1,297 research outputs found
On the macroion virial contribution to the osmotic pressure in charge-stabilized colloidal suspensions
Our interest goes to the different virial contributions to the equation of
state of charged colloidal suspensions. Neglect of surface effects in the
computation of the colloidal virial term leads to spurious and paradoxical
results. This pitfall is one of the several facets of the danger of a naive
implementation of the so called One Component Model, where the micro-ionic
degrees of freedom are integrated out to only keep in the description the
mesoscopic (colloidal) degrees of freedom. On the other hand, due incorporation
of wall induced forces dissolves the paradox brought forth in the naive
approach, provides a consistent description, and confirms that for salt-free
systems, the colloidal contribution to the pressure is dominated by the
micro-ionic one. Much emphasis is put on the no salt case but the situation
with added electrolyte is also discussed
The Importance of Reporting Housing and Husbandry in Rat Research
In 1963, the National Institutes of Health (NIH) first issued guidelines for animal housing and husbandry. The most recent 2010 revision emphasizes animal care âin ways judged to be scientifically, technically, and humanely appropriateâ (National Institutes of Health, 2010, p. XIII). The goal of these guidelines is to ensure humanitarian treatment of animals and to optimize the quality of research. Although these animal care guidelines cover a substantial amount of information regarding animal housing and husbandry, researchers generally do not report all these variables (see Table âTable1).1). The importance of housing and husbandry conditions with respect to standardization across different research laboratories has been debated previously (Crabbe et al., 1999; Van Der Staay and Steckler, 2002; Wahlsten et al., 2003; Wolfer et al., 2004; Van Der Staay, 2006; Richter et al., 2010, 2011). This paper focuses on several animal husbandry and housing issues that are particularly relevant to stress responses in rats, including transportation, handling, cage changing, housing conditions, light levels and the lightâdark cycle. We argue that these key animal housing and husbandry variables should be reported in greater detail in an effort to raise awareness about extraneous experimental variables, especially those that have the potential to interact with the stress response
Fixing the renormalisation scheme in NNLO perturbative QCD using conformal limit arguments
We discuss how the renormalisation scheme ambiguities in QCD can be fixed,
when two observables are related, by requiring the coefficients in the
perturbative expansion relating the two observables to have their conformal
limit values, i.e. to be independent of the -function of the
renormalised coupling. We show how the next-to-leading order BLM automatic
scale fixing method can be extended to next-to-next-to-leading order to fix
both the renormalisation scale and in a unique way. As an example we
apply the method to the relation between Bjorken's sum rule and and
compare with experimental data as well as other scheme fixing methods.Comment: 14 pages LaTeX, uses revtex.sty, 1 encapsulated PostScript figur
Infrared renormalons and analyticity structure in pQCD
Relation between the infrared renormalons, the Borel resummation
prescriptions, and the analyticity structure of Green functions in perturbative
QCD (pQCD) is investigated. A specific recently suggested Borel resummation
prescription resulted in the Principal Value and an additional power-suppressed
correction that is consistent with the Operator Product Expansion. Arguments
requiring the finiteness of the result for any power coefficient of the leading
infrared renormalon, and the consistency in the case of the absence of that
renormalon, require that this prescription be modified. The apparently most
natural modification leads to the result represented by the Principal Value.
The analytic structure of the amplitude in the complex coupling plane, obtained
in this way, is consistent with that obtained in the literature by other
methods.Comment: 6 pages, revtex4, 1 eps-figure; improved version - the paragraph
containing Eqs.(18) and (19) is new, as well as the next paragraph; the Title
modified; some references added; version to appear in Phys. Rev.
Relating Physical Observables in QCD without Scale-Scheme Ambiguity
We discuss the St\"uckelberg-Peterman extended renormalization group
equations in perturbative QCD, which express the invariance of physical
observables under renormalization-scale and scheme-parameter transformations.
We introduce a universal coupling function that covers all possible choices of
scale and scheme. Any perturbative series in QCD is shown to be equivalent to a
particular point in this function. This function can be computed from a set of
first-order differential equations involving the extended beta functions. We
propose the use of these evolution equations instead of perturbative series for
numerical evaluation of physical observables. This formalism is free of
scale-scheme ambiguity and allows a reliable error analysis of higher-order
corrections. It also provides a precise definition for as the pole in the associated 't Hooft scheme. A concrete application to
is presented.Comment: Plain TEX, 4 figures (available upon request), 22 pages,
DOE/ER/40322-17
Pade-related resummations of the pressure of quark-gluon plasma by approximate inclusion of g**6-terms
We perform various resummations of the hot QCD pressure based on the actual
knowledge of the perturbation series which includes the g**6 ln(1/g) and part
of the g**6 terms. Resummations are performed separately for the short- and
long-distance parts. The g**6 term of the short-distance pressure is estimated
on the basis on the known UV cutoff dependence of the long-distance part. The
resummations are of the Pade and Borel-Pade type, using in addition the
(Pade-)resummed expression for the squared screening mass mE**2 and for the
EQCD coupling parameter gE**2. The resummed results depend weakly on the yet
unknown g**6 terms and on the the short-range renormalization scale, at all
temperatures. The dependence on the long-range renormalization scale is
appreciable at low temperatures T < 1 GeV. The resulting dependence of pressure
on temperature T is compatible with the results of the lattice calculations at
low T.Comment: 25 pages, 15 double figures, 4 single figures, revtex4; thoroughly
extended analysis; more figures; conclusions more clearly formulated; new
references added; title slightly changed; accepted for publication in
Phys.Rev.
Seismicity induced during the development of the Rittershoffen geothermal field, France
The development of the Rittershoffen deep geothermal field (Alsace, Upper Rhine Graben) between 2012 and 2014 induced unfelt seismicity with a local magnitude of less than 1.6. This seismicity occurred during two types of operations: (1) mud losses in the Muschelkalk formation during the drilling of both wells of the doublet and (2) thermal and hydraulic stimulations of the GRT-1 well. Seismicity was also observed 4 days after the main hydraulic stimulation, although no specific operation was performed. During chemical stimulation, however, no induced seismicity was detected. In the context of all field development operations and their injection parameters (flow rates, overpressures, volumes), we detail the occurrence or lack of seismicity, its magnitude distribution and its spatial distribution. The observations suggest the presence of the rock stress memory effect (Kaiser effect) of the geothermal reservoir as well as uncritically stressed zones connected to the GRT-1 well and/or rock cohesion. A reduction of the seismic rate concurrent with an increase of injectivity was noticed as well as the reactivation of a couple of faults, including the Rittershoffen fault, which was targeted by the wells. These results are derived from the homogeneous and consistent catalogue of more than 1300 local earthquakes that is provided. This reference catalogue is based on a standard detection method, whose output was manually verified and improved. The given absolute locations have been computed in a calibrated, geologically realistic 3D velocity model. Our work builds on previous analyses addressing the seismicity induced by the GRT-1 hydraulic stimulation and places the results into a historical context, thus considering the full dynamics of the observed phenomena. This paper also complements existing descriptions of the hydrothermal characteristics of the deep reservoir by providing insights separate from the wells
The Meson Production in Proton-Proton Collisions in Next-To-Leading Order and Infrared Renormalons
In this article, we investigate the next-to-leading order contribution of the
higher-twist Feynman diagrams to the large- inclusive pion production
cross section in proton-proton collisions and present the general formulae for
the higher-twist differential cross sections in the case of the running
coupling and frozen coupling approaches. We compared the resummed
next-to-leading order higher-twist cross sections with the ones obtained in the
framework of the frozen coupling approach and leading-twist cross section. The
structure of infrared renormalon singularities of the higher twist subprocess
cross section and it's resummed expression (the Borel sum) are found. It is
shown that the resummed result depends on the choice of the meson wave
functions used in the calculations. We discuss the phenomenological
consequences of possible higher-twist contributions to the meson production in
proton-proton collisions in next-to-leading order at RHIC.Comment: 33 pages, 15 figures, 4 table
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