bluuebunny/crossref_metadata_2025 huggingface dataset:
Vocal mechanics in Darwin's finches: correlation of beak gape and song frequency
Authors: Podos Jeffrey , Southall Joel A. , Rossi-Santos Marcos R.
Published: January 2004

Recent studies of vocal mechanics in songbirds have identified a functional role for the beak in sound production. The vocal tract (trachea and beak)filters harmonic overtones from sounds produced by the syrinx, and birds can fine-tune vocal tract resonance properties through changes in beak gape. In this study, we examine patterns of beak gape during song production in seven species of Darwin's finches of the Galápagos Islands. Our principal goals were to characterize the relationship between beak gape and vocal frequency during song production and to explore the possible influence therein of diversity in beak morphology and body size. Birds were audio and video recorded (at 30 frames s–1) as they sang in the field, and 164 song sequences were analyzed. We found that song frequency regressed significantly and positively on beak gape for 38 of 56 individuals and for all seven species examined. This finding provides broad support for a resonance model of vocal tract function in Darwin's finches. Comparison among species revealed significant variation in regression y-intercept values. Body size correlated negatively with y-intercept values, although not at a statistically significant level. We failed to detect variation in regression slopes among finch species, although the regression slopes of Darwin's finch and two North American sparrow species were found to differ. Analysis within one species (Geospiza fortis) revealed significant inter-individual variation in regression parameters; these parameters did not correlate with song frequency features or plumage scores. Our results suggest that patterns of beak use during song production were conserved during the Darwin's finch adaptive radiation, despite the evolution of substantial variation in beak morphology and body size.
Modular organization of the silkmoth antennal lobe macroglomerular complex revealed by voltage-sensitive dye imaging
Authors: Ai Hiroyuki , Kanzaki Ryohei
Published: January 2004

We succeeded in clarifying the functional synaptic organization of the macroglomerular complex (MGC) of the male silkmoth Bombyx mori by optical recording with a voltage-sensitive dye. Sensory neurons in the antennae send their axons down either the medial nerve (MN) or lateral nerve(LN), depending on whether they are located on the medial or lateral flagella. Pheromone-sensitive fibers in the MN are biased towards the medial MGC, and those in the LN are biased towards the lateral MGC in the antennal lobe. In our optical recording experiments, the postsynaptic activities in the MGC were characterized by pharmacological analysis. Postsynaptic activities in the MGC were separated from sensory activities under Ca2+-free conditions,and subsequently the inhibitory postsynaptic activities were separated by applying bicuculline. We found that the inhibitory postsynaptic responses always preceded the postsynaptic responses separated under Ca2+-free conditions. Moreover, the excitatory postsynaptic activities were calculated by subtracting the inhibitory potentials from the posysynaptic activities separated under Ca2+-free conditions. When the MN was stimulated, the amplitudes of the excitatory postsynaptic activities in the central toroid, the medial toroid and the medial cumulus were selectively higher than those in the other areas. By contrast, when the LN was stimulated, excitatory postsynaptic activities were evoked in areas in both the lateral toroid and the lateral cumulus. The inhibitory postsynaptic activities were equally distributed throughout the whole MGC. These data suggest that there is a modular organization to the MGC such that information from the two main branches of the antenna is segregated to different sub-regions of the MGC glomeruli.
Purification and cDNA cloning of the ovigerous-hair stripping substance(OHSS) contained in the hatch water of an estuarine crab Sesarma haematocheir
Authors: Gusev Oleg , Ikeda Hideki , Okochi Tetsushi , Lee Jae Min , Hatakeyama Masatsugu , Kobayashi Chiyoko , Agata Kiyokazu , Yamada Hidenori , Saigusa Masayuki
Published: January 2004

The egg attachment system of an estuarine crab Sesarma haematocheir is formed on the maternal ovigerous hairs just after egg laying, and slips off these hairs just after hatching. The stripping is caused by an active factor that we call OHSS (ovigerous-hair stripping substance),which is released by the embryo upon hatching. OHSS was purified, and its active form had a molecular mass of 25 kDa. The cDNA of OHSS cloned from an embryonic cDNA library was 1759 bp long, encoding 492 amino acids in a single open reading frame (ORF). The C-terminal part of the predicted protein was composed of a trypsin-like serine protease domain, with homology to counterparts in other animals of 33–38%. The predicted protein (54.7 kDa) secreted as a zymogen may be cleaved post-translationally, separating the C-terminal from the N-terminal region. The OHSS gene was expressed in the embryo at least 2 weeks before hatching. Expression was also detected in the zoea larva 1 day after hatching and in the brain of the female. However, it was not detected in the muscle, hepatopancreas or ovigerous seta of the female. Ultrastructural analysis indicated that the material investing maternal ovigerous hair, i.e. the outermost layer (E1) of the egg case, is attached at the special sites (attachment sites) arranged at intervals of 130–160 nm on the hair. It is suggested that OHSS acts specifically at these sites, lysing the bond with the coat, thus disposing of the embryo attachment system. This enables the female to prepare the next clutch of embryos without ecdysis.
The thermogenesis of digestion in rattlesnakes
Authors: Tattersall Glenn J. , Milsom William K. , Abe Augusto S. , Brito Simone P. , Andrade Denis V.
Published: January 2004

Some snakes have a feeding regime characterized by the infrequent ingestion of relatively large meals, causing impressive increments in post-prandial metabolism. Metabolism remains elevated for many days, while digestion proceeds, resulting in considerable investment of time and energy. Snakes actively adjust thermoregulatory behavior to raise their body temperature during digestion, exhibiting a post-prandial thermophilic response that accelerates digestion at the expense of higher metabolic rates. In the present study, we investigated the possibility that endogenously derived heat,originating as a byproduct of the post-prandial increase in metabolism, could itself contribute to the elevated body temperature during digestion in the South American rattlesnake Crotalus durissus. We assessed heat production, at a constant environmental temperature, by taking infrared (IR)images of snakes during fasting and after being fed meals varying from 10% to 50% of their own body masses. Our results show clearly that digesting rattlesnakes have significantly increased body temperatures, even when precluded from adjusting their thermoregulatory behavior. The feeding-derived thermogenesis caused the surface body temperature of rattlesnakes to increase by 0.9–1.2°C, a temperature change that will significantly affect digestive performance. The alterations in body temperature following feeding correlated closely with the temporal profile of changes in post-prandial metabolism. Moreover, the magnitude of the thermogenesis was greater for snakes fed large meals, as was the corresponding metabolic response. Since IR imaging only assesses surface temperatures, the magnitude of the thermogenesis and the changes in deep core temperature could be even more pronounced than is reported here.
Effects of temperature and anoxia upon the performance ofin situperfused trout hearts
Authors: Overgaard Johannes , Stecyk Jonathan A. W. , Gesser Hans , Wang Tobias , Farrell Anthony P.
Published: January 2004

Rainbow trout (Oncorhynchus mykiss) are likely to experience acute changes in both temperature and oxygen availability and, like many other organisms, exhibit behavioural selection of low temperatures during hypoxia that acts to reduce metabolism and alleviate the demands on the heart. To investigate whether low temperature protects cardiac performance during anoxia, we studied the effects of an acute temperature change, from 10°C to either 5°C, 15°C or 18°C, upon the performance of in situ perfused trout hearts before, during and after exposure to 20 min of anoxia. Routine cardiac workload mimicked in vivo conditions at the given temperatures, and the effects of anoxia were evaluated as maximal cardiac performance before and after 20 min of anoxic perfusion. Functional data were related to maximal activities of glycolytic enzymes and energetic status of the heart at the termination of the experiment.

At high oxygenation, maximum cardiac output and power output increased with temperature (Q10 values of 1.8 and 2.1, respectively) as a result of increased heart rate. Hypoxia tolerance was inversely related to temperature. At 5°C, the hearts maintained routine cardiac output throughout the 20 min period of anoxia, and maximal cardiac performance was fully restored following reoxygenation. By contrast, cardiac function failed sooner during anoxia as temperature was increased and maximal performance after reoxygenation was reduced by 25%, 35% and 55% at 10°C, 15°C and 18°C, respectively. Increased functional impairment following anoxic exposure at elevated temperature occurred even though both cardiac glycolytic enzyme activity and the rate of lactate production were increased proportionally with cardiac work. Nonetheless, there was no indication of myocardial necrosis, as biochemical and energetic parameters were generally unaffected by anoxia.
Maternal effects of egg size on emuDromaius novaehollandiaeegg composition and hatchling phenotype
Authors: Dzialowski Edward M. , Sotherland Paul R.
Published: January 2004

Parental investment in eggs and, consequently, in offspring can profoundly influence the phenotype, survival and ultimately evolutionary fitness of an organism. Avian eggs are excellent model systems to examine maternal allocation of energy translated through egg size variation. We used the natural range in emu Dromaius novaehollandiae egg size, from 400 g to>700 g, to examine the influence of maternal investment in eggs on the morphology and physiology of hatchlings. Female emus provisioned larger eggs with a greater absolute amount of energy, nutrients and water in the yolk and albumen. Variation in maternal investment was reflected in differences in hatchling size, which increased isometrically with egg size. Egg size also influenced the physiology of developing emu embryos, such that late-term embryonic metabolic rate was positively correlated with egg size and embryos developing in larger eggs consumed more yolk during development. Large eggs produced hatchlings that were both heavier (yolk-free wet and dry mass) and structurally larger (tibiotarsus and culmen lengths) than hatchlings emerging from smaller eggs. As with many other precocial birds, larger hatchlings also contained more water, which was reflected in a greater blood volume. However,blood osmolality, hemoglobin content and hematocrit did not vary with hatchling mass. Emu maternal investment in offspring, measured by egg size and composition, is significantly correlated with the morphology and physiology of hatchlings and, in turn, may influence the success of these organisms during the first days of the juvenile stage.
Mechanical work and muscular efficiency in walking children
Authors: Schepens B. , Bastien G. J. , Heglund N. C. , Willems P. A.
Published: January 2004

The effect of age and body size on the total mechanical work done during walking is studied in children of 3–12 years of age and in adults. The total mechanical work per stride (Wtot) is measured as the sum of the external work, Wext (i.e. the work required to move the centre of mass of the body relative to the surroundings), and the internal work, Wint (i.e. the work required to move the limbs relative to the centre of mass of the body, Wint,k,and the work done by one leg against the other during the double contact period, Wint,dc). Above 0.5 m s–1, both Wext and Wint,k, normalised to body mass and per unit distance (J kg–1 m–1), are greater in children than in adults; these differences are greater the higher the speed and the younger the subject. Both in children and in adults, the normalised Wint,dc shows an inverted U-shape curve as a function of speed, attaining a maximum value independent of age but occurring at higher speeds in older subjects. A higher metabolic energy input (J kg–1 m–1) is also observed in children,although in children younger than 6 years of age, the normalised mechanical work increases relatively less than the normalised energy cost of locomotion. This suggests that young children have a lower efficiency of positive muscular work production than adults during walking. Differences in normalised mechanical work, energy cost and efficiency between children and adults disappear after the age of 10.
Moments and power generated by the horse (Equus caballus) hind limb during jumping
Authors: Dutto Darren J. , Hoyt Donald F. , Clayton Hilary M. , Cogger Edward A. , Wickler Steven J.
Published: January 2004

The ability to jump over an obstacle depends upon the generation of work across the joints of the propelling limb(s). The total work generated by one hind limb of a horse and the contribution to the total work by four joints of the hind limb were determined for a jump. It was hypothesized that the hip and ankle joints would have extensor moments performing positive work, while the knee would have a flexor moment and perform negative work during the jump. Ground reaction forces and sagittal plane kinematics were simultaneously recorded during each jumping trial. Joint moment, power and work were determined for the metatarsophalangeal (MP), tarsal (ankle), tibiofemoral(knee) and coxofemoral (hip) joints. The hip, knee and ankle all flexed and then extended and the MP extended and then flexed during ground contact. Consistent with our hypothesis, large extensor moments were observed at the hip and ankle joints and large flexor moments at the knee and MP joints throughout ground contact of the hind limb. Peak moments tended to occur earlier in stance in the proximal joints but peak power generation of the hind limb joints occurred at similar times except for the MP joint, with the hip and ankle peaking first followed by the MP joint. During the first portion of ground contact (≈40%), the net result of the joint powers was the absorption of power. During the remainder of the contact period, the hind limb generated power. This pattern of power absorption followed by power generation paralleled the power profiles of the hip, ankle and MP joints. The total work performed by one hind limb was 0.71 J kg-1. Surprisingly, the knee produced 85% of the work (0.60 J kg-1) done by the hind limb, and the positive work performed by the knee occurred during the first 40% of the take-off. There is little net work generated by the other three joints over the entire take-off. Velocity of the tuber coxae (a landmark on the pelvis of the animal) was negative (downward) during the first 40% of stance, which perhaps reflects the negative work performed to decrease the potential energy during the first 40% of contact. During the final 60% of contact, the hip,ankle and MP joints generate positive work, which is reflected in the increase of the animal's potential energy.
Dynamical analysis reveals individuality of locomotion in goldfish
Authors: Neumeister H. , Cellucci C. J. , Rapp P. E. , Korn H. , Faber D. S.
Published: January 2004

Goldfish swimming was analysed quantitatively to determine if it exhibits distinctive individual spatio-temporal patterns. Due to the inherent variability in fish locomotion, this hypothesis was tested using five nonlinear measures, complemented by mean velocity. A library was constructed of 75 trajectories, each of 5 min duration, acquired from five fish swimming in a constant and relatively homogeneous environment. Three nonlinear measures, the `characteristic fractal dimension' and `Richardson dimension',both quantifying the degree to which a trajectory departs from a straight line, and `relative dispersion', characterizing the variance as a function of the duration, have coefficients of variation less than 7%, in contrast to mean velocity (30%). A discriminant analysis, or classification system, based on all six measures revealed that trajectories are indeed highly individualistic,with the probability that any two trajectories generated from different fish are equivalent being less than 1%. That is, the combination of these measures allows a given trajectory to be assigned to its source with a high degree of confidence. The Richardson dimension and the `Hurst exponent', which quantifies persistence, were the most effective measures.
The dichotomous oxyregulatory behaviour of the planktonic crustaceanDaphnia magna
Authors: Pirow R. , Buchen I.
Published: January 2004

The dual function of appendage movement (food acquisition, ventilation)proved to be the key to explaining the peculiar oxyregulatory repertoire of the planktonic filter feeder Daphnia magna. Short-term hypoxic exposure experiments with normoxia-acclimated animals under varying food concentrations revealed a dichotomous response pattern with a compensatory tachycardia under food-free conditions and a ventilatory compensation prevailing under food-rich conditions. Food-free, normoxic conditions resulted in maximum appendage beating rates (fa) and half-maximum heart rates (fh), which restricted the scope for oxyregulation to the circulatory system. Food-rich conditions (105algal cells ml-1), on the contrary, had a depressing effect on fa whereas fh increased to 83% of the maximum. In this physiological state, D. magna was able to respond to progressive hypoxia with a compensatory increase in ventilation. A conceptual and mathematical model was developed to analyse the efficiency of ventilatory and circulatory adjustments in improving oxygen transport to tissue. Model predictions showed that an increase in perfusion rate was most effective under both food-free and food-rich conditions in reducing the critical ambient oxygen tension (PO2crit) at which oxygen supply to the tissue started to become impeded. By contrast, a hypothetical increase in ventilation rate had almost no effect on PO2crit under food-free conditions, indicating that appendage movement is driven by nutritive rather than respiratory requirements. However, the model predicted a moderate reduction of PO2crit by hyperventilation under food-rich conditions. Since the regulatory scope for an adjustment in fh was found to be limited in D. magna under these conditions, the increase in ventilation rate is the means of choice for a fed animal to cope with short-term, moderate reductions in ambient oxygen availability. Under long-term and more severe hypoxic conditions, however, the increase in the concentration and oxygen affinity of haemoglobin represents the one and only measure for improving the transport of oxygen from environment to cells.
Glucose dehydrogenase is required for normal sperm storage and utilization in femaleDrosophila melanogaster
Authors: Iida Kaori , Cavener Douglas R.
Published: January 2004

Female sperm storage is a key factor for reproductive success in a variety of organisms, including Drosophila melanogaster. The spermathecae,one of the Drosophila sperm storage organs, has been suggested as a long-term storage organ because its secreted substances may enhance the quality of sperm storage. Glucose dehydrogenase (GLD) is widely expressed and secreted in the spermathecal ducts among species of the genus Drosophila. This highly conserved expression pattern suggests that this enzyme might have an important role in female fertility. Here, we examine the function of GLD in sperm storage and utilization using Gld-null mutant females. The absence of GLD reduced the amount of sperm stored in the spermathecae and led to a highly asymmetrical sperm distribution in the two spermathecal capsules of the mutant females. The storage defect was especially severe when the mutant females were crossed to a Gld-mutant male that had previously mated a few hours before the experimental cross. Under this mating condition, the mutant females stored in the spermathecae only one-third of the sperm amount of the wild-type control females. In addition, the mutant females used stored sperm at a slower rate over a longer period compared with wild-type females. Thus, our results indicate that GLD facilitates both sperm uptake and release through the spermathecal ducts.
Modelling of the cutting temperature distribution under the tool flank wear effect
Authors: Huang Y , Liang S Y
Published: January 2004

The understanding of cutting temperature distribution at the presence of tool wear can aid in addressing important metal cutting issues such as part surface integrity, tool life and dimensional tolerance under practical operating conditions. The effect of tool wear on the cutting temperature distribution was first modelled by Chao and Trigger and there have been very few followers since. In Chao's model, the primary heat source was assumed to have no effect on the workpiece temperature rise and the chip temperature rise was treated as a bulk quantity. This paper analytically quantifies the tool wear effect by taking into account the contributions of the primary heat source and considering the distribution of chip temperature rise. On the chip side, the primary shear zone is modelled as a uniform moving oblique band heat source and the secondary shear zone as a non-uniform moving band heat source within a semi-infinite medium. On the tool side, the effects of both the secondary and the rubbing heat sources are modelled as non-uniform static rectangular heat sources within a semi-infinite medium. For the workpiece side, the study models the primary shear zone as a uniform moving oblique band heat source and the rubbing heat source as a non-uniform moving band heat source within a semi-infinite medium. The proposed model is verified based on the published experimental data in the orthogonal cutting of Armco iron. Furthermore, a comparison case is presented on the temperature variation with respect to cutting speed, feed rate and flank wear length.
A study on the focusing phenomenon of a weak shock wave
Authors: Kim H-D , Kweon Y-H , Setoguchi T , Matsuo S
Published: January 2004

When a plane shock wave reflects from a concave wall or when a curved shock wave reflects from a straight wall, it is focused at a certain location, resulting in extremely high local pressure and temperature. This focusing is due to a non-linear phenomenon of a shock wave. This focusing phenomenon has been extensively applied in a variety of engineering and medical areas. In the current study, the focusing phenomenon of a weak shock wave over a reflector is numerically investigated using a computational fluid dynamics (CFD) method. The total variation diminishing (TVD) scheme is used to solve the unsteady, two-dimensional, compressible, Euler equations. The Mach number of the incident shock wave is changed in the range from 1.1 to 1.5. Several different types of reflectors are employed to investigate the effect of the reflector on the focusing phenomenon of the weak shock wave. The focusing characteristics of the shock wave are investigated in terms of peak pressure, gas dynamic and geometrical foci. The results obtained are compared with previous experiment results that are available. The results show that the peak pressure of shock wave focusing and its location strongly depend on the Mach number of the incident shock wave and the reflector geometry. The location of the gas dynamic focus is always shorter than that of the geometrical one. This tendency is more remarkable as the incident shock wave becomes stronger. The present computations predict the experimental results with a very good accuracy.
The performance characteristics of single-stage and multistage regenerative flow compressors for natural gas compression application
Authors: Raheel M , Engeda A , Hamrin D , Rouse G
Published: January 2004

The compact size, high reliability and low maintenance required by regenerative flow compressors (RFCs) have made them very useful for low-pressure (0.2–15 lb/in2 gauge) natural gas compression required by microturbine systems. Very limited test data are available in the literature on gases as working fluids in regenerative turbomachines, resulting in a scarcity of design information. Most of the testing conducted in the past was on single-stage RFCs and no evidence of experimental data on multistage RFCs is available in the literature. This paper presents a large amount of single-stage test data along with an investigation for the first time of performance characteristics of a four-stage RFC. Testing is carried out over a wide range of speeds using natural gas and air as working fluids. Experimental data are presented in terms of various non-dimensional performance parameters. Several correlations are developed between these non-dimensional performance parameters and RFC geometry. Single-stage test data are used to study the effect of blade geometry, channel geometry, channel area ratio and pitch-cord ratio on performance. A few important sources of losses in RFCs are identified. Moreover, through the presented non-dimensional test data and available test data in the literature, a generalized design procedure is proposed, which can be very useful for designers and engineers working in regenerative turbomachinery.
A compressible flow theory for regenerative compressors with aerofoil blades
Authors: Song J W , Raheel M , Engeda A
Published: January 2004

Regenerative flow compressors (RFCs) are rotodynamic machines capable of producing high heads at very low flowrates. They have very low specific speed and share some of the characteristics of positive displacement machines such as a roots blower, but without the problems of lubrication and wear. They can produce heads equivalent to that of several centrifugal stages from a single rotor with comparable tip speed. The compression process is usually not regarded as efficient. Typically they produce efficiency of less than 50 per cent but still they have found many applications because they allow the use of fluid dynamic compressors in place of positive displacement compressors for duties requiring high heads at low flowrates.

There are very few mathematical models in the literature that explain the behaviour of regenerative turbomachines and predict the performance. Most of these models assumed incompressible flow, thus limiting their use to only pumps and blowers. Moreover, they needed extensive experimental support for performance prediction. Hence, it is very interesting from an industrial point of view to find efficient theoretical means that are able to forecast regenerative compressor performances, using easy to find geometric and fluid dynamic parameters.

A compressible flow theory is thus presented for the first time in this paper to describe complex three-dimensional corkscrew flow patterns in regenerative compressors. Conventional RFC were designed with radial, non-radial or semicircular impeller blades. In the present investigation, the authors have discussed RFCs with aerofoil blades and an annular flow channel containing a core to direct circulating flow to the blades with a minimum amount of losses.

The effects of various geometric elements on the performance of RFCs are studied. All the major sources of losses in blade and channel region are identified. Governing equations for the flow in the compressor are derived and a performance prediction code based on governing equations and loss models is developed. Theoretical performance results are compared with published test data on aerofoil blade RFCs. Based on sensitivity analysis from the code, design changes are suggested for performance improvement.
The force transmissibility of planar multiloop linkages
Authors: Lin C-C , Chang W-T
Published: January 2004

A procedure for analysing the force transmissibility of. planar multiloop linkage mechanisms is introduced. The procedure considers the power flow paths in a multiloop linkage. By using a normalized force transmission index based on the ‘gain per unit cost’ concept, the force transmission performance of multiloop linkages can be characterized and measured quantitatively. The result shows that a multiloop mechanism may transmit effective force to the output link when it is at a singularity of motion. In such a condition, the power can reach the output link without passing through the singular-related joints in a multiloop mechanism.
A Rosenbrock-Nystrom state space implicit approach for the dynamic analysis of mechanical systems: I—theoretical formulation
Authors: Sandu A , Negrut D , Haug E J , Potra F A , Sandu C
Published: January 2004

When performing dynamic analysis of a constrained mechanical system, a set of index three differential-algebraic equations (DAE) describes the time evolution of the system. The paper presents a state space based method for the numerical solution of the resulting DAE. A subset of so-called independent generalized coordinates, equal in number to the number of degrees of freedom of the mechanical system, is used to express the time evolution of the mechanical system. The second-order state space ordinary differential equations (SSODE) that describe the time variation of independent coordinates are numerically integrated using a Rosenbrock-type formula specialized to second-order systems of differential equations. Rosenbrock methods are known to be efficient for medium accuracy integration of stiff systems; they do not require the solution of non-linear systems for the stage values, and possess optimal linear stability properties for stiff integration. The computation of exact Jacobians needed by Rosenbrock formulas is discussed in the context of multibody systems. The companion paper [19] discusses a choice of method coefficients based on a four-stage L-stable Rosenbrock formula and presents numerical results.
A Rosenbrock-Nystrom state space implicit approach for the dynamic analysis of mechanical systems: II—method and numerical examples
Authors: Negrut D , Sandu A , Haug E J , Potra F A , Sandu C
Published: January 2004

When performing dynamic analysis of a constrained mechanical system, a set of index three differential-algebraic equations (DAE) describes the time evolution of the system. A state-space based method for the numerical solution of the resulting DAE has also been developed. The numerical method uses a linearly implicit time stepping formula of the Rosenbrock type, which is suitable for medium accuracy integration of stiff systems. This paper discusses choices of method coefficients and presents numerical results. For stiff mechanical systems, the proposed algorithm is shown to reduce significantly simulation times when compared to state of the art existent algorithms. The better efficiency is due to the use of an L-stable integrator, and a rigorous and general approach to providing analytical derivatives required by it.
Load change reactions of passenger cars: Method of investigation and improvement
Authors: Schumacher Th , Biermann J-W , Jansz N , Willey J , Köpper K
Published: January 2004

Customer demand for good vehicle agility consists of a quick reaction of the vehicle with actuation of the throttle pedal on the one hand and a high comfort level with respect to vibration and noise within the vehicle on the other hand, which means a reduction in disturbing side effects. In order to achieve a satisfactory compromise it is necessary to gain a deeper understanding of the complex, high dynamic vibration ‘vehicle/drivetrain’ system. For 2 years ika has been carrying out such detailed vehicle investigations and test bench measurements in addition to comprehensive computer aided engineering (CAE) analysis for various research projects.
Non-linear free vibration analysis of laminated non-homogeneous orthotropic cylindrical shells
Authors: Sofiyev A H , Aksogan O
Published: January 2004

The free vibrations of laminated non-homogeneous orthotropic thin cylindrical shells are studied, with geometric non-linearity taken into account. The basic relations and equations of motion, based on the Donnel-Mushtari shell equations considering finite deformations and the Airy stress function, are obtained for laminated thin cylindrical shells, the elasticity modulus and density of which vary piecewise continuously in the through-thickness direction. Applying the Galerkin method to the foregoing equations, a non-linear time dependent differential equation is obtained for the displacement amplitude. The frequency is obtained from this equation as a function of the shell displacement amplitude and then compared with the results in the literature. Finally, the effect of non-linearity, non-homogeneity and the number and ordering of layers on the frequency is found for different mode numbers, presented graphically and compared with other work.
Subharmonic vibrations of a roll tube supported by plain journal bearings
Authors: Hannukainen P , Sopanen J , Mikkola A
Published: January 2004

This study presents a dynamic model for describing a journal bearing with circumferential waviness of the shaft journal. The journal bearing model is based on an analytical solution of the Reynolds equation and defines the non-linear hydrodynamic forces that act on the journal bearing. The waviness of the shaft journal is modelled through the use of a Fourier cosine series to describe the shape of the film thickness of the bearing. The waviness of the shaft journal can lead to subharmonic vibrations in which the natural vibration mode of the rotor is excited when the rotation speed is a fraction of the natural frequency of the rotor-bearing system. This phenomenon is investigated in this study utilizing the proposed bearing model in a rotor system simulation. The rotor system under investigation consists of a roll tube, two journal bearings and the supporting structure. The proposed journal bearing model can be used in a general multi-body or rotor dynamics computer code as the interface element between the rotor and the bearing housing. In this study, the model of the journal bearing is implemented in a commercial multi-body simulation software application. This approach enables a detailed analysis of the rotor-bearing system in such a way that the dynamic interaction of the rotor with the bearing is taken into consideration. The simulation result agrees with the experimental measurements obtained from a real roll tube system.
Incorrect NICS-Based Prediction on the Aromaticity of the Pentalene Dication
Authors: Aihara Jun-ichi
Published: January 2004

Nucleus-independent chemical shift (NICS) values do not always reflect aromaticity. The pentalene dication exhibits large negative NICS values at the two ring centers although it is antiaromatic with a large negative topological resonance energy (TRE).
Synthesis of Mono- and Tri-Nuclear Ruthenium Carbonyl Complexes Containing the Pyridine-2-thiolato Ligand and Reactivity of a Bis(pyridine-2-thiolato) Chelated Ruthenium Dicarbonyl Complex with a Novel Cobalt-Containing Diphosphine Ligand
Authors: Hong Fung-E , Chang Yu-Chang , Chen Shu-Chun
Published: January 2004

The reaction of 3-cyano-4,6-dimethyl-pyridine-2-thiol with Ru3(CO)12 in toluene at 55 °C for 20 h gave three complexes: [Ru3(CO)10(μ-H)(μ-4,6-CH3-3-CN-2-S-py)] 5, [Ru(4,6-CH3-3-CN-py-κN-thiol-κS)2(CO)2] 7 and presumably [Ru3(CO)9(μ-H)(μ-4,6-CH3-3-CN-2-S-py)] 6. The deprotonated mercaptopyridine acts either as a bridging ligand in 5 and 6 or as a chelating ligand in 7. Further reaction of 7 with a novel cobalt-containing diphosphine ligand, [Co2(CO)4{μ-PPh2CH2PPh2}{μ-PPh2C≡CPPh2}] 8,1 probably resulted in the formation of probably a 8-chelated complex, [Ru(μ-4,6-CH3-3-CN-2-S-py)(4,6-CH3-3-CN-2-S-py-κS)(PPh2CH2PPh2)({μ-PPh2CH2PPh2}Co2(CO)4{μ-PPh2C≡CPPh2})] 10. All the compounds were characterized by spectroscopic means; furthermore, compounds 5 and 7 were studied by X-ray diffraction methods.
A Priori Assessment of the Maximum Possible Entrainment Effect Attainable during Preferential Crystallization. The Case of the Simultaneous Resolution of (±)-Ephedrine and (±)-Mandelic Acid
Authors: Dufour Fabrice , Perez Guy , Coquerel Gérard
Published: January 2004

The strong link observed between the detection of unstable or metastable racemic compounds in the systems studied and the maximum entrainment effect attainable during preferential crystallization (PC) (assessed by the maximum value of the enantiomeric excess of the mother solution at the end of PC (eefmax)) is confirmed by the results obtained with the simultaneous resolution of enantiomorphous p and p′ salts of (±)-ephedrine and (±)-mandelic acid (eefmax = 10.6% with no racemic compound detected). The detection of such a racemic compound indicates that strong heterochiral interactions at one or more (hkl) crystal–mother liquor interfaces are favorable to the 2D nucleation of the counter enantiomer as soon as its local supersaturation at these interfaces (β*hkl) attains a threshold above which the desorption of a docked counter-enantiomer molecule is no longer probable. Therefore, the mode and the rate of stirring must be optimized in order to keep β*hkl as close as possible to the overall supersaturation of the counter enantiomer β*bulk, while minimizing the damaging effects on the particles. The crystal structures of an unstable racemic compound and of a new polymorphic form of 1-phenylethylammonium hydratropate salts are reported and contribute to the understanding of the limited entrainment effect (eefmax = 5.2%).
Spin-Probe Study on the Dynamics and Distribution of Solution Molecules in the Nano-Channel of MCM-41
Authors: Okazaki Masaharu , Toriyama Kazumi , Sawaguchi Naoya , Oda Kiichi
Published: January 2004

The ESR spectrum of a spin-probe in 2-propanol, which was condensed into the nano-channel of MCM-41 from its vapor, showed three well-separated nitrogen hyperfine lines. This observation indicates that the system exists in the liquid state in the nano-channel, though the rotational diffusion of the spin probe molecule is considerably suppressed and anisotropic. In a mixed solvent composed of 2-propanol and cyclohexane, on the other hand, the ESR spectrum for the system prepared by the above procedure comprised two components, indicating that the solution is phase-separated in the nano-channel. When all of the space in the MCM-41 layer, including that among the granules, is filled with the solution, the molecules obtain a higher mobility and phase separation is suppressed even in the nano-channel. The distribution and dynamics of the solution molecules are discussed.
Excited High-Spin Quartet (S = 3/2) State of a Novel π-Conjugated Organic Spin System, Pyrene–Verdazyl Radical
Authors: Teki Yoshio , Kimura Mituhiro , Narimatsu Shinsuke , Ohara Keishi , Mukai Kazuo
Published: January 2004

The excited high-spin quartet (S = 3/2) state of the intramolecular triplet–radical pair between the excited triplet state of pyrene and a dangling verdazyl radical was reported. A novel verdazyl radical with the pyrene moiety was designed and synthesized. The time-resolved ESR spectrum and a DFT calculation show the photo-induced ferromagnetic spin alignment between the excited triplet state of the pyrene moiety and the dangling verdazyl radical. This is the first observation of the high-spin (S > 1) excited state of the π-conjugated pyrene–radical pair.
Does Antitrust Policy Improve Consumer Welfare? Assessing the Evidence
Authors: Crandall Robert W , Winston Clifford
Published: January 2004

This paper reviews the literature and assesses the effects of antitrust policy and enforcement on consumer welfare. We find no evidence that antitrust policy in the areas of monopolization, collusion, and mergers has provided much benefit to consumers and, in some instances, we find evidence that it may have lowered consumer welfare. We also do not find any evidence that antitrust policy has deterred firms from engaging in actions that could harm consumers. We identify various reasons for the apparent ineffectiveness of antitrust policy, offer preliminary policy recommendations, and suggest ways in which economists could more fully assess antitrust policy.
The Case for Antitrust Enforcement
Authors: Baker Jonathan B
Published: January 2004

This paper provides evidence of the necessity and success of antitrust enforcement. It begins with examples of socially beneficial antitrust challenges by the federal antitrust agencies to price-fixing and other forms of collusion; to mergers that appear likely to harm competition; and to monopolists that use anticompetitive exclusionary practices to obtain or maintain their market power. It then reviews systematic empirical evidence on the value of antitrust derived from informal experiments involving the behavior of U.S. firms during periods without effective antitrust enforcement, and the behavior of firms across different national antitrust regimes. Overall, it concludes, the benefits of antitrust enforcement to consumers and social welfare -- particularly in deterring the harms from anticompetitive conduct across the economy -- appear to be far larger than what the government spends on antitrust enforcement and firms spend directly or indirectly on antitrust compliance.
The Unholy Trinity of Financial Contagion
Authors: Kaminsky Graciela L , Reinhart Carmen M , Végh Carlos A
Published: January 2004

Over the last 20 years, some financial events, such as devaluations or defaults, have triggered an immediate adverse chain reaction in other countries -- which we call fast and furious contagion. Yet, on other occasions, similar events have failed to trigger any immediate international reaction. We argue that fast and furious contagion episodes are characterized by “the unholy trinity”: (i) they follow a large surge in capital flows; (ii) they come as a surprise; and (iii) they involve a leveraged common creditor. In contrast, when similar events have elicited little international reaction, they were widely anticipated and took place at a time when capital flows had already subsided.
Restructuring Sovereign Debt
Authors: Eichengreen Barry
Published: January 2004

This paper provides new empirical evidence relevant to the debate over the desirability of reforms to the way that financial markets and the international community deal with sovereign debt crises. In particular, given the ongoing opposition of investors and some sovereigns to greater use of collective action clauses (CACs) in emerging market bonds, we present new evidence on the way that financial markets have priced the use or non-use of CACs.
The Mirage of Exchange Rate Regimes for Emerging Market Countries
Authors: Calvo Guillermo A , Mishkin Frederic S
Published: January 2004

This paper argues that much of the debate on choosing an exchange rate regime misses the boat. It begins by discussing the standard theory of choice between exchange rate regimes, and then explores the weaknesses in this theory, especially when it is applied to emerging market economies. It then discusses a range of institutional traits that might predispose a country to favor either fixed or floating rates, and then turns to the converse question of whether the choice of exchange rate regime may favor the development of certain desirable institutional traits. The conclusion from the analysis is that the choice of exchange rate regime is likely to be of second order importance to the development of good fiscal, financial, and monetary institutions in producing macroeconomic success in emerging market countries. This suggests that less attention should be focused on the general question whether a floating or a fixed exchange rate is preferable, and more on these deeper institutional arrangements. A focus on institutional reforms rather than on the exchange rate regime may encourage emerging market countries to be healthier and less prone to the crises that we have seen in recent years.
Education, Poverty and Terrorism: Is There a Causal Connection?
Authors: Krueger Alan B , Malečková Jitka
Published: January 2004

The paper investigates whether there is a connection between poverty or low education and terrorism. We review evidence on hate crimes, which are closely related to terrorism; the occurrence of hate crimes is largely independent of economic conditions. We analyze data on support for attacks against Israeli targets from public opinion polls conducted in the West Bank and Gaza Strip; support for violent attacks does not decrease among those with higher education and higher living standards. The core contribution of the paper is a statistical analysis of the determinants of participation in Hezbollah militant activities; having a living standard above the poverty line or a secondary or higher education is positively associated with participation in Hezbollah. We also find that Israeli Jewish settlers who attacked Palestinians in the West Bank in the early 1980s were overwhelmingly from high-paying occupations. Although our results are tentative and exploratory, they suggest that neither poverty nor education has a direct, causal impact on terrorism.
Escaping from a Liquidity Trap and Deflation: The Foolproof Way and Others
Authors: Svensson Lars E.O
Published: January 2004

Existing proposals to escape from a liquidity trap and deflation, including my “Foolproof Way,” are discussed in the light of the optimal way to escape. The optimal way involves three elements: (1) an explicit central-bank commitment to a higher future price level; (2) a concrete action that demonstrates the central bank's commitment, induces expectations of a higher future price level and jump-starts the economy; and (3) an exit strategy that specifies when and how to get back to normal. A currency depreciation is a direct consequence of expectations of a higher future price level and hence an excellent indicator of those expectations. Furthermore, an intentional currency depreciation and a crawling peg, as in the Foolproof Way, can implement the optimal way and, in particular, induce the desired expectations of a higher future price level. I conclude that the Foolproof Way is likely to work well for Japan, which is in a liquidity trap now, as well as for the euro area and the United States, in case either would fall into a liquidity trap in the future.
The Demographic Transition: Three Centuries of Fundamental Change
Authors: Lee Ronald
Published: January 2004

The global demographic transition began around 1800 in Europe with declining mortality followed by declining fertility, trends which spread around the world and continue in this century. At the aggregate level, population size greatly increased, growth accelerated and declined with many countries now shrinking, and age distributions inevitably moved from young to old. Population aging has not yet run its course, Its effects exacerbated by declining retirement ages, straining pensions systems and prompting their reform. These aggregate demographic trends reflect profound changes in risks and behavior for individuals and families, and in the shape of the economic life cycle.
Anomalies: The Law of One Price in Financial Markets
Authors: Lamont Owen A , Thaler Richard H
Published: January 2004

The Law of One price states that identical goods (or securities) should sell for identical prices. In financial markets the law of one price is thought to hold almost exactly, and is the basis for much of financial economic theory. We present evidence on several examples of violations of this law, including closed-end country funds, twin shares, dual class shares, and corporate spinoffs. We analyze the causes of these violations, and show they all stem from some limits on the extent to which rational arbitrageurs can intervene.