Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy I. Free radical absorption spectra in acetylene combustion

1953 ◽  
Vol 216 (1125) ◽  
pp. 165-183 ◽  
Keyword(s):  
Absorption Spectra ◽  
Total Pressure ◽  
Flash Photolysis ◽  
Initial Period ◽  
Kinetic Spectroscopy ◽  
Radical Concentration ◽  
Stage 4 ◽  
Explosive Reaction ◽  
Stage 1 ◽  
Flash Spectroscopy

The explosive oxidation of acetylene, initiated homogeneously by the flash photolysis of a small quantity of nitrogen dioxide, has been investigated by flash spectroscopy. The absorption spectra of OH, CH, C 2 (singlet and triplet), C 3 , CN and NH, a number of which have not previously been observed, are described, and the relative concentrations, at all times throughout the explosion, are given. Four stages have been distinguished in the explosive reaction: 1. An initial period during which only OH appears. 2. A rapid chain branching involving all the diatomic radicals. 3. Further reaction, occurring only when oxygen is present in excess of equimolecular proportions, during which the OH concentration rises exponentially and the other radicals are totally consumed. 4. A relatively slow exponential decay of the excess radical concentration remaining after completion of stages 2 and 3. The duration of stage 1 is 0 to 3 ms. In an equimolecular mixture at 20 mm total pressure, containing 1.5 mm NO 2 , the durations of both stage 2 and stage 3 are approximately 10 -4 s and the half-life of OH in stage 4 is 0.28 ms. A preliminary interpretation of these changes and of the radical reactions is given.

Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy - II. Comparative investigations of hydrocarbons and a study of the continuous absorption spectra

1955 ◽  
Vol 227 (1171) ◽  
pp. 423-433 ◽  
Keyword(s):  
Absorption Spectra ◽  
Thermal Equilibrium ◽  
Flash Photolysis ◽  
Total Carbon ◽  
Carbon Particles ◽  
Continuous Absorption ◽  
Flash Spectroscopy ◽  
Characteristic Maximum ◽  
The Continuum ◽  
Carbon Molecule

The absorption spectra of explosions of ethylene, ethane and methane with oxygen, initiated by the flash photolysis of nitrogen dioxide, have been studied kinetically by flash spectroscopy and the results are compared with those already given for acetylene. The occurrence of the diatomic radical spectra is qualitatively similar in the four hydrocarbons, but there are important quantitative differences in the stoicheiometry of the mixtures which give equivalent spectroscopic results. The continuous spectra and the spectrum of C 3 have been studied in more detail. The continuum which is present after the explosion is shown to be due to absorption by carbon particles. A second intense continuous spectrum, which has a characteristic maximum at 3900 Å and whose occurrence follows closely that of the radicals C 2 and C 3 , is attributed to a carbon molecule which is in approximate thermal equilibrium and whose concentration must form a considerable fraction of the total carbon present in the vapour during the explosion.

Spectroscopic studies of the hydrogen-oxygen explosion initiated by the flash photolysis of nitrogen dioxide

1952 ◽  
Vol 210 (1103) ◽  
pp. 439-460 ◽  
Keyword(s):  
Nitrogen Dioxide ◽  
Flash Photolysis ◽  
Spectroscopic Studies ◽  
Reaction Scheme ◽  
Oh Radical ◽  
Time Intervals ◽  
Induction Periods ◽  
Photochemical Decomposition ◽  
Explosive Reaction ◽  
Flash Spectroscopy

The method of flash photolysis has been used to initiate the reaction between hydrogen and oxygen, using a small amount of nitrogen dioxide as sensitizer. The dependence of the ignition limits on total pressure, capacity and the pressure of nitrogen dioxide have been studied, as well as the flash photochemical decomposition of nitrogen dioxide alone. The explosive reaction is complete in a few milliseconds, and very short induction periods are found whose duration can be explained in terms of the initial temperature rise. It is shown that the initiation of the explosion in this way is reproducible to less than 10 -4 s and flash spectroscopy is used to study the development of the reactions with time. The spectra obtained are described and the reactions of the OH radical are investigated by means of its absorption spectrum , whose intensity variations with partial pressure of hydrogen, oxygen, nitrogen and water vapour over time intervals of 0·2 ms throughout the reaction are given. Addition of hydrogen accelerates the reaction, but oxygen in excess has the same effect as an inert gas which is to decrease the rate. It is shown that the important propagation steps are exclusively bimolecular and the main reactions of the OH radical are identified. The mechanism of the overall explosion reaction is discussed and a reaction scheme is given which is in accordance with the results.

The combustion of gaseous aldehydes studied by flash photolysis and kinetic spectroscopy

1960 ◽  
Vol 254 (1277) ◽  
pp. 147-162 ◽  
Keyword(s):  
Free Radicals ◽  
Formic Acid ◽  
High Temperatures ◽  
Flash Photolysis ◽  
Kinetic Mechanism ◽  
Kinetic Spectroscopy ◽  
Elementary Reactions ◽  
Slow Reaction ◽  
Explosive Reaction ◽  
Explosive Combustion

The identity and behaviour of free radicals produced during the combustion of gaseous aldehydes has been examined. The flash-initiated combustion of formaldehyde was investigated under conditions of slow and explosive combustion. The behaviour of formaldehyde and the derived radicals OH and HCO was followed during the course of the reaction. It was found that HCO radicals react rapidly with oxygen during the slow reaction, but decompose into H atoms and CO at the high temperatures produced during the explosive reaction. Further information on the reaction between HCO radicals and oxygen was obtained by flash - photolyzing gaseous formic acid in presence of oxygen and nitrogen under isothermal conditions. The results of this investigation are consistent with the kinetic observations previously made by Axford & Norrish. With one modification relating to the participation of HCO radicals they confirm the kinetic mechanism previously deduced by these authors. The flash-initiated combustion of acetaldehyde was also investigated under conditions of slow and explosive combustion, and information on several of the elementary reactions proceeding under these conditions has been obtained.

The combustion of hydrogen sulphide studied by flash photolysis and kinetic spectroscopy

1957 ◽  
Vol 240 (1222) ◽  
pp. 293-303 ◽  
Keyword(s):  
Low Temperature ◽  
Absorption Spectra ◽  
Hydrogen Sulphide ◽  
Sulphur Dioxide ◽  
Flash Photolysis ◽  
Light Emission ◽  
Inert Gas ◽  
Large Excess ◽  
Kinetic Spectroscopy ◽  
Combustion Of Hydrogen

The combustion of hydrogen sulphide has been investigated by the method of kinetic spectroscopy and flash photolysis. If no large excess of inert gas is present the reaction produces sulphur dioxide. The reaction has been shown to take place in steps in which the radicals SH and OH participate. Simultaneously with the appearance of the sulphur dioxide; a light emission has been observed which is attributed to the process: SO + O→SO2 + hv . In the presence of a large excess of inert gas the reaction results in S 2 O 2 . It has been shown that the formation of S 2 O 2 is favoured by a low temperature. Flash photolysis of hydrogen sulphide, sulphur dioxide and S 2 O 2 has also been investigated. In the last two cases the absorption spectra disappear temporarily. Inert gas prevents the disappearance of the SO 2 , but not that of S 2 O 2 . From an analysis of our results a mechanism for the combustion of hydrogen sulphide is derived and discussed.

Kinetic spectroscopy in the far ultra-violet: the flash photolysis of ethyl compounds

1958 ◽  
Vol 243 (1235) ◽  
pp. 555-560 ◽  
Keyword(s):  
Absorption Spectra ◽  
Lithium Fluoride ◽  
Flash Photolysis ◽  
Ultra Violet ◽  
Transient Species ◽  
Methyl Radical ◽  
Kinetic Spectroscopy ◽  
Ethyl Radicals

An apparatus is described for the recording of the far u. v. absorption spectra of transient species produced by flash photolysis. Using lithium fluoride windows, observations can be made down to 1250 Å. The flash photolysis of mercury diethyl and lead tetraethyl yield appreciable amounts of the methyl radical, and it is thought that these are formed by reaction between ethyl radicals, one of which is excited.

Alterations in the number of motoneurons containing immunoreactive calcitonin gene-related peptide(CGRP)& choline acetyltransferase(ChAT) in the cervical spinal cord of the wobbler mouse during the development of the motoneuron disease

1995 ◽  
Vol 53 ◽  
pp. 970-971
Author(s):  
L. Vacca-Galloway ◽  
Y.Q. Zhang ◽  
P. Bose ◽  
S.H. Zhang
Keyword(s):  
Spinal Cord ◽  
Early Stage ◽  
Cervical Spinal Cord ◽  
Wild Type Mouse ◽  
Reflex Response ◽  
Mouse Strains ◽  
Behavioral Tests ◽  
Wobbler Mouse ◽  
Stage 4 ◽  
Stage 1

The Wobbler mouse (wr) has been studied as a model for inherited human motoneuron diseases (MNDs). Using behavioral tests for forelimb power, walking, climbing, and the “clasp-like reflex” response, the progress of the MND can be categorized into early (Stage 1, age 21 days) and late (Stage 4, age 3 months) stages. Age-and sex-matched normal phenotype littermates (NFR/wr) were used as controls (Stage 0), as well as mice from two related wild-type mouse strains: NFR/N and a C57BI/6N. Using behavioral tests, we also detected pre-symptomatic Wobblers at postnatal ages 7 and 14 days. The mice were anesthetized and perfusion-fixed for immunocytochemical (ICC) of CGRP and ChAT in the spinal cord (C3 to C5).Using computerized morphomety (Vidas, Zeiss), the numbers of IR-CGRP labelled motoneurons were significantly lower in 14 day old Wobbler specimens compared with the controls (Fig. 1). The same trend was observed at 21 days (Stage 1) and 3 months (Stage 4). The IR-CGRP-containing motoneurons in the Wobbler specimens declined progressively with age.

Novel staging classification of primary mitral regurgitation based on the presence of cardiac damage

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A.L Van Wijngaarden ◽  
Y.L Hiemstra ◽  
P Van Der Bijl ◽  
V Delgado ◽  
N Ajmone Marsan ◽  
...  
Keyword(s):  
Mitral Regurgitation ◽  
Kidney Function ◽  
Left Ventricular ◽  
Prognostic Impact ◽  
Cardiac Damage ◽  
Stage 4 ◽  
All Cause Mortality ◽  
Primary Mitral Regurgitation ◽  
Stage 1 ◽  
Staging Classification

Abstract Background The indication for surgery in patients with severe primary mitral regurgitation (MR) is currently based on the presence of symptoms, left ventricular (LV) dilatation and dysfunction, atrial fibrillation and pulmonary hypertension. The aim of this study was to evaluate the prognostic impact of a new staging classification based on cardiac damage including the known risk factors but also including global longitudinal strain (GLS), severe left atrial (LA) dilatation and right ventricular (RV) dysfunction. Methods In total 614 patients who underwent surgery for severe primary MR with available baseline transthoracic echocardiograms were included. Patients were classified according to the extent of cardiac damage (Figure): Stage 0-no cardiac damage, Stage 1-LV damage, Stage 2-LA damage, Stage 3-pulmonary vasculature or tricuspid valve damage and Stage 4-RV damage. Patients were followed for all-cause mortality. Results Based on the proposed classification, 172 (28%) patients were classified as Stage 0, 102 (17%) as Stage 1, 134 (21%) as Stage 2, 135 (22%) as Stage 3 and 71 (11%) as Stage 4. The more advanced the stage, the older the patients were with worse kidney function, more symptoms and higher EuroScore. Kaplan-Meier curve analysis revealed that patients with more advanced stages of cardiac damage had a significantly worse survival (log-rank chi-square 35.2; p<0.001) (Figure). On multivariable analysis, age, male, chronic obstructive pulmonary disease, kidney function, and stage of cardiac damage were independently associated with all-cause mortality. For each stage increase, a 22% higher risk for all-cause mortality was observed (95% CI: 1.064–1.395; p=0.004). Conclusion In patients with severe primary MR, a novel staging classification based on the extent of cardiac damage, may help refining risk stratification, particularly including also GLS, LA dilatation and RV dysfunction in the assessment. Funding Acknowledgement Type of funding source: None

A Description of Middle School Male Singers’ Voice Change and Voice Part Assignment

2021 ◽  
pp. 875512332110182
Author(s):  
Ryan Austin Fisher ◽  
Nancy L. Summitt ◽  
Ellen B. Koziel
Keyword(s):  
Middle School ◽  
Sixth Grade ◽  
Eighth Grade ◽  
Voice Change ◽  
Stage 4 ◽  
Public Middle School ◽  
Middle School Choir ◽  
Choral Programs ◽  
Stage 1 ◽  
The Voice

The purpose of this study was to describe the voice change and voice part assignment of male middle school choir members. Volunteers ( N = 92) were recruited from three public middle school choral programs (Grades 6-8). Participants were audio-recorded performing simple vocal tasks in order to assess vocal range and asked to share the music they were currently singing in class. Results revealed 23.91% of participants’ voices could be categorized as unchanged, 14.13% as Stage 1, 3.26% as Stage 2, 10.87% as Stage 3, 26.09% as Stage 4, and 21.74% as Stage 5. The majority of sixth-grade participants were classified as unchanged or in Stage 1 of the voice change and the majority of eighth-grade participants were classified in Stages 4 to 5 of the voice change. Of the participants labeled “tenors” in their choir, over 60% were classified as either unchanged voices or in Stage 1 of the voice change.

scholarly journals Temporal changes of quantitative CT findings from 102 patients with COVID-19 in Wuhan, China: A longitudinal study

2021 ◽  
Vol 29 ◽  
pp. 297-309
Author(s):  
Xiaohui Chen ◽  
Wenbo Sun ◽  
Dan Xu ◽  
Jiaojiao Ma ◽  
Feng Xiao ◽  
...  
Keyword(s):  
Lung Diseases ◽  
Early Stage ◽  
Temporal Changes ◽  
Time Interval ◽  
Lesion Area ◽  
Quantitative Ct ◽  
Diagnosis And Prognosis ◽  
Ct Findings ◽  
Stage 4 ◽  
Stage 1

BACKGROUND: Computed tomography (CT) imaging combined with artificial intelligence is important in the diagnosis and prognosis of lung diseases. OBJECTIVE: This study aimed to investigate temporal changes of quantitative CT findings in patients with COVID-19 in three clinic types, including moderate, severe, and non-survivors, and to predict severe cases in the early stage from the results. METHODS: One hundred and two patients with confirmed COVID-19 were included in this study. Based on the time interval between onset of symptoms and the CT scan, four stages were defined in this study: Stage-1 (0 ∼7 days); Stage-2 (8 ∼ 14 days); Stage-3 (15 ∼ 21days); Stage-4 (> 21 days). Eight parameters, the infection volume and percentage of the whole lung in four different Hounsfield (HU) ranges, ((-, -750), [-750, -300), [-300, 50) and [50, +)), were calculated and compared between different groups. RESULTS: The infection volume and percentage of four HU ranges peaked in Stage-2. The highest proportion of HU [-750, 50) was found in the infected regions in non-survivors among three groups. CONCLUSIONS: The findings indicate rapid deterioration in the first week since the onset of symptoms in non-survivors. Higher proportion of HU [-750, 50) in the lesion area might be a potential bio-marker for poor prognosis in patients with COVID-19.

Absorption Spectra of Substituted 2-Phenylindan-1,3-Dion-2-YL Radicals in Solution

1983 ◽  
Vol 38 (12) ◽  
pp. 1337-1341
Author(s):  
J. Zechner ◽  
N. Getoff ◽  
I. Timtcheva ◽  
F. Fratev ◽  
St. Minchef
Keyword(s):  
Free Energy ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Bathochromic Shift ◽  
Substitution Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Abstract Flash photolysis of a series of 2-phenylindandione-1,3 derivatives substituted in the 4′ position results in both the formation of stable benzylidenephthalides and of phenylindan-1,3-dion-2-yl radicals. The u. v. absorption maxima of these radicals are dependent on the solvent and show a bathochromic shift upon substitution. These substitution effects were correlated by means of a linear free energy relationship. Attempts were made to draw conclusions concerning the changes in the gap of the states involved and their curvature due to substitution.

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