Effects of relative phase in an open ladder system without incoherent pumping

We studied effects of the relative phase between the probe and driving fields on the absorption and dispersion properties in an open three-level ladder system with spontaneously generated coherence but without incoherent pumping. It is shown that by the phase controlling, switching from absorption to lasing without inversion (LWI) and enhancing remarkablely LWI gain can be realized; large index of refraction with zero absorption and the electromagnetically induced transparency can be obtained. We also find that varying the atomic injection and exit rates has a considerable influence on the phase dependent-absorption property of the probe field, existent of the atomic injection and exit rates gives the necessary condition of the realization of LWI, getting LWI is impossible in the corresponding closed system without incoherent pumping. We studied effects of the relative phase between the probe and driving fields on the absorption and dispersion properties in an open three-level ladder system with spontaneously generated coherence but without incoherent pumping. It is shown that by the phase controlling, switching from absorption to lasing without inversion (LWI) and enhancing remarkablely LWI gain can be realized; large index of refraction with zero absorption and the electromagnetically induced transparency can be obtained. We also find that varying the atomic injection and exit rates has a considerable influence on the phase dependent-absorption property of the probe field, existent of the atomic injection and exit rates gives the necessary condition of the realization of LWI, getting LWI is impossible in the corresponding closed system without incoherent pumping.

Two-colour laser-induced electron dynamics in two-level quantum system

To attempt to control the quantum state of a physical system with a femtosecond two-colour laser field, a model for the two-level system is analysed as a first step. We investigate the coherent control of the two-colour laser pulses propagating in a two-level medium. Based on calculating the influence of the laser field with various laser parameters on the electron dynamics, it is found the electronic state can be changed up and down by choosing the appropriate laser pulses and the coherent control of the two-colour laser pulses can substantially modify the behaviour of the electronic dynamics: a quicker change of two states can be produced even for small pulse duration. Moreover, the oscillatory structures around the resonant frequency and the propagation features of the laser pulses depend sensitively on the relative phase of the two-colour laser pulses. Finally, the influence of a finite lifetime of the upper level is discussed in brief.

Generation of attosecond pulses in a system with permanent dipole moment

The generation of attosecond pulses in a two-level system with permanent dipole moment is investigated. It is shown due to the presence of permanent dipole moments, that the plateau of the high-order harmonic generation spectrum can be extended to X-ray range. Moreover, attosecond pulses with higher intensity can be synthesized by using both even and odd harmonics because of their quantum interference. (c) 2006 Elsevier B.V. All rights reserved.

Electromagnetically induced negative refractive index in a V-type four-level atomic system

We propose a scheme for realizing negative refractive index in a V-type four-level atomic system. It is shown that the negative refractive index can be achieved in a wide frequency band based on the effect of quantum coherence. It is also found that the frequency band of negative refractive index and the absorption property of left-handed material are manipulated by the pump and control fields. Furthermore, left-handed material with reduced absorption is possible by choosing appropriate parameters. (c) 2006 Elsevier B.V. All rights reserved.

Upper level and phase controlling group velocity in V-type system

With the external field coupling the two upper levels, we investigate the light pulse propagation properties with weak probe field in a V-type system. Due to the external upper level (UL) coupling field, the dispersion of the system has been influenced by the relative phase. It is shown that the UL field and the relative phase can be regarded as switches to manipulate light propagation between subluminal and superluminal. (c) 2007 Elsevier B.V. All rights reserved.

Method for measuring the lateral aberrations of a lithographic projection system with mirror-symmetric FOCAL marks

A novel method for measuring the imaging quality of a projection system with mirror-symmetric FOCAL marks is proposed, and the principle of the method is described. Through experiments, it is demonstrated that not only the axial aberrations but also the lateral aberrations can be measured with high accuracy by the method. The advantages of the method include obtaining more aberrations than the FOCAL technique and making it much simpler to perform a full-scale measurement of the imaging quality of a lithographic projection system. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

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.

Method for measuring the lateral aberrations of a lithographic projection system with mirror-symmetric FOCAL marks

A novel method for measuring the imaging quality of a projection system with mirror-symmetric FOCAL marks is proposed, and the principle of the method is described. Through experiments, it is demonstrated that not only the axial aberrations but also the lateral aberrations can be measured with high accuracy by the method. The advantages of the method include obtaining more aberrations than the FOCAL technique and making it much simpler to perform a full-scale measurement of the imaging quality of a lithographic projection system. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

A novel method to measure coma aberration of projection system

A novel method to measure coma aberration by pattern displacements at different defocus positions is proposed in this paper. The effect of defocus on coma-induced pattern displacement is analyzed. The measuring principle of the method is described in detail. Using the simulation program PROLITH, the proportionality factors between pattern displacement and coma aberration at different defocus positions are calculated. It is proved that the method is simple to perform and the measurement accuracy of coma can increase approximately by 25% by this novel method. (c) 2006 Elsevier GmbH. All rights reserved.

System error removal and structure optimization based on Fizeau interferometer

In the process of interferometric testing, the measurement result is influenced by the system structure, which reduces the measurement accuracy. To obtain an accurate test result, it is necessary to analyze the test system, and build the relationship between the measurement error and the system parameters. In this paper, the influences of the system elements which include the collimated lens and the standard surface on the interferometric testing are analyzed, the expressions of phase distribution and wavefront error on the detector are obtained, the method to remove some element errors is introduced, and the optimization structure relationships are given. (C) 2006 Elsevier GmbH. All rights reserved.

A novel polarization modulator for a Moire system with grating imaging

A polarization modulator based on splitting with a Savart plate and rotation of an analyzer for a moire system with grating imaging is presented, and its modulation principle is analyzed. The polarization modulator is simple and achromatic. It is composed of a polarizer, a Savart plate, and an analyzer. The polarizer and the Savart plate are placed in front of the index grating to split the image of the scale grating in the moire system. The analyzer is placed behind the grating and rotated to realize the modulation of the moire signal. The analyzer can be rotated either continually with high speed or step by step with low speed to form different modulation modes. The polarization modulator makes the moire system insensitive to the change of initial intensity. In experiments, we verified the usefulness of the polarization modulator.

Antioxidant Peptidomics Reveals Novel Skin Antioxidant System

It is generally agreed that reactive oxygen species (ROS) contribute to skin aging, skin disorders, and skin diseases. Skin possesses an extremely efficient antioxidant system. This antioxidant activity is conferred by two systems: antioxidant enzymes and

Involvement of Fas/FasL system in apoptotic signaling in testicular germ cells of male Wistar rats injected i.v. with microcystins

Previous studies have shown that gonads were the second target organ of microcystins (MCs), and that MCs exposure exerted obvious toxic effects on male reproductive system of mammals. However, relevant molecular evidences are still lacking. Fas-signaling pathway plays a key role in toxicant-induced germ cell apoptosis. This study was to evaluate the responses of Fas/FasL system related genes and proteins in testes of rats injected intravenously with MCs. Enhanced apoptosis of germ cells in the testes of MCs-treated rats was detected by the terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling (TUNEL) associated with up-regulation of the Fas/FasL system. Both Fas and FasL protein expression were induced evidently from I h post-injection, and this high expression level maintained throughout the experiment. In addition, the activation of caspase-8 and caspase-3 protein was also observed, which were indicators of apoptosis. These results suggested the likely involvement of Fas/FasL system in the MCs-induced germ cell apoptosis. It is also suggested that MCs can cause damage to Sertoli cells directly. (C) 2009 Elsevier Ltd. All rights reserved.

Allelopathic mechanism of pyrogallol to Microcystis aeruginosa PCC7806 (Cyanobacteria): From views of gene expression and antioxidant system

Pyrogallol is a potent allelochemical on Microcystis aeruginosa, but its allelopathic mechanism is not fully known. In order to explore this mechanism, gene expressions for prx, mcyB, psbA, recA, grpE, fabZ under pyrogallol stress were studied, and activities of the main antioxidant enzymes were also measured. The results showed that expression of grpE and recA showed no significant change under pyrogallol stress, while psbA and mcyB were up-regulated at 4 mg L-1. Both prx and fabZ were up-regulated even under exposure to 1 mg L-1 pyrogallol concentration. The activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced under pyrogallol stress. Levels of malodialdehyde (MDA) at 2 and 4 mg L-1 pyrogallol were significantly higher than those of the controls. It was concluded that oxidant damage is an important mechanism for the allelopathic effect of pyrogallol on M. aeruginosa. (c) 2009 Elsevier Ltd. All rights reserved.

Effects of constructed wetland system on the removal of dibutyl phthalate (DBP)

Phthalic acid esters (PAEs) have become widely diffused in the environment via the manufacturing process. Numerous experiments have shown that the bioaccumulation of PAEs occurred in the aquatic and terrestrial food chain; meanwhile, it was found that some of PAEs were considered as potential carcinogens, teratogens and mutagens. In this research, two vertical/reverse-vertical flow constructed wetland systems were set up to study its removal efficiency of dibutyl, phthalate (DBP) pollution. The results showed that the constructed wetland system could remove DBP effectively, and the removal rates reached nearly 100%. Substrate microorganism and enzymatic activities probably played key roles during DBP removal, and the removal of DBP probably mainly took place in the upper layer of chamber A in the constructed wetland systems. (C) 2007 Elsevier GmbH. All rights reserved.