46 research outputs found
Local Moment Formation in the Periodic Anderson Model with Superconducting Correlations
We study local moment formation in the presence of superconducting
correlations among the f-electrons in the periodic Anderson model. Local
moments form if the Coulomb interaction U>U_cr. We find that U_cr is
considerably stronger in the presence of superconducting correlations than in
the non-superconducting system. Our study is done for various values of the
f-level energy and electronic density. The smallest critical U_cr values occur
for the case where the number of f- electrons per site is equal to one. In the
presence of d-wave superconducting correlations we find that local moment
formation presents a quantum phase transition as function of pressure. This
quantum phase transition separates a region where local moments and d-wave
superconductivity coexist from another region characterized by a
superconducting ground state with no local moments. We discuss the possible
relevance of these results to experimental studies of the competition between
magnetic order and superconductivity in CeCu_2Si_2.Comment: 4 pages. accepted for publication in Phys. Rev.
Influence of gap structures to specific heat in oriented magnetic fields: Application to the orbital dependent superconductor, SrRuO
We discuss influence of modulation of gap function and anisotropy of Fermi
velocity to field angle dependences of upper critical field, , and
specific heat, , on the basis of the approximate analytic solution in the
quasiclassical formalism. Using 4-fold modulation of the gap function and the
Fermi velocity in the single-band model, we demonstrate field and temperature
dependence of oscillatory amplitude of and . We apply the method to
the effective two-band model to discuss the gap structure of SrRuO,
focusing on recent field angle-resolved experiments. It is shown that the gap
structures with the intermediate magnitude of minima in direction for
band, and tiny minima of gaps in directions for and
bands give consistent behaviors with experiments. The interplay of the
above two gaps also explains the anomalous temperature dependence of in-plane
anisotropy, where the opposite contribution from the passive
band is pronounced near .Comment: 7 pages, 11 figures in JPSJ forma
Stratification of PD-1 blockade response in melanoma using pre- and post-treatment immunophenotyping of peripheral blood
Efficacy of checkpoint inhibitor therapies in cancer varies greatly, with some patients showing complete responses while others do not respond and experience progressive disease. We aimed to identify correlates of response and progression following PD-1-directed therapy by immunophenotyping peripheral blood samples from 20 patients with advanced malignant melanoma before and after treatment with the PD-1 blocking antibody pembrolizumab. Our data reveal that individuals responding to PD-1 blockade were characterised by increased CD8 T cell proliferation following treatment, while progression was associated with an increase in CTLA-4-expressing Treg. Remarkably, unsupervised clustering analysis of pre-treatment T cell subsets revealed differences in individuals that went on to respond to PD-1 blockade compared to individuals that did not. These differences mapped to expression of the proliferation marker Ki67 and the costimulatory receptor CD28 as well as the inhibitory molecules 2B4 and KLRG1. While these results require validation in larger patient cohorts, they suggest that flow cytometric analysis of a relatively small number of T cell markers in peripheral blood could potentially allow stratification of PD-1 blockade treatment response prior to therapy initiation
Coexistence of antiferromagnetism and superconductivity in the Anderson lattice
We study the interplay between antiferromagnetism and superconductivity in a
generalized infinite- Anderson lattice, where both superconductivity and
antiferromagnetic order are introduced phenomenologically in mean field theory.
In a certain regime, a quantum phase transition is found which is characterized
by an abrupt expulsion of magnetic order by d-wave superconductivity, as
externally applied pressure increases. This transition takes place when the
d-wave superconducting critical temperature, , intercepts the magnetic
critical temperature, , under increasing pressure. Calculations of the
quasiparticle bands and density of states in the ordered phases are presented.
We calculate the optical conductivity in the clean limit. It
is shown that when the temperature drops below a double peak structure
develops in .Comment: 18 pages, 13 figure
IL-21 shapes germinal center polarization via light zone B cell selection and cyclin D3 upregulation
Germinal center (GC) dysregulation has been widely reported in the context of autoimmunity. Here, we show that interleukin 21 (IL-21), the archetypal follicular helper T cell (Tfh) cytokine, shapes the scale and polarization of spontaneous chronic autoimmune as well as transient immunization-induced GC. We find that IL-21 receptor deficiency results in smaller GC that are profoundly skewed toward a light zone GC B cell phenotype and that IL-21 plays a key role in selection of light zone GC B cells for entry to the dark zone. Light zone skewing has been previously reported in mice lacking the cell cycle regulator cyclin D3. We demonstrate that IL-21 triggers cyclin D3 upregulation in GC B cells, thereby tuning dark zone inertial cell cycling. Lastly, we identify Foxo1 regulation as a link between IL-21 signaling and GC dark zone formation. These findings reveal new biological roles for IL-21 within GC and have implications for autoimmune settings where IL-21 is overproduced
IL-21 shapes germinal center polarization via light zone B cell selection and cyclin D3 upregulation
Global carbon budget 2022
Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2021, EFOS increased by 5.1% relative to 2020, with fossil emissions at 10.1±0.5GtCyr-1 (9.9±0.5GtCyr-1 when the cement carbonation sink is included), and ELUC was 1.1±0.7GtCyr-1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 10.9±0.8GtCyr-1 (40.0±2.9GtCO2). Also, for 2021, GATM was 5.2±0.2GtCyr-1 (2.5±0.1ppmyr-1), SOCEAN was 2.9 ±0.4GtCyr-1, and SLAND was 3.5±0.9GtCyr-1, with a BIM of -0.6GtCyr-1 (i.e. the total estimated sources were too low or sinks were too high). The global atmospheric CO2 concentration averaged over 2021 reached 414.71±0.1ppm. Preliminary data for 2022 suggest an increase in EFOS relative to 2021 of +1.0% (0.1% to 1.9%) globally and atmospheric CO2 concentration reaching 417.2ppm, more than 50% above pre-industrial levels (around 278ppm). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959-2021, but discrepancies of up to 1GtCyr-1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extratropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set. The data presented in this work are available at 10.18160/GCP-2022 (Friedlingstein et al., 2022b)
Global Carbon Budget 2022
Accurate assessment of anthropogenic carbon dioxide (CO) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO emissions (E) are based on energy statistics and cement production data, while emissions from land-use change (E), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO concentration is measured directly, and its growth rate (G) is computed from the annual changes in concentration. The ocean CO sink (S) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO sink (S) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (B), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ.
For the year 2021, E increased by 5.1 % relative to 2020, with fossil emissions at 10.1 ± 0.5 GtC yr (9.9 ± 0.5 GtC yr when the cement carbonation sink is included), and E was 1.1 ± 0.7 GtC yr, for a total anthropogenic CO emission (including the cement carbonation sink) of 10.9 ± 0.8 GtC yr (40.0 ± 2.9 GtCO). Also, for 2021, G was 5.2 ± 0.2 GtC yr (2.5 ± 0.1 ppm yr), S was 2.9  ± 0.4 GtC yr, and S was 3.5 ± 0.9 GtC yr, with a B of −0.6 GtC yr (i.e. the total estimated sources were too low or sinks were too high). The global atmospheric CO concentration averaged over 2021 reached 414.71 ± 0.1 ppm. Preliminary data for 2022 suggest an increase in E relative to 2021 of +1.0 % (0.1 % to 1.9 %) globally and atmospheric CO concentration reaching 417.2 ppm, more than 50 % above pre-industrial levels (around 278 ppm). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2021, but discrepancies of up to 1 GtC yr persist for the representation of annual to semi-decadal variability in CO fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) a low agreement between the different methods on the magnitude of the land CO flux in the northern extratropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set. The data presented in this work are available at https://doi.org/10.18160/GCP-2022 (Friedlingstein et al., 2022b)