bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology predicts suction feeding performance in centrarchid fishes
Authors: Carroll Andrew M. , Wainwright Peter C. , Huskey Stephen H. , Collar David C. , Turingan Ralph G. 
Published: October 2004

SUMMARYSuction feeding fish differ in their capacity to generate subambient pressure while feeding, and these differences appear to relate to morphological variation. We developed a morphological model of force transmission in the fish head and parameterized it with measurements from individual fish. The model was applied to 45 individuals from five species of centrarchid fishes: Lepomis macrochirus, Lepomis punctatus, Lepomis microlophus, Micropterus salmoides and Pomoxis nigromaculatus. Measurements of epaxial cross-sectional area, epaxial moment arm, buccal area and buccal area moment arm were combined to estimate pressure generation capacity for individual fish. This estimation was correlated with pressure measured in fish feeding on elusive prey to test the model's ability to predict pressure generation from morphology. The model explained differences in pressure generation found among individuals (P&lt;0.001, r2=0.71) and produced a realistic estimate of normalized muscle stress during suction feeding (68.5±6.7 kPa). Fish with smaller mouths, larger epaxial cross-sectional area and longer epaxial moments, such as L. macrochirus (bluegill sunfish), generated lower pressures than fish with larger mouths, smaller cross-sectional area and shorter moments,such as M. salmoides (largemouth bass). These results reveal a direct trade-off between morphological requirements of feeding on larger prey (larger mouth size relative to body depth) and the ability to generate subambient pressure while suction feeding on elusive prey.
The effects of head and tail stimulation on the withdrawal startle response of the rope fish (Erpetoichthys calabaricus)
Authors: Bierman Hilary S. , Schriefer Julie E. , Zottoli Steven J. , Hale Melina E. 
Published: October 2004

SUMMARYWhile most actinopterygian fishes perform C-start or S-start behaviors as their primary startle responses, many elongate species instead use a withdrawal movement. Studies of withdrawal have focused on the response to head-directed or nonspecific stimuli. During withdrawal, the animal moves its head back from the stimulus, often resulting in several tight bends in the body. In contrast to C-start or S-start behaviors, withdrawal to a head stimulus generally does not involve a subsequent propulsive stage of movement. We examined intraspecific diversity in withdrawal behavior and muscle activity patterns of the rope fish, Erpetoichthys calabaricus, in response to stimulation of the head and the tail. In addition, we describe the anatomy of the Mauthner cells and their axon caps, structures that are generally absent in species with a withdrawal startle. We recorded high-speed video (250 Hz)and electromyograms (EMGs) from 12 electrodes in the axial muscle during the behavioral response. We used Bodian silver staining techniques to visualize Mauthner cell and axon cap morphology. We found that E. calabaricus responds with a withdrawal to both head and tail stimulation. Tail stimulation elicits a stronger kinematic and muscle activity response than head stimulation. While withdrawal movement generally constitutes the entire response to head stimuli, withdrawal was followed by propulsive movements when the tail was stimulated, suggesting that withdrawal can both act alone and serve as the first stage of a propulsive startle. Unexpectedly, bilaterality of muscle activity was variable for responses to both head and tail stimuli. In addition, we were surprised to find that E. calabaricus has a distinct axon cap associated with its Mauthner cell. These data suggest that the withdrawal response is a more diverse functional system than has previously been believed.
Neuromuscular control of aerodynamic forces and moments in the blowfly,Calliphora vicina
Authors: Balint Claire N. , Dickinson Michael H. 
Published: October 2004

SUMMARYFlies are among the most agile of flying insects, a capacity that ultimately results from their nervous system's control over steering muscles and aerodynamic forces during flight. In order to investigate the relationships among neuromuscular control, musculo-skeletal mechanics and flight forces, we captured high-speed, three-dimensional wing kinematics of the blowfly, Calliphora vicina, while simultaneously recording electromyogram signals from prominent steering muscles during visually induced turns. We used the quantified kinematics to calculate the translational and rotational components of aerodynamic forces and moments using a theoretical quasi-steady model of force generation, confirmed using a dynamically scaled mechanical model of a Calliphora wing. We identified three independently controlled features of the wingbeat trajectory –downstroke deviation, dorsal amplitude and mode. Modulation of each of these kinematic features corresponded to both activity in a distinct steering muscle group and a distinct manipulation of the aerodynamic force vector. This functional specificity resulted from the independent control of downstroke and upstroke forces rather than the independent control of separate aerodynamic mechanisms. The predicted contributions of each kinematic feature to body lift, thrust, roll, yaw and pitch are discussed.
Heart rate and energetics of free-ranging king penguins (Aptenodytes patagonicus)
Authors: Froget G. , Butler P. J. , Woakes A. J. , Fahlman A. , Kuntz G. , Le Maho Y. , Handrich Y. 
Published: October 2004

SUMMARYThe main objective of this study was to determine heart rate(fh) and the energetic costs of specific behaviours of king penguins while ashore and while foraging at sea during their breeding period. In particular, an estimate was made of the energetic cost of diving in order to determine the proportion of dives that may exceed the calculated aerobic dive limit (cADL; estimated usable O2 stores/estimated rate of oxygen consumption during diving).An implanted data logger enabled fh and diving behaviour to be monitored from 10 free-ranging king penguins during their breeding period. Using previously determined calibration equations, it was possible to estimate rate of oxygen consumption(V̇O2) when the birds were ashore and during various phases of their foraging trips. Diving behaviour showed a clear diurnal pattern, with a mixture of deep (&gt;40 m),long (&gt;3 min) and shallow (&lt;40 m), short (&lt;3 min) dives from dawn to dusk and shallow, short dives at night. Heart rate during dive bouts and dive cycles (dive + post-dive interval) was 42% greater than that when the birds were ashore. During diving, fh was similar to the `ashore'value (87±4 beats min–1), but it did decline to 76% of the value recorded from king penguins resting in water. During the first hour after a diving bout, fh was significantly higher than the average value during diving (101±4 beats min–1) and for the remainder of the dive bout.Rates of oxygen consumption estimated from these (and other) values of fh indicate that when at sea, metabolic rate (MR) was 83%greater than that when the birds were ashore [3.15 W kg–1(–0.71, +0.93), where the values in parentheses are the computed standard errors of the estimate], while during diving bouts and dive cycles,it was 73% greater than the `ashore' value. Although estimated MR during the total period between dive bouts was not significantly different from that during dive bouts [5.44 W kg–1 (–0.30, +0.32)], MR during the first hour following a dive bout was 52% greater than that during a diving bout. It is suggested that this large increase following diving(foraging) activity is, at least in part, the result of rewarming the body,which occurs at the end of a diving bout. From the measured behaviour and estimated values of V̇O2, it was evident that approximately 35% of the dives were in excess of the cADL. Even if V̇O2 during diving was assumed to be the same as when the birds were resting on water,approximately 20% of dives would exceed the cADL. As V̇O2 during diving is, in fact, that estimated for a complete dive cycle, it is quite feasible that V̇O2 during diving itself is less than that measured for birds resting in water. It is suggested that the regional hypothermia that has been recorded in this species during diving bouts may be at least a contributing factor to such hypometabolism.
Comparison of the cost of short flights in a nectarivorous and a non-nectarivorous bird
Authors: Hambly C. , Pinshow B. , Wiersma P. , Verhulst S. , Piertney S. B. , Harper E. J. , Speakman J. R. 
Published: October 2004

SUMMARYAlthough most birds are accustomed to making short flights, particularly during foraging, the flight patterns during these short periods of activity differ between species. Nectarivorous birds, in particular, often spend time hovering, while non-nectarivorous birds do not. The cost of short flights is likely therefore to differ between nectarivorous and non-nectarivorous birds because of the different energetic contributions of different flight types to the behaviour. The 13C-labelled bicarbonate technique was used to measure the energy cost of short flights in the nectarivorous Palestine sunbird Nectarinia osea (mean mass 6.17±0.16 g, N=8)and the non-nectarivorous starling Sturnus vulgaris (mean mass 70.11±1.11 g, N=9). The technique was initially calibrated in five individuals for each species at temperatures ranging from 1 to 35°C,by comparing the isotope elimination rate to the metabolic rate measured simultaneously by indirect calorimetry. The cost for short intermittent flight was then measured by encouraging birds to fly between two perches at either end of a narrow corridor (perch distance for sunbirds, 6 m; for starlings, 5 m), and measuring the amount of isotope eliminated during the flight. The isotope elimination rate was interpolated onto the calibration equation to predict flight cost, as a direct calibration could not be performed during flight. Mean energy expenditure during flight was 1.64±0.32 W in sunbirds, while in starlings the flight costs averaged 20.6±0.78 W. Energy cost of flight relative to basal metabolic rate was substantially greater in the starling than the sunbird. Phylogenetic analysis of different modes of flight in these and additional species suggests that differences in flight behaviour may cause these elevated costs in slow flying non-nectarivores such as starlings, compared to birds that are more prone to short intermittent flights like the sunbirds.
The energy cost of loaded flight is substantially lower than expected due to alterations in flight kinematics
Authors: Hambly C. , Harper E. J. , Speakman J. R. 
Published: October 2004

SUMMARY
The effect of experimentally increased wing loading on the energy cost of flight was examined in cockatiels Nyphicus hollandicus. Five individuals were flown for periods of approximately 2 min, while carrying additional payload mass amounting to between 5 and 20% of unloaded body mass. The energy cost of flight was measured using the 13C-labelled bicarbonate technique, which was also calibrated in a separate experiment on resting birds, by comparing the elimination rate of 13C in breath with a simultaneous measurement of oxygen consumption by indirect calorimetry. It was not possible to perform a similar calibration during flight when energy costs were higher, so we extrapolated the relationship from the resting calibration to predict flight cost. Flight cost in the pre-manipulated individuals averaged 16.7±1.8 W. Flight cost in the pre-manipulated birds was significantly related to the interaction between downstroke duration and flight speed. There was no significant increase in flight cost with increases in payload mass. The birds responded to payload masses between 5 and 15% of their unloaded body mass by decreasing flight speed relative to unloaded birds, while maintaining wing beat frequency(Fb). At a payload mass equivalent to 20% of body mass,however, the birds flew at higher speeds than unloaded controls, and had a significantly higher Fb, generated by a reduction in both the upstroke and downstroke durations. Wing amplitude was unaffected by the increase in loading. Using the measured flight parameters, the effect of loading was not significantly different than predicted using aerodynamic models.
Blue integumentary structural colours in dragonflies (Odonata) are not produced by incoherent Tyndall scattering
Authors: Prum Richard O. , Cole Jeff A. , Torres Rodolfo H. 
Published: October 2004

SUMMARYFor nearly 80 years, the non-iridescent, blue, integumentary structural colours of dragonflies and damselflies (Odonata) have been attributed to incoherent Tyndall or Rayleigh scattering. We investigated the production of the integumentary structural colours of a damselfly – the familiar bluet, Enallagma civile (Coenagrionidae) – and a dragonfly– the common green darner, Anax junius (Aeshnidae) –using fibre optic spectrophotometry and transmission electron microscopy(TEM). The reflectance spectra of both species showed discrete reflectance peaks of ∼30% reflectance at 475 and 460 nm, respectively. These structural colours are produced by light scattering from closely packed arrays of spheres in the endoplasmic reticulum of box-shaped epidermal pigment cells underlying the cuticle. The observed reflectance spectra do not conform to the inverse fourth power relationship predicted for Tyndall/Rayleigh scattering. Two-dimensional (2-D) Fourier analysis of the TEM images of the colour-producing arrays reveals ring-shaped distributions of Fourier power at intermediate spatial frequencies, documenting a quasiordered nanostructure. The nanostructured Fourier power spectra falsify the assumption of spatial independence of scatterers that is required for incoherent scattering. Radial averages of the Fourier power spectrum indicate that the spheres are substantially nanostructured at the appropriate spatial scale to produce visible colours by coherent scattering. However, the spatial periodicity of the arrays is apparently too large to produce the observed colour by coherent scattering. The nanospheres could have expanded substantially (∼50%)during preparation for TEM. Alternatively, coherent light scattering could be occurring both from the surfaces and from structures at the centre of the spheres. These arrays of colour-producing spheres within pigment cells have convergently evolved at least 11–14 times independently within the Odonata. Structural colouration from arrays in living cells has also fostered the convergent evolution of temperature-dependent colour change in numerous odonate lineages.
Laplace transform to avoid numerical instabilities due to the effect of Peclet number in thermal problems
Authors: Bou-Saïd B , Colin F , Kane M 
Published: October 2004

It is well known that thermal analysis is important in tribology in both dry and lubricated cases. In lubricated contacts, the effect of temperature for high speeds and high loads governs the parameters that characterize the contact behaviour (frictional force, carrying capacity, flow, etc.). Thus the thermal analysis in the fluid and in the surrounding bodies is necessary to model the contact correctly. The finite element method (FEM) has proved in recent years to be one of the most general and useful procedures for prediction of the characteristics of lubricated contacts. However, where thermal effects are taken into account the method has limitations and can cause oscillations and inaccuracies to occur in solutions at high velocity (high Peclet number). For example, oscillations occur in the solutions for a 0.04m shaft running at 6r/min (Peclet number ≅ 9). Clearly, the range of velocity magnitudes that leads to good results with the FEM is unable to cover a broad range of industrial applications. Some remedies have already been suggested (smaller elements, hybrid formulation, the weighted residual method with a weighting function different from the interpolation function, etc.). An altogether different approach is to modify the initial equation. It is well known that the oscillations and numerical instabilities arise from the fact that the thermal problem is not self-adjoint. The essential point, not usually stressed, concerns the symmetry of a linear operator (as for a matrix), which is not an absolute notion. It is relative to a bilinear form. If the given problem does not ensure this symmetry condition (as in the present case) an attempt may be made to transform the given problem into another that fulfils the symmetry conditions. A method based on Gurtin's theorem is proposed here which allows a preliminary transformation of an equation into an integral-differential one and the convolution product of two functions. This method leads to a variational formulation of any linear initial value problems. Therefore, if the problem has a variational formulation the operator is symmetric and the stiffness matrix obtained from numerical discretization (here FEM) is also symmetric. When this is the case the effect of the Peclet number disappears. This method has been applied here to the thermal problem for slider and journal bearings and obtained very promising results in order to generalize this method to non-linear conditions in stationary thermal problems.
Relevance of the thermoelastohydrodynamic model in the analysis of a plain journal bearing subjected to severe operating conditions
Authors: Bouyer J , Fillon M 
Published: October 2004

Bearings, which were initially designed to support loads, are nowadays being used more and more in machines and most of them are subjected to severe operating conditions as far as temperature or minimum film thickness are concerned. This can be considered as the result of the increases in speed and load, which increase the dissipated power in the lubricant, and also the temperature, thus significantly modifying the lubricant characteristics and bearing performance. This leads, on the one hand, to a decrease in the lubricant viscosity, and therefore the load capacity, and, on the other hand, to mechanical and thermal deformations of the contact surfaces which can, under severe operating conditions, be greater than the minimum film thickness. The present study investigates the relevance of taking into account the deformations and how they can influence bearing performance prediction. The operating conditions are variable, with the radial load ranging up to 150kN and the rotational speed ranging up to 15000r/min. The thermoelastohydrodynamic (TEHD) model is compared to an existing thermohydrodynamic (THD) model in order to find the point at which it is necessary to take into account deformations in the numerical simulation and thus ensure good prediction of bearing behaviour. Under severe conditions, the THD model was found not to give good results for bearing performance and geometry; i.e. the hydrodynamic pressure can be dangerously overestimated, the minimum film thickness can be underestimated and the bearing operating radial clearance can be increased by over 10 per cent.
The Capital Asset Pricing Model: Theory and Evidence
Authors: Fama Eugene F , French Kenneth R 
Published: October 2004

The capital asset pricing model (CAPM) of William Sharpe (1964) and John Lintner (1965) marks the birth of asset pricing theory (resulting in a Nobel Prize for Sharpe in 1990). Before their breakthrough, there were no asset pricing models built from first principles about the nature of tastes and investment opportunities and with clear testable predictions about risk and return. Four decades later, the CAPM is still widely used in applications, such as estimating the cost of equity capital for firms and evaluating the performance of managed portfolios. And it is the centerpiece, indeed often the only asset pricing model taught in MBA level investment courses. The attraction of the CAPM is its powerfully simple logic and intuitively pleasing predictions about how to measure risk and about the relation between expected return and risk. Unfortunately, perhaps because of its simplicity, the empirical record of the model is poor - poor enough to invalidate the way it is used in applications. The model's empirical problems may reflect true failings. (It is, after all, just a model.) But they may also be due to shortcomings of the empirical tests, most notably, poor proxies for the market portfolio of invested wealth, which plays a central role in the model's predictions. We argue, however, that if the market proxy problem invalidates tests of the model, it also invalidates most applications, which typically borrow the market proxies used in empirical tests. For perspective on the CAPM's predictions about risk and expected return, we begin with a brief summary of its logic. We then review the history of empirical work on the model and what it says about shortcomings of the CAPM that pose challenges to be explained by more complicated models.
Gene Expression Analysis in Platelets from a Single Donor: Evaluation of a PCR-Based Amplification Technique
Authors: Rox Jutta Maria , Bugert Peter , Müller Jens , Schorr Alexander , Hanfland Peter , Madlener Katharina , Klüter Harald , Pötzsch Bernd 
Published: October 2004

Abstract
Background: Genetic analysis of platelet mRNA may facilitate the diagnosis of disorders affecting the megakaryocytic-platelet lineage. Its use, however, is limited by the exceptionally small yield of platelet mRNA and the risk of leukocyte contamination during platelet preparation.
Methods: We depleted platelet suspensions of leukocytes by filtration and used a PCR-based RNA amplification step [switching mechanism at the 5′ end of RNA templates (SMART)]. We tested the reliability and precision of the RNA amplification procedure by use of real-time PCR to measure quantities of specific transcripts: von Willebrand factor (vWF), A-subunit of coagulation factor XIII (F13A), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Microarray analysis was performed on platelet RNA with and without amplification.
Results: Microgram quantities of platelet-specific cDNAs were produced from as little as 50 ng of total platelet RNA or 40 mL of whole blood. At cycle numbers &lt;16, amplification of all transcripts tested was exponential with slightly more efficient amplification of low-abundance transcripts. Expression profiling of 9850 genes gave identical results for 9815 genes (1576 positive/8239 negative). Eight transcripts failed to be amplified by the SMART procedure. Expression of vWF, F13A, and GAPDH transcripts showed only minor day-to-day variations in three healthy individuals.
Conclusion: The proposed protocol makes extremely small amounts of platelet RNA available for gene expression analysis in single patients.
The Biochemistry of Gene Therapy for AIDS
Authors: Savarino Andrea , Piero Pescarmona Gian , Turco Emilia , Gupta Phalguni 
Published: October 2004

Abstract
Gene therapy has enormous potential and could in the near future involve the clinical biochemist in monitoring its efficacy. The involvement of clinical biochemists in this field could be not only in evaluating the impact of a gene-based strategy on disease progression, but also in measuring the expression of the products of therapeutic genes in treated individuals. Indeed, gene therapy presents new possibilities for the treatment of many diseases and, in particular, merits consideration in the treatment of a fatal disease like AIDS. The aim of this paper is to review the biochemical basis and clinical relevance of the gene therapy approaches directed towards the inhibition of human immunodeficiency virus type-1. We discuss the goals which have been achieved, the problems which have occurred and the efforts that are being made to solve them. In this regard, particular attention is paid to new strategies targeting ‘therapeutic’ enzymes to human immunodeficiency virus type-1 nucleic acids.