1,091 research outputs found

    Control of quantum interference in molecular junctions: Understanding the origin of Fano and anti- resonances

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    We investigate within a coarse-grained model the conditions leading to the appearance of Fano resonances or anti-resonances in the conductance spectrum of a generic molecular junction with a side group (T-junction). By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the different electronic parameters determining the regimes where Fano resonances or anti-resonances in the low-energy conductance spectrum can be expected. The results obtained within the coarse-grained model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.Comment: 5 pages, 5 figure

    In Situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated CeIV-Based Metal–Organic Frameworks with UiO-66 and MIL-140 Architectures

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    We report on the results of an in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated CeIV-based metal–organic frameworks (MOFs), analogues of the already well investigated ZrIV-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as reagents, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds, varying parameters such as temperature, amount of the protonation modulator nitric acid and amount of the coordination modulator acetic acid. When only HNO3 is present in the reaction environment, only F4_MIL-140A(Ce) is obtained. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products are obtained. F4_UiO-66(Ce) is always formed faster, and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate-determining step. A higher amount of HNO3 favours the formation of F4_MIL-140A(Ce), whereas increasing the amount of AcOH favours the formation of F4_UiO-66(Ce). Based on the in situ results, a new optimised route to achieving a pure, high-quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified

    The regional economic impact of more graduates in the labour market: a “micro-to-macro” analysis for Scotland

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    This paper explores the system-wide impact of graduates on the regional economy. Graduates enjoy a significant wage premium, often interpreted as reflecting their greater productivity relative to non-graduates. If this is so there is a clear and direct supply-side impact of HEI activities on regional economies. We use an HEI-disaggregated computable general equilibrium model of Scotland to estimate the impact of the growing proportion of graduates in the Scottish labour force that is implied by the current participation rate and demographic change, taking the graduate wage premium in Scotland as an indicator of productivity enhancement. While the detailed results vary with alternative assumptions about the extent to which wage premia reflect productivity, they do suggest that the long-term supply-side impacts of HEIs provide a significant boost to regional GDP. Furthermore, the results suggest that the supply-side impacts of HEIs are likely to be more important than the expenditure impacts that are the focus of most HEI impact studies

    Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food: outcome of the collaborative trial IMEP-41

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    A collaborative trial was conducted to determine the performance characteristics of an analytical method for the quantification of inorganic arsenic (iAs) in food. The method is based on (i) solubilisation of the protein matrix with concentrated hydrochloric acid to denature proteins and allow the release of all arsenic species into solution, and (ii) subsequent extraction of the inorganic arsenic present in the acid medium using chloroform followed by back-extraction to acidic medium. The final detection and quantification is done by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS). The seven test items used in this exercise were reference materials covering a broad range of matrices: mussels, cabbage, seaweed (hijiki), fish protein, rice, wheat, mushrooms, with concentrations ranging from 0.074 to 7.55 mg kg(-1). The relative standard deviation for repeatability (RSDr) ranged from 4.1 to 10.3%, while the relative standard deviation for reproducibility (RSDR) ranged from 6.1 to 22.8%. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

    Impact of meteorological variation on hospital visits of patients with tree pollen allergy

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    <p>Abstract</p> <p>Background</p> <p>Climate change could affect allergic diseases, especially due to pollen. However, there has been no epidemiologic study to demonstrate the relationship between meteorological factors, pollen, and allergic patients. We aimed to investigate the association between meteorological variations and hospital visits of patients with tree pollen allergy.</p> <p>Methods</p> <p>The study subjects were adult patients who received skin prick tests between April and July from 1999 to 2008. We reviewed the medical records for the test results of 4,715 patients. Patients with tree pollen allergy were defined as those sensitized to more than 1 of 12 tree pollen allergens. We used monthly means of airborne tree pollen counts and meteorological factors: maximum/average/minimum temperature, relative humidity, and precipitation. We analyzed the correlations between meteorological variations, tree pollen counts, and the patient numbers. Multivariable logistic regression analyses were used to investigate the associations between meteorological factors and hospital visits of patients.</p> <p>Results</p> <p>The minimum temperature in March was significantly and positively correlated with tree pollen counts in March/April and patient numbers from April through July. Pollen counts in March/April were also correlated with patient numbers from April through July. After adjusting for confounders, including air pollutants, there was a positive association between the minimum temperature in March and hospital visits of patients with tree pollen allergy from April to July(odds ratio, 1.14; 95% CI 1.03 to 1.25).</p> <p>Conclusions</p> <p>Higher temperatures could increase tree pollen counts, affecting the symptoms of patients with tree pollen allergy, thereby increasing the number of patients visiting hospitals.</p

    Greater risk of incident asthma cases in adults with Allergic Rhinitis and Effect of Allergen Immunotherapy: A Retrospective Cohort Study

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    Asthma and rhinitis are often co-morbid conditions. As rhinitis often precedes asthma it is possible that effective treatment of allergic rhinitis may reduce asthma progression. The aim of our study is to investigate history of allergic rhinitis as a risk factor for asthma and the potential effect of allergen immunotherapy in attenuating the incidence of asthma. Hospital-referred non-asthmatic adults, aged 18–40 years between 1990 and 1991, were retrospectively followed up until January and April 2000. At the end of follow up, available subjects were clinically examined for asthma diagnosis and history of allergen specific immunotherapy, second-hand smoking and the presence of pets in the household. A total of 436 non-asthmatic adults (332 subjects with allergic rhinitis and 104 with no allergic rhinitis nor history of atopy) were available for final analyses. The highest OR (odds ratio) associated with a diagnosis of asthma at the end of follow-up was for the diagnosis of allergic rhinitis at baseline (OR, 7.8; 95%CI, 3.1–20.0 in the model containing the covariates of rhinitis diagnosis, sex, second-hand smoke exposure, presence of pets at home, family history of allergic disorders, sensitization to Parietaria judaica; grass pollen; house dust mites; Olea europea: orchard; perennial rye; and cat allergens). Female sex, sensitization to Parietaria judaica and the presence of pets in the home were also significantly predictive of new onset asthma in the same model. Treatment with allergen immunotherapy was significantly and inversely related to the development of new onset asthma (OR, 0.53; 95%CI, 0.32–0.86). In the present study we found that allergic rhinitis is an important independent risk factor for asthma. Moreover, treatment with allergen immunotherapy lowers the risk of the development of new asthma cases in adults with allergic rhinitis
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