The microscopic network structure of mussel (Mytilus) adhesive plaques

Marine mussels of the genus Mytilus live in the hostile intertidal zone, attached to rocks, bio-fouled surfaces and each other via collagen-rich threads ending in adhesive pads, the plaques. Plaques adhere in salty, alkaline seawater, withstanding waves and tidal currents. Each plaque requires a force of several newtons to detach. Although the molecular composition of the plaques has been well studied, a complete understanding of supra-molecular plaque architecture and its role in maintaining adhesive strength remains elusive. Here, electron microscopy and neutron scattering studies of plaques harvested from Mytilus californianus and Mytilus galloprovincialis reveal a complex network structure reminiscent of structural foams. Two characteristic length scales are observed characterizing a dense meshwork (approx. 100 nm) with large interpenetrating pores (approx. 1 µm). The network withstands chemical denaturation, indicating significant cross-linking. Plaques formed at lower temperatures have finer network struts, from which we hypothesize a kinetically controlled formation mechanism. When mussels are induced to create plaques, the resulting structure lacks a well-defined network architecture, showcasing the importance of processing over self-assembly. Together, these new data provide essential insight into plaque structure and formation and set the foundation to understand the role of plaque structure in stress distribution and toughening in natural and biomimetic materials.     

Understanding the variability of wind power costs

Wind power has a significant contribution to make in efforts to abate CO₂ emissions from global energy systems. Currently, wind power generation costs are approaching parity with costs attributed to conventional, carbon-based sources of energy but the economic advantage still rests decidedly with conventional sources. Therefore, there is an imperative to ensure that wind power projects are developed in the most economically optimal fashion. For wind power project developers, shaving a few tenths of a cent off of the kilowatts per hour cost of wind power can mean the difference between a commercially viable project and a non-starter. For civic authorities who are responsible for managing municipally supported wind power projects, optimizing the economics of such projects can attenuate stakeholder opposition. This paper attempts to contribute to a better understanding of how to economically optimise wind power projects by conflating research from the fields of energy economics, wind power engineering, aerodynamics, geography and climate science to identify critical factors that influence the economic optimization of wind power projects.     

Titania and Noble Metals Deposited Titania Catalysts in the Photodegradation of Tartazine

Nanoparticles of TiO₂ were synthesised by sol–gel technique and photo deposition of about 1% noble metal (M/TiO₂, M = Ag, Au, and Pt) on TiO₂ was carried out. The catalysts were characterised by XRD, TEM, BET, FT-IR, and UV–Visible spectroscopy. Using commercial TiO₂ (P-25 Degussa), the conditions such as dye concentration, catalyst weight and pH were optimized for complete decolourisation of textile dye tartazine (TAZ) under UV and visible irradiations. Among the catalysts tested, the synthesised TiO₂ showed better photocatalytic activity than TiO₂ (P-25 Degussa). Whereas, M/TiO₂ catalysts showed remarkable photocatalytic activity towards the decolourisation of TAZ even under visible irradiation. This enhanced activity of M/TiO₂ catalyst may be attributed to the trapping of conduction band electrons by noble metals.     

Reduction of lead oxide (PbO2) by iodide and formation of iodoform in the PbO2/I(-)/NOM system

Lead oxide (PbO2) can be an important form of lead mineral scale occurring in some water distribution systems. It is believed to be formed by the oxidation of lead-containing plumbing materials by free chlorine. Its reactivity in water, however, has not been well studied. Iodide is also found in source drinking waters, albeit at low concentrations. Consideration of thermodynamics suggests that iodide can be oxidized by PbO2. In this investigation, iodide ion was used as a probe compound to study the reduction of PbO2 and the formation of iodoform, which has been predicted to be a carcinogen, in the presence of natural organic matter (NOM). The reduction of PbO2 by iodide can be expressed as PbO2 + 31(-) + 4H+ --> Pb(2+) + I3(-) + 2H2O, and the reaction kinetics has been determined in this study. In the presence of NOM, I3- reacts with NOM to form iodoform and its concentration is proportional to the NOM concentration. Our results indicate that PbO2 is a very powerful oxidant and can possibly serve as an oxidant reservoir for the formation of iodinated disinfection byproduct through a novel reaction pathway.     

Paralleling of Preamplifier Input Stages for a Low-Noise, Wideband Termination of Low-Impedance Transmission Lines

A new concept of paralleling input stages was developed to meet the requirements for a low-noise, wideband preamplifier that matches the transmissionline impedance of ultrahigh-sensitivity fission counters. The prototypic preamplifier consists of four dual-feedback-path amplifiers and a summing amplifier. It has an 18-pA/?Hz equivalent input noise current density, a 60-MHz bandwidth, a 25-? input impedance, and a 5-k? transimpedance.     

Ionized magnesium concentrations in critically ill children

OBJECTIVE: To test the hypothesis that many critically ill children exhibit ionized hypomagnesemia despite having normal total magnesium (TMg) concentrations. DESIGN: A prospective, observational study with convenience sampling. SETTING: Pediatric and cardiovascular intensive care units of a large children's hospital. PATIENTS: Patients aged 1 day to 21 yrs admitted from January 1 to October 31, 1996. Patients with chronic renal failure or weight <3 kg were excluded. A group of healthy children involved in a school-based nutritional assessment study were also studied. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Sixty-seven patients (5.4+/-5.7 [SD] yrs) and 24 healthy children (10.84+/-0.93 yrs, p< .001) were studied. Plasma was assayed for ionized magnesium (IMg) using a blood analyzer. Forty (59%)/67 critically ill subjects had IMg concentrations <0.40 mmol/L, the lowest published normal value and the lowest value observed in our group of healthy children. Of these, 24 (60%)/40 had normal TMg concentrations. IMg was significantly (p=.00) lower in critically ill subjects than in the group of healthy children (0.37+/-0.10 mmol/L vs. 0.46+/-0.03 mmol/L). IMg did not correlate strongly with ionized calcium (r2=0.49), albumin (r2=0.09), or pH (r2=0.18). CONCLUSION: Many critically ill children exhibit ionized hypomagnesemia with normal TMg concentrations. These children would not be recognized as magnesium-deficient based on routine TMg testing. Critically ill children exhibited significantly lower concentrations of IMg than a group of healthy children.     

Electrodermal activity in euthymic patients with affective disorders: One-year retest stability and the effects of stimulus intensity and significance.

Examined the effects of stimulus intensity and meaningfulness on the electrodermal activity (EDA) of patients with remitted major affective disorders in 22 unipolar (mean age 41 yrs), 22 bipolar (mean age 38.5 yrs), and 26 normal control (mean age 41.5 yrs) Ss. 29 of the affective disorder patients and 23 of the control Ss participated in a study of EDA conducted 1 yr earlier by the 1st author and colleagues (1983). Ss blew up a balloon until it burst and were exposed to 8 86-db tones, 12 105-db tones and 8 familiar sounds that reached a peak intensity of 105 db. Skin conductance was recorded bilaterally and averaged over hands. Results indicate that, compared to the control Ss, the affective disorder patients responded significantly less to the balloon task, the 105-db tones, and the familiar sounds. The affective-disorder groups had lower tonic levels than did the controls. Several measures of EDA displayed moderately high 1-yr retest stability. The pattern of findings is consistent with the hypothesis that depressed EDA may be a trait characterizing those who are prone to major affective disorder. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)