Photoemission Spectra from Reduced Density Matrices: the Band Gap in Strongly Correlated Systems

We present a method for the calculation of photoemission spectra in terms of reduced density matrices. We start from the spectral representation of the one-body Green's function G, whose imaginary part is related to photoemission spectra, and we introduce a frequency-dependent effective energy that accounts for all the poles of G. Simple approximations to this effective energy give accurate spectra in model systems in the weak as well as strong correlation regime. In real systems reduced density matrices can be obtained from reduced density-matrix functional theory. Here we use this approach to calculate the photoemission spectrum of bulk NiO: our method yields a qualitatively correct picture both in the antiferromagnetic and paramagnetic phases, contrary to mean-field methods, in which the paramagnet is a metal

Reduced Density-Matrix Functional Theory: correlation and spectroscopy

In this work we explore the performance of approximations to electron correlation in reduced density-matrix functional theory (RDMFT) and of approximations to the observables calculated within this theory. Our analysis focuses on the calculation of total energies, occupation numbers, removal/addition energies, and spectral functions. We use the exactly solvable Hubbard molecule at 1/4 and 1/2 filling as test systems. This allows us to analyze the underlying physics and to elucidate the origin of the observed trends. For comparison we also report the results of the $GW$ approximation, where the self-energy functional is approximated, but no further hypothesis are made concerning the approximations of the observables. In particular we focus on the atomic limit, where the two sites of the molecule are pulled apart and electrons localize on either site with equal probability, unless a small perturbation is present: this is the regime of strong electron correlation. In this limit, using the Hubbard molecule at 1/2 filling with or without a spin-symmetry-broken ground state, allows us to explore how degeneracies and spin-symmetry breaking are treated in RDMFT. We find that, within the used approximations, neither in RDMFT nor in $GW$ the signature of strong correlation are present in the spin-singlet ground state, whereas both give the exact result for the spin-symmetry broken case. Moreover we show how the spectroscopic properties change from one spin structure to the other. Our findings can be generalized to other situations, which allows us to make connections to real materials and experiment

Removal From Play Following Concussions In Pediatric Soccer Athletes

Participation in youth soccer and sport-related concussion incidence has increased dramatically over the last decade. Established medical guidelines and Texas state law require immediate removal from play and prohibit athletes from same-day return to play if a concussion is suspected. However, there is limited literature examining the rate at which immediate removal from play is occurring. PURPOSE: To identify the frequency of immediate removal from play in pediatric soccer players with sport-related concussions. METHODS: A retrospective review was performed of 41 athletes diagnosed with a concussion sustained while playing soccer seen consecutively over a one year period. All patients were seen at a pediatric sports medicine center by a single provider. Medical records were reviewed for patient reported symptoms, as identified on the SCAT-3, and patient reported removal from play on the same day as the mechanism of injury. Demographics, previous history of concussion, soccer position, location of head impact, loss of consciousness, memory loss, and mechanism of injury were also reviewed when available. RESULTS: Of 41 patients treated for a soccer-related concussion, 14 were males and 27 were females, with a mean age of 14 (range 7-18). 16 (39%) patients reported delayed removal from play on the same day as initial injury. Although not considered statistically significant, 13 out of 27 females (48.1%) reported delayed removal from play after initial injury as compared to only 3 out of 14 males (21.4%). Additionally, no significant differences were noted in age, previous history of concussion, position, mechanism of injury, or impact location between those who were removed from play immediately and those who had delayed removal. Patients who experienced a loss of consciousness on day of injury were statistically more likely to experience immediate removal from play (p\u3c.05). There were no statistically significant differences noted in severity of symptoms between groups on the day of injury. Patients who were delayed in their removal from play reported a more severe symptom of “not feeling right” (p=.026) on the day of initial clinic visit. CONCLUSION: With a goal of immediate removal from play and no same-day return to play, increased education may help athletes and coaches better identify concussion symptoms and comply with current medical guidelines and applicable Texas state law. In the future, reviewing a larger sample size may improve understanding of the impact of delayed removal from play on recovery patterns and return to play

Anti-CD20 therapy depletes activated myelin-specific CD8+ T cells in multiple sclerosis.

CD8+ T cells are believed to play an important role in multiple sclerosis (MS), yet their role in MS pathogenesis remains poorly defined. Although myelin proteins are considered potential autoantigenic targets, prior studies of myelin-reactive CD8+ T cells in MS have relied on in vitro stimulation, thereby limiting accurate measurement of their ex vivo precursor frequencies and phenotypes. Peptide:MHC I tetramers were used to identify and validate 5 myelin CD8+ T cell epitopes, including 2 newly described determinants in humans. The validated tetramers were used to measure the ex vivo precursor frequencies and phenotypes of myelin-specific CD8+ T cells in the peripheral blood of untreated MS patients and HLA allele-matched healthy controls. In parallel, CD8+ T cell responses against immunodominant influenza epitopes were also measured. There were no differences in ex vivo frequencies of tetramer-positive myelin-specific CD8+ T cells between MS patients and control subjects. An increased proportion of myelin-specific CD8+ T cells in MS patients exhibited a memory phenotype and expressed CD20 compared to control subjects, while there were no phenotypic differences observed among influenza-specific CD8+ T cells. Longitudinal assessments were also measured in a subset of MS patients subsequently treated with anti-CD20 monoclonal antibody therapy. The proportion of memory and CD20+ CD8+ T cells specific for certain myelin but not influenza epitopes was significantly reduced following anti-CD20 treatment. This study, representing a characterization of unmanipulated myelin-reactive CD8+ T cells in MS, indicates these cells may be attractive targets in MS therapy

A haplotype-resolved draft genome of the European sardine (Sardina pilchardus)

The European sardine (Sardina pilchardus Walbaum, 1792) is culturally and economically important throughout its distribution. Monitoring studies of sardine populations report an alarming decrease in stocks due to overfishing and environmental change, which has resulted in historically low captures along the Iberian Atlantic coast. Important biological and ecological features such as population diversity, structure, and migratory patterns can be addressed with the development and use of genomics resources.Agência financiadora Portuguese national funds from FCT-Foundation for Science and Technology: UID/Multi/04326/2016; European Regional Development Fund (FEDER): 22153-01/SAICT/2016; ALG-01-0145-FEDER-022121; ALG-01-0145-FEDER-022231; MAR2020 operational programme of the European Maritime and Fisheries Fund (project SARDI-NOMICS): MAR-01.04.02-FEAMP-0024; European Union's Horizon 2020 research and innovation programme: 654008info:eu-repo/semantics/publishedVersio

Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum

Measurements of small-scale turbulence made over the complex-terrain atmospheric boundary layer during the MATERHORN Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels at four towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The multi-level observations made during a 30-day long MATERHORN-Fall field campaign in September-October 2012 allowed studying of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence and their variations in katabatic winds. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along the slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed downward (upward) whereas the horizontal heat flux is downslope (upslope) below (above) the wind maximum. Our study therefore suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the horizontal heat flux) to derive the height where flux becomes zero. It is shown that the standard deviations of all wind speed components (therefore the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases where the vertical and horizontal heat fluxes are compensated. Turbulence above the wind-speed maximum is decoupled from the surface, and follows the classical local z-less predictions for stably stratified boundary layer.Comment: Manuscript submitted to Boundary-Layer Meteorology (05 December 2014

Screened extended Koopmans' theorem: photoemission at weak and strong correlation

By introducing electron screening in the extended Koopmans' theorem we correctly describe the band gap opening in weakly as well as strongly correlated systems. We show this by applying our method to bulk LiH, Si, and paramagnetic as well as antiferromagnetic NiO. Although incorrect features remain in the full photoemission spectra, this is a remarkable result for an ab-initio electronic structure method and it opens the way to a unified description of photoemission spectra at weak and strong correlation

Mechanisms of HIV-1 Nucleocapsid Protein Inhibition by Lysyl-Peptidyl-Anthraquinone Conjugates

The Nucleocapsid protein NCp7 (NC) is a nucleic acid chaperone responsible for essential steps of the HIV-1 life cycle and an attractive candidate for drug development. NC destabilizes nucleic acid structures and promotes the formation of annealed substrates for HIV-1 reverse transcription elongation. Short helical nucleic acid segments bordered by bulges and loops, such as the Trans-Activation Response element (TAR) of HIV-1 and its complementary sequence (cTAR), are nucleation elements for helix destabilization by NC and also preferred recognition sites for threading intercalators. Inspired by these observations, we have recently demonstrated that 2,6-disubstituted peptidylanthraquinone-conjugates inhibit the chaperone activities of recombinant NC in vitro, and that inhibition correlates with the stabilization of TAR and cTAR stem-loop structures. We describe here enhanced NC inhibitory activity by novel conjugates that exhibit longer peptidyl chains ending with a conserved Nterminal lysine. Their efficient inhibition of TAR/cTAR annealing mediated by NC originates from the combination of at least three different mechanisms, namely, their stabilizing effects on nucleic acids dynamics by threading intercalation, their ability to target TAR RNA substrate leading to a direct competition with the protein for the same binding sites on TAR, and, finally, their effective binding to the NC protein. Our results suggest that these molecules may represent the stepping-stone for the future development of NC-inhibitors capable of targeting the protein itself and its recognition site in RNA