5,436 research outputs found
Formation and Equilibrium Properties of Living Polymer Brushes
Polydisperse brushes obtained by reversible radical chain polymerization
reaction onto a solid substrate with surface-attached initiators, are studied
by means of an off-lattice Monte Carlo algorithm of living polymers (LP).
Various properties of such brushes, like the average chain length and the
conformational orientation of the polymers, or the force exerted by the brush
on the opposite container wall, reveal power-law dependence on the relevant
parameters. The observed molecular weight distribution (MWD) of the grafted LP
decays much more slowly than the corresponding LP bulk system due to the
gradient of the monomer density within the dense pseudo-brush which favors
longer chains. Both MWD and the density profiles of grafted polymers and chain
ends are well fitted by effective power laws whereby the different exponents
turn out to be mutually self-consistent for a pseudo-brush in the
strong-stretching regime.Comment: 33 pages, 11 figues, J.Chem. Phys. accepted Oct. 199
The impact of management practices on employee productivity: a field experiment with airline captains
Increasing evidence indicates the importance of management in determining firms’ productivity. Yet causal evidence regarding the effectiveness of management practices is scarce, especially for skilled labor in the developed world. In a field experiment measuring commercial airline captains’ productivity, we test four distinct management practices: performance monitoring, performance feedback, target setting, and prosocial incentives. These practices—particularly monitoring and target setting—significantly increase captains’ productivity on the targeted fuel-saving dimensions, with positive spillovers on job satisfaction and CO 2 emissions. The study reveals an uncharted research opportunity to delve into the black box of firms to examine the determinants of productivity among skilled labor
The changing UK careers landscape : tidal waves, turbulence and transformation
This article explores how the UK careers landscape in each of the four home nations is changing in response to neo-liberal policies. In this context, careers services are increasingly under pressure to demonstrate their added value, impact and returns on investment. As fiscal arrangements tighten and governments state their preferences and priorities for national careers services, differing strategic responses are beginning to emerge. A quasi-market, experimental approach is now the dominant discourse in England, in contrast to differing and complementary arrangements in Northern Ireland, Scotland and Wales. The article suggests that insofar as these developments are transforming national careers services, they are also creating significant challenges which require new forms of policy imagery and imagination for high-impact, all-age careers services
The Ultrasensitivity of Living Polymers
Synthetic and biological living polymers are self-assembling chains whose
chain length distributions (CLDs) are dynamic. We show these dynamics are
ultrasensitive: even a small perturbation (e.g. temperature jump) non-linearly
distorts the CLD, eliminating or massively augmenting short chains. The origin
is fast relaxation of mass variables (mean chain length, monomer concentration)
which perturbs CLD shape variables before these can relax via slow chain growth
rate fluctuations. Viscosity relaxation predictions agree with experiments on
the best-studied synthetic system, alpha-methylstyrene.Comment: 4 pages, submitted to Phys. Rev. Let
Patterning High Surface Area Silica with Lysozyme: Adsorption Kinetics, Fluorescence Quenching, and Protein Readsorption Studies To Evaluate the Templated Surface
A method was developed for using an inexpensive and widely available protein, hen egg white lysozyme, as a patterning agent for commercial high surface area silicas. The basic patterning methodology involved spontaneous adsorption of the protein from aqueous solution, alkylation of the uncovered surface with an alkylsiloxane, and protein desorption in a slightly alkaline solution of morpholine. Adsorption kinetic studies using Bradford assays assisted in determining protein deposition conditions. These studies were generally consistent with results on more planar silica surfaces and indicated that the protein quickly and strongly adsorbs along its long axis at low surface coverages. A modified fluorescence resonance energy transfer (FRET) technique was developed and employed to evaluate protein spacing. This technique showed that the proteins are well dispersed at low coverages. Readsorption experiments show that the templated regions are robust, retaining the size and shape of the original protein templates
Labelling, Deviance and Media
Labelling theory is a perspective that emerged as a distinctive approach to criminology during the 1960s, and was a major seedbed of the radical and critical perspectives that became prominent in the 1970s. It represented the highpoint of an epistemological shift within the social sciences away from positivism – which had dominated criminological enquiry since the late-1800s – and toward an altogether more relativistic stance on the categories and concepts of crime and control. It inspired a huge amount of work throughout the 1960s and 1970s, and still resonates powerfully today. This short chapter maps out some of the ways in which labelling, deviance, media and justice interact at the levels of definition and process. It presents an overview and analysis of key mediatised labelling processes, such as the highly influential concept of moral panics. It discusses how the interconnections between labelling, crime and criminal justice are changing in a context of technological development, cultural change and media proliferation. The conclusion offers an assessment and evaluation of labelling theory’s long-term impact on criminology
Scotland, Catalonia and the “right” to self-determination: a comment suggested by Kathryn Crameri’s “Do Catalans Have the Right to Decide?
No abstract available
Application of a Self-Similar Pressure Profile to Sunyaev-Zel'dovich Effect Data from Galaxy Clusters
We investigate the utility of a new, self-similar pressure profile for
fitting Sunyaev-Zel'dovich (SZ) effect observations of galaxy clusters. Current
SZ imaging instruments - such as the Sunyaev-Zel'dovich Array (SZA) - are
capable of probing clusters over a large range in physical scale. A model is
therefore required that can accurately describe a cluster's pressure profile
over a broad range of radii, from the core of the cluster out to a significant
fraction of the virial radius. In the analysis presented here, we fit a radial
pressure profile derived from simulations and detailed X-ray analysis of
relaxed clusters to SZA observations of three clusters with exceptionally high
quality X-ray data: A1835, A1914, and CL J1226.9+3332. From the joint analysis
of the SZ and X-ray data, we derive physical properties such as gas mass, total
mass, gas fraction and the intrinsic, integrated Compton y-parameter. We find
that parameters derived from the joint fit to the SZ and X-ray data agree well
with a detailed, independent X-ray-only analysis of the same clusters. In
particular, we find that, when combined with X-ray imaging data, this new
pressure profile yields an independent electron radial temperature profile that
is in good agreement with spectroscopic X-ray measurements.Comment: 28 pages, 6 figures, accepted by ApJ for publication (probably April
2009
Nanometallic Glasses: Size Reduction Brings Ductility, Surface State Drives Its Extent
We report tensile experiments on Ni_(80)P_20 metallic glass samples fabricated via a templated electroplating process and via focused ion beam milling, which differed only in their surface energy states: Ga-ion-irradiated and as-electroplated. Molecular dynamics simulations on similar Ni_(80)Al_20 systems corroborate the experimental results, which suggest that the transition from brittle to ductile behavior is driven by sample size, while the extent of ductility is driven by surface state
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