Versatile, Cheap, Readily Modifiable Sample Delivery Method for Analysis of Air-/Moisture-Sensitive Samples Using Atmospheric Pressure Solids Analysis Probe Mass Spectrometry.

A cheap, versatile, readily modified, and reusable glass probe system enabling delivery of solid air-/moisture-sensitive samples for mass spectrometric (MS) analysis using an Atmospheric pressure Solids Analysis Probe (ASAP) is described. The simplicity of the design allows quick and easy ASAP MS analyses of sensitive solid and liquid samples without the need for any modifications to commercially available vertically loaded ASAP mass spectrometers. A comparison of ASAP mass spectra obtained for metal complexes under air and an inert atmosphere is given.

Wild legumes maintain beneficial soil rhizobia populations despite decades of nitrogen deposition.

Natural landscapes are increasingly impacted by nitrogen enrichment from aquatic and airborne pollution sources. Nitrogen enrichment in the environment can eliminate the net benefits that plants gain from nitrogen-fixing microbes such as rhizobia, potentially altering host-mediated selection on nitrogen fixation. However, we know little about the long-term effects of nitrogen enrichment on this critical microbial service. Here, we sampled populations of the legume Acmispon strigosus and its associated soil microbial communities from sites spanning an anthropogenic nitrogen deposition gradient. We measured the net growth benefits plants obtained from their local soil microbial communities and quantified plant investment into nodules that house nitrogen-fixing rhizobia. We found that plant growth benefits from sympatric soil microbes did not vary in response to local soil nitrogen levels, and instead varied mainly among plant lines. Soil nitrogen levels positively predicted the number of nodules formed on sympatric plant hosts, although this was likely due to plant genotypic variation in nodule formation, rather than variation among soil microbial communities. The capacity of all the tested soil microbial communities to improve plant growth is consistent with plant populations imposing strong selection on rhizobial nitrogen fixation despite elevated soil nitrogen levels, suggesting that host control traits in A. strigosus are stable under long-term nutrient enrichment.

Simulating the Feasibility of Using Liquid Micro-Jets for Determining Electron-Liquid Scattering Cross-Sections.

The extraction of electron-liquid phase cross-sections (surface and bulk) is proposed through the measurement of (differential) energy loss spectra for electrons scattered from a liquid micro-jet. The signature physical elements of the scattering processes on the energy loss spectra are highlighted using a Monte Carlo simulation technique, originally developed for simulating electron transport in liquids. Machine learning techniques are applied to the simulated electron energy loss spectra, to invert the data and extract the cross-sections. The extraction of the elastic cross-section for neon was determined within 9% accuracy over the energy range 1-100 eV. The extension toward the simultaneous determination of elastic and ionisation cross-sections resulted in a decrease in accuracy, now to within 18% accuracy for elastic scattering and 1% for ionisation. Additional methods are explored to enhance the accuracy of the simultaneous extraction of liquid phase cross-sections.

Recurrent mutualism breakdown events in a legume rhizobia metapopulation.

Bacterial mutualists generate major fitness benefits for eukaryotes, reshaping the host phenotype and its interactions with the environment. Yet, microbial mutualist populations are predicted to generate mutants that defect from providing costly services to hosts while maintaining the capacity to exploit host resources. Here, we examined the mutualist service of symbiotic nitrogen fixation in a metapopulation of root-nodulating Bradyrhizobium spp. that associate with the native legume Acmispon strigosus. We quantified mutualism traits of 85 Bradyrhizobium isolates gathered from a 700 km transect in California spanning 10 sampled A. strigosus populations. We clonally inoculated each Bradyrhizobium isolate onto A. strigosus hosts and quantified nodulation capacity and net effects of infection, including host growth and isotopic nitrogen concentration. Six Bradyrhizobium isolates from five populations were categorized as ineffective because they formed nodules but did not enhance host growth via nitrogen fixation. Six additional isolates from three populations failed to form root nodules. Phylogenetic reconstruction inferred two types of mutualism breakdown, including three to four independent losses of effectiveness and five losses of nodulation capacity on A. strigosus. The evolutionary and genomic drivers of these mutualism breakdown events remain poorly understood.

A Complete Cross Section Data Set for Electron Scattering by Pyridine: Modelling Electron Transport in the Energy Range 0-100 eV.

Electron scattering cross sections for pyridine in the energy range 0-100 eV, which we previously measured or calculated, have been critically compiled and complemented here with new measurements of electron energy loss spectra and double differential ionization cross sections. Experimental techniques employed in this study include a linear transmission apparatus and a reaction microscope system. To fulfill the transport model requirements, theoretical data have been recalculated within our independent atom model with screening corrected additivity rule and interference effects (IAM-SCAR) method for energies above 10 eV. In addition, results from the R-matrix and Schwinger multichannel with pseudopotential methods, for energies below 15 eV and 20 eV, respectively, are presented here. The reliability of this complete data set has been evaluated by comparing the simulated energy distribution of electrons transmitted through pyridine, with that observed in an electron-gas transmission experiment under magnetic confinement conditions. In addition, our representation of the angular distribution of the inelastically scattered electrons is discussed on the basis of the present double differential cross section experimental results.

Interspecific conflict and the evolution of ineffective rhizobia.

Microbial symbionts exhibit broad genotypic variation in their fitness effects on hosts, leaving hosts vulnerable to costly partnerships. Interspecific conflict and partner-maladaptation are frameworks to explain this variation, with different implications for mutualism stability. We investigated the mutualist service of nitrogen fixation in a metapopulation of root-nodule forming Bradyrhizobium symbionts in Acmispon hosts. We uncovered Bradyrhizobium genotypes that provide negligible mutualist services to hosts and had superior in planta fitness during clonal infections, consistent with cheater strains that destabilise mutualisms. Interspecific conflict was also confirmed at the metapopulation level - by a significant negative association between the fitness benefits provided by Bradyrhizobium genotypes and their local genotype frequencies - indicating that selection favours cheating rhizobia. Legumes have mechanisms to defend against rhizobia that fail to fix sufficient nitrogen, but these data support predictions that rhizobia can subvert plant defenses and evolve to exploit hosts.

Analysis of air-, moisture- and solvent-sensitive chemical compounds by mass spectrometry using an inert atmospheric pressure solids analysis probe.

A novel method has been developed that enables chemical compounds to be transferred from an inert atmosphere glove box and into the atmospheric pressure ion source of a mass spectrometer whilst retaining a controlled chemical environment. This innovative method is simple and cheap to implement on some commercially available mass spectrometers. We have termed this approach inert atmospheric pressure solids analysis probe ( iASAP) and demonstrate the benefit of this methodology for two air-/moisture-sensitive chemical compounds whose characterisation by mass spectrometry is now possible and easily achieved. The simplicity of the design means that moving between iASAP and standard ASAP is straightforward and quick, providing a highly flexible platform with rapid sample turnaround.

Nonnodulating Bradyrhizobium spp. Modulate the Benefits of Legume-Rhizobium Mutualism.

UNLABELLED: Rhizobia are best known for nodulating legume roots and fixing atmospheric nitrogen for the host in exchange for photosynthates. However, the majority of the diverse strains of rhizobia do not form nodules on legumes, often because they lack key loci that are needed to induce nodulation. Nonnodulating rhizobia are robust heterotrophs that can persist in bulk soil, thrive in the rhizosphere, or colonize roots as endophytes, but their role in the legume-rhizobium mutualism remains unclear. Here, we investigated the effects of nonnodulating strains on the native Acmispon-Bradyrhizobium mutualism. To examine the effects on both host performance and symbiont fitness, we performed clonal inoculations of diverse nonnodulating Bradyrhizobium strains on Acmispon strigosus hosts and also coinoculated hosts with mixtures of sympatric nodulating and nonnodulating strains. In isolation, nonnodulating Bradyrhizobium strains did not affect plant performance. In most cases, coinoculation of nodulating and nonnodulating strains reduced host performance compared to that of hosts inoculated with only a symbiotic strain. However, coinoculation increased host performance only under one extreme experimental treatment. Nearly all estimates of nodulating strain fitness were reduced in the presence of nonnodulating strains. We discovered that nonnodulating strains were consistently capable of coinfecting legume nodules in the presence of nodulating strains but that the fitness effects of coinfection for hosts and symbionts were negligible. Our data suggest that nonnodulating strains most often attenuate the Acmispon-Bradyrhizobium mutualism and that this occurs via competitive interactions at the root-soil interface as opposed to in planta IMPORTANCE: Rhizobia are soil bacteria best known for their capacity to form root nodules on legume plants and enhance plant growth through nitrogen fixation. Yet, most rhizobia in soil do not have this capacity, and their effects on this symbiosis are poorly understood. We investigated the effects of diverse nonnodulating rhizobia on a native legume-rhizobium symbiosis. Nonnodulating strains did not affect plant growth in isolation. However, compared to inoculations with symbiotic rhizobia, coinoculations of symbiotic and nonnodulating strains often reduced plant and symbiont fitness. Coinoculation increased host performance only under one extreme treatment. Nonnodulating strains also invaded nodule interiors in the presence of nodulating strains, but this did not affect the fitness of either partner. Our data suggest that nonnodulating strains may be important competitors at the root-soil interface and that their capacity to attenuate this symbiosis should be considered in efforts to use rhizobia as biofertilizers.

Conceptual frameworks and terminology in doctoral nursing research.

AIM: To define conceptual frameworks and their inherent dichotomies, and integrate them with concomitant concepts to help early nursing doctoral researchers to develop their understanding of and engage with discourse further, so that nursing can demonstrate its ability to contribute to the meta-theoretical debate of doctoral research alongside other practices and theory-based disciplines. BACKGROUND: Conceptual frameworks are central to nursing doctoral studies as they map and contextualise the philosophical assumptions of the research in relation to paradigms and ontological, epistemological and methodological foundations. They shape all aspects of the research design and provide a structure for theorising. They can also be a challenge for researchers and are under-discussed in the literature. REVIEW METHODS: Literature review. DISCUSSION: The key aspects of the conceptual framework debate in terms of objectivist, subjectivist paradigms and the wider paradigm debate, including retroduction and abduction, are reviewed here together with consideration of how these apply to nursing doctoral research. CONCLUSION: Conceptual frameworks are pivotal to nursing doctoral research as they clarify and integrate philosophical, methodological and pragmatic aspects of doctoral thesis while helping the profession to be seen as a research-based discipline, comfortable with the language of meta-theoretical debate. IMPLICATIONS FOR RESEARCH/PRACTICE: Conceptual frameworks should form the methodological foundation for all nursing doctoral research.

Modification of a gas chromatography/atmospheric pressure chemical ionisation time-of-flight mass spectrometer as an alternative to automated atmospheric pressure solids analysis probe.

RATIONALE: The atmospheric pressure solids analysis probe (ASAP) has been successfully introduced into laboratories as a routine analytical tool but the technique is labour-intensive and is not easily automated. This paper describes the modifications made to an existing atmospheric pressure gas chromatography (APGC) system to enable the automated analysis of samples that would have otherwise been analysed by ASAP. METHODS: Liquid samples were injected into a 1 m piece of fused silica guard column using a standard split/splitless gas chromatography (GC) inlet, oven and autosampler. A novel timing delay circuit was developed and integrated into the system to control acquisition start times and a bespoke heating block/calibrant delivery system was used to transport either the calibration or reference compound into the ionisation source. RESULTS: The modified system has allowed the successful analysis of those samples requiring ASAP to be carried out in a fully automated manner using APGc. The analysis is rapid and can be carried out in less than 2 min. The results obtained are directly comparable with those obtained by ASAP. A typical mass accuracy of better than 5 mm/z units was achieved, allowing the molecules to be identified based on their elemental formulae. CONCLUSIONS: An existing APGC system has been successfully modified and is suitable for the automatic analysis of samples normally analysed by ASAP. The APGC instrument incorporates the use of a novel reference compound and delivery system which allows accurate mass measurements to be performed. This and the other modifications described have allowed the technique to be incorporated into an existing suite of mass spectrometry-based experiments for use in the characterisation of organic molecules.

The spatialization of decent work and the role of employability empowerment for minority ethnic young people in emerging economies.

Global rises in precarious labour conditions have prompted further empirical work in Decent Work, a special category of employment characterised by equitable pay, treatment, and healthy working conditions. Despite this, research has tended to be conducted in developed countries with privileged groups such as those with typical working arrangements and rely on psychologically framed individual characteristics to explain marginalising factors. We propose a more sociologically framed, spatialised perspective on Decent Work which posits that marginalising factors are spatially variable and determined but moderated by employability empowerment. We measure our propositions across three spatially different sites of Vietnam through (1) a survey of minority ethnic students and graduates (N = 1071) and (2) a survey of stakeholders involved in the recruitment and employment of this group (N = 204). We find support for most of our propositions and call for more spatialised empirical work in the field of Decent Work.

Effect of simulated learning on blood pressure measurement skills.

AIM: To explore whether additional teaching and simulated learning of one-hour duration could improve the blood pressure measurement skills of nursing students. METHOD: A post-test experimental method was used to measure the outcome of additional, targeted simulated learning of blood pressure monitoring beyond normal curriculum content in adult branch nursing students in module one of a three-year nursing programme. RESULTS: One hour of additional teaching and simulated learning improved the ability of nursing students to measure blood pressure accurately, with the data revealing a statistical difference between experimental and control groups in the systolic and diastolic accuracy of blood pressure monitoring. CONCLUSION: In a changing practice environment with fewer opportunities to develop clinical skills under supervision, there is a need for nurse educators and mentors to reconsider and research further methods used for blood pressure monitoring and other skills teaching using simulation for effective learning and skills acquisition.

The conceptual framework and the iterative elements of doctoral nursing research design.

BACKGROUND: Conceptual frameworks are central to doctoral nursing theses; they include the pragmatic and philosophical elements of the research design and their interrelationships. While the research process may seem to stem in a straightforward, linear manner from the research question, it is a more complex iterative enterprise. AIM: To build on Durham et al ( 2015 ) by reviewing the ostensibly static nature of research design and associated philosophical elements of the conceptual framework, reconsidering these in relation to the iterative nature of the research process, and translating these into implications for presenting the final draft of a doctoral nursing thesis. DISCUSSION: All doctoral nursing theses will have limitations and experience difficulties. They do not follow a rigid, sequential process with a defined start and end, but progress tentatively, with the relationship between the elements of the research design and philosophical assumptions following an iterative process. CONCLUSION: The research design element of the conceptual framework of doctoral nursing theses should reflect the iterative reality of the process and the associated interrelationships that occur. IMPLICATIONS FOR PRACTICE: The absence in doctoral nursing theses of a full description of the philosophical and iterative processes of the research architecture and conceptual framework weakens the transparency of the research. Therefore, doctoral nursing students need to move beyond simple description of their inductive or deductive position and research design to help develop trust and confidence in their research.

Plant Genomics: Evolution and Development of a Major Crop Parasite.

Parasitic plants in the genus Striga bedevil crop production throughout Africa and Asia. A new genome assembly reveals how repurposing of developmental pathways, gene gains and losses, and horizonal gene transfer all contributed to the evolution of these destructive pathogens.

Production and certification of four frozen human serum certified reference materials containing creatinine and electrolytes.

BACKGROUND: This paper describes the preparation, analysis and certification of four frozen human serum certified reference materials (CRMs) containing creatinine and the electrolytes calcium, lithium, magnesium, potassium and sodium. These materials have been prepared to give concentrations of these analytes that cover the currently accepted analytical range. METHODS: The analysis of the materials for certification purposes has been carried out using methodology traceable to primary standards, and which is acceptable as a reference method. The certification methods include liquid chromatography-mass spectrometry (LC-MS) with exact-matching isotope dilution calibration (EM-IDMS) for creatinine, inductively-coupled plasma optical emission spectroscopy (ICP-OES), ICP-MS and isotope-dilution inductively-coupled plasma mass spectroscopy (ID-ICP-MS) for the electrolytes. RESULTS: The uncertainties estimated for these certified values include a component from the characterization measurements, as well as contributions from possible inhomogeneity and long-term instability. The certified values have been corroborated by measurements obtained in a major UK External Quality Assessment scheme, which have, with the exception of the determination of creatinine at a particularly low concentration, given excellent agreement. CONCLUSIONS: The materials are intended for use by pathology laboratories and manufacturers of in vitro diagnostic (IVD) kits for validation of existing routine methodology to a traceable standard, which will promote harmonization between the different methods, instruments and IVD kits used in these laboratories.

Third-order transport coefficients for localised and delocalised charged-particle transport.

We derive third-order transport coefficients of skewness for a phase-space kinetic model that considers the processes of scattering collisions, trapping, detrapping and recombination losses. The resulting expression for the skewness tensor provides an extension to Fick's law which is in turn applied to yield a corresponding generalised advection-diffusion-skewness equation. A physical interpretation of trap-induced skewness is presented and used to describe an observed negative skewness due to traps. A relationship between skewness, diffusion, mobility and temperature is formed by analogy with Einstein's relation. Fractional transport is explored and its effects on the flux transport coefficients are also outlined.

Generalized balance equations for charged particle transport via localized and delocalized states: Mobility, generalized Einstein relations, and fractional transport.

A generalized phase-space kinetic Boltzmann equation for highly nonequilibrium charged particle transport via localized and delocalized states is used to develop continuity, momentum, and energy balance equations, accounting explicitly for scattering, trapping and detrapping, and recombination loss processes. Analytic expressions detail the effect of these microscopic processes on mobility and diffusivity. Generalized Einstein relations (GER) are developed that enable the anisotropic nature of diffusion to be determined in terms of the measured field dependence of the mobility. Interesting phenomena such as negative differential conductivity and recombination heating and cooling are shown to arise from recombination loss processes and the localized and delocalized nature of transport. Fractional transport emerges naturally within this framework through the appropriate choice of divergent mean waiting time distributions for localized states, and fractional generalizations of the GER and mobility are presented. Signature impacts on time-of-flight current transients of recombination loss processes via both localized and delocalized states are presented.

Solution of a generalized Boltzmann's equation for nonequilibrium charged-particle transport via localized and delocalized states.

We present a general phase-space kinetic model for charged-particle transport through combined localized and delocalized states, capable of describing scattering collisions, trapping, detrapping, and losses. The model is described by a generalized Boltzmann equation, for which an analytical solution is found in Fourier-Laplace space. The velocity of the center of mass and the diffusivity about it are determined analytically, together with the flux transport coefficients. Transient negative values of the free particle center-of-mass transport coefficients can be observed due to the trapping to, and detrapping from, localized states. A Chapman-Enskog-type perturbative solution technique is applied, confirming the analytical results and highlighting the emergence of a density gradient representation in the weak-gradient hydrodynamic regime. A generalized diffusion equation with a unique global time operator is shown to arise, reducing to the standard diffusion equation and a Caputo fractional diffusion equation in the normal and dispersive limits. A subordination transformation is used to solve the generalized diffusion equation by mapping from the solution of a corresponding standard diffusion equation.

A comparison of enzymatic digestion for the quantitation of an oligonucleotide by liquid chromatography-isotope dilution mass spectrometry.

DNA is a universal analyte found in almost every organism. It is the code that dictates our genetic make-up and it provides a vast library of information. DNA sequences can indicate genetic modification of foodstuffs, how we may metabolise pharmaceuticals and the likelihood of suffering particular diseases. The basis for many of these genetic tests would benefit greatly from procedures that can accurately quantitate DNA in an absolute manner. This would then provide a sound and universally consistent foundation for regulatory and diagnostic decision making. This work compares two different enzymatic digestion systems as precursor steps to high accuracy isotope dilution mass spectrometry (IDMS) quantitation of a 20mer oligonucleotide. In the first approach, snake venom phosphodiesterase (SVP) digests the oligonucleotide to its constituent deoxynucleotides (dNMPs), followed by liquid chromatography-IDMS (LC-IDMS) quantitation. The second enzyme digestion approach used a combination of snake venom phosphodiesterase and shrimp alkaline phosphatase (SAP) which reduces the oligonucleotide to its constituent deoxynucleosides (dNs). This was then followed by an alternative LC separation and equivalent IDMS measurements. Total phosphorous content of the 20mer oligonucleotide was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). This provided independent data for comparison with the two enzyme digestion-IDMS based procedures. The most appropriate method of quantitation was found to be the combined SVP and SAP digestion. This approach negates the need to consider and/or account for the lack of a 5' terminal phosphate residue. It also enables the use of positive ion mass spectrometry which simplifies the chromatographic requirements. Based on the exact matched IDMS of the adenine deoxynucleoside, the concentration of the original 20mer oligonucleotide was found to be 110+/-9 microg g(-1). This showed good agreement with the ICP-OES data based on the measurement of phosphorus which gave an equivalent value for the original 20mer oligonucleotide of 108+/-5microg g(-1) (uncertainties at the 95% confidence interval). It is intended that this high accuracy methodology should be used to produce high calibre reference standards. These, in turn, could then be used to underpin the quality and consistency of routine measurements involving a variety of more commonly encountered methodologies. It should be noted that the IDMS procedures are equally applicable to both sequenced and non-sequenced oligonucleotide materials.

HPA hyperactivity with increased plasma cortisol affects dexamethasone metabolism and DST outcome.

Data suggests that dexamethasone bioavailability or pharmacokinetic factors contribute importantly to the outcome of the dexamethasone suppression test, and a relationship between plasma cortisol and plasma dexamethasone levels has been shown. To evaluate these data further, we studied plasma dexamethasone pharmacokinetics in 24 patients with major depression (15 suppressors and nine nonsuppressors) who received a 1 mg IV dexamethasone bolus at 09:00 h with blood samples collected at intervals over the next 14 h. We found that nonsuppressors had significantly shorter plasma dexamethasone half-life (P = 0.003) as well as significantly lower dexamethasone levels 10 h (P = 0.02) following IV dexamethasone administration. Moreover, upon clinical improvement of patients, the shortened dexamethasone half-life and lower dexamethasone levels disappeared in the five patients who switched from nonsuppression to suppression and were restudied by IV bolus. These 10-h post IV plasma dexamethasone level findings paralleled the results of the 1 mg overnight oral DST performed in these depressed patients (N = 22) where we found significantly lower 10 h plasma dexamethasone levels in nonsuppressors on admission compared to suppressors (P = 0.002) and again at discharge (P = 0.007). Interestingly, in the few patients who switched from suppression to nonsuppression over the course of hospitalization, 10-h post dose plasma dexamethasone levels simultaneously dropped. No difference in dexamethasone half-life was observed in the patients studied by oral and IV dexamethasone administration. These findings support the concept that metabolism of dexamethasone is significantly related to the activity of the HPA axis (particularly by plasma cortisol levels), and that dexamethasone pharmacokinetics can be modified by state-dependent phenomena.