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01 Jan 2007-
About: The article was published on 2007-01-01 and is currently open access. It has received 742 citations till now.
Citations
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01 Jan 2012TL;DR: In this article, the authors argue that success lies in being able to communicate, share, and use information to solve complex problems, in adapting and innovating in response to new demands and changing circumstances, in marshaling and expanding the power of technology to create new knowledge, and in expanding human capacity and productivity.
Abstract: As the previous chapter indicates, there has been a significant shift in advanced economies from manufacturing to information and knowledge services. Knowledge itself is growing ever more specialized and expanding exponentially. Information and communication technology is transforming the nature of how work is conducted and the meaning of social relationships. Decentralized decision making, information sharing, teamwork, and innovation are key in today’s enterprises. No longer can students look forward to middle class success in the conduct of manual labor or use of routine skills – work that can be accomplished by machines. Rather, whether a technician or a professional person, success lies in being able to communicate, share, and use information to solve complex problems, in being able to adapt and innovate in response to new demands and changing circumstances, in being able to marshal and expand the power of technology to create new knowledge, and in expanding human capacity and productivity.
1,056 citations
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TL;DR: The lubridate package for R is presented, which facilitates working with dates and times and introduces a conceptual framework for arithmetic with date-times in R.
Abstract: This paper presents the lubridate package for R, which facilitates working with dates and times. Date-times create various technical problems for the data analyst. The paper highlights these problems and offers practical advice on how to solve them using lubridate. The paper also introduces a conceptual framework for arithmetic with date-times in R.
834 citations
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TL;DR: The authors review the literature on climate change impacts on livestock and livestock systems in developing countries, and identify some key knowledge and data gaps, and also list some of the broad researchable issues associated with how smallholders and pastoralists might respond to climate change.
813 citations
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TL;DR: This paper first reviews the historical development of the formulae for decomposing dissimilarities into replacement, richness difference and nestedness indices, and shows that local contributions of replacement and richness difference to total beta diversity can be computed and mapped.
Abstract: AimThe variation in species composition among sites, or beta diversity, can be decomposed into replacement and richness difference. A debate is ongoing in the literature concerning the best ways of computing and interpreting these indices. This paper first reviews the historical development of the formulae for decomposing dissimilarities into replacement, richness difference and nestedness indices. These formulae are presented for species presence‐absence and abundance using a unified algebraic framework. The indices decomposing beta play different roles in ecological analysis than do beta-diversity indices. InnovationReplacement and richness difference indices can be interpreted and related to ecosystem processes. The pairwise index values can be summed across all pairs of sites; these sums form a valid decomposition of total beta diversity into total replacement and total richness difference components. Different communities and study areas can be compared: some may be dominated by replacement, others by richness/abundance difference processes. Within a region, differences among sites measured by these indices can then be analysed and interpreted using explanatory variables or experimental factors. The paper also shows that local contributions of replacement and richness difference to total beta diversity can be computed and mapped. A case study is presented involving fish communities along a river. Main conclusionsThe different forms of indices are based upon the same functional numerators. These indices are complementary; they can help researchers understand different aspects of ecosystemfunctioning. The methods of analysis used in this paper apply to any of the indices recently proposed. Further work, based on ecological theory and numerical simulations, is required to clarify the precise meaning and domain of application of the different forms. The forms available for presence‐absence and quantitative data are both useful because these different data types allow researchers to answer different types of ecological or biogeographic questions.
640 citations
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TL;DR: A new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens is reported.
Abstract: The maximum imaging resolution in classical optics is limited to approximately the wavelength of light used, and subwavelength resolution can only be achieved by advanced imaging schemes. The appeal of the super-oscillatory lens optical microscope described here is that it enables subwavelength imaging with, in principle, unlimited resolution using a modified conventional microscope. The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry–Veselago negative index superlens1, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it2,3,4,5,6, or work only for a narrow class of samples, such as intensely luminescent7,8 or sparse9 objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens. This non-invasive subwavelength imaging paradigm uses a binary amplitude mask for direct focusing of laser light into a subwavelength spot in the post-evanescent field by precisely tailoring the interference of a large number of beams diffracted from a nanostructured mask. The new technology, which—in principle—has no physical limits on resolution, could be universally used for imaging at any wavelength and does not depend on the luminescence of the object, which can be tens of micrometres away from the mask. It has been implemented as a straightforward modification of a conventional microscope showing resolution better than λ/6.
587 citations
References
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TL;DR: The impact evaluation of a conditional cash transfer program was performed by the Nicaraguan Red de Proteccion Social (RPS) as discussed by the authors, which evaluated the effectiveness of the program.
Abstract: Impact evaluation of a conditional cash transfer program :the Nicaraguan Red de Proteccion Social , Impact evaluation of a conditional cash transfer program :the Nicaraguan Red de Proteccion Social , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
538 citations
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TL;DR: The advantages and disadvantages of experiments in comparison with other research techniques are examined and the circumstances where randomized trials should be preferred over other methods are described.
Abstract: Social experiments have been used in research since the 1960s, yet the technique of controlled experimentation still arouses controversy among social scientists. The crucial element that distinguishes a controlled experiment from other forms of research is random assignment of treatment to the observational units of study. Because treatment differences in the sample occur as a result of random chance, the effects of the treatment on behavior can be measured with high reliability. This paper examines the advantages and disadvantages of experiments in comparison with other research techniques and describes the circumstances where randomized trials should be preferred over other methods.
350 citations
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01 Jan 2001
TL;DR: One of the major components of the PROGRESA program has been directed toward improving the nutritional status of small children in poor rural communities in Mexico as mentioned in this paper, which has been shown to have a substantial effect on lifetime productivities and earnings of currently small children.
Abstract: One of the major components of the PROGRESA program has been directed toward improving the nutritional status of small children in poor rural communities in Mexico. Results suggest that PROGRESA may be having fairly substantial effects on lifetime productivities and earnings of currently small children in poor households.
245 citations
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TL;DR: The authors used a Markov schooling transition model applied to the experimental data to assess the impact of the educational subsidy program along several dimensions, including effects on initial ages of school entry, dropout rates, grade repetition rates, and school reentry rates.
Abstract: A new anti-poverty program in Mexico, PROGRESA, provides monetary transfers to families that are contingent upon their children's regular attendance at school. The benefit levels are intended to offset the opportunity costs of not sending children to school and vary with the grade level and gender of the child. The initial phase of the program was implemented as a randomized social experiment. This paper uses a Markov schooling transition model applied to the experimental data to assess the impact of the educational subsidy program along several dimensions, including effects on initial ages of school entry, dropout rates, grade repetition rates, and school reentry rates. The findings show that the program effectively reduces drop-out rates and facilitates progression through the grades, particularly during the transition from primary to secondary school. Results based on a simulation evaluating the effects of longer terms of exposure to the program indicate that if children were to participate in the program between ages 6 to 14, they would experience an increase of 0.6 years in average educational attainment levels years and an increase of 19% in the percentage of children attending junior secondary school.
217 citations
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01 Jan 2004TL;DR: Conditional cash transfer as discussed by the authors is a departure from more traditional approaches to social assistance, that represents an innovative, and increasingly popular channel for the delivery of social services that represents a demand-side complement to the supply of health, and education services.
Abstract: Conditional cash transfers are a departure from more traditional approaches to social assistance, that represents an innovative, and increasingly popular channel for the delivery of social services. Conditional cash transfers provide money to poor families, contingent upon certain behavior, usually investments in human capital, such as sending children to school, or bringing them to health centers on a regular basis. They seek both to address traditional short-term income support objectives, as well as to promote the longer-term accumulation of human capital, by serving as a demand-side complement to the supply of health, and education services. Evaluation results from a first generation of programs reveal that this innovative design has been quite successful in addressing many of the criticisms of social assistance, such as poor poverty targeting, disincentive effects, and limited welfare impacts. There is clear evidence of success from programs in Brazil, Colombia, Mexico and Nicaragua in increasing enrollment rates, improving preventive health care and raising household consumption. Despite this promising evidence, many questions remain unanswered about conditional cash transfer programs, including the replicability of their success under different conditions, their role within a broader social protection system, and their long-term effectiveness in preventing the inter- generational transmission of poverty. One of the main challenges facing policymakers today is how to build off of the established success of conditional cash transfer programs, to tackle the more difficult issues of improving the quality of health, and education services, and providing a more holistic approach to both social protection, and chronic poverty.
208 citations