Journal articles: 'Pulsed field ionisation'

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Suzuki, Kazunari, Shun-ichi Ishiuchi, Makoto Sakai, and Masaaki Fujii. "Pulsed field ionisation—ZEKE photoelectron spectrum of o-, m- and p-tolunitrile." Journal of Electron Spectroscopy and Related Phenomena 142, no. 3 (March 2005): 215–21. http://dx.doi.org/10.1016/j.elspec.2004.09.020.

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Purdie, PH, and J. Fletcher. "Charged Particle Transport in Gaseous Nitrogen at Intermediate E/N using the Voltage Transient Method." Australian Journal of Physics 45, no. 1 (1992): 75. http://dx.doi.org/10.1071/ph920075.

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A pulsed swarm of charged particles crossing an inter-electrode gap under the influence of an applied electric field E will produce a pulsed current in the external circuit which, when integrated over time, will result in a transient voltage pulse, the shape and magnitude of which is characteristic of the number and type of charged particles. This voltage transient technique has been used to investigate a gas discharge in nitrogen gas at values of EIN (the ratio of applied electric field to gas number density), such that ionisation is non-negligible. The voltage transients have been subjected to a theoretical analysis, which has previously been reported, which includes not only cathode and anode image terms but also both electron and ion diffusion terms. Electron transport parameters are reported for EIN ::; 350 Td (1 Td = 10-17 V cm2). Data are also obtained for the drift velocities and diffusion coefficients of the ions operative within the nitrogen discharge. An estimate is obtained for the collisional decay rate of Nt.

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Dieckmann, Ralf, Jens Andre Hammerl, Hartmut Hahmann, Amal Wicke, Sylvia Kleta, Piotr Wojciech Dabrowski, Andreas Nitsche, Maren Stämmler, Sascha Al Dahouk, and Peter Lasch. "Rapid characterisation of Klebsiella oxytoca isolates from contaminated liquid hand soap using mass spectrometry, FTIR and Raman spectroscopy." Faraday Discussions 187 (2016): 353–75. http://dx.doi.org/10.1039/c5fd00165j.

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Microbiological monitoring of consumer products and the efficiency of early warning systems and outbreak investigations depend on the rapid identification and strain characterisation of pathogens posing risks to the health and safety of consumers. This study evaluates the potential of three rapid analytical techniques for identification and subtyping of bacterial isolates obtained from a liquid hand soap product, which has been recalled and reported through the EU RAPEX system due to its severe bacterial contamination. Ten isolates recovered from two bottles of the product were identified as Klebsiella oxytoca and subtyped using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI TOF MS), near-infrared Fourier transform (NIR FT) Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Comparison of the classification results obtained by these phenotype-based techniques with outcomes of the DNA-based methods pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST) and single nucleotide polymorphism (SNP) analysis of whole-genome sequencing (WGS) data revealed a high level of concordance. In conclusion, a set of analytical techniques might be useful for rapid, reliable and cost-effective microbial typing to ensure safe consumer products and allow source tracking.

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Unnikrishnan, K. "Renormalised Perturbation Theory of Resonant Multiphoton Ionisation." Australian Journal of Physics 48, no. 5 (1995): 835. http://dx.doi.org/10.1071/ph950835.

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Perturbation theory of multiphoton ionisation due to a classical electromagnetic field is modified to allow for intermediate resonances with bound states. Complex energies, generally associated with resonances, do not enter into this formalism. For a monochromatic field of frequency u, a constant ionisation rate can then be defined unambiguously and only such continuum states are excited which correspond to the absorption of energy in integral multiples of hu. As an application, differential and total cross sections for the two-photon ionisation of hydrogen, for frequencies below the n = 3 resonance region, are obtained in closed form. Existing data for generalised cross sections, calculated numerically using the complex coordinate method, are in good agreement with the present results. Finally, the mean fractional ionisation resulting from a pulse of finite duration is estimated on the basis of the associated power spectrum. For short pulses, the time dependence of ionisation exhibits a departure from that expected of a time-independent rate.

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Malissiova, Eleni, Theofilos Papadopoulos, Aikaterini Kyriazi, Maria Mparda, Christina Sakorafa, Antonios Katsioulis, Anna Katsiaflaka, Maria Kyritsi, Antonios Zdragas, and Christos Hadjichristodoulou. "Differences in sheep and goats milk microbiological profile between conventional and organic farming systems in Greece." Journal of Dairy Research 84, no. 2 (March 15, 2017): 206–13. http://dx.doi.org/10.1017/s0022029917000103.

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The aim of this study was to examine differences in the microbiological profile and antimicrobial resistance of bacteria isolated from milk from organic and conventional sheep and goat farms. Twenty-five organic and 25 conventional sheep and goat farms in the region of Thessaly, Greece participated in this study. A standardised detailed questionnaire was used to describe farming practices. A total of 50 samples were collected and analysed for total viable count (TVC), total coliform count (TCC) and somatic cell count (SCC), whileStaphylococcus aureusandEscherichia coliwere isolated using standard methods. Isolates were identified at species level by Api-test and Matrix-Assisted Laser Desorption/Ionisation-Time of Flight Mass Spectrometry (MALDI-TOF MS). Susceptibility to a panel of 20 forE. coliand 16 forS. aureusantimicrobials was determined by the agar dilution method. Pulsed Field Gel Electrophoresis (PFGE) was performed forS. aureusandE. coliisolates to determine predominant clones. Lower counts of TVC, TCC and SCC were identified in milk from the organic farms, possibly due to differences in the hygienic farming practices found on those farms. API-tests and MALDI-TOF MS showed no significant differences in theS. aureusandE. coliisolates. Overall, antimicrobial resistance rates were low, while a statistically higher percentage was estimated among strains originating from conventional farms in comparison with organic farms, possibly due to the restriction of antibiotic use in organic farming. PFGE revealed diversity amongS. aureusandE. colipopulations in both organic and conventional farms indicating circulation of 2–3 main clones changing slightly during their evolution. Consequently, there is evidence that milk from the organic farms presents a better microbiological profile when compared with milk from conventional farms.

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Bernier Gosselin, Véronique, Simon Dufour, Pamela R. F. Adkins, and John R. Middleton. "Persistence of coagulase negative staphylococcal intramammary infections in dairy goats." Journal of Dairy Research 86, no. 2 (May 2019): 211–16. http://dx.doi.org/10.1017/s0022029919000311.

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AbstractThe objectives of the research described here were to describe the persistence of intramammary infections (IMI) caused by coagulase negative staphylococci (CNS) in goats using strain-typing, and to evaluate the relationship between species-specific CNS IMI and somatic cell score (SCS) at the udder-half level. Udder-half milk samples were collected from all 909 lactating goats (1817 halves; 1 blind half) in a single herd. Milk samples were cultured on Columbia blood agar, and 220 goats with at least one half yielding a single colony type CNS were enrolled for two additional half-level samplings at approximately 1-month intervals. Isolates were identified to the species level by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry or PCR amplification and partial sequencing of tuf or rpoB. An IMI was defined as persistent when ≥1 follow-up sample yielded the same species and strain as on Day 0 based on pulsed-field gel electrophoresis. A generalised mixed linear model was used to evaluate the odds of persistence as a function of CNS species. A mixed linear model was used to evaluate the relationship between IMI status on a given day and SCS. Among 192 IMI, 69.8% were persistent based on species and strain-type. Staphylococcus simulans IMI had higher odds of persistence than Staphylococcus arlettae IMI. In primiparous goats, Staphylococcus epidermidis IMI was associated with higher SCS than S. arlettae, Staphylococcus xylosus and ‘other CNS’ IMI. The differences detected in the present study between CNS species, with regard to persistence of IMI and association with SCS, highlight the need to study CNS at the species and strain level to understand the pathogenicity and epidemiology of CNS in goats.

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Liu, Hang, and Li-Qiang Feng. "Selection of Single Harmonic Emission Peak for Producing Isolated Attosecond Pulse via Chirped-UV Combined Field." Zeitschrift für Naturforschung A 75, no. 1 (December 18, 2019): 1–10. http://dx.doi.org/10.1515/zna-2019-0220.

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AbstractA potential method to produce isolated attosecond pulses (IAPs) by using low-intensity chirped-UV combined field has been investigated. The results can be separated into three parts. First, by properly introducing the mid-chirp or down-chirp of the low-intensity laser field, the harmonic cutoff can be extended and achieve the referenced value, which is produced from the high-intensity referenced field. Moreover, the spectral continuum is contributed by a single harmonic emission peak, which is beneficial to produce IAPs. However, the harmonic yield is very low due to the lower driven laser intensity. Second, by properly adding a UV pulse, the harmonic yield can be enhanced and achieve the referenced value due to the UV resonance ionisation. The intensity of the combined field is lower than that of the referenced field, which reduces the experimental requirements for producing high-intensity spectral continuum. Third, with the introduction of the positive or negative inhomogeneous effect of the mid-chirped combined field or down-chirped combined field, respectively, the similar harmonic cutoff and harmonic yield can also be obtained but with a much lower driven laser intensity. Finally, by superposing the harmonics on the spectral continuum, the IAPs with the durations of sub-38 as can be obtained.

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Liperovsky, V. A., C. V. Meister, E. V. Liperovskaya, and V. V. Bogdanov. "On the generation of electric field and infrared radiation in aerosol clouds due to radon emanation in the atmosphere before earthquakes." Natural Hazards and Earth System Sciences 8, no. 5 (October 28, 2008): 1199–205. http://dx.doi.org/10.5194/nhess-8-1199-2008.

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Abstract. The non-stationary Frenkel model of the generator of spikes of the local electric field with time scales of 1–100 min in the atmosphere near seismic fracture regions some days before strong earthqukes is analysed. The model suggests an aerosol cloud, an increased ionisation velocity (e.g. by radon emanation), and an upward flow of air. It was found that during times of earthquake activity (that means a few days before an earthquake), for realistic increases of the ionization intensity of the atmosphere, mosaic-likely occurring and disappearing pulses of local electric fields with intensities of the order of 103−3×103 Vm−1 should be observable. These electric fields would also cause spikes of non-equilibrium IR emissions (0.7–20 μm) and local spikes of the magnetic field. The authors propose to perform special complex Earth-based observations of the night-time emissions of the atmosphere in the IR region and of the magnetic as well as quasi-stationary electric fields at some points near to fracture regions in seismo-active belts.

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9

Umarov, I. R., and N. E. Andreev. "Effect of optical field ionisation on the generation of wake fields by femtosecond laser pulses in an inhomogeneous plasma." Quantum Electronics 50, no. 8 (August 6, 2020): 770–75. http://dx.doi.org/10.1070/qel17312.

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Kuzelev, M. V., and A. A. Rukhadze. "Generation of laser-pulse-field harmonics in a gas upon impact ionisation of atoms." Quantum Electronics 37, no. 10 (October 31, 2007): 924–26. http://dx.doi.org/10.1070/qe2007v037n10abeh013658.

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11

Cooper, Bridgette, Přemysl Kolorenč, Leszek J. Frasinski, Vitali Averbukh, and Jon P. Marangos. "Analysis of a measurement scheme for ultrafast hole dynamics by few femtosecond resolution X-ray pump–probe Auger spectroscopy." Faraday Discuss. 171 (2014): 93–111. http://dx.doi.org/10.1039/c4fd00051j.

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Ultrafast hole dynamics created in molecular systems as a result of sudden ionisation is the focus of much attention in the field of attosecond science. Using the molecule glycine we show through ab initio simulations that the dynamics of a hole, arising from ionisation in the inner valence region, evolves with a timescale appropriate to be measured using X-ray pulses from the current generation of SASE free electron lasers. The examined pump–probe scheme uses X-rays with photon energy below the K edge of carbon (275–280 eV) that will ionise from the inner valence region. A second probe X-ray at the same energy can excite an electron from the core to fill the vacancy in the inner-valence region. The dynamics of the inner valence hole can be tracked by measuring the Auger electrons produced by the subsequent refilling of the core hole as a function of pump–probe delay. We consider the feasibility of the experiment and include numerical simulation to support this analysis. We discuss the potential for all X-ray pump-X-ray probe Auger spectroscopy measurements for tracking hole migration.

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Gabdrakhmanov, I. M., and V. Yu Bychenkov. "Generation of a quasi-static magnetic field by a circularly polarised laser pulse due to tunnelling gas ionisation." Quantum Electronics 50, no. 9 (September 2, 2020): 838–43. http://dx.doi.org/10.1070/qel17261.

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13

Erattupuzha, Sonia, Cody L. Covington, Arthur Russakoff, Erik Lötstedt, Seyedreza Larimian, Václav Hanus, Sergiy Bubin, et al. "Enhanced ionisation of polyatomic molecules in intense laser pulses is due to energy upshift and field coupling of multiple orbitals." Journal of Physics B: Atomic, Molecular and Optical Physics 50, no. 12 (May 31, 2017): 125601. http://dx.doi.org/10.1088/1361-6455/aa7098.

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14

Churak, Amara, Chaithep Poolkhet, Yutaka Tamura, Tomomi Sato, Akira Fukuda, and Sukanya Thongratsakul. "Evaluation of nosocomial infections through contact patterns in a small animal hospital using social network analysis and genotyping techniques." Scientific Reports 11, no. 1 (January 18, 2021). http://dx.doi.org/10.1038/s41598-021-81301-9.

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AbstractNosocomial infections or hospital-acquired infections (HAIs) are common health problems affecting patients in human and animal hospitals. Herein, we hypothesised that HAIs could be spread through human and animal movement, contact with veterinary medical supplies, equipment, or instruments. We used a combination of social network analysis and genotyping techniques to find key players (or key nodes) and spread patterns using Escherichia coli as a marker. This study was implemented in the critical care unit, outpatient department, operation room, and ward of a small animal hospital. We conducted an observational study used for key player determination (or key node identification), then observed the selected key nodes twice with a one-month interval. Next, surface swabs of key nodes and their connecting nodes were analysed using bacterial identification, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry, and pulsed-field gel electrophoresis. Altogether, our results showed that veterinarians were key players in this contact network in all departments. We found two predominant similarity clusters; dendrogram results suggested E. coli isolates from different time points and places to be closely related, providing evidence of HAI circulation within and across hospital departments. This study could aid in limiting the spread of HAIs in veterinary and human hospitals.

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Rakici, Erva, Abdullah Altunisik, Kazim Sahin, and Osman Birol Ozgumus. "Determination and molecular analysis of antibiotic resistance in Gram-negative enteric bacteria isolated from Pelophylax sp. in the Eastern Black Sea Region." Acta Veterinaria Hungarica, September 27, 2021. http://dx.doi.org/10.1556/004.2021.00039.

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Abstract The aim of this study was to evaluate the prevalence and types of antimicrobial resistance among Gram-negative enteric bacteria isolated from Pelophylax sp. Fifty-four frogs were collected from six provinces in the Eastern Black Sea Region of Turkey. In the cloacal swab cultures, bacteria from 160 different colonies were identified by biochemical tests, automated systems, and matrix-assisted laser desorption ionisation-time of flight mass spectrometry. The antimicrobial susceptibility tests were performed by the disk diffusion method. The observed drug resistance rate was the highest to ampicillin and cefazolin, while the lowest against ciprofloxacin and tetracycline. In the molecular assays, bla TEM (8 Citrobacter spp.), bla SHV (2 Escherichia coli, 1 Hafnia alvei, and a Serratia liquefaciens), tetA genes (E. coli and Klebsiella spp.) and a class 1 integron without any gene cassette (E. coli) were detected. Among the strains, no plasmid-mediated quinolone resistance [qnrA, qnrB, qnrS, qepA and aac (6 ′)-Ib-cr] was found. However, two of three quinolone-resistant Klebsiella strains showed the novel amino acid substitution in the gyrA gene resulting in Ser83Asp and Asp87Glu.The clonality between E. coli isolates was also examined by pulsed-field gel electrophoresis. We consider that multidrug-resistant Gram-negative enteric bacteria in the intestinal microbiota of a cosmopolitan frog species might be a reservoir for antibiotic resistance genes.

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Jiang, Fei, Ziyan Kong, Chen Cheng, Haiquan Kang, Bing Gu, and Ping Ma. "Overestimated discriminatory power of MALDI-TOF mass spectrometry for typing of carbapenem-resistant Klebsiella pneumoniae clones." Epidemiology and Infection 147 (2019). http://dx.doi.org/10.1017/s0950268819002097.

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Abstract Homology surveillance of carbapenem-resistant Klebsiella pneumoniae (CRKP) is critical to monitor and prevent outbreaks of nosocomial infections. In the present study, a matrix-assisted laser desorption/ionisation-time of flight (MALDI-TOF MS)-based method was evaluated as a rapid tool for typing CRKP in comparison with pulsed-field gel electrophoresis (PFGE) and multi locus sequence typing (MLST). Drug-resistant phenotypes and genotypes of 44 CRKP isolates were detected by microdilution broth method and polymerase chain reaction, and typed by PFGE, MLST and MALDI-TOF MS. Simpson's Index of Diversity was used to evaluate taxonomic diversity, Adjusted Rand Index (ARI) for congruence between the typing methods and Wallace coefficients (W) for the ability of either method to predict each other. Forty-four CRKP isolates of 15 sequence types (STs) produced either NDM-1 (n = 16), NDM-5 (n = 9) or KPC-2 (n = 19) carbapenemases. PFGE differentiated these isolates into 16 distinct types, and two deoxyribonucleic acid profiles were assigned to ST337 and ST11, respectively. MALDI-TOF MS failed to clearly delineate between clusters on dendrograms based on principal components analysis and main spectrum profile. The chosen parameters resulted in a maximum ARI of 0.310 (95% CI 0.088–0.531) between MALDI-TOF MS typing and the PFGE reference, indicating a low ability of the former to correctly identify related isolates. Likewise, the maximum W coefficient of 0.367 (95% CI 0.203–0.532) showed that MALDI-TOF MS had a lower predictive power than PFGE. We conclude that MALDI-TOF MS lacks the discriminatory power necessary for clone assignment of CRKP isolates and consequently cannot be considered as a rapid and creditable method for this purpose.

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Ginzburg, D. "Ionisation Chamber for Measurement of Pulsed Photon Radiation Fields." Radiation Protection Dosimetry, June 24, 2016. http://dx.doi.org/10.1093/rpd/ncw145.

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Kang, Yuxin, Emilio Pisanty, Marcelo Ciappina, Maciej Lewenstein, Carla Figueira de Morisson Faria, and Andrew S. Maxwell. "Conservation laws for electron vortices in strong-field ionisation." European Physical Journal D 75, no. 7 (July 2021). http://dx.doi.org/10.1140/epjd/s10053-021-00214-4.

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Abstract We investigate twisted electrons with a well-defined orbital angular momentum, which have been ionised via a strong laser field. By formulating a new variant of the well-known strong field approximation, we are able to derive conservation laws for the angular momenta of twisted electrons in the cases of linear and circularly polarised fields. In the case of linear fields, we demonstrate that the orbital angular momentum of the twisted electron is determined by the magnetic quantum number of the initial bound state. The condition for the circular field can be related to the famous ATI peaks, and provides a new interpretation for this fundamental feature of photoelectron spectra. We find the length of the circular pulse to be a vital factor in this selection rule and, employing an effective frequency, we show that the photoelectron OAM emission spectra are sensitive to the parity of the number of laser cycles. This work provides the basic theoretical framework with which to understand the OAM of a photoelectron undergoing strong field ionisation. Graphic Abstract

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19

Middleton, Damien, Katravulapally Tejaswi, and Lampros Nikolopoulos. "A rate equation method for the sequential double ionisation, including autoionising state excitation, of a noble gas." Open Physics 11, no. 9 (January 1, 2013). http://dx.doi.org/10.2478/s11534-013-0232-2.

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AbstractA set of rate equations have been tested against a more robust set of Time-Dependent Density Matrix (TDDM) equations [D. P. W. Middleton, L. A. A. Nikolopoulos, J. Mod. Opti. 59, 1650 (2012)] by using them to determine the populations of ion species and autoionising states (AIS) in noble gas atoms when interacting with a strong external field. Two field shapes were tested here — sinusoidal and square — and a variety of pulse characteristics were examined, i.e. intensity, duration and photon energy, for the neon atomic system. It was found that the rate equations were sufficiently accurate only when the external field is way off-resonant with the AIS. Moreover, analytical solutions of the rate equations in the square pulse case agree with the numerical solutions for a time-dependent pulse containing many cycles. An attempt to model a stochastic field was also made and it was found that the use of such a field diminished and broadened the ion yield ratio due to the presence of an added bandwidth.

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Journal articles on the topic 'Pulsed field ionisation'

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