Investigating bacteriophages targeting the opportunistic pathogen Acinetobacter baumannii

The multi-drug resistance of the opportunistic pathogen Acinetobacter baumannii is of growing concern, with many clinical isolates proving to be resistant to last resort as well as front line antibiotic treatments. The use of bacteriophages is an attractive alternative to controlling and treating this emerging nosocomial pathogen. In this study, we have investigated bacteriophages collected from hospital wastewater in Thailand and we have explored their activity against clinical isolates of A. baumannii. Bacteriophage vB_AbaM_PhT2 showed 28% host range against 150 multidrug resistant (MDR) isolates and whole genome sequencing did not detect any known virulence factors or antibiotic resistance genes. Purified vB_AbaM_PhT2 samples had endotoxin levels below those recommended for preclinical trials and were not shown to be directly cytotoxic to human cell lines in vitro. The treatment of human brain and bladder cell lines grown in the presence of A. baumannii with this bacteriophage released significantly less lactate dehydrogenase compared to samples with no bacteriophage treatment, indicating that vB_AbaM_PhT2 can protect from A. baumannii induced cellular damage. Our results have also indicated that there is synergy between this bacteriophage and the end line antibiotic colistin. We therefore propose bacteriophage vB_AbaM_PhT2 as a good candidate for future research and for its potential development into a surface antimicrobial for use in hospitals. View Full-Tex

Large-scale forcing of the European Slope Current and associated inflows to the North Sea

Drifters drogued at 50?m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988–2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely ''recruited'' from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25–50?% reductions of these density gradients over 1996–1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10–40?% of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a clear decline in this Atlantic inflow over 1988–2007. The influence of variable Slope Current transport on the northern North Sea is also expressed in salinity, which declines through the hindcast period, and there is evidence for a similar freshening trend in observational records. A proxy for Atlantic inflow may be found in sea level records. Variability of Slope Current transport is implicit in mean sea level differences between Lerwick (Shetland) and Torshavn (Faeroes), in both tide gauge records and a longer model hindcast spanning 1958–2013. Potential impacts of this variability on North Sea biogeochemistry and ecosystems, via associated changes in seasonal stratification and nutrient fluxes, are discussed

Observed variability of the North Atlantic current in the Rockall Trough from four years of mooring measurements

The Rockall Trough is one of the main conduits for warm Atlantic Water to the Nordic Seas. Ocean heat anomalies, originating from the eastern subpolar gyre, are known to influence Arctic sea ice extent, marine ecosystems, and continental climate. Knowledge of the transport through this basin has previously been limited to estimates from hydrographic sections which cannot characterise the intra‐annual and multi‐annual variability. As part of the Overturning in the Subpolar North Atlantic Programme (OSNAP), a mooring array was deployed in the Rockall Trough in order to obtain the first continuous measurements of transport. Here, we define the methodology and the errors associated with estimating these transports. Results show a 4‐year mean northward transport of 6.6 Sv (1 Sv = 106 m3/s) by the North Atlantic Current (NAC) in the east and interior of the Rockall Trough (2014‐2018). A mean transport of ‐2.0 Sv (southward) is observed in the west of the basin, which could be part of a recirculation around the Rockall Plateau. The 90‐day low‐pass filtered transport shows large sub‐annual and inter‐annual variability (‐1.6 Sv to 9.1 Sv), mostly resulting from changes in the mid‐basin geostrophic transport. Satellite altimetry reveals the periods of low and high transport are associated with significant changes in the Rockall Trough circulation. There is a detectable seasonal signal, with the greatest transport in spring and autumn

Large-scale forcing of the European Slope Current and associated inflows to the North Sea

Drifters drogued at 50?m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988–2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely ''recruited'' from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25–50?% reductions of these density gradients over 1996–1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10–40?% of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a clear decline in this Atlantic inflow over 1988–2007. The influence of variable Slope Current transport on the northern North Sea is also expressed in salinity, which declines through the hindcast period, and there is evidence for a similar freshening trend in observational records. A proxy for Atlantic inflow may be found in sea level records. Variability of Slope Current transport is implicit in mean sea level differences between Lerwick (Shetland) and Torshavn (Faeroes), in both tide gauge records and a longer model hindcast spanning 1958–2013. Potential impacts of this variability on North Sea biogeochemistry and ecosystems, via associated changes in seasonal stratification and nutrient fluxes, are discussed

Can rogue waves be predicted using characteristic wave parameters?

Rogue waves are ocean surface waves larger than the surrounding sea that can pose a danger to ships and offshore structures. They are often deemed unpredictable without complex measurement of the wave field and computationally intensive calculation which is infeasible in most applications, consequently there a need for fast predictors. Here we collate, quality control, and analyse the largest dataset of single‐point field measurements from surface following wave buoys to search for predictors of rogue wave occurrence. We find that analysis of the sea state parameters in bulk yields no predictors, as the subset of seas containing rogue waves sits within the set of seas without. However, spectral bandwidth parameters of rogue seas display different probability distributions to normal seas, but these parameters are rarely provided in wave forecasts. When location is accounted for, trends can be identified in the occurrence of rogue waves as a function of the average seas state characteristics at that location. These trends follow a power law relationship with the characteristic sea state parameters: mean significant wave height and mean zero up‐crossing wave period. We find that frequency of occurrence of rogue waves and their generating mechanism is not spatially uniform, and each location is likely to have its own unique sensitivities which increase in the coastal seas. We conclude that forecastable predictors of rogue wave occurrence will need to be location specific and reflective of their generation mechanism. Therefore, given location and a sufficiently long historical record of sea state characteristics, the likelihood of occurrence can be obtained for mariners and offshore operators. Plain Language Summary Rogue waves are waves much larger than expected for the surrounding sea state and their size and unexpected nature can pose a danger to ships and offshore structures. They are often thought to be unpredictable without complex computational calculation. Here we try to find the relationship between rogue wave occurrence and the characteristics of the sea state they occur in to circumnavigate this and allow prediction. Here we find that when all the data is analysed in bulk only weak relationships can be seen; however, when the data is analysed spatially relationships can be found between wave height and wave period and rogue wave occurrence. We find that the number of rogue waves and their cause differs spatially and note that each location is likely to have its own unique sensitivities which increase in the coastal seas. We conclude that forecastable predictors of rogue wave occurrence will need to be location specific, reflecting their cause. Therefore, given location and a sufficiently long historical record of sea state characteristics, the likelihood of occurrence can be obtained for mariners and offshore operators

Residual stress control of multipass welds using low transformation temperature fillers

Low transformation temperature (LTT) weld fillers can be used to replace tensile weld residual stresses with compressive ones and reduce the distortion of single-pass welds in austenitic plates. By contrast, weld fillers in multipass welds experience a number of thermal excursions, meaning that the benefit of the smart LTT fillers may not be realised. Here, neutron diffraction and the contour method are used to measure the residual stress in an eight pass groove weld of a 304 L stainless steel plate using the experimental LTT filler Camalloy 4. Our measurements show that the stress mitigating the effect of Camalloy 4 is indeed diminished during multipass welding. We propose a carefully selected elevated interpass hold temperature and demonstrate that this restores the LTT capability to successfully mitigate residual tensile stresses

Seasonal intensification and trends of rogue wave events on the US western seaboard

Studies of changes in wave climate typically consider trends in sea state statistics, such as the significant wave height. However, the temporal variability of individual rogue waves, which pose a hazard to users of the sea and coastal environment has not been investigated. We use time series of continuous surface elevation over 124–270 months (spanning 1994–2016), from 15 wave buoys along the US western seaboard, to investigate regional trends in significant wave height and individual rogue waves. We find high spatial variability in trends in significant wave height and rogue waves across the region. Rogue wave occurrence displays a mostly decreasing trend, but the relative height – or severity – of the waves is increasing. We also identify seasonal intensification in rogue waves with increased rogue wave occurrence, of higher severity, in the winter than in the summer. Therefore, the common practice of stating a single occurrence likelihood for an ocean basin is not valid. In addition, the buoy data show that the magnitude and significance of trends in significant wave height increases towards higher percentiles, supporting previous findings

Twitter-based analysis of the dynamics of collective attention to political parties

Large-scale data from social media have a significant potential to describe complex phenomena in real world and to anticipate collective behaviors such as information spreading and social trends. One specific case of study is represented by the collective attention to the action of political parties. Not surprisingly, researchers and stakeholders tried to correlate parties' presence on social media with their performances in elections. Despite the many efforts, results are still inconclusive since this kind of data is often very noisy and significant signals could be covered by (largely unknown) statistical fluctuations. In this paper we consider the number of tweets (tweet volume) of a party as a proxy of collective attention to the party, identify the dynamics of the volume, and show that this quantity has some information on the elections outcome. We find that the distribution of the tweet volume for each party follows a log-normal distribution with a positive autocorrelation of the volume over short terms, which indicates the volume has large fluctuations of the log-normal distribution yet with a short-term tendency. Furthermore, by measuring the ratio of two consecutive daily tweet volumes, we find that the evolution of the daily volume of a party can be described by means of a geometric Brownian motion (i.e., the logarithm of the volume moves randomly with a trend). Finally, we determine the optimal period of averaging tweet volume for reducing fluctuations and extracting short-term tendencies. We conclude that the tweet volume is a good indicator of parties' success in the elections when considered over an optimal time window. Our study identifies the statistical nature of collective attention to political issues and sheds light on how to model the dynamics of collective attention in social media.Comment: 16 pages, 7 figures, 3 tables. Published in PLoS ON

Downstream effects on human low density lipoprotein of homocysteine exported from endothelial cells in an in vitro system

A model system is presented using human umbilical vein endothelial cells (HUVECs) to investigate the role of homocysteine (Hcy) in atherosclerosis. HUVECs are shown to export Hcy at a rate determined by the flux through the methionine/Hcy pathway. Additional methionine increases intracellular methionine, decreases intracellular folate, and increases Hcy export, whereas additional folate inhibits export. An inverse relationship exists between intracellular folate and Hcy export. Hcy export may be regulated by intracellular S-adenosyl methionine rather than by Hcy. Human LDLs exposed to HUVECs exporting Hcy undergo time-related lipid oxidation, a process inhibited by the thiol trap dithionitrobenzoate. This is likely to be related to the generation of hydroxyl radicals, which we show are associated with Hcy export. Although Hcy is the major oxidant, cysteine also contributes, as shown by the effect of glutamate. Finally, the LDL oxidized in this system showed a time-dependent increase in uptake by human macrophages, implying an upregulation of the scavenger receptor. These results suggest that continuous export of Hcy from endothelial cells contributes to the generation of extracellular hydroxyl radicals, with associated oxidative modification of LDL and incorporation into macrophages, a key step in atherosclerosis. Factors that regulate intracellular Hcy metabolism modulate these effects. Copyright © 2005 by the American Society for Biochemistry and Molecular Biology, Inc