Journal Articles, Hindawi Press

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A 52-Year-Old HIV-Positive Man with Abdominal Pain
Mehmood, Tashfeen; Chua, Matt J.; Khasawneh, Faisal A. (Hindawi, 2015-01-01)
Acceleration Feedback-Based Active and Semi-Active Seismic Response Control of Rail-Counterweight Systems of Elevators
Singh, Rildova; Singh, Mahendra P. (Hindawi, 2005-01-01)
Based on the observations in the past earthquake events, the traction elevators in buildings are known to be vulnerable to earthquake induced ground motions. Among several components of an elevator, the counterweight being heaviest is also known to be more susceptible than others. The inertial effects of the counterweight can overstress the guide rails on which it moves. Here we investigate to use the well-known acceleration feedback-based active and semi-active control methods to reduce stresses in the rails. The only way a control action can be applied to a moving counterweight-rail system is through a mass damper placed in the plane of the counterweight. For this, a part of the counterweight mass can be configured as a mass damper attached to a small actuator for an active scheme or to a magneto-rheological damper for a semi-active scheme. A comprehensive numerical study is conducted to evaluate the effectiveness of the proposed configuration of control system. It is observed that the two control schemes are effective in reducing the stress response by about 20 to 25% and improve the system fragility over a good range of seismic intensities.
Active Vibration Isolation Using an Induced Strain Actuator with Application to Automotive Seat Suspensions
Malowicki, Mark; Leo, Donald J. (Hindawi, 2001-01-01)
Active vibration isolation of automotive seats requires actuators that achieve millimeter-range displacements and forces on the order of 300 N. Recent developments in piezoceramic actuator technology provide a means for achieving these force and displacement levels in a compact device. This work demonstrates that prestressed, curved piezoceramic actuators achieve the force and displacement levels required for active isolation of automotive seats. An estimate of the force and displacement requirements are obtained from numerical simulations on a four-degree-of-freedom car and seat model that utilize representive road accelerations as inputs. An actuator that meets these specifications is designed using piezoceramic materials. Free displacement of 4.4 mm and blocked force greater than 300 N are measured. The actuator is integrated within a dead mass setup that simulates the isolation characteristics of an automotive seat. Control experiments demonstrate that active vibration is achievable with realistic road disturbances. Feedback control is able to eliminate any amplification due to mechanical resonance and reduce the isolation frequency from 9.5 Hz to 2 Hz.
Adaptive Control of the Atmospheric Plasma Spray Process for Functionally Graded Thermal Barrier Coatings
Guduri, Balachandar; Batra, Romesh C. (Hindawi, 2022-11-23)
Functionally graded coatings (FGCs) have a material composition continuously varying through the thickness but uniform in the surface parallel to the coated substrate. When used as a thermal barrier on a metallic substrate, the coating composition varies from an almost pure metal near the substrate to a pure ceramic adjacent to the outer surface exposed to a hot environment. Challenging issues in producing high quality FGCs in the presence of external disturbances with an atmospheric plasma spray process (APSP) include controlling the mean temperature, the mean axial velocity, and the positions of the constituent material particles when they arrive at the substrate to be coated. The unavoidable disturbances include fluctuations in the arc voltage and clogging of the powder in the delivery system. For a two-constituent coating, this work proposes using three modified robust model reference adaptive controllers based on the σ-modified laws and low frequency learning. One controller adjusts the current and flow rates of argon and hydrogen into the torch. The other two controllers adjust the distance of the two powder injector ports from the plasma jet axis and the average injection velocity of each powder. It is shown through numerical experiments that the three controllers implemented in an APSP consistently produce high-quality FGCs.
Adult Intestinal Intussusception Caused by the Gastrojejunostomy Tube: An Endoscopically Treatable Phenomenon
Zhang, Kermit S.; Bansal, Jash; Bansal, Anmol; Chitnavis, Vikas (Hindawi, 2021-06-11)
Adult duodenoduodenal intussusception is extremely rare due to the retroperitoneal fixation of the second, third, and fourth parts of the duodenum. A majority of clinically significant intussusception with identifiable etiologies is typically neoplastic with more rare causes including retained food and indwelling enteral tubes, specifically with gastrojejunostomy (GJ) tubes. Herein, we discuss the case of a 23-year-old male who developed duodenoduodenal intussusception upon a PEGJ placement with associated gastroduodenal dilation and telescope phenomenon. To the best of our knowledge, there are no reports of intussusception found to be caused by GJ tubes in the adult population. The reported patient was found to have a 4-cm enteroenteric intussusception without obstruction or ischemia with bowel thickening proximal to the pathology. Although adult intussusception cases are typically managed surgically, we were able to reduce the intussusception via endoscopy due to rapid diagnosis upon presentation and intervention before the bowel wall could be compromised.
Advective Heat Transport and the Salt Chimney Effect: A Numerical Analysis
Canova, David P.; Fischer, Mark P.; Jayne, Richard S.; Pollyea, Ryan M. (Hindawi, 2018-07-09)
We conducted numerical simulations of coupled fluid and heat transport in an offshore, buried salt diapir environment to determine the effects of advective heat transport and its relation to the so-called “salt chimney effect.” Model sets were designed to investigate (1) salt geometry, (2) depth-dependent permeability, (3) geologic heterogeneity, and (4) the relative influence of each of these factors. Results show that decreasing the dip of the diapir induces advective heat transfer up the side of the diapir, elevating temperatures in the basin. Depth-dependent permeability causes upwelling of warm waters in the basin, which we show to be more sensitive to basal heat flux than brine concentration. In these model scenarios, heat is advected up the side of the diapir in a narrower zone of upward-flowing warm water, while cool waters away from the diapir flank circulate deeper into the basin. The resulting fluid circulation pattern causes increased discharge at the diapir margin and fluid flow downward, above the crest of the diapir. Geologic heterogeneity decreases the overall effects of advective heat transfer. The presence of low permeability sealing horizons reduces the vertical extent of convection cells, and fluid flow is dominantly up the diapir flank. The combined effects of depth-dependent permeability coupled with geologic heterogeneity simulate several geologic phenomena that are reported in the literature. In this model scenario, conductive heat transfer dominates in the basal units, whereas advection of heat begins to affect the middle layers of the model and dominates the upper units. Convection cells split by sealing layers develop within the upper units. From our highly simplified models, we can predict that advective heat transport (i.e., thermal convection) likely dominates in the early phases of diapirism when sediments have not undergone significant compaction and retain high porosity and permeability. As the salt structures mature into more complex geometries, advection will diminish due to the increase in dip of the salt-sediment interface and the increased hydraulic heterogeneity due to complex stratigraphic architecture.
Aging and the Social Cognitive Determinants of Physical Activity Behavior and Behavior Change: Evidence from the Guide to Health Trial
Anderson-Bill, Eileen Smith; Winett, Richard A.; Wojcik, Janet R.; Williams, David M. (Hindawi, 2011-04-28)
Part one of this study investigated the effect of aging on social-cognitive characteristics related to physical activity (PA) among adults in the baseline phase of a health promotion intervention. Participants' questionnaire responses and activity logs indicated PA levels and self-efficacy declined with age, while social support and the use of self-regulatory behaviors (e.g., goal setting, planning, and keeping track) increased. With age participants were also less likely to expect PA to interfere with their daily routines and social obligations. Part two of the study was among overweight/obese, inactive participants completing the intervention; it examined whether improvements in psychosocial variables might counteract declining PA associated with age. After treatment, participants were more active and decreased body weight regardless of age, and improved self-efficacy, outcome expectations, and self-regulatory behaviors. In a causal model, increases in self-efficacy at 7-months lead to increased PA levels and, albeit marginally, weight loss at 16 months; increased PA was associated with greater weight loss. Aging adults who were more confident exercised more and as a result lost more weight. This longitudinal study suggests interventions that offset the effect of aging on self-efficacy may be more successful in helping older participants become more active and avoid weight gain.
Aging, resistance training, and diabetes prevention
Flack, Kyle D.; Davy, Kevin P.; Hulver, Matthew W.; Winett, Richard A.; Frisard, Madlyn I.; Davy, Brenda M. (2010-12-15)
With the aging of the baby-boom generation and increases in life expectancy, the American population is growing older. Aging is associated with adverse changes in glucose tolerance and increased risk of diabetes; the increasing prevalence of diabetes among older adults suggests a clear need for effective diabetes prevention approaches for this population. The purpose of paper is to review what is known about changes in glucose tolerance with advancing age and the potential utility of resistance training (RT) as an intervention to prevent diabetes among middle-aged and older adults. Age-related factors contributing to glucose intolerance, which may be improved with RT, include improvements in insulin signaling defects, reductions in tumor necrosis factor-α, increases in adiponectin and insulin-like growth factor-1 concentrations, and reductions in total and abdominal visceral fat. Current RT recommendations and future areas for investigation are presented.
An Alarming Mimicry of Intra-Abdominal Infections: Acute Appendiceal Diverticulitis
Kim, Youseung; Kesar, Varun; Grider, Douglas J.; Chitnavis, Maithili V. (Hindawi, 2021-11-12)
A 65-year-old woman presented with three days of colicky abdominal pain. Abdominal imaging illustrated small bowel enteritis, ascites in both paracolic gutters, and incidental hepatic steatosis. Although ascites fluid demonstrated high neutrophil count consistent with peritonitis and the patient received adequate antibiotics, she clinically deteriorated. Subsequent exploratory laparotomy revealed necrotic appendix and multiple intra-abdominal abscesses. Histopathology showed acute suppurative appendicitis with multiple other intact small diverticula, indicating likely perforation of inflamed appendiceal diverticula with subsequent abscess formation and abdominal peritonitis. This case highlights the importance of ascites fluid analysis and continued clinical correlation, especially in cases of rare entities with atypical presentations.
Ammonium Bisphosphonate Polymeric Magnetic Nanocomplexes for Platinum Anticancer Drug Delivery and Imaging with Potential Hyperthermia and Temperature-Dependent Drug Release
Zhang, Rui; Fellows, Benjamin; Pothayee, Nikorn; Hu, Nan; Pothayee, Nipon; Jo, Ami; Bohórquez, Ana C.; Rinaldi, Carlos; Mefford, Olin Thompson; Davis, Richey M.; Riffle, Judy S. (Hindawi, 2018-08-05)
Novel magnetite-ammonium bisphosphonate graft ionic copolymer nanocomplexes (MGICs) have been developed for potential drug delivery, magnetic resonance imaging, and hyperthermia applications. The complexes displayed relatively uniform sizes with narrow size distributions upon self-assembly in aqueous media, and their sizes were stable under simulated physiological conditions for at least 7 days. The anticancer drugs, cisplatin and carboplatin, were loaded into the complexes, and sustained release of both drugs was observed. The transverse NMR relaxivities (s) of the complexes were 244 s−1 (mM Fe)−1 which is fast compared to either the commercial T2-weighted MRI agent Feridex IV® or our previously reported magnetite-block ionomer complexes. Phantom MRI images of the complexes demonstrated excellent negative contrast effects of such complexes. Thus, the bisphosphonate-bearing MGICs could be promising candidates for dual drug delivery and magnetic resonance imaging. Moreover, the bisphosphonate MGICs generate heat under an alternating magnetic field of 30 kA·m−1 at 206 kHz. The temperature of the MGIC dispersion in deionized water increased from 37 to 41°C after exposure to the magnetic field for 10 minutes, corresponding to a specific absorption rate of 77.0 W·g−1. This suggests their potential as hyperthermia treatment agents as well as the possibility of temperature-dependent drug release, making MGICs more versatile in potential drug delivery applications.
Analytical and Experimental Vibration of Sandwich Beams Having Various Boundary Conditions
Joubaneh, Eshagh F.; Barry, Oumar R.; Tanbour, Hesham E. (Hindawi, 2018-06-25)
Generalized differential quadrature (GDQ) method is used to analyze the vibration of sandwich beams with different boundary conditions. The equations of motion of the sandwich beam are derived using higher-order sandwich panel theory (HSAPT). Seven partial differential equations of motions are obtained through the use of Hamilton’s principle. The GDQ method is utilized to solve the equations of motion. Experiments are conducted to validate the proposed theory. The results from the analytical model are also compared to those from the literature and finite element method (FEM). Parametric studies are conducted to investigate the effects of different parameters on the natural frequency and response of the sandwich beam under various boundary conditions.
Anti-Swing Control of Gantry and Tower Cranes Using Fuzzy and Time-Delayed Feedback with Friction Compensation
Omar, Hanafy M.; Nayfeh, Ali H. (Hindawi, 2005-01-01)
We designed a feedback controller to automate crane operations by controlling the load position and its swing. First, a PD tracking controller is designed to follow a prescribed trajectory. Then, another controller is added to the control loop to damp the load swing. The anti-swing controller is designed based on two techniques: a time-delayed feedback of the load swing angle and an anti-swing fuzzy logic controller (FLC). The rules of the FLC are generated by mapping the performance of the time-delayed feedback controller. The same mapping method used for generating the rules can be applied to mimic the performance of an expert operator. The control algorithms were designed for gantry cranes and then extended to tower cranes by considering the coupling between the translational and rotational motions. Experimental results show that the controller is effective in reducing load oscillations and transferring the load in a reasonable time. To experimentally validate the theory, we had to compensate for friction. To this end, we estimated the friction and then applied a control action to cancel it. The friction force was estimated by assuming a mathematical model and then estimating the model coefficients using an off-line identification technique, the method of least squares (LS).
Application of Recursive Least Square Algorithm on Estimation of Vehicle Sideslip Angle and Road Friction
Ding, Nenggen; Taheri, Saied (Hindawi Publishing Corporation, 2010)
A recursive least square (RLS) algorithm for estimation of vehicle sideslip angle and road friction coefficient is proposed. The algorithm uses the information from sensors onboard vehicle and control inputs from the control logic and is intended to provide the essential information for active safety systems such as active steering, direct yaw moment control, or their combination. Based on a simple two-degree-of-freedom (DOF) vehicle model, the algorithm minimizes the squared errors between estimated lateral acceleration and yaw acceleration of the vehicle and their measured values. The algorithm also utilizes available control inputs such as active steering angle and wheel brake torques. The proposed algorithm is evaluated using an 8-DOF full vehicle simulation model including all essential nonlinearities and an integrated active front steering and direct yaw moment control on dry and slippery roads.
Application of Smartphones in Pavement Profile Estimation Using SDOF Model-Based Noisy Deconvolution
Moghadam, Amin; Sarlo, Rodrigo (Hindawi, 2021-03-24)
The new generation of smartphones, equipped with various sensors, such as a three-axis accelerometer, has shown potential as an intelligent, low-cost monitoring platform over the past few years. This paper reports the results of an analytical and experimental study on a proposed SDOF model-based noisy deconvolution (SMND) coupled with a deechoing technique to estimate pavement profiles and to modify their geometry using a smartphone inside a vehicle. In the analytical study, the acceleration response of the car was obtained, where the input was a road profile with an arbitrary pattern. Two different methods, classical band-pass filter and wavelet-denoising technique, were used for denoising the acceleration response. In a 2-step deconvolution process coupled with a deechoing technique, the pavement profile was extracted and compared with the original pavement profile, demonstrating good agreement. In the next step, a parametric study was performed to evaluate the effect of vehicle characteristics and speeds. Then, a case study was conducted in Blacksburg, VA, to evaluate the capability of the proposed method in identifying profile types such as potholes and speed bumps. The acceleration-versus-time responses in vertical direction were recorded using smartphone accelerometers located in a moving vehicle. Then, the proposed approach was applied to remove the echo and vehicle dynamics effects to obtain the pavement profiles and to modify their geometry. The results showed that the proposed approach can remove the echo and vehicle dynamics effect from the response to obtain the pavement profile even if the vehicle characteristics and speed are changed.
Application of the Spectral Element Method in a Surface Ship Far-Field UNDEX Problem
Lu, Zhaokuan; Brown, Alan J. (Hindawi, 2019-07-25)
The prediction of surface ship response to a far-field underwater explosion (UNDEX) requires the simulation of shock wave propagation in the fluid, cavitation, fluid-structure interaction, and structural response. Effective approaches to model the fluid include cavitating acoustic finite element (CAFE) and cavitating acoustic spectral element (CASE) methods. Although the spectral element method offers the potential for greater accuracy at lower computational cost, it also generates more spurious oscillations around discontinuities which are difficult to avoid in shock-related problems. Thus, the advantage of CASE remains unproven. In this paper, we present a 3D-partitioned FSI framework and investigate the application of CAFE and CASE to a surface ship early-time far-field UNDEX problem to determine which method has the best computational efficiency for this problem. We also associate the accuracy of the structural response with the modeling of cavitation distribution. A further contribution of this work is the examination of different nonmatching mesh information exchange schemes to demonstrate how they affect the structural response and improve the CAFE/CASE methodologies.
Applications of Different Weighting Schemes to Improve Pathway-Based Analysis
Ha, Sook S.; Kim, Inyoung; Wang, Yue; Xuan, Jianhua (Hindawi, 2011-05-22)
Conventionally, pathway-based analysis assumes that genes in a pathway equally contribute to a biological function, thus assigning uniform weight to genes. However, this assumption has been proved incorrect, and applying uniform weight in the pathway analysis may not be an appropriate approach for the tasks like molecular classification of diseases, as genes in a functional group may have different predicting power. Hence, we propose to use different weights to genes in pathway-based analysis and devise four weighting schemes. We applied them in two existing pathway analysis methods using both real and simulated gene expression data for pathways. Among all schemes, random weighting scheme, which generates random weights and selects optimal weights minimizing an objective function, performs best in terms of 𝑷 value or error rate reduction. Weighting changes pathway scoring and brings up some new significant pathways, leading to the detection of disease-related genes that are missed under uniform weight.
Assessing Urban Landscape Variables’ Contributions to Microclimates
Parece, Tammy E.; Li, Jie; Campbell, James B. Jr.; Carroll, David F. (Hindawi, 2015-12-24)
The well-known urban heat island (UHI) effect recognizes prevailing patterns of warmer urban temperatures relative to surrounding rural landscapes. Although UHIs are often visualized as single features, internal variations within urban landscapes create distinctive microclimates. Evaluating intraurban microclimate variability presents an opportunity to assess spatial dimensions of urban environments and identify locations that heat or cool faster than other locales. Our study employs mobile weather units and fixed weather stations to collect air temperatures across Roanoke, Virginia, USA, on selected dates over a two-year interval. Using this temperature data, together with six landscape variables, we interpolated (using Kriging and Random Forest) air temperatures across the city for each collection period. Our results estimated temperatures with small mean square errors (ranging from 0.03 to 0.14); landscape metrics explained between 60 and 91% of temperature variations (higher when the previous day’s average temperatures were included as a variable). For all days, similar spatial patterns appeared for cooler and warmer areas in mornings, with distinctive patterns as landscapes warmed during the day and over successive days. Our results revealed that the most potent landscape variables vary according to season and time of day. Our analysis contributes new dimensions and new levels of spatial and temporal detail to urban microclimate research.
Assessing Variation in the Individual-Level Impacts of a Multihost Pathogen
Lewin, Zachary M.; Astorga, Francisca; Escobar, Luis E.; Carver, Scott (Hindawi, 2023-05-27)
Most pathogens infect more than one host species, and given infection, the individual-level impact they have varies among host species. Nevertheless, variation in individual-level impacts of infection remains poorly characterised. Using the impactful and host-generalist ectoparasitic mite Sarcoptes scabiei (causing sarcoptic mange), we assessed individual-level variation in pathogen impacts by (1) compiling all documented individual-level impacts of S. scabiei across free-living host species, (2) quantifying and ranking S. scabiei impacts among host species, and (3) evaluating factors associated with S. scabiei impacts. We compiled individual-level impacts of S. scabiei infection from 77 host species, spanning 31 different impacts, and totalling 683 individual-level impact descriptions. The most common impacts were those affecting the skin, alopecia (130 descriptions), and hyperkeratosis coverage (106). From these impacts, a standardised metric was generated for each species (average impact score (AIS) with a 0-1 range), as a proxy of pathogen virulence allowing quantitative comparison of S. scabiei impacts among host species while accounting for the variation in the number and types of impacts assessed. The Japanese raccoon dog (Nyctereutes viverrinus) was found to be the most impacted host (AIS 0.899). We applied species inclusion criteria for ranking and found more well-studied species tended to be those impacted more by S. scabiei (26/27 species AIS ud_less_than 0.5). AIS had relatively weak relationships with predictor variables (methodological, phylogenetic, and geographic). There was a tendency for Diprotodontia, Artiodactyla, and Carnivora to be the most impacted taxa and for research to be focussed in developed regions of the world. This study is the first quantitative assessment of individual-level pathogen impacts of a multihost parasite. The proposed methodology can be applied to other multihost pathogens of public health, animal welfare, and conservation concern and enables further research to address likely causes of variation in pathogen virulence among host species.
Assessment of Deep Partial Thickness Burn Treatment with Keratin Biomaterial Hydrogels in a Swine Model
Poranki, D.; Goodwin, C.; Van Dyke, M. (Hindawi, 2016-01-01)
Partial thickness burns can advance to full thickness after initial injury due to inadequate tissue perfusion and increased production of inflammatory cytokines, which has been referred to as burn wound progression. In previous work, we demonstrated that a keratin biomaterial hydrogel appeared to reduce burn wound progression. In the present study, we tested the hypothesis that a modified keratin hydrogel could reduce burn wound progression and speed healing. Standardized burn wounds were created in Yorkshire swine and treated within 30 minutes with keratin hydrogel (modified and unmodified), collagen hydrogel, or silver sulfadiazine (SSD). Digital images of each wound were taken for area measurements immediately prior to cleaning and dressing changes. Wound tissue was collected and assessed histologically at several time points. Wound area showed a significant difference between hydrogels and SSD groups, and rates of reepithelialization at early time points showed an increase when keratin treatment was used compared to both collagen and SSD. A linear regression model predicted a time to wound closure of approximately 25 days for keratin hydrogel while SSD treatment required 35 days. There appeared to be no measurable differences between the modified and unmodified formulations of keratin hydrogels.
Assessment of Nutrient Limitation in Floodplain Forests with Two Different Techniques
Neatrour, Matthew A.; Jones, Robert H.; Golladay, Stephen W. (Hindawi, 2008-05-15)
We assessed nitrogen and phosphorus limitation in a floodplain forest in southern Georgia in USA using two commonly used methods: nitrogen to phosphorus (N:P) ratios in litterfall and fertilized ingrowth cores. We measured nitrogen (N) and phosphorus (P) concentrations in litterfall to determine N:P mass ratios. We also installed ingrowth cores within each site containing native soil amended with nitrogen (N), phosphorus (P), or nitrogen and phosphorus (N + P) fertilizers or without added fertilizer (C). Litter N:P ratios ranged from 16 to 22, suggesting P limitation. However, fertilized ingrowth cores indicated N limitation because fine-root length density was greater in cores fertilized with N or N + P than in those fertilized with P or without added fertilizer. We feel that these two methods of assessing nutrient limitation should be corroborated with fertilization trials prior to use on a wider basis.

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