bluuebunny/crossref_metadata_2025 huggingface dataset:
The finite-frequency sensitivity kernel for migration residual moveout and its applications in migration velocity analysis
Authors: Xie Xiao-Bi , Yang Hui
Published: November 2008

We have derived a broadband sensitivity kernel that relates the residual moveout (RMO) in prestack depth migration (PSDM) to velocity perturbations in the migration-velocity model. We have compared the kernel with the RMO directly measured from the migration image. The consistency between the sensitivity kernel and the measured sensitivity map validates the theory and the numerical implementation. Based on this broadband sensitivity kernel, we propose a new tomography method for migration-velocity analysis and updating — specifically, for the shot-record PSDM and shot-index common-image gather. As a result, time-consuming angle-domain analysis is not required. We use a fast one-way propagator and multiple forward scattering and single backscattering approximations to calculate the sensitivity kernel. Using synthetic data sets, we can successfully invert velocity perturbations from the migration RMO. This wave-equation-based method naturally incorporates the wave phenomena and is best teamed with the wave-equation migration method for velocity analysis. In addition, the new method maintains the simplicity of the ray-based velocity analysis method, with the more accurate sensitivity kernels replacing the rays.
Orexin-A Hyperphagia: Hindbrain Participation in Consummatory Feeding Responses
Authors: Baird John-Paul , Choe Angela , Loveland Jasmine L. , Beck Janine , Mahoney Carrie E. , Lord Julia S. , Grigg Lindsay A.
Published: November 2008

Orexin-A (ORXA) is an orexigenic neuropeptide produced by the lateral hypothalamus that increases food intake when injected into the brain ventricles or forebrain nuclei. We used a licking microstructure analysis to evaluate hindbrain and forebrain ORXA effects in intact and hindbrain-lesioned rats, to identify the motivational and anatomical bases of ORXA hyperphagia. Intact rats with cannulas in the fourth brain ventricle (4V) received vehicle (artificial cerebrospinal fluid) or ORXA (0.1, 0.4, 1, or 10 nm) injections before 90 min access to 0.1 m sucrose. Meal size and frequency were increased in a double-dissociated manner by the 1 and 10 nm doses, respectively. In experiment 2, 4V 1 nm ORXA was applied to rats offered solutions varied in caloric and gustatory intensity (water and 0.1 and 1 m sucrose). ORXA increased meal frequency for all tastants. ORXA increased meal size only for 0.1 m sucrose, by prolonging the meal without affecting early ingestion rate or lick burst size, suggesting that 4V ORXA influenced inhibitory postingestive feedback rather than taste evaluation. In experiment 3, rats with cannulas in the third ventricle (3V) received dorsal medullary lesions centered on the area postrema (APX group) or sham procedures, and licking for water and 0.1 and 1 m sucrose was evaluated after 1 nm 3V ORXA/artificial cerebrospinal fluid injections. The 3V ORXA increased 0.1 m sucrose meal size and meal frequency for all tastants in the sham group, as observed after 4V ORXA in experiment 2. In the APX group, 3V ORXA injections influenced meal frequency, but they no longer increased meal size. However, the APX rats increased meal size for 0.1 m sucrose after food and water deprivation and after 3V angiotensin II injection. They also showed meal size suppression after 3V injection of the melanocortin-3/4 receptor agonist melanotan II (1 nm). These findings suggest that the area postrema and subjacent nucleus of the solitary tract are necessary for increases in consummatory (meal size) but not appetitive (meal frequency) responses to 3V ORXA. The meal size increases may be due to reduced postingestive feedback inhibition induced by ORXA delivered to either the hindbrain or forebrain ventricles.

Orexin-A increases meal size via gut feedback disinhibition, not enhanced gustatory evaluation. Medullary lesions abolish meal size but not frequency increases, indicating dissociable sites for orexin-A feeding actions.
The Glucagon-Like Peptide-1 Receptor Regulates Endogenous Glucose Production and Muscle Glucose Uptake Independent of Its Incretin Action
Authors: Ayala Julio E. , Bracy Deanna P. , James Freyja D. , Julien Brianna M. , Wasserman David H. , Drucker Daniel J.
Published: November 2008

Glucagon-like peptide-1 (GLP-1) diminishes postmeal glucose excursions by enhancing insulin secretion via activation of the β-cell GLP-1 receptor (Glp1r). GLP-1 may also control glucose levels through mechanisms that are independent of this incretin effect. The hyperinsulinemic-euglycemic clamp (insulin clamp) and exercise were used to examine the incretin-independent glucoregulatory properties of the Glp1r because both perturbations stimulate glucose flux independent of insulin secretion. Chow-fed mice with a functional disruption of the Glp1r (Glp1r−/−) were compared with wild-type littermates (Glp1r+/+). Studies were performed on 5-h-fasted mice implanted with arterial and venous catheters for sampling and infusions, respectively. During insulin clamps, [3-3H]glucose and 2[14C]deoxyglucose were used to determine whole-body glucose turnover and glucose metabolic index (Rg), an indicator of glucose uptake. Rg in sedentary and treadmill exercised mice was determined using 2[3H]deoxyglucose. Glp1r−/− mice exhibited increased glucose disappearance, muscle Rg, and muscle glycogen levels during insulin clamps. This was not associated with enhanced muscle insulin signaling. Glp1r−/− mice exhibited impaired suppression of endogenous glucose production and hepatic glycogen accumulation during insulin clamps. This was associated with impaired liver insulin signaling. Glp1r−/− mice became significantly hyperglycemic during exercise. Muscle Rg was normal in exercised Glp1r−/− mice, suggesting that hyperglycemia resulted from an added drive to stimulate glucose production. Muscle AMP-activated protein kinase phosphorylation was higher in exercised Glp1r−/− mice. This was associated with increased relative exercise intensity and decreased exercise endurance. In conclusion, these results show that the endogenous Glp1r regulates hepatic and muscle glucose flux independent of its ability to enhance insulin secretion.

During increased glucose flux, the glucagon-like peptide-1 receptor regulates endogenous glucose production and muscle glucose uptake independent of its ability to stimulate insulin secretion.
Differential Neuroendocrine Expression of Multiple Brain-Derived Neurotrophic Factor Transcripts
Authors: Kidane Adhanet H. , Heinrich Gerhard , Dirks Ron P. H. , de Ruyck Brechje A. , Lubsen Nicolette H. , Roubos Eric W. , Jenks Bruce G.
Published: November 2008

Brain-derived neurotrophic factor (BDNF) is a neurotrophin with important growth-promoting properties. We report here the first characterization of a BDNF gene in an amphibian, Xenopus laevis, and demonstrate that environmental factors can activate this gene in a promoter-specific fashion. The Xenopus BDNF gene contains six promoter-specific 5′-exons and one 3′-protein-encoding exon. We examined the expression of promoter-specific transcripts in Xenopus neuroendocrine melanotrope cells. These cells make a good model to study how environmental factors control gene expression. In animals placed on a black background melanotrope cells more actively produce and release αMSH than in animals on a white background. BDNF is cosequestered and coreleased with αMSH and stimulates biosynthesis of proopiomelanocortin (POMC), the precursor protein for αMSH. Our analysis of the expression of the BDNF transcripts revealed that there is differential use of some BDNF promoters in melanotrope cells, depending on the adaptation state of the frog. During black-background adaptation, stimulation of expression of BDNF transcript IV preceded that of the POMC transcript, suggesting the BDNF gene is an effector gene for POMC expression. The possible mechanisms regulating expression of the various transcripts are discussed on the basis of the potential calcium- and cAMP-responsive elements in the promoter region of exon IV. Finally, we show that the upstream open reading frames of BDNF transcripts I and IV markedly decrease BDNF translation efficiency, giving the first indication for a functional role of untranslated BDNF exons.

We show promoter-specific expression of BDNF transcripts in neuroendocrine melanotrope cells and provide evidence that upstream open reading frames of BDNF transcripts decrease translation efficiency.
Cells Expressing RFamide-Related Peptide-1/3, the Mammalian Gonadotropin-Inhibitory Hormone Orthologs, Are Not Hypophysiotropic Neuroendocrine Neurons in the Rat
Authors: Rizwan Mohammed Z. , Porteous Robert , Herbison Allan E. , Anderson Greg M.
Published: November 2008

An RFamide peptide named gonadotropin-inhibitory hormone, which directly inhibits gonadotropin synthesis and secretion from the anterior pituitary gland, has recently been discovered in the avian hypothalamus. It is not known whether the mammalian orthologs of gonadotropin-inhibitory hormone and RFamide-related peptide (RFRP)-1 and -3 act in the same way. We used a newly generated antibody against the rat RFRP precursor combined with retrograde tract tracing to characterize the cell body distribution and fiber projections of RFRP-1 and -3 neurons in rats. RFRP-1/3-immunoreactive cell bodies were found exclusively within the dorsomedial hypothalamus. Immunoreactive fibers were observed in the septal-preoptic area, hypothalamus, midbrain, brainstem, and hippocampus but not in the external zone of the median eminence. Intraperitoneal injection of the retrograde tracer Fluoro-Gold in rats resulted in the labeling of the majority of GnRH neurons but essentially no RFRP-1/3 neurons. In contrast, intracerebral injections of Fluoro-Gold into the rostral preoptic area and CA2/CA3 hippocampus resulted in the labeling of 75 ± 5% and 21 ± 8% of RFRP-1/3 cell bodies, respectively. To assess actions at the pituitary in vivo, RFRP-3 was administered as an iv bolus to ovariectomized rats and plasma LH concentration measured at 0, 2.5, 5, 10, and 30 min. RFRP-3 had no effects on basal secretion, but GnRH-stimulated LH release was reduced by about 25% at 5 min. Together these observations suggest that RFRP-3 is not a hypophysiotropic neuroendocrine hormone in rats.

Hypothalamic RFRP-1/3 neurons project to the preoptic area and hippocampus but not the median eminence, suggesting that RFRP-1/3 is not a hypophysiotropic gonadotropin inhibitor in the rat.
Blockade of Estrogen Receptor Signaling Inhibits Growth and Migration of Medulloblastoma
Authors: Belcher Scott M. , Ma Xiaolan , Le Hoa H.
Published: November 2008

Medulloblastoma (MD) is the most common malignant brain tumor in children. These invasive neuroectodermal tumors arise from cerebellar granule cell-like precursors. In the developing cerebellum, estrogen influences growth and viability of granule cell precursors that transiently express elevated levels estrogen receptor-β (ERβ) during differentiation. Immunoanalysis revealed that ERβ was expressed in the maturing human cerebellum, in all 22 primary MD tumors analyzed, and in two MD-derived cell lines (D283Med and Daoy). Very low levels of ERα-like proteins were detected in each cell line and 41% of tumor samples. Physiological concentrations of the 17β-estradiol- or the ERβ-selective agonist 2,3-bis(4-hydroxyphenyl)-propionitrile diarylpropionitrile dose-dependently increased MD growth and cellular migration. In contrast, the ERα-selective agonist (4-propyl-[1H]pyrazole-1,3,5-triyl) trisphenol did not influence MD growth. Similar to previous studies in normal cerebellar granule cell precursors, these studies demonstrate that the physiological actions of estrogens in MD are mediated by ERβ. Preclinical studies assessing the therapeutic efficacy of antiestrogen chemotherapeutics for treating human MD were performed. It was found that pharmacological inhibition of ER-mediated signaling with the ER antagonist drug Faslodex (ICI182,780) blocked all estrogen-mediated effects in both cell culture and xenograft models of human MD. These studies have revealed that functional ERβ expression is a fundamental aspect of MD biology and has defined antiestrogen therapy as a potentially efficacious clinical approach to improve the long-term outcomes for MD patients.

Estrogens, via ERβ, stimulate growth of medulloblastoma. ICI182,780 and the antiestrogen drug Faslodex block estrogen-stimulated tumor growth in vitro and in xenograft models of medulloblastoma.
Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Inhibits Experimental Autoimmune Thyroiditis by the Expansion of CD4+CD25+ Regulatory T Cells
Authors: Wang Su He , Chen Gwo-Hsiao , Fan Yongyi , Van Antwerp Mary , Baker James R.
Published: November 2008

There have been several reports that TNF-related apoptosis-inducing ligand (TRAIL) has the ability to suppress the development of experimental autoimmune diseases, including a mouse model of experimental autoimmune encephalomyelitis, a rabbit model of rheumatoid arthritis, type 1 diabetes mellitus, in mice and experimental autoimmune thyroiditis (EAT) in mice. However, the mechanism underlying TRAIL effect is not well defined. In the present study, we specifically examined TRAIL effects on CD4+CD25+ regulatory T cells. CD4+CD25+ T cells prepared from mouse thyroglobulin (mTg)-immunized CBA/J mice proliferate in the presence of TRAIL and dendritic cells in vitro. These CD4+CD25+ T cells included both CD4+CD25+CD45RBLow (regulatory) and CD4+CD25+CD45RBHigh (effector) T cells. Our results demonstrated that mTg-immunized mice treated with TRAIL showed significant increases in the number of CD4+CD25+CD45RBLow T cells compared with mice immunized with mTg alone. CD4+CD25+CD45RBLow T cells expressed much higher levels of the forkhead family transcription factor, IL-10, and TGFβ1 than CD4+CD25+CD45RBHigh T cells, and these cells can completely suppress the proliferation of the mTg-primed splenocytes in lower concentrations than the unfractionated CD4+CD25+ T cells. Furthermore, transfer of these cells into CBA/J mice prior to mTg-primed splenocyte injection could markedly reduce the frequency and severity of EAT development. CD4+CD25+CD45RBLow T cells were more effective at suppressing histological thyroiditis than unfractionated cells. These results indicated that TRAIL can increase the number of mTg-specific CD4+CD25+CD45RBLow T cells, inhibiting autoimmune responses and preventing the progression of EAT. These findings reveal a novel mechanism by which TRAIL could inhibit autoimmune disease.
Honeybees can learn the relationship between the solar ephemeris and a newly-experienced landscape
Authors: Towne William F.
Published: November 2008

Many species learn the sun's daily pattern of azimuthal movement (the solar ephemeris function) for use in sun-compass orientation. In honeybees, this learning is accomplished with much innate guidance and yields stubborn,imprinting-like retention of certain aspects of the stored information. One such case involves the failure of transplanted bees to update their memories of the relationship between the solar ephemeris and a new landscape, even after many days' experience at the new site. In the present study, I ask whether the bees in previous transplantation experiments failed to update their memories of the relationship between the sun and landscape because the source and recipient landscapes were (rotated) panoramic twins of each other,each dominated by a conspicuous treeline. To test this hypothesis, I transplanted bees from their natal site at the bottom of a valley to a panoramically different, treelined site and later tested the bees' knowledge of the sun's course in relation to the treeline. The test involved observing the bees' communicative dances under overcast skies at a second treeline that was a mirror image of the first. The cloudy-day dances show that the bees had indeed learned the relationship between sun's pattern of movement and the(panoramically novel) treelined site, indicating that the bees' memory of the relationship between the ephemeris function and the landscape is not incapable of revision as the earlier results had suggested. I discuss these results in the context of a brief summary of our current understanding of solar ephemeris learning in bees.
Branchial FXYD protein expression in response to salinity change and its interaction with Na+/K+-ATPase of the euryhaline teleost Tetraodon nigroviridis
Authors: Wang Pei-Jen , Lin Chia-Hao , Hwang Hau-Hsuan , Lee Tsung-Han
Published: November 2008

Na+/K+-ATPase (NKA) is a ubiquitous membrane-bound protein crucial for teleost osmoregulation. The enzyme is composed of two essential subunits, a catalytic α subunit and a glycosylated βsubunit which is responsible for membrane targeting of the enzyme. In mammals,seven FXYD members have been found. FXYD proteins have been identified as the regulatory protein of NKA in mammals and elasmobranchs, it is thus interesting to examine the expression and functions of FXYD protein in the euryhaline teleosts with salinity-dependent changes of gill NKA activity. The present study investigated the expression and distribution of the FXYD protein in gills of seawater (SW)- or freshwater (FW)-acclimated euryhaline pufferfish(Tetraodon nigroviridis). The full-length pufferfish FXYD gene(pFXYD) was confirmed by RT-PCR. pFXYD was found to be expressed in many organs including gills of both SW and FW pufferfish. pFXYD mRNA abundance in gills, determined by real-time PCR, was significantly higher in FW fish than in SW fish. An antiserum raised against a partial amino acid sequence of pFXYD was used for the immunoblots of gill homogenates and a major band at 13 kDa was detected. The relative amounts of pFXYD protein and mRNA in gills of SW and FW pufferfish were identical, but opposite to the expression levels of NKA. Immunofluorescent staining of frozen sections demonstrated that pFXYD was colocalized to NKA-immunoreactive cells in the gill filaments. In addition, interaction between pFXYD and NKA was demonstrated by co-immunoprecipitation. Taken together, salinity-dependent expression of pFXYD protein and NKA, as well as the evidence for their colocalization and interaction in pufferfish gills suggested that pFXYD regulates NKA activity in gills of euryhaline teleosts upon salinity challenge.
Sensory coding of nest-site value in honeybee swarms
Authors: Seeley Thomas D. , Visscher P. Kirk
Published: November 2008

This study investigates the first stage of the decision-making process of a honeybee swarm as it chooses a nest site: how a scout bee codes the value of a potential nest site in the waggle dances she produces to represent this site. We presented honeybee swarms with a two-alternative choice between a high-value site and a medium-value site and recorded the behavior of individually identifiable scout bees as they reported on these two alternatives. We found that bees performed equally lengthy inspections at the two sites, but that, on the swarm cluster, they performed more dance circuits per bee for the high-value site. We also found that there was much individual-level noise in the coding of site value, but that there were clear population-level differences in total dance circuits produced for the two sites. The first bee to find a site had a high probability of reporting the site with a waggle dance, regardless of its value. This discoverer-should-dance phenomenon may help ensure that a swarm gives attention to all discovered sites. There was rapid decay in the dance response; the number of dance circuits produced by a bee after visiting a site decreased linearly over sequential visits, and eventually each bee ceased visiting her site. This decay, or `leakage', in the accumulation of bees at a site improves a swarm's decision-making ability by helping a swarm avoid making fast-decision errors.
Better mate in the shade: enhancement of male mating behaviour in the cabbage butterfly, Pieris rapae crucivora, in a UV-rich environment
Authors: Obara Yoshiaki , Koshitaka Hisaharu , Arikawa Kentaro
Published: November 2008

Ultraviolet (UV) vision is widespread in a variety of animals, playing important roles in behaviours such as foraging and reproduction. Despite accumulated information about UV vision and UV-dependent behaviours of animals, little is known about the effect of temporal changes and local variations in UV light on UV-dependent behaviour. Here we report the mating behaviour of male cabbage butterfly, Pieris rapae crucivora, in environments with varying content of UV light. We first confirmed that the relative UV content is higher in shaded places than in sunny places. We furthermore arranged experimental areas with varying UV contents in the field,where we compared three aspects of male mating behaviour: visual localization of females, female-searching flight and copulation success rate. In all aspects males performed more actively in UV-rich environments: males searched females for longer, approached females preferentially in the shade and copulated there more frequently. Apparently, female-searching males detect females more easily in a UV-rich environment. The present findings should be taken into consideration when UV-dependent behaviours, visual mate choice in particular, are studied.
The connection between landscapes and the solar ephemeris in honeybees
Authors: Towne William F. , Moscrip Heather
Published: November 2008

Honeybees connect the sun's daily pattern of azimuthal movement to some aspect of the landscape around their nests. In the present study, we ask what aspect of the landscape is used in this context – the entire landscape panorama or only sectors seen along familiar flight routes. Previous studies of the solar ephemeris memory in bees have generally used bees that had experience flying a specific route, usually along a treeline, to a feeder. When such bees were moved to a differently oriented treeline on overcast days,the bees oriented their communicative dances as if they were still at the first treeline, based on a memory of the sun's course in relation to some aspect of the site, possibly the familiar route along the treeline or possibly the entire landscape or skyline panorama. Our results show that bees lacking specific flight-route training can nonetheless recall the sun's compass bearing relative to novel flight routes in their natal landscape. Specifically, we moved a hive from one landscape to a differently oriented twin landscape, and only after transplantation under overcast skies did we move a feeder away from the hive. These bees nonetheless danced accurately by memory of the sun's course in relation to their natal landscape. The bees'knowledge of the relationship between the sun and landscape, therefore, is not limited to familiar flight routes and so may encompass, at least functionally,the entire panorama. Further evidence suggests that the skyline in particular may be the bees' preferred reference in this context.
Foraging behavior of humpback whales: kinematic and respiratory patterns suggest a high cost for a lunge
Authors: Goldbogen Jeremy A. , Calambokidis John , Croll Donald A. , Harvey James T. , Newton Kelly M. , Oleson Erin M. , Schorr Greg , Shadwick Robert E.
Published: November 2008

Lunge feeding in rorqual whales is a drag-based feeding mechanism that is thought to entail a high energetic cost and consequently limit the maximum dive time of these extraordinarily large predators. Although the kinematics of lunge feeding in fin whales supports this hypothesis, it is unclear whether respiratory compensation occurs as a consequence of lunge-feeding activity. We used high-resolution digital tags on foraging humpback whales (Megaptera novaengliae) to determine the number of lunges executed per dive as well as respiratory frequency between dives. Data from two whales are reported,which together performed 58 foraging dives and 451 lunges. During one study,we tracked one tagged whale for approximately 2 h and examined the spatial distribution of prey using a digital echosounder. These data were integrated with the dive profile to reveal that lunges are directed toward the upper boundary of dense krill aggregations. Foraging dives were characterized by a gliding descent, up to 15 lunges at depth, and an ascent powered by steady swimming. Longer dives were required to perform more lunges at depth and these extended apneas were followed by an increase in the number of breaths taken after a dive. Maximum dive durations during foraging were approximately half of those previously reported for singing (i.e. non-feeding) humpback whales. At the highest lunge frequencies (10 to 15 lunges per dive), respiratory rate was at least threefold higher than that of singing humpback whales that underwent a similar degree of apnea. These data suggest that the high energetic cost associated with lunge feeding in blue and fin whales also occurs in intermediate sized rorquals.
Compass gait mechanics account for top walking speeds in ducks and humans
Authors: Usherwood James R. , Szymanek Katie L. , Daley Monica A.
Published: November 2008

The constraints to maximum walking speed and the underlying cause of the walk–run transition remains controversial. However, the motions of the body and legs can be reduced to a few mechanical principles, which, if valid,impose simple physics-based limits to walking speed. Bipedal walking may be viewed as a vaulting gait, with the centre of mass (CoM) passing over a stiff stance leg (an `inverted pendulum'), while the swing leg swings forward (as a pendulum). At its simplest, this forms a `compass gait' walker, which has a maximum walking speed constrained by simple mechanics: walk too fast, or with too high a step length, and gravity fails to keep the stance foot attached to the floor. But how useful is such an extremely reductionist model? In the present study, we report measurements on a range of duck breeds as example unspecialized, non-planar, crouch-limbed walkers and contrast these findings with previous measurements on humans, using the theoretical framework of compass gait walking. Ducks walked as inverted pendulums with near-passive swing legs up to relative velocities around 0.5, remarkably consistent with the theoretical model. By contrast, top walking speeds in humans cannot be achieved with passive swing legs: humans, while still constrained by compass gait mechanics, extend their envelope of walking speeds by using relatively high step frequencies. Therefore, the capacity to drive the swing leg forward by walking humans may be a specialization for walking, allowing near-passive vaulting of the CoM at walking speeds 4/3 that possible with a passive(duck-like) swing leg.
Episodic swimming behavior in the nematodeC. elegans
Authors: Ghosh Rajarshi , Emmons Scott W.
Published: November 2008

Controlling the choice of behavioral output is a central function of the nervous system. Here we document a novel spontaneous behavioral transition in C. elegans locomotion. Upon transfer of the nematode from a solid surface into a liquid environment, swimming occurs in two phases: an initial,1–2 h phase of continuous swimming, followed by a second phase during which swimming is episodic. During the second, episodic phase, periods of active swimming alternate in a highly regular fashion with a quiescent state lasting for several minutes. We analyzed the nature of the quiescent state and the basis for spontaneous switching between swimming and quiescence. The transition from swimming to quiescence is promoted by acetylcholine signaling and initially during quiescence body wall muscles are in a state of contraction. After the first minute, quiescent worms respond to prodding and resume swimming normally. The major command interneurons that control the locomotory circuits are not necessary for quiescence since swimming–quiescence cycling occurs after ablation of command interneurons. However, when subsets of neurons including the command interneurons are killed, the switching pattern becomes less regular,suggesting that a timer governing switching may lie within circuitry controlling motor neurons. The results show that the motor circuits have a tendency to switch spontaneously between active and inactive behavioral states. This property might be important to the animal in a uniform environment where sensory input is invariant.
A new three-dimensional aerofoil diffuser for centrifugal compressors
Authors: Abdelwahab A , Gerber G
Published: November 2008

Aerofoil diffusers have been extensively used in industrial centrifugal compressors. However, these diffusers are two-dimensional and have fixed solidity in the spanwise direction. Two types of two-dimensional aerofoil diffusers exist: the first characterized by a solidity value less than 1 (low solidity diffuser) and the second characterized by a solidity value greater than 1 (high solidity diffusers). In this article a new three-dimensional aerofoil diffuser is introduced. This diffuser has a varying solidity and stagger angle in the spanwise direction as well as a varying lean angle along the streamwise direction. The use of these three-dimensional configurations leads to the development of an aerofoil diffuser that combines the wide operating range characteristic of the low solidity diffusers with the high performance that is characteristic of the high solidity diffusers. Experimental and numerical analyses of several impeller—diffuser configurations are presented. The analyses are performed between the newly introduced three-dimensional aerofoil diffuser and the conventional diffusers with high and low solidities. The results of the analyses are presented in terms of the aerodynamic performance of both the diffusers and the overall stage performance. The analyses performed indeed indicate the superiority of the proposed new diffuser geometry over the analysed conventional aerofoil diffusers in terms of extending the operating range of the compressor stage as well as improving its efficiency.
Efficiency enhancement in a Rankine cycle power plant: Combined cycle approach
Authors: Murugan R S , Subbarao P M V
Published: November 2008

Efficiency enhancement in a Rankine cycle power plant operating on a condensing mode is one of the challenging tasks for researchers. In a modern fossil-fired steam power plant even a fraction of percentage difference in efficiency can mean very large savings in annual fuel costs. In this study, effort was put into improving the cycle efficiency by reducing energy loss and irreversibility in the major portion of the cycle such as heat input part, work output part, and heat rejection part. In this study, a new combined cycle concept is proposed to reduce: energy loss in the condenser; power output and efficiency loss in the low pressure turbine due to expansion of low grade or low temperature steam; and irreversibility in the boiler due to higher degree of enthalpy of evaporation. The proposed combined cycle plant uses water as a working fluid in the topping cycle and an ammonia—water mixture in the bottoming cycle and it is 4 per cent more efficient than the standalone Rankine cycle operating on a condensing mode.
Experimental study of the effect of some geometric variables and number of nozzles on the performance of a subsonic air—air ejector
Authors: Meakhail T A , Zien Y , Elsallak M , AbdelHady S
Published: November 2008

An ejector is a pumping device that uses a high-speed primary fluid jet to entrain a secondary stream. The pumping action is due to the exchange of momentum between the primary and secondary streams. The air ejectors are widely used in mixing systems and many engineering applications.

The purpose of the present work is to study experimentally the effects of using different numbers of nozzles with various geometric variables on the performance of the air ejector. The test rig, which is designed particularly for this study, is constructed so that the overall performance of the air ejector can be measured under various operating conditions.

To the best knowledge of the authors, there is no published work concerning the study of all the geometric variables with different numbers of nozzles, showing their effect on the ejector performance. The experimental investigations consist of the performance measurements for 52 ejectors. They are classified into three main groups

The following conclusions were drawn
Experimental investigation of polymer electrolyte membrane fuel cells with ramification flow fields
Authors: Weng F-B , Hsu C-Y , Su A , Chan S-H , Lin C-Y
Published: November 2008

This study reports the finding of a fuel cell using a ramification flow field design inspired from the biological system far more efficient in uniformly distributing species. Various flow stoi-chiometries and relative humidities of the cathode inlet gas to the ramification flow field in a polymer electrolyte membrane (PEM) fuel cell were investigated. The voltage range, in this study, was within the mass transport region of the polarization curve (<0.55 V). The PEM fuel cell was made of transparent material to allow the flow visualization. It was observed that, at high humidified conditions, cyclic flooding and unstable performance occurred, whereas the performance can be stabilized by increasing the cathode gas stoichiometry. Furthermore, compared with a serpentine flow field design, the ability to retain water in the ramification flow field was improved when the cell was operated at low humidity or even at dry inlet gas conditions.
Controller design and implementation of six-degree-of-freedom magnetically levitated positioning system with high precision
Authors: Yu H , Kim W-J
Published: November 2008

This paper presents the controller design and implementation of a high-precision six-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix and a triangular single moving part that carries three three-phase permanent-magnet planar-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and potentially low-cost. The three planar levitation motors based on the Lorentz force law not only produce the vertical force to levitate the triangular platen but also control the platen's position and orientation in the horizontal plane. The main contribution of this paper is that all 6-DOF motions are solely controlled by magnetic forces without any other means to support the platen's weight against gravity, and the most suitable controller of the magnetic levitation system was designed and implemented. The platen can be regarded as a pure mass, and the spring and damping effects are neglected except for the vertical directions. Single-input single-output digital lead-lag controllers were designed and implemented on a digital signal processor. This 6-DOF fully magnetically levitated positioner has a total mass of 5.91 kg and exhibits a 120×120 mm maximum travel range. The position resolution of 20 nm and position noise of 10-nm root mean square are demonstrated. The positioner has sub-microradian angular resolution in about the x, y, and z-axes. A maximum velocity of 24.8 mm/s in y is achieved. This single-moving-part maglev positioner structure is highly suitable for semiconductor manufacturing applications such as wafer steppers. Several experimental motion profiles are presented to demonstrate the maglev stage's capability of accurately tracking any planar and three-dimensional paths.
Experimental and theoretical study of the electrical failures in a fault-tolerant direct-drive servovalve for primary flight actuators
Authors: Di Rito G , Galatolo R
Published: November 2008

The current paper deals with the study of the electrical failures in fault-tolerant flight actuators, with particular reference to the short circuits of the servovalve coils. A high-fidelity model of the servovalve of a modern fly-by-wire actuator is developed and validated through experiments, focusing attention on the characterization of the component dynamics in case of partial and total short circuits of the direct-drive motor coils. The servovalve model is then used to simulate a typical on-ground built-in-test procedure to determine the limit condition for the detection of a partial short circuit. Finally, once different possible combinations of short circuits are injected, the degradation of performances of the whole actuator is characterized through experiments, and the servovalve model is used to justify the test results, highlighting and discussing the effects of the failures on the system dynamics.
Sliding mode control for an electrohydraulic actuator system with discontinuous non-linear friction
Authors: Wang S , Habibi S , Burton R
Published: November 2008

This paper considers the application of a sliding mode controller (SMC) to a high-precision electrohydraulic actuator (EHA) system with non-linear discontinuous friction effects. An important consideration in such systems is the oscillations that occur in the system response owing to friction for small input signals at cross-over regions where the velocity changes sign. A new model for a high-precision hydrostatic actuation system is developed to investigate the effects of discontinuous and non-linear friction. This model is used in the development of a sliding mode control strategy. A significant result from this study is that the SMC can suppress such oscillations. In addition, the paper uses a linear quadratic approach for defining a discrete-time sliding surface for non-linear systems. A comparative study involving the application of the proposed SMC versus a gain-scheduled proportional controller is presented.
An improved model-free adaptive control with G function fuzzy reasoning regulation design and its applications
Authors: Lü F L , Wang J F , Fan C J , Chen S B
Published: November 2008

This paper proposes an improved model-free adaptive control with G function fuzzy reasoning regulation (MFCF) for general systems where the equations governing the system are unknown. Such an approach has potential advantages in accommodating complex systems with possibly time-varying dynamics and uncertainties. Model-free adaptive control basic algorithm (MFCB) has two features: first, it does not need any mathematical model; second, the control algorithm is simple and is feasible to be applied in actual industry. This paper considers the use of fuzzy reasoning system, which also only requires observed system input—output data. Moreover this improved control algorithm can make use of human experiences. Related to this, a convergence proof of this improved control algorithm is established. The scheme has been used in the control of welding pool dynamics of the arc welding process, and the experiment results validate the control scheme developed. At the same time, this improved controller can enhance control performance.
A Superior Representation Method for Piecewise Linear Functions
Authors: Li Han-Lin , Lu Hao-Chun , Huang Chia-Hui , Hu Nian-Ze
Published: November 2008

Many nonlinear programs can be piecewisely linearized by adding extra binary variables. For the last four decades, several techniques of formulating a piecewise linear function have been developed. By expressing a piecewise linear function with m + 1 break points, the current method requires us to use m additional binary variables and 4m constraints, which causes heavy computation when m is large. This study proposes a superior way of expressing the same piecewise linear function, where only ⌈ log 2 m ⌉ binary variables and 8 + 8 ⌈ log 2 m ⌉ additive constraints are used. Various numerical experiments demonstrate that the proposed method is more computationally efficient than current methods.
Accelerating Benders Decomposition by Local Branching
Authors: Rei Walter , Cordeau Jean-François , Gendreau Michel , Soriano Patrick
Published: November 2008

This paper shows how local branching can be used to accelerate the classical Benders decomposition algorithm. By applying local branching throughout the solution process, one can simultaneously improve both the lower and upper bounds. We also show how Benders feasibility cuts can be strengthened or replaced with local branching constraints. To assess the performance of the different algorithmic ideas presented in this hybrid solution approach, extensive computational experiments were performed on two families of network design problems. Numerical results clearly illustrate their benefits.
The moderating effect of conformism values on the relations between other personal values, social norms, moral obligation, and single altruistic behaviours
Authors: Lönnqvist Jan‐Erik , Walkowitz Gari , Wichardt Philipp , Lindeman Marjaana , Verkasalo Markku
Published: November 2008

Three studies predicted and found that the individual's conformism values are one determinant of whether behaviour is guided by other personal values or by social norms. In Study 1 (N =50), pro‐gay law reform participants were told they were either in a minority or a majority in terms of their attitude towards the law reform. Only participants who were high in conformism values conformed to the group norm on public behaviour intentions. In studies 2 (N =42) and 3 (N =734), participants played multiple choice prisoner's dilemma games with monetary incentives. Only participants who considered conformism values to be relatively unimportant showed the expected connections between universalism values and altruistic behaviour. Study 3 also established that the moderating effect of conformism values on the relation between universalism values and altruistic behaviour was mediated through experienced sense of moral obligation.
Effect of spectrophotometric errors on color difference
Authors: Kishncr S. J.
Published: November 2008

The effects of random errors in measurements of diffuse reflectance made on an abridged spectrophotometer are evaluated by means of Monte Carlo computer-simulation techniques. These techniques allow the analysis of nonadditive or non-Gaussian errors such as signal-dependent noise and quantization of the photometric scale. The effects of measurement error are evaluated in terms of computed color difference, with results based on the largest color difference errors that occur in 500 measurements. Analysis of representative colors demonstrates that neutrals are at least as sensitive to measurement errors as any of the colors considered. It is demonstrated that relative errors with a standard deviation near 0.1% result in negligible color difference errors. Colors of high luminous reflectance are shown to be more susceptible to relative errors than are dark colors. Analysis of linear and logarithmic quantization schemes shows that logarithmic quantization uses considerably fewer quantization levels than a linear quantization scheme having the same color difference error. The results presented in this paper are applicable as guidelines in the design of abridged spectrophotometers.
Glyceryl ether monooxygenase resembles aromatic amino acid hydroxylases in metal ion and tetrahydrobiopterin dependence
Authors: Watschinger Katrin , Keller Markus A. , Hermetter Albin , Golderer Georg , Werner-Felmayer Gabriele , Werner Ernst R.
Published: November 2008

Glyceryl ether monooxygenase is a tetrahydrobiopterin-dependent membrane-bound enzyme which catalyses the cleavage of lipid ethers into glycerol and the corresponding aldehyde. Despite many different characterisation and purification attempts, so far no gene and primary sequence have been assigned to this enzyme. The seven other tetrahydrobiopterin-dependent enzymes can be divided in the family of aromatic amino acid hydroxylases – comprising phenylalanine hydroxylase, tyrosine hydroxylase and the two tryptophan hydroxylases – and into the three nitric oxide synthases. We tested the influences of different metal ions and metal ion chelators on glyceryl ether monooxygenase, phenylalanine hydroxylase and nitric oxide synthase activity to elucidate the relationship of glyceryl ether monooxygenase to these two families. 1,10-Phenanthroline, an inhibitor of non-heme iron-dependent enzymes, was able to potently block glyceryl ether monooxygenase as well as phenylalanine hydroxylase, but had no effect on inducible nitric oxide synthase. Two tetrahydrobiopterin analogues, N5-methyltetrahydrobiopterin and 4-aminotetrahydrobiopterin, had a similar impact on glyceryl ether monooxygenase activity, as has already been shown for phenylalanine hydroxylase. These observations point to a close analogy of the role of tetrahydrobiopterin in glyceryl ether monooxygenase and in aromatic amino acid hydroxylases and suggest that glyceryl ether monooxygenase may require a non-heme iron for catalysis.
Expansion of CD133-Expressing Liver Cancer Stem Cells in Liver-Specific Phosphatase and Tensin Homolog Deleted on Chromosome 10-Deleted Mice
Authors: Rountree C. Bart , Ding Wei , He Lina , Stiles Bangyan
Published: November 2008

PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a lipid phosphatase that regulates mitogenic signaling pathways, and deficiency of PTEN results in cell proliferation, survival, and malignancy. Murine liver-specific Pten deletion models develop liver malignancy by 12 months of age. Using this model, we describe a population of CD133+ liver cancer stem cells isolated during the chronic injury phase of disease progression and before primary carcinoma formation. We performed immunohistochemistry and flow cytometry isolation using livers from 3- and 6-month-old PtenloxP/loxP; Alb−Cre+ mice (mutants) and controls. CD133+CD45− nonparenchymal (NP) cells were analyzed for gene expression profile and protein levels. Single CD133+CD45− oval cells were isolated for clonal expansion and tumor analysis. Cultured and freshly isolated liver CD133+CD45− and CD133−CD45− NP cells were injected into immune-deficient and immune-competent mice. In mutant mice, the NP fraction increased in CD133+CD45− cells in 3- and 6-month-old Pten-deleted animals compared with controls. Clone lines expanded from single CD133+CD45− cells demonstrated consistent liver progenitor cell phenotype, with bilineage gene expression of hepatocyte and cholangiocyte markers. CD133+ cells from expanded clone lines formed robust tumors in immune-deficient and immune-competent mice. Furthermore, freshly isolated CD133+CD45− NP liver cells from 6-month-old mutants formed tumors in vivo, and CD133−CD45− NP cells did not. Consistent with a cancer stem cell phenotype, CD133+ cells demonstrate resistance to chemotherapy agents compared with CD133− cells. CD133+CD45− nonparenchymal cells from chronic injury PtenloxP/loxP; Alb−Cre+ mice represent a bipotent liver progenitor cell population with cancer stem cell phenotype.