Quantitation of the Lateral Orientational Order in Poly(p-Phenylene Terephthalamide) Fibers with X-ray Linear Dichroism Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 812-813
Author(s):  
A. P. Smith ◽  
A. Garcia ◽  
H. Ade
Keyword(s):  
Internal Structure ◽  
Orientational Order ◽  
Analytical Techniques ◽  
Polymeric Materials ◽  
Linear Dichroism ◽  
Specific Chemical ◽  
X Ray ◽  
Radial Orientation ◽  
First Time

Determination of internal structure of complex polymeric materials often requires a variety of analytical techniques. One technique that we have developed and recently employed for the first time for quantitative analysis is x-ray linear dichroism microscopy. With sensitivity to the presence and orientation of specific chemical functionalities within polymer molecules, x-ray linear dichroism microscopy provides a powerful tool to probe the internal structure of such molecules. We have used this ability to quantitatively analyze the lateral orientational order (tangential and radial orientation of transverse sections) within different grades of poly(p-phenylene terephthalamide) (Kevlar) fibers.Kevlar fibers are highly crystalline and possess a complicated internal structure that exhibits lateral radial orientation. Figure 1 shows x-ray micrographs of (a) Kevlar 149, (b) Kevlar 49 and (c) Kevlar 29 fibers imaged at a photon energy specific to the aromatic functionality.

Sphere-like CoS with nanostructures as peroxidase mimics for colorimetric determination of H2O2 and mercury ions

RSC Advances ◽  
2016 ◽  
Vol 6 (71) ◽  
pp. 66963-66970 ◽  
Author(s):  
Haiguan Yang ◽  
Junqi Zha ◽  
Peng Zhang ◽  
Yuhao Xiong ◽  
Linjing Su ◽  
...  
Keyword(s):  
Solvothermal Method ◽  
Analytical Techniques ◽  
Colorimetric Determination ◽  
Mercury Ions ◽  
Peroxidase Mimics ◽  
First Time ◽  
Facile Solvothermal Method

CoS, which was prepared using a facile solvothermal method, and characterized using various analytical techniques, was demonstrated for the first time to exhibit intrinsic peroxidase-like activity.

scholarly journals Unraveling the long-pursued Au144 structure by x-ray crystallography

2018 ◽  
Vol 4 (10) ◽  
pp. eaat7259 ◽  
Author(s):  
Nan Yan ◽  
Nan Xia ◽  
Lingwen Liao ◽  
Min Zhu ◽  
Fengming Jin ◽  
...  
Keyword(s):  
Metal Nanoparticles ◽  
Weak Interactions ◽  
Gold Nanoclusters ◽  
Atomic Level ◽  
High Quality ◽  
X Ray ◽  
X Ray Crystallography ◽  
Quantum Size ◽  
First Time

The transition from nanocluster to nanocrystal is a central issue in nanoscience. The atomic structure determination of metal nanoparticles in the transition size range is challenging and particularly important in understanding the quantum size effect at the atomic level. On the basis of the rationale that the intra- and interparticle weak interactions play critical roles in growing high-quality single crystals of metal nanoparticles, we have reproducibly obtained ideal crystals of Au144(SR)60 and successfully solved its structure by x-ray crystallography (XRC); this structure was theoretically predicted a decade ago and has long been pursued experimentally but without success until now. Here, XRC reveals an interesting Au12 hollow icosahedron in thiolated gold nanoclusters for the first time. The Au–Au bond length, close to that of bulk gold, shows better thermal extensibility than the other Au–Au bond lengths in Au144(SR)60, providing an atomic-level perspective because metal generally shows better thermal extensibility than nonmetal materials. Thus, our work not only reveals the mysterious, long experimentally pursued structure of a transition-sized nanoparticle but also has important implications for the growth of high-quality, single-crystal nanoparticles, as well as for the understanding of the thermal extensibility of metals from the perspective of chemical bonding.

Synthesis of 2', 6'-Dihydroxychalcones by Using Tetrahydropyran-2-yl and Trialkylsilyl Protective Groups; the Crystal Structure Determination of 2',6'-Dihydroxy-2,4,6-trimethoxychalcone

1989 ◽  
Vol 42 (7) ◽  
pp. 1103 ◽  
Author(s):  
CO Miles ◽  
L Main ◽  
BK Nicholson
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Silyl Ether ◽  
X Ray ◽  
Protective Groups ◽  
Intramolecular Hydrogen ◽  
First Time ◽  
Mild Acid

Two improved general routes to 2′,6′-dihydroxychalcones are described in which the final step is protective-group removal from O 2′ under mild acid conditions. The first involves base-catalysed condensation of benzaldehydes with 2′-hydroxy-6′-tetrahydropyran-2-yloxyacetophenone, the second ring-opening of 5-hydroxyflavanones with 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a trialkylchlorosilane to trap out the chalcone as a bis silyl ether. Chalcones prepared by the first route are 2',6'-dihydroxychalcone (1), and its 4-methoxy (2), 3,4-dimethoxy (3), 3,4,5-trimethoxy (4), and 2,4,6-trimethoxy (5) derivatives. The 4-chloro derivative (6) and the chalcone from hesperetin are prepared by the second method. .The X-ray crystal structure of 2',6'-dihydroxy-2,4,6-trimethoxychalcone (5), the first for a 2',6′-dihydroxychalcone, is reported, the hydrogen involved in intramolecular hydrogen-bonding between the carbonyl and phenolic oxygens being located for the first time for any 2'-hydroxychalcone derivative. The O 6' involved in the intramolecular hydrogen-bonding is also hydrogen-bonded intermolecularly to the hydrogen of the other (2'-)hydroxy group of a neighbouring molecule in the lattice. 13C n.m.r. data are the first reported for a series of 2',6'-dihydroxychalcones.

Determination of the photoelectron emission probability with inclined X-ray Laue diffraction

1986 ◽  
Vol 42 (1) ◽  
pp. 24-29 ◽  
Author(s):  
A. M. Afanas'ev ◽  
R. M. Imamov ◽  
E. Kh. Mukhamedzhanov ◽  
A. N. Chuzo
Keyword(s):  
Angular Dependence ◽  
Direct Method ◽  
Simple Relation ◽  
Photoelectron Emission ◽  
Laue Diffraction ◽  
X Ray ◽  
Different Depths ◽  
First Time ◽  
A Direct Method

A simple relation has been established between the Fourier component of the probability density P(z) of photoelectron emission from different depths of a crystal and the angular dependence of the emission of photoelectrons formed in inclined X-ray Laue diffraction, which for the first time permitted the use of a direct method for the reconstruction of the P(z) function. Accurate measurements of the angular dependence of photoelectron emission were carried out on a silicon single crystal with diffraction of Cu Kα radiation for different energy ranges. Photoelectrons were recorded by a proportional gas counter specially designed for the energy analysis of photoelectrons under inclined Laue diffraction conditions. The laws predicted by the theory have been fully confirmed, and the corresponding P(z) functions have been obtained.

Erratum: Determination of the Orbital Polarization inYTiO3by Using Soft X-Ray Linear Dichroism [Phys. Rev. Lett.93, 257207 (2004)]

2006 ◽  
Vol 97 (13) ◽  
Author(s):  
F. Iga ◽  
M. Tsubota ◽  
M. Sawada ◽  
H. B. Huang ◽  
S. Kura ◽  
...  
Keyword(s):  
Linear Dichroism ◽  
X Ray

Mass Absorption Coefficient Determination Using Compton Scattered Tube Radiation: Applications, Limitations and Pitfalls

1990 ◽  
Vol 34 ◽  
pp. 243-261
Author(s):  
J. P. Willis
Keyword(s):  
Matrix Effects ◽  
Analytical Techniques ◽  
Trace Element Determination ◽  
Element Determination ◽  
X Ray ◽  
Mass Absorption ◽  
Peak Intensity ◽  
Almost All ◽  
The Relationship

Trace element determination by X-ray fluorescence spectrometry is subject, like almost all instrumental analytical techniques, to systematic errors, also known as matrix effects. This paper deals with the determination of mass absorption coefficients (MACs), using Compton peak intensities, for the correction of matrix effects arising only from elemental absorption in the sample.When absorption effects are significant the relationship between net analyte peak intensity and concentration will no longer be constant, and corrections will be necessary for accurate analyses.

scholarly journals Quick Analysis of Organic Amendments via Portable X-ray Fluorescence Spectrometry

2019 ◽  
Vol 16 (22) ◽  
pp. 4317 ◽  
Author(s):  
Rafael López-Núñez ◽  
Fátima Ajmal-Poley ◽  
José A. González-Pérez ◽  
Miguel Angel Bello-López ◽  
Pilar Burgos-Doménech
Keyword(s):  
Organic Matter Content ◽  
Organic Amendments ◽  
Analytical Techniques ◽  
Matter Content ◽  
Field Analysis ◽  
Elemental Content ◽  
Aqua Regia ◽  
X Ray ◽  
Total Elemental Content

The determination of heavy metals in soils and organic amendments, such as compost, manure, biofertilizer, and sludge, generally involves the digestion of samples with aqua regia, and the determination of those in the solution using various techniques. Portable X-ray fluorescence (PXRF) has many advantages in relation to traditional analytical techniques. However, PXRF determines the total elemental content and, until now, its use for the analysis of organic amendments has been limited. The objective of this work is the calibration of a PXRF instrument to determine the aqua regia-soluble elemental contents directly in solid samples of organic amendments. Our proposal will avoid the digestion step and the use of other laboratory techniques. Using a training set of samples, calibration functions were obtained that allow the determination of the aqua regia-soluble contents from the PXRF readings of total contents. The calibration functions (obtained by multiple linear regression) allowed the quantitative determination of the aqua regia-soluble contents of Fe, K, P, S, Zn, Cu, Pb, Sr, Cr, and Mn, as well as the organic matter content and a semi-quantitative assessment of Al, Ca, V, Ba, Ni, and As contents. The readings of Si, Fe, Al, Ca, K, or S were used as correction factors, indicating that the calibrations functions found are truly based on the chemical composition of the sample matrix. This study will allow a fast, cheap, and reliable field analysis of organic amendments and of other biomass-based materials.

scholarly journals The First Occurrence of Asbestiform Magnesio-Riebeckite in Schists in the Frido Unit (Pollino Unesco Global Geopark, Southern Italy)

Fibers ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 79 ◽  
Author(s):  
Salvatore Laurita ◽  
Giovanna Rizzo
Keyword(s):  
Southern Italy ◽  
Analytical Techniques ◽  
X Ray ◽  
Toxicological Studies ◽  
Xrf Scanning ◽  
First Occurrence ◽  
Micro Analysis ◽  
First Time ◽  
Index Mineral

In this paper, new mineralogical and petrographical data of asbestiform Magnesio-riebeckite from ophiolite cropping out in the Pollino Unesco Global Geopark (southern Italy) are presented. Magnesio-riebeckite schists with HP-LT index mineral assemblage recorded metamorphic events in blueschist facies in the Frido Unit. Previous toxicological studies showed that asbestiform Magnesio-riebeckite species exhibited high carcinogenicity in previous intraperitoneal injection experiments with rats. The results have been obtained using different analytical techniques such as X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and electron probe micro analysis (EPMA). Results show that all the samples contain fibrous Magnesio-riebeckite and/or prismatic, acicular crystals in aggregates. The concentration of elements in Magnesio-riebeckite crystals is: Na2O (4.12–6.26 wt%), MgO (8.22–10.87 wt%), FeO (19.07–23.81 wt%), SiO2 (52.05–56.06 wt%), CaO (1.12–4.53 wt%), Al2O3 (1.34–1.93 wt%), and MnO (0.10–0.34 wt%). Magnesio-riebeckite crystals are documented in the Pollino Unesco Global Geopark for the first time. For this reason, the aim of this paper is the characterization of Magnesio-riebeckite to improve the knowledge of this mineral in the studied area, because the release of fibers into the environment is dangerous for human health.

High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VI: Study of the Degradation of 271 Pesticide Residues in Aged Oolong Tea by Gas Chromatography-Tandem Mass Spectrometry and Its Application in Predicting the Residue Concentrations of Target Pesticides

2016 ◽  
Vol 99 (4) ◽  
pp. 1049-1057 ◽  
Author(s):  
Qiao-Ying Chang ◽  
Guo-Fang Pang ◽  
Chun-Lin Fan ◽  
Hui Chen ◽  
Zhi-Bin Wang
Keyword(s):  
Pesticide Residues ◽  
Analytical Techniques ◽  
Regression Equations ◽  
Oolong Tea ◽  
Chemical Pollutants ◽  
Chromatography Tandem Mass Spectrometry ◽  
Degradation Rates ◽  
Logarithmic Functions ◽  
First Time

Abstract The degradation rate of 271 pesticide residues in aged Oolong tea at two spray concentrations, named a and b (a < b), were monitored for 120 days using GC–tandem MS (GC-MS/MS). To research the degradation trends and establish regression equations, determination days were plotted as horizontal ordinates and the residue concentrations of pesticide were plotted as vertical ordinates. Here, we consider the degradation equations of 271 pesticides over 40 and 120 days, summarize the degradation rates in six aspects (A–F), and discuss the degradation trends of the 271 pesticides in aged Oolong tea in detail. The results indicate that >70% of the determined pesticides coincide with the degradation regularity of trends A, B, and E, i.e., the concentration of pesticide will decrease within 4 months. Next, 20 representative pesticides were selected for further study at higher spray concentrations, named c and d (d > c > b > a), in aged Oolong tea over another 90 days. The determination days were plotted on the x-axis, and the differences between each determined result and first-time-determined value of target pesticides were plotted on the y-axis. The logarithmic function was obtained by fitting the 90-day determination results, allowing the degradation value of a target pesticide on a specific day to be calculated. These logarithmic functions at d concentration were applied to predict the residue concentrations of pesticides at c concentration. Results revealed that 70% of the 20 pesticides had the lower deviation ratios of predicted and measured results.

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