1,410 research outputs found
F-19-nanoparticles: platform for in vivo delivery of fluorinated biomaterials for F-19-MRI
Fluorine-19 (F-19) magnetic resonance imaging (MRI) features one of the most investigated and innovative techniques for quantitative and unambiguous cell tracking, providing information for both localization and number of cells. Because of the relative insensitivity of the MRI technique, a high number of magnetically equivalent fluorine atoms are required to gain detectable signals. However, an increased amount of F-19 nuclei induces low solubility in aqueous solutions, making fluorine-based probes not suitable for in vivo imaging applications. In this context, nanoparticle-based platforms play a crucial role, since nanoparticles may carry a high payload of F-19-based contrast agents into the relevant cells or tissues, increase the imaging agents biocompatibility, and provide a highly versatile platform. In this review, we present an overview of the F-19-based nanoprobes for sensitive F-19-MRI, focusing on the main nanotechnologies employed to date, such as fluorine and theranostic nanovectors, including their design and applications.Cardiovascular Aspects of Radiolog
Two-Photon Doppler cooling of alkaline-earth-metal and ytterbium atoms
A new possibility of laser cooling of alkaline-earth-metal and Ytterbium
atoms using a two-photon transition is analyzed. We consider a -
transition, with excitation in near resonance with the
level. This greatly increases the two-photon transition rate, allowing an
effective transfer of momentum. The experimental implementation of this
technique is discussed and we show that for Calcium, for example, two-photon
cooling can be used to achieve a Doppler limit of 123 microKelvin. The
efficiency of this cooling scheme and the main loss mechanisms are analyzed.Comment: 7 pages, 5 figure
Diagnosis, Prognosis, and Therapy of Transthyretin Amyloidosis
AbstractTransthyretin amyloidosis is a fatal disorder that is characterized primarily by progressive neuropathy and cardiomyopathy. It occurs in both a mutant form (with autosomal dominant inheritance) and a wild-type form (with predominant cardiac involvement). This article guides clinicians as to when the disease should be suspected, describes the appropriate diagnostic evaluation for those with known or suspected amyloidosis, and reviews the interventions currently available for affected patients
Higgs Boson Decay into Hadronic Jets
The remarkable agreement of electroweak data with standard model (SM)
predictions motivates the study of extensions of the SM in which the Higgs
boson is light and couples in a standard way to the weak gauge bosons.
Postulated new light particles should have small couplings to the gauge bosons.
Within this context it is natural to assume that the branching fractions of the
light SM-like Higgs boson mimic those in the standard model. This assumption
may be unwarranted, however, if there are non-standard light particles coupled
weakly to the gauge bosons but strongly to the Higgs field. In particular, the
Higgs boson may effectively decay into hadronic jets, possibly without
important bottom or charm flavor content. As an example, we present a simple
extension of the SM, in which the predominant decay of the Higgs boson occurs
into a pair of light bottom squarks that, in turn, manifest themselves as
hadronic jets. Discovery of the Higgs boson remains possible at an
electron-positron linear collider, but prospects at hadron colliders are
diminished substantially.Comment: 30 pages, 7 figure
Microscopic mechanisms of spin-dependent electric polarization in 3d oxides
We present a short critical overview of different microscopic models for
nonrelativistic and relativistic magnetoelectric coupling including the
so-called "spin current scenario", ab-initio calculations, and several recent
microscopic approaches to a spin-dependent electric polarization in 3d oxides.Comment: 8 pages, 3 figure
Grain Surface Models and Data for Astrochemistry
AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of âŒ25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions
Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays
Bose-Einstein correlations of both neutral and like-sign charged pion pairs
are measured in a sample of 2 million hadronic Z decays collected with the L3
detector at LEP. The analysis is performed in the four-momentum difference
range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be
smaller than that of charged pions. This result is in qualitative agreement
with the string fragmentation model
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV
A search for a Higgs boson decaying into invisible particles is performed
using the data collected at LEP by the L3 experiment at centre-of-mass energies
of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1
and 176.4 pb^-1. The observed candidates are consistent with the expectations
from Standard Model processes. In the hypothesis that the production cross
section of this Higgs boson equals the Standard Model one and the branching
ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set
at 95% confidence level
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