1,316 research outputs found
Structure Constants of the Fractional Supersymmetry Chiral Algebras
The fractional supersymmetry chiral algebras in two-dimensional conformal
field theory are extended Virasoro algebras with fractional spin currents. We
show that associativity and closure of these algebras determines their
structure constants in the case that the Virasoro algebra is extended by
precisely one current. We compute the structure constants of these algebras
explicitly and we show that correlators of the currents satisfy non-Abelian
braiding relations.Comment: 44 page
Nanobeam photonic crystal cavity quantum dot laser
The lasing behavior of one dimensional GaAs nanobeam cavities with embedded
InAs quantum dots is studied at room temperature. Lasing is observed throughout
the quantum dot PL spectrum, and the wavelength dependence of the threshold is
calculated. We study the cavity lasers under both 780 nm and 980 nm pump,
finding thresholds as low as 0.3 uW and 19 uW for the two pump wavelengths,
respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to
7 nm by employing a fiber taper in near proximity to the cavities. The fiber
taper is used both to efficiently pump the cavity and collect the cavity
emission.Comment: 8 pages; 6 figure
Construction of the K=8 Fractional Superconformal Algebras
We construct the K=8 fractional superconformal algebras. There are two such
extended Virasoro algebras, one of which was constructed earlier, involving a
fractional spin (equivalently, conformal dimension) 6/5 current. The new
algebra involves two additional fractional spin currents with spin 13/5. Both
algebras are non-local and satisfy non-abelian braiding relations. The
construction of the algebras uses the isomorphism between the Z_8 parafermion
theory and the tensor product of two tricritical Ising models. For the special
value of the central charge c=52/55, corresponding to the eighth member of the
unitary minimal series, the 13/5 currents of the new algebra decouple, while
two spin 23/5 currents (level-2 current algebra descendants of the 13/5
currents) emerge. In addition, it is shown that the K=8 algebra involving the
spin 13/5 currents at central charge c=12/5 is the appropriate algebra for the
construction of the K=8 (four-dimensional) fractional superstring.Comment: 53 pages (or 82/2 = 41 pages in reduced format
Discovery of kpc-scale line emission in barred galaxies, not linked to AGN or star formation
We present an analysis of the optical line emission from nearby barred galaxies, and in particular look at the radial range occupied by the bar. In many cases this region is marked by what we term a 'star formation desert', with a marked deficit of HII regions in optical narrow-band H-alpha imaging. Here we present long-slit spectroscopy revealing that such regions do have line emission, but that it is low-level, spatially smooth and almost ubiquitous. The relative strengths of the H-alpha and the spectrally adjacent [NII] lines in the regions are completely discrepant from those associated with star formation regions, and more closely match expectations for 'LINER' regions. We quantify the total line emission from these extended, kpc-scale regions, and determine the spurious contribution it would make to the determined star formation rate of these galaxies if interpreted as normal H-alpha emission. We concur with previous studies that link this LINER emission to old stellar populations, e.g. post-asymptotic giant branch stars, and propose these strongly-barred early-type spirals as a prime location for further tests of such emission
Childhood tonsillectomy alters the primary distribution of HPV‐related oropharyngeal squamous cell carcinoma
ObjectivesWe investigated how tonsillectomy during childhood may influence the distribution of human papillomavirus (HPV) positive cancer of the tonsils in adult life using p16 as a surrogate marker for HPV infection.Study DesignRetrospective observational study.MethodsA total of 280 patients diagnosed with oropharyngeal squamous cell carcinoma (OPSCC) and known p16 status were eligible for this study. Each participant was called to obtain the childhood tonsillectomy history. Respondents were subgrouped by p16 status and the primary tumor location. Patient demographic and clinical information was analyzed for association with Fisher’s exact and Wilcoxon rank sum tests. Location of tumor was modeled using univariate (UVA) and multivariate (MVA) logistic regression with associated odds ratios (OR) and 95% confidence intervals.ResultsOf the 280 patients, 115 (41%) were respondents: 104 (90.4%) were p16 positive and 11 (9.6%) were p16 negative. For p16 positive patients, we observed a majority (93%) of intact tonsils in those with tonsil cancer, compared to 45% of intact tonsils in patients with p16 positive cancer elsewhere in the oropharynx (P < .001). MVA logistic regression showed that female gender (OR = 4.16, P = .0675), prior smoking history (OR = 2.6, P = .0367), and intact tonsils (OR = 15.2, P < .0001) were associated with tonsillar OPSCC.ConclusionWe found that patients with p16 positive OPSCC at a non‐tonsil site were much more likely to have had prior tonsillectomy vs those with p16 positive OPSCC arising within the tonsil. Nevertheless, we do not advocate tonsillectomies as a public health policy to reduce HPV‐related OPSCC.Level of Evidence6Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154902/1/lio2342_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154902/2/lio2342.pd
Granular flow down a rough inclined plane: transition between thin and thick piles
The rheology of granular particles in an inclined plane geometry is studied
using molecular dynamics simulations. The flow--no-flow boundary is determined
for piles of varying heights over a range of inclination angles . Three
angles determine the phase diagram: , the angle of repose, is the
angle at which a flowing system comes to rest; , the maximum angle
of stability, is the inclination required to induce flow in a static system;
and is the maximum angle for which stable, steady state flow is
observed. In the stable flow region , three
flow regimes can be distinguished that depend on how close is to
: i) : Bagnold rheology, characterized by a
mean particle velocity in the direction of flow that scales as
, for a pile of height , ii)
: the slow flow regime, characterized by a linear
velocity profile with depth, and iii) : avalanche flow
characterized by a slow underlying creep motion combined with occasional free
surface events and large energy fluctuations. We also probe the physics of the
initiation and cessation of flow. The results are compared to several recent
experimental studies on chute flows and suggest that differences between
measured velocity profiles in these experiments may simply be a consequence of
how far the system is from jamming.Comment: 19 pages, 14 figs, submitted to Physics of Fluid
Feature integration in natural language concepts
Two experiments measured the joint influence of three key sets of semantic features on the frequency with which artifacts (Experiment 1) or plants and creatures (Experiment 2) were categorized in familiar categories. For artifacts, current function outweighed both originally intended function and current appearance. For biological kinds, appearance and behavior, an inner biological function, and appearance and behavior of offspring all had similarly strong effects on categorization. The data were analyzed to determine whether an independent cue model or an interactive model best accounted for how the effects of the three feature sets combined. Feature integration was found to be additive for artifacts but interactive for biological kinds. In keeping with this, membership in contrasting artifact categories tended to be superadditive, indicating overlapping categories, whereas for biological kinds, it was subadditive, indicating conceptual gaps between categories. It is argued that the results underline a key domain difference between artifact and biological concepts
Carrier-mediated magnetoelectricity in complex oxide heterostructures
While tremendous success has been achieved to date in creating both single
phase and composite magnetoelectric materials, the quintessential
electric-field control of magnetism remains elusive. In this work, we
demonstrate a linear magnetoelectric effect which arises from a novel
carrier-mediated mechanism, and is a universal feature of the interface between
a dielectric and a spin-polarized metal. Using first-principles density
functional calculations, we illustrate this effect at the SrRuO/SrTiO
interface and describe its origin. To formally quantify the magnetic response
of such an interface to an applied electric field, we introduce and define the
concept of spin capacitance. In addition to its magnetoelectric and spin
capacitive behavior, the interface displays a spatial coexistence of magnetism
and dielectric polarization suggesting a route to a new type of interfacial
multiferroic
NQO2 is a reactive oxygen species generating off-target for acetaminophen
[Image: see text] The analgesic and antipyretic compound acetaminophen (paracetamol) is one of the most used drugs worldwide. Acetaminophen overdose is also the most common cause for acute liver toxicity. Here we show that acetaminophen and many structurally related compounds bind quinone reductase 2 (NQO2) in vitro and in live cells, establishing NQO2 as a novel off-target. NQO2 modulates the levels of acetaminophen derived reactive oxygen species, more specifically superoxide anions, in cultured cells. In humans, NQO2 is highly expressed in liver and kidney, the main sites of acetaminophen toxicity. We suggest that NQO2 mediated superoxide production may function as a novel mechanism augmenting acetaminophen toxicity
Differences in the signaling pathways of α1A- and α1B-adrenoceptors are related to different endosomal targeting
Aims: To compare the constitutive and agonist-dependent endosomal trafficking of α1A- and α1B-adrenoceptors (ARs) and to establish if the internalization pattern determines the signaling pathways of each subtype.
Methods: Using CypHer5 technology and VSV-G epitope tagged α1A- and α1B-ARs stably and transiently expressed in HEK 293 cells, we analyzed by confocal microscopy the constitutive and agonist-induced internalization of each subtype, and the temporal relationship between agonist induced internalization and the increase in intracellular calcium (determined by FLUO-3 flouorescence), or the phosphorylation of ERK1/2 and p38 MAP kinases (determined by Western blot).
Results and Conclusions: Constitutive as well as agonist-induced trafficking of α1A and α1B ARs maintain two different endosomal pools of receptors: one located close to the plasma membrane and the other deeper into the cytosol. Each subtype exhibited specific characteristics of internalization and distribution between these pools that determines their signaling pathways: α1A-ARs, when located in the plasma membrane, signal through calcium and ERK1/2 pathways but, when translocated to deeper endosomes, through a mechanism sensitive to β-arrestin and concanavalin A, continue signaling through ERK1/2 and also activate the p38 pathway. α1B-ARs signal through calcium and ERK1/2 only when located in the membrane and the signals disappear after endocytosis and by disruption of the membrane lipid rafts by methyl-β-cyclodextrin
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