Search results for "Gradation"
showing 10 items of 1275 documents
The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink
2022
We assessed the potential of dead seagrass Posidonia oceanica matte to act as a biogeochemical sink and provide a coherent archive of environmental change in a degraded area of the Mediterranean Sea (Augusta Bay, Italy). Change in sediment properties (dry bulk density, grain size), concentration of elements (Corg, Cinorg, N, Hg) and stable isotope ratios (δ13C, δ 15N) with sediment depth were measured in dead P. oceanica matte and unvegetated (bare) sediments in the polluted area, and an adjacent P. oceanica meadow. Principal Component Analysis (PCA) revealed a clear clustering by habitat, which explained 72% of variability in our samples and was driven mainly by the accumulation of N and H…
ZigBee networks performance under WLAN 802.11b/g interference
2009
ZigBee is a standard protocol suite for low rate wireless personal area networks (LR-WPANs) and has been widely utilized in various fields. Since both ZigBee and WLAN (802.11b/g) operate in the 2.4GHz unlicensed industrial scientific medical (ISM) frequency band, mutual interference is likely to exist and cause signal degradation. In this paper, an interference analysis model is suggested to obtain an estimate of Packet Error Rate (PER) of a ZigBee network. A ZigBee evaluation kit, AVR RZ200, was implemented for measurement of Packet Loss Ratio (PLR). The measured PLR matches the estimated PER, with varied distances and different center frequency offsets of different channels.
The effect of Shallow Tillage on soil erosion in a semi-arid vineyard
2019
Soil erosion has been considered a threat for semi-arid lands due to the removal of solid materials by water and wind. Although water erosion is currently considered the most important process of soil degradation, a growing interest has been drawn to the impact of soil tillage. Although numerous studies on tillage erosion have been carried out on arable land using a moldboard plow, a chisel, and a tandem disc for different crops, there are no studies on the effect of shallow tillage on soil redistribution in vineyards. The aim of this work was to evaluate the soil tillage erosion rate in a vineyard using a 13C natural abundance tracer. A strip of soil (C3-C soil) was removed, mixed with C4-…
A microcosm experiment to evaluate the influence of location and quality of plant residues on residue decomposition and genetic structure of soil mic…
2007
The effects of location (soil surface vs. incorporated in soil) and nature of plant residues on degradation processes and indigenous microbial communities were studied by means of soil microcosms incubation in which the different soil zones influenced by decomposition i.e. residues, soil adjacent to residues (detritusphere) and distant soil unaffected by decomposition (bulk soil) were considered. Plant material decomposition, organic carbon assimilation by the soil microbial biomass and soil inorganic N dynamics were studied with 13 C labelled wheat straw and young rye. The genetic structure of the community in each soil zone were compared between residue locations and type by applying B- a…
Design and evaluation of self-healing solutions for future wireless networks
2016
This doctoral dissertation is aimed at the creation of comprehensive and innovative Self-Organizing Networks (SON) solutions for the Network Management of future wireless networks. More specifically, the thesis focuses on the Self-Healing (SH) part of SON. Faults can appear at several functional areas of a complex cellular network. However, the most critical domain from a fault management viewpoint is the Radio Access Network (RAN). The fault management of network elements is not only difficult but also imposes high costs both in capital investment (CAPEX) and operational expenditures (OPEX). The SON concept has emerged with the goal to foster automation and to reduce human involvement in man…
Thermal degradation of microcrystalline cellulose in concentrated phosphoric acid as assessed by HPLC, high field NMR spectroscopy and low field NMR …
2011
The most common renewable fuel is ethanol. It is a liquid produced by fermentation of glucose which is very abundant in cellulose based material sources. Plants produce about 180 billion tons of cellulose per year globally. For this reason cellulose is the largest organic carbon reservoir on Earth. Cellulose is composed exclusively of glucose units linked via B-1,4 glycosidic bonds. Each D-(+)-glucose unit contains three hydroxyl groups, which can form complex spatial networks of inter- and intra- molecular hydrogen bonds. They are responsible for the high crystallinity and compactness of cellulose, thereby making it very resistant to biological and chemical attack. In the presence of miner…
Electro-conversion as sustainable method for the fine chemical production from the biopolymer lignin
2018
Lignin, one of the most abundant polymers in nature, qualifies itself by the polyphenolic structure as potential renewable feedstock for the production of bio-based aromatic fine chemicals. However, the natural complexity and degradation stability of lignin make the depolymerization a highly challenging task. Several efforts have been pursued for the selective degradation of the biopolymer into suitable compounds. However, there are only a few technical approaches for the degradation of lignin to aromatic fine chemicals. Organic electrosynthesis is the synthetic method that enables the direct use of electricity for the production of valuable compounds. Moreover, electro-organic synthesis re…
Hydrothermal degradation of biobased poly(butylene succinate)/nanofibrillated cellulose composites
2021
Biobased polymers and composites have gained increased global attention due to their abundance, renewability, and biodegradability. Natural fillers such as cellulose-based fillers improve the mechanical properties of biopolymers, extending their application range, while maintaining the eco-friendly characteristics of the materials. Mowing towards engineering applications, requirements imposed on materials’ durability with regard to their environmental impact and high performance is necessary. Variations of ambient humidity and temperature could essentially reduce the service lifetime of biobased polymer composites. This study is focused on the hydrothermal degradation of poly(butylene succi…
Biodegradable microtablets made of low molecular weight polyglycolic acid: Bioabbaubare Mikrotabletten aus niedermolekularer Polyglycolsäure
1991
Research work in developing pharmaceutical dosage forms with biodegradable polymers seldom dealt with polyglycolic acid (PGA)1,2. This because of difficult processing procedures and low solubility of PGA in common organic solvents2,3. The only licensed product of the homoplymer in medical use is the sufgical suture Dexon®4
Ability of Kocuria varians LTH 1540 To Degrade Putrescine: Identification and Characterization of a Novel Amine Oxidase.
2015
This work describes the identification and characterization of an amine oxidase from Kocuria varians LTH 1540 (syn. Micrococcus varians) primarily acting on putrescine. Data from MALDI-TOF MS/MS and the identification of Δ(1)-pyrroline as degradation product from putrescine indicate that the enzyme is a flavin-dependent putrescine oxidase (PuO). Properties of partially purified enzyme have been determined. The enzyme oxidizes diamines, putrescine and cadaverine, and, to a lesser extent, polyamines, such as spermidine, but not monoamines. The kinetic constants (Km and Vmax) for the two major substrates were 94 ± 10 μM and 2.3 ± 0.1 μmol/min·mg for putrescine and 75 ± 5 μM and 0.15 ± 0.02 μmo…