Safety and immunogenicity of an oral DNA vaccine encoding Sip of Streptococcus agalactiae from Nile tilapia Oreochromis niloticus delivered by live attenuated Salmonella typhimurium.

Attenuated Salmonella typhimurium SL7207 was used as a carrier for a reconstructed DNA vaccine against Streptococcus agalactiae. A 1.02 kb DNA fragment, encoding for a portion of the surface immunogenic protein (Sip) of S. agalactiae was inserted into pVAX1. The recombinant plasmid pVAX1-sip was transfected in EPC cells to detect the transient expression by an indirect immunofluorescence assay, together with Western blot analysis. The pVAX1-sip was transformed by electroporation into SL7207. The stability of pVAX1-sip into Salmonella was over 90% after 50 generations with antibiotic selection in vitro while remained stable over 80% during 35 generations under antibiotic-free conditions. The LD50 of SL/pVAX1-sip was 1.7 × 10(11) CFU/fish by intragastric administration which indicated a quite low virulence. Tilapias were inoculated orally at 10(8) CFU/fish, the recombinant bacteria were found present in intestinal tract, spleens and livers and eventually eliminated from the tissues 4 weeks after immunization. Fish immunized at 10(7), 10(8) and 10(9) CFU/fish with different immunization times caused various levels of serum antibody and an effective protection against lethal challenge with the wild-type strain S. agalactiae. Integration studies showed that the pVAX1-sip did not integrate with tilapia chromosomes. The DNA vaccine SL/pVAX1-sip was proved to be safe and effective in protecting tilapias against S. agalactiae infection.

Structural features of biomass in a hybrid MBBR reactor.

The structural features of biomass present in the hybrid MBBR (Moving Bed Biofilm Reactor) aeration tank were studied in two subsequent periods, which differed in hydraulic and substrate loads. The physical characteristics of attached-growth biomass, such as, biofilm thickness, density, porosity, inner and surface fractal dimensions, and those of suspended-growth biomass, such as, floc size distribution, density, porosity, inner and surface fractal dimensions, were investigated in each study period and then compared. The results indicated that biofilm always had a higher density, geometric porosity, and a larger boundary fractal dimension than flocs. Both types of biomass were found to exhibit at least two distinct Sierpinski fractal dimensions, indicating two major different pore space populations. With the increasing wastewater flow, both types of biomass were found to shift their structural properties to larger values, except porosity and surface roughness, which decreased. Floc density and biomass Sierpinski fractals were not affected much by the system loadings.

Pulse distortion of a scattered chirped pulse.

We have studied the time-dependent properties of a chirped short pulse when the pulse is scattered by a spherical particle. We used generalized Lorentz-Mie formulas to study the scattered electrical field and pulse distortion. Plane wave Gaussian pulses of different chirps with a constant pulse-filling coefficient l(0) = 1.98 have been studied. A morphology-dependent resonance causes a prolonged trailing edge (small scattering angle) and oscillations (large scattering angle) in the scattered pulse. When frequency sweeping superimposes on a morphology-dependent resonance, the pulse chirp affects the scattered pattern and distorts the scattered intensity. Multisecondary pulses are generated because of the pulse chirp and even subsecondary pulses occur if the incident pulse is deeply chirped. The pulse widths of secondary and subsecondary pulses are shorter than those of an incident pulse.

Temporal properties of the second-harmonic generation of a short pulse.

The time-dependent characteristics of the second-harmonic generation of a short pulse are investigated theoretically. Transient coupled-wave equations are necessary to describe the time-dependent process of the second-harmonic generation of a short pulse. It is found that the fundamental waves experience both pulse broadening and compression with different waveform distortion during the frequency-doubling process. The pulse width of a frequency-doubled wave broadens monotonically along the crystal length. There is no phase distortion in the case of exact phase matching. Phase modulation (i.e., chirp) occurs only when there is phase mismatch and chirp can be determined by the phase mismatch.

Chirped femtosecond pulse scattering by spherical particles.

Generalized Lorentz-Mie formulas are used to study the scattering characteristics when a chirped femtosecond pulse illuminates a spherical particle. For a linear chirped Gaussian pulse with the envelope function g(τ) = exp[-π(1 + ib)τ(2)], dimensionless parameter b is defined as a chirp. The calculation illustrated that even for pulses with a constant carrier wavelength (λ(0) = 0.5 µm) and pulse-filling coefficient (l(0) = 1.98), the efficiencies for extinction and scattering differ very much between the carrier wave and the different chirped pulses. The slowly varying background of the extinction and the scattering curves is damped by the chirp. When the pulse is deeply chirped, the maxima and minima of the background curves reduce to the point where they disappear, and the efficiency curves illustrate a steplike dependence on the sphere size. Another feature is that the chirped-pulse scattering seems blind: it depends only on the amount of chirp (|b|), regardless of upchirp (b > 0) or downchirp (b< 0).

[Experimental study on the Biomaterial/Porous Titanium composite dental implants]

This study investigated the tissue compatibility of bone morphogenetic protein (BMP) /biologic ceramic/porous titanium implant,BMP/porous titanium implant,biologic ceramic/porous titanium implant and porous titanium implant by LM,SEM,EDXA.The results showed that the new bone formation and new bone mature were earlier in the BMP composite implants treated group.BMP uncomposite implants had no evident difference in the time of new bone formation, but the interface bonding ways had significant difference.