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531.
Climate-driven trends in contemporary ocean productivity   总被引:6,自引:0,他引:6  
Contributing roughly half of the biosphere's net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks. Each day, more than a hundred million tons of carbon in the form of CO2 are fixed into organic material by these ubiquitous, microscopic plants of the upper ocean, and each day a similar amount of organic carbon is transferred into marine ecosystems by sinking and grazing. The distribution of phytoplankton biomass and NPP is defined by the availability of light and nutrients (nitrogen, phosphate, iron). These growth-limiting factors are in turn regulated by physical processes of ocean circulation, mixed-layer dynamics, upwelling, atmospheric dust deposition, and the solar cycle. Satellite measurements of ocean colour provide a means of quantifying ocean productivity on a global scale and linking its variability to environmental factors. Here we describe global ocean NPP changes detected from space over the past decade. The period is dominated by an initial increase in NPP of 1,930 teragrams of carbon a year (Tg C yr(-1)), followed by a prolonged decrease averaging 190 Tg C yr(-1). These trends are driven by changes occurring in the expansive stratified low-latitude oceans and are tightly coupled to coincident climate variability. This link between the physical environment and ocean biology functions through changes in upper-ocean temperature and stratification, which influence the availability of nutrients for phytoplankton growth. The observed reductions in ocean productivity during the recent post-1999 warming period provide insight on how future climate change can alter marine food webs.  相似文献   
532.
During immune responses, antibodies are selected for their ability to bind to foreign antigens with high affinity, in part by their ability to undergo homotypic bivalent binding. However, this type of binding is not always possible. For example, the small number of gp140 glycoprotein spikes displayed on the surface of the human immunodeficiency virus (HIV) disfavours homotypic bivalent antibody binding. Here we show that during the human antibody response to HIV, somatic mutations that increase antibody affinity also increase breadth and neutralizing potency. Surprisingly, the responding naive and memory B cells produce polyreactive antibodies, which are capable of bivalent heteroligation between one high-affinity anti-HIV-gp140 combining site and a second low-affinity site on another molecular structure on HIV. Although cross-reactivity to self-antigens or polyreactivity is strongly selected against during B-cell development, it is a common serologic feature of certain infections in humans, including HIV, Epstein-Barr virus and hepatitis C virus. Seventy-five per cent of the 134 monoclonal anti-HIV-gp140 antibodies cloned from six patients with high titres of neutralizing antibodies are polyreactive. Despite the low affinity of the polyreactive combining site, heteroligation demonstrably increases the apparent affinity of polyreactive antibodies to HIV.  相似文献   
533.
534.
The research described in this paper is undertaken under the banner of the smart city, a concept that captures the way urban spaces are re-made by the incursion of new technology. Much of smart is centred on converting everyday activities into data, and using this data to generate knowledge mediated by technology. Ordinary citizens, those that may have their lives impacted by the technology, usually are not properly involved in the ‘smartification’ process. Their perceptions, concerns and expectations should inform the conception and development of smart technologies at the same extent. How to engage general public with smart cities research is the central challenge for the Making Metrics Meaningful (MMM) project. Applying a rapid participatory method, ‘Imagine’ over a five-month period (March – July) the research sought to gain insights from the general public into novel forms of information system innovation. This brief paper describes the nature of the accelerated research undertaken and explores some of the themes which emerged in the analysis. Generic themes, beyond the remit of an explicit transport focus, are developed and pointers towards further research directions are discussed. Participatory methods, including engaging with self-selected transport users actively through both picture creation and programmatically specific musical ‘signatures’ as well as group discussion, were found to be effective in eliciting users’ own concerns, needs and ideas for novel information systems.  相似文献   
535.
Throughout much of the 20th century, philosophers of science maintained a position known as the value-free ideal, which holds that non-epistemic (e.g., moral, social, political, or economic) values should not influence the evaluation and acceptance of scientific results. In the last few decades, many philosophers of science have rejected this position by arguing that non-epistemic values can and should play an important role in scientific judgment and decision-making in a variety of contexts, including the evaluation and acceptance of scientific results. Rejecting the value-free ideal creates some new and vexing problems, however. One of these is that relinquishing this philosophical doctrine may undermine the integrity of scientific research if practicing scientists decide to allow non-epistemic values to impact their judgment and decision-making. A number of prominent philosophers of science have sought to show how one can reject the value-free ideal without compromising the integrity of scientific research. In this paper, we examine and critique their views and offer our own proposal for protecting and promoting scientific integrity. We argue that the literature on research ethics and its focus on adherence to norms, rules, policies, and procedures that together promote the aims of science can provide a promising foundation for building an account of scientific integrity. These norms, rules, policies, and procedures provide a level of specificity that is lacking in most philosophical discussions of science and values, and they suggest an important set of tasks for those working in science and values—namely, assessing, justifying, and prioritizing them. Thus, we argue that bringing together the literature on research ethics with the literature on science and values will enrich both areas and generate a more sophisticated and detailed account of scientific integrity.  相似文献   
536.
Learning history is a well delineated action research process consisting of consecutive stages of inquiry where groups and individuals engage in learning and reflecting on their past shared, but often multiple, experiences as these are recorded in a ‘learning history’. Learning history has much in common with other forms of action research in that it configures first-, second- and third-person processes of inquiry in a particular way and enacts research qualities of rigour, relevance and reflexivity. Yet these and other links have as yet been tacit and under articulated - resulting in learning history often conceived as a distinctive linear method with the practice of learning history likewise confined. This reflective article opens out and makes explicit the inherent first- second- and third- person dynamics of learning history. These dynamics are explored from the point of view of different actors – the historian, the participant and the reader - in a learning history process and connections to a general empirical method are made. Finally questions of quality in a learning history are discussed. The aim of this article is to establish firmer methodological foundations for the learning history approach and to provide practical insight into how action researchers might engage more readily in learning history work.  相似文献   
537.
538.
Antibodies against metal chelates   总被引:11,自引:0,他引:11  
Because monoclonal antibodies can recognize and bind to specific groups of atoms such as tumour antigens, they have promise for use in vivo as carriers of radionuclides, drugs or other appended molecules for diagnosis and treatment of disease. Attachment of metal ions to antibodies by means of bifunctional chelating agents can add the diverse nuclear, physical and chemical properties of the metallic elements to these specific binding proteins (ref. 4 and refs therein). With the ultimate aim of engineering probe-binding properties into the antibodies themselves, we have now prepared monoclonal antibodies against the EDTA chelate of indium. These antibodies show a remarkable preference for indium chelates; changing to another metal such as scandium or gallium can decrease the antibody-binding constant by more than three orders of magnitude. These antibodies also introduce a new degree of control over the biological distributions of chelated radionuclides, markedly altering their uptake in tumours and normal organs.  相似文献   
539.
David P 《Nature》1983,305(5931):173
A statute banning nuclear weapons research in Cambridge, Massachusetts, is scheduled for a referendum vote in November 1983. If passed, the act would require the city to fine or imprison violators after the ban takes effect in October 1985, and could have an impact on work done at Harvard University and the Massachusetts Institute of Technology, as well as at the Charles Stark Draper Laboratory. Lawyers for Draper and the local anti-nuclear group that drafted the statute, Mobilization for Survival, are expected to appear before the state's supreme court to decide whether or not the act will be allowed on the ballot.  相似文献   
540.
Bugs protected     
Dickson D 《Nature》1980,285(5766):528
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