bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction of the Value Function and Optimal Rules in Optimal Stopping of One-Dimensional Diffusions
Authors: Helmes Kurt , Stockbridge Richard H.
Published: March 2010

A new approach to the solution of optimal stopping problems for one-dimensional diffusions is developed. It arises by imbedding the stochastic problem in a linear programming problem over a space of measures. Optimizing over a smaller class of stopping rules provides a lower bound on the value of the original problem. Then the weak duality of a restricted form of the dual linear program provides an upper bound on the value. An explicit formula for the reward earned using a two-point hitting time stopping rule allows us to prove strong duality between these problems and, therefore, allows us to either optimize over these simpler stopping rules or to solve the restricted dual program. Each optimization problem is parameterized by the initial value of the diffusion and, thus, we are able to construct the value function by solving the family of optimization problems. This methodology requires little regularity of the terminal reward function. When the reward function is smooth, the optimal stopping locations are shown to satisfy the smooth pasting principle. The procedure is illustrated using two examples.
Simultaneous Multifractal Analysis of the Branching and Visibility Measure on a Galton-Watson Tree
Authors: Kinnison Adam L. , Mörters Peter
Published: March 2010

On the boundary of a Galton-Watson tree we can define the visibility measure by splitting mass equally between the children of each vertex, and the branching measure by splitting unit mass equally between all vertices in the nth generation and then letting n go to infinity. The multifractal structure of each of these measures is well studied. In this paper we address the question of a joint multifractal spectrum, i.e. we ask for the Hausdorff dimension of the boundary points which simultaneously have an unusual local dimension for both these measures. The resulting two-parameter spectrum exhibits a number of surprising new features, among them the emergence of a swallowtail-shaped spectrum for the visibility measure in the presence of a nontrivial condition on the branching measure.
Coalescent theory for a Monoecious Random Mating Population with a Varying Size
Authors: Pollak Edward
Published: March 2010

Consider a monoecious diploid population with nonoverlapping generations, whose size varies with time according to an irreducible, aperiodic Markov chain with statesx1N,…,xKN, whereK≪N. It is assumed that all matings except for selfing are possible and equally probable. At time 0 a random sample ofn≪Ngenes is taken. Given two successive population sizesxjNandxiN, the numbers of gametes that individual parents contribute to offspring can be shown to be exchangeable random variables distributed asGij. Under minimal conditions on the first three moments ofGijfor alliandj, a suitable effective population sizeNeis derived. Then if time is recorded in a backward direction in units of 2Negenerations, it can be shown that coalescent theory holds.
A Damped Telegraph Random Process with Logistic Stationary Distribution
Authors: Di Crescenzo Antonio , Martinucci Barbara
Published: March 2010

We introduce a stochastic process that describes a finite-velocity damped motion on the real line. Differently from the telegraph process, the random times between consecutive velocity changes have exponential distribution with linearly increasing parameters. We obtain the probability law of the motion, which admits a logistic stationary limit in a special case. Various results on the distributions of the maximum of the process and of the first passage time through a constant boundary are also given.
Two New Models for the Two-Person Red-And-Black Game
Authors: Chen May-Ru , Hsiau Shoou-Ren
Published: March 2010

In a two-person red-and-black game, each player holds an integral amount of chips. At each stage of the game, each player can bet any integral amount in his possession, winning the chips of his opponent with a probability which is a function of the ratio of his bet to the sum of both players' bets and is called a win probability function. Both players seek to maximize the probability of winning the entire fortune of his opponent. In this paper we propose two new models. In the first model, at each stage, there is a positive probability that two players exchange their bets. In the second model, the win probability functions are stage dependent. In both models, we obtain suitable conditions on the win probability functions such that it is a Nash equilibrium for the subfair player to play boldly and for the superfair player to play timidly.
On Occurrences ofF-SStrings in Linearly and Circularly Ordered Binary Sequences
Authors: Makri Frosso S.
Published: March 2010

Consider a sequence of exchangeable or independent binary trials ordered on a line or on a circle. The statistics denoting the number of times anF-Sstring of length (at least)k1+k2, that is, (at least)k1failures followed by (at least)k2successes innsuch trials, are studied. The associated waiting time for therth occurrence of anF-Sstring of length (at least)k1+k2in linearly ordered trials is also examined. Exact formulae, lower/upper bounds and approximations are derived for their distributions. Mean values and variances of the number of occurrences ofF-Sstrings are given in exact formulae too. Particular exchangeable and independent sequences of binary random variables, used in applied research, combined with numerical examples clarify further the theoretical results.
Duration Distribution of the Conjunction of Two Independent F Processes
Authors: Alodat M. T. , Al-Rawwash M. , Jebrini M. A.
Published: March 2010

In this paper we obtain an approximation for the duration distribution of the excursion set generated by the minimum of two independent F random processes above a high threshold u. Moreover, we obtain a closed-form approximation for the mean duration of the conjunction of these two F processes. As an illustration, we conduct a simulation study to compare the performances of the approximated distribution and the exact distribution.
The Joint Signature of Coherent Systems with Shared Components
Authors: Navarro Jorge , Samaniego Francisco J. , Balakrishnan N.
Published: March 2010

System signatures are useful tools in the study and comparison of coherent systems. In this paper, we define and study a similar concept, called the joint signature, for two coherent systems which share some components. Under an independent and identically distributed assumption on component lifetimes, a pseudo-mixture representation based on this joint signature is obtained for the joint distribution of the lifetimes of both systems. Sufficient conditions are given based on the respective joint signatures of two pairs of systems, each with shared components, to ensure various forms of bivariate stochastic orderings between the joint lifetimes of the two pairs of systems.
Generalized Increasing Convex and Directionally Convex Orders
Authors: Denuit Michel M. , Mesfioui Mhamed
Published: March 2010

In this paper, the componentwise increasing convex order, the upper orthant order, the upper orthant convex order, and the increasing directionally convex order for random vectors are generalized to hierarchical classes of integral stochastic order relations. The elements of the generating classes of functions possess nonnegative partial derivatives up to some given degrees. Some properties of these new stochastic order relations are studied. Particular attention is paid to the comparison of weighted sums of the respective components of ordered random vectors. By providing a unified derivation of standard multivariate stochastic orderings, the present paper shows how some well-known results derive from a common principle.
A Characterization Related to the Equilibrium Distribution Associated with a Polynomial Structure
Authors: Bar-Lev Shaul K. , Boxma Onno , Letac Gérard
Published: March 2010

Let f be a probability density function on (a, b) ⊂ (0, ∞), and consider the class Cf of all probability density functions of the form Pf, where P is a polynomial. Assume that if X has its density in Cf then the equilibrium probability density x ↦ P(X > x) / E(X) also belongs to Cf: this happens, for instance, when f(x) = Ce−λx or f(x) = C(b − x)λ−1. We show in the present paper that these two cases are the only possibilities. This surprising result is achieved with an unusual tool in renewal theory, by using ideals of polynomials.
Is there an energetic-based trade-off between thermoregulation and the acute phase response in zebra finches?
Authors: Burness Gary , Armstrong Christopher , Fee Thomas , Tilman-Schindel Elinor
Published: March 2010

There has been recent interest in understanding trade-offs between immune function and other fitness-related traits. At proximate levels, such trade-offs are presumed to result from the differential allocation of limited energy resources. Whether the costs of immunity are sufficient to necessitate such energy reallocation remains unclear. We tested the metabolic and behavioural response of male zebra finches (Taeniopygia guttata) to the combined effects of thermoregulation and generation of an acute phase response (APR). The APR is the first line of defence against pathogens, and is considered energetically costly. We predicted that at cold temperatures zebra finches would exhibit an attenuated APR when compared with individuals at thermoneutrality. We challenged individuals with bacterial lipopolysaccharide (LPS), an immunogenic compound that stimulates an APR. Following LPS injection, we measured changes in food intake, body mass, activity, and resting and total energy expenditure. When challenged with LPS under ad libitum food, individuals at both temperatures decreased food intake and activity, resulting in similar mass loss. In contrast to predicted energetic trade-offs, cold-exposed individuals injected with LPS increased their nocturnal resting energy expenditure more than did individuals held at thermoneutrality, yet paradoxically lost less mass overnight. Although responding to LPS was energetically costly, resulting in a 10% increase in resting expenditure and 16% increase in total expenditure, there were few obvious energetic trade-offs. Our data support recent suggestions that the energetic cost of an immune response may not be the primary mechanism driving trade-offs between immune system function and other fitness-related traits.
Male moths bearing transplanted female antennae express characteristically female behaviour and central neural activity
Authors: Kalberer N. M. , Reisenman C. E. , Hildebrand J. G.
Published: March 2010

The primary olfactory centres of the sphinx moth Manduca sexta, the antennal lobes, contain a small number of sexually dimorphic glomeruli: the male-specific macroglomerular complex and the large female glomeruli. These glomeruli play important roles in sex-specific behaviours, such as the location of conspecific females and the selection of appropriate host plants for oviposition. The development of sexually dimorphic glomeruli depends strictly on the ingrowth of sex-specific olfactory receptor cell afferents. In the present study we tested the role of female-specific olfactory receptor cells (ORCs) in mediating female-specific host plant approach behaviour and in determining the response of downstream antennal lobe neurons. We generated male gynandromorphs by excising one imaginal disc from a male larva and replacing it with the antennal imaginal disc from a female donor. Most male gynandromorphs had an apparently normal female antenna and a feminised antennal lobe. These gynandromorphs were tested for flight responses in a wind tunnel towards tomato plants, a preferred host plant for oviposition in M. sexta. Male gynandromorphs landed on host plants as often as normal females, demonstrating that the presence of the induced female-specific glomeruli was necessary and sufficient to produce female-like, odour-oriented behaviour, i.e. orientation towards host plants. We also characterised the physiological and morphological properties of antennal lobe neurons of male gynandromorphs. We found that projection neurons with arborisations in the induced female-specific glomeruli showed physiological responses akin to those of female-specific projection neurons in normal females. These results therefore indicate that ORCs confer specific odour tuning to their glomerular targets and, furthermore, instruct odour-specific behaviour.
Neural responses to one- and two-tone stimuli in the hearing organ of the dengue vector mosquito
Authors: Arthur Ben J. , Wyttenbach Robert A. , Harrington Laura C. , Hoy Ronald R.
Published: March 2010

Recent studies demonstrate that mosquitoes listen to each other's wing beats just prior to mating in flight. Field potentials from sound-transducing neurons in the antennae contain both sustained and oscillatory components to pure and paired tone stimuli. Described here is a direct comparison of these two types of response in the dengue vector mosquito, Aedes aegypti. Across a wide range of frequencies and intensities, sustained responses to one- and two-tone stimuli are about equal in magnitude to oscillatory responses to the beats produced by two-tone stimuli. All of these responses are much larger than the oscillatory responses to one-tone stimuli. Similarly, the frequency range extends up to at least the fifth harmonic of the male flight tone for sustained responses to one- and two-tone stimuli and oscillatory responses at the beat frequency of two-tone stimuli, whereas the range of oscillatory response to a one-tone stimulus is limited to, at most, the third harmonic. Thresholds near the fundamental of the flight tone are lower for oscillatory responses than for sustained deflections, lower for males than for females, and within the behaviorally relevant range. A simple model of the transduction process can qualitatively account for both oscillatory and sustained responses to pure and paired tones. These data leave open the question as to which of several alternative strategies underlie flight tone matching behavior in mosquitoes.
A wake-based correlate of swimming performance and foraging behavior in seven co-occurring jellyfish species
Authors: Dabiri J. O. , Colin S. P. , Katija K. , Costello J. H.
Published: March 2010

It is generally accepted that animal–fluid interactions have shaped the evolution of animals that swim and fly. However, the functional ecological advantages associated with those adaptations are currently difficult to predict on the basis of measurements of the animal–fluid interactions. We report the identification of a robust, fluid dynamic correlate of distinct ecological functions in seven jellyfish species that represent a broad range of morphologies and foraging modes. Since the comparative study is based on properties of the vortex wake – specifically, a fluid dynamical concept called optimal vortex formation – and not on details of animal morphology or phylogeny, we propose that higher organisms can also be understood in terms of these fluid dynamic organizing principles. This enables a quantitative, physically based understanding of how alterations in the fluid dynamics of aquatic and aerial animals throughout their evolution can result in distinct ecological functions.
When surfacers do not dive: multiple significance of extended surface times in marine turtles
Authors: Hochscheid S. , Bentivegna F. , Hamza A. , Hays G. C.
Published: March 2010

Marine turtles spend more than 90% of their life underwater and have been termed surfacers as opposed to divers. Nonetheless turtles have been reported occasionally to float motionless at the surface but the reasons for this behaviour are not clear. We investigated the location, timing and duration of extended surface times (ESTs) in 10 free-ranging loggerhead turtles (Caretta caretta) and the possible relationship to water temperature and diving activity recorded via satellite relay data loggers for 101–450 days. For one turtle that dived only in offshore areas, ESTs contributed 12% of the time whereas for the other turtles ESTs contributed 0.4–1.8% of the time. ESTs lasted on average 90 min but were mostly infrequent and irregular, excluding the involvement of a fundamental regulatory function. However, 82% of the ESTs occurred during daylight, mostly around noon, suggesting a dependence on solar radiation. For three turtles, there was an appreciable (7°C to 10.5°C) temperature decrease with depth for dives during periods when ESTs occurred frequently, suggesting a re-warming function of EST to compensate for decreased body temperatures, possibly to enhance digestive efficiency. A positive correlation between body mass and EST duration supported this explanation. By contrast, night-active turtles that exceeded their calculated aerobic dive limits in 7.6–16% of the dives engaged in nocturnal ESTs, probably for lactate clearance. This is the first evidence that loggerhead turtles may refrain from diving for at least two reasons, either to absorb solar radiation or to recover from anaerobic activity.
Morphology–flow interactions lead to stage-selective vertical transport of larval sand dollars in shear flow
Authors: Clay T. W. , Grünbaum D.
Published: March 2010

Many larvae and other plankton have complex and variable morphologies of unknown functional significance. We experimentally and theoretically investigated the functional consequences of the complex morphologies of larval sand dollars, Dendraster excentricus (Eschscholtz), for hydrodynamic interactions between swimming and turbulent water motion. Vertical shearing flows (horizontal gradients of vertical flow) tilt organisms with simple geometries (e.g. spheres, ellipsoids), causing these organisms to move horizontally towards downwelling water and compromising their abilities to swim upwards. A biomechanical model of corresponding hydrodynamic interactions between turbulence-induced shear and the morphologically complex four-, six- and eight-armed stages of sand dollar larvae suggests that the movements of larval morphologies differ quantitatively and qualitatively across stages and shear intensities: at shear levels typical of calm conditions in estuarine and coastal environments, all modeled larval stages moved upward. However, at higher shears, modeled four- and eight-armed larvae moved towards downwelling, whereas six-armed larvae moved towards upwelling. We also experimentally quantified larval movement by tracking larvae swimming in low-intensity shear while simultaneously mapping the surrounding flow fields. Four- and eight-armed larvae moved into downwelling water, but six-armed larvae did not. Both the model and experiments suggest that stage-dependent changes to larval morphology lead to differences in larval movement: four- and eight-armed stages are more prone than the six-armed stage to moving into downwelling water. Our results suggest a mechanism by which differences can arise in the vertical distribution among larval stages. The ability to mitigate or exploit hydrodynamic interactions with shear is a functional consequence that potentially shapes larval evolution and development.
Dynamics of optomotor responses in Drosophila to perturbations in optic flow
Authors: Theobald Jamie C. , Ringach Dario L. , Frye Mark A.
Published: March 2010

For a small flying insect, correcting unplanned course perturbations is essential for navigating through the world. Visual course control relies on estimating optic flow patterns which, in flies, are encoded by interneurons of the third optic ganglion. However, the rules that translate optic flow into flight motor commands remain poorly understood. Here, we measured the temporal dynamics of optomotor responses in tethered flies to optic flow fields about three cardinal axes. For each condition, we used white noise analysis to determine the optimal linear filters linking optic flow to the sum and difference of left and right wing beat amplitudes. The estimated filters indicate that flies react very quickly to perturbations of the motion field, with pure delays in the order of ~20 ms and time-to-peak of ~100 ms. By convolution the filters also predict responses to arbitrary stimulus sequences, accounting for over half the variance in 5 of our 6 stimulus types, demonstrating the approximate linearity of the system with respect to optic flow variables. In the remaining case of yaw optic flow we improved predictability by measuring individual flies, which also allowed us to analyze the variability of optomotor responses within a population. Finally, the linear filters at least partly explain the optomotor responses to superimposed and decomposed compound flow fields.
Short-term group fission processes in macaques: a social networking approach
Authors: Sueur C. , Petit O. , Deneubourg J. L.
Published: March 2010

Living in groups necessarily involves a certain amount of within-group competition for food. Group members may have different motivations, implying the reaching of a consensus to stay cohesive. In some cases individuals fail to reach a common decision and the group splits; this can be temporary, as seen in fission–fusion dynamics, or even irreversible. Most studies on fission–fusion dynamics published to date have focused on the influence of environmental constraints on sub-grouping patterns, but little is known about how social relationships affect individual choices for sub-groups. In this study, we used an agent-based model to understand the mechanisms underlying group fission in two semi-free-ranging groups of macaques: one group of Tonkean macaques (Macaca tonkeana) and one of rhesus macaques (M. mulatta). The results showed that sub-grouping patterns were mainly influenced by affiliative relationships. Moreover, the species-specific social style appeared to affect the probability of choosing a particular sub-group. In the tolerant Tonkean macaques, mechanisms underlying sub-grouping patterns resembled anonymous mimetism, while in the nepotistic rhesus macaques, kinship influenced the mechanisms underlying group fissions. As previous studies have shown, fission–fusion society may be a way to avoid social conflicts induced either by food or by social competition.
γ-Amino butyric acid (GABA) release in the ciliated protozoonParameciumoccurs by neuronal-like exocytosis
Authors: Ramoino P. , Milanese M. , Candiani S. , Diaspro A. , Fato M. , Usai C. , Bonanno G.
Published: March 2010

Paramecium primaurelia expresses a significant amount of γ-amino butyric acid (GABA). Paramecia possess both glutamate decarboxylase (GAD)-like and vesicular GABA transporter (vGAT)-like proteins, indicating the ability to synthesize GABA from glutamate and to transport GABA into vesicles. Using antibodies raised against mammalian GAD and vGAT, bands with an apparent molecular weight of about 67 kDa and 57 kDa were detected. The presence of these bands indicated a similarity between the proteins in Paramecium and in mammals. VAMP, syntaxin and SNAP, putative proteins of the release machinery that form the so-called SNARE complex, are present in Paramecium. Most VAMP, syntaxin and SNAP fluorescence is localized in spots that vary in size and density and are primarily distributed near the plasma membrane. Antibodies raised against mammal VAMP-3, sintaxin-1 or SNAP-25 revealed protein immunoblot bands having molecular weights consistent with those observed in mammals. Moreover, P. primaurelia spontaneously releases GABA into the environment, and this neurotransmitter release significantly increases after membrane depolarization. The depolarization-induced GABA release was strongly reduced not only in the absence of extracellular Ca2+ but also by pre-incubation with bafilomycin A1 or with botulinum toxin C1 serotype. It can be concluded that GABA occurs in Paramecium, where it is probably stored in vesicles capable of fusion with the cell membrane; accordingly, GABA can be released from Paramecium by stimulus-induced, neuronal-like exocytotic mechanisms.
High-precision tracking of sperm swimming fine structure provides strong test of resistive force theory
Authors: Friedrich B. M. , Riedel-Kruse I. H. , Howard J. , Jülicher F.
Published: March 2010

The shape of the flagellar beat determines the path along which a sperm cell swims. If the flagellum bends periodically about a curved mean shape then the sperm will follow a path with non-zero curvature. To test a simple hydrodynamic theory of flagellar propulsion known as resistive force theory, we conducted high-precision measurements of the head and flagellum motions during circular swimming of bull spermatozoa near a surface. We found that the fine structure of sperm swimming represented by the rapid wiggling of the sperm head around an averaged path is, to high accuracy, accounted for by resistive force theory and results from balancing forces and torques generated by the beating flagellum. We determined the anisotropy ratio between the normal and tangential hydrodynamic friction coefficients of the flagellum to be 1.81±0.07 (mean±s.d.). On time scales longer than the flagellar beat cycle, sperm cells followed circular paths of non-zero curvature. Our data show that path curvature is approximately equal to twice the average curvature of the flagellum, consistent with quantitative predictions of resistive force theory. Hence, this theory accurately predicts the complex trajectories of sperm cells from the detailed shape of their flagellar beat across different time scales.
Hindlimb interarticular coordinations inMicrocebus murinusin maximal leaping
Authors: Legreneur Pierre , Thévenet François-Régis , Libourel Paul-Antoine , Monteil Karine M. , Montuelle Stéphane , Pouydebat Emmanuelle , Bels Vincent
Published: March 2010

The purpose of this study was to investigate the pattern of coordinations of the hindlimb joints in the world's smallest living primate (Microcebus murinus). The sequencing and timing of joint rotations have been analyzed in five adult males performing maximal leaping from a take-off immobile platform to their own wooden nest. Angular kinematics of hip, knee, angle and metatarso-phalangeal (MT) joints were deduced from high-speed X-ray films in the sagittal plane of the animals. The body mass center (BMC) of the lemurs was assimilated to their iliac crest. The maximal airborne performance of the lemurs was 0.33±0.04 m, which represented 2.55±0.36 times their snout–vent length. Take-off instant occurred 72±7 ms after the start of the push-off, with a BMC velocity of 3.23±0.48 m s−1, oriented 55±14 deg. with the horizontal plane. The kinematic analysis of the joints and musculo-tendon architecture of the M. murinus plantar flexors pointed out mechanical power amplifier mechanisms (i.e. stretch-shortening cycle of hindlimb muscles and proximo-to-distal sequence).
Study of the Effect of Residual Elements (Cr, Ni e Cu) on the Machinability of Free-Machining Steel AISI 12L14 Using Design of Experiment
Authors: Almeida M C , Ferreira J R , Luis N E , Machado Á R , Oliveira D C , Pimentel M F
Published: March 2010

Free machining steel, because of its high levels of sulfur, manganese, and lead, is known for its good machinability. These three residual elements, which act to guarantee easy chip formation, are not, however, acting alone to influence this steel's good machinability. It is their influence, certainly, that is best understood, but researchers have yet to adequately understand the influence of three other residual elements, chrome (Cr), nickel (Ni), and copper (Cu). The present study aimed to determine some measure of the impact of these elements on machinability. In particular their influence on the machinability of AISI 12L14 steel was investigated. Employing the design of experiment (DOE) technique, the tool life was measured for nine batches of steel, each containing, within the tolerable amount, different levels of chrome, nickel, and copper. By analysing the results with statistical tools, it was found that levels of their presence do indeed influence the machinability of AISI 12L14 steel. Therefore, even within the variability allowed by the standards, steel-makers should manage the levels of these residual elements.
Enhancement of Axle Bearing Quality in Sewing Machines Using Six Sigma
Authors: Huang C-F , Chen K-S , Sheu S-H , Hsu T-S
Published: March 2010

In today's world there is increasing emphasis on personal style and individuality, and hence a preference for semi-finished, customizable products over finished products. Consequently, sales of do-it-yourself products are increasing, including the high-quality equipment necessary to complete semi-finished goods. A representative example is the sewing machine; sewing machines must have high process yield to keep after-sales service costs low. In the current paper, a key component of sewing machines, the upper axle bearing, is used to present an implementation of Six Sigma via the measure-analyse-improve-control (MAIC) approach. Four bearing characteristics are identified as being critical to quality and are used to develop process capability indices for evaluating bearing quality. Then, a multi-characteristic product capability analysis chart (MPCAC) is used to identify and analyse the factors affecting bearing quality. Finally, the results of experiments and statistical tests using control charts to identify the optimum process levels are presented. The results show that the MAIC approach will help manufacturers and suppliers of sewing machines achieve Six Sigma quality.
Pareto-Based Optimization of Part Orientation in Stereolithography
Authors: Nezhad A Sanati , Barazandeh F , Rahimi A R , Vatani M
Published: March 2010

This paper presents a Pareto-based optimization algorithm to determine a series of best part orientations in stereolithography systems. Previous methods could apply limit objective functions (OFs). Moreover, methods with multiple OFs had abstracted them into a single fitness function. A single fitness function never reflects the characteristics of individual OFs properly. The method proposed here handles several OFs individually. The objective functions are the build time and support volume under a desired surface finish. The optimization was performed using the multi-objective genetic algorithm (MOGA). At each genetic algorithm step, the surface finish was achieved by applying the adaptive layer thickness method. Pareto-based optimization finds a series of best part orientations with minimum build time and volume support. It is a multi-objective optimization that handles complex CAD files. The algorithm was developed using MATLAB. The codes were run for some case studies and the results were very promising.
Selection of Process Parameters for Optimizing the Weld Strength in Laser Transmission Welding of Acrylics
Authors: Acherjee B , Kuar A S , Mitra S , Misra D
Published: March 2010

In this paper, an experimental investigation into laser transmission welding of acrylics is carried out. The Taguchi method of parameter design is used as a statistical design of experiment technique to set the optimal process parameters. Experiments are designed and conducted by using Taguchi's L16 orthogonal array. Maximization of weld strength is selected as the quality target. The signal-to-noise ratio and the analysis of variance are used to find the optimum levels within the window of parameters selected and to identify the order of importance of the process parameters. With the frame of this work the effects of process parameters on weld strength is also discussed. Finally, a confirmation test is conducted, which verifies that optimal laser transmission welding parameters can be determined effectively so as to improve weld strength through the Taguchi method.
Cutting Force Estimation in a Micromilling Process
Authors: Huang B W , Cai J Z , Hsiao W L
Published: March 2010

The cutting force estimation of a micro-mill in a milling process was investigated in the present study. As the micro-machining cutting force is so small, the force is difficult to measure using the traditional load cell and therefore cutting force estimation in a milling process was considered. The finite element method and experimental analyses were employed to estimate the micro-milling cutting force in this work. The vibration amplitude in a milling process is dependent on the cutting force, so this vibration amplitude was used to estimate the cutting force. To make it easier, only the maximum cutting force was estimated. Moreover, only the maximum vibration amplitude was measured and simulated to estimate the maximum cutting force. The results indicate that the vibration amplitude could be used to estimate the cutting force. It was found that the estimated micro-milling force agreed with the results from a previous published investigation. The vibration of a micro-mill in the milling process was also considered.
Practical torsional analysis and coupling selection for multi-machine complex process rotating equipment trains
Authors: Almasi A
Published: March 2010

A multi-machine train consists of several complex shafts, rotors, or crankshafts and relatively flexible shaft extensions and couplings. It may also include gear unit, clutch, or flywheel. As connected machines function as spring systems in series, the potential exists for torsional resonance and torsional fatigue damage. Couplings are often modified to tune the overall system. Practical torsional analysis method, useful recommendations, and optimum coupling selection are addressed. Case studies for rigid connection (flange-to-flange connection without coupling), high torsional stiffness coupling, and flexible coupling are also investigated.
Multi-objective controller design for uncertain large-scale stochastic systems with time delays via linear matrix inequality optimizations
Authors: Chang K-Y , Wu W-B , Chang Y-H , Chen P-C
Published: March 2010

The present paper investigates the problem of robustly decentralized asymptotical stabilization with an
Ventilation system airflow dynamics
Authors: Whalley R , Abdul-Ameer A
Published: March 2010

Ventilation system airways comprising ducting and ventilation shafts of various lengths and diameters are considered. Conventional modelling methods for these systems, for automatic control purposes are commented upon. Analytical techniques which combine the distributed and relatively lumped parameter properties, of spatially dispersed systems, are introduced. General, distributed, and lumped realizations and structures are devised for the components, for typical ventilation system configurations. The formulation of multivariable, integrated, distributed parameter, hybrid models, for spatially dispersed ventilation systems comprising the transmission, energy storage, and dissipation elements, are proposed. Transfer function derivation methods enabling the airflow transients, at strategic system locations to be predicted, are presented. Typical application studies are outlined.
Using life curves as input to quantitative risk analysis in electricity distribution system asset management
Authors: Nordgärd D E , Welte T M , Heggset J
Published: March 2010

Electricity distribution companies are developing asset management strategies where different aspects of risk are addressed, including also intangible risks such as safety and environmental impact. Providing methods for risk-informed decision making is hence an important task. This applies to both risk analysis methods and methods for input data acquisition and preparation. The current paper presents a procedure wherein results from life curves are used as input to a quantitative risk analysis (QRA) model, with the aim to support distribution company asset management decision making. The procedure is illustrated by a case study concerned with safety risk analysis and maintenance strategy for making medium-voltage switch disconnectors in an electricity distribution company.
Preparation, Structures, and Physical Properties of Tetrakis(alkylthio)tetraselenafulvalene (TTCn-TSeF, n = 1–15)
Authors: Saito Gunzi , Yoshida Yukihiro , Murofushi Hidenobu , Iwasawa Naoko , Hiramatsu Takaaki , Otsuka Akihiro , Yamochi Hideki , Isa Kimio , Mineo-Ota Eriko , Konno Michiko , Mori Takehiko , Imaeda Ken-ichi , Inokuchi Hiroo
Published: March 2010

A series of tetrakis(alkylthio)tetraselenafulvalene compounds (TTCn-TSeF, n = 1–15) were prepared by a one-step reaction between dialkyl disulfide and tetralithiated TSeF. Molecular properties (redox potentials and optical absorptions in solution) and solid-state properties (thermal behaviors, electric conductivities, and molecular and crystal structures for n = 1 and 10) were studied. TTCn-TSeF compounds are weak electron donor molecules and characterized by small on-site Coulomb repulsion. TTC1-TSeF has a high-dimensional conduction network owing to the presence of high-dimensional heteroatomic contacts, “Atomic-Wire Effect.” The π-moieties of TTC10-TSeF were fastened by the alkyl chains (“Fastener Effect”) to form π-columns and there are a variety of short heteroatomic contacts resulting in two-dimensional electronic structure. Electrical conductivity exhibited peculiar enhancement for n = 1 and 7 ≤ n ≤ 14 owing to the presence of high-dimensional conduction paths. These compounds may manifest high carrier mobility, and are good candidates for the field-effect transistor channel based on the advantageous features: low dark conductivity, low donor ability, on-site Coulomb repulsion energy, high-dimensional π-electron structure, and high solubility in organic solvents.
BEDT-TTF Tris(oxalato)germanate(IV) Salts with Novel Donor Packing Motifs
Authors: Martin Lee , Day Peter , Nakatsuji Shin’ichi , Yamada Jun-ichi , Akutsu Hiroki , Horton Peter N
Published: March 2010

The synthesis, crystal structure, and conducting properties of two new BEDT-TTF charge-transfer salts containing tris(oxalato)germanate(IV) anions are described. (BEDT-TTF)5[Ge(C2O4)3]2 (1) crystallizes in the monoclinic space group C2, a = 23.0994(11) Å, b = 11.0200(5) Å, c = 19.5455(9) Å, β = 117.628(4)°, V = 4408.1(4) Å3, T = 120(2) K, Z = 2, R1 = 0.0659 [F2 > 2σ(F2)]. Compound 2 (BEDT-TTF)7[(Ge(C2O4)3]2·0.87CH2Cl2·0.09H2O crystallizes in the monoclinic space group C2/c, a = 37.081(2) Å, b = 11.5449(7) Å, c = 28.6415(13) Å, β = 93.7767(9)°, V = 12234.8(12) Å3, T = 293(2) K, Z = 4, R1 = 0.0834 [F2 > 2σ(F2)]. Electrical resistivity measurements show that 1 and 2 are both semiconductors.
Linearly Aligned Metal Clusters: Versatile Reactivity and Bonding Nature of Tetrametal M–Mo–Mo–M Complexes (M = Pt, Pd, Ir, and Rh) Supported by 6-Diphenylphosphino-2-pyridonato Ligand
Authors: Mashima Kazushi
Published: March 2010

A tridentate ligand, pyphos (6-diphenylphosphino-2-pyridonato), was utilized to prepare tetrametal complexes since this ligand has unique coordinating sites comprised of three different elements, i.e., phosphorus, nitrogen, and oxygen, in almost linear fashion. By using pyphos ligand, linearly aligned tetrametal complexes of group 10 metals [Mo2M2(pyphos)4X2n] (M = Pt and Pd; n = 0, 1, and 2) were prepared, and for group 9 metals, [Mo2M2(pyphos)4(RNC)4X2n]2+ (M = Ir and Rh; n = 0 and 1). Fully metal-to-metal bonded complexes were obtained by reduction of MII to MI for group 10 metals and by oxidation of MI to MII for group 9 metals. Both reactions afforded complexes having unique M–Mo≡Mo–M skeletons, i.e., metalla-2-butyne. Structural and chemical properties were systematically investigated for M0 (M = Pt and Pd) and MI (M = Ir and Rh). Thus, oxidative reactions of Pd0 complexes [Mo2Pd2(pyphos)4] and IrI complexes [Mo2Ir2(pyphos)4(RNC)4]2+ with RX or X2 were studied and unique 1,4-addition reaction was demonstrated. Dichromium complexes analogous to dimolybdenum complexes were prepared and axial donation of PtMe2 moiety significantly elongated the Cr–Cr bond, due to the dative bonding interaction between CrII and PtII units.
Quantitative Structure–Toxicity Prediction of log(1/EC50) for Some Benzene Derivatives from Their Density Functional Theory Calculated Molecular Descriptors
Authors: Haghdadi Mina , Fatemi Mohammad H
Published: March 2010

In this work the 50% effective inhibition concentration after 48 h (log(1/EC50)) of 39 substituted benzenes to the algae Scenedesmus obliquus was predicted by quantitative structure–toxicity relationship (QSTR) approaches. Descriptors which appeared in the best model are; highest occupied molecular orbital, molecular weight, lowest unoccupied molecular orbital, chemical potential, zero point energy, and hardness parameters. These descriptors were obtained from density functional theory (DFT) calculation at B3LYP level together with 6-31G* basis set. Results of this modeling provide the statistics of R = 0.91, F = 19, and SE = 0.30 for training set and R = 0.91, F = 18, and SE = 0.34 for test set. Also the average error and average absolute error in the prediction of log(1/EC50) are −0.00041 and 0.198 for training set and for prediction set are −0.056 and 0.217, respectively. Moreover, the credibility of the model was tested by cross-validation and Y-scrambling, the results of these tests indicated the reliability of the model. The results of this investigation show that it was possible to predict the molecular toxicity of organic compounds from their DFT-calculated molecular descriptors.
The Evaluation Theory of Free Radical Scavenging and the Application to Xanthine Oxidase
Authors: Mitsuta Keiichi
Published: March 2010

A competitive reaction theory in which flexibility is given to the orders of reaction has been established. As a result of an analysis based on this novel theory, the stoichiometric coefficients of the reactions between superoxide dismutase (SOD) and superoxide radicals (O2−•), between xanthine oxidase (XOD) and O2−•, and between 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and O2−• have all been estimated to be 1:1. Furthermore, the hitherto unknown second-order rate constant for the reaction between XOD and O2−• has been estimated to be 1.4 × 106 or ca. 8.0 × 105 M−1 s−1. It is considered that the presence of the SOD-like activity possessed by XOD itself is one of the causes of the puzzling fact reported that the amount of O2−• observed in a xanthine–XOD system is smaller than the anticipated amount by one order of magnitude. In addition, this SOD-like activity of XOD may cause researchers to underestimate the rate constant for the reaction between O2−• and a spin-trapping agent when the spontaneous dismutation of O2−• in the presence of XOD was used as a competitor against the spin-trapping reaction for O2−•.
Salt Effects on the Rates and Mechanisms of Solvolysis Reaction of Organic Halides and Water Structure Distortion in N,N-Dimethylformamide– and N,N-Dimethylacetamide–Water Mixed Solvents
Authors: Hojo Masashi , Ueda Tadaharu , Ueno Eriko , Hamasaki Tensei , Nakano Toshiyuki
Published: March 2010

In 50% (v/v) DMF– and DMA–H2O mixed solvents, salt effects on the solvolysis reaction rates of aliphatic halides and related compounds (RX) have been examined for further exploring. Compared with previous results obtained in other organic solvent systems, such as 50% (v/v) acetone–, 1,4-dioxane–, or sulfolane–H2O, no exceptional behavior was observed in the “pseudo” first-order rate constants (k/s−1) of all the typical SN1 and SN2 substrates by the addition of alkali metal and alkaline earth metal perchlorates or many kinds of tetraalkylammonium salts in 50% (v/v) DMF– and DMA–H2O mixed solvents. The detailed examination of Δlog(k/s−1)/Δ[LiClO4] for 1-adamantyl bromide vs. the contents of organic solvents (CH3CN, DMA, and DMSO) suggested that the observed different salt effects were caused by the different solvation abilities of the solvents toward the leaving-group anion as well as the metal cation. As a new highlight in the present paper, we were able to demonstrate a proportionality or correlation between the LiClO4 effects in the solvolysis rates and the carbocation stabilities expressed by the Gibbs free energy values (ΔGo) of RX in the gas phase. Based on the Raman spectra of DMA–H2O and DMA–D2O as well as DMF–D2O mixed solvents, we discuss the distortion of the bulk water structure.
Organoammonium Salt-Catalyzed Enantioselective Cycloaddition Reactions with α-(Acyloxy)- or α-Diacylaminoacroleins
Authors: Sakakura Akira , Ishihara Kazuaki
Published: March 2010

The rational design of small-molecule chiral catalysts is an important subject in the development of practical organic syntheses. We have designed primary ammonium salt catalysts for enantioselective cycloaddition reactions with α-substituted acroleins such as α-(acyloxy)acroleins and α-diacylaminoacroleins. Ammonium salts of an aliphatic triamine derived from H–l-Phe–l-Leu–N(CH2CH2)2 successfully promote the Diels–Alder reaction of α-(acyloxy)acroleins and α-(N,N-diacylamino)acroleins, and the [2 + 2] cycloaddition reaction of α-(acyloxy)acroleins with high enantioselectivity. An ammonium salt of a C2-symmetric aromatic diamine, 1,1′-binaphthyl-2,2′-diamine, with a superacid is also an efficient catalyst and shows high activity and enantioselectivity for the Diels–Alder reaction of cyclic dienes with α-(acyloxy)acroleins.
Calcium dobesilate and oxerutin: effectiveness of combination therapy
Authors: Akbulut B
Published: March 2010

Objectives

Chronic venous insufficiency (CVI) is an important cause of discomfort and inability to work. Hydroxyethylrutosides (Venoruton®; 0-[beta-hydroxyethyl]-rutosides) has been used for decades for the treatment of CVI. Studies have reported symptomatic relief and a decreased capillary filtration after the administration of the oral preparations. Calcium dobesilate is a synthetic venoactive drug acting on several levels. It inhibits capillary permeability; it has antioxidant properties; and it inhibits the synthesis of prostaglandins and thromboxanes, reducing platelet and erythrocyte aggregation, as well as blood viscosity. The aim of this study is to determine whether the combination of both drugs is more effective in decreasing patients' complaints.

Methods

One hundred and fifty patients with primary venous insufficiency were randomized into three groups: Group A receiving calcium dobesilate only, Group B receiving oxerutin only and Group C receiving both calcium dobesilate and oxerutin. Patients were evaluated with a questionnaire before and four weeks after treatment regarding following parameters: itching, fatigue, heaviness, numbness, cramp, swelling and sensitiveness. Patients rated their symptoms from 0 to 4 (0: absent; 1: mild; 2: moderate; 3: severe; 4: very severe).

Results

Complaints, which were scored by patients before and after treatment, decreased. Among the single-drug groups, itching score decreased more in Group B, whereas scores of fatigue, heaviness, numbness, cramp and swelling decreased more in Group A. But the difference was not significant, statistically. But all complaints decreased significantly in Group C. Difference of scores after treatment revealed no statistical significance in Group A and B, but scores of Group C produced a significant difference when compared with Group A and B.

Conclusion

Results demonstrate that a combination of calcium dobesilate and oxerutin shows a better improvement of complaints. These observations have to be confirmed in larger series with objective tests. Changes of quality of life after a combination therapy might also be of interest.