222 research outputs found

    Towards Weyl fermions on the lattice without artefacts

    Full text link
    In spite of the breakthrough in non-perturbative chiral gauge theories during the last decade, the present formulation has stubborn artefacts. Independently of the fermion representation one is confronted with unwanted CP violation and infinitely many undetermined weight factors. Renormalization group identifies the culprit. We demonstrate the procedure on Weyl fermions in a real representation

    Effect of electron-nuclear spin interactions on electron-spin qubits localized in self-assembled quantum dots

    Get PDF
    The effect of electron-nuclear spin interactions on qubit operations is investigated for a qubit represented by the spin of an electron localized in a self-assembled quantum dot. The localized electron wave function is evaluated within the atomistic tight-binding model. The magnetic field generated by the nuclear spins is estimated in the presence of an inhomogeneous environment characterized by a random nuclear spin configuration, by the dot-size distribution, by alloy disorder, and by interface disorder. Due to these inhomogeneities, the magnitude of the nuclear magnetic field varies from one qubit to another by the order of 100 G, 100 G, 10 G, and 0.1 G, respectively. The fluctuation of the magnetic field causes errors in exchange operations due to the inequality of the Zeeman splitting between two qubits. We show that the errors can be made lower than the quantum error threshold if an exchange energy larger than 0.1 meV is used for the operation.Comment: 15 pages, 2 figure

    Modification of the Ames 40- by 80-foot wind tunnel for component acoustic testing for the second generation supersonic transport

    Get PDF
    The development of a large-scale anechoic test facility where large models of engine/airframe/high-lift systems can be tested for both improved noise reduction and minimum performance degradation is described. The facility development is part of the effort to investigate economically viable methods of reducing second generation high speed civil transport noise during takeoff and climb-out that is now under way in the United States. This new capability will be achieved through acoustic modifications of NASA's second largest subsonic wind tunnel: the 40-by 80-Foot Wind Tunnel at the NASA Ames Research Center. Three major items are addressed in the design of this large anechoic and quiet wind tunnel: a new deep (42 inch (107 cm)) test section liner, expansion of the wind tunnel drive operating envelope at low rpm to reduce background noise, and other promising methods of improving signal-to-noise levels of inflow microphones. Current testing plans supporting the U.S. high speed civil transport program are also outlined

    Shuntchirurgie in Europa und den USA: Ein kritischer Vergleich

    Get PDF
    Zusammenfassung: Nach einem anfĂ€nglich gemeinsamen Weg in der Fistelchirurgie begann in den USA ab etwa 1975 der bevorzugte Einsatz von Prothesenshunts. In bis zu 80% wurden bei Erstoperationen GefĂ€ĂŸprothesen implantiert, mit entsprechend hoher Komplikationsrate und hohen Folgekosten. Europa pflegte, mit lokalen Unterschieden, das Konzept der vorzugsweisen Verwendung von arteriovenösen Fisteln weiter (AVF). Der Prothesenanteil war nie höher als 40%. UnterstĂŒtzt von Richtlinien, versuchen die USA seit 1997 einen deutlichen Umschwung herbeizufĂŒhren. Der Anteil primĂ€rer AVF ist seither angestiegen, bei allerdings wohl erhöhter initialer Versagerquote im internationalen Vergleich. Über Richtlinien hinaus sollte fĂŒr beide Kontinente als vordringliche Aufgaben die interdisziplinĂ€re Zusammenarbeit aller beteiligten Fachgebiete gelten: DurchfĂŒhrung zertifizierter, interdisziplinĂ€rer Kurse mit konsensfĂ€higen Inhalten, Einrichtung von Referenzzentren mit einheitlicher, umfassender Dokumentation, Aufbau von Datenbanken zur QualitĂ€tskontrolle mit abrufbaren Komplikations- und Funktionsraten, Standardisierung der Überwachung von GefĂ€ĂŸzugĂ€ngen im Dialysezentru

    A comparison of machine learning classifiers for pediatric epilepsy using resting-state functional MRI latency data

    Get PDF
    Epilepsy affects 1 in 150 children under the age of 10 and is the most common chronic pediatric neurological condition; poor seizure control can irreversibly disrupt normal brain development. The present study compared the ability of different machine learning algorithms trained with resting-state functional MRI (rfMRI) latency data to detect epilepsy. Preoperative rfMRI and anatomical MRI scans were obtained for 63 patients with epilepsy and 259 healthy controls. The normal distribution of latency z-scores from the epilepsy and healthy control cohorts were analyzed for overlap in 36 seed regions. In these seed regions, overlap between the study cohorts ranged from 0.44-0.58. Machine learning features were extracted from latency z-score maps using principal component analysis. Extreme Gradient Boosting (XGBoost), Support Vector Machines (SVM), and Random Forest algorithms were trained with these features. Area under the receiver operating characteristics curve (AUC), accuracy, sensitivity, specificity and F1-scores were used to evaluate model performance. The XGBoost model outperformed all other models with a test AUC of 0.79, accuracy of 74%, specificity of 73%, and a sensitivity of 77%. The Random Forest model performed comparably to XGBoost across multiple metrics, but it had a test sensitivity of 31%. The SVM model did not perform \u3e70% in any of the test metrics. The XGBoost model had the highest sensitivity and accuracy for the detection of epilepsy. Development of machine learning algorithms trained with rfMRI latency data could provide an adjunctive method for the diagnosis and evaluation of epilepsy with the goal of enabling timely and appropriate care for patients

    Intravenous Immunoglobulin Treatment in Multifocal Motor Neuropathy

    Get PDF
    # The Author(s) 2010. This article is published with open access at Springerlink.com Introduction Multifocal motor neuropathy (MMN) is characterized by asymmetric weakness of limbs and the electrophysiological finding of conduction block in motor nerves. Conduction block is the inability of nerves to propagate action potentials and is probably caused b

    Infants with esophageal atresia and right aortic arch: Characteristics and outcomes from the Midwest Pediatric Surgery Consortium

    Get PDF
    Purpose Right sided aortic arch (RAA) is a rare anatomic finding in infants with esophageal atresia with or without tracheoesophageal fistula (EA/TEF). In the presence of RAA, significant controversy exists regarding optimal side for thoracotomy in repair of the EA/TEF. The purpose of this study was to characterize the incidence, demographics, surgical approach, and outcomes of patients with RAA and EA/TEF. Methods A multi-institutional, IRB approved, retrospective cohort study of infants with EA/TEF treated at 11 children's hospitals in the United States over a 5-year period (2009 to 2014) was performed. All patients had a minimum of one-year follow-up. Results In a cohort of 396 infants with esophageal atresia, 20 (5%) had RAA, with 18 having EA with a distal TEF and 2 with pure EA. Compared to infants with left sided arch (LAA), RAA infants had a lower median birth weight, (1.96 kg (IQR 1.54–2.65) vs. 2.57 kg (2.00–3.03), p = 0.01), earlier gestational age (34.5 weeks (IQR 32–37) vs. 37 weeks (35–39), p = 0.01), and a higher incidence of congenital heart disease (90% vs. 32%, p  0.29). Conclusion RAA in infants with EA/TEF is rare with an incidence of 5%. Compared to infants with EA/TEF and LAA, infants with EA/TEF and RAA are more severely ill with lower birth weight and higher rates of prematurity and complex congenital heart disease. In neonates with RAA, surgical repair of the EA/TEF is technically feasible via thoracotomy from either chest. A higher incidence of anastomotic strictures may occur with a right-sided approach
    • 

    corecore