We review salient structural and electronic features associated with the concomitant Peierls–charge density wave (CDW) instabilities observed in most one-dimensional (1D) inorganic and organic ...electronic conductors. First of all, the genesis of these concepts is placed in an historical perspective. We then present basic experimental facts supporting the general description of these 1D electron–phonon coupled systems developed in the 1970s. In this framework we shall consider in particular the role of 1D fluctuations on both lattice and electronic degrees of freedom, and of the inter-chain Coulomb coupling between CDWs in stabilizing in 3D the Peierls transition at finite temperature. We also clarify, in relation with experimental findings, the various conditions of adiabaticity of the electron–phonon coupling. Finally we illustrate by recent structural measurements the pioneering work of Jacques Friedel on CDW elasticity and plasticity and CDW pinning to defects through the appearance of Friedel oscillations.
Nous passons en revue les principaux aspects structuraux et électroniques de l'instabilité Peierls–onde de densité de charge (ODC) observée dans la plupart des conducteurs inorganiques et organiques à une dimension (1D). Nous commençons par replacer la genèse de ces concepts dans une perspective historique. Puis nous présentons les faits expérimentaux à la base de la description générale de ces systèmes 1D couplés électron–phonon développée à partir des années 1970. Dans ce cadre, nous considérerons en particulier l'effet des fluctuations 1D sur les degrés de liberté structuraux et électroniques et le rôle du couplage coulombien inter-chaine dans le mécanisme de stabilisation 3D de la transition de Peierls à température finie. Nous clarifions aussi, en relation avec les données expérimentales, les différentes conditions d'adiabaticité du couplage électron–phonon. Finalement, nous illustrons avec des mesures structurales récentes les travaux pionniers de Jacques Friedel sur l'élasticité et la plasticité des ODC et leur accrochage aux défauts via la formation d'oscillations de Friedel.
Targeted alpha therapy (TAT) using alpha particle-emitting radionuclides is in the spotlight after the approval of
223
RaCl
2
for patients with metastatic castration-resistant prostate cancer and the ...development of several alpha emitter-based radiopharmaceuticals. It is acknowledged that alpha particles are highly cytotoxic because they produce complex DNA lesions. Hence, the nucleus is considered their critical target, and many studies did not report any effect in other subcellular compartments. Moreover, their physical features, including their range in tissues (<100 μm) and their linear energy transfer (50–230 keV/μm), are well-characterized. Theoretically, TAT is indicated for very small-volume, disseminated tumors (e.g., micrometastases, circulating tumor cells). Moreover, due to their high cytotoxicity, alpha particles should be preferred to beta particles and X-rays to overcome radiation resistance. However, clinical studies showed that TAT might be efficient also in quite large tumors, and biological effects have been observed also away from irradiated cells. These distant effects are called bystander effects when occurring at short distance (<1 mm), and systemic effects when occurring at much longer distance. Systemic effects implicate the immune system. These findings showed that cells can die without receiving any radiation dose, and that a more complex and integrated view of radiobiology is required. This includes the notion that the direct, bystander and systemic responses cannot be dissociated because DNA damage is intimately linked to bystander effects and immune response. Here, we provide a brief overview of the paradigms that need to be revisited.
Rich Polymorphism of Layered NbS3 Conejeros, Sergio; Guster, Bogdan; Alemany, Pere ...
Chemistry of materials,
07/2021, Letnik:
33, Številka:
14
Journal Article
Recenzirano
Odprti dostop
Layered group V transition-metal trichalcogenides are paradigmatic low-dimensional materials providing an ever increasing series of unusual properties. They are all based on the same basic building ...units, one-dimensional MX3 (M = Nb, Ta; X = S, Se) trigonal-prismatic chains that condense into layers, but their electronic structures exhibit significant differences leading to a broad spectrum of transport properties, ranging from metals with one, two, or three charge density wave instabilities to semimetals with potential topological properties or semiconductors. The different physical and chemical properties are shown to be related with subtle structural differences within the layers that result in half-, third-, or quarter-filled quasi-one-dimensional Nb d z 2-type bands, providing a clear-cut illustration of the intimate link between structural and electronic features within a family of solids. An interesting yet not sufficiently explored feature of these solids is the polymorphism. Based on both experimental and new theoretical results, we examine this aspect for NbS3 and show that at least seven different polymorphs with a stability compatible with the presently known phases of this compound are possible. We discuss a simple rationale for the physical properties of the presently known polymorphs as well as predictions for those that have still not been characterized or prepared. It is argued that some of the presently unknown polymorphs may have been prepared in an uncontrolled way as mixtures of different phases which could not be structurally characterized. The rich landscape of structures and properties found for this van der Waals material is suggested to represent an ideal platform for the preparation of flakes with fine-tuned properties for applications in new electronic and optoelectronic devices.
In the past decade, radiation therapy (RT) entered the era of personalized medicine, following the striking improvements in radiation delivery and treatment planning optimization, and in the ...understanding of the cancer response, including the immunological response. The next challenge is to identify the optimal radiation regimen(s) to induce a clinically relevant anti-tumor immunity response. Organs at risks and the tumor microenvironment (e.g. endothelial cells, macrophages and fibroblasts) often limit the radiation regimen effects due to adverse toxicities. Here, we reviewed how RT can modulate the immune response involved in the tumor control and side effects associated with inflammatory processes. Moreover, we discussed the versatile roles of tumor microenvironment components during RT, how the innate immune sensing of RT-induced genotoxicity, through the cGAS-STING pathway, might link the anti-tumor immune response, radiation-induced necrosis and radiation-induced fibrosis, and how a better understanding of the switch between favorable and deleterious events might help to define innovative approaches to increase RT benefits in patients with cancer.
Conventional external-beam radiation therapy is dedicated to the treatment of localized disease, whereas radioimmunotherapy represents an innovative tool for the treatment of local or diffuse tumors. ...Radioimmunotherapy involves the administration of radiolabeled monoclonal antibodies that are directed specifically against tumor-associated antigens or against the tumor microenvironment. Although many tumor-associated antigens have been identified as possible targets for radioimmunotherapy of patients with hematological or solid tumors, clinical success has so far been achieved mostly with radiolabeled antibodies against CD20 ((131)I-tositumomab and (90)Y-ibritumomab tiuxetan) for the treatment of lymphoma. In this Review, we provide an update on the current challenges aimed to improve the efficacy of radioimmunotherapy and discuss the main radiobiological issues associated with clinical radioimmunotherapy.
Recent work aiming at a deeper understanding of the electronic properties of classical and novel charge‐transfer (CT) complexes is reviewed herein. From a variety of studied CT salts, the ...prototypical examples TTF‐TCNQ, (TMTTF)2SbF6, (TMTSF)2PF6, and TMP/HMP‐TCNQ have been selected. Three different types of electron and X‐ray spectroscopies were applied, namely ultraviolet photoelectron spectroscopy (UPS), hard X‐ray photoelectron spectroscopy (HAXPES), and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy. Using UPS, the development of the valence band structure during co‐deposition of the donor and acceptor moieties TMP/HMP and TCNQ has been studied. The spectra reveal characteristic level shifts and a strong reduction of the HOMO–LUMO gap upon formation of the complex. HAXPES probes the core levels and reveals characteristic shifts of the binding energies in (TMTTF)2SbF6 at the phase transition to the low‐temperature charge‐ordered state. NEXAFS is a local, element‐specific probe for the unoccupied bands above the Fermi level and reveals changes in the population of specific orbitals when the CT complex is formed. As an outlook, the novel method of photoelectron momentum microscopy is presented, giving access to the valence bands and core‐levels and in particular to high‐resolution X‐ray photoelectron diffraction patterns.
Three different types of electron and X‐ray spectroscopies are applied, namely ultraviolet photoelectron spectroscopy (UPS), hard X‐ray photoelectron spectroscopy (HAXPES), and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy, for studying prototypical charge‐transfer salts, such as TTF‐TCNQ, (TMTTF)2SbF6, (TMTSF)2PF6, and TMP/HMP‐TCNQ.
We review the basic aspects of the charge density wave (CDW) and bond order wave (BOW) instabilities observed in one dimension (1D) organic conductors at either the 2k sub(F) and/or 4k sub(F) ...critical wave vectors. We start by recalling the main features of the coupled structural/electronic Peierls instabilities observed in donor-acceptor (D-A) charge transfer (CT) salts. Then we consider the specific case of 2:1 salts D sub(2)X where X is a monovalent anion. We show that the incipient CDW/BOW instabilities of the Bechgaard and Fabre salts are those of the parent quarter-filled CT salts TMTSF-DMTCNQ and TMTTF-DMTCNQ respectively. We also consider more specifically the influence of specific features of D sub(2)X salts such as the stack dimerization, the Fermi surface warping and the coupling to the anions. Then we discuss more generally the role of the anions in the Bechgaard and Fabre salts by pointing out the influence of polarization and charge displacement induced by the anion shift. Finally we show that some of these features are also relevant to understand the subtle interplay between structural and electronic degrees of freedom in 2D quarter-filled organic salts such as the (BEDT-TTF) sub(2)X series.
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