The frequency of cyclic processes in biological multistate systems

Summary Cyclic processes in stochastic models of macromolecular biological systems are considered. The diagram solution of the model equations (master equation) gives rise to special functions of the rate constants, called the circuit (or one-way cycle) fluxes. As Hill has shown, these functions are the fundamental theoretical components of the operational fluxes, i.e., of the rates of reaction, of transport, of energy conversion, etc. Evidence recently has been found by Monte Carlo simulations that the circuit fluxes can be interpreted as the frequencies of circuit completions. Making use of the theory of graphs, we prove that this physical interpretation of the circuit fluxes is generally valid.     

Effect of low-intensity monochromatic electromagnetic fields of the millimeter range on biological processes

A short systematized analysis of Soviet and foreign published materials is presented dealing with biological and physical factors responsible for the effects of monochromatic electromagnetic radiations of low power on the living activity.     

Warming and increased precipitation frequency on the Colorado Plateau: implications for biological soil crusts and soil processes

Aims

Changes in temperature and precipitation are expected to influence ecosystem processes worldwide. Despite their globally large extent, few studies to date have examined the effects of climate change in desert ecosystems, where biological soil crusts are key nutrient cycling components. The goal of this work was to assess how increased temperature and frequency of summertime precipitation affect the contributions of crust organisms to soil processes.

Methods

With a combination of experimental 2°C warming and altered summer precipitation frequency applied over 2?years, we measured soil nutrient cycling and the structure and function of crust communities.

Results

We saw no change in crust cover, composition, or other measures of crust function in response to 2°C warming and no effects on any measure of soil chemistry. In contrast, crust cover and function responded to increased frequency of summer precipitation, shifting from moss to cyanobacteria-dominated crusts; however, in the short timeframe we measured, there was no accompanying change in soil chemistry. Total bacterial and fungal biomass was also reduced in watered plots, while the activity of two enzymes increased, indicating a functional change in the microbial community.

Conclusions

Taken together, our results highlight the limited effects of warming alone on biological soil crust communities and soil chemistry, but demonstrate the substantially larger effects of altered summertime precipitation.     

Helicon plasma source in the ion-acoustic frequency range

A helicon plasma source operating in the ion cyclotron frequency range is studied theoretically. It is shown that, even with a purely inductive antenna exciting a helicon wave in a plasma at ion-acoustic frequencies, the effective resistance characterizing the absorption of high-frequency field energy is determined by the ion-acoustic field generated by the helicon wave. Calculations show that such a plasma source can operate very efficiently.     

Photo-induced charge transfer. A critical test of the mechanism and range of biological electron transfer processes.

The vibronic coupling theory of electron tunneling between biomolecules requires that all such tunnelings involve vibronic coupling, finds temperature dependence to tunneling at finite temperatures, and predicts relatively short tunneling distances. This theory might be expected to apply to most electron transfers involved in the membrane-bound electron transfer reactions of photosynthesis and oxidative phosphorylation. This paper calculates the properties of a weak charge-transfer optical absorption band, whose predicted characteristics are a direct and simple consequence of the model that describes vibronically coupled tunneling. The new absorption band provides the basis for a critical experimental test of the constructs and parameters of the tunneling theory. If the tunneling theory is valid, the oscillator strength of such bands will be the most reliable measure of the tunneling matrix element and of the distance between the sites exchanging an electron.     

The range of micrometeorological diversity in the biological environment

The range of temperature and humidity conditions that can exist simultaneously at or near the ground surface on a bright summer day in a temperate climate are shown in a diagram. Cool and warm conditions are defined as having respectively a lower and a higher temperature than the air at a height of 1.50 m above the surface of the ground. Similarly, humid and dry conditions are defined by a lower and a higher saturation deficit (S.D.), respectively. Cool, humid conditions are found in the open shade where only diffuse solar radiation is received. In high reed vegetations on wet soil, temperatures can lie 8°C below that of the free atmosphere and humidity is close to the saturation point. Warm and humid conditions are found in thin vegetations on damp soil with a temperature excess of up to 10°C and a strongly reduced S.D. In dry grassland, air temperatures 1 cm above the ground are up to 20°C higher and S.D. up to 40 mm Hg higher than at a height of 1.50 m. On suitably oriented slopes covered with dark organic material, surface temperatures can reach 50°C above the air temperature.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, Israel.     

Expanding the range of free calcium regulation in biological solutions

Many biological systems use ethylene glycol bis (beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) to regulate the free calcium concentration ([Ca(2+)](free)) in the presence of physiological levels of free Mg(2+) ([Mg(2+)](free)). Frequently, it is necessary to work at [Ca(2+)](free) beyond EGTA's buffering capabilities. Therefore, we have developed methods to extend the buffering range by adding nitrilotriacetic acid (NTA) to solutions containing EGTA. This extension results from NTA having a lower K'(dCa) than EGTA. Such equilibria are solved by pCa Calculator, a computer program designed to aid in the study of Ca(2+)-dependent physiological processes while accounting for the effects of pH, temperature, and ionic strength. With multiple chelators and pH buffers from which to choose, pCa Calculator calculates the total concentration of each species required to achieve specified free concentrations of Ca(2+), ATP, and Mg(2+). The program is intuitive, user-friendly, and flexible enough to fix or vary the [Mg-ATP(2-)] and ionic strength. Moreover, it can account for increases in experimental volume from calcium addition. A comparative analysis is reported for testing solutions in the presence and absence of NTA by measuring the calcium binding affinity of fluorescent cardiac troponin C. These findings demonstrate that EGTA, when used in conjunction with NTA, improves and expands the regulation of free calcium in solution.     

Acoustic characterisation of thoracic body tissues in the audible frequency range

A previous study by Jones and Thomas [2] suggests that data relating to the physiological condition within the thoracic cavity may be obtainable utilising low frequency acoustic signals applied to the mouth and detected on the chest wall. In order to evaluate the contribution to the mouth to chest wall frequency response of the separate elements within the thorax, and to estimate the effect on this response when the lung physiology changes, an acoustic model of the thorax is required. To aid the development of this model, experiments have been carried out in order to establish the frequency dependence of the acoustic attenuation and speed of propagation through thoracic tissue samples in the audible frequency range 20–500 Hz. Samples from the porcine family were used due to their physical similarity to those of humans and their being obtainable within a short time of death.The results of this work can be utilised in the development of an acoustic model of the human thorax, this in turn enabling simulation and analysis of low frequency acoustic transmission from the trachea to the chest wall.     

Energy deposition in a model of man in the near field

The spatial distribution of the specific absorption rate (SAR) was measured in a full-scale model of man using implantable electric field probes. The model was exposed in the near-field of linear and aperture antennas at 350 MHz. Effects of the wave polarization, antenna position and antenna gain on the SAR distribution and the average SAR in the whole-body and body parts are reported.     

Monitoring biological wastewater treatment processes: recent advances in spectroscopy applications

Biological processes based on aerobic and anaerobic technologies have been continuously developed to wastewater treatment and are currently routinely employed to reduce the contaminants discharge levels in the environment. However, most methodologies commonly applied for monitoring key parameters are labor intensive, time-consuming and just provide a snapshot of the process. Thus, spectroscopy applications in biological processes are, nowadays, considered a rapid and effective alternative technology for real-time monitoring though still lacking implementation in full-scale plants. In this review, the application of spectroscopic techniques to aerobic and anaerobic systems is addressed focusing on UV–Vis, infrared, and fluorescence spectroscopy. Furthermore, chemometric techniques, valuable tools to extract the relevant data, are also referred. To that effect, a detailed analysis is performed for aerobic and anaerobic systems to summarize the findings that have been obtained since 2000. Future prospects for the application of spectroscopic techniques in biological wastewater treatment processes are further discussed.     

Entropy in biological binding processes: Estimation of translational entropy loss

The loss of translational degrees of freedom makes an important, unfavorable contribution to the free energy of binding. Examination of experimental values suggest that calculation of this entropy using the Sackur–Tetrode equation produces largely overestimated values. Better agreement is obtained using the cratic entropy. Theoretical considerations suggest that the volumes available for the movement of a ligand in solution and in a complex are rather similar, suggesting also that the cratic entropy provides the best estimate of the loss of translational entropy. © 1994 John Wiley & Sons, Inc.     

Microevolution in biological control: Mechanisms, patterns, and processes

Microevolution may determine both the safety and efficacy of classical biological control. Despite a growing body of literature, there are several key unanswered questions regarding the role of evolution in biological control: (1) How common is local adaptation of natural enemies to their hosts or the environment in the native range? How critical is it for success of biological control to find locally adapted agents for importation? (2) Does adaptive evolution following introductions play an important role in biological control? (3) Do introductions of biological control agents impose bottlenecks in population size that reduce genetic variation, and is reduced genetic variation associated with low fitness and poor performance? (4) How great is the risk of evolution of host range of biological control agents? (5) What is the risk of target pests evolving resistance to biological control agents? If pests evolve increased resistance, will biological control agents evolve mechanisms to overcome that resistance? Here, we review the four fundamental processes of microevolution, and discuss how they interact in the context of biological control. We discuss our current state of knowledge regarding the outstanding questions, highlight the types of experiments that can address them, and suggest ways to use microevolution to define risks, and enhance efficacy and safety of biological control.     

The role of lysosphingolipids in the regulation of biological processes

This review summarizes data on the role of lysosphingolipids (glucosyl- and galactosylsphingosines, sphingosine-1-phosphate, sphingosine-1-phosphocholine) in the regulation of various biological processes in normal and pathological states.     

GOTax: investigating biological processes and biochemical activities along the taxonomic tree

We describe GOTax, a comparative genomics platform that integrates protein annotation with protein family classification and taxonomy. User-defined sets of proteins, protein families, annotation terms or taxonomic groups can be selected and compared, allowing for the analysis of distribution of biological processes and molecular activities over different taxonomic groups. In particular, a measure of functional similarity is available for comparing proteins and protein families, establishing functional relationships independent of evolution.     

Investigation of the tissue growth processes in porous implant

Investigation of the cell (osteocytes, fibroblasts and keratinocytes) adhesion and penetration in pores of the titanium pylon in vivo on the laboratory animals (Wistar rats) has been performed. The titanium pylon has been implanted in bone of a rat's thigh residuum. Electronic scanning and morphological analysis demonstrated the certain integration of the pylon with the surrounding tissues. The latter opens a possibility for development of direct skeletal attachment of limb prostheses.