77 research outputs found
Loss of SNAP29 Impairs Endocytic Recycling and Cell Motility
Intracellular membrane trafficking depends on the ordered formation and consumption of transport intermediates and requires that membranes fuse with each other in a tightly regulated and highly specific manner. Membrane anchored SNAREs assemble into SNARE complexes that bring membranes together to promote fusion. SNAP29 is a ubiquitous synaptosomal-associated SNARE protein. It interacts with several syntaxins and with the EH domain containing protein EHD1. Loss of functional SNAP29 results in CEDNIK syndrome (Cerebral Dysgenesis, Neuropathy, Ichthyosis and Keratoderma). Using fibroblast cell lines derived from CEDNIK patients, we show that SNAP29 mediates endocytic recycling of transferrin and β1-integrin. Impaired β1-integrin recycling affected cell motility, as reflected by changes in cell spreading and wound healing. No major changes were detected in exocytosis of VSVG protein from the Golgi apparatus, although the Golgi system acquired a dispersed morphology in SNAP29 deficient cells. Our results emphasize the importance of SNAP29 mediated membrane fusion in endocytic recycling and consequently, in cell motility
Jet Medium interactions at Quark Matter 09
The suppression of the yield of high transverse momentum hadrons in
heavy-ion collisions, referred to as "jet-quenching", has now developed into a
comprehensive science. Jets are now used as probes of a variety of properties
of the dense medium through which they propagate. Major theoretical
improvements include jet modification in a 3-D fluid dynamical medium, the
first set of in-medium Monte-Carlo implementations, an understanding of
multi-hadron observables and energy flow within perturbative QCD, along with
improvements in the AdS/CFT description of energy loss. On the experimental
side, high statistics data are allowing for the first discriminatory test of
various theoretical models and approximations while the new measurements of
full jet reconstruction pose a challenge to theory.Comment: 11 pages, 6 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, typos corrected,
references adde
Can holography reproduce the QCD Wilson line?
Recently a remarkable agreement was found between lattice simulations of long
Wilson lines and behavior of the Nambu Goto string in flat space-time. However,
the latter fails to fit the short distance behavior since it admits a tachyonic
mode for a string shorter than a critical length. In this paper we examine the
question of whether a classical holographic Wilson line can reproduce the
lattice results for Wilson lines of any length. We determine the condition on
the the gravitational background to admit a Coulombic potential at short
distances. We analyze the system using three different renormalization schemes.
We perform an explicit best fit comparison of the lattice results with the
holographic models based on near extremal D3 and D4 branes, non-critical near
extremal AdS6 model and the Klebanov Strassler model. We find that all the
holographic models examined admit after renormalization a constant term in the
potential. We argue that the curves of the lattice simulation also have such a
constant term and we discuss its physical interpretation
Drag and jet quenching of heavy quarks in a strongly coupled N=2* plasma
The drag of a heavy quark and the jet quenching parameter are studied in the
strongly coupled N=2* plasma using the AdS/CFT correspondence. Both increase in
units of the spatial string tension as the theory departs from conformal
invariance. The description of heavy quark dynamics using a Langevin equation
is also considered. It is found that the difference between the velocity
dependent factors of the transverse and longitudinal momentum broadening of the
quark admit an interpretation in terms of relativistic effects, so the
distribution is spherical in the quark rest frame. When conformal invariance is
broken there is a broadening of the longitudinal momentum distribution. This
effect may be useful in understanding the jet distribution observed in
experiments.Comment: 30 pages, 5 figures, references added, minor corrections. To be
published in JHE
Five Easy Pieces: The Dynamics of Quarks in Strongly Coupled Plasmas
We revisit the analysis of the drag a massive quark experiences and the wake
it creates at a temperature T while moving through a plasma using a gravity
dual that captures the renormalisation group runnings in the dual gauge theory.
Our gravity dual has a black hole and seven branes embedded via Ouyang
embedding, but the geometry is a deformation of the usual conifold metric. In
particular the gravity dual has squashed two spheres, and a small resolution at
the IR. Using this background we show that the drag of a massive quark receives
corrections that are proportional to powers of log T when compared with the
drag computed using AdS/QCD correspondence. We use the perturbation produced by
the quark strings to compute the wake and compare with the results obtained
using AdS/QCD correspondence. We also study the shear viscosity with running
couplings, analyze the viscosity to entropy ratio and compare the result with
the known bound. In the presence of higher order curvature square corrections
from the back-reactions of the embedded D7 branes, we argue the possibility of
the entropy to viscosity bound being violated. Finally, we show that our set-up
could in-principle allow us to study a family of gauge theories at the boundary
by cutting off the dual geometry respectively at various points in the radial
direction. All these gauge theories can have well defined UV completions, and
more interestingly, we demonstrate that any thermodynamical quantities derived
from these theories would be completely independent of the cut-off scale and
only depend on the temperature at which we define these theories. Such a result
would justify the holographic renormalisabilities of these theories which we,
in turn, also demonstrate. We give physical interpretations of these results
and compare them with more realistic scenarios.Comment: 130 pages, 12 eps figures, LaTex; v4: final version with corrected
typos, numerous additional references and enlargement of some sections. The
published version, that appears in Nucl. Phys. B, differs slightly in section
3 where there is more emphasis on holographic renormalisabilty and less on
the wake, compared to this versio
Early-Time Energy Loss in a Strongly-Coupled SYM Plasma
We carry out an analytic study of the early-time motion of a quark in a
strongly-coupled maximally-supersymmetric Yang-Mills plasma, using the AdS/CFT
correspondence. Our approach extracts the first thermal effects as a small
perturbation of the known quark dynamics in vacuum, using a double expansion
that is valid for early times and for (moderately) ultrarelativistic quark
velocities. The quark is found to lose energy at a rate that differs
significantly from the previously derived stationary/late-time result: it
scales like T^4 instead of T^2, and is associated with a friction coefficient
that is not independent of the quark momentum. Under conditions representative
of the quark-gluon plasma as obtained at RHIC, the early energy loss rate is a
few times smaller than its late-time counterpart. Our analysis additionally
leads to thermally-corrected expressions for the intrinsic energy and momentum
of the quark, in which the previously discovered limiting velocity of the quark
is found to appear naturally.Comment: 39 pages, no figures. v2: Minor corrections and clarifications.
References added. Version to be published in JHE
Qualitative study of system-level factors related to genomic implementation
PURPOSE:
Research on genomic medicine integration has focused on applications at the individual level, with less attention paid to implementation within clinical settings. Therefore, we conducted a qualitative study using the Consolidated Framework for Implementation Research (CFIR) to identify system-level factors that played a role in implementation of genomic medicine within Implementing GeNomics In PracTicE (IGNITE) Network projects.
METHODS:
Up to four study personnel, including principal investigators and study coordinators from each of six IGNITE projects, were interviewed using a semistructured interview guide that asked interviewees to describe study site(s), progress at each site, and factors facilitating or impeding project implementation. Interviews were coded following CFIR inner-setting constructs.
RESULTS:
Key barriers included (1) limitations in integrating genomic data and clinical decision support tools into electronic health records, (2) physician reluctance toward genomic research participation and clinical implementation due to a limited evidence base, (3) inadequate reimbursement for genomic medicine, (4) communication among and between investigators and clinicians, and (5) lack of clinical and leadership engagement.
CONCLUSION:
Implementation of genomic medicine is hindered by several system-level barriers to both research and practice. Addressing these barriers may serve as important facilitators for studying and implementing genomics in practice
Developing a Common Framework for Evaluating the Implementation of Genomic Medicine Interventions in Clinical Care: The IGNITE Network’s Common Measures Working Group
Purpose
Implementation research provides a structure for evaluating the clinical integration of genomic medicine interventions. This paper describes the Implementing GeNomics In PracTicE (IGNITE) Network’s efforts to promote: 1) a broader understanding of genomic medicine implementation research; and 2) the sharing of knowledge generated in the network.
Methods
To facilitate this goal the IGNITE Network Common Measures Working Group (CMG) members adopted the Consolidated Framework for Implementation Research (CFIR) to guide their approach to: identifying constructs and measures relevant to evaluating genomic medicine as a whole, standardizing data collection across projects, and combining data in a centralized resource for cross network analyses.
Results
CMG identified ten high-priority CFIR constructs as important for genomic medicine. Of those, eight didn’t have standardized measurement instruments. Therefore, we developed four survey tools to address this gap. In addition, we identified seven high-priority constructs related to patients, families, and communities that did not map to CFIR constructs. Both sets of constructs were combined to create a draft genomic medicine implementation model.
Conclusion
We developed processes to identify constructs deemed valuable for genomic medicine implementation and codified them in a model. These resources are freely available to facilitate knowledge generation and sharing across the field
Holographic QCD: Past, Present, and Future
At the dawn of a new theoretical tool based on the AdS/CFT correspondence for
nonperturbative aspects of quantum chromodynamics, we give an interim review on
the new tool, holographic QCD, with some of its accomplishment. We try to give
an A-to-Z picture of the holographic QCD, from string theory to a few selected
top-down holographic QCD models with one or two physical applications in each
model. We may not attempt to collect diverse results from various holographic
QCD model studies.Comment: 80 pages, 18 figures, LaTeX; references added, published version +
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