Influence of vagal activity on classically conditioned heart rate in rats.

Examined the relative contributions of parasympathetic and sympathetic activity in controlling classically conditioned heart rate (HR) in 112 female Long-Evans rats in a 2 * 2 * 2 factorial design involving comparisons of the following factors: (a) conditioning vs sensitization, (b) vagal blockade vs nonblockade, and (c) acquisition vs extinction. Vagal blockade led to a substantial reduction in the performance level of the decelerative HR CR, but it did not appear to interfere with the learning of the CR as measured during extinction under saline. It is concluded that the magnitude of the CR was primarily mediated by increased vagal activity and that sympathetic involvement was minor. Results are related to a central state hypothesis which links together decelerative conditioned HR and inhibition of motor activity in the rat. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Empirical Bayes Approach to Reliability

A Bayesian reliability estimation technique known as the ``empirical Bayes approach' is developed which uses previous experience nce to get a Bayesian point estimator. The techniques require no knowledge of the form of the unknown prior distribution and are robust to assumptions about its form. Empirical Bayes techniques are applicable to situations in which prior, independent observations of the random variable X from the random couple (?, X) are available where ? is the observed parameter of interest distributed in accordance with the unknown prior distribution. Performance comparisons of the empirical Bayes and other well established techniques are developed by examples for the binomial, exponential, Normal, and Poisson situations which often occur in reliability problems. In all cases the empirical Bayes estimator performed better than the classical estimator in minimizing the average squared error.     

Nanostructured electrochemical sensors based on functionalized nanoporous silica for voltammetric analysis of lead, mercury, and copper

We have successfully developed electrochemical sensors based on functionalized nanostructured materials for voltammetric analysis of toxic metal ions. Glycinylurea self-assembled monolayers on mesoporous silica (Gly-UR SAMMS) were incorporated in carbon paste electrodes for the detection of toxic metal ions such as lead, copper, and mercury based on adsorptive stripping voltammetry (AdSV). The electrochemical sensor yields a linear response at a low ppb level of Pb2+ (i.e., 2.5-50 ppb) after a 2-min preconcentration period, with reproducible measurements (%RSD = 3.5, N = 6) and an excellent detection limit (1 ppb). By exploiting the interfacial functionality of Gly-UR SAMMS, the sensor is selective for the target species, does not require the use of a mercury film, and can be easily regenerated in dilute acid solution. The rigid, open, parallel pore structure, combined with suitable interfacial chemistry of SAMMS, also results in fast analysis times (2-3 min). The nanostructured SAMMS materials enable the development of miniature sensing devices that are compact and low cost, have low energy consumption, and are easily integrated into field-deployable units.     

Incorporation of hydroxypyridinone ligands into self-assembled monolayers on mesoporous supports for selective actinide sequestration

In this study, three isomers of hydroxypyridinones (1,2-HOPO, 3,2-HOPO, and 3,4-HOPO) were attached to self-assembled monolayers on mesoporous silica (SAMMS). The HOPO-SAMMS materials have superior solid adsorbents properties: they do not suffer from solvent swelling; their rigid, open pore structure allows rapid sorption kinetics; their extremely high surface area enables the installation of high functional density; and being silica-based, they are compatible with vitrification into a final vitreous waste form. Kinetics, equilibrium, and selectivity of the adsorptions of actinide on the HOPO-SAMMS at various pH values and in the presence of other metal cations, anions, and competing ligands are reported. Rapid sequestration of U(VI), Np(V), and Pu(IV) was observed. Very little competition from transition metal cations and common species was observed.     

LOCA hydroloads calculations with multidimensional nonlinear fluid-structure interaction

A methodology for realistically analyzing three-dimensional fluid-structure interaction effects and the resulting hydrodynamic loads during the subcooled portion of a hypothetical loss of coolant accident (LOCA) in a pressurized water reactor (PWR) is discussed. The methodology uses a hydrodynamic computer program, STEALTH 3D, coupled with a structural response program, WHAMSE 3D, to calculate the dynamic interaction of fluid and structure during a reactor vessel blowdown. This coupled program is user oriented and highly versatile in modeling the various components in complex reactor systems. Assessment of the methodology is provided by STEALTH/WHAMSE 3D calculations of blowdown tests in the German Battelle-Frankfurt RS-16B facility (Test DWR5) and the HDR facility (Test V31.1). The calculations are described and the results compared with experimental data. Agreement between the calculational results and experimental data is extremely good.     

Reading ability and utilization of orthographic structure in reading.

Used a perceptual-recognition task to assess whether utilization of orthographic structure in letter recognition varies with reading ability. Anagrams of words were made to create strings that orthogonally combined frequency and regularity measures of orthographic structure. These strings and the original words were used as test stimuli in a letter-recognition task. 22 good and poor undergraduate readers (selected by their scores on the Nelson-Denny Reading Test) showed equally large effects of orthographic structure on task accuracy, whereas in a 2nd experiment, 10 poor 6th-grade readers did not utilize orthographic structure to the same degree as 10 very good 6th-grade readers. To facilitate the teaching of orthographic structure, some of the important constraints in written English and various games for teaching these constraints are presented. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Software development of interactive microcomputer programs used in teaching mathematics: A case history

This paper presents the experience of using microcomputers in the teaching of mathematics to undergraduates at Paisley College of Technology. The production of software for use by students has been a sizeable undertaking and the paper presents an account of the software development programme whose first stage was a formative and experimental period on which was based the specification of the software developed in the second stage. The definition and development of software tools for interactive programs to be used in mathematics teaching has been found to be of prime importance in producing the required software in a relatively efficient manner.     

Sulfamethazine water medication pharmacokinetics and contamination in a commercial pig production unit

Sulfamethazine is often used to treat disease in the swine industry. Sulfamethazine is available as water or feed medication and historically (over the past 40 years) has been associated with residue violations in both the United States and Europe. Despite sulfamethazine's approval for use as a water medication, little research on the pharmacokinetics of the water formulation is available. Therefore, a pilot study was performed to determine the plasma levels of an approved sulfamethazine water medication. Plasma levels in pigs treated with an oral bolus (250 mg/kg), which is equivalent to the total drug consumed within a 24-h period, achieved therapeutic concentrations (50 microg/ml). Noncompartmental-based pharmacokinetic model parameters for clearance, half-life, and volume of distribution were consistent with previously published values in swine. However, the above treatment resulted in exposure of pen mates to sulfamethazine at levels currently above tolerance (0.1 ppm). Using a physiologically based pharmacokinetic model, the treatment dose simulation was compared with observed plasma levels of treated pigs. Flexibility of the physiologically based pharmacokinetic model also allowed simulation of control-pig plasma levels to estimate contamination exposure. A simulated exposure to 0.15 mg/kg twice within approximately 8 h resulted in detectable levels of sulfamethazine in the control pigs. After initial exposure, a much lower dose of 0.059 mg/kg maintained the contamination levels above tolerance for at least 3 days. These results are of concern for producers and veterinarians, because in commercial farms, the entire barn is often treated,and environmental contamination could result in residues of an unknown duration.     

Comb Polymer Architecture Effects on the Rheological Property Evolution of Concentrated Cement Suspensions

We have studied the rheological behavior of concentrated cement suspensions in the absence and presence of comb polymers comprised of a polyacrylic acid (PAA) backbone and charge-neutral, poly(ethylene oxide) (PEO) teeth. These species possessed a uniform backbone molecular weight and graft density, with varying teeth molecular weight. Both PAA, a linear polyelectrolyte, and PAA/PEO comb polymers imparted initial stability to concentrated cement suspensions above a critical weight fraction, w * of 4 mg/(g of cement). Cement–PAA suspensions, however, set prematurely. Their rapid, irreversible stiffening stemmed from deleterious interactions between PAA and multivalent counterions in solution. Interestingly, the presence of PEO teeth comprised of only a few monomer units in length mitigated such interactions. The rheological property evolution of concentrated cement–PAA/PEO suspensions exhibited complex behavior ranging from the reversible gel-like response observed at short teeth lengths to a remarkable gel-to-fluid transition observed during the deceleratory period for systems comprised of longer PEO teeth. At longer hydration times, all cement–PAA/PEO suspensions exhibited initial elastic modulus values, G_i '∼ exp( t /τ_c) before the onset of the acceleratory period, followed by initial set. Their characteristic hydration time, τ_c, and set time depended strongly on the concentration of "free" carboxylic acid groups [COO⁻] arising from non-adsorbed polyelectrolyte species in solution.