11,009 research outputs found
Modeling agricultural production risk and the adaptation to climate change
A model that integrates biophysical simulations in an economic model is used to analyze the impact of climate change on crop production. The biophysical model simulates future plant-management-climate relationships and the economic model simulates farmers' adaptation actions to climate change using a nonlinear programming approach. Beyond the development of average yields, special attention is devoted to the impact of climate change on crop yield variability. This study analyzes corn and winter wheat production on the Swiss Plateau with respect to climate change scenarios that cover the period of 2030-2050. In our model, adaptation options such as changes in seeding dates, changes in production intensity and the adoption of irrigation farming are considered. Different scenarios of climate change, output prices and farmers' risk aversion are applied in order to show the sensitivity of adaptation strategies and crop yields, respectively, on these factors. Our results show that adaptation actions, yields and yield variation highly depend on both climate change and output prices. The sensitivity of adaptation options and yields, respectively, to prices and risk aversion for winter wheat is much lower than for corn because of different growing periods. In general, our results show that both corn and winter wheat yields increase in the next decades. In contrast to other studies, we find the coefficient of variation of corn and winter wheat yields to decrease. We therefore conclude that simple adaptation measures are sufficient to take advantage of climate change in Swiss crop farming.climate change, robust estimation, yield variation, corn, winter wheat, market liberalization, Environmental Economics and Policy, Production Economics, Risk and Uncertainty,
Unconditional security from noisy quantum storage
We consider the implementation of two-party cryptographic primitives based on
the sole assumption that no large-scale reliable quantum storage is available
to the cheating party. We construct novel protocols for oblivious transfer and
bit commitment, and prove that realistic noise levels provide security even
against the most general attack. Such unconditional results were previously
only known in the so-called bounded-storage model which is a special case of
our setting. Our protocols can be implemented with present-day hardware used
for quantum key distribution. In particular, no quantum storage is required for
the honest parties.Comment: 25 pages (IEEE two column), 13 figures, v4: published version (to
appear in IEEE Transactions on Information Theory), including bit wise
min-entropy sampling. however, for experimental purposes block sampling can
be much more convenient, please see v3 arxiv version if needed. See
arXiv:0911.2302 for a companion paper addressing aspects of a practical
implementation using block samplin
Successive Induction in Larval Zebrafish
Activating one reflex often facilitates another, antagonistic one. Since Charles Sherrington first identified successive induction more than 100 years ago, it has been demonstrated in a wide range of species, from aphids to grasshoppers to dogs and humans. We show a particularly orderly example in zebrafish (Danio rerio) larvae and identify the simple dynamic process that seems to underlie it
Understanding the negative thermal expansion in planar graphite–metal composites
The addition of graphitic fibers and flakes as fillers is commonly used to control the thermal expansion of metals. Sintered metal matrix composites with a planar distribution of graphite flakes show a low or negative thermal expansion coefficient perpendicular to the orientation plane of the graphite (z-CTE). Since the metal matrix has a positive isotropic expansion and graphite has a high z-CTE, this effect cannot be explained by a simple model of stapled metal–graphite layers. Instead, a mechanical interaction between graphite and matrix must be considered. With neutron scattering measurements, we show that there is little or no strain of the graphite flakes caused by the matrix, which can be explained by the high modulus of graphite. Instead, we suggest that a macroscopic crumpling of the flakes is responsible for the low z-CTE of the composite. The crumpled flakes are thicker at low temperature and get stretched and flattened by the expanding matrix at high temperature, explaining the reduction in the thermal expansion across the orientation plane
Infrared and Ultraviolet Observations of VIRGOHI 21 and NGC 4254's Outer Disk
We present the results of Spitzer and Galex observations of gas/dust and star formation activities in the extreme outer disk of Virgo galaxy NGC 4254 and its surrounding regions. These observations were motivated in part by the potential existence of a “dark galaxy” in the vicinity. In the intergalactic VIRGOHI 21 region where the free-floating HI gas is found, neither UV nor mid-IR shows corresponding emission, thus providing stringent upper limits on the stellar mass and star formation rate in these clouds.On the other hand, we find clearly discernible excess ultraviolet emission in parts of the extended disk of NGC 4254, which is yet unseen in the optical and infrared. These UV emission appears different from the so-called “XUV disks” of other nearby galaxies in both their distribution pattern and physical origin, which we suggest is directly related to the gas concentration of VIRGOHI 21
The Impact of Transit-Oriented Development on Social Capital
This paper focuses on the ability of Transit Oriented Development (TOD) to improve social capital and interactions within a community. The expectation is that TOD has a positive impact on the lifestyle and activities of individuals who reside, work, and frequent these locations, and that this can include increases in social capital. Using data from a survey of transit station locations in New Jersey, the authors examine how proximity to the station and various built environment variables are associated with different measures of social capital, derived from responses to survey questions. These questions inquire about respondents’ perceptions of their neighborhood as a place to live, sense of community, knowing their neighbors, trust, and whether their community is a good place to raise a child. The authors also include a question on volunteering in the community. These questions reflect various domains of social capital as established in the literature. Results generally do not support the hypothesis that social capital is associated with transit station proximity and TOD. Features of the built environment, proxied by population and employment density, are also not associated with increased social capital, and in some cases have a negative association. While there are some limited positive associations with some of the social capital variables, one of the strongest indicators is living in a detached family home
Bringing BCI into everyday life: Motor imagery in a pseudo realistic environment
Bringing Brain-Computer Interfaces (BCIs) into everyday life is a challenge because an out-of-lab environment implies the presence of variables that are largely beyond control of the user and the software application. This can severely corrupt signal quality as well as reliability of BCI control. Current BCI technology may fail in this application scenario because of the large amounts of noise, nonstationarity and movement artifacts. In this paper, we systematically investigate the performance of motor imagery BCI in a pseudo realistic environment. In our study 16 participants were asked to perform motor imagery tasks while dealing with different types of distractions such as vibratory stimulations or listening tasks. Our experiments demonstrate that standard BCI procedures are not robust to theses additional sources of noise, implicating that methods which work well in a lab environment, may perform poorly in realistic application scenarios. We discuss several promising research directions to tackle this important problem.BMBF, 01GQ1115, Adaptive Gehirn-Computer-Schnittstellen (BCI) in nichtstationären Umgebunge
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