2,450 research outputs found
Transverse-Longitudinal Coupling by Space Charge in Cyclotrons
A method is presented that enables to compute the parameters of matched beams
with space charge in cyclotrons with emphasis on the effect of the
transverse-longitudinal coupling. Equations describing the
transverse-longitudinal coupling and corresponding tune-shifts in first order
are derived for the model of an azimuthally symmetric cyclotron. The
eigenellipsoid of the beam is calculated and the transfer matrix is transformed
into block-diagonal form. The influence of the slope of the phase curve on the
transverse-longitudinal coupling is accounted for. The results are generalized
and numerical procedures for the case of an AVF cyclotron are presented. The
algorithm is applied to the PSI Injector II and Ring cyclotron and the results
are compared to TRANSPORT.Comment: 8 pages, 2 figure
A coupled finite volume and material point method for two-phase simulation of liquid-sediment and gas-sediment flows
Mixtures of fluids and granular sediments play an important role in many
industrial, geotechnical, and aerospace engineering problems, from waste
management and transportation (liquid--sediment mixtures) to dust kick-up below
helicopter rotors (gas--sediment mixtures). These mixed flows often involve
bulk motion of hundreds of billions of individual sediment particles and can
contain both highly turbulent regions and static, non-flowing regions. This
breadth of phenomena necessitates the use of continuum simulation methods, such
as the material point method (MPM), which can accurately capture these large
deformations while also tracking the Lagrangian features of the flow (e.g.\ the
granular surface, elastic stress, etc.).
Recent works using two-phase MPM frameworks to simulate these mixtures have
shown substantial promise; however, these approaches are hindered by the
numerical limitations of MPM when simulating pure fluids. In addition to the
well-known particle ringing instability and difficulty defining inflow/outflow
boundary conditions, MPM has a tendency to accumulate quadrature errors as
materials deform, increasing the rate of overall error growth as simulations
progress. In this work, we present an improved, two-phase continuum simulation
framework that uses the finite volume method (FVM) to solve the fluid phase
equations of motion and MPM to solve the solid phase equations of motion,
substantially reducing the effect of these errors and providing better accuracy
and stability for long-duration simulations of these mixtures
Does the presence of chondral lesions negatively affect patient-determined outcomes after arthroscopic rotator cuff repair?
Background: There are limited data available to guide patients to their prognosis when glenohumeral chondral lesions are found during arthroscopic rotator cuff repair.
Hypothesis: The primary hypothesis was that patients with glenohumeral chondral lesions will have inferior outcomes after arthroscopic rotator cuff repair compared with patients without chondral lesions. The secondary hypothesis was that patients with concomitant chondral lesions will have more severe preoperative symptoms compared with those without chondral lesions.
Study Design: Cohort study; Level of evidence, 3.
Methods: A retrospective analysis was performed of patients who underwent arthroscopic rotator cuff repair between 2008 and 2012. We examined the effects of chondral lesions on patient-determined outcomes, which included the Western Ontario Rotator Cuff Index (WORC), American Shoulder and Elbow Surgeons (ASES) score, Simple Shoulder Test (SST), Single Assessment Numeric Evaluation (SANE), and the Shoulder Activity Level (SAL). Shoulders without chondral lesions were compared with shoulders with chondral lesions to determine whether differences in severity of preoperative symptoms as well as postoperative improvements were statistically significant.
Results: A total of 281 shoulders were included from 273 patients, with a mean follow-up of 3.7 years. In total, 90 shoulders (32%) had concomitant chondral lesions in the glenohumeral joint. The presence and degree of chondral damage were not associated with the severity of preoperative symptoms or the amount of improvement after arthroscopic rotator cuff repair, as determined by patient outcome scores. Shoulders with bipolar chondral lesions had less postoperative improvement in their outcome scores compared with shoulders with unipolar lesions, with significant differences found in the SST (
Conclusion: At a mean 3.7-year follow-up, the presence of chondral damage did not appear to negatively affect the improvement in patient-determined outcomes after arthroscopic rotator cuff repair. However, improvement in outcomes was negatively affected by the presence of bipolar chondral lesions
A new charge-transfer complex in UHV co-deposited tetramethoxypyrene and tetracyanoquinodimethane
UHV-deposited films of the mixed phase of tetramethoxypyrene and
tetracyanoquinodimethane (TMP1-TCNQ1) on gold have been studied using
ultraviolet photoelectron spectroscopy (UPS), X-ray-diffraction (XRD), infrared
(IR) spectroscopy and scanning tunnelling spectroscopy (STS). The formation of
an intermolecular charge-transfer (CT) compound is evident from the appearance
of new reflexes in XRD (d1= 0.894 nm, d2= 0.677 nm). A softening of the CN
stretching vibration (red-shift by 7 cm-1) of TCNQ is visible in the IR
spectra, being indicative of a CT of the order of 0.3e from TMP to TCNQ in the
complex. Characteristic shifts of the electronic level positions occur in UPS
and STS that are in reasonable agreement with the prediction of from DFT
calculations (Gaussian03 with hybrid functional B3LYP). STS reveals a HOMO-LUMO
gap of the CT complex of about 1.25 eV being much smaller than the gaps (>3.0
eV) of the pure moieties. The electron-injection and hole-injection barriers
are 0.3 eV and 0.5 eV, respectively. Systematic differences in the positions of
the HOMOs determined by UPS and STS are discussed in terms of the different
information content of the two methods.Comment: 20 pages, 6 figure
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The atmospheric background situation in northern Scandinavia during January/February 2003 in the context of the MaCWAVE campaign
The atmosphere background wind field controls the propagation of gravity waves from the troposphere through the stratosphere into the mesosphere. During January 2003 the MaCWAVE campaign took place at Esrange, with the purpose of observing vertically ascending waves induced by orography. Temperature data from the U. Bonn lidar at Esrange (68° N/21° E) and the ALOMAR RMR lidar (69° N/16° E), wind data from Esrange MST radar ESRAD, as well as wind data from the ECMWF T106 model, are used to analyse the atmospheric background situation and its effect on mountain wave propagation during January/February 2003. Critical levels lead to dissipation of vertically ascending waves, thus mountain waves are not observable above those levels. In the first half of January a minor as well as a major stratospheric warming dominated the meteorological background situation. These warmings led to a wind reversal, thus to critical level filtering and consequently prevented gravity waves from propagating to high altitudes. While the troposphere was not transparent for stationary gravity waves most of the time, there was a period of eight days following the major warming with a transparent stratosphere, with conditions allowing gravity waves generated in the lower troposphere to penetrate the stratosphere up to the stratopause and sometimes even into the lower mesosphere. In the middle of February a minor stratospheric warming occurred, which again led to critical levels such that gravity waves were not able to ascend above the middle stratosphere. Due to the unfavourable troposphere and lower stratosphere conditions for gravity wave excitation and propagation, the source of the observed waves in the middle atmosphere is probably different from orography
Real-Time MEG Source Localization Using Regional Clustering
With its millisecond temporal resolution, Magnetoencephalography (MEG) is well suited for real-time monitoring of brain activity. Real-time feedback allows the adaption of the experiment to the subject’s reaction and increases time efficiency by shortening acquisition and off-line analysis. Two formidable challenges exist in real-time analysis: the low signal-to-noise ratio (SNR) and the limited time available for computations. Since the low SNR reduces the number of distinguishable sources, we propose an approach which downsizes the source space based on a cortical atlas and allows to discern the sources in the presence of noise. Each cortical region is represented by a small set of dipoles, which is obtained by a clustering algorithm. Using this approach, we adapted dynamic statistical parametric mapping for real-time source localization. In terms of point spread and crosstalk between regions the proposed clustering technique performs better than selecting spatially evenly distributed dipoles. We conducted real-time source localization on MEG data from an auditory experiment. The results demonstrate that the proposed real-time method localizes sources reliably in the superior temporal gyrus. We conclude that real-time source estimation based on MEG is a feasible, useful addition to the standard on-line processing methods, and enables feedback based on neural activity during the measurements.Deutsche Forschungsgemeinschaft (grant Ba 4858/1-1)National Institutes of Health (U.S.) (grants 5R01EB009048 and 2P41EB015896)Universitätsschule Jena (J21)German Academic Exchange Servic
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