Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

https://dspace.stir.ac.uk/bitstream/1893/30981/1/intcal20_northern_hemisphere_radiocarbon_age_calibration_curve_055_cal_kbp.pdf

The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0-55 cal kBP)

Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.

Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009

Glacial melting in the Tibetan Plateau affects the water resources of millions of people. This study finds that—partly owing to changes in atmospheric circulations and precipitation patterns—the most intensive glacier shrinkage is in the Himalayan region, whereas glacial retreat in the Pamir Plateau region is less apparent.

Different glacier status with atmospheric circulations in Tibetan Plateau and surroundings

Identifying which trees are more vulnerable to extreme climatic events is a challenging problem in our understanding of forest and even ecosystem dynamics under climate change scenarios. As one of the most widely distributed tree species across the arid and semi-arid northeastern Tibetan Plateau, Qilian juniper (Juniperus przewalskii Kom.), is the main component of the local forest ecosystem, providing critical insurance for the ecological security of the surrounding areas. However, this species's ability to cope with climate extremes (especially drought) has not been adequately assessed. Here, we apply a dendroecological approach that considers indices of resistance and resilience to quantify the vulnerability of Qilian junipers to the extreme drought events of 1957, 1966, 1979, and 1995. A total of 532 Qilian juniper trees from different age stages (100-1,100 years) and altitudes [3,500-4,000 m above sea level (a.s.l.)] were studied to assess their response characteristics during these four drought extremes. We conclude that drought extremes have a significant negative impact on the growth of Qilian juniper. The oldest Qilian junipers at the lower altitudes constituted the most vulnerable populations across the northeastern Tibetan Plateau and were characterized by the lowest resistance values, the narrowest annual rings, and the highest proportion of missing rings during the four drought years. Tree resilience after droughts was strongly related to the intensity of the drought event and did not change with tree age or elevation. A threshold of tree tolerance to drought may exist, with the more vulnerable tree individuals (e.g., the oldest Qilian junipers from lower altitudes) being exposed to the highest mortality risk when drought intensity exceeds the threshold value. Such a threshold needs further consideration, through the study of trees that have died (or are about to die) due to extreme droughts.

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The Vulnerability of Qilian Juniper to Extreme Drought Events.

Characterization of polysaccharide structure in Citrus reticulate 'Chachi' peel during storage and their bioactivity.

Structure identification of a polysaccharide in mushroom Lingzhi spore and its immunomodulatory activity

BACKGROUND: The Maillard reaction is a complex series of reactions between reducing sugars and amino groups. Changing any of reaction parameters would alter the reaction pathway. This study investigated the effect of xylose concentration on the molecular and particle size distribution of Maillard reaction products (MRPs) derived from peanut hydrolysate and xylose to discuss their formation mechanism.



RESULTS: Molecular weight and particle size distribution analyses indicated that both peptide degradation and peptide cross-linking occurred during the Maillard reaction. Heat treatment would make the high-molecular-weight peptides degrade into low-molecular-weight peptides and free amino acids. Maillard reaction increased the molecular weight and particle sizes of products as the xylose concentration increased from 1% to 4%.



CONCLUSION: The study shows that both peptide degradation and peptide cross-linking occurred during the Maillard reaction. The thermal degradation product (TDP) and MRPs had significantly different molecular size distribution, and the particle size distribution of TDPs and MRPs had similar change tendency to that of the molecular size distribution. These would provide an insight into the formation mechanism of MRPs. Copyright © 2011 Society of Chemical Industry

Effect of xylose on the molecular and particle size distribution of peanut hydrolysate in Maillard reaction system

Cinnamon is an important herbal medicine with good effects of health promotion and disease prevention. In this work, the volatile compounds of cinnamon bark were extracted by hydrodistillation and solid phase microextraction techniques. Gas chromatography/mass spectrometry was used to identify and quantify the volatile compound composition. The results indicated that trans-cinnamaldehyde was the major component with the highest area percentage of 68.67% in the volatile oils extracted by hydrodistillation. The next were glycerol 1-methyl ether and o-methoxycinnamaldehyde with area percentages of 23.29 and 1.44%, respectively. The number of alkenes, alkanes, alcohols, aldehydes, amines, carboxylic acids, ethers, esters and ketones were 17, 1, 12, 8, 2, 2, 6, 3 and 6, respectively. The volatile compounds extracted by headspace solid phase microextraction were apparently different from those by hydrodistillation. Three major volatile compounds were 1,2,3,4,4a,5,6,8a-octahydro-7-methyl-4-methylene-1-(1-methylethyl)-naphthalene, 1,2,3,4a,5,8,8a-hexahydro-4,7-methyl-1-methylene-1-(1-methylethyl)-naphthalene and copaene with area percentages of 20.18%, 17.21% and 16.51%, respectively. Alkenes (31), alcohols (10), aldehydes (4), carboxylic acids (2) and ethers (3) were found in this assay.



PRACTICAL APPLICATIONS

Cinnamon bark has been taken as an important traditional herbal medicine due to its disease prevention effect. The volatile compounds of cinnamon bark contribute much to its bioactivities. In this work, the volatile oils were extracted by hydrodistillation technique. Head space solid phase microextraction technique was also used to detect the volatile compounds. Gas chromatography/mass spectrometry analysis showed the significant difference of volatile compound composition between two extractions. trans-Cinnamaldehyde was confirmed to be the major component of volatile oils that has good pharmacological properties. This work is helpful for extensive development of this medicinal herb.

Comparison of volatile compound composition of cinnamon (cinnamomum cassia presl) bark prepared by hydrodistillation and headspace solid phase microextraction

Bao Yang

Papers

The Vulnerability of Qilian Juniper to Extreme Drought Events.

Characterization of polysaccharide structure in Citrus reticulate 'Chachi' peel during storage and their bioactivity.

Structure identification of a polysaccharide in mushroom Lingzhi spore and its immunomodulatory activity

Effect of xylose on the molecular and particle size distribution of peanut hydrolysate in Maillard reaction system

Comparison of volatile compound composition of cinnamon (cinnamomum cassia presl) bark prepared by hydrodistillation and headspace solid phase microextraction