On the question of professional standards for computer-based test interpretation.

Comments on J. D. Matarazzo's (see record 1986-19878-001) discussion of computer-based test interpretation (CBTI) and R. D. Fowler and J. N. Butcher's (see record 1986-20446-001) response to Matarazzo. The call for the development of CBTI guidelines both by individuals with reservations about some CBTI programs (e.g., Matarazzo) and by those who are more positive about the present status of CBTI development (e.g., Fowler and Butcher) is emphasized. Matarazzo's reply to the author immediately follows this comment. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The effects of water-to-alkoxide ratio on the properties of gels and sol-gel derived high Tc ceramic superconductors

Type II (Y₁Ba₂Cu₃O_6+k) superconductors have been fabricated via sol-gel processing. Cu(II) ethoxide, Ba-methoxyethoxide, and Y-methoxyethoxide were synthesized from high purity metals. Gels were formed by mixing metal alkoxides, water, and solvents. The water-to-metal alkoxide ratio was chosen to be 1:1, 2:1, and 4:1 which resulted in a sol-to-gel transition time ranging from two to five days. The dried gels were fired at 950° C in flowing oxygen for 15 hrs and then slowly cooled to room temperature. The microstructure of the superconductors consisted of several phases. Susceptibility vs temperature curves showed that both the transition temperature (78 to 83 K) and the sharpness of the paramagnetic to diamagnetic transition were affected by the water-to-metal alkoxide ratio.     

Hypertonic saline dextran prime reduces increased intracranial pressure during cardiopulmonary bypass in pigs

Children and adults who develop neurologic deficits after cardiac surgery may experience cerebral ischemia during cardiopulmonary bypass. Increased intracranial pressure (ICP) may contribute to cerebral ischemia during bypass. Hypertonic saline dextran (HSD), a hyperosmotic, hyperoncotic resuscitation solution, decreases ICP in trauma resuscitation. We hypothesized that HSD would decrease ICP, reduce brain water, and reduce intravascular fluid requirements during bypass. Twelve swine were divided into two bypass groups: Group 1 (ISO = isotonic) received as prime 1 L of lactated Ringer's solution and 500 mL of 6% hydroxyethyl starch. Group 2 (HSD = hypertonic saline/dextran) received as prime 1 L of lactated Ringer's solution, 500 mL of 6% hydroxyethyl starch, and 1 mL/kg of 24% hypertonic saline/25% dextran. Normothermic bypass was instituted at 100 mL.kg-1.min-1. ICP increased significantly during bypass with ISO prime but not with HSD. Brain water in the cerebrum did not differ between groups but was reduced in the cerebellum to 75.9% +/- 1.4%. We conclude that HSD prevented any significant increase in ICP during normothermic bypass, and substantially improved fluid balance during bypass. In cardiac surgery patients in whom maintaining decreased ICP and reducing isotonic fluid administration is important, HSD may be a useful addition to the bypass prime solution.     

Graphics applied to medical image registration

Software that has been developed to automate and standardize comparison of 3D images is discussed. The major approaches to image registration are examined. The authors' registration and reconstruction software is described. Studies carried out to determine the relative accuracy of the present registration methods are reported. The main goal of the authors is to improve on commercial SPECT reconstruction algorithms and provide quantification accuracy sufficient for numerical assessment of tracer distribution     

Thermal runaway of nylon 6–10 during drawing under constant load

Anhydrous nylon 6–10 filaments were cold drawn (by propagation of a preexisting neck) under constant load. The extension rate i, which is proportional to the neck velocity, was observed to be a continuous function of the load up to a certain critical extension rate i_c above which i increased discontinuously (“runaway”) by approximately two orders of magnitude. If the filaments is in N₂ gas, i_c ? 0.4 cm/min, whereas if it is in He gas, i_c ? 1 cm/min. The structure of the drawn filament produced by runaway is an opaque, microvoid structure which, after a suitable change in load, forms first in the center of a filament and spreads toward the surface. This instability is attributed to the heating of the shoulder of the neck during neck motion. An analysis based on the measured activation enthalpy for neck motion and the thermal properties of nylon and the gas is used to predict i_c values that are in rough agreement with experiment.     

Computational modeling of type I collagen fibers to determine the extracellular matrix structure of connective tissues

A method is presented for generating computer models of biological tissues. The method uses properties of extracellular matrix proteins to predict the structure and physical chemistry of the elements that make up the tissue. The method begins with Protein Data Bank coordinate positions of amino acids as input into TissueLab software. From the amino acid sequence, a type I collagen-like triple helix backbone was computationally constructed and boundary spheres were added based on known chemical and physical properties of the amino acids. Boundary spheres determined the contact surface characteristics of the collagen molecules and intermolecular interactions were then determined by considering the relationships of the contact surfaces and by resolving the energy-minimum state using feasible sequential quadratic programming. From this, the software created fibrils that corresponded exactly to known collagen parameters and were further confirmed by finite element modeling. Computationally derived fibrils were then used to create collagen fibers and three-dimensional collagen matrices. By resolving the energy-minimum state, large complex components of the extracellular space as well as other structures can be determined to provide three-dimensional structure of molecules, molecular interactions and the tissues that they form.     

Conversation disrupts change detection in complex traffic scenes

A set of studies examined the effects of cognitive distraction on visual scanning and change detection in natural traffic scenes. Experiment 1 found that a naturalistic hands-free phone conversation could disrupt change detection, thereby degrading the encoding of visual information and increasing the frequency of undetected changes. Data also revealed a tendency for conversation to impair knowledge-driven orienting of attention in older adults. Experiment 2 found that an attentive listening task produced no such effects. Actual or potential applications of this research include the design of displays and interventions to minimize the effects of cognitive distraction on human performance.     

Application of scanning probe microscopy to the characterization and fabrication of hybrid nanomaterials

Scanning probe microscopy (SPM) is a widely used experimental technique for characterizing and fabricating nanostructures on surfaces. In particular, due to its ability to spatially map variations in materials properties with nanometer spatial resolution, SPM is particularly well suited to probe the subcomponents and interfaces of hybrid nanomaterials, i.e., materials that are made up of distinct nanometer scale components with distinguishable properties. In addition, the interaction of the SPM tip with materials can be intentionally tuned such that local surface modification is achieved. In this manner, hybrid nanostructures can also be fabricated on solid substrates using SPM. This report reviews recent developments in the characterization and fabrication of hybrid nanomaterials with SPM. Specific attention is given to nanomaterials that consist of both organic and inorganic components including individual biomolecules mounted on inorganic substrates. SPM techniques that are particularly well suited for characterizing the mechanical and electrical properties of such hybrid systems in atmospheric pressure environments are highlighted, and specific illustrative examples are provided. This review concludes with a brief discussion of the remaining challenges and promising future prospects for this field.     

Microstructure-critical current relationships in hard superconductors

The pinning of the flux line lattice (FLL) by crystal lattice defects gives rise to a critical current density J_c for hard superconductors. The volume pinning force density F_p = ‖BXJ_c‖ however, depends both on the elementary interaction force f_p between a single defect and the FLL and on the nature of the summation of these many f_p’s. The latter will depend on the spatial arrangement of defects and on the elastic and plastic deformation properties of the FLL. For localized defects the f_p is a strong function of defect “size”, reaching a maximum when the size is approximately the coherence length, and is approximately proportional to H_c ²(T) (1−h) where H_c is the thermodynamic critical field and h is the reduced magnetic field H/H_c2. The summation model must give a F_p which obeys the following empirical rules: 1) F_p has a maximum at a reduced field h_p which decreases with increasing defect density ρ and f . 2) F_p at h > h_p is structure insensitive while F_p at h < h_p is structure sensitive. 3) A scaling law is obeyed if T is changed, i.e., F_p = H_c2(T)_m .f(h), where m is ∿2.5 andf(h) is only a function of reduced field and microstructure. Experimental evidence for these generalizations is presented and a model which predicts these results is outlined and quantitatively tested. Work supported by the U. S. Energy Research and Development Administration.