765 research outputs found
Kinetic Modeling of Vacuum Gas Oil Hydrotreatment using a Molecular Reconstruction Approach
International audienceVacuum Gas Oils (VGO) are heavy petroleum cuts (boiling points ranging from 350 to 550 ËšC) that can be transformed into valuable fuels (gasolines, diesels) by fluid catalytic cracking or hydrocracking. Prior to these conversion processes, hydrotreating is required in order to eliminate the impurities in VGOs. The hydrotreatment process enables to meet the environmental specifications (total sulfur contents) and to prevent nitrogen poisoning of conversion catalysts. In order to develop a kinetic model based on an accurate VGOs molecular description, innovative analytical tools and molecular reconstruction techniques were used in this work. A lumped model using a Langmuir-Hinshelwood representation was developed for hydrodearomatization, hydrodesulfurization and hydrodenitrogenation of the VGO. This lumped model was successfully applied to the experimental feed pretreatment data and was able to predict evolution of concentration of the aromatics, nitrogen and sulfur species
Partially ordered distributed computations on asynchronous point-to-point networks
Asynchronous executions of a distributed algorithm differ from each other due
to the nondeterminism in the order in which the messages exchanged are handled.
In many situations of interest, the asynchronous executions induced by
restricting nondeterminism are more efficient, in an application-specific
sense, than the others. In this work, we define partially ordered executions of
a distributed algorithm as the executions satisfying some restricted orders of
their actions in two different frameworks, those of the so-called event- and
pulse-driven computations. The aim of these restrictions is to characterize
asynchronous executions that are likely to be more efficient for some important
classes of applications. Also, an asynchronous algorithm that ensures the
occurrence of partially ordered executions is given for each case. Two of the
applications that we believe may benefit from the restricted nondeterminism are
backtrack search, in the event-driven case, and iterative algorithms for
systems of linear equations, in the pulse-driven case
L’affichage des prix et la promotion des livres dans les annonces de librairie au XVIIIe siècle
Clocking the Lyme Spirochete
In order to clear the body of infecting spirochetes, phagocytic cells must be able to get hold of them. In real-time phase-contrast videomicroscopy we were able to measure the speed of Borrelia burgdorferi (Bb), the Lyme spirochete, moving back and forth across a platelet to which it was tethered. Its mean crossing speed was 1,636 µm/min (N = 28), maximum, 2800 µm/min (N = 3). This is the fastest speed recorded for a spirochete, and upward of two orders of magnitude above the speed of a human neutrophil, the fastest cell in the body. This alacrity and its interpretation, in an organism with bidirectional motor capacity, may well contribute to difficulties in spirochete clearance by the host
Four Butterflies: End of Life Stories of Transition and Transformation
In this article, the author discusses her experiences as an Artist In Residence in the
Department of Palliative Care and Rehabilitation Medicine at the University of Texas M. D.
Anderson Cancer Center. Emphasis is placed on the ways in which end of life images and
narratives often unfold in the fragile yet powerful space where conceptions of aesthetics and
spirituality intersect with critical issues in the medical humanities. Drawing on four vivid
case studies, the author examines the ways in which end of life narratives shed valuable light on
conceptions of the subtlety of human embodiment; issues of violation, sorrow, and forgiveness;
the mystical dimensions of traditional cultural beliefs; and the capacity for perceiving the
natural world as a living symbol of grace. In so doing, she explores how the themes of transition
and transformation become invested with meaningful existential and symbolic dimensions in
artworks that give voice and presence to some of the most vulnerable, and often invisible,
members of our societyï¾—people at the end of life
Fiber-Flux Diffusion Density for White Matter Tracts Analysis: Application to Mild Anomalies Localization in Contact Sports Players
We present the concept of fiber-flux density for locally quantifying white
matter (WM) fiber bundles. By combining scalar diffusivity measures (e.g.,
fractional anisotropy) with fiber-flux measurements, we define new local
descriptors called Fiber-Flux Diffusion Density (FFDD) vectors. Applying each
descriptor throughout fiber bundles allows along-tract coupling of a specific
diffusion measure with geometrical properties, such as fiber orientation and
coherence. A key step in the proposed framework is the construction of an FFDD
dissimilarity measure for sub-voxel alignment of fiber bundles, based on the
fast marching method (FMM). The obtained aligned WM tract-profiles enable
meaningful inter-subject comparisons and group-wise statistical analysis. We
demonstrate our method using two different datasets of contact sports players.
Along-tract pairwise comparison as well as group-wise analysis, with respect to
non-player healthy controls, reveal significant and spatially-consistent FFDD
anomalies. Comparing our method with along-tract FA analysis shows improved
sensitivity to subtle structural anomalies in football players over standard FA
measurements
Xq27 FRAXA locus is a strong candidate for dyslexia: evidence from a genome-wide scan in French families.
Dyslexia is a frequent neurodevelopmental
learning disorder. To date, nine susceptibility loci have
been identified, one of them being DYX9, located in Xq27.
We performed the first French SNP linkage study followed
by candidate gene investigation in dyslexia by studying 12
multiplex families (58 subjects) with at least two children
affected, according to categorical restrictive criteria for
phenotype definition. Significant results emerged on
Xq27.3 within DYX9. The maximum multipoint LOD
score reached 3,884 between rs12558359 and rs454992.
Within this region, seven candidate genes were investigated
for mutations in exonic sequences (CXORF1,
CXORF51, SLITRK2, FMR1, FMR2, ASFMR1, FMR1NB),
all having a role during brain development. We further
looked for 50
UTR trinucleotide repeats in FMR1 and FMR2
genes. No mutation or polymorphism co-segregating with
dyslexia was found. This finding in French families with
Dyslexia showed significant linkage on Xq27.3 enclosing
FRAXA, and consequently confirmed the DYX9 region as
a robust susceptibility locus. We reduced the previously
described interval from 6.8 (DXS1227–DXS8091) to 4 Mb
also disclosing a higher LOD score
The thing about pain: The remaking of illness narratives in chronic pain expressions on social media
In this article, we analyse chronic pain narratives on Flickr and Tumblr. We focus on how, by incorporating visual and multimodal elements, chronic pain expressions in social media significantly extend and challenge the logic, function and effects of traditional ‘illness narratives’. We examine a sample of images and blogs related to chronic pain and formulate a typology of chronic pain expressions on these sites. Flickr brings a form of narrative immediacy, making the pain experience visible, eliciting empathy and marking chronicity. Tumblr lends itself to more networked forms of interaction through the circulation of multimodal memes, and support communities are built through humour and social criticism. We argue that new forms of mediation and social media dynamics transform pain narratives. This has implications for our understandings of the forms and formats of pain communication and offers new possibilities for communicating pain within and beyond clinical contexts
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