82 research outputs found
Variación espacial y estacional de Cianobacterias y sus tasas de fijación de nitrógeno en la BahÃa de Sanya en el Sur del Mar de China
The nitrogen fixation rates of planktonic and intertidal benthic cyanobacteria were investigated in Sanya Bay from 2003 to 2005. Trichodesmium thiebautii was the dominant species of planktonic cyanobacteria during our study. Significant seasonal and spatial variations in Trichodesmium spp. abundance were observed (P<0.01). The highest Trichodesmium concentrations occurred during intermonsoon periods and in the outer region of Sanya Bay (Outer Bay stations). At fixed station S03 the abundance of T. thiebautii ranged from 1.14×103 to 2060×103 trichomes m–2, with an annual mean of 273×103 trichomes m–2. The average nitrogen fixation rate per colony of T. thiebautii was 0.27 nmol N h-1 colony-1 and it did not show any obvious seasonal variations. Nitrogen fixation by planktonic cyanobacteria was highest in the Outer Bay stations, where the estimated amount of new nitrogen introduced by Trichodesmium contributed 0.03 to 1.63% of the total primary production and up to 11.64% of the new production. Statistical results showed that significant seasonal and spatial variations of nitrogen fixation rates were found among the intertidal communities. The main benthic nitrogen-fixing cyanobacteria were identified as members of the genera Anabaena, Calothrix, Lyngbya, Nostoc and Oscillatoria. The highest nitrogen fixation rate was found in microbial mats and the lowest in reefs and rocky sediments. All the benthic communities studied presented their highest nitrogen fixation activity in summer, with an average nitrogen fixation rate of 33.31 µmol N h-1 m-2, whereas the lowest nitrogen activity was detected in winter, with an average nitrogen fixation rate of 5.66 µmol N h-1 m-2. A Pearson correlation analysis indicated that the nitrogen fixation rate of three types of intertidal communities was significantly positively correlated to seawater temperature (P<0.05), whereas only the nitrogen fixation rate of the reefs and rock communities was significantly negatively correlated to seawater salinity (P<0.05).Las tasas de fijación de nitrógeno de cianobacterias intermareales y bentónicas fueron investigadas en la BahÃa de Sanya, desde 2003 a 2005. Trichodesmium thiebautii era la especie dominante de las cianobacterias planctónicas durante nuestra investigación. Se observaron variaciones espaciales y estacionales significativas (P<0.01) en la abundancia de Trichodesmium spp. La concentración más elevada de Trichodesmium se observó durante los perÃodos de intermonzón y en la región exterior de la BahÃa de Sanya (estaciones fuera de la BahÃa). En la estación fija S03 la abundancia de T. thiebautii variaba desde 1.14×103 a 2060×103 tricomas m–2, con una media anual de 273×103 tricomas m–2. El promedio de la tasa de fijación de nitrógeno por colonia de T. thiebautii era de 0.27 nmol N h-1 colonia y no mostraba una clara variación estacional. La fijación de nitrógeno por las cianobacterias planctónicas era superior en las estaciones de fuera de la BahÃa, donde la cantidad estimada de nitrógeno nuevo introducido por Trichodesmium contribuÃa del 0.03 al 1.63% del total de la producción primaria y hasta el 11.64% de la producción nueva. EstadÃsticamente los resultados mostraban que las variaciones espaciales y estacionales significativas de las tasas de fijación de nitrógeno fueron encontradas entre las comunidades intermareales. Las principales cianobacterias bentónicas fijadoras de nitrógeno fueron identificadas como miembros de los géneros Anabaena, Calothrix, Lyngbya, Nostoc y Oscillatoria. La tasa de fijación de nitrógeno más alta fue encontrada en los tapetes microbianos y las más bajas en los arrecifes y sedimentos rocosos. Todas las comunidades bentónicas estudiadas presentaban la mayor actividad de fijación de nitrógeno en verano, con un promedio de tasas de fijación de 33.31 ?mol N h-1 m-2, mientras que la menor actividad de fijación de nitrógeno fue detectada en invierno, con un promedio de 5.66 ?m N h-1 m-2. Análisis de correlación (Pearson) indicaban que las tasas de fijación de nitrógeno en los tres tipos de comunidades intermareales estaban significativamente correlacionados con la temperatura del agua (P<0.05). Mientras que la tasa de fijación de nitrógeno de las comunidades de los arrecifes y sedimentos rocosos estaban correlacionadas significativamente con la salinidad del agua de mar (P<0.05)
Distribución del fitoplancton y su relación con variables ambientales en Sanya Bay, mar del Sur de la China
Phytoplankton quantification was conducted in Sanya Bay from January 2005 to February 2006. A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups (green algae, diatoms and dinoflagellates, cryptophytes and cyanobacteria) was used. Seasonal variation of total chlorophyll a concentration showed that high value appeared in summer and low concentration occurred in spring. Diatoms and dinoflagellates group was the predominant phytoplankton all year in the Bay. The stable stratification of phytoplankton vertical distribution came into being in July. During the stratification event, the total chlorophyll a concentration of deep layer was much higher than the surface; cyanobacteria and cryptophyta groups decreased and almost disappeared, however, the concentration of green algae and diatoms and dinoflagellates groups increased. In deep layer, the concentration of diatoms and dinoflagellates group increased sharply, which was about eight times more than that in the surface layer. The vertical profiles character of phytoplankton showed that from inshore stations to outer bay the stratification of phytoplankton vertical distribution gradually strengthened. Dissolved inorganic nutrient especially phosphate and inorganic nitrogen and cold-water upwelling were the main regulating factor for phytoplankton distribution.Desde enero 2005 a febrero 2006, en Sanya Bay se llevó a cabo la cuantificación del fitoplancton. Para ello se usó un espectrofotómetro sumergible in situ que permitÃa la diferenciación de cuatro grupos de algas (algas verdes, diatomeas y dinoflagelados, criptofitas y cianobacterias). La variación estacional de la concentración de clorofila a, mostraba que los valores altos aparecÃan en verano y los bajos en invierno. Durante todo el año el grupo de fitoplancton predominante era el de dinoflagelados y diatomeas. La estratificación estable de la distribución vertical del fitoplancton aparecÃa en julio. Durante la estratificación la concentración total de la clorofila a de la capa profunda era más alta que en la superficie; los grupos de crisófitas y cianobacterias decrecÃan hasta casi desaparecer, sin embargo la concentración de algas verdes y diatomeas se incrementaba. En la capa profunda la concentración del grupo formado por diatomeas y dinoflagelados se incrementaba considerablemente con concentraciones ocho veces más elevadas que en la superficie. El carácter de los perfiles verticales de fitoplancton desde las estaciones costeras hasta fuera de la BahÃa aparecÃa gradualmente más definido. Los nutrientes inorgánicos correspondientes a fósforo y nitrógeno junto con la subida de agua frÃa eran los factores principales que regulaban la distribución del fitoplancton
Estructura de la comunidad bacteriana en sedimentos de manglares en relación a variables medioambientales mediante análisis de fragmentos del gen 16S rRNA y electroforesis en geles desnaturalizantes
Bacterial community structure and the relationship between environmental variables and microbial communities in the surface sediments of tropical mangrove ecosystems were investigated in Sanya, Hainan Island, China. Profiles of bacterial communities were generated using culture-independent PCR-denaturing gradient gel electrophoresis (DGGE), and the results were interpreted with multivariate statistical analysis. Findings suggested that microbial communities varied with sample collection sites and seasons. The samples collected from the same sample sites at the same time had more similar microbial communities except samples SH3 and AB5, which also had unique sediment quality. Canonical correspondence analysis (CCA) revealed that the organic carbon concentration of the sediments accounted for a significant amount of the variability in the bacterial community composition. Phylogenetic analysis was used to identify the major groups of the predominant bacterial phylotypes. 16S rRNA gene-V3 fragments from 17 individual DGGE bands were sequenced and the corresponding bacteria were found in mangrove sediments for the first time based on BLAST results. Predominant bacterial phylotypes clustered with various taxonomic groups, including Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria and Firmicutes.La estructura de la comunidad bacteriana y la relación entre variables ambientales y las comunidades microbianas de la superficie de sedimentos de los ecosistemas tropicales de manglares fueron investigados en Sanya, Hainan Island, China. Los perfiles de las comunidades bacterianas fueron obtenidos utilizando electroforesis de gradiente de gel desnaturalizante (DGE), cultivo-independiente, y los resultados fueron interpretados con un análisis estadÃstico multivariante. Los resultados sugerÃan que las comunidades microbianas variaban con los lugares de muestreo y las estaciones. Las muestras recogidas en el mismo lugar de muestreo y al mismo tiempo tenÃan comunidades microbianas similares, excepto las muestras SH3 y AB5, que tenÃan diferente calidad de sedimentos. El análisis de correspondencia (CCA) mostró que la concentración de carbono orgánico en sedimentos explicaba una parte importante de la variabilidad en la composición de la comunidad bacteriana. Los análisis filogenéticos fueron usados para identificar los grupos más importantes de filotipos predominantes de bacterias. Se secuenciaron fragmentos 16 rRNA gene-V3 de 17 bandas individuales de DGE y las bacterias correspondientes fueron encontradas por primera vez en sedimentos de manglares en base a resultados de BLAST. Los filotipos de bacterias predominantes se agrupaban con varios grupos taxonómicos que incluyen Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria y Firmicutes
Modeling Studies of Gravity Wave Dynamics in Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, and Induced Flow Responses
A compressible numerical model is applied for three-dimensional (3-D) gravity wave (GW) packets undergoing momentum deposition, self-acceleration (SA), breaking, and secondary GW (SGW) generation in the presence of highly-structured environments enabling thermal and/or Doppler ducts, such as a mesospheric inversion layer (MIL), tidal wind (TW), or combination of MIL and TW. Simulations reveal that ducts can strongly modulate GW dynamics. Responses modeled here include reflection, trapping, suppressed transmission, strong local instabilities, reduced SGW generations, higher altitude SGW responses, and induced large-scale flows. Instabilities that arise in ducts experience strong dissipation after they emerge, while trapped smaller-amplitude and smaller-scale GWs can survive in ducts to much later times. Additionally, GW breaking and its associated dynamics enhance the local wind along the GW propagation direction in the ducts, and yield layering in the wind field. However, these dynamics do not yield significant heat transport in the ducts. The failure of GW breaking to induce stratified layers in the temperature field suggests that such heat transport might not be as strong as previously assumed or inferred from observations and theoretical assessments. The present numerical simulations confirm previous finding that MIL generation may not be caused by the breaking of a transient high-frequency GW packet alone
Classification of knee osteoarthritis based on quantum-to-classical transfer learning
Quantum machine learning takes advantage of features such as quantum computing superposition and entanglement to enable better performance of machine learning models. In this paper, we first propose an improved hybrid quantum convolutional neural network (HQCNN) model. The HQCNN model was used to pre-train brain tumor dataset (MRI) images. Next, the quantum classical transfer learning (QCTL) approach is used to fine-tune and extract features based on pre-trained weights. A hybrid quantum convolutional network structure was used to test the osteoarthritis of the knee dataset (OAI) and to quantitatively evaluate standard metrics to verify the robustness of the classifier. The final experimental results show that the QCTL method can effectively classify knee osteoarthritis with a classification accuracy of 98.36%. The quantum-to-classical transfer learning method improves classification accuracy by 1.08%. How to use different coding techniques in HQCNN models applied to medical image analysis is also a future research direction
Thermo-Responsive Molecularly Imprinted Hydrogels for Selective Adsorption and Controlled Release of Phenol From Aqueous Solution
In this study, thermo-responsive molecularly imprinted hydrogels (T-MIHs) were developed as an effective potential adsorbent for selectively adsorption phenol from wastewater. During the process, N-isopropyl acrylamide (NIPAm) was used as thermal responsive monomer. The obtained materials were characterized in detail by fourier transform infrared (FT-IR) spectrometer, scanning electron microscope (SEM), and thermo gravimetric analysis (TGA). A series of static adsorption studies were performed to investigate the kinetics, specific adsorption equilibrium, and selective recognition ability of phenol. Reversible adsorption and release of phenol were realized by changing temperatures. Three type of phenols, namely 3-chlorophenols (3-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) were selected as model analytes to evaluate the selective recognition performance of T-MIHs. The T-MIHs have good selectivity, temperature response, and reusability, making them ideal in applying in the controlled separation and release of phenol pollutants
Phytoplankton distribution and their relationship to environmental variables in Sanya Bay, South China Sea
Bacterial community structure of mangrove sediments in relation to environmental variables accessed by 16S rRNA gene-denaturing gradient gel electrophoresis fingerprinting
Optimization of Total Flavonoid Compound Extraction from Gynura medica Leaf Using Response Surface Methodology and Chemical Composition Analysis
Optimization of total flavonoid compound (TFC) extraction from Gynura medica leaf was investigated using response surface methodology (RSM) in this paper. The conditions investigated were 30–60% (v/v) ethanol concentration (X1), 85–95 °C extraction temperature (X2) and 30–50 (v/w) liquid-to-solid ratio (X3). Statistical analysis of the experiments indicated that temperature and liquid-to-solid ratio significantly affected TFC extraction (p < 0.01). The Box-Behnken experiment design showed that polynomial regression models were in good agreement with the experimental results, with the coefficients of determination of 0.9325 for TFC yield. The optimal conditions for maximum TFC yield were 55% ethanol, 92 °C and 50 (v/w) liquid-to-solid ratio with a 30 min extraction time. Extracts from these conditions showed a moderate antioxidant value of 54.78 μmol quercetin/g dry material (DM), 137.3 μmol trolox/g DM for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 108.21 μmol quercetin/g DM, 242.31 μmol trolox/g DM for 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS+), respectively. HPLC-DAD-MS analysis showed that kaempferol-3-O-glucoside was the principal flavonoid compound in Gynura medica leaf
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