Constrained Environments Research Articles

Nonresonant and Local Field Effects in Peptidic Nanostructures Bearing Oligo(p-phenylenevinylene) Units

Peptide nanostructures with built-in electronic functions offer a new platform for biomaterial science. In this report, we interrogate the influences of the immediate peptide environment around oligo(p-phenylenevinylene) (OPV3) electronic units embedded within one-dimensional peptide nanostructures on the resulting photophysics as assessed by UV-vis, photoluminescence (PL), and circular dichroism spectroscopies. To do so, we studied peptide-core-peptide molecules where the core was either OPV3 or an aliphatic n-decyl chain. Coassemblies of these molecules wherein the π-core was diluted as a minority component within a majority aliphatic matrix allowed for the variation of interchromophore exciton coupling commonly found in homoassemblies of peptide-OPV3-peptide monomers. Upon coassembly of the peptides, a hydrophilic tripeptide sequence (Asp-Asp-Asp-, DDD-) promoted the dilution/isolation of the peptide-π-peptide molecules in the majority peptide-decyl-peptide matrix whereas a hydrophobic tripeptide sequence (Asp-Val-Val-, DVV-) promoted the formation of self-associated stacks within the nanostructures. We also performed temperature variation studies to induce the reorganization of π-electron units in the spatially constrained n-decyl environment. This study elucidates the nonresonant (e.g., conformational) and local peptide field effects enforced within the internal environment of peptide nanomaterials and how they lead to varied photophysical properties of the embedded π-electron cores. It offers new insights on tuning the optoelectronic properties of these types of materials on the basis of the local electronic and steric environment available within the nanostructures.

The STREAM Mechanism for CPS Security <italic>The Case of the Smart Grid</italic>

Cyber-physical systems (CPSs) integrate computation, communication, and physical capabilities to interact with the physical world and humans. In this paper, we develop a novel strategic resource availability management (STREAM) system to improve information integrity and availability in an energy constrained CPS environment under the presence of malicious adversaries. The term “resource” here can be any component of a CPS. The main elements of STREAM are: 1) difficult but realistic “repeated (adversary-defender) game” settings and 2) a set of provably optimal defender strategies plus effective heuristics, against equally potent adversary moves. STREAM is based on the concept of dynamic games in sequential game theory, and is the first system to incorporate the realistic behavioral aspect that in many CPSs, both, the class of adversaries, as well as the class of CPS protectors, could move in a covert and stealthy manner in order to outwit the other in the war on “resource control.” In order to demonstrate the effectiveness of STREAM strategies to improve CPS resource availability to the nonadversary, we first conduct a thorough theoretical analysis on a model smart grid CPS as a representative example of a CPS. We then follow up the analysis with an extensive simulation study on the standard IEEE 14 smart power grid architecture. The results show that STREAM strategies improve smart grid system integrity and availability by approximately upto 67% when compared to nonstrategic approaches. Our proposed (analysis, simulation) suite for the grid is extendible to general CPS application domains.

Environmental Enrichment in Kennelled Pit Bull Terriers (Canis lupus familiaris)

Simple SummaryRescue shelters, although set-up with good intentions, may lead to poor welfare of the animals that they house, especially when the shelter organisation is under-resourced. This study therefore investigated the behavioural effects of cheap and locally accessible objects added to the cages of rescued Pit Bull Terrier type dogs in the Philippines to determine whether it is possible for shelter organisations with limited funds and staffing to improve the welfare of their dogs with minimal additional pressure on their time and financial budgets. The addition of enrichment (coconuts; cardboard bed; or cardboard partition) to the dogs’ kennels positively affected their behavior but no one treatment was better at achieving this result. The results therefore suggest that it is possible for under-resourced rescue shelters to use cheap, locally available objects to improve the welfare of dogs in their care.Although social enrichment can be considered beneficial in helping dogs cope with the kennel environment, when taking individual needs into account, it places a large demand on the carers and may not be appropriate in under-resourced kennels. Some kennels are also designed in such a way that there is too much social interaction, in that individuals cannot choose to distance themselves from conspecifics. This study therefore aimed to assess the effects of easily accessible enrichment on the behaviour of kennelled Pit Bull Terrier type dogs rescued from a dog-fighting ring in the Philippines. Thirty-six dogs were allocated to one of three treatment groups following a matched-subject design: (i) cardboard bed provision; (ii) coconut provision; and (iii) visual contact with dogs housed in adjacent cages obstructed with cardboard partitions. Behavioural diversity and the duration and frequency of individual behaviours were analysed using linear mixed-effect models. Yawning frequencies and time spent lying down and sitting decreased during treatment. No particular treatment was more influential in these behavioural changes. In conclusion, enrichment, regardless of type, affected the dogs’ behaviour, with some effects depending on the sex of the dogs. Therefore, it is possible to cheaply and sustainably enrich the lives of dogs living in highly constrained environments, however, further research is required to refine the methods used.

Multi-agent Rapidly-exploring Pseudo-random Tree

Real-time motion planning and control for groups of heterogeneous and under-actuated robots subject to disturbances and uncertainties in cluttered constrained environments is the key problem addressed in this paper. Here we present the Multi-agent Rapidly-exploring Pseudo-random Tree (MRPT), a novel technique based on a classical Probabilistic Road Map (PRM) algorithm for application in robot team cooperation. Our main contribution lies in the proposal of an extension of a probabilistic approach to be used as a deterministic planner in distributed complex multi-agent systems, keeping the main advantages of PRM strategies like simplicity, fast convergence, and probabilistic completeness. Our methodology is fully distributed, addressing missions with multi-robot teams represented by high nonlinear models and a great number of Degrees of Freedom (DoFs), endowing each agent with the ability of coordinating its own movement with other agents while avoiding collisions with obstacles. The inference of the entire team’s behavior at each time instant by each individual agent is the main improvement of our method. This scheme, which is behavioral in nature, also makes the system less susceptible to failures due to intensive traffic communication among robots. We evaluate the time complexity of our method and show its applicability in planning and executing search and rescue missions for a group of robots in S E3 outdoor scenarios and present both simulated and real-world results.

Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps

The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius rQ = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.

Visual Servoing of Soft Robot Manipulator in Constrained Environments With an Adaptive Controller

It is unavoidable for a soft manipulator to interact with environments during some tasks. These interactions may affect the soft manipulator and make the kinematic model different from the one in free space, e.g., the soft manipulator's effective length and the target positions might change. In order to apply the soft manipulator to constrained environments, an adaptive visual servo controller based on piecewise-constant curvature kinematic, without knowing the true values of the manipulator's length and the target positions, is proposed in this paper. Experimental results in the free space, constrained environment, and the gravity-influenced environment, demonstrate the convergence of the image errors under the proposed controller.

Determinants of microfinance outreach in Sub-Saharan Africa: A panel approach

Orientation: The study focused on analysing the outreach performance of microfinance institutions (MFIs) in providing critical services for the poor using innovative lending techniques within constrained environments. Research purpose: The study examined the trade-off relations between the depth and the breadth of outreach and identified institutional level factors that influence MFIs outreach in sub-Saharan Africa (SSA). Motivation for the study: MFIs continue to play critical roles in extending financial services to the poor and yet previous studies have not analysed comprehensively the dimensions of outreach necessary for financial inclusion. Research design, approach and methods: The study employed correlation analysis and random effects methodology to panel data regression analysis (619 observations, 71 MFIs across 10 countries) to establish the trade-off relations and the determinants of outreach in SSA. Main findings: It was established that a trade-off exists between the depth of outreach (access to credit disbursement by poor clients) and breadth of outreach (number of clients served). The results further revealed that gross loan portfolio, portfolio at risk, borrower per staff member, interest rate, and operating expenses to assets ratio are the main institutional determinants of MFIs outreach in SSA. Practical/managerial implications: The policy implication is that MFIs that concentrate efforts in reaching the relatively poor do so at the expense of reaching a large number of poor clients. We suggest that effective monitoring of depth and breadth and the adoption and implementation of cost-saving outreach technologies by MFIs could enable them to operate sustainably and efficiently. Contribution/value added: A major contribution of the study is the trade-off relations revealed between the depth of outreach and the breadth of outreach of MFIs which advances the outreach literature.

Comprehensive characterization of neutrophil genome topology

Neutrophils are responsible for the first line of defense against invading pathogens. Their nuclei are uniquely structured as multiple lobes that establish a highly constrained nuclear environment. Here we found that neutrophil differentiation was not associated with large-scale changes in the number and sizes of topologically associating domains (TADs). However, neutrophil genomes were enriched for long-range genomic interactions that spanned multiple TADs. Population-based simulation of spherical and toroid genomes revealed declining radii of gyration for neutrophil chromosomes. We found that neutrophil genomes were highly enriched for heterochromatic genomic interactions across vast genomic distances, a process named supercontraction. Supercontraction involved genomic regions located in the heterochromatic compartment in both progenitors and neutrophils or genomic regions that switched from the euchromatic to the heterochromatic compartment during neutrophil differentiation. Supercontraction was accompanied by the repositioning of centromeres, pericentromeres, and long interspersed nuclear elements (LINEs) to the neutrophil nuclear lamina. We found that Lamin B receptor expression was required to attach centromeric and pericentromeric repeats but not LINE-1 elements to the lamina. Differentiating neutrophils also repositioned ribosomal DNA and mininucleoli to the lamina-a process that was closely associated with sharply reduced ribosomal RNA expression. We propose that large-scale chromatin reorganization involving supercontraction and recruitment of heterochromatin and nucleoli to the nuclear lamina facilitates the folding of the neutrophil genome into a confined geometry imposed by a multilobed nuclear architecture.

Using Heuristics for Supportability Analysis of Adaptive Weapon Systems in Combat

Abstract : The new U.S. Army vision contends that heuristics are practical tools for achieving innovation. Overcoming complex terrain and adaptive hybrid threats in Syria, Iraq, and Afghanistan requires technological innovation. Supportability issues result from modifying deployed weapon systems with new technology for countering these types of threats. Collecting detailed data on deployed weapon systems is constrained in combat zones. A solution for modeling supportability requirements of adaptive weapon systems in a constrained data environment involves heuristics. This modeling effort is achieved by modifying a decision matrix to include heuristics as an alternative field data source.

Simplex Solutions for Optimal Control Flight Paths in Urban Environments

This paper identifies feasible fight paths for Small Unmanned Aircraft Systems in a highly constrained environment. Optimal control software has long been used for vehicle path planning and has proven most successful when an adequate initial guess is presented to an optimal control solver. Leveraging computer animation techniques, a large search space is discretized into a set of simplexes where a Dubins path solution is generated and contained in a polygonal search corridor free of path constraints. Direct optimal control methods are then used to determine the optimal flight path through the newly defined search corridor. Two scenarios are evaluated. The first is limited to heading rate control only, requiring the air vehicle to maintain constant speed. The second allows for velocity control which permits slower speeds, reducing the vehicles minimum turn radius and increasing the search domain. Results illustrate the benefits gained when including speed control to path planning algorithms by comparing trajectory and convergence times, resulting in a reliable, hybrid solution method to the SUAS constrained optimal control problem.

An Efficient Broadcast Authentication Scheme in Wireless Sensor Networks

Abstract: Broadcast source authentication is a challenging topic in wireless sensor networks. This security service allows senders to broadcast messages to multiple receivers in a secure way. Although several authentication mechanisms have been proposed to address the need for security in WSNs, most of them are resource consuming and are inadequate for constrained environments. In this paper, we shed the light to the security vulnerabilities of symmetric key based authentication mechanisms, and their inability to tackle memory DoS attacks. Moreover, we provide a new efficient broadcast authentication scheme based on a Bloom filter data structure in order to reduce the communication overhead. Finally, we run a thorough set of simulations to assess the efficiency of our approach compared to some state of the art solutions in terms of energy consumption, communication and computation overhead. Our results provide insight into the suitability of our approach for use in WSNs.

The promise and pitfalls of social media use in Higher Education

Social media is pervasive in all aspects of modern life, including health, education, parenting, entertainment personal relationships and current affairs. In Higher Education however, social media is becoming a site of tension between those pursuing connected and innovative educational practice on one hand and an increasingly constrained policy environment reacting to reputational damage resulting from subversive and risky online behaviour by students and staff on the other. Social media has polarised academics, many of whom dismiss it as time-wasting and trivialising academic work and others who embrace it as an open and evolving form of scholarship and academic practice. Students engage with it for learning despite the expected norms of traditional academic practice. This symposium will highlight and explore key issues dominating current debates around the use and misuse of social media in Higher Education drawing on the wisdom of the crowd to find solutions to such challenges.

Hybrid noise predictions of a radial notebook blower

The tonal noise of a notebook radial blower in a free-field environment is investigated using an hybrid method based on unsteady Reynolds Averaged Navier–Stokes simulations and an Ffowcs Williams and Hawking’s analogy to compute the acoustic far-field from the wall-pressure fluctuations recorded in the simulations. Incompressible and compressible simulations have been performed to demonstrate the effect of the compressibility on the noise sources in the very constrained environment due to the casing specific design. The complex flow in the blower yields distributed noise sources. The tongue interaction with the blade wakes and the inlet flow distortions are major contributors at the blade passing frequency, while smaller structures in the clearance are important noise sources at higher harmonics. The influence of a daisy obstruction on one of the blower inlet is also investigated. The additional inlet distortion strongly affects the noise levels at the blade passing frequency. The acoustic predictions are compared to experimental measurements and provide good agreement within the variability of the acoustic level measured between blowers of the same conception batch. The compressible simulations provide the best agreement at higher frequency when the compactness limit is overpassed.

Development of a slender continuum robotic system for on-wing inspection/repair of gas turbine engines

The maintenance works (e.g. inspection, repair) of aero-engines while still attached on the airframes requires a desirable approach since this can significantly shorten both the time and cost of such interventions as the aerospace industry commonly operates based on the generic concept power by the hour. However, navigating and performing a multi-axis movement of an end-effector in a very constrained environment such as gas turbine engines is a challenging task. This paper reports on the development of a highly flexible slender (i.e. low diameter-to-length ratios) continuum robot of 25 degrees of freedom capable to uncoil from a drum to provide the feeding motion needed to navigate into crammed environments and then perform, with its last 6 DoF, complex trajectories with a camera equipped machining end-effector for allowing in-situ interventions at a low-pressure compressor of a gas turbine engine. This continuum robot is a compact system and presents a set of innovative mechatronics solutions such as: (i) twin commanding cables to minimise the number of actuators; (ii) twin compliant joints to enable large bending angles (ź90°) arranged on a tapered structure (start from 40mm to 13mm at its end); (iii) feeding motion provided by a rotating drum for coiling/uncoiling the continuum robot; (iv) machining end-effector equipped with vision system. To be able to achieve the in-situ maintenance tasks, a set of innovative control algorithms to enable the navigation and end-effector path generation have been developed and implemented. Finally, the continuum robot has been tested both for navigation and movement of the end-effector against a specified target within a gas turbine engine mock-up proving that: (i) max. deviations in navigation from the desired path (1000mm length with bends between 45° and 90°) are ź10mm; (ii) max. errors in positioning the end-effector against a target situated at the end of navigation path is 1mm. Thus, this paper presents a compact continuum robot that could be considered as a step forward in providing aero-engine manufacturers with a solution to perform complex tasks in an invasive manner. A novel slender continuum robot is introduced for in-situ repair/inspection of jet engines.A new kinematic model is introduced for the new tapered design.Modes of control for the continuum robot were developed, including tip-following, feeding-in/out, Machining commands.Navigation and inspection/machining tests in engine model were introduced.

Indium Tin Oxide Microsystem for Electrochemical Detection of Exocytosis of Migratory Dendritic Cells

AbstractThe design, fabrication and test of an indium tin oxide (ITO) microdevice to investigate exocytotic behaviors of migratory dendritic cells (DCs) in confined three‐dimensional environment were reported in this work. Indeed, immature DCs were able to migrate into micro‐fabricated biocompatible polydimethylsiloxane (PDMS) channels that mimic their natural constrained environment of tissues for patrolling in search of danger associated antigens through an endocytotic process called macropinocytosis. In order to coordinate membrane trafficking and prevent cell volume increment, DCs will release part of their contents back to the extracellular medium while migrating. Through electrochemical measurements, we demonstrated that exocytotic events of migratory DCs could be monitored by our ITO microdevice. In addition, the transparency of ITO electrode should facilitate future combining assays of exocytosis with other fluorescence‐based measurements of cell physiology.

Safe Coordinated Maneuvering of Teams of Multirotor Unmanned Aerial Vehicles: A Cooperative Control Framework for Multivehicle, Time-Critical Missions

Multirotor unmanned aerial vehicles (UAVs) have experienced a very fast-paced technological development over the past years. Flight control systems have evolved from simple stability augmentation systems, barely enabling an external pilot to remotely fly a multirotor UAV, to full-fledged command augmentation systems, opening up the possibilities of autonomous operations of multirotors. Due to their small size, low cost, and high agility, multirotors draw a plethora of applications, including multiple vehicles operations, where the vehicles cooperate and jointly execute a mission, in constrained complex environments such as crowd monitoring and utility line inspection.

Model-Less Hybrid Position/Force Control: A Minimalist Approach for Continuum Manipulators in Unknown, Constrained Environments

Continuum manipulators are designed to operate in constrained environments that are often unknown or unsensed, relying on body compliance to conform to obstacles. The interaction mechanics between the compliant body and unknown environment present significant challenges for traditional robot control techniques based on modeling these interactions exactly. In this letter, we describe a hybrid position/force control method that uses a model-less approach. Model-less control is a recently-described approach to control that learns the continuum manipulator Jacobian and adapts to constraints in the environment in a safe manner. When interacting with the environment using the end-effector, these tip-constraints can affect the manipulator Jacobian estimates to become ill-conditioned. This letter addresses this issue by defining a hybrid control approach for simultaneously controlling end-effector position and forces while still maintaining the minimalist approach of model-less control. Under this method, continuum manipulators can safely and effectively interact with the environment, even when these interactions are arbitrary and unknown constraints.

Compensation for Unconstrained Catheter Shaft Motion in Cardiac Catheters.

Cardiac catheterization with ultrasound (US) imaging catheters provides real time US imaging from within the heart, but manually navigating a four degree of freedom (DOF) imaging catheter is difficult and requires extensive training. Existing work has demonstrated robotic catheter steering in constrained bench top environments. Closed-loop control in an unconstrained setting, such as patient vasculature, remains a significant challenge due to friction, backlash, and physiological disturbances. In this paper we present a new method for closed-loop control of the catheter tip that can accurately and robustly steer 4-DOF cardiac catheters and other flexible manipulators despite these effects. The performance of the system is demonstrated in a vasculature phantom and an in vivo porcine animal model. During bench top studies the robotic system converged to the desired US imager pose with sub-millimeter and sub-degree-level accuracy. During animal trials the system achieved 2.0 mm and 0.65° accuracy. Accurate and robust robotic navigation of flexible manipulators will enable enhanced visualization and treatment during procedures.

Probing Framework-Restricted Metal Axial Ligation and Spin State Patterns in a Post-Synthetically Reduced Iron-Porphyrin-Based Metal-Organic Framework.

An iron-porphyrin-based metal organic framework PCN-222(Fe) is investigated upon postsynthetic reduction with piperidine. Fe K-edge X-ray absorption and Kβ mainline emission spectroscopy measurements reveal the local coordination geometry, oxidation, and spin state changes experienced by the Fe sites upon reaction with this axially coordinating reducing agent. Analysis and fitting of these data confirm the binding pattern predicted by a space-filling model of the structurally constrained pore environments. These results are further supported by UV-vis diffuse reflectance, IR, and resonance Raman spectroscopy data.

Balancing Priorities in America's European Strategy

ABSTRACT: This article examines how regional and global priorities challenge America's evolving European strategy. The need to reassure Eastern and Central European allies in the face of Russian assertiveness calls for greater US strategic engagement in Europe. Conversely, defense-budgetary pressures, the Asia rebalance, and the willingness to avoid excessive escalation with Russia constitute ongoing limitations to a significant US military engagement in and around Europe. That is the essence of America's European dilemma--how to invest sufficient resources in Europe as toensure credible while keeping enough military and diplomatic bandwidth to pursue other global geopolitical objectives ********** Russian revisionism compels the United States to up its game in Europe. However, current discussions about US strategy and force posture on that continent cannot be isolated from broader geopolitical considerations. After all, Washington remains intent on rebalancing its strategic focus towards the Asia-Pacific, and the demand signal for US military engagement in the Middle East is unlikely to recede any time soon. In an increasingly constrained resource environment, the United States must grapple with the ever-relevant question of how to prioritize different regions, competitors, and challenges--a question that often boils down to striking an appropriate balance between Europe, East Asia and the Middle East. Coming up with a satisfactory way to address that question is more complex than it already sounds, not least as there is an important degree of geopolitical crossover amongst those three vital regions. During the Cold War, Washington understood the preservation of a balance of power in the Middle East was essential to ensuring the supply of oil for key allies in Europe and East Asia--and to the security and thriving of a US-led order in those vital regions. Today, the high dependence of China, Japan, and South Korea on Middle Eastern oil means US influence in the Middle East can constitute an important source of strategic leverage in the Asia-Pacific. In turn, Europe remains an important base of operations and source of diplomatic and operational support to America's initiatives in the Middle East. While US strategy in Europe will no doubt be largely driven by the evolving regional threat environment, it is nonetheless important to take heed of some of the ways in which global geopolitical considerations may affect or constrain America's strategic picture in Europe. This article examines how regional and global priorities may intersect in the context of Washington's evolving European strategy. On the one hand, the need to reassure Eastern and Central European allies in light of Russian revisionism constitutes a strong pressure for greater US strategic engagement in Europe. On the other hand, that pressure has been tempered by defense-budgetary constrains, the commitment to rebalance to Asia and a willingness to avoid excessive escalation with Russia. So far, these competing pressures have coalesced around a strategy of through readiness, through an improvement of United States and NATO rapid-reaction capabilities and an enhanced pattern of rotational deployments, training, and exercises in Central and Eastern Europe. This has allowed Washington to address the concerns of its frontline allies while avoiding devoting too many resources to the European theatre of operations. Russia's impending military modernization and its improving military-strategic position in north-eastern and south-eastern Europe beg the question of whether a readiness-only approach is likely to create lasting security in Europe. This is a question that appears to be gaining traction in US and NATO circles. Indeed, as the Alliance approaches its July 2016 Summit in Warsaw, the narrative shift from reassurance to deterrence signals a progressive hardening of US policy in Europe, and the intent to go beyond readiness and to emphasize the need for more presence. …