scholarly journals Emerging role of local and extended range molecular structures on functionalities of topological phases of (Na 2 O) x (P 2 O 5 ) 100‐ x glasses using Raman scattering and modulated DSC

2020 ◽  
Vol 12 (1) ◽  
pp. 89-110 ◽  
Author(s):  
Avik Mandal ◽  
Vamshi Kiran Gogi ◽  
Chandi Mohanty ◽  
Ralph Chbeir ◽  
Punit Boolchand
Keyword(s):  
Raman Scattering ◽  
Molecular Structures ◽  
Modulated Dsc ◽  
Topological Phases ◽  
Extended Range

Exchange Spin Coupling from Gaussian Process Regression

2020 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Natnael Mogos ◽  
Jonny Proppe ◽  
Carmen Herrmann
Keyword(s):  
Machine Learning ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
Molecular Magnets ◽  
Molecular Structures ◽  
Spin Coupling ◽  
Structure Property ◽  
Data Set ◽  
Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

The Role of microRNAs in the Viral Infections

2019 ◽  
Vol 24 (39) ◽  
pp. 4659-4667 ◽  
Author(s):  
Mona Fani ◽  
Milad Zandi ◽  
Majid Rezayi ◽  
Nastaran Khodadad ◽  
Hadis Langari ◽  
...  
Keyword(s):  
Viral Infections ◽  
Rna Viruses ◽  
Regulation Of Gene Expression ◽  
Molecular Structures ◽  
Main Function ◽  
Cellular Functions ◽  
Viral Genes ◽  
Non Coding Rnas ◽  
Post Transcriptional Regulation

MicroRNAs (miRNAs) are non-coding RNAs with 19 to 24 nucleotides which are evolutionally conserved. MicroRNAs play a regulatory role in many cellular functions such as immune mechanisms, apoptosis, and tumorigenesis. The main function of miRNAs is the post-transcriptional regulation of gene expression via mRNA degradation or inhibition of translation. In fact, many of them act as an oncogene or tumor suppressor. These molecular structures participate in many physiological and pathological processes of the cell. The virus can also produce them for developing its pathogenic processes. It was initially thought that viruses without nuclear replication cycle such as Poxviridae and RNA viruses can not code miRNA, but recently, it has been proven that RNA viruses can also produce miRNA. The aim of this articles is to describe viral miRNAs biogenesis and their effects on cellular and viral genes.

The role of meteors in extended-range VHF propagation

2005 ◽  
Author(s):  
V. Eshleman ◽  
L. Manning ◽  
A. Peterson ◽  
O. Villard
Keyword(s):  
Extended Range

scholarly journals Simple Modeling of the Ratio of Fields at a Tip and a Contacting Surface with External Illumination

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
E. Bortchagovsky
Keyword(s):  
External Field ◽  
Raman Scattering ◽  
External Excitation ◽  
Exciting Field ◽  
Rayleigh Approximation ◽  
Surface Configuration ◽  
Standard Configuration ◽  
Enhanced Raman Scattering ◽  
Simple Modeling

The analysis of the relation of fields generated at a tip and a contacting surface is performed in the Rayleigh approximation of a simple dipole model for the standard configuration of tip-enhanced Raman scattering experiments with external excitation. A comparison of the present results with the previous ones obtained for the case of tip-source reveals the role of tip-surface configuration as the amplifier of the exciting field and the stronger influence of roughness on the field distribution at external illumination, as roughness is directly excited by the external field producing second source of field in addition to the tip.

Characterization of Thermophilic Bacteria Using Surface-Enhanced Raman Scattering

2008 ◽  
Vol 62 (11) ◽  
pp. 1226-1232 ◽  
Author(s):  
Mustafa Çulha ◽  
Ahmet Adigüzel ◽  
M. MÜGE Yazici ◽  
Mehmet Kahraman ◽  
Fikrettin Slahin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Raman Scattering ◽  
Elevated Temperatures ◽  
Thermophilic Bacteria ◽  
Surface Enhanced Raman Scattering ◽  
Molecular Structures ◽  
E Coli ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) can provide molecular-level information about the molecules and molecular structures in the vicinity of nanostructured noble metal surfaces such as gold and silver. The three thermophilic bacteria Bacillus licheniformis, Geobacillus stearothermophilus, and Geobacillus pallidus, a Gram-negative bacterium E. coli, and a Gram-positive bacterium B. megaterium are comparatively characterized using SERS. The SERS spectra of thermophilic bacteria are similar, while they show significant differences compared to E. coli and B. megaterium. The findings indicate that a higher number of thiol residues and possible S–S bridges are present in the cell wall structure of thermophilic bacteria, providing their stability at elevated temperatures. Incubating the thermophilic bacteria with colloidal silver suspension at longer times improved the bacteria–silver nanoparticle interaction kinetics, while increased temperature does not have a pronounced effect on spectral features. A tentative assignment of the SERS bands was attempted for thermophilic bacteria. The results indicate that SERS can be a useful tool to study bacterial cell wall molecular differences.

Studies Of Orientational Order Of Some Nematogens By Means Of Raman Scattering Spectroscopy

2004 ◽  
Vol 59 (7-8) ◽  
pp. 510-516 ◽  
Author(s):  
Ewa Chrzumnicka ◽  
Mirosław Szybowicz ◽  
Danuta Bauman
Keyword(s):  
Liquid Crystals ◽  
Raman Scattering ◽  
Orientational Order ◽  
Polarized Light ◽  
Molecular Structures ◽  
Raman Scattering Spectroscopy ◽  
Linearly Polarized ◽  
Scattering Spectra ◽  
Raman Scattering Spectra ◽  
Molecular Distribution Function

The orientational behaviour of some liquid crystals with various molecular structures was studied by means of the Raman scattering depolarization method. The Raman scattering spectra of linearly polarized light were recorded as a function of temperature in the nematic phase. On the basis of these spectra the order parameters 〈P2〉 and 〈P4〉 as well as the molecular distribution function were determined. The obtained data were compared with those estimated on the basis of polarized light absorption and emission measurements. The influence of the molecular structure on the orientational order of liquid crystals was discussed.

Unexpected formation and conversion: role of substituents of 1,3-ynones in the reactivity and product distribution during their reactions with Ru3(CO)12

2019 ◽  
Vol 43 (3) ◽  
pp. 1478-1486
Author(s):  
Lei Xu ◽  
Liping Jiang ◽  
Shasha Li ◽  
Guofang Zhang ◽  
Weiqiang Zhang ◽  
...  
Keyword(s):  
Product Distribution ◽  
Molecular Structures ◽  
Steric Effects ◽  
Unexpected Formation ◽  
Electronic And Steric Effects

Electronic and steric effects of the substituents in 1,3-ynones play key roles in the product distribution and molecular structures.

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