Search

Graphical abstract Abstract Interactions between kaolinite (KGa-2) and a typical anionic surfactant bis(2-ethylhexyl) sulfosuccinate sodium (AOT) have been study to obtain a better knowledge of this system. Firstly, adsorption isotherms of AOT on kaolinite are realized as a function of pH. Stability experiments have been performed between the surfactant and the clay mineral and the bed sediments structure have been studied with Small Angle X-ray Scattering (SAXS).In acidic media, the shape of the adsorption isotherm leads to the following suggestions: firstly, for surfactant concentration below the CMC a surfactant monolayer is adsorbed on the positively charged edge surfaces, and then, for surfactant concentrations above the CMC, a bilayer is adsorbed on the edge surfaces. Consequently, in the first case, the surface becomes hydrophobic and in the second case, the surface becomes hydrophilic and this assumption is verified with hydrophobicity tests. Under alkaline conditions no surfactant is adsorbed on surfaces confirming the adsorption on the edge surfaces in acidic conditions. Significant stabilization of kaolinite suspensions can be observed in the presence of high surfactant concentration, in both pH conditions. Finally, structural studies by SAXS provide data about the organization of particles in the bed sedimentation. [ABSTRACT FROM AUTHOR]

Introduction: Water ice forms in the interstellar clouds along with preexisting silicate grains forming amorphous structures that sublimate and re-condense with temperature changes, developing the precursors to protoplanetary disks [1]. Throughout the formation process, planetesimals inside the snowline tend to outgas any H2O that may have been trapped in the silicate grains. This leads to a depletion of H2O in terrestrial planets. However, the simplicity ends there because planets forming in regions where adsorbed H2O has been lost, but absorbed water is still locked into the silicate grains, can still contain a significant amount of water. In fact, analysis of basaltic magma shows that H2O content was at least 3 wt.% H2O or higher [2]. Knowing the temperatures at which adsorbed, and absorbed, H2O leaves silicate grains is crucial in understanding planetary formation, transfer of H2O across the solar system, sequestration of gases, and habitability, amongst others. Laboratory experiments can better constrain the temperatures at which H2O remains incorporated in planetary formation. Methods: Amorphous Mg-silicate smokes, similarly synthesized in procedures by Nuth, et al. 2002 [3], was used for this study. These were chosen because the formation for the smokes are indicative of high-temperature processes in the circumstellar outflows. The amorphous Mg-silicate samples were powdered and placed in the sample holder of a AABSPEC #2000-A multimode system. The cell was pumped under vacuum to pressures of 9.3e-6 bar and initial spectral measurements were taken at 300 K. Subsequent measurements were taken in 50K increments up to 1000K. Each measurement consisted of 1000 scans with a resolution of 4 cm-1 to ensure high resolution data. Spectra was collected using a Mattson RS-10000 Fourier Transform InfraRed (FTIR) spectrometer operating in the near and mid-IR regimes (2 m - 17 m). The data for each sample was normalized and plotted to demonstrate the change in features with increasing temperature. Results: The preliminary results of this investigation indicate that the solid state H2O contained within the smokes is removed from the sample between 725 and 750K. Initial spectra of the Mg-silicate smoke sample before it was heated up clearly displayed the 3µm and 4.4µm water bands. The bands are broad and relatively smooth, indicating that they are solid-state absorption features. The characteristic 10µm silicate feature is also visible, although it is very weak compared to the intensity of the other bands. At 700K the spectra show the H2O still in the solid-state at around 3µm and 4.4µm. In the 750K measurement, H2O emission features replace the solid state features. Emission features that were present in the spectra taken at higher temperatures were diminished as the temperature increased, until they disappeared almost completely at 950K. After the sample was heated up to temperatures of 1000K and cooled back down to 300K, in 100K increments, the emission features returned, all while retaining the 10µm feature. Post-ramp spectra of the silicate smoke was collected after it had been cooled down to 300K. The spectra shows the water bands in the same position, but after being subjected to heat, the bands are now emission features, indicating that the H2O being measured is in the gas phase. The 10µm silicate feature remains and is more pronounced, suggesting that the chemical integrity of the sample remained intact over the course of the heating run. The solid-state H2O features did not return, indicating that the H2O in the samples had been removed completely. Conclusions & Future Work: Preliminary results from this study suggest that the samples started losing their solid-state H2O features between 725 and 750K. This suggests that planetesimals forming within the snow line could have a higher water content. The procedures outlined in this abstract will be repeated in order to clearly quantify the temperature at which water is released from the amorphous smokes. Further work will also involve kinetic studies to determine the activation energy of the H2O in order to determine exactly how much water can be released, and how long it would take to release it. [ABSTRACT FROM AUTHOR]

The adenomatous polyposis coli (APC) protein is a negative regulator of the mitogenic transcription factor β-catenin by stimulating its proteasomal degradation. This involves several APC domains, including the binding sites for axin/conductin, the recently described β-Catenin Inhibitory Domain (CID) and the third 20 amino acid repeat (20R3) that is a β-catenin-binding site. The four 15 amino acid repeats (15R) and the 20R1 are also β-catenin-binding sites, but their role in β-catenin degradation has remained unclear. We show here that binding of β-catenin to the 15R of APC is necessary and sufficient to target β-catenin for degradation whereas binding to the 20R1 is neither necessary nor sufficient. The first 15R displays the highest affinity for β-catenin in the 15R-20R1 module. Biallelic mutations of the APC gene lead tocolon cancer in familial adenomatous polyposis coli (FAP) and result in the synthesis of truncated products lacking domains involved in β-catenin degradation but still having a minimal length. The analysis of the distribution of truncating mutations along the APC sequence in colorectal tumours from FAP patients revealed that the first 15R is one target of the positive selection of mutations that lead to tumour development. [ABSTRACT FROM AUTHOR]

Many object-related actions can be recognized both by their sound and by their vision. Here we describe a population of neurons in the ventral premotor cortex of the monkey that discharge both when the animal performs a specific action and when it hears or sees the same action performed by another individual. These 'audiovisual mirror neurons' therefore represent actions independently of whether these actions are performed, heard or seen. The magnitude of auditory and visual responses did not differ significantly in half the neurons. A neurometric analysis revealed that based on the response of these neurons, two actions could be discriminated with 97% accuracy. [ABSTRACT FROM AUTHOR]

Assesses in juveniles and adult pig-tailed macaques the capacity to use eye cues only to follow the gaze of an experimenter. Finding that in monkeys, as in humans, there are neural correlates of eye direction detection; Biological stimuli presented.

Anterior and posterior meningoceles are the severest clinical expression of dural ectasia in patients with Marfan syndrome. Meningoceles and pseudomeningoceles have been reported from either asymptomatic, to causing headache, back pain, leg pain, radiculopathy, constipation and/or urinary symptoms. This article includes a case report of a 31-year-old woman, who presented with recurrent transient loss of consciousness thought to be secondary to acute changes in intracranial pressure transmitted from a pseudomeningocele. [ABSTRACT FROM AUTHOR]

The source of the unusually high radar reflectivity signal found on the highlands of Venus is hypothesized to be caused by a mineral with a high dielectric constant. We propose that this source could be a combination of tellurium, sulfur, and bismuth. All three elements are commonly outgassed in terrestrial eruption plumes and thus are likely to be found on Venus. To test our hypothesis, we used a Venus simulation chamber and studied the stability of various tellurium, bismuth, and sulfur mixtures at Venus temperatures and pressures and in atmospheres of CO 2 , 100 ppm SO 2 in CO 2 , or 100 ppm COS in CO 2. When mixed together bismuth, tellurium, and sulfur phases preferentially formed tetradymite (Bi 2 Te 2 S). The remaining minerals that formed in each experiment strongly depended on the initial mixture. For instance the Bi 2 S 3 /Bi 2 Te 3 mixture experiments resulted in the original minerals as well as BiTe at hotter temperatures, meanwhile the Bi/Te/S mixture produced Bi 2 S 3 and occasionally Bi 2 Te 3 , Bi(S,Te), and Bi 4 (S,Te) 3 depending on the temperature/pressure. There is evidence that COS, but not SO 2 , affected the stability of some minerals. Due to the presence of these elements in volcanic gases we propose that they can be present in the highlands and can, at least in part, account for the high radar reflectivity signal on the highlands. • Bismuth, tellurium, and sulfur formed tetradymite (Bi 2 Te 2 S) in all experiments • There were no minerals that only formed in the highland condition (380 °C/45 bar) • More minerals formed in the lowland condition (460 °C/95 bar) compared to the highland condition (380 °C/45 bar) experiments • COS (g) can affect the stability of some minerals depending on the starting bismuth, tellurium, and sulfur mixture [ABSTRACT FROM AUTHOR]

Electronically shuttered solid-state imagers are being developed for high-speed imaging applications. A 5 cm×5 cm, 512×512-element, multiframe charge-coupled device (CCD) imager has been fabricated for the Los Alamos National Laboratory DARHT facility that collects four sequential image frames at megahertz rates. To operate at fast frame rates with high sensitivity, the imager uses an electronic shutter technology designed for back-illuminated CCDs. The design concept and test results are described for the burst-frame-rate imager. Also discussed is an evolving solid-state imager technology that has interesting characteristics for creating large-format x-ray detectors with short integration times (100 ps to 1 ns). Proposed device architectures use CMOS technology for high speed sampling (tens of picoseconds transistor switching times). Techniques for parallel clock distribution, that triggers the sampling of x-ray photoelectrons, will be described that exploit features of CMOS technology. [ABSTRACT FROM AUTHOR]

The continuous-wave room-temperature operation of an electrically pumped 1.55 mm wavelength vertical-cavity surface-emitting laser (VCSEL) with up to 1.7 mW output power is reported. The laser comprises an optimised multi-quantum-well active region and an improved mirror design for reduced optical losses. [ABSTRACT FROM AUTHOR]