How Do Smut Fungi Use Plant Signals to Spatiotemporally Orientate on and In Planta?

Smut fungi represent a large group of biotrophic plant pathogens that cause extensive yield loss and are also model organisms for studying plant–pathogen interactions. In recent years, they have become biotechnological tools. After initial penetration of the plant epidermis, smut fungi grow intra—and intercellularly without disrupting the plant-plasma membrane. Following the colonialization step, teliospores are formed and later released. While some smuts only invade the tissues around the initial penetration site, others colonize in multiple plant organs resulting in spore formation distal from the original infection site. The intimate contact zone between fungal hyphae and the host is termed the biotrophic interaction zone and enables exchange of signals and nutrient uptake. Obviously, all steps of on and in planta growth require fine sensing of host conditions as well as reprogramming of the host by the smut fungus. In this review, we highlight selected examples of smut fungal colonization styles, directional growth in planta, induction of spore formation, and the signals required, pointing to excellent reviews for details, to draw attention to some of the open questions in this important research field.

Larde-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison with Experiments

During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler-Lagrange description of the liquid spray, an energy deposition model to mimic ignition and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this lift-off takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.

Microscopic Estimation of Freeway Vehicle Positions from the Behavior of Connected Vehicles

Given the current connected vehicles program in the United States, as well as other similar initiatives in vehicular networking, it is highly likely that vehicles will soon wirelessly transmit status data, such as speed and position, to nearby vehicles and infrastructure. This will drastically impact the way traffic is managed, allowing for more responsive traffic signals, better traffic information, and more accurate travel time prediction. Research suggests that to begin experiencing these benefits, at least 20% of vehicles must communicate, with benefits increasing with higher penetration rates. Because of bandwidth limitations and a possible slow deployment of the technology, only a portion of vehicles on the roadway will participate initially. Fortunately, the behavior of these communicating vehicles may be used to estimate the locations of nearby noncommunicating vehicles, thereby artificially augmenting the penetration rate and producing greater benefits. We propose an algorithm to predict the locations of individual noncommunicating vehicles based on the behaviors of nearby communicating vehicles by comparing a communicating vehicle's acceleration with its expected acceleration as predicted by a car-following model. Based on analysis from field data, the algorithm is able to predict the locations of 30% of vehicles with 9-m accuracy in the same lane, with only 10% of vehicles communicating. Similar improvements were found at other initial penetration rates of less than 80%. Because the algorithm relies on vehicle interactions, estimates were accurate only during or downstream of congestion. The proposed algorithm was merged with an existing ramp metering algorithm and was able to significantly improve its performance at low connected vehicle penetration rates and maintain performance at high penetration rates.

Study on spudcan reinstallation next to a footprint using large deformation finite element method

Safety problems may occur to the jack-up rig when it is installed near the old footprint. In this study, three-dimensional large deformation finite element simulations using the Coupled Eulerian–Lagrangian (CEL) method have been carried out on the spudcan–footprint interaction problem. The correctness of the CEL method is verified through comparison with existing centrifuge tests. Uniform and non-uniform clays with different shear strength profiles encompassing the typical strength range of practical interest are considered as the subsea soil. The principle of thermo-mechanical coupled analysis is provided, after which this method is used to realize the updating of clay strength profiles in non-uniform clays. The influences of initial penetration depth, offset distance and shear strength profile on horizontal and moment loads are investigated. Distributions of soil load on the spudcan are presented, and their effect on the resulted inclined loads during spudcan reinstallation is analyzed. In both uniform and non-uniform clays, two peak values are obtained on the horizontal and moment load profiles during the reinstallation near the footprint. The relationship between the normalized maximum value of the horizontal load and initial penetration depth is described as a combination of linear and quadratic equations. While for the peak moment load, the offset distance is the main influencing factor. Finally, failure mechanisms of the surrounding soil during the penetration influenced by the footprint are discussed by defining four failure mechanism stages.

Experimental measurement of monotonic and cyclic lateral resistance of risers and pipelines in Gulf of Mexico clays

The location near the touchdown zone of a steel catenary riser at the seabed is a primary “hot spot” for fatigue assessment, with seabed stiffness having a major influence on the predicted fatigue life. This paper presents the results of laboratory model tests in the lateral direction with the motivation to appropriately capture the fundamental mechanism of soil interaction with the pipeline or riser in the lateral direction. The objectives of this study are to evaluate (i) the fundamental mechanism of soil interaction with the pipeline or riser in the lateral direction subjected to monotonic and cyclic loading, (ii) the evolution of lateral resistance with different (small to large) displacement amplitudes, (iii) the degradation of lateral resistance while increasing the number of cycles, and (iv) the recovery of the soil strength with time. The primary findings from the tests are that (i) the lateral resistance on the riser–pipeline drops sharply after trench formation, (ii) the lateral resistance across the trench approaches zero and reaches a steady state at a large number of cycles, (iii) the shape of trenches depends on the lateral displacement amplitude and the initial penetration depth, and (iv) some regain in strength occurs after a period for consolidation.

Large-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison With Experiments

During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler-Lagrange description of the liquid spray, an energy deposition model to mimic ignition and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this lift-off takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.

Liquefied Strength Ratio with Stress Densification and Low Stresses

This paper presents a comparison of four (4) assumptions or approaches for using a liquefied shear strength ratio for sandy soils in cases where there has been a large increase in effective vertical stress, e.g., structure raising or remedial measure, that is outside the effective stresses of the case histories used to develop the empirical liquefied shear strength ratio and penetration resistance correlations. Changes in penetration resistance due to an increase in effective vertical stress are used in an example to illustrate the following four (4) assumptions for determining a liquefied shear strength ratio in such a post-liquefaction stability analysis: (1) initial effective vertical stress and initial penetration resistance, (2) initial effective vertical stress and the expected increase in penetration resistance due to the increase in effective vertical stress, (3) final effective vertical stress and initial penetration resistance, which is suggested, and (4) final effective vertical stress and final penetration resistance. This paper also presents suggestions for using a liquefied strength ratio at low effective vertical stresses, e.g., approaching the toe of a dam or embankment, in a post-liquefaction stability analysis.

Resistive Force Analysis for Design of Rubber Tire Loader Buckets

Rubber tire loaders are key loading equipment for surface and underground mines and can load up to 35 t of material in a pass. Efficient initial penetration into the pile improves the overall efficiency of the loading operation. For efficient design for good initial penetration, we need to predict accurately the resistive forces encountered by these buckets during initial penetration. This paper examines the resistive forces on the bucket as a function of rake angle, height above the digging floor, speed, and tractive effort during initial penetration. A 1/16th scaled representative model of an 18 t (19.8 ton) capacity load haul dump is used for experimentation to understand the effects of rake angle, height above the floor, speed, and tractive effort. The results show that resistive forces are not associated with rake angle or height above the floor but significantly associated with speed, tractive effort, combined effects of speed and tractive effort, and combined effects of speed and rake angle. Future research should focus on conducting similar experiments on different materials and different buckets to better understand the ground engagement for mining and construction equipment. These insights are important to understand the full range of forces during bucket and equipment design.

Implosion-Induced Collapse Effect of Initial Penetration Damage on Concrete Structures with Finite Thickness

Attacks using penetration-explosion warheads can cause the backside of concrete targets to collapse. Current research on collapse damage mainly focuses on the damage caused by external explosions and the damage of targets with prefabricated holes under internal blasts. However, the penetration effect also affects the destructive effect of the explosion-induced collapse, so experiments on prefabricated borehole charges cannot fully reflect real implosions. To study the effect of the initial penetration damage of imploding concrete structures with finite thickness on their collapse, in this study, field experiments are carried out on concrete targets with different initial penetration damage. The collapse damage of the targets is analyzed, and the dimensional analysis method is used to fit the experimental data and obtain the rules and prediction methods of the effect of the initial penetration damage on the relative collapse thickness. The collapse depth of the concrete targets is found to decrease with the increase in the impact energy factor; this increase is found to reduce gradually until stabilization. The conclusion has been verified and analyzed in depth through numerical simulations. The results of this study can provide a basis for subsequent simulations of the actual penetration and explosion effects and a reference for the optimal protection design of concrete structures and the optimal damage design of penetration-explosion warheads.

Mars Regolith Properties as Constrained from HP3 Mole Operations and Thermal Measurements

<p>The Heat Flow and Physical Properties Package HP<sup>3</sup> onboard the Nasa InSight mission has been on the surface of Mars for more than one Earth year. The instrument's primary goal is to measure Mars' surface heat flow through measuring the geothermal gradient and the thermal condunctivity at depths between 3 and 5m. To get to depth, the package includes a penetrator nicknamed the "Mole"  equipped with sensors to precisely measure the thermal conductivity. The Mole tows a tether with printed temperature sensors;  a device to measure the length of the tether towed and a tiltmeter will help to track the path of the Mole and the tether. Progress of the Mole has been stymied by difficulties of digging into the regolith. The Mole functions as a mechanical diode with an internal hammer mechanism that drives it forward. Recoil is balanced mostly by internal masses but a remaining 3 to 5N has to be absorbed by hull friction. The Mole was designed to work in cohesionless sand but at the InSight landing a cohesive duricrust of at least 7cm thickness but possibly 20cm thick was found. Upon initial penetration to 35cm depth, the Mole punched a hole about 6cm wide and 7cm deep into the duricrust, leaving more than a fourth of its length without hull friction.  It is widely agreed that the lack of friction is the reason for the failure to penetrate further. The HP<sup>3</sup> team has since used the robotic arm with its scoop to pin the Mole to the wall of the hole and helped it penetrate further to almost 40cm. The initial penetration rate of the Mole has been used to estimate a penetration resistance of 300kPa. Attempts to crush the duricrust a few cm away from the pit have been unsuccessful from which a lower bound to the compressive strength of 350kPa is estimated.  Analysis of the slope of the steep walls of the hole gave a lower bound to cohesion of 10kPa. As for thermal properties, a measurement of the thermal conductivity of the regolith with the Mole thermal sensors resulted in 0.045 Wm<sup>-1</sup>K<sup>-1</sup>.  The value is considerably uncertain because part of the Mole having contact to air.  The HP³ radiometer has been monitoring the surface temperature next to the lander and a thermal model fitted to the data give a regolith thermal inertia of  189 ± 10 J m<sup>-2</sup> K<sup>-1</sup> s<sup>-1/2</sup>. With best estimates of heat capacity and density, this corresponds to a thermal conductivity of 0.045 Wm<sup>-1</sup>K<sup>-1</sup>, consistent with the above measurement using the Mole. The data can be fitted well with a homogeneous soil model, but observations of Phobos eclipses in March 2019 indicate that there possibly is a thin top layer of lower thermal conductivity. A model with a top 5 mm layer of 0.02 Wm-1K-1 above a half-space of 0.05 Wm-1K-1 matches the amplitudes of both the diurnal and eclipse temperature curves. Another set of eclipses will occur in April 2020.</p><p> </p>