Klippel–Trénaunay syndrome (KTS) is a rare congenital disorder defined by a triad of capillary malformation, venous malformation, and soft tissue or bone hypertrophy most commonly affecting ...unilateral lower limbs. Due to the rarity of KTS, evidence‐based guidelines for the management of pregnancy in people with KTS are still lacking. A 34‐year‐old woman (gravidity 1; parity 0) presented at 25 weeks of gestation with malformations of the right side of her body. The extent of the KTS affecting the vulva, pelvis, and right leg was remarkable. As the prenatal MRI showed massive vascular malformations of the pelvis and vulva, we performed an elective cesarean section to avoid severe perinatal hemorrhage during a vaginal delivery. Intraoperatively, we observed varices on the parietal peritoneum within the vesico‐uterine pouch and the isthmocervical transition of the uterus, which were not identifiable in the preoperative MRI. Although KTS patients have been discouraged from pregnancy in the past because of a high risk for complications, successful and uncomplicated pregnancies are possible. For this purpose, we believe a multidisciplinary strategy that is crucial.
To lower the risk for complications in pregnancies for people with excessive KTS, a multidisciplinary strategy including prenatal consultations with radiology, anesthesia, hemostaseology, and pediatrics is crucial.
Pelvic organ prolapse constitutes a prevalent condition associated with a considerable impact on the quality of life. The utilization of transvaginal mesh surgery for managing POP has been a subject ...of extensive debate. Globally, trends in TVM surgery experienced significant shifts subsequent to warnings issued by the FDA.
This study aims to explore temporal patterns in transvaginal mesh surgery in the German healthcare system. A comprehensive analysis was conducted on in-patient data from the German Federal Statistical Office spanning 2006 to 2021. A total of 1,150,811 operations, each associated with specific codes, were incorporated into the study. Linear regression analysis was employed to delineate discernible trends.
The trends in transvaginal mesh surgery within the anterior compartment exhibited relative stability (
= 0.147); however, a significant decline was noted in all other compartments (posterior:
< 0.001, enterocele surgery:
< 0.001). A subtle increasing trend was observed for uterine-preserving transvaginal mesh surgery (
= 0.045).
Surgical trends over the specified timeframe demonstrate how POP management has evolved globally. Notably, despite observed fluctuations, transvaginal mesh surgery remains a viable option, particularly for specific cases with a high risk of relapse and contraindications to alternative surgical approaches.
This paper presents an approach towards a better understanding of spatter formation in laser beam welding. Hereunto, experimental investigations and numerical simulation are carried out. For the ...study, various steels and aluminium alloys were selected to investigate the influences of alloying elements upon spatter formation. The welding was performed by applying a laser beam oscillation technique in which weld seam is generated by a spiral movement of the laser beam, in order to check the influence of weld pool movement according to spatter formation. This strategy was also transferred to the numerical simulation to get a detailed insight into the processes taking place in the keyhole when spatters form. Furthermore, a new detection method is presented which allows a three-dimensional tracking of spatters by using a pair of synchronised stereo cameras.
Over the last few years lightweight construction became increasingly important in modern cars. Motivated by reducing greenhouse gas emission the car industry is currently working on different ...approaches to decrease the weight of structural body parts. In this regard, a reduced sheet thickness of these components and therefore a reduced overall weight can be achieved by using high-strength steels. Hot stamping has been established as a suitable manufacturing process for these steel grades, in which a hot austenitic blank is formed and quenched simultaneously. The high strength of the formed parts is realized by the phase transformation of an austenitic to a martensitic structure during hot stamping. Due to the alternating thermo-mechanical loads, which occur during forming and quenching, the hot stamping tools are highly stressed. In addition, when the blank slides over the surface of its counterpart, a substantial adhesive wear occurs, which is the predominant wear mechanism in hot stamping. The aim of this study is, to increase the wear resistance of the tools by modifying the surface. In this context, the chemical affinity between the interacting components need to be reduced in order to decrease the adhesive wear on the hot stamping tool, which is possible by alloying the base material. For this reason, the wear development is investigated for samples alloyed with different materials with a modified pin-on-disc test. This experimental setup enables a continuous contact of the tool with the blank and thermal alternating stress of the pin. The contact area is investigated with a laser-scanning microscope to qualify the tool surface before and after the experiments by measuring the tool topographies. The results of an unalloyed and alloyed tool will be compared with each other to evaluate the wear behavior. In order to quantify the amount of wear the wear volume will be calculated with an algorithm of the software WinSam. The experiments will be carried out under process like conditions to ensure transferability to the real hot forming process.
Over the last few years, hot stamping has been established as a suitable manufacturing process to produce high-strength structural parts. A tensile strength up to 1500 MPa and a high shape accuracy ...of the hot stamping parts are achievable. The hot forming tools are thereby stressed by varying thermo-mechanical loads resulting in increased surface wear. In order to reduce expensive and time consuming rework of the forming tools, an analysis of the tribological conditions is required. Purpose of this work is to increase the wear resistance of the tool surface and to investigate the wear behavior. In this regard, a laser alloying process is developed to influence the properties of the base material. Firstly, the alloying elements are selected and the element concentration is determined. Results for the composition of NiCrMo90 are presented, which is added by a wire fed laser alloying process unlike the previously used and already researched methods of powder bed fusion. This wire fed method is engineered to ensure a higher material utilization and to simplify the material feeding. After the alloying process the wear behavior of the alloyed surfaces are examined and compared to a not alloyed control group of pins under similar thermo-mechanical conditions.
As weld pool geometry and thermomechanical strains are known to affect formation of solidification cracks, the influence of a superimposed beam oscillation on these characteristics is investigated ...for this paper. In this context the effects of the oscillation frequency and focal diameter on the weld pool and temperature field are determined by means of infrared thermography. As a result an increase of the weld pool size for larger focal diameters and a more even shape of the seam edges for higher frequencies can be identified.
Costs of power consumption, efficiency improvement and a green image are increasing issues for automotive manufacturers. One possibility to reduce energy consumption is to increase process efficiency ...of the established laser beam welding. For this reason this contribution examines whether the laser output power of a direct diode laser can be reduced whilst keeping weld seam volumes constant. This is realized by a reduced spot diameter from initial 664 µm to 368 µm in combination with beam oscillation in order to generate blind seams in 22MnB5 and DC01 steel. It is shown that energy consumption can be reduced significantly.
Laser Beam Welding of Brass Hugger, Florian; Hofmann, Konstantin; Stein, Stefan ...
Physics procedia,
2014, 2014-00-00, Letnik:
56
Journal Article
Odprti dostop
Up to date the evaporation process in laser beam welding of alloys with volatile elements is not completely understood. This paper discusses the phenomena occurring at the welding process of brass ...with 37m% zinc. Since copper has a solidification temperature of 1,087°C and zinc vaporizes at a temperature of 907°C, a strong evaporation takes place and anelongation of the keyhole can be observed. Depending upon welding velocity, the ratio of keyhole length to width is between one and six. Furthermore it is observed that a defect free weld seam is formed. Since the melt pool does not leak also for high ratios of keyhole length to width, the conventional keyhole model with a dynamic flow around the laser beam has to be adapted to a model in which the melt flow at the side of the capillary is stabilized also outside of the interaction zone of the laser beam with the melt due to strong evaporation at the flank of the keyhole.
Investigations concerning the growth of intermetallic phases during the heat input both at the diffusion annealing of copper aluminum roll claddings and the subsequent welding process of ...copper-aluminum connections by using roll cladded inserts are compared to the analytical determination of phase growth. The temperature distribution in the cladding interface has been determined by thermal simulation, in order to calculate the growth of the intermetallic phases. A comparison between the width of the phases in the analytical calculation and the experiment is achieved. In consideration of high welding speeds, the energy input during the welding process is appraised in order to grade the growth of intermetallic phases. Furthermore the prevention of damage in the roll cladding interface by means of unadapted material thicknesses or welding parameters can be assessed analytically and numerically. The numerical simulations can determine the critical thickness of the roll cladding to avoid damage like exceeding growth of intermetallic phases.
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