Radiological Evaluation of Postsurgical Course of Perforators in Retrograde Posterior Tibial Fasciocutaneous Flaps for Distal Leg and Foot Defects

Background Mapping of vascular perforators by various methodologies have been described for planning of a variety of flaps in the lower limbs. We attempted to assess the changes in posterior tibial perforators after transfer of fasciocutaneous flaps for leg defects. Methods 20 patients with distal leg and foot defects were studied by computed tomography angiography (CTA) and preoperative audio Doppler to ascertain perforators of posterior tibial artery. Fasciocutaneous flaps were raised, based on these perforators, depending on the site and size of soft-tissue defects. The number of perforators and their distance from the medial malleolus were also studied. Postoperative CTA was performed on the 7th to 10th day, with emphasis on postoperative changes of the perforators on which the flaps were based. Results One to four posterior tibial perforators were found between 5 cm and 8 cm proximal to the medial malleolus. After flap transfer, the perforators could be traced to variable distance through the total length of the flap. The perforators formed small vascular loop in 12 patients, following retrograde posterior tibial flap transfer. The height of the loop, the number of such loops, the dilatation and tortuosity of the perforators, and their longitudinal orientation were studied in detail. Most of the findings can be explained by mechanical realignment of perforators as well as by the delay phenomenon associated with retrograde fasciocutaneous flaps. Conclusion It was concluded that the morphological changes associated with the perforators explained the vascular rationality and success of these flaps.

Uncovering the impact of delay phenomenon on random walks in a family of weighted m-triangulation networks

Uncovering the impact of special phenomena on dynamical processes in more distinct weighted network models is still needed. In this paper, we investigate the impact of delay phenomenon on random walk by introducing delayed random walk into a family of weighted m-triangulation networks. Specifically, we introduce delayed random walk into the networks. Then one and three traps are deployed, respectively, on the networks in two rounds of investigation. In both rounds of investigation, average trapping time (ATT) is applied to measure trapping efficiency and derived analytically by harnessing iteration rule of the networks. The analytical solutions of ATT obtained in both investigations show that ATT increases sub-linearity with the size of the network no matter what value the parameter [Formula: see text] manipulating delayed random walk takes. But [Formula: see text] can quantitatively change both its leading scaling and prefactor. So, introduction of delay phenomenon can control trapping efficiency quantitatively. Besides, parameters [Formula: see text] and [Formula: see text] governing networks’ evolution quantitatively impact both the prefactor and leading scaling of ATT simultaneously. In summary, this work may provide incremental insight into understanding the impact of observed phenomena on special trapping process and general random walks in complex systems.

Delayed Spiking Neural P Systems with Scheduled Rules

Due to the inevitable delay phenomenon in the process of signal conversion and transmission, time delay is bound to occur between neurons. Therefore, it is necessary to introduce the concept of time delay into the membrane computing models. Spiking neural P systems (SN P systems), as an attractive type of neural-like P systems in membrane computing, are widely followed. Inspired by the phenomenon of time delay, in our work, a new variant of spiking neural P systems called delayed spiking neural P systems (DSN P systems) is proposed. Compared with normal spiking neural P systems, the proposed systems achieve time control by setting the schedule on spiking rules and forgetting rules, and the schedule is also used to realize the system delay. A schedule indicates the time difference between receiving and outputting spikes, and it also makes the system work in a certain time, which means that a rule can only be used within a specified time range. We specify that each rule is performed only in the continuous schedule, during which the neuron is locked and cannot send or receive spikes. If the neuron is not available at a given time, it will not receive or send spikes due to the lack of a schedule for this period of time. Moreover, the universality of DSN P systems in both generating and accepting modes is proved. And a universal DSN P system having 81 neurons for computing functions is also proved.

Limb Salvage Procedure in a Patient of High-tension Electric Burns Utilising Delay Phenomenon in Perforator-based Flap- A Case Report

Electric burn is a devastating injury causing tissue and organ loss. We present here a case of an electric burn injury over a bilateral lower limb and bilateral upper limb. The patient had undergone left above-knee amputation, thus cross-leg flap from the left side was not possible and due to electric burns, the vascularity of the right leg was also doubtful therefore a delayed flap was planned to cover the exposed defect over the right knee and defect over the right tibia. The Flaps underwent a delay procedure before the final inset so that the flap undergo ischemic preconditioning and the neovascularization that increases the size of the flap and chances of survival of the flap by manifold.

On the radio frequency dependence of the pulse delay phenomenon in PSR B0943+10

We report the result of measurements of a gradual shift of the integrated pulses towards later spin phase of the anomalous pulsar B0943+10 at the high radio frequencies. We have used observations from the Arecibo Observatory and the GMRT at 327 and 325 MHz correspondingly. For the measurements we have proposed a special method for calculating the correct positions of the partially merged two components of the pulse profile shape with significant temporal changes in their amplitude ratio. The exponential change in the pulse phase with an amplitude of 4 ms and characteristic time of about 1 hour has been found. Comparison of our measurements at 325 and 327 MHz with those at the lower frequencies of 25–80, 62 and 112 MHz have shown that the character of the process does not depend on frequency across a wide frequency range. The result is very important for constraining the nature of the delay. It supports the assumption that the process results from changes in the vacuum gap near the surface of the pulsar. The further correlation between changes in the pulse phase and its intensity is discussed.

Analysis of rotor aerodynamic response during ramp collective pitch increase by CFD method

In order to study the aerodynamic response characteristics of the helicopter rotor during ramp collective pitch increase, the moving-embedded grid technique is employed for numerical simulation. The governing equations are modeled via Navier-Stokes equations, as well as one equation S-A turbulence model. In order to improve the precision of unsteady simulation of the rotor flowfield, the three-order scheme known as Roe-WENO scheme is employed for the spatial discretization of convective fluxes, and the implicit LU-SGS scheme is adopted for the temporal discretization. The flowfield and aerodynamic characteristics of the SA349/2 Gazelle helicopter rotor are computed for verification, and thereafter, the present method is used to simulate the transient aerodynamic response of the rotor under different collective pitch increment rates. The unsteady flowfield and aerodynamic characteristics of the rotor under ramp collective pitch increase are obtained and compared with the experimental data. The results show that the numerical method not only can accurately predict the unsteady aerodynamic loads of the rotor in steady state, but also is capable of effectively simulating the transient aerodynamic response of the rotor, characterized by overshoot and delay phenomenon, during ramp collective pitch increase. Finally, the opposite ramp decrease in collective pitch and the influence of pre-twist on aerodynamic response are analyzed. The result shows that the transient aerodynamic response of the rotor under ramp collective pitch increase and decrease present a certain of symmetry. The change in pre-twist of blades only affects the thrust coefficient in steady state, while have little influence on the transient maneuvering process of collective pitch.

Experimental Study on Aerodynamic Characteristics of a Gurney Flap on a Wind Turbine Airfoil under High Turbulent Flow Condition

The objective of the current work is to experimentally investigate the effect of turbulent flow on an airfoil with a Gurney flap. The wind tunnel experiments were performed for the DTU-LN221 airfoil under different turbulence level (T.I. of 0.2%, 10.5% and 19.0%) and various flap configurations. The height of the Gurney flaps varies from 1% to 2% of the chord length; the thickness of the Gurney flaps varies from 0.25% to 0.75% of the chord length. The Gurney flap was vertical fixed on the pressure side of the airfoil at nearly 100% measured from the leading edge. By replacing the turbulence grille in the wind tunnel, measured data indicated a stall delay phenomenon while increasing the inflow turbulence level. By further changing the height and the thickness of the Gurney flap, it was found that the height of the Gurney flap is a very important parameter whereas the thickness parameter has little influence. Besides, velocity in the near wake zone was measured by hot-wire anemometry, showing the mechanisms of lift enhancement. The results demonstrate that under low turbulent inflow condition, the maximum lift coefficient of the airfoil with flaps increased by 8.47% to 13.50% (i.e., thickness of 0.75%), and the Gurney flap became less effective after stall angle. The Gurney flap with different heights increased the lift-to-drag ratio from 2.74% to 14.35% under 10.5% of turbulence intensity (i.e., thickness of 0.75%). However, under much a larger turbulence environment (19.0%), the benefit to the aerodynamic performance was negligible.

Hydrate Formation in Water-in-Oil Emulsions in the Presence of Resins

Gas hydrate is one of the main concerns in the flow assurance issues for under water multiphase pipelines. Hydrate nucleation and growth in the water-in-oil emulsions have not been completely understood due to the complex factors, such as the composition of crude oils. Resins, as a common component in crude oil, can pose great effects on hydrate formation, which is still lack of investigation. This paper aims to bridge this gap with a custom-designed high pressure autoclave. Different with other hydrate investigation apparatus, an online viscometer was equipped for the real time viscosity measurement. Resins were separated from the Venezuelan residue for the purpose, following the saturates, aromatics, resins, and asphaltenes fractionation method. A series of experiments of hydrate formation were carried out in the emulsions with the presence of different resin contents, under the condition of 2.7 °C, 2.6 MPa, and 40 vol. % water cut. It was observed that resins hindered hydrate formation in water-in-oil emulsions. The induction time increased with the increasing of resin content. The induction time in the emulsion with the presence of 1.0 wt. % resin content was almost 200 min longer than that in the emulsion without resins. It was found that an increase in resin concentration led to the significant reduction in temperature peak. In addition, a time delay phenomenon of temperature and pressure in the growth onset was found in the system with 0.5 or 1.0 wt. % resin content, by virtue of the online viscometer. It demonstrated the impeding effect of resins on hydrate growth. Moreover, the microphotographs of water-in-oil emulsions were obtained. It was observed that the resins can be adsorbed on the water droplet surface, and hence occupied the hydrate nucleation sites and formed a barrier for the further penetration of gas molecules. The adsorption phenomenon can preliminarily account for the inhibiting effect of resins on hydrate formation. It provides a scientific understanding for the effect of resins on hydrate formation in water-in-oil emulsions, excluding the interference of wax and other components. It would be useful to an appropriate flow assurance strategy designing for the under-water multiphase pipelines.