Ascent

Distribution by Scientific Domains
Distribution within Earth and Environmental Science


Selected Abstracts


Description and Prescription: How Gender Stereotypes Prevent Women's Ascent Up the Organizational Ladder

JOURNAL OF SOCIAL ISSUES, Issue 4 2001
Madeline E. Heilman
This review article posits that the scarcity of women at the upper levels of organizations is a consequence of gender bias in evaluations. It is proposed that gender stereotypes and the expectations they produce about both what women are like (descriptive) and how they should behave (prescriptive) can result in devaluation of their performance, denial of credit to them for their successes, or their penalization for being competent. The processes giving rise to these outcomes are explored, and the procedures that are likely to encourage them are identified. Because of gender bias and the way in which it influences evaluations in work settings, it is argued that being competent does not ensure that a woman will advance to the same organizational level as an equivalently performing man. [source]


Wittgenstein, Augustine and the Fantasy of Ascent

PHILOSOPHICAL INVESTIGATIONS, Issue 2 2002
Caleb Thompson
First page of article [source]


Book review: Molecular Nutrition and Genomics: Nutrition and the Ascent of Humankind

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 2 2008
Jim Kaput
No abstract is available for this article. [source]


The higher they climb: plasma levels of angiogenic and lymphangiogenic factors during ascent to Mount Everest

ACTA PHYSIOLOGICA, Issue 2 2009
Joachim FandreyArticle first published online: 30 APR 200
No abstract is available for this article. [source]


Pentecostals: The Power of the Powerless

DIALOG, Issue 1 2002
Lene Sjųrup
Many researchers interpret Pentecostalism in terms of external factors such as European and North American history or economics. In this article Pentecostalism is examined from below, through qualitative interviews with women living in poverty in Santiago, Chile. The analysis shows how Pentecostalism led to a new theology where the believer became the subject of her own life. Social ascent was made through ecstatic experiences of the spirit in a caring community which directed the individual towards "a female ethos." This subjective change affected social changes in Chile under dictatorship but not in state politics because parts of the Pentecostal hierarchy collaborated with Pinochet. [source]


Evidence of Robust Coupling of Atrioventricular Mechanical Function of the Right Side of the Heart: Insights from M-Mode Analysis of Annular Motion

ECHOCARDIOGRAPHY, Issue 6 2008
Raveen Bazaz M.D.
Background: Extensive data exist regarding annular descent and ventricular function. We have already demonstrated significant differences in amplitude and timing of events between maximal mitral (MAPSE) and tricuspid (TAPSE) annular plane systolic excursion as well as described quantitative temporal differences in annular ascent (AA) between the right and left sides of the heart. However, whether any relationship exists between annular ascent and descent components remains uninvestigated. Methods: Left ventricular ejection fraction (LVEF), right ventricular fractional area change (RVFAC), MAPSE, TAPSE, MV, and TV AA as well as pulsed tissue Doppler of the lateral MV and TV annuli were recorded from 53 patients. Results: In this population (age 55 ± 17 years) mean LVEF was 55 ± 19%, mean RVFAC was 47 ± 20%, mean MAPSE was 2.11 ± 0.72 cm, mean TAPSE was 1.48 ± 0.44 cm, mean MV AA was 0.52 ± 0.17 cm, TV AA was 0.96 ± 0.47, MV A-wave 0.10 ± 0.04 cm/s, and TV A-wave was 0.13 ± 0.05 cm/s. A more robust correlation was seen between TV AA and RVFAC than between MV AA and LVEF and also between TV AA and pulsed TDI TV A-wave velocity than between MV AA and pulsed TDI MV A-wave. Conclusion: Our data reveal that mechanical systolic functions of the atria and the ventricles are more closely coupled on the right than on the left side of the heart. Whether this is a result of anatomic linking or chamber geometry will require further study. [source]


Diel interactions between prey behaviour and feeding in an invasive fish, the round goby, in a North American river

FRESHWATER BIOLOGY, Issue 4 2006
STEPHANIE M. CARMAN
Summary 1. We studied the diet of the invasive round goby (Neogobius melanostomus) on a diel basis in the Flint River, a warmwater stream in Michigan, U.S.A. Diet and available prey samples were collected seven times over a 24 h period in four consecutive months. The section of river studied lacked zebra mussels (Dreissena polymorpha), the primary prey of adult round gobies elsewhere in the Great Lakes region. 2. Diet changed on a diel basis with hydropsychid caddisfly and chironomid larvae predominating during the day, chironomid pupae dominating in the evening and heptageniid mayflies dominating at night. Simultaneous study of macroinvertebrate drift suggested that caddisfly and chironomid larvae were most likely picked from submerged rocks, chironomid pupae were most likely taken during their emergent ascent and mayflies were either captured from the drift or picked from rocks. 3. The Flint River lacks a diverse darter (Family: Percidae) and sculpin (Family: Cottidae) fauna and it appears that the round goby has occupied a generalised darter/sculpin niche. Our results indicate that round gobies have the potential to invade successfully riverine systems, particularly those lacking a diverse benthic fish assemblage. [source]


Pax6 transcription factor is required for the interkinetic nuclear movement of neuroepithelial cells

GENES TO CELLS, Issue 9 2007
Hiroshi Tamai
The mammalian cerebral cortex develops from proliferative neuroepithelial cells that exhibit a cell cycle-dependent nuclear movement (interkinetic nuclear migration; INM). Pax6 transcription factor plays pivotal roles in various aspects of corticogenesis. From live observation using cultured cortical slices from the Pax6 mutant rat, we identified the premature descent of S phase cells, the unsteady ascent or descent of G2 phase cells, and ectopic cell division within the basal side of the ventricular zone (VZ). The centrosome normally stayed at the most apical side, apart from the nucleus, in the neuroepithelial cell during the S to G2 phase, while the Pax6 mutant showed unstable movement of the centrosome associated with an abnormal INM. Our results suggest the possibility that Pax6 regulates the INM by stabilizing the centrosome at the apical side. [source]


Earthquake effects on the Anatolian Motorway, Turkey

GEOLOGY TODAY, Issue 2 2009
Hayrettin Koral
On 12 November 1999, the Anatolian earthquake in Turkey damaged a partially completed motorway viaduct. The viaduct, which is some 2.3 km long, passes over the Düzce Fault as the route starts its ascent into the Turkish plateau. The Düzce Fault is a northern offshoot of the main North Anatolian Fault (NAF) Zone, and cuts the viaduct at an acute angle of 15 degrees. Movements along the NAF have been identified as the prime cause of the earthquake. Alternatives to a viaduct crossing had been considered in the feasibility stage, but were ruled out because of the rugged landslide-influenced terrain and requirements for an even motorway ascent grade. The relative displacement of around 120 equally spaced piers identified the nature of the ground displacements and gave an indication as to the likely areas of foundation damage. This article examines the damage caused to the viaduct during the earthquake. [source]


Analytical and 3-D numerical modelling of Mt. Etna (Italy) volcano inflation

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2005
A. Bonaccorso
SUMMARY Since 1993, geodetic data obtained by different techniques (GPS, EDM, SAR, levelling) have detected a consistent inflation of the Mt. Etna volcano. The inflation, culminating with the 1998,2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions, is interpreted in terms of magma ascent and refilling of the volcanic plumbing system and reservoirs. We have modelled the 1993,1997 EDM and GPS data by 3-D pressurized sources to infer the position and dimension of the magma reservoir. We have performed analytical inversions of the observed deformation using both spheroidal and ellipsoidal sources embedded in a homogeneous elastic half-space and by applying different inversion methods. Solutions for these types of sources show evidence of a vertically elongated magma reservoir located 6 km beneath the summit craters. The maximum elevation of topography is comparable to such depth and strong heterogeneities are inferred from seismic tomography; in order to assess their importance, further 3-D numerical models, employing source parameters extracted from analytical models, have been developed using the finite-element technique. The deformation predicted by all the models considered shows a general agreement with the 1993,1997 data, suggesting the primary role of a pressure source, while the complexities of the medium play a minor role under elastic conditions. However, major discrepancies between data and models are located in the SE sector, suggesting that sliding along potential detachment surfaces may contribute to amplify deformation during the inflation. For the first time realistic features of Mt. Etna are studied by a 3-D numerical model characterized by the topography and lateral variations of elastic structure, providing a framework for a deeper insight into the relationships between internal sources and tectonic structures. [source]


Simulation of the intraseasonal and the interannual variability of rainfall over West Africa with RegCM3 during the monsoon period

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010
M. B. Sylla
Abstract Intraseasonal and interannual variability of rainfall is simulated using the International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM3) over West Africa. The intraseasonal variability of rainfall showing three distinct phases and the monsoon jump is well reproduced in the simulation. In addition, the regional model shows that while the monsoon rainbelt moves to the Sahel, the African Easterly Jet (AEJ) undergoes a northward migration and a weakening from June to August, when the core is at its northernmost location. This coexists with the appearance and the strengthening of the Tropical Easterly Jet (TEJ), the development and increased activity of the African Easterly Waves (AEWs), and the intensification and northward shift of the ascent between the AEJ and the TEJ core levels and axis. Similarly, the simulated interannual variability of rainfall over West Africa, the Guinea region, and the Sahel, as well as the variability of atmospheric features during contrasting wet and dry years, is also well captured. In fact, in the simulation during dry years the AEWs activity is decreased while the AEJ is strengthened and migrates southward, the TEJ becomes weaker, and the ascent between the levels of the AEJ and the TEJ decreases. The simulated rainfall variability and the behavior of the related features during the rainy season and during contrasting wet and dry years are in line with previous studies that used observations and reanalysis. We conclude that this model performance is of sufficient quality for application to the study of climate processes and mechanisms over West Africa. Copyright © 2009 Royal Meteorological Society [source]


The Contribution of Foot Problems to Mobility Impairment and Falls in Community-Dwelling Older People

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 12 2001
Hylton B. Menz B Pod (Hons)
OBJECTIVES: To investigate the relationship between foot problems, balance, and functional ability in community-dwelling older people and to determine whether older people with a history of multiple falls exhibit greater foot impairment than those who have not fallen or who have fallen once only. DESIGN: A cross-sectional, retrospective study. SETTING: Falls and Balance Laboratory, Royal North Shore Hospital, Sydney, Australia. PARTICIPANTS: One hundred thirty-five community-dwelling men and women age 75 to 93 (mean age ± standard deviation, 79.8 ± 4.1). MEASURES: Foot problem score; postural sway; coordinated stability; stair ascent and descent; an alternate stepping test; timed 6-meter walk; and tests of vision, sensation, strength, and reaction time. RESULTS: Eighty-seven percent of the sample had at least one foot problem. Women had a significantly higher foot problem score than did men. The foot problem score was significantly associated with performance on the coordinated stability test, stair ascent and descent, alternate stepping test, and timed 6-meter walk. Multiple regression analyses revealed that the foot problem score was a significant independent predictor of performance in the coordinated stability test, stair ascent and descent, and the alternate stepping test. Subjects with a history of multiple falls had a significantly higher foot problem score than did those who had not fallen or who had fallen once only, but the prevalence of individual foot conditions or the presence of foot pain did not differ between these groups. CONCLUSIONS: Foot problems are common in older people and are associated with impaired balance and performance in functional tests. Furthermore, older people with a history of multiple falls have greater foot impairment than non- or once-only fallers. These findings provide further evidence that foot problems are a falls risk factor and suggest that the cumulative effect of multiple foot problems is more important in increasing falls risk than the presence or absence of individual foot conditions. [source]


The para-aortic ridge plays a key role in the formation of the renal, adrenal and gonadal vascular systems

JOURNAL OF ANATOMY, Issue 6 2010
Sumio Isogai
Abstract Renal, adrenal, gonadal, ureteral and inferior phrenic arteries vary in their level of origin and in their calibre, number and precise anatomical relationship to other structures. Studies of the origin and early development of these arteries have evoked sharp disputes. The ladder theory of Felix, which states that ,All the mesonephric arteries may persist; from them are formed the phrenic, suprarenal, renal and internal spermatic arteries' has been generally quoted in the anatomical textbooks without rigorous verification for 100 years. In this study, we re-examined this theory by performing micro-injection of dye and resin into rat (Rattus norvegicus) embryos. Our results revealed that most of the mesonephric arteries had degenerated before the metanephros started its ascent. The definitive renal, adrenal, gonadal, ureteral and inferior phrenic arteries appeared as new branches from the gonadal artery and/or directly from the abdominal aorta to the para-aortic ridge. Coincidental to this, the anatomical architecture of the inter-renal vascular cage, which consists of the interlobar and arcuate arteries and their collateral veins, was completed within the developing metanephros. We demonstrated that the delicate renal vascular cage switched from the primary renal artery to the definitive renal artery and that the route of venous drainage changed from the posterior cardinal vein to the inferior (caudal) vena cava. [source]


Habitat-specific normal and reverse diel vertical migration in the plankton-feeding basking shark

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2005
DAVID W. SIMS
Summary 1Megaplanktivores such as filter-feeding sharks and baleen whales are at the apex of a short food chain (phytoplankton,zooplankton,vertebrate) and are sensitive indicators of sea-surface plankton availability. Even though they spend the majority of their time below the surface it is still not known how most of these species utilize vertical habitat and adapt to short-term changes in food availability. 2A key factor likely to control vertical habitat selection by planktivorous sharks is the diel vertical migration (DVM) of zooplankton; however, no study has determined whether specific ocean-habitat type influences their behavioural strategy. Based on the first high-resolution dive data collected for a plankton-feeding fish species we show that DVM patterns of the basking shark Cetorhinus maximus reflect habitat type and zooplankton behaviour. 3In deep, well-stratified waters sharks exhibited normal DVM (dusk ascent,dawn descent) by tracking migrating sound-scattering layers characterized by Calanus and euphausiids. Sharks occupying shallow, inner-shelf areas near thermal fronts conducted reverse DVM (dusk descent,dawn ascent) possibly due to zooplankton predator,prey interactions that resulted in reverse DVM of Calanus. 4These opposite DVM patterns resulted in the probability of daytime-surface sighting differing between these habitats by as much as two orders of magnitude. Ship-borne surveys undertaken at the same time as trackings reflected these behavioural differences. 5The tendency of basking sharks to feed or rest for long periods at the surface has made them vulnerable to harpoon fisheries. Ship-borne and aerial surveys also use surface occurrence to assess distribution and abundance for conservation purposes. Our study indicates that without bias reduction for habitat-specific DVM patterns, current surveys could under- or overestimate shark abundance by at least 10-fold. [source]


Corporate Governance in India

JOURNAL OF APPLIED CORPORATE FINANCE, Issue 1 2008
Rajesh Chakrabarti
The Indian corporate governance system has both supported and held back India's ascent to the top ranks of the world's economies. While on paper the country's legal system provides some of the best investor protection in the world, enforcement is a major problem, with overburdened courts and significant corruption. Ownership remains concentrated and family business groups continue to be the dominant business model, with significant pyramiding and evidence of tunneling activity that transfers cash flow and value from minority to controlling shareholders. But for all its shortcomings, Indian corporate governance has taken major steps toward becoming a system capable of inspiring confidence among institutional and, increasingly, foreign investors. The Securities and Exchanges Board of India (SEBI), which was established as part of the comprehensive economic reforms launched in 1991, has made considerable progress in becoming a rigorous regulatory regime that helps ensure transparency and fair practice. And the National Stock Exchange of India, also established as part of the reforms, now functions with enough efficiency and transparency to be generating the third-largest number of trades in the world, just behind the NASDAQ and NYSE. Among more recent changes, the enactment of Sarbanes,Oxley type measures in 2004,which includes protections for minority shareholders in family- or "promoter"-led businesses,has contributed to recent increases in institutional and foreign stock ownership. And while family- and government-controlled business groups continue to be the rule, India has also seen the rise of successful companies like Infosys that are free of the influence of a dominant family or group and have made the individual shareholder their central governance focus. [source]


Effect of origin, sex and sea age of Atlantic salmon on their recapture rate after river ascent

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2006
E. Jokikokko
Summary The recapture rate of Atlantic salmon (Salmo salar L.) after river ascent was examined by the trapping and tagging of ascending spawners in the lower reaches of the Simojoki River, which flows into the northern Baltic Sea. In 1997 and 1998, altogether 825 Carlin-tagged salmon were released to continue their upstream migration. Of these, 800 could be sexed and categorized as reared (91%) or wild (9%) salmon. In 1997, most of the ascending salmon were multi-sea-winter (MSW) fish, whereas in 1998 almost all were one-sea-winter (1SW) male grilse due to the late trapping season. About 10% of all tagged fish were recaptured, two-thirds of which were caught in the river before their descent to the sea. There was no difference in the recapture rate between salmon of wild (8.5%) or reared (9.5%) origin, or between females (11.6%) and males (9.3%). Generalized linear models for data from 1997 showed that the recapture rate increased with length and age of females, but that the opposite was true for males. River fishing did not seem to remove proportionally more early ascending salmon than fish that ascended later. [source]


Tufted ducks Aythya fuligula do not control buoyancy during diving

JOURNAL OF AVIAN BIOLOGY, Issue 3 2005
Lewis G. Halsey
Work against buoyancy during submergence is a large component of the energy costs for shallow diving ducks. For penguins, buoyancy is less of a problem, however they still seem to trade-off levels of oxygen stores against the costs and benefits of buoyant force during descent and ascent. This trade-off is presumably achieved by increasing air sac volume and hence pre-dive buoyancy (Bpre) when diving deeper. Tufted ducks, Aythya fuligula, almost always dive with nearly full oxygen stores so these cannot be increased. However, the high natural buoyancy of tufted ducks guarantees a passive ascent, so they might be expected to decrease Bpre before particularly deep, long dives to reduce the energy costs of diving. Body heat lost to the water can also be a cause of substantial energy expenditure during a dive, both through dissipation to the ambient environment and through the heating of ingested food and water. Thus dive depth (dd), duration and food type can influence how much heat energy is lost during a dive. The present study investigated the relationship between certain physiological and behavioural adjustments by tufted ducks to dd and food type. Changes in Bpre, deep body temperature (Tb) and dive time budgeting of four ducks were measured when diving to two different depths (1.5 and 5.7 m), and for two types of food (mussels and mealworms). The hypothesis was that in tufted ducks, Bpre decreases as dd increases. The ducks did not change Bpre in response to different diving depths, and thus the hypothesis was rejected. Tb was largely unaffected by dives to either depth. However, diving behaviour changed at the greater dd, including an increase in dive duration and vertical descent speed. Behaviour also changed depending on the food type, including an increase in foraging duration and vertical descent speed when mussels were present. Behavioural changes seem to represent the major adjustment made by tufted ducks in response to changes in their diving environment. [source]


Dry spots and wet spots in the Andean hotspot

JOURNAL OF BIOGEOGRAPHY, Issue 8 2007
Timothy J. Killeen
Abstract Aim, To explain the relationship between topography, prevailing winds and precipitation in order to identify regions with contrasting precipitation regimes and then compare floristic similarity among regions in the context of climate change. Location, Eastern slope of the tropical Andes, South America. Methods, We used information sources in the public domain to identify the relationship between geology, topography, prevailing wind patterns and precipitation. Areas with contrasting precipitation regimes were identified and compared for their floristic similarity. Results, We identify spatially separate super-humid, humid and relatively dry regions on the eastern slope of the Andes and show how they are formed by the interaction of prevailing winds, diurnally varying atmospheric circulations and the local topography of the Andes. One key aspect related to the formation of these climatically distinct regions is the South American low-level jet (SALLJ), a relatively steady wind gyre that flows pole-ward along the eastern slopes of the Andes and is part of the gyre associated with the Atlantic trade winds that cross the Amazon Basin. The strongest winds of the SALLJ occur near the ,elbow of the Andes' at 18° S. Super-humid regions with mean annual precipitation greater than 3500 mm, are associated with a ,favourable' combination of topography, wind-flow orientation and local air circulation that favours ascent at certain hours of the day. Much drier regions, with mean annual precipitation less than 1500 mm, are associated with ,unfavourable' topographic orientation with respect to the mean winds and areas of reduced cloudiness produced by local breezes that moderate the cloudiness. We show the distribution of satellite-estimated frequency of cloudiness and offer hypotheses to explain the occurrence of these patterns and to explain regions of anomalously low precipitation in Bolivia and northern Peru. Floristic analysis shows that overall similarity among all circumscribed regions of this study is low; however, similarity among super-humid and humid regions is greater when compared with similarity among dry regions. Spatially separate areas with humid and super-humid precipitation regimes show similarity gradients that are correlated with latitude (proximity) and precipitation. Main conclusions, The distribution of precipitation on the eastern slope of the Andes is not simply correlated with latitude, as is often assumed, but is the result of the interplay between wind and topography. Understanding the phenomena responsible for producing the observed precipitation patterns is important for mapping and modelling biodiversity, as well as for interpreting both past and future climate scenarios and the impact of climate change on biodiversity. Super-humid and dry regions have topographic characteristics that contribute to local climatic stability and may represent ancestral refugia for biodiversity; these regions are a conservation priority due to their unique climatic characteristics and the biodiversity associated with those characteristics. [source]


Factors affecting river entry of adult Atlantic salmon in a small river

JOURNAL OF FISH BIOLOGY, Issue 4 2007
B. Jonsson
In this study, effects of stock origin, fish size, water flow and temperature on time of river ascent of adult Atlantic salmon Salmo salar were tested. Brood stocks were collected in eight Norwegian rivers situated between 59 and 69° N. The fish were reared to smolts, individually tagged and released in the River Imsa, south-west Norway (59° N). Adults from all stocks approached the Norwegian coast concurrently, but Atlantic salmon ,70 cm in natural tip length entered coastal water slightly earlier during summer than smaller fish. Atlantic salmon <70 cm, however, ascended the river significantly earlier and at lower water flow and higher water temperature than larger fish. Although largest in size, the fish from the northern populations (62,69° N) ascended the River Imsa almost 1 month earlier than those from the south (59,60° N). They seemed less restricted by the environmental factors than the fish originating from the more southern rivers. There was no apparent trend among years in time of river ascent. Maximum ascent per day occurred at water discharges between 12·5 and 15 m3 s,1 and at water temperatures between 10 and 12·5° C. There was a significant positive correlation between water flow and river ascent during the first part of the upstream run from July to September with best correlation for September, when multiple regression analysis indicated that water temperature had an additional positive effect. Stock origin, fish size and water discharge were important variables influencing the upstream migration of Atlantic salmon in small rivers. [source]


Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterparts

JOURNAL OF FISH BIOLOGY, Issue 4 2006
E. Niemelä
Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989,2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2,4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system. [source]


Partial melting of metagreywacke: a calculated mineral equilibria study

JOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2008
T. E. JOHNSON
Abstract Greywacke occurs in most regionally metamorphosed orogenic terranes, with depositional ages from Archean to recent. It is commonly the dominant siliciclastic rock type, many times more abundant than pelite. Using calculated pseudosections in the Na2O,CaO,K2O,FeO,MgO,Al2O3,SiO2,H2O,TiO2,O system, the partial melting of metagreywacke is investigated using several natural protolith compositions that reflect the main observed compositional variations. At conditions appropriate for regional metamorphism at mid-crustal depths (6,8 kbar), high- T subsolidus assemblages are dominated by quartz, plagioclase and biotite with minor garnet, orthoamphibole, sillimanite, muscovite and/or K-feldspar (±Fe,Ti oxides). Modelled solidus temperatures are dependent on bulk composition and vary from 640 to 690 °C. Assuming minimal melting at the H2O-saturated solidus, initial prograde anatexis at temperatures up to ,800 °C is characterized by very low melt productivity. Significant melt production in commonly occurring (intermediate) metagreywacke compositions is controlled by the breakdown of biotite and production of orthopyroxene (±K-feldspar) across multivariant fields until biotite is exhausted at 850,900 °C. Assuming some melt is retained in the source, then at temperatures beyond that of biotite stability, melt production occurs via the consumption of plagioclase, quartz and any remaining K-feldspar as the melt becomes progressively more Ca-rich and H2O-undersaturated. Melt productivity with increasing temperature across the melting interval in metagreywacke is generally gradational when compared to metapelite, which is characterized by more step-like melt production. Comparison of the calculated phase relations with experimental data shows good consistency once the latter are considered in terms of the variance of the equilibria involved. Calculations on the presumed protolith compositions of residual granulite facies metagreywacke from the Archean Ashuanipi subprovince (Quebec) show good agreement with observed phase relations. The degree of melt production and subsequent melt loss is consistent with the previously inferred petrogenesis based on geochemical mass balance. The results show that, for temperatures above 850 °C, metagreywacke is sufficiently fertile to produce large volumes of melt, the separation from source and ascent of which may result in large-scale crustal differentiation if metagreywacke is abundant. [source]


Formation of spinel-cordierite-feldspar-glass coronas after garnet in metapelitic xenoliths: reaction modelling and geodynamic implications

JOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2007
A. M. ĮLVAREZ-VALERO
Abstract Spinel + cordierite + K-feldspar + plagioclase + glass form coronas around garnet in metapelitic xenoliths at El Hoyazo and Mazarrón, two localities of the Neogene Volcanic Province (NVP) of SE Spain. The presence of fresh glass (quenched melt) in all phases shows that corona development occurred under partial melting conditions. Algebraic analysis of mass balance in the NCKFMASH system suggests the reaction Grt + Sil + Bt + Pl = Spl + Crd + Kfs + melt as the most plausible model for the development of coronas in the El Hoyazo sample, and indicates that biotite was required as reactant for the formation of cordierite. The P,T conditions for the formation of coronas are estimated at ,820 ± 50 °C, 4.5 ± 0.6 kbar at El Hoyazo, and ,820 ± 50 °C, 4.0 ± 0.4 kbar at Mazarrón. The El Hoyazo xenoliths record a complex P,T history, characterized by early melt production during heating and additional melting during decompression. A local cooling event characterized by minor retrograde reaction and melt crystallization preceded ascent and eruption. This study shows that detailed xenolith analysis may be used to track magma evolution in a chamber. [source]


Thermal structure of the Alboran Domain in the Rif (northern Morocco) and the Western Betics (southern Spain).

JOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2006
Constraints from Raman spectroscopy of carbonaceous material
Abstract In the Rif (northern Morocco) and the Western Betics (southern Spain), the Alboran Domain forms a complex stack of metamorphic nappes including mantle peridotites (Beni Bousera and Ronda). We present in this paper new temperature data obtained in the Alboran Domain based on Raman spectroscopy of carbonaceous material (RSCM thermometry). In the lower metamorphic nappes of the Alboran Domain (lower Sebtides,Alpujįrrides) temperature ranges from > 640 °C at the base of the metapelitic sequence to 500 °C at the top. The relationships between field isotherms and nappe structure show that peak temperatures were reached during strong ductile thinning of these nappes whereas they partly postdate this main episode in the Rif. In the upper nappes of the Alboran Domain (Ghomarides,Malįguides), generally supposed to be only weakly metamorphosed, temperatures range from ,500 °C at their base down to < 330 °C at the top. This temperature gradient is consistent with progressive Cenozoic resetting of K,Ar and 40Ar,39Ar ages. These nappes were thus affected by a significant thermal metamorphism, and the available age data in the underlying Sebtides,Alpujįrrides show that this metamorphism is related to the metamorphic evolution of the whole Alboran Domain during the Late Oligocene,Early Miocene. Such thermal structure and metamorphic evolution can be explained by generalized extension in the whole Alboran Domain crustal sequence. At a larger scale, the present thermal structure of the Alboran Domain is roughly spatially consistent around the Beni Bousera peridotites in the Rif, but much more affected by late brittle tectonics around the Ronda peridotites in the Western Betics. Therefore, on the basis of the observed thermal structure, the metamorphic evolution of the Alboran Domain can be interpreted as the result of the ascent of hot mantle units contemporaneous with thinning of the whole lithosphere during an Oligo-Miocene extensional event. The resulting structure has however been dismembered by late brittle tectonics in the Western Betics. [source]


Vertical extrusion and middle crustal spreading of omphacite granulite: a model of syn-convergent exhumation (Bohemian Massif, Czech Republic)

JOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2004
tķpskį
Abstract The exhumation of eclogite facies granulites (Omp,Plg,Grt,Qtz,Rt) in the Rychleby Mts, eastern Czech Republic, was a localised process initiated by buckling of crustal layers in a thickened orogenic root. Folding and post-buckle flattening was followed by the main stage of exhumation that is characterized by vertical ductile extrusion. This process is documented by structural data, and the vertical ascent of rocks from a depth of c. 70 to c. 35 km is documented by metamorphic petrology. SHRIMP 206Pb/238U and 207Pb/206Pb evaporation zircon ages of 342 ± 5 and 341.4 ± 0.7 Ma date peak metamorphic conditions. The next stage of exhumation was associated with sideways flat thrusting associated with lateral viscous spreading of granulites and surrounding rocks over indenting adjacent continental crust at a depth of c. 35,30 km. This stage was associated with syntectonic intrusion of a granodiorite sill at 345,339 Ma, emplaced at a crustal depth of c. 25 km. The time required for cooling of the sill as well as for heating of the country rocks brackets this event to a maximum of 250 000 years. Therefore, similar ages of crystallization for the granodiorite magma and the peak of eclogite facies metamorphism of the granulite suggest a very short period of exhumation, limited by the analytical errors of the dating methods. Our calculations suggest that the initial exhumation rate during vertical extrusion was 3,15 mm yr,1, followed by an exhumation rate of 24,40 mm yr,1 during further uplift along a magma-lubricated shear zone. The extrusion stage of exhumation was associated with a high cooling rate, which decreased during the stage of lateral spreading. [source]


Metamorphism and microstructures along a high-temperature metamorphic field gradient: the north,eastern boundary of the Krįlovskż hvozd unit (Bohemian Massif, Czech Republic)

JOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2002
D. Scheuvens
Abstract A metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite,kyanite zone, a muscovite,sillimanite zone, a K-feldspar,sillimanite zone, and a K-feldspar,cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid-absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite,staurolite zone and the muscovite- and K-feldspar,sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn-anatectic shearing (melt-enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb-accommodated dislocation creep) to prism slip and high-temperature (fast) grain boundary migration in quartz (b) to the activity of diffusion creep in quartz,feldspar layers, and (c) to accommodation of strain by intense shearing in fibrolite,biotite layers. It is suggested that any combination of these deformation mechanisms will profoundly affect the rheological characteristics of high-grade metamorphic rocks and significantly lower rock strength. Hence, the boundary between these zones marks a major rheological barrier in the investigated cross section and probably also in other low- to medium-pressure/high-temperature areas. At still higher metamorphic grades (K-feldspar-cordierite zone), where the rheologically critical melt percentage is reached, rock rheology is mainly governed by the melt and other deformation mechanisms are of minor importance. In the study area, the switch in deformation mechanism(s) is responsible for large-scale strain partitioning and concentration of deformation within the higher-temperature hanging wall during top-to-the-S thrusting, thus preserving a more complete petrostructural record within the rocks of the footwall including indications for a ?Devonian high- to medium-pressure/medium-temperature metamorphic event. Thrusting is accompanied by diapiric ascent of diatexites of the K-feldspar-cordierite zone and infolding of the footwall, suggesting local crustal overturn in this part of the Moldanubian zone. [source]


Wear, delamination, and fatigue resistance of melt-annealed highly crosslinked UHMWPE cruciate-retaining knee inserts under activities of daily living

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 9 2010
Oludele O. Popoola
Abstract The wear, delamination, and fatigue resistance of artificially aged gamma irradiation-sterilized conventional polyethylene (CPE) and gas-plasma-sterilized melt-annealed highly crosslinked polyethylene tibial inserts (HXPE) were compared. Six CPE and 12 HXPE (six irradiated at 58,kGy and six at 72,kGy) left knee inserts were wear tested for 5.5 million cycles (Mc) under loads and motions that mimic activities of daily living, such as walking, chair rise, stair ascent, and deep squatting. Another six HXPE (72,kGy) and six CPE inserts were also tested under conditions that could produce severe delamination for 8 Mc. Ten other knees (five 72,kGy HXPE and five CPE) were subjected to posterior edge loading fatigue testing for 5 Mc. The HXPE inserts had an average wear rate reduction of about 80% relative to their CPE counterparts during all activities. All of the CPE inserts delaminated and fractured during high cycle deep squat (152° flexion) motions, while all the HXPE remained intact. None of the HXPE inserts delaminated after 8 Mc, while all of the CPE inserts developed delamination damage within 1.5,5.8 Mc of delamination testing. All CPE inserts developed subsurface cracks and delamination within 2.8 Mc during posterior edge loading fatigue studies, while none of the HXPE inserts showed cracking or delamination after 5 Mc. These results show that aged HXPE has higher wear and fatigue resistance than aged CPE, and offers potential long-term advantages for young active patients with sustained activities of daily living. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1120,1126, 2010 [source]


Swimming speed and foraging strategies of New Zealand sea lions (Phocarctos hookeri)

JOURNAL OF ZOOLOGY, Issue 2 2001
D. E. Crocker
Abstract Lactating New Zealand sea lions (Phocarctos hookeri) have recently been reported to be the longest and deepest-diving otariid. An unusually large proportion of dives exceeded a theoretical aerobic dive limit, predicted from estimated oxygen stores and measurements of diving metabolic rate. We investigated swimming speed, a key variable in both the management of oxygen stores and foraging strategies, and its relation to diving behaviour in New Zealand sea lions. Diving behaviour was nearly continuous with short inter-dive intervals. Mean diving swimming speeds ranged from 1.6 to 2.4 m/s. Mean surface swimming speeds ranged from 0.9 to 1.8 m/s and were significantly lower than diving speeds in all subjects. New Zealand sea lions spend significant but variable amounts of time resting at the surface. Diving and swimming speed patterns were consistent with foraging on the benthos. Time in the foraging zone was maintained in deeper dives by increasing dive duration. This increased duration cannot be accounted for by a decreased metabolic rate resulting from slower swimming speeds, as speeds increased with the maximum depth of dives. Patterns of swimming speed and acceleration suggest the use of a gliding phase during descent. For most females, the extended duration of deeper dives did not impact on surface times, suggesting the use of aerobic metabolism. Females exhibited significantly slower swim speeds during the bottom segments of foraging dives than during descent or ascent. These findings suggest that swimming behaviour should be considered a critical component when modelling energetic costs for diving animals. [source]


THREE-DIMENSIONAL DIVING BEHAVIORS OF RINGED SEALS (PHOCA HISPIDA)

MARINE MAMMAL SCIENCE, Issue 4 2001
Michael A. Simpkins
Abstract Dives of five freely diving ringed seals were classified into three-dimentional movement types. Horizontally convoluted dives, defined as dives with angular velocity > 15°/sec, appeared to be foraging or social dives. Simple dives that did not include convoluted movements (angular velocity < 10°/sec) were considered to be exploration dives. Directional dives with nearly linear horizontal travel (horizontal directionality >0.6, on a scale of 0,1) were presumed to be travel dives. Each three-dimensional dive type was observed with similar frequency in dives with two distinct time-depth profiles: V-shaped profiles in which ascent immediately followed descent, and U-shaped profiles in which >7 sec were spent at depth between descent and ascent. The lack of behavioral differences between dives with distinct time-depth profiles suggested that time-depth profiles are not a reliable means of inferring dive behaviors for ringed seals. [source]


Virus DNA translocation: progress towards a first ascent of Mount Pretty Difficult

MOLECULAR MICROBIOLOGY, Issue 1 2006
Nasib K. Maluf
Summary Virion DNA molecules of large dsDNA viruses are highly condensed. To pack the DNA, an ATP hydrolysis-powered motor translocates the DNA into a preformed empty protein shell, the prohead. The icosahedral prohead has a special fivefold vertex, the portal vertex, where the translocation machinery acts. The portal vertex contains the portal protein, a gear-shaped dodecamer of radially disposed subunits with a central channel for DNA entry. The symmetry mismatch between the fivefold symmetry of the shell vertex and the 12-fold symmetry of the portal protein has prompted DNA packaging models in which ATP-driven portal protein rotation drives DNA translocation. In this issue of Molecular Microbiology, Baumann and colleagues test portal rotation models using bacteriophage T4. A fusion between the gp20 portal protein and the HOC external shell decoration protein is used to create a block to portal rotation. Finding that DNA packaging is unimpeded in proheads containing the fusion argues that portal rotation is not crucial to DNA translocation. The paper is a landmark for describing direct testing of the mechanism of DNA translocation. [source]


China's "Soft" Naval Power in the Indian Ocean

PACIFIC FOCUS, Issue 1 2010
Toshi Yoshihara
For the past several years, Beijing has been attempting to "shape" the diplomatic and strategic environment in maritime Asia, projecting an image of itself as an innately trustworthy great power. As a part of this public relations campaign, Chinese leaders have retailed the story of Zheng He, the Ming Dynasty eunuch admiral who voyaged to destinations throughout the South China Sea and the Indian Ocean six centuries ago. They have touted the feats of Zheng He, who sojourned in maritime Asia without attempting military conquest, as a metaphor for China's current peaceful ascent in the maritime domain. In doing so, Beijing hopes to convince key audiences in Southeast Asia and South Asia that it remains pacific in outlook , and thus can be counted on not to abuse the sea power it is amassing. An attractive vision of China, they hope, will avert the tendency of regional states to band together to balance Chinese power. Until now, Chinese diplomats have had the luxury of telling their story how they wanted to, as deployments of China's naval forces beyond East Asia remained abstract. Beijing neither saw the need nor boasted the capacity to maintain strong forces far from Chinese shores. However, the headline-grabbing dispatch of two destroyers and a combat logistics ship to the Gulf of Aden on counter-piracy duty in late 2008 has put China squarely in the spotlight. By depicting itself as an inherently defensive power, China has set a high standard for its behavior at sea. Fellow Asian powers will hold Beijing to this lofty benchmark , measuring its actions against the storyline Chinese leaders have developed around Zheng He's voyages. Beijing's anti-piracy mission thus offers an ideal opportunity to empirically test the efficacy of Chinese soft power at sea. To this end, this paper explores the motives behind the Zheng He narrative and assesses the key messages that Chinese leaders are attempting to convey to Asian capitals. This study then examines the extent to which China's unprecedented naval presence in the Indian Ocean has dovetailed with the Zheng He storyline and with the larger strategy of easing regional misgivings about Chinese maritime power. Finally, the paper analyzes how India, a target audience, is responding to China's narrative, drawing several preliminary conclusions about the effectiveness and the prospects of Chinese soft power in the Indian Ocean. [source]