380 research outputs found

    Performance Assessment of Screw Piles Embedded in Soft Clay

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    Screw piles are widely used in a variety engineering applications supplying stability against compression, overturning moment, uplift tension, and horizontal loads. Screw pile is a famous solution for support light structures, roads and rail signs which have relatively low-capacity foundation. In this study, the behavior of circular (10) mm solid screw pile models embedded in a bed of soft clay soil covering a layer of sandy soil has been studied. The 200 mm thick sand layer was compacted in a steel container with a diameter of 300 mm into four sublayers. The sandy soil layer was compacted at a relative density of 70%. The 300 mm thick soft clay soil bed with Cu (30) kPa was compacted in six sub-layers on the sandy bottom layer. Model tests are carried out with screw piles with a length of 300 mm, 350 mm and 400 mm and a helix diameter of 30 mm. Also, single and double helix and different S/Dh ratio were used for these piles and a comparative study between screw piles and ordinary piles (without helices) is accomplished. This study revealed that introducing screw pile of double helix increases its bearing capacity in soft clay soil by up to a (4-8) % as compared to a single helix screw pile. The results showed that the behavior of screw pile essentially depends on the geometric properties of the pile. According to the achievements, compressive load capacity of screw piles depends on embedded length, spacing ratio (S/Dh) and number of helical plates

    Aqra Anticline: A Growing Structure in the Iraqi Kurdistan Region

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    Aqra Anticline is a double plunging anticline, oriented NW–SE with a steep southwestern limb and even overturned. Geomorphological features are interpreted using satellite images, as a result, it was found that the anticline shows clear geomorphological and structural features which indicate the lateral growth of the anticline. Among those features are water gaps, wind gaps, forked-shaped valleys, curved valleys, inclined valleys and dislocated and abandoned alluvial fans. Some of the vague interpreted features were checked and confirmed in the field

    Tailoring the chemical structure of cellulose nanocrystals by amine functionalization

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    The surface functionalization of cellulose nanocrystals is presently considered a useful and straightforward tool for accessing very reliable biocompatible and biodegradable nanostructures with tailored physical and chemical properties. However, to date the fine characterization of the chemical appendages introduced onto cellulose nanocrystals remains a challenge, due to the low sensitivity displayed by the most common techniques towards surface functionalization. In this paper, we demonstrate the easy functionalization of cellulose nanocrystals with aliphatic and aromatic amines, demonstrating the tunability of their properties in dependence on the selected functionality. Then, we apply to colloidal suspensions of modified nanocrystals 1H NMR analysis to elucidate their surface structure. To the best of our knowledge, this is the first report where such investigation was performed on cellulose nanocrystals presenting both surface and reducing end modification. These results involve interesting implications for the fields of cultural heritage and of materials chemistry

    The Genetic Structure and History of Africans and African Americans.

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    Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations across the continent has been enigmatic. We studied 121 African populations, four African American populations, and 60 non-African populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral population clusters in Africa that correlate with self-described ethnicity and shared cultural and/or linguistic properties. We observed high levels of mixed ancestry in most populations, reflecting historical migration events across the continent. Our data also provide evidence for shared ancestry among geographically diverse hunter-gatherer populations (Khoesan speakers and Pygmies). The ancestry of African Americans is predominantly from Niger-Kordofanian (approximately 71%), European (approximately 13%), and other African (approximately 8%) populations, although admixture levels varied considerably among individuals. This study helps tease apart the complex evolutionary history of Africans and African Americans, aiding both anthropological and genetic epidemiologic studies

    Przygotowanie jelita do kolonoskopii: Zalecenia Europejskiego Towarzystwa Endoskopii Przewodu Pokarmowego

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     CEL: Niniejsze zalecania są oficjalnym stanowiskiem Europejskiego Towarzystwa Endoskopii Przewodu Pokarmowego (ESGE, European Society of Gastrointestinal Endoscopy) na temat wyboru sposobu przygotowania jelita do kolonoskopii.METODY: Zalecania opracowano na podstawie przeglądu literatury ukierunkowanego na dowody dotyczące przygotowania jelita do kolonoskopii. Siła zaleceń i jakość dowodów, na których je oparto zostały określone przy użyciu systemu GRADE (Grading of Recommendations Assessment, Development and Evaluation).WYNIKI: Najważniejsze zalecenia są następujące:1. ESGE zaleca w dniu poprzedzającym kolonoskopię dietę ubogoresztkową (słabe zalecenie, dowody umiarkowanej jakości);2. ESGE zaleca w rutynowym przygotowaniu do kolonoskopii 4 litry roztworu glikolu polietylenowego (PEG) w dwóch dawkach podzielonych lub, w przypadku kolonoskopii wykonywanej po południu, w jednorazowej dawce porannej. Alternatywą, szczególnie w przygotowaniu do kolonoskopii w warunkach ambulatoryjnych, może być podanie 2 l PEG z kwasem askorbinowym lub pikosiarczanu sodu z cytrynianem magnezu w dwóch dawkach podzielonych lub, w przypadku kolonoskopii wykonywanej po południu, w jednorazowej dawce porannej (silne zalecenie, dowody wysokiej jakości). Odstęp pomiędzy ostatnią dawką preparatu do przygotowania a kolonoskopią nie powinien przekraczać 4 godzin;3. ESGE radzi ze względów bezpieczeństwa nie używać rutynowo do przygotowania do kolonoskopii preparatów fosforanu sodu (silne zalecenie, dowody niskiej jakości).

    Numerical Investigation on Hollow Pultruded Fibre Reinforced Polymer Tube Columns

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    As the axial behaviour of hollow pultruded fibre reinforced polymer (PFRP) profiles is governed by the instability conditions due to the local and global buckling, the determination of the safe load carrying capacity of FRP columns is vital. The compressive performance of PFRP tube depends on many factors such as fibre type, fibre content, and orientation of fibre layers, cross-section, thickness and height of the column member. In this study, concentric compressive testing was conducted using PFRP short columns. Based on the fibre orientation and thickness, the samples were divided into two groups of tubes in a square shape and two groups in a circular shape. The height of columns is designed to keep the slenderness ratio (length/lateral dimension) of 5. The axial behaviour of FRP columns was simulated using STRAND7 finite element software package. The laminate method was followed to define the mechanical properties of the FRP material. Failure was investigated by using the Tsai-Wu failure criterion. The experimental results show that the failure mode of the hollow square tube was either local buckling or corner splitting at the mid-height followed by buckling. Although both types of circular tubes failed in a similar way by crushing one end with high noise, followed by separation of the crushed end into strips, the stiffness and the load capacity of PFRP column was higher for the profiles with fibres oriented close to the axial direction. The numerical results are in close agreement with the peak value of the experimental results. This can be extended to study the effects of all factors that influence the axial behaviour of PFRP columns numerically

    Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

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    BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

    Association of the MTHFR A1298C Variant with Unexplained Severe Male Infertility

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    The methylenetetrahydrofolate reductase (MTHFR) gene is one of the main regulatory enzymes involved in folate metabolism, DNA synthesis and remethylation reactions. The influence of MTHFR variants on male infertility is not completely understood. The objective of this study was to analyze the distribution of the MTHFR C677T and A1298C variants using PCR-Restriction Fragment Length Polymorphism (RFLP) in a case group consisting of 344 men with unexplained reduced sperm counts compared to 617 ancestry-matched fertile or normozoospermic controls. The Chi square test was used to analyze the genotype distributions of MTHFR polymorphisms. Our data indicated a lack of association of the C677T variant with infertility. However, the homozygous (C/C) A1298C polymorphism of the MTHFR gene was present at a statistically high significance in severe oligozoospermia group compared with controls (OR = 3.372, 95% confidence interval CI = 1.27–8.238; p = 0.01431). The genotype distribution of the A1298C variants showed significant deviation from the expected Hardy-Weinberg equilibrium, suggesting that purifying selection may be acting on the 1298CC genotype. Further studies are necessary to determine the influence of the environment, especially the consumption of diet folate on sperm counts of men with different MTHFR variants
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