2,348 research outputs found
Nanoparticles in optic nerve trauma: nanoscaffolding, visualization and regeneration
Session 1 - Nanotechnology / Vision Restoration: Concepts, Possibilities, Challengespostprin
Nanoscale technologies: nano-knitting, healing powers and hemostasis
Session 2 - Nanotechnology / Vision Restoration: Clinical Usespostprin
Specialized Vasculature in the Rostral Migratory Stream as a Neurogenic Niche and Scaffold for Neuroblast Migration
published_or_final_versio
Longitudinal 1H MRS of hamster superior colliculus following retinotectal deafferentation
Session: Applications of MRS to the Animal Brain - TRADpublished_or_final_versionThe 17th Scientific Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honlolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 200
A Self-assembling Nanomaterial Reduces Acute Brain Injury and Enhances Functional Recovery in a Rat Model of Hypertensive Intracerebral Hemorrhage
published_or_final_versio
Visual function due to regeneration of optic nerve or optic tract through peripheral nerve homografts
Segments of sciatic nerve from one leg were used to induce regeneration of transected optic nerve (ON) or tract in Syrian hamsters. In the first group, the nerve graft was sutured to the stump of the transected ON of the right eye in young adult animals, and the other end was placed below the surface of the ipsilateral superior colliculus (SC); the opposite eye was removed. In one animal, orienting movements in the wrong direction were elicited and recorded on videotape, beginning when the animal was more than 1.5 yr old, over 1 yr after surgery. In the second group, a similar procedure was used but with the nerve going to the contralateral SC. In 3 of 4 long-term survivors, visually elicited turning was obtained and recorded, most reliably in the final 4 mo of their 2-yr life. Regenerating retinofugal axons were traced and their terminations in SC reconstructed using a CT-B procedure and immunohistochemistry (secondary AB conjugated to Alexa-488) and fluorescence microscopy. The visually unresponsive animal had no regeneration, and the most responsive animal had the greatest amount of regeneration. In a 3rd procedure, the right brachium of SC was transected, and 2 or 3 segments of sciatic nerve were implanted as bridges to elicit optic tract regeneration. The first 3 of these animals were operated at age 13-19 days; considerable regeneration was verified anatomically in each case, after behavioral demonstration of visual orienting.
Supported by NIH grant EY00126.published_or_final_versio
Probing EWSB Naturalness in Unified SUSY Models with Dark Matter
We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the
context of two unified Supersymmetry scenarios: the Constrained Minimal
Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM),
in light of current and upcoming direct detection dark matter experiments. We
consider both those models that satisfy a one-sided bound on the relic density
of neutralinos, , and also the subset that satisfy
the two-sided bound in which the relic density is within the 2 sigma best fit
of WMAP7 + BAO + H0 data. We find that current direct detection searches for
dark matter probe the least fine-tuned regions of parameter-space, or
equivalently those of lowest Higgs mass parameter , and will tend to probe
progressively more and more fine-tuned models, though the trend is more
pronounced in the CMSSM than in the NUHM. Additionally, we examine several
subsets of model points, categorized by common mass hierarchies; M_{\chi_0}
\sim M_{\chi^\pm}, M_{\chi_0} \sim M_{\stau}, M_{\chi_0} \sim M_{\stop_1}, the
light and heavy Higgs poles, and any additional models classified as "other";
the relevance of these mass hierarchies is their connection to the preferred
neutralino annihilation channel that determines the relic abundance. For each
of these subsets of models we investigated the degree of fine-tuning and
discoverability in current and next generation direct detection experiments.Comment: 26 pages, 10 figures. v2: references added. v3: matches published
versio
Behavioral testing and preliminary analysis of the hamster visual system
The dependence of visual orienting ability in hamsters on the axonal projections from retina to midbrain tectum provides experimenters with a good model for assessing the functional regeneration of this central nervous system axonal pathway. For reliable testing of this behavior, male animals at least 10-12 weeks old are prepared by regular pretesting, with all procedures carried out during the less active portion of the daily activity cycle. Using a sunflower seed attached to a small black ball held at the end of a stiff wire, and avoiding whisker contact, turning movements toward visual stimuli are video recorded from above. Because at the eye level, the nasal-most 30° of the visual field can be seen by both the eyes, this part of the field is avoided in assessments of a single side. Daily sessions consist of ten presentations per side. Measures are frequency of responding and detailed turning trajectories. Complete assessment of the functional return of behavior in this testing paradigm takes 3-6 months to complete.postprin
Background Rejection in the DMTPC Dark Matter Search Using Charge Signals
The Dark Matter Time Projection Chamber (DMTPC) collaboration is developing
low-pressure gas TPC detectors for measuring WIMP-nucleon interactions. Optical
readout with CCD cameras allows for the detection for the daily modulation in
the direction of the dark matter wind, while several charge readout channels
allow for the measurement of additional recoil properties. In this article, we
show that the addition of the charge readout analysis to the CCD allows us too
obtain a statistics-limited 90% C.L. upper limit on the rejection factor
of for recoils with energies between 40 and 200
keV. In addition, requiring coincidence between charge signals
and light in the CCD reduces CCD-specific backgrounds by more than two orders
of magnitude.Comment: 8 pages, 6 figures. For proceedings of DPF 2011 conferenc
Constraints on Low-Mass WIMP Interactions on 19F from PICASSO
Recent results from the PICASSO dark matter search experiment at SNOLAB are
reported. These results were obtained using a subset of 10 detectors with a
total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low
backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be
obtained which results in an increased sensitivity to interactions from Weakly
Interacting Massive Particles (WIMPs) with masses below 10 GeV/c^2. No dark
matter signal was found. Best exclusion limits in the spin dependent sector
were obtained for WIMP masses of 20 GeV/c^2 with a cross section on protons of
sigma_p^SD = 0.032 pb (90% C.L.). In the spin independent sector close to the
low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections
larger than sigma_p^SI = 1.41x10^-4 pb (90% C.L.) are excluded.Comment: 23 pages, 7 figures, to be published in Phys. Lett.
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