Characterization of the life history of Bangia fuscopurpurea (Bangiaceae, Rhodophyta) in connection with its cultivation in China

Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.

Computation of turbulent-flow in a square duct - aspects of the secondary flow and its origin

A numerical study of turbulent flow in a straight duct of square cross-section is made. An order-of-magnitude analysis of the 3-D, time-averaged Navier-Stokes equations resulted in a parabolic form of the Navier-Stokes equations. The governing equations, expressed in terms of a new vector-potential formulation, are expanded as a multi-deck structure with each deck characterized by its dominant physical forces. The resulting equations are solved using a finite-element approach with a bicubic element representation on each cross-sectional plane. The numerical integration along the streamwise direction is carried out with finite-difference approximations until a fully-developed state is reached. The computed results agree well with other numerical studies and compare very favorably with the available experimental data. One important outcome of the current investigation is the interpretation analytically that the driving force of the secondary flow in a square duct comes mainly from the second-order terms of the difference in the gradients of the normal and transverse Reynolds stresses in the axial vorticity equation.

Control of the lasing wavelength by a sampled grating in a complex-coupled DFB laser

The lasing wavelength of a complex-coupled DFB laser is controlled by a sampled grating. The key concepts of the approach are to utilize the -1st order (negative first order) reflection of a sampled grating for laser single mode operation, and use conventional holographic exposure combined with the usual photolithography to fabricate the sampled grating. The typical threshold current of the sampled grating based DFB laser is 32 mA, and the optical output is about 10 mW at an injected current of 100 mA. The lasing wavelength of the device is 1.5356 mu m, which is the -1st order wavelength of the sampled grating.

Determination of the macroscopic optical properties for the NAEC/PEK-c guest-host polymer films

The polyetherketone (PEK-c) guest-host polymer films doped with (4'-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The films were poled by corona-onset poling at elevated temperature (COPET). The orientational order parameter of the chromophores NAEC in poled polymer film was determined by measuring the absorption spectra of the films before and after being poled. By using the two-level model, the measured dispersion of the refractive index of the polymer film, and the dispersion of the first hyperpolarizability of chromophore NAEC, the dispersion of the macroscopic second-order nonlinear optical (NLO) and linear electrooptic (EO) coefficients was evaluated for the NAEC/PEK-c guest-host polymer film. (C) 2001 Elsevier Science Ltd. All rights reserved.

Investigation on the nonlinear optical properties of the DCNP/PEK-c guest-host polymer films

The polyetherketone (PEK-c) guest-host polymer thin films doped with 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1H-pryazole (DCNP) were prepared. The polymer films were investigated with in situ second-harmonic generation (SHG) measurement. The corona poling temperature was optimized by the temperature dependence of the in situ SHG signal intensity under the poling electric field applying. The temporal and temperature stability of the second-order properties of the poled polymer film were measured by the in situ SHG signal intensity probing. The second-order NLO coefficient chi ((2))(33) = 32.65 pm/V at lambda = 1064 nm was determined by using the Makel fringe method after poling under the optimal poling condition. The dispersion of the NLO coefficient of the guest-host polymer system was determined by the measured value of chi ((2))(33) at 1064 nm and the two-level model.

Tunable high-order harmonic generation and the role of the folded quantum path

We theoretically demonstrate the selective enhancement of high-order harmonic generation (HHG) in two-color laser fields consisting of a single-cycle fundamental wave (800 nm wavelength) and a multicycle subharmonic wave (2400 nm wavelength). By performing time-frequency analyses based on a single-active-electron model, we reveal that such an enhancement is a result of the modified electron trajectories in the two-color field. Furthermore, we show that selectively enhanced HHG gives rise to a bandwidth-controllable extreme ultraviolet supercontinuum in the plateau region, facilitating the generation of intense single isolated attosecond pulses.

The effect of the group delay ripple of chirped fiber grating on composite second-order in optical fiber CATV system

The effect of group delay ripple of chirped fiber gratings on composite second-order (CSO) performance in optical fiber CATV system is investigated. We analyze the system CSO performances for different ripple amplitudes, periods and residual dispersion amounts in detail. It is found that the large ripple amplitude and small ripple period will deteriorate the system CSO performance seriously. Additionally, the residual dispersion amount has considerable effect on CSO performance in the case of small ripple amplitude and large ripple period. (c) 2004 Elsevier B.V. All rights reserved.

Modelling and simulation of the second-order Doppler error of a laser dual-frequency interferometer

Only the first- order Doppler frequency shift is considered in current laser dual- frequency interferometers; however; the second- order Doppler frequency shift should be considered when the measurement corner cube ( MCC) moves at high velocity or variable velocity because it can cause considerable error. The influence of the second- order Doppler frequency shift on interferometer error is studied in this paper, and a model of the second- order Doppler error is put forward. Moreover, the model has been simulated with both high velocity and variable velocity motion. The simulated results show that the second- order Doppler error is proportional to the velocity of the MCC when it moves with uniform motion and the measured displacement is certain. When the MCC moves with variable motion, the second- order Doppler error concerns not only velocity but also acceleration. When muzzle velocity is zero the second- order Doppler error caused by an acceleration of 0.6g can be up to 2.5 nm in 0.4 s, which is not negligible in nanometric measurement. Moreover, when the muzzle velocity is nonzero, the accelerated motion may result in a greater error and decelerated motion may result in a smaller error.