747 research outputs found
A FGF-Hh feedback loop controls stem cell proliferation in the developing larval brain of drosophila melanogaster
The adult Drosophila central nervous system is produced by two phases of
neurogenesis: the first phase occurs during embryonic development where the larval
brain is formed and the second occurs during larval development to form the adult brain.
Neurogenesis in both phases is caused by the activation of neural stem cell division and
subsequent progenitor cell division and terminal differentiation. Proper activation of
neural stem cell division in the larval brain is essential for proper patterning and
functionality of the adult central nervous system. Initiation of neural stem cell
proliferation requires signaling from the Fibroblast Growth Factor (FGF) homolog
Branchless (Bnl) and by the Hedgehog (Hh) growth factor. I have focused on the
interactions between both of these signaling pathways with respect to post-embryonic
neural stem cell proliferation using the Drosophila larval brain.
Using proliferation assays and quantitative real-time PCR, I have shown that Bnl
and Hh signaling is inter-dependent in the 1st instar larval brain and activates neural stem cell proliferation. I have also shown that overexpression of bnl can rescue
signaling and neuroblast proliferation in a hh mutant. However, overexpression of hh
does not rescue signaling or neuroblast proliferation in a bnl mutant, suggesting that Bnl
is the signaling output of the Bnl-Hh feedback loop and that all central brain and optic
lobe neural stem cells require Bnl signaling to initiated proliferation
Single system image: A survey
Single system image is a computing paradigm where a number of distributed computing resources are aggregated and presented via an interface that maintains the illusion of interaction with a single system. This approach encompasses decades of research using a broad variety of techniques at varying levels of abstraction, from custom hardware and distributed hypervisors to specialized operating system kernels and user-level tools. Existing classification schemes for SSI technologies are reviewed, and an updated classification scheme is proposed. A survey of implementation techniques is provided along with relevant examples. Notable deployments are examined and insights gained from hands-on experience are summarized. Issues affecting the adoption of kernel-level SSI are identified and discussed in the context of technology adoption literature
Decision making from economic and signal detection perspectives: development of an integrated framework
A Component-Based Approach for Scientific Services for Education and Research (Scientific SEARCH)
Today’s challenge for retrieving digital information by users such as “students,” educators,” or “researchers” is coping, more than ever before, with the excessive data and information available. The problem is further compounded because of the way scientific knowledge is structured, in terms of expert interviews, articles, conference coverage, journal scans etc. Great progress has been made in digital library research. The NSF/NSDL through their initiatives has assembled a great set of tools and techniques that hold significant potential. Many projects are now underway applying these tools and techniques to meet the information needs of different user communities. The primary focus of Scientific SEARCH project is enhancing access to high quality learning materials and resources, modules, and other digital objects targeted towards scientific consumer and scientific producer. The project will use a multi-phased approach to achieve the objective. The paper describes the first-phase work submitted to NSF 04-542 solicitation
Massive skyrmions in quantum Hall ferromagnets
We apply the theory of elasticity to study the effects of skyrmion mass on
lattice dynamics in quantum Hall systems. We find that massive Skyrme lattices
behave like a Wigner crystal in the presence of a uniform perpendicular
magnetic field. We make a comparison with the microscopic Hartree-Fock results
to characterize the mass of quantum Hall skyrmions at and investigate
how the low temperature phase of Skyrme lattices may be affected by the
skyrmion mass.Comment: 6 pages and 2 figure
Structure of thymidylate kinase from Ehrlichia chaffeensis
A 2.15 Å resolution apo structure of thymidylate kinase from E. chaffeensis is reported
The field theory of Skyrme lattices in quantum Hall ferromagnets
We report the application of the nonlinear model to study the
multi-skyrmion problem in the quantum Hall ferromagnet system. We show that the
ground state of the system can be described by a ferromagnet triangular Skyrme
lattice near where skyrmions are extremely dilute. We find a transition
into antiferromagnet square lattice by increasing the skyrmion density and
therefore . We investigate the possibility that the square Skyrme
lattice deforms to a single skyrmion with the same topological charge when the
Zeeman energy is extremely smaller than the Coulomb energy. We explicitly show
that the energy of a skyrmion with charge two is less than the energy of two
skyrmions each with charge one when . By taking the quantum
fluctuations into account, we also argue the possibility of the existence of a
non-zero temperature Kosterlitz-Thouless and a superconductor-insulator phase
transition.Comment: 17 page
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