1,986 research outputs found
Kraichnan-Leith-Batchelor similarity theory and two-dimensional inverse cascades
No full textWe study the scaling properties and Kraichnan-Leith-Batchelor (KLB) theory of forced inverse cascades in generalized two-dimensional (2D) fluids (-turbulence models) simulated at resolution . We consider (surface quasigeostrophic flow), (2D vorticity dynamics) and . The forcing scale is well-resolved, a direct cascade is present and there is no large-scale dissipation. Coherent vortices spanning a range of sizes, most larger than the forcing scale, are present for both and . The active scalar field for contains comparatively few and small vortices. The energy spectral slopes in the inverse cascade are steeper than the KLB prediction in all three systems. Since we stop the simulations well before the cascades have reached the domain scale, vortex formation and spectral steepening are not due to condensation effects; nor are they caused by large-scale dissipation, which is absent. One- and two-point pdfs, hyperflatness factors and structure functions indicate that the inverse cascades are intermittent and non-Gaussian over much of the inertial range for and , while the inverse cascade is much closer to Gaussian and non-intermittent. For the steep spectrum is close to that associated with enstrophy equipartition. Continuous wavelet analysis shows approximate KLB scaling () and () in the interstitial regions between the coherent vortices. Our results demonstrate that coherent vortex formation ( and ) and non-realizability () cause 2D inverse cascades to deviate from the KLB predictions, but that the flow between the vortices exhibits KLB scaling and non-intermittent statistics for and . The results will appear in \cite{BurgessEA2015}, which has been accepted to the \emph{Journal of Fluid Mechanics}
Bombus (Pyrobombus) taiwanensis Williams, Sung, Lin & Lu 2022
No full textBombus (Pyrobombus) taiwanensis Williams, Sung, Lin & Lu, 2022 Figs 1‒4 [Bombus sp. non descripta Chiu 1948: 71.] [Bombus (Pyrobombus) nr. hypnorum Starr, 1992: 149.] Bombus (Pyrobombus) taiwanensis Williams et al., 2022: 438. Holotype by original designation: ♀, Mt Hehuan, Taiwan (TFRI). Examined. Diagnosis Female Distinguished by: clypeus in the central area smooth and shining with only a few large punctures, mostly spaced by much more than their own widths; ocello-ocular area with the inner eye margin mostly shining with few small punctures and the few larger, medium punctures forming a single row parallel to the eye margin; front, middle and hind leg basitarsi all with the exoskeleton lighter brown than for the tibiae; hair predominantly black but with metasomal T4‒6 a dull sandy-brown or pale orange. Male Distinguished by: front, middle and hind leg basitarsi all with the integument lighter brown than the tibiae; genitalia with the gonostylus inner anterior (basal) projection separated from the gonocoxa by less than the breadth of the recurved hook of the penis-valve head. Material examined Material sequenced or examined CHINA – Taiwan • 1 ♀ (worker); Nantou Hsien, Tsuifeng [Cuifeng]; 24.1060° N, 121.1988° E; alt. 2300 m; 23‒25 Jun. 1983; K.S. Lin and C. Lin leg.; BOLD-1550A06-TWN; PW • 1 ♂; Hualien Hsien, Tayuling; 23.9767° N, 121.5206° E; alt. 2560 m; 9‒16 Jun. 1980; K.S. Lin and B.H. Chen leg.; BOLD- 1550A07-TWN; PW. Other material sequenced GenBank: MZ831884, MZ831885, MZ831886, MZ831887, MZ831891, MZ831892. Distribution Endemic to the mountains of Taiwan, where it is extremely rare, at elevations of 2300‒3100 m (Williams et al. 2022).Published as part of Williams, Paul H., Dorji, Phurpa, Ren, Zongxin, Xie, Zhenghua & Orr, Michael, 2022, Bumblebees of the hypnorum-complex world-wide including two new near-cryptic species (Hymenoptera: Apidae), pp. 46-72 in European Journal of Taxonomy 847 on page 56, DOI: 10.5852/ejt.2022.847.1981, http://zenodo.org/record/735916
Soluble and multivalent Jag1 DNA origami nanopatterns activate Notch without pulling force
No full textFunding Information: The authors would like to acknowledge support from the NIH grant number R35GM133482 for V.C.L., the Knut and Alice Wallenberg Foundation (Grants KAW 2017.0114 for B.H. and A.I.T. and KAW 2017.0276 for B.H.), from the European Research Council ERC for B.H. (Acronym: Cell Track GA No. 724872) and A.I.T (Acronym: MechComm GA No. 617711), and from the Swedish Research Council for B.H. (grant no. 2019-01474) and from the Göran Gustafsson Foundation for B.H. And from the Academy of Finland for B.S. (grant no. 341908). lt-NES samples were obtained from, and initial culture protocols was made possible with the help of Anna Falk’s team and the iPS Core facility at Karolinska Institutet. Part of this work was performed at the Karolinska Institutet/SciLifeLab Protein Science Core Facility (PSF). Part of this work was performed at the Karolinska Institutet Biomedicum Imaging Core (BIC). EM data was collected at the Karolinska Institutet 3D-EM facility. Publisher Copyright: © 2024, The Author(s).The Notch signaling pathway has fundamental roles in embryonic development and in the nervous system. The current model of receptor activation involves initiation via a force-induced conformational change. Here, we define conditions that reveal pulling force-independent Notch activation using soluble multivalent constructs. We treat neuroepithelial stem-like cells with molecularly precise ligand nanopatterns displayed from solution using DNA origami. Notch signaling follows with clusters of Jag1, and with chimeric structures where most Jag1 proteins are replaced by other binders not targeting Notch. Our data rule out several confounding factors and suggest a model where Jag1 activates Notch upon prolonged binding without appearing to need a pulling force. These findings reveal a distinct mode of activation of Notch and lay the foundation for the development of soluble agonists.Peer reviewe
Multimode interference couplers: Design and applications
No full textElectrical Engineering, Mathematics and Computer Scienc
High Capacity Integrated Optical Receivers
No full textElectrical Engineering, Mathematics and Computer Scienc
InP-based Photonic Integrated Circuits for Wavelength Routing and Switching
No full textElectrical Engineering, Mathematics and Computer Scienc
Phased-array wavelength demultiplexers and their integration with photodetectors
No full textElectrical Engineering, Mathematics and Computer Scienc
Compact integrated optical components for telecommunication networks
No full textElectrical Engineering, Mathematics and Computer Scienc
Transferência eletrônica em sistemas moleculares
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2012O presente trabalho apresenta uma análise teórica do fenômeno de transferência eletrônica (ET) para dois sistemas moleculares. Inicialmente é apresentada uma breve introdução sobre o processo de transferência eletrônica, seguida de uma descrição de seu papel em dispositivos fotovoltaicos orgânicos e poliméricos. Prossegue-se com uma descrição detalhada da teoria usada nesta dissertação e das diferentes técnicas computacionais utilizadas para realizar a propagação temporal de pacotes de onda eletrônicos em sistemas moleculares. Dois modelos físicos são investigados pelo formalismo. No primeiro caso apresenta-se uma análise do fenômeno de transferência eletrônica em um sistema doador-aceitador assistido por ponte: dois átomos de berílio atuam como o par doado-aceitador, para os quais a transferência é intermediada por uma estrutura molecular rígida (cadeia de polietileno) C17H36. Examinou-se as consequência para a transferência dos diferentes comprimentos de ligação que conectam doador e aceitador com a ponte, e a variação do número de unidades de etileno na ponte. Os cálculos demonstram a transição entre a transferência de carácter ôhmico e a super-trânsferência, em acordo com outros formalismos. O segundo modelo de estudo consiste de uma cadeia triatômica dinâmica idealizada para a investigação dos efeitos do movimento iônico sobre a dinâmica eletrônica. Fica evidenciado que em frequências nucleares baixas a dinâmica eletrônica é de carácter adiabático. Em contrapartida, frequências maiores conduzem à efeitos de carácter não adiabático.Abstract : This work presents a theoretical analysis of the electron transfer process for two types of molecular systems. It begins with a brief introduction about the electron transfer process, which is followed by a discussion about the relevance of the process to the operation of organic and polymeric photovoltaic devices. In the sequence, the relevant theory is explained in detail, particularly the computational methods that are used to time propagate electronic wavepackets in molecular structures. Two physical models are investigated with the formalism. In the first case, the analysis of the electron transfer mechanism is carried for a donor-acceptor system coupled by a bridge: two beryllium atoms act as the donor-acceptor pair, and the electronic transfer takes place through a rigid molecular structure (polyethylene chain) C17H36. The effects caused by changing bond lengths between donor/acceptor sites and the bridge as well as varying the number of ethylene units in the bridge were investigated. The calculations show a transition of the transfer behaviour from ohmic to super-exchange, in accordance with predictions made by different formalisms. The second model system consists of a tri-atomic dynamic chain, which is thought for studying the effects of the ionic motion on the electronic dynamics. The present study shows that the electronic dynamics is adiabatic at low nuclear frequencies whereas at high nuclear frequencies non-adiabatic effects arise
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