ionization source
Recently Published Documents


TOTAL DOCUMENTS

629
(FIVE YEARS 139)

H-INDEX

45
(FIVE YEARS 6)

Author(s):  
Lucas Fuster ◽  
Gerjan J M Hagelaar ◽  
Romain Pascaud ◽  
Antoine Simon ◽  
Patrick Hoffmann ◽  
...  

Abstract Plasma-based microwave power limitation in a suspended microstrip transmission line integrating a micro hollow cathode discharge (MHCD) in its center is experimentally and numerically studied. Transient and steady state microwave power measurements exhibit a limitation threshold of 28 dBm and time responses of 25 microseconds. Intensified charge-coupled device (ICCD) imaging shows that microwave breakdown occurs at the top of the MHCD. The plasma then extends towards the microwave source within the suspended microstrip transmission line. Besides, a self-consistent model is proposed to simulate the non-linear interaction between microwave and plasma. It gives numerical results in great agreement with the measurements, and show that the plasma expansion during the transient response is related to a shift between the ionization source term and the electron density maximum. The propagation speed, under the tested conditions, depends mainly on the stepwise ionization from the excited states.


2021 ◽  
pp. 393-404
Author(s):  
М.П. Разгонова ◽  
А.Ш. Сабитов ◽  
Е.В. Перминова ◽  
Н.М. Михайлова ◽  
К.С. Голохваст

Виноград амурский Vitis amurensis Ruprecht содержит большое количество полифенольных комплексов, являющихся биологически активными соединениями. В данной работе впервые проведено сравнительное метаболомное исследование биологически активных веществ дикого винограда, собранного из пяти различных мест Приморского и Хабаровского краёв. Для идентификации целевых аналитов в этанольных экстрактах ягод винограда использована высокоэффективная жидкостная хроматография (ВЭЖХ) в комплексе с ионной ловушкой amaZon SL, оснащенной источником ионизации электрораспылением ESI в режимах отрицательных и положительных ионов. Масс-спектрометр использовался в диапазоне сканирования m/z 100 - 1.700 для MС и МС/МС. Использовано фрагментирование 4-го порядка. Первичные масс-спектрометрические результаты показали присутствие 94 биологически активных соединений, соответствующих виду V. Amurensis ; причем сальвианоловые кислоты F, D и G, олеаноловая, урсоловая, миристолеиновая кислоты, берберицинин, меарнсетин, эскулин, невадензин, стигмастерол, фукостерол, флоризин, триптофан идентифицированы впервые в V. amurensis . Vitis amurensis Ruprecht contains a large number of polyphenolic compounds which are the biologically active components. In this work, for the first time, a comparative metabolomic study of biologically active substances of wild grapes collected from five different places of the Primorsky and Khabarovsk territories is carried out. To identify target analytes in ethanol extracts of grape berries, high performance liquid chromatography (HPLC) was used in combination with an amaZon SL ion trap (manufactured by BRUKER DALTONIKS, Germany) equipped with an ESI electrospray ionization source in negative and positive ion modes. The mass spectrometer was used in the scan range m / z 100 - 1.700 for MS and MS/MS. The fragmentation of the 4 order was used. Primary mass spectrometric results showed presence of 94 biologically active compounds corresponding to the species V. amurensis ; moreover, salvianolic acids F, D and G, oleanoic, ursolic, myristoleic acids, berbericinin, mearnsetin, esculin, nevadensin, stigmasterol, fucosterol, phlorizin, L-tryptophan were identified for the first time in V. amurensis .


Author(s):  
Süleyman Gökce ◽  
Ayşen Höl ◽  
Ibrahim Bulduk

Aims: Favipiravir (FVP) is a drug developed against RNA viruses. It is a drug that is used actively in the treatment of coronavirus. In vitro and in vivo investigations have shown that it inhibits the virus. In this study, a recovery study of tablet formulations was carried out by developing a UPLC-MS/MS method, which is used extensively in pandemic conditions. In addition, stability studies of favipiravir agent under forced conditions were conducted. The validated method is selective, robust, simple and applicable for tablet analysis. C18 (4.6 mm × 50 mm, 2.7 μm) column was used as the stationary phase and water-methanol (80-20 v/v) containing 0.1% formic acid was used as the mobile phase. UPLC optimization; It was conducted at a wavelength of 222 nm and a flow rate of 0.8 mL/min at 40 °C, retention time was 1.155 min. The electrospray jet stream ionization source was analyzed using mass spectrometry in negative ion mode. The molecular peak for Favipiravir was [M-1] 155.9, and the daughter ion determined 112.6. The stability test method was carried out in accordance with the ICH procedure. Reaction and degradation rates of the active substance under various forced conditions (acidic, basic, oxidative, UV light and thermal conditions) were investigated. The products formed by the decomposition of the active substance under stress conditions were determined by mass spectroscopy.


2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Avinash Dalmia ◽  
Erasmus Cudjoe ◽  
Jacob Jalali ◽  
Feng Qin

Abstract Background Pesticide testing for hemp has traditionally focused on techniques like QuEChERS with dSPE and SPE which demand time-consuming sample preparation, typically resulting in poor recovery rates for some pesticides, and requires the use of both LC-MS/MS and GC-MS/MS based instruments to cover the analysis for all regulated pesticides. In this study, we describe a streamlined approach for working with LC-MS/MS featuring a dual electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources using solvent extraction for faster and easier sample preparation and with 80–120% recovery for the analysis of all of 66 pesticides (regulated by California state in cannabis) with low detection limits in hemp. Methods A simple solvent extraction with acetonitrile was used to extract pesticides from hemp. A LC-MS/MS system with dual ESI and APCI source was used to determine sensitivity for the analysis of 66 pesticides in hemp matrix, 62 pesticides were analyzed using an 18-min LC-MS/MS method with an ESI source and the other 4 pesticides were measured using a 6-min LC-MS/MS method with an APCI source. Results The limit of quantitation (LOQ) of all 66 pesticides in hemp was in the range of 0.0025–0.1 μg/g which was well below the California state action limits of these analytes in cannabis products. A simple, fast, and cost-effective solvent extraction method was used for sample preparation to get good recovery in the range of 80–120% with RSD less than 20%. The unique ionization mechanism of chlorinated pesticides such as pentachloronitrobenzene using the LC-MS/MS system with an APCI source was elucidated. The proficiency test report generated with the LC-MS/MS method showed acceptable results for all of 66 pesticides in hemp with all of th z scores less than 2 with no false positives and negatives. The stability data collected over 5 days showed RSD less than 20% for 66 pesticides in hemp, and this demonstrated the robustness of the LC-MS/MS system used in this work. Conclusions A LC-MS/MS method with dual ESI and APCI sources was developed for the analysis of 66 pesticides in hemp. The recovery of all pesticides from a hemp matrix was in the acceptable range of 80–120% with RSD less than 20%.


2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Ana Cláudia Raposo ◽  
Carlito Lebrilla ◽  
Ricardo Wagner Portela ◽  
Gege Xu ◽  
Arianne Pontes Oriá

Abstract Background Glycoproteins are important tear components that participate in the stability of the ocular surface. However, the glycopeptides that are present in the tears of wild animals have not yet been described. This work aimed to describe the glycoproteomic profile of roadside hawk (Rupornis magnirostris) and caiman (Caiman latirostris) tears. Methods Tears collected from 10 hawks and 70 caimans using Schirmer tear test strips were used in this study. The samples were submitted to trypsin digestion and separated using a reverse-phase column coupled to a mass spectrometer associated to a nanospray ionization source. The glycoproteins were categorized as: cellular components, biological processes and molecular function, according to the UniProt Knowledgebase. Results As shown by the liquid chromatography–mass spectrometry, all glycopeptides found were classified as N-type. Of the 51 glycoproteins that were identified in the hawk tear film, the most abundant were ovotransferrin, globulins and complement system proteins. In the caiman tear film, 29 glycoproteins were identified. The most abundant caiman glycoproteins were uncharacterized proteins, ATPases, globulins and proteasome components. Ontological characterization revealed that the glycoproteins were extracellular, and the most identified molecular function was endopeptidase activity for both species. Conclusion Glycoproteins are abundant in the tear film of the bird and reptile species studied herein, and all these molecules were shown to have N-type modifications. Location at the extracellular space and an endopeptidase inhibitor activity were the main cell component and molecular function for both species, respectively. These profiles showed differences when compared to human tears, are possibly linked to adaptive processes and can be the basis for further studies on the search of disease biomarkers.


2021 ◽  
Author(s):  
Livia Casali ◽  
David Eldon ◽  
Adam G McLean ◽  
Tom H Osborne ◽  
Anthony W Leonard ◽  
...  

Abstract A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behaviour between the two impurities is confirmed by SOLPS-ITER modelling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral-neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modelling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.


2021 ◽  
Author(s):  
Ahmad Muhammad ◽  
Fatih Külahcı

Abstract The exhalation of geochemical entities from soil to air is significant to understand Lithosphere-Atmospheric relationships. Some of these geochemical entities are capable of modifying the lower atmosphere, and they are employed in various studies. Radon is one of the geochemical gasses widely recognized as a dominant ionization source in near ground regions of the troposphere. The steady state Rn transport equation is considered in many cases for estimating Rn migration from soil to air on the condition that the time evolution is ignored. A method is proposed for estimating radon space-time transport from soil to air. This is achieved by solving the radon transport equation in soil with special boundary conditions. Similar results are obtained with some experimented models, as well as reported radon values in literature for some set of parameter combinations. Strengths and limitations of the method are discussed. The model is useable to study Lithosphere-Atmosphere relationships. It can also be significant in other studies like the Global Electric Circuit or Seismo-Ionospheric studies.


Sign in / Sign up

Export Citation Format

Share Document