985 resultados para Other Natural Sciences


Relevância:

90.00% 90.00%

Publicador:

Resumo:

Rare earth element and yttrium (REE+Y) concentrations were determined in 49 Late Devonian reefal carbonates from the Lennard Shelf, Canning Basin, Western Australia. Shale-normalized (SN) REE+Y patterns of the Late Devonian samples display features consistent with the geochemistry of well-oxygenated, shallow seawater. A variety of different ancient limestone components, including microbialites, some skeletal carbonates (stromatoporoids), and cements, record seawater-like REE+Y signatures. Contamination associated with phosphate, Fe-oxides and shale was tested quantitatively, and can be discounted as the source of the REE+Y patterns. Co-occurring carbonate components that presumably precipitated from the same seawater have different relative REE concentrations, but consistent REE+Y patterns. Clean Devonian early marine cements (n = 3) display REE+Y signatures most like that of modern open ocean seawater and the highest Y/Ho ratios (e.g., 59) and greatest light REE (LREE) depletion (average Nd-SN/Yb-SN = 0.413, SD = 0.076). However, synsedimentary cements have the lowest REE concentrations (e.g., 405 ppb). Non-contaminated Devonian microbialite samples containing a mixture of the calcimicrobe Renalcis and micritic thrombolite aggregates in early marine cement (n = 11) have the highest relative REE concentrations of tested carbonates (average total REE = 11.3 ppm). Stromatoporoid skeletons, unlike modern corals, algae and molluscs, also contain well-developed, seawater-like REE patterns. Samples from an estuarine fringing reef have very different REE+Y patterns with LREE enrichment (Nd-SN/Yb-SN > 1), possibly reflecting inclusion of estuarine colloidal material that contained preferentially scavenged LREE from a nearby riverine input source. Hence, Devonian limestones provide a proxy for marine REE geochemistry and allow the differentiation of co-occurring water masses on the ancient Lennard Shelf. Although appropriate partition coefficients for quantification of Devonian seawater REE concentrations from out data are unknown, hypothetical Devonian Canning Basin seawater REE patterns were obtained with coefficients derived from modern natural proxies and experimental values. Resulting Devonian seawater patterns are slightly enriched in LREE compared to most modem seawaters and suggest higher overall REE concentrations, but are very similar to seawaters from regions with high terrigenous inputs. Our results suggest that most limestones should record important aspects of the REE geochemistry of the waters in which they precipitated, provided they are relatively free of terrigenous contamination and major diagenetic alteration from fluids with high, non-seawater-like REE contents. Hence, we expect that many other ancient limestones will serve as seawater REE proxies, and thereby provide information on paleoceanography, paleogeography and geochemical evolution of the oceans. Copyright (C) 2004 Elsevier Ltd.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The properties of commercial directly and indirectly heated UHT milks, both after heating and during storage at room temperature for 24 weeks, were studied. Thermally induced changes were examined by changes in lactulose, furosine and acid-soluble whey proteins. The results confirmed previous reports that directly heated UHT milks suffer less heat damage than indirectly heated milk. During storage, furosine increased and bovine serum albumin in directly heat-treated milks decreased significantly. The changes in lactulose, alpha-lactalbumin and beta-lactoglobulin were not statistically significant. The data suggest that heat treatment indicators should be measured as soon as possible after processing to avoid any misinterpretations of the intensity of the heat treatment.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

This article shows how macroeconomic indicators of sustainable development can be applied to the Queensland economy. While recognising the complex and contentious theoretical and practical issues in deriving the Genuine Savings Rate (GSR) to serve as such an indicator, we use the World Bank's methodology, which includes only mineral depletion, deforestation and carbon dioxide emissions as environmental terms, to estimate GSRs for Queensland for the period 1989 to 1999, and compare these to World Bank estimates of Australia's GSR for the same period. We find that Queensland has a higher rate of natural resource depletion and a lower GSR than the whole of Australia. We also examine how well the World Bank GSR performs as a 'headline' measure of overall sustainability, review criticisms of the GSR, and compare its implicit policy implications with those of net state savings, and of the GSR plus a suite of other indicators.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The best way of finding “natural groups” in management research remains subject to debate and within the literature there is no accepted consensus. The principle motivation behind this study is to explore the effect of choices of method upon strategic group research, an area that has suffered enduring criticism, as we believe that these method choices are still not fully exploited. Our study is novel in the use of a variety of more robust clustering and validation techniques, rarely used in management research, some borrowed from the natural sciences, which may provide a useful and more robust base for this type of research. Our results confirm that methods do exist to address the concerns over strategic group research and adoption of our chosen methods will improve the quality of management research.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

We hear much about 'race' and 'racism' in public discourse, but these terms are frequently used without clear definitions or practical examples of how these phenomena actually work. Racisms introduces practical methods which enable students to think coherently and sociologically about this complex feature of the global landscape. This text: - Defines 'race', 'racism' 'instiutional racism' and 'racialization' - Provides examples of how these function in fields like the natural sciences and asylum seeking - Clearly sets out theoretical arguments around collective identities ('race', class, gender, nation, religion) - Uses empirical case studies, including some drawn from the author's own fieldwork - Points students and other readers toward sources of further web and text-based information.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

2000 Mathematics Subject Classification: 12D10.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Tanulmányomban, amint azt a cím is jelzi, használni szeretném a paradigma fogalmát. Ezt Kuhn vezette be a tudományelméletbe klasszikus művében (Kuhn [1962]). Kuhn nem adott egyértelmű definíciót, s maga a fogalom sok vitára adott okot. A konferenciára készülve, újraolvastam számos művet az általános tudományelmélet és speciálisan a közgazdaságtani metodológia köréből. Ha más nem, már ez a meghökkentő olvasmányélmény is óvatosságra int. Nyoma sincsen konszenzusnak, még az alapfogalmak értelmezésében sem. Ingerült konfrontatív vita zajlik. A szűkebben vett tudományelmélet és tudománytörténet alternatív iskolái közötti egyet nem értés mélyen gyökeredzik híveiknek egymástól eltérő filozófiai felfogásában. Szeretném elkerülni ezt az aknamezőt. Ez késztet arra, hogy fogalmi tisztázással kezdjem a fejtegetést, az esetleges félreértések elkerülésére. Nem kívánok hozzászólni ahhoz, hogy mennyiben volt Poppernek, Kuhnnak, Lakatosnak vagy másnak igaza a tudomány történetének elemzésében. A korrekt tárgyalásA szerző a cikk bevezetőjében ismerteti, milyen értelmezésben használja a társadalomtudományokra vonatkozóan a paradigma fogalmát, amelyet T. S. Kuhn eredetileg a természettudományok történetétől ihletve alkotott meg. Az új paradigma nem okvetlenül váltja fel a korábbit; több paradigma munkaképesen működhet egymás mellett. A rendszerparadigma kialakulásának mérföldkövei: Marx, Mises, Hayek, Polányi, Schumpeter és Eucken munkái. Noha filozófiájukat és politikai állásfoglalásukat tekintve igen heterogén a névsor, közös bennük a rendszerszemlélet\". Nemcsak a gazdaság egy-egy részletével foglalkoznak, hanem a rendszer egészével; nemcsak a gazdasággal, hanem a politikai, ideológiai és a társadalmi dimenziókkal is, s különös figyelmet fordítanak valamennyi szféra interakcióira. A rendszerparadigma nagy vizsgafeladata a posztszocialista átmenet kutatása. Ehhez nélkülözhetetlen; a magyarázó erőt tekintve semmilyen más paradigmával nem pótolható. Viszont a rendszerparadigma alkalmazói előrejelzéseikben (akárcsak más paradigmák művelői) sokszor súlyosan tévedtek. A rendszerparadigma prediktív ereje korlátozott, s ez szerénységre inti felhasználóit. / === / The notion of paradigm was originally created by T. S. Kuhn and inspired by the history of natural sciences. The introduction of the article explains the interpreation of the notion as used in social sciences. In this context a new paradigm does not necessarily replace the earlier one, several paradigms can operate beside each other. The milestones of the system paradigm are the works of Marx, Mises, Hayek, Polányi, Schumpeter and Eucken. Although the list is rather heterogeneous as regards the philosophies and political stand of the authors, common to them is the \"systemic approach\". They discuss not some detail of the economy, but the system as a whole; not only the economy, but the political, ideological and societal dimensions as well, and they pay particular attention to the interactions among all spheres. It is a great examination task of the system paradigm to research the post-socialist transition. It is indispensable for that; as regards explanatory power, it cannot be replaced by any other paradigm. On the other hand, the users of the system paradigm frequently made grave errors in their forecasts (similarly to those using other paradigms). The predictive power of the system paradigm is restricted and this warns its users to caution.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The management and restoration of the Biscayne Bay Coastal Wetlands (BBCW) is a complex issue. Unlike other natural areas under the supervision of the National Park System, the BBCW had endured many years of neglect and abuse by homesteaders who, prior to the establishment of Biscayne National Monument in 1968, had free reign of the area and tried to farm and develop the land by ditching and infilling. Furthermore, public works projects, dating back to the early 1900’s for mosquito control, land reclamation, and storm surge protection along with homesteader activities have combined to compartmentalize the coastal wetlands of present Biscayne National Park and adjacent marshes.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Dissertação apresentada à Escola Superior de Educação de Santarém para a obtenção do grau de mestre em Ciências da educação - Supervisão e orientação pedagógica

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Abundant material of turtles from the early Oligocene site of Boutersem-TGV (Boutersem, Belgium), is presented here. No information on the turtles found there was so far available. All the turtle specimens presented here are attributable to a single freshwater taxon that is identified as a member of Geoemydidae, Cuvierichelys. It is the first representative of the ‘Palaeochelys s. l.–Mauremys’ group recognized in the Belgian Paleogene record. This material, which allows to know all the elements of both the carapace and the plastron of the taxon, cannot be attributed to the only species of the genus Cuvierichelys so far identified in the Oligocene, the Spanish form Cuvierichelys iberica. The taxon from Boutersem is recognized as Cuvierichelys parisiensis. Thus, both the paleobiogeographic and the biostratigraphic distributions of Cuvierichelys parisiensis are extended, its presence being confirmed for the first time outside the French Eocene record. The validity of some European forms is refuted, and several characters previously proposed as different between Cuvierichelys iberica and Cuvierichelys parisiensis are recognized as subjected to intraspecific variability.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Rin de Aveiro is a coastal lagoon located at the Central Region of Portugal subjected to the influence of the tides, resulting in a set of characteristic biotopes favouring anthropic and natural processes. Once managed and controlled correctly, each of these biotopes will allow simultaneously the biodiversity and integration in the making of the wetland landscape. In 1998, one of the final conclusions of the "MARIA" Demonstration Programme for the Integrated Management of Ria de Aveiro was that the poor current state of the environment area resulted from a set of interrelated factors. The Programme selected four (4) pilot-projects towards the integrated management of the lagoon biotopes as possible scenarios for an intervention. This selection was based in criteria related to environmental priorities and the maintenance of traditional economic activities in the region. The idea of choosing projects that would involve the whole geographic space of the Ria, without forgetting the other important themes interrelated with the Management Structure, emerged as a relevant aspect for their definition. Thus, and as a first test of this Management Structure functionality, the following task forces were put forward: Recovery and valorisation of the piers; Recovery of the former salt pans; Management of the agricultural fields of Baixo-Vouga; Implementation of measures for the classification of the Protected Landscape Area of the River Caster Mouth. This payer will report the main results of these pilot-projects attained during their first year period, especially the intervention strategies defined by the Partnership created for this aim.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Eukaryotic genomes contain repetitive DNA sequences. This includes simple repeats and more complex transposable elements (TEs). Many TEs reach high copy numbers in the host genome, owing to their amplification abilities by specific mechanisms. There is growing evidence that TEs contribute to gene transcriptional regulation. However, excess of TE activity may lead to reduced genome stability. Therefore, TEs are suppressed by the transcriptional gene silencing machinery via specific chromatin modifications. In contrary, effectiveness of the epigenetic silencing mechanisms imposes risk for TE survival in the host genome. Therefore, TEs may have evolved specific strategies for bypassing epigenetic control and allowing the emergence of new TE copies. Recent studies suggested that the epigenetic silencing can be, at least transiently, attenuated by heat stress in A. thaliana. Heat stress induced strong transcriptional activation of COPIA78 family LTR-retrotransposons named ONSEN, and even their transposition in mutants deficient in siRNA-biogenesis. ONSEN transcriptional activation was facilitated by the presence of heat responsive elements (HREs) within the long terminal repeats, which serve as a binding platform for the HEAT SHOCK FACTORs (HSFs). This thesis focused on the evolution of ONSEN heat responsiveness in Brassicaceae. By using whole-transcriptome sequencing approach, multiple Arabidopsis lyrata ONSENs with conserved heat response were found and together with ONSENs from other Brassicaceae were used to reconstruct the evolution of ONSEN HREs. This indicated ancestral situation with two, in palindrome organized, HSF binding motifs. In the genera Arabidopsis and Ballantinia, a local duplication of this locus increased number of HSF binding motifs to four, forming a high-efficiency HRE. In addition, whole transcriptome analysis revealed novel heat-responsive TE families COPIA20, COPIA37 and HATE. Notably, HATE represents so far unknown COPIA family which occurs in several Brassicaceae species but is absent in A. thaliana. Putative HREs were identified within the LTRs of COPIA20, COPIA37 and HATE of A. lyrata, and could be preliminarily validated by transcriptional analysis upon heat induction in subsequent survey of Brassicaeae species. Subsequent phylogenetic analysis indicated a repeated evolution of heat responsiveness within Brassicaceae COPIA LTR-retrotransposons. This indicates that acquisition of heat responsiveness may represent a successful strategy for survival of TEs within the host genome.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Oogenesis is a prerequisite for embryogenesis in Metazoa. During both biological processes important decisions must be made to form the embryo and hence ensure the next generation: (1) Maternal gene products (mRNAs, proteins and nutrients) must be supplied to the embryo. (2) Polarity must be established and axes must be specified. While incorporation of maternal gene products occurs during oogenesis, the time point of polarity establishment and axis specification varies among species, as it is accomplished either prior, during, or after fertilisation. But not only the time point when these events take place varies among species but also the underlying mechanisms by which they are triggered. For the nematode model Caenorhabditis elegans the underlying pathways and gene regulatory networks (GRNs) are well understood. It is known that there the sperm entry point initiates a primary polarity in the 1-celled egg and with it the establishment of the anteroposterior axis. However, studies of other nematodes demonstrated that polarity establishment can be independent of sperm entry (Goldstein et al., 1998; Lahl et al., 2006) and that cleavage patterns, symmetry formation and cell specification also differ from C. elegans. In contrast to the studied Chromadorea (more derived nematodes including C. elegans), embryos of some marine Enoplea (more basal representatives) even show no discernible early polarity and blastomeres can adopt variable cell fates (Voronov and Panchin 1998). The underlying pathways controlling the obviously variant embryonic processes in non-Caenorhabditis nematodes are essentially unknown. In this thesis I addressed this issue by performing a detailed unbiased comparative transcriptome analysis based on microarrays and RNA sequencing of selected developmental stages in a variety of nematodes from different phylogenetic branches with C. elegans as a reference system and a nematomorph as an outgroup representative. In addition, I made use of available genomic data to determine the presence or absence of genes for which no expression had been detected. In particular, I focussed on components of selected pathways or GRNs which are known to play essential roles during C. elegans development and/or other invertebrate or vertebrate model systems. Oogenesis must be regulated differently in non-Caenorhabditis nematodes, as crucial controlling components of Wnt and sex determination signaling are absent in these species. In this respect, I identified female-specific expression of potential polarity associated genes during gonad development and oogenesis in the Enoplean nematode Romanomermis culicivorax. I could show that known downstream components of the polarity complexes PAR-3/-6/PKC-3 and PAR-1/-2 are absent in non-Caenorhabditis species. Even PAR-2 as part of the polarity complex does not exist in these nematodes. Instead, transcriptomes of nematodes (including C. elegans), show expression of other polarity-associated complexes such as the Lgl (Lethal giant larvae) complex. This result could pose an alternative route for nematodes and nematomorphs to initiate polarity during early embryogenesis. I could show that crucial pathways of axis specification, such as Wnt and BMP are very different in C. elegans compared to other nematodes. In the former, Wnt signaling, for instance, is mediated by four paralogous beta-catenins, while other Chromadorea have fewer and Enoplea only one beta-catenin. The transcriptomes of R. culicivorax and the nematomorph show that regulators of BMP (e.g. Chordin), are specifically expressed during early embryogenesis only in Enoplea and the close outgroup of nematomorphs. In conclusion, my results demonstrate that the molecular machinery controlling oogenesis and embryogenesis in nematodes is unexpectedly variable and C. elegans cannot be taken as a general model for nematode development. Under this perspective, Enoplean nematodes show more similarities with outgroups than with C. elegans. It appears that certain pathway components were lost or gained during evolution and others adopted new functions. Based on my findings I can conjecture, which pathway components may be ancestral and which were newly acquired in the course of nematode evolution.