2,932 research outputs found
Interacting Electrons on a Square Fermi Surface
Electronic states near a square Fermi surface are mapped onto quantum chains.
Using boson-fermion duality on the chains, the bosonic part of the interaction
is isolated and diagonalized. These interactions destroy Fermi liquid behavior.
Non-boson interactions are also generated by this mapping, and give rise to a
new perturbation theory about the boson problem. A case with strong repulsions
between parallel faces is studied and solved. There is spin-charge separation
and the square Fermi surface remains square under doping. At half-filling,
there is a charge gap and insulating behavior together with gapless spin
excitations. This mapping appears to be a general tool for understanding the
properties of interacting electrons on a square Fermi surface.Comment: 25 pages, Nordita preprint 94/22
Effects of Electrical Stimulation on Wound Closure in Mice with Experimental Diabetes Mellitus
The purpose of the present study was to examine the effect of electrical stimulation (ES) on the closure of full-thickness excisional wounds in mice with type-1 experimental diabetes mellitus (DM). Alloxon monohydrate (100mg/kg) was used to induce experimental DM in mole CD-1 mice (n = 88). Full-thickness skin excisions (1cm2) in diabetic (urine glucose \u3e 0) and non-diabetic (urine glucose = 0) mice were administered 1, 3, or 5 treatments of ES (200ÎĽs, 200 Hz) for 15 minutes, at 0 (sham), 5, 10, or 12.5 volts. Alloxon injection resulted in a positive urine glucose test in 48 mice yielding an induction rate for DM of 54.5 percent. All groups exhibited decreases in wound length, perimeter, and surface area between days 2 and 16 following the creation of wounds. Non-diabetic wounds treated with ES hod the greatest percentage (60%) of closure. Diabetic wounds treated with ES hod a greater percentage of cloÂsure (36%) compared with sham-treated diabetic animals (12.5%). Treatment of wounds with the highest voltage of ES (12.5V) produced significant (P \u3c 0.01) decreases in the surface area, and significant (P \u3c 0.01) changes in the shapes of wounds in both diabetic and non-diabetic animals compared with sham-treated animals. These results support the clinical use of this adjunctive therapy to accelerate the closure of ulcers due to OM
Arabella, I\u27ll Be Your Fellah
https://digitalcommons.library.umaine.edu/mmb-vp/3934/thumbnail.jp
Ablation of solids by femtosecond lasers: ablation mechanism and ablation thresholds for metals and dielectrics
The mechanism of ablation of solids by intense femtosecond laser pulses is
described in an explicit analytical form. It is shown that at high intensities
when the ionization of the target material is complete before the end of the
pulse, the ablation mechanism is the same for both metals and dielectrics. The
physics of this new ablation regime involves ion acceleration in the
electrostatic field caused by charge separation created by energetic electrons
escaping from the target. The formulae for ablation thresholds and ablation
rates for metals and dielectrics, combining the laser and target parameters,
are derived and compared to experimental data. The calculated dependence of the
ablation thresholds on the pulse duration is in agreement with the experimental
data in a femtosecond range, and it is linked to the dependence for nanosecond
pulses.Comment: 27 pages incl.3 figs; presented at CLEO-Europe'2000 11-15 Sept.2000;
papers QMD6 and CTuK11
Correlations in the Sine-Gordon Model with Finite Soliton Density
We study the sine-Gordon (SG) model at finite densities of the topological
charge and small SG interaction constant, related to the one-dimensional
Hubbard model near half-filling. Using the modified WKB approach, we find that
the spectrum of the Gaussian fluctuations around the classical solution
reproduces the results of the Bethe ansatz studies. The modification of the
collective coordinate method allows us to write down the action, free from
infra-red divergencies. The behaviour of the density-type correlation functions
is non-trivial and we demonstrate the existence of leading and sub-leading
asymptotes. A consistent definition of the charge-raising operator is
discussed. The superconducting-type correlations are shown to decrease slowly
at small soliton densities, while the spectral weight of right (left) moving
fermions is spread over neighboring "4k_F" harmonics.Comment: 12 pages, 3 eps figures, REVTEX; a discussion of fermions is adde
Field-theoretical renormalization group for a flat two-dimensional Fermi surface
We implement an explicit two-loop calculation of the coupling functions and
the self-energy of interacting fermions with a two-dimensional flat Fermi
surface in the framework of the field theoretical renormalization group (RG)
approach. Throughout the calculation both the Fermi surface and the Fermi
velocity are assumed to be fixed and unaffected by interactions. We show that
in two dimensions, in a weak coupling regime, there is no significant change in
the RG flow compared to the well-known one-loop results available in the
literature. However, if we extrapolate the flow to a moderate coupling regime
there are interesting new features associated with an anisotropic suppression
of the quasiparticle weight Z along the Fermi surface, and the vanishing of the
renormalized coupling functions for several choices of the external momenta.Comment: 16 pages and 22 figure
Dynamic Nonlinear X-waves for Femtosecond Pulse Propagation in Water
Recent experiments on femtosecond pulses in water displayed long distance
propagation analogous to that reported in air. We verify this phenomena
numerically and show that the propagation is dynamic as opposed to self-guided.
Furthermore, we demonstrate that the propagation can be interpreted as due to
dynamic nonlinear X-waves whose robustness and role in long distance
propagation is shown to follow from the interplay between nonlinearity and
chromatic dispersion.Comment: 4 page
Single Proton Knock-Out Reactions from 24,25,26F
The cross sections of the single proton knock-out reactions from 24F, 25F,
and 26F on a 12C target were measured at energies of about 50 MeV/nucleon.
Ground state populations of 6.6+-.9 mb, 3.8+-0.6 mb for the reactions
12C(24F,23O) and 12C(25F,24O) were extracted, respectively. The data were
compared to calculations based on the many-body shell model and the eikonal
theory. In the reaction 12C(26F,25O) the particle instability of 25O was
confirmed
Three-body correlations in the ground-state decay of 26O
Background: Theoretical calculations have shown that the energy and angular
correlations in the three-body decay of the two-neutron unbound O26 can provide
information on the ground-state wave function, which has been predicted to have
a dineutron configuration and 2n halo structure.
Purpose: To use the experimentally measured three-body correlations to gain
insight into the properties of O26, including the decay mechanism and
ground-state resonance energy.
Method: O26 was produced in a one-proton knockout reaction from F27 and the
O24+n+n decay products were measured using the MoNA-Sweeper setup. The
three-body correlations from the O26 ground-state resonance decay were
extracted. The experimental results were compared to Monte Carlo simulations in
which the resonance energy and decay mechanism were varied.
Results: The measured three-body correlations were well reproduced by the
Monte Carlo simulations but were not sensitive to the decay mechanism due to
the experimental resolutions. However, the three-body correlations were found
to be sensitive to the resonance energy of O26. A 1{\sigma} upper limit of 53
keV was extracted for the ground-state resonance energy of O26.
Conclusions: Future attempts to measure the three-body correlations from the
ground-state decay of O26 will be very challenging due to the need for a
precise measurement of the O24 momentum at the reaction point in the target
Conical emission, pulse splitting and X-wave parametric amplification in nonlinear dynamics of ultrashort light pulses
The precise observation of the angle-frequency spectrum of light filaments in
water reveals a scenario incompatible with current models of conical emission
(CE). Its description in terms of linear X-wave modes leads us to understand
filamentation dynamics requiring a phase- and group-matched, Kerr-driven
four-wave-mixing process that involves two highly localized pumps and two
X-waves. CE and temporal splitting arise naturally as two manifestations of
this process
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