196,030 research outputs found
Characterisation of the Fe(III):H+ Defect Centre in Natural Amethyst
No full textA natural single crystal of amethyst was investigated by means of continuous-wave and pulsed Electron Paramagnetic Resonance (EPR), with the aim of structurally characterizing the substitutional S2 Fe(III):H+ centre. In this centre, Fe(III) replaces Si(IV) in the tetrahedral site, whereas H+ is coupled to Fe(III) to maintain the charge balance. The spectroscopic investigations, mainly the interpretation of the Electron Spin Echo Envelope Modulation, allowed a detailed localisation of the proton to be obtained. H+ occurs in the channels crossing the crystal parallel to the crystallographic c axis, in a largely eccentric position. The Fe(III)-H+ distance, evaluated in 2.70 Å, is found associated with a non-negligible isotropic hyperfine coupling, which can be linked to the relative stability of the S2 centre in natural amethyst
Impact of nifedipine on vascular smooth muscle cell differentiation. Implications for atherogenesis.
No full textEcho detected EPR as a tool for detecting radiation-induced defect signals in pottery
No full textArchaeological fragments of pottery have been investigated by using CW-EPR and Echo Detected EPR (EDEPR). EDEPR allows to remove the CW-EPR dominant Fe(III) background spectrum, hiding much weaker signals potentially useful for dating purpose. EDEPR spectra attributed to a methyl radical and to feldspar defects have been recorded at room and low temperature for an Iron Age cooking ware (700 B.C.). A study on the dependence of EDEPR intensity over absorbed dose on a series of gamma-irradiated brick samples (estimated age of 562 +/- 140 B.C.) has confirmed the potential efficacy of the proposed method for spotting defect signals out of the strong iron background. (C) 2011 Elsevier Ltd. All rights reserved
Application of multispectral imaging and portable spectroscopic instruments to the analysis of an ancient persian illuminated manuscript
No full textIlluminated manuscripts are, in general, the final products of a wise and complex interaction of different competencies. In particular, each manuscript reflects uses and techniques rooted in the historical and geographical traditions of the area of realization. Defining the characteristics and the materials in these valuable artefacts is an essential element to reconstruct their history and allow a more precise collocation and a possible comparison with other works in similar periods and areas. Non-invasive methods, mainly using portable instruments, offer undoubtedly good support in these studies. Recent analyses of an ancient Persian illuminated manuscript, combining multispectral imaging and spectroscopic measurements made with portable instruments (XRF, FORS, micro-Raman, IR-ATR) on selected points, provided new data for an improved understanding of this rare book. This study details the possibilities offered by combining these non-invasive methods for an in-depth understanding of the techniques and practices behind the realization of Middle Eastern illuminated manuscripts and provided new perspectives for multidisciplinary approaches to research in this field
Electron paramagnetic resonance and petrographic analysis for dating Mesolithic and Neolithic pottery from Al Khiday (Sudan)
No full textDevelopment and validation of an integrated computational approach for the modeling of cw-ESR spectra of free radicals in solution: p-(methylthio)phenyl nitronylnitroxide in toluene as a case study
No full textIn this work we address the interpretation, via an ab initio integrated computational approach, of continuous wave electron spin resonance (cw-ESR) spectra of p-(methylthio)phenyl nitronylnitroxide (MTPNN) dissolved in toluene. Our approach is based on the determination of the spin Hamiltonian, averaged with respect to fast vibrational motions, with magnetic tensor parameters (Zeeman and hyperfine tensors) characterized by quantum mechanical density functional calculations. The system is then described by a stochastic Liouville equation, with inclusion of diffusive rotational dynamics. Parametrization of diffusion rotational tensor is provided by a hydrodynamic model. Cw-ESR spectra of MTPNN are simulated for a wide range of temperatures (155−292 K) with minimal resorting to fitting procedures, proving that the combination of sensitive ESR spectroscopy and sophisticated modeling can be highly helpful in providing structural and dynamic information on molecular systems
Multifrequency EPR study and DFT calculations of a C60 bisadduct anion
No full textThe monoanion of bis-TRANS2-[N-methyl-3,4-fulleropyrrolidine] (TRANS2−) was investigated by continuous wave (CW) and pulsed EPR. X-band spectra showed signals due to 14N and 13C hyperfine couplings (hcc). DFT calculations of 14N and 13C isotropic hcc were performed on TRANS2− for different conformations of the pyrrolidinic rings. Calculated values, averaged over the conformations, match well with the experimental values. Accurate g-tensor principal values were obtained by high frequency EPR. The possible dynamical processes affecting the electron spin relaxation are discussed to explain the temperature dependence of the EPR line widths and of the T2 and T1 relaxation times obtained by pulsed methods
Increasing referrals to emergency department for psychiatric consultation and treatment among 50,056 adolescents and young adults: Predictors and implications
No full textObjectives: To identify predictors and time trends over 10 years of psychiatric consultation or treatment in adolescents and young adults referring to Emergency Department (ED). Methods: Real-world cohort data from 50,056 adolescents and young adults referring 105,596 times to ED between 2007 and 2016. We tested whether gender, age, triage code (red, yellow, green, white with decreasing severity), and referral modality predicted primary (psychiatric consultation) or secondary outcomes (anxiolytic treatment, sedative treatment, psychiatric admission), and whether these outcomes increased over the last 10 years. Results: Mean age was 19.57(SD = 2.52), female percentage was 48.77%. Overall, 6.93% underwent psychiatric consultation, treatment, or admission. Among 2,547 adolescents and young adults undergoing a psychiatric consultation, 58.07% had either yellow or red triage code, and 47.2% were brought by ambulance. Female gender predicted psychiatric consultation and anxiolytic treatment, male gender predicted sedative treatment, suggesting gender differences in help-seeking behaviors. Older age predicted all outcomes. Severe triage presentation and being brought by ambulance increased the risk of primary and secondary outcomes. Psychiatric consultation (1.77% to 3.64%), anxiolytic (3.04% to 6.15%), or admission (0.40% to 0.98%) roughly doubled, and sedative (0.27% to 1.23%) treatment had a four-fold increase from 2007 to 2016. Conclusions: Among adolescents and young adults aged 15 to 24 years old ED appears to be necessary for young help-seeking subjects given the severe presentations and the increasing number of adolescents referring to ED. More studies should assess whether ED might be helpful in detecting subjects with sub-threshold or early psychiatric symptoms, or at risk for severe mental illness
Development and Validation of an Integrated Computational Approach for the Modeling of cw-ESR Spectra of Free Radicals in Solution: p-(Methylthio)phenyl Nitronylnitroxide in Toluene as a Case Study.
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