The potential for biochar and hydrochar to adsorb phosphate and ammonium is important for understanding the influence of these materials when added to soils, compost or other high nutrient containing ...environments. The influence of physicochemical properties such as mineral content, surface functionality, pH and cation exchange capacity has been investigated for a range of biochars and hydrochars produced from waste-derived biomass feedstocks. Hydrochars produced from hydrothermal carbonisation at 250 °C have been compared to low and high temperature pyrolysis chars produced at 400–450 °C and 600–650 °C respectively for oak wood, presscake from anaerobic digestate (AD), treated municipal waste and greenhouse waste. In spite of differences in char physicochemical properties and processing conditions, PO4–P and NH4–N sorption capacities ranged from about 0 to 30 mg g−1 and 105.8–146.4 mg g−1 respectively. Chars with high surface areas did not possess better ammonium adsorption capacities than low surface area chars, which suggests that surface area is not the most important factor influencing char ammonium adsorption capacity, while char calcium and magnesium contents may influence phosphate adsorption. Desorption experiments only released a small fraction of adsorbed ammonium or phosphate (<5 mg g−1 and a maximum of 8.5 mg g−1 respectively).
•Biochars and hydrochars possess similar sorption capacities.•Physisorption is not the dominant mechanism for NH4-N uptake.•PO4-P uptake is best described by pseudo-second order kinetics.
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The performance of the upgraded solid deuterium ultracold neutron source at the pulsed reactor TRIGA Mainz is described. The current configuration stage comprises the installation of a He liquefier ...to run UCN experiments over long-term periods, the use of stainless steel neutron guides with improved transmission as well as sputter-coated non-magnetic
58
NiMo alloy at the inside walls of the thermal bridge and the converter cup. The UCN yield was measured in a “standard” UCN storage bottle (stainless steel) with a volume of 32 litres outside the biological shield at the experimental area yielding UCN densities of 8.5/cm
3
; an increase by a factor of 3.5 compared to the former setup. The measured UCN storage curve is in good agreement with the predictions from a Monte Carlo simulation developed to model the source. The growth and formation of the solid deuterium converter during freeze-out are affected by the ortho/para ratio of the H
2
premoderator.
1,8-Naphthalenediol, 5, and its 4-methoxy derivative, 6, were found to be potent H-atom transfer (HAT) compounds on the basis of their rate constants for H-atom transfer to the ...2,2-di(4-t-octylphenyl)-1-picrylhydrazyl radical (DOPPH•), k ArOH/DOPPH • , or as antioxidants during inhibited styrene autoxidation, k ArOH/ROO • , initiated with AIBN. The rate constants showed that 5 and 6 are more active HAT compounds than the ortho-diols, catechol, 1, 2,3-naphthalenediol, 2, and 3,5-di-tert-butylcatechol, 3. Compound 6 has almost twice the antioxidant activity, k ArOH/ROO • = 6.0 × 106 M-1 s-1, of that of the vitamin E model compound, 2,2,5,7,8-pentamethyl-6-chromanol, 4. Calculations of the O−H bond dissociation enthalpies compared to those of phenols, (ΔBDEs), of 1 − 6 predict a HAT order of reactivity of 2 < 1 < 3 ≈ 4 < 5 < 6 in general agreement with kinetic results. Calculations on the diols show that intramolecular H-bonding stabilizes the radicals formed on H-atom transfer more than it does the parent diols, and this effect contributes to the increased HAT activity of 5 and 6 compared to the activities of the catechols. For example, the increased stabilization due to the intramolecular H-bond of 5 radical over 5 parent of 8.6 kcal/mol was about double that of 2 radical over 2 parent of 4.6 kcal/mol. Linear free energy plots of log k ArOH/DOPPH • and log k ArOH/ROO • versus ΔBDEs for compounds 1−6 along with available literature values for nonsterically hindered monophenols placed the compounds on common scales. The derived Evans−Polanyi constants from the plots for the two reactions, αDOPPH • = 0.48 > αROO • = 0.32, gave the expected order, since the ROO• reaction is more exothermic than the DOPPH• reaction. Compound 6 is sufficiently reactive to react directly with oxygen, and it lies off the log k ArOH/ROO • versus ΔBDE plot.
Catechols and 1,8-naphthalene diols contain one “free” hydroxyl and one intramolecularly H-bonded hydroxyl group. The “free” hydroxyls are strong hydrogen-bond donors (HBDs) with α2 H values (Abraham ...et al. J. Chem. Soc., Perkin Trans. 2 1989, 699) ranging from 0.685 to 0.775, indicating that these compounds have similar HBD properties to those of strongly acidic phenols such as 4-chlorophenol (α2 H = 0.670) and 3, 5-dichlorophenol (α2 H = 0.774). Kinetic effects on H-atom abstractions from the diols in HB acceptor (HBA) solvents can be quantitatively accounted for over at least 50% of the available range of solvent HBA activities (as measured by their β2 H values; see Abraham et al. J. Chem. Soc. Perkin Trans. 2 1990, 521) on the basis of a single reactive OH group, the “free” OH. This free OH group is an outstanding H-atom donor in poor HBA solvents; e.g., in hexane rate constants for reaction with the DPPH• radical are 2.1 × 104 M-1 s-1 for 3,5-di-tert-butyl catechol and 2 × 106 M-1 s-1 for 4-methoxy-1,8-naphthalene diol, but only 7.4 × 103 M-1 s-1 for α-tocopherol (vitamin E). The diols are much more reactive than simple phenols because the O−H bond dissociation enthalpy of the “free” OH group is weakened by 5−9 kcal/mol by the intramolecular H-bond. The IR spectra of all the diols in CCl4 show two fairly sharp O−H stretching bands of roughly equal intensity separated by 42−138 cm-1. Addition of a low concentration of DMSO, a strong HBA, causes the band due to the intramolecularly H-bonded OH group to decrease in intensity to roughly half the extent that the “free” OH band loses intensity. The latter forms an intermolecular H-bond with the DMSO, the former does not. What has been overlooked in earlier work is that as the DMSO concentration is increased the band due to the intramolecularly H-bonded OH group first broadens and then evolves into a new, lower frequency (by 19−92 cm-1) band. The magnitude of the shift in the frequency of the intramolecular OH band caused by H-bonding of HBAs to the “free” OH group, Δν, increases linearly as the HBA activity of the additive increases, e.g., for 3,5-di-tert-butylcatechol, Δν/cm-1 = 33.8 β2 H (R 2 = 0.986). This may provide a new and simple method for determining β2 H values.
To study the mechanisms that activate expression of the atrial natriuretic factor (ANF) gene during pressure-induced hypertrophy, we have developed and characterized an in vivo murine model of ...myocardial cell hypertrophy. We employed microsurgical techniques to produce a stable 35- to 45-mmHg pressure gradient across the thoracic aorta of the mouse that is associated with rapid and transient expression of an immediate-early gene program (c-fos/c-jun/junB/Egr-1/nur-77), an increase in heart weight/body weight ratio, and up-regulation of the endogenous ANF gene. These responses that are identical to those in cultured cell and other in vivo models of hypertrophy. To determine whether tissue-specific and inducible expression of the ANF gene can be segregated, we used a transgenic mouse line in which 500 base pairs of the human ANF promoter region directs atrial-specific expression of the simian virus 40 large tumor antigen (T antigen), with no detectable expression in the ventricles. Thoracic aortic banding of these mice led to a 20-fold increase in the endogenous ANF mRNA in the ventricle but no detectable expression of the T-antigen marker gene. This result provides evidence that atrial-specific and inducible expression of the ANF gene can be segregated, suggesting that a distinct set of regulatory cis sequences may mediate the up-regulation of the ANF gene during in vivo pressure overload hypertrophy. This murine model demonstrates the utility of microsurgical techniques to study in vivo cardiac physiology in transgenic mice and should allow the application of genetic approaches to identify the mechanisms that activate ventricular expression of the ANF gene during in vivo hypertrophy.
This paper presents a new resonant dual active bridge (DAB) topology, which uses a tuned inductor-capacitor-inductor (LCL) network. In comparison to conventional DAB topologies, the proposed topology ...significantly reduces the bridge currents, lowering both conduction and switching losses and the VA rating associated with the bridges. The performance of the DAB is investigated using a mathematical model under various operating conditions. Experimental results of a 2.5-kW prototype, which has an efficiency of 96% at rated power, are also presented with discussions to demonstrate the improved performance of the tuned LCL DAB topology. Results clearly indicate that the proposed DAB topology offers higher efficiency over a wide range of both input voltage and load in comparison to conventional DAB topologies.
A Dual-Active Bridge Topology With a Tuned CLC Network Twiname, Ross P.; Thrimawithana, Duleepa J.; Madawala, Udaya K. ...
IEEE transactions on power electronics,
2015-Dec., 2015-12-00, 20151201, Letnik:
30, Številka:
12
Journal Article
Recenzirano
This paper proposes a resonant dual-active bridge (DAB) converter, which uses a tuned capacitor-inductor-capacitor network. In comparison to the conventional DABs, the proposed topology significantly ...reduces the bridge currents, lowering both conduction and switching losses and improving the bridge power factors. A mathematical model, which predicts the behavior of the proposed system, is presented to show that both the magnitude and direction of the power flow can be controlled through either relative phase angle or pulse width modulation of voltages produced by the bridges. The viability of the proposed concept is verified through simulation. Experimental results of a 4- kW prototype converter, which has an efficiency of 95% at rated power, are also presented with discussions to demonstrate the improved performance of this topology.
The effects of proton irradiation at various energies are reported for AlGaN/GaN high electron mobility transistors (HEMTs). The devices exhibit little degradation when irradiated with 15-, 40-, and ...105-MeV protons at fluences up to 10/sup 13/ cm/sup -2/, and the damage completely recovers after annealing at room temperature. For 1.8-MeV proton irradiation, the drain saturation current decreases 10.6% and the maximum transconductance decreases 6.1% at a fluence of 10/sup 12/ cm/sup -2/. The greater degradation measured at the lowest proton energy considered here is caused by the much larger nonionizing energy loss of the 1.8-MeV protons.
The design of the n2EDM experiment Ayres, N. J.; Ban, G.; Bienstman, L. ...
The European physical journal. C, Particles and fields,
2021/6, Letnik:
81, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a ...high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.
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