194 research outputs found

    Metamict zircon and structural characters: Pütürge metamorphite example

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    Mineralogical studies (rock named, zircon separate), geochemical analysis(LA-ICPMS) and cathodoluminescence (CL) image were applied to samples of the Pütürge metamorphites representing different facies such as amphibolites and greenschiste. Pütürge metamorphites are made up of pelite/semi-pelite, psammite, metagranite gneisse, schist, amphibolite, marble and quartzite type rocks. Mineral paragenesis, the transformation of the garnet mineral advancing on the kyanite-almandine-muscovite and staurolite-almandine sub-facies of the amphibolite facies of the massive to chlorite and biotite minerals along with the transformation of the kyanite mineral to muscovite mineral show that the massive has undergone two retrograde metamorphisms on the greenschist facies. The exhumation process of the metamorphites is seen as the cause of the retrograde metamorphism. The cathodoluminescence images of zircon minerals show a zoning that indicates a metamorphic growth where partial radiation damage in the shape of oscillatory zoning and porous structure also occurs pointing out the magmatic root. A zircon type with different textural and chemical components which might be called partially metamictte has developed. The luminescence feature in partially radiated zircon particles rich in radiogenetic minerals is rather high in comparison with other zircon particles. High temperature during the metamorphism of the massive and the ratio of the radiogenetic elements like U and Th in the mineral are effective in the textural and chemical difference between the core and rims of zirconsPütürge metamorfitlerinde mineralojik (kayaç adlandırılması, zirkon ayrımı), jeokimyasal (LA-ICPMS) ve Kathödölüminesans (CL) incelemeleri Pütürge metamorfitlerinin amfibolit ve yeşilşist fasiyesi gibi farklı fasiyesleirn özelliğini yansıtacak örneklerden alınmıştır. Pütürge metamorfitleri, pelit/semi-pelit, pisamit, metagranit, gnays, şist, amfibolit, mermer ve kuvarsitten oluşur. Mineral parajenezleri, masifin amfibolit fasiyesinin disten-almandin-muskovit ve stavrolit-almandin alt fasiyeslerinde ilerleyen, granat mineralinin klorit ve biyotit minerallerine dönüşümleri ve disten mineralinin muskovit mineralinine dönüşümü gibi özelliklerden yeşilşist fasiyesinde gerileyen türden iki metamorfizma geçirmiş olduğunu göstermektedir. Gerileyen metamorfizmaya metamorfitlerin yükselme süreci sebep olarak görülmektedir. Zirkon minerallerinin kathödölüminesans görüntülerinde, magmatik kökeni işaret eden ilksel (oscilatory) zonlanma ve gözenekli yapı şeklinde, kısmen radyasyon hasarının da geliştiği büyüme zonlanması görülür. Dokusal ve kimyasal bileşimleri farklı olan, kısmen metamikt diyebileceğimiz zirkon değişimi gelişmiştir. Radyojenetik kapantı minerallerince zengin metamikt zirkon tanelerinde, luminesans özellik diğer zirkon tanelerine nazaran yüksektir. Zirkonda, çekirdek ve kenar kısımları arasındaki dokusal ve kimyasal farklılığa, masifin metamorfizması sırasındaki yüksek sıcaklık ve U, Th gibi radyojenetik elementlerin mineral içerisindeki oranı etkili olmuştur

    Rex Shunt Preoperative Imaging: Diagnostic Capability of Imaging Modalities

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    The purpose of this study was to evaluate the diagnostic capability of imaging modalities used for preoperative mesenteric-left portal bypass (“Rex shunt”) planning. Twenty patients with extrahepatic portal vein thrombosis underwent 57 preoperative planning abdominal imaging studies. Two readers retrospectively reviewed these studies for an ability to confidently determine left portal vein (PV) patency, superior mesenteric vein (SMV) patency, and intrahepatic left and right PV contiguity. In this study, computed tomographic arterial portography allowed for confident characterization of left PV patency, SMV patency and left and right PV continuity in 100% of the examinations. Single phase contrast-enhanced CT, multi-phase contrast-enhanced CT, multiphase contrast-enhanced MRI, and transarterial portography answered all key diagnostic questions in 33%, 30%, 0% and 8% of the examinations, respectively. In conclusion, of the variety of imaging modalities that have been employed for Rex shunt preoperative planning, computed tomographic arterial portography most reliably allows for assessment of left PV patency, SMV patency, and left and right PV contiguity in a single study

    Proactive environmental strategy in a supply chain context: The mediating role of investments

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    Abstract: There is a growing body of knowledge on the link between environmental management and supply chain management, but there is contradicting evidence on the impact of a proactive environmental strategy on environmental performance. Therefore, this paper investigates the impact of proactive environmental strategy on environmental performance as mediated by environmental investments. We also consider the antecedents of the adoption of proactive environmental strategy. We develop and test hypotheses, using data collected from 96 Turkish manufacturers through an online questionnaire. The model was tested using Partial Least Squares (PLS), a structural equation modelling method. The results show that a proactive environmental strategy leads to higher environmental investments; both internally and externally in collaboration with suppliers. Our findings support our hypothesis that environmental investments acts as a mediating variable between proactive environmental strategy and environmental performance. The results also show that customer pressure and, particularly, organizational commitment positively impact the extent to which firms adopt a proactive environmental strategy

    Use and detailed metric properties of patient-reported outcome measures for rheumatoid arthritis: a systematic review covering two decades

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    Introduction The importance of patient-reported outcome measures (PROMs) for rheumatoid arthritis (RA) clinical studies has been recognised for many years. The current study aims to describe the RA PROMs used over the past 20 years, and their performance metrics, to underpin appropriate tool selection. Methods The study included a systematic search for PROMs that have been in use over the period 2000–2019, with detailed documentation of their psychometric properties, and a user-friendly presentation of the extensive evidence base. Results 125 PROMs were identified with psychometric evidence available. The domains of pain, fatigue, emotional functions, mobility, physical functioning and work dominated, with self-efficacy and coping as personal factors. Domains such as stiffness and sleep were poorly served. The most frequently used PROMs included the Health Assessment Questionnaire Disability Index (HAQ), the Short Form 36 (SF-36), the EuroQoL and the Modified HAQ which, between them, appeared in more than 3500 papers. Strong psychometric evidence was found for the HAQ, and the SF-36 Physical Functioning and Vitality (fatigue) domains. Otherwise, all domains except stiffness, sleep, education and health utility, had at least one PROM with moderate level of psychometric evidence. Conclusion There is a broad range of PROMs for measuring RA outcomes, but the quality of psychometric evidence varies widely. This work identifies gaps in key RA domains according to the biopsychosocial model

    Hearing impairment risk and interaction of folate metabolism related gene polymorphisms in an aging study

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    <p>Abstract</p> <p>Background</p> <p>Recent investigations demonstrated many genetic contributions to the development of human age-related hearing impairment (ARHI), however, reports of factors associated with a reduction in the ARHI risk are rare. Folate metabolism is essential for cellular functioning. Despite the extensive investigations regarding the roles of folate metabolism related gene polymorphisms in the pathophysiology of complex diseases, such as cancer, cardio-cerebrovascular disease, and atherosclerosis, little is known about the association with ARHI. The aim of this study is to investigate the effects of the methionine synthase (MTR) A2756G and methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphisms on the risk of hearing impairment in middle-aged and elderly Japanese.</p> <p>Methods</p> <p>Data were collected from community-dwelling Japanese adults aged 40-84 years who participated in the Longitudinal Study of Aging biennially between 1997 and 2008. We analyzed cumulative data (5,167 samples in accumulated total) using generalized estimating equations.</p> <p>Results</p> <p>The MTHFR 677T allele was significantly associated with a reduced risk of hearing impairment only when the subjects were wild-type homozygotes for MTR A2756G. The per-T allele odds ratio of MTHFR for the risk of developing hearing impairment was 0.7609 (95% CI: 0.6178-0.9372) in the MTR AA genotype. In addition, a subgroup analysis demonstrated that the favorable effect of the MTHFR 677T allele on the risk of developing hearing impairment was independent of folate and homocysteine level, whereas plasma total homocysteine level was independently associated with an increased risk of developing hearing impairment. The interactive effect of gene polymorphisms associated with folate metabolism may modify the risk of developing hearing impairment after middle age. These results contribute to the elucidation of the causes of ARHI.</p> <p>Conclusions</p> <p>The present study has found that the MTHFR 677T allele has a favorable effect on a risk of hearing impairment in the middle-aged and elderly population, only when the individuals were wild-type homozygotes for MTR A2756G.</p
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