8,504 research outputs found
Ciidae of Michigan (Insecta: Coleoptera)
The family Ciidae Leach, 1819, occurs worldwide with approximately 720 species. In the United States there are 84 species in 13 genera. Given their relatively small size (~0.5 to 6 mm) and cryptic habitats, feeding in decaying fungi, recent regional fauna studies are lacking including the northeastern United States. To alleviate this gap in knowledge, in part, we review and identify 2,123 undetermined specimens collected in Michigan. We provide new state records for four species: Ceracis pecki Lawrence 1971, Cis americanus Mannerheim, 1852, Cis submicans Abeille de Perrin, 1874, Dolicocis manitoba Dury, 1919 which increases the total for Michigan to 25 species and update records for Michigan counties. In addition, we provide a modified key to Michigan species
Two-dimensional wave propagation in layered periodic media
We study two-dimensional wave propagation in materials whose properties vary
periodically in one direction only. High order homogenization is carried out to
derive a dispersive effective medium approximation. One-dimensional materials
with constant impedance exhibit no effective dispersion. We show that a new
kind of effective dispersion may arise in two dimensions, even in materials
with constant impedance. This dispersion is a macroscopic effect of microscopic
diffraction caused by spatial variation in the sound speed. We analyze this
dispersive effect by using high-order homogenization to derive an anisotropic,
dispersive effective medium. We generalize to two dimensions a homogenization
approach that has been used previously for one-dimensional problems.
Pseudospectral solutions of the effective medium equations agree to high
accuracy with finite volume direct numerical simulations of the
variable-coefficient equations
Symbiotic stars in X-rays II: faint sources detected with XMM-Newton and Chandra
We report the detection, with and XMM-, of
faint, soft X-ray emission from four symbiotics stars that were not known to be
X-ray sources. These four object show a -type X-ray spectrum, i.e. their
spectra can be modeled with an absorbed optically thin thermal emission with
temperatures of a few million degrees. Photometric series obtained with the
Optical Monitor on board XMM- from V2416 Sgr and NSV 25735
support the proposed scenario where the X-ray emission is produced in a
shock-heated region inside the symbiotic nebulae.Comment: 5 pages, 1 figure, 2 tables; A&A publishe
On the nature of transverse coronal waves revealed by wavefront dislocations
Coronal waves are an important aspect of the dynamics of the plasma in the
corona. Wavefront dislocations are topological features of most waves in nature
and also of magnetohydrodynamic waves. Are there dislocations in coronal waves?
The finding and explanation of dislocations may shed light on the nature and
characteristics of the propagating waves, their interaction in the corona and
in general on the plasma dynamics. We positively identify dislocations in
coronal waves observed by the Coronal Multi-channel Polarimeter (CoMP) as
singularities in the Doppler shifts of emission coronal lines. We study the
possible singularities that can be expected in coronal waves and try to
reproduce the observed dislocations in terms of localization and frequency of
appearance. The observed dislocations can only be explained by the interference
of a kink and a sausage wave modes propagating with different frequencies along
the coronal magnetic field. In the plane transverse to the propagation, the
cross-section of the oscillating plasma must be smaller than the spatial
resolution, and the two waves result in net longitudinal and transverse
velocity components that are mixed through projection onto the line of sight.
Alfv\'en waves can be responsible of the kink mode, but a magnetoacoustic
sausage mode is necessary in all cases. Higher (flute) modes are excluded. The
kink mode has a pressure amplitude that is smaller than the pressure amplitude
of the sausage mode, though its observed velocity is larger. This concentrates
dislocations on the top of the loop. To explain dislocations, any model of
coronal waves must include the simultaneous propagation and interference of
kink and sausage wave modes of comparable but different frequencies, with a
sausage wave amplitude much smaller than the kink one.Comment: 11 pages. 5 figures. Accepted for publication in A&
Eveleth, Minnesota: A Portrait of My Home Town
This 30-minute documentary film provides snapshots of the small northeastern iron mining town of Eveleth, Minnesota, on the Mesabi Iron Range. It uses a two-pronged approach: 1) a first-person return to the town by the filmmaker almost 50 years after graduating from high school to see how the town may have changed, 2) a look at some historical and cultural factors which made the town what it was when the filmmaker was growing up and what continues to animate the town in the face of iron mining’s decline and rebirth. The latter include the immigrant experience and influence as the town was being developed from the early 20th century to the present, the contribution of ice hockey to the culture of the town, and an exploration of Eveleth as the quintessential iron mining town of the Mesabi Iron Range of northeastern Minnesota. Information obtained from the first-person filming visits is provided primarily by interviews and conversations with key members of the town, including the mayor, a former bar owner and member of the city council, a pharmacist and owner of the major retail establishment on the main street, the director of the US Hockey Hall of Fame, as well as some residents and former residents of the town, a historian specialist in the area, and an economist from a nearby university, among others. The goal is to tell the story of this unique little town and what distinguishes it from the many small rural communities in the United States. For copies of the actual film, contact [email protected]
Inclusion of [H3PW12O40] and [H4SiW12O40] into a silica gel matrix via "sol-gel" methodology
Indexación: Web of Science; Scopus.Here we report the inclusion of two Keggin Polyoxometalates (POMs), [H3PW12O40] and [H4SiW12O40], into silica gels by integrating them during the preparation of the SiO2 matrix via "sol-gel" methods. Aerogels were produced by supercritical drying of the wet gels impregnated with the POMs, and lyogels were obtained by means of a lyophilization process. These materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy and thermoanalytical techniques (TGA-DSC). We found that a large fraction of POMs are lost during the aging time, and solvent exchange for lyophilization. However the thermal stability of the bare matrix is modified by the inclusion of POMs. Some aggregates with a high content of POMs were found via SEM-EDX.http://ref.scielo.org/3fg9t
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