Fast Build-up Research Articles

Terahertz pulse emission from photoexcited bulk crystals of transition metal dichalcogenides

Multilayer MoS2, MoSe2, and WSe2 crystals were excited with femtosecond optical pulses of various wavelengths. The emitted terahertz (THz) radiation pulses were found to be the most intense at photon energies coinciding with the direct energy gap at the K points of the Brillouin zone of corresponding materials. It was shown that the transition metal dichalcogenides of different dopant type emit THz pulses of opposite polarity, suggesting that the surface field plays a role in THz emission. Nevertheless, the optical pump–THz probe experiments contradicted THz emission observations, demonstrating a decrease in photoconductivity at higher energy quanta. The proposed THz pulse generation mechanism, therefore, assumes the accumulation of excitonic electric dipoles during optical pulse absorption and a fast build-up of the internal electric field inside the samples. This assumption was supported by double optical pulse investigations.

Impact of cow manure application as soil amendment on essential oil composition and metal contents in fennel (Foeniculum vulgare Mill)

The natural resources and agriculture ecosystem are adversely damaged due to the fast buildup of toxic pollutants such as radionuclide, organic contaminants and heavy metals emitted from industries and other anthropogenic activities. A polyhouse experiment was conducted to assess the capability of fennel (Foeniculum vulgare) to remediate a metal contaminated soil, collected from Moradabad (a hub of electroplating industries), by the application of different levels of cow manure. Metal analysis of root and aerial parts was performed using AAS and essential oil composition by GC and GC/MS. The results revealed that the use of cow manure at 52 t ha-1 gave highest plant growth and oil yield. Limonene, trans-anethole and dillapiole were the major constituents among all the amendments. The highest content of trans-anethole (56.05%) was noticed at 52 t ha-1. The addition of cow manure reduced Zn, Ni, Cu and Cr concentration in plant tissues. Maximum reduction was found at 104 t ha-1. Cr showed highest BCF at 0 t ha-1, while Cu showed lowest BCF at 104 t ha-1. Therefore, cow manure use in the metal contaminated soils had favourable impact on the growth characters and essential oil composition of fennel.

A functional genomics approach to dissect spotted alfalfa aphid resistance in Medicago truncatula

Aphids are virus-spreading insect pests affecting crops worldwide and their fast population build-up and insecticide resistance make them problematic to control. Here, we aim to understand the molecular basis of spotted alfalfa aphid (SAA) or Therioaphis trifolii f. maculata resistance in Medicago truncatula, a model organism for legume species. We compared susceptible and resistant near isogenic Medicago lines upon SAA feeding via transcriptome sequencing. Expression of genes involved in defense and stress responses, protein kinase activity and DNA binding were enriched in the resistant line. Potentially underlying some of these changes in gene expression was the finding that members of the MYB, NAC, AP2 domain and ERF transcription factor gene families were differentially expressed in the resistant versus susceptible lines. A TILLING population created in the resistant cultivar was screened using exome capture sequencing and served as a reverse genetics tool to functionally characterise genes involved in the aphid resistance response. This screening revealed three transcription factors (a NAC, AP2 domain and ERF) as important regulators in the defence response, as a premature stop-codon in the resistant background led to a delay in aphid mortality and enhanced plant susceptibility. This combined functional genomics approach will facilitate the future development of pest resistant crops by uncovering candidate target genes that can convey enhanced aphid resistance.

Landscape Connectivity Limits the Predicted Impact of Fungal Pathogen Invasion.

Infectious diseases are major drivers of biodiversity loss. The risk of fungal diseases to the survival of threatened animals in nature is determined by a complex interplay between host, pathogen and environment. We here predict the risk of invasion of populations of threatened Mediterranean salamanders of the genus Lyciasalamandra by the pathogenic chytrid fungus Batrachochytrium salamandrivorans by combining field sampling and lab trials. In 494 samples across all seven species of Lyciasalamandra, B. salamandrivorans was found to be absent. Single exposure to a low (1000) number of fungal zoospores resulted in fast buildup of lethal infections in three L. helverseni. Thermal preference of the salamanders was well within the thermal envelope of the pathogen and body temperatures never exceeded the fungus’ thermal critical maximum, limiting the salamanders’ defense opportunities. The relatively low thermal host preference largely invalidates macroclimatic based habitat suitability predictions and, combined with current pathogen absence and high host densities, suggests a high probability of local salamander population declines upon invasion by B. salamandrivorans. However, the unfavorable landscape that shaped intraspecific host genetic diversity, lack of known alternative hosts and rapid host mortality after infection present barriers to further, natural pathogen dispersal between populations and thus species extinction. The risk of anthropogenic spread stresses the importance of biosecurity in amphibian habitats.

Structural build-up, hydration and strength development of cement-based materials with accelerators

Fast structural build-up and strength development of fresh/hardened cement-based materials are always desired in many scenarios, where accelerators are often used. In this paper, the hydration, structural build-up and strength development of cement pates with different accelerators were investigated. The growth of static yield stress was used to characterize the structural build-up of fresh cement paste with 1% nano silica. Calorimetric curves, zeta potential and conductivity of pastes and strength development of mortars were also measured. Results showed that accelerators promote the reaction of C3S or C3A at different stages and in different mechanisms. Mechanical efficiency of C-S-H determined by growth of elastic modulus or yield stress over cumulated hydration heat may give wrong ranking on the efficiency of C-S-H. Apart from formation of C-S-H gel, structural build-up may originate from other sources.

Approaches to multi-scale analyses of mechanically and thermally-driven migration of fluid inclusions in salt rocks

Fluid inclusions are found within mineral crystals or along grain boundaries in many sedimentary rocks, notably in evaporite formations, and can migrate along a thermal or hydro-mechanical gradient. Shale and salt rocks have been considered potential host rocks for radioactive waste disposal, due to their low permeability. Previously stagnant inclusions may become mobilised by a perturbation of the in situ state by a geotechnical installation or the emplacement of heat-generating waste. The migration of fluid inclusions can thus have important impacts on the long-term performance of a geologic repository for high-level radioactive waste disposal. As a part of the international research project DECOVALEX-2019, two aspects of fluid inclusion migration in rock salt are currently investigated under different boundary conditions: a) altered hydro-mechanical conditions as a consequence of tunnel excavation or borehole drilling and b) coupled thermo-hydro-mechanical-chemical conditions during the heating period of the post-closure phase of a repository.To obtain a mechanistic understanding of underlying physical processes for fluid inclusion migration, a multi-scale modelling strategy has been developed. Microscale hydraulic and time-dependent mechanical conditions related to the creep behaviour of rock salt are constrained by considering the macroscale stress evolution of an underground excavation. An analysis using a coupled two-phase flow and elasto-plastic model with a consideration of permeability variation indicates that a pathway dilation along the halite grain boundary may increase the permeability by two orders of magnitude. The calculated high flow velocity may explain the fast pressure build-up observed in the field. In addition, a mathematical model for the migration and morphological evolution of a single fluid inclusion under a thermal gradient has been formulated. A first-order analysis of the model leads to a simple mathematical expression that is able to explain the key observations of thermally driven inclusion migration in salt. Finally, numerical methods such as a phase field method for solving a moving boundary problem of fluid inclusion migration have also been explored.

Initiating Large-Scale Storage in the Netherlands Offshore

The Netherlands government has a stated objective to develop CCS for industrial sources and waste incineration on a large scale, aiming to achieve a capture and storage rate of 7 Mpta by 2030. Generating about 15% of the total national greenhouse gas emissions, the industrial cluster in the Port of Rotterdam aims to capture and store up to 5 Mtpa by the mid 2020’s, to realise part of the government’s objective. This target requires a fast and efficient build-up of CO2 transport and storage infrastructure that connects the main Port of Rotterdam industrial region with offshore storage capacity. This paper presents a timeline of the activities required to realise the CCS ambitions for, initially, the Rotterdam cluster and, later, other industrial regions. The paper highlights some key offshore transport and storage requirements and discusses the options for offshore transport and storage network development.

Variable-Gain Control for Respiratory Systems.

In this paper, we introduce a variable-gain control strategy for mechanical ventilators in the respiratory systems. Respiratory systems assist the patients who have difficulty breathing on their own. For the comfort of the patient, fast pressure buildup (and release) and a stable flow response are desired. However, linear controllers typically need to balance between these conflicting objectives. In order to balance this tradeoff in a more desirable manner, a variable-gain controller is proposed, which switches the controller gain based on the magnitude of the patient flow. The effectiveness of the control strategy is demonstrated in experiments on different test lungs.

The increase of soil organic carbon as proposed by the “4/1000 initiative” is strongly limited by the status of soil development - A case study along a substrate age gradient in Central Europe

During COP 21 in Paris 2015, several states and organizations agreed on the “4/1000” initiative for food security and climate. This initiative aims to increase world's soil organic carbon (SOC) stocks by 4‰ annually. The influence of soil development status on SOC dynamics is very important but usually not considered in studies. We analyse SOC accumulation under forest, grassland and cropping systems along a soil age gradient (10–17,000years) to show the influence of soil development status on SOC increase.SOC stocks (0–40cm) and accumulation rates along a chronosequence in alluvial soils of the Danube River in the Marchfeld (eastern Austria) were analysed. The analysed Fluvisols and Chernozems have been used as forest, grassland and cropland for decades or hundreds of years.The results showed that there is a fast build-up of OC stocks (0–40cm) in young soils with accumulation of ~1.3tha−1a−1 OC in the first 100years and ~0.5tha−1a−1 OC between 100 and 350years almost independent of land use. Chernozems with a sediment deposition age older than 5.000years have an accumulation rate<0.01tOCha−1a−1 (0–40cm).Radiocarbon dating showed that the topsoil (0–10cm) consists mainly of “>modern” and “modern” carbon indicating a fast carbon cycling. Carbon in subsoil is less exposed to decomposition and OC can be stored at long-time scales in the subsoil (14C age of 3670±35 BP).In view of the ‘4/1000’ initiative, soils with constant carbon input (forest & grassland) fulfil the intended 4‰ growth rate of SOC stocks only in the first 60years of soil development. We proclaim that under the present climate in Central Europe, the increase of SOC stocks in soil is strongly affected by the state of soil development.

Symmetry Breaking and Strong Persistent Plasma Currents via Resonant Destabilization of Atoms.

The ionization rate of an atom in a strong optical field can be resonantly enhanced by the presence of long-living atomic levels (so-called Freeman resonances). This process is most prominent in the multiphoton ionization regime, meaning that the ionization event takes many optical cycles. Nevertheless, here, we show that these resonances can lead to rapid subcycle-scale plasma buildup at the resonant values of the intensity in the pump pulse. The fast buildup can break the cycle-to-cycle symmetry of the ionization process, resulting in the generation of persistent macroscopic plasma currents which remain after the end of the pulse. This, in turn, gives rise to a broadband radiation of unusual spectral structure, forming a comb from terahertz to visible. This radiation contains fingerprints of the attosecond electron dynamics in Rydberg states during ionization.

Ultrasonic Electric Scalpels Based on a Sliding-Mode Controller With an Auxiliary PLL Frequency Discriminator.

The first monolithic state-of-the-art controller was proposed and implemented for an electric scalpel system. A piezoelectric transducer (PT) is driven in ultrasonic resonant frequency to generate electromechanical power for thermal sealing and cold dissection operations. The band-pass filter based oscillator was developed to automatically track the PT's optimal longitudinal resonance. However, under heavy loading conditions, the PT will lock to other unwanted transverse resonant modes and deliver no usable power to the surgical tip. To prevent this abnormal operation, a phase-locked loop based frequency discriminator with intervention and release logic was developed to ensure that the PT always operates at the proper frequency of 55.5kHz. Another crucial challenge is that the changing of loading conditions induces a motional current sensing mismatch and a pole-zero pair, consequently causing instability and poor response time. Therefore, a sliding mode control method with reduced-order sensing was proposed to handle the extreme load changes and provide a fast power build-up time of 9.2 ms, which is 8% faster than previously reported designs and 49% faster than the best commercial product. Sealing and dissection surgical operations are realized with 17.5 W maximum power.

REST-UV ABSORPTION LINES AS METALLICITY ESTIMATOR: THE METAL CONTENT OF STAR-FORMING GALAXIES AT z ∼ 5

ABSTRACT We measure a relation between the depth of four prominent rest-UV absorption complexes and metallicity for local galaxies and verify it up to . We then apply this relation to a sample of 224 galaxies at ( ) in the Cosmic Evolution Survey (COSMOS), for which unique UV spectra from the Deep Imaging Multi-object Spectrograph (DEIMOS) and accurate stellar masses from the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) are available. The average galaxy population at and is characterized by 0.3–0.4 dex (in units of ) lower metallicities than at z ∼ 2, but comparable to . We find galaxies with weak or no Lyα emission to have metallicities comparable to z ∼ 2 galaxies and therefore may represent an evolved subpopulation of galaxies. We find a correlation between metallicity and dust in good agreement with local galaxies and an inverse trend between metallicity and star-formation rate consistent with observations at z ∼ 2. The relation between stellar mass and metallicity (MZ relation) is similar to , but there are indications of it being slightly shallower, in particular for the young, Lyα-emitting galaxies. We show that, within a “bathtub” approach, a shallower MZ relation is expected in the case of a fast (exponential) build-up of stellar mass with an e-folding time of 100–200 Myr. Because of this fast evolution, the process of dust production and metal enrichment as a function of mass could be more stochastic in the first billion years of galaxy formation compared to later times.

A COHERENT STUDY OF EMISSION LINES FROM BROADBAND PHOTOMETRY: SPECIFIC STAR FORMATION RATES AND [O iii]/Hβ RATIO AT 3 &lt; z &lt; 6

ABSTRACT We measure the Hα and [O iii] emission line properties as well as specific star formation rates (sSFRs) of spectroscopically confirmed 3 &lt; z &lt; 6 galaxies in COSMOS from their observed colors versus redshift evolution. Our model describes consistently the ensemble of galaxies including intrinsic properties (age, metallicity, star formation history), dust attenuation, and optical emission lines. We forward-model the measured Hα equivalent widths (EW) to obtain the sSFR out to z ∼ 6 without stellar mass fitting. We find a strongly increasing rest-frame Hα EW that is flattening off above z ∼ 2.5 with average EWs of 300–600 Å at z ∼ 6. The sSFR is increasing proportionally to ( 1 + z ) 2.4 at z &lt; 2.2 and to ( 1 + z ) 1.5 at higher redshifts, indicative of a fast build-up of mass in high-z galaxies within e-folding times of 100–200 Myr at z ∼ 6. The redshift evolution at z &gt; 3 cannot be fully explained in a picture of growth driven by cold accretion. We find a progressively increasing [O iii]λ5007/Hβ ratio out to z ∼ 6, consistent with the ratios in local galaxies selected by increasing Hα EW (i.e., sSFR). This demonstrates the potential of using “local high-z analogs” to investigate the spectroscopic properties and relations of galaxies in the re-ionization epoch.

How much does weather control fire size and intensity in the Mediterranean region?

Abstract. This study investigates the synoptic conditions favorable to wildfires in the Mediterranean region, in terms of fire intensity and burnt area. As reported in the literature, Mediterranean large wildfires are associated with a blocking situation. However, this study shows the existence of two types of wildfires controlled by the blocking high intensity: (1) fast build-up of a weak blocking produces intense wildfires associated with strong winds which allow propagation over long distances; (2) longer build-up of strong blocking situation produces less intense wildfires associated with weaker winds which also propagate over long distances. Another major step forward of this study in the understanding of the drivers of those wildfires is the evidence of a perfect match between the period of wildfire activity and the persistence of the favorable synoptic conditions: the wildfire activity starts at the onset of the blocking situation and ends with the transition to a less favorable synoptic weather pattern. Such strong control of the wildfire activity by the concomitant weather is a very promising result regarding fire risk management, especially considering the accidental nature of the Mediterranean wildfires.

Binding interaction and gelation in aqueous mixtures of poly(N-isopropylacrylamide) and hectorite clay.

The binding interaction between poly(N-isopropylacrylamide) (PNIPAm) chains and hectorite clay platelets was directly detected by quartz crystal microbalance with dissipation (QCM-D) to explore the cross-linking mechanism in the strong nanocomposite hydrogel (NC gel), which is in situ polymerized with NIPAm in the clay suspension. PNIPAm chains were allowed to be adsorbed on the gold surface of the QCM electrode. A large frequency shift Δf in the QCM as introducing the clay indicated that a large amount of clay platelets were adsorbed on the deposited PNIPAm layer. The relationship between the dissipation shift ΔD and Δf revealed that the adsorption included two steps of fast initial buildup and following densification of the clay platelets. In dilute aqueous mixtures, the PNIPAm chain and clay formed aggregates as observed from the hydrodynamic diameter. A gelation state diagram was established for concentrated aqueous PNIPAm-clay mixtures. The Raman spectrum pointed out the conformation change of the PNIPAm chains in aqueous solutions when the clay was added, which would be caused by the adsorption of PNIPAm chains to the clay platelets.

Effects on inorganic nitrogen compounds release of contaminated sediment treatment with in situ calcium nitrate injection.

Notable releases of nitrate, nitrite, and ammonia are often observed in contaminated sediment treatment works implementing in situ calcium nitrate injection. In order to provide extended information for making best decision of employing this in situ sediment remediation technology, in this study the releases of nitrate, nitrite, and ammonia from the sediment after the calcium nitrate addition operation was investigated in column setups designed to simulate the scenarios of a stagnant water (e.g., a pound or small lake) and a tidal-influenced water (e.g., a river mouth), respectively. Comparison with published aquatic toxicity data or authorized criteria was conducted to assess if there is any toxic effect that might be induced. Along with the vigorous N2 emission due to the denitrification reactions which occurred in the treated sediment, external loaded nitrate, intermediately produced nitrite, and indigenous ammonia in the sediment showed being mobilized and released out. Their promoted release and fast buildup in the overlying water to an excessive level probably cause toxic effects to sensitive freshwater living species. Among them, the potential ecological risk induced by the promoted sediment ammonia release is the greatest, and cautions shall be raised for applying the calcium nitrate injection in ammonia-rich sediments. The caused impacts shall be less violent in a tidal-influenced water body, and comparatively, the continuous and fast accumulation of the released inorganic nitrogen compounds in a stagnant water body might impose severer influences to the ecosystem until being further transferred to less harmful forms.

Thermal photon v3 at LHC from fluctuating initial conditions

We calculate the triangular flow parameter $v_3$ of thermal photons for 0--40\% central collisions of Pb nuclei at LHC using an event-by-event hydrodynamic model with fluctuating initial conditions. Thermal photon $v_3$ with respect to the the participant plane angle is found to be positive and significant compared to the elliptic flow parameter $v_2$ of thermal photons. In addition, photon $v_3$ as a function of $p_T$ shows similar qualitative nature to photon $v_2$ in the region $1< p_T <6$ GeV/$c$. We argue that while $v_3$ originates from $\epsilon_3$ deformations of the initial state density distribution, fast buildup of radial flow due to fluctuations is the main driving mechanism for the observed large value.

Influence of molecular hydrogen on acetylene pyrolysis: Experiment and modeling

The effect of molecular hydrogen on the formation of molecular carbonaceous species important for soot formation is studied through a combination of shock-tube experiments with high-repetition-rate time-of-flight mass spectrometry and detailed chemistry modeling. The experiment allows to simultaneously measure the concentration–time profiles for various species with a time resolution of 10μs. Concentration histories of reactants and polyacetylene intermediates (C2xH2, x=1–4) are measured during the pyrolysis of acetylene with and without H2 added to the gas mixture for a wide range of conditions. In the 1760–2565K temperature range, reasonable agreement between the experiment and the model predictions for C2H2, C4H2, C6H2, and C8H2 is achieved. H2 addition leads to the depletion of important building blocks for particle formation, namely of polyacetylenes due to an enhanced consumption of important radicals by H2, which are required for the fast build-up of carbonaceous material.

On-chip electrophoresis in supported lipid bilayer membranes achieved using low potentials.

A micro supported lipid bilayer (SLB) electrophoresis method was developed, which functions at low potentials and appreciable operating times. To this end, (hydroxymethyl)-ferrocene (FcCH2OH) was employed to provide an electrochemical reaction at the anode and cathode at low applied potential to avoid electrolysis of water. The addition of FcCH2OH did not alter the SLB characteristics or affect biomolecule function, and pH and temperature variations and bubble formation were eliminated. Applying potentials of 0.25–1.2 V during flow gave homogeneous electrical fields and a fast, reversible, and strong build-up of a charged dye-modified lipid in the direction of the oppositely charged electrode. Moreover, streptavidin mobility could be modulated. This method paves the way for further development of analytical devices.

Estimating CO2 Fluxes Along Leaky Wellbores

Summary Large-scale geological storage of carbon dioxide (CO2) is likely to bring CO2 plumes into contact with a large number of existing wellbores. The flux of CO2 along a leaking wellbore requires a model of fluid properties and of transport along the leakage pathway. Knowing the range of effective permeability of faulty cement is essential for estimating the risk of CO2 leakage. The central premise of this paper is that the leakage pathway in wells that exhibit sustained casing pressure (SCP) is analogous to the rate-limiting part of the leakage pathway in any wellbore that CO2 might encounter. Thus, field observations of SCP can be used to estimate transport properties of a CO2-leakage pathway. Uncertainty in the estimate can be reduced by accounting for constraints from well-construction geometry and from physical considerations. We then describe a simple CO2-leakage model. The model accounts for variation in CO2 properties along the leakage path and allows the path to terminate in an unconfined (constant-pressure) exit. The latter assumption provides a worst-case leakage flux. By use of pathway permeabilities consistent with observations in SCP wells, we obtain a range of CO2 fluxes for the cases of buoyancy-driven (post-injection) and pressure-driven (during injection) leakage. Assuming the frequency distribution is representative of SCP wells, we observe that in leakage pathways corresponding to the slow but nonnegligible buildup of casing pressure (several psi/D), the effective permeability of the leakage path is in the range of microdarcies to hundreds of microdarcies, and the corresponding CO2 fluxes are comparable with naturally occurring background fluxes observed at the ground surface. In pathways corresponding to intermediate and fast buildup rate of casing pressure (tens to hundreds of psi/D), the effective permeability is in the range of tenths to tens of millidarcies, and the CO2 fluxes are comparable with surface flux measurements at the Illinois basin and at the natural seep at Crystal Geyser (Utah). In pathways corresponding to very fast buildup rate (thousands of psi/D), the effective permeability is from tens to hundreds of millidarcies and the CO2 fluxes are up to three orders of magnitude higher than those measured at Crystal Geyser.