Measurements of the Refractive Index Increment on Hydroxyethyl Starch as a Basis for Absolute Molecular Weight Determinations

Solutions of hydroxyethyl starch are used as a blood plasma substitute. If their physiological efficiency is to be optimized, they need to be accurately characterized in terms of their molecular weight and its distribution. The absolute determination of molecular weight and molecular weight distribution by means of light scattering require a knowledge of the refractive index increment. Although numerous investigations of the refractive index increment of hydroxyethyl starch have already been published, the results vary significantly due to the use of different samples and the choice of different measuring parameters. There was therefore an urgent need to examine the extent to which the refractive index increment depends on molecular parameters, the experimental method used and the type of processing. Here it was found that different sample preparations result in different contents of solid matter, so that an exact determination of the quantity is required. Hydroxyethyl starches in the molecular weight range of about Mw = 200.000 g/mol and varying degrees of substitution between DS 0.38 and 0.50 which are regarded as optimal for clinical use give a refractive index increment of dn/dc^633nm = 0.146 = 0.005 cm³/g (solvent: H₂O/0.02% NaN₃; T = 25°C).     

Untersuchungen zu Mesityldimethylhalogensilanen als Schutzgruppenreagenzien für Alkohole

Investigation on Mesityldimethylhalosilanes as Protectiv Reagents for Alcohols The use of mesityldimethylhalosilanes as protecting reagents for steroid alcohols was investigated. The resistance of the obtained silyl ethers was tested in various media. The reaction pathway of the acidic hydrolyses of the silyl ethers is explained.     

靴套的创新开发--QualiFlex靴套

对比了QualiFlex Q型,QualiFlex QX型、QualiFlex QV型三种聚胺酯材料靴套的性能,从而说明独特的QualiFlex靴套性能,使纸幅横幅水分的均匀性得到改善,纸幅出压榨干度得以维持恒定.     

Neutronic characterization of the MEGAPIE target

The MEGAPIE project aimed to design, build and operate a liquid metal spallation neutron target of about 1 MW beam power in the SINQ facility at the Paul Scherrer Institut (Villigen, Switzerland). This project is an important step in the roadmap towards the demonstration of the accelerator driven system (ADS) concept and high power liquid metal targets in general. Following the design phase, an experimental program was defined to provide a complete characterization of the facility by performing a “mapping” of the neutron flux at different points, from the center of the target to the beam lines. The neutronic performance of the target was studied using different experimental techniques with the goals of validating the Monte Carlo codes used in the design of the target; additionally, the performance was compared with the solid lead targets used before and after the MEGAPIE experiment.     

Reproducibility and the Concept of Numerical Solution

Minds and Machines - In this paper, we show that reproducibility is a severe problem that concerns simulation models. The reproducibility problem challenges the concept of numerical solution and...     

Solubility of poly(n-alkylmethacrylate)s in hydrocarbons and in alcohols

Poly(methylmethacrylate) (PMMA), poly(butylmethacrylate) (PBMA), and poly(decylmethacrylate) (PDMA) are completely miscible with toluene at normal pressure from room temperature up to the boiling point of the solvent. In alkanes (C₆ to C₁₀) and 1-pentanol the solubility increases with the length of the side chain of the polymer: PMMA always exhibits a solubility gap within the above temperature range, PBMA shows upper critical solution temperatures (except n-hexane, which is a non-solvent), and PDMA mixes completely with all alkanes under consideration. Alcohols (up to C₄) are non-solvents for PMMA but theta solvents for PBMA and PDMA (except ethanol which is a non-solvent for the latter). The low temperature demixing of ethanol/PBMA is shifted towards lower temperatures by pressure.     

The Estimation of the Molecular Weight of Polytetrafluoroethylene Based on the Heat of Crystallisation. A Comment on Suwa's Equation

Summary: The influence of number‐average molecular weight ranging from 1.4 · 10⁴ to 1.2 · 10⁶ g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and ¹⁹F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.

Concentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.     

Cell-Based Optimization of Covalent Reversible Ketoamide Inhibitors Bridging the Unprimed to the Primed Site of the Proteasome β5 Subunit

The ubiquitin-proteasome system (UPS) is an established therapeutic target for approved drugs to treat selected hematologic malignancies. While drug discovery targeting the UPS focuses on irreversibly binding epoxyketones and slowly-reversibly binding boronates, optimization of novel covalent-reversibly binding warheads remains largely unattended. We previously reported α-ketoamides to be a promising reversible lead motif, yet the cytotoxic activity required further optimization. This work focuses on the lead optimization of phenoxy-substituted α-ketoamides combining the structure-activity relationships from the primed and the non-primed site of the proteasome β5 subunit. Our optimization strategy is accompanied by molecular modeling, suggesting occupation of P1′ by a 3-phenoxy group to increase β5 inhibition and cytotoxic activity in leukemia cell lines. Key compounds were further profiled for time-dependent inhibition of cellular substrate conversion. Furthermore, the α-ketoamide lead structure 27 does not affect escape response behavior in Danio rerio embryos, in contrast to bortezomib, which suggests increased target specificity.     

In situ scanning tunneling microscopy study of selective dissolution of Au3Cu and Cu3Au (0 0 1)

We present an electrochemical study of Au₃Cu (0 0 1) single crystal surfaces in 0.1 mol dm⁻³ H₂SO₄ and 0.1 mol dm⁻³ H₂SO₄ + 0.1 mmol dm⁻³ HCl, and of Cu₃Au (0 0 1) in 0.1 mol dm⁻³ H₂SO₄. The focus is on in situ scanning tunneling microscopy experiments. The changes of the surface morphology, which are time- and potential-dependent, have been observed, clearly resolving single atomic steps and mono-atomic islands and pits. Chloride additives enhance the surface diffusion and respective morphologies are observed earlier. All surfaces have shown considerable roughening already in the passive region far below the critical potential.