bluuebunny/crossref_metadata_2025 huggingface dataset:
Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue-emitting layer
Authors: Hsiao Chih-Hung , Lin Chi-Feng , Lee Jiun-Haw
Published: November 2007

White organic light-emitting devices (OLEDs) consisting of ambipolar 9,10-bis(2′-naphthyl) anthracene (ADN) as a host of blue-emitting layer (EML) were investigated. A thin codoped layer of yellow 5,6,11,12-Tetraphenylnaphthacene (rubrene) served as a probe for detecting the position of maximum recombination rate in the 4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped-ADN EML. Due to the energy barrier and bipolar carrier transport, the maximum recombination rate was found to be close to but not exactly at the interface of the hole-transporting layer and the EML. With appropriate tuning in the thickness, position, and dopant concentrations of the codoped layer (rubrene:DPAVBi:ADN) in the EML, the device driving voltage decreased by 21.7%, nearly 2 V in reduction, due to the increased recombination current from the faster exciton relaxation induced by the yellow dopants. Among the advantages of introducing the codoped layer over conventional single-doped layers are the elimination of the trapping effect to avoid increasing the device driving voltage, the alleviation of the dependence of the recombination zone on the applied voltage for improving color stability, and the utilization of excitons in a more efficient way to enhance device efficiency. Without using any electrically conductive layers such as the p-i-n structure, we were able to successfully generate 112 cd∕m2 at 4 V from our white OLED simply by engineering the structure of the EML.
The role of ultraviolet radiation during ultralow k films curing: Strengthening mechanisms and sacrificial porogen removal
Authors: Zenasni Aziz , Jousseaume Vincent , Holliger Philippe , Favennec Laurent , Gourhant Olivier , Maury Patrick , Gerbaud Guillaume
Published: November 2007

This work proposes a fundamental understanding of structural transformation occurring during porogen extraction from as-deposited ultralow k (ULK) materials when exposed to ultraviolet (UV) radiation during thermal curing. Specific explanations are provided for as deposited films at high temperature (T>250 °C). This temperature range is sufficient to assess thin-film stability. Two distinguished regimes were identified in the curing process. During the first stage, the film shrinks strongly in similar proportion to SiCH3 break. Preferential impact of UV radiation on hydrocarbon porogen bonds leads also to a break of SiCH3 structures. In this work, 5 min of curing is enough to remove the porogen and create the max of porosity (33%). After the porogen removal step, the porous film shrinks under UV radiation leading to an increase of SiOSi bond concentration. A structural rearrangement of the bulk is initiated since the porogen is totally evacuated from the film. The increase of normalized infrared SiOSi peak during UV curing (related in literature to an improvement of mechanical properties) is mainly due to film densification (a few SiOSi bonds creation). The origin of shrinkage is explained by the breaking of SiCH3 which could turn into a SiH bond leading to a free volume reduction within the film. In this case, a correlation is found between shrinkage and elastic modulus. The resulting SiOSi structure densification drives, at first order, the improvement of the mechanical properties. UV radiation exposure shows no effect in silanol condensation and acts mainly on the porogen decomposition and bulk densification. Si-CH2-Si structure formation, pointed out in the literature as a possible reaction way to enhance film crosslinking, is identified in the nuclear magnetic resonance (NMR) broadband spectrum of the ULK film. However, resulted NMR and infrared peaks intensities suggest its formation as a minor. This study gives a full understanding of UV curing impact on ULK films (k≤2.5) where structure densification is identified as a main process to enhance the film strength in addition to the crosslinking.
Growth stresses in α-Cr2O3 thermal oxide films determined by in situ high temperature Raman spectroscopy
Authors: Kemdehoundja M. , Grosseau-Poussard J. L. , Dinhut J. F. , Panicaud B.
Published: November 2007

Growth stresses have been investigated in relation with the microstructure in the case of α-Cr2O3 growing oxide films on NiCr30 alloy. The equibiaxial growth stresses have been measured thanks to a technique coupling Raman spectroscopy and in situ high temperature oxidation of the NiCr30 alloy in the temperature range (700−900 °C). It is established that the compressive growth stress in such oxide films can reach more than 2 GPa, before additional thermal stress arises on cooling. Moreover, the growth stress kinetics—subsequent establishment and relaxation—are highly microstructure sensitive: in particular, as the oxidation temperature rises, the chromia mean grain size also increases, and it consequently retards the occurrence of the creep relaxation phenomena which needs an additional stress level to start.
Reproducible resistive switching in nonvolatile organic memories
Authors: Verbakel Frank , Meskers Stefan C. J. , Janssen René A. J. , Gomes Henrique L. , Cölle Michael , Büchel Michael , de Leeuw Dago M.
Published: November 2007

Resistive switching in nonvolatile, two terminal organic memories can be due to the presence of a native oxide layer at an aluminum electrode. Reproducible solid state memories can be realized by deliberately adding a thin sputtered Al2O3 layer to nominal electron-only, hole-only, and bipolar organic diodes. Before memory operation, the devices have to be formed at an electric field of 109V∕m, corresponding to soft breakdown of Al2O3. After forming, the structures show pronounced negative differential resistance and the local maximum in the current scales with the thickness of the oxide layer. The polymer acts as a current limiting series resistance.
Surface plasmon excitation via Au nanoparticles in n-CdSe∕p-Si heterojunction diodes
Authors: Konda R. B. , Mundle R. , Mustafa H. , Bamiduro O. , Pradhan A. K. , Roy U. N. , Cui Y. , Burger A.
Published: November 2007

We report on the significant enhancement of photocurrent in pn heterojunction diode, consisting of n-CdSe∕p-Si substrates, in situ deposited with Au nanoparticles on the surface by the pulsed-laser deposition technique. This is attributed due to the large enhancement in electromagnetic field that occurs in the vicinity of the metal surface, causing surface plasmons. The large enhancement in Raman and photoluminescence intensity was observed due to surface plasmon resonance. Our results suggest that the photodetectors, optoelectronic, such as high-performance thin-film solar cells, optical communication, and sensing devices, including bio- and molecular sensors, can be fabricated with improved functionality.
Migration of oxygen vacancy in HfO2 and across the HfO2∕SiO2 interface: A first-principles investigation
Authors: Capron Nathalie , Broqvist Peter , Pasquarello Alfredo
Published: November 2007

Oxygen vacancy migration is studied in monoclinic HfO2 and across its interface with SiO2 through density functional calculations. In HfO2, long-range diffusion shows activation barriers of 2.4 and 0.7eV for the neutral and doubly positively charged vacancy, respectively. In the latter case, the migration preferentially occurs along one-dimensional pathways. A HfO2∕SiO2 interface model is constructed to address O vacancy migration across high-κ gate stacks. The vacancy is shown to stabilize in its neutral charge state upon entering the SiO2 layer.
Monolithically integrated low-loss silicon photonic wires and three-dimensional tapered couplers fabricated by self-profile transformation
Authors: Lee Ming-Chang M. , Chiu Wei-Chao , Yang Tse-Ming , Chen Chin-Hung
Published: November 2007

A subwavelength silicon photonic wire integrated with three-dimensional (3D) tapered couplers fabricated through self-profile transformation is presented. Unlike the conventional process of defining the silicon wire by etching, the profile transformation, which is induced by surface diffusion of silicon atoms during hydrogen annealing, is applied on as-etch silicon structures to make photonic wires. Additionally, this process is able to reduce sidewall roughness to be less than 1nm, substantially meliorating the unwanted scattering loss. Exploiting this technology, the authors demonstrated that the photonic wire has low propagation loss of 1.26dB∕cm and the 3D tapered coupler has coupling efficiency of 54%.
Environmental Risk, Uncertainty, and Participation: Mapping an Emergent Epistemic Community
Authors: Chilvers Jason
Published: November 2007

Amid increasing interest in participatory forms of environmental appraisal and decision making, the actors shaping these new governance spaces remain understudied. This paper seeks to refocus accounts of public engagement in science onto these participatory appraisal experts, or ‘experts of community’, through drawing on in-depth empirical research that followed them through networks building up around participatory appraisal practice in the UK environmental-risk domain. A mapping of the general nature and character of this emerging epistemic community provides the context within which to analyse how it has evolved and has begun to influence policy processes in the area of radioactive waste. Prospects for studying networks of public engagement experts at the science–policy interface and wider implications for deliberative democracy under uncertainty are explored.
Revision of the genus Haplomesus (Isopoda:Asellota:Ischnomesidae) with erection of four new genera
Authors: Kavanagh Fiona A. , Wilson George D. F.
Published: November 2007

This paper presents a revision of Haplomesus Richardson, 1908 (Ischnomesidae). Poor character definition, ineffective diagnosis of the genus and inadequate or poor descriptions and illustrations have resulted in difficulties in identification of species and generic membership. This study is based on type material and descriptions in the literature and encompasses 28 species. Four new genera are created, justified by a phylogenetic analysis of 37 ingroup taxa and two outgroup taxa. Three species of the ingroup were excluded owing to missing data. Four species are retained in Haplomesus sensu stricto, two species are removed to Cornuamesus, gen. nov., 11 species are removed to Fortimesus, gen. nov. and 12 species are removed to Gracilimesus, gen. nov. One species, Haplomesus franklinae Merrin & Poore, 2003 is removed from the group and placed in Contrarimesus, gen. nov. with another species, Ischnomesus curtispinis Brandt, 1992. The species level is conferred on Haplomesus insignis orientalis Birstein, 1960. Haplomesus quadrispinosus sensu Brandt (1992) is removed from H. quadrispinosus (Sars, 1879) and Haplomesus ?gorbunovi sensu Svavarsson (1984) is removed from Gracilimesus gorbunovi (Gurjanova, 1946).
Taxonomic revision and phylogenetic relationships of apomorphic sabellids (Polychaeta) from Australia
Authors: Capa María
Published: November 2007

Knowledge about the diversity and distribution of Australian coastal sabellids (Polychaeta) is still scarce. Examination of specimens housed in museum collections has increased the number of species recorded in Australia and helped to clarify the relationships among certain taxa of Sabellidae. Australian specimens belonging to a group of genera considered the most derived of the Sabellidae were the subject of this taxonomic revision, resulting in the description of five new species in four genera (Laonome calida, sp. nov.; Perkinsiana anodina, sp. nov.; P. longa, sp. nov.; Potaspina australiensis, sp. nov.; and Pseudopotamilla monoculata, sp. nov.). In addition, this is the first record of Potaspina Hartman, 1969 and Perkinsiana Knight-Jones, 1983 in Australia. A phylogenetic analysis of these and other apomorphic sabellids revealed their evolutionary relationships and supported the monophyly of most genera with the exception of Perkinsiana and Pseudopotamilla Bush, 1905. Some characters not considered in previous cladistic analyses were proven useful in elucidating relationships within Sabellidae. The diagnoses of Perkinsiana, Potaspina and Pseudopotamilla were emended. A dichotomous key is presented for identification of Australian apomorphic sabellids.
Impact of vegetation removal and soil aridation on diurnal temperature range in a semiarid region: Application to the Sahel
Authors: Zhou Liming , Dickinson Robert E. , Tian Yuhong , Vose Russell S. , Dai Yongjiu
Published: November 2007

Increased clouds and precipitation normally decrease the diurnal temperature range (DTR) and thus have commonly been offered as explanation for the trend of reduced DTR observed for many land areas over the last several decades. Observations show, however, that the DTR was reduced most in dry regions and especially in the West African Sahel during a period of unprecedented drought. Furthermore, the negative trend of DTR in the Sahel appears to have stopped and may have reversed after the rainfall began to recover. This study develops a hypothesis with climate model sensitivity studies showing that either a reduction in vegetation cover or a reduction in soil emissivity would reduce the DTR by increasing nighttime temperature through increased soil heating and reduced outgoing longwave radiation. Consistent with empirical analyses of observational data, our results suggest that vegetation removal and soil aridation would act to reduce the DTR during periods of drought and human mismanagement over semiarid regions such as the Sahel and to increase the DTR with more rainfall and better human management. Other mechanisms with similar effects on surface energy balance, such as increased nighttime downward longwave radiation due to increased greenhouse gases, aerosols, and clouds, would also be expected to have a larger impact on DTR over drier regions.
Evidence for a navigational map stretching across the continental U.S. in a migratory songbird
Authors: Thorup Kasper , Bisson Isabelle-A. , Bowlin Melissa S. , Holland Richard A. , Wingfield John C. , Ramenofsky Marilyn , Wikelski Martin
Published: November 2007

Billions of songbirds migrate several thousand kilometers from breeding to wintering grounds and are challenged with crossing ecological barriers and facing displacement by winds along the route. A satisfactory explanation of long-distance animal navigation is still lacking, partly because of limitations on field-based study. The navigational tasks faced by adults and juveniles differ fundamentally, because only adults migrate toward wintering grounds known from the previous year. Here, we show by radio tracking from small aircraft that only adult, and not juvenile, long-distance migrating white-crowned sparrows rapidly recognize and correct for a continent-wide displacement of 3,700 km from the west coast of North America to previously unvisited areas on the east coast. These results show that the learned navigational map used by adult long-distance migratory songbirds extends at least on a continental scale. The juveniles with less experience rely on their innate program to find their distant wintering areas and continue to migrate in the innate direction without correcting for displacement.
An
in vivo
expression technology screen for
Vibrio cholerae
genes expressed in human volunteers
Authors: Lombardo Mary-Jane , Michalski Jane , Martinez-Wilson Hector , Morin Cara , Hilton Tamara , Osorio Carlos G. , Nataro James P. , Tacket Carol O. , Camilli Andrew , Kaper James B.
Published: November 2007

In vivo
expression technology (IVET) has been widely used to study gene expression of human bacterial pathogens in animal models, but has heretofore not been used in humans to our knowledge. As part of ongoing efforts to understand
Vibrio cholerae
pathogenesis and develop improved
V. cholerae
vaccines, we have performed an IVET screen in humans for genes that are preferentially expressed by
V. cholerae
during infection. A library of 8,734 nontoxigenic
V. cholerae
strains carrying transcriptional fusions of genomic DNA to a resolvase gene was ingested by five healthy adult volunteers. Transcription of the fusion leads to resolvase-dependent excision of a
sacB
-containing cassette and thus the selectable phenotype of sucrose resistance (Suc
R
). A total of ≈20,000 Suc
R
isolates, those carrying putative
in vivo
-induced fusions, were recovered from volunteer stool samples. Analysis of the fusion junctions from >7,000 Suc
R
isolates from multiple samples from multiple volunteers identified 217 candidate genes for preferential expression during human infection. Of genes or operons induced in three or more volunteers, the majority of those tested (65%) were induced in an infant mouse model. VC0201 (
fhuC
), which encodes the ATPase of a ferrichrome ABC transporter, is one of the identified
in vivo
-induced genes and is required for virulence in the mouse model.
Interaction of endosialin/TEM1 with extracellular matrix proteins mediates cell adhesion and migration
Authors: Tomkowicz Brian , Rybinski Katherine , Foley Brian , Ebel Wolfgang , Kline Brad , Routhier Eric , Sass Philip , Nicolaides Nicholas C. , Grasso Luigi , Zhou Yuhong
Published: November 2007

Endosialin/TEM1 was originally discovered as a human embryonic fibroblast-specific antigen and was later found to be differentially expressed in tumor stroma and endothelium. Endosialin/TEM1 overexpression has been observed in many cancers of various tissue origin, including colon, breast, pancreatic, and lung. The knockout (KO) mouse model showed the absence of endosialin/TEM1 expression reduced growth, invasion, and metastasis of human tumor xenografts. In addition, lack of endosialin/TEM1 led to an increase in small immature blood vessels and decreased numbers of medium and large tumor vessels. This abnormal angiogenic response could be responsible for the reduced tumor growth and invasion observed in endosialin/TEM1 KO mice, suggesting a role for endosialin/TEM1 in controlling the interaction among tumor cells, endothelia, and stromal matrix. Here we report the identification of fibronectin (FN) and collagen types I and IV as specific ligands for endosialin/TEM1. More importantly, cells expressing endosialin/TEM1 exhibit enhanced adhesion to FN as well as enhanced migration through matrigel, although these properties could be blocked by a humanized antibody directed against human endosialin/TEM1. Our results pinpoint to a molecular mechanism by which expression of endosialin/TEM1 in the tumor stroma and endothelium may support tumor progression and invasion.
Leptin replacement alters brain response to food cues in genetically leptin-deficient adults
Authors: Baicy Kate , London Edythe D. , Monterosso John , Wong Ma-Li , Delibasi Tuncay , Sharma Anil , Licinio Julio
Published: November 2007

A missense mutation in the
ob
gene causes leptin deficiency and morbid obesity. Leptin replacement to three adults with this mutation normalized body weight and eating behavior. Because the neural circuits mediating these changes were unknown, we paired functional magnetic resonance imaging (fMRI) with presentation of food cues to these subjects. During viewing of food-related stimuli, leptin replacement reduced brain activation in regions linked to hunger (insula, parietal and temporal cortex) while enhancing activation in regions linked to inhibition and satiety (prefrontal cortex). Leptin appears to modulate feeding behavior through these circuits, suggesting therapeutic targets for human obesity.
PAX3-FOXO1 controls expression of the
p57Kip2
cell-cycle regulator through degradation of EGR1
Authors: Roeb Wendy , Boyer Antonia , Cavenee Webster K. , Arden Karen C.
Published: November 2007

The chimeric protein PAX3-FOXO1, resulting from a translocation between chromosomes 2 and 13, is the most common genetic aberration in the alveolar subtype of the human skeletal muscle tumor, rhabdomyosarcoma. To understand how PAX3-FOXO1 contributes to tumor development, we isolated and characterized muscle cells from transgenic mice expressing
PAX3-FOXO1
under control of the
PAX3
promoter. We demonstrate that these myoblasts are unable to complete myogenic differentiation because of an inability to up-regulate
p57Kip2
transcription. This defect is caused by reduced levels of the EGR1 transcriptional activator resulting from a direct, destabilizing interaction with PAX3-FOXO1. Neither PAX3 nor FOXO1 share the ability to regulate
p57Kip2
transcription. Thus, the breakage and fusion of the genes encoding these transcription factors creates a unique chimeric protein that controls a key cell-cycle and -differentiation regulator.
Synthesis and Magnetic Properties of Co3O4 Nanoflowers
Authors: Zhang Yuan-guang , Chen You-cun , Zhao Yin-guo
Published: November 2007

Co3O4 nanoflowers were prepared through a sequential process of a hydrothermal reaction and heat treatment. The as-synthesized products were characterized by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and infrared spectrum. These nanoflowers consist of numerous Co3O4 nanofibers, which have diameters of 20-40 nm, and lengths ranging from 100 nm to 500 nm. They have pore structures and Brunauer-Emmett-Teller surface area of 34.61 m2/g. The temperature dependence curves of magnetization in zero-field-cooled conditions and field-cooled indicate mainly antiferromagnetism and weak ferromagnetism of Co3O4 nanoflowers at blocking temperature of 34 K respectively.
Thermal tolerance, acclimatory capacity and vulnerability to global climate change
Authors: Calosi Piero , Bilton David T , Spicer John I
Published: November 2007

Despite evidence that organismal distributions are shifting in response to recent climatic warming, we have little information on direct links between species' physiology and vulnerability to climate change. We demonstrate a positive relationship between upper thermal tolerance and its acclimatory ability in a well-defined clade of closely related European diving beetles. We predict that species with the lowest tolerance to high temperatures will be most at risk from the adverse effects of future warming, since they have both low absolute thermal tolerance and poor acclimatory ability. Upper thermal tolerance is also positively related to species' geographical range size, meaning that species most at risk are already the most geographically restricted ones, being endemic to Mediterranean mountain systems. Our findings on the relationship between tolerance and acclimatory ability contrast with results from marine animals, suggesting that generalizations regarding thermal tolerance and responses to future rapid climate change may be premature.
Locomotion pattern generation and mechanisms of a new biped walking machine
Authors: Lim Hun-ok , Ogura Y , Takanishi Atsuo
Published: November 2007

This paper describes the mechanism of a 16 d.f. biped walking machine, Waseda biped humanoid robot-2 lower limb (WABIAN-2LL), which has two 7 d.f. legs and a 2 d.f. waist actuated by DC servo motors with reduction gears. WABIAN-2LL is designed with large movable angle ranges like those of a human. Its height and weight are 1200 mm and 40 kg, respectively. It is able to walk with its knees stretched using the redundancy of the legs and to move around an object using a hip-bending motion without touching the object. A knee-stretched locomotion pattern generation is also proposed in this paper, which separately creates joint angles in a supporting and a swinging phase. During knee-stretched walking, the joint rate of the knee will approach infinitely when the knee is stretched. This singularity problem is solved by using the motion of the waist, not the posture of the trunk. The effectiveness of the mechanisms and pattern generations of WABIAN-2LL is verified through dynamic walking experiments.
The island rule: made to be broken?
Authors: Meiri Shai , Cooper Natalie , Purvis Andy
Published: November 2007

The island rule is a hypothesis whereby small mammals evolve larger size on islands while large insular mammals dwarf. The rule is believed to emanate from small mammals growing larger to control more resources and enhance metabolic efficiency, while large mammals evolve smaller size to reduce resource requirements and increase reproductive output. We show that there is no evidence for the existence of the island rule when phylogenetic comparative methods are applied to a large, high-quality dataset. Rather, there are just a few clade-specific patterns: carnivores; heteromyid rodents; and artiodactyls typically evolve smaller size on islands whereas murid rodents usually grow larger. The island rule is probably an artefact of comparing distantly related groups showing clade-specific responses to insularity. Instead of a rule, size evolution on islands is likely to be governed by the biotic and abiotic characteristics of different islands, the biology of the species in question and contingency.
Echolocation behaviour adapted to prey in foraging Blainville's beaked whale (Mesoplodon densirostris)
Authors: Johnson M , Hickmott L.S , Aguilar Soto N , Madsen P.T
Published: November 2007

Toothed whales echolocating in the wild generate clicks with low repetition rates to locate prey but then produce rapid sequences of clicks, called buzzes, when attempting to capture prey. However, little is known about the factors that determine clicking rates or how prey type and behaviour influence echolocation-based foraging. Here we study Blainville's beaked whales foraging in deep water using a multi-sensor DTAG that records both outgoing echolocation clicks and echoes returning from mesopelagic prey. We demonstrate that the clicking rate at the beginning of buzzes is related to the distance between whale and prey, supporting the presumption that whales focus on a specific prey target during the buzz. One whale showed a bimodal relationship between target range and clicking rate producing abnormally slow buzz clicks while attempting to capture large echoic targets, probably schooling prey, with echo duration indicating a school diameter of up to 4.3 m. These targets were only found when the whale performed tight circling manoeuvres spending up to five times longer in water volumes with large targets than with small targets. The result indicates that toothed whales in the wild can adjust their echolocation behaviour and movement for capture of different prey on the basis of structural echo information.
The number of subordinates moderates intrasexual competition among males in cooperatively breeding meerkats
Authors: Kutsukake Nobuyuki , Clutton-Brock Tim H
Published: November 2007

For dominant individuals in cooperatively breeding species, the presence of subordinates is associated with both benefits (i.e. increased reproductive output and other group-living benefits) and costs (i.e. intrasexual competition on reproduction). The biological market theory predicts that dominant individuals are tolerant to same-sex group members when there are only a few subordinates, so as to maximize their own reproductive success. We investigated factors affecting aggression by dominant males and submission by subordinate males for a cooperatively breeding mammal, meerkats,Suricata suricatta. In this species, reproductive conflict occurs between the dominant male and the non-offspring males. As predicted, the number of subordinates in a group was positively associated with the aggression frequency by the dominant male and with the submission frequency by the subordinate males. Relative to the aggression frequency against male offspring, the frequency of aggression against non-offspring males was comparable in small groups, but was higher in large groups. These results indicate that reproductive conflict is present between the dominant male and the non-offspring males but is moderated in groups with small numbers of subordinates. This study provides an empirical data agreeing with the biological market theory in the context of intrasexual competition in cooperatively breeding species.
Isotopic analysis of the sources of organic carbon for zooplankton in shallow subarctic and arctic waters
Authors: Rautio Milla , F. Vincent Warwick
Published: November 2007

Shallow high‐latitude lakes and ponds are usually characterized by an oligotrophic water column overlying a biomass‐rich, highly productive benthos. Their pelagic food webs often contain abundant zooplankton but the importance of benthic organic carbon versus seston as their food sources has been little explored. Our objectives were to measure the δ13C and δ15N isotopic signatures of pelagic and benthic particulate organic matter (POM) in shallow water bodies in northern Canada and to determine the relative transfer of this material to zooplankton and other aquatic invertebrates. Fluorescence analysis of colored dissolved organic matter (CDOM) indicated a relatively strong terrestrial carbon influence in five subarctic waterbodies whereas the CDOM in five arctic water columns contained mostly organic carbon of autochthonous origin. The isotopic signatures of planktonic POM and cohesive benthic microbial mats were distinctly different at all study sites, while non‐cohesive microbial mats often overlapped in their δ13C signals with the planktonic POM. Zooplankton isotopic signatures indicated a potential trophic link with different fractions of planktonic POM and the non‐cohesive mats whereas the cohesive mats did not appear to be used as a major carbon source. The zooplankton signals differed among species, indicating selective use of resources and niche partitioning. Most zooplankton had δ13C values that were intermediate between the values of putative food sources and that likely reflected selective feeding on components of the pelagic or benthic POM. The results emphasize the likely importance of benthic‐pelagic coupling in tundra ecosystems, including for species that are traditionally considered pelagic and previously thought to be dependent only on phytoplankton as their food source.
Investigating spatial structure in specific tree species in ancient semi‐natural woodland using remote sensing and marked point pattern analysis
Authors: Atkinson Peter M. , Foody Giles M. , Gething Peter W. , Mathur Ajay , Kelly Colleen K.
Published: November 2007

Remote sensing classification has the potential to provide important information, such as tree species distribution maps, to ecologists, at a range of spatial and temporal scales. However, standard classification procedures often fail to provide the high accuracies required for many ecological applications. Previously, a modified remote sensing classification technique was used to provide very high classification accuracies for one or two classes (e.g. species) of interest. The aim of this paper was to demonstrate that the output from the method can be suitable for spatial ecological analyses, and to provide a generic simulation framework for assessing the adequacy of any given remote sensing classification for such analyses. Marked point pattern analysis (MPPA) was applied to tree species distribution data obtained for sycamoreAcer pseudoplatanusand ashFraxinus excelsiorfrom a 400 ha ancient semi‐natural woodland in southern England using the modified remote sensing classification method to test several hypotheses of ecological interest relating to the spatial distribution and interaction of these species. Monte Carlo simulation methods were then used to evaluate the data and data quality requirements of the MPPA to check that the classified tree species maps for sycamore and ash were adequate. Using the combined method the spatial distributions for sycamore and ash were found to be aggregated and inter‐dependent at a range of spatial scales. Together, the remote sensing classification and simulation approaches provide the basis for exploiting more fully the potential of remote sensing to provide information of value to ecologists.
Neighbourhood analyses of tree seed predation by introduced rodents in a New Zealand temperate rainforest
Authors: J. Wilson Deborah , F. Wright Elaine , D. Canham Charles , A. Ruscoe Wendy
Published: November 2007

House mice Mus musculus and other introduced rodents represent a novel source of predation on tree seeds in New Zealand forests. In the northern temperate forests where these rodents are native, spatial and temporal variation in tree seed production can result in dramatic fluctuations in the distribution and abundance of seed predators, with subsequent feedbacks on the distribution and abundance of seedlings. We use neighbourhood models to examine variation in rodent predation on seeds of 4 tree species of the temperate rainforests of New Zealand as a function of 1) spatial variation in local canopy composition and 2) spatial and temporal variation in mouse activity. We placed seeds throughout mapped stands of mixed forests in alluvial valley bottoms and on elevated marine terraces in the Waitutu Forest, South Island. The risk of predation on seeds of 2 dominant canopy trees – rimu Dacrydium cupressinum and mountain beech Nothofagus solandri var. cliffortioides– peaked in neighbourhoods dominated by those species and by silver beech N. menziesii, particularly in a year of plentiful seed rain from these species. The risk of predation on rimu and beech seed was also related to measures of local mouse activity. These relationships suggest that the highest local abundance of mice was concentrated in rimu and beech neighbourhoods because of the food provided by seed rain from those trees. Predation on seed of miro Prumnopitys ferruginea, which is eaten by rats but not mice, was low in rimu neighbourhoods and where mouse activity was high. These patterns may reflect spatial segregation in the activity of rats versus mice within stands. Our results suggest that the spatial distribution of canopy trees translates into predictable patterns of variation in mouse activity and seed predation. Heterogeneity in rodent activity and seed predation within stands may have important implications for tree population dynamics.
Using the spatial information implicit in the habitat specificity of the burrowing crayfish Distocambarus crockeri to identify a lost landscape component
Authors: Welch Shane M. , Eversole Arnold G. , Riley Jeanne
Published: November 2007

Historical ecology can be used to model past environments and identify reference conditions for restoration efforts. The primary burrowing crayfish Distocambarus crockeri exhibits a high degree of habitat specialization and is largely limited to open canopied terrestrial habitats maintained along roadsides, utility rights‐of‐way, and agricultural field edges within a portion of the South Carolina piedmont, USA. Crayfish abundance, vegetation structure, and negative binomial regression were used to model the habitat of D. crockeri. Modeling indicated that within a community‐defined landscape patch context, D. crockeri was a prairie specialist. Historical descriptions of areas within the species’ range indicated that prairie‐like habitats (piedmont prairies) were a regular component of the landscape. The congruence between habitat models and historical data indicate that prairie habitat was a natural component of the historic piedmont landscape and that the habitat specificity of D. crockeri contained spatial information about this lost landscape component.
Territory size of wolvesCanis lupus: linking local (Białowieża Primeval Forest, Poland) and Holarctic‐scale patterns
Authors: J ędrzejewski Włodzimierz , Schmidt Krzysztof , Theuerkauf Jörn , J ędrzejewska Bogumiła , Kowalczyk Rafał
Published: November 2007

Factors affecting territory size in wolvesCanis lupuswere studied at 2 scales, the local population (Białowieża Primeval Forest (BPF), eastern Poland) and the geographic range of species (literature review from 14 localities in the Holarctic). Four packs of wolves were studied by radio‐tracking in BPF from 1994 to 1999. The annual territories of packs (Minimum convex polygons with 95% of locations) averaged 201 km2(SD 63, range 116–310). Core areas of territories (50% MCP) covered from 14 to 78 km2(mean 35). Territory sizes and core areas both were negatively correlated to the encounter rates of ungulates (mean number of ungulates seen per unit time spent in the forest by human observers). Pack size (3–8 wolves) did not influence territory size. Home ranges of individual wolves from the same pack varied with season as well as the age, sex, and reproductive status of the wolf. Review of literature from North America and Europe (42–66oN), showed that latitude and prey biomass were essential factors shaping the biogeographic variation in wolf territory size. Territories increased with latitude and declined with growing biomass of prey. The analysis showed that latitude acted partly independently of the south–north gradient in prey abundance. At similar standing crop of ungulate biomass (100 kg km−2), wolf territories would average 140 km2at 40oN, 370 km2at 50oN, and 950 km2at 60oN. Pack size was larger at northern latitudes, but the increase did not keep pace with enlargement of territories. Within‐territory density of wolves declined from 2.5–3 wolves 100 km−2at 40–45oN to 0.7 wolves 100 km−2at 60oN. Our analyses documented similarities regarding the role of prey resources in shaping wolf territoriality at the different scales. Furthermore, a macroecological approach revealed additional factors affecting wolf territory size that were not emergent from knowledge of local population.
Contemporary richness of holarctic trees and the historical pattern of glacial retreat
Authors: Montoya Daniel , Rodríguez Miguel A. , Zavala Miguel A. , Hawkins Bradford A.
Published: November 2007

The length of time land has been available for colonization by plants and other organisms could provide a partial explanation of the contemporary richness gradients of trees. According to this hypothesis, increasing times of land availability entail higher chances of recolonization, which eventually have positive effects on tree richness. To test this, we generated a dataset of the Holarctic trees and evaluated the influence of cell age, a measure of the time since an area became free of ice, on the observed tree richness gradients. We found that cell age is associated with richness in both Europe and North America, after controlling for contemporary climate patterns, suggesting that the historical pattern of glacial retreat in response to post‐Pleistocene global warming has left a signal still detectable after at least 14 000 yr. The results were consistent using a range of modelling approaches or whether Europe and North America were analyzed separately or in concert. We conclude that, although secondary to contemporary climate, the post‐glacial recolonization hypothesis is broadly supported at temperate latitudes.
Breeding phenology in relation to NDVI variability in free‐ranging African elephant
Authors: Wittemyer George , Barner Rasmussen Henrik , Douglas‐Hamilton Iain
Published: November 2007

The phenology of reproduction is often correlated with resource availability and is hypothesized to be shaped by selective forces in order to maximize lifetime reproductive success. African elephants have the distinctive life history traits of a 22 month gestation and extended offspring investment, necessitating a long‐term strategy of energy acquisition and reproductive expenditure to ensure successful offspring recruitment.

We investigated the relationship between the reproductive phenology of a wild elephant population and resource availability using remotely sensed Normalized Differential Vegetation Index (NDVI) data as a measure of time‐specific primary productivity and hence forage quality.

The initiation of female elephants’ 3+yr reproductive bout was dependent on conditions during the season of conception but timed so parturition occurred during the most likely periods of high primary productivity 22 months later. Thus, the probability of conception is linked to the stochastic variation in seasonal quality and the phenology of parturition is related to the predictable seasonality of primary productivity, indicating elephants integrate information on known current and expected future conditions when reproducing.

Juvenile mortality was not correlated with ecological variability, hence female fecundity rather than calf mortality appears to drive demographic processes in the study population.

Extreme climatic events, such as those associated with the El Niño‐Southern‐Oscillation (ENSO), acted to synchronize female fecundity in the population. This study suggests that the relationship between fecundity and ecological variability instigates the characteristic demographic fluctuations in elephant populations, rather than the mortality‐driven fluctuations observed in many ungulate populations.
Identifying spatial relationships at multiple scales: principal coordinates of neighbour matrices (PCNM) and geostatistical approaches
Authors: Bellier Edwige , Monestiez Pascal , Durbec Jean‐Pierre , Candau Jean‐Noël
Published: November 2007

We compared two methodological approaches – principal coordinate analysis of neighbour matrices (PCNM) and geostatistics – that both aim at extracting several spatial scales in order to identify spatial relationships between organisms and environmental variables at multiple scales. From a statistical point of view, PCNM analysis and geostatistics come from “two different worlds”– PCNM is based on classical “data analysis” while geostatistical modelling is developed in a probabilistic context. These two methods were used to investigate the spatial relationships between defoliation caused by spruce budwormChoristoneura fumiferanaand bioclimatic conditions in Ontario since 1941 through a wide range of scales. On the one hand, PCNM variables related to defoliation frequency were partitioned into four spatial submodels representing respectively four spatial scales: very broad scale (ca>300 km), broad scale (ca 180 km), fine (ca 100 km), and very fine (<80 km). On the other hand, nested variogram modelling was used to identify the relevant scales. The nested variogram model was composed of four variograms with different characteristic scales close to those of the PCNM spatial submodels. Maps of PCNM submodels and kriging components revealed similar spatial patterns of defoliation frequency at very broad and broad scales while spatial patterns at fine and very fine scales looked quite different. Both methods showed that defoliation by spruce budworm occurs at the broader spatial scales but may be explained by fluctuations at the smaller scales. Finally, results based on geostatistics using a Linear Model of Coregionalisation suggested that climatic conditions can be considered to act at the level of outbreak dynamics while the tree community of spruce budworm's principal hosts controls local population dynamics.
Awesome or ordinary? Global diversity patterns of oribatid mites
Authors: Maraun Mark , Schatz Heinrich , Scheu Stefan
Published: November 2007

Diversity of most above‐ground organisms increases with decreasing latitude, but the biogeographical and macroecological diversity patterns of below‐ground animals have been poorly studied. We investigated the latitudinal diversity gradient in a primarily below‐ground living soil taxon, oribatid mites. Furthermore, oribatid mite species richness from islands and mainlainds was tested for correlation with the size of the respective area (island or mainland) to evaluate if their species–area relationships are similar to those of above‐ground taxa. The results suggest that for oribatid mites 1) diversity increases from the boreal to the warm temperate region but not further to the tropics, and 2) species–area relationships for islands and mainlands are similar to those of above‐ground taxa, but this is mainly caused by very small islands, such as Cocos islands, and very large islands, such as Madagascar. When these islands are excluded the species–area relationship strongly differs from those of typical islands. The results support the view that below‐ground animal taxa are generalists that inhabit wide niches. Most small islands have relatively rich oribatid mite faunas, supporting the observation that a large number of species can coexist in a small area (high α‐diversity).
Habitat area affects arthropod communities directly and indirectly through top predators
Authors: Östman Örjan , Griffin Nicholas W. , Strasburg Jared L. , Brisson Jennifer A. , Templeton Alan R. , Knight Tiffany M. , Chase Jonathan M.
Published: November 2007

Both habitat area and predators are known to affect the diversity and composition of species that live in a locality. In addition, habitat area can influence the presence of predators, indirectly affecting the diversity of prey. Thus, habitat area may influence species diversity directly and indirectly through the presence of top predators. Here we examine the effects of habitat area and predators on the species richness and composition of a foliage living arthropod community in a fragmented complex of glades (small grassland patches within a forested matrix) in the Ozark Plateau, Missouri. We find that a top predator, the eastern collared lizardCrotaphytus collaris collaris, occurs primarily on larger glades. Glade area was positively correlated with arthropod diversity, but only after removing the effect of collared lizard presence. Moreover, collared lizards reduced overall arthropod richness, and shifted the dominance from predatory arthropods (e.g. spiders) and Orthopteran grasshoppers to Homopterans (planthoppers). This study shows the importance of accounting for variation in the presence of a top predator when studying the effect of landscape‐level processes on species richness and composition.
Survival of the fattest: body stores on migration and survival in red knots Calidris canutus islandica
Authors: Guy Morrison R. I. , Davidson Nick C. , Wilson Jim R.
Published: November 2007

Severe summer weather in Greenland and Arctic Canada in 1972 and 1974 caused very poor breeding success and elevated adult mortality in red knots Calidris canutus islandica. We show that those individual knots that are known to have survived these summers were in better than average nutritional condition shortly before departure from their late spring staging area in west Iceland. The condition index of previously banded or subsequently recovered birds captured in Iceland was positively related to the number of summers they were known to have survived. Body stores carried from the last spring staging area to the breeding grounds appear to offer Arctic‐breeding shorebirds significant selective advantages: they are used for physical transformation from migration to breeding condition, and in years when weather is difficult may enable survival after arrival on the breeding grounds.