3,732 research outputs found
A Comparison of Pencil and Paper Procedures. PMO, Free · Electron PMO, and Structure-Resonance Theory Calculations for Proton Affinities
Pencil and paper quantum chemical procedures are applied
to correlations of electrophilic substitution and proton affinity data.
The data are also compared with other types of MO calculations,
including SCF results, and simplified methods are found to give
as satisfactory correlation as the more complex procedures
Moduli Stacks of Vector Bundles and Frobenius Morphisms
We describe the action of the different Frobenius morphisms on the cohomology
ring of the moduli stack of algebraic vector bundles of fixed rank and
determinant on an algebraic curve over a finite field in characteristic p and
analyse special situations like vector bundles on the projective line and
relations with infinite Grassmannians.Comment: 19 page
Unusual suppression of the superconducting energy gap and critical temperature in atomically thin NbSe2
It is well known that superconductivity in thin films is generally suppressed
with decreasing thickness. This suppression is normally governed by either
disorder-induced localization of Cooper pairs, weakening of Coulomb screening,
or generation and unbinding of vortex-antivortex pairs as described by the
Berezinskii-Kosterlitz-Thouless (BKT) theory. Defying general expectations,
few-layer NbSe2 - an archetypal example of ultrathin superconductors - has been
found to remain superconducting down to monolayer thickness. Here we report
measurements of both the superconducting energy gap and critical temperature in
high-quality monocrystals of few-layer NbSe2, using planar-junction tunneling
spectroscopy and lateral transport. We observe a fully developed gap that
rapidly reduces for devices with the number of layers N < 5, as does their
ctitical temperature. We show that the observed reduction cannot be explained
by disorder, and the BKT mechanism is also excluded by measuring its transition
temperature that for all N remains very close to Tc. We attribute the observed
behavior to changes in the electronic band structure predicted for mono- and
bi- layer NbSe2 combined with inevitable suppression of the Cooper pair density
at the superconductor-vacuum interface. Our experimental results for N > 2 are
in good agreement with the dependences of the gap and Tc expected in the latter
case while the effect of band-structure reconstruction is evidenced by a
stronger suppression of the gap and the disappearance of its anisotropy for N =
2. The spatial scale involved in the surface suppression of the density of
states is only a few angstroms but cannot be ignored for atomically thin
superconductors.Comment: 21 pages, including supporting informatio
Conformal blocks and generalized theta functions
Let M(r) be the moduli space of rank r vector bundles with trivial
determinant on a Riemann surface X . This space carries a natural line bundle,
the determinant line bundle L . We describe a canonical isomorphism of the
space of global sections of L^k with a space known in conformal field theory as
the ``space of conformal blocks", which is defined in terms of representations
of the Lie algebra sl(r, C((z))).Comment: 43 pages, Plain Te
A novel microfluidic device capable of maintaining functional thyroid carcinoma specimens ex vivo provides a new drug screening platform
© 2019 The Author(s). Background: Though the management of malignancies has improved vastly in recent years, many treatment options lack the desired efficacy and fail to adequately augment patient morbidity and mortality. It is increasingly clear that patient response to therapy is unique to each individual, necessitating personalised, or 'precision' medical care. This demand extends to thyroid cancer; ~ 10% patients fail to respond to radioiodine treatment due to loss of phenotypic differentiation, exposing the patient to unnecessary ionising radiation, as well as delaying treatment with alternative therapies. Methods: Human thyroid tissue (n = 23, malignant and benign) was live-sliced (5 mm diameter × 350-500 μm thickness) then analysed or incorporated into a microfluidic culture device for 96 h (37 °C). Successful maintenance of tissue was verified by histological (H&E), flow cytometric propidium iodide or trypan blue uptake, immunohistochemical (Ki67 detection/ BrdU incorporation) and functional analysis (thyroxine [T4] output) in addition to analysis of culture effluent for the cell death markers lactate dehydrogenase (LDH) and dead-cell protease (DCP). Apoptosis was investigated by Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Differentiation was assessed by evaluation of thyroid transcription factor (TTF1) and sodium iodide symporter (NIS) expression (western blotting). Results: Maintenance of gross tissue architecture was observed. Analysis of dissociated primary thyroid cells using flow cytometry both prior to and post culture demonstrated no significant change in the proportion of viable cells. LDH and DCP release from on-chip thyroid tissue indicated that after an initial raised level of release, signifying cellular damage, detectable levels dropped markedly. A significant increase in apoptosis (p < 0.01) was observed after tissue was perfused with etoposide and JNK inhibitor, but not in control tissue incubated for the same time period. No significant difference in Ki-67 positivity or TTF1/NIS expression was detected between fresh and post-culture thyroid tissue samples, moreover BrdU positive nuclei indicated on-chip cellular proliferation. Cultured thyroid explants were functionally viable as determined by production of T4 throughout the culture period. Conclusions: The described microfluidic platform can maintain the viability of thyroid tissue slices ex vivo for a minimum of four days, providing a platform for the assessment of thyroid tissue radioiodine sensitivity/adjuvant therapies in real time
Review of group A rotavirus strains reported in swine and cattle
Group A rotavirus (RVA) infections cause severe economic losses in intensively reared livestock animals, particularly in herds of swine and cattle. RVA strains are antigenically heterogeneous, and are classified in multiple G and P types defined by the two outer
capsid proteins, VP7 and VP4, respectively. This study summarizes published literature on the genetic and antigenic diversity of porcine and bovine RVA strains published over
the last 3 decades. The single most prevalent genotype combination among porcine RVA strains was G5P[7], whereas the predominant genotype combination among bovine RVA strains was G6P[5], although spatiotemporal differences in RVA strain distribution were observed. These data provide important baseline data on epidemiologically important RVA strains in swine and cattle and may guide the development of more effective vaccines for veterinary use
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