Single particles accelerate final stages of capillary break up

Droplet formation of suspensions is present in many industrial and technological processes such as coating and food engineering. Whilst the finite time singularity of the minimum neck diameter in capillary break-up of simple liquids can be described by well known self-similarity solutions, the pinching of non-Brownian suspension depends in a complex way on the particle dynamics in the thinning thread. Here we focus on the very dilute regime where the filament contains only isolated beads to identify the physical mechanisms leading to the pronounced acceleration of the filament thinning observed. This accelerated regime is characterized by an asymmetric shape of the filament with an enhanced curvature that depends on the size and the spatial distribution of the particles within the capillary thread.Comment: accepted for Europhysics Letter

Bio-psycho-social aspects of severe multiple trauma

Subjects with severe multiple trauma present great challenges in rehabilitation, and investigations with a holistic bio-psycho-social point of view have been scarce. In the main part of this investigation all 146 patients with severe multiple trauma (ISS 16) admitted to a regional hospital in 1990. were target. Ten years survival probability for those discharged alive from the Department of Surgery (fl: 91) was 82%. Mortality rates were significantly higher than those of the general population, particularly during the first year after discharge, during which the main cause of death was traumatic brain injury. Later, overuse of alcohol and drugs, were the main causes of death. A principal aim was to analyse the relations between impairments/ functions. disabilities/ abilities and psychological and social well-being. In a three year follow-up investigation of 69 subjects (84% of those available), 80% had one or more residual impairments: 74% had physical and 32°/g cognitive impairment. Very few subjects (n=4) were ADL-dependent. Vocational disability was present in 19% and leisure disability in 76%. Vocational disability was associated with higher age, blue collar work and cognitive impairment. Leisure disability was most prevalent in those with severe physical impairments and residual pain. Cognitive performance was significantly related both to the severity of traumatic brain injury and to degree of psychological distress. A consecutive series of subjects with severe multiple trauma without brain injury (n:26), were investigated at admission to the rehabilitation hospital, at discharge and at follow-up 1- 3.5 year following trauma. Both retrospectively and prospectively, the subjects experienced significant decreases in satisfaction with life as a whole from before to after trauma. Furthermore, compared to before trauma, significantly fewer subjects reported to be satisfied (5-6) with life as a whole, and with the domains: Sexual life. ADL, contact with friends, leisure, vocational situation and financial situation. Among the life satisfaction domains, the most important contributors for global life satisfaction after trauma. were satisfaction with leisure, family life and vocation. In multiple regression analyses, having a sufficient social network, and also a strong sense of coherence, could buffer the negative influence of disabilities on life satisfaction following trauma. Though level of sense of coherence was closely related to simultaneously measured social well-being, the SOC was not stable over time, and the hypothesis about a strong sense of coherence as protective against future distress and reduced satisfaction after stressful life events could not be confirmed, at least not the first years after multiple trauma

Thermodynamic reaction control of nucleoside phosphorolysis

Nucleoside analogs represent a class of important drugs for cancer and antiviral treatments. Nucleoside phosphorylases (NPases) catalyze the phosphorolysis of nucleosides and are widely employed for the synthesis of pentose‐1‐phosphates and nucleoside analogs, which are difficult to access via conventional synthetic methods. However, for the vast majority of nucleosides, it has been observed that either no or incomplete conversion of the starting materials is achieved in NPase‐catalyzed reactions. For some substrates, it has been shown that these reactions are reversible equilibrium reactions that adhere to the law of mass action. In this contribution, we broadly demonstrate that nucleoside phosphorolysis is a thermodynamically controlled endothermic reaction that proceeds to a reaction equilibrium dictated by the substrate‐specific equilibrium constant of phosphorolysis, irrespective of the type or amount of NPase used, as shown by several examples. Furthermore, we explored the temperature‐dependency of nucleoside phosphorolysis equilibrium states and provide the apparent transformed reaction enthalpy and apparent transformed reaction entropy for 24 nucleosides, confirming that these conversions are thermodynamically controlled endothermic reactions. This data allows calculation of the Gibbs free energy and, consequently, the equilibrium constant of phosphorolysis at any given reaction temperature. Overall, our investigations revealed that pyrimidine nucleosides are generally more susceptible to phosphorolysis than purine nucleosides. The data disclosed in this work allow the accurate prediction of phosphorolysis or transglycosylation yields for a range of pyrimidine and purine nucleosides and thus serve to empower further research in the field of nucleoside biocatalysis.DFG, 390540038, EXC 2008: UniSysCatTU Berlin, Open-Access-Mittel - 201

Human Deoxycytidine Kinase Is a Valuable Biocatalyst for the Synthesis of Nucleotide Analogues

Natural ribonucleoside-5’-monophosphates are building blocks for nucleic acids which are used for a number of purposes, including food additives. Their analogues, additionally, are used in pharmaceutical applications. Fludarabine-5´-monophosphate, for example, is effective in treating hematological malignancies. To date, ribonucleoside-5’-monophosphates are mainly produced by chemical synthesis, but the inherent drawbacks of this approach have led to the development of enzymatic synthesis routes. In this study, we evaluated the potential of human deoxycytidine kinase (HsdCK) as suitable biocatalyst for the synthesis of natural and modified ribonucleoside-5’-monophosphates from their corresponding nucleosides. Human dCK was heterologously expressed in E. coli and immobilized onto Nickel-nitrilotriacetic acid (Ni-NTA) superflow. A screening of the substrate spectrum of soluble and immobilized biocatalyst revealed that HsdCK accepts a wide range of natural and modified nucleosides, except for thymidine and uridine derivatives. Upon optimization of the reaction conditions, HsdCK was used for the synthesis of fludarabine-5´-monophosphate using increasing substrate concentrations. While the soluble biocatalyst revealed highest product formation with the lowest substrate concentration of 0.3 mM, the product yield increased with increasing substrate concentrations in the presence of the immobilized HsdCK. Hence, the application of immobilized HsdCK is advantageous upon using high substrate concentration which is relevant in industrial applications.DFG, 392246628, Chemo-enzymatische Synthese von Selen-modifizierten Nukleosiden, Nukleotiden und OligonukleotidenTU Berlin, Open-Access-Mittel - 201

Serpentine channels: micro -- rheometers for fluid relaxation times

We propose a novel device capable of measuring the relaxation time of viscoelastic fluids as small as 1\,ms. In contrast to most rheometers, which by their very nature are concerned with producing viscometric or nearly-viscometric flows, here we make use of an elastic instability which occurs in the flow of viscoelastic fluids with curved streamlines. To calibrate the rheometer we combine simple scaling arguments with relaxation times obtained from first normal-stress difference data measured in a classical shear rheometer. As an additional check we also compare these relaxation times to those obtained from Zimm theory and good agreement is observed. Once calibrated, we show how the serpentine rheometer can be used to access smaller polymer concentrations and lower solvent viscosities where classical measurements become difficult or impossible to use due to inertial and/or resolution limitations. In the absence of calibration the serpentine channel can still be a very useful comparative or index device.Comment: accepted for for publication in Lab on a chi

Accompanying “in-service teaching” internships of prospective mathematics teachers – a model for encouraging exchange between theory and practice using the triple coaching approach

Developing professional expertise of prospective teachers not only in terms of theoretical knowledge but also in terms of competencies of designing challenging and cognitively activating learning opportunities in the mathematics classroom is certainly one of the key aims of internship phases in pre-service mathematics teacher training. As mathematics-related theoretical contents of teacher training and practice-related learning opportunities of school internships are not always linked in an optimal way, this paper aims at discussing a model of an intensive internship phase combined with a triple coaching approach partly integrated in a course accompanying the internship phase