Evidence for nonlinear binding of PAHs to dissolved humic acids

Binding of pyrene, fluoranthene, and phenanthrene to dissolved humic acids (HA) was determined by the fluorescence quenching (FQ) and complexation-flocculation (CF) methods. Determinations by the CF method, using varying contaminant concentrations and a constant HA concentration, yielded nonlinear Freundlich-type isotherms (n = 0.65-0.84). Experiments using both the CF and the FQ methods with varying HA concentrations and a constant contaminant concentration yielded curved "Stern-Volmer"-type plots that also indicate nonlinear binding. These findings suggest that linear partitioning or site complexation in the presence of excess available sites cannot fully describe the interactions of hydrophobic compounds with dissolved humic material. Site-specific hydrophobic interactions at limited interior or external molecular surfaces may be considered.     

Activity of units in the hippocampal circuit of the rat during differential classical conditioning.

Recorded unit activity from electrodes chronically implanted in various hippocampal areas of 17 male Holtzman albino rats during differential classical conditioning. 1 auditory frequency signaled food, another signaled electric shock. Unit activity was recorded during 1 sec. prior to applications of the tones and during the 1-sec CS-UCS intervals. Response latencies and changes in frequency of unit activity throughout the recording period were determined. Units in the dentate had longer latencies than units in the hippocampus, some of which responded within 16 msec. of the application of the CS. The dentate was the only area to show excitation in response to a positive signal and inhibition in response to a negative signal. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organic groups and molecular weight distribution in tertiary effluents and renovated waters

Group composition and MW distribution of soluble organics in effluents from successive biological and chemical treatment stages were investigated.In secondary effluents, most of the organics fell within the high MW range. Lime treatment caused marked reduction of the latter group, combined with removal of proteins, humics, and carbohydrates. (The overall removal amounted to approx. 65–75%). Simultaneously, there was an increase in the lowest MW range group—strongly hydrophilic, unidentifiable compounds outside the classification scheme used.     

Convergence of sensory input on units in the hippocampal system of the rat.

Recorded unit responses to auditory and visual stimuli from chronically implanted electrodes in the limbic system of 22 albino male Holtzman rats. The stimuli were presented first in a random order and later in a classical sensory conditioning paradigm in which a flash of light followed a tone. Short latency unit responses to both light and tone were found in the medial septum and the cingulate cortex. The conditioning paradigm did not cause significant changes in the firing rates of nonresponding units and did not significantly change existing responses. Only small transient changes were noticed in CA1 hippocampal units. It is concluded that sensory responses could be detected in the hippocampus and its afferents, but a classical sensory paradigm is not an efficient way to enhance hippocampal responsiveness to neutral stimuli. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optical properties of transparent polycrystalline ruby (Cr:Al2O3) fabricated by high-pressure spark plasma sintering

Doped transparent ceramics with high optical quality can serve as materials for photonic applications such as laser gain media. In that regard, transparent polycrystalline alumina has potential for high-power applications due to its excellent physical and chemical properties, combined with unique doping possibilities. However, optical birefringence of Al₂O₃ crystals make achieving sufficiently high optical transmittance a processing challenge. In the present study, we demonstrated fabrication of highly transparent 0.5 at.% Cr:Al₂O₃ ceramics by high-pressure spark plasma sintering (HPSPS). The optical properties of these polycrystalline ruby ceramics were analyzed in order to assess possible laser operation (at 694.3 nm). The obtained ceramics exhibit high in-line transmittance (～72.5 % at 700 nm), equivalent to a scattering coefficient of 2.15 cm^?1, and characteristic ruby photoluminescence. The theoretically estimated lasing threshold and percentage of absorbed pump power indicate that such ruby ceramic lasers could operate at reasonable thresholds of 80?225 mW with short lengths of 0.5?5 mm. Thus, HPSPS is a promising method for producing laser-quality doped transparent ceramics for compact laser systems.     

Acid-assisted consolidation of powder compacts: cold-welding or cold sintering

Silver powder that has been treated in dilute fluoroboric acid solution and compacted at room temperature displays surprisingly elevated flexural and even tensile strength. The density and mechanical strength values increase with increasing compaction pressure. The flexural strength and the elastic moduli of silver powder compacted at 1 GPa, as determined by sound velocity measurements, reach values comparable to those of bulk silver. The results can be tentatively interpreted either in terms of an ambient temperature self-soldering effect of silver in the presence of the fluoroboric acid, acting as a fluxing agent, or as cold liquid-phase sintering in an aqueous liquid medium.     

Is object-based attention mandatory? Strategic control over mode of attention.

Is object-based attention mandatory or under strategic control? In an adapted spatial cuing paradigm, participants focused initially on a central arrow cue that was part of a perceptual group (Experiment 1) or a uniformly connected object (Experiment 2), encompassing one of the potential target locations. The cue always pointed to an opposite, different-object location. By varying cue validity, the strategic incentive to prevent the spread of attention to the entire cue object, and consequently to the same-object location, was manipulated: With invalid cuing and (consequently) equal probability of targets at same-object and different-object locations, a same-object target identification advantage was observed. With highly valid cuing and targets much more probable at the different-object location than at the same-object location, the same-object advantage disappeared. Object-based attention appears to be a default mode that may be ecologically adaptive but can be overridden by strategic control when there is a strong immediate benefit in doing so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired Functional Connectivity Underlies Fragile X Syndrome

Fragile X syndrome (FXS), the most common form of inherited intellectual disability, is caused by a developmentally regulated silencing of the FMR1 gene, but its effect on human neuronal network development and function is not fully understood. Here, we isolated isogenic human embryonic stem cell (hESC) subclones—one with a full FX mutation and one that is free of the mutation (control) but shares the same genetic background—differentiated them into induced neurons (iNs) by forced expression of NEUROG-1, and compared the functional properties of the derived neuronal networks. High-throughput image analysis demonstrates that FX-iNs have significantly smaller cell bodies and reduced arborizations than the control. Both FX- and control-neurons can discharge repetitive action potentials, and FX neuronal networks are also able to generate spontaneous excitatory synaptic currents with slight differences from the control, demonstrating that iNs generate more mature neuronal networks than the previously used protocols. MEA analysis demonstrated that FX networks are hyperexcitable with significantly higher spontaneous burst-firing activity compared to the control. Most importantly, cross-correlation analysis enabled quantification of network connectivity to demonstrate that the FX neuronal networks are significantly less synchronous than the control, which can explain the origin of the development of intellectual dysfunction associated with FXS.     

Volatile organic acids in raw wastewater and in physico-chemical treatment

The purpose of the present study was to identify soluble organics, which comprise the high BOD remaining in the effluent from direct physico-chemical treatment of strong raw sewage. Salts of volatile organic acids were found to be the main constituents of the organic fraction remaining after chemical treatment and activated carbon adsorption. The fate of the volatile acids such as acetic, propionic, butyric, valeric, isovaleric and hexanoic acids was followed in each stage of the physicochemical treatment.     

Modulation of object-based attention by spatial focus under endogenous and exogenous orienting.

In R. Egly, J. Driver, and R. D. Rafal's (1994) influential double-rectangle spatial-cuing paradigm, exogenous cues consistently induce object-based attention, whereas endogenous cues generally induce space-based attention. This difference suggests an interdependency between mode of orienting (endogenous vs exogenous) and mode of selection (object based vs space based). However, mode of orienting is generally confounded with initial focus of attention: Endogenous orienting begins with attention focused on a central cue, whereas exogenous orienting begins with attention widely spread. In this study, an attentional-focusing hypothesis is examined and supported by experiments showing that for both endogenous and exogenous cuing, object-based effects are obtained under conditions that encourage spread attention, but they are attenuated under conditions that encourage focused attention. General implications for object-based attention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)