2,440 research outputs found
Active specific immunotherapy for solid tumors
Pinedo, H.M. [Promotor]Scheper, R.J. [Promotor]Eertwegh, A.J.M. van den [Copromotor]Gruijl, T.D. de [Copromotor
Utilizing the Washington Water Markets for the Preservation of Columbia River Basin Salmon Stock
Salmon preservation efforts in Washington State demonstrate the competitive and interconnected nature of water management issues in a water scarce environment. The decline in stream flows in Washington State and the negative impact of low stream flows on anadromous species has severely hindered rehabilitation of endangered Columbia River Basin salmon stocks. Through examining the National Marine Fisheries Service (NMFS) anemic efforts to preserve endangered stocks, primarily through the Endangered Species Act, and through analyzing the Washington Department of Ecology\u27s (DOE) regulatory structure for water market transfers, I propose several changes in the regulatory structure for water that may positively impact the preservation of Columbia River Basin salmon stocks. Decentralizing DOE regulatory authority to enable local water basin planning groups to approve water transfers will decrease transaction costs and improve security of water rights. In turn, programs such as the Washington Water Trust and the incentive based Water Acquisition Program will encourage water rights holder to divert less water from the river. Also, the development of an options market for water transfers will provide further security for water rights holders and will eliminate the need for the antiquated use it or lose it clause. These improvements to Washington State\u27s water markets will help salmon preservationists by easing the process with which the Washington Water Trust can purchase or lease water for in-stream use
Unbiased flux calibration methods for spectral-line radio observations
Position and frequency switching techniques used for the removal of the
bandpass dependence of radio astronomical spectra are presented and discussed
in detail. Both methods are widely used, although the frequency dependence of
the system temperature and/or noise diode is often neglected. This leads to
systematic errors in the calibration that potentially have a significant impact
on scientific results, especially when using large-bandwidth receivers or
performing statistical analyses. We present methods to derive an unbiased
calibration using a noise diode, which is part of many heterodyne receivers. We
compare the proposed methods and describe the advantages and bottlenecks of the
various approaches. Monte Carlo simulations are used to qualitatively
investigate both systematics and the error distribution of the reconstructed
flux estimates about the correct flux values for the new methods but also the
'classical' case. Finally, the determination of the frequency-dependent noise
temperature of the calibration diode using hot-cold measurements or
observations of well-known continuum sources is also briefly discussed.Comment: 25 pages, 30 figures. Accepted for publication in A&
Radio Emission Signatures in the Crab Pulsar
Our high time resolution observations of individual pulses from the Crab
pulsar show that both the time and frequency signatures of the interpulse are
distinctly different from those of the main pulse. Main pulses can occasionally
be resolved into short-lived, relatively narrow-band nanoshots. We believe
these nanoshots are produced by soliton collapse in strong plasma turbulence.
Interpulses at centimeter wavelengths are very different. Their dynamic
spectrum contains regular, microsecond-long emission bands. We have detected
these bands, proportionately spaced in frequency, from 4.5 to 10.5 GHz. The
bands cannot easily be explained by any current theory of pulsar radio
emission; we speculate on possible new models.Comment: 26 pages, 10 figures, to appear in Ap
Near-Field Radio Holography of Large Reflector Antennas
We summarise the mathematical foundation of the holographic method of
measuring the reflector profile of an antenna or radio telescope. In
particular, we treat the case, where the signal source is located at a finite
distance from the antenna under test, necessitating the inclusion of the
so-called Fresnel field terms in the radiation integrals. We assume a ``full
phase'' system with reference receiver to provide the reference phase. We
describe in some detail the hardware and software implementation of the system
used for the holographic measurement of the 12m ALMA prototype submillimeter
antennas. We include a description of the practicalities of a measurement and
surface setting. The results for both the VertexRSI and AEC
(Alcatel-EIE-Consortium) prototype ALMA antennas are presented.Comment: 14 pages, 14 figures, to appear in IEEE Antennas and Propagation
Magazine, Vol. 49, No. 5, October 2007. Version 2 includes nice mug-shots of
the author
The late time radio emission from SN 1993J at meter wavelengths
We present the investigations of SN 1993J using low frequency observations
with the Giant Meterwave Radio Telescope. We analyze the light curves of SN
1993J at 1420, 610, 325 and 243 MHz during years since explosion.The
supernova has become optically thin early on in the 1420 MHz and 610 MHz bands
while it has only recently entered the optically thin phase in the 325 MHz
band. The radio light curve in the 235 MHz band is more or less flat. This
indicates that the supernova is undergoing a transition from an optically thick
to optically thin limit in this frequency band. In addition, we analyze the SN
radio spectra at five epochs on day 3000, 3200, 3266, 3460 and 3730 since
explosion. Day 3200 spectrum shows a synchrotron cooling break. SN 1993J is the
only young supernova for which the magnetic field and the size of the radio
emitting region are determined through unrelated methods. Thus the mechanism
that controls the evolution of the radio spectra can be identified. We suggest
that at all epochs, the synchrotron self absorption mechanism is primarily
responsible for the turn-over in the spectra. Light curve models based on free
free absorption in homogeneous or inhomogeneous media at high frequencies
overpredict the flux densities at low frequencies. The discrepancy is
increasingly larger at lower and lower frequencies. We suggest that an extra
opacity, sensitively dependent on frequency, is likely to account for the
difference at lower frequencies. The evolution of the magnetic field
(determined from synchrotron self absorption turn-over) is roughly consistent
with . Radio spectral index in the optically thin part
evolves from at few tens of days to in about
10 years.Comment: 37 pages, 9 figures in LaTex; scheduled for ApJ 10 September 2004,
v612 issue; send comments to: [email protected]
The Spectral Aerosol Extinction Monitoring System (SǼMS): setup, observational products, and comparisons
The Spectral Aerosol Extinction Monitoring System (SÇMS) is presented that allows us to continuously measure the spectral extinction coefficient of atmospheric aerosol particles along an approximately 2.7 km long optical path at 30–50 m height above ground in Leipzig (51.3° N, 12.4° E), Germany. The fully automated instrument measures the ambient aerosol extinction coefficients from 300 to 1000 nm. The main goal of (SÇMS) observations are long-term studies of the relationship between particle extinction and relative humidity from below 40% to almost 100%. The setup is presented and observations (a case study and statistical results for 2009) are discussed in terms of time series of 550 nm particle optical depth, Ångström exponent, and particle size distribution retrieved from the spectrally resolved extinction. The SǼMS measurements are compared with simultaneously performed EARLINET (European Aerosol Research Lidar Network) lidar, AERONET (Aerosol Robotic Network) sun photometer, and in situ aerosol observations of particle size distribution and related extinction coefficients on the roof of our institute. Consistency between the different measurements is found, which corroborates the quality of the SǼMS observations. Statistical results of a period of 1 yr (2009) show mode extinction values of 0.09 km−1 (SÇMS), 0.075 km−1 (AERONET), and 0.03 km−1 (in situ). Ångström exponents for this period are 0.19 (390–880 nm,(SÇMS) and 1.55 (440–870 nm, AERONET)
Imaging the Radio Photospheres of Mira Variables
We have used the VLA at 43 GHz to image the radio continuum emission from o
Ceti, R Leo, and W Hya and to precisely locate their SiO maser emission with
respect to the star. The radio continuum emission region for all three stars
has a diameter close to 5.6 AU. These diameters are similar to those measured
at infrared wavelengths in bands containing strong molecular opacity and about
twice those measured in line-free regions of the infrared spectrum. Thus, the
radio photosphere and the infrared molecular layer appear to be coextensive.
The 43 GHz continuum emission is consistent with temperatures near 1600 K and
opacity from H-minus free-free interactions. While the continuum image of o
Ceti appears nearly circular, both R Leo and W Hya display significant
elongations. The SiO masers for all three stars show partial rings with
diameters close to 8 AU.Comment: 14 pages; 3 figure
Recommended from our members
The spectral aerosol extinction monitoring system (SÇMS): Setup, observational products, and comparisons
The Spectral Aerosol Extinction Monitoring System (SÇMS) is presented that allows us to continuously measure the spectral extinction coefficient of atmospheric aerosol particles along an approximately 2.7 km long optical path at 30–50 m height above ground in Leipzig (51.3° N, 12.4° E), Germany. The fully automated instrument measures the ambient aerosol extinction coefficients from 300 to 1000 nm. The main goal of (SÇMS) observations are long-term studies of the relationship between particle extinction and relative humidity from below 40% to almost 100%. The setup is presented and observations (a case study and statistical results for 2009) are discussed in terms of time series of 550 nm particle optical depth, Ångström exponent, and particle size distribution retrieved from the spectrally resolved extinction. The SǼMS measurements are compared with simultaneously performed EARLINET (European Aerosol Research Lidar Network) lidar, AERONET (Aerosol Robotic Network) sun photometer, and in situ aerosol observations of particle size distribution and related extinction coefficients on the roof of our institute. Consistency between the different measurements is found, which corroborates the quality of the SǼMS observations. Statistical results of a period of 1 yr (2009) show mode extinction values of 0.09 km−1 (SÇMS), 0.075 km−1 (AERONET), and 0.03 km−1 (in situ). Ångström exponents for this period are 0.19 (390–880 nm,(SÇMS) and 1.55 (440–870 nm, AERONET)
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