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Few clinical retrospective studies have reported the risk factors of pedicled flap necrosis in hand soft tissue reconstruction. The aim of this study was to identify non-technical risk factors associated with pedicled flap perioperative necrosis in hand soft tissue reconstruction via a multivariate logistic regression analysis.For patients with hand soft tissue reconstruction, we carefully reviewed hospital records and identified 163 patients who met the inclusion criteria. The characteristics of these patients, flap transfer procedures and postoperative complications were recorded. Eleven predictors were identified. The correlations between pedicled flap necrosis and risk factors were analysed using a logistic regression model.Of 163 skin flaps, 125 flaps survived completely without any complications. The pedicled flap necrosis rate in hands was 11.04%, which included partial flap necrosis (7.36%) and total flap necrosis (3.68%). Soft tissue defects in fingers were noted in 68.10% of all cases. The logistic regression analysis indicated that the soft tissue defect site (P = 0.046, odds ratio (OR) = 0.079, confidence interval (CI) (0.006, 0.959)), flap size (P = 0.020, OR = 1.024, CI (1.004, 1.045)) and postoperative wound infection (P0.001, OR = 17.407, CI (3.821, 79.303)) were statistically significant risk factors for pedicled flap necrosis of the hand.Soft tissue defect site, flap size and postoperative wound infection were risk factors associated with pedicled flap necrosis in hand soft tissue defect reconstruction.

Objective: To study the functional changes of median nerve after removing a certain bundle of it and to explore the functional reserve of median nerves. Methods: 220 three-month old SD rats were randomly divided into experimental groups and sham groups. And the experimental group was further divided as 1/8 group, 1/4 group, 1/3 group, 1/2 group, and 2/3 group according to ratio of the resection portion, with 22 rats in each group. The section of the lowest level on median nerve trunks were exposed, and a certain portion of it were separated and resected in experimental group, while in sham groups, the nerve was only separated without resection. The general state of health of all rats were observed, and the α motor neurons in cornu anterior medullae spinalis were studied 1 week, 2 weeks and 2 months postoperatively. Neuro-electrophysiology and function of dominated muscles were studied 2 weeks, 2 months, 3 months, and 4 months postoperatively. Results: All rats survived without infection and obvious ulcer. The number of the α motor neurons in cornuanterior medullae spinalis didn’t change (P>0.05), and obvious superstructure changes were observed in early stage in 1/2 and 2/3 group, but restored after 2 months. There was no significant changes in latencies of motor neuron evoked potentials between experimental groups and sham group (P>0.05), however, there is significant difference if the 2 week group was compared with 2 month, 3 month and 4 month group (P

We show in this paper that N-coupled lasers can be treated as a special case of N weakly coupled nonlinear oscillators. The dynamical behaviour can be described as the evolution on N-dimensional tori. We examine the simplest case of two elements and discuss some characteristics of the coupled laser system, which include the stability of the trivial solution, the stability of the inphase and out-of-phase solutions, and some symmetry considerations.

We have studied the degree to which beamlet step-size impacts the quality of intensity modulated radiation therapy (IMRT) treatment plans. Treatment planning for IMRT begins with the application of a grid that divides each beam's-eye-view of the target into a number of smaller beamlets (pencil beams) of radiation. The total dose is computed as a weighted sum of the dose delivered by the individual beamlets. The width of each beamlet is set to match the width of the corresponding leaf of the multileaf collimator (MLC). The length of each beamlet (beamlet step-size) is parallel to the direction of leaf travel. The beamlet step-size represents the minimum stepping distance of the leaves of the MLC and is typically predetermined by the treatment planning system. This selection imposes an artificial constraint because the leaves of the MLC and the jaws can both move continuously. Removing the constraint can potentially improve the IMRT plan quality. In this study, the optimized results were achieved using an aperture-based inverse planning technique called direct aperture optimization (DAO). We have tested the relationship between pencil beam step-size and plan quality using the American College of Radiology's IMRT test case. For this case, a series of IMRT treatment plans were produced using beamlet step-sizes of 1, 2, 5, and 10 mm. Continuous improvements were seen with each reduction in beamlet step size. The maximum dose to the planning target volume (PTV) was reduced from 134.7% to 121.5% and the mean dose to the organ at risk (OAR) was reduced from 38.5% to 28.2% as the beamlet step-size was reduced from 10 to 1 mm. The smaller pencil beam sizes also led to steeper dose gradients at the junction between the target and the critical structure with gradients of 6.0, 7.6, 8.7, and 9.1 dose%/mm achieved for beamlet step sizes of 10, 5, 2, and 1 mm, respectively.

We show that high power picosecond pulses can be generated from a InGaAsP compressively strained two-section MQW laser diode by setting an optimal amplitude and time delay between the electrical pulses applied to each section of the device.

In this paper we report the results of a numerical study on the operation of double tapered laser diodes. Our device simulation use the generalized travelling wave equations, where the effects of diffraction in lateral direction and carrier-induced refractive index variation are both taken into account. Our study suggests that the double tapered device can deliver a higher optical output power, as compared with standard broad area devices, before the onset of the filamentation.

The operation of various tapered stripe devices have been investigated theoretically by using generalized travelling wave equations, where the effects of diffraction and carrier-induced refractive index variation are taken into account. The partial differential equations are solved by using a modified beam-propagation-method, which is computationally intensive, requiring a large number of longitudinal segments and lateral mesh points. The simulation also involves calculating the carrier density by integrating the carrier diffusion equation at time increments of less than 0.5ps, and obtains the full dynamics of filament formation.

Under a continuum approximation we derive a complex Ginzburg-Landau equation describing either a set of weakly coupled class A lasers, or the fast-time dynamics of a set of weakly coupled class B lasers. We show that phase locked behavior is described by the so-called Stokes wave solution and by performing a linear stability analysis we confirm analytically some numerical observations--namely that the Stokes wave can often be made unstable for perturbations of sufficiently short wavelength and that the coupling phase plays at least as significant a role in determining the spatio-temporal behavior of the system as does the coupling strength. As with our previous work on the simulation of discrete systems a stable phase-locked solution is found to be particularly difficult to achieve as the relative coupling phase approaches (pi) /2. The continuum approach also highlights other scalings, not immediately apparent from the discrete model. The coupling strength, for example, is shown to set the scale of spatial fluctuations.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Two-dimensional optoelectronic device arrays have considerable potential for applications ranging from the production of high power coherent beams (i.e. 2D laser arrays) to processing based on multichannel optical interconnects in neural computation. It is quite clear, however, that modeling such complex systems with various inter-element coupling schemes is not an easy task.

In analyzing practical examples of extended coupled systems such as multistripe semiconductor laser arrays or various types of surface-emitting structures, we have established a simplified model for N nearly-identical coupled elements. A complex coupling constant has been assumed (so that both direct and evanescent coupling is included) as well as a variable coupling strength which ranges from nearest-neighbor only to all-to-all coupling. In our numerical experiments, for N = 100 elements, we have defined the parameter regimes for achieving phase-locking, partial phase-locking and phase-unlocking. These regimes have been established with respect to variations in cavity resonance frequencies, drive currents and coupling strengths. It was found that for a purely real coupling constant, the synchronization is much easier than for purely imaginary coupling.

A simulation has been carried out on N coupled lasers. A complex coupling parameter has been used, thus accounting for the phase of the interacting fields; the phase of the coupling parameter turns out to be a key parameter that determines the dynamics of the system. Nonlocal coupling is considered, in which cooperative effects in the oscillator community are emphasized. It is shown that achieving a phase-locked or synchronized state is crucially dependent on the statistical width of the distribution of cavity resonance frequencies and also on the coupling mechanism.

Under some simplifying assumptions, an inequality is derived which must be satisfied for a pair of index guided coupled waveguide semiconductor lasers to be phase-locked. The physically realistic situation of small technological differences between the devices is included. If this criterion is not met then, in the most severe case, the system operates in a scanning mode whereby the far-field pattern scans with a period of a few hundred picoseconds. If phase locking is only weakly broken a stable far-field pattern results, punctuated by periodic phase jumps of 2 pi . >