Abstract

Several computational visual saliency models have been pro-posed in the context of viewing natural scenes. We aim to investigate the relevance of computational saliency models in medical images in the context of abnormality detection.We report on two studies aimed at understanding the role of visual saliency in medical images. Diffuse lesions in ChestX-Ray images, which are characteristic of Pneumoconiosis and high contrast lesions such as ‘Hard Exudates’ in retinal images were chosen for the study. These approximately correspond to conjunctive and disjunctive targets in a visual search task. Saliency maps were computed using three popular models namely Itti-Koch [7], GBVS [3] and SR [4].The obtained maps were evaluated against gaze maps and ground truth from medical experts. Our results show that GBVS is seen to perform the best(Mdn. ROC area= 0.77) for chest X-Ray images while SRperforms the best (ROC area= 0.73) for retinal images,thus asserting that searching for conjunctive targets calls for a more local examination of an image while disjunctive targets call for a global examination. Based on the results of the above study, we propose extensions for the two best performing models. The first extension makes use of top down knowledge such as lung segmentation. This is shown to improve the performance of GBVS to some extent. Inthe second case the extension is by way of including multi-scale information. This is shown to significantly (by 28.76%)improve abnormality detection. The key insight from these studies is that bottom saliency continues to play a predominant role in examining medical images.

Abstract

The blood perfusion measurement is done by injecting a bolus of contrast agent in the brain followed by imaging over a period of time (scan). This process can extend into minutes and hence any patient motion mid-scan results in corrupted data. This is often observed in dynamic magnetic resonance(MR) imaging for both susceptibility (DSC) and contrast enhanced (DCE) scans. Motion correction done after scanning is typically the most time-intensive step in the entire measurement process since it involves registering each volume in the time-series to a reference volume. We argue that detecting the presence of motion prior to correction can mitigate this problem by reducing the number of volumes to be corrected. The challenge in motion detection is that the injected contrast alters the signal intensity as a function of time leading to false alarms. We present a robust multi-stage method: subdivision of the time series data into bolus and non bolus phases; clustering-based identification of bolus-affected pixels followed by correction of their intensity using a Gamma variate function fitting-based method and a 2Dblock-wise phase correlation for detecting motion between adjacent volumes in DSC-MRI data. The proposed method was tested on a DSC MR sequence with simulated motion of varying degrees. The experimental results show that the entropy of the derived motion fields is a good metric for detecting and categorizing the motion. The proposed scheme when applied prior to correction can achieve on average a37% reduction in the time required for motion correction

Abstract

Most queries in wireless sensor network (WSN) applications are issued at the point of the base station or gateway node of the network. However, for critical applications of WSNs there is a great need to access the real-time data inside the WSN from the nodes, because the real-time data may no longer be accessed through the base station only. So, the real-time data can be given access directly to the external users (parties) those who are authorized to access data as and when they demand. The user authentication plays a vital role for this purpose. In this paper, we propose a new password-based user authentication scheme in hierarchical wireless sensor networks. Our proposed scheme achieves better security and efficiency as compared to those for other existing password-based approaches. In addition, our scheme has merit to change dynamically the user's password locally without the help of the base station or gateway node. Furthermore, our scheme supports dynamic nodes addition after the initial deployment of nodes in the existing sensor network.

Abstract

Several key management schemes for dynamic access control in a user hierarchy are proposed in the literature based on elliptic curve cryptosystem (ECC) and polynomial interpolation. Since the elliptic curve scalar multiplication and construction of interpolating polynomials are time-consuming operations, most of the proposed schemes require high storage and computational complexity. Further, most of the proposed schemes are vulnerable to different attacks including the man-in-the-middle attacks. In this paper, we propose a novel key management scheme for hierarchical access control based on linear polynomials only. We show that our scheme is secure against different attacks including the man-in-the-middle attack, which are required for an idle access control scheme. Moreover, the computational cost and the storage space are significantly reduced in our scheme while compared to the recently proposed related schemes.

Abstract

In a key management scheme for hierarchy based access control, each security class having higher clearance can derive the cryptographic secret keys of its other security classes having lower clearances. In 2008, Chung et al. proposed an efficient scheme on access control in user hierarchy based on elliptic curve cryptosystem [Information Sciences 178 (1) (2008) 230–243]. Their scheme provides solution of key management efficiently for dynamic access problems. However, in this paper, we propose an attack on Chung et al.’s scheme to show that Chung et al.’s scheme is insecure against the exterior root finding attack. We show that under this attack, an attacker (adversary) who is not a user in any security class in a user hierarchy attempts to derive the secret key of a security class by using the root finding algorithm. In order to remedy this attack, we further propose a simple improvement on Chung et al.’s scheme. Overall, the main theme of this paper is very simple: a security flaw is presented on Chung et al.’s scheme and then a fix is provided in order to remedy the security flaw found in Chung et al.’s scheme.

Abstract

The objective of this paper is to suggest a fresh approach to introductory programming curricula in the Indian school and engineering college context. The approach allows the student to connect high-school (up to 10+2) mathematics to the fundamentals of computing, algorithms and problem solving. The bridge connecting algebra and computing is functional programming, a paradigm confined over forty years to the computer science research community but now gaining popularity in industry as well as undergraduate education in some schools across the world. We show, using several examples, why and how functional programming is easier to master than traditional imperative programming. We conclude with the results of our attempts so far at introducing functional programming to students in IT colleges in India.

Abstract

This paper addresses the issue of moving object tracking from video. Two steps of processing are PCA reconstruction for classification the area and Optical flow-based tracking of feature points. Optimal flow-based tracking algorithm predicts and restores the feature of area in the real time object tracking. The proposed system is computationally more efficient for learning of dynamic object and object tracking to shape information. PCA based method compare to other methods is powerful algorithm in object detection and the Optical flowbased tracking algorithm could be used for decreasing the false point tracking and remove the error of the motion tracking in real time system tracking. The proposed algorithm tracks a set of feature points; during the tracking, feature is restored inside the predicted region. One important contribution of this work is to provide a restoration process for missing feature points, which occurs at almost every frame under realistic, noisy environment.

Abstract

Rapid urbanization is resulting in the irreversible land use and land cover (LULC) changes, which is the prime driver of global warming and consequent climate changes. This communication investigates landscape dynamics assessed through spatio-temporal pattern analysis using free and open source softwares [FOSS, http://ces. iisc. ernet. in/foss]. Bangalore has been experiencing urbanization tide since globalisation era and is one of the fastest growing cities in India. Migration and policy decision of setting up major facilities and industries seem to be the reason for rapid urbanisation with impacts on the local ecology and natural resources. As the city centre has reached the threshold of urbanisation, intense sprawl has been noticed at outskirts. In order to understand the urbanisation and sprawl dynamics, spatio-temporal analysis has been done in the city administrative region with 10 km buffer. To understand the dynamics at local level with drivers, spatial metrics is computed for the study region, which is divided into eight zones (radial), 13 circles of 2 km incrementing radius. The results show that extensive land conversion to urban utility has occurred since 1992 within the city and from 2000 conversion started at periphery, especially by industrialisation activities. The land scape metrics exhibited remarkable spatial and temporal variations and urban sprawl. Overall changes in the land use from 1973 to 2012 shows the increase in the built-up (paved surface) area from 1.87% to 29.33% and decrease in vegetation cover from 62.38% to 33.68%. The landscape metrics depicts the city is more concentrated at center and fragmented towards its …

Abstract

Tropical islands are special and sensitive ecosystems which are subjected to various disturbances imposed by human activities and natural disasters. A detailed study about the changing landscape scenarios of these fragile island systems induced by various driving factors could be used for setting up measurements in support of conservation and sustainable development projects. The current research is a meta-analysis of the studies carried out in Andaman and Nicobar islands which analyzed the impact of tsunami of 2004 using geospatial tools. Based on the analysis, it was observed that the Nicobar islands were more affected compared to the Andaman islands. The majority of the researchers used pre- and post-tsunami satellite imagery and adopted visual interpretation method to delineate the changed classes. The study infers uplift of land in Andaman (exposing) and subsidence in Nicobar islands …

Abstract

Riboswitches constitute an important class of non coding RNAs, present in the UTR of mRNAs. The ligand discriminating aptamer domain of a riboswitch can undergo conformational changes in absence or presence of its binding cognate metabolite affecting the downstream expression platform, through the activation or attenuation of either transcription or translation. The preQ1 responsive family of riboswitches, which show high affinity towards the guanine derived metabolites such as 7-cyano-7-deazaguanine (PreQ0) and 7-aminomethyl-7-deazaguanine (PreQ1), consist of the smallest riboswitches known. There are two subclasses of preQ1 riboswitches categorised based on sequence and structural differences: Class I and Class II. Class I is further subdivided into Type I and Type II, based on the mechanism of gene regulation. Class I Type I riboswitches regulate gene expression at translational level, and Class I Type II riboswitches regulate gene expression at transcriptional level. X-ray crystal structures of aptamer domains of Class I Types I and II riboswitches bound with cognate ligands preQ0 and preQ1 have been reported. However, the ligand free structure of only Class I Type I is available. We have modelled both ligand bound and ligand free structures of Class I Type I riboswitches belonging to Thermoanaerobacter tengcongensis. Crystal structures show that the presence or absence of ligand results in changes in molecular interactions within the binding pocket, eventually resulting in either sequestration or opening of ribosomal binding site leading to translational regulation. In order to study the stability of base pairs in the aptamer region, we have modelled the interactions observed in binding pocket, both pairing and stacking, and carried out gas phase quantum chemical studies. The ideal geometries and interaction energies of the complexes, evaluated at B3LYP/6-31G(d,p)//RIMP2/aug-cc-pVDZ respectively. The effect of stacking interactions in the complex is evaluated with DFT-D calculations at PBE/6-31G(d,p) level of theory. Morokuma energy decomposition is performed to investigate the contributions of various non covalent interactions to the total energy of the complex. We have identified the contributions of different interactions towards the stability of binding pocket and recognition of the ligands. Our studies also provide insights into the differential ligand affinities of the aptamer domain towards two similar ligands: preQ0 and preQ1.