Alternierende copolymere über komplexierte monomere

The copolymerization of olefins and acrylic monomers in the presence of alkylaluminum halides was studied in dichloromethane at ?70°C. It was found that the copolymerization does not start spontaneously but is initiated only upon addition of oxygen or organic peroxides. The role of the aluminumorganic compound is dual in that it acts as a coinitiator and as complexing agent for the acrylic monomer as well as the resulting strictly alternating copolymer. High Lewis acid strength of the of the ethylaluminum chloride is advantageous with regard to the yield and the molecular weight of the copolymers, which are also effected by the relative and absolute concentrations of the various components in the system. Some of the material properties of the alternating copolymers are unique as compared to the corresponding (hypothetical) statistical copolymers and the parent homopolymers.     

On the Road to Personalized Medicine: Multiscale Computational Modeling of Bone Tissue

Personalized medicine is an emerging field, considered by many in the biomedical community to be among the upcoming approaches to medical treatment. To embrace this new challenge, physicians need a better understanding of the biological processes in the human body, as well as precise diagnostic tools and patient-specific treatments. In response, the last three decades have witnessed a major shift in tissue engineering development, from treating bone tissue at the macro-scale level only to treating it at complex multiscale levels. Researchers have begun striving for a better understanding of bone structure and mechanics, and then applying this knowledge in designing new medical treatments and procedures. Today computational methods, including finite element analyses, are the tool of choice for biomechanical research of bone tissues. Moreover, bone multiscale modeling can become a vital part of a comprehensive computerized diagnostic system for patient-specific treatment of metabolic bone diseases, fractures and bone cancer. This review paper describes the state of the art in multiscale computational methods used in analyzing bone tissue. The discussed methods and techniques can serve as a base for the creation of such an envisioned diagnostic system.     

Die zerlegung eines gemisches von kohlenoxyd,stickstoff und wasserstoff

Zusammenfassung Es werden die Gleichgewichtsbedingungen für ein Dampfgemisch von Kohlenoxyd, Stickstoff und Wasserstoff und ein Flüssigkeitsgemisch von Kohlenoxyd und Stickstoff aufgestellt und auf einen besonderen Fall der Zerlegung dieses Gemisches angewendet. In Erg?nzung dazu folgt eine allgemeine thermodynamische Darstellung des Trennungsvorganges, aus der sich die eingangs verwendeten Gleichungen durch Vereinfachungen ergeben.     

Interrogation of “surface,” “skin,” and “core” orientation in thermotropic liquid‐crystalline copolyester moldings by near‐edge X‐ray absorption fine structure and wide‐angle X‐ray scattering

Injection molding thermotropic liquid‐crystalline polymers (TLCPs) usually results in the fabrication of molded articles that possess complex states of orientation that vary greatly as a function of thickness. “Skin‐core” morphologies are often observed in TLCP moldings. Given that both “core” and “skin” orientation states may often differ both in magnitude and direction, deconvolution of these complex orientation states requires a method to separately characterize molecular orientation in the surface region. A combination of two‐dimensional wide‐angle X‐ray scattering (WAXS) in transmission and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy is used to probe the molecular orientation in injection molded plaques fabricated from a 4,4′‐dihydroxy‐α‐methylstilbene (DHαMS)‐based thermotropic liquid crystalline copolyester. Partial electron yield (PEY) mode NEXAFS is a noninvasive ex situ characterization tool with exquisite surface sensitivity that samples to a depth of 2 nm. The effects of plaque geometry and injection molding processing conditions on surface orientation in the regions on‐ and off‐ axis to the centerline of injection molded plaques are presented and discussed. Quantitative comparisons are made between orientation parameters obtained by NEXAFS and those from 2D WAXS in transmission, which are dominated by the microstructure in the skin and core regions. Some qualitative comparisons are also made with 2D WAXS results from the literature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Simultaneous visualization of the flow inside and around droplets generated in microchannels

This paper reports the visualization of droplet formation in co-flowing microfluidic devices using food-grade aqueous biopolymer–surfactant solutions as the dispersed droplet phase and sunflower oil as the continuous phase. Microparticle image velocimetry and streak imaging techniques are utilized to simultaneously recover the velocity profiles both within and around the dispersed phase during droplet formation and detachment. Different breakup mechanisms are found for Newtonian–Newtonian and non-Newtonian–Newtonian model water-in-oil emulsions, emphasizing the influence of process and material parameters such as the flow rates of both phases, interfacial tension, and the elastic properties of the non-Newtonian droplet phase on the droplet formation detachment dynamics.     

Creativity and evolution: a metadesign perspective

Abstract

In a world that is not predictable, improvisation and evolution are more than a luxury: they are a necessity. The challenge of design is not a matter of getting rid of the emergent, but rather of making it an opportunity for more creative and more sustainable solutions. User-centered and participatory design approaches have focused primarily on activities taking place at design time. These approaches have not given enough emphasis and they have provided few mechanisms to support systems as living entities that can evolve over time. Metadesign is a unique design approach concerned with opening up solution spaces rather than complete solutions (hence the prefix meta-), and aimed at creating social and technical infrastructures in which new forms of collaborative design can take place. This approach extends the traditional notion of design beyond the original development of a system to include co-adaptive processes between users and systems that enable the users to act as designers in personally meaningful activities and be creative.     

Cellular location of thymus-leukemia (TL) antigen as shown by immuno-cryoultramicrotomy

Thymus-leukemia (TL) antigen is a class I molecule of the major histocompatibility complex that is expressed on the surface of mouse cortical thymocytes. Though not expected, it has been reported that TL antigen can be found on isolated mitochondria of TL⁺ cells. We used immuno-cryoultramicrotomy to look for TL on mitochondria in situ, thereby avoiding the plasma membrane contamination that occurs when isolating organelles. Establishing optimal fixation conditions was crucial, as mitochondrial structure was not preserved by the low concentrations of fixative needed for detection of antibody labeling. The plasma membranes of tissue culture and thymus cells were labeled well with anti-TL antibody and protein A-gold conjugate, while mitochondria within the cells were not labeled. Isolation of mitochondria on a one-step Ficoll gradient resulted in a purer organelle preparation than did isolation of mitochondria by centrifugation alone. Generally, mitochondria within this purer preparation were not labeled. Our data show that under conditions where contamination by plasma membrane is not a major concern, TL antigen cannot be detected on mitochondria.     

Scanning near-field optical microscopy (SNOM)

SNOM is a non-contact stylus microscopy analogous to STM. Optical near-field interaction is used to sense approach and optical properties on the nanometre scale (?1 nm normal, 20–50 nm lateral). SNOM was demonstrated in transmission and reflection, in a topographic mode, and with amplitude as well as phase objects. The excitation of plasmons in the SNOM ‘tip’, a very recent development, greatly enhances sensitivity and permits intriguing new optical experiments. Overcoming the limit of diffraction, SNOM turns a long-held dream of optical microscopists into reality.