Magnetic properties of porous iron compacts

Magnetic hysteresis measurements, magnetoacoustic emission, and the Barkhausen effect have been used to investigate the magnetic properties of six porous iron compacts with porosities in the range 0.3–6.2% and pore sizes in the range 1.6–13.2 µm. Coercivity and maximum permeability varied with pore size, showing respectively a maximum and a minimum for pore areas in the range 50–100 (µm)², corresponding to pore diameters 8–11 µm. Significant correlations were found between several of the magnetic parameters including a fundamental relationship between coercivity, initial permeability, and maximum differential permeability. There were also indications of a correlation between magnetic properties and the initial molding pressure, although these were not conclusive. However, none of the magnetic properties was found to vary in a progressive manner with percentage porosity, although it is conceivable that if all other variables, such as pore size and grain size, remained constant, that changes in magnetic properties with porosity could be detected from magnetic measurements.     

Siderophore-manganese(III) interactions. I. Air-oxidation of manganese(ll) promoted by desferrioxamine B

Recent studies suggest that aqueous Mn(ll) complexes, particularly those with non-carboxylated ligands such as microbial siderophores, may be stable in soil and aquatic environments. In this paper, we determine the stability constants for Mn(ll) and Mn(lll) complexes with the common trihydroxamate siderophore, desferrioxamine B (DFOB). Base and redox titrations were conducted to determine DFOB conditional protonation constants and conditional stability constants for 1:1 DFOB complexes with Mn(ll) and Mn(lll). The conditional protonation constants agree well with literature values. We determined stability constants for three Mn(ll)-DFOB species and one Mn(lll)-DFOB species at 25 degrees C in 0.1 M NaCl. The Mn(lll) HDFOB+ complex can be formed readily by air-oxidation of Mn(ll)-DFOB. This reaction exhibits pseudo first-order kinetics with a rate coefficient that can be characterized as the product of oxygen concentration with a linear combination of the concentrations of the three Mn(ll)-DFOB complexes. The second-order rate coefficients appearing in this linear combination are 1 to 2 orders of magnitude smaller than that associated with oxidation of the hydrolytic species Mn(OH)(0)2. The Mn(lll)HDFOB+ complex is stable for pH in the range of 7.0-11.3; but, at pH < 7.0 it decomposes by internal electron transfer, yielding oxidized DFOB products and Mn(ll). For p[H+] > 11.3, the complex degrades by disproportionation, yielding Mn(ll) and solid MnO2. This range of pH stability supports the hypothesis that aqueous Mn(lll) may play a vital role in the biogeochemical cycling of not only manganese, but also other elements, such as carbon, sulfur, nitrogen, oxygen, and redox-active metals.     

Are toxicological responses in laboratory (inbred) zebrafish representative of those in outbred (wild) populations? - A case study with an endocrine disrupting chemical

Laboratory animals tend to be more inbred and less genetically diverse than wild populations, and thus may differ in their susceptibility to chemical stressors. We tested this hypothesis by comparing the responses of related inbred (theoretical inbreeding F(IT) = n + 0.25) and outbred (F(IT) = n) zebrafish (Danio rerio) WIK/Wild family lines to an endocrine disrupting chemical, clotrimazole. Exposure of inbred and outbred zebrafish to 2.9 μg clotrimazole/L had no effect on survival, growth, or gonadal development. Exposure of both lines to 43.7 μg clotrimazole/L led to male-biased sex ratios compared with controls (87% versus 55% and 92% vs 64%, for inbred and outbred males, respectively), advanced germ cell development, and reduced plasma 11-ketotestosterone concentrations in males. However, outbred males (but not inbred males) developed testis that were more than twice the weight of controls, which corresponded with a proliferation of Leydig cells and maintenance of the expression (rather than down-regulation occurring in inbreds) of gonadal aromatase (cyp19a1a) and insulin-like growth factor (igf1). Our results illustrate that the effects of an endocrine disrupting chemical (clotrimazole) on some end points (here testis development) can differ between inbred and outbred zebrafish. This highlights the need for reporting pedigree/genetic information and consistency in the responses of laboratory animals (e.g., by using model compounds as positive controls).     

Artificial Situation Awareness for Increased Autonomy of Unmanned Aerial Systems in the Terminal Area

Situation awareness is the human function of perceiving, comprehending and projecting the state of the environment which is of critical importance to the safe operation of aircraft. A highly autonomous Unmanned Aerial System (UAS) must replicate this behaviour in order to maintain an acceptable level of safety verses a manned vehicle. Nowhere in the flight is situation awareness more critical than during operation in the terminal area. Of primary concern during this stage of flight is the awareness of other traffic heading for the same airfield. This paper presents of a novel method of spatial projection of traffic vehicles encountered by an autonomous UAS in the terminal stage of flight. This projection method relies on a cooperative means of traffic perception, such as Automated Dependant Surveillance - Broadcast (ADS-B) and assumes there is a predefined route which vehicles follow through the terminal region. Whilst this is the case at the majority of airfield, traffic vehicles will not follow this path perfectly. This uncertainty in path following accuracy is captured by utilising a curvilinear reference frame and dealing with discrete transitions (such as the initiation of a turn) separately. It is shown that whilst this technique increases the computational complexity of the problem it can offer significant performance benefit.     

Acidic Attack of Perfluorinated Alkyl Ether Lubricant Molecules by Metal Oxide Surfaces

The reactions of linear perfluoropolyalkylether (PFAE) lubricants with α-Fe₂O₃ and Fe₂O₃-based solid superacids were studied. The reaction with α-Fe₂O₃ proceeded in two stages. The first stage was an initial slow catalytic decomposition of the fluid. This reaction released reactive gaseous products which attacked the metal oxide and converted it to FeF₃. The second stage was a more rapid decomposition of the fluid, effected by the surface FeF³. A study of the initial breakdown step was performed using α-Fe²O³, α-Fe²O³ preconverted to FeF³, and sulfate-promoted α-Fe²O³ superacids. The results indicate that the breakdown reaction involves acidic attack at fluorine atoms on acetal carbons in the linear PFAE. Possible approaches to combat the problems are outlined.     

A computational framework for automating generation of sizing function in assembly meshing via disconnected skeletons

This paper proposes a framework for generating mesh sizing functions for assembly models. Size control is crucial in obtaining a high-quality mesh with a reduced number of elements. The reduction in the number of elements will decrease computation time and memory use during mesh generation and analysis. The framework consists of a background octree lattice for storing the sizing function, a set of source entities for providing sizing information based on geometric information, and an interpolation module for calculating the sizing on the background octree lattice using the source entities. Source entities are generated by performing a detailed systematic study to identify all the geometric factors of an assembly. Disconnected skeletons are extracted and used as tools to measure 3D proximity and 2D proximity, which are two of the geometric factors. The framework facilitates the generation of a variety of meshes with a low computational cost, to meet industry needs. The framework has been tested on many industrial parts, and sizing control on a few typical assemblies has been presented to demonstrate the effectiveness of the proposed framework.     

Reading speech and hearing print: Constraining models of visual word recognition by exploring connections with speech perception.

Current models of reading and speech perception differ widely in their assumptions regarding the interaction of orthographic and phonological information during language perception. The present experiments examined this interaction through a 2-alternative, forced-choice paradigm, and explored the nature of the connections between graphemic and phonemic processing subsystems. Exps 1 and 2 demonstrated a facilitation-dominant influence (i.e., benefits exceed costs) of graphemic contexts on phoneme discrimination, which is interpreted as a sensitivity effect. Exps 3 and 4 demonstrated a symmetrical influence (i.e., benefits equal costs) of phonemic contexts on grapheme discrimination, which can be interpreted as either a bias effect, or an equally facilitative/inhibitory sensitivity effect. General implications for the functional architecture of language processing models are discussed, as well as specific implications for models of visual word recognition and speech perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A prospective study of short- and long-term neuropsychological outcomes after traumatic brain injury in children.

Longitudinal neuropsychological outcomes of traumatic brain injury (TBI) were investigated in 53 children with severe TBI, 56 children with moderate TBI, and 80 children with orthopedic injuries only. Neuropsychological functioning was assessed at baseline, at 6- and 12-month follow-ups, and at an extended follow-up (a mean of 4 years postinjury). Mixed model analyses revealed persistent neuropsychological sequelae of TBI that generally did not vary as a function of time postinjury. Some recovery occurred during the first year postinjury, but recovery reached a plateau after that time, and deficits were still apparent at the extended follow-up. Further recovery was uncommon after the first year postinjury. Family factors did not moderate neuropsychological outcomes, despite their demonstrated influence on behavior and academic achievement after childhood TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The deformation mechanics of interlock tubes

Interlock tubes are one of the key structural layers of most flexible pipes of composite construction for offshore oil and gas transmission and water injection applications. The design and manufacture of such a tube based on a good understanding of its deformation mechanics are undoubtedly of significance to the integrity and safety of flexible pipes and pipe systems. This paper describes a semi-empirical model for the evaluation of the deformations in the critical sections of the interlock tube as it responds to the overall pipe loading and configuration. Results of a finite element analysis and radiographic tests are incorporated to verify and supplement the model.     

AR model order selection based on bispectral cross correlation

A novel method is presented for optimal model order selection for autoregressive (AR) bispectrum estimation. The method depends solely on the data and requires no a priori information about the process. The method selects the model order that maximizes the cross correlation between the direct (fast Fourier transform-based) bispectrum estimate and the autoregressive bispectrum estimate. Simulation results are reviewed which demonstrate the method's performance for the case of quadratically coupled sinusoids embedded in white Gaussian noise