bluuebunny/crossref_metadata_2025 huggingface dataset:
Connexin 43 regulates epicardial cell polarity and migration in coronary vascular development
Authors: Rhee David Y. , Zhao Xiao-Qing , Francis Richard J. B. , Huang Guo Ying , Mably John D. , Lo Cecilia W.
Published: August 2009

Connexin 43 knockout (Cx43 KO) mice exhibit conotruncal malformations and coronary artery defects. We observed epicardial blisters in the Cx43 KO hearts that suggest defects in epicardial epithelial-mesenchymal transformation(EMT), a process that generates coronary vascular progenitors. Analysis using a three-dimensional collagen gel invasion assay showed that Cx43 KO epicardial cells are less invasive and that, unlike wild-type epicardial cells, they fail to organize into thin vessel-like projections. Examination of Cx43 KO hearts using Wt1 as an epicardial marker revealed a disorganized pattern of epicardial cell infiltration. Time-lapse imaging and motion analysis using epicardial explants showed a defect in directional cell migration. This was associated with changes in the actin/tubulin cytoskeleton. A defect in cell polarity was indicated by a failure of the microtubule-organizing center to align with the direction of cell migration. Forced expression of Cx43 constructs in epicardial explants showed the Cx43 tubulin-binding domain is required for Cx43 modulation of cell polarity and cell motility. Pecam staining revealed early defects in remodeling of the primitive coronary vascular plexuses in the Cx43 KO heart. Together, these findings suggest an early defect in coronary vascular development arising from a global perturbation of the cytoarchitecture of the cell. Consistent with this, we found aberrant myocardialization of the outflow tract, a process also known to be EMT dependent. Together, these findings suggest cardiac defects in the Cx43 KO mice arise from the disruption of cell polarity, a process that may be dependent on Cx43-tubulin interactions.
The maternal-to-zygotic transition: a play in two acts
Authors: Tadros Wael , Lipshitz Howard D.
Published: August 2009

All animal embryos pass through a stage during which developmental control is handed from maternally provided gene products to those synthesized from the zygotic genome. This maternal-to-zygotic transition (MZT) has been extensively studied in model organisms, including echinoderms, nematodes, insects, fish,amphibians and mammals. In all cases, the MZT can be subdivided into two interrelated processes: first, a subset of maternal mRNAs and proteins is eliminated; second, zygotic transcription is initiated. The timing and scale of these two events differ across species, as do the cellular and morphogenetic processes that sculpt their embryos. In this article, we discuss conserved and distinct features within the two component processes of the MZT.
CBP-mediated acetylation of histone H3 lysine 27 antagonizesDrosophilaPolycomb silencing
Authors: Tie Feng , Banerjee Rakhee , Stratton Carl A. , Prasad-Sinha Jayashree , Stepanik Vincent , Zlobin Andrei , Diaz Manuel O. , Scacheri Peter C. , Harte Peter J.
Published: August 2009

Trimethylation of histone H3 lysine 27 (H3K27me3) by Polycomb repressive complex 2 (PRC2) is essential for transcriptional silencing of Polycomb target genes, whereas acetylation of H3K27 (H3K27ac) has recently been shown to be associated with many active mammalian genes. The Trithorax protein (TRX),which associates with the histone acetyltransferase CBP, is required for maintenance of transcriptionally active states and antagonizes Polycomb silencing, although the mechanism underlying this antagonism is unknown. Here we show that H3K27 is specifically acetylated by Drosophila CBP and its deacetylation involves RPD3. H3K27ac is present at high levels in early embryos and declines after 4 hours as H3K27me3 increases. Knockdown of E(Z)decreases H3K27me3 and increases H3K27ac in bulk histones and at the promoter of the repressed Polycomb target gene abd-A, suggesting that these indeed constitute alternative modifications at some H3K27 sites. Moderate overexpression of CBP in vivo causes a global increase in H3K27ac and a decrease in H3K27me3, and strongly enhances Polycomb mutant phenotypes. We also show that TRX is required for H3K27 acetylation. TRX overexpression also causes an increase in H3K27ac and a concomitant decrease in H3K27me3 and leads to defects in Polycomb silencing. Chromatin immunoprecipitation coupled with DNA microarray (ChIP-chip) analysis reveals that H3K27ac and H3K27me3 are mutually exclusive and that H3K27ac and H3K4me3 signals coincide at most sites. We propose that TRX-dependent acetylation of H3K27 by CBP prevents H3K27me3 at Polycomb target genes and constitutes a key part of the molecular mechanism by which TRX antagonizes or prevents Polycomb silencing.
Evolving enhancer-promoter interactions within the tinman complex of the flour beetle,Tribolium castaneum
Authors: Cande Jessica Doran , Chopra Vivek S. , Levine Michael
Published: August 2009

Modifications of cis-regulatory DNAs, particularly enhancers, underlie changes in gene expression during animal evolution. Here, we present evidence for a distinct mechanism of regulatory evolution, whereby a novel pattern of gene expression arises from altered gene targeting of a conserved enhancer. The tinman gene complex (Tin-C) controls the patterning of dorsal mesodermal tissues, including the dorsal vessel or heart in Drosophila. Despite broad conservation of Tin-C gene expression patterns in the flour beetle(Tribolium castaneum), the honeybee (Apis mellifera) and the fruit fly (Drosophila melanogaster), the expression of a key pericardial determinant, ladybird, is absent from the dorsal mesoderm of Tribolium embryos. Evidence is presented that this loss in expression is replaced by expression of C15, the neighboring gene in the complex. This switch in expression from ladybird to C15appears to arise from an inversion within the tinman complex, which redirects a conserved ladybird 3′ enhancer to regulate C15. In Drosophila, this enhancer fails to activate C15 expression owing to the activity of an insulator at the intervening ladybird early promoter. By contrast, a chromosomal inversion allows the cardiac enhancer to bypass the ladybird insulator in Tribolium. Given the high frequency of genome rearrangements in insects, it is possible that such enhancer switching might be widely used in the diversification of the arthropods.
Dampened Hedgehog signaling but normal Wnt signaling in zebrafish without cilia
Authors: Huang Peng , Schier Alexander F.
Published: August 2009

Cilia have been implicated in Hedgehog (Hh) and Wnt signaling in mouse but not in Drosophila. To determine whether the role of cilia is conserved in zebrafish, we generated maternal-zygotic (MZ) oval(ovl; ift88) mutants that lack all cilia. MZovlmutants display normal canonical and non-canonical Wnt signaling but show defects in Hh signaling. As in mouse, zebrafish cilia are required to mediate the activities of Hh, Ptc, Smo and PKA. However, in contrast to mouse Ift88 mutants, which show a dramatic reduction in Hh signaling,zebrafish MZovl mutants display dampened, but expanded, Hh pathway activity. This activity is largely due to gli1, the expression of which is fully dependent on Hh signaling in mouse but not in zebrafish. These results reveal a conserved requirement for cilia in transducing the activity of upstream regulators of Hh signaling but distinct phenotypic effects due to differential regulation and differing roles of transcriptional mediators.
Feedback linearization and sliding mode control for active hydropneumatic suspension of a special-purpose vehicle
Authors: Shi J-W , Li X-W , Zhang J-W
Published: August 2009

Based on modelling and experimental validation of the hydropneumatic spring, a non-linear dynamic model is developed for active hydropneumatic suspensions of a special-purpose vehicle. In order to improve the system response to off-road terrain unevenness and vertical impact force, the non-linear system is transformed into a linear one by means of feedback linearization. Furthermore, a sliding mode control strategy is introduced for the purpose of raising the robustness of the system. The simulation results indicate that the present non-linear controller combining the feedback linearization with the linear control algorithm possesses high control accuracy and strong robustness, and the unique requirements for the special-purpose vehicle are therefore fairly well satisfied.
Obstacle avoidance of autonomous vehicles based on model predictive control
Authors: Park J-M , Kim D-W , Yoon Y-S , Kim H J , Yi K-S
Published: August 2009

This paper presents an obstacle avoidance scheme for autonomous vehicles as an active safety procedure in unknown environments. Safe trajectories are generated using the non-linear model predictive framework, in which the simplified dynamics of the vehicle are used to predict the state of the vehicle over the look-ahead horizon. To compensate for the slight dissimilarity between the simplified model and the actual vehicle, a separate controller is designed to track the generated trajectory. The longitudinal dynamics of the vehicle are controlled using the inverse dynamics of the vehicle powertrain model, and the lateral dynamics are controlled using a linear quadratic regulator. In the non-linear model predictive framework, to obtain safe trajectories, local obstacle information is incorporated into the performance index using a parallax-based method. Simulation results on a full non-linear vehicle model show that the proposed combination of model-predictive-control-based trajectory generation and tracking controller gives satisfactory online obstacle avoidance performance.
Effect of grouped-hole nozzle geometry on the improvement of biodiesel fuel atomization characteristics in a compression ignition engine
Authors: Suh H K , Park S W , Lee C S
Published: August 2009

This paper describes the influence of grouped-hole nozzle geometry on the atomization characteristics of a biodiesel fuel. The effects of injection rate profile, spray evolution, droplet mean diameter, and mean velocity of the droplets are investigated in a high-pressure injection system.

A grouped-hole nozzle with 16 holes driven by piezo stack was used in the experiments and the obtained results are compared with those obtained using a single-hole nozzle with the same overall nozzle area. The effect of using a split fuel injection strategy on the spray atomization was analysed using a grouped-hole nozzle with 12 holes. The time-based injection rate profiles for a biodiesel fuel, i.e. the mass flowrate of the fuel injector nozzle were obtained from the pressure variation generated when the fuel was injected into a tube filled with fuel. The spray and atomization performance for biodiesel fuel injected through a grouped-hole nozzle were visualized and measured by a visualization system and droplet analyser system, respectively.

It was revealed that the biodiesel injection rate profile from a single-hole nozzle with the same overall nozzle area shows a similar injection rate profile to that of the grouped-hole nozzle. The injection rate profiles for a split injection strategy are lower than for a single injection and the peak value of the second injection is lower than for the first injection. The Sauter mean diameter distributions of biodiesel from the grouped-hole nozzle have a larger diameter because the small droplets injected through the grouped-hole nozzle collide and coalesce with each other, which leads to an increase in droplet diameter. From these results, it can be concluded that the use of a grouped-hole nozzle and split injection strategy does not improve on the fuel atomization performance for biodiesel fuel for a single-hole nozzle.
Design of a projector headlamp without using a screen
Authors: Liou Yuan Chang
Published: August 2009

A design for a projector headlamp that does not use a screen for low-beam lighting is proposed in this paper. The design not only enhances the light source utilization rate but also the elimination of the screen element prevents heat accumulation. The surface of the headlamp reflector is partitioned into six zones and, since there are no steps between reflectors, the zones are smoothly connected. A design equation for the reflector that combines varied lengths for both the circumference and optical axis is proposed and utilized for the surface design of each zone. Thus the reflector has the built-in ability to control light distribution in both the circumference and optical axis directions; consequently, it is able to create a very flexible light pattern, and is able to control all light rays to be below the cut-off line. As a result, the proposed projector headlamp can create a light distribution that meets the low-beam requirements of the ECE R112 standard.
Karanja oil utilization in a direct-injection engine by preheating. Part 1: experimental investigations of engine performance, emissions, and combustion characteristics
Authors: Agarwal A K , Dhar A
Published: August 2009

Vegetable oils have an energy content suitable for use as a fuel in diesel engines. Some of these oils have already been evaluated as substitutes for diesel fuels. However, several operational and durability problems of using straight vegetable oils in diesel engines have been reported in the literature, caused by their relatively higher viscosity and low volatility compared to mineral diesel. This viscosity can be brought into the acceptable range by transesterification, by blending of vegetable oil with diesel, or by preheating the vegetable oil using the waste heat of exhaust gases. The reduction in the viscosity by blending or exhaust gas preheating saves the processing cost incurred in the transesterification process involving expensive chemicals.

Experimental investigations were carried out for the combustion, performance, and emission characteristics of heated Karanja oil in a direct-injection compression ignition engine at different loads at a constant engine speed of 1500r/min. Analysis of the cylinder pressure rise, instantaneous heat release, and cumulative heat release was carried out. Combustion phasing of preheated Karanja oil was found to be identical with that of mineral diesel. Heating the vegetable oil substantially reduces the combustion duration. The brake specific fuel consumption and exhaust gas temperatures for heated Karanja oil were found to be higher than mineral diesel. The thermal efficiency was slightly lower for heated Karanja oil than for diesel. The carbon dioxide, carbon monoxide, hydrocarbon, and nitric oxide emissions were lower for heated Karanja oil than for diesel.
Steady-state hierarchical control for the drift correction of a constellation in highly elliptical orbits
Authors: Capó-Lugo P A , Bainum P M
Published: August 2009

The hierarchical control scheme is used to obtain the solutions of two-point boundary value problems to correct the separation distance drifts of a pair of satellites within a constellation in highly elliptical orbits according to mission constraints. One of these solutions is the drift correction that shows a faster correction than the solution of the two-point boundary value problem for the station-keeping process of a pair of satellites within a constellation. For the drift correction, the hierarchical control scheme uses an iterative method to obtain the solution for the drift correction. Thus, the hierarchical control scheme is re-expressed as a steady-state system to reduce the computational process and time. In summary, the steady-state hierarchical control scheme is used to correct the drift between a pair of satellites within a constellation in which the computational process is minimized.
Verifiable control of a swarm of unmanned aerial vehicles
Authors: Bennet D J , McInnes C R
Published: August 2009

This article considers the distributed control of a swarm of unmanned aerial vehicles (UAVs) investigating autonomous pattern formation and reconfigurability. A behaviour-based approach to formation control is considered with a velocity field control algorithm developed through bifurcating potential fields. This new approach extends previous research into pattern formation using potential field theory by considering the use of bifurcation theory as a means of reconfiguring a swarm pattern through a free parameter change. The advantage of this kind of system is that it is extremely robust to individual failures, is scalable, and also flexible. The potential field consists of a steering and repulsive term with the bifurcation of the steering potential resulting in a change of the swarm pattern. The repulsive potential ensures collision avoidance and an equally spaced final formation. The stability of the system is demonstrated to ensure that desired behaviours always occur, assuming that at large separation distances the repulsive potential can be neglected through a scale separation that exists between the steering and repulsive potential. The control laws developed are applied to a formation of ten UAVs using a velocity field tracking approach, where it is shown numerically that desired patterns can be formed safely ensuring collision avoidance.
A hierarchical decision and information system for multi-aircraft combat missions
Authors: Léchevin N , Rabbath C A
Published: August 2009

Designing decision, control and information systems is motivated, in part, by the need to support the deployment of multiple aircraft, such as combat vehicles, unmanned combat air vehicles, unmanned aerial vehicles, and weapons, in missions taking place in a dynamic, although uncertain, environment. Such systems aim at ensuring mission success without overloading the operating crew, the pilots, and the commanders. One of the main design challenges lies in obtaining some sort of coherent behaviour of the fleet, by means of solutions to potentially NP-hard problems, given incomplete and imperfect information, and despite limited computational and communication capabilities. In this context, this article proposes a hierarchical decision and information system aiming at providing, in real-time, coordinated aircraft path planning and deceptive engagement assignments. The blue—red engagement policy is obtained by minimizing, and balancing, the energy expenditure among the vehicles while constraining information exchanges to a minimum defined by a risk of inconsistency. The proposed system relies on dynamic programming, online heuristic techniques and stochastic, consistency-checking methods. Numerical simulations show that the proposed approach compares advantageously to a random process and to a law that seeks to minimize the cost of the confrontation at a given time regardless of past moves. However, there is a trade-off between increasing the level of deception and the level of energy consumption.
Sensor fault detection and accommodation using neural networks with application to a non-linear unmanned air vehicle model
Authors: Samy I , Postlethwaite I , Gu D-W
Published: August 2009

Model-based fault detection and isolation (FDI) systems have become a crucial step towards autonomy in aerospace engineering. Traditional methods such as observer-based methods have already been developed and widely applied. Novel approaches make use of online learning neural networks (NN) which have seen an increase in FDI applications over the years. However, few publications consider FDI applications to unmanned air vehicles (UAV) where high levels of autonomy are required. This article demonstrates such an application, where an extended minimum resource allocation network radial basis function (RBF) NN is used for modelling purposes. A novel residual generation approach is also presented and found to outperform a conventional approach by reducing the number of false alarms and missed faults. All tests are carried out in simulation where single sensor faults are assumed to occur in the pitch gyro of a non-linear UAV model.
Desirable eigenstructure for good short-term helicopter handling qualities: The rate command response case
Authors: Pomfret A , Clarke T
Published: August 2009

Existing work, to generate an eigenstructure suitable for achieving good short-term attitude command response in a generic single rotor helicopter, is extended here to provide eigenvectors appropriate to the (more complex) rate command case. The generated eigenstructure is, like the original, consistent with the physical relationships between the state variables. It achieves appropriate mode decoupling, and translates exactly into ideal transfer functions for use with a variety of control design methodologies. A simple numerical example is provided to show that the behaviour of a system with this eigenstructure displays the expected response.
Hybrid magnetic attitude control gain selection
Authors: Damaren C J
Published: August 2009

For spacecraft in low Earth orbits, attitude control via the torques provided by the geomagnetic field is an attractive option. Recent research has demonstrated that asymptotic pointing of attitude setpoints is possible using a linear combination of Euler parameter and angular velocity feedback. However, given the time-varying nature of the magnetic field, the size of the gains leading to stability is restricted. The present work looks at a hybrid scheme consisting of magnetic control using on-board dipole moments and an independent three-axis actuation scheme (i.e. reaction wheels or thrusters). A stability analysis is presented using passivity concepts that shows that the limitation on magnetic control gains can be removed if a minimum level of three-axis actuation augments the magnetic scheme.
Ultrasound image segmentation and tissue characterization
Authors: Noble J A
Published: August 2009

Ultrasound image segmentation deals with delineating the boundaries of structures, as a step towards semi-automated or fully automated measurement of dimensions or for characterizing tissue regions. Ultrasound tissue characterization (UTC) is driven by knowledge of the physics of ultrasound and its interactions with biological tissue, and has traditionally used signal modelling and analysis to characterize and differentiate between healthy and diseased tissue. Thus, both aim to enhance the capabilities of ultrasound as a quantitative tool in clinical medicine, and the two end goals can be the same, namely to characterize the health of tissue. This article reviews both research topics, and finds that the two fields are becoming more tightly coupled, even though there are key challenges to overcome in each area, influenced by factors such as more open software-based ultrasound system architectures, increased computational power, and advances in imaging transducer design.
Ultrasonic microscanning
Authors: Vogt M , Opretzka J , Perrey C , Ermert H
Published: August 2009

A detailed review is given of the application of high-frequency ultrasound (HFUS) at frequencies of 20 MHz and above for high-resolution, cross-sectional imaging of biological soft tissue. The state of the art of HFUS imaging systems is discussed with respect to the underlying engineering concepts, system designs, and available transducer technology. Furthermore, the dependency of the spatial resolution on the system's parameters is analysed. Skin imaging, eye imaging, small animal imaging for preclinical research, and intravascular ultrasound in coronary arteries for arteriosclerotic disease diagnostics are presented as examples for the application of HFUS imaging in medical diagnostics. It is shown that, in the frame of the indicated applications, ultrasound in the frequency range 20—100 MHz gives a good compromise between the contrary demands for a good spatial resolution and a sufficiently large penetration depth of ultrasound waves into the tissue. Scanning schemes for the imaging of tissue morphology are considered, including spatial compounding as a multidirectional imaging technique.
A finite element method parametric study of the dynamic response of the human brain with different cerebrospinal fluid constitutive properties
Authors: Chafi M Sotudeh , Dirisala V , Karami G , Ziejewski M
Published: August 2009

A major role for the cerebrospinal fluid (CSF) is to provide effective damping against sudden intracranial brain motions during dynamic head impact. This paper examines the roles of CSF properties on human brain responses under certain impact loadings. The brain is assumed to have a hyperviscoelastic material behaviour, while CSF is considered to be fluid-like elastic, viscoelastic, and nearly incompressible elastic with a low shear modulus and a high bulk modulus. A finite element parametric investigation on a head model under different scenarios of impact is conducted. In the study, the CSF material parameters are varied within the expected range of change, while other components of the head model are kept constant. The results indicate that the solutions from the modelling of CSF by a fluid-like medium are more realistic and support the findings of the experiment. The results also indicate that varying CSF properties did not have a major impact on the peak intracranial pressures but the impact on brain principal and shear strains are relatively significant. A sizeable impact on the relative motion of the brain, with respect to the skull, can also be observed.
Effect of Carbon Source on the Textural and Electrochemical Properties of Novel Cage-type Mesoporous Carbon as a Replica of KIT-5 Mesoporous Silica
Authors: Inagaki Satoshi , Oikawa Koji , Kubota Yoshihiro
Published: August 2009

Novel cage-type mesoporous carbon “carbon nanocage (CNC),” which is prepared as a carbon replica of KIT-5 mesoporous silica, showed a high electrochemical performance as an electrode material, due to the high specific surface area and mesopore volume as well as the sparse carbon network.
Trading in Networks: A Normal Form Game Experiment
Authors: Gale Douglas M , Kariv Shachar
Published: August 2009

This paper reports an experimental study of trading networks. Networks are incomplete in the sense that each trader can only exchange assets with a limited number of other traders. The greater the incompleteness of the network, the more intermediation is required to transfer the assets between initial and final owners. The uncertainty of trade in networks constitutes a potentially important market friction. Nevertheless, we find the pricing behavior observed in the laboratory converges to competitive equilibrium behavior in a variety of treatments. However, the rate of convergence varies depending on the network, pricing rule, and payoff function. (JEL C91, C92, G10, G19)
Market Culture: How Rules Governing Exploding Offers Affect Market Performance
Authors: Niederle Muriel , Roth Alvin E
Published: August 2009

Many markets encounter difficulty maintaining a thick marketplace because they experience transactions made at dispersed times. To address such problems, many markets try to establish norms concerning when offers can be made, accepted, and rejected. Examining such markets suggests it is difficult to establish a thick market at an efficient time if firms can make exploding offers, and workers cannot renege on early commitments. Laboratory experiments allow us to isolate the effects of exploding offers and binding acceptances. In a simple experiment, we find inefficient early contracting when firms can make exploding offers and applicants' acceptances are binding. (JEL C91, D40, D81)
Corruptible Advice
Authors: Durbin Erik , Iyer Ganesh
Published: August 2009

We study information transmission to a decision maker from an advisor who values a reputation for incorruptibility in the presence of a third party who offers unobservable payments/bribes. While it is common to ascribe negative effects to such bribes, we show that given reputational concerns, bribes can play a positive role by restoring truthful communication that would otherwise not occur. Thus, while bribes can influence self-interested bad advisors to lie about the unfavorable state, they can also be used to motivate good advisors who care more about the decision maker's utility to truthfully report the favorable state. (JEL D82, D83)
A Comment on Bernheim's Appraisal of Neuroeconomics
Authors: Gul Faruk , Pesendorfer Wolfgang
Published: August 2009

This paper comments on “On the Potential of Neuroeconomics: A Critical (but Hopeful) Appraisal” by B. Douglas Beinheim (JEL D01, D87)
Is There a Method of Neuroeconomics?
Authors: Rustichini Aldo
Published: August 2009

This note tries to state, precisely, the method of neuroecomics, and is based on the discussion in B. Douglas Bernheim's (2009) appraisal. We claim that the theory formulates hypotheses modeling the choice process as an algorithmic procedure. The hypothesis of the algorithmic procedure imposes restriction on the neural processes implementing it, and, so, a joint test of the hypothesis based on behavioral and neural data is possible, increasing the statistical and the explanatory power of the theory. (JEL B41, D87)
Neuroeconomics: A Comment on Bernheim
Authors: Sobel Joel
Published: August 2009

This paper comments on “On the Potential of Neuroeconomics: A Critical (but Hopeful) Appraisal” by B. Douglas Bernheim. (JEL D01, D87)
How Do Gasoline Prices Affect Fleet Fuel Economy?
Authors: Li Shanjun , Timmins Christopher , von Haefen Roger H
Published: August 2009

Exploiting a rich dataset of passenger vehicle registrations in 20 US MSAs from 1997 to 2005, we examine the effects of gasoline prices on the automotive fleet's composition. We find that high gasoline prices affect fleet fuel economy through two channels: shifting new auto purchases towards more fuel-efficient vehicles, and speeding the scrappage of older, less fuel-efficient used vehicles. Policy simulations suggest that a 10 percent increase in gasoline prices from 2005 levels will generate a 0.22 percent increase in fleet fuel economy in the short run and a 2.04 percent increase in the long run. (JEL H25, L11, L69, L71)
The Divergence of Legal Procedures
Authors: Balas Aron , La Porta Rafael , Lopez-de-Silanes Florencio , Shleifer Andrei
Published: August 2009

Simeon Djankov et al. (2003) introduce a measure of the quality of contract enforcement—the formalism of civil procedure—for 109 countries as of 2000. For 40 of these countries, we compute procedural formalism every year since 1950. We find that large differences in procedural formalism between common and civil law countries existed in 1950 and widened by 2000. For this area of law, the findings are inconsistent with the hypothesis that national legal systems are converging, and support the view that legal origins exert long lasting influence on legal rules. (JEL K41, O17)
Heterogeneity in Intra-Monthly Consumption Patterns, Self-Control, and Savings at Retirement
Authors: Mastrobuoni Giovanni , Weinberg Matthew
Published: August 2009

Using data from the Continuing Survey of Food Intake by Individuals, this paper describes the shape of consumption profiles over the month for Social Security benefit recipients that have saved different amounts for retirement. Individuals with income mostly made up of Social Security and savings smooth consumption over the pay period, while individuals without savings consume 25 percent fewer calories the week before they receive checks relative to the week afterwards. The findings for individuals without savings, who comprise about a fourth of our sample, are inconsistent with the standard Life Cycle-Permanent Income Hypothesis but are consistent with hyperbolic discounting. (JEL D14, E21, J26)
Is the Taxable Income Elasticity Sufficient to Calculate Deadweight Loss? The Implications of Evasion and Avoidance
Authors: Chetty Raj
Published: August 2009

Martin Feldstein's (1999) widely used taxable income formula for deadweight loss assumes the marginal social cost of evasion and avoidance equals the tax rate. This condition is likely to be violated in practice for two reasons. First, some of the costs of evasion and avoidance are transfers to other agents. Second, some individuals overestimate the costs of evasion and avoidance. In such situations, excess burden depends on a weighted average of the taxable income and total earned income elasticities, with the weight determined by the resource cost of sheltering income from taxation. This generalized formula implies the efficiency cost of taxing high income individuals is not necessarily large despite evidence that their reported incomes are highly sensitive to marginal tax rates. (JEL H21, H24, H26)
Tax Sensitivity and Home State Preferences in Internet Purchasing
Authors: Ellison Glenn , Ellison Sara Fisher
Published: August 2009

Data on memory modules sales are used to explore aspects of e-retail demand. Aggregate sales are examined in state-level regressions. Discrete choice techniques are used to examine (incomplete) hourly sales data from a price comparison site. We find a strong relationship between e-retail sales to a given state and sales tax rates that apply to purchases from offline retailers, suggesting substantial online-offline substitution and the importance of tax avoidance motives. Geography matters in two ways: consumers prefer purchasing from firms in nearby states and appear to have a separate preference for buying from in-state firms. (JEL D12, H25, H71, L81)
Incomplete Environmental Regulation, Imperfect Competition, and Emissions Leakage
Authors: Fowlie Meredith L
Published: August 2009

Environmental regulation of industrial pollution is often incomplete; regulations apply to only a subset of facilities contributing to a pollution problem. Policymakers are increasingly concerned about the emissions leakage that may occur if unregulated production can be easily substituted for regulated production. This paper analyzes emissions leakage in an incompletely regulated and imperfectly competitive industry. The analytical model is used to simulate outcomes under incomplete, market-based regulation of carbon dioxide emissions in California's electricity sector. Regulation that exempts out-of-state producers achieves approximately one-third of the total emissions reductions achieved under complete regulation at more than twice the cost per ton. (JEL L94, Q53, Q58)
Biochemical and nutritional indices as cardiovascular risk factors among Iranian firefighters
Authors: Azabdaftari Nazli , Amani Reza , Taha Jalali Mohammad
Published: August 2009

Aim

Limited cardiovascular disease (CVD) risk data are available for firefighters worldwide. This comparative study was aimed at investigating the biochemical and nutritional indices of firefighters in Iran.

Materials and methods

Individuals’ anthropometric measurements, including weight, height, and waist and hip circumferences, were measured and the percent of body fat (BF%) was also obtained. Blood sampling was done in order to determine lipid profile, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), lipoprotein a (Lp(a)) and fasting blood sugar (FBS) concentrations. Systolic and diastolic blood pressures (SBP and DBP) were also measured.

Results

The mean ages of firefighters and administrative staff were 42.45 ± 6.75 and 44.64 ± 5.83 y, respectively. The prevalence of overweight and obesity was 45% and 24% in firefighters and 54% and 23% in administrative staff, respectively. High waist-to-hip and waist-to-stature ratios were detected in 26.4% and 81.3% of firefighters versus 33.3% and 89.7% of the control group, respectively. No significant differences were observed between the mean of TC, TG, HDL-C, LDL-C and FBS concentrations. The mean of Lp(a) was significantly higher among firefighters ( P<0.05). About half of the subjects in both groups had TC >5.17, TG >1.69, HDL-C <1.03 nmol/L and Lp(a) >25 mg/dL. There were no significant differences between the SBP and DBP of subjects. There was no significant difference in smoking habits between the two groups.

Conclusions

Considering the high prevalence of overweight and obesity, high TC, TG and Lp(a) and low HDL-C concentrations among all firefighters, it seems necessary to provide fitness-promotion and nutritional education programs for the prevention of obesity-related chronic diseases such as CVD.
Distinct kinetic determinants for the stepwise CCA addition to tRNA
Authors: Kim Sangbumn , Liu Cuiping , Halkidis Konstantine , Gamper Howard B. , Hou Ya-Ming
Published: August 2009

The universally conserved CCA sequence is present at the 3′ terminal 74–76 positions of all active tRNA molecules as a functional tag to participate in ribosome protein synthesis. The CCA enzyme catalyzes CCA synthesis in three sequential steps of nucleotide addition at rapid and identical rates. However, the kinetic determinant of each addition is unknown, thus limiting the insights into the kinetic basis of CCA addition. Using our recently developed single turnover kinetics of Escherichia coli CCA enzyme as a model, we show here that the identical rate of the stepwise CCA addition is determined by distinct kinetic parameters. Specifically, the kinetics of C74 and C75 addition is controlled by the chemistry of nucleotidyl transfer, whereas the kinetics of A76 addition is controlled by a prechemistry conformational transition of the active site. In multiple turnover condition, all three steps are controlled by slow product release, indicating enzyme processivity from one addition to the next. However, the processivity decreases as the enzyme progresses to complete the CCA synthesis. Together, these results suggest the existence of a network of diverse kinetic parameters that determines the overall rate of CCA addition for tRNA maturation.
An electrochemiluminescent aptamer switch for a high-throughput assay of an RNA editing reaction
Authors: Liang Shuang , Connell Gregory J.
Published: August 2009

An RNA editing reaction that is both essential and specific to the trypanosomatid parasites is an attractive target for new drug development. Although high-throughput screening of chemical libraries is a powerful strategy often used to identify new drugs, the available in vitro editing assays do not have the necessary sensitivity and format for this approach to be feasible. A ruthenium labeled reporter RNA is described here that overcomes these limitations as it can both detect edited product in the low femtomole range and is ideal for high-throughput format. The reporter RNA consists of an RNA editing substrate linked to a streptavidin-binding aptamer that is initially held within an inactive conformation. An in vitro selection strategy optimized the linkage so that the streptavidin-binding aptamer is only activated by an editing-induced conformational change. An electrochemiluminescent signal results from the ruthenium label when the reporter is bound to the bottom of a streptavidin-coated microtiter plate where it can be stimulated by a carbon electrode. Chemical probing, mutagenesis, and binding affinity measurements were used to characterize the reporter. The highly sensitive assay could be adapted to a broad range of RNA processing reactions.
A Decision Analysis Approach to Solving the Signaling Game
Authors: Cobb Barry R. , Basuchoudhary Atin
Published: August 2009

Decision analysis has traditionally been applied to choices under uncertainty involving a single decision maker. Game theory has been applied to solving games of strategic interaction between two or more players. Building upon recent work of van Binsbergen and Marx (van Binsbergen, J. H., L. M. Marx. 2007. Exploring relations between decision analysis and game theory. Decision Anal. 4(1) 32–40), this paper defines a modified decision-theoretic approach to solving games of strategic interaction between two players. Using this method, the choices of the two players are modeled with separate decision trees comprised entirely of chance nodes. Optimal policies are reflected in the probabilities in the decision trees of each player. In many cases, the Nash equilibrium strategy for each player can be obtained by rolling back the opponent's decision tree. Results are demonstrated for the multistage signaling game, which is difficult to model using decision nodes to represent strategies, as in the approach of van Binsbergen and Marx.
The Impact of Online Auction Duration
Authors: Haruvy Ernan , Leszczyc Peter T. L. Popkowski
Published: August 2009

One view regarding auction duration suggests that longer auctions would result in more bidders and more bids, which in turn would result in higher prices. An opposing view is that shorter auctions might appeal to impatient bidders, or alternatively, that shorter duration might lead to more competitive dynamics. To examine these competing notions, we conduct pairwise comparisons of simultaneous auctions identical in all but duration. The auctions are conducted on two different platforms—eBay and a local auction site. We find that in eBay auctions, longer duration increases the number of bidders and bids, and consequently increases final prices by about 11%. On the local auction website, with far fewer auctions and a more steady set of participants, the effect is reversed, and shorter auctions generate higher prices by about 20%. Both sets of effects are robust and significant. We look at bidding activity on both sites to try to get at the root of that reversal. We find that in eBay auctions, the higher price in the longer-duration auction is accompanied by a higher number of participating bidders and a higher number of bids placed in the auction. In the local site, we find that the auction duration does not significantly affect the number of participating bidders or the number of bids placed in an auction. However, the magnitude of jump bids is negatively and significantly correlated with duration. These jump bids are in turn shown to impact final prices.
Diagnosis of Skin Lesions by Trainee Surgeons: Experience Improves Accuracy
Authors: Pearl RA , Townley W , Stott D , Grobbelaar AO
Published: August 2009

INTRODUCTION

Accurate clinical diagnosis depends on the reliable recognition of signs and symptoms. This expertise comes from experience in seeing patients which has been traditionally gained over a long training period. Shortened specialist training (Modernising Medical Careers) has led to a greater reliance on structured teaching and skills transfer programmes. The accuracy of clinical diagnosis and the rate at which diagnostic skills improve during training is important for the assessment of trainees, and the delivery of care.

PATIENTS AND METHODS

This study assessed the accuracy of clinical diagnosis of skin lesions by two junior plastic surgery trainees. They were asked to diagnose 120 consecutive skin lesions seen in a pigmented skin lesion clinic in 2005, with the histological diagnosis being confirmed following subsequent excision. The process was repeated a year later in 2006 to enable the rate of correct diagnosis to be compared.

RESULTS

Initially, 53.3% of diagnoses were correct. A year later, this had risen to 65.0%. Twenty-two different skin pathologies were present in excised specimens, and skin cancers comprised 30%. The trainees demonstrated 93.8% sensitivity in their initial diagnosis of malignancy (95% CI, 79.2–99.2) and 97.4% a year later (95% CI, 86.5–99.9). However, specificity was 69.3% (95% CI, 58.6–78.7) in 2005 and 71.6% (95% CI, 60.5–71.4) in 2006.

CONCLUSIONS

Accuracy in the diagnosis of the wide range of skin conditions presenting to an out-patient clinic was shown to increase over a 1-year period. We feel that this improvement resulted from regular clinical exposure supported by a structured learning programme. The shortening of the specialist training period may affect the acquisition of diagnostic skills by trainees and impact on the confidence with which they commence consultant practice.
Use of the Internet by Patients Undergoing Elective Hernia Repair or Cholecystectomy
Authors: Tamhankar AP , Mazari FAK , Everitt NJ , Ravi K
Published: August 2009

INTRODUCTION

Patient-directed information available on the internet is not always regulated; it may be confusing and sometimes just overwhelming. We aimed to establish the proportion of patients undergoing two common surgical procedures, who searched the internet for information about their operations and to assess the usefulness of the information they received.

PATIENTS AND METHODS

A total of 105 consecutive patients undergoing elective abdominal wall hernia repair (n = 54) or laparoscopic cholecystectomy (n = 51) in a single surgical firm were included in the study. Patients were counselled about their operation in pre-operative assessment clinics and standard trust information leaflets were provided without any mention of this study. Patients were then asked to complete a questionnaire on the morning of their operation.

RESULTS

All patients completed the questionnaire. Of the patients, 59% stated that they had access to the internet and 77% of these accessed the internet over 2 h a week. Of the patients with internet access, 31% used it to acquire additional information about their operations and 58% used internet search engines. Of the patients who searched the internet regarding their operations, 26% were confused and/or worried by the information they received.

CONCLUSIONS

A significant proportion of patients undergoing common surgical procedures used the internet and about one-third of them specifically sought information about their operation on the internet. Such information can cause worry and confusion in patients. Our study highlights the need for regulated, comprehensible, patient information on hospital websites to which patients should be directed.
Urethral Venous Malformation: An Unusual Cause of Recurrent Post-Coital Gross Haematuria in Association with Haematospermia
Authors: Gkougkousis EG , Khan M , Terry TR , Mellon JK
Published: August 2009

Three cases of recurrent post-coital haematuria are described. Extensive protracted investigations pinpointed urethral varicosities as the likely cause. All patients were successfully treated with diathermy fulguration.