3,002 research outputs found
The Kato square root problem on vector bundles with generalised bounded geometry
We consider smooth, complete Riemannian manifolds which are exponentially
locally doubling. Under a uniform Ricci curvature bound and a uniform lower
bound on injectivity radius, we prove a Kato square root estimate for certain
coercive operators over the bundle of finite rank tensors. These results are
obtained as a special case of similar estimates on smooth vector bundles
satisfying a criterion which we call generalised bounded geometry. We prove
this by establishing quadratic estimates for perturbations of Dirac type
operators on such bundles under an appropriate set of assumptions.Comment: Slight technical modification of the notion of "GBG constant section"
on page 7, and a few technical modifications to Proposition 8.4, 8.6, 8.
Giant Planet Formation, Evolution, and Internal Structure
The large number of detected giant exoplanets offers the opportunity to
improve our understanding of the formation mechanism, evolution, and interior
structure of gas giant planets. The two main models for giant planet formation
are core accretion and disk instability. There are substantial differences
between these formation models, including formation timescale, favorable
formation location, ideal disk properties for planetary formation, early
evolution, planetary composition, etc. First, we summarize the two models
including their substantial differences, advantages, and disadvantages, and
suggest how theoretical models should be connected to available (and future)
data. We next summarize current knowledge of the internal structures of solar-
and extrasolar- giant planets. Finally, we suggest the next steps to be taken
in giant planet exploration.Comment: Accepted for publication as a chapter in Protostars and Planets VI,
to be published in 2014 by University of Arizona Pres
Dynamical description of vesicle growth and shape change
We systematize and extend the description of vesicle growth and shape change
using linear nonequilibrium thermodynamics. By restricting the study to shape
changes from spheres to axisymmetric ellipsoids, we are able to give a
consistent formulation which includes the lateral tension of the vesicle
membrane. This allows us to generalize and correct a previous calculation. Our
present calculations suggest that, for small growing vesicles, a prolate
ellipsoidal shape should be favored over oblate ellipsoids, whereas for large
growing vesicles oblates should be favored over prolates. The validity of this
prediction is examined in the light of the various assumptions made in its
derivation.Comment: 6 page
Functional analysis of epilepsy-associated variants in STXBP1/Munc18-1 using humanised Caenorhabditis elegans
Objective:
Genetic variants in STXBP1 , which encodes the conserved exocytosis protein Munc18â1, are associated with a variety of infantile epilepsy syndromes. We aimed to develop an in vivo Caenorhabditis elegans model that could be used to test the pathogenicity of such variants in a costâeffective manner.
Methods:
The CRISPR/Cas9 method was used to introduce a null mutation into the uncâ18 gene (the C. elegans orthologue of STXBP1 ), thereby creating a paralyzed worm strain. We subsequently rescued this strain with transgenes encoding the human STXBP1/Munc18â1 protein (wildâtype and eight different epilepsyâassociated missense variants). The resulting humanized worm strains were then analyzed via behavioral, electrophysiological, and biochemical approaches.
Results:
Transgenic expression of wildâtype human STXBP1 protein fully rescued locomotion in both solid and liquid media to the same level as the standard wildâtype worm strain, Bristol N2. Six variant strains (E59K, V84D, C180Y, R292H, L341P, R551C) exhibited impaired locomotion, whereas two (P335L, R406H) were no different from worms expressing wildâtype STXBP1. Electrophysiological recordings revealed that all eight variant strains displayed less frequent and more irregular pharyngeal pumping in comparison to wildâtype STXBP1âexpressing strains. Four strains (V84D, C180Y, R292H, P335L) exhibited pentylenetetrazolâinduced convulsions in an acute assay of seizureâlike activity, in contrast to worms expressing wildâtype STXBP1. No differences were seen between wildâtype and variant STXBP1 strains in terms of mRNA abundance. However, STXBP1 protein levels were reduced to 20%â30% of wildâtype in all variants, suggesting that the mutations result in STXBP1 protein instability.
Significance:
The approach described here is a costâeffective in vivo method for establishing the pathogenicity of genetic variants in STXBP1 and potentially other conserved neuronal proteins. Furthermore, the humanized strains we created could potentially be used in the future for highâthroughput drug screens to identify novel therapeutics
Emotions in context: examining pervasive affective sensing systems, applications, and analyses
Pervasive sensing has opened up new opportunities for measuring our feelings and understanding our behavior by monitoring our affective states while mobile. This review paper surveys pervasive affect sensing by examining and considering three major elements of affective pervasive systems, namely; âsensingâ, âanalysisâ, and âapplicationâ. Sensing investigates the different sensing modalities that are used in existing real-time affective applications, Analysis explores different approaches to emotion recognition and visualization based on different types of collected data, and Application investigates different leading areas of affective applications. For each of the three aspects, the paper includes an extensive survey of the literature and finally outlines some of challenges and future research opportunities of affective sensing in the context of pervasive computing
Electrospun gelatin-based scaffolds as a novel 3D platform to study the function of contractile smooth muscle cells in vitro
Contractile dysfunction of smooth muscle (SM) is a feature of chronic cardiovascular, respiratory and gastro-intestinal diseases. Owing to the low availability of human ex vivo tissue for the assessment of SM contractile function, the aim of this study was to develop a novel in vitro SM model that possesses the ability to contract, and a method to measure its contractility. A range of electrospun scaffolds were produced from crosslinked gelatin and methacrylated gelatin (GelMA), generating highly aligned scaffolds with average fibre diameters ranging from 200 nm to several micrometres. Young's moduli of the scaffolds ranged from 1x105 to 1x107 Pa. Primary aortic smooth muscle cells (AoSMCs; rat) cells readily adhered to and proliferated on the fibrous scaffolds for up to 10 days. They formed highly aligned populations following the topographical cues of the aligned scaffolds and stained positive for SM markers, indicating a contractile phenotype. Cell-seeded GelMA scaffolds were able, upon stimulation with uridine 5'-triphosphate (UTP), to contract and their attachment to a force transducer allowed the force of contraction to be measured. Hence, these electrospun GelMA fibres can be used as biomimetic scaffolds for SM cell culture and in vitro model development, and enables the contractile forces generated by the aligned three-dimensional sheet of cells to be directly measured. This will supplement in vitro drug screening tools and facilitate discovery of disease mechanisms
Impact mitigation in environmental impact assessment: paper promises or the basis of consent conditions?
Pulmonary MRI contrast using Surface Quadrupolar Relaxation (SQUARE) of hyperpolarized 83Kr
Hyperpolarized 83Kr has previously been demonstrated to enable MRI contrast that is sensitive to the chemical composition of the surface in a porous model system. Methodological advances have lead to a substantial increase in the 83Kr hyperpolarization and the resulting signal intensity. Using the improved methodology for spin exchange optical pumping of isotopically enriched 83Kr, internal anatomical details of ex vivo rodent lung were resolved with hyperpolarized 83Kr MRI after krypton inhalation. Different 83Kr relaxation times were found between the main bronchi and the parenchymal regions in ex vivo rat lungs. The T1 weighted hyperpolarized 83Kr MRI provided a first demonstration of surface quadrupolar relaxation (SQUARE) pulmonary MRI contrast
The Swift X-ray flaring afterglow of GRB 050607
The unique capability of the Swift satellite to perform a prompt and
autonomous slew to a newly detected Gamma-Ray Burst (GRB) has yielded the
discovery of interesting new properties of GRB X-ray afterglows, such as the
steep early lightcurve decay and the frequent presence of flares detected up to
a few hours after the GRB trigger. We present observations of GRB 050607, the
fourth case of a GRB discovered by Swift with flares superimposed on the
overall fading X-ray afterglow. The flares of GRB 050607 were not symmetric as
in previously reported cases, showing a very steep rise and a shallower decay,
similar to the Fast Rise, Exponential Decay that are frequently observed in the
gamma-ray prompt emission. The brighter flare had a flux increase by a factor
of approximately 25,peaking for 30 seconds at a count rate of approximately 30
counts s-1, and it presented hints of addition short time scale activity during
the decay phase. There is evidence of spectral evolution during the flares. In
particular, at the onset of the flares the observed emission was harder, with a
gradual softening as each flare decayed. The very short time scale and the
spectral variability during the flaring activity are indicators of possible
extended periods of energy emission by the GRB central engine. The flares were
followed by a phase of shallow decay, during which the forward shock was being
refreshed by a long-lived central engine or by shells of lower Lorentz factors,
and by a steepening after approximately 12 ks to a decay slope considered
typical of X-ray afterglows.Comment: 23 pages, 5 figures, Accepted by the Astrophysical Journa
- âŠ