Search

The unicellular green microalga Desmodesmus sp. S1 can produce total lipid over 50% of cell dry weight. A mutant D90G-19 induced by 12C6+ heavy ion irradiation generates more lipid which is 20% higher than its wild type (WT) under high light. The gene expression profiles in the photosynthetic pathway between the Desmodesmus sp. S1 WT and D90G-19 were compared, and several key genes were verified using qRT-PCR and western blotting. The psbA and psbD encoding the D1 and D2 subunits of PSII in D90G-19 were upregulated and higher than WT under high light, while an LHCB gene of Desmodesmus sp. was downregulated dramatically. The expression level of LHCB of D90G-19 was less than that of WT. The improved photoprotection capacity of D90G-19 was attributed to LHCII antennae probably due to the mutation of LHCB gene, which led to less photon into the electron transport chain. Furthermore, LHCBM, a homologous gene of LHCB in model microalgae N. gaditana Cas9+ strain, was knocked out using CRISPR/Cas9. The resulting mutant NgCas9-LHCBM showed an improved capacity to protect the photosynthetic complexes by dissipating extra light energy through non-photochemical quenching pathway. Therefore, the photoprotection capacity of microalgae can be improved by engineering the quantity of PSII subunits to fine-tune PSII reaction centers and the adjacent LHCII antennae.

Processive hydrolysis of crystalline cellulose by cellulases is a critical step for lignocellulose deconstruction. The classic Trichoderma reesei exoglucanase TrCel7A, which has a closed active-site tunnel, starts each processive run by threading the tunnel with a cellulose chain. Loop regions are necessary for tunnel conformation, resulting in weak thermostability of fungal exoglucanases. However, endoglucanase CcCel9A, from the thermophilic bacterium Clostridium cellulosi, comprises a glycoside hydrolase (GH) family 9 module with an open cleft and five carbohydrate-binding modules (CBMs) and hydrolyzes crystalline cellulose processively. How CcCel9A and other similar GH9 enzymes bind to the smooth surface of crystalline cellulose to achieve processivity is still unknown. Our results demonstrate that the C-terminal CBM3b and three CBMX2s enhance productive adsorption to cellulose, while the CBM3c adjacent to the GH9 is tightly bound to 11 glucosyl units, thereby extending the catalytic cleft to 17 subsites, which facilitates decrystallization by forming a supramodular binding surface. In the open cleft, the strong interaction forces between substrate-binding subsites and glucosyl rings enable cleavage of the hydrogen bonds and extraction of a single cellulose chain. In addition, subsite -4 is capable of drawing the chain to its favored location. Cellotetraose is released from the open cleft as the initial product to achieve high processivity, which is further hydrolyzed to cellotriose, cellobiose and glucose by the catalytic cleft of the endoglucanase. On this basis, we propose a wirewalking mode for processive degradation of crystalline cellulose by an endoglucanase, which provides insights for rational design of industrial cellulases.

Large-scale production of biofuels and other high-value products from microalgae focuses on strain selection with desired characteristics such as high lipid productivity and robustness. However, microalgae often suffer severe biomass losses due to contamination that comes in the form of herbivores, especially rotifers. In this study, we found that the total lipid content of 54 microalgal strains from Eastern China ranged from 12.6 to 59.9% of dry cell weight (dw), with an average of 35.4% dw. Lipid productivity of these microalgal strains varied from 0.04 to 0.14 g L−1 day−1, and 15 showed lipid production rates over 0.10 g L−1 day−1. The fatty acid profiles of 34 microalgal strains with lipid content over 40% dw were analyzed by gas chromatography. We found that the amount of C18:1 increased with increasing total lipid content, whereas C14:0 and C16:0 showed a negative correlation to the total amount of lipids. An experimental rotifer-microalgae predator-prey model was constructed, and the anti-rotifer robustness of these microalgal strains was evaluated. We found that Didymogenes sp. HN-4 can depress the growth of rotifers significantly. This study demonstrates the biodiversity of the native Chinese microalgae in lipid productivity and robustness, which lays the groundwork for mass algal culture.

An electro-optic tunable lithium-niobate (LN) waveguide Mach-Zehnder interferometer (MZI) is designed and fabricated with the annealed proton-exchange process. The MZI consists of a straight waveguide arm and a bent waveguide arm with a SiO2 film deposited on the two sides. The residual stress generated by the SiO2 film can enhance the index contrast of the bent waveguide arm and thus reduce the bending loss of the MZI. A comparison of several experimental devices fabricated on the same chip size of $50 ~{\rm mm} \times 7$ mm confirms significant reduction of the insertion loss by incorporating the SiO2 film. For our best sample, which functions as a tunable comb filter with a channel spacing of 0.75 nm in the C-band, the insertion losses of the two output ports are 13.5 and 6 dB, respectively, and the corresponding maximum extinction ratios are $\sim 23$ and $\sim 1.5$ dB. The device has an electrical wavelength-tuning sensitivity of $\sim 0.2$ nm/V and a temperature sensitivity of $\sim 0.1$ nm/°C. Our design approach can significantly improve the quality of LN devices that require waveguide bends.

Some new direct criteria of boundedness in terms of two measures for impulsive integro-differential systems with fixed moments of impulse effects are established by Lyapunov functions coupled with Razumikhin techniques.

Since CO2 concentrations in industrial flue gases are usually 10%-20%, one of the prerequisites for efficient CO2 removal by algae is the level of tolerance of microalgal species to exposure to high concentrations of CO2. A newly isolated microalgal strain, Chlorella sp. MRA-1, could retain growth with high concentrations of CO2 up to 15%. The highest lipid productivity for Chlorella sp. MRA-1 was 0.118 g/l/day with a 5% CO2 concentration. Octadecenoic acid and hexadecanoic acid, the main components of biodiesel, accounted for 70% of the total fatty acids. A lipid content of 52% of dry cell weight was achieved with limited amounts of nitrogen. Chlorella sp. MRA-1 seems to be an ideal candidate for biodiesel production when cultured with high concentrations of CO2.

Harmful algal blooms (Habs) caused great harm to the human environment. Habs occurrence was connected with other types of plankton. This relationship may be restrictive, and may also be promotional. Selectivity of zooplankton grazing has an important influence on the Habs. The behavior of zooplankton selective grazing was studied in the plankton ecosystem formed by three populations of nontoxic phytoplankton-toxic phytoplankton-zooplankton (NTP-TTP-Z) system. The selective grazing function of zooplankton on toxic phytoplankton and non-toxic phytoplankton was built based on Holling type IV functional response. Numerical simulation was given depending on the laboratory data. Results show that the models nicely explained the selective grazing behavior of zooplankton in the three species ecosystem, and provided key parameters for the marine ecosystem dynamics models.

A strain-introduced Mach-Zehnder interferometer (MZI) interleaver on lithium niobate (LiNbO3) is proposed. The structure of the strain-introduced waveguide is designed in detail, and is produced by depositing a SiO2 film on the annealed proton-exchanged LiNbO3 waveguide. Considering the sensitivities of the edge strain to the deposition temperature and the thickness of the SiO2 film, an optimum design of 50 GHz interleaver on this structure is given through analyzing the effective index changes for Epqx mode by finite difference method (FDM). The length of the bending waveguide in this interleaver is just two thirds of that in the conventional interleaver due to the high refractive index difference.

This paper proposes a framework for the design of blended learning that consists of three key considerations: what to blend, how to blend and effects of blending. “Blending (what to blend)” involves four aspects: the blending of traditional classroom-based, e-learning and real learning contexts, the integration of various learning resources (contents, tools and social support), the combination of formal and informal learning, and the convergence of different learning methods (individual, group, class-based collective learning).

Learning itself is substantially ubiquitous, while real ubiquitous learning needs can only be supported by appropriate learning technologies. Technology enhanced personalized learning service is indispensable for ubiquitous learning. This paper discusses several key issues for personalized learning service provision in ubiquitous learning environments, including learner modeling, context management, ontology adoption and service visualization.

Purpose To evaluate the usefulness of contrast-enhanced sonography (CEUS) in the diagnosis of small hepatocellular carcinoma (HCC) measuring ≤2 cm in diameter. Methods We identified 104 focal liver lesions measuring ≤2 cm in 104 consecutive patients who were enrolled for baseline sonography (BUS) and CEUS examination (49 HCCs, 55 non-HCCs). A real-time, contrast-specific mode of contrast pulse sequencing and a sulphur hexafluoride-filled microbubble contrast agent were used for CEUS. The diagnostic performances of BUS and CEUS in differentiating focal liver lesions (HCC or non-HCC) were analyzed and compared. Results On CEUS, 43 (87.8%) of the 49 HCC lesions were hyperenhanced, 5 (10.2%) were isoenhanced, and 1 (2%) was hypoenhanced during the arterial phase when compared with adjacent liver tissue. Thirty-nine (79.6%) HCCs exhibited washout from the portal phase to the late phase. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy before and after contrast agent administration were 28.6% (14/49) versus 79.6% (39/49) (p 0.05), 82.4% (14/17) versus 90.7% (39/43) (p > 0.05), 59.8% (52/87) versus 90.7% (39/43) (p < 0.01), and 63.5% (66/104) versus 86.5% (90/104) (p < 0.001), respectively. No significant difference in diagnostic performance of CEUS was found between lesions measuring ≤1.5 cm and those 1.6–2 cm and between lesions located at a depth of ≤6 cm from the skin and those located deeper. Conclusions CEUS significantly improved the diagnostic performance in characterization of small HCCs ≤2 cm compared with BUS. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2008

Percutaneous microwave ablation and radiofrequency ablation are two commonly used modalities for the treatment of hepatocellular carcinoma; however, comparisons of them have not been documented adequately.Of 102 patients with biopsy-proved hepatocellular carcinoma, 49 (98 nodules) were treated percutaneously with microwave ablation and 53 (72 nodules) with radiofrequency ablation. The local tumor control, complications related to treatment, and long-term results of the two modalities were compared retrospectively.The complete ablation rates were 94.9% (93/98) using microwave ablation vs 93.1% (67/72) using radiofrequency ablation (P = 0.75), and no significant differences were found either in the ablation of tumors of 3.0 cm or less (P = 1.00) or in those of more than 3.0 cm (P = 1.00) between the two modalities. The local recurrence rates were 11.8% (11/93) using microwave ablation vs 20.9% (14/67) using radiofrequency ablation (P = 0.12), and there were no significant differences between the two modalities either in tumors of 3.0 cm or less (P = 0.36) or in those of more than 3.0 cm (P = 0.82). The rates of major complications associated with microwave ablation and radiofrequency ablation were 8.2% (4/49) vs 5.7% (3/53; P = 0.71). The disease-free survival rates in the microwave ablation group were 45.9%, 26.9%, 26.9%, and 13.4% at 1, 2, 3, and 4 years, respectively, and those in the radiofrequency ablation group were 37.2%, 20.7%, and 15.5% at 1, 2 and 3 years, respectively (P = 0.53). The 1-, 2-, 3-, and 4-year cumulative survival rates for patients who underwent microwave ablation were 81.6%, 61.2%, 50.5%, and 36.8%, respectively, and for patients who underwent radiofrequency ablation the rates were 71.7%, 47.2%, 37.6%, and 24.2%, respectively (P = 0.12).Percutaneous microwave ablation and radiofrequency ablation are both effective methods in treating hepatocellular carcinomas. The local tumor control, complications related to treatment, and long-term survivals were equivalent for the two modalities.