Modelling crystal aggregation and deposition\ud in the catheterised lower urinary tract

Urethral catheters often become encrusted with crystals of magnesium struvite and calcium phosphate. The encrustation can block the catheter, which can cause urine retention in the bladder and reflux into the kidneys. We develop a mathematical model to investigate crystal deposition on the catheter surface, modelling the bladder as a reservoir of fluid and the urethral catheter as a rigid channel. At a constant rate, fluid containing crystal particles of unit size enters the reservoir, and flows from the reservoir through the channel and out of the system. The crystal particles aggregate, which we model using Becker–Döring coagulation theory, and are advected through the channel, where they continue to aggregate and are deposited on the channel’s walls. Inhibitor particles also enter the reservoir, and can bind to the crystals, preventing further aggregation and deposition. The crystal concentrations are spatially homogeneous in the reservoir, whereas the channel concentrations vary spatially as a result of advection, diffusion and deposition. We investigate the effect of inhibitor particles on the amount of deposition. For all parameter values, we find that crystals deposit along the full length of the channel, with maximum deposition close to the channel’s entrance

Decision Support Design for Workload Mitigation in Human Supervisory Control of Multiple Unmanned Aerial Vehicles

As UAVs become increasingly autonomous, the multiple personnel currently required to operate a single UAV may eventually be superseded by a single operator concurrently managing multiple UAVs. Instead of lower-level tasks performed by today’s UAV teams, the sole operator would focus on high-level supervisory control tasks such as monitoring mission timelines and reacting to emergent mission events. A key challenge in the design of such single-operator systems will be the need to minimize periods of excessive workload that could arise when critical tasks for several UAVs occur simultaneously. To a certain degree, it is possible to predict and mitigate such periods in advance. However, actions that mitigate a particular period of high workload in the short term may create long term episodes of high workload that were previously non-existent. Thus some kind of decision support is needed that facilitates an operator’s ability to evaluate different options for managing a mission schedule in real-time. This paper describes two decision support visualizations designed for supervisory control of four UAVs performing a time-critical targeting mission. A configural display common to both visualizations, named the StarVis, was designed to highlight potential periods of high workload corresponding to the current mission timeline, as well as “what if” projections of possible high workload periods based upon different operator options. The first visualization design allows an operator to compare different high workload mitigation options for individual UAVs. This is termed the local visualization. The second visualization is indicates the combined effects of multiple high workload mitigation decisions on the timeline. This is termed the global visualization. The main advantage of the local visualization is that options can be compared directly; however, the possible effects of these options on the mission timeline are only indicated for the individual UAV primarily affected by the decision. For the global visualization, different decisions can be combined to show possible effects on the system propagated across all UAVs, but the different alternatives of a single decision option alternative cannot be directly compared. An experiment was conducted testing these visualizations against a control with no visualization. Results showed that subject using the local visualization had better performance, higher situational awareness, and no significant increase in workload over the other two experimental conditions. This occurred despite the fact that the local and global StarVis displays were very similar. Not only did the Global StarVis produce degraded results as compared to the local StarVis, but those participants with no visualization performed as well as those with the global StarVis. This disparity in performance despite strong visual similarities in the StarVis designs is attributed to operators’ inability to process all the information presented in the global StarVis as well as the fact that participants with the local StarVis were able to rapidly develop effective cognitive problem strategies. This research effort highlights a very important design consideration, in that a single decision support design can produce very different performance results when applied at different levels of abstraction.Prepared for Kevin Burns, The MITRE Corporatio

An Experimental Platform for Investigating Decision and Collaboration Technologies in Time-Sensitive Mission Control Operations

This report describes the conceptual design and detailed architecture of an experimental platform developed to support investigations of novel decision and collaboration technologies for complex, time-critical mission control operations, such as military command and control and emergency response. In particular, the experimental platform is designed to enable exploration of novel interface and interaction mechanisms to support both human-human collaboration and human-machine collaboration for mission control operations involving teams of human operators engaged in supervisory control of intelligent systems, such as unmanned aerial vehicles (UAVs). Further, the experimental platform is designed to enable both co-located and distributed collaboration among operations team members, as well as between team members and relevant mission stakeholders. To enable initial investigations of new information visualization, data fusion, and data sharing methods, the experimental platform provides a synthetic task environment for a representative collaborative time-critical mission control task scenario. This task scenario involves a UAV operations team engaged in intelligence, surveillance, and reconnaissance (ISR) activities. In the experimental task scenario, the UAV team consists of one mission commander and three operators controlling multiple, homogeneous, semi-autonomous UAVs. In order to complete its assigned missions, the UAV team must coordinate with a ground convoy, an external strike team, and a local joint surveillance and target attack radar system (JSTARS). This report details this task scenario, including the possible simulation events that can occur and the logic governing the simulation dynamics. In order to perform human-in-the-loop experimentation within the synthetic task environment, the experimental platform also consists of a physical laboratory designed to emulate a miniature command center. The Command Center Laboratory comprises a number of large-screen displays, multi-screen operator stations, and mobile, tablet-style devices. This report details the physical configuration and hardware components of this Command Center Laboratory. Details are also provided of the software architecture used to implement the synthetic task environment and experimental interface technologies to facilitate user experiments in this laboratory. The report also summarizes the process of conducting an experiment in the experimental platform, including details of scenario design, hardware and software instrumentation, and participant training. Finally, the report suggests several improvements that could be made to the experimental platform based on insights gained from initial user experiments that have been conducted in this environment.Prepared For Boeing, Phantom Work

Cognitive Task Analysis for the LCS Operator

In support of Plan Understanding for Mixed-initiative control of Autonomous systems (PUMA)The following Tables and Figures detail the cognitive task analysis (CTA) performed to determine the information requirements needed to support a single operator located aboard the futuristic Littoral Combat Ship (LCS). This operator is responsible for controlling four underwater unmanned vehicles in conjunction with a UAV operating on a shared network. • Table 1 is a scenario task overview that breaks the overall mission into 3 phases (planning, execution, and recovery) and then details the subtasks for each of the 3 mission phases. • Figure 1 is an event flow diagram that demonstrates what events must occur in a temporal order for each of the 3 phases. There are three basic event types in Figure 1: 1) a loop (L) that represents a process that occurs in a looping fashion until some predetermined event occurs, 2) a decision (D) that represents some decision that is required from the LCS operator, and 3) a process (P) which requires some human-computer interaction to support the required tasks. In each event block, an alphanumeric code is included which labels that particular event type (L#, D#, P#). This label is important because later information requirements will be mapped to one of these events. • Table 2, which details the situation awareness (SA) requirements for the LCS Operator for each of the 3 mission phases and associated subtasks. Each of these SA requirements is mapped directly to one or more events in Figure 1. Because the decisions in Figure 1 represent critical events that require detailed understanding of what information and knowledge is needed to support the operator’s decision-making process, decision ladders were constructed for the diamonds and loops in Figure 1 that correspond to an involved decision process to resolve the question being posed at that stage in the event flow (Figures 2-4). Decision ladders are modeling tools that capture the states of knowledge and information-processing activities necessary to reach a decision. Decision ladders can help identify the information that either the automation and/or the human will need to perform or monitor a task. Decision Ladders, illustrate the need not only for the same information identified by the cognitive task analysis, but the need for several other pieces of information such as the need for visual or aural alerts in contingency situations. In Figures 2-4, three versions are included that detail (a) the basic decision ladder, (b) the decision ladder with corresponding display requirements, and (c) the decision ladder with possible levels of automation. • Figure 2 represents the automated target recognition (ATR) decision ladder (D3 from Event Flow): (a) decision ladder, (b) decision ladder with corresponding display requirements, and (c) decision ladder with possible levels of automation. • Figure 3 shows the decision ladder information and knowledge requirements for the sentry handoff (L3 from Event Flow). • Figure 4, the UUV Recovery Decision Ladder (D7 from Event Flow), illustrates what information is nominally needed. Since this phase was not a major focus, the decision ladder is not as detailed as it could be. This should be a point of focus in Phase II. Lastly Figure 5 demonstrates the coordination loop that must occur in the case where a handoff failure occurs (for a number of reasons to include equipment failure, communication delays, etc.) Again, because the multi-player coordination issues are not a primary focus in Phase I but are a significant consideration for any follow-on phases.Prepared for Charles River Analytic

Fluorescence measurements of expanding strongly-coupled neutral plasmas

We report new detailed density profile measurements in expanding strongly-coupled neutral plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9/cm^3 with a time resolution limit as small as 7 ns. Strong-coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong-coupling at late times is presented, confirming a recent theoretical result.Comment: submitted to PR

Promotion of endometriosis in mice by polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls.

Previous studies showed exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) enhances the development of endometriotic lesions. In this study we examined the effects of other polyhalogenated aromatic hydrocarbons on endometriotic proliferation. B6C3F1 female mice were treated via oral gavage a total of five times, with 3 weeks between each dosing, with 0, 1, 3, or 10 micrograms 2,3,7,8,-TCDD/kg body weight (bw); 3 or 30 mg 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153)/kg bw; 100, 300, or 1000 micrograms 3,3',4,4',5-pentachlorobiphenyl (PCB 126)/kg bw; 10, 30, or 100 micrograms 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF)/kg bw; or 2 or 20 mg 1,3,6,8-TCDD/kg at 10 ml/kg bw. Endometriosis was surgically induced during the week of the second dosing. Three weeks following the final dose, the mice were euthanized and endometriotic lesions, whole body, liver, ovaries, uterine horn, and thymus were weighted, and lesion diameters were measured. Lesions, uterine horns, and ovaries were fixed for histopathology and livers were processed for measurement of ethoxyresorufin O-deethylase (EROD) activity. Both 2,3,7,8-TCDD (1 and 3 micrograms/kg bw) and 4-PeCDF (100 micrograms/kg bw) significantly enhanced the growth of endometrial lesions. No statistically significant increase in endometriotic lesion size was detected in animals treated with either PCB 126 or with the highest dose of 2,3,7,8-TCDD, possibly due to the effects of histologically observed ovarian toxicity. The nondioxin-like compounds, PCB 153 and 1,3,6,8-TCDD, produced no observable effects on endometriosis. Hepatic EROD activity was significantly induced by 2,3,7,8-TCDD, 4-PeCDF, and PCB 126, but not by PCB 153 or 1,3,6,8-TCDD. The results of this study provide preliminary support for the hypothesis that halogenated aromatic hydrocarbon-promoted endometriosis may be Ah receptor mediated

Collision avoidance interface for safe piloting of unmanned vehicles using a mobile device

Autonomous robots and vehicles can perform tasks that are unsafe or undesirable for humans to do themselves, such as investigate safety in nuclear reactors or assess structural damage to a building or bridge after an earthquake. In addition, improvements in autonomous modes of such vehicles are making it easier for minimally-trained individuals to operate the vehicles. As the autonomous capabilities advance, the user's role shifts from a direct teleoperator to a supervisory control role. Since the human operator is often better suited to make decisions in uncertain situations, it is important for the human operator to have awareness of the environment in which the vehicle is operating in order to prevent collisions and damage to the vehicle as well as the structures and people in the vicinity. In this paper, we present the Collision and Obstacle Detection and Alerting (CODA) display, a novel interface to enable safe piloting of a Micro Aerial Vehicle with a mobile device in real-world settings.Boeing Compan

Reverse rotations in the circularly-driven motion of a rigid body

We study the dynamical response of a circularly-driven rigid body, focusing on the description of intrinsic rotational behavior (reverse rotations). The model system we address is integrable but nontrivial, allowing for qualitative and quantitative analysis. A scale free expression defining the separation between possible spinning regimes is obtained.Comment: This work is accepted for publication as a Rapid Communication in Physical Review

Assisting Interruption Recovery in Mission Control Operations

Frequent interruptions are commonplace in modern work environments. The negative impacts of interruptions are well documented and include increased task completion and error rates in individual task activities, as well as interference with team coordination in team-based activities. The ramifications of an interruption in mission control operations, such as military command and control and emergency response, can be particularly costly due to the time and life-critical nature of these operations. The negative impacts of interruptions have motivated recent developments in software tools, called interruption recovery tools, which help mitigate the effects of interruptions in a variety of task environments. However, mission control operations introduce particular challenges for the design of these tools due to the dynamic and highly collaborative nature of these environments. To address this issue, this report investigates methods of reducing the negative consequences of interruptions in complex, mission control operations. In particular, this report focuses on supporting interruption recovery for team supervisors in these environments, as the research has shown that supervisors are particularly susceptible to frequent interruptions. Based on the results of a requirements analysis, which involved a cognitive task analysis of a representative mission control task scenario, a new interruption recovery tool, named the Interruption Recovery Assistance (IRA) tool, was developed. In particular, the IRA tool was designed to support a military mission commander overseeing a team of unmanned aerial vehicle (UAV) operators performing ground force protection operations. The IRA tool provides the mission commander a visual summary of mission changes, in the form of an event bookmark timeline. It also provides interactive capabilities to enable the commander to view additional information on the primary task displays when further detail about a particular mission event is needed. The report also presents the findings from a user study that was conducted to evaluate the effectiveness of the IRA tool on interruption recovery during collaborative UAV mission operations. The study produced mixed results regarding the effectiveness of the IRA tool. The statistical analysis indicated a negative impact on recovery time, while indicating a positive impact on decision accuracy, especially in complex task situations. The study also indicated that the effect of the IRA tool varied across differ user populations. In particular, the IRA tool tended to provide greater benefits to participants without military experience, compared to military participants involved in the study. The qualitative findings from the study provided key insights into the impact and utility of the IRA tool. These insights were used to identify several future research and design directions related to interruption recovery in mission control operations.Prepared for Boeing Phantom Work

Direct excitation of the forbidden clock transition in neutral 174Yb atoms confined to an optical lattice

We report direct single-laser excitation of the strictly forbidden (6s^2)^1S_0 -(6s6p)^3P_0 clock transition in the even 174Yb isotope confined to a 1D optical lattice. A small (~1.2 mT) static magnetic field was used to induce a nonzero electric dipole transition probability between the clock states at 578.42 nm. Narrow resonance linewidths of 20 Hz (FHWM) with high contrast were observed, demonstrating a record neutral-atom resonance quality factor of 2.6x10^13. The previously unknown ac Stark shift-canceling (magic) wavelength was determined to be 759.35+/-0.02 nm. This method for using the metrologically superior even isotope can be easily implemented in current Yb and Sr lattice clocks, and can create new clock possibilities in other alkaline earth-like atoms such as Mg and Ca.Comment: Submitted to Physics Review Letter