Determination of lowest energy state in single-electron circuits

1998 ◽  
Vol 34 (25) ◽  
pp. 2401 ◽  
Author(s):  
I. Karafyllidis
Keyword(s):  
Energy State ◽  
Single Electron

Introduction to light absorption: visible and ultraviolet spectra

2000 ◽  
Author(s):  
Robert K. Poole ◽  
Uldis Kalnenieks
Keyword(s):  
Electromagnetic Radiation ◽  
Light Absorption ◽  
Energy State ◽  
Monochromatic Light ◽  
Heat Radiation ◽  
Infrared Light ◽  
Visible Radiation ◽  
Absorption Of Light ◽  
The Difference

Light is a form of electromagnetic radiation, usually a mixture of waves having different wavelengths. The wavelength of light, expressed by the symbol λ, is defined as the distance between two crests (or troughs) of a wave, measured in the direction of its progression. The unit used is the nanometre (nm, 10-9 m). Light that the human eye can sense is called visible light. Each colour that we perceive corresponds to a certain wavelength band in the 400-700 nm region. Spectrophotometry in its biochemical applications is generally concerned with the ultraviolet (UV, 185-400 nm), visible (400-700 nm) and infrared (700-15 000 nm) regions of the electromagnetic radiation spectrum, the former two being most common in laboratory practice. The wavelength of light is inversely related to its energy (E), according to the equation: . . . E = ch/ λ . . . where c denotes the speed of light, and h is Planck’s constant. UV radiation, therefore, has greater energy than the visible, and visible radiation has greater energy than the infrared. Light of certain wavelengths can be selectively absorbed by a substance according to its molecular structure. Absorption of light energy occurs when the incident photon carries energy equal to the difference in energy between two allowed states of the valency electrons, the photon promoting the transition of an electron from the lower to the higher energy state. Thus biochemical spectrophotometry may be referred to as electronic absorption spectroscopy. The excited electrons afterwards lose energy by the process of heat radiation, and return to the initial ground state. An absorption spectrum is obtained by successively changing the wavelength of monochromatic light falling on the substance, and recording the change of light absorption. Spectra are presented by plotting the wavelengths (generally nm or μm) on the abscissa and the degree of absorption (transmittance or absorbance) on the ordinate. For more information on the theory of light absorption, see Brown (1) and Chapters 2, 3 and 4. The most widespread use of UV and visible spectroscopy in biochemistry is in the quantitative determination of absorbing species (chromophores), known as spectrophotometry.

scholarly journals Highly Excited Molecular Hydrogen in Orion

1989 ◽  
Vol 120 ◽  
pp. 323-326
Author(s):  
Hans H. Hippelein ◽  
Guido Münch
Keyword(s):  
Molecular Hydrogen ◽  
Rotational Temperature ◽  
Energy State ◽  
Low Energy ◽  
Line Of Sight ◽  
Temperature Measuring ◽  
Molecule Formation ◽  
J 13 ◽  
Excitation Mechanisms

Observations of H2 lines in the IR have been mostly restricted to those with upper levels of low energy, which can be excited either collisionally in shocks or radiatively by UV starlight. In order to discriminate between the two excitation mechanisms we have measured in 11 μm range lines of the v=2-0 band arising from high rotational levels J≤;13. Their intensities, together with those of the IR lines, allow an estimate of the line of sight effective extinction and a determination of the rotational temperature measuring their joint degree of excitation. The latter parameter provides information about the energy state of the molecules at their formation and ejection from grain surfaces and thus constrains the hypothetical models for H2 molecule formation.

Statistical Model Explaining the Fine Structure and Interface Reference of Localized Excitons in Type-II GaAs/AlAs Superlattices

1998 ◽  
Vol 07 (01) ◽  
pp. 13-35 ◽  
Author(s):  
M. V. Belousov ◽  
A. Yu. Chernyshov ◽  
I. V. Ignatev ◽  
I. E. Kozin ◽  
A. V. Kavokin ◽  
...  
Keyword(s):  
Statistical Model ◽  
Energy State ◽  
Integer Number ◽  
Type Ii ◽  
Interface Quality ◽  
Alas Layer ◽  
Densities Of States ◽  
Fine Structures ◽  
Localized Excitons

Raman scattering experiments have allowed the determination of the spatial distribution of the thicknesses of GaAs and AlAs layers in a gradient GaAs/AlAs superlattice. A statistical model is developed which is consistent with all the data and ways to improve interface quality are suggested. The fine structures of XΓ and ΓΓ excitons observed in photoluminescence and differential reflection are found to be governed by the fractional parts of the average thickness of the layer (in monolayers). We conclude that each structure has two scales of fluctuations which form the relief of the AlAs surface. The largest fluctuations repeat the relief of the GaAs surface. The second scale has the size of a typical XΓ exciton Bohr radius. The smaller fluctuations disappear when the thickness of the AlAs layer is equal to an integer number of monolayers, which provide interfaces of the quality. The correlation of macro-rough fluctuations on the surface of AlAs and GaAs causes an asymmetry in the densities of states of type II excitons located at either AlAs-on-GaAs or GaAs-on-AlAs interfaces. Hence the lowest PL line is formed by excitons localized across the AlAs-on-GaAs interface. On the other hand, in structures with micro-rough but uncorrelated AlAs surfaces, the lowest energy state is expected to be occupied by excitons localized across the GaAs-on-AlAs interface.

scholarly journals Conditions for activity of glutaminase in kidney mitochondria

1970 ◽  
Vol 118 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Z. Kovačević ◽  
J. D. McGivan ◽  
J. B. Chappell
Keyword(s):  
Enzyme Activity ◽  
Mitochondrial Membrane ◽  
Energy State ◽  
Rat Kidney ◽  
Antimycin A ◽  
Ph Optimum ◽  
Rapid Reduction ◽  
Kidney Mitochondria ◽  
Glutaminase Activity

1. Rat kidney mitochondria oxidize glutamate very slowly. Addition of glutamine stimulates this respiration two- to three-fold. Addition of glutamate also stimulates respiration in the presence of glutamine. 2. By measuring mitochondrial swelling in iso-osmotic solutions of glutamine or of ammonium glutamate it was shown that glutamine penetrates the mitochondrial membrane rapidly whereas ammonium glutamate penetrates very slowly. 3. Experiments in which reduction of NAD(P)+ was measured in preparations of intact and broken mitochondria indicated that glutamate dehydrogenase shows the phenomenon of `latency'. On the addition of glutamine rapid reduction of nicotinamide nucleotides in intact mitochondria was obtained. 4. During the action of glutaminase there is an accumulation of glutamate inside the mitochondria. 5. When the mitochondria were suspended in a medium containing glutamine, Pi and rotenone the rate of production of ammonia was stimulated by the addition of a substrate, e.g. succinate. Addition of an uncoupler or antimycin A abolished this stimulation. 6. The effects of succinate and uncoupler were especially pronounced in the presence of glutamate, which is an inhibitor of glutaminase activity by competition with Pi. 7. Determination of the enzyme activity in media at different pH values showed that the optimum pH for glutaminase activity in the preparation of broken mitochondria was 8, whereas for intact mitochondria it was dependent on the energy state. In the presence of succinate as an energy source it was pH 8.5, but in the presence of uncoupler or antimycin A it was 9. This displacement of the pH optimum to a higher value was especially pronounced in the presence of both glutamate and uncoupler. 8. If nigericin was present in potassium chloride medium the pH optimum for enzyme activity in intact non-respiring mitochondria was nearly the same as in the preparation of broken mitochondria; however, its presence in K+-free medium displaced the pH optimum for glutaminase activity to a very high value. 9. It is postulated that because of low permeability of the kidney mitochondrial membrane to glutamate the latter accumulates inside the mitochondria, and that this leads to the inhibition of the enzyme by competition with Pi and also by lowering the pH of the intramitochondrial space. With succinate as substrate for respiration there is an outward translocation of H+ ions, which together with accumulation of Pi increases glutaminase activity. Translocation of K+ ions inward increases the enzyme activity, perhaps by increasing the pH of the internal spaces and causing an accumulation of Pi. 10. The importance of the location of the enzyme in the mitochondria in relation to its biological function and conditions for activity is discussed.

Global least-squares determination of Eulerian angles from single electron diffraction patterns of tilted crystals

2000 ◽  
Vol 33 (4) ◽  
pp. 1088-1101 ◽  
Author(s):  
Eva Dimmeler ◽  
Rasmus R. Schröder
Keyword(s):  
Electron Diffraction ◽  
Least Squares ◽  
Three Dimensional ◽  
Test Sample ◽  
Single Electron ◽  
Dimensional Structure ◽  
Diffraction Spot ◽  
Linear Fit ◽  
Diffraction Patterns

Three-dimensional structure determination using electron diffraction of crystalline samples necessitates the determination of the Eulerian angles of tilted samples. For experimental tilt series, even with approximately known tilt, the resolution of the final three-dimensional reconstructions is reduced as a result of the large errors of the refined tilt angles and crystal axes positions. The presented new least-squares procedure determines the orientation of the crystal with very high accuracy from a single electron diffraction pattern. Instead of evaluating the averaged pattern geometry, each diffraction spot position is individually included in an analytical non-linear fit. This procedure is very stable against potential experimental errors, as demonstrated by Monte Carlo simulations. As a test sample, a three-dimensional microcrystal of an organic crystal compound was used. Contrary to the conventional method, which produced erroneous Miller indices for some reflections, the indexing obtained with the new algorithm was more consistent for each individual pattern. Preliminary data from frozen hydrated protein crystals, the samples of which are beam sensitive and for which only a few patterns can be recorded from a single crystal, indicate that the new angle determination promises to be particularly beneficial under such conditions.

scholarly journals Defining a standardized methodology for the determination of the antioxidant capacity: case study of Pistacia atlantica leaves

The Analyst ◽  
2020 ◽  
Vol 145 (2) ◽  
pp. 557-571 ◽  
Author(s):  
Ziyad Ben Ahmed ◽  
Yousfi Mohamed ◽  
Viaene Johan ◽  
Bieke Dejaegher ◽  
Kristiaan Demeyer ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Electron Transfer ◽  
Hydrogen Atom ◽  
Antioxidant Capacity ◽  
Hydrogen Atom Transfer ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Pistacia Atlantica

Antioxidant activity can be measured by a variety of methods, that include hydrogen atom transfer (HAT) and single electron transfer (ET) methods.

scholarly journals Effect of Iodoacetate on Local Cerebral Blood Flow and Glucose Metabolism in Cats: A Double-Radionuclide Autoradiographic Study

1985 ◽  
Vol 5 (2) ◽  
pp. 290-294 ◽  
Author(s):  
Kortaro Tanaka ◽  
Stephen C. Jones ◽  
Eors Dora ◽  
Joel H. Greenberg ◽  
Martin Reivich
Keyword(s):  
Blood Flow ◽  
Energy State ◽  
Severe Depression ◽  
Autoradiographic Study ◽  
Local Cerebral Blood Flow ◽  
Cellular Energy ◽  
Cranial Window ◽  
Glycolytic Activity ◽  
Left Parietal Cortex

The effect of iodoacetate (IAA), an inhibitor of glycolysis, on local CBF (LCBF) and local CMRglu (LCMRglu) was studied in cats by means of a double-radionuclide autoradiographic method. Artificial CSF containing 5 m M IAA was superfused on the left parietal cortex under a cranial window for 30 min. [14C]2-Deoxyglucose and [123I]iodoantipyrine were injected for the determination of LCMRglu and LCBF, respectively. A marked increase in LCBF, accompanied by a moderate to severe depression of LCMRglu, was observed in the IAA-superfused cortex. This result suggests that LCBF may be closely regulated by the cellular energy state associated with glycolytic activity in brain tissue.

Containment forces in low energy states of plasmoids

1987 ◽  
Vol 38 (2) ◽  
pp. 263-274 ◽  
Author(s):  
Daniel R. Wells ◽  
Lawrence Carl Hawkins
Keyword(s):  
Free Energy ◽  
Vector Fields ◽  
Energy State ◽  
Lagrange Equations ◽  
Magnus Force ◽  
Side Condition ◽  
Gas Laws ◽  
Relationship Of ◽  
The Relationship

The application of Hamilton's principle to the problem of the determination of the structure of low free energy state plasmoids is discussed. It is shown that Clebsch representations of the vector fields and representations involving side conditions on the functional result in the same sets of Euler–Lagrange equations. The relationship of these representations to the problem of containment forces in vortex structures (plasmoids) is considered. It is demonstrated that the lowest free energy state of an incompressible plasma is always Lorentz force and Magnus force free. For a compressible plasma obeying the adiabatic gas laws, the Magnus force is finite. Introduction of conservation of angular momentum as an additional side condition also results in finite containment forces.

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