106 research outputs found

    Object-oriented database management system case study for declarative query language

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    Object-Oriented database management systems (OODBMS) combine the abstraction power of objects with the query and performance capabilities of database management systems. Existing query notations were missing many object related features until recently. The introduction of a new query notation, known by Object Comprehensions, allows queries to be expressed clearly and processed efficiently. Our work is to establish a testbed for the processing of Object Comprehension Language (OCL) queries using an experimented object-oriented database, Ode. This thesis overviews object-oriented databases evolution, and object query processing, then introduces an object-oriented database system, Ode, whose programming language O\sp{++} is based on C\sp{++}. A university data model is built using O\sp{++}, stored into the Ode database, and utilities, such as bag, list and set, are written to support the processing of OCL queries. The translation of OCL queries into O\sp{++} is not part of this thesis, but is part of a related project

    Modeling the visco-hyperelastic–viscoplastic behavior of photodegraded semi-crystalline low-density polyethylene films

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    In this work we propose to model the mechanical and fracture response of semi-crystalline low-density polyethylene (LDPE) films exposed to accelerated ultraviolet (UV) ageing using a physically based visco-hyperelastic–viscoplastic approach. UV irradiation induces an alteration of the chemical and structural properties of the semi-crystalline polymer, which affects significantly its mechanical behavior. In this work, pristine and oxidized low-density polyethylene films are characterized by conventional physico-chemical and mechanical techniques (FTIR spectroscopy, DSC, HT-GPC, and uniaxial tensile testing). Polyethylene exhibits an oxidation-induced strengthening for a low range of UV radiation doses and a cavitation-induced softening for higher UV radiation doses. A competing multi-scale phenomena induced by UV radiation are incorporated into the constitutive model to capture the macroscopically observed mechanical and fracture behavior. Namely, the model will incorporate at the nano scale, chain scissions and cross-linking and at the meso and macro scales, oxidation-induced cracking, chemi-crystallization, and mechanical damage. The model used the high-temperature gel permeation chromatography-measured molecular weight as degradation indicator. The model was able to capture accurately the evolution of the macroscopically observed mechanical and fracture behavior over a wide range of UV irradiation doses

    Mandibular Canine Dimorphism in Establishing Sex Identity in the Lebanese Population

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    Background and Objective. In forensic investigations, mandibular canines provide excellent materials to identify gender since they are more likely to survive disasters. The objective of this study was to investigate gender dimorphism by comparing the mesiodistal width of mandibular permanent canines and intercanine distance in a group of Lebanese population. Methods. Participants consisted of undergraduate students from the School of Dentistry, Lebanese University, for two academic years who fulfilled the inclusion criteria. Canine widths and intercanine distance were measured by one operator directly on dental casts using a digital caliper. Results. One hundred thirty-three Lebanese dental students (54 males and 69 females) aged 18–25 were included in the study. The intercanine distance was significantly greater in males (P value < 0.0001). The right and the left canine widths were significantly greater in males than in females (P value < 0.0001). However, no significant difference was found between left and right canines for males (P value > 0.05) and females (P value > 0.05). The mean width of canine was greater than 7.188 mm for males. Conclusion. The parameters measured in the present study are of great help in sex identification in forensic investigations in the Lebanese adult population

    Experimental investigation and modeling attempt on the effects of ultraviolet aging on the fatigue behavior of an LDPE semi-crystalline polymer

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    The objective of this study was to investigate the effect of UV irradiation on the fatigue life of a bulk semi-crystalline polymer. Low-density polyethylene samples exposed to different UV irradiation doses were fatigue tested. Fatigue indicator based on dissipated energy per cycle was found to present the best correlation with the experimental fatigue results. A master curve unifying the experimental fatigue results for as-received and UV-aged materials was obtained when subtracting the dissipated energy threshold from the total dissipated energy. Finally, the evolution of the damage with cyclic loading was analyzed and preliminary modeling was attempted.This research was supported by the Qatar National Research Fund (NPRP grant No. 7-1562-2-571). We would like to acknowledge the fruitful discussions with Profs. Eddine Gherdaoui and Jean-Michel Gloaguen of the University of Lille

    New developments in fracture of rubbers: Predictive tools and influence of thermal aging

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    In this work, the influence of thermal oxidative aging on the ultimate mechanical properties of rubbers is investigated. Two new approaches to predict failure properties are proposed. The first one is the stress limiter approach that uses a “damage” parameter allowing determination of the failure stress and strain of an aged material knowing both the mechanical properties and macromolecular network characteristics of an as-received material. The second one is an extension of the energy limiter approach that suggests capturing the drop of the stress at failure by replacing the strain energy density function of an as-received elastomeric material by a function expressed in terms of an energy limiter. The predictive capabilities of these two approaches are validated using experimental results for two elastomeric materials: an EPDM and a polychloroprene (CR), both of which exhibit a largely predominant post-crosslinking (over chain scissions) during aging. Comparison between the predictions and the experimental results in terms of failure stresses and strains under uniaxial tension showed a good agreement. Consequently, these two approaches are promising tools for designing elastomeric parts subjected to thermal oxidative aging

    Neurological disorders in HIV:Hope despite challenges

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    INTRODUCTION: Human Immunodeficiency virus (HIV) is a virus that causes several diseases by attacking the human immune system. It is transmitted by contact with certain bodily fluids of an infected person, most commonly during unprotected sex, through sharing needles, or from mother to baby during pregnancy, birth or breastfeeding. The central nervous system is not spared from this virus, as HIV has been shown to induce several neurological disorders. However most neurological pathologies (such as dementia, infections, meningitis, and neuropathy) rarely show until late stages, in this case, after the patients develop acquired immunodeficiency syndrome (AIDS). This article aims to review the neurological disorders in the HIV population and the attempts initiated to limit the disease. METHODOLOGY: Data were collected from medical journals published on PubMed, Ovid MEDLINE, Science Direct and Embase bibliographical databases with a predefined search strategy. All articles considering neurological disorders associated with HIV were considered. RESULTS: To date, the pathogenesis of HIV‐associated neurological complications remains poorly elucidated; thus, imposing a hindrance and limitations on the treatment options. Nevertheless, some studies have reported alterations in dendritic spine as the causative agent for developing brain damage. CONCLUSION: HIV remains one of the most serious global health challenges, with neurological manifestations imposing a major concern among patients with HIV. Despite the availability and efficacy of antiretroviral therapies, yet, the risk of developing neurological complications remains relatively high among patients with HIV. Thus, the 2030 HIV vision must focus on further preventive measures to protect HIV patients from developing such neurological complications

    All-Cause Mortality in Type 2 Diabetes Patients Hospitalized for COVID-19 and Treated with Corticosteroids: A Single Center Cross-Sectional Study

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    Objective: This study aims to compare all-cause mortality and other hospital outcomes of hospitalized coronavirusdisease of 2019 patients using corticosteroids. Materials and methods: A comparative cross-sectional study was performed over three months by collecting data from patients’ medical charts. Results: The sample included 129 patients with type 2 diabetes (T2D) and 293 patients without diabetes, with more men than women in both groups. Patients withT2D were older, namely, those aged more than 70 years (54.3%) with the majority having abnormal glucose levels on admission (76.1%) and at discharge (76.9%). As a primary outcome, higher all-cause mortality was reported among patients without diabetes having more than two comorbidities (38.2%) compared to those with two or single comorbidities (21.0% and 13.9% respectively; p = 0.009). It significantly increased if patients without diabetes had abnormal glucose levels at admission (51.7%; p &lt; 0.001) and discharge (44.7%; p &lt; 0.001) compared to those with normal levels. Critical cases had higher all-cause mortality compared to less severe cases in patients with T2D (58.8%; p &lt; 0.001) and without diabetes (61.0%; p &lt; 0.001). Among secondary outcomes, a higher length of stay in the hospital was noted among patients with T2D (8.4 vs. 7.3 days; p = 0.015), in addition to a significantly higher number of ventilator-free days (2.7 vs. 1.6 days; p = 0.039). Conclusions: Although the treatment with corticosteroids was comparable between patients with and without T2D, hospital outcomes varied between the groups. Findings from this study can help provide additional clinical support for patients with T2D to allow better in-hospital management of COVID-19 cases

    Study of ordered hadron chains with the ATLAS detector

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