Die unterschätzte Rolle des Recyclings intakter Metabolite für die Umsatzraten der organischen Bodensubstanz

Obwohl Sorption an Mineraloberflächen als dominierender Prozess zur Erklärung des langsamen Umsatzes mineralassoziierter organischer Bodensubstanz (OBS) dient, widerspricht diese Idee einer zunehmenden Zahl an Inkubationsstudien, die zeigen, dass für niedermolekulare Substanzen nicht nur die mikrobielle Aufnahme kompetitivier als die Sorption ist, sondern auch sorbierte Substanzen in hohem Maße desorbiert und mikrobiell verwertet werden können. Dabei wurde gezeigt, dass sich die Verstoffwechselung desorbierter Substanzen zugunsten eines erhöhten Recyclings verschiebt. Dies wirft die Frage auf, ob Recycling von intakten Metaboliten, d.h. unter Erhalt des Kohlenstoffgerüstes, generell ein bisher stark unterschätzter Prozess ist, der die relativ hohen 14C Alter der OBS teilweise erklären kann. Nach Applikation hoher Toxindosen konnte nachgewiesen werden, dass die nachfolgende Reetablierung der mikrobiellen Gemeinschaft zu großem Anteil auf Recycling der Nekromasskomponenten der Vorgeneration basiert. Intaktes Metabolitrecycling ist jedoch unter steady-state Bedingungen nur äußerst schwierig von der direkten Stabiliserung zu unterscheiden. Um diesen Prozess im Fließgleichgewicht nachzuweisen muss 1) ein Biomolekül untersucht werden, dessen Biosyntheseweg so aufwändig ist, dass Recycling einen deutlichen Vorteil für die Zelle im Vergleich zur Neusynthese darstellt, 2) dieses Biomolkül in lebenden Zellen in einer anderen Form gebunden sein, als die zu recycelnde Einheit in der Bodenlösung, so dass beide Zustandsformen unterschieden werden können und 3) dieses Biomolekül positionsspezifisch isotopenmarkiert zugegeben werden, so dass über einen identischen Einbau der Positionen die Intaktheit des Kohlenstoffgerüstes nachgewiesen werden kann. Am Beispiel der Alkylketten von Fettsäuren, die in mikrobiellen Zellen primär als Phospholipide in den Membranen gebunden sind, soll dieses Prinzip veranschaulicht werden. Eine erste Abschätzung des intakten Recyclings von Alkylketten durch Mikroorganismen in Böden zeigt, dass von den 0.03% der basierend auf Alkyl-Kohlenstoff neugebildeten PLFA mehr als 75% aus intaktem Recycling dieser Ketten hervor gingen. Obwohl der Beitrag des Recyclings intakter Metabolite zur Umsatzzeit der gesamten OBS aufgrund der geringen Anzahl bisher untersuchter Metabolite noch nicht final quantifiziert werden kann, untermauern die hier vorgestellten Ergebnisse jedoch die hohe Relevanz dieses Prozesses für die Dynamik der OBS

Semiconductor-cavity QED in high-Q regimes: Detuning effect

The non-resonant interaction between the high-density excitons in a quantum well and a single mode cavity field is investigated. An analytical expression for the physical spectrum of the excitons is obtained. The spectral properties of the excitons, which are initially prepared in the number states or the superposed states of the two different number states by the resonant femtosecond pulse pumping experiment, are studied. Numerical study of the physical spectrum is carried out and a discussion of the detuning effect is presented.Comment: 7 pages, 8 figure

The use of activity diaries for understanding the daily lives of farmers and their livelihood choices

This paper reviews the use of activity diaries in two Australian Centre for International Agricultural Research (ACIAR) projects in PNG: a smallholder cocoa project in the East New Britain province (ASEM/2006/127) and a smallholder coffee project in Eastern Highlands province (ASEM/2008/036). Both projects were similarly concerned with identifying the production constraints on cocoa- and coffee-farming households and to better understand the range of socioeconomic and cultural factors influencing farmer decision-making and the allocation of household labour among various livelihood activities. In PNG, the household is the principal production unit underpinning livelihood activities such as commodity production. It is at the household level that decisions and negotiations are made regarding the organisation, mobilisation and management of family and extended family labour. Thus, examining in detail the daily economic and social livelihood activities of household members, through time-allocation studies, helps researchers to understand more comprehensively the factors influencing smallholder decision-making regarding livelihood choices, agricultural practices and the adoption of agricultural innovations. This paper outlines two different techniques using activity diaries employed in the projects, and discusses the methodological advantages and challenges of these techniques in smallholder studies in PNG

Tradeoffs in jet inlet design: a historical perspective

The design of the inlet(s) is one of the most demanding tasks of the development process of any gas turbine-powered aircraft. This is mainly due to the multi-objective and multidisciplinary nature of the exercise. The solution is generally a compromise between a number of conflicting goals and these conflicts are the subject of the present paper. We look into how these design tradeoffs have been reflected in the actual inlet designs over the years and how the emphasis has shifted from one driver to another. We also review some of the relevant developments of the jet age in aerodynamics and design and manufacturing technology and we examine how they have influenced and informed inlet design decision

The UK clinical aptitude test and clinical course performance at Nottingham: a prospective cohort study

Background The UK Clinical Aptitude Test (UKCAT) was introduced in 2006 as an additional tool for the selection of medical students. It tests mental ability in four distinct domains (Verbal Reasoning, Quantitative Reasoning, Abstract Reasoning, and Decision Analysis), and the results are available to students and admission panels in advance of the selection process. Our first study showed little evidence of any predictive validity for performance in the first two years of the Nottingham undergraduate course. The study objective was to determine whether the UKCAT scores had any predictive value for the later parts of the course, largely delivered via clinical placements. Methods Students entering the course in 2007 and who had taken the UKCAT were asked for permission to use their anonymised data in research. The UKCAT scores were incorporated into a database with routine pre-admission socio-demographics and subsequent course performance data. Correlation analysis was followed by hierarchical multivariate linear regression. Results The original study group comprised 204/254 (80%) of the full entry cohort. With attrition over the five years of the course this fell to 185 (73%) by Year 5. The Verbal Reasoning score and the UKCAT Total score both demonstrated some univariate correlations with clinical knowledge marks, and slightly less with clinical skills. No parts of the UKCAT proved to be an independent predictor of clinical course marks, whereas prior attainment was a highly significant predictor (p <0.001). Conclusions This study of one cohort of Nottingham medical students showed that UKCAT scores at admission did not independently predict subsequent performance on the course. Whilst the test adds another dimension to the selection process, its fairness and validity in selecting promising students remains unproven, and requires wider investigation and debate by other schools

Tailored climate projections to assess site-specific vulnerability of tea production

Tailored climate change information is essential to understand future climate risks and identify relevant adaptation strategies. However, distilling and effectively communicating decision-relevant information from climate science remains challenging. In this paper, we develop and apply an iterative stakeholder engagement approach and a Site Specific Synthesis of Projected Range (SPR), to co-produce future climate information for Africa’s largest tea producing nations - Kenya and Malawi - for the mid-and late-21st century. SPR provides a novel analysis approach, which combines long-term station observations with projections from 29 global climate models and the first convection-permitting high-resolution climate projection for Africa (CP4A). This addresses the mismatch between spatial scales of projections, large-scale modelling uncertainties and stakeholder need for site-specific information. Iterative stakeholder engagement and communication helped to build trust, allowed use of new observation data and improved visualisations of climate information for stakeholders. SPR demonstrates site-specificity in changes in all metrics, showing risks of large changes in tea crop sensitive metrics. All nine locations analysed show substantial (up to four times) increases in heatwave days and large decreases in cold nights by 2050s compared to the current climate. While tea producers are already witnessing changing climatic conditions, potential future changes will greatly affect the resilience of tea production, thereby affecting the sustainability and quality of tea production in the region. Site specific climate information iteratively co-produced with stakeholders helps them to identify location-specific adaptation strategies and investment priorities, potentially safeguarding supply-chains and millions of livelihoods

Boundary-layer transition detection by thermography and numerical method around bionic train model in wind tunnel test

Methods of diagnosing aerodynamic characteristics are constantly developing in order to conduct the precise and energy efficient wind tunnel testing of transport vehicles in the prototype design early stages. This is of a special importance when facing the time/cost consumption problems of detection of the transition zone over the simplified design of the high-speed train. Herein the applied thermodynamics found a very significant role in the field of experimental aerodynamics. With the intention of detecting the boundary-layer transition zone the following measurements were applied: the infrared thermography, flow visualization, and drag force measurements. In addition, the CFD was applied to predict the flow behaviour and transition zone, solving PDE consisting of the Reynolds-averaged Navier-Stokes equations, energy equation, and the equation of state for an ideal gas employing density-based solver. The thermal imaging defined the transition zone by simple application, and fast recognition, while the transition bounds were defined in the analysis. The flow visualization confirmed thermography results and the method itself as favourable, especially in the most expensive early phases of redesigning for aerodynamically optimized and energy efficient solutions. The numerical method was confirmed by the experiments, resulting in acceptable differences in the definition of the transition zone. For a better understanding of the phenomenon, the overlapped implementation of the presented methods focused on forced convection showed as the best solution. Based on the experiences of this research, development of the additional equipment and adjustments will be introduced in the future experiments

Do personality traits assessed on medical school admission predict exit performance?:A UK-wide longitudinal cohort studyA2

We thank the UKCAT Research Group for funding this independent evaluation and thank Rachel Greatrix and Sandra Nicholson of the UKCAT Consortium for their support throughout this project, and their feedback on the draft paper. We also thank Professor Amanda Lee and Ms Katie Wilde for their input into the application for funding, and ongoing support.Peer reviewedPublisher PD

Rapid Microbiological Testing: Monitoring the Development of Bacterial Stress

The ability to respond to adverse environments effectively along with the ability to reproduce are sine qua non conditions for all sustainable cellular forms of life. Given the availability of an appropriate sensing modality, the ubiquity and immediacy of the stress response could form the basis for a new approach for rapid biological testing. We have found that measuring the dielectric permittivity of a cellular suspension, an easily measurable electronic property, is an effective way to monitor the response of bacterial cells to adverse conditions continuously. The dielectric permittivity of susceptible and resistant strains of Escherichia coli and Staphylococcus aureus, treated with gentamicin and vancomycin, were measured directly using differential impedance sensing methods and expressed as the Normalized Impedance Response (NIR). These same strains were also heat-shocked and chemically stressed with Triton X-100 or H2O2. The NIR profiles obtained for antibiotic-treated susceptible organisms showed a strong and continuous decrease in value. In addition, the intensity of the NIR value decrease for susceptible cells varied in proportion to the amount of antibiotic added. Qualitatively similar profiles were found for the chemically treated and heat-shocked bacteria. In contrast, antibiotic-resistant cells showed no change in the NIR values in the presence of the drug to which it is resistant. The data presented here show that changes in the dielectric permittivity of a cell suspension are directly correlated with the development of a stress response as well as bacterial recovery from stressful conditions. The availability of a practical sensing modality capable of monitoring changes in the dielectric properties of stressed cells could have wide applications in areas ranging from the detection of bacterial infections in clinical specimens to antibiotic susceptibility testing and drug discovery