Light Attenuation Coefficient Research Articles

Compatibilities of Cyprinus carpio with Varied Colors of Robotic Fish

Visual selection plays a fundamental role in various aspects of animal behavior, such as colony formation, maintenance, defense, and courtship. This study investigated the effect of bionic robot fish color on carp behavior based on physiological characteristics that were observed during behavioral experiments. Through computer image processing and analysis of light attenuation, we observed changes in the number and positioning of carp with bionic robotic fish of different colors (white, red, blue, green, and yellow). The results indicated that (1) the attenuation coefficient of visible light in freshwater was red > yellow > green > blue; (2) the order of the average change in the number of carp responding to different colors of robotic fish was white > red > green > yellow > blue, and carp were more sensitive and responsive to white and red robotic fish; and (3) the order of the distances between different colors of robotic fish and carp was white < yellow < blue < green < red, and white and yellow robotic fish were more attractive to carp. Therefore, the use of white or yellow robotic fish for relevant operations can reduce disturbance to fish schools.

Effects of combined ecological restoration measures on water quality and underwater light environment of Qingshan Lake, an urban eutrophic lake in China

Ecological restoration is vital in the management of eutrophic lakes. However, the effect of combined ecological restoration measures on the improvement of water quality and the light environment of urban eutrophic lakes requires further exploration. This study considered Qingshan Lake, a typical urban eutrophic lake in the middle reaches of the Yangtze River in China and explored the changes in the water quality and light environment before and after the implementation of combined ecological restoration measures from 2021 to 2022. The results showed that: (1) Ecological restoration significantly improved the transparency of Qingshan Lake (P < 0.05), with transparency increased from 33.1 cm to 96.0 cm. Total phosphorus, total nitrogen, chlorophyll a, permanganate index, suspended solids and turbidity decreased by 52.11 %, 65.47 %, 73.84 %, 92.11 %, 83.11 % and 77.52 %; respectively (P < 0.05). (2) Following ecological restoration, Qingshan Lake converted from severe eutrophication to mesotrophication, and the trophic level index decreased from 75.29 to 49.65 (P < 0.05). (3) Ecological restoration had a significant effect on improving underwater light environments. After ecological restoration, the light attenuation coefficient changed between 1.61–3.12 m−1, and the annual mean value decreased by 61.96 % (P < 0.05). The euphotic zone depth changed from 1.85 to 6.19 m, an increase of 167.68 %. (4) Ecological restoration reduced the attenuation of blue light, which reduced the red-blue ratio (R/B) of water. In general, turbidity had the greatest impact on light attenuation and R/B of Qingshan Lake, and ecological restoration combined with multiple measures had a positive effect on the management of eutrophic lakes.

Do attenuation coefficients based on luminescence bleaching fronts reflect true light attenuation in rocks?

The emerging technique of rock surface luminescence dating employs a double-exponential fitting dating model based on the Bouguer-Lambert law. The accuracy of exposure age determination is sensitive to the light attenuation coefficient, μ, which is usually derived from fitting the luminescence profile as a function of depth into the rock. Alternatively, μ might be determined by direct measurement using a spectrophotometer. However, their directly measured values of μ were significantly larger than those estimated from field luminescence bleaching data. Here, we aim to confirm these previous results by measuring the luminescence-depth profiles of both IRSL and IRPL signals from granite rock exposed to different light sources, including sunlight, SOL2 and IR LEDs under controlled conditions. We also measured monochromatic light (blue LED: (470 ± 30) nm, green LED: (520 ± 30) nm, and infrared LED: (850 ± 30) nm) attenuation in granite rock slices of varying thickness (0.62–2.60 mm) using a high-sensitivity photodiode. Finally, we use a camera-based measurement system and a Risø Luminescence Imager to investigate spatial variation in transmitted light as a function of slice thickness. The spatial correlation between direct light transmission and luminescence emission is then investigated, to investigate the underlying reasons for the difference between direct measurement and luminescence-based estimates of μ. We find that light attenuation through a granite rock slice is very heterogeneous; most light penetrates through localized low attenuation light paths corresponding to transmission through the most transparent grains, presumably quartz. The light penetration and escape into the surrounding matrix are assumed to be influenced by the surface area of quartz grains. As a result, transmissive light paths result in a significant area of feldspar grains at depth in the slice being exposed to more light than might be expected from average attenuation measurement. When the incident light predominantly travels through feldspar minerals, simultaneously stimulating luminescence from within any potassium feldspar (K-feldspar), the attenuation coefficients derived from the luminescence-depth profiles tend to be smaller than the average of 1.18 ± 0.07 (n = 79) irrespective of the kinetic model used for fitting. Thus, luminescence-based attenuation coefficient estimates appear to be affected by the distribution of light attenuation across and within the rock slice, making such estimates preferable to directly measured (average) estimates of light attenuation coefficients. These insights are important for our understanding of the significance of light attenuation coefficients in rock samples; they contribute to the reassessment of parameters and measurement methods in dating models and so to improvements in accuracy of rock surface luminescence dating techniques.

Algorithms to retrieve the spectral diffuse attenuation coefficient of light in the ocean from remote sensing.

We recently found a significant bias between spectral diffuse attenuation coefficient (Kd(λ)) retrievals by common ocean color algorithms and measurements from profiling floats [Remote. Sens.14, 4500 (2022)10.3390/rs14184500]. Here we show, using a multi-satellite match-up dataset, that the bias is markedly reduced by simple "tuning" of the algorithm's empirical coefficients. However, while the float dataset encompasses a larger proportion of the ocean's variability than previously used datasets, it does not cover the whole range of variability of observed remote sensing reflectance (Rrs). Thus, using algorithms tuned to this more comprehensive dataset may still result in a temporal and/or geographical bias in global application. To address this generalization issue, we evaluated a variety of analytical algorithms based on radiative transfer theory and settled on a specific one. This algorithm computes Kd(λ) from inherent optical properties (IOPs) obtained from an Rrs inversion and information about the angular distribution of the radiance transmitted through the air/ocean interface. The resulting Kd(λ) estimates at 412 and 490 nm were not appreciably biased against the float measurements. Evaluation using other in-situ datasets and radiative transfer simulations was also satisfactory. Statistical performance was good in both clear and turbid waters. Further work should be conducted to examine whether the tuned algorithms and/or the new analytical algorithm demonstrate adequate hyperspectral performance.

Degradation of fishing grounds in North Waters of Banten Province, Indonesia

The high level of fishing activity with small fishing vessels has resulted in relatively high utilization of marine space in coastal areas, manifesting changes in fishing grounds. Thus, this research aimed to analyze water quality, fishing intensity and to determine the level of degradation of fishing grounds in the northern waters of Banten Province. This research was conducted from June to August 2023 in the northern waters of Banten Province. Data collection was carried out using survey, remote sensing, and interview methods. Water quality data consisting of sea surface temperature, brightness, salinity, light attenuation coefficient, total suspended solids, and chlorophyll-a were analyzed descriptively. Eco-friendly capture fisheries data were taken directly from 120 fishermen and analyzed based on the CCRF criteria. Degradation status was determined by combining weight of water quality conditions and eco-friendly capture fisheries. Based on the research results, the northern waters of Banten Province is in good condition for biota life. Fishing equipment is dominated by eco-friendly fishing gear. Nevertheless, several parts of northern waters in Banten Province have experienced light degradation of fishing areas (18.28%) and the heavy degradation (7.71%). The use of marine space for capture fisheries in the northern waters of Banten Province is relatively high, around 50 units of fishing gear for 1 hectare of water.Keywords:EnvironmentFishing intensityFishing gearSpatial mappingWater quality

Northward range expansions are not the full story: A case study of Sabellaria alveolata in Great Britain

Warming oceans are causing changes in the distribution of numerous species. If greenhouse gas production continues to follow current trends, further distribution changes will result. It is often assumed that range shifts into higher latitudes may mitigate threats to susceptible species. Sabellaria alveolata is an important intertidal ecosystem engineer and protected by the UK Biodiversity Action Plan. In this study we created a habitat suitability model for S. alveolata around Great Britain and quantified changes in coastal suitability with increasing sea surface temperatures (SST) using Representative Concentration Pathway (RCP) scenarios modelled by the International Panel on Climate Change. The model included maximum and minimum SST, substrate, slope, kinetic energy due to waves and currents, photosynthetically active radiation, and the coefficient of light attenuation. The model performed very well (AUC = 0.932, 50.2% of deviance explained) and all variables explaining comparable deviance (up to 10%). Recent SST was then combined with predicted SST increases, leading to suitable habitat locations expanding across the southern and western GB coastlines and resulting in larger patches, hence potential for connectivity. Some northern extension was observed; however, this was limited and patchy. The greatest extensions were seen on the south coast, with most of the south coast becoming a continuous network with excellent suitability. With an increase of 1.2 °C, the extent of coast in the excellent suitability class was increased by 5.75% compared to 2020, and by 38.1% with 3.2 °C. Despite the importance of winter temperature in driving S. alveolata distribution, over-riding environmental constraints prevented any major northward migration. The assertion that potential for range shifts to higher latitudes may mitigate the effects of climate change depends on niche availability which may not always be realised.

Annual and Interannual Variability in the Diffuse Attenuation Coefficient and Turbidity in Urbanized Washington Lake from 2013 to 2022 Assessed Using Landsat-8/9

Water clarity, defined in this study using measurements of the downwelling diffuse light attenuation coefficient (Kd) and turbidity, is an important indicator of lake trophic status and ecosystem health. We used in-situ measurements to evaluate existing semi-analytical models for Kd and turbidity, developed a regional turbidity model based on spectral shape, and evaluated the spatial and temporal trends in Lake Washington from 2013 to 2022 using Landsat-8/9 Operational Land Imager (OLI). We found no significant trends from 2013 to 2022 in Kd or turbidity when both the annual and full datasets were considered. In addition to the spring peak lasting from April through June, autumn Kd peaks were present at all sites, a pattern consistent with seasonal chlorophyll a and zooplankton concentrations. There existed no autumn peak in the monthly turbidity dataset, and the spring peak occurred two months before the Kd peak, nearly mirroring seasonal variability in the Cedar River discharge rates over the same period. The Kd and turbidity algorithms were thus each more sensitive to different sources of water clarity variability in Lake Washington.

Light response uniformity of LuAG:Ce scintillating single crystal fiber grown by laser heated pedestal growth method

Own to its fine granularity and sub-millimeter position information, scintillating single crystal fibers (SSCFs) hold great potential for various applications such as electromagnetic calorimeters, positron emission tomography, and radiotherapy dosimetry. The light response uniformity of scintillating fibers is an important parameter for precise measurements of ionizing radiation. Three methods were designed to investigate the light response uniformity of the 184-mm-long LuAG:Ce SCCF. Relatively longitudinal-distributed uniformity of cerium element was obtained in this SSCF. The scintillation light attenuation coefficient of the SSCF is 0.27 cm−1 induced by X-ray photons with single-end readout mode and about 0.29 cm−1 induced by gamma rays with dual-end readout mode. The Ce3+ ions self-absorption along the longitudinal light propagation process is one of main reasons for the scintillation light attenuation. Weakening the Ce3+ ions’ self-absorption effect is a possible way to improve the light response uniformity of the LuAG:Ce SSCF.

Spatial-Temporal Regularities of Hydrooptical Characteristics of the Ob River

Field studies conducted in spring (March 26 — April 9, 2022) and summer (June 5-16, 2022) in the Ob River mouth region at the three hydromorphological stations „Kazym-Mys“, „Azovy“, and „Salemal“ (YaNAO) to obtain new data on the hydrooptical characteristics of water in the Lower Ob river. Also, the trophic status and ecological state of the Lower Ob river region were assessed. The greatly varying light attenuation coefficient ε(λ) was calculated at the four characteristic wavelengths of 430, 450, 550, and 670 nm, respectively. It ranges from 9.3 m-1 to 22.1 m-1 during the winter low water (freeze-up) period and from 7.3 m-1 to 33.0 m-1 during the open water (high water) period. The calculated relative spectral contributions of major optically active components of water (pure water, suspension, yellow substance, chlorophyll) to ε(λ) suggest that suspension and yellow substance make up the maximal contribution at different horizons. Additionally, the calculated coefficient of light absorption by yellow substance кys(λ) varies within the ranges from 5.5 m-1 to 9.9 m-1 (spring) and from 3.1 m-1 to 17.0 m-1 (summer), respectively. The relative transparency was measured using the Secchi disc. The concentrations of yellow substance and major photosynthetic pigments — chlorophylls a, b, c, and carotenoids — were estimated alongside. The obtained results could be useful for environmental monitoring and predicting the dynamics of aquatic ecosystems in the region under climate change and increased anthropogenic pressure caused by the use of natural resources.

A fjord with a land-terminating glacier: Meltwater, bio-optics, particulate matter, nutrients, phytoplankton species, and primary production in west Greenland

Land-terminating glaciers and submarine melting of marine-terminating glaciers are significant features in Arctic regions and are foreseen to become more frequent as marine-terminating glaciers ultimately develop into a land-terminated state. A transition driven by the continuous rise in Arctic air temperatures, and emphasizes the importance of studies of land-terminating glaciers their bio-optical properties and biogeochemistry. Kangerlussuaq in west Greenland with a land-terminating glaciers and was selected for this study. During a research cruise we measured spectral and PAR attenuation, particulate matter concentrations, salinity, nutrient concentrations, Chla, and phytoplankton species composition, along a transect from river outlet to open marine waters. Results showed that surface waters in Kangerlussuaq were strongly influenced by meltwater with low salinities, high particulate matter concentrations, high PAR and spectral light attenuation coefficients, and low nutrient concentrations. Spectral composition was also affected by the particulate matter. PAR photic depths varied between 4 and 9 m dependent on particulate matter concentrations. There was a decrease with distance from outlet in silicate concentrations, and opposite for phosphate, which increased significantly from river outlet to the marine. Phytoplankton species number (42) and diversity were high at the marine station but low (3) in turbid waters dominated by the diatom Skeletonema costatum in high numbers. A meltwater plume covered about 50 % of the Kangerlussuaq at average discharges in early August. Primary production was quantified with a simple model based on light attenuation coefficients, and showed a near exponential decrease in production with increase in attenuation.

Gross pelagic primary production in the Ems-Dollard estuary

Anthropogenic changes to estuaries, usually highly productive systems, may result in increased turbidity levels, suppress pelagic primary production and negatively affect ecosystem functions. The Ems-Dollard estuary, enclosed between the Netherlands and Germany, is such an estuary with a long history of human induced changes. From the mid-19th century until 1992, discharges of potato starch and straw-board industry waste water, with high contents of organic matter, negatively affected oxygen concentrations and increased nutrient levels of the system. The growing awareness of the deteriorating effects of these discharges on the ecosystem invoked a large research program, BOEDE, between 1976 and 1980. The aim of the current paper was to establish the recent gross pelagic primary production, to compare the results with the late seventies data and to relate possible changes to environmental variables such as suspended matter and nutrients. To this end, six stations from the North Sea into the inner area of the Dollard were visited 39 times in 2012–2013. During each sampling cruise, a so-called PocketBox, containing a number of sensors, provided a high spatial data resolution between stations. At each station, samples were collected for carbon fixation incubations using 14C. Average chlorophyll-a concentrations as reported in this study were lower compared to 1978–1980 for the seaward stations, and higher for the most inward station in 2012 and almost similar in 2013. Light attenuation coefficients in the outer areas were lower in 2012–2013 (1.22 m−1) compared to the values reported in the period 1976–1980 (1.59 m−1), indicating somewhat less turbid conditions. For the two other stations, light attenuation coefficients in the present study were similar to the late seventies' values, for the station near the entrance of the Ems River in the Ems-Dollard area, the coefficient was substantially higher. Pelagic primary production in the 2012–2013 period was about 120 g C m−2 y−1, mainly determined by the most seaward areas. The largest differences in gross primary production in the current study compared to the 1976–1980 period were found at the seaward stations where production in the late seventies was about 60% higher. In the Dollard-area, production hardly changed since the late seventies, but also stations near the Ems-river entrance into the Ems-Dollard area showed a clear decrease. Changes at the inward stations are to be contributed to an increased turbidity; the decrease at the outer areas to a decreased nutrient level, especially dissolved phosphorus and silicate, but possibly also nitrogen.

Use of Digital Images as a Low-Cost System to Estimate Surface Optical Parameters in the Ocean

Ocean color is the result of absorption and scattering, as light interacts with the water and the optically active constituents. The measurement of ocean color changes enables monitoring of these constituents (dissolved or particulate materials). The main objective of this research is to use digital images to estimate the light attenuation coefficient (Kd), the Secchi disk depth (ZSD), and the chlorophyll a (Chla) concentration and to optically classify plots of seawater using the criteria proposed by Jerlov and Forel using digital images captured at the ocean surface. The database used in this study was obtained from seven oceanographic cruises performed in oceanic and coastal areas. Three approaches were developed for each parameter: a general approach that can be applied under any optical condition, one for oceanic conditions, and another for coastal conditions. The results of the coastal approach showed higher correlations between the modeled and validation data, with rp values of 0.80 for Kd, 0.90 for ZSD, 0.85 for Chla, 0.73 for Jerlov, and 0.95 for Forel-Ule. The oceanic approach failed to detect significant changes in a digital photograph. The most precise results were obtained when images were captured at 45° (n = 22; Fr cal=11.02>Fr crit=5.99). Therefore, to ensure precise results, the angle of photography is key. This methodology can be used in citizen science programs to estimate ZSD, Kd, and the Jerlov scale.

Nanocomposites based on halloysite nanotubes and sulphated galactan from red seaweed Gloiopeltis: Properties and delivery capacity of sodium diclofenac

We developed novel composite films based on biocompatible components, such as halloysite clay nanotubes and sulphated galactan (Funori) from red seaweed Gloiopeltis. The filling of the nanotubes within the sulphated galactan matrix was carried out by a green protocol (aqueous casting method) assuring that Funori/halloysite nanocomposites can be totally considered as sustainable materials. The amount of halloysite in the composites was systematically changed to explore the effects of the nanofiller concentration on the mesoscopic properties of the films. We observed that the halloysite content significantly affects the initial water contact angle and the light attenuation coefficient of the Funori based films. These results were interpreted according to SEM images, which showed that the surface morphologies of the nanocomposites depend on the halloysite amounts filled within the polymeric matrix. The mechanical characterization of the nanocomposites was conducted by tensile experiments performed using a linear stress ramp. Moreover, tensile tests were conducted in oscillatory regime at variable temperature to investigate the viscoelastic properties of the nanocomposites.Finally, we filled the biopolymeric matrix with halloysite nanotubes containing sodium diclofenac. The drug release kinetics from the nanocomposites at variable halloysite contents were studied to evaluate their suitability as oral dissolving films for pharmaceutical applications.

Caracterización limnológica, estructura del fitoplancton y batimetría de Laguna Negra, un lago coloreado del Parque Nacional Tierra del Fuego (Argentina)

The 4% of the Argentinian sector from Tierra del Fuego is covered with water. Colored lakes are among the most conspicuous water bodies in the Andean area, and Laguna Negra, in the National Park Tierra del Fuego, is one of them. The main physical and chemical variables were monitored and phytoplankton samples were obtained with a monthly frequency during the ice-free period, between September 2016 and March 2018 (n=15). Laguna Negra was deeper than expected, with a maximum depth of 15.5 m. In addition, this lake has high pH values (7.5±0.55), which were quite stable during the study (variation coefficient, VC=8.3%). These characteristics preclude us from considering this lake as a shallow peatland lake. Dissolved and total nutrients were low and did not show a temporal pattern of fluctuation during the study period. The same trend of no clear fluctuation was also shared by dissolved organic carbon concentration (DOC=7.7±0.78 mg/L). Taxa richness ranged between 6 and 13 throughout the study. The biovolume was inversely correlated with the vertical attenuation coefficient of light (Kd). Phytoplankton biomass (chlorophyll-a concentration, abundance, and biovolume) was generally low, with Dinobryon divergens, Mallomonas sp. and Parvodinium cf. inconspicuum being the dominant taxa. Depending on the classification used, Laguna Negra might be regarded as a humic or dystrophic lake because its color is at the edge of values used in the current literature to consider a lake as humic.

Impact of ashes from the 2022 Tonga volcanic eruption on satellite ocean color signatures

A powerful eruption within the Hunga Tonga-Hunga Ha’apai (HTHH) volcano (20.64°S, 175.19°W) in the Kingdom of Tonga, occurred on 15 January 2022. The volcanic blast was enormous, leading many scientists to investigate the full impact and magnitude of this event via satellite observations. In this study, we describe a new ocean color signature from a discolored water patch created by the HTHH eruption using NASA and CMEMS products of satellite-derived biological and optical properties. Elevated surface chlorophyll-a concentration (Chl-a) between 0.15 to 2.7 mg.m-3 was not associated with phytoplankton growth, but to basalt-andesitic ash material expelled by the volcano and into the ocean, which resulted in erroneous Chl-a estimates. Distribution of the patch over time was aligned with CMEMS ocean currents for 19 days. The gradual decrease of light attenuation or diffuse attenuation coefficient for downward irradiance at 490 nm, Kd(490), was interpreted as due to the sinking of ash particles with time. It is suggested that due to high porosity of 30-40%, a density close to that of seawater, ash particles stay suspended in the water column for more than 10 days with sustained high values of satellite-derived Chl-a, Kd(490), and particulate backscattering coefficient at 443 nm. The high attenuation of light due to ash, reducing the penetration depth to less than 10 meters during the first period after the eruption may have had implications on ecological processes and biogeochemical cycles in Tongan waters.

Clarifying water clarity: A call to use metrics best suited to corresponding research and management goals in aquatic ecosystems

Clarifying water clarity: A call to use metrics best suited to corresponding research and management goals in aquatic ecosystems

Photoinhibition of comammox reaction in Nitrospira inopinata in a dose- and wavelength-dependent manner.

Apparent contribution of complete ammonia-oxidizing organisms (comammox) to the global nitrogen cycle highlights the necessity for understanding niche differentiation of comammox bacteria among other ammonia oxidizers. While the high affinity for ammonia of the comammox species Nitrospira inopinata suggests their niche partitioning is expected to be centered in oligotrophic environments, their absence in nutrient-depleted environments (such as the oceans) suggests that other (abiotic) factors might control their distribution and spatial localization within microbial communities. Many ammonia- and nitrite-oxidizing organisms are sensitive to light; however, the photosensitivity of comammox has not been explored. Since comammox bacteria encode enzymatic machinery homologous to canonical ammonia-and nitrite-oxidizers, we hypothesized that comammox N. inopinata, the only available pure culture of this group of microorganisms, may be inhibited by illumination in a similar manner. We evaluated the impact of light intensity, wavelength, and duration on the degree of photoinhibition for cultures of the comammox species N. inopinata and the soil ammonia-oxidizing archaea Nitrososphaera viennensis. Both species were highly sensitive to light. Interestingly, mimicking diurnal light exposure caused an uncoupling of ammonia and nitrite oxidation in N. inopinata, indicating nitrite oxidation might be more sensitive to light exposure than ammonia oxidation. It is likely that light influences comammox spatial distribution in natural environments such as surface fresh waters according to diurnal cycles, light attenuation coefficients, and the light penetration depths. Our findings therefore provide ecophysiological insights for further studies on comammox both in field and laboratory settings.

V. Relationships Between Bio-Optical Parameters of the Black Sea Waters and Spectral Reflectance Coefficient in Spring 2019

The paper presents an analysis of field measurements of the spectral reflectance of the Black Sea and the bio-optical and colorimetric characteristics calculated from it, as well as chlorophyll concentrations and the Secchi disk depth. For the regions of the Black Sea with different characteristics, the averaged values of the calculated characteristics are presented: the effective and dominant wavelength in the reflectance spectrum, the purity of the water color. Using the previously developed bio-optical algorithm, the concentration of chlorophyll, absorption by dissolved organic matter, backscattering by suspended matter, and the vertical light attenuation coefficient were calculated.Inverse relationships are established between the Secchi disk depth and the maximum reflectance, as well as between the Secchi disk depth and the dominant wavelength. Linear relationships with high correlation coefficients are obtained between the surface chlorophyll concentration and the effective and dominant wavelength. A significant relationship was also established between the surface chlorophyll concentration and the maximum reflectance. Among the relationships between bio-optical and colorimetric parameters, a high correlation is observed between the vertical light attenuation coefficient and color purity.Chlorophyll concentrations calculated from the data of the spectral reflectance coefficient using a semi-analytical algorithm are in good agreement with the data of field measurements. Comparison of calculated and measured chlorophyll concentrations with satellite products of optical ocean color scanners shows an overestimation of chlorophyll concentrations by satellite data processing algorithms. The obtained correlations can be used in the future to assess bio-optical parameters in the northern part of the Black Sea.

Variation in Leaf Type, Canopy Architecture, and Light and Nitrogen Distribution Characteristics of Two Winter Wheat (Triticum aestivum L.) Varieties with High Nitrogen-Use Efficiency

Studies of traits related to nitrogen (N)-use efficiency (NUE) in wheat cultivars are important for breeding N-efficient cultivars. Canopy structure has a major effect on NUE, as it determines the distribution of light and N. However, the mechanism by which canopy structure affects the distribution of light and N within the canopy remains unclear. The N-efficient winter wheat varieties YM49 and ZM27 and N-inefficient winter wheat varieties XN509 and AK58 were grown in the field under two N levels. Light transmittance was enhanced, and the leaf area index and photosynthetically active radiation were lower in the N-efficient cultivar population, which was characterized by moderately sized flag leaves, a low frequency of canopy leaf curling, a low light attenuation coefficient (KL), and high plant compactness. Reductions in the amount of shade increased the distribution of light and N resources to the middle and lower layers. The photosynthetic rate, transpiration rate, instant water-use efficiency, and canopy photosynthetic NUE were higher, N remobilization of the upper and middle canopy leaves was reduced, and the leaf N content was high in the N-efficient cultivars. A higher ratio of the N extinction coefficient (KN) to KL reflects the assimilation ability of the N-efficient winter wheat cultivars, resulting in improved canopy structure and distribution of light and N, higher 1000-grain weight and grain yield, and significantly increased light and NUE. An improved match between gradients of light and N in the leaf canopy promotes balanced C and N metabolism and reduces energy and nutrient losses. This should be a goal when breeding N-efficient wheat cultivars and implementing tillage regimes.

In-situ evolution of temperature dependent attenuation coefficients of plasmonic silver nanostructures

With a growing interest in high temperature applications of plasmonic metal nanostructures, the morphological modulation and the evolution of optical constants of these plasmonic nanostructures have become important both from fundamental growth dynamics point of view and from optical applications viewpoint. In the present investigation, set of plasmonic silver nanostructures (thickness range 5–25 nm) have been grown by e-beam evaporation technique with varying deposition time. They have been subjected to temperature dependent in-situ spectroscopic ellipsometry measurements for optical analysis at room temperatures (25 °C) and at various elevated temperatures (80 °C–530 °C). The evolutions of optical and surface morphological parameters of these Ag nanostructures as a function of thicknesses have also been investigated. The optical attenuation coefficients (400–700 nm) of these Ag nanostructures are found to evolve in a different fashion depending upon thickness controlled nano-morphology. For low thickness films (5–16 nm), which consists of discrete Ag grains, the light attenuation coefficient initially decreases up to ∼130 °C and subsequently increases with increasing temperature up to 300 °C. This is due to the competition of two counteracting phenomena of reduction of electron-grain boundary scattering and increase in LSPR absorption effect due to temperature induced grain expansion. In contrast, for the relatively thicker films (>16 nm), the optical attenuation coefficient was found to decrease with increasing temperature due to dominance of former effect over later which is caused by larger grain size and network-like nano-morphology. The investigated temperature dependent evolution of optical properties is relevant in studies of physical processes at elevated temperatures and also for accurate modeling of plasmonic devices in high-temperature applications.