Excitonic ferromagnetism in the hexaborides

A ferromagnet with a small spontaneous moment but with a high Curie temperature can be obtained by doping an excitonic insulator made from a spin triplet exciton condensate. Such a condensate can occur in a semimetal with a small overlap or a semiconductor with a small bandgap. We propose that it is responsible for the unexpected ferromagnetism in the doped hexaboride material Ca_{1-x}La_xB_6.Comment: 4 pages, 3 figure

Temperature dependent photoluminescence of single CdS nanowires

Temperature dependent photoluminescence (PL) is used to study the electronic properties of single CdS nanowires. At low temperatures, both near-band edge (NBE) photoluminescence (PL) and spatially-localized defect-related PL are observed in many nanowires. The intensity of the defect states is a sensitive tool to judge the character and structural uniformity of nanowires. As the temperature is raised, the defect states rapidly quench at varying rates leaving the NBE PL which dominates up to room temperature. All PL lines from nanowires follow closely the temperature-dependent band edge, similar to that observed in bulk CdS.Comment: 11 pages, 4 figure

Low temperature photoluminescence imaging and time-resolved spectroscopy of single CdS nanowires

Time-resolved photoluminescence (PL) and micro-PL imaging were used to study single CdS nanowires at 10 K. The low-temperature PL of all CdS nanowires exhibit spectral features near energies associated with free and bound exciton transitions, with the transition energies and emission intensities varying along the length of the nanowire. In addition, several nanowires show spatially localized PL at lower energies which are associated with morphological irregularities in the nanowires. Time-resolved PL measurements indicate that exciton recombination in all CdS nanowires is dominated by non-radiative recombination at the surface of the nanowires.Comment: 9 pages, 3 figures, to be published in Applied Physics Letter

On the Theory of Evolution Versus the Concept of Evolution: Three Observations

Here we address three misconceptions stated by Rice et al. in their observations of our article Paz-y-Miño and Espinosa (Evo Edu Outreach 2:655–675, 2009), published in this journal. The five authors titled their note “The Theory of Evolution is Not an Explanation for the Origin of Life.” First, we argue that it is fallacious to believe that because the formulation of the theory of evolution, as conceived in the 1800s, did not include an explanation for the origin of life, nor of the universe, the concept of evolution would not allow us to hypothesize the possible beginnings of life and its connections to the cosmos. Not only Stanley Miller’s experiments of 1953 led scientists to envision a continuum from the inorganic world to the origin and diversification of life, but also Darwin’s own writings of 1871. Second, to dismiss the notion of Rice et al. that evolution does not provide explanations concerning the universe or the cosmos, we identify compelling scientific discussions on the topics: Zaikowski et al. (Evo Edu Outreach 1:65–73, 2008), Krauss (Evo Edu Outreach 3:193–197, 2010), Peretó et al. (Orig Life Evol Biosph 39:395–406, 2009) and Follmann and Brownson (Naturwissenschaften 96:1265–1292, 2009). Third, although we acknowledge that the term Darwinism may not be inclusive of all new discoveries in evolution, and also that creationists and Intelligent Designers hijack the term to portray evolution as ideology, we demonstrate that there is no statistical evidence suggesting that the word Darwinism interferes with public acceptance of evolution, nor does the inclusion of the origin of life or the universe within the concept of evolution. We examine the epistemological and empirical distinction between the theory of evolution and the concept of evolution and conclude that, although the distinction is important, it should not compromise scientific logic

Cirsium species show disparity in patterns of genetic variation at their range-edge, despite similar patterns of reproduction and isolation

Genetic variation was assessed across the UK geographical range of Cirsium acaule and Cirsium heterophyllum. A decline in genetic diversity and increase in population divergence approaching the range edge of these species was predicted based on parallel declines in population density and seed production reported seperately. Patterns were compared with UK populations of the widespread Cirsium arvense.Populations were sampled along a latitudinal transect in the UK and genetic variation assessed using microsatellite markers. Cirsium acaule shows strong isolation by distance, a significant decline in diversity and an increase in divergence among range-edge populations. Geographical structure is also evident in C. arvense, whereas no such patterns are seen in C.heterophyllum. There is a major disparity between patterns of genetic variation in C. acaule and C. heterophyllum despite very similar patterns in seed production and population isolation in these species. This suggests it may be misleading to make assumptions about the geographical structure of genetic variation within species based solely on the present-day reproduction and distribution of populations

Evaluation of early and late presentation of patients with ocular mucous membrane pemphigoid to two major tertiary referral hospitals in the United Kingdom

PURPOSE: Ocular mucous membrane pemphigoid (OcMMP) is a sight-threatening autoimmune disease in which referral to specialists units for further management is a common practise. This study aims to describe referral patterns, disease phenotype and management strategies in patients who present with either early or established disease to two large tertiary care hospitals in the United Kingdom.\ud \ud PATIENTS AND METHODS: In all, 54 consecutive patients with a documented history of OcMMP were followed for 24 months. Two groups were defined: (i) early-onset disease (EOD:<3 years, n=26, 51 eyes) and (ii) established disease (EstD:>5 years, n=24, 48 eyes). Data were captured at first clinic visit, and at 12 and 24 months follow-up. Information regarding duration, activity and stage of disease, visual acuity (VA), therapeutic strategies and clinical outcome were analysed.\ud \ud RESULTS: Patients with EOD were younger and had more severe conjunctival inflammation (76% of inflamed eyes) than the EstD group, who had poorer VA (26.7%=VA<3/60, P<0.01) and more advanced disease. Although 40% of patients were on existing immunosuppression, 48% required initiation or switch to more potent immunotherapy. In all, 28% (14) were referred back to the originating hospitals for continued care. Although inflammation had resolved in 78% (60/77) at 12 months, persistence of inflammation and progression did not differ between the two phenotypes. Importantly, 42% demonstrated disease progression in the absence of clinically detectable inflammation.\ud \ud CONCLUSIONS: These data highlight that irrespective of OcMMP phenotype, initiation or escalation of potent immunosuppression is required at tertiary hospitals. Moreover, the conjunctival scarring progresses even when the eye remains clinically quiescent. Early referral to tertiary centres is recommended to optimise immunosuppression and limit long-term ocular damage.\ud \u

Synthesis and Characterization of Ultrathin Silver Sulfide Nanoplatelets

© 2017 American Chemical Society. We report the synthesis of ultrathin silver sulfide (Ag2S) nanoplatelets (NPLs) synthesized via a one-pot method in ethylene glycol with 3-mercaptopropionic acid serving as both the sulfur precursor and the platelet ligand. The colloidally synthesized nanoplatelets are exceptionally thin, with a thickness of only 3.5 ± 0.2 Å and a 1S exciton Bohr diameter to confinement ratio of ∼12.6. The NPL growth is shown to be quantized by layer thickness using absorption and photoluminescence (PL) spectroscopy. Transmission electron microscopy, atomic force microscopy, and X-ray diffraction analyses of the NPLs show that they correspond to the (202) plane of the β-Ag2S structure. The PL quantum yield of these NPLs is ∼30%, suggesting their potential use in biomedical imaging. Optoelectronic properties were evaluated via sensitized photocurrent spectroscopy with the resulting spectra closely matching the distinctive absorption spectral shape of the Ag2S NPLs