23 research outputs found
An assessment of the causes of the errors in the 2015 UK General Election opinion polls
The opinion polls undertaken prior to the 2015 UK General Election under-estimated the Conservative lead over Labour by an average of 7 percentage points. This collective failure led politicians and commentators to question the validity and utility of political polling and raised concerns regarding a broader public loss of confidence in survey research. In this paper, we assess the likely causes of the 2015 polling errors. We begin by setting out a formal account of the statistical methodology and assumptions required for valid estimation of party vote shares using quota sampling. We then describe the current approach of polling organisations for estimating sampling variability and suggest a new method based on bootstrap re-sampling. Next, we use poll micro-data to assess the plausibility of different explanations of the polling errors. Our conclusion is that the primary cause of the polling errors in 2015 was unrepresentative sampling
Cross-Interface Emulsification for Generating Size-Tunable Droplets
We
report cross-interface emulsification (XiE), a simple method
for the generation of monodisperse droplets of controllable volumes
from picoliter to nanoliter. A device is set up in which a fused-silica
capillary is vibrating across the surface of the continuous phase
(mineral oil) in a reservoir, and the flow of the dispersed phase
(aqueous solution) in the capillary is segmented into monodisperse
droplets at the air/oil interface. We find that the volume of droplets
is mainly dominated by the flow rate and vibrating frequency and not
significantly influenced by other factors, such as the viscosity of
the continuous phase and dispersed phase, the inner diameter of the
capillary (20–100 μm), or the shape of the tip (tapered
or flat). These features reflect high robustness, flexibility, and
precision of XiE for on-demand volume control of droplets. The droplets
automatically assemble into planar monolayer droplet arrays (PMDA)
in flat-bottomed microwells of 96-well plates, offering excellent
convenience for imaging of droplets. As a representative application,
we carry out digital loop-mediated isothermal amplification using
PMDAs with multivolume droplets for the absolute quantification of
nucleic acids. Our results demonstrate that XiE is simple and controllable
for the production of monodisperse size-tunable droplets, and it offers
opportunities for common laboratories, even without microfabrication
facilities, to perform digital quantification, single cell analysis,
and other biochemical assays with high throughput
Cross-Interface Emulsification for Generating Size-Tunable Droplets
We
report cross-interface emulsification (XiE), a simple method
for the generation of monodisperse droplets of controllable volumes
from picoliter to nanoliter. A device is set up in which a fused-silica
capillary is vibrating across the surface of the continuous phase
(mineral oil) in a reservoir, and the flow of the dispersed phase
(aqueous solution) in the capillary is segmented into monodisperse
droplets at the air/oil interface. We find that the volume of droplets
is mainly dominated by the flow rate and vibrating frequency and not
significantly influenced by other factors, such as the viscosity of
the continuous phase and dispersed phase, the inner diameter of the
capillary (20–100 μm), or the shape of the tip (tapered
or flat). These features reflect high robustness, flexibility, and
precision of XiE for on-demand volume control of droplets. The droplets
automatically assemble into planar monolayer droplet arrays (PMDA)
in flat-bottomed microwells of 96-well plates, offering excellent
convenience for imaging of droplets. As a representative application,
we carry out digital loop-mediated isothermal amplification using
PMDAs with multivolume droplets for the absolute quantification of
nucleic acids. Our results demonstrate that XiE is simple and controllable
for the production of monodisperse size-tunable droplets, and it offers
opportunities for common laboratories, even without microfabrication
facilities, to perform digital quantification, single cell analysis,
and other biochemical assays with high throughput
Heterogeneous Nanostructures Cause Anomalous Diffusion in Lipid Monolayers
The diffusion and mobility in biomembranes are crucial
for various
cell functions; however, the mechanisms involved in such processes
remain ambiguous due to the complex membrane structures. Herein, we
investigate how the heterogeneous nanostructures cause anomalous diffusion
in dipalmitoylphosphatidylcholine (DPPC) monolayers. By identifying
the existence of condensed nanodomains and clarifying their impact,
our findings renew the understanding of the hydrodynamic description
and the statistical feature of the diffusion in the monolayers. We
find a universal characteristic of the multistage mean square displacement
(MSD) with an intermediate crossover, signifying two membrane viscosities
at different scales: the short-time scale describes the local fluidity
and is independent of the nominal DPPC density, and the long-time
scale represents the global continuous phase taking into account nanodomains
and increases with DPPC density. The constant short-time viscosity
reflects a dynamic equilibrium between the continuous fluid phase
and the condensed nanodomains in the molecular scale. Notably, we
observe an “anomalous yet Brownian” phenomenon exhibiting
an unusual double-peaked displacement probability distribution (DPD),
which is attributed to the net dipolar repulsive force from the heterogeneous
nanodomains around the microdomains. The findings provide physical
insights into the transport of membrane inclusions that underpin various
biological functions and drug deliveries
PKC and downstream NF-κB are required for IL-6-induced proliferation in CD45<sup>+</sup> myeloma cells.
<p>CD45<sup>+</sup> U266 cells (A) or CD45<sup>+</sup> CD138<sup>+</sup> primary cells (B) were incubated with or without PKC inhibitor Ro31-8220 (1 μM), or NF-κB inhibitor BAY11-7082 (5 μM) for 1 hour and stimulated with IL-6 (10 ng/ml). PKC phosphorylation level was measured after 10 minutes of stimulation with IL-6, and the IκB phosphorylation level was analyzed after 60 minutes stimulation. Western blotting was performed by using specific antibodies. The representative blots of three independent experiments are shown. BrdU incorporation was used to detect the DNA synthesis by IL-6 after 72 hours. DMSO is used as a control. Data are shown as mean ± SD of triplicate cultures and are from one experiment representative of three performed. ** <i>p</i> < 0.01 vs DMSO control in the absence of IL-6; ## <i>p</i> < 0.01 vs DMSO control in the presence of IL-6 by a one-way ANOVA with HSD test.</p
Probing Non-Gaussianity in Confined Diffusion of Nanoparticles
Confined diffusion is ubiquitous
in nature. Ever since the “anomalous
yet Brownian” motion was observed, the non-Gaussianity in confined
diffusion has been unveiled as an important issue. In this Letter,
we experimentally investigate the characteristics and source of non-Gaussian
behavior in confined diffusion of nanoparticles suspended in polymer
solutions. A time-varied and size-dependent non-Gaussianity is reported
based on the non-Gaussian parameter and displacement probability distribution,
especially when the nanoparticle’s size is smaller than the
typical polymer mesh size. This non-Gaussianity does not vanish even
at the long-time Brownian stage. By inspecting the displacement autocorrelation,
we observe that the nanoparticle–structure interaction, indicated
by the anticorrelation, is limited in the short-time stage and makes
little contribution to the non-Gaussianity in the long-time stage.
The main source of the non-Gaussianity can therefore be attributed
to hopping diffusion that results in an exponential probability distribution
with the large displacements, which may also explain certain processes
dominated by rare events in the biological environment
Model of CD45 isoforms-mediated IL-6 signaling in multiple myeloma cells.
<p>Engagement of IL-6R with IL-6 leads to complex formation of IL-6R, gp130, Lyn as well as CD45RO/RB in raft microdomains. In response to IL-6 stimulation, CD45RO/RB moves into lipid rafts to induce dephosphorylation of the negative regulatory of Tyr507, phosphorylation of Tyr396, and subsequent conformation change and Lyn activation [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119780#pone.0119780.ref017" target="_blank">17</a>]. We confirmed our hypothesis that lipid rafts-targeted CD45RO/RB facilitates IL-6-induced STAT3 and Lyn/PKC/NF-κB activation in rafts microdomains, while raft-excluded CD45RA remains outside of lipid rafts after IL-6 stimulation and negatively regulates ERK-activation.</p
Effects of Exogenously expressed CD45RO, RB, or RA-EGFP on phosphorylation of STAT3, MAPK, PKC and IκB.
<p>CD45<sup>-</sup> U266 cells were transfected with untagged (mock) or CD45RO-EGFP, CD45RB-EGFP or CD45RA-EGFP expression plasmids, and either treated or untreated with IL-6 (10 ng/ml) at different time points. The representative blots are from three independent experiments and separate blotting using antibodies to P-STAT3, STAT3 (A), P-ERK, ERK (B), P-PKC, PKC (C) and P-IκB, IκB (D) are shown. The densities of protein bands were determined by densitometry and the data represent a change from the control mock density. * <i>p</i> < 0.05 vs mock control in the presence of IL-6; ** <i>p</i> < 0.01 vs mock control in the presence of IL-6 by a one-way ANOVA with HSD test.</p