Investigation of stable pulse mode-locking regimes in a NALM figure-9 Er-doped fiber laser.

We demonstrate three typical mode-locking processes of a nonlinear amplifying loop mirror (NALM) fiber laser via a general nonlinear Schrödinger equation-based (GNLSE) simulation model. First, the pulse evolutions in the NALM cavity were separately simulated under asymmetric and weakly asymmetric conditions. We found that the splitting ratio and positions of the gain fiber can result in a suitable phase bias between clockwise and counter-clockwise beams, enabling the realization of a self-starting low-threshold operating condition. To assess the roles of the splitting ratio and gain in the mode-locking process, we simulated three pulse formation processes: in the soliton, stretched-pulse, and dissipative soliton mode-locking regimes. The simulation results show that the splitting ratio, gain, and dispersion directly influence the mode-locking condition and pulse characteristics, thereby providing effective quantified guidance for high-quality pulse generation. Finally, an experimental NALM oscillation operating under stretched pulse conditions was established to investigate the impact of the splitting ratio and pump power on the pulse characteristics. The experimental results prove that the splitting ratio, gain, and dispersion can be used to manipulate the mode-locking threshold, self-starting threshold, nonlinear effects, and pulse characteristics.

Comparison of pyrethroid resistance in adults and larvae of Culex pipiens pallens (Diptera: Culicidae) from four field populations in China.

The susceptibility of adults and larvae from four field populations of Culex pipiens pallens (Coguillett) (Diptera: Culicidae) in China to deltamethrin, beta-cypermethrin, and permethrin was investigated using the World Health Organization standard susceptibility test methods. One to 2 d old nonblood fed female mosquitoes emerged from pupae resulting from wild-caught larvae (F1 laboratory reared adults) were exposed to various doses of the pyrethroids. The larval bioassay was conducted using a range of concentrations to determine the LC50 values. Using allele-specific polymerase chain reaction, the frequency of the kdr resistance gene was determined in each population. The bioassay data indicated that deltamethrin was the most active larvicide in all four populations with resistance ratios (RR) of 1.6-3.9-fold. This was followed by beta-cypermethrin with RR of 1.1-3.3-fold, while larvae from three mosquito populations from Beijing, Jinan, and Kaifeng had developed resistance to permethrin with RR of 12.6-, 24.0-, and 18.8-fold, respectively. The overall RR of larvae for all insecticides in ascending order was Changchun < Beijing < Kaifeng < Jinan; and ranking of the adult mortality was Changchun < Jinan = Kaifeng < Beijing. For the three pyrethroids tested, the correlation coefficient among the three test methods on the four populations and one lab strain was quite weak. The R value was 0.113-0.320 when we compared kdr detection for kdr% with LC50, -0.565 to -0.793 when kdr% versus adult mortality test, and -0.750 to 0.505 for LC50 versus adult mortality. Permethrin showed the best correlation (R = -0.793) between kdr frequency and adult mortality. This indicates that levels of susceptibility changes to an insecticide should not be based on a single method of assessment.

[Resistance of Anopheles sinensis to insecticides in Huaibin County of Henan Province].

Anopheles sinensis adults were captured from Huaibin County and raised in laboratory. Larvae dipping method and the WHO tubes were used to determine the resistance of F1 IV-stage larvae and 3-5 day-old adult mosquitoes to dimethyl dichlorovinyl phosphate (DDVP), deltamethrin, and arprocarb. The activity of acetylcholine esterase (AChE) of larvae and adult mosquitoes was measured by colorimetric method before and after the respective addition of the 3 insecticides. The results showed that the mortality of adult mosquitoes in 0.05% deltamethrin testing tube (0.017 8 g/m2) was 51.2%, which was less than 80% and judged as resistant group. The LC50 of larvae to DDVP, deltamethrin, and arprocarb were 2.76, 320.85, 754.32 mg/L, respectively. The inhibition rates of 0.005 mmol/L DDVP, deltamethrin, and arprocarb to AChE activity were 77.8%, 62.8%, and 58.9% in larvae, while 76.1%, 62.2%, and 58.22% in adults, respectively, showing a significant inhibition on the AChE activity of An. sinensis (P < 0.01).

[Effect of acidity on the interaction of Ofloxacin and bovine serum albumin].

Bovine serum albumin (BSA) exists as N(pH -7.0), B(pH -9.0), and E (pH < 3.5) = isomeric forms in the solution of different pH. Acid effect on the structure of bovine serum albumin and the interaction of different structure of BSA with Ofloxacin were studied by UV-Vis and fluorescence spectroscopy. Based on the fluorescence quenching of bovine serum albumin and Förster energy transfer mechanism, the quenching constants, energy transfer efficiencies and the binding distances were determined at four different pHs. The results showed that Ofloxacin has the ability to quench bovine serum albumin fluorescence with the optimal condition of fluorescence quenching constants of 1.928 1 x 10(5) L x mo l(-1), binding distance of r = 2.55 nm and quenching efficiency of 8.63 x 10(4) L x mo x l(-1) at pH 4.9. Non-radiative energy transfer and static quenching were the cause of fluorescence quenching. The influence on the binding of Ofloxacin and bovine serum albumin under neutral, subacidity and alkalescent conditions was not obviously observed, and the electrostatic interaction was not the main force. The effect of Oflx on the conformation of BSA was also investigated using synchronous fluorescence spectrometry.

[Case study on groundwater health risk assessment and remediation strategy based on exposure pathway].

The carcinogenic risk originated from benzene in contaminated groundwater of a large-scale coke plant in Beijing was analyzed and assessed for different land use zones according to the site redevelopment plan. The results revealed that indoor vapor inhalation was the key exposure pathway for all the three zones. The carcinogenic risk in zone A as commercial area was 6.37 x 10(-8), below the maximum allowable level (1.0 x 10(-6)), but was 2.20 x 10(-4) in zone B as industrial park and 7.49 x 10(-5) in zone C as residential/commercial area, both beyond the acceptable level. Further, the remediation target for benzene was calculated at 118 microg x L(-1) and the corresponding remediation area was contoured to be 165 000 m2. Given the high permeability of the aquifer and the excellent volatility of benzene, air-sparging with a combination of engineering control measure was recommended to mitigate the risk of the groundwater contamination.