Synthesis and characterization of in situ anionically polymerized p-aminobenzoylcaprolactam using di-and tri-functional initiator systems

Summary p-Aminobenzoylcaprolactam has been polymerized anionically in a two-step process to produce aramide-amide copolymers. Both drawn fibers and unoriented films may be produced using this method. The samples were characterized using FTIR, solution NMR, thermal analysis, viscosity, and mechanical testing. FTIR and NMR revealed the incorporation of both the aramid and amide linkages into the polymer backbone. TGA results gave a lower decomposition temperature than that of both aramide and nylon 6 materials. Intrinsic viscosities averaged 0.5 dL/g for the drawn copolymer samples polymerized by the di-functional initiator. Light microscopy displayed crystalline domains that did not appear to melt even up to 300°C. Mechanical testing showed that the initial moduli of drawn fiber samples to be in the range of 30–80 MPa, while homopolymers of nylon 6 and p-benzamide possessed values of 25 MPa and 2.70×10³ MPa, respectively.     

Short- and long-term joint symbolic dynamics of heart rate and blood pressure in dilated cardiomyopathy

Autonomic cardiovascular control involves complex interactions of heart rate and blood pressure. In patients with dilated cardiomyopathy (DCM), this control is impaired and parameters for its quantification might be of prognostic importance. In this paper, we introduce methods based on joint symbolic dynamics (JSD) for the enhanced analysis of heart rate and blood pressure interactions. To assess the coarse-grained dynamics beat-to-beat changes of heart rate and blood pressure are encoded in symbol strings. Subsequently, the distribution properties of short symbol sequences (words) as well as the scaling properties of the whole symbol string are assessed. The comparison of joint symbolic heart rate and blood pressure dynamics in DCM (n = 75) with those in healthy controls (n = 75) showed significant changes. Both, the distribution of words and the scaling properties indicate a loss in heart rate dynamics associated with blood pressure regulation in DCM. In conclusion, the analyses of short- and long-term JSDs provide insights into complex physiological heart rate and blood pressure interactions and furthermore reveal patho-physiological cardiovascular control in DCM.     

Extending the lifetime of the running electrolyte in capillary electrophoresis by using additional compartments for external electrolysis

The use of two additional reservoirs to accommodate the electrodes of the power source is proposed to improve the stability of the running electrolyte in capillary electrophoresis. The basic idea is to use salt bridges to connect those reservoirs to the ones containing the capillary ends. Although simple, there are several issues that can be considered in the design and implementation of such system in order to prevent undesired transference of material between the electrolysis and the main reservoirs. The use of a sealed electrolysis reservoir without a gas phase, the use of materials that ensure volume stability, and the use of bridges as long as possible are three basic directions. A compromise is involved in the dimensions of the sectional area of the bridge, because a small area diminishes the amount of a species transferred by diffusion but leads to an undesirable increase of the electrical field during the electrophoretic running. Thus, a bridge composed of a main wide-bore tube connected to a small-bore capillary seems to give the best performance for practical use. A simple electrolysis-separated system was adapted to a preexisting capillary electrophoresis system, and its performance was evaluated with a mixture of tartaric, malic, and succinic acids that was separated in sodium benzoate solution (pH 5.5) using the original equipment and the modified one. Due to the water electrolysis and the small buffering capacity of the electrolyte, there was a significant pH change and consequently changes in the effective mobilities of the analytes and loss of resolution after a few runs using the original equipment. Using the electrolysis-separated system, no significant change in the migration time and resolution was observed even after 15 runs. Besides the freedom to prepare running electrolytes with electroactive species or unbuffered solution, high throughput and the use of small reservoirs, such as the ones used in microfluidic devices, are the main advantages of the system.     

Spatio-temporal coding in complex media for optimum beamforming: the iterative time-reversal approach

Spatio-temporal encoding in transmit and receive modes is of major importance in the development of ultrasound imaging devices. Classically, the assumption of constant sound speed in the medium allows one to restrict the beamforming process to the application of a cylindrical time-delay law on the elements of a multiple-transducer array. Here is proposed an iterative time-reversal method capable of taking into account all the heterogeneities of the medium, concerning density, speed of sound, and absorption variations. It will be shown that this iterative focusing process converges toward a spatio-temporal inverse filter focusing, the first step of the process being a time-reversal focusing on the targeted point. This method can be seen as a calibration process and has been successfully applied to transskull focusing and intraplate echoes suppression. It is leading the way to promising applications such as high-resolution ultrasonic brain imaging and high-resolution focusing through complex reverberating media, in nondestructive testing and telecommunications. This work highlights the advantages of using spatio-temporal coding to focus through complex media. Such codes require the use of fully programmable, multichannel electronics to implement this technique in real time.     

Evaluation of microsatellites as a potential tool for product tracing of ground beef mixtures

Microsatellite genotyping was evaluated as a potential tool for DNA-based tracing of ground beef product. DNA from mixtures containing different numbers of individuals was analysed with a set of cattle microsatellite markers frequently used for parentage testing. As samples contained DNA from several animals, the microsatellite markers showed multiple peaks. The method could distinguish between mixtures containing equal amounts of meat from three different individuals, meat from three individuals mixed in different proportions, ground beef mixtures purchased in different cities, and different batches of ground beef patties. Limitations occurred when batches contained large numbers of individuals (>10) and different batches used meat from the same individuals. We conclude that DNA microsatellites may be useful for DNA traceability of ground beef mixtures prepared from less than 10 individuals, but where larger numbers of animals contribute to a mixture the method is not consistently accurate.     

Molecular thermodynamics of liquids containing supercritical compounds

The changes of pressure and activity coefficients with component densities are expressed in terms of statistical mechanical direct correlation function     

Texture development of strip cast ferritic stainless steel

The textures and the mechanical properties of a strip cast, cold rolled and recrystallized ferritic stainless steel with 16% Cr have been investigated and compared to conventionally processed hot band. The strip cast initial material exposed three improvements. First, the textures were weaker and more homogeneous through the sheet thickness. Second, it revealed a higher Lankfort value and third, the complete elimination of the ridging phenomenon.     

Influence of Surface Topography on the Tribological Behaviour of Aluminium Alloy 5182 with EDT Surface

Friction is one of the most important parameters in sheet metal forming. Friction conditions are influenced by the texture of the sheet surface, by the surface or coating of the tools and by the lubrication. The aluminium alloy AA 5182 with EDT surface has been studied and tested at various angles between rolling and sliding direction. The friction behaviour observed in experiments at different normal pressures based on Coulomb’s friction law are shown and discussed in this article. Moreover, local surface topography and lubricant distribution in the contact area are described.     

Sputtered metal lift-off for grating fabrication on InP based optical devices

Sputtered metal gratings have been realized using lift-off process based on bilayer resist electron beam lithography (EBL). The lithography mask is composed of PMMA (poly(methylméthacrylate)) layer deposited under HSQ (hydrogen silsesquioxane) inorganic resist. EBL is performed in HSQ, whereas PMMA is used to ease final lift-off. We demonstrate the possibility of patterning by lift-off metals with different sputtering yields and deposition conditions. Gratings with period of 200 nm and filling factor of 50% are obtained.