The geometry and motion of reaction-diffusion waves on closed two-dimensional manifolds

Chemical or biological systems modelled by reaction diffusion (R.D.) equations which support simple one-dimensional travelling waves (oscillatory or otherwise) may be expected to produce intricate two or three-dimensional spatial patterns, either stationary or subject to certain motion. Such structures have been observed experimentally. Asymptotic considerations applied to a general class of such systems lead to fundamental restrictions on the existence and geometrical form of possible structures. As a consequence of the geometrical setting, it is a straightforward matter to consider the propagation of waves on closed two-dimensional manifolds. We derive a fundamental equation for R.D. wave propagation on surfaces and discuss its significance. We consider the existence and propagation of rotationally symmetric and double spiral waves on the sphere and on the torus.On leave of absence from: Department of Mathematics, Glasgow College of Technology, Cowcaddens Road, Glasgow G4 0BA, Scotland, UK     

A model for microcarrier motion inside a horizontally rotating bioreactor for animal cell culture

The motion of microcarriers inside the horizontally rotating bioreactor was simulated in order to obtain some insight as to how particle motion can affect radial mass transfer. Fluid motion was modeled taking into account momentum transfer induced by particle motion. The force balance on the particle included the viscous drag, inertia, gravitational and buoyant forces. The main characteristics of observed particle motion under conditions of low particle concentration were reproduced by the model. Some implications of particle motion to mass transfer are discussed.     

Molecular dynamics simulation of single-walled carbon nanotubes inside liquid crystals

Molecular dynamic simulations of systems of single-walled carbon nanotubes (CNTs) in liquid crystalline solvents were performed, in order to investigate the effect of the molecular structure and phase of the liquid crystal (LC) on the interactions between the CNTs. Three different LC molecules (5CB, 8CB and 5CF) were considered in our study. Our results with 5CB and 8CB suggest that increasing the chain length of the hydrophobic part of the LC molecule by three carbon atoms is insufficient to decrease the tendency for the CNTs to aggregate in the LCs. Additionally, varying the phase of the LC is also insufficient to decrease the aggregation tendency of the CNTs. However, simulations with 5CF (which has fluorine atoms in the head group of the LC molecule) suggest that this LC solvent can decrease the tendency of the CNTs to aggregate. This study is relevant to assist experimentalists with the development of high-quality dispersions of large concentrations of CNTs in the LCs.     

Influence of size of culture vessel on in vitro proliferation of grape in a liquid medium

The in vitro proliferation of Vitis vinifera L. cv. Liemberger in a liquid medium was compared in 125 and 250 ml Erlenmeyer flasks and in 473 ml (pint) Mason jars. After 6 weeks of culture the jars yielded a significantly greater number of shoots 3 mm or longer than the flasks. Jars yielded the greatest number of shoots 7 mm or longer, followed by 250 ml, then 125 ml flasks. The mean length of shoots in the 250 ml flasks was significantly greater than that of shoots in 125 ml flasks. The final mean fresh weight of the cultures in jars was significantly less than that of the cultures in flasks. Thus the size of vessel used influenced the in vitro proliferation of grapevines in liquid culture.     

Pattern formation of powder on a vibrating disc

Fine grain powder placed on a regularly vibrating disk shows dissipative patterns. This behaviour was investigated and a mathematical model was developed. The pattern formation can be explained through a nonlinear diffusion term.Presented at the 9th Cybernetics-Congress, Göttingen, March 1986     

High-performance liquid chromatographic technique for detection of a fluorescent analogue of ADP-ribose in isolated blood vessel preparations

Analysis of endogenous nucleotides in biologic media is hampered by rapid degradation and low final concentrations that are difficult to detect. A reversed-phase high-performance liquid chromatographic (HPLC) technique is described that efficiently detects a stable fluorescence derivative of adenosine 5'-diphosphoribose (ADPR), 1,N6-etheno-ADPR (epsilon-ADPR), at low femtomolar concentration range in vascular tissue superfusates. epsilon-ADPR was formed by the reaction of ADPR with chloroacetaldehyde at 80 degrees C and pH 4.0. Gradient elution with 0.1 M KH2PO4 (pH 6.0), increasing methanol (0-35% over 18 min), and a 25-cm by 4.5-mm (5 microm) silica ODS-AM column were employed. epsilon-ADPR was detected by fluorescence at an excitation wavelength of 230 nm and an emission wavelength of 410 nm. The detection sensitivity for epsilon-ADPR was approximately 10 fmol. Linearity of the HPLC detection method was demonstrated in the range from 0.0125 to 1 pmol epsilon-ADPR. The method was validated in terms of within-day and between-day reproducibility of retention times and peak areas of standard nucleotide. Matrix-assisted laser desorption/ionization mass spectrometry measurements confirmed the presence of an etheno ring after reaction of ADPR with chloroacetaldehyde. The method was applied to quantitate the overflow of ADPR upon electrical field stimulation (8 Hz, 0.3 ms, 15 V, 1-2 min) of both canine and guinea-pig isolated mesenteric artery segments.     

Intercalation activating fluorescence DNA probe and its application to homogeneous quantification of a target sequence by isothermal sequence amplification in a closed vessel

We developed a completely homogeneous and isothermal method of detecting RNA sequences and demonstrated ultrarapid and direct quantification of pathogenic gene expression with high sensitivity. The assay is based on performing isothermal RNA sequence amplification in the presence of our novel DNA probe, an intercalation activating fluorescence DNA probe, and measuring the fluorescence intensity of the reaction mixture. When detecting mecA gene expression of methicillin-resistant Staphylococcus aureus, we quantified starting copies ranging from 10 to 10(7) copies within 10min. The primer sequences were designed to bind to secondary structure-free sites of the target RNA, which enabled a totally isothermal protocol to quantify mRNA specifically in a sample of existing genomic DNA. When we applied this to quantifying the expression of marker genes of Vibrio parahaemolyticus and Mycobacterium bovis BCG strain, the results correlated well with the viability of each bacterium. We also demonstrated monitoring Pab gene expression of M. bovis BCG during cultivation with antibiotics. The present method can potentially realize rapid antimicrobial susceptibility testing of slowly growing organisms, such as tuberculosis.     

Brownian dynamics simulation of substrate motion near active site of enzyme entrapped inside reverse micelle

Brownian dynamics simulation has been applied to analyze the influence of the electrostatic field of a reverse micelle on the enzyme-substrate complex formation inside a micelle. The probability that the enzyme-substrate complex will form from serine protease (trypsin) and the specific hydrophilic cationic substrate Nα-benzoyl-l-arginine ethyl ester has been studied within the framework of the encounter complex formation theory. It has been shown that surfactant charge, dipole moments created by charged surfactant molecules and counterions, and permittivity of the inner core of reverse micelles can all be used as regulatory parameters to alter the substrate orientation near the active site of the enzyme and to change the probability that the enzyme-substrate complex will form.     

Dynamic motion of La atom inside the C74 (D 3h) cage: a relativistic DFT study

The interaction between lanthanum atom (La) and C₇₄ (D _3h) was investigated by all-electron relativistic density function theory (DFT). With the aid of the representative patch of C₇₄ (D _3h), we studied the interaction between C₇₄ (D _3h) and La and obtained the interaction potential. Optimized structures show that there are three equivalent stable isomers, with La located about 1.7 Å off center. There is one transition state between every two stable isomers. According to the minimum energy pathway, the possible movement trajectory of La atoms in the C₇₄ (D _3h) cage was explored. The calculated energy barrier for La atoms moving from the stable isomer to the transition state is 18.4 kcal mol^?1. In addition, the dynamic NMR spectra of La@C₇₄ according to the trajectory was calculated.

Non-invasive measurement of bioelectric currents with a vibrating probe

Small d.c. electrical signals have been detected in many biological systems and often serve important functions in cells and organs. For example, we have recently found that they play a far more important role in directing cell migration in wound healing than previously thought. Here, we describe the manufacture and use of a simplified ultrasensitive vibrating probe system for measuring extracellular electrical currents. This vibrating probe is an insulated, sharpened metal wire with a small platinum-black tip (10-30 microm), which can detect ionic currents in the microA cm(-2) range in physiological saline. The probe is vibrated at about 300 Hz by a piezoelectric bender. In the presence of an ionic current, the probe detects a voltage difference between the extremes of its movement. The basic, low-cost system we describe is readily adaptable to most laboratories interested in measuring physiological electric currents associated with wounds, developing embryos and other biological systems.     

The mitochondrial genome, a growing interest inside an organelle

Mitochondria are semi-autonomously reproductive organelles within eukaryotic cells carrying their own genetic material, called the mitochondrial genome (mtDNA). Until some years ago, mtDNA had primarily been used as a tool in population genetics. As scientists began associating mtDNA mutations with dozens of mysterious disorders, as well as the aging process and a variety of chronic degenerative diseases, it became increasingly evident that the information contained in this genome had substantial potential applications to improve human health. Today, mitochondria research covers a wide range of disciplines, including clinical medicine, biochemistry, genetics, molecular cell biology, bioinformatics, plant sciences and physiology. The present review intends to present a summary of the most exiting fields of the mitochondrial research bringing together several contributes in terms of original prospective and future applications.     

The dynamic motion of a M (M = Ca, Yb) atom inside the C74 (D 3h) cage: a relativistic DFT study

The interaction between M (M?=?Ca, Yb) atom and C₇₄ (D _3h) has been investigated by all electron relativistic density function theory. With the aid of the representative patch of C₇₄ (D _3h), we studied the interaction between C₇₄ (D _3h) and M (M?=?Ca, Yb) atom and obtained the interaction potential. Optimized structures show that there are three equivalent stable isomers and there is one transition state between every two stable isomers. According to the minimum energy pathway, the possible movement trajectory of M (M?=?Ca, Yb) atom in the C₇₄ (D _3h) cage is explored. The calculated energy barrier for Yb atoms moving from the stable isomer to the transition state is 10.4 kcal mol^?1 and the energy barrier for Ca atoms is 6.1 kcal mol^?1. The calculated NMR spectra of M@C₇₄ (M?=?Ca, Yb) are in good agreement with the experimental data. There are nine lines in the spectra: one 1/6 intensity signal, four half intensity signals and four full intensity signals.     

Validation and use of an enzymic time-temperature integrator to monitor thermal impacts inside a solid/liquid model food

Heat denaturation kinetics of Bacillus licheniformis alpha-amylase, equilibrated at 81% equilibrium relative humidity at 4 degrees C (BLA81), was studied with help of isothermal and nonisothermal conditions by monitoring the decrease in enthalpy associated with the heat denaturation of the enzyme. Due to its low water content, BLA81 denaturation could be studied in the range of 118-124 degrees C. Two batches of BLA81 were successfully validated under nonisothermal conditions allowing the determinations of process values (reference temperature of 121.1 degrees C) in the range of 1-15 min. In a second step, BLA81 was used as a time-temperature integrator (TTI) to investigate potential differences of process values received by freely moving spherical particles as compared to a centrally fixed particle (single-position impact) inside cans containing water as brine. Results showed that the process value received by freely moving particles can be from 5.6% (4 rpm) to 19.7% (8 rpm) smaller than the process value received by the centrally fixed sphere. This means that evaluating the process value by means of a particle fixed at the critical point in a package can lead to potentially overestimations of the actual process value with possible hazardous quality/safety implications. These results highlight the potentials of the TTI technology to monitor the safety of heat-processed agitated solid/liquid foodstuffs.