scholarly journals Relationship between diffraction peak, network topology, and amorphous-forming ability in silicon and silica

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinji Kohara ◽  
Motoki Shiga ◽  
Yohei Onodera ◽  
Hirokazu Masai ◽  
Akihiko Hirata ◽  
...  
Keyword(s):  
Network Topology ◽  
Volume Ratio ◽  
Diffraction Peak ◽  
Ring Size ◽  
Topological Features ◽  
Structural Descriptor ◽  
Significant Difference ◽  
Pairwise Correlations ◽  
Diffraction Patterns ◽  
Rule Out

AbstractThe network topology in disordered materials is an important structural descriptor for understanding the nature of disorder that is usually hidden in pairwise correlations. Here, we compare the covalent network topology of liquid and solidified silicon (Si) with that of silica (SiO2) on the basis of the analyses of the ring size and cavity distributions and tetrahedral order. We discover that the ring size distributions in amorphous (a)-Si are narrower and the cavity volume ratio is smaller than those in a-SiO2, which is a signature of poor amorphous-forming ability in a-Si. Moreover, a significant difference is found between the liquid topology of Si and that of SiO2. These topological features, which are reflected in diffraction patterns, explain why silica is an amorphous former, whereas it is impossible to prepare bulk a-Si. We conclude that the tetrahedral corner-sharing network of AX2, in which A is a fourfold cation and X is a twofold anion, as indicated by the first sharp diffraction peak, is an important motif for the amorphous-forming ability that can rule out a-Si as an amorphous former. This concept is consistent with the fact that an elemental material cannot form a bulk amorphous phase using melt quenching technique.

scholarly journals Experimental method to quantify the ring size distribution in silicate glasses and simulation validation thereof

2021 ◽  
Vol 7 (28) ◽  
pp. eabh1761
Author(s):  
Qi Zhou ◽  
Ying Shi ◽  
Binghui Deng ◽  
Jörg Neuefeind ◽  
Mathieu Bauchy
Keyword(s):  
Neutron Diffraction ◽  
Size Distribution ◽  
Diffraction Peak ◽  
Range Order ◽  
Silicate Glasses ◽  
Ring Size ◽  
Medium Range Order ◽  
Simulation Validation ◽  
Medium Range ◽  
Diffraction Patterns

Silicate glasses have no long-range order and exhibit a short-range order that is often fairly similar to that of their crystalline counterparts. Hence, the out-of-equilibrium nature of glasses is largely encoded in their medium-range order. However, the ring size distribution—the key feature of silicate glasses’ medium-range structure—remains invisible to conventional experiments and, hence, is largely unknown. Here, by combining neutron diffraction experiments and force-enhanced atomic refinement simulations for two archetypical silicate glasses, we show that rings of different sizes exhibit a distinct contribution to the first sharp diffraction peak in the structure factor. On the basis of these results, we demonstrate that the ring size distribution of silicate glasses can be determined solely from neutron diffraction patterns, by analyzing the shape of the first sharp diffraction peak. This method makes it possible to uncover the nature of silicate glasses’ medium-range order.

scholarly journals Simultaneous Multi-Bragg Peak Coherent X-ray Diffraction Imaging

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 312
Author(s):  
Florian Lauraux ◽  
Stéphane Labat ◽  
Sarah Yehya ◽  
Marie-Ingrid Richard ◽  
Steven J. Leake ◽  
...  
Keyword(s):  
Bragg Reflection ◽  
Volume Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Substrate ◽  
In Series ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Lattice Planes ◽  
Oriented Parallel

The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a goniometer so that two lattice planes fulfill the Bragg condition at the same time. The Au 111 and Au 200 Bragg peaks were measured simultaneously by scanning the energy of the incident X-ray beam and recording the diffraction patterns with two two-dimensional detectors. While the former Bragg reflection is not sensitive to the twin boundary, which is oriented parallel to the crystal–substrate interface, the latter reflection is only sensitive to one part of the crystal. The volume ratio between the two parts of the twinned crystal is about 1:9, which is also confirmed by Laue microdiffraction of the same crystal. The parallel measurement of multiple Bragg reflections is essential for future in situ and operando studies, which are so far limited to either a single Bragg reflection or several in series, to facilitate the precise monitoring of both the strain field and defects during the application of external stimuli.

Plastic deformations in kyanites by tectonometamorphic processes: a single-crystal X-ray diffraction study

2009 ◽  
Vol 73 (3) ◽  
pp. 359-371 ◽  
Author(s):  
G. D. Gatta ◽  
N. Rotiroti ◽  
M. Zucali
Keyword(s):  
Single Crystal ◽  
X Ray Diffraction ◽  
Plastic Deformations ◽  
X Ray ◽  
Deformational History ◽  
Significant Difference ◽  
Elliptical Section ◽  
History Of ◽  
Diffraction Patterns ◽  
Two Stages

AbstractThe crystalch emistry and crystal structure of naturalky anite crystals from the Eclogitic Micaschists Complex of the Sesia-Lanzo Zone, Western Italian Alps, have been investigated by means of optical microscopy, wavelength dispersive X-ray microanalysis, and single-crystal X-ray diffraction. The association of kyanite + garnet + phengitic-mica + chloritoid suggests that the eclogite-facies stages occurred at P ≤ 2.1 GPa and T ≤ 650ºC. Kyanite grains are large (cm-sized) porphyroblasts grown dynamically during one of the deformational events related to the subduction of the Austroalpine continentalcr ust. Under the polarizing microscope, kyanite grains show almost homogeneous cores, whereas rims are sometimes symplectitic aggregates of quartz and kyanite, confirming at least two stages of growth most likely related to the multistage deformational history of these rocks. Chemical analysis shows that Fe3+ is the major substituting cation for Al3+, ranging between 0.038 and 0.067 a.p.f.u.The single-crystal X-ray diffraction investigation of the kyanites shows severely textured patterns on the (h0l)*-plane. Such evidence is not observed in the unwarped diffraction patterns on (0kl)* and (hk0)*. The most significant difference between the structuralp arameters refined in this study, with respect to those of previously published unstrained gem-quality crystals, concerns the displacement parameters. The anisotropic displacement ellipsoids of all the atomic sites are significantly larger than those previously described, and systematically oriented with the largest elliptical section almost perpendicular to [010]. The larger ellipsoids in the kyanite crystal investigated here reflect the displacement of the centre of gravity of the electron distribution, rather than an anomalous atomic thermal motion. The magnitude and orientation of the displacement parameters and the textured/strained diffraction pattern may be the result of two combined effects: (1) that the kyanite crystals are actually composed of several blocks; (2) the crystals are affected by a pervasive residual strain, as a result of tectonometamorphic plastic deformations and re-crystallization.

scholarly journals Quantitative CT imaging features for COVID-19 evaluation: The ability to differentiate COVID-19 from non- COVID-19 (highly suspected) pneumonia patients during the epidemic period

PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0256194
Author(s):  
Shengkun Peng ◽  
Lingai Pan ◽  
Yang Guo ◽  
Bo Gong ◽  
Xiaobo Huang ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Ct Imaging ◽  
Lesion Volume ◽  
Component Ratio ◽  
Imaging Features ◽  
Quantitative Ct ◽  
Epidemic Period ◽  
Significant Difference ◽  
Sensitivity Specificity ◽  
Ct Features

Objectives COVID-19 and Non-Covid-19 (NC) Pneumonia encountered high CT imaging overlaps during pandemic. The study aims to evaluate the effectiveness of image-based quantitative CT features in discriminating COVID-19 from NC Pneumonia. Materials and methods 145 patients with highly suspected COVID-19 were retrospectively enrolled from four centers in Sichuan Province during January 23 to March 23, 2020. 88 cases were confirmed as COVID-19, and 57 patients were NC. The dataset was randomly divided by 3:2 into training and testing sets. The quantitative CT radiomics features were extracted and screened sequentially by correlation analysis, Mann-Whitney U test, the least absolute shrinkage and selection operator (LASSO) logistic regression (LR) and backward stepwise LR with minimum AIC methods. The selected features were used to construct the LR model for differentiating COVID-19 from NC. Meanwhile, the differentiation performance of traditional quantitative CT features such as lesion volume ratio, ground glass opacity (GGO) or consolidation volume ratio were also considered and compared with Radiomics-based method. The receiver operating characteristic curve (ROC) analysis were conducted to evaluate the predicting performance. Results Compared with traditional CT quantitative features, radiomics features performed best with the highest Area Under Curve (AUC), sensitivity, specificity and accuracy in the training (0.994, 0.942, 1.0 and 0.965) and testing sets (0.977, 0.944, 0.870, 0.915) (Delong test, P < 0.001). Among CT volume-ratio based models using lesion or GGO component ratio, the model combining CT lesion score and component ratio performed better than others, with the AUC, sensitivity, specificity and accuracy of 0.84, 0.692, 0.853, 0.756 in the training set and 0.779, 0.667, 0.826, 0.729 in the testing set. The significant difference of the most selected wavelet transformed radiomics features between COVID-19 and NC might well reflect the CT signs. Conclusions The differentiation between COVID-19 and NC could be well improved by using radiomics features, compared with traditional CT quantitative values.

scholarly journals Teething Problems and Parental Beliefs in Nigeria

2009 ◽  
Vol 10 (4) ◽  
pp. 75-82 ◽  
Author(s):  
Foluso J. Owotade ◽  
Morenike O. Folayan ◽  
Temitope A. Esan ◽  
Elizabeth O. Oziegbe ◽  
Comfort A. Adekoya-Sofowora
Keyword(s):  
Signs And Symptoms ◽  
Cross Sectional Study ◽  
Parental Beliefs ◽  
Cross Sectional ◽  
Socioeconomic Class ◽  
Low Socioeconomic ◽  
Significant Difference ◽  
And Gender ◽  
Symptoms And Signs ◽  
Rule Out

Abstract Aim To determine signs and symptoms associated with teething, parental beliefs about teething, and the effects of socioeconomic status on teething in Nigerian children. Methods and Materials A cross-sectional study consisting of 1,013 mothers of children between the ages four to 36 months who visited the immunization clinics at the Community Health Centres in Ife Central and Ife East Local Government Areas. Data was analyzed using STATA (Intercooled release 9) for Windows. Results A total of 765 mothers (75.5%) reported systemic signs and symptoms in their children. Fever (51.8%), diarrhea (12.5%), and vomiting (2.9%) were the most prevalent symptoms and signs reported. Teething problems were reported by 60% of mothers from a high socioeconomic class, as well as 76.7% and 77.9% from middle and low socioeconomic classes, respectively. Interestingly, 65.5% of mothers believed teething should be accompanied with systemic signs and symptoms such as fever (42.1%), diarrhea (13.9%), and vomiting (0.6%). No significant difference was noted between breastfeeding status, gender of the child, and reported systemic signs and symptoms noticed by the mothers. Conclusion Most mothers in the study reported signs and symptoms adduced to teething in their children irrespective of their beliefs. Fever ranked highest of the signs and symptoms reported. Mothers of children from the high socioeconomic class reported fewer teething symptoms. Breastfeeding status and gender of the child had no effect on teething problems in the children studied. Clinical Significance Most signs and symptoms adduced to teething by parents may actually be due to underlying infections. Thus, there is a need to rule out occult infection during the tooth eruption period. Citation Oziegbe EO, Folayan MO, Adekoya-Sofowora CA, Esan TA, Owotade FJ. Teething Problems and Parental Beliefs in Nigeria. J Contemp Dent Pract 2009 July; (10)4:075-082.

scholarly journals Enhanced Bactericidal Efficacy of NaOCl at pH 12 Followed by Acidified NaOCl at pH 6.5 on Enterococcus faecalis Biofilm

2020 ◽  
Vol 10 (17) ◽  
pp. 6096
Author(s):  
Ronald Wigler ◽  
Shlomo Matalon ◽  
Tomer Goldberger ◽  
Anat Or Lerner ◽  
Anda Kfir
Keyword(s):  
Contact Time ◽  
Laser Scanning ◽  
Saline Solution ◽  
Volume Ratio ◽  
Bactericidal Effect ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Red Fluorescence ◽  
Bactericidal Efficacy ◽  
Significant Difference

This study aimed to determine the bactericidal efficacy of sequential use of NaOCl pH 12 followed by acidified NaOCl pH 6.5, and compare it to that of either of these NaOCl solutions alone. E. faecalis biofilm was grown on standardized dentine specimens for four weeks. The specimens were randomly divided into four groups: (A) 4 min exposure to 0.9% saline solution (control); (B) 4 min exposure to 4% NaOCl pH 12; (C) 4 min exposure to 4% NaOCl pH 6.5; and (D) 2 min exposure to 4% NaOCl pH 12 followed by 2 min exposure to 4% NaOCl pH 6.5. The bactericidal activity was evaluated after the 4 min of contact time using confocal laser scanning microscopy. The volume ratio of red fluorescence to green and red fluorescence indicated the proportion of dead cells in the biofilm. The percent of dead cells in the saline solution group was significantly lower than those in the other groups. There was no significant difference between NaOCl pH 12 compared to NaOCl pH 6.5. The sequential use of NaOCl pH 12 followed by pH 6.5 significantly increased the percent of dead cells compared to both the samples exposed to either NaOCl pH 12 or pH 6.5. These results show that sequential irrigation protocol had a stronger bactericidal effect than the commonly used NaOCl pH 12.

scholarly journals Synthesis and Characterization of Reduced Graphene Oxide (rGO) Started from Graphene Oxide (GO) Using the Tour Method with Different Parameters

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Adere Tarekegne Habte ◽  
Delele Worku Ayele
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Potassium Permanganate ◽  
Chemical Reduction ◽  
Volume Ratio ◽  
Graphite Powder ◽  
Green Approach ◽  
Synthesis Strategy ◽  
Reduced Graphene ◽  
Diffraction Patterns

A new approach to synthesize graphene is oxidizing graphite powder with a mixture of H2SO4/H3PO4 acids and potassium permanganate. Parameters such as reaction time, reaction temperature, and amount of concentration were varied to study the degree of oxidation of graphite to graphene oxide. Currently, an improved method for the preparation of graphene oxide was the most common one. A mixture of H2SO4/H3PO4 (9 : 1 volume ratio) instead of only H2SO4 resulted in increased hydrophilic and oxidized GO without the emission of toxic gas, which differs from the traditional Hummers’ method. The graphene oxide (GO) was converted to reduced graphene oxide (rGO) by chemical reduction using ascorbic acid as the reducing agent. The GO and rGO were characterized by UV-visible spectroscopy, FTIR spectroscopy, and X-ray diffraction patterns. The result showed that treating graphite powder with potassium permanganate (1 : 9) and a mixture of concentrated H2SO4/H3PO4 acids at 50°C for 12 hours resulted in a better oxidation degree. The designed synthesis strategy could be easily controlled and is an alternative green approach for the production of graphene oxide and reduced graphene oxide.

UMWEG-98: a program for calculation and graphical representation of multiple diffraction patterns

1999 ◽  
Vol 32 (2) ◽  
pp. 355-361 ◽  
Author(s):  
Elisabeth Rossmanith
Keyword(s):  
Graphical Representation ◽  
Software Tool ◽  
Crystal Structure Analysis ◽  
Diffraction Peak ◽  
Current Version ◽  
Multiple Diffraction ◽  
Peak Location ◽  
Diffraction Patterns ◽  
Diffraction Effects ◽  
A Current

UMWEG-XX was designed as a software tool for taking into account multiple diffraction effects in many areas of crystal structure analysis. TheUMWEG-98 version of the program makes possible the calculation and graphical representation of multiple diffraction patterns (Renninger scans, multiple diffraction peak location plots) of forbidden and weak reflections and can be applied to synchrotron as well asKα1,2radiation. The program is written in standard Fortran90 and may be ported to Unix platforms, such as HP, Sun, Silicon Graphics and IBM, as well as to DOS and Windows platforms. The program runs without any commercial subroutine libraries. Consequently it can be used without licence problems. A current version is distributedviahttp://www.rrz.uni-hamburg.de/mpi/rossmanith. Executable (binary) files are available free of charge for academic use only.

High-resolution TEM and XRD simulation of stacking disorder in 2:1 phyllosilicates

2008 ◽  
Vol 223 (01-02) ◽  
Author(s):  
Toshihiro Kogure ◽  
Jun Kameda
Keyword(s):  
High Resolution ◽  
Lateral Displacement ◽  
X Ray ◽  
Transmission Electron ◽  
Significant Difference ◽  
High Resolution Tem ◽  
Interlayer Region ◽  
Diffraction Patterns ◽  
Two Alternatives ◽  
Stacking Disorder

Stacking disorder is a common phenomenon in phyllosilicates but its nature is difficult to be deduced using conventional diffraction techniques. In contrast, recent investigations using high-resolution transmission electron microscopy (HRTEM) have elucidated the structure of stacking disorder in various phyllosilicates, by directly observing individual layers and stacking sequences. Furthermore, simulations of X-ray or electron diffraction patterns using the information from the HRTEM results can complement the limited analysis area in TEM and quantify the density of the stacking disorder.Although the bonding between adjacent layers is similar, there is a significant difference in the stacking disorder between two counterparts of dioctahedral and trioctahedral 2 : 1 phyllosilicates: pyrophyllite vs. talc and sudoite vs. trioctahedral chlorite. In pyrophyllite and sudoite, stacking disorder is caused mainly by two alternatives of the lateral displacement directions between the two tetrahedral sheets across the interlayer region. On the other hand, rotation of 2 : 1 layer is also an origin of the stacking disorder in talc and trioctahedral chlorite. This difference is explained by the corrugation of basal oxygen planes on the dioctahedral 2 : 1 layer formed by the tetrahedral tilting to enlarge

scholarly journals EEG functional network topology is associated with disability in patients with amyotrophic lateral sclerosis

2016 ◽  
Author(s):  
Matteo Fraschini ◽  
Matteo Demuru ◽  
Arjan Hillebrand ◽  
Lorenza Cuccu ◽  
Silvia Porcu ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Network Topology ◽  
Resting State ◽  
Minimum Spanning Tree ◽  
Clinical Status ◽  
Functional Network ◽  
Phase Lag ◽  
Beta Band ◽  
Significant Difference ◽  
Lateral Sclerosis

ABSTRACTAmyotrophic Lateral Sclerosis (ALS) is one of the most severe neurodegenerative diseases, which is known to affect upper and lower motor neurons. In contrast to the classical tenet that ALS represents the outcome of extensive and progressive impairment of a fixed set of motor connections, recent neuroimaging findings suggest that the disease spreads along vast non-motor connections. Here, we hypothesised that functional network topology is perturbed in ALS, and that this reorganisation is associated with disability. We tested this hypothesis in 21 patients affected by ALS at several stages of impairment using resting-state electroencephalography (EEG) and compared the results to 16 age-matched healthy controls. We estimated functional connectivity using the Phase Lag Index (PLI), and characterized the network topology using the minimum spanning tree (MST). We found a significant difference between groups in terms of MST dissimilarity and MST leaf fraction in the beta band. Moreover, some MST parameters (leaf, hierarchy and kappa) significantly correlated with disability. These findings suggest that the topology of resting-state functional networks in ALS is affected by the disease in relation to disability. EEG network analysis may be of help in monitoring and evaluating the clinical status of ALS patients.

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