3,699 research outputs found
A new geometric invariant on initial data for Einstein equations
For a given asymptotically flat initial data set for Einstein equations a new
geometric invariant is constructed. This invariant measure the departure of the
data set from the stationary regime, it vanishes if and only if the data is
stationary. In vacuum, it can be interpreted as a measure of the total amount
of radiation contained in the data.Comment: 5 pages. Important corrections regarding the generalization to the
non-time symmetric cas
Enhanced Integrin α4β1-Mediated Adhesion Contributes to a Mobilization Defect of Endothelial Progenitor Cells in Diabetes.
Diabetes is associated with a deficit of circulating endothelial progenitor cells (EPCs), which has been attributed to their defective mobilization from the bone marrow. The basis for this mobilization defect is not completely understood, and we sought to determine if hyperglycemic conditions enhanced EPC adhesion. We found that culturing EPCs in high glucose media increased adhesion to bone marrow stromal cells. This enhanced adhesion was associated with decreased expression of protein kinase A regulatory subunit 1β (PRKAR1β), activation of protein kinase A (PKA), and phosphorylation of α4-integrin on serine 988. This potentiated adhesion was reversed by treatment with a PKA inhibitor, overexpression of PRKAR1β, or expression of a phosphorylation-defective α4-integrin variant (α4[S988A]). Using a model of type 1 diabetes, we showed that α4(S988A)-expressing mice have more circulating EPCs than their wild-type counterparts. Moreover, diabetic α4(S988A) mice demonstrate enhanced revascularization after hind limb ischemia. Thus, we have identified a novel signaling mechanism activating PKA in diabetes (downregulation of an inhibitory regulatory subunit) that leads to deficits of circulating EPCs and impaired vascular repair, which could be reversed by α4-integrin mutation
Long-term efficacy of endoscopic cyclophotocoagulation in the management of glaucoma following cataract surgery in children
Purpose
To report the long-term efficacy of endoscopic cyclophotocoagulation (ECP) in pediatric glaucoma following cataract surgery (GFCS).
Methods
ECP was performed on 35 eyes of 25 patients 24 mm Hg, alternative glaucoma procedure following ECP, or occurrence of visually significant complications. Analysis was performed to estimate risk factors for failure.
Results
A total of 27 aphakic and 8 pseudophakic eyes were included. Pretreatment IOP averaged 33.9 ± 7.9 mm Hg. Final IOP after a mean follow-up period of 7.2 years was 18.9 ± 8.8 mm Hg (P < 0.001). The success rate was 54% (19/35 eyes). The failure rate was not increased in pseudophakic patients relative to aphakic patients. Patients with single ECP demonstrated preserved visual acuity from baseline to final follow-up.
Conclusions
In this patient cohort, with average follow-up period of 7.2 years, ECP was useful in the treatment of pediatric GFCS
Echocardiographic abnormalities and disease severity in Fabry's disease
Fabry's disease is an X-linked recessive genetic deficiency of the enzyme alpha-galactosidase A, which leads to the pathologic deposition of neutral glycosphingolipids in lysosomes of the vascular endothelium of the heart, brain and kidney. The disease is progressive in hemizygous male patients, with increasing involvement of the major organs leading to death. Because cardiac involvement is a constant feature, echocardiograms were performed on 35 patients with Fabry's disease, 23 hemizygotes (aged 28.6 ± 14 years) and 12 heterozygotes (aged 31.6 ± 6 years), to determine whether cardiac involvement could be detected noninvasively.The results demonstrated that hemizygous male patients had a greater aortic root diameter, thicker interventricular septum and greater ventricular mass than did heterozygous female patients. Left ventricular mass per square meter of body surface area correlated well with clinical disease severity (r = 0.68, p < 0.05), suggesting progressive glycosphingolipid deposition. Older heterozygotes (>25 years old) had more severe evidence of cardiac disease than did younger male patients. Although mitral valve prolapse was identified in 12 (54%) of 23 male hemizygotes and in 7 (58%) of 12 female heterozygotes, its presence did not correlate with clinical disease severity or other echocardiographic variables. Therefore, echocardiographic evidence of Fabry's disease appears to correlate with age-related disease severity and may be a useful noninvasive marker to follow disease progression and possible regression when appropriate therapy becomes available
The Newtonian Limit for Asymptotically Flat Solutions of the Vlasov-Einstein System
It is shown that there exist families of asymptotically flat solutions of the
Einstein equations coupled to the Vlasov equation describing a collisionless
gas which have a Newtonian limit. These are sufficiently general to confirm
that for this matter model as many families of this type exist as would be
expected on the basis of physical intuition. A central role in the proof is
played by energy estimates in unweighted Sobolev spaces for a wave equation
satisfied by the second fundamental form of a maximal foliation.Comment: 24 pages, plain TE
Adsorption models of hybridization and post-hybridisation behaviour on oligonucleotide microarrays
Analysis of data from an Affymetrix Latin Square spike-in experiment
indicates that measured fluorescence intensities of features on an
oligonucleotide microarray are related to spike-in RNA target concentrations
via a hyperbolic response function, generally identified as a Langmuir
adsorption isotherm. Furthermore the asymptotic signal at high spike-in
concentrations is almost invariably lower for a mismatch feature than for its
partner perfect match feature. We survey a number of theoretical adsorption
models of hybridization at the microarray surface and find that in general they
are unable to explain the differing saturation responses of perfect and
mismatch features. On the other hand, we find that a simple and consistent
explanation can be found in a model in which equilibrium hybridization followed
by partial dissociation of duplexes during the post-hybridization washing
phase.Comment: 26 pages, 6 figures, some rearrangement of sections and some
additions. To appear in J.Phys.(condensed matter
Seasonal variation of serotonin turnover in human cerebrospinal fluid, depressive symptoms and the role of the 5-HTTLPR.
Studying monoaminergic seasonality is likely to improve our understanding of neurobiological mechanisms underlying season-associated physiological and pathophysiological behavior. Studies of monoaminergic seasonality and the influence of the serotonin-transporter-linked polymorphic region (5-HTTLPR) on serotonin seasonality have yielded conflicting results, possibly due to lack of power and absence of multi-year analyses. We aimed to assess the extent of seasonal monoamine turnover and examined the possible involvement of the 5-HTTLPR. To determine the influence of seasonality on monoamine turnover, 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured in the cerebrospinal fluid of 479 human subjects collected during a 3-year period. Cosine and non-parametric seasonal modeling were applied to both metabolites. We computed serotonin (5-HT) seasonality values and performed an association analysis with the s/l alleles of the 5-HTTLPR. Depressive symptomatology was assessed using the Beck Depression Inventory-II. Circannual variation in 5-HIAA fitted a spring-peak cosine model that was significantly associated with sampling month (P=0.0074). Season of sampling explained 5.4% (P=1.57 × 10(-7)) of the variance in 5-HIAA concentrations. The 5-HTTLPR s-allele was associated with increased 5-HIAA seasonality (standardized regression coefficient=0.12, P=0.020, N=393). 5-HIAA seasonality correlated with depressive symptoms (Spearman's rho=0.13, P=0.018, N=345). In conclusion, we highlight a dose-dependent association of the 5-HTTLPR with 5-HIAA seasonality and a positive correlation between 5-HIAA seasonality and depressive symptomatology. The presented data set the stage for follow-up in clinical populations with a role for seasonality, such as affective disorders
3+1 Approach to the Long Wavelength Iteration Scheme
Large-scale inhomogeneities and anisotropies are modeled using the Long
Wavelength Iteration Scheme. In this scheme solutions are obtained as
expansions in spatial gradients, which are taken to be small. It is shown that
the choice of foliation for spacetime can make the iteration scheme more
effective in two respects: (i) the shift vector can be chosen so as to dilute
the effect of anisotropy on the late-time value of the extrinsic curvature of
the spacelike hypersurfaces of the foliation; and (ii) pure gauge solutions
present in a similar calculation using the synchronous gauge vanish when the
spacelike hypersurfaces have extrinsic curvature with constant trace. We
furthermore verify the main conclusion of the synchronous gauge calculation
which is large-scale inhomogeneity decays if the matter--considered to be that
of a perfect-fluid with a barotropic equation of state--violates the
strong-energy condition. Finally, we obtain the solution for the lapse function
and discuss its late-time behaviour. It is found that the lapse function is
well-behaved when the matter violates the strong energy condition.Comment: 21 pages, TeX file, already publishe
Absorption spectrum in the wings of the potassium second resonance doublet broadened by helium
We have measured the reduced absorption coefficients occurring in the wings
of the potassium 4S-5P doublet lines at 404.414 nm and at 404.720 nm broadened
by helium gas at pressures of several hundred Torr. At the experimental
temperature of 900 K, we have detected a shoulder-like broadening feature on
the blue wing of the doublet which is relatively flat between 401.8 nm and
402.8 nm and which drops off rapidly for shorter wavelengths, corresponding to
absorption from the X doublet Sigma+ state to the C doublet Sigma+ state of the
K-He quasimolecule. The accurate measurements of the line profiles in the
present work will sharply constrain future calculations of potential energy
surfaces and transition dipole moments correlating to the asymptotes He-K(5p),
He-K(5s), and He-K(3d).Comment: 2 figure
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