共查询到20条相似文献,搜索用时 125 毫秒
1.
Recent paleogeographic scenarios postulate the isolation of continental Africa during the Late Cretaceous. The absence of abelisaurid theropods from Upper Cretaceous African strata was offered as support of hypothesized African isolation with the acknowledgement that the paucity of African abelisaurids may be mostly an issue of sampling. Here we report on a shed theropod tooth from the Upper Cretaceous (Maastrichtian, ∼70 Ma) Duwi Formation of Egypt. The tooth was referred to the Malagasy abelisaurid “Megalosaurus” crenatissimus (=Majungasaurus crenatissimus) in 1921. A discriminant function analysis was run to test for morphological congruence between the Egyptian tooth and the dentitions of 24 theropod taxa. The analysis correctly classified 96.6% of the teeth in the sample and assigned the tooth to Majungasaurus. As current paleogeographic reconstructions posit Madagascar had attained its current position relative to Africa before the Late Cretaceous, it is unlikely that the Egyptian tooth actually pertains to Majungasaurus. Nevertheless, its classification as an abelisaurid supports its referral to the clade. This tooth thus constitutes defensible evidence of an abelisaurid from the post-Cenomanian Cretaceous of mainland Africa. Combined with recent discoveries of abelisaurids in Niger and Morocco, the result indicates that Abelisauridae was a diverse group in Africa during the Cretaceous, existing in multiple places for at least ∼25 Ma and weakens support for hypotheses of an isolated Africa during the Late Cretaceous.Electronic Supplementary Material Supplementary material is available for this article at
相似文献
Joshua B. Smith (Corresponding author)Email: Phone: +1-314-9357033Fax: +1-314-9357361 |
Matthew C. LamannaEmail: |
2.
A temnospondyl ilium from the uppermost Toutunhe Formation (Middle Jurassic, Callovian) of the southern Junggar Basin is described. Among the known temnospondyls it is very unusual in morphology because of its very long and slender shaft. It compares closely only to the ilium of one of the latest known trematosaurids from the Ladinian of southern Germany. The Toutunhe Formation has also yielded vertebrae and skull fragments of temnospondyls which belong to the brachyopid Gobiops from the Upper Jurassic of Mongolia. Brachyopoid ilia do not, however, display a morphology similar to that of the new specimen. It is therefore concluded that this specimen represents a second taxon of temnospondyl from the Toutunhe Formation, which probably represents the latest surviving trematosauroid. The Trematosauroidea, which was hitherto exclusively known from the Lower to early Upper Triassic, therefore joins the Brachyopoidea – and possibly the Capitosauroidea – as another group of temnospondyls which survived the end-Triassic mass extinction. 相似文献
3.
Approaches to semi-synthetic minimal cells: a review 总被引:1,自引:0,他引:1
Following is a synthetic review on the minimal living cell, defined as an artificial or a semi-artificial cell having the
minimal and sufficient number of components to be considered alive. We describe concepts and experiments based on these constructions,
and we point out that an operational definition of minimal cell does not define a single species, but rather a broad family
of interrelated cell-like structures. The relevance of these researches, considering that the minimal cell should also correspond
to the early simple cell in the origin of life and early evolution, is also explained. In addition, we present detailed data
in relation to minimal genome, with observations cited by several authors who agree on setting the theoretical full-fledged
minimal genome to a figure between 200 and 300 genes. However, further theoretical assumptions may significantly reduce this
number (i.e. by eliminating ribosomal proteins and by limiting DNA and RNA polymerases to only a few, less specific molecular
species). Generally, the experimental approach to minimal cells consists in utilizing liposomes as cell models and in filling
them with genes/enzymes corresponding to minimal cellular functions. To date, a few research groups have successfully induced
the expression of single proteins, such as the green fluorescence protein, inside liposomes. Here, different approaches are
described and compared. Present constructs are still rather far from the minimal cell, and experimental as well as theoretical
difficulties opposing further reduction of complexity are discussed. While most of these minimal cell constructions may represent
relatively poor imitations of a modern full-fledged cell, further studies will begin precisely from these constructs. In conclusion,
we give a brief outline of the next possible steps on the road map to the minimal cell.
相似文献
Pier Luigi Luisi (Corresponding author)Email: |
Francesca FerriEmail: |
Pasquale StanoEmail: |
4.
P. Sudha V. Ramprasad M. D. V. Nagendra H. D. Kulkarni N. H. Ravindranath 《Mitigation and Adaptation Strategies for Global Change》2007,12(6):1131-1152
This paper addresses methodological issues in estimating carbon (C) sequestration potential, baseline determination, additionality
and leakage in Khammam district, Andhra Pradesh, southern part of India. Technical potential for afforestation on cultivable
wastelands, fallow, and marginal croplands was considered for Eucalyptus clonal plantations. Field studies for aboveground and belowground biomass, woody litter, and soil organic carbon for baseline
and project scenarios were conducted to estimate the carbon sequestration potential. The baseline carbon stock was estimated
to be 45.3 t C/ha, predominately in soils. The additional carbon sequestration potential under the project scenario for 30 years
is estimated to be 12.8 t C/ha/year inclusive of harvest regimes and carbon emissions due to biomass burning and fertilizer
application. Considering carbon storage in harvested wood, an additional 45% carbon benefit can be accounted. The project
scenario has a higher benefit/cost ratio compared to the baseline scenario. The initial investment cost requirement, however,
is high and lack of access to investment is a significant barrier for adoption of agroforestry in the district.
相似文献
N. H. RavindranathEmail: |
5.
Shimpei Iwasaki Bam Haja Nirina Razafindrabe Rajib Shaw 《Mitigation and Adaptation Strategies for Global Change》2009,14(4):339-355
Climate change combined with human activities poses significant risks to people’s livelihood especially in developing countries.
Adaptation at the community level is of crucial importance in enabling them to respond to the direct and indirect effects
of changes in climate. In a case study of fishing communities in Chilika lagoon, India, the focus is made on understanding
climate change adaptation at the community level and scaling it up into the policy perspective through application of Sustainable
Livelihood Approach. This article challenges the research and policy community to encourage the identification of locally
negative constraints and positive strengths toward climate resilient communities in rural areas.
相似文献
Rajib ShawEmail: |
6.
Greenhouse gas mitigation in developing countries through technology transfer?: a survey of empirical evidence 总被引:1,自引:0,他引:1
Sonja Peterson 《Mitigation and Adaptation Strategies for Global Change》2008,13(3):283-305
While greenhouse gas (GHG) emissions are projected to rise primarily in the developing countries, the potential for developing
new GHG mitigation technologies exists primarily in the industrialized countries. It is thus important, not only for predictions
about future emission paths but also for climate change mitigation policies, to understand how the international diffusion
of such technologies takes place and how it affects the energy infrastructure and GHG emissions in developing countries. This
paper provides an overview of the channels through which these technologies diffuse and focuses on the empirical evidence
pertaining to the effects these technologies have on GHG emissions in developing countries.
相似文献
Sonja PetersonEmail: |
7.
Pablo del Río 《Mitigation and Adaptation Strategies for Global Change》2009,14(3):203-213
Internal mitigation projects have recently been proposed as an additional flexibility mechanism, particularly in the context
of the European Union. Their main objective is to engage sectors not included in the European Union emissions trading scheme
(EU ETS) in cost-effective emissions reductions. However, in this paper it is argued that, when assessed in terms of dynamic
efficiency, the instrument is likely to be, at best, irrelevant to induce the scale of systemic technological changes which
are required to tackle the climate change problem and, at worst, detrimental for this task. Insights from the Evolutionary
Economics of technological change complemented with political economy considerations are used to support this claim.
相似文献
Pablo del RíoEmail: |
8.
Over the past decade “bicellar” lipid mixtures composed of the long-chain dimyristoyl phosphatidylcholine (DMPC) and the short-chain
dihexanoyl PC (DHPC) molecules have emerged as a powerful medium for studying membrane associated, biologically relevant macromolecules
and assemblies. Depending on temperature, lipid concentration and composition these lipid mixtures can assume a variety of
morphologies, some of them alignable in the presence of a magnetic field. This article will examine the biophysical studies
that have elucidated the various morphologies assumed by these lipid mixtures, and their use in the biochemical studies of
biomolecules.
相似文献
John KatsarasEmail: |
9.
Community-based vulnerability assessment has often assumed that the local is the relevant level of adaptation to climate change.
This paper suggests that not only do a number of levels from the international to the regional influence which adaptations
can take place locally, but the governance network that is made up by actors on different levels may to a large extent be
formed in responses to globalising factors, such as internationalisation of economies and the changing role of the state.
The paper presents a study of adaptation in reindeer (Rangifier tarandus) herding, forestry and fishing communities in northern Norway, Sweden, and Finland, with a focus on assessing stakeholders’
own perceptions of environmental, socio-political and economic factors that affect them. In general, the paper illustrates
the integration of non-subsistence economies into large and complex interactions where local adaptation is a result of the
sum of stresses impacting individual entrepreneurs, and the potential they have to adapt their practices given governance
(and their access to support) on different scales.
相似文献
E. Carina H. KeskitaloEmail: |
10.
Earliest zygodactyl bird feet: evidence from Early Cretaceous roadrunner-like tracks 总被引:2,自引:2,他引:0
Fossil footprints are important in understanding Cretaceous avian diversity because they constitute evidence of paleodiversity
and paleoecology that is not always apparent from skeletal remains. Early Cretaceous bird tracks have demonstrated the existence
of wading birds in East Asia, but some pedal morphotypes, such as zygodactyly, common in modern and earlier Cenozoic birds
(Neornithes) were unknown in the Cretaceous. We, herein, discuss the implications of a recently reported, Early Cretaceous
(120–110 million years old) trackway of a large, zygodactyl bird from China that predates skeletal evidence of this foot morphology
by at least 50 million years and includes the only known fossil zygodactyl footprints. The tracks demonstrate the existence
of a Cretaceous bird not currently represented in the body fossil record that occupied a roadrunner (Geococcyx)-like niche, indicating a previously unknown degree of Cretaceous avian morphological and behavioral diversity that presaged
later Cenozoic patterns.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Masaki MatsukawaEmail: |
11.
Molecular topology is an application of graph theory and statistics in fields like chemistry, biology, and pharmacology, in
which the molecular structure matters. Its scope is the topological characterization of molecules by means of numerical invariants,
called topological indices, which are the main ingredients of the molecular topological models. These are statistical models
that are instrumental in the discovery of new applications of naturally occurring molecules, as well as in the design of synthetic
molecules with specific chemical, biological, or pharmacological properties. In this review, we focus on pharmacology, which
is a novel field of application of molecular topology. Besides summarizing some recent developments, we also seek to bring
closer this interesting biomedical application of mathematics to an interdisciplinary readership.
相似文献
Vincent M. VillarEmail: |
12.
Veronika Dornburg Gregg Marland 《Mitigation and Adaptation Strategies for Global Change》2008,13(3):211-217
Kirschbaum (Mitig Adapt Strat Glob Change 11:1151–1164, 2006) explores the climatic impact over time of temporarily sequestering carbon from the atmosphere. He concludes that temporary
storage of carbon in the terrestrial biosphere “achieves effectively no climate-change mitigation”. His strongly worded statement
begs for a response. This paper argues that Kirschbaum’s conclusion is an artifact of the specific perspective of his analysis
and his choice of a definition for climate-change impact. Even temporary sinks put us on a lower path for climate change,
a path that will not otherwise be accessible. For carbon sinks in the terrestrial biosphere, we argue that sooner is better
and longer is better, but even known temporary sinks have value.
相似文献
Gregg Marland (Corresponding author)Email: |
13.
Intrageneric differences in the four stereoisomers of stenusine in the rove beetle genus, Stenus (Coleoptera, Staphylinidae) 总被引:1,自引:1,他引:0
Lusebrink I Burkhardt D Gedig T Dettner K Mosandl A Seifert K 《Die Naturwissenschaften》2007,94(2):143-147
Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine
from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers:
(2′R,3R)-, (2′S,3R)-, (2′S,3S)-, and (2′R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible
that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.
相似文献
Inka LusebrinkEmail: |
14.
Further evidence of nuclear reactions in the Pd/D lattice: emission of charged particles 总被引:1,自引:1,他引:0
Almost two decades ago, Fleischmann and Pons reported excess enthalpy generation in the negatively polarized Pd/D-D2O system, which they attributed to nuclear reactions. In the months and years that followed, other manifestations of nuclear
activities in this system were observed, viz. tritium and helium production and transmutation of elements. In this report,
we present additional evidence, namely, the emission of highly energetic charged particles emitted from the Pd/D electrode
when this system is placed in either an external electrostatic or magnetostatic field. The density of tracks registered by
a CR-39 detector was found to be of a magnitude that provides undisputable evidence of their nuclear origin. The experiments
were reproducible. A model based upon electron capture is proposed to explain the reaction products observed in the Pd/D-D2O system.
相似文献
Pamela A. Mosier-BossEmail: |
15.
Upasna Sharma Anand Patwardhan 《Mitigation and Adaptation Strategies for Global Change》2008,13(8):819-831
Differences in impacts of climate hazards across exposed units are determined by many factors including the severity of the
hazard itself, the population that is exposed to the hazard and the coping capacity of the exposed units to the hazard. Coping
capacity or adaptive capacity results from a combination of development status (generic capacity) and interventions pertinent
to the hazard (specific capacity). This paper explores the extent to which the generic adaptive capacity may explain the variation
in tropical cyclone impacts. Therefore this paper offers an empirical approach by which adaptive capacity may be measured
and validated against actual outcomes. Results not only validate the role of generic adaptive capacity in explaining variations
in impact but also reveal that general development indicators are not very important as far as predicting outcomes is concerned.
Those indicators of development that can be linked to the impact process are significant in explaining and predicting impact.
This can help identify those aspects of generic adaptive capacity which are important from the perspective of policy action
for enhancing adaptive capacity to a particular climate hazard.
相似文献
Anand PatwardhanEmail: |
16.
Males of the gypsy moth, Lymantria dispar, are attracted by a pheromone released by females. Pheromones are detected by olfactory neurons housed in specialized sensory
hairs located on the antennae of the male moth. Once pheromone molecules enter the sensilla lymph, a highly abundant pheromone-binding
protein (PBP) transports the molecule to the sensory neuron. The PBPs are members of the insect odorant-binding protein family,
with six conserved cysteine residues. In this study, the disulfide bond connectivities of the pheromone-binding proteins PBP1
and PBP2 from the gypsy moth were found to be cysteines 19–54, 50–109, and 97–118 for PBP1, and cysteines 19–54, 50–110, and
97–119 for PBP2, as determined by cyanylation reactions and cyanogen bromide chemical cleavage. We have discovered that the
second disulfide linkage is the most easily reduced of the three, and this same linkage is missing among four cysteine-containing
insect odorant-binding proteins (OBPs). We are the first to identify the unique steric and electronic properties of this second
disulfide linkage.
Electronic Supplementary Material Supplementary material is available for this article at
相似文献
Erika PlettnerEmail: |
17.
Alexander Golub Jos Cozijnsen Annie Petsonk 《Mitigation and Adaptation Strategies for Global Change》2009,14(5):433-453
This article examines possibilities for linkage between the European Union Emissions Trading System (EU ETS) and Russia, with
a view to enhancing cooperation on a broader scale than the project-based approaches that have been tested thus far. Three
paths for possible EU-Russia linkage are presented by which the Russian Assigned Amount under the Kyoto Protocol can be greened
in order to stimulate emissions trading: 1. Joint implementation—reductions earned via individual projects in Russia; 2. Greened
allowances or green investment schemes; and 3. Linked cap-and-trade systems, in which a Russian domestic emissions trading
system would link with the European Union Emissions Trading System. The authors conclude that the third option, emissions
trading through linked domestic emissions trading systems, offers the best opportunities at the lowest transaction costs.
The authors discuss useful innovative instruments like call options and slip level arrangements on government-to-government
and business-to-business levels.
相似文献
Annie PetsonkEmail: |
18.
Linking emissions trading schemes allows the combined emissions cap to be achieved at lower cost. Linking is usually environmentally
neutral, but some design features can lead to higher aggregate emissions if schemes are linked. Technical solutions to limit
the potential emissions increases due to design differences implemented when schemes are linked are not sufficient to ensure
the environmental effectiveness of the linked schemes over time. Technological, economic, administrative and other changes
that can lead to higher aggregate emissions are inevitable. The administrators of the linked schemes must ensure the stringency
of the emissions cap relative to the “business as usual” emissions of affected sources, the accuracy of the emissions reported
by affected sources, the integrity of the allowance registry, effective compliance enforcement, and the environmental integrity
of the credits issued for emission reduction projects over time. This will require a process for agreeing on revisions to
the regulations of the linked schemes, a mechanism to provide assurance of the environmental effectiveness of each of the
linked schemes, and a procedure for terminating the linking agreement.
相似文献
X. WangEmail: |
19.
Sonia Akter Roy Brouwer Saria Choudhury Salina Aziz 《Mitigation and Adaptation Strategies for Global Change》2009,14(3):215-229
The study aims to assess the commercial viability of a potential crop insurance market in Bangladesh. In a large scale household
survey, agricultural farm households were asked for their preferences for a hypothetical crop insurance scheme using double
bounded (DB) contingent valuation (CV) method. Both revenue and production cost based indemnity payment approaches were applied
to assess the commercial viability of a crop insurance program assuming a partner-agent (PA) model of insurance supply. Crop
insurance is found marginally commercially viable in riverine flood plain areas. The expected indemnity payable consistently
exceeds the expected insurance premium receivable by the insurer for the households living in wetland basin and coastal floodplain.
We conclude that a uniform structure of crop insurance market does not exist in Bangladesh. The nature of the disaster risks
faced by the farm households and the socio-economic characteristics of the rural farm communities need to be taken into careful
consideration while designing such an insurance scheme.
相似文献
Sonia AkterEmail: |
20.
Serge I. P. Stalpers André R. van Amstel Rob B. Dellink Ivo Mulder Saskia E. Werners Carolien Kroeze 《Mitigation and Adaptation Strategies for Global Change》2008,13(4):359-378
This article discusses an approach for identification and evaluation of short-term greenhouse gas (GHG) emission reduction
options in firms. The approach is based on lessons learnt from a project using Participatory Integrated Assessment (PIA) and
builds on the idea that effective public climate policy for firms requires options that have support from stakeholders and
are practically feasible. Scenarios are used to provide a link with short-term policy developments and a model assists to
communicate quantitative effects of options to participating stakeholders. Our approach can be seen as a first step towards
a framework that meets the need for more systematic approaches to PIAs identifying effective public policies for short-term
GHG emission reduction options in firms. In order to identify effective options for non-carbon dioxide GHG emission reductions,
our approach has been applied to Dutch dairy farms, after which it has been refined. The case study suggests that our approach
can provide balance between practical, context specific issues and scientific-theoretical aspects, thereby avoiding common
pitfalls of participatory research projects to focus too much on either theory or practical issues.
相似文献
Serge I. P. StalpersEmail: |