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.
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.
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.
We present the BOSS Lyman- alpha (Ly alpha ) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with z sub(qso) > 2.15 suitable for Ly alpha forest analysis. This data set ...probes the intergalactic medium with absorption redshifts 2.0 < z sub( alpha ) < 5.7 over an area of 3275 deg super(2), and encompasses an approximate comoving volume of 20 h super(-3) Gpc super(3). With each spectrum, we have included several products designed to aid in Ly alpha forest analysis: improved sky masks that flag pixels where data may be unreliable, corrections for known biases in the pipeline estimated noise, masks for the cores of damped Ly alpha systems and corrections for their wings, and estimates of the unabsorbed continua so that the observed flux can be converted to a fractional transmission. The continua are derived using a principal component fit to the quasar spectrum redward of rest-frame Ly alpha (lambda. > 1216 A), extrapolated into the forest region and normalized by a linear function to fit the expected evolution of the Ly alpha forest mean flux. The estimated continuum errors are lap 5% rms. We also discuss possible systematics arising from uncertain spectrophotometry and artifacts in the flux calibration; global corrections for the latter are provided. Our sample provides a convenient starting point for users to analyze clustering in BOSS Ly alpha forest data, and it provides a fiducial data set that can be used to compare results from different analyses of baryon acoustic oscillations in the Ly alpha forest. The full data set is available from the SDSS-III DR9 Web site.
Matrix metalloproteinases (MMPs) have been implicated as possible mediators of invasion and metastasis in some cancers. Our objective was to investigate which MMPs were constitutively expressed in ...breast tumor cells versus those that could be up-regulated by a number of agents known to affect MMP expression in other cell systems.
We evaluated expression of MMPs 1-16 in breast tumor cell lines MDA-MB-231, T47D, and MCF-7 using semiquantitative RT-PCR and gelatin zymography. Exposure to 12-O-tetradecanoylphorbal-3-acetate (TPA), concanavalin-A (Con-A), the fibronectin-mimetic peptide GRGDSP (RGD), extracellular matrix (ECM) components, and anti-integrin antibodies was used to test for possible MMP up-regulation. Mitogen-activated protein kinase inhibitors (MAPK-I) were used to evaluate signal transduction pathways and regulation of MMP expression.
MMPs 1, 2, 7-11, 13, 14, and 16 were constitutively expressed in some tumor cell lines but not in normal breast epithelial cells. Administration of TPA, Con-A, and RGD increased the expression of MMPs 1, 2, 9, and 10. No MMP up-regulation was seen in MDA-MB-231 or MCF-7 after exposure to ECM components or after exposure to anti-integrin antibodies. MAPK-I had no effect on constitutive MMP expression but reduced or abolished the TPA up-regulation of MMP-9 in MDA-MB-231 and MCF-7.
Breast tumor cell lines constitutively express a number of MMPs. Because MMP expression can be up-regulated by Con-A, the fibronectin-mimetic peptide RGD, and TPA while being susceptible to inhibition by MAPK antagonists, MAPK signaling appears to play a role in this expression.
From the phase behavior we establish that 1:10 crosslinked polystyrene microgel colloids in a good solvent can be considered as hard spheres whereas 1:50 crosslinked particles are slightly softer. ...Nevertheless, the glass transition dynamics of 1:10 microgels and a binary mixtures of 1:50 microgels can be described in both cases within the mode coupling theory for hard spheres. The only difference is that the increase of the polydispersity from about 7% to about 13% when going from the one-component system to the mixture is accompanied by a shift of the glass transition from
ϕ
g≈0.56 to
ϕ
g≈0.595. On addition of linear polystyrene to the 1:50 binary mixture we find a tremendous acceleration of the density fluctuations and the melting of a colloidal glass. This is accompanied by a significant decrease of the first peak of the static structure factor and its shift to higher scattering vectors. The presence of free polymer in colloidal dispersions is known to act as an effective attraction via the `depletion effect'. Thus, our observations are consistent with the predictions of recent extensions of mode coupling theory Phys. Rev. E 63 (2001) 1401 where the inclusion of short-ranged attractions has been found to shift the glass transition line to significantly higher volume fractions.
PDF
