Range Of Energy States Research Articles

Energy states of soil water – a thermodynamic perspective on soil water dynamics and storage-controlled streamflow generation in different landscapes

Abstract. The present study confirms that a thermodynamic perspective on soil water is well suited to distinguishing the typical interplay of gravity and capillarity controls on soil water dynamics in different landscapes. To this end, we express the driving matric and gravity potentials by their energetic counterparts and characterize soil water by its free energy state. The latter is the key to defining a new system characteristic determining the possible range of energy states of soil water, reflecting the joint influences of soil physical properties and height over nearest drainage (HAND) in a stratified manner. As this characteristic defines the possible range of energy states of soil water in the root zone, it also allows an instructive comparison of top soil water dynamics observed in two distinctly different landscapes. This is because the local thermodynamic equilibrium at a given HAND and the related equilibrium storage allow a subdivision of the possible free energy states into two different regimes. Wetting of the soil in local equilibrium implies that free energy of soil water becomes positive, which in turn implies that the soil is in a state of storage excess, while further drying of the soil leads to a negative free energy and a state of storage deficit. We show that during 1 hydrological year the energy states of soil water visit distinctly different parts of their respective energy state spaces. The two study areas compared here exhibit furthermore a threshold-like relation between the observed free energy of soil water in the riparian zone and observed streamflow, while the tipping points coincide with the local equilibrium state of zero free energy. We found that the emergence of a potential energy excess/storage excess in the riparian zone coincides with the onset of storage-controlled direct streamflow generation. While such threshold behaviour is not unusual, it is remarkable that the tipping point is consistent with the underlying theoretical basis.

Numerically efficient representation of anisotropic valence bands in semiconductor quantum-well optoelectronic devices

We present a computationally efficient approach to representing valence band (VB) anisotropies in semiconductor quantum-well optoelectronic devices. The VB dispersion is calculated along the high-symmetry lang100rang and lang110rang axes with the four-band kmiddotp method. The VB isoenergy contours are represented by a first-order Fourier series expansion, which is used to calculate the subband density of states (DOS), the optical DOS and gain. In this way, each photon is allowed to interact with electrons and holes over a finite range of energy states, even without including lifetime broadening effects

Distortable symmetrical double well: effect of local relaxation on dielectric response

Abstract The effect of medium local relaxation, resulting from dipole reorientation, on a complex dielectric susceptibility is analyzed. The system of dipoles that have two possible orientations in space is considered. They can jump from one orientation into another. The dipoles are immersed into a condensed medium which adopts itself to a concrete orientation decreasing in such a manner the energy of the cluster including a dipole molecule (group) and the nearest environment. This process forms the range of energy states. Following from general continuity equations, the evolution of state populations was considered under initial conditions implying that the constant electric field was suddenly switched off. The decay of polarization is calculated which, in turn, allows one to calculate the frequency dependence of complex dielectric permeability using a one-side Fourier transform. Two relaxation maxima are observed to arise at low relaxation rate and with changes in the relaxation depth by a value comparable with kT . Both of the relaxation processes are interrelated. The high-frequency ( β -) maximum is determined by dipole reorientation. The low-frequency ( α -) maximum is determined by relaxation of the local environment followed by the change in dipole position. It is shown that the relaxation strength of both relaxation processes depends on the value of energy change with the local relaxation of a medium.

Cerebrospinal fluid and plasma glucose concentrations of ovine pregnancy toxaemia cases, inappetant ewes and normal ewes during late gestation

Cerebrospinal fluid (CSF) and plasma glucose concentrations of spontaneous ovine pregnancy toxaemia cases, determined within 24 h of the onset of clinical signs, were significantly lower (P < 0.01) compared to inappetant ewes and healthy ewes at a similar stage of gestation. A highly significant correlation (P < 0.001, r = 0.91) was present between the plasma and CSF glucose concentrations when the data from the three groups were combined. The data suggest that plasma glucose concentration accurately reflects CSF glucose concentration across the range of energy states in pregnant ewes and may provide support for the postulate that the neurological signs of ovine pregnancy toxaemia result from cerebral hypoglycaemia, as reflected by CSF glucose concentration. No cerebral glucose estimations were undertaken in this series.

In vivo control of phosphofructokinase: system models suggest new experimental protocols

There is still uncertainty as to how much control of in vivo rates of glycolysis by phosphofructokinase (PFK) depends on cytosolic phosphate energy state. Three models of PFK kinetics incorporating sensitivity to pH, adenine nucleotides, and inorganic phosphate (Pi) were embedded in the physiological "phosphate energy system" of creatine-containing tissues [Connett, R.J. Am. J. Physiol. 254 (Regulatory Integrative Comp. Physiol. 23): R949-R959, 1988]. Effects of changes in phosphate energy state and total adenine nucleotide and phosphate pools on steady-state kinetics were examined. Analyses mimicking in vitro experiments indicated no activity at the pH and [ATP] of working muscles. When tested using the coordinated changes in Pi and adenine nucleotides expected in vivo, all models showed reasonable activity. Control was dominated by [Pi] in the normal physiological range of energy states. The almost linear response to phosphate energy state, measured by creatine charge (phosphocreatine/total creatine), is insensitive to the absolute size of the adenine nucleotide pool. A step to almost full activation occurred when phosphocreatine buffering of [ATP] was exceeded. Several experimental studies are suggested.

A unified model for the magnetic band structure of cadmium antimonide

The authors calculate the Landau states in the valence bands of CdSb using the two-band model first proposed by Yamada (1973, 1974). The model should be valid for the whole range of energy states of physical interests in these bands. Approximate analytic formulae are obtained for the Landau energies in each band, from which are deduced the cyclotron effective masses as functions of energy or concentration for arbitrary directions of the magnetic field. They calculate also the integrated density of states as a function of energy and hence the Fermi energy as a function of carrier concentration. Finally, they propose tentative values of the band-structure parameters consistent with recent experimental data from magneto-transport experiments. With these parameters the double-hump structure of Yamada is largely suppressed, but the E-k relationship is quite flat near the top of the upper band. Thus the effective-mass anomaly mentioned in their earlier paper occurs at low hole energy. Detailed numerical calculations have been carried out for each of the cases in which the magnetic field is in the direction of a principal symmetry axis.

WHAT CHEMISTRY OWES TO X-RAYS*

IN the nineteenth century, the table of atomic weights and the periodic classification of the elements were obtained by classical chemical methods. In the twentieth century, X-ray methods have added to these, atomic numbers and atomic radii. The twin sciences of X-ray spectroscopy and X-ray crystallography were founded in 1912 by the famous von Laue experiment. By measuring the X-ray spectra of all the known elements from aluminium to gold, Moseley, in 1913, was able to show that each element could be assigned a number (not always in the order of the known atomic weights) which was later identified with the charge on the nucleus in the Rutherford-Bohr atom, or the number of extra-nuclear electrons in the neutral atom. But while the ideas of integral nuclear charge and of the K, L, M9 etc., orbits of electrons were primarily due to investigations of X-ray spectra, the study of X-ray scattering by the rare gases has shown that the Bohr orbital model is inadequate, and has demonstrated the superiority of the Sommerfeld wave-mechanical model of the atom, with its statistical electron -density distribution and its range of energy states. Atomic structure is fundamental to chemistry.