Cortical Dynamics of Navigation and Steering in Natural Scenes: Motion-Based Object Segmentation, Heading, and Obstacle Avoidance

Visually guided navigation through a cluttered natural scene is a challenging problem that animals and humans accomplish with ease. The ViSTARS neural model proposes how primates use motion information to segment objects and determine heading for purposes of goal approach and obstacle avoidance in response to video inputs from real and virtual environments. The model produces trajectories similar to those of human navigators. It does so by predicting how computationally complementary processes in cortical areas MT-/MSTv and MT+/MSTd compute object motion for tracking and self-motion for navigation, respectively. The model retina responds to transients in the input stream. Model V1 generates a local speed and direction estimate. This local motion estimate is ambiguous due to the neural aperture problem. Model MT+ interacts with MSTd via an attentive feedback loop to compute accurate heading estimates in MSTd that quantitatively simulate properties of human heading estimation data. Model MT interacts with MSTv via an attentive feedback loop to compute accurate estimates of speed, direction and position of moving objects. This object information is combined with heading information to produce steering decisions wherein goals behave like attractors and obstacles behave like repellers. These steering decisions lead to navigational trajectories that closely match human performance.National Science Foundation (SBE-0354378, BCS-0235398); Office of Naval Research (N00014-01-1-0624); National Geospatial Intelligence Agency (NMA201-01-1-2016

Thermal and non-thermal emission from reconnecting twisted coronal loops

Twisted magnetic fields should be ubiquitous in flare-producing active regions where the magnetic fields are strongly non-potential. It has been shown that reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops. This scenario can be an alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. We use a combination of MHD simulations and test-particle methods, which describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD, and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us estimate thermal X-ray emission intensities. The electric and magnetic fields obtained are used to calculate electron trajectories using the guiding-centre approximation. These trajectories combined with the MHD plasma density distributions let us deduce synthetic HXR bremsstrahlung intensities. Our simulations emphasise that the geometry of the emission patterns produced by hot plasma in flaring twisted coronal loops can differ from the actual geometry of the underlying magnetic fields. The twist angles revealed by the emission threads (SXR) are consistently lower than the field-line twist present at the onset of the kink-instability. HXR emission due to the interaction of energetic electrons with the stratified background are concentrated at the loop foot-points in these simulations, even though the electrons are accelerated everywhere within the coronal volume of the loop. The maximum of HXR emission consistently precedes that of SXR emission, with the HXR light-curve being approximately proportional to the temporal derivative of the SXR light-curve.Comment: (accepted for publication on A&A

Exploratory analyses of crime-scene characteristics in cyber-related homicides

Despite the alarming nature of homicides in which the offender meets the victim online, or cyber-initiated homicides, little empirical attention has been devoted to this phenomenon. The present study was designed to explore the behavioral patterns found prior to and during a cyber-initiated homicide event. Data on 61 homicide cases from various countries were collected through news media and legal sources. Smallest space analysis revealed that cyber homicides were characterized by four distinct themes: Excessive violence; fatal escalation; crime-related incidents; and predatory behavior. Implications of the findings and avenues for future research are discussed

Life-limiting fetal conditions: Are Australian student midwives prepared? A mixed-methods survey

Aim: To document current teaching methods, curriculum, and perceived educational preparation related to the teaching of life-limiting fetal conditions, termination, and perinatal palliative care to Australian student midwives. Background: Australian women receiving a diagnosis of a life-limiting fetal condition are generally offered a choice between termination of pregnancy and perinatal palliative care. Midwives are often involved with caring for these women. What Australian student midwives are being taught about life-limiting fetal conditions, termination of pregnancy, and perinatal palliative care during their entry-to-practice program is unknown. Design: This study utilised a mixed-methods descriptive approach for data collection and analysis. Methods: Academic Leads of all Australian entry-to-practice midwifery programs received a questionnaire exploring topics taught, teaching time, teacher role, and perceived effectiveness of student preparation. Data was analysed statistically and thematically. Results: Twelve of 24 Academic Leads responded (50%); only five stated their programs taught all three areas. More respondents taught about termination of pregnancy (10/12) than perinatal palliative care (7/12). On average 5.8 ( ± 2.8) total hours was spent teaching about life-limiting fetal conditions, termination of pregnancy, and perinatal palliative care during the entire midwifery program, with a range of 1 – 10 h. The free-text data identified three central themes: lack of value within the curriculum; disconnect between the university and the placement hospital; and preparation for practice. Most (10/12) Academic Leads did not believe student midwives are prepared to care for affected families. Conclusions: Entry-to-practice midwifery programs vary considerably in their education surrounding life-limiting fetal conditions, however teaching hours overall were low and most Academic leads did not feel (or know if) their students were adequately prepared. Further research is required to determine if early career midwives find their university education in life-limiting fetal conditions adequate preparation for practice, and to then remediate identified deficiencies

Correlating Nonlinear Static and Dynamic Analysis of Reinforced Concrete Frames

Nonlinear static and dynamic analyses for the design of reinforced concrete frames for strong ground motion are explored in the study. The objectives of the study are to determine 1) the correlation between results from nonlinear static and dynamic analyses, 2) the optimallateralloading distnbution for static analysis, 3) the simplest lateral load distribution that provides adequate results, and 4) the parameters that are reasonably calculated using static analysis for use in design. Parameters included in the study were four number of stories, three frame configurations, four lateral loading distributions for use in static analysis, and ten strong ground motion records for use in dynamic analysis. The key design items were base shear, location of member yielding, column ductility, controlling mechanism, distorted shape of the frame, story drift ratio, and shear and rotation in the members. Results indicated that static analysis provided fair estimates of base shear, general member yielding, distorted shape, and story drift, but gave insufficient estimates of member shear and rotation and the exact location of the controlling mechanism in the frames. The uniform loading distribution best estimated base shear and member shear and rotation, whereas the loading distribution based on provisions in FEMA-356 best estimated the distorted shape, story drift, and column ductility. Overall, precise results from static analysis can not be expected because the results from dynamic analysis vary widely

Magmatic overpressures, volatile exsolution and potential explosivity of fissure eruptions inferred via dike aspect ratios

Buoyant magmas abundant in exsolved volatiles (bubbles) drive the rapid upward-propagation of feeder dikes from magma chambers. The consequence of a feeder dike reaching the surface can result in an explosive volcanic eruption depending, partly, on the retention of volatiles. Therefore, timely detection of the vesicularity and overpressure of the magma during feeder dike ascent is critical for the prediction of the explosivity of any future eruption. In this study, we evaluated the explosivity of eruptions based on field investigations of the erupted products and the overpressure of magma in the conduit based on the dimensions of exposed feeder dikes. We found a positive correlation between the explosivity of eruptions and the magma overpressure generated in the conduit during recent fissure eruptions of Miyakejima volcano. Because the buoyancy of low-density magma produces positive overpressure at the dike’s top, feeder dikes with highly-vesiculated magmas possess high amounts of overpressure. An enlargement of the opening width of a feeder dike by magmatic overpressure results in a higher flux of vesiculated magma, which causes vigorous explosive activity. Our results suggest the possibility of forecasting the explosivity of an impending eruption if the width (or opening) of an ascending feeder dike is monitored in real-time through measurements of ground deformation and seismicity induced by the dike

Comparison of Boer, Kiko, and Spanish meat goat does for stayability and cumulative reproductive output in the humid subtropical southeastern United States

Background: Longevity is the amount of time breeding females stay active in a herd by avoiding death or culling because of illness or reproductive failure. This is a trait of economic relevance in commercial small ruminant breeding herds as it affects lifetime reproductive output. The purpose of this study was to determine if breed of meat goat influences breeding doe survival rates and cumulative reproductive performance under semi-intensive management. Results: Boer (n = 132), Kiko (n = 92) and Spanish (n = 79) does were evaluated for longevity trends and cumulative kid production. The herd was managed on humid subtropical pasture. Does had the chance to complete 2 to 6 production years. Survival curves were analyzed for 2 culling methods. The actual culling practice removed does after two failures to wean a kid. An alternative culling protocol removed doe records after the first failure to wean a kid. Kid production traits analyzed across herd life were the total number of kids weaned and cumulative kid weight weaned to the 2-, 3-, and 5-year stayability endpoints. Most (82%) doe exits were illness-related under the actual culling method. Reproductive failure represented 51% of doe exits under the alternative culling protocol. Boer does had greater survival declines (P \u3c 0.01) from 2 to 6 years of herd life compared with Kiko and Spanish under both culling protocols. Boer does had lower stayability rates (P \u3c 0.01) at each year endpoint for both culling protocols. Under the alternative protocol, over 50% of Boer does failed to complete 2 years, whereas over 50% of Kiko and Spanish does successfully completed 4 years. Boer does had lower (P \u3c 0.01) total number of kids weaned and cumulative weight weaned through each stayability endpoint compared with Kiko and Spanish. Conclusion: Boer does had low stayability and cumulative kid production rates compared with Kiko and Spanish does. Poor health was the primary driver of does exiting the herd. Kiko and Spanish does did not differ for longevity and lifetime performance indicators

Void-mediated formation of Sn quantum dots in a Si matrix

Atomic scale analysis of Sn quantum dots (QDs) formed during the molecular beam-epitaxy (MBE) growth of Sn_xSi_(1−x) (0.05 ⩽ x ⩽ 0.1) multilayers in a Si matrix revealed a void-mediated formation mechanism. Voids below the Si surface are induced by the lattice mismatch strain between Sn_xSi_(1−x) layers and Si, taking on their equilibrium tetrakaidecahedron shape. The diffusion of Sn atoms into these voids leads to an initial rapid coarsening of quantum dots during annealing. Since this formation process is not restricted to Sn, a method to grow QDs may be developed by controlling the formation of voids and the diffusion of materials into these voids during MBE growth