Hanging by a thread: unusual nocturnal resting behaviour in a jumping spider

Background For diurnal animals that heavily rely on vision, a nocturnal resting strategy that offers protection when vision is compromised, is crucial. We found a population of a common European jumping spider (Evarcha arcuata) that rests at night by suspending themselves from a single silk thread attached overhead to the vegetation, a strategy categorically unlike typical retreat-based resting in this group. Results In a comprehensive study, we collected the first quantitative field and qualitative observation data of this surprising behaviour and provide a detailed description. We tested aspects of site fidelity and disturbance response in the field to assess potential functions of suspended resting. Spiders of both sexes and all developmental stages engage in this nocturnal resting strategy. Interestingly, individual spiders are equally able to build typical silk retreats and thus actively choose between different strategies inviting questions about what factors underlie this behavioural choice. Conclusions Our preliminary data hint at a potential sensory switch from visual sensing during the day to silk-borne vibration sensing at night when vision is compromised. The described behaviour potentially is an effective anti-predator strategy either by acting as an early alarm system via vibration sensing or by bringing the animal out of reach for nocturnal predators. We propose tractable hypotheses to test an adaptive function of suspended resting. Further studies will shed light on the sensory challenges that animals face during resting phases and should target the mechanisms and strategies by which such challenges are overcome.

Tuning Rules for Active Disturbance Rejection Controllers via Multiobjective Optimization—A Guide for Parameters Computation Based on Robustness

A set of tuning rules for Linear Active Disturbance Rejection Controller (LADRC) with three different levels of compromise between disturbance rejection and robustness is presented. The tuning rules are the result of a Multiobjective Optimization Design (MOOD) procedure followed by curve fitting and are intended as a tool for designers who seek to implement LADRC by considering the load disturbance response of processes whose behavior is approximated by a general first-order system with delay. The validation of the proposed tuning rules is done through illustrative examples and the control of a nonlinear thermal process. Compared to classical PID (Proportional-Integral-Derivative) and other LADRC tuning methods, the derived functions offer an improvement in either disturbance rejection, robustness or both design objectives.

Robust MFC anti-windup scheme for LTI systems with norm-bounded uncertainty

On the basic of the fact that all signals in the practical system are always bounded, this paper proposes a 4-degree-of-freedom (DoF) anti-windup scheme for saturated systems with parametric uncertainty. A fairly straightforward tuning rule is introduced to the robust stability analysis for the proposed anti-windup structure under the framework of IQC (Integral Quadratic Constraint). And the sufficient stability conditions are derived to check the reasonable definiteness of the related transfer function. Moreover, the control design for disturbance response and set-point tracking response are two separate part in this proposed scheme. Numerical example demonstrates the effectiveness and the considerable performance improvement of the anti-windup compensator that is designed by the proposed technique.

2 kW Dual-Output Isolated DC/DC Converter Based on Current Doubler and Step-Down Chopper

In the context of the auxiliary power for motor-driven vehicles having two systems, we propose a new topology for a dual-output isolated DC/DC converter, which offers advantages in terms of efficiency and size. The proposed circuit consists of an H-bridge inverter, a transformer, and an integrated circuit of a current doubler and step-down chopper. Considering the high power and high frequency, our objective was to evaluate and identify the issues of an actual device with a power output of 2 kW and switching frequency of 400 kHz. The circuit feasibility was examined through measurements of the prototype, and both the voltage target response and load disturbance response characteristics were confirmed to operate as designed. The maximum and minimum efficiencies of this circuit were 81.3 and 61.5%, respectively, demonstrating that the load loss of the step-down chopper had a significant impact on the efficiency. The loss analysis revealed that the loss at the integrated circuit on the secondary side accounted for more than 50% of the total loss. Moreover, issues such as the behavior at power-on, efficiency, and size were identified and evaluated, thereby achieving the objectives of the study.

Repeatable ecological dynamics govern response of experimental community to antibiotic pulse perturbation

In an era of pervasive anthropogenic ecological disturbances, there is a pressing need to understand the factors constituting community response and resilience. A detailed understanding of disturbance response needs to go beyond associations and incorporate features of disturbances, species traits, rapid evolution and dispersal. Multispecies microbial communities experiencing antibiotic perturbation represent a key system with important medical dimensions. However, previous microbiome studies on the theme have relied on high-throughput sequencing data from uncultured species without the ability to explicitly account for the role of species traits and immigration. Here we serially passaged a 34-species defined bacterial community through different levels of pulse antibiotic disturbance, manipulating the presence or absence of species immigration. To understand the ecological community response measured by amplicon sequencing, we combined initial trait data measured for each species separately and metagenome sequencing data revealing adaptive mutations during the experiment. We found that the ecological community response was highly repeatable within the experimental treatments, owing to an increasingly strong yet canalized response at increasing antibiotic levels, which could be partly attributed to key species traits (antibiotic susceptibility and growth rate). Increasing antibiotic levels were also coupled with increasing species extinction probability, making species immigration preventing this critical for community resilience. Moreover, we could detect signals of antibiotic resistance evolution occurring within species at the same time scale, leaving evolutionary changes in communities despite recovery at the species compositional level. Together these observations reveal a disturbance response which appears as classic species sorting but is nevertheless accompanied by rapid within-species evolution.