Net Radial Research Articles

Artificial Intelligence Models Predict Operative Versus Nonoperative Management of Patients with Adult Spinal Deformity with 86% Accuracy

Patients with ASD show complex and highly variable disease. The decision to manage patients operatively is largely subjective and varies based on surgeon training and experience. We sought to develop models capable of accurately discriminating between patients receiving operative versus nonoperative treatment based only on baseline radiographic and clinical data at enrollment. This study was a retrospective analysis of a multicenter consecutive cohort of patients with ASD. A total of 1503 patients were included, divided in a 70:30 split for training and testing. Patients receiving operative treatment were defined as those undergoing surgery up to 1 year after their baseline visit. Potential predictors included available demographics, past medical history, patient-reported outcome measures, and premeasured radiographic parameters from anteroposterior and lateral films. In total, 321 potential predictors were included. Random forest, elastic net regression, logistic regression, and support vector machines (SVMs) with radial and linear kernels were trained. Of patients in the training and testing sets, 69.0% (n= 727) and 69.1% (n= 311), respectively, received operative management. On evaluation with the testing dataset, performance for SVM linear (area under the curve=0.910), elastic net (0.913), and SVM radial (0.914) models was excellent, and the logistic regression (0.896) and random forest (0.830) models performed very well for predicting operative management of patients with ASD. The SVM linear model showed 86% accuracy. This study developed models showing excellent discrimination (area under the curve >0.9) between patients receiving operative versus nonoperative management, based solely on baseline study enrollment values. Future investigations may evaluate the implementation of such models for decision support in the clinical setting.

The Net Radial Flow Velocity of the Neutral Hydrogen in the Oval Distortion of NGC 4736

Abstract The net radial flow velocity of gas is an important parameter for understanding galaxy evolution. It is difficult to measure in the presence of the elliptical orbits of an oval distortion because the mathematical model describing the observed velocity is degenerate in the unknown velocity components. A method is developed in this paper that breaks the degeneracy using additional information about the angular frequency of the oval distortion. The method is applied to the neutral hydrogen in the oval distortion of NGC 4736. The neutral hydrogen is flowing inward at a mean rate of −6.1 ± 1.9 km s−1. At this rate, it takes 400 Myr, or 1.7 rotations of the oval distortion, for the neutral hydrogen to travel the 2.5 kpc from the end to the beginning of the oval distortion. The mean mass flow rate of the neutral hydrogen in this region is −0.25 ± 0.11 M ⊙ yr−1, which is similar to estimates for the star formation rate reported in the literature.

21. Machine learning models to predict operative vs nonoperative management of adult spinal deformity patients

BACKGROUND CONTEXT Adult spinal deformity (ASD) patients exhibit complex and highly variable pathology. The decision to manage patients operatively is subjective and varies based on training and experience. Machine learning algorithms have shown promise in supporting clinical decision-making. PURPOSE We sought to develop models capable of accurately discriminating between patients receiving operative vs nonoperative treatment based only on baseline radiographic and clinical data at enrollment. STUDY DESIGN/SETTING Retrospective analysis of a multicenter, prospectively-defined, consecutive cohort of ASD patients. PATIENT SAMPLE A total of 1,503 patients were included in this study, divided in a 70:30 split for training and testing. OUTCOME MEASURES Patients receiving operative treatment were defined as those undergoing surgery up to 1 year after their baseline visit. METHODS Potential predictors included available demographics, past medical history, HRQoL, and premeasured radiographic parameters from AP and lateral films. Variables with >10% missing data were discarded, and the remainder underwent median imputation. In total, 321 potential predictors were included. Random forest, elastic net regression, and support vector machines (SVMs) with radial and linear kernels were trained. Model performance was evaluated by area under the receiver operating characteristic curve (AUC). RESULTS Of the patients, 69.0% (n=727) and 69.1% (n=311) in the training and testing sets received operative management, respectively. Upon evaluation with the testing dataset, performance for SVM linear (AUC=0.910), elastic net (0.913), and SVM radial (0.914) models was excellent, and the random forest model performed very well (0.830). In our SVM radial model, HRQoL metrics were particularly important for making predictions; the top 3 most important variables were SRS appearance, SRS total, and ODI. CONCLUSIONS This study developed models exhibiting excellent discrimination (AUC>0.9) between patients receiving operative vs nonoperative management, based solely on baseline enrollment values. HRQoL metrics were strongest in making these predictions. Future investigations may evaluate the implementation of such models for decision support in the clinical setting. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Plasma flows in Saturn's nightside magnetosphere

AbstractThe plasma properties, especially the flow parameters, obtained from numerical integration of Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer measurements during intervals when the CAPS field of view encompassed both inward and outward flow directions relative to corotation are examined for nightside data (18–06 local time) during 2006, 2009, and 2010. The results show good agreement with previously reported values derived using different selection criteria and a different analysis technique. Nightside flows are predominantly in or near the corotation direction, indicating continuing influence of connection to the ionosphere. There is no evidence for a quasi‐steady reconnection x line within the surveyed region of the tail, although dynamic events attributable to transient reconnection have been observed. There is a net radial mass outflow, leading to an estimated net mass loss between 18 and 03 local time of ~34 kg/s. Part of this mass loss occurs as a “planetary wind” along the dusk flank. The remainder probably occurs ultimately much deeper in the tail and along the distant dawn magnetopause, when the mass disconnects from the weakened planetary magnetic field.

Secondary Eyewall Formation and Eyewall Replacement Cycles in a Simulated Hurricane: Effect of the Net Radial Force in the Hurricane Boundary Layer

Abstract Multiple secondary eyewall formations (SEFs) and eyewall replacement cycles (ERCs) are simulated with the fifth-generation Pennsylvania State University (PSU)–National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) at horizontal grid spacing of 0.67 km. The simulated hurricane is initialized from a weak, synthetic vortex in a quiescent environment on an f plane. After spinup and rapid intensification, the hurricane enters a mature phase during which the intensity change is relatively slow. Convective clouds then organize into a ring with a secondary tangential wind maximum at radii beyond the hurricane’s primary eyewall. This secondary eyewall (SE) then contracts and strengthens. The primary eyewall weakens and is eventually replaced by the SE. The hurricane grows in size and the radius of maximum wind (RMW) increases as similar ERCs repeat 5 times during the simulation. Two existing hypotheses on SEF are evaluated using the simulation output. Then, model diagnostics are used to reveal that crucial linked components of SEF are (i) a broadening of the swirling flow, (ii) the structure of the evolving secondary circulation, and (iii) the structure of the net radial force (NRF) in the boundary layer (with largest contributions from the agradient and frictional forces). During SEF, there exists strong positive NRF in the region of the primary eyewall, a secondary positive maximum over the SEF region, and a minimum between the two. As a response of the boundary layer depth–integrated radial flow to the NRF, a secondary maximum convergence zone (SMCZ) in the boundary layer develops at the SEF radii. Eventually moist convection in the SMCZ becomes active as the SEF develops.

EFFECTS OF ASYMMETRIC FLOWS IN SOLAR CONVECTION ON OSCILLATION MODES

Many helioseismic measurements suffer from substantial systematic errors. A particularly frustrating one is that time-distance measurements suffer from a large center to limb effect which looks very similar to the finite light travel time, except that the magnitude depends on the observable used and can have the opposite sign Zhao et al. (2012). This has frustrated attempts to determine the deep meridional flow in the solar convection zone, with Zhao et al. (2012) applying an ad hoc correction with little physical basis to correct the data. In this letter we propose that part of this effect can be explained by the highly asymmetrical nature of the solar granulation which results in what appears to the oscillation modes as a net radial flow, thereby imparting a phase shift on the modes as a function of observing height and thus heliocentric angle.

Investigation of laminar flow in a stirred vessel at low Reynolds numbers

Many mixing applications involve viscous fluids and laminar flows where the detailed as well as overall flow structures are important. In order to understand the fluid dynamic characteristics of low Re laminar flows in mixing vessels, the flow induced by a Rushton impeller for three Re namely, 1, 10 and 28, was studied both experimentally and computationally. It was found that for the highest Re, the flow exhibited the familiar outward pumping action associated with radial impellers under turbulent flow conditions. However, as the Re decreases, the net radial flow during one impeller revolution was reduced and for the lowest Re a reciprocating motion with negligible net pumping was observed. This behaviour has not been reported in the literature in the past and represents a highly undesirable flow pattern from the standpoint of effective mixing. The CFD results successfully reproduced this behaviour. In order to elucidate the physical mechanism responsible for the observed flow pattern, the forces acting on a fluid element in the radial direction were analysed. The analysis indicated that for the lowest Re, the material derivative of radial velocity near the blade tip is small thus a balance exists between pressure and viscous forces; the defining characteristic of creeping flow. The velocity and pressure forces are in phase because the velocity is driven by the pressure field generated by the rotation of the impeller. Based on these findings, a simplified analytic model of the flow was developed that gives a good qualitative as well as quantitative representation of the flow.

Three‐Dimensional Magnetohydrodynamic Modeling of the Gaseous Structure of the Galaxy: Description of the Simulations

As we have discussed previously, the extra stiffness that a magnetic field adds to the interstellar medium (ISM) changes the way the ISM reacts to the presence of a spiral perturbation. At intermediate to high z, the gas shoots up before the arm, then flows over and falls behind the arm as it approaches the next arm. This generates a multicell circulation pattern, within each of which the net radial mass flux is positive near the midplane and negative at higher z. The flow distorts the magnetic field lines. In the arm region, the gas flows nearly parallel to the arm, and therefore the magnetic field adopts a similar pitch angle. Between the arms, the gas flows out in radius, generating a negative pitch angle in the magnetic field. The intensity and direction of the field yield synthetic synchrotron maps that reproduce some features of the synchrotron maps of external galaxies, such as the islands of emission and the displacement between the gaseous and synchrotron arms. When comparing the magnitude of the field with the local gas density, two distinctive relations appear, depending on whether the magnetic pressure is dominant. Above the plane, the density structure develops a shape resembling a breaking wave. This structure collapses and rises again with a period of about 60 Myr, similar to that of a vertical oscillation mode. The falling gas plays an important part in the overall hydrostatics, since its deceleration compresses the low-z gas, raising the average midplane pressure in the interarm region above that provided by the weight of the material above.

Multichannel visible spectroscopy diagnostic for particle transport studies in the H-1 heliac

A multichannel spectroscopy diagnostic has been developed to study cross-field particle transport in the radiation-dominated low-temperature plasmas (Te<100 eV) in the H-1 heliac. The optical setup covers the full plasma minor radius in the poloidal plane collecting light from ten parallel chords arranged tangentially to the flux surfaces. The light collected from the plasma is coupled into optical fibers and through interference filters into photomultipliers. Two such ten-fiber arrays are aligned parallel to one another to allow the simultaneous monitoring of two different spectral lines. The net radial electron particle flux is determined from the continuity equation by integrating over the ionization source term in the steady-state partially ionized plasma. The diagnostic measures the neutral line intensities and their ratios (in case of helium using the line ratio technique) and also measures excited neutral and ion spectral lines (in case of the argon plasma transport studies). A comparative analysis of the radial particle transport in the low- and high-confinement regimes is presented.

Finite element solution of micropolar fluid flow from an enclosed rotating disc with suction and injection

The steady flow of a micropolar fluid over a finite rotating disc enclosed within a coaxial cylindrical casing has been studied. The governing equations were solved numerically by using the finite element method. Maximum values ξ 1 and ξ 2 of the dimensionless radial distance at which there is no-recirculation for the cases of net radial outflow and net radial inflow respectively, increase with an increase in the micropolar effects. The velocities at ξ 1 and ξ 2 as well as at some fixed radii have been calculated and the associated phenomena of no-recirculation/recirculation is discussed. The change in the flow phenomenon due to a reversal of the direction of the net radial flow has also been studied.

Numerical Simulation of Flow around a Tall Isolated Seamount. Part II: Resonant Generation of Trapped Waves

A sigma-coordinate, primitive equation ocean circulation model is used to explore the problem of the remnant generation of trapped waves about a tall, circular, isolated seamount by an incident oscillatory barotropic current. The numerical solutions are used to extend prior studies into the fully nonlinear regime, and in particular to quantify and interpret the occurrence of residual circulation. Specific attention is also devoted to the dependence of the resonance and rectification mechanisms on stratification, forcing frequency, and choice of subgrid-scale viscous closure. Resonantly generated trapped waves of significant amplitude are found to occur broadly in parameter space; a precise match between the frequency of the imposed incident current and the frequency of the trapped free wave is not necessary to produce substantial excitation of the trapped wave. The maximum amplification factors produced in these numerical solutions, O(100) times the strength of the incident current, are consistent with previous studies. In the presence of nonlinear advection, strong residual currents are produced. The time-mean circulation about the seamount is dominated by a strong bottom-intensified, anticyclonic circulation closely trapped to the seamount. Maximum local time-mean current amplitudes are found to be as large as 37% of the magnitude of the propagating waves. In addition to the strong anticyclonic residual flow, there is a weaker secondary circulation in the vertical-radial plane characterized by downwelling over the top of the seamount at all depths. Maximum vertical downwelling rates of several tens of meters per day occur at the summit of the seamount. The vertical mass flux implied by this systematic downwelling is balanced by a slow radial flux of mass directed outward along the flanks of the seamount. Time-mean budgets for the radial and azimuthal components of momentum show that horizontal eddy fluxes of momentum are responsible for transporting net radial and azimuthal momentum from the far field to the upper flanks of the seamount. There, Coriolis and pressure gradient forces provide the dominant balances in the radial direction. However, the Coriolis force and viscous effects provide the primary balance for the azimuthal component.

Discs and Drums: The Thermo-Fluid Dynamics of Rotating Surfaces

This paper reviews long-term experimental and theoretical research programmes concerned with flow and heat transfer over the large rotating surfaces, commonly discs, often drums but sometimes conical, used to support the blades in turbomachinery. The account begins with a geometry found in turbomachinery from the oldest steam plant to the most modern gas turbine, in which a disc rotates near to a stationary, usually coaxial, member. The flow in the intervening ‘wheel-space’ is well understood, but external conditions can affect the extent and nature of ingress from the surrounding fluid. In the gas turbine this fluid is the mainstream hot gas, an inflow of which could have serious consequences, so that the study of ingress has become the principal subject of research for rotor-stator systems and recent work is fully reported here. In many turbo-machines, especially compressors, adjacent coaxial surfaces rotate together and thus enclose a cavity subject to unusual forces in which a wide range of flow regimes can obtain. The precise form depends largely on whether the cavity allows a net radial inflow or outflow of fluid or whether the only access and egress are from near the axis of the system, the so-called ‘axial through-flow’ case. Systems with a net radial flow, inward or outward, are well understood. In their absence, the flows are often four dimensional, varying with time and in the three space coordinates. Such regimes remain incompletely understood although recent congruence between experimental and theoretical studies is encouraging. Finally, attention is turned to surfaces nearer parallel than orthogonal to the axis of rotation, as in the drums used in older steam turbines and commonly in compressors. Here the main concern has been with the effect of stationary blading, where the close clearance between the blading and the rotating surface modifies the boundary layers and thus the friction and heat transfer on the latter.

North‐south coupling study

AbstractAn empirical study of stationkeeping data on several RCA series 3000 spacecraft which was used to analyse coupling effects during inclination manoeuvres has yielded valuable data on changes in east‐west drift and eccentricity which result from these manoeuvres. The major origins of these effects are thruster alignments and plume impingement on the north solar panel. While thruster alignments for a given spacecraft will differ depending on its centre of mass, plume impingement showed a higher order seasonal influence over the basic cant angle differences between thruster pairs on opposite sides of a satellite, i.e. when the solar arrays are at a ‘near zero’ angle (array panel directly facing earth) the net radial vector bias is attenuated. Plume impingement has a primary seasonal influence in tangential coupling, however: when the solar array was ‘looking east’, eastward drift was observed, and likewise when the solar panel was west‐oriented, there was a westward drift effect. Recommendations are made as to how this information might be used to improve an operator's stationkeeping schedule.

Analysis of Confined Magnetohydrodynamic Vortex Flows

The vortex flow of a viscous, incompressible, and electrically conducting fluid confined between two finite flat plates (with a net radial mass flow) in the presence of an applied axial magnetic field is considered. The details of the velocity field including boundary‐layer thickness and redistribution of radial mass flow are of primary concern. The analysis is limited to the case of the separation distance between the two end plates being small compared with the radius of the plates; this allows the momentum equations to be uncoupled from the electromagnetic equations. The momentum equations are linearized and solved for the velocities and the pressure as Fourier series. It is found that magnetic effects tend to decrease the boundary‐layer thickness by a small percentage and tend to decrease substantially the mass flow drawn into the boundary layers.

The equations for a problem arising in Dungey's investigation of Bailey's theory of sunspot noise

Abstract In the preceding investigation (p. 148) of wave amplification, Dr. J. W. Dungey has paid particular attention to the possibility of wave amplification in an axially symmetric model of the solar atmosphere over a sunspot. In the present paper the differential equations of a small radiation field in a non-uniform ionised gas are shown to possess particular solutions, which, along the axis of symmetry, correspond to ordinary circularly polarised waves. By taking one of these solutions subject to the condition that there be no net radial flow of wave energy either into, or away from, the axis, the electric vector e 0 of the wave along the axis and the associated electron velocity u 0 are found to be related by the equations These equations form the starting point of Dungey's investigation of wave amplification in the axially symmetric model.