Artigos de revistas sobre o tema "Semi-conducteur à large bande"
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Baili, G., M. Alouini, D. Dolfi e F. Bretenaker. "Laser semi-conducteur de classe A et de très faible bruit sur une large bande passante". Journal de Physique IV (Proceedings) 135, n.º 1 (outubro de 2006): 165–66. http://dx.doi.org/10.1051/jp4:2006135042.
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Naudan, F., C. Nicolas e J. P. Huignard. "Filtrage des modes latéraux d'un laser semi-conducteur à cavité large par rétroinjection conjuguée". Annales de Physique 20, n.º 5-6 (1995): 599–600. http://dx.doi.org/10.1051/anphys:199556030.
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Pan, Hengxing, Danail Obreschkow, Cullan Howlett, Claudia del P. Lagos, Pascal J. Elahi, Carlton Baugh e Violeta Gonzalez-Perez. "Multiwavelength consensus of large-scale linear bias". Monthly Notices of the Royal Astronomical Society 493, n.º 1 (25 de janeiro de 2020): 747–64. http://dx.doi.org/10.1093/mnras/staa222.
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ABSTRACT We model the large-scale linear galaxy bias bg(x, z) as a function of redshift z and observed absolute magnitude threshold x for broad-band continuum emission from the far-infrared to ultraviolet, as well as for prominent emission lines, such as the H α, H β, Ly a, and [O ii] lines. The modelling relies on the semi-analytic galaxy formation model galform, run on the state-of-the-art N-body simulation surfs with the Planck 2015 cosmology. We find that both the differential bias at observed absolute magnitude x and the cumulative bias for magnitudes brighter than x can be fitted with a five-parameter model: bg(x, z) = a + b(1 + z)e(1 + exp [(x − c)d]). We also find that the bias for the continuum bands follows a very similar form regardless of wavelength due to the mixing of star-forming and quiescent galaxies in a magnitude-limited survey. Differences in bias only become apparent when an additional colour separation is included, which suggest extensions to this work could look at different colours at fixed magnitude limits. We test our fitting formula against observations, finding reasonable agreement with some measurements within 1σ statistical uncertainties, and highlighting areas of improvement. We provide the fitting parameters for various continuum bands, emission lines, and intrinsic galaxy properties, enabling a quick estimation of the linear bias in any typical survey of large-scale structure.
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Partamies, Noora, James M. Weygand e Liisa Juusola. "Statistical study of auroral omega bands". Annales Geophysicae 35, n.º 5 (7 de setembro de 2017): 1069–83. http://dx.doi.org/10.5194/angeo-35-1069-2017.
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Abstract. The presence of very few statistical studies on auroral omega bands motivated us to test-use a semi-automatic method for identifying large-scale undulations of the diffuse aurora boundary and to investigate their occurrence. Five identical all-sky cameras with overlapping fields of view provided data for 438 auroral omega-like structures over Fennoscandian Lapland from 1996 to 2007. The results from this set of omega band events agree remarkably well with previous observations of omega band occurrence in magnetic local time (MLT), lifetime, location between the region 1 and 2 field-aligned currents, as well as current density estimates. The average peak emission height of omega forms corresponds to the estimated precipitation energies of a few keV, which experienced no significant change during the events. Analysis of both local and global magnetic indices demonstrates that omega bands are observed during substorm expansion and recovery phases that are more intense than average substorm expansion and recovery phases in the same region. The omega occurrence with respect to the substorm expansion and recovery phases is in a very good agreement with an earlier observed distribution of fast earthward flows in the plasma sheet during expansion and recovery phases. These findings support the theory that omegas are produced by fast earthward flows and auroral streamers, despite the rarity of good conjugate observations.
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Marcati, Carmen Regina, Veronica Angyalossy e Ray Franklin Evert. "SEASONAL VARIATION IN WOOD FORMATION OF CEDRELA FISSILIS (MELIACEAE)". IAWA Journal 27, n.º 2 (2006): 199–211. http://dx.doi.org/10.1163/22941932-90000149.
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Cambial activity and periodicity of secondary xylem formation in Cedrela fissilis, a semi-ring-porous species, were studied. Wood samples were collected periodically from 1996 to 2000. The phenology was related to climate data of the region. The cambium has one active and one dormant period per year. The active period coincides with the wet season when trees leaf-out. The dormant period coincides with the dry season when trees lose their leaves. Growth rings are marked by parenchyma bands that begin to be formed, together with the small latewood vessels, just before the cambium becomes dormant at the beginning of the dry season. These bands are added to when the cambium reactivates in the wet season. At this time, the large earlywood vessels of the growth rings are also formed. As these bands consist of both terminal and initial parenchyma, we suggest the general term marginal bands be used to describe them. The growth layers vary in width among and within the trees.
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Li, Zongrui, Jun Pan, Zhuoer Zhang, Mi Wang e Likun Liu. "MTCSNet: Mean Teachers Cross-Supervision Network for Semi-Supervised Cloud Detection". Remote Sensing 15, n.º 8 (12 de abril de 2023): 2040. http://dx.doi.org/10.3390/rs15082040.
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Cloud detection methods based on deep learning depend on large and reliable training datasets to achieve high detection accuracy. There will be a significant impact on their performance, however when the training data are insufficient or when the label quality is low. Thus, to alleviate this problem, a semi-supervised cloud detection method, named the mean teacher cross-supervision cloud detection network (MTCSNet) is proposed. This method enforces both consistency and accuracy on two cloud detection student network branches, which are perturbed with different initializations, for the same input image. For each of the two student branches, the respective teacher branches, used to generate high-quality pseudo labels, are constructed using an exponential moving average method (EMA). A pseudo one-hot label, produced by one teacher network branch, supervises the other student network branch with the standard cross-entropy loss, and vice versa. To incorporate additional prior information into the model, the presented method uses near-infrared bands instead of red bands as model inputs and injects strong data augmentations on unlabeled images fed into the student model. This induces the model to learn richer representations and ensure consistency constraints on the predictions of the same unlabeled image across different batches. To attain a more refined equilibrium between the supervised and semi-supervised loss in the training process, the proposed cloud detection network learns the optimal weights based on homoscedastic uncertainty, thus effectively exploiting the advantages of semi-supervised tasks and elevating the overall performance. Experiments on the SPARCS and GF1-WHU public cloud detection datasets show that the proposed method outperforms several state-of-the-art semi-supervised algorithms when only a limited number of labeled samples are available.
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Cabrera, Densil, Shuai Lu, Jonothan Holmes e Manuj Yadav. "Sound Reflections in Indian Stepwells: Modelling Acoustically Retroreflective Architecture". Acoustics 4, n.º 1 (2 de março de 2022): 227–47. http://dx.doi.org/10.3390/acoustics4010014.
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Retroreflection is rarely used as a surface treatment in architectural acoustics but is found incidentally with building surfaces that have many simultaneously visible concave right-angle trihedral corners. Such surfaces concentrate reflected sound onto the sound source, mostly at high frequencies. This study investigated the potential for some Indian stepwells (stepped ponds, known as a kund or baori/baoli in Hindi) to provide exceptionally acoustically retroreflective semi-enclosed environments because of the unusually large number of corners formed by the steps. Two cases—Panna Meena ka Kund and Lahan Vav—were investigated using finite-difference time-domain (FDTD) acoustic simulation. The results are consistent with retroreflection, showing reflected energy concentrating on the source position mostly in the high-frequency bands (4 kHz and 2 kHz octave bands). However, the larger stepped pond has substantially less retroreflection, even though it has many more corners, because of the greater diffraction loss over the longer distances. Retroreflection is still evident (but reduced) with non-right-angle trihedral corners (80°–100°). The overall results are sufficiently strong to indicate that acoustic retroreflection should be audible to an attuned visitor in benign environmental conditions, at least at moderately sized stepped ponds that are in good geometric condition.
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Ayres, J. F., R. D. Murison, A. D. Turner e S. Harden. "A rapid semi-quantitative procedure for screening hydrocyanic acid in white clover (Trifolium repens L.)". Australian Journal of Experimental Agriculture 41, n.º 4 (2001): 515. http://dx.doi.org/10.1071/ea97069.
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The presence of cyanogenic glucosides in white clover (Trifolium repens L.) is an anti-nutritional factor due to the potential for cyanide to pre-dispose selenium deficiency in grazing animals. Considerable genotypic variation in cyanogenesis occurs in white clover and it is important that highly cyanogenic white clover lines are identified to ensure that germpasm used in breeding programs does not lead to the release of cultivars that exceed safe levels. A procedure for rapid semi-quantitative screening of large white clover germplasm collections is described. This procedure is based on the picrate assay and utilises computer imagery and calibration relationships between spectral intensity (red, green, blue bands) of the colour reaction on picrate paper with cyanide in standard solutions to predict hydrocyanic acid concentration in white clover leaf.
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Dagbovie, Ayawoa S., e Jonathan A. Sherratt. "Pattern selection and hysteresis in the Rietkerk model for banded vegetation in semi-arid environments". Journal of The Royal Society Interface 11, n.º 99 (6 de outubro de 2014): 20140465. http://dx.doi.org/10.1098/rsif.2014.0465.
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Banded vegetation is a characteristic feature of semi-arid environments. It occurs on gentle slopes, with alternating stripes of vegetation and bare ground running parallel to the contours. A number of mathematical models have been proposed to investigate the mechanisms underlying these patterns, and how they might be affected by changes in environmental conditions. One of the most widely used models is due to Rietkerk and co-workers, and is based on a water redistribution hypothesis, with the key feedback being that the rate of rainwater infiltration into the soil is an increasing function of plant biomass. Here, for the first time, we present a detailed study of the existence and stability of pattern solutions of the Rietkerk model on slopes, using the software package wavetrain ( www.ma.hw.ac.uk/wavetrain ). Specifically, we calculate the region of the rainfall–migration speed parameter plane in which patterns exist, and the sub-region in which these patterns are stable as solutions of the model partial differential equations. We then perform a detailed simulation-based study of the way in which patterns evolve when the rainfall parameter is slowly varied. This reveals complex behaviour, with sudden jumps in pattern wavelength, and hysteresis; we show that these jumps occur when the contours of constant pattern wavelength leave the parameter region giving stable patterns. Finally, we extend our results to the case in which a diffusion term for surface water is added to the model equations. The parameter regions for pattern existence and stability are relatively insensitive to small or moderate levels of surface water diffusion, but larger diffusion coefficients significantly change the subdivision into stable and unstable patterns.
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Oliveira Santos, Victor, Bruna Monallize Duarte Moura Guimarães, Iran Eduardo Lima Neto, Francisco de Assis de Souza Filho, Paulo Alexandre Costa Rocha, Jesse Van Griensven Thé e Bahram Gharabaghi. "Chlorophyll-a Estimation in 149 Tropical Semi-Arid Reservoirs Using Remote Sensing Data and Six Machine Learning Methods". Remote Sensing 16, n.º 11 (24 de maio de 2024): 1870. http://dx.doi.org/10.3390/rs16111870.
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It is crucial to monitor algal blooms in freshwater reservoirs through an examination of chlorophyll-a (Chla) concentrations, as they indicate the trophic condition of these waterbodies. Traditional monitoring methods, however, are expensive and time-consuming. Addressing this hindrance, we conducted a comprehensive investigation using several machine learning models for Chla modeling. To this end, we used in situ collected water sample data and remote sensing data from the Sentinel-2 satellite, including spectral bands and indices, for large-scale coverage. This approach allowed us to conduct a comprehensive analysis and characterization of the Chla concentrations across 149 freshwater reservoirs in Ceará, a semi-arid region of Brazil. The implemented machine learning models included k-nearest neighbors, random forest, extreme gradient boosting, the least absolute shrinkage, and the group method of data handling (GMDH); in particular, the GMDH approach has not been previously explored in this context. The forward stepwise approach was used to determine the best subset of input parameters. Using a 70/30 split for the training and testing datasets, the best-performing model was the GMDH model, achieving an R2 of 0.91, an MAPE of 102.34%, and an RMSE of 20.4 μg/L, which were values consistent with the ones found in the literature. Nevertheless, the predicted Chla concentration values were most sensitive to the red, green, and near-infrared bands.
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DE, P., S. Bhakat e A. K. Sinha. "Redescription of Oligodon arnensis, Shaw, 1802 (Reptilia: Colubridae) collected from Birbhum, West Bengal, India". Indian Journal of Pharmaceutical and Biological Research 6, n.º 01 (31 de março de 2018): 42–47. http://dx.doi.org/10.30750/ijpbr.6.1.7.
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Oligodon arnensis, Shaw, 1802 commonly known as kukri snake, a semi- fossorial snake species is taken for study as it is a most challenging group of snake. A morphometric study on several aspects like the number of supra-labials , infra-labials, ventrals, dorsals, distance between eye to nostril, eye diameter, number of bands, shape of banding etc. are reported. A significant correlation is present in between snout-vent length and tail length and in between eye diameter and distance from eye to nostril a possible explanation of large eye size related to habitat is given in the study.
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Pereira-Pires, João E., Valentine Aubard, Rita A. Ribeiro, José M. Fonseca, João M. N. Silva e André Mora. "Semi-Automatic Methodology for Fire Break Maintenance Operations Detection with Sentinel-2 Imagery and Artificial Neural Network". Remote Sensing 12, n.º 6 (12 de março de 2020): 909. http://dx.doi.org/10.3390/rs12060909.
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The difficult job of fighting fires and the nearly impossible task to stop a wildfire without great casualties requires an imperative implementation of proactive strategies. These strategies must decrease the number of fires, the burnt area and create better conditions for the firefighting. In this line of action, the Portuguese Institute of Nature and Forest Conservation defined a fire break network (FBN), which helps controlling wildfires. However, these fire breaks are efficient only if they are correctly maintained, which should be ensured by the local authorities and requires verification from the national authorities. This is a fastidious task since they have a large network of thousands of hectares to monitor over a full year. With the increasing quality and frequency of the Earth Observation Satellite imagery with Sentinel-2 and the definition of the FBN, a semi-automatic remote sensing methodology is proposed in this article for the detection of maintenance operations in a fire break. The proposed methodology is based on a time-series analysis, an object-based classification and a change detection process. The change detection is ensured by an artificial neural network, with reflectance bands and spectral indices as features. Additionally, an analysis of several bands and spectral indices is presented to show the behaviour of the data during a full year and in the presence of a maintenance operation. The proposed methodology achieved a relative error lower than 4% and a recall higher than 75% on the detection of maintenance operations.
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Marcati, Carmen Regina, Leandro Roberto Longo, Alex Wiedenhoeft e Claudia Franca Barros. "Comparative wood anatomy of root and stem of Citharexylum myrianthum (Verbenaceae)". Rodriguésia 65, n.º 3 (setembro de 2014): 567–76. http://dx.doi.org/10.1590/2175-7860201465301.
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Root and stem wood anatomy of C. myrianthum (Verbenaceae) from a semideciduous seasonal forest in Botucatu municipality (22º52’20”S and 48º26’37”W), São Paulo state, Brazil, were studied. Growth increments demarcated by semi-ring porosity and marginal bands of axial parenchyma were observed in the wood of both root and stem. Many qualitative features were the same in both root and stem: fine helical thickenings, and simple and multiple perforation plates in vessel elements; large quantities of axial parenchyma in the growth rings, grading from marginal bands and confluent forming irregular bands in earlywood to lozenge aliform in latewood; axial parenchyma cells forked, and varied wall projections and undulations; septate fibres; forked and diverse fibre endings. Quantitative features differing between root and stem wood were evaluated using student’s t-test, and vessel frequency, vessel element length, vessel diameter, ray height, and vulnerability and mesomorphy indices differed significantly. Root wood had lower frequency of vessels, narrower and longer vessel elements, and taller rays than wood of the stem. The calculated vulnerability and mesomorphy indices indicated that C. myrianthum plants are mesomorphic. Roots seem to be more susceptible to water stress than the stem.
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Jiang, Fugen, Andrew R. Smith, Mykola Kutia, Guangxing Wang, Hua Liu e Hua Sun. "A Modified KNN Method for Mapping the Leaf Area Index in Arid and Semi-Arid Areas of China". Remote Sensing 12, n.º 11 (10 de junho de 2020): 1884. http://dx.doi.org/10.3390/rs12111884.
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As an important vegetation canopy parameter, the leaf area index (LAI) plays a critical role in forest growth modeling and vegetation health assessment. Estimating LAI is helpful for understanding vegetation growth and global ecological processes. Machine learning methods such as k-nearest neighbors (kNN) and random forest (RF) with remote sensing images have been widely used for mapping LAI. However, the accuracy of mapping LAI in arid and semi-arid areas using these methods is limited due to remote and large areas, the high cost of collecting field data, and the great spatial variability of the vegetation canopy. Here, a novel and modified kNN method was presented for mapping LAI in arid and semi-arid areas of China using Sentinel-2 and Landsat 8 images with field data collected in Ganzhou and Kangbao of China. The modified kNN was developed by integrating the traditional kNN estimation and RF classification. The results were compared with those from kNN and RF regression alone using three sets of input predictors: (i) spectral reflectance bands (input 1); (ii) vegetation indices (input 2); and (iii) a combination of spectral reflectance bands and vegetation indices (input 3). Our analysis showed that in Ganzhou, the red-edge bands of the Sentinel-2 image had a high correlation with LAI. Using the red-edge band-derived vegetation indices increased the accuracy of mapping LAI compared with using other spectral variables. Among the three sets of input predictors, input 3 resulted in the highest prediction accuracy. Based on the combination, the values of RMSE obtained by the traditional kNN, RF, and modified kNN were 0.526, 0.523, and 0.372, respectively, and the modified kNN significantly improved the accuracy of LAI prediction by 29.3% and 28.9% compared with the kNN and RF alone, respectively. A similar improvement was achieved for input 1 and input 2. In Kangbao, the improvement of the prediction accuracy obtained by the modified kNN was 31.4% compared with both the kNN and RF. Therefore, this study implied that the modified kNN provided the potential to improve the accuracy of mapping LAI in arid and semi-arid regions using the images.
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Sherratt, Jonathan A. "Pattern solutions of the Klausmeier model for banded vegetation in semi-arid environments II: patterns with the largest possible propagation speeds". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, n.º 2135 (29 de junho de 2011): 3272–94. http://dx.doi.org/10.1098/rspa.2011.0194.
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Pattern formation at the ecosystem level is a rapidly growing area of spatial ecology. The best studied example is vegetation stripes running along contours in semi-arid regions. Theoretical models are a widely used tool for studying these banded vegetation patterns, and one important model is the system of advection–diffusion equations proposed by Klausmeier. The present study is part of a series of papers whose objective is a comprehensive understanding of patterned solutions of the Klausmeier model. The author focuses on the region of parameter space in which the propagation speed of the patterns is close to its maximum possible value. Exploiting the large value of one of the model parameters, a leading order approximation is obtained for the maximum propagation speed, and the author undertakes a detailed investigation of the parameter region in which there are patterns with speeds close to this maximum.
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Schulze-Brüninghoff, Damian, Michael Wachendorf e Thomas Astor. "Potentials and Limitations of WorldView-3 Data for the Detection of Invasive Lupinus polyphyllus Lindl. in Semi-Natural Grasslands". Remote Sensing 13, n.º 21 (28 de outubro de 2021): 4333. http://dx.doi.org/10.3390/rs13214333.
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Semi-natural grasslands contribute highly to biodiversity and other ecosystem services, but they are at risk by the spread of invasive plant species, which alter their habitat structure. Large area grassland monitoring can be a powerful tool to manage invaded ecosystems. Therefore, WorldView-3 multispectral sensor data was utilized to train multiple machine learning algorithms in an automatic machine learning workflow called ‘H2O AutoML’ to detect L. polyphyllus in a nature protection grassland ecosystem. Different degree of L. polyphyllus cover was collected on 3 × 3 m2 reference plots, and multispectral bands, indices, and texture features were used in a feature selection process to identify the most promising classification model and machine learning algorithm based on mean per class error, log loss, and AUC metrics. The best performance was achieved with a binary classification of lupin-free vs. fully invaded 3 × 3 m2 plot classification with a set of 7 features out of 763. The findings reveal that L. polyphyllus detection from WorldView-3 sensor data is limited to large dominant spots and not recommendable for lower plant coverage, especially single plant detection. Further research is needed to clarify if different phenological stages of L. polyphyllus as well as time series increase classification performance.
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Norman, AB, JC Caudle e CW Henderson. "Measurement of Gas Diffusion Capacity of Cigarette Papers". Beiträge zur Tabakforschung International/Contributions to Tobacco Research 21, n.º 8 (1 de dezembro de 2005): 425–34. http://dx.doi.org/10.2478/cttr-2013-0810.
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AbstractApparatus suitable for measuring gas diffusion capacity of cigarette paper was assembled and evaluated. The apparatus provides semi-automated means for measuring the concentration of carbon dioxide diffusing through a small area of the paper, and computation of a paper thickness-dependent diffusion capacity of the sample. Measurements are rapid and can be made in about 30 s. Diffusion capacity measurements were repeatable and reproducible to within about 1%. Variability of the diffusion capacity values was much lower than that observed for permeability measurements. For these reasons, the apparatus is useful for quality assessment and research applications. Diffusion capacity was measured for cigarette papers of inherent permeability ranging from 6 to 62 cm/min. As expected from prevailing theory, the diffusion capacity values generally increased with permeability. The diffusion capacity measured for electrostatically perforated papers was only slightly higher (about 6-11%) than the unperforated base paper despite large increases in permeability. This result indicates that diffusion capacity is governed by small pores in the paper. The apparatus is capable of measuring banded areas of papers designed for reduced ignition propensity. Diffusion capacity values for banded areas were lower than those of non-banded paper of similar permeability, suggesting that the band material preferentially occludes small pores in the paper.
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Fujimoto, Takaaki, Hiroyuki Yamamoto e Satoru Tsuchikawa. "Estimation of Wood Stiffness and Strength Properties of Hybrid Larch by Near-Infrared Spectroscopy". Applied Spectroscopy 61, n.º 8 (agosto de 2007): 882–88. http://dx.doi.org/10.1366/000370207781540150.
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This work was undertaken to investigate the feasibility of near-infrared (NIR) spectroscopy for estimating wood mechanical properties, i.e., modulus of elasticity (MOE) and modulus of rupture (MOR) in bending tests. Two sample sets having large and limited density variation were prepared to examine the effects of wood density on estimation of MOE and MOR by the NIR technique. Partial least squares (PLS) analysis was employed and it was found that the relationships between laboratory-measured and NIR-predicted values were good in the case of sample sets having large density variation. MOE could be estimated even when density variation in the sample set was limited. It was concluded that absorption bands due to the OH group in the semi-crystalline or crystalline regions of cellulose strongly influenced the calibrations for bending stiffness of hybrid larch. This was also suggested from the result that both α-cellulose content and cellulose crystallinity showed moderate positive correlation to wood stiffness.
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Ikutomo, R., Masato Tsujikawa, Makoto Hino, Hisamichi Kimura, Kunio Yubuta e Akihisa Inoue. "Fine Crystalline Phase Dispersion in Zr-Based Bulk Metallic Glass by Laser Irradiation". Advanced Materials Research 26-28 (outubro de 2007): 747–50. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.747.
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Bulk metallic glass (BMG) exhibits remarkable properties such as high strength, good stiffness and good corrosion resistance. However, the wear resistance of amorphous metals is not excellent as expected their high strength. It is thought that large local shear bands easily change into cracks for debris formation. The effective obstruction of shear band formation might be applied to improve the wear resistance of BMG. In this study, we tried to suppress shear band deformation by fine crystalline phase dispersion formed by semi-conductor laser irradiation. The microstructures of irradiated Zr-based BMG specimens were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The fine dispersions of crystalline phases are observed in the amorphous matrix. The optimum condition for laser irradiation was discussed.
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Khan, A., e J. S. Roy. "Thinned Smart Antenna of a Semi-circular Dipole Array for Massive MIMO Systems". Advanced Electromagnetics 12, n.º 4 (9 de dezembro de 2023): 17–25. http://dx.doi.org/10.7716/aem.v12i4.2303.
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Massive MIMO (multiple-input multiple-output) is a multi-user MIMO technology that can provide high-speed multimedia services in 5G wireless networks using sub-6 GHz and millimeter wave bands. The massive MIMO (MMIMO) installs array antennas in the base stations, using hundreds of transceivers with other RF modules. One of the drawbacks of the MMIMO system is its huge power consumption, and the beamforming network with RF modules for a large number of antennas is the main contributor to the power consumption. In this paper, a novel beamforming method is proposed for the low power consumption of an MMIMO system. The proposed thinned smart antenna (TSA) of a semi-circular array produces a secure beam toward the user’s terminal with reduced interference. By thinning the antenna array, some of the antenna elements are kept off, resulting in less power consumption, while the array pattern remains the same as a fully populated array with a reduced side lobe level (SLL). The sub-6 GHz band of 5 GHz is used for the design of thinned array antennas. The genetic algorithm (GA) is used to determine the array sequence in thinning, and the adaptive signal processing algorithms least mean square (LMS), recursive least square (RLS), and sample matrix inversion (SMI) are used for the beamforming of the TSA, and the corresponding algorithms are GA-LMS, GA-RLS, and GA-SMI. The power saving of 40% to 55% is achieved using TSA. The maximum SLL reductions of 13 dB, 12 dB, and 14 dB are achieved for TSA using GA-LMS, GA-RLS, and GA-SMI algorithms, respectively.
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Gigante, V., V. Iacobellis, S. Manfreda, P. Milella e I. Portoghese. "Influences of Leaf Area Index estimations on water balance modeling in a Mediterranean semi-arid basin". Natural Hazards and Earth System Sciences 9, n.º 3 (25 de junho de 2009): 979–91. http://dx.doi.org/10.5194/nhess-9-979-2009.
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Abstract. In the present work, the role played by vegetation parameters, necessary to the hydrological distributed modeling, is investigated focusing on the correct use of remote sensing products for the evaluation of hydrological losses in the soil water balance. The research was carried out over a medium-sized river basin in Southern Italy, where the vegetation status is characterised through a data-set of multi-temporal NDVI images. The model adopted uses one layer of vegetation whose status is defined by the Leaf Area Index (LAI), which is often obtained from NDVI images. The inherent problem is that the vegetation heterogeneity – including soil disturbances – has a large influence on the spectral bands and so the relation between LAI and NDVI is not unambiguous. We present a rationale for the basin scale calibration of a non-linear NDVI-LAI regression, based on the comparison between NDVI values and literature LAI estimations of the vegetation cover in recognized landscape elements of the study catchment. Adopting a process-based model (DREAM) with a distributed parameterisation, the influence of different NDVI-LAI regression models on main features of water balance predictions is investigated. The results show a significant sensitivity of the hydrological losses and soil water regime to the alternative LAI estimations. These crucially affects the model performances especially in low-flows simulation and in the identification of the intermittent regime.
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Barbosa, Patrícia Alves, e Izabel Fernanda Machado. "Strain Rate Effect on the Mechanical Behavior of Austenitic Stainless Steel during Machining". Advanced Materials Research 223 (abril de 2011): 332–39. http://dx.doi.org/10.4028/www.scientific.net/amr.223.332.
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Machining is characterized by a large amount of localized plastic strain on material due to chip formation; hence, there is a commitment among the strain process, strain hardening, and heat softening, generating shear bands. Understanding these shear zones is important because it contains information that can be applied to the improvement of machining techniques related to process optimization, and to materials and tools innovation. In this sense, the aim is to analyze the strain and the strain hardening with the strain rate variation as from the chip formed during the austenitic stainless steel AISI 304 turning. The results showed that the cut type, orthogonal or semi-orthogonal machining, affects the way the material strains, and that the strain rate has no significant effect on the strain and strain hardening of the austenitic stainless steel AISI 304 for the range investigated.
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Lin, Zhe-Yu Daniel, Chin-Fei Lee, Zhi-Yun Li, John J. Tobin e Neal J. Turner. "Inferring (sub)millimetre dust opacities and temperature structure in edge-on protostellar discs from resolved multiwavelength continuum observations: the case of the HH 212 disc". Monthly Notices of the Royal Astronomical Society 501, n.º 1 (26 de novembro de 2020): 1316–35. http://dx.doi.org/10.1093/mnras/staa3685.
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ABSTRACT (Sub)millimetre dust opacities are required for converting the observable dust continuum emission to the mass, but their values have long been uncertain, especially in discs around young stellar objects. We propose a method to constrain the opacity κν in edge-on discs from a characteristic optical depth τ0,ν, the density ρ0, and radius R0 at the disc outer edge through κν = τ0,ν/(ρ0R0), where τ0,ν is inferred from the shape of the observed flux along the major axis, ρ0 from gravitational stability considerations, and R0 from direct imaging. We applied the 1D semi-analytical model to the embedded, Class 0, HH 212 disc, which has high-resolution data in Atacama Large Millimetre/submillimetre Array (ALMA) bands 9, 7, 6, and 3 and Very Large Array Ka band (λ = 0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modelling is extended to 2D through RADMC-3D radiative transfer calculations. We find a dust opacity of κν ≈ 1.9 × 10−2, 1.3 × 10−2, and 4.9 × 10−3 cm2 g−1 of gas and dust for ALMA bands 7, 6, and 3, respectively, with uncertainties dependent on the adopted stellar mass. The inferred opacities lend support to the widely used prescription κλ = 2.3 × 10−2(1.3mm/λ) cm2 g−1 . We inferred a temperature of ∼45 K at the disc outer edge that increases radially inwards. It is well above the sublimation temperatures of ices such as CO and N2, which supports the notion that the disc chemistry cannot be completely inherited from the protostellar envelope.
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Guo, Jifa, Shihong Du, Hongyuan Huo, Shouji Du e Xiuyuan Zhang. "Modelling the Spectral Uncertainty of Geographic Features in High-Resolution Remote Sensing Images: Semi-Supervising and Weighted Interval Type-2 Fuzzy C-Means Clustering". Remote Sensing 11, n.º 15 (25 de julho de 2019): 1750. http://dx.doi.org/10.3390/rs11151750.
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The spectral uncertainty refers to the diversity and variations of spectral characteristics within a single geographic object or across different objects of the same class. Usually, existing methods represent the spectral characteristics as precise single-valued curves. Thus, the spectral variations cannot be modeled, which further restricts the analysis and classification performance of remote sensing images. On the other hand, unsupervised methods have poor performance in classification and modeling uncertainty, while supervised methods need a large number of samples with high quality. Fuzzy semi-supervised clustering (FSSC) methods achieve a high accuracy with limited labelled samples. Thus, currently, FSSC methods attract more and more attention. This paper proposes a novel method to model the spectral uncertainty for very-high-resolution (VHR) images based on interval type-2 fuzzy sets (IT2 FSs), namely the hierarchical semi-supervising and weighted interval type-2 fuzzy c-means for objects (hierarchical SSW-IT2FCM-O) clustering method. In this method, the VHR image is segmented into image objects to reduce spectral uncertainty within objects. Spectral values, spectral indices and textures were weighted for object-based image classification. To further reduce spectral uncertainty across different objects of the same class, the spectral characteristics of land cover types were represented as banded curves with certain widths instead of precise single-valued spectral curves. The experimental results show that the banded spectral curves produced by the hierarchical SSW-IT2FCM-O can effectively model the spectral uncertainty of geographic objects. From the perspective of classification, four typical validity indices along with the confusion matrix and kappa coefficient were used to test the effectiveness of the hierarchical SSW-IT2FCM-O method, and these indices show that the presented method SSW-IT2FCM-O has greater classification accuracy than the existing FSSC methods and, more importantly, it requires smaller training samples than the existing methods.
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Poletaev, A. V., E. A. Seregina, A. V. Pshonkin, N. A. Karamyan, D. V. Fedorova, S. A. Plyasunova e P. A. Zharkov. "Von Willebrand factor multimeric assay: novel diagnostics capabilities". Russian Journal of Pediatric Hematology and Oncology 8, n.º 2 (12 de julho de 2021): 35–41. http://dx.doi.org/10.21682/2311-1267-2021-8-2-35-41.
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Introduction. Distinguishing between Von Willebrand disease (vWD) types often requires multimer gel analysis. The current techniques for vWF multimer structure are manual, complicated, non-standardized and time consuming. The aim of this study was to evaluate diagnostic capabilities of new automated vWF multimer screening assay.Materials and methods. Children with vWD, acquired von Willebrand Syndrome (aVWS) and 8 healthy donors as a control group were enrolled in this study. Von Willebrand factor antigen (vWF Ag); ristocetin cofactor activity (VWF:Rco); vWF collagen binding (VWF:CB); ristocetin-induced platelet aggregation (RIPA); factor VIII clotting activity (FVIII:C) and vWF factor VIII binding activity (vWF:FVIIIb) were performed to evaluate vWD. Multimer analysis was carried out using the commercial HYDRAGEL 5 von Willebrand Multimers kit on semi-automatic gel electrophoresis instrument HYDRASYS (SEBIA).Results. The samples from control group had 9—12 bands of vWF multimers with the same distribution as control plasma. Patients with type I vWD had the proportional decrease in the intensity of the bands with preservation of the normal distribution of the band. Patients with type III vWD reveal the complete absence of the multimer bands on the gel. Multimer analysis in type IIA shows the absence of high molecular weight multimer bands. In other patients the distribution of vWF multimers was normal against the changes in functional properties of vWF (types IIM, N). Most of the children with aVWS also revealed normal distribution of vWF multimers, however, in some patients, the slight decrease in large multimeric forms was observed visually on the gel.Conclusion. Multimer analysis allows to visualize the multimer distribution in various types of von Willebrand disease. The method is easy to perform and can be useful for distinguishing between the subtypes of vWD. But only the full test panel including genetic tests would allow the differentiantion of vWD types with high precision.
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Vuorinne, Ilja, Janne Heiskanen e Petri K. E. Pellikka. "Assessing Leaf Biomass of Agave sisalana Using Sentinel-2 Vegetation Indices". Remote Sensing 13, n.º 2 (12 de janeiro de 2021): 233. http://dx.doi.org/10.3390/rs13020233.
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Biomass is a principal variable in crop monitoring and management and in assessing carbon cycling. Remote sensing combined with field measurements can be used to estimate biomass over large areas. This study assessed leaf biomass of Agave sisalana (sisal), a perennial crop whose leaves are grown for fibre production in tropical and subtropical regions. Furthermore, the residue from fibre production can be used to produce bioenergy through anaerobic digestion. First, biomass was estimated for 58 field plots using an allometric approach. Then, Sentinel-2 multispectral satellite imagery was used to model biomass in an 8851-ha plantation in semi-arid south-eastern Kenya. Generalised Additive Models were employed to explore how well biomass was explained by various spectral vegetation indices (VIs). The highest performance (explained deviance = 76%, RMSE = 5.15 Mg ha−1) was achieved with ratio and normalised difference VIs based on the green (R560), red-edge (R740 and R783), and near-infrared (R865) spectral bands. Heterogeneity of ground vegetation and resulting background effects seemed to limit model performance. The best performing VI (R740/R783) was used to predict plantation biomass that ranged from 0 to 46.7 Mg ha−1 (mean biomass 10.6 Mg ha−1). The modelling showed that multispectral data are suitable for assessing sisal leaf biomass at the plantation level and in individual blocks. Although these results demonstrate the value of Sentinel-2 red-edge bands at 20-m resolution, the difference from the best model based on green and near-infrared bands at 10-m resolution was rather small.
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Zhu-Qing, Ren, Xiong Yuan-Zhu, Deng Chang-Yang, Lei Ming-Gang, Zuo Bo, Zheng Rong, Li Feng-E, Jiang Si-Wen e Jiang Xun-Ping. "Isolation, cloning and sequence analysis of differentially expressed genes in the backfat tissue between hybrids and parents in pigs". Chinese Journal of Agricultural Biotechnology 3, n.º 1 (abril de 2006): 47–52. http://dx.doi.org/10.1079/cjb200592.
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AbstractIn order to reveal the molecular basis of heterosis, Large White (LW), an introduced European pig breed, and Meishan (MS), a Chinese indigenous pig breed, were selected to hybridize directly and reciprocally in the present experiment. mRNA differential display (DD) technique was performed to identify genes that were differentially expressed in the backfat tissues of hybrids (LW×MS, MS×LW) and purebred (LW×LW, MS×MS) pigs. The ten anchor primers in combination with ten arbitrary primers (100 sets in total) were used and nearly 1500 reproducible bands were observed in polyacrylamide gels. The 40 differentially displayed bands were selected for cloning and sequencing. Thirty-six out of 40 expressed sequence tags (ESTs) proved to be novel and the sequences were submitted to GenBank (accession No. CV507051-CV507087); the other four showed similarity to known genes published in GenBank. Three among 36 novel ESTs were chosen for further identification with semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The result showed that two ESTs were differentially expressed, and the third showed no obvious difference between hybrids and purebreds. In order to reduce the percentage of false-positive DD, RNA pools of four types of pigs were constructed, by mixing samples from six pigs of the same genotype, and subjected to DD. Stringent annealing temperature was applied and only bands that could be repeated in duplicate PCR were used for further study. The results showed that the expression pattern of these 36 ESTs differed among the four genotypes of pigs, suggesting that the genes corresponding to these differentially expressed ESTs might be related to the heterosis occurring in fat tissue.
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Stadler, Johannes, Thomas Schmid, Lothar Opilik, Phillip Kuhn, Petra S. Dittrich e Renato Zenobi. "Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers". Beilstein Journal of Nanotechnology 2 (30 de agosto de 2011): 509–15. http://dx.doi.org/10.3762/bjnano.2.55.
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Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS) was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH) and 4-mercaptopyridine (4-PySH)) in a self-assembled monolayer (SAM) on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process. Using specific marker bands at 1000 cm−1 for 2-PySH and 1100 cm−1 for 4-PySH, both isomers could be localized on the surface and semi-quantitative information was deduced from the band intensities. Even though nanometer size resolution information was not required, the large signal enhancement of TERS was employed here to detect a monolayer coverage of weakly scattering analytes that were not detectable with normal Raman spectroscopy, emphasizing the usefulness of TERS.
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Basel, J., e N. Pantha. "Substitutional Lithium Doping on Germanene: A First-principles Study". Journal of Nepal Physical Society 7, n.º 2 (6 de agosto de 2021): 33–41. http://dx.doi.org/10.3126/jnphyssoc.v7i2.38620.
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The density functional theory (DFT) based first-principles calculations have been adopted for the study of structural, electronic and magnetic properties of pure and single Lithium (Li) atom doped germanene monolayer. Due to the higher intrinsic carrier mobilities and large spin orbit gap, germanene has great possibility of being integrated into the silicon based semiconductor industry. Different studies have been done to change the band gap value from its’ pristine zero band gap state. We have doped the single Li atom into the germanene system with the intention of tuning the band gap and other electronic and magnetic properties. Band structure calculations show pristine germanene is semi-metallic in nature whereas the Li doped system is fully metallic with the overlapping of the conduction and valance bands in the Fermi level. Under density of states (DOS) calculations, it is evident that both pristine and doped system are non-magnetic in nature with symmetric DOS plot.
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Rodrigues, Rodrigo Antonio de Freitas, Juliana Pertille, Fernanda Gervasoni, Paola Bruno Arab, Thales Sebben Petry, Marina Luiza Jordão Martins, Áquila Ferreira Mesquita, Jorge Henrique Laux, Breno Souza Martins e Lívia Brochi Nascimento. "Tonian Continental Arc Magmatism of the Porongos Complex, Dom Feliciano Belt, Southern Brazil". Geologia USP. Série Científica 23, n.º 3 (17 de agosto de 2023): 19–45. http://dx.doi.org/10.11606/issn.2316-9095.v23-208078.
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This study provides new information on the deformation, metamorphism, and tectonic setting of the metavolcanic rocks of the southern portion of the Porongos Complex, southern Brazil. The structural analysis enabled the identification of three deformational phases, formed under ductile to semi-ductile conditions. D1 progressed through deformation partitioning, comprising closed to isoclinal folds and an axial plane foliation. Then, simple shear prevailed, resulting in isoclinal folds, sigma-type porphyroclasts, foliation transposition, and mylonitic rocks. D2 comprises open to gentle folds and an axial plane cleavage. The formation of shear bands is ascribed to the semi-ductile D3. The mineral assemblage represented by phengite + chlorite + clinozoisite-epidote + actinolite + albite + quartz associated with the temperatures obtained through the chlorite geothermometer (316°C) indicates greenschist facies conditions. The protoliths of these metavolcanic rocks are geochemically discriminated as calc-alkaline, dacite-to-rhyodacite, with peraluminous compositions. The bulk trace element compositions show enrichment in large-ion lithophile elements and light rare-earth elements and depletion in heavy rare-earth elements. Also, negative Nb, P, Ti, and Ta anomalies are observed in the multielement diagram. All these geochemical features are typical of rocks formed in continental magmatic arcs. Geochemical comparison with other pre-collisional Tonian orthometamorphic rocks from the Dom Feliciano Belt demonstrates strong similarities, which corroborates the prior interpretation of a continental arc setting for the origin of these Tonian rocks.
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YABE, REGINA DE SOUZA, ELIÉZER JOSÉ MARQUES e MIGUEL ÂNGELO MARINI. "Movements of birds among natural vegetation patches in the Pantanal, Brazil". Bird Conservation International 20, n.º 4 (19 de abril de 2010): 400–409. http://dx.doi.org/10.1017/s0959270910000067.
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SummaryThe ability of birds to move through the landscape is a key parameter for ecological and conservation studies. We studied bird movements among natural vegetation patches surrounded by native grassland and tested the effect of inter-patch distance on bird movements/hour and assessed the distances travelled for species of different body mass. We made observations of 1,138 bird movements among 11 forest patches and banded 368 birds obtaining 69 recaptures (42 recaptures in the same patch where the birds were banded and 27 recaptures in other patches). We used seven patches as observation points and capture sites in the Pantanal wetland, Brazil during one year. Movements/hour decreased significantly with inter-patch distance. Median or maximum distance travelled increased significantly with body mass. Small-bodied Passeriformes, however, did not increase the distance travelled with body mass, since they seldom moved more than 286 m. The majority of forest dependent or semi-dependent birds seem able to adapt to natural fragmented landscapes. However, small forest patches may be inappropriate habitat for many large-bodied species, and it is more difficult for small-bodied species to use more isolated forest patches. Thus, size and spatial arrangement of habitat patches may act as a filter in which large and close fragments seem to protect the highest number of bird species. The findings of this study indicate that stepping stones provide a viable alternative to continuous biological corridors if the latter are not available. However, the type of species in an area and the size and distance between vegetation patches are all critical factors that must be considered in projects that aim to use forest patches as stepping stones to increase or maintain local bird biodiversity.
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Liu, Zefei, Jinqing Li, Xiaoqiang Di, Zhenlong Man e Yaohui Sheng. "A Novel Multiband Remote-Sensing Image Encryption Algorithm Based on Dual-Channel Key Transmission Model". Security and Communication Networks 2021 (18 de novembro de 2021): 1–27. http://dx.doi.org/10.1155/2021/9698371.
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With the rapid development of remote sensing technology, satellite remote sensing images have been involved in many areas of people’s lives. Remote sensing images contain military secrets, land profiles, and other sensitive data, so it is urgent to encrypt remote sensing images. This paper proposes a dual-channel key transmission model. The plaintext related key is embedded into the ciphertext image through bit-level key hiding transmission strategy, which enhanced the ability of ciphertext image to resist known-plaintext attack and chosen plaintext attack. In addition, a multiband remote sensing image encryption algorithm based on Boolean cross-scrambling and semi-tensor product diffusion is designed. Firstly, the pixel positions of each band of the remote sensing image are disturbed. Then, the random sequence generated by the four-dimensional chaotic system is processed and deformed to obtain a Boolean matrix. Based on the generated Boolean matrix and certain rules, the cross-confusion between the bands is carried out. Finally, the semi-tensor product operation is used in the diffusion process. Simulation results and experimental analysis show that the proposed algorithm obtains a larger key space and has stronger antiattack ability than other remote sensing image encryption algorithms. It can meet the security transmission of multiband remote sensing image in open space.
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Tronchin, Lamberto, Angelo Farina, Antonella Bevilacqua, Francesca Merli e Pietro Fiumana. "Comparison Failure and Successful Methodologies for Diffusion Measurements Undertaken inside Two Different Testing Rooms". Applied Sciences 11, n.º 22 (9 de novembro de 2021): 10523. http://dx.doi.org/10.3390/app112210523.
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The scattering phenomenon is known to be of great importance for the acoustic quality of a performance arts space. The scattering of sound can be achieved in different ways: it can be obtained by the presence of architectural and/or decorating elements inside a room (e.g., columns, statues), by the geometry and roughness of a surface (e.g., Quadratic Residue Diffuser (QRD)) and by the diffraction effect occurring when a sound wave hits the edges of an obstacle. This article deals with the surface scattering effects and the diffusion phenomenon only related to MDF and plywood panels tested by disposing the wells both horizontally and vertically. The test results undertaken inside a semi-reverberant room and inside a large reverberant room have been compared to highlight the success and the failure of the measuring methodologies. In detail, according to the existing standards and regulations (i.e., ISO 17497—Part 2), diffusion measurements have been undertaken on a few selected types of panel: two QRD panels (made of Medium Density Fiberboard (MDF) and plywood) with and without a smooth painted solid wood placed behind the QRD. The panels have been tested inside two rooms of different characteristics: a semi-anechoic chamber (Room A) and a large reverberant room (Room B). The volume size influenced the results that have been analyzed for both chambers, showing an overlap of reflections on panels tested inside Room A and a clear diffusion response for the panels tested inside Room B. In terms of the diffusion coefficient in all the octave bands between 125 Hz and 8 kHz, results should not be considered valid for panels tested in Room A because they were negatively impacted by extraneous reflections, while they are reliable for panels tested in Room B.
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Carneiro, Gustavo Fluminense, Matheus Pinheiro Ferreira e Carlos Frederico de Sá Volotão. "Multi-source remote sensing data improves the classification accuracy of natural forests and eucalyptus plantations". Revista Brasileira de Cartografia 72, n.º 1 (30 de março de 2020): 110–25. http://dx.doi.org/10.14393/rbcv72n1-50477.
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It is challenging to map the spatial distribution of natural and planted forests based on satellite images because of the high correlation among them. This investigation aims to increase accuracies in classifications of natural forests and eucalyptus plantations by combining remote sensing data from multiple sources. We defined four vegetation classes: natural forest (NF), planted eucalyptus forest (PF), agriculture (A) and pasture (P), and sampled 410,251 pixels from 100 polygons of each class. Classification experiments were performed by using a random forest algorithm with images from Landsat-8, Sentinel-1, and SRTM. We considered four texture features (energy, contrast, correlation, and entropy) and NDVI. We used F1-score, overall accuracy and total disagreement metrics, to assess the classification performance, and Jeffries–Matusita (JM) distance to measure the spectral separability. Overall accuracy for Landsat-8 bands alone was 88.29%. A combination of Landsat-8 with Sentinel-1 bands resulted in a 3% overall accuracy increase and this band combination also improved the F1-score of NF, PF, P and A in 2.22%, 2.9%, 3.71%, and 8.01%, respectively. The total disagreement decreased from 11.71% to 8.71%. The increase in the statistical separability corroborates such improvement and is mainly observed between NF-PF (11.98%) and A-P (45.12%). We conclude that combining optical and radar remote sensing data increased the classification accuracy of natural and planted forests and may serve as a basis for large-scale semi-automatic mapping of forest resources.
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Díaz-Martínez, Julia Patricia, Eugenio De Jesús Carpizo-Ituarte e Francisco Benítez-Villalobos. "Reproductive patterns of the black starry sea urchin Arbacia stellata in Punta Banda, Baja California, Mexico". Journal of the Marine Biological Association of the United Kingdom 99, n.º 06 (8 de maio de 2019): 1379–91. http://dx.doi.org/10.1017/s0025315419000316.
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AbstractWidely distributed species such as Arbacia stellata adjust patterns of their life history according to local conditions. In the present study the reproductive cycle of this species was analysed throughout a sampling year. Gonadal development cycle, sex ratio, actual fecundity and oocyte size distribution were characterized and the relationship of these reproductive characteristics with environmental variables such as sea surface temperature, photoperiod, chlorophyll a and net primary production evaluated. Our results showed that A. stellata is a gonochoric sea urchin. Gametogenesis was classified into six stages for both sexes (immature, growth, pre-maturity I, pre-maturity II, mature and spawning) and no synchrony was observed for the gonads between individuals. The female to male ratio was close to 1:1 in most months. The gonadosomatic index (GSI) showed significant differences between sexes or months; however, the highest values were observed during spring, with positive correlation with chlorophyll a. No significant differences were observed in the maturity index (MI) between sexes, with a positive correlation with temperature but negative with chlorophyll. Actual fecundity showed wide variations throughout the year and correlation with chlorophyll a and temperature. Oocyte size distribution was unimodal and the predominant frequency was that of mature oocytes. The reproductive cycle of A. stellata has a semi-continuous pattern for both sexes and partial spawning throughout the year in the sampling site. We observed nutrient assimilation in the gonads during spring and a larger reproductive activity from late summer to early winter.
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Lapteva, E., E. Kravchenko, I. Odaryuk, V. Doroshkevich e O. Baranova. "SIMULATION OF THE ELECTRONIC ABSORPTION SPECTRA OF PHENOLS AND PRODUCTS OF THEIR ENZYMATIVE OXIDATION". Russian Journal of Biological Physics and Chemisrty 8, n.º 3 (27 de maio de 2024): 288–92. http://dx.doi.org/10.29039/rusjbpc.2023.0623.
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The possibility of obtaining absorption spectra of phenols and products of their laccase oxidation by quantum-chemical modeling methods is considered. The primary optimization of the structures was carried out by the semi-empirical PM3 method, and the spectra were simulated within the framework of the density functional theory by the DFT/B3LYP/6-311G++dp method in an aqueous medium using the Gamess US program. For most of the studied phenols and their corresponding quinones, spectra containing one absorption band were obtained by calculation methods, for some - a larger number of bands, while in the experimental absorption spectra of these substances in the operating range of the spectrophotometer, as a rule, two bands are visible with different reliability. For most substances, the wavelengths of the absorption maxima of the calculated spectra differ from the experimental ones by no more than 10 nm. The calculated extinction coefficients, as a rule, exceed the experimental ones by 1,5–2 times. For phenols that cannot be directly oxidized to quinones, oligomeric products are considered as products. Their calculated spectra also correlate quite well with the experimental spectrum of the reaction mixture. The spectral characteristics obtained by modeling under these conditions can be used for a rough estimate of the composition of the reaction mixture, but additional studies are needed for their use in accurate quantitative analysis and kinetic studies.
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Wang, Wanneng, Zongli Hu, Jinzhe Li e Guoping Chen. "Expression characterization and actual function of the second pucBA in Rhodobacter sphaeroides". Bioscience Reports 29, n.º 3 (3 de março de 2009): 165–72. http://dx.doi.org/10.1042/bsr20080061.
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The puc2BA operon of Rhodobacter sphaeroides is highly similar to the original puc1BA operon. Genetic, biochemical and spectroscopic approaches were used to investigate the function of puc2BA; the puc1BA and puc2BA structural genes were amplified and cloned into the pRK415 vector controlled by the puc promoter from R. sphaeroides, which was then introduced into R. sphaeroides mutant strains. The results indicated that puc2BA was normally expressed and puc2BA-encoded polypeptides were assembled into membrane LHII (light-harvesting II) complexes, although the puc2A-encoded polypeptide was much larger than the puc1A-encoded polypeptide. Semi-quantitative RT-PCR (reverse transcription-PCR) and SDS/PAGE indicated that puc1BA and puc2BA were expressed in R. sphaeroides when integrated into the genome or expressed from vectors. Furthermore, the polypeptides from the puc1BA and puc2BA genes were both involved in LHII assembly, and pucC is also necessary to assemble LHII complexes. Nevertheless, the LHII complexes synthesized from puc2BA in R. sphaeroides have blue-shift absorption bands at 801 and 846 nm.
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Batista, Jael Soares, Carlos Iberê Alves Freitas, Kaline Alessandra Rodrigues De Paiva, Jardel Bezerra Da Silva, Francisco Silvestre Brilhante Bezerra, Roberio Gomes De Olinda, Taciana Melo Fernandes e Andréia Freitas Oliveira. "Hepatic Lipidosis in Banded Armadillos (Euphractus sexcinctus) Bred in Captivity". Acta Scientiae Veterinariae 44, n.º 1 (16 de janeiro de 2016): 4. http://dx.doi.org/10.22456/1679-9216.84774.
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Background: Wild animals bred in captivity may develop steatosis due to unbalanced dietary intake and obesity caused by sedentary behaviour. In some rural areas, six-banded armadillos are raised in captivity inside some metal barrels, with restricted space, and are often overfeed. After getting fattening, armadillos they are slaughtered and used as food. Theunfavorable conditions may somehow contribute to likely underlie the development of many diseases, among them we can including hepatic steatosis. The present report aims to describe the pathological fndings of hepatic lipidosis in banded armadillos (Euphractus sexcinctus), bred in captivity.Case: The animals were three female adult six-banded armadillos (Euphractus sexcinctus), caught in the native forest of the city of Natal, Rio Grande do Norte, Brazil and raised in domestic environment in a small enclosure and fed with human food leftovers. After eight months kept in these conditions armadillos had severe obesity and then were donated to the city zoo, where they were quarantined and presented clinical symptoms of anorexia for two weeks, weight loss and exhaustion. After being found dead during daily inspection carried out by the veterinarian zoo, the six-banded armadillos were sent to the Animal Pathology Laboratory of Federal Rural University of the Semi-Arid (UFERSA) for pathological examination.The animals presented with a history of anorexia were extremely obese and the autopsy detected had extensive deposits of fat in the carcass and liver. Histopathologically, the liver cells hepatocytes showed marked intracytoplasmic vacuolization and with peripheral displacement of the nucleus to the periphery, with and positive staining for lipids using scarlet Sudan III. To our knowledge, this is the frst report of hepatic lipidosis in banded.Discussion: Hepatic lipidosis can be categorized into normal liver and mild, moderate, or severe fatty liver. In severe cases, it is estimated that 80% of the hepatocytes are affected. Therefore, we classifed the hepatic lipidosis of the three studied female six-banded armadillos as severe, since the lipids were deposited diffusely. Based on the severity of the lesions and absence of other fndings, we concluded here that hepatic lipidosis contributed to the cause of the six-banded armadil los death. The weight of the animals in this report may be associated with innapropriate enclosure dimensions and a diet based on human food leftovers. Such diet was reportedly composed of rice, beens, spaghetti, and bread, which are food with high levels of carbohydrate. The armadillos of the Euphractus sexcinctus species usually weigh between 3 and 6 kg and hence, the animals of this report showed twice the normal weight. The occurrence of hepatic lipidosis associated with anorexia triggered by a stressful event such as a change of environment and diet armadillos observed in the present study is in agreement with literature data pointing anorexia in obese animals as a major predisposing factors for the occurrence of hepatic lipidosis by promoting energy restriction, peripheral lipolysis and large intake of fatty acids to the liver.Keywords: Euphractus sexcinctus, armadillos, anatomopathology, liver, lipidosis.
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Lacy, M., J. A. Surace, D. Farrah, K. Nyland, J. Afonso, W. N. Brandt, D. L. Clements et al. "A Spitzer survey of Deep Drilling Fields to be targeted by the Vera C. Rubin Observatory Legacy Survey of Space and Time". Monthly Notices of the Royal Astronomical Society 501, n.º 1 (30 de novembro de 2020): 892–910. http://dx.doi.org/10.1093/mnras/staa3714.
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ABSTRACT The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will observe several Deep Drilling Fields (DDFs) to a greater depth and with a more rapid cadence than the main survey. In this paper, we describe the ‘DeepDrill’ survey, which used the Spitzer Space Telescope Infrared Array Camera (IRAC) to observe three of the four currently defined DDFs in two bands, centred on 3.6 and 4.5 μm. These observations expand the area that was covered by an earlier set of observations in these three fields by the Spitzer Extragalactic Representative Volume Survey (SERVS). The combined DeepDrill and SERVS data cover the footprints of the LSST DDFs in the Extended Chandra Deep Field–South (ECDFS) field, the ELAIS-S1 field (ES1), and the XMM-Large-Scale Structure Survey field (XMM-LSS). The observations reach an approximate 5σ point-source depth of 2 μJy (corresponding to an AB magnitude of 23.1; sufficient to detect a 10$^{11} \, \mathrm{M}_{\odot}$ galaxy out to z ≈ 5) in each of the two bands over a total area of $\approx 29\,$ deg2. The dual-band catalogues contain a total of 2.35 million sources. In this paper, we describe the observations and data products from the survey, and an overview of the properties of galaxies in the survey. We compare the source counts to predictions from the Shark semi-analytic model of galaxy formation. We also identify a population of sources with extremely red ([3.6]−[4.5] >1.2) colours which we show mostly consists of highly obscured active galactic nuclei.
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Ursella, L., V. Kovačević e M. Gačić. "Tidal variability of the motion in the Strait of Otranto". Ocean Science 10, n.º 1 (13 de fevereiro de 2014): 49–67. http://dx.doi.org/10.5194/os-10-49-2014.
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Abstract. Various current data, collected in the Strait of Otranto during the period 1994–2007, have been analysed with the aim of describing the characteristics of the tidal motions and their contribution to the total flow variance. The principal tidal constituents in the area were the semi-diurnal (M2) and the diurnal (K1), with the latter one predominant. The total flow was, in general, more energetic along the flanks than in the middle of the strait. Specifically, it was most energetic over the western shelf and in the upper layer along the eastern flank. In spite of the generally low velocities (a few cm s−1) of the principal tidal constituents, the tidal variance has a pattern similar to that of the total flow variance, that is, it was large over the western shelf and low in the middle. The proportion of non-tidal (comprising the inertial and sub-inertial low-frequency bands) to tidal flow variances was quite variable in both time and space. The low-frequency motions dominated over the tidal and inertial ones in the eastern portion of the strait during the major part of the year, particularly in the upper and intermediate layers. In the deep, near-bottom layer the variance was evenly distributed between the low frequency, diurnal and semi-diurnal bands. An exception was observed near the western shelf break during the summer season when the contribution of the tidal signal to the total variance reached 77%. This high contribution was mainly due to the intensification of the diurnal signal at that location at both upper and bottom current records (velocities of about 10 cm s−1). Local wind and sea level data were analysed and compared with the flow to find the possible origin of this diurnal intensification. Having excluded the sea-breeze impact on the intensification of the diurnal tidal signal, the most likely cause remains the generation of the topographically trapped internal waves and the diurnal resonance in the tidal response. These waves were sometimes generated by the barotropic tidal signal in the presence of summer stratification and the strong bottom slope. This phenomenon may stimulate diapycnal mixing during the stratified season and enhance ventilation of the near-bottom layers.
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Nolde, Michael, Simon Plank e Torsten Riedlinger. "An Adaptive and Extensible System for Satellite-Based, Large Scale Burnt Area Monitoring in Near-Real Time". Remote Sensing 12, n.º 13 (6 de julho de 2020): 2162. http://dx.doi.org/10.3390/rs12132162.
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In the case of ongoing wildfire events, timely information on current fire parameters is crucial for informed decision making. Satellite imagery can provide valuable information in this regard, since thermal sensors can detect the exact location and intensity of an active fire at the moment the satellite passes over. This information can be derived and distributed in near-real time, allowing for a picture of current fire activity. However, the derivation of the size and shape of an already affected area is more complex and therefore most often not available within a short time frame. For urgent decision making though, it would be desirable to have this information available in near-real time, and on a large scale. The approach presented here works fully automatic and provides perimeters of burnt areas within two hours after the satellite scene acquisition. It uses the red and near-infrared bands of mid-resolution imagery to facilitate continental-scale monitoring of recently occurred burnt areas. To allow for a high detection capacity independent of the affected vegetation type, segmentation thresholds are derived dynamically from contextual information. This is done by using a Morphological Active Contour approach for perimeter determination. The results are validated against semi-automatically derived burnt areas for five wildfire incidents in Europe. Furthermore, these results are compared with three widely used burnt area datasets on a country-wide scale. It is shown that a high detection quality can be reached in near real-time. The large-scale inter-comparison shows that the results coincide with 63% to 76% of the burnt area in the reference datasets. While these established datasets are only available with a time lag of several months or are created by using manual interaction, the presented approach produces results in near-real time fully automatically. This work is therefore supposed to represent a valuable improvement in wildfire related rapid damage assessment.
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Soffiatti, Patricia, e Veronica Angyalossy. "Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger and Brasilicereus Backeberg". Acta Botanica Brasilica 21, n.º 4 (dezembro de 2007): 813–22. http://dx.doi.org/10.1590/s0102-33062007000400006.
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(Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger wâBrasilicereus Backeberg). Arrojadoa, Stephanocereus and Brasilicereus are endemic Brazilian Cereeae, occurring along the Espinhaço Range, in the campos rupestres, cerrados and caatingas, from northern Minas Gerais to southern Bahia. The genera are columnar, erect to semi-erect cacti, except for one species, A bahiensis, which is globose. This study describes the anatomy of dermal, fundamental and vascular systems, aiming to find diagnostic characters for the genera and species. Basal portions of stems were sectioned transversely and longitudinally, and stained with Astrablue and Safranin. The species share a uniseriate epidermis, with thick cuticle; well developed collenchymatic hypodermis, containing prismatic crystals; cortex with numerous mucilage cells, druses and vascular bundles; outside cortex as a palisade parenchyma; periderm composed of lignified cork cells alternating with suberized cells; pheloderm consisting of a few layers of thin-walled cells; phloem composed of solitary or multiple of two to three sieve tube elements, companion cells, axial and radial parenchyma; secondary xylem with solitary to multiple vessels, with simple perforation plates and alternate bordered to semi-bordered pits; axial parenchyma scanty vasicentric to incomplete; libriform septate fibres; large rays. Unlignified parenchyma is seen in the secondary xylem, varying from a few cells to bands among axial and radial elements. The following are considered diagnostic characters: the shape of lignified phellem cells, cubic to radially elongate, which individualizes S. leucostele; an underdeveloped hypodermis and the occurrence of sclereids in the cortex are exclusive to Brasilicereus markgrqfii.
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Wang, Yaqin, Haimei Yang, Wenbo Fan, Changlu Qiao e Kai Sun. "Dynamic Variability of Wind Erosion Climatic Erosivity and Their Relationships with Large-Scale Atmospheric Circulation in Xinjiang, China". Atmosphere 13, n.º 3 (4 de março de 2022): 419. http://dx.doi.org/10.3390/atmos13030419.
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Xinjiang has a serious wind erosion problem due to its fragile ecological condition and sensitivity to climate change. Wind erosion climatic erosivity is a measure of climatic factors influencing wind erosion; evaluating its spatiotemporal variations and relationship with the large-scale circulation pattern can contribute to the understanding of the climate change effect on wind erosion risk. Thus, this study quantified the wind erosion climatic erosivity and examined the connections between climatic erosivity and climate indices using trend analysis, geo-statistical analysis, and cross-wavelet analysis based on the observed daily meteorological data from 64 weather stations in Xinjiang, China during 1969–2019 (50 years). The results indicated that the climatic erosivity showed a significant downward trend at seasonal and annual scales over the past 50 years. Strong seasonality in the C-factor was found, with its highest values in the spring and summer and its lowest values in the winter. The average climatic erosivity was weaker during El Niño events than during La Niña events. The impact of El Niño events on climatic erosivity in Xinjiang continued from the beginning of the event to two months after the end of the events. The La Niña events had a lag effect on the climatic erosivity in Xinjiang, with a lag period of 4 months. From a statistical perspective, the El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO) indices showed relationships to the climatic erosivity in Xinjiang in terms of their correlation and periodicity. The relationships between the climatic erosivity and ENSO were not clearly positive or negative, with many correlations advanced or delayed in phase. The NAO and AO indices showed a consistent in-phase relationship with climatic erosivity on significant bands, whereas the profound mechanisms involved in this require further study. The results of this study provide a preliminary perspective on the effect of large-scale atmospheric circulation on wind erosion risk in arid and semi-arid regions.
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Niu, Sida, Liqun Zhao, Xiaoju Lin, Tong Chen, Yingchao Wang, Lingchao Mo, Xianglong Niu et al. "Mineralogical Characterization of Manganese Oxide Minerals of the Devonian Xialei Manganese Deposit". Minerals 11, n.º 11 (9 de novembro de 2021): 1243. http://dx.doi.org/10.3390/min11111243.
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The Guangxi Zhuang Autonomous Region is an important manganese ore district in Southwest China, with manganese ore resource reserves accounting for 23% of the total manganese ore resource reserves in China. The Xialei manganese deposit (Daxin County, Guangxi) is the first super-large manganese deposit discovered in China. The Mn oxide in the supergene oxidation zone of the Xialei deposit was characterized using scanning electron microscopy (SEM), energy spectrometer (EDS), transmission electron microscopy (TEM, HRTEM), and X-ray diffraction analysis (XRD). The Mn oxides have a gray-black/steel-gray color, a semi-metallic-earthy luster, and appear as oolitic, pisolitic, banded, massive, and cellular textures. Scanning electron microscopy images show that the manganese oxide minerals are present as fine-spherical particles with an earthy surface. TEM and HRTEM indicate the presence of oriented bundled and staggered nanorods, and nanopores between the crystals. The Mn oxide ore can be classified into two textural types: (1) oolitic and pisolitic (often with annuli) Mn oxide, and (2) massive Mn oxide. Pyrolusite, cryptomelane, and hollandite are the main Mn oxide minerals. The potassium contents of cryptomelane and pyrolusite are discussed. The unit cell parameters of pyrolusite are refined.
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Wang, Cong, Zhiyuan Xu, Ke Xu e Guoying Gao. "Excellent Room-Temperature Thermoelectricity of 2D GeP3: Mexican-Hat-Shaped Band Dispersion and Ultralow Lattice Thermal Conductivity". Molecules 26, n.º 21 (21 de outubro de 2021): 6376. http://dx.doi.org/10.3390/molecules26216376.
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Although some atomically thin 2D semiconductors have been found to possess good thermoelectric performance due to the quantum confinement effect, most of their behaviors occur at a higher temperature. Searching for promising thermoelectric materials at room temperature is meaningful and challenging. Inspired by the finding of moderate band gap and high carrier mobility in monolayer GeP3, we investigated the thermoelectric properties by using semi-classical Boltzmann transport theory and first-principles calculations. The results show that the room-temperature lattice thermal conductivity of monolayer GeP3 is only 0.43 Wm−1K−1 because of the low group velocity and the strong anharmonic phonon scattering resulting from the disordered phonon vibrations with out-of-plane and in-plane directions. Simultaneously, the Mexican-hat-shaped dispersion and the orbital degeneracy of the valence bands result in a large p-type power factor. Combining this superior power factor with the ultralow lattice thermal conductivity, a high p-type thermoelectric figure of merit of 3.33 is achieved with a moderate carrier concentration at 300 K. The present work highlights the potential applications of 2D GeP3 as an excellent room-temperature thermoelectric material.
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Kasheba, M., e B. Melekh. "Comparison of the photoionisation modelling results for planetary nebulae with the observed data". Advances in Astronomy and Space Physics 10, n.º 1 (2020): 12–20. http://dx.doi.org/10.17721/2227-1481.10.12-20.
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The grid of new photoionisation models for planetary nebulae (PNe) along the evolutionary tracks of their nuclei was calculated, taking into account the dust presence with abundances that correspond to the averaged ones for Milky Way and Large Magellanic Cloud. The calculations were performed by the last version of G. Ferland's code Cloudy v17.01 using the semi-empirical law derived by Golovatyy-Mal'kov to describe the radial density distribution of matter in the nebular envelope of PN. Resulting modelling spectra were compared with the corresponding observed emission line spectra of PNe in optical range, obtained previously by other authors. Also the database of observations by the Infrared Space Observatory and Spitzer have been used to compare the results of synthetic photometry with the observed photometric data. It was shown that the intensities of strong emission lines in optical range as well as the observed color-color diagrams obtained using total fluxes in the 3.6 μm, 4.5μm, 8.0μm and 24.0 μm bands are reproduced very well by our models, while the results of synthetic IR-photometry based on total fluxes in the band 5.8 μm show discrepancies with corresponding observed data.
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Bousbih, Safa, Mehrez Zribi, Charlotte Pelletier, Azza Gorrab, Zohra Lili-Chabaane, Nicolas Baghdadi, Nadhira Ben Aissa e Bernard Mougenot. "Soil Texture Estimation Using Radar and Optical Data from Sentinel-1 and Sentinel-2". Remote Sensing 11, n.º 13 (27 de junho de 2019): 1520. http://dx.doi.org/10.3390/rs11131520.
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This paper discusses the combined use of remotely sensed optical and radar data for the estimation and mapping of soil texture. The study is based on Sentinel-1 (S-1) and Sentinel-2 (S-2) data acquired between July and early December 2017, on a semi-arid area about 3000 km2 in central Tunisia. In addition to satellite acquisitions, texture measurement samples were taken in several agricultural fields, characterized by a large range of clay contents (between 13% and 60%). For the period between July and August, various optical indicators of clay content Short-Wave Infrared (SWIR) bands and soil indices) were tested over bare soils. Satellite moisture products, derived from combined S-1 and S-2 data, were also tested as an indicator of soil texture. Algorithms based on the support vector machine (SVM) and random forest (RF) methods are proposed for the classification and mapping of clay content and a three-fold cross-validation is used to evaluate both approaches. The classifications with the best performance are achieved using the soil moisture indicator derived from combined S-1 and S-2 data, with overall accuracy (OA) of 63% and 65% for the SVM and RF classifications, respectively.
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Dong, Naghedolfeizi, Aberra e Zeng. "Spectral–Spatial Discriminant Feature Learning for Hyperspectral Image Classification". Remote Sensing 11, n.º 13 (29 de junho de 2019): 1552. http://dx.doi.org/10.3390/rs11131552.
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Sparse representation classification (SRC) is being widely applied to target detection in hyperspectral images (HSI). However, due to the problem in HSI that high-dimensional data contain redundant information, SRC methods may fail to achieve high classification performance, even with a large number of spectral bands. Selecting a subset of predictive features in a high-dimensional space is an important and challenging problem for hyperspectral image classification. In this paper, we propose a novel discriminant feature learning (DFL) method, which combines spectral and spatial information into a hypergraph Laplacian. First, a subset of discriminative features is selected, which preserve the spectral structure of data and the inter- and intra-class constraints on labeled training samples. A feature evaluator is obtained by semi-supervised learning with the hypergraph Laplacian. Secondly, the selected features are mapped into a further lower-dimensional eigenspace through a generalized eigendecomposition of the Laplacian matrix. The finally extracted discriminative features are used in a joint sparsity-model algorithm. Experiments conducted with benchmark data sets and different experimental settings show that our proposed method increases classification accuracy and outperforms the state-of-the-art HSI classification methods.
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Ngongolo, Kelvin, e Andrew Chota. "Effect of management systems, practices, flock size, and age group on the growth performance of chicks from local chickens farmers". Berkala Penelitian Hayati 27, n.º 1 (2 de agosto de 2021): 1–5. http://dx.doi.org/10.23869/bphjbr.27.1.20211.
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The improved growth performance of chicks determines the production efficiency of chicken to local chicken farmers. Little has been done to understand the contribution of management systems and practices to the growth performance of chicks from farmers who are involved in rearing local chickens in Dodoma. We focused on assessing how the growth performance of chicks (length and weight) from local chicken farmers is affected by management systems (Free range and semi-intensive systems), management practices such as water provision, supplement feeding, regular cleaning, flock size, and size of banda (hut) used to raise chickens. Data were collected for 8 rounds within 2 months (once per week) from 5 farmers in three wards: Nkuhungu (n=2), Mbwanga (n=2), and Mtube (n=1). In each round, data were collected from 10 chicks per farmer (n=400 chicks for all 8 rounds and 5 farmers). Kruskal Wallis was used to determine the variation in growth performance while generalized linear model was used to assess the effect of flock size, management system on the growth performance of chicks. Growth performance was significantly increased and affected by age (P<0.05). The management system significantly contributed to the growth performance of the chicks (P less than 0.001). In addition, the small size of the banda (hut) with large flock size reduced the growth performance of chicks due to increased competition in terms of space, supplements, water supplied, feed provided, and treatment (P less than 0.05). In raising local chicken, local farmers need to be concerned in applying management practices such as supplement feeding, treatment, flock size and size of huts.
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Baker, Denise. "Post-levy apprenticeships in the NHS – early findings". Higher Education, Skills and Work-Based Learning 9, n.º 2 (13 de maio de 2019): 189–99. http://dx.doi.org/10.1108/heswbl-10-2018-0114.
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Purpose The purpose of this paper is to investigate apprenticeship developments in two National Health Service (NHS) organisations since the introduction of the apprenticeship levy in April 2017 and considers potential impact on social mobility. This is a pilot for a broader exploration of implementation of government apprenticeship policy in the NHS. Design/methodology/approach Following ethical approval, semi-structured interviews were conducted with two key informants with responsibility for education and training in their respective organisations. Interviews were recorded and transcribed verbatim. Thematic analysis was undertaken to identify major and sub-themes of the interviews. Findings Four major themes were identified – organisational readiness, the apprenticeship offer, opportunities for further development and potential problems with implementation. Both organisations were actively seeking opportunities to spend their levy and had developed local strategies to ensure this. The levy was being used to develop both new and existing staff, with leadership and management being particularly identified as an area of growth. Similarly, both organisations were using levy monies to develop the bands 1–4 roles, including the nursing associate. The affordability and bureaucracy of apprenticeships were seen as potential problems to the wider implementation of apprenticeships in the NHS. Practical implications Although the apprenticeship levy is being spent in the NHS, there are some challenges for employers in their delivery. The levy is offering new and existing staff the opportunity to undertake personal and professional development at a range of educational levels. This has the potential to increase and upskill the NHS workforce, improve social mobility and possibly lead to larger cultural and professional changes. Originality/value This paper offers an early insight into the implementation of apprenticeship policy in a large public sector employer such as the NHS.