Ball-Scale Based Hierarchical Multi-Object Recognition in 3D Medical Images

This paper investigates, using prior shape models and the concept of ball scale (b-scale), ways of automatically recognizing objects in 3D images without performing elaborate searches or optimization. That is, the goal is to place the model in a single shot close to the right pose (position, orientation, and scale) in a given image so that the model boundaries fall in the close vicinity of object boundaries in the image. This is achieved via the following set of key ideas: (a) A semi-automatic way of constructing a multi-object shape model assembly. (b) A novel strategy of encoding, via b-scale, the pose relationship between objects in the training images and their intensity patterns captured in b-scale images. (c) A hierarchical mechanism of positioning the model, in a one-shot way, in a given image from a knowledge of the learnt pose relationship and the b-scale image of the given image to be segmented. The evaluation results on a set of 20 routine clinical abdominal female and male CT data sets indicate the following: (1) Incorporating a large number of objects improves the recognition accuracy dramatically. (2) The recognition algorithm can be thought as a hierarchical framework such that quick replacement of the model assembly is defined as coarse recognition and delineation itself is known as finest recognition. (3) Scale yields useful information about the relationship between the model assembly and any given image such that the recognition results in a placement of the model close to the actual pose without doing any elaborate searches or optimization. (4) Effective object recognition can make delineation most accurate.Comment: This paper was published and presented in SPIE Medical Imaging 201

Transport in a thin topological insulator with potential and magnetic barriers

We study transport across either a potential or a magnetic barrier which is placed on the top surface of a three-dimensional thin topological insulator (TI). For such thin TIs, the top and bottom surfaces interact via a coupling $\lambda$ which influences the transport properties of junctions constructed out of them. We find that for junctions hosting a potential barrier, the differential conductance oscillates with the barrier strength. The period of these oscillations doubles as the coupling $\lambda$ changes from small values to a value close to the energy of the incident electrons. In contrast, for junctions with a magnetic barrier, the conductance approaches a non-zero constant as the barrier strength is increased. This feature is in contrast to the case of transport across a single TI surface where the conductance approaches zero as the strength of a magnetic barrier is increased. We also study the spin currents for these two kinds of barriers; in both cases, the spin current is found to have opposite signs on the top and bottom surfaces. Thus this system can be used to split applied charge currents to spin currents with opposite spin orientations which can be collected by applying opposite spin-polarized leads to the two surfaces. We show that several of these features of transport across finite width barriers can be understood analytically by studying the $\delta$-function barrier limit. We discuss experiments which may test our theory.Comment: 18 pages, 14 figures; added some references and made minor corrections; this is the published versio

Significance of interactions of low molecular weight crystallin fragments in lens aging and cataract formation

Analysis of aged and cataract lenses shows the presence of increased amounts of crystallin fragments in the high molecular weight aggregates of water-soluble and water-insoluble fractions. However, the significance of accumulation and interaction of low molecular weight crystallin fragments in aging and cataract development is not clearly understood. In this study, 23 low molecular mass (<3.5-kDa) peptides in the urea-soluble fractions of young, aged, and aged cataract human lenses were identified by mass spectroscopy. Two peptides, B-(1-18) (MDIAIHHPWIRRPFFPFH) and A3/A1-(59-74)(SD(N)AYHIERLMSFRPIC), present in aged and cataract lens but not young lens, and a third peptide, S-(167-178) (SPAVQSFRRIVE) present in all three lens groups were synthesized to study the effects of interaction of these peptides with intact -, -, and -crystallins and alcohol dehydrogenase, a protein used in aggregation studies. Interaction of B-(1-18) and A3/A1-(59-74) peptides increased the scattering of light by - and -crystallin and alcohol dehydrogenase. The ability of -crystallin subunits to function as molecular chaperones was significantly reduced by interaction with B-(1-18) and A3/A1-(59-74) peptides, whereas S peptide had no effect on chaperone-like activity of -crystallin. The A3/A1-(59-74 peptide caused a 5.64-fold increase in B-crystallin oligomeric mass and partial precipitation. Replacing hydrophobic residues in B-(1-18) and A3/A1-(59-74) peptides abolished their ability to induce crystallin aggregation and light scattering. Our study suggests that interaction of crystallin-derived peptides with intact crystallins could be a key event in age-related protein aggregation in lens and cataractogenesis

Medical image segmentation using object atlas versus object cloud models

Medical image segmentation is crucial for quantitative organ analysis and surgical planning. Since interactive segmentation is not practical in a production-mode clinical setting, automatic methods based on 3D object appearance models have been proposed. Among them, approaches based on object atlas are the most actively investigated. A key drawback of these approaches is that they require a time-costly image registration process to build and deploy the atlas. Object cloud models (OCM) have been introduced to avoid registration, considerably speeding up the whole process, but they have not been compared to object atlas models (OAM). The present paper fills this gap by presenting a comparative analysis of the two approaches in the task of individually segmenting nine anatomical structures of the human body. Our results indicate that OCM achieve a statistically significant better accuracy for seven anatomical structures, in terms of Dice Similarity Coefficient and Average Symmetric Surface Distance.Medical image segmentation is crucial for quantitative organ analysis and surgical planning. Since interactive segmentation is not practical in a production-mode clinical setting, automatic methods based on 3D object appearance models have been proposed.9415CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO303673/2010-9; 479070/2013-0; 131835/2013-0sem informaçãoSPIE - international society for optical engineering. medical imagin

One-dimensional spin-orbit coupled Dirac system with extended ss-wave superconductivity: Majorana modes and Josephson effects

Motivated by the spin-momentum locking of electrons at the boundaries of topological insulators, we study a one-dimensional system of spin-orbit coupled massless Dirac electrons with $s$-wave superconducting pairing. As a result of the spin-orbit coupling, our model has only two kinds of linearly dispersing modes, which we take to be right-moving spin-up and left-moving spin-down. Both lattice and continuum models are studied. In the lattice model, we find that a single Majorana zero energy mode appears at each end of a finite system provided that the $s$-wave pairing has an extended form, with the nearest-neighbor pairing being larger than the on-site pairing. We confirm this both numerically and analytically by calculating the winding number. Next we study a lattice version of a model with both Schr\"odinger and Dirac-like terms and find that the model hosts a topological transition between topologically trivial and non-trivial phases depending on the relative strength of the Schr\"odinger and Dirac terms. We then study a continuum system consisting of two $s$-wave superconductors with different phases of the pairing. Remarkably, we find that the system has a {\it single} Andreev bound state which is localized at the junction. When the pairing phase difference crosses a multiple of $2 \pi$, an Andreev bound state touches the top of the superconducting gap and disappears, and a different state appears from the bottom of the gap. We also study the AC Josephson effect in such a junction with a voltage bias that has both a constant $V_0$ and a term which oscillates with a frequency $\omega$. We find that, in contrast to standard Josephson junctions, Shapiro plateaus appear when the Josephson frequency $\omega_J= 2eV_0/\hbar$ is a rational fraction of $\omega$. We discuss experiments which can realize such junctions.Comment: 16 pages, 9 figures; made some significant changes, added a figure and several reference

Recovery of Certain Non-ferrous Metals from Industrial by Products

The primary resources of certain non-ferrous metals that are of great industrial value, such as copper, zinc and lead are lean in our country and the entire demand for the same cannot be met fully but for the import. Quite a good percentage of the total consumption is available as a good percentage of the total consumption is avail-able as byproduct oxides and hydroxides. Any attempt to recover the metals from such byproducts will be great value especially with respect to saving foreign exchange. In this communication, the methods for the recovery of copper, zinc and lead from byproducts are reviewed. Well known thermal and electrolytic processes are briefly discussed and two processes that have been developed for the recovery, by the authors are discussed in detail. The first method involves direct electrolytic reduction of the byproduct oxide or hydroxide to the respective metal powder when the same is kept as a sediment on a metal cathode immersed in an alkaline medium. The character-istics of the metal powder obtaine depends on those of the starting material.In the other method, known as susp-ension electrolysis, the finely powdered byproduct is suspended in a suitable medium and the suspension is then electrolysed. The metal can be recovered either in the form of powder or sheet by varying the conditions of electrolysis. The above mentioned methods as applied to the recovery of copper, zinc, lead and silver are discussed