Temperature dependent stiffness and visco-elastic behaviour of lipid coated microbubbles using atomic force microscopy.

yesThe compression stiffness of a phospholipid microbubble was determined using force-spectroscopy as a function of temperature. The stiffness was found to decrease by approximately a factor of three from 0.08 N m 1, at 10 C, down to 0.03 N m 1 at 37 C. This temperature dependence indicates that the surface tension of lipid coating is the dominant contribution to the microbubble stiffness. The timedependent material properties, e.g. creep, increased non-linearly with temperature, showing a factor of two increase in creep-displacement, from 24 nm, at 10 C, to 50 nm, at 37 C. The standard linear solid model was used to extract the visco-elastic parameters and their determination at different temperatures allowed the first determination of the activation energy for creep, for a microbubble, to be determined.EPSR

The anterior pathway for intelligible speech: insights from univariate and multivariate methods

Whilst there is broad agreement concerning the existence of an anterior processing stream in the human brain concerned with extracting meaning from speech, there is an ongoing controversy as to whether intelligible speech is first resolved in left anterior or bilateral posterior temporal fields (Hickok and Poeppel, 2007;Rauschecker and Scott, 2009). Proponents of the bilateral processing model argue that bilateral responses are driven by the acoustic properties of the speech signal, whilst proponents of the left lateralised model suggest that left lateralisation is driven by access to linguistic representations. This thesis directly addresses these controversies using Functional Magnetic Resonance Imaging (fMRI) and univariate and multivariate analysis methods. Two main questions are addressed: (1) where are responses to intelligible, and intelligible but degraded speech, separated from responses to acoustic complexity and (2) does the resulting pattern of lateralisation, or otherwise, derive from the acoustic properties or the linguistic status of speech. The results of this thesis reconcile, to some degree, the two theoretical positions. I show that the most consistent and largest amplitude responses to intelligible, and degraded but intelligible speech, are found in the left anterior Superior Temporal Sulcus (STS). Additional responses were also found in right anterior and left posterior STS, however, these were less consistently identified. Regions of the left posterior STS showed sensitivity to resolved intelligible speech and also showed a response likely to reflect acoustic-phonetic processing supporting the resolving of intelligibility. Right posterior STS responses to intelligible speech were noticeably absent across all studies. No evidence was found for a relative acoustic basis for hemispheric lateralisation in the case of speech derived manipulations of spectrum and amplitude, but evidence was found in support of a left hemisphere specialism for resolving intelligible speech, supporting a relative left lateralisation to speech driven by linguistic rather than acoustic factors

Integral Field Spectroscopy of a peculiar Supernova Remnant MF16 in NGC6946

We present a study of a peculiar Supernova Remnant MF16, associated with the Ultraluminous X-ray Source (ULX) NGC6946 ULX-1. Observations were taken with the MultiPupil Fiber Spectrograph (MPFS) with 6-m telescope on January 2005. The nebula is found to be highly asymmetric, one of the parts being much denser and colder. The two-component structure of the emission lines and radial velocity gradient argue for a non-spherical nebula, expanding with a velocity of about 100 km/s. Neither shock models nor the X-ray emission can adequately explain the actual emission line spectrum of MF16, so we suggest an additional ultraviolet source with a luminosity of about 10E40 erg/s. We confirm coincidence of the ULX with the central star, and identify radio emission observed by VLA with the most dense part of the nebula.Comment: Proceedings of the ESO and Euro3D Workshop "Science Perspectives for 3D Spectroscopy", Garching (Germany), October 10-14, 2005. M. Kissler-Patig, M.M. Roth and J.R. Walsh (eds.

Effect of Temperature and Electrolyte Composition on the Susceptibility of Alloy 22 to Localized Corrosion

The study of the electrochemical behavior of Alloy 22 has been carried out in various concentrated environments using different sample configurations. Comparisons were made between the electrochemical behaviors of Alloy 22 in concentrated chloride solutions, and in concentrated chloride solutions with nitrate ions (NO{sub 3}{sup -}). In other experiments, the effect of fluoride ions (F{sup -}) was investigated. These comparative studies were performed at various temperatures. The rate of corrosion was found to increase with increase in temperature. The presence of nitrate ions reduced corrosion attack on Alloy 22. F{sup -} was found to be more benign to Alloy 22 compared with chloride ions (Cl{sup -}). However a combination of F{sup -} and Cl{sup -} was found to initiate deeper crevices compared with the only Cl{sup -} in the electrolyte

Evidence for a transfer-to-trap mechanism of fluorophore concentration quenching in lipid bilayers

It is important to understand the behaviors of fluorescent molecules because, firstly, they are often utilized as probes in biophysical experiments and, secondly, they are crucial cofactors in biological processes such as photosynthesis. A phenomenon called “fluorescence quenching” occurs when fluorophores are present at high concentrations, but the mechanisms for quenching are debated. Here, we used a technique called “in-membrane electrophoresis” to generate concentration gradients of fluorophores within a supported lipid bilayer, across which quenching was expected to occur. Fluorescence lifetime imaging microscopy (FLIM) provides images where the fluorescence intensity in each pixel is correlated to fluorescence lifetime: the intensity provides information about the location and concentration of fluorophores and the lifetime reveals the occurrence of energy-dissipative processes. FLIM was used to compare the quenching behavior of three commonly used fluorophores: Texas Red (TR), nitrobenzoaxadiazole (NBD), and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY). FLIM images provided evidence of quenching in regions where the fluorophores accumulated, but the degree of quenching varied between the different fluorophores. The relationship between quenching and concentration was quantified and the “critical radius for trap formation,” representing the relative quenching strength, was calculated as 2.70, 2.02, and 1.14 nm, for BODIPY, TR, and NBD, respectively. The experimental data support the theory that quenching takes place via a “transfer-to-trap” mechanism which proposes, firstly, that excitation energy is transferred between fluorophores and may reach a “trap site,” resulting in immediate energy dissipation, and, secondly, that trap sites are formed in a concentration-dependent manner. Some previous work suggested that quenching occurs only when fluorophores aggregate, or form long-lived dimers, but our data and this theory argue that traps may be “statistical pairs” of fluorophores that exist only transiently. Our findings should inspire future work to assess whether these traps can be charge-transfer states, excited-state dimers, or something else

Algae in Selected Illinois Streams, 1971-1976

During the 5-year period, October 1971 through September 1976, samples of water from 21 Illinois streams at 26 locations were collected monthly and examined to determine the concentration and genera of algae. Data have been evaluated for algal composition, density, diversity indices, and seasonal succession for each stream location. At most sampling locations, algal densities ranged from 500 to 2000 cts/ml. The 5-year geometric means extended from 880 to 1500 cts/ml. From 24 to 30 different algal genera were recovered from each station and, in all, 56 genera were detected. The average diversity index for each station ranged from 1.11 to 1.36 bits per individual. The highest density of 60,000 cts/ml occurred on July 11, 1975, in the Fox River at Algonquin. The diatoms Navicula and Cyclotella were the most frequently observed algae. In addition to these, the green algae Scenedesmus and Crucigenia and the diatom Melosira were often dominant. From sample to sample, season to season, and year to year, the genera found at any sampling station varied considerably. Generally, the annual maximum population occurred in the spring. However, the experience gained from this study supports the conclusion that it is impossible to predict algal density, composition, or succession in the flowing streams of Illinois.publishedpeer reviewedOpe

Algal removal by alum coagulation

Includes bibliographical references.Enumeration continues through succeeding title."The removal of algae in natural waters by coagulation with liquid alum was investigated in the laboratory using the jar test technique. Various amounts of alum (up to 40 mg/l) were added to water samples collected from the Illinois River at Peoria. Algal enumerations as well as some pertinent chemical analyses were performed before and after the process of coagulation and flocculation. The efficiency of algal removal was found to be dependent upon alum dosage, initial algal concentrations, and the types, shapes, and other specific characteristics of the algae. Optimum coagulant dosage for algal reduction was found to be similar to that for turbidity removal. Results should be useful in defining problems encountered in water treatment plants where algae are troublesome.

Concentration and Genera of Algae in Selected Illinois Streams, 197I-1973

During the period October 1971 to September 1973, samples of water from 35 Illinois streams at 41 locations were collected monthly and examined to determine the type, genera, and concentration of algae. Data for the 2-year period have been evaluated for algal density, composition, diversity indices, and seasonal succession for each location. Most stations had algal densities of from 500 to 2000 cts/ml, had between 15 and 24 different algal genera (41 genera total), and had a diversity index equal to or greater than 1.10. Stations on the Fox, Des Plaines, and Kaskaskia Rivers had algal densities in excess of 5000 cts/ml. This report should be useful to persons responsible for developing, regulating, or managing water resources in Illinois.publishedpeer reviewedOpe

Enzymatic and catalytic behaviour of low-dimensional gold nanomaterials in modular nano-composite hydrogels

Inorganic nanoparticles have long been applied as catalysts and nanozymes with exceptional rate constants arising from their large surface areas. While it is understood that high surface area-to-volume ratios and low average atomic coordination are responsible for their exceptional catalytic properties, these facets remain under exploited in the design of gold nanoparticle catalysts and nanozymes. Here we have developed 3D, 2D, and quasi-1D gold nanoparticles for use as catalysts in reducing 4-nitrophenol by sodium borohydride. Each morphology was characterised with transmission electron microscopy and UV–vis absorption spectroscopy, while the highest catalytic activity was achieved when the perimeter-to-surface area, or amount of 'edge', was maximised. The particles were then applied as nanozymes in modular nano-composite hydrogels. Independent hydrogel tiles containing either the substrate or catalyst were bonded in stacks, which allowed reagent transport across their interface for the colourimetric detection of hydrogen peroxide. This work presents novel insight into the catalytic activity of low-dimension nanoparticles and their potential application in nanozyme-based diagnostic devices