702 research outputs found
Measuring Inaccessible Residual Stresses Using Multiple Methods and Superposition
The traditional contour method maps a single
component of residual stress by cutting a body carefully in
two and measuring the contour of the cut surface. The cut also
exposes previously inaccessible regions of the body to
residual stress measurement using a variety of other techniques,
but the stresses have been changed by the relaxation
after cutting. In this paper, it is shown that superposition of
stresses measured post-cutting with results from the contour
method analysis can determine the original (pre-cut) residual
stresses. The general superposition theory using Buecknerâs
principle is developed and limitations are discussed. The
procedure is experimentally demonstrated by determining the
triaxial residual stress state on a cross section plane. The 2024-
T351 aluminum alloy test specimen was a disk plastically
indented to produce multiaxial residual stresses. After cutting
the disk in half, the stresses on the cut surface of one half were
determined with X-ray diffraction and with hole drilling on
the other half. To determine the original residual stresses, the
measured surface stresses were superimposed with the change
stress calculated by the contour method. Within uncertainty,
the results agreed with neutron diffraction measurements
taken on an uncut disk
Demographic dynamics of the SuyĂĄ, a JĂȘ people of the Xingu Indigenous Park, Central Brazil, 1970-2004
High-pressure behavior and phase stability of Na2B4O6(OH)2·3H2O (kernite)
The high-pressure behavior of kernite [ideally Na2B4O6(OH)2\ub73H2O, a ~ 7.02 \u212b,
b ~ 9.16 \u212b, c ~ 15.68 \u212b, \u3b2 = 108.9\ub0, Sp Gr P21/c, at ambient conditions], an important
B-bearing raw material (with B2O3 48 51 wt%) and a potential B-rich aggregate
in radiation shielding materials, has been studied by single-crystal synchrotron X-ray
diffraction up to 14.6 GPa. Kernite undergoes an iso-symmetric phase transition at
1.6-2.0 GPa (to kernite-II). Between 6.6-7.5 GPa, kernite undergoes a second phase
transition, possibly iso-symmetric in character (to kernite-III). The crystal structure
of kernite-II was solved and refined. The isothermal bulk modulus (KV0 = \u3b2-1
P0,T0, where \u3b2P0,T0 is the volume compressibility coefficient) of the ambient-pressure polymorph
of kernite was found to be KV0 = 29(1) GPa and a marked anisotropic compressional
pattern, with K(a)0: K(b)0: K(c)0~1:3:1.5., was observed. In kernite-II, the
KV0 increases to 43.3(9) GPa and the anisotropic compressional pattern increases
pronouncedly. The mechanisms, at the atomic scale, which govern the structure deformation,
have been described
Sense or sensibility? The neuro-functional basis of the structural matching effect in persuasion
The present study investigates the neural pathways underlying individual susceptibility to affective or cognitive information in persuasive communication, also known as the structural matching effect. Expanding on the presumed involvement of the ventromedial prefrontal cortex (vMPFC) in persuasion, we hypothesized that the vMPFC contributes to the evaluation of persuasive information depending on its match with the recipientâs affective or cognitive predominance. During functional magnetic resonance imaging, 30 participants evaluated 10 consumable products presented with both affective and cognitive persuasive messages. All participants were characterized on a continuum regarding their personal orientation in terms of individual differences in need for affect (NFA) and need for cognition (NFC). The results showed that the vMPFC, posterior cingulate cortex, and cerebellum are more strongly activated when the persuasive message content, either affective or cognitive, matched the recipientâs individual affective or cognitive orientation. Interestingly, this effect in the vMPFC was found specifically when participants evaluated the products presented by the persuasive messages, whereas the correlation in the posterior cingulate cortex and cerebellum activity was detected when reading the messages. These results confirm the hypothesis that the vMPFC plays a role in subjectively weighting persuasive message content depending on individual differences in affective and cognitive orientation. Such a structural matching effect might involve the vMPFC particularly during explicit expressions of subjective valuations. These novel findings also further develop the conceptualisation of the role of the vMPFC in self-related processing
Chandra Observation of Abell 2142: Survival of Dense Subcluster Cores in a Merger
We use Chandra data to map the gas temperature in the central region of the
merging cluster A2142. The cluster is markedly nonisothermal; it appears that
the central cooling flow has been disturbed but not destroyed by a merger. The
X-ray image exhibits two sharp, bow-shaped, shock-like surface brightness edges
or gas density discontinuities. However, temperature and pressure profiles
across these edges indicate that these are not shock fronts. The pressure is
reasonably continuous across these edges, while the entropy jumps in the
opposite sense to that in a shock (i.e. the denser side of the edge has lower
temperature, and hence lower entropy). Most plausibly, these edges delineate
the dense subcluster cores that have survived a merger and ram pressure
stripping by the surrounding shock-heated gas.Comment: Latex, 9 pages, 5 figures (including color), uses emulateapj.sty.
Submitted to Ap
Bibliometrics of systematic reviews : analysis of citation rates and journal impact factors
Background:
Systematic reviews are important for informing clinical practice and health policy. The aim of this study was to examine the bibliometrics of systematic reviews and to determine the amount of variance in citations predicted by the journal impact factor (JIF) alone and combined with several other characteristics.
Methods:
We conducted a bibliometric analysis of 1,261 systematic reviews published in 2008 and the citations to them in the Scopus database from 2008 to June 2012. Potential predictors of the citation impact of the reviews were examined using descriptive, univariate and multiple regression analysis.
Results:
The mean number of citations per review over four years was 26.5 (SD +/-29.9) or 6.6 citations per review per year. The mean JIF of the journals in which the reviews were published was 4.3 (SD +/-4.2). We found that 17% of the reviews accounted for 50% of the total citations and 1.6% of the reviews were not cited. The number of authors was correlated with the number of citations (r = 0.215, P =5.16) received citations in the bottom quartile (eight or fewer), whereas 9% of reviews published in the lowest JIF quartile (<=2.06) received citations in the top quartile (34 or more). Six percent of reviews in journals with no JIF were also in the first quartile of citations.
Conclusions:
The JIF predicted over half of the variation in citations to the systematic reviews. However, the distribution of citations was markedly skewed. Some reviews in journals with low JIFs were well-cited and others in higher JIF journals received relatively few citations; hence the JIF did not accurately represent the number of citations to individual systematic reviews
Observation of TeV gamma rays from the Cygnus region with the ARGO-YBJ experiment
We report the observation of TeV gamma-rays from the Cygnus region using the
ARGO-YBJ data collected from 2007 November to 2011 August. Several TeV sources
are located in this region including the two bright extended MGRO J2019+37 and
MGRO J2031+41. According to the Milagro data set, at 20 TeV MGRO J2019+37 is
the most significant source apart from the Crab Nebula. No signal from MGRO
J2019+37 is detected by the ARGO-YBJ experiment, and the derived flux upper
limits at 90% confidence level for all the events above 600 GeV with medium
energy of 3 TeV are lower than the Milagro flux, implying that the source might
be variable and hard to be identified as a pulsar wind nebula. The only
statistically significant (6.4 standard deviations) gamma-ray signal is found
from MGRO J2031+41, with a flux consistent with the measurement by Milagro.Comment: 14 pages, 4 figure
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