132 research outputs found
Topological properties of punctual Hilbert schemes of almost-complex fourfolds (I)
In this article, we study topological properties of Voisin's punctual Hilbert
schemes of an almost-complex fourfold . In this setting, we compute their
Betti numbers and construct Nakajima operators. We also define tautological
bundles associated with any complex bundle on , which are shown to be
canonical in -theory
Quantitative plane-resolved crystal growth and dissolution kinetics by coupling in situ optical microscopy and diffusion models : the case of salicylic acid in aqueous solution
The growth and dissolution kinetics of salicylic acid crystals are investigated in situ by focusing on individual microscale crystals. From a combination of optical microscopy and finite element method (FEM) modeling, it was possible to obtain a detailed quantitative picture of dissolution and growth dynamics for individual crystal faces. The approach uses real-time in situ growth and dissolution data (crystal size and shape as a function of time) to parametrize a FEM model incorporating surface kinetics and bulk to surface diffusion, from which concentration distributions and fluxes are obtained directly. It was found that the (001) face showed strong mass transport (diffusion) controlled behavior with an average surface concentration close to the solubility value during growth and dissolution over a wide range of bulk saturation levels. The (1Ě…10) and (110) faces exhibited mixed mass transport/surface controlled behavior, but with a strong diffusive component. As crystals became relatively large, they tended to exhibit peculiar hollow structures in the end (001) face, observed by interferometry and optical microscopy. Such features have been reported in a number of crystals, but there has not been a satisfactory explanation for their origin. The mass transport simulations indicate that there is a large difference in flux across the crystal surface, with high values at the edge of the (001) face compared to the center, and this flux has to be redistributed across the (001) surface. As the crystal grows, the redistribution process evidently can not be maintained so that the edges grow at the expense of the center, ultimately creating high index internal structures. At later times, we postulate that these high energy faces, starved of material from solution, dissolve and the extra flux of salicylic acid causes the voids to close
Dosimetric uncertainties related to the elasticity of bladder and rectal walls: Adenocarcinoma of the prostate
Purpose. - Radiotherapy is an important treatment for prostate cancer.During
treatment sessions, bladder and rectal repletion is difficult to quantify and
cannot be measured with a single and initial CT scan acquisition. Some methods,
such as image-guided radiation therapy and dose-guided radiation therapy, aimto
compensate thismissing information through periodic CT acquisitions. The aimis
to adapt patient's position, beam configuration or prescribed dose for a
dosimetric compliance. Methods. -We evaluated organmotion (and repletion) for
54 patients after having computed the original ballistic on a new CT scan
acquisition. A new delineation was done on the prostate, bladder and rectum to
determine the newdisplacements and define organ dosesmistakes (equivalent
uniformdose, average dose and dose-volume histograms). Results. - The new CT
acquisitions confirmed that bladder and rectal volumes were not constant during
sessions. Some cases showed that previously validated treatment plan became
unsuitable. A proposed solution is to correct dosimetries when bladder volume
modifications are significant. The result is an improvement for the stability
of bladder doses, D50 error is reduced by 25.3%, mean dose error by 5.1% and
equivalent uniform dose error by 2.6%. For the rectum this method decreases
errors by only 1%. This process can reduce the risk of mismatch between the
initial scan and following treatment sessions. Conclusion. - For the
proposedmethod, the cone-beamCT is necessary to properly position the isocenter
and to quantify bladder and rectal volume variation and deposited doses. The
dosimetries are performed in the event that bladder (or rectum) volume
modification limits are exceeded. To identify these limits, we have calculated
that a tolerance of 10% for the equivalent uniformdose (compared to the initial
value of the first dosimetry), this represents 11% of obsolete dosimetries for
the bladder, and 4% for the rectum
Radio Astronomy
Contains summary of research and reports on seven research projects.National Science Foundation (Grant AST82-14296)National Aeronautics and Space Administration (Grant NAGW-373)National Aeronautics and Space Administration (Contract NAS5-28410)U.S. Navy - Office of Naval Research (Contract N00014-84-C-2082)M.I.T. Sloan Fund for Basic ResearchNational Oceanic and Atmospheric Administration (Grant 04-8-M01-1)National Aeronautics and Space Administration (Grant NAG5-10)Defense Advanced Research Project Agency (Contract MDA 903-84-K-0297
Radio Astronomy
Contains reports on five research projects.National Science Foundation (Grant AST82-14296)National Aeronautics and Space Administration (Grant NAG W-373)National Aeronautics and Space Administration (Grant NAG5-537)U.S. Navy - Office of Naval Research (Contract N00014-84-C-2082)SM Systems and Research, Inc.Defense Advanced Research Project Agency (Contract MDA903-82-K-0521
Induced pseudoscalar coupling of the proton weak interaction
The induced pseudoscalar coupling is the least well known of the weak
coupling constants of the proton's charged--current interaction. Its size is
dictated by chiral symmetry arguments, and its measurement represents an
important test of quantum chromodynamics at low energies. During the past
decade a large body of new data relevant to the coupling has been
accumulated. This data includes measurements of radiative and non radiative
muon capture on targets ranging from hydrogen and few--nucleon systems to
complex nuclei. Herein the authors review the theoretical underpinnings of
, the experimental studies of , and the procedures and uncertainties
in extracting the coupling from data. Current puzzles are highlighted and
future opportunities are discussed.Comment: 58 pages, Latex, Revtex4, prepared for Reviews of Modern Physic
Mutations specific to the Rac-GEF domain of <i>TRIO</i> cause intellectual disability and microcephaly
Background: Neurodevelopmental disorders have challenged clinical genetics for decades, with over 700 genes implicated and many whose function remains unknown. The application of whole-exome sequencing is proving pivotal in closing the genotype/phenotype gap through the discovery of new genes and variants that help to unravel the pathogenic mechanisms driving neuropathogenesis. One such discovery includes TRIO, a gene recently implicated in neurodevelopmental delay. Trio is a Dbl family guanine nucleotide exchange factor (GEF) and a major regulator of neuronal development, controlling actin cytoskeleton dynamics by activating the GTPase Rac1.Methods: Whole-exome sequencing was undertaken on a family presenting with global developmental delay, microcephaly and mild dysmorphism. Father/daughter exome analysis was performed, followed by confirmatory Sanger sequencing and segregation analysis on four individuals. Three further patients were recruited through the deciphering developmental disorders (DDD) study. Functional studies were undertaken using patient-specific Trio protein mutations.Results: We identified a frameshift deletion in TRIO that segregated autosomal dominantly. By scrutinising data from DDD, we further identified three unrelated children with a similar phenotype who harboured de novo missense mutations in TRIO. Biochemical studies demonstrated that in three out of four families, the Trio mutations led to a markedly reduced Rac1 activation.Conclusions: We describe an inherited global developmental delay phenotype associated with a frameshift deletion in TRIO. Additionally, we identify pathogenic de novo missense mutations in TRIO associated with the same consistent phenotype, intellectual disability, microcephaly and dysmorphism with striking digital features. We further functionally validate the importance of the GEF domain in Trio protein function. Our study demonstrates how genomic technologies are yet again proving prolific in diagnosing and advancing the understanding of neurodevelopmental disorders.<br/
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