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We present the theory and simulation of attosecond transient absorption in helium atoms under the single-active-electron approximation. This study investigates the attosecond dynamics of intrinsic atomic states that interact with a field comprising vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) fields. The absorption spectrum of the helium atom is obtained from the response function, which is constructed by numerically solving the three-dimensional time-dependent Schrödinger equation. We observe a fine structure near the intrinsic atomic level, which is modulated with a 0.2 fs period. Based on high-order time-dependent perturbation theory, the frequency-dependent phase of the dipole response induced by the VUV and XUV fields is analytically obtained, and the fine structure is well explained by the phase difference. In addition, the absorption fringes are dependent on the chirp of the VUV field. This study investigates the features of the attosecond transient absorption in the VUV region, which may have valuable applications in the study of ultrafast phenomena in atoms, molecules, and solids.

In this study, the attosecond transient absorption (ATA) spectrum below the excited states of the helium atom was investigated by numerically solving the fully three-dimensional time-dependent Schrödinger equation. Under single-active electron approximation, the helium atom was illuminated by a combined field comprising of extreme ultraviolet (XUV) and delayed infrared (IR) fields. The response function demonstrates that the absorption near the central frequency (ωX) of the XUV field is periodically modulated during the overlapping between the XUV and IR pulses. Using the time-dependent perturbation, the absorption near ωX is attributed to the wavepacket excited by the XUV pulse. The wave function oscillating at the frequency of the XUV pulse was obtained. Furthermore, the chirp-dependent absorption spectrum near ωX potentially provides an all-optical method for characterizing the attosecond pulse duration. Finally, these results can extend to other systems, such as solids or liquids, indicating a potential for application in photonic devices, and they may be meaningful for quantum manipulation.

Polyacrylamide (HPAM) is commonly used as a thickener in water-based fracturing fluids due to its good solubility and thickening ability. However, drawbacks such as the formation of high temperature and high salinity in oil and gas production currently limit its use as a thickening agent for fracturing fluids. To solve this problem, a hydrophobic associating polymer, DSAM (acrylamide/2-acrylamido-2-methylpropanesulfonic acid/acrylic acid/hydrophobic monomer AMD-12), with a good temperature and salt resistance was synthesized via complex initiated polymerization. The molecular structure of the synthesized polymer DSAM was confirmed using IR and 1H NMR. The water solubility, thickening properties, and salt resistance of DSAM polymers were investigated. The results showed that the DSAM polymer solution’s apparent viscosity initially decreased with the addition of NaCl. However, as the salt concentration further increased, the DSAM polymer solution’s polarity also increased, as well as the hydrophobic association between molecules, resulting in a denser hydrophobic association network structure and an increase in the apparent viscosity of the polymer solution. The viscoelasticity test revealed that as the salt concentration increased, the viscoelastic polymer solution increased after initially decreasing, which was consistent with previous salt tolerance test results. Additionally, it exhibited superior temperature resistance, shear tolerance, and shear recovery capabilities compared with conventional HPAM. Meanwhile, the DSAM polymer can be completely broken down in the industry-standard time without residue. The benefits of DSAM polymers include salt thickening, high-temperature resistance, and thorough gel breaking. Thus, it has huge potential as a thickening agent for temperature-tolerant and salt-resistant fracturing fluid.

The generation of the below threshold harmonics (BTHs) under different driving laser intensities is investigated. The linearly shifting of photon energy and resonantly enhancement of photon yield of the harmonics from 23rd (H23) to 27th (H27) are found by changing the laser intensity around 18.6 TW/cm2. It is identified that this driving laser intensity dependence is due to the transient ac Stark-shifted resonance between the first excited state and the ground state. With this transient ac Stark, the linearly shifting of the photon energy can be interpreted very well by considering the sub-cycle electron dynamics for BTH generation, which shows that the generation of the BTHs is surprisingly similar to the plateau harmonics.

In order to solve the easily scalable problem of evaporative condensing equipment, re-search was conducted on the development of a new type of self-priming scaling evaporative condenser with a built-in electrochemical scale absorber which changes the traditional water quality treatment cycle method from “preventing scaling” to “self-priming scaling”, integrating treatment devices and an evaporative condenser in order to realize the integration and modularization of the equipment. Experimental results show that the new self-priming scaling evaporative condenser has a condensing temperature range of 36.7~38.9 °C, heat rejection range of 716.69~768.66 kW, and, under different load rates, a condensing temperature range of 22.7~36.7 °C. The new self-priming scaling evaporative condenser system’s energy efficiency ratio COP has a range of 3.26~3.44. The coefficient of performance IPLV is 3.9, which exceeds the design index value. After the unit ECT electrochemistry meter is turned on, it effectively reduces the concentration multiplier of water quality: the total hardness increase per minute is reduced from 0.4 mg/L to 0.23 mg/L, a reduction of 42.5%. Turning on the electrochemistry meter also effectively reduces the increase in the total hardness and reduces the occurrence of scaling in the evaporative condenser unit.

Head or ear blight, mainly caused by Fusarium species, can devastate almost all staple cereal crops (particularly wheat), resulting in great economic loss and imposing health threats on both human beings and livestock 1 – 3 . However, achievement in breeding for highly resistant cultivars is still not satisfactory. Here, we isolated the major-effect wheat quantitative trait locus, Qfhs.njau-3B , which confers head blight resistance, and showed that it is the same as the previously designated Fhb1 . Fhb1 results from a rare deletion involving the 3′ exon of the histidine-rich calcium-binding-protein gene on chromosome 3BS. Both wheat and Arabidopsis transformed with the Fhb1 sequence showed enhanced resistance to Fusarium graminearum spread. The translation products of this gene’s homologs among plants are well conserved and might be essential for plant growth and development. Fhb1 could be useful not only for curbing Fusarium head blight in grain crops but also for improving other plants vulnerable to Fusarium species. Genetic mapping and functional studies show that mutation of a histidine-rich calcium-binding-protein gene at the Fhb1 locus confers resistance to Fusarium head blight in wheat. Notably, transgenic plants expressing the R allele show enhanced resistance to infection.

Carbon nanotubes (CNTs) exhibit high strength and high modulus, excellent electrical and thermal conductivity, good chemical stability, and unique electronic and optical properties. These characteristics make them a one-dimensional nanomaterial with extensive potential applications in fields such as composite materials, electronic devices, energy, aerospace, and medical technology. Cement-based materials are the most widely used and extensively applied construction materials. However, these materials have disadvantages such as low tensile strength, brittleness, porosity, shrinkage, and cracking. In order to compensate for these shortcomings, in recent years, relevant scholars have proposed to integrate CNTs into cement-based materials. Incorporating CNTs into cement-based materials not only enhances the microstructure of these materials but also improves their mechanical, electrical, and durability properties. The characteristics and fabrication process of CNTs are reviewed in this paper. The different effects of CNTs on the physical properties and hydration properties of cement-based materials due to the design parameters, dispersion methods, and temperature were analyzed. The results show that the compressive and flexural strength of CNT cement-based materials with 0.02% content increased by 9.33% and 10.18% from 3 d to 28 d. In terms of reducing the shrinkage and carbonization resistance of the cement base, there is an optimal amount of carbon nanotubes. The addition of dispersed carbon nanotubes reduces the resistivity, and the nucleation of carbon nanotubes promotes the hydration reaction. In general, under the optimal dosage, carbon nanotubes with uniform dispersion and short length–diameter ratio have a significant effect on the cement-based lifting effect. In the future, CNT cement-based materials will develop high strength, multifunctionality, and low cost, realizing intelligent self-sensing and self-repair and promoting green and low-carbon manufacturing. Breakthroughs in decentralized technology and large-scale applications are key, and they are expected to help sustainable civil engineering with intelligent infrastructure.

We have studied the magnetic and electrical transport properties of epitaxial NiAs-type CrTe thin films grown on SrTiO 3 (111) substrates. Unlike rectangle hysteresis loops obtained from magnetic measurements, we have identified intriguing extra bump/dip features from anomalous Hall experiments on the films with thicknesses less than 12 nm. This observed Hall anomaly is phenomenologically consistent with the occurrence of a topological Hall effect(THE) in chiral magnets with a skyrmion phase. Furthermore, the THE contribution can be tuned by the film thickness, showing the key contribution of asymmetric interfaces in stabilizing Néel-type skyrmions. Our work demonstrates that a CrTe thin film on SrTiO 3 (111) substrates is a good material candidate for studying real-space topological transport.

Exploring the spatiotemporal characteristics of park visitors and the “push and pull” factors that shape this mobility is critical to designing and managing urban parks to meet the demands of rapid urbanization. In this paper, 56 parks in Shenzhen were studied in 2019. First, cell phone signaling data were used to extract information on visitors’ departure locations and destination parks. Second, the bivariate Moran’s I and bivariate local Moran’s I (BiLISA) methods were used to identify the statistical correlation between the factors of the built environment and the park recreation trips. Finally, linear regression models were constructed to quantify the factors influencing the attractiveness of the park. Our study showed the following: (1) Recreation visitors at large parks varied significantly among population subgroups. Compared with younger adults, teenagers and older adults traveled lower distances and made fewer trips, and in particular, older adults of different genders differed significantly in park participation. (2) Recreational trips in large parks were related to the functional layout of the built environment around their residence. In areas with rich urban functions (e.g., southern Shenzhen), trips to large parks for leisure are more aggregated. (3) The findings reinforce the evidence that remote sensing data for urban vegetation can be an effective factor in characterizing park attractiveness, but the explanatory power of different vegetation data varies widely. Our study integrated the complementary human activity and remote sensing data to provide a more comprehensive understanding of urban park use and preferences. This will be important for future park planning.