Communication Aware Mobile Robot Teams

The type of scenarios that could benefit from a team of robots that are able to self configure into an ad-hoc multi-hop mobile communication network while completing a task in an unknown environment, range from search and rescue in a partially collapsed building to providing a security perimeter around a region of interest. In this thesis, we present a hybrid system that enables a team of robots to maintain a prescribed end-to-end data rate while moving through a complex unknown environment, in a distributed manner, to complete a specific task. This is achieved by a systematic decomposition of the real-time situational awareness problem into subproblems that can be efficiently solved by distributed optimization. The validity of this approach is demonstrated through multiple simulations and experiments in which the a team of robots is able to accurately map an unknown environment and then transition to complete a traditional situational awareness task. We also present MCTP, a lightweight communication protocol that is specifically designed for use in ad-hoc multi-hop wireless networks composed of low-cost low-power transceivers. This protocol leverages the spatial diversity found in mobile robot teams as well as recently developed robust routing systems designed to minimize the variance of the end-to-end communication link. The combination of the hybrid system and MCTP results in a system that is able to complete a task, with minimal global coordination, while providing near loss-less communication over an ad-hoc multi-hop network created by the members of the team in unknown environments

Security Applications of Formal Language Theory

We present an approach to improving the security of complex, composed systems based on formal language theory, and show how this approach leads to advances in input validation, security modeling, attack surface reduction, and ultimately, software design and programming methodology. We cite examples based on real-world security flaws in common protocols representing different classes of protocol complexity. We also introduce a formalization of an exploit development technique, the parse tree differential attack, made possible by our conception of the role of formal grammars in security. These insights make possible future advances in software auditing techniques applicable to static and dynamic binary analysis, fuzzing, and general reverse-engineering and exploit development. Our work provides a foundation for verifying critical implementation components with considerably less burden to developers than is offered by the current state of the art. It additionally offers a rich basis for further exploration in the areas of offensive analysis and, conversely, automated defense tools and techniques. This report is divided into two parts. In Part I we address the formalisms and their applications; in Part II we discuss the general implications and recommendations for protocol and software design that follow from our formal analysis

Bioactive Membranes and Nanocoatings for Guided Tissue Regeneration in Periodontal Diseases

Periodontal diseases are highly prevalent in population of all ages. Initiated by bacterial accumulation at the interface of bone and soft tissue, they lead to the loss of gingival tissue adherent to the root surface and, eventually, to tooth loss. Regenerative approaches to treat periodontitis offer exciting possibilities; guided tissue/bone regeneration (GTR/GBR) approaches are promising because, through the insertion of a physical barrier, they can exclude unwanted epithelial and gingival connective tissue cells from the healing area and allow bone tissue cells to repopulate the bony defect. Different resorbable and non-resorbable membranes have been developed. Expanded polytetrafluoroethylene (ePTFE) membranes are the “gold standard” for GTR/GBR applications but they are non-resorbable and they need a second surgical operation to repair dehiscence. Biodegradable synthetic membranes avoid a second surgical operation but they show drawbacks concerning the capacity of space maintenance, early/late absorption, mechanical properties and bacterial infection during degradation. Collagen membranes have advantages related to collagen biological properties but are characterized by low mechanical strength. The “ideal” membrane for use in periodontal regenerative therapy has yet to be developed. The main purpose of this thesis was the design of biologically active products, with improved osteoconductive and antimicrobial properties, for GTR/GBR applications in periodontal diseases. In a more traditional approach, a commercially available membrane (based on PTFE) was surface modified by environmentally friendly technique to allow rapid bone re-growth and exert antimicrobial action. Binding ability of 3,4-dihydroxy-DL-phenylalanine (DOPA) to samples of any type, size and shape was exploited to improve PTFE surface properties. In particular, a hydroxyapatite nanoparticles (HAp) coating was applied by DOPA self-polymerization on PTFE surface in the presence of HAp nanoparticles, to promote the bone re-growth properties of PTFE films. Chemical composition analysis demonstrated the successful deposition of polyDOPA and HAp on coated films. Morphological and topographical characterizations further confirmed the total surface coverage causing an increase in surface roughness (39.8±5.2 nm for PTFE films vs 236.5±12.0 nm for polyDOPA/HAp coated films) and wettability (110.8±2.8° for PTFE films vs 46.1±12.4° for polyDOPA/HAp coated samples). A discontinuous HAp coating was still present after 14 days of incubation of coated PTFE films in phosphate buffered saline. Pre-osteoblastic MC3T3-E1 cells cultured on polyDOPA/HAp coated films showed a pronounced increase of cell proliferation and adhesion. Regarding the antimicrobial action, silver nanoparticles (AgNPs) have been selected due to their good antimicrobial efficacy against bacteria, viruses and other eukaryotic micro-organisms. The successful deposition of AgNPs on PTFE surface, through the functional groups of DOPA, has been demonstrated by physico-chemical and morphological analyses. Nanoparticles exhibited a diameter around 68 nm and were homogeneously distributed on the surface. In vitro cell tests with fibroblast NIH 3T3 cells showed an inhibition of cells proliferation on AgNPs functionalized films after 3 days of culture, while good cell adhesion was observed with cells randomly distributed on sample surface and extensively spread. The antimicrobial efficiency was demonstrated against S. aureus and Ag release was sustained for at least 14 days. The mussel-inspired coated PTFE membrane could find potential application as GTR/GBR strategy for the treatment of periodontal diseases. In a highly innovative approach, a bi-layered bioabsorbable membrane was developed, by the assembly of a compact and a porous layer. GTR/GBR membranes can be considered an interface-implant between gingival connective tissue/epithelium and alveolar bone tissue. Developing a multi-component structure membrane with compositional and structural gradients that meet the local functional requirements could represent a challenge. Binary blends of poly(DL-lactide-co-ε-caprolactone) (PLCL) and poly(DL-lactide-co-glycolide) (PLGA) with various compositions (100/0, 75/25, 50/50, 25/75, 0/100 wt/wt) were prepared by solvent casting technique as compact layer of the bi-layered membrane. Morphological analysis did not evidence phase separation between PLCL and PLGA and the behavior of blend glass transition temperatures as a function of composition suggested some degree of blend compatibility. However, blends elastic modulus showed a negative deviation from the additive law of mixture. In vitro cell tests with fibroblast NIH 3T3 cells showed improved cell adhesion and growth on PLCL/PLGA 25/75 blend. Due to its biocompatibility, its superior mechanical properties (E=10.2±0.6 MPa, σmax=0.8±0.0 MPa, and εmax=548.8±57.9%) and compatibility between the components, PLCL/PLGA 25/75 blend was selected for this application. Compact films were then surface modified via layer-by-layer (LbL) technique to enhance fibroblast cell response and confer antibacterial efficacy. A surface priming treatment (aminolysis) was optimized before depositing LbL coating. The following parameters were used: C=0.08 g/mL, t=8 min and T=37 °C. Then, multilayered chondroitin sulfate/chitosan (CHS/CH) coatings were deposited on the aminolysed films. The feasibility of multilayer coating was confirmed by QCM-D analysis. Further confirmations derived from water contact angle measurements (contact angle jumped alternatively between 45° and 65° depending on the outmost layer component) and FTIR-ATR analysis (appearance of absorbance peaks characteristics of CHS and CH). FTIC-labelled CH was also employed to follow LbL built up by fluorescence microscopy analysis. In vitro cell tests demonstrated the ability of coated samples to improve NIH 3T3 fibroblast adhesion and proliferation. Biocompatibility properties increased with increasing the layer number and were superior in the case of CH-terminating layers but no antibacterial activity was observed for films coated with 16 layers. Three dimensional sponge-like composite membranes fabricated by freeze-drying, with a composition similar to natural bone, and based on β-tricalcium phosphate (TCP) dispersed in a chitosan/gelatin (CH/G) network cross-linked with genipin (GP) and disodium phosphate salt (DSP) were developed as porous layer of the bi-layered device. Three membranes were developed (CH/G, CH/G+GP-DSP and CH/G/TCP+GP-DSP) and characterized. Successful double cross-linking of CH/G network was confirmed by Kaiser test, chemical and thermal analysis. All membranes showed a typical foam-like morphology with interconnected pores having an average diameter of 100-200 μm. Both cross-linking and TCP presence caused a marked increase of membrane stability in water solution, as well as of tensile modulus and maximum tensile strength (respectively, 14.9±5.1 MPa and 0.6±0.0 MPa for CH/G, and 29.4±2.7 MPa and 0.8±0.1 MPa for CH/G/TCP+GP-DSP.). Compared to CH/G samples, CH/G+GP-DSP and CH/G/TCP+GP-DSP membranes showed improved MG-63 human osteoblast-like cells response, in terms of cell viability and morphology. The assembly process of the compact and porous layer was developed based on the insertion of an intermediate adhesive layer composed by a polyvinylpyrrolidone/polyethylene glycol 70/30 wt/wt blend. Preliminary characterizations were carried out. Morphological analysis did not show changes in compact and porous layer structure due to the presence of the adhesive. The final device showed an elastic modulus of about 61 MPa in dry condition that markedly decreased in wet state (to about 5 MPa). Qualitative analysis of membrane manageability revealed its ability to adapt to mandible conformation after immersion in physiological solution. Despite the need for additional tests, the bi-layered membrane appeared promising for GTR/GBR applications

Osteochondral Tissue Engineering: The Potential of Electrospinning and Additive Manufacturing

The socioeconomic impact of osteochondral (OC) damage has been increasing steadily over time in the global population, and the promise of tissue engineering in generating biomimetic tissues replicating the physiological OC environment and architecture has been falling short of its projected potential. The most recent advances in OC tissue engineering are summarised in this work, with a focus on electrospun and 3D printed biomaterials combined with stem cells and biochemical stimuli, to identify what is causing this pitfall between the bench and the patients' bedside. Even though significant progress has been achieved in electrospinning, 3D-(bio)printing, and induced pluripotent stem cell (iPSC) technologies, it is still challenging to artificially emulate the OC interface and achieve complete regeneration of bone and cartilage tissues. Their intricate architecture and the need for tight spatiotemporal control of cellular and biochemical cues hinder the attainment of long-term functional integration of tissue-engineered constructs. Moreover, this complexity and the high variability in experimental conditions used in different studies undermine the scalability and reproducibility of prospective regenerative medicine solutions. It is clear that further development of standardised, integrative, and economically viable methods regarding scaffold production, cell selection, and additional biochemical and biomechanical stimulation is likely to be the key to accelerate the clinical translation and fill the gap in OC treatment

2015 IMSAloquium, Student Investigation Showcase

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Dynamics of embodied dissociated cortical cultures for the control of hybrid biological robots.

The thesis presents a new paradigm for studying the importance of interactions between an organism and its environment using a combination of biology and technology: embodying cultured cortical neurons via robotics. From this platform, explanations of the emergent neural network properties leading to cognition are sought through detailed electrical observation of neural activity. By growing the networks of neurons and glia over multi-electrode arrays (MEA), which can be used to both stimulate and record the activity of multiple neurons in parallel over months, a long-term real-time 2-way communication with the neural network becomes possible. A better understanding of the processes leading to biological cognition can, in turn, facilitate progress in understanding neural pathologies, designing neural prosthetics, and creating fundamentally different types of artificial cognition. Here, methods were first developed to reliably induce and detect neural plasticity using MEAs. This knowledge was then applied to construct sensory-motor mappings and training algorithms that produced adaptive goal-directed behavior. To paraphrase the results, most any stimulation could induce neural plasticity, while the inclusion of temporal and/or spatial information about neural activity was needed to identify plasticity. Interestingly, the plasticity of action potential propagation in axons was observed. This is a notion counter to the dominant theories of neural plasticity that focus on synaptic efficacies and is suggestive of a vast and novel computational mechanism for learning and memory in the brain. Adaptive goal-directed behavior was achieved by using patterned training stimuli, contingent on behavioral performance, to sculpt the network into behaviorally appropriate functional states: network plasticity was not only induced, but could be customized. Clinically, understanding the relationships between electrical stimulation, neural activity, and the functional expression of neural plasticity could assist neuro-rehabilitation and the design of neuroprosthetics. In a broader context, the networks were also embodied with a robotic drawing machine exhibited in galleries throughout the world. This provided a forum to educate the public and critically discuss neuroscience, robotics, neural interfaces, cybernetics, bio-art, and the ethics of biotechnology.Ph.D.Committee Chair: Steve M. Potter; Committee Member: Eric Schumacher; Committee Member: Robert J. Butera; Committee Member: Stephan P. DeWeerth; Committee Member: Thomas D. DeMars

06. 2015 IMSAloquium Student Investigation Showcase

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On Improving Efficiency of Data-Intensive Applications in Geo-Distributed Environments

Distributed systems are pervasively demanded and adopted in nowadays for processing data-intensive workloads since they greatly accelerate large-scale data processing with scalable parallelism and improved data locality. Traditional distributed systems initially targeted computing clusters but have since evolved to data centers with multiple clusters. These systems are mostly built on top of homogeneous, tightly integrated resources connected in high-speed local-area networks (LANs), and typically require data to be ingested to a central data center for processing. Today, with enormous volumes of data continuously generated from geographically distributed locations, direct adoption of such systems is prohibitively inefficient due to the limited system scalability and high cost for centralizing the geo-distributed data over the wide-area networks (WANs). More commonly, it becomes a trend to build geo-distributed systems wherein data processing jobs are performed on top of geo-distributed, heterogeneous resources in proximity to the data at vastly distributed geo-locations. However, critical challenges and mechanisms for efficient execution of data-intensive applications in such geo-distributed environments are unclear by far. The goal of this dissertation is to identify such challenges and mechanisms, by extensively using the research principles and methodology of conventional distributed systems to investigate the geo-distributed environment, and by developing new techniques to tackle these challenges and run data-intensive applications with efficiency at scale. The contributions of this dissertation are threefold. Firstly, the dissertation shows that the high level of resource heterogeneity exhibited in the geo-distributed environment undermines the scalability of geo-distributed systems. Virtualization-based resource abstraction mechanisms have been introduced to abstract the hardware, network, and OS resources throughout the system, to mitigate the underlying resource heterogeneity and enhance the system scalability. Secondly, the dissertation reveals the overwhelming performance and monetary cost incurred by indulgent data sharing over the WANs in geo-distributed systems. Network optimization approaches, including linear- programming-based global optimization, greedy bin-packing heuristics, and TCP enhancement, are developed to optimize the network resource utilization and circumvent unnecessary expenses imposed on data sharing in WANs. Lastly, the dissertation highlights the importance of data locality for data-intensive applications running in the geo-distributed environment. Novel data caching and locality-aware scheduling techniques are devised to improve the data locality.Doctor of Philosoph

Hackback: Permitting Retaliatory Hacking by Non-State Actors as Proportionate Countermeasures to Transboundary Cyberharm

Cyberespionage has received even greater attention in the wake of reports of persistent and brazen cyberexploitation of U.S. and Canadian firms by the Chinese military. But the recent disclosures about NSA surveillance programs have made clear that a national program of cyberdefense of private firms\u27 intellectual property is politically infeasible. Following the lead of companies like Google, private corporations may increasingly resort to the use of self-defense, hacking back against cross-border incursions on the Internet. Most scholarship, however, has surprisingly viewed such actions as outside the ambit of international law. This Note provides a novel account of how international law should govern cross-border hacks by private actors, and especially hackbacks. It proposes that significant harm to a state\u27s intellectual property should be viewed as transboundary cyberharm and can be analyzed under traditional international legal principles, including the due diligence obligation to prevent significant harm to another state\u27s territorial sovereignty. Viewing cyber espionage within this framework, international law may presently permit states to allow private actors to resort to self-defense as proportionate countermeasures. By doing so, this Note offers a prescription for how states might regulate private actors to prevent unnecessary harm or vigilantism while preserving the right of self-defense