Generalized Gradient Methods of Nondifferentiable Optimization Employing Space Dilatation Operations

1983 ◽  
pp. 501-529 ◽  
Author(s):  
N. Z. Shor
Keyword(s):  
Nondifferentiable Optimization ◽  
Gradient Methods ◽  
Generalized Gradient

ELECTRON DENSITY FUNCTIONAL THEORY

1999 ◽  
Vol 13 (05n06) ◽  
pp. 511-523 ◽  
Author(s):  
J. F. DOBSON
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Gradient Methods ◽  
Density Functionals ◽  
Generalized Gradient ◽  
Electronic Density ◽  
Functional Theory ◽  
Energy Functionals ◽  
Electron Density Functional Theory ◽  
Recent Developments

A brief summary is given of electronic density functional theory, including recent developments: generalized gradient methods, hybrid functionals, time dependent density functionals and excited states, van der Waals energy functionals.

Interstitial vs. Substitutional Metal Insertion in V2O5 as Post-Lithium Ion Battery Cathode: A Comparative GGA/GGA+U Study with Localized Bases

2020 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Electronic Structure ◽  
Plane Wave ◽  
Transition Metal Oxides ◽  
Reasonable Agreement ◽  
Correction Term ◽  
Lithium Ion ◽  
Generalized Gradient ◽  
Main Group Metals ◽  
Generalized Gradient Approximation ◽  
Metal Insertion

<p></p><p>The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter <i>U</i>. We tune <i>U</i> to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. We find the value for <i>U</i> to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being in reasonable agreement with experiments. We use this computational setup to calculate interstitial and substitutional <a>insertion energies of main group metals in vanadium pentoxide</a> and find <a>interstitial doping to be thermodynamically favored</a>.</p><p></p>

Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Complex Refractive Index ◽  
Single Layer ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Wide Range ◽  
Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

EFFECTIVENESS OF "SWIM-UP" AND "GRADIENT" METHODS IN SPERM PREPARATION FOR ARTIFICIAL INSEMINATION

2014 ◽  
pp. 25-29
Author(s):  
Minh Tam Le ◽  
Van Trung Nguyen ◽  
Thi Tam An Nguyen ◽  
Quang Trung Phan ◽  
Ngoc Thanh Cao
Keyword(s):  
Gradient Method ◽  
Artificial Insemination ◽  
Sperm Count ◽  
Gradient Methods ◽  
Infertility Treatment ◽  
University Hospital ◽  
Preparation Methods ◽  
Sperm Preparation ◽  
Abnormal Morphology ◽  
Sperm Washing

Objectives: Artificial insemination with sperm preparation and inseminate to the uterus is a common method of infertility treatment. Currently two methods used for sperm washing is “swim-up” and “gradient”. Materials and methods:cross-sectional description in 166 cycles of artificial insemination in Hue University Hospital from April, 2012 to March, 2013 in order to compare effectiveness between “swim-up” and “gradient” methods. Samples were collected randomly into two methods. Results:Results of sperm preparation in both methods are equivalent in terms of the following parameters total sperm count, total number of progressive sperm, total good morphology sperm. However, “gradient” method results in higher number of progressive sperm in case with slow motility (38.3% vs. 26.1%) or abnormal morphology (34.9% vs. 19.7 %) compared with “swim-up” method. Pregnancy rates after artificial insemination were similar between two preparation methods. Conclusion:In case of slow motility sperm and abnormal morphology, “gradient” method should be used to increase the number of progressive sperms. Pregnancy outcome depends on many factors other than preparation methods. Key words: Artificial insemination, sperm preparation, infertility treatment

LC–MS-MS Method for the Determination of Antidepressants and Benzodiazepines in Meconium

2020 ◽  
Vol 44 (6) ◽  
pp. 580-588
Author(s):  
A López-Rabuñal ◽  
E Lendoiro ◽  
M Concheiro ◽  
M López-Rivadulla ◽  
A Cruz ◽  
...  
Keyword(s):  
Extraction Efficiency ◽  
Solid Phase ◽  
Gradient Methods ◽  
Reversed Phase ◽  
Process Efficiency ◽  
Limit Of Quantification ◽  
Mode 2 ◽  
Positive Mode ◽  
Compound Method

Abstract An LC–MS-MS method for the determination of 14 benzodiazepines (BZDs) (alprazolam, α-hydroxyalprazolam, clonazepam, bromazepam, diazepam, nordiazepam, lorazepam, lormetazepam, oxazepam, flunitrazepam, 7-aminoflunitrazepam, triazolam, midazolam and zolpidem) and 15 antidepressants (ADs) (amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, norclomipramine, fluoxetine, norfluoxetine, sertraline, norsertraline, paroxetine, venlafaxine, desmethylvenlafaxine, citalopram and desmethylcitalopram) in meconium was developed and validated. Meconium samples (0.25 ± 0.02 g) were homogenized in methanol and subjected to mixed-mode cation exchange solid-phase extraction. Chromatographic separation was performed in reversed phase, with a gradient of 0.1% formic acid in 2 mM ammonium formate and acetonitrile. Two different chromatographic gradient methods were employed, one for the separation of ADs and another for BZDs. Analytes were monitored by tandem mass spectrometry employing electrospray positive mode in MRM mode (2 transitions per compound). Method validation included: linearity [n = 5, limit of quantification (LOQ) to 400 ng/g], limits of detection (n = 6, 1–20 ng/g), LOQ (n = 9, 5–20 ng/g), selectivity (no endogenous or exogenous interferences), accuracy (n = 15, 90.6–111.5%), imprecision (n = 15, 0–14.6%), matrix effect (n = 10, −73 to 194.9%), extraction efficiency (n = 6, 35.9–91.2%), process efficiency (n = 6, 20.1–188.2%), stability 72 h in the autosampler (n = 3, −8.5 to 9%) and freeze/thaw stability (n = 3, −1.2 to −47%). The method was applied to four meconium specimens, which were analyzed with and without hydrolysis (enzymatic and alkaline). The authentic meconium samples tested positive for alprazolam, α-hydroxyalprazolam, clonazepam, diazepam, nordiazepam, fluoxetine, norfluoxetine, clomipramine and norclomipramine. Therefore, the present LC–MS-MS method allows a high throughput determination of the most common BZDs and ADs in meconium, which could be useful in clinical and forensic settings.

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