In order to address the present difficulty in experimentally generating the relativistic Laguerre-Gaussian laser, primarily due to damage caused to optical modulators, a high-reflectivity phase ...mirror is applied in the femtosecond petawatt laser system to generate a relativistic hollow laser at the highest intensity of 6.3 × 1019 W / cm2 for the first time. A simple optical model is used to verify that the vortex laser may be generated in this new scheme; using such a relativistic vortex laser, the hollow plasma drill and acceleration are achieved experimentally and proven by particle-in-cell simulations. With the development of the petawatt laser, this scheme opens up possibilities for the convenient production of the relativistic hollow laser at high repetition and possible hollow plasma acceleration, which is important for a wide range of applications such as the generation of radiation sources with orbital angular momentum, fast ignition for inertial confinement fusion, and jet research in the astrophysical environment.
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A simple, efficient scheme was developed to obtain near-gigaelectronvolt electron beams with energy spreads of few per-mille level in a single-stage laser wakefield accelerator. Longitudinal plasma ...density was tailored to control relativistic laser-beam evolution, resulting in injection, dechirping, and a quasi-phase-stable acceleration. With this scheme, electron beams with peak energies of 780–840 MeV, rms energy spreads of 2.4‰–4.1‰, charges of 8.5–23.6 pC, and rms divergences of 0.1–0.4 mrad were experimentally obtained. Quasi-three-dimensional particle-in-cell simulations agreed well with the experimental results. The dechirping strength was estimated to reach up to 11 TeV/mm/m, which is higher than previously obtained results. Such high-quality electron beams will boost the development of compact intense coherent radiation sources and x-ray free-electron lasers.
Silver (Ag)-doped diamond-like carbon (Ag-DLC) films were deposited on Si wafer and Co-Cr-Mo alloy substrates using a hybrid deposition technique that combined high-power pulsed magnetron sputtering ...(HPPMS) and high-power pulsed plasma-enhanced chemical vapor deposition (HPP-PECVD). The Ag concentration (0.0–10.0 at.%) in Ag-DLC films was controlled by adjusting the number of Ag rods in the mosaic silver-graphite target. The effects of Ag doping on the microstructure, chemical bonding, mechanical properties, and adhesion stability of DLC films were systematically investigated. The results demonstrated that Ag doping could refine the columnar structure in DLC films and change the shape and size of DLC surface hillocks. The residual stress in the DLC films decreased as the Ag concentration increased, which effectively improved the adhesion between the films and substrates. The fraction of sp3 bonds in the carbon structure decreased with increasing Ag concentration, which resulted in a reduction in the film hardness when the Ag concentration was higher than 3.2 at.%. Ag doping could improve the wear performance of DLC films, and the Ag-DLC film with 3.2 at.% Ag had excellent wear resistance. Compared with pure DLC films, the Ag-DLC films had better adhesion stability in physiological solutions, which is beneficial for the long-term service of DLC films in vivo applications.
•Ag doping can refine the columnar structure in DLC films to create a compact structure.•Ag doping reduces residual stress without reducing hardness for Ag concentrations less than 3.2 at.%.•Ag-DLC films with 3.2 at.% Ag have excellent wear resistance.•Ag doping can improve adhesion performance and adhesion stability of DLC films in PBS.
We investigate the heat transfer and coherent structures in Taylor–Couette (TC) flows that undergo thermal convection driven by an axially applied temperature gradient. Direct numerical simulations ...are performed in a Rayleigh number range $10^6 \leq Ra \leq 3 \times 10^8$ for Prandtl number $Pr = 4.38$ and with the shear Reynolds number up to $Re = 10^4$. When the rotation number $R_f$ increases, the flows undergo a transition from buoyancy-dominated ($R_f<1$) to shear-dominated convection ($R_f>1$). In the buoyancy-dominated regime with weak rotations, the flow features are similar to those in Rayleigh–Bénard (RB) convection with large-scale plumes emanating from the thermal boundary layers. In this regime, the $Re$-dependence of heat transport $Nu$ is sensitive to $Ra$. We find that for low $Ra$, $Nu$ decreases with increasing $Re$ and becomes independent of $Re$ at high $Ra$. In the shear-dominated regime, the flow structures are characterised by Taylor vortices (TVs), which effectively enhance the heat transport. With sufficiently high Reynolds number for $2000< Re \le 10\,000$, the flow structures are dominated by turbulent TVs, and the transport scaling laws of heat and angular velocity fluxes become independent of buoyancy. We report that in this turbulent regime the axial heat-transport scaling $(Nu\sim Re^{0.578\pm 0.018})$ is consistent with the scaling of radial angular-momentum transport $(Nu_{\omega }\sim Re^{0.581\pm 0.026})$.
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•Addition of Fe3+, Fe2+, and Cu2+ ions alters the tertiary structure of BSA.•Fe3+ and Cu2+ ions promote BSA structural transformation from α-helix to β-sheet.•More tyrosine acts as ...hydrogen-bond donor after adding Fe3+, Cu2+, and Co2+ ions.•Addition of Cu2+ ions promotes the aggregation of BSA molecules.
Metal ions released from metallic implants can affect the conformation and structural stability of proteins in biological fluids, which eventually affects the biocompatibility of implants. The present study aimed at understanding the interactions between the metal ions (Mn2+, Fe2+, Fe3+, Co2+, Cu2+, and Zn2+) and bovine serum albumin (BSA) molecules in physiological context. The structural information of BSA molecules and the microenvironment of functional groups were investigated using UV, Raman, and circular dichroism spectroscopy. The results revealed that addition of Fe3+, Fe2+, and Cu2+ ions alters the tertiary structure of BSA molecules and exposes the aromatic heterocyclic hydrophobic group of BSA amino acid residues. The addition of Fe3+ and Cu2+ ions results in increased viscosity and decreased intensity of the water peak in the BSA solution. Furthermore, Fe3+ and Cu2+ ions evidently promote the α-helix to β-sheet transformation of BSA molecules due to decreased disulfide bond stability. Tryptophan residues of BSA and metal ions containing BSA (Me+/BSA) solutions were found to be in a hydrophilic environment. Moreover, the addition of metal ions to BSA results in several of tyrosine residues acting as hydrogen-bond donors. Coomassie brilliant blue staining revealed that the addition of Cu2+ ions promotes the aggregation of BSA molecules. The findings of this study will be helpful for evaluating the biocompatibility of metallic implants.
Dual-phase high entropy alloys have been proved to have the ability to overcome the strength-ductility trade-off. However, high-entropy alloy films are difficult to obtain a dual-phase structure due ...to the extremely high cooling rate during the preparation process and the high-entropy effect of the film itself. In this paper, the dual-phase CuNiTiNbCr high-entropy alloy films were prepared by high-power pulsed magnetron sputtering at different working pressures. The composition, microstructures, mechanical properties and electrochemical corrosion performance were tested by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), nano-indentation, Vickers indentation and electrochemical polarization. The CuNiTiNbCr films exhibited a dual-phase structure composed of FCC matrix phase and Cu-rich BCC precipitated phase. The film presented a two-layer structure, the single FCC phase structure near the substrate and the FCC + BCC structure above. Comparing with FCC phase, the dual-phase structure exhibited higher hardness. With the increase of deposition pressure, the structure of the film became looser, and the hardness, toughness and corrosion resistance were all decreased due to the influence of the structure. It is proved that high-power pulsed magnetron sputtering is a feasible way for the phase structure regulation and performance improvement of high-entropy alloy films.
•CuNiTiNbCr films were deposited by high-power pulsed magnetron sputtering.•CuNiTiNbCr films present a FCC + BCC nano dual-phase structure.•The formation of Cu-rich phase is related to the substrate temperature.•The dual-phase HEAFs deposited at 0.4 Pa present a high hardness of 11.35 GPa.
TiN film has been used in the surface modification of orthopaedic implants due to its favorable biocompatibility and tribological properties. Copper ions have low toxicity and biological functions. ...In this study, copper was doped to TiN film to enhance the viability of osteoblast and decrease the inflammatory response of macrophages for TiCuN film applications in orthopaedic implants. TiCuN films with different Cu contents were deposited on Si wafers by direct current (DC) magnetron sputtering technique. The effects of Cu content on the TiCuN film structure, surface morphology, and surface energy were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements. The results demonstrated that Cu doping could suppress the columnar structure of TiN films, change the surface of the TiN film from hydrophilic to hydrophobic, and reduce its surface energy. When the Cu content reached 11.1 at.%, Cu nanocrystals were formed in the TiCuN film. The biocompatibility of the TiCuN films with different Cu contents was analyzed based on osteoblasts and macrophages. The results demonstrated that the viability and morphology of osteoblasts on the TiCuN films with a Cu content of 2.4 at.% were significantly improved compared with those of the CoCrMo alloy and TiN film. The inflammatory response induced by the TiCuN films with Cu contents of 2.4 and 4.2 at.% was lower than that induced by the CoCrMo alloy and TiN film without Cu doping. The TiCuN film with optimum Cu content of 2.4 at.% promoted the viability of osteoblasts and reduced the inflammatory response of macrophages.
•As Cu content increases, columnar structure of the TiN film gradually transforms into a dense and featureless structure.•When the Cu content reaches 11.1 at.%, Cu nanocrystals are formed in the TiCuN film.•TiCuN film with a Cu content of 2.4 at.% promoted osteoblast viability and reduced the macrophage inflammatory response.
Thin layers of in-plane anisotropic materials can support ultraconfined polaritons, whose wavelengths depend on the propagation direction. Such polaritons hold potential for the exploration of ...fundamental material properties and the development of novel nanophotonic devices. However, the real-space observation of ultraconfined in-plane anisotropic plasmon polaritons (PPs)-which exist in much broader spectral ranges than phonon polaritons-has been elusive. Here we apply terahertz nanoscopy to image in-plane anisotropic low-energy PPs in monoclinic Ag
Te platelets. The hybridization of the PPs with their mirror image-by placing the platelets above a Au layer-increases the direction-dependent relative polariton propagation length and the directional polariton confinement. This allows for verifying a linear dispersion and elliptical isofrequency contour in momentum space, revealing in-plane anisotropic acoustic terahertz PPs. Our work shows high-symmetry (elliptical) polaritons on low-symmetry (monoclinic) crystals and demonstrates the use of terahertz PPs for local measurements of anisotropic charge carrier masses and damping.
Silver-doped diamond-like carbon (Ag-DLC) films offer low residual stress, good adhesion, and excellent wear resistance, and thus are promising materials for surface modification of joint prostheses. ...Further, as proteins are the most abundant component of joint fluid, the wear performance of Ag-DLC films in protein environments warrants investigation. We prepared DLC and 10.0 at.% Ag-DLC films using hybrid deposition technique by combining high-power pulsed magnetron sputtering and high-power pulsed plasma-enhanced chemical vapor deposition. The wear performance of the films was tested using bovine serum albumin (BSA) solution. A biofilm of denatured proteins formed at the friction interface of the Ag-DLC film, which improve wear resistance. Subsequent protein adsorption, Ag+ ions release, and spectroscopic evaluation of the interaction between Ag+ ions and BSA molecules revealed the mechanism of biofilm formation. Ag doping promoted the protein adsorption on film surface and friction interface of Ag-DLC films. Meanwhile, Ag-DLC films released Ag+ ions when exposed in physiological solutions. The released Ag+ ions break the hydrogen bonds and disulfide bonds in proteins and transform the α-helix structure to β-sheet and β-turn structure, thus unfolding the protein, exposing the inner hydrophobic groups, and inducing protein deposition and biofilm formation. The study elucidates the biofilm formation mechanism at the friction interface of Ag-DLC films and counterparts and can aid in design of hardwearing joint implants.
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•Ag doping improves the wear resistance of DLC film in BSA solutions.•Biofilm on the counterpart of Ag-DLC film is composed of denatured proteins.•Released Ag+ ions promote the adsorption and denaturation of BSA molecules.•Ag+ ions break the hydrogen and disulfide bonds, unfolding the protein structure.
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