Asymptotic sampling errors in closed-loop hybrid systems

A vector differential equation for the error due to sampling in closed-loop hybrid systems is developed using several approximations derived with Taylor series expansions. The equation is valid for both linear and nonlinear hybrid systems under the condition that the sampling period is small. The error equation is linear. Its homogeneous part is independent of how the hybrid system is subdivided into subsystems, but its forcing function depends on the characteristics of the analog and digital subsystems. Both parts of the error equation depend on the system state variables. The form of the equation shows that asymptotic sampling error depends on the first power of the sampling period and that the execution time of the digital subsystem has a predominant effect similar to that of the sampling period but weighted twice as heavily. The equation can be applied in compensating as well as evaluating hybrid systems. An example is included to illustrate the use and accuracy of the equations.     

Cerebral blood flow changes in cluster headache

Serial cerebral blood flow studies performed by the intra-carotid 133Xenon method were fortuitously determined during the course of a cluster headache in a 32 year old man. The initial study was performed about 10 min after the headache began and showed values at the upper limit of normal. Twenty min after the headache started a second procedure showed that the autoregulatory response on hyperventilation was normal. Ergotamine tartrate was given intra-muscularly 23 min after the headache began and there was partial relief. A third cerebral blood flow estimation showed abnormally high values. The probable reasons for this are discussed.     

An emulsion method for the sensory evaluation of edible oils

The flavor intensity of soybean oils was evaluated in emulsions stabilized with gum acacia. A 10-point scale was used with a blank to establish the bland end of the scale and a standard diacetyl solution to establish a point near midscale. Tasting oils in emulsion gave significantly different scores than tasting oil directly. Evaluation in emulsion decreased panel error for poor quality oils but not for very bland oils. At least six samples could be tasted in emulsion without casusing panel fatigue or reducing accuracy. The concentration of oil in the emulsion could be adjusted to increase sensitivity to weak flavors or improve the evaluation of intensely flavored oils. Soybean oils containing various amounts of linolenic acid were evaluated by the emulsion method, and those with lesser amounts of linolenic acid were shown to be more stable. A gas Chromatographic total volatile method was shown to correlate fairly well with sensory evaluation of oils tasted in emulsions under conditions where both flavors scores and total volatiles changed significantly with time. Journal Paper no. J-10442 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project no. 2143.     

Estimating average growth trajectories in shape-space using kernel smoothing

In this paper, we show how a dense surface point distribution model of the human face can be computed and demonstrate the usefulness of the high-dimensional shape-space for expressing the shape changes associated with growth and aging. We show how average growth trajectories for the human face can be computed in the absence of longitudinal data by using kernel smoothing across a population. A training set of three-dimensional surface scans of 199 male and 201 female subjects of between 0 and 50 years of age is used to build the model.     

Treating another's actions as one's own: Children's memory of and learning from joint activity.

Children often overestimate their contribution to collaborative activities. Across 2 studies, the authors investigated whether this memory bias supports internalization of the actions of others in the context of joint exchanges. After taking turns with (high collaborative condition; Studies 1 and 2) or working independently of (low collaborative condition; Study 2) an adult experimenter to create a series of novel toys, children's agent memory and reconstruction ability were assessed. Children in the high collaborative condition but not the low collaborative condition systematically overclaimed the actions of their social partner, more frequently reporting having completed steps performed by the experimenter than vice versa. This "I did it" bias was related to learning performance: high collaborative children outperformed low collaborative children both during an immediate reconstruction task and 4 months later, and the strength of the bias predicted children's independent toy-building accuracy. It is argued that the "I did it" bias may emerge as part of a general process of learning from others and is supported by a common framework for representing self-actions and other actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immobilization of acrylamide-modified oligonucleotides by co-polymerization

A flexible chemistry for solid phase attachment of oligonucleotides is described. Oligonucleotides bearing 5'-terminal acrylamide modifications efficiently co-polymerize with acrylamide monomers to form thermally stable DNA-containing polyacrylamide co-polymers. Co-polymerization attachment is specific for the terminal acrylamide group. Stable probe-containing layers are easily fabricated on supports bearing exposed acrylic groups, including plastic microtiter plates and silanized glass. Attachment can be accomplished using standard polyacrylamide gel recipes and polymerization techniques. Supports having a high surface density of hybridizable oligonucleotide (approximately 200 fmol/mm2) can be produced.     

Effect of protein aggregation in the aqueous phase on the binding of membrane proteins to membranes

Analysis of the binding of hydrophobic peptides or proteins to membranes generally assumes that the solute is monomeric in both the aqueous phase and the membrane. Simulations were performed to examine the effect of solute self-association in the aqueous phase on the binding of monomeric solute to lipid vesicles. Aggregation lowered the initial concentration of monomeric solute, which was then maintained at a relatively constant value at the expense of the aggregated solute, as the lipid concentration was increased. The resultant binding isotherm has a more linear initial portion rather than the classic hyperbolic shape. Although this shape is diagnostic of solute self-association in the aqueous phase, various combinations of values for the membrane partition coefficient and the solute self-association constant will generate similar isotherms. Data for cytochrome b5 were analyzed and, when the self-association constant was estimated by gel filtration, a unique value for the membrane partition coefficient was obtained. Thus, to obtain a true partition coefficient the state of the solute in the aqueous phase must be known. If the concentration of the monomeric solute species in the aqueous phase can be independently determined, then, even with heterogeneous aggregates, the true partition coefficient can be obtained.