7,706 research outputs found
GreenCare for Children -- Measuring Environmental Hazards in the Childcare Industry
Presents findings from a two-year survey administered to a random sampling of childcare providers. Developed and interpreted by a diverse team of industry, technical, and educational experts
Suppression of spin-torque in current perpendicular to the plane spin-valves by addition of Dy cap layers
We demonstrate that the addition of Dy capping layers in current
perpendicular to the plane giant magneto-resistive spin-valves can increase the
critical current density beyond which spin-torque induced instabilities are
observed by about a factor of three. Current densities as high as 5e7 A/cm2 are
measured provided that the electron current flows from the free to the
reference layer. While Dy capped samples exhibit nonmagnetic 1/f noise, it is
sufficiently small to be unimportant for read head operation at practical data
rates.Comment: 13 pages (manuscript form), with 5 figures. Submitted for publicatio
Thermal Effects on the Magnetic Field Dependence of Spin Transfer Induced Magnetization Reversal
We have developed a self-aligned, high-yield process to fabricate CPP
(current perpendicular to the plane) magnetic sensors of sub 100 nm dimensions.
A pinned synthetic antiferromagnet (SAF) is used as the reference layer which
minimizes dipole coupling to the free layer and field induced rotation of the
reference layer. We find that the critical currents for spin transfer induced
magnetization reversal of the free layer vary dramatically with relatively
small changes the in-plane magnetic field, in contrast to theoretical
predictions based on stability analysis of the Gilbert equations of
magnetization dynamics including Slonczewski-type spin-torque terms. The
discrepancy is believed due to thermal fluctuations over the time scale of the
measurements. Once thermal fluctuations are taken into account, we find good
quantitative agreement between our experimental results and numerical
simulations.Comment: 14 pages, 4 figures, Submitted to Appl. Phys. Lett., Comparison of
some of these results with a model described by N. Smith in cond-mat/040648
A Catalog of MIPSGAL Disk and Ring Sources
We present a catalog of 416 extended, resolved, disk- and ring-like objects
as detected in the MIPSGAL 24 micron survey of the Galactic plane. This catalog
is the result of a search in the MIPSGAL image data for generally circularly
symmetric, extended "bubbles" without prior knowledge or expectation of their
physical nature. Most of the objects have no extended counterpart at 8 or 70
micron, with less than 20% detections at each wavelength. For the 54 objects
with central point sources, the sources are nearly always seen in all IRAC
bands. About 70 objects (16%) have been previously identified, with another 35
listed as IRAS sources. Among the identified objects, those with central
sources are mostly listed as emission-line stars, but with other source types
including supernova remnants, luminous blue variables, and planetary nebulae.
The 57 identified objects (of 362) without central sources are nearly all PNe
(~90%).which suggests that a large fraction of the 300+ unidentified objects in
this category are also PNe. These identifications suggest that this is
primarily a catalog of evolved stars. Also included in the catalog are two
filamentary objects that are almost certainly SNRs, and ten unusual compact
extended objects discovered in the search. Two of these show remarkable spiral
structure at both 8 and 24 micron. These are likely background galaxies
previously hidden by the intervening Galactic plane
Tracing the energetics and evolution of dust with Spitzer : a chapter in the history of the Eagle Nebula
Context. The Spitzer GLIMPSE and MIPSGAL surveys have revealed a wealth of details about the Galactic plane in the infrared (IR)with orders of magnitude higher sensitivity, higher resolution, and wider coverage than previous IR observations. The structure of the interstellar medium (ISM) is tightly connected to the countless star-forming regions. We use these surveys to study the energetics and dust properties of the Eagle Nebula (M16), one of the best known star-forming regions.
Aims. We present MIPSGAL observations of M16 at 24 and 70 μm and combine them with previous IR data. The mid-IR image
shows a shell inside the well-known molecular borders of the nebula, as in the ISO and MSX observations from 15 to 21 μm. The morphologies at 24 and 70 μm are quite different, and its color ratio is unusually warm. The far-IR image resembles the one at 8 μm that enhances the structure of the molecular cloud and the "pillars of creation". We use this set of IR data to analyze the dust energetics and properties within this template for Galactic star-forming regions.
Methods. We measure IR spectral energy distributions (SEDs) across the entire nebula, both within the inner shell and the photodissociation regions (PDRs).We use the DUSTEM model to fit these SEDs and constrain the dust temperature, the dust-size distribution, and the radiation field intensity relative to that provided by the star cluster NGC 6611 (χ/χ0). Results. Within the PDRs, the inferred dust temperature (~35 K), the dust-size distribution, and the radiation field intensity (χ/χ0 < 1) are consistent with expectations. Within the inner shell, the dust is hotter (~70 K). Moreover, the radiation field required to fit the
SED is larger than that provided by NGC 6611 (χ/χ0 > 1). We quantify two solutions to this problem: (1) The size distribution of the dust in the shell is not that of interstellar dust. There is a significant enhancement of the carbon dust-mass in stochastically heated
very small grains. (2) The dust emission arises from a hot (~10^6 K) plasma where both UV and collisions with electrons contribute to the heating. Within this hypothesis, the shell SED may be fit for a plasma pressure p/k ~ 5 × 10^7 K cm^(−3).
Conclusions. We suggest two interpretations for the M16 inner shell: (1) The shell matter is supplied by photo-evaporative flows arising from dense gas exposed to ionized radiation. The flows renew the shell matter as it is pushed out by the pressure from stellar winds. Within this scenario, we conclude that massive-star forming regions such as M16 have a major impact on the carbon dustsize
distribution. The grinding of the carbon dust could result from shattering in grain-grain collisions within shocks driven by the dynamical interaction between the stellar winds and the shell. (2) We also consider a more speculative scenario where the shell is a supernova remnant. In this case, we would be witnessing a specific time in the evolution of the remnant where the plasma pressure and temperature would enable the remnant to cool through dust emission
Who knows who we are? Questioning DNA analysis in disaster victim identification
The use of DNA analysis as a mode of identification of disaster victims has become increasingly predominant to other, traditional, methods of identification in recent years. Scientific advances of the technological processes, high-profile use in identification efforts across the globe (such as after 9/11 or in the Asian Tsunami of 2004), and its inclusion in popular media, have led to its popular adoption as one of the primary modes of identification in disaster scenarios, and to the expectation of its use in all cases by the lay public and media. It is increasingly argued to be integral to post-disaster management. However, depending on the circumstances, location, and type of disaster, this technology may not be appropriate, and its use may instead conflict with socio-political and cultural norms and structures of power. Using examples primarily from Cambodia and Iraq this article will explore what these conflicts may be, and in doing so, question the expanding assumption that DNA analysis is a universally appropriate intervention in disaster victim identification. It will argue instead that its use may be a result of a desire for the political and social capital that this highly prestigious technological intervention offers rather than a solely humanitarian intervention on behalf of survivors and the dead
Senescence can play an essential role in modelling and estimation of vector based epidemiological indicators: demographical approach
In the paper basic epidemiological indicators, produced by an aging population of vectors, are calculated. In the study we follow two lines: calculations for demographically structured population and individual life-history approach. We discuss the advantages and limitations of these approaches and compare the results of our calculations with epidemiological indicators obtained for non-aging population of vectors.Gibraltar, age effect, disease control, gerontology
Separation of the first- and second-order contributions in magneto-optic Kerr effect magnetometry of epitaxial FeMn/NiFe bilayers
The influence of second-order magneto-optic effects on Kerr effect
magnetometry of epitaxial exchange coupled FeMn/NiFe-bilayers is investigated.
A procedure for separation of the first- and second-order contributions is
presented. The full angular dependence of both contributions during the
magnetization reversal is extracted from the experimental data and presented
using gray scaled magnetization reversal diagrams. The theoretical description
of the investigated system is based on an extended Stoner-Wohlfarth model,
which includes an induced unidirectional and fourfold anisotropy in the
ferromagnet, caused by the coupling to the antiferromagnet. The agreement
between the experimental data and the theoretical model for both the first- and
second-order contributions are good, although a coherent reversal of the
magnetization is assumed in the model.Comment: 6 pages, 7 figures, submitted to J. Appl. Phy
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