257 research outputs found
First person – Gaurav Barve
No full textABSTRACT
First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Gaurav Barve is the first author on ‘Septins are involved at the early stages of macroautophagy in S. cerevisiae’, published in Journal of Cell Science. Gaurav is a PhD student in the laboratory of Ravi Manjithaya at Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India, investigating the role of septins in autophagy.</jats:p
Linguistic representations of visual events
No full textThis thesis explores the nature of linguistic representations that correspond to verbal descriptions of events. In two experiments, participants watched captioned videos and decided whether the captions accurately described the videos. In the videos, two geo-metric shapes moved around the screen. [In half of the trials, the geometric shapes had "eyes."] The verbs used to describe the shapes' actions were either source-to-goal verbs (chase, follow, trail ) or goal-to-source verbs (flee, lead, guide). Sometimes the captions were active sentences (e.g., The circle is chasing the square) and sometimes passive sentences (The square is chased by the circle). Analyses of participants' reaction times indicate that the level of linguistic and visual detail encoded reflected the complexity of the task participants had to perform. These results are consistent with "good enough" models of language processing (e.g., Ferreira and Henderson (2007)) in which people process sentences heuristically or syntactically depending on the nature of the task they must perform.M.S.Includes bibliographical referencesby Gaurav Kharkwa
Semantic parsing using lexicalized well-founded grammars
No full textResearch in semantic parsing has focused on developing computational systems capable of simultaneously performing syntactic, i.e. structural, and semantic, i.e., meaning-based, analyses of given sentences. We present an implementation of a semantic parsing system using a constraint-based grammatical formalism called Lexicalized Well-Founded Grammars (LWFGs). LWFGs are a type of Definite Clause Grammars, and use an ontology-based framework to represent syntactico-semantic information in the form of compositional and interpretation constraints. What makes LWFGs particularly interesting is the fact that these are the only constraint-based grammars that are provably learnable. Furthermore, there exist tractable learning algorithms for LWFGs, which make these especially useful in resource-poor language settings. In this thesis, we present a revised parsing implementation for Lexicalized Well-Founded Grammars. Previous work implemented semantic parsers using Prolog, a declarative language, which is slow and does not allow for an easy extension to a stochastic parsing framework. Our implementation utilizes Python's Natural Language Toolkit which not only allows us to easily interface our work with the natural language processing community, but also allows for a future possibility of extending the parser to support broad-coverage and stochastic parsing.M.S.Includes bibliographical referencesby Gaurav Kharkwa
Nonlinear Vibration and Instability of a Randomly Distributed CNT-Reinforced Composite Plate Subjected to Localized In-plane Parametric Excitation
No full textThis study presents a semi-analytical formulation for the nonlinear vibration and dynamic instability of a randomly distributed carbon nanotube-reinforced composite (RD-CNTRC) plate. Three cases of localized in-plane periodic loadings are studied. The analytical stress fields within the RD-CNTRC plate for all the in-plane stress components (σij, (i, j = x, y)) are developed by solving the in-plane elastic problem using Airy's stress approach. The effective mechanical properties of the RD-CNTRC plate are evaluated by the Eshelby-Mori-Tanaka technique. The plate is modeled based on higher-order shear deformation theory (HSDT) in conjunction with the von-Kármán nonlinearity. Using Hamilton's principle, the governing partial differential equations (PDEs) are derived, whose approximate solution is sought, referring to the Galerkin method. The resulting nonlinear ODEs are solved using the Incremental Harmonic Balance (IHB) Method to compute the nonlinear vibration response of the RD-CNTRC plate. Further dropping the nonlinear terms, these ODEs are solved by Bolotin's method to trace the instability region. The proposed semi-analytical method is an effective strategy for studying the influence of different parameters such as agglomeration models, CNT mass fraction, pre-loading, and boundary conditions on the nonlinear vibration and dynamic instability characteristics of the RD-CNTRC plates. The reduced computational effort allows the design phase to be supported in selecting parameters when designing RD-CNTRC plates with stability and vibration requirements
Altered Expression of the CB1 Cannabinoid Receptor in the Triple Transgenic Mouse Model of Alzheimer's Disease
No full textThe endocannabinoid system has gained much attention as a new potential pharmacotherapeutic target in various neurodegenerative diseases, including Alzheimer's disease (AD). However, the association between CB1 alterations and the development of AD neuropathology is unclear and often contradictory. In this study, brain CB1 mRNA and CB1 protein levels were analyzed in 3 × Tg-AD mice and compared to wild-type littermates at 2, 6 and 12 months of age, using in-situ hybridization and immunohistochemistry, respectively. Semiquantitative analysis of CB1 expression focused on the prefrontal cortex (PFC), prelimbic cortex, dorsal hippocampus (DH), basolateral amygdala complex (BLA), and ventral hippocampus (VH), all areas with high CB1 densities that are strongly affected by neuropathology in 3 × Tg-AD mice. At 2 months of age, there was no change in CB1 mRNA and protein levels in 3 × Tg-AD mice compared to Non-Tg mice in all brain areas analyzed. However, at 6 and 12 months of age, CB1 mRNA levels were significantly higher in PFC, DH, and BLA, and lower in VH in 3 × Tg-AD mice compared to wild-type littermates. CB1 immunohistochemistry revealed that CB1 protein expression was unchanged in 3 × Tg-AD at 2 and 6 months of age, while a significant decrease in CB1 receptor immunoreactivity was detected in the BLA and DH of 12-month-old 3 × Tg-AD mice, with no sign of alteration in other brain areas. The altered CB1 levels appear, rather, to be age-and/or pathology-dependent, indicating an involvement of the endocannabinoid system in AD pathology and supporting the ECS as a potential novel therapeutic target for treatment of AD
Poverty comparisons with absolute poverty lines estimated from survey data
No full text"The objective of measuring poverty is usually to make comparisons over time or between two or more groups. Common statistical inference methods are used to determine whether an apparent difference in measured poverty is statistically significant. Studies of relative poverty have long recognized that when the poverty line is calculated from sample survey data, both the variance of the poverty line and the variance of the welfare metric contribute to the variance of the poverty estimate. In contrast, studies using absolute poverty lines have ignored the poverty line variance, even when the poverty lines are estimated from sample survey data. Including the poverty line variance could either reduce or increase the precision of poverty estimates, depending on the specific characteristics of the data. This paper presents a general procedure for estimating the standard error of poverty measures when the poverty line is estimated from survey data. Based on bootstrap methods, the approach can be used for a wide range of poverty measures and methods for estimating poverty lines. The method is applied to recent household survey data from Mozambique. When the sampling variance of the poverty line is taken into account, the estimated standard errors of Foster-Greer- Thorbecke and Watts poverty measures increase by 15 to 30 percent at the national level, with considerable variability at lower levels of aggregation." -- Authors' AbstractPoverty measurement, Surveys -- Statistical methods, Household surveys, Poverty lines
The role of endocannabinoid signaling in the molecular mechanisms of neurodegeneration in Alzheimer's disease
No full textAlzheimer's disease (AD) is the most common form of progressive neurodegenerative disease characterized by cognitive impairment and mental disorders. The actual cause and cascade of events in the progression of this pathology is not fully determined. AD is multifaceted in nature and is linked to different multiple mechanisms in the brain. This aspect is related to the lack of efficacious therapies that could slow down or hinder the disease onset/progression. The ideal treatment for AD should be able to modulate the disease through multiple mechanisms rather than targeting a single dysregulated pathway. Recently, the endocannabinoid system emerged as a novel potential therapeutic target to treat AD. In fact, exogenous and endogenous cannabinoids seem to be able to modulate multiple processes in AD, although the mechanisms that are involved are not fully elucidated. This review provides an update of this area. In this review, we recapitulate the role of endocannabinoid signaling in AD and the probable mechanisms through which modulators of the endocannabinoid system provide their effects, thus highlighting how this target might provide more advantages over other therapeutic targets
Aberrant insulin signaling in Alzheimer’s disease: current knowledge
No full textAlzheimer’s disease (AD) is the most common form of dementia affecting elderly people. AD is a multifaceted pathology characterized by accumulation of extracellular neuritic plaques, intracellular neurofibrillary tangles (NFTs) and neuronal loss mainly in the cortex and hippocampus. AD etiology appears to be linked to a multitude of mechanisms that have not been yet completely elucidated. For long time, it was considered that insulin signaling has only peripheral actions but now it is widely accepted that insulin has neuromodulatory actions in the brain. Insulin signaling is involved in numerous brain functions including cognition and memory that are impaired in AD. Recent studies suggest that AD may be linked to brain insulin resistance and patients with diabetes have an increased risk of developing AD compared to healthy individuals. Indeed insulin resistance, increased inflammation and impaired metabolism are key pathological features of both AD and diabetes. However, the precise mechanisms involved in the development of AD in patients with diabetes are not yet fully understood. In this review we will discuss the role played by aberrant brain insulin signaling in AD. In detail, we will focus on the role of insulin signaling in the deposition of neuritic plaques and intracellular NFTs. Considering that insulin mitigates beta-amyloid deposition and phosphorylation of tau, pharmacological strategies restoring brain insulin signaling, such as intranasal delivery of insulin, could have significant therapeutic potential in AD treatment
Framework for Investigating Functional Encryption
No full textThesis: M. Eng. in Computer Science and Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 95-102).In functional encryption, keys are associated with functions, and ciphertexts with messages. Decrypting a message with a key gives the evaluation of the associated function on that message. We look at bounded-collusion functional encryption, where the number of keys for which security is guaranteed is bounded, as it is possible to realize using standard building blocks. For such schemes we aim to understand their practicality for real-world applications. There are some theoretical constructions of functional encryption, but few implementations. We rectify this by creating the Framework for Investigating Functional Encryption (FIFE). FIFE includes the first implementations for Sahai and Seyalioglu's one-key scheme (CCS 2010), and Gorbunov, Vaikuntanathan, and Wee's bounded-collusion scheme (CRYPTO 2012), and is easily extendable. We used FIFE to evaluate their performance, and to measure the impact of using different public-key or secret-key encryption schemes, bounds on collusion, and security levels, for interesting classes of functions.by Gaurav Singh.M. Eng. in Computer Science and Engineerin
Design and analysis of fiber reinforced elastomeric enclosures with application in upper arm orthosis
No full textFiber Reinforced Elastomeric Enclosures (FREEs) are soft pneumatic actuators that deform in a predetermined fashion upon inflation. They are constructed using a hollow elastomeric cylinder reinforced by two families of helical fibers. This thesis analyzes the deformation behavior of FREEs by formulating a simple calculus of variations problem that involves constrained maximization of the enclosed volume. The model accurately captures the deformed shape (kinematics) for FREEs with any general fiber angle orientation, and its relation with actuation pressure, material properties and applied load (kinetostatics). The accuracy of the model is verified by benchmarking with existing models for a popular McKibben Pneumatic Artificial muscle (PAM) actuator with two helically wrapped families of fibers having equal and opposite orientations. For FREEs with any general fiber orientations and other novel designs with no prior literature, the model is validated experimentally. This model is deemed to be useful in the design synthesis of fiber reinforced elastomeric actuators for any desired motion and force requirement. FREEs are soft, compliant, and have a high power to weight ratio, which makes them suitable for orthotic devices for upper extremities.
The second part of the thesis considers the design and fabrication of a soft pneumatic sleeve for arm orthosis that uses a contracting FREE is shown. The sleeve is designed to reduce wrist loads in patients that use crutches for ambulation, thereby reducing the risk of joint injury. It forms an alternate load path between the crutch and the forearm, circumventing the wrist. The constricting force generated by the sleeve on the arm is analyzed by a string model and validated with experiments.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-12-01The student, Gaurav Singh, accepted the attached license on 2016-12-06 at 16:32.The student, Gaurav Singh, submitted this Thesis for approval on 2016-12-06 at 16:48.This Thesis was approved for publication on 2016-12-07 at 08:36.DSpace SAF Submission Ingestion Package generated from Vireo submission #10459 on 2017-02-28 at 14:43:20Made available in DSpace on 2017-03-01T17:02:06Z (GMT). No. of bitstreams: 2
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