214 research outputs found

    Development of constitutive model for precast prestressed concrete segmental columns

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    The interest of using precast segmental columns in construction of concrete bridges has significantly increased in recent years. One research area of concrete bridges is the application of Precast Prestressed Concrete Segmental (PPCS) Column in any structural analysis software or FE program code. Modeling a PPCS column, which consists of various materials with interaction between them, is complicated and time-consuming. This research attempts to formulate the stiffness matrix of PPCS columns in order to form the constitutive model in linear form to evaluate the response of the columns. A two-dimensional finite element model is presented in the finite element package ANSYS. Parametric studies are conducted by finite element models to verify the constitutive models for the PPCS column with a different number of concrete segments. Comparison between the constitutive model and the FE program results indicates that the constitutive model is accurate enough to predict the deformation of the PPCS columns

    Processing and characterization of nanostructured Grade 2 Ti processed by combination of warm isothermal ECAP and extrusion

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    In this study, combined multi pass equal channel angular pressing (ECAP), and subsequent warm extrusion at different temperatures are performed on commercial purity titanium. Mechanical and microstructural evolutions are then investigated. Since it was observed that the four passes ECAP processed sample showed the best strength and reasonable elongation, this sample was selected for studying the extrusion temperature effects on the structure and mechanical properties of Grade 2 titanium. Therefore, the 4th passes ECAP processed sample was extruded at different temperatures of 300 °C, 350 °C, 400 °C, 450 °C and 500 °C. The result revealed that the best mechanical properties were achieved from the specimen processed by four passes ECAP followed by warm extrusion at 300 °C. The strength, and hardness of this sample were considerably improved in comparison with that of the unprocessed sample. Also, its ultra-fine grained and nanograined microstructure were homogeneous, with a grain size ranged from 40 to 200 nm with an average grain size of about 123 nm. It was seen that the mechanical properties of some samples after applying this combined process (ECAP + warm extrusion) are comparable with those of Grade 5 titanium which is commonly used in medical applications but contains alloying elements that are toxic to human health

    The Relationship between Gestational Diabetes and Polycystic Ovary Syndrome

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    BACKGROUND AND OBJECTIVE: Women with polycystic ovary syndrome (PCOS) are at risk of insulin resistance and pregnancy complications. The aim of this study is to determine the relationship between gestational diabetes and polycystic ovary syndrome. METHODS: This cross-sectional study was performed on 126 pregnant women with PCOS and infertility history who became pregnant after stimulation of ovulation and referred to Imam Khomeini Hospital in Ahvaz. These patients underwent screening with 75 g OGTT (Oral Glucose Tolerance Test) during the first trimester and during 24-28 weeks of gestation. They were divided into two groups of PCOS with gestational diabetes and without gestational diabetes. Variables such as age, gestational diabetes, parity and BMI were measured and the relationship between BMI and gestational diabetes was examined. FINDINGS: The mean age of patients in the two PCOS groups with and without gestational diabetes was 26.09±2.03 and 27.07±3.03 years, respectively. Of the 126 pregnant women with PCOS, 30 (23.8%) patients were diagnosed with gestational diabetes in the first trimester of pregnancy and 11 (8.7%) patients during 24-28 weeks of gestation. Overall, 41(32.5%) patients had gestational diabetes and 85 (67.5%) patients did not have gestational diabetes. There was no significant difference in the mean BMI between the two PCOS groups with and without gestational diabetes. CONCLUSION: The results of the study showed that more than one third of women with PCOS experience gestational diabetes during pregnancy

    Barriers to Physical Activity in Pregnant Women: An Explanatory Sequential Mixed-method Study (Study Protocol)

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    Background: Gaining insight into the obstacles holding women from engaging in physical activity during pregnancy is crucial for planning future interventions to enhance their physical activity during this period. This research aims to identify barriers to physical activity among pregnant women using an explanatory sequential mixed-methods approach. The study protocol is explained in this article. Methods: This research employs an explanatory sequential mixed-methods design. The project will be implemented in two separate phases. In the first phase, a quantitative cross-sectional study will be conducted on 358 eligible pregnant women aged 18-45 years living in Babol City, Iran. Quantitative data collection will involve using the barriers to physical activity during pregnancy scale (BPAPS) and questionnaires gathering demographic and obstetric data. The qualitative investigation will employ individual semi-structured interviews utilizing a content analysis approach. Ultimately, incorporating qualitative data will inform the interpretation of quantitative findings. Results: The results will be presented in alignment with the study objectives. Initially, the mean score of BPAPS and its subscales, along with the correlation between demographic and obstetric variables, will be reported. Subsequently, the qualitative phase will encompass the reporting of categories and the main themes. Finally, the quantitative phase findings will be interpreted, incorporating insights gained from the qualitative phase. Conclusion: Since regular physical activity during pregnancy has many benefits for maternal and fetal health, the study’s findings after its implementation can play a vital role in strategic planning to address women’s false beliefs and misconceptions regarding physical activity during pregnancy. In addition, this study will contribute to designing interventions to remove barriers to physical activity and encourag

    Seizure as the early and main manifestation of infantile vanishing white matter disease: A case report

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    Introduction: Vanishing white matter disease (VWM) is considered as one of the most frequent types of inherited childhood leukoencephalopathies. Various neurological and non-neurological manifestations have been reported in this type of leukodystrophy; however, seizures are rarely described in infantile type of VWM. Case Presentation: To patient is a 12 months old boy who experienced frequent seizures at 4th month of age. The seizures were resistant to anti-epileptic drugs and caused 3 periods of hospitalization. Magnetic resonance imaging (MRI) demonstrated demyeli-nating pattern and whole exome sequencing (WES) reported homozygous mutation (c.922G > A) in EIF2B2 gene in exon 8 leading to an amino-acid substitution (p.Val308Met). Conclusions: Infantile onset of vanishing white matter disease can be considered as one of few childhood leukodystrophies that are associated with early onset seizures. © 2018, Iranian Journal of Pediatrics

    Bare Bones Pattern Formation: A Core Regulatory Network in Varying Geometries Reproduces Major Features of Vertebrate Limb Development and Evolution

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    BACKGROUND: Major unresolved questions regarding vertebrate limb development concern how the numbers of skeletal elements along the proximodistal (P-D) and anteroposterior (A-P) axes are determined and how the shape of a growing limb affects skeletal element formation. There is currently no generally accepted model for these patterning processes, but recent work on cartilage development (chondrogenesis) indicates that precartilage tissue self-organizes into nodular patterns by cell-molecular circuitry with local auto-activating and lateral inhibitory (LALI) properties. This process is played out in the developing limb in the context of a gradient of fibroblast growth factor (FGF) emanating from the apical ectodermal ridge (AER). RESULTS: We have simulated the behavior of the core chondrogenic mechanism of the developing limb in the presence of an FGF gradient using a novel computational environment that permits simulation of LALI systems in domains of varying shape and size. The model predicts the normal proximodistal pattern of skeletogenesis as well as distal truncations resulting from AER removal. Modifications of the model's parameters corresponding to plausible effects of Hox proteins and formins, and of the reshaping of the model limb, bud yielded simulated phenotypes resembling mutational and experimental variants of the limb. Hypothetical developmental scenarios reproduce skeletal morphologies with features of fossil limbs. CONCLUSIONS: The limb chondrogenic regulatory system operating in the presence of a gradient has an inherent, robust propensity to form limb-like skeletal structures. The bare bones framework can accommodate ancillary gene regulatory networks controlling limb bud shaping and establishment of Hox expression domains. This mechanism accounts for major features of the normal limb pattern and, under variant geometries and different parameter values, those of experimentally manipulated, genetically aberrant and evolutionary early forms, with no requirement for an independent system of positional information

    Antibody Repertoires in Humanized NOD-scid-IL2Rγnull Mice and Human B Cells Reveals Human-Like Diversification and Tolerance Checkpoints in the Mouse

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    Immunodeficient mice reconstituted with human hematopoietic stem cells enable the in vivo study of human hematopoiesis. In particular, NOD-scid-IL2Rγnull engrafted mice have been shown to have reasonable levels of T and B cell repopulation and can mount T-cell dependent responses; however, antigen-specific B-cell responses in this model are generally poor. We explored whether developmental defects in the immunoglobulin gene repertoire might be partly responsible for the low level of antibody responses in this model. Roche 454 sequencing was used to obtain over 685,000 reads from cDNA encoding immunoglobulin heavy (IGH) and light (IGK and IGL) genes isolated from immature, naïve, or total splenic B cells in engrafted NOD-scid-IL2Rγnull mice, and compared with over 940,000 reads from peripheral B cells of two healthy volunteers. We find that while naïve B-cell repertoires in humanized mice are chiefly indistinguishable from those in human blood B cells, and display highly correlated patterns of immunoglobulin gene segment use, the complementarity-determining region H3 (CDR-H3) repertoires are nevertheless extremely diverse and are specific for each individual. Despite this diversity, preferential DH-JH pairings repeatedly occur within the CDR-H3 interval that are strikingly similar across all repertoires examined, implying a genetic constraint imposed on repertoire generation. Moreover, CDR-H3 length, charged amino-acid content, and hydropathy are indistinguishable between humans and humanized mice, with no evidence of global autoimmune signatures. Importantly, however, a statistically greater usage of the inherently autoreactive IGHV4-34 and IGKV4-1 genes was observed in the newly formed immature B cells relative to naïve B or total splenic B cells in the humanized mice, a finding consistent with the deletion of autoreactive B cells in humans. Overall, our results provide evidence that key features of the primary repertoire are shaped by genetic factors intrinsic to human B cells and are principally unaltered by differences between mouse and human stromal microenvironments
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