bluuebunny/crossref_metadata_2025 huggingface dataset:
Gene expression patterns in brain cortex of three different animal models of depression
Authors: Urigüen L. , Arteta D. , Díez‐Alarcia R. , Ferrer‐Alcón M. , Díaz A. , Pazos A. , Meana J. J.
Published: March 2008

Animal models represent a very useful tool for the study of depressive‐like behavior and for the evaluation of the therapeutic efficacy of antidepressants. Nevertheless, gene expression patterns of these different animal models and whether genes classically associated with human major depression are present in these genetic profiles remain unknown. Gene expression was evaluated in three animal models of depression: acute treatment with reserpine, olfactory bulbectomy and chronic treatment with corticosterone. Gene expression analysis was carried out using the Affymetrix GeneChip® technology. The results were evaluated using the GeneChip Operating software (Gcos 1.3) and analyzed with the GeneSpring GX v7.3 bioinformatics software (Agilent) and dChip 2005 software. Expression changes were validated with quantitative real‐time polymerase chain reaction (RT‐PCR) assays. Many transcripts were differentially expressed in the cortex of depressed‐like animals in each model. Gene ontology analysis showed that significant gene changes were clustered primarily into functional neurochemical pathways associated with apoptosis and neuronal differentiation. When expression profiles were compared among the three models, the number of transcripts differentially expressed decreased and only two transcripts (complement component 3 and fatty acid‐binding protein 7) were differentially expressed in common. Both genes were validated with RT‐PCR. Moreover, five (Htr2a, Ntrk3, Crhr1, Ntrk2 and Crh) of the genes classically related to human major depression were differentially expressed in at least one of these models. The different animal models of depression share relevant characteristics although gene expression patterns are different among them. Moreover, some of the classical genes related to human major depression are differentially expressed in these models.
Toy Recalls and China: Emotion vs. Evidence
Authors: Beamish Paul W. , Bapuji Hari
Published: March 2008

Product recalls in 2007 raised serious questions about the safety of products made in China and resulted in widespread outrage. Our analysis of toy recalls in the USA between 1988 and 2007 revealed that the vast majority of recalls were due to flaws in product designs, conducted in the corporate headquarters of toy companies, rather than to poor manufacturing by factories in Asian countries. We also found that the recalls have increased over the years, due both to design and manufacturing flaws. Our findings generated widespread interest and influenced the course of debate on import product safety. Our findings and experiences have significant implications for the research on product quality in international operations and the role that systematic research evidence can play in shaping management practice and public debate.
Optical afterglow luminosities in the Swift epoch: confirming clustering and bimodality
Authors: Nardini M. , Ghisellini G. , Ghirlanda G.
Published: March 2008

We show that gamma-ray bursts (GRBs) of known redshift and rest-frame optical extinction detected by the Swift satellite fully confirm earlier results concerning the distribution of the optical afterglow luminosity at 12 h after trigger (rest-frame time). This distribution is bimodal and relatively narrow, especially for the high-luminosity branch. This is intriguing, given that Swift GRBs have, on average, a redshift larger than pre-Swift ones, and is unexpected in the common scenario explaining the GRB afterglow. We investigate if the observed distribution can be the result of selection effects affecting a unimodal parent luminosity distribution, and find that either the distribution is intrinsically bimodal, or most (60 per cent) of the bursts are absorbed by a substantial amount of grey dust. In both cases we suggest that most dark bursts should belong to the underluminous optical family.
Transatlantic Similarities and Contrasts in Rural Development Policies Transatlantische Ähnlichkeiten und Gegensätze bei den Politiken zur Entwicklung des ländlichen Raums Points communs et divergences transatlantiques sur le développement rural
Authors: Cochrane Nancy , Wojan Tim
Published: March 2008

Transatlantic Similarities and Contrasts in Rural Development Policies

The United States (US) and European Union (EU) share many general policy aims for rural areas, but they differ in the ways in which they try to achieve these aims. The principal difference lies in the role envisioned by agriculture in overall rural development. EU policies treat agriculture as a provider of public goods, and many of its ‘rural’ programmes target agriculture. In the US, very few Federal rural development programs are focused solely on agriculture. Differences of approach may be linked to different farm distributions, population densities, historical settlement patterns, and the historical policy process per se. In particular, in the US rural development policy does not cover the environment or income support to farmers; these are addressed through other programmes. In contrast, the EU classifies its agri‐environmental programmes as rural development, claiming that more environmentally‐friendly farm practices bring benefits to the broader rural economy. US State and local initiatives emphasize many themes found in the EU’s Pillar II programmes, such as value‐added or sustainable agriculture. Overall, although there are marked differences in the ways in which policies are implemented, the coverage of these policies in the EU and US is rather similar.
Human and Social Capital in Rural Development – EU and US Perspectives Human‐ und Sozialkapital in der Entwicklung des ländlichen Raums – Perspektiven aus der EU und den USA Le capital social et humain dans le développement rural: Perspectives aux États‐Unis et dans l’Union européenne
Authors: Dwyer Janet , Findeis Jill
Published: March 2008

Human and Social Capital in Rural Development – EU and US Perspectives

Human and social capital play critical roles in rural development, in both the US and Europe. The development of these resources at the individual and community levels is both an ultimate goal of sustainable rural development (RD), and a key means to pursue it. Rural areas face a range of specific issues and challenges for human and social capital. In this article we examine some of these, finding similarity in many issues faced by EU and US rural areas, including the trend toward counter‐urbanization in some locations. We also give examples of some apparently useful policy and grass‐root approaches in the EU and US used to support farmers and in some cases rural people more generally. We assert that the US lags behind the EU in recognising the value of social capital development, but that it could learn from EU experience in terms of alternative approaches and their successes or failures. Traditionally, policies which promote the enhancement of rural human capital and strengthen social capital in rural areas have failed to attract large‐scale RD funding or prominence. They have, however, gained in credibility, and influence within the policy rhetoric, in recent years. We suggest that they deserve a higher profile in RD policies given likely future trends and challenges.
Infrastructure and Rural Development: US and EU Perspectives Infrastruktur und Entwicklung des ländlichen Raums: Perspektiven aus den USA und der EU Infrastructures et développement rural : Perspectives aux États‐Unis et dans l’Union européenne
Authors: Blandford David , Boisvert Richard N. , Davidova Sophia
Published: March 2008

Infrastructure and Rural Development: US and EU Perspectives

Infrastructural development remains a cornerstone of rural development policy in both the United States and Europe. It is evident that rural development objectives differ, but similar policy measures are used. The economic rationale for infrastructure development centres on efficiency and creation of competitive advantage. Policy intervention is justified because of the added costs of infrastructure provision in remote, sparsely populated areas. Although this policy focus does not guarantee success, regions leading in economic development typically have better physical infrastructure. In the United States, policy must adapt to challenges posed by an ageing rural infrastructure and demographic change that will increase demands on social infrastructure such as housing and health facilities. There will be greater local responsibility for funding, and expanded use of public/private partnerships. In the European Union, the major challenge is in redirecting resources to new member states, where there is urgent need for both large new investments in transport networks and small investments to improve local access. Although two current options for funding these diverse needs focus on European policies only, investments in non‐farm physical capital and public infrastructure cannot be sustained without active national policies to complement the European efforts, perhaps through co‐financing requirements.
5‐HT1A, but not 5‐HT2 and 5‐HT7, receptors in the nucleus raphe magnus modulate hypoxia‐induced hyperpnoea
Authors: Nucci T. B. , Branco L. G. S. , Gargaglioni L. H.
Published: March 2008

Aim:  In the present study, we assessed the role of 5‐hydroxytryptamine (5‐HT) receptors (5‐HT1A, 5‐HT2 and 5‐HT7) in the nucleus raphe magnus (NRM) on the ventilatory and thermoregulatory responses to hypoxia.

Methods:  To this end, pulmonary ventilation (VE) and body temperature (Tb) of male Wistar rats were measured in conscious rats, before and after a 0.1 μL microinjection of WAY‐100635 (5‐HT1A receptor antagonist, 3 μg 0.1μL−1, 56 mm), ketanserin (5‐HT2 receptor antagonist, 2 μg 0.1μL−1, 36 mm) and SB269970 (5‐HT7 receptor antagonist, 4 μg 0.1 μL−1, 103 mm) into the NRM, followed by 60 min of severe hypoxia exposure (7% O2).

Results:  Intra‐NMR microinjection of vehicle (control rats) or 5‐HT antagonists did not affect VE or Tb during normoxic conditions. Exposure of rats to 7% O2 evoked a typical hypoxia‐induced anapyrexia after vehicle microinjections, which was not affected by microinjection of WAY‐100635, SB269970 or ketanserin. The hypoxia‐induced hyperpnoea was not affected by SB269970 and ketanserin intra‐NMR. However, the treatment with WAY‐100635 intra‐NRM attenuated the hypoxia‐induced hyperpnoea.

Conclusion:  These data suggest that 5‐HT acting on 5‐HT1A receptors in the NRM increases the hypoxic ventilatory response.
CFTR and its key role in in vivo resting and luminal acid‐induced duodenal HCO3− secretion
Authors: Singh A. K. , Sjöblom M. , Zheng W. , Krabbenhöft A. , Riederer B. , Rausch B. , Manns M. P. , Soleimani M. , Seidler U.
Published: March 2008

Background and aims:  We investigated the role of the recently discovered, villous‐expressed anion exchanger Slc26a6 (PAT1) and the predominantly crypt‐expressed cystic fibrosis transmembrane regulator (CFTR) in basal and acid‐stimulated murine duodenal HCO3− secretion in vivo, and the influence of blood HCO3− concentration on both.

Methods:  The proximal duodenum of anaesthetized mice was perfused in situ, and HCO3− secretion was determined by back‐titration. Duodenal mucosal permeability was assessed by determining 51Cr‐EDTA leakage from blood to lumen.

Results:  Compared with wild type (WT) littermates basal duodenal HCO3− secretory rates were slightly reduced in Slc26‐deficient mice at low (∼21 mm), and markedly reduced at high blood HCO3− concentration (∼29 mm). In contrast, basal HCO3− secretion was markedly reduced in CFTR‐deficient mice compared with WT littermates both at high and low blood HCO3− concentration. A short‐term application of luminal acid increased duodenal HCO3− secretory rate in Slc26a6‐deficient and WT mice to the same degree, but had no stimulatory effect in the absence of CFTR. Luminal acidification to pH 2.5 did not alter duodenal permeability.

Conclusions:  The involvement of Slc26a6 in basal HCO3− secretion in murine duodenum in vivo is critically dependent on the systemic acid/base status, and this transporter is not involved in acid‐stimulated HCO3− secretion. The presence of CFTR is essential for basal and acid‐induced HCO3− secretion irrespective of acid/base status. This suggests a coupled action of Slc26a6 with CFTR for murine basal duodenal HCO3− secretion, but not acid‐stimulated secretion, in vivo.
Here, There, Everywhere: The Ubiquitous Geographies of Heteronormativity
Authors: Hubbard Phil
Published: March 2008

From its first tentative forays into questions of gay and lesbian residence, the discipline of geography has made increasingly important contributions to literatures on sexual identities, practices and politics. In this paper, I seek to highlight the breadth and depth of recent work on sexuality and space by exploring the contributions made by geographers to the theorisation of heteronormativity. Specifically, this paper explores how heterosexual norms are constructed ansd reproduced spatially, noting the increasing corpus of work which moves beyond examination of heterosexuality's Other (i.e. homosexuality) to consider the multiple desires and bodies that can be accommodated within the category ‘heterosexual’. Moving from urban to rural contexts, this paper hence reviews literatures detailing how particular heterosexualities are rendered normal and concludes that the literature is usefully shifting from a focus on identity and community to questions of practice and performance.
Understanding Dryland Landscape Dynamics: Do Biological Crusts Hold the Key?
Authors: Viles Heather A.
Published: March 2008

Understanding landscape dynamics in arid and semi‐arid areas is becoming increasingly important, as global change threatens to upset linked ecological and geomorphological systems with potentially serous impacts on livelihoods and environments. Biological crusts (composed of lichens, algae, fungi and bacteria) cover many rock, soil and sediment surfaces in arid and semi‐arid areas and provide a key to understanding future dryland landscape dynamics. Such crusts have been found to play a number of key geomorphic and ecological roles, and are identified as important ecosystem engineers and biogeomorphological agents that could be used in environmental restoration. However, they have also been reported to be highly fragile and susceptible to disturbance, and damage to them may result in non‐linear consequences for linked dryland geomorphological and ecological systems. This paper outlines the current state of knowledge on biological crusts in arid and semi‐arid areas and calls for increased collaboration between geomorphologists and ecologists and better links between studies of biological crusts on rock and soil surfaces.
Diasporic and Transnational Social Practices in Central Asia
Authors: Diener Alexander C.
Published: March 2008

Diaspora has become such a popular concept in recent years because it so effectively challenges the authenticity of the nation‐state and the bounded identities it supports. A core premise of this critique is thatnotevery diaspora or nation‐state is the same. An ideal context in which to explore this idea is the region of Central Asia. Transnational practices emerging among dispersed members of each state's population draw into question the very idea ofdiasporaas connoting a condition of displacement andnationas relating to a discreet territorially fixed identity community. The complexity of the diasporic form among Central Asia's dispersed communities highlights the need to be mindful of the material, historical, and political settings within which individuals and groups create and sustain their own social and cultural networks. This essay reviews major debates and offers a survey of diasporic conditions within Central Asia.
Analysis of Extreme Summer Rainfall Using Climate Teleconnections and Typhoon Characteristics in South Korea1
Authors: Kwon Hyun‐Han , Khalil Abedalrazq F. , Siegfried Tobias
Published: March 2008

Abstract:  It is now widely acknowledged that climate variability modulates the frequency of extreme hydrological events. Traditional methodologies for hydrologic frequency analysis are not devised to account for variation in the exogenous teleconnections. Flood frequency analysis is further plagued by the assumptions of stationary in the causal structure as well as ergodicity. Here, we propose a dynamical hierarchical Bayesian analysis to account for exogenous forcing that govern the summer season rainfall. The precursors for Korean summer rainfall at different frequencies are identified utilizing wavelet and independent component analyses. The sea surface temperatures, the ensemble of rainfall predictions by General Circulation Model, in addition to the typhoon attributes were found to have direct correlation with extreme rainfall events and were used as inputs to the logistic regression model. The model parameters are estimated using Markov Chain Monte Carlo and the resulting posterior distributions associated with individual inputs are analyzed to advance our understanding of the spatiotemporal impact of the teleconnections. Eight rainfall stations throughout Korea are considered in this analysis. We demonstrate that the probability of occurrence of extreme events could be successfully projected at a 90% rate of correct classification of extreme events.
Distinct roles for angiotensin‐converting enzyme 2 and carboxypeptidase A in the processing of angiotensins within the murine heart
Authors: Garabelli Paul J. , Modrall J. Gregory , Penninger Josef M. , Ferrario Carlos M. , Chappell Mark C.
Published: March 2008

Angiotensin‐converting enzyme 2 (ACE2), a homologue of angiotensin‐converting enzyme (ACE), converts angiotensin (Ang) I to Ang(1–9) and Ang II to Ang(1–7), but does not directly process Ang I to Ang II. Cardiac function is compromised in ACE2 null mice; however, the importance of ACE2 in the processing of angiotensin peptides within the murine heart is not known. We determined the metabolism of angiotensins in wild‐type (WT), ACE (ACE−/−) and ACE2 null mice (ACE2−/−). Angiotensin II was converted almost exclusively to Ang(1–7) in the cardiac membranes of WT and ACE−/− strains, although generation of Ang(1–7) was greater in the ACE−/− mice (27.4 ± 4.1 versus 17.5 ± 3.2 nmol−1 mg h−1 for WT). The ACE2 inhibitor MLN4760 significantly attenuated Ang II metabolism and the subsequent formation of Ang(1–7) in both strains. In the ACE2−/− hearts, Ang II metabolism and the generation of Ang(1–7) were significantly attenuated; however, the ACE2 inhibitor reduced the residual Ang(1–7)‐forming activity in this strain. Angiotensin I was primarily converted to Ang(1–9) (WT, 28.9 ± 3.1 nmol−1 mg h−1; ACE−/−, 49.8 ± 5.3 nmol−1 mg h−1; and ACE2−/−, 35.9 ± 5.4 nmol−1 mg h−1) and to smaller quantities of Ang(1–7) and Ang II. Although the ACE2 inhibitor had no effect on Ang(1–9) formation, the carboxypeptidase A inhibitor benzylsuccinate essentially abolished the formation of Ang(1–9) and increased the levels of Ang I in cardiac membranes. In conclusion, our studies in the murine heart suggest that ACE2 is the primary pathway for the metabolism of Ang II and the subsequent formation of Ang(1–7), a peptide that, in contrast to Ang II, exhibits both antifibrotic and antiproliferative actions.
Exercise training in late middle‐aged male Fischer 344 × Brown Norway F1‐hybrid rats improves skeletal muscle aerobic function
Authors: Betik Andrew C. , Baker David J. , Krause Daniel J. , McConkey Marina J. , Hepple Russell T.
Published: March 2008

The Fischer 344 × Brown Norway F1‐hybrid (F344BN) rat has become an increasingly popular and useful strain for studying age‐related declines in skeletal muscle function because this strain lives long enough to experience significant declines in muscle mass. Since exercise is often considered a mechanism to combat age‐related declines in muscle function, determining the utility of this strain of rat for studying the effects of exercise on the ageing process is necessary. The purpose of this study was to evaluate the plasticity of skeletal muscle aerobic function in late middle‐aged male rats following 7 weeks of treadmill exercise training. Training consisted of 60 min per day, 5 days per week with velocity gradually increasing over the training period according to the capabilities of individual rats. The final 3 weeks involved 2 min high‐intensity intervals to increase the training stimulus. We used in situ skeletal muscle aerobic metabolic responses and in vitro assessment of muscle mitochondrial oxidative capacity to describe the adaptations of aerobic function from the training. Training increased running endurance from 11.3 ± 0.6 to 15.5 ± 0.8 min, an improvement of ∼60%. Similarly, distal hindlimb muscles from trained rats exhibited a higher maximal oxygen consumption in situ (23.2 ± 1.3 versus 19.7 ± 0.8 μmol min−1 for trained versus sedentary rats, respectively) and greater citrate synthase and complex IV enzyme activities in gastrocnemius (29 and 19%, respectively) and plantaris muscles (24 and 28%, respectively) compared with age‐matched sedentary control animals. Our results demonstrate that skeletal muscles from late middle‐aged rats adapt to treadmill exercise by improving skeletal muscle aerobic function and mitochondrial enzyme activities. This rat strain seems suitable for further investigations using exercise as an intervention to combat ageing‐related declines of skeletal muscle aerobic function.
Diverse properties of store‐operated TRPC channels activated by protein kinase C in vascular myocytes
Authors: Saleh Sohag N. , Albert Anthony P. , Peppiatt‐Wildman C. M. , Large William A.
Published: March 2008

In vascular smooth muscle, store‐operated channels (SOCs) contribute to many physiological functions including vasoconstriction and cell growth and proliferation. In the present work we compared the properties of SOCs in freshly dispersed myocytes from rabbit coronary and mesenteric arteries and portal vein. Cyclopiazonic acid (CPA)‐induced whole‐cell SOC currents were sixfold greater at negative membrane potentials and displayed markedly different rectification properties and reversal potentials in coronary compared to mesenteric artery myocytes. Single channel studies showed that endothelin‐1, CPA and the cell‐permeant Ca2+ chelator BAPTA‐AM activated the same 2.6 pS SOC in coronary artery. In 1.5 mm[Ca2+]o the unitary conductance of SOCs was significantly greater in coronary than in mesenteric artery. Moreover in 0 mm[Ca2+]o the conductance of SOCs in coronary artery was unaltered whereas the conductance of SOCs in mesenteric artery was increased fourfold. In coronary artery SOCs were inhibited by the protein kinase C (PKC) inhibitor chelerythrine and activated by the phorbol ester phorbol 12,13‐dibutyrate (PDBu), the diacylglycerol analogue 1‐oleoyl‐2‐acetyl‐sn‐glycerol (OAG) and a catalytic subunit of PKC. These data infer an important role for PKC in activation of SOCs in coronary artery similar to mesenteric artery and portal vein. Anti‐TRPC1 and ‐TRPC5 antibodies inhibited SOCs in coronary and mesenteric arteries and portal vein but anti‐TRPC6 blocked SOCs only in coronary artery and anti‐TRPC7 blocked SOCs only in portal vein. Immunoprecipitation showed associations between TRPC1 and TRPC5 in all preparations but between TRPC5 and TRPC6 only in coronary artery and between TRPC5 and TRPC7 only in portal vein. Finally, flufenamic acid increased SOC activity in coronary artery but inhibited SOCs in mesenteric artery and portal vein myocytes. These data provide strong evidence that vascular myocytes express diverse SOC isoforms, which are likely to be composed of different TRPC proteins and have different physiological functions.
Serotonin transporter knockout mice have a reduced ventilatory response to hypercapnia (predominantly in males) but not to hypoxia
Authors: Li Aihua , Nattie Eugene
Published: March 2008

Medullary serotonergic (5‐HT) neurons are implicated in central chemoreception and 5‐HT abnormalities are present in many cases of the sudden infant death syndrome (SIDS). Mice with a targeted disruption of the serotonin transporter (5‐HTT) develop in the presence of excess 5‐HT in brain extracellular fluid (ECF). As adults they exhibit reduced 5‐HT neuron activity and 5‐HT1Areceptor binding with varying changes in postsynaptic 5‐HT receptor function. They exhibit behavioural phenotypes (anxiety, reduced aggression) but little is known about their control of breathing. We show that conscious adult male and female 5‐HTT knockout mice breathing air at room temperature have a higher resting, breathing frequency andbut a normal body temperature andratio (the ventilatory equivalent) compared to wild‐type (WT) controls. In hypercapnia, there is a reduced ventilatory response (expressed as theratio) that is much more prominent in males (−68%) than females (−22%). In hypoxia, both males and females exhibit a higher,and body temperature but theirratio is normal. We conclude that 5‐HTT knockout mice have a diminished function of the medullary 5‐HT system, which is manifest most remarkably in a substantial loss of CO2sensitivity predominantly in males. This finding supports the importance of medullary 5‐HT neurons in central chemoreception. Females either rely less on 5‐HT neurons in chemoreception or adapt more readily to the loss of 5‐HT function. This genetic model allows examination of the role of excess 5‐HT in ECF in the development of the control of breathing and central chemoreception, which may be pertinent to SIDS.
Balancing of Flexible Rotors Using Convex Optimization Techniques: Optimum Min-Max LMI Influence Coefficient Balancing
Authors: Untaroiu Costin D. , Allaire Paul E. , Foiles William C.
Published: March 2008

In some industrial applications, influence coefficient balancing methods fail to find the optimum vibration reduction due to the limitations of the least-squares optimization methods. Previous min-max balancing methods have not included practical constraints often encountered in industrial balancing. In this paper, the influence coefficient balancing equations, with suitable constraints on the level of the residual vibrations and the magnitude of correction weights, are cast in linear matrix inequality (LMI) forms and solved with the numerical algorithms developed in convex optimization theory. The effectiveness and flexibility of the proposed method have been illustrated by solving two numerical balancing examples with complicated requirements. It is believed that the new methods developed in this work will help in reducing the time and cost of the original equipment manufacturer or field balancing procedures by finding an optimum solution of difficult balancing problems. The resulting method is called the optimum min-max LMI balancing method.
An Optimum Embossment of Rectangular Section in Panel to Minimize Noise Power
Authors: Jeon Jin-Young , Okuma Masaaki
Published: March 2008

In this paper, the authors propose a new method for optimum design of embossed panel sections on vibrating panel-like structures to reduce noise. It is proposed in the method to use the mapping of sound pressure level on the vibrating panel’s surface for best positioning of an embossed panel section, which means a raised panel section, in other words, and to apply the particle swarm optimization algorithm for determining the best dimensions of the embossed panel section. The optimum design method is applied to a rectangular aluminum panel whose size is 0.45m×0.4m with thickness 0.001m under the boundary condition of clamping four edge lines. Then, according to the optimum design, an embossed section is actually made in each panel by embossing using a press machine, and experiments are carried out to the panels for verification. The application study is carried out for two cases of different positions of a point force excitation on the panels. The two applications demonstrate that the embossed panel sections designed by the optimization method can realize good reduction of sound power.
Nonlinear Transverse Vibrations and 3:1 Internal Resonances of a Beam With Multiple Supports
Authors: Özkaya E. , Bağdatlı S. M. , Öz H. R.
Published: March 2008

In this study, nonlinear transverse vibrations of an Euler–Bernoulli beam with multiple supports are considered. The beam is supported with immovable ends. The immovable end conditions cause stretching of neutral axis and introduce cubic nonlinear terms to the equations of motion. Forcing and damping effects are included in the problem. The general arbitrary number of support case is considered at first, and then 3-, 4-, and 5-support cases are investigated. The method of multiple scales is directly applied to the partial differential equations. Natural frequencies and mode shapes for the linear problem are found. The correction terms are obtained from the last order of expansion. Nonlinear frequencies are calculated and then amplitude and phase modulation figures are presented for different forcing and damping cases. The 3:1 internal resonances are investigated. External excitation frequency is applied to the first mode and responses are calculated for the first or second mode. Frequency-response and force-response curves are drawn.
Shock Isolation Systems Using Magnetorheological Dampers
Authors: Choi Young-Tai , Wereley Norman M.
Published: March 2008

This study addresses the feasibility and applicability of a semiactive magnetorheological (MR) shock isolation system to replace a conventional passive shock isolation system for commercial-off-the-shelf (COTS) equipment. To this end, an analysis of a shock isolation system with an MR damper was theoretically developed. To improve shock mitigation performance, semiactive control strategies such as skyhook and sliding mode control were incorporated into our analysis. Controlled responses of the semiactive MR shock isolation system were simulated and compared with those of a conventional passive shock isolation system for two different representative shock loads for COTS equipment.
Modeling and Control of Torsional Beam Vibrations: A Wave-Based Approach
Authors: Moallem M.
Published: March 2008

This paper presents a wave-based modeling and control approach for suppressing torsional vibrations of an elastic shaft driven by a motor at one end and an inertial load at the other end. A two-port network model representing the dynamics of torsional displacements is obtained starting from the partial differential equations governing a shaft in torsion. By incorporating appropriate boundary conditions, the infinite dimensional transfer function of the system is obtained. Furthermore, the system is represented by delay elements that can be used for simulation purposes. An inversion-based controller that can be used to suppress vibrations while rotating the shaft according to a specific trajectory is then developed. The performance of the controller is further studied using numerical simulations.
Operational Bearing Parameters and Acoustic Emission Generation
Authors: Couturier J. , Mba D.
Published: March 2008

In further developing the acoustic emission (AE) technology for bearing monitoring, it is essential that a relationship is determined between bearing operational parameters, such as speed and load, and the generation of AE activity. Hitherto, almost all published investigations on the application of AE technology to bearing monitoring have been based on systems that operate at fixed speed and/or load conditions. In reality, a significant proportion of bearings operate under variable speed and load conditions; therefore, the growth of AE technology in monitoring bearings under such conditions requires an understanding of the influence of bearing operational parameters on the generation of AE. This paper presents experimental tests undertaken at near isothermal conditions aimed at understanding the influence of speed and load on the generation of AE. The results of the program lead to the introduction of AE operational maps. It is concluded that under an elastohydrodynamic lubrication regime, AE activity can be directly related to the theoretically predicted specific film thickness within the bearing.
A Generic Approach to Coat Carbon Nanotubes With Nanoparticles for Potential Energy Applications
Authors: Zhu Liying , Lu Ganhua , Chen Junhong
Published: March 2008

A generic and material-independent dry route based on electrostatic force directed assembly (ESFDA) is used to assemble various nanoparticles onto multiwalled carbon nanotubes (CNTs). Charged and nonagglomerated aerosol nanocrystals are first produced using a mini-arc plasma source and then delivered in an inert carrier gas to electrically biased CNTs. The electric field near the CNT is significantly enhanced, and the aerosol nanoparticles are attracted to the external surface of CNTs. For the first time, CNTs have been sequentially coated with nanoparticles of multiple materials to realize the multicomponent coating. High resolution transmission electron microscopy images show that the nonagglomerated entity of nanoparticles and the crystallinity of both nanoparticles and CNTs are preserved during the assembly. The ESFDA technique enables unique hybrid nanostructures attractive for various energy applications.
Thermal Conductivity Equations Based on Brownian Motion in Suspensions of Nanoparticles (Nanofluids)
Authors: Yang Bao
Published: March 2008

Thermal conductivity equations for the suspension of nanoparticles (nanofluids) have been derived from the kinetic theory of particles under relaxation time approximations. These equations, which take into account the microconvection caused by the particle Brownian motion, can be used to evaluate the contribution of particle Brownian motion to thermal transport in nanofluids. The relaxation time of the particle Brownian motion is found to be significantly affected by the long-time tail in Brownian motion, which indicates a surprising persistence of particle velocity. The long-time tail in Brownian motion could play a significant role in the enhanced thermal conductivity in nanofluids, as suggested by the comparison between the theoretical results and the experimental data for the Al2O3-in-water nanofluids.
A Photoelectrochemical Model of Proton Exchange Water Electrolysis for Hydrogen Production
Authors: Nie Jianhu , Chen Yitung , Boehm Robert F. , Katukota Shanthi
Published: March 2008

A photoelectrochemical model for hydrogen production from water electrolysis using proton exchange membrane is proposed based on Butler-Volmer kinetics for electrodes and transport resistance in the polymer electrolyte. An equivalent electrical circuit analogy is proposed for the sequential kinetic and transport resistances. The model provides a relation between the applied terminal voltage of electrolysis cell and the current density in terms of Nernst potential, exchange current densities, and conductivity of polymer electrolyte. Effects of temperature on the voltage, power supply, and hydrogen production are examined with the developed model. Increasing temperature will reduce the required power supply and increase the hydrogen production. An increase of about 11% is achieved by varying the temperature from 30°Cto80°C. The required power supply decreases as the illumination intensity becomes greater. The power supply due to the cathode overpotential does not change too much with the illumination intensity. Effects of the illumination intensity can be observed as the current density is relatively small for the examined illumination intensities.
Modeling the Thermal Conductivity and Phonon Transport in
Nanoparticle Composites Using Monte Carlo Simulation
Authors: Jeng Ming-Shan , Yang Ronggui , Song David , Chen Gang
Published: March 2008

This paper presents a Monte Carlo simulation scheme to study the phonon transport and the thermal conductivity of nanocomposites. Special attention has been paid to the implementation of periodic boundary condition in Monte Carlo simulation. The scheme is applied to study the thermal conductivity of silicon germanium (Si–Ge) nanocomposites, which are of great interest for high-efficiency thermoelectric material development. The Monte Carlo simulation was first validated by successfully reproducing the results of (two-dimensional) nanowire composites using the deterministic solution of the phonon Boltzmann transport equation reported earlier and the experimental thermal conductivity of bulk germanium, and then the validated simulation method was used to study (three-dimensional) nanoparticle composites, where Si nanoparticles are embedded in Ge host. The size effects of phonon transport in nanoparticle composites were studied, and the results show that the thermal conductivity of nanoparticle composites can be lower than that of the minimum alloy value, which is of great interest to thermoelectric energy conversion. It was also found that randomly distributed nanopaticles in nanocomposites rendered the thermal conductivity values close to that of periodic aligned patterns. We show that interfacial area per unit volume is a useful parameter to correlate the size effect of thermal conductivity in nanocomposites. The key for the thermal conductivity reduction is to have a high interface density where nanoparticle composites can have a much higher interface density than the simple 1D stacks, such as superlattices. Thus, nanocomposites further benefit the enhancement of thermoelectric performance in terms of thermal conductivity reduction. The thermal conductivity values calculated by this work qualitatively agrees with a recent experimental measurement of Si–Ge nanocomposites.
Effect of Brownian Motion on Thermal Conductivity of Nanofluids
Authors: Shukla Ratnesh K. , Dhir Vijay K.
Published: March 2008

Nanofluids, i.e., liquids containing nanometer sized metallic or nonmetallic solid particles, show an increase in thermal conductivity compared to that of the pure liquid. In this paper, a simple model for predicting thermal conductivity of nanofluids based on Brownian motion of nanoparticles in the liquid is developed. A general expression for the effective thermal conductivity of a colloidal suspension is derived by using ensemble averaging under the assumption of small departures from equilibrium and the presence of pairwise additive interaction potential between the nanoparticles. The resulting expression for thermal conductivity enhancement is applied to the nanofluids with a polar base fluid, such as water or ethylene glycol, by assuming an effective double layer repulsive potential between pairs of nanoparticles. It is shown that the model predicts a particle size and temperature dependent thermal conductivity enhancement. The results of the calculation are compared with the experimental data for various nanofluids containing metallic and nonmetallic nanoparticles.
Experimental Investigation of Turbulent Convective Heat Transfer and Pressure Loss of Alumina/Water and Zirconia/Water Nanoparticle Colloids (Nanofluids) in Horizontal Tubes
Authors: Williams Wesley , Buongiorno Jacopo , Hu Lin-Wen
Published: March 2008

The turbulent convective heat transfer behavior of alumina (Al2O3) and zirconia (ZrO2) nanoparticle dispersions in water is investigated experimentally in a flow loop with a horizontal tube test section at various flow rates (9000<Re<63,000), temperatures (21–76°C), heat fluxes (up to ∼190kW∕m2), and particle concentrations (0.9–3.6vol% and 0.2–0.9vol% for Al2O3 and ZrO2, respectively). The experimental data are compared to predictions made using the traditional single-phase convective heat transfer and viscous pressure loss correlations for fully developed turbulent flow, Dittus–Boelter, and Blasius/MacAdams, respectively. It is shown that if the measured temperature- and loading-dependent thermal conductivities and viscosities of the nanofluids are used in calculating the Reynolds, Prandtl, and Nusselt numbers, the existing correlations accurately reproduce the convective heat transfer and viscous pressure loss behavior in tubes. Therefore, no abnormal heat transfer enhancement was observed in this study.
Measurements of Three-Dimensional Flow in Microchannel With Complex Shape by Micro-Digital-Holographic Particle-Tracking Velocimetry
Authors: Satake Shin-ichi , Anraku Takafumi , Kanamori Hiroyuki , Kunugi Tomoaki , Sato Kazuho , Ito Tomoyoshi
Published: March 2008

High time-resolution flow field measurement in two microchannels with a complex shape is performed by a micro-digital-holographic particle-tracking velocimetry (micro-DHPTV). The first microchannel has a Y junction that combines the flow of fluid from two inlets into one outlet. In this case, two laminar velocity profiles from the inlet regions merge into one laminar velocity profile. The second microchannel has a convergence region from where a fluid flows into a divergence region. At this region, two recirculation regions appear. Consequently, approximately 250 velocity vectors in both cases can be obtained instantaneously. For a microchannel with the convergence region, the two recirculation regions that appear at the divergence point are captured from a three-dimensional vector field, with which the axes of recircular vortices have some alignment. The reason why we can observe this phenomenon is that a three-dimensional velocity, including the depth direction, can be obtained by micro-DHPTV.
Practical Considerations for Waveguide-Ballistic Thermal Energy Conversion
Authors: Wieckowski Michael , Margala Martin
Published: March 2008

The potential of converting heat energy into electrical energy using a previously reported waveguide-ballistic device is presented. The interactions between incident electromagnetic waves and free electrons in a metal waveguide are analyzed with respect to their transport through a high-frequency ballistic rectifier using finite element method simulation. It was determined that the resulting conversion efficiency to a dc potential is approximately 6%, yielding a power density on the order of 30W∕m2.
Free Vibration Analysis of Frames Using the Transfer Dynamic Stiffness Matrix Method
Authors: Tu Tsung-Hsien , Yu Jen-Fang , Lien Hsin-Chung , Tsai Go-Long , Wang B. P.
Published: March 2008

A method for free vibration of 3D space frame structures employing transfer dynamic stiffness matrix (TDSM) method based on Euler–Bernoulli beam theory is developed in this paper. The exact TDSM of each member is assembled to obtain the system matrix that is frequency dependent. All free vibration eigensolutions including coincident roots for the characteristic equation can be obtained to any desired accuracy using the algorithm developed by Wittrick and Williams (1971, “A General Algorithm for Computing Natural Frequencies of Elastic Structures,” Q. J. Mech. Appl. Math., 24, pp. 263–284). Exact eigenfunction of structures can then be computed using the dynamic shape function and the corresponding eigenvector. The results showed good agreement with those computed by finite element method.
Finite Element Modeling and Analysis of Friction-Wedge Dampers During Suspension Pitch Modes
Authors: Sun Y. Q. , Cole C.
Published: March 2008

A two-dimensional finite element model has been developed to investigate the friction damping characteristics of suspensions with so-called “constant-damping” friction wedges widely used in three-piece bogie wagons in Australia. The model was used to simulate the suspension during pitch modes. The simulation results show that the friction damping force in the suspension pitch modes is dependent on the friction conditions on the wedge contact surfaces, wagon speed, and the wedge shape and elasticity effects including the stuck state. The suspension pitch movements of a three-piece bogie with dry friction wedges can cause wedge rotation and partial separation of wedge contacting surfaces, which seriously affects the wedge friction damping effectiveness. The curved shape of wedge angular surface can significantly improve the friction damping characteristics of three-piece bogie suspensions.
Two-Dimensional Input Shaping for One-Dimensional Continua
Authors: Lotfi-Gaskarimahalle Amir , Rahn Christopher D.
Published: March 2008

This paper extends input shaping control to one-dimensional continua. Unlike discrete systems where the input is shaped only in the temporal domain, temporal and spatial input shaping can produce zero residual vibration in setpoint position control of distributed strings and beams. For collocated and noncollocated boundary control of strings and domain control of strings and pinned beams, the response to step inputs is solved in closed form using delays. For a clamped beam model, a closed form infinite modal series is used. The boundary controlled string can be setpoint regulated using two-pulse zero vibration (ZV) and three-pulse zero vibration and derivative (ZVD) shapers but ZVD is not more robust to parameter variations than ZV, a unique characteristic of second-order partial differential equations systems. Noncollocated ZV and ZVD boundary control enables rigid body translation of a string with zero residual vibration. Domain controlled strings and pinned beams with spatial input distributions that satisfy certain orthogonality conditions (e.g., midspan point load or uniformly distributed load) can be setpoint regulated with shaped inputs. For the cantilevered beam, modal shaping of the input distribution and ZV or ZVD temporal shaping drives the tip to the desired position with zero residual vibration.
Dynamic Modeling and Experimental Validation of Eddy Current Dampers and Couplers
Authors: Tonoli Andrea , Amati Nicola
Published: March 2008

The interest in eddy current dampers is increasing especially in aeronautic and automotive industry. Such devices seem to be a valid alternative to conventional fluid film and viscoelastc dampers. Even if several papers have been published on this topic, an electromechanical model taking into account both the resistance and the inductance of the conductor is still lacking. The aim of the present paper is to model the electromagnetic interaction of an eddy current device operating as a damper or as a coupler and to validate it by means of experimental tests performed at steady state and vibrating about a fixed position. The study is based on the computation of the damping torque starting from the basic principles. The analytical models are developed using the bond graph formalism that allows to obtain purely mechanical analogs of the electromechanical system. The main results are the identification of eddy current damper dynamic model and the definition of a set of “conversion rules” allowing to readily obtain the mechanical impedance from the torque to slip speed characteristic and vice versa. The experimental results confirm the band limited effect of the damping, which cannot be neglected for practical applications. The effect can be exploited in eddy current couplers to filter higher order disturbances.
The Energy-Absorbing Characteristics of Tubular Structures With Geometric and Material Modifications: An Overview
Authors: Yuen S. Chung Kim , Nurick G. N.
Published: March 2008

For better crashworthiness performance, vehicles must protect its occupants by maintaining structural integrity and converting the large amount of kinetic energy into other forms of energy in a controllable and predictable manner in a crash situation. In doing so, lower crushing force would provide better safety for the vehicle occupants. This paper reviews the axial response of “modified” tubular sections with imperfections and fillers subjected to axial impact loads relevant to the field of structural crashworthiness. The use of imperfections sets the mode and initiation of collapse of a tube at a specific location and reduces the maximum crush force, hence improving the energy-absorbing characteristics of tubular structures. The types of imperfections discussed include prebuckle, parallel and dished indentations, cutouts, stiffeners, fillers, and wrapping.