222 research outputs found
Het verziltingsproces in de ondergrond van Noord-Holland
In het kader van het Noord-Holland onderzoek heeft de kwaliteit van het grondwater en wel in het bijzonder de verzilting de nodige aandacht gekregen. Bij een analyse van de hydrologische processen in de ondergrond is komen vast te staan dat stijghoogteverschillen in horizontale en verticale richting, die verantwoordelijk zijn voor de optredende grondwaterstromingen, gedeeltelijk kunnen worden toegeschreven aan de verdeling van het zoute en zoete grondwater
Bodemconstanten in de omgeving van de Zuid-Willemsvaart tussen 's Hertogenbosch en Donk
Door de Directie Noord-Brabant van de Rijkswaterstaat zijn plannen ontworpen ter verbetering van de Zuid-Willemsvaart. Het betreft hier voornamelijk verbreding en verdieping van het kanaalprofiel, terwijl de oude sluizen zullen worden vervangen door een kleiner aantal nieuwe sluizen. Deze maatregelen zullen hun invloed uitoefenen op het grondwaterregime in de omgeving van het kanaal met als gevolg dat daar schade kan optreden voor landbouw, natuurterreinen en bebouwing. Ten behoeve van het geohydrologisch onderzoek dat de grootte van de peilveranderingen en de daaruit voortvloeiende schade moet voorspellen, wordt in deze nota verslag uitgebracht van de onderzoekingen die zich speciaal hebben gericht op het aspect van het doorlaatvermogen (kD) in de watervoerende pakketten in de ondergrond, en de weerstand (c) tegen grondwaterstroming in de onregelmatig voorkomende kleilagen
A Far-Ultraviolet View of Starburst Galaxies
Recent observational and theoretical results on starburst galaxies related to
the wavelength regime below 1200 A are discussed. The review covers stars,
dust, as well as hot and cold gas. This wavelength region follows trends
similar to those seen at longer wavelengths, with several notable exceptions.
Even the youngest stellar populations show a turn-over in their spectral energy
distributions, and line-blanketing is much more pronounced. Furthermore, the O
VI line allows one to probe gas at higher temperatures than possible with lines
at longer wavelengths. Molecular hydrogen lines (if detected) provide a glimpse
of the cold phase. I cover the crucial wavelength regime below 912 A and the
implications of recent attempts to detect the escaping ionizing radiation.Comment: 8 pages, 3 figures, Invited Talk, Starbursts--From 30 Doradus to
Lyman-Break Galaxies, ed. R. de Grijs & R. M. Gonzalez Delgado (Dordrecht:
Kluwer
Interruption of torus doubling bifurcation and genesis of strange nonchaotic attractors in a quasiperiodically forced map : Mechanisms and their characterizations
A simple quasiperiodically forced one-dimensional cubic map is shown to
exhibit very many types of routes to chaos via strange nonchaotic attractors
(SNAs) with reference to a two-parameter space. The routes include
transitions to chaos via SNAs from both one frequency torus and period doubled
torus. In the former case, we identify the fractalization and type I
intermittency routes. In the latter case, we point out that atleast four
distinct routes through which the truncation of torus doubling bifurcation and
the birth of SNAs take place in this model. In particular, the formation of
SNAs through Heagy-Hammel, fractalization and type--III intermittent mechanisms
are described. In addition, it has been found that in this system there are
some regions in the parameter space where a novel dynamics involving a sudden
expansion of the attractor which tames the growth of period-doubling
bifurcation takes place, giving birth to SNA. The SNAs created through
different mechanisms are characterized by the behaviour of the Lyapunov
exponents and their variance, by the estimation of phase sensitivity exponent
as well as through the distribution of finite-time Lyapunov exponents.Comment: 27 pages, RevTeX 4, 16 EPS figures. Phys. Rev. E (2001) to appea
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV
Mid-rapidity transverse mass spectra and multiplicity densities of charged
and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC.
The spectra are exponential in transverse mass, with an inverse slope of about
280 MeV in central collisions. The multiplicity densities for these particles
scale with the negative hadron pseudo-rapidity density. The charged kaon to
pion ratios are and
for the most central collisions. The ratio is lower than the same
ratio observed at the SPS while the is higher than the SPS result.
Both ratios are enhanced by about 50% relative to p+p and +p
collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl
Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV
We present the first measurement of directed flow () at RHIC. is
found to be consistent with zero at pseudorapidities from -1.2 to 1.2,
then rises to the level of a couple of percent over the range . The latter observation is similar to data from NA49 if the SPS rapidities
are shifted by the difference in beam rapidity between RHIC and SPS.
Back-to-back jets emitted out-of-plane are found to be suppressed more if
compared to those emitted in-plane, which is consistent with {\it jet
quenching}. Using the scalar product method, we systematically compared
azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow
from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure
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