scholarly journals A Comparative Study of the UV Laser Ablation of Van Der Waals Films of Benzene Derivatives

1997 ◽  
Vol 17 (2) ◽  
pp. 73-95 ◽  
Author(s):  
S. Georgiou ◽  
A. Koubenakis ◽  
P. Kontoleta ◽  
M. Syrrou
Keyword(s):  
High Sensitivity ◽  
Chem Phys ◽  
Uv Laser ◽  
Quadrupole Mass ◽  
Absorbed Energy ◽  
Efficient Energy Transfer ◽  
The Matrix ◽  
History Of ◽  
193 Nm ◽  
Sputtering Yields

Ablation of thick (≈ 15 μm) films of C6H6, C6H5CH3 and C6H5CI at 248 nm and 193 nm is studied by means of time-of-flight quadrupole mass spectrometry. The dependence of the desorbate most probable translational energies on laser fluence is determined over the ≈20–200 mJ/cm2 range. In all cases, the corresponding diagrams are found to exhibit “plateaus”, in accord with the report by Braun and Hess [J. Chem. Phys. 99 (1993) 8330]. However, no specific correlation with the thermodynamic properties of the compounds is observed, thereby questioning the attribution of the “plateaus” to phase transformation of the films under ablation conditions. A high sensitivity of the distributions and intensities on the rate of deposition and the irradiation history of the films is observed, indicating the importance of the matrix “structure” for the distribution of the absorbed energy. On the other hand, the analysis of the total translational energies of the desorbates suggests that during ablation, efficient energy transfer occurs in the film. This possibility is further demonstrated by the observation of high translational energies and sputtering yields for C6H12(nonabsorbing at 248 nm) condensed in thickness of ≈ I μm on top of C6H5CH3 films. These observations can be qualitatively explained in terms of the collisional sequence model. Alternatively, a photothermal model may be applicable under the provision that energy distribution in the films is limited due to imperfections introducing barriers (bottlenecks) to its ‘flow’.

scholarly journals New UHPLC-QqQ-MS/MS Method for the Rapid and Sensitive Analysis of Ascorbic and Dehydroascorbic Acids in Plant Foods

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1632 ◽  
Author(s):  
Nieves Baenas ◽  
Francisco J. Salar ◽  
Raúl Domínguez-Perles ◽  
Cristina García-Viguera
Keyword(s):  
Matrix Effect ◽  
High Performance ◽  
High Selectivity ◽  
Dehydroascorbic Acid ◽  
High Sensitivity ◽  
Practical Application ◽  
Quadrupole Mass ◽  
Internal Standards ◽  
The Matrix

A new method using ultra high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS) methodology was developed for the determination of ascorbic acid (AA) and dehydroascorbic acid (DHAA) contents in liquid and solid vegetable samples. The advantages of this method are speed, high sensitivity and practical application. In accordance with these advantages, the present method allows the simultaneous determination of AA and DHAA without previous reduction/derivatization of DHAA and without the use of internal standards in the samples. This is of high interest in routine analysis, providing a simpler sample preparation, as well as enhanced accuracy and robustness. Its validation included selectivity, sensitivity and linearity, precision and accuracy, matrix effect, and recovery. The results showed high selectivity and sensitivity, with calibration curves ranging from 10 to 500 ng mL−1 and from 50 to 500 ng mL−1 for AA and DHAA, respectively. Appropriate dilutions for each sample are necessary to avoid the matrix effect with accepted recoveries.

scholarly journals In situ Rb-Sr dating by collision cell, multicollection inductively-coupled plasma mass-spectrometry with pre-cell mass-filter, (CC-MC-ICPMS/MS).

2021 ◽  
Author(s):  
Dan Bevan ◽  
Christopher David Coath ◽  
Jamie Lewis ◽  
Johannes B Schwieters ◽  
Nicholas Selwyn Lloyd ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Cell Mass ◽  
Quadrupole Mass Filter ◽  
Collision Cell ◽  
Uv Laser ◽  
Quadrupole Mass ◽  
Mass Filter ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

We document the utility for in situ Rb-Sr dating of a one-of-a-kind tribrid mass spectrometer, ‘Proteus’, coupled to a UV laser ablation system. Proteus combines a pre-cell quadrupole mass-filter,collision cell,...

scholarly journals Analytical angular solutions for the atom–diatom interaction potential in a basis set of products of two spherical harmonics: two approaches

2021 ◽  
Author(s):  
Mariusz Pawlak ◽  
Marcin Stachowiak
Keyword(s):  
Spherical Harmonics ◽  
Interaction Potential ◽  
Chem Phys ◽  
Basis Set ◽  
Matrix Elements ◽  
Trigonometric Functions ◽  
Variational Theory ◽  
Molecular Collision ◽  
The Matrix ◽  
Analytical Expressions

AbstractWe present general analytical expressions for the matrix elements of the atom–diatom interaction potential, expanded in terms of Legendre polynomials, in a basis set of products of two spherical harmonics, especially significant to the recently developed adiabatic variational theory for cold molecular collision experiments [J. Chem. Phys. 143, 074114 (2015); J. Phys. Chem. A 121, 2194 (2017)]. We used two approaches in our studies. The first involves the evaluation of the integral containing trigonometric functions with arbitrary powers. The second approach is based on the theorem of addition of spherical harmonics.

scholarly journals Patients With a History of Idiopathic Deep Venous Thrombosis Have Long-Term Increased Levels of Inflammatory Markers and Markers of Endothelial Damage

2016 ◽  
Vol 23 (2) ◽  
pp. 124-131 ◽  
Author(s):  
Mateja Kaja Jezovnik ◽  
Jawed Fareed ◽  
Pavel Poredos
Keyword(s):  
Inflammatory Markers ◽  
High Sensitivity ◽  
Endothelial Damage ◽  
Control Group ◽  
Necrosis Factor Alpha ◽  
Reactive Protein ◽  
Inflammatory Parameters ◽  
History Of ◽  
Hemostatic Markers

Introduction: Although the role of inflammation in DVT has been investigated in different studies, there is no definite answer as to whether increased systemic inflammation is the cause or the consequence of DVT. Aim: To follow inflammatory parameters in a cohort of patients with idiopathic DVT. Methods: Out of 49 patients with an acute idiopathic DVT, which were investigated four months after an acute episode (DEVTA 1), 43 patients were included in the follow-up study investigating inflammatory markers and hemostatic markers of endothelial damage five years after an acute DVT (DEVTA 2). A control group consisted of 43 sex and age matched healthy subjects (CONTROLS). Results: The levels of inflammatory markers were significantly higher in DEVTA 2 in comparison to CONTROLS: tumor necrosis factor alpha 2.0 pg/mL (1.1-2.3) vs 1.3 pg/mL (0.8-1.9), p < .001, high sensitivity C-reactive protein 3.2 mg/L (1.5-5.2) vs 1.7 mg/L (0.9-3.0), p = .008, interleukin-6 (IL-6) 2.7 pg/mL (2.0-3.5) vs 2.1 pg/mL (1.5-2.6), p = .025, IL-8 5.0 pg/mL (3.6-7.3) vs 2.4 pg/mL (1.8-2.8), p < .001. IL-10 was significantly decreased (0.9 pg/mL (0.7-1.8) vs 1.8 (1.5-2.2), p < .001. Most of the proinflammatory markers remained elevated in the DEVTA 2 in comparison to DEVTA 1. Markers of endothelial damage were higher in DEVTA 2 in comparison to CONTROLS and higher than in DEVTA 1. Conclusion: Patients with idiopathic DVT have long-term increased inflammatory markers and markers of endothelial damage. These findings favor the hypothesis that inflammation is a cause and not merely a consequence of acute DVT.

High-sensitivity quadrupole mass spectometry system for the determination of hydrogen in irradiated materials

2000 ◽  
Vol 283-287 ◽  
pp. 1006-1010 ◽  
Author(s):  
B.M Oliver ◽  
F.A Garner ◽  
L.R Greenwood ◽  
J.A Abrefah
Keyword(s):  
High Sensitivity ◽  
Quadrupole Mass ◽  
Mass Spectometry

scholarly journals New data towards the development of a comprehensive taphonomic framework for the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, Central Utah

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3368 ◽  
Author(s):  
Joseph E. Peterson ◽  
Jonathan P. Warnock ◽  
Shawn L. Eberhart ◽  
Steven R. Clawson ◽  
Christopher R. Noto
Keyword(s):  
Late Jurassic ◽  
Data Sets ◽  
Morrison Formation ◽  
Multiple Sources ◽  
Theropod Dinosaurs ◽  
The Matrix ◽  
Significant Step ◽  
Primary Driver ◽  
History Of ◽  
Bone Fragments

The Cleveland-Lloyd Dinosaur Quarry (CLDQ) is the densest deposit of Jurassic theropod dinosaurs discovered to date. Unlike typical Jurassic bone deposits, it is dominated by the presence ofAllosaurus fragilis. Since excavation began in the 1920s, numerous hypotheses have been put forward to explain the taphonomy of CLDQ, including a predator trap, a drought assemblage, and a poison spring. In an effort to reconcile the various interpretations of the quarry and reach a consensus on the depositional history of CLDQ, new data is required to develop a robust taphonomic framework congruent with all available data. Here we present two new data sets that aid in the development of such a robust taphonomic framework for CLDQ. First, x-ray fluorescence of CLDQ sediments indicate elevated barite and sulfide minerals relative to other sediments from the Morrison Formation in the region, suggesting an ephemeral environment dominated by periods of hypereutrophic conditions during bone accumulation. Second, the degree of abrasion and hydraulic equivalency of small bone fragments dispersed throughout the matrix were analyzed from CLDQ. Results of these analyses suggest that bone fragments are autochthonous or parautochthonous and are derived from bones deposited in the assemblage rather than transported. The variability in abrasion exhibited by the fragments is most parsimoniously explained by local periodic re-working and re-deposition during seasonal fluctuations throughout the duration of the quarry assemblage. Collectively, these data support previous interpretations that the CLDQ represents an attritional assemblage in a poorly-drained overbank deposit where vertebrate remains were introduced post-mortem to an ephemeral pond during flood conditions. Furthermore, while the elevated heavy metals detected at the Cleveland-Lloyd Dinosaur Quarry are not likely the primary driver for the accumulation of carcasses, they are likely the result of multiple sources; some metals may be derived from post-depositional and diagenetic processes, and others are potentially produced from an abundance of decomposing vertebrate carcasses. These new data help to support the inferred depositional environment of the quarry as an ephemeral pond, and represent a significant step in understanding the taphonomy of the bonebed and Late Jurassic paleoecology in this region.

scholarly journals Determination of oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin in mouse blood by UPLC-MS/MS and its application to pharmacokinetics

2021 ◽  
Author(s):  
Zheng Yu ◽  
Fan Chen ◽  
Yinan Jin ◽  
Minyue Zhou ◽  
Xianqin Wang ◽  
...  
Keyword(s):  
Mobile Phase ◽  
High Sensitivity ◽  
Gradient Elution ◽  
Oroxylin A ◽  
Mouse Blood ◽  
Multiple Reactions ◽  
Caudal Vein ◽  
The Matrix ◽  
Positive Ion

Abstract In this study, a UPLC-MS/MS method was developed to measure the concentrations of the flavonoids oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin in the blank mouse blood, and the method was then used in the measurement of the pharmacokinetics of the compounds in mice. Oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin were administered intravenously at a dose of 5 mg kg−1, and the mouse blood (20 μL) was withdrawn from the caudal vein 0.08333, 0.25, 0.5, 1, 2, 4, 6, 8, and 10 h after administration. The mobile phase used for chromatographic separation by gradient elution was composed of acetonitrile and water (0.1% formic acid). The analytes were detected by operating in electrospray ionization (ESI) positive-ion mode using multiple reactions monitoring (MRM). The intra-day and inter-day accuracy ranged from 86.2 to 109.3%, the intra-day precision was less than 14%, and the inter-day precision was less than 15%. The matrix effect ranged from 85.3 to 111.3%, and the recovery of the analytes after protein precipitation were all above 78.2%. This method had the advantages of high sensitivity, accuracy, and recovery, and it had excellent selectivity, which enabled it to be applied to measuring the pharmacokinetics of the analytes in mice.

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