1,186 research outputs found
Two-gap superconductivity with line nodes in CsCaFeAsF
We report the results of a muon-spin rotation (SR) experiment to
determine the superconducting ground state of the iron-based superconductor
CsCaFeAsF with K. This compound is
related to the fully-gapped superconductor CaCsFeAs, but here the
Ca-containing spacer layer is replaced with one containing CaF. The
temperature evolution of the penetration depth strongly suggests the presence
of line nodes and is best modelled by a system consisting of both an - and a
-wave gap. We also find a potentially magnetic phase which appears below
K but does not appear to compete with the superconductivity. This
compound contains the largest alkali atom in this family of superconductors and
our results yield a value for the in-plane penetration depth of
nm.Comment: 6 pages, 2 figure
Correlated singlet phase in the one-dimensional Hubbard-Holstein model
We show that a nearest-neighbor singlet phase results (from an effective
Hamiltonian) for the one-dimensional Hubbard-Holstein model in the regime of
strong electron-electron and electron-phonon interactions and under
non-adiabatic conditions (). By mapping the system of
nearest-neighbor singlets at a filling onto a hard-core-boson (HCB)
- model at a filling , we demonstrate explicitly that
superfluidity and charge-density-wave (CDW) occur mutually exclusively with the
diagonal long range order manifesting itself only at one-third filling.
Furthermore, we also show that the Bose-Einstein condensate (BEC) occupation
number for the singlet phase, similar to the for a HCB tight
binding model, scales as ; however, the coefficient of in
the for the interacting singlet phase is numerically demonstrated to be
smaller.Comment: Corrected a few reference
Make the most out of your SIMD investments: Counter control flow divergence in compiled query pipelines
Increasing single instruction multiple data (SIMD) capabilities in modern hardware allows for compiling efficient data-parallel query pipelines. This means GPU-alike challenges arise: control flow divergence causes underutilization of vector-processing units. In this paper, we present efficient algorithms for the AVX-512 architecture to address this issue. These algorithms allow for fine-grained assignment of new tuples to idle SIMD lanes. Furthermore, we present strategies for their integration with compiled query pipelines without introducing inefficient memory materializations. We evaluate our approach with a high-performance geospatial join query, which shows performance improvements of up to 35%
Make the most out of your SIMD investments: counter control flow divergence in compiled query pipelines
Increasing single instruction multiple data (SIMD) capabilities in modern hardware allows for the compilation of data-parallel query pipelines. This means GPU-alike challenges arise: control flow divergence causes the underutilization of vector-processing units. In this paper, we present efficient algorithms for the AVX-512 architecture to address this issue. These algorithms allow for the fine-grained assignment of new tuples to idle SIMD lanes. Furthermore, we present strategies for their integration with compiled query pipelines so that tuples are never evicted from registers. We evaluate our approach with three query types: (i) a table scan query based on TPC-H Query 1, that performs up to 34% faster when addressing underutilization, (ii) a hashjoin query, where we observe up to 25% higher performance, and (iii) an approximate geospatial join query, which shows performance improvements of up to 30%
Toward microbioreactor arrays : a slow-responding xxygen sensor for monitoring of microbial cultures in standard 96-well plates
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In this study, a slow-responding chemo-optical sensor for dissolved oxygen (DO) integrated into a 96-well plate was developed. The slow response time ensures that the measured oxygen value does not change much during plate transport to the microplate reader. The sensor therefore permits at-line DO measurement of microbial cultures. Moreover, it eliminates the necessity of individual optical measurement systems for each culture plate, as many plates can be measured successively. Combined with the 96-well format, this increases the experimental throughput enormously. The novel sensor plate (Slow OxoPlate) consists of fluorophores suspended in a polymer matrix that were placed into u-bottom 96-well plates. Response time was measured using sodium sulfite, and a t90 value of 9.7 min was recorded. For application, DO values were then measured in Escherichia coli and Saccharomyces cerevisiae cultures grown under fed-batch–like conditions. Depending on the DO sensor’s response time, different information on the oxygenation state of the culture plate was obtained: a fast sensor variant detects disturbance through sampling, whereas the slow sensor indicates oxygen limitation during incubation. A combination of the commercially available OxoPlate and the Slow OxoPlate enables operators of screening facilities to validate their cultivation procedures with regard to oxygen availability.BMBF, 02PJ1150, Plattformtechnologien für automatisierte Bioprozessentwicklung (AutoBio
Noise-free scattering of the quantized electromagnetic field from a dispersive linear dielectric
We study the scattering of the quantized electromagnetic field from a linear,
dispersive dielectric using the scattering formalism for quantum fields. The
medium is modeled as a collection of harmonic oscillators with a number of
distinct resonance frequencies. This model corresponds to the Sellmeir
expansion, which is widely used to describe experimental data for real
dispersive media. The integral equation for the interpolating field in terms of
the in field is solved and the solution used to find the out field. The
relation between the in and out creation and annihilation operators is found
which allows one to calculate the S-matrix for this system. In this model, we
find that there are absorption bands, but the input-output relations are
completely unitary. No additional quantum noise terms are required.Comment: Revtex, submitted to Physical Review
Reentrant charge ordering caused by polaron formation
Based on a two-dimensional extended Hubbard model with electron-phonon
interaction, we have studied the effect of polaron formation on the charge
ordering (CO) transition. It is found that for fully ferromagnetically ordered
spins the CO state may go through a process of appearance, collapse and
reappearance with decreasing temperature. This is entirely due to a
emperature-dependent polaron bandwidth. On the other hand, when a paramagnetic
spin state is considered, only a simple reentrant behavior of the CO transition
is found, which is only partly due to polaron effect. This model is proposed as
an explanation of the observed reentrant behavior of the CO transition in the
layered manganite LaSrMnO.Comment: 4 pages, 2 eps figures, revised version accepted by Phys. Rev. Let
Adaptive geospatial joins for modern hardware
Geospatial joins are a core building block of connected
mobility applications. An especially challenging problem
are joins between streaming points and static polygons. Since
points are not known beforehand, they cannot be indexed.
Nevertheless, points need to be mapped to polygons with low
latencies to enable real-time feedback.
We present an adaptive geospatial join that uses true hit
filtering to avoid expensive geometric computations in most
cases. Our technique uses a quadtree-based hierarchical grid
to approximate polygons and stores these approximations in a
specialized radix tree. We emphasize on an approximate version
of our algorithm that guarantees a user-defined precision. The
exact version of our algorithm can adapt to the expected point
distribution by refining the index. We optimized our implementation
for modern hardware architectures with wide SIMD vector
processing units, including Intel’s brand new Knights Landing.
Overall, our approach can perform up to two orders of magnitude
faster than existing techniques
Approximate geospatial joins with precision guarantees
Geospatial joins are a core building block of con-
nected mobility applications. An especially challenging problem
are joins between streaming points and static polygons. Since
points are not known beforehand, they cannot be indexed.
Nevertheless, points need to be mapped to polygons with low
latencies to enable real-time feedback.
We present an approximate geospatial join that guarantees
a user-defined precision. Our technique uses a quadtree-based
hierarchical grid to approximate polygons and stores these
approximations in a specialized radix tree. Our approach can
perform up to several orders of magnitude faster than existing
techniques while providing sufficiently precise results for many
applications
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