Cultivation of the microalga, Chlorella pyrenoidosa, in biogas wastewater

Biogas wastewater is always a problem as a result of its extremely high concentrations of nitrogen and phosphorus, which is the main reason for the eutrophication of the surrounding water. The microalga, Chlorella pyrenoidosa, can utilize the nitrogen and phosphorus in wastewater for its growth. Therefore, the microalga was introduced to be cultivated in the biogas wastewater, which could not only bioremediate the wastewater, but also produce plenty of the microalga biomass that could be used for the exploitation of fertilizers, feed additives and biofuels. This study showed that the microalga, C. pyrenoidosa could grow well in the biogas wastewater under optimal condition: initial cell density of 0.15 (OD680), pH 8 and illumination intensity of 10000 LX. Under the optimal condition, the dry cell weight of the microalgae reached 0.1 g/L after cultivation in the wastewater for fourteen (14) days; in the meantime, the microalga also removed 71.8% of phosphorus, 100% of ammoniacal nitrogen (NH4+-N), 52.8% of nitrate nitrogen (NO3-N) and 23.0% of nitrite nitrogen (NO2-N) from the biogas wastewater, suggesting that the cultivation of C. pyrenoidosa in biogas wastewater would be efficient for the treatment of wastewater. This study also provided a low-cost way to produce the microalga and its relevant products.Key words: Chlorella pyrenoidosa, biogas wastewater, cultivation, phosphorus, nitrogen

A Comprehensive Analysis of Swift/XRT Data: III. Jet Break Candidates in X-ray and Optical Afterglow Lightcurves

The Swift/XRT data of 179 GRBs (from 050124 to 070129) and the optical afterglow data of 57 pre- and post-Swift GRBs are analyzed, in order to systematically investigate the jet-like breaks in the X-ray and optical afterglow lightcurves. We find that not a single burst can be included in the ``Platinum'' sample, in which the data satisfy all the criteria of a jet break. By releasing one or more requirements to define a jet break, some candidates of various degrees could be identified. In the X-ray band, 42 out of the 103 well-sampled X-ray lightcurves have a decay slope of the post-break segment >1.5 (``Bronze'' sample), and 27 of them also satisfy the closure relations of the forward models (``Silver'' sample). The numbers of the ``Bronze'' and ``Silver'' candidates in the optical lightcurves are 27 and 23, respectively. Thirteen bursts have well-sampled optical and X-ray lightcurves, but only seven cases are consistent with an achromatic break, but even in these cases only one band satisfies the closure relations (``Gold'' sample). The observed break time in the XRT lightcurves is systematically earlier than that in the optical bands. All these raise great concerns in interpreting the jet-like breaks as jet breaks and further inferring GRB energetics from these breaks. By assuming that these breaks are jet breaks, we perform a similar analysis as previous work to calculate the jet opening angle (theta_j) and energetics (E_k) with the ``Silver'' and ``Gold'' jet break candidates. The derived E_K distribution reveals a much larger scatter than the pre-Swift sample. A tentative anti-correlation between theta_j and E_{K,iso} is found for both the pre-Swift and Swift GRBs, indicating that the E_K could still be quasi-universal, if the breaks in discussion are indeed jet breaks(abridge).Comment: 48 pages, including 5 tables and 8 figures. Accepted for publication in ApJ. This is the third paper of a series. Paper I and II see astro-ph/0612246 (ApJ, 2007, 666,1002) and arXiv:0705.1373 (ApJ, 2007, 669, n2,in press

Transitions To the Long-Resident State in coupled chaotic oscillators

The behaviors of coupled chaotic oscillators before complete synchronization were investigated. We report three phenomena: (1) The emergence of long-time residence of trajectories besides one of the saddle foci; (2) The tendency that orbits of the two oscillators get close becomes faster with increasing the coupling strength; (3) The diffusion of two oscillator's phase difference is first enhanced and then suppressed. There are exact correspondences among these phenomena. The mechanism of these correspondences is explored. These phenomena uncover the route to synchronization of coupled chaotic oscillators.Comment: 3 pages, 5 figure

Design of a new hairpin DNAzyme: The activity controlled by TMPyP4

A new 10-23 hairpin DNAzyme with a G-quadruplex structure stem was designed. The formation and stability of the G-quadruplex structure as the DNAzyme stem in the absence or the presence of TMPyP4 were investigated by UV-visible spectroscopy, circular dichroism (CD) and differential scanning calorimetry (DSC) methods, respectively. The results showed that the stability of this DNAzyme can be enhanced greatly due to the interaction between TMPyP4 and the DNAzyme. The relationship between structural stability and activity of the DNAzyme was studied by in vitro catalytic reaction. The activity of this DNAzyme was regulated by the stability of DNAzyme when TMPyP4 was intercalated into Gquadruplex structure stem. The catalytic activity of the 10-23 hairpin DNAzyme decreased and even inactivated due to the enhanced stability of G-quadruplex structure by TMPyP4 molecules. This DNAzyme is controllable to cleavage substrate and has some potential significance in gene therapy.Key words: 10-23 DNAzyme, hairpin DNAzyme, G-quadruplex structure, TMPyP4

Structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 single crystal

We have studied the structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 using single crystals grown by a floating-zone technique. The structure analysis by Rietveld refinements reveals that the Ca substitution for Sr intensifies the structure distortion; the rotation angle of the RuO6 octahedron increases. This structure change tunes magnetic and transport properties dramatically. The magnetic ground state switches from an itinerant metamagnetic state for Sr3Ru2O7 to a nearly ferromagnetic state for (Sr0.9Ca0.1)3Ru2O7. The Fermi liquid behavior occurs in Sr3Ru2O7, but is suppressed in (Sr0.9Ca0.1)3Ru2O7. These results strongly suggest that lattice, spin, and charge degrees of freedom are strongly coupled in this system. The band width narrowing caused by the structure distortion should be responsible for the enhancement of ferromagnetic correlations and the change of transport propertie

Structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 single crystal

We have studied the structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 using single crystals grown by a floating-zone technique. The structure analysis by Rietveld refinements reveals that the Ca substitution for Sr intensifies the structure distortion; the rotation angle of the RuO6 octahedron increases. This structure change tunes magnetic and transport properties dramatically. The magnetic ground state switches from an itinerant metamagnetic state for Sr3Ru2O7 to a nearly ferromagnetic state for (Sr0.9Ca0.1)3Ru2O7. The Fermi liquid behavior occurs in Sr3Ru2O7, but is suppressed in (Sr0.9Ca0.1)3Ru2O7. These results strongly suggest that lattice, spin, and charge degrees of freedom are strongly coupled in this system. The band width narrowing caused by the structure distortion should be responsible for the enhancement of ferromagnetic correlations and the change of transport propertie