574 research outputs found
A life cycle assessment of the construction phase of eleven micro-hydropower installations in the UK
Crossover between ionic/covalent and pure ionic bonding in magnesium oxyde clusters
An empirical potential with fluctuating charges is proposed for modelling
(MgO)_n clusters in both the molecular (small n) and bulk (n->infty) regimes.
Vectorial polarization forces are explicitely taken into account in the
self-consistent determination of the charges. Our model predicts cuboid cluster
structures, in agreement with previous experimental and theoretical results.
The effective charge transferred between magnesium and oxygen smoothly
increases from 1 to 2, with an estimated crossover size above 300 MgO
molecules
Distinguishing Among Strong Decay Models
Two competing models for strong hadronic decays, the and
models, are currently in use.
Attempts to rule out one or the other have been hindered by a poor
understanding of final state interactions and by ambiguities in the treatment
of relativistic effects.
In this article we study meson decays in both models, focussing on certain
amplitude ratios for which the relativistic uncertainties largely cancel out
(notably the ratios in and
), and using a Quark Born Formalism to estimate the
final state interactions.
We find that the model is strongly favoured.
In addition, we predict a amplitude ratio of for the decay
.
We also study the parameter-dependence of some individual amplitudes (as
opposed to amplitude ratios), in an attempt to identify a ``best'' version of
the model.Comment: 20 pages, uuencoded postscript file with 7 figures, MIT-CTP-2295;
CMU-HEP94-1
State sampling dependence of the Hopfield network inference
The fully connected Hopfield network is inferred based on observed
magnetizations and pairwise correlations. We present the system in the glassy
phase with low temperature and high memory load. We find that the inference
error is very sensitive to the form of state sampling. When a single state is
sampled to compute magnetizations and correlations, the inference error is
almost indistinguishable irrespective of the sampled state. However, the error
can be greatly reduced if the data is collected with state transitions. Our
result holds for different disorder samples and accounts for the previously
observed large fluctuations of inference error at low temperatures.Comment: 4 pages, 1 figure, further discussions added and relevant references
adde
The newly observed open-charm states in quark model
Comparing the measured properties of the newly observed open-charm states
D(2550), D(2600), D(2750), D(2760), D_{s1}(2710), D_{sJ}(2860), and
D_{sJ}(3040) with our predicted spectroscopy and strong decays in a constituent
quark model, we find that: (1) the D(2\,^1S_0) assignment to D(2550) remains
open for its too broad width determined by experiment; (2) the D(2600) and
can be identified as the 2\,^3S_1-1\,^3D_1 mixtures; (3) if
the D(2760) and D(2750) are indeed the same resonance, they would be the
D(1\,^3D_3); otherwise, they could be assigned as the D(1\,^3D_3) and
, respectively; (4) the could be either the
's partner or the D_s(1\,^3D_3); and (5) both the
and interpretations for the seem likely. The
and radiative decays of these sates are also studied. Further
experimental efforts are needed to test the present quarkonium assignments for
these new open-charm states.Comment: 26 pages,7 figures, journal versio
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
Measurement of the Nucleon Structure Function F2 in the Nuclear Medium and Evaluation of its Moments
We report on the measurement of inclusive electron scattering off a carbon
target performed with CLAS at Jefferson Laboratory. A combination of three
different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an
invariant mass of the final-state hadronic system W~2.4 GeV with four-momentum
transfers Q2 ranging from 0.2 to 5 GeV2. These data, together with previous
measurements of the inclusive electron scattering off proton and deuteron,
which cover a similar continuous two-dimensional region of Q2 and Bjorken
variable x, permit the study of nuclear modifications of the nucleon structure.
By using these, as well as other world data, we evaluated the F2 structure
function and its moments. Using an OPE-based twist expansion, we studied the
Q2-evolution of the moments, obtaining a separation of the leading-twist and
the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist
contributions to the F2 moments exhibits the well known EMC effect, compatible
with that discovered previously in x-space. The total higher-twist term in the
carbon nucleus appears, although with large systematic uncertainites, to be
smaller with respect to the deuteron case for n<7, suggesting partial parton
deconfinement in nuclear matter. We speculate that the spatial extension of the
nucleon is changed when it is immersed in the nuclear medium.Comment: 37 pages, 15 figure
Cells and gene expression programs in the adult human heart
Cardiovascular disease is the leading cause of death worldwide. Advanced insights into disease mechanisms and strategies to improve therapeutic opportunities require deeper understanding of the molecular processes of the normal heart. Knowledge of the full repertoire of cardiac cells and their gene expression profiles is a fundamental first step in this endeavor. Here, using large-scale single cell and nuclei transcriptomic profiling together with state-of-the-art analytical techniques, we characterise the adult human heart cellular landscape covering six anatomical cardiac regions (left and right atria and ventricles, apex and interventricular septum). Our results highlight the cellular heterogeneity of cardiomyocytes, pericytes and fibroblasts, revealing distinct subsets in the atria and ventricles indicative of diverse developmental origins and specialized properties. Further we define the complexity of the cardiac vascular network which includes clusters of arterial, capillary, venous, lymphatic endothelial cells and an atrial-enriched population. By comparing cardiac cells to skeletal muscle and kidney, we identify cardiac tissue resident macrophage subsets with transcriptional signatures indicative of both inflammatory and reparative phenotypes. Further, inference of cell-cell interactions highlight a macrophage-fibroblast-cardiomyocyte network that differs between atria and ventricles, and compared to skeletal muscle. We expect this reference human cardiac cell atlas to advance mechanistic studies of heart homeostasis and disease
Collective perspective on advances in Dyson-Schwinger Equation QCD
We survey contemporary studies of hadrons and strongly interacting quarks
using QCD's Dyson-Schwinger equations, addressing: aspects of confinement and
dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and
transition form factors, from small- to large-Q^2; parton distribution
functions; the physics of hadrons containing one or more heavy quarks; and
properties of the quark gluon plasma.Comment: 56 pages. Summary of lectures delivered by the authors at the
"Workshop on AdS/CFT and Novel Approaches to Hadron and Heavy Ion Physics,"
2010-10-11 to 2010-12-03, hosted by the Kavli Institute for Theoretical
Physics, China, at the Chinese Academy of Science
Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments
Inclusive electron scattering off the deuteron has been measured to extract
the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer
(CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement
covers the entire resonance region from the quasi-elastic peak up to the
invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum
transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous
measurements of the proton structure function F2 and cover a similar
two-dimensional region of Q2 and Bjorken variable x. Determination of the
deuteron F2 over a large x interval including the quasi-elastic peak as a
function of Q2, together with the other world data, permit a direct evaluation
of the structure function moments for the first time. By fitting the Q2
evolution of these moments with an OPE-based twist expansion we have obtained a
separation of the leading twist and higher twist terms. The observed Q2
behaviour of the higher twist contribution suggests a partial cancellation of
different higher twists entering into the expansion with opposite signs. This
cancellation, found also in the proton moments, is a manifestation of the
"duality" phenomenon in the F2 structure function
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