2,060 research outputs found
Conceptual Frameworks for Multimodal Social Signal Processing
This special issue is about a research area which is developing rapidly. Pentland gave it a name which has become widely used, âSocial Signal Processingâ (SSP for short), and his phrase provides the title of a European project, SSPnet, which has a brief to consolidate the area. The challenge that Pentland highlighted was understanding the nonlinguistic signals that serve as the basis for âsubconscious discussions between humans about relationships, resources, risks, and rewardsâ. He identified it as an area where computational research had made interesting progress, and could usefully make more
Multiplicities for LHC Nuclear Collisions Using HERA Structure Functions
We compute in QCD perturbation theory the transverse energy carried by
gluons, quarks and antiquarks with GeV in Pb+Pb
collisions at GeV by using structure functions compatible
with the small- increase observed at HERA. This gives a perturbative
estimate for the energy and entropy density of the bulk system at times
fm. The predicted initial gluon entropy density gives a lower
limit of about 2200...3400 for the final charged multiplicity. Sources of
further entropy increase are discussed.Comment: HU-TFT-94-6, 7 pages, 3 PostScript figures included in the end of the
tex-fil
The Effect of Shadowing on Initial Conditions, Transverse Energy and Hard Probes in Ultrarelativistic Heavy Ion Collisions
The effect of shadowing on the early state of ultrarelativistic heavy ion
collisions is investigated along with transverse energy and hard process
production, specifically Drell-Yan, , and production. We
choose several parton distributions and parameterizations of nuclear shadowing,
as well as the spatial dependence of shadowing, to study the influence of
shadowing on relevant observables. Results are presented for Au+Au collisions
at GeV and Pb+Pb collisions at TeV.Comment: Submitted to Phys. Rev.
Morphology and distribution of taste papillae and oral denticles in the developing oropharyngeal cavity of the bamboo shark, Chiloscyllium punctatum.
Gustation in sharks is not well understood, especially within species that ingest food items using suction. This study examines the morphological and immunohistochemical characterisation of taste papillae and oral denticles in the oropharynx of the brown-banded bamboo shark Chiloscyllium punctatum and compares their distribution during development. Taste papillae of the brown-banded bamboo shark Chiloscyllium punctatum are located throughout the oropharyngeal region and are most concentrated on the oral valves (2,125-3,483 per cm(2) in embryos; 89-111 per cm(2) in mature adults) close to the tooth territories. Papillae appearance is comparable at all stages of development, with the exception of the embryos (unhatched specimens), where no microvilli are present. Oral valve papillae are comparable in structure to Type I taste buds of teleost fishes, whereas those of the rest of the oropharyngeal region are comparable to Type II. Both types of papillae show immunofluorescence for a number of markers of taste buds, including ÎČ-Catenin and Sox2. Taste papillae densities are highest in embryos with 420-941 per cm(2) compared to 8-29 per cm(2) in mature adults. The total number of papillae remains around 1,900 for all stages of development. However, the papillae increase in diameter from 72±1 ”m in embryos to 310±7 ”m in mature individuals. Microvilli protrude in multiple patches at the apical tip of the papilla covering âŒ0.5% of the papillar surface area. We further document the relationship between taste papillae and the closely associated oral denticles within the shark orophayngeal cavity. Oral denticles first break through the epithelium in the antero-central region of the dorsal oral cavity, shortly after the emergence of teeth, around time of hatching. Denticles are located throughout the oropharyngeal epithelium of both immature and mature stages, with the highest concentrations in the antero-dorsal oral cavity and the central regions of the pharynx. These denticle-rich areas of the mouth and pharynx are therefore thought to protect the epithelium, and importantly the taste papillae, from abrasion since they correlate with regions where potential food items are processed or masticated for consumption. Taste papillae and denticles are more dense in anterior oropharyngeal regions in close association with the oral jaws and teeth, and in the juvenile/hatchling shark taste units are functional, and innervated, allowing the shark to seek out food in utero, at birth or on emergence from the egg case
Developing an ancient epithelial appendage: FGF signalling regulates early tail denticle formation in sharks
Background: Vertebrate epithelial appendages constitute a diverse group of organs that includes integumentary
structures such as reptilian scales, avian feathers and mammalian hair. Recent studies have provided new evidence for
the homology of integumentary organ development throughout amniotes, despite their disparate fnal morphologies.
These structures develop from conserved molecular signalling centres, known as epithelial placodes. It is not yet
certain whether this homology extends beyond the integumentary organs of amniotes, as there is a lack of knowledge
regarding their development in basal vertebrates. As the ancient sister lineage of bony vertebrates, extant chondrichthyans
are well suited to testing the phylogenetic depth of this homology. Elasmobranchs (sharks, skates and
rays) possess hard, mineralised epithelial appendages called odontodes, which include teeth and dermal denticles
(placoid scales). Odontodes constitute some of the oldest known vertebrate integumentary appendages, predating
the origin of gnathostomes. Here, we used an emerging model shark (Scyliorhinus canicula) to test the hypothesis that
denticles are homologous to other placode-derived amniote integumentary organs. To examine the conservation
of putative gene regulatory network (GRN) member function, we undertook small molecule inhibition of fbroblast
growth factor (FGF) signalling during caudal denticle formation.
Results: We show that during early caudal denticle morphogenesis, the shark expresses homologues of conserved
developmental gene families, known to comprise a core GRN for early placode morphogenesis in amniotes. This
includes conserved expression of FGFs, sonic hedgehog (shh) and bone morphogenetic protein 4 (bmp4). Additionally,
we reveal that denticle placodes possess columnar epithelial cells with a reduced rate of proliferation, a conserved
characteristic of amniote skin appendage development. Small molecule inhibition of FGF signalling revealed
placode development is FGF dependent, and inhibiting FGF activity resulted in downregulation of shh and bmp4
expression, consistent with the expectation from comparison to the amniote integumentary appendage GRN.
Conclusion: Overall, these fndings suggest the core GRN for building vertebrate integumentary epithelial appendages
has been highly conserved over 450 million years. This provides evidence for the continuous, historical homology
of epithelial appendage placodes throughout jawed vertebrates, from sharks to mammals. Epithelial placodes
constitute the shared foundation upon which diverse vertebrate integumentary organs have evolved
Shark tooth regeneration reveals common stem cell characters in both human rested lamina and ameloblastoma
The human dentition is a typical diphyodont mammalian system with tooth replacement of most positions. However, after dental replacement and sequential molar development, the dental lamina undergoes apoptosis and fragments, leaving scattered epithelial units (dental lamina rests; DLRs). DLRs in adult humans are considered inactive epithelia, thought to possess limited capacity for further regeneration. However, we show that these tissues contain a small proportion of proliferating cells (assessed by both Ki67 and PCNA) but also express a number of common dental stem cell markers (Sox2, Bmi1, ÎČ-catenin and PH3) similar to that observed in many vertebrates that actively, and continuously regenerate their dentition. We compared these human tissues with the dental lamina of sharks that regenerate their dentition throughout life, providing evidence that human tissues have the capacity for further and undocumented regeneration. We also assessed cases of human ameloblastoma to characterise further the proliferative signature of dental lamina rests. Ameloblastomas are assumed to derive from aberrant lamina rests that undergo changes, which are not well understood, to form a benign tumour. We suggest that dental lamina rests can offer a potential source of important dental stem cells for future dental regenerative therapy. The combined developmental genetic data from the shark dental lamina and ameloblastoma may lead to the development of novel methods to utilise these rested populations of adult lamina stem cells for controlled tooth replacement in humans
EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
We present a next-to-leading order (NLO) global DGLAP analysis of nuclear
parton distribution functions (nPDFs) and their uncertainties. Carrying out an
NLO nPDF analysis for the first time with three different types of experimental
input -- deep inelastic +A scattering, Drell-Yan dilepton production in
p+ collisions, and inclusive pion production in d+Au and p+p collisions at
RHIC -- we find that these data can well be described in a conventional
collinear factorization framework. Although the pion production has not been
traditionally included in the global analyses, we find that the shape of the
nuclear modification factor of the pion -spectrum at
midrapidity retains sensitivity to the gluon distributions, providing evidence
for shadowing and EMC-effect in the nuclear gluons. We use the Hessian method
to quantify the nPDF uncertainties which originate from the uncertainties in
the data. In this method the sensitivity of to the variations of the
fitting parameters is mapped out to orthogonal error sets which provide a
user-friendly way to calculate how the nPDF uncertainties propagate to any
factorizable nuclear cross-section. The obtained NLO and LO nPDFs and the
corresponding error sets are collected in our new release called {\ttfamily
EPS09}. These results should find applications in precision analyses of the
signatures and properties of QCD matter at the LHC and RHIC.Comment: 34 pages, 16 figures. The version accepted for publicatio
Shadowing Effects on Vector Boson Production
We explore how nuclear modifications to the nucleon structure functions,
shadowing, affect massive gauge boson production in heavy ion collisions at
different impact parameters. We calculate the dependence of , and
production on rapidity and impact parameter to next-to-leading order in
Pb+Pb collisions at 5.5 TeV/nucleon to study quark shadowing at high . We
also compare our Pb+Pb results to the rapidity distributions at 14 TeV.Comment: 25 pages ReVTeX, 12 .eps figures, NLO included, version accepted for
publication in Physical Review
The extraction of nuclear sea quark distribution and energy loss effect in Drell-Yan experiment
The next-to-leading order and leading order analysis are performed on the
differential cross section ratio from Drell-Yan process. It is found that the
effect of next-to-leading order corrections can be negligible on the
differential cross section ratios as a function of the quark momentum fraction
in the beam proton and the target nuclei for the current Fermilab and future
lower beam proton energy. The nuclear Drell-Yan reaction is an ideal tool to
study the energy loss of the fast quark moving through cold nuclei. In the
leading order analysis, the theoretical results with quark energy loss are in
good agreement with the Fermilab E866 experimental data on the Drell-Yan
differential cross section ratios as a function of the momentum fraction of the
target parton. It is shown that the quark energy loss effect has significant
impact on the Drell-Yan differential cross section ratios. The nuclear
Drell-Yan experiment at current Fermilab and future lower energy proton beam
can not provide us with more information on the nuclear sea quark distribution.Comment: 17 pages, 4 figure
- âŠ