Performing light scattering experiments we show that introducing short-ranged attraction to a colloid suspension of nearly hard spheres by addition of a free polymer produces new glass-transition ...phenomena. We observe a dramatic acceleration of the density fluctuations amounting to the melting of a colloidal glass. Upon increasing the strength of the attractions the system freezes into another nonergodic state sharing some qualitative features with gel states occurring at lower colloid packing fractions. This re-entrant glass transition is in qualitative agreement with recent theoretical predictions.
Colloidal Laves phases (LPs) are promising precursors for photonic materials. Laves phases have not yet been observed to form in experiments on colloidal suspensions of hard spheres (HS), even though ...they have been reported in computer simulations. LP formation so far has been achieved only for binary mixtures of colloidal charged spheres or ligand-stabilized nano-particles after drying. Using static light scattering, we monitored LP formation and annealing in a binary mixture of buoyant hard sphere approximants (size ratio Γ = 0.77, number or molar fraction of small spheres xS = 0.76) for volume fractions in the fluid-crystal coexistence regions. All samples spontaneously formed MgZn2 type LPs on the time scale of weeks to months via bulk nucleation and growth. Irrespective of the initial suspension volume fractions, the LP volume fraction at coexistence is ΦCOEX = 0.59 which is significantly below the close packing limit ΦMAX = 0.615 and remarkably close to the expectation from simulation. At low volume fractions, crystals anneal to high quality during coarsening which is in line with recent theoretical expectations for the thermodynamic stability of different LP types. At large volume fractions, however, the diffractograms evolve towards a more MgCu2-like appearance which we attribute to the formation of randomly stacked LPs. Such structures are not known from atomic systems.
By means of the Forced Rayleigh Scattering (holographic grating relaxation) technique the diffusion of dye molecules in bulk films of polymer below entanglement molecular weight was investigated ...around the glass transition temperature. In the temperature range Tg-20К; Tg+ 5К a splitting of the dye diffusion coefficient into two separate branches was revealed. The phenomenon was found to be similar to that reported for thin polymer films, which may prove the dominating role of dynamic heterogeneities in the investigated temperature region.
To examine the association between maternal country of birth and the risk of preeclampsia+preterm birth (PTB).
We completed a population-based study in the entire province of Ontario, where there is ...universal access to obstetrical care. We included 881 700 singleton livebirths among Canadian-born mothers and 305 547 births among immigrant mothers. Adjusted risk ratios (aRRs) were adjusted for maternal age, parity and income quintile.
Compared with a rate of preeclampsia+PTB of 4.0 per 1000 among Canadian-born mothers, the aRR of preeclampsia+PTB at 24 to 36 weeks was significantly higher for immigrant women from Nigeria (1.79, 95% confidence interval (CI) 1.12 to 2.84), the Philippines (1.54, 95% CI 1.30 to 1.86), Colombia (1.68, 95% CI 1.04 to 2.73), Jamaica (2.06, 95% CI 1.66 to 2.57) and Ghana (2.12, 95% CI 1.40 to 3.21). The aRRs generally followed a similar pattern for secondary outcomes. Specifically, women from Ghana were at highest risk of preeclampsia+very PTB (4.55, 95% CI 2.57 to 8.06), and women from Jamaica at the highest risk of preeclampsia+indicated PTB (1.89, 95% CI 1.43 to 2.50).
The risk of preeclampsia+PTB is highest among women from a select number of countries. This information can enhance initiatives aimed at reducing the risk of PTB related to preeclampsia.
Abstract A large-volume Time Projection Chamber (TPC) is the main tracking and particle identification (PID) detector of the ALICE experiment at the CERN LHC. PID in the TPC is performed via specific ...energy-loss measurements (d E /d x ), which are derived from the average pulse-height distribution of ionization generated by charged-particle tracks traversing the TPC volume. During Runs 1 and 2, until 2018, the gas amplification stage was based on multiwire proportional chambers (MWPC). Signals from the MWPC show characteristic long negative tails after an initial positive peak due to the long ion drift times in the MWPC amplification region. This so-called ion tail can lead to a significant amplitude loss in subsequently measured signals, especially in the high-multiplicity environment of high-energy Pb-Pb collisions, which results in a degradation of the d E /d x resolution. A detailed study of the signal shapes measured with the ALICE TPC with the Ne-CO 2 (90-10) and Ar-CO 2 (90-10) gas mixtures is presented, and the results are compared with three-dimensional Garfield simulations. The impact of the ion tail on the PID performance is studied employing the ALICE simulation framework and the feasibility of an offline correction procedure to account for the ion tail is demonstrated.
Nurses are assigned a key role in pandemic response, with work engagement considered to be pivotal. The job demands-resources theory assumes that work engagement depends on job resources and job ...demands. Key job resources and demands have already been proposed for nurses. However, there is no evidence on their importance under pandemic conditions. Hence, the aim of this study was to investigate their relevance to nurses' work engagement during the second wave of the COVID-19 pandemic.
The study was carried out in a cross-sectional design and addressed nurses in direct health care settings in Germany. Data was collected administering a quantitative online survey using valid and reliable measures during the second wave of the pandemic. A convenience sample was obtained, including the use of social media, randomly selected health care facilities, and all universities with nursing-related programs in Germany. The dataset for analyses comprised a total of 1,027 cases. The sample included nurses of various educational levels and from different sectors. Multiple linear regression analysis after multiple imputation was used to examine the relevance of key resources and demands for work engagement.
Key resources and demands explained 36% of the variance in nurses' work engagement during the COVID-19 pandemic. Positive associations were found between the key resources of autonomy (β¯
=0.072, 95% CI 0.011; 0.133), professional resources (β¯
=0.204, 95% CI 0.124; 0.285), and interpersonal relationships (β¯
=0.178, 95% CI 0.117; 0.240) and nurses' work engagement. On the demands side, lack of formal rewards negatively (β¯
=-0.312, 95% CI -0.380; -0.245) affected work engagement, whereas work overload (β¯
=0.063, 95% CI 0.001; 0.126) was positively associated with work engagement.
The job demands-resources theory is suitable for explaining nurses' work engagement even in times of crisis. Taken together, key resources and demands have a significant influence on nurses' work engagement under pandemic conditions. However, not all so-called key resources and demands actually have a key status in a pandemic.
Any lack of formal rewards should be countered, professional resources should be sustainably secured, and the autonomy of nurses and their interpersonal relationships should be strengthened. Nursing management decisions should be made not only with the current pandemic but also the post-pandemic period in mind.
The relationships between gender and malingering have received little attention in the literature. Our study examined data from 1,748 patients committed as incompetent to stand trial between 2008 and ...2017, of whom 397 were women. Scores on a structured assessment of feigned psychiatric symptoms were only slightly higher for men than for women. Yet evaluators believed that over 23 percent of men but less than 15 percent of women were malingering. Our data suggest that these gender differences in rates of malingering may be attributable to symptom constellations and extent of criminal arrest history.
By studying the phase behaviour and the short range order of polystyrene microgel colloids in a good solvent we demonstrated that these particles can be considered as hard spheres or nearly hard ...spheres if the internal cross link density is made sufficiently high. A binary mixture of 1:50 crosslinked (1 crosslink per 50 monomers) particles with a size ratio R(small)/R(large) = 0.83 and a number ratio N(small)/N(large) = 2.7 was characterized with respect to the short range order and glass transition dynamics. We found that this mixture can be mapped onto a one-component hard sphere system with an effective polydispersity of 11%, even though for the particle interactions an inverse power potential u(r) alpha r(-35) was established. The only significant difference observed was a shift of the glass transition to a higher volume fraction of 0.595. Thus, the binary mixture was used as a non-crystallizing reference system to study the effect of free polymer on interactions and glass transition dynamics. Addition of linear polystyrene with a size ratio delta = R(g,polymer)/R(colloid) = 0.054 induced short-ranged depletion attractions between microgel particles. In the case of a glassy sample already a rather small amount of polymer leads to melting of the glass and a re-entrant glass transition is observed at high polymer content. From the difference of the line shapes of the density autocorrelation functions on approaching the different transition lines. measured over the full dynamic range, a change of the freezing mechanism from a packing-driven glass transition at low polymer content to a bonding-driven glass transition at high polymer content was deduced.
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