scholarly journals NMR Crystallography of the Polymorphs of Metergoline

Crystals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 378 ◽  
Author(s):  
Jiri Czernek ◽  
Martina Urbanova ◽  
Jiri Brus
Keyword(s):  
Unit Cell ◽  
Chemical Shift Tensors ◽  
Exchange Correlation ◽  
13C Chemical Shift ◽  
Drug Compound ◽  
Nmr Crystallography ◽  
Projector Augmented Wave ◽  
Principal Elements ◽  
Theoretical Results

Two polymorphs of the drug compound metergoline (C25H29N3O2) were investigated in detail by solid-state NMR measurements. The results have been analysed by an advanced procedure, which uses experimental input together with the results of quantum chemical calculations that were performed for molecular crystals. In this way, it was possible to assign the total of 40 1H–13C correlation pairs in a highly complex system, namely, in the dynamically disordered polymorph with two independent molecules in the unit cell of a large volume of 4234 Å3. For the simpler polymorph, which exhibits only small-amplitude motions and has just one molecule in the unit cell with a volume of 529.0 Å3, the values of the principal elements of the 13C chemical shift tensors were measured. Additionally, for this polymorph, a set of crystal structure predictions were generated, and the {13C, 1H} isotropic and 13C anisotropic chemical shielding data were computed while using the gauge-including projector augmented-wave approach combined with the “revised Perdew-Burke-Ernzerhof“ exchange-correlation functional (GIPAW-RPBE). The experimental and theoretical results were combined in an application of the newly developed strategy to polymorph discrimination. This research thus opens up new routes towards more accurate characterization of the polymorphism of drug formulations.

scholarly journals Characterization of Tiled Architecture for C-Band 1-Bit Beam-Steering Transmitarray

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1259
Author(s):  
Dmitry Kozlov ◽  
Irina Munina ◽  
Pavel Turalchuk ◽  
Vitalii Kirillov ◽  
Alexey Shitvov ◽  
...  
Keyword(s):  
Communication Systems ◽  
Beam Steering ◽  
Unit Cell ◽  
Electromagnetic Simulations ◽  
Fifth Generation ◽  
Full Wave ◽  
Array Architecture ◽  
Modulation Pattern ◽  
Good Agreement

A new implementation of a beam-steering transmitarray is proposed based on the tiled array architecture. Each pixel of the transmitarray is manufactured as a standalone unit which can be hard-wired for specific transmission characteristics. A set of complementary units, providing reciprocal phase-shifts, can be assembled in a prescribed spatial phase-modulation pattern to perform beam steering and beam forming in a broad spatial range. A compact circuit model of the tiled unit cell is proposed and characterized with full-wave electromagnetic simulations. Waveguide measurements of a prototype unit cell have been carried out. A design example of a tiled 10 × 10-element 1-bit beam-steering transmitarray is presented and its performance benchmarked against the conventional single-panel, i.e., unibody, counterpart. Prototypes of the tiled and single-panel C-band transmitarrays have been fabricated and tested, demonstrating their close performance, good agreement with simulations and a weak effect of fabrication tolerances. The proposed transmitarray antenna configuration has great potential for fifth-generation (5G) communication systems.

Electrostatic lattice energy in ionic crystals: optimization of the convergence of Ewald series

1978 ◽  
Vol 34 (6) ◽  
pp. 974-979 ◽  
Author(s):  
M. Catti
Keyword(s):  
Lattice Energy ◽  
Rates Of Convergence ◽  
Unit Cell ◽  
Group Symmetry ◽  
Cube Root ◽  
Cell Dimensions ◽  
Madelung Energy ◽  
Direct Lattice ◽  
Unit Cell Dimensions ◽  
Theoretical Results

Ewald's method is reconsidered to express the dependence of Madelung energy on the ionic charges explicitly, also taking into account the space-group symmetry of the structure. Upper bounds for the residues of the two partial series have been calculated by integral approximation; that relative to the direct-lattice series is shown to depend on the cube root of the unit-cell volume. The optimum value of the parameter A, which equalizes the rates of convergence of the two sums and minimizes the total number of terms, has been determined numerically for a given termination error and for a range of unit-cell dimensions. Theoretical results are tested by calculations on some specific crystal structures.

scholarly journals A Discrete Mathematical Modeling and Optimal Control of the Rumor Propagation in Online Social Network

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Amine El Bhih ◽  
Rachid Ghazzali ◽  
Soukaina Ben Rhila ◽  
Mostafa Rachik ◽  
Adil El Alami Laaroussi
Keyword(s):  
Optimal Control ◽  
Online Social Network ◽  
Discrete Version ◽  
Optimal Controls ◽  
Optimal Control Strategy ◽  
Rumor Spreading ◽  
Rumor Propagation ◽  
Theoretical Results ◽  
Forward Backward Sweep Method

In this paper, a new rumor spreading model in social networks has been investigated. We propose a new version primarily based on the cholera model in order to take into account the expert pages specialized in the dissemination of rumors from an existing IRCSS model. In the second part, we recommend an optimal control strategy to fight against the spread of the rumor, and the study aims at characterizing the three optimal controls which minimize the number of spreader users, fake pages, and corresponding costs; theoretically, we have proved the existence of optimal controls, and we have given a characterization of controls in terms of states and adjoint functions based on a discrete version of Pontryagin’s maximum principle. To illustrate the theoretical results obtained, we propose numerical simulations for several scenarios applying the forward-backward sweep method (FBSM) to solve our optimality system in an iterative process.

An Antagonistic Flexural Unit Cell for Design of Shape Morphing Structures

Aerospace ◽  
2004 ◽  
Author(s):  
Aarash Y. N. Sofla ◽  
Dana M. Elzey ◽  
Haydn N. G. Wadley
Keyword(s):  
Shape Memory ◽  
Unit Cell ◽  
External Energy ◽  
Full Characterization ◽  
Shape Morphing ◽  
Cyclic Operation ◽  
Unit Cells ◽  
External Forces ◽  
Reversed Cyclic

An antagonistic flexural unit cell (AFC) concept for the design and fabrication of novel 2-D and 3-D lightweight shape morphing structures is introduced. A fully reversible flexural shape changing cell utilizing opposing one-way shape memory alloy (SMA) actuators is shown to require no spring-like bias elements. The SMA actuating elements are arranged such that the actuation (contraction) of one of them stretches the other one in the cell, preparing it to be actuated later to reverse a flexural displacement. This antagonistic operation allows fully reversed cyclic operation. The focus of this paper is an assessment of performance at the single cell level. The cell logically provides four possible configurations in different stages of its cycle. Two of them are of particular interest because they provide two different fixed shapes for the cell that can be maintained without the continuous supply of external energy. The final deformations of the cell and equilibrium stresses in the SMA elements depend on the amount of stored shape memory strain in each element, external forces and cell geometry. A model is developed, which allows a full characterization of the AFC. The model is used to study NiTi SMA-based AFCs and the results are therefore directly applicable to the design of shape morphing structures using such unit cells.

scholarly journals Achieving Fairness in the Stochastic Multi-Armed Bandit Problem

2020 ◽  
Vol 34 (04) ◽  
pp. 5379-5386
Author(s):  
Vishakha Patil ◽  
Ganesh Ghalme ◽  
Vineet Nair ◽  
Y. Narahari
Keyword(s):  
Learning Algorithm ◽  
Complete Characterization ◽  
Bandit Problem ◽  
Fairness Constraints ◽  
Two Parameters ◽  
The Cost ◽  
Primary Contribution ◽  
Theoretical Results ◽  
Natural Way

We study an interesting variant of the stochastic multi-armed bandit problem, which we call the Fair-MAB problem, where, in addition to the objective of maximizing the sum of expected rewards, the algorithm also needs to ensure that at any time, each arm is pulled at least a pre-specified fraction of times. We investigate the interplay between learning and fairness in terms of a pre-specified vector denoting the fractions of guaranteed pulls. We define a fairness-aware regret, which we call r-Regret, that takes into account the above fairness constraints and extends the conventional notion of regret in a natural way. Our primary contribution is to obtain a complete characterization of a class of Fair-MAB algorithms via two parameters: the unfairness tolerance and the learning algorithm used as a black-box. For this class of algorithms, we provide a fairness guarantee that holds uniformly over time, irrespective of the choice of the learning algorithm. Further, when the learning algorithm is UCB1, we show that our algorithm achieves constant r-Regret for a large enough time horizon. Finally, we analyze the cost of fairness in terms of the conventional notion of regret. We conclude by experimentally validating our theoretical results.

LINEAR AND INTEGER PROGRAMMING TECHNIQUES FOR COOPERATIVE GAMES

2002 ◽  
Vol 13 (05) ◽  
pp. 653-666 ◽  
Author(s):  
Qizhi Fang ◽  
Shanfeng Zhu
Keyword(s):  
Integer Programming ◽  
Cooperative Game ◽  
Cooperative Games ◽  
Value Function ◽  
Linear Program ◽  
Grand Coalition ◽  
The Core ◽  
Programming Techniques ◽  
Theoretical Results

Let Γ = (N, v) be a cooperative game with the player set N and value function v : 2N → R. A solution of the game is in the core if no subset of players could gain advantage by breaking away from the grand coalition of all players. This paper surveys theoretical results on the cores for some cooperative game models. These results proved that the linear program duality characterization of the core is a very powerful tool. We will focus on linear and integer programming techniques applied in this area.

13C Chemical Shift Tensors in Hypoxanthine and 6-Mercaptopurine: Effects of Substitution, Tautomerism, and Intermolecular Interactions

2010 ◽  
Vol 114 (4) ◽  
pp. 1985-1995 ◽  
Author(s):  
Kateřina Maliňáková ◽  
Lucie Novosadová ◽  
Manu Lahtinen ◽  
Erkki Kolehmainen ◽  
Jiří Brus ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Intermolecular Interactions ◽  
Chemical Shift Tensors ◽  
13C Chemical Shift
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