3,145 research outputs found
Elastic response of filamentous networks with compliant crosslinks
Experiments have shown that elasticity of disordered filamentous networks
with compliant crosslinks is very different from networks with rigid
crosslinks. Here, we model and analyze filamentous networks as a collection of
randomly oriented rigid filaments connected to each other by flexible
crosslinks that are modeled as worm-like chains. For relatively large
extensions we allow for enthalpic stretching of crosslinks' backbones. We show
that for sufficiently high crosslink density, the network linear elastic
response is affine on the scale of the filaments' length. The nonlinear regime
can become highly nonaffine and is characterized by a divergence of the elastic
modulus at finite strain. In contrast to the prior predictions, we do not find
an asymptotic regime in which the differential elastic modulus scales linearly
with the stress, although an approximate linear dependence can be seen in a
transition from entropic to enthalpic regimes. We discuss our results in light
of the recent experiments.Comment: 10 pages, 11 figure
Histological investigations on the thyroid glands of marine mammals (Phoca vitulina, Phocoena phocoena) and the possible implications of marine pollution
In 1988 and 1989, thousands of harbor seals (Phoca vitulina) died in the North Sea from phocine distemper infection. The morphology of thyroid glands from 40 harbor seals found dead on the North Sea coastlines of Schleswig-Holstein, Federal Republic of Germany, during an epizootic of phocine distemper, was compared with the morphology of thyroid glands from five healthy harbor seals collected in Iceland. Thyroid glands from seven harbor porpoises (Phocoena phocoena) found dead in 1990 on the North Sea coastlines also were evaluated. Colloid depletion and fibrosis were found in the thyroid glands of harbor seals which died during the epizootic, but not in animals from Iceland. Thyroid glands of the porpoises showed similar lesions, but to a lesser degree, than those observed in the North Sea seals
Efficient HTTP based I/O on very large datasets for high performance computing with the libdavix library
Remote data access for data analysis in high performance computing is
commonly done with specialized data access protocols and storage systems. These
protocols are highly optimized for high throughput on very large datasets,
multi-streams, high availability, low latency and efficient parallel I/O. The
purpose of this paper is to describe how we have adapted a generic protocol,
the Hyper Text Transport Protocol (HTTP) to make it a competitive alternative
for high performance I/O and data analysis applications in a global computing
grid: the Worldwide LHC Computing Grid. In this work, we first analyze the
design differences between the HTTP protocol and the most common high
performance I/O protocols, pointing out the main performance weaknesses of
HTTP. Then, we describe in detail how we solved these issues. Our solutions
have been implemented in a toolkit called davix, available through several
recent Linux distributions. Finally, we describe the results of our benchmarks
where we compare the performance of davix against a HPC specific protocol for a
data analysis use case.Comment: Presented at: Very large Data Bases (VLDB) 2014, Hangzho
Slave to the rhythm: seasonal signals in otolith microchemistry reveal age of eastern Baltic cod (Gadus morhua)
Annual growth zones in cod otoliths from the eastern Baltic stock are less discrete than in other cod stocks leading to biased age reading, which recently led to a failure of age-based assessment in the eastern Baltic cod stock. In this study, we explored the applicability of minor and trace element patterns in cod otoliths for age determination. By first identifying elements of interest in a stock without ageing problems, western Baltic cod, we then tested their applicability on another stock without ageing problems, North Sea cod, and finally applied this knowledge to estimate age of eastern Baltic cod. In western Baltic cod, matching patterns with respect to occurrence of minima and maxima in both otolith opacity and element concentrations were found for Cu, Zn, and Rb, and inverse patterns with Mg and Mn. No match was found for Pb, Ba, and Sr. In the test stock, the North Sea cod, the same patterns in Cu, Zn, Rb, Mg, and Mn signals occurred. All eastern Baltic cod with low visual contrast between growth zones exhibited clearly defined synchronous cycles in Cu, Zn, Rb and Pb. Using a combined finite differencing method and structural break models approach, the statistical significance of the local profile minima were identified, based on which their age could be estimated. Despite extensive environmental differences between the three areas examined, the element concentrations of Cu, Zn, and Rb were strongly correlated in all individuals with similar correlations in all three areas, suggesting that the incorporation mechanisms are the same for these elements and independent of environmental concentrations
Quantum key distribution using non-classical photon number correlations in macroscopic light pulses
We propose a new scheme for quantum key distribution using macroscopic
non-classical pulses of light having of the order 10^6 photons per pulse.
Sub-shot-noise quantum correlation between the two polarization modes in a
pulse gives the necessary sensitivity to eavesdropping that ensures the
security of the protocol. We consider pulses of two-mode squeezed light
generated by a type-II seeded parametric amplification process. We analyze the
security of the system in terms of the effect of an eavesdropper on the bit
error rates for the legitimate parties in the key distribution system. We also
consider the effects of imperfect detectors and lossy channels on the security
of the scheme.Comment: Modifications:added new eavesdropping attack, added more references
Submitted to Physical Review A [email protected]
Osmotic stress tolerance in semi-terrestrial tardigrades
Heidemann, Nanna W. T., Smith, Daniel K., Hygum, Thomas L., Stapane, Lilian, Clausen, Lykke K. B., Jørgensen, Aslak, Helix-Nielsen, Claus, Møbjerg, Nadja (2016): Osmotic stress tolerance in semi-terrestrial tardigrades. Zoological Journal of the Linnean Society 178 (4): 912-918, DOI: 10.1111/zoj.12502, URL: http://dx.doi.org/10.1111/zoj.1250
Orbitally Driven Spin Pairing in the 3D Non-Magnetic Mott Insulator BaVS3: Evidence from Single Crystal Studies
Static electrical and magnetic properties of single crystal BaVS_3 were
measured over the structural (T_S=240K), metal-insulator (T_MI=69K), and
suspected orbital ordering (T_X=30K) transitions. The resistivity is almost
isotropic both in the metallic and insulating states. An anomaly in the
magnetic anisotropy at T_X signals a phase transition to an ordered low-T
state. The results are interpreted in terms of orbital ordering and spin
pairing within the lowest crystal field quasi-doublet. The disordered insulator
at T_X<T<T_MI is described as a classical liquid of non-magnetic pairs.Comment: 4 pages, 5 figures, revtex, epsf, and multicol style. Problem with
figures fixed. To appear in Phys. Rev. B Rap. Com
- …