560 research outputs found
Electronic and magnetic properties of the graphene-ferromagnet interface
The article presents the work on the investigation of the surface structure
as well as electronic and magnetic properties of graphene layer on a lattice
matched surface of a ferromagnetic material, Ni(111).Comment: accepted in New J. Phy
First Order Static Excitation Potential: Scheme for Excitation Energies and Transition Moments
We present an approximation scheme for the calculation of the principal
excitation energies and transition moments of finite many-body systems. The
scheme is derived from a first order approximation to the self energy of a
recently proposed extended particle-hole Green's function. A hermitian
eigenvalue problem is encountered of the same size as the well-known Random
Phase Approximation (RPA). We find that it yields a size consistent description
of the excitation properties and removes an inconsistent treatment of the
ground state correlation by the RPA. By presenting a hermitian eigenvalue
problem the new scheme avoids the instabilities of the RPA and should be well
suited for large scale numerical calculations. These and additional properties
of the new approximation scheme are illuminated by a very simple exactly
solvable model.Comment: 15 pages revtex, 1 eps figure included, corrections in Eq. (A1) and
Sec. II
Review of biorthogonal coupled cluster representations for electronic excitation
Single reference coupled-cluster (CC) methods for electronic excitation are
based on a biorthogonal representation (bCC) of the (shifted) Hamiltonian in
terms of excited CC states, also referred to as correlated excited (CE) states,
and an associated set of states biorthogonal to the CE states, the latter being
essentially configuration interaction (CI) configurations. The bCC
representation generates a non-hermitian secular matrix, the eigenvalues
representing excitation energies, while the corresponding spectral intensities
are to be derived from both the left and right eigenvectors. Using the
perspective of the bCC representation, a systematic and comprehensive analysis
of the excited-state CC methods is given, extending and generalizing previous
such studies. Here, the essential topics are the truncation error
characteristics and the separability properties, the latter being crucial for
designing size-consistent approximation schemes. Based on the general order
relations for the bCC secular matrix and the (left and right) eigenvector
matrices, formulas for the perturbation-theoretical (PT) order of the
truncation errors (TEO) are derived for energies, transition moments, and
property matrix elements of arbitrary excitation classes and truncation levels.
In the analysis of the separability properties of the transition moments, the
decisive role of the so-called dual ground state is revealed. Due to the use of
CE states the bCC approach can be compared to so-called intermediate state
representation (ISR) methods based exclusively on suitably orthonormalized CE
states. As the present analysis shows, the bCC approach has decisive advantages
over the conventional CI treatment, but also distinctly weaker TEO and
separability properties in comparison with a full (and hermitian) ISR method
Naturally Acquired Sarcoptes scabiei Infestation in a Captive Southern Tamandua (Tamandua tetradactyla) and a Capybara (Hydrochoeris hydrochaeris)
A privately-owned southern tamandua (Tamandua tetradactyla) and a capybara (Hydrochoeris hydrochaeris) were presented for severe pruritus. Superficial skin scrapings revealed numerous Sarcoptes scabiei mites. Morphological examination and mitochondrial DNA sequencing revealed that both patients were infested with Sarcoptes scabiei. The animals were treated with selamectin (9 mg/kg) topically once, and the owner was instructed to repeat treatment in two weeks. The tamandua died of unknown causes three weeks after initial examination before reevaluation could occur. Clinical signs and skin lesions in the capybara resolved after two treatments with selamectin. This is the first documented report of sarcoptic mange in a southern tamandua. In addition, this is the first documented case of natural transmission of Sarcoptes mites between a tamandua and capybara in captivity. Finally, this is the first described use of topical selamectin for the treatment and resolution of sarcoptic mange in a capybara
Deconstructing sarcomeric structure-function relations in titin-BioID knock-in mice
Proximity proteomics has greatly advanced the analysis of native protein complexes and subcellular structures in culture, but has not been amenable to study development and disease in vivo. Here, we have generated a knock-in mouse with the biotin ligase (BioID) inserted at titin's Z-disc region to identify protein networks that connect the sarcomere to signal transduction and metabolism. Our census of the sarcomeric proteome from neonatal to adult heart and quadriceps reveals how perinatal signaling, protein homeostasis and the shift to adult energy metabolism shape the properties of striated muscle cells. Mapping biotinylation sites to sarcomere structures refines our understanding of myofilament dynamics and supports the hypothesis that myosin filaments penetrate Z-discs to dampen contraction. Extending this proof of concept study to BioID fusion proteins generated with Crispr/CAS9 in animal models recapitulating human pathology will facilitate the future analysis of molecular machines and signaling hubs in physiological, pharmacological, and disease context
Mapping the unique and shared functions of oncogenic KRAS and RIT1 with proteome and transcriptome profiling
Aberrant activation of RAS oncogenes is prevalent in lung adenocarcinoma, with somatic mutation of KRAS occurring in ∼30% of tumors. Recently, we identified somatic mutation of the RAS-family GTPase RIT1 in lung adenocarcinoma, but relatively little is known about the biological pathways regulated by RIT1 and how these relate to the oncogenic KRAS network. Here we present quantitative proteomic and transcriptomic profiles from KRAS-mutant and RIT1-mutant isogenic lung epithelial cells and globally characterize the signaling networks regulated by each oncogene. We find that both mutant KRAS and mutant RIT1 promote S6 kinase, AKT, and RAF/MEK signaling, and promote epithelial-to-mesenchymal transition and immune evasion via HLA protein loss. However, KRAS and RIT1 diverge in regulation of phosphorylation sites on EGFR, USO1, and AHNAK proteins. The majority of the proteome changes are related to altered transcriptional regulation, but a small subset of proteins are differentially regulated by both oncoproteins at the post-transcriptional level, including intermediate filament proteins, metallothioneins, and MHC Class I proteins. These data provide the first global, unbiased characterization of oncogenic RIT1 network and identify the shared and divergent functions of oncogenic RIT1 and KRAS GTPases in lung cancer
Comparison of Zn_{1-x}Mn_xTe/ZnTe multiple-quantum wells and quantum dots by below-bandgap photomodulated reflectivity
Large-area high density patterns of quantum dots with a diameter of 200 nm
have been prepared from a series of four Zn_{0.93}Mn_{0.07}Te/ZnTe multiple
quantum well structures of different well width (4 nm, 6 nm, 8 nm and 10 nm) by
electron beam lithography followed by Ar+ ion beam etching. Below-bandgap
photomodulated reflectivity spectra of the quantum dot samples and the parent
heterostructures were then recorded at 10 K and the spectra were fitted to
extract the linewidths and the energy positions of the excitonic transitions in
each sample. The fitted results are compared to calculations of the transition
energies in which the different strain states in the samples are taken into
account. We show that the main effect of the nanofabrication process is a
change in the strain state of the quantum dot samples compared to the parent
heterostructures. The quantum dot pillars turn out to be freestanding, whereas
the heterostructures are in a good approximation strained to the ZnTe lattice
constant. The lateral size of the dots is such that extra confinement effects
are not expected or observed.Comment: 23 pages, LaTeX2e (amsmath, epsfig), 7 EPS figure
Self-consistent Green's function approaches
We present the fundamental techniques and working equations of many-body
Green's function theory for calculating ground state properties and the
spectral strength. Green's function methods closely relate to other polynomial
scaling approaches discussed in chapters 8 and 10. However, here we aim
directly at a global view of the many-fermion structure. We derive the working
equations for calculating many-body propagators, using both the Algebraic
Diagrammatic Construction technique and the self-consistent formalism at finite
temperature. Their implementation is discussed, as well as the inclusion of
three-nucleon interactions. The self-consistency feature is essential to
guarantee thermodynamic consistency. The pairing and neutron matter models
introduced in previous chapters are solved and compared with the other methods
in this book.Comment: 58 pages, 14 figures, Submitted to Lect. Notes Phys., "An advanced
course in computational nuclear physics: Bridging the scales from quarks to
neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor
Surveys for ticks on wildlife hosts and in the environment at Asian longhorned tick (\u3ci\u3eHaemaphysalis longicornis\u3c/i\u3e)-positive sites in Virginia and New Jersey, 2018
Haemaphysalis longicornis, the Asian longhorned tick (ALT), is native to eastern Asia, but it has become invasive in several countries, including Australia, New Zealand and recently in the eastern United States (US). To identify wild mammal and avian host species in the US, we conducted active wildlife surveillance in two states with known ALT infestations (Virginia and New Jersey). In addition, we conducted environmental surveys in both states. These surveillance efforts resulted in detection of 51 ALTinfested individuals from seven wildlife species, including raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), red fox (Vulpes vulpes), woodchuck (Marmota monax), eastern cottontail (Sylvilagus floridanus), striped skunk (Mephitis mephitis) and white-tailed deer (Odocoileus virginianus). We found ALT in the environment in both states and also collected three native tick species (Amblyomma americanum, Dermacentor variablis and Ixodes scapularis) that are vectors of pathogens of public health and veterinary importance. This study provides important specific information on the wildlife host range of ALT in the US
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