119,560 research outputs found
A Macrocycle – Molecular Clip Complex that Functions as a Quadruply Controllable Molecular Switch
No full text我們在此論文當中成功的合成出一具有TTF之分子夾1a。我們以文獻上已知之glycoluril為基礎之分子夾2為基礎，與2-thioxo-1,3-dithiole在酸催化下進行縮合反應得到分子夾3。利用triethylene glycol monomethyl ether tosylate在鹼性條件之下修飾分子夾3上之酚基，得到分子夾5a，以Hg(OAc)2進行一個硫氧置換反應得到分子夾6a，以此分子夾與1,3-dithiole-2-thione進行一個HWE反應得到分子夾1a。
我們發現具TTF側臂之分子夾與缺乏電子之大環分子之間可形成大環–分子夾之錯合體。運用鉀離子–穴醚、酸–鹼、氧化–還原、冷卻–加熱等外加刺激，可控制此一大環–分子夾錯合體循環於解離與錯合的二種不同狀態。
由於此二種狀態各自呈現不同顏色，此一大環–分子夾錯合體不但可作為一個四向控制之分子開關，還能模擬一個三輸入NOR邏輯閘的表現。Herein, we synthesized a TTF contained molecular clip 1a. Under acidic condition, the known molecular clip 2 underwent a condensation reaction with 2-thioxo-1,3-dithiole. The resulting product 3 was then modified on the phenolic groups with triethylene glycol monomethyl ether tosylate to get molecular clip 5a. 5a was treated with Hg(OAc)2 to convert thione into ketone (6a). Then the resulting molecular clip 6a was reacted with 1,3-dithiole-2-thione in presence of P(OEt)3 to afford 1a.
We found such TTF contained molecular clip that forms a macrocycle – molecular clip complex with a electronic complementary macrocycle. Four different sets of external stimuli – the K+/[2,2,2]cryptand, NH4+/Et3N, (p-PhBr)3NSbCl6/Zn pairs and heating/cooling cycles – allow the movement of this molecular switch to be controlled between its threaded and unthreaded states.
The macrocycle – molecular clip complex not only considered as a quadruply controllable molecular switch but also can be operated by three of these stimuli as a three-input molecular NOR-functioning logic gate that may be monitored by UV-Vis spectroscopy.摘要 ················································· I
論文發表 ············································· III
目錄 ················································· IV
圖表 ················································· VI
表格 ················································· IX
壹、緒 論 ············································ 1
1.1 前言 ·········································· 1
1.2 人造超分子系統 ································ 3
1.2.1 早期的人造分子機械 ······················· 3
1.2.2 利用酸鹼控制的分子開關 ··················· 3
1.2.3 以可逆氧化還原反應控制之分子開關 ········· 5
1.2.4 以光化學控制的分子開關 ··················· 7
1.2.5 分子構型對於鍵結的影響 ··················· 8
1.3 多向控制分子開關的設計方向與問題 ·············· 10
貳、結 果 與 討 論 ··································· 12
2.1 研究動機與研究方向 ···························· 12
2.1.1 研究動機 ································· 12
2.1.2 大環–分子夾錯合體之設計及預期之功能 ······ 12
V
2.2 含TTF分子夾之合成 ··························· 15
2.3 分子夾上TTF之重要性研究 ····················· 18
2.4 構築大環–分子夾錯合體 ························ 21
2.4.1大環分子9·2PF6與分子夾1a生成之大環–分子夾
錯合體 ····································21
2.4.2 分子夾1a-c的性質探討 ····················· 24
2.4.3 構築可控制版本之大環–分子夾錯合體 ······· 26
2.5 以大環–分子夾錯合體構築之分子開關功能研究 ···· 28
2.5.1 以大環分子接受外加刺激的分子開關控制方法 · 28
2.5.2 利用溫度改變超分子錯狀態之分子開關控制方法 32
2.5.3 利用氧化還原分子夾上TTF部份之分子開關控制
方法 ····································· 33
2.6 大環–分子夾錯合體建構之四向控制分子開關及其功能 35
參、結 論 ··········································· 37
肆、實 驗 部 份 ····································· 38
伍、參 考 文 獻 ····································· 52
附 錄：Job plot與結合常數測量、1H與13C核磁共振光
PiNN: A Python Library for Building Atomic Neural Networks of Molecules and Materials
No full textAtomic neural networks (ANNs) constitute a class of machine learning
methods for predicting potential energy surfaces and physicochemical
properties of molecules and materials. Despite many successes, developing
interpretable ANN architectures and implementing existing ones efficiently
are still challenging. This calls for reliable, general-purpose, and
open-source codes. Here, we present a python library named PiNN as
a solution toward this goal. In PiNN, we designed a new interpretable
and high-performing graph convolutional neural network variant, PiNet,
as well as implemented the established Behler–Parrinello neural
network. These implementations were tested using datasets of isolated
small molecules, crystalline materials, liquid water, and an aqueous
alkaline electrolyte. PiNN comes with a visualizer called PiNNBoard
to extract chemical insight “learned” by ANNs. It provides
analytical stress tensor calculations and interfaces to both the atomic
simulation environment and a development version of the Amsterdam
Modeling Suite. Moreover, PiNN is highly modularized, which makes
it useful not only as a standalone package but also as a chain of
tools to develop and to implement novel ANNs. The code is distributed
under a permissive BSD license and is freely accessible at https://github.com/Teoroo-CMC/PiNN/ with full documentation and tutorials
PiNN : A Python Library for Building Atomic Neural Networks of Molecules and Materials
No full textAtomic neural networks (ANNs) constitute a class of machine learning methods for predicting potential energy surfaces and physicochemical properties of molecules and materials. Despite many successes, developing interpretable ANN architectures and implementing existing ones efficiently are still challenging. This calls for reliable, general-purpose, and open-source codes. Here, we present a python library named PiNN as a solution toward this goal. In PiNN, we designed a new interpretable and high-performing graph convolutional neural network variant, PiNet, as well as implemented the established Behler-Parrinello neural network. These implementations were tested using datasets of isolated small molecules, crystalline materials, liquid water, and an aqueous alkaline electrolyte. PiNN comes with a visualizer called PiNNBoard to extract chemical insight "learned" by ANNs. It provides analytical stress tensor calculations and interfaces to both the atomic simulation environment and a development version of the Amsterdam Modeling Suite. Moreover, PiNN is highly modularized, which makes it useful not only as a standalone package but also as a chain of tools to develop and to implement novel ANNs. The code is distributed under a permissive BSD license and is freely accessible at https://github.com/Teoroo-CMC/PiNN/with full documentation and tutorials
Numerical analysis of a 3-D printed porous trailing edge for broadband noise reduction
No full textLattice Boltzmann simulations were carried out to investigate the noise mitigation mechanisms of a 3-D printed porous trailing-edge insert, elucidating the link between noise reduction and material permeability. The porous insert is based on a unit cell resembling a lattice of diamond atoms. It replaces the last 20 % chord of a NACA 0018 at zero angle-of-attack. A partially blocked insert is considered by adding a solid partition between 84 % and 96 % of the aerofoil chord. The regular porous insert achieves a substantial noise reduction at low frequencies, although a slight noise increase is found at high frequencies. The partially blocked porous insert exhibits a lower noise reduction level, but the noise emission at mid-to-high frequency is slightly affected. The segment of the porous insert near the tip plays a dominant role in promoting noise mitigation, whereas the solid-porous junction contributes, in addition to the rough surface, towards the high-frequency excess noise. The current study demonstrates the existence of an entrance length associated with the porous material geometry, which is linked to the pressure release process that is responsible for promoting noise mitigation. This process is characterised by the aerodynamic interaction between pressure fluctuations across the porous medium, which is found at locations where the porous insert thickness is less than twice the entrance length. Present results also suggest that the noise attenuation level is related to both the chordwise extent of the porous insert and the streamwise turbulent length scale. The porous inserts also cause a slight drag increase compared to their solid counterpart. Wind Energ
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Direct P-Wave Seismic Noise Interferometry for Groundwater Monitoring: A Modelling Study
No full textIn this study, we monitor the depth variation of an unconfined aquifer by applying seismic noise interferometry to synthetic data modelled with a 2D finite-difference software. We consider two models with the same subsurface geological structure, but with different water table levels representing two monitoring periods. The receivers are placed at the topographic surface and collect the seismic signals generated by a source located at the bottom of the aquifer to simulate a pumping system. First, cross-correlation of seismic traces with a reference one is used to produce interferograms (i.e., virtual surveys) for both the tested models. Then, direct P-wave arrivals identified in the two interferograms are compared through the stretching technique in order to estimate the relative velocity changes (dv/v). Finally, the estimated dv/v values are related to theoretical ones obtained using a reference subsurface model to produce the water level depth in the considered monitoring period.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.Applied Geophysics and Petrophysic
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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