1,887 research outputs found
Distinct nature of static and dynamic magnetic stripes in cuprate superconductors
We present detailed neutron scattering studies of the static and dynamic
stripes in an optimally doped high-temperature superconductor,
LaCuO. We find that the dynamic stripes do not disperse towards the
static stripes in the limit of vanishing energy transfer. We conclude that the
dynamic stripes observed in neutron scattering experiments are not the
Goldstone modes associated with the broken symmetry of the simultaneously
observed static stripes, but rather that the signals originate from different
domains in the sample. These domains may be related by structural twinning, or
may be entirely different phases, where the static stripes in one phase are
pinned versions of the dynamic stripes in the other. Our results explain
earlier observations of unusual dispersions in underdoped
LaSrCuO () and LaBaCuO ().
Our findings are relevant for all compounds exhibiting magnetic stripes, and
may thus be a vital part in unveiling the nature of high temperature
superconductivity
Neutron production by cosmic-ray muons at shallow depth
The yield of neutrons produced by cosmic ray muons at a shallow depth of 32
meters of water equivalent has been measured. The Palo Verde neutrino detector,
containing 11.3 tons of Gd loaded liquid scintillator and 3.5 tons of acrylic
served as a target. The rate of one and two neutron captures was determined.
Modeling the neutron capture efficiency allowed us to deduce the total yield of
neutrons neutrons per muon
and g/cm. This yield is consistent with previous measurements at similar
depths.Comment: 12 pages, 3 figure
Effects of Long-Term Hypoxia on Enzymes of Carbohydrate Metabolism in the Gulf killifish, Fundulus grandis
The goal of the current study was to generate a comprehensive, multi-tissue perspective of the effects of chronic hypoxic exposure on carbohydrate metabolism in the Gulf killifish Fundulus grandis. Fish were held at approximately 1.3¡mg¡lâ1 dissolved oxygen (~3.6¡kPa) for 4¡weeks, after which maximal activities were measured for all glycolytic enzymes in four tissues (white skeletal muscle, liver, heart and brain), as well as for enzymes of glycogen metabolism (in muscle and liver) and gluconeogenesis (in liver). The specific activities of enzymes of glycolysis and glycogen metabolism were strongly suppressed by hypoxia in white skeletal muscle, which may reflect decreased energy demand in this tissue during chronic hypoxia. In contrast, several enzyme specific activities were higher in liver tissue after hypoxic exposure, suggesting increased capacity for carbohydrate metabolism. Hypoxic exposure affected fewer enzymes in heart and brain than in skeletal muscle and liver, and the changes were smaller in magnitude, perhaps due to preferential perfusion of heart and brain during hypoxia. The specific activities of some gluconeogenic enzymes increased in liver during long-term hypoxic exposure, which may be coupled to increased protein catabolism in skeletal muscle. These results demonstrate that when intact fish are subjected to prolonged hypoxia, enzyme activities respond in a tissue-specific fashion reflecting the balance of energetic demands, metabolic role and oxygen supply of particular tissues. Furthermore, within glycolysis, the effects of hypoxia varied among enzymes, rather than being uniformly distributed among pathway enzymes
Excitations from a Bose-Einstein condensate of magnons in coupled spin ladders
The weakly coupled quasi-one-dimensional spin ladder compound
(CH)CHNHCuCl is studied by neutron scattering in magnetic
fields exceeding the critical field of Bose-Einstein condensation of magnons.
Commensurate long-range order and the associated Goldstone mode are detected
and found to be similar to those in a reference 3D quantum magnet. However, for
the upper two massive magnon branches the observed behavior is totally
different, culminating in a drastic collapse of excitation bandwidth beyond the
transition point.Comment: 4 pages, 4 figure
Antigen receptor repertoires of one of the smallest known vertebrates
The rules underlying the structure of antigen receptor repertoires are not yet fully defined, despite their enormous importance for the understanding of adaptive immunity. With current technology, the large antigen receptor repertoires of mice and humans cannot be comprehensively studied. To circumvent the problems associated with incomplete sampling, we have studied the immunogenetic features of one of the smallest known vertebrates, the cyprinid fish Paedocypris sp. âSingkepâ (âminifishâ). Despite its small size, minifish has the key genetic facilities characterizing the principal vertebrate lymphocyte lineages. As described for mammals, the frequency distributions of immunoglobulin and T cell receptor clonotypes exhibit the features of fractal systems, demonstrating that self-similarity is a fundamental property of antigen receptor repertoires of vertebrates, irrespective of body size. Hence, minifish achieve immunocompetence via a few thousand lymphocytes organized in robust scale-free networks, thereby ensuring immune reactivity even when cells are lost or clone sizes fluctuate during immune responses
Constraints on Parity-Even Time Reversal Violation in the Nucleon-Nucleon System and Its Connection to Charge Symmetry Breaking
Parity-even time reversal violation (TRV) in the nucleon-nucleon interaction
is reconsidered. The TRV -exchange interaction on which recent analyses
of measurements are based is necessarily also charge-symmetry breaking (CSB).
Limits on its strength relative to regular -exchange are
extracted from recent CSB experiments in neutron-proton scattering. The result
(95% CL) is considerably lower than limits
inferred from direct TRV tests in nuclear processes. Properties of
-exchange and limit imposed by the neutron EDM are briefly discussed.Comment: RevTex, 8 pages. Factor ten error in cited neutron EDM corrected,
discussion and two references adde
Insulin autoantibodies as determined by competitive radiobinding assay are positively correlated with impaired beta-cell function â The Ulm-Frankfurt population study
Out of a random population of 4208 non-diabetic pupils without a family history of Type I diabetes 44 (1.05%) individuals had islet cell antibody (ICA) levels greater or equal to 5 Juvenile Diabetes Foundation (JDF) units. 39 of these ICA-positives could be repeatedly tested for circulating insulin autoantibodies (CIAA) using a competitive radiobinding assay. The results were compared with the insulin responses in the intravenous glucose tolerance tests (IVGTT) and with HLA types. Six pupils were positive for CIAA. All of them had complement-fixing ICA, and 5 of them were HLA-DR4 positive. Three of the 6 showed a first-phase insulin response below the first percentile of normal controls. Our data indicate that in population-based studies CIAA can be considered as a high risk marker for impaired beta-cell function in non-diabetic ICA-positive individuals
Evidence for magnetic quasiparticle phase separation in a quasi-one-dimensional quantum magnet
Magnetic systems composed of weakly coupled spin-1/2 chains are fertile
ground for hosting the fractional magnetic excitations that are intrinsic to
interacting fermions in one-dimension (1D). However, the exotic physics arising
from the quantum many-body interactions beyond 1D are poorly understood in
materials of this class. Spinons and psinons are two mutually exclusive
low-energy magnetic quasiparticles; the excitation seen depends on the ground
state of the spin chain. Here, we present inelastic neutron scattering and
neutron diffraction evidence for their coexistence in SrCoVO
at milli-Kelvin temperatures in part of the N\'eel phase (2.4 T
H 3.9 T) and possibly also the field-induced spin density
wave phase up to the highest field probed (H 3.9 T,
H = 5.5 T). These results unveil a
novel spatial phase inhomogeneity for the weakly coupled spin chains in this
compound. This quantum dynamical phase separation is a new phenomenon in
quasi-1D quantum magnets, highlighting the non-trivial consequences of
inter-chain coupling.Comment: 8 pages, 6 figure
Neutrino oscillations in Kerr-Newman space-time
The mass neutrino oscillation in Kerr-Newman(K-N) space-time is studied in
the plane , and the general equations of oscillation phases
are given. The effect of the rotation and electric charge on the phase is
presented. Then, we consider three special cases: (1) The neutrinos travel
along the geodesics with the angular momentum in the equatorial plane.
(2) The neutrinos travel along the geodesics with L=0 in the equatorial plane.
(3) The neutrinos travel along the radial geodesics at the direction
. At last, we calculate the proper oscillation length in the K-N
space time. The effect of the gravitational field on the oscillation length is
embodied in the gravitational red shift factor. When the neutrino travels out
of the gravitational field, the blue shift of the oscillation length takes
place. We discussed the variation of the oscillation length influenced by the
gravitational field strength, the rotation and charge .Comment: 20 pages, no figure
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