Large deflection nonlinear mechanics of curved cantilevers under contact point loading

Presented here is a comprehensive model for hook bending behavior under contact loading conditions, motivated by the relevance of this problem to reusable hook attachment systems in nature and engineering. In this work, a large deflection model that can describe the bending of hooks, taken as precurved cantilevers with uniform initial curvature, was derived and compared with physical testing. Physical testing was performed with stainless-steel and aluminum hooks shaped as semicircular arcs. The force versus displacement behavior exhibited a linear portion for small displacements but at large displacements there was an asymptotic relation where the force approached some limit and remained flat as further displacement occurred. Comparison with testing showed that the model developed in this paper gave good agreement with the physical testing. Surprisingly, in dimensionless form, all parameters to define the hook transform to approximately linear functions of displacement. Using these linear relations, several equations are presented that rapid calculation of the dimensional force versus displacement for a hook.

FreeClimber: Automated quantification of climbing performance in Drosophila

Negative geotaxis (climbing) performance is a useful metric for quantifying Drosophila health. Manual methods to quantify climbing performance are tedious and often biased, while many available computational methods have challenging hardware or software requirements. We present an alternative: FreeClimber. This open source, Python-based platform subtracts a video's static background to improve detection for flies moving across heterogeneous backgrounds. FreeClimber calculates a cohort's velocity as the slope of the most linear portion of a mean-vertical position vs. time curve. It can run from a graphical user interface for optimization or a command line interface for high-throughput and automated batch processing, improving accessibility for users with different expertise. FreeClimber outputs calculated slopes, spot locations for follow up analyses (e.g. tracking), and several visualizations and plots. We demonstrate FreeClimber's utility in a longitudinal study for endurance exercise performance in Drosophila mitonuclear genotypes using six distinct mitochondrial haplotypes paired with a common w1118 nuclear background.

Design an Enzyme-Less Sensitive Sensor for Cholesterol Detection Based on Poly Brucine/Polyvinylpyrrolidone Film

In the current study, the main focus is designing a new enzyme-less modified electrode based on the electro deposition of Poly Brucine/Polyvinylpyrrolidone on pencil graphite electrode and its utilizing for cholesterol quantification. The electrochemical responses of the proposed sensor were recorded using cyclic and square wave voltammetry techniques for detection of cholesterol at optimized pH =2. The morphology investigations of the modified surfaces were performed by scanning electron microscopy and the obtained images verified Nano formations in the structure of the sensor. The proposed electrochemical sensor revealed a good electro catalytic response to cholesterol concerning the parameters α = 0.83, log Ks = 3.11 and Γ = 8.55 × 10T8. Besides, the calibration plot was acquired with a linear portion in the concentration ranges of 25 to 95 nmol L−1 (nM) and the detection limit (LOD = 8.28 nM). The designed sensor demonstrated the reproducible and repeat-able outputs, the high sensitivity and stability in analyzing cholesterol as well as recoveries in blood serum samples without any side serious interferences.

Hammerstein modeling and hybrid control of force and position for a novel integration of actuating and sensing ionic polymer metal composite gripper

An innovative integration of actuating and sensing ionic polymer metal composite (IPMC) gripper is proposed and fabricated in this paper. The IPMC gripper is composed of a stationary copper finger and an IPMC finger attached to a force sensor. In order to make IPMC gripper useful in bio-manipulation application, control strategy is a critical factor to resist nonlinear characteristic of IPMC. Hammerstein model of IPMC output displacement is constructed with static nonlinear portion and dynamic linear portion. We utilize creep operator superposition and auto-regression (ARX) models to represent static nonlinear and dynamic linear portions respectively by modeling methods based on data. Then a novel control scheme is proposed and designed using inverse creep compensator for static nonlinear portion and uncertainty state feedback robust control based on state observer for dynamic linear portion. When IPMC reaches a constant displacement to grasp a miniature object, the grasping force may not be provided enough to complete grasping task. Finally, hybrid control of force and position strategy for IPMC gripper is conducted and realized on physical experimental platform. The experimental results demonstrate the effectiveness of control system to guarantee stable manipulation.

Магнитные свойства допированных висмутом титанатов-пирохлоров иттербия и гольмия

Bismuth-doped ytterbium and holmium titanates have been synthesized and their magnetic properties have been investigated. The magnetization curves and temperature dependences of the susceptibility in fields of up to 30 kOe at temperatures from 2 to 300 K have been obtained. The properties of the doped and undoped titanates have been compared. It has been established that the temperature dependences of the product of susceptibility and temperature contains a linear portion and the slope sign in these dependences changes upon doping for both the Ho_2Ti_2O_7 and Yb_2Ti_2O_7 titanates. Based on the investigated temperature dependences of the susceptibility, the magnetic dipole and exchange couplings in the titanates have been analyzed.

Magnetic properties of ZnO:Co layers obtained by pulsed laser deposition method

We have studied magnetic properties of zinc oxide (ZnO) composite doped with Co ions. The samples were obtained by pulsed laser deposition (PLD) method. Electron magnetic resonance (EMR) measurements were carried out and temperature dependence of EMR spectra was obtained. Analysis of temperature dependence of the integral intensity of EMR spectra was carried out using Curie-Weiss law. Reciprocal of susceptibility of an antiferromagnetic (AFM) material shows a discontinuity at the Néel temperature and extrapolation of the linear portion to negative Curie temperature. The results of temperature dependence of EMR spectra for the ZnO:Co sample and linear extrapolation to the Curie-Weiss law indicated the AFM interaction between Co ions characterized by the Néel temperatures TN = 50 K and TN = 160 K for various samples. The obtained g-factor is similar to g-factors of nanocrystals presented in literature, and the results confirm that in the core of these nanocrystals Co was incorporated as Co2+, occupying Zn2+ sites in wurtzite structure of ZnO.

Heterodyne light rangefinder

In this paper, we consider the possibilities and ways to improve the accuracy of linear measurements and reduce modulation power, as well as their implementation in the construction of a new high-precision laser rangefinder. To do this, it is necessary to implement the transition to a new method of the modulation method that occurs when the operating point of the light modem goes over to the average linear portion of the modulation characteristic of light (MHS). In this case, the dependence of the amplitude-modulated reception light on the distance is characterized by a first-order Bessel function J1 (x) instead of J0 (x), which takes place at the compensation method of the extremum. In addition, such a transition leads not only to a decrease in modulation power, but also to nonlinear distortions and spreads of the modulation phase. All this leads to the fact that there is an increase in the accuracy of linear measurements by almost an order of magnitude. The phase error m? of linear measurements is estimated at hundredths of a millimeter, 0,015–0,02 mm. However, for the implementation of this method, there are difficulties associated with the process of phase detection of the receiving modulated light. There are no photoelectric multipliers operating at a frequency of 600–1200 MHz. The proposed work provides a schematic diagram of the heterodyne laser range finder, which makes it possible to realize the operation of a light-range meter with circular polarization of light by using an auxiliary generator-heterodyne.

Potential Relationship between Passive Plantar Flexor Stiffness and Running Performance

The present study aimed to determine the relationship between passive stiffness of the plantar flexors and running performance in endurance runners. Forty-eight well-trained male endurance runners and 24 untrained male control subjects participated in this study. Plantar flexor stiffness during passive dorsiflexion was calculated from the slope of the linear portion of the torque-angle curve. Of the endurance runners included in the present study, running economy in 28 endurance runners was evaluated by measuring energy cost during three 4-min trials (14, 16, and 18 km/h) of submaximal treadmill running. Passive stiffness of the plantar flexors was significantly higher in endurance runners than in untrained subjects. Moreover, passive plantar flexor stiffness in endurance runners was significantly correlated with a personal best 5000-m race time. Furthermore, passive plantar flexor stiffness in endurance runners was significantly correlated with energy cost during submaximal running at 16 km/h and 18 km/h, and a trend towards such significance was observed at 14 km/h. The present findings suggest that stiffer plantar flexors may help achieve better running performance, with greater running economy, in endurance runners. Therefore, in the clinical setting, passive stiffness of the plantar flexors may be a potential parameter for assessing running performance.

Comparative Effect of Heat Shock on Survival of O157:H7 and Non-O157 Shiga Toxigenic Escherichia coli and Salmonella in Lean Beef with or without Moisture-Enhancing Ingredients

ABSTRACT Thermal tolerance of pathogenic bacteria has been shown to increase after exposure to sublethal elevated temperatures, or heat shock. We evaluated the effect of heat shock at 48°C on thermal tolerance (D55°C) of cocktails of O157 and non-O157 Shiga toxigenic Escherichia coli (STEC) and Salmonella in lean ground beef with or without moisture-enhancing ingredients. Beef was moisture enhanced to 110% (w) with a 5% NaCl–2.5% sodium tripolyphosphate (w/w) brine. Meat, with or without added brine, was inoculated (∼108 CFU/g) and heat shocked at 48°C for 0, 5, or 30 min, followed by isothermal heating at 55°C. Inoculated control samples were unenhanced and were not subject to heat shock. From the linear portion of the log CFU per gram surviving cells over time plots, D55°C-values (minutes) were calculated. D55°C was 20.43, 28.78, and 21.15 min for O157, non-O157, and Salmonella controls, respectively. Overall, heat shock significantly increased D55°C, regardless of pathogen (P < 0.05). After 30 min of heat shock, D55°C increased 89 and 160% for O157 STEC, 32 and 49% for non-O157 STEC, and 29 and 57% for Salmonella, in unenhanced and enhanced samples, respectively, relative to the pathogen control. D55°C for Salmonella was the same or significantly less than for O157 and non-O157 STEC, regardless of heat shock, and was significantly less than for O157 and non-O157 STEC in all trials with moisture-enhanced meat (P < 0.05). Moisture-enhancing ingredients significantly increased D55°C, regardless of pathogen (P < 0.05). We suggest that thermal processes validated against Salmonella may not prove effective against STEC in all cases and that regulators of the beef industry should focus attention on STEC in nonintact moisture-enhanced beef products.

Propagation of Front Waves in Myelinated Nerve Fibres

In this paper, the authors examine the propagation of wave fronts in myelinated nerve fibres and applications as electrical transmission lines constituted of linear and nonlinear portions. Numerical simulations show that the front introduced in the nonlinear portion deforms itself in the linear portion, but recovers its initial profile and velocity in the next nonlinear portion. The phenomenon of deformation and recovery can be used for the development of new and low cost electrical transmission lines that can be used to transport localized excitations.