bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Different Metal Film Thicknesses of COC-Substrate Polymerase Chain Reaction Chips With Single-Side and Double-Side Heaters
Authors: Chung Yung-Chiang , Lai Li-Wei , Yang Lung-Jieh , Liao Wei-Jen
Published: June 2010

We fabricated PCR chips of different metal film thicknesses. The PCR machine with/without top heater and the single-side/double-side heater PCR chips were compared. The substrate was transparent COC (Cyclic Olefin Copolymers), and the gold film was fabricated on the substrate by evaporation without any adhesive layer. Then the results after polymerase chain reaction for the DNA of Escherichia coli TG-1 cell were obtained. The concentrations of amplifying 225 bps DNA were 0.78–0.82 ng/μl (64% of the result of PCR machine).
Ablation and Separation of Dermis via Ultra-Short Pulsed Laser
Authors: Huang Huan , Guo Zhixiong
Published: June 2010

Dermal tissue ablation and layer-separation with minimal thermal damage to the surrounding tissue via an ultra-short pulsed (USP) laser has been investigated. At first, a parametric study for wet tissue surface line ablation was investigated. The line features were measured by both microscope and scanning electron microscopy. The dermis ablation threshold and the incubation factor were determined through the line ablation results. It is found that a general microscope may give inflated ablation line width. Following the ablation experiment, histological view of ablated wet tissue samples with different combinations of laser parameters has been undertaken to obtain proper laser parameters for tissue separation with minimal thermal damage. The separation of a whole piece of wet dermal tissue into two thin layers was presented. A thin dermal tissue layer pushing to 220 μm thickness was obtained.
Tikhonov Regularization Methods for the Inverse Scalp Electroencephalography
Authors: Wu Menglu , Chen Xiaolin
Published: June 2010

Electroencephalography (EEG) source localization of brain activity is of high diagnostic value. Noninvasive numerical procedures can be developed to help reconstruct the cortical brain activities from the low-spatial-resolution scalp EEG measurement. In this paper, Tikhonov regularization methods are employed to tackle the solution difficulty associated with the ill-posed reconstruction problem. Three different techniques, namely the L-curve method, the generalized cross validation (GCV) and the discrepancy principle (DP), are implemented to help identify an optimum parameter for the numerical regularization. The numerical procedures are verified by comparing reconstruction results with available theoretical potential solutions for a simplified concentric sphere head model. All three parameter selection methods achieve good results and the L-curve method produces the best regularization effect among the three when the noise level is high in the contaminated scalp data input. More studies are performed on a computational model of an anatomically realistic human head. Our results show that the combination of Tikhonov regularization with the L-curve parameter selection method can effectively regularize the ill-posed inverse EEG problem for brain potential reconstruction.
A Study of Vocal Fold Vibration Using a Slightly Compressible Fluid Domain
Authors: Daily D. J. , Thomson S. L.
Published: June 2010

During human voice production, air forced from the lungs through the larynx induces vibration of the vocal folds. Computational models of this coupled fluid-solid system have traditionally utilized an incompressible fluid domain. However, studies have shown that coupling of tracheal acoustics with vocal fold dynamics is significant. Further, in the absence of compressibility, some models fail to achieve self-sustained vibration. This presentation discusses a slightly compressible airflow model, fully coupled with a vocal fold tissue model, as a possible substitute for the traditional incompressible approach. The derivation and justification of the slightly compressible fluid model are discussed. Results are reported of a study of the nature of the coupling between the fluid and vocal fold regions for both slightly compressible and incompressible fluid domains using a commercial fluid-solid finite element package. Three different types of inlet boundary conditions, including constant pressure, constant velocity, and moving wall, are explored. The incompressible and slightly compressible models with the three boundary conditions are compared with each other and with experimental data obtained using synthetic self-oscillating vocal fold models. The results are used to validate the slightly compressible flow model as well as to explore candidate boundary conditions for vocal fold vibration simulations.
Dependance of Lindenmayer System (L-System) Parameters on Flow Characteristics in Engineered Biomaterials
Authors: Yasar Ozlem , Lan Shih Feng , Starly Binil
Published: June 2010

Large thick tissue constructs have reported limited success primarily due to the inability of cells to survive deep within the scaffold. Without access to adequate nutrients, cells placed deep within the tissue construct will die out, leading to non-uniform tissue regeneration. In this research, we present several Lindenmayer system generated conduit networks in two and three-dimensional architecture with several degrees of complexity. The conduit network maintains a parent-child relationship between each branch of the network. Several L-system parameters have been studied—branching angle, branch length, ratio of parent to child branch diameter etc. We have developed a multi-physics based numerical model to predict the dependence of these L-system design parameters on the flow characteristics within the tissue construct. The implication of the simulation results will be discussed in terms of the design of 3D in-vitro tissue model systems.
Bicomponent Fibrous Scaffolds of Controlled Composition for Tissue Engineering Applications
Authors: Kang Jia-Chen , Wang Min , Yuan Xiao-Yan
Published: June 2010

Electrospinning has been widely studied for constructing tissue engineering scaffolds because of the morphological and size effects of electrospun fibers on cell behavior. Research on electrospun tissue engineering scaffolds has been based mainly on using solutions of single polymer or blends of polymers dissolved in common solvents, which has put limitations to scaffolds that can be built. There is an increasing need for using the multi-source and multi-power electrospinning approach to fabricate multicomponent fibrous scaffolds because these scaffolds have great potential for tissue engineering and controlled (drug) release applications. In the present study, bicomponent fibrous scaffolds were fabricated through dual-source and dual-power electrospinning using poly(L-lactic acid) (PLLA) and gelatin polymers. The experimental setup ensured that the solution and electrospinning parameters for each electrospun fibrous component were controlled separately and hence the morphology of electrospun fibers could be controlled and optimized. By adjusting the number of syringes that fed polymer solutions, the composition of bicomponent scaffolds (i.e. the weight percentage of gelatin varying from 0 to 100%) could also be controlled. Such controls would yield scaffolds of desired properties (hydrophilicity, degradation rate, strength, etc.) After electrospinning, pure gelatin scaffolds and bicomponent scaffolds were crosslinked by glutaraldehyde (GA) and genipin, respectively, using different crosslinking methods. Both crosslinked and non-crosslinked scaffolds were studied using various techniques (scanning electron microscopy (SEM) for scaffold morphology, differential scanning calorimetry (DSC) for polymer crystallinity, contact angle measurement for hydrophilicity, tensile testing for mechanical properties and crosslinking efficiency, etc.). It was found that the bicomponent scaffolds were more hydrophilic than pure PLLA scaffolds due to the presence of gelatin fibers. The tensile strength of bicomponent scaffolds was also increased after crosslinking. Using our experimental setup, bicomponent scaffolds could be constructed for tissue engineering with enhanced mechanical properties, biocompatibility and biodegradability. Furthermore, in the bicomponent scaffolds, while PLLA fibers could act as the structural component with a slower degradation rate, the gelatin fibers could be used as a carrier for therapeutic agents (drugs and therapeutic biomolecules). With controlled degrees of the crosslinking of gelatin, the release of therapeutic agents from gelatin fibers would be controlled.
Tissue-Engineered Cartilage in Three-Dimensional Cultured Chondrocytes by Ultrasound Stimulation and Collagen Sponge as Scaffold
Authors: Shiraishi Toshihiko , Matsunaga Ietomo , Morishita Shin , Takeuchi Ryohei , Saito Tomoyuki , Mikuni-Takagaki Yuko
Published: June 2010

This paper describes the effects of ultrasound stimulation on chondrocytes in three-dimensional culture in relation to the production of regenerative cartilage tissue, using collagen sponges as a carrier and supplementation with hyaluronic acid (used in the conservative treatment of osteoarthritis). It has been shown that cell proliferation and matrix production can be facilitated by considering the mechanical environment of the cultured chondrocytes and the mechanical properties of the scaffold structure used in the culture and of the stimulation used.
Physical and Mechanical Properties of Poly(E-Caprolactone)–Hydroxyapatite Composites for Bone Tissue Engineering Applications
Authors: Leung Linus H. , DiRosa Amanda , Naguib Hani E.
Published: June 2010

Tissue engineering using bioscaffolds is a promising technique that may provide new treatments for various diseases and injuries. These bioscaffolds can be temporary or permanent materials that can be implanted in a patient for tissue repair. Poly(ε-caprolactone) (PCL) is a biocompatible and biodegradable polymer, and hence suitable for usage in tissue engineering applications. Depending on the targeted tissue to be repaired, scaffold properties need to be altered to match that of the tissue. In load bearing applications, such as bone repair, the mechanical properties need to be sufficiently high to prevent material failure. To strengthen the scaffold, various composites have been proposed in the literature, and one of these composites includes PCL with hydroxyapatite (HA). To be able to control the processing of these materials into scaffolds, the characterization of fundamental material properties need to be investigated. In this study, the physical, thermal, mechanical, and viscoelastic properties of PCL:HA at three different weight compositions of 80:20, 70:30, and 60:40 wt% were characterized and compared to neat PCL. PCL/HA composites were fabricated by blending using a twin-screw compounder, and disc-shaped samples were fabricated by compression molding at an elevated temperature. Analysis using a differential scanning calorimeter demonstrated that the glass transition and melting temperatures of the composites remained nearly unaffected by the HA content at −56 °C and 56 °C, respectively; however, depending on the cooling method used for processing, the degree of crystallinity can be controlled. Thermogravimetric analysis was also performed to study the thermal degradation profile. PCL-HA composite samples were tested in compression to determine the effects of HA content on the mechanical properties. Compared to neat PCL, incorporating HA at 40 wt% increased the modulus nearly twofold from 85 to 155 MPa. Lastly, to study the viscoelastic properties of the solid materias, frequency dependency and creep experiments were performed using a dynamic mechanical analyzer. The composites at high HA concentrations were more compliant to creep and other viscoelastic effects. The results found in this study are important in developing novel processing techniques or scaffolds and in controlling final scaffold properties such that any desired properties may be fabricated.
Natural Frequency Response of Intraaortic Balloons
Authors: Grant K. B. , Saigal A.
Published: June 2010

An Intraaortic Balloon (IAB) is a cardiac assist device that consists of a catheter (lumen) and a balloon at the catheter’s distal end. A balloon pump, or IABP, and a transducer are connected to the hub of the catheter that remains outside of the body. Connecting the inner lumen to the balloon pump through the hub of the catheter is typically used to monitor pressures within the human body and can be characterized as a catheter-transducer system. The three main components of this system and their functions are as follows: the IAB gives access to the blood pressure system through the inner lumen; a transducer converts a mechanical impulse of a pressure wave into an electrical signal; the IABP records the electrical signals for the pump operator’s and pump’s interpretation. The pump analyzes the incoming electrical signal and, in turn, triggers the appropriate IAB inflate and deflate times. Catheter-transducer systems can be modeled as underdamped, second-order dynamic systems. Each system has both a characteristic frequency and a damping coefficient, where damping refers to the accuracy of the monitoring set-up to reproduce pressure waveform characteristics. To achieve an accurate pressure reading, optimal damping must be achieved. If the system is underdamped, very little damping in the system, the pressure readings tend to overestimate the systolic blood pressure and underestimate the diastolic blood pressure, and vice versa. The ability for the pressure monitoring system to detect changes quickly is called the frequency response. Catheter-transducer systems are characterized as underdamped because the addition of damping causes the response of the system to decrease. In order to counteract this, the system must have a high natural or undamped frequency — the frequency that would occur in the absence of frictional forces or damping. A high natural frequency will reduce the effects of damping such that underdamped or overdamped waveforms are unlikely to appear. This study compares the natural frequency and damping coefficients of four different IABs: Datascope Fidelity, Arrow Nitinol, Arrow Stainless Steel and Arrow Polyimide. Each of these IABs had a natural frequency greater than the minimum specified value of 20 Hz. The Arrow Polymide inner lumen had the lowest natural frequency response. This is due to the flexibility of the Polyimide, which absorbs some of the pressure wave’s energy, and thus distorts the pressure wave output. Likewise, the Arrow Nitinol, with the stiffest inner lumen, had the highest natural frequency. The damping coefficients for these IABs varied from 0.16 to 0.38. None of the four IABs achieved an average damping coefficient near the optimal range of 0.60 to 0.75 and thus all of them can be characterized as underdamped systems.
Silicon Based Pore Systems for Emerging Biosensor Applications
Authors: Mathew Trupthi , Joshi Punarvasu , Prasad Shalini , Goryll Michael , Spanias Andreas , Thornton Trevor J.
Published: June 2010

Recent research in the domain of single molecule biosensors aims at using silicon pore systems for the electrical detection of charged entities. Detection is achieved through resistive pulse measurements also known as Coulter counting. This work demonstrates the use of silicon based cylindrical micropores which can be used to detect biomolecules with high selectivity and robustness. The micropores used in the experiment were patterned using semiconductor processing techniques to have a final diameter of 5μm and a length of 30μm on a siliconsubstrate. The probes used in the study were silica beads which have been functionalized to detect two types of protein immunocomplexes: (i) biotin-avidin and (ii) immunoglobulin-G using its specific antibody within the silicon micropore system.
Individualized Transfer Functions for the Noninvasive Estimation of Central Pressure From Brachial Pressure Readings
Authors: Mookerjee Ashis , Al-Jumaily Ahmed M. , Lowe Andrew
Published: June 2010

A model-based investigation is carried out with the aim of developing an ab-initio methodology for the patient-specific estimation of central pressures from brachial blood pressure readings. The subclavian root-brachial artery segment is modeled as a 1-D tube with all model parameters linked to patient characteristics. A simulation is also run with typical physiological parameters, which gives a “first estimate” of the transfer function (TF). The TF derived using the patient characteristics is studied in detail to investigate the change in the arterial TF occurring with changes in patient characteristics. This TF is compared with the “first estimate” to evaluate the feasibility of using standard arterial properties.
Materials Considerations for Improved Flash/Flame Protection
Authors: Paquin Jeremy D. , Martinez Francisco J. , Hitt Joseph , Arnas A. O¨zer
Published: June 2010

To investigate the capabilities of protective clothing materials to withstand the initial radiant energy effects and secondary flame impingement from a blast and devise suggestions for new materials, better configuration designs, and manufacturability of those designs must be considered. This paper discusses results that will directly benefit soldiers and others with risk to exposure of flash/flames due to explosions. Dismounted soldiers need a material that has improved flash/flame protective qualities to better protect them in combat situations that may result in burn injuries from fires that originate from a blast. This paper investigates why the burns occurred, how the materials used in the current configuration of clothing could be improved upon, and what new materials choices can be made in other configurations to better protect dismounted soldiers. The causes of failure have been evaluated, and by way of reverse and forward engineering, alternative choice of materials and improved designs has been considered. As a result, a prototype can/will be built based on the design characteristics, tested, and potentially fielded for use by soldiers. The paper provides sufficient background information on the anatomy of explosions, physiology of burn injuries, and blast type and burn relationships. Current testing methods for testing burn-protection materials are discussed including both bench scales and full scale tests and the pros and cons of each. The engineering requirements for current fire resistant clothing are broken down. Then, a description of the assumptions is listed, and the engineering design process is applied to the problem to determine which characteristics are most important in this type of fire-resistant material. This process includes a survey and several design tools to narrow the design criteria to the most important engineering characteristics required for a successful application of the design. Another aspect is introduced by including an analysis of the heat transfer characteristics of fire-resistant materials to help narrow the criteria and better understand the problem.
Biomechanical Basis of Oscillometric Blood Pressure Measuring Technique
Authors: Lan H. , Al-Jumaily A. M. , Hing W. , Lowe A.
Published: June 2010

Non-invasive blood pressure (BP) measurement has been used clinically for over a century to diagnose hypertension. Compared with the auscultatory technique, the oscillometric technique requires less professional training and is widely used in automatic BP measurement devices. Currently, most of these devices measure and record amplitude of cuff pressure oscillation, and then calculate diastolic and systolic pressure using characteristic ratios and designed algorithms. A finite element (FE) model is developed to study the biomechanical basis of this technique. The model identifies that errors were caused by mechanical factors of the soft tissue and the shape of the arm. By personalizing the parameters for each patient, the accuracy of the measurement will be improved for all age groups.
Temperature Effect on the Dynamic Characteristic of the Aircraft Seat Cushion
Authors: Thorbole Chandrashekhar K. , Lankarani Hamid M. , Costello Tom
Published: June 2010

The aim of this study is to identify the affect of significant variables like cushion thickness, rate sensitivity and temperature influencing the pelvic lumbar load of the seated occupant during vertical crash. Aircraft seat cushions are exposed to varying temperature ranges during their lifetime. Currently the Federal Aviation Regulations require the seat cushions to be tested and certified at room temperature. The objective of this study is achieved by conducting quasi-static test on cushions with different rate sensitivity and with different thickness, at extreme temperatures to determine the variations in their dynamic characteristics. The various seat cushions are tested with different combination of the factors to determine their characteristics and to predict their dynamic behavior. The prediction is based on the mathematical model developed suing biodynamic code MADYMO which is validated with one of the Dynamic sled test. The sensitivity analysis is carried on this validated model to understand the percentage contribution of various input factors affecting the lumbar load. Factorial design is selected at two levels for each factor. This sensitivity analysis facilitates different combinations of these factors to get better insight in the relation between the response and the factors.
A Procedure to Evaluate the Thermal Response of a Multilayered Thermal Protection System Subjected to Aerodynamic Heating
Authors: Ferraiuolo Michele , Manca Oronzio , Riccio Aniello
Published: June 2010

Next generation reusable re-entry vehicles must be capable of sustaining consistent repeated aero-thermal loads without damage or deterioration. This means that such structures must tolerate the high temperatures engendered by aero-thermal re-entry fluxes due to the establishment of a hypersonic regime over the body. Thermal Protection Systems (TPS) are used to maintain a reusable launch vehicle’s structural temperature within acceptable limits during re-entry flights; that is, internal temperature should not overcome the temperature limit use of the internal structure. TPS are usually composed by several layers made of different materials. Heat transfer through a multilayer insulation during atmospheric re-entry involves combined modes of heat transfer: heat conduction through the solid, heat radiation to the outer space etc. In the frame of TPS design activities a procedure based on one dimensional analytical solutions of transient nonlinear analyses has been developed in order to estimate the temperature variation with time and space of a multilayered body subjected to aerodynamic heating inside a radiating space. Since internal temperature values of TPSs of re-entry vehicles cannot exceed certain values, that procedure allows to quickly evaluate those temperature values and to preliminary size layer thicknesses before preparing and performing Finite Element analyses.
The Stent Artery Interaction
Authors: Gu Linxia , Muttyam Aswini K.
Published: June 2010

Experimental and clinical evidence indicate that degree of arterial injury after stent implantation is strongly linked with various stent designs. In this study, Computational models are developed to predict stents-induced arterial strain and stress during the stenting procedure. The intramural stresse filed in the stenotic vessel wall is obtained to understand the injuries caused by stent implantation. Circumferential tensile stresses are maximal in the wall near the plaque edge, and the stress values are much higher than the tensile strength of the wall medial. Stress gradient at the interface among the stent, plaque and artery are also high. These results indicate a possibility of the injury near the edge of contact surface. The stress gradient and the vessel injury may be reduced by alternating stent designs.
Quantitative Images of Elastic Modulus Using Tissue Dynamics in the Region of Impulsive Acoustic Radiation Force Excitation
Authors: Palmeri Mark L. , Xu David , Wang Michael , Nightingale Kathryn
Published: June 2010

Focused, impulsive, acoustic radiation force excitations can generate shear waves with microns of displacement in tissue. The speed of shear wave propagation is directly related to the tissue’s shear modulus, which can be correlated with tissue pathology to diagnose disease and to follow disease progression. Shear wave speed reconstruction has conventionally been measured over spatial domains that are spatially-offset from the region of excitation (ROE). While these methods are very robust in clinical studies characterizing large, homogeneous organs, their spatial resolution can be limited when generating quantitative images of shear elasticity. The ROETTP algorithm measures time-to-peak (TTP) displacements along the axis-of-symmetry in the ROE of an impulsive acoustic radiation force excitation. These TTP displacements are inversely proportional to shear stiffness and are dependent on the excitation-beam geometry. Lookup tables (LUTs) specific to an excitation/displacement tracking transducer configuration were generated from simulated data, and shear stiffnesses were estimated from experimental data as a function of depth using the LUTs. Quantitative ROETTP shear elasticity images of spherical inclusions in a calibrated tissue-mimicking phantom have been generated. Shear wave reflections and interference can lead to an underestimation of the absolute reconstructed shear modulus (20–25%), but the ratio of absolute shear stiffnesses is well-preserved (3.3 vs. 3.5).
Computational Fluid Dynamics Analysis of Surgical Adjustment of Ventricular Assist Device Implantation to Minimize Stroke Risk
Authors: Osorio Andres F. , Kassab Alain J. , Divo Eduardo A. , Argueta-Morales I. Ricardo , DeCampli William M.
Published: June 2010

Presently, mechanical support is the most promising alternative to cardiac transplantation. Ventricular Assist Devices (VADs) were originally used to provide mechanical circulatory support in patients waiting planned heart transplantation (“bridge-to-transplantation” therapy). The success of short-term bridge devices led to clinical trials evaluating the clinical suitability of long-term support (“destination” therapy) with left ventricular assist devices (LVADs). The first larger-scale, randomized trial that tested long-term support with a LVAD reported a 44% reduction in the risk of stroke or death in patients with a LVAD. In spite of the success of LVADs as bridge-to-transplantation and long-term support. Patients carrying these devices are still at risk of several adverse events. The most devastating complication is caused by embolization of thrombi formed within the LVAD or inside the heart into the brain. Prevention of thrombi formation is attempted through anticoagulation management and by improving LVADs design; however there is still significant occurrence of thromboembolic events in patients. Investigators have reported that the incidence of thromboembolic cerebral events ranges from 14% to 47% over a period of 6–12 months. An alternative method to reduce the incidence of cerebral embolization has been proposed by one of the co-authors, namely William DeCampli M.D., Ph.D. The hypothesis is that it is possible to minimize the number of thrombi flowing into the carotid arteries by an optimal placement of the LVAD outflow conduit, and/or the addition of aortic bypass connecting the ascending aorta (AO) and the innominate artery (IA), or left carotid artery (LCA). This paper presents the computational fluid dynamics (CFD) analysis of the aortic arch hemodynamics using a representative geometry of the human aortic arch and an alternative aortic bypass. The alternative aortic bypass is intended to reduce thrombi flow incidence into the carotid arteries in patients with LVAD implants with the aim to reduce thromboembolisms. In order to study the trajectory of the thrombi within the aortic arch, a Lagrangian particle-tracking model is coupled to the CFD model. Results are presented in the form of percentage of thrombi flowing to the carotid arteries as a function of LVAD conduit placement and aortic bypass implantation, revealing promising improvement.
Dynamic Waterbed With Pressure Modulation by Turbulent Jets
Authors: Martins Luis A. S. B. , Fernandes Carlos M. C. , Nunes Antonio V. A. , Carvalho Miguel A. F.
Published: June 2010

This work is part of a multidisciplinary project designated “Sense4me - Monitoring and control system of discomfort, for disabled persons and surgical patients”. When an individual is confined to prolonged recumbent or sitting positions, a process of ulceration is likely to occur at sites with prominent bony structures, called pressure-sore or pressure-ulcer. Pressure-sores are an increasing problem within our society, with high prevalence amongst hospitalized patients or physically handicapped persons, often leading to premature deaths [1]. In the USA the overall annual cost of dealing with this problem is estimated to be between 5 to 9 billion dollars [2]. The main objective of the study is to analyze the viability of a novel active mattress system, based on turbulent waterjets impinging onto the mattress-cover, which will allow the control of pressure and temperature on the contact-surface with the human skin, thus decreasing the risk of pressure-ulcer formation. A small fluid-mattress prototype was designed and is being constructed. It consists on a chamber with a rectangular cover-area of 500 by 500 mm and a deepness of 100 mm. The bottom surface is a metal plate with equally-spaced orifices forming a matrix. The fluid jets, emerging from these orifices, impinge onto the pliable membrane-cover. The fluid is then collected from the sides and directed to a leveling tank and to a water-pump. This pump discharges the fluid into a plenum chamber, located behind the main plate with the orifices, thus completing the hydraulic circuit. The relevant physical and geometric parameters for the prototype definition (orifice diameter and matrix spacing, distance plate/membrane, plenum pressures, minimum body sustainable pressure, total jet momentum, etc) are described and studied. This included the realization of static pressure measurements with an inflatable mattress supporting a human body in different positions, as well as essays with a high velocity air-jet impinging on a surface. Preliminary calculations were made for the prototype running with a selected pump. The results indicate that the additional pressure exerted on the membrane will lead to a force in excess of 150 N, for a flow-rate between 20 and 40 m3/h, and a plenum pressure from 1 to 4 bar, depending on orifice diameter. The work currently follows with tests involving weights located on the membrane surface, to verify the calculations and the soundness of the jet impingement principle. Further work will entail the division of the plenum in 16 sub-chambers with inlet flow valves, thus allowing the local modulation of membrane pressure by variation of the jets exit velocities, and temperature through sub-chamber individual control of water supply temperature.
Techniques in Finite Element Modeling of Helmeted-Head Biomechanics
Authors: Przekwas Andrzej , Tan X. G. , Chen Z. J. , Zhou Xianlian , Reeves Debbie , Wilkerson Patrick , Yang H. Q. , Harrand Vincent , Chancey Valeta Carol
Published: June 2010

Generally a helmet comprises two main components: the shell and the fitting system. Despite the variations in designs due to the different usage requirements, typically helmets are intended to protect the user’s head through an energy absorption mechanism. The weight and volume are important factors in helmet design since both may alter the injury risk to the head and neck. The helmet outer shell is usually made of hard material that will deform when it is hit by hard objects. This action disperses energy from the impact to lessen the force before it reaches the head. The fitting system frequently includes a dense layer that cushions and absorbs the energy as a result of relative motion between the helmet and the head. A balance needs to be achieved on how strong and how stiff a helmet should be to provide the best possible protection. If a helmet is too stiff it can be less able to prevent brain injury in the kinds of impacts that may occur. If it is too flexible or soft, it might not protect the user in a violent, high-energy crash. For military applications, the requirements for helmet performance may be even more demanding. Not only do helmets have to protect a Soldier’s head from blunt impacts, but helmets also are expected to provide mounting platforms for ancillary devices and to function in ballistic and blast events as well.
Liquid Micro-Jet Array Impingement Cooling for Large Area Systems
Authors: Bhunia Avijit , Chen C. L.
Published: June 2010

The necessity for high heat flux cooling over large areas is growing rapidly with the increasing push towards more electric systems. A significant amount of research over the past two decades has conclusively proved the suitability of impingement cooling, such as jet and droplet array, spray, etc. However all these works are focused on a small heat source area, typically about a few cm2. Can a large array of impingement pattern covering a much wider area achieve similar heat flux levels? In pursuit of an answer, this article presents liquid micro-jet array impingement cooling of a heat source that is about two orders of magnitude larger in size compared to the previous works. Experiments are carried out with 441 jets of water and dielectric liquid HFE7200, each 200 μm diameter, impinging on a 189 cm2 area surface, in free surface and confined jet configurations. The measured values of average heat transfer coefficient are compared with correlations from the literature. While some correlations show excellent agreement, others deviate significantly. The ensuing discussion suggests that the post impingement liquid dynamics, particularly the collision between the liquid fronts on the surface created from surrounding jets, is the most important criterion dictating the average heat transfer coefficient. Thus, similar thermal performance can be achieved irrespective of the length scale, as long as the flow dynamics are similar. These results decisively prove the scalability of the liquid micro-jet array impingement technique for cooling a few cm2 area to 100s of cm2 area.
Computational Fluid Dynamics Applicable to Cloth Design
Authors: Cunha Ana M. F. , Teixeira Jose´ C. F. , Teixeira Senhorinha F. C. F.
Published: June 2010

Increasingly, different concepts such as safety, hygiene and comfort interact in the characterization of the workplaces. Being comfortable during periods of low activity, seems to be a requirement for most people and, secondly, in other sectors where performance is critical, the priorities are different. In both cases, the intellectual and physical performance is strongly affected by the sensation of thermal comfort. Thus, various approaches can be applied to provide comfort, for example, in the design of buildings and the selection of appropriate clothing. Comfortable clothing is a complex and interdisciplinary concept, consisting of a balance of the sensorial, psychological and physiological aspects [1, 2]. In objective terms, the behavior of the human body depends on several factors: temperature, air velocity and humidity, production of metabolic heat and clothing insulation. All these factors determine the heat and mass transfer processes between the human body and the environment. The Computational Fluid Dynamics (CFD) numerical simulation has been a powerful tool in this investigation field. A combined simulation of a room and a thermal manikin has been developed in the FLUENT code. Using a manikin with real dimensions, divided into parts with different temperatures, seems important to give accurate fluid flow and moisture distributions.
Modeling and Dynamic Control of a Bioreactor for Glycerin Conversion to 1,3 Propanediol
Authors: Villalba Pedro , San-Juan-Vergara Homero , Sanjuan Marco
Published: June 2010

The increasing production of biodiesel generates high quantities of glycerin as major co-product in the process. The potential use of glycerol includes pharmaceutical, cosmetics and food industries; furthermore, its bioconversion to 1,3 propanediol (PDO) represents a novel application in biopolymers area. This investigation focuses on the development of a dynamic model and control of 1,3 PDO production from residual glycerol of biodiesel process by Clostridium diolis strain in a continuous bioreactor. The biological conversion was simulated using the Monod model with product inhibition factor and includes temperature and Ph influence on biomass growth rate. Dynamic behavior of the bioreactor showed a maximum mass flow of 1,3 PDO equal to 79.95 mM*h−1 with a dilution rate 0.23 h−1, while the maximum concentration of the product 539.5 mM*L−1 was achieved with 0.1 h−1 as dilution rate. Based on the model evaluated, two control strategies were implemented, a proportional integral control (PI) and a dynamic matrix control (DMC), its performance was compared using the integral of the absolute error (IAE) at four operating conditions; the results showed IAE values of 13.5 and 53.4 for the best DMC performance (λ = 1) and for the PID 11.9 and 54.8. Also, the integral of the average valve signal (IMV) was evaluated showing a 40% reduction for DMC performance respect to PID performance, improving as well the use of the control valve during continuous operation.
Study and Development of Spacers for Pressurized Inhaler Devices: A Project Review
Authors: Silva Lui´s F. , Teixeira Senhorinha , Teixeira Jose´ Carlos , Rebelo Rita , Oliveira Ricardo , Antunes Henedina
Published: June 2010

In recent years, allergic diseases, particularly asthma, have been acquiring an increasing importance in the developed countries, due to the rising of its prevalence and morbidity and the economic burden associated, becoming a serious public health problem. Recent therapeutic approaches in asthma patients may help to prevent most of the crisis and remain free of symptoms. Several inhalation devices are available for drug delivery to the lungs, including metered-dose inhalers (MDIs), dry powder inhalers (PDIs) and nebulizers. Although this variety of devices used for drug delivery to the bronchial tree have shown encouraging results, a great amount of the drug does not reach the goal and remains in the mouth (less than 20% of the drug can reach the lungs) and higher airways. This causes not only a loss of drug but also increases costs and produces undesirable side effects. For better efficiency of the process, spacers, such as the Volumatic® used in the study herein reported, are used. This paper will describe and summarize part of the developments being carried out so far at the University of Minho in this domain, as well as the latest developments in order to understand the characteristics of the used spacer and the parameters affecting its performance. By using computational fluid Dynamics (CFD) techniques, the behavior of the drug flow inside the spacer, combined with a pressurized metered-dose inhaler (pMDI), the discrete phase model (DPM) flow inside the Volumatic® is also reported. The results obtained are also analyzed and discussed, using two different 3D grid types (Cooper and T-Grid). The insight provided by the detailed data of the flow patterns inside the Volumatic® provides possible options for new geometry possibilities for the spacer devices.
The Effect of the Frontal Plane Tibiofemoral Angle on the Stress and Strain at the Knee Cartilage During the Stance Phase of the Gait Cycle
Authors: Yang Nicholas , Nayeb-Hashemi Hamid , Canavan Paul
Published: June 2010

Three-dimensional (3-D) finite element analysis (FEA) knee models were created to determine the effect of the frontal plane tibiofemoral angle on the stress and strain at the knee cartilage during the stance phase of the gait cycle. Knee models of three healthy subjects of different tibiofemoral angles and weight were created from sagittal view magnetic resonance images (MRI) of the knee. The loading conditions were determined from motion analysis and force platform data and a muscle force reduction model. During the stance phase, the subjects exhibited a valgus-varus-valgus knee moment pattern that determined the location and magnitude of the maximum stress and strain in the cartilage on the lateral or medial compartment of the knee. The highest values of the normal stress, Tresca shear stress and normal strain for each subject occurred at 25% of the stance phase of the gait cycle, where the maximum compressive load and varus knee moment occurred. The individual with the varus aligned knee had the largest stress and strain at the medial compartment of the knee compared to the normal aligned and valgus aligned individuals due to the larger varus knee moment exhibited during the stance phase of the gait cycle in the varus aligned individual. The results from the FEA data may be used by health care professional to identify individuals most susceptible to knee osteoarthritis (OA) and assist in developing preventive measure to slow and possibly stop the initiation and progression of OA.
NOCing PPAR-γ into the Nucleus?
Authors: Adler Elizabeth M.
Published: June 2010

Nocturnin promotes the nuclear translocation of PPAR-γ2 and thereby adipogenesis.
Platelet NF-κB–PKA Complex
Authors: Gough Nancy R.
Published: June 2010

Platelet aggregation is kept in check by inhibitory signaling from protein kinase A released from the IKK (inhibitor of nuclear factor κB kinase) complex.
Too Much of a Good Thing
Authors: Hines Pamela J.
Published: June 2010

To prevent too much myelin from causing trouble, two proteins act to limit insulation of axons.
Complete Nucleotide Sequence of
Klebsiella pneumoniae
Multidrug Resistance Plasmid pKP048, Carrying
bla
KPC-2
,
bla
DHA-1
,
qnrB4
, and
armA
Authors: Jiang Yan , Yu Dongliang , Wei Zeqing , Shen Ping , Zhou Zhihui , Yu Yunsong
Published: June 2010

The
Klebsiella pneumoniae
multidrug resistance plasmid pKP048 was completely sequenced. This plasmid carries several important resistance determinants, such as
bla
KPC-2
,
bla
DHA-1
,
qnrB4
, and
armA
, which confer resistance to carbapenems, cephalosporins, fluoroquinolones, and aminoglycosides, respectively. Analysis of the finished 151,188-bp sequence data revealed 163 putative genes, 108 of which were assigned functions such as replication, stable inheritance, antibiotic resistance, a mobile element, conjugal transfer, and a restriction-modification system, showing the strong phylogenetic mosaicism and plasticity of the plasmid.
Underestimation of Vancomycin and Teicoplanin MICs by Broth Microdilution Leads to Underdetection of Glycopeptide-Intermediate Isolates of
Staphylococcus aureus
Authors: Vaudaux Pierre , Huggler Elzbieta , Bernard Louis , Ferry Tristan , Renzoni Adriana , Lew Daniel P.
Published: June 2010

Broth microdilution was compared with tube macrodilution and a simplified population analysis agar method for evaluating vancomycin and teicoplanin MICs and detecting glycopeptide-intermediate isolates of
Staphylococcus aureus
. Modal vancomycin and teicoplanin MICs recorded by tube macrodilution and the agar plate assay, which both used inocula of 10
6
CFU, were significantly higher (2 μg/ml) against a panel of borderline glycopeptide-susceptible and glycopeptide-intermediate methicillin-resistant
S. aureus
(MRSA) bloodstream isolates compared to broth microdilution (1 μg/ml). Vancomycin and teicoplanin MIC distributions by tube macrodilution and agar testing were also markedly different from those evaluated by broth microdilution. The 20-fold-lower inoculum size used for broth microdilution compared to macrodilution and agar MIC assays explained in part, but not entirely, the systematic trend toward lower vancomycin and teicoplanin MICs by microdilution compared to other methods. Broth microdilution assay led to underdetection of the vancomycin-intermediate
S. aureus
(VISA) phenotype, yielding only three VISA isolates, for which vancomycin MICs were 4 μg/ml compared to 8 and 19 VISA isolates detected by macrodilution and agar testing, respectively. While macrodilution and agar testing detected 7 and 22 isolates with elevated teicoplanin MICs (8 μg/ml), respectively, broth microdilution failed to detect such isolates. Detection rates of isolates with elevated vancomycin and teicoplanin MICs by macrodilution and agar testing assays were higher at 48 h than at 24 h. In conclusion, the sensitivity of broth microdilution MIC testing is questionable for reliable detection and epidemiological surveys of glycopeptide-intermediate resistance in
S. aureus
isolates.
A Clinical Isolate of
Candida albicans
with Mutations in
ERG11
(Encoding Sterol 14α-Demethylase) and
ERG5
(Encoding C22 Desaturase) Is Cross Resistant to Azoles and Amphotericin B
Authors: Martel Claire M. , Parker Josie E. , Bader Oliver , Weig Michael , Gross Uwe , Warrilow Andrew G. S. , Kelly Diane E. , Kelly Steven L.
Published: June 2010

A clinical isolate of
Candida albicans
was identified as an
erg5
(encoding sterol C22 desaturase) mutant in which ergosterol was not detectable and ergosta 5,7-dienol comprised >80% of the total sterol fraction. The mutant isolate (CA108) was resistant to fluconazole, voriconazole, itraconazole, ketoconazole, and clotrimazole (MIC values, 64, 8, 2, 1, and 2 μg ml
−1
, respectively); azole resistance could not be fully explained by the activity of multidrug resistance pumps. When susceptibility tests were performed in the presence of a multidrug efflux inhibitor (tacrolimus; FK506), CA108 remained resistant to azole concentrations higher than suggested clinical breakpoints for
C. albicans
(efflux-inhibited MIC values, 16 and 4 μg ml
−1
for fluconazole and voriconazole, respectively). Gene sequencing revealed that CA108 was an
erg11 erg5
double mutant harboring a single amino acid substitution (A114S) in sterol 14α-demethylase (Erg11p) and sequence repetition (10 duplicated amino acids), which nullified C22 desaturase (Erg5p) function. Owing to a lack of ergosterol, CA108 was also resistant to amphotericin B (MIC, 2 μg ml
−1
). This constitutes the first report of a
C. albicans erg5
mutant isolated from the clinic.
Staphylococcus aureus
TargetArray: Comprehensive Differential Essential Gene Expression as a Mechanistic Tool To Profile Antibacterials
Authors: Xu H. Howard , Trawick John D. , Haselbeck Robert J. , Forsyth R. Allyn , Yamamoto Robert T. , Archer Rich , Patterson Joe , Allen Molly , Froelich Jamie M. , Taylor Ian , Nakaji Danny , Maile Randy , G. C. Kedar , Pilcher Marshall , Brown-Driver Vickie , McCarthy Melissa , Files Amy , Robbins David , King Paula , Sillaots Susan , Malone Cheryl , Zamudio Carlos S. , Roemer Terry , Wang Liangsu , Youngman Philip J. , Wall Daniel
Published: June 2010

The widespread emergence of antibiotic-resistant bacteria and a lack of new pharmaceutical development have catalyzed a need for new and innovative approaches for antibiotic drug discovery. One bottleneck in antibiotic discovery is the lack of a rapid and comprehensive method to identify compound mode of action (MOA). Since a hallmark of antibiotic action is as an inhibitor of essential cellular targets and processes, we identify a set of 308 essential genes in the clinically important pathogen
Staphylococcus aureus
. A total of 446 strains differentially expressing these genes were constructed in a comprehensive platform of sensitized and resistant strains. A subset of strains allows either target underexpression or target overexpression by heterologous promoter replacements with a suite of tetracycline-regulatable promoters. A further subset of 236 antisense RNA-expressing clones allows knockdown expression of cognate targets. Knockdown expression confers selective antibiotic hypersensitivity, while target overexpression confers resistance. The antisense strains were configured into a TargetArray in which pools of sensitized strains were challenged in fitness tests. A rapid detection method measures strain responses toward antibiotics. The TargetArray antibiotic fitness test results show mechanistically informative biological fingerprints that allow MOA elucidation.