11,649 research outputs found
Triple point determinations of monomethylhydrazine and nitrogen tetroxide, 2.2 percent by weight nitric oxide
A series of tests was performed to ascertain the triple points of monomethylhydrazine and nitrogen tetroxide. A laboratory method indicated a triple point for monomethylhydrazine, but tests in a large vacuum chamber indicated that a triple point does not occur in spacelike conditions because the mono-methylhydrazine tends to supercool. Instead, an effective freezing point (with agitation) was obtained. New experimental values for liquid monomethylhydrazine vapor pressure were determined for temperatures from 275.2 to 207.6 K. The values were used to derive vapor pressure equations. Tentative values were obtained for the effective freezing point of nitrogen tetroxide spacelike conditions
That\u27s the Way We Flow : Hip Hop as Oral Literature
This thesis examines Hip Hop as a genre of oral literature. To begin this study, I examine a wide range of scholarship on orality, including what is considered the canonical work, Orality and Literature, by Walter Ong. This theoristâs conclusion draws a binary opposition between orality and writing. Hip Hop music encourages a broader definition of orality that approaches what African author Ngugi wa Thiongâo calls orature. I use Hip Hop to push back on Ongâs conclusions, and demonstrate how orality and writing can coexist in a culture. I found that there were three categories of Hip Hop songs that demonstrated the link between orality and writing. First, there are two types of Hip Hop songs that that form an intertextual relation with other songs through sampling. The first kind features a DJ that samples words and phrases to make it appear as if they are speaking over the beat. The second kind, reinterprets what the original speakerâs message was by sampling their music in a new song. Second, there is a group of Hip Hop songs that feature unique vocal styles that demonstrate how the artist intends to give an oral performance, even though they wrote the lyrics before performing them. Through these examples, my thesis examines how Hip Hop acts as orature, and broadens the definition of orality. Third, there are certain Hip Hop songs that play off of the traditional storytelling form of Western culture, demonstrating how oral culture can influence written and oral styles of storytelling
Accelerating Asymptotically Exact MCMC for Computationally Intensive Models via Local Approximations
We construct a new framework for accelerating Markov chain Monte Carlo in
posterior sampling problems where standard methods are limited by the
computational cost of the likelihood, or of numerical models embedded therein.
Our approach introduces local approximations of these models into the
Metropolis-Hastings kernel, borrowing ideas from deterministic approximation
theory, optimization, and experimental design. Previous efforts at integrating
approximate models into inference typically sacrifice either the sampler's
exactness or efficiency; our work seeks to address these limitations by
exploiting useful convergence characteristics of local approximations. We prove
the ergodicity of our approximate Markov chain, showing that it samples
asymptotically from the \emph{exact} posterior distribution of interest. We
describe variations of the algorithm that employ either local polynomial
approximations or local Gaussian process regressors. Our theoretical results
reinforce the key observation underlying this paper: when the likelihood has
some \emph{local} regularity, the number of model evaluations per MCMC step can
be greatly reduced without biasing the Monte Carlo average. Numerical
experiments demonstrate multiple order-of-magnitude reductions in the number of
forward model evaluations used in representative ODE and PDE inference
problems, with both synthetic and real data.Comment: A major update of the theory and example
The Gut Microbiota and Mucosal T Cells
It is intuitive that immune cells in the gut may require microbiota-derived cues for their differentiation. The proximity between host and microbe in the intestine would seemingly necessitate co-adaptation. However, it has been challenging to determine the members and features of the gut microbiota that influence immune system development and function. The recent identification of immunomodulatory members of the commensal microbiota is providing insight into the dependence of select, intestinal immune cell subsets on specific microbial species. In this review, we focus on the gut microbiota's influence on the development and function of mucosal T cells subsets, specifically intraepithelial lymphocytes and lamina propria CD4 T cells
An X-Ray Study of the Supernova Remnant G290.1-0.8
G290.1-0.8 (MSH 11-61A) is a supernova remnant (SNR) whose X-ray morphology
is centrally bright. However, unlike the class of X-ray composite SNRs whose
centers are dominated by nonthermal emission, presumably driven by a central
pulsar, we show that the X-ray emission from G290.1-0.8 is thermal in nature,
placing the remnant in an emerging class which includes such remnants as W44,
W28, 3C391, and others. The evolutionary sequence which leads to such X-ray
properties is not well understood. Here we investigate two scenarios for such
emission: evolution in a cloudy interstellar medium, and early-stage evolution
of a remnant into the radiative phase, including the effects of thermal
conduction. We construct models for these scenarios in an attempt to reproduce
the observed center-filled X-ray properties of G290.1-0.8, and we derive the
associated age, energy, and ambient density conditions implied by the models.
We find that for reasonable values of the explosion energy, the remnant age is
of order (1 - 2) x 10^{4} yr. This places a fairly strong constraint on any
association between G290.1-0.8 and PSR J1105-610, which would require an
anomalously large velocity for the pulsar.Comment: 7 pages, 7 figures, ApJ, accepte
Is the Cepheus E Outflow driven by a Class 0 Protostar?
New early release observations of the Cepheus E outflow and its embedded
source, obtained with the Spitzer Space Telescope, are presented. We show the
driving source is detected in all 4 IRAC bands, which suggests that traditional
Class 0 classification, although essentially correct, needs to accommodate the
new high sensitivity infrared arrays and their ability to detected deeply
embedded sources. The IRAC, MIPS 24 and 70 microns new photometric points are
consistent with a spectral energy distribution dominated by a cold, dense
envelope surrounding the protostar. The Cep E outflow, unlike its more famous
cousin the HH 46/47 outflow, displays a very similar morphology in the near and
mid-infrared wavelengths, and is detected at 24 microns. The interface between
the dense molecular gas (where Cep E lies) and less dense interstellar medium,
is well traced by the emission at 8 and 24 microns, and is one of the most
exotic features of the new IRAC and MIPS images. IRS observations of the North
lobe of the flow confirm that most of the emission is due to the excitation of
pure H2 rotational transitions arising from a relatively cold (Tex~700 K) and
dense (N{H}~9.6E20 cm-2 molecular gas.Comment: 14 pages (pre-print format), including 6 figures. Published in ApJ
Special Spitzer Issue (2004
Recommended from our members
Solute Trapping of Group III, IV, and V Elements in Silicon by an Aperiodic Stepwise Growth Mechanism
With rapid solidification following pulsed laser melting, we have measured the dependence on
interface orientation of the amount of solute trapping of several group III, IV, and V elements (As,
Ga, Ge, In, Sb, Sn) in Si. The aperiodic stepwise growth model of Goldman and Aziz accurately fits
both the velocity and orientation dependence of solute trapping of all of these solutes except Ge. The
success of the model implies a ledge structure for the crystal/melt interface and a step-flow
mechanism for growth from the melt. In addition, we have observed an empirical inverse correlation
between the two free parameters (-âdiffusive speedsâ) in this model and the equilibrium solute
partition coefficient of a system. This correlation may be used to estimate values of these free
parameters for other systems in which solute trapping has not or cannot be measured. The possible
microscopic origin of such a correlation is discussed.Engineering and Applied Science
A cause of ulnar neuropathy in a baseball pitcher
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66653/2/10.1177_036354658601400518.pd
Ontology Summit 2008 Communiqué: Towards an open ontology repository
Each annual Ontology Summit initiative makes a statement appropriate to each Summits theme as part of our general advocacy designed to bring ontology science and engineering into the mainstream. The theme this year is "Towards an Open Ontology Repository". This communiqué represents the joint position of those who were engaged in the year's summit discourse on an Open Ontology Repository (OOR) and of those who endorse below. In this discussion, we have agreed that an "ontology repository is a facility where ontologies and related information artifacts can be stored, retrieved and managed."
We believe in the promise of semantic technologies based on logic, databases and the Semantic Web, a Web of exposed data and of interpretations of that data (i.e., of semantics), using common standards. Such technologies enable distinguishable, computable, reusable, and sharable meaning of Web and other artifacts, including data, documents, and services. We also believe that making that vision a reality requires additional supporting resources and these resources should be open, extensible, and provide common services over the ontologies
History as reflective practice: a model for integrating historical studies into nurse education
The role of history in developing professional identity in nursing is well known, and the discipline of nursing history research continues to flourish. Yet this work often struggles to find its way into undergraduate university nurse education courses. We put forward a model for history as reflective practice in which we suggest that historical studies can be used as a form of evidence to develop critical thinking and clinical reasoning, as well as situate nursing practice within its social and political context. In this model, we draw on historical scholarship related to the profession, practice and person, focusing on work which demonstrates nursing\u27s contribution to broader systems of health care. Drawing on Lewenson and Lynaugh\u27s \u27history by stealth\u27 approach, curriculum mapping and constructive alignment techniques are used to identify the moments in an existing programme where historical scholarship is relevant to an intended learning outcome. We then use an interdisciplinary team to develop learning activities and assessment tasks drawing on both primary and secondary sources that are then embedded within existing subjects. This model encourages students to consider history as a way of knowing and as a form of evidence within their reflective practice. Furthermore, it creates knowledge that continues to foster and acknowledge nurses\u27, and nursing\u27s, contribution to the development of human health
- âŠ