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Small angle light scattering (SALS) and differential scanning calorimetry DSC have been applied to investigate the melting of spherulites isothermally crystallized polylactide. At an isothermal crystallization temperature high enough, pure α‐phase crystals are formed. Exposed to a temperature gradient, the crystals first melt and then recrystallize before they finally melt. With decreasing crystallization temperature, an increasing fraction of polylactide is crystallizing in the less stable α ′‐phase. α ′‐crystals also melt upon increasing the temperature but recrystallize to the more stable α‐phase. A constant spherulite size is revealed by SALS for both processes, the α/α and α ′/α melt‐recrystallization, until completion of the final melting, thereby supporting integrity of the spherulites throughout the entire processes. Joint DSC and SALS experiments demonstrate that the depolarized scattering invariant correlates with the heat flow recorded by DSC and thus offer an alternative measure for the degree of crystallinity. The following mechanism is identified for both processes: initial melting and recrystallization overlay each other. Crystallinity is not fully recovered upon recrystallization because only part of the original lamellae survives the melt‐recrystallization, though with an increased thickness. While lamellae are melting and reforming or simply transforming their phase, the spherulites survive the process until final melting. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1483–1495

Masterstudenten der Uni Paderborn absolvieren im Wahlpflichtblock “Synthese und Struktur” ein dreitagiges Praktikum zur Neutronenstreuung am Forschungsreaktor FRM II in Garching.

In this article, we investigate tapping mode atomic force microscopy images of intermediate states along the coil to globule transition of sodium polyacrylate coils containing Ca2+ as specifically binding ions. The structural correlations within single adsorbed molecules are established using power spectral density (PSD) curves. The PSD curves of several single molecules are averaged to give the so called 2D form factor so as to obtain information of higher statistical merit. A proper interpretation of the 2D form factor and comparison with form factor analysis of the very same sample solution available through small angle neutron scattering provides an alternative quantification of changes in conformation which a single polyacrylate molecule undergoes as it moves from 3D solution to 2D surface and is inevitably distorted in shape because of sample history. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1553–1561, 2010

The bis(guanidine)-stabilised zinc complexes [N1,N2-bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]dichloridozinc(II), [Zn(DMEG2e)Cl2] (C1), diacetato[N1,N2-bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II),[Zn(DMEG2e)(CH3COO)2] (C2), and bis[N1,N2-bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II) bis(trifluoromethanesulfonate), [Zn(DMEG2e)2](CF3SO3)2 (C3), have been synthesised and completely characterised by means of X-ray structure analysis, NMR spectroscopy and mass spectrometry. These [bis(guanidine)]zinc complexes were investigated regarding their activity in the bulk polymerisation of D,L-lactide. It could be shown that these compounds are able to act as initiators for lactide polymerisation, and polylactides with molecular weights (Mw) of around 18000–59000 g/mol could be obtained. Variation of the reaction temperature revealed that the molecular weights decrease with increasing temperature. Additionally, the correlation of the intrinsic viscosity with the molecular weight demonstrates that the obtained polymers are linear and structurally homogeneous.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A synthetic route towards surface modified, monodisperse, spherical particles is presented. The precursor particles exhibit epoxy-functionalities which can be opened afterwards with an appropriate nucleophile. Via this route, dye labeled particles are obtained. Copyright © 2004 John Wiley & Sons, Ltd.

The particle scattering behaviour of a pearl necklace chain is derived. The chain is composed of sphere-like pearls, separated by rod-like segments of fixed length, which have no angular restrictions. By calculating several series of model scattering curves, the important structural features are retrieved. The model is believed to be useful in interpreting intermediate structures of collapsing macromolecules or polyelectrolytes. A first application to a shrinking polyelectrolyte coil generated by molecular dynamic simulations (Limbach and Holm, J.Phys.Chem. 2003) is presented and used to discuss the potentials and limits of the model.

A synthetic route is presented for the preparation of electrically charged colloidal particles with either sign from the same precursor. In the first step, methyl methacrylate was copolymerized with ω-bromoalkyl acrylate and a cross-linker, leading to monodisperse, bromo-functionalized colloids. Substitution of the bromo-functions by either trimethylamine of Na 2 SO 3 transformed the neutral precursors into positively or negatively charged particles, respectively. The charge density could be varied in two ways: (i) by varying the fraction of bromo-functionalized monomers; (ii) by increasing the degree of substitution of the bromo-functions. Derivation of the charged particles from the same precursor colloid made it easier to explain various interesting physical properties of the charged colloidal particles. Higher charge densities were achieved for the cationic colloids. If a threshold value for the charge density of 55 μC .cm -2 was surpassed, the particles showed a significant swelling in aqueous solution.

Several techniques for the enrichment of nucleated fetal red blood cells present in maternal blood have been reported. Here we describe the use of a quantitative fluorescence in situ hybridization (FISH) method and in vitro suspension cultures of erythroid cells from newborn cord blood and maternal peripheral blood. Together with a rapid high performance liquid chromatography (HPLC) method, that allows us to determine as few as 100 cells containing haemoglobin F (HbF), we have scrutinized the reported enrichment methods for fetal nucleated cells in peripheral maternal blood. One hundred FISH analyses on maternal peripheral blood were performed. The method comprises a cell lysis method for depletion of red cells with minimal losses of nucleated cells, uniform numbers of cells (750 000 cells each) on microscopic slides, and inclusion of internal controls to monitor the efficacy of hybridization. Twenty-six cultures of pure erythroid progenitor cells from maternal peripheral blood were analysed for the expansion of fetal cells. To generate these in vitro cultures, nucleated cells from 10–20 ml of peripheral blood from 26 pregnant women were grown in media containing growth factors and hormones to yield over 107 of immature erythroid cells within two weeks. Of those, 13 cultures were from pregnancies with confirmed male fetuses. A total of approximately 8×108 maternal cells were added into tissue culture medium for these 13 cultures, resulting in about 2×108 nearly pure erythroid cells after two weeks. Whereas fetal cells, alone or added into cultures of peripheral blood, grow rapidly and can be detected quantitatively, we could not find any fetal cells in cultures from maternal blood. Likewise, in 7.5×107 peripheral blood cells probed by FISH analysis (half of which were from pregnancies with male fetuses) no single Y chromosome was detected. In summary, suspension cultures of erythroid cells can be established routinely and easily. With the quantitative FISH technique used, 750 000 cells per slide can be screened reliably for cells with Y chromosomes. However, the stringent quality-criteria and most elaborate methods indicate that fetal cells in maternal peripheral blood can not be found using the current technology. Copyright © 2000 John Wiley & Sons, Ltd.

The secretion of placental isoferritin (PLF) during pregnancy could be responsible for the diminished immunoreaction of maternal lymphocytes against the embryo. In this study, serum levels of PLF in 335 pregnant women were correlated with birth weight, percentile of birth weight, gestational age, and pulsatility index of the uterine artery, as well as with diastolic notching. Women with small-for-gestational age (SGA) infants (birth weight below or equal to the tenth percentile) showed significantly lower PLF levels (11.7 U/ml) compared with women whose newborns were of normal weight (19.4 U/ml) (P < 0.05). In line with this finding, a strong correlation was observed between PLF levels and the percentile of birth weight, pulsatility index of the uterine artery, and the presence of diastolic notching. The strong correlation of low PLF values and SGA newborns suggests that determination of PLF could serve as a marker to identify women at risk of having such babies.

A design method for filters having duobinary signal pulses as impulse response is presented.