1,351 research outputs found
Grand unification through gravitational effects
We systematically study the unification of gauge couplings in the presence of
(one or more) effective dimension-5 operators cHGG/4MPl, induced into the grand
unified theory by gravitational interactions at the Planck scale MPl. These
operators alter the usual condition for gauge coupling unification, which can,
depending on the Higgs content H and vacuum expectation value, result in
unification at scales MX significantly different than naively expected. We find
non-supersymmetric models of SU(5) and SO(10) unification, with natural Wilson
coefficients c, that easily satisfy the constraints from proton decay.
Furthermore, gauge coupling unification at scales as high as the Planck scale
seems feasible, possibly hinting at simultaneous unification of gauge and
gravitational interactions. In the Appendix we work out the group theoretical
aspects of this scenario for SU(5) and SO(10) unified groups in detail; this
material is also relevant in the analysis of non-universal gaugino masses
obtained from supergravity.Comment: 27 pages, 5 figures, 8 tables, 1 appendix, revtex; v2: introduction
and conclusion expanded, references added, minor changes, version published
in PR
New Production Mechanism of Neutral Higgs Bosons with Right scalar tau neutrino as the LSP
Motived by the neutrino oscillation data, we consider the lightest tau
sneutrino (which is mostly the right tau sneutrino) to be
the lightest supersymmetric particle (LSP) in the framework of the minimal
supersymmetric Standard Model. Both the standard and the non-standard trilinear
scalar coupling terms are included for the right tau sneutrino interactions.
The decay branching ratio of
can become so large that the production rate of the lightest neutral Higgs
boson () can be largely enhanced at electron or hadron colliders, either
from the direct production of or from the decay of
charginos, neutralinos, sleptons, and the cascade decay of squarks and gluinos,
etc. Furthermore, because of the small LSP annihilation rate, can be a good candidate for cold dark matter.Comment: 11 pages, RevTex, 3 eps figures. We clarify the theoretical framework
of this study, with a note added in the end, and correct an equation, with
updated figure
Fine-tuning the functional properties of carbon nanotubes via the interconversion of encapsulated molecules
Tweaking the properties of carbon nanotubes is a prerequisite for their
practical applications. Here we demonstrate fine-tuning the electronic
properties of single-wall carbon nanotubes via filling with ferrocene
molecules. The evolution of the bonding and charge transfer within the tube is
demonstrated via chemical reaction of the ferrocene filler ending up as
secondary inner tube. The charge transfer nature is interpreted well within
density functional theory. This work gives the first direct observation of a
fine-tuned continuous amphoteric doping of single-wall carbon nanotubes
Novas neuroterapĂȘuticas em psiquiatria: racional e uso da estimulação transcraniana por corrente contĂnua no transtorno depressivo maior
Background : Transcranial direct current stimulation (tDCS) is a novel non-pharmacological intervention being investigated for the treatment of major depressive disorder (MDD). Objective : To perform an updated review of tDCS for MDD. Method : Systematic review in Medline/PubMed and other databases of all clinical studies evaluating the clinical efficacy of tDCS in MDD, from the first date available to December/2013. Results : Out of 55 articles, 24 were included, being 6 open-label studies; 8 randomized, double-blind, sham-controlled trials; 2 follow-up studies; 2 meta-analyses and 6 case reports. We observed an improvement of 20-40% in depressive symptoms, being slightly better in open studies. Five randomized clinical trials displayed positive results. The meta-analyses presented mixed results; although none included the study of Brunoni et al. (2013) that represents almost 50% of the evaluated sample. Open-label studies and case reports also investigated tDCS in bipolar depression, post-stroke depression and employed different parameters of stimulation. Discussion : TDCS is a novel, promising treatment for MDD. Definite evidence from large, ongoing clinical trials will be available in the next years.Contexto : A estimulação transcraniana por corrente contĂnua (ETCC) Ă© uma nova intervenção nĂŁo farmacolĂłgica investigada como tratamento no transtorno depressivo maior (TDM). Objetivo : Apresentar uma revisĂŁo atualizada da ETCC no TDM. MĂ©todo : RevisĂŁo sistemĂĄtica no banco de dados Medline/PubMed e outros de todos os estudos clĂnicos publicados avaliando a eficĂĄcia da ETCC no TDM, da primeira data disponĂvel a dezembro/2013. Resultados : De 55 artigos, 24 foram incluĂdos, sendo 6 estudos abertos; 8 ensaios clĂnicos randomizados, duplo-cego, placebo controlados; 2 estudos de seguimento; 2 metanĂĄlises e 6 relatos de caso. Observa-se uma melhora de 20-40% nos sintomas depressivos, sendo ligeiramente maior nos estudos abertos. Entre os ensaios controlados, 5 demonstraram eficĂĄcia da tĂ©cnica. As metanĂĄlises divergiram quanto aos resultados, mostrando presença e ausĂȘncia de eficĂĄcia e ausĂȘncia da ETCC. PorĂ©m, nenhuma incluiu o estudo de Brunoni et al. (2013), que representa quase 50% da população estudada. Estudos abertos e relatos de caso tambĂ©m investigaram o uso da ETCC na depressĂŁo bipolar, na depressĂŁo pĂłs-AVC e usaram variaçÔes nos parĂąmetros de estimulação. ConclusĂ”es : A ETCC Ă© uma tĂ©cnica promissora no tratamento da TDM. EvidĂȘncias definitivas devem estar disponĂveis nos prĂłximos anos, com a divulgação de resultados de grandes ensaios clĂnicos em andamento
Tight--binding description of the quasiparticle dispersion of graphite and few--layer graphene
A universal set of third--nearest neighbour tight--binding (TB) parameters is
presented for calculation of the quasiparticle (QP) dispersion of stacked
graphene layers () with stacking sequence. The QP
bands are strongly renormalized by electron--electron interactions which
results in a 20% increase of the nearest neighbour in--plane and out--of--plane
TB parameters when compared to band structure from density functional theory.
With the new set of TB parameters we determine the Fermi surface and evaluate
exciton energies, charge carrier plasmon frequencies and the conductivities
which are relevant for recent angle--resolved photoemission, optical, electron
energy loss and transport measurements. A comparision of these quantitities to
experiments yields an excellent agreement. Furthermore we discuss the
transition from few layer graphene to graphite and a semimetal to metal
transition in a TB framework.Comment: Corresponding author: A. Gr\"uneis Tel.: +49 351 4659 519 e--mail:
[email protected]
Clinical efficacy of long-acting neuraminidase inhibitor, laninamivir octanoate hydrate, in postmarketing surveillance
On the complementarity of Hyper-K and LBNF
The next generation of long-baseline experiments is being designed to make a
substantial step in the precision of measurements of neutrino-oscillation
probabilities. Two qualitatively different proposals, Hyper-K and LBNF, are
being considered for approval. This document outlines the complimentarity
between Hyper-K and LBNF.Comment: 5 pager
Initial report from the ICFA Neutrino Panel
In July 2013 ICFA established the Neutrino Panel with the mandate "To promote
international cooperation in the development of the accelerator-based
neutrino-oscillation program and to promote international collaboration in the
development a neutrino factory as a future intense source of neutrinos for
particle physics experiments". This, the Panel's Initial Report, presents the
conclusions drawn by the Panel from three regional "Town Meetings" that took
place between November 2013 and February 2014.
After a brief introduction and a short summary of the status of the knowledge
of the oscillation parameters, the report summarises the approved programme and
identifies opportunities for the development of the field. In its conclusions,
the Panel recognises that to maximise the discovery potential of the
accelerator-based neutrino-oscillation programme it will be essential to
exploit the infrastructures that exist at CERN, FNAL and J-PARC and the
expertise and resources that reside in laboratories and institutes around the
world. Therefore, in its second year, the Panel will consult with the
accelerator-based neutrino-oscillation community and its stakeholders to:
develop a road-map for the future accelerator-based neutrino-oscillation
programme that exploits the ambitions articulated at CERN, FNAL and J-PARC and
includes the programme of measurement and test-beam exposure necessary to
ensure the programme is able to realise its potential; develop a proposal for a
coordinated "Neutrino RD" programme, the accelerator and detector R&D programme
required to underpin the next generation of experiments; and to explore the
opportunities for the international collaboration necessary to realise the
Neutrino Factory.Comment: ICFA Neutrino Panel 2014(01
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