590 research outputs found
Localization dynamics of fluids in random confinement
The dynamics of two-dimensional fluids confined within a random matrix of
obstacles is investigated using both colloidal model experiments and molecular
dynamics simulations. By varying fluid and matrix area fractions in the
experiment, we find delocalized tracer particle dynamics at small matrix area
fractions and localized motion of the tracers at high matrix area fractions. In
the delocalized region, the dynamics is subdiffusive at intermediate times, and
diffusive at long times, while in the localized regime, trapping in finite
pockets of the matrix is observed. These observations are found to agree with
the simulation of an ideal gas confined in a weakly correlated matrix. Our
results show that Lorentz gas systems with soft interactions are exhibiting a
smoothening of the critical dynamics and consequently a rounded
delocalization-to-localization transition.Comment: 5 pages, 3 figure
2PI Effective Action and Evolution Equations of N = 4 super Yang-Mills
We employ nPI effective action techniques to study N = 4 super Yang-Mills,
and write down the 2PI effective action of the theory. We also supply the
evolution equations of two-point correlators within the theory.Comment: 16 pages, 6 figures. Figure 2 replaced, approximation scheme
clarified, references adde
Semiquantitative Assessment of Bowel Habits and Its Relation with Calcium Metabolism after Gastric Bypass Surgery: A Retrospective Study
Background. Calcium malabsorption after bariatric surgery may be harmful to skeletal health and demands for optimal skeletal management. Methods. 103 Patients were evaluated retrospectively at 12 months after surgery. The evaluation included a questionnaire about stool frequency and consistency and laboratory assessments. Results. 103 Patients, 27 males and 76 females, were included in the study. 83 Patients had an alimentary limb of 100 cm and 20 patients one of 150 cm. At 12 months after surgery, 77.7% reported changes of bowel habits, albumin adjusted calcium levels were normal in all but 2 patients, and PTH levels were increased in 35%. Correlations between semiquantified bowel scores (fecal scores) and data from the laboratory demonstrated increasing PTH values along with more frequent and softer/watery stools (RR 30.5, CI 6.2–149.2, P < .001). There was a trend for higher PTH levels in patients with an alimentary limb of 150 cm. Normal PTH levels were more frequently found in case of calcium and vitamin D3 use (RR 14.3, CI 3.6–56.5, P < .001). Conclusion. This study demonstrates interrelationships between semi-quantified fecal scores, PTH levels, and the compliance of taking calcium/vitamin D3 suppletion. However, prospective randomized studies are necessary to show causal relationships
Prevalence of Anemia and Related Deficiencies in the First Year following Laparoscopic Gastric Bypass for Morbid Obesity
Background. Anemia associated with deficiencies in iron, folic acid, and vitamin B12 are very common after Laparoscopic Roux-en-Y Gastric Bypass (LRYGB) surgery for morbid obesity. This study was conducted to evaluate the prevalence of anemia after LRYGB. Patients and Methods. A total of 377 morbid obese patients were included in our study. All patients underwent a LRYGB. Hematologic parameters were obtained prior to and after surgery on standardized time intervals. Results. Anemia was present in 21 (P = 0.02) patients after surgery. Iron, folic acid, and vitamin B12 deficiencies were diagnosed in 66%, 15%, and 50% of patients, respectively. In 86% of patients, anemia was accompanied by one of these deficiencies. Conclusion. These results show that anemia and deficiencies for iron, folic acid deficiency, and vitamin B12 are very common within the first year after LRYGB. We advise a minimal daily intake of 65 mg of iron in male and 100 mg in female patients, 350 μg of vitamin B12, and 400 μg of folic acid. Patients undergoing LRYGB must be closely monitored for deficiencies pre- and postoperative and supplemented when deficiencies occur
Debye screening in strongly coupled N=4 supersymmetric Yang-Mills plasma
Using the AdS/CFT correspondence, we examine the behavior of correlators of
Polyakov loops and other operators in N=4 supersymmetric Yang-Mills theory at
non-zero temperature. The implications for Debye screening in this strongly
coupled non-Abelian plasma, and comparisons with available results for thermal
QCD, are discussed.Comment: 21 pages, 5 figures, significantly expanded discussion of Polyakov
loop correlator and static quark-antiquark potentia
Magnetic state in URu2Si2, UPd2Al3 and UNi2Al3 probed by point contacts
The antiferromagnetic (AFM) state has been investigated in the three
heavy-fermion compounds URu2Si2, UPd2Al3, and UNi2Al3 by measuring dV/dI(V)
curves of point contacts at different temperatures (1.5-20 K) and magnetic
fields (0-28 T). The zero-bias maximum in dV/dI(V) for URu2Si2 points to a
partially gapped Fermi-surface related to the itinerant nature of the AFM state
contrary to UPd2Al3 where analogous features have not been found. The AFM state
in UNi2Al3 has more similarities with URu2Si2. For URu2Si2, the same critical
field of about 40 T along the easy c axis is found for all features in dV/dI(V)
corresponding to the Neel temperature, the gap in the electronic density of
states, and presumably the ordered moments.Comment: 10 pages incl. 5 figures, LaTex 2
QCD with Chemical Potential in a Small Hyperspherical Box
To leading order in perturbation theory, we solve QCD, defined on a small
three sphere in the large N and Nf limit, at finite chemical potential and map
out the phase diagram in the (mu,T) plane. The action of QCD is complex in the
presence of a non-zero quark chemical potential which results in the sign
problem for lattice simulations. In the large N theory, which at low
temperatures becomes a conventional unitary matrix model with a complex action,
we find that the dominant contribution to the functional integral comes from
complexified gauge field configurations. For this reason the eigenvalues of the
Polyakov line lie off the unit circle on a contour in the complex plane. We
find at low temperatures that as mu passes one of the quark energy levels there
is a third-order Gross-Witten transition from a confined to a deconfined phase
and back again giving rise to a rich phase structure. We compare a range of
physical observables in the large N theory to those calculated numerically in
the theory with N=3. In the latter case there are no genuine phase transitions
in a finite volume but nevertheless the observables are remarkably similar to
the large N theory.Comment: 44 pages, 18 figures, jhep3 format. Small corrections and
clarifications added in v3. Conclusions cleaned up. Published versio
The Long Journey from Ab Initio Calculations to Density Functional Theory for Nuclear Large Amplitude Collective Motion
At present there are two vastly different ab initio approaches to the
description of the the many-body dynamics: the Density Functional Theory (DFT)
and the functional integral (path integral) approaches. On one hand, if
implemented exactly, the DFT approach can allow in principle the exact
evaluation of arbitrary one-body observable. However, when applied to Large
Amplitude Collective Motion (LACM) this approach needs to be extended in order
to accommodate the phenomenon of surface-hoping, when adiabaticity is strongly
violated and the description of a system using a single (generalized) Slater
determinant is not valid anymore. The functional integral approach on the other
hand does not appear to have such restrictions, but its implementation does not
appear to be straightforward endeavor. However, within a functional integral
approach one seems to be able to evaluate in principle any kind of observables,
such as the fragment mass and energy distributions in nuclear fission. These
two radically approaches can likely be brought brought together by formulating
a stochastic time-dependent DFT approach to many-body dynamics.Comment: 9 page
Resonant nucleation of spatio-temporal order via parametric modal amplification
We investigate, analytically and numerically, the emergence of
spatio-temporal order in nonequilibrium scalar field theories. The onset of
order is triggered by destabilizing interactions (DIs), which instantaneously
change the interacting potential from a single to a double-well, tunable to be
either degenerate (SDW) or nondegenerate (ADW). For the SDW case, we observe
the emergence of spatio-temporal coherent structures known as oscillons. We
show that this emergence is initially synchronized, the result of parametric
amplification of the relevant oscillon modes. We also discuss how these ordered
structures act as bottlenecks for equipartition. For ADW potentials, we show
how the same parametric amplification mechanism may trigger the rapid decay of
a metastable state. For a range of temperatures, the decay rates associated
with this resonant nucleation can be orders of magnitude larger than those
computed by homogeneous nucleation, with time-scales given by a simple power
law, , where depends weakly on the
temperature and is the free-energy barrier of a critical
fluctuation.Comment: 38 pages, 20 figures now included within the tex
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