bluuebunny/crossref_metadata_2025 huggingface dataset:
The Anglican Church of Rwanda: domestic agendas and international linkages
Authors: Cantrell Phillip A.
Published: July 2007

The article analyses the relationship between the Anglican Church of Rwanda and evangelical Episcopalians in the United States. In 2000, the archbishop of Rwanda, Emmanuel Kolini, in a move that gained great support for Rwanda's post-genocide recovery, ordained several bishops to preside over congregations of orthodox, evangelical Americans who had severed their relationship with the Episcopalian Church of the United States over issues such as the blessing of same-sex marriages and the ordination of openly gay clergy. The result was the creation of the Anglican Mission in the Americas, a missionary province in the United States that acknowledges Kolini as its archbishop. Such actions have made Rwanda the currentcause célèbrenot only of AMIA but the wider evangelical community. While the relationship offers great support for Rwanda's recovery, the Anglican Church has presented to American evangelicals a misleading narrative of Rwanda's past and present political situation.
Programming of body composition by early growth and nutrition
Authors: Wells Jonathan C. K. , Chomtho Sirinuch , Fewtrell Mary S.
Published: July 2007

There is now compelling evidence that growth patterns in early life are associated with risk of the metabolic syndrome in adulthood, although the relative importance of prenatal v. postnatal growth for such associations remains controversial. Body composition may play a key role in the ‘programming’ of such diseases, through itself being programmed by early growth, and perhaps also by being a mediator of the programming process. Early studies reporting positive associations between birth weight and adult BMI suggested a tendency for large babies to become obese adults. Such findings appeared contradictory to the many studies linking low birth weight with increased risk of the metabolic syndrome. Recent studies now indicate that birth weight is strongly predictive of later lean mass, and has a much weaker association with later fatness. Studies that link low birth weight with a more central adipose distribution in later life remain controversial, and require confirmation using more sophisticated methodologies. Findings for infant growth rate appear population-specific, with infant weight gain predicting subsequent lean mass in developing countries, but predicting subsequent fat mass and obesity in industrialised populations. Further studies are required on this issue, to ensure that appropriate public health policies are recommended for countries across the range of economic development. Although the links between early growth and later disease risk implicate early-life nutrition, either in utero or during infancy, few prospective studies have explored the influence of early diet on later body composition. Many studies have associated breast-feeding with a reduced prevalence of obesity categorised by BMI; however, the few studies directly evaluating childhood fatness provide little support for this hypothesis. Recent advances in the ability to measure body composition during the infant period offer a major opportunity to improve the understanding of the nutritional programming of body composition and its contribution, or lack thereof, to subsequent disease risk.
Innovative chemotherapeutical treatment options for alveolar and cystic echinococcosis
Authors: HEMPHILL A. , SPICHER M. , STADELMANN B. , MUELLER J. , NAGULESWARAN A. , GOTTSTEIN B. , WALKER M.
Published: July 2007

Echinococcus granulosusandEchinococcus multilocularisare cestode parasites, of which the metacestode (larval) stages cause the diseases cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Albendazole and mebendazole are presently used for chemotherapeutical treatment. However, these benzimidazoles do not appear to be parasiticidalin vivoagainst AE. In addition, failures in drug treatments as well as the occurrence of side-effects have been reported. New drugs are needed to cure AE and CE, which are considered to be neglected diseases. Strategies currently being implemented to identify novel chemotherapeutical treatment options include (i) conventional primaryin vitrotesting of broad-spectrum anti-infective drugs, either in parallel with, or followed by, animal experimentation; (ii) studies of drugs which interfere with the proliferation of cancer cells and ofEchinococcusmetacestodes; (iii) exploitation of the similarities between the parasite and mammalian signalling machineries, with a special focus on targeting specific signalling receptors; (iv)in silicoapproaches, employing the currentEchinococcusgenomic database information to search for suitable targets for compounds with known modes of action. In the present article, we review the efforts toward obtaining better anti-parasitic compounds which have been undertaken to improve chemotherapeutical treatment of echinococcosis, and summarize the achievements in the field of host-parasite interactions which may also lead to new immuno-therapeutical options.
A singular perturbation problem and the existence of non-commutative non-rotationally symmetric scalar solitons
Authors: Magnus Robert J.
Published: July 2007

The existence of solitons in non-commutative scalar field theories is proved for large values of the non-commutativity parameter using functional analysis. In the case of even phase-space dimensions greater than or equal to four, the solitons include some that are not rotationally symmetric.
On Cahn—Hilliard systems with elasticity
Authors: Garcke Harald
Published: July 2007

Elastic effects can have a pronounced effect on the phase-separation process in solids. The classical Ginzburg—Landau energy can be modified to account for such elastic interactions. The evolution of the system is then governed by diffusion equations for the concentrations of the alloy components and by a quasi-static equilibrium for the mechanical part. The resulting system of equations is elliptic-parabolic and can be understood as a generalization of the Cahn—Hilliard equation. In this paper we give a derivation of the system and prove an existence and uniqueness result for it.
Non-existence of global smooth solutions to symmetrizable nonlinear hyperbolic systems
Authors: Yang Tong , Zhu Changjiang
Published: July 2007

In this paper, we consider the Cauchy problem of general symmetrizable hyperbolic systems in multi-dimensional space. When some components of the initial data have compact support, we give a sufficient condition on the non-existence of global C1 solutions. This non-existence theorem can be applied to some physical systems, such as Euler equations for compressible flow in multi-dimensional space. The blow-up phenomena here can come from the singularity developed at the interface, such as vacuum boundary, rather than the shock formation as studied in the previous works on strictly hyperbolic systems. Therefore, the systems considered here include those which are non-strictly hyperbolic.
Uniqueness of positive solutions of nonlinear elliptic equations with exponential growth
Authors: Tarsi Cristina
Published: July 2007

By combining a technique inspired to the theory of sublinear elliptic equations with the Emden-Fowler inversion technique of Atkinson and Peletier, we obtain uniqueness of positive solutions of the following equation

where B ⊂ Rn is the ball of radius one, λ > 0 and 1 < ϑ ≤ 2.
Energy and pointwise bounds in some non-standard parabolic problems
Authors: Ames K. A. , Payne L. E. , Schaefer P. W.
Published: July 2007

We study a class of initial-boundary-value problems for which an auxiliary condition of the form

is prescribed. We determine bounds on an energy expression by means of differential inequalities and derive pointwise bounds for the solution and its gradient by use of a parabolic maximum principle.
A symmetry-breaking phenomenon and asymptotic profiles of least-energy solutions to a nonlinear Schrödinger equation
Authors: Kurata Kazuhiro , Watanabe Tatsuya , Shibata Masataka
Published: July 2007

In this paper, we study a symmetry-breaking phenomenon of a least-energy solution to a nonlinear Schrödinger equation

under suitable assumptions on V(x), where λ > 1, p > 2 and χA is the characteristic function of the set A = [−(l + 2), −l] ∪ [l,l + 2] with l > 0. We also study asymptotic profiles of least-energy solutions for the singularly perturbed problem

for small ε > 0.
Classification of singular solutions of porous media equations with absorption
Authors: Chen Xinfu , Qi Yuanwei , Wang Mingxin
Published: July 2007

We consider, for m ∈ (0, 1) and q > 1, the porous media equation with absorption

We are interested in those solutions, which we call singular solutions, that are non-negative, non-trivial, continuous in Rn × [0, ∞)\{(0, 0)}, and satisfy u(x, 0) = 0 for all x ≠ 0. We prove the following results. When q ≥ m + 2/n, there does not exist any such singular solution. When q < m + 2/n, there exists, for every c > 0, a unique singular solution u = u(c), called the fundamental solution with initial mass c, which satisfies ∫Rnu(·, t) → c as t ↘ 0. Also, there exists a unique singular solution u = u∞, called the very singular solution, which satisfies ∫Rnu∞(·, t) → ∞ as t ↘ 0.

In addition, any singular solution is either u∞ or u(c) for some finite positive c, u(c1) < u(c2) when c1 < c2, and u(c) ↗ u∞ as c ↗ ∞.

Furthermore, u∞ is self-similar in the sense that u∞(x, t) = t−αw(|x| t−αβ) for α = 1/(q − 1), β = ½(q − m), and some smooth function w defined on [0, ∞), so that

is a finite positive constant independent of t > 0.
On the quenching set for a fast diffusion equation: regional quenching
Authors: Ferreira R. , de Pablo A. , Quirós F. , Rossi J. D.
Published: July 2007

We study positive solutions of a very fast diffusion equation, ut = (um−1ux)x, m < 0, in a bounded interval, 0 < x < L, with a quenching-type boundary condition at one
end, u (0, t) = (T − t)1/(1 − m) and a zero-flux boundary condition at the other, (um −1ux)(L, t) = 0. We prove that for m ≥ −1 regional quenching is not possible: the quenching set is either a single point or the whole interval. Conversely, if m < −1 single-point quenching is impossible, and quenching is either regional or global. For some lengths the above facts depend on the initial data. The results are obtained by studying the corresponding blow-up problem for the variable v = um −1.
Cases of equality and strict inequality in the extended Hardy–Littlewood inequalities
Authors: Hajaiej Hichem
Published: July 2007

Extended Hardy-Littlewood inequalities are

where {ui}1≤i≤m are non-negative functions and denote their Schwarz symmetrization.

In this paper, we determine appropriate conditions under which equality in (*) occurs if and only if {ui}1≤i≤m are Schwarz symmetric.
Dependence of Friedrichs' constant on boundary integrals
Authors: Auchmuty Giles , Emamizadeh Behrouz , Zivari Mohsen
Published: July 2007

This note extends the results in ‘Optimal coercivity inequalities in W1,p(Ω)’ (G. Auchmuty, Proc. R. Soc. Edinb. A 135, 915–933.) describing the dependence of the optimal constant in the p-version of Friedrichs' inequality on the boundary integral term. In particular, it is shown that this constant is continuous, increasing, concave and increases to the optimal constant for the Dirichlet problem as s → ∞.
On the validity of the Picard algorithm for nonlinear parabolic equations
Authors: Cannone Marco , Karch Grzegorz
Published: July 2007

We discuss some ill-posedness results for solutions arising from the Picard iterations algorithm (i.e. the Banach fixed-point theorem) in the case of the nonlinear heat equation, the viscous Hamilton–Jacobi equation, the convection–diffusion equation and the incompressible Navier–Stokes system.
Existence and uniqueness results for a class of elliptic equations with exponential nonlinearity
Authors: Choe Kwangseok
Published: July 2007

We establish existence results for a class of semilinear elliptic equations with exponential nonlinearity by studying a suitable eigenvalue problem. We also establish a uniqueness result for those equations by making use of the implicit function theorem.
Characterization of isochronous foci for planar analytic differential systems
Authors: Giné Jaume , Grau Maite
Published: July 2007

We consider the two-dimensional autonomous systems of differential equations of the form

where P(x,y) and Q(x,y) are analytic functions of order greater than or equal to 2. These systems have a focus at the origin if λ ≠ 0, and have either a centre or a weak focus if λ = 0. In this work we study the necessary and sufficient conditions for the existence of an isochronous critical point at the origin. Our result is, to the best of our knowledge, original when applied to weak foci and gives known results when applied to strong foci or to centres.
Global averaging and parametric resonances in damped semilinear wave equations
Authors: Zelik S.
Published: July 2007

The long-time behaviour of solutions to a semilinear damped wave equation in a three-dimensional bounded domain with the nonlinearity rapidly oscillating in time (f = f(ε, u, t/ε)) is studied. It is proved that (under natural assumptions) the behaviour of solutions whose initial energy is not very large can be described in terms of global (uniform) attractors Aε of the corresponding dynamical processes and that, as ε → 0, these attractors tend to the global attractor A0 of the corresponding averaged system. We also give the detailed description of these attractors in the case where the limit attractor A0 is regular.

Moreover, we give explicit examples of semilinear hyperbolic equations where the uniform attractor Âε (for the initial data belonging to the whole energy phase space) contains the irregular resonant part, which tends to infinity as ε → 0, and formulate the additional restrictions on the nonlinearity f which guarantee that this part is absent.
Role of the fundamental solution in Hardy—Sobolev-type inequalities
Authors: Adimurthi  , Sekar Anusha
Published: July 2007

Let n ≥ 3, Ω ⊂ Rn be a domain with 0 ∈ Ω, then, for all the Hardy–Sobolev inequality says that

and equality holds if and only if u = 0 and ((n − 2)/2)2 is the best constant which is never achieved. In view of this, there is scope for improving this inequality further. In this paper we have investigated this problem by using the fundamental solutions and have obtained the optimal estimates. Furthermore, we have shown that this technique is used to obtain the Hardy–Sobolev type inequalities on manifolds and also on the Heisenberg group.
Acute: High-level programming language design for distributed computation
Authors: SEWELL PETER , LEIFER JAMES J. , WANSBROUGH KEITH , NARDELLI FRANCESCO ZAPPA , ALLEN-WILLIAMS MAIR , HABOUZIT PIERRE , VAFEIADIS VIKTOR
Published: July 2007

Existing languages provide good support for typeful programming of stand-alone programs. In a distributed system, however, there may be interaction between multiple instances of many distinct programs, sharing some (but not necessarily all) of their module structure, and with some instances rebuilt with new versions of certain modules as time goes on. In this paper, we discuss programming-language support for such systems, focussing on their typing and naming issues. We describe an experimental language, Acute, which extends an ML core to support distributed development, deployment, and execution, allowing type-safe interaction between separately built programs. The main features are (1) type-safe marshalling of arbitrary values; (2) type names that are generated (freshly and by hashing) to ensure that type equality tests suffice to protect the invariants of abstract types, across the entire distributed system; (3) expression-level names generated to ensure that name equality tests suffice for type safety of associated values, for example, values carried on named channels; (4) controlled dynamic rebinding of marshalled values to local resources; and (5) thunkification of threads and mutexes to support computation mobility. These features are a large part of what is needed for typeful distributed programming. They are a relatively lightweight extension of ML, should be efficiently implementable, and are expressive enough to enable a wide variety of distributed infrastructure layers to be written as simple library code above the byte-string network and persistent store APIs. This disentangles the language run-time from communication intricacies. This paper highlights the main design choices in Acute. It is supported by a full language definition (of typing, compilation, and operational semantics), by a prototype implementation, and by example distribution libraries.
Efficiency and kinetics of the in vitro fertilization process in bovine oocytes with different meiotic competence
Authors: Horakova J. , Hanzalova K. , Reckova Z. , Hulinska P. , Machatkova M.
Published: July 2007

The aim of the study was to investigate the efficiency and kinetics of fertilization in oocytes with different meiotic competence, as defined by the phase of the follicular wave and follicle size. Oocytes were recovered from cows with synchronized estrus cycles, slaughtered in either the growth (day 3) or the dominant (day 7) phase, separately from large, medium and small follicles. The oocytes were matured and fertilized by a standard protocol. Twenty-four hours after fertilization, the oocytes were denuded from cumulus cells, fixed and stained with bisbensimid Hoechst–PBS. Fertilization was more efficient and the first cleavage was accelerated in growth phase-derived oocytes, as shown by significantly higher (p ≤ 0.01) proportions of both normally fertilized and cleaved oocytes (68.8 and 25.1%), in comparison with dominant phase-derived oocytes (44.2 and 10.3%). In the growth-phase derived oocytes, proportions of normally fertilized and cleaved oocytes were significantly higher (p ≤ 0.01) in oocytes from large (100.0 and 36.4%) and medium (83.3 and 36.5%) follicles than in those from small (54.8 and 14.6%) follicles. The dominant phase-derived oocytes showed higher proportions of normally fertilized and cleaved oocytes in the populations recovered from small (51.5 and 10.0%) and medium (43.1 and 12.0%) follicles than in those from large (25.0 and 0%) follicles; however, the differences were not significant. It can be concluded that: (i) efficiency and kinetics of fertilization differ in relation to oocyte's meiotic competence; (ii) improved development of embryos from oocytes with greater meiotic competence is associated with a more effective fertilization process.
Structural and ultrastructural characteristics of the yolk syncytial layer inProchilodus lineatus(Valenciennes, 1836) (Teleostei; Prochilodontidae)
Authors: Ninhaus-Silveira A. , Foresti F. , de Azevedo A. , Agostinho C.A. , Veríssimo-Silveira R.
Published: July 2007

The yolk syncytial layer (YSL) has been regarded as one of the main obstacles for a successful cryopreservation of fish embryos. The purpose of this study was to identify and characterize the YSL inProchilodus lineatus, a fish species found in southeastern Brazil and considered a very important fishery resource. Embryos were obtained through artificial breeding by hormonal induction. After fertilization, the eggs were incubated in vertical incubators with a controlled temperature (28 °C). Embryos were collected in several periods of development up to hatching and then fixed with 2% glutaraldehyde and 4% paraformaldehyde in 0.1 M sodium phosphate buffer (pH 7.3). Morphological analyses were carried out under either light, transmission or scanning electron microscopy. The formation of the YSL inP. lineatusembryos starts at the end of the cleavage stage (morula), mainly at the margin of the blastoderm, and develops along the embryo finally covering the entire yolk mass (late gastrula) and producing a distinct intermediate zone between the yolk and the endodermal cells. The YSL was characterized by the presence of microvilli on the contact region with the yolk endoderm. A cytoplasmic mass, full of mitochondria, vacuoles, ribosomes, endomembrane nets and euchromatic nuclei, indicated a high metabolic activity. This layer is shown as an interface between the yolk and the embryo cells that, besides sustaining and separating the yolk, acts as a structure that makes it available for the embryo. The structural analyses identified no possible barriers to cryoprotectant penetration.
“THE POETRY OF SCIENCE”: CHARLES DICKENS, GEOLOGY, AND VISUAL AND MATERIAL CULTURE IN VICTORIAN LONDON
Authors: Buckland Adelene
Published: July 2007

DESPITE THE WELL-ESTABLISHED CONNECTIONSbetween Dickens's novels and Victorian popular entertainment, and between Victorian show business and the display and dissemination of science, critics have not yet explored the possible links between scientific shows and Dickens's fiction. Work on Dickens and science has proliferated since George Levine's work inDarwin and the Novelists, but its central problem has been the fact that, as Francis O’Gorman described it, Dickens's scientific reading was “nugatory” (252). The most well-represented branch of science on his bookshelves was natural history; in even this, Dickens displayed only the “intelligent interest that would be expected of a man of the world” (Hill 203). Levine's influential “one culture” model surmounted the problem by pointing out the similar structural patterns implicit in the worlds described by Dickens and Darwin, but in an attempt to develop more direct links between Dickens's work and evolutionary science, almost all subsequent studies have focused on Dickens's 1860s novels, written after the publication of theOrigin of Species(1859) (Morris 179–93; Fulweiler 50–74; Morgentaler 707–21). There has not been a study that explores Dickens's acquaintance with natural history at different points in his career, or through the visual and material cultures with which he was so familiar.
A NOISE TRADER MODEL AS A GENERATOR OF APPARENT FINANCIAL POWER LAWS AND LONG MEMORY
Authors: ALFARANO SIMONE , LUX THOMAS
Published: July 2007

In various agent-based models, the stylized facts of financial markets (unit roots, fat tails, and volatility clustering) have been shown to emerge from the interactions of agents. However, the complexity of these models often limits their analytical accessibility. In this paper we show that even a very simple model of a financial market with heterogeneous interacting agents is capable of reproducing these ubiquitous statistical properties. The simplicity of our approach permits us to derive some analytical insights using concepts from statistical mechanics. In our model, traders are divided into two groups, fundamentalists and chartists, and their interactions are based on a variant of the herding mechanism introduced by A. Kirman (Ants, rationality, and recruitment, Quarterly Journal of Economics 108, 137–156, 1993). The statistical analysis of simulated data points toward long-term dependence in the autocorrelations of squared and absolute returns and hyperbolic decay in the tail of the distribution of raw returns, both with estimated decay parameters in the same range as those of empirical data. Theoretical analysis, however, excludes the possibility of “true” scaling behavior because of the Markovian nature of the underlying process and the boundedness of returns. The model, therefore, only mimics power law behavior. Similarly to the phenomenological volatility models analyzed by LeBaron (Stochastic volatility as a simple generator of apparent financial power laws and long memory, Quantitative Finance 1, 621–631, 2001), the usual statistical tests are not able to distinguish between true and pseudo-scaling laws in the dynamics of our artificial market.
ENDOGENOUS CROSS CORRELATIONS
Authors: SATCHELL STEPHEN E. , YANG STEFFI J.-H.
Published: July 2007

This paper studies the relationship between rational herding and cross correlations in security returns. It demonstrates analytically and numerically that herding, as a temporary, fragile convergence of investment behavior, can endogenously induce asset dependency. Furthermore, there exists a self-reinforcing process, in which market extreme events amplify the herd effect, which further exacerbates asset dependency. Considering the Taiwan and U.K. equity markets, we find that the simulated markets in the presence of herding have results closer to the real patterns of asset dependency than a static model with isolated, noninteracting individuals. Our findings cast doubts on the current view that transparent financial regulation is always desirable. Moreover, this paper finds statistical evidence of asymmetric correlation patterns in both the top 50 stocks in the U.K. and Taiwan equity markets. This suggests that portfolio diversification as a means of managing portfolio risk is unlikely to be effective in periods of extreme losses in these markets.
AN INTERVIEW WITH PETER DIAMOND
Authors: Moscarini Giuseppe , Wright Randall
Published: July 2007

Peter Diamond is one of the major contributors to economics during the last half century. His many contributions include research on growth, Social Security, public finance more generally, the economics of uncertainty, search theory, in particular, and economic dynamics, in general. This work has shaped the way we think about many economic problems, and the way in which we formalize them. Among his long list of honors and awards, he is a fellow of the Econometric Society, a Guggenheim Fellow, a Fellow of the American Academy of Arts and Sciences, a Member of the National Academy of Sciences, and a Nemmers Prize winner. The National Science Foundation has supported his work for the last 40 years. A recent check indicated 9 books and 132 published articles, and there are few signs of any slowdown.
Comparison of Compositional and Morphological Atom-Probe Tomography Analyses for a Multicomponent Fe-Cu Steel
Authors: Kolli R. Prakash , Seidman David N.
Published: July 2007

A multicomponent Fe-Cu based steel is studied using atom-probe tomography. The precipitates are identified using two different methodologies and subsequent morphological and compositional results are compared. The precipitates are first identified using a maximum separation distance algorithm, the envelope method, and then by a concentration threshold method, an isoconcentration surface. We discuss in detail the proper selection of the parameters needed to delineate precipitates utilizing both methods. The results of the two methods exhibit a difference of 44 identified precipitates, which can be attributed to differences in the basis of both methods and the sensitivity of our results to user-prescribed parameters. The morphology of the precipitates, characterized by four different precipitate radii and precipitate size distribution functions (PSDs), are compared and evaluated. A variation of less than ∼8% is found between the different radii. Two types of concentration profiles are compared, giving qualitatively similar results. Both profiles show Cu-rich precipitates containing Fe with elevated concentrations of Ni, Al, and Mn near the heterophase interfaces. There are, however, quantitative disagreements due to differences in the basic foundations of the two analysis methods.
Panspermia in the context of the timing of the origin of life and microbial phylogeny
Authors: Line M.A.
Published: July 2007

The synthesis of physical information on early Earth (or Mars) with recent knowledge arising from microbial genomic, proteomic and phylogenetic studies, strongly indicates that there was insufficient time (∼600 000 years) for life to arise and evolve to reach the biochemical complexity evident within the Last Common Community (LCC). If recent strong evidence of fossil cyanobacteria in carbonaceous meteorites is accepted, then the LCC would have existed prior to the origin of life on Earth and the planet would then have been seeded with representatives of the three domains once it became habitable. The existence of intermittently active cyanobacteria in comets opens the possibility for the evolution of microaerobic bacterial metabolism, elements of which appear at a deep level of the microbial phylogeny, at or below the depth of the LCC. It is also notable from a panspermia perspective that recent phylogenetic evidence indicates that the Gram-positive lineage (representatives of which are endowed with long-lived radiation-resistant spores) lies at the deepest level of domain Bacteria, with Archaea and Eukarya evolving from this lineage probably before 3.6 Gigayears ago (Gya).
Glial cell development and function in the Drosophila visual system
Authors: Chotard Carole , Salecker Iris
Published: July 2007

In the developing nervous system, building a functional neuronal network relies on coordinating the formation, specification and survival to diverse neuronal and glial cell subtypes. The establishment of neuronal connections further depends on sequential neuron–neuron and neuron–glia interactions that regulate cell-migration patterns and axon guidance. The visual system of Drosophila has a highly regular, retinotopic organization into reiterated interconnected synaptic circuits. It is therefore an excellent invertebrate model to investigate basic cellular strategies and molecular determinants regulating the different developmental processes that lead to network formation. Studies in the visual system have provided important insights into the mechanisms by which photoreceptor axons connect with their synaptic partners within the optic lobe. In this review, we highlight that this system is also well suited for uncovering general principles that underlie glial cell biology. We describe the glial cell subtypes in the visual system and discuss recent findings about their development and migration. Finally, we outline the pivotal roles of glial cells in mediating neural circuit assembly, boundary formation, neural proliferation and survival, as well as synaptic function.
Crustal structure beneath the eastern margin of the Tibetan Plateau and its tectonic implications
Authors: Wang Chun‐Yong , Han Wei‐Bin , Wu Jian‐Ping , Lou Hai , Chan W. Winston
Published: July 2007

Two crustal cross sections through the eastern margin of the Tibetan Plateau are jointly determined from deep seismic sounding. The E–W trending line AA’ passes through the western Sichuan plateau (including the Songpan‐Garze terrane and the Longmenshan fault belt) and ends in the Sichuan basin (a part of the Yangtze craton). Line BB’ has a trend of NNE and crosses the Songpan‐Garze terrane. Two‐dimensional crustal structures along the profiles were jointly determined by the additional use of existing deep seismic sounding data. Our seismic velocity models indicate that the western Sichuan plateau and the Sichuan basin have crustal thicknesses of 62 and 43 km, average crustal P wave velocities of 6.27 and 6.45 km/s and lower crustal (Vp > 6.5 km/s) thicknesses of 27 and 15 km, respectively. Density models constructed from the seismic velocity models are consistent with observed Bouguer gravity anomalies. We infer that collision between the Tibetan Plateau and the Yangtze craton has caused thickening of the lower crust and uplift of the western Sichuan plateau. We detect a low‐velocity layer in the upper crust of the western Sichuan plateau but observe no equivalence in the Sichuan basin; west dipping thrusts may detach into this low‐velocity layer. The seismic phase PmP in the western Sichuan plateau has low amplitude, suggesting high attenuation in the lower crust (Qp of 100–300). We suggest that the high attenuation is a consequence of lower crustal flow caused by the large lower crustal thickness beneath the western Sichuan plateau.
First determination of gas hydrate crystallite size distributions using high‐energy synchrotron radiation
Authors: Klapp S. A. , Klein H. , Kuhs W. F.
Published: July 2007

Due to experimental difficulties grain size distributions of gas hydrate crystallites are largely unknown in natural samples. For the first time, we were able to determine grain size distributions of six natural gas hydrates for samples retrieved from the Gulf of Mexico and from Hydrate Ridge offshore Oregon from varying depths. High‐energy synchrotron radiation provides high photon fluxes as well as high penetration depth and thus allows for investigation of bulk sediment samples. The gas hydrate crystallites appear to be (log‐) normally distributed in the natural samples and to be of roughly globular shape. The mean grain sizes are in the range from 300–600 μm with a tendency for bigger grains to occur in greater depth, possibly indicating a difference in the formation age. Laboratory produced methane hydrate, starting from ice and aged for 3 weeks, shows half a log‐normal curve with a mean value of ∼40 μm. This one order‐of‐magnitude smaller grain sizes suggests that care must be taken when transposing grain‐size sensitive (petro‐)physical data from laboratory‐made gas hydrates to natural settings.
Upper mantle structure beneath the Galápagos Archipelago from surface wave tomography
Authors: Villagómez Darwin R. , Toomey Douglas R. , Hooft Emilie E. E. , Solomon Sean C.
Published: July 2007

We present a Rayleigh wave tomographic study of the upper mantle beneath the Galápagos Archipelago. We analyze waves in 12 separate frequency bands (8–50 mHz) sensitive to shear wave velocity (VS) structure in the upper 150 km. Average phase velocities are up to 2 and 8% lower than for 0‐ to 4‐My‐old and 4‐ to 20‐My‐old Pacific seafloor, respectively. Laterally averaged VS is 0.05–0.2 km/s lower between 75‐ and 150‐km depth than for normal Pacific mantle of comparable age, corresponding to an excess temperature of 30 to 150°C and ∼0.5% melt. A continuous low‐velocity volume that tilts in a northerly direction as it shoals extends from the bottom of our model to the base of a high‐velocity lid, which is located at depths varying from 40 to 70 km. We interpret this low‐velocity volume as an upwelling thermal plume that flattens against the base of the high‐velocity lid. The high‐velocity lid is ∼30 km thicker than estimated lithospheric thickness beneath the southwestern archipelago, above the main region of plume upwelling. We attribute the thicker‐than‐normal high‐velocity lid to residuum from hot spot melting. The thickness of the lid appears to control the final depth of melting and the variability of basalt composition in the archipelago. At depths less than 100–120 km, plume material spreads in directions both toward and against eastward plate motion, indicating that plume buoyancy forces dominate over plate drag forces and suggesting a relatively high plume buoyancy flux (B ≥ 2000 kg/s).
Influence of meteorological processes on the spatial and temporal variability of atmospheric dimethyl sulfide in the high Arctic summer
Authors: Lundén J. , Svensson G. , Leck C.
Published: July 2007

Near‐surface observations of gas phase dimethyl sulfide, DMS(g), over the central Arctic Ocean display large temporal variability. By using a three‐dimensional numerical model, the atmospheric part of COAMPS2.0®, we show that meteorological processes such as transport and mixing cause variability in DMS(g) of the same order as in the observations. The observations used in this study were taken on board the icebreaker Oden that cruised the high Arctic during the following three expeditions: the International Arctic Ocean Expedition 1991, the Arctic Ocean Expedition 1996, and the Arctic Ocean Experiment 2001. Calculation of air‐sea flux and photochemical decay of DMS(g) was added to COAMPS2.0®. A 10‐day period in August 2001 was modeled. The time development of observed DMS(g) is captured by the model, correlation coefficient 0.76, in spite of a simplified treatment of DMS processes. Also, the model results clearly show that DMS(g) is advected over the pack ice in plumes originating from different source areas around the pack ice.
Effect of thermospheric neutral density upon inner trapped‐belt proton flux
Authors: Wilson Thomas L. , Lodhi M. A. K. , Diaz Abel B.
Published: July 2007

We wish to point out that a secular change in the Earth's atmospheric neutral density alters charged‐particle lifetime in the inner trapped radiation belts, in addition to the changes recently reported as produced by greenhouse gases. Heretofore, changes in neutral density have been of interest primarily because of their effect on the orbital drag of satellites. We extend this to include the orbital lifetime of charged particles in the lower radiation belts. It is known that the charged‐belt population is coupled to the neutral density of the atmosphere through changes induced by solar activity, an effect produced by multiple scattering off neutral and ionized atoms along with ionization loss in the thermosphere where charged and neutral populations interact. It will be shown here that trapped‐belt flux J is bivariant in energy E and thermospheric neutral density ρ, as J(E, ρ). One can conclude that proton lifetimes in these belts are also directly affected by secular changes in the neutral species populating the Earth's thermosphere. This result is a consequence of an intrinsic property of charged‐particle flux, that flux is not merely a function of E but is dependent upon density ρ when a background of neutrals is present.
Stirring in three‐dimensional mantle convection models and implications for geochemistry: 2. Heavy tracers
Authors: Huang Jinshui , Davies Geoffrey F.
Published: July 2007

Three‐dimensional, spherical models of subduction and stirring of oceanic crust, taking account of the excess density of subducted oceanic crust in the mantle, confirm the main results from previous two‐dimensional models. Thus we find that the excess density of subducted crust significantly increases the ages of ocean island basalt (OIB) samples, assumed to come from the bottom 100 km of the mantle, but has little influence on the age of mid‐ocean ridge basalt (MORB) samples from the top of the mantle. The degree of processing of the mantle through melting zones is also little affected, and the Earth's mantle is still about 98% processed after 4.5 Ga. The latter results indicate that the processing time is still the main parameter controlling mantle processing and apparent MORB source ages, even with heavy tracers. However, the mean age of model OIB samples is significantly larger than observed apparent isotopic ages. Simplified estimates indicate that this discrepancy can be resolved by assuming that a population of ancient tracers in the OIB sampling zone, evident in the numerical models, is only marginally sampled by plumes because they are concentrated in denser accumulations at the bottom of the compositional boundary layer.
Intraglandular application of botulinum toxin leads to structural and functional changes in rat acinar cells
Authors: Teymoortash A , Sommer F , Mandic R , Schulz S , Bette M , Aumüller G , Werner J A
Published: July 2007

Background and purpose:

Intraglandular injection of botulinum toxin (BoNT) leads to a transient denervation of the submandibular gland and this is associated with reduced salivary secretion. The purpose of the present study was to verify whether temporary acinar atrophy occurs simultaneously with chemical denervation of the glands.

Experimental approach:

Tissue specimens of the right submandibular gland taken from 18 Wistar rats after intraglandular injection of BoNT A, BoNT B, or a combination of both were examined. As a sham control, an equivalent volume of saline was injected into the left submandibular gland. Morphometric measurements, immunohistochemistry, electron microscopy and western blot analysis were used to analyse the morphological and functional changes of the denervated glands.

Key results:

Morphological and ultrastructural analyses of the cell organelles and secretory granula showed a clear atrophy of the acini, which was more prominent in glands injected with the combination of BoNT/A and B. Morphometric measurements of the glandular acini revealed a significant reduction of the area of the acinar cells after injection of BoNT (P=0.031). The expression of amylase was significantly reduced in BoNT treated glands.

Conclusions and implications:

Intraglandular application of BoNT induces structural and functional changes of the salivary glands indicated by glandular atrophy. These effects may be due to glandular denervation induced by the inhibition of the soluble N‐ethylmaleimide‐sensitive fusion protein attachment protein receptors (SNAREs) involved in acetylcholine release at the neuroglandular junction and also specially inhibition of those involved in exocytosis of the granula of the acinar cells.

British Journal of Pharmacology (2007) 152, 161–167; doi:10.1038/sj.bjp.0707375
Synergistic effect of formoterol and mometasone in a mouse model of allergic lung inflammation
Authors: Wyss D , Bonneau O , Trifilieff A
Published: July 2007

Background and purpose:

Controversy still exists as to whether or not inhaled β2‐adrenoceptor agonists and corticosteroids act synergistically in vivo. In this study, we have used a murine model of lung inflammation to study the synergistic effect of an inhaled β2‐adrenoceptor agonists (formoterol) and an inhaled corticosteroid (mometasone).

Experimental approach:

Actively sensitized mice were challenged with aerosolized ovalbumin, once a day, for three consecutive days. Three days after the last of the three challenges, a final allergen challenge was given. Allergen‐induced increase in Penh was measured 4 h after the last challenge. A day after the last challenge, increased airway sensitivity to aerosolized methacholine was demonstrated and this was concomitant with an influx of inflammatory cells in the bronchoalveolar lavage fluids.

Key results:

Mometasone (0.1 to 3 mg kg−1) given intranasally either an hour before or after the last allergen challenge, dose‐dependently inhibited all parameters. When given intranasally either one or three hours after the last allergen challenge, but not an hour before, formoterol (1.5 to 150 μg kg−1) also dose‐dependently inhibited most of the parameters to different degree. A synergistic effect on the allergen‐induced increase in Penh was demonstrated for mometasone and formoterol given in combination, an hour after the challenge, at the following doses: mometasone/formoterol (in μg kg−1) 1/10, 1/100, 5/10, and 5/100.

Conclusions and implications:

Our results support the hypothesis that when given as a fixed combination, inhaled corticosteroid and β2‐adrenoceptor agonist act synergistically in vivo.

British Journal of Pharmacology (2007) 152, 83–90; doi:10.1038/sj.bjp.0707381
Catalytic mechanism of the glutathione peroxidase-type tryparedoxin peroxidase of Trypanosoma brucei
Authors: Schlecker Tanja , Comini Marcelo A. , Melchers Johannes , Ruppert Thomas , Krauth-Siegel R. Luise
Published: July 2007

Trypanosoma brucei, the causative agent of African sleeping sickness, encodes three nearly identical genes for cysteine-homologues of the selenocysteine-containing glutathione peroxidases. The enzymes, which are essential for the parasites, lack glutathione peroxidase activity but catalyse the trypanothione/Tpx (tryparedoxin)-dependent reduction of hydroperoxides. Cys47, Gln82 and Trp137 correspond to the selenocysteine, glutamine and tryptophan catalytic triad of the mammalian selenoenzymes. Site-directed mutagenesis revealed that Cys47 and Gln82 are essential. A glycine mutant of Trp137 had 13% of wild-type activity, which suggests that the aromatic residue may play a structural role but is not directly involved in catalysis. Cys95, which is conserved in related yeast and plant proteins but not in the mammalian selenoenzymes, proved to be essential as well. In contrast, replacement of the highly conserved Cys76 by a serine residue resulted in a fully active enzyme species and its role remains unknown. Thr50, proposed to stabilize the thiolate anion at Cys47, is also not essential for catalysis. Treatment of the C76S/C95S but not of the C47S/C76S double mutant with H2O2 induced formation of a sulfinic acid and covalent homodimers in accordance with Cys47 being the peroxidative active site thiol. In the wild-type peroxidase, these oxidations are prevented by formation of an intramolecular disulfide bridge between Cys47 and Cys95. As shown by MS, regeneration of the reduced enzyme by Tpx involves a transient mixed disulfide between Cys95 of the peroxidase and Cys40 of Tpx. The catalytic mechanism of the Tpx peroxidase resembles that of atypical 2-Cys-peroxiredoxins but is distinct from that of the selenoenzymes.
Evolutionary Urban Transportation Planning: An Exploration
Authors: Bertolini Luca
Published: July 2007

For urban transportation planners these are challenging times. Mounting practical concerns are mirrored by more fundamental critiques. The latter comes together in the observation that conventional approaches do not adequately account for the irreducible uncertainty of future developments. The author's central aim is to explore whether and how an evolutionary approach can help overcome this limit. Two core hypotheses are formulated. The first is that the urban transportation system behaves in an evolutionary fashion. The second hypothesis is that, because of this, urban transportation planning needs to focus on enhancing the resilience and adaptability of the system. Changes in transport and land-use development patterns and policies, and in the broader context of the postwar period in the Amsterdam region, are analysed in order to illustrate the two core hypotheses. More general implications are also drawn.
Comparing Multipliers in the Social Accounting Matrix Framework: The Case of Catalonia
Authors: Llop Maria
Published: July 2007

Structural decomposition analysis, which is usually used within an input-output framework, allows changes in economic variables to be broken down into their determinants. Structural decomposition techniques can also be applied in social accounting matrix (SAM) models, which provide a complete representation of circular flow by adding factor-income generation and household-income distribution to the intersectorial transactions. The author uses structural decomposition analysis to reveal the factors that contribute to the changes in SAM multipliers over time. In particular, she analyses how modifying the patterns of intermediate demand, private consumption, and factor-income distribution modifies the income-generation process. Two SAMs are used, one for 1990 and one for 1994, in an empirical application for the Catalan economy. The results show that the regional multipliers in 1994 were smaller than in 1990, mainly because of a reduction in the structural coefficients of the model.