1,619 research outputs found
A Morphological Assessment of Bovine Chondrocytes Cultured on Poly(Ethyl Methacrylate)/Tetrahydrofurfuryl Methacrylate
A heterocyclic methacrylate polymer system, PEMA/THFMA, has shown potential as a biomaterial for cartilage repair in a rabbit model and has properties making it suitable for use clinically. The ability of the polymer system, PEMA/THFMA, and a related system, PEMA/HEMA, to support chondrocytes in vitro was assessed by scanning electron microscopy. Chondrocytes adhered to the surface of the PEMA/THFMA by day one, having a rounded morphology and clustered appearance opposed to the Thermanox® control, where the cells had spread out and become fibroblastic in appearance. The chondrocytes divided rapidly on the PEMA/ THFMA system by day three and had completely covered the surface by day seven. In contrast, chondrocytes did not adhere well to the more hydrophilic PEMA/ HEMA system. A few cells were seen on the surface by day one and by days three and seven, there was no evidence of cell growth or spreading across the surface.
In conclusion, the PEMA/THFMA system can support chondrocytes in vitro, whereas the PEMA/HEMA system does not
Grid computing in image analysis
Diagnostic surgical pathology or tissue–based diagnosis still remains the most reliable and specific diagnostic medical procedure. The development of whole slide scanners permits the creation of virtual slides and to work on so-called virtual microscopes. In addition to interactive work on virtual slides approaches have been reported that introduce automated virtual microscopy, which is composed of several tools focusing on quite different tasks. These include evaluation of image quality and image standardization, analysis of potential useful thresholds for object detection and identification (segmentation), dynamic segmentation procedures, adjustable magnification to optimize feature extraction, and texture analysis including image transformation and evaluation of elementary primitives
Neutrino oscillations from the splitting of Fermi points
As was shown previously, oscillations of massless neutrinos may be due to the
splitting of multiply degenerate Fermi points. In this Letter, we give the
details and propose a three-flavor model of Fermi point splittings and neutrino
mixings with only two free parameters. The model may explain recent
experimental results from the K2K and KamLAND collaborations. There is also
rough agreement with the data on atmospheric neutrinos (SuperK) and solar
neutrinos (SNO), but further analysis is required. Most importantly, the Ansatz
allows for relatively strong T-violating (CP-nonconserving) effects in the
neutrino sector.Comment: 6 pages with jetplFRK.cls, v4: published versio
Neutrino wave function and oscillation suppression
We consider a thought experiment, in which a neutrino is produced by an
electron on a nucleus in a crystal. The wave function of the oscillating
neutrino is calculated assuming that the electron is described by a wave
packet. If the electron is relativistic and the spatial size of its wave packet
is much larger than the size of the crystal cell, then the wave packet of the
produced neutrino has essentially the same size as the wave packet of the
electron. We investigate the suppression of neutrino oscillations at large
distances caused by two mechanisms: 1) spatial separation of wave packets
corresponding to different neutrino masses; 2) neutrino energy dispersion for
given neutrino mass eigenstates. We resolve contributions of these two
mechanisms.Comment: 7 page
Remarks upon the mass oscillation formulas
The standard formula for mass oscillations is often based upon the
approximation and the hypotheses that neutrinos have been
produced with a definite momentum or, alternatively, with definite energy
. This represents an inconsistent scenario and gives an unjustified
reduction by a factor of two in the mass oscillation formulas. Such an
ambiguity has been a matter of speculations and mistakes in discussing flavour
oscillations. We present a series of results and show how the problem of the
factor two in the oscillation length is not a consequence of gedanken
experiments, i.e. oscillations in time. The common velocity scenario yields the
maximum simplicity.Comment: 9 pages, AMS-Te
Upper Bounds on Lepton-number Violating Processes
We consider four lepton-number violating (\lv) processes: (a) neutrinoless
double-beta decay (0\nu\beta\beta), (b) Delta L = 2 tau decays, (c) Delta L = 2
rare meson decays and (d) nuclear muon-positron conversion. In the absence of
exotic \lv interactions, the rates for these processes are determined by
effective neutrino masses _{\ell_1\ell_2}, which can be related to the sum
of light neutrino masses, the neutrino mass-squared differences, the neutrino
mixing angles, a Dirac phase and two Majorana phases. We sample the
experimentally allowed ranges of _{\ell_1\ell_2} based on neutrino
oscillation experiments as well as cosmological observations, and obtain a
stringent upper bound _{\ell_1\ell_2} \lsim 0.14 eV. We then calculate the
allowed ranges for _{\ell_1\ell_2} from the experimental rates of direct
searches for the above Delta L = 2 processes. Comparing our calculated rates
with the currently or soon available data, we find that only the
experiment may be able to probe _{ee} with a sensitivity
comparable to the current bound. Muon-positron conversion is next in
sensitivity, while the limits of direct searches for the other Delta L = 2
processes are several orders of magnitude weaker than the current bounds on
_{\ell_1\ell_2}. Any positive signal in those direct searches would indicate
new contributions to the \lv interactions beyond those from three light
Majorana neutrinos.Comment: 20 pages, revtex4, 2 figures (5 files), Version published in Physical
Review
Neutralino Pair Production and 3-Body Decays at Linear Colliders as Probes of CP Violation in the Neutralino System
In the CP-invariant supersymmetric theories, the steep S-wave (slow P-wave)
rise of the cross section for any non-diagonal neutralino pair production in
annihilation, (), near threshold is accompanied by the slow P-wave (steep S-wave) decrease
of the fermion invariant mass distribution of the 3-body neutralino decay,
( or ), near the end
point. These selection rules, unique to the neutralino system due to its
Majorana nature, guarantee that the observation of simultaneous sharp S-wave
excitations of the production cross section near threshold and the lepton and
quark invariant mass distribution near the end point is a qualitative,
unambiguous evidence for CP violation in the neutralino system.Comment: 11 pages, 1 eps figure, a reference adde
Lectin ligands: New insights into their conformations and their dynamic behavior and the discovery of conformer selection by lectins
The mysteries of the functions of complex glycoconjugates have enthralled scientists over decades. Theoretical considerations have ascribed an enormous capacity to store information to oligosaccharides, In the interplay with lectins sugar-code words of complex carbohydrate structures can be deciphered. To capitalize on knowledge about this type of molecular recognition for rational marker/drug design, the intimate details of the recognition process must be delineated, To this aim the required approach is garnered from several fields, profiting from advances primarily in X-ray crystallography, nuclear magnetic resonance spectroscopy and computational calculations encompassing molecular mechanics, molecular dynamics and homology modeling. Collectively considered, the results force us to jettison the preconception of a rigid ligand structure. On the contrary, a carbohydrate ligand may move rather freely between two or even more low-energy positions, affording the basis for conformer selection by a lectin. By an exemplary illustration of the interdisciplinary approach including up-to-date refinements in carbohydrate modeling it is underscored why this combination is considered to show promise of fostering innovative strategies in rational marker/drug design
Neutrino oscillations and the effect of the finite lifetime of the neutrino source
We consider a neutrino source at rest and discuss a condition for the
existence of neutrino oscillations which derives from the finite lifetime
of the neutrino source particle. This condition is present if the
neutrino source is a free particle such that its wave function is
non-stationary. For a Gaussian wave function and with some simplifying
assumptions, we study the modification of the usual oscillation probability
stemming from . In the present accelerator experiments the effect of
can be neglected. We discuss some experimental situations where the
source lifetime becomes relevant in the oscillation formula.Comment: 13 pages latex file with 2 figure
Neutrino Physics, Superbeams, and the Neutrino Factory
We summarize what has been learned about the neutrino mass spectrum and
neutrino mixing, identify interesting open questions that can be answered by
accelerator neutrino facilities of the future, and discuss the importance and
physics of answering them.Comment: To appear in the Proceedings of the 4th International Workshop on
Neutrino Factories (Nu Fact 02). LaTeX, 10 pages, 1 eps figur
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