1,721,176 research outputs found
Three-Dimensional Circulation Driving Chemical Disequilibrium in WASP-43b
Get PDFSpectral features in the observed spectra of exoplanets depend on the composition of their atmospheres. A good knowledge of the main atmospheric processes that drive the chemical distribution is therefore essential to interpret exoplanetary spectra. An atmosphere reaches chemical equilibrium if the rates of the forward and backward chemical reactions converge to the same value. However, there are atmospheric processes, such as atmospheric transport, that destabilize this equilibrium. In this work we study the changes in composition driven by a 3D wind field in WASP-43b using our Global Circulation Model, THOR. Our model uses validated temperature- and pressure-dependent chemical timescales that allow us to explore the disequilibrium chemistry of CO, CO2, H2O, and CH4. In WASP-43b the formation of the equatorial jet has an important impact on the chemical distribution of the different species across the atmosphere. At low latitudes the chemistry is longitudinally quenched, except for CO2 at solar abundances. The polar vortexes have a distinct chemical distribution since these are regions with lower temperature and atmospheric mixing. Vertical and latitudinal mixing have a secondary impact on the chemical transport. We determine graphically the effect of disequilibrium on the observed emission spectra. Our results do not show any significant differences in the emission spectra between the equilibrium and disequilibrium solutions for C/O = 0.5. However, if C/O is increased to 2.0, differences in the spectra due to the disequilibrium chemistry of CH4 become non-negligible. In some spectral ranges the emission spectra can have more than 15% departure from the equilibrium solution
THOR 2.0: Major Improvements to the Open-Source General Circulation Model
Get PDFTHOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or Solar System-centric tunings. It solves the general non-hydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building upon the work of Mendonça et al. (2016). First, while the Horizontally Explicit Vertically Implicit (HEVI) integration scheme is the same as that described in Mendonça et al. (2016), we provide a clearer description of the scheme and improved its implementation in the code. The differences in implementation between the hydrostatic shallow (HSS), quasi-hydrostatic deep (QHD) and non-hydrostatic deep (NHD) treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally-locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and non-hydrostatic simulations are negligible in the Earth case, but pronounced in the hot Jupiter case. Finally, the effects of the so-called "sponge layer", a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR
Gene-based Optimal Dynamic Algorithm for Traffic Signal Control
No full textTechnical Session, 14th World Congress on ITS, Beijing, China, Oct.10-14, 200
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Study on calcium-induced proteolytic cleavage of DNA topoisomerases
No full text時間與空間上的嚴格控制對鈣蛋白酶來調控它的蛋白質水解活性功能是很重要的。這裡，我們證實位於細胞質中的鈣蛋白酶2可以切割水解位於細胞核的人類拓樸異構酶1（hTOP1）及拓樸異構酶2 beta (hTOP2 beta)，而拓樸異構酶2 alpha (hTOP2 alpha)並不會被水解切割,此現象可能透過Ca2+所誘導的鈣蛋白酶2進入細胞核而發生。此由以下的證據支持：(一)細胞處理Ca2+或Ca2+離子載體(ionophores)會造成在細胞核內的hTOP1及hTOP2 beta蛋白質被快速切割水解。 （二）兩種Ca2+螯合物都能有效地阻止ionomycin (一種Ca2 +離子載體)所引起的hTOP1及hTOP2 beta的蛋白質切割；而且添加Ca2+可以直接活化細胞萃取物中蛋白酶切割hTOP1與hTOP2 beta的現象；都支持細胞內的鈣離子濃度[Ca2 +]i對於hTOP1與hTOP2 beta蛋白質的切割是必要的。（三）進一步，我們利用重組蛋白質，實驗顯示鈣蛋白酶2 比鈣蛋白酶 1具有更高的效率去切割hTOP1蛋白質。(四)與以上概念一致，我們推論鈣蛋白酶2可能是主要Ca2 +活化切割hTOP1的蛋白酶之一，因為在降低鈣蛋白酶2表現(si-Capn2)的細胞中hTOP1對於ionomycin 誘導的蛋白質切割有高的抗性。(五)另外，我們的實驗也發現hTOP2 beta與hTOP1均是鈣蛋白酶2的新受質，且hTOP2 beta似乎較hTOP1更容易在相同濃度的ionomycin處理下被切割。(六)鈣蛋白酶2所切割hTOP1蛋白質的位置位於hTOP1的N端(N-terminus)第158及183個胺基酸賴胺酸(K158 and K183)上，而切割後的大片斷hTOP1(hTOP1tr)蛋白質則具有更強解螺旋 (relaxation)的能力。（七）此外，hTOP1tr蛋白質依然保有可以和DNA及喜樹鹼(camptothesin，CPT)形成可切割複合體（TOP1 cleavable complex，TOP1cc），並具有與核仁蛋白質nucleolin的蛋白交互作用能力。（八）細胞處理ionomycin後，鈣蛋白酶 2的活化似乎可以保護細胞免於CPT所引起的細胞毒殺害作用。總結,我們的結果為細胞質中的鈣蛋白酶2如何切割細胞核內蛋白質提供了良好的說明與實驗證據支持：在被Ca2+活化後的鈣蛋白酶2會藉由細胞質-核穿梭運輸，讓鈣蛋白酶 2 從細胞質到細胞核從而接觸到並切割其核內受質。Crucial to calpain function is the tight regulation of its proteolytic activity, which is temporally and spatially controlled. Here, we demonstrated that the cytoplasm-located calpain 2 cleaves human nuclear topoisomerases I (hTOP1) and II beta (hTOP2 beta) but not II alpha (hTOP2 alpha) possibly through the Ca2+-induced nuclear translocation of active proteases. This is supported by the followings: (I) Treatments of cells with Ca2+ or Ca2+ ionophores caused a rapid proteolytic cleavage of hTOP1 and 2 beta in the nucleus. (II) Elevated intracelluar [Ca2+] is responsible for this hTOP1 and 2 beta proteolysis event as suggested by the observations that two Ca2+ chelators could both effectively block the ionomycin-induced cleavage of hTOP1 and 2 beta and addition of Ca2+ in the in vitro protease activation assay caused hTOP1 and 2 beta proteolysis. (III) Using recombinant proteins, our in vitro experiments showed that calpain 2 cleaved hTOP1 more efficient than calpain 1 did.(IV) Consistent with above notion that calpain 2 as a main protease responsible for Ca2+-activated proteolysis of hTOP1, hTOP1 proteins in calpain 2-knockdown (si-Capn2) cells were resistant to the ionomycin-induced proteolysis. (V) Similar to hTOP1, hTOP2 beta has also been identified as a novel substrate for calpain 2. In addition, Ca2+-activated calpain 2 appeared to cleave hTOP2 beta more completed than hTOP1 in the same dose of ionomycin treatment. (VI) The calpain 2 cleavage sites of hTOP1 were mapped at its N’-terminus K158 and K183 and the resulting hTOP1tr exhibited an enhanced relaxation activity. (VII) In addition, the hTOP1tr proteins remained the abilities to form the hTOP1-DNA-camptothecin (CPT) cleavable complex (hTOP1cc) and to interact with nucleolin proteins. (VIII) Ionomycin treatment caused a calpain 2-dependent protection of cells from cytotoxic killing by CPT. In sum, our results provided a good support for the regulation of calpain in the proteolytic cleavage of nuclear proteins via a cytoplasmic-to-nuclear trafficking of calpain 2
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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