scholarly journals Formic Acid Ionization and Fragmentation by Multiphoton Absorption

Author(s):  
C. Cisneros ◽  
T. Bautista ◽  
C. F. Betancourt ◽  
E. Prieto ◽  
A. Guerrero ◽  
...  

Multiphoton absorption is an intensity dependent nonlinear effect related to the excitation of virtual intermediate states. In the present work, multiphoton ionization and dissociation of the formic acid molecule (HCOOH) by the interaction with photons from 532 Nd: YAG laser at different intensities are discussed, using different carrier gases. The induced fragmentation-ionization patterns show up to 17 fragments and dissociation channels are proposed. Some evidence of small clusters formation and conformational memory from the ratio of the detected products, CO+ and CO2+, on the light of the available results, it is possible to conclude that they arise from trans and cis formic acid. Our results are compared with those obtained in other laboratories under different experimental conditions, some of them show only partial agreement and differences are discussed. Following the Keldysh description it is possible, from our experimental parameters, characterize our results, in the multiphoton absorption regime.

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
An Zheng ◽  
Michael Lamkin ◽  
Yutong Qiu ◽  
Kevin Ren ◽  
Alon Goren ◽  
...  

Abstract Background A major challenge in evaluating quantitative ChIP-seq analyses, such as peak calling and differential binding, is a lack of reliable ground truth data. Accurate simulation of ChIP-seq data can mitigate this challenge, but existing frameworks are either too cumbersome to apply genome-wide or unable to model a number of important experimental conditions in ChIP-seq. Results We present ChIPs, a toolkit for rapidly simulating ChIP-seq data using statistical models of key experimental steps. We demonstrate how ChIPs can be used for a range of applications, including benchmarking analysis tools and evaluating the impact of various experimental parameters. ChIPs is implemented as a standalone command-line program written in C++ and is available from https://github.com/gymreklab/chips. Conclusions ChIPs is an efficient ChIP-seq simulation framework that generates realistic datasets over a flexible range of experimental conditions. It can serve as an important component in various ChIP-seq analyses where ground truth data are needed.


2021 ◽  
Vol 11 (40) ◽  
pp. 168-169
Author(s):  
Denise Lessa Aleixo ◽  
Leoni Vilano Bonamin ◽  
Silvana Marques De Araujo

Introduction: The use of homeopathic medicines has increased, once traditional medicines sometimes do not produce the desired effects and because side effects sometimes compromise the treatment. In recent years, research on homeopathy has clearly developed, both in the implementation of more consistent methodologies and in the description of the data and published methods, improvement are still required in these matters. The acknowledgment of homeopathy depends on the credibility of the groups researching this topic Objective: list and criticize articles highlighting main effects, schedule of treatment and potencies used in different animals models. Material and Methods: A review of articles published since 2000 in journals indexed in the PubMed/Scielo databases was performed. Keywords used were parasitosis/homeopathy and parasitosis/ultra-diluted, in English and Portuguese. Specialized journals such as Homeopathy, International Journal of High Dilution Research, and Brazilian Homeopathic Journal were also used. The contents of each issue of these journals were examined for the "Use of highly diluted medication in parasitic infections." Results and Discussion: Thirty nine papers have been gathered. The methodology of the articles surveyed did not meet the requirements listed in the REHBaR[1]. Thirty seven reports have shown the benefits/effects of highly diluted medicine in the treatment of infectious diseases. In models where experimental conditions are carefully controlled, the conclusions follow the same pattern as those observed in the treatment of farm animals, where, even without completely controlled conditions, clinical result is positive. In fourteen reports using the same model, eight where animals were treated in a constant and prolonged way shown a better result, compared with six reports in which animals were treated for a short period of time, receiving a single daily dose. Several authors have conducted clinical trials using commercial formulas, which do not always provide their composition and/or dynamization, making it difficult to reproducing the experiment. In some of the articles, it was not mentioned if the experiments were repeated at least twice. Conclusions: In parasitic infections, the effect of homeopathic medications is still controversial, and the experimental parameters for evaluation shoud be carefully chosen to avoid isolated analyses of data. Researchers should consider results regarding environmental and sanitary conditions of the animal as a whole. The improvement of techniques and expansion of knowledge about highly diluted medicines may lead to a viable alternative to treat parasitic infections. Precise and detailed descriptions will contribute to advances in the use of homeopathy, so that the wider community can benefit, in practice, from these findings. Keywords: homeopathy, parasitic infections, CAM (Complementary and Alternative Medicine). Reference [1] Lüdtke R, Musial F, Wijk R, Witt C, Baumgartner S. Reporting experiments in homeopathic basic research (REHBaR) – A detailed guideline for authors. Homeopathy. 2009; 98:287-298.


1998 ◽  
Vol 76 (2) ◽  
pp. 228-233
Author(s):  
Kiyohisa Ohta ◽  
Youko Ueda ◽  
Satoshi Nakaguchi ◽  
Takayuki Mizuno

The photocatalytic reduction of CO2 using copper-loaded silicate rocks has been reported. The Cu-silicate rock powders suspended in the solution were illuminated with sunlight. Amphibolite, gneiss, granite, granodiorite, phyllite, quartzdiorite, and shale, which are quite ordinary rocks, were tested as substrates (silicate rock) of the catalyst. These catalysts were specific for the formation of formic acid. The effects of amounts of copper, illumination time, and temperature were investigated on photoreduction of CO2. The 30% Cu-loaded quartzdiorite (0.3 g/g) in these Cu rocks was the best catalyst. The formation of formic acid on the Cu-silicate rock increased with time up to 10 h after which the formation decreased, and then became constant. The formic acid formation decreased with temperature for 10 h sunlight illumination. For the photochemical reduction of CO2, a relatively low temperature was suitable. With photochemical reduction, the maximum yield of formic acid was 54 nmol/g under optimum experimental conditions. The carbon dioxide reduction system developed might well become of practical interest for the photochemical production of raw materials for the photochemical industry.Key words: photocatalytic reduction of carbon dioxide, formic acid, copper-loaded silicate rocks, temperature effect, illumination time.


1993 ◽  
Vol 13 (2) ◽  
pp. 159-165
Author(s):  
D. Charalambidis ◽  
Y. L. Shao ◽  
S. D. Moustaizis ◽  
C. Fotakis

The abundance of the 83Kr isotope, determined by ion mass analysis following three photon resonant four photon ionization via the 5s’ [1/2]1 state with a broadband laser is found to differ from the expected natural value. This effect is discussed in terms of a change of the ionization response due to the decay of coherence in the intermediate state to its hyperfine structure coupling. The nonzero nuclear spin isotopes of Xe have not shown any effect of this type in three different ionization schemes under the present experimental conditions.


2015 ◽  
Vol 68 (7) ◽  
pp. 1108 ◽  
Author(s):  
Osmundo Dantas Pessoa-Neto ◽  
Tiago Almeida Silva ◽  
Vagner Bezerra dos Santos ◽  
Orlando Fatibello-Filho

A compact environmentally friendly microcontrolled microfluidic device ideal for in situ phosphate determination was developed based on a microsystem based on low-temperature co-fired ceramics (LTCC) coupled to a light-emitting diode (LED)–photometer with a multicommutation flow analysis (MCFA) approach. The experimental parameters of the MCFA analyzer were optimized by chemometric studies. Under the best experimental conditions, limits of detection and quantification of 0.02 mg P L–1 and 0.07 mg P L–1, respectively, and a sampling frequency of 67 h–1 were estimated. Moreover, a low sample consumption of only 60 μL per determination was the other advantage that fully meets the requirements of sustainable research and green chemistry purposes.


2009 ◽  
Vol 6 (3) ◽  
pp. 737-742 ◽  
Author(s):  
T. Santhi ◽  
S. Manonmani ◽  
S. Ravi

A new, low cost, locally available biomaterial was tested for its ability to remove cationic dyes from aqueous solution. A granule prepared from a mixture of leafs, fruits and twigs ofMuntingia calaburahad been utilized as a sorbent for uptake of three cationic dyes, methylene blue (MB), methylene red (MR) and malachite green (MG). The effects of various experimental parameters (e.g.,contact time, dye concentration, adsorbent dose and pH) were investigated and optimal experimental conditions were ascertained. Above the value of initial pH 6, three dyes studied could be removed effectively. The isothermal data fitted the Langmuir and Freundlich isotherm models for all three dyes sorption. The biosorption processes followed the pseudo-first order rate kinetics. The results in this study indicated thatMuntingia calaburawas an attractive candidate for removing cationic dyes from the dye wastewater.


1993 ◽  
Vol 47 (11) ◽  
pp. 1907-1912 ◽  
Author(s):  
Josef B. Simeonsson ◽  
George W. Lemire ◽  
Rosario C. Sausa

A new method for detecting trace vapors of NO2-containing compounds near atmospheric conditions has been demonstrated with the use of one-color-laser photofragmentation/ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X2II electronic ground state and the other in its A2Σ+ excited state. Ionization of ground-state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via its A2Σ+ ← X2II (3, 0), B2II ← X2II (7, 0) and/or D2Σ+ ← X2II (0, 1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/ionization mass spectra.


2005 ◽  
Vol 109 (12) ◽  
pp. 2836-2839 ◽  
Author(s):  
E. Martínez-Núñez ◽  
S. A. Vázquez ◽  
I. Borges, ◽  
A. B. Rocha ◽  
C. M. Estévez ◽  
...  

1975 ◽  
Vol 53 (16) ◽  
pp. 2436-2440 ◽  
Author(s):  
John H. Carey ◽  
Cooper H. Langford

When methanol, 2-propanol, and formic acid are used as scavengers in the ligand to metal charge transfer (l.m.c.t.) photolysis of Fe(OH2)63+, Fe(OH2)5CI2+, Fe2(OH2)8(OH)24+, or FeEDTA, there is a linear relationship between quantum yield for Fe(II) production and scavenger concentration, [S], at higher [S] values. Extrapolation of the linear portions to [S] = 0 gives an intercept corresponding to the limiting yields observed for scavenging with tert-butyl alcohol. Butanol scavenging at the limit has been shown to give the primary free radical yields from photolysis of aquo iron(III) species. Nuclear magnetic resonance relaxation time studies show that alcohols do not coordinate to Fe(III) and calculations from known stability constants indicate that formic acid does not coordinate under the experimental conditions. The increase of Fe(II) yields with [S] is attributed to an outer sphere oxidation of noncoordinated organic species by the charge transfer excited states of Fe(III) species. There is no discrimination among the organic reductants. The results may be understood without postulating a long lifetime for the Fe(III) l.m.c.t. states if the reaction is assumed to occur only with organic molecules in encounter with the Fe(III) complex at the time of excitation. Organic products were formaldehyde from methanol oxidation and acetone from 2-propanol oxidation. The Fe(II): formaldehyde stoichiometry was 2:1.


The relative concentrations of hydrogen atoms were measured during the oscillatory ignition of hydrogen in a well stirred flow reactor. Comparisons were made with the experimental concentration—time profiles of the hydroxyl radical obtained previously under similar experimental conditions. The predicted concentration profiles obtained from numerical analysis of a thermokinetic model were also compared with the experimental results. Experiments were performed in a 600 cm 3 Pyrex glass, jet-stirred reactor with the reactants, 2H 2 + O 2 , at a total pressure of 16 Torr ( ca . 2132.8 Pa) and at a vessel temperature of 753 K. The mean residence time was 1.2 s. Oscillatory ignition was established at a period of 3 s in which high radical concentrations were attained and in which the temperature rise was almost adiabatic. The concentration-time profile of hydrogen atoms was obtained by a resonance enhanced multiphoton ionization (rempi) which was induced by a laser pulse at energies in the vicinity of 364 nm, with ion collection at a stainless steel probe inserted into the reactor. Supplementary studies were made to characterize the signals and to identify effects of the probe within the reaction volume. A measurement of the relative concentrations of hydrogen atoms was obtained from an integration of the area of the rempi spectrum determined over the laser wavelength range 363.8-364.6 nm. The spectrum was measured at successive times in the oscillatory cycle by imposing a variable delay on the laser firing signal. The results show that, during oscillatory ignition, the maximum concentration of hydrogen atoms was reached and a sharp decay was already well advanced before that of the hydroxyl radicals was attained. The numerical analysis was in very good quantitative accord with this experimental result. The phase difference of the cyclic variation in the H atoms relative to that of OH radicals is a key feature of the kinetic mechanisms which control the oscillatory oxidation of hydrogen.


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