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Selected AbstractsCitation counting, citation ranking, and h -index of human-computer interaction researchers: A comparison of Scopus and Web of ScienceJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 11 2008Lokman I. Meho This study examines the differences between Scopus and Web of Science in the citation counting, citation ranking, and h -index of 22 top human-computer interaction (HCI) researchers from EQUATOR,a large British Interdisciplinary Research Collaboration project. Results indicate that Scopus provides significantly more coverage of HCI literature than Web of Science, primarily due to coverage of relevant ACM and IEEE peer-reviewed conference proceedings. No significant differences exist between the two databases if citations in journals only are compared. Although broader coverage of the literature does not significantly alter the relative citation ranking of individual researchers, Scopus helps distinguish between the researchers in a more nuanced fashion than Web of Science in both citation counting and h -index. Scopus also generates significantly different maps of citation networks of individual scholars than those generated by Web of Science. The study also presents a comparison of h -index scores based on Google Scholar with those based on the union of Scopus and Web of Science. The study concludes that Scopus can be used as a sole data source for citation-based research and evaluation in HCI, especially when citations in conference proceedings are sought, and that researchers should manually calculate h scores instead of relying on system calculations. [source] Prey availability influences habitat tolerance: an explanation for the rarity of peregrine falcons in the tropicsECOGRAPHY, Issue 3 2001Andrew R. Jenkins The density and productivity of peregrine falconFalco peregrinus populations correlate positively with distance from the Equator, while habitat specificity increases with proximity to the Equator. Low peregrine densities in the tropics may he a result of competition with similar conveners (e.g. the lanner falcon F. biarmicus in Africa), which replace them in many areas. Alternatively, tropical peregrines may he limited by resource deficiencies that do not affect their close relatives. Data from peregrine and lanner populations in South Africa support the resource deficiency hypothesis, and there is no evidence to suggest direct competition between the two species. In areas where prey are not spatially or temporally concentrated, or otherwise particularly vulnerable to attack, morphological and behavioural specializations of peregrines probably restrict them to optimal foraging conditions. The relative dynamics of.Arctic and temperate vs tropical prey populations is suggested as an important factor determining peregrine distribution globally. Populations of other widespread hut particularly specialized avian predators (e.g. osprey Pandion haliaetus) may he similarly controlled. Food limitation (in terms of a dearth of particularly vulnerable prey) in the tropics has resulted in specialization and rarity in peregrines and generalization and relative abundance in similar congeners. [source] Prey availability influences habitat tolerance: an explanation for the rarity of peregrine falcons in the tropicsECOGRAPHY, Issue 3 2001Article first published online: 30 JUN 200 The density and productivity of peregrine falcon Falco peregrinus populations correlate positively with distance from the Equator, while habitat specificity increases with proximity to the Equator. Low peregrine densities in the tropics may be a result of competition with similar congeners (e.g. the lanner falcon F. biarmicus in Africa), which replace them in many areas. Alternatively, tropical peregrines may be limited by resource deficiencies that do not affect their close relatives. Data from peregrine and lanner populations in South Africa support the resource deficiency hypothesis, and there is no evidence to suggest direct competition between the two species. In areas where prey are not spatially or temporally concentrated, or otherwise particularly vulnerable to attack, morphological and behavioural specializations of peregrines probably restrict them to optimal foraging conditions. The relative dynamics of Arctic and temperate vs tropical prey populations is suggested as an important factor determining peregrine distribution globally. Populations of other widespread but particularly specialized avian predators (e.g. osprey Pandion haliaetus) may be similarly controlled. Food limitation (in terms of a dearth of particularly vulnerable prey) in the tropics has resulted in specialization and rarity in peregrines and generalization and relative abundance in similar congeners. [source] The spatial and temporal behaviour of the lower stratospheric temperature over the Southern Hemisphere: the MSU view.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2001Part I: data, methodology, temporal behaviour Abstract The lower stratosphere monthly temperature anomalies over the Southern Hemisphere derived from soundings made by the Microwave Sounding Unit (MSU) between 1979 and 1997 are analysed. Specifically MSU channel 4 temperature retrievals are considered. Principal component (PC) analysis with the S-mode approach is used in order to isolate grid points that covary in a similar manner and to determine the main features of their temporal behaviour. The first six PCs explain 81.3% of the variance and represent the different time variability patterns observed over the Southern Hemisphere for the ten area clusters determined by the method. The most important feature is common to all the PC score pattern,time series and corresponds to a negative linear trend present in almost all the Southern Hemisphere except over New Zealand and surrounding areas. The negative trend is largest over Antarctica. The remaining features of the temporal variability are different for each PC score and therefore for each cluster region over the Southern Hemisphere. The first PC score pattern shows the impact of the Chichón and Mt Pinatubo eruptions that each produced a 2-year warming over the tropical and sub-tropical lower stratosphere. This variability is orthogonal with the behaviour present over Antarctica. There are different anomalies between 1987 (El Niño) and 1988 (La Niña). This second PC does not show any evidence whatsoever of the volcanic eruptions. The semi-annual wave is present in the anomaly recurrence at mid to high latitudes. Over very low latitudes, close to the Equator, the Quasi-Biennial Oscillation (QBO) band of frequency is also present. Copyright © 2001 Royal Meteorological Society [source] In search of zonal circulations in the equatorial Atlantic sector from the NCEP,NCAR reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2001Stefan Hastenrath Abstract The National Center for Environmental Prediction,National Center for Atmospheric Research (NCEP,NCAR) 1958,1997 upper-air dataset has been evaluated for evidence of equatorial zonal circulation cells over the Atlantic and adjacent continents. For January, April, July and October, maps are presented of mid-tropospheric vertical motion, upper-tropospheric divergent flow, and zonal,vertical cross-sections of vertical and divergent zonal motion and total zonal flow. In the boreal winter half-year, a centre of intense ascending motion and upper-tropospheric, mainly northward-directed outflow is located off the mouth of the Amazon. From this centre there is also some outflow into centres of upper-tropospheric convergence and subsidence over the equatorial eastern Pacific and eastern Atlantic, respectively. From January to April, the near-equatorial band of ascending motion shifts southward, and the upper-tropospheric convergence centre is displaced from the Equator into the South Atlantic. In the boreal summer half-year, the band of strongest ascending motion is displaced northward, and two separate centres of upper-tropospheric divergent outflow are found over northern hemispheric Africa and the Central American Seas. From these centres, the outflow is directed approximately southward into the southern hemisphere. The analysis points to the existence of an equatorial zonal circulation cell in the Atlantic sector confined to around January. Copyright © 2001 Royal Meteorological Society [source] Using the extended quarter degree grid cell system to unify mapping and sharing of biodiversity dataAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009R. Larsen Abstract Information on the distribution of animal populations is essential for conservation planning and management. Unfortunately, shared coordinate-level data may have the potential to compromise sensitive species and generalized data are often shared instead to facilitate knowledge discovery and communication regarding species distributions. Sharing of generalized data is, unfortunately, often ad hoc and lacks scalable conventions that permit consistent sharing at larger scales and varying resolutions. One common convention in African applications is the Quarter Degree Grid Cells (QDGC) system. However, the current standard does not support unique references across the Equator and Prime Meridian. We present a method for extending QDGC nomenclature to support unique references at a continental scale for Africa. The extended QDGC provides an instrument for sharing generalized biodiversity data where laws, regulations or other formal considerations prevent or prohibit distribution of coordinate-level information. We recommend how the extended QDGC may be used as a standard, scalable solution for exchange of biodiversity information through development of tools for the conversion and presentation of multi-scale data at a variety of resolutions. In doing so, the extended QDGC represents an important alternative to existing approaches for generalized mapping and can help planners and researchers address conservation issues more efficiently. Résumé L'information sur la distribution des populations animales est essentielle pour la planification de la conservation et la gestion. Malheureusement, les données partagées au niveau des coordonnées risquent de compromettre les espèces sensibles, et les données généralisées sont souvent partagées pour faciliter la découverte et la communication des connaissances concernant la distribution des espèces. Le partage de données généralisées est, malheureusement, souvent opportuniste et manque de conventions mesurables qui permettraient le partage cohérent sur une plus grande échelle et à des résolutions variées. Une convention commune pour des applications africaines est le système de Quarter Degree Grid Cells (QDGC). Cependant, la norme actuelle ne supporte pas l'emploi des références uniques à travers l'Equateur et le premier méridien. Nous présentons une méthode pour étendre la nomenclature QDGC pour soutenir l'adoption de références uniques à l'échelle du continent, en Afrique. Le QDGC étendu fournit un instrument pour partager les données généralisées sur la biodiversité là où les lois, les réglementations et les autres considérations formelles empêchent ou interdisent la distribution de l'information au niveau coordonné. Nous disons dans quelle mesure le QDGC étendu peut être utilisé comme norme, une solution mesurable pour l'échange d'informations sur la biodiversité grâce au développement d'instruments pour la conversion et la présentation de données àéchelle multiple à des résolutions diverses. Ce faisant, le QDGC étendu représente une alternative importante aux approches existantes pour la cartographie généralisée et il peut aider les planificateurs et les chercheurs à traiter les problèmes de conservation plus efficacement. [source] Two major modes of variability of the East Asian summer monsoonTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 649 2010Xuguang Sun Abstract We study the two primary modes of variability associated with the East Asian summer monsoon, as identified using a multivariate Empirical Orthogonal Function (EOF) analysis. The second mode is shown to be related to changes in intensity of the South Asian High at 100 hPa while, consistent with previous work, the first mode is associated with an index for the shear vorticity of the 850 hPa zonal wind over the monsoon region. We show that a linear, dry dynamical model, when driven by the diabatic heating anomalies associated with each mode, can reproduce many of the anomalous circulation features, especially for the first EOF and in the lower troposphere. The model results indicate the importance of diabatic heating anomalies over the tropical Indian Ocean in the dynamics of both modes, especially EOF-1, and illustrate the role of local diabatic feedback for intensifying the circulation anomalies; in particular, the subtropical anticyclonic anomalies that are found in the positive phase of both modes, and the circulation anomaly associated with the Meiyu/Changma/Baiu rain band. A running cross-correlation analysis shows that the second EOF is consistently linked to both the decaying and the onset phase of El Niño/Southern Oscillation (ENSO) events throughout the study period (1958,2001). We attribute the connection in the onset phase to zonal wind anomalies along the Equator in the west Pacific associated with this mode. On the other hand, a link between the first EOF and ENSO is found only in the post-1979 period. We note also the role of sea-surface temperature anomalies in the tropical Indian Ocean in the dynamics of EOF-1, and a link to the variability of the Indian summer monsoon in the case of EOF-2. Copyright © 2010 Royal Meteorological Society [source] Addition of Carbene to the Equator of C70 To Produce the Most Stable C71H2 Isomer: 2,aH -2(12)a-Homo(C70 - D5h(6))[5,6]fullerene,ANGEWANDTE CHEMIE, Issue 5 2010Bao Li Dr. Endlich ist es gelungen, das schwer fassbare thermodynamisch stabilste Isomer von C71H2 (siehe Struktur) zu synthetisieren, und zwar durch Addition von CH2 an eine äquatoriale Bindung von C70,, und damit an eine Stelle, an der eine solche Reaktion kinetisch ungünstig ist. Rechnungen zufolge ist die verwendete pyrogene Synthesemethode der Grund, dass die Reaktanten die höhere Aktivierungsbarriere bei äquatorialer Addition überwinden können. [source] Distance Decay of Tree Species Similarity in Protected Areas on Terra Firme Forests in Colombian AmazoniaBIOTROPICA, Issue 5 2009Álvaro Duque ABSTRACT In this study, we investigated the pattern of floristic similarity as a function of geographical distances and environmental variability in well-drained uplands (terra firme) in Colombian Amazonia. The study site comprised three National Natural Parks, Tinigua, Chiribiquete, and Amacayacu, located in different geological units that represent a soil fertility gradient linked to parental materials. Differences in species richness between sites were compared using rarefaction analysis. A clear floristic transition appeared in the east,west direction following a soil fertility gradient along the first PCoA axis. In multiple regression analyses based on distance matrices, both geographical distances and geology explained 64 percent of the total floristic variation. Geographical distances alone accounted for 12 percent of variation in floristic similarities among plots, while geology alone accounted for 1 percent, and the joint effect of both explained 51 percent of the floristic variation. The species richness trend supports the existence of a latitudinal corridor southward of the geographical Equator in the Amazon basin, where tree diversity reaches the maximum expected values. A coupled effect of stochastic dispersal limitation and habitat specialization would certainly appear to be an appropriate explanation for tree species turnover in terra firme forests in Colombian Amazonia, strongly emphasizing that competition and neutrality must be supplementary rather than mutually exclusive processes. This result pinpoints the effect of dispersal on floral mixing as an ongoing active process for structuring tree communities in NW Amazonia, and the size of the reserves as a relevant issue to protect rare species from extinction by chance. [source] Myosin localization during meiosis I of crane-fly spermatocytes gives indications about its role in divisionCYTOSKELETON, Issue 2 2003Rosalind V. Silverman-Gavrila Abstract We showed previously that in crane-fly spermatocytes myosin is required for tubulin flux [Silverman-Gavrila and Forer, 2000a: J Cell Sci 113:597,609], and for normal anaphase chromosome movement and contractile ring contraction [Silverman-Gavrila and Forer, 2001: Cell Motil Cytoskeleton 50:180,197]. Neither the identity nor the distribution of myosin(s) were known. In the present work, we used immunofluorescence and confocal microscopy to study myosin during meiosis-I of crane-fly spermatocytes compared to tubulin, actin, and skeletor, a spindle matrix protein, in order to further understand how myosin might function during cell division. Antibodies to myosin II regulatory light chain and myosin II heavy chain gave similar staining patterns, both dependent on stage: myosin is associated with nuclei, asters, centrosomes, chromosomes, spindle microtubules, midbody microtubules, and contractile rings. Myosin and actin colocalization along kinetochore fibers from prometaphase to anaphase are consistent with suggestions that acto-myosin forces in these stages propel kinetochore fibres poleward and trigger tubulin flux in kinetochore fibres, contributing in this way to poleward chromosome movement. Myosin and actin colocalization at the cell equator in cytokinesis, similar to studies in other cells [e.g., Fujiwara and Pollard, 1978: J Cell Biol 77:182,195], supports a role of actin-myosin interactions in contractile ring function. Myosin and skeletor colocalization in prometaphase spindles is consistent with a role of these proteins in spindle formation. After microtubules or actin were disrupted, myosin remained in spindles and contractile rings, suggesting that the presence of myosin in these structures does not require the continued presence of microtubules or actin. BDM (2,3 butanedione, 2 monoxime) treatment that inhibits chromosome movement and cytokinesis also altered myosin distributions in anaphase spindles and contractile rings, consistent with the physiological effects, suggesting also that myosin needs to be active in order to be properly distributed. Cell Motil. Cytoskeleton 55:97,113, 2003. © 2003 Wiley-Liss, Inc. [source] Dynamics of the endoplasmic reticulum during early development of Drosophila melanogasterCYTOSKELETON, Issue 3 2003Yves Bobinnec Abstract In this study, we analyze for the first time endoplasmic reticulum (ER) dynamics and organization during oogenesis and embryonic divisions of Drosophila melanogaster using a Protein Disulfide Isomerase (PDI) GFP chimera protein. An accumulation of ER material into the oocyte takes place during the early steps of oogenesis. The compact organization of ER structures undergoes a transition to an expanded reticular network at fertilization. At the syncytial stage, this network connects to the nuclear envelope as each nucleus divides. Time-lapse confocal microscopy on PDI transgenic embryos allowed us to characterize a rapid redistribution of the ER during the mitotic phases. The ER network is massively recruited to the spindle poles in prophase. During metaphase most of the ER remains concentrated at the spindle poles and shortly thereafter forms several layers of membranes along the ruptured nuclear envelope. Later, during telophase an accumulation of ER material occurs at the spindle equator. We also analyzed the subcellular organization of the ER network at the ultrastructural level, allowing us to corroborate the results from confocal microscopy studies. This dynamic redistribution of ER suggests an unexpected regulatory function for this organelle during mitosis. Cell Motil. Cytoskeleton 54:217,225, 2003. © 2003 Wiley-Liss, Inc. [source] Identification of asymmetrically localized transcripts along the animal,vegetal axis of the Xenopus eggDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 8 2005Kensuke Kataoka In many organisms, proper embryo development depends on the asymmetrical distribution of mRNA in the cytoplasm of the egg. Here we report comprehensive screening of RNA localized in the animal or vegetal hemisphere of the Xenopus egg. Macroarrays including over 40 000 independent embryonic cDNA clones, representing at least 17 000 unigenes, were differentially hybridized with labeled probes synthesized from the mRNA of animal or vegetal blastomeres. After two rounds of screening, we identified 33 clones of transcripts that may be preferentially distributed in the vegetal region of the early stage embryo, but transcripts localized in the animal region were not found. To assess the array results, we performed northern blot and quantitative real-time reverse transcription,polymerase chain reaction analysis. As a result, 21 transcripts of the 33 were confirmed to be localized in the vegetal region of the early stage embryo. Whole-mount in situ hybridization analysis revealed that 11 transcripts, including 7 previously reported genes, were localized in the vegetal hemisphere of the egg. These 11 transcripts were categorized into three groups according to their expression patterns in the egg. The first group, which contained four transcripts, showed uniform expression in the vegetal hemisphere, similar to VegT. The second group, which contained three transcripts, showed gradual expression from the vegetal pole to the equator, similar to Vg1. The last group, which contained three transcripts, was expressed at the germ plasm, similar to Xdazl. One transcript, Xwnt11, showed both the second and the third expression patterns. [source] Geographic body size gradients in tropical regions: water deficit and anuran body size in the Brazilian CerradoECOGRAPHY, Issue 4 2009Miguel Á. Olalla-Tárraga A recent interspecific study found Bergmann's size clines for Holarctic anurans and proposed an explanation based on heat balance to account for the pattern. However, this analysis was limited to cold temperate regions, and exploring the patterns in warmer tropical climates may reveal other factors that also influence anuran body size variation. We address this using a Cerrado anuran database. We examine the relationship between mean body size in a grid of 1° cells and environmental predictors and test the relative support for four hypotheses using an AIC-based model selection approach. Also, we considered three different amphibian phylogenies to partition the phylogenetic and specific components of the interspecific variation in body size using a method analogous to phylogenetic eigen vector regression (PVR). To consider the potential effects of spatial autocorrelation we use eigenvector-based spatial filters. We found the largest species inhabiting high water deficit areas in the northeast and the smallest in the wet southwest. Our results are consistent with the water availability hypothesis which, coupled with previous findings, suggests that the major determinant of interspecific body size variation in anurans switches from energy to water towards the equator. We propose that anuran body size gradients reflect effects of reduced surface to volume ratios in larger species to control both heat and water balance. [source] Mollusk species diversity in the Southeastern Pacific: why are there more species towards the pole?ECOGRAPHY, Issue 2 2003Claudio Valdovinos The most ubiquitous and well recognized diversity pattern at large spatial scales is the latitudinal increase in species richness near the equator and decline towards the poles. Although several exceptions to this pattern have been documented, shallow water mollusks, the most specious group of marine invertebrates, are the epitome of the monotonic decline in species diversity toward higher latitudes along the Pacific and Atlantic coasts of North America. Here we analyze the geographic diversity of 629 mollusk species along the Pacific South American shelf. Our analyses are based on the most complete database of invertebrates assembled for this region of the world, consisting of latitudinal ranges of over 95% of all described mollusks between 10° and 55°S. Along this coast, mollusk diversity did not follow the typical latitudinal trend. The number of species remained constant and relatively low at intermediate latitudes and sharply increased toward higher latitudes, south of 42°S. This trend was explained by changes in shelf area, but not by sea surface temperature, unlike the pattern documented for Northern Hemisphere mollusks. Direct sampling of soft bottom communities along the gradient suggests that regional trends in species richness are produced by increased alpha diversity, and not only by artifacts produced by the increase in sampling area. We hypothesize that increased shelf area south of 42°S, geographic isolation produced by divergence of major oceanic currents, and the existence of refugia during glaciations, enabled species diversification. Radiation could have been limited by narrow continental shelves between 10°,42°. Asymmetries in latitudinal diversity trends between hemispheres show that there is not a single general factor determining large-scale diversity patterns. [source] Does a latitudinal gradient in seedling survival favour larger seeds in the tropics?ECOLOGY LETTERS, Issue 10 2004Angela T. Moles Abstract The mean size of seeds produced by plants at the equator is two to three orders of magnitude higher than the mean size of seeds produced by plants at 60°. We compiled data from the literature to assess the possibility that this latitudinal gradient in seed size allows species to cope with more difficult seedling establishment conditions in tropical environments. We found no relationship between latitude and seedling survival through 1 week (P = 0.27, n = 112 species). There was also no evidence that a larger seed mass is required to gain a given level of seedling survival in tropical environments (P = 0.37, n = 112 species), and no relationship between latitude and the duration of the juvenile period (P = 0.57, n = 132 species). Thus, our results are not compatible with the idea that seedling establishment is more difficult in the tropics. [source] Biodiversity hotspots, centres of endemicity, and the conservation of coral reefsECOLOGY LETTERS, Issue 6 2002Terry P. Hughes Abstract On land, biodiversity hotspots typically arise from concentrations of small-range endemics. For Indo-Pacific corals and reef fishes, however, centres of high species richness and centres of high endemicity are not concordant. Moreover ranges are not, on average, smaller inside the Central Indo-Pacific (CI-P) biodiversity hotspot. The disparity between richness and endemicity arises because corals and reef fishes have strongly skewed range distributions, with many species being very widespread. Consequently, the largest ranges overlap to generate peaks in species richness near the equator and the CI-P biodiversity hotspot, with only minor contributions from endemics. Furthermore, we find no relationship between the number of coral vs. fish endemics at locations throughout the Indo-Pacific, even though total richness of the two groups is strongly correlated. The spatial separation of centres of endemicity and biodiversity hotspots in these taxa calls for a two-pronged management strategy to address conservation needs. [source] Stress concentration factors of a general triaxial ellipsoidal cavityFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2008CHUN-RON CHIANG ABSTRACT The equivalent inclusion method is applied to solve the stress concentration problem concerning the disturbing effect of a general triaxial ellipsoidal cavity on an otherwise uniform normal stress state. Several useful solutions in simple form for limiting cases are derived and numerical results for general cases are obtained. These findings show the general features of the stress concentration factors around the base equator of the cavity. It is found that (1) when Poisson's ratio of the material is zero, the stress concentration factor does not vary along the equator of the cavity; (2) When the aspect ratio c/b of the cavity is very small, the stress concentration factor is also constant along the equator; (3) In general, the variation of stress concentration factors around the equator is less than 0.17 regardless of Poisson's ratio of the material. Thus, it is concluded that the stress concentration factor may be treated as constant around the equator of an ellipsoidal cavity with only a slight error. [source] Analysis of the trophy sport fishery for the speckled peacock bass in the Rio Negro River, BrazilFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2008M. H. HOLLEY Abstract, The middle portion of the Rio Negro River in Brazil near the equator supports a popular recreational sport fishery for speckled peacock bass, Cichla temensis (Humboldt). The objective of this study was to determine the effect of fishing mortality on this population. Fish were collected from sport-fishing (n = 72) and commercial (n = 103) catches and otoliths were aged to estimate longevity, growth and natural mortality. Recreational anglers in this region seek to catch, then release, larger speckled peacock bass; and fish larger than 62 cm standard length (SL) (about 4.5 kg) served as a bench mark to assess the potential impact of subsistence and commercial harvest on the abundance of larger fish in the sport fishery. Time of opaque band formation on otoliths generally coincided with the dry season (November to April); these bands appeared to form once per year, but formation was highly variable. Speckled peacock bass grew to 62 cm SL on average in 6.4 years, but some fish obtained this size in 4,5 years. Maximum age was 9 years, but most fish were less than 7 years. Instantaneous annual natural mortality (M) estimated from maximum size, longevity and growth ranged from 0.19 to 0.44. Simulation modelling predicted that exploitation rates of fish >25 cm SL similar to the estimated natural mortality rates would reduce the abundance of fish >62 cm by 67,89% compared with no harvest. Even modest exploitation rates of 5% and 10% would result in approximately 30,50% reduction, respectively, of these larger fish. Abundance of large speckled peacock bass that sustains the sport fishery is susceptible to low rates of exploitation in this remote region of Brazil. [source] Hypolithic Plants from Carruthers Peak, Snowy Mountains, New South Wales, AustraliaGEOGRAPHICAL RESEARCH, Issue 4 2009GREGG MÜLLER Abstract Hypolithic plants, plants growing under rocks, have been found from a number of climatically extreme, mostly arid sites from the poles to the equator, but there are limited reports from temperate zones. A brief survey in the Kosciuszko Alpine Area of New South Wales, Australia, revealed four species of moss and one liverwort growing beneath diaphanous quartz pebbles in feldmark vegetation communities. The probable restricted nature of this phenomenon and the likely impact of global warming, tourists and recreation management activities raise concerns for its conservation. [source] Palaeomagnetic evidence for the Gondwanian origin of the Taurides and rotation of the Isparta Angle, southern TurkeyGEOLOGICAL JOURNAL, Issue 4 2002John D. A. Piper Abstract The Taurides, the southernmost of the three major tectonic domains that constitute present-day Turkey, were emplaced following consumption of the Tethyan Ocean in Late Mesozoic to mid-Tertiary times. They are generally assigned an origin at the northern perimeter of Gondwana. To refine palaeogeographic control we have investigated the palaeomagnetism of a range of Jurassic rocks. Forty-nine samples of Upper Jurassic limestones preserve a dual polarity remanence (D/I=303/,9°, ,95=6°) interpreted as a primary magnetization acquired close to the equator and rotated during emplacement of the Taurides. Result from mid-Jurassic dolerites confirm a low palaeolatitude for the Tauride Platform during Jurassic times at the Afro,Arabian sector of Gondwana. Approximately 4000,km of Tethyan closure subsequently occurred between Late Jurassic and Eocene times. Although related Upper Jurassic limestones and Liassic redbeds preserve a sporadic record of similar remanence, the dominant signature in these latter rocks is an overprint of probable mid-Miocene age, probably acquired during a single polarity chron and imparted by migration of a fluid front during nappe loading. This is now rotated consistently anticlockwise by c. 30° and conforms to results of previous studies recording bulk Neogene rotation of the Isparta region following Lycian nappe emplacement. The regional distribution of this overprint implies that the Isparta Angle (IA) has been subject to only small additional closure (<10°) since Late Miocene time. A smaller amount (c. 6°) of clockwise rotation within the IA since Early Pliocene times is associated with an ongoing extensional regime and reflects an expanding curvature of the Tauride arc produced by southwestward extrusion of the Anatolian collage as a result of continuing northward motion of Afro,Arabia. Copyright © 2002 John Wiley & Sons, Ltd. [source] Variations in the Earth's gravity field caused by torsional oscillations in the coreGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004Mathieu Dumberry SUMMARY We investigate whether a component of the flow in the Earth's fluid core, namely torsional oscillations, could be detected in gravity field data at the surface and whether it could explain some of the observed time variations in the elliptical part of the gravity field (J2). Torsional oscillations are azimuthal oscillations of rigid coaxial cylindrical surfaces and have typical periods of decades. This type of fluid motion supports geostrophic pressure gradients, which produce deformations of the core,mantle boundary. Because of the density discontinuity between the core and the mantle, such deformations produce changes in the gravity field that, because of the flow geometry, are both axisymmetric and symmetric about the equator. Torsional oscillations are thus expected to produce time variations in the zonal harmonics of even degree in the gravity field. Similarly, the changes in the rotation rates of the mantle and inner core that occur to balance the change in angular momentum carried by the torsional oscillations also produce zonal variations in gravity. We have built a model to calculate the changes in the gravity field and in the rotation rates of the mantle and inner core produced by torsional oscillations. We show that the changes in the rotation rate of the inner core produce changes in J2 that are a few orders of magnitude too small to be observed. The amplitudes of the changes in J2 from torsional oscillations are 10 times smaller than the temporal changes that are observed to occur about a linear secular trend. However, provided the mechanism responsible for these changes in J2 is identified and that this contribution is removed from the data, it may be possible in the future to detect the lowest harmonic degrees of the torsional oscillations in the gravity field data. We also show that torsional oscillations have contributed to the linear secular change in J2 by about ,0.75 × 10,12 per year in the last 20 years. Finally, the associated change in the vertical ground motion at the surface of the Earth that is predicted by our mechanism is of the order of 0.2 mm, which is too small to be detected with the current precision in measurements. [source] Magnetic field annihilators: invisible magnetization at the magnetic equatorGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003S. Maus SUMMARY Some distributions of magnetization give rise to magnetic fields that vanish everywhere above the surface, rendering these distributions of magnetization completely invisible. They are the annihilators of the magnetic inverse problem. Known examples are the infinite sheet with constant magnetization and the spherical shell of constant susceptibility magnetized by an arbitrary internal field. Here, we show that remarkably more interesting annihilators exist for the Earth's dipole-dominated inducing field. Indeed, any susceptibility profile along the magnetic equator can be extended north/south into an annihilator. Consequently, the induced magnetization along the magnetic equator is entirely undetermined by the visible magnetic field. In contrast to the Backus effect, this ambiguity persists even if the full magnetic vector field is known. [source] Palaeomagnetic records of the Brunhes/Matuyama polarity transition from ODP Leg 124 (Celebes and Sulu seas)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2000Hirokuni Oda Palaeomagnetic records of the Brunhes/Matuyama geomagnetic polarity transition were obtained from deep-sea sediments of ODP Leg 124 in the Celebes and Sulu seas. Advanced piston core (APC) samples with high magnetization intensities (2,200 mA m,1,) and high sedimentation rates (8.4,10 cm kyr,1,) were recovered from this cruise. Rock-magnetic measurements revealed the carrier of the remanence to be nearly pure magnetite in the pseudo-single-domain range. Pass-through measurements at intervals of 5 mm on APC cores across the Brunhes/Matuyama polarity transition for Holes 767B, 769A and 769B were deconvolved with the magnetometer sensor response using the ABIC-minimizing method. Discrete samples were also taken from the polarity transition zones and subjected to either thermal or alternating field stepwise demagnetization. The results were generally consistent with the pass-through data after the deconvolution. Results from the three holes are in good agreement, particularly those from the two holes 100 m apart at Site 769. The transitional VGP paths from these two holes show two small loops near New Zealand before the equator is crossed. The VGPs continue to swing eastwards to the North Atlantic and then move to the northeastern margin of the Pacific Ocean. The positions of the VGP loops obtained from Site 769 are different from the VGP clusters obtained from both the known volcanic records and the sediment records at the Boso Peninsula and the North Atlantic sites with high sedimentation rates. Such a difference may imply the predominance of the non-dipole field during the transition. Relatively stable mid-high northern latitude VGPs are recognized on all three cores just after the reversal, lasting about 4000 years. The plot of relative intensity versus VGP latitude for the sediment records from the North Atlantic (DSDP Hole 609B) shows a remarkable similarity with our records. Similar patterns were also obtained for the plot of the palaeointensity versus VGP latitude for the La Palma volcanic lava records. These results may suggest the existence of a metastable state of the geodynamo, producing a zonal component just after the Brunhes/Matuyama boundary, which may have played a role in the change of the field intensity. [source] Can the tropical conservatism hypothesis explain temperate species richness patterns?GLOBAL ECOLOGY, Issue 4 2009An inverse latitudinal biodiversity gradient in the New World snake tribe Lampropeltini ABSTRACT Aim, A latitudinal gradient in species richness, defined as a decrease in biodiversity away from the equator, is one of the oldest known patterns in ecology and evolutionary biology. However, there are also many known cases of increasing poleward diversity, forming inverse latitudinal biodiversity gradients. As only three processes (speciation, extinction and dispersal) can directly affect species richness in areas, similar factors may be responsible for both classical (high tropical diversity) and inverse (high temperate diversity) gradients. Thus, a modified explanation for differential species richness which accounts for both patterns would be preferable to one which only explains high tropical biodiversity. Location, The New World. Methods, We test several proposed ecological, temporal, evolutionary and spatial explanations for latitudinal diversity gradients in the New World snake tribe Lampropeltini, which exhibits its highest biodiversity in temperate regions. Results, We find that an extratropical peak in species richness is not explained by latitudinal variation in diversification rate, the mid-domain effect, or Rapoport's rule. Rather, earlier colonization and longer duration in the temperate zones allowing more time for speciation to increase biodiversity, phylogenetic niche conservatism limiting tropical dispersal and the expansion of the temperate zones in the Tertiary better explain inverse diversity gradients in this group. Main conclusions, Our conclusions are the inverse of the predictions made by the tropical conservatism hypothesis to explain higher biodiversity near the equator. Therefore, we suggest that the processes invoked are not intrinsic to the tropics but are dependent on historical biogeography to determine the distribution of species richness, which we refer to as the ,biogeographical conservatism hypothesis'. [source] Performance of recalibration systems for GCM forecasts for southern AfricaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2006Mxolisi E. Shongwe Abstract Two regression-based methods that recalibrate the ECHAM4.5 general circulation model (GCM) output during austral summer have been developed for southern Africa, and their performance assessed over a 12-year retroactive period 1989/90,2000/01. A linear statistical model linking near-global sea-surface temperatures (SSTs) to regional rainfall has also been developed. The recalibration technique is model output statistics (MOS) using principal components regression (PCR) and canonical correlation analysis (CCA) to statistically link archived records of the GCM to regional rainfall over much of Africa, south of the equator. The predictability of anomalously dry and wet conditions over each rainfall region during December,February (DJF) using the linear statistical model and MOS models has been quantitatively evaluated. The MOS technique outperforms the raw-GCM ensembles and the linear statistical model. Neither the PCR-MOS nor the CCA-MOS models show clear superiority over the other, probably because the two methods are closely related. The need to recalibrate GCM predictions at regional scales to improve their skill at smaller spatial scales is further demonstrated in this paper. Copyright © 2006 Royal Meteorological Society. [source] Climate dynamics of atmosphere and ocean in the equatorial zone: a synthesisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2004Stefan Hastenrath Abstract A synopsis is offered of circulation mechanisms in the oceanic regions of the equatorial zone. Over the eastern Atlantic and Pacific, and especially in boreal summer, cross-equatorial flow from the Southern Hemisphere is strong and induces a tongue of cold surface waters, centred to the south of the equator. Upon crossing the equator in these sectors, owing to the Coriolis effect and a kinetic energy imbalance, the airstream speeds up and divergence develops, producing the Intertropical Divergence Zone (ITDZ). Once these processes result in the wind recurving from southeasterly to southwesterly, the flow slows down and becomes convergent, manifest in the Intertropical Convergence Zone, with a maximum to the south of the wind confluence. By contrast, over the western Atlantic and central Pacific and especially in boreal winter, winds in the equatorial band are predominantly from the east, upper-ocean Ekman transport is directed away from the equator, and the upwelling and cold tongue are centred on the equator. Cross-equatorial flow is insufficient to produce recurvature, the ITDZ is narrower and weaker, the divergence maximum is at the equator rather than in low northern latitudes, and the convergence maximum straddles the wind confluence. Over the Indian Ocean, the wind field is dominated by the alternation between the predominantly meridional flow of the winter and summer monsoons. Equatorial westerlies are limited to the short monsoon transition seasons. Essential for their origin is an eastward pressure gradient along the equator and weak southern trade winds, allowing recurvature somewhat south of the equator. Because the zonal pressure gradient is strongest in boreal summer and the southern trade winds are weakest in austral summer, the equatorial westerlies peak in spring and autumn. The boreal autumn equatorial westerlies are the surface manifestation of a powerful zonal,vertical circulation cell along the Indian Ocean equator. Equatorial zonal,vertical circulation cells require well-developed zonal flow in the lower troposphere along the equator and, therefore, appear confined to the oceanic longitudes and certain seasons. Thus, they are found over the Atlantic only in boreal winter and over the Indian Ocean only in boreal autumn, whereas over the Pacific they prevail all year round. Copyright © 2004 Royal Meteorological Society [source] Exploring the predictability of the ,Short Rains' at the coast of East AfricaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2004Stefan Hastenrath Abstract The boreal autumn ,Short Rains' at the coast of East Africa are deficient when there is weak development of a zonal circulation cell along the Indian Ocean equator, an anomalously low sea-surface temperature in the western portion of the basin, and in the high phase of the southern oscillation. Such large-scale circulation departures and their precursors are described by compact indices. September values of these indices for the period 1958,96 are used to explore the predictability of an index (RON) of October,November rainfall at the coast of East Africa. Regressions with cross-validation over the entire 1958,96 period are evaluated for the early (1958,77) and late (1978,96) halves of the record. In complementary experiments, the entire record is separated into 1958,77 as a training period and 1978,96 as a verification period. In all experiments, correlation of calculated versus observed rainfall is high for the early record and low for the late half of the record, a behaviour not noted in cross-validation over the entire 39 year time span. The 11-year sliding correlations of the indicated circulation indices with RON all reveal a drastic deterioration of relationships from the early to the late half of the record, although the equatorial zonal circulation cell appears to remain strong throughout. Copyright © 2004 Royal Meteorological Society [source] Interdecadal Pacific Oscillation and South Pacific climateINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2001M.J. Salinger Abstract The Interdecadal Pacific Oscillation (IPO) has been shown to be associated with decadal climate variability over parts of the Pacific Basin, and to modulate interannual El Niño,Southern Oscillation (ENSO)-related climate variability over Australia. Three phases of the IPO have been identified during the 20th century: a positive phase (1922,1944), a negative phase (1946,1977) and another positive phase (1978,1998). Climate data are analysed for the two most recent periods to describe the influence of the IPO on decadal climate trends and interannual modulation of ENSO teleconnections throughout the South West Pacific region (from the equator to 55°S, and 150°E to 140°W). Data coverage was insufficient to include the earliest period in the analysis. Mean sea level pressure (SLP) in the region west of 170°W increased for the most recent positive IPO period, compared with the previous negative phase. SLP decreased to the east of 170°W, with generally more southerly quarter geostrophic flow over the region. Annual surface temperature increased significantly southwest of the South Pacific Convergence Zone (SPCZ) at a rate similar to the average Southern Hemisphere warming. Northwest of the SPCZ temperature increases were less, and northeast of the SPCZ more than the hemispheric warming in surface temperature. Increases of annual precipitation of 30% or more occurred northeast of the SPCZ, with smaller decreases to the southwest, associated with a movement in the mean location of the SPCZ northeastwards. The IPO modulates teleconnections with ENSO in a complex way, strengthening relationships in some areas and weakening them in others. For New Zealand, there is a consistent bias towards stronger teleconnections for the positive IPO period. These results demonstrate that the IPO is a significant source of climate variation on decadal time scales throughout the South West Pacific region, on a background which includes global mean surface temperature increases. The IPO also modulates interannual ENSO climate variability over the region. Copyright © 2001 Royal Meteorological Society [source] Climate of the seasonal cycle in the North Pacific and the North Atlantic oceansINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2001Igor M. Yashayaev Abstract Time series of monthly sea-surface temperature (SST), air temperature (AT) and sea level pressure (SLP) were constructed from merged releases of the Comprehensive Ocean-Atmosphere Data Set (COADS). The time series were decomposed into seasonal and non-seasonal (short and long-term) components. The contribution of the seasonal cycle to the total variance of SST and AT exceeds 80% in the mid and in some high latitude locations and reaches its peak (>95%) in the centres of subtropical gyres. In most cases, a combination of annual and semiannual harmonics accounts for more than 95% of the seasonal variability. Amplitudes of SST and AT annual cycles are highest near the western boundaries of the oceans; annual phases of SST and AT increase toward the eastern tropical oceans, revealing a southeastern propagation of the annual cycle over the Northern Hemisphere oceans. The annual cycle of AT leads that of SST by 1,3 weeks. The largest phase differences are observed in the regions of western boundary currents in the North Pacific and the North Atlantic oceans. This is consistent with spatial patterns of integral air,sea heat fluxes. Annual phases of SST increase along the Gulf Stream and the Kuroshio Current. This points to the importance of signal transport by the major ocean currents. The lowest annual amplitudes of SLP are observed along the equator (0°,10°N) in both oceans. There are three distinct areas of high annual amplitudes of SLP in the North Pacific Ocean: Asian, Aleutian and Californian. Unlike the North Pacific, only one such area exists in the North Atlantic centred to the west of Iceland. A remarkable feature in the climate of the North Pacific is a maximum of semiannual SLP amplitudes, centred near 40°N and 170°W. It is also an absolute maximum in the entire Northern Hemisphere. Analysis of phases of harmonics of SLP seasonal cycle has revealed the trajectories of propagation of the annual and semiannual cycles. Analysis of semiannual to annual amplitudes ratio has revealed the regions of semiannual cycle dominance. Copyright © 2001 Royal Meteorological Society [source] Flea species richness and parameters of host body, host geography and host ,milieu'JOURNAL OF ANIMAL ECOLOGY, Issue 6 2004BORIS R. KRASNOV Summary 1We have assessed how different host parameters affect species richness of flea assemblages using the independent contrasts method. Three groups of host parameters were examined. The first group included host body parameters (body size, basal and average daily metabolic rates), the second group included parameters of geographical range size and position of this range in relation to the equator (latitude) and the third group comprised parameters related to the number of sympatric closely related species. 2None of the host body parameters correlated with species richness of flea assemblages. 3Flea species richness increased with an increase in latitude of the geographical range centre of a host as well as with an increase in a composite variable that described the size of the geographical range. 4The number of sympatric closely related species both across the entire geographical range and locally was correlated positively with species richness of fleas. 5Our results show that species richness of ectoparasites is affected little by parameters of the host body and to a greater extent by parameters related to the host environment. 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