57 research outputs found
CaloCube: a novel calorimeter for high-energy cosmic rays in space
In order to extend the direct observation of high-energy cosmic rays up to
the PeV region, highly performing calorimeters with large geometrical
acceptance and high energy resolution are required. Within the constraint of
the total mass of the apparatus, crucial for a space mission, the calorimeters
must be optimized with respect to their geometrical acceptance, granularity and
absorption depth. CaloCube is a homogeneous calorimeter with cubic geometry, to
maximise the acceptance being sensitive to particles from every direction in
space; granularity is obtained by relying on small cubic scintillating crystals
as active elements. Different scintillating materials have been studied. The
crystal sizes and spacing among them have been optimized with respect to the
energy resolution. A prototype, based on CsI(Tl) cubic crystals, has been
constructed and tested with particle beams. Some results of tests with
different beams at CERN are presented.Comment: Seven pages, seven pictures. Proceedings of INSTR17 Novosibirs
Effects of Boson Dispersion in Fermion-Boson Coupled Systems
We study the nonlinear feedback in a fermion-boson system using an extension
of dynamical mean-field theory and the quantum Monte Carlo method. In the
perturbative regimes (weak-coupling and atomic limits) the effective
interaction among fermions increases as the width of the boson dispersion
increases. In the strong coupling regime away from the anti-adiabatic limit,
the effective interaction decreases as we increase the width of the boson
dispersion. This behavior is closely related with complete softening of the
boson field. We elucidate the parameters that control this nonperturbative
region where fluctuations of the dispersive bosons enhance the delocalization
of fermions.Comment: 14 pages RevTeX including 12 PS figure
Island phases and charge order in two-dimensional manganites
The ferromagnetic Kondo lattice model with an antiferromagnetic interaction
between localized spins is a minimal description of the competing kinetic t and
magnetic K energy terms which generate the rich physics of manganite systems.
Motivated by the discovery in one dimension of homogeneous ``island phases'',
we consider the possibility of analogous phases in higher dimensions. We
characterize the phases present at commensurate fillings, and consider in
detail the effects of phase separation in all filling and parameter regimes. We
deduce that island and flux phases are stable for intermediate values of K/t at
the commensurate fillings n = 1/4, 1/3, 3/8, and 1/2. We discuss the connection
of these results to the charge and magnetic ordering observed in a wide variety
of manganite compounds.Comment: 13 pages, 17 figure
Lattice anisotropy as microscopic origin of static stripes in cuprates
Structural distortions in cuprate materials offer a microscopic origin for
anisotropies in electron transport in the basal plane. Using a real-space
Hartree-Fock approach, we consider the ground states of the anisotropic Hubbard
(t_x \ne t_y) and t-J (t_x \ne t_y, J_x \ne J_y) models. Symmetrical but
inhomogeneous (``polaronic'') charge structures in the isotropic models are
altered even by rather small anisotropies to one-dimensional, stripe-like
features. We find two distinct types of stripe, namely uniformly filled,
antiphase domain walls and non-uniform, half-filled, in-phase ones. We
characterize their properties, energies and dependence on the model parameters,
including filling and anisotropy in t (and J). We discuss the connections among
these results, other theoretical studies and experimental observation.Comment: 18 pages, 16 figures, 8 table
Follow-up assessment of high-risk newborns in Switzerland
Target population High-risk newborns in the context of these
guidelines are children who were born very preterm (before 32 weeks gestational age) or children who developed a ypoxic ischaemic encephalopathy (Sarnat grade 2–3) during the first hours of life
High-Tc Superconductivity and Antiferromagnetism in Multilayered Copper Oxides - A New Paradigm of Superconducting Mechanism -
High-temperature superconductivity (HTSC) in copper oxides emerges on a
layered CuO2 plane when an antiferromagnetic Mott insulator is doped with
mobile hole carriers. We review extensive studies of multilayered copper oxides
by site-selective nuclear magnetic resonance (NMR), which have uncovered the
intrinsic phase diagram of antiferromagnetism (AFM) and HTSC for a
disorder-free CuO2 plane with hole carriers. We present our experimental
findings such as the existence of the AFM metallic state in doped Mott
insulators, the uniformly mixed phase of AFM and HTSC, and the emergence of
d-wave SC with a maximum Tc just outside a critical carrier density, at which
the AFM moment on a CuO2 plane disappears. These results can be accounted for
by the Mott physics based on the t-J model. The superexchange interaction J_in
among spins plays a vital role as a glue for Cooper pairs or mobile
spin-singlet pairs, in contrast to the phonon-mediated attractive interaction
among electrons established in the Bardeen-Cooper-Schrieffer (BCS) theory. We
remark that the attractive interaction for raising the of HTSC up to
temperatures as high as 160 K is the large J_in (~0.12 eV), which binds
electrons of opposite spins to be on neighboring sites, and that there are no
bosonic glues. It is the Coulomb repulsive interaction U(> 6 eV) among Cu-3d
electrons that plays a central role in the physics behind high-Tc phenomena. A
new paradigm of the SC mechanism opens to strongly correlated electron matter.Comment: 20 pages, 25 figures, Special topics "Recent Developments in
Superconductivity" in J. Phys. Soc. Jpn., Published December 26, 201
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
Rate , correlates and outcomes of repeat pregnancy in HIV-infected women
Objectives: The aim of the study was to assess the rate, determinants, and outcomes of repeat pregnancies in women with HIV infection. Methods: Data from a national study of pregnant women with HIV infection were used. Main outcomes were preterm delivery, low birth weight, CD4 cell count and HIV plasma viral load. Results: The rate of repeat pregnancy among 3007 women was 16.2%. Women with a repeat pregnancy were on average younger than those with a single pregnancy (median age 30 vs. 33 years, respectively), more recently diagnosed with HIV infection (median time since diagnosis 25 vs. 51 months, respectively), and more frequently of foreign origin [odds ratio (OR) 1.36; 95% confidence interval (CI) 1.10–1.68], diagnosed with HIV infection in the current pregnancy (OR: 1.69; 95% CI: 1.35–2.11), and at their first pregnancy (OR: 1.33; 95% CI: 1.06–1.66). In women with sequential pregnancies, compared with the first pregnancy, several outcomes showed a significant improvement in the second pregnancy, with a higher rate of antiretroviral treatment at conception (39.0 vs. 65.4%, respectively), better median maternal weight at the start of pregnancy (60 vs. 61 kg, respectively), a higher rate of end-of-pregnancy undetectable HIV RNA (60.7 vs. 71.6%, respectively), a higher median birth weight (2815 vs. 2885 g, respectively), lower rates of preterm delivery (23.0 vs. 17.7%, respectively) and of low birth weight (23.4 vs. 15.4%, respectively), and a higher median CD4 cell count (+47 cells/μL), with almost no clinical progression to Centers for Disease Control and Prevention stage C (CDC-C) HIV disease (0.3%). The second pregnancy was significantly more likely to end in voluntary termination than the first pregnancy (11.4 vs. 6.1%, respectively). Conclusions: Younger and foreign women were more likely to have a repeat pregnancy; in women with sequential pregnancies, the second pregnancy was characterized by a significant improvement in several outcomes, suggesting that women with HIV infection who desire multiple children may proceed safely and confidently with subsequent pregnancies
Good prenatal detection rate of major birth defects in HIV-infected pregnant women in Italy
What's already known about this topic? Exposure to antiretroviral treatment in pregnancy does not seem to increase the risk of birth defects, but there is no information on the rate of prenatal detection of such defects. What does this study adds? We provide for the first time, in a national case series, information about prenatal detection rate in women with HIV (51.6% for any major defect, 66.7% for chromosomal abnormalities, and 85% for severe structural defect
Methanogens, sulphate and heavy metals: a complex system
Anaerobic digestion (AD) is a well-established technology used for the treatment of wastes and wastewaters with high organic content. During AD organic matter is converted stepwise to methane-containing biogasa renewable energy carrier. Methane production occurs in the last AD step and relies on methanogens, which are rather sensitive to some contaminants commonly found in wastewaters (e.g. heavy metals), or easily outcompeted by other groups of microorganisms (e.g. sulphate reducing bacteria, SRB). This review gives an overview of previous research and pilot-scale studies that shed some light on the effects of sulphate and heavy metals on methanogenesis. Despite the numerous studies on this subject, comparison is not always possible due to differences in the experimental conditions used and parameters explained. An overview of the possible benefits of methanogens and SRB co-habitation is also covered. Small amounts of sulphide produced by SRB can precipitate with metals, neutralising the negative effects of sulphide accumulation and free heavy metals on methanogenesis. Knowledge on how to untangle and balance sulphate reduction and methanogenesis is crucial to take advantage of the potential for the utilisation of biogenic sulphide as a metal detoxification agent with minimal loss in methane production in anaerobic digesters.The research was financially supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013 under REA agreement 289193
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