98 research outputs found
Screening effects in a density functional theory based description of molecular junctions in the Coulomb blockade regime
We recently introduced a method based on density functional theory (DFT) and
non-equilibrium Green's function techniques (NEGF) for calculating the addition
energies of single molecule nano-junctions in the Coulomb blockade (CB) regime.
Here we apply this approach to benzene molecules lying parallel and at various
distances from two aluminum fcc (111) surfaces, and discuss the distance
dependence in our calculations in terms of electrostatic screening effects. The
addition energies near the surface are reduced by about a factor of two, which
is comparable to previously reported calculations employing a computationally
far more demanding quasi-particle description
Towards a theoretical description of molecular junctions in the Coulomb blockade regime based on density functional theory
Non-equilibrium Greens function techniques (NEGF) combined with Density
Functional Theory (DFT) calculations have become a standard tool for the
description of electron transport through single molecule nano-junctions in the
coherent tunneling regime. However, the applicability of these methods for
transport in the Coulomb blockade (CB) regime is still under debate. We present
here NEGF-DFT calculations performed on simple model systems in the presence of
an effective gate potential. The results show that: i) the CB addition energies
can be predicted with such an approach with reasonable accuracy; ii) neither
the magnitude of the Kohn-Sham gap nor the lack of a derivative discontinuity
in the exchange-correlation functional represent a problem for this purpose
A multideterminant assessment of mean field methods for the description of electron transfer in the weak coupling regime
Multideterminant calculations have been performed on model systems to
emphasize the role of many-body effects in the general description of charge
quantization experiments. We show numerically and derive analytically that a
closed-shell ansatz, the usual ingredient of mean-field methods, does not
properly describe the step-like electron transfer characteristic in weakly
coupled systems. With the multideterminant results as a benchmark, we have
evaluated the performance of common ab initio mean field techniques, such as
Hartree Fock (HF) and Density Functional Theory (DFT) with local and hybrid
exchange correlation functionals, with a special focus on spin-polarization
effects. For HF and hybrid DFT, a qualitatively correct open-shell solution
with distinct steps in the electron transfer behaviour can be obtained with a
spin-unrestricted (i.e., spin-polarized) ansatz though this solution differs
quantitatively from the multideterminant reference. We also discuss the
relationship between the electronic eigenvalue gap and the onset of charge
transfer for both HF and DFT and relate our findings to recently proposed
practical schemes for calculating the addition energies in the Coulomb blockade
regime for single molecule junctions from closed-shell DFT within the local
density approximation
Strong polarization-induced reduction of addition energies in single-molecule nanojunctions
We address polarization-induced renormalization of molecular levels in
solid-state based single-molecule transistors and focus on an organic conjugate
molecule where a surprisingly large reduction of the addition energy has been
observed. We have developed a scheme that combines a self-consistent solution
of a quantum chemical calculation with a realistic description of the screening
environment. Our results indeed show a large reduction, and we explain this to
be a consequence of both (a) a reduction of the electrostatic molecular
charging energy and (b) polarization induced level shifts of the HOMO and LUMO
levels. Finally, we calculate the charge stability diagram and explain at a
qualitative level general features observed experimentally.Comment: 9 pages, 5 figure
The number of transmission channels through a single-molecule junction
We calculate transmission eigenvalue distributions for Pt-benzene-Pt and
Pt-butadiene-Pt junctions using realistic state-of-the-art many-body
techniques. An effective field theory of interacting -electrons is used to
include screening and van der Waals interactions with the metal electrodes. We
find that the number of dominant transmission channels in a molecular junction
is equal to the degeneracy of the molecular orbital closest to the metal Fermi
level.Comment: 9 pages, 8 figure
Global patterns of care in advanced stage mycosis fungoides/Sezary syndrome: a multicenter retrospective follow-up study from the Cutaneous Lymphoma International Consortium
ABSTRACT Background Advanced-stage mycosis fungoides (MF)/Sezary syndrome (SS) patients are weighted by an unfavorable prognosis and share an unmet clinical need of effective treatments. International guidelines are available detailing treatment options for the different stages but without recommending treatments in any particular order due to lack of comparative trials. The aims of this second CLIC study were to retrospectively analyze the pattern of care worldwide for advanced-stage MF/SS patients, the distribution of treatments according to geographical areas (USA versus non-USA), and whether the heterogeneity of approaches has potential impact on survival. Patients and methods This study included 853 patients from 21 specialist centers (14 European, 4 USA, 1 each Australian, Brazilian, and Japanese). Results Heterogeneity of treatment approaches was found, with up to 24 different modalities or combinations used as first-line and 36% of patients receiving four or more treatments. Stage IIB disease was most frequently treated by total-skin-electron-beam radiotherapy, bexarotene and gemcitabine; erythrodermic and SS patients by extracorporeal photochemotherapy, and stage IVA2 by polychemotherapy. Significant differences were found between USA and non-USA centers, with bexarotene, photopheresis and histone deacetylase inhibitors most frequently prescribed for first-line treatment in USA while phototherapy, interferon, chlorambucil and gemcitabine in non-USA centers. These differences did not significantly impact on survival. However, when considering death and therapy change as competing risk events and the impact of first treatment line on both events, both monochemotherapy (SHR = 2.07) and polychemotherapy (SHR = 1.69) showed elevated relative risks. Conclusion This large multicenter retrospective study shows that there exist a large treatment heterogeneity in advanced MF/SS and differences between USA and non-USA centers but these were not related to survival, while our data reveal that chemotherapy as first treatment is associated with a higher risk of death and/or change of therapy and thus other therapeutic options should be preferable as first treatment approach
Malignant inflammation in cutaneous T-cell lymphoma: a hostile takeover
Cutaneous T-cell lymphomas (CTCL) are characterized by the presence of chronically inflamed skin lesions containing malignant T cells. Early disease presents as limited skin patches or plaques and exhibits an indolent behavior. For many patients, the disease never progresses beyond this stage, but in approximately one third of patients, the disease becomes progressive, and the skin lesions start to expand and evolve. Eventually, overt tumors develop and the malignant T cells may disseminate to the blood, lymph nodes, bone marrow, and visceral organs, often with a fatal outcome. The transition from early indolent to progressive and advanced disease is accompanied by a significant shift in the nature of the tumor-associated inflammation. This shift does not appear to be an epiphenomenon but rather a critical step in disease progression. Emerging evidence supports that the malignant T cells take control of the inflammatory environment, suppressing cellular immunity and anti-tumor responses while promoting a chronic inflammatory milieu that fuels their own expansion. Here, we review the inflammatory changes associated with disease progression in CTCL and point to their wider relevance in other cancer contexts. We further define the term "malignant inflammation" as a pro-tumorigenic inflammatory environment orchestrated by the tumor cells and discuss some of the mechanisms driving the development of malignant inflammation in CTCL
Dendritic cells in cancer immunology and immunotherapy
Dendritic cells (DCs) are a diverse group of specialized antigen-presenting cells with key roles in the initiation and regulation of innate and adaptive immune responses. As such, there is currently much interest in modulating DC function to improve cancer immunotherapy. Many strategies have been developed to target DCs in cancer, such as the administration of antigens with immunomodulators that mobilize and activate endogenous DCs, as well as the generation of DC-based vaccines. A better understanding of the diversity and functions of DC subsets and of how these are shaped by the tumour microenvironment could lead to improved therapies for cancer. Here we will outline how different DC subsets influence immunity and tolerance in cancer settings and discuss the implications for both established cancer treatments and novel immunotherapy strategies.S.K.W. is supported by a European Molecular Biology Organization Long- Term Fellowship (grant ALTF 438– 2016) and a CNIC–International Postdoctoral Program Fellowship (grant 17230–2016). F.J.C. is the recipient of a PhD ‘La Caixa’ fellowship. Work in the D.S. laboratory is funded by the CNIC, by the European Research Council (ERC Consolidator Grant 2016 725091), by the European Commission (635122-PROCROP H2020), by the Ministerio de Ciencia, Innovación e Universidades (MCNU), Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional (FEDER) (SAF2016-79040-R), by the Comunidad de Madrid (B2017/BMD-3733 Immunothercan- CM), by FIS- Instituto de Salud Carlos III, MCNU and FEDER (RD16/0015/0018-REEM), by Acteria Foundation, by Atresmedia (Constantes y Vitales prize) and by Fundació La Marató de TV3 (201723). The CNIC is supported by the Instituto de Salud Carlos III, the MCNU and the Pro CNIC Foundation, and is a Severo Ochoa Centre of Excellence (SEV-2015-0505).S
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