Chladnis Beiträge zur Raumakustik

A lot of publications on the acoustics of theatres and churches were published around the turn of the 18th to the 19th century.The authors were architects who were interested in acoustical problems. Chladni was the first physicist who published on the acoustics of rooms, he introduced the term “reverberation” into this field. His publications on this subject are reviewed. They have been the basis for the great progress of room acoustics since 1900.

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Zum 250. Geburtstag des Gelehrten     

Microstructure and physical properties of transparent thoria-yttria ceramics

The investigation of microstructure, some electrical and optical parameters of transparent ThO₂-15 mol % yo_1.5 ceramics has shown: (a) a very low porosity, close to zero; (b) a higher electrical conductivity than is usual for ThO₂ ceramics of the same composition, with the activation energy 1.12 eV; (c) a relative permittivity _r 33 under the given conditions; (d) confirmation of a single-phase fluorite-type cubic structure by means of Raman and infrared spectra.     

Utilizing deontic operators in information systems specification

One major task in requirements specification is to capture the rules relevant to the problem at hand. Declarative, rule-based approaches have been suggested by many researchers in the field. However, when it comes to modeling large systems of rules, not only for the behavior of the computer system but also for the organizational environment surrounding it, current approaches have problems with limited expressiveness, flexibility, and poor comprehensibility. Hence, rule-based approaches may benefit from improvements in two directions: (1) improvement of the rule languages themselves and (2) better integration with other, complementary modeling approaches.In this article, both issues are addressed in an integrated manner. The proposal is presented in the context of the Tempora project on rule-based information systems development, but has also been integrated with PPP. Tempora has provided a rule language based on an executable temporal logic working on top of a temporal database. The rule language is integrated with static (ER-like) and dynamic (SA/RT-like) modeling approaches. In the current proposal, the integration with complementary modeling approaches is extended by including organization modeling (actors, roles), and the expressiveness of the rule language is increased by introducing deontic operators and rule hierarchies. The main contribution of the article is not seen as any one of the above-mentioned extensions, but as the resulting comprehensive modeling support. The approach is illustrated by examples taken from an industrial case study done in connection with Tempora.C. List of Symbols Subset of set - Not subset of set - Element of set - Not element of set - Equivalent to - Not equivalent to - ¬ Negation - Logical and - Logical or - Implication - Sometime in past - Sometime in future - Always in past - Always in future - Just before - Just after - u Until - s Since - Trigger - Condition - _s State condition - Consequence - _a Action - _s State - Role - Actor - ¬ - General deontic operator - O Obligatory - R Recommended - P Permitted - D Discouraged - F Forbidden - (/–) General rule - t _R Real time - t _M Model time     

In vitro experiments on the working of combinations of gentamicin and beta-lactam antibiotics against Pseudonomas aeruginosa (author's transl)

The M.B.C.'s of gentamicin and carbenicillin against Pseudonomas aeruginosa NCTC 10490 were measured under controlled conditions using a Biophotometer. The M.B.C. of gentamicin was 15 mug/ml but even in a concentration of 1,000 mug/ml carbenicillin was not bactericidal. In further experiments, subinhibitory concentrations of gentamicin (1 mug/ml) together with varying concentrations of carbenicillin were added to a log phase culture of the organism. Under these conditions the M.B.C. of carbenicillin was now 6 mug/ml. In tube dilution test the M.B.C. of carbenicillin alone was 15.6 mug/ml and for gentamicin 3.9 mug/ml. The M.B.C.'s of other beta-lactam antibiotics (ampicillin, penicillin G and cephalothin) were four to five times as great as for carbenicillin whereas that for ticarcillin was identical. Parallel to the "multiplication inhibition" test in the Biophotometer we investigated 51 strains of Pseudomonas aeruginosa freshly isolated from clinical material. Their M.B.C.'s were determined in tube dilution tests against doubling dilutions of beta-lactam antibiotics, with and without the addition of 1 mug/ml gentamicin. With this concentration of gentamicin, the M.B.C.'s of carbenicillin and ticarcillin were considerably lower than for these substances alone. In comparison to carbenicillin, ticarcillin was more effective against Pseudomonas aeruginosa. Our findings indicate that for Pseudomonas aeruginosa infections the combination of gentamicin with other beta-lactam antibiotics (ampicillin, penicillin G and cephalothin) is to be avoided. But the combination of gentamicin with either carbenicillin or ticarcillin appeared to be effective.     

打破固定／移动电信网络界限 WiMax 802．16e行动自如

WiMax最大的胜利是吸引了一群无线宽带厂商，同时通过最佳技术、标准平台和开放协议让业界对下一代宽带无线基础设施达成广泛共识。本文将从市场应用和上市时间的角度探讨WiMax带给无线宽带产业的商机，以及对于生产制造和服务业的正面影响，并剖析固网业者如何透过它进入移动服务市场以扩大营收来源。     

Application of the Tauc-Lorentz formulation to the interband absorption of optical coating materials

Recent progress in ellipsometry instrumentation permits precise measurement and characterization of optical coating materials in the deep-UV wavelength range. Dielectric coating materials exhibit their first electronic interband transition in this spectral range. The Tauc-Lorentz model is a powerful tool with which to parameterize interband absorption above the band edge. The application of this model for the parameterization of the optical absorption of TiO2, Ta2O5, HfO2, Al2O3, and LaF3 thin-film materials is described.     

Unter welchen Voraussetzungen bewähren sich Korrosionsschutzauskleidungen aus Fluorkunststoff-Folien

Under what conditions are anticorrosion liners made from fluorinated plastic film effective ? Equipment lined with fluorinated plastics is nowadays making a major contribution to the solution of difficult materials problems. If such equipment is to be used successfully, it is essential that its manufacturer is familiar with the specific properties of the lining materials and takes them into account in the design and production of the equipment. However, it is just as important for the operator to adjust to the material when operating the plant. On the basis of many years of experience, the most important problems associated with loose liners made from polytetrafluoroethylene (PTFE) – viz. leakproofness and permeability of the liner, flange system, dimensional stability towards vacuum, handling, and installation – are indicated and possible solutions stated.     

Engineering the S1' subsite of trypsin: design of a protease which cleaves between dibasic residues

The serine protease trypsin was converted into a site-specific protease which hydrolyzes peptides between dibasic residues. Trypsin exhibits a high S1 specificity for Arg and Lys residues. However, the S1' specificity of trypsin is very broad, with only a slight preference for hydrophobic residues in P1'. We replaced Lys60 with Glu and Asp to introduce a high specificity for basic residues into the S1' site of trypsin. Both mutations cause a dramatic increase in the S1' specificity for Arg and Lys as measured by acyl transfer reactions. In K60E, the preference for Arg increases 70-fold while the preference for P1'-Lys increases 12-fold. In contrast, the preferences for other P1' residues either decrease slightly or remain the same. Thus, K60E prefers P1'-Arg over most other P1' residues by 2 orders of magnitude. Similar results are obtained when P1' specificity is measured in peptide cleavage assays. K60D exhibits an S1' specificity profile very similar to that of K60E, although the P1'-Arg preference is reduced by a factor of 2.5. Molecular modeling studies suggest that the high S1' specificity for Arg in K60E may be due to the formation of a salt bridge between Glu60 and the P1'-Arg of the substrate.