On the Graph Theory of Majority Illusions

The popularity of an opinion in one’s direct circles is not necessarily a good indicator of its popularity in one’s entire community. For instance, when confronted with a majority of opposing opinions in one’s circles, one might get the impression that one belong s to a minority. From this perspective, network structure makes local information about global properties of the group potentially inaccurate. However, the way a social network is wired also determines what kind of information distortion can actually occur. In this paper, we discuss which classes of networks allow for a majority of agents to have the wrong impression about what the majority opinion is, that is, to be in a ‘majority illusion’.</p

RobUSt-An Autonomous Robotic Ultrasound System for Medical Imaging

Medical ultrasound (US) systems are widely used for the diagnosis of internal tissues. However, there are challenges associated with acquiring and interpreting US images, such as incorrect US probe placement and limited available spatial information. In this study, we expand the capabilities of medical US imaging using a robotic framework with a high level of autonomy. A 3D camera is used to capture the surface of an anthropomorphic phantom as a point cloud, which is then used for path planning and navigation of the US probe. Robotic positioning of the probe is realised using an impedance controller, which maintains stable contact with the surface during US scanning and compensates for uneven and moving surfaces. Robotic US positioning accuracy is measured to be 1.19 +/- 0.76mm. The mean force along US probe z-direction is measured to be 6.11 +/- 1.18N on static surfaces and 6.63 +/- 2.18N on moving surfaces. Overall lowest measured force of 1.58N demonstrates constant probe-to-surface contact during scanning. Acquired US images are used for the 3D reconstruction and multi-modal visualization of the surface and the inner anatomical structures of the phantom. Finally, K-means clustering is used to segment different tissues. Best segmentation accuracy of the jugular vein according to Jaccard similarity coefficient is measured to be 0.89. With such an accuracy, this system could substantially improve autonomous US acquisition and enhance the diagnostic confidence of clinicians

Collaborative Surgical Robots:Optical Tracking During Endovascular Operations

Endovascular interventions usually require meticulous handling of surgical instruments and constant monitoring of the operating room workspace. To address these challenges, robotic- assisted technologies and tracking techniques are increasingly being developed. Specifically, the limited workspace and potential for a collision between the robot and surrounding dynamic obstacles are important aspects that need to be considered. This article presents a navigation system developed to assist clinicians with the magnetic actuation of endovascular catheters using multiple surgical robots. We demonstrate the actuation of a magnetic catheter in an experimental arterial testbed with dynamic obstacles. The motions and trajectory planning of two six degrees of freedom (6-DoF) robotic arms are established through passive markerguided motion planning. We achieve an overall 3D tracking accuracy of 2.3 ± 0.6 mm for experiments involving dynamic obstacles. We conclude that integrating multiple optical trackers with the online planning of two serial-link manipulators is useful to support the treatment of endovascular diseases and aid clinicians during interventions

National contributions for decarbonizing the world economy in line with the G7 agreement

In June 2015, the G7 agreed to two global mitigation goals: 'a decarbonization of the global economy over the course of this century' and 'the upper end of the latest Intergovernmental Panel on Climate Change (IPCC) recommendation of 40%–70% reductions by 2050 compared to 2010'. These IPCC recommendations aim to preserve a likely (>66%) chance of limiting global warming to 2 °C but are not necessarily consistent with the stronger ambition of the subsequent Paris Agreement of 'holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels'. The G7 did not specify global or national emissions scenarios consistent with its own agreement. Here we identify global cost-optimal emissions scenarios from Integrated Assessment Models that match the G7 agreement. These scenarios have global 2030 emissions targets of 11%–43% below 2010, global net negative CO2 emissions starting between 2056 and 2080, and some exhibit net negative greenhouse gas emissions from 2080 onwards. We allocate emissions from these global scenarios to countries according to five equity approaches representative of the five equity categories presented in the Fifth Assessment Report of the IPCC (IPCCAR5): 'capability', 'equality', 'responsibility-capability-need', 'equal cumulative per capita' and 'staged approaches'. Our results show that G7 members' Intended Nationally Determined Contribution (INDCs) mitigation targets are in line with a grandfathering approach but lack ambition to meet various visions of climate justice. The INDCs of China and Russia fall short of meeting the requirements of any allocation approach. Depending on how their INDCs are evaluated, the INDCs of India and Brazil can match some equity approaches evaluated in this study

The ARMM System-Autonomous Steering of Magnetically-Actuated Catheters:Towards Endovascular Applications

Positioning conventional endovascular catheters is not without risk, and there is a multitude of complications that are associated with their use in manual surgical interventions. By utilizing surgical manipulators, the efficacy of remote-controlled catheters can be investigated in vivo. However, technical challenges, such as the duration of catheterizations, accurate positioning at target sites, and consistent imaging of these catheters using non-hazardous modalities, still exist. In this paper, we propose the integration of multiple sub-systems in order to extend the clinical feasibility of an autonomous surgical system designed to address these challenges. The system handles the full synchronization of co-operating manipulators that both actuate a clinical tool. The experiments within this study are conducted within a clinically-relevant workspace and inside a gelatinous phantom that represents a life-size human torso. A catheter is positioned using magnetic actuation and proportional-integral (PI) control in conjunction with real-time ultrasound images. Our results indicate an average error between the tracked catheter tip and target positions of 2:09 0:49 mm. The median procedure time to reach targets is 32:6 s. We expect that our system will provide a step towards collaborative manipulators employing mobile electromagnets, and possibly improve autonomous catheterization procedures within endovascular surgeries

Design and Evaluation of a Magnetic Rotablation Catheter for Arterial Stenosis

Arterial stenosis is a high-risk disease accompanied by large amounts of calcified deposits and plaques that develop inside the vasculature. These deposits should be reduced to improve blood flow. However, current methods used to reduce stenosis require externally-controlled actuation systems resulting in limited workspace or patient risks. This results in an unexplored preference regarding the revascularization strategy for symptomatic artery stenosis. In this paper, we propose a novel internally-actuated solution: a magnetic spring-loaded rotablation catheter. The catheter is developed to achieve stenosis-debulking capabilities by actuating drill bits using two internal electromagnetic coils and a magnetic reciprocating spring-loaded shaft. The state-space model of the catheter is validated by comparing the simulation results of the magnetic fields of the internal coils with the experimental results of a fabricated prototype. Contact forces of the catheter tip are measured experimentally, resulting in a maximum axial force of 2.63 N and a torque of 5.69 mN-m. Finally, we present interventions in which the catheter is inserted to a vascular target site and demonstrate plaque-specific treatment using different detachable actuator bits. Calcified deposits are debulked and visualized via ultrasound imaging. The catheter can reduce a stenosis cross-sectional area by up to 35%, indicating the potential for the treatment of calcified lesions, which could prevent restenosis

Appel Botha Cornelitz : the abc of a three hundred year old divorce case

In 1683 Maria Kickers and Jan Cornelitz got married in Cape Town. Today, 330 years later, the living patrilineal descendants of Maria’s four sons, number in excess of 76,000 people. Curiously, none of them carry the surname Cornelitz – in fact, they are all called Botha and include former President P.W. Botha, general Louis Botha and Minister Pik Botha. The reason for this anomaly is also the reason why Jan got divorced from Maria in 1700. According to Maria’s testimonies she did indeed have a long term relationship with Frederik Botha, but in her defence she claimed that her husband was impotent and that he actually encouraged her. Other witnesses, presumably prompted by Jan, gave testimonies that implied that Maria was in fact licentious. We combined haplotyping with the AmpF‘STR1 YfilerTM kit with deep-rooting genealogies to show that Maria’s first son was actually fathered by Ferdinandus Appel and that roughly half the living Bothas (38,000 people) actually descend from Ferdinandus Appel while the remaining three sons all stem from the same father, presumably Frederik Botha, and this implies that Maria’s husband did not father any of her sons.This work was supported by Grant 77256 from the National Research Foundation to JMG.http://www .elsevier.com /locate/fsighb201

Three hundred years of low non-paternity in a human population

When cuckoldry is frequent we can expect fathers to withhold investment in offspring that may not be theirs. Human paternal investment can be substantial and is in line with observations from tens of thousands of conceptions that suggest that cuckoldry is rare in humans. The generality of this claim seems to be in question as the rate of cuckoldry varies across populations and studies have mostly been on Western populations. Two additional factors complicate our conclusions, 1) current estimates of the rate of cuckoldry in humans may not reflect our past behaviour as adultery can be concealed by the use of contraceptives; and 2) it is difficult to obtain samples that are random with respect to their paternity certainty. Studies that combine genealogies with Y-chromosome haplotyping are able to circumvent some of these problems by probing into humans’ historical behaviour. Here we use this approach to investigate 1273 conceptions over a period of 330 years in 24 families of the Afrikaner population in South Africa. We use haplotype frequency and diversity and coalescent simulations to show that the male population did not undergo a severe bottleneck and that paternity exclusion rates are high for this population. The rate of cuckoldry in this Western population was 0.9% (95%CI 0.4 – 1.5%) and we argue that given the current data on historical populations we have to conclude that, at least for Western human populations, cuckoldry rate is probably in the range of 1%.National Research Foundation (NRF) grants 65696, 72737 and 77256 to JMG. JCE was supported by a free-standing NRF scarce skills grant.http://www.nature.com/hdy2016-05-31hb201

Characterising Probabilistic Processes Logically

In this paper we work on (bi)simulation semantics of processes that exhibit both nondeterministic and probabilistic behaviour. We propose a probabilistic extension of the modal mu-calculus and show how to derive characteristic formulae for various simulation-like preorders over finite-state processes without divergence. In addition, we show that even without the fixpoint operators this probabilistic mu-calculus can be used to characterise these behavioural relations in the sense that two states are equivalent if and only if they satisfy the same set of formulae.Comment: 18 page