Ultra fast imaging NMR method for measuring fast transport processes in thin porous media

Measuring moisture distributions during fast transport processes in thin porous media is a challenging task. In this paper, Ultra Fast Imaging (UFI) NMR is proposed as a valuable measurement technique for investigating moisture uptake in porous media by achieving a temporal resolution of 10 ms and spatial resolution between 14.5 and 18 μm. This paper gives a detailed explanation about the methodology and the interpretation of the signal intensity. It is shown that there exist specific T 1- and T 2- relaxation time conditions for performing UFI experiments with signal-to-noise ratios that are sufficiently high. In most cases, a contrast agent is required to optimize these relaxation times and achieve the optimal measurement conditions. In the first part of this paper, both CuSO4 and Clariscan are discussed as possible contrast agents. Furthermore, it is shown that the signal intensity can be linked to the moisture content for water based liquids. The second part of this paper covers penetration experiments on porous PVDF membranes. These measurements show that the technique is able to measure moisture profiles during fast capillary penetration and allows to extract moisture front positions. Those front positions follow a linear time behavior in PVDF membranes. Lastly the NMR-measurements showed similar results when compared to scanning absorptometry (ASA). </p

Dispersion force for materials relevant for micro and nanodevices fabrication

The dispersion (van der Waals and Casimir) force between two semi-spaces are calculated using the Lifshitz theory for different materials relevant for micro and nanodevices fabrication, namely, gold, silicon, gallium arsenide, diamond and two types of diamond-like carbon (DLC), silicon carbide, silicon nitride and silicon dioxide. The calculations were performed using recent experimental optical data available in the literature, usually ranging from the far infrared up to the extreme ultraviolet bands of the electromagnetic spectrum. The results are presented in the form of a correction factor to the Casimir force predicted between perfect conductors, for the separation between the semi-spaces varying from 1 nanometre up to 1 micrometre. The relative importance of the contributions to the dispersion force of the optical properties in different spectral ranges is analyzed. The role of the temperature for semiconductors and insulators is also addressed. The results are meant to be useful for the estimation of the impact of the Casimir and van der Waals forces on the operational parameters of micro and nanodevices

Impacts of Climate Change on SOC Dynamic and Crop Yield of Italian Rainfed Wheat-Maize Cropping Systems Managed with Conventional or Conservation Tillage Practices

There is still uncertainty on the ability of conservation tillage (i.e., reduced- RT and no till - NT) in contributing to the resilience of cropping systems to climate change pressures (Powlson et al 2016). RT or NT can improve soil physical and biological proprieties thus increasing water holding capacity and fertility, stabilizing soil structure and enhancing soil biodiversity and functions. They are also frequently proposed as mitigation practices as they can contribute to increase soil organic carbon (SOC) compared to conventional moldboard ploughing practices (Gonzalez-Sanchezet al., 2012). However, SOC increase occurs mostly in the upper soil layer but not always in the deeper profile (Haddaway et al., 2016) where SOC measurements are less frequently measured. In this study, we used data obtained from long term field experiments(LTE) coupled with three crop simulation models in order to assess the long-term effects of different tillage management practices on crop yield and on changes in SOC stocks in both superficial (0-20cm) and deeper layers (20-50cm) in Mediterranean rainfed cereal cropping systems at current and future climate scenarios

On the early evolution of Local Group dwarf galaxy types:Star formation and supernova feedback

According to star formation histories (SFHs), Local Group dwarf galaxies can be broadly classified in two types: those forming most of their stars before $z=2$ (${\it fast}$) and those with more extended SFHs (${\it slow}$). The most precise SFHs are usually derived from deep but not very spatially extended photometric data; this might alter the ratio of old to young stars when age gradients are present. Here we correct for this effect and derive the mass formed in stars by $z=2$ for a sample of 16 Local Group dwarf galaxies. We explore early differences between ${\it fast}$ and ${\it slow}$ dwarfs, and evaluate the impact of internal feedback by supernovae (SN) on the baryonic and dark matter (DM) component of the dwarfs. ${\it Fast}$ dwarfs assembled more stellar mass at early times and have larger amounts of DM within the half-light radius than ${\it slow}$ dwarfs. By imposing that ${\it slow}$ dwarfs cannot have lost their gas by $z=2$, we constrain the maximum coupling efficiency of SN feedback to the gas and to the DM to be $\sim$10%. We find that internal feedback alone appears insufficient to quench the SFH of ${\it fast}$ dwarfs by gas deprivation, in particular for the fainter systems. Nonetheless, SN feedback can core the DM halo density profiles relatively easily, producing cores of the sizes of the half-light radius in ${\it fast}$ dwarfs by $z=2$ with very low efficiencies. Amongst the "classical" Milky Way satellites, we predict that the smallest cores should be found in Draco and Ursa Minor, while Sculptor and Fornax should host the largest ones.Comment: 15 pages, 3 figures, 2 tables. Accepted for publication in MNRA

Increasing resolution of climate assessment and projection of temperature and precipitation in an alpine area

In mountain regions, important differences in the time trends of climate series can be detected even within relatively small areas, leading to uncertainty when assessing climate change. The paper deals with a structured algorithm for high-resolution downscaling of climate characterisation in a region (precipitation and temperature), leading to a twofold application: increasing spatial resolution of past climate definition for the area and attaining high-resolution downscaling for climate projections. In the first stage, multi-variate analysis (‘partial least squares’ regression) was applied to a number of time series (10) in order to obtain climate averages for a larger number of sites. Predictions made with single-site values (such as seasonal means) can in some cases be improved by applying ‘random perturbation’ of the value and averaging single predictions in the ensemble. This analysis laid the foundation for implementing the same technique to the output of statistical downscaling of multi-model climate projections. Climate shift in the study area (Trentino), located in the north-eastern Italian Alps, was simulated for two 30-year time windows: 2021–2050 and 2071–2099. Progressive warming is predicted, being stronger in the summer, along with a mixed, seasonally differentiated trend for precipitatio

Eco-city indicators: governance challenges

According to the most recent (2011) global census of eco-city initiatives, there are currently 178 eco-city initiatives under development, representing a significant mainstreaming of urban sustainability in the last decade. As the number of eco-city initiatives grows, so the question of how to define eco-city indicators and establish standards becomes more pressing. While there are many sustainability standards and certification schemes available for use at building level (e.g. LEED, BREEAM), similar sustainability assessment and endorsement frameworks for the urban level have only recently begun to emerge. This article surveys the current situation by: (i) proposing a conceptual model of urban sustainability indicators from a governance perspective; (ii) presenting the findings of a comparative analysis of the use of urban sustainability indicators in nine eco-city initiatives; and (iii) outlining key challenges for the future development of international urban sustainability standards. It argues that the current situation is marked by a considerable diversity of practice and governance functions, and an ongoing tension between place-specificity and universal applicability as goals of urban sustainability

High-speed laser speckle imaging to unravel picoliter drop-on-demand to substrate interaction

Understanding phenomena such as evaporation and imbibition of picoliter droplets into porous substrates is crucial in printing industry to achieve a higher printing quality and print speed. After printing, the residual pigment must remain fixed at the desired location on a substrate and be of a desired volume to yield a high resolution and vibrantly printed page that has become the expectation of modern printing technology. Current research entails not only chemical composition of the ink but also how this links to the dynamics and interactions that occur between the ink and the substrate at every stage of the printed spot formation, including evaporation, wetting, and imbibition. In this paper, we present an instrument that can print on-demand picoliter volume droplets of ink onto substrates and then immediately record on evolution of the resulting dynamics when these two materials interact. This high-speed laser speckle imaging (HS-LSI) technique has been developed to monitor nanometer displacement of the drying and imbibing ink droplet at a high frame rate, up to 20000 Hz, given the short timescales of these interactions. We present the design of the instrument, discuss the related challenges and the theory underlying the LSI technique, specifically how photons non-evasively probe opaque objects in a multiple scattering regime, and show how this technique can unravel the dynamics of drying and imbibition. We will finish giving a validation on the instrument and an example of its usage