14,155 research outputs found
Síntese de 1,3-diinos via acoplamento de acetilenos terminais catalisada por CuI sob irradiação de micro-ondas
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2015.No presente trabalho, desenvolveu-se uma nova metodologia sintética eficiente, simples e ambientalmente adequada para a síntese de compostos 1,3-diinos simétricos e não-simétricos. O esqueleto 1,3-diino ocorre em diversos produtos naturais com potenciais atividades biológicas e/ou farmacológicas. Além disso, os diacetilenos conjugados são blocos construtores importantes numa série de reações orgânicas.A metodologia envolve homoacoplamento e acoplamento cruzado de alcinos terminais, na presença de 1,5 eq de TMEDA e CuI em quantidade catalítica. As reações foram conduzidas a 100 ºC sob irradiação de micro-ondas em tempos de 10 minutos na ausência de solvente. A estratégia sintética adotada permitiu a obtenção de diferentes compostos 1,3-diinos simétricos e não-simétricos em rendimentos variando de 21 a 98%.Como principais vantagens do método desenvolvido, podem-se citar a economia energética, uma vez que a irradiação de micro-ondas proporcionou a diminuição dos tempos reacionais, a não utilização de bases e/ou solventes, a simplicidade operacional e a minimização na geração de resíduos.Abstract : In the present work, we developed a simple, efficient and environmentally friendly synthetic methodology for the synthesis of symmetric and asymmetric 1,3-diynes compounds. The 1,3-diyne skeleton occurs in several natural products with potential biological and/or pharmacological activities. Besides, conjugated diynes are important building blocks in several organic reactions.The methodology involves homocoupling and cross-coupling of terminal alkynes in the presence of 1.5 eq. of TMEDA and catalytic amount of CuI. The reactions were carried out at 100 °C for 10 minutes under microwave irradiation in the absence of solvent. The synthetic strategy adopted afforded different compounds 1,3- diynes symmetrical and ansymmetrical in 21-98 % yield.The main advantage of the developed method, may be mentioned saving of energy, since microwave irradiation gave the decrease in reaction times, no use of bases and / or solvents, operational simplicity and minimizing the generation of waste
Native p-type transparent conductive CuI via intrinsic defects
No full textThe ability of CuI to be doped p-type via the introduction of native defects has been investigated using first-principles pseudopotential calculations based on density functional theory. The Cu vacancy has a lower formation energy than any of the other native defects, which include I vacancy (V(I)), Cu interstitial (Cu(i)), I interstitial (I(i)), Cu antisite (Cu(I)), and I antisite (I(Cu)). Combined with its shallow acceptor level, it offers sufficient hole concentrations in CuI. The natural band alignments as compared to zinc-blende ZnS, ZnSe, and ZnTe have also been calculated in order to further identify the p-type dopability of CuI. It is found that CuI has a relatively high valence band maximum and conduction band minimum, which also makes it easy to dope CuI p-type in terms of the doping limit rule. In addition, the small effective mass of the light hole-about 0.303m(0)-can provide high mobility and p-type conductivity in CuI. All of these results make CuI an ideal candidate for native p-type materials (C) 2011 American Institute of Physics. [doi:10.1063/1.3633220
Youthhood
No full textTESTING-GROUND issue 03, Youthhood, examines worlds through youthful eyes, makes evident young ambitions, and questions how we can better empower young people to design cities, landscapes, and a planet that works for them. The issue includes contributions from: Carmel Keren, Jude Daniel Smith, Claire Edwards, Kazeem Kuteyi, Emmanuel Adarkwah, Reza Nik, Dan Cui, Kristofer Cullum-Fernandez, Fida Sassi, Simeon Shtebunaev, Daze Aghaji, Averill Dimabuyu, Sarri Elfaitouri, Rebecca McDonald-Balfour, and Ed Wall.
Rebecca McDonald-Balfour (Author), Jude Daniel Smith (Author), Daze Aghaji (Author), Carmel Keran (Author), Alexis Liu (Author), Dan Cui (Author), Kristofer Cullum-Fernandez (Author), Fida Sassi (Author), Averill Dimabuyu (Author), Ed
Il Workaholism
No full textIl contributo si propone di approndire cause, conseguenze e modelli teorici del workaholism, ovvero quella particolare forma di dipendenza comportamentale in cui non è implicato l'intervento di alcuna sostanza chimica
Substantial Overestimation of Terrestrial Water Storage Loss in Headwater Basins on Earth's Third Pole
No full textAbstract The Tibetan Plateau (TP) is suffering from a substantial decline in terrestrial water storage (TWS) in exorheic basins, threatening water resources that are critical for ∼2 billion people downstream. TWS changes are commonly estimated using gravity satellites through observations of the total terrestrial mass storage (TMS) change, with an implicit assumption of a negligible contribution from sediment transport. Through long‐term (2002–2017) sediment flux observations in seven headwater basins on the TP, we reveal that the gravity satellite‐derived TMS has decreased at a rate of 3.85 ± 0.23 Gt yr−1 in the seven basins, of which 0.35 ± 0.04 Gt yr−1 is contributed by sediment transport. Neglecting this contribution leads to an overestimation of the TWS loss by 10.1 ± 1.3%, equivalent to the annual water demand of an additional 0.62 million people in the surrounding nations. Regionally, the overestimation is surprisingly high in the Indus River and Yarkant River basins, reaching up to 50.8%–77.6%
Impact damage of composite laminates with high-speed waterjet
No full textRain erosion may cause substantial damage to aircrafts during supersonic flight. Such event is investigated here via high-speed waterjet impact on composite laminates. An experimental setup is developed to produce waterjets with the speed up to 700m/s and a finite element model of the waterjet-composite impact event is established. The consistency of experiment and simulation results validates the adopted numerical methods. The distribution of the water-hammer pressure is non-uniform and the maximum pressure occurs near the contact periphery when the water is about to eject laterally. After a high-speed (300∼560m/s) waterjet impacts a composite laminate, the impacted surface depression is observed, and the typical surface damage presents a central region with no visible surface damage surrounded by a faded “failure ring” with resin removal, matrix cracking and minor fiber fracture. Delamination occurs at the interfaces of adjacent layers with unequal dimensions and longitudinal matrix cracking appears on the back surface. Both the velocity and the diameter of waterjets are crucial factors on CFRP damage extents. Water-hammer pressure, the stagnation pressure and propagation of stress waves are failure mechanisms for most matrix damage in CFRP impacted by waterjets.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Meta-Path-based Fake News Detection Leveraging Multi-level Social Context Information
No full textFake news, false or misleading information presented as news, has a significant impact on many aspects of society, such as in politics or healthcare domains. Due to the deceiving nature of fake news, applying Natural Language Processing (NLP) techniques to the news content alone is insufficient. Therefore, more information is required to improve fake news detection, such as the multi-level social context (news publishers and engaged users in social media) information and the temporal information of user engagement. The proper usage of this information, however, introduces three chronic difficulties: 1) multi-level social context information is hard to be used without information loss, 2) temporal information of user engagement is hard to be used along with multi-level social context information, and 3) news representation with multi-level social context and temporal information is hard to be learned in an end-to-end manner. To overcome all three difficulties, we propose a novel fake news detection framework, Hetero-SCAN. We use Meta-Path, a composite relation connecting two node types, to extract meaningful multi-level social context information without loss. We then propose Meta-Path instance encoding and aggregation methods to capture the temporal information of user engagement and learn news representation end-to-end. According to our experiment, Hetero-SCAN yields significant performance improvement over state-of-the-art fake news detection methods
Templated tetramerization of dicyanobenzenes to form mixed porphyrinato and phthalocyaninato rare earth (III) triple-decker complexes
No full textHeteroleptic porphyrinato/phthalocyaninato rare earth(III) triple-decker compounds M-2(Por)(2)(Pc') (1a-4a) and M-2(Por)(Pc')(2) (1c-4c) (M = Eu, Tb; Por = TDOPP, Pc' = OOPc or Por = TpClPP, Pc' = Pc where H-2(TDOPP) = 5,10,15,20-tetrakis(4-n-dodecyloxyphenyl)porphyrin, H-2[OOPc] = 2,3,9,10,16,17,23,24-octakis(n-octyloxy)phthalocyanine, H-2(TpClPP) = 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin, H-2(Pc') = general phthalocyanine, and H-2(PC) = unsubstituted phthalocyanine) were obtained by the cyclic tetramerization of the corresponding dicyanobenzenes 7 using monoporphyrinato rare earth(III) acetylacetonates M(Por)acac as templates with catalysis by the organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Double-decker complexes M(Por)(Pc') (M = Eu, Tb; Por = TDOPP, Pc' = OOPc or Por = TpClPP, Pc' = Pc) (1b-4b) were isolated as side products. For the purpose of comparative study, homo- and hetero-dinuclear rare earth triple-deckers with one porphyrinato and two phthalocyaninato ligands M-2(Por)(Pc')(2) (1c, 2c) (M = Eu, Tb; Por = TDOPP, Pc' = OOPc) and (Por)M(Pc')M'(Pc') (M not equal M' = Eu, Tb) (5c, 6c) were also prepared using the raise-by-one-story method. The complexes were characterized by UV-vis, near-IR, IR and mass spectra. The comparison between H-1 NMR spectra of the two series of triple-decker compounds a and c, and also between the substituted phthalocyanine- and unsubstituted phthalocyanine-containing europium triple-deckers, renders it possible to assign the aromatic proton signals unambiguously. Copyright (C) 2002 Society of Porphyrins & Phthalocyanines.Chemistry, MultidisciplinarySCI(E)14ARTICLE5347-357
Sampling and Reconstruction of Signals on Product Graphs
No full textIn this paper, we consider the problem of subsampling and reconstruction of signals that reside on the vertices of a product graph, such as sensor network time series, genomic signals, or product ratings in a social network. Specifically, we leverage the product structure of the underlying domain and sample nodes from the graph factors. The proposed scheme is particularly useful for processing signals on large-scale product graphs. The sampling sets are designed using a low-complexity greedy algorithm and can be proven to be near-optimal. To illustrate the developed theory, numerical experiments based on real datasets are provided for sampling 3D dynamic point clouds and for active learning in recommender systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu
No full textLi, Qian = 半導體异质结构在光催化和光電催化中的研究 / 李乾.Thesis Ph.D. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 145-162).Abstracts also in Chinese.Title from PDF title page (viewed on 30, December, 2016).Li, Qian = Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu / Li Qian
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