A high voltage programmable ramp generator

In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1 ns and provides continuous speed variation from 6 to 30 ns for a ramp of 500 V. This is being developed as a part of automated streak camera for deflection of electron beam.     

Quantitative analysis of microstructure refinement in ultrafine-grained strips of Al6063 fabricated using large strain extrusion machining

Abstract

In present research work, ultrafine-grained strips of Al-6063 alloy were fabricated using hybrid extrusion machining technique known as “large strain extrusion machining (LSEM).” Fabrication of strips was done using the customized HSS tools of different rake angles varying from 0° to 10° under different machining conditions. Microstructural and mechanical characterizations of these strips were done to ascertain the effect of different parameters on their properties. From the results of hardness measurement of strips, it was concluded that hardness of the strips increased by 34–97% of the base material as of the refinement of grain size occurred. Surface lay was improved by 30% with higher cutting velocity and rake angle. Crystallite size was found to decrease with increase in the rate of strain. The shear strain was increased as chip compression ratio increased and rake angle decreased. Fabrication ability of strips increased due to increase in strain hardening exponent and it may result in the large scope of their applications. Nano-hardness of the strips was found to be more than bulk alloy. These above said results showed that ultrafine strips fabricated using LSEM process can become a good choice for future material fabrication.     

FRAPP: a framework for high-accuracy privacy-preserving mining

To preserve client privacy in the data mining process, a variety of techniques based on random perturbation of individual data records have been proposed recently. In this paper, we present FRAPP, a generalized matrix-theoretic framework of random perturbation, which facilitates a systematic approach to the design of perturbation mechanisms for privacy-preserving mining. Specifically, FRAPP is used to demonstrate that (a) the prior techniques differ only in their choices for the perturbation matrix elements, and (b) a symmetric positive-definite perturbation matrix with minimal condition number can be identified, substantially enhancing the accuracy even under strict privacy requirements. We also propose a novel perturbation mechanism wherein the matrix elements are themselves characterized as random variables, and demonstrate that this feature provides significant improvements in privacy at only a marginal reduction in accuracy. The quantitative utility of FRAPP, which is a general-purpose random-perturbation-based privacy-preserving mining technique, is evaluated specifically with regard to association and classification rule mining on a variety of real datasets. Our experimental results indicate that, for a given privacy requirement, either substantially lower modeling errors are incurred as compared to the prior techniques, or the errors are comparable to those of direct mining on the true database. A partial and preliminary version of this paper appeared in the Proc. of the 21st IEEE Intl. Conf. on Data Engineering (ICDE), Tokyo, Japan, 2005, pgs. 193–204.     

Sustained release microspheres of diclofenac sodium using PEGylated rosin derivatives

The PEGylated derivatives of rosin-PD-1 and PD-2 synthesized and characterized earlier (Nande et al., 2006) were investigated as potential materials for sustained release microsphere prepared by emulsion solvent evaporation method using diclofenac sodium (DCS) as model drug. All the microspheres exhibited smooth surfaces intercepted by pores; their sizes (d(90)) ranged between 11-24 microm. The entrapment efficiency (< 80%) of the microspheres increased proportionally with derivative concentration. Presence of solvent like isopropyl alcohol or dichloromethane rendered the microspheres with large sizes but with reduced drug entrapment. Microspheres with small size were obtained at an optimum viscosity of liquid paraffin; any change lead to increase in the particle size. Magnesium stearate was found to be most suitable detackifier in the present system. The drug release was directly related to the particle size--small sized microspheres released drug at a faster rate. The dissolution data complied with Higuchi equation while the mechanism of drug release was Fickian diffusion (n approximately 0.5). Controlled inhibition of edema, as tested by hind paw edema method, was observed for 10 h when the microspheres were administered intraperitoneally. The present study found the derivatives as promising materials for preparing microspheres for sustained delivery of DCS.     

Truncated O-Glycan-Bearing MUC16 Enhances Pancreatic Cancer Cells Aggressiveness via α4β1 Integrin Complexes and FAK Signaling

Elevated levels of Mucin-16 (MUC16) in conjunction with a high expression of truncated O-glycans is implicated in playing crucial roles in the malignancy of pancreatic ductal adenocarcinoma (PDAC). However, the mechanisms by which such aberrant glycoforms present on MUC16 itself promote an increased disease burden in PDAC are yet to be elucidated. This study demonstrates that the CRISPR/Cas9-mediated genetic deletion of MUC16 in PDAC cells decreases tumor cell migration. We found that MUC16 enhances tumor malignancy by activating the integrin-linked kinase and focal adhesion kinase (ILK/FAK)-signaling axis. These findings are especially noteworthy in truncated O-glycan (Tn and STn antigen)-expressing PDAC cells. Activation of these oncogenic-signaling pathways resulted in part from interactions between MUC16 and integrin complexes (α4β1), which showed a stronger association with aberrant glycoforms of MUC16. Using a monoclonal antibody to functionally hinder MUC16 significantly reduced the migratory cascades in our model. Together, these findings suggest that truncated O-glycan containing MUC16 exacerbates malignancy in PDAC by activating FAK signaling through specific interactions with α4 and β1 integrin complexes on cancer cell membranes. Targeting these aberrant glycoforms of MUC16 can aid in the development of a novel platform to study and treat metastatic pancreatic cancer.     

Active vibration control of piezolaminated stiffened plates

The aim of this work is to present active vibration control of stiffened plates. A stiffened plate finite element with piezoelectric effects is formulated. The characteristic feature of the stiffener is that it can have any shape in plan and need not pass through the nodal lines of the finite element mesh. The coupling between the direct and the converse piezoelectric effects is neglected for simplicity. A velocity feedback algorithm is employed in the active control. Numerical examples for vibration control of isotropic and orthotropic stiffened plates have been presented.     

Wet shells and dry tales: the evolutionary ‘Just-So’ stories behind the structure–function of biominerals

The ability of evolution to shape organic form involves the interactions of multiple systems of constraints, including fabrication, phylogeny and function. The tendency to place function above everything else has characterized some of the historical biological literature as a series of ‘Just-So’ stories that provided untested explanations for individual features of an organism. A similar tendency occurs in biomaterials research, where features for which a mechanical function can be postulated are treated as an adaptation. Moreover, functional adaptation of an entire structure is often discussed based on the local characterization of specimens kept in conditions that are far from those in which they evolved. In this work, environmental- and frequency-dependent mechanical characterization of the shells of two cephalopods, Nautilus pompilius and Argonauta argo, is used to demonstrate the importance of multi-scale environmentally controlled characterization of biogenic materials. We uncover two mechanistically independent strategies to achieve deformable, stiff, strong and tough highly mineralized structures. These results are then used to critique interpretations of adaptation in the literature. By integrating the hierarchical nature of biological structures and the environment in which they exist, biomaterials testing can be a powerful tool for generating functional hypotheses that should be informed by how these structures are fabricated and their evolutionary history.     

Binning algorithm for high-resolution IRS-P4 OCM chlorophyll image

Daily chlorophyll-a concentration from the Ocean Colour Monitor (OCM) sensor onboard the Indian Remote Sensing satellite (IRS-P4) is used to make weekly and monthly chlorophyll-a concentration maps. The pathwise swath data at 12 noon for every alternate day over the north Indian Ocean (NIO) during February 2004 and February 2005 were used to compare the existing algorithms for binning the data. Atmospherically corrected and geocorrected OCM data were used in the comparative study of three averaging algorithms – arithmetic mean (AVG), geometric mean (GEO) and maximum likelihood estimator (MLE). The analysis shows that the AVG algorithm is best suited when compared with the two other algorithms. However, for case 1 water, MLE gives nearly the same value as AVG. Based on this result, AVG was selected for operational weekly and monthly averaging of OCM data over the NIO. These high-resolution-derived chlorophyll-a weekly and monthly products will be useful to resolve inter-annual-to-decadal changes in chlorophyll-a concentration over the NIO.     

Sparse Adaptive Parameterization of Variability in Image Ensembles

This paper introduces a new parameterization of diffeomorphic deformations for the characterization of the variability in image ensembles. Dense diffeomorphic deformations are built by interpolating the motion of a finite set of control points that forms a Hamiltonian flow of self-interacting particles. The proposed approach estimates a template image representative of a given image set, an optimal set of control points that focuses on the most variable parts of the image, and template-to-image registrations that quantify the variability within the image set. The method automatically selects the most relevant control points for the characterization of the image variability and estimates their optimal positions in the template domain. The optimization in position is done during the estimation of the deformations without adding any computational cost at each step of the gradient descent. The selection of the control points is done by adding a L ¹ prior to the objective function, which is optimized using the FISTA algorithm.