scholarly journals X. The colour-physiology of higher crustacea

1904 ◽  
Vol 196 (214-224) ◽  
pp. 295-388 ◽  
Keyword(s):  
Chemical Reactions ◽  
Mode Of Action ◽  
Experimental Methods ◽  
Present Knowledge ◽  
Experimental Proof ◽  
Biological Literature

The chromatophores of Crustacea present many problems physiological and morpho­logical. The first attempt to formulate these problems, and, by experimental methods, to solve them, is due to Pouchet. His Memoir, ‘Changements de Coloration sous l’influence des nerfs,’ is a classic of biological literature. It forms the basis of our present knowledge of the colour-physiology of Crustacea. The scope of Pouchet’s work is very wide. It includes the histology of the chromatophores, the chief chemical reactions of the more common pigments, the phenomena of pigment-movement under various extrinsic stimuli, such as light, electricity and drugs, the analysis of the effective light-factor, and experimental proof of the mode of action of this factor. These investigations were carried out chiefly on Palærnon serratus and Crangon vulgaris ; of other forms, young lobsters and Hippolyte were occasionally employed.

Photoacoustic Calorimetry

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Thermal Expansion ◽  
Chemical Reactions ◽  
Thermodynamic Data ◽  
Chemical Species ◽  
Experimental Methods ◽  
Sound Waves ◽  
Ambient Conditions ◽  
Photoacoustic Effect ◽  
Photoacoustic Calorimetry ◽  
Present Understanding

“Any chemical species, which under ambient conditions (i.e., a temperature around 25°C, and a pressure close to 1 atm) will, for a combination of kinetic and thermodynamic reasons, decay on a timescale ranging from microseconds, or even nanoseconds, to a few minutes” can be classified as a short-lived compound. According to this definition, suggested by Almond, it is clear that the experimental methods described in previous chapters can only be used to study the thermochemistry of long-lived substances. The technique that we address here, known as photoacoustic calorimetry (PAC) or laser-induced optoacoustic calorimetry (LIOAC), is suitable for investigating the energetics of molecules with lifetimes smaller than about 1μs. It relies on the photoacoustic effect, which was discovered by Bell more than 100 years ago. With the assistance of Tainter, he was able to “devise a method of producing sounds by the action of an intermittent beam of light” and conclude that the method “can be adapted to solids, liquids, and gases”. Figure 13.1 shows a photophone, “an apparatus for the production of sound by light,” used by Bell to investigate the photoacoustic effect. The controversy around the origin of this phenomenon was settled by Bell himself and by Lord Rayleigh; their views were rather close to our present understanding: When a light pulse is absorbed by a substance, a given amount of heat is deposited, producing a local thermal expansion; this thermal expansion propagates through the medium, generating sound waves. The basic theory of the photoacoustic effect was described by Tam and Patel and some of its applications were presented in a review by Braslavsky and Heibel. The first use of PAC to determine enthalpies of chemical reactions was reported by the groups of Peters and Braslavsky. The same groups have also played an important role in developing the methodologies to extract those thermodynamic data from the experimentally measured quantities. In the ensuing discussion, we closely follow a publication where the use of the photoacoustic calorimety technique as a thermochemical tool was examined. Consider the elementary design of a photoacoustic calorimeter, shown in figure 13.3. The cell contains the sample, which is, for instance, a dilute solution of a photoreactive species.

scholarly journals VII. Experimental researches in electricity.-Twenty-third Series

1850 ◽  
Vol 140 ◽  
pp. 171-188 ◽  
Keyword(s):  
Magnetic Field ◽  
Mode Of Action ◽  
Royal Society ◽  
The Other ◽  
Experimental Proof ◽  
Philosophical Paper ◽  
Iron Nickel ◽  
The One ◽  
Experimental Researches ◽  
The Magnetic Field

Four years ago I suggested that all the phenomena presented by diamagnetic bodies, when subjected to the forces in the magnetic field, might be accounted for by assuming that they then possessed a polarity the same in kind as, but the reverse in direction of, that acquired by iron, nickel and ordinary magnetic bodies under the same circumstances (2429. 2430.). This view was received so favourably by Plücker, Reich and others, and above all by W. Weber, that I had great hopes it would be confirmed; and though certain experiments of my own (2497.) did not increase that hope, still my desire and expectation were in that direction. Whether bismuth, copper, phosphorus, &c., when in the magnetic field, are polar or not, is however an exceedingly important question; and very essential and great differences, in the mode of action of these bodies under the one view or the other, must be conceived to exist. I found that in every endeavour to proceed by induction of experiment from that which is known in this department of science to the unknown, so much uncertainty, hesitation and discomfort arose from the unsettled state of my mind on this point, that I determined, if possible, to arrive at some experimental proof either one way or the other. This was the more needful, because of the conclusion in the affirmative to which Weber had come in his very philosophical paper; and so important do I think it for the progress of science, that, in those imperfectly developed regions of knowledge, which form its boundaries, our conclusions and deductions should not go far beyond, or at all events not aside from the results of experiment (except as suppositions), that I do not hesitate to lay my present labours, though they arrive at a negative result, before the Royal Society.

scholarly journals Summary of the Joint Discussion: Atomic Data of Importance for Ultraviolet and X-Ray Astronomy

1971 ◽  
Vol 2 ◽  
pp. 580-583
Author(s):  
A. G. Hearn
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Ground Level ◽  
Experimental Methods ◽  
Present Knowledge ◽  
Atomic Data ◽  
The Sun ◽  
X Ray ◽  
Lyman Continuum

AbstractThis Joint Discussion is in two parts. The first part is a description of recent observations which illustrate the need for atomic data and the second part is a description of what atomic data are available or could readily be produced by the latest theoretical and experimental methods. The purpose of this summary is to highlight the immediate requirements for atomic data of current observations which are not met by our present knowledge and thereby indicate where further work is necessary in providing atomic data.Although this is a discussion of atomic data the problems of assuming local thermodynamic equilibrium have inevitably been raised. The importance of considering whether departures from LTE are significant or not in the interpretation of observations is is clearly illustrated by the work of the Harvard group on the Lyman continuum emitted by the Sun which has shown a departure coefficient as large as 200 for the ground level of hydrogen.

Abnormal Heat Triggered by Pressure Change in a D/Pd Gas-Loading System

2013 ◽  
Vol 724-725 ◽  
pp. 1011-1016
Author(s):  
Hong Yu Wang ◽  
Xin Le Zhao ◽  
Bing Jun Shen ◽  
Li Hong Jin ◽  
Xin Lu ◽  
...  
Keyword(s):  
Data Acquisition ◽  
System Design ◽  
Chemical Reactions ◽  
Experimental System ◽  
Pressure Change ◽  
Experimental Methods ◽  
Recording System ◽  
Loading System ◽  
Deuterium Gas

This article by palladium deuterium gas-solid experimental system design, combined with the DH1716A program-controlled DC stabilized current supply and Keithley 2700 data acquisition and recording system, respectively at five different pressures, pressures triggered by experimental methods, making experiments of deuterated Palladium chemical reactions within the system, resulting in a tile level under different pressures is overheating.

scholarly journals Probing the Antimalarial Mechanism of Artemisinin and OZ277 (Arterolane) with Nonperoxidic Isosteres and Nitroxyl Radicals

2009 ◽  
Vol 54 (3) ◽  
pp. 1042-1046 ◽  
Author(s):  
Matthias A. Fügi ◽  
Sergio Wittlin ◽  
Yuxiang Dong ◽  
Jonathan L. Vennerstrom
Keyword(s):  
Plasmodium Falciparum ◽  
Chemical Reactions ◽  
Mode Of Action ◽  
Spin Trap ◽  
Nitroxide Radical ◽  
Nitroxyl Radicals ◽  
Lower Proportion ◽  
Drug Resistant ◽  
Peroxide Bond ◽  
Subsequent Chemical

ABSTRACT Peroxidic antimalarials such as the semisynthetic artemisinins are critically important in the treatment of drug-resistant malaria. Nevertheless, their peroxide bond-dependent mode of action is still not well understood. Using combination experiments with cultured Plasmodium falciparum cells, we investigated the interactions of the nitroxide radical spin trap, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), and four of its analogs with artemisinin and the ozonide drug development candidate OZ277. The antagonism observed for combinations of artemisinin or OZ277 with the TEMPO analogs supports the hypothesis that the formation of carbon-centered radicals is critical for the activity of these two antimalarial peroxides. The TEMPO analogs showed a trend toward greater antagonism with artemisinin than they did with OZ277, an observation that can be explained by the greater tendency of artemisinin-derived carbon-centered radicals to undergo internal self-quenching reactions, resulting in a lower proportion of radicals available for subsequent chemical reactions such as the alkylation of heme and parasite proteins. In a further mechanistic experiment, we tested both artemisinin and OZ277 in combination with their nonperoxidic analogs. The latter had no effect on the antimalarial activities of the former. These data indicate that the antimalarial properties of peroxides do not derive from reversible interactions with parasite targets.

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