26 resultados para Research Subject Categories::NATURAL SCIENCES::Chemistry::Organic chemistry::Polymer chemistry


Relevância:

100.00% 100.00%

Publicador:

Resumo:

The radiative forcing due to a distinct pattern of persistent contrails that form into contrail-induced cirrus near and over the UK is investigated in detail for a single case study during March 2009. The development of the contrail-induced cirrus is tracked using a number of high-resolution polar orbiting and lower-resolution geostationary satellite instruments and is found to persist for a period of around 18 h, and at its peak, it covers over 50,000 km2. The shortwave (SW) and longwave (LW) radiative forcing of the contrail-induced cirrus is estimated using a combination of geostationary satellite instruments, numerical weather prediction models, and surface observation sites. As expected, the net radiative effect is a relatively small residual of the much stronger but opposing SW and LW effects, locally totaling around 10 W m−2 during daylight hours and 30 W m−2 during nighttime. A simple estimate indicates that this single localized event may have generated a global-mean radiative forcing of around 7% of recent estimates of the persistent contrail radiative forcing due to the entire global aircraft fleet on a diurnally averaged basis. A single aircraft operating in conditions favorable for persistent contrail formation appears to exert a contrail-induced radiative forcing some 5000 times greater (in W m−2 km−1) than recent estimates of the average persistent contrail radiative forcing from the entire civil aviation fleet. This study emphasizes the need to establish whether similar events are common or highly unusual for a confident assessment of the total climate effect of aviation to be made.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The banded patterns of cloud and wind are among the most striking features of the atmospheres of Jupiter and Saturn, but their dynamical origin remains poorly understood. Most approaches towards understanding zonation so far (also in the terrestrial oceans) have used highly idealized models to show that it might originate from dynamical anisotropy in a shallow turbulent fluid layer due to the planetary β-effect. Here we report the results of laboratory experiments, conducted on a 14-m diameter turntable, which quantitatively confirm that multiple zonal jets may indeed be generated and maintained by this mechanism in the presence of deep convection and a topographic β-effect. At the very small values of Ekman number (≤2 × 10−5) and large local Reynolds numbers (≥2000, based on jet scales) achieved, the kinetic energy spectra suggest the presence of both energy-cascading and enstrophy-cascading inertial ranges in addition to the zonation near twice the Rhines wave number.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Inertia-gravity waves exist ubiquitously throughout the stratified parts of the atmosphere and ocean. They are generated by local velocity shears, interactions with topography, and as geostrophic (or spontaneous) adjustment radiation. Relatively little is known about the details of their interaction with the large-scale flow, however. We report on a joint model/laboratory study of a flow in which inertia-gravity waves are generated as spontaneous adjustment radiation by an evolving large-scale mode. We show that their subsequent impact upon the large-scale dynamics is generally small. However, near a potential transition from one large-scale mode to another, in a flow which is simultaneously baroclinically-unstable to more than one mode, the inertia-gravity waves may strongly influence the selection of the mode which actually occurs.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Despite the importance of microphysical cloud processes on the climate system, some topics are under-explored. For example, few measurements of droplet charges in nonthunderstorm clouds exist. Balloon carried charge sensors can be used to provide new measurements. A charge sensor is described for use with meteorological balloons, which has been tested over a range of atmospheric temperatures from -60 to 20 degrees C, in cloudy and clear air. The rapid time response of the sensor (to >10 V s(-1)) permits charge densities from 100 fC m(-3) to 1 nC m(-3) to be determined, which is sufficient for it to act as a cloud edge charge detector at weakly charged horizontal cloud boundaries.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Answering many of the critical questions in conservation, development and environmental management requires integrating the social and natural sciences. However, understanding the array of available quantitative methods and their associated terminology presents a major barrier to successful collaboration. We provide an overview of quantitative socio-economic methods that distils their complexity into a simple taxonomy. We outline how each has been used in conjunction with ecological models to address questions relating to the management of socio-ecological systems. We review the application of social and ecological quantitative concepts to agro-ecology and classify the approaches used to integrate the two disciplines. Our review included all published integrated models from 2003 to 2008 in 27 journals that publish agricultural modelling research. Although our focus is on agro-ecology, many of the results are broadly applicable to other fields involving an interaction between human activities and ecology. We found 36 papers that integrated social and ecological concepts in a quantitative model. Four different approaches to integration were used, depending on the scale at which human welfare was quantified. Most models viewed humans as pure profit maximizers, both when calculating welfare and predicting behaviour. Synthesis and applications. We reached two main conclusions based on our taxonomy and review. The first is that quantitative methods that extend predictions of behaviour and measurements of welfare beyond a simple market value basis are underutilized by integrated models. The second is that the accuracy of prediction for integrated models remains largely unquantified. Addressing both problems requires researchers to reach a common understanding of modelling goals and data requirements during the early stages of a project.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Focuses on recent advances in research on block copolymers, covering chemistry (synthesis), physics (phase behaviors, rheology, modeling), and applications (melts and solutions). Written by a team of internationally respected scientists from industry and academia, this text compiles and reviews the expanse of research that has taken place over the last five years into one accessible resource. Ian Hamley is the world-leading scientist in the field of block copolymer research Presents the recent advances in the area, covering chemistry, physics and applications. Provides a broad coverage from synthesis to fundamental physics through to applications Examines the potential of block copolymers in nanotechnology as self-assembling soft materials

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Bioscience Horizons (BH)commenced publication in 2008 and features research papers and reviews written by graduating UK bioscience students. The journal is run by a consortium of UK universities (the Universities of Nottingham, Reading, Leeds and Chester) in association with Oxford University Press. Its submissions encompass the full range of subjects taught by UK bioscience departments, ranging from agronomy to zoology and including animal behaviour, cancer research, environmental biology, microbial sciences, molecular biology, pharmacolgy, primatology, taxonomy and other areas. BH receives manuscripts from recent graduates (with a bachelor of science or equivalent first degree) describing research carried out during their undergraduate studies, usually as a final-year research project. All submissions undergo expert review and have to meet strict criteria for scientific excellence and originality. Articles are written by a single author and published with the agreement of the graduate's home university department. The journal has an ISSN number and is open-access; articles are freely 'cite-able' contributions to the bioscience research literature.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The study of intuition is an emerging area of research in psychology, social sciences, and business studies. It is increasingly of interest to the study of management, for example in decision-making as a counterpoint to structured approaches. Recently work has been undertaken to conceptualize a construct for the intuitive nature of technology. However to-date there is no common under-standing of the term intuition in information systems (IS) research. This paper extends the study of intuition in IS research by using exploratory research to cate-gorize the use of the word “intuition” and related terms in papers published in two prominent IS journals over a ten year period. The entire text of MIS Quarterly and Information Systems Research was reviewed for the years 1999 through 2008 using searchable PDF versions of these publications. As far as could be deter-mined, this is the first application of this approach in the analysis of the text of IS academic journals. The use of the word “intuition” and related terms was catego-rized using coding consistent with Grounded Theory. The focus of this research was on the first two stages of Grounded Theory analysis - the development of codes and constructs. Saturation of coding was not reached: an extended review of these publications would be required to enable theory development. Over 400 incidents of the use of “intuition”, and related terms were found in the articles reviewed. The most prominent use of the term of “intuition” was coded as “Intui-tion as Authority” in which intuition was used to validate a research objective or finding; representing approximately 37 per cent of codes assigned. The second most common coding occurred in research articles with mathematical analysis, representing about 19 per cent of the codes assigned, for example where a ma-thematical formulation or result was “intuitive”. The possibly most impactful use of the term “intuition” was “Intuition as Outcome”, representing approximately 7 per cent of all coding, which characterized research results as adding to the intui-tive understanding of a research topic or phenomena. This research contributes to a greater theoretical understanding of intuition enabling insight into the use of intuition, and the eventual development of a theory on the use of intuition in academic IS research publications. It also provides potential benefits to practi-tioners by providing insight into and validation of the use of intuition in IS man-agement. Research directions include the creation of reflective and/or formative constructs for intuition in information systems research.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Climate change as a global problem has moved relatively swiftly into high profile political debates over the last 20 years or so, with a concomitant diffusion from the natural sciences into the social sciences. The study of the human dimensions of climate change has been growing in momentum through research which attempts to describe, evaluate, quantify and model perceptions of climate change, understand more about risk and assess the construction of policy. Cultural geographers’ concerns with the construction of knowledge, the workings of social relations in space and the politics and poetics of place-based identities provide a lens through which personal, collective and institutional responses to climate change can be evaluated using critical and interpretative methodologies. Adopting a cultural geography approach, this paper examines how climate change as a particular environmental discourse is constructed through memory, observation and conversation, as well as materialised in farming practices on the Lizard Peninsula, Cornwall, UK