Search results for " nitrogen"

On the operation of silicon photomultipliers at temperatures of 1–4 kelvin

2016

Abstract SiPM operation at cryogenic temperatures fails for many common devices. A particular type from Zecotek with deep channels in the silicon substrate instead of quenching resistors was tested at liquid helium temperature. Two similar types were thoroughly characterized from room temperature down to liquid nitrogen temperature by illuminating them with low light levels. At cryogenic temperatures the SiPMs show an unchanged rise-time and a fast recovery time, practically no after-pulses, and exhibit no increased cross-talk probability. Charge collection spectra were measured to extract the pixel gain and its variation, both comparable to room temperature at the same over-voltage. The qu…

Investigation of a Ge nanoparticle film by means of electron stimulated photon emission spectroscopy

2014

Abstract Electron stimulated photon emission spectroscopy was used for the study of the electronic structure of Ge nanoparticles. A nanoparticle film was prepared by thermal deposition on a quartz substrate. Photon emission was stimulated by electron bombardment at energies of several hundred electron volts. Electron field emission from a W-tip was used at tip voltage U t  = 100–600 eV. A spectrometer in combination with a liquid nitrogen cooled charge-coupled device (CCD) camera was used for light detection. Light emission spectra were measured in the energy range 1.18–4.2 eV. They are characterized by features at ∼1.6 and ∼3.1 eV. A comparison with light emission spectra obtained with ano…

Glycine-functionalized copper(ii) hydroxide nanoparticles with high intrinsic superoxide dismutase activity

2017

Superoxide dismutases (SOD) are a group of enzymes that catalyze the dismutation of superoxide (O2−) radicals into molecular oxygen (O2) and H2O2 as a first line of defense against oxidative stress. Here, we show that glycine-functionalized copper(II) hydroxide nanoparticles (Gly-Cu(OH)2 NPs) are functional SOD mimics, whereas bulk Cu(OH)2 is insoluble in water and catalytically inactive. In contrast, Gly-Cu(OH)2 NPs form water-dispersible mesocrystals with a SOD-like activity that is larger than that of their natural CuZn enzyme counterpart. Based on this finding, we devised an application where Gly-Cu(OH)2 NPs were incorporated into cigarette filters. Cigarette smoke contains high concent…

Dataset of a globally relevant stock of soil nitrogen in the Yedoma permafrost domain

2022

This dataset merges nitrogen data from the Yedoma domain. It includes numerous fieldwork campaigns, which take place since 1998. In total 467 samples from the active layer (seasonally thawed layer), 175 samples from perennially frozen Holocene cover deposits, 479 samples from thermokarst deposits in drained thermokarst, 175 in-situ thawed, diagenetically (anaerobic microbial decomposition possible during unfrozen phase) altered Yedoma deposits (called Taberite), and 917 samples from frozen Yedoma deposits are included. Moreover it includes a NH4+ and NO3- quantification basing on of 658 samples, including 378 data points for NH4+ (active layer, 93; Holocene cover, 108; thermokarst sediment,…

Symbiotic N2 fixation activity in relation to C economy of Pisum sativum L. as a function of plant phenology

2003

The relationships between symbiotic nitrogen fixation (SNF) activity and C fluxes were investigated in pea plants (Pisum sativum L. cv. Baccara) using simultaneous 13 C and 15 N labelling. Analysis of the dynamics of labelled CO 2 efflux from the nodulated roots allowed the different components associated with SNF activity to be calculated, together with root and nodule synthetic and maintenance processes. The carbon costs for the synthesis of roots and nodules were similar and decreased with time. Carbon lost by turnover, associated with maintenance processes, decreased with time for nodules while it increased in the roots. Nodule turnover remained higher than root turnover until flowering…

Optimizing [13N]N2 radiochemistry for nitrogen-fixation in root nodules of legumes

2010

Here we explored the conditions for synthesizing [ 13 N]N 2 in a state that is suitable for the administration to plant root nodules enabling studies of nitrogen fixation. [ 13 N]N 2 was prepared batchwise, starting with [ 13 N]NO ― 3 from the 16 O(p,α) 13 N nuclear reaction on a liquid water target. [ 13 N]NO ― 3 was first reduced to [ 13 N]NH 3 using Devarda's alloy, and then the [ 13 N]NH 3 was oxidized to [ 13 N]N 2 by hypobromite using carrier-added NH 4 CI. The amounts of carrier NH 4 CI and hypobromite were varied to determine the effects these parameters had on the radiochemical yield, and on the radiotracer specific activity. As expected, increasing the amount of carrier NH 4 CI im…

Effects of yeast proteolytic activity on Oenococcus oeni and malolactic fermentation

2006

International audience; Alcoholic fermentation of synthetic must was performed using either Saccharomyces cerevisiae or a mutant Delta pep4, which is deleted for the proteinase A gene. Fermentation with the mutant Delta pep4 resulted in 61% lower levels of free amino acids, and in 62% lower peptide concentrations at the end of alcoholic fermentation than in the control. Qualitative differences in amino acid composition were observed. Changes observed in amino acids in peptides were mainly quantitative. After alcoholic fermentation each medium was inoculated with Oenococcus oeni. Malolactic fermentation in the medium with the Delta pep4 strain took 10 days longer than the control. This diffe…

THE EFFECT OF ROOTS CONFINEMENT ON THE RELATIVE GROWTH OF ROOTS AND CANOPY OF OPUNTIA FICUS-INDICA

Summary The influence of soil volume on roots and canopy growth performance of cactus pear (Opuntia ficus-indica) was studied at Palermo University. In November 2014, 1-year-old Opuntia ficusindica cladodes were planted in five different volumes of soil 50, 33, 18, 9 and 5 Liters. Three replicates (plants) per pot size were dug out at 6 and 12, 18 and 24 month intervals, thus in total, there were 5 x 3 x 4= 60 experimental plots. The resulting experimental design was a completely randomized design with combinations of two factors, soil volume and month of the sampling, with three replications. Roots of each plant were washed and visually divided into three groups depending on their diameter…

Spatial variability of ecophysiological performances and invasive potential of alien acacias (Acacia spp.) in Sicily and Lampedusa island (Pelagie Ar…

2012

Acacia spp. are among the most widespread and prominent invaders within Mediterranean-type ecosystems, where have already shown the capability to deeply change the characters and the functioning of invaded ecosystems (like in Portugal or S Africa: e.g. Holmes & Cowling, 1997; Hellmann et al., 2011). In Sicily, just in the last few years, two Australian Acacias, notably Acacia cylops A. Cunn. ex G. Don and A. saligna (Labill.) H.L.Wendl., started to regenerate abundantly within different areas (especially afforested sites). However their naturalization process has not been studied up to now.

Effect of Afforestation on Soil Carbon and Nitrogen Content on a Mediterranean Island (Lampedusa, Italy)

2015

During the 20th century, large surfaces in the Mediterranean countries were subject to afforestation activities, mostly affecting abandoned agricultural lands. Under semi-arid climate conditions, Pinus spp. were the most frequently used species for these activities. The effect of pine plantations on soil organic carbon (SOC) and nitrogen (N) content in Lampedusa Island (South Italy) was investigated. SOC and soil N content under pine plantations of different ages (14, 24 and 43 years since plantation) were compared with SOC and soil N content in garrigue communities, which were dominated by shrubs, subshrubs and perennial herbs. The results showed that SOC content is affected by plantation …