Coordination Compounds of Lanthanides as Materials for Luminescent Turn Off Sensors

This review aims at describing the possible use of lanthanide coordination compounds as materials for luminescent sensors now more necessary due to the continuous requirements from the society of electroluminescent and lighting devices, for example analytical sensors and imaging instruments. This is the first part of a work describing the photophysical foundations of the luminescence of complex compounds of lanthanides in the context of design materials with a sensory response, and also considers in detail materials with the most common type of response - turn off sensors

Topological Superconductivity induced by Ferromagnetic Metal Chains

Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity can be realized experimentally by placing transition metal atoms that form a ferromagnetic chain on a superconducting substrate. We address some properties of this type of systems by using a Slater-Koster tight-binding model. We predict that topological superconductivity is nearly universal when ferromagnetic transition metal chains form straight lines on superconducting substrates and that it is possible for more complex chain structures. The proximity induced superconducting gap is $\sim \Delta E_{so} / J$ where $\Delta$ is the $s$-wave pair-potential on the chain, $E_{so}$ is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and $J$ is the exchange-splitting of the ferromagnetic chain $d$-bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. We find, in agreement with experiment, that when the chain and substrate orbitals are strongly hybridized, Majorana end modes are substantially reduced in amplitude when separated from the chain end by less than the coherence length defined by the $p$-wave superconducting gap. We conclude that Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong $s-$wave pairing and strong Rashba spin-orbit coupling, but that there is an opportunity to optimize properties by varying the atomic composition and structure of the chain. Finally, we note that in the absence of disorder a new chain magnetic symmetry, one that is also present in the crystalline topological insulators, can stabilize multiple Majorana modes at the end of a single chain.Comment: 19 pages, 15 figures; an analysis of Majorana decay length scale has been added in the revised versio

Observation of Majorana Fermions in Ferromagnetic Atomic Chains on a Superconductor

Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero energy end states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.Comment: 18 pages, 5 figures, and supplementary information. appears in Science (2014

One-dimensional Topological Edge States of Bismuth Bilayers

The hallmark of a time-reversal symmetry protected topologically insulating state of matter in two-dimensions (2D) is the existence of chiral edge modes propagating along the perimeter of the system. To date, evidence for such electronic modes has come from experiments on semiconducting heterostructures in the topological phase which showed approximately quantized values of the overall conductance as well as edge-dominated current flow. However, there have not been any spectroscopic measurements to demonstrate the one-dimensional (1D) nature of the edge modes. Among the first systems predicted to be a 2D topological insulator are bilayers of bismuth (Bi) and there have been recent experimental indications of possible topological boundary states at their edges. However, the experiments on such bilayers suffered from irregular structure of their edges or the coupling of the edge states to substrate's bulk states. Here we report scanning tunneling microscopy (STM) experiments which show that a subset of the predicted Bi-bilayers' edge states are decoupled from states of Bi substrate and provide direct spectroscopic evidence of their 1D nature. Moreover, by visualizing the quantum interference of edge mode quasi-particles in confined geometries, we demonstrate their remarkable coherent propagation along the edge with scattering properties that are consistent with strong suppression of backscattering as predicted for the propagating topological edge states.Comment: 15 pages, 5 figures, and supplementary materia

Post-Operative Functional Outcomes in Early Age Onset Rectal Cancer

Background: Impairment of bowel, urogenital and fertility-related function in patients treated for rectal cancer is common. While the rate of rectal cancer in the young (<50 years) is rising, there is little data on functional outcomes in this group. Methods: The REACCT international collaborative database was reviewed and data on eligible patients analysed. Inclusion criteria comprised patients with a histologically confirmed rectal cancer, <50 years of age at time of diagnosis and with documented follow-up including functional outcomes. Results: A total of 1428 (n=1428) patients met the eligibility criteria and were included in the final analysis. Metastatic disease was present at diagnosis in 13%. Of these, 40% received neoadjuvant therapy and 50% adjuvant chemotherapy. The incidence of post-operative major morbidity was 10%. A defunctioning stoma was placed for 621 patients (43%); 534 of these proceeded to elective restoration of bowel continuity. The median follow-up time was 42 months. Of this cohort, a total of 415 (29%) reported persistent impairment of functional outcomes, the most frequent of which was bowel dysfunction (16%), followed by bladder dysfunction (7%), sexual dysfunction (4.5%) and infertility (1%). Conclusion: A substantial proportion of patients with early-onset rectal cancer who undergo surgery report persistent impairment of functional status. Patients should be involved in the discussion regarding their treatment options and potential impact on quality of life. Functional outcomes should be routinely recorded as part of follow up alongside oncological parameters

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Luminescent Materials with <em>Turn-on</em> and <em>Ratiometric</em> Sensory Response Based on Coordination Compounds of Lanthanides

Luminescent lanthanide complexes serve as a unique set of tools for creating sensory materials. The most significant types of sensory response in such materials are the turn-on/off response, when the analyte causes an increase or decrease in the emission intensity, respectively, as well as the ratiometric response, which manifests itself as a change in the ratio of luminescence intensities at different wavelengths. In this paper, we consider two of the most technologically advanced types of luminescent sensor materials based on lanthanide compounds—“turn on” and ratiometric sensors. The production of such materials is not only of importance per their possible application but is especially interesting from a fundamental point of view, since their design requires the implementation of non-trivial solutions

Higher Denticity Ligands

Since the first edition of Comprehensive Coordination Chemistry (CCC, 1987) was published, the number of known multidentate ligands has increased dramatically. The pursuit of multidentate ligands for applications in catalysis, bioinorganic and material chemistry is a primary concern of organic and inorganic chemistry alike. Much of the current impetus is provided by the need for cheap, efficient, nontoxic, water-soluble catalysts, for models of metalloenzymes in which bi- and multimetallic centers occur in the active sites, and for efficient chelating agents toward lanthanide and actinide ions used in bioinorganic chemistry and materials science. Complexes containing multidentate ligands have been investigated to understand the role of metal ions in multielectron redox reactions and in the activation of small molecules such as O2 and N2, as well as toco ntrol possible cooperative phenomena between the two metal centers. For example, suitably designed multimetallic complexes formed by binucleating ligands possessing four- to six-coordinate sites could provide reactivity patterns distinct from those shown by analogous monometallic species. The design of appropriate ligand cores, providing coordination sites with well-defined metal– metal separations, is highly desirable. Studies on the assembly of double- and triple-helicate complexes are also actually a major area in coordination chemistry. It has been observed that the formation of architecturally complex systems is directed by the interplay between simple parameters such as the stereoelectronic preference of the metal ions and the disposition of the binding sites in the ligand. How a polydentate ligand becomes partitioned into distinct metalbinding sites is a key parameter in the assembly of helicates. Recent progress in the field of crystal engineering based on polymeric coordination has been devoted to the use of novel polydentate ligands. Much study has centered upon the use of supramolecular contacts between suitable molecules to generate multidimensional arrays or networks. The simple strategy of combining metal centers with polyhapto ligands can generate crystalline architecture, with obvious implications for the rational design of new and varied topological types. There are numerous examples of polymeric sheet or network materials involving bifunctional building blocks connected by coordination to metal centres. This chapter covers the coordination chemistry of ligands with four or more donor atoms (N, O, or S) that are referred to as high-denticity or multidentate. Particular emphasis has been devoted to N- and O-donor ligands, which present several distinct advantages: they are often largely available in pure form and are easy to synthesize; some sulfur donors are also included. A large number of organic molecules with at least four donor atoms have been shown to coordinate metal cations. Many of them contain different substituents (amine, amide, hydroxy, oxo, carboxy, etc.), which makes it impossible to classify them based on the nature of their functional groups. Here we divided them into several classes taking into consideration: (i) the arrangement of the ligand around the metal center; (ii) the nature of donor groups and heteroatoms. The multidentate donors that belong to a separate, well-defined group, such as tetraketones, polypyridines, etc., are discussed in the appropriate chapters. Systematic names are cumbersome, and a variety of trivial names have been used. Both will be avoided in this chapter, and the better-known system of abbreviations, or a code number, will be used

On fractal cubes in dimension 3 and their components.

We show that a fractal cube $F$ in $\mathbb R^3$ may have an uncountable set $Q$ of connected components which are not contained in any plane, and the set $Q$ is a totally disconnected self-similar subset of the hyperspace $C(\mathbb R^3)$, isomorphic to a Cantor set