Temperature induced solubility transitions of various poly(2-oxazoline)s in ethanol-water solvent mixtures

The solution behavior of a series of poly(2-oxazoline)s with different side chains, namely methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, phenyl and benzyl, are reported in ethanol-water solvent mixtures based on turbidimetry investigations. The LCST transitions of poly(2-oxazoline) s with propyl side chains and the UCST transitions of the poly(2-oxazoline) s with more hydrophobic side chains are discussed in relation to the ethanol-water solvent composition and structure. The poly(2-alkyl-2-oxazoline) s with side chains longer than propyl only dissolved during the first heating run, which is discussed and correlated to the melting transition of the polymers

High molar mass segmented macromolecular architectures by nitroxide mediated polymerisation

A straightforward synthetic pathway based on nitroxide mediated polymerisation (NMP) for the synthesis of a variety of high molar mass segmented copolymers comprising both polystyrene (PS) and polyether segments is reported. First, various precursors such as linear or star-shaped polyether macromonomers, containing either a-methylstyrene or styrene functions at one polymer terminus, as well as PS and polyether macroalkoxyamines bearing either 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) or N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (SG1) end-groups, were prepared. In a second step, these prepolymers were used to design different copolymer architectures such as block, graft, star-grafted, toothbrush and palm tree structures, in which PS constituted the backbone and polyether the side chains. Block copolymers were obtained by NMP of styrene initiated with polyether macroalkoxyamines. Copolymerisation of styrene with linear and star-shaped polyether macromonomers by NMP resulted in graft and star-grafted copolymers, respectively. A toothbrush copolymer was produced in a similar way with the exception of the initiator, which was a PS macroalkoxyamine. Likewise, palm tree architectures were obtained by homopolymerising polyether macromonomers initiated by PS macroinitiators. Advanced characterisation of the different polymer structures was performed, including 2D chromatography

Regulation of cell-­nonautonomous proteostasis in metazoans

Cells have developed robust adaptation mechanisms to survive environmental conditions that challenge the integrity of their proteome and ensure cellular viability. These are stress-­signalling pathways that integrate extracellular signals with the ability to detect and efficiently respond to protein-­folding perturbations within the cell. Within the context of an organism, the cell autonomous effects of these signalling mechanisms are superimposed by cell-­nonautonomous stress signalling pathways that allow coordination of stress responses across tissues. These transcellular stress signalling pathways orchestrate and maintain the cellular proteome at an organismal level. This review focuses on mechanisms in both invertebrate and vertebrate organisms that activate stress responses in a cell-­nonautonomous manner. We discuss emerging insights and provide specific examples on how components of the cell-­nonautonomous proteostasis network are used in cancer and protein-­folding diseases to drive disease progression across tissues

Galaxy Disks

The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in the largest systems. Their HI layers display warps whenever HI can be detected beyond the stellar disk, with low-level star formation going on out to large radii. Stellar disks display abundance gradients which flatten at larger radii and sometimes even reverse. The existence of a well-defined baryonic Tully-Fisher relation hints at an approximately uniform baryonic to dark matter ratio. Thick disks are common in disk galaxies and their existence appears unrelated to the presence of a bulge component; they are old, but their formation is not yet understood. Disk formation was already advanced at redshifts of $\sim 2$, but at that epoch disks were not yet quiescent and in full rotational equilibrium. Downsizing is now well-established. The formation and history of star formation in S0s is still not fully understood.Comment: This review has been submitted for Annual Reviews of Astronomy & Astrophysics, vol. 49 (2011); the final printed version will have fewer figures and a somewhat shortened text. A pdf-version of this preprint with high-resolution figures is available from http://www.astro.rug.nl/~vdkruit/jea3/homepage/disks-ph.pdf. (table of contents added; 71 pages, 24 figures, 529 references

Social justice praxis in education: Towards sustainable management strategies

Social justice, defined as an impetus towards a socially just educational world, is based on the assumption that all people, irrespective of belief or societal position, are entitled to be treated according to the values of human rights, human dignity and equality. Diverging from the classical positivist approach in social science research that takes injustice as its impetus, the researchers departed from a socio-rationalist approach into exploring sustainable management strategies for effective social justice praxis. This approach has enabled the construction of a conceptual-theoretical framework and an iterative qualitative inquiry, which has as its central principal the sustainable management strategies for effective social justice praxis. Four key findings affirmed the belief that good praxis was to be found in Gemeinschaft relationships, in the influence exerted by government and education systems and structures, where government and principals were found to be co-responsible in ensuring that the best interest of the child was served. This responsibility included practices found in collaborative efforts, where communities became the guardians of their schools due to a disciplined school that followed constitutional values. Lastly, these practitioners aligned their management strategies with human rights values, as well as human dignity and equality, and their strategies found pride of place in extant ubuntu principles.Keywords: determinants; education; human rights; management strategies; restorative; social justice praxis; sustainable development; transformative; ubunt

The Caring School Leadership Questionnaire (CSLQ)

The purpose of this research was to develop the Caring School Leadership Questionnaire (CSLQ) as a valid and reliableinstrument to measure the extent of care being given by school leaders (principals) to teachers. The research involved 1,041teachers and 65 principals from 68 primary schools in the North-West Province of South Africa. The construct validity ofthe CSLQ was determined by means of a confirmatory factor analysis. The three main constructs regarding caring thatemerged from the factor analysis proved to be the same as those theoretically identified as the three main determinants ofcare. Cronbach’s Alpha coefficients furthermore proved the CSLQ to be reliable. The key finding flowing from theinvestigation was that the CSLQ may be applied with good effect in 180º-, 360º-, as well as self-evaluations of school leaders.Keywords: caring, caring school leadership, determinants of care, management, measuring instrument for caring schoolleadership, measuring care in leadershi

Passwords and the evolution of imperfect authentication

Theory on passwords has lagged practice, where large providers use back-end smarts to survive with imperfect technology.This is the author accepted manuscript. The final version is available from ACM via http://dx.doi.org/10.1145/269939

Herschel/SPIRE observations of the dusty disk of NGC 4244

We present Herschel/SPIRE images at 250, 350, and 500 mu m of NGC 4244, a typical low-mass, disk-only and edge-on spiral galaxy. The dust disk is clumpy and shows signs of truncation at the break radius of the stellar disk. This disk coincides with the densest part of the Hi disk. We compare the spectral energy distribution (SED), including the new SPIRE fluxes, to 3D radiative transfer models; a smooth model disk and a clumpy model with embedded heating. Each model requires a very high value for the dust scale-length (h(d) = 2-5 h(*)), higher dust masses than previous models of NGC 4244 (M-d = 0.47-1.39 x 10(7) M-circle dot) and a face-on optical depth of tau(f.o.)(V) = 0.4-1.12, in agreement with previous disk opacity studies. The vertical scales of stars and dust are similar. The clumpy model much better mimics the general morphology in the sub-mm images and the general SED. The inferred gas-to-dust mass ratio is compatible with those of similar low-mass disks. The relatively large radial scale-length of the dust disk points to radial mixing of the dusty ISM within the stellar disk. The large vertical dust scale and the clumpy dust distribution of our SED model are both consistent with a scenario in which the vertical structure of the ISM is dictated by the balance of turbulence and self-gravity