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Reducing hot cracking is essential for ensuring seamless production of nickel superalloys, which are extensively used in welded structures for aircraft engines. The prevalence of hot cracking in precipitation-strengthened alloy 718 is primarily governed by two factors: firstly, the chemical composition and the coarse microstructure formed during solidification, and secondly, the activation of hot cracking mechanisms, which is particularly critical in mushroom-shaped welding morphologies. In this study, different nickel-based superalloys welded using laser beam welding (LBW), more specifically bead on plate welding (BoP), specimens are compared. The cracking susceptibility of both wrought and two investment casting 718 alloys with tailored chemical compositions is examined through the application of both continuous and pulsed LBW. Additionally, various pre-weld treatments, including with and without Pre-HIP (hot isostatic pressing), are analyzed. The influences of chemical composition, LBW parameters and pre- and post-welding treatments on both internal and external cracks determined by conventional and advanced non-destructive tests are studied. A clear reduction of hot cracking susceptibility and overall welding quality improvement was observed in a tailored 718 alloy with relatively high Ni (55.6% wt) and Co (1.11% wt) contents. [ABSTRACT FROM AUTHOR]

Sand is a highly dissipative system, where the local spatial arrangements and densities depend strongly on the applied forces, resulting in fluid-like or solid-like behaviour. This makes sand swimming challenging and intriguing, raising questions about the nature of the motion and how to optimize the design of artificial swimmers able to swim in sand. Recent experiments suggest that lateral undulatory motion enables efficient locomotion, with a non-monotonic dependence of the swimming speed on the undulatory frequency and the height of the sediment bed. Here, we propose a 2D granular model, where the effect of the sediment height is modeled by an effective frictional force with the substrate. We show that the optimal frequency coincides with the second vibrational mode of the swimmer and explain the underlying mechanism through a characterization of the rheology of the medium. Potential implications in the design of artificial swimmers are discussed.

The local navigation of pedestrians is assumed to involve no anticipation beyond the most imminent collisions, in most models. These typically fail to reproduce some key features experimentally evidenced in dense crowds crossed by an intruder, namely, transverse displacements toward regions of higher density due to the anticipation of the intruder's crossing. We introduce a minimal model based on mean-field games, emulating agents planning out a global strategy that minimizes their overall discomfort. By solving the problem in the permanent regime thanks to an elegant analogy with the nonlinear Schrödinger's equation, we are able to identify the two main variables governing the model's behavior and to exhaustively investigate its phase diagram. We find that, compared to some prominent microscopic approaches, the model is remarkably successful in replicating the experimental observations associated with the intruder experiment. In addition, the model can capture other daily-life situations such as partial metro boarding.

We present experimental results of pedestrian evacuations through a narrow door under a prescribed safety distancing of either 1.5 or 2 meters. In this situation, flow rate augments with pedestrian velocity due to a complete absence of flow interruptions or clogs. Accordingly, the evacuation improves when the prescribed physical distance is reduced, as this implies shortening the time lapses between the exit of consecutive pedestrians. In addition, the analysis of pedestrian trajectories reveals that the distance to the first neighbor in the evacuation process is rather similar to the one obtained when pedestrians were just roaming within the arena, hence suggesting that this magnitude depends more on the crowd state (desired speed, prescribed safety distance, etc.) than on the geometry where the pedestrian flow takes place. Also, an important difference in pedestrian behavior is observed when people are asked to walk at different speeds: whereas slow pedestrians evidence a clear preference for stop-and-go motion, fast walkers display detouring and stop-and-go behavior roughly in the same proportion.

The emergence of coherent vortices has been observed in a wide variety of many-body systems such as animal flocks, bacteria, colloids, vibrated granular materials or human crowds. Here, we experimentally demonstrate that pedestrians roaming within an enclosure also form vortex-like patterns which, intriguingly, only rotate counterclockwise. By implementing simple numerical simulations, we evidence that the development of swirls in many-particle systems can be described as a phase transition in which both the density of agents and their dissipative interactions with the boundaries play a determinant role. Also, for the specific case of pedestrians, we show that the preference of right-handed people (the majority in our experiments) to turn leftwards when facing a wall is the symmetry breaking mechanism needed to trigger the global counterclockwise rotation observed., (© 2022. The Author(s).)

Background: Neurocysticercosis is the most frequent parasitic disease of the central nervous system and the first cause of acquired epilepsy in endemic areas. Our aim in is to use clinical and radiological criteria to orientate diagnosis where there is suspicion of neurocysticercosis, presenting a clinical case as an example., Materials and Methods: We present the case of a 43 year old woman of Bolivian origin, who came to accidents and emergencies after suffering a generalized convulsive crisis, witnessed by relatives of the patient., Results: A cranial computerized axial tomography was taken, which together with her clinical history led to suspicion of neurocysticercosis. She was admitted to the neurosurgery department for completion of the study, which confirmed the diagnosis of suspicion. She received treatment with albendazol and corticoids, with a good evolution., Conclusions: Neurocysticercosis is an emergent pathology in developed countries, due to the increase of immigration from endemic areas, mainly from Latin America. Epilepsy is the most frequent clinical expression, but presentation can vary greatly. A high degree of suspicion is necessary in order to be able to diagnose this disease.

Offences involving sexual assault are an issue of the greatest current interest in different social fields (legal, medical, police, criminological...). They are significant due to their frequency and to the legal, physical and psychological repercussions involved. It is therefore important to clearly understand the pattern of action in Accidents and Emergencies facing such cases. Great detail is required in the gynaecological report and the taking of samples, prophylaxes for sexually transmitted diseases and unwanted pregnancies must be given and psychological support provided.

Objective: to determine the incidence of hypertransaminasemia in adult patients with celiac disease with or without relevant chronic liver disease, and to evaluate the response after a gluten-free diet., Patients and Methods: retrospective study of 20 cases of adult celiac disease (> 14 years old at diagnosis). Patients were included in the study if they fulfilled the revised EPSGAN criteria. If laboratory tests of liver function revealed alterations, hepatitis B and C viral serology, thyroid hormones, and use of alcohol and drugs were investigated, and liver ultrasound scans were done. Liver biopsy and endoscopic retrograde cholangiopancreatography were done only in patients for whom these studies were considered necessary., Results: ten patients had hypertransaminasemia (50%), ascribed to benzodiazepine use in 1 patient, chronic HCV hepatitis in 1, and celiac disease in 8. In all of these last patients except 1 (benzodiazepine use), laboratory values returned to normal after 4-10 months on a gluten-free diet., Conclusions: celiac disease was frequently associated with hypertransaminasemia. In most patients transaminase levels returned to normal within 1 year after dietary gluten intake was restricted. If alterations in laboratory values persist, other causes that may be related (e.g., autoimmunity or tumors) or unrelated to celiac disease (e.g., virus) must be ruled out.

Objective: To test the validity of Ottawa ankle rules (OAR) in our field. To test the agreement physician/nurse in the assessment of the patient with acute ankle injuries., Design: Observational, with application of rules and prospective outcome measurement., Setting: Hospital emergency departments., Participants: Adults who attended at the emergency department, suffering from a secondary ankle pain to a traumatic injury, from 1st March to 30th September, 1997., Measurements and Main Results: Physicians who participated applied the OAR to the patients and asked for a control radiograph, independently from the result of rules application. 100 patients were valued by a physician and a nurse in order to measure the agreement level. Data from 564 patients were recorded, getting a global sensitivity of the OAR of 97.3% (95% CI 89.7-99.5); specificity of 33.3% (95% CI 29.5-37.3). The positive predictive value was of 15.6 (95% CI 12.4-19.3). Thanks to the application of the rules radiography would reduce by 29.5%. 74 (13.1%) patients suffered form fracture: 48 (8.5%), of the maleolar zone and 26 (4.6%) of the midfoot zone. Attending to the OAR criteria, radiographs wouldn't be necessary in two cases of fracture., Conclusions: We consider the OAR clinically valuable and useful in our field. They can help to work on the basis of uniform criteria when decisions must be taken and to use properly sanitary resources. Triage nurses can apply them.

Background: Several options are available for treating patients with a first episode of primary spontaneous pneumothorax (ISP). The aim of this study was to compare the efficacy of two treatment alternatives: puncture-aspiration (PA) using a small caliber catheter, and pleural drainage through a chest tube (DCT)., Patients and Methods: We compared a current series of 91 patients treated with PA with a retrospective series of 216 patients treated with DCT. PA was performed by emergency room physicians and DCT was performed by chest surgeons. Patients were followed for a period of 24 months., Results: The immediate efficacy of PA was superior to DCT (86.7% versus 76%, p < 0.05). The proportion of recurrences after each treatment was similar (23% and 17%, respectively, NS). Duration of hospital stay was shorter for PA-treated patients (24 h) than for DCT-treated patients (138 h) (p < 0.05). The efficacy of the two procedures 24 months later was similar (63.7% and 62.9%, respectively, NS), and the cost of PA was three times less than that of DCT., Conclusions: PA is as effective a treatment procedure as DCT. PA is simple enough for emergency room physicians to perform correctly. Inconvenience to the patient, cost to the health care system, and time of hospital stay are all significantly less with PA.

The case of a 60-year-old patient who was repeatedly admitted for ascitic decompensation secondary to hyperflow portal hypertension provoked by congenital arteriovenous malformation of the superior mesenteric artery is presented. Diagnosis was performed by arteriography. Surgical treatment was conducted with total resection of the malformation thereby achieving complete resolution and normalization of portal pressure. The literature is reviewed and the pathophysiologic mechanism as well as the clinical manifestations, diagnosis and treatment are discussed.