637 research outputs found
Surface and electronic structure of MOCVD-grown Ga(0.92)In(0.08)N investigated by UV and X-ray photoelectron spectroscopies
The surface and electronic structure of MOCVD-grown layers of
Ga(0.92)In(0.08)N have been investigated by means of photoemission. An
additional feature at the valence band edge, which can be ascribed to the
presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface
was prepared by argon ion sputtering and annealing. Stability of chemical
composition of the investigated surface subjected to similar ion etching was
proven by means of X-ray photoemission spectroscopy.Comment: 13 pages, 6 figure
Generalized glycogen storage and cardiomegaly in a knockout mouse model of Pompe disease
Glycogen storage disease type II (GSDII; Pompe disease), caused by
inherited deficiency of acid alpha-glucosidase, is a lysosomal disorder
affecting heart and skeletal muscles. A mouse model of this disease was
obtained by targeted disruption of the murine acid alpha-glucosidase gene
(Gaa) in embryonic stem cells. Homozygous knockout mice (Gaa -/-) lack Gaa
mRNA and have a virtually complete acid alpha-glucosidase deficiency.
Glycogen-containing lysosomes are detected soon after birth in liver,
heart and skeletal muscle cells. By 13 weeks of age, large focal deposits
of glycogen have formed. Vacuolar spaces stain positive for acid
phosphatase as a sign of lysosomal pathology. Both male and female
knockout mice are fertile and can be intercrossed to produce progeny. The
first born knockout mice are at present 9 months old. Overt clinical
symptoms are still absent, but the heart is typically enlarged and the
electrocardiogram is abnormal. The mouse model will help greatly to
understand the pathogenic mechanism of GSDII and is a valuable instrument
to explore the efficacy of different therapeutic interventions
Markov Properties of Electrical Discharge Current Fluctuations in Plasma
Using the Markovian method, we study the stochastic nature of electrical
discharge current fluctuations in the Helium plasma. Sinusoidal trends are
extracted from the data set by the Fourier-Detrended Fluctuation analysis and
consequently cleaned data is retrieved. We determine the Markov time scale of
the detrended data set by using likelihood analysis. We also estimate the
Kramers-Moyal's coefficients of the discharge current fluctuations and derive
the corresponding Fokker-Planck equation. In addition, the obtained Langevin
equation enables us to reconstruct discharge time series with similar
statistical properties compared with the observed in the experiment. We also
provide an exact decomposition of temporal correlation function by using
Kramers-Moyal's coefficients. We show that for the stationary time series, the
two point temporal correlation function has an exponential decaying behavior
with a characteristic correlation time scale. Our results confirm that, there
is no definite relation between correlation and Markov time scales. However
both of them behave as monotonic increasing function of discharge current
intensity. Finally to complete our analysis, the multifractal behavior of
reconstructed time series using its Keramers-Moyal's coefficients and original
data set are investigated. Extended self similarity analysis demonstrates that
fluctuations in our experimental setup deviates from Kolmogorov (K41) theory
for fully developed turbulence regime.Comment: 25 pages, 9 figures and 4 tables. V3: Added comments, references,
figures and major correction
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
Analysis of the X(1835) and related baryonium states with Bethe-Salpeter equation
In this article, we study the mass spectrum of the baryon-antibaryon bound
states , , ,
, , ,
and with the Bethe-Salpeter
equation. The numerical results indicate that the ,
, , ,
, bound states maybe exist, and
the new resonances X(1835) and X(2370) can be tentatively identified as the
and (or ) bound states respectively
with some gluon constituents, and the new resonance X(2120) may be a
pseudoscalar glueball. On the other hand, the Regge trajectory favors
identifying the X(1835), X(2120) and X(2370) as the excited
mesons with the radial quantum numbers , 4 and 5, respectively.Comment: 13 pages, 2 figures, revise a numbe
Is X(3872) {\sl Really} a Molecular State?
After taking into account both the pion and sigma meson exchange potential,
we have performed a dynamical calculation of the system.
The meson exchange potential is repulsive from heavy quark symmetry
and numerically important for a loosely bound system. Our analysis disfavors
the interpretation of X(3872) as a loosely bound molecular state if we use the
experimental coupling constant and a reasonable cutoff
around 1 GeV, which is the typical hadronic scale. Bound state solutions with
negative eigenvalues for the system exist only with either a
very large coupling constant (two times of the experimental value) or a large
cutoff ( GeV or GeV). In contrast, there
probably exists a loosely bound S-wave molecular state. Once
produced, such a molecular state would be rather stable since its dominant
decay mode is the radiative decay through . Experimental
search of these states will be very interesting.Comment: 11 pages, 7 figures, 9 tables. The version to appear in EPJ
Heavy-flavor production and medium properties in high-energy nuclear collisions --What next?
Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma
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