4,493 research outputs found
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Distinct roles of class I PI3K isoforms in multiple myeloma cell survival and dissemination
Constraints from Solar and Reactor Neutrinos on Unparticle Long-Range Forces
We have investigated the impact of long-range forces induced by unparticle
operators of scalar, vector and tensor nature coupled to fermions in the
interpretation of solar neutrinos and KamLAND data. If the unparticle couplings
to the neutrinos are mildly non-universal, such long-range forces will not
factorize out in the neutrino flavour evolution. As a consequence large
deviations from the observed standard matter-induced oscillation pattern for
solar neutrinos would be generated. In this case, severe limits can be set on
the infrared fix point scale, Lambda_u, and the new physics scale, M, as a
function of the ultraviolet (d_UV) and anomalous (d) dimension of the
unparticle operator. For a scalar unparticle, for instance, assuming the
non-universality of the lepton couplings to unparticles to be of the order of a
few per mil we find that, for d_UV=3 and d=1.1, M is constrained to be M >
O(10^9) TeV (M > O(10^10) TeV) if Lambda_u= 1 TeV (10 TeV). For given values of
Lambda_u and d, the corresponding bounds on M for vector [tensor] unparticles
are approximately 100 [3/Sqrt(Lambda_u/TeV)] times those for the scalar case.
Conversely, these results can be translated into severe constraints on
universality violation of the fermion couplings to unparticle operators with
scales which can be accessible at future colliders.Comment: 13 pages, 3 figures. Minor changes due to precision in numerical
factors and correction in figure labels. References added. Conclusions remain
unchange
Order and disorder - An integrative structure of the full-length human growth hormone receptor
Because of its small size (70 kilodalton) and large content of structural disorder (>50%), the human growth hormone receptor (hGHR) falls between the cracks of conventional high-resolution structural biology methods. Here, we study the structure of the full-length hGHR in nanodiscs with small-angle x-ray scattering (SAXS) as the foundation. We develop an approach that combines SAXS, x-ray diffraction, and NMR spectroscopy data obtained on individual domains and integrate these through molecular dynamics simulations to interpret SAXS data on the full-length hGHR in nanodiscs. The hGHR domains reorient freely, resulting in a broad structural ensemble, emphasizing the need to take an ensemble view on signaling of relevance to disease states. The structure provides the first experimental model of any full-length cytokine receptor in a lipid membrane and exemplifies how integrating experimental data from several techniques computationally may access structures of membrane proteins with long, disordered regions, a widespread phenomenon in biology
Ion size effects at ionic exclusion from dielectric interfaces and slit nanopores
A previously developed field-theoretic model [R.D. Coalson et al., J. Chem.
Phys. 102, 4584 (1995)] that treats core collisions and Coulomb interactions on
the same footing is investigated in order to understand ion size effects on the
partition of neutral and charged particles at planar interfaces and the ionic
selectivity of slit nanopores. We introduce a variational scheme that can go
beyond the mean-field (MF) regime and couple in a consistent way pore modified
core interactions, steric effects, electrostatic solvation and image-charge
forces, and surface charge induced electrostatic potential. We show that in the
dilute limit, the MF and the variational theories agree well with MC simulation
results, in contrast to a recent RPA method. The partition of charged Yukawa
particles at a neutral dielectric interface (e.g air-water or protein-water
interface) is investigated. It is shown that as a result of the competition
between core collisions that push the ions towards the surface, and repulsive
solvation and image forces that exclude them from the interface, a
concentration peak of finite size ions sets in close to the dielectric
interface. We also characterize the role played by the ion size on the ionic
selectivity of neutral slit nanopores. We show that the complex interplay
between electrostatic forces, excluded volume effects induced by core
collisions and steric effects leads to an unexpected reversal in the ionic
selectivity of the pore with varying pore size: while large pores exhibits a
higher conductivity for large ions, narrow pores exclude large ions more
efficiently than small ones
Constraints on Astro-unparticle Physics from SN 1987A
SN 1987A observations have been used to place constraints on the interactions
between standard model particles and unparticles. In this study we calculate
the energy loss from the supernovae core through scalar, pseudo scalar, vector,
pseudo vector unparticle emission from nuclear bremsstrahlung for degenerate
nuclear matter interacting through one pion exchange. In order to examine the
constraints on we considered the emission of scalar, pseudo
scalar, vector, pseudo vector and tensor through the pair annihilation process
. In addition we have re-examined other pair
annihilation processes. The most stringent bounds on the dimensionless coupling
constants for and are obtained from
nuclear bremsstrahlung process for the pseudo scalar and pseudo-vector
couplings and for
tensor interaction, the best limit on dimensionless coupling is obtained from
and we get .Comment: 12 pages, 2 postscript figure
Challenges to the development of antigen-specific breast cancer vaccines
Continued progress in the development of antigen-specific breast cancer vaccines depends on the identification of appropriate target antigens, the establishment of effective immunization strategies, and the ability to circumvent immune escape mechanisms. Methods such as T cell epitope cloning and serological expression cloning (SEREX) have led to the identification of a number target antigens expressed in breast cancer. Improved immunization strategies, such as using dendritic cells to present tumor-associated antigens to T lymphocytes, have been shown to induce antigen-specific T cell responses in vivo and, in some cases, objective clinical responses. An outcome of successful tumor immunity is the evolution of antigen-loss tumor variants. The development of a polyvalent breast cancer vaccine, directed against a panel of tumor-associated antigens, may counteract this form of immune escape
Mechanical and Electronic Properties of MoS Nanoribbons and Their Defects
We present our study on atomic, electronic, magnetic and phonon properties of
one dimensional honeycomb structure of molybdenum disulfide (MoS) using
first-principles plane wave method. Calculated phonon frequencies of bare
armchair nanoribbon reveal the fourth acoustic branch and indicate the
stability. Force constant and in-plane stiffness calculated in the harmonic
elastic deformation range signify that the MoS nanoribbons are stiff quasi
one dimensional structures, but not as strong as graphene and BN nanoribbons.
Bare MoS armchair nanoribbons are nonmagnetic, direct band gap
semiconductors. Bare zigzag MoS nanoribbons become half-metallic as a
result of the (2x1) reconstruction of edge atoms and are semiconductor for
minority spins, but metallic for the majority spins. Their magnetic moments and
spin-polarizations at the Fermi level are reduced as a result of the
passivation of edge atoms by hydrogen. The functionalization of MoS
nanoribbons by adatom adsorption and vacancy defect creation are also studied.
The nonmagnetic armchair nanoribbons attain net magnetic moment depending on
where the foreign atoms are adsorbed and what kind of vacancy defect is
created. The magnetization of zigzag nanoribbons due to the edge states is
suppressed in the presence of vacancy defects.Comment: 11 pages, 5 figures, first submitted at November 23th, 200
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Booms and busts in commodity markets: bubbles or fundamentals?
This paper considers whether there were periodically collapsing rational speculative bubbles in commodity prices over a 40-year period from the late 1960s. We apply a switching regression approach to a broad range of commodities using two different measures of fundamental values—estimated from convenience yields and from a set of macroeconomic factors believed to affect commodity demand. We find reliable evidence for bubbles only among crude oil and feeder cattle, showing the popular belief that the extreme price movements observed in commodity markets were caused by pure speculation to be unsustainabl
Interaction imaging with amplitude-dependence force spectroscopy
Knowledge of surface forces is the key to understanding a large number of
processes in fields ranging from physics to material science and biology. The
most common method to study surfaces is dynamic atomic force microscopy (AFM).
Dynamic AFM has been enormously successful in imaging surface topography, even
to atomic resolution, but the force between the AFM tip and the surface remains
unknown during imaging. Here, we present a new approach that combines high
accuracy force measurements and high resolution scanning. The method, called
amplitude-dependence force spectroscopy (ADFS) is based on the
amplitude-dependence of the cantilever's response near resonance and allows for
separate determination of both conservative and dissipative tip-surface
interactions. We use ADFS to quantitatively study and map the nano-mechanical
interaction between the AFM tip and heterogeneous polymer surfaces. ADFS is
compatible with commercial atomic force microscopes and we anticipate its
wide-spread use in taking AFM toward quantitative microscopy
A Large Hadron Electron Collider at CERN
This document provides a brief overview of the recently published report on
the design of the Large Hadron Electron Collider (LHeC), which comprises its
physics programme, accelerator physics, technology and main detector concepts.
The LHeC exploits and develops challenging, though principally existing,
accelerator and detector technologies. This summary is complemented by brief
illustrations of some of the highlights of the physics programme, which relies
on a vastly extended kinematic range, luminosity and unprecedented precision in
deep inelastic scattering. Illustrations are provided regarding high precision
QCD, new physics (Higgs, SUSY) and electron-ion physics. The LHeC is designed
to run synchronously with the LHC in the twenties and to achieve an integrated
luminosity of O(100) fb. It will become the cleanest high resolution
microscope of mankind and will substantially extend as well as complement the
investigation of the physics of the TeV energy scale, which has been enabled by
the LHC
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