3,790 research outputs found
The simulated effect of the lightning first short stroke current on a multi-layered cylindrical model of the human leg
A dissertation submitted to the Faculty of Engineering and the Built Environment,
University of the Witwatersrand, Johannesburg, in ful lment of the requirements
for the degree of Master of Science in Engineering.
Johannesburg, 2015This research investigates the e ects of the frequency components of the lightning
First Short Stroke (FSS) on the current pathway through human tissues using frequency
domain analysis. A Double Exponential Function (DEF) is developed to
model the FSS with frequency components in the range 10 Hz 100 kHz. Human
tissues are simulated using Finite Element Analysis (FEA) in COMSOL and
comprises of two types of models: Single Layer Cylindrical Model (SLCM) and
Multi-layered Cylindrical Model (MLCM). The SLCM models 54 human tissues independently
and the MLCM models the human leg with ve tissue layers: bone
marrow, cortical bone, muscle, blood and fat.
Three aspects are analysed: current density, complex impedance and power dissipation.
From the SLCM results, aqueous tissues have the lowest impedances and tissue
heat dissipation is proportional to tissue impedance. Results from the MLCM show
that 85% of the FSS current
ows through muscle, 11%
ows through blood, 3:5%
through fat and the rest through cortical bone and bone marrow. From the results,
frequency dependent equivalent circuit models consisting of resistors and capacitors
connected in series are proposed.
The simulation results are correlated with three main clinical symptoms of lightning
injuries: neurological, cardiovascular and external burns. The results of this work are
applicable to the analysis of High Voltage (HV) injuries at power frequencies.MT201
Quaternized wood as sorbent for hexavalent chromium
The potential of quaternized wood (QW) chips in removing hexavalent chromium from synthetic solution and chrome waste under both batch and continuous-flow conditions was investigated. Sorption was found to be dependent on pH, metal concentration, and temperature. QW chips provide higher sorption capacity and wider pH range compared with untreated wood chips. The equilibrium data could be fitted into the Langmuir isotherm model, and maximum sorption capacities were calculated to be 27.03 and 25.77 mg/g in synthetic chromate solution and chrome waste, respectively. The presence of sulfate in high concentration appeared to suppress the uptake of chromium by QW chips. Column studies showed that bed depth influenced the breakthrough time greatly whereas flow rate of influent had little effect on its sorption on the column
Stimulatory Effect of 5-Hydroxytryptamine (5-HT) on Rat Capsaicin-Sensitive Lung Vagal Sensory Neurons via Activation of 5-HT\u3csub\u3e3\u3c/sub\u3e Receptors
5-hydroxytryptamine (5-HT) is an inflammatory mediator known to be released in lung. Capsaicin-sensitive lung vagal (CSLV) afferents function as a primary sensor for detecting chemical stimuli and produce consequent reflexes during lung inflammation. To characterize the effect of 5-HT on CSLV afferents, responses of cardiorespiratory reflexes and single-unit C-fiber afferents to right-atrial injections of 5-HT were investigated in anesthetized Sprague-Dawley rats. Bolus injection of 5-HT (8 μg/kg) caused an immediate augmented breath and apnea, accompanied by hypotension and bradycardia. These initial responses were then followed by a brief pressor response and a more sustained depressor response. After a perineural treatment of both cervical vagi with capsaicin to block the conduction of C fibers, 5-HT still triggered the augmented breath, but no longer evoked the apnea, bradycardia and hypotension, indicating an involvement of C-fiber activation. The remaining augmented breath induced by 5-HT after perineural capsaicin treatment was totally eliminated by vagotomy. To further study the effect of 5-HT on CSLV afferents, activities arising from these afferents were determined using the single-fiber recording technique. Right-atrial injection of 5-HT evoked an intense discharge in CSLV afferents in a dose-dependent manner. The highest dose of 5-HT (16 μg/kg) activated 79% (19/24) of CSLV afferents which were also sensitive to capsaicin (0.8 μg/kg). The pretreatment of tropisetron, a selective antagonist of the 5-HT3 receptor, completely blocked CSLV-afferents stimulation induced by 5-HT but did not affect that by capsaicin. Furthermore, a similar afferent response of CSLV afferents was mimicked by phenylbiguanide, a selective agonist of the 5-HT3 receptor. In isolated rat lung vagal C neurons, 5-HT induced intense calcium transients in a dose-dependent manner. The highest concentration (3 μM) of 5-HT activated 67% (18/27) of the CSLV neurons. The 5-HT-induced response was totally abolished by pretreatment of tropisetron. In conclusion, 5-HT exerts an intense stimulatory effect on lung C-fiber terminals mediated through an activation of the 5-HT3 receptor, which may contribute to the airway hypersensitivity under lung inflammation
Gender Trends in Dental Leadership and Academics: A Twenty-Two-Year Observation
The purpose of this study was to examine gender disparities in dental leadership and academics in the United States. Nine journals that represent the dental specialties and high published impact factors were selected to analyze the percentage of female dentists’ first and senior authorship for the years 1986, 1990, 1995, 2000, 2005, and 2008. Data on appointment status and female deanship were collected from the American Dental Association (ADA) survey, and the trends were studied. The proportion of female presidents in ADA-recognized specialty organizations was also calculated. Overall, the increase in first female authorship was not statistically significant, but the increase of last female authorship was statistically significant in a linear trend over the years. The percentage of tenured female faculty members and female deans in U.S. dental schools increased by factors of 1.7 and 9, respectively, during the study period. However, female involvement in professional organizations was limited. Findings from this study indicate that female participation in authorship and leadership has increased over time. Nevertheless, females are still a minority in dental academics and leadership
Design and Implementation of Service-Oriented Expert System
In recent years, the Internet technologies are well developed and the Internet is filled with all kinds of information. Since the data storage is increasingly distributed and data formats are more diverged, data collection and integration for providing value- added services have gradually become important topics. In this study, we propose the Service-Oriented Expert System (SOES) based on Service Component Architecture (SCA) which can make the services on different platforms turn into a common service component on the Internet, concatenate all the service components by combining with the Enterprise Service Bus (ESB), and use both expert rules and data mining techniques to perform the data classification. The SOES is applied to analyze the annual financial information derived from electronic industry in the Taiwan Economic Journal (TEJ) during 2006 to 2008 for discovering the financial crisis enterprises. The experiment results show that using expert rules and decision tree to find the financial crisis enterprise is higher performance
Hemolytic Uremic Syndrome Caused by Enteroviral Infection
A 4-year-old boy presented with enteroviral infection complicated with atypical hemolytic uremic syndrome (aHUS). Enterovirus RNA was detected by reverse transcription polymerase chain reaction (RT-PCR) of both blood and kidney biopsy specimens. A survey of the complement system did not reveal a specific complement defect. Supportive therapy with blood components transfusion, plasma therapy, and immunosuppressants was administered, however, renal function did not recover. The results of this report demonstrate that the enterovirus is the cause of aHUS
Towards Relating Fragile-To-Strong Transition to Fragile Glass
Glass formers are in general classified as strong or fragile depending on
whether their relaxation rates follow Arrhenius or super-Arrhenius temperature
dependence. There are however notable exceptions such as water, which exhibit a
fragile-to-strong (FTS) transition and behave as fragile and strong
respectively at high and low temperatures. In this work, the FTS transition is
studied using a distinguishable-particle lattice model previously demonstrated
to be capable of simulating both strong and fragile glasses [Phys. Rev. Lett.
125, 265703 (2020)]. Starting with a bimodal pair-interaction distribution
appropriate for fragile glasses, we show that by narrowing down the energy
dispersion in the low-energy component of the distribution, a FTS transition is
observed. The transition occurs at a temperature at which the stretching
exponent of the relaxation is minimized, in agreement with previous molecular
dynamics simulations
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