Simulation of brittle damage for fracture process of endodontically treated tooth

The mechanics of brittle damage in porcelain of an endodontically treated maxilla incisor tooth was simulated using finite element method (FEM). For this purpose a very complex composite structure of endodontically treated tooth is simulated under transverse loading. Three dimensional (3D) model of human maxilla incisor tooth root was developed based on Computed Tomography (CT) scan images. Crown, core cement, resin core, dental post, post cement and dentin were created using SolidWorks software, and then the model was imported into ABAQUS-6.9EF software for nonlinear behavior analysis. This study utilizes finite element method to simulate onset and propagation of crack in ceramic layer (porcelain) by the cause of both tension and compression loading related to complexity of the geometry of tooth implant. The simulation has been done using brittle damaged model available in ABAQUS/Explicit in quasi-static load condition. The load-displacement response of whole structure is measured from the top of porcelain by controlling displacement on a rigid rod. Crack initiated at the top of porcelain bellow the location of the rod caused by tension damage at equivalent load of 590 N. Damage in porcelain accounts for up to 63% reduction of whole structure stiffness from the undamaged state. The failure process in porcelain layer can be described by an exponential rate of fracture energy dissipation. This study demonstrated that the proposed finite element model and analysis procedure can be use to predict the nonlinear behavior of tooth implant

Instrumentation enabling study of plant physiological response to elevated night temperature

<p>Abstract</p> <p>Background</p> <p>Global climate warming can affect functioning of crops and plants in the natural environment. In order to study the effects of global warming, a method for applying a controlled heating treatment to plant canopies in the open field or in the greenhouse is needed that can accept either square wave application of elevated temperature or a complex prescribed diurnal or seasonal temperature regime. The current options are limited in their accuracy, precision, reliability, mobility or cost and scalability.</p> <p>Results</p> <p>The described system uses overhead infrared heaters that are relatively inexpensive and are accurate and precise in rapidly controlling the temperature. Remote computer-based data acquisition and control via the internet provides the ability to use complex temperature regimes and real-time monitoring. Due to its easy mobility, the heating system can randomly be allotted in the open field or in the greenhouse within the experimental setup. The apparatus has been successfully applied to study the response of rice to high night temperatures. Air temperatures were maintained within the set points ± 0.5°C. The incorporation of the combination of air-situated thermocouples, autotuned proportional integrative derivative temperature controllers and phase angled fired silicon controlled rectifier power controllers provides very fast proportional heating action (i.e. 9 ms time base), which avoids prolonged or intense heating of the plant material.</p> <p>Conclusion</p> <p>The described infrared heating system meets the utilitarian requirements of a heating system for plant physiology studies in that the elevated temperature can be accurately, precisely, and reliably controlled with minimal perturbation of other environmental factors.</p

Effects of High Nighttime Temperature and Role of Plant Growth Regulators on Growth, Development and Physiology of Rice Plants

Seasonally high nighttime temperatures (HNT) along the United States Gulf Coast and in regions of similar climate, during the critical stages of development, could reduce rice yield and quality. To study the effects of HNT on plant physiology, a method for applying a controlled heating treatment to plant canopies was developed using overhead infrared heaters, which are relatively inexpensive and are accurate, precise and reliable in rapidly controlling the temperature. The apparatus successfully maintained air temperatures within the set points plus/minus 0.5 degrees C, and was used for all the experiments. Several experiments were conducted to determine the response of various physiological parameters during and following exposure of rice plants to HNT (32 degrees C) or ambient nighttime temperature (ANT) (27 degrees C) starting from 2000 h until 0600 h, and with or without plant growth regulator treatments. The plant growth regulator treatments included alpha-tocopherol (vitamin E), glycine betaine (GB), and salicylic acid (SA), which play different roles in inducing thermo-tolerance in plants. High nighttime temperature had no effect on plant height, number of tillers and panicles, or rice net leaf photosynthetic rates. However, HNT increased leaf respiration (dark respiration in the night) (21%) and decreased membrane thermo-stability (60%), pollen germination (20%), spikelet fertility (18% as a % of total spikelets), grain length (2%), and grain width (2%). The HNT also hastened plant development. The combinations of these effects decreased rice yield by 90%. Moreover, under HNT, there were decreases in leaf chlorophyll concentration (7%) and nitrogen concentration (18%). Application of GB and SA increased total antioxidant capacity of the rice plants by 17%, thereby decreasing the leaf respiration rates, increasing membrane thermo-stability, pollen germination, and spikelet fertility, thus increasing the yield. High nighttime temperature decreased leaf starch concentration (14%), grain total nonstructural carbohydrate (TNC) concentration (9%), and grain extractable invertase activity (20%). Vitamin E- or GB-treated plants had greater grain soluble-sugar concentrations, whereas SA-treated plants had greater leaf soluble-sugar concentrations and lower grain TNC concentrations. Invertase activity was shown to be not rate limiting or required for sucrose degradation for starch synthesis in grain of 'Cocodrie' rice under short-term high nighttime temperatures exposures during grain filling. In conclusion, HNT decreased rice yield by increasing plant respiration, rate of crop development, and decreasing membrane thermo-stability, pollen germination, spikelet fertility and grain dimensions. Exogenous application of GB and SA increased yields under HNT, possibly acting through increased antioxidant levels, which might have protected the membranes and enzymes against heat-induced ROS-mediated degradation

Haematopoietic and Immunomodulatory Activity of Sap of Borassus flabellifer against Cyclophosphamide Mediated Haematotoxicity and Immunosuppression in Wistar Rats

Recent scientific evidence recommends that many of the adverse effects of chemotherapy can be prevented by remedying treatment with antioxidants, minerals, carbohydrates, proteins, and organic acids. The current research was performed to assess haematopoietic and immunomodulatory effects using sap of traditional tree, Borassus flabellifer, in cyclophosphamide induced haematotoxicity and immunosuppression in wistar rats. For eleven consecutive days, the animals were orally pre-treated with Borassus flabellifer sap (3.6 mL/kg). These animals were intra-peritoneally injected on the sixth day with cyclophosphamide (150 mg/kg) and sacrificed five days later. On the final day of the trial, blood samples were obtained from each rat and carried out evaluation of haematological (red blood cells, haemoglobin, mean corpuscular haemoglobin concentration, reticulocytes &amp; serum iron content) and immunomodulatory (total leucocyte count, cellular immune response &amp; tumor necrosis factor-α) parameters. To determine their index values, each rat's thymus and spleen were separated. By elevating red blood cells, haemoglobin, mean corpuscular haemoglobin concentration, reticulocytes &amp; serum iron content, sap of Borassus flabellifer demonstrated an important protective role in cyclophosphamide mediated haematotoxicity. It has also shown substantial resistance against immunosuppression caused by cyclophosphamide by increasing the immunity boosting white blood cells and decreasing the hypersensitivity reaction and tumor necrosis factor-α level at the 3.6 mL/kg dose. The current research shows that therapy with traditional Borassus flabellifer sap has a major protective effect against oxidative stress, haematotoxicity and immunosuppression against cyclophosphamide induced haematotoxicity and immunosuppression

Assessment of disturbed voltage supply effects on steady-state performance of an induction motor

An electric power system is usually exposed to unequal and variable loads across its three phases, which leads to voltage unbalance and variation, making the three-phase voltages asymmetrical in nature at the distribution end. This problem is clearly evident in Iraq country, particularly with regard to the fluctuating voltage levels of electricity distribution during peak hours. Providing a three-phase motor with asymmetric voltages is badly affecting its working performance. Estimating the performance of this motor at steady-state under different conditions of voltage disturbances is investigated in this paper through Matlab simulation using Symmetrical component approach. The motor performance represented by active and reactive input powers, output put power, developed torque, power losses, efficiency and power factor is analyzed under full load conditions. Also, the steady-state power losses- and torque-slip characteristics at certain degrees of voltage unbalance have been calculated and plotte

Estimation of land surface Temperature of Maiduguri Metropolitan Area: A Case Study of Jere & some part of Mafa using Landsat 8 Operational Land Image (OLI)

Estimation of land surface Temperature of Maiduguri Metropolitan Area: A Case Study of Jere &amp; some part of Mafa using Landsat 8 Operational Land Image (OLI) the research revealedmean solar radiance as 10.54 W/m2/str/μm the calculated minimum and maximum NDVI values are respectively -0.01674 and 0.5489, used to obtain proportion to vegetation which is then used to determine the emmissivity of the area having minimum emmissivity of 0.986 and maximum of 0.99, the minimum and maximum land surface temperature of Maiduguri Metropolitan areas are respectively 41.16 oC and 26.11 oC. KEY WORDS:- Landsat 8 satellite images, Temperature, Solar Radiance and Emmissivity DOI: 10.7176/APTA/83-06 Publication date: March 31st, 202

Delivery of Poorly Soluble Drugs via Mesoporous Silica: Impact of Drug Overloading on Release and Thermal Profiles

Among the many methods available for solubility enhancement, mesoporous carriers are generating significant industrial interest. Owing to the spatial confinement of drug molecules within the mesopore network, low solubility crystalline drugs can be converted into their amorphous counterparts, which exhibit higher solubility. This work aims to understand the impact of drug overloading, i.e., above theoretical monolayer surface coverage, within mesoporous silica on the release behaviour and the thermal properties of loaded drugs. The study also looks at the inclusion of hypromellose acetate succinate (HPMCAS) to improve amorphisation. Various techniques including DSC, TGA, SEM, assay and dissolution were employed to investigate critical formulation factors of drug-loaded mesoporous silica prepared at drug loads of 100–300% of monolayer surface coverage, i.e., monolayer, double layer and triple layer coverage. A significant improvement in the dissolution of both Felodipine and Furosemide was obtained (96.4% and 96.2%, respectively). However, incomplete drug release was also observed at low drug load in both drugs, possibly due to a reversible adsorption to mesoporous silica. The addition of a polymeric precipitation inhibitor HPMCAS to mesoporous silica did not promote amorphisation. In fact, a partial coating of HPMCAS was observed on the exterior surface of mesoporous silica particles, which resulted in slower release for both drugs

DEWAXING OF DISTILLATE OIL FRACTION (400- 500 ºC) USING UREA

De-waxing of lubricating oil distillate (400-500 ºC) by using urea was investigated in the present study. Lubricating oil distillate produced by vacuum distillation and refined by furfural extraction was taken from Al-Daura refinery. This oil distillate has a pour point of 34 ºC. Two solvents were used to dilute the oil distillate, these are methyl isobutyl ketone and methylene chloride. The operating conditions of the urea adduct formation with n-paraffins in the presence of methyl isobutyl ketone were studied in details, these are solvent to oil volume ratio within the range of 0 to 2, mixer speed 0 to 2000 rpm, urea to wax weight ratio 0 to 6.3, time of adduction 0 to 71 min and temperature 30-70 ºC). Pour point of de-waxed oil and yield of wax produced were determined to show the effect of these operating conditions. The most favorable operating conditions were solvent to oil volume ratio of 1, mixer speed of 1500 rpm, urea to wax weight ratio of 5, time of adduction of 13 min and temperature of 30-52 ºC

Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters

Other test method (OTM) 33A has been used to quantify emissions from natural gas sites since it was introduced by the Environmental Protection Agency (EPA). The method relies on point source Gaussian (PSG) assumptions to estimate emissions rates from a targeted site or source. However, the method often results in low accuracy (typically ±70%, even under conducive conditions). These accuracies were verified with controlled-release experiments. Typically, controlled releases were performed for short periods (15–20 min) under atmospheric conditions that were ideal for effective plume transport. We examined three methane release rates from three distances over various periods of time ranging from seven hours to seven days. Data were recorded continuously from a stationary tower. Atmospheric conditions were highly variable and not always conducive to conventional OTM 33A calculations. OTM 33A estimates were made for 20-min periods when the mean wind direction corresponded to ±90° of the direction from the controlled release to the tower. Further analyses were performed by varying the frequency of the data, the length of the individual OTM 33A periods and the size of the wind angle used to filter data. The results suggested that different (than conventionally used) period lengths, wind filters, data acquisition frequencies and data quality filters impacted the accuracy of OTM 33A when applied to long term measurements

Cloud Computing in VANETs: Architecture, Taxonomy, and Challenges

Cloud Computing in VANETs (CC-V) has been investigated into two major themes of research including Vehicular Cloud Computing (VCC) and Vehicle using Cloud (VuC). VCC is the realization of autonomous cloud among vehicles to share their abundant resources. VuC is the efficient usage of conventional cloud by on-road vehicles via a reliable Internet connection. Recently, number of advancements have been made to address the issues and challenges in VCC and VuC. This paper qualitatively reviews CC-V with the emphasis on layered architecture, network component, taxonomy, and future challenges. Specifically, a four-layered architecture for CC-V is proposed including perception, co-ordination, artificial intelligence and smart application layers. Three network component of CC-V namely, vehicle, connection and computation are explored with their cooperative roles. A taxonomy for CC-V is presented considering major themes of research in the area including design of architecture, data dissemination, security, and applications. Related literature on each theme are critically investigated with comparative assessment of recent advances. Finally, some open research challenges are identified as future issues. The challenges are the outcome of the critical and qualitative assessment of literature on CC-V