A GUPIX-based approach to interpreting the PIXE-plus-XRF spectra from the Mars Exploration rovers: II geochemical reference materials

A detailed examination of the original calibration data for the laboratory version of the Mars Exploration Rover alpha particle X-ray spectrometer is undertaken to ascertain if the results from a suite of certified geochemical reference materials (GRMs) agree with the APXS calibration based upon homogeneous standards which was established in the previous paper. Various discrepancies, some of them large, are observed for specific elements in specific rock types, and it is argued on the basis of X-ray diffraction analyses of the GRMS that these are caused by the mineral phase structure of the rocks. Elements present in accessory mineral phases can be subject to very large errors, necessitating caution in interpretation of trace element results from the APXS. Some of the discrepancies can be dealt with by developing sub-calibrations, each of which is “tuned” to a specific rock type. This approach has the potential to provide more accurate APXS analysis of unknown rocks than a calibration scheme based upon a simple averaging over many rock types within a GRM suite, or over a mix of rock and homogeneous standards. It also has the potential to measure the content of mineralogically bound water provided that a means of determining the distance from sample to detector is available.     

Assessment of cochlear damage after pneumococcal meningitis using otoacoustic emissions

Three cases are reported of children in Ghana with pneumococcal meningitis and differing degrees of hearing loss. The children were examined up to 12 d after admission by means of otoacoustic emissions. The technique is objective, non-invasive, quick (< 5 min per ear) and suitable for use in paediatric wards.     

Between Psoriasis and Ptarmigan: American encyclopedia portrayals of psychology, 1880–1940.

Articles in encyclopedias represented 1 of several avenues that the new experimental psychologists of the late 19th and early 20th centuries had to portray their science to the public, and as such, these entries are important documents in understanding the agenda of the psychologist authors and the bases for the public's understanding of psychology. This article describes a content analysis of the psychology entries from 174 American encyclopedias published between 1880 and 1940. The analysis focuses on the changes in this content over time and the correspondence of those changes to the evolution of American psychology. The data show that the encyclopedia entries were slow in reporting changes in psychology and often promoted a singular view of the subject matter of psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural studies of synthetic peptides dissected from the voltage-gated sodium channel

Peptides representing transmembrane regions of the alpha-subunit of the voltage-gated sodium channel were synthesised and their structures analysed, using 1H NMR and CD, in trifluoroethanol and in dodecylphosphocholine micelles. Sequence analysis suggests that the channel has six regions, S1 to S6, predicted to span the membrane in four homologous domains, designated, I, II, III and IV. Presented here are studies of representatives examples of possible single spanning segments (IS2, IS4, IVS4) and a double spanning segment, IS34, composed of segments IS3 and IS4. In addition, we investigated ISlink56, the putative linker region between segments IS5 and IS6. All of the peptides were found to have predominantly alpha-helical structures in both solvent systems. There was some evidence for bending of the longer helices but there was no discernible evidence for well-defined tertiary structure.     

A neuronal ryanodine receptor mediates light-induced phase delays of the circadian clock

Circadian clocks are complex biochemical systems that cycle with a period of approximately 24 hours. They integrate temporal information regarding phasing of the solar cycle, and adjust their phase so as to synchronize an organism's internal state to the local environmental day and night. Nocturnal light is the dominant regulator of this entrainment. In mammals, information about nocturnal light is transmitted by glutamate released from retinal projections to the circadian clock in the suprachiasmatic nucleus of the hypothalamus. Clock resetting requires the activation of ionotropic glutamate receptors, which mediate Ca2+ influx. The response induced by such activation depends on the clock's temporal state: during early night it delays the clock phase, whereas in late night the clock phase is advanced. To investigate this differential response, we sought signalling elements that contribute solely to phase delay. We analysed intracellular calcium-channel ryanodine receptors, which mediate coupled Ca2+ signalling. Depletion of intracellular Ca2+ stores during early night blocked the effects of glutamate. Activators of ryanodine receptors induced phase resetting only in early night; inhibitors selectively blocked delays induced by light and glutamate. These findings implicate the release of intracellular Ca2+ through ryanodine receptors in the light-induced phase delay of the circadian clock restricted to the early night.     

Kinetics of heavy metal bioleaching from sewage sludge—II. Mathematical model

A conceptual model of the overall process of metal bioleaching from sewage sludge has been developed on the basis of experimental observations. Sludge pH was identified as the parameter which controls bacterial growth and thus the overall process. Quantitative relationships among the various process parameters were incorporated in the conceptual model, giving a mathematical model for the process. Bacterial growth, sulfate concentration and pH profiles simulated using the model were found to match experimental observations. The degree of solubilization of each metal was found to depend on the sludge pH and the type of the sludge and is given as a set of solubilization curves.     

Geochemical changes in sulfidic mine tailings stored under a shallow water cover

The objective of this study was to assess the effectiveness of an engineered shallow water cover in reducing the oxidation of sulfidic mine tailings and thus preventing the development of acid rock drainage. Fresh tailings were submerged under a 0.3-m water cover in experimental field cells. From 1996 to 1998, we followed the chemistry of the interstitial water near the tailings-overlying water interface using in situ dialysis, and determined pH and dissolved oxygen (DO) profiles across the tailing water interface using micro-electrodes. Penetration of DO into the tailings was limited to <7 mm, even in the presence of DO produced by benthic periphyton. Anoxia in the tailings was further demonstrated by the appearance of dissolved sigmaH2S, Fe and Mn in pore water at depths -1.5 cm below the interface. However, there was clear evidence of surface oxidation of the mine tailings at the mm scale (i.e., DO depletion, coupled with localized increases in [H+] and [SO4(2-)]). Mobilization of Cd and Zn from this surface layer was indicated by the presence of sub-surface peaks in the concentrations of these two metals in the tailings interstitial water and by a change in their solid phase partitioning from refractory to more labile fractions. In contrast, mobilization of Cu from tailings was less evident. Unlike previous reports, which suggested that submerged tailings were effectively inert, our results show alteration of the superficial layer over time.     

When Static Media Promote Active Learning: Annotated Illustrations Versus Narrated Animations in Multimedia Instruction.

In 4 experiments, students received a lesson consisting of computer-based animation and narration or a lesson consisting of paper-based static diagrams and text. The lessons used the same words and graphics in the paper-based and computer-based versions to explain the process of lightning formation (Experiment 1), how a toilet tank works (Experiment 2), how ocean waves work (Experiment 3), and how a car's braking system works (Experiment 4). On subsequent retention and transfer tests, the paper group performed significantly better than the computer group on 4 of 8 comparisons, and there was no significant difference on the rest. These results support the static media hypothesis, in which static illustrations with printed text reduce extraneous processing and promote germane processing as compared with narrated animations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of partially depleted absorber waveguide photodiodes

This paper presents the analysis and characterization of partially depleted absorber (PDA) photodiodes. Coupling to these photodiodes is achieved through a planar short multimode waveguide (PSMW) structure. Electric transport in the PDA structure has been investigated and an equivalent electric circuit was developed. Measurements on 5/spl times/20 /spl mu/m/sup 2/ PSMW PDA photodiodes have shown 0.80 A/W responsivity with a fiber mode diameter as high as 6 /spl mu/m. The transverse electric/transverse magnetic polarization dependence was <0.5/spl plusmn/0.3 dB with -1-dB input coupling tolerances as high as /spl plusmn/2.0 and /spl plusmn/1.3 /spl mu/m for horizontal and vertical directions. The -3-dB bandwidth was 50 GHz, and the -1-dB compression current at 40 GHz was 17 mA corresponding to +4.5 dBm radio frequency (RF) power. Compared to similar evanescently coupled p-i-n photodiodes, the saturation current has been significantly improved while maintaining comparable bandwidth and high responsivity.