1,065 research outputs found
Rapid antimicrobial sensitivity testing by single cell nanoscale optical interference
Growing antimicrobial resistance (AMR) is a serious global threat to human health, with estimates of AMR leading to 10 million deaths per year and costing the global economy $100tn by 20501,2. Current methods to detect resistance include phenotypic antibiotic sensitivity testing (AST) which measures bacterial growth and is therefore hampered by slow time to result (~12-24 hours). Therefore new rapid phenotypic methods for AST are urgently needed3. Here we describe a novel method for detecting phenotypic antibiotic resistance in ~45 minutes, capable of detecting single bacteria. The method uses a sensitive laser and detector system to measure nanoscale optical interference of single bacterial cells present in media, with simple sample preparation. This provides a read out of bacterial antibiotic resistance by detecting growth (resistant) or death (sensitive), much faster than current methods. We demonstrate the potential of this technique by determining resistance in both lab and clinical strains of E. coli, a key species for clinically burdensome urinary tract infections. This work provides the basis for a simple and fast diagnostic tool to detect antibiotic resistance in bacteria, reducing the health and economic burdens of AMR
Second Order Perturbations of Flat Dust FLRW Universes with a Cosmological Constant
We summarize recent results concerning the evolution of second order
perturbations in flat dust irrotational FLRW models with . We
show that asymptotically these perturbations tend to constants in time, in
agreement with the cosmic no-hair conjecture. We solve numerically the second
order scalar perturbation equation, and very briefly discuss its all time
behaviour and some possible implications for the structure formation.Comment: 6 pages, 1 figure. to be published in "Proceedings of the 5th
Alexander Friedmann Seminar on Gravitation and Cosmology", Int. Journ. Mod.
Phys. A (2002). Macros: ws-ijmpa.cls, ws-p9-75x6-50.cl
A novel approach to process brittle ice for continuous flow analysis of stable water isotopes
Nonlinear Effects in the Cosmic Microwave Background
Major advances in the observation and theory of cosmic microwave background
anisotropies have opened up a new era in cosmology. This has encouraged the
hope that the fundamental parameters of cosmology will be determined to high
accuracy in the near future. However, this optimism should not obscure the
ongoing need for theoretical developments that go beyond the highly successful
but simplified standard model. Such developments include improvements in
observational modelling (e.g. foregrounds, non-Gaussian features), extensions
and alternatives to the simplest inflationary paradigm (e.g. non-adiabatic
effects, defects), and investigation of nonlinear effects. In addition to well
known nonlinear effects such as the Rees-Sciama and Ostriker-Vishniac effects,
further nonlinear effects have recently been identified. These include a
Rees-Sciama-type tensor effect, time-delay effects of scalar and tensor
lensing, nonlinear Thomson scattering effects and a nonlinear shear effect.
Some of the nonlinear effects and their potential implications are discussed.Comment: Invited contribution to Relativistic Cosmology Symposium (celebrating
the 60th year of GFR Ellis); to appear Gen. Rel. Gra
Skewness in the Cosmic Microwave Background Anisotropy from Inflationary Gravity Wave Background
In the context of inflationary scenarios, the observed large angle anisotropy
of the Cosmic Microwave Background (CMB) temperature is believed to probe the
primordial metric perturbations from inflation. Although the perturbations from
inflation are expected to be gaussian random fields, there remains the
possibility that nonlinear processes at later epochs induce ``secondary''
non-gaussian features in the corresponding CMB anisotropy maps. The
non-gaussianity induced by nonlinear gravitational instability of scalar
(density) perturbations has been investigated in existing literature. In this
paper, we highlight another source of non-gaussianity arising out of higher
order scattering of CMB photons off the metric perturbations. We provide a
simple and elegant formalism for deriving the CMB temperature fluctuations
arising due to the Sachs-Wolfe effect beyond the linear order. In particular,
we derive the expression for the second order CMB temperature fluctuations. The
multiple scattering effect pointed out in this paper leads to the possibility
that tensor metric perturbation, i.e., gravity waves (GW) which do not exhibit
gravitational instability can still contribute to the skewness in the CMB
anisotropy maps. We find that in a flat universe, the skewness in
CMB contributed by gravity waves via multiple scattering effect is comparable
to that from the gravitational instability of scalar perturbations for equal
contribution of the gravity waves and scalar perturbations to the total rms CMB
anisotropy. The secondary skewness is found to be smaller than the cosmic
variance leading to the conclusion that inflationary scenarios do predict that
the observed CMB anisotropy should be statistically consistent with a gaussian
random distribution.Comment: 10 pages, Latex (uses revtex), 1 postscript figure included. Accepted
for publication in Physical Review
A Texture Bestiary
Textures are topologically nontrivial field configurations which can exist in
a field theory in which a global symmetry group is broken to a subgroup
, if the third homotopy group \p3 of is nontrivial. We compute this
group for a variety of choices of and , revealing what symmetry breaking
patterns can lead to texture. We also comment on the construction of texture
configurations in the different models.Comment: 34 pages, plain Tex. (Minor corrections to an old paper.
Cosmic Microwave Background anisotropies from second order gravitational perturbations
This paper presents a complete analysis of the effects of second order
gravitational perturbations on Cosmic Microwave Background anisotropies, taking
explicitly into account scalar, vector and tensor modes. We also consider the
second order perturbations of the metric itself obtaining them, for a universe
dominated by a collision-less fluid, in the Poisson gauge, by transforming the
known results in the synchronous gauge. We discuss the resulting second order
anisotropies in the Poisson gauge, and analyse the possible relevance of the
different terms. We expect that, in the simplest scenarios for structure
formation, the main effect comes from the gravitational lensing by scalar
perturbations, that is known to give a few percent contribution to the
anisotropies at small angular scales.Comment: 15 pages, revtex, no figures. Version to be published in Phys. Rev.
The development of intermodal freight transport in Poland from 2007 to 2016: Barriers and opportunities to its further development
International transport has grown dynamically in Poland since it becomes a European Union (EU) member. This being the case, it is now, more than ever, important to identify the approaches that are most suitable for delivering sustainable freight transport to the nation. Intermodal options appear to be the most appropriate for this task. This study examines the development of intermodal freight transport in Poland from 2007 to 2016. It considers the barriers overcome and that remain to be overcome as well as identifying opportunities for further development. Initially, secondary data sourced from the Główny Urząd Statystyczny, Urząd Transportu Kolejowego and Eurostat databases, was utilised to explore the situation. This was then reinforced by primary data collection, in the form of a survey, the aim of which being to validate the reviewed literature and the findings of the derived from the database data with the subjective perspective of the respondents. It was found that although the prevalence of intermodal transport has an upward trend in Poland its uptake remains significantly lower than in other EU member states. The major issue inhibiting the development of intermodal transport in Poland is the condition of the nation’s infrastructure. This is accompanied by an element of concern for the external costs generated by intermodal carriers. However, Poland’s participation in a range of EU funded projects that support the modernisation of its ageing infrastructure has been, and remains, a major driving force behind the ongoing development of the intermodal transportation of freight within the country
Regulation of cell survival by sphingosine-1-phosphate receptor S1P1 via reciprocal ERK-dependent suppression of bim and PI-3-kinase/protein kinase C-mediated upregulation of Mcl-1
Although the ability of bioactive lipid sphingosine-1-phosphate (S1P) to positively regulate anti-apoptotic/pro-survival responses by binding to S1P1 is well known, the molecular mechanisms remain unclear. Here we demonstrate that expression of S1P1 renders CCL39 lung fibroblasts resistant to apoptosis following growth factor withdrawal. Resistance to apoptosis was associated with attenuated accumulation of pro-apoptotic BH3-only protein Bim. However, although blockade of extracellular signal-regulated kinase (ERK) activation could reverse S1P1-mediated suppression of Bim accumulation, inhibition of caspase-3 cleavage was unaffected. Instead S1P1-mediated inhibition of caspase-3 cleavage was reversed by inhibition of phosphatidylinositol-3-kinase (PI3K) and protein kinase C (PKC), which had no effect on S1P1 regulation of Bim. However, S1P1 suppression of caspase-3 was associated with increased expression of anti-apoptotic protein Mcl-1, the expression of which was also reduced by inhibition of PI3K and PKC. A role for the induction of Mcl-1 in regulating endogenous S1P receptor-dependent pro-survival responses in human umbilical vein endothelial cells was confirmed using S1P receptor agonist FTY720-phosphate (FTY720P). FTY720P induced a transient accumulation of Mcl-1 that was associated with a delayed onset of caspase-3 cleavage following growth factor withdrawal, whereas Mcl-1 knockdown was sufficient to enhance caspase-3 cleavage even in the presence of FTY720P. Consistent with a pro-survival role of S1P1 in disease, analysis of tissue microarrays from ER+ breast cancer patients revealed a significant correlation between S1P1 expression and tumour cell survival. In these tumours, S1P1 expression and cancer cell survival were correlated with increased activation of ERK, but not the PI3K/PKB pathway. In summary, pro-survival/anti-apoptotic signalling from S1P1 is intimately linked to its ability to promote the accumulation of pro-survival protein Mcl-1 and downregulation of pro-apoptotic BH3-only protein Bim via distinct signalling pathways. However, the functional importance of each pathway is dependent on the specific cellular context
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