400 research outputs found
Nieuwe bruggen naar de toekomst : weergave van een speurtocht naar nieuwe perspectieven voor het Gelders landelijk gebied : "het landelijk gebied is voor iedereen", Eusebiuskerk, 16 januari 2003
De factoren (1) economische groei en (2) stuurkracht van de overheid hebben een aanzienlijke impact op de ontwikkeling van gebieden, maar laten zich moeilijk door beleidsstrategieën beïnvloeden. Zij hebben daarom een grote onvoorspelbaarheid op toekomstige ontwikkelingen. Om toch meer zicht te krijgen op die ontwikkelingen, ondanks genoemde onzekerheden, is het beschrijven van scenario's een methode die daarbij kan helpen. De nota 'Nieuwe bruggen naar de toekomst' van de provincie Gelderland werkt dit principe uit in een viertal scenario's die sterk uiteenlopende beelden schetsen van hoe de provincie er anno 2025 voor staat op het gebied van 'maatschappelijke orde', 'menselijke contacten', 'regionale perspectieven' en 'relevante beleidsthema's'. Voor het Rivierenland geeft elk van deze scenario's aan, dat het gebied door zijn waterlandschap gevrijwaard blijft van intensieve verstedelijking. Het beeld 'parkenland', als bruikbare metafoor voor Nederland vanuit het oogpunt van ruimtelijk beleid, wordt door het Rivierengebied krachtig ondersteund
Розкадровка як мистецький твір
The amino acid L-tryptophan is known to be a modulator of many processes of cell metabolism. In this contribution we show that L-tryptophan interferes with some biological effects of the antileukemic and anti-human immunodeficiency virus agent avarol, possibly by different mechanisms. Avarol has been shown to be able to modulate posttranscriptional events of mRNA synthesis, resulting in an increase of the base-sequence complexities of the nonabundant and rare mRNA classes. Here it is demonstrated that this change in mRNA abundancy distribution is accompanied by an increase in the level of some specific, low abundant mRNAs (ras and c-myc). Addition of L-tryptophan was found to abolish avarol-caused gene relaxation in 1,1210 mouse leukemia cells. In addition, L-tryptophan suppressed the induction of γ-interferon mRNA production in human peripheral blood lymphocytes. At the level of DNA, L-tryptophan inhibited the production of strand breaks by cytotoxic avarol concentrations in Friend erythroleukemia cells in vitro. Moreover, it competed with avarol for binding to the nuclear envelope binding site; this effect was not shown by other amino acids. © 1989, American Association for Cancer Research. All rights reserved
Separable potential model for interactions at low energies
The effective separable meson-baryon potentials are constructed to match the
equivalent chiral amplitudes up to the second order in external meson momenta.
We fit the model parameters (low energy constants) to the threshold and low
energy data. In the process, the -proton bound state problem is
solved exactly in the momentum space and the 1s level characteristics of the
kaonic hydrogen are computed simultaneously with the available low energy
cross sections. The model is also used to describe the
mass spectrum and the energy dependence of the amplitude.Comment: 31 pages, v2 - added corrections to make it compatible with the
published versio
Determination of pi-N scattering lengths from pionic hydrogen and pionic deuterium data
The pi-N s-wave scattering lengths have been inferred from a joint analysis
of the pionic hydrogen and the pionic deuterium x-ray data using a
non-relativistic approach in which the pi-N interaction is simulated by a
short-ranged potential. The pi-d scattering length has been calculated exactly
by solving the Faddeev equations and also by using a static approximation. It
has been shown that the same very accurate static formula for pi-d scattering
length can be derived (i) from a set of boundary conditions; (ii) by a
reduction of Faddeev equations; and (iii) through a summation of Feynman
diagrams. By imposing the requirement that the pi-d scattering length,
resulting from Faddeev-type calculation, be in agreement with pionic deuterium
data, we obtain bounds on the pi-N scattering lengths. The dominant source of
uncertainty on the deduced values of the pi-N scattering lengths are the
experimental errors in the pionic hydrogen data.Comment: RevTeX, 20 pages,4 PostScript figure
Towards a high precision calculation for the pion-nucleus scattering lengths
We calculate the leading isospin conserving few-nucleon contributions to pion
scattering on H, He, and He. We demonstrate that the strong
contributions to the pion-nucleus scattering lengths can be controlled
theoretically to an accuracy of a few percent for isoscalar nuclei and of 10%
for isovector nuclei. In particular, we find the -He scattering length
to be where the uncertainties are
due to ambiguities in the -N scattering lengths and few-nucleon effects,
respectively. To establish this accuracy we need to identify a suitable power
counting for pion-nucleus scattering. For this purpose we study the dependence
of the two-nucleon contributions to the scattering length on the binding energy
of H. Furthermore, we investigate the relative size of the leading two-,
three-, and four-nucleon contributions. For the numerical evaluation of the
pertinent integrals, aMonte Carlo method suitable for momentum space is
devised. Our results show that in general the power counting suggested by
Weinberg is capable to properly predict the relative importance of -nucleon
operators, however, it fails to capture the relative strength of - and
-nucleon operators, where we find a suppression by a factor of 5
compared to the predicted factor of 50. The relevance for the extraction of the
isoscalar -N scattering length from pionic H and He is discussed.
As a side result, we show that beyond the calculation of the -H
scattering length is already beyond the range of applicability of heavy pion
effective field theory.Comment: 24 pages, 14 figures, 10 table
Chiral unitary approach to S-wave meson baryon scattering in the strangeness S=0 sector
We study the S-wave interaction of mesons with baryons in the strangeness S=0
sector in a coupled channel unitary approach. The basic dynamics is drawn from
the lowest order meson baryon chiral Lagrangians. Small modifications inspired
by models with explicit vector meson exchange in the t-channel are also
considered. In addition the pi pi N channel is included and shown to have an
important repercussion in the results, particularly in the isospin 3/2 sector.Comment: 23 pages, LaTeX, 21 figure
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
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