1,702 research outputs found
InternalâRotation in Hydrogen Peroxide: The FarâInfrared Spectrum and the Determination of the Hindering Potential
The torsional oscillation between the two OH groups of the hydrogen peroxide molecule is investigated through a study of the farâinfrared absorption spectrum of the molecule. A 1âmâfocalâlength vacuum grating monochromator was used to scan the region from 15 to 700 cmâ1 with an average resolution of 0.3 cmâ1. The observed spectrum contains seven perpendicularâtype bands of which only the Q branches are resolved. The centers of the seven bands are at 11.43, 116.51, 198.57, 242.76, 370.70, 521.68, and 557.84 cmâ1. These bands result from transitions between different states of the internal rotation and their identification makes it possible to construct the internalârotation energy level scheme through the first five excited states. Relative to the torsional ground state, these levels occur at 11.43, 254.2, 370.7, 569.3, and 775.9 cmâ1.A theory of internal rotation in the hydrogen peroxide molecule is developed for use in the analysis of the farâinfrared spectra. In this theory, the Hamiltonian is constructed assuming all structural distances and angles fixed except the dihedral angle x defining the relative position of the two OH bars. By the use of a contact transformation the Hamiltonian is put in the form H (asymmetric top)+H(internal rotation) where the interaction between the internal and overâall rotations arises through the x dependence of the inertial parameters of H(asymmetric top). It is assumed that the relative position of the two OH bars is governed by a potentialâenergy function of the form V(x) = V1cosx+V2cos2x+V3cos3xV(x)=V1cosx+V2cos2x+V3cos3x. The internalârotation wave equation [αpx2+V(x)]M(x) = EM(x)[αpx2+V(x)]M(x)=EM(x) is solved numerically by an electronicâcomputer and the potential function parameters V1=993 cmâ1, V2=636 cmâ1, and V3=44 cmâ1 are chosen to fit the internalârotation energyâlevel scheme. The trans and cis potential barrier heights are 386 and 2460 cmâ1, respectively, and the potentialâfunction minima are located 111.5° from the cis configuration. Diagonalization of the matrix of the complete Hamiltonian to second order by the use of perturbation theory is sufficient to account for the observed Qâbranch shapes in the far infrared region.Two microwave frequencies observed by Massey and Bianco at 22 054.5 and 27 639.6 Mc/sec are identified from their Stark effects as the first excitedâstate transitions J, K, n, Ï=8, 6, 1, 1â7, 5, 1, 3 and J, K, n, Ï=8, 5, 1, 3â9, 6, 1, 1, respectively, where the internalârotation quantum number n=1 denotes the first excited torsional state and where Ï denotes trans symmetric (Ï=1 and 2) or antisymmetric (Ï=3 and 4) states. The form of the dipole moment operator is assumed to be ÎŒ0 cos(x/2) and ÎŒ0 is found to be 3.15 D in agreement with the value obtained from the torsional groundâstate transitions.Two J=0 microwave series observed by Massey, Beard, and Jen in a mixed sample of the deuterated species D2O2 and HOOD give confirmation of the potential function determined from the H2O2 analysis. The K=4â5 series is identified as the D2O2 first excited torsional state transition n=1â1, Ï=4â2. The K=0â1 series is identified as the HOOD torsional groundâstate transition n=0â0, Ï=4â2. Only very small changes in the trans barrier height are necessary to fit the constant terms of these series exactly. These changes, which are expected to arise from vibrationâinternal rotation interactions, show a reasonable progression from H2O2 to D2O2: V (trans, HOOH) = 386 cmâ1, V (trans, HOOD) = 381 cmâ1 and V (trans, DOOD) = 378 cmâ1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71115/2/JCPSA6-42-6-1931-1.pd
Iron(III)-catalyzed chlorination of activated arenes
A general and regioselective method for the chlorination of activated arenes has been developed. The transformation uses iron(III) triflimide as a powerful Lewis acid for the activation of N-chlorosuccinimide and the subsequent chlorination of a wide range of anisole, aniline, acetanilide and phenol derivatives. The reaction was utilized for the late-stage mono- and di-chlorination of a range of target compounds such as the natural product nitrofungin, the antibacterial agent chloroxylenol and the herbicide chloroxynil. The facile nature of this transformation was demonstrated with the development of one-pot tandem iron-catalyzed dihalogenation processes allowing highly regioselective formation of different carbon-halogen bonds. The synthetic utility of the resulting dihalogenated aryl compounds as building blocks was established with the synthesis of natural products and pharmaceutically relevant targets
Defining Prostatic Vascular Pedicle Recurrence and the Anatomy of Local Recurrence of Prostate Cancer on Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography.
Background
The term local recurrence in prostate cancer is considered to mean persistent local disease in the prostatic bed, most commonly at the site of the vesicourethral anastomosis (VUA). Since the introduction of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging for assessment of early biochemical recurrence (BCR), we have found histologically confirmed prostate cancer in the prostatic vascular pedicle (PVP). If a significant proportion of local recurrences are distant to the VUA, it may be possible to alter adjuvant and salvage radiation fields in order to reduce the potential morbidity of radiation in selected patients.
Objective
To describe PVP local recurrence and to map the anatomic pattern of prostate bed recurrence on PSMA PET/CT.
Design setting and participants
This was a retrospective multicentre study of 185 patients imaged with PSMA PET/CT following radical prostatectomy (RP) between January 2016 and November 2018. All patient data and clinical outcomes were prospectively collected. Recurrences were documented according to anatomic location. For patients presenting with local recurrence, the precise location of the recurrence within the prostate bed was documented.
Intervention
PSMA PET/CT for BCR following RP.
Results and limitations
A total of 43 local recurrences in 41/185 patients (22%) were identified. Tumour recurrence at the PVP was found in 26 (63%), VUA in 15 (37%), and within a retained seminal vesicle and along the anterior rectal wall in the region of the neurovascular bundle in one (2.4%) each. Histological and surgical evidence of PVP recurrence was acquired in two patients. The study is limited by its retrospective nature with inherent selection bias. This is an observational study reporting on the anatomy of local recurrence and does not include follow-up for patient outcomes.
Conclusions
Our study showed that prostate cancer can recur in the PVP and is distant to the VUA more commonly than previously thought. This may have implications for RP technique and for the treatment of selected patients in the local recurrence setting.
Patient summary
We investigated more precise identification of the location of tumour recurrence after removal of the prostate for prostate cancer. We describe a new definition of local recurrence in an area called the prostatic vascular pedicle. This new concept may alter the treatment recommended for recurrent disease
Descriptive Topological Spaces for Performing Visual Search
Accepted versionThis article presents an approach to performing the task of visual search in the context of descriptive topological spaces. The presented algorithm forms the basis of a descriptive visual search system (DVSS) that is based on the guided search model (GSM) that is motivated by human visual search. This model, in turn, consists of the bottom-up and top-down attention models and is implemented within the DVSS in three distinct stages. First, the bottom-up activation process is used to generate saliency maps and to identify salient objects. Second, perceptual objects, defined in the context of descriptive topological spaces, are identified and associated with feature vectors obtained from a VGG deep learning convolutional neural network. Lastly, the top-down activation process makes decisions on whether the object of interest is present in a given image through the use of descriptive patterns within the context of a descriptive topological space. The presented approach is tested with images from the ImageNet ILSVRC2012 and SIMPLIcity datasets. The contribution of this article is a descriptive pattern-based visual search algorithm."This research has been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant 418413, and the Faculty of Graduate
Studies at the University of Winnipeg."https://link.springer.com/chapter/10.1007/978-3-662-58768-3_
Measurement of the muon anti-neutrino double-differential cross section for quasi-elastic scattering on hydrocarbon at~ GeV
We present double-differential measurements of anti-neutrino quasi-elastic
scattering in the MINERvA detector. This study improves on a previous single
differential measurement by using updated reconstruction algorithms and
interaction models, and provides a complete description of observed muon
kinematics in the form of a double-differential cross section with respect to
muon transverse and longitudinal momentum. We include in our signal definition
zero-meson final states arising from multi-nucleon interactions and from
resonant pion production followed by pion absorption in the primary nucleus. We
find that model agreement is considerably improved by a model tuned to MINERvA
inclusive neutrino scattering data that incorporates nuclear effects such as
weak nuclear screening and two-particle, two-hole enhancements.Comment: 47 pages, 31 figure
Genetic variation in the MBL2 gene is associated with Chlamydia trachomatis infection and host humoral response to Chlamydia trachomatis infection
This study aims to assess the potential association of MBL2 gene single nucleotide polymorphisms (SNPs) to Chlamydia trachomatis infection. We analysed a selected sample of 492 DNA
and serum specimens from Dutch Caucasian women. Women were categorized into four groups of
infection status based on the results of DNA and antibody tests for C. trachomatis: Ct-DNA+/IgG+, CtDNA+/IgGâ, Ct-DNAâ/IgG+, and Ct-DNAâ/IgGâ. We compared six MBL2 SNPs (â619G > C (H/L),
â290G > C (Y/X), â66C > T (P/Q), +154C > T (A/D), +161A > G (A/B), and +170A > G (A/C)) and
their respective haplotypes in relation to these different subgroups. The â619C (L) allele was less
present within the Ct-DNAâ/IgG+ group compared with the Ct-DNAâ/IgGâ group (OR = 0.49;
95% CI: 0.28â0.83), while the +170G (C) allele was observed more in the Ct-DNA+/IgG+ group as
compared with the Ct-DNAâ/IgGâ group (OR = 2.4; 95% CI: 1.1â5.4). The HYA/HYA haplotype
was more often present in the Ct-DNAâ/IgGâ group compared with the Ct-DNA+/IgG+ group
(OR = 0.37; 95% CI: 0.16â0.87). The +170G (C) allele was associated with increased IgG production
(p = 0.048) in C. trachomatis PCR-positive women. This study shows associations for MBL in immune
reactions to C. trachomatis. We showed clear associations between MBL2 genotypes, haplotypes, and
individualsâ stages of C. trachomatis DNA and IgG positivity.NGI Life Sciences Pre-Seed and a EuroTransBio grant.https://www.mdpi.com/journal/ijerphMedical Microbiolog
The X-ray emission of the gamma Cassiopeiae stars
Long considered as the "odd man out" among X-ray emitting Be stars, \gamma
Cas (B0.5e IV) is now recognized as the prototype of a class of stars that emit
hard thermal X-rays. Our classification differs from the historical use of the
term "gamma Cas stars" defined from optical properties alone. The luminosity
output of this class contributes significantly to the hard X-ray production in
massive stars in the Galaxy. The gamma Cas stars have light curves showing
variability on a few broadly-defined timescales and spectra indicative of an
optically thin plasma consisting of one or more hot thermal components. By now
9--13 Galactic \approx B0-1.5e main sequence stars are judged to be members or
candidate members of the \gamma Cas class. Conservative criteria for this
designation are for a \approxB0-1.5e III-V star to have an X-ray luminosity of
10^{32}--10^{33} ergs s^{-1}, a hot thermal spectrum containing the short
wavelength Ly \alpha FeXXV and FeXXVI lines and the fluorescence FeK feature
all in emission. If thermality cannot be demonstrated, for example from either
the presence of these Ly \alpha lines or curvature of the hard continuum; these
are the gamma Cas candidates. We discuss the history of the discovery of the
complicated characteristics of the variability in the optical, UV, and X-ray
domains, leading to suggestions for the physical cause of the production of
hard X-rays. These include scenarios in which matter from the Be star accretes
onto a degenerate secondary star and interactions between magnetic fields on
the Be star and its decretion disk. The greatest aid to the choice of the
causal mechanism is the temporal correlations of X-ray light curves and spectra
with diagnostics in the optical and UV wavebands. We show why the magnetic
star-disk interaction scenario is the most tenable explanation for the creation
of hard X-rays on these stars.Comment: Review paper for "X-ray Emissions from Hot Stars and their Winds"
compendium to be published by Advances in Space Research in mid-2016. Paper
is comprised of 66 pages, 15 figure
Advances in Improving Tolerance to Waterlogging in \u3cem\u3eBrachiaria\u3c/em\u3e Grasses
Poor drainage is found on about 11.3% of agricultural land in Latin America where physiography promotes flooding, high groundwater tables, or stagnant surface water (waterlogging). Waterlogging drastically reduces oxygen diffusion into the soil causing hypoxia which is the main limitation that reduces root aerobic respiration and the absorption of minerals and water. Under waterlogging conditions plants can adapt with traits and mechanisms that improve root aeration such as production of aerenchyma and development of adventitious roots. During the rainy season Brachiaria pastures are exposed to waterlogging conditions that can severely limit pasture productivity and hence animal production. The main objective of an inter-institutional and multidisciplinary project was to identify Brachiaria hybrids combining waterlogging tolerance with high forage yield and quality to improve meat and milk production and mitigate the impacts of climate change in the humid areas of Latin America. Researchers at the Centro Internacional de Agricultura Tropical (CIAT) have developed a screening method to evaluate waterlogging tolerance in Brachiaria. Using this method, 71 promising hybrids derived from three Brachiaria species (B. ruziziensis, B. brizantha, and B. decumbens) were evaluated. Four hybrids were identified as superior in waterlogging tolerance. Their superiority was based on greater green leaf biomass production, a greater proportion of green leaf to total leaf biomass, greater green leaf area, leaf chlorophyll content, and photosynthetic efficiency, and reduced dead leaf biomass. These hybrids together with previously selected hybrids and germplasm accessions are being field-tested for waterlogging tolerance in collaboration with National Agricultural Research Institutions and farmers from Colombia, Nicaragua, and Panama
- âŠ