality radio continuum images of a nearby spiral galaxy. These radio data were combined with deconvolved Spitzer IRAC 8 μm and MIPS 24 μm images to search for and investigate local changes in the radio-IR correlation. Utilizing wavelet decomposition, we compare the distribution of the radio and IR emission on spatial scales between 200 pc and 30 kpc. We show that the radio-IR correlation is not uniform across the galactic disk. It presents a complex behavior with local extrema corresponding to various galactic structures, such as complexes of H II regions, spiral arms, and interarm filaments, indicating that the contribution of the thermal and non-thermal radio emission is a strong function of environment. In particular, the relation of the 24 μm and 20 cm emission presents a linear relation within the spiral arms and globally over the galaxy, while it deviates from linearity in the interarm and outer regions as well in the inner region, with two different behaviors: it is sublinear in the interarm and outer region and overlinear in the central 3.5 kpc. Our analysis suggests that the changes in the radio/IR correlation reflect variations of interstellar medium properties between spiral arms and interarm region. The good correlation in the spiral arms implies that 24 μm and 20 cm are tracing recent star formation, while a change in the dust opacity, "Cirrus" contribution to the IR emission and/or the relation between the magnetic field strength and the gas density can explain the different relations found in the interarm, outer, and inner regions
Quantum Chessboards in the Deuterium Molecular Ion
We present a new algorithm for vibrational control in deuterium molecules
that is feasible with current experimental technology. A pump mechanism is used
to create a coherent superposition of the D2+ vibrations. A short, intense
infrared control pulse is applied after a chosen delay time to create selective
interferences. A `chessboard' pattern of states can be realized in which a set
of even- or odd-numbered vibrational states can be selectively annihilated or
enhanced. A technique is proposed for experimental realization and observation
of this effect using 5 fs pulses of 790 nm radiation, with intermediate
intensity (5e13 W/cm2)Comment: 12 pages, 5 figure
The biochemical, physiological, and metabolic effects of Apollo nominal mission and contingency diets on human subjects while on a simulated Apollo mission Final report, Feb. - Jun. 1966
Biochemical, physiological, and metabolic effects of simulated Apollo mission with space diet on human
Eclipsing high-mass binaries I. Light curves and system parameters for CPD-518946, PISMIS24-1 and HD319702
We present first results of a comprehensive photometric O-star survey
performed with a robotic twin refractor at the Universit\"atssternwarte Bochum
located near Cerro Armazones in Chile. For three high-mass stars, namely
Pismis24-1, CPD-518946 and HD319702, we determined the period through the
Lafler-Kinman algorithm and model the light curves within the framework of the
Roche geometry. For Pismis24-1, a previously known eclipsing binary, we provide
first light curves and determined a photometric period of 2.36 days together
with an orbital inclination of 61.8 degrees. The best-fitting model solution to
the light curves suggest a detached configuration. With a primary temperature
of T1 = 42520K we obtain the temperature of the secondary component as T2 =
41500K. CPD-518946 is another known eclipsing binary for which we present a
revised photometric period of 1.96 days with an orbital inclination of 58.4
degrees. The system has likely a semi-detached configuration and a mass ratio q
= M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34550K we obtain T2 =
21500K for the secondary component. HD319702 is a newly discovered eclipsing
binary member of the young open cluster NGC6334. The system shows well-defined
eclipses favouring a detached configuration with a period of 2.0 days and an
orbital inclination of 67.5 degrees. Combining our photometric result with the
primary spectral type O8 III(f) (T1 = 34000K) we derive a temperature of T2 =
25200K for the secondary component.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
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