Silicate dust grains in the interstellar medium are known to be mostly amorphous, yet crystalline silicate grains have been observed in many long-period comets and in protoplanetary disks. Annealing of amorphous silicate grains into crystalline grains requires temperatures > ∼ 1000K, but exposure of dust grains in comets to such high temperatures is incompatible with the generally low temperatu...

We present here the first infrared spectra of meteoritic SiC grains. The mid-infrared transmission spectra of meteoritic SiC grains isolated from the Murchison meteorite were measured in the wavelength range 2.5–16.5 μm, in order to make available the optical properties of presolar SiC grains. These grains are most likely stellar condensates with an origin predominately in carbon stars. Measure...

Interstellar dust grains exhibit complex dynamics which is essential for understanding many key interstellar processes that involve dust, including grain alignment, grain growth, grain shattering etc. Grain rotational and translational motions are affected not only by gaseous collisions, but also by interactions with ions, photons, magnetic fields etc. Some of those interactions, e.g. interacti...

Received ; accepted – 2 – ABSTRACT Since the classical work by Purcell (1979) it has been generally accepted that most interstellar grains rotate suprathermally. Suprathermally rotating grains would be nearly perfectly aligned with the magnetic field by paramagnetic dissipation if not for " crossovers " , intervals of low angular velocity resulting from reversals of the torques responsible for ...

Introduction: Most presolar SiC grains (~93%) have Si isotopic ratios that fall along the so-called mainstream correlation line of 1.37 on a Si three isotope plot [1]. Z grains, which constitute only ~1% of the total presolar SiC population, plot on the 30 Si-rich side of this line and typically have negative δ 29 Si/ 28 Si values, suggesting that they originated in asymptotic giant branch star...

Presolar grains are considered to have traces in their birth before the solar system formation in their isotopic and elemental features. Most of silicon carbide type X (SiC X) and low density graphite grains show the excesses of 12C and 28Si. These isotopic features suggest that SiC X and low density graphite are originating from supernovae. On the other hand, elemental signatures of the grains...

A search was conducted for grains of the potential core-collapse supernova (SN) condensate minerals corundum (Al2O3), hibonite (CaAl12O19), and spinel (MgAl2O4) among grains filtered from the 308.6 m Guliya ice core recovered from the Qinghai-Tibetan plateau in China. Simple models are developed and calculations are presented to estimate the number of Al2O3 grains that would be deposited per cm...

Investigations have been carried out on the distribution of AgBr-grains in unexposed photographic plates (type Q2, 11 f o r d Ltd.) used for ion detection in mass-spectrometers. Electron micrographs show that a large fraction of the grains protrude about halfway out of the gelatine matrix and that these grains are covered by a very thin gelatine layer on the side facing the ions. The mean proje...

The interaction of dust grains originating from the local interstellar cloud with the environment inside the heliosphere is investigated. As a consequence of this interaction the spatial distribution of interstellar dust grains changes with time. Since dust grains are charged in the interplanetary plasma and radiation environment, the interaction of small grains with the heliosphere is dominate...

Raising pigs in large groups in deep bedded hoop barns is receiving increased attention from producers and consumers interested in systems that are perceived to provide improved welfare for pigs. Unfortunately, these systems usually produce pigs that are fatter than similar pigs raised in conventional confinement housing systems. So, our objectives were to determine if dietary manipulation may ...