bluuebunny/crossref_metadata_2025 huggingface dataset:
Focusing blow-up for quasilinear parabolic equations
Authors: Budd C. J. , Galaktionov V. A. , Chen Jianping
Published: November 2011

We study the behaviour of the non-negative blowing up solutions to the quasilinear parabolic equation with a typical reaction–diffusion right-hand side and with a singularity in the space variable which takes the form

where m ≧ 1,p> 1 are arbitrary constants, in the critical exponent caseq= (p–1)/m> 0. We impose zero Dirichlet boundary conditions at the singular pointx= 0 and atx= 1, and take large initial data. For a class of ‘concave’ initial functions, we prove focusing at the origin of the solutions astapproaches the blow-up timeTin the sense thatx= 0 belongs to the blow-up set. The proof is based on an application of the intersection comparison method with an explicit ‘separable’ solution which has the same blow-up time asu. The method has a natural generalisation to the case of more general nonlinearities in the equation. A description of different fine structures of blow-up patterns in the semilinear casem= 1 and in the quasilinear onem> 1 is also presented. A numerical study of the semilinear equation is also made using an adaptive collocation method. This is shown to give very close agreement with the fine structure predicted and allows us to make some conjectures about the general behaviour.
On the l1-algebra of certain monoids
Authors: Crabb M. J. , Munn W. D.
Published: November 2011

The monoids considered are the free monoid Mx and the free monoid-with-involution MIx on a nonempty set X. In each case, relative to a simply-defined involution, an explicit construction is given for a separating family of continuous star matrix representations of the l1-algebra of the monoid and it is shown that this algebra admits a faithful trace. The results are based on earlier work by M. J. Crabb et al. concerning the complex semigroup algebras of Mx and MIx.
On the regularity of stochastic difference equations in hyperfinite-dimensional vector spaces and applications to -valued stochastic differential equations
Authors: Wu Jiang-Lun
Published: November 2011

Nonstandard analysis is used, in this paper, to give a construction of a Wiener -process Wt, t ∈ [0, ∞). From this, a hyperfinite representation of stochastic integrals for operatorvalued processes with respect to Wt is derived, and existence theorems in the spirit of Keisler are proved for (infinite-dimensional) stochastic differential equations of Itô's type one and a certain kind of Itô's type two, via regularity of hyperfinite stochastic difference equations.
Multiple solutions for nonhomogeneous elliptic equations involving critical Sobolev exponent
Authors: Cao Dao-Min , Li Gong-Bao , Zhou Huan-Song
Published: November 2011

We consider the following problem:

where is continuous on RN and h(x)≢0. By using Ekeland's variational principle and the Mountain Pass Theorem without (PS) conditions, through a careful inspection of the energy balance for the approximated solutions, we show that the probelm (*) has at least two solutions for some λ* > 0 and λ ∈ (0, λ*). In particular, if p = 2, in a different way we prove that problem (*) with λ ≡ 1 and h(x) ≧ 0 has at least two positive solutions as
Decay rates of the solutions of nonlinear dispersive equations
Authors: Bisognin Vanilde , Menzala Gustavo Perla
Published: November 2011

We consider a family of dispersive equations whose simplest representative would be a Benjamin–Bona–Mahony equation with a Burger's type dissipation. The effect of possible unevenness of the bottom surface is considered and our main result gives decay rates of the solutions in Lβ(ℝ) spaces, 2 ≦ β ≦ + ∞.
Approximation of attractors for nongradient systems
Authors: Kostin I. N.
Published: November 2011

The problem of approximation of attractors for semidynamical systems (SDSs) in a metric space is studied. Let some (exact) SDS possessing an attractor M be inaccurately defined, i.e. let another (approximate) SDS, which is close in some sense to the exact one, be given. The problem is to construct a set , which is close to M in the Hausdorff metric.

The suggested procedure for constructing is finite, which makes it possible to use it in computations. The results obtained are suitable for numerical approximation of attractors for a rather large class of semidynamical systems, including ones generated by the Lorenz equations and the Navier–Stokes equations.
Weighted Poincaré inequalities and Minkowski content
Authors: Edmunds D. E. , Hurri-Syrjänen R.
Published: November 2011

Weighted Poincaré inequalities are established in any bounded domain D in ℝn (n ≧ 2), and their connection with the Minkowski content of ∂D is explored.
Sturmian comparison theorem for half-linear second-order differential equations
Authors: Li Horng Jaan , Yeh Cheh Chih
Published: November 2011

Let φ:ℝ→ℝ be defined by φ(s) = |s|p−2s, with p > 1 a fixed number. We extend Sturm Comparison Theorem of the linear differential equation

to the nonlinear differential equation

by using the Wirtinger inequality. A Lyapunov inequality and some oscillation criteria of (E) are also given.
Linear spaces of real matrices of large rank
Authors: Rees Elmer G.
Published: November 2011

For every k1 0 < k < m ≧ n, there are linear spaces of real n × m matrices which have dimension (m − k)(n − k) and every nonzero element has rank greater than k. Examples of such spaces are constructed and conditions are given under which they have the largest possible dimension.
Exponential length and traces
Authors: Phillips N.Christopher
Published: November 2011

We define a quantity called the reduced C* exponential rank rcel (A) of a C*-algebra A, which satisfies rcel (A) ≦ cel (A). We show that rcel (A) = ∞ whenever A has two distinct normalised traces which agree on K0(A), and we prove a partial converse. This gives some understanding of why cel (A) = π cer (A) for some C*-algebras A but not for others. We also characterise rcel (A) as the supremum of the rectifiable distances from unitaries in the identity component of the unitary group to the commutator subgroup of this component.
Weak solutions to a hydrodynamic model for semiconductors: the Cauchy problem
Authors: Marcati Pierangelo , Natalini Roberto
Published: November 2011

We investigate the Cauchy problem for a hydrodynamic model for semiconductors. An existence theorem of global weak solutions with large initial data is obtained by using the fractional step Lax—Friedrichs scheme and Godounov scheme.
Weighted inequalities for the Stieltjes transform and the maximal spherical partial sum operator on radial functions
Authors: Andersen Kenneth F.
Published: November 2011

If TRf(x) is the spherical partial sum of the Fourier transform of f and T*f(x) = SUPR > 0 | TRf(x)|, sufficient conditions are given on the non-negative weight function ω(x) which ensure that T* restricted to radial functionsis bounded on the Lorentz space Lp,s(Rn,ω) into Lp,q(Rn, ω) For power weights, these conditions are also necessary. The weight pairs (u,v) for which the generalised Stieltjes transform Sλ is bounded from LP,S(R+, v)into Lp,q(R+, u)are also characterised. These are an essential ingredient for the study of T*.
Semilinear elliptic problems with singular potentials in ℝN
Authors: Badiale Marino , Tchou Nicoletta A.
Published: November 2011

Synopsis

We study a semilinear elliptic problem on ℝN where a potential is not a bounded function but can also be an infinite measure. We analyse the lack of compactness of the problem, obtaining a structure theorem for Palais-Smale sequences. This result allows us to obtain different kinds of existence theorems by a variational approach.
A reduction principle for topological classification of nonautonomous differential equations
Authors: Minh Nguyen Van
Published: November 2011

Synopsis

The paper is concerned with equations of the form x' = A(t)x +f(t, x), where A is a continuous matrix function defined on ℝ, f is a continuous vector-valued function of (t, x) with f(t, 0) = 0. It is proved that if x' = A(t)x has an exponential trichotomy, A is bounded and f satisfies the Lipschitz condition with coefficient sufficiently small, then these equations are topologically equivalent to the systems of equations of the form , where B, g satisfy the same conditions as A, f.
Hyperasymptotics and the Stokes' phenomenon
Authors: Daalhuis A. B. Olde
Published: November 2011

Synopsis

Hyperasymptotic expansions were recently introduced by Berry and Howls, and yield refined information by expanding remainders in asymptotic expansions. In a recent paper of Olde Daalhuis, a method was given for obtaining hyperasymptotic expansions of integrals that represent the confluent hypergeometric U-function. This paper gives an extension of that method to neighbourhoods of the so-called Stokes lines. At each level, the remainder is exponentially small compared with the previous remainders. Two numerical illustrations confirm these exponential improvements.
Solutions in Lebesgue spaces of the Navier-Stokes equations with dynamic boundary conditions
Authors: Dalsen Marié Grobbelaar-Van , Sauer Niko
Published: November 2011

Synopsis

This paper, although self-contained, is a continuation of the work done in [8], where the motion of a viscous, incompressible fluid is considered in conjunction with the rotation of a rigid body which is immersed in the fluid. The resulting mathematical model is a Navier-Stokes problem with dynamic boundary conditions. In [8] a uniqueL2,3solution is constructed under certain regularity assumptions on the initial states. In this paper we consider the Navier-Stokes problem with dynamic boundary conditions in the Lebesgue spacesLr,3(3<r<∞) and prove the existence of a unique solution, local in time, without imposing any regularity conditions on the initial states.
On inhomogeneous biharmonic equations involving critical exponents
Authors: Deng Yinbin , Wang Gengsheng
Published: November 2011

In this paper, we consider the existence of multiple solutions of biharmonic equations boundary value problem

where Ω is a bounded smooth domain in ℝN, N ≥ 5; λ ∈ ℝ1 is a given constant; p = 2N/(N − 4) is the critical Sobolev exponent for the embedding ; Δ2 = ΔΔ denotes iterated N-dimensional Laplacian; f(x) is a given function. Some results on the existence and non-existence of multiple solutions for the above problem have been obtained by Ekeland's variational principle and the mountain-pass lemma under some assumptions on f(x) and N.
Semilinear elliptic equations with near critical growth rates
Authors: Budd C.
Published: November 2011

Synopsis

We discuss the symmetric solutions of the semilinear elliptic equation Δu + λ(u+ u|u|p−1) = 0, u|∂B = 0 (*), where B is the unit ball in ℝ3. The value of p is taken close to 5, the critical Sobolev exponent for ℝ3. An asymptotic description of the solutions of (*) with large norm is obtained. This predicts a fold bifurcation if p > 5 and the structure of this bifurcation is studied in the limit p – 5→ 0. We find good agreement between the asymptotic description and some numerical calculations. These results are illuminated by recasting the problem (*) in the form of a dynamical system by means of a suitable change of variables. When |p – 5|≪1 and ∥u ≫1, the transformed solutions of (*) are also solutions of a perturbed Hamiltonian system and we study the behaviour of these solutions by using Melnikov methods.
Extremals in Landau's inequality for the difference operator
Authors: Kwong Man Kam , Zettl A.
Published: November 2011

Synopsis

The best constants in Landau's inequality for the difference operator in the classical sequence spaces lp are known explicitly only for p = 1, 2, ∞. This is true in both the infinite N = (0, 1, 2, …) and biinfinite Z= (… − 1, 0, 1, …) cases. It is known that there are no extremals when p = 2 in both the infinite and biinfinite cases. Also, it is known that there are extremals when p = ∞ in the biinfinite case. Here we prove that there are no extremals in the other three cases where the best constants are known explicitly. The proofs for these three cases are quite different from each other.
Adjoints and self-adjointness for a differential operator with a varying structure
Authors: Das P. C. , Prasad Uma Shanker
Published: November 2011

Synopsis

In this paper the adjoint operator is derived for a multi-point differential operator with a varying structure in a suitably chosen Hilbert space. The formal differential operator is given by different differential expressions in the adjoining intervals. This form of adjoint operator is used to characterize self-adjointness.
Semiprimitivity of inverse semigroup algebras
Authors: Munn W. D.
Published: November 2011

Synopsis

Let S be an inverse semigroup and F a field. It is shown that if F has characteristic 0 and is not algebraic over its prime subfield then the algebra of S over F is semiprimitive (i.e. Jacobson semisimple). This generalises a well-known theorem on group algebras due to Amitsur. Similar results for the case in which F has prime characteristic are obtained under the additional hypotheses that S is completely semisimple or that S is E-unitary with a totally ordered semilattice.
On bounds for Titchmarsh–Weyl m-coefficients and for spectral functions for second-order differential operators
Authors: Atkinson F. V.
Published: November 2011

Synopsis

Order-of-magnitude results are extended to the case of general second-order term, with coefficient not necessarily of fixed sign, with general positive weight-function. The bounds are used to establish the expression for the Titchmarsh–Weyl function m(λ) as a Nevanlinna function in terms of the spectral function.
A general version of the Hardy–Littlewood–Polya–Everitt (HELP) inequality
Authors: Bennewitz Christer
Published: November 2011

Synopsis

The inequality (0·1) below is naturally associated with the equation −(pu′)′ + qu = λu. By assuming that one end-point of the interval (a, b) is regular and the other limit-point for this equation, Everitt characterized the best constant K in tems of spectral properties of the equation. This paper sketches a theory for more general inequalities (0·2), (0·3) similarly related to the equation Su = λTu. Here S and T are ordinary, symmetric differential expressions. A characterization of the best constants in (0·2), (0·3) is given which generalises that of Everitt.

For the case when S is of order 1 and T is multiplication by a positive function, all possible inequalities are given together with the best constants and cases of equality. Furthermore, an example is given of a valid inequality (0·1) on an interval with both end-points regular for the corresponding differential equation. This contradicts a conjecture by Everitt and Evans. Finally, the general theory for the left-definite inequality (0·3) is specialised to the case when S is a Sturm-Liouville expression. A family of examples is given for which the best constants can be explicitly calculated.
Spiral motion for components of a Dirac system of limit circle type
Authors: Halvorsen S. G. , Shaw J. K.
Published: November 2011

Synopsis

The components of a two (complex) dimensional Dirac system are studied as trajectories in the complex plane. The system, defined on an interval [a, b) of regular points, is assumed to be of limit circle type at t = b, and to be non-oscillatory there. By introducing moduli ρ1(t) = |y1(t)|, ρ2(t) = |y2(t)| and continuous complex arguments θ1(t) = arg y1(t), θ2(t) = arg y2(t) for the components, the principal result proved is that θ1(t) and θ2(t) are bounded as t → b. Examples show that monotonicity of the argument function θ1(t), which is a feature of the corresponding problem for Sturm–Liouville equations, fails for Dirac systems.
On the Spectrum of a one-dimensional Schrödinger operator whose potential is a limit of finite-zone potentials
Authors: Levitan B. M.
Published: November 2011

Synopsis

Denote by (αj, βj), j = 1, 2, … an infinite set of disjoint open intervals on the half-line (0, ∞). Suppose that the following conditions are fulfilled:

With the aid of the first two trace formula presented earlier by the author, we prove in this paper that there exists a function q, defined on the whole real line, such that for the Schrödinger equation −y″ + q(x)y = λy (−∞<x<∞), the intervals (αj, βj) are spectrum lacunae. As an example, we consider the case when the intervals (αj, βj) are adjacent intervals of the Cantor trinary perfect set.
Deficiency indices of an odd-order differential operator
Authors: Paris R. B. , Wood A. D.
Published: November 2011

Synopsis

We obtain asymptotic solutions of odd-order formally self-adjoint differential equations with power coefficients and discuss possible values for the deficiency indices of the associated operators.
On the essential self-adjointness of powers of Schrödinger operators
Authors: Read Thomas T.
Published: November 2011

Synopsis

Sufficient conditions are given for the minimal operator T0 generated by the elliptic differential expression τ = ρ−1 (−Σ DjajkDk + q) to be essentially self-adjoint in the weighted Hilbert space , and for all powers of T0 to be essentially self-adjoint.
A note on primeness of semigroup rings
Authors: Silva Pedro V.
Published: November 2011

Synopsis

This note discusses primeness for semigroup rings of semigroups satisfying a certain condition, weaker than the u.p. property. These semigroups include free products of semigroups, semigroups presented by a single relator and at least three generators, and free inverse semigroups of infinite rank.
The compact weak topology on a Banach space
Authors: González Manuel , Gutiérrez Joaquín M.
Published: November 2011

Synopsis

The compact weak topology (kw) on a Banach space is defined as the finest topology that agrees with the weak topology on weakly compact subsets. It appears in a natural manner in the study of certain classes of continuous and holomorphic maps between Banach spaces. In this paper we treat the kw topology and the finest locally convex topology contained in kw, which we call the ckw topology. We prove that kw = ckw if and only if the space is reflexive or Schur, and we derive characterisations of Banach spaces not containing l1, and of other classes of Banach spaces, in terms of these topologies. We also show that ckw is the topology of uniform convergence on (L)-subsets of the dual space. As a consequence, Banach spaces with the reciprocal Dunford–Pettis property are characterised.
Hankel operators with PC symbols and the space H∞ + PC
Authors: Bonsall F. F. , Gillespie T. A.
Published: November 2011

Synopsis

We obtain an explicit formula for the essential norm of a Hankel operator with its symbol in the space PC, which is the closure in L∞ of the space of piecewise continuous functions on the unit circle . It follows from this formula that functions in PC can be approximated as closely by functions in C, the continuous functions on the circle, as by functions in the much larger space H∞ + C. This is an example of the way in which properties of the Hardy spaces can be derived from properties of Hankel operators.
Semi-discrete Galerkin approximation method applied to initial boundary value problems for Maxwell's equations in anisotropic, inhomogeneous media
Authors: Neittaanmäki Pekka , Saranen Jukka
Published: November 2011

Synopsis

In this paper the semi-discrete Galerkin approximation of initial boundary value problems for Maxwell's equations is analysed. For the electric field a hyperbolic system of equations is first derived. The standard Galerkin method is applied to this system and a priori error estimates are established for the approximation.
Spectral properties of two-parameter eigenvalue problems
Authors: Binding Paul , Browne Patrick J.
Published: November 2011

Synopsis

We study the self-adjoint eigenvalue problem W(λ)x = 0, (*), in Hilbert space for one equation in two parameters. Here

is bounded below with compact resolvent for each λ = (λ1, λ2). We give necessary and sufficient conditions for the existence of λ so that (*) holds with W(λ)= ≧0 and we investigate the geometry of the set Z0 of such λ. We also discuss higher order solution sets Zi where the ith eigenvalue of W(λ) vanishes, deriving various asymptotic results in a unified fashion.
Direct products of finite monogenic inverse semigroups
Authors: Trueman D. C.
Published: November 2011

Synopsis

We characterize direct products of finite monogenic inverse semigroups; we show that a finite monogenic inverse semigroup which is not a group is directly indecomposable and that a finite semigroup which is decomposable into a direct product of monogenic inverse semigroups which are not groups is uniquely so decomposable. We determine when a finite semigroup can be decomposed into a direct product of non-group monogenic inverse semigroups and show how the direct factors, if they exist, can be found.
TheM-ideal structure of some algebras of bounded linear operators
Authors: Kalton Nigel J. , Werner Dirk
Published: November 2011

Let 1 <p, q< ∞. It is shown for complex scalars that there are no nontrivialM-ideals in ℒ(Lp[0, 1]) ifp≠ 2, andis the only nontrivialM-ideal in.
Optimal control of quasilinear parabolic equations
Authors: Casas Eduardo , Fernández Luis A. , Yong Jiongmin
Published: November 2011

This paper deals with optimal control problems governed by quasilinear parabolic equations in divergence form, whose cost functional is of Lagrangian type. Our aim is to prove the existence of solutions and derive some optimality conditions. To attain this second objective, we accomplish the sensitivity analysis of the state equation with respect to the control, proving that, under some assumptions, this relation is Gâteaux differentiable. Finally, a regularising procedure along with Ekeland's variational principle allow us to treat some other problems for which this differentiability property cannot be stated.
On the unitarity of the wave operators for AC-Stark Hamiltonians
Authors: Huang Min-Jei
Published: November 2011

We study a class of AC-Stark HamiltoniansH1(t) =H0(t) +V, whereH0(t)= −Δ +E·xcos ωt.For a class of repulsive potentials, we show that the wave operators exist and are unitary, provided that |E|/ω2is small. If |E|/ω2is sufficiently large, the result remains true as long asVis sufficiently small.
Novel Techniques for Microspectroscopy and Chemical Imaging Analysis of Soybean Seeds and Embryos
Authors: Baianu I. , You Tiefeng , Costescu Doina
Published: November 2011

Novel methodologies are currently being evaluated for the Chemical Analysis of soybean seeds as well as developing mature soybean embryos by FT-IR/NIR Microspectroscopy. This is the first report of FT-NIR Chemical Images obtained with 1 micron resolution. NIR spectra of Proteins, Oil and DNA fibers are obtained for regions as small as 1μ^2^.
Anti‐tumour activity of 4‐(4‐fluorophenyl)amino‐5,6,7‐trimethoxyquinazoline against tumour cells in vitro
Authors: Huang Yinjiu , Liu Fang , Zhao Li , Wu Huazhang , Liu Hui
Published: November 2011

In order to create novel, potent and selective anti‐cancer agents, the action of 4‐(4‐fluorophenyl)amino‐5,6,7‐trimethoxyquinazoline (compound 1018) on 10 different kinds of tumour cells were assayed by MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide]. It possesses a broad spectrum of anti‐cancer activity. The mechanism of action of 4‐(4‐fluorophenyl)amino‐5,6,7‐trimethoxyquinazoline (hereafter referred to as compound 1018) against tumour cells was studied in androgen‐independent prostate cancer PC‐3 cells by microscopic observation, LDH (lactate dehydrogenase) release assay and Western blotting. Its activity was dose‐dependent, with an IC50 of 13.0±1.4 μM after 72 h treatment. Microscopy and LDH release assay indicated that the effect was through anti‐proliferation rather than cytotoxicity. Western blot analysis also showed that treatment of cells with 50 μM compound 1018 for 30 min almost completely inhibited EGF (epidermal growth factor)‐induced phosphorylation of ERK1/2 (extracellular‐signal‐regulated kinase 1/2), which suggests that its anti‐proliferative effect is largely associated due to ERK1/2 activation being inhibited. Thus compound 1018 is a potential anti‐cancer agent.
Astrocyte pVHL and HIF-α isoforms are required for embryonic-to-adult vascular transition in the eye
Authors: Kurihara Toshihide , Westenskow Peter D. , Krohne Tim U. , Aguilar Edith , Johnson Randall S. , Friedlander Martin
Published: November 2011

Successful transition from embryonic to adult circulation is critical for survival of mammalian organisms. This shift occurs in the central cardiovascular circulation and in the eye as oxygen tension increases. However, its regulation is not well understood. We have used combinatorial gene deletion and overexpression assays to assess the effect of astrocyte-targeted deletion of von Hippel–Lindau tumor suppressor (Vhl), hypoxia-inducible factor-αs (Hif-αs), and Vegf on the normal regression of the hyaloidal vessels, the fetal ocular circulation system. Astrocytic Vhl deletion induced accelerated hyaloidal regression and subsequent massive secondary outgrowth. Combinatorial gene deletion involving Vhl, Hif-αs, and Vegf genes revealed that HIF-2α/vascular endothelial growth factor signaling induces secondary outgrowth in Vhl mutants. Conversely, HIF-1α regulated macrophage migration inhibitory factor and promoted macrophage infiltration that accelerates hyaloidal vessel regression. The phenotype observed in Vhl mutants strongly resembles human persistent hyperplastic primary vitreous cases and may provide insights into vascular remodeling mechanisms in other systems.
Constraints on gravity on cosmic scales with upcoming large-scale structure surveys
Authors: Bean Rachel
Published: November 2011

We consider how upcoming, prospective large-scale structure surveys, measuring galaxy weak lensing and position in tandem with the cosmic microwave background temperature anisotropies, constrain cosmic scale modifications to general relativity. In such theories, both the homogeneous expansion history and the growth of large-scale structure can have signatures of the modification. We consider an equation of state figure of merit parameter, and introduce an analogous figure of merit parameter for modified gravity, to quantify the relative constraints. We discuss how assumptions about the presence of astrophysical and instrumental systematics such as galaxy bias, intrinsic alignments, weak lensing shear calibration uncertainties and photometric redshift offsets can impact the prospective dark energy constraints.
Model-independent tests of cosmic gravity
Authors: Linder Eric V.
Published: November 2011

Gravitation governs the expansion and fate of the universe, and the growth of large-scale structure within it, but has not been tested in detail on these cosmic scales. The observed acceleration of the expansion may provide signs of gravitational laws beyond general relativity (GR). Since the form of any such extension is not clear, from either theory or data, we adopt a model-independent approach to parametrizing deviations to the Einstein framework. We explore the phase space dynamics of two key post-GR functions and derive a classification scheme, and an absolute criterion on accuracy necessary for distinguishing classes of gravity models. Future surveys will be able to constrain the post-GR functions' amplitudes and forms to the required precision, and hence reveal new aspects of gravitation.
Structural insights into anaphase-promoting complex function and mechanism
Authors: Barford David
Published: November 2011

The anaphase-promoting complex or cyclosome (APC/C) controls sister chromatid segregation and the exit from mitosis by catalysing the ubiquitylation of cyclins and other cell cycle regulatory proteins. This unusually large E3 RING-cullin ubiquitin ligase is assembled from 13 different proteins. Selection of APC/C targets is controlled through recognition of short destruction motifs, predominantly the D box and KEN box. APC/C-mediated coordination of cell cycle progression is achieved through the temporal regulation of APC/C activity and substrate specificity, exerted through a combination of co-activator subunits, reversible phosphorylation and inhibitory proteins and complexes. Recent structural and biochemical studies of the APC/C are beginning to reveal an understanding of the roles of individual APC/C subunits and co-activators and how they mutually interact to mediate APC/C functions. This review focuses on the findings showing how information on the structural organization of the APC/C provides insights into the role of co-activators and core APC/C subunits in mediating substrate recognition. Mechanisms of regulating and modulating substrate recognition are discussed in the context of controlling the binding of the co-activator to the APC/C, and the accessibility and conformation of the co-activator when bound to the APC/C.
Translational regulation of the cell cycle: when, where, how and why?
Authors: Kronja Iva , Orr-Weaver Terry L.
Published: November 2011

Translational regulation contributes to the control of archetypal and specialized cell cycles, such as the meiotic and early embryonic cycles. Late meiosis and early embryogenesis unfold in the absence of transcription, so they particularly rely on translational repression and activation of stored maternal mRNAs. Here, we present examples of cell cycle regulators that are translationally controlled during different cell cycle and developmental transitions in model organisms ranging from yeast to mouse. Our focus also is on the RNA-binding proteins that affect cell cycle progression by recognizing special features in untranslated regions of mRNAs. Recent research highlights the significance of the cytoplasmic polyadenylation element-binding protein (CPEB). CPEB determines polyadenylation status, and consequently translational efficiency, of its target mRNAs in both transcriptionally active somatic cells as well as in transcriptionally silent matureXenopusoocytes and early embryos. We discuss the role of CPEB in mediating the translational timing and in some cases spindle-localized translation of critical regulators ofXenopusoogenesis and early embryogenesis. We conclude by outlining potential directions and approaches that may provide further insights into the translational control of the cell cycle.
Switches and latches: a biochemical tug-of-war between the kinases and phosphatases that control mitosis
Authors: Domingo-Sananes Maria Rosa , Kapuy Orsolya , Hunt Tim , Novak Bela
Published: November 2011

Activation of the cyclin-dependent kinase (Cdk1) cyclin B (CycB) complex (Cdk1:CycB) in mitosis brings about a remarkable extent of protein phosphorylation. Cdk1:CycB activation is switch-like, controlled by two auto-amplification loops—Cdk1:CycB activates its activating phosphatase, Cdc25, and inhibits its inhibiting kinase, Wee1. Recent experimental evidence suggests that parallel to Cdk1:CycB activation during mitosis, there is inhibition of its counteracting phosphatase activity. We argue that the downregulation of the phosphatase is not just a simple latch that suppresses futile cycles of phosphorylation/dephosphorylation during mitosis. Instead, we propose that phosphatase regulation creates coherent feed-forward loops and adds extra amplification loops to the Cdk1:CycB regulatory network, thus forming an integral part of the mitotic switch. These network motifs further strengthen the bistable characteristic of the mitotic switch, which is based on the antagonistic interaction of two groups of proteins: M-phase promoting factors (Cdk1:CycB, Cdc25, Greatwall and Endosulfine/Arpp19) and interphase promoting factors (Wee1, PP2A–B55 and a Greatwall counteracting phosphatase, probably PP1). The bistable character of the switch implies the existence of a CycB threshold for entry into mitosis. The end of G2 phase is determined by the point where CycB level crosses the CycB threshold for Cdk1 activation.
Development of a New Curriculum in a Positive Youth Development Program: The Project P.A.T.H.S. in Hong Kong
Authors: Shek Daniel T. L. , Ma Hing Keung , Sun Rachel C. F.
Published: November 2011

The design of a new curriculum in a positive youth development program (Project P.A.T.H.S.) in Hong Kong is outlined. The Tier 1 Program of the original phase of the Project P.A.T.H.S. is a universal positive youth development program for students in Secondary 1 to Secondary 3 with the curricula developed by a research team comprising scholars in different disciplines (e.g., social work, psychology, and education). The 120 teaching units are designed with reference to 15 positive youth development constructs identified in the successful positive youth development programs. In the extension phase of the project, a new curriculum with 60 teaching units is developed in accordance with these 15 constructs with specific reference to five major adolescent developmental issues. These issues include substance abuse, sexuality issue, Internet addiction, bullying, and money and success issues. The principles underlying the program development and implementation strategies are outlined.
Effects of hydrocortisone on acute β‐adrenoceptor blocker and histamine induced bronchoconstriction
Authors: Short Philip M. , Williamson Peter A. , Lipworth Brian J.
Published: November 2011

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• β‐adrenoceptor blockers are avoided in asthma due to concerns of the potential for β‐adrenoceptor blocker induced bronchoconstriction with the greatest risk after first dose.

WHAT THIS STUDY ADDS

• Nebulized salbutamol and ipratropium produced a full recovery of lung function in the presence of acute β‐adrenoceptor blocker and histamine induced bronchoconstriction. Salbutamol reversibility was not potentiated by intravenous hydrocortisone.

AIMS

β‐adrenoceptor blockers are avoided in asthma due to concerns of bronchoconstriction. We investigated the safety of acute exposure to propranolol in asthmatics, sequentially challenged with histamine to mimic an asthma exacerbation and evaluated the role of intravenous hydrocortisone in potentiating salbutamol reversibility.

METHODS

Persistent atopic asthmatics, requiring ≤1000 µg day−1 budesonide, performed a randomized double‐blind placebo‐controlled crossover study. Following 10 mg or 20 mg of oral propranolol, patients received 400 mg intravenous hydrocortisone or placebo, followed by histamine challenge with nebulized salbutamol 5 mg and ipratropium 500 µg recovery.

RESULTS

Thirteen patients completed per protocol. Hydrocortisone did not potentiate salbutamol recovery post propranolol and histamine challenge vs. placebo (mean difference in FEV1 0.04 ml, 95% CI −0.07, 0.15, P= 0.417). β‐adrenoceptor blocker induced bronchoconstriction was demonstrated by spirometry and impulse oscillometry. For the placebo visit, FEV1 fell 4.7% 2 hours post propranolol (95% CI 1.8, 7.5, P= 0.008) whilst total airway resistance (R5%) increased 31.3% (95% CI 15.6, 47.0, P= 0.04). On both visits FEV1% and R5% returned to baseline after salbutamol post histamine.

CONCLUSION

Nebulized salbutamol and ipratropium produced a full recovery after propranolol and histamine induced bronchoconstriction, independent of hydrocortisone use. Since the greatest risk of β‐adrenoceptor blockade is after first dose, our findings offer reassurance to those undertaking further evaluation of chronic β‐adrenoceptor blockade as a potential treatment for mild‐to‐moderate asthma.
Investigation of six selected bacterial species in endo‐periodontal lesions
Authors: Didilescu A. C. , Rusu D. , Anghel A. , Nica L. , Iliescu A. , Greabu M. , Bancescu G. , Stratul S. I.
Published: November 2011

Didilescu AC, Rusu D, Anghel A, Nica L, Iliescu A, Greabu M, Bancescu G, Stratul SI. Investigation of six selected bacterial species in endo‐periodontal lesions. International Endodontic Journal, 45, 282–293, 2012.

Aim  To investigate and determine possible associations of six tested bacteria belonging to ‘orange’ and ‘green’ complexes, in endo‐periodontal lesions: Parvimonas micra, Fusobacterium nucleatum, Campylobacter rectus, Eubacterium nodatum, Eikenella corrodens and Capnocytophaga sputigena.

Methodology  Forty‐six patients presenting with different types of endo‐periodontal lesions were investigated. Clinical examinations, periapical radiographs and microbiological sampling from the canal system (endo) and periodontal pockets (perio) were performed. Qualitative and semiquantitative evaluation of bacteria was performed by polymerase chain reaction (PCR) and DNA–DNA hybridization (micro‐IDent plus; Hain Lifescience, Germany).

Results  Extremely high bacterial loads in endodontic samples were recorded for P. micra, F. nucleatum and C. sputigena, while periodontal samples were often colonized by the same species, plus C. rectus. Significant association was recorded between F. nucleatum‐endo and P. micra‐endo (P = 0.03, Fisher’s exact test). There was marginal evidence of associations between: (i) C. sputigena‐endo and C. sputigena‐perio (P = 0.06, Fisher’s exact test); (ii) P. micra‐endo and P. micra‐perio (P = 0.05, Fisher’s exact test). Sensitivity to percussion was associated with an increased chance of cases with P. micra‐endo (P = 0.03, Pearson chi‐square test).

Conclusion  The findings suggest that F. nucleatum, P. micra and C. sputigena may play a role in the pathogenesis of endo‐periodontal lesions.
Social capital and knowledge sharing: effects on patient safety
Authors: Chang Chia‐Wen , Huang Heng‐Chiang , Chiang Chi‐Yun , Hsu Chiu‐Ping , Chang Chia‐Chen
Published: November 2011

chang c.‐w., huang h.‐c., chiang c.‐y., hsu c.‐p. & chang c.‐c. (2011) Social capital and knowledge sharing: effects on patient safety. Journal of Advanced Nursing68(6), 1793–1803.

Aims.  This article is a report on a study that empirically examines the influence of social capital on knowledge sharing and the impact of knowledge sharing on patient safety.

Background.  Knowledge sharing is linked to many desirable managerial outcomes, including learning and problem‐solving, which are essential for patient safety. Rather than studying the tangible effects of rewards, this study examines whether social capital (including social interaction, trust and shared vision) directly supports individual knowledge sharing in an organization.

Methods.  This cross‐sectional study analysed data collected through a questionnaire survey of nurses from a major medical centre in northern Taiwan. The data were collected over a 9‐month period from 2008 to 2009. The data analysis was conducted using the Partial Least Squares Graph v3.0 program to evaluate the measurement properties and the structural relationships specified in the research model.

Findings.  Based on a large‐scale survey, empirical results indicate that Registered Nurses’ perceptions of trust and shared vision have statistically significant and direct effects on knowledge sharing. In addition, knowledge sharing is significantly and positively associated with patient safety.

Conclusion.  The findings suggest that hospital administrators should foster group trust and initiate a common vision among Registered Nurses. In addition, administrators and chief knowledge officers of hospitals should encourage positive intentions towards knowledge sharing.
Change and stasis in marine hybrid zones in response to climate warming
Authors: Hilbish Thomas J. , Lima Fernando P. , Brannock Pamela M. , Fly Elizabeth K. , Rognstad Rhiannon L. , Wethey David S.
Published: November 2011

Aim We test the prediction that hybrid zones between warm‐ and cold‐adapted species will move towards the territory formerly occupied by the cold‐adapted species in response to a warming climate. We use multiple tests of this prediction to distinguish amongst potential mechanistic hypotheses of responses to climate change.

Location We sampled 97 locations on the Atlantic coast of Spain and France and the English Channel that span three hybrid zones formed between two species of marine mussels (Mytilus galloprovincialisandM. edulis).

Methods Mussels were sampled in 2005–07 and analysed at a nuclear gene (Glu‐5′) that is diagnostically differentiated between the subject species. Results were compared to those of studies made in the same region over the past two decades. Historical change in sea surface temperature (SST) was analysed using National Oceanic and Atmospheric Administration (NOAA) Optimum Interpolation Daily SST. Species distribution models (random forest and maximum entropy) of the current distribution of mussels were constructed and validated by hindcasting the historical distributions of these species. Validated models were used in combination with forecasts of SST to predict changes in mussel distribution to 2050 and 2100.

Results We show that over the past two decades two of the hybrid zones in France have not changed in either position or shape. The third hybrid zone, however, has shifted in the predicted direction,c. 100 km eastward into the warming English Channel. Species distribution modelling strongly implicates changes in winter cold SST as driving this change in the position of one of the hybrid zones. Forecasts of future SST indicate that rapid changes in distribution will occur over the next century.

Main conclusions Hybrid zones can be used to conduct repeated tests of ecological responses to climate change and can be valuable in sorting among prospective mechanistic hypotheses that underlie that change. Winter temperatures, but not seasonal high temperature, appear to control the distribution of both species. Species distribution modelling indicates that the collapse of these hybrid zones is imminent, with the rapid expansion of the subtropical species in response to continuing SST warming.
Cross‐cultural adaptation and psychometric properties of the Brazilian–Portuguese version of the Duke Anticoagulation Satisfaction Scale
Authors: Pelegrino Flávia M , Dantas Rosana AS , Corbi Inaiara SA , da Silva Carvalho Ariana R , Schmidt André , Filho Antônio Pazin
Published: November 2011

Aim. The aim of this study was to evaluate the internal reliability and validity of the Brazilian–Portuguese version of Duke Anticoagulation Satisfaction Scale (DASS) among cardiovascular patients.

Background. Oral anticoagulation is widely used to prevent and treat thromboembolic events in several conditions, especially in cardiovascular diseases; however, this therapy can induce dissatisfaction and reduce the quality of life.

Design. Methodological and cross‐sectional research design.

Methods. The cultural adaptation of the DASS included the translation and back‐translation, discussions with healthcare professionals and patients to ensure conceptual equivalence, semantic evaluation and instrument pretest. The Brazilian–Portuguese version of the DASS was tested among subjects followed in a university hospital anticoagulation outpatient clinic. The psychometric properties were assessed by construct validity (convergent, known groups and dimensionality) and internal consistency/reliability (Cronbach’s alpha).

Results. A total of 180 subjects under oral anticoagulation formed the baseline validation population. DASS total score and SF‐36 domain correlations were moderate for General health (r = −0·47,p < 0·01), Vitality (r = −0·44,p < 0·01) and Mental health (r = −0·42,p < 0·01) (convergent). Age and length on oral anticoagulation therapy (in years) were weakly correlated with total DASS score and most of the subscales, except Limitation (r = −0·375,p < 0·01) (Known groups). The Cronbach’s alpha coefficient was 0·79 for the total scale, and it ranged from 0·76 (hassles and burdens)–0·46 (psychological impact) among the domains, confirming the internal consistency reliability.

Conclusions. The Brazilian–Portuguese version of the DASS has shown levels of reliability and validity comparable with the original English version.

Relevance to clinical practice. Healthcare practitioners and researchers need internationally validated measurement tools to compare outcomes of interventions in clinical management and research tools in oral anticoagulation therapy.
Functional rather than immunoreactive levels of IgG4 correlate closely with clinical response to grass pollen immunotherapy
Authors: Shamji M. H. , Ljørring C. , Francis J. N. , A Calderon M. , Larché M. , Kimber I. , Frew A. J. , Ipsen H. , Lund K. , Würtzen P. A. , Durham S. R.
Published: November 2011

To cite this article: Shamji MH, Ljørring C, Francis JN, Calderon MA, Larché M, Kimber I, Frew AJ, Ipsen H, Lund K, Würtzen PA, Durham SR. Functional rather than immunoreactive levels of IgG4 correlate closely with clinical response to grass pollen immunotherapy. Allergy 2012; 67: 217–226.

Background:  Induction of allergen‐specific IgG4 antibodies is the most consistent immunological finding in immunotherapy trials. However, quantitative assessments of IgG4 antibodies have not proven beneficial in evaluating clinical changes during or after immunotherapy. In the current study, we investigated the relationship between clinical outcome and allergen‐specific IgG4 titres or functional antibody responses following immunotherapy. We hypothesized that functional assays of serum IgG–associated inhibitory activity such as inhibition of IgE–allergen interactions (IgE‐blocking factor) and inhibition of CD23‐dependent IgE‐facilitated allergen binding (IgE‐FAB) correlate more closely with clinical outcome and may be biomarkers of clinical response.

Methods:  In an 8‐month dose–response randomized double‐blind placebo‐controlled study, 221 polysensitized subjects with severe seasonal rhinitis received Alutard SQ, Phleum pratense 100 000 SQ‐U, 10 000 SQ‐U or placebo injections. Serum specimens were collected before treatment, after up‐dosing, during the peak season and at the end of the study. Allergen‐specific IgG4 titres and IgG‐associated inhibitory activity were evaluated.

Results:  A time‐ and dose‐dependent increase in serum inhibitory activity for both the IgE‐blocking factor and IgE‐FAB was observed, which paralleled increases in grass pollen–specific IgG4 antibodies. A modest but significant inverse relationship was demonstrated between postimmunotherapy serum inhibitory activity and combined symptom–rescue medication scores (IgE‐FAB: r = −0.25, P = 0.0002; IgE‐blocking factor: r = −0.28, P < 0.0001), whereas this was not observed for immunoreactive IgG4 levels (r = −0.11, P = 0.12).

Conclusions:  Functional assays of inhibitory IgG4 and IgE‐blocking factor may be more useful surrogates of clinical response than IgG4. Whether these antibody effects may serve as predictive biomarkers of clinical efficacy in individual patients requires further investigation.