scholarly journals Composition Changes in the Boreal Mixedwood Forest of Western Quebec Since Euro-Canadian Settlement

2020 ◽  
Vol 8 ◽  
Author(s):  
Mathilde Marchais ◽  
Dominique Arseneault ◽  
Yves Bergeron
Keyword(s):  
Boreal Mixedwood Forest ◽  
Composition Changes

Problems in Thin-Film X-ray Quantification

1990 ◽  
Vol 48 (2) ◽  
pp. 458-459
Author(s):  
J N Chapman ◽  
W A P Nicholson
Keyword(s):  
Thin Film ◽  
Specimen Thickness ◽  
X Rays ◽  
Characteristic Peak ◽  
Local Composition ◽  
X Ray ◽  
Measured Ratio ◽  
Path Lengths ◽  
Composition Changes

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.

scholarly journals Compensation Mechanism of the Photosynthetic Apparatus in Arabidopsis thaliana ch1 Mutants

2020 ◽  
Vol 22 (1) ◽  
pp. 221
Author(s):  
Joanna Wójtowicz ◽  
Adam K. Jagielski ◽  
Agnieszka Mostowska ◽  
Katarzyna B. Gieczewska
Keyword(s):  
Light Stress ◽  
Photosynthetic Apparatus ◽  
Protein Composition ◽  
Mrna Levels ◽  
Chlorophyll B ◽  
Low Light ◽  
Plant Acclimation ◽  
Chlorophyll B Deficiency ◽  
Composition Changes

The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the main aim of this study was to find the strategy in plants for compensation of low chlorophyll content by characterizing and comparing the performance and spectral properties of the photosynthetic apparatus related to the lipid and protein composition in four selected Arabidopsis ch1 mutants and two Arabidopsis ecotypes. Mutation in different loci of the CAO gene, viz., NW41, ch1.1, ch1.2 and ch1.3, manifested itself in a distinct chlorina phenotype, pigment and photosynthetic protein composition. Changes in the CAO mRNA levels and chlorophyllide a (Chlide a) content in ecotypes and ch1 mutants indicated their significant role in the adjustment mechanism of the photosynthetic apparatus to low-light conditions. Exposure of mutants with a lower chlorophyll b content to short-term (1LL) and long-term low-light stress (10LL) enabled showing a shift in the structure of the PSI and PSII complexes via spectral analysis and the thylakoid composition studies. We demonstrated that both ecotypes, Col-1 and Ler-0, reacted to high-light (HL) conditions in a way remarkably resembling the response of ch1 mutants to normal (NL) conditions. We also presented possible ways of regulating the conversion of chlorophyll a to b depending on the type of light stress conditions.

Body Mass and Body Composition Changes over 7 Years in a Male Professional Rugby Union Team

2021 ◽  
Author(s):  
Clíodhna McHugh ◽  
Karen Hind ◽  
Aoife O'Halloran ◽  
Daniel Davey ◽  
Gareth Farrell ◽  
...  
Keyword(s):  
Body Composition ◽  
Body Mass ◽  
Body Fat ◽  
Lean Mass ◽  
Total Mass ◽  
Rugby Union ◽  
Body Fat Percentage ◽  
Fat Percentage ◽  
Dxa Scans ◽  
Composition Changes

AbstractThe purpose of this study was to investigate longitudinal body mass and body composition changes in one professional rugby union team (n=123), (i) according to position [forwards (n=58) versus backs (n=65)], analysis of players with 6 consecutive seasons of DXA scans (n=21) and, (iii) to examine differences by playing status [academy and international], over 7 years. Players [mean age: 26.8 y, body mass index: 28.9+kg.m2] received DXA scans at fourtime points within each year. A modest (but non-significant) increase in mean total mass (0.8 kg) for professional players was reflected by increased lean mass and reduced body fat mass. At all-time points, forwards had a significantly greater total mass, lean mass and body fat percentage compared to backs (p<0.05). Academy players demonstrated increased total and lean mass and decreased body fat percentage over the first 3 years of senior rugby, although this was not significant. Senior and academy international players had greater lean mass and lower body fat percentage (p<0.05) than non-international counterparts. Despite modest increases in total mass; reflected by increased lean mass and reduced fat mass, no significant changes in body mass or body composition, irrespective of playing position were apparent over 7 years.

Visceral Fat and Body Composition Changes in a Female Population After RYGBP: a Two-Year Follow-Up by DXA

2014 ◽  
Vol 25 (3) ◽  
pp. 443-451 ◽  
Author(s):  
Alberto Bazzocchi ◽  
Federico Ponti ◽  
Stefano Cariani ◽  
Danila Diano ◽  
Luca Leuratti ◽  
...  
Keyword(s):  
Body Composition ◽  
Visceral Fat ◽  
Female Population ◽  
Composition Changes
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