scholarly journals Shannon Entropy in Confined He-Like Ions within a Density Functional Formalism

2020 ◽  
Vol 2 (1) ◽  
pp. 189-207 ◽  
Author(s):  
Sangita Majumdar ◽  
Amlan K. Roy
Keyword(s):  
Shannon Entropy ◽  
Electron Correlation ◽  
Density Functional ◽  
Exchange Potential ◽  
Functional Formalism ◽  
Systematic Analysis ◽  
Free System ◽  
Linear Gradient ◽  
The Impact ◽  
Qualitative Discussion

Shannon entropy in position ( S r ) and momentum ( S p ) spaces, along with their sum ( S t ) are presented for unit-normalized densities of He, Li + and Be 2 + ions, spatially confined at the center of an impenetrable spherical enclosure defined by a radius r c . Both ground, as well as some selected low-lying singly excited states, viz., 1sns (n = 2–4) 3S, 1snp (n = 2–3) 3P, 1s3d 3D, are considered within a density functional methodology that makes use of a work function-based exchange potential along with two correlation potentials (local Wigner-type parametrized functional, as well as the more involved non-linear gradient- and Laplacian-dependent Lee-Yang-Parr functional). The radial Kohn-Sham (KS) equation is solved using an optimal spatial discretization scheme via the generalized pseudospectral (GPS) method. A detailed systematic analysis of the confined system (relative to the corresponding free system) is performed for these quantities with respect to r c in tabular and graphical forms, with and without electron correlation. Due to compression, the pattern of entropy in the aforementioned states becomes characterized by various crossovers at intermediate and lower r c regions. The impact of electron correlation is more pronounced in the weaker confinement limit and appears to decay with the rise in confinement strength. The exchange-only results are quite good to provide a decent qualitative discussion. The lower bounds provided by the entropic uncertainty relation hold well in all cases. Several other new interesting features are observed.

Exile, Diaspora, and Return

2017 ◽  
Author(s):  
Luis Roniger ◽  
Leonardo Senkman ◽  
Saúl Sosnowski ◽  
Mario Sznajder
Keyword(s):  
Systematic Analysis ◽  
The Arts ◽  
Scientific Disciplines ◽  
Early Twenty ◽  
Transnational Connections ◽  
Late Twentieth ◽  
Institutional Impact ◽  
Global Arena ◽  
Education Science ◽  
The Impact

This book explores how Argentina, Chile, Paraguay, and Uruguay have been affected by postexilic relocations, transnational migrant displacements, and diasporas. It provides a systematic analysis of the formation of exile communities and diaspora politics, the politics of return, and the agenda of democratization in the late twentieth and early twenty-first centuries, focusing on the impact of intellectuals, academics, activists, and public figures who had experienced exile on the reconstitution and transformation of their societies following democratization. Readers are offered a kaleidoscope of intellectual itineraries, debates, and contributions held in the public domain by individuals who confronted and fought authoritarian rule. The book covers their contributions to the restructuring and transformation of scientific disciplines and of the humanities and the arts, as well as their collective institutional impact on higher education, science and technology, and public institutions. Bringing together sociopolitical, cultural, and policy analysis with the testimonies of dozens of intellectuals, academics, political activists, and policymakers, the book addresses the impact of exile on people’s lives and on their fractured experiences, the debates and prospects of return, the challenges of dis-exile and postexilic trends, and, finally, the ways in which those who experienced exile impacted democratized institutions, public culture, and discourse. It also follows some crucial shifts in the frontiers of citizenship, moving analysis to transnational connections and permanent diasporas, including the diasporas of knowledge that increasingly changed the very meaning of being national and transnational, while connecting those countries to the global arena.

scholarly journals Combinations of Freeze-Dried Amorphous Vardenafil Hydrochloride with Saccharides as A Way to Enhance Dissolution Rate and Permeability

2021 ◽  
Vol 14 (5) ◽  
pp. 453
Author(s):  
Gabriela Wiergowska ◽  
Dominika Ludowicz ◽  
Kamil Wdowiak ◽  
Andrzej Miklaszewski ◽  
Kornelia Lewandowska ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Density Functional ◽  
Hydroxypropyl Methylcellulose ◽  
Fold Increase ◽  
Crystalline Form ◽  
Amorphous Form ◽  
Freeze Dried ◽  
Apparent Solubility ◽  
Gastrointestinal Epithelium ◽  
The Impact

To improve physicochemical properties of vardenafil hydrochloride (VAR), its amorphous form and combinations with excipients—hydroxypropyl methylcellulose (HPMC) and β-cyclodextrin (β-CD)—were prepared. The impact of the modification on physicochemical properties was estimated by comparing amorphous mixtures of VAR to their crystalline form. The amorphous form of VAR was obtained as a result of the freeze-drying process. Confirmation of the identity of the amorphous dispersion of VAR was obtained through the use of comprehensive analysis techniques—X-ray powder diffraction (PXRD) and differential scanning calorimetry (DSC), supported by FT-IR (Fourier-transform infrared spectroscopy) coupled with density functional theory (DFT) calculations. The amorphous mixtures of VAR increased its apparent solubility compared to the crystalline form. Moreover, a nearly 1.3-fold increase of amorphous VAR permeability through membranes simulating gastrointestinal epithelium as a consequence of the changes of apparent solubility (Papp crystalline VAR = 6.83 × 10−6 cm/s vs. Papp amorphous VAR = 8.75 × 10−6 cm/s) was observed, especially for its combinations with β-CD in the ratio of 1:5—more than 1.5-fold increase (Papp amorphous VAR = 8.75 × 10−6 cm/s vs. Papp amorphous VAR:β-CD 1:5 = 13.43 × 10−6 cm/s). The stability of the amorphous VAR was confirmed for 7 months. The HPMC and β-CD are effective modifiers of its apparent solubility and permeation through membranes simulating gastrointestinal epithelium, suggesting a possibility of a stronger pharmacological effect.

scholarly journals An Evaluation of the Impact of the Amount of Potassium Hydroxide on the Porous Structure Development of Activated Carbons

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2045
Author(s):  
Mirosław Kwiatkowski ◽  
Elżbieta Broniek ◽  
Vanessa Fierro ◽  
Alain Celzard
Keyword(s):  
Density Functional Theory ◽  
Porous Structure ◽  
Potassium Hydroxide ◽  
Density Functional ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Appropriate Technology ◽  
Functional Theory ◽  
Homogeneous Surface ◽  
The Impact

This paper presents the results of an evaluation of the impact of the amount of potassium hydroxide on the obtained porous structure of the activated carbons derived from the shells of pistachios, hazelnuts, and pecans by carbonization and subsequent chemical activation with potassium hydroxide by different adsorption methods: Brunauer–Emmett–Teller, Dubinin–Raduskevich, the new numerical clustering-based adsorption analysis, Quenched Solid Density Functional Theory, and 2D-Non-linear Density Functional Theory for Heterogeneous Surfaces, applied to nitrogen adsorption isotherms at −196 °C. Based on the conducted research, a significant potential for the production of activated carbons from waste materials, such as nut shells, has been demonstrated. All the activated carbons obtained in the present study at the activator/char mass ratio R = 4 exhibited the most developed porous structure, and thus very good adsorption properties. However, activated carbons obtained from pecan shells deserve special attention, as they were characterized by the most homogeneous surface among all the samples analyzed, i.e., by a very desirable feature in most adsorption processes. The paper demonstrates the necessity of using different methods to analyze the porous structure of activated carbons in order to obtain a complete picture of the studied texture. This is because only a full spectrum of information allows for correctly selecting the appropriate technology and conditions for the production of activated carbons dedicated to specific industrial applications. As shown in this work, relying only on the simplest methods of adsorption isotherm analysis can lead to erroneous conclusions due to lack of complete information on the analyzed porous structure. This work thus also explains how and why the usual characterizations of the porous structure of activated carbons derived from lignocellulosic biomass should not be taken at face value. On the contrary, it is advisable to cross reference several models to get a precise idea of the adsorbent properties of these materials, and therefore to propose the most suitable production technology, as well as the conditions of the preparation process.

scholarly journals Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Faizan ◽  
K. C. Bhamu ◽  
Ghulam Murtaza ◽  
Xin He ◽  
Neeraj Kulhari ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Perovskite Solar Cells ◽  
Dielectric Constants ◽  
Maximum Efficiency ◽  
Exchange Potential ◽  
Double Perovskites ◽  
Electronic And Optical Properties

AbstractThe highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

scholarly journals Effect of vacancy defects on the electronic transport properties of an Ag–ZnO–Pt sandwich structure

2021 ◽  
Vol 20 (2) ◽  
pp. 798-804
Author(s):  
G. R. Berdiyorov ◽  
F. Boltayev ◽  
G. Eshonqulov ◽  
H. Hamoudi
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Density Functional ◽  
Practical Importance ◽  
Functional Formalism ◽  
Vacancy Defects ◽  
Electronic Transport Properties ◽  
Charge Localization ◽  
Metal Insulator Metal ◽  
Current Rectification

AbstractThe effect of zinc and oxygen vacancy defects on the electronic transport properties of Ag(100)–ZnO(100)–Pt(100) sandwich structures is studied using density functional theory in combination with the nonequilibrium Green’s functional formalism. Defect-free systems show clear current rectification due to voltage dependent charge localization in the system as revealed in our transmission eigenstates analysis. Regardless of the location, oxygen vacancies result in enhanced current in the system, whereas Zn vacancy defects reduce the charge transport across the junction. The current rectification becomes less pronounced in the presence of both types of vacancy defects. Our findings can be of practical importance for developing metal-insulator-metal diodes.

scholarly journals Effect of chemical modification on electronic transport properties of carbyne

2021 ◽  
Author(s):  
G. R. Berdiyorov ◽  
U. Khalilov ◽  
H. Hamoudi ◽  
Erik C. Neyts
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Density Functional ◽  
Structural Changes ◽  
Carbon Chain ◽  
Functional Formalism ◽  
Functional Theory ◽  
Carbon Allotrope ◽  
Electronic Transport Properties ◽  
Interface Structures

AbstractUsing density functional theory in combination with the Green’s functional formalism, we study the effect of surface functionalization on the electronic transport properties of 1D carbon allotrope—carbyne. We found that both hydrogenation and fluorination result in structural changes and semiconducting to metallic transition. Consequently, the current in the functionalization systems increases significantly due to strong delocalization of electronic states along the carbon chain. We also study the electronic transport in partially hydrogenated carbyne and interface structures consisting of pristine and functionalized carbyne. In the latter case, current rectification is obtained in the system with rectification ratio up to 50%. These findings can be useful for developing carbyne-based structures with tunable electronic transport properties.

scholarly journals University students’ representations of Europe and self-identification as Europeans: a synthesis of qualitative evidence for future policy formulation

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Esther Cores-Bilbao ◽  
María del Carmen Méndez-García ◽  
M. Carmen Fonseca-Mora
Keyword(s):  
University Students ◽  
Evidence Synthesis ◽  
Foreign Language Learning ◽  
Educational Interventions ◽  
Policy Formulation ◽  
Qualitative Evidence Synthesis ◽  
The European Union ◽  
Systematic Analysis ◽  
Qualitative Evidence ◽  
The Impact

AbstractThe current European context is characterised by the emergence of socio-political tensions that threaten to derail the cohesion objectives traditionally promoted by the authorities of the European Union. With EU citizenship in the shadow of Brexit, the fear of dismemberment of the current Europe of the 28 looms over a renewed debate on concepts like European identity, European citizenship or EU legitimacy and the involvement of its constituents in European affairs, as well as the role of education for promoting democratic awareness among young Europeans. This work aims to collect, appraise and synthesise qualitative evidence obtained in primary research exploring the perceptions of European university students about their civic and cultural identity. This systematic analysis sets out to identify predictors of positive self-identification with the EU and its institutions, focusing on the impact that different educational interventions have had on the attitudes and perceptions expressed by university students, and the importance of foreign language learning in the results obtained. The authors report their assessment of quality of the findings in a Cochrane-style qualitative evidence synthesis (QES), based on the GRADE-CERQual (Confidence in Evidence from Reviews of Qualitative research) method. The 12 informed findings described in this study support decision-making in future education policy formulation.

Magnetic Properties of Embedded Rh Clusters in Ni Matrix

1995 ◽  
Vol 384 ◽  
Author(s):  
Zhi-Qiang Li ◽  
Yuichi Hashi ◽  
Jing-Zhi Yu ◽  
Kaoru Ohno ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Functional Formalism ◽  
Rhodium Clusters ◽  
Spin Polarized ◽  
Local Density Functional

ABSTRACTThe electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

First-principles Studies of Phase Stability and the Neutral Atomic Vacancies in LiNbO3, NaNbO3 and KNbO3

2005 ◽  
Vol 902 ◽  
Author(s):  
Akio Shigemi ◽  
Takahiro Wada
Keyword(s):  
Enthalpy Of Formation ◽  
Density Functional ◽  
Formation Energy ◽  
Type Structure ◽  
Enthalpies Of Formation ◽  
Functional Formalism ◽  
Reducing Atmosphere ◽  
Perovskite Type Oxide ◽  
Formation Energies ◽  
Perovskite Type

AbstractWe overall evaluated the enthalpies of formation and the formation energies of neutral vacancies in ANbO3 (A = Li, Na, K) using a plane-wave pseudopotential method within a density functional formalism. The LiNbO3 phase with the LiNbO3-type structure was confirmed to have lower enthalpy of formation than that with perovskite- or ilmenite-type structure. The NaNbO3 (R3c) and KNbO3 (Bmm2 and R3m) phases with the lowest symmetry were found to have the lowest enthalpy of formation. The formation energy of a A vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist.

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