Artery-vein separation via MRA--an image processing approach

This paper presents a near-automatic process for separating vessels from background and other clutter as well as for separating arteries and veins in contrast-enhanced magnetic resonance angiographic (CE-MRA) image data, and an optimal method for three-dimensional visualization of vascular structures. The separation process utilizes fuzzy connected object delineation principles and algorithms. The first step of this separation process is the segmentation of the entire vessel structure from the background and other clutter via absolute fuzzy connectedness. The second step is to separate artery from vein within this entire vessel structure via iterative relative fuzzy connectedness. After seed voxels are specified inside artery and vein in the CE-MRA image, the small regions of the bigger aspects of artery and vein are separated in the initial iterations, and further detailed aspects of artery and vein are included in later iterations. At each iteration, the artery and vein compete among themselves to grab membership of each voxel in the vessel structure based on the relative strength of connectedness of the voxel in the artery and vein. This approach has been implemented in a software package for routine use in a clinical setting and tested on 133 CE-MRA studies of the pelvic region and two studies of the carotid system from six different hospitals. In all studies, unified parameter settings produced correct artery-vein separation. When compared with manual segmentation/separation, our algorithms were able to separate higher order branches, and therefore produced vastly more details in the segmented vascular structure. The total operator and computer time taken per study is on the average about 4.5 min. To date, this technique seems to be the only image processing approach that can be routinely applied for artery and vein separation.     

Grazing-incidence hyperboloid-hyperboloid designs for wide-field x-ray imaging applications

The classical Wolter type I grazing-incidence x-ray telescope consists of a paraboloidal primary mirror and a confocal hyperboloidal secondary mirror. This design exhibits stigmatic imaging on-axis but suffers from coma, astigmatism, field curvature, and higher-order aberrations such as oblique spherical aberration. Wolter-Schwarzschild designs have been developed that strictly satisfy the Abbe sine condition and thus exhibit no spherical aberration or coma. However, for wide-field applications such as the solar x-ray imager (SXI), there is little merit in a design with stigmatic imaging on-axis. Instead, one needs to optimize some area-weighted-average measure of resolution over the desired operational field of view. This has traditionally been accomplished by mere despacing of the focal plane of the classical Wolter type I telescope. Here we present and evaluate in detail a family of hyperboloid-hyperboloid grazing-incidence x-ray telescope designs whose wide-field performance is much improved over that of an optimally despaced Wolter type I and even somewhat improved over that of an optimally despaced Wolter-Schwarzschild design.     

TGF-beta and colorectal carcinogenesis

There is substantial evidence to support the contention that the Smad portion of the TGF-beta signal transduction pathway provides an important tumor-suppressor function. Mutational loss of function of Smad pathway members have been associated with the development of human cancers and appear to be causative in selected rodent carcinogenesis models. TGF-beta also has multiple other actions that appear to be independent of the growth-inhibitory/tumor suppressor effects. The predominant effect of TGF-beta appears to be dependent on the context of the responding cell. Once transformation has occurred, TGF-beta effects may be detrimental and may actually promote tumor cell survival, invasion, and metastasis. Recent work suggests that these effects may involve TGF-beta regulation of COX-2 and other pathways that may contribute to tumor cell aggressiveness. In gaining a better understanding of the mechanisms by which TGF-beta may promote tumor progression, it is likely that new therapeutic strategies may be developed that preserve tumor-suppressor function of TGF-beta while inhibiting the tumor-promoting effects.     

Strengthening of alumina by cerium-zirconate (Ce2Zr2O7)

Composite powders of Al₂O₃ and 0 to 30 vol% Ce₂Zr₂O₇ are prepared by a hybrid sol-gel method using Al₂O₃ powders and a sol formed from Zr-alkoxide and cerium nitrate. All the Zr from the sol goes to form the cerium zirconate phase when the powders are calcined in N₂. Pressureless sintering in air at 1500°C yields composites with high density (98%). Maximum values of fracture toughness and strength, 6.5 MPa and 620 MPa respectively, (e.g. 3.5 MPa and 350 MPa for pure Al₂O₃) are obtained in 10 vol% Ce₂Zr₂O₇ composite sintered in air. The dominant mechanism for enhancement in K _IC is believed to be crack bridging. Crack bridging activity in the 10 vol% composite is found to be maximum and extends upto 190 m from the crack tip.     

Evaluation of high‐resolution and mobile display systems for digital radiology in dark and bright environments using human and computational observers

Abstract— As digital display systems replace film traditionally used for reading radiographic images, resource‐intensive acceptance testing must be performed to ensure that quality meets and maintains desired specifications. If machine observers can replace human readers, whose performances are highly variable, the results will be more consistent and less costly. To be effective, however, the automated observers must track human performance. An approach for a model observer, validated with human readers, for the evaluation of the visibility of low‐contrast small targets in high‐resolution and mobile displays under different ambient illumination, will be described. The displays were tested using CDMAM‐like digital phantoms containing disks of varying diameters and contrasts on a flat background. For this task, we find the best indicator of display performance to be the display's ability to represent small luminance contrast, not resolution or pixel size. The results confirm that high‐resolution systems perform better under low illumination while illuminance has a minor impact on the mobile‐display performance. Finally, the results show that the machine observer tracks the performance of human readers. Machine observers with proper validation can replace humans in the acceptance testing procedures, saving the testers both time and money.     

Some remarks on Bianchi type-II, VIII, and IX models

Within the scope of anisotropic non-diagonal Bianchi type-II, VIII, and IX spacetimes it is shown that the off-diagonal components of the Einstein equations impose severe restrictions on the components of the energy-momentum tensor (EMT) in general. We begin with a metric with three functions of time, a(t), b(t), and c(t), and two spatial ones, f(z) and h(z). It is shown that if the EMT is assumed to be diagonal, and f = f(z), in all cosmological models in question b ∝ c, and the matter distribution is isotropic, i.e., T ₁ ¹ = T ₂ ² = T ₃ ³ . If f = const, which is a special case of BII models, the matter distribution may be anisotropic, but only the z axis is distinguished, and in this case b(t) is not necessarily proportional to c(t).     

Change detection for moving object segmentation with robust background construction under Wronskian framework

Although background subtraction techniques have been used for several years in vision systems for moving object detection, many of them fail to provide good results in presence of noise, illumination variation, non-static background, etc. A basic requirement of background subtraction scheme is the construction of a stable background model and then comparing each incoming image frame with it so as to detect moving objects. The novelty of the proposed scheme is to construct a stable background model from a given video sequence dynamically. The constructed background model is compared with different image frames of the same sequence to detect moving objects. In the proposed scheme the background model is constructed by analyzing a sequence of linearly dependent past image frames in Wronskian framework. The Wronskian based change detection model is further used to detect the changes between the constructed background scene and the considered target frame. The proposed scheme is an integration of Gaussian averaging and Wronskian change detection model. Gaussian averaging uses different modes which arise over time to capture the underlying richness of background, and it is an approach for background building by considering temporal modes. Similarly, Wronskian change detection model uses a spatial region of support in this regard. The proposed scheme relies on spatio-temporal modes arising over time to build the appropriate background model by considering both spatial and temporal modes. The results obtained by the proposed model is found to provide accurate shape of moving objects. The effectiveness of the proposed scheme is verified by comparing the results with those of some of the existing state of the art background subtraction techniques on public benchmark databases. We found that the average F-measure is significantly improved by the proposed scheme from that of the state-of-the-art techniques.     

Rates of change of total ozone column and surface relative humidity: seasonal variations over Dum Dum (22° 38′ N, 88° 26′ E)

This article presents a study of the seasonal variability of the rate of change of total ozone column (TOC) and the rate of change of surface relative humidity (RH) over Dum Dum (22° 38′ N, 88° 26′ E) during different seasons of the period 1997–2005. The rate of formation of TOC was a maximum during the pre-monsoon and winter seasons and the rate of decrease of TOC was a maximum during the monsoon and post-monsoon seasons throughout the period of study. The rate of increase of surface RH was a maximum in the pre-monsoon season and the rate decreased during the other seasons. At the monsoon and post-monsoon seasons the rate of decrease of TOC increased with the rate of decrease of surface RH.     

Augmenting the performance of acrylonitrile–butadiene–styrene plastics for low‐noise dynamic applications

The main objective of this study was to enhance the performance of acrylonitrile–butadiene–styrene (ABS) plastics for dynamic structural applications, including those of automobile relevance. First, ABS was modified by blending with maleic anhydride grafted styrene–ethylene–butadiene–styrene block copolymer (MA‐g‐SEBS) in various proportions. Squeaking noise characteristics were evaluated by measurement of the frictional behavior in an in‐house fabricated friction testing apparatus, and the results are explained on the basis of the change in surface energy upon modification. Detailed dynamic mechanical analyses (strain, frequency, and temperature sweep) revealed significant improvements in the damping characteristics of the modified ABS, especially that modified with 10 wt % MA‐g‐SEBS, without much sacrifice in its mechanical strength. The modulus values predicted with Kerner's model of the blends were well correlated with the morphological changes upon modification. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Optimal pricing and lot-sizing for perishable inventory with price and time dependent ramp-type demand

Product perishability is an important aspect of inventory control. To minimise the effect of deterioration, retailers in supermarkets, departmental store managers, etc. always want higher inventory depletion rate. In this article, we propose a dynamic pre- and post-deterioration cumulative discount policy to enhance inventory depletion rate resulting low volume of deterioration cost, holding cost and hence higher profit. It is assumed that demand is a price and time dependent ramp-type function and the product starts to deteriorate after certain amount of time. Unlike the conventional inventory models with pricing strategies, which are restricted to a fixed number of price changes and to a fixed cycle length, we allow the number of price changes before as well as after the start of deterioration and the replenishment cycle length to be the decision variables. Before start of deterioration, discounts on unit selling price are provided cumulatively in successive pricing cycles. After the start of deterioration, discounts on reduced unit selling price are also provided in a cumulative way. A mathematical model is developed and the existence of the optimal solution is verified. A numerical example is presented, which indicates that under the cumulative effect of price discounting, dynamic pricing policy outperforms static pricing strategy. Sensitivity analysis of the model is carried out.