1,835 research outputs found
Recovering piecewise smooth functions from nonuniform Fourier measurements
In this paper, we consider the problem of reconstructing piecewise smooth
functions to high accuracy from nonuniform samples of their Fourier transform.
We use the framework of nonuniform generalized sampling (NUGS) to do this, and
to ensure high accuracy we employ reconstruction spaces consisting of splines
or (piecewise) polynomials. We analyze the relation between the dimension of
the reconstruction space and the bandwidth of the nonuniform samples, and show
that it is linear for splines and piecewise polynomials of fixed degree, and
quadratic for piecewise polynomials of varying degree
Quenching of lamellar ordering in an n-alkane embedded in nanopores
We present an X-ray diffraction study of the normale alkane nonadecane
C_{19}H_{40} embedded in nanoporous Vycor glass. The confined molecular crystal
accomplishes a close-packed structure by alignment of the rod-like molecules
parallel to the pore axis while sacrificing one basic principle known from the
bulk state, i.e. the lamellar ordering of the molecules. Despite this disorder,
the phase transitions observed in the confined solid mimic the phase behavior
of the 3D unconfined crystal, though enriched by the appearance of a true
rotator phase known only from longer alkane chains.Comment: 7 pages, 3 figure
Male infertility due to germ cell apoptosis in mice lacking the thiamin carrier, Tht1. A new insight into the critical role of thiamin in spermatogenesis.
A mouse model of thiamin-responsive megaloblastic anemia (diabetes mellitus, deafness, megaloblastic anemia) lacking functional Slc19a2 has been generated and unexpectedly found to have a male-specific sterility phenotype. We describe here the characterization of the testis-specific effects of absence of the high-affinity thiamin transporter, Tht1. Null males were found to have hypoplastic testes secondary to germ cell depletion. Morphologic and expression analysis revealed that under conditions of standard thiamin intake, tissues affected in the syndrome (pancreatic beta-cell, hematopoietic cells, auditory nerve) maintained normal function but pachytene stage spermatocytes underwent apoptosis. Under conditions of thiamin challenge, the apoptotic cell loss extended to earlier stages of germ cells but spared Sertoli cells and Leydig cells. Injection of high-dose thiamin was effective in reversing the spermatogenic failure, suggesting that the absence of the thiamin carrier could be overcome by diffusion-mediated transport at supranormal thiamin concentrations. These observations demonstrated that male germ cells, particularly those with high thiamin transporter expression beyond the blood-testis barrier, were more susceptible to apoptosis triggered by intracellular thiamin deficiency than any other tissue type. The findings described here highlight an unexpected and critical role for thiamin transport and metabolism in spermatogenesis
Perioperative Hypothermia (33°C) Does Not Increase theOccurrence of Cardiovascular Events in PatientsUndergoing Cerebral Aneurysm SurgeryFindings from the Intraoperative Hypothermia for AneurysmSurgery Trial
The IHAST Trial randomized patients undergoing cerebral aneurysm surgery to intraoperative hypothermia or normothermia.
Cardiovascular events were prospectively
followed until 3-month follow-up and were compared in
hypothermic and normothermic patients.
Conclusion: In patients undergoing cerebral aneurysm surgery,
perioperative hypothermia was not associated with an
increased occurrence of cardiovascular events
Soft disks in a narrow channel
The pressure components of "soft" disks in a two dimensional narrow channel
are analyzed in the dilute gas regime using the Mayer cluster expansion and
molecular dynamics. Channels with either periodic or reflecting boundaries are
considered. It is found that when the two-body potential, u(r), is singular at
some distance r_0, the dependence of the pressure components on the channel
width exhibits a singularity at one or more channel widths which are simply
related to r_0. In channels with periodic boundary conditions and for
potentials which are discontinuous at r_0, the transverse and longitudinal
pressure components exhibit a 1/2 and 3/2 singularity, respectively. Continuous
potentials with a power law singularity result in weaker singularities of the
pressure components. In channels with reflecting boundary conditions the
singularities are found to be weaker than those corresponding to periodic
boundaries
Reclaiming revolutionary feminism
Generally, saying: âfeministâ, is revolutionary enough in this day and age, itâs far more of a statement now than it was back in the eighties. And no, I wouldnât say I was a Revolutionary Feminist now âcos Iâm less separatist than I was at that time and I think itâs got overladen with such baggage that Iâd have to spend about ten minutes defining what I meant. (Interview with Al Garthwaite, Leeds, 20 January 2012)In this article, I shall explore some understandings, and misunderstandings, of the school or type of feminism known as Revolutionary Feminism, a uniquely British school of feminism, founded in 1977. The quote above is taken from my interview with a prominent and influential British Revolutionary Feminist activist named Al Garthwaite. The interview forms the basis of this article and the research was part of my PhD on the British Womenâs Liberation Movement (WLM) from the 1970s to today. Among many of her legacies, Al founded the Reclaim the Night (RTN) marches in the United Kingdom in November 1977, traditionally womenâs night-time, street protest marches against male violence against women (VAW). Also involved in the establishment and running of the UK WLM national newsletter âWIRESâ,1 Al was at the hub of organising in the feminist hotbed that was Leeds, in Yorkshire in the North of England, in the 1970s and 1980s
On the New Conditions for a Total Neutrino Conversion in a Medium
We show that the arguments forming the basis for the claim that the
conditions for total neutrino conversion derived and studied in detail in [1,2]
``are just the conditions of the parametric resonance of neutrino oscillations
supplemented by the requirement that the parametric enhancement be complete'',
given in [4] have flaws which make the claim physically questionable. We show
also that in the case of the transitions in the Earth of the
Earth-core-crossing solar and atmospheric neutrinos the peaks in the relevant
transitions probabilities , associated with the new conditions, , are of physical relevance - in contrast to what is suggested in
[4]. Actually, the enhancement of in any region of the corresponding
parameter space are essentially determined by these absolute maxima of . We comment on few other aspects of the results derived in [1,2,3] which
have been misunderstood and/or misinterpreted in [4].Comment: 8 pages, late
Adsorption in non interconnected pores open at one or at both ends: A reconsideration of the origin of the hysteresis phenomenon
We report on an experimental study of adsorption isotherme of nitrogen onto
porous silicon with non interconnected pores open at one or at both ends in
order to check for the first time the old (1938) but always current idea based
on Cohan's description which suggests that the adsorption of gaz should occur
reversibly in the first case and irreversibly in the second one. Hysteresis
loops, the shape of which is usually associated to interconnections in porous
media, are observed whether the pores are open at one or at both ends in
contradiction with Cohan's model.Comment: 5 pages, 4 EPS figure
Fast Ensemble Smoothing
Smoothing is essential to many oceanographic, meteorological and hydrological
applications. The interval smoothing problem updates all desired states within
a time interval using all available observations. The fixed-lag smoothing
problem updates only a fixed number of states prior to the observation at
current time. The fixed-lag smoothing problem is, in general, thought to be
computationally faster than a fixed-interval smoother, and can be an
appropriate approximation for long interval-smoothing problems. In this paper,
we use an ensemble-based approach to fixed-interval and fixed-lag smoothing,
and synthesize two algorithms. The first algorithm produces a linear time
solution to the interval smoothing problem with a fixed factor, and the second
one produces a fixed-lag solution that is independent of the lag length.
Identical-twin experiments conducted with the Lorenz-95 model show that for lag
lengths approximately equal to the error doubling time, or for long intervals
the proposed methods can provide significant computational savings. These
results suggest that ensemble methods yield both fixed-interval and fixed-lag
smoothing solutions that cost little additional effort over filtering and model
propagation, in the sense that in practical ensemble application the additional
increment is a small fraction of either filtering or model propagation costs.
We also show that fixed-interval smoothing can perform as fast as fixed-lag
smoothing and may be advantageous when memory is not an issue
Back reaction of a long range force on a Friedmann-Robertson-Walker background
It is possible that there may exist long-range forces in addition to gravity.
In this paper we construct a simple model for such a force based on exchange of
a massless scalar field and analyze its effect on the evolution of a
homogeneous Friedmann-Robertson-Walker cosmology. The presence of such an
interaction leads to an equation of state characterized by positive pressure
and to resonant particle production similar to that observed in preheating
scenarios.Comment: 14 pages, 6 color Postscript figures, LaTe
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