THE CHEMISTRY OF SINGLET AND TRIPLET METHYLENE

1965 ◽  
Vol 43 (6) ◽  
pp. 1631-1644 ◽  
Author(s):  
R. F. W. Bader ◽  
John I. Generosa
Keyword(s):  
Trans Isomer ◽  
Singlet State ◽  
Gas Pressure ◽  
The Other ◽  
Inert Gases ◽  
Inert Gas ◽  
Initial Decrease ◽  
Percentage Yield ◽  
Excited Molecules ◽  
Subsequent Rise

Results are reported for the photolysis of small, fixed amounts of diazomethane and cis-butene-2 in the presence of increasing pressures of the inert gases He, Ar, Xe, N2, and CF4. The variation in the percentage yield of the trans-dimethylcyclopropane as a function of the inert gas pressure indicates that two basic mechanisms, with opposite dependencies on the inert gas pressure, are responsible for its formation. An initial decrease in the percentage yield of this trans isomer with increasing pressure indicates that a source is an isomerization of energized molecules. These excited molecules result from the addition of methylene in a singlet state to cis-butene-2. A subsequent rise in the yield of the trans isomer with further increases in the pressure indicates that another mechanism, one whose rate is increased by an increase in pressure, must be present. This is attributed to a mechanism involving triplet methylene. The pressure regions for the observation of the singlet or triplet behavior of methylene are thus known and the modes of formation of the other C5 products may be determined.

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

scholarly journals The interaction of inert gases

1930 ◽  
Vol 129 (811) ◽  
pp. 686-698 ◽  
Keyword(s):  
Orthogonal Transformation ◽  
Special Kind ◽  
Point Of View ◽  
The Other ◽  
Inert Gases ◽  
Inert Gas ◽  
Quantum Mechanical ◽  
Exchange Degeneracy ◽  
Electron Pairs ◽  
Binding Force

The following paper studies from a quantum mechanical point of view a special kind of chemical reaction, namely, the inertness of the inert gases. In the development of the quantum theory of homopolar binding this chapter has hitherto been omitted for the following reason: not only is the charge distribution of an inert gas atom spherically symmetrical, but the whole ψ-function, which depends in the case of n electrons on 3 n space co-ordinated and n spin co-ordinates, is invariant under a simultaneous orthogonal transformation of all co-ordinates. This means that there is no space degeneracy. If now this atom is brought near to another similar one, the disappearance of direction symmetry is not followed by a disappearance of degeneracy—the stationary state does not split up into several states as in most cases of chemical binding, but remains single and seems to correspond, under ordinary conditions, to repulsion. On the other hand, Heitler and London in their well-known treatment of the H 2 -problem, found that it was just the removal of a degeneracy, which they called “exchange degeneracy,” which gave rise to large resonance forces and thus led to binding in one of the resultant states and repulsion in the other. This induced subsequent workers to suppose that the antiparallel copuling of two electron spins in different atoms always entails a binding force. This was supported from the theorectical side by the fact that the interaction energy could actually be worked out as a sum of terms each belonging to such as coupling. Such a theory could not fail to fit the experiments as it established the rules Lewis’ theory of electron pairs—a theory already proved to have wide validity.

Factors determining temporal pattern of isobaric supersaturation

1981 ◽  
Vol 51 (4) ◽  
pp. 852-857 ◽  
Author(s):  
C. Young ◽  
B. G. D'Aoust
Keyword(s):  
Temporal Pattern ◽  
Gas Pressure ◽  
Inert Gases ◽  
Inert Gas ◽  
Blood Flows ◽  
Arterial Blood ◽  
Diffusion Constants ◽  
Dependent Model ◽  
Ambient Gas ◽  
Krogh Cylinder

It is possible to produce a transient supersaturation or undersaturation in tissues and blood by sequentially breathing gases with different equilibration rates. If the ambient gas pressure is sufficiently high, the induced supersaturation can produce vascular bubbles. By means of the classical perfusion-dependent model of inert gas elimination, which assumes that the effects of diffusion are minimal, the magnitude of the total inert gas pressure can be predicted. If, however, the effects of diffusion cannot be ignored, the supersaturation could be substantially larger. This paper estimates the effects of diffusion in a Krogh cylinder on the supersaturation produced by suddenly changing the inert gas partial pressure in the blood. The results of these estimates indicate that diffusion plays a role in this transient supersaturation only in long Krogh cylinders with high blood flows. The effects of diffusion are further reduced by the finite time necessary to switch the inert gases in arterial blood. The conclusions are supported by experiments that measure vascular bubble production after a switch of the inert portion of the inspired gas. These experiments further show that the formation of vascular bubbles after such a switch cannot be entirely explained by the different diffusion constants of the gases used.

Effect of inert gas switching at depth on decompression outcome in rats

1989 ◽  
Vol 67 (4) ◽  
pp. 1354-1363 ◽  
Author(s):  
R. S. Lillo ◽  
M. E. MacCallum
Keyword(s):  
Gas Exchange ◽  
Exchange Rates ◽  
Rattus Norvegicus ◽  
Decompression Sickness ◽  
Gas Pressure ◽  
The Other ◽  
Inert Gas ◽  
Experimental Conditions ◽  
Gas Switch ◽  
Rapid Decompression

The present investigation was performed to determine whether inert gas sequencing at depth would affect decompression outcome in rats via the phenomenon of counterdiffusion. Unanesthetized rats (Rattus norvegicus) were subjected to simulated dives in either air, 79% He-21% O2, or 79% Ar-21% O2; depths ranged from 125 to 175 feet of seawater (4.8–6.3 atmospheres absolute). After 1 h at depth, the dive chamber was vented (with depth held constant) over a 5-min period with the same gas as in the chamber (controls) or one of the other two inert gas-O2 mixtures. After the gas switch, a 5- to 35-min period was allowed for gas exchange between the animals and chamber atmosphere before rapid decompression to the surface. Substantial changes in the risk of decompression sickness (DCS) were observed after the gas switch because of differences in potencies (He less than N2 less than Ar) for causing DCS and gas exchange rates (He greater than Ar greater than N2) among the three gases. Based on the predicted gas exchange rates, transient increases or decreases in total inert gas pressure would be expected to occur during these experimental conditions. Because of differences in gas potencies, DCS risk may not directly follow the changes in total inert gas pressure. In fact, a decline in predicted DCS risk may occur even as total inert gas pressure in increasing.

Inert gas-exchange theory using an electric analogue

1964 ◽  
Vol 19 (6) ◽  
pp. 1193-1198 ◽  
Author(s):  
W. W. Mapleson
Keyword(s):  
Alveolar Ventilation ◽  
The Body ◽  
Exchange Theory ◽  
Inert Gases ◽  
Inert Gas ◽  
Respiratory Pattern ◽  
Whole Body ◽  
High Solubility ◽  
Systematic Analysis ◽  
Inhaled Anesthetics

When an inert gas of moderate or high solubility in blood is inhaled, the rate at which the alveolar concentration rises toward the inspired concentration increases as the inspired concentration is increased. The only previous systematic analysis of whole-body uptake of inert gases to allow for this effect was restricted to a single, artificial, respiratory pattern and the numerical calculations had to be made on a digital computer. This paper develops the theory for a range of respiratory patterns and shows how the computations may be made on a slightly modified form of a simple electric analogue. It is shown that the rate of saturation of the body increases less markedly with inspired concentration if the inspired alveolar ventilation, rather than the expired alveolar ventilation, is kept constant during the saturation process. Conversely, washout is more rapid with a constant inspired ventilation than with a constant expired ventilation. The theory is extended to show how the uptake of one inert gas may substantially affect the uptake of another, administered simultaneously. uptake, distribution and elimination; induction; recovery; drugs; inhaled anesthetics; nitrous oxide; diethyl ether; halothane; computers; ventilation; concentration effect; alveolar ventilation Submitted on February 13, 1964

scholarly journals STUDIES ON IMMUNITY TO PNEUMOCOCCUS MUCOSUS (TYPE III)

1927 ◽  
Vol 45 (6) ◽  
pp. 1093-1106 ◽  
Author(s):  
William S. Tillett
Keyword(s):  
Biological Property ◽  
Infected Animal ◽  
Virulent Strain ◽  
The Other ◽  
Natural Resistance ◽  
Type Iii ◽  
Mechanism Of Resistance ◽  
Initial Decrease ◽  
High Degree ◽  
Highly Virulent

The observations recorded in this paper on the infectivity of Type III pneumococci for rabbits may be summarized as follows: 1. Of eleven strains of Type III isolated from human sources, ten were found to possess low virulence for rabbits. This was true despite the fact that all the strains tested possessed large capsules and a high degree of virulence for mice. 2. One strain of Type III pneumococcus was rendered highly virulent for rabbits. Since it possessed no other biological property demonstrably different from the other strains, its virulence must reside in some additional property. 3. An initial decrease in the number of circulating organisms following the injection of virulent bacteria is a well known occurrence, and it was observed in rabbits injected with the rabbit virulent strain of Type III. However, the extent of the reduction was in inverse proportion to the degree of virulence of the strain; a fact which makes mechanical explanations of the phenomenon insufficient. 4. The bacteremia produced in rabbits by Type III pneumococci, avirulent for this species, runs a characteristic course. It differs from that produced by non-encapsulated R forms of pneumococci although in both instances survival of the infected animal ensues. This is evidence that the mechanism of resistance against encapsulated and non-encapsulated pneumococci is not identical. 5. Phagocytosis of Type III pneumococci by circulating rabbit leucocytes was not demonstrable by a vital stain technique, whereas under the same conditions the ingestion of non-encapsulated R forms occurred. This is further evidence that the process whereby non-encapsulated pneumococci are disposed of, is insufficient to explain the natural resistance of rabbits to infection with encapsulated Type III pneumococci.

Religion, Violence, and the State

2018 ◽  
pp. 226-262
Author(s):  
Muhammad Qasim Zaman
Keyword(s):  
Political Violence ◽  
War On Terror ◽  
The State ◽  
The Other ◽  
Islamic Tradition ◽  
State And Society ◽  
The Us ◽  
The World ◽  
The Military ◽  
Subsequent Rise

This chapter focuses on religio-political violence, whose widespread incidence—after Pakistan's realignment in the US-led War on Terror in the aftermath of September 11, 2001, and the subsequent rise of a new, Pakistani Taliban—has threatened the very fabric of state and society. It examines the violence in question from two broad and intertwined perspectives, one relating to the state, and the other to Islam and those speaking in its terms. Part of the concern in this chapter is to contribute to an understanding of how the governing elite and the military have often fostered the conditions in which the resort to religiously inflected violence has been justified. It also suggests that the nonstate actors—ideologues and militants—have had an agency of their own, which is not reducible to the machinations of the state. Their resort to relevant facets of the Islamic tradition also needs to be taken seriously in order to properly understand their view of the world and such appeal as they have had in particular circles.

Respiratory and inert gas exchange during high-frequency ventilation

1982 ◽  
Vol 52 (3) ◽  
pp. 683-689 ◽  
Author(s):  
H. T. Robertson ◽  
R. L. Coffey ◽  
T. A. Standaert ◽  
W. E. Truog
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Gas Flow ◽  
Inert Gases ◽  
Inert Gas ◽  
High Frequency Ventilation ◽  
Physiological Dead Space ◽  
Volume Ventilation ◽  
Frequency Ventilation ◽  
Carrier Gases

Pulmonary gas exchange during high-frequency low-tidal volume ventilation (HFV) (10 Hz, 4.8 ml/kg) was compared with conventional ventilation (CV) and an identical inspired fresh gas flow in pentobarbital-anesthetized dogs. Comparing respiratory and infused inert gas exchange (Wagner et al., J. Appl. Physiol. 36: 585--599, 1974) during HFV and CV, the efficiency of oxygenation was not different, but the Bohr physiological dead space ratio was greater on HFV (61.5 +/- 2.2% vs. 50.6 +/- 1.4%). However, the elimination of the most soluble inert gas (acetone) was markedly enhanced by HFV. The increased elimination of the soluble infused inert gases during HFV compared with CV may be related to the extensive intraregional gas mixing that allows the conducting airways to serve as a capacitance for the soluble inert gases. Comparing as exchange during HFV with three different density carrier gases (He, N2, and Ar), the efficiency of elimination of Co2 or the intravenously infused inert gases was greatest with He-O2. However, the alveolar-arterial partial pressure difference for O2 on He-O2 exceeded that on N2-O2 by 5.4 Torr during HFV. The finding agrees with similar observations during CV, suggesting that this aspect of gas exchange is not substantially altered by HFV.

scholarly journals LAMB AND WOOL PRODUCTION FROM FIVE BREEDS ON RANGE

1966 ◽  
Vol 46 (1) ◽  
pp. 9-18 ◽  
Author(s):  
J. A. Vesely ◽  
H. F. Peters ◽  
S. B. Slen
Keyword(s):  
Body Weight ◽  
The Other ◽  
Production Traits ◽  
Weaning Weight ◽  
Wool Production ◽  
Breed Differences ◽  
Percentage Yield ◽  
Ewe Lamb ◽  
Fleece Weight ◽  
Staple Length

Rambouillet, Romnelet, Columbia, Targhee, and Suffolk sheep were evaluated under range conditions for the production of lamb and wool in the period 1960–1963. The production traits analyzed were: birth and weaning weight; face cover and neck wrinkling; fertility, prolificacy, weaned lamb production, and body weight of ewe; lamb survival to weaning; grease and clean fleece weight, staple length, wool grade, and percentage yield of clean wool by yearling and mature ewes.Lambs of Romnelet were lighter at birth than those of the other breeds. Targhee and Suffolk were the heaviest at birth. Romnelet and Columbia lambs were lighter at weaning than those of Rambouillet, Targhee, and Suffolk.Fertility, prolificacy, and weaned lamb production were essentially the same in the four range breeds. Suffolk produced more weaned lamb than the other four breeds. There were no breed differences in the survival of lambs.Columbia exceeded all other breeds in production of grease and clean fleece weight. Suffolk produced the smallest amount of wool. Staple length of Columbia ewes was 4.3, 7.5, 18.6, 23.7 mm longer than that of Romnelet, Targhee, Suffolk, and Rambouillet ewes.

Effects of physical properties of the breathing gas on decompression-sickness bubbles

1995 ◽  
Vol 79 (5) ◽  
pp. 1828-1836 ◽  
Author(s):  
M. E. Burkard ◽  
H. D. Van Liew
Keyword(s):  
Partition Coefficient ◽  
Physical Properties ◽  
Numerical Simulations ◽  
Bubble Growth ◽  
Decompression Sickness ◽  
Inert Gases ◽  
Inert Gas ◽  
Half Time ◽  
Bubble Density ◽  
Mathematical Relationships

To explore the relative dangers of different inert gases, we developed mathematical relationships concerned with bubble growth, using equations that separate gas properties from other variables. Predictions for saturation exposures were as follows. 1) Peak volume of a bubble is proportional to solubility in tissue when bubble density is high and to the 3/2 power of the ratio of the permeation coefficient to the partition coefficient when density is low. 2) Bubble duration is inversely proportional to the partition coefficient for the inert gas. 3). Sizes and durations of bubbles for one inert gas relative to another depend on whether the tissue is aqueous or lipid but are independent of the magnitude of the decompression and tissue half time. 4). He should give smaller bubbles than N2, except in aqueous tissue with low bubble density; our prediction correlates qualitatively with relative dangers observed with animals but seems to overestimate the safety afforded by He. Numerical simulations illustrate how nonsaturation dives are less predictable because more variables are involved.

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