Amplitude-mode dynamics of polariton condensates

We study the stability of collective amplitude excitations in non-equilibrium polariton condensates. These excitations correspond to renormalized upper polaritons and to the collective amplitude modes of atomic gases and superconductors. They would be present following a quantum quench or could be created directly by resonant excitation. We show that uniform amplitude excitations are unstable to the production of excitations at finite wavevectors, leading to the formation of density-modulated phases. The physical processes causing the instabilities can be understood by analogy to optical parametric oscillators and the atomic Bose supernova.Comment: 4 pages, 2 figure

Compilation of an Arabic Children’s Corpus

Inspired by the Oxford Children's Corpus, we have developed a prototype corpus of Arabic texts written and/or selected for children. Our Arabic Children's Corpus of 2950 documents and nearly 2 million words has been collected manually from the web during a 3-month project. It is of high quality, and contains a range of different children's genres based on sources located, including classic tales from The Arabian Nights, and popular fictional characters such as Goha. We anticipate that the current and subsequent versions of our corpus will lead to interesting studies in text classification, language use, and ideology in children's texts

The Limited Role of Mutually Unbiased Product Bases in Dimension Six

We show that a complete set of seven mutually unbiased bases in dimension six, if it exists, cannot contain more than one product basis.Comment: 8 pages, identical to published versio

Multi-Qubit Systems: Highly Entangled States and Entanglement Distribution

A comparison is made of various searching procedures, based upon different entanglement measures or entanglement indicators, for highly entangled multi-qubits states. In particular, our present results are compared with those recently reported by Brown et al. [J. Phys. A: Math. Gen. 38 (2005) 1119]. The statistical distribution of entanglement values for the aforementioned multi-qubit systems is also explored.Comment: 24 pages, 3 figure

Shock Index Values and Trends in Pediatric Sepsis: Predictors or Therapeutic Targets? A retrospective observational study

BACKGROUND: Shock index (SI) (heart rate/systolic blood pressure) has been used to predict outcome in both adult and pediatric sepsis within the intensive care unit (ICU). We aimed to evaluate the utility of SI prior to pediatric ICU (PICU) admission. METHODS: We conducted a retrospective observational study of children referred to a pediatric intensive care transport service (PICTS) between 2005 and 2011. The predictive value of SI, heart rate and blood pressure at three pre-specified time points (at referral to PICTS, at PICTS arrival at the referring hospital, and at PICU admission), and changes in SI between the time points, were evaluated. Death within the first 48 hours of ICU admission (early death) was the primary outcome variable. RESULTS: Over the seven-year period, 572 children with sepsis were referred to the PICTS. Thirty-nine children died prior to transport to a PICU, while 474 were transported alive. Adjusting for age, time-points and time duration in a multi-level regression analysis, SI was significantly higher in those who died early. There was a significant improvement in SI with the transport team in survivors but not in non-survivors. However, the predictive value of a change in SI for mortality was no better than either a change in heart rate or blood pressure. CONCLUSIONS: The absolute or change in SI does not predict early death any more than heart rate and systolic blood pressure individually in children with sepsis

Iron overload in paediatrics undergoing cardiopulmonary bypass

AbstractPathological changes in iron status are known to occur during bypass and will be superimposed upon physiological abnormalities in iron distribution, characteristic of the neonatal period. We have sought to define the severity of iron overload in these patients. Plasma samples from 65 paediatric patients undergoing cardiopulmonary bypass (CPB) were analysed for non-haem iron, total iron binding capacity, transferrin and bleomycin-detectable iron. Patients were divided into four age groups for analysis. Within each age group, patients who were in iron overload at any time point were statistically compared to those who were not. The most significant changes in iron chemistry were seen in the plasma of neonates, with 25% in a state of plasma iron overload. 18.5% of infants and 14.3% of children at 1–5 years were also in iron overload at some time point during CPB. No children over 5 years, however, went into iron overload. Increased iron saturation of transferrin eliminates its ability to bind reactive forms of iron and to act as an antioxidant. When transferrin is fully saturated with iron, reactive forms of iron are present in the plasma which can stimulate iron-driven oxidative reactions. Our data suggest that paediatric patients are at greater risk of iron overload during CPB, and that some form of iron chelation therapy may be advantageous to decrease oxidative stress

The Emissions of Water Vapour and NOx from Modelled Hydrogen-Fuelled Aircraft and the Impact of NOx Reduction on Climate Compared with Kerosene-Fuelled Aircraft

A kerosene fuelled aircraft was modelled within a performance tool and fuel burn and the emissions of nitrogen oxides (NOx) and water vapour at different stages of flight throughout the mission were estimated. Adaptions were made to engine and aircraft parameters within the performance tool to accommodate a liquid hydrogen fuel over the same given mission. Once an iterative design process had been completed to ensure the aircraft could perform the given mission, the performance tool was again used to calculate total fuel burn. Fuel burn results alongside predicted emission indices were used to estimate the emissions of NOx, water vapour from hydrogen-fuelled aircraft. The use of hydrogen fuel over kerosene fuel in the modelled aircraft resulted in the removal of carbon-based emission species alongside 86% reduction in NOx and 4.3 times increase in water vapour emission. The climate impact of this switch with the reduction in NOx emission was assessed by a 3D global atmospheric chemistry and transport model, STOCHEM-CRI, which found a significant reduction in the concentration of a potent greenhouse gas, ozone, and an oxidizing agent, OH, by up to 6% and 25%, respectively. The reduction of OH levels could induce a positive radiative forcing effect as the lifetime of another important greenhouse gas, methane, is increased. However, the magnitude of this increase is very small (~0.3%), thus the overall impact of the reduction in NOx emissions is likely to have a net negative radiative forcing effect, improving aviation’s impact on the environment. However, further work is warranted on effects of other emission species, specifically water vapour, particulate matter and unburned hydrogen

Ribosome profiling of the retrovirus murine leukemia virus

Background The retrovirus murine leukemia virus (MuLV) has an 8.3 kb RNA genome with a simple 5′-gag-pol-env-3′ architecture. Translation of the pol gene is dependent upon readthrough of the gag UAG stop codon; whereas the env gene is translated from spliced mRNA transcripts. Here, we report the first high resolution analysis of retrovirus gene expression through tandem ribosome profiling (RiboSeq) and RNA sequencing (RNASeq) of MuLV-infected cells. Results Ribosome profiling of MuLV-infected cells was performed, using the translational inhibitors harringtonine and cycloheximide to distinguish initiating and elongating ribosomes, respectively. Meta-analyses of host cell gene expression demonstrated that the RiboSeq datasets specifically captured the footprints of translating ribosomes at high resolution. Direct measurement of ribosomal occupancy of the MuLV genomic RNA indicated that ~7% of ribosomes undergo gag stop codon readthrough to access the pol gene. Initiation of translation was found to occur at several additional sites within the 5′ leaders of the gag and env transcripts, upstream of their respective annotated start codons. Conclusions These experiments reveal the existence of a number of previously uncharacterised, ribosomally occupied open reading frames within the MuLV genome, with possible regulatory consequences. In addition, we provide the first direct measurements of stop codon readthrough efficiency during cellular infection.Sir Henry Wellcome Postdoctoral Fellowship (Wellcome Trust) to N.I.; Wellcome Trust grant [106207] and European Research Council (ERC) grant [646891] to A.E.F.; U.K. Biotechnology and Biological Research Council (BBSRC) grant [BB/G020272/1] and U.K. Medical Research Council (MRC) grant [MR/M011747/1] to I.B. The funders played no role in the study, or writing of the manuscript

Pliocene warmth and gradients

The Pliocene epoch (5.3–2.6 Ma) generates continued debate as an example of a warm climate with external forcing similar to the present day. O'Brien et al. presented new multi-proxy sea surface temperature (SST) reconstructions from the South China Sea, adding to this debate. Based on their records, and a hypothesized seawater chemistry adjustment to temperature reconstructions previously derived from the Mg/Ca ratios of planktonic foraminifera, they suggest that the western Pacific warm pool was “2 °C warmer than today” in the Pliocene. This contradicts previous evidence of long-term stability in warm pool SSTs, but possibly reconciles temperature reconstructions and climate model simulations. Here we raise several points contrary to those conclusions

Setting a precautionary catch limit for Antarctic krill

A revised precautionary catch limit for Antarctic krill (Euphausia superba) in the Scotia Sea of 4 million tons was recently adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The limit was based on a total biomass of 44.3 million tons, as estimated from an acoustic and net survey of krill across the Scotia Sea sector of the Southern Ocean, and a harvest rate of 9.1%, as determined from an analysis of the risks of exceeding defined conservation criteria. We caution, however, that before the fishery can expand to the 4-inillion-ton level it will be necessary to establish mechanisms to avoid concentration of fishing effort, particularly in proximity to colonies of land-breeding krill predators, and to consider the effects of krill immigrating into the region from multiple sources