Meist enden ähnliche Gespräche über Mathematik etwa an diesem Punkt, ohne dass der Nichtmathematiker von der Sinnhaftigkeit mathematischer Forschung, ja mathematischer Tätigkeit generell überzeugt werden konnte. Ich glaube nicht, dass dem Laien Blindheit für die Großartigkeit unserer Wissenschaft vorzuwerfen ist, wenn hier keine befriedigendere Kommunikation zustande kommt. Ich sehe als Ursache eher ein stark verkürztes Bild von der Mathematik, welches auch Fachleute oft zeichnen, weil ihnen eine angemessenere Darstellung ihres Faches zu viel Mühe macht - und das obwohl Mathematik nur betreiben kann, wer geistige Mühen sonst keineswegs scheut. Ich will versuchen, den Ursachen dieses eigentümlichen Phänomens auf den Grund zu gehen.
Sauer, Daniela; Schülli-Maurer, Isabelle; Sperstad, Ragnhild; Sørensen, Rolf
We studied two soil chronosequences in S Norway to identify processes involved in Albeluvisol formation. For this purpose, field observation of vertical and horizontal sections of soil profiles, soil chemical and mineralogical analyses were carried out, and in particular, micromorphological analysis was applied. The study area is located at the western and eastern side of the Oslofjord, S Norway, in the counties Vestfold and Østfold. This region is characterized by continuous glacio-isostatic uplift over the entire Holocene. Hence, the age of the land surface continuously increases from the coast towards higher elevations. Twelve soil profiles in loamy marine sediments were studied. Based on macro- and micromorphological observations and analytical data progressive soil formation is characterized as follows: As soon as the land surface is raised above sea level, five major processes are initiated: 1) development of deep desiccation cracks, forming a polygonal pattern; 2) compaction, taking place as soon as the coarse pores have been drained; 3) pyrite oxidation and release of sulfuric acid; 4) carbonate dissolution by acids from pyrite and iron oxidation resulting in rapid decarbonatization of the originally calcareous sediments; 5) precipitation of iron hypocoatings and coatings in the capillary fringe Soon after these very early processes have taken place, limited water permeability of the fine-textured sediments leads to horizon differentiation into Ah, Eg and Btg horizons within less than 2.1 ka. Eg horizons become lighter in colour with time. Also illuvial clay is already observed in the 2.1 ka-old soil. Soil pH in the upper part of the E horizon of this soil is already too low for significant clay mobilization. Clay illuviation is still active in all soils studied, but the upper boundary of the zone where pH favours clay mobilization is at 20-50 cm depth. Progressive clay illuviation over time is recorded in increasing thickness of clay coatings and proportion of voids having clay coatings. Clay mobilization and iron co-eluviation in the upper Eg horizon ceases within less than 2.1 ka, whereas weathering and formation of clay minerals and iron oxides continue, leading to formation of a BE horizon in the upper part of the Eg horizon. Albeluvic tongues start to form after 4.6-6.2 ka, developing preferably along desiccation cracks. Albeluvic material is washed into the cracks, and also enhanced leaching of bases and clay eluviation take place in the cracks. As both processes proceed, the albeluvic tongues get longer and wider. Clayey intercalations occur in the older soils (Stagnic Albeluvisols), and the following concept is suggested to explain their genesis: When after snow melt or a rainy period infiltrating water arrives at the lower end of an albeluvic tongue, the tongue fills up with water. Perched water accumulates also on top of the dense Btg horizon. Water, carrying suspended clay, penetrates under the pressure of the overlying water column from the tongue into the Btg horizon, where additional clay is mobilized. The clay settles when the velocity of the water decreases, forming clayey intercalations in the dense matrix of the Btg horizon.
North Korea is estimated to have 5,000 metric tons of nerve agent stored along the DMZ, in addition to its stockpiles of blood, blister and...June 1997. 15. Nonlethal Weapons: Terms and References. Robert J. Bunker, July 1997. 16. Threat Perceptions in the Philippines, Malaysia , and... Makros and Jeremy C. Saunders, June 2001. 41. The Common European Security and Defense Policy (ESDP), Edward G. Gunning, Jr., July 2001. 42
Comparative in vitro study of the proliferation and growth of ovine osteoblast-like cells on various alloplastic biomaterials manufactured for augmentation and reconstruction of tissue or bone defects.
Schmitt, Sandra C; Wiedmann-Al-Ahmad, Margit; Kuschnierz, Jens; Al-Ahmad, Ali; Huebner, Ute; Schmelzeisen, Rainer; Gutwald, Ralf
In this in vitro study ovine osteoblast-like cells were cultured on seven different alloplastic biomaterials used for augmentation and for reconstruction of bone defects in dental and craniomaxillofacial surgery. The aim of this study was to examine the growth behaviour (viability, cell density and morphology) of ovine osteoblast-like cells on the investigated biomaterials to get knowledge which biomaterial is qualified to act as a cell carrier system in further in vivo experiments. The biomaterials were either synthetically manufactured or of natural origin. As synthetically manufactured biomaterials Ethisorb, MakroSorb, PalacosR, and PDS film were used. As biomaterials of natural origin BeriplastP, Bio-Oss and Titanmesh were investigated. The cell proliferation and cell colonization were analyzed by a proliferation assay and scanning electron microscopy. Osteoblast-like cells proliferated and attached on all biomaterials, except on Beriplast. On Ethisorb the highest cell proliferation rate was measured followed by PalacosR. Both biomaterials offer suitable growth and proliferation conditions for ovine osteoblast-like cells. The proliferation rates of Bio-Oss, MakroSorb, PDS-film and Titanmesh were low and SEM examinations of these materials showed less spread osteoblast-like cells. The results showed that ovine osteoblast-like cells appear to be sensitive to substrate composition and topography. This in vitro study provides the basis for further in vivo studies using the sheep model to examine the biocompatibility and the long-term interaction between the test material and tissue (bone regeneration).
Askar, Enis; Schröder, Volkmar; Acikalin, Aydan; Steinbach, Jörg
A calculation method for flammability limits of gas phases with ethylene oxide in sterilisers was developed. Using the Software GasEq and the newly developed Makro "SterEx" for MS-Excel, flammability limits of mixtures with ethylene oxide, air and inert gases at temperatures between 20 degrees C and 100 degrees C and pressures between 0.4 bar and 1.0 bar can be calculated. This method can be used to easily determine safe operating conditions. The used semi-empirical model is based upon the assumption of constant flame temperature profiles at the flammability limits subject to the EO-concentration for different mixtures. To collect model parameters and to validate the model, several experiments with mixtures of ethylene oxide, nitrogen, carbon dioxide, water vapour and air were carried out to determine flammability limits. To simulate the structural conditions of sterilisers, the experiments were conducted in accordance to DIN EN 1839-B in a closed autoclave with temperatures and pressures relevant for sterilisation processes. The calculation of flammability limits of process gas mixtures with "SterEx" provides good agreement with flammability limits that were determined in experiments.
Khodyreva, E. Ya.; Khodyrev, Yu. P.
. Soil is an important component of the earth's biosphere because of its crucial role in the hydrological cycle. For revealing possible correlation between spatial distributions of the valuable elements contained both in industrial waters and in tests of soils, 79 samples are prepared and investigated. These tests are selected at superficial geochemical shooting (field monitoring methods of studies) Aznakaevskoi, Karamalinskoi and Sabanchinskoi areas of joint-stock company " Tatneft ". Circuits of distribution of valuable elements on the investigated territory are constructed also a quantitative estimation of the maintenance makro- and microcomponents is given. From the found out elements the greatest interest Na, Mg, K, Ca, Cl, Br and their connections represent because of very high concentration and scandium owing to the cost. Now cost of scandium in the world market approximately in 25 times exceeds cost of gold and is not observed yet tendencies to its decrease. Presence of impurity of salts of heavy metals and their connections in soils, drinking, underground and stratum waters, definition of their concentration and comparison from maximum concentration limit allows to establish the control over dynamics of ecohydrological conditions and in due time to take measures on reduction of negative influence of processes of development of hydrocarbon raw material by an environment.