219 research outputs found
Ultrafast dynamics of neutral superexcited Oxygen: A direct measurement of the competition between autoionization and predissociation
Using ultrafast extreme ultraviolet pulses, we performed a direct measurement
of the relaxation dynamics of neutral superexcited states corresponding to the
nl\sigma_g(c^4\Sigma_u^-) Rydberg series of O_2. An XUV attosecond pulse train
was used to create a temporally localized Rydberg wavepacket and the ensuing
electronic and nuclear dynamics were probed using a time-delayed femtosecond
near-infrared pulse. We investigated the competing predissociation and
autoionization mechanisms for superexcited molecules and found that
autoionization is dominant for the low n Rydberg states. We measured an
autoionization lifetime of 92+/-6 fs and 180+/-10 fs for (5s,4d)\sigma_g and
(6s,5d)\sigma_g Rydberg state groups respectively. We determine that the
disputed neutral dissociation lifetime for the \nu=0 vibrational level of the
Rydberg series is 1100+/-100fs.Comment: 5 pages, 4 figure
Possible Relevance of Odd Frequency Pairing to Heavy Fermion Superconductivity
What is the character of the gapless quasiparticles in heavy fermion
superconductors (HFSC)? We discuss an odd-frequency pairing interpretation of
HFSC which leads to a two component model for the quasiparticle excitations. In
this picture, line zeroes of unpaired electrons may coexist with gapless
surfaces of paired electrons, with vanishing spin and charge coherence factors
Phase diagram of UPt in the model
The phase diagram of the unconventional superconductor UPt is explained
under the long-standing hypothesis that the pair wavefunction belongs to the
representation of the point group. The main objection to this theory
has been that it disagrees with the experimental phase diagram when a field is
applied along the c-axis. By a careful analysis of the free energy this
objection is shown to be incorrect. This singlet theory also explains the
unusual anisotropy in the upper critical field curves, often thought to
indicate a triplet pair function.Comment: 11 pages, Revtex, 2 figures (uuencoded, gzip'ed Postscript
Pathological study of elective nephrectomies for a two year period
Background: Nephrectomies whether partial, total or radical are common surgical procedures these days with trauma being the most common cause of an emergency nephrectomy. The indications of elective nephrectomies vary with different age groups- malignancies being common in the elderly age group and non-neoplastic indications of nephrectomy may present in any age group. The present study was undertaken in view of the increasing elective nephrectomies in our area thus analyzing the common causes requiring nephrectomy as a treatment. The present study also aimed at determining the age and sex distribution of various renal lesions requiring a nephrectomy.Methods: It was a prospective study for a period of 2 years - January 2013 to December 2014. A total of 45 nephrectomies were included in the study. Detailed clinical, biochemical and imaging findings were taken into consideration before analyzing each case. Results: There was a male predominance(64.4%) and 26.6% of the cases were in the age group of 40-50 years. 95.5% of the nephrectomies were performed for a non-neoplastic indication. Involvement of the right and left kidney was almost equal in the study. Chronic pyelonephritis was the most common histopathological diagnosis(68.8%).Conclusion: Inflammatory causes more commonly required a nephrectomy in the study population. Chronic calculous pyelonephritis was the most common underlying pathophysiology leading to a nonfunctioning kidney thus highlighting the early treatment of renal calculi.
Evolutionary Models in Software Engineering
Software development life cycle models play a vital role in developing a software application. This research deals with such advanced models which are the evolutionary models namely: incremental model, and spiral model. Both these models have their own advantages and disadvantages as well. The main objective of this research paper is to represent the two evolutionary modelsrsquo features and limitations
Heat Transport and the Nature of the Order Parameter in Superconducting
Recent thermal conductivity data on the heavy fermion superconductor
have been interpreted as offering support for an model of the order
parameter as opposed to an model. In this paper, we analyze this issue
from a theoretical standpoint including the detailed effects of Fermi surface
and gap anisotropy. Our conclusion is that although current data put strong
constraints on the gap anisotropy, they cannot definitively distinguish between
these two models. Measurements on samples of varying quality could be decisive
in this regard, however.Comment: 8 pages, revtex, 15 uunencoded postscript figure
Evidence for depinning of a Wigner crystal in Hg-Cd-Te
We report measurements of the nonlinear current-voltage characteristics on low-carrier-concentration n-type samples of Hg_(0.76)Cd_(0.24)Te at high magnetic fields and low temperatures. We find the onset of nonlinear conductivity occurs at applied electric fields of less than 1 mV/cm. The effect can be easily distinguished from sample heating and is consistent with collective transport produced by the sliding of a Wigner crystal pinned by disorder. We estimate a disorder-induced correlation length of tens of micrometers
Transport and the Order Parameter of Superconducting UPt3
We calculate the ultrasonic absorption and the thermal conductivity in the
superconducting state of UPt as functions of temperature and direction of
propagation and polarization. Two leading candidates for the superconducting
order parameter are considered: the and representations. Both
can fit the data except for the ultrasonic absorption in the phase. To do
that, it is necessary to suppose that the system has only a single domain, and
that must be chosen as the most favorable one. However, the theory
requires fine-tuning of parameters to fit the low temperature thermal
conductivity. Thus, transport data favor the theory. Measurements of
the thermal conductivity as a function of pressure at low temperature could
help to further distinguish the two theories.Comment: 7 pages, 4 figure
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