2,499 research outputs found
Relation between positional specific heat and static relaxation length: Application to supercooled liquids
A general identification of the {\em positional specific heat} as the
thermodynamic response function associated with the {\em static relaxation
length} is proposed, and a phenomenological description for the thermal
dependence of the static relaxation length in supercooled liquids is presented.
Accordingly, through a phenomenological determination of positional specific
heat of supercooled liquids, we arrive at the thermal variation of the static
relaxation length , which is found to vary in accordance with in the quasi-equilibrium supercooled temperature regime, where
is the Vogel-Fulcher temperature and exponent equals unity. This
result to a certain degree agrees with that obtained from mean field theory of
random-first-order transition, which suggests a power law temperature variation
for with an apparent divergence at . However, the phenomenological
exponent , is higher than the corresponding mean field estimate
(becoming exact in infinite dimensions), and in perfect agreement with the
relaxation length exponent as obtained from the numerical simulations of the
same models of structural glass in three spatial dimensions.Comment: Revised version, 7 pages, no figures, submitted to IOP Publishin
Oiling global capital accumulation : analyzing the principles, practices and geographical distribution of Islamic financial services
This article focuses on the Islamic financial services (IFS) sector, which originated in the Middle East, but is now rapidly becoming a global sector. First, Islamic economic ideology is discussed, which resulted in the foundation of IFS firms after the 1973 oil crisis, and then an overview of the most common IFS is provided. The third part discusses the global distribution of IFS firms and Shari'a compliant assets. The Middle East is at the apex of the IFS sector, with the Islamized economies of Iran and Pakistan and prime hubs such as Manama and Dubai. Outside the Middle East, Malaysia is identified as an important growing market for IFS, while outside the Muslim world, London is increasingly profiling itself as a global IFS hub
Activation of inflammatory responses in human U937 macrophages by particulate matter collected from dairy farms: an in vitro expression analysis of pro-inflammatory markers
Abstract Background The purpose of the present study was to investigate activation of inflammatory markers in human macrophages derived from the U937 cell line after exposure to particulate matter (PM) collected on dairy farms in California and to identify the most potent components of the PM. Methods PM from different dairies were collected and tested to induce an inflammatory response determined by the expression of various pro-inflammatory genes, such as Interleukin (IL)-8, in U937 derived macrophages. Gel shift and luciferase reporter assays were performed to examine the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Toll-like-receptor 4 (TLR4). Results Macrophage exposure to PM derived from dairy farms significantly activated expression of pro-inflammatory genes, including IL-8, cyclooxygenase 2 and Tumor necrosis factor-alpha, which are hallmarks of inflammation. Acute phase proteins, such as serum amyloid A and IL-6, were also significantly upregulated in macrophages treated with PM from dairies. Coarse PM fractions demonstrated more pro-inflammatory activity on an equal-dose basis than fine PM. Urban PM collected from the same region as the dairy farms was associated with a lower concentration of endotoxin and produced significantly less IL-8 expression compared to PM collected on the dairy farms. Conclusion The present study provides evidence that the endotoxin components of the particles collected on dairies play a major role in mediating an inflammatory response through activation of TLR4 and NF-κB signaling
What do we teach when we teach the Learning Sciences? A document analysis of 75 graduate programs
The learning sciences, as an academic community investigating human learning, emerged more than 30 years ago. Since then, graduate learning sciences programs have been established worldwide. Little is currently known, however, about their disciplinary backgrounds and the topics and research methods they address. In this document analysis of the websites of 75 international graduate learning sciences programs, we examine central concepts and research methods across institutions, compare the programs, and assess the homogeneity of different subgroups. Results reveal that the concepts addressed most frequently were real-world learning in formal and informal contexts, designing learning environments, cognition and metacognition, and using technology to support learning. Among research methods, design-based research (DBR), discourse and dialog analyses, and basic statistics stand out. Results show substantial differences between programs, yet programs focusing on DBR show the greatest similarity regarding the other concepts and methods they teach. Interpreting the similarity of the graduate programs using a community of practice perspective, there is a set of relatively coherent programs at the core of the learning sciences, pointing to the emergence of a discipline, and a variety of multidisciplinary and more heterogeneous programs “orbiting” the core in the periphery, shaping and innovating the field
Slow dynamics near glass transitions in thin polymer films
The -process (segmental motion) of thin polystyrene films supported
on glass substrate has been investigated in a wider frequency range from
10 Hz to 10 Hz using dielectric relaxation spectroscopy and thermal
expansion spectroscopy. The relaxation rate of the -process increases
with decreasing film thickness at a given temperature above the glass
transition. This increase in the relaxation rate with decreasing film thickness
is much more enhanced near the glass transition temperature. The glass
transition temperature determined as the temperature at which the relaxation
time of the -process becomes a macroscopic time scale shows a distinct
molecular weight dependence. It is also found that the Vogel temperature has
the thickness dependence, i.e., the Vogel temperature decreases with decreasing
film thickness. The expansion coefficient of the free volume is
extracted from the temperature dependence of the relaxation time within the
free volume theory. The fragility index is also evaluated as a function of
thickness. Both and are found to decrease with decreasing film
thickness.Comment: 9 pages, 7 figures, and 2 table
Luminosity Measurement in the L3 Detector at LEP
One of the limiting factors in the determination of the electroweak parameters from cross section measurements of e+e- annihilation close to the Z pole is the precision of the luminosity measurement. The luminosity monitor of the L3 detector at LEP and the analysis of its data are described. Using a combination of a BGO calorimeter and a 3-layer silicon tracker, the absolute luminosity has been measured with an experimental precision of 0.08% in 1993 and 0.05% in 1994. The measurement relies on a detailed understanding of small-angle elastic e+e-(Bhabha) scattering from the experimental and theoretical point of view, as well as an excellent knowledge of the detector geometry
Measurement of the rate of nu_e + d --> p + p + e^- interactions produced by 8B solar neutrinos at the Sudbury Neutrino Observatory
Solar neutrinos from the decay of B have been detected at the Sudbury
Neutrino Observatory (SNO) via the charged current (CC) reaction on deuterium
and by the elastic scattering (ES) of electrons. The CC reaction is sensitive
exclusively to nu_e's, while the ES reaction also has a small sensitivity to
nu_mu's and nu_tau's. The flux of nu_e's from ^8B decay measured by the CC
reaction rate is
\phi^CC(nu_e) = 1.75 +/- 0.07 (stat)+0.12/-0.11 (sys.) +/- 0.05(theor) x 10^6
/cm^2 s.
Assuming no flavor transformation, the flux inferred from the ES reaction
rate is
\phi^ES(nu_x) = 2.39+/-0.34 (stat.)+0.16}/-0.14 (sys) x 10^6 /cm^2 s.
Comparison of \phi^CC(nu_e) to the Super-Kamiokande Collaboration's precision
value of \phi^ES(\nu_x) yields a 3.3 sigma difference, providing evidence that
there is a non-electron flavor active neutrino component in the solar flux. The
total flux of active ^8B neutrinos is thus determined to be 5.44 +/-0.99 x
10^6/cm^2 s, in close agreement with the predictions of solar models.Comment: 6 pages (LaTex), 3 figures, submitted to Phys. Rev. Letter
Evidence for t\bar{t}\gamma Production and Measurement of \sigma_t\bar{t}\gamma / \sigma_t\bar{t}
Using data corresponding to 6.0/fb of ppbar collisions at sqrt(s) = 1.96 TeV
collected by the CDF II detector, we present a cross section measurement of
top-quark pair production with an additional radiated photon. The events are
selected by looking for a lepton, a photon, significant transverse momentum
imbalance, large total transverse energy, and three or more jets, with at least
one identified as containing a b quark. The ttbar+photon sample requires the
photon to have 10 GeV or more of transverse energy, and to be in the central
region. Using an event selection optimized for the ttbar+photon candidate
sample we measure the production cross section of, and the ratio of cross
sections of the two samples. Control samples in the dilepton+photon and
lepton+photon+\met, channels are constructed to aid in decay product
identification and background measurements. We observe 30 ttbar+photon
candidate events compared to the standard model expectation of 26.9 +/- 3.4
events. We measure the ttbar+photon cross section to be 0.18+0.08 pb, and the
ratio of the cross section of ttbar+photon to ttbar to be 0.024 +/- 0.009.
Assuming no ttbar+photon production, we observe a probability of 0.0015 of the
background events alone producing 30 events or more, corresponding to 3.0
standard deviations.Comment: 9 pages, 3 figure
Combined search for the standard model Higgs boson decaying to a bb pair using the full CDF data set
We combine the results of searches for the standard model Higgs boson based
on the full CDF Run II data set obtained from sqrt(s) = 1.96 TeV p-pbar
collisions at the Fermilab Tevatron corresponding to an integrated luminosity
of 9.45/fb. The searches are conducted for Higgs bosons that are produced in
association with a W or Z boson, have masses in the range 90-150 GeV/c^2, and
decay into bb pairs. An excess of data is present that is inconsistent with the
background prediction at the level of 2.5 standard deviations (the most
significant local excess is 2.7 standard deviations).Comment: To be published in Phys. Rev. Lett (v2 contains minor updates based
on comments from PRL
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