330,136 research outputs found
The role of social interaction in farmers' climate adaptation choice
Adaptation to climate change might not always occur, with potentially\ud
catastrophic results. Success depends on coordinated actions at both\ud
governmental and individual levels (public and private adaptation). Even for a âwetâ country like the Netherlands, climate change projections show that the frequency and severity of droughts are likely to increase. Freshwater is an important factor for agricultural production. A deficit causes damage to crop production and consequently to a loss of income. Adaptation is the key to decrease farmersâ vulnerability at the micro level and the sectorâs vulnerability at the macro level. Individual adaptation decision-making is determined by the behavior of economic agents and social interaction among them. This can be best studied with agentbased modelling. Given the uncertainty about future weather conditions and the costs and effectiveness of adaptation strategies, a farmer in the model uses a cognitive process (or heuristic) to make adaptation decisions. In this process, he can rely on his experiences and on information from interactions within his social network. Interaction leads to the spread of information and knowledge that causes learning. Learning changes the conditions for individual adaptation decisionmaking. All these interactions cause emergent phenomena: the diffusion of adaptation strategies and a change of drought vulnerability of the agricultural sector. In this paper, we present a conceptual model and the first implementation of an agent-based model. The aim is to study the role of interaction in a farmerâs social network on adaptation decisions and on the diffusion of adaptation strategies\ud
and vulnerability of the agricultural sector. Micro-level survey data will be used to parameterize agentsâ behavioral and interaction rules at a later stage. This knowledge is necessary for the successful design of public adaptation strategies, since governmental adaptation actions need to be fine-tuned to private adaptation behavior
Analysis of acid-stressed Bacillus cereus reveals a major oxidative response and inactivation-associated radical formation
Acid stress resistance of the food-borne human pathogen Bacillus cereus may contribute to its survival in acidic environments, such as encountered in soil, food and the human gastrointestinal tract. The acid stress responses of B. cereus strains ATCC 14579 and ATCC 10987 were analysed in aerobically grown cultures acidified to pH values ranging from pH 5.4 to pH 4.4 with HCI. Comparative phenotype and transcriptome analyses revealed three acid stressinduced responses in this pH range: growth rate reduction, growth arrest and loss of viability. These physiological responses showed to be associated with metabolic shifts and the induction of general stress response mechanisms with a major oxidative component, including upregulation of catalases and superoxide dismutases. Flow cytometry analysis in combination with the hydroxyl (OH center dot) and peroxynitrite (ONOO-)-specific fluorescent probe 3'-(phydroxyphenyl) fluorescein (HPF) showed excessive radicals to be formed in both B. cereus strains in bactericidal conditions only. Our study shows that radicals can indicate acid-induced malfunctioning of cellular processes that lead to cell death
Dense and warm molecular gas in the envelopes and outflows of southern low-mass protostars
Observations of dense molecular gas lie at the basis of our understanding of
the density and temperature structure of protostellar envelopes and molecular
outflows. We aim to characterize the properties of the protostellar envelope,
molecular outflow and surrounding cloud, through observations of high
excitation molecular lines within a sample of 16 southern sources presumed to
be embedded YSOs. Observations of submillimeter lines of CO, HCO+ and their
isotopologues, both single spectra and small maps were taken with the FLASH and
APEX-2a instruments mounted on APEX to trace the gas around the sources. The
HARP-B instrument on the JCMT was used to map IRAS 15398-3359 in these lines.
HCO+ mapping probes the presence of dense centrally condensed gas, a
characteristic of protostellar envelopes. The rare isotopologues C18O and
H13CO+ are also included to determine the optical depth, column density, and
source velocity. The combination of multiple CO transitions, such as 3-2, 4-3
and 7-6, allows to constrain outflow properties, in particular the temperature.
Archival submillimeter continuum data are used to determine envelope masses.
Eleven of the sixteen sources have associated warm and/or dense quiescent as
characteristic of protostellar envelopes, or an associated outflow. Using the
strength and degree of concentration of the HCO+ 4-3 and CO 4-3 lines as a
diagnostic, five sources classified as Class I based on their spectral energy
distributions are found not to be embedded YSOs. The C18O 3-2 lines show that
for none of the sources, foreground cloud layers are present. Strong molecular
outflows are found around six sources, .. (continued in paper)Comment: Accepted by A&A, 13 figure
Geometry of Scattering at Planckian Energies
We present an alternative derivation and geometrical formulation of Verlinde
topological field theory, which may describe scattering at center of mass
energies comparable or larger than the Planck energy. A consistent trunckation
of 3+1 dimensional Einstein action is performed using the standard geometrical
objects, like tetrads and spin connections. The resulting topological invariant
is given in terms of differential forms.Comment: 8
The Westerbork HI Survey of Spiral and Irregular Galaxies I. HI Imaging of Late-type Dwarf Galaxies
Neutral hydrogen observations with the Westerbork Synthesis Radio Telescope
are presented for a sample of 73 late-type dwarf galaxies. These observations
are part of the WHISP project (Westerbork HI Survey of Spiral and Irregular
Galaxies). Here we present HI maps, velocity fields, global profiles and radial
surface density profiles of HI, as well as HI masses, HI radii and line widths.
For the late-type galaxies in our sample, we find that the ratio of HI extent
to optical diameter, defined as 6.4 disk scale lengths, is on average 1.8+-0.8,
similar to that seen in spiral galaxies. Most of the dwarf galaxies in this
sample are rich in HI, with a typical M_HI/L_B of 1.5. The relative HI content
M_HI/L_R increases towards fainter absolute magnitudes and towards fainter
surface brightnesses. Dwarf galaxies with lower average HI column densities
also have lower average optical surface brightnesses. We find that lopsidedness
is as common among dwarf galaxies as it is in spiral galaxies. About half of
the dwarf galaxies in our sample have asymmetric global profiles, a third has a
lopsided HI distribution, and about half shows signs of kinematic lopsidedness.Comment: Accepted for publication in A&A. 18 pages. 39 MB version with all
figures is available http://www.robswork.net/publications/WHISPI.ps.g
Image charge dynamics in time-dependent quantum transport
In this work we investigate the effects of the electron-electron interaction
between a molecular junction and the metallic leads in time-dependent quantum
transport. We employ the recently developed embedded Kadanoff-Baym method
[Phys. Rev. B 80, 115107 (2009)] and show that the molecule-lead interaction
changes substantially the transient and steady-state transport properties. We
first show that the mean-field Hartree-Fock (HF) approximation does not capture
the polarization effects responsible for the renormalization of the molecular
levels neither in nor out of equilibrium. Furthermore, due to the time-local
nature of the HF self-energy there exists a region in parameter space for which
the system does not relax after the switch-on of a bias voltage. These and
other artifacts of the HF approximation disappear when including correlations
at the second-Born or GW levels. Both these approximations contain polarization
diagrams which correctly account for the screening of the charged molecule. We
find that by changing the molecule-lead interaction the ratio between the
screening and relaxation time changes, an effect which must be properly taken
into account in any realistic time-dependent simulation. Another important
finding is that while in equilibrium the molecule-lead interaction is
responsible for a reduction of the HOMO-LUMO gap and for a substantial
redistribution of the spectral weight between the main spectral peaks and the
induced satellite spectrum, in the biased system it can have the opposite
effect, i.e., it sharpens the spectral peaks and opens the HOMO-LUMO gap.Comment: 18 pages, 26 figure
Routing for analog chip designs at NXP Semiconductors
During the study week 2011 we worked on the question of how to automate certain aspects of the design of analog chips. Here we focused on the task of connecting different blocks with electrical wiring, which is particularly tedious to do by hand. For digital chips there is a wealth of research available for this, as in this situation the amount of blocks makes it hopeless to do the design by hand. Hence, we set our task to finding solutions that are based on the previous research, as well as being tailored to the specific setting given by NXP.
This resulted in an heuristic approach, which we presented at the end of the
week in the form of a protoype tool. In this report we give a detailed account of the ideas we used, and describe possibilities to extend the approach
- âŠ