954 resultados para Vibrational spectrum of a lattice
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We have studied the effect of pressure on the structural and vibrational properties of lanthanum tritungstate La2(WO4)3. This compound crystallizes under ambient conditions in the modulated scheelite-type structure known as the α phase. We have performed x-ray diffraction and Raman scattering measurements up to a pressure of 20 GPa, as well as ab initio calculations within the framework of the density functional theory. Up to 5 GPa, the three methods provide a similar picture of the evolution under pressure of α-La2(WO4)3. At 5 GPa, we begin to observe some structural changes, and above 6 GPa we find that the x-ray patterns cannot be indexed as a single phase. However, we find that a mixture of two phases with C2/c symmetry accounts for all diffraction peaks. Our ab initio study confirms the existence of several C2/c structures, which are very close in energy in this compression range. According to our measurements, a state with medium-range order appears at pressures above 9 and 11 GPa, from x-ray diffraction and Raman experiments, respectively. Based upon our theoretical calculations we propose several high-pressure candidates with high cationic coordinations at these pressures. The compound evolves into a partially amorphous phase at pressures above 20 GPa.
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Inherited retinal dystrophies present extensive phenotypic and genetic heterogeneity, posing a challenge for patients' molecular and clinical diagnoses. In this study, we wanted to clinically characterize and investigate the molecular etiology of an atypical form of autosomal recessive retinal dystrophy in two consanguineous Spanish families. Affected members of the respective families exhibited an array of clinical features including reduced visual acuity, photophobia, defective color vision, reduced or absent ERG responses, macular atrophy and pigmentary deposits in the peripheral retina. Genetic investigation included autozygosity mapping coupled with exome sequencing in the first family, whereas autozygome-guided candidate gene screening was performed by means of Sanger DNA sequencing in the second family. Our approach revealed nucleotide changes in CDHR1; a homozygous missense variant (c.1720C > G, p.P574A) and a homozygous single base transition (c.1485 + 2T > C) affecting the canonical 5' splice site of intron 13, respectively. Both changes co-segregated with the disease and were absent among cohorts of unrelated control individuals. To date, only five mutations in CDHR1 have been identified, all resulting in premature stop codons leading to mRNA nonsense mediated decay. Our work reports two previously unidentified homozygous mutations in CDHR1 further expanding the mutational spectrum of this gene.
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Substances emitted into the atmosphere by human activities in urban and industrial areas cause environmental problems such as air quality degradation, respiratory diseases, climate change, global warming, and stratospheric ozone depletion. Volatile organic compounds (VOCs) are major air pollutants, emitted largely by industry, transportation and households. Many VOCs are toxic, and some are considered to be carcinogenic, mutagenic, or teratogenic. A wide spectrum of VOCs is readily oxidized photocatalytically. Photocatalytic oxidation (PCO) over titanium dioxide may present a potential alternative to air treatment strategies currently in use, such as adsorption and thermal treatment, due to its advantageous activity under ambient conditions, although higher but still mild temperatures may also be applied. The objective of the present research was to disclose routes of chemical reactions, estimate the kinetics and the sensitivity of gas-phase PCO to reaction conditions in respect of air pollutants containing heteroatoms in their molecules. Deactivation of the photocatalyst and restoration of its activity was also taken under consideration to assess the practical possibility of the application of PCO to the treatment of air polluted with VOCs. UV-irradiated titanium dioxide was selected as a photocatalyst for its chemical inertness, non-toxic character and low cost. In the present work Degussa P25 TiO2 photocatalyst was mostly used. In transient studies platinized TiO2 was also studied. The experimental research into PCO of following VOCs was undertaken: - methyl tert-butyl ether (MTBE) as the basic oxygenated motor fuel additive and, thus, a major non-biodegradable pollutant of groundwater; - tert-butyl alcohol (TBA) as the primary product of MTBE hydrolysis and PCO; - ethyl mercaptan (ethanethiol) as one of the reduced sulphur pungent air pollutants in the pulp-and-paper industry; - methylamine (MA) and dimethylamine (DMA) as the amino compounds often emitted by various industries. The PCO of VOCs was studied using a continuous-flow mode. The PCO of MTBE and TBA was also studied by transient mode, in which carbon dioxide, water, and acetone were identified as the main gas-phase products. The volatile products of thermal catalytic oxidation (TCO) of MTBE included 2-methyl-1-propene (2-MP), carbon monoxide, carbon dioxide and water; TBA decomposed to 2-MP and water. Continuous PCO of 4 TBA proceeded faster in humid air than dry air. MTBE oxidation, however, was less sensitive to humidity. The TiO2 catalyst was stable during continuous PCO of MTBE and TBA above 373 K, but gradually lost activity below 373 K; the catalyst could be regenerated by UV irradiation in the absence of gas-phase VOCs. Sulphur dioxide, carbon monoxide, carbon dioxide and water were identified as ultimate products of PCO of ethanethiol. Acetic acid was identified as a photocatalytic oxidation by-product. The limits of ethanethiol concentration and temperature, at which the reactor performance was stable for indefinite time, were established. The apparent reaction kinetics appeared to be independent of the reaction temperature within the studied limits, 373 to 453 K. The catalyst was completely and irreversibly deactivated with ethanethiol TCO. Volatile PCO products of MA included ammonia, nitrogen dioxide, nitrous oxide, carbon dioxide and water. Formamide was observed among DMA PCO products together with others similar to the ones of MA. TCO for both substances resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide and water. No deactivation of the photocatalyst during the multiple long-run experiments was observed at the concentrations and temperatures used in the study. PCO of MA was also studied in the aqueous phase. Maximum efficiency was achieved in an alkaline media, where MA exhibited high fugitivity. Two mechanisms of aqueous PCO – decomposition to formate and ammonia, and oxidation of organic nitrogen directly to nitrite - lead ultimately to carbon dioxide, water, ammonia and nitrate: formate and nitrite were observed as intermediates. A part of the ammonia formed in the reaction was oxidized to nitrite and nitrate. This finding helped in better understanding of the gasphase PCO pathways. The PCO kinetic data for VOCs fitted well to the monomolecular Langmuir- Hinshelwood (L-H) model, whereas TCO kinetic behaviour matched the first order process for volatile amines and the L-H model for others. It should be noted that both LH and the first order equations were only the data fit, not the real description of the reaction kinetics. The dependence of the kinetic constants on temperature was established in the form of an Arrhenius equation.
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Statistical properties of binary complex networks are well understood and recently many attempts have been made to extend this knowledge to weighted ones. There are, however, subtle yet important considerations to be made regarding the nature of the weights used in this generalization. Weights can be either continuous or discrete magnitudes, and in the latter case, they can additionally have undistinguishable or distinguishable nature. This fact has not been addressed in the literature insofar and has deep implications on the network statistics. In this work we face this problem introducing multiedge networks as graphs where multiple (distinguishable) connections between nodes are considered. We develop a statistical mechanics framework where it is possible to get information about the most relevant observables given a large spectrum of linear and nonlinear constraints including those depending both on the number of multiedges per link and their binary projection. The latter case is particularly interesting as we show that binary projections can be understood from multiedge processes. The implications of these results are important as many real-agent-based problems mapped onto graphs require this treatment for a proper characterization of their collective behavior.
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One of the more challenging tasks in the understanding of dynamical properties of models on top of complex networks is to capture the precise role of multiplex topologies. In a recent paper, Gómez et al. [ Phys. Rev. Lett. 110 028701 (2013)], some of the authors proposed a framework for the study of diffusion processes in such networks. Here, we extend the previous framework to deal with general configurations in several layers of networks and analyze the behavior of the spectrum of the Laplacian of the full multiplex. We derive an interesting decoupling of the problem that allow us to unravel the role played by the interconnections of the multiplex in the dynamical processes on top of them. Capitalizing on this decoupling we perform an asymptotic analysis that allow us to derive analytical expressions for the full spectrum of eigenvalues. This spectrum is used to gain insight into physical phenomena on top of multiplex, specifically, diffusion processes and synchronizability.
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There is much evidence that alcohol use disorders (AUD) often co-occur with posttraumatic stress disorders (PTSD), and that the comorbid condition is associated with a more severe clinical profile than that of PTSD without AUD. However, little is known about the role of childhood adversities as specific risk factors for the development of AUD in individuals presenting with PTSD. The aim of the study was to explore whether specific stressors from the spectrum of trauma and childhood adversities contribute to the development of AUD among subjects with PTSD. From a large community sample, of N=140 individuals with PTSD, N=24 (17.14%) received an additional diagnosis of AUD with an onset after the onset of PTSD. Those with comorbid PTSD/AUD and those with PTSD only were compared regarding type and features of their trauma, childhood adversities and psychiatric comorbidity. Compared to PTSD alone, PTSD/AUD was associated with higher levels of stress in terms of childhood adversities; in particular, sexual abuse below the age of 16, but also with having been brought up in a foster home. PTSD/AUD was also associated with an earlier age of adverse events. Treatment of AUD should include standardized assessments of trauma, especially of trauma experienced during childhood.
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BACKGROUND: Since recombinant human growth hormone (rhGH) became available in 1985, the spectrum of indications has broadened and the number of treated patients increased. However, long-term health-related quality of life (HRQoL) after childhood rhGH treatment has rarely been documented. We assessed HRQoL and its determinants in young adults treated with rhGH during childhood. METHODOLOGY/PRINCIPAL FINDINGS: For this study, we retrospectively identified former rhGH patients in 11 centers of paediatric endocrinology, including university hospitals and private practices. We sent a questionnaire to all patients treated with rhGH for any diagnosis, who were older than 18 years, and who resided in Switzerland at time of the survey. Three hundred participants (58% of 514 eligible) returned the questionnaire. Mean age was 23 years; 56% were women; 43% had isolated growth hormone deficiency, or idiopathic short stature; 43% had associated diseases or syndromes, and 14% had growth hormone deficiency after childhood cancer. Swiss siblings of childhood cancer survivors and the German norm population served as comparison groups. HRQoL was assessed using the Short Form-36. We found that the Physical Component Summary of healthy patients with isolated growth hormone deficiency or idiopathic short stature resembled that of the control group (53.8 vs. 54.9). Patients with associated diseases or syndromes scored slightly lower (52.5), and former cancer patients scored lowest (42.6). The Mental Component Summary was similar for all groups. Lower Physical Component Summary was associated with lower educational level (coeff. -1.9). Final height was not associated with HRQoL. CONCLUSIONS/SIGNIFICANCE: In conclusion, HRQoL after treatment with rhGH in childhood depended mainly on the underlying indication for rhGH treatment. Patients with isolated growth hormone deficiency/idiopathic short stature or patients with associated diseases or syndromes had HRQoL comparable to peers. Patients with growth hormone deficiency after childhood cancer were at high risk for lower HRQoL. This reflects the general impaired health of this vulnerable group, which needs long-term follow-up.
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Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the industrialized world. The prevalence of NAFLD is increasing, becoming a substantial public health burden. NAFLD includes a broad spectrum of disorders, from simple conditions such as steatosis to severe manifestations such as fibrosis and cirrhosis. The relationship of NAFLD with metabolic alterations such as type 2 diabetes is well described and related to insulin resistance, with NAFLD being recognized as the hepatic manifestation of metabolic syndrome. However, NAFLD may also coincide with endocrine diseases such as polycystic ovary syndrome, hypothyroidism, growth hormone deficiency or hypercortisolism. It is therefore essential to remember, when discovering altered liver enzymes or hepatic steatosis on radiological exams, that endocrine diseases can cause NAFLD. Indeed, the overall prognosis of NAFLD may be modified by treatment of the underlying endocrine pathology. In this review, we will discuss endocrine diseases that can cause NALFD. Underlying pathophysiological mechanisms will be presented and specific treatments will be reviewed.
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CONTEXT: Complex steroid disorders such as P450 oxidoreductase deficiency or apparent cortisone reductase deficiency may be recognized by steroid profiling using chromatographic mass spectrometric methods. These methods are highly specific and sensitive, and provide a complete spectrum of steroid metabolites in a single measurement of one sample which makes them superior to immunoassays. The steroid metabolome during the fetal-neonatal transition is characterized by (a) the metabolites of the fetal-placental unit at birth, (b) the fetal adrenal androgens until its involution 3-6 months postnatally, and (c) the steroid metabolites produced by the developing endocrine organs. All these developmental events change the steroid metabolome in an age- and sex-dependent manner during the first year of life. OBJECTIVE: The aim of this study was to provide normative values for the urinary steroid metabolome of healthy newborns at short time intervals in the first year of life. METHODS: We conducted a prospective, longitudinal study to measure 67 urinary steroid metabolites in 21 male and 22 female term healthy newborn infants at 13 time-points from week 1 to week 49 of life. Urine samples were collected from newborn infants before discharge from hospital and from healthy infants at home. Steroid metabolites were measured by gas chromatography-mass spectrometry (GC-MS) and steroid concentrations corrected for urinary creatinine excretion were calculated. RESULTS: 61 steroids showed age and 15 steroids sex specificity. Highest urinary steroid concentrations were found in both sexes for progesterone derivatives, in particular 20α-DH-5α-DH-progesterone, and for highly polar 6α-hydroxylated glucocorticoids. The steroids peaked at week 3 and decreased by ∼80% at week 25 in both sexes. The decline of progestins, androgens and estrogens was more pronounced than of glucocorticoids whereas the excretion of corticosterone and its metabolites and of mineralocorticoids remained constant during the first year of life. CONCLUSION: The urinary steroid profile changes dramatically during the first year of life and correlates with the physiologic developmental changes during the fetal-neonatal transition. Thus detailed normative data during this time period permit the use of steroid profiling as a powerful diagnostic tool.
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In this diploma work advantages of coherent anti-Stokes Raman scattering spectrometry (CARS) and various methods of the quantitative analysis of substance structure with its help are considered. The basic methods and concepts of the adaptive analysis are adduced. On the basis of these methods the algorithm of automatic measurement of a scattering strip size of a target component in CARS spectrum is developed. The algorithm uses known full spectrum of target substance and compares it with a CARS spectrum. The form of a differential spectrum is used as a feedback to control the accuracy of matching. To exclude the influence of a background in CARS spectra the differential spectrum is analysed by means of its second derivative. The algorithm is checked up on the simulated simple spectra and on the spectra of organic compounds received experimentally.
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A comparison is established between the contributions of transverse and longitudinal components of both the propagating and the evanescent waves associated to freely propagating radially polarized nonparaxial beams. Attention is focused on those fields that remain radially polarized upon propagation. In terms of the plane-wave angular spectrum of these fields, analytical expressions are given for determining both the spatial shape of the above components and their relative weight integrated over the whole transverse plane. The results are applied to two kinds of doughnut-like beams with radial polarization, and we compare the behavior of such fields at two transverse planes.
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The present work describes the development of a fast and robust analytical method for the determination of 53 antibiotic residues, covering various chemical groups and some of their metabolites, in environmental matrices that are considered important sources of antibiotic pollution, namely hospital and urban wastewaters, as well as in river waters. The method is based on automated off-line solid phase extraction (SPE) followed by ultra-high-performance liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (UHPLC–QqLIT). For unequivocal identification and confirmation, and in order to fulfill EU guidelines, two selected reaction monitoring (SRM) transitions per compound are monitored (the most intense one is used for quantification and the second one for confirmation). Quantification of target antibiotics is performed by the internal standard approach, using one isotopically labeled compound for each chemical group, in order to correct matrix effects. The main advantages of the method are automation and speed-up of sample preparation, by the reduction of extraction volumes for all matrices, the fast separation of a wide spectrum of antibiotics by using ultra-high-performance liquid chromatography, its sensitivity (limits of detection in the low ng/L range) and selectivity (due to the use of tandem mass spectrometry) The inclusion of β-lactam antibiotics (penicillins and cephalosporins), which are compounds difficult to analyze in multi-residue methods due to their instability in water matrices, and some antibiotics metabolites are other important benefits of the method developed. As part of the validation procedure, the method developed was applied to the analysis of antibiotics residues in hospital, urban influent and effluent wastewaters as well as in river water samples
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Si l'examen clinique revêt une importance essentielle en lymphologie et exige des praticiens expérimentés, la lymphoscintigraphie et plus récemment la lympho-fluoroscopie au vert d'indocyanine constituent des moyens d'investigation précieux dans la prévention, le diagnostic et le traitement des pathologies vasculaires lymphatiques. L'intérêt de la lymphoscintigraphie réside dans l'analyse qualitative et quantitative de la migration des macromolécules par les vaisseaux lymphatiques et l'évaluation du secteur lymphatique profond. La lympho-fluoroscopie se distingue de la lymphoscintigraphie par l'obtention d'une cartographie détaillée des vaisseaux lymphatiques superficiels et d'images dynamiques en temps réel. Elle apporte à l'angiologue et au physiothérapeute des informations irremplaçables sur leur contractilité et la présence de dérivations compensatoires à privilégier lors du drainage lymphatique manuel. Venous thromboembolism is a frequent disease with an annual incidence of 0.75-2.69/1000 reaching 2-7/1000 > 70 years. Deep vein thrombosis (DVT) and pulmonary embolism are two manifestations of the same underlying disease. Most frequent localization of DVT is at lower limbs. The diagnostic workup begins with an estimation of DVT risk, a judicious use of D-Dimers, and compression venous ultrasound depending on DVT probability. The development of direct oral anticoagulants and recent data on interventional DVT treatment, in selected cases, have widened the therapeutic spectrum of DVT. The present article aims at informing the primary care physician of the optimized workup of patients with lower limb suspicion of DVT.
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Mono- and bi-allelic mutations in the low-density lipoprotein receptor related protein 5 (LRP5) may cause osteopetrosis, autosomal dominant and recessive exudative vitreoretinopathy, juvenile osteoporosis, or persistent hyperplastic primary vitreous (PHPV). We report on a child affected with PHPV and carrying compound mutations. The father carried the splice mutation and suffered from severe bone fragility since childhood. The mother carried the missense mutation without any clinical manifestations. The genetic diagnosis of their child allowed for appropriate treatment in the father and for the detection of osteopenia in the mother. Mono- and bi-allelic mutations in LRP5 may cause osteopetrosis, autosomal dominant and recessive exudative vitreoretinopathy, juvenile osteoporosis, or PHPV. PHPV is a component of persistent fetal vasculature of the eye, characterized by highly variable expressivity and resulting in a wide spectrum of anterior and/or posterior congenital developmental defects, which may lead to blindness. We evaluated a family diagnosed with PHPV in their only child. The child presented photophobia during the first 3 weeks of life, followed by leukocoria at 2 months of age. Molecular resequencing of NDP, FZD4, and LRP5 was performed in the child and segregation of the observed mutations in the parents. At presentation, fundus examination of the child showed a retrolental mass in the right eye. Ultrasonography revealed retinal detachment in both eyes. Thorough familial analysis revealed that the father suffered from many fractures since childhood without specific fragility bone diagnosis, treatment, or management. The mother was asymptomatic. Molecular analysis in the proband identified two mutations: a c.[2091+2T>C] splice mutation and c.[1682C>T] missense mutation. We report the case of a child affected with PHPV and carrying compound heterozygous LRP5 mutations. This genetic diagnosis allowed the clinical diagnosis of the bone problem to be made in the father, resulting in better management of the family. It also enabled preventive treatment to be prescribed for the mother and accurate genetic counseling to be provided.
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Over the past two decades, electrophysiology has undergone unprecedented changes thanks to technical improvements, which simplify measurement and analysis and allow more compact data storage. This book covers in detail the spectrum of electrophysiology applications in patients with disorders of consciousness. Its content spans from clinical aspects of the management of subjects in the intensive care unit, including EEG, evoked potentials and related implications in terms of prognosis and patient management to research applications in subjects with ongoing consciousness impairment. While the first section provides up-to-date information for the interested clinician, the second part highlights the latest developments in this exciting field. The book comprehensively combines clinical and research information related to neurophysiology in disorder-of- consciousness patients, making it an easily accessible reference for neuro-ICU specialists, epileptologists and clinical neurophysiologists as well as researchers utilizing EEG and event-related potentials.