20,181 research outputs found
(1S)-1-phenylethanaminium 4-{[(1S,2S)-1-hydroxy-2,3-dihydro-1H,1'H-[2,2'-biinden]-2-yl]methyl}benzoate
Copyright 2012 © International Union of Crystallography.The title molecular salt, C8H12N+·C26H21O3-, contains a dimeric indane pharmacophore that demonstrates potent anti-inflammatory activity. The indane group of the anion exhibits some disorder about the [alpha]-C atom, which appears common to many structures containing this group. A model to account for the slight disorder was attempted, but this was deemed unsuccessful because applying bond-length constraints to all the bonds about the [alpha]-C atom led to instability in the refinement. The absolute configuration was determined crystallographically as S,S,S by anomalous dispersion methods with reference to both the Flack parameter and Bayesian statistics on Bijvoet differences. The configuration was also determined by an a priori knowledge of the absolute configuration of the (1S)-1-phenylethanaminium counter-ion. The molecules pack in the crystal structure to form an infinite two-dimensional hydrogen-bond network in the (100) plane of the unit cell
A FEM Seepage Analysis for Upstream Cofferdam of Xiluodu Hydraulic Power Station
The upstream cofferdam of Xiluodu hydraulic power station project, with height of 72 meters, is designed as the main body of the project. It is characterized by its high retaining water head, short construction period and complex geological conditions. Presented in this paper is a three-dimensional FEM analysis used to investigate the seepage behavior of the upstream cofferdam for two different design schemes. In the analysis, the cracks in cut-off wall which may be caused in construction are also properly considered. Based on 3D seepage model of saturated-unsaturated flow for non-uniform soils, a fixed-mesh FEM is used in the seepage analysis of the upstream cofferdam. As the results of the analysis, the distribution of water head and discharge of seepage are obtained and compared. The seepage stability of the cofferdam is analyzed to be safe enough based on the new concept called critical gradient zone
Simplified Evaluation for Dynamic Layered Soils-Structure Interaction
An analytical method is presented or the evaluation of dynamic soil-structure response under a simpler condition where a structure is semi-buried in level ground of layered soils. Formulas are proposed to determine the lateral soil-wall displacement and corresponding earth pressures against the sidewalls of the structure during an earthquake. The key factors affecting the dynamic response of the soil-structure system are also discusse
Behavior of pile group foundation for offshore wind generator
As one of the most promising clean energy, offshore wind power attracted increasing attention recently. A lot of large-scale offshore wind generators were constructed in many countries. Large-diameter single pile was commonly used as the foundation for the wind generator. Its deformation and bearing capacity were investigated using different approaches. Field tests were conducted to observ
Early diagenetic mobilization of rare earth elements and implications for the Ce anomaly as a redox proxy
The Rare Earth Elements (REE) archived in carbonate rocks retain a wealth of information on paleo-seawater chemistry and local-regional redox conditions. However, interpretations are often ambiguous due to the potential for REE remobilization in marine environments. In this regard, many carbonate rocks that retain primary seawater isotopic signatures exhibit non-seawater-like REE patterns, implying either unusual REE behaviour in seawater or diagenetic overprinting of otherwise well-preserved rock samples. Here, we apply sequential leaching to constrain the possible effects of different REE-bearing phases on measured carbonate REE patterns in order to address this quandary. Our results show that the exchangeable phase contains negligible REE, but could be an important host phase for other elements such as Sr, Ba and K. The acidified hydroxylamine hydrochloride leach is shown here not only to dissolve Fe–Mn oxides but also phosphate minerals, which induces middle REE enrichment in corresponding leachates of dolostone samples in our study. The demonstrable Fe–Mn oxide phase in limestone samples is characterized by middle and/or light REE enrichment and positive Eu anomalies, which are attributed to hydrothermal processes and continuing exchange with marine fluids after initial precipitation. The non-seawater-like REE patterns observed in the carbonate phase of otherwise well-preserved limestones resemble those of the co-existing Fe–Mn oxide fraction, and are interpreted to reflect the dissolution of REE carrier phases during early diagenesis. This view is supported by fluid-rock interaction modelling, which shows how REE can be mobilized at relatively low fluid/rock ratios in shallow porewaters. Non-seawater-like REE patterns may therefore be caused by the incorporation of REE from shallow porewaters before final lithification due to an elevated flux of particulate REE carrier phases, e.g. Fe–Mn oxides and organic matter, to the seafloor. In spite of the sensitivity of carbonate REE patterns to early diagenetic exchange, the co-occurrence of non-seawater-like patterns with primary strontium and carbon isotope values suggests that REE should not be viewed as a general indicator for the preservation of other geochemical proxies. Importantly, Ce anomalies of the carbonate phase will also be affected by porewaters, masking primary seawater values. Our results favour a reevaluation of redox interpretations by taking into account REE patterns as a whole
In-Home Daily-Life Captioning Using Radio Signals
This paper aims to caption daily life --i.e., to create a textual description
of people's activities and interactions with objects in their homes. Addressing
this problem requires novel methods beyond traditional video captioning, as
most people would have privacy concerns about deploying cameras throughout
their homes. We introduce RF-Diary, a new model for captioning daily life by
analyzing the privacy-preserving radio signal in the home with the home's
floormap. RF-Diary can further observe and caption people's life through walls
and occlusions and in dark settings. In designing RF-Diary, we exploit the
ability of radio signals to capture people's 3D dynamics, and use the floormap
to help the model learn people's interactions with objects. We also use a
multi-modal feature alignment training scheme that leverages existing
video-based captioning datasets to improve the performance of our radio-based
captioning model. Extensive experimental results demonstrate that RF-Diary
generates accurate captions under visible conditions. It also sustains its good
performance in dark or occluded settings, where video-based captioning
approaches fail to generate meaningful captions. For more information, please
visit our project webpage: http://rf-diary.csail.mit.eduComment: ECCV 2020. The first two authors contributed equally to this pape
Drawing Planar Graphs with Few Geometric Primitives
We define the \emph{visual complexity} of a plane graph drawing to be the
number of basic geometric objects needed to represent all its edges. In
particular, one object may represent multiple edges (e.g., one needs only one
line segment to draw a path with an arbitrary number of edges). Let denote
the number of vertices of a graph. We show that trees can be drawn with
straight-line segments on a polynomial grid, and with straight-line
segments on a quasi-polynomial grid. Further, we present an algorithm for
drawing planar 3-trees with segments on an
grid. This algorithm can also be used with a small modification to draw maximal
outerplanar graphs with edges on an grid. We also
study the problem of drawing maximal planar graphs with circular arcs and
provide an algorithm to draw such graphs using only arcs. This is
significantly smaller than the lower bound of for line segments for a
nontrivial graph class.Comment: Appeared at Proc. 43rd International Workshop on Graph-Theoretic
Concepts in Computer Science (WG 2017
Tailoring ferromagnetic chalcopyrites
If magnetic semiconductors are ever to find wide application in real
spintronic devices, their magnetic and electronic properties will require
tailoring in much the same way that band gaps are engineered in conventional
semiconductors. Unfortunately, no systematic understanding yet exists of how,
or even whether, properties such as Curie temperatures and band gaps are
related in magnetic semiconductors. Here we explore theoretically these and
other relationships within 64 members of a single materials class, the Mn-doped
II-IV-V2 chalcopyrites, three of which are already known experimentally to be
ferromagnetic semiconductors. Our first-principles results reveal a variation
of magnetic properties across different materials that cannot be explained by
either of the two dominant models of ferromagnetism in semiconductors. Based on
our results for structural, electronic, and magnetic properties, we identify a
small number of new stable chalcopyrites with excellent prospects for
ferromagnetism.Comment: 6 pages with 4 figures, plus 3 supplementary figures; to appear in
Nature Material
The Ediacaran ‘Miaohe Member’ of South China: new insights from palaeoredox proxies and stable isotope data
Throughout the Ediacaran Period, variable water-column redox conditions persisted along productive ocean margins due to a complex interplay between nutrient supply and oceanographic restriction. These changing conditions are considered to have influenced early faunal evolution, with marine anoxia potentially inhibiting the development of the ecological niches necessary for aerobic life forms. To understand this link between oxygenation and evolution, the combined geochemical and palaeontological study of marine sediments is preferable. Located in the Yangtze Gorges region of southern China, lagoonal black shales at Miaohe preserve alga and putative metazoans, including Eoandromeda, a candidate total-group ctenophore, thereby providing one example of where integrated study is possible. We present a multi-proxy investigation into water-column redox variability during deposition of these shales (c. 560–551 Ma). For this interval, reactive iron partitioning indicates persistent water-column anoxia, while trace metal enrichments and other geochemical data suggest temporal fluctuations between ferruginous, euxinic and rare suboxic conditions. Although trace metal and total organic carbon values imply extensive basin restriction, sustained trace metal enrichment and δ15Nsed data indicate periodic access to open-ocean inventories across a shallow-marine sill. Lastly, δ13Corg values of between −35‰ and −40‰ allow at least partial correlation of the shales at Miaohe with Member IV of the Doushantuo Formation. This study provides evidence for fluctuating redox conditions in the lagoonal area of the Yangtze platform during late Ediacaran time. If these low-oxygen environments were regionally characteristic, then the restriction of aerobic fauna to isolated environments can be inferred
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