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Communication infratructure for a distibuted actor systemGandhi, Rajiv 30 March 2010 (has links)
<p>The goal of this project was to develop part of the environment that would allow the
creation of distributed applications in ACT++. ACT++ is a programming framework in
which concurrent object-oriented programs can be written in C++. The concurrent objects
in ACT ++ are called actors. Specifically, the project is concerned with the development of
a communication infrastructure that configures a collection of heterogeneous machines for
use in the distributed version of ACT++.</p>
<p>
A utility, "ActorControl," was implemented through which the user can specify how
ACT ++ is to run on each of the nodes by means of a configuration file. The "ActorControl"
utility starts a process on each of the nodes specified in the configuration file and establishes
TCP socket based connections among all of them. To simplify the communication between
the different nodes, a special type of actor called an interface actor is used. Instead of
issuing communication requests directly to sockets, a request is directed to an interface
actor that is responsible for that socket. A related project is concerned with the problems
of creation, destruction and invocation of the methods on the remote machine.</p>
<p>
Thus the project consists of two parts. The first part is the implementation of the
"Actor Control" utility that establishes socket connections among all the nodes participating
in the distributed ACT ++. The second part is the implementation of the interface actors
that are present at each end of the connection between any pair of machines.</p> / Master of Science
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Early events in cytokine receptor signalingGandhi, Hetvi 27 February 2014 (has links)
Ligand-activated signal transduction is a process critical to cell survival and function as it serves as a means of communication between the cells and their environment. Endocytosis is generally thought to down-regulate incoming signals by reducing the surface availability of receptors. However, increasing evidence in many systems suggests a notion which is referred to as the „signalling endosome" hypothesis - that endocytosis can also actively contribute to signalling apart from clearance of activated receptors and thereby attenuation of signalling. The functional aspect of signalling endosomes has been well-characterized in several pathways including RTK and TGF-β signalling. There are, however, various other signalling pathways where the active mechanism of endocytotic regulation is yet to be understood.
In this study, we probe this aspect in the cytokine signalling system, where the receptors are known to internalize but the significance of such internalization and precise mechanism is unclear. My thesis aims to elucidate the function and molecular details of internalization of cytokine receptor using interleukin-4 receptor (IL-4R) signalling as a model. IL-4 and IL-13 ligands can induce assembly of three distinct complexes: IL4 induced IL-4Rα – IL-2Rγ (type I), IL-4 induced IL-4Rα – IL-13Rα1 (type II) or the IL-13 induced IL-13Rα1-IL-4Rα (type II). The formation of any of these complexes triggers signalling through the JAK/STAT pathway. However, models of how the oligomerization of the transmembrane receptors and activation takes place are very diverse and lack a clear molecular and biophysical understanding of the underlying receptor dynamics.
Previous results of the lab had shown that the affinities between subunits are low, precluding complex formation at the plasma membrane at physiological concentrations. In addition, IL-4R subunits localize in to endosomal structures adjacent to the plasma membrane. It had already been shown that the shared IL-4R subunit IL-2Rγ is internalized by a specific, actin dependent, Rac1/Pak1 regulated endocytosis route in the IL-2 context. We could show that pharmacological suppression of this endocytosis pathway also prevented IL-4 induced JAK/STAT signalling, placing endocytosis upstream of signalling.
Here I show using immuno-EM techniques that these endosomal structures are multivesicular bodies. Importantly, I could show that receptor subunits are highly enriched in the limiting membrane of these endosomes relative to the adjacent plasma membrane. Using quantitative loading assays I could furthermore demonstrate that this enrichment is achieved by constitutive internalization of receptors from the cell surface into cortical endosomes. The trafficking kinetics of the receptor subunits is independent of ligand occupancy. Pharmacological inhibition shows that receptors and ligand traffic via the previously identified Rac1/Pak1 pathway. Finally, Vav2 was identified as a candidate Guanine Exchange Factor (GEF) that may regulate Rac1 activity and thereby control the actin polymerization cascade driving IL-4R endocytosis. Immunoprecipitations showed that Vav2 interacts both with the cytoplasmic tail region of the receptors and the receptor associated 2 kinase JAK3. Vav2 may thus couple the receptor/JAK complexes to the Rac1/Pak1 mediated endocytosis route.
Taken together, our results suggests that stable „signalling endosomes‟ adjacent to the plasma membrane act as enrichment centres, where ligand and receptor concentrations are locally increased by constitutive trafficking. The confined environment of the endosome then compensates for the weak affinities between the ligand and receptor and facilitates ligand-mediated receptor dimerization. Importantly, overexpression of both type II IL-4R subunits renders signal transduction resistant to endocytosis inhibition, strongly suggesting that the critical factor effecting signalling is sufficient concentration, which the endosomes facilitate achieving. The endosomes are thus dispensable as signalling scaffolds when the receptors are in sufficient concentration, where activated receptors could interact with downstream pathway components.
Endocytosis thus provides a crucial means for the signalling process to overcome the thermodynamic hurdles for receptor oligomerization. In conclusion, our data propose a novel, purely thermodynamic role of endosomes in regulating cytokine receptor signalling not seen in any other signalling pathway.
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Using Gaze Tracking to Tackle Duplicate Questions on Community Based Question Answering Websites: A Case Study of IfixitGandhi, Pankti 01 June 2018 (has links)
The number of unanswered questions on Community based Question Answering (CQA) websites has increased significantly due to the rising number of duplicate questions. This is a serious problem, one that could lead to the decline of such beneficial websites.
This thesis presents novel avenues that use gaze tracking technology and behavioral testing to tackle this problem. Based on prior studies on web search behaviors, we assumed that adding contextual information (snippets) to proposed related questions displayed on the `Ask a Question' page of the CQA website iFixit would improve the asker experience and reduce their tendency to post a new duplicate question. The first lab experiment where this web page was redesigned and compared to the original one was conducted on 8 participants. Results confirmed that participants were more likely to find an answer to their question on the redesigned page. A second experiment, conducted remotely and on a larger sample of 74 participants, aimed to discover strategic attributes that increase the perceived similarity of question pairs. These attributes were used in the third lab experiment (20 participants) to redesign and assess the snippets from Experiment 1. Results indicated that snippets containing `symptom(s)' and `cause(s)' attributes constitute an incremental improvement over basic snippets: they are perceived as slightly more relevant and require significantly less gaze fixations on the asker's part.
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Sensor-Based Methods for Characterizing Technology Impact in Low-Resource SettingsGandhi, Amit 25 February 2022 (has links)
The development of appropriate technologies aimed at improving the livelihoods of people living in poverty has been a focal area of international aid. These technologies can have a transformative impact on economic growth and individual health when designed and implemented properly. Long-term usage and performance of these products are difficult to measure accurately through self-reporting, and the use of low-cost sensors allows researchers and designers to better assess their overall impact. The first part of the thesis presents a methodology for implementing sensor technologies in lowresource settings. The second part of the thesis presents the design of a novel sensorbased data collection system that was developed for design and impact research. The third part of this thesis presents three case studies where this system is used to evaluate wheelchairs, improved cookstoves, and evaporative coolers. The wheelchair case study in Indonesia compares the performance of different wheelchairs ranging in cost from $100 to $300 and finds little variation between improved wheelchairs in frequency of use and distance traveled. All of the improved wheelchairs show significant benefits when compared to hospital style chairs. The improved cookstove case study demonstrates the effectiveness of using a household air pollution monitor in combination with a stove use monitor to identify cooking events and measure cookstove adoption in a research pilot in India. Particulate matter concentrations in all of the households using improved cookstoves were significantly higher than World Health Organization (WHO) recommended levels. The evaporative cooling case study demonstrates that clay pot coolers are effective at keeping fresh produce more than 5°C cooler than ambient temperatures in the hottest months of the year in Mali. The final part of this thesis examines the ethical challenges that may arise from incorporating sensors for field research and best practices for addressing some of these concerns. / Ph.D.
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Extracting Symptoms from Narrative Text using Artificial IntelligenceGandhi, Priyanka 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Electronic health records collect an enormous amount of data about patients. However, the information about the patient’s illness is stored in progress notes that are in an un- structured format. It is difficult for humans to annotate symptoms listed in the free text. Recently, researchers have explored the advancements of deep learning can be applied to pro- cess biomedical data. The information in the text can be extracted with the help of natural language processing. The research presented in this thesis aims at automating the process of symptom extraction. The proposed methods use pre-trained word embeddings such as BioWord2Vec, BERT, and BioBERT to generate vectors of the words based on semantics and syntactic structure of sentences. BioWord2Vec embeddings are fed into a BiLSTM neural network with a CRF layer to capture the dependencies between the co-related terms in the sentence. The pre-trained BERT and BioBERT embeddings are fed into the BERT model with a CRF layer to analyze the output tags of neighboring tokens. The research shows that with the help of the CRF layer in neural network models, longer phrases of symptoms can be extracted from the text. The proposed models are compared with the UMLS Metamap tool that uses various sources to categorize the terms in the text to different semantic types and Stanford CoreNLP, a dependency parser, that analyses syntactic relations in the sentence to extract information. The performance of the models is analyzed by using strict, relaxed, and n-gram evaluation schemes. The results show BioBERT with a CRF layer can extract the majority of the human-labeled symptoms. Furthermore, the model is used to extract symptoms from COVID-19 tweets. The model was able to extract symptoms listed by CDC as well as new symptoms.
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Saturated Solution Effects on Crystal Breakage Experiments in Stirred VesselsGandhi, Devkant 06 August 2011 (has links)
Crystallization is a key unit operation in the fine chemical and pharmaceutical industries, many of which employ batch stirred vessels for crystallization. Although using stirred vessels for crystallization has advantages such as better mixing and faster cooling, one of the disadvantages is that due to the presence of mechanical parts in the vessel such as baffles, impeller etc., crystals break up while stirring and generate unwanted secondary nucleation. This process contributes to a wide crystal size distribution with a smaller than desired mean crystal size. For studying crystal breakage phenomenon, experimentalists choose to use nonsolvents for crystal breakage experiments to isolate breakage from simultaneously occurring phenomena such as Ostwald-ripening, aging and agglomeration. Although performing experiments in non-solvents eliminates other phenomena and helps isolate breakage, the results can not always be correlated to saturated solutions due to density and viscosity differences between the two conditions. In this research, the effects of Ostwald ripening, aging and agglomeration on the crystal size and shape distributions are quantitatively measured. Micro and macro scale experiments were performed in both non-solvents and saturated solutions and the results were compared to determine the effects. Both in situ focused beam reflectance method (FBRM) and off-line analyses were performed to characterize the crystal size distributions. Results from experiments show that there is significant difference between the breakage behavior of crystals in non-solvents and in saturated solutions, mplying significant impacts of Ostwald ripening, aging, agglomeration and dissolution in saturated solutions. Calculations using Zwietering correlation also show that the difference between the viscosities and densities in the two systems may also be a contributing factor to the difference in the breakage profiles. It was also found that growth rates of crystals can differ when they are subjected to stress and strain. In macroscale experiments, dissolution was found to have a significant impact on the crystal size distribution. Abrasion was found to be the dominating fracture mechanism for most systems. Extent of breakage and morphological changes were found to be dependent on stirring rates, suspension density, shape and hardness of crystals and the type of system.
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Analyzing and defending against adverserial samples in machine learning algorithmsGandhi, Rajveer January 2020 (has links)
No description available.
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Analysis of Sensing Technologies for Collision Avoidance for Small Rotary-Wing Uncrewed Aerial VehiclesGandhi, Manav 22 June 2022 (has links)
As UASs (Uncrewed Aerial System) are further integrated into operations, the need for on-board environmental perception and sensing is necessitated. An accurate and reliable creation of a 3D map resembling an aircraft's surrounding is crucial for accurate collision avoidance and path planning. Consumer UASs are now being equipped with sensors to fulfill such a requirement – but no system has been proven as capable of being fully relied upon. With many sensing options available, there are several constraints regarding size, weight, and cost that must be considered when developing a sensing solution. Additionally, the robustness of the system must not be diminished when moving to a system that minimizes size, weight, or cost.
An analysis of different sensing technologies that small rotary-wing aircraft (below 25kg) can be outfitted with for collision avoidance is performed. Several sensing technologies are initially compared through technology analyses and controlled experiments. The topmost systems were then further integrated onto a small low-cost quadcopter for flight testing and data acquisition. Ultimately, a fusion between stereo vision imagery and radar was deemed the most reliable method for providing environmental data needed for collision avoidance. / Master of Science / As drones become further integrated in several industries, it is important that their operations are conducted in a safe manner. Most drones today have a limited ability to sense and react to the environment around them. This results in the risk of the drone colliding with people or obstacles such as buildings, trees, light poles, etc. Thus, an accurate and reliable creation of a 3D map resembling a drone's surrounding is crucial for collision avoidance. This would allow for the avoidance of people and obstacles during automated flights where the drone may encounter obstacles during flight. With many sensing options available, there are several constraints regarding size, weight, and cost that must be considered when developing a sensing solution. Additionally, the reliability of the system must be of the topmost priority to ensure safe operations.
An analysis of different sensing technologies that small rotary-wing aircraft (below 25kg) can be outfitted with for collision avoidance is performed. Rotary-wing aircraft are a specific subset of drones that are capable of vertical takeoff, landing, and hover (i.e not planes). An analysis regarding the several sensing technologies was first conducted to select the three topmost solutions. These solutions were then integrated onto a small low-cost quadcopter for data collection and flight testing. Ultimately, a combination of stereo vision imagery and radar was deemed the most reliable method for collecting collision avoidance data.
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The effect of treatment with the mast cell stabilizer ketotifen fumarate on chronic widespread pain in teenagersGandhi, Isha January 2022 (has links)
No description available.
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A safe-parking framework to handle faults in nonlinear process systemsGandhi, Rahul 03 1900 (has links)
<p> This thesis considers the problem of control of nonlinear process systems subject to
input constraints and faults in the control actuators and process equipments. Faults
are considered that preclude the possibility of continued operating at the nominal
equilibrium point and a framework (which we call the safe-parking framework) is
developed to enable efficient resumption of nominal operation upon fault-recovery.
First, Lyapunov-based model predictive controllers, that allow for an explicit characterization
of the stability region subject to constraints on the manipulated input,
are designed. The stability region characterization is utilized in selecting 'safe-park'
points from the safe-park candidates (equilibrium points subject to failed actuators).
This safe-park point is chosen as a temporary operating point where process is to
be operated during fault rectification. This ensures that process can be safely operated
during fault rectification and the nominal operation can be resumed upon fault
recovery. When multiple candidate safe-park points are available, performance considerations,
such as ease of transition from and to the safe-park point and cost of
running the process at the safe-park point, are quantified and utilized in choosing the
optimal safe-park point. </p> <p> Next, we extend the safe-parking framework to handle practical issues such as plant-model mismatch, disturbances and unavailability of all process state measurements.
\i\Te first consider the presence of constraints and uncertainty and develop
a robust Lyapunov-based model predictive controller. This controller is utilized to
characterize robust stability region which, subsequently, is utilized to select 'safepark'
points. Then we consider the problem of availability of limited measurements.
An output feedback Lyapunov-based model predictive controller, with high-gain observer
to estimate unmeasured states, is formulated and its stability region explicitly
characterized. An algorithm is then presented that accounts for the estimation errors
in the implementation of the safe-parking framework. </p> <p> We then further extend the framework to handle faults in large scale chemical
plants where multiple process units are connected via material, energy and information
streams. In plant-wide setting, the safe-park point for the faulty unit is chosen
such that the safe-parking has no or minimum effect on downstream units, and hence,
the nominal operation in the downstream units can be continued. Next we consider
the scenario where no viable safe-park point for the faulty unit exists such that its
effect can be completely absorbed in the subsequent unit. A methodology is developed
that allows simultaneous safe-parking of the consecutive units. The efficacy of
the proposed framework is illustrated using a chemical reactor example, a styrene
polymerization process and two CSTRs in series example. </p> <p> Finally, we demonstrate the efficacy of proposed Lyapunov based Model Predictive
Controller and Safe-Parking framework on a polymerization reactor model to control
the polymerization reactor and to handle faults that dont allow continuation of the
nominal operation in the reactor. </p> / Thesis / Doctor of Philosophy (PhD)
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