1,468 research outputs found
Shape-resonant superconductivity in nanofilms: from weak to strong coupling
Ultrathin superconductors of different materials are becoming a powerful
platform to find mechanisms for enhancement of superconductivity, exploiting
shape resonances in different superconducting properties. Here we evaluate the
superconducting gap and its spatial profile, the multiple gap components, and
the chemical potential, of generic superconducting nanofilms, considering the
pairing attraction and its energy scale as tunable parameters, from weak to
strong coupling, at fixed electron density. Superconducting properties are
evaluated at mean field level as a function of the thickness of the nanofilm,
in order to characterize the shape resonances in the superconducting gap. We
find that the most pronounced shape resonances are generated for weakly coupled
superconductors, while approaching the strong coupling regime the shape
resonances are rounded by a mixing of the subbands due to the large energy gaps
extending over large energy scales. Finally, we find that the spatial profile,
transverse to the nanofilm, of the superconducting gap acquires a flat behavior
in the shape resonance region, indicating that a robust and uniform multigap
superconducting state can arise at resonance.Comment: 7 pages, 4 figures. Submitted to the Proceedings of the Superstripes
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Toward Establishing Integrated, Comprehensive, and Sustainable Meningitis Surveillance in Africa to Better Inform Vaccination Strategies
Large populations across sub-Saharan Africa remain at risk of devastating acute bacterial meningitis epidemics and endemic disease. Meningitis surveillance is a cornerstone of disease control, essential for describing temporal changes in disease epidemiology, the rapid detection of outbreaks, guiding vaccine introduction and monitoring vaccine impact. However, meningitis surveillance in most African countries is weak, undermined by parallel surveillance systems with little to no synergy and limited laboratory capacity. African countries need to implement comprehensive meningitis surveillance systems to adapt to the rapidly changing disease trends and vaccine landscapes. The World Health Organization and partners have developed a new investment case to restructure vaccine-preventable disease surveillance. With this new structure, countries will establish comprehensive and sustainable meningitis surveillance systems integrated with greater harmonization between population-based and sentinel surveillance systems. There will also be stronger linkage with existing surveillance systems for vaccine-preventable diseases, such as polio, measles, yellow fever, and rotavirus, as well as with other epidemic-prone diseases to leverage their infrastructure, transport systems, equipment, human resources and funding. The implementation of these concepts is currently being piloted in a few countries in sub-Saharan Africa with support from the World Health Organization and other partners. African countries need to take urgent action to improve synergies and coordination between different surveillance systems to set joint priorities that will inform action to control devastating acute bacterial meningitis effectively
Recent trends in molecular diagnostics of yeast infections : from PCR to NGS
The incidence of opportunistic yeast infections in humans has been increasing over recent years. These infections are difficult to treat and diagnose, in part due to the large number and broad diversity of species that can underlie the infection. In addition, resistance to one or several antifungal drugs in infecting strains is increasingly being reported, severely limiting therapeutic options and showcasing the need for rapid detection of the infecting agent and its drug susceptibility profile. Current methods for species and resistance identification lack satisfactory sensitivity and specificity, and often require prior culturing of the infecting agent, which delays diagnosis. Recently developed high-throughput technologies such as next generation sequencing or proteomics are opening completely new avenues for more sensitive, accurate and fast diagnosis of yeast pathogens. These approaches are the focus of intensive research, but translation into the clinics requires overcoming important challenges. In this review, we provide an overview of existing and recently emerged approaches that can be used in the identification of yeast pathogens and their drug resistance profiles. Throughout the text we highlight the advantages and disadvantages of each methodology and discuss the most promising developments in their path from bench to bedside
Heavy Quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature
We calculate the heavy quarkonium energy levels and decay widths in a
quark-gluon plasma, whose temperature T and screening mass m_D satisfy the
hierarchy m alpha_s >> T >> m alpha_s^2 >> m_D (m being the heavy-quark mass),
at order m alpha_s^5. We first sequentially integrate out the scales m, m
alpha_s and T, and, next, we carry out the calculations in the resulting
effective theory using techniques of integration by regions. A collinear region
is identified, which contributes at this order. We also discuss the
implications of our results concerning heavy quarkonium suppression in heavy
ion collisions.Comment: 25 pages, 2 figure
Interfacing External Quantum Devices to a Universal Quantum Computer
We present a scheme to use external quantum devices using the universal quantum computer previously constructed. We thereby show how the universal quantum computer can utilize networked quantum information resources to carry out local computations. Such information may come from specialized quantum devices or even from remote universal quantum computers. We show how to accomplish this by devising universal quantum computer programs that implement well known oracle based quantum algorithms, namely the Deutsch, Deutsch-Jozsa, and the Grover algorithms using external black-box quantum oracle devices. In the process, we demonstrate a method to map existing quantum algorithms onto the universal quantum computer
Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2.
Transition metal dichalcogenides (TMDs) are emerging as promising two-dimensional (2D) semiconductors for optoelectronic and flexible devices. However, a microscopic explanation of their photophysics, of pivotal importance for the understanding and optimization of device operation, is still lacking. Here, we use femtosecond transient absorption spectroscopy, with pump pulse tunability and broadband probing, to monitor the relaxation dynamics of single-layer MoS2 over the entire visible range, upon photoexcitation of different excitonic transitions. We find that, irrespective of excitation photon energy, the transient absorption spectrum shows the simultaneous bleaching of all excitonic transitions and corresponding red-shifted photoinduced absorption bands. First-principle modeling of the ultrafast optical response reveals that a transient bandgap renormalization, caused by the presence of photoexcited carriers, is primarily responsible for the observed features. Our results demonstrate the strong impact of many-body effects in the transient optical response of TMDs even in the low-excitation-density regime
Revisiting the S-matrix approach to the open superstring low energy effective lagrangian
The conventional S-matrix approach to the (tree level) open string low energy
effective lagrangian assumes that, in order to obtain all its bosonic
order terms, it is necessary to know the open string (tree level)
-point amplitude of massless bosons, at least expanded at that order in
. In this work we clarify that the previous claim is indeed valid for
the bosonic open string, but for the supersymmetric one the situation is much
more better than that: there are constraints in the kinematical bosonic terms
of the amplitude (probably due to Spacetime Supersymmetry) such that a much
lower open superstring -point amplitude is needed to find all the
order terms. In this `revisited' S-matrix approach we have
checked that, at least up to order, using these kinematical
constraints and only the known open superstring 4-point amplitude, it is
possible to determine all the bosonic terms of the low energy effective
lagrangian. The sort of results that we obtain seem to agree completely with
the ones achieved by the method of BPS configurations, proposed about ten years
ago. By means of the KLT relations, our results can be mapped to the NS-NS
sector of the low energy effective lagrangian of the type II string theories
implying that there one can also find kinematical constraints in the -point
amplitudes and that important informations can be inferred, at least up to
order, by only using the (tree level) 4-point amplitude.Comment: 34 pages, 3 figure, Submitted on Aug 4, 2012, Published on Oct 15,
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