1,011 research outputs found
Antiproton annihilation on light nuclei at very low energies
The recent experimental data obtained by the OBELIX group on D and
He total annihilation cross sections are analyzed. The combined
analysis of these data with existing antiprotonic atom data allows, for the
first time, the imaginary parts of the S-wave scattering lengths for the two
nuclei to be extracted. The obtained values are: for D and for He. This
analysis indicates an unexpected behaviour of the imaginary part of the
-nucleus S-wave scattering length as a function of the atomic weight
A: (p) > (D) > (He).Comment: 13 pages, 5 figure
The {\it ab initio} calculation of spectra of open shell diatomic molecules
The spectra (rotational, rotation-vibrational or electronic) of diatomic
molecules due to transitions involving only closed-shell ()
electronic states follow very regular, simple patterns and their theoretical
analysis is usually straightforward. On the other hand, open-shell electronic
states lead to more complicated spectral patterns and, moreover, often appear
as a manifold of closely lying electronic states, leading to perturbations with
even larger complexity. This is especially true when at least one of the atoms
is a transition metal. Traditionally these complex cases have been analysed
using approaches based on perturbation theory, with semi-empirical parameters
determined by fitting to spectral data.
Recently the needs of two rather diverse scientific areas have driven the
demand for improved theoretical models of open-shell diatomic systems based on
an \emph{ab initio} approach, these areas are ultracold chemistry and the
astrophysics of "cool" stars, brown dwarfs and most recently extrasolar
planets. However, the complex electronic structure of these molecules combined
with the accuracy requirements of high-resolution spectroscopy render such an
approach particularly challenging. This review describes recent progress in
developing methods for directly solving the effective Schr\"odinger equation
for open-shell diatomic molecules, with a focus on molecules containing a
transtion metal. It considers four aspects of the problem: 1. The electronic
structure problem, 2. Non-perturbative treatments of the curve couplings, 3.
The solution of the nuclear motion Schr\"odinger equation, 4. The generation of
accurate electric dipole transition intensities. Examples of applications are
used to illustrate these issues.Comment: Topical Revie
On the Evaluation of the Hyperthermic Efficiency of Magnetic Scaffolds
Goal: Deep-seated tumors (DST) can be treated using thermoseeds exposed to a radiofrequency magnetic field for performing local interstitial hyperthermia treatment (HT). Several research efforts were oriented to the manufacturing of novel biocompatible magnetic nanostructured thermo-seeds, called magnetic scaffolds (MagS). Several iron-doped bioceramics or magnetic polymers in various formulations are available. However, the crucial evaluation of their heating potential has been carried out with significantly different, lab specific, variable experimental conditions and protocols often ignoring the several error sources and inaccuracies estimation. Methods: This work comments and provides a perspective analysis of an experimental protocol for the estimation methodology of the specific absorption rate (SAR) of MagS for DST HT. Numerical multiphysics simultions have been performed to outline the theoretical framework. After the in silico analysis, an experimental case is considered and tested. Results: From the simulations, we found that large overestimation in the SAR values can be found, due to the axial misplacement in the radiofrequency coil, while the radial misplacement has a lower impact on the estimated SAR value. Conclusions: The averaging of multiple temperature records is needed to reliably and effectively estimate the SAR of MagS for DST HT
Journal off Mechanical Design The Application of Curvature Theory to the Trajectory Generation Problem of Robot Manipulators
This paper illustrates a new application of planar curvature theory to the geometric problem of trajectory generation by a two-link manipulator. The theory yields the instantaneous speed ratio, and the rate of change of the speed ratio, which correspond to the geometry of a desired point trajectory. Separate from the purely geometric speed ratio problem (i.e., the coordination problem) is the time based problem of controlling the joint rates in order to move with the specified path variables. Introduction A rigid body, constrained to move in a plane with N independent degrees of freedom, where 1 < N < 3, is known as a planar TV-parameter motion, denoted by M N . This paper discusses the arm-subassembly of a planar manipulator, whose terminal link is a planar M 2 motion. The purpose is to illustrate a new application of classical curvature theory to the problem of trajectory generation by a multi-degree-of-freedom rigid body system, in this case a planar robot manipulator. Previously, curvature theory has been applied to the dimensional synthesis of planar mechanisms. The new application of the theory illustrated here is a problem of motion synthesis by industrial manipulators
World Workshop on Oral Medicine VII : Relative frequency of oral mucosal lesions in children, a scoping review
Objective: To detail a scoping review on the global and regional relative frequencies of oral mucosal disorders in the children based on both clinical studies and those reported from biopsy records. Materials and Methods: A literature search was completed from 1 January 1990 to 31 December 2018 using PubMed and EMBASE. Results: Twenty clinical studies (sample size: 85,976) and 34 studies from biopsy services (40,522 biopsies) were included. Clinically, the most frequent conditions were aphthous ulcerations (1.82%), trauma-associated lesions (1.33%) and herpes simplex virus (HSV)-associated lesions (1.33%). Overall, the most commonly biopsied lesions were mucoceles (17.12%), fibrous lesions (9.06%) and pyogenic granuloma (4.87%). By WHO geographic region, the pooled relative frequencies of the most common oral lesions were similar between regions in both clinical and biopsy studies. Across regions, geographic tongue (migratory glossitis), HSV lesions, fissured tongue and trauma-associated ulcers were the most commonly reported paediatric oral mucosal lesions in clinical studies, while mucoceles, fibrous lesions and pyogenic granuloma were the most commonly biopsied lesions. Conclusions: The scoping review suggests data from the clinical studies and biopsy records shared similarities in the most commonly observed mucosal lesions in children across regions. In addition, the majority of lesions were benign in nature
ExoMol molecular line lists - XXVI::spectra of SH and NS
Line lists for the sulphur-containing molecules SH (the mercapto radical) and
NS are computed as part of the ExoMol project. These line lists consider
transitions within the ground state for SH, SH,
SH and SD, and NS, NS,
NS, NS and NS. Ab initio potential
energy (PEC) and spin-orbit coupling (SOC) curves are computed and then
improved by fitting to experimentally observed transitions. Fully ab initio
dipole moment curves (DMCs) computed at high level of theory are used to
produce the final line lists. For SH, our fit gives a root-mean-square (rms)
error of 0.03 cm between the observed (, ) and calculated transitions wavenumbers; this is extrapolated such that
all rotational-vibrational-electronic (rovibronic) bound states are
considered. For SH the resulting line list contains about 81000
transitions and 2300 rovibronic states, considering levels up to and . For NS the refinement used a combination of
experimentally determined frequencies and energy levels and led to an rms
fitting error of 0.002 cm. Each NS calculated line list includes around
2.8 million transitions and 31000 rovibronic states with a vibrational range up
to and rotational range to , which covers up to 23000
cm. Both line lists should be complete for temperatures up to 5000 K.
Example spectra simulated using this line list are shown and comparisons made
to the existing data in the CDMS database. The line lists are available from
the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases
Urinary markers of intrarenal renin-angiotensin system activity in vivo
Recent interest focuses on urinary renin and angiotensinogen as markers of renal renin-angiotensin system activity. Before concluding that these components are independent markers, we need to exclude that their presence in urine, like that of albumin (a protein of comparable size), is due to (disturbed) glomerular filtration. This review critically discusses their filtration, reabsorption and local release. Given the close correlation between urinary angiotensinogen and albumin in human studies, it concludes that, in humans, urinary angiotensinogen is a filtration barrier damage marker with the same predictive power as urinary albumin. In contrast, in animals, tubular angiotensinogen release may occur, although tubulus-specific knockout studies do not support a functional role for such angiotensinogen. Urinary renin levels, relative to albumin, are >200-fold higher and unrelated to albumin. This may reflect release of renin from the urinary tract, but could also be attributed to activation of filtered, plasma-derived prorenin and/or incomplete tubular reabsorption
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