Infrared spectroscopy of the skin: influencing the stratum corneum with cosmetic products

The stratum corneum is the outermost layer of the skin and, as such, represents the decisive barrier between the body and the environment. The combination of horny cells and lamellar lipid layers prevents water loss from the body and protects it against penetration by exogenous substances. For selective investigation of the thin outermost stratum corneum layer ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopy has proved itself in practice. It provides information about the sebum content, type of fatty substances, water content and degree of order of the lamellar lipid film in the stratum corneum. Different types of skin (dry, normal and greasy) differ mainly in their sebum content but also in the composition of their fats and the degree of order of their lipids. A comparison with model lipid mixtures shows that the stratum corneum lipids are mainly present in a fixed gel form under physiological conditions. In cleansing processes a large part of the sebum is removed from the skin. The skin reacts to the defatting process by the rapid secretion of sebum. After cleansing with a mild face cleansing emulsion the re-achievement of the same fat status takes longer than with a surfactant shower gel. Skin creams cause alterations to the skin moisture and in the degree of order of the stratum corneum lipids. A lamellar cream with a structure similar to that of the stratum corneum lipids increases the degree of order of the alkyl chains of the skin lipid film (biomimetic principle), whereas a conventional w/o cream reduces this degree of order. Skin moisture increases after the use of the creams.     

An analytic study of a scalable video buffer

In this contribution, we investigate the performance of the output buffer of an ‘on-demand’ video streaming server. The server maintains a local database of stored video clips and movies which can be streamed to the users upon request. We assume that the stored video is encoded in a scalable way, which means that the data streams contain a base layer ensuring a minimum of guaranteed quality and a stack of additional enhancement layers progressively improving the quality of the video. For the purpose of performance analysis, we assume that a video stream is split up in logical units called frames. Every frame consists of a number of packets, each containing information of one layer only. When the output buffer gets congested, one may choose to drop the transmission of some of the layers in a frame, thus reducing the frame transmission time and expediting the restoration of the buffer size to normal levels. A discrete-time finite capacity queueing model with buffer size dependent transmission times is proposed. Using a probability generating function approach, we focus on the characteristics of idle and busy periods. We obtain performance measures such as the frame loss ratio and the average frame transmission time. The latter measure relates to the quality of the video stream. We conclude with some numerical examples, including a realistic case study.     

Unsteady jet impingement: Heat transfer on smooth and non-smooth surfaces

Often studies that determine the influence of unsteadiness on flat plate impinging jet heat transfer implicitly assume that the effect of unsteadiness found on smooth impingement surfaces also holds on surfaces with certain obstacles on them. In order to test this assumption a single roughness element was added to an otherwise smooth surface, and it was found that the steady heat transfer was almost the same as that for a totally smooth surface. The effect of unsteadiness, however, can be fundamentally different when roughness elements are added to a smooth surface. Slight changes in the surface geometry thus can have strong impact with respect to the effect of unsteadiness on heat transfer under impinging jets and cannot be neglected a priori.     

Performance analysis of a discrete-time queueing system with priority jumps

Supporting multiple types of traffic with different Quality of Service (QoS) requirements is not an easy task in modern communication networks. An efficient priority scheduling scheme is thus of great importance. The static, Head-Of-Line (HOL) priority scheme achieves differentiation between different types of traffic, but may have a too severe impact on the performance level of lower-priority traffic. We therefore propose a priority scheme with priority jumps in this paper: the Head-Of-Line Jump-If-Arrival (HOL-JIA) scheme. We show that the use of probability generating functions (pgfs) is suitable for analytically studying the system, and for illustrating the impact of priority jumps on the performance of the system.     

Qualitätsprüfung nach den Vorschriften des Stahl-Eisen-Prüfblattes 1570/71 mittels eines automatischen Bildanalysesystems

Untersuchung von Stahlproben auf nichtmetallische Einschlüsse gemäß Stahl-Eisen-Prüfblatt. Entwicklung eines vollautomatischen Verfahrens zur Klassierung unterschiedlicher Einschlüsse nach Form und Größe entsprechend dem Prüfblatt. Messung von Formparametern und Anschliffflächen der Einschlüsse mit Hilfe eines automatischen Bildanalysators. Erkennung von Zeilen durch Clusterung über Feret-Durchmesser in und quer zur Zeilenrichtung. Bewertung der Stahlqualität über das K- bzw. M-Verfahren des Prüfblattes.     

Local Entropy Production in Turbulent Shear Flows： A Tool for Evaluating Heat Transfer Performance

Performance evaluation of heat transfer devices can be based on the overall entropy production in these devices. In our study we therefore provide equations for the systematic and detailed determination of local entropy production due to dissipation of mechanical energy and due to heat conduction, both in turbulent flows. After turbulence modeling has been incorporated for the fluctuating parts the overall entropy production can be determined by integration with respect to the whole flow domain. Since, however, entropy production rates show very steep gradients close to the wall, numerical solutions are far more effective with wall functions for the entropy production terms. These wall functions are mandatory when high Reynolds number turbulence models are used. For turbulent flow in a pipe with an inserted twisted tape as heat transfer promoter it is shown that based on the overall entropy production rate a clear statement from a thermodynamic point of view is possible. For a certain range of twist strength there is a decrease in overall entropy production compared to the case without insert. Also, the optimum twist strength can be determined. This information is unavailable when only pressure drop and heat transfer data are given.     

The transformation of requirements into software primitives: Studying evolvability based on systems theoretic stability

Evolvability is widely considered to be a crucial characteristic of software architectures, particularly in the area of information systems. Although many approaches have been proposed for improving evolvability, most indications are that it remains challenging to deliver the required levels of evolvability. In this paper, we present a theoretical approach to how the concept of systems theoretic stability can be applied to the evolvability of software architectures of information systems. We define and formalize the transformation of a set of basic functional requirements into a set of instantiations of software constructs. We define this transformation using both a static and a dynamic perspective. In the latter perspective, we formulate the postulate that information systems should be stable against new requirements. Based on this postulate, we derive a number of design theorems for software implementation. Using this transformation we use theoretical arguments to derive that these theorems contribute to achieving stability.