Search

Two new diatom species belonging to the genus Gomphonemopsis are described, Gomphonemopsis nana sp. nov. and Gomphonemopsis gaoi sp. nov. These two species were compared in detail with congeners. Gomphonemopsis nana is distinguished by its high stria density and small size. This species was found so far to be epiphytic only on the eelgrass collected from Qingdao Bay (Yellow Sea). Gomphonemopsis gaoi is characterized by its isopolar valves, simple proximal raphe endings and acutely rounded apices. This taxon was separated from the exoskeleton of marine copepods sampled from the Futian Mangrove Nature Reserve (South China Sea). In addition, two new combinations, Gomphonemopsis oahuensis (Hustedt) Lang Li, Yuhang Li & Changping Chen, comb. nov. and Gomphonemopsis platypus (Østrup) Lang Li, Yuhang Li & Junxiang Lai, comb. nov. are proposed. This study increases the records and knowledge of Gomphonemopsis along the coast of China. [ABSTRACT FROM AUTHOR]

Nonlinear bending analysis was performed of magnetoelectroelastic (MEE) composite plates under a mechanical and magnetoelectric (ME) load by using von Karman's nonlinear geometric equation and the higher order shear deformation theory (HSDT). Nonlinear higher order partial differential equations for MEE plates were derived by using Hamiltonian equilibrium equation. The MEE plate is considered to have clamped boundary condition. The nonlinear high-order equations can turn into algebraic equations through Galerkin method. Then the effects of scale effect of MEE plate (for instance, the aspect ratio) and external load (for instance, mechanical) on the displacement of the considered MEE plate were investigated. [ABSTRACT FROM AUTHOR]

Microalgae are considered as attractive feedstocks for biofuel production nowadays because of their high lipid contents and easy cultivation. In the present study, two diatoms, Thalassiosira weissflogii and Chaetoceros muelleri, were cultured under various nutrient-limitation conditions to explore their comprehensive lipid accumulation profiles for further commercialization. In T. weissflogii, the highest neutral lipid accumulation and highest lipid productivity (14.28 mg L−1 day−1) were both recorded under P-limitation. In C. muelleri, the highest lipid content (35.03% of dry cell weight), highest neutral lipid accumulation, and highest lipid productivity (29.07 mg L−1 day−1) were all recorded under N-limitation. Besides, the predominant fatty acids of T. weissflogii and C. muelleri were myristic acid (C14:0), palmitic acid (C16:0), and palmitoleic acid (C16:1), with the amounts of 58.4-74.4 and 74.1-87.7% of the total fatty acids, respectively. Moreover, nutrient limitations led to a lower proportion of polyunsaturated fatty acids (PUFA) than that of saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) in both species. The ratios of (SFA + MUFA) to PUFA were from 1.65 to 3.01 in T. weissflogii, and up to 3.61 to 8.59 in C. muelleri. Our results suggested the feasibility of C. muelleri as biodiesel feedstock due to its more suitable fatty acid composition and higher lipid productivity compared to T. weissflogii. [ABSTRACT FROM AUTHOR]

With employing the von Karman plate theory, and considering the linearly thickness variation in one direction, the bending problem of a rectangular magnetoelectroelastic plates with linear variable thickness is investigated. According to the Maxwell’s equations, when applying the magnetoelectric load on the plate’s surfaces and neglecting the in-plane electric and magnetic fields in thin plates, the electric and magnetic potentials varying along the thickness direction for the magnetoelectroelastic plates are determined. The nonlinear differential equations for magnetoelectroelastic plates with linear variable thickness are established based on the Hamilton’s principle. The Galerkin procedure is taken to translate a set of differential equations into algebraic equations. The numerical examples are presented to discuss the influences of the aspect ratio and span–thickness ratio on the nonlinear load–deflection curves for magnetoelectroelastic plates with linear variable thickness. In addition, the induced electric and magnetic potentials are also presented with the various values of the taper constants. [ABSTRACT FROM AUTHOR]

A mechanical model is proposed to describe the vibration of a taut inclined cable excited by a deck. The dynamic system is simplified into a one-degree-of-freedom nonlinear system with non-dimensional parameters by using the Galerkin and non-dimensional analysis methods. The periodicity ratio (PR) method is improved and applied to the parameter analysis for the cable system. The frequency ratio between the natural frequency of the cable and the vibration frequency of the deck and the amplitude of deck vibration are the main variable parameters, and nonlinear motion is diagnosed for a large range of parameters. Several forms of motion are distinguished, and the evolution between the forms is studied. Meanwhile, several types of parametric resonance are revealed in different ranges of parameters. The results indicate that the parametric resonance in the case of a 3:2 frequency ratio is significant and should be given more attention. [ABSTRACT FROM AUTHOR]

Diatoms are important components of marine ecosystems and contribute greatly to the world’s primary production. Despite their important roles in ecosystems, the molecular basis of how diatoms cope with oxidative stress caused by nutrient fluctuations remains largely unknown. Here, an isobaric tags for relative and absolute quantitation (iTRAQ) proteomic method was coupled with a series of physiological and biochemical techniques to explore oxidative stress- and cell fate decision-related cellular and metabolic responses of the diatom Thalassiosira pseudonana to nitrate (N) and inorganic phosphate (P) stresses. A total of 1151 proteins were detected; 122 and 56 were significantly differentially expressed from control under N- and P-limited conditions, respectively. In N-limited cells, responsive proteins were related to reactive oxygen species (ROS) accumulation, oxidative stress responses and cell death, corresponding to a significant decrease in photosynthetic efficiency, marked intracellular ROS accumulation, and caspase-mediated programmed cell death activation. None of these responses were identified in P-limited cells; however, a significant up-regulation of alkaline phosphatase proteins was observed, which could be the major contributor for P-limited cells to cope with ambient P deficiency. These findings demonstrate that fundamentally different metabolic responses and cellular regulations are employed by the diatom in response to different nutrient stresses and to keep the cells viable. [ABSTRACT FROM AUTHOR]

Investigation of the production and structural characteristics of the extracellular polysaccharides (ECPS) released by diatoms according to nutrient status is urgently necessary for our understanding of the roles of ECPS in aquatic ecosystem. In this study, the effects of N and P depletion and variable nutrient sources on the production and structural characterization of the soluble ECPS released by the marine diatom Thalassiosira pseudonana in batch culture were examined. The abundance of the soluble ECPS produced under N (NO) depletion was higher than that obtained in the P (PO) depletion and control treatments. NH rather than NO and urea and sodium-glycerophosphate rather than PO were found to induce a higher abundance of soluble ECPS production at the end of the experiment, indicating that the abundance of soluble ECPS is also affected by the nutrient source. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis of the structural characteristics of the soluble ECPS samples showed that the degree of polymerization (d.p.) profiles and the distribution of the polymers with different molecular masses varied in response to nutrient depletion and different nutrient sources. An increase in the proportion of both low- and high-molecular-weight polymers under the N (NO) and P (PO) depletion treatments was found. Based on the different characteristics of high- and low-molecular-weight polymers, our results suggest that the production of soluble ECPS may be one of the strategies that T. pseudonana utilizes to survive under nutrient stress conditions. [ABSTRACT FROM AUTHOR]

A new complementary metal oxide semiconductor UV/blue-extended photodiode was presented for light detection in the UV/blue spectral range. Photoelectric characteristics of this presented photodiode were studied by numerical modeling and device simulation. Technology computer aided design simulation was done first to analyze its photoelectric characteristics. The structure characteristic and depletion situation of space between two adjacent P anodes were discussed. The reverse characteristic, spectral response characteristic and DC characteristic were discussed in detail. For the numerical modeling, dead layer effect is considered in the building of analytical mode. Dead layer is a space in which the boron doping profile decreases towards the surface due to high doping effects and boron redistribution, which affects the sensitivity of photodiode in the UV range seriously. Reverse characteristics and spectral response characteristics were modeled and analyzed typically. At last, silicon test results were given and compared with the simulated result, which shows reasonable match for each. [ABSTRACT FROM AUTHOR]

A novel composite ultraviolet (UV)/blue photodetector is proposed in this paper. Lateral ring-shaped PN junction is used to separate photogenerated carriers and inject the non-equilibrium excess carriers to the bulk, changing the bulk potential and shifting the threshold voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) as well as the drain current. Numerical simulation is carried out, and the simulation results show that the composite photodetector has the enhanced responsivity for UV/blue spectrum. It exhibits very high sensitivity to weak and especially ultra-weak light. A responsivity of 7000 A/W is obtained when the photodetector is illuminated under incident optical power of 0.01 μW. As a result, this proposed combined photodetector has great potential for UV/blue and ultra-weak light applications. [ABSTRACT FROM AUTHOR]

The extracellular polysaccharides (ECPS) released by diatoms have significant roles in marine ecosystems and have potential applications including drug-discovery and biopharmaceutical precursors. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technology was used in the structural analysis of the ECPS released by Thalassiosira pseudonana (Bacillariophyta). Three different deproteinization methods, the Sevag method, the trichloroacetic acid (TCA) method, and the enzymolysis method, were compared in the purification of ECPS. Our results suggested that TCA was the best deproteinization method among the three methods for subsequent MALDI-TOF MS investigation because of its high ECPS yield, protein removal ability and reliable MALDI-TOF MS fingerprint. The degree of polymerization (d.p.) profiles, the molecular weight of the ECPS and the distribution pattern of the polymers with different molecular mass were described from the MALDI-TOF MS spectra. This work represents the whole-level composition of the ECPS released by the diatom and has improved our knowledge of the structural characterization of ECPS. [ABSTRACT FROM AUTHOR]

Based on rigid kinematics theory and lumped mass method, a mathematical model of the two net cages of grid mooring system under waves is developed. In order to verify the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and the experimental results, it can be found that the simulated and the experimental results agree well in each wave condition. Then, the forces on the mooring lines and the floating collar movement are calculated under different wave conditions. Numerical results show that under the same condition, the forces on the bridle ropes are the largest, followed by forces on the main ropes and the grid ropes. The horizontal and the vertical float collar motion amplitudes increase with the increase of wave height, while the relationship of the horizontal motion amplitude and the wave period is indistinct. The vertical motion amplitude of the two cages is almost the same, while on the respect of horizontal motion amplitude, cage B (behind cage A, as shown in Fig. 4) moves much farther than cage A under the same wave condition. The inclination angle of the floating system both in clockwise along y axis and the counter one enlarges a little with the increase of wave height. [ABSTRACT FROM AUTHOR]

A novel integrated ultraviolet (UV) photodetector has been proposed, which realizes a high UV selectivity by combining a conventional UV-selective photodiode with an extra infrared (IR) photodiode. The IR photodiode is designed for compensating the photocurrent response of the UV photodiode in the infrared band and is 15 times smaller than the UV one. The integrated photodetector has been fabricated in a 0.35 μm standard CMOS technology. Some critical performance indices of this new structure photodetector, such as spectral responsivity, breakdown voltage, quenching waveform, and transient response, are measured and analyzed. Test results show that the complementary UV–IR photodetector has a maximum spectral responsivity of 0.27 A·W−1 at the wavelength of 400 nm. The device has a high UV selectivity of 3000, which is much higher than that of the single UV photodiode. [ABSTRACT FROM AUTHOR]