6,595 research outputs found
Sustainable Habitat Restoration: Fish, Farms, and Ecosystem Services
Biomass burning impacts biogeochemical cycling, vegetation dynamics and climate. However, interactions between fire, climate and vegetation are not well understood and therefore studies have attempted to reconstruct fire and vegetation history under different climatic conditions using sedimentary archives. Here we focus on levoglucosan, a thermal by-product of cellulose generated during biomass burning, and, therefore, a potential fire biomarker in the marine sedimentary archive. However, before levoglucosan can be applied as a biomass burning proxy in marine sediments, there is a need for studies on how levoglucosan is transported to the marine environment, how it is reflecting biomass burning on continents, as well as the fate of levoglucosan in the marine water column and during deposition in marine sediments. Here we present analyses of levoglucosan, using an improved Ultra High Pressure Liquid Chromatography-Electro Spray Ionization/High Resolution Mass Spectrometry (UHPLC-ESI/HRMS) method, in atmospheric particles, in particulate matter settling through the water column and in marine surface sediments on a longitudinal transect crossing the tropical North Atlantic Ocean at 12°N. Levoglucosan was detected in the atmosphere, although in low concentration, possibly due to the sampled particle size, the source area of the aerosols, or the short time interval of sampling by which large burning events may have been missed. In sinking particles in the tropical North Atlantic Ocean we find that levoglucosan deposition is influenced by a mineral ballast effect associated with marine biogenic particles, and that levoglucosan is not transported in association with mineral dust particles. Highest levoglucosan concentrations and seasonal differences in sinking particles were found close to continents and low concentrations and seasonal differences were found in the open ocean. Close to Africa, levoglucosan concentration is higher during winter, reflecting seasonal burning in northwestern Africa. However, close to South America levoglucosan concentrations appear to be affected by riverine transport from the Amazon River. In surface sediments close to South America, levoglucosan concentration is higher than in the middle of the Atlantic Ocean, implying that here the influence from the South American continent is important and perennial. Our study provides evidence that degradation of levoglucosan during settling in the marine water column is not substantial, but is substantial at the sedimentâwater interface. Nevertheless, levoglucosan was detected in all surface sediments throughout the tropical North Atlantic, indicating its presence in the marine sedimentary record, which reveals the potential for levoglucosan as a biomass burning proxy in marine sediments
Perceptions of Iranian women regarding breast cancer screening behavior
Background: Breast cancer is the leading cause of death among women aged 20â59 years worldwide, with 58% of deaths occurring in less-developed countries. In the Islamic Republic of Iran, breast cancer constitutes 21% of all cancers, with an incidence rate of 22 per 100Â 000 women. Aims: Since research into breast cancer screening among Iranian women is scarce and results are contradictory, we aimed to explore womenâsâ perceptions regarding breast cancer screening behaviour and provide insights into how breast cancer is perceived and approached. This could aid policy-makers in drafting effective interventions to stimulate women to perform regular screening. Methods: We used the Health Belief Model as a theoretical framework. In-depth interviews with 22 women in Tehran were performed, based on a topic-list exploring the 6 constructs of the Health Belief Model: perceived barriers, perceived severity, perceived susceptibility, perceived benefits, self-efficacy and cues to action. Data-analysis was based on the Constructive Grounded Theory Method. Results: The main barriers were fear, low priority and cultural values. Perceived severity was low for the majority of women, while perceived susceptibility was high for about half of them. Perceived benefit of screening was high for all women. Womenâsâ self-efficacy was low when it came to breast self-examination. Talking about breast cancer screening and having somebody in their environment adopting screening behaviour were important cues for taking up breast cancer screening. Conclusions: Interventions should focus on diminishing barriers and increasing womenâsâ self-efficacy and interpersonal communication about breast cancer screening
Ready to Eat Nectarines - Assuring Quality in the Chain
Time-resolved reflectance spectroscopy, coupled to the modelling of firmness decrease, was used to predict at harvest softening behaviour of nectarines. Selected fruit were used in an export trial from Italy to The Netherlands. Quality assessed after shelf life was in agreement with the predicted firmness for fruit of different stages of maturity, showing that it is possible to select fruit at harvest for different market destinations and prevent transportation of fruit unsuitable for consumption
Calibrating the glycerol dialkyl glycerol tetraether temperature signal in speleothems
Palaeotemperature proxies based on glycerol dialkyl glycerol tetraethers (GDGTs) lipids have been established for marine and lacustrine environments, but there has been relatively little study of their application in speleothems. In this study we analyse the GDGT content of 33 speleothem samples from 16 different sites around the globe, and test whether proxies based on isoprenoid tetraethers (TEX86) or branched tetraethers (MBT/CBT) are correlated with measured surface and cave mean annual air temperature (MAT). The results show that the TEX86 has a strong relationship with measured temperature (r2 = 0.78, standard error of the estimate 2.3 C, when calibrated with surface MAT). Furthermore, the MBT/CBT also showed a significant relationship with temperature (r2 = 0.73, standard error of the estimate 2.7 C, when calibrated with surface MAT). Some issues remain requiring future work, in particular the development of a larger calibration sample set with measured cave temperature data, and the investigation of controls other than temperature on GDGT distribution, but overall the results indicate that GDGT based proxies derived from speleothems may be highly viable new methods for reconstructing continental palaeotemperatures
Incremental Distance Transforms (IDT)
A new generic scheme for incremental implementations of distance transforms (DT) is presented: Incremental Distance Transforms (IDT). This scheme is applied on the cityblock, Chamfer, and three recent exact Euclidean DT (E2DT). A benchmark shows that for all five DT, the incremental implementation results in a significant speedup: 3.4Ăâ10Ă. However, significant differences (i.e., up to 12.5Ă) among the DT remain present. The FEED transform, one of the recent E2DT, even showed to be faster than both city-block and Chamfer DT. So, through a very efficient incremental processing scheme for DT, a relief is found for E2DTâs computational burden
Gold catalyzed propene epoxidation - a study in catalytic activity and reaction mechanism
Direct epoxidation of propene using hydrogen and oxygen on gold-titania catalyst was studied. A series of low gold loaded catalysts were tested for catalytic activity, hydrogen efficiency and stability. A thorough kinetic study was done on the best catalysts. Finally, a reaction mechanism was proposed to explain the experimental data
Depth-related distribution of a key gene of the tetraether lipid biosynthetic pathway in marine Thaumarchaeota
The distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGT) lipids synthesized by Thaumarchaeota has been shown to be temperature-dependent in world oceans. Depth-related differences in the ammonia monooxygenase (amoA) of Thaumarchaeota have led to the classification of âshallowâ and âdeep waterâ clusters, potentially affecting GDGT distributions. Here, we investigate if this classification is also reflected in a key gene of the thaumarchaeotal lipid biosynthetic pathway coding for geranylgeranylglyceryl phosphate (GGGP) synthase. We investigated metagenomic databases, suspended particulate matter and surface sediment of the Arabian Sea oxygen minimum zone. These revealed significant differences in amoA and GGGP synthase between âshallowâ and âdeep waterâ Thaumarchaeota. Intriguingly, amoA and GGGP synthase sequences of benthic Thaumarchaeota clustered with the âshallow waterâ rather than with âdeep waterâ Thaumarchaeota. This suggests that pressure and temperature are unlikely factors that drive the differentiation, and suggests an important role of ammonia concentration that is higher in benthic and âshallow waterâ niches. Analysis of the relative abundance of GDGTs in the Arabian Sea and in globally distributed surface sediments showed differences in GDGT distributions from subsurface to deep waters that may be explained by differences in the GGGP synthase, suggesting a genetic control on GDGT distributions
Palaeoclimate - A balmy Arctic
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62910/1/432814a.pd
Water loss in horticultural products. Modelling, data analysis and theoretical considerations
The water loss of individual fruit (melon, plum and mandarin) was analysed using the traditional diffusion based approach and a kinetic approach. Applying simple non linear regression, both approaches are the same, resulting in a quite acceptable analysis. However, by applying mixed effects non linear regression analysis, explicitly including the variation over the individuals, the kinetic approach was found to reflect the processes occurring during mass loss better than the diffusion approach. All the variation between the individuals in a batch could be attributed to the initial mass or size of the individuals. The fraction of the fruit mass that is available for transpiration is the key item in the water loss process, rather than the skin resistance and fruit area. Obtained explained parts are well over 99%
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