191 research outputs found
Synthesis and structure characterization of [Co(H2O)2(DMSO)2(4-nba)]4-nba (DMSO = dimethylsulfoxide; 4-nba = 4-nitrobenzoate)
51-56Dissolution of a fine powder obtained by mechanochemical grinding of cobaltous carbonate with 4-nitrobenzoic acid (4-nbaH) in hot dimethylsulfoxide (DMSO) followed by slow evaporation of the solvent resulted in the formation of cis-diaquabis(dimethylsul-foxide)4-nitrobenzoatocobalt(II) 4-nitrobenzoate 1 in good yield. The title compound [Co(H2O)2(DMSO)2(4-nba)]4-nba 1 crystallizes in the centrosymmetric monoclinic P21/c space group. The structure of 1 consists of two crystallographically independent Co(II) ions. Each unique cobalt exhibits octahedral geometry and is bonded to a pair of terminal aqua ligands situated cis to each other and a bidentate 4-nba ligand which form the square base of the octahedron. A pair of DMSO ligands disposed trans to each other complete the hexa coordination around the central metal. The [Co(H2O)2(DMSO)2 (4-nba)]+ cations and the 4-nba anions are interlinked with the aid of several weak H-bonding interactions. A comparative study of several 4-nitrobenzoate compounds of cobalt is described
SeeBridge information delivery manual (IDM) for next generation bridge inspection
Innovative solutions for rapid and intelligent survey and assessment methods are required in maintenance, repair, retrofit and rebuild of enormous numbers of bridges in service throughout the world. Motivated by this need, a next-generation integrated bridge inspection system named SeeBridge is proposed. To frame the system, an Information Delivery Manual (IDM) was compiled to specify the technical components, activities and information exchanges in the SeeBridge process. The IDM supports development of the system by rigorously defining the information and data repositories that structure bridge engineers' knowledge. The SeeBridge process is mapped, parts of the data repositories are presented and the future use of the IDM is discussed
Crystal structure of potassium hydrogen phthalate revisited
1785-1792The present study provides new insight into the structure of potassium hydrogen phthalate 1. The single crystal X-ray structure of 1 consists of a crystallographically independent potassium cation and a unique hydrogen phthalate anion. The µ4-heptadentate binding mode of the unique hydrogen phthalate ligand organizes the K+ ions into a layer resulting in a two-dimensional (2D) coordination polymer. As a result parallel chains of face-sharing {KO7} polyhedra extending along c are formed. The parallel chains are flanked on either side by hydrogen phthalate wings and are interlinked by vertex sharing of three polyhedra to extend the connectivity along a axis. The structure of 1 is stabilised by π∙∙∙π stacking interactions. A comparative study of the structures of alkali metal hydrogen phthalates is described
SeeBridge Next Generation Bridge Inspection: Overview, Information Delivery Manual and Model View Definition
Innovative solutions for rapid and intelligent survey and assessment methods are required in maintenance, repair, retrofit and rebuild of enormous numbers of bridges in service throughout the world. Motivated by this need, a next-generation integrated bridge inspection system, called SeeBridge, has been proposed. An Information Delivery Manual (IDM) was compiled to specify the technical components, activities and information exchanges in the SeeBridge process, and a Model View Definition (MVD) was prepared to specify the data exchange schema to serve the IDM. The MVD was bound to the IFC4 Add2 data schema standard. The IDM and MVD support research and development of the system by rigorously defining the information and data that structure bridge engineers' knowledge. The SeeBridge process is mapped, parts of the data repositories are presented, and the future use of the IDM is discussed. The development underlines the real potential for automated inspection of infrastructure at large, because it demonstrates that the hurdles in the way of automated acquisition of detailed and semantically rich models of existing infrastructure are computational in nature, not instrumental, and are surmountable with existing technologies
Edge state transmission, duality relation and its implication to measurements
The duality in the Chalker-Coddington network model is examined. We are able
to write down a duality relation for the edge state transmission coefficient,
but only for a specific symmetric Hall geometry. Looking for broader
implication of the duality, we calculate the transmission coefficient in
terms of the conductivity and in the diffusive
limit. The edge state scattering problem is reduced to solving the diffusion
equation with two boundary conditions
and
.
We find that the resistances in the geometry considered are not necessarily
measures of the resistivity and () holds only
when is quantized. We conclude that duality alone is not sufficient
to explain the experimental findings of Shahar et al and that Landauer-Buttiker
argument does not render the additional condition, contrary to previous
expectation.Comment: 16 pages, 3 figures, to appear in Phys. Rev.
Optical clock intercomparison with precision in one hour
Improvements in atom-light coherence are foundational to progress in quantum
information science, quantum optics, and precision metrology. Optical atomic
clocks require local oscillators with exceptional optical coherence due to the
challenge of performing spectroscopy on their ultra-narrow linewidth clock
transitions. Advances in laser stabilization have thus enabled rapid progress
in clock precision. A new class of ultrastable lasers based on cryogenic
silicon reference cavities has recently demonstrated the longest optical
coherence times to date. In this work we utilize such a local oscillator, along
with a state-of-the-art frequency comb for coherence transfer, with two Sr
optical lattice clocks to achieve an unprecedented level of clock stability.
Through an anti-synchronous comparison, the fractional instability of both
clocks is assessed to be for an averaging time
in seconds. Synchronous interrogation reveals a quantum projection noise
dominated instability of , resulting in a
precision of after a single hour of averaging. The
ability to measure sub- level frequency shifts in such short
timescales will impact a wide range of applications for clocks in quantum
sensing and fundamental physics. For example, this precision allows one to
resolve the gravitational red shift from a 1 cm elevation change in only 20
minutes
Substrate-transferred GaAs/AlGaAs crystalline coatings for gravitational-wave detectors: A review of the state of the art
In this Perspective we summarize the status of technological development for
large-area and low-noise substrate-transferred GaAs/AlGaAs (AlGaAs) crystalline
coatings for interferometric gravitational-wave (GW) detectors. These topics
were originally presented in a workshop{\dag} bringing together members of the
GW community from the laser interferometer gravitational-wave observatory
(LIGO), Virgo, and KAGRA collaborations, along with scientists from the
precision optical metrology community, and industry partners with extensive
expertise in the manufacturing of said coatings. AlGaAs-based crystalline
coatings present the possibility of GW observatories having significantly
greater range than current systems employing ion-beam sputtered mirrors. Given
the low thermal noise of AlGaAs at room temperature, GW detectors could realize
these significant sensitivity gains, while potentially avoiding cryogenic
operation. However, the development of large-area AlGaAs coatings presents
unique challenges. Herein, we describe recent research and development efforts
relevant to crystalline coatings, covering characterization efforts on novel
noise processes, as well as optical metrology on large-area (~10 cm diameter)
mirrors. We further explore options to expand the maximum coating diameter to
20 cm and beyond, forging a path to produce low-noise AlGaAs mirrors amenable
to future GW detector upgrades, while noting the unique requirements and
prospective experimental testbeds for these novel materials.Comment: 13pages, 3 figure
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SEIS: Insight's Seismic Experiment for Internal Structure of Mars.
By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars' surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking's Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars' surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of M w ∼ 3 at 40 ∘ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution.Electronic supplementary materialThe online version of this article (10.1007/s11214-018-0574-6) contains supplementary material, which is available to authorized users
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