bluuebunny/crossref_metadata_2025 huggingface dataset:
Discordant cellular and organ transplantation from bench to bedside
Authors: Reichart Bruno
Published: April 2014

It is more than 1 year since our Consortium commenced. The following abstracts provide an account of what has been achieved so far and document our understanding of xenotransplantation and some of our future strategies:

Since (microencapsulated) islets are the first in the clinic, our basic research focuses on immediate (innate) rejection reactions and means of counteracting them. Once transplanted and working, porcine and primate islets may respond differently, for example to glucose challenges.

We will gain preclinical experience regarding the safety of genetically modified islets as quickly as possible.

We are currently in dialogue with German authorities (Paul‐Ehrlich‐Institution as representative of the European Medicines Agency) to decide how best to formulate a successful clinical application within European standards.

Are there any ethical objections from within German society? A recent 3‐day meeting, held at the Munich Catholic Academy explored the issues, including opinions from the Jewish and Islamic communities. In brief, the outcome revealed no major objections as long as xenogeneic procedures are safe and effective. All talks will be published in German, with abstracts in English. There will also be an English review of the meeting possibly published in the journal Xenotransplantation.

Successful preclinical organ (heart, kidney) xenotransplantation is still difficult to achieve. Heterotopic thoracic (working) heart transplantation has been established with consistent results. It seems that hyperacute and delayed humoral rejection reactions are manageable; but thrombotic microangiopathy currently presents the main obstacle. Porcine hearts that express human thrombomodulin will be used next, together with complement antibodies and/or co‐stimulation blockade. Human thrombomodulin has provided promising results in the laboratory (cell based).

Porcine heart valves will be tested using single and multiple antigen knock out.

In conclusion, the German Xenotransplantation Consortium supported by the German Research Foundation (DFG) is on track for a successful (first?) period. There seems to be broad support from a majority of German cardiovascular surgeons, and this is spreading to those in other parts of Europe [1].

Reference

[1] Reichart B., Guethoff S., Mayr T. et al. Discordant cardiac xenotransplantation – broadening the horizons. Eur J Cardiothorac Surg 2013; Epub ahead of print.
After decellularization of porcine heart valves: no non‐Gal antigeneic epitopes detectable by non conditioned human sera
Authors: Ramm Robert , Hilfiker Andres
Published: April 2014

Background

Patients that undergo heart valve replacement surgery with glutaraldehyde fixated porcine grafts do not face acute rejection as recipients of native porcine organs and tissues do, however, grafts calcify over time and fail after 10–20 years in adults and 3–4 years in children. Responsible for hyperacute and acute rejection of unfixated tissue are preformed antibodies that recognize xenoantigens. Major targets are carbohydrates like the αGal epitope or Neu5Gc linked to proteins as well as to lipids on cells and extracellular matrix. To overcome the limited availability of decellularized allogeneic heart valve grafts, which show the ability to remodel and to grow by ingrowth of autologous cells, a characteristics lacking in glutaraldehyde fixated heart valve grafts, we want to develop a porcine derived decellularized matrix that is well tolerated in humans.

Methods

The generation of such optimal porcine heart valves matrices is dependent on a successful elimination of bound xenoantigens. To quantify the amount of xenoantigens present on decellularized matrix, we established an inhibition ELISA by exposing human IgG to crushed matrix and measuring unbound IgG in an ELISA set up. High levels of measured IgG means low levels of xenoantigens present on the decelllularized matrix. To enhance the specificity of IgG tested in the ELISA, human sera were perfused through porcine kidneys, followed by intensive washing and elution of bound xenoantibodies. Total amount of IgG and αGal specific antibodies was monitored to control the purification steps. Inhibition ELISA was performed with matrices derived from Landrace pigs, GalT‐KO pigs and humans. Binding of total IgG as well as αGal specific antibodies was assayed.

Results

The amount of total IgG binding correlates with the amount of αGal specific antibodies binding to decellularized porcine matrix indicating the presence of remaining αGal epitopes on the porcine matrix after decellularization. However, decellularized GalT‐KO pig and decellularized human matrix showed no binding of αGal specific antibodies and comparable amounts of total IgG binding.

Conclusion

Our results indicate that only αGal epitopes present on decellularized porcine heart valve matrixes are recognized by preformed xenoantibodies while no other xenoantigens are detected. Therefore, further evaluation focusing on induction of immunogeneic reactions has to be conducted in an in vivo model like the humanized mouse utilizing decellularized heart valve material derived from GalT‐KO pigs.
Generation of transgenic pigs carrying siRNA vector directed against human tissue factor expression
Authors: Ahrens Hellen , Petersen Björn , Herrmann Doris , Lucas‐Hahn Andrea , Hassel Petra , Ziegler Maren , Kues Wilfried , Niemann Heiner
Published: April 2014

Background

The acute vascular rejection (AVR) is the major obstacle to successful pig‐to‐primate xenotransplantation. Changes of the endothelium to a procoagulant state which occur after xenotransplantation entail an increased expression of Tissue Factor (TF). This initiates the extrinsic coagulation cascade and results in microvascular thrombosis and rapid loss of organ function. Organs from pigs with a decreased expression of TF could be promising to overcome AVR. Since a homozygous TF knockout had shown to be lethal in mice [1], we decided to use siRNA‐technology to knockdown TF to a basal level.

Methods

Different siRNAs directed against TF expression were tested in initial studies for their efficacy. A vector coding for the siRNA providing the highest decrease of TF mRNA levels was kindly provided by Dr. Joachim Denner, RKI Berlin. Porcine fetal fibroblasts were co‐transfected with this plasmid and a vector (DsRed, Clontech) which confers neomycin resistance and red fluorescence. After 14 days of selection with 800 μg/ml Geneticin (G418), cells were screened for siRNA expression prior to somatic cell nuclear transfers (SCNTs). Subsequently, the reconstructed embryos were transferred to synchronised recipient sows. Liveborn offspring were analysed by real‐time PCR for TF mRNA quantification. The production of the siRNA was detected via RT‐PCR followed by real‐time PCR.

Results

An average of 95 embryos per sow was transferred to 28 synchronized recipients. The pregnancy rate was 54%. One sow was sacrificed on day 25 of pregnancy and one fetus (#893/1) was obtained. The candidate siRNA could be detected fetal tissues. Real‐time PCR analysis revealed decreased TF mRNA expression in fibroblasts of fetus #893/1 compared to wild‐type fibroblasts. Therefore, somatic cells from fetus #893/1 was used for recloning. A total of 12 live born piglets could be obtained; five piglets died within few days after delivery. The mRNA levels and production of the siRNA are currently determined. Protein expression analysis by fluorescence cytometry and functionality assessment by coagulation assays are planned for the near future with collaborating laboratories at the Medical School Hannover.

Conclusions

The AVR is currently the bottleneck in porcine‐to‐primate organ xenotransplantation. Controlling TF‐induced coagulation might provide protective effects for porcine xenografts. Thus, TF knockdown pigs could be critical in producing the ultimate multi‐transgenic pig as organ donor for human patients.

References

[1] Toomey J, Kratzer K, Lasky N, Stanton J, Broze GJ. Targeted disruption of the murine tissue factor gene results in embryonic lethality. Blood. 1996; 88(5): 1583–1587.
Early islet xenograft dysfunction in humanized mice
Authors: Reinke Soeren , Ludwig Barbara , Chavakis Triantafyllos , Waskow Claudia
Published: April 2014

Allogeneic transplantation of human islets improves metabolic control in patients that suffer from type 1 diabetes but is limited by the supply of sufficient numbers of human donor islets. Therefore, the xenogenic transplantation of porcine islets potentially represents an attractive alternative. The immediate blood‐mediated inflammatory reaction (IBMIR) that results in early graft rejection is one of the major hurdles preventing xenotransplantation from clinical applications. Thus, characterizing and modulating IBMIR could be the key to realize clinical porcine islet transplantation. IBMIR is mediated by multiple components of the innate immune system and in order to assess composition and function of distinct myeloid cell types involved in the rejection process, we established a humanized mouse model to study IBMIR in vivo. We combined immune deficient mice that lack T, B, and NK cells with a mutant Kit receptor affecting the function of HSCs allowing for robust engraftment of HSCs and mature myeloid cells types over long periods of time. We could show that human myeloid cells repopulate peripheral organs such as spleen and liver – a prerequisite for the study of IBMIR in a humanized mouse model. We will now engage these mice to transplant porcine islets into the liver via the portal vein to induce immediate rejection of the graft. In this scenario presence of human myeloid cells in the liver of our new mouse model will facilitate a detailed characterization of the human IBMIR against pig islets and will also allow attempts to suppress this immune reaction by specific targeting of human leukocytes.
Study of Economic Feasibility to Recharge Different Types of Electric Vehicles With Photovoltaic Solar Panels
Authors: Valero Verdú Sergio , Senabre Blanes Carolina , López Sánchez Demetrio
Published: April 2014

The article presents an economical study of the use of electric vehicles (Evs) in terms of years of amortization money saved and cost and expenses, etc. It has been compared combustion vehicles with the electric counterparts in terms of power and features appreciated by the user in the automobile market. The purpose of the study was to analyze the feasibility to recharge different electric vehicles by solar photovoltaic modules, so that energy generation would not contribute to any CO2 emissions, when the system would be installed and ready to supply these vehicles. The study also shows a comparative analysis of the cost of purchasing electricity to the distributor compared with the using of a photovoltaic system designed to recharge the vehicle, even it has also been calculated the depreciation. Finally, it has been analyzed comparatively the type of the solar photovoltaic system considered more economically viable for recharging a pure EV, therefore it has been compared projects on houses and on a parking to recharge several vehicles.
Comparison of Warpage Measurement Capabilities and Results Obtained by Using Laser and Digital Fringe Projection Methods
Authors: Kang Sungbum , Charles Ume I.
Published: April 2014

Electronic packaged devices are becoming increasingly smaller in size and higher in density while requiring higher performance and superior reliability. Warpage is one of the crucial factors for the thermomechanical reliability of electronic packages and warpage control becomes a more crucial process during the printed wiring board (PWB) fabrication and package assembly processes. This requirement necessitates more accurate methods of measuring warpage. The fringe projection methods are recent trends for measuring the warpage of chip packages, PWBs, and PWB assemblies (PWBAs) because of their noncontact, full-field, and high-resolution measurement capabilities. This paper presents a comparison of two fringe projection methods: laser fringe projection (LFP) (projection moiré) and digital fringe projection (DFP). Experimental results show that digital fringe projection has higher practical resolution, and better accuracy and precision than laser fringe projection.
Effect of Weld Residual Stress Fitting on Stress Intensity Factor for Circumferential Surface Cracks in Pipe
Authors: Shim Do-Jun , Xu Steven , Kerr Matthew
Published: April 2014

Recent studies have shown that the crack growth of primary water stress corrosion cracking (PWSCC) is mainly driven by the weld residual stress (WRS) within the dissimilar metal weld. The existing stress intensity factor (K) solutions for surface cracks in pipe typically require a fourth order polynomial stress distribution through the pipe wall thickness. However, it is not always possible to accurately represent the through thickness WRS with a fourth order polynomial fit and it is necessary to investigate the effect of the WRS fitting on the calculated Ks. In this paper, two different methods were used to calculate the K for a semi-elliptical circumferential surface crack in a pipe under a given set of simulated WRS. The first method is the universal weight function method (UWFM) where the through thickness WRS distribution is represented as a piece-wise monotonic cubic fit. In the second method, the through thickness WRS profiles are represented as a fourth order polynomial curve fit (both using the entire wall thickness data and only using data up to the crack-tip). In addition, three-dimensional finite element (FE) analyses (using the simulated weld residual stress) were conducted to provide a reference solution. The results of this study demonstrate the potential sensitivity of Ks to fourth order polynomial fitting artifacts. The piece-wise WRS representations used in the UWFM were not sensitive to these fitting artifacts and the UWFM solutions were in good agreement with the FE results. In addition, in certain cases, it was demonstrated that more accurate crack growth calculations of PWSCC are made when the UWFM is used.
On the Mechanics of Fatigue and Fracture in Teeth
Authors: Yahyazadehfar Mobin , Ivancik Juliana , Majd Hessam , An Bingbing , Zhang Dongsheng , Arola Dwayne
Published: April 2014

Tooth fracture is a major concern in the field of restorative dentistry. However, knowledge of the causes for tooth fracture has developed from contributions that are largely based within the field of mechanics. The present manuscript presents a technical review of advances in understanding the fracture of teeth and the fatigue and fracture behavior of their hard tissues (i.e., dentin and enamel). The importance of evaluating the fracture resistance of these materials, and the role of applied mechanics in developing this knowledge will be reviewed. In addition, the complex microstructures of tooth tissues, their roles in resisting tooth fracture, and the importance of hydration and aging on the fracture resistance of tooth tissues will be discussed. Studies in this area are essential for increasing the success of current treatments in dentistry, as well as in facilitating the development of novel bio-inspired restorative materials for the future.
Analytical and Experimental Investigation of Thermocapillary Flow in Pulsed Laser Micropolishing
Authors: Ma Chao , Vadali Madhu , Li Xiaochun , Duffie Neil A. , Pfefferkorn Frank E.
Published: April 2014

The objective of this paper is to define and derive a dimensionless number as a function of material properties and process parameters to quantify the extent (magnitude) of thermocapillary flow in pulsed laser micropolishing (PLμP). Experimental work has shown that thermocapillary flow can tremendously reduce surface roughness (smoothing effect) although it inevitably introduces additional surface features (roughening effect) at the same time. Both the smoothing and roughening effects increase as the extent of thermocapillary flow increases. The extent of thermocapillary flow is the bridge from the available information (i.e., initial surface profile, material properties, and process parameters) to the polished surface profile to be predicted. A dimensionless number, called the normalized average displacement of a liquid particle in a single laser pulse, is proposed and derived via analytical heat transfer and fluid flow equations. The calculated normalized displacement is found to be proportional to the measured slope of the introduced features on Ti6Al4V surface polished with various process parameters, which indicates that the dimensionless number successfully describes the extent of thermocapillary flow. The normalized average displacement will be very useful for prediction of polished surface profile and hence parameter selection and process optimization in the future.
Modeling of Two-Phase Evaporative Heat Transfer in Three-Dimensional Multicavity High Performance Microprocessor Chip Stacks
Authors: Madhour Yassir , d'Entremont Brian P. , Braz Marcinichen Jackson , Michel Bruno , Richard Thome John
Published: April 2014

Three-dimensional (3D) stacking of integrated-circuit (IC) dies increases system density and package functionality by vertically integrating two or more dies with area-array through-silicon-vias (TSVs). This reduces the length of global interconnects and the signal delay time and allows improvements in energy efficiency. However, the accumulation of heat fluxes and thermal interface resistances is a major limitation of vertically integrated packages. Scalable cooling solutions, such as two-phase interlayer cooling, will be required to extend 3D stacks beyond the most modest numbers of dies. This paper introduces a realistic 3D chip stack along with a simulation method for the heat spreading and flow distribution among the channels of the evaporators. The model includes the significant sensitivity of each channel's friction factor to vapor quality, and hence mass flow to heat flux, which characterizes parallel two-phase flows. Simulation cases explore various placements of hot spots within the stack and effects which are unique to two-phase interlayer cooling. The results show that the effect of hot spots on individual dies can be mitigated by strong interlayer heat conduction if the relative position of the hot spots is selected carefully to result in a heat load and flow which are well balanced laterally.
Use of ANCF Surface Geometry in the Rigid Body Contact Problems: Application to Railroad Vehicle Dynamics
Authors: Hamper Martin B. , Wei Cheng , Shabana Ahmed A.
Published: April 2014

In the analysis of multibody system (MBS) dynamics, contact between two arbitrary rigid bodies is a fundamental feature in a variety of models. Many procedures have been proposed to solve the rigid body contact problem, most of which belong to one of the two categories: offline and online contact search methods. This investigation will focus on the development of a contact surface model for the rigid body contact problem in the case where an online three-dimensional nonconformal contact evaluation procedure, such as the elastic contact formulation—algebraic equations (ECF-A), is used. It is shown that the contact surface must have continuity in the second-order spatial derivatives when used in conjunction with ECF-A. Many of the existing surface models rely on direct linear interpolation of profile curves, which leads to first-order spatial derivative discontinuities. This, in turn, leads to erroneous spikes in the prediction of contact forces. To this end, an absolute nodal coordinate formulation (ANCF) thin plate surface model is developed in order to ensure second-order spatial derivative continuity to satisfy the requirements of the contact formulation used. A simple example of a railroad vehicle negotiating a turnout, which includes a variable cross-section rail, is tested for the cases of the new ANCF thin plate element surface, an existing ANCF thin plate element surface with first-order spatial derivative continuity, and the direct linear profile interpolation method. A comparison of the numerical results reveals the benefits of using the new ANCF surface geometry developed in this investigation.
Numerical Synthesis of Six-Bar Linkages for Mechanical Computation
Authors: Plecnik Mark M. , Michael McCarthy J.
Published: April 2014

This paper presents a design procedure for six-bar linkages that use eight accuracy points to approximate a specified input–output function. In the kinematic synthesis of linkages, this is known as the synthesis of a function generator to perform mechanical computation. Our formulation uses isotropic coordinates to define the loop equations of the Watt II, Stephenson II, and Stephenson III six-bar linkages. The result is 22 polynomial equations in 22 unknowns that are solved using the polynomial homotopy software Bertini. The bilinear structure of the system yields a polynomial degree of 705,432. Our first run of Bertini generated 92,736 nonsingular solutions, which were used as the basis of a parameter homotopy solution. The algorithm was tested on the design of the Watt II logarithmic function generator patented by Svoboda in 1944. Our algorithm yielded his linkage and 64 others in 129 min of parallel computation on a Mac Pro with 12 × 2.93 GHz processors. Three additional examples are provided as well.
Development and Validation of Endovascular Chemotherapy Filter Device for Removing High-Dose Doxorubicin: Preclinical Study
Authors: Patel Anand S. , Saeed Maythem , Yee Erin J. , Yang Jeffrey , Lam Gregory J. , Losey Aaron D. , Lillaney Prasheel V. , Thorne Bradford , Chin Albert K. , Malik Sheena , Wilson Mark W. , Chen Xi C. , Balsara Nitash P. , Hetts Steven W.
Published: April 2014

To develop a novel endovascular chemotherapy filter (CF) able to remove excess drug from the blood during intra-arterial chemotherapy delivery (IAC), thus preventing systemic toxicities and thereby enabling higher dose IAC. A flow circuit containing 2.5 mL of ion-exchange resin was constructed. Phosphate-buffered saline (PBS) containing 50 mg doxorubicin (Dox) was placed in the flow model with the hypothesis that doxorubicin would bind rapidly to resin. To simulate IAC, 50 mg of doxorubicin was infused over 10 min into the flow model containing resin. Similar testing was repeated with porcine serum. Doxorubicin concentrations were measured over 60 min and compared to controls (without resin). Single-pass experiments were also performed. Based on these experiments, an 18F CF was constructed with resin in its tip. In a pilot porcine study, the device was deployed under fluoroscopy. A control hepatic doxorubicin IAC model (no CF placed) was developed in another animal. A second CF device was created with a resin membrane and tested in the infrarenal inferior vena cava (IVC) of a swine. In the PBS model, resin bound 76% of doxorubicin in 10 min, and 92% in 30 min (P < 0.001). During IAC simulation, 64% of doxorubicin bound in 10 min and 96% in 60 min (P < 0.001). On average, 51% of doxorubicin concentration was reduced during each pass in single pass studies. In porcine serum, 52% of doxorubicin bound in 10 min, and 80% in 30 min (P < 0.05). CF device placement and administration of IAC were successful in three animals. No clot was present on the resin within the CF following the in vivo study. The infrarenal IVC swine study demonstrated promising results with up to 85% reduction in peak concentration by the CF device. An endovascular CF device was developed and shown feasible in vitro. An in vivo model was established with promising results supporting high-capacity rapid doxorubicin filtration from the blood that can be further evaluated in future studies.
Axisymmetric Elastoplasticity of a Temperature-Sensitive Functionally Graded Cylindrical Vessel
Authors: Sadeghian Mojtaba , Ekhteraei Toussi Hamid
Published: April 2014

Based on the small deformation theory and Tresca's yield criterion an axisymmetric, plane strain, elastoplastic, thermal stress analysis for a cylindrical vessel made of functionally graded elastic, perfectly plastic material is offered. Elastic modulus and yield strength coefficients are assumed to be power functions of radius and linear functions of temperature. A cylindrical vessel is taken to be composed of two or more nested fully elastic and perfectly plastic cylinders. By comparing the values of the deformation or stress components in the interfaces of the neighboring cylinders, a system of equations is formed. The interfacial boundary values of the fully elastic or perfectly plastic regions are obtained by simultaneous solution of the resulting interfacial consistency conditions. Having prepared the closed form solutions for the stress fields in purely elastic and purely plastic regions, the distribution of stress throughout the vessel can be obtained. Using this model, in some sample problems, the influences of temperature and pressure on the stress, strain, and plastic zone patterns are studied. The location of plastic zones is obtained for a class of material property compositions.
Natural Convection Heat Transfer Enhancement in a Differentially Heated Parallelogrammic Enclosure Filled With Copper-Water Nanofluid
Authors: Hadi Hussain Salam , Kadhim Hussein Ahmed
Published: April 2014

Laminar natural convection of a nanofluid consists of water and copper in a differentially heated parallelogrammic enclosure has been studied numerically using the finite volume method (FVM). Governing equations are solved over a wide range of Rayleigh numbers (104 ≤ Ra ≤ 106), skew angles (−60 deg ≤ Φ ≤ +60 deg), aspect ratios (0.5 ≤ AR ≤ 4), and solid volume fractions (0 ≤ φ ≤ 0.2). Effects of all these parameters on flow and thermal fields are presented in form of streamline, isotherm contours and average Nusselt number. It is shown that the heat transfer rate increases remarkably by the addition of copper-water nanofluid and the shape of the convection vortices is sensitive to the skew angle variation.
Insights Into Flexoelectric Solids From Strain-Gradient Elasticity
Authors: Mao Sheng , Purohit Prashant K.
Published: April 2014

A material is said to be flexoelectric when it polarizes in response to strain gradients. The phenomenon is well known in liquid crystals and biomembranes but has received less attention in hard materials such as ceramics. Here we derive the governing equations for a flexoelectric solid under small deformation. We assume a linear constitutive relation and use it to prove a reciprocal theorem for flexoelectric materials as well as to obtain a higher-order Navier equation in the isotropic case. The Navier equation is similar to that in Mindlin's theory of strain-gradient elasticity. We also provide analytical solutions to several boundary value problems. We predict size-dependent electromechanical properties and flexoelectric modulation of material behavior. Our results can be used to interpret experiments on flexoelectric materials which are becoming increasingly sophisticated due to the advent of nanoscale probes.
An Improved Reliability Analysis Method for Mooring Dolphin Structures
Authors: Farag Reda , Haldar Achintya , El-Meligy Mahmoud
Published: April 2014

A novel reliability evaluation procedure is proposed for analysis and design of offshore mooring dolphin structures (MDS). It is a hybrid approach consisting of an improved response surface method (IRSM), second-order reliability method (SORM), and several advanced factorial schemes. It is denoted as IRSM-SORM. Several schemes of IRSM-SORM are proposed and clarified with the help of an illustrative example.
Rigid-Object Water-Entry Impact Dynamics: Finite-Element/Smoothed Particle Hydrodynamics Modeling and Experimental Validation
Authors: Challa Ravi , Yim Solomon C. , Idichandy V. G. , Vendhan C. P.
Published: April 2014

A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project to determine the maximum force for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element (FE) arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle, and object weight. The numerical results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered, and the impact acceleration varies practically linearly with increase in drop height. In view of the good comparison between the experimental and numerical simulations, both models can readily be employed for parametric studies and for studying the prototype splashdown under more realistic field conditions in the oceans.
Steady-State Responses of Pulley-Belt Systems With a One-Way Clutch and Belt Bending Stiffness
Authors: Ding Hu , Zu Jean W.
Published: April 2014

A nonlinear hybrid discrete-continuous dynamic model is established to analyze the steady-state response of a pulley-belt system with a one-way clutch and belt bending stiffness. For the first time, the translating belt spans in pulley-belt systems coupled with one-way clutches are modeled as axially moving viscoelastic beams. Moreover, the model considers the rotations of the driving pulley, the driven pulley, and the accessory. The differential quadrature and integral quadrature methods are developed for space discretization of the nonlinear integropartial-differential equations in the dynamic model. Furthermore, the four-stage Runge–Kutta algorithm is employed for time discretization of the nonlinear piecewise ordinary differential equations. The time series are numerically calculated for the driven pulley, the accessory, and the translating belt spans. Based on the time series, the fast Fourier transform is used for obtaining the natural frequencies of the nonlinear vibration. The torque-transmitting directional behavior of the one-way clutch is revealed by the steady-state of the clutch torque in the primary resonances. The frequency-response curves of the translating belt, the driven pulley, and the accessory show that the one-way clutch reduces the resonance of the pulley-belt system. Furthermore, the belt cross section's aspect ratio significantly affects the dynamic response.
Finite Element Analysis of the Seismic Response of Damped Structural Systems Including Fractional Derivative Models
Authors: Cortés Fernando , Jesús Elejabarrieta María
Published: April 2014

This paper presents a finite element formulation for the seismic response of damped structural systems. Damping is obtained using a viscoelastic material, which is characterized by a constitutive law with fractional derivatives. The weighted residue method is applied resulting in a fractional motion equation, which is numerically integrated through an implicit scheme in combination with the constant acceleration Newmark method. An example of application is presented, in which the response of a cantilever beam with free layer damping is analyzed. The material properties are identified from the material experimental characterization, where the parameters of the fractional model were identified by curve fitting. The results of the simulation are compared with the experimental ones, concluding that the tendencies observed in the measurements are reproduced.
Thermal Resistance Approach: An Engineering Tool for Improvement of Conductive Constructal Configurations
Authors: Eslami M. , Jafarpur K.
Published: April 2014

In the last decade, various conductive networks for cooling heat generating bodies have been proposed, analyzed, and optimized. Nevertheless, many of these studies have not been based on an analytical or mathematical formulation of the effective parameters. In this trend, a new geometry is assumed and analyzed (by analytical or numerical methods) hoping to decrease the total thermal resistance of the system. Therefore, the objective of the present paper is to illustrate how to analyze a conductive cooling network and improve it using the analytical procedures based on the general formulation of thermal resistance. As an example, the conventional rectangular elemental volumes with I shaped conductive link is modified to V shaped and pencil shaped designs and optimized analytically. Moreover, general expressions for optimum local thickness and thermal resistance of the links with variable cross section in an arbitrary network are provided. It is shown that improvements up to 50% can be achieved easily by simple geometrical changes if the designer is equipped with a profound knowledge of the important governing parameters.
Effect of Volatiles on Soot Based Deposit Layers
Authors: Salvi Ashwin , Hoard John , Bieniek Mitchell , Abarham Mehdi , Styles Dan , Assanis Dionissios
Published: April 2014

The implementation of exhaust gas recirculation (EGR) coolers has recently been a widespread methodology for engine in-cylinder NOx reduction. A common problem with the use of EGR coolers is the tendency for a deposit, or fouling layer to form through thermophoresis. These deposit layers consist of soot and volatiles and reduce the effectiveness of heat exchangers at decreasing exhaust gas outlet temperatures, subsequently increasing engine out NOx emission. This paper presents results from a novel visualization rig that allows for the development of a deposit layer while providing optical and infrared access. A 24 h, 379-micron-thick deposit layer was developed and characterized with an optical microscope, an infrared camera, and a thermogravimetric analyzer. The in situ thermal conductivity of the deposit layer was calculated to be 0.047 W/mK. Volatiles from the layer were then evaporated off and the layer reanalyzed. Results suggest that the removal of volatile components affect the thermophysical properties of the deposit. Hypotheses supporting these results are presented.
A State Space Method for Surface Instability of Elastic Layers With Material Properties Varying in Thickness Direction
Authors: Wu Zhigen , Meng Jixiang , Liu Yihua , Li Hao , Huang Rui
Published: April 2014

A state space method is proposed for analyzing surface instability of elastic layers with elastic properties varying in the thickness direction. By assuming linear elasticity with nonlinear kinematics, the governing equations for the incremental stress field from a fundamental state are derived for arbitrarily graded elastic layers subject to plane-strain compression, which lead to an eigenvalue problem. By discretizing the elastic properties into piecewise constant functions with homogeneous sublayers, a state space method is developed to solve the eigenvalue problem and predict the critical condition for onset of surface instability. Results are presented for homogeneous layers, bilayers, and continuously graded elastic layers. The state space solutions for elastic bilayers are in close agreement with the analytical solution for thin film wrinkling within the limit of linear elasticity. Numerical solutions for continuously graded elastic layers are compared to finite element results in a previous study (Lee et al., 2008, J. Mech. Phys. Solids, 56, pp. 858–868). As a semi-analytical approach, the state space method is computationally efficient for graded elastic layers, especially for laminated multilayers.
Thermal Simulations of Thermocouple Tips in Hot Jets
Authors: Etemad Sassan
Published: April 2014

Computational fluid dynamics (CFD) simulations have been carried out for the turbulent convective heat transfer, conduction and radiation for metal thermocouple tips, accommodated in hot gas jets to study the measurement accuracy of the thermocouples. The study covers several thermocouple sizes, jet temperatures, and Reynolds numbers. The spherical bead, representing the tip, becomes so hot that it radiates some heat to the colder surrounding surfaces. This phenomenon is responsible for a gap between the jet temperature and the bead temperature. The mentioned temperature difference is significant. It grows both with bead size and gas temperatures but decreases with the Reynolds number.
Analysis of an Early Intervention Tibial Component for Medial Osteoarthritis
Authors: Chaudhary M. E. , Walker P. S.
Published: April 2014

Tibial component loosening is an important failure mode in unicompartmental knee arthroplasty (UKA) which may be due to the 6–8 mm of bone resection required. To address component loosening and fixation, a new early intervention (EI) design is proposed which reverses the traditional material scheme between femoral and tibial components. The EI design consists of a plastic inlay for the distal femur and a thin metal plate for the proximal tibia. With this reversed materials scheme, the EI design requires minimal tibial bone resection compared with traditional UKA. This study investigated, by means of finite element (FE) simulations, the advantages of a thin metal tibial component compared with traditional UKA tibial components, such as an all-plastic inlay or a metal-backed onlay. We hypothesized that an EI tibial component would produce comparable stress, strain, and strain energy density (SED) characteristics to an intact knee and more favorable values than UKA components, due primarily to the preservation of dense cancellous bone near the surface. Indeed, FE results showed that stresses in the supporting bone for an EI design were close to intact, while stresses, strains, and strain energy densities were reduced compared with an all-plastic UKA component. Analyzed parameters were similar for an EI and a metal-backed onlay, but the EI component had the advantage of minimal resection of the stiffest bone.
Evaluation of Meniscal Mechanics and Proteoglycan Content in a Modified Anterior Cruciate Ligament Transection Model
Authors: Fischenich Kristine M. , Coatney Garrett A. , Haverkamp John H. , Button Keith D. , DeCamp Charlie , Haut Roger C. , Haut Donahue Tammy L.
Published: April 2014

Post-traumatic osteoarthritis (PTOA) develops as a result of traumatic loading that causes tears of the soft tissues in the knee. A modified transection model, where the anterior cruciate ligament (ACL) and both menisci were transected, was used on skeletally mature Flemish Giant rabbits. Gross morphological assessments, elastic moduli, and glycosaminoglycan (GAG) coverage of the menisci were determined to quantify the amount of tissue damage 12 weeks post injury. This study is one of the first to monitor meniscal changes after inducing combined meniscal and ACL transections. A decrease in elastic moduli as well as a decrease in GAG coverage was seen.
The Pattern of Change in the Abundances of Specific Bacterioplankton Groups Is Consistent across Different Nutrient-Enriched Habitats in Crete
Authors: Fodelianakis Stilianos , Papageorgiou Nafsika , Pitta Paraskevi , Kasapidis Panagiotis , Karakassis Ioannis , Ladoukakis Emmanuel D.
Published: April 2014

A common source of disturbance for coastal aquatic habitats is nutrient enrichment through anthropogenic activities. Although the water column bacterioplankton communities in these environments have been characterized in some cases, changes in α-diversity and/or the abundances of specific taxonomic groups across enriched habitats remain unclear. Here, we investigated the bacterial community changes at three different nutrient-enriched and adjacent undisturbed habitats along the north coast of Crete, Greece: a fish farm, a closed bay within a town with low water renewal rates, and a city port where the level of nutrient enrichment and the trophic status of the habitat were different. Even though changes in α-diversity were different at each site, we observed across the sites a common change pattern accounting for most of the community variation for five of the most abundant bacterial groups: a decrease in the abundance of thePelagibacteraceaeand SAR86 and an increase in the abundance of theAlteromonadaceae,Rhodobacteraceae, andCryomorphaceaein the impacted sites. The abundances of the groups that increased and decreased in the impacted sites were significantly correlated (positively and negatively, respectively) with the total heterotrophic bacterial counts and the concentrations of dissolved organic carbon and/or dissolved nitrogen and chlorophyll α, indicating that the common change pattern was associated with nutrient enrichment. Our results provide anin situindication concerning the association of specific bacterioplankton groups with nutrient enrichment. These groups could potentially be used as indicators for nutrient enrichment if the pattern is confirmed over a broader spatial and temporal scale by future studies.
A Novel Angular Dioxygenase Gene Cluster Encoding 3-Phenoxybenzoate 1′,2′-Dioxygenase in Sphingobium wenxiniae JZ-1
Authors: Wang Chenghong , Chen Qing , Wang Rui , Shi Chao , Yan Xin , He Jian , Hong Qing , Li Shunpeng
Published: April 2014

Sphingobium wenxiniae
JZ-1 utilizes a wide range of pyrethroids and their metabolic product, 3-phenoxybenzoate, as sources of carbon and energy. A mutant JZ-1 strain, MJZ-1, defective in the degradation of 3-phenoxybenzoate was obtained by successive streaking on LB agar. Comparison of the draft genomes of strains JZ-1 and MJZ-1 revealed that a 29,366-bp DNA fragment containing a putative angular dioxygenase gene cluster (
pbaA1A2B
) is missing in strain MJZ-1. PbaA1, PbaA2, and PbaB share 65%, 52%, and 10% identity with the corresponding α and β subunits and the ferredoxin component of dioxin dioxygenase from
Sphingomonas wittichii
RW1, respectively. Complementation of
pbaA1A2B
in strain MJZ-1 resulted in the active 3-phenoxybenzoate 1′,2′-dioxygenase, but the enzyme activity in
Escherichia coli
was achieved only through the coexpression of
pbaA1A2B
and a glutathione reductase (GR)-type reductase gene,
pbaC
, indicating that the 3-phenoxybenzoate 1′,2′-dioxygenase belongs to a type IV Rieske non-heme iron aromatic ring-hydroxylating oxygenase system consisting of a hetero-oligomeric oxygenase, a [2Fe-2S]-type ferredoxin, and a GR-type reductase. The
pbaC
gene is not located in the immediate vicinity of
pbaA1A2B
. 3-Phenoxybenzoate 1′,2′-dioxygenase catalyzes the hydroxylation in the 1′ and 2′ positions of the benzene moiety of 3-phenoxybenzoate, yielding 3-hydroxybenzoate and catechol. Transcription of
pbaA1A2B
and
pbaC
was induced by 3-phenoxybenzoate, but the transcriptional level of
pbaC
was far less than that of
pbaA1A2B
, implying the possibility that PbaC may not be the only reductase that can physiologically transfer electrons to PbaA1A2B in strain JZ-1. Some GR-type reductases from other sphingomonad strains could also transfer electrons to PbaA1A2B, suggesting that PbaA1A2B has a low specificity for reductase.
Structure-Based Mutational Studies of Substrate Inhibition of Betaine Aldehyde Dehydrogenase BetB from Staphylococcus aureus
Authors: Chen Chao , Joo Jeong Chan , Brown Greg , Stolnikova Ekaterina , Halavaty Andrei S. , Savchenko Alexei , Anderson Wayne F. , Yakunin Alexander F.
Published: April 2014

Inhibition of enzyme activity by high concentrations of substrate and/or cofactor is a general phenomenon demonstrated in many enzymes, including aldehyde dehydrogenases. Here we show that the uncharacterized protein BetB (SA2613) from
Staphylococcus aureus
is a highly specific betaine aldehyde dehydrogenase, which exhibits substrate inhibition at concentrations of betaine aldehyde as low as 0.15 mM. In contrast, the aldehyde dehydrogenase YdcW from
Escherichia coli
, which is also active against betaine aldehyde, shows no inhibition by this substrate. Using the crystal structures of BetB and YdcW, we performed a structure-based mutational analysis of BetB and introduced the YdcW residues into the BetB active site. From a total of 32 mutations, those in five residues located in the substrate binding pocket (Val288, Ser290, His448, Tyr450, and Trp456) greatly reduced the substrate inhibition of BetB, whereas the double mutant protein H448F/Y450L demonstrated a complete loss of substrate inhibition. Substrate inhibition was also reduced by mutations of the semiconserved Gly234 (to Ser, Thr, or Ala) located in the BetB NAD
+
binding site, suggesting some cooperativity between the cofactor and substrate binding sites. Substrate docking analysis of the BetB and YdcW active sites revealed that the wild-type BetB can bind betaine aldehyde in both productive and nonproductive conformations, whereas only the productive binding mode can be modeled in the active sites of YdcW and the BetB mutant proteins with reduced substrate inhibition. Thus, our results suggest that the molecular mechanism of substrate inhibition of BetB is associated with the nonproductive binding of betaine aldehyde.
Variables Influencing Extraction of Nucleic Acids from Microbial Plankton (Viruses, Bacteria, and Protists) Collected on Nanoporous Aluminum Oxide Filters
Authors: Mueller Jaclyn A. , Culley Alexander I. , Steward Grieg F.
Published: April 2014

Anodic aluminum oxide (AAO) filters have high porosity and can be manufactured with a pore size that is small enough to quantitatively capture viruses. These properties make the filters potentially useful for harvesting total microbial communities from water samples for molecular analyses, but their performance for nucleic acid extraction has not been systematically or quantitatively evaluated. In this study, we characterized the flux of water through commercially produced nanoporous (0.02 μm) AAO filters (Anotop; Whatman) and used isolates (a virus, a bacterium, and a protist) and natural seawater samples to test variables that we expected would influence the efficiency with which nucleic acids are recovered from the filters. Extraction chemistry had a significant effect on DNA yield, and back flushing the filters during extraction was found to improve yields of high-molecular-weight DNA. Using the back-flush protocol, the mass of DNA recovered from microorganisms collected on AAO filters was ≥100% of that extracted from pellets of cells and viruses and 94% ± 9% of that obtained by direct extraction of a liquid bacterial culture. The latter is a minimum estimate of the relative recovery of microbial DNA, since liquid cultures include dissolved nucleic acids that are retained inefficiently by the filter. In conclusion, we demonstrate that nucleic acids can be extracted from microorganisms on AAO filters with an efficiency similar to that achievable by direct extraction of microbes in suspension or in pellets. These filters are therefore a convenient means by which to harvest total microbial communities from multiple aqueous samples in parallel for subsequent molecular analyses.