This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.
Background: Alterations in the microhardness and roughness are commonly used to analyze the possible negative effects of bleaching products on restorative materials. This in vitro study evaluated the effect of in-office bleaching (SDI pola office +) on the surface roughness and micro-hardness of four newly developed composite materials (Z350XT –nano-filled, Z250XT-nano-hybrid, Z250-mico-hybrid and Silorane-silorane based). Materials and methods: Eighty circular samples with A3 shading were prepared by using Teflon mold 2mm thickness and 10mm in diameter. 20 samples for each material, 10 samples for base line measurement (surface roughness by using portable profillometer, and micro-hardness by usingDigital Micro Vickers Hardness Test
... Show MoreThis review article summarizes our research focused on Cu(In, Ga)Se2 (CIGS) nanocrystals, including their synthesis and implementation as the active light absorbing material in photovoltaic devices (PVs). CIGS thin films were prepared by arrested precipitation from molecular precursors consisting of CuCl, InCl3, GaCl3 and Se metal onto Mo/soda-lime glass (SLG) substrates. We have sought to use CIGS nanocrystals synthesized with the desired stoichiometry to deposit PV device layers without high temperature processing. This approach, using spray deposition of the CIGS light absorber layers, without high temperature selenization, has enabled up to 1.5 % power conversion efficiency under AM 1.5 solar illumination. The composition and morphology
... Show MoreABSTRACT
The current research aims at highlighting the role of engagement of a sample of employees who works in some of the Iraqi private banks in terms of their interaction , commitment and enthusiasm and the positive impact they own regarding their job and devote their efforts to achieve the core purpose which is customer loyalty. The problem was expressed through a number of intellectual and practical questions.
In order to achieve the aim of the research the quantitative analytical method was used depending on a questionnaire as a basic tool to collect research data and the qualitative survey method depending on semi-structured interviews which were distrib
... Show MoreAsthma is a chronic inflammatory disease of airways mediated by T-helper 2 (Th2) cells involving complex signaling pathways. Although resveratrol has previously been shown to attenuate allergic asthma, the role of miRNA in this process has not been studied. We investigated the effect of resveratrol on ovalbumin-induced experimental allergic asthma in mice. To that end, BALB/c mice were immunized with ovalbumin (OVA) intraperitoneally followed by oral gavage of vehicle (OVA-veh) or resveratrol (100 mg/kg body) (OVA-res). On day 7, the experimental groups received intranasal challenge of OVA followed by 7 days of additional oral gavage of vehicle or resveratrol. At day 15, all mice were euthanized and bronchioalveolar fluid (BALF), se
... Show MoreClopidogrel is a prodrug that must be transformed into an active metabolite by hepatic cytochrome P450 (CYP) isoenzymes to prevent platelet clotting. Polymorphisms of the CYP2C19 gene can cause a reduction or complete loss of CYP2C19 enzyme activity resulting in inhibiting clopidogrel metabolism, effectiveness and increase stroke recurrence risk in ischemic stroke patients. This study aims to investigate the correlation between genetic polymorphisms in CYP2C19*2 and*3 and recurrent risk in patients with ischemic stroke taking clopidogrel 75mg in Kurdistan region –Iraq. This retrospective case-control study was carried out at Kurdistan, Erbil, Medicina medical center, and Rizgary general hospital from January 2021 to
... Show MoreKE Sharquie, RA Najim, RK Al-Hayani, AA Al-Nuaimy, DM Maroof, Saudi medical journal, 2008 - Cited by 74
Objectives: The study aims at:
1- Measuring the level of lead in workers’ saliva and blood in the factory.
2- Studying the correlation between the saliva lead level and the infection that caused by microorganisms, isolation and
identification.
3-Studying the influence of high blood lead level on the total white blood cells.
Methodology: This study has been conducted for the period from March 15th, 2010 to May, 20th
, 2010. A total of (60)
saliva and blood samples were collected from workers in batteries industry factory in Baghdad and another (20) samples
were collected as a control group. Lead level had been measured in blood and saliva samples, then microorganisms were
isolated the from the saliva samples.
Genetic material is the most important component of cells because it contains the genetic information; hence any disruption to the structure chromosome of cells could lead to very bad results. Genotoxicity use to evaluate the safety of any chemical compounds on genetic materials. Artificial food flavoring additive are chemical substances to produce specific placebo effects added to foods but impart specific flavor to it.
The present study evaluates the genotoxic effect of artificial food flavoring additive on structure of chromosomes at three different concentrations (50%, 100%and 150%) on both bone marrow cells and spleen cells in mice for fourteen successive days. It was found that artificial food flavoring addit
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