Traitement des fractures de l'enfant par enclouage centro-médullaire élastique stable (ECMES) [Treatment of pediatric fractures by intramedullary stable elastic pinning]

During the past decade several new techniques for the treatment of children's fractures respecting the specificity of the growing bone have been described. The goal of all these techniques was to mechanically stabilise the fracture however to preserve a certain instability of the fracture gap itself inducing early callus formation and subsequent consolidation. The dynamic external fixation as well as the elastic stable intramedullary pinning have become accepted means in the treatment of long bone fractures in the paediatric age group. We report our experience of the last seven years with the intramedullary pinning of 105 fractures. Eighty-four were fractures of the femur, 9 of the humerus, 8 of the forearm, and a further 4 of the tibial shaft. The intramedullary elastic pinning represents a simple technique which supports or even enhances the natural process of fracture healing of the growing bone. The method is not very invasive, is cost effective, and allows short hospitalisation. Early physical activity is guaranteed due to early consolidation of the fracture. Complications are rare and the final orthopedic and cosmetic outcome is excellent.

A pseudo-spectral method for the simulation of poro-elastic seismic wave propagation in 2D polar coordinates using domain decomposition

We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in 2D polar coordinates. An important application of this method and its extensions will be the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh, which can be arbitrarily heterogeneous, consisting of two or more concentric rings representing the fluid in the center and the surrounding porous medium. The spatial discretization is based on a Chebyshev expansion in the radial direction and a Fourier expansion in the azimuthal direction and a Runge-Kutta integration scheme for the time evolution. A domain decomposition method is used to match the fluid-solid boundary conditions based on the method of characteristics. This multi-domain approach allows for significant reductions of the number of grid points in the azimuthal direction for the inner grid domain and thus for corresponding increases of the time step and enhancements of computational efficiency. The viability and accuracy of the proposed method has been rigorously tested and verified through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently bench-marked solution for 2D Cartesian coordinates. Finally, the proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is adequately handled.

Government spending and re-election: Quasi-experimental evidence from Brazilian municipalities

Does additional government spending improve the electoral chances of incumbent politicalparties? This paper provides the first quasi-experimental evidence on this question. Our researchdesign exploits discontinuities in federal funding to local governments in Brazil around severalpopulation cutoffs over the period 1982-1985. We show that extra fiscal transfers resulted in a20% increase in local government spending per capita, and an increase of about 10 percentagepoints in the re-election probability of local incumbent parties. In the context of an agency modelof electoral accountability, as well as existing results indicating that the revenue jumps studiedhere had positive impacts on education outcomes and earnings, these results suggest that expectedelectoral rewards encouraged incumbents to spend additional funds in ways that were valued byvoters.

Financing local development: Quasi-experimental evidence from municipalities in Brazil, 1980-1991

This paper uses a regression discontinuity design to estimate the impact of additional unrestrictedgrant financing on local public spending, public service provision, schooling, literacy, andincome at the community (municipio) level in Brazil. Additional transfers increased local publicspending per capita by about 20% with no evidence of crowding out own revenue or otherrevenue sources. The additional local spending increased schooling per capita by about 7% andliteracy rates by about 4 percentage points. The implied marginal cost of schooling -accountingfor corruption and other leakages- amounts to about US$ 126, which turns out to be similar tothe average cost of schooling in Brazil in the early 1980s. In line with the effect on human capital,the poverty rate was reduced by about 4 percentage points, while income per capita gains werepositive but not statistically significant. Results also suggest that additional public spending hadstronger effects on schooling and literacy in less developed parts of Brazil, while poverty reductionwas evenly spread across the country.

A non-quasi-competitive Cournot oligopoly with stability

This paper presents a classical Cournot oligopoly model with some peculiar features: it is non--quasi--competitive as price under N-poly is greater than monopoly price; Cournot equilibrium exists and is unique with each new entry; the successive equilibria after new entries are stable under the adjustment mechanism that assumes that actual output of each seller is adjusted proportionally to the difference between actual output and profit maximizing output. Moreover, the model tends to perfect competition as N goes to infinity, reaching the monopoly price again.

The quasi-judicial role of large retailers: An efficiency hypothesis of their relation with suppliers

The paper explores an efficiency hypothesis regarding the contractual process between large retailers, such as Wal-Mart and Carrefour, and their suppliers. The empirical evidence presented supports the idea that large retailers play a quasi-judicial role, acting as "courts of first instance" in their relationships with suppliers. In this role, large retailers adjust the terms of trade to on-going changes and sanction performance failures, sometimes delaying payments. A potential abuse of their position is limited by the need for re-contracting and preserving their reputations. Suppliers renew their confidence in their retailers on a yearly basis, through writing new contracts. This renovation contradicts the alternative hypothesis that suppliers are expropriated by large retailers as a consequence of specific investments.

When are layoffs acceptable? Evidence from a quasi-experiment

Many authors have discussed a decline in internal labor markets and an apparent shift to a new employment contract, characterized by less commitment between employer and employee and more portable skills. These discussions occur without much evidence on what employment contract employees currently feel is fair. We perfomed quasi-experimental surveys to study when employees in the U.S. andCanada feel that layoffs are fair.Layoffs were perceived as more fair if they were due to lower product demand than if the result of employee suggestions. This result appears to be solely due to norms of reciprocity (companiesshould not punish employees for their efforts), rather than norms of sharing rents, as new technology was also considered a justification for layoffs.Consistent with theories of distributive and procedural equity, layoffs were perceived as more fair if the CEO voluntarily shared the pain. CEO bonuses due to layoffs lowered their reported fairness only slightly.Respondents in Silicon Valley were not more accepting of layoffsthan were those in Canada on average, although the justificationsconsidered valid differed slightly.

Quantitative comparison of simulations of seismic wave propagation in heterogeneous poro-elastic media involving fluid-solid interfaces and in equivalent visco-elastic solids

There is increasing evidence to suggest that the presence of mesoscopic heterogeneities constitutes the predominant attenuation mechanism at seismic frequencies. As a consequence, centimeter-scale perturbations of the subsurface physical properties should be taken into account for seismic modeling whenever detailed and accurate responses of the target structures are desired. This is, however, computationally prohibitive since extremely small grid spacings would be necessary. A convenient way to circumvent this problem is to use an upscaling procedure to replace the heterogeneous porous media by equivalent visco-elastic solids. In this work, we solve Biot's equations of motion to perform numerical simulations of seismic wave propagation through porous media containing mesoscopic heterogeneities. We then use an upscaling procedure to replace the heterogeneous poro-elastic regions by homogeneous equivalent visco-elastic solids and repeat the simulations using visco-elastic equations of motion. We find that, despite the equivalent attenuation behavior of the heterogeneous poro-elastic medium and the equivalent visco-elastic solid, the seismograms may differ due to diverging boundary conditions at fluid-solid interfaces, where there exist additional options for the poro-elastic case. In particular, we observe that the seismograms agree for closed-pore boundary conditions, but differ significantly for open-pore boundary conditions. This is an interesting result, which has potentially important implications for wave-equation-based algorithms in exploration geophysics involving fluid-solid interfaces, such as, for example, wave field decomposition.

Post-detection analysis for grating-based ultra-small angle X-ray scattering.

Until recently, the hard X-ray, phase-sensitive imaging technique called grating interferometry was thought to provide information only in real space. However, by utilizing an alternative approach to data analysis we demonstrated that the angular resolved ultra-small angle X-ray scattering distribution can be retrieved from experimental data. Thus, reciprocal space information is accessible by grating interferometry in addition to real space. Naturally, the quality of the retrieved data strongly depends on the performance of the employed analysis procedure, which involves deconvolution of periodic and noisy data in this context. The aim of this article is to compare several deconvolution algorithms to retrieve the ultra-small angle X-ray scattering distribution in grating interferometry. We quantitatively compare the performance of three deconvolution procedures (i.e., Wiener, iterative Wiener and Lucy-Richardson) in case of realistically modeled, noisy and periodic input data. The simulations showed that the algorithm of Lucy-Richardson is the more reliable and more efficient as a function of the characteristics of the signals in the given context. The availability of a reliable data analysis procedure is essential for future developments in grating interferometry.

Elongation behaviour of elastic stitch types in household sewing machines: stretch-stitches versus serger overlock stitces

Lectio praecursoria

A pseudo-spectral method for simulating of poro-elastic seismic wave propagation in complex borehole environments

We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in cylindrical coordinates. An important application of this method is the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh consisting of three concentric domains representing the borehole fluid in the center, the borehole casing and the surrounding porous formation. The spatial discretization is based on a Chebyshev expansion in the radial direction, Fourier expansions in the other directions, and a Runge-Kutta integration scheme for the time evolution. A domain decomposition method based on the method of characteristics is used to match the boundary conditions at the fluid/porous-solid and porous-solid/porous-solid interfaces. The viability and accuracy of the proposed method has been tested and verified in 2D polar coordinates through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. The proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is handled adequately.