3,222 research outputs found
Black Hole Production by Cosmic Rays
Ultra-high energy cosmic rays create black holes in scenarios with extra
dimensions and TeV-scale gravity. In particular, cosmic neutrinos will produce
black holes deep in the atmosphere, initiating quasi-horizontal showers far
above the standard model rate. At the Auger Observatory, hundreds of black hole
events may be observed, providing evidence for extra dimensions and the first
opportunity for experimental study of microscopic black holes. If no black
holes are found, the fundamental Planck scale must be above 2 TeV for any
number of extra dimensions.Comment: 4 pages, 4 figures, PRL versio
RNAi Reduces Expression and Intracellular Retention of Mutant Cartilage Oligomeric Matrix Protein
Mutations in cartilage oligomeric matrix protein (COMP), a large extracellular glycoprotein expressed in musculoskeletal tissues, cause two skeletal dysplasias, pseudoachondroplasia and multiple epiphyseal dysplasia. These mutations lead to massive intracellular retention of COMP, chondrocyte death and loss of growth plate chondrocytes that are necessary for linear growth. In contrast, COMP null mice have only minor growth plate abnormalities, normal growth and longevity. This suggests that reducing mutant and wild-type COMP expression in chondrocytes may prevent the toxic cellular phenotype causing the skeletal dysplasias. We tested this hypothesis using RNA interference to reduce steady state levels of COMP mRNA. A panel of shRNAs directed against COMP was tested. One shRNA (3B) reduced endogenous and recombinant COMP mRNA dramatically, regardless of expression levels. The activity of the shRNA against COMP mRNA was maintained for up to 10 weeks. We also demonstrate that this treatment reduced ER stress. Moreover, we show that reducing steady state levels of COMP mRNA alleviates intracellular retention of other extracellular matrix proteins associated with the pseudoachondroplasia cellular pathology. These findings are a proof of principle and the foundation for the development of a therapeutic intervention based on reduction of COMP expression
Freak Waves in Random Oceanic Sea States
Freak waves are very large, rare events in a random ocean wave train. Here we
study the numerical generation of freak waves in a random sea state
characterized by the JONSWAP power spectrum. We assume, to cubic order in
nonlinearity, that the wave dynamics are governed by the nonlinear Schroedinger
(NLS) equation. We identify two parameters in the power spectrum that control
the nonlinear dynamics: the Phillips parameter and the enhancement
coefficient . We discuss how freak waves in a random sea state are more
likely to occur for large values of and . Our results are
supported by extensive numerical simulations of the NLS equation with random
initial conditions. Comparison with linear simulations are also reported.Comment: 7 pages, 6 figures, to be published in Phys. Rev. Let
Measurement of the Condensation Coefficient of Water in the UMR Simulation Chamber
The UMR Cloud Simulation Facility is described. The facility is designed to provide a controlled environment simulating the conditions of natural atmospheric processes. It consists of two cooled-wall expansion cloud chambers and peripheral instrumentation for generation and characterization of aerosols used for cloud formation studies. Results of initial studies of the growth of warm cloud droplets and inferred measurements of the condensation coefficient are described
Pennsylvania Folklife Vol. 11, No. 2
• Walter Ellsworth Boyer (1911-1960) • The Meaning of Human Figures in Pennsylvania Dutch Folk Art • Meadow Irrigation in Pennsylvania • Receipt Books-New and Old • Pennsylvania Cave and Ground Cellars • The Amish in Their One-Room Schoolhouses • Collectaneahttps://digitalcommons.ursinus.edu/pafolklifemag/1007/thumbnail.jp
Updated Limits on TeV-Scale Gravity from Absence of Neutrino Cosmic Ray Showers Mediated by Black Holes
We revise existing limits on the D-dimensional Planck scale M_D from the
nonobservation of microscopic black holes produced by high energy cosmic
neutrinos in scenarios with D=4+n large extra dimensions. Previous studies have
neglected the energy radiated in gravitational waves by the multipole moments
of the incoming shock waves. We include the effects of energy loss, as well as
form factors for black hole production and recent null results from cosmic ray
detectors. For n>4, we obtain M_D > 1.0 - 1.4 TeV. These bounds are among the
most stringent and conservative to date.Comment: 11 pages, 4 figure
Pennsylvania Folklife Vol. 11, No. 1
• A Dunker Weekend Love Feast of 100 Years Ago • The Peacock in Pennsylvania • The Get-Togethers of the Young Amish Folk • Church and Meetinghouse Stables and Sheds • Abraham Harley Cassel - Dunkard Bibliophile • Mennonite Folklore • Springs and Springhouses • Finishing Wooden Surfaces • Early Funeral Notices • Collecting Dialect Folk Songshttps://digitalcommons.ursinus.edu/pafolklifemag/1006/thumbnail.jp
Itinerant Electron Ferromagnetism in the Quantum Hall Regime
We report on a study of the temperature and Zeeman-coupling-strength
dependence of the one-particle Green's function of a two-dimensional (2D)
electron gas at Landau level filling factor where the ground state is
a strong ferromagnet. Our work places emphasis on the role played by the
itinerancy of the electrons, which carry the spin magnetization and on
analogies between this system and conventional itinerant electron ferromagnets.
We discuss the application to this system of the self-consistent Hartree-Fock
approximation, which is analogous to the band theory description of metallic
ferromagnetism and fails badly at finite temperatures because it does not
account for spin-wave excitations. We go beyond this level by evaluating the
one-particle Green's function using a self-energy, which accounts for
quasiparticle spin-wave interactions. We report results for the temperature
dependence of the spin magnetization, the nuclear spin relaxation rate, and
2D-2D tunneling conductances. Our calculations predict a sharp peak in the
tunneling conductance at large bias voltages with strength proportional to
temperature. We compare with experiment, where available, and with predictions
based on numerical exact diagonalization and other theoretical approaches.Comment: 29 pages, 20 figure
Scaling of Aharonov-Bohm couplings and the dynamical vacuum in gauge theories
Recent results on the vacuum polarization induced by a thin string of
magnetic flux lead us to suggest an analogue of the Copenhagen `flux spaghetti'
QCD vacuum as a possible mechanism for avoiding the divergence of perturbative
QED, thus permitting consistent completion of the full, nonperturbative theory.
The mechanism appears to operate for spinor, but not scalar, QED.Comment: 11 pages, ITP-SB-92-40, (major conceptual evolution from original
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