bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency-temperature response of ferroelectromagnetic Pb(Fe1∕2Nb1∕2)O3 ceramics obtained by different precursors. Part I. Structural and thermo-electrical characterization
Authors: Raymond O. , Font R. , Suárez-Almodovar N. , Portelles J. , Siqueiros J. M.
Published: April 2005

With the purpose of fabricating ceramics where ferroelectric and magnetic order coexist, ceramics of Pb(Fe1∕2Nb1∕2)O3 have been prepared using the traditional ceramic method following three different routes. The first is a direct via starting from oxide reagents and the other two use different kinds of FeNbO4 precursors with either monoclinic or orthorhombic structures. Crystallographic and surface morphological studies were carried out by the powder x-ray diffraction and scanning microscopy techniques. The presence of Fe2+, detrimental to the ferroelectric and magnetic performance, was evaluated by x-ray photoelectron spectroscopy. The samples showed no structural differences, uniformly distributed grains, a ferro-paraelectric transition temperature at 110°C and a normal diffuse phase transition (nonrelaxor behavior). Differences in the degree of diffuseness, densities and grain size were observed depending on the kind of precursor. Measurements of dc and ac electrical resistivity, dielectric constant and dielectric loss were made as functions of temperature from room temperature to 250°C, at different frequency values (between 20Hz and 1MHz). Four conduction mechanisms were identified: hopping charge corresponding to low temperatures, small polarons and oxygen vacancies conduction at intermediate temperatures, and intrinsic ionic conduction at high temperatures. The best set of values of dielectric loss and dielectric constant, from the ferroelectricity point of view, were obtained when the precursor with orthorhombic structure was employed.
Microstructural and morphological properties of homoepitaxial (001)ZnTe layers investigated by x-ray diffuse scattering
Authors: Di Luccio T. , Scalia G. , Tapfer L. , Morales P. , Traversa M. , Prete P. , Lovergine N.
Published: April 2005

The microstructural and morphological properties of homoepitaxial (001)ZnTe layers grown by metalorganic vapor phase epitaxy at a temperature (TG) between 325°C and 400°C are investigated by x-ray diffuse scattering. High resolution reciprocal space maps (RSMs) recorded close to the ZnTe (004) Bragg peak show different diffuse scattering features that can be ascribed to (i) the specific surface morphology of the sample, and (ii) the presence of extended lattice defects in the epilayers. One kind of cross-shaped diffuse scattering streaks, appearing for TG⩾350°C, extend along ⟨111⟩ directions and can be attributed to stacking faults (SFs) occurring at the epilayer–substrate interface, within the epilayers. The SF diameter was estimated around 200–300nm, while their density increases with TG. Another kind of cross-shaped diffuse streaks, inclined at an angle β≈80° with respect to the ⟨110⟩ in-plane direction, arises from the morphology of epilayers grown above 360°C, their surfaces being covered by pairs of pyramidal hillocks up to a density of 106–107cm−2. Atomic force microscopy (AFM) measurements showed that the apex angles of the pyramids compare well with the value of 2β. The hillock formation is ascribed to Te adatoms experiencing a Schwoebel potential barrier at the step edges around pairs of partial dislocations (dipoles) bounding the SFs. In a quite narrow growth temperature interval around 350°C no β-crossed diffuse streaks are instead observed in the RSMs, indicating a smooth ZnTe surface. Finally, at a lower growth temperature (TG=325°C) a diffuse scattering intensity distribution defined by an angle γ≈63° with respect to the ⟨110⟩ in-plane direction is observed, corresponding to a dense ridging of the epilayer surface along the perpendicular direction. Both RSM analysis and AFM measurements indicate that the ridge sidewalls are {113} planes.
Superdipole liquid scenario for the dielectric primary relaxation in supercooled polar liquids
Authors: Huang Y. N. , Wang C. J. , Riande E.
Published: April 2005

We propose a dynamic structure of coupled dynamic molecular strings for supercooled small polar molecule liquids and accordingly we obtain the Hamiltonian of the rotational degrees of freedom of the system. From the Hamiltonian, the strongly correlated supercooled polar liquid state is renormalized to a normal superdipole liquid state. This scenario describes the following main features of the primary or α-relaxation dynamics in supercooled polar liquids: (1) the average relaxation time evolves from a high temperature Arrhenius to a low temperature non-Arrhenius or super-Arrhenius behavior; (2) the relaxation function crosses over from the high temperature exponential to low temperature nonexponential form; and (3) the temperature dependence of the relaxation strength shows non-Curie features. According to the present model, the crossover phenomena of the first two characteristics arise from the transition between the superdipole gas and the superdipole liquid. The model predictions are quantitatively compared with the experimental results of glycerol, a typical glass former.
Plane wave/pseudopotential implementation of excited state gradients in density functional linear response theory: A new routevia implicit differentiation
Authors: Doltsinis Nikos L. , Kosov D. S.
Published: April 2005

This work presents the formalism and implementation of excited state nuclear forces within density functional linear response theory using a plane wave basis set. An implicit differentiation technique is developed for computing nonadiabatic coupling between Kohn–Sham molecular orbital wave functions as well as gradients of orbital energies which are then used to calculate excited state nuclear forces. The algorithm has been implemented in a plane wave/pseudopotential code taking into account only a reduced active subspace of molecular orbitals. It is demonstrated for the H2 and N2 molecules that the analytical gradients rapidly converge to the exact forces when the active subspace of molecular orbitals approaches completeness.
A reliable ab initio potential energy surface and vibrational states for the ground electronic state of HgH2(XΣg+1)
Authors: Li Hui , Xie Daiqian , Guo Hua
Published: April 2005

A three-dimensional global potential energy surface for the ground (XΣg+1) electronic state of HgH2 is constructed from more than 13 000 ab initio points. These points are generated using an internally contracted multireference configuration interaction method with the Davidson correction and a large basis set. Low-lying vibrational energy levels of HgH2, HHgD, and HgD2 calculated using the Lanczos algorithm are found to be in good agreement with the available experimental band origins. The majority of the vibrational energy levels up to 9000cm−1 are assigned with normal mode quantum numbers. Our results indicate a gradual transition for the stretching vibrations from the normal mode regime at low energies to the local mode regime near 9000 and 8000cm−1 for HgH2 and HgD2, respectively, as evidenced by a decreasing energy gap between the (0,0,n3) and (1,0,n3−1) vibrational states and bifurcation of the corresponding wave functions.
The symmetries of the Dirac–Pauli equation in two and three dimensions
Authors: Adam C. , Sánchez-Guillén J.
Published: April 2005

We calculate all symmetries of the Dirac–Pauli equation in two-dimensional and three-dimensional Euclidean space. Further, we use our results for an investigation of the issue of zero mode degeneracy. We construct explicitly a class of multiple zero modes with their gauge potentials.
Central potentials on spaces of constant curvature: The Kepler problem on the two-dimensional sphere S2 and the hyperbolic plane H2
Authors: Cariñena José F. , Rañada Manuel F. , Santander Mariano
Published: April 2005

The Kepler problem is a dynamical system that is well defined not only on the Euclidean plane but also on the sphere and on the hyperbolic plane. First, the theory of central potentials on spaces of constant curvature is studied. All the mathematical expressions are presented using the curvature κ as a parameter, in such a way that they reduce to the appropriate property for the system on the sphere S2, or on the hyperbolic plane H2, when particularized for κ>0, or κ<0, respectively; in addition, the Euclidean case arises as the particular case κ=0. In the second part we study the main properties of the Kepler problem on spaces with curvature, we solve the equations and we obtain the explicit expressions of the orbits by using two different methods, first by direct integration and second by obtaining the κ-dependent version of the Binet’s equation. The final part of the paper, that has a more geometric character, is devoted to the study of the theory of conics on spaces of constant curvature.
Charge-trapping device structure of SiO2∕SiN∕high-k dielectric Al2O3 for high-density flash memory
Authors: Lee Chang-Hyun , Hur Sung-Hoi , Shin You-Cheol , Choi Jeong-Hyuk , Park Dong-Gun , Kim Kinam
Published: April 2005

We present a device structure of SiO2∕SiN∕Al2O3 (SANOS). The use of a high-k dielectric material, specially Al2O3, in the blocking oxide concentrates the electric fields across the tunnel oxide and SiN, and releases it across the blocking oxide under program and erase mode. This effect leads to lower program and erase voltage as well as faster erase speed than the conventional SiO2∕SiN∕SiO2 (SONOS) device. Moreover, it is shown that the fast erase operation is performed even at a thicker tunnel oxide over 30Å where the hole direct tunneling current through the tunnel oxide is reduced significantly and thus the SANOS device has the excellent bake retention.
Improvement of recoverability of a nanoporous energy absorption system by using chemical admixture
Authors: Kong X. , Qiao Y.
Published: April 2005

In this paper, the behaviors of nanoporous energy absorption systems subjected to cyclic loadings are investigated. The systems consist of hydrophobic mesoporous silica particles immersed in aqueous solutions of sodium chloride (NaCl). In the first loading-unloading loop, increasing NaCl concentration, c, causes only slight increases in infiltration pressure and energy absorption efficiency. In the following loops, however, the system behaviors are strongly dependent on c. As c increases from 0%to25.9wt.%, the recoverability is improved by a factor of 3, indicating clearly that the addition of NaCl has a beneficial effect to promoting the outflow in the nanoenvironment.
Waveguide dye laser including a SiO2 nanoparticle-dispersed random scattering active layer
Authors: Watanabe Hirofumi , Oki Yuji , Maeda Mitsuo , Omatsu Takashige
Published: April 2005

We presented a dual-layered waveguide dye laser including a random active layer with nanoparticle doping. A slope efficiency of 12.0% and an energy threshold of 0.34μJ were obtained in a single-longitudinal-mode operation.
Pretransitional enhancement of the optical nonlinearity of thin dye-doped liquid crystals in the nematic phase
Authors: Lucchetti L. , Gentili M. , Simoni F.
Published: April 2005

We report a critical enhancement of the nonlinear optical response of dye-doped liquid crystals obtained by approaching the clearing point in the nematic phase. The enhancement of the nonlinear diffraction efficiency has been measured in the range 0.2–0.3 deg below the nematic-isotropic transition temperature. It allows reaching a nonlinear refractive index higher than 40cm2∕W in all the tested cells.
Tunable gap in the transmission spectrum of a periodic waveguide
Authors: Pogrebnyak Victor A. , Akray Eser , Küçükaltun A. Neşet
Published: April 2005

Wave phenomena in a planar periodically corrugated waveguide are investigated experimentally at the microwave range of frequency. Measurements of the transmission properties show that the location of the gap in the frequency spectrum as well as its width depends on the relative position of two corrugated plates. The transmission varies from zero to a maximum value upon a shift of one periodic plate with respect to another on the half period of the corrugation. The results confirm the theoretical prediction of the geometry-driven spectrum transformation from a band-structure form to a gapless one upon such a shift of the plates. In physics of solids, this transformation corresponds to metal–insulator transition.
Auditory Saltation in the Vertical Midsagittal Plane
Authors: Boehnke Susan E , Phillips Dennis P
Published: April 2005

Auditory saltation is an illusion in which a train of clicks, the first half of which is presented at one location and the other half of which is presented from a second location, is perceived as originating not only from the anchor points, but also from locations between them. That is, intermediate members of the series of clicks have their spatial locations systematically misperceived. In the present study, auditory saltation was examined for the first time in the vertical midsagittal plane. Subjects rated the perceived continuity of motion for 8-click trains systematically varied in inter-click interval (ICI), direction of motion (up, down), and trial type (‘saltation’ versus ‘real’ motion). In all listeners, saltation stimuli supported robust saltation, but only for trials with ICIs less than about 120 ms. Real motion was rated as continuous for all ICIs. These data indicate that the auditory-saltation illusion can exploit monaural stimulus cues for source location in the generation of the illusory motion percept.
Visual Analysis of Changes of Motion in Reaction-Time Tasks
Authors: Mateeff Stefan , Genova Biljana , Hohnsbein Joachim
Published: April 2005

Subjects observed a random-dot pattern moving uniformly in the vertical direction (vector V1). The motion vector abruptly changed to V2, both in speed and direction simultaneously. It was found that the time of simple reaction to such changes V1 → V2 can be described by a function of a single variable, | w( V1 — V2C) + (1 – w) V2N|, 0 < w < 0.5, where V2C and V2N are the components of V2 collinear with and normal to V1. The choice-reaction time for changes in direction that are accompanied by changes in speed can be described by a function solely of the absolute value of V2N. Unlike the simple-reaction time, the choice-reaction time was independent of the initial speed of motion. The processes that may be engaged in simple and choice reactions to motion are discussed.
Effect of Attention on the Detection and Identification of Masked Spatial Patterns
Authors: Põder Endel
Published: April 2005

The effect of attention on the detection and identification of vertically and horizontally oriented Gabor patterns in the condition of simultaneous masking with obliquely oriented Gabors was studied. Attention was manipulated by varying the set size in a visual-search experiment. In the first experiment, small target Gabors were presented on the background of larger masking Gabors. In the detection task, the effect of set size was as predicted by unlimited-capacity signal detection theory. In the orientation identification task, increasing the set size from 1 to 8 resulted in a much larger decline in performance. The results of the additional experiments suggest that attention can reduce the crowding effect of maskers.
The Trajectory Effect in Intermodal Temporal Order Judgments
Authors: Craig James C
Published: April 2005

Subjects judged which one of two patterns, a visual or a tactile pattern, had been presented first. The visual and tactile displays were placed in close spatial proximity. The patterns appeared to move across their respective displays. Although irrelevant to the temporal order judgment (TOJ), the direction of motion of the patterns—the trajectory—affected the judgments. When the leading pattern was moving towards the trailing pattern (consistent movement), subjects tended to judge it, correctly, as leading. When the leading pattern was moving away from the trailing pattern (inconsistent movement), subjects tended to judge it, incorrectly, as trailing. Changing the spatial position of the arrays such that the pattern trajectories were no longer towards one another eliminated the effect of movement on TOJs. Although there was a substantial difference in performance on consistent and inconsistent trials, there were no differences in subjects' ratings of their performances. The results demonstrate that the trajectory effect can be obtained multimodally. The issues whether the effect of motion alters the perceived temporal separation between the visual and tactile patterns, and whether the visual and tactile patterns are represented by a common framework, are discussed.
Reaction coordinates and rates from transition paths
Authors: Best Robert B. , Hummer Gerhard
Published: April 2005

The molecular mechanism of a reaction in solution is reflected in its transition-state ensemble and transition paths. We use a Bayesian formula relating the equilibrium and transition-path ensembles to identify transition states, rank reaction coordinates, and estimate rate coefficients. We also introduce a variational procedure to optimize reaction coordinates. The theory is illustrated with applications to protein folding and the dipole reorientation of an ordered water chain inside a carbon nanotube. To describe the folding of a simple model of a three-helix bundle protein, we variationally optimize the weights of a projection onto the matrix of native and nonnative amino acid contacts. The resulting one-dimensional reaction coordinate captures the folding transition state, with formation and packing of helix 2 and 3 constituting the bottleneck for folding.
Comparative study of generalized Born models: Protein dynamics
Authors: Fan Hao , Mark Alan E. , Zhu Jiang , Honig Barry
Published: April 2005

In this work, we compare the results of molecular dynamics simulations involving the application of three generalized Born (GB) models to 10 different proteins. The three GB models, the Still, HCT, and modified analytical generalized Born models, were implemented in the computationally efficient
gromacs
package. The performance of each model was assessed from the backbone rms deviation from the native structure, the number of native hydrogen bonds retained in the simulation, and the experimental and calculated radius of gyration. Analysis of variance (ANOVA) was used to analyze the results of the simulations. The rms deviation measure was found to be unable to distinguish the quality of the results obtained with the three different GB models, whereas the number of native hydrogen bonds and radius of gyration yielded a statistically meaningful discrimination among models. Our results suggest that, of the three, modified analytical generalized Born yields the best agreement between calculated and experimentally derived structures. More generally, our study highlights the need both to evaluate the effects of different variables on the results of simulations and to verify that the results of molecular dynamics simulations are statistically meaningful.
Structure theorems and the dynamics of nitrogen catabolite repression in yeast
Authors: Boczko Erik M. , Cooper Terrance G. , Gedeon Tomas , Mischaikow Konstantin , Murdock Deborah G. , Pratap Siddharth , Wells K. Sam
Published: April 2005

By using current biological understanding, a conceptually simple, but mathematically complex, model is proposed for the dynamics of the gene circuit responsible for regulating nitrogen catabolite repression (NCR) in yeast. A variety of mathematical “structure” theorems are described that allow one to determine the asymptotic dynamics of complicated systems under very weak hypotheses. It is shown that these theorems apply to several subcircuits of the full NCR circuit, most importantly to the URE2–GLN3 subcircuit that is independent of the other constituents but governs the switching behavior of the full NCR circuit under changes in nitrogen source. Under hypotheses that are fully consistent with biological data, it is proven that the dynamics of this subcircuit is simple periodic behavior in synchrony with the cell cycle. Although the current mathematical structure theorems do not apply to the full NCR circuit, extensive simulations suggest that the dynamics is constrained in much the same way as that of the URE2–GLN3 subcircuit. This finding leads to the proposal that mathematicians study genetic circuits to find new geometries for which structure theorems may exist.
Common chromosomal fragile site FRA16D mutation in cancer cells
Authors: Finnis Merran , Dayan Sonia , Hobson Lynne , Chenevix-Trench Georgia , Friend Kathryn , Ried Karin , Venter Deon , Woollatt Erica , Baker Elizabeth , Richards Robert I.
Published: April 2005

Neither the molecular basis for common fragile site DNA instability nor the contribution of this form of chromosomal instability to cancer is clearly understood. Fragile site FRA16D (16q23.2) is within regions of frequent loss-of-heterozygosity (LOH) in breast and prostate cancers, is associated with homozygous deletions in various adenocarcinomas and t(14;16) chromosomal translocations in multiple myeloma. The FOR (WWOX) gene spans FRA16D and encodes a partner of p53 that also has a role in apoptosis. Previously untested 53 cancer cell lines were screened for deletions within the FOR/WWOX gene. Deletions were detected in Co115, KM12C and KM12SM. Homozygous deletions in these and two previously identified tumour cell lines were intragenic on both alleles, indicating a distinct mutation mechanism from that causing LOH. Identical FRA16D deletions in two cell lines (one derived from the primary carcinoma and the other from a secondary metastasis) demonstrate that FRA16D DNA instability can be an early, transient event. Sequence analysis across one deletion locates one endpoint within a polymorphic AT-dinucleotide repeat and the other adjacent to an AT-rich mini-satellite repeat implicating AT-rich repeats in FRA16D DNA instability. Another deletion is associated with de novo repetition of the 9 bp AT-rich sequence at one of the deletion endpoints. FRA16D deleted cells retain cytogenetic fragile site expression indicating that the deletions are susceptible sites for breakage rather than regions that confer fragility. Most cell lines with FRA16D homozygous deletions also have FRA3B deletions, therefore common fragile sites represent highly susceptible genome-wide targets for a distinct form of mutation.
Catching Proteus: the collaborations of Wallis and Brounker. I. Squaring the circle
Authors: Stedall Jacqueline A.
Published: April 2005

William Brouncker (
ca.
1620–1684) was the inaugural President of The Royal Society, and John Wallis (1616–1703) one of its founder members. The two collaborated closely during the 1650s on some original and unusual mathematics, but while Wallis acquired a lasting reputation, Brouncker's work is no longer well known. The two parts of this paper analyse the joint work of Wallis and Brouncker and attempt to separate their respective contributions and very different mathematical styles. The main subject of Part I is Brouncker's discovery of continued fractions. He gave few clues as to how he obtained his results and I offer a possible reconstruction of his work. His quadrature of the hyperbola and rectification of the semicubical parabola are also discussed. Brouncker emerges as a skilled and intuitive mathematician.
The growth of shear bands in the catastrophic failure of soils
Authors: Puzrin A.M , Germanovich L.N
Published: April 2005

This paper is an attempt to apply the Palmer–Rice fracture mechanics approach to the shear band propagation in sands and normally consolidated clays. This approach, proposed 30 years ago for overconsolidated clays, had a tremendous advantage of treating a shear band evolution as a true physical process and not just as a sufficient mathematical condition for its existence. Extension of this approach to a wider variety of soils requires for non-elastic soil properties (e.g. isotropic hardening plasticity, strain softening, lack of tensile strength, dilatancy, active and passive failure modes, etc.) to be taken into account. This paper demonstrates how the energy balance and process zone approaches can be applied to the simple problem of the shallow shear band propagation in an infinite slope built of such a soil. The energy balance approach appears to be the most conservative one. It allows for catastrophic and progressive types of soil failure to be properly identified, and dramatically effects the results of the slope stability analysis.
Energy bounds for some non-standard problems in thermoelasticity
Authors: Quintanilla R , Straughan B
Published: April 2005

A.E. Green F.R.S. and P.M. Naghdi developed two theories of thermoelasticity, called type II and type III, which are likely to be more natural candidates for the identification of a thermoelastic body than the usual theory. We here derive energy bounds for a class of problem in which the ‘initial data’ are given as a combination of data at timet=0 and at a later timet=T. Such problems are in vogue in the mathematical literature and may be used, for example, to give estimates of solution behaviour in an improperly posed problem where one wishes to continue a solution backward in time.
Trapped modes in curved elastic plates
Authors: Gridin Dmitri , Craster Richard V , Adamou Alexander T.I
Published: April 2005

We investigate the existence of trapped modes in elastic plates of constant thickness, which possess bends of arbitrary curvature and flatten out at infinity; such trapped modes consist of finite energy localized in regions of maximal curvature. We present both an asymptotic model and numerical evidence to demonstrate the trapping. In the asymptotic analysis we utilize a dimensionless curvature as a small parameter, whereas the numerical model is based on spectral methods and is free of the small-curvature limitation. The two models agree with each other well in the region where both are applicable. Simple existence conditions depending on Poison's ratio are offered, and finally, the effect of energy build-up in a bend when the structure is excited at a resonant frequency is demonstrated.
MHC odours are not required or sufficient for recognition of individual scent owners
Authors: Hurst Jane L , Thom Michael D , Nevison Charlotte M , Humphries Richard E , Beynon Robert J
Published: April 2005

To provide information about specific depositors, scent marks need to encode a stable signal of individual ownership. The highly polymorphic major histocompatibility complex (MHC) influences scents and contributes to the recognition of close kin and avoidance of inbreeding when MHC haplotypes are shared. MHC diversity between individuals has also been proposed as a primary source of scents used in individual recognition. We tested this in the context of scent owner recognition among male mice, which scent mark their territories and countermark scents from other males. We examined responses towards urine scent according to the scent owner's genetic difference to the territory owner (MHC, genetic background, both and neither) or genetic match to a familiar neighbour. While urine of a different genetic background from the subject always stimulated greater scent marking than own, regardless of familiarity, MHC-associated odours were neither necessary nor sufficient for scent owner recognition and failed to stimulate countermarking. Urine of a different MHC type to the subject stimulated increased investigation only when this matched both the MHC and genetic background of a familiar neighbour. We propose an associative model of scent owner recognition in which volatile scent profiles, contributed by both fixed genetic and varying non-genetic factors, are learnt in association with a stable involatile ownership signal provided by other highly polymorphic urine components.
Cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus)
Authors: Arrese Catherine A , Oddy Alison Y , Runham Philip B , Hart Nathan S , Shand Julia , Hunt David M , Beazley Lyn D
Published: April 2005

The potential for trichromacy in mammals, thought to be unique to primates, was recently discovered in two Australian marsupials. Whether the presence of three cone types, sensitive to short- (SWS), medium- (MWS) and long- (LWS) wavelengths, occurs across all marsupials remains unknown. Here, we have investigated the presence, distribution and spectral sensitivity of cone types in two further species, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus). Immunohistochemistry revealed that SWS cones in the quokka are concentrated in dorso-temporal retina, while in the quenda, two peaks were identified in naso-ventral and dorso-temporal retina. In both species, MWS/LWS cone spatial distributions matched those of retinal ganglion cells. Microspectrophotometry (MSP) confirmed that MWS and LWS cones are spectrally distinct, with mean wavelengths of maximum absorbance at 502 and 538 nm in the quokka, and at 509 and 551 nm, in the quenda. Although small SWS cone outer segments precluded MSP measurements, molecular analysis identified substitutions at key sites, accounting for a spectral shift from ultraviolet in the quenda to violet in the quokka.

The presence of three cone types, along with previous findings in the fat-tailed dunnart and honey possum, suggests that three spectrally distinct cone types are a feature spanning the marsupials.
A comparative analysis of the evolutionary relationship between diet and enzyme targeting in bats, marsupials and other mammals
Authors: Birdsey Graeme M , Lewin Jackie , Holbrook Joanna D , Simpson Victor R , Cunningham Andrew A , Danpure Christopher J
Published: April 2005

The subcellular distribution of the enzyme alanine : glyoxylate aminotransferase (AGT) in the livers of different mammals appears to be related to their natural diets. Thus, AGT tends to be mitochondrial in carnivores, peroxisomal in herbivores, and both mitochondrial and peroxisomal in omnivores. To what extent this relationship is an incidental consequence of phylogenetic structure or an evolutionarily meaningful adaptive response to changes in dietary selection pressure is unknown. In order to distinguish between these two possibilities, we have determined the subcellular distribution of AGT in the livers of 22 new mammalian species, including members of three orders not studied before. In addition, we have analysed the statistical relationship between AGT distribution and diet in all 77 mammalian species, from 12 different orders, for which the distribution is currently known. Our analysis shows that there is a highly significant correlation between AGT distribution and diet, independent of phylogeny. This finding is compatible with the suggestion that the variable intracellular targeting of AGT is an adaptive response to episodic changes in dietary selection pressure. To our knowledge, this is the first example of such a response being manifested at the molecular and cellular levels across the breadth of Mammalia.
Monitoring change in the abundance and distribution of insects using butterflies and other indicator groups
Authors: Thomas J.A
Published: April 2005

Conservative estimates suggest that 50–90% of the existing insect species on Earth have still to be discovered, yet the named insects alone comprise more than half of all known species of organism. With such poor baseline knowledge, monitoring change in insect diversity poses a formidable challenge to scientists and most attempts to generalize involve large extrapolations from a few well-studied taxa. Butterflies are often the only group for which accurate measures of change can be obtained. Four schemes, used successfully to assess change in British butterflies, that are increasingly being applied across the world are described: Red Data Books (RDB) list the best judgements of experts of the conservation status of species in their field of expertise; mapping schemes plot the changing distributions of species at scales of 1–100 km2; transect monitoring schemes generate time series of changes in abundance in sample populations of species on fixed sites across the UK; and occasional surveys measure the number, boundaries and size of all populations of a (usually RDB) species at intervals of 10–30 years. All schemes describe consistent patterns of change, but if they are to be more generally useful, it is important to understand how well butterflies are representative of other taxa. Comparisons with similarly measured changes in native bird and plant species suggest that butterflies have declined more rapidly that these other groups in Britain; it should soon be possible to test whether this pattern exists elsewhere. It is also demonstrated that extinction rates in British butterflies are similar to those in a range of other insect groups over 100 years once recording bias is accounted for, although probably lower than in aquatic or parasitic taxa. It is concluded that butterflies represent adequate indicators of change for many terrestrial insect groups, but recommended that similar schemes be extended to other popular groups, especially dragonflies, bumblebees, hoverflies and ants. Given institutional backing, similar projects could be employed internationally and standardized. Finally, a range of schemes designed to monitor change in communities of aquatic macro-invertebrates is described. Although designed to use invertebrates as a bio-indicator of water quality for human use, these programmes could be extended to monitor the 2010 biodiversity targets of the World Summit on Sustainable Development.
Measuring the extent and effectiveness of protected areas as an indicator for meeting global biodiversity targets
Authors: Chape S , Harrison J , Spalding M , Lysenko I
Published: April 2005

There are now over 100 000 protected areas worldwide, covering over 12% of the Earth's land surface. These areas represent one of the most significant human resource use allocations on the planet. The importance of protected areas is reflected in their widely accepted role as an indicator for global targets and environmental assessments.

However, measuring the number and extent of protected areas only provides a unidimensional indicator of political commitment to biodiversity conservation. Data on the geographic location and spatial extent of protected areas will not provide information on a key determinant for meeting global biodiversity targets: ‘effectiveness’ in conserving biodiversity. Although tools are being devised to assess management effectiveness, there is no globally accepted metric.

Nevertheless, the numerical, spatial and geographic attributes of protected areas can be further enhanced by investigation of the biodiversity coverage of these protected areas, using species, habitats or biogeographic classifications.

This paper reviews the current global extent of protected areas in terms of geopolitical and habitat coverage, and considers their value as a global indicator of conservation action or response. The paper discusses the role of the World Database on Protected Areas and collection and quality control issues, and identifies areas for improvement, including how conservation effectiveness indicators may be included in the database to improve the value of protected areas data as an indicator for meeting global biodiversity targets.
Measuring the fate of plant diversity: towards a foundation for future monitoring and opportunities for urgent action
Authors: Nic Lughadha E , Baillie J , Barthlott W , Brummitt N.A , Cheek M.R , Farjon A , Govaerts R , Hardwick K.A , Hilton-Taylor C , Meagher T.R , Moat J , Mutke J , Paton A.J , Pleasants L.J , Savolainen V , Schatz G.E , Smith P , Turner I , Wyse-Jackson P , Crane P.R
Published: April 2005

Vascular plants are often considered to be among the better known large groups of organisms, but gaps in the available baseline data are extensive, and recent estimates of total known (described) seed plant species range from 200 000 to 422 000. Of these, global assessments of conservation status using International Union for the Conservation of Nature (IUCN) categories and criteria are available for only approximately 10 000 species. In response to recommendations from the Conference of the Parties to the Convention on Biological Diversity to develop biodiversity indicators based on changes in the status of threatened species, and trends in the abundance and distribution of selected species, we examine how existing data, in combination with limited new data collection, can be used to maximum effect. We argue that future work should produce Red List Indices based on a representative subset of plant species so that the limited resources currently available are directed towards redressing taxonomic and geographical biases apparent in existing datasets. Sampling the data held in the world's major herbaria, in combination with Geographical Information Systems techniques, can produce preliminary conservation assessments and help to direct selective survey work using existing field networks to verify distributions and gather population data. Such data can also be used to backcast threats and potential distributions through time. We outline an approach that could result in: (i) preliminary assessments of the conservation status of tens of thousands of species not previously assessed, (ii) significant enhancements in the coverage and representation of plant species on the IUCN Red List, and (iii) repeat and/or retrospective assessments for a significant proportion of these. This would result in more robust Sampled Red List Indices that can be defended as more representative of plant diversity as a whole; and eventually, comprehensive assessments at species level for one or more major families of angiosperms. The combined results would allow scientifically defensible generalizations about the current status of plant diversity by 2010 as well as tentative comments on trends. Together with other efforts already underway, this approach would establish a firmer basis for ongoing monitoring of the status of plant diversity beyond 2010 and a basis for comparison with the trend data available for vertebrates.
Background and interpretation of the ‘Marine Trophic Index’ as a measure of biodiversity
Authors: Pauly Daniel , Watson Reg
Published: April 2005

Since the demonstration, in 1998, of the phenomenon now widely known as ‘fishing down marine food webs’, and the publication of a critical rejoinder by Food and Agricultural Organization (FAO) staff, a number of studies have been conducted in different parts of the world, based on more detailed data than the global FAO fisheries statistics originally used, which established the validity and ubiquity of this phenomenon. In this contribution, we briefly review how, rather than being an artefact of biased data, this phenomenon was in fact largely masked by such data, and is in fact more widespread than was initially anticipated. This is made visible here by comparing two global maps of trophic level (TL) changes from the early 1950s to the present. The first presents the 50-year difference of the grand mean TL values originally used to demonstrate the fishing down effect, while the second is based on means above a cut-off TL (here set at 3.25), thus eliminating the highly variable and abundant small pelagic fishes caught throughout the world. Based on this, we suggest that using mean TL as ‘Marine Trophic Index’ (MTI), as endorsed by the Convention on Biological Diversity , always be done with an explicitly stated cut-off TL (i.e.
cut
MTI), chosen (as is the case with our proposed value of 3.25) to emphasize changes in the relative abundance of the more threatened, high-TL fishes. We also point out the need to improve the taxonomic resolution, completeness and accuracy of the national and international fisheries catch data series upon which the
cut
MTI is to be based.
Putting your sons in the right place: the spatial distribution of fig wasp offspring inside figs
Authors: Zavodna M. , Compton S. G. , Biere A. , Gilmartin P. M. , Van Damme J. M. M.
Published: April 2005

Abstract. 1. Pollinating fig wasps (Hymenoptera, Agaonidae) display sex ratio adjustment, producing less female‐biased combined sex ratios as the number of ovipositing females (foundresses) inside a fig increases. Because males have low mobility, the oviposition sites (galled ovules) chosen by each foundress are likely to have consequences for the mating structure of wasp populations within the figs.

2. In this study, the spatial location of male and female progeny of the pollinating fig waspLiporrhopalum tentacularisdeveloping within figs of its host plantFicus montanawas examined to investigate two questions: (i) are male and/or female wasp offspring clustered together or interspersed? and (ii) is their distribution affected by whether one or two foundresses are present? Microsatellite markers were used to identify the progeny of different foundresses in dual‐foundress figs.

3. More offspring developed in the central part of the figs, compared with the ostiolar and basal parts, irrespective of foundress number. Neither male nor female wasp offspring were clustered within a fig.

4. The sons of the second foundress to enter a fig were positioned at similar minimum distances to both sibling and non‐sibling females, whereas the sons of the first foundress were closer to their sibling females than to non‐sibling females. If male wasps mate predominantly with females in adjacent galls, then the positioning of sons by the second foundresses is beneficial for them both in terms of reduced sibling mating and because they are provided with ready access to the female progeny of the first foundress.
Does intraspecific size variation in bumblebees allow colonies to efficiently exploit different flowers?
Authors: Peat J. , Tucker J. , Goulson D.
Published: April 2005

Abstract.  1. It has long been known that foraging bumblebee workers vary greatly in size, within species, and within single nests. This phenomenon has not been adequately explained. Workers of their relatives within the Apidae exhibit much less size variation.

2. For the bumblebee Bombus terrestris size, as measured by thorax width, was found to correspond closely with tongue length, so that larger bees are equipped to feed from deeper flowers.

3. The mean size of worker bees attracted to flowers was found to differ between plant species, and larger bees with longer tongues tended to visit deeper flowers.

4. Finally, handling time depended on the match between corolla depth and tongue length: large bees were slower than small bees when handling shallow flowers, but quicker than small bees when handling deep flowers.

5. Size variation within bumblebees may be adaptive, since it enables the colony as a whole to efficiently exploit a range of different flowers. Possible explanations for the marked differences in size variation exhibited by bumblebees compared with Apis species and stingless bees (Meliponinae) are discussed.
Patterns of species richness for blackflies (Diptera: Simuliidae) in the Nearctic and Neotropical regions
Authors: McCreadie John W. , Adler Peter H. , Hamada Neusa
Published: April 2005

Abstract.  1. Patterns of simuliid species richness were examined over a variety of scales at 532 stream sites in the Nearctic (394) and Neotropical (138) regions. In Nearctic streams, species richness of immature blackflies both within and across ecoregions and over two seasons was examined. Stream variables at each site included seston, width, depth, velocity, discharge, conductivity, pH, dissolved oxygen, water temperature, dominant streambed‐particle size, canopy cover, and riparian vegetation. These variables were subjected to a principal component analysis and derived principal components were related back to richness, using regression analysis. At the level of the stream reach, richness was not highly correlated with single‐point measurements of stream conditions.

2. Using data from both Nearctic and Neotropical sites, the effect of regional richness on local richness was examined. As regional richness increased, local diversity reached an asymptote in which further increases in regional richness were not matched by increases in local richness. Hence, simuliid communities are best described as saturated (type II) communities, consistent with the current view of lotic communities as non‐equilibrium systems.

3. The well‐established pattern of greater species richness in tropical regions was not observed in this study. To the contrary, blackfly richness is higher in temperate streams than in tropical streams at both local and regional scales.
Growth of silver hake within the U.S. continental shelf ecosystem of the northwest Atlantic Ocean
Authors: Helser T. E.
Published: April 2005

Von Bertalanffy growth parameters were estimated for silver hake Merluccius bilinearis within four regions of the United States continental shelf ecosystem of the northwest Atlantic Ocean during 1975–1980, 1982–1987 and 1988–1992. Differences in silver hake growth were found between the Middle Atlantic and southern Georges Bank regions (P<0–01) over all three time periods. Growth also differed between northern Georges Bank and the Gulf of Maine (P<0–01) during 1975–1980 and 1982–1987, and significant differences between southern Georges Bank and northern Georges Bank were found only during 1982–1987. Silver hake in the Gulf of Maine exhibited larger asymptotic sizes, but attained their asymptotic size at slower rates (L00= 47 cm and K=0–33) in comparison to silver hake in the Middle Atlantic (L00= 43 cm and K=0–51), while growth parameter estimates for silver hake on Georges Bank were intermediate between these. Although significant differences in growth of silver hake between the various regions are consistent with separate stocks in the U.S. continental shelf ecosystem, the growth characteristics from the different regions are inconsistent with the presently assigned stock boundaries. (c) 1996 The Fisheries Society of the British Isles
Distribution and biology of Alepocephalus rostvatus from the Mediterranean Sea
Authors: Morales‐Nin B. , Massutí E. , Stefanescu C.
Published: April 2005

In the Catalan Sea (NW Mediterranean) A. rostratus was found on the bottom below 500 m and reached its maximum abundance and biomass at 1100–1300 m depth, being captured down to 2209 m. Mean fish size increased progressively with depth. Larger fish were predominantly females, and 50% of maturity was reached at 23–6 and 27–7 cm in males and females, respectively. Although a high percentage of the population was mature all year round, a peak was attained in autumn, coinciding with the slowest growth of the species. Size‐at‐age indicated a slow growth rate. The greatest observed age was 23 years, although most of individuals were 7–12 years old. Overall, A. rostratus can be considered as a typical K‐strategist, showing a good adaptation to the oligotropic deepsea environment.