bluuebunny/crossref_metadata_2025 huggingface dataset:
THE BOUNDED LIFE: ADORNO, DICKENS, AND METAPHYSICS
Authors: Small Helen
Published: December 2004

THEODOR ADORNO'S LATE LECTURESonMetaphysicspropose a “shocking thesis”: “metaphysics began with Aristotle” (15). A “doubly shocking” thesis, Adorno tells his audience, because it gives credit where credit is not usually given, and declines to give it where most students of philosophy would understand that it belongs–with Plato (18). The Platonic doctrine of Ideas misses the essential criterion for metaphysics. Plato never fully accepted that the tension between the sphere of transcendence and the sphere of “direct experience” is not merely an adjunct of metaphysical inquiry but its defining subject matter (18). Aristotle understood this, and understood also that metaphysics has always a “twofold aim”; for, even as Aristotelian metaphysics criticizes Plato's attempt to define essence in opposition to the world of the senses, it tries to “extract an essential being from the sensible, empirical world, and thereby to save it.” True metaphysics, Adorno claims, is an effort to go beyond thought in the very act of defining the boundaries of thought. In his words, it is “the exertion of thought to save what at the same time it destroys” (20).
MORRIS, CARPENTER, WILDE, AND THE POLITICAL AESTHETICS OF LABOR
Authors: Livesey Ruth
Published: December 2004

IN JUNE1885 a group of radical intellectual Londoners gathered for the evening at that hub of nineteenth-century free thought, the South Place Institute. The event was organized by the Socialist League, a revolutionary socialist organization which counted William Morris, Eleanor Marx, and Edward Aveling as its most prominent members at that point in time. But this was no ordinary meeting. There were no lectures and no debates, just popular songs and dramatic recitations that had been carefully rehearsed by the membership in order to entertain for the cause. William Morris drafted a poem for the occasion, urging these “Socialists at Play” to cast their “care aside while song and verse/Touches our hearts.” Play, however, was not to lull the audience into a “luxurious mood”:
A new multiscale flow network generation scheme for land surface models
Authors: Guo Jianzhong , Liang Xu , Leung L. Ruby
Published: December 2004

This paper presents a new multiscale approach for generating flow networks for land surface models that are applied at different spatial scales. This new approach has the following advantages: (1) it allows runoff in a land surface model grid to exit by multiple directions simultaneously, rather than be limited to one of the eight directions as in many other methods; and (2) it introduces a scaling factor, the tortuosity coefficient, to determine hydrologic parameters for more accurate flow routing across different spatial scales. The new flow network generation scheme has been applied, in conjunction with a kinematic wave routing method, to the Blue River basin in Oklahoma at different spatial resolutions. Comparison of the routed streamflows shows clear advantages of the new approach over the widely used eight directions (D8) method, especially at coarser resolutions. This method is particularly suitable for macroscale hydrologic models and climate models where the accuracy of river routing can be severely limited by the coarse spatial resolution.
Snow and the ground temperature record of climate change
Authors: Bartlett Marshall G. , Chapman David S. , Harris Robert N.
Published: December 2004

Borehole temperature‐depth profiles contain a record of surface ground temperature (SGT) changes with time and complement surface air temperature (SAT) analysis to infer climate change over multiple centuries. Ground temperatures are generally warmer than air temperatures due to solar radiation effects in the summer and the insulating effect of snow cover during the winter. The low thermal diffusivity of snow damps surface temperature variations; snow effectively acts as an insulator of the ground during the coldest part of the year. A numerical model of snow‐ground thermal interactions is developed to investigate the effect of seasonal snow cover on annual ground temperatures. The model is parameterized in terms of three snow event parameters: onset time of the annual snow event, duration of the event, and depth of snow during the event. These parameters are commonly available from meteorological and remotely sensed data making the model broadly applicable. The model is validated using SAT, subsurface temperature from a depth of 10 cm, and snow depth data from the 6 years of observations at Emigrant Pass climate observatory in northwestern Utah and 217 station years of National Weather Service data from sites across North America. Measured subsurface temperature‐time series are compared to changes predicted by the model. The model consistently predicts ground temperature changes that compare well with those observed. Sensitivity analysis of the model leads to a nonlinear relationship between the three snow event parameters (onset, duration, and depth of the annual snow event) and the influence snow has on mean annual SGT.
The unfolding of the P pili quaternary structure by stretching is reversible, not plastic
Authors: Fällman Erik , Schedin Staffan , Jass Jana , Uhlin Bernt‐Eric , Axner Ove
Published: December 2004

P pili are protein filaments expressed by uropathogenic Escherichia coli that mediate binding to glycolipids on epithelial cell surfaces, which is a prerequisite for bacterial infection. When a bacterium, attached to a cell surface, is exposed to external forces, the pili, which are composed of ∼103 PapA protein subunits arranged in a helical conformation, can elongate by unfolding to a linear conformation. This property is considered important for the ability of a bacterium to withstand shear forces caused by urine flow. It has hitherto been assumed that this elongation is plastic, thus constituting a permanent conformational deformation. We demonstrate, using optical tweezers, that this is not the case; the unfolding of the helical structure to a linear conformation is fully reversible. It is surmised that this reversibility helps the bacteria regain close contact to the host cells after exposure to significant shear forces, which is believed to facilitate their colonization.
Enhanced photoluminescence from GaAsSb quantum wells
Authors: Kost Alan R. , Sun Xiaolan , Peyghambarian Nasser , Eradat Nayer , Selvig Espen , Fimland Bjorn-Ove , Chow David H.
Published: December 2004

We describe promising semiconductor materials for optoelectronics. GaAsSb/AlSb quantum wells on GaSb substrates show photoluminescence near 1.54 μm (0.8 eV) that increases with increasing arsenic fraction. The materials can be monolithically integrated with AlGaSb/AlSb or AlGaAsSb/AlAsSb Bragg mirrors.
Chaotic systems that are robust to added noise
Authors: Carroll Thomas L.
Published: December 2004

While added noise can destroy synchronization in synchronized chaotic systems, it was shown that some chaotic systems were not sensitive to added noise. In this paper, the mechanism for this noise resistance is explored. It is seen that part of the chaotic system acts like it is resonant, reducing the noise sensitivity of the system. By comparing to a model of a neuron, it is speculated that similar mechanisms may also be present in biological systems.
Family behavior of the optical transition energies in single-wall carbon nanotubes of smaller diameters
Authors: Samsonidze Ge. G. , Saito R. , Kobayashi N. , Grüneis A. , Jiang J. , Jorio A. , Chou S. G. , Dresselhaus G. , Dresselhaus M. S.
Published: December 2004

Using the extended tight-binding model that allows bond lengths and angles to vary, the optical transition energies Eii in single-wall carbon nanotubes are calculated as a function of inverse tube diameter. After geometrical structure optimization, the 2n+m=constant family behavior observed in photoluminescence (PL) experiments is obtained, and detailed agreement between the calculations and PL experiments is achieved after including many-body corrections.
Universal shapes of self-organized semiconductor quantum dots: Striking similarities between InAs∕GaAs(001) and Ge∕Si(001)
Authors: Costantini G. , Rastelli A. , Manzano C. , Songmuang R. , Schmidt O. G. , Kern K. , Känel H. von
Published: December 2004

The model systems for self-organized quantum dots formed from elemental and compound semiconductors, namely Ge grown on Si(001) and InAs on GaAs(001), are comparatively studied by scanning tunneling microscopy. It is shown that in both material combinations only two well-defined families of faceted and defect-free nanocrystals exist (and coexist). These three-dimensional islands, pyramids, and domes show common morphological characteristics, independent of the specific material system. A universal behavior is further demonstrated in the capping-passivation process that turns the nanocrystals in true quantum dots.
Density profiles and electrical properties of thermally grown oxide nanofilms on p-type 6H–SiC(0001)
Authors: Hazra S. , Chakraborty S. , Lai P. T.
Published: December 2004

Thermally grown silicon oxide films on p-type 6H–silicon carbide substrate under different oxidation and nitridation conditions have been characterized by x-ray reflectivity technique. An electron density profile obtained from the analysis of the x-ray reflectivity data shows that the thickness, density of the oxide film, and structure of the oxide-SiC interface strongly depend on the different growth conditions. In particular, the density of the oxide film for all samples other than that grown in NO is found to be much lower and also not fixed within. It is maximum at the interface and gradually decreases toward the top in all samples except for the sample grown in O2 followed by NO nitridation. For the latter, a very low density at the interface region has been observed. The sample grown in NO shows the best performance in capacitance–voltage characteristic and reliability studies suggesting that the bad performance of the oxide grown on the p-type SiC system as metal–oxide–semiconductor devices, is mainly linked to the low-density oxide film and can be overcome under proper growth condition.
Single-molecule signal enhancement using a high-impedance ground plane substrate
Authors: Ray Krishanu , Mason Michael D. , Yang Celeste , Li Zhipan , Grober Robert D.
Published: December 2004

We introduce a “high-impedance ground plane” (HIGP) substrate for use in single-molecule imaging applications. The HIGP is a quarter-wave-thick layer of dielectric material is deposited over a regular metallic mirror. Comparison of confocal fluorescence images of single DiI molecules on HIGP substrates and on glass substrates indicates a dramatic increase in the number of collected photons for the HIGP substrate. Signal enhancement ranges from a factor of 8 at low excitation powers to a lifetime-limited factor of 2 at higher powers.
Al
–
Si
multilayers: A synthetic material with large thermoelectric anisotropy
Authors: Kyarad A. , Lengfellner H.
Published: December 2004

A synthetic material with large thermoelectric anisotropy has been prepared from a metal–semiconductor multilayer structure. By an alloying process, a multilayer stack A–B–A…, where A and B are pure aluminum and n-silicon, is produced with a thermoelectric anisotropy ΔS=S‖−S⊥≅1.5mV∕K, where S‖ and S⊥ are the absolute Seebeck coefficients along and perpendicular to the layers, respectively. The use of this synthetic material for light sensing applications is demonstrated.
Photoluminescence mapping study of gettering effect of polycrystalline Si on ultrathin silicon-on-insulator
Authors: Li Z. Q. , Tajima M. , Kitai N. , Yoshida H. , Kishino S.
Published: December 2004

High-resolution photoluminescence (PL) mapping measurement was performed to study the gettering effect of polycrystalline Si on ultrathin silicon-on-insulator (SOI) wafers. A 150-mm-diam Unibond SOI wafer was patterned and partially gettered by polycrystalline Si process at 600 °C for 1 h. Then the wafer was annealed in H2 atmosphere at 400 °C for 1 h. PL mapping clearly demonstrated the difference between the gettered and ungettered parts, before and after H2 annealing. Before H2 annealing, almost no variation was obvious between the gettered and ungettered parts. After H2 annealing, however, we found the PL intensity was substantially increased, and the gettered area gave 24.7% higher PL intensity than the ungettered part. This coincided with the results of charge pumping measurements, which indicated a negligible difference of the interface trap density for the two areas before H2 annealing, while remarkable decrease of this density for the gettered region after H2 annealing. H2 annealing thus decreased the interface trap density, and made the gettering effect more obvious. This result indicated that PL mapping is effective and sensitive in characterizing the gettering effect of ultrathin SOI structures.
Conductivity and Hall effect of free-standing highly resistive epitaxial GaN:Fe substrates
Authors: Kordoš P. , Morvic M. , Betko J. , Novák J. , Flynn J. , Brandes G. R.
Published: December 2004

Free-standing highly resistive Fe-doped GaN layers grown by hydride vapor phase epitaxy were characterized by temperature-dependent conductivity and Hall effect measurements. Samples with a room-temperature resistivity of 1.6×107–6×108Ωcm and a Hall mobility of ∼330cm2V−1s−1 showed simple band conduction with the mobility power x=−1.5 and an activation energy 0.58–0.60eV, which can be attributed to a Fe acceptor. Samples with a lower mobility, ⩽10cm2V−1s−1, exhibited an increase of the mobility with temperature. Here, the conduction seems to be strongly influenced by potential barriers at inhomogeneities, with an activation energy of 0.21eV and a barrier height of 0.14–0.18eV. The activation energy 0.36 and 0.40eV, evaluated from the resistivity measurements, does not correspond to that of the Fe acceptor.
Reduced defect densities in the ZnO epilayer grown on Si substrates by laser-assisted molecular-beam epitaxy using a ZnS epitaxial buffer layer
Authors: Onuma T. , Chichibu S. F. , Uedono A. , Yoo Y.-Z. , Chikyow T. , Sota T. , Kawasaki M. , Koinuma H.
Published: December 2004

Nonradiative photoluminescence (PL) lifetime (τnr) and point defect density in the (0001) ZnO epilayer grown on (111) Si substrates by laser-assisted molecular-beam epitaxy (L-MBE) using a (0001) ZnS epitaxial buffer layer were compared with those in the ZnO films on (111) and (001) Si substrates prepared by direct transformation of ZnS epilayers on Si by thermal oxidation [Yoo et al., Appl. Phys. Lett. 78, 616 (2001)]. Both the ZnO films exhibited excitonic reflectance anomalies and corresponding PL peaks at low temperature, and the density or size of vacancy-type point defects (Zn vacancies), which were measured by the monoenergetic positron annihilation measurement, in the L-MBE epilayer was lower than that in the films prepared by the oxidation transformation. The ZnO epilayer grown on a (0001) ZnS epitaxial buffer on (111) Si exhibited longer τnr of 105ps at room temperature.
Investigation of electric internal field in congruent LiNbO3 by electro-optic effect
Authors: Paturzo Melania , Alfieri Domenico , Grilli Simonetta , Ferraro Pietro , De Natale Paolo , de Angelis Marella , De Nicola Sergio , Fińizio Andrea , Pierattini Giovanni
Published: December 2004

We investigate the effect of the defect-induced internal field on the electro-optic behavior of z-cut congruent lithium niobate crystals. We measure, by a spatially resolved interferometric technique, the phase retardation due to an external applied voltage occurring in two regions with opposite ferroelectric polarization. When measurements are performed just after electrical poling, the two opposite domains show a different electro-optic behavior. We interpret this as due to an elastic component of the internal field. In fact, the asymmetric behavior disappears when the sample is thermally annealed, i.e., when the internal field vanishes.
Dimensional structural transition in CdTe∕CdxZn1−xTe nanostructures
Authors: Lee H. S. , Park H. L. , Kim T. W.
Published: December 2004

CdTe nanostructures were grown on CdxZn1−xTe buffer layers by using molecular-beam epitaxy and atomic-layer epitaxy. The atomic force microscopy image showed that uniform CdTe quantum dots were formed on ZnTe buffer layer. Photoluminescence measurements showed that the excitonic peak corresponding to the interband transitions from the ground electronic subband to the ground heavy-hole band in the CdTe∕CdxZn1−xTe nanostructure shifted to a higher energy with increasing Cd mole fraction. The activation energy of the electrons confined in the CdTe∕ZnTe quantum dots was higher than those of electrons in CdTe∕CdxZn1−xTe nanostructures. These results can help improve understanding of the dimensional structural transition in CdTe∕CdxZn1−xTe nanostructures.
Hardness of cubic spinel Si3N4
Authors: He Julong , Guo Licong , Yu Dongli , Liu Riping , Tian Yongjun , Wang Hui-Tian
Published: December 2004

The hardness of cubic spinel Si3N4 was calculated by using our microscopic model of hardness combined with first principles calculation. The calculated Vickers hardness is only 33.3GPa in good agreement with its experimental values reported recently, indicating that the cubic spinel Si3N4 is not a superhard material. Our calculation results also implicate a more important fact that predicting the hardness of a material based on its bulk modulus or shear modulus is impertinent.
Near-infrared intersubband transitions in delta-doped InAs∕AlSb multi-quantum wells
Authors: Sasa S. , Nakajima Y. , Nakai M. , Inoue M. , Larrabee D. C. , Kono J.
Published: December 2004

Intersubband transitions (ISBTs) in narrow InAs∕AlSb multiple quantum wells (MQWs) were investigated for well widths, d, ranging from 5 nm down to 1.8 nm with 10, 20, or 60 periods. In order to observe a strong ISBT signal, a heavy silicon doping was made in each InAs quantum well. Delta doping was employed for the narrowest wells to prevent silicon incorporation into the AlSb barrier layers. As the well width decreased, the ISBT signal of the MQWs decreased. However, it persisted down to d=2.1nm with a sheet doping density in each quantum well of 9×1012cm−2 and 60 periods. The ISBT signal observed for d=2.1nm was peaked at an energy of 650 and 670 meV at 300 and 77 K, respectively. These are the highest energy values ever observed for ISBTs in InAs∕AlSb MQWs.
Suppression of thermal atomic interdiffusion in C-doped InGaAs∕AlGaAs quantum well laser structures using TiO2 dielectric layers
Authors: Gareso P. L. , Buda M. , Fu L. , Tan H. H. , Jagadish C.
Published: December 2004

The effects of thermal annealing on C-doped InGaAs∕AlGaAs quantum well laser structures capped with titanium dioxide (TiO2) layers were investigated. The atomic interdiffusion was greatly suppressed by the presence of a TiO2 capping layer during annealing, inhibiting even the thermal intermixing observed in the uncapped sample. An increase in the amount of lattice contraction associated with the presence of substitutional carbon CAs after annealing without a capping layer was observed, but not after annealing with a TiO2 capping layer. Capacitance–voltage measurements confirmed the electrical activation of carbon after annealing without a dielectric layer and show a negligible change after annealing using a TiO2 capping layer. The possible mechanisms involving both the atomic intermixing on the group III sublattice and carbon activation on the group V sublattice and the implications for optoelectronic device integration using impurity-free intermixing are discussed.
Structure evolution and ferroelectric and dielectric properties of Bi3.5Nd0.5Ti3O12 thin films under a moderate temperature annealing
Authors: Zhong X. L. , Wang J. B. , Zheng X. J. , Zhou Y. C. , Yang G. W.
Published: December 2004

Bi 3.5 Nd 0.5 Ti 3 O 12 (BNT) ferroelectric thin films were fabricated on Pt∕Ti∕SiO2∕Si(100) substrates by chemical solution deposition. Structure evolution and ferroelectric and dielectric properties of the as-prepared thin films under a moderate temperature (600–750°C) annealing were studied in detail. The experimental results showed that the BNT thin films annealed at 700°C exhibit preferred (00l) orientation, and the remnant polarization (2Pr) and dielectric constant (εr) are higher (the values of 2Pr and εr at 100kHz are 54μC∕cm2 and 448, respectively) than those of the deposited films annealed at other temperatures. Additionally, the mechanism concerning the dependence of electrical properties of the BNT ferroelectric thin films on the annealing temperature was discussed.
Decentralization or Recentralization? A Question of Household versus Population Enumeration, Canadian Metropolitan Areas 1971–1996
Authors: Bunting Trudi E
Published: December 2004

The author considers patterns of population growth and density occurring in Canadian metropolitan areas (CMAs) over the 25-year period 1971–96. Two different sets of data, population and household, are examined with the aid of distance-decay density gradients and enumeration of intrazonal change in census tracts defined as core area (census tracts immediately adjacent to the central business district), inner city, and suburban. Important differences are found when household data are used in lieu of population data. In the core and inner city, household change points towards an overall pattern of recentralization and, in the suburbs, to intensification of development—albeit muted. This contrasts with an accentuated trend to decentralization witnessed in the population-based analyses. The author concludes that centralization is an active force in most CMAs, although it is not as strong a force as decentralization. It is also suggested that there is great diversity between the twenty-two CMAs that make up the dataset. Most important is the demonstration that evidence based on population trends alone is not sufficient to gauge changing patterns of intrametropolitan population distribution.
Factors That Identify Industrial Districts: An Application in Spanish Manufacturing Firms
Authors: Molina-Morales F Xavier , Martínez-Fernández M Teresa
Published: December 2004

The authors review ideas from the industrial district literature. They argue that district firms possess a number of collective or shared resources that account for firms' membership. These factors include: common reputation, intensity of exchange and combination of resources, and participation of local institutions. Their empirical research drew upon a sample of 220 Spanish manufacturing firms. Findings suggest a significant contribution of the chosen variables to overall discrimination between district member and nonmember firms.
Devolution, State Personnel, and the Production of New Territories of Governance in the United Kingdom
Authors: Jones Rhys , Goodwin Mark , Jones Martin , Simpson Glenn
Published: December 2004

As a result of the creation of a Scottish Parliament, Welsh and Northern Irish Assemblies, and the devolution of power to various regional bodies in England, there has been a substantial territorial refocusing of governance within the United Kingdom. Much has been written in the social and political sciences concerning this change, especially with regard to the formation of new institutions of governance. Less is known concerning the connections between state personnel and this institutional and territorial transformation. In this paper we seek to remedy this deficiency. Drawing on empirical evidence from the English regions, we suggest that devolution is shaped by, and also shapes, the actions and strategies of a variety of state personnel in the different territories. Developing the idea of the state as a ‘peopled organisation’, we thus emphasise the significance of state personnel in actively producing the United Kingdom's new territories and scales of governance. This allows for an examination of the ways in which state personnel, working within different territorial branches and scales of the state, are able to accommodate, revise, or resist broader political
A simple dynamic model of photosynthesis in oak leaves: coupling leaf conductance and photosynthetic carbon fixation by a variable intracellular CO2 pool
Authors: Noe Steffen M. , Giersch Christoph
Published: December 2004

Modelling the diurnal course of photosynthesis in oak leaves (Quercus robur L.) requires appropriate description of the dynamics of leaf photosynthesis of which diurnal variations in leaf conductance and in CO2 assimilation are essential components. We propose and analyse a simple photosynthesis model with three variables: leaf conductance (gs), the CO2 partial pressure inside the leaf (pi), and a pool of Calvin cycle intermediates (aps). The environmental factors light (I) and vapour pressure deficit (VPD) are used to formulate a target function G(I, VPD) from which the actual leaf conductance is calculated. Using this gs value and a CO2 consumption term representing CO2 fixation, a differential equation for pi is derived. Carboxylation corresponds to the sink term of the pi pool and is assumed to be feedback-inhibited by aps. This simple model is shown to produce reasonable to excellent fits to data on the diurnal time courses of photosythesis, pi and gs sampled for oak leaves.
Identification of small-molecule antagonists that inhibit an activator:coactivator interaction
Authors: Best Jennifer L. , Amezcua Carlos A. , Mayr Bernhard , Flechner Lawrence , Murawsky Christopher M. , Emerson Beverly , Zor Tsaffrir , Gardner Kevin H. , Montminy Marc
Published: December 2004

Phosphorylation of the cAMP response element binding protein (CREB) at Ser-133 in response to hormonal stimuli triggers cellular gene expression via the recruitment of the histone acetylase coactivator paralogs CREB binding protein (CBP) and p300 to the promoter. The NMR structure of the CREB:CBP complex, using relevant interaction domains called KID and KIX, respectively, reveals a shallow hydrophobic groove on the surface of KIX that accommodates an amphipathic helix in phospho (Ser-133) KID. Using an NMR-based screening approach on a preselected small-molecule library, we identified several compounds that bind to different surfaces on KIX. One of these, KG-501 (2-naphthol-AS-E-phosphate), targeted a surface distal to the CREB binding groove that includes Arg-600, a residue that is required for the CREB:CBP interaction. When added to live cells, KG-501 disrupted the CREB: CBP complex and attenuated target gene induction in response to cAMP agonist. These results demonstrate the ability of small molecules to interfere with second-messenger signaling cascades by inhibiting specific protein–protein interactions in the nucleus.
Stopping the Drain: Third‐party Responses to California's Water Market
Authors: Hanak Ellen
Published: December 2004

Concerns over potential adverse effects of a state‐sponsored water market have prompted many rural California counties to adopt ordinances restricting groundwater exports since the early 1990 s. Results from panel regressions that rely on original water market and institutional data indicate that these local restrictions have significantly reduced water exports. The optimality of this policy is assessed. In the presence of a water market, export restrictions appear as a low‐cost management alternative to common property within source regions. The substantial statewide benefits of a market weigh in favor of broader public support to more comprehensive, non‐discriminatory groundwater management initiatives. (JEL Q25, Q21)
Natural selection on mitochondrial DNA inParusand its relevance for phylogeographic studies
Authors: Zink Robert M.
Published: December 2004

I examined mitochondrial ND2 sequences in species of tits (genusParus) to determine whether substitutions were neutral or under selection. Haplotype trees in these species are shallow and geographically unstructured, which could be a signature of recent demographic expansion or purifying selection. McDonald-Kreitman tests revealed a pattern of excess replacement polymorphisms for closely related taxa. Replacement substitutions tended to be less common in the basal parts of haplotype trees, suggesting that they are selected against over evolutionary time. Thus, the pattern of selection is consistent with a model of mildly deleterious haplotypes. To investigate the significance of this selection, the ND2 gene was subdivided into surface and transmembrane portions, and synonymous-non-synonymous sites, andFST-values (the amount of variance distributed among populations) computed for each. Among sampling localities inP.major, both partitions gave similar estimates ofFST, which is consistent with demographic expansion as the cause of the shallow trees. InP.montanus, two localities contained high percentages of individuals that had a single replacement substitution in the transmembrane portion of the gene, which inflatedFST-values relative to the surface sites. Thus, the interpretation of the genetic differentiation of these two sites could be either geographical isolation or selection. Given that the sole substitution causing the highFST-values was a replacement one, selection is implicated. However, this substitution occurred in only 2 of 12 localities, revealing that overall the phylogeographic pattern was not biased by selection, once the cause of the two high pairwiseFST-comparisons was recognized. Investigators should consider the source of significant genetic heterogeneity within species, to determine if the variation is likely caused by demographic isolation or selection. However, it seems unlikely that most phylogeographic analyses are invalidated by the effects of natural selection.
Resistance variation within and among host populations in a plant–pathogen metapopulation: implications for regional pathogen dynamics
Authors: LAINE ANNA‐LIISA
Published: December 2004

Studies conducted on natural host‐pathogen metapopulations have revealed considerable diversity of host resistance phenotypes within populations. The resistance structure of non‐infected populations has, however, been largely ignored and the role of among‐population variation in resistance profiles in the dynamics of natural pathogen populations is poorly understood.

ThePlantago lanceolata–Podosphaera plantaginispathosystem in the Åland Islands in south‐west Finland is characterized by the highly fragmented distribution of the host. Only a small fraction of the host populations is infected at one point in time and pathogen turnover rate is high. I studied a sample of these populations to find out whether adjacent host populations are differentiated in their resistance structure and whether variable levels of disease resistance among host populations could be linked to disease incidence patterns.

Results show striking differences in the resistance structure both within and among host populations. Sixteen resistance phenotypes were identified in a sample of 64 host individuals. Populations varied from one in which all sampled individuals represented a different resistance phenotype, to one in which half showed identical resistance responses.

There was no association between local resistance composition and the geographical distance between populations, suggesting that within‐population processes, such as founder effects and genetic drift, largely determine local resistance structure.

Non‐infected populations showed significantly higher mean levels of resistance than infected populations, suggesting that differences in the mean level of resistance among host populations may retard the spread of the fungus and thereby decrease the probability of regional epidemics.
Patch–background contrast and patch density have limited effects on root proliferation and plant performance in Abutilon theophrasti
Authors: LAMB E. G. , HAAG J. J. , CAHILL J. F.
Published: December 2004

We examined biomass and root proliferation responses of Abutilon theophrasti Medic. to the density of high nutrient patches and the patch–background contrast. Contrast in nutrient content between a patch and the background soil, as well as patch density, are important features of heterogeneous soil environments that have received little research attention.

Plants were grown in pots with no, one or two organic nutrient patches, and the equivalent nutrition of no, one or two patches in the background soil in a factorial design. Plant performance (root and shoot biomass) and root proliferation (root length inside and outside high‐nutrient patches) were measured.

Root and shoot biomass increased with increasing nutrient heterogeneity, and root biomass declined with increased background soil nutrient availability. Patch–background contrast did not alter root or shoot biomass, nor allocation to roots. Biomass responses appeared to be driven by heterogeneity, as plants with access to the same total nutrients were larger when nutrients were concentrated in patches. The root proliferation response was not affected by either the density of patches or the degree of contrast.

A conceptual model is presented describing how a plant's overall nutrient status could respond to changes in the patch–background contrast. The model predicts that nutrient‐sufficient plants should not respond to patches, but nutrient‐limited plants should proliferate roots proportionally to the contrast. The proliferation response should saturate when the total nutrients in both patch and background are no longer limiting.
Species richness and susceptibility to heat and drought extremes in synthesized grassland ecosystems: compositionalvsphysiological effects
Authors: VAN PEER L. , NIJS I. , REHEUL D. , DE CAUWER B.
Published: December 2004

We investigated effects of declining plant species richness (S) on resistance to extremes in grassland communities.

Synthesized model ecosystems of differentS, grown outdoors in containers, were exposed to a stress peak combining heat and drought. The heat wave was induced experimentally by infrared irradiation in free air conditions.

Before the heat wave, the more species‐rich communities produced more biomass as a result of a large and positive complementarity effect that outweighed a small negative selection effect.

Water use during the heat wave was likewise enhanced byS, which could not be attributed to dominance of ‘water‐wasting’ species. Instead, water consumption at highSexceeded that expected from changes in community biomass and biomass composition. The observed enhancement of resource (water) acquisition under stress with increasingStherefore probably originated from complementarity.

Despite enhanced water use in the more diverse communities, plant survival was significantly less, affecting all species alike. Physiological stress, recorded as photochemical efficiency of photosystem II electron transport, was significantly greater. Before the heat wave, the changes in biomass composition that coincided with increasingSdid not favour species that would later prove intrinsically sensitive or insensitive.

Complementarity in resource use for biomass production had a cost in terms of reduced survival under stress, despite the likelihood of complementarity in water acquisition during exposure. The greater loss of individuals from the more diverse grasslands suggests enhanced risk of local extinction.
Increasing accuracy of causal inference in experimental analyses of biodiversity
Authors: BENEDETTI‐CECCHI L.
Published: December 2004

Manipulative experiments are often used to identify causal linkages between biodiversity and productivity in terrestrial and aquatic habitats.

Most studies have identified an effect of biodiversity, but their interpretation has stimulated considerable debate. The main difficulties lie in separating the effect of species richness from those due to changes in identity and relative density of species.

Various experimental designs have been adopted to circumvent problems in the analysis of biodiversity. Here I show that these designs may not be able to maintain the probability of type I errors at the nominal level (α = 0·05) under a true null hypothesis of no effect of species richness, in the presence of effects of density and identity of species.

Alternative designs have been proposed to discriminate unambiguously the effects of identity and density of species from those due to number of species. Simulations show that the proposed experiments may have increased capacity to control for type I errors when effects of density and identity of species are also present. These designs have enough flexibility to be useful in the experimental analysis of biodiversity in various assemblages and under a wide range of environmental conditions.
Differences between structural and functional environmental heterogeneity caused by seed dispersal
Authors: GÓMEZ J. M. , VALLADARES F. , PUERTA‐PIÑERO C.
Published: December 2004

This paper explores the idea that functional heterogeneity (variability of a system property affecting ecological processes) is only a fraction of the available structural heterogeneity (variability of a property measured without reference to ecological effects) caused by non‐random propagule dispersal. We report the effect of acorn dispersal by jays on the light environment experienced by Holm Oaks (Quercus ilex L.) during early recruitment in a Mediterranean montane forest.

Four light variables were estimated by studying hemispherical photographs: direct site factor (DSF); indirect site factor (ISF); and potential direct radiation during April (PDRApril) and August (PDRAugust). Means and variances of these variables were compared before and after the dispersal of acorns by jays.

The landscape occupied by Holm Oaks was very heterogeneous, which translated into differences in the available light among microhabitats of up to one order of magnitude.

Because of the spatial pattern of acorn dispersal, the light environment of the oaks during their establishment was much more homogeneous than that in the whole landscape.

This demonstrates that the heterogeneity relevant for plant recruitment is not necessarily that of the landscape as a whole.
Seasonal variation in the contribution of different behavioural mechanisms to lizard thermoregulation
Authors: DÍAZ J. A. , CABEZAS‐DÍAZ S.
Published: December 2004

We studied seasonal changes in the thermoregulatory behaviour of the lacertid lizard Psammodroums algirus in a Mediterranean evergreen forest. Body temperatures (Tb), environmental operative temperatures (Te) and upper and lower limits of the selected thermal range (Tsel) were lower in May than in July.

On average, mean deviations of Tb from Tsel (0·7 °C in both seasons) were much smaller than those of Te (8·3 °C in both seasons). Thus both the accuracy (average difference between Tb and Tsel) and effectiveness (the extent to which Tb are closer than Te to Tsel) of thermoregulation were high, and similar in both seasons.

However the thermoregulatory contribution of two distinct behavioural mechanisms varied markedly between seasons. Daily activity contributed significantly to the regulation of Tb in May (when a population of Te thermometers matching lizard activity patterns would be, on average, 1·0 °C closer to Tsel than were randomly available Te), but not in July (when such a population would be only 0·2 °C closer to Tsel than were randomly available Te). The selection of sun–shade patches, the contribution of which was larger than that of daily activity in both seasons, was more important in July (when it produced a distribution of Te that would be, on average, 3·1 °C closer to Tsel than were randomly distributed Te) than in May (when a population of thermometers matching the lizards’ pattern of exposure to sunlight would be 1·3 °C closer to Tsel than were randomly available Te).

These changes are discussed in the light of seasonal differences in the daily patterns of among‐patch variation in Te. In spring, lizard activity was low in the early morning because even the selection of sunlit patches was of limited utility to attain Tb within Tsel; in summer, lizards could remain active at midday, despite low overall thermal suitability, by selecting shaded patches. Thus the contribution of patch selection to thermoregulation was important in the early basking period of both seasons, and at summer midday hours.

Our data suggest that shuttling between sun and shade, rather than selecting sun or shade, may be an additional mechanism of behavioural thermoregulation, the importance of which would be greatest at times of day when lizards use patches at random (e.g. spring midday hours), and that their mean Tb is closer to the grand mean of full sun and full shade Te than to the mean equilibrium Te within any type of patch.
Morphological acclimation of aquatic Littorella uniflora to sediment CO2 concentration and wave exposure
Authors: BAGGER J. , MADSEN T. V.
Published: December 2004

Species of the isoetid life form have many physiological, anatomical and morphological traits that can be seen as adaptations to the environmental characteristics of softwater lakes. Among these, dependence on CO2 from the interstitial water for photosynthesis is one of the more distinctive.

To assess the impact of environmental conditions on morphology and resource allocation of Littorella uniflora (L.) Ascherson, and to test whether CO2 supply from the sediment constrains the maximum attainable leaf length of these plants, a suite of morphological plant traits were measured along a gradient of sediment CO2 availability. The sediment CO2 gradient (0·4–7 mol CO2 m−3 interstitial water) was obtained by collecting specimen from 13 Faroese lakes.

Along the CO2 gradient, the maximum leaf length of the plants more than doubled and was significantly correlated to sediment CO2 concentration. In addition to leaf length, plant size, leaf number and below : above‐ground biomass ratio were also correlated with sediment CO2 concentration, whereas only weak or no correlations between wave exposure and morphological features of the plants were found. Likewise, no correlation between the nutrient status of the plants and morphology was observed.

The results obtained emphasize the importance of sediment CO2 for the performance of L. uniflora and support the suggestion that the maximum attainable leaf length of these plants is set by the CO2 concentration in the interstitial water.
Meta‐analysis: phytotherapy of functional dyspepsia with the herbal drug preparation STW 5 (Iberogast)
Authors: Melzer J. , Rösch W. , Reichling J. , Brignoli R. , Saller R.
Published: December 2004

Background : Despite a long‐standing use of herbal drugs with dyspeptic symptoms, little attention has been paid to their clinical evaluation.

Aim : To assess efficacy and safety of the herbal drug preparation STW 5 (containing, e.g. Iberis, peppermint, chamomile) in the treatment of functional dyspepsia.

Methods : Research in electronic databases, consultation of experts and of the producer identified STW 5 (Iberogast) as descriptor in six randomized‐controlled trials. The raw data of three placebo‐controlled studies which met the selection criteria, were reanalysed and pooled for meta‐analysis; one reference‐controlled study supported the safety analysis (STW 5: n = 199, control: n = 198).

Results : Pooled data showed verum (n = 138) to be more effective than placebo (n = 135) with regard to the severity of the most bothersome gastrointestinal symptom (P‐value: 0.001, odds ratio: 0.22, 95% CI: 0.11–0.47). A fourth randomized‐controlled trial showed no significant difference between STW 5 and cisapride. As to safety, adverse events were similar with verum and placebo; no serious adverse events occurred.

Discussions : From the point of view of efficacy and safety, the herbal medicinal product STW 5 appears to be a valid therapeutic option for patients seeking phytotherapy for their symptoms of functional dyspepsia.
Frequency analyses of gastric pH in control and gastro‐oesophageal reflux disease subjects treated with a proton‐pump inhibitor
Authors: Gardner J. D. , Sloan S. , Robinson M. , Miner Jr P. B.
Published: December 2004

Background : We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other pH value to assess gastric acidity.

Aim : To examine the frequency of different gastric pH values in control and GERD subjects.

Methods : Gastric pH was measured for 24 h in 26 control subjects, 26 gastro‐oesophageal reflux disease subjects at baseline and the same 26 gastro‐oesophageal reflux disease subjects during treatment with a proton‐pump inhibitor. Histograms were constructed using the 21 600 values generated from each recording and bins of 0.25 pH units.

Results : The distribution of gastric pH values in gastro‐oesophageal reflux disease subjects was significantly different from that in controls and in some instances the distributions detected significant differences that were not detected by integrated acidity. Proton‐pump inhibitor treatment significantly altered the distribution of gastric pH values and the nature of this alteration during the postprandial period was different from that during the nocturnal period. Using time pH≤4 can significantly underestimate the magnitude of inhibition of gastric acidity caused by a proton‐pump inhibitor.

Conclusions : The distribution of gastric pH values provides a rationale for selecting a particular pH value to assess gastric acidity. In some instances, the distribution of gastric pH values detects significant differences between gastro‐oesophageal reflux disease and normal subjects that are not detected by integrated acidity.
Plant isolation reduces outcross pollen receipt in a partially self‐compatible herb
Authors: DUNCAN DAVID H. , NICOTRA ADRIENNE B. , WOOD JEFF T. , CUNNINGHAM SAUL A.
Published: December 2004

Few studies of pollination success in fragmented systems measure stigmatic pollen load, and those that do often find it unrelated to plant or population density, size or isolation. Reduced reproductive output, however, is commonly reported, probably because incompatible pollen is contributing substantially to pollen loads of isolated flowers.

We used manipulated floral arrays of a bee‐pollinated species (Dianella revoluta) to investigate isolation effects on deposition of outcross pollen, while precluding self‐pollen transfer.

Outcross pollen receipt declined significantly over short distances up to approximately 50 m but even the most isolated flowers received some pollen grains. In contrast, heterospecific pollen did not decline, indicating that the outcross‐pollen decline was not due to reduced pollinator visitation. Increased distance of experimental arrays from a nature reserve did not reduce the probability of pollen receipt.

Many flowers were damaged by flower feeding beetles in the genus Arsipoda, which would be likely to substantially reduce the efficiency with which flowers are converted to fruits. The probability of flower damage from these predators was significantly lower in arrays that were more distant from the nature reserve.

This study indicates that reduced plant density and increased isolation from a source of outcrossed pollen can lead to a substantial decline in the probability of outcrossing, even when pollinator visitation is maintained at a high level. Depending on the mating system, this process will lead to reduced seed set or increased inbreeding for plants in fragmented habitats, even when pollinator abundance and behaviour are unaffected.