A White Room:piano quartet for young musicians

for piano, violin, violin or viola, cello

Forensic analysis of architectural finishes using fourier transform infrared and raman spectroscopy, part II:White paint

White household paints are commonly encountered as evidence in the forensic laboratory but they often cannot be readily distinguished by color alone so Fourier transform infrared (FT-IR) microscopy is used since it can sometimes discriminate between paints prepared with different organic resins. Here we report the first comparative study of FT-IR and Raman spectroscopy for forensic analysis of white paint. Both techniques allowed the 51 white paint samples in the study to be classified by inspection as either belonging to distinct groups or as unique samples. FT-IR gave five groups and four unique samples; Raman gave seven groups and six unique samples. The basis for this discrimination was the type of resin and/ or inorganic pigments/extenders present. Although this allowed approximately half of the white paints to be distinguished by inspection, the other half were all based on a similar resin and did not contain the distinctive modifiers/pigments and extenders that allowed the other samples to be identified. The experimental uncertainty in the relative band intensities measured using FT-IR was similar to the variation within this large group, so no further discrimination was possible. However, the variation in the Raman spectra was larger than the uncertainty, which allowed the large group to be divided into three subgroups and four distinct spectra, based on relative band intensities. The combination of increased discrimination and higher sample throughput means that the Raman method is superior to FT-IR for samples of this type. © 2005 Society for Applied Spectroscopy.

The not-so-extreme white dwarf of the CV GD 552

GD 552 is a cataclysmic binary which was previously believed to be composed of an M-star and a white dwarf, the latter having an extreme mass of 1.4 solar masses. In a recent paper we showed that this is not compatible with new observational evidence and presented an alternative model in which the white dwarf has a typical mass and the companion is a brown dwarf, making the system a likely member of the elusive group of CVs which have already evolved through minimum orbital period. Here we present additional spectroscopical evidence supporting this conclusion by means of skew mapping.

Ash from Changbaishan Millennium eruption recorded in Greenland ice: Implications for determining the eruption's timing and impact

Major volcanic eruptions can impact on global climate by injecting large quantities of aerosols and ash into the atmosphere that alter the radiative balance and chemical equilibrium of the stratosphere. The Millennium eruption of Tianchi (Paektu), China/North Korea, was one of the largest Late Holocene eruptions. Uncertainty about the precise timing of the eruption has hindered the recognition of its climate impact in palaeoclimate and historical records. Here we report the compelling identification of the eruption's volcanic signal in Greenland ice cores through the association of geochemically-characterized volcanic glass, represented in by bimodal populations that compare with proximal material from the source eruption. The eruption most probably occurred in the AD 940?s, seven years after the Eldgjá eruption on Iceland. We examine the eruption's potential for climate forcing using the sulfate records from the ice-cores and conclude that it was unlikely to have had a global or extra-regional impact.

EL CVn-type binaries - Discovery of 17 helium white dwarf precursors in bright eclipsing binary star systems

The star 1SWASP J024743.37-251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP 0247-25 B). The remnant is in a rarely observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low mass white dwarf composed almost entirely of helium, i.e. it is a pre-helium white dwarf (pre-He-WD). We have used the photometric database from theWide Angle Search for Planets (WASP) to find 17 eclipsing binary stars with orbital periods P = 0.7-2.2 d with similar light curves to 1SWASP J024743.37-251549.2. The only star in this group previously identified as a variable star is the brightest one, EL CVn, which we adopt as the prototype for this class of eclipsing binary star. The characteristic light curves of EL CVn-type stars show a total eclipse by an A-type dwarf star of a smaller, hotter star and a secondary eclipse of comparable depth to the primary eclipse. We have used new spectroscopic observations for six of these systems to confirm that the companions to the A-type stars in these binaries have very low masses (≈0.2M⊙). This includes the companion to EL CVn which was not previously known to be a pre-He-WD. EL CVn-type binary star systems will enable us to study the formation of very low mass white dwarfs in great detail, particularly in those cases where the pre-He-WD star shows non-radial pulsations similar to those recently discovered in WASP0247-25 B. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

SN 2010LP - A type IA supernova from a violent merger of two carbon-oxygen white dwarfs

SN 2010lp is a subluminous Type Ia supernova (SN Ia) with slowly evolving lightcurves. Moreover, it is the only subluminous SN Ia observed so far that shows narrow emission lines of [O I] in late-time spectra, indicating unburned oxygen close to the center of the ejecta. Most explosion models for SNe Ia cannot explain the narrow [O I] emission. Here, we present hydrodynamic explosion and radiative transfer calculations showing that the violent merger of two carbon-oxygen white dwarfs of 0.9 and 0.76 M adequately reproduces the early-time observables of SN 2010lp. Moreover, our model predicts oxygen close to the center of the explosion ejecta, a pre-requisite for narrow [O I] emission in nebular spectra as observed in SN 2010lp. © 2013. The American Astronomical Society. All rights reserved.

Alkali Activated Fuel Ash and Slag Mixes:Optimization Study from Mortars to Concrete Building Blocks

Alkali activated binders, based on ash and slag, also known as geopolymers, can play a key role in reducing the carbon footprint of the construction sector by replacing ordinary Portland cement in some concretes. Since 1970s, research effort has been ongoing in many research institutions. In this study, pulverized fuel ash (PFA) from a UK power plant, ground granulated blast furnace slag (GGBS) and combinations of the two have been investigated as geopolymer binders for concrete applications. Activators used were sodium hydroxide and sodium silicate solutions. Mortars with sand/binder ratio of 2.75 with several PFA and GGBS combinations have been mixed and tested. The optimization of alkali dosage (defined as the Na2O/binder mass ratio) and modulus (defined as the Na2O/SiO2 mass ratio) resulted in strengths in excess of 70 MPa for tested mortars. Setting time and workability have been considered for the identification of the best combination of PFA/GGBS and alkali activator dosage for different precast concrete products. Geopolymer concrete building blocks have been replicated in laboratory and a real scale factory trial has been successfully carried out. Ongoing microstructural characterization is aiming to identify reaction products arising from PFA/GGBS combinations.

High-precision ultra-distal Holocene tephrochronology in North America

Far-travelled volcanic ashes (tephras) from Holocene eruptions in Alaska and the Pacific northwest have been traced to the easternmost extent of North America, providing the basis for a new high-precision geochronological framework throughout the continent through tephrochronology (the dating and correlation of tephra isochrons in sedimentary records). The reported isochrons are geochemically distinct, with seven correlated to documented sources in Alaska and the Cascades, including the Mazama ash from Oregon (w7600 years old) and the eastern lobe of the White River Ash from Alaska (~1150 years old). These findings mark the beginning of a tephrochronological framework of enhanced precision across North America, with applications in palaeoclimate, surface process and archaeological studies. The particle travel distances involved (up tow7000 km) also demonstrate the potential for continent-wide or trans-Atlantic socio-economic disruption from similar future eruptions.

The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash in small Scottish lakes

An extensive micro-tephrostratigraphic survey of three small lakes in the Scottish Inner Hebrides was conducted encompassing the Last Glacial–Interglacial Transition (LGIT). The lakes are highly contrasting in terms of lake area to catchment ratio, the presence or absence of stream inlets draining the catchment, and in the complexity of the catchment drainage network. A suite of distal Icelandic volcanic ashes was consistently detected in all three lakes, with three, namely Penifiler Tephra, Vedde Ash and Ashik Tephra, being common to all the lakes. These ashes were chosen to examine the taphonomic intercomparability of ash location and concentration among the lakes. Findings reveal that the part played by catchment inlets in determining ash concentration and within-basin location applies to microtephra layers as much as it does in studies of macrotephra layer thickness. The position of ash concentration maxima is also shown to vary significantly for different LGIT periods and may be a consequence of lake-level changes, especially during the early Holocene. High-resolution stratigraphic analysis through the Vedde Ash visible macrotephra at Loch Ashik reveals a high degree of complexity in taphonomic behaviour between the different geochemical components, with possible implications for the correct interpretation of the isochron position. The detection of multiple intact ash isochrons and the taphonomic processes responsible for their deposition should prove useful in future tephrostratigraphic surveys, as well as having applications within other palaeolimnological disciplines.