bluuebunny/crossref_metadata_2025 huggingface dataset:
Individual variations in infectiousness explain long‐term disease persistence in wildlife populations
Authors: Kramer‐Schadt Stephanie , Fernández Néstor , Eisinger Dirk , Grimm Volker , Thulke Hans‐Hermann
Published: November 2008

Viral disease persistence in species without a reservoir host is of importance for public health and disease management. But how can disease persistence be explained? We developed a spatially‐explicit individual‐based model that takes into account both ecological and viral traits as well as variable space to test disease persistence hypotheses under debate. We introduce a novel concept of modeling alternative disease courses at the individual level, causing transient infections or killing infected animals, with the lethally infected having a variable life‐expectancy. We systematically distinguish between disease invasion and persistence. We use classical swine fever (CSF), an economically very important livestock disease in a social host, the wild boar, as a reference system to test and rank the persistence hypotheses under debate. Parameter values for host population demographics and CSF epidemiology reflect current knowledge. Sensitivity analysis of the model parameters revealed that the most important factor for disease persistence is a disease profile with mostly transient, i.e. surviving individuals requiring immunity, and some chronically, long‐term infected animals. Immune individuals can constantly produce susceptible offspring, while some chronically infected individuals act as ‘super spreaders’ in time. Thus, variations in the course of the disease at the individual level are important factors determining persistence, which is usually not taken into account in the prominent measure of epidemiology, i.e. the basic reproductive number R0, which reflects the ‘reproductive potential’ of the infected sub‐population. We discuss our results with regard to the general issues of modeling epidemics and disease management issues.
Deterministic control on community assembly peaks at intermediate levels of disturbance
Authors: Lepori Fabio , Malmqvist Björn
Published: November 2008

Despite long‐standing research, the processes that drive community assembly remain poorly understood. We censused macroinvertebrate communities and measured flood disturbance in 17 Scandinavian mountain streams to assess the hypothesis that communities are shaped by stochastic processes under stable conditions, and increasingly by deterministic processes as disturbance becomes more severe. Each study stream was categorized as being stable (n=5), intermediate (n=7), or disturbed (n=5) depending on the severity of scouring floods. Following spring floods, the number of potential colonisers decreased with increasing disturbance, suggesting that disturbance filtered out species unable to cope with the stress involved. Communities at stable sites had the highest beta diversity, indicating that stochastic processes of community assembly were most important under the least disturbed conditions. In partial contrast with our predictions, the lowest beta diversity occurred between intermediate (not disturbed) sites, suggesting that increasing disturbance first enhances determinism but then rekindles stochasticity at severity levels beyond intermediate. Macroinvertebrate communities were shaped by deterministic processes, which recruit potential regional colonists depending on niche differences and disturbance conditions and by stochastic processes, which distribute the selected species randomly among individual localities. Although often considered opposing, stochastic and deterministic processes interact hierarchically, with relative strength modified by disturbance.
Tolerance traits and the stability of mutualism
Authors: Oliver Tom H. , Leather Simon R. , Cook James M.
Published: November 2008

Identifying factors which allow the evolution and persistence of cooperative interactions between species is a fundamental issue in evolutionary ecology. Various hypotheses have been suggested which generally focus on mechanisms that allow cooperative genotypes in different species to maintain interactions over space and time. Here, we emphasise the fact that even within mutualisms (interactions with net positive fitness effects for both partners), there may still be inherent costs, such as the occasional predation by ants upon aphids. Individuals engaged in mutualisms benefit from minimising these costs as long as it is not at the expense of breaking the interspecific interaction, which offers a net positive benefit. The most common and obvious defence traits to minimise interspecific interaction costs are resistance traits, which act to reduce encounter rate between two organisms. Tolerance traits, in contrast, minimise fitness costs to the actor, but without reducing encounter rate. Given that, by definition, it is beneficial to remain in mutualistic interactions, the only viable traits to minimise costs are tolerance‐based ‘defence’ strategies. Thus, we propose that tolerance traits are an important factor promoting stability in mutualisms. Furthermore, because resistance traits tend to propagate coevolutionary arms races between antagonists, whilst tolerance traits do not, we also suggest that tolerance‐based defence strategies may be important in facilitating the transition from antagonistic interactions into mutualisms. For example, the mutualism between ants and aphids has been suggested to have evolved from parasitism. We describe how phenotypic plasticity in honeydew production may be a tolerance trait that has prevented escalation into an antagonistic arms race and instead led to mutualistic coevolution.
Predator–prey interactions under climate change: the importance of habitat vs body temperature
Authors: Broitman B. R. , Szathmary P. L. , Mislan K. A. S. , Blanchette C. A. , Helmuth B.
Published: November 2008

Habitat temperature is often assumed to serve as an effective proxy for organism body temperature when making predictions of species distributions under future climate change. However, the determinants of body temperature are complex, and organisms in identical microhabitats can occupy radically different thermal niches. This can have major implications of our understanding of how thermal stress modulates predator–prey relationships under field conditions. Using body temperature data from four different sites on Santa Cruz Island, California, we show that at two sites the body temperatures of a keystone predator (the seastar Pisaster ochraceus) and its prey (the mussel Mytilus californianus) followed very different trajectories, even though both animals occupied identical microhabitats. At the other two sites, body temperatures of predator and prey were closely coupled across a range of scales. The dynamical differences between predator and prey body temperatures depended on the location of pairs of sites, at the extremes of a persistent landscape‐scale weather pattern observed across the island. Thus, the well understood predator–prey interaction between Pisaster and Mytilus cannot be predicted based on habitat‐level information alone, as is now commonly attempted with landscape‐level (‘climate envelope’) models.
Combination of an EGFR blocker and a COX‐2 inhibitor for the treatment of advanced cutaneous squamous cell carcinoma
Authors: Jalili Ahmad , Pinc Alice , Pieczkowski Friederike , Karlhofer Franz M. , Stingl Georg , Wagner Stephan N.
Published: November 2008

Cutaneous squamous cell carcinoma (SCC) is one of the most common cancers worldwide. Epidermal growth factor receptor (EGFR) is expressed at the cell surface by more than 90% of SCCs and its activation is responsible for cell cycle progression, proliferation, survival, angiogenesis and metastasis. Cyclooxygenase‐2 (COX‐2) is an enzyme up‐regulated through EGFR signaling and responsible for some of the EGFR‐dependent biological effects. An 88‐year‐old man presented with a recurrent, locoregionally meta‐static SCC of the right parietal region, which was resistant to radiotherapy. With a combination therapy of an EGFR blocker (cetuximab) and a COX‐2 inhibitor (celecoxib), the tumor regressed partially and the patient's Karnofsky index improved. We speculate that the combined use of cetuxi‐mab and COX‐2 inhibitors can be a new and effective therapy for advanced and recurrent cutaneous SCCs.
The occurrence of riboflavin kinase and FAD synthetase ensures FAD synthesis in tobacco mitochondria and maintenance of cellular redox status
Authors: Giancaspero Teresa A. , Locato Vittoria , de Pinto Maria C. , De Gara Laura , Barile Maria
Published: November 2008

Intact mitochondria isolated from Nicotiana tabacum cv. Bright Yellow 2 (TBY‐2) cells can take up riboflavin via carrier‐mediated systems that operate at different concentration ranges and have different uptake efficiencies. Once inside mitochondria, riboflavin is converted into catalytically active cofactors, FMN and FAD, due to the existence of a mitochondrial riboflavin kinase (EC 2.7.1.26) and an FAD synthetase (EC 2.7.7.2). Newly synthesized FAD can be exported from intact mitochondria via a putative FAD exporter. The dependence of FMN synthesis rate on riboflavin concentration shows saturation kinetics with a sigmoidal shape (S0.5, Vmax and Hill coefficient values 0.32 ± 0.12 μm, 1.4 nmol·min−1·mg−1 protein and 3.1, respectively). The FAD‐forming enzymes are both activated by MgCl2, and reside in two distinct monofunctional enzymes, which can be physically separated in mitochondrial soluble and membrane‐enriched fractions, respectively.
Summarizing Item Difficulty Variation with Parcel Scores
Authors: Camilli Gregory , Prowker Adam , Dossey John A. , Lindquist Mary M. , Chiu Ting‐Wei , Vargas Sadako , De La Torre Jimmy
Published: November 2008

A new method for analyzing differential item functioning is proposed to investigate the relative strengths and weaknesses of multiple groups of examinees. Accordingly, the notion of a conditional measure of difference between two groups (Reference and Focal) is generalized to a conditional variance. The objective of this article is to present and illustrate a strategy for aggregating results across sets of similar items that exhibit item difficulty variation. Logically, this aggregation strategy is related to the idea of DIF amplification, but estimation is ultimately carried out in the framework of a confirmatory multidimensional Rasch model. Grade 4 data from the 2000 National Assessment of Educational Progress are used to illustrate the technique.
Social Welfare Attitudes and Ambivalence about the Role of Government
Authors: Gainous Jason , Craig Stephen C. , Martinez Michael D.
Published: November 2008

Evidence suggests that mistrust of government contributes directly to a lack of support for social welfare programs. An alternative explanation, however, is that many citizens are ambivalent concerning government and the role that it should play in society today and, as result, are less likely to support such programs. Based on our analysis of data from a 2004 telephone survey of Florida residents, we conclude that, first, ambivalent feelings concerning the federal, state, and local levels of government in the United States are fairly common; second, ambivalence has consequences for people's opinions on matters of public policy—specifically, those with conflicted feelings are less likely to endorse progressive action in the social welfare realm; third, self‐identified conservatives tend to be more ambivalent concerning government than liberals; and finally, the observed negative relationship between ambivalence and social welfare liberalism is especially pronounced among conservatives.
Gravitational unloading inhibits the regenerative potential of atrophied soleus muscle in mice
Authors: Matsuba Y. , Goto K. , Morioka S. , Naito T. , Akema T. , Hashimoto N. , Sugiura T. , Ohira Y. , Beppu M. , Yoshioka T.
Published: November 2008

Aim:  The present study was performed to investigate the influence of unloading on the regeneration of atrophied and injured skeletal muscle.

Methods:  Male mice (C57BL/6J), aged 8 weeks, were used. Cardiotoxin (CTX) was injected into soleus muscles bilaterally. Gravitational unloading on soleus muscle was performed by hind limb suspension for 2 weeks before and additionally 6 weeks after CTX injection in one group. Soleus muscles in the remaining groups were loaded keeping the mice in the cages and were dissected 14, 28 and 42 days after the injection.

Results:  Recovery of the wet weight and protein content of soleus in the CTX‐injected group was inhibited by unloading. Increase in satellite cell number, induced by CTX injection and loading, was also inhibited by unloading. Disappearance of infiltration of mononucleated cells into the necrotic area was also delayed. This phenomenon suggests that regeneration, which is indicated by the appearance of fibres with central nuclei, was inhibited by unloading.

Conclusion:  Results suggested that loading plays an important role in the activation of the regenerating potential of injured skeletal muscle.
Effects of ischemic postconditioning on reperfusion injury in rat liver grafts after orthotopic liver transplantation
Authors: Wang Nan , Lu Jian G. , He Xian L. , Li Na , Qiao Qing , Yin Ji K. , Ma Qing J.
Published: November 2008

Aim:  The effects of ischemic postconditioning (IPostC) on ischemia reperfusion (IR) injury of liver grafts was examined in rats after orthotopic liver transplantation (OLT).

Methods:  Male Wistar rats were used as donors and recipients to establish a liver transplantation model. The animals were randomly divided into four groups: sham‐operated (SO, n = 6), IR (n = 6), IPostC1 (n = 6) and IPostC2 (n = 6). IPostC was achieved by several intermittent interruptions of blood flow in the early phase of reperfusion. Several parameters of hepatic damage, oxidative stress, neutrophil infiltration and the expression of TNF‐α and MIP‐2 were detected as well as microscopic examination. Nitric oxide release and liver NO synthases (endothelial NO synthase and inducible NO synthase) expression were also measured.

Results:  We observed that a significant reduction in alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase values in two IPostC groups when compared with IR group. The increases in hepatic malondialdehyde, and decreases in superoxide dismutase and reduced glutathione levels after orthotopic liver transplantation were significantly inhibited by IPostC. IR induced increase in hepatic myeloperoxidase content, TNF‐α and MIP‐2 expression were also lowered by IPostC. The increases in NO content and NOS protein expression were much more prominent in IPostC treated groups. Animals treated with IPostC presented minimal hemorrhage and reduced signs of liver injury. There was no significant difference between two IPostC treated groups.

Conclusions:  IPostC provided significant protection against IR injury to liver grafts. The protective effect of IPostC is closely related to the NO production following the increase in endothelial and inducible NO synthases expression and the suppression of tumor necrosis factor‐α and macrophage inflammatory protein‐2 overproduction.
Analysis of hepatic genes involved in the metabolism of fatty acids and iron in nonalcoholic fatty liver disease
Authors: Mitsuyoshi Hironori , Yasui Kohichiroh , Harano Yuichi , Endo Mio , Tsuji Kazuhiro , Minami Masahito , Itoh Yoshito , Okanoue Takeshi , Yoshikawa Toshikazu
Published: November 2008

Aims:  Hepatic steatosis and iron cause oxidative stress, thereby progressing steatosis to steatohepatitis. We quantified the expression of genes involved in the metabolism of fatty acids and iron in patients with nonalcoholic fatty liver disease (NAFLD).

Methods:  The levels of transcripts for the following genes were quantified from biopsy specimens of 74 patients with NAFLD: thioredoxin (Trx), fatty acid transport protein 5 (FATP5), sterol regulatory element‐binding protein 1c (SREBP1c), fatty acid synthase (FASN), acetyl‐coenzyme A carboxylase (ACAC), peroxisome proliferative activated receptor α (PPARα), cytochrome P‐450 2E1 (CYP2E1), acyl‐coenzyme A dehydrogenase (ACADM), acyl‐coenzyme A oxidase (ACOX), microsomal triglyceride transfer protein (MTP), transferrin receptor 1 (TfR1), transferrin receptor 2 (TfR2) and hepcidin. Twelve samples of human liver RNA were used as controls. Histological evaluation followed the methods of Brunt.

Results:  The levels of all genes were significantly higher in the NAFLD patients than in controls. The Trx level increased as the stage progressed. The levels of FATP5, SREBP1c, ACAC, PPARα, CYP2E1, ACADM and MTP significantly decreased as the stage and grade progressed (P < 0.05). Hepatic iron score (HIS) increased as the stage progressed. The TfR1 level significantly increased as the stage progressed (P < 0.05), whereas TfR2 level significantly decreased (P < 0.05). The ratio of hepcidin mRNA/ferritin (P < 0.001) or hepcidin mRNA/HIS (P < 0.01) was significantly lower in NASH patients than simple steatosis patients.

Conclusions:  Steatosis‐related metabolism is attenuated as NAFLD progresses, whereas iron‐related metabolism is exacerbated. Appropriate therapies should be considered on the basis of metabolic changes.
KCNE4 domains required for inhibition of KCNQ1
Authors: Manderfield Lauren J. , Daniels Melissa A. , Vanoye Carlos G. , George Jr Alfred L.
Published: November 2008

Voltage‐gated potassium (Kv) channels are modulated in distinct ways by members of the KCNE family of single transmembrane domain accessory subunits. KCNE4 has a dramatic inhibitory effect on KCNQ1 that differs substantially from the activating effects of KCNE1 and KCNE3. The structural features of KCNE4 that enable this behaviour are unknown. We exploited chimeras of KCNE1, KCNE3 and KCNE4 to identify specific domains responsible for the inhibitory effects on heterologously expressed KCNQ1. Previous structure–function analysis of KCNE1 and KCNE3 identified a critical tripeptide motif within the transmembrane domain that accounts for the differences in KCNQ1 modulation evoked by these two KCNE proteins. Swapping the transmembrane tripeptide motif of KCNE4 with the corresponding amino acid sequence of KCNE1 did not influence the behaviour of either protein. Similarly, exchanging the tripeptide regions of KCNE3 and KCNE4 further demonstrated that this transmembrane motif does not explain the activity of KCNE4. Using a more systematic approach, we demonstrated that the KCNE4 C‐terminus was critical for KCNQ1 modulation. Replacement of the KCNE1 or KCNE3 C‐termini with that of KCNE4 created chimeric proteins that strongly inhibited KCNQ1. Additional evidence supported a cooperative role of the KCNE4 transmembrane domain. Although the C‐terminus was necessary for KCNE4 activity, we demonstrated that a surrogate transmembrane domain derived from the cytokine receptor CD8 did not enable inhibition of KCNQ1, indicating that the KCNE4 C‐terminus alone was not sufficient for KCNQ1 modulation. We further demonstrated that the KCNE4 C‐terminus interacts with KCNQ1. Our data reveal important structure–function relationships for KCNE4 that help advance our understanding of potassium channel modulation by KCNE proteins.
Pharmacological targeting of the serotonergic system for the treatment of obesity
Authors: Garfield Alastair S. , Heisler Lora K.
Published: November 2008

The attenuation of food intake as induced by an increase in serotonergic (5‐hydroxytryptamine, 5‐HT) efficacy has been a target of antiobesity pharmacotherapies. However, the induction of tolerance and/or side‐effects limited the clinical utility of the earliest serotonin‐related medications. With the global prevalence of obesity rising, there has been renewed interest in the manipulation of the serotonergic system as a point of pharmacological intervention. The serotonin2Creceptor (5‐HT2CR), serotonin1B(rodent)/serotonin1Dβ(human) receptor (5‐HT1B/1DβR) and serotonin6receptor (5‐HT6R) represent the most promising serotonin receptor therapeutic targets. Canonical serotonin receptor compounds have given way to a myriad of novel receptor‐selective ligands, many of which have observable anorectic effects. Here we review serotonergic compounds reducing ingestive behaviour and discuss their clinical potential for the treatment of obesity.
Performances and Degradation Phenomena of Solid Oxide Anode Supported Cells With LSM and LSCF Cathodes: An Experimental Assessment
Authors: Lanzini A. , Leone P. , Santarelli M. , Asinari P. , Calì M. , Borchiellini R.
Published: November 2008

The performance of solid oxide fuel cells is affected by various polarization losses, usually grouped in Ohmic, activation, and concentration polarizations. Under typical operating conditions, these polarization losses are largely dependent on cell materials, electrode microstructures, and cell geometry: as an example, the performance of a tubular cell is strongly limited by the Ohmic polarization due to the long current path of electrons, while in a planar cell each of these losses has a comparable effect. It is therefore of interest, in the case of planar geometry, to investigate the main performance limiting factors. In this paper, a performance evaluation of planar circular-shaped seal-less SOFC cells was performed. Two different designs of planar cells are considered. Both have a porous NiO-YSZ (yttria stabilized zirconia) anode as mechanical support, a NiO-YSZ anode active layer, and an YSZ electrolyte, and they only differ in the cathode design: (1) strontium doped lanthanum manganate (LSM)-YSZ cathode functional layer and LSM cathode current collector layer; (2) yttria doped ceria blocking layer and lanthanum strontium cobalt ferrite oxide (LSCF) functional layer. The characterization was performed by taking V-I measurements over a range of temperatures between 650°C and 840°C with hydrogen as fuel and air as oxidant. The experimental data analysis consisted in the analysis of some typical performance indicators (maximum power density (MPD); current density at 0.7V). The dependence of the cell performance on the various polarization contributions was rationalized on the basis of an analytical model—through a parameter estimation of the experimental data—devoted to the determination of the main polarization losses. Based on the results of the investigation, it is concluded that LSCF cathodes are really effective in decreasing the cathode activation polarization, allowing the reduction in operating temperature.
Synthesis and Characterization of a Composite Membrane for Polymer Electrolyte Fuel Cell
Authors: Das Susanta K. , Kolavennu Panini , Hedrick J. , Beholz L. , Zand Ali R. , Berry K. J.
Published: November 2008

A new proton exchange membrane (PEM) has been fabricated using a novel patented polymer structure modification technology. It has been shown that the new membrane has a higher proton transfer rate and lower resistance as compared to Nafion®. This paper discusses issues related to membrane fabrication and testing procedures. (i) A brief fabrication procedure of PEM is outlined. The fabrication technique used here separates the proton exchange and structural requirements of the PEM allowing greater flexibility in membrane design. The proton exchange material developed herein is a terpolymer composed of various ratios of acrylic acid, styrene, and vinylsulfonic acid. Following a patented polymer structure modification technology, these materials were bound to an ethylene-tetrafluoroethylene copolymer mesh that had been rendered adhesive by hydroxylation in a two-step water-borne process. (ii) A previously developed theoretical model is used to calculate the relative resistance and proton transfer rate. According to the model, a simple second order differential equation describes the entire process and established a relationship between the membrane resistance and the total time taken for a specific amount of protons to pass through it. Finally, (iii) a simple two-cell experimental procedure is developed to calculate the relative membrane resistance and proton transfer capacity. The results show that theoretical predictions are in excellent agreement with the experimental observations. The new membrane could transfer protons approximately 80% faster than Nafion® per unit area under the test conditions utilized. Membrane resistance is also 71% lower compared to Nafion®. These results suggest that there is now a new route of fabricating cost effective proton exchange membranes for fuel cell applications wherein one may focus more on the proton exchange capacity of the membrane allowing the structural properties of the membrane to be considered separately.
Proton Exchange Membrane Fuel Cell High Carbon Monoxide Tolerance Operation Using Pulsed Heating and Pressure Swing
Authors: Guo S. M. , Hasan A. B. M.
Published: November 2008

Proton exchange membrane fuel cells (PEMFCs) are attractive power plants for use in many applications, including portable power sources, electric vehicles, and on-site combined power/heat plants. Despite the advantages, one of the significant obstacles to PEMFC commercialization is the low tolerance to carbon monoxide (CO). Ideally, PEMFCs should use pure hydrogen fuel. However, because of the difficulties inherent in storing hydrogen onboard, there is an increasing interest in using hydrogen-rich gases produced by reforming hydrocarbon fuels. Fuel reformer produces hydrogen containing a small amount of CO. PEMFC performance degrades when CO is present in the fuel gas, referred to as CO poisoning. This paper presents the results of a novel PEMFC performance study using a pulsed heating device and the feeding channel pressure swing method to mitigate the CO poisoning problem. The effectiveness of these strategies is demonstrated through simulation and experimental work on a single cell. By applying a transient localized heating to the catalyst layer while maintaining the PEMFC membrane at a normal temperature (below 80°C) and by using the feeding channel pressure swing, significant enhancement in the carbon monoxide tolerance level of PEMFCs was found. These approaches could potentially eliminate the need for an expensive selective oxidizer. The CO poisoning process is generally slow and reversible. After applying pulsed heating, the transient high temperature in the catalyst layer could help the recovery of the PEMFC from CO poisoning. By using feeding channel pressure swing, oxygen can easily diffuse into the membrane electrode assembly (MEA) from the outlet port and promote a quick recovery. Using these operational strategies, a PEMFC could operate continually using a high CO concentration fuel.
Fabrication and Characterization of a Balloon Actuator Array for Haptic Feedback in Robotic Surgery
Authors: King Chih-Hung , Franco Miguel , Culjat Martin O. , Higa Adrienne T. , Bisley James W. , Dutson Erik , Grundfest Warren S.
Published: November 2008

Robot-assisted surgery is characterized by a total loss of haptic feedback, requiring surgeons to rely solely on visual cues. A pneumatically-driven balloon actuator array, suitable for mounting on robotic surgical master controls, has been developed to provide haptic feedback to surgeons. The actuator arrays consist of a molded polydimethylsiloxane substrate with cylindrical channels and a spin-coated silicone film that forms the array of balloons. Preliminary human perceptual studies have demonstrated that balloon diameters greater than 1.0mm may provide effective haptic feedback to the index finger. Before conducting further human perceptual tests, refinements of the fabrication process and performance data of the actuator are required. Balloons with diameters ranging between 1.5mm and 4.0mm were fabricated with film thicknesses of 200μm and 300μm. Inflation pressure versus balloon deflection tests and cyclic actuation tests were performed to characterize each balloon type. The results demonstrated a high linearity between inflation pressure and balloon deflection (R2>0.93) and negligible hysteresis effects between inflation and deflation over 100,000cycles. The studies indicated that 300μm films are optimal for 3.0mm and 4.0mm diameter balloons, and 200μm films are optimal for 1.5mm, 2.0mm, and 2.5mm diameter balloons. Due to its compact size and high performance, the described pneumatic actuator can provide sensory input that is otherwise unavailable during robotic surgery.
Further Development of Flashless Forging Operations for Flat Long Pieces
Authors: Behrens B. A. , Reinsch S. , Specker A.
Published: November 2008

Flashless forging operations, which are also known as precision forging operations, generate high quality parts concerning the quality of surfaces and dimensional accuracy. Precision forging processes have been industrially established for axis-symmetric parts e.g. gearwheels and steering pinions. Further development of the technology to more complex parts e.g. helical gears, connecting rods and crankshafts is expected to lead to a wider implementation of the technology into forging industry. Heavy-duty automotive components offer a wide application field for flashless forged parts. Advantages like shortened production cycles which are achieved by eliminating machining operations and the saving of raw material contribute to the ongoing cost-saving trend in the automobile industry. The design process for complex precision forged parts has to fulfill special requirements to consider the distinctions of this technique. This article explains the adopted methods and a development process of a precision forging process describing the design of a connecting rod and a crankshaft.
Some CHP Options for Wood-Fired Fuel Cells
Authors: McIlveen-Wright D. R. , McMullan J. T. , Guiney D. J.
Published: November 2008

The possibility of integrating biomass gasifiers with fuel cells has already been explored and shown to offer a method for using renewable energy to generate electricity at a small scale. A preliminary study of applying such a system for use in an isolated community and for several selected buildings has been made and the results of these studies reported earlier. In this study wood gasification integrated with fuel cell (WGIFC) systems in CHP configurations for five building systems with different energy demand profiles, are assessed. These are a hospital, a hotel, a leisure centre, a multi-residential community and a university hall of residence. Heat and electricity use profiles for typical examples of these buildings were obtained and the WGIFC system scaled to the power demand. Detailed technical, environmental and economic analyses of each version are made, using the ECLIPSE process simulation package. Various factors influencing the economic viability of each application are examined and a sensitivity analysis for each system produced. The WGIFC system was modelled for two different types of fuel cell, the Molten Carbonate and the Phosphoric Acid. In each case an oxygen-fired gasification system is proposed, in order to eliminate the need for a methane reformer. Technical, environmental and economic analyses of each version were made, using ECLIPSE. Since fuel cell lifetimes are not yet precisely known, economics for a range of fuel cell lifetimes have been produced. While the wood-fired Phosphoric Acid Fuel Cell (WFPAFC) system was found to have low electrical efficiency (13–16%), the wood-fired Molten Carbonate Fuel Cell (WFMCFC) system was found to be quite efficient for electricity generation (24 to 27%). Much of the waste heat could be recovered for the WFPAFC, so that the overall efficiency was 64 to 67%, and some waste heat, but potentially of higher grade, could be recovered by the WFMCFC to give an overall energy efficiency of 60 to 63%. The capital costs of both systems are still expected to be very high, but the examination of wood fuel prices, fuel cell costs, fuel cell lifetime and waste heat selling prices on the break-even selling price for electricity, as well as comparative sensitivity analyses, can help identify which other factors would have the main impacts on the system economics.
Analytical Determination of Shock Response Spectra for an Impulse-Loaded Proportionally Damped System
Authors: Hampton R. David , Wiedenman Nathan S. , Li Ting H.
Published: November 2008

Many military systems must be capable of sustained operation in the face of mechanical shocks due to projectile or other impacts. The most widely used method of quantifying a system’s vibratory transient response to shock loading is called the shock response spectrum (SRS). The system response for which the SRS is to be determined can be due, physically, either to a collocated or to a noncollocated shock loading. Taking into account both possibilities, one can define the SRS as follows: the SRS presents graphically the maximum transient response (output) of an imaginary ideal mass-spring-damper system at one point on a flexible structure, to a particular mechanical shock (input) applied to an arbitrary (perhaps noncollocated) point on the structure, as a function of the natural frequency of the imaginary mass-spring-damper system. For a response point sufficiently distant from the impact area, many Army platforms (such as vehicles) can be accurately treated as linear systems with proportional damping. In such cases the output due to an impulsive mechanical-shock input can be decomposed into exponentially decaying sinusoidal components, using normal-mode orthogonalization. Given a shock-induced loading comprising such components, this paper provides analytical expressions for the various common SRS forms. The analytical approach to SRS-determination can serve as a verification of, or an alternative to, the numerical approaches in current use for such systems. No numerical convolution is required, because the convolution integrals have already been accomplished analytically (and exactly), with the results incorporated into the algebraic expressions for the respective SRS forms.
Hybrid Model for a Drive Line of a Vehicle Dynamometer
Authors: Abdul-Ameer A. A. , Khanipour A.
Published: November 2008

This paper describes the development and application of a simulation model for a vehicle Rolling-Road dynamometer. Due to the topology of such a system it cannot be considered as a purely lumped system nor would it be practical to assume it to be purely distributed. Consequently a partially distributed and partially lumped assumption is adapted. This technique has been successfully applied to a variety of engineering applications in which the system parameters are partially distributed and partially lumped. The drive line of the vehicle dynamometer lends itself to this method since the inertia of the rolls and shaft are distributed whilst the damping due to the bearings and the motor can be considered as lumped systems/elements. This method enables the analysis of the dynamic performance of the dynamometer, which is not possible using lumped or point wise techniques. The dynamic performance of the dynamometer is investigated in this paper, using a conventional three-term controller for maintaining the roll speed under step, ramp and impulse disturbances.
Giant Magnetoimpedance Effect in a Co-Based Microwire for Quick-Response Magnetic Sensor Applications
Authors: Phan Manh-Huong , Peng Hua-Xin , Wisnom Michael R. , Yu Seong-Cho
Published: November 2008

Development of autobiased linear field sensors based on asymmetrical giant magnetoimpedance (AGMI) effect in Corich amorphous microwires upon the application of a biasing dc current is approached. Upon biasing dc currents, the highest field sensitivity of AGMI of 20%/Oe was found at a biasing dc current of 10 mA. The reduction of the AGMI under a biasing dc current of 25 mA and a frequency of 10 MHz has been observed. The result indicates that an optimum design of autobiased linear field sensors based on AGMI can be achieved by applying the biasing dc current of 10 mA and in the frequency range of 100 kHz–5 MHz. A stress-induced change in AGMI has also been found in these microwires and this offers a new approach to the development of stress sensors. All these features make the Co-rich amorphous microwire a multifunctional and smart material that can be used for different purposes of sensing applications.
Shock Event Analysis, Characteristic Considerations and Conservativeness Influence in High Pressure Injection System Cavitating Flow Simulations
Authors: Ferrari Alessandro , Manno Michele , Mittica Antonio
Published: November 2008

A comparison between conservative and nonconservative models has been carried out for evaluating the influence of conservativeness on predicting transient flows in presence of cavitation induced discontinuities inside high-pressure injection systems. Even if nonconservative models can assure satisfactory accuracy in the evaluation of the wave propagation phenomena, they introduce fictitious source terms in the discretized equations. Such terms are usually negligible, but can play a significant role when discontinuities in the flow properties occur, producing appreciable errors on the pressure wave speed estimation. An analysis based on fluid characteristics around both the rarefaction and compression wave fronts has been carried out, showing that cavitation desinence is a shock occurrence, leading to a transition from a supersonic to a subsonic flow. For a significant evaluation of conservative and nonconservative model performances a conventional pump-line-nozzle injection system was considered because the pipe flow presented interesting cases of cavitation-induced shocks. The validity of the conservative model is substantiated by the comparison between computed pressure time-histories and experimental results at two pipe locations. The Rankine-Hugoniot jump conditions have been usefully applied to the numerical results obtained by the conservative model in order to calculate the sound speed of the traveling compression waves in the presence of cavitation. A novel algorithm of general application to calculate the shock speed predicted by nonconservative models, which points out the contribution of the internal fictitious fluxes in the wrong estimation of the shock velocity, has been introduced and validated through its application to Burgers’ equation.
Independently Rotating Wheels With Induction Motors for High Speed Trains
Authors: Liang B. , Iwnicki S. D. , Swift F. J.
Published: November 2008

Railway vehicles with conventional sets often cause problems of hunting and severe wear. The use of an independently rotating wheel set (IRW) would eliminate the cause of wheel set hunting and wear since an IRW can decouple the wheels. This paper presents an investigation into the design of a suitable motor configuration and controller for IRW in order to provide the stability required to satisfy the performance requirements. A computer model of the mechanical and electrical parts of the system was developed. Simulation and experiments of the wheelsets with active driving motor control have demonstrated that a wheelset with independently driven wheels has a good stability performance over a traditional wheelset. Controllers with indirect field orientation control for dynamic control of a motor have shown to be suitable for this application in both its response and its controllability.
Analysis and Statistic Evaluation of Distributed Generation in Italy
Authors: Desideri Umberto , Proietti Stefania , Arcioni Livia
Published: November 2008

This paper presents a complete analysis of the state of the art and the legislation of distributed generation in Italy, which is similar to other EU countries, and statistic data on combined heat and power plants installed in Italy. Data was collected from a large number of sources, because most of the small size plants are operated by IPP without an electrical exchange contract with the grid and are not documented. The results of this research has allowed to show that 22.000 MW can be generated by over 1600 power plants spread over the Italian territory. A more detailed analysis and validation of the information was done with reference to Umbria, a central Italian region. The whole database was examined with several correlations in order to facilitate the analysis of the national situation. It is thus possible to query the database in order to determine the types of users, the typical size for different users and their geographic distribution. This tool is extremely helpful in the design of new power plants and in the definition of the potential future market.
How Organizational Artefacts Fail to Protect Designed Systems
Authors: Busby J. S. , Hibberd R. E.
Published: November 2008

One of the main difficulties faced by designers of socio-technical systems is to understand how far they can rely on organizational, rather than physical, artifacts to protect such systems. Often it is not technically feasible or cost effective to devise purely physical protective measures. Organizational artifacts are entities such as rules, procedures, authority structures, records and so on that are artificial constructions, like physical equipment, but have organizational functions rather than physical ones. They typically work by providing constraints. For example, traffic rules constrain legitimate maneuvers, making the choice of maneuver simpler, and helping to protect the system against hazardous maneuvers. Nonetheless, these organizational artifacts are often implicated in failure, and a study was conducted to investigate what role they had played in the failure of maritime systems. This used the principle of distributed cognition as the theoretical starting point, and involved an analysis of 35 investigators’ reports of maritime accidents. For each case, an attempt was made to 1) identify organizational artifacts implicated in the accidents, 2) characterize the constraints they provided, and 3) describe their failure modes. From this analysis, several inferences were made. First, people’s cognitions with organizational artifacts are influenced by their cognitions about artifacts in various ways, and it is important to analyze both when understanding systems of distributed cognition. For example, if we design operating procedures to protect systems we need to understand the cultural assumptions that are made about such procedures in the environment in question. Second, artifacts are typically introduced when systems are problematic because they are under-constrained; but, in dynamic systems, situations then tend to arise in which the system becomes over-constrained. For example, traffic rules provide constraints that are typically ignored when other constraints (such as maintaining movement schedules) attain higher priority levels. Third, the constraints provided by organizational artifacts generally reduce people’s choice sets, and this reduction has three functions: it makes a person’s problem solving more tractable, it makes a person’s subsequent actions more predictable to others, and it reduces the likelihood that these actions will be hazardous to the system. For example traffic rules reduce the predictions that the master of one vessel has to make about the intentions of another vessel’s master.
Computing of Nonlinear Damping Using the Moving Autoregressive Model Method
Authors: Wu Ziying , Liu Hongzhao , Liu Lilan , Yuan Daning , Zhang Zhongming
Published: November 2008

Strictly speaking, internal damping of alloy materials is a function of temperature, frequency, strain and strain time rate and so on. Most of the previous papers with regard to damping computing only give a volumetric average when the alloy material is subjected to alternative stress. They cannot accurately describe the natural characteristic of damping. In this paper, the moving autoregressive model method (MARM) is presented to research the relationship between loss factor, strain and frequency of the alloys (Al-33Zn-6Si and Zn-27Al-1Cu). The experimental results show that the loss factor of alloy increases with the increasing strain, and increases with the increasing frequency in low-frequency region (below 400Hz). The damping appears strong nonlinear behavior. The three-dimension graph of the loss factor versus strain and frequency provides useful information for the optimum design of machine parts made from damping alloy.
Electromagnetic Compatibility and Spectrum Management Issues of the ISM Band for Wireless Communication in Healthcare Facilities
Authors: Bozec Didier , Robinson Martin , Pearce Dave , Marshmann Chris
Published: November 2008

In recent years, advancements in the field of wireless communications have led to a proliferation of devices emitting and receiving radio frequencies in the 2.4-gigahertz (GHz) frequency region, also known as the 2.4GHz unlicensed Industrial, Scientific and Medical (ISM) band. These recent advances in wireless technology such as Wireless Local Area Network (WLANs) (e.g. 802.11 (Wi-Fi), Wireless Person Area Networks (WPANs) including short-range wireless systems such as Bluetooth, and wireless telemetry equipment for patient monitoring, offer great opportunities for more advanced, efficient and cost effective communications in healthcare facilities. However, the popularity of such devices has the potential to lead to electromagnetic interference (EMI) between electronic transmitting devices and medical equipment, and to disruption in essential communications caused by interference from other devices using the increasingly overloaded ISM band. Problems occur since the EMI could lead to subtle malfunctions of medical equipment that might go undetected for long period. Most importantly, such EMI has the potential to cause malfunction that could impact upon patient safety.
Research on Multi Diagnosis Methods for Hydro-Generator Sets
Authors: Chen Xiyang , Zhang Kewei , Peng Yucheng
Published: November 2008

Hydro-Generator Sets Condition Monitoring and Predictive Maintenance activity has increased dramatically over the past few years. The Fault Diagnostic System is the key technique for the Predictive Maintenance. This paper discusses the Fault Diagnostic System function structure, system design and inferential strategy of Multi-Fault Diagnostic System of the Hydro-Generator Sets. The developing of the power system to big unit requires the higher automation and reliability of the power station. Electrical power systems are constantly exposed to faults and disturbances. This may lead to damage or it may pose a threat to reliable power system operation if a faulty cannot be quickly isolated from the system operation. In accordance with diversity and complexity of Hydro-Generator Sets faults, this paper brings forward a type of fault diagnosis method based on Multi-Diagnosis methods. The Multi-Diagnosis system is constituted of two Sub-Diagnosis systems: one is On-Line Sub-Diagnosis system that based on Bayesian Network (BN) just for the modeling with Bayesian Network has been a powerful tool to solve many uncertainty problems and also with the ability of predicting the future diagnosis; the other is Off-Line Sub-Diagnosis System that based on Model of a hydraulic Turbine-Generator Rotor-Bearing. In order to apply the Bayesian Network model to the engineering fields, we have to solve the problem of constructing the Bayesian Network. Then it suggests a method of constructing Bayesian Network based on the Fault Trees that widely used by the engineers. Base on the construction method, we will construct the Bayesian Network quickly, and Bayesian Network is more suitable for Hydro-Generator Sets fault diagnosis. In accordance with the On-Line Diagnosis Sub-System, it adopts Case-Based Reasoning to make the decision of final diagnosis result or further diagnosis. However, the method mentioned above is limited because of its bottleneck of the knowledge acquisition. The model strategy of the Rotor-Bearing system of Hydro-Generator is discussed and a multi-degree-freedom nonlinear model is developed. It proposes the simulation in accordance with the three fields such as: waterpower, electric and machine. Mechanical, electrical and hydraulic forces acting on rotor externally can be taken into account during the model calculating process. The transient responses of the system are calculated by combined used the transfer matrix method. This paper brings forward a prototype of Hydro-Generator Sets Fault Diagnostic System in order to make a more efficient fault diagnostic decision.