Can we really walk straight?

Twenty healthy men were asked to walk as straight as possible to a target 60 m away at normal speed. A series of footprints was recorded for each subject by having him wear socks soaked with red ink and walk on white paper fixed flat to the floor. Fourier analysis was applied to determine whether the subjects actually were able to walk straight, and the results revealed that all walked in a sinuous line rather than a straight line. Periodicity and amplitude of the meandering differed from subject to subject. These facts suggest that none of us can walk in a strictly straight line; rather, we meander, primarily due to a slight structural or functional imbalance of our limbs, which produces a gait asymmetry, and secondarily due to feedback from our sense of sight, which acts to correct the shifted walking course.     

Measuring straight line segments using HT butterflies

This paper addresses the features of Hough Transform (HT) butterflies suitable for image-based segment detection and measurement. The full segment parameters such as the position, slope, width, length, continuity, and uniformity are related to the features of the HT butterflies. Mathematical analysis and experimental data are presented in order to demonstrate and build the relationship between the measurements of segments and the features of HT butterflies. An effective method is subsequently proposed to employ these relationships in order to discover the parameters of segments. Power line inspection is considered as an application of the proposed method. The application demonstrates that the proposed method is effective for power line inspection, especially for corner detection when they cross poles.     

A simple strategy for jumping straight up

Jumping from a stationary standing position into the air is a transition from a constrained motion in contact with the ground to an unconstrained system not in contact with the ground. A simple case of the jump, as it applies to humans, robots and humanoids, is studied in this paper. The dynamics of the constrained rigid body are expanded to define a larger system that accommodates the jump. The formulation is applied to a four-link, three-dimensional system in order to articulate the ballistic motion involved. The activity of the muscular system and the role of the major sagittal muscle groups are demonstrated. The control strategy, involving state feedback and central feed forward signals, is formulated and computer simulations are presented to assess the feasibility of the formulations, the strategy and the jump.     

Kinetics of thermophilic,anaerobic oxidation of straight and branched chain butyrate and valerate

The degradation kinetics of normal and branched chain butyrate and valerate are important in protein-fed anaerobic systems, as a number of amino acids degrade to these organic acids. Including activated and primary wastewater sludge digesters, the majority of full-scale systems digest feeds with a significant or major fraction of COD as protein. This study assesses the validity of using a common kinetic parameter set and biological catalyst to represent butyrate, n-valerate, and i-valerate degradation in dynamic models. The i-valerate degradation stoichiometry in a continuous, mixed population system is also addressed, extending previous pure-culture and batch studies. A previously published mathematical model was modified to allow competitive uptake of i-valerate, and used to model a thermophilic manure digester operated over 180 days. The digester was periodically pulsed with straight and branched chain butyrate and valerate. Parameters were separately optimized to describe butyrate, i-valerate, and n-valerate degradation, as well as a lumped set optimized for all three substrates, and nonlinear, correlated parameter spaces estimated using an F distribution in the objective function (J). Each parameter set occupied mutually exclusive parameter spaces, indicating that all were statistically different from each other. However, qualitatively, the influence on model outputs was similar, and the lumped set would be reasonable for mixed acid digestion. The main characteristic not represented by Monod kinetics was a delay in i-valerate uptake, and was compensated for by a decreased maximum uptake rate (k(m)). Therefore, the kinetics need modification if fed predominantly i-valerate. Butyrate (i- and n-) and n-valerate could be modeled using stoichiometry consistent with beta-oxidation degradation pathways. However, i-valerate produced acetate only, supporting the stoichiometry of a reaction determined by other researchers in pure culture. Therefore, lumping i-valerate stoichiometry with that of n-valerate will not allow good system representation, especially when the feed consists of proteins high in leucine (which produces i-valerate), and the modified model structure and stoichiometry as proposed here should be used. This requires no additional kinetic parameters and one additional dynamic concentration state variable (i-valerate) in addition to the variables in the base model.     

The Genome Sequencer FLX System--longer reads, more applications, straight forward bioinformatics and more complete data sets

The Genome Sequencer FLX System (GS FLX), powered by 454 Sequencing, is a next-generation DNA sequencing technology featuring a unique mix of long reads, exceptional accuracy, and ultra-high throughput. It has been proven to be the most versatile of all currently available next-generation sequencing technologies, supporting many high-profile studies in over seven applications categories. GS FLX users have pursued innovative research in de novo sequencing, re-sequencing of whole genomes and target DNA regions, metagenomics, and RNA analysis. 454 Sequencing is a powerful tool for human genetics research, having recently re-sequenced the genome of an individual human, currently re-sequencing the complete human exome and targeted genomic regions using the NimbleGen sequence capture process, and detected low-frequency somatic mutations linked to cancer.     

Visual control of straight flight in Drosophila melanogaster

Summary The optomotor system of Drosophila is investigated in a flight simulator in which the fly's yaw torque controls the angular velocity of the panorama (striped drum, negative feedback). Flies in the flight simulator maintain a stable orientation even in a homogeneously textured panorama without landmarks. During straight flight, torque is not zero. It consists of small pulses mostly alternating in polarity. The course is controlled by the duration (and possibly amplitude) of the pulses. The system operates under reafference control. By comparing the pulses with the visual input the system continuously measures and adjusts the efficacy of the torque output. The comparison, however, is not between angular velocity and yaw torque but, instead, between visual acceleration and pretorque, the first time derivative of torque. For comparison, the system first computes a cross-correlation. If the correlation coefficient is above a certain threshold the system calculates the external gain and adjusts its internal gain so as to keep the total gain constant. With the correlation coefficient below threshold, however, the system keeps the internal gain low despite the infinitely small external gain. We propose that for a reafferent optomotor system the coupling coefficient and the correlation coefficient of pretorque and visual acceleration are more relevant than the distinction between exafference and reafference.Abbreviation EMD elementary movement detector