616 research outputs found
Large negative thermal expansion in GdFe(CN)6 driven by unusual low-frequency modes
No full textUnderstanding the negative thermal expansion (NTE) mechanism is of great importance. In this work, we consider the new NTE compound GdFe(CN)6 (alpha v = -34.2 x10-6 K-1) as a case study to investigate the NTE mechanism from the perspective of the lattice vibrational dynamics. The atomic mean-square displace-ments suggest that the NTE of GdFe(CN)6 comes from the strong tension effect induced by the transverse vibrations of the atomic -Fe-C equivalent to N-Gd- linkages, with the largest contribution given by N atoms. Lattice dynamics calculations show that three low-frequency optical modes at about 50 cm-1 show the largest negative Gruneisen parameters thus providing the largest contribution to the NTE. The existence of these unusual low-frequency vibrational modes can be ascribed to the presence of GdN6 trigonal prisms in the framework structure of GdFe(CN)6.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences
PiCO QL: A software library for runtime interactive queries on program data
No full textAbstractPico ql is an open source c/c++ software whose scientific scope is real-time interactive analysis of in-memory data through sql queries. It exposes a relational view of a system’s or application’s data structures, which is queryable through sql. While the application or system is executing, users can input queries through a web-based interface or issue web service requests. Queries execute on the live data structures through the respective relational views. pico ql makes a good candidate for ad-hoc data analysis in applications and for diagnostics in systems settings. Applications of pico ql include the Linux kernel, the Valgrind instrumentation framework, a gis application, a virtual real-time observatory of stellar objects, and a source code analyser
The “Global Ximage” QL pipeline of AGILE-GRID
No full textA new Quick Look (QL) pipeline optimised for the AGILE spinning observing mode has been developed. It runs over the Level 2 AGILE-GRID data (photon lists EVT and LOG files) produced by the QLSTD pipeline. The pipeline runs the detect task of the HEASOFT XIMAGE package for source detection over a RA-DEC sky map created by merging 48 hours of GRID data. The spots with excess events found by XIMAGE are then considered as centres for the COUNTS, EXP and GAS maps produced using the tasks of the AGILE SW. This procedure allows to identify the interesting sky positions in the considered time period getting full sky coverage without selecting “a priori” centres for the COUNTS and EXP maps, and following automatically the drifting of the Sun/Anti-Sun exclusion regions
On (in)tractability of OBDA with OWL 2 QL
No full textWe show that, although conjunctive queries over OWL 2 QL ontologies are reducible to database queries, no algorithm can construct such a reduction in polynomial time without changing the data. On the other hand, we give a polynomial reduction for OWL2QL ontologies without role inclusions
Data From: Unpacking the drivers of diurnal dynamics of sun-induced chlorophyll fluorescence (SIF): Canopy structure, plant physiology, instrument configuration and retrieval methods
No full textPlease cite as: Chang et al. (2022). Data from: Unpacking the drivers of diurnal dynamics of sun-induced chlorophyll fluorescence (SIF): Canopy structure, plant physiology, instrument configuration and retrieval methods [Dataset]. Cornell University Library eCommons Repository. https://doi.org/10.7298/mqfk-hs97Data in support of research:
Sun-induced chlorophyll fluorescence (SIF) from spaceborne sensors is a promising tool for global carbon cycle monitoring, but its application is constrained by insufficient understanding of the drivers underlying diurnal SIF dynamics. SIF measurements from ground-based towers can reveal diurnal SIF dynamics across biomes and environmental conditions; however, meaningful interpretation of diurnal variations requires disentangling impacts from canopy structure, plant physiology, instrument configuration and retrieval methods, which often interact with and confound each other. This study aims to unpack these drivers using 1) concurrent ground and airborne canopy-scale and leaf-scale measurements at a corn field, 2) a mechanistic SIF model that explicitly considers the dynamics of photochemistry (via the fraction of open photosystem II reaction centers, qL) and photoprotection (via nonphotochemical quenching, NPQ) as well as their interactive dependence on the sub-canopy light environment, and 3) cross-comparison of SIF instrument configurations and retrieval methods. We found that crop row orientations and sun angles can introduce a distinctive midday dip in SIF in absence of stress, due to a midday drop of absorbed photosynthetically active radiation (APAR) when crop rows are north-south oriented. Canopy structure caused distinctive responses in both qL and NPQ at different positions within the vertical canopy that collectively influenced fluorescence quantum yield (ΦF) at the leaf scale. Once integrated at the canopy scale, diurnal dynamics of both APAR and canopy escape probability (ε) are critical for accurately shaping diurnal SIF variations. While leaf-level qL and NPQ exhibited strong diurnal dynamics, their influence was attenuated at the canopy scale due to opposing effects on SIF at different canopy layers. Furthermore, different system configurations (i.e., bi-hemispherical vs. hemispherical-conical) and retrieval methods can bias the SIF magnitude and distort its diurnal shapes, therefore confounding the interpretation of inherent strength and dynamics of SIF emission. Our findings demonstrate the importance of crop row structures, interactive variations in canopy structure and plant physiology, instrument configuration, and retrieval method in shaping the measured dynamics of diurnal SIF. This study highlights the necessity to account for these factors to accurately interpret satellite SIF, and informs future synthesis work with different SIF instrumentation and retrieval methods across sites.USDA-NIFA Postdoctoral Fellowship to CYC, Grant #: 2018-67012-27985
USDA-NIFA Hatch Award to YS, Grant #: 1014740
This research is also supported by the US Department of Energy (DOE), Office of Science, Biological and Environmental Research Program. ORNL is managed by UT-Battelle, LLC, for DOE under contract DE-AC05-00OR22725
Conjunctive query inseparability of OWL 2 QL TBoxes
No full textThe OWL2 profile OWL 2 QL, based on the DL-Lite family of description logics, is emerging as a major language for developing new ontologies and approximating the existing ones. Its main application is ontology based data access, where ontologies are used to provide background knowledge for answering queries over data. We investigate the corresponding notion of query inseparability (or equivalence) for OWL 2 QL ontologies and show that deciding query inseparability is PSpace-hard and in ExpTime. We give polynomial-time (incomplete) algorithms and demonstrate by experiments that they can be used for practical module extraction
Niche-independent symmetrical self-renewal of a mammalian tissue stem cell.
Get PDFPluripotent mouse embryonic stem (ES) cells multiply in simple monoculture by symmetrical divisions. In vivo, however, stem cells are generally thought to depend on specialised cellular microenvironments and to undergo predominantly asymmetric divisions. Ex vivo expansion of pure populations of tissue stem cells has proven elusive. Neural progenitor cells are propagated in combination with differentiating progeny in floating clusters called neurospheres. The proportion of stem cells in neurospheres is low, however, and they cannot be directly observed or interrogated. Here we demonstrate that the complex neurosphere environment is dispensable for stem cell maintenance, and that the combination of fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF) is sufficient for derivation and continuous expansion by symmetrical division of pure cultures of neural stem (NS) cells. NS cells were derived first from mouse ES cells. Neural lineage induction was followed by growth factor addition in basal culture media. In the presence of only EGF and FGF-2, resulting NS cells proliferate continuously, are diploid, and clonogenic. After prolonged expansion, they remain able to differentiate efficiently into neurons and astrocytes in vitro and upon transplantation into the adult brain. Colonies generated from single NS cells all produce neurons upon growth factor withdrawal. NS cells uniformly express morphological, cell biological, and molecular features of radial glia, developmental precursors of neurons and glia. Consistent with this profile, adherent NS cell lines can readily be established from foetal mouse brain. Similar NS cells can be generated from human ES cells and human foetal brain. The extrinsic factors EGF plus FGF-2 are sufficient to sustain pure symmetrical self-renewing divisions of NS cells. The resultant cultures constitute the first known example of tissue-specific stem cells that can be propagated without accompanying differentiation. These homogenous cultures will enable delineation of molecular mechanisms that define a tissue-specific stem cell and allow direct comparison with pluripotent ES cells
Experimental study of the effects of thermochemical sulfate reduction on low molecular weight hydrocarbons in confined systems and its geochemical implications
No full textAdherent neural stem (NS) cells from fetal and adult forebrain
No full textStable in vitro propagation of central nervous system (CNS) stem cells would offer expanded opportunities to dissect basic molecular, cellular, and developmental processes and to model neurodegenerative disease. CNS stem cells could also provide a source of material for drug discovery assays and cell replacement therapies. We have recently reported the generation of adherent, symmetrically expandable, neural stem (NS) cell lines derived both from mouse and human embryonic stem cells and from fetal forebrain (Conti L, Pollard SM, Gorba T, Reitano E, Toselli M, Biella G, Sun Y, Sanzone S, Ying QL, Cattaneo E, Smith A. 2005. Niche-independent symmetrical self-renewal of a mammalian tissue stem cell. PLoS Biol 3(9):e283). These NS cells retain neuronal and glial differentiation potential after prolonged passaging and are transplantable. NS cells are likely to comprise the resident stem cell population within heterogeneous neurosphere cultures. Here we demonstrate that similar NS cell cultures can be established from the adult mouse brain. We also characterize the growth factor requirements for NS cell derivation and self-renewal. We discuss our current understanding of the relationship of NS cell lines to physiological progenitor cells of fetal and adult CN
Extracting typed values from XML data
No full textValues of existing typed programming languages are increas- ingly generated and manipulated outside the language juris- diction. Instead, they often occur as fragments of XML docu- ments, where they are uniformly interpreted as labelled trees in spite of their domain-specific semantics. In particular, the values are divorced from the high-level type with which they are conveniently, safely, and efficiently manipulated within the language. We propose language-specific mechanisms which extract language values from arbitrary XML documents and inject them in the language. In particular, we provide a general framework for the formal interpretation of extraction mecha- nisms and then instantiate it to the definition of a mechanism for a sample language core L. We prove that such mechanism can be built by giving a sound and complete algorithm that implements it. The values, types, and type semantics of L are sufficiently general to show that extraction mechanisms can be defined for many existing typed languages, including object-oriented languages. In fact, extraction mechanisms for a large class of existing languages can be directly derived from L's. As a proof of this, we introduce the SNAQue prototype system, which transforms XML fragments into CORBA objects and exposes them across the ORB framework to any CORBA-compliant language
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