scholarly journals The continuous absorption of light in potassium vapour

1928 ◽  
Vol 117 (777) ◽  
pp. 486-508 ◽  
Keyword(s):  
Vapour Pressure ◽  
Alkali Metals ◽  
Wave Length ◽  
Experimental Conditions ◽  
General Application ◽  
Continuous Absorption ◽  
Wide Range ◽  
Absorption Of Light ◽  
Relative Absorption ◽  
Band Absorption

While considerable attention has been paid to the line and band absorption of the alkali metals, very little work has been done on the continuous absorption. R. W. Wood and Holtzmark have observed the existence of this absorption, and Harrison has made some measurements on the continuous absorption of sodium in the region 2500 Å. U. - 2150 Å. U. In the present paper, results are given for potassium over a wide range of wave-length (4000 Å. U. - 2200 Å. U.) and under widely different experimental conditions. The ordinary methods of spectrophotometry have usually been designed to measure the absorption of solutions, etc., and are not suitable for measuring the absorption in a vapour unless the vapour pressure can be kept absolutely constant. A method of spectrophotometry has been developed by which it is possible to obtain measurements of the relative absorption coefficients for different wave-lengths correct to about 2 per cent, without keeping the vapour pressure absolutely constant. While the method is specially suitable for the measurement of an absorption which is not quite steady, it is really of quite general application.

The continuous absorption of light in alkali-metal vapours

1953 ◽  
Vol 219 (1136) ◽  
pp. 89-101 ◽  
Keyword(s):  
Cross Section ◽  
Alkali Metals ◽  
Theoretical Calculations ◽  
Wave Length ◽  
Energy Difference ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Sodium Vapour ◽  
Good Agreement ◽  
Dipole Length

The first section of this paper is an account of some experiments on the absorption of light in sodium vapour from the series limit at 2412 Å to about 1600 Å (an energy difference of 2·6 eV). The absorption cross-section at the limit is 11·6 ± 1·2 x 10 -20 cm 2 . The cross-section decreases giving a minimum of 1·3 ± 0·6 x 10 -20 cm 2 at 1900 Å and then increases to 1600 Å. A theoretical calculation by Seaton based on the dipole-length formula gives good agreement with the experiments at the series limit and also correctly predicts the wave-length for the minimum, but it predicts a significantly lower absorption at the minimum. The experiments described in the first section of the paper conclude a series on the absorption of light in the alkali metals. The second section consists of a general discussion of the results of these experiments and of their relation to theoretical calculations. There is good agreement between theory and experiment except in regard to the magnitude of the absorption at the minimum.

scholarly journals On the absorption of light by crystals

1938 ◽  
Vol 167 (930) ◽  
pp. 384-391 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Short Wave ◽  
Point Of View ◽  
Theoretical Point ◽  
Lattice Vibrations ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Positive Hole

The purpose of this paper is to discuss the absorption of light by non-metallic solids, and in particular the mechanism by which the energy of the light absorbed is converted into heat. If one considers from the theoretical point of view the absorption spectrum of an insulation crystal, one finds that it consists of a series of sharp lines leading up to a series limit, to the short wave-length side of which true continuous absorption sets in (Peierls 1932; Mott 1938). In practice the lattice vibrations will broaden the lines to a greater of less extent. When a quantum of radiation is absorbed in the region of true continuous absorption, a free electron in the conduction band and a "positive hole" are formed with enough energy to move away from one another and to take part in a photocurrent within the crystal. When, however, a quantum is absorbed in one of the absorption lines , the positive hole and electron formed do not have enough energy to separate, but move in one another's field in a quantized state. An electron in a crystal moving in the field of a positive hole has been termed by Frenkel (1936) an "exciton".

scholarly journals The absorption spectrum of nitrous-oxide and the heat of dissociation of nitrogen

1932 ◽  
Vol 138 (834) ◽  
pp. 84-91 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Absorption Spectrum ◽  
Wave Length ◽  
Accurate Estimation ◽  
Selective Absorption ◽  
Vapour State ◽  
Continuous Absorption ◽  
Band Absorption ◽  
Heat Of Dissociation

In some previous papers it has been shown by the author and others that saturated compounds of most substances in the vapour state show continuous absorption. A typical example is SO 3 -vapour, which was recently studied by the author and which enabled him to make an accurate estimation of the heat of dissociation of oxygen. In the present work, the absorption spectrum of N 2 O was investigated with a view to determining the heat of dissociation of nitrogen. Leifson was the first to investigate the absorption spectrum of N 2 O gas and found that the gas shows no selective absorption in the Schumann region. He states that the absorption is in the form of two continuous bands, the first extending from λ 2000 to λ 1680 and the second from λ 1550 beyond the range of observation. Recently Wulf and Melvin showed that when N 2 O is illuminated with light of wave-length λ 2300, it is decomposed photochemically into NO and N; they also noticed that N 2 O possesses no band absorption.

scholarly journals Continuous absorption of light in cæsium vapour

1934 ◽  
Vol 143 (849) ◽  
pp. 472-481 ◽  
Keyword(s):  
Wave Length ◽  
Principal Series ◽  
Short Wave ◽  
Main Difficulty ◽  
Absorption Cell ◽  
Absorption Tube ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Photo Ionization

A region of continuous absorption lying on the short wave-length side of the limit of the principal series and corresponding to the photo-ionization of the atom is to be expected in the alkali metal vapours. The currents due to photo-ionization have been measured and several attempts have been made to observe the absorption. The main difficulty is in the action of the vapour on the windows of the absorption cell. This has usually been overcome by keeping the ends of the absorption tube cool and checking the diffusion of the vapour from the centre of the tube by means of a foreign gas. This gas produces a large and complicated effect on the absorption (Harrison). In the present experiments it has been found possible to avoid the use of a foreign gas by employing a long absorption tube and a low vapour pressure. Cæsium was used because it gives a sufficient pressure at a moderate temperature and because its series limit lies in the most convenient region of the spectrum.

scholarly journals Regularities in the arc spectrum of arsenic

1929 ◽  
Vol 125 (796) ◽  
pp. 238-246 ◽  
Keyword(s):  
Vapour Pressure ◽  
Wave Length ◽  
Characteristic Line ◽  
Continuous Absorption ◽  
Line Absorption ◽  
Empirical Scheme

In the course of an investigation of the spectrum of arsenic under different conditions of excitation several regularities has been detected among the lines due to As I, and it is the purpose of the present paper to give an account of these. Besides the very early work of Kayser and Runge, previous investigations on the analysis of the arc spectrum of arsenic consist chiefly of two contributions. Ruark, Mohler, Foote and Chenault have made measurements of the critical potentials of As, and, with the aid of these and the recurring frequency differences pointed out by Kayser and Runge, have suggested an empirical scheme of terms with accounted for many of the more intense lines of the arc. But a large number of lines of wave-length below λ 2100 have not entered into the above scheme and remained unclassified. A study of the absorption by the normal vapour of arsenic failed to show any characteristic line absorption, for the vapour has been found to exhibit continuous absorption in the ultraviolet which spreads towards longer wave-lengths as the vapour pressure rises.

scholarly journals EVIDENCE FOR THERMAL REACTIONS FOLLOWING EXPOSURE OF DIDINIUM TO INTERMITTENT ULTRAVIOLET RADIATIONS

1956 ◽  
Vol 40 (2) ◽  
pp. 311-325 ◽  
Author(s):  
A. C. Giese ◽  
D. C. Shepard ◽  
J. Bennett ◽  
A. Farmanfarmaian ◽  
C. L. Brandt
Keyword(s):  
High Intensity ◽  
Dark Period ◽  
Wave Length ◽  
Reasonable Assumption ◽  
Lower Intensity ◽  
Division Rate ◽  
General Application ◽  
Thermal Reactions ◽  
Wide Range ◽  
Continuous Radiation

1. The nature of ultraviolet injury and its variation with the same dose given at different intensities and wave lengths have been investigated in the protozoan Didinium nasutum, using time to the fourth division as a measure of injury. 2. The injury has been found to consist of a "slowdown" of division rate, which always occurs, and a "stasis," usually at the second division after irradiation, which appears in varying degrees among more severely injured samples. 3. Injury was found to be almost independent of intensity at three wave lengths out of four studied over a wide range of intermediate and high intensities, but was found to rise sharply with lower intensity at all except the longest wave length. 4. Flashed UV of high intensity is much more effective than the same dose of continuous radiation at high intensity and shorter total time of treatment. It is also more effective than the same dose at low intensity and equal time of treatment, though only slightly so. 5. An increase of injury with rise of temperature and with increase of dark period clearly indicates that injury depends on thermochemical reactions following the absorption of UV in Didinium. 6. The most reasonable assumption is that a similar conclusion applies to other organisms as well, and that its general application may be useful in the investigation of UV effects on protoplasm.

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

scholarly journals Review of the Upright Balance Assessment Based on the Force Plate

2021 ◽  
Vol 18 (5) ◽  
pp. 2696
Author(s):  
Baoliang Chen ◽  
Peng Liu ◽  
Feiyun Xiao ◽  
Zhengshi Liu ◽  
Yong Wang
Keyword(s):  
Postural Balance ◽  
Force Plate ◽  
Assessment Method ◽  
Balance Assessment ◽  
Experimental Conditions ◽  
Methodological Research ◽  
Assessment Tests ◽  
Wide Range ◽  
Foot Posture ◽  
Plate System

Quantitative assessment is crucial for the evaluation of human postural balance. The force plate system is the key quantitative balance assessment method. The purpose of this study is to review the important concepts in balance assessment and analyze the experimental conditions, parameter variables, and application scope based on force plate technology. As there is a wide range of balance assessment tests and a variety of commercial force plate systems to choose from, there is room for further improvement of the test details and evaluation variables of the balance assessment. The recommendations presented in this article are the foundation and key part of the postural balance assessment; these recommendations focus on the type of force plate, the subject’s foot posture, and the choice of assessment variables, which further enriches the content of posturography. In order to promote a more reasonable balance assessment method based on force plates, further methodological research and a stronger consensus are still needed.

scholarly journals Towards Reduced CNNs for De-Noising Phase Images Corrupted with Speckle Noise

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 255
Author(s):  
Marie Tahon ◽  
Silvio Montresor ◽  
Pascal Picart
Keyword(s):  
Phase Error ◽  
Speckle Noise ◽  
Experimental Conditions ◽  
Benchmark Data ◽  
Wide Range ◽  
Phase Images ◽  
Different Depths ◽  
Phase Data ◽  
Do So

Digital holography is a very efficient technique for 3D imaging and the characterization of changes at the surfaces of objects. However, during the process of holographic interferometry, the reconstructed phase images suffer from speckle noise. In this paper, de-noising is addressed with phase images corrupted with speckle noise. To do so, DnCNN residual networks with different depths were built and trained with various holographic noisy phase data. The possibility of using a network pre-trained on natural images with Gaussian noise is also investigated. All models are evaluated in terms of phase error with HOLODEEP benchmark data and with three unseen images corresponding to different experimental conditions. The best results are obtained using a network with only four convolutional blocks and trained with a wide range of noisy phase patterns.

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