693 research outputs found
When Reintroductions are Augmentations: The Genetic Legacy of Fishers (Martes Pennanti) in Montana
Fishers (Martes pennanti) were purportedly extirpated from Montana by 1930 and extant populations are assumed to be descended from translocated fishers. To determine the lineage of fisher populations, we sequenced 2 regions of the mitochondrial DNA genome from 207 tissue samples from British Columbia, Minnesota, Wisconsin, and Montana. In northwestern Montana, fishers share haplotypes with samples from the upper Midwest and British Columbia; in west-central Montana, we detected haplotypes found in British Columbia samples, but also detected a control region and cytochrome-b haplotype not found in source populations. Based on the unique haplotypes found in west-central Montana, we propose that individuals with these haplotypes are descended from a relic population. Fishers in northwestern Montana are likely descended from fishers from the Midwest and British Columbia
Rearrangement of cluster structure during fission processes
Results of molecular dynamics simulations of fission reactions and are presented. Dependence
of the fission barriers on isomer structure of the parent cluster is analyzed.
It is demonstrated that the energy necessary for removing homothetic groups of
atoms from the parent cluster is largely independent of the isomer form of the
parent cluster. Importance of rearrangement of the cluster structure during the
fission process is elucidated. This rearrangement may include transition to
another isomer state of the parent cluster before actual separation of the
daughter fragments begins and/or forming a "neck" between the separating
fragments
Impurity effects on the melting of Ni clusters
We demonstrate that the addition of a single carbon impurity leads to
significant changes in the thermodynamic properties of Ni clusters consisting
of more than a hundred atoms. The magnitude of the change induced is dependent
upon the parameters of the Ni-C interaction. Hence, thermodynamic properties of
Ni clusters can be effectively tuned by the addition of an impurity of a
particular type. We also show that the presence of a carbon impurity
considerably changes the mobility and diffusion of atoms in the Ni cluster at
temperatures close to its melting point. The calculated diffusion coefficients
of the carbon impurity in the Ni cluster can be used for a reliable estimate of
the growth rate of carbon nanotubes.Comment: 27 pages, 13 figure
Rotational cooling of heteronuclear molecular ions with ^1-Sigma, ^2-Sigma, ^3-Sigma and ^2-Pi electronic ground states
The translational motion of molecular ions can be effectively cooled
sympathetically to translational temperatures below 100 mK in ion traps through
Coulomb interactions with laser-cooled atomic ions. The ro-vibrational degrees
of freedom, however, are expected to be largely unaffected during translational
cooling. We have previously proposed schemes for cooling of the internal
degrees of freedom of such translationally cold but internally hot
heteronuclear diatomic ions in the simplest case of ^1-Sigma electronic ground
state molecules. Here we present a significant simplification of these schemes
and make a generalization to the most frequently encountered electronic ground
states of heteronuclear molecular ions: ^1-Sigma, ^2-Sigma, ^3-Sigma and ^2-Pi.
The schemes are relying on one or two laser driven transitions with the
possible inclusion of a tailored incoherent far infrared radiation field.Comment: 16 pages, 13 figure
Geospatial information infrastructures
Manual of Digital Earth / Editors: Huadong Guo, Michael F. Goodchild, Alessandro Annoni .- Springer, 2020 .- ISBN: 978-981-32-9915-3Geospatial information infrastructures (GIIs) provide the technological, semantic,organizationalandlegalstructurethatallowforthediscovery,sharing,and use of geospatial information (GI). In this chapter, we introduce the overall concept and surrounding notions such as geographic information systems (GIS) and spatial datainfrastructures(SDI).WeoutlinethehistoryofGIIsintermsoftheorganizational andtechnologicaldevelopmentsaswellasthecurrentstate-of-art,andreflectonsome of the central challenges and possible future trajectories. We focus on the tension betweenincreasedneedsforstandardizationandtheever-acceleratingtechnological changes. We conclude that GIIs evolved as a strong underpinning contribution to implementation of the Digital Earth vision. In the future, these infrastructures are challengedtobecomeflexibleandrobustenoughtoabsorbandembracetechnological transformationsandtheaccompanyingsocietalandorganizationalimplications.With this contribution, we present the reader a comprehensive overview of the field and a solid basis for reflections about future developments
Associations between tooth wear and dental sleep disorders : A narrative overview
Objectives Tooth wear is a common finding in adult patients with dental sleep disorders. The aim of this paper was to review the literature on the possible associations between tooth wear and the following dental sleep disorders: sleep-related oro-facial pain, oral moistening disorders, gastroesophageal reflux disease (GERD), obstructive sleep apnoea syndrome (OSAS) and sleep bruxism. Methods A PubMed search was performed on 1 June 2018 using MeSH terms in the following query: Tooth Wear AND (Facial Pain OR Temporomandibular Joint Disorders OR Xerostomia OR Sialorrhea OR Gastroesophageal Reflux OR Sleep Apnea Syndrome OR Sleep Bruxism). Results The query yielded 706 reports on tooth wear and the mentioned dental sleep disorders. Several associations between tooth wear and the dental sleep disorders were suggested in the literature. It could be concluded that: (a) tooth wear is associated with dental pain and/or hypersensitivity; (b) oral dryness is associated with tooth wear, oro-facial pain and sleep bruxism; (c) GERD is associated with tooth wear, oro-facial pain, oral dryness, OSAS and sleep bruxism; (d) OSAS is associated with oral dryness, GERD and sleep bruxism; and (e) sleep bruxism is associated with tooth wear. Conclusions Tooth wear is associated with the dental sleep disorders oro-facial pain, oral dryness, GERD and sleep bruxism. The dental sleep disorders are interlinked with each other, which leads to indirect associations as well, and makes the consequences of each single condition difficult to disentangle. Knowledge of these associations is clinically relevant, but more research is needed to confirm their validity.Peer reviewe
Extended Hartree-Fock method based on pair density functional theory
A practical electronic structure method in which a two-body functional is the
fundamental variable is constructed. The basic formalism of our method is
equivalent to Hartree-Fock density matrix functional theory [M. Levy in {\it
Density Matrices and Density Functionals}, Ed. R. Erdahl and V. H. Smith Jr.,
D. Reidel, (1987)]. The implementation of the method consists of solving
Hartree-Fock equations and using the resulting orbitals to calculate two-body
corrections to account for correlation. The correction terms are constructed so
that the energy of the system in the absence of external potentials can be made
to correspond to approximate expressions for the energy of the homogeneous
electron gas. In this work the approximate expressions we use are based on the
high-density limit of the homogeneous electron gas. Self-interaction is
excluded from the two-body functional itself. It is shown that our pair density
based functional does not suffer from the divergence present in many density
functionals when homogeneous scaling is applied. Calculations based on our pair
density functional lead to quantitative results for the correlation energies of
atomic test cases.Comment: to appear in Physical Review
The Adsorption of Chlorofluoromethane on Pristine, Al‐, Ga‐, P‐, and As‐doped Boron Nitride Nanotubes: A PBC‐DFT, NBO, and QTAIM Study
The feasibility of detecting a Chlorofluoromethane (CFM) gas molecule on the outer surface of a pristine single‐walled boron nitride nanotube as well as Al‐, Ga‐, P‐, and As‐doped structures. A periodic boundary condition (PBC), within a density functional theory (DFT) method, using the Perdew, Burke, and Ernzerhof exchange‐correlation (PBE0) functional, together with a 6‐311G(d) basis set was used. Subsequently, the B3LYP, CAM−B3LYP, ωB97XD, and M06‐2X functionals were also employed to consider the single point energies. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) were implemented by using the PBE0/6‐311G(d). To explore the nature of the intermolecular interactions, density of state (DOS), Wiberg bond index (WBI), natural charge, natural electron configuration, donor–acceptor natural bond orbital interactions, the second‐order perturbation energies tests, and noncovalent interaction (NCI) analysis are performed. The sensitivity of the adsorption will be increased when the gas molecule interacts with decorated nanotubes; therefore, the change of electronic properties can be used to design suitable nanosensors
Synthesis of a fullerene-based one-dimensional nanopolymer through topochemical transformation of the parent nanowire
Large-scale practical applications of fullerene (C60) in nanodevices could be
significantly facilitated if the commercially-available micrometer-scale raw
C60 powder were further processed into a one-dimensional (1D) nanowire-related
polymer displaying covalent bonding as molecular interlinks and resembling
traditional important conjugated polymers. However, there has been little study
thus far in this area despite the abundant literature on fullerene. Here we
report the synthesis and characterization of such a C60-based nanowire polymer,
(-C60TMB-)n, where TMB=1,2,4-trimethylbenzene, which displays a well-defined
crystalline structure, exceptionally large length-to-width ratio and excellent
thermal stability. The material is prepared by first growing the corresponding
nanowire through a solution phase of C60 followed by a topochemical
polymerization reaction in the solid state. Gas chromatography, mass
spectrometry and 13C nuclear magnetic resonance evidence is provided for the
nature of the covalent bonding mode adopted by the polymeric chains.
Theoretical analysis based on detailed calculations of the reaction energetics
and structural analysis provides an in-depth understanding of the
polymerization pathway. The nanopolymer promises important applications in
biological fields and in the development of optical, electrical, and magnetic
nanodevices.Comment: 30 pages, 12 figures, 2 table
Further investigation of confirmed urinary tract infection (UTI) in children under five years: a systematic review.
Background: Further investigation of confirmed UTI in children aims to prevent renal scarring and future complications. Methods: We conducted a systematic review to determine the most effective approach to the further investigation of confirmed urinary tract infection (UTI) in children under five years of age. Results: 73 studies were included. Many studies had methodological limitations or were poorly reported. Effectiveness of further investigations: One study found that routine imaging did not lead to a reduction in recurrent UTIs or renal scarring. Diagnostic accuracy: The studies do not support the use of less invasive tests such as ultrasound as an alternative to renal scintigraphy, either to rule out infection of the upper urinary tract (LR- = 0.57, 95%CI: 0.47, 0.68) and thus to exclude patients from further investigation or to detect renal scarring (LR+ = 3.5, 95% CI: 2.5, 4.8). None of the tests investigated can accurately predict the development of renal scarring. The available evidence supports the consideration of contrast-enhanced ultrasound techniques for detecting vesico-ureteric reflux (VUR), as an alternative to micturating cystourethrography (MCUG) (LR+ = 14.1, 95% CI: 9.5, 20.8; LR- = 0.20, 95%CI: 0.13, 0.29); these techniques have the advantage of not requiring exposure to ionising radiation. Conclusion: There is no evidence to support the clinical effectiveness of routine investigation of children with confirmed UTI. Primary research on the effectiveness, in terms of improved patient outcome, of testing at all stages in the investigation of confirmed urinary tract infection is urgently required
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