7,590 research outputs found
Stability, Adsorption and Diffusion of CH4, CO2 and H2 in Clathrate Hydrates
We present a study of the adsorption and diffusion of CH4, CO2 and H2
molecules in clathrate hydrates using ab initio van der Waals density
functional formalism [Dion et al. Phys. Rev. Lett. 92, 246401 (2004)]. We find
that the adsorption energy is dominated by van der Waals interactions and that,
without them, gas hydrates would not be stable. We calculate the maximum
adsorption capacity as well as the maximum hydrocarbon size that can be
adsorbed.The relaxation of the host lattice is essential for a good description
of the diffusion activation energies, which are estimated to be of the order of
0.2, 0.4, and 1.0 eV for H2, CO2, and CH4, respectively.Comment: 4 pages, 4 figures, 3 table
The Road from Medical Injury to Claims Resolution: How No-Fault and Tort Differ
In the area of medical malpractice, no-fault has been offered as a response to the criticisms leveled against tort litigation for medical injuries. Five issues of no-fault are examined within the context of obstetrical malpractice
Force and energy dissipation variations in non-contact atomic force spectroscopy on composite carbon nanotube systems
UHV dynamic force and energy dissipation spectroscopy in non-contact atomic
force microscopy were used to probe specific interactions with composite
systems formed by encapsulating inorganic compounds inside single-walled carbon
nanotubes. It is found that forces due to nano-scale van der Waals interaction
can be made to decrease by combining an Ag core and a carbon nanotube shell in
the Ag@SWNT system. This specific behaviour was attributed to a significantly
different effective dielectric function compared to the individual
constituents, evaluated using a simple core-shell optical model. Energy
dissipation measurements showed that by filling dissipation increases,
explained here by softening of C-C bonds resulting in a more deformable
nanotube cage. Thus, filled and unfilled nanotubes can be discriminated based
on force and dissipation measurements. These findings have two different
implications for potential applications: tuning the effective optical
properties and tuning the interaction force for molecular absorption by
appropriately choosing the filling with respect to the nanotube.Comment: 22 pages, 6 figure
Dusty OB stars in the Small Magellanic Cloud - II: Extragalactic Disks or Examples of the Pleiades Phenomenon?
We use mid-infrared Spitzer spectroscopy and far-infrared Herschel photometry
for a sample of twenty main sequence O9--B2 stars in the Small Magellanic Cloud
(SMC) with strong 24 micron excesses to investigate the origin of the mid-IR
emission. Either debris disks around the stars or illuminated patches of dense
interstellar medium (ISM) can cause such mid-IR emission. In a companion paper,
Paper I, we use optical spectroscopy to show that it is unlikely for any of
these sources to be classical Be stars or Herbig Ae/Be stars. We focus our
analysis on debris disks and cirrus hot spots. We find three out of twenty
stars to be significantly extended in the mid-IR, establishing them as cirrus
hot spots. We then fit the IR spectral energy distributions to determine dust
temperatures and masses. We find the dust masses in the SMC stars to be larger
than for any known debris disks, although this evidence against the debris disk
hypothesis is circumstantial. Finally, we created a local comparison sample of
bright mid-IR OB stars in the Milky Way (MW) by cross-matching the WISE and
Hipparcos catalogs. All such local stars in the appropriate luminosity range
that can be unambiguously classified are young stars with optical emission
lines or are spatially resolved by WISE with sizes too large to be plausible
debris disk candidates. We conclude that the very strong mid-IR flux excesses
are most likely explained as cirrus hot spots, although we cannot rigorously
rule out that a small fraction of the sample is made up of debris disks or
transition disks. We present suggestive evidence that bow-shock heating around
runaway stars may be a contributing mechanism to the interstellar emission.
These sources, interpreted as cirrus hot spots, offer a new localised probe of
diffuse interstellar dust in a low metallicity environment. (Abridged)Comment: Accepted for publication in ApJ, 23 pages, 11 figures, 8 table
Searching for magnetic monopoles trapped in accelerator material at the Large Hadron Collider
If produced in high energy particle collisions at the LHC, magnetic monopoles
could stop in material surrounding the interaction points. Obsolete parts of
the beam pipe near the CMS interaction region, which were exposed to the
products of pp and heavy ion collisions, were analysed using a SQUID-based
magnetometer. The purpose of this work is to quantify the performance of the
magnetometer in the context of a monopole search using a small set of samples
of accelerator material ahead of the 2013 shutdown.Comment: 11 page
A University Engagement Model for Achieving Technology Adoption and Performance Improvement in Healthcare, Manufacturing, and Government
The Purdue Technical Assistance Program (TAP) offers a model of university engagement and service that is achieving technology adoption and performance improvement impacts in health care, manufacturing, government, and other sectors. The TAP model focuses on understanding and meeting the changing and challenging needs of those served, always seeking to engage a mix of faculty, staff, students, and others that best meet these needs. Although the TAP mission is focused on the needs of those served, participating faculty and students have experienced significant benefits, and faculty rarely decline an opportunity to participate. This essay presents the evolution of Purdue University’s engagement and service missions, and their alignment with the current thinking of engagement scholars and practitioners. The operational model for TAP is described as an important part of Purdue’s engagement mission, along with the elements necessary for its success, examples of successful engagement, and future challenges and opportunities
Trap Target Studies
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
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