797 research outputs found
Constraint-based run-time state migration for live modeling
Live modeling enables modelers to incrementally update models as they are running and get immediate feedback about the impact of their changes. Changes introduced in a model may trigger inconsistencies between the model and its run-time state (e.g., deleting the current state in a statemachine); effectively requiring to migrate the run-time state to comply with the updated model. In this paper, we introduce an approach that enables to automatically migrate such runtime state based on declarative constraints defined by the language designer. We illustrate the approach using Nextep, a meta-modeling language for defining invariants and migration constraints on run-time state models. When a model changes, Nextep employs model finding techniques, backed by a solver, to automatically infer a new run-time model that satisfies the declared constraints. We apply Nextep to define migration strategies for two DSLs, and report on its expressiveness and performance
Fission of a multiphase membrane tube
A common mechanism for intracellular transport is the use of controlled
deformations of the membrane to create spherical or tubular buds. While the
basic physical properties of homogeneous membranes are relatively well-known,
the effects of inhomogeneities within membranes are very much an active field
of study. Membrane domains enriched in certain lipids in particular are
attracting much attention, and in this Letter we investigate the effect of such
domains on the shape and fate of membrane tubes. Recent experiments have
demonstrated that forced lipid phase separation can trigger tube fission, and
we demonstrate how this can be understood purely from the difference in elastic
constants between the domains. Moreover, the proposed model predicts timescales
for fission that agree well with experimental findings
Universal Algebraic Relaxation of Velocity and Phase in Pulled Fronts generating Periodic or Chaotic States
We investigate the asymptotic relaxation of so-called pulled fronts
propagating into an unstable state. The ``leading edge representation'' of the
equation of motion reveals the universal nature of their propagation mechanism
and allows us to generalize the universal algebraic velocity relaxation of
uniformly translating fronts to fronts, that generate periodic or even chaotic
states. Such fronts in addition exhibit a universal algebraic phase relaxation.
We numerically verify our analytical predictions for the Swift-Hohenberg and
the Complex Ginzburg Landau equation.Comment: 4 pages Revtex, 2 figures, submitted to Phys. Rev. Let
Quantum transport through a DNA wire in a dissipative environment
Electronic transport through DNA wires in the presence of a strong
dissipative environment is investigated. We show that new bath-induced
electronic states are formed within the bandgap. These states show up in the
linear conductance spectrum as a temperature dependent background and lead to a
crossover from tunneling to thermal activated behavior with increasing
temperature. Depending on the strength of the electron-bath coupling, the
conductance at the Fermi level can show a weak exponential or even an algebraic
length dependence. Our results suggest a new environmental-induced transport
mechanism. This might be relevant for the understanding of molecular conduction
experiments in liquid solution, like those recently performed on poly(GC)
oligomers in a water buffer (B. Xu et al., Nano Lett 4, 1105 (2004)).Comment: 5 pages, 3 figure
Suicides among Danish cancer patients 1971–1999
Compared to the general population, the suicide risk among Danish cancer patients diagnosed in 1971–1986 was increased by 50% for men and 30% for women. We updated the earlier study to evaluate both long-term and recent trends in the suicide risk. Cancer patients with a first cancer diagnosed between 1971 and 1999 in Denmark were followed-up for completed suicide through 1999. Excluding nonmelanoma skin cancer, 564 508 cancer patients were included and 1241 suicides observed. Both the standardised mortality ratio (SMR) of suicide relative to the general population and the suicide rates were analysed with Poisson regression methods. The overall SMR was increased to 1.7 (95% CI. 1.6–1.9) for men and 1.4 (95% CI: 1.3–1.5) for women. Following the cancer diagnosis, the suicide risk was highest in the first 3 months for men and between months 3 and 12 for women. The risk was higher for nonlocalised cancer and for cancers with perceived poor prognosis. Breast cancer patients had a higher risk than other cancer patients with similar good prognosis. The suicide rates among cancer patients decreased with calendar time, but less so than the rates in the general population. The suicide risk among cancer patients has not decreased as much as in the Danish population and reasons for this should be explored. Breast cancer might be believed by patients to be more life threatening than it is. Assessment and treatment of depression could improve the quality of life for cancer patients who suffer from unrecognised depressions and in turn reduce the risk of suicide in cancer patients
A view of the European carbon flux landscape through the lens of the ICOS atmospheric observation network
The ICOS (Integrated Carbon Observation System) network
of atmospheric measurement stations produces standardized data on greenhouse
gas concentrations at 46 stations in 16 different European countries (March
2023). The placement of instruments on tall towers and mountains results in
large influence regions (“concentration footprints”). The combined
footprints for all the individual stations create a “lens” through which
the network sees the European CO2 flux landscape. In this study, we
summarize this view using quantitative metrics of the fluxes seen by
individual stations and by the current and extended ICOS networks. Results
are presented from both country level and pan-European perspectives, using
open-source tools that we make available through the ICOS Carbon Portal. We
target anthropogenic emissions from various sectors, as well as the land
cover types found across Europe and their spatiotemporally varying fluxes.
This recognizes different interests of different ICOS stakeholders. We
specifically introduce “monitoring potential maps” to identify which
regions have a relative underrepresentation of biospheric fluxes. This
potential changes with the introduction of new stations, which we
investigate for the planned ICOS expansion with 19 stations over the next
few years.
In our study focused on the summer of 2020, we find that the ICOS
atmospheric station network has limited sensitivity to anthropogenic fluxes,
as was intended in the current design. Its representation of biospheric
fluxes follows the fractional representation of land cover and is generally
well balanced considering the pan-European view. Exceptions include
representation of grass and shrubland and broadleaf forest which are
abundant in south-eastern European countries, particularly Croatia and
Serbia. On the country scale, the representation shows larger imbalances, even
within relatively densely monitored countries. The flexibility to consider individual ecosystems, countries, or their integrals across Europe
demonstrates the usefulness of our analyses and can readily be reproduced
for any network configuration within Europe.</p
Multifunctional Devices and Logic Gates With Undoped Silicon Nanowires
We report on the electronic transport properties of multiple-gate devices
fabricated from undoped silicon nanowires. Understanding and control of the
relevant transport mechanisms was achieved by means of local electrostatic
gating and temperature dependent measurements. The roles of the source/drain
contacts and of the silicon channel could be independently evaluated and tuned.
Wrap gates surrounding the silicide-silicon contact interfaces were proved to
be effective in inducing a full suppression of the contact Schottky barriers,
thereby enabling carrier injection down to liquid-helium temperature. By
independently tuning the effective Schottky barrier heights, a variety of
reconfigurable device functionalities could be obtained. In particular, the
same nanowire device could be configured to work as a Schottky barrier
transistor, a Schottky diode or a p-n diode with tunable polarities. This
versatility was eventually exploited to realize a NAND logic gate with gain
well above one.Comment: 6 pages, 5 figure
Elasticity of semiflexible polymers with and without self-interactions
A {\it new} formula for the force vs extension relation is derived from the
discrete version of the so called {\it worm like chain} model. This formula
correctly fits some recent experimental data on polymer stretching and some
numerical simulations with pairwise repulsive potentials. For a more realistic
Lennard-Jones potential the agreement with simulations is found to be good when
the temperature is above the temperature. For lower temperatures a
plateau emerges, as predicted by some recent experimental and theoretical
results, and our formula gives good results only in the high force regime. We
briefly discuss how other kinds of self-interactions are expected to affect the
elasticity of the polymer.Comment: 8 pages, 10 figure
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