Staphylococcus aureus is a human commensal and also an opportunist pathogen causing life threatening infections. During S. aureus disease, the abscesses that characterise infection can be clonal, ...whereby a large bacterial population is founded by a single or few organisms. Our previous work has shown that macrophages are responsible for restricting bacterial growth such that a population bottleneck occurs and clonality can emerge. A subset of phagocytes fail to control S. aureus resulting in bacterial division, escape and founding of microabscesses that can seed other host niches. Here we investigate the basis for clonal microabscess formation, using in vitro and in silico models of S. aureus macrophage infection. Macrophages that fail to control S. aureus are characterised by formation of intracellular bacterial masses, followed by cell lysis. High-resolution microscopy reveals that most macrophages had internalised only a single S. aureus, providing a conceptual framework for clonal microabscess generation, which was supported by a stochastic individual-based, mathematical model. Once a threshold of masses was reached, increasing the number of infecting bacteria did not result in greater mass numbers, despite enhanced phagocytosis. This suggests a finite number of permissive, phagocyte niches determined by macrophage associated factors. Increased understanding of the parameters of infection dynamics provides avenues for development of rational control measures.
A ground-based Fourier transform spectrometer has been developed to measure the atmospheric downwelling infrared radiance spectrum at the earth's surface with high absolute accuracy. The Atmospheric ...Emitted Radiance Interferometer (AERI) instrument was designed and fabricated by the University of Wisconsin Space Science and Engineering Center (UW-SSEC) for the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program. This paper emphasizes the key features of the UW-SSEC instrument design that contribute to meeting the AERI instrument requirements for the ARM Program. These features include a highly accurate radiometric calibration system, an instrument controller that provides continuous and autonomous operation, an extensive data acquisition system for monitoring calibration temperatures and instrument health, and a real-time data processing system. In particular, focus is placed on design issues crucial to meeting the ARM requirements for radiometric calibration, spectral calibration, noise performance, and operational reliability. The detailed performance characteristics of the AERI instruments built for the ARM Program are described in a companion paper. PUBLICATION ABSTRACT
Abstract
The Atmospheric Emitted Radiance Interferometer (AERI) instrument was developed for the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program by the University of ...Wisconsin Space Science and Engineering Center (UW-SSEC). The infrared emission spectra measured by the instrument have the sensitivity and absolute accuracy needed for atmospheric remote sensing and climate studies. The instrument design is described in a companion paper. This paper describes in detail the measured performance characteristics of the AERI instruments built for the ARM Program. In particular, the AERI systems achieve an absolute radiometric calibration of better than 1% (3σ) of ambient radiance, with a reproducibility of better than 0.2%. The knowledge of the AERI spectral calibration is better than 1.5 ppm (1σ) in the wavenumber range 400– 3000 cm−1.
The exchange of solutes between surface and pore waters is an important control over stream ecology and biogeochemistry. Free‐stream turbulence is known to enhance transport across the sediment‐water ...interface (SWI), but the link between turbulent momentum and solute transport within the hyporheic zone remains undetermined due to a lack of in situ observations. Here, we relate turbulent momentum and solute transport using measurements within a streambed with 0.04 m diameter sediment. Pore water velocities were measured using endoscopic particle image velocimetry and used to generate depth profiles of turbulence statistics. Solute transport was observed directly within the hyporheic zone using an array of microsensors. Solute injection experiments were used to assess turbulent fluxes across the SWI and patterns of hyporheic mixing. Depth profiles of fluctuations in solute concentration were compared with profiles of turbulence statistics, and profiles of mean solute concentration were compared to an effective dispersion model. Fluorescent visualization experiments at a Reynolds number of
Re≥ 27,000 revealed the presence of large‐scale motions that ejected tracer from the pore waters, and that these events were not present at
Re = 13,000. Turbulent shear stresses and high‐frequency concentration fluctuations decayed greatly within 1–2 grain diameters below the SWI. However, low‐frequency concentration fluctuations penetrated to greater depths than high‐frequency fluctuations. Comparison with a constant‐coefficient dispersion model showed that hyporheic mixing was enhanced in regions where turbulent stresses were observed. Together, these results show that the penetration of turbulence into the bed directly controls both interfacial exchange and mixing within a transition layer below the SWI.
Plain Language Summary
Streams and rivers continuously exchange water with their underlying sediments in a region called the hyporheic zone. This zone is a hotspot of transformation for many societally relevant chemicals, including carbon, nutrients, and contaminants. Accurate predictions for how much transformation occurs in the hyporheic zone requires an improved understanding of how reactive chemicals are transported into, and within, this region of a riverbed. Although fluid turbulence can be the dominant process controlling surface‐subsurface exchange in gravel‐bed streams, its influence is poorly understood due to the difficulty of measuring turbulent fluid velocities and concentrations within the streambed. In this experimental study, we show that turbulence strongly couples surface waters with hyporheic waters in a thin layer where the water column and stream sediments meet. As a result, fluid transport and mixing are enhanced several centimeters into the hyporheic zone of gravel‐bed streams. These findings support recent theoretical arguments that surface and subsurface waters are not independent and must instead be treated as a single unit to accurately model solute, particulate and pollutant transport in streams and rivers.
Key Points
High‐frequency concentration variability and enhanced mixing are directly linked to penetration of turbulence into the hyporheic zone
Regions of enhanced mixing directly correspond to the penetration depth of intermittent turbulent flow structures
Low‐frequency fluctuations in solute concentration propagate deeper into the hyporheic zone but do not enhance mixing
Interest continues to grow in the use of room temperature ionic liquids (RTILs) as electrolytes in a range of electrochemical applications, such as lithium batteries, supercapacitors and ...dye-sensitized solar cells. Underpinning this growth, investigations into the electrochemical behaviour of RTILs and RTIL-based systems rely on accurate and precise data on the potentials of redox processes. While most researchers have continued the practice (developed with non-aqueous solvents) of reporting potentials relative to one of the metal-organic standards (such as ferrocene), little attention has been given to the development of a reliable reference electrode, based on an ionic liquid. Such an electrode is always valuable, especially in situations where addition of a reference material is not possible.
We report a Ag∣Ag
+ reference electrode, incorporating a known concentration of silver trifluoromethanesulfonate (AgTf) in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (P
14TFSI), which provides a stable and reproducible reference potential. Voltammetric monitoring of the redox potentials for ferrocene and cobalticinium hexafluorophosphate have shown that the electrode Ag∣Ag
+(10
mM AgTf, P
14TFSI) is stable to within a millivolt, over a period of around three weeks, when used in an argon atmosphere at room temperature. Higher concentrations of silver ion reveal close-to-Nernstian behaviour. All Ag∣Ag
+ configurations were significantly more stable than a silver wire quasi-reference electrode, even when the latter was separated in a salt-bridge. Voltammetric data recorded in a range of different ionic liquids, against the Ag∣Ag
+ (10
mM AgTf, P
14TFSI) reference electrode, produced apparent junction potentials of a few tens of mV. Changes in sign of the junction potential are usefully discussed in terms of the relative mobilities of the anions and cations present, while the magnitude can be discussed in the terms of a classic molten salt treatment.
Background and purpose
Research indicates that patients with myotonic dystrophy type 1 (DM1) are at increased risk of cancer and early death. Family data may provide insights given DM1 phenotypic ...heterogeneity, the broad range of non‐muscular manifestations and the usual delays in the diagnosis of DM1.
Method
Family history data were collected from 397 genetically and/or clinically confirmed DM1 patients (respondents) enrolled in the US or UK myotonic dystrophy registries. Standardized mortality ratios were calculated for DM1 first‐degree relatives (parents, siblings and offspring) by their reported DM1 status (affected, unaffected or unknown). For cancer‐related analyses, mixed effects logistic regression models were used to evaluate factors associated with cancer development in DM1 families, including familial clustering.
Results
A total of 467 deaths and 337 cancers were reported amongst 1737 first‐degree DM1 relatives. Mortality risk amongst relatives reported as DM1‐unaffected was comparable to that of the general population standardized mortality ratio (SMR) 0.82, P = 0.06, whilst significantly higher mortality risks were noted in DM1‐affected relatives (SMR = 2.47, P < 0.0001) and in those whose DM1 status was unknown (SMR = 1.60, P < 0.0001). In cancer risk analyses, risk was higher amongst families in which the DM1 respondent had cancer (odds ratio 1.95, P = 0.0001). Unknown DM1 status in the siblings (odds ratio 2.59, P = 0.004) was associated with higher cancer risk.
Conclusion
There is an increased risk of death, and probably cancer, in relatives with DM1 and in those whose DM1 status is unknown. This suggests a need to perform a careful history and physical examination, supplemented by genetic testing, to identify family members at risk for DM1 and who might benefit from disease‐specific clinical care and surveillance.
Aims: Pulsed‐field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR) profiles of 195 epidemiologically unrelated Salmonella Typhimurium strains isolated in 1997–2004 from pigs were ...analysed and the results compared to establish the discriminatory ability of each method. In order to investigate the epidemiology of S. Typhimurium from different populations, the VNTR profiles from pigs were compared with those obtained from 190 S. Typhimurium strains isolated from poultry and 186 strains isolated from human cases of gastroenteritis.
Methods and Results: A total of 195 strains of S. Typhimurium were tested by PFGE and VNTR. For PFGE, the restriction enzyme XbaI was used, and for VNTR, the number of repeats at five loci (STTR 9, 5, 6, 10pl and 3) were counted and assigned an allele number based on an established VNTR scheme. The results obtained showed improved discrimination of VNTR when compared with PFGE with 34 PFGE profiles identified compared with 96 different VNTR profiles for the pig isolates and 56 different VNTR types within the most common PFGE type. Within the three different populations, VNTR showed distinct subpopulations of VNTR type related not only to source, but also demonstrated common VNTR types within samples obtained from humans, poultry and pigs, especially in strains of phage type DT104.
Conclusions: VNTR has taken the discrimination to a further level than that obtained through PFGE, and demonstrated an overlap in the genetic diversity of isolates tested across the three different populations, confirming previous suggestions that animals have an involvement in the dissemination of S. Typhimurium through the food chain.
Significance and Impact of the Study: Salmonella Typhimurium remains an important concern as a food‐borne zoonotic agent. The VNTR strategy described provides an accurate method of tracing strain dissemination, and adds a further level of discrimination to the PFGE type, providing potential benefits to epidemiological studies and the possibility of deciphering source attribution of cases.
A simple and efficient method for removal of phenolic methoxymethyl ethers in the presence of 30 mol% of bismuth trichloride in acetonitrile/water is described. Notable features of the cleavage ...protocol entail use of an ecofriendly bismuth reagent, ease of handling, low cost, operational simplicity, and good functional group compatibility. A number of structurally varied phenolic methoxymethyl ethers were cleaved in good to excellent yields.
The Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) is described, and some examples of the environmental variables that can be derived from its measurements and the types of research that ...these can support are briefly presented. The M-AERI is a robust- accurate, self-calibrating, seagoing Fourier-transform interferometric infrared spectroradiometer that is deployed on marine platforms to measure the emission spectra from the sea surface and marine atmosphere.
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