131 research outputs found

    Experimental Verification of the Chemical Sensitivity of Two-Site Double Core-Hole States Formed by an X-ray FEL

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    We have performed X-ray two-photon photoelectron spectroscopy (XTPPS) using the Linac Coherent Light Source (LCLS) X-ray free-electron laser (FEL) in order to study double core-hole (DCH) states of CO2, N2O and N2. The experiment verifies the theory behind the chemical sensitivity of two-site (ts) DCH states by comparing a set of small molecules with respect to the energy shift of the tsDCH state and by extracting the relevant parameters from this shift.Comment: 11 pages, 2 figure

    Competition between decay and dissociation of core-excited OCS studied by X-ray scattering

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    We show the first evidence of dissociation during resonant inelastic soft X-ray scattering. Carbon and oxygen K-shell and sulfur L-shell resonant and non-resonant X-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur, L2,3 -> {\pi}*, {\sigma}* excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast the carbon and oxygen spectra show weaker line shape variations and no atomic lines. The spectra are compared to results from ab initio calculations and the discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies.Comment: 12 pages, 6 pictures, 2 tables, http://link.aps.org/doi/10.1103/PhysRevA.59.428

    Ultraintense X-Ray Induced Ionization, Dissociation, and Frustrated Absorption in Molecular Nitrogen

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    Sequential multiple photoionization of the prototypical molecule N_2 is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single-pulse imaging applications

    Clinical significance of VEGF-A, -C and -D expression in esophageal malignancies

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    Vascular endothelial growth factors ( VEGF)- A, - C and - D are members of the proangiogenic VEGF family of glycoproteins. VEGF-A is known to be the most important angiogenic factor under physiological and pathological conditions, while VEGF-C and VEGF-D are implicated in the development and sprouting of lymphatic vessels, so called lymphangiogenesis. Local tumor progression, lymph node metastases and hematogenous tumor spread are important prognostic factors for esophageal carcinoma ( EC), one of the most lethal malignancies throughout the world. We found solid evidence in the literature that VEGF expression contributes to tumor angiogenesis, tumor progression and lymph node metastasis in esophageal squamous cell carcinoma ( SCC), and many authors could show a prognostic value for VEGF-assessment. In adenocarcinoma (AC) of the esophagus angiogenic properties are acquired in early stages, particularly in precancerous lesions like Barrett's dysplasia. However, VEGF expression fails to give prognostic information in AC of the esophagus. VEGF-C and VEGF-D were detected in SCC and dysplastic lesions, but not in normal mucosa of the esophagus. VEGF-C expression might be associated with lymphatic tumor invasion, lymph node metastases and advanced disease in esophageal SCC and AC. Therapeutic interference with VEGF signaling may prove to be a promising way of anti-angiogenic co-treatment in esophageal carcinoma. However, concrete clinical data are still pending

    Inequalities in education and national income are associated with poorer diet: pooled analysis of individual participant data across 12 European countries

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    Background: Malnutrition linked to noncommunicable diseases presents major health problems across Europe. The World Health Organisation encourages countries to conduct national dietary surveys to obtain data to inform public health policies designed to prevent noncommunicable diseases. Methods: Data on 27334 participants aged 19-64y were harmonised and pooled across national dietary survey datasets from 12 countries across the WHO European Region. Weighted mean nutrient intakes were age-standardised using the Eurostat 2013 European Standard Population. Associations between country-level Gross Domestic Product (GDP) and key nutrients and nutrient densities were investigated using linear regression. The potential mitigating influence of participant-level educational status was explored. Findings: Higher GDP was positively associated with total sugar intake (5·0% energy for each 10% increase in GDP, 95% CI 0·6, 9·3). Scandinavian countries had the highest vitamin D intakes. Participants with higher educational status had better nutritional intakes, particularly within lower GDP countries. A 10% higher GDP was associated with lower total fat intakes (-0·2% energy, 95% CI -0·3, -0·1) and higher daily total folate intakes (14µg, 95% CI 12, 16) in higher educated individuals. Interpretation: Lower income countries and lower education groups had poorer diet, particularly for micronutrients. We demonstrate for the first time that higher educational status appeared to have a mitigating effect on poorer diet in lower income countries. It illustrates the feasibility and value of harmonising national dietary survey data to inform European policy regarding access to healthy diets, particularly in disadvantaged groups. It specifically highlights the need for strong policies supporting nutritional intakes, prioritising lower education groups and lower income countries

    The role of intramolecular scattering in K-shell photoionization

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    We report evidence of intramolecular scattering occurring in inner shell photoionization of small molecules. Pronounced oscillations of the ratios between vibrationally resolved cross sections (v-ratios) as a function of photon energy have been observed theoretically and experimentally. Qualitative agreement with a 1st Born model confirms that they are due to intramolecular scattering: when an electron is ejected from a very localized region in the center of a polyatomic molecule, such as the C(1s) orbital in a CF4 molecule, it is diffracted by the surrounding atomic centers, encoding the geometry of the molecule [1, 2]
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