883 research outputs found
Capillary forces in the acoustics of patchy-saturated porous media
A linearized theory of the acoustics of porous elastic formations, such as
rocks, saturated with two different viscous fluids is generalized to take into
account a pressure discontinuity across the fluid boundaries. The latter can
arise due to the surface tension of the membrane separating the fluids. We show
that the frequency-dependent bulk modulus for wave lengths
longer than the characteristic structural dimensions of the fluid patches has a
similar analytic behavior as in the case of a vanishing membrane stiffness and
depends on the same parameters of the fluid-distribution topology. The effect
of the capillary stiffness can be accounted by renormalizing the coefficients
of the leading terms in the low-frequency asymptotic of .Comment: 27 pages, 3 figure
Modifying memory for a museum tour in older adults: reactivation-related updating that enhances and distorts memory is reduced in ageing
Memory reactivation, the activation of a latent memory trace when we are reminded of a past experience, strengthens memory but can also contribute to distortions if new information present during reactivation is integrated with existing memory. In a previous study in young adults (St. Jacques & Schacter, 2013; Psychological Science) we found that the quality of memory reactivation, manipulated using the principle of encoding specificity and indexed by recollection ratings, modulated subsequent true and false memories for events experienced during a museum tour. Here, we examined age-related changes in the quality of memory reactivation on subsequent memory. Young and older adults reactivated memories for museum stops immediately followed by the presentation of a novel lure photo from an alternate tour version (i.e., reactivation plus new information). There was an increase in subsequent true memories for reactivated targets and for subsequent false memories for lures that followed reactivated targets, when compared to baseline target and lure photos. However, the influence of reactivation on subsequent memories was reduced in older adults. These data reveal that aging alters reactivation-related updating processes that allow memories to be strengthened and updated with new information- consequently reducing memory distortions in older compared to young adults
Antimicrobial Drug–Resistant Escherichia coli from Humans and Poultry Products, Minnesota and Wisconsin, 2002–2004
Similarities were found between drug-resistant E. coli from humans and poultry products
A new integral representation for quasiperiodic fields and its application to two-dimensional band structure calculations
In this paper, we consider band-structure calculations governed by the
Helmholtz or Maxwell equations in piecewise homogeneous periodic materials.
Methods based on boundary integral equations are natural in this context, since
they discretize the interface alone and can achieve high order accuracy in
complicated geometries. In order to handle the quasi-periodic conditions which
are imposed on the unit cell, the free-space Green's function is typically
replaced by its quasi-periodic cousin. Unfortunately, the quasi-periodic
Green's function diverges for families of parameter values that correspond to
resonances of the empty unit cell. Here, we bypass this problem by means of a
new integral representation that relies on the free-space Green's function
alone, adding auxiliary layer potentials on the boundary of the unit cell
itself. An important aspect of our method is that by carefully including a few
neighboring images, the densities may be kept smooth and convergence rapid.
This framework results in an integral equation of the second kind, avoids
spurious resonances, and achieves spectral accuracy. Because of our image
structure, inclusions which intersect the unit cell walls may be handled easily
and automatically. Our approach is compatible with fast-multipole acceleration,
generalizes easily to three dimensions, and avoids the complication of
divergent lattice sums.Comment: 25 pages, 6 figures, submitted to J. Comput. Phy
The evolution and evaluation of a whole blood polymerase chain reaction assay for the detection of invasive aspergillosis in hematology patients in a routine clinical setting
Background.Invasive aspergillosis (IA) is associated with high mortality. Successful outcome with treatment is linked to early diagnosis. The utility of classic diagnostic methods, however, is limited.
Methods.To aid in the diagnosis of IA, we retrospectively assessed our diagnostic service, using real?time polymerase chain reaction (PCR) and galactomannan sandwich enzyme?linked immunosorbent assay (ELISA).
Results.A total of 203 patients at risk of invasive fungal infection were screened by PCR, and 116 of the patients were also tested by ELISA. The patient group comprised 176 patients with hematological malignancy and 28 control patients with evidence of invasive candidal infection. Consensus European Organisation for Research and Treatment of Cancer and Mycoses Study Group criteria were used to classify fungal infection, which, by definition, excluded the PCR result. The PCR method was sensitive (up to 92.3% sensitivity) and specific (up to 94.6% specificity) and had good agreement with the galactomannan ELISA (76.7%) and high?resolution computed tomography scan results.
Conclusions.A negative PCR result can be used to rule out IA and to limit the need for empirical antifungal therapy; thus, it has a role in diagnosing IA infections, especially in combination with antigen testing. PCR?positive cases classified as “false positives” regularly reflect the limitations of classic microbiological procedures or restricted use of consensus clinical methods employed to classify infection
Cephalosporin-resistant Escherichia coli among Summer Camp Attendees with Salmonellosis
Investigation of an acute gastroenteritis outbreak involving >100 persons
at a summer camp in Girona, Spain, in June 2002 led to the detection of
Salmonella and extended-spectrum cephalosporin-resistant
Escherichia coli (ESCREC). Stool cultures were performed
for 22 symptomatic campers, three asymptomatic food handlers, and 10 healthy
household members. Of the 22 campers, 19 had Salmonella
enterica, 9 had an ESCREC strain carrying an extended-spectrum
β-lactamase, and 2 had a second ESCREC strain carrying a plasmidic
cephamycinase. Related ESCREC were detected in two (salmonella-negative)
asymptomatic food handlers and in none of the healthy household members. Fecal
ESCREC and its β-lactamases and plasmids were extensively
characterized. Three of the five ESCREC clones were recovered from multiple
hosts. The apparent dissemination of ESCREC suggests a food or water vehicle.
The observed distribution of resistance plasmids and β-lactamase
genes in several clones indicates a high degree of horizontal transfer.
Heightened vigilance and increased efforts must be made to discover the
reservoirs and vehicles for community dissemination of ESCREC
The fundamental pro-groupoid of an affine 2-scheme
A natural question in the theory of Tannakian categories is: What if you
don't remember \Forget? Working over an arbitrary commutative ring , we
prove that an answer to this question is given by the functor represented by
the \'etale fundamental groupoid \pi_1(\spec(R)), i.e.\ the separable
absolute Galois group of when it is a field. This gives a new definition
for \'etale \pi_1(\spec(R)) in terms of the category of -modules rather
than the category of \'etale covers. More generally, we introduce a new notion
of "commutative 2-ring" that includes both Grothendieck topoi and symmetric
monoidal categories of modules, and define a notion of for the
corresponding "affine 2-schemes." These results help to simplify and clarify
some of the peculiarities of the \'etale fundamental group. For example,
\'etale fundamental groups are not "true" groups but only profinite groups, and
one cannot hope to recover more: the "Tannakian" functor represented by the
\'etale fundamental group of a scheme preserves finite products but not all
products.Comment: 46 pages + bibliography. Diagrams drawn in Tik
Observation of trapped light within the radiation continuum
The ability to confine light is important both scientifically and technologically. Many light confinement methods exist, but they all achieve confinement with materials or systems that forbid outgoing waves. These systems can be implemented by metallic mirrors, by photonic band-gap materials, by highly disordered media (Anderson localization) and, for a subset of outgoing waves, by translational symmetry (total internal reflection) or by rotational or reflection symmetry. Exceptions to these examples exist only in theoretical proposals. Here we predict and show experimentally that light can be perfectly confined in a patterned dielectric slab, even though outgoing waves are allowed in the surrounding medium. Technically, this is an observation of an ‘embedded eigenvalue’—namely, a bound state in a continuum of radiation modes—that is not due to symmetry incompatibility. Such a bound state can exist stably in a general class of geometries in which all of its radiation amplitudes vanish simultaneously as a result of destructive interference. This method to trap electromagnetic waves is also applicable to electronic and mechanical waves.United States. Army Research Office (Institute for Soldier Nanotechnologies under contract no. W911NF-07-D0004)United States. Department of Energy (grant no. DE-SC0001299)National Science Foundation (U.S.) (NSF grant no. DMR-0819762
Racism, the media … and alternative (sonic) culture
This essay develops Titley’s discussion of racism and the media through a concerted engagement with popular culture, and specifically with sound and YouTube video culture. Expanding Titley’s notion of “debatability”, it asks what alternatives to racism are held in popular culture, and in a time of nationalist, racist and authoritarian assertion, why the identification of such alternatives might matter for a leftist anti-racist project
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