The feasibility of using feature-flow and label transfer system to segment medical images with deformed anatomy in orthopedic surgery

In computer-aided surgical systems, to obtain high fidelity three-dimensional models, we require accurate segmentation of medical images. State-of-art medical image segmentation methods have been used successfully in particular applications, but they have not been demonstrated to work well over a wide range of deformities. For this purpose, I studied and evaluated medical image segmentation using the feature-flow based Label Transfer System described by Liu and colleagues. This system has produced promising results in parsing images of natural scenes. Its ability to deal with variations in shapes of objects is desirable. In this paper, we altered this system and assessed its feasibility of automatic segmentation. Experiments showed that this system achieved better recognition rates than those in natural-scene parsing applications, but the high recognition rates were not consistent across different images. Although this system is not considered clinically practical, we may improve it and incorporate it with other medical segmentation tools

Multi-epoch, multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A

We present the observational results of the Gamma-ray blazar, 3C 66A, at 2.3, 8.4, and 22 GHz at 4 epochs during 2004-05 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. As combined with some previous results to investigate the proper motions of the jet components, it is found the kinematics of 3C 66A is quite complicated with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by new-born components. The possible reason could be non-stationarity of the core due to opacity change.Comment: 24 pages, 4 figure

Intertwined dipolar and multipolar order in the triangular-lattice magnet TmMgGaO4_4

A phase transition is often accompanied by the appearance of an order parameter and symmetry breaking. Certain magnetic materials exhibit exotic hidden-order phases, in which the order parameters are not directly accessible to conventional magnetic measurements. Thus, experimental identification and theoretical understanding of a hidden order are difficult. Here we combine neutron scattering and thermodynamic probes to study the newly discovered rare-earth triangular-lattice magnet TmMgGaO$_4$. Clear magnetic Bragg peaks at K points are observed in the elastic neutron diffraction measurements. More interesting, however, is the observation of sharp and highly dispersive spin excitations that cannot be explained by a magnetic dipolar order, but instead is the direct consequence of the underlying multipolar order that is "hidden" in the neutron diffraction experiments. We demonstrate that the observed unusual spin correlations and thermodynamics can be accurately described by a transverse field Ising model on the triangular lattice with an intertwined dipolar and ferro-multipolar order.Comment: Published versio

Group II Intron Protein Localization and Insertion Sites Are Affected by Polyphosphate

Mobile group II introns consist of a catalytic intron RNA and an intron-encoded protein with reverse transcriptase activity, which act together in a ribonucleoprotein particle to promote DNA integration during intron mobility. Previously, we found that the Lactococcus lactis Ll.LtrB intron-encoded protein (LtrA) expressed alone or with the intron RNA to form ribonucleoprotein particles localizes to bacterial cellular poles, potentially accounting for the intron's preferential insertion in the oriC and ter regions of the Escherichia coli chromosome. Here, by using cell microarrays and automated fluorescence microscopy to screen a transposon-insertion library, we identified five E. coli genes (gppA, uhpT, wcaK, ynbC, and zntR) whose disruption results in both an increased proportion of cells with more diffuse LtrA localization and a more uniform genomic distribution of Ll.LtrB-insertion sites. Surprisingly, we find that a common factor affecting LtrA localization in these and other disruptants is the accumulation of intracellular polyphosphate, which appears to bind LtrA and other basic proteins and delocalize them away from the poles. Our findings show that the intracellular localization of a group II intron-encoded protein is a major determinant of insertion-site preference. More generally, our results suggest that polyphosphate accumulation may provide a means of localizing proteins to different sites of action during cellular stress or entry into stationary phase, with potentially wide physiological consequences.This work was supported by National Institutes of Health R01 grants GM037949 to AML and GM076536 to EMM, Welch Foundation grants F-1607 to AML and F-1515 to EMM, and a Packard Foundation fellowship to EMM.Cellular and Molecular Biolog

An hourglass model for the flare of HST-1 in M87

To explain the multi-wavelength light curves (from radio to X-ray) of HST-1 in the M87 jet, we propose an hourglass model that is a modified two-zone system of Tavecchio & Ghisellini (hereafter TG08): a slow hourglass-shaped or Laval nozzle-shaped layer connected by two revolving exponential surfaces surrounding a fast spine, through which plasma blobs flow. Based on the conservation of magnetic flux, the magnetic field changes along the axis of the hourglass. We adopt the result of TG08---the high-energy emission from GeV to TeV can be produced through inverse Compton by the two-zone system, and the photons from radio to X-ray are mainly radiated by the fast inner zone system. Here, we only discuss the light curves of the fast inner blob from radio to X-ray. When a compressible blob travels down the axis of the first bulb in the hourglass, because of magnetic flux conservation, its cross section experiences an adiabatic compression process, which results in particle acceleration and the brightening of HST-1. When the blob moves into the second bulb of the hourglass, because of magnetic flux conservation, the dimming of the knot occurs along with an adiabatic expansion of its cross section. A similar broken exponential function could fit the TeV peaks in M87, which may imply a correlation between the TeV flares of M87 and the light curves from radio to X-ray in HST-1. The Very Large Array (VLA) 22 GHz radio light curve of HST-1 verifies our prediction based on the model fit to the main peak of the VLA 15 GHz radio light curve.Comment: 14 pages, 2 figures, accepted for publication in A

Design on low noise and lightweight of aircraft equipment cabin based on genetic algorithm and variable-complexity model

Aircraft equipment cabin noise will not only affect the comfort of passengers, but also affect the normal operations of the internal equipments of the aircraft, or even result in fatigue and damage to the aircraft structure itself. In the design, only to add ribs onto the panel or conduct structural-acoustic optimization on the ribs will dramatically increase the structural weight. In this paper, frequency response analysis was carried out on the structural-acoustic coupling system of the cavity panel. The cabin door panel was divided into six regions by ribs. Then, the lightweight optimization model of the cabin door panel was eventually established, with the cabin door panel thicknesses of each region and the cross-sectional areas of the ribs as the design variables, and the average sound pressure of the structural-acoustic coupling system as the constraint condition. And subsequently, the cabin door panel structure with the minimum mass and satisfying the sound pressure constraint condition was eventually obtained through genetic algorithm (GA). Moreover, so as to lighten the optimization burden, the finite element simulation model of the cabin door panel was substituted by the Kriging meta-model during the optimization process to evaluate the sound pressure response of the structural-acoustic coupling system. Furthermore, in order to narrow the difference between the meta-model and the physical one, the optimization idea of the variable-complexity model (VCM) was employed. As a result, the analysis result of the highly accurate simulation model was utilized to modify that of the Kriging meta-model. Overall, the work in this paper has an important engineering guidance value for the weight and noise reduction design of panel structure with ribs

Characterization of Colloidal Particles Using Electrical Impedance Spectroscopy in Two-electrode System with Carbon Probe

The colloidal particles have an electrical double layer associated with their surfaces when suspended in an aqueous medium. Under the influence of an alternating electric field, an induced electrical dipole moment can be formed due to the polarization of the electrical double layer. The electrical impedance spectroscopy (EIS) measurement can record the complex impedance, conductivity, relaxation frequency and phase angle caused by the polarization of the electrical double layer. These impedance parameters are in relation to particle characteristics, for example, the particle size. The research about particle size effect on electrical impedance spectra was carried out in a four-electrode system and the result indicated that impedance parameters shows a capability for characterizing the particle size. This paper reports the experimental results from electrical impedance spectroscopy measurements on silica suspensions in a two-electrode system with carbon probe. The main aim is to study the particle size effect on impedance parameters, especially the relaxation frequency and phase angle, to compare the data with those obtained from a four-electrode system with stainless steel electrodes and verify the capability for characterizing colloidal particles in different electrode systems. The particle size effect on the relaxation frequency and impedance phase angle was studied in two different electrode systems and a similar tendency can be observed. It indicates that the capability of impedance parameters for particle characterization is not limited in a four-electrode system, but commonly applicable in different electrode systems

Effect of mixing on mass transfer characterization in continuous slugs and dispersed droplets in biphasic slug flow microreactors

The mass transfer of slug flow, a widely applied flow pattern in microreactors, is still difficult to predict mainly due to the competing nature between convection and diffusion. This work focused on the influence of the mixing mechanism on the mass transfer performance under gas–liquid and liquid–liquid slug flow, in both continuous slugs and dispersed droplets. Colorimetric study with the resazurin oxidation system was implemented, where the mass transfer resistance was constantly located in the aqueous phase. In the hydrophilic glass microreactor, the convection featured by intensive internal circulation and/or inter-slug leakage flow dominated diffusion, leading to nearly-constant kLa along the channel under given flow rates. However, in the hydrophobic PTFE capillary, the stagnant region constituted a significant share in the aqueous droplet, indicating the prominent role of diffusion against convection therein. As a result, kLa values decreased along the main channel length in fixed operating conditions. Accordingly, prediction models were respectively correlated depending on mixing mechanisms. Moreover, mass transfer contributions from the bubble and droplet formation stages were also investigated. This work is expected to shed light on judicious process design and reliable predictions in microreactor operations

Analysis of nonlinear suspension power harvest potential

Because the power consumption of a controlled suspension is huge, the power harvest potential of a nonlinear controlled suspension is analyzed. Instead of simplifying the suspension to a linear model or adopting some control strategies to solve the problem, this paper investigates the effect of the nonlinear characteristics on the power harvesting potential. A mathematic model is introduced to calculate the nonlinear vibration, and the amount of harvested power was obtained using the multi-scale method. A numerical validation is carried out at the end of this study. The results show that the investigated mechanical parameters affect both the vibration amplitude and the induced current, while the electric parameters only affect the induced current. The power harvesting potential of the nonlinear suspension is generally greater than the linear suspension because the frequency band of the actual pavement also contains bandwidth surrounding the body resonance point. The only exception occurs if the vehicle travels on a road with a particular profile, e.g. a sine curve. To optimize harvested power, it is better to consider the nonlinear characteristics rather than simplifying the suspension to a linear model