Karl Sommer

Prolonged high-pressure treatments in mammalian skeletal muscle result in loss of functional sodium channels and altered calcium channel kinetics

Activation and inactivation of ion channels involve volume changes from conformal rearrangements of channel proteins. These volume changes are highly susceptible to changes in ambient pressure. Depending on the pressure level, channel function may be irreversibly altered by pressure. The corresponding structural changes persist through the post-decompression phase. High-pressure applications are a useful tool to evaluate the pressure dependence as well as pressure limits for reversibility of such alterations. Mammalian cells are only able to tolerate much lower pressures than microorganisms. Although some limits for pressure tolerance in mammalian cells have been evaluated, the mechanisms of pressure-induced alteration of membrane physiology, in particular of channel function, are unknown. To address this question, we recorded fast inward sodium (INa) and slowly activating L-type calcium (ICa) currents in single mammalian muscle fibers in the post-decompression phase after a prolonged 3-h, high-pressure treatment of up to 20 MPa. INa and ICa peak amplitudes were markedly reduced after pressure treatment at 20 MPa. This was not from a general breakdown of membrane integrity as judged from in situ high-pressure fluorescence microscopy. Membrane integrity was preserved even for pressures as high as 35 MPa at least for pressure applications of shorter durations. Therefore, the underlying mechanisms for the observed amplitude reductions have to be determined from the activation (time-to-peak [TTP]) and inactivation (τdec) kinetics of INa and ICa. No major changes in INa kinetics, but marked increases, both in TTP and τdec for ICa, were detected after 20 MPa. The apparent molecular volume changes (activation volumes) ΔV ‡ for the pressure-dependent irreversible alteration of channel gating approached zero for Na+ channels. For Ca2+ channels, ΔV‡ was very large, with approx 2.5-fold greater values for channel activation than inactivation (approx 210 Å3). We conclude, that in skeletal muscle, high pressure differentially and irreversibly affects the gating properties and the density of functional Na+ and Ca2+ channels. Based on these results, a model of high pressure-induced alterations to the channel conformation is proposed.

Flow and compression properties of feed solids for roll-type presses and extrusion presses

Abstract In the chemical, pharmaceutical and food industry, many problems in transport, storage and handling of pulverised products are caused by formation of dust. Using roll-type presses to compact such materials, dust-free products can be realised. The operating conditions are mostly found in experiments and cannot be transferred by scaling up. Starting with the theory of Johanson, a differential equation can be derived from the equilibrium conditions of the rollers. lt describes the stress function in relation to geometric parameters and the plastic yield laws of the material. The boundary conditions and the influence of different parameters will be discussed. The throughput capacity of the rollers is determined by the prepressure at the feed point given by the feeding equipment. However, there must also be an influence of the roller speed, which is not considered in the theory. In this connection, flow speed properties of the bulk material must be introduced to calculate the effect on the throughput.

A thin film dryer approach for the determination of water diffusion coefficients in viscous products

Abstract A thin film dryer (TFD) device has been used to study the drying behavior of viscous products and their water diffusivities. The thin product film was dried convectively using different air velocities, air temperatures, air humidities, initial solid concentrations, initial film thicknesses and optional addition of agar. A mathematical model was developed based on the external and internal heat and mass transfer with ideal shrinkage. A coordinate system attached to the solids was used and later transformed to the initial height to facilitate the numerical implementation. The diffusion coefficient of the product was expressed as a function of water content and temperature by fitting the model to the experimental drying kinetics (for different conditions) obtained for a given product. The diffusion coefficients obtained for maltodextrin and PVP show good agreement with literature. They are significantly reduced when the material changes from the rubbery to the glassy state and can be well expressed by the Williams–Landel–Ferry (WLF) equation.

Liquid absorption capacity of carriers in the food technology

If a liquid should be sprayed on a powder that acts as a carrier, the Concentrated Powder Form (CPF) technology can be used. In the food industry, there is a large number of products available in powder form, which can be used as carriers for liquid components. But there is a big difference between them in view of the maximum liquid absorption capacity. To find out which attributes affect the liquid absorption capacity of these carriers, several natural substances and model particles with defined uniform diameter and spherical shape were loaded with increasing amounts of different liquids. The aim of this study is to find out more about the casual relationship between the characteristics of powders and liquids, as well as the loading capacity. Therefore, a correlation between the tapped density and the maximum loading capacity is discussed. To determine the maximum loading capacity, a simple method using a filter was developed.

Caking of Water-Soluble Amorphous and Crystalline Food Powders

Water-soluble chemicals, detergents, pharmaceuticals, and food powders often become sticky during handling at high temperature or humidity. Increasing the storage time at elevated temperature and humidity frequently leads to a time consolidation (called caking) of such powders. To clarify the mechanism of stickiness and caking, it is required that one understands the adhesion forces between single particles. The adhesion forces are dependent on material properties such as the hygroscopicity and viscosity of the substances composing the particles. Caking of crystalline water-soluble solids is caused by dissolution and re-crystallization of the crystalline substance. Time consolidation of amorphous water-soluble solids is primarily linked to sinter processes. The sinter kinetic strongly depends on the materials viscosity, which is a function of moisture content and temperature. In the current study, the caking and stickiness of different water-soluble powders such as dextrose syrup, yeast extract, sodium chloride, and milk powder are discussed based on the relevant adhesion mechanism.

The Variance as Measured Variable for the Evaluation of a Mixing Process or for the Comparison of Mixtures and Mixers

In the DFG program: “Analysis, modelling and calculation of flow mixers with and without chemical reactions (SPP 1441)” there are used different mixing machines (reactors), different objectives and different dimensions. All research programs, however, have in common, that they have to evaluate the mixture concerning its “quality”. There are totally different measured variables, measuring methods and methods of taking samples employed. Together with different “mixedness definitions”, it is difficult, if not impossible, to compare the results with regard to their “mixing efficiency”. The publication presented tries to express the fundamental requirements and dependencies of the definition “mixedness” to avoid these problems.

Characterization of Products Consisting of Synthetic, Amorphous Silica and Water with Different Moistures by Means of NMR

Mixtures of liquid and powder have usually totally different structures dependent on the moisture content. They vary from dry powders with small amounts of liquid to suspensions with a low solid concentration. For all moisture contents the binding mechanisms between the solid particles and the molecules of the liquid play an important role. In order to study these interactions, various products composed of synthetic, amorphous precipitated silica and water were produced using a special spraying technology with supercritical carbon dioxide. Thus, it is possible to produce disperse solid/fluid systems with high homogeneity. All samples were studied by means of nuclear magnetic resonance (NMR) which allows to distinguish between different types of water with regard to their mobility. The aim of this study is to develop a method for the characterization of solid/liquid systems in terms of their loading capacity of the liquid.

Rheology of Coating Materials and Their Coating Characteristics

Lots of particles used in the pharmaceutical and the food industry are coated to protect the core material. But almost no investigations about the coating material behavior do exist. In this study the focus was on the rheological material properties of fat based coating materials. Rotational shear experiments to determine the viscosity of a material were compared to oscillatory shear tests to get information about the vicoelastic behavior of the coating materials. At the liquid state the viscosity and the viscoelastic properties showed a good analogy. The viscoelastic properties of the solid coating materials yielded differences between materials that have the same properties at the liquid state.

Sampling for Grain-Size Analysis

The object of particle-size analysis is to determine the particle-size distribution or a part range, a moment or a mean of the particle-size distribution of a given population20). As is the case in any problem of sampling, the population is frequently too large to be investigated completely and a sample has to be taken which can be handled by the means of investigation available in the laboratory, and is then reduced in one or more stages to the size of an analytical sample. Inferences about the population Q must then be based on the value Q* of the distribution measured on the analytical sample. Since the analytical error is usually very small (about 2%), the sampling error, which alone will be considerd below, should be smaller or, at most, of the same order of size.

Fundamentals of Statistics

The basis of our scientific reasoning rests on classical physics taught in school and taught to engineers also during their studies. In classical physics it is assumed that processes occur in a determinate manner, ie. given data concerning the initial state, the final state can be calculated unambiguously. However, sooner or later every scientist is forced to recognize that many processes are not fully determinable. It does not actually matter whether this indeterminacy is founded in nature, as eg. in quantum physics or whether the causes are indeterminable in practice, such as the fluctuations in measurements in experiments and in sampling. As the number of individual results increases to a certain level, it is not too difficult to recognize that even these indeterminable processes have regularities which, though not valid for the individual result, hold for the total collection as such. However, suitable observational material has to be used. This process, called descriptive statistics, was for a long time the main content of statistics. The object is to collect observational material, organize it, and represent it graphically or using formulae. This type of statistics still finds expression nowadays in the population and economic statistics published in the form of year books.