Turn Angle Research Articles

Age-Dependent Search Behavior in the Colorado Checkered Whiptail (Aspidoscelis neotesselatus)

We compared movement and space use patterns of foraging adult and juvenile Colorado checkered whiptails (Aspidoscelis neotesselatus) in pinyon pine–juniper woodland. Through focal observations, we characterized (1) movement paths as a series of step lengths and turn angles at 30-s intervals, and (2) habitat use reflected by the proportion of time spent in different vegetation types and in the open. Adults and juveniles differed in both movement and habitat use. Adults spent more time in the open and in association with mountain mahogany (Cercocarpus montanus), while juveniles were more frequently found in association with dead wood, grass, and juniper (Juniperus monosperma). Adults also moved greater distances than juveniles and made use of larger areas. Movement patterns differed between age classes, with adults having longer step lengths. Adults and juveniles also engaged in different step length–turn angle sequences. For both classes, movement characteristics differed with habitat type.

OPTIMAL NAVAL PATH PLANNING IN ICE-COVERED WATERS

The Northern Sea Route (NSR) links the Atlantic and Pacific oceans through the Arctic and it is critical for global trade as it provides a route between Asia and Europe that is significantly shorter than the alternatives. NSR is soon expected to open for intercontinental shipping due to global warming and thus presents tremendous opportunities for reductions in shipping time, cost, and environmental impacts. On the other hand, facilitating this route requires innovative approaches due to the navigation risks associated with its ice-covered waters. This study presents a graph-theoretical approach for optimal naval navigation in ice-covered sea routes with flexible turn angles based on the idea of large-adjacency grid graphs. Our model allows for asymmetric left and right turn radii as well as turn speeds that vary as a function of the turn angle and it offers natural-looking navigation paths.

Selenium abates manganese-induced striatal and hippocampal toxicity via abrogation of neurobehavioral deficits, biometal accumulation, oxidative stress, inflammation, and caspase-3 activation in rats.

Excessive exposure to manganese (Mn) is associated with neurotoxicity characterized by oxidative stress, inflammation, and apoptosis induction. Selenium (Se) has been shown to possess antioxidant, anti-inflammatory, and anti-apoptotic properties in humans and animals. The present study investigated the neuroprotective mechanism of Se in rats sub-chronically treated with Mn at 30mg/kg body weight or orally co-treated with Se at 0.2 and 0.4mg/kg body weight for 35 consecutive days. Locomotive and exploratory profiles were recorded and computed with the aid of ANY-Maze (a video-tracking software) for 5-min trial, in a novel apparatus. The ANY-Maze analysis showed that Se significantly (p < 0.05) abated Mn-induced locomotive impairment evidenced by increased in maximum speed, total time traveled, absolute turn angle, number of line crossing, rotation and forelimb grip and decreased total time immobile, grooming, and negative geotaxis as verified by the enhanced track plot density. Furthermore, the striatum and hippocampus of the rats were excised and the levels of Mn and Se, oxidative stress markers, proinflammatory cytokines including acetylcholinesterase and caspase-3 activities were assayed. The result shows that Se abates Mn-mediated accumulation of Mn. Also, Se ameliorated Mn-induced decrease in antioxidant enzymes as well as glutathione level and increase in acetylcholinesterase activity, lipid peroxidation, proinflammatory cytokines (i.e., interleukin (IL)-6, IL-1β, tumor necrosis factor alpha), and caspase-3 activation in the striatum and hippocampus of the rats. Collectively, Se abated Mn-induced striatal and hippocampal toxicity via abrogation of neurobehavioral deficits, biometal accumulation, oxidative stress, inflammation, and caspase-3 activation in rats. Se may serve as a neuroprotective agent against Mn-mediated neurotoxicity.

Influence of habitat quality and resource density on breeding‐season female monarch butterfly Danaus plexippus movement and space use in north‐central USA agroecosystem landscapes

Abstract The eastern North American monarch butterfly is at risk of quasi‐extinction due, in part, to the loss of breeding habitat in agricultural landscapes of the USA Midwest. Because adult females are not patch residents, egg abundance and distribution across the landscape are a function of their perceptual range, flight directionality and flight step lengths. Conservation actions that account for habitat use in agricultural landscapes can enhance functional connectivity. Field‐captured females (n = 114) were released in a 64‐ha area containing restored prairies, grass‐dominated fields and crop fields in Floyd County, Iowa, USA, and two 1,000 m linear north–south sections of grass‐dominated roadside along secondary roads (~35 ha) with different proximity to prairie habitat in rural Story County, Iowa. Radio‐tagged or untagged monarchs were released in areas with high density, low density and zero density of forage and oviposition resources, as well as on habitat edges between high‐ and zero‐density habitats. Monarchs were observed for 1 hr. Radio‐tagged individuals that flew beyond visual detection were relocated using handheld radiotelemetry. Monarchs moved within and between habitat classes and typically performed upwind search behaviour. Monarchs successfully located resources, with some flying over 500 m to find high‐density areas, providing evidence that the monarch's perceptual distance is &gt;100 m. Regardless of habitat class or field site, most step lengths were &lt;50 m, and turn angles were directional. Large steps (≥50 m) crossing habitat boundaries occurred with approximately half of the monarchs, which may indicate initiation of long‐range searches for suitable habitat, consistent with their vagile behaviour. Establishing habitat patches 50 m apart in agricultural landscapes would facilitate efficient movement. Synthesis and applications. This study provides an extensive dataset of directly observed breeding‐season monarch butterflies to assess the utilization of agricultural landscapes. Documentation of step lengths &gt;50 m in complex, agricultural landscapes would not have been possible without the aid of radiotelemetry. Results provide improved estimates of perceptual range and flight patterns within and between habitat patches that support models that simulate natural population dynamics to enable conservation planning at a landscape scale.

A Study on a Slotless Brushless DC Motor with Toroidal Winding

In this study we developed a brushless DC (BLDC) slotless motor with toroidal winding. The proposed toroidal winding is a method of winding a coil around a ring-type stator yoke in the circumferential direction. As there is no need for a slot or tooth structure, it can be designed with a slotless motor structure that is advantageous for vibration and noise. The basic principle of operation and motor characteristics of a slotless motor with toroidal winding were explained using an analytical method and finite element analysis (FEA). Further, the air gap flux density, winding factor, and back electromotive force (EMF) for changes in the winding angle and number of coil turns were calculated using the analytical method and compared with the FEA results. Finally, the resistance, back EMF, cogging torque, and performance of the prototype were measured and compared with the FEA results. The results show that the air gap flux density and winding factor were approximately the same with an error of &lt;2%, while the back EMF had an error of ~10% from the analysis result. Thus, the proposed slotless motor provides a basic design for conveniently manufacturing brushless DC (BLDC) slotless motors with toroidal windings.

Long-lasting behavioral effects of quinpirole exposure on zebrafish

The human brain matures into a complex structure, and to reach its complete development, connections must occur along exact paths. If at any stage, the processes are altered, interrupted, or inhibited, the consequences can be permanent. Dopaminergic signaling participates in the control of physiological functions and behavioral processes, and alterations in this signaling pathway are related to the pathogenesis of several neurological disorders. For this reason, the use of pharmacological agents able to interact with the dopaminergic signaling may elucidate the biological bases of such disorders. We investigated the long-lasting behavioral effects on adult zebrafish after quinpirole (a dopamine D2/D3 receptor agonist) exposure during early life stages of development (24 h exposure at 5 days post-fertilization, dpf) to better understand the mechanisms underlying neurological disorders related to the dopaminergic system. Quinpirole exposure at the early life stages of zebrafish led to late behavioral alterations. When evaluated at 120 dpf, zebrafish presented increased anxiety-like behaviors. At the open tank test, fish remained longer at the bottom of the tank, indicating anxiety-like behavior. Furthermore, quinpirole-treated fish exhibited increased absolute turn angle, likely an indication of elevated erratic movements and a sign of increased fear or anxiety. Quinpirole-treated fish also showed altered swimming patterns, characterized by stereotypic swimming. During the open tank test, exposed zebrafish swims from corner to corner in a repetitive manner at the bottom of the tank. Moreover, quinpirole exposure led to memory impairment compared to control fish. However, quinpirole administration had no effects on social and aggressive behavior. These findings demonstrate that dopaminergic signaling altered by quinpirole administration in the early life stages of development led to late alterations in behavioral parameters of adult zebrafish.

Magnetic phase diagram of helimagnetic Ba(Fe1−xScx)12O19 (0 ≤ x ≤ 0.2) hexagonal ferrite

Hexagonal ferrite Ba(Fe1−xScx)12O19 is an important magnetic oxide material in both science and engineering because it exhibits helimagnetism around room temperature (300 K). In this study, the magnetic phase diagram of Ba(Fe1−xScx)12O19 consisting of ferri-, heli-, antiferro-, and paramagnetic phases has been completed through magnetization and neutron diffraction measurements. The magnetic phase transition temperature to paramagnetism decreases with the increase in x, and the temperature at which the magnetization reaches a maximum, which corresponds to the magnetic phase transition from heli- to ferrimagnetism, is determined for low x crystals. The temperatures at which helimagnetism appears are precisely determined by observing the magnetic satellite reflection peaks in neutron diffraction at various temperatures, which characterize helimagnetism. Based on these results, the magnetic phase diagram of the Ba(Fe1−xScx)12O19 system is constructed in the T-x plane. Helimagnetism appears at x ≳ 0.06, and magnetism with antiferromagnetic components appears as the extension phase of helimagnetism at x ≳ 0.19 through the coexistence region. The turn angle ϕ0 of the helix for each x crystal is calculated from the relationship, ϕ0 = 2πδ, where δ is the incommensurability. The turn angle ϕ0 decreases with the increase in temperature for the same x crystal, and increases with the increase in x at the same temperature. Furthermore, it is found that there are clear thresholds at which ϕ0 cannot take values between 0°<ϕ0 ≲ 90° and 170° ≲ ϕ0< 180°.

Directional Persistence of Cell Migration in Schizophrenia Patient-Derived Olfactory Cells.

Cell migration is critical for brain development and linked to several neurodevelopmental disorders, including schizophrenia. We have shown previously that cell migration is dysregulated in olfactory neural stem cells from people with schizophrenia. Although they moved faster than control cells on plastic substrates, patient cells were insensitive to regulation by extracellular matrix proteins, which increase the speeds of control cells. As well as speed, cell migration is also described by directional persistence, the straightness of movement. The aim of this study was to determine whether directional persistence is dysregulated in schizophrenia patient cells and whether it is modified on extracellular matrix proteins. Directional persistence in patient-derived and control-derived olfactory cells was quantified from automated live-cell imaging of migrating cells. On plastic substrates, patient cells were more persistent than control cells, with straighter trajectories and smaller turn angles. On most extracellular matrix proteins, persistence increased in patient and control cells in a concentration-dependent manner, but patient cells remained more persistent. Patient cells therefore have a subtle but complex phenotype in migration speed and persistence on most extracellular matrix protein substrates compared to control cells. If present in the developing brain, this could lead to altered brain development in schizophrenia.

Shock-Wave/Boundary-Layer Interactions on an Axisymmetric Body at Mach 2

The flow physics associated with shock-wave/boundary-layer interactions (SBLIs) on an axisymmetric body, simulating a projectile near an aircraft, is of significant interest to the aerodynamic community. The main objective of this experimental study is to investigate SBLIs on an axisymmetric configuration involving curved surfaces as compared to two-dimensional and three-dimensional (3-D) canonical configurations with flat surfaces. The experiments were carried out at Mach 2, and the planar shock wave was generated using a wedge-shaped shock generator with a turn angle of 10 deg. Measurements include steady and unsteady pressures, surface oil flow, and shadowgraph flow visualizations on the axisymmetric body. Results of the surface flow visualizations and steady pressure contours show that the separation on the body is an open-type region similar to that observed for 3-D SBLI canonical configurations. Flow separation on the surface is driven by pressure gradients caused by both the impingement of the oblique shock and the curvature of the body. Unsteady pressure measurements reveal that the shock impingement on the surface is governed by large-amplitude pressure fluctuations beneath the shock foot and flow reattachment regions.

Behavioral effects of acute ethanol in larval zebrafish (D. rerio) depend on genotype and volume of experimental well

Ethanol consumption is a worldwide problem. Sensitivity to acute effects of ethanol influences the development of chronic ethanol abuse and ethanol dependence. Environmental and genetic factors have been found to contribute to differential effects of acute ethanol. Animal models have been employed to investigate these factors. An increasingly frequently utilized animal model in ethanol research is the zebrafish. A large proportion of ethanol studies with zebrafish have been conducted with adult zebrafish. However, high throughput drug and mutation screens are particularly well adapted to larval zebrafish. These studies are often carried out using the 96-well-plate that allows monitoring large numbers of fish efficiently. Here, we investigate the effects of acute (30 min long) ethanol exposure in 8-day post-fertilization (dpf) old zebrafish. We compare four genetically distinct populations (strains) of zebrafish, measuring numerous parameters of their swim path in two well sizes, i.e., in the 96-well-plate (small volume wells) and in the 6-well-plate (large volume wells). In general, we found that the highest dose of ethanol (1% vol/vol) reduced swim speed, increased duration of immobility, increased turn angle, and increased intra-individual variance of turn angle, while the intermediate dose (0.5%) had a less strong effect, compared to control. However, we also found that these ethanol effects were strain dependent and, in general, were better detected in the larger volume well. We conclude that larval zebrafish are appropriate for quantification of acute ethanol effects and also for the analysis of environmental and genetic factors that influence these effects. We also speculate that using larger wells will likely increase sensitivity of detection and precision in screening applications.

Calibration of rotary encoders with different interfaces by means of a dynamic goniometer

Rotary optical encoders are widely used in all areas of industry, robotics, and special equipment. The accurate measurement of their characteristics is a necessary task for their successful implementation. We attempt to find a unified approach to determining the accuracy of rotary encoders. The proposed approach is based on statistics and code reliability, which characterizes the probability that the measured code corresponds to the specified code. To determine the code reliability, one has to measure the turn angle with a goniometric device and compare the measured values with the encoder codes. The paper considers the dynamic goniometer for determining the error of absolute angle encoders, which allows for highly accurate measurements in a wide range of rotation rates. The measurement is made at certain moments of time, depending on the electrical interface of the encoder. In the case of a parallel interface, the time points are determined by the moment when the encoder code changes. This data collection allows for obtaining a general population. In the case of an encoder, with the sequential approach to reading the code, it is not possible to obtain the general population in a wide range of rotation rates. We analyze the above-mentioned case in detail and present experimental data obtained with a dynamic goniometer and the results of code reliability calculations.

Distinguishing between Epipactis leptochila (Narrow-lipped Helleborine), Epipactis helleborine (Broad-leaved Helleborine) and their putative hybrid, Epipactis x stephensonii at the Warburg reserve, Oxfordshire

A drought in May 2020 curtailed snail damage to a population of Epipactis leptochila (Godfrey) Godfrey (Narrow-lipped Helleborine) such that in July there were 33 flowering plants in an area well known for this species at the Warburg nature reserve in Oxfordshire (v.c.23). Despite growing in a heavily-shaded area under beech, the typical habitat of E. leptochila, some of these plants were actually E. helleborine L. (Crantz) (Broad-leaved Helleborine) based on recognized distinguishing characteristics. We took morphological measurements (19 floral characters and 10 vegetative characters) for all the flowering plants present and were able to confirm by statistical analysis our initial species identifications. We were able also to discriminate between the species reasonably accurately using leaf characters alone, such as leaf colour, leaf length to width ratios and the angle of turn of the bottom three leaves. Using the outcomes from this analysis we were able to make predictions about the identity of most of the 82 non-flowering plants present. There were 4 plants that defied clear initial allocation to one or the other species and were suspected to be the hybrid E. x stephensonii Godfrey. Statistical analysis confirmed that these plants were indeed distinguishable from either parent, and most characters were intermediate to some degree between the two. The morphology of these putative hybrids is described pending molecular confirmation of their identity.

Nonlinear optimal control for multi‐DOF robotic manipulators with flexible joints

AbstractA main problem in the control of flexible‐joint robots and in the precise positioning of their end‐effector, is synchronization between the turn angles of the robots' joints and the turn angles of the motors that provide actuation to these joints. In this article, a nonlinear optimal (H‐infinity) control method is proposed for multi‐DOF robotic manipulators with flexible joints. The dynamic model of these robotic manipulators is shown to be underactuated and to satisfy differential flatness properties. The state‐space description of these robots undergoes approximate linearization around a temporary operating point which is recomputed at each iteration of the control method. The linearization procedure makes use of first‐order Taylor‐series expansion and relies on the computation of Jacobian matrices. For the approximately linearized model of these multi‐DOF robotic systems an H‐infinity feedback controller is designed. This controller stands for the solution of the robots' optimal control problem under model uncertainty and external disturbances. The computation of the controller's feedback gain requires the solution of an algebraic Riccati equation, which is performed again at each time‐step of the control algorithm. The stability properties of the control scheme are proven trough Lyapunov analysis. First, it is confirmed that the controller satisfies the H‐infinity tracking performance criterion which ascertains its robustness. Moreover, it is proven that the control loop is globally asymptotically stable. Finally, to implement sensorless control for such robotic systems the H‐infinity Kalman Filter is used as a robust state estimator. The proposed control method for multi‐DOF robotic manipulators with flexible joints retains the advantages of linear optimal control, that is fast and accurate tracking of its reference setpoints under moderate variations of the control inputs.

Modes of unsteadiness in shock wave and separation region interaction in hypersonic flow over a double wedge geometry

This study investigates different modes of unsteadiness that could be seen in a hypersonic flow over a double wedge configuration with a large separation region size. In the previous studies with a double wedge or a double cone configuration, small turn angles of the surfaces are seen to produce a small separation region that does not interact with the outside shock structures and produce a steady flow. However, a large separation region can be observed with large wedge angles that could interact with the outside shock waves and produce different types of unsteady flows. Some recent numerical studies on the double wedge configuration with a large fore-wedge angle (θ1) of 30° and various aft-wedge angles (θ2) at the free-stream flow Mach number (M∞) of 7 have shown that the flow exhibits periodically oscillating states. The current study investigates this geometric configuration over the parameter space of wedge length ratios (L1/L2) of 0.5, 1.0, 1.5, and 2.0 and aft-wedge angles (θ2) of 45°, 50°, 55°, and 60°. Three modes of unsteadiness are observed, namely, vibration mode, oscillation mode, and pulsation mode. The effect of the variation in geometric parameters on switching between different modes of unsteadiness is assessed, and it is shown that the unsteady characteristics of the flow are determined by the size of the separation region and location of the shock waves with respect to it.

Recognition of LHD Position and Maneuvers in Underground Mining Excavations—Identification and Parametrization of Turns

The Inertial Measurement Unit (IMU) is widely used in the monitoring of mining assets. A good example is the Polish underground copper ore mines of KGHM, where research work with the use of the IMU has been carried out for several years. The potential of inertial sensors was ensured by the development of advanced analytics using machine learning methods to support the maintenance management of an extensive machine park and machine manufacturer in adapting various construction elements to mining conditions. The key algorithms developed in the field of inertial data concern: identification of cycles and components of the haulage process operations, identification of dynamic overloads, technical diagnostics of rotating elements, assessment of road conditions (bumps, slopes, damages), assessment of the technical condition of the pavement, assessment of the operator’s driving style, and finally the machine location in the mining excavation. One of the key operational contexts, necessary in the development of analytics for underground mining vehicles, is the identification of the turning moment of the machine at the intersection together with the determination of the driving direction and the turn angle. In the case of a mine with a room-and-pillar system, where the excavation system has the Manhattan structure, it is possible to use many simplifications to correctly estimate the machine motion path. The identification of the spatial context and the turning maneuver is of key importance both in the development of the machine location system, but also in multi-dimensional analyzes, including the analysis of dynamic overloads or the assessment of the operator’s driving style and work safety. The article presents a comparison of several mathematical models used for the machine turn detection problem, which were trained and tested on the real-life industrial data recorded using IMU during a single working shift of the self-propelled machine.

Estimating Perceptual Range of Female Monarch Butterflies (Danaus plexippus) to Potted Vegetative Common Milkweed (Asclepias syriaca) and Blooming Nectar Resources.

Habitat loss in the summer breeding range contributes to eastern North American monarch (Lepidoptera: Nymphalidae) population decline. Habitat restoration efforts include increasing native prairie plants for adult forage and milkweed (Asclepias spp.) for oviposition and larval development. As the monarch is a vagile species, habitat establishment at a grain that matches the monarch perceptual range will facilitate efficient movement, decrease fitness costs of dispersal, and increase oviposition. We released 188 experimental monarch females 5, 25, 50, and 75 m downwind from potted milkweed and blooming forbs in 4-32 ha sod fields. Perceptual range was estimated from monarchs that flew towards and landed on the milkweed and forbs. Flight patterns of 49 non-experimental monarchs that landed on the resources were also observed. In our experimental, resource-devoid setting, wind-facilitated movement occurred most frequently. Monarchs performed direct displacement as evidenced by shallow turn angles and similarity of Euclidian and total distances traveled. We hypothesize similar monarch flight behavior when traveling over other resource-devoid areas, such as crop fields. Although the majority of experimental monarchs flew downwind, eight experimental and 49 non-experimental monarchs were observed flying upwind toward, and landing on, the potted resources from distances ranging from 3 to 125 m (mean = 30.98 m, median = 25 m, mode = 25 m). A conservative estimate of the perceptual range is 125 m, as longer distances cannot be precluded; however, the majority of observations were ≤50 m. Our findings suggest establishing habitat patches ~ 50 m apart would create functional connectivity across fragmented agricultural landscapes.

Research on anxiety-like neurobehavior of zebrafish caused by lead exposure and its mechanism

Objective: This study aims to explore whether lead exposure could cause anxiety of zebrafish larvae, and to explore its mechanism. Methods: In May 2020, zebrafish embryos 4 hours after fertilization (4 hpf) were collected, E3 culture medium was used as the control group, and different lead exposure concentrations (6, 12, 24, 48 μmol/L) as the poisoned group during the time was 140 h. The mortalities, hatching rates and deformity rates were calculated, the behavioral changes of 144 hpf larvae were observed (moving speed, moving distance, activity, absolute turn angle, the light-evoked startle response, darkness-evoked escape response and thigmotaxis) . The levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were detected in zebrafish larvae in the heads. ELISA kits were used to detect the expression of 5-hydroxytryptamine (5-HT) , dopamine (DA) , noradrenaline (NA) and corticotropin-releasing hormone (CRH) related to anxiety. Results: The mortalities rates of zebrafish embryos in the lead exposure concentration of 12, 24 and 48 μmol/L were higher than the control group, and the embryo hatching rates were lower than control group. The deformity rates of zebrafish larvae in the lead exposure concentration of 24 and 48 μmol/L were higher than control group (P<0.01) . The movement speed, activity and thigmotaxis of zebrafish larvae in the lead exposure concentration of 24 and 48 μmol/L were significantly lower than control group, the absolute turn angle were higher than control group (P<0.01) . The moving distance and darkness-evoked escape response of zebrafish larvae in the lead exposure concentration of 48 μmol/L group were lower than control group (P<0.05) . The light-evoked startle response of zebrafish larvae in the lead exposure concentration of 12, 24 and 48 μmol/L groups were lower than control group (P<0.05) . The ROS levels and MDA concentrations in the heads of larvae in the lead exposure concentration of 24 and 48 μmol/L were higher than control group (P<0.05) . The levels of NA and DA in the heads of the larvae in the lead exposure groups of 12, 24 and 48 μmol/L were lower than control group, and the levels of 5-HT and CRH in the heads of the larvae in the lead exposure groups of 24 and 48 μmol/L were higher than control group (P<0.05) . Conclusion: Lead exposure is toxic to zebrafish embryonic development and may cause anxiety-like neurobehavior changes and oxidative stress in zebrafish.

Biased reorientation in the chemotaxis of peritrichous bacteria Salmonella enterica serovar Typhimurium

Many kinds of peritrichous bacteria that repeat runs and tumbles by using multiple flagella exhibit chemotaxis by sensing a difference in the concentration of the attractant or repellent between two adjacent time points. If a cell senses that the concentration of an attractant has increased, their flagellar motors decrease the switching frequency from counterclockwise to clockwise direction of rotation, which causes a longer run in swimming up the concentration gradient than swimming down. We investigated the turn angle in tumbles of peritrichous bacteria swimming across the concentration gradient of a chemoattractant because the change in the switching frequency in the rotational direction may affect the way tumbles. We tracked several hundreds of runs and tumbles of single cells of Salmonella enterica serovar Typhimurium in the concentration gradient of L-serine and found that the turn angle depends on the concentration gradient that the cell senses just before the tumble. The turn angle is biased toward a smaller value when the cells swim up the concentration gradient, whereas the distribution of the angle is almost uniform (random direction) when the cells swim down the gradient. The effect of the observed bias in the turn angle on the degree of chemotaxis was investigated by random walk simulation. In the concentration field where attractants diffuse concentrically from the point source, we found that this angular distribution clearly affects the reduction of the mean-square displacement of the cell that has started at the attractant source, that is, the bias in the turn angle distribution contributes to chemotaxis in peritrichous bacteria.

Molecular-field-theory fits to magnetic susceptibilities of antiferromagnetic GdCu2Si2, CuO, LiCrO2, and [formula omitted]-CaCr2O4 single crystals below their Néel temperatures

A recently-developed molecular field theory (MFT) has been used to fit single-crystal magnetic susceptibility χ versus temperature T data below the respective antiferromagnetic ordering temperature TN for a variety of collinear and coplanar noncollinear Heisenberg antiferromagnets. The spins in the system are assumed to interact by Heisenberg exchange and to be identical and crystallographically equivalent. The fitting parameters for χ(T) of collinear antiferromagnets are measurable quantities: the Weiss temperature θp in the Curie–Weiss law, TN,χ(TN), and the spin S. For coplanar noncollinear helix and cycloid structures, an additional fitting parameter is the turn angle between layers of ferromagnetically-aligned spins. Here MFT fits to anisotropic χ(T) data from the literature for single crystals of the collinear antiferromagnets GdCu2Si2 and CuO and the noncollinear antiferromagnets LiCrO2 with a 120° cycloidal structure and α-CaCr2O4 with a 120° helical structure below their respective Néel temperatures are presented. The MFT fit to the anisotropic χ(T⩽TN) data for CuO is poor, whereas the fits to the data for GdCu2Si2, LiCrO2, and α-CaCr2O4 are quite good. The poor fit for CuO is attributed to the influence of strong quantum fluctuations associated with the small Cu spin and the quasi-one-dimensional magnetism that are not taken into account by the MFT. The magnetic contribution to the zero-field heat capacity of the collinear antiferromagnet GdNiGe3 at T⩽TN is also fitted by the MFT.

Freely Behaving Mice Can Brake and Turn During Optogenetic Stimulation of the Mesencephalic Locomotor Region.

A key function of the mesencephalic locomotor region (MLR) is to control the speed of forward symmetrical locomotor movements. However, the ability of freely moving mammals to integrate environmental cues to brake and turn during MLR stimulation is poorly documented. Here, we investigated whether freely behaving mice could brake or turn, based on environmental cues during MLR stimulation. We photostimulated the cuneiform nucleus (part of the MLR) in mice expressing channelrhodopsin in Vglut2-positive neurons in a Cre-dependent manner (Vglut2-ChR2-EYFP) using optogenetics. We detected locomotor movements using deep learning. We used patch-clamp recordings to validate the functional expression of channelrhodopsin and neuroanatomy to visualize the stimulation sites. In the linear corridor, gait diagram and limb kinematics were similar during spontaneous and optogenetic-evoked locomotion. In the open-field arena, optogenetic stimulation of the MLR evoked locomotion, and increasing laser power increased locomotor speed. Mice could brake and make sharp turns (~90°) when approaching a corner during MLR stimulation in the open-field arena. The speed during the turn was scaled with the speed before the turn, and with the turn angle. Patch-clamp recordings in Vglut2-ChR2-EYFP mice show that blue light evoked short-latency spiking in MLR neurons. Our results strengthen the idea that different brainstem neurons convey braking/turning and MLR speed commands in mammals. Our study also shows that Vglut2-positive neurons of the cuneiform nucleus are a relevant target to increase locomotor activity without impeding the ability to brake and turn when approaching obstacles, thus ensuring smooth and adaptable navigation. Our observations may have clinical relevance since cuneiform nucleus stimulation is increasingly considered to improve locomotion function in pathological states such as Parkinson’s disease, spinal cord injury, or stroke.