5,819 research outputs found
Momentum Spectra in the Current Region of the Breit Frame in Deep Inelastic Scattering at HERA
The production of charged particles has been measured in deep inelastic
scattering (DIS) with the ZEUS detector. The evolution of the moments of the
scaled momenta distributions in and has been investigated in the
current fragmentation region of the Breit frame. The results in the current
region are compared to data and QCD analytical calculations. The
results are consistent with the universality of single-particle spectra in DIS
and annihilation at high The results at low disagree with
analytical calculations based on the modified leading log approximation (MLLA)
and local parton hadron duality (LPHD).Comment: 3 pages. 1 postscript figure + 1 postscript preprint logo + 1 LaTeX
file + 1 style fil
Obesity: A Biobehavioral Point of View
Excerpt: If you ask an overweight person, “Why are you fat?’, you will, almost invariably, get the answer, “Because 1 eat too much.” You will get this answer in spite of the fact that of thirteen studies, six find no significant differences in the caloric intake of obese versus nonobese subjects, five report that the obese eat significantly less than the nonobese, and only two report that they eat significantly more
Preliminary Investigation of Novel Bone Graft Substitutes based on Strontium-Calcium-Zinc-Silicate Glasses
Bone graft procedures typically require surgeons to harvest bone from a second site on a given patient (Autograft) before repairing a bone defect. However, this results in increased surgical time, excessive blood loss and a significant increase in pain. In this context a synthetic bone graft with excellent histocompatibility, built in antibacterial efficacy and the ability to regenerate healthy tissue in place of diseased tissue would be a significant step forward relative to current state of the art philosophies. We developed a range of calcium-strontium-zinc-silicate glass-based bone grafts and characterized their structure and physical properties, then evaluated their in vitro cytotoxicity and in vivo biocompatibility using standardized models from the literature. A graft (designated BT109) of composition 0.28SrO/0.32ZnO/0.40 SiO2 (mol fraction) was the best performing formulation in vitro shown to induce extremely mild cytopathic effects (cell viability up to 95%) in comparison with the commercially available bone graft Novabone® (cell viability of up to 72%). Supplementary to this, the grafts were examined using the standard rat femur healing model on healthy Wister rats. All grafts were shown to be equally well tolerated in bone tissue and new bone was seen in close apposition to implanted particles with no evidence of an inflammatory response within bone. Complimentary to this BT109 was implanted into the femurs of ovariectomized rats to monitor the response of osteoporotic tissue to the bone grafts. The results from this experiment indicate that the novel grafts perform equally well in osteoporotic tissue as in healthy tissue, which is encouraging given that bone response to implants is usually diminished in ovariectomized rats. In conclusion these materials exhibit significant potential as synthetic bone grafts to warrant further investigation and optimisation. © 2008 Springer Science+Business Media, LLC
Computer Simulation of Final-Stage Sintering: II, Influence of Initial Pore Size
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65612/1/j.1151-2916.1990.tb06687.x.pd
Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback
We introduce the Making Galaxies in a Cosmological Context (MaGICC) program
of smoothed particle hydrodynamics (SPH) simulations. We describe a parameter
study of galaxy formation simulations of an L* galaxy that uses early stellar
feedback combined with supernova feedback to match the stellar mass--halo mass
relationship. While supernova feedback alone can reduce star formation enough
to match the stellar mass--halo mass relationship, the galaxy forms too many
stars before z=2 to match the evolution seen using abundance matching. Our
early stellar feedback is purely thermal and thus operates like a UV ionization
source as well as providing some additional pressure from the radiation of
massive, young stars. The early feedback heats gas to >10^6 K before cooling to
10^4 K. The pressure from this hot gas creates a more extended disk and
prevents more star formation prior to z=1 than supernovae feedback alone. The
resulting disk galaxy has a flat rotation curve, an exponential surface
brightness profile, and matches a wide range of disk scaling relationships. The
disk forms from the inside-out with an increasing exponential scale length as
the galaxy evolves. Overall, early stellar feedback helps to simulate galaxies
that match observational results at low and high redshifts.Comment: 13 pages, 14 figures, accepted MNRAS, movies at
http://www.mpia.de/~stinson/magic
Characterizing Short-Wave Infrared Fluorescence of Conventional Near-Infrared Fluorophores
The observed behavior of short-wave infrared (SWIR) light in tissue, characterized by relatively low scatter and subdiffuse photon transport, has generated considerable interest for the potential of SWIR imaging to produce high-resolution, subsurface images of fluorescence activity in vivo. These properties have important implications for fluorescence-guided surgery and preclinical biomedical research. Until recently, translational efforts have been impeded by the conventional understanding that fluorescence molecular imaging in the SWIR regime requires custom molecular probes that do not yet have proven safety profiles in humans. However, recent studies have shown that two readily available near-infrared (NIR-I) fluorophores produce measurable SWIR fluorescence, implying that other conventional fluorophores produce detectable fluorescence in the SWIR window. Using SWIR spectroscopy and wide-field SWIR imaging with tissue-simulating phantoms, we characterize and compare the SWIR emission properties of eight commercially available red/NIR-I fluorophores commonly used in preclinical and clinical research, in addition to a SWIR-specific fluorophore. All fluorophores produce measurable fluorescence emission in the SWIR, including shorter wavelength dyes such as Alexa Fluor 633 and methylene blue. This study is the first to report SWIR fluorescence from six of the eight conventional fluorophores and establishes an important comparative reference for developing and evaluating SWIR imaging strategies for biomedical applications
Deconfinement Transition and Bound States in Frustrated Heisenberg Chains: Regimes of Forced and Spontaneous Dimerization
We use recently developed strong-coupling expansion methods to study the
two-particle spectra for the frustrated alternating Heisenberg model,
consisting of an alternating nearest neighbor antiferromagnetic exchange and a
uniform second neighbor antiferromagnetic exchange. Starting from the limit of
weakly coupled dimers, we develop high order series expansions for the
effective Hamiltonian in the two-particle subspace. In the limit of a strong
applied dimerization, we calculate accurately various properties of singlet and
triplet bound states and quintet antibound states. We also develop series
expansions for bound state energies in various sectors, which can be
extrapolated using standard methods to cases where the external
bond-alternation goes to zero. We study the properties of singlet and triplet
bound states in the latter limit and suggest a crucial role for the bound
states in the unbinding of triplets and deconfinement of spin-half excitations.Comment: 17 figures, revte
Yttrium-Catalyzed Amine–Silane Dehydrocoupling: Extended Reaction Scope with a Phosphorus-Based Ligand
The
scope of the catalytic dehydrocoupling of primary and secondary
amines with phenylsilanes has been investigated using [Y{N(SiMe<sub>3</sub>)<sub>2</sub>}<sub>3</sub>] and a four-coordinate analogue
bearing a cyclometalated phosphonium methylide ligand. Inclusion of
the phosphorus-based ligand on yttrium results in increased substrate
scope in comparison to the tris(amide) analogue. While reversible
C–H bond activation of the cyclometalated ligand was observed
in stoichiometric experiments, D-labeling experiments and DFT calculations
suggest that reversible ligand activation is not involved in silazane
formation under catalytic conditions. We suggest that the extended
reaction scope with the four-coordinate yttrium phosphonium methylide
complex relative to the three-coordinate yttrium (tris)amide complex
is a result of differences in the ease of amine inhibition of catalysis
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