bluuebunny/crossref_metadata_2025 huggingface dataset:
Arenavirus budding resulting from viral-protein-associated cell membrane curvature
Authors: Schley David , Whittaker Robert J. , Neuman Benjamin W.
Published: July 2013

Viral replication occurs within cells, with release (and onward infection) primarily achieved through two alternative mechanisms: lysis, in which virions emerge as the infected cell dies and bursts open; or budding, in which virions emerge gradually from a still living cell by appropriating a small part of the cell membrane. Virus budding is a poorly understood process that challenges current models of vesicle formation. Here, a plausible mechanism for arenavirus budding is presented, building on recent evidence that viral proteins embed in the inner lipid layer of the cell membrane. Experimental results confirm that viral protein is associated with increased membrane curvature, whereas a mathematical model is used to show that localized increases in curvature alone are sufficient to generate viral buds. The magnitude of the protein-induced curvature is calculated from the size of the amphipathic region hypothetically removed from the inner membrane as a result of translation, with a change in membrane stiffness estimated from observed differences in virion deformation as a result of protein depletion. Numerical results are based on experimental data and estimates for three arenaviruses, but the mechanisms described are more broadly applicable. The hypothesized mechanism is shown to be sufficient to generate spontaneous budding that matches well both qualitatively and quantitatively with experimental observations.
Cell-type-specific modelling of intracellular calcium signalling: a urothelial cell model
Authors: Appleby Peter A. , Shabir Saqib , Southgate Jennifer , Walker Dawn
Published: July 2013

Calcium signalling plays a central role in regulating a wide variety of cell processes. A number of calcium signalling models exist in the literature that are capable of reproducing a variety of experimentally observed calcium transients. These models have been used to examine in more detail the mechanisms underlying calcium transients, but very rarely has a model been directly linked to a particular cell type and experimentally verified. It is important to show that this can be achieved within the general theoretical framework adopted by these models. Here, we develop a framework designed specifically for modelling cytosolic calcium transients in urothelial cells. Where possible, we draw upon existing calcium signalling models, integrating descriptions of components known to be important in this cell type from a number of studies in the literature. We then add descriptions of several additional pathways that play a specific role in urothelial cell signalling, including an explicit ionic influx term and an active pumping mechanism that drives the cytosolic calcium concentration to a target equilibrium. The resulting one-pool model of endoplasmic reticulum (ER)-dependent calcium signalling relates the cytosolic, extracellular and ER calcium concentrations and can generate a wide range of calcium transients, including spikes, bursts, oscillations and sustained elevations in the cytosolic calcium concentration. Using single-variate robustness and multivariate sensitivity analyses, we quantify how varying each of the parameters of the model leads to changes in key features of the calcium transient, such as initial peak amplitude and the frequency of bursting or spiking, and in the transitions between bursting- and plateau-dominated modes. We also show that, novel to our urothelial cell model, the ionic and purinergic P2Y pathways make distinct contributions to the calcium transient. We then validate the model using human bladder epithelial cells grown in monolayer cell culture and show that the model robustly captures the key features of the experimental data in a way that is not possible using more generic calcium models from the literature.
Molecular mechanisms of cell–cell spread of intracellular bacterial pathogens
Authors: Ireton Keith
Published: July 2013

Several bacterial pathogens, includingListeria monocytogenes,Shigella flexneriandRickettsiaspp., have evolved mechanisms to actively spread within human tissues. Spreading is initiated by the pathogen-induced recruitment of host filamentous (F)-actin. F-actin forms a tail behind the microbe, propelling it through the cytoplasm. The motile pathogen then encounters the host plasma membrane, forming a bacterium-containing protrusion that is engulfed by an adjacent cell. Over the past two decades, much progress has been made in elucidating mechanisms of F-actin tail formation.ListeriaandShigellaproduce tails of branched actin filaments by subverting the host Arp2/3 complex. By contrast,Rickettsiaforms tails with linear actin filaments through a bacterial mimic of eukaryotic formins. Compared with F-actin tail formation, mechanisms controlling bacterial protrusions are less well understood. However, recent findings have highlighted the importance of pathogen manipulation of host cell–cell junctions in spread.Listeriaproduces a soluble protein that enhances bacterial protrusions by perturbing tight junctions.Shigellaprotrusions are engulfed through a clathrin-mediated pathway at ‘tricellular junctions’—specialized membrane regions at the intersection of three epithelial cells. This review summarizes key past findings in pathogen spread, and focuses on recent developments in actin-based motility and the formation and internalization of bacterial protrusions.
Mechanics of spreading cells probed by atomic force microscopy
Authors: Pietuch Anna , Janshoff Andreas
Published: July 2013

Cellular adhesion and motility are fundamental processes in biological systems such as morphogenesis and tissue homeostasis. During these processes, cells heavily rely on the ability to deform and supply plasma membrane from pre-existing membrane reservoirs, allowing the cell to cope with substantial morphological changes. While morphological changes during single cell adhesion and spreading are well characterized, the accompanying alterations in cellular mechanics are scarcely addressed. Using the atomic force microscope, we measured changes in cortical and plasma membrane mechanics during the transition from early adhesion to a fully spread cell. During the initial adhesion step, we found that tremendous changes occur in cortical and membrane tension as well as in membrane area. Monitoring the spreading progress by means of force measurements over 2.5 h reveals that cortical and membrane tension become constant at the expense of excess membrane area. This was confirmed by fluorescence microscopy, which shows a rougher plasma membrane of cells in suspension compared with spread ones, allowing the cell to draw excess membrane from reservoirs such as invaginations or protrusions while attaching to the substrate and forming a first contact zone. Concretely, we found that cell spreading is initiated by a transient drop in tension, which is compensated by a decrease in excess area. Finally, all mechanical parameters become almost constant although morphological changes continue. Our study shows how a single cell responds to alterations in membrane tension by adjusting its overall membrane area. Interference with cytoskeletal integrity, membrane tension and excess surface area by administration of corresponding small molecular inhibitors leads to perturbations of the spreading process.
J. Matlock's Young ladies guide to the knowledge of the English tongue (1715): contextualising the first grammar of English for ladies
Authors: Percy Carol
Published: July 2013

Recently rediscovered, The Young Ladies Guide to the Knowledge of the English Tongue (1715) is now the earliest known grammar of English for females. After considering its possible authorship by the writing master John Matlock, I use his residence of Lichfield to exemplify the various ways in which girls might acquire vernacular literacy. Drawing on the Eighteenth‐Century English Grammars database (ECEG), I compare the Guide with contemporary grammars and spelling books, linking its latinate lexis, ‘ungrammatical’ sentences and non‐traditional grammatical terms and categories to an audience of Ladies who are stereotypically not classically educated but nonetheless distinct from charity school girls. I also contextualise this text in such ongoing changes as the movement from classical to vernacular grammar, the role of periodicals in commodifying vernacular education and debates about women's education.
The place of pronunciation in eighteenth‐century grammars of English
Authors: Beal Joan C.
Published: July 2013

The entry on ‘grammar’ in the first edition of theOED(volume 4, 1901) includes the following information: ‘Until a not very distant date, Grammar was divided by English writers (following the precedent of Latin grammarians) into Orthography, Etymology, Syntax, and Prosody, to which Orthoëpy was added by some authors’. TheECEGdatabase is a useful tool for investigating the nature and extent to which eighteenth‐century grammars paid attention to matters of pronunciation. Although a search fororthoëpyas a division of grammar only yields ten hits, the facility for searching within the comments sections allows the researcher to find many more grammars which include information about pronunciation. In this paper, I report on the use of theECEGdatabase to answer the following research questions: (i) does the rise of the elocution movement in the second half of the eighteenth century lead to a greater or lesser emphasis on pronunciation in grammars published after 1760? (ii) is there any evidence of grammar‐writers being influenced by elocutionists such as Thomas Sheridan (,) and John Walker ()? Finally, I report on the ways in which this information might be included in a planned database of eighteenth‐century phonology.
No pain, no gain: Depressed clients' experiences of cognitive behavioural therapy
Authors: Barnes Maria , Sherlock Sofie , Thomas Laura , Kessler David , Kuyken Willem , Owen‐Smith Amanda , Lewis Glyn , Wiles Nicola , Turner Katrina
Published: July 2013

Objectives

Cognitive behavioural therapy (CBT) is an effective treatment for depression, but many clients do not complete therapy. What clients find difficult about CBT is poorly understood. This study explored clients' views and experiences of face‐to‐face CBT.

Design

A mixed methods design was used to collect data as part of the CoBalT trial.

Method

Participants randomized to CBT indicated their reasons for never starting or stopping therapy on the follow‐up questionnaires. In‐depth qualitative interviews took place with a purposive sample (n = 26) of those randomized to CBT. Framework analysis was used to analyse across the data.

Results

Seventy‐four participants withdrew from therapy or were discharged for non‐adherence. A total of 54 (73%) gave reasons for not starting or stopping CBT; mostly the time/location was inconvenient or they had other commitments.

Interviews identified that clients could struggle in, and between, CBT sessions. This was true for those who did and did not complete therapy. CBT homework was the biggest challenge and was often associated with negative school homework experiences. Although clients may have disliked aspects of CBT, those who attended more than one session felt that they had gained insight into managing their depression.

Conclusion

Highlighting the possible barriers to adherence in CBT can help clinicians to better prepare clients in making an informed choice about therapy. Exploring these issues during therapy may also help with engagement. Despite the challenges, clients can still benefit from CBT by learning strategies that enable them to effectively deal with their depression.

Practitioner points

Talking to participants about the challenges of CBT – such as homework – can help clinicians better prepare clients in making an informed choice about therapy.

Exploration of possible barriers during therapy may also help with engagement and completion of therapy.

Despite the challenges, clients report benefiting from CBT; in particular learning strategies which help identify negative thought patterns and enable them to deal more effectively with their depression.
A Shape‐Aware Model for Discrete Texture Synthesis
Authors: Landes Pierre‐Edouard , Galerne Bruno , Hurtut Thomas
Published: July 2013

We present a novel shape‐aware method for synthesizing 2D and 3D discrete element textures consisting of collections of distinct vector graphics objects. Extending the long‐proven point process framework, we propose a shape process, a novel stochastic model based on spatial measurements that fully take into account the geometry of the elements. We demonstrate that our approach is well‐suited for discrete texture synthesis by example. Our model enables for both robust statistical parameter estimation and reliable output generation by Monte Carlo sampling. Our numerous experiments show that contrary to current state‐of‐the‐art techniques, our algorithm manages to capture anisotropic element distributions and systematically prevents undesirable collisions between objects.
Temporally Coherent Adaptive Sampling for Imperfect Shadow Maps
Authors: Barák T. , Bittner J. , Havran V.
Published: July 2013

We propose a new adaptive algorithm for determining virtual point lights (VPL) in the scope of real‐time instant radiosity methods, which use a limited number of VPLs. The proposed method is based on Metropolis‐Hastings sampling and exhibits better temporal coherence of VPLs, which is particularly important for real‐time applications dealing with dynamic scenes. We evaluate the properties of the proposed method in the context of the algorithm based on imperfect shadow maps and compare it with the commonly used inverse transform method. The results indicate that the proposed technique can significantly reduce the temporal flickering artifacts even for scenes with complex materials and textures. Further, we propose a novel splatting scheme for imperfect shadow maps using hardware tessellation. This scheme significantly improves the rendering performance particularly for complex and deformable scenes. We thoroughly analyze the performance of the proposed techniques on test scenes with detailed materials, moving camera, and deforming geometry.
Factorized Point Based Global Illumination
Authors: Wang Beibei , Huang Jing , Buchholz Bert , Meng Xiangxu , Boubekeur Tamy
Published: July 2013

The Point‐Based Global Illumination (PBGI) algorithm is composed of two major steps: a caching step and a multiview rasterization step. At caching time, a dense point‐sampling of the scene is shaded and organized in a spatial hierarchy, with internal nodes approximating the radiance of their subtrees using spherical harmonics. At rasterization time, a microbuffer is instantiated at the unprojected position of each image pixel (receiver). Then, a view‐adaptive level‐of‐detail of the scene is extracted in the form of a tree cut and rasterized in the receiver's microbuffer, solving for visibility using a local variant of the z‐buffer. Finally, the pixel color is computed by convolving its filled microbuffer with the surface BRDF. This noise‐free indirect lighting method is widely used in the industry and captures several critical lighting effects, including ambient occlusion, color bleeding, (indirect) soft‐shadows and environment lighting. However, we observe a large redundancy in this algorithm, both in cuts and receivers'microbuffers, which stems from their relatively low resolution. In this paper, we propose an evolution of PBGI which exploits spatial coherence to reduce these redundant computations. Starting from a similarity‐based variational clustering of the receivers, we compute a single tree cut and rasterize a single microbuffer for each cluster. This per‐cluster microbuffer provides a faithful approximation of the incident radiance for distant nodes and is composited over a receiver‐specific microbuffer rasterizing only the closest nodes of the cluster's cut. This factorized approach is easy to integrate in any existing PBGI implementation and offers a significant rendering speed‐up for a negligible and controllable approximation error.
The Sulham Gap and the Pangbourne flood of 2007 in their geological context, SE England
Authors: Worsley Peter
Published: July 2013

The Sulham Gap is a distinctive valley in the English county of Berkshire. Following a late Devensian drainage diversion, the Sulham Gap lowland was left as a poorly drained former floodplain. A major flood, with an unprecedented magnitude, occurred in July 2007 sourced primarily from the River Pang which enters the gap on the western side. Its physical impact was exacerbated by: 1, medieval extraction of postglacial peat; and 2, the building of leats for watermills. The flood water drained across the topographically lower drainage network of the diminutive Sulham Brook to the eastern side of the gap and backed‐up behind culverts beneath both a road and a railway embankment resulting in some 140 homes being inundated.
Understanding diversity in collective representation: common principles underlying the performance of workplace representatives in different representation regimes
Authors: Dufour Christian , Hege Adelheid
Published: July 2013

The international literature on workplace representation tends to focus on distinctive characteristics of different representation regimes to the detriment of an understanding of how groups of workplace representatives actually do their work. This article identifies cross‐cutting principles underlying the role of workplace representatives, making the argument that these principles, rather than institutional characteristics, explain commonalities and differences in workplace representation.
Editorial: From correlations to causation: the value of preventive interventions in studying pathogenic mechanisms in childhood psychiatric disorders
Authors: Peterson Bradley S.
Published: July 2013

The ultimate goal of all research in childhood psychiatric disorders is to provide knowledge that will be useful in treating or preventing illness. To be useful in treating or preventing illness, research studies must provide valid information about the causes of illness, because only by targeting those causes can we prevent or counter their effects in a truly rational way. Until now, the discovery of interventions has largely been by serendipity, yielding medications and behavioral interventions that produce too little therapeutic response, in too few people, and with too many side effects. The selection of which specific intervention to use for which child is based on trial‐and‐error guesswork and the personal preferences and idiosyncrasies of the treating clinician, with little or no empirical support, and at great cost to children, families, and health care systems. Guesswork in treatment will decline only when we have more detailed knowledge of the differing causal pathways that produce differing subtypes of the same disease phenotype. Identifying more homogeneous subtypes of disease that have more uniform natural histories and treatment responses will permit development of more genuinely rational and individualized interventions, or more truly personalized medicine (Insel, 2009).

Identifying causal pathways in human disease, however, is especially challenging because the classic method of experimental investigation – isolating and manipulating at will a variable that is hypothesized to exert a causal influence on the illness in order to understand its effects on other variables – is not possible when studying the causes of human illness, for obvious ethical reasons. We are therefore left with a variety of methods for identifying probable causal pathways in human illness, all of which have varying strengths and limitations in the weight of evidence that they provide that a variable has a true causal influence on the disorder.
Is It Possible and Sometimes Desirable for States to Forgive?
Authors: Wolterstorff Nicholas
Published: July 2013

After discussing at some length the nature of interpersonal forgiveness and its relation to punishment, the author addresses the main question of the essay: are states the sorts of entities that can forgive; and if they are, is it sometimes desirable that they forgive? The author argues that states can forgive and very often do; and that sometimes it is desirable that they do so. The essay closes by considering the complexities that arise when the state wants to forgive but the victim does not, and conversely.
Balancing Justice and Mercy
Authors: Newman Louis E.
Published: July 2013

The concept of forgiveness is analyzed as a moral gesture toward the offender designed to help restore that individual's moral standing. Jewish sources on the conditions under which forgiveness is obligatory are explored and two contrasting positions are presented: one in which the obligation to forgive is conditional on the repentance of the offender and another in which people are required to forgive unconditionally. These two positions are shown to represent different ways of framing the offending behavior that rest, in turn, on different ways of balancing the need for justice and for mercy respectively. In the final analysis, Judaism's two contrasting attitudes toward forgiveness are rooted in different theological assumptions and different ways of construing the very goals of the moral life. The author points out the merits and shortcomings of both positions and concludes with the suggestion that the two complement each other in important ways.
Reconciliation Between Muslims and Christians
Authors: Malik Anas
Published: July 2013

“A Common Word Between Us,” an open letter from Muslim scholars to Christian leaders, is the most developed effort at Muslim‐Christian reconciliation to date. Endorsed by well‐known Muslim scholars from diverse sects and backgrounds, the letter emphasizes the central role of love of God and the Golden Rule in both religions and cites the catastrophic consequences of conflict. The signatories frame a norm of interreligious covenant for constructive collaborations, present their argument as an authoritative Islamic position, and effectively reject the clash‐of‐civilizations narrative. Using game‐theory models to articulate strategic challenges facing interreligious initiatives, this essay argues that a norm of interreligious covenant can potentially produce successful collective action in situations resembling both coordination and prisoner's dilemma games, depending on the success of norm entrepreneurship.
The Use of Party Brand Labels in Congressional Election Campaigns
Authors: Neiheisel Jacob R. , Niebler Sarah
Published: July 2013

In spite of the centrality of partisanship to many theories of lawmaking, and the important role that party cues play in shaping voters' evaluations of political candidates, remarkably little is known about the circumstances under which congressional candidates use partisan symbols on the campaign trail. Employing data on candidates' televised advertisements over six elections (1998–2008), the present study explores the “supply side” of partisan cues and finds that candidates are strategic about their use of party symbols. And while personal and district‐level factors influence how candidates utilize partisan rhetoric, we show that the institutional context in which they campaign also matters.
Radiant Fin Performance Using Fractal-like Geometries
Authors: Dannelley Daniel , Baker John
Published: July 2013

The results of a computational study into the thermal performance of thermally radiating fractal-like fins are presented. Previous experimental studies have shown that fractal patterns increase the heat transfer surface area while simultaneously reducing mass. Two fractal patterns were used for comparison, the modified Koch snowflake and the Sierpinski carpet. For an isothermal base fin radiating to free space, the fin effectiveness and fin efficiency are presented for the zeroth and first four fractal iterations in order to quantify the performance. Emissivity, width/thickness ratio, base temperature, and fin material were varied to better understand their impact on the performance of fractal-like fins. Based upon the observed results, fractal-like fins greatly improve the fin effectiveness per unit mass. In certain cases, fin effectiveness per unit mass was found to increase by up to 46%. As the cost of access to space is significant, this reduction in mass could lead to savings for spacecraft thermal management applications.
Mathematical Modeling and Multi-Objective Optimization of a Mini-Channel Heat Exchanger Via Genetic Algorithm
Authors: Selleri Tommaso , Najafi Behzad , Rinaldi Fabio , Colombo Guido
Published: July 2013

In the present paper a mathematical model for a mini-channel heat exchanger is proposed. Multiobjective optimization using genetic algorithm is performed in the next step in order to obtain a set of geometrical design parameters, leading to minimum pressure drops and maximum overall heat transfer coefficient. Multiobjective optimization procedure provides a set of optimal solutions, called Pareto front, each of which is a trade-off between the objective functions and can be freely selected by the user according to the specifications of the project. A sensitivity analysis is also carried out to study the effects of different geometrical parameters on the considered functions. The whole system has been modeled based on advanced experimental correlations in matlab environment using a modular approach.
Genetic Algorithm Optimization of a Finned-Tube Heat Exchanger Modeled With Volume-Averaging Theory
Authors: Geb David , Zhou Feng , DeMoulin George , Catton Ivan
Published: July 2013

This paper proposes and implements a new methodology for optimizing finned-tube heat exchangers (FTHEs) using a volume-averaging theory (VAT) hierarchical physical model and a genetic algorithm (GA) numerical optimizer. This method allows for multiple-parameter constrained optimization of FTHEs by design of their basic morphological structures. A consistent model is used to describe transport phenomena in a FTHE based on VAT, which allows for the volume-averaged conservation of mass, momentum, and energy equations to be solved point by point, with the morphology of the structure directly incorporated into the field equations and full conjugate effects included. The equations differ from those often presented in porous media modeling and are developed using a rigorous averaging technique, hierarchical modeling methodology, and fully turbulent models with Reynolds stresses and fluxes in every pore space. These averaged equations have additional integral and differential terms that must be dealt with in order for the equation set to be closed, and recent work has provided this closure for FTHEs. The resulting governing equation set is relatively simple and is discretized and quickly solved numerically. Such a computational solution algorithm is fast running, but still able to present a detailed picture of the temperature fields in both of the fluid flows as well as in the solid structure of the heat exchanger. A GA is integrated with the VAT-based solver to carry out the FTHE numerical optimization, which is a ten parameter problem, and the FTHE is optimized subject to imposed constraints. This method of using the VAT-based solver fully integrated with a GA optimizer results in a new all-in-one tool for performing multiple-parameter constrained optimization on FTHEs.
Multicylinder HCCI Control With Coupled Valve Actuation Using Model Predictive Control
Authors: Erlien Stephen M. , Jungkunz Adam F. , Gerdes J. Christian
Published: July 2013

Recent work in homogeneous charge compression ignition (HCCI) engine control has focused on the use of variable valve timing (VVT) as a near term implementation strategy. Valve timing has a significant influence on combustion phasing and can be implemented with cam-based VVT systems already available in production vehicles. However, these systems introduce cylinder coupling via a shared actuator. This paper presents a model predictive control (MPC) framework that explicitly accounts for this intercylinder coupling as a constraint on the system. The execution time step of this MPC controller is shorter than the prediction time step, enabling consideration of a common actuator across otherwise independent systems as the engine cycle progresses. This enables effective use of the cylinder independent actuators to augment the shared actuator in achieving the control objectives. Experiments on a multicylinder HCCI engine test bed validate this approach to handling coupled actuation and illustrate effective use of cylinder independent actuators in response to limited capabilities of the shared actuator.
Pulse Width Modulation of Water Jet Propulsion Systems Using High-Speed Coanda-Effect Valves
Authors: Mazumdar Anirban , Asada H. Harry
Published: July 2013

An integrated high-speed valve switching and pump output control scheme are developed for precision maneuvering of underwater vehicles. High-speed Coanda-effect valves combined with a centrifugal pump allow for precise control of thrust force using a unique pulse width modulation (PWM) control scheme, where both pulse width and pulse height are controlled in a coordinated manner. Dead zones and other complex nonlinear dynamics of traditional propeller thrusters and water jet pumps are avoided with use of the integrated pump-valve control. Three control algorithms for coordinating valve switching and pump output are presented. A simplified nonlinear hydrodynamic model of underwater vehicles is constructed, and design trade-offs between PWM frequency and pulse height, with regard to steady state oscillations, are addressed. The control algorithms are implemented on a prototype underwater vehicle and the theoretical results are verified through experiments.
Osseointegrated Lower Limb Prosthetic Force Limiting Connection
Authors: Gasser Benjamin W. , Bridges Loren E. , Kargar Soudabeh , Bardot Dawn M.
Published: July 2013

A goal in the design of prosthetic limbs is to mimic the use, feel, and behavior of the missing natural limb. A promising area of research focused on these goals is osseointegration. Osseointegration is the direct attachment of the prosthetic device to the bone. In the case of the above knee amputee, it would involve placing a fixture in the femur with a pin (abutment) that extends through the skin and allows the prosthetic leg to be directly attached to the bone structure, and creates a more natural force path which offers a variety of benefits when compared with the stump and socket approach. First, it eliminates the pressure placed on soft tissues. The skin and muscles of the leg were never designed to be part of the load transfer path. With an osseointegrated fixture, the load is transferred directly into the bone and into the rest of the body using the same force path a natural leg would generate.
A Comparison of the Finite Element Method and Bench Testing for the Fatigue to Fracture Evaluation of a Group of Self-Expanding Nitinol Stents
Authors: Swift Richard , Choules Brian , Kim Seoggwan
Published: July 2013

The design of self-expanding nitinol stents to treat peripheral arterial disease offers a number of unique challenges. Primary among these is the potentially complex loading environment that these stents must endure, without fracture, for an extended period. As an example, for the superficial femoral artery (SFA), the loading environment on a stent can consist of axial, bending, torsional and pulsatile loads. These loads induce alternating strain that must be accommodated in the device design to ensure suitable fatigue life. Other stent design criteria relate to satisfactory radial force, as well as the ability to achieve delivery system requirements (i.e., volumetric constraints, good compression and deployment characteristics).
Portable Plasma Biomedical Device for Cancer Treatment
Authors: Thiyagarajan Magesh
Published: July 2013

This research study examined the effect of non-thermal portable atmospheric air plasma system on leukemia cancer cells. Acute monocytic leukemia cells (THP-1) were exposed to atmospheric pressure non-thermal plasma. To assess death caused by plasma exposure, cells were subjected to trypan blue exclusion assays and a kill-curve and assessment of death overtime were compiled using data from the assays. In addition to this, DNA was harvested from treated and untreated samples to determine if apoptotic ladders were present. Results have indicated that non-thermal plasma can cause cell death in THP-1 cells overtime, and the death that occurs corresponds directly to the amount of time that the cells were exposed to ionized plasma. Preliminary fluorescent imaging of the treated cells revealed that higher treatment doses are not only more likely to induce cellular death but are likely to induce necrotic death, while lower treatment doses that are capable of inducing death may induce apoptotic or programmed cellular death. Ideally the results obtained from these experiments will allow for further investigation of the effects of ionized non-thermal plasma on melanoma cell lines and will lead to an inexpensive method for treating early stage skin cancer and cancerous lesions.
Collection of Cancer Cells From Blood Samples Using Inertial Migration Forces
Authors: Tanaka T. , Ishikawa T. , Numayama-Tsuruta K. , Imai Y. , Ueno H. , Matsuki N. , Yamaguchi T.
Published: July 2013

Circulating Tumor Cell (CTC) test has been widely adopted for evaluating the prognosis or cure effect of breast cancer. In this test, situations of breast cancer patients are evaluated by counting the number of CTCs in peripheral blood samples. Since conventional method needs fluorescent staining to count CTCs, there are problems of high costs and long process time.
Development of a Microdevice for Sorting Motile Bacteria
Authors: Shioiri T. , Ishikawa T. , Numayama-Tsuruta K. , Imai Y. , Ueno H. , Yamaguchi T.
Published: July 2013

Bacteria are distributed in various places in nature and in industries, examples include human intestine, sewage treatment, food production and even food poisoning. Thus, the separation of bacteria from various samples is an important technique for medical and industrial applications. In recent years, separation of bacteria was commonly performed by a colony count method. This method, however, takes long time of operation and cannot be applied to bacteria for which culture method has not been established.
Using Forelimb EMG to Control an Electronic Spinal Bridge to Facilitate Hindlimb Stepping After Complete Spinal Cord Lesion
Authors: Gad Parag , Woodbridge Jonathan , Lavrov Igor , Gerasimenko Yury , Zhong Hui , Roy Roland R. , Sarrafzadeh Majid , Edgerton V. Reggie
Published: July 2013

A complete spinal cord transection results in loss of all supraspinal motor control below the level of the injury. The neural circuitry in the lumbosacral spinal cord, however, can generate locomotor patterns in the hindlimbs of rats and cats with the aid of epidural stimulation and administration of serotoninergic agonists. We hypothesized that there are patterns of EMG signals from the forelimbs during quadrupedal locomotion that uniquely represent a signal for the “intent” to step with the hindlimbs. These observations led us to determine whether “indirect” volitional control of stepping can be restored after a complete spinal cord injury. We developed an electronic bridge that can trigger specific patterns of EMG activity from the forelimbs to enable quadrupedal stepping after a complete spinal cord transection in rats. We found dominant frequencies of 180–220 Hz in the EMG of forelimb muscles during active periods, whereas the frequencies were between 0–10 Hz when the muscles were inactive. A moving window detection algorithm was implemented in a small microprocessor to detect bilateral activity in the biceps brachii that then was used to initiate and terminate epidural stimulation. This detection algorithm was successful in detecting stepping under different pharmacological conditions and at various treadmill speeds and in facilitating quadrupedal stepping after a complete mid-thoracic spinal cord transection.
Three-Dimensional Design Optimization of Multistage Axial Flow Turbines Using a RSM Based Approach
Authors: Cravero Carlo , Macelloni Paolo , Briasco Giuseppe
Published: July 2013

The problem of the automatic design optimization for multistage axial flow turbines is considered and a design strategy based on a 3D Navier-Stokes solver and a RSM (Response Surface Method) approach is described. A multi-objective optimization code based on non-dominated sorting genetic algorithm (NSGA-2) is used to drive the optimization process in order to maximize the specific power while keeping the massflow rate constrained. In the present work the meridional channel is kept unchanged while for each blade the spanwise distribution of the profile restaggering is considered together with the inclusion of compound lean. The performance from the multistage turbine for the optimization loop are obtained from surrogate models built through a set of artificial neural networks. The neural networks are trained and tested using large DoEs and are not updated during the optimization process. This aspect is considered important to guarantee that the optimization converges to an optimum. The use of the 3D flow solver with coarse meshes in order to validate large DoEs in short times is discussed in some details. The above strategy has been applied to a four stage axial turbine from the open literature.
Aerodynamic Investigations of Root Sections of Long Rotor Blades Applied at the Last Stages of Steam Turbines
Authors: Šimurda David , Luxa Martin , Šafařík Pavel , Synáč Jaroslav , Šťastný Miroslav
Published: July 2013

The aerodynamics of root sections appears to be a crucial problem in the design and operation of the last stages of large output steam turbines. The reasons are transonic flow, high flow turning, and difficulties with keeping their design aerodynamic conditions during operation.

Investigations were performed on planar blade cascades representing root sections of 1085mm and 1220mm long rotor blades. The basic conception of the two root sections differs. The aerodynamic loading of the 1220mm blade root section is lowered in order to ensure that the design parameters are kept during turbine stage operation. We present the results of optical and pneumatic measurements i.e. dependencies of the kinetic energy loss coefficient and exit flow angle on the exit isoentropic Mach number and the angle of incidence, as well as images of the flow fields. The experimental data is analyzed in order to assess and document the difference between the two root section designs.
Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade
Authors: El-Gabry Lamyaa A. , Saha Ranjan , Fridh Jens , Fransson Torsten
Published: July 2013

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream.

Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.
Differential Equation Specification of Integral Turbulence Length Scales
Authors: Jefferson-Loveday Richard , Tucker Paul , Nagabhushana Rao V. , Northall John
Published: July 2013

A Hamilton-Jacobi differential equation is used to naturally and smoothly (via Dirichlet boundary conditions) set turbulence length scales in separated flow regions based on traditional expected length scales. Such zones occur for example in rim-seals. The approach is investigated using two test cases, flow over a cylinder at a Reynolds number of 140,000 and flow over a rectangular cavity at a Reynolds number of 50,000. The Nee-Kovasznay turbulence model is investigated using this approach.

Predicted drag coefficients for the cylinder test-case show significant (15%) improvement over standard steady RANS and are comparable with URANS results. The mean flow-field also shows a significant improvement over URANS. The error in reattachment length is improved by 180% compared with the steady RANS k–ω model. The wake velocity profile at a location downstream shows improvement and the URANS profile is inaccurate in comparison.

For the cavity case the HJ-NK approach is generally comparable with the other RANS models for measured velocity profiles. Predicted drag coefficients are compared with large eddy simulation. The new approach shows a 20–30% improvement in predicted drag coefficients compared with standard one and two equation RANS models. The shape of the recirculation region within the cavity is also much improved.
On the Flow Evolution Through a LP Turbine With Wide-Chord Vanes in an S-Shaped Channel
Authors: Spataro Rosario , Santner Cornelia , Lengani Davide , Göttlich Emil
Published: July 2013

The paper discusses the time averaged flow field in a test facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to reproduce the flow leaving a transonic turbine through a following counter rotating low pressure stage. This configuration is common in modern multi-shaft jet engines and will become a standard in the future.

The discussion on the flow field is based on numerical results obtained by a commercial CFD code and validated by aerodynamic measurements and oil flow visualization performed on the facility itself. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. Within the duct turning struts lead the flow to the following rotor. The LP stage inlet condition is given by the outlet flow of the high pressure turbine whose spanwise distribution is strongly affected by the shape of the downstream S-channel. A special focus is concentrated on the generation and propagation of secondary flows in such a turning mid turbine frame (TMTF). The aim of the present work is to isolate the flow structures moving from the outlet of the transonic stage through the low pressure stage and identify their effect on the time-averaged flow.

The main outcome of this paper is that, whenever a TMTF is placed between counter-rotating high pressure and low pressure turbines, the structures coming from the upstream rotor will not decay (like in a co-rotating setup), but they will be convected and transported towards the downstream rotor. Moreover, the turning of the struts will enhance the vorticities generated by the upstream turbine. The application of technical solutions such as embedded TMTF designs or endwall contouring should be aimed to reach LP rotor uniform inlet conditions, minimize the TMTF secondary flows and thus to damp the rotor-rotor interaction.
Aerodynamic and Structure Considerations in Centrifugal Compressor Design: Blade Lean Effects
Authors: Xu C. , Amano R. S.
Published: July 2013

Optimization procedures are demanded by turbomachinery industries that enable to enhance compressor efficiency and wide operating ranges. Most of the design processes focuseither on aerodynamics or structure. However, the compressor design is an integration between aerodynamics and structure.

This paper presents some recent developments of the aerodynamic and structural integral design system. The design process including the meanline design, through-flow optimization and three-dimensional viscous analysis was used in the centrifugal compressor design. The aerodynamic and structural design need to be optimized at the same time. Normally most of the favorable aerodynamic features do not correspond with the structural reliability of the compressor wheel. The optimization between aerodynamic performance and structural reliability is critical to provide the maximal potential of the compressor performance. The main purpose of the current study is to discuss the importance of the aerodynamic and structural optimizations through a centrifugal compressor wheel lean effects. The study demonstrated that the integral design of the aerodynamics and structure is very important.
Experimental Investigation of High Pressure Ratio Centrifugal Compressor With Axisymmetric and Non-Axisymmetric Recirculation Device
Authors: Tamaki Hideaki , Zheng Xinqian , Zhang Yangjun
Published: July 2013

Centrifugal compressors used for turbochargers are required to have a wide operating range. A recirculation device, which consists of a bleed slot, an upstream slot and an annular cavity connecting both slots, is often used with them. It improves the incidence angle of the impeller leading edge, i.e. the blade loading of the inducer, at low flow rates due to the recirculation flow supplied to the compressor inlet. However the compressor efficiency drops when there is a recirculation flow from the bleed slot to the upstream slot. A one dimensional analysis in the first section of this paper showed that the reduction in the compressor efficiency can be lowered by decreasing the pressure drop or reducing the recirculation flow rate within the recirculation device. This study examined the possibility of improvement in the compressor efficiency by the use of a recirculation device with an asymmetric bleed slot.

An impeller of a turbocharger compressor is normally contained in a volute. Since the geometry of the volute is not axisymmetric, the impeller is surrounded by an asymmetric flow field. Hence each impeller passage, which is formed by two adjacent full blades, is operated at a different operating point. This means that some of passages need the improvement in the blade loading by the recirculation device but others do not. There is a possibility that this is realized by a recirculation device with an asymmetrically-distributed bleed slot, called a non-axisymmetric recirculation device in this paper. If the asymmetric bleed slot shortens the average distance between the bleed slot and upstream slot or reduces the area of the bleed slot, it can reduce the pressure drop or recirculation flow rate within the recirculation device, and hence can improve the compressor efficiency.

This study discusses the characteristics of high pressure ratio compressors for turbochargers without the recirculation device and those with the recirculation device with an axisymmetric bleed slot. Further, the effects of non-axisymmetric recirculation devices on the compressor characteristics are experimentally investigated. Two types of non-axisymmetric recirculation devices were tested. One had the bleed slot of a sine wave pattern. The other had the bleed slot partially channeled in the circumferential direction. There were appropriate positions relative to the volute for both non-axisymmetric recirculation devices. The compressor efficiency with non-axisymmetric recirculation devices was higher than that with axisymmetric recirculation devices, and the surge lines of the compressor with non-axisymmetric recirculation devices were located at flow rate lower than or equal to those with the axisymmetric recirculation devices.