bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitotic phosphorylation: breaking the balance of power by a tactical retreat
Authors: Poon Randy Y. C.
Published: March 2007

Profound changes in the phosphorylation state of many proteins occur during mitosis. It is well established that many of these mitotic phosphorylations are carried out by archetypal mitotic kinases that are activated only during mitosis, shifting the equilibrium of kinases and phosphatases towards phosphorylation. However, many studies have also detailed the phosphorylation of proteins at mitosis by kinases that are constitutively active throughout the cell cycle. In most cases, it is uncertain how kinases and phosphatases that appear to be constitutively active can induce phosphorylations specifically at mitosis. In this issue of the Biochemical Journal, Escargueil and Larsen provide evidence of an interesting alternative mechanism to attain specific mitotic phosphorylation. A mitosis-specific phosphorylation site in DNA topoisomerase IIα, which is recognized by the MPM-2 antibody, is phosphorylated by protein kinase CK2. The authors found that phosphorylation of this site is suppressed during interphase due to competing dephosphorylation by protein phosphatase 2A. Interestingly, protein phosphatase 2A is excluded from the nucleus during early mitosis, allowing CK2 to phosphorylate topoisomerase IIα. It is possible that similar mechanisms are used to regulate the phosphorylation of other proteins.
Blood and Tears in the Mirror of Memory: Palestinian Trauma in Liana Badr's The Eye of the Mirror
Authors: Kohlke Marie–Luise
Published: March 2007

Liana Badr's The Eye of the Mirror explores the historical trauma of the 1975–6 siege of the Palestinian refugee camp Tal el–Zaatar in Beirut and the massacre of thousands of its inhabitants by Christian militias. Analogous to Holocaust writing, Badr's fictionalized history, grounded in actual survivor testimonies, enacts a complex politics of cultural memory, but does so from a specifically female perspective. Collapsing the personal and political, private and public, inside and outside through figured violations of bodies and psyches, Badr repositions women at the centre of the Palestinians’ struggle for and story of survival. Badr's novel traces the annihilation of the possibility of address, accompanied by self–loss and the ability to witness, and the laborious recreation of address. Claiming authority on the basis of the emotional, visceral truth of suffering, she seeks to break the endless cycle of an oppressive and impotent masculine history, constructing an alternative history which at least attempts to address the voice of cultural, national, and gender difference.
‘You like to Mix things up on Purpose …? Hoy, what are you trying to Prove?’: Representations of Recent (hi)Stories in Jessica Hagedorn's The Gangster of Love
Authors: Echano Marta Vizcaya
Published: March 2007

This paper examines how The Gangster of Love (1996), the second novel by Filipino American artist and writer Jessica Hagedorn, dismantles ready-made assumptions about the construction of minority and mainstream cultures. Spanning the period from the 1970s to the early 1990s, Gangster depicts the life of Rocky Rivera, a Filipina American young artist. As it portrays Rocky's family and friends, the novel examines the drastic re-articulation of the US's self-image brought about by Filipino Americans and other groups marginalized as minorities by virtue of their ethnic, socio–cultural, and/or sexual identities. The narrative challenges dominant notions of who and what makes history, juxtaposing historical references with fictionalizations of real episodes and completely fictional incidents, and making a constant use of parody, irony, jokes and clichés. This paper studies Rocky's reworks of her multiple ethnic and sociocultural allegiances in connection with her passion for music and popular culture, placing these reworks in the context of the Philippines’ colonial and neo–colonial background and multi-cultural US history. It also considers succinctly how Gangster's postcolonial dimensions intersect with a feminist and postmodern consciousness in a gendered strategy of socio–cultural resistance and critique.
The wave function evolution of an exciton in a bilayer system: Turning on a static in-plane electric field
Authors: Wang Li
Published: March 2007

The time evolution of the ground state wave function of an exciton in an ideal bilayer system is investigated within the framework of the effective-mass approximation. All of the moduli squared of the ground state wave functions evolve with time as cosine functions after an in-plane electric field is applied to the bilayer system. The variation amplitude and period of the modulus squared of the ground state wave function increase with the in-plane electric field Fr for a fixed in-plane relative coordinate r and fixed separation d between the electron and hole layers. Moreover, the variation amplitude and period of the modulus squared of the ground state wave function increase with the separation d for a fixed r and fixed in-plane electric field. Additionally, the modulus squared of the ground state wave function decreases as r increases at a given time t for fixed values of d and Fr.
Overlapping resonances in the control of intramolecular vibrational redistribution
Authors: Gerbasi D. , Sanz A. S. , Christopher P. S. , Shapiro M. , Brumer P.
Published: March 2007

Coherent control of bound state processes via the interfering overlapping resonance scenario [Christopher et al., J. Chem. Phys. 123, 064313 (2006)] is developed to control intramolecular vibrational redistribution (IVR). The approach is applied to the flow of population between bonds in a model of chaotic OCS vibrational dynamics, showing the ability to significantly alter the extent and rate of IVR by varying quantum interference contributions.
Nonequilibrium multiscale computational model
Authors: Liu Xiaohu , Li Shaofan
Published: March 2007

A computational multiscale method is proposed to simulate coupled, nonequilibrium thermomechanical processes. This multiscale framework couples together thermomechanical equations at the coarse scale with nonequilibrium molecular dynamics at the fine scale. The novel concept of distributed coarse scale thermostats enables subsets of fine scale atoms to be attached to different coarse scale nodes which act as thermostats. The fine scale dynamics is driven by the coarse scale mean field. A coarse-grained Helmholtz free energy is used to derive macroscopic quantities. This new framework can reproduce the correct thermodynamics at the fine scale while providing an accurate coarse-grained result at the coarse scale.
Absolute line intensities for formic acid and dissociation constant of the dimer
Authors: Vander Auwera J. , Didriche K. , Perrin A. , Keller F.
Published: March 2007

Absolute line intensities in the ν6 and ν8 interacting bands of trans-HCOOH, observed near 1105.4 and 1033.5cm−1, respectively, and the dissociation constant of the formic acid dimer (HCOOH)2 have been measured using Fourier transform spectroscopy at a resolution of 0.002cm−1. Eleven spectra of formic acid, at 296.0(5)K and pressures ranging from 14.28(25)to314.0(24)Pa, have been recorded between 600 and 1900cm−1 with an absorption path length of 19.7(2)cm. 437 integrated absorption coefficients have been measured for 72 lines in the ν6 band. Analysis of the pressure dependence yielded the dissociation constant of the formic acid dimer, Kp=361(45)Pa, and the absolute intensity of the 72 lines of HCOOH. The accuracy of these results was carefully estimated. The absolute intensities of four lines of the weak ν8 band were also measured. Using an appropriate theory, the integrated intensity of the ν6 and ν8 bands was determined to be 3.47×10−17 and 4.68×10−19cm−1∕(moleculecm−2) respectively, at 296K. Both the dissociation constant and integrated intensities were compared to earlier measurements.
Vertical inertial sliding drive for coarse and fine approaches in scanning probe microscopy
Authors: Stieg A. Z. , Wilkinson P. , Gimzewski J. K.
Published: March 2007

Mechanisms for controlled approach of a probe tip toward the sample surface are essential in high resolution imaging by scanning probe microscopy (SPM). This work describes the development and performance of an inertial sliding drive capable of translating a relatively large mass (25g) at up to 1mm∕s over 1cm with step sizes of 10–250nm in ambient conditions using various wave forms as measured by fiber optic interferometry. The drive functions independent of orientation with a threshold voltage of less than 15V using a single drive signal. Use of piezotube actuators in a radially symmetric arrangement provides guided motion and minimizes differential thermal expansion between critical components. Controlled translation of the entire scanning component in both ambient and electrochemical scanning tunneling microscopy has been routinely achieved with no evidence of tip crash. This device has been specifically designed for use in in situ SPM applications where stability of the sample and that of the liquid environment are paramount.
Influence of the filling gas on plasma focus assisted diamondlike carbon coating at room temperature
Authors: Zeb Shaista , Murtaza Ghulam , Zakaullah M.
Published: March 2007

Amorphous diamondlike carbon films (up to 60 μm thick) are deposited by dense plasma focus system using nitrogen, methane, and neon gases. The peak intensity ratio of the D-band to G-band (ID/IG) and the G-peak position in the Raman spectra are used to characterize the films deposited on silicon substrate placed at different axial and angular positions with respect to focus axis. Stress and sp2 cluster size present in the films are discussed with shift in G-peak position, since higher sp2 content and residual compressive growth stress shifts the G-peak position to higher frequencies. The peak intensity ratio ID/IG is related to sp3/sp2 ratio to estimate the fourfold carbon networks. Thickness values obtained by cross-sectional scanning electron microscopy point toward the high film deposition rates. X-ray diffraction spectra verify the deposition of amorphous carbon a-C films which identifies no crystalline peak.
Magnetostatic bias in a composite hard/soft/hard microlayer
Authors: Kraus L. , Pirota K. R. , Torrejón J. , Vázquez M.
Published: March 2007

A composite magnetically hard/soft/hard trilayer ribbon with micrometric thickness has been prepared by combined melt-spinning and electroplating techniques. Its main peculiarities relate to the existence of a magnetic coupling between hard and soft magnetic phases resulting in bias magnetic field acting on the soft layer. A systematic study of the low-field hysteresis loops has been performed after premagnetizing under a direct current saturating field as a function of the geometrical dimensions of both types of layers. The analysis of the observed bias effect has allowed us to conclude the magnetostatic origin of the tailorable coupling. The present investigation in microscale system points out to the potential technological applications that in a further step can be developed in nanomagnetic systems.
Physical origin of residual thermal stresses in a multilayer ceramic capacitor
Authors: Shin Hyunho , Park Jong-Sung , Hong Kug Sun , Jung Hyun Suk , Lee Jung-Kun , Rhee Kyong Yop
Published: March 2007

The physical origin of the residual stresses developed in the ceramic layer of the active region in a multilayer ceramic capacitor was numerically investigated. The compressive in-plane stress components σ11 and σ22 originate without regard to the presence of the margins but rather from the difference in in-plane thermal shrinkage between ceramic and metal electrode. The out-of-plane stress component σ33 physically originates mainly through the presence of the housing margin; the presence of the lateral margin is a minor source: the more ceramic-rich margins hinder the apparent vertical shrinkage of the active region to yield tensile σ33.
Charge carrier generation and electron blocking at interlayers in polymer solar cells
Authors: Yin Chunhong , Pieper Björn , Stiller Burkhard , Kietzke Thomas , Neher Dieter
Published: March 2007

The authors show that an electron-donating polymer interlayer and a spin coated layer of an electron-accepting polymer form a defined polymer-polymer heterojunction. Directional photoinduced charge transfer and efficient electron blocking at this heterojunction is clearly seen in Kelvin probe measurements. The photocurrent characteristics of this well-defined bilayer structure as well as of the respective blend device can be consistently fitted by models taking into account only the field dependence of charge carrier generation. Apparently, the efficiency to form free carriers is the determining process in both types of polymer-polymer solar cell structures.
In situ azimuthal rotation device for linear dichroism measurements in scanning transmission x-ray microscopy
Authors: Hernández-Cruz D. , Hitchcock A. P. , Tyliszczak T. , Rousseau M.-E. , Pézolet M.
Published: March 2007

A novel miniature rotation device used in conjunction with a scanning transmission x-ray microscope is described. It provides convenient in situ sample rotation to enable measurements of linear dichroism at high spatial resolution. The design, fabrication, and mechanical characterization are presented. This device has been used to generate quantitative maps of the spatial distribution of the orientation of proteins in several different spider and silkworm silks. Specifically, quantitative maps of the dichroic signal at the C 1s→π*amide transition in longitudinal sections of the silk fibers give information about the spatial orientation, degree of alignment, and spatial distribution of protein peptide bonds. A new approach for analyzing the dichroic signal to extract orientation distributions, in addition to magnitudes of aligned components, is presented and illustrated with results from Nephila clavipes dragline spider silk measured using the in situ rotation device.
Electric energy density of dielectric nanocomposites
Authors: Li J. Y. , Zhang L. , Ducharme Stephen
Published: March 2007

Dielectric materials with large electric energy density are actively pursued for many applications. The authors analyze the effective permittivity, breakdown strength, and electric energy density of dielectric nanocomposites using an effective medium approximation, modeling the nanocomposite as a three-phase material by the double-inclusion method. The addition of nanoparticles enhances the permittivity but reduces the breakdown strength, making the potential gain in electric energy density small. In addition, the interfacial interaction shifts the “percolation” threshold toward lower volume fraction of nanoparticles. The analysis suggests that the microstructure of nanocomposites must be carefully controlled to maintain high dielectric strength and therefore realize enhanced electric energy density.
Vortex motion in chilarity-controlled pair of magnetic disks
Authors: Kimura T. , Otani Y. , Masaki H. , Ishida T. , Antos R. , Shibata J.
Published: March 2007

The authors investigate the influence of the vortex chirality on the magnetization processes of a magnetostatically coupled pair of magnetic disks. The magnetic vortices with opposite chiralities are realized by introducing asymmetry into the disks. The motion of the paired vortices are studied by measuring the magnetoresistance with a lock-in resistance bridge technique. The vortex annihilation process is found to depend on the moving directions of the magnetic vortices. The experimental results are well reproduced by the micromagnetic simulation.
Flow behavior of an Eyring fluid in a nanotube: The effect of the slip boundary condition
Authors: Yang Fuqian
Published: March 2007

The flow of an Eyring fluid in a nanotube is analyzed by using continuum mechanics. The results reveal that the Eyring fluid flows like a Newtonian fluid at small pressure gradient and a pluglike fluid at high pressure gradient. The flow rate of the Eyring fluid in the nanotube at high pressure gradient with the Navier slip condition is several orders of magnitude higher than the Hagen-Poiseuille result for the flow of Newtonian fluids in the nanotube. This trend is similar to the experimental results reported in literature, suggesting that the Eyring fluid can be used to model nanoscale fluid flow.
Ab initio study of the effects of orientation and corrugation for H2 adsorbed on polycyclic aromatic hydrocarbons
Authors: Donchev A. G.
Published: March 2007

This paper reports state-of-the-art ab initio calculations at the second order of Møller-Plesset perturbation theory of molecular hydrogen interaction with polycyclic aromatic hydrocarbons (PAHs) up to coronene (C24H12). The effects of both H2 orientation with respect to the PAH plane and of PAH corrugation have been carefully investigated. It was found that the energetic preference for the perpendicular H2 orientation over the parallel one decreases rapidly as the PAH grows. The detailed study of coronene-H2 potential energy surface has made it possible to estimate from first principles the graphite-H2 binding energy. This ab initio estimate is shown to be in fair agreement with experiment. As revealed by the example of benzene-H2 dimer, the electrostatic energy component plays an important role in PAH-H2 interactions, that stems largely from the charge penetration effect and, therefore, cannot be reproduced by the simple quadrupole-quadrupole interaction model.
Recognition of C-terminal amino acids in tubulin by pore loops in Spastin is important for microtubule severing
Authors: White Susan Roehl , Evans Katia J. , Lary Jeffrey , Cole James L. , Lauring Brett
Published: March 2007

Spastin, an AAA ATPase mutated in the neurodegenerative disease hereditary spastic paraplegia, severs microtubules. Many other AAA proteins form ring-shaped hexamers and contain pore loops, which project into the ring's central cavity and act as ratchets that pull on target proteins, leading, in some cases, to conformational changes. We show that Spastin assembles into a hexamer and that loops within the central pore recognize C-terminal amino acids of tubulin. Key pore loop amino acids are required for severing, including one altered by a disease-associated mutation. We also show that Spastin contains a second microtubule binding domain that makes a distinct interaction with microtubules and is required for severing. Given that Spastin engages the MT in two places and that both interactions are required for severing, we propose that severing occurs by forces exerted on the C-terminal tail of tubulin, which results in a conformational change in tubulin, which releases it from the polymer.
Cooperation of the Conserved Aspartate 439 and Bound Amino Acid Substrate Is Important for High-Affinity Na+ Binding to the Glutamate Transporter EAAC1
Authors: Tao Zhen , Grewer Christof
Published: March 2007

The neuronal glutamate transporter EAAC1 contains several conserved acidic amino acids in its transmembrane domain, which are possibly important in catalyzing transport and/or binding of co/countertransported cations. Here, we have studied the effects of neutralization by site-directed mutagenesis of three of these amino acid side chains, glutamate 373, aspartate 439, and aspartate 454, on the functional properties of the transporter. Transport was analyzed by whole-cell current recording from EAAC1-expressing mammalian cells after applying jumps in voltage, substrate, or cation concentration. Neutralization mutations in positions 373 and 454, although eliminating steady-state glutamate transport, have little effect on the kinetics and thermodynamics of Na+ and glutamate binding, suggesting that these two positions do not constitute the sites of Na+ and glutamate association with EAAC1. In contrast, the D439N mutation resulted in an approximately 10-fold decrease of apparent affinity of the glutamate-bound transporter form for Na+, and an ∼2,000-fold reduction in the rate of Na+ binding, whereas the kinetics and thermodynamics of Na+ binding to the glutamate-free transporter were almost unchanged compared to EAAC1WT. Furthermore, the D439N mutation converted l-glutamate, THA, and PDC, which are activating substrates for the wild-type anion conductance, but not l-aspartate, into transient inhibitors of the EAAC1D439 anion conductance. Activation of the anion conductance by l-glutamate was biphasic, allowing us to directly analyze binding of two of the three cotransported Na+ ions as a function of time and [Na+]. The data can be explained with a model in which the D439N mutation results in a dramatic slowing of Na+ binding and a reduced affinity of the substrate-bound EAAC1 for Na+. We propose that the bound substrate controls the rate and the extent of Na+ interaction with the transporter, depending on the amino acid side chain in position 439.
Is there a role for antioxidant carotenoids in limiting self-harming immune response in invertebrates?
Authors: Cornet Stéphane , Biard Clotilde , Moret Yannick
Published: March 2007

Innate immunity relies on effectors, which produce cytotoxic molecules that have not only the advantage of killing pathogens but also the disadvantage of harming host tissues and organs. Although the role of dietary antioxidants in invertebrate immunity is still unknown, it has been shown in vertebrates that carotenoids scavenge cytotoxic radicals generated during the immune response. Carotenoids may consequently decrease the self-harming cost of immunity. A positive relationship between the levels of innate immune defence and circulating carotenoid might therefore be expected. Consistent with this hypothesis, we show that the maintenance and use of the prophenoloxidase system strongly correlate with carotenoid concentration in haemolymph within and among natural populations of the crustacean
Gammarus pule
x.
Predicting conditions for migration: effects of density dependence and habitat quality
Authors: Taylor Caz M , Norris D. Ryan
Published: March 2007

Migration is widespread among animals, but the factors that influence the decision to migrate are poorly understood. Within a single species, populations may be completely migratory, completely sedentary or partially migratory. We use a population model to derive conditions for migration and demonstrate how migratory survival, habitat quality and density dependence on both the breeding and non-breeding grounds influence conditions for migration and the proportion of migrants within a population. Density dependence during the season in which migratory and sedentary individuals use separate sites is necessary for partial migration. High levels of density dependence at the non-shared sites widen the range of survival values within which we predict partial migration, whereas increasing the strength of density dependence at the shared sites narrows the range of survival values within which we predict partial migration. Our results have important implications for predicting how contemporary populations with variable migration strategies may respond to changes in the quality or quantity of habitat.
Evaluating molecular clock calibrations using Bayesian analyses with soft and hard bounds
Authors: Sanders Kate L , Lee Michael S.Y
Published: March 2007

A limiting factor in many molecular dating studies is shortage of reliable calibrations. Current methods for choosing calibrations (e.g. cross-validation) treat them as either correct or incorrect, whereas calibrations probably lie on a continuum from highly accurate to very poor. Bayesian relaxed clock analysis permits inclusion of numerous candidate calibrations as priors: provided most calibrations are reliable, the model appropriate and the data informative, the accuracy of each calibration prior can be evaluated. If a calibration is accurate, then the analysis will support the prior so that the posterior estimate reflects the prior; if a calibration is poor, the posterior will be forced away from the prior. We use this approach to test two fossil dates recently proposed as standard calibrations within vertebrates. The proposed bird–crocodile calibration (approx. 247 Myr ago) appears to be accurate, but the proposed bird–lizard calibration (approx. 255 Myr ago) is substantially too recent.
An integrated systems biology approach to understanding the rules of keratinocyte colony formation
Authors: Sun Tao , McMinn Phil , Coakley Simon , Holcombe Mike , Smallwood Rod , MacNeil Sheila
Published: March 2007

Closely coupledin vitroandin virtuomodels have been used to explore the self-organization of normal human keratinocytes (NHK). Although it can be observed experimentally, we lack the tools to explore many biological rules that govern NHK self-organization. An agent-based computational model was developed, based on rules derived from literature, which predicts the dynamic multicellular morphogenesis of NHK and of a keratinocyte cell line (HaCat cells) under varying extracellular Ca++concentrations. The model enablesin virtuoexploration of the relative importance of biological rules and was used to test hypothesesin virtuowhich were subsequently examinedin vitro. Results indicated that cell–cell and cell–substrate adhesions were critically important to NHK self-organization. In contrast, cell cycle length and the number of divisions that transit-amplifying cells could undergo proved non-critical to the final organization. Two further hypotheses, to explain the growth behaviour of HaCat cells, were exploredin virtuo—an inability to differentiate and a differing sensitivity to extracellular calcium.In vitroexperimentation provided some support for both hypotheses. For NHKs, the prediction was made that the position of stem cells would influence the pattern of cell migration post-wounding. This was then confirmed experimentally using a scratch wound model.
Topography, energy and the global distribution of bird species richness
Authors: Davies Richard G , Orme C. David L , Storch David , Olson Valerie A , Thomas Gavin H , Ross Simon G , Ding Tzung-Su , Rasmussen Pamela C , Bennett Peter M , Owens Ian P.F , Blackburn Tim M , Gaston Kevin J
Published: March 2007

A major goal of ecology is to determine the causes of the latitudinal gradient in global distribution of species richness. Current evidence points to either energy availability or habitat heterogeneity as the most likely environmental drivers in terrestrial systems, but their relative importance is controversial in the absence of analyses of global (rather than continental or regional) extent. Here we use data on the global distribution of extant continental and continental island bird species to test the explanatory power of energy availability and habitat heterogeneity while simultaneously addressing issues of spatial resolution, spatial autocorrelation, geometric constraints upon species' range dynamics, and the impact of human populations and historical glacial ice-cover. At the finest resolution (1°), topographical variability and temperature are identified as the most important global predictors of avian species richness in multi-predictor models. Topographical variability is most important in single-predictor models, followed by productive energy. Adjusting for null expectations based on geometric constraints on species richness improves overall model fit but has negligible impact on tests of environmental predictors. Conclusions concerning the relative importance of environmental predictors of species richness cannot be extrapolated from one biogeographic realm to others or the globe. Rather a global perspective confirms the primary importance of mountain ranges in high-energy areas.
No genomic mosaicism in a putative hybrid butterfly species
Authors: Kronforst Marcus R , Salazar Camilo , Linares Mauricio , Gilbert Lawrence E
Published: March 2007

Recent descriptions of hybrid animal species have spurred interest in this phenomenon, but little genomic data exist to support it. Here, we use frequency variation for 657 amplified fragment length polymorphism (AFLP) markers and DNA sequence variation from 16 genes to determine whether the genome ofHeliconius pachinus, a suspected hybrid butterfly species, is a mixture of the putative parental species,Heliconius cydnoandHeliconius melpomene. Despite substantial shared genetic variation among all three species, we show that the genome ofH. pachinusis not a mosaic; both AFLP and DNA sequence data overwhelmingly associateH. pachinuswith just one of the potential parents,H. cydno. This pattern also applies to the genewingless, which is tightly linked to the locus that determines forewing colour—one specificH. pachinustrait that has been hypothesized to have originated fromH. melpomene. As a whole, the data support a traditional, bifurcating model of speciation in whichH. pachinussplit from a common ancestor withH. cydnowithout a genetic contribution fromH. melpomene. However, comparison of our data to DNA sequence data for another putative hybridHeliconiusspecies,Heliconius heurippa, suggests that theH. heurippagenome may be a mosaic.
High relatedness selects against hypermutability in bacterial metapopulations
Authors: Harrison Freya , Buckling Angus
Published: March 2007

Mutation rate and cooperation have important ecological and evolutionary consequences and, moreover, can affect pathogen virulence. While hypermutability accelerates adaptation to novel environments, hypermutable lineages (‘mutators’) are selected against in well-adapted populations. Using the model organismPseudomonas aeruginosa, we previously demonstrated a further potential disadvantage to hypermutability, namely, that it can accelerate the breakdown of cooperation. We now investigate how this property of mutators can affect their persistence in metapopulations. Mutator and wild-type bacteria were competed for 250 generations in globally competing metapopulations, imposing conditions of high or low intra-deme relatedness. High relatedness favours cooperating groups, so we predicted that mutators should achieve lower equilibrium frequencies under high relatedness than under low relatedness. This was observed in our study. Consistent with our hypothesis, there was a positive correlation between mean mutator and cheat frequencies. We conclude that when dense population growth requires cooperation, and when cooperation is favoured (high relatedness), demes containing high frequencies of mutators are likely to be selected against because they also contain high frequencies of non-cooperating cheats. We have also identified conditions where mutator lineages are likely to dominate metapopulations; namely, when low relatedness reduces kin selection for cooperation. These results may help to explain clinical distributions of mutator bacteria.
First trace and body fossil evidence of a burrowing, denning dinosaur
Authors: Varricchio David J , Martin Anthony J , Katsura Yoshihiro
Published: March 2007

A fossil discovery in the mid-Cretaceous Blackleaf Formation of southwest Montana, USA, has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of
Oryctodromeus cubicularis
gen. et sp. nov., a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports
Oryctodromeus
as the burrow maker. Additionally,
Oryctodromeus
exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria. As with modern vertebrate cursors that dig, burrowing in
Oryctodromeus
may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous–Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality.
Secondary sexual ornamentation and non-additive genetic benefits of female mate choice
Authors: Reid Jane M
Published: March 2007

Ornamental secondary sexual traits are hypothesized to evolve in response to directional mating preferences for more ornamented mates. Such mating preferences may themselves evolve partly because ornamentation indicates an individual's additive genetic quality (good genes). While mate choice can also confer non-additive genetic benefits (compatible genes), the identity of the most ‘compatible’ mate is assumed to depend on the choosy individual's own genotype. It is therefore unclear how choice for non-additive genetic benefits could contribute to directional mating preferences and consequently the evolution of ornamentation. In free-living song sparrows (Melospiza melodia), individual males varied in their kinship with the female population. Furthermore, a male's song repertoire size, a secondary sexual trait, was negatively correlated with kinship such that males with larger repertoires were less closely related to the female population. After excluding close relatives as potential mates, individual females were on average less closely related to males with larger repertoires. Therefore, female song sparrows expressing directional preferences for males with larger repertoires would on average acquire relatively unrelated mates and produce relatively outbred offspring. Such non-additive genetic fitness benefits of directional mating preferences, which may reflect genetic dominance variance expressed in structured populations, should be incorporated into genetic models of sexual selection.
Chromosome painting among Proboscidea, Hyracoidea and Sirenia: support for Paenungulata (Afrotheria, Mammalia) but not Tethytheria
Authors: Pardini A.T , O'Brien P.C.M , Fu B , Bonde R.K , Elder F.F.B , Ferguson-Smith M.A , Yang F , Robinson T.J
Published: March 2007

Despite marked improvements in the interpretation of systematic relationships within Eutheria, particular nodes, including Paenungulata (Hyracoidea, Sirenia and Proboscidea), remain ambiguous. The combination of a rapid radiation, a deep divergence and an extensive morphological diversification has resulted in a limited phylogenetic signal confounding resolution within this clade both at the morphological and nucleotide levels. Cross-species chromosome painting was used to delineate regions of homology between
Loxodonta africana
(2
n
=56),
Procavia capensis
(2
n
=54),
Trichechus manatus latirostris
(2
n
=48) and an outgroup taxon, the aardvark (
Orycteropus afer
, 2
n
=20). Changes specific to each lineage were identified and although the presence of a minimum of 11 synapomorphies confirmed the monophyly of Paenungulata, no change characterizing intrapaenungulate relationships was evident. The reconstruction of an ancestral paenungulate karyotype and the estimation of rates of chromosomal evolution indicate a reduced rate of genomic repatterning following the paenungulate radiation. In comparison to data available for other mammalian taxa, the paenungulate rate of chromosomal evolution is slow to moderate. As a consequence, the absence of a chromosomal character uniting two paenungulates (at the level of resolution characterized in this study) may be due to a reduced rate of chromosomal change relative to the length of time separating successive divergence events.
Holocene radiative forcing impact of northern peatland carbon accumulation and methane emissions
Authors: FROLKING STEVE , ROULET NIGEL T.
Published: March 2007

Throughout the Holocene, northern peatlands have both accumulated carbon and emitted methane. Their impact on climate radiative forcing has been the net of cooling (persistent CO2uptake) and warming (persistent CH4emission). We evaluated this by developing very simple Holocene peatland carbon flux trajectories, and using these as inputs to a simple atmospheric perturbation model. Flux trajectories are based on estimates of contemporary CH4flux (15–50 Tg CH4 yr−1), total accumulated peat C (250–450 Pg C), and peatland initiation dates. The contemporary perturbations to the atmosphere due to northern peatlands are an increase of ∼100 ppbv CH4and a decrease of ∼35 ppmv CO2. The net radiative forcing impact northern peatlands is currently about −0.2 to −0.5 W m−2(a cooling). It is likely that peatlands initially caused a net warming of up to +0.1 W m−2, but have been causing an increasing net cooling for the past 8000–11 000 years. A series of sensitivity simulations indicate that the current radiative forcing impact is determined primarily by the magnitude of the contemporary methane flux and the magnitude of the total C accumulated as peat, and that radiative forcing dynamics during the Holocene depended on flux trajectory, but the overall pattern was similar in all cases.
CK17 and p16 expression patterns distinguish (atypical) immature squamous metaplasia from high‐grade cervical intraepithelial neoplasia (CIN III)
Authors: Regauer S , Reich O
Published: March 2007

Aims:  Atypical immature metaplasia (AIM) refers to a full‐thickness intraepithelial basaloid lesion in the uterine cervix that features both metaplasia and atypia and is therefore difficult to distinguish from high‐grade cervical intraepithelial neoplasia (CIN III). p16 is a marker for human papillomavirus (HPV)‐induced dysplasia. Cytokeratin (CK) 17 is a marker for cervical reserve (stem) cells, which give rise to metaplasia. The aim was to determine whether AIM can be reclassified into metaplasia and CIN III based on p16 and CK17 immunohistochemistry.

Material and results:  Seventy‐five cervical biopsy specimens, curettings and cone excisions containing varying proportions of dysplasia and metaplasia and 20 cases regarded as AIM were analysed immunohistochemically with antibodies to CK17, p16 and p63. In immature metaplasia all proliferating cells were immunoreactive with antibodies to CK17 and p63, while p16 was negative. All dysplastic cells of CIN III demonstrated uniform immunoreactivity for p16 and p63, but were CK17–. Based on the reciprocal immunoreactivity of p16 and CK17, 17/20 cases of AIM were reclassified as metaplasia (n = 10) and CIN III (n = 7). Three cases of AIM stained for both CK17 and p16 and were classified as CIN III.

Conclusion:  ‘AIM’ is a helpful histological descriptor but it should not be used as a final diagnosis. Immunohistochemistry for p16 and CK17 allows distinction between metaplasia and high‐grade CIN.
Heterogeneity of protein kinase C β2 expression in lymphoid malignancies
Authors: Decouvelaere A‐V , Morschhauser F , Buob D , Copin M C , Dumontet C
Published: March 2007

Aims:  Protein kinase C (PKC) β is an important regulator of lymphoid survival and its expression has been shown to be altered in lymphomas. The aim was to determine the expression of PKC β2 in various subtypes of lymphoproliferative diseases by immunohistochemistry.

Methods and results:  One hundred and forty archival samples representing various subtypes of lymphoproliferative diseases were analysed. Certain subtypes, such as mantle cell, lymphocytic or follicular lymphoma, were found to express PKC β2 in > 90% of the samples. In follicular lymphomas, the follicular lymphomatous areas were constantly labelled, whereas residual germinal centres remained negative. In follicular hyperplasia, PKC β2+ cells were found in the mantle and marginal zones. Most angioimmunoblastic T‐cell lymphomas, lymphoblastic T‐cell lymphomas and marginal zone/mucosa‐associated lymphoid tissue (MALT) lymphomas were labelled with anti‐PKC βII antibody, but the pattern of expression was more heterogeneous in these subtypes. A minority of diffuse large B‐cell lymphomas were stained and most plasma cell malignancies were negative. None of the cases of Hodgkin's disease and anaplastic large cell lymphoma expressed PKC β2.

Conclusions:  PKC β2 expression varies significantly among lymphoproliferative diseases. In our series, the highest level of expression was found in mantle cell lymphomas and chronic lymphocytic lymphoma.
Does a ruderal strategy dominate the endemic flora of the West African forests?
Authors: Holmgren Milena , Poorter Lourens
Published: March 2007

Aim To understand the distribution pattern of endemic plant species in West African rain forests, one of the global priority areas for biodiversity conservation.

Location Upper Guinean forests, West Africa (Senegal, Guinea‐Bissau, Guinea, Sierra Leone, Liberia, Côte d'Ivoire, Ghana and Togo).

Methods We used herbarium collections from the whole Upper Guinean region (sensuWhite 1981) to analyse the distribution patterns of 216 vascular plant species (approximately one‐third of the endemic flora ranging from herbs to trees) that are restricted to these rain forests. We related species distribution ranges and species commonness to the main environmental variables and species life‐history traits.

Results We found that most endemic species of West African forests have large distribution ranges and ruderal strategies. Among all plant life‐forms, species with small ranges were restricted to very moist places whereas more widespread species were less dependent on the availability of water. These more common species seem able to tolerate drier conditions, indicated by the minimum rainfall conditions where they are found and the positive correlation with local habitat openness. Light‐demanding endemics were more common and widespread than shade‐tolerant species, and there was a trend towards wind‐dispersed species having a higher proportion of records in open places. This suggests that how widespread and common an endemic species is depends on being able to tolerate open and drier conditions.

Main conclusions A ruderal strategy seems to be key for understanding the success of endemics in the Upper Guinean forests, and indicates the important role of disturbances in shaping the composition of these tropical forests. Our results have large implications for predicting the potential effect of increasing drought on rare endemic plant species of West African forests.
Phylogeographical and speciation patterns in subterranean worm lizards of the genus Blanus (Amphisbaenia: Blanidae)
Authors: ALBERT E. M. , ZARDOYA R. , GARCÍA‐PARÍS M.
Published: March 2007

The peculiar lifestyle of subterranean reptiles must determine their modes of speciation and diversification. To further understand the evolutionary biology of subterranean reptiles, we studied the phylogeny of worm lizards of the genus Blanus and the phylogeography of its Iberian representatives. We used mitochondrial (ND4 and 16S rRNA) and nuclear (anonymous) partial gene sequences to resolve phylogenetic relationships within Blanus. The Eastern Mediterranean Blanus strauchi was recovered as sister group of Western Mediterranean species. Iberian and North African Blanus were recovered as reciprocally monophyletic groups. The same genes were used to determine phylogeography of 47 populations of Blanus cinereus. Mitochondrial and nuclear sequence data recovered two highly supported Iberian clades. Parapatry and high sequence divergences between them suggest that these clades may represent independent taxonomic units. A molecular clock was calibrated considering that the split between Iberian and North African Blanus was due to the re‐opening of the Betic Strait in the Upper Tortonian (8–9 million years ago). Differentiation between the two Iberian clades was estimated to date back to 5.2 million years ago. The Central Iberian clade included five mitochondrial haplotype lineages (A–E). Geographical ranges of two of them broadly overlap in the central Iberian plateau. After testing alternative hypotheses, the most likely explanation for this striking phylogeographical pattern involves recent dispersal of one of the lineages (C) over the geographical range of the other (B). The inferred recent dispersal of this fossorial reptile is explained in terms of demographic advantages associated to underground lifestyle.
The expression of BAFF‐binding receptors is not altered in multiple sclerosis or myasthenia gravis
Authors: Thangarajh M. , Kisiswa L. , Pirskanen R. , Hillert J.
Published: March 2007

Multiple sclerosis (MS) is a chronic, progressive disease of the central nervous system (CNS) characterized by consistent myelin injury. Antibody‐mediated death of oligodendrocytes is a pathological feature in a subset of MS patients and may be of relevance to disease pathogenesis. In myasthenia gravis (MG), acetylcholine receptors (AChR) situated at the neuromuscular endplate are destroyed by autoreactive antibodies. B‐cell activating factor of the tumour necrosis factor (TNF) superfamily (BAFF) is essential for B‐cell survival. Using flow cytometry, we evaluated the expression of three BAFF‐binding receptors, namely, BAFF‐receptor (BAFF‐R), B‐cell maturation antigen (BCMA), and transmembrane activator and calcium modulating and cyclophilin ligand interactor (TACI) in peripheral‐blood lymphocytes. Nearly all CD19+ B cells and CD19+CD27+ memory B cells expressed BAFF‐R. The intensity of BAFF‐R expression was not statistically different in MS or MG compared with healthy controls. Very few T cells expressed BAFF‐R. BCMA expression was strictly limited to B cells. Although both B and T cells expressed TACI, levels were much higher on B cells compared with levels on T cells. The percentages of B and T cells expressing BCMA and TACI did not differ significantly in MS or MG versus controls. We conclude that the expression of BAFF‐binding receptors is not appreciably altered in MS or MG.
Loss‐of‐function mutations in the Nav1.7 gene underlie congenital indifference to pain in multiple human populations
Authors: Goldberg YP , MacFarlane J , MacDonald ML , Thompson J , Dube M‐P , Mattice M , Fraser R , Young C , Hossain S , Pape T , Payne B , Radomski C , Donaldson G , Ives E , Cox J , Younghusband HB , Green R , Duff A , Boltshauser E , Grinspan GA , Dimon JH , Sibley BG , Andria G , Toscano E , Kerdraon J , Bowsher D , Pimstone SN , Samuels ME , Sherrington R , Hayden MR
Published: March 2007

Congenital indifference to pain (CIP) is a rare condition in which patients have severely impaired pain perception, but are otherwise essentially normal. We identified and collected DNA from individuals from nine families of seven different nationalities in which the affected individuals meet the diagnostic criteria for CIP. Using homozygosity mapping and haplotype sharing methods, we narrowed the CIP locus to chromosome 2q24–q31, a region known to contain a cluster of voltage‐gated sodium channel genes. From these prioritized candidate sodium channels, we identified 10 mutations in the SCN9A gene encoding the sodium channel protein Nav1.7. The mutations completely co‐segregated with the disease phenotype, and nine of these SCN9A mutations resulted in truncation and loss‐of‐function of the Nav1.7 channel. These genetic data further support the evidence that Nav1.7 plays an essential role in mediating pain in humans, and that SCN9A mutations identified in multiple different populations underlie CIP.