Effects of past and current crop management on leaching losses, soil microbial community composition and activity

A lysimeter experiment was conducted to investigate the effect of past and current management practices on soil microbial biomass, activity and community composition. Intact monolith lysimeters were taken from sites of the same soil type that had been under long-term organic and conventional crop management. They were subjected to the same crop rotation and managed according to best organic and conventional practices. Mineral N loss was determined in leachates and soil samples taken before the experiment and after 30 months were analysed for biological soil properties, including microbial diversity. Results indicated that leaching losses were similar for all treatments and that crop was the main influence on microbial biomass composition and size, while microbial activity was determined by management history

Change point algorithms appliedto the detection of vortex structures in turbulent flows

En este trabajo se presenta el análisis de la aplicación del modelo de un algoritmo de punto de cambio (Change Point Model, CPM), basado en tests no paramétricos, para la detección de estructuras turbulentas en un flujo de aire. Se busca detectar los vórtices generados en la estela de un perfil aerodinámico dotado de un dispositivo de control pasivo de flujo (mini flap de Gurney) ubicado en el borde de fuga. De la muestra de datos obtenida se analiza la aplicación de modelos CPM, con el fin de determinar los posibles cambios de la fluctuación de la velocidad sensada, comparando los resultados con análisis tradicionales. El objetivo principal del estudio es el de detectar las frecuencias características de las estructuras turbulentas inmersas en el campo del flujo. De los resultados obtenidos se desprende que el modelo CPM basado en el test de Cramer-von Mises (CPM-CvM) presenta una buena concordancia con las detecciones esperadas (diferencias menores al 9,5%), mostrando ser una herramienta alternativa para el análisis de estos tipos de flujo en tiempo real. Este trabajo muestra, finalmente, una nueva aplicación para CPM en la detección de cambios en señales aleatorias dependientes del tiempo que tienen una distribución, a priori, desconocida.The present work shows the application of a change point model (CPM) algorithm, based on non-parametric tests, to turbulent structures detection in an airflow. It seeks to detect the vortices generated in the wake of an airfoil, equipped with a passive flow control device (Gurney mini flap) in its trailing edge. By applying CPM models to the sample data, this paper seeks to determine the possible changes to the velocity fluctuations and compare the models effectiveness to traditional methods. The main objective of this study is to detect the characteristic frequencies of the turbulent structures immersed in the airflow. The results show that the CPM methodology, based on the Cramer- von Mises (CPM-CvM) test, produces results that coincide with values predicted by traditional methods (less than 9.5% of mismatch), validating its use as a real time alternative tool for the analysis of these types of flows. Finally, this work shows a new application of CPM for detecting changes in a timedependent random signal, which has an a priori unknown distribution.Peer Reviewe

Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum

Measurements of small-scale turbulence made over the complex-terrain atmospheric boundary layer during the MATERHORN Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels at four towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The multi-level observations made during a 30-day long MATERHORN-Fall field campaign in September-October 2012 allowed studying of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence and their variations in katabatic winds. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along the slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed downward (upward) whereas the horizontal heat flux is downslope (upslope) below (above) the wind maximum. Our study therefore suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the horizontal heat flux) to derive the height where flux becomes zero. It is shown that the standard deviations of all wind speed components (therefore the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases where the vertical and horizontal heat fluxes are compensated. Turbulence above the wind-speed maximum is decoupled from the surface, and follows the classical local z-less predictions for stably stratified boundary layer.Comment: Manuscript submitted to Boundary-Layer Meteorology (05 December 2014

The motherhood penalties : insights from women in UK academia

We use an original survey of academic women in the UK to investigate different dimensions of the motherhood penalty. Being a mother has no effect on salaries, but still slows down career progression even in such a high-skilled sector. Motherhood has an ambivalent impact on women’s perception of their working environment: improving satisfaction, but reducing perception of salary fairness relative to men. Our paper also explores how different policies can mitigate the motherhood penalties. We find that more generous maternity provisions are associated with higher salary, potentially because generosity reduces the crowding out of research activity. Better availability of childcare and an even distribution of responsibilities within the household correlate positively with earnings. Our findings also highlight the importance of a supportive work environment for mothers’ career and well-being at the workplace. Taken together, these findings suggest the necessity of a multi-faceted policy response to the motherhood penalties

Motherhood in academia : a novel dataset with an application to maternity leave uptake

Legislation over the past two decades enhanced the availability and quantity of statutory maternity leave in the United Kingdom. In high-skilled sectors, many employers top up this maternity leave in an effort to retain and develop the careers of women. As leave provision became more generous, debates emerged as to the role, if any, these enhanced benefits have in retaining women in high status occupation and facilitating their career growth. Further, individual situations and employment status may prevent women from taking advantage of enhanced benefits. This paper presents findings from a comprehensive survey of thousands of women in the UK Higher Education sector and documents how the lives of academic mothers changed over the past quarter century. Contract status and the partner’s participation in parenting has significant effects on the types of maternity leave taken. We reflect on these findings and discuss future research in the area of labour market equity and productivity the availability of this comprehensive quantitative survey of academic women can facilitate

A Variational Fock-Space Treatment of Quarkonium

The variational method and the Hamiltonian formalism of QCD are used to derive relativistic, momentum space integral equations for a quark-antiquark system with an arbitrary number of gluons present. As a first step, the resulting infinite chain of coupled equations is solved in the nonrelativistic limit by an approximate decoupling method. Comparison with experiment allows us to fix the quark mass and coupling constant, allowing for the calculation of the spectra of massive systems such as charmonium and bottomonium. Studying the results with and without the nonAbelian terms, we find that the presence of the nonAbelian factors yields better agreement with the experimental spectra.Comment: TEX, no figure