4,138 research outputs found
Coupled Cluster Channels in the Homogeneous Electron Gas
We discuss diagrammatic modifications to the coupled cluster doubles (CCD)
equations, wherein different groups of terms out of rings, ladders,
crossed-rings and mosaics can be removed to form approximations to the coupled
cluster method, of interest due to their similarity with various types of
random phase approximations. The finite uniform electron gas is benchmarked for
14- and 54-electron systems at the complete basis set limit over a wide density
range and performance of different flavours of CCD are determined. These
results confirm that rings generally overcorrelate and ladders generally
undercorrelate; mosaics-only CCD yields a result surprisingly close to CCD. We
use a recently developed numerical analysis [J. J. Shepherd and A. Gr\"uneis,
Phys. Rev. Lett. 110, 226401 (2013)] to study the behaviours of these methods
in the thermodynamic limit. We determine that the mosaics, on forming the
Brueckner Hamltonian, open a gap in the effective one-particle eigenvalues at
the Fermi energy. Numerical evidence is presented which shows that methods
based on this renormalisation have convergent energies in the thermodynamic
limit including mosaic-only CCD, which is just a renormalised MP2. All other
methods including only a single channel, namely ladder-only CCD, ring-only CCD
and crossed-ring-only CCD, appear to yield divergent energies; incorporation of
mosaic terms prevents this from happening.Comment: 9 pages, 4 figures, 1 table. Comments welcome: [email protected]
An enhanced debugger for real-time fault injection
Chip debug infrastructures, present in most recentmicroprocessors, to execute real time fault injectioncampaigns. It is based on a debugger customized forfault injection and designed for maximum performanceand flexibility. The developed methodology can beapplied on the verification of dependable systems
Accurate Hartree-Fock energy of extended systems using large Gaussian basis sets
Calculating highly accurate thermochemical properties of condensed matter via
wave function-based approaches (such as e.g. Hartree-Fock or hybrid
functionals) has recently attracted much interest. We here present two
strategies providing accurate Hartree-Fock energies for solid LiH in a large
Gaussian basis set and applying periodic boundary conditions. The total
energies were obtained using two different approaches, namely a supercell
evaluation of Hartree-Fock exchange using a truncated Coulomb operator and an
extrapolation toward the full-range Hartree-Fock limit of a Pad\'e fit to a
series of short-range screened Hartree-Fock calculations. These two techniques
agreed to significant precision. We also present the Hartree-Fock cohesive
energy of LiH (converged to within sub-meV) at the experimental equilibrium
volume as well as the Hartree-Fock equilibrium lattice constant and bulk
modulus.Comment: 7.5 pages, 2 figures, submitted to Phys. Rev. B; v2: typos removed,
References adde
Impact of Natural Blind Spot Location on Perimetry.
We study the spatial distribution of natural blind spot location (NBSL) and its impact on perimetry. Pattern deviation (PD) values of 11,449 reliable visual fields (VFs) that are defined as clinically unaffected based on summary indices were extracted from 11,449 glaucoma patients. We modeled NBSL distribution using a two-dimensional non-linear regression approach and correlated NBSL with spherical equivalent (SE). Additionally, we compared PD values of groups with longer and shorter distances than median, and larger and smaller angles than median between NBSL and fixation. Mean and standard deviation of horizontal and vertical NBSL were 14.33° ± 1.37° and -2.06° ± 1.27°, respectively. SE decreased with increasing NBSL (correlation: r = -0.14, p \u3c 0.001). For NBSL distances longer than median distance (14.32°), average PD values decreased in the upper central (average difference for significant points (ADSP): -0.18 dB) and increased in the lower nasal VF region (ADSP: 0.14 dB). For angles in the direction of upper hemifield relative to the median angle (-8.13°), PD values decreased in lower nasal (ADSP: -0.11 dB) and increased in upper temporal VF areas (ADSP: 0.19 dB). In conclusion, we demonstrate that NBSL has a systematic effect on the spatial distribution of VF sensitivity
Real-time fault injection using enhanced on-chip debug infrastructures
The rapid increase in the use of microprocessor-based systems in critical areas, where failures imply risks to human lives, to the environment or to expensive equipment, significantly increased the need for dependable systems, able to detect, tolerate and eventually correct faults. The verification and validation of such systems is frequently performed via fault injection, using various forms and techniques. However, as electronic devices get smaller and more complex, controllability and observability issues, and sometimes real time constraints, make it harder to apply most conventional fault injection techniques. This paper proposes a fault injection environment and a scalable methodology to assist the execution of real-time fault injection campaigns, providing enhanced performance and capabilities. Our proposed solutions are based on the use of common and customized on-chip debug (OCD) mechanisms, present in many modern electronic devices, with the main objective of enabling the insertion of faults in microprocessor memory elements with minimum delay and intrusiveness. Different configurations were implemented starting from basic Components Off-The-Shelf (COTS) microprocessors, equipped with real-time OCD infrastructures, to improved solutions based on modified interfaces, and dedicated OCD circuitry that enhance fault injection capabilities and performance. All methodologies and configurations were evaluated and compared concerning performance gain and silicon overhead
Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes
An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.CNPqFAPES
Constrained Local UniversE Simulations: A Local Group Factory
Near field cosmology is practiced by studying the Local Group (LG) and its
neighbourhood. The present paper describes a framework for simulating the near
field on the computer. Assuming the LCDM model as a prior and applying the
Bayesian tools of the Wiener filter (WF) and constrained realizations of
Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities,
constrained simulations of our cosmic environment are performed. The aim of
these simulations is to reproduce the LG and its local environment. Our main
result is that the LG is likely a robust outcome of the LCDM scenario when
subjected to the constraint derived from CF2 data, emerging in an environment
akin to the observed one. Three levels of criteria are used to define the
simulated LGs. At the base level, pairs of halos must obey specific isolation,
mass and separation criteria. At the second level the orbital angular momentum
and energy are constrained and on the third one the phase of the orbit is
constrained. Out of the 300 constrained simulations 146 LGs obey the first set
of criteria, 51 the second and 6 the third. The robustness of our LG factory
enables the construction of a large ensemble of simulated LGs. Suitable
candidates for high resolution hydrodynamical simulations of the LG can be
drawn from this ensemble, which can be used to perform comprehensive studies of
the formation of the LGComment: 13 pages, accepted for publication in MNRA
Scalars from Top-condensation Models at Hadron Colliders
We study the production and decay of neutral scalars and pseudo-scalars at
hadron colliders, in theories where the top-quark mass is the result of a
condensate. We show that the dominant decay channel for masses below
the threshold is the flavor changing mode . This is a consequence
of the non-universal nature of the underlying interactions in all
top-condensation models and provides a model-independent signature of these
scenarios. We show that an upgraded Tevatron is sensitive to a sizeable region
of the interesting parameter space and that the LHC will highly constrain these
models through this flavor violating channel.Comment: 4 pages, 4 figures. Minor changes in figures for readibility. final
version to appear in PR
Straining Flow Spinning of Artificial Silk Fibers: A Review
This work summarizes the main principles and some of the most significant results
of straining flow spinning (SFS), a technology developed originally by the authors of this work.
The principles on which the technology is based, inspired by the natural spinning system of silkworms
and spiders, are presented, as well as some of the main achievements of the technique. Among these
achievements, spinning under environmentally friendly conditions, obtaining high-performance
fibers, and imparting the fibers with emerging properties such as supercontraction are discussed.
Consequently, SFS appears as an efficient process that may represent one of the first realizations of a
biomimetic technology with a significant impact at the production level.Ministerio de EconomÃa y Competitividad MAT2016-75544-C2-1-RMinisterio de EconomÃa y Competitividad MAT2016-79832-RMinisterio de EconomÃa y Competitividad CPI2016-78887-C3-1-RComunidad de Madrid NEUROCENTRO-B2017Comunidad de Madrid BMD-376
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