579 research outputs found

    Translating solitons over Cartan-Hadamard manifolds

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    We prove existence results for entire graphical translators of the mean curvature flow (the so-called bowl solitons) on Cartan-Hadamard manifolds. We show that the asymptotic behaviour of entire solitons depends heavily on the curvature of the manifold, and that there exist also bounded solutions if the curvature goes to minus infinity fast enough. Moreover, it is even possible to solve the asymptotic Dirichlet problem under certain conditions.Comment: This replaces the first version. We have deleted the whole Section 3 from the previous version due to a gap in a proof. We are grateful to Dr. Hengyu Zhou for pointing out the gap in the proof of Lemma 3.3 in the previous versio

    Non-parametric mean curvature flow with prescribed contact angle in Riemannian products

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    Assuming that there exists a translating soliton u(infinity) with speed C in a domain Omega and with prescribed contact angle on partial derivative Omega, we prove that a graphical solution to the mean curvature flow with the same prescribed contact angle converges to u(infinity) + Ct as t -> infinity. We also generalize the recent existence result of Gao, Ma, Wang and Weng to non-Euclidean settings under suitable bounds on convexity of Omega and Ricci curvature in Omega.Peer reviewe

    On the stability of two-chunk file-sharing systems

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    We consider five different peer-to-peer file sharing systems with two chunks, with the aim of finding chunk selection algorithms that have provably stable performance with any input rate and assuming non-altruistic peers who leave the system immediately after downloading the second chunk. We show that many algorithms that first looked promising lead to unstable or oscillating behavior. However, we end up with a system with desirable properties. Most of our rigorous results concern the corresponding deterministic large system limits, but in two simplest cases we provide proofs for the stochastic systems also.Comment: 19 pages, 7 figure

    Incremental Condition Estimation

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    Enzymatic assay for urine lactose in the assessment of recent intravenous abuse of buprenorphine

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    Urine samples were analyzed for lactose to investigate if elevated lactose concentrations indicate recent (<48 hours) intravenous abuse of substances containing lactose as an excipient. Elevated lactose levels were found in samples given by patients who had recently injected substances intravenously, verified by fresh injection marks. Urine lactose assay can support clinical and toxicological findings when assessing substance abuse.Peer reviewe

    Learning curve in robotic-assisted lobectomy for non-small cell lung cancer is not steep after experience in video-assisted lobectomy; single-surgeon experience using cumulative sum analysis

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    Publisher Copyright: © 2021Background: Robotic assistance in lung lobectomy has been suggested to enhance the adoption of minimally invasive techniques among surgeons. However, little is known of learning curves in different minimally invasive techniques. We studied learning curves in robotic-assisted versus video- assisted lobectomies for lung cancer. Methods: A single surgeon performed his first 75 video-assisted thoracic surgery (VATS) lobectomies from April 2007 to November 2012, and his 75 first robotic-assisted thoracic surgery (RATS) lobectomies between August 2011 and May 2018. A retrospective chart review was done. Cumulative sum (CUSUM) analysis was used to identify the learning curve. Results: No operative deaths occurred for VATS patients or RATS patients. Conversion-to-open rate was significantly lower in the RATS group (2.7% vs. 13.3%, p = 0.016). Meanwhile, 90-day mortality (1.3% vs. 5.3%, p = 0.172), postoperative complications (24% vs. 24%, p = 0.999), re- operation rates (4% vs. 5.3%, p = 0.688), operation time (170±56 min vs. 178±66 min, p = 0.663) and length of stay (8.9 ± 7.9 days vs. 8.2 ± 5.8 days, p = 0.844) were similar between the two groups. Based on CUSUM analysis, learning curves were similar for both procedures, although slightly shorter for RATS (proficiency obtained with 53 VATS cases vs. 45 RATS cases, p = 0.198). Conclusions: Robotic-assisted thoracoscopic lung lobectomy can be implemented safely and efficiently in an expert center with earlier experience in VATS lobectomies. However, there seems to be a learning curve of its own despite the surgeon's previous experience in conventional thoracoscopic surgery.Peer reviewe

    The Clinical Presentation of Puumala Hantavirus Induced Hemorrhagic Fever with Renal Syndrome Is Related to Plasma Glucose Concentration

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    Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome characterized by thrombocytopenia, increased capillary leakage, and acute kidney injury (AKI). As glucosuria at hospital admission predicts the severity of PUUV infection, we explored how plasma glucose concentration associates with disease severity. Plasma glucose values were measured during hospital care in 185 patients with PUUV infection. They were divided into two groups according to maximum plasma glucose concentration: P-Gluc < 7.8 mmol/L (n = 134) and P-Gluc ≥ 7.8 mmol/L (n = 51). The determinants of disease severity were analyzed across groups. Patients with P-Gluc ≥7.8 mmol/L had higher hematocrit (0.46 vs. 0.43; p < 0.001) and lower plasma albumin concentration (24 vs. 29 g/L; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. They presented with higher prevalence of pulmonary infiltrations and pleural effusion in chest radiograph, higher prevalence of shock and greater weight change during hospitalization. Patients with P-Gluc ≥ 7.8 mmol/L were characterized by lower platelet count (50 vs. 66 × 109/L; p = 0.001), more severe AKI (plasma creatinine 272 vs. 151 µmol/L; p = 0.001), and longer hospital treatment (8 vs. 6 days; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. Plasma glucose level is associated with the severity of capillary leakage, thrombocytopenia, inflammation, and AKI in patients with acute PUUV infection

    Multifractal products of stochastic processes: Construction and some basic properties

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    Abstract In various fields, such as teletraffic and economics, measured time series have been reported to adhere to multifractal scaling. Classical cascading measures possess multifractal scaling, but their increments form a non-stationary process. To overcome this problem we introduce a construction of random multifractal measures based on iterative multiplication of stationary stochastic processes, a special form of T-martingales. We study L 2 -convergence, non-degeneracy and continuity of the limit process. Establishing a power law for its moments we obtain a formula for the multifractal spectrum and hint at how to prove the full formalism
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