Search results for: exposure limit
Commenced in January 2007
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Edition: International
Paper Count: 3444

Search results for: exposure limit

2934 Concomitant Exposure of Bacoside A and Bromelain Relieves Dichlorvos Toxicity in Mice Serum

Authors: Sonam Agarwal, Renu Bist

Abstract:

Current study emphasizes the toxic effects of dichlorvos on serum in terms of oxidative stress. Meanwhile, a protective action of bacoside A and bromelain was investigated against the biochemical alterations in serum. The experimental design included six groups of mice: saline was given as a vehicle to the control mice (group I). Mice belonging to groups II, III and IV, were administered with dichlorvos (40 mg/kg b.w.), bromelain and bacoside A, respectively. The fifth group received a combination of bromelain and bacoside A. In group VI, Bacoside A, and bromelain were administered 20 minutes prior to exposure of dichlorvos. Thiobarbituric acid reactive substances (TBARS), protein carbonyl content (PCC), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH) level were used as biochemical test of toxic action for dichlorvos intoxication. Significantly increased TBARS and PCC level in second group suggests that dichlorvos enhances the production of free radicals in serum of mice (p< 0.05). Antioxidants treatment significantly decreased the levels of TBARS and PCC (p< 0.05). Dichlorvos administration causes a significant reduction in the level of CAT, SOD, GPx and GSH (p< 0.05) which was restored significantly by co-administration of bromelain and Bacoside A in dichlorvos exposed mice (p< 0.05). Treatment of bromelain and Bacoside A in combination served as better scavengers of toxicity induced by dichlorvos.

Keywords: bacoside A, bromelain, dichlorvos, serum

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2933 Assessment of the Efficacy of Routine Medical Tests in Screening Medical Radiation Staff in Shiraz University of Medical Sciences Educational Centers

Authors: Z. Razi, S. M. J. Mortazavi, N. Shokrpour, Z. Shayan, F. Amiri

Abstract:

Long-term exposure to low doses of ionizing radiation occurs in radiation health care workplaces. Although doses in health professions are generally very low, there are still matters of concern. The radiation safety program promotes occupational radiation safety through accurate and reliable monitoring of radiation workers in order to effectively manage radiation protection. To achieve this goal, it has become mandatory to implement health examination periodically. As a result, based on the hematological alterations, working populations with a common occupational radiation history are screened. This paper calls into question the effectiveness of blood component analysis as a screening program which is mandatory for medical radiation workers in some countries. This study details the distribution and trends of changes in blood components, including white blood cells (WBCs), red blood cells (RBCs) and platelets as well as received cumulative doses from occupational radiation exposure. This study was conducted among 199 participants and 100 control subjects at the medical imaging departments at the central hospital of Shiraz University of Medical Sciences during the years 2006–2010. Descriptive and analytical statistics, considering the P-value<0.05 as statistically significance was used for data analysis. The results of this study show that there is no significant difference between the radiation workers and controls regarding WBCs and platelet count during 4 years. Also, we have found no statistically significant difference between the two groups with respect to RBCs. Besides, no statistically significant difference was observed with respect to RBCs with regards to gender, which has been analyzed separately because of the lower reference range for normal RBCs levels in women compared to men and. Moreover, the findings confirm that in a separate evaluation between WBCs count and the personnel’s working experience and their annual exposure dose, results showed no linear correlation between the three variables. Since the hematological findings were within the range of control levels, it can be concluded that the radiation dosage (which was not more than 7.58 mSv in this study) had been too small to stimulate any quantifiable change in medical radiation worker’s blood count. Thus, use of more accurate method for screening program based on the working profile of the radiation workers and their accumulated dose is suggested. In addition, complexity of radiation-induced functions and the influence of various factors on blood count alteration should be taken into account.

Keywords: blood cell count, mandatory testing, occupational exposure, radiation

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2932 Fatigue Strength of S275 Mild Steel under Cyclic Loading

Authors: T. Aldeeb, M. Abduelmula

Abstract:

This study examines the fatigue life of S275 mild steel at room temperature. Mechanical components can fail under cyclic loading during period of time, known as the fatigue phenomenon. In order to prevent fatigue induced failures, material behavior should be investigated to determine the endurance limit of the material for safe design and infinite life, thus leading to reducing the economic cost and loss in human lives. The fatigue behavior of S275 mild steel was studied and investigated. Specimens were prepared in accordance with ASTM E3-11, and fatigue tests of the specimen were conducted in accordance with ASTM E466-07 on a smooth plate, with a continuous radius between ends (hourglass-shaped plate). The method of fatigue testing was applied with constant load amplitude and constant frequency of 4 Hz with load ratio (Fully Reversal R= -1). Surface fractures of specimens were investigated using Scanning Electron Microscope (SEM). The experimental results were compared with the results of a Finite Element Analysis (FEA), using simulation software. The experiment results indicated that the endurance fatigue limit of S275 mild steel was 195.47 MPa.

Keywords: fatigue strength, fatigue life, finite element analysis(FEA), S275 mild steel, scanning electron microscope (SEM)

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2931 Seismic Isolation of Existing Masonry Buildings: Recent Case Studies in Italy

Authors: Stefano Barone

Abstract:

Seismic retrofit of buildings through base isolation represents a consolidated protection strategy against earthquakes. It consists in decoupling the ground motion from that of the structure and introducing anti-seismic devices at the base of the building, characterized by high horizontal flexibility and medium/high dissipative capacity. This allows to protect structural elements and to limit damages to non-structural ones. For these reasons, full functionality is guaranteed after an earthquake event. Base isolation is applied extensively to both new and existing buildings. For the latter, it usually does not require any interruption of the structure use and occupants evacuation, a special advantage for strategic buildings such as schools, hospitals, and military buildings. This paper describes the application of seismic isolation to three existing masonry buildings in Italy: Villa “La Maddalena” in Macerata (Marche region), “Giacomo Matteotti” and “Plinio Il Giovane” school buildings in Perugia (Umbria region). The seismic hazard of the sites is characterized by a Peak Ground Acceleration (PGA) of 0.213g-0.287g for the Life Safety Limit State and between 0.271g-0.359g for the Collapse Limit State. All the buildings are isolated with a combination of free sliders type TETRON® CD with confined elastomeric disk and anti-seismic rubber isolators type ISOSISM® HDRB to reduce the eccentricity between the center of mass and stiffness, thus limiting torsional effects during a seismic event. The isolation systems are designed to lengthen the original period of vibration (i.e., without isolators) by at least three times and to guarantee medium/high levels of energy dissipation capacity (equivalent viscous damping between 12.5% and 16%). This allows the structures to resist 100% of the seismic design action. This article shows the performances of the supplied anti-seismic devices with particular attention to the experimental dynamic response. Finally, a special focus is given to the main site activities required to isolate a masonry building.

Keywords: retrofit, masonry buildings, seismic isolation, energy dissipation, anti-seismic devices

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2930 Murine Pulmonary Responses after Sub-Chronic Exposure to Environmental Ultrafine Particles

Authors: Yara Saleh, Sebastien Antherieu, Romain Dusautoir, Jules Sotty, Laurent Alleman, Ludivine Canivet, Esperanza Perdrix, Pierre Dubot, Anne Platel, Fabrice Nesslany, Guillaume Garcon, Jean-Marc Lo-Guidice

Abstract:

Air pollution is one of the leading causes of premature death worldwide. Among air pollutants, particulate matter (PM) is a major health risk factor, through the induction of cardiopulmonary diseases and lung cancers. They are composed of coarse, fine and ultrafine particles (PM10, PM2.5, and PM0.1 respectively). Ultrafine particles are emerging unregulated pollutants that might have greater toxicity than larger particles, since they are more abundant and consequently have higher surface area per unit of mass. Our project aims to develop a relevant in vivo model of sub-chronic exposure to atmospheric particles in order to elucidate the specific respiratory impact of ultrafine particles compared to fine particulate matter. Quasi-ultrafine (PM0.18) and fine (PM2.5) particles have been collected in the urban industrial zone of Dunkirk in north France during a 7-month campaign, and submitted to physico-chemical characterization. BALB/c mice were then exposed intranasally to 10µg of PM0.18 or PM2.5 3 times a week. After 1 or 3-month exposure, broncho alveolar lavages (BAL) were performed and lung tissues were harvested for histological and transcriptomic analyses. The physico-chemical study of the collected particles shows that there is no major difference in elemental and surface chemical composition between PM0.18 and PM2.5. Furthermore, the results of the cytological analyses carried out show that both types of particulate fractions can be internalized in lung cells. However, the cell count in BAL and preliminary transcriptomic data suggest that PM0.18 could be more reactive and induce a stronger lung inflammation in exposed mice than PM2.5. Complementary studies are in progress to confirm these first data and to identify the metabolic pathways more specifically associated with the toxicity of ultrafine particles.

Keywords: environmental pollution, lung affect, mice, ultrafine particles

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2929 Numerical Solutions of Fredholm Integral Equations by B-Spline Wavelet Method

Authors: Ritu Rani

Abstract:

In this paper, we apply minimalistically upheld linear semi-orthogonal B-spline wavelets, exceptionally developed for the limited interim to rough the obscure function present in the integral equations. Semi-orthogonal wavelets utilizing B-spline uniquely developed for the limited interim and these wavelets can be spoken to in a shut frame. This gives a minimized help. Semi-orthogonal wavelets frame the premise in the space L²(R). Utilizing this premise, an arbitrary function in L²(R) can be communicated as the wavelet arrangement. For the limited interim, the wavelet arrangement cannot be totally introduced by utilizing this premise. This is on the grounds that backings of some premise are truncated at the left or right end purposes of the interim. Subsequently, an uncommon premise must be brought into the wavelet development on the limited interim. These functions are alluded to as the limit scaling functions and limit wavelet functions. B-spline wavelet method has been connected to fathom linear and nonlinear integral equations and their systems. The above method diminishes the integral equations to systems of algebraic equations and afterward these systems can be illuminated by any standard numerical methods. Here, we have connected Newton's method with suitable starting speculation for solving these systems.

Keywords: semi-orthogonal, wavelet arrangement, integral equations, wavelet development

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2928 Fatigue Analysis and Life Estimation of the Helicopter Horizontal Tail under Cyclic Loading by Using Finite Element Method

Authors: Defne Uz

Abstract:

Horizontal Tail of helicopter is exposed to repeated oscillatory loading generated by aerodynamic and inertial loads, and bending moments depending on operating conditions and maneuvers of the helicopter. In order to ensure that maximum stress levels do not exceed certain fatigue limit of the material and to prevent damage, a numerical analysis approach can be utilized through the Finite Element Method. Therefore, in this paper, fatigue analysis of the Horizontal Tail model is studied numerically to predict high-cycle and low-cycle fatigue life related to defined loading. The analysis estimates the stress field at stress concentration regions such as around fastener holes where the maximum principal stresses are considered for each load case. Critical element identification of the main load carrying structural components of the model with rivet holes is performed as a post-process since critical regions with high-stress values are used as an input for fatigue life calculation. Once the maximum stress is obtained at the critical element and the related mean and alternating components, it is compared with the endurance limit by applying Soderberg approach. The constant life straight line provides the limit for several combinations of mean and alternating stresses. The life calculation based on S-N (Stress-Number of Cycles) curve is also applied with fully reversed loading to determine the number of cycles corresponds to the oscillatory stress with zero means. The results determine the appropriateness of the design of the model for its fatigue strength and the number of cycles that the model can withstand for the calculated stress. The effect of correctly determining the critical rivet holes is investigated by analyzing stresses at different structural parts in the model. In the case of low life prediction, alternative design solutions are developed, and flight hours can be estimated for the fatigue safe operation of the model.

Keywords: fatigue analysis, finite element method, helicopter horizontal tail, life prediction, stress concentration

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2927 Total-Reflection X-Ray Spectroscopy as a Tool for Element Screening in Food Samples

Authors: Hagen Stosnach

Abstract:

The analytical demands on modern instruments for element analysis in food samples include the analysis of major, trace and ultra-trace essential elements as well as potentially toxic trace elements. In this study total reflection, X-ray fluorescence analysis (TXRF) is presented as an analytical technique, which meets the requirements, defined by the Association of Official Agricultural Chemists (AOAC) regarding the limit of quantification, repeatability, reproducibility and recovery for most of the target elements. The advantages of TXRF are the small sample mass required, the broad linear range from µg/kg up to wt.-% values, no consumption of gases or cooling water, and the flexible and easy sample preparation. Liquid samples like alcoholic or non-alcoholic beverages can be analyzed without any preparation. For solid food samples, the most common sample pre-treatment methods are mineralization, direct deposition of the sample onto the reflector without/with minimal treatment, mainly as solid suspensions or after extraction. The main disadvantages are due to the possible peaks overlapping, which may lower the accuracy of quantitative analysis and the limit in the element identification. This analytical technique will be presented by several application examples, covering a broad range of liquid and solid food types.

Keywords: essential elements, toxic metals, XRF, spectroscopy

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2926 A Study on the Safety Evaluation of Pier According to the Water Level Change by the Monte-Carlo Method

Authors: Minho Kwon, Jeonghee Lim, Yeongseok Jeong, Donghoon Shin, Kiyoung Kim

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Recently, global warming phenomenon has led to natural disasters caused by global environmental changes, and due to abnormal weather events, the frequency and intensity of heavy rain storm typhoons are increasing. Therefore, it is imperative to prepare for future heavy rain storms and typhoons. This study selects arbitrary target bridges and performs numerical analysis to evaluate the safety of bridge piers in the event that the water level changes. The numerical model is based on two-dimensional surface elements. Actual reinforced concrete was simulated by modeling concrete to include reinforcements, and a contact boundary model was applied between the ground and the concrete. The water level applied to the piers was considered at 18 levels between 7.5 m and 16.1 m. The elastic modulus, compressive strength, tensile strength, and yield strength of the reinforced concrete were calculated using 250 random combinations and numerical analysis was carried out for each water level. In the results of analysis, the bridge exceeded the stated limit at 15.0 m. At the maximum water level of 16.1m, the concrete’s failure rate was 35.2%, but the probability that the reinforcement would fail was 61.2%.

Keywords: Monte-Carlo method, pier, water level change, limit state

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2925 Changing Body Ideals of Ethnically Diverse Gay and Heterosexual Men and the Proliferation of Social and Entertainment Media

Authors: Cristina Azocar, Ivana Markova

Abstract:

A survey of 565 male undergraduates examined the effects of exposure to social networking sites and entertainment media on young men’s body image. Exposure to social and to entertainment media was found to have negative effects on men’s body satisfaction, social comparison, and thin ideal internalization. Findings indicated significant differences in those men who were more exposed to social and to entertainment media than those who were not as exposed. Consistent with past studies, gay men were found to be more dissatisfied with their bodies than straight men. Gay men compared themselves to other better-looking individuals and internalized ideal body types seen in media significantly more than their straight counterparts. Surprisingly, straight men seem to care as much about their physical attractiveness/appearance as gay men do, but only in public settings such as at the beach, at athletic events (including gyms) and social events. Although on average ethnic groups were more similar than different, small but significant differences occurred with Asian men indicating significantly higher body dissatisfaction than White/European men and Middle Eastern/Arab men their counterparts. The study increases our knowledge about SNS and entertainment use and its associated body image, and body satisfaction affects among low-income ethnic minority men.

Keywords: body dissatisfaction, body image, entertainment media, gay men, race and ethnicity, social economic status, social comparison, social media

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2924 Impact of Mhealth Tools on Psycho-Social Predictors of Behaviour Regarding Contraceptive Use

Authors: Preeti Tiwari, Jay Wood, Duncan Babbage

Abstract:

Family planning plays a role in saving lives across the globe by preventing unwanted pregnancies. The purpose of this multidisciplinary research was to determine the impact of mHealth tools have on psychosocial determinants of behaviour for family planning. The present study examines a topic that is very relevant in times where human-technology interaction is at its peak. It is probably one of the first studies that have investigated the impact of mobile phone technology on the underlying mechanisms of behaviour change for family planning using primary data. To examine the association between exposure to mHealth tools and predictors of behaviour, data was collected from mHealth intervention areas in India. A post-intervention quasi-experimental study with a 2x2 factorial design was conducted among 831 men and women from the state of Bihar. The quantitative data analysis evaluated the extent of influence that predictors of behaviour (beliefs, social norms, perceived behaviour control, and outcome behaviour) have on a woman’s decisions about family planning. The results indicated an association between exposure to mHealth tools and improved communication about family planning among various family members after receiving health information from a health worker (H1). A relationship between exposure to mHealth tools and increased support women received from their husbands and extended family (mothers-in-law specifically) and peers (H2) was also found. A further result showed that knowledge about family planning was greater among users of family planning (H4). mHealth tools empower women to communicate with family members. This has important implications for developing mobile phone-based tools, as they can be used as a crucial communication channel that can be an effective method of increasing communication among family members about contraceptives. Thus, it can be implied that where women feel nervous talking about contraception, the successful application of mHealth tools can strengthen the interactivity of the health communication and could increase the likelihood of using contraception. However, while it may improve health communication that can inform health decisions, it may be insufficient on its own to cause behaviour change.

Keywords: contraceptive, e-health, psycho-social, women

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2923 Modeling the Performance of Natural Sand-Bentonite Barriers after Infiltration with Polar and Non-Polar Hydrocarbon Leachates

Authors: Altayeb Qasem, Mousa Bani Baker, Amani Nawafleh

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The complexity of the sand-bentonite liner barrier system calls for an adequate model that reflects the conditions depending on the barrier materials and the characteristics of the permeates which lead to hydraulic conductivity changes when liners infiltrated with polar, no-polar, miscible and immiscible liquids. This paper is dedicated to developing a model for evaluating the hydraulic conductivity in the form of a simple indicator for the compatibility of the liner versus leachate. Based on two liner compositions (95% sand: 5% bentonite; and 90% sand: 10% bentonite), two pressures (40 kPa and 100 kPa), and three leachates: water, ethanol and biofuel. Two characteristics of the leacahtes were used: viscosity of permeate and its octanol-water partitioning coefficient (Kow). Three characteristics of the liners mixtures were evaluated which had impact on the hydraulic conductivity of the liner system: the initial content of bentonite (%), the free swelling index, and the shrinkage limit of the initial liner’s mixture. Engineers can use this modest tool to predict a potential liner failure in sand-bentonite barriers.

Keywords: liner performance, sand-bentonite barriers, viscosity, free swelling index, shrinkage limit, octanol-water partitioning coefficient, hydraulic conductivity, theoretical modeling

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2922 Acrylamide-Induced Thoracic Spinal Cord Axonopathy

Authors: Afshin Zahedi, Keivan Jamshidi

Abstract:

This study was conducted to determine the neurotoxic effects of different doses of ACR on the thoracic axons of the spinal cord of rat. To evaluate this hypothesis in the thoracic axons, amino-cupric silver staining technique of the de Olmos was conducted to define the histopathologic characteristic (argyrophilia) of axonal damage following ACR exposure. For this purpose 60 adult male rats (Wistar, approximately 250 g) were selected. Rats were hosed in polycarbonate boxes as two per each. Randomly assigned groups of rats (10 rats per exposure group, total 5 exposure groups as A, B, C, D and E) were exposed to 0.5, 5, 50, 100 and 500 mg/kg per day×11days intraperitoneal injection (IP injection) respectively. The remaining 10 rats were housed in group (F) as control group. Control rats received daily injections of 0.9% saline (3ml/kg). As indices of developing neurotoxicity, weight gain, gait scores and landing hindlimb foot splay (LHF) were determined. Weight gains were measured daily prior to injection. Gait scoring involved observation of spontaneous open field locomotion, included evaluations of ataxia, hopping, rearing and hind foot placement, and hindlimb foot splay were determined 3-4 times per week. Gait score was assigned from 1-4. After 11 days, two rats for silver stain, were randomly selected, dissected and proper samples were collected from thoracic portion of the spinal cord of rat. Results did show no neurological behavior in groups A, B and F, whereas severe neurotoxicity was observed in groups C and D. Rats in groups E died within 1-2 hours due to severe toxemia. In histopathological studies based on the de Olmos technique no argyrophilic neurons or processes were observed in stained sections obtained from the thoracic portion of the spinal cord of rats belong to groups A, B and F, while moderate to severe argyrophilic changes were observed in different stained sections obtained from the thoracic portion of the spinal cord of rats belong to groups C and D.

Keywords: acrylamide, rat, axonopathy, argyrophily, de Olmos

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2921 Wood Dust and Nanoparticle Exposure among Workers during a New Building Construction

Authors: Atin Adhikari, Aniruddha Mitra, Abbas Rashidi, Imaobong Ekpo, Jefferson Doehling, Alexis Pawlak, Shane Lewis, Jacob Schwartz

Abstract:

Building constructions in the US involve numerous wooden structures. Woods are routinely used in walls, framing floors, framing stairs, and making of landings in building constructions. Cross-laminated timbers are currently being used as construction materials for tall buildings. Numerous workers are involved in these timber based constructions, and wood dust is one of the most common occupational exposures for them. Wood dust is a complex substance composed of cellulose, polyoses and other substances. According to US OSHA, exposure to wood dust is associated with a variety of adverse health effects among workers, including dermatitis, allergic respiratory effects, mucosal and nonallergic respiratory effects, and cancers. The amount and size of particles released as wood dust differ according to the operations performed on woods. For example, shattering of wood during sanding operations produces finer particles than does chipping in sawing and milling industries. To our knowledge, how shattering, cutting and sanding of woods and wood slabs during new building construction release fine particles and nanoparticles are largely unknown. General belief is that the dust generated during timber cutting and sanding tasks are mostly large particles. Consequently, little attention has been given to the generated submicron ultrafine and nanoparticles and their exposure levels. These data are, however, critically important because recent laboratory studies have demonstrated cytotoxicity of nanoparticles on lung epithelial cells. The above-described knowledge gaps were addressed in this study by a novel newly developed nanoparticle monitor and conventional particle counters. This study was conducted in a large new building construction site in southern Georgia primarily during the framing of wooden side walls, inner partition walls, and landings. Exposure levels of nanoparticles (n = 10) were measured by a newly developed nanoparticle counter (TSI NanoScan SMPS Model 3910) at four different distances (5, 10, 15, and 30 m) from the work location. Other airborne particles (number of particles/m3) including PM2.5 and PM10 were monitored using a 6-channel (0.3, 0.5, 1.0, 2.5, 5.0 and 10 µm) particle counter at 15 m, 30 m, and 75 m distances at both upwind and downwind directions. Mass concentration of PM2.5 and PM10 (µg/m³) were measured by using a DustTrak Aerosol Monitor. Temperature and relative humidity levels were recorded. Wind velocity was measured by a hot wire anemometer. Concentration ranges of nanoparticles of 13 particle sizes were: 11.5 nm: 221 – 816/cm³; 15.4 nm: 696 – 1735/cm³; 20.5 nm: 879 – 1957/cm³; 27.4 nm: 1164 – 2903/cm³; 36.5 nm: 1138 – 2640/cm³; 48.7 nm: 938 – 1650/cm³; 64.9 nm: 759 – 1284/cm³; 86.6 nm: 705 – 1019/cm³; 115.5 nm: 494 – 1031/cm³; 154 nm: 417 – 806/cm³; 205.4 nm: 240 – 471/cm³; 273.8 nm: 45 – 92/cm³; and 365.2 nm: Keywords: wood dust, industrial hygiene, aerosol, occupational exposure

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2920 Evaluation of Earthquake Induced Cost for Mid-Rise Buildings

Authors: Gulsah Olgun, Ozgur Bozdag, Yildirim Ertutar

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This paper mainly focuses on performance assessment of buildings by associating the damage level with the damage cost. For this purpose a methodology is explained and applied to the representative mid-rise concrete building residing in Izmir. In order to consider uncertainties in occurrence of earthquakes, the structural analyses are conducted for all possible earthquakes in the region through the hazard curve. By means of the analyses, probability of the structural response being in different limit states are obtained and used to calculate expected damage cost. The expected damage cost comprises diverse cost components related to earthquake such as cost of casualties, replacement or repair cost of building etc. In this study, inter-story drift is used as an effective response variable to associate expected damage cost with different damage levels. The structural analysis methods performed to obtain inter story drifts are response spectrum method as a linear one, accurate push-over and time history methods to demonstrate the nonlinear effects on loss estimation. Comparison of the results indicates that each method provides similar values of expected damage cost. To sum up, this paper explains an approach which enables to minimize the expected damage cost of buildings and relate performance level to damage cost.

Keywords: expected damage cost, limit states, loss estimation, performance based design

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2919 Mechanistic Structural Insights into the UV Induced Apoptosis via Bcl-2 proteins

Authors: Akash Bera, Suraj Singh, Jacinta Dsouza, Ramakrishna V. Hosur, Pushpa Mishra

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Ultraviolet C (UVC) radiation induces apoptosis in mammalian cells and it is suggested that the mechanism by which this occurs is the mitochondrial pathway of apoptosis through the release of cytochrome c from the mitochondria into the cytosol. The Bcl-2 family of proteins pro-and anti-apoptotic is the regulators of the mitochondrial pathway of apoptosis. Upon UVC irradiation, the proliferation of apoptosis is enhanced through the downregulation of the anti-apoptotic protein Bcl-xl and up-regulation of Bax. Although the participation of the Bcl-2 family of proteins in apoptosis appears responsive to UVC radiation, to the author's best knowledge, it is unknown how the structure and, effectively, the function of these proteins are directly impacted by UVC exposure. In this background, we present here a structural rationale for the effect of UVC irradiation in restoring apoptosis using two of the relevant proteins, namely, Bid-FL and Bcl-xl ΔC, whose solution structures have been reported previously. Using a variety of biophysical tools such as circular dichroism, fluorescence and NMR spectroscopy, we show that following UVC irradiation, the structures of Bcl-xlΔC and Bid-FL are irreversibly altered. Bcl-xLΔC is found to be more sensitive to UV exposure than Bid-FL. From the NMR data, dramatic structural perturbations (α-helix to β-sheet) are seen to occur in the BH3 binding region, a crucial segment of Bcl-xlΔC which impacts the efficacy of its interactions with pro-apoptotic tBid. These results explain the regulation of apoptosis by UVC irradiation. Our results on irradiation dosage dependence of the structural changes have therapeutic potential for the treatment of cancer.

Keywords: Bid, Bcl-xl, UVC, apoptosis

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2918 Assessment of Genotoxic Effects of a Fungicide (Propiconazole) in Freshwater Fish Gambusia Affinis Using Alkaline Single-Cell Gel Electrophoresis (Comet Essay)

Authors: Bourenane Bouhafs Naziha

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ARTEA330EC is a fungicide used to inhibit the growth of many types of fungi on and cereals and rice, it is the single largest selling agrochemical that has been widely detected in surface waters in our area (Northeast Algerian). The studies on long-term genotoxic effects of fugicides in different tissues of fish using genotoxic biomarkers are limited. Therefore, in the present study DNA damage by propiconazole in freshwater fish Gambusia affinis by comet assays was investigated. The LC(50)- 96 h of the fungicide was estimated for the fish in a semi-static system. On this basis of LC(50) value sublethal and nonlethal concentrations were determined (25; 50; 75; and 100 ppm). The DNA damage was measured in erythrocytes as the percentage of DNA in comet tails of fishes exposed to above concentrations the fungicide. In general,non significant effects for both the concentrations and time of exposure were observed in treated fish compared with the controls. However It was found that the highest DNA damage was observed at the highest concentration and the longest time of exposure (day 12). The study indicated comet assay to be sensitive and rapid method to detect genotoxicity of propiconasol and other pesticides in fishes.

Keywords: genotoxicity, fungicide, propiconazole, freshwater, Gambusia affinis, alkaline single-cell gel electrophoresis

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2917 Assessing the Risk of Socio-economic Drought: A Case Study of Chuxiong Yi Autonomous Prefecture, China

Authors: Mengdan Guo, Zongmin Wang, Haibo Yang

Abstract:

Drought is one of the most complex and destructive natural disasters, with a huge impact on both nature and society. In recent years, adverse climate conditions and uncontrolled human activities have exacerbated the occurrence of global droughts, among which socio-economic droughts are closely related to human survival. The study of socio-economic drought risk assessment is crucial for sustainable social development. Therefore, this study comprehensively considered the risk of disaster causing factors, the exposure level of the disaster-prone environment, and the vulnerability of the disaster bearing body to construct a socio-economic drought risk assessment model for Chuxiong Prefecture in Yunnan Province. Firstly, a threedimensional frequency analysis of intensity area duration drought was conducted, followed by a statistical analysis of the drought risk of the socio-economic system. Secondly, a grid analysis model was constructed to assess the exposure levels of different agents and study the effects of drought on regional crop growth, industrial economic growth, and human consumption thresholds. Thirdly, an agricultural vulnerability model for different irrigation levels was established by using the DSSAT crop model. Industrial economic vulnerability and domestic water vulnerability under the impact of drought were investigated by constructing a standardized socio-economic drought index and coupling water loss. Finally, the socio-economic drought risk was assessed by combining hazard, exposure, and vulnerability. The results show that the frequency of drought occurrence in Chuxiong Prefecture, Yunnan Province is relatively high, with high population and economic exposure concentrated in urban areas of various counties and districts, and high agricultural exposure concentrated in mountainous and rural areas. Irrigation can effectively reduce agricultural vulnerability in Chuxiong, and the yield loss rate under the 20mm winter irrigation scenario decreased by 10.7% compared to the rain fed scenario. From the perspective of comprehensive risk, the distribution of long-term socio-economic drought risk in Chuxiong Prefecture is relatively consistent, with the more severe areas mainly concentrated in Chuxiong City and Lufeng County, followed by counties such as Yao'an, Mouding and Yuanmou. Shuangbai County has the lowest socio-economic drought risk, which is basically consistent with the economic distribution trend of Chuxiong Prefecture. And in June, July, and August, the drought risk in Chuxiong Prefecture is generally high. These results can provide constructive suggestions for the allocation of water resources and the construction of water conservancy facilities in Chuxiong Prefecture, and provide scientific basis for more effective drought prevention and control. Future research is in the areas of data quality and availability, climate change impacts, human activity impacts, and countermeasures for a more comprehensive understanding and effective response to drought risk in Chuxiong Prefecture.

Keywords: DSSAT model, risk assessment, socio-economic drought, standardized socio-economic drought index

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2916 Modelling Tyre Rubber Materials for High Frequency FE Analysis

Authors: Bharath Anantharamaiah, Tomas Bouda, Elke Deckers, Stijn Jonckheere, Wim Desmet, Juan J. Garcia

Abstract:

Automotive tyres are gaining importance recently in terms of their noise emission, not only with respect to reduction in noise, but also their perception and detection. Tyres exhibit a mechanical noise generation mechanism up to 1 kHz. However, owing to the fact that tyre is a composite of several materials, it has been difficult to model it using finite elements to predict noise at high frequencies. The currently available FE models have a reliability of about 500 Hz, the limit which, however, is not enough to perceive the roughness or sharpness of noise from tyre. These noise components are important in order to alert pedestrians on the street about passing by slow, especially electric vehicles. In order to model tyre noise behaviour up to 1 kHz, its dynamic behaviour must be accurately developed up to a 1 kHz limit using finite elements. Materials play a vital role in modelling the dynamic tyre behaviour precisely. Since tyre is a composition of several components, their precise definition in finite element simulations is necessary. However, during the tyre manufacturing process, these components are subjected to various pressures and temperatures, due to which these properties could change. Hence, material definitions are better described based on the tyre responses. In this work, the hyperelasticity of tyre component rubbers is calibrated, using the design of experiments technique from the tyre characteristic responses that are measured on a stiffness measurement machine. The viscoelasticity of rubbers are defined by the Prony series for rubbers, which are determined from the loss factor relationship between the loss and storage moduli, assuming that the rubbers are excited within the linear viscoelasticity ranges. These values of loss factor are measured and theoretically expressed as a function of rubber shore hardness or hyperelasticities. From the results of the work, there exists a good correlation between test and simulation vibrational transfer function up to 1 kHz. The model also allows flexibility, i.e., the frequency limit can also be extended, if required, by calibrating the Prony parameters of rubbers corresponding to the frequency of interest. As future work, these tyre models are used for noise generation at high frequencies and thus for tyre noise perception.

Keywords: tyre dynamics, rubber materials, prony series, hyperelasticity

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2915 Flexural Fatigue Performance of Self-Compacting Fibre Reinforced Concrete

Authors: Surinder Pal Singh, Sanjay Goel

Abstract:

The paper presents results of an investigation conducted to study the flexural fatigue characteristics of Self Compacting Concrete (SCC) and Self Compacting Fibre Reinforced Concrete (SCFRC). In total 360 flexural fatigue tests and 270 static flexural strength tests were conducted on SCC and SCFRC specimens to obtain the fatigue test data. The variability in the distribution of fatigue life of SCC and SCFRC have been analyzed and compared with that of NVC and NVFRC containing steel fibres of comparable size and shape. The experimental coefficients of fatigue equations have been estimated to represent relationship between stress level (S) and fatigue life (N) for SCC and SCFRC containing different fibre volume fractions. The probability of failure (Pf) has been incorporated in S-N relationships to obtain families of S-N-Pf relationships. A good agreement between the predicted curves and those obtained from the test data has been observed. The fatigue performance of SCC and SCFRC has been evaluated in terms of two-million cycles fatigue strength/endurance limit. The theoretic fatigue lives were also estimated using single-log fatigue equation for 10% probability of failure to estimate the enhanced extent of theoretic fatigue lives of SCFRC with reference to SCC and NVC. The reduction in variability in the fatigue life, increased endurance limit and increased theoretiac fatigue lives demonstrates an overall better fatigue performance for SCC and SCFRC.

Keywords: fatigue life, fibre, probability of failure, self-compacting concrete

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2914 The Association between Prior Antibiotic Use and Subsequent Risk of Infectious Disease: A Systematic Review

Authors: Umer Malik, David Armstrong, Mark Ashworth, Alex Dregan, Veline L'Esperance, Lucy McDonnell, Mariam Molokhia, Patrick White

Abstract:

Introduction: The microbiota lining epithelial surfaces is thought to play an important role in many human physiological functions including defense against pathogens and modulation of immune response. The microbiota is susceptible to disruption from external influences such as exposure to antibiotic medication. It is thought that antibiotic-induced disruption of the microbiota could predispose to pathogen overgrowth and invasion. We hypothesized that antibiotic use would be associated with increased risk of future infections. We carried out a systematic review of evidence of associations between antibiotic use and subsequent risk of community-acquired infections. Methods: We conducted a review of the literature for observational studies assessing the association between antibiotic use and subsequent community-acquired infection. Eligible studies were published before April 29th, 2016. We searched MEDLINE, EMBASE, and Web of Science and screened titles and abstracts using a predefined search strategy. Infections caused by Clostridium difficile, drug-resistant organisms and fungal organisms were excluded as their association with prior antibiotic use has been examined in previous systematic reviews. Results: Eighteen out of 21,518 retrieved studies met the inclusion criteria. The association between past antibiotic exposure and subsequent increased risk of infection was reported in 16 studies, including one study on Campylobacter jejuni infection (Odds Ratio [OR] 3.3), two on typhoid fever (ORs 5.7 and 12.2), one on Staphylococcus aureus skin infection (OR 2.9), one on invasive pneumococcal disease (OR 1.57), one on recurrent furunculosis (OR 16.6), one on recurrent boils and abscesses (Risk ratio 1.4), one on upper respiratory tract infection (OR 2.3) and urinary tract infection (OR 1.1), one on invasive Haemophilus influenzae type b (Hib) infection (OR 1.51), one on infectious mastitis (OR 5.38), one on meningitis (OR 2.04) and five on Salmonella enteric infection (ORs 1.4, 1.59, 1.9, 2.3 and 3.8). The effect size in three studies on Salmonella enteric infection was of marginal statistical significance. A further two studies on Salmonella infection did not demonstrate a statistically significant association between prior antibiotic exposure and subsequent infection. Conclusion: We have found an association between past antibiotic exposure and subsequent risk of a diverse range of infections in the community setting. Our findings provide evidence to support the hypothesis that prior antibiotic usage may predispose to future infection risk, possibly through antibiotic-induced alteration of the microbiota. The findings add further weight to calls to minimize inappropriate antibiotic prescriptions.

Keywords: antibiotic, infection, risk factor, side effect

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2913 Hematological Malignancies in Children and Parental Occupational Exposure

Authors: H. Kalboussi, A. Aloui, W. Boughattas, M. Maoua, A. Brahem, S. Chatti, O. El Maalel, F. Debbabi, N. Mrizak, Y. Ben Youssef, A. Khlif, I. Bougmiza

Abstract:

Background: In recent decades, the incidence of children's hematological malignancies has been increasing worldwide including Tunisia. Their severity is reflected in the importance of the medical, social and economic impact. This increase remains fully unexplained, and the involvement of genetic, environmental and occupational factors is strongly suspected. Materials and Methods: Our study is a cross-sectional survey of the type case-control conducted in the University Hospital of Farhat Hached of Sousse during the period ranging between 1 July 2011 and 30 June 2012,and which included children with acute leukemia compared to children unharmed by neoplastic disease . Cases and controls were matched by age and gender. Our objective was to: - Describe the socio-occupational characteristics of the parents of children with acute leukemia. - Identify potential occupational factors implicated in the genesis of acute leukemia. Result: The number of acute leukemia cases in the Hematology Service and day hospital of the University Hospital of Farhat Hached during the study period was 66 cases divided into in 40 boys and 26 girls with a sex ratio of 1.53. Our cases and controls were matched by age and gender. The risk of incidence of leukemia in children from smoking fathers was higher (p = 0.02, OR = 2.24, IC = [1.11 - 4.52]). The risk of incidence of leukemia in children from alcoholic fathers was higher with p = 0,009, OR = 3.9; CI = [1.33 - 11.39]. After adjusting different variables, the difference persisted significantly with pa = 0.03 and ORa = 3.5; ICa = [1.09 -11.6]. 25.7 % of cases had a family history of blood disease and neoplasia, whereas no control presented that. The difference was statistically significant (p = 0.006), OR = 1.46, IC = [1.38 - 1.56]. The parental occupational exposures associated to the occurrence of acute leukemia in children were: - Pesticides with a statistically significant difference (p = 0.03), OR = 2.94, IC = [1.06 - 8.13]. This difference persisted after adjustment with different variables pa = 0.01, ORa 3.75; ICa = [1.27 - 11.03]. - Cement without a statistically non-significant difference (p = 0.2). This difference has become significant after adjustment with the different variables pa = 0.03; ORa = 2.67; ICa = [1.06 - 6.7]. Conclusion: Parental exposure to occupational risk factors may play a role in the pathogenesis of acute leukemia in children.

Keywords: hematological malignancies, children, parents, occupational exposure

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2912 Assessment of Air Quality Status Using Pollution Indicators in Industrial Zone of Brega City

Authors: Tawfig Falani, Abdulalaziz Saleh

Abstract:

Air pollution has become a major environmental issue with definitive repercussions on human health. Global concerns have been raised about the health effects of deteriorating air quality due mainly to widespread industrialization and urbanization. To assess the quality of air in Brega, air quality indicators were calculated using the U.S. Environmental Protection Agency procedure. Air quality was monitored from 01/10/2019 to 28/02/2021 with a daily average measuring six pollutants of particulate matter <2.5µm (PM2.5), and <10µm (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), and carbon monoxide (CO). The result indicated that air pollution at general air quality monitoring sites for sulphur dioxide, carbon monoxide, PM₁₀ and PM2.5 and nitrogen dioxide are always within the permissible limit. Referring to a monthly average of Pollutants in the Brega Industrial area, all months were out of AQG limit for NO₂, and the same with O₃ except for two months. For PM2.5 and PM₁₀ 7, 5 out of 17 months were out of limits, respectively. Relative AQI for ozone is found in the range of moderate category of general air pollution, and the worst month was Nov. 2020, which was marked as Very Unhealthy category, then the next two months (Dec. 2020 and Jan. 2021 ) were Unhealthy categories. It's the first time that we have used the AQI in SOC, and not usually used in Libya to identify the quality of air pollution. So, I think it will be useful if AQI is used as guidance for specified air pollution. That dictate putting monitoring stations beside any industrial activity that has emissions of the six major air pollutants.

Keywords: air quality, air pollutants, air quality index (AQI), particulate matter

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2911 Carbon-Nanodots Modified Glassy Carbon Electrode for the Electroanalysis of Selenium in Water

Authors: Azeez O. Idris, Benjamin O. Orimolade, Potlako J. Mafa, Alex T. Kuvarega, Usisipho Feleni, Bhekie B. Mamba

Abstract:

We report a simple and cheaper method for the electrochemical detection of Se(IV) using carbon nanodots (CNDTs) prepared from oat. The carbon nanodots were synthesised by green and facile approach and characterised using scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The CNDT was used to fabricate an electrochemical sensor for the quantification of Se(IV) in water. The modification of glassy carbon electrode (GCE) with carbon nanodots led to an increase in the electroactive surface area of the electrode, which enhances the redox current peak of [Fe(CN)₆]₃₋/₄‒ in comparison to the bare GCE. Using the square wave voltammetry, the detection limit and quantification limit of 0.05 and 0.167 ppb were obtained under the optimised parameters using deposition potential of -200 mV, 0.1 M HNO₃ electrolyte, electrodeposition time of 60 s, and pH 1. The results further revealed that the GCE-CNDT was not susceptible to many interfering cations except Cu(II) and Pb(II), and Fe(II). The sensor fabrication involves a one-step electrode modification and was used to detect Se(IV) in a real water sample, and the result obtained is in agreement with the inductively coupled plasma technique. Overall, the electrode offers a cheap, fast, and sensitive way of detecting selenium in environmental matrices.

Keywords: carbon nanodots, square wave voltammetry, nanomaterials, selenium, sensor

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2910 Physiotherapy Program for Frozen Shoulder on Length of Follow up and Range of Motions

Authors: Orawan Vichiansan, J. Kraipoj, K.Phandech, P. Sirasaporn

Abstract:

Generally, frozen shoulder will improve over time, although it may take a long time up to year. The symptoms of frozen shoulder present by pain around shoulder and consequently limit range of motions. The effect of frozen shoulder leads to limit activities daily living life and high medical care cost. Physiotherapy is well known treatment for frozen shoulder but there was no data about the treatment of physiotherapy in frozen shoulder and length of follow up. Thus the aim of this study was to investigate physiotherapy program for frozen shoulder on range of motion and length of follow up. A retrospective study design was conducted. 469 medical records of patients with frozen shoulder were reviewed. These frozen shoulders were treated at physiotherapy unit, department of Rehabilitation last 3 years (January, 2014- December, 2016). The data consist of range of motions and length of follow up was recorded. The medical record of 183 males and 286 females with average aged 57.82±12.32 years were reviewed in this study. There was a statistically significant increase in shoulder flexion [mean difference 30.24 with 95%CI were [24.37-36.12], shoulder abduction [mean difference 34.93 with 95%CI were 27.8-42.0], shoulder internal rotation [mean difference 17.25 with 95%CI were 12.55-21.95] and shoulder external rotation [mean difference 17.71 with 95%CI were [13.07-22.36] respectively. In addition, the length of follow up averaged 84 days. In summary, the retrospective study show physiotherapy program likely to be benefit for patients with frozen shoulder in term of range of motion and short length of follow up.

Keywords: frozen shoulder, physiotherapy, range of motions, length of follow up

Procedia PDF Downloads 157
2909 Compression Index Estimation by Water Content and Liquid Limit and Void Ratio Using Statistics Method

Authors: Lizhou Chen, Abdelhamid Belgaid, Assem Elsayed, Xiaoming Yang

Abstract:

Compression index is essential in foundation settlement calculation. The traditional method for determining compression index is consolidation test which is expensive and time consuming. Many researchers have used regression methods to develop empirical equations for predicting compression index from soil properties. Based on a large number of compression index data collected from consolidation tests, the accuracy of some popularly empirical equations were assessed. It was found that primary compression index is significantly overestimated in some equations while it is underestimated in others. The sensitivity analyses of soil parameters including water content, liquid limit and void ratio were performed. The results indicate that the compression index obtained from void ratio is most accurate. The ANOVA (analysis of variance) demonstrates that the equations with multiple soil parameters cannot provide better predictions than the equations with single soil parameter. In other words, it is not necessary to develop the relationships between compression index and multiple soil parameters. Meanwhile, it was noted that secondary compression index is approximately 0.7-5.0% of primary compression index with an average of 2.0%. In the end, the proposed prediction equations using power regression technique were provided that can provide more accurate predictions than those from existing equations.

Keywords: compression index, clay, settlement, consolidation, secondary compression index, soil parameter

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2908 Development of Lipid Architectonics for Improving Efficacy and Ameliorating the Oral Bioavailability of Elvitegravir

Authors: Bushra Nabi, Saleha Rehman, Sanjula Baboota, Javed Ali

Abstract:

Aim: The objective of research undertaken is analytical method validation (HPLC method) of an anti-HIV drug Elvitegravir (EVG). Additionally carrying out the forced degradation studies of the drug under different stress conditions to determine its stability. It is envisaged in order to determine the suitable technique for drug estimation, which would be employed in further research. Furthermore, comparative pharmacokinetic profile of the drug from lipid architectonics and drug suspension would be obtained post oral administration. Method: Lipid Architectonics (LA) of EVR was formulated using probe sonication technique and optimized using QbD (Box-Behnken design). For the estimation of drug during further analysis HPLC method has been validation on the parameters (Linearity, Precision, Accuracy, Robustness) and Limit of Detection (LOD) and Limit of Quantification (LOQ) has been determined. Furthermore, HPLC quantification of forced degradation studies was carried out under different stress conditions (acid induced, base induced, oxidative, photolytic and thermal). For pharmacokinetic (PK) study, Albino Wistar rats were used weighing between 200-250g. Different formulations were given per oral route, and blood was collected at designated time intervals. A plasma concentration profile over time was plotted from which the following parameters were determined:

Keywords: AIDS, Elvitegravir, HPLC, nanostructured lipid carriers, pharmacokinetics

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2907 Remedying the Scourge of Poverty as a Social Problem: The Islamic Perspective

Authors: Maryam Umar Ladan, Arshad Munir

Abstract:

Poverty has always been a constant feature of society throughout history. It has existed in the lives of people and it is a fact that although the majority of people lives in poverty, the remaining minority lives in luxury. While some countries called the first World countries lives in luxury, the third World countries lives in poverty. It remains an undesirable phenomenon affecting a vast number of people across the globe despite governmental, institutional and private organizations’ interventions with measures aimed at cushioning its adverse effects. Unequal distribution of societal resources, accumulated wealth in the hands of few, lack of access to education and employment, individual responsibility among others, were highlighted as factors associated with poverty. Poverty predisposes the poor individual to malnutrition and starvation, exposure to disease, thereby resulting to violence, crimes, and experiencing lifelong problems. Evidence show that about 50 percent of the world population lives on less than 2.50 dollar a day, 90 percent of whom are from Sub-Saharan Africa and South Asia including countries where Islam is the major if not one adherent religion. As a solution to poverty, Islam prescribes a system of annual Zakat (charity). The Islamic law prescribes that every person who has a saving that reaches a certain limit should give out 2.5 percent of the total annual earning (as in income, money, farm produce) to deserving and prescribed citizens. This is to, among others; reduce the level of inequality through distribution of wealth among the Muslim Ummah (community). Furthermore, Islam encourages the rich in several places in the Qur’an to spend their wealth on poor people other than the compulsory 2.5%. Therefore, it is inarguable that the Islamic system of distribution of resources (as zakat) is the best strategy to poverty eradication. Thus, strongly recommended for desired results in poverty eradication efforts. If every rich person gives Zakat sincerely, poverty will be eradicated in the world, and not a single person will die of want of food or material things.

Keywords: Islam, charity, poverty, zakat

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2906 Effect of Tooth Bleaching Agents on Enamel Demineralisation

Authors: Najlaa Yousef Qusti, Steven J. Brookes, Paul A. Brunton

Abstract:

Background: Tooth discoloration can be an aesthetic problem, and tooth whitening using carbamide peroxide bleaching agents are a popular treatment option. However, there are concerns about possible adverse effects such as demineralisation of the bleached enamel; however, the cause of this demineralisation is unclear. Introduction: Teeth can become stained or discoloured over time. Tooth whitening is an aesthetic solution for tooth discoloration. Bleaching solutions of 10% carbamide peroxide (CP) have become the standard agent used in dentist-prescribed and home-applied ’vital bleaching techniques’. These materials release hydrogen peroxide (H₂O₂), the active whitening agent. However, there is controversy in the literature regarding the effect of bleaching agents on enamel integrity and enamel mineral content. The purpose of this study was to establish if carbamide peroxide bleaching agents affect the acid solubility of enamel (i.e., make teeth more prone to demineralisation). Materials and Methods: Twelve human premolar teeth were sectioned longitudinally along the midline and varnished to leave the natural enamel surface exposed. The baseline behavior of each tooth half in relation to its demineralisation in acid was established by sequential exposure to 4 vials containing 1ml of 10mM acetic acid (1 minute/vial). This was followed by exposure to 10% CP for 8 hours. After washing in distilled water, the tooth half was sequentially exposed to 4 further vials containing acid to test if the acid susceptibility of the enamel had been affected. The corresponding tooth half acted as a control and was exposed to distilled water instead of CP. The mineral loss was determined by measuring [Ca²⁺] and [PO₄³⁻] released in each vial using a calcium ion-selective electrode and the phosphomolybdenum blue method, respectively. The effect of bleaching on the tooth surfaces was also examined using SEM. Results: Exposure to carbamide peroxide did not significantly alter the susceptibility of enamel to acid attack, and SEM of the enamel surface revealed a slight alteration in surface appearance. SEM images of the control enamel surface showed a flat enamel surface with some shallow pits, whereas the bleached enamel appeared with an increase in surface porosity and some areas of mild erosion. Conclusions: Exposure to H₂O₂ equivalent to 10% CP does not significantly increase subsequent acid susceptibility of enamel as determined by Ca²⁺ release from the enamel surface. The effects of bleaching on mineral loss were indistinguishable from distilled water in the experimental system used. However, some surface differences were observed by SEM. The phosphomolybdenum blue method for phosphate is compromised by peroxide bleaching agents due to their oxidising properties. However, the Ca²⁺ electrode is unaffected by oxidising agents and can be used to determine the mineral loss in the presence of peroxides.

Keywords: bleaching, carbamide peroxide, demineralisation, teeth whitening

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2905 An Evaluation of the Impact of Social Media on Nigerian Youths

Authors: Haruna Shola Adeosun, Lekan M. Togunwa, Ajoke F. Adebiyi

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This paper examines the impact of social media on Nigerian Youths particularly in Nigeria. This study reviewed secondary sources data. The research adopted survey method which involves the use of questionnaire that was administered to gather primary data analysis and presentation were done with the use of tables, figures, percentages and chi-square were used to test the hypotheses formulated. The study revealed that social media consumers, especially Facebook are prone to the benefits or risks aspect of its contents. At this expense, what user derived, seeks, sought and gains from such media depend on the motive they are being used for. The study also revealed that users have the tendency to be positively influenced through heavy or over exposure to numerous contents that are damaging and harmful. This means that social media usage may be considered as good or bad. As its contents may or may not subject consumers to vulnerable use depending on what is saved from it. The study recommends that the use of Facebook should be subjected to gate keeping and monitoring in order to control the activities of users that embrace depression, bullying, sexing and sexual harassment as a way of life. Parents should close watch on their children and caution them towards cultivating the habit of over exposure to social sites so at to protect them form risks social media poses.

Keywords: evaluation, impact, soocial media, nigerian youths

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