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141.
Dr. Gilles Ulrich Dr. Alberto Barsella Dr. Alex Boeglin Dr. Songlin Niu Dr. Raymond Ziessel 《Chemphyschem》2014,15(13):2693-2700
A set of linear and dissymmetric BODIPY‐bridged push–pull dyes are synthesized. The electron‐donating substituents are anisole and dialkylanilino groups. The strongly electron‐accepting moiety, a 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) group, is obtained by insertion of an electron‐rich ethyne into tetracyanoethylene. A nonlinear push–pull system is developed with a donor at the 5‐position of the BODIPY core and the acceptor at the 2‐position. All dyes are fully characterized and their electrochemical, linear and nonlinear optical properties are discussed. The linear optical properties of dialkylamino compounds show strong solvatochromic behavior and undergo drastic changes upon protonation. The strong push–pull systems are non‐fluorescent and the TCBD‐BODIPY dyes show diverse photochemistry and electrochemistry, with several reversible reduction waves for the tetracyanobutadiene moiety. The hyperpolarizability μβ of selected compounds is evaluated using the electric‐field‐induced second‐harmonic generation technique. Two of the TCBD‐BODIPY dyes show particularly high μβ (1.907 μm) values of 2050×10?48 and 5900×10?48 esu. In addition, one of these dyes shows a high NLO contrast upon protonation–deprotonation of the donor residue. 相似文献
142.
Anthony Marshall Martin Tkaczyk Alex G. Harrison 《Journal of the American Society for Mass Spectrometry》1991,2(4):292-298
The negative ion chemical ionization mass spectra of twentyeight C4 to C7 carbonyl compounds were recorded using the oxide radical anion O?? as reagent ion. As noted earlier, the reactions occurring include H+ abstraction, H 2 +? abstraction, H? atom displacement, and alkyl radical displacement. In addition, the [M?2H]? ions fragment further by alkyl radical elimination. The relative importance of these reactions depends strongly on molecular structure, with the result that isomer distinction frequently is possible. Where this is not possible, as for isomeric aldehydes, the collisional charge inversion mass spectra of common product ions provides isomer distinction. The H 2 +? abstraction reaction is shown to involve abstraction not only of two hydrogens from the same α-carbon but also, in part, abstraction of one hydrogen from each α-carbon. 相似文献
143.
Daniel K. L. Oi Alex Ling James A. Grieve Thomas Jennewein Aline N. Dinkelaker Markus Krutzik 《Contemporary Physics》2017,58(1):25-52
Bringing quantum science and technology to the space frontier offers exciting prospects for both fundamental physics and applications such as long-range secure communication and space-borne quantum probes for inertial sensing with enhanced accuracy and sensitivity. But despite important terrestrial pathfinding precursors on common microgravity platforms and promising proposals to exploit the significant advantages of space quantum missions, large-scale quantum test beds in space are yet to be realised due to the high costs and lead times of traditional ‘Big Space’ satellite development. But the ‘small space’ revolution, spearheaded by the rise of nanosatellites such as CubeSats, is an opportunity to greatly accelerate the progress of quantum space missions by providing easy and affordable access to space and encouraging agile development. We review space quantum science and technology, CubeSats and their rapidly developing capabilities and how they can be used to advance quantum satellite systems. 相似文献
144.
Mourad Benlamri Kyle M. Bothe Alex M. Ma Gem Shoute Amir Afshar Himani Sharma Arash Mohammadpour Manisha Gupta Kenneth C. Cadien Ying Y. Tsui Karthik Shankar Douglas W. Barlage 《固体物理学:研究快报》2014,8(10):871-875
A high effective electron mobility of 33 cm2 V–1 s–1 was achieved in solution‐processed undoped zinc oxide (ZnO) thin films. The introduction of silicon nitride (Si3N4) as growth substrate resulted in a mobility improvement by a factor of 2.5 with respect to the commonly used silicon oxide (SiO2). The solution‐processed ZnO thin films grown on Si3N4, prepared by low‐pressure chemical vapor deposition, revealed bigger grain sizes, lower strain and better crystalline quality in comparison to the films grown on thermal SiO2. These results show that the nucleation and growth mechanisms of solution‐processed films are substrate dependent and affect the final film structure accordingly. The substantial difference in electron mobilities suggests that, in addition to the grain morphology and crystalline structure effects, defect chemistry is a contributing factor that also depends on the particular substrate. In this respect, interface trap densities measured in high‐κ HfO2/ZnO MOSCAPs were about ten times lower in those fabricated on Si3N4 substrates. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)
145.
We investigate finite lattice approximations to the Wilson renormalization group in models of unconstrained spins. We discuss first the properties of the renormalization group transformation (RGT) that control the accuracy of this type of approximation and explain different methods and techniques to practically identify them. We also discuss how to determine the anomalous dimension of the field. We apply our considerations to a linear sigma model in two dimensions in the domain of attraction of the Ising fixed point using a Bell–Wilson RGT. We are able to identify optimal RGTs which allow accurate computations of quantities such as critical exponents, fixed-point couplings and eigenvectors with modest statistics. We finally discuss the advantages and limitations of this type of approach. 相似文献
146.
We calculate the average resistanceR(L) of lattice animals spanningL×L cells on the square lattice using exact and Monte Carlo methods. The dynamical resistivity exponent, defined asR(L) L
, is found to be =1.36±0.07. This contradicts the Alexander-Orbach conjecture, which predicts 0.8. Our value for differs from earlier measurements of this quantity by other methods yielding =1.17±0.05 and 1.22±0.08 by Havlin et al.On leave from the Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China. 相似文献
147.
This paper proposes a novel ant colony optimisation (ACO) algorithm tailored for the hierarchical multi-label classification problem of protein function prediction. This problem is a very active research field, given the large increase in the number of uncharacterised proteins available for analysis and the importance of determining their functions in order to improve the current biological knowledge. Since it is known that a protein can perform more than one function and many protein functional-definition schemes are organised in a hierarchical structure, the classification problem in this case is an instance of a hierarchical multi-label problem. In this type of problem, each example may belong to multiple class labels and class labels are organised in a hierarchical structure—either a tree or a directed acyclic graph structure. It presents a more complex problem than conventional flat classification, given that the classification algorithm has to take into account hierarchical relationships between class labels and be able to predict multiple class labels for the same example. The proposed ACO algorithm discovers an ordered list of hierarchical multi-label classification rules. It is evaluated on sixteen challenging bioinformatics data sets involving hundreds or thousands of class labels to be predicted and compared against state-of-the-art decision tree induction algorithms for hierarchical multi-label classification. 相似文献
148.
Conventional design of radiation detectors uses sintered ceramic insulating modules. The major drawback of these ceramic components
is their inherent brittleness. Ion chambers, in which these ceramic spacers are replaced by metallic components with plasma
spray coated alumina, have been developed in our Research Centre. These components act as thin spacers that have good mechanical
strength as well as high electrical insulation and replace alumina insulators with the same dimensions. As a result, the design
of the beam loss monitor ion chamber for CAT could be simplified by coating the outer surface of the HT electrode with alumina.
One of the chambers developed for isotope calibrator for brachytherapy gamma sources has its outer aluminium electrode (60
mm dia × 220 mm long) coated with 250 μ thick alumina (97%) + titania (3%).
In view of potential applications in neutron-sensitive ion chambers used in reactor control instrumentation, studies were
carried out on alumina 100 μ to 500 μ thick coatings on copper, aluminium and SS components. The electrical insulation varied
from 108 ohms to 1012 ohms for coating thicknesses above 200 μ. The porosity in the coating resulted in some fall in electrical insulation due
to moisture absorption. An improvement could be achieved by providing the ceramic surface with moisture-repellent silicone
oil coating. Irradiation at Apsara reactor core location showed that the coating on aluminium was found to be unaffected after
exposure to 1017 nvt fluence. 相似文献
149.
For any ordered set P, the join dense completions of P form a complete lattice K(P) with least element O(P), the lattice of order ideals of P, and greatest element M(P), the Dedekind–MacNeille completion P. The lattice K(P) is isomorphic to an ideal of the lattice of all closure operators on the lattice O(P). Thus it inherits some local structural properties which hold in the lattice of closure operators on any complete lattice. In particular, if K(P) is finite, then it is an upper semimodular lattice and an upper bounded homomorphic image of a free lattice, and hence meet semidistributive. 相似文献
150.
We find that a defect state treatment of localized excitations in LiF within the local density functional formalism accounts remarkably well for the observed experimental (core plus optical gap) excitations — in contrast to the failure of the one-electron band model. We show that when electron relaxation, self-interaction and charge polarization effects are taken into account by treating the excitation as a localized points defect, the improved band model predicts the correct excitation and interband states. 相似文献