823 research outputs found
An Analysis of the Vascular Flora of Annapolis Heathlands, Nova Scotia
A description and analysis of the vascular plant composition of heathlands in the Annapolis valley were undertaken to provide a basis for biodiversity preservation within a system of protected sites. Species presence and abundance were recorded at 23 remnant sites identified using topographic maps, air photos, and Nova Scotia Department of Natural Resources records. A total of 126 species was recorded, of which 94 were native and 31 introduced. The Annapolis heathland remnants are strongly dominated by Corema conradii with Comptonia peregrina, Vaccinium angustifolium and Pteridium aquilinum var. latiusculum. A number of species, including Solidago bicolor, Carex tonsa var. rugosperma, Dichanthelium depauperatum, Lechea intermedia, Melampyrum lineare, and Rubus hispidus, were characteristic of heathland remnants, although they usually contributed little to the total cover. The most frequent alien species were Hieracium pilosella and Festuca filiformis, but Pinus sylvestris, present at 7 of 18 sites, appeared to have the greatest impact in displacing native species. Species listed as at risk and sensitive in Nova Scotia, including Helianthemun canadense, Hudsonia ericoides and Viola sagittata var. ovata, occur in open disturbed sand in the Corema heathlands. Distinctive patterns of variation occur in several species and variation in crop relatives is noted with particular reference to the genera Rubus (blackberries), Amelanchier (Juneberries, Saskatoon) and Vaccinium (Blueberries). The available evidence suggests that the heathlands and sandy barrens in the Annapolis valley differ from those further west in Canada and from anthropogenic and coastal heathlands of Nova Scotia in their species composition including particularly the presence of Corema conradii, Hudsonia ericoides and Amelanchier lucida. The need to protect representative examples is supported
Vector meson photoproduction studied in its radiative decay channel
We provide an analysis of vector meson photoproduction in the channel of the
vector meson decaying into a pseudoscalar meson plus a photon, i.e. . It is shown that non-trivial kinematic correlations arise from the
measurement of the angular distributions in the overall c.m. system
in comparison with those in the vector-meson-rest frame. In terms of the vector
meson density matrix elements, the implication of such kinematic correlations
in the measurement of polarization observables is discussed. For the
meson production, due to its relatively large branching ratios for
, additional events from this channel may enrich the
information about the reaction mechanism and improve the statistics of the
recent measurement of polarized beam asymmetries by the GRAAL Collaboration.
For , , and , we expect
that additional information about the spin structure of the vector meson
production vertex can be derived.Comment: Revtex, 14 pages, 2 eps figures; Version accepted by PR
N-d scattering above the deuteron breakup threshold
The complex Kohn variational principle and the (correlated) Hyperspherical
Harmonics technique are applied to study the N--d scattering above the deuteron
breakup threshold. The configuration with three outgoing nucleons is explicitly
taken into account by solving a set of differential equations with outgoing
boundary conditions. A convenient procedure is used to obtain the correct
boundary conditions at values of the hyperradius fm. The
inclusion of the Coulomb potential is straightforward and does not give
additional difficulties. Numerical results have been obtained for a simple
s-wave central potential. They are in nice agreement with the benchmarks
produced by different groups using the Faddeev technique. Comparisons are also
done with experimental elastic N--d cross section at several energies.Comment: LaTeX, 13 pages, 3 figure
Effects of perturbative exchanges in a QCD-string model
The QCD-string model for baryons derived by Simonov and used for the
calculation of baryon magnetic moments in a previous paper is extended to
include also perturbative gluon and meson exchanges. The mass spectrum of the
baryon multiplet is studied. For the meson interaction either the pseudoscalar
or pseudovector coupling is used. Predictions are compared with the
experimental data. Besides these exchanges the influence of excited quark
orbitals on the baryon ground state are considered by performing a multichannel
calculation. The nucleon-Delta splitting increases due to the mixing of higher
quark states while the baryon magnetic momenta decrease. The multichannel
calculation with perturbative exchanges is shown to yield reasonable magnetic
moments while the mass spectrum is close to experiment.Comment: 37 pages Revtex with 2 figures, to be published in Phys. Atom. Nucl.
dedicated to the 70th Birthday of Yu. A. Simono
Post-Training Reward Partially Restores Chronic Stress Induced Effects in Mice
Reduced responsiveness to positive stimuli is a core symptom of depression, known as anhedonia. In the present study, we assessed the expression of anhedonia in our chronic stress mouse model using a subset of read-out parameters. In line with this, we investigated in how far chronic stress would affect the facilitating effect of post-training self-administration of sugar, as we previously observed in naïve mice. Male C57BL/6J mice were repeatedly and at unpredictable times exposed to rats (no physical contact) over the course of two weeks. Following novelty exploration, (non-) spatial learning and memory processes with and without post-training sugar acting as reinforcer, emotionality, reward sensitivity and corticosterone levels were determined. We found that (1) the effects of chronic stress persisted beyond the period of the actual rat exposure. (2) Post-training self-administration of sugar as reinforcer improved spatial performance in naïve mice, whereas (3) in stressed mice sugar partially “normalized” the impaired performance to the level of controls without sugar. Chronic stress (4) increased behavioral inhibition in response to novelty; (5) induced dynamic changes in the pattern of circadian corticosterone secretion during the first week after rat stress and (6) increased the intake of sucrose and water. (7) Chronic stress and sugar consumed during spatial training facilitated the memory for the location of the sucrose bottle weeks later. Concluding, our chronic stress paradigm induces the expression of anhedonia in mice, at different levels of behavior. The behavioral inhibition appears to be long lasting in stressed mice. Interestingly, sugar consumed in close context with spatial learning partially rescued the stress-induced emotional and cognitive impairments. This suggests that reward can ameliorate part of the negative consequences of chronic stress on memory
Genetic Markers in Long-Term Survivors of Glioblastoma Multiforme
Scope: Genistein from foods or supplements is metabolized by the gut microbiota and the human body, thereby releasingmany different metabolites into systemic circulation. The order of their appearance in plasma and the possible influence of food format are still unknown. This study compared the nutrikinetic profiles of genistein metabolites. Methods and results: In a randomized cross-over trial, 12 healthy young volunteers were administered a single dose of 30mggenistein provided as a genistein tablet, a genistein tablet in low fat milk, and soy milk containing genistein glycosides. A high mass resolution LC-LTQ-Orbitrap FTMS platform detected and quantified in human plasma: free genistein, seven of its phase-II metabolites and 15 gut-derived metabolites. Interestingly, a novel metabolite, genistein-4- glucuronide-7-sulfate (G-4 G7S) was identified. Nutrikinetic analysis using population-based modeling revealed the order of appearance of five genistein phase II metabolites in plasma: (1) genistein-4,7-diglucuronide, (2) genistein-7-sulfate, (3) genistein-4--sulfate-7-glucuronide, (4) genistein-4-glucuronide, and (5) genistein-7-glucuronide, independent of the food matrix. Conclusion: The conjugated genistein metabolites appear in a distinct order in human plasma. The specific early appearance of G-4 ,7-diG suggests a multistep formation process for the mono and hetero genistein conjugates, involving one or two deglucuronidation steps
Brain activation during fear conditioning in humans depends on genetic variations related to functioning of the hypothalamic–pituitary–adrenal axis: first evidence from two independent subsamples
Spin observables of the reactions NN -> DeltaN and pd -> Delta (pp)(1S0) in collinear kinematics
A general formalism for double and triple spin-correlations of the reaction
NN -> DeltaN is developed for the case of collinear kinematics. A complete
polarization experiment allowing to reconstruct all of the four amplitudes
describing this process is suggested. Furthermore, the spin observables of the
inelastic charge-exchange reaction pd -> Delta^0(pp)(1S0) are analyzed in
collinear kinematics within the single pN scattering mechanism involving the
subprocess pn -> Delta^0p. The full set of spin observables related to the
polarization of one or two initial particles and one final particle is obtained
in terms of three invariant amplitudes of the reaction pd -> Delta (pp)(1S0)
and the transition form factor d->(pp)(1S0). A complete polarization experiment
for the reaction pd -> Delta^0(pp)(1S0) is suggested which allows one to
determine three independent combinations of the four amplitudes of the
elementary subprocess NN -> DeltaN.Comment: 12 pages, 1 figur
\pi\pi, K\pi and \pi N potential scattering and a prediction of a narrow \sigma meson resonance
Low energy scattering and bound state properties of the \pi N, \pi\pi and
K\pi systems are studied as coupled channel problems using inversion potentials
of phase shift data. In a first step we apply the potential model to explain
recent measurements of pionic hydrogen shift and width. Secondly, predictions
of the model for pionium lifetime and shift confirm a well known and widely
used effective range expression. Thirdly, as extension of this confirmation, we
predict an unexpected medium effect of the pionium lifetime which shortens by
several orders of magnitude. The \sigma meson shows a narrow resonance
structure as a function of the medium modified mass with the implication of
being essentially energy independent. Similarly, we see this medium resonance
effect realized for the K\pi system. To support our findings we present also
results for the \rho meson and the \Delta(1232) resonance.Comment: 42 pages, 17 PS figures, REFTeX, epsfig.sty needed, submitted to
Phys. Re
Baryon magnetic moments in the effective quark Lagrangian approach
An effective quark Lagrangian is derived from first principles through
bilocal gluon field correlators. It is used to write down equations for
baryons, containing both perturbative and nonperturbative fields. As a result
one obtains magnetic moments of octet and decuplet baryons without introduction
of constituent quark masses and using only string tension as an input. Magnetic
moments come out on average in reasonable agreement with experiment, except for
nucleons and . The predictions for the proton and neutron are shown
to be in close agreement with the empirical values once we choose the string
tension such to yield the proper nucleon mass. Pionic corrections to the
nucleon magnetic moments have been estimated. In particular, the total result
of the two-body current contributions are found to be small. Inclusion of the
anomalous magnetic moment contributions from pion and kaon loops leads to an
improvement of the predictions.Comment: 24 pages Revte
- …