Shaping attosecond pulses via high-order harmonic generation driven by two mixed Laguerre-Gaussian vortex beams.

Shaping the waveform of attosecond pulses is crucial for controlling electron dynamics and is typically achieved using a high-order harmonic generation (HHG) spectrum containing a minimum. Here, we propose a novel method for shaping attosecond pulses via HHG without carrying orbital angular momentum (OAM), driven by two mixed Laguerre-Gaussian vortex beams with oppositely signed OAMs. We show that the waveform of an attosecond pulse train synthesized using low-divergent, non-vortical high harmonics in the far field can be significantly regulated; specifically, the number of emission bursts within half an optical cycle of the driving laser increases to five compared to one or two bursts in the previous studies.

Reinforcement mechanism of black tea on the gel properties of preserved egg protein: Metal ion "pore-blocking effect" and EWP denaturation-aggregation-reorganization.

Black tea is vital for superior gel properties in preserved eggs, but the standardized usage guidelines are lacking due to limited understanding of its role in preserved egg white (PEW) formation. Thus, this study investigates the impact of black tea on gel properties of PEW and elucidates the underlying molecular mechanisms. Our findings reveal that black tea significantly improves PEW gel properties, with optimal effects at 1 % concentration.

Enhancing the albumen viscosity and permeability of whole egg: an approach utilizing multimodal ultrasonic technology.

Background: Improving the permeability of eggshell (ES) and eggshell membrane (ESM), while decreasing the albumen viscosity are conducive to accelerate the penetration rates of sodium chloride (NaCl) during the processing of salted duck eggs. This study systematically evaluated the effect of mono- and multi-frequency ultrasound (US) on ES/ESM permeability and internal quality of whole egg in aqueous- and salt-phase systems.

Results: Key findings demonstrated that 40 kHz and a combination of 20/40/60 kHz US significantly reduced the albumen viscosity in salt-phase system and enlarged the pore size of ES and ESM (P < 0.

Enhancement of harmonic generation by an intense driving laser with high-order waveguide modes in a high-pressure gas-filled hollow waveguide.

High-order harmonics have been widely used as reliable tabletop coherent radiation sources recently, but their applications have often been limited by the available pulse energy. Here, we report that by using an overdriven intense laser in a long waveguide with high-pressure gas, phase matching can be achieved in three distinct "regimes". In the third regime, favorable phase matching is achieved at near-axis positions to enhance harmonic yields.

Variation pattern, influential factors, and prediction models of PM2.5 concentrations in typical urban functional zones of northeast China.

This study investigated the spatial and temporal variations of PM2.5 concentrations in Harbin, China, under the influence of meteorological parameters and gaseous pollutants. The complex relationship between meteorological parameters and pollutants was explored using Pearson correlation analysis and interaction effect analysis.

Controlling laser-dressed resonance line shape using attosecond extreme-ultraviolet pulse with a spectral minimum.

High-harmonic generation from a gas target exhibits sharp spectral features and rapid phase variation near the Cooper minimum. By applying spectral filtering, shaped isolated attosecond pulses can be generated where the pulse is split into two in the time domain. Using such shaped extreme-ultraviolet (XUV) pulses, we theoretically study attosecond transient absorption (ATA) spectra of helium [Formula: see text] autoionizing state which is resonantly coupled to the [Formula: see text] dark state by a time-delayed infrared laser.

Predict the Gelling Properties of Alkali-Induced Egg White Gel Based on the Freshness of Duck Eggs.

Preserved egg white (PEW) has excellent gelling properties but is susceptible to the freshness of raw eggs. In this study, the correlation between the comprehensive freshness index (CFI) of raw eggs and the gelling properties of alkali-induced egg white gel (EWG) was elucidated. Results showed that the CFI, established by a principal component analysis (PCA) and stepwise regression analysis (SRA) methods, can be used to predict the freshness of duck eggs under storage conditions of 25 °C and 4 °C.

Role of the Porras factor in phase matching of high-order harmonic generation driven by focused few-cycle laser pulses.

We investigate the role of the Porras factor (or laser focusing effect) on the macroscopic high-order harmonic generation (HHG) driven by a focused broadband few-cycle laser beam. By employing a non-adiabatic phase-matching analysis method, we reveal that phase mismatch due to the induced-dipole phase varies with the Porras factor, which is dominant in phase matching at low gas pressure. We also find that in a strongly ionized medium when gas pressure is high, the nonlinear propagation is dominated by a plasma effect such that the focusing effect is mitigated, resulting in similar poor phase matching of HHG regardless of the Porras factor.

Extension of the bright high-harmonic photon energy range via nonadiabatic critical phase matching.

The concept of critical ionization fraction has been essential for high-harmonic generation, because it dictates the maximum driving laser intensity while preserving the phase matching of harmonics. In this work, we reveal a second, nonadiabatic critical ionization fraction, which substantially extends the phase-matched harmonic energy, arising because of the strong reshaping of the intense laser field in a gas plasma. We validate this understanding through a systematic comparison between experiment and theory for a wide range of laser conditions.

Optimal generation and isolation of attosecond pulses in an overdriven ionized medium.

We identify optimal conditions for the generation and isolation of attosecond pulses in an overdriven ionized medium. In a high-pressure and highly ionized gas, the spatiotemporal wavefront rotation of a driving laser can be optimized, leading to complete spatial separation of successive attosecond bursts in the far field. The resulting isolated attosecond pulses (IAPs) are much more divergent such that they are spatially separated from the driving laser in the far field.

[Cloning and expression of a biotinylated multiple-epitope HCV fusion antigen gene].

The aim was to develop a single multiple-epitope fusion antigen which incorporates all of the major immunodominant epitopes from the six functional regions of the HCV genome. A nucleic acid sequence consisting of viral core, E1, E2, NS3, NS4, and NS5 regions was constructed and inserted into the Promega Pinpoint Xa-1 T vector for inducing expression. The protein was expressed in JM109 (DE3) as a fusion protein with a 13 kD biotinlated tag to be used for detection and affinity purification.