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CANDOTTO CARNIEL, Fabio, Elisa PELLEGRINI, Federica BOVE, Matteo CROSERA, Gianpiero ADAMI, Cristina NALI, Giacomo LORENZINI et Mauro TRETIACH. « Acetone washing for the removal of lichen substances affects membrane permeability ». Lichenologist 49, no 4 (juillet 2017) : 387–95. http://dx.doi.org/10.1017/s0024282917000263.
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AbstractRemoving lichen substances from dry lichen thalli using pure acetone is the least detrimental method. Measurements of properties strictly related to the photobiont, such as chlorophyllafluorescence (ChlaF), are frequently used to verify acetone toxicity but they cannot reveal possible damage accumulated at the whole thallus level. Here, measurements of ChlaF have been integrated with others concerning the status of cell membranes and photobiont population (potassium leakage, malondialdehyde and photosynthetic pigment content). Dry thalli ofFlavoparmelia caperata,Parmotrema perlatumandXanthoria parietinawere subjected to sequential acetone washings according to standard protocols. Membrane permeability was assessed before and after the washing treatment, and after a recovery period of 48 hours. Measurements of ChlaF were taken in a parallel experiment. Acetone washings increased potassium leakage in all the species from 3·9 to 6·6 times greater than the control level. After recovery, onlyP. perlatumreturned to the control level. ChlaF was affected only inF. caperata, with a 20% decrease inFv/Fmwhich had not fully recovered after 48 hours. There was neither an increase in lipid peroxidation of membranes nor a change in the photosynthetic pigment content. The sensitivity ofF. caperatato this method and the impact of the results on its future application are discussed.
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BERTUZZI, Stefano, et Mauro TRETIACH. « Hydrogen sulphide inhibits PSII of lichen photobionts ». Lichenologist 45, no 1 (janvier 2013) : 101–13. http://dx.doi.org/10.1017/s0024282912000667.
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AbstractThe effects of hydrogen sulphide (H2S) on five lichens with different photobionts, ecology, and tolerance to the pollutant were studied by means of samples exposed in closed chambers containing two known H2S solutions. The H2S concentration in the void volume at equilibrium with the liquid phase was measured by gas chromatography-mass spectrometry, combined with the use of solid phase micro extraction (GC/MS SPME). It was determined as 8 and 28 ppm H2S in the absence of lichen material, andc. 2 and 10 ppm H2S respectively with living lichen material inserted for 8 hours in the exposure chambers. Significant differences in the species-specific emission of chlorophyllafluorescence (ChlaF) were observed, with a pronounced depression ofFv/Fmalready detectable after 2 h exposure at 28 ppm H2S in all the species. The decreased intensity was positively correlated to sample surface and, to a lesser extent, to the species-specific pre-exposureFv/Fmvalue. Dark-exposed samples were less affected than light-exposed ones. All four chlorolichens could recover the pre-exposure ChlaF emission after two days in the absence of H2S, both in the light and in the dark, whereas the cyanolichen did not recover when kept in the dark. The results are thoroughly discussed on the basis of the known action mechanisms of H2S on the photosynthetic apparatus of vascular plants and cyanobacteria.
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Steffens, M., M. A. Granskog, H. Kaartokallio, H. Kuosa, K. Luodekari, S. Papadimitriou et D. N. Thomas. « Spatial variation of biogeochemical properties of landfast sea ice in the Gulf of Bothnia, Baltic Sea ». Annals of Glaciology 44 (2006) : 80–87. http://dx.doi.org/10.3189/172756406781811169.
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AbstractHorizontal variation of landfast sea-ice properties was studied in the Gulf of Bothnia, Baltic Sea, during March 2004. In order to estimate their variability among and within different spatial levels, 72 ice cores were sampled on five spatial scales (with spacings of 10 cm, 2.5 m, 25 m, 250m and 2.5 km) using a hierarchical sampling design. Entire cores were melted, and bulk-ice salinity, concentrations of chlorophylla(Chla), phaeophytin (Phaeo), dissolved nitrate plus nitrite (DIN) as well as dissolved organic carbon (DOC) and nitrogen (DON) were determined. All sampling sites were covered by a 5.5–23 cm thick layer of snow. Ice thicknesses of cores varied from 26 to 58 cm, with bulk-ice salinities ranging between 0.2 and 0.7 as is typical for Baltic Sea ice. Observed values for Chla(range: 0.8–6.0 mg ChlaL–1; median: 2.9 mg ChlaL–1) and DOC (range: 37–397 μM; median: 95 μM) were comparable to values reported by previous sea-ice studies from the Baltic Sea. Analysis of variance among different spatial levels revealed significant differences on the 2.5km scale for ice thickness, DOC and Phaeo (with the latter two being positively correlated with ice thickness). For salinity and Chla, the 250 m scale was found to be the largest scale where significant differences could be detected, while snow depth only varied significantly on the 25 m scale. Variability on the 2.5 m scale contributed significantly to the total variation for ice thickness, salinity, Chlaand DIN. In the case of DON, none of the investigated levels exhibited variation that was significantly different from the considerable amount of variation found between replicate cores. Results from a principal component analysis suggest that ice thickness is one of the main elements structuring the investigated ice habitat on a large scale, while snow depth, nutrients and salinity seem to be of secondary importance.
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Pitterle, D. M., et K. V. Rajagopalan. « Two proteins encoded at the chlA locus constitute the converting factor of Escherichia coli chlA1. » Journal of Bacteriology 171, no 6 (1989) : 3373–78. http://dx.doi.org/10.1128/jb.171.6.3373-3378.1989.
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YEMETS, Olena A., Knut Asbjørn SOLHAUG et Yngvar GAUSLAA. « Spatial dispersal of airborne pollutants and their effects on growth and viability of lichen transplants along a rural highway in Norway ». Lichenologist 46, no 6 (23 octobre 2014) : 809–23. http://dx.doi.org/10.1017/s0024282914000449.
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AbstractThis study aims to quantify dispersal of airborne traffic-related elemental pollutants and concurring responses – relative growth rate (RGR), maximal quantum yield of PSII (Fv/Fm), and chlorophylls (Chlab) – in four epiphytic lichens (Lobaria pulmonaria,Parmelia sulcata,Ramalina farinacea,Usnea dasopoga). Lichens were transplanted from 25 September to 26 March to 1·5 m tall stands in open farmlands at 10, 15, 30, 50 and 100 m from the E6 highway (SE Norway), along three transects on each side usnea dasopoga of the road. The concentrations of most elements (Ca, Mg,Na,Fe,Al, Zn,Ba,Cu,V,Cr,Ni,Co,Sn, As, Mo) significantly increased with increasing proximity to the road. Elements inboldhad elevated concentrations relative to controls, at least in some species at 100 m. The heavy metal accumulation increased from foliose to fruticose lichens in the order:P. sulcata>L. pulmonaria>R. farinacea≫U. dasopoga.However,L. pulmonariawas the only species with strong pollutant-dependent reductions in growth,Fv/Fm, Chlab, and Chla/b-ratio. The RGR and viability parameters were adversely affected by the roadside environment near the road only (≤15 m), and only after substantial heavy metal accumulation. Measurement of metal accumulation in lichens is thus a far more sensitive way of monitoring road pollutants than recording growth and lichen viability. Despite strong species-specific contrasts in elemental concentrations, most road pollutant elements responded similarly to distance from the road in all species.
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Hirata, T., N. J. Hardman-Mountford, R. J. W. Brewin, J. Aiken, R. Barlow, K. Suzuki, T. Isada et al. « Synoptic relationships quantified between surface Chlorophyll-<i>a</i> ; and diagnostic pigments specific to phytoplankton functional types ». Biogeosciences Discussions 7, no 5 (1 septembre 2010) : 6675–704. http://dx.doi.org/10.5194/bgd-7-6675-2010.
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Abstract. Error-quantified, synoptic-scale relationships between chlorophyll-a (Chla) and phytoplankton pigment groups at the sea surface are presented. A total of nine pigment groups were considered to represent nine phytoplankton functional types (PFTs) including microplankton, nanoplankton, picoplankton, diatoms, dinoflagellates, green algae, picoeukaryotes, prokaryotes and Prochlorococcus sp. The observed relationships between Chla and pigment groups were well-defined at the global scale to show that Chla can be used as an index of not only phytoplankton abundance but also community structure; large (micro) phytoplankton monotonically increase as Chla increases, whereas the small (pico) phytoplankton community generally decreases. Within these relationships, we also found non-monotonic variations with Chla for certain pico-plankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp.) and for Green Algae and nano-sized phytoplankton. The relationships were quantified with a least-square fitting approach in order to estimate the PFTs from Chla alone. The estimated uncertainty of the relationships quantified depends on both phytoplankton types and Chla concentration. Maximum uncertainty over all groups (34.7% Chla) was found from diatom at approximately Chla = 1.07 mg m−3. However, the mean uncertainty of the relationships over all groups was 5.8 [% Chla] over the entire Chla range observed (0.02 < Chla < 6.84 mg m−3). The relationships were applied to SeaWiFS satellite Chla data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting ~9.0 [% Chla] of the phytoplankton community at the global surface, in which diatoms explain ~6.0 [% Chla]. Nanoplankton are ubiquious throught much of the global surface oceans except subtropical gyres, acting as a background population, constituting ~44.2 [% Chla]. Picoplankton are mostly limited in subtropical gyres, constituting ~46.8 [% Chla] globally, in which prokaryotes are the major species explaining 32.3 [% Chla] (prochlorococcus sp. explaining 21.5 [% Chla]), while pico-eukaryotes are notably abundant in the Southern Pacific explaining ~14.5 [% Chla]. These results may be used to constrain or validate global marine ecosystem models.
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ABSC, CHLA. « CHLA/ABSC Announcements ». Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada 39, no 3 (23 novembre 2018) : 126–27. http://dx.doi.org/10.29173/jchla29400.
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Iwasaki, Suginori. « Daily Variation of Chlorophyll-A Concentration Increased by Typhoon Activity ». Remote Sensing 12, no 8 (16 avril 2020) : 1259. http://dx.doi.org/10.3390/rs12081259.
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The chlorophyll-a (Chla) concentration product of the Himawari-8 geostationary meteorological satellite is used to show the temporal variation of Chla owing to the passage of typhoons, namely, tropical cyclones in the western North Pacific Ocean. The daily Chla variation shows that Chla usually increases along the paths of typhoons, whereas the same observations are almost impossible when using the data of polar-orbiting satellites as shown in previous studies. This is because the temporal resolution of Himawari-8 is ten times more than that of polar-orbiting satellites, and the daily Chla distribution contains a few disturbances attributed to clouds after compositing cloud-free data. Chla usually increases on the day of typhoon arrival, but mostly, the ratio of Chla increased by a typhoon to the background Chla, R Chla HIMA , is less than 2. Only a few typhoons considerably increased Chla. As a whole, R Chla HIMA is proportional to the maximum 10-min sustained wind speed up to 85 knots (44 m s−1), namely, 0.01 mg m−3 knot−1 (0.019 mg s m−4). However, there is no clear dependence between Chla and the wind speed in seas with higher Chla, such as the South China Sea. The result that typhoons are usually cultivating the ocean is important for studies of primary ocean productivity and carbon flux between the atmosphere and ocean.
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Ahmad, Ahyar. « MOLECULAR CLONING, EXPRESSION AND FUNCTIONAL INTERACTION OF p48 SUBUNIT OF CHICKEN CHROMATIN ASSEMBLY FACTOR 1 WITH HISTONE DEACETYLASE 2 AND HISTONE ACETYLTRANSFERASE 1 ». Indonesian Journal of Chemistry 12, no 1 (9 mars 2012) : 77–83. http://dx.doi.org/10.22146/ijc.21375.
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We cloned and sequenced cDNA encoding p48 subunit of the chicken CAF-1, chCAF-1p48, and histone acetyltransferase-1, chHAT-1 from chicken DT40 cell lines. We showed that the p48 subunit of CAF-1 tightly binds to two regions of chicken histone deacetylase 2, chHDAC-2, located between amino acid residues 82-180 and 245-314, respectively. We also established that two N-terminal, two C-terminal, or one N-terminal and one C-terminal WD repeat motif of chCAF-1p48 are required for this interaction. The GST pulldown assay, involving truncated and missense mutants of chCAF-1p48, revealed not only that a region containing the seventh WD dipeptide motif of chCAF-1p48, comprising amino acids 376-405, binds to chHAT-1 in vitro, but also that mutation of the motif has no influence on the in vitro interaction. We also established that the region, which is located between amino acids 380-408 of chHAT-1 and contains a leucine zipper motif, is required for its in vitro interaction with chCAF-1p48. Mutation on each of four Leu residues in the leucine zipper motif of chHAT-1 causes the disappearance of the interaction with chCAF-1p48. These results should be useful information for understanding the participation of chCAF-1p48 protein as histones chaperone in DNA-utilizing processes, such as replication, recombination, repair and gene expression in DT40 chicken B cell.
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Eitel, Jan U. H., Lee A. Vierling, Dan S. Long, Marcy Litvak et Karla C. B. Eitel. « Simple assessment of needleleaf and broadleaf chlorophyll content using a flatbed color scanner ». Canadian Journal of Forest Research 41, no 7 (juillet 2011) : 1445–51. http://dx.doi.org/10.1139/x11-058.
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Total chlorophyll a and b content (Chlab) of leaves is an important indicator of the photosynthetic capacity, nutritional condition, and health status of plants. Developing low-cost, easily accessible methods for estimating foliar Chlab of needleleaf species would enable a broad range of forestry applications. We evaluated data acquired using an off-the-shelf flatbed color scanner to assess its utility in quantifying needleleaf Chlab. Red and green digital numbers (DN) of the scan image were obtained from needle leaves of oneseed juniper ( Juniperus monosperma (Engelm.) Sarg.) and piñon pine ( Pinus edulis Engelm.) in addition to two broadleaf species for comparison purposes. Values of laboratory-determined Chlab (range 1.5–64.0 µg·cm–2) were then predicted using the DN values from the scanner-imaged needle leaves as a regression estimator. The red or green DN values of the scanner-imaged needle leaves were curvilinearly related to Chlab with an r2 of 0.67 (RMSE = 4.72 µg·cm–2, p < 0.001) for juniper needles and an r2 of 0.54 (RMSE = 5.51 µg·cm–2, p < 0.001) for pine needles. Although our results suggest that flatbed scanner derived Chlab estimates are not suitable for applications where highly accurate Chlab estimates are required, the technique is likely to be a useful tool for forest practitioners in managing tree nutrition and health.
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Aiken, Jim, James Fishwick, Gerald Moore et Katharine Pemberton. « The annual cycle of phytoplankton photosynthetic quantum efficiency, pigment composition and optical properties in the western English Channel ». Journal of the Marine Biological Association of the United Kingdom 84, no 2 (avril 2004) : 301–13. http://dx.doi.org/10.1017/s0025315404009191h.
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Phytoplankton photosynthetic quantum efficiency (PQE), pigments, absorption characteristics, species composition (converted to phytoplankton carbon, Cph) and other variables were measured at an offshore site in the western English Channel throughout 2001, using an opportunistic weekly sampling schedule. The variation of chlorophyll-a (Chla) and other phytoplankton pigments followed the classical seasonal cycle, driven by incident light, patterns of stratification and nutrient availability. Phytoplankton and pigment concentrations were low in the winter, rising to a peak in the spring ‘bloom’, with episodic blooms throughout the summer, an autumn bloom and a decline to the winter minimum. Surface layer Chla and total pigment (Tpig) concentrations were highly correlated for the whole year, yet it was observed that the fraction of Chla in Tpig (Chla/Tpig) was not constant and had a distinct seasonal pattern, low in winter and higher in spring, summer and autumn blooms. Chlorophyll-a/Tpig was linearly correlated with recent ambient light fluxes and maximum PQE (PQEm) throughout most of the year, though more significantly within seasonal periods. Chlorophyll-a and Tpig were both linearly correlated to Cph and the Chla/Cph ratio was significantly correlated with both Chla/Tpig and PQEm. Also the optical absorption ratios, a674/a443 and a674/a490 were significantly correlated with PQE and Chla/Tpig, indicating probable optical signatures for these two parameters. The seasonal cycle of measurements of photosynthetic quantum efficiency provided a bench-mark against which all the photosynthetically-driven seasonal changes of biological properties can be understood, in terms of incident solar radiation and nutrient availability. We conclude that phytoplankton synthesize Chla preferentially to other pigments or carbon compounds in conditions beneficial to growth. The PQEm, the ratios of Chla/Tpig, Chla/Cph and a674/a443 are greater when plants are growing actively. In periods of nutrient sufficiency, PQEm, Chla/Tpig and a674/a443 are all linear functions of the mean total photon flux for the recent few days. Photosynthetically driven changes in Chla synthesis, cause observed changes of Chla/Tpig and Chla/Cph ratios.
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Zou, Wei, Guangwei Zhu, Hai Xu, Mengyuan Zhu, Chaoxuan Guo, Boqiang Qin et Yunlin Zhang. « Atmospheric Stilling Promotes Summer Algal Growth in Eutrophic Shallow Lakes ». Biology 10, no 12 (23 novembre 2021) : 1222. http://dx.doi.org/10.3390/biology10121222.
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Algal blooms are environmental challenges confronting lakes worldwide and are significantly influenced by chlorophyll a yields per unit phosphorus (Chla/TP), or nitrogen (Chla/TN). Here, the influence of inter-annual hydrometeorological variations on Chla/TP and Chla/TN were evaluated in eutrophic shallow Lake Taihu, China. Our results demonstrated significant increases (p < 0.001) in both Chla/TN and Chla/TP from 2005 to 2017, and increased Chla yields during the winter months were mainly correlated with higher water temperature and longer sunshine hours, which may cause severer blooms in winter and spring. In remaining months from 2005 to 2017, typical associations between atmospheric stilling (or water level elevation) and higher Chla yields were observed. The results also indicate that atmospheric stilling and water level elevation significantly (p < 0.001) decreased background turbidity and promoted buoyant cyanobacterial biomass, alleviating phytoplankton light limitation. Given the subtropical location, eutrophic status, and high background turbidity of Lake Taihu, light may be the critical limiting factor for summer phytoplankton growth; thus, improved light availability would promote Chla yields until self-shading caused further light limitations. If the mechanism is general, promoting the effect of atmospheric stilling on annual peak Chla in shallow lakes may be greatly underestimated, and our finding will affect future bloom mitigation efforts in such systems.
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Zhuang, Jie, Yonglin Wang, Yonggang Chi, Lei Zhou, Jijing Chen, Wen Zhou, Jun Song, Ning Zhao et Jianxi Ding. « Drought stress strengthens the link between chlorophyll fluorescence parameters and photosynthetic traits ». PeerJ 8 (24 septembre 2020) : e10046. http://dx.doi.org/10.7717/peerj.10046.
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Chlorophyll fluorescence (ChlF) has been used to understand photosynthesis and its response to climate change, particularly with satellite-based data. However, it remains unclear how the ChlF ratio and photosynthesis are linked at the leaf level under drought stress. Here, we examined the link between ChlF ratio and photosynthesis at the leaf level by measuring photosynthetic traits, such as net CO2 assimilation rate (An), the maximum carboxylation rate of Rubisco (Vcmax), the maximum rate of electron transport (Jmax), stomatal conductance (gs) and total chlorophyll content (Chlt). The ChlF ratio of the leaf level such as maximum quantum efficiency of PSII (Fv/Fm) is based on fluorescence kinetics. ChlF intensity ratio (LD685/LD740) based on spectrum analysis was obtained. We found that a combination of the stomatal limitation, non-stomatal limitation, and Chlt regulated leaf photosynthesis under drought stress, while Jmax and Chlt governed the ChlF ratio. A significant link between the ChlF ratio and An was found under drought stress while no significant correlation in the control, which indicated that drought stress strengthens the link between the ChlF ratio and photosynthetic traits. These results suggest that the ChlF ratio can be a powerful tool to track photosynthetic traits of terrestrial ecosystems under drought stress.
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Lin, Yi-Ching, Yi-Fan Li et Tung-liang Chiang. « Healthy living practices in families and child health : 5-year follow-up of Taiwan Birth Cohort Study ». BMJ Open 10, no 7 (juillet 2020) : e033613. http://dx.doi.org/10.1136/bmjopen-2019-033613.
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ObjectivesWe have previously developed the Child Healthy Living Practices in Family (CHLPF) Index and found that the CHLPF Index was concurrently associated with the health of children at age 3. In this follow-up study, we aimed to examine whether healthy living practices in family at age 3 predicted health of children at school age.Design and settingData came from the Taiwan Birth Cohort Study designed to assess the development and health of 24 200 children born in 2005.ParticipantsA total of 18 553 cohort members whose mothers or primary caregivers had completed 6-month, 3-year, 5-year and 8-year surveys were included for analysis, representing a response rate of 87.3%.Outcome measuresA multiple logistic regression model was used to test the relationship between mother-rated children’s health at age 8 and the CHLPF Index level, after controlling for sex, birth outcomes, family structure, parental education, residential area, family income and mother-rated child’s health at age 3.ResultsThe percentage of mother-rated good health at age 8 was 79.7%. Compared with the low CHLPF level, the adjusted OR of mother-rated good health was 1.38 (95% CI 1.19 to 1.60), 1.21 (95% CI 1.10 to 1.35) and 1.17 (95% CI 1.07 to 1.29), respectively, for high, high–low and mid-low CHLPF levels. Moreover, the prevalence of mother-rated good health at age 8 with high-level CHLPF Index in the low-income group was similar to that of the high-income group (83.72% vs 84.18%); the prevalence with low-level CHLPF Index in the low-income group was much lower than that of the high-income group (70.21% vs 78.98%).ConclusionsOur study underscores that high level of healthy living practices in early childhood is positively associated with good health at school age, particularly for children from disadvantaged families.
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Yuvaraj, N., et P. Thangaraj. « An Extended Cross Layer Approach Handling Asymmetry with Quality of Service, Congestion Avoidance and Congestion Aware Routing ». Journal of Computational and Theoretical Nanoscience 15, no 2 (1 février 2018) : 676–84. http://dx.doi.org/10.1166/jctn.2018.7143.
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Nodes in wireless multi-hop networks establish links with their neighbors that are used for data transmission. In Wireless Mesh Networks (WMNs) working in an ad hoc model, a transmission region of mesh routers and mesh clients is heterogeneous which cause link asymmetry. The cross-layer framework was developed to handle link asymmetry problems such as unidirectional link issue, heterogeneous exposed problem and heterogeneous hidden problem. Additionally, congestion control and quality of service (QoS) requirements are required to enhance the performance of network. Hence, in this paper, the Cross Layer approach Handling Link Asymmetry (CHLA) is extended as quality-of-service aware routing (CHLA-QSAR) and quality-of-service with congestion control aware routing (CHLA-QSCCAR). QoS requirements are achieved by Signal strength estimation, network capacity estimation, MAC scheduling, Link Scheduling and Slot assignment. Congestion is controlled by a proposed bandwidth management mechanism by congestion window management dependent on the dynamic incidents of traffic conditions. Moreover, congestion avoidance mechanism is also proposed with Quality of Service with Congestion aware routing (QSCACAR). The simulation is conducted for CHLA, CHLA-QSAR, and CHLA-QSCCAR and CHLA-QSCACAR methods in terms of bit error rate, end to end delay, latency, routing overheads and throughput. The simulation results proved that each proposed work is consecutively improving the performance than CHLA.
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Campra, Noelia Anahí, Laura Noelia Cariddi, Franco Matias Escobar, María Carola Sabini, Celio Geraldo Freire-de-Lima, Debora Decote-Ricardo, Dardo Roma et Fernando Mañas. « Protective role of chlorogenic acid on DNA damage caused by ochratoxin A exposure ». Analecta Veterinaria 40, no 2 (21 octobre 2020) : 049. http://dx.doi.org/10.24215/15142590e049.
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Chlorogenic acid (ChlA) has shown short-term protective effects against the cyto-genotoxic effects of ochratoxin A (OTA). The present study evaluated the effect of oral administration of ChlA in male Wistar rats exposed to OTA. OTA (0.4 mg/kg bw/day), ChlA (5 mg/kg bw/day), or the combination of both, were administered orally to animals during 28 days. No deaths, decrease in feed consumption or change in the body weight of animals were observed in any group. In the OTA-treated group a decrease in locomotion as well as increased DNA damage in blood, kidney and bone marrow cells were observed. ChlA alone was not genotoxic for animals. The combination of OTA+ChlA decreased the DNA damage by 37% in blood cells, by 55% in kidney cells and by 80% in bone marrow cells compared to OTA-treated group. In conclusion, oral treatment with ChlA showed a good protective effect on genotoxicity produced by OTA in rats during 28 days exposure.
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Cai, Lina, Juan Bu, Danling Tang, Minrui Zhou, Ru Yao et Shuyi Huang. « Geosynchronous Satellite GF-4 Observations of Chlorophyll-a Distribution Details in the Bohai Sea, China ». Sensors 20, no 19 (24 septembre 2020) : 5471. http://dx.doi.org/10.3390/s20195471.
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We analyzed the distribution of chlorophyll-a (Chla) in the Bohai Sea area based on data from the geosynchronous orbit optical satellite Gaofen-4 (GF-4), which was launched in 2015, carrying a panchromatic multispectral sensor (PMS). This is the first time the geosynchronous orbit optical satellite GF-4 remote-sensing data has been used in China to detect the Chla change details in the Bohai Sea. A new GF-4 retrieved model was established based on the relationship between in situ Chla value and the reflectance combination of 2 and 4 bands, with the R2 of 0.9685 and the total average relative error of 37.42%. Twenty PMS images obtained from 2017 to 2019 were applied to analyze Chla in Bohai sea. The results show that: (1) the new built Chla inversion model PMS-1 for the GF-4 PMS sensor can extract Chla distribution details in the Bohai Sea well. The high Chla content in the Bohai Sea is mainly located in coastal areas, such as the top of Laizhou Bay, Bohai Bay and Liaodong Bay, with the value being around 13 µg/L. The concentration of Chla in the Bohai Strait and northern Yellow Sea is relatively low with the value being around 5 µg/L. (2). Taking full advantage of the continuous observation of geostationary orbit satellite, GF-4 with a high-resolution sensor PMS of 50 m can effectively detect short-term change (changes within 10 min) in Chla concentration. The changes mainly appear at the southwest and northeast costal area as well as in the center of Bohai Sea with the change value of around 3 µg/L. (3) The change of Chla concentration in the Bohai sea is related to the environmental factors such as seawater temperature, salinity, illumination and nutrient salts, as well as the dynamic factors such as wind, flow field and tidal current.
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Jia, Min, Dong Li, Roberto Colombo, Ying Wang, Xue Wang, Tao Cheng, Yan Zhu et al. « Quantifying Chlorophyll Fluorescence Parameters from Hyperspectral Reflectance at the Leaf Scale under Various Nitrogen Treatment Regimes in Winter Wheat ». Remote Sensing 11, no 23 (29 novembre 2019) : 2838. http://dx.doi.org/10.3390/rs11232838.
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Chlorophyll fluorescence (ChlF) parameters, especially the quantum efficiency of photosystem II (PSII) in dark- and light-adapted conditions (Fv/Fm and Fv’/Fm’), have been used extensively to indicate photosynthetic activity, physiological function, as well as healthy and early stress conditions. Previous studies have demonstrated the potential of applying hyperspectral data for the detection of ChlF parameters in vegetation. However, the performance of spectral features that have been documented to estimate ChlF is not ideal and is poorly understood. In this study, ChlF parameters and leaf reflectance were collected in two field experiments involving various wheat cultivars, nitrogen (N) applications, and plant densities, during the growing seasons of 2014 to 2015 and 2015 to 2016. Three types of spectral features, including vegetation indices (VIs), red edge position (REP), and wavelet features, were used to quantify ChlF parameters Fv/Fm and Fv’/Fm’. The results indicated that traditional chlorophyll fluorescence vegetation indices (ChlF VIs), such as the curvature index (CUR) and D705/D722 were capable of detecting Fv/Fm and Fv’/Fm’ under various scenarios. However, the wavelet-based REP (WREP-S4) and the wavelet feature (WF) (704 nm, scale 4) yielded higher accuracy than other spectral features in calibration and validation datasets. Moreover, the bands used to calculate WREP-S4 and WF (704 nm, scale 4) were all centered in the red edge region (680 to 760 nm), which highlighted the role of the red edge region in tracking the change of active ChlF signal. Our results are supported by previous studies, which have shown that the red edge region is vital for estimating the chlorophyll content, and also the ChlF parameters. These findings could help to improve our understanding of the relationships among active ChlF signal and reflectance spectra.
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Nababan, Bisman. « SEA SURFACE TEMPERATURE DAN CHLOROPHYLL-A CONCENTRATION VARIABILITIES OF JAKARTA BAY AND ITS SURROUNDING WATERS ». Jurnal Ilmu dan Teknologi Kelautan Tropis 8, no 1 (11 novembre 2016) : 385–402. http://dx.doi.org/10.29244/jitkt.v8i1.13915.
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Variability of sea surface temperature (SST) and the concentration of chlorophyll-a (Chla) in Jakarta Bay and its surrounding waters were analyzed based on the time series data of monthly mean SST and Chla estimated by NOAA AVHRR, SeaWiFS, and MODIS satellites for 17 years (1997 to 2014). Generally, the monthly mean SST values fluctuated seasonally with the semi-annual pattern with the maximum value occurred in the second transitional season (Oct-Nov) and relatively high in the first transitional season (Mar). In contrast, the minimum of monthly mean SST values was found during the east season (Jul) and relatively low during the west season (Des-Jan). SST variabilities were generally associated with the sun position, sea water circulation, and rainfall. Based on MODIS data, the minimum-maximum of monthly mean SST ranged of 28.39°C-32.58°C. Seasonal fluctuations with the semi-annual pattern also occurred in the monthly mean Chla values with the maximum value occurred during the west season (Des-Jan) and relatively high values occurred during the east season (Jun). In contrast, the minimum of the monthly mean Chla was found during the second transition season (Sep-Oct) and relatively low during the first transitional season (March-Apr). The minimum-maximum of monthly mean Chla ranged of 0.09 mg/m3-2.50 mg/m3. Chla fluctuations were generally associated with the variabilities of rainfall, river water discharge, and sea water circulation of the Java Sea. Anomalous climatic factors such as El Nino Southern Oscillation (ENSO) and La Nina produced a significant impact on the SST and Chla interannual variability. Generally, the ENSO phenomenon lo-wers the value SST and Chla, while La Nina events tended to increase Chla values.Keywords: sea surface temperature, chlorophyll-a, fluctuation, NOAA AVHRR, SeaWiFS, MODIS
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Cendrero-Mateo, M. Pilar, A. Elizabete Carmo-Silva, Albert Porcar-Castell, Erik P. Hamerlynck, Shirley A. Papuga et M. Susan Moran. « Dynamic response of plant chlorophyll fluorescence to light, water and nutrient availability ». Functional Plant Biology 42, no 8 (2015) : 746. http://dx.doi.org/10.1071/fp15002.
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Chlorophyll molecules absorb photosynthetic active radiation (PAR). The resulting excitation energy is dissipated by three competing pathways at the level of photosystem: (i) photochemistry (and, by extension, photosynthesis); (ii) regulated and constitutive thermal energy dissipation; and (iii) chlorophyll-a fluorescence (ChlF). Because the dynamics of photosynthesis modulate the regulated component of thermal energy dissipation (widely addressed as non-photochemical quenching (NPQ)), the relationship between photosynthesis, NPQ and ChlF changes with water, nutrient and light availability. In this study we characterised the relationship between photosynthesis, NPQ and ChlF when conducting light-response curves of photosynthesis in plants growing under different water, nutrient and ambient light conditions. Our goals were to test whether ChlF and photosynthesis correlate in response to water and nutrient deficiency, and determine the optimum PAR level at which the correlation is maximal. Concurrent gas exchange and ChlF light-response curves were measured for Camelina sativa (L.) Crantz and Triticum durum (L.) Desf plants grown under (i) intermediate light growth chamber conditions, and (ii) high light environment field conditions respectively. Plant stress was induced by withdrawing water in the chamber experiment, and applying different nitrogen levels in the field experiment. Our study demonstrated that ChlF was able to track the variations in photosynthetic capacity in both experiments, and that the light level at which plants were grown was optimum for detecting both water and nutrient deficiency with ChlF. The decrease in photosynthesis was found to modulate ChlF via different mechanisms depending on the treatment: through the action of NPQ in response to water stress, or through the action of changes in leaf chlorophyll concentration in response to nitrogen deficiency. This study provides support for the use of remotely sensed ChlF as a proxy to monitor plant stress dynamics from space.
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Sammartino, Michela, Salvatore Marullo, Rosalia Santoleri et Michele Scardi. « Modelling the Vertical Distribution of Phytoplankton Biomass in the Mediterranean Sea from Satellite Data : A Neural Network Approach ». Remote Sensing 10, no 10 (21 octobre 2018) : 1666. http://dx.doi.org/10.3390/rs10101666.
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Knowledge of the vertical structure of the bio-chemical properties of the ocean is crucial for the estimation of primary production, phytoplankton distribution, and biological modelling. The vertical profiles of chlorophyll-a (Chla) are available via in situ measurements that are usually quite rare and not uniformly distributed in space and time. Therefore, obtaining estimates of the vertical profile of the Chla field from surface observations is a new challenge. In this study, we employed an Artificial Neural Network (ANN) to reconstruct the 3-Dimensional (3D) Chla field in the Mediterranean Sea from surface satellite estimates. This technique is able to reproduce the highly nonlinear nature of the relationship between different input variables. A large in situ dataset of temperature and Chla calibrated fluorescence profiles, covering almost all Mediterranean Sea seasonal conditions, was used for the training and test of the network. To separate sources of errors due to surface Chla and temperature satellite estimates, from errors due to the ANN itself, the method was first applied using in situ surface data and then using satellite data. In both cases, the validation against in situ observations shows comparable statistical results with respect to the training, highlighting the feasibility of applying an ANN to infer the vertical Chla field from surface in situ and satellite estimates. We also analyzed the usefulness of our approach to resolve the Chla prediction at small temporal scales (e.g., day) by comparing it with the most widely used Mediterranean climatology (MEDATLAS). The results demonstrated that, generally, our method is able to reproduce the most reliable profile of Chla from synoptical satellite observations, thus resolving finer spatial and temporal scales with respect to climatology, which can be crucial for several marine applications. We demonstrated that our 3D reconstructed Chla field could represent a valid alternative to overcome the absence or discontinuity of in situ sampling.
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Ma, Ji Ping, Cui Jie Rui, Jian Hua Ge, Yu Hua Liu, Zhi Wen Song et Jie Li. « Correlation between Chlorophyll-a Concentration and Environmental Factors in Jihongtan Reservoir ». Advanced Materials Research 356-360 (octobre 2011) : 959–62. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.959.
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Based on the Jihogntan reservoir’s monitoring data from 2006 to 2009, eutrophication of Jihongtan reservoir was assessed. The result showed that the nutrition level of the Jihongtan reservoir was middle in recent years. The average concentration of chlorophyll-a(Chla) was higher in summer and autumn than in spring and winter. The correlation between concentration of Chla and some environmental factors was studied by statistical method, and seasonal variation of Chla and the extent of eutrophication were also analyzed. The results showed that the correlations between Chla and total nitrogen(TN), dissolved oxygen(DO) and transparency were significantly negative, and that between Chla and total phosphorus(TP), temperature(T) and potassium permanganate index(COD Mn) were significantly positive. The growth of phytoplankton was promoted by TP and TN at low concentrations, and inhibited by TN at high concentrations.
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Xiao, Xiao, Biyu Song, Xiongfei Wen, Dengzhong Zhao, Xuejun Cheng, Chengfang Hu, Jian Xu et Zhaohui Wang. « VIP-BP model for retrieving chlorophyll a concentration in the river by using remote sensing data ». Water Quality Research Journal 52, no 2 (24 mai 2015) : 136–50. http://dx.doi.org/10.2166/wqrj.2017.055.
Texte intégralRésumé :
Chlorophyll a (Chla) is an important indicator of phytoplankton biomass in waters, and its concentration can reflect the degree of eutrophication. This paper is aimed to develop a highly accurate and universally applicable retrieval model for the concentration of Chla in rivers using remote sensing data. Taking the middle and lower reaches of the Han River as the study area, the Chla retrieval model (VIP-BP model) is established by combining the Variable Importance Projection Index and BP neural algorithm and then calibrated by the measured data from 2012 to 2013. This model uses the VIP index for selection of the appropriate spectrum transformation form and input bands. Then, the BP neural network algorithm is integrated to estimate Chla concentration. After validation and comparison with the three-band model, the results suggest that the VIP-BP model could more accurately and really reflect the changes in Chla concentration than the three-band model in the study area. When Chla concentration decreases, the retrieval error of both models increases, while the error of the VIP-BP model is significantly lower than that of the three-band model, which indicates that the VIP-BP model is more stable and preferred.
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Prairie, Yves T., Carlos M. Duarte et Jacob Kalff. « Unifying Nutrient–Chlorophyll Relationships in Lakes ». Canadian Journal of Fisheries and Aquatic Sciences 46, no 7 (1 juillet 1989) : 1176–82. http://dx.doi.org/10.1139/f89-153.
Texte intégralRésumé :
We used data drawn from the literature to test some basic predictions derived from nutrient limitation theory. Contrary to expectation, nitrogen was not better correlated to chlorophyll in nitrogen limited lakes (as measured by the total nitrogen:total phosphorus (TN:TP) ratio). We also examined whether the variability in published relationships between chlorophyll a (Chla) and nutrient levels in lakes can be explained by differences in the relative concentrations of nitrogen and phosphorus (TN:TP ratio). Our results show that the coefficients and precision of the Chla = f(TP) and Chla = f(TN) regression equations vary systematically and concomitantly with TN:TP ratios, and are highest for lakes with TN:TP ratios of 23–28 (by weight). These findings were confirmed with independent data and explain the variability of published Chla = f(TP) relationships. We propose a model that predicts the coefficients of Chla = f(TP) and Chla = f(TN) equations for lakes with different TN:TP ratios. This model proved useful in predicting the chlorophyll trajectories of lakes over time. The results imply an "optimal" TN:TP ratio beyond which the relative rates of increase in chlorophyll with increasing nutrient concentrations are reduced.
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Qin, Zihong, Baozhen Ruan, Jian Yang, Zushuai Wei, Weiwei Song et Qiang Sun. « Long-Term Dynamics of Chlorophyll-a Concentration and Its Response to Human and Natural Factors in Lake Taihu Based on MODIS Data ». Sustainability 14, no 24 (15 décembre 2022) : 16874. http://dx.doi.org/10.3390/su142416874.
Texte intégralRésumé :
Chlorophyll-a plays an essential biochemical role in the eutrophication process, and is widely considered an important water quality indicator for assessing human activity’s effects on aquatic ecosystems. Herein, 20 years of moderate resolution imaging spectroradiometer (MODIS) data were applied to investigate the spatiotemporal patterns and trends of chlorophyll-a concentration (Chla) in the eutrophic Lake Taihu, based on a new empirical model. The validated results suggested that our developed model presented appreciable performance in estimating Chla, with a root mean square error (MAPE) of 12.95 μg/L and mean absolute percentage error (RMSE) of 29.98%. Long-term MODIS observations suggested that the Chla of Lake Taihu experienced an overall increasing trend and significant spatiotemporal heterogeneity during 2002–2021. A driving factor analysis indicated that precipitation and air temperature had a significant impact on the monthly dynamics of Chla, while chemical fertilizer consumption, municipal wastewater, industrial sewage, precipitation, and air temperature were important driving factors and together explained more than 81% of the long-term dynamics of Chla. This study provides a 20 year recorded dataset of Chla for inland waters, offering new insights for future precise eutrophication control and efficient water resource management.
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Anderson, Melanie. « CHLA/ABSC 2013 Conference Announcement ». Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada 33, no 3 (22 juillet 2014) : 157. http://dx.doi.org/10.5596/c12-045.
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Clairoux, Natalie, et Lindsey Sikora. « ABSC–CHLA 2014 Conference Announcement ». Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada 34, no 3 (9 décembre 2013) : 135. http://dx.doi.org/10.5596/c13-042.
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Editorial Team. « CHLA/ABSC 2008 Conference Announcement ». Evidence Based Library and Information Practice 3, no 1 (17 mars 2008) : 87. http://dx.doi.org/10.18438/b85g7s.
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I'm pleased to announce that registration for the 2008 CHLA/ABSC Conference to be held in Halifax, NS, from May 26 to 30, is now open. Visit the conference website at http://www.chla-absc.ca/2008/ and click on "Registration". The rate for the full conference for members is $300 for early bird registration. After April 11, a late charge of $80 will be charged.
CE details for most sessions are now on the website. Please note that registration for each of these sessions is limited to 25. A wide array of topics is being presented.
Project Management
Joanne Fraser
Learning Styles: Are You Smarter Than a Millennial? The challenges of generations working and learning together
Daniel Phelan and Sarah Wickett
Getting Started in Research
Andrew Booth
Evidence-Based Practice
Ann McKibbon
Grey Matters! Finding Grey Literature
Sarah Normandin and Amanda Hodgson
Canadian Copyright Law: Current Issues for Librarians
Teresa Scassa
Current Awareness Tools – Web 2.0
Ryan Deschamps and Kelli Wooshue
Creating Online Tutorials
Gwendolyn MacNairn
Come for the programme, come for the social events, come for the lobster, come for the history, come for the famous down east hospitality! A lot of effort is being expended to ensure this year's conference will be a very successful one.
Tim Ruggles
Publicity Committee
CHLA/ABSC 2008
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Ishikawa, Mayra, Luziadne Gurski, Tobias Bleninger, Harald Rohr, Nils Wolf et Andreas Lorke. « Hydrodynamic Drivers of Nutrient and Phytoplankton Dynamics in a Subtropical Reservoir ». Water 14, no 10 (11 mai 2022) : 1544. http://dx.doi.org/10.3390/w14101544.
Texte intégralRésumé :
Chlorophyll-a (chla) is an important parameter to assess water quality in lakes and reservoirs, since it is a proxy for phytoplankton biomass and primary production. The increasing availability of data with high spatial and temporal resolution allows assessing short-term dynamics and small-scale variations of chla within larger water bodies. In freshwater reservoirs, the nutrient concentrations and the physical conditions that control phytoplankton growth vary along their longitudinal extend. Here, we analyze how the flow paths of the inflowing river water into density-stratified reservoirs affect the vertical and longitudinal distribution of nutrients and chla. We combine spatially resolved and high-frequency measurements of chla from satellite remote sensing and in-situ sensors, with numerical simulations using a three-dimensional hydrodynamic model to assess the influence of density currents on chla dynamics along a subtropical drinking water reservoir in the south of Brazil. Chla did not have pronounced seasonal dynamics (4.9 ± 1.2 µg L−1, at the continuous measurement station); instead, spatial variability along the reservoir was more pronounced (4.4 ± 2.1 µg L−1, all monitored points within the euphotic zone). Most of the nutrients from the inflowing river were consumed in the upstream region, and phytoplankton in the lacustrine zone depended on internal loading. Temporal variability was observed only in the upstream region, and phytoplankton produced in that area was transported downstream by density currents, resulting in large concentrations of chla below the euphotic zone. The results of a hydrodynamic model that simulates the present state are in good agreement with the observations. Two simulated scenarios, where the density current patterns were altered, resulted only in slight variations in density currents, indicating that the influence of the main inflow was of minor relevance in chla concentrations in downstream regions of the reservoir. Our results highlight the importance of two-dimensional hydrodynamic processes in regulating phytoplankton dynamics in reservoirs.
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Lamont, Tarron, et Tesha Toolsee. « Spatial and Seasonal Variations of the Island Mass Effect at the Sub-Antarctic Prince Edward Islands Archipelago ». Remote Sensing 14, no 9 (29 avril 2022) : 2140. http://dx.doi.org/10.3390/rs14092140.
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At the sub-Antarctic Prince Edward Islands (PEIs) in the Southern Ocean, the Island Mass Effect (IME) plays an important role in maintaining an ecosystem able to support diverse biological communities; however, limited in situ sampling has severely constrained our understanding of it. As such, our study used satellite chlorophyll a (chla) to provide the first detailed characterisation of the spatial extent and seasonal variability of the IME at the PEIs. Seasonal surface chla variations were remarkable, with localised increases observed from mid-austral spring to the end of autumn (October to May). In contrast, during June to September, there were no distinguishable differences between chla at the PEIs and that further afield. Seasonal chla changes were significantly correlated with higher light levels, warmer waters, and shallow upper mixed layer depths reflecting enhanced water column stability during summer and autumn, with the opposite pattern in winter and spring. The IME extended northeast of the islands and remained spatially distinct from elevated chla around the northern branch of the sub-Antarctic Front and the southern branch of the Antarctic Polar Front. From December to February, the IME was spatially connected to the island shelf. In contrast, during March–May and in October, higher chla was observed only to the northeast, some distance away from the islands, suggesting a delayed IME, which has not previously been observed at the PEIs. The clear association of this higher chla with the weak mean geostrophic circulation northeast of the islands suggested retention and accumulation of nutrients and phytoplankton biomass, which was likely aided by wind-driven northeastward transport of water from the shelf. Climatological mean chla to the northeast was generally higher than that on the PEI shelf, and further research is required to determine the importance of this region to ecosystem functioning at the islands.
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Zheng, Ling, Evelyn L. Teng, Rohit Varma, Wendy J. Mack, Dan Mungas, Po H. Lu et Helena C. Chui. « Chinese-Language Montreal Cognitive Assessment for Cantonese or Mandarin Speakers : Age, Education, and Gender Effects ». International Journal of Alzheimer's Disease 2012 (2012) : 1–10. http://dx.doi.org/10.1155/2012/204623.
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The Montreal Cognitive Assessment Chinese-Language Los Angeles version (MoCA-ChLA) was developed and administered during an in-home interview to 1,192 participants (mean age 62.5 years, mean education 11.6 years) in a population-based Chinese American Eye Study (CHES) in Los Angeles. The MoCA-ChLA score (mean ± SD) was23.8±4.2with little ceiling and no floor effects. The score increased with higher education, decreased with advancing age, and was not related to gender. Compared to the education 1–6 years group, the mean MoCA-ChLA score was 2.6 and 4.6 higher in the education 7–11 and 12–20 years groups, respectively. The Mandarin- (n=612) and Cantonese- (n=612) speaking subgroups performed comparably; Cronbach's alpha of the MoCA-ChLA score was 0.78 and 0.79 for these two groups, respectively. Item response theory analysis showed good discriminating power for executive function and memory. These properties support the MoCA-ChLA as a useful screening tool for aging and dementia studies for Mandarin or Cantonese speakers.
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Ventura, Dhalton Luiz Tosetto, Jean-Michel Martinez, José Luiz de Attayde, Eduardo Sávio Passos Rodrigues Martins, Nilva Brandini et Luciane Silva Moreira. « Long-Term Series of Chlorophyll-a Concentration in Brazilian Semiarid Lakes from Modis Imagery ». Water 14, no 3 (28 janvier 2022) : 400. http://dx.doi.org/10.3390/w14030400.
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By monitoring the chlorophyll a concentration (chla), it is possible to keep track of the eutrophication status of a lake and to describe the temporal dynamics of the phytoplankton biomass. Such monitoring must be both extensive and intensive to account for the short- and long-term biomass variations. This may be achieved by the remote estimation of chla through an orbital sensor with high temporal resolution. In this study, we used MODIS imagery to produce 21-year time series of chla for three strategic lakes of the Brazilian semi-arid region: Eng. Armando Ribeiro Gonçalves, Castanhão, and Orós. We used data collected in 13 lakes of the region to test new and published regression models for chla estimation. The selected model was validated and applied to daily MODIS images for the three largest lakes. The resulting chla time series revealed that the temporal dynamics of the phytoplankton biomass is associated with the hydraulic regime of the lakes, with chla plummeting upon intense water renewal and keeping high during persistent dry periods. The intense rainy season of 2004 reduced the phytoplankton biomass and its effects even extended to the subsequent years. Our results encourage the exploration of the MODIS archived imagery in limnological studies.
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Campbell, Sandra Melody, Kelly Hatch et Nazi Torabi. « Identifying Research Support Needs of Members of the Canadian Health Libraries Association / Association des bibliothèques de la santé du Canada ». Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada 39, no 1 (4 avril 2018) : 3–15. http://dx.doi.org/10.29173/jchla29354.
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Introduction: The CHLA/ABSC Special Committee on Research undertook this project to identify potential ways in which the Association could support its members in undertaking research. The goal was to inform future CHLA/ABSCresearch-related service and program offerings. A literature review revealed limited publication related to health librarians' research needs. Method: The Committee developed and distributed an online survey to CHLA/ABSC’s membership. The questions related to demographics, previous research engagement or experience, current research support, work-related research requirements and expectations, barriers and enablers for conducting research, desired research support (topic and format) from CHLA/ABSC, and types of programs that would benefit members the most. Both qualitative and quantitative data were collated and analysed. Data from open-ended questions were examined to identify relevant themes. Results: Survey participants (45) were nearly equally divided between academic health libraries and hospital libraries. Forty-three members responded to the English survey, while two responded to the French version. Results showed that the barriers to research, and the research supports needed are similar for both academic health librarians and hospital librarians. Results showed a strong desire for methodological and statistical training. Conclusion: Through this study CHLA/ABSC members identified several kindsof preferred research support. CHLA/ABSC can use these findingsto guide the selection and delivery of furthercontinuing education products, as well as the development of specific research support services such as a peer-review program, a research question and answer blog and research mentorship; and also improve communications around CHLA/ABSC’s research services.
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Xu, Zhao, Xu Qian, Baoguo Shan, Jinhui Duan et Xiangdong Sun. « A fuzzy function model for remote evaluation of chlorophyll-a concentration in the Northern of South China Sea-Hong Kong ». E3S Web of Conferences 158 (2020) : 05001. http://dx.doi.org/10.1051/e3sconf/202015805001.
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Chlorophyll-a (Chla) concentration is an important indicator to monitor eutrophication, which is a persistent problem that affects the ecological health of coastal water or shallow lakes. We have applied a Gaussian-like fuzzy function model for the estimation of Chla concentration in Hong Kong Coastal Waters, based on the spectral signature using the HJ-1A /1B CCD images and measured data. The method of this paper is as follows. Firstly, reflectance peak and fluorescence band were used to figure out the bands or bands combination which impact the Chla concentration significantly; and then calculated the value of all the pixels without measured data according to their similarity degree with the measured points; finally, the full Chla concentration maps in the study area were produced by GIS spatial interpolation. It is concluded in this paper that the method can retrieve the Chla concentration accurately and the result of changes detected coincides with the observed result extremely, what’s more, the maps generated are continuous and smooth which are quite different from traditional RS maps that can only accurate to pixel size.
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Li, Haitao, Xuetong Xie, Xiankun Yang, Bowen Cao et Xuening Xia. « An Integrated Model of Summer and Winter for Chlorophyll-a Retrieval in the Pearl River Estuary Based on Hyperspectral Data ». Remote Sensing 14, no 9 (8 mai 2022) : 2270. http://dx.doi.org/10.3390/rs14092270.
Texte intégralRésumé :
Chlorophyll-a (Chla) is an important parameter for water quality. For remote sensing-based methods for the measurement of Chla, in-situ hyperspectral data is crucial for building retrieval models. In the Pearl River Estuary, we used 61 groups of in-situ hyperspectral data and corresponding Chla concentrations collected in July and December 2020 to build a Chla retrieval model that takes the two different seasons and the turbidity of water into consideration. The following results were obtained. (1) Based on the pre-processing techniques for hyperspectral data, it was shown that the first-derivative of 680 nm is the optimal band for the estimation of Chla in the Pearl River Estuary, with R2 > 0.8 and MAPE of 26.03%. (2) To overcome the spectral resolution problem in satellite image retrieval, based on the simulated reflectance from the Sentinel-2 satellite and the shape of the discrete spectral curve, we constructed a multispectral model using the slope difference index method, which reached a R2 of 0.78 and MAPE of 35.21% and can integrate the summer and winter data. (3) The slope difference method applied to the Sentinel-2 image shows better performance than the red-NIR ratio method. Therefore, the method proposed in this paper is practicable for Chla monitoring of coastal waters based on both in-situ data and images.
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Chu, Hone-Jay, Yu-Chen He, Wachidatin Nisa’ul Chusnah, Lalu Muhamad Jaelani et Chih-Hua Chang. « Multi-Reservoir Water Quality Mapping from Remote Sensing Using Spatial Regression ». Sustainability 13, no 11 (4 juin 2021) : 6416. http://dx.doi.org/10.3390/su13116416.
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Regional water quality mapping is the key practical issue in environmental monitoring. Global regression models transform measured spectral image data to water quality information without the consideration of spatially varying functions. However, it is extremely difficult to find a unified mapping algorithm in multiple reservoirs and lakes. The local model of water quality mapping can estimate water quality parameters effectively in multiple reservoirs using spatial regression. Experiments indicate that both models provide fine water quality mapping in low chlorophyll-a (Chla) concentration water (study area 1; root mean square error, RMSE: 0.435 and 0.413 mg m−3 in the best global and local models), whereas the local model provides better goodness-of-fit between the observed and derived Chla concentrations, especially in high-variance Chla concentration water (study area 2; RMSE: 20.75 and 6.49 mg m−3 in the best global and local models). In-situ water quality samples are collected and correlated with water surface reflectance derived from Sentinel-2 images. The blue-green band ratio and Maximum Chlorophyll Index (MCI)/Fluorescence Line Height (FLH) are feasible for estimating the Chla concentration in these waterbodies. Considering spatially-varying functions, the local model offers a robust approach for estimating the spatial patterns of Chla concentration in multiple reservoirs. The local model of water quality mapping can greatly improve the estimation accuracy in high-variance Chla concentration waters in multiple reservoirs.
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Sun, Dawei, Yueming Zhu, Haixia Xu, Yong He et Haiyan Cen. « Time-Series Chlorophyll Fluorescence Imaging Reveals Dynamic Photosynthetic Fingerprints of sos Mutants to Drought Stress ». Sensors 19, no 12 (12 juin 2019) : 2649. http://dx.doi.org/10.3390/s19122649.
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Resistance to drought stress is one of the most favorable traits in breeding programs yet drought stress is one of the most poorly addressed biological processes for both phenomics and genetics. In this study, we investigated the potential of using a time-series chlorophyll fluorescence (ChlF) analysis to dissect the ChlF fingerprints of salt overly sensitive (SOS) mutants under drought stress. Principle component analysis (PCA) was used to identify a shifting pattern of different genotypes including sos mutants and wild type (WT) Col-0. A time-series deep-learning algorithm, sparse auto encoders (SAEs) neural network, was applied to extract time-series ChlF features which were used in four classification models including linear discriminant analysis (LDA), k-nearest neighbor classifier (KNN), Gaussian naive Bayes (NB) and support vector machine (SVM). The results showed that the discrimination accuracy of sos mutants SOS1-1, SOS2-3, and wild type Col-0 reached 95% with LDA classification model. Sequential forward selection (SFS) algorithm was used to obtain ChlF fingerprints of the shifting pattern, which could address the response of sos mutants and Col-0 to drought stress over time. Parameters including QY, NPQ and Fm, etc. were significantly different between sos mutants and WT. This research proved the potential of ChlF imaging for gene function analysis and the study of drought stress using ChlF in a time-series manner.
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Hong, Tran Thi My, Young-Gyu Park et Jun Myoung Choi. « Divergence Observation in a Mesoscale Eddy during Chla Bloom Revealed in Submesoscale Satellite Currents ». Remote Sensing 15, no 4 (10 février 2023) : 995. http://dx.doi.org/10.3390/rs15040995.
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Oceanic mesoscale eddies continuously regulate the horizontal and vertical transport of mass, heat, salt, carbon, and nutrients throughout the ocean system owing to their ubiquity, three-dimensionality, and long-term persistence. Although satellites have been the main platforms used to observe mesoscale eddies and chlorophyll-a (Chla) distributions, they cannot support submesoscale physical–biological interactions. Contemporary satellite observations of Eulerian velocity fields are unable to resolve submesoscale processes that govern vertical migration and mixing, which are crucial for controlling the nutrients and light for phytoplankton in the surface layer. We explored the physical–biological interaction between the anticyclonic mesoscale eddy and the Chla secondary bloom that occurred after the spring bloom in the East/Japan Sea using the Geostationary Ocean Color Imager (GOCI). The GOCI currents were generated using GOCI Chla data and were used to map streamlines, vorticity, and divergence to characterize the surface current near the eddy. In the early spring bloom period, the eddy interior showed Chla depletion as the eddy was trapped externally. We found that the second bloom period coincided with a higher divergence or upwelling period in the eddy core, and a sharp Chla peak was observed when wind-induced Ekman suction was pronounced. This study describes the first satellite observation of surface layer divergence inside an anticyclonic mesoscale eddy with internal Chla blooms, utilizing a submesoscale-permitting GOCI-based surface current.
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Ganf, GG, RL Oliver et AE Walsby. « Optical properties of Gas-vacuolate cells and colonies of Microcystis in relation to light Attenuation in a Turbid, Stratified Reservoir (Mount Bold Reservoir, South Australia) ». Marine and Freshwater Research 40, no 6 (1989) : 595. http://dx.doi.org/10.1071/mf9890595.
Texte intégralRésumé :
Profiles of downwelling and upwelling irradiance were measured in a stratified, turbid reservoir, when Microcystis aeruginosa formed a significant proportion of the phytoplankton community. The attenuation coefficient (Kd) was c. 2.1 m-1 and the reflectance (R) c. 0.03. Application of Kirk's simulation model relating apparent and inherent optical properties enabled calculation of coefficients of absorption (a; 1.3-1.6 m-') and scattering (6; 5-7 m-1). The asymptotic diffuse backscattering coefficient (0.2 m-1) was derived from the relationship b′b = 3.6 RaKd, a slight modification of Kirk's original equation. Turbidity measurements supported the general rule that nephelometric turbidity was numerically equivalent to the scattering coefficient. There was good agreement between the measured light profile and one reconstructed from inherent optical properties using the relationship between Kd, a and b. The optical properties of cells and colonies of Microcystis were investigated before and after the collapse of gas vacuoles. The Chla-specific absorption coefficient for cells (0.0138 m2 mg,-1 Chla) was higher than for colonies (0.0106 m2 mg,-1 Chla) at a depth equivalent to 0.2 m. Both coefficients decreased with increasing depth as the spectral composition changed. The Chla-specific scattering coefficient for vacuolate cells (0.14 m2 mg,-1 Chla) was greater than for colonies (0.11 m2 mg,-1 Chla), and a similar correspondence occurred for non-vacuolate cells and colonies (0.029 and 0.020 m2 mg,-1 Chla respectively). These measurements illustrate the package effect and also that c. 80% of light scattering is due to gas vacuoles. The relationship between pressure-sensitive turbidity and gas-vacuole volume suggested that 1 gL mL-1 was equivalent to a turbidity of 2 NTU. These optical characteristics, combined with the buoyant nature of Microcystis, suggest that it is a canopy species.
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Rajewicz, Paulina, Jon Atherton, Luis Alonso et Albert Porcar-Castell. « Leaf-Level Spectral Fluorescence Measurements : Comparing Methodologies for Broadleaves and Needles ». Remote Sensing 11, no 5 (5 mars 2019) : 532. http://dx.doi.org/10.3390/rs11050532.
Texte intégralRésumé :
Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650–850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF spectral bands, and photosynthetic functionality. Despite its importance and significance, the various methodologies for the estimation of leaf-level ChlF spectral properties have not yet been compared, especially when applied to leaves with complex morphology, such as needles. Here we present, to the best of our knowledge, a first comparison of protocols for measuring leaf-level ChlF spectra: a custom-made system designed to measure ChlF spectra at ambient and 77 K temperatures (optical chamber, OC), the widely used FluoWat leaf clip (FW), and an integrating sphere setup (IS). We test the three methods under low-light conditions, across two broadleaf species and one needle-like species. For the conifer, we characterize the effect of needle arrangements: one needle, three needles, and needle mats with as little gap fraction as technically possible. We also introduce a simple baseline correction method to account for non-fluorescence-related contributions to spectral measurements. Baseline correction was found especially useful in recovering the spectra nearby the filter cut-off. Results show that the shape of the leaf-level ChlF spectra remained largely unaffected by the measurement methodology and geometry in OC and FW methods. Substantially smaller red/far-red ratios were observed in the IS method. The comparison of needle arrangements indicated that needle mats could be a practical solution to investigate temporal changes in ChlF spectra of needle-like leaves as they produced more reproducible results and higher signals.
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Soondur, Mouneshwar, Sundy Ramah, Ravindra Boojhawon, Deepeeka Kaullysing et Ranjeet Bhagooli. « Spatial distribution of surface chlorophyll a and micro-phytoplankton density and diversity around two islands and at two banks of the Mascarene region ». Western Indian Ocean Journal of Marine Science, no 2/2021 (20 juillet 2022) : 33–51. http://dx.doi.org/10.4314/wiojms.si2021.2.3.
Texte intégralRésumé :
The present study validated the use of AquaMODIS sea surface chlorophyll a (Chla) concentrations and investigated the spatial variation in density and diversity of micro-phytoplankton around two islands and two fishing banks of the Mascarene region. The study included areas around Mauritius (MRU) and Rodrigues (ROD) Islands, at Nazareth (NZ) Bank, and in the Joint Management Area (JMA) between the Republic of Mauritius and the Republic of Seychelles, more specifically at the Saya de Malha (SM) Bank. The AquaMODIS data were based on 67 match-up data points of in-situ against satellite Chla concentrations. The micro-phytoplankton community structure was investigated by determining the density variation and using the Shannon Wiener (H’) and Evenness (Evar) diversity indices. The satellite and in-situ Chla data were significantly and positively correlated when pooled for the four sites studied (R2 = 0.441; r = 0.642, P < 0.01), and when analysed separately for islands (R2 = 0.480; r = 0.694), and banks (R2 = 0.233; r = 0.483). However, the Chla satellite values tended to be lower than the in-situ Chla data. The highest densities of micro-phytoplankton were observed in the eastern and northern regions for MRU and ROD, respectively. The most dominant genera of micro-phytoplankton were Coscinodiscus, Navicula, Chaetoceros and Ceratium. The Shannon-Wiener diversity index values for diatoms were all above 2.5 with waters around the islands having higher diversity compared to the banks. Overall, the different micro-phytoplankton around the islands, except for the group of cyanobacteria at ROD Island, were more evenly distributed (Evar > 0.6) compared to the banks. This study indicated that AquaMODIS Chla satellite data is valid and may be potentially used as a proxy for in-situ Chla concentration on the Mascarene Plateau. The results of this study also provide detailed insight into the spatial variation in micro-phytoplankton density and diversity on the Mascarene Plateau in the Western Indian Ocean. Further long-term studies are warranted to thoroughly understand the temporal (including seasonal and inter-annual) variations in Chla and micro-phytoplankton distribution for adequate and appropriate management of these ocean territories.
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Syariz, Muhammad Aldila, Chao-Hung Lin, Dewinta Heriza, Umboro Lasminto, Bangun Muljo Sukojo et Lalu Muhamad Jaelani. « A Transfer Learning Technique for Inland Chlorophyll-a Concentration Estimation Using Sentinel-3 Imagery ». Applied Sciences 12, no 1 (25 décembre 2021) : 203. http://dx.doi.org/10.3390/app12010203.
Texte intégralRésumé :
Chlorophyll-a (Chla) concentration, which serves as a phytoplankton substitute in inland waters, is one of the leading indicators for water quality. Generally, water samples are analyzed in professional laboratories, and Chla concentrations are measured regularly for the purpose of water quality monitoring. However, limited spatial water sampling and the labor-intensive nature of data collection make global and long-term monitoring difficult. The developments of remote-sensing optical sensors and technologies make the long-term monitoring of Chla concentrations for an entire water body more achievable. Many studies based on machine learning techniques, such as regression and artificial neural network (ANN) methods, have recently been proposed for Chla concentration estimation using optical satellite images. The methods based on machine learning can achieve accurate estimation. However, overfitting problems may arise because the in situ Chla dataset is generally insufficient to train a complicated machine learning model, which makes trained models inapplicable. In this study, an ANN model containing three convolutional and two fully connected layers with 4953 unknown parameters is designed. A transfer learning method, consisting of model pretraining, main-training, and fine-tuning stages, is proposed to ease the problem of insufficient in situ samples. In the model pretraining stage, the ANN model is pretrained and initialized using samples derived from an existing Chla concentration model. The pretrained ANN model is then fine-tuned using the proposed transfer learning technique with in situ samples collected in five different campaigns carried out during early 2019 from Laguna Lake, the Philippines. Before the transfer learning, data augmentation and rebalancing methods are conducted to enrich the variability and to near-uniformly distribute the in situ samples in Chla concentration space, respectively. To estimate the alleviation of model overfitting, the trained ANN model, using an in situ dataset from Laguna Lake, was tested using an in situ dataset from Lake Victoria, Uganda, obtained in 2019, which has a similar trophic state as Laguna Lake. The experimental results from Sentinel-3 imagery indicated that the overfitting problem was significantly alleviated and the trained ANN model outperformed related models in terms of the root-mean-squared error of the estimated Chla concentrations.
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Sakuno, Yuji, Akihiro Maeda, Akihiro Mori, Shuji Ono et Akihiro Ito. « A Simple Red Tide Monitoring Method using Sentinel-2 Data for Sustainable Management of Brackish Lake Koyama-ike, Japan ». Water 11, no 5 (20 mai 2019) : 1044. http://dx.doi.org/10.3390/w11051044.
Texte intégralRésumé :
We proposed and validated a method for monitoring red tides in the brackish Lake Koyama-ike, Japan, using Sentinel-2 Multispectral Instrument (MSI) data with a 10 m spatial resolution. To achieve this objective, we acquired 36 spectral reflectance/Chla data points in the field from 2012 to 2018. We obtained a high correlation of Chla (R2 = 0.83) using the proposed red tide model (RIKY = [MSI Band 5 – MSI Band 4]/[MSI Band 5 + MSI Band 4]) and field data. Based on our results, the proposed model was also validated using five Sentinel-2/Chla datasets from April to August 2017. Chla and red tide distribution characteristics estimated from Sentinel-2 data hardly appeared from April to July, and then spread rapidly throughout the lake (more than 70%) in August. Thus, Sentinel-2 data proved to be a very powerful tool in monitoring red tides in Lake Koyama-ike.
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Wang, Shuai, Dianyuan Chen, Xi Zhang, Junping Xu, Wanying Lei, Changyan Zhou, Chen Chen, Fanghui Li et Nan Wang. « Humus composition of mineral–microbial residue from microbial utilization of lignin involving different mineral types ». Canadian Journal of Soil Science 99, no 2 (1 juin 2019) : 208–16. http://dx.doi.org/10.1139/cjss-2018-0135.
Texte intégralRésumé :
This study explored the mineral contribution of lignin to humus (HS) formation through the change of HS composition in microbial–mineral residue (MMR). The liquid shake flask culture method was adopted to collect the MMR formed through the microbial utilization of lignin in the presence of goethite, bayerite, δ-MnO2, kaolinite, and montmorillonite. The carbon (C) contents of humic-like acid (HLA), fulvic-like acid (FLA), and humin-like (HLu) in MMR, represented as CHLA, CFLA, and CHLu, respectively, coupled with the ΔlogK of the HLA alkali-soluble extract and CHLA/CFLA ratio were analyzed at 10, 30, 60, and 110 d. In terms of improving HLA aggregated on minerals, the following rule was observed: goethite > bayerite > montmorillonite > kaolinite ≈δ-MnO2. Goethite was most likely to adsorb organic molecules with a high degree of polymerization. Compared with kaolinite and montmorillonite, goethite, bayerite, and δ-MnO2 were more helpful for decreasing the molecular weight and the degree of HLA condensation. Goethite, δ-MnO2, and montmorillonite presented the greatest advantages in enhancing the relative proportions of CHLA, CFLA, and CHLu, respectively, in MMR. In MMR formed in the presence of kaolinite, goethite, and bayerite, CHLA was decreased by 14.8%, 12.0%, and 5.8%, respectively, at the end of culture, whereas the CHLA associated with δ-MnO2 was increased by 12.0%. δ-MnO2 contributed the most to the conversion of CFLA to CHLA. Due to expandability and a much greater adsorption capacity, montmorillonite was most beneficial to the accumulation of CHLu.
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Hilborn, Andrea, et Maycira Costa. « Applications of DINEOF to Satellite-Derived Chlorophyll-a from a Productive Coastal Region ». Remote Sensing 10, no 9 (11 septembre 2018) : 1449. http://dx.doi.org/10.3390/rs10091449.
Texte intégralRésumé :
A major limitation for remote sensing analyses of oceanographic variables is loss of spatial data. The Data INterpolating Empirical Orthogonal Functions (DINEOF) method has demonstrated effectiveness for filling spatial gaps in remote sensing datasets, making them more easily implemented in further applications. However, the spatial and temporal coverage of the input image dataset can heavily impact the outcomes of using this method and, thus, further metrics derived from these datasets, such as phytoplankton bloom phenology. In this study, we used a three-year time series of MODIS-Aqua chlorophyll-a to evaluate the DINEOF reconstruction output accuracy corresponding to variation in the form of the input data used (i.e., daily or week composite scenes) and time series length (annual or three consecutive years) for a dynamic region, the Salish Sea, Canada. The accuracy of the output data was assessed considering the original chla pixels. Daily input time series produced higher accuracy reconstructing chla (95.08–97.08% explained variance, RMSExval 1.49–1.65 mg m−3) than did all week composite counterparts (68.99–76.88% explained variance, RMSExval 1.87–2.07 mg m−3), with longer time series producing better relationships to original chla pixel concentrations. Daily images were assessed relative to extracted in situ chla measurements, with original satellite chla achieving a better relationship to in situ matchups than DINEOF gap-filled chla, and with annual DINEOF-processed data performing better than the multiyear. These results contribute to the ongoing body of work encouraging production of ocean color datasets with consistent processing for global purposes such as climate change studies.
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Балаев, Д. А., С. И. Попков, А. А. Красиков, А. Д. Балаев, А. А. Дубровский, С. В. Столяр, Р. Н. Ярославцев, В. П. Ладыгина et Р. С. Исхаков. « Температурное поведение антиферромагнитной восприимчивости нано-ферригидрита из измерений кривых намагничивания в полях до 250 kOe ». Физика твердого тела 59, no 10 (2017) : 1920. http://dx.doi.org/10.21883/ftt.2017.10.44959.115.
Texte intégralRésumé :
Рассмотрена проблема кроссовинга температурной зависимости антиферромагнитной восприимчивости наночастиц ферригидрита. Атомы железа Fe3+ в ферригидрите упорядочены антиферромагнитно, однако наличие дефектов на поверхности и в объеме наночастиц индуцирует нескомпенсированный магнитный момент, что приводит к типичному суперпарамагнитному поведению ансамбля наночастиц с характерной температурой блокировки. В разблокированном состоянии кривые намагничивания таких объектов описываются как суперпозиция функции Ланжевена и линейного по полю вклада от антиферромагнитной "сердцевины" частиц. По результатам большого количества исследований кривых намагничивания, проводимых на наночастицах ферригидрита (и родственного ему ферритина) в диапазоне полей до 60 kOe, зависимость chiAF(T) убывает с ростом температуры, что связывалось ранее с эффектом суперантиферромагнетизма. При увеличении диапазона магнитных полей до 250 kOe значения chiAF, получаемые из анализа кривых намагничивания, становятся меньшими по величине, однако изменяется характер температурной эволюции chiAF: теперь зависимость chiAF(T) --- возрастающая функция. Последнее типично для системы AF частиц со случайной ориентацией кристаллографических осей. Для корректного определения антиферромагнитной восприимчивости AF наночастиц (по крайней мере, ферригидрита) и поиска эффектов, связанных с эффектом суперантиферромагнетизма, необходимо в эксперименте использовать диапазон полей, значительно превышающий используемый в большинстве работ стандартное значение 60 kOe. Анализ температурной эволюции кривых намагничивания показал, что обнаруженный кроссовер обусловлен наличием малых магнитных моментов в образцах. Исследование выполнено при финансовой поддержке Российского фонда фундаментальных исследований, Правительства Красноярского края, Красноярского краевого фонда поддержки научной и научно-технической деятельности в рамках научных проектов N 17-42-240138, 17-43-240527. DOI: 10.21883/FTT.2017.10.44959.115
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Blanchard, Laurie. « 2012 CHLA/ABSC Association Award Winners ». Journal of the Canadian Health Libraries Association / Journal de l'Association des bibliothèques de la santé du Canada 33, no 2 (21 juillet 2014) : 35. http://dx.doi.org/10.5596/c2012-028.
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Sosa, Ivan J., Mark D. Krieger et J. Gordon McComb. « Craniopharyngiomas of childhood : the CHLA experience ». Child's Nervous System 21, no 8-9 (18 juin 2005) : 785–89. http://dx.doi.org/10.1007/s00381-005-1225-2.
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Song, Yumeng, et Jing Zhang. « Monitoring and simulating the distribution of phytoplankton in constructed wetlands based on SPOT 6 images ». Open Geosciences 13, no 1 (1 janvier 2021) : 454–68. http://dx.doi.org/10.1515/geo-2020-0243.
Texte intégralRésumé :
Abstract We integrated hyperspectral and field-measured chlorophyll-a (Chl-a) data from the Kristalbad constructed wetland in the Netherlands. We developed a best-fit band ratio empirical algorithm to generate a distribution map of Chl-a concentration (C chla) from SPOT 6 imagery. The C chla retrieved from remote sensing was compared with a water quality model established for a wetland pond system. The retrieved satellite results were combined with a water quality model to simulate and predict the changes in phytoplankton levels. The regression model provides good retrievals for Chl-a. The imagery-derived C chla performed well in calibrating the simulation results. For each pond, the modeled C chla showed a range of values similar to the Chl-a data derived from SPOT 6 imagery (10–25 mg m−3). The imagery-derived and prediction model results could be used as the guiding analytical tools to provide information covering an entire study area and to inform policies.
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Hou, Pengfei, Yi Luo, Kun Yang, Chunxue Shang et Xiaolu Zhou. « Changing Characteristics of Chlorophyll a in the Context of Internal and External Factors : A Case Study of Dianchi Lake in China ». Sustainability 11, no 24 (17 décembre 2019) : 7242. http://dx.doi.org/10.3390/su11247242.
Texte intégralRésumé :
During the past 20 years, the ecological environment of Dianchi Lake has been adversely affected by climate change and human activities, which directly affected the ecosystem and biodiversity of the Dianchi Lake watershed. Analyzing the spatiotemporal variation of chlorophyll a (Chla) concentration of Dianchi Lake and exploring the internal and external factors effect on Chla concentration is the basis for controlling and improving the water ecological environment of Dianchi Lake, and it is also the key to prevent and control the water pollution of Dianchi Lake. In this study, the water quality of Dianchi Lake was examined using 12 water quality indicators from 10 water quality monitoring sites for the duration between 2000 to 2017. The changing characteristics of Chla in the context of internal and external factors were analyzed. The spatiotemporal evolution process of Chla concentration in the past 20 years was also evaluated. The results indicated that Chla concentration was significantly and positively correlated with the chemical oxygen demand (CODCr), the Dianchi Lake watershed gross domestic product (GDP), and the impervious surface area (ISA) of the watershed, in addition to the total phosphorus (TP), biochemical oxygen demand (BOD5), ammonia hydrogen (NH3-N), water temperature (WT), and civil vehicle ownership. Moreover, a significant and negative correlation was noticed between Dianchi Lake watershed GDP and NH3-N, BOD5, TP, total nitrogen (TN), and comprehensive nutrition state index (TLI). The Dianchi Lake population was negatively correlated with TP, TLI, and BOD5. The concentration of Chla in Dianchi Lake was affected by both internal factors, and external factors such as anthropogenic activities, the latter of which was the main cause of the continuous deterioration of the lake water quality.