179,630 research outputs found
Odderon with a running coupling constant
The running coupling is introduced into the equation for the odderon via the
bootstrap relation. It is shown that the previously found odderon state with a
maximal intercept, which is constructed from antisymmetric pomeron wave
function, continues to exist in the running coupling case. Its intercept is
found to remain equal to unity independent of the behaviour assumed for the
running coupling at low momenta.Comment: 9 pages, LaTe
On the inclusive gluon jet production from the triple pomeron vertex in the perturbative QCD
Single and double inclusive cross-sections for gluon jet production from
within the triple pomeron vertex are studied in the reggeized gluon technique.
It is shown that to satisfy the AGK rules the vertex has to be fully symmetric
in all four reggeized gluons which form the two final pomerons. The single
inclusive cross-sections are found for different cuttings of the triple pomeron
vertex. They sum into the expression obtained by Yu.Kovchegov and K.Tuchin in
the colour dipole picture. The found double inclusive cross-sections satisfy
the AGK rules.Comment: 17 pages in LaTex, 6 figures, revised version with partially changed
rsult
A control volume-based finite element method for plane micropolar elasticity
This paper describes the development of a numerical procedure for predicting deformations and stresses in a loaded two-dimensional membrane exhibiting micropolar or Cosserat constitutive behaviour. The procedure employs a conventional finite element (FE) mesh together with a dual mesh of interconnected control volumes, each of which must satisfy equilibrium. A series of patch tests covering a variety of simple strain states are used to validate the procedure that is then employed to predict the stress concentration in a membrane containing a small hole. The predictions provided by the procedure are compared with those given previously by FEs
Residual, restarting and Richardson iteration for the matrix exponential
A well-known problem in computing some matrix functions iteratively is a lack of a clear, commonly accepted residual notion. An important matrix function for which this is the case is the matrix exponential. Assume, the matrix exponential of a given matrix times a given vector has to be computed. We interpret the sought after vector as a value of a vector function satisfying the linear system of ordinary differential equations (ODE), whose coefficients form the given matrix. The residual is then defined with respect to the initial-value problem for this ODE system. The residual introduced in this way can be seen as a backward error. We show how the residual can efficiently be computed within several iterative methods for the matrix exponential. This completely resolves the question of reliable stopping criteria for these methods. Furthermore, we show that the residual concept can be used to construct new residual-based iterative methods. In particular, a variant of the Richardson method for the new residual appears to provide an efficient way to restart Krylov subspace methods for evaluating the matrix exponential.\u
Connexin43 hemichannels in satellite glial cells, can they influence sensory neuron activity?
Indexación: Scopus.In this review article, we summarize the current insight on the role of Connexin- and Pannexin-based channels as modulators of sensory neurons. The somas of sensory neurons are located in sensory ganglia (i.e., trigeminal and nodose ganglia). It is well known that within sensory ganglia, sensory neurons do not form neither electrical nor chemical synapses. One of the reasons for this is that each soma is surrounded by glial cells, known as satellite glial cells (SGCs). Recent evidence shows that connexin43 (Cx43) hemichannels and probably pannexons located at SGCs have an important role in paracrine communication between glial cells and sensory neurons. This communication may be exerted via the release of bioactive molecules from SGCs and their subsequent action on receptors located at the soma of sensory neurons. The glio-neuronal communication seems to be relevant for the establishment of chronic pain, hyperalgesia and pathologies associated with tissue inflammation. Based on the current literature, it is possible to propose that Cx43 hemichannels expressed in SGCs could be a novel pharmacological target for treating chronic pain, which need to be directly evaluated in future studies.https://www.frontiersin.org/articles/10.3389/fnmol.2017.00374/ful
The new and reinstated genera of agglutinated foraminifera published between 1986 and 1996
In the 10 years following the publication of "Foraminiferal Genera and their Classification"
by Loeblich & Tappan (1987), some 91 new genera of agglutinated foraminifera have been
proposed by various authors. Additionally, at least four of the genera listed by Loeblich &
Tappan as junior synonyms have been resurrected by subsequent authors. This
compilation is an attempt at bringing together the nomenclatorial changes to the
agglutinated foraminiferal genera that have appeared in the accessible literature
The utility of deep-water agglutinated Foraminiferal acmes for correlating Eocene to Oligocene abyssal sediments in the North Atlantic and Western Tethys
Quantitative analysis of Deep-water Agglutinated Foraminifera (DWAF) assemblages from key ODP sites in the North Atlantic reveal the presence of stratigraphically-significant abundance maxima, that may be useful for correlating sedimentary sequences deposited beneath the CCD. The DWAF record from ODP Hole 647A in the Labrador Sea was re-studied and abundances were recalculated by excluding calcareous benthic foraminifera. This hole is a key locality, as it provides direct calibration of the DWAF biostratigraphy to the standard chronostratigraphy. Eight DWAF acmes are recognised in the Eocene to lower Oligocene at Site 647 and at other North Atlantic and Norwegian Sea sites. These are: The Paleocene-Eocene Thermal Maximum (PETM) Glomospira Acme, a lower Eocene N. excelsa acme, an early/middle Eocene Glomospira Acme, a Karrerulina acme, a middle Eocene Reticulophragmium amplectens acme, a middle/late Eocene Spiroplecta- mmina acme, a latest Eocene-early Oligocene Ammodiscus latus acme, and an early Oligocene Spirosigmoilinella acme. Some of these acmes can be correlated with similar events occurring at onshore localities in the Western Tethys (northern Spain, Moroccan Rif, Italian Appenines, Western Carpathians). The occurrence of these DWAF acmes is caused by variations in the trophic continuum which is a consequence of the profound climatic and oceanographic changes that took place in the deep ocean during the Eocene and early Oligocene
A block Krylov subspace time-exact solution method for linear ODE systems
We propose a time-exact Krylov-subspace-based method for solving linear ODE (ordinary differential equation) systems of the form and , where is the unknown function. The method consists of two stages. The first stage is an accurate piecewise polynomial approximation of the source term , constructed with the help of the truncated SVD (singular value decomposition). The second stage is a special residual-based block Krylov subspace method. The accuracy of the method is only restricted by the accuracy of the piecewise polynomial approximation and by the error of the block Krylov process. Since both errors can, in principle, be made arbitrarily small, this yields, at some costs, a time-exact method. Numerical experiments are presented to demonstrate efficiency of the new method, as compared to an exponential time integrator with Krylov subspace matrix function evaluations
On Ad-hoc Upwind Implicit Difference Schemes for Parabolic P.D.E. of the Convection-Diffusion Type
Agglutinated foraminifera from neritic to bathyal facies in the Palaeogene of Spitsbergen and the Barents Sea
Late Palaeocene to Early Eocene foraminiferal assemblages have been analysed from an
exploratory well (7119/7-1) drilled in the Tromsø Basin (southwestern Barents Sea) and from
two onshore sections, Basilikaelva and Kovalskifjella, exposed in the Central Tertiary Basin of
Spitsbergen. The assemblages reveal marked differences in taxonomic composition and
diversity, reflecting inner neritic to middle bathyal conditions. Within this depth range, four
foraminiferal biofacies (FB) are distinguished:
FB 1 occurs in the Kolthoffberget Member (of the Firkanten Formation, Late Palaeocene)
sampled in the Basilikaelva section. The member consists of interbedded shales, siltstones
and sandstones deposited in a transitional delta front - prodelta environment, according to
current sedimentological interpretation. The foraminiferal assemblages are entirely
agglutinated, show extremely low species diversities and strong dominance of
Reticulophragmium arcticum followed by Labrospira aff. turbida.
FB 2 is recognised in the Basilika Formation (Late Palaeocene) exposed in the
Kovalskifjella section. The formation consists of silty claystones deposited in a prodelta shelf
setting. The foraminiferal assemblages show an increased species diversity, and consist
mainly of agglutinated taxa with a strongly subordinate calcareous component. The two
most abundant species are R. arcticum and L. aff. turbida. Species of Verneuilinoides and
Trochammina occur in significant numbers while tubular taxa are rare.
FB 3 is found in the Lower Eocene clay interval composing the upper part of the Torsk
Formation in well 7119/7-1. It contains entirely agglutinated assemblages with
comparatively high diversities. The dominant species are Recurvoides aff. turbinatus and
Budashevaella multicamerata, while Reticulophragmium amplectens is typical and common in
these strata. Tubular forms referred to Rhizammina occur locally in significant quantities. The
diversity and composition of the assemblages suggest an outer neritic to upper bathyal
environment.
FB 4 is developed in Palaeocene claystones comprising the lower part of the Torsk
Formation in well 7119/7-1. In this interval the species diversity, as well as the frequency of
tubular forms (referred to Rhizammina, Bathysiphon and Hyperammina) attains maximum
values. Other common to dominant taxa include Spiroplectammina spectabilis,
Haplophragmoides walteri, Ammosphaeroidina pseudopauciloculata, and Recurvoides sp. These
wholly agglutinated assemblages are interpreted as reflecting upper to middle bathyal
conditions
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