Dynamics of generalized PT-symmetric dimers with time-periodic gain–loss

A parity-time (PT)-symmetric system with periodically varying-in-time gain and loss modeled by two coupled Schrödinger equations (dimer) is studied. It is shown that the problem can be reduced to a perturbed pendulum-like equation. This is done by finding two constants of motion. Firstly, a generalized problem using Melnikov-type analysis and topological degree arguments is studied for showing the existence of periodic (libration), shift- periodic (rotation), and chaotic solutions. Then these general results are applied to the PT-symmetric dimer. It is interestingly shown that if a sufficient condition is satisfied, then rotation modes, which do not exist in the dimer with constant gain–loss, will persist. An approximate threshold for PT-broken phase corresponding to the disappearance of bounded solutions is also presented. Numerical study is presented accompanying the analytical results

4e congrès sur les lambeaux perforants CHU-Amiens Picardie. 2e Workshop d’échographie pour chirurgien plasticien

International audienc

Bases anatomiques du tégument facial appliquées à la chirurgie du rajeunissement facial

International audienceThe understanding of the face anatomy is mandatory before to be able to appreciate the different surgical techniques of face lifting. Despite numerous controversies and anatomical variations, we can find in the literature several keystone works that allows us to understand that the soft tissues of the face are not only a superposition of layers but also a tridimensionnal structure with a fibrous system that links the different layers. This structures creates a mix loose spaces, fat and retaining ligament that can be describe in a quite systematic manner. This systematisation can help the surgeon during the surgical procedure to search and find the area where there is no danger and alert him around the retaining for example, which is where we can often find a vessel or a branch of the facial nerve that we want to avoid. This article summarizes these anatomical knowledge

Approximate shortest descent path on a terrain

A path from a point s to a point t on the surface of a polyhedral terrain is said to be descent if for every pair of points p = (x(p), y(p), z(p)) and q = (x(q), y(q), z(q)) on the path, if dist(s,p) z(q), where dist(s,p) denotes the distance of p from s along the aforesaid path. Although an efficient algorithm to decide if there is a descending path between two points is known for more than a decade, no efficient algorithm is yet known to find a shortest descending path from s to t in a polyhedral terrain. In this paper we propose an (1 + ε-approximation algorithm running in polynomial time for the same

Superficial Circumflex Iliac Artery Perforator flap (SCIP flap): Revival of the inguinal donor site?

International audienceThe SCIP flap based on a superficial circumflex iliac perforator artery (SCIA) was described for the first time by Koshima in 2004 as a large and thin groin flap, with a low morbidity. The purpose of this study is to demonstrate the benefits of SCIP flap to cover cutaneous defects. We present a retrospective study from January 2007 to August 2016. Twelve patients had a SCIP flap reconstruction in the plastic surgery department of Amiens hospital. Thirteen flaps were performed. The average preoperative doppler mapping time was 8minutes. The average size of flaps was 62.5cm2[21; 180cm2]. The average time required for raising flaps was 61min [52; 82min]. It has not been observed any complication of the flap or donor site. The SCIP flap has a thin paddle and the donor site morbidity is minimal. The surgical technique is safe, accessible and precision is increased by preoperative color doppler mapping. The many strengths of the SCIP flap make it a must in the algorithm for defects management and come to revitalize the inguinal donor site

Le portfolio de l’interne de chirurgie plastique : un outil d’aide à la formation des internes de chirurgie plastique en France ?

International audienceA recent reform of the French government has shortened the plastic surgery residency from 5 to 4 years. Until today, the evaluation and validation of the residency was shared between the local coordinator for practical skills and, after the residency, by the French College of Plastic Surgery for theorical knowledges. The new reform suggests to add a portfolio that will follow the resident during his surgical training. Based on the French reform and syllabus of others medical specialities, we designed a surgical portfolio that will help the resident both with his practical progression and his knowledges acquisition. The aim of the portfolio is to get a national unity of the plastic surgery training. As a first step we will describe the actual plastic surgery residency. Then, we will detail what the reform is going to change. At last, we will introduce the surgical portfolio, its content, its use and its goals.La réforme du troisième cycle des études médicales a modifié le modèle d’apprentissage des internes de chirurgie plastique, en lui amputant une année de formation. La réforme précise qu’un portfolio devra suivre l’interne au cours de sa formation. Jusqu’à présent la formation pratique des internes de chirurgie plastique était exclusivement dévolue au coordonnateur local de la spécialité et aucun contrôle officiel des connaissances n’avait lieu avant l’examen national du DESC. Prenant en compte ces faits nous avons imaginé le portfolio de l’interne de chirurgie plastique qui permettrait de guider l’interne dans sa progression pratique et dans l’acquisition de ses connaissances théoriques. Il permettrait aussi d’homogénéiser la formation nationale de la spécialité et pourrait, à terme, servir de support à une évaluation formelle des compétences pratiques des internes de chirurgie plastique. Dans un premier temps nous faisons un état des lieux de la formation avant l’apparition de la réforme. Puis nous détaillons les changements qui seront apportés par la réforme. Enfin nous décrivons le portfolio en détail, son contenu, son utilisation et son intérêt

Euclidean spanners: short, thin, and lanky

Euclidean spanners are important data structures in geometric algorithm design, because they provide a means of approximating the complete Euclidean graph with only O(n) edges, so that the shortest path length between each pair of points is not more than a constant factor longer than the Euclidean distance between the points. In many applications of spanners, it is important that the spanner possess a number of additional properties: low tot al edge weight, bounded degree, and low diameter. Existing research on spanners has considered one property or the other. We show that it is possible to build spanners in optimal O(n log n) time and O(n) space that achieve optimal or near optimal tradeoffs between all combinations of thes

Dorsal median lipectomy (the arrow technique): A new approach for the treatment of the circumferential truncal skin and fatty tissue excess

International audienceThe increase in the number of patients who undergo massive weight loss surgery has led to an increasing number of patients who complain of circumferential abdominal skin and soft tissue excess. Currently, the only surgical option to treat soft tissue excess is vertical median abdominal lipectomy (fleur-de-lys technique). However, many patients are reluctant to undergo this surgery because of the position of the scar. We presented a new surgical approach to manage circumferential excess -~dorsal median lipectomy (arrow technique)~- in which the dorsal scar is well-tolerated by patients

Technique de prélèvement d’un lambeau perforant thoracodorsal : mise au point

International audienceLe lambeau perforant thoracodorsal (TDAP) est une méthode de reconstruction fiable dont les indications n’ont cessé d’augmenter ces dernières années. Plusieurs variantes chirurgicales existent et différentes techniques de prélèvement ont été décrites. Cependant, face à une dissection parfois complexe et chronophage du pédicule, l’utilisation fréquente de cette méthode de couverture nous a amené à adapter la technique de prélèvement de ce lambeau. L’objectif de cette étude descriptive est d’établir une mise au point quant à la méthode de dissection du pédicule du lambeau perforant thoracodorsal. La préservation du réseau nerveux et la préservation d’une collerette musculaire sur un diamètre de deux centimètres à l’entrée du pédicule dans le muscle en sont les points clefs.The thoracodorsal artery perforator (TDAP) flap is a reliable method of reconstruction by which the indications were on a constant rise during the last few years. Several surgical variants exist and different harvesting techniques were described. However, with our experience using this flap for substance-loss coverage, we frequently faced a complex and relatively time-consuming pedicle dissection. This brought us to adapt our harvesting technique according to the anatomical situations of the neighboring structures. The purpose of this study is to revisit and adapt the method of the pedicle dissection for the TDAP flap. The conservation of both the nervous network and a section of a circumferential muscular collar with a diameter of two centimeters are the main keys of our study

Change of paradigm in thoracic radionecrosis management

International audienceClassically, muscular or omental flaps are the gold standard in the management of thoracic defects following radionecrosis debridement. Their vascular supply and antibacterial property was supposed to enhance healing compared with cutaneous flaps. The evolution of reconstructive surgery allowed us to challenge this dogma. Therefore, we present five consecutive cases of thoracic radionecrosis reconstructed with cutaneous perforator flaps. In four patients, we performed a free deep inferior epigastric perforator (DIEP) flap and one patient had a thoracodorsal perforator (TDAP) flap. Median time healing was 22.6 days with satisfactory cutaneous covering and good aesthetic results. There were no flap necrosis, no donor site complications. We believe that perforator flaps are a new alternative, reliable and elegant option that questions the dogma of muscular flaps in the management of thoracic radionecrosis