10,248 research outputs found
Low scale B-L extension of the Standard Model at the LHC
The fact that neutrinos are massive indicates that the Standard Model (SM)
requires extension. We propose a low energy (<TeV) B-L extension of the SM,
which is based on the gauge group SU(3)_C x SU(2)_L x U(1)_Y x U(1)_{B-L}. We
show that this model provides a natural explanation for the presence of three
right-handed neutrinos in addition to an extra gauge boson and a new scalar
Higgs. Therefore, it can lead to very interesting phenomenological implications
different from the SM results which can be tested at the LHC. Also we analyze
the muon anomalous magnetic moment in this class of models. We show that
one-loop with exchange Z' may give dominant new contribution ~ few x 10^{-11}.Comment: 12 page
Sterile neutrino dark matter in extension of the standard model and galactic 511 keV line
Sterile right-handed neutrinos can be naturally embedded in a low scale
gauged extension of the standard model. We show that, within a low
reheating scenario, such a neutrino is an interesting candidate for dark
matter. We emphasize that if the neutrino mass is of order of MeV, then it
accounts for the measured dark matter relic density and also accommodates the
observed flux of 511 keV photons from the galactic bulge.Comment: 10 pages, 1 figure, references added, final version appeared in JCA
Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells
In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-is(neopentyloxy)-3-(neopentyloxycarbonyl)- 1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature
process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide
nanowires (TiO2 NWs) and subsequent squeegee method to apply TiO2
NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm2. The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO2 NWs/TiO2 NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually
Plasma-cell-rich infiltrates in paediatric renal transplant biopsies are associated with increased risk of renal allograft failure
BACKGROUND: Increased plasma cell infiltration in renal allograft biopsies is a rare finding associated with poor outcome in adult renal transplant recipients. The clinical impact of increased plasma cell infiltrates in paediatric renal transplant recipients (pRTR) remains unknown. METHODS: We conducted a retrospective case-control study from April 1996 to March 2014 comparing the outcome of pRTR with increased (>10Â % of infiltrate) plasma cells in renal transplant biopsies to a control cohort of pRTR without increased plasma cell infiltration but similar grade of rejection according to Banff classification. RESULTS: Increased plasma cell infiltrates were present in 14 of 162 (9Â %) reviewed pRTR aged 3.2-17.5 (median 13.4) years at time of transplantation. Compared with 14 pRTR renal transplant biopsies without significantly increased plasma cells, there were no significant differences in mismatch and baseline estimated glomerular filtration rate (eGFR). Plasma cells were present in case biopsies at a maximal density of 14-116 (median 33) plasma cells/HPF. Increased plasma cells were associated with decreased eGFR at biopsy (22 vs. 49Â ml/min/1.73Â m(2); pâ<â0.001) and 4Â weeks post-biopsy (26 vs. 56Â ml/min/1.73Â m(2); pâ<â0.001) despite comparable eGFR 4 weeks prior to biopsy. Increased plasma cells were further associated with significantly increased frequency of renal allograft loss (71Â % vs. 7Â %; pâ<â0.001) at 0-27 (median 2) months after biopsy. CONCLUSION: Increased plasma cell infiltrates in pRTR are uncommon but associated with significantly reduced renal allograft survival as well as significantly reduced allograft function in surviving grafts
Fermion Masses and Mixing in Four and More Dimensions
We give an overview of recent progress in the study of fermion mass and
flavor mixing phenomena. Mass matrix ansatze are considered within the SM and
SUSY GUTs where some predictive frameworks based on SU(5) and SO(10) are
reviewed. We describe a variety of schemes to construct quark mass matrices in
extra dimensions focusing on four major classes: models with the SM residing on
3-brane, models with universal extra dimensions, models with split fermions and
models with warped extra dimensions. We outline how realistic patterns of quark
mass matrices could be derived from orbifold models in heterotic superstring
theory. Finally, we address the fermion mass problem in intersecting D-branes
scenarios, and present models with D6-branes able to give a good quantitatively
description of quark masses and mixing. The role of flavor/CP violation problem
as a probe of new physics is emphasized.Comment: a review based on seminars presented by S.K. in different places, 34
pages, late
Two-Dimensional Infrared Spectroscopy of Antiparallel ÎČ-Sheet Secondary Structure
We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel ÎČ-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel ÎČ-sheet. In the proteins with antiparallel ÎČ-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic âZâ-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.
On Flux Compactification and Moduli Stabilization
We study the effect of adding charged matter fields to both D3 and D7 branes
in type IIB string theory compactification with fluxes. Generically, charged
matter fields induce additional terms to the Kahler form, the superpotential
and the D-terms. These terms allow for minima with positive or zero
cosmological constants, even in the absence of non-perturbative effects. We
show this result first by decoupling the dilaton field along the lines of the
KKLT, and second by reincorporating it in the action with the Kahler moduli.Comment: 9 page
Low energy consequences from supersymmetric models with left-right symmetry
We consider several low energy consequences arising from a class of
supersymmetric models based on the gauge groups and in which the gauge
hierarchy and problems have been resolved. There are important
constraints on the MSSM parameters , and
, and we discuss how they are reconciled with radiative electroweak
breaking. We also consider the ensuing sparticle and Higgs spectroscopy, as
well as the decays and . The latter process
may be amenable to experimental tests through an order of magnitude increase in
sensitivity.Comment: 17 pages, latex2
- âŠ