1,906 research outputs found
Towards Efficient Verification of Population Protocols
Population protocols are a well established model of computation by
anonymous, identical finite state agents. A protocol is well-specified if from
every initial configuration, all fair executions reach a common consensus. The
central verification question for population protocols is the
well-specification problem: deciding if a given protocol is well-specified.
Esparza et al. have recently shown that this problem is decidable, but with
very high complexity: it is at least as hard as the Petri net reachability
problem, which is EXPSPACE-hard, and for which only algorithms of non-primitive
recursive complexity are currently known.
In this paper we introduce the class WS3 of well-specified strongly-silent
protocols and we prove that it is suitable for automatic verification. More
precisely, we show that WS3 has the same computational power as general
well-specified protocols, and captures standard protocols from the literature.
Moreover, we show that the membership problem for WS3 reduces to solving
boolean combinations of linear constraints over N. This allowed us to develop
the first software able to automatically prove well-specification for all of
the infinitely many possible inputs.Comment: 29 pages, 1 figur
Inherited Agglomeration Effects in Hedge Fund Spawns
This paper studies inherited agglomeration effects, which we define as human capital that managers acquire while working in an industry hub that may be transferred to a spinoff. We test for inherited agglomeration effects in the hedge fund industry and find that hedge fund managers who previously worked in New York and London outperform their peers by about one percent per year. The results are driven by managers who worked in investment management positions previously, and are at least as large as traditional agglomeration effects that arise from being located in an industry hub contemporaneously. The evidence suggests that inherited agglomeration effects are an important, but as yet overlooked, factor influencing the performance of new firms
Resolution of intramolecular dipoles and push-back effect of individual molecules on a metal surface
Molecules consisting of a donor and an acceptor moiety can exhibit large
intrinsic dipole moments. Upon deposition on a metal surface, the dipole may be
effectively screened and the charge distribution altered due to hybridization
with substrate electronic states. Here, we deposit Ethyl-Diaminodicyanoquinone
molecules, which exhibit a large dipole moment in gas phase, on a Au(111)
surface. Employing a combination of scanning tunneling microscopy and
non-contact atomic force microscopy, we find that a significant dipole moment
persists in the flat-lying molecules. Density-functional theory calculations
reveal that the dipole moment is even increased on the metal substrate as
compared to the gas phase. We also show that the local contact potential across
the molecular islands is decreased by several tens of meV with respect to the
bare metal. We explain this by the induced charge-density redistribution due to
the adsorbed molecules, which confine the substrate's wavefunction at the
interface. Our local measurements provide direct evidence of this so-called
push-back or cushion effect at the scale of individual molecules.Comment: This document is the unedited Author's version of a Submitted Work
that was subsequently accepted for publication in Journal of Physical
Chemistry
Vesicle transport and growth dynamics in Aspergillus niger: Microscale modeling of secretory vesicle flow and centerline extraction from confocal fluorescent data
In this paper, we present a mathematical model to describe filamentous fungal growth based on intracellular secretory vesicles (SVs), which transport cell wall components to the hyphal tip. Vesicular transport inside elongating hyphae is modeled as an advectionâdiffusionâreaction equation with a moving boundary, transformed into fixed coordinates, and discretized using a highâorder weighted essentially nonoscillatory discretization scheme. The model describes the production and the consumption of SVs with kinetic functions. Simulations are subsequently compared against distributions of SVs visualized by enhanced green fluorescent protein in young Aspergillus niger hyphae after germination. Intensity profile data are obtained using an algorithm scripted in ImageJ that extracts mean intensity distributions from 3D timeâlapse confocal measurement data. Simulated length growth is in good agreement with the experimental data. Our simulations further show that a decrease of effective vesicle transport velocity towards the tip can explain the observed tip accumulation of SVs.DFG, 273937032, SPP 1934: DispersitĂ€ts-, Struktur- und PhasenĂ€nderungen von Proteinen und biologischen Agglomeraten in biotechnologischen ProzessenTU Berlin, Open-Access-Mittel â 202
Towards integrated superconducting detectors on lithium niobate waveguides
Superconducting detectors are now well-established tools for low-light
optics, and in particular quantum optics, boasting high-efficiency, fast
response and low noise. Similarly, lithium niobate is an important platform for
integrated optics given its high second-order nonlinearity, used for high-speed
electro-optic modulation and polarization conversion, as well as frequency
conversion and sources of quantum light. Combining these technologies addresses
the requirements for a single platform capable of generating, manipulating and
measuring quantum light in many degrees of freedom, in a compact and
potentially scalable manner. We will report on progress integrating tungsten
transition-edge sensors (TESs) and amorphous tungsten silicide superconducting
nanowire single-photon detectors (SNSPDs) on titanium in-diffused lithium
niobate waveguides. The travelling-wave design couples the evanescent field
from the waveguides into the superconducting absorber. We will report on
simulations and measurements of the absorption, which we can characterize at
room temperature prior to cooling down the devices. Independently, we show how
the detectors respond to flood illumination, normally incident on the devices,
demonstrating their functionality.Comment: 7 pages, 4 figure
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