Generation of Isolated Attosecond Pulse from Asymmetric Molecular Ions by Introducing Half-Cycle-Like Laser Fields

We propose an efficient method for the generation of an isolated attosecond pulse from the asymmetric molecular ions HeH^2＋ by adding a half-cycle-like field （HCLF） to the fundamental driving laser field. The high-order harmonic generation （HHG） is investigated by numerically sowing the time-dependent Schrodinger equation. By performing the time-frequency distributions and the electronic wave packet probability densities, we find that the optimizing combined field is not only useful for extending the HHG cutoff, but also for simplifying the recombination channels through controlling the electron localization. In addition, by adjusting the intensity of the HCLF, a dominant short quantum path is selected to contribute the HHG spectrum. As a result, a 75-as isolated attosecond pulse is obtained by superposing a proper range of the harmonics.

Peak Profile Analysis in High Field Asymmetric Wave Ion Mobility Spectrometry

High field asymmetric wave ion mobility spectrometry （FAIMS） is a powerful tool to detect and characterize gas-phase ions, while the unsolvable partial differential equation of ions moving in ion drift tube poses a big challenge to FAIMS spectral peak analysis. In this work, a universal and effective model of FAIMS spectral peak profile has been proposed by introducing ion trajectory and loss height. With this model, the influence of the structure of ion drift tube, dispersion voltages, compensation voltages, and carrier gas flow rate on the FAIMS spectral peak characteristics like peak shape, full width at half maximum and peak height is analyzed and discussed. The results show that the influence of different factors on the FAIMS spectral peak profile can be qualitatively described by the model which agrees with the experimental data.

Indexes of Indoor Thermal Environment with Asymmetrical Radiant Field

The main features of top-flcor rooms with natural ventilation are identified by investigating indoor thermal environment in summer season. One is high indoor air temperature, for this reason the indoor climate is far beyond the thermal comfort standard; the other is the inhomogeneons temperature distribution of the inner wall surfaces, and high temperature of the inner surface of the roof causes much scorching to the head of occupant. This is the characteristic of such rooms. Both features mentioned above should be considered comprehensively for the evaluation of indoor thermal environment of the top-floor rooms with asymmetric radiant field. In order to characterize the indoor thermal environment of the rooms, the heat stress index, HSI and radiant heat flux reaching human head, Q_R should be introduced simultaneously as thermal indexes for the indoor climate evaluation. The application of the indexes to a topfloor room is presented and analyzed.

Corneal Biomechanical Parameters and Asymmetric Visual Field Damage in Patients with Untreated Normal Tension Glaucoma

Background： High intraocular pressure （IOP） and low central corneal thickness （CCT） are important validated risk factors for glaucoma, and some studies also have suggested that eyes with more deformable corneas may be in higher risk of the development and worsening of glaucoma. In the present study, we aimed to evaluate the association between corneal biomechanical parameters and asymmetric visual field （VF） damage using a Corvis-ST device in patients with untreated normal tension glaucoma （NTG）. Methods： In this observational, cross-sectional study, 44 newly diagnosed NTG patients were enrolled. Of these, 31 had asymmetric VF damage, which was defined as a 5-point difference between the eyes according to the Advanced Glaucoma Intervention Study scoring system. Corneal biomechanical parameters were obtained using a Corvis-ST device, such as time from start until the first and second applanation is reached （time A 1 and time A2, respectively）, cord length of the first and second applanation （length A 1 and length A2, respectively）, corneal speed during the first and second applanation （velocity A1 and velocity A2, respectively）, time from start until highest concavity is reached （time HC）, maximum amplitude at the apex of highest concavity （def ampl HC）, distance between the two peaks at highest concavity （peak dist HC）, and central concave curvature at its highest concavity （radius HC）. Results： Time A 1 （7.19 q- 0.28 vs. 7.37 ~ 0.41 ms, P = 0.010）, length A 1 （1.73 [ 1.70-1.76] vs. 1.78 [ 1.76-1.79] mm, P = 0.007）, length A2 （1.58 [1.46-1.70] vs. 1.84 [h76-1.92] mm, P 〈 0.001）, peak dist HC （3.53 [3.08-4.00] vs. 4.33 [3.92-4.74] mm, P = 0.010）, and radius HC （6.20 ± 0.69 vs. 6.59 i h 18 mm, P = 0.032） were significantly lower in the worse eyes than in the better eyes, whereas velocity A 1 and def ampl HC were significantly higher （0.156 [0.149-0.163] vs. 0.145 [0.138-0.152] m/s, P= 0.002 and 1.19 ± 0.13 vs. 1.15 ± 0.13 mm, P = 0.005, respectively）. There was no significant difference in time A2, velocity A2, and time HC between the two groups. In addition, no difference was observed in lOP, CCT, and axial length. In the univariate and multivariate analyses, some of the Corvis-ST parameters, including time A1 and def ampl HC, were correlated with known risk factors for glaucoma, and there was also a significant positive correlation between def ampl HC and age. Conclusions： There were differences in dynamic corneal response parameters but not IOP or CCT between the paired eyes of NTG patients with asymmetric VF damage. We suggest that the shape of the cornea is more easily altered in the worse eyes of asymmetric NTG patients.

Electron-positron pair production in a strong asymmetric laser electric field

By solving the quantum Vlasov equation, electron positron pair production in a strong electric field with asymmetric laser pulses has been investigated. We consider three different situations of subcycle, cycle and supercycle laser pulses. It is found that in asymmetric laser pulse field, i.e.. when the pulse length of one rising or falling side is fixed while the pulse length of the other side is changed, the pair production rate and mnnber density can be significantly modified comparable to symmetric situation. For each ca,se of these three different cycle pulses, when one side pulse length is constant and the other side pulse length becomes shorter, i.e., the whole pulse is compressed, the more pairs can be produced than that in tile vice versa case, i.e., the whole pulse is elongated. In compressed pulse case there exists an optimum pulse length ratio of asylnmetric pulse lengths which makes the pair number density maximunn. Moreover, the created maximum pair number density by subcycle pulse is larger than that by cycle or/and supercycle pulse. In elongated pulse case, however, only for supercycle laser pulse the created pairs is enhanced and there exists also an optimum asymmetric pulse length ratio that maximizes the pair number density. On the other hand. surprisingly, in both cases of subcycle and cycle elongated laser pulses, the pair number density is monotonically decreasing as the asymmetry of pulse increases.