Probing time delay of strong-field resonant above-threshold ionization

The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization(ATI)of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4 f and 5 f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale.

260 fs,403 W coherently combined fiber laser with precise high‑order dispersion management

An ultrafast fiber laser system comprising two coherently combined amplifier channels is reported.Within this system,each channel incorporates a rod-type fiber power amplifier,with individual operations reaching approximately 233 W.The active-locking of these coherently combined channels,followed by compression using gratings,yields an output with a pulse energy of 504μJ and an average power of 403 W.Exceptional stability is maintained,with a 0.3%root mean square(RMS)deviation and a beam quality factor M^(2)<1.2.Notably,precise dispersion management of the front-end seed light effectively compensates for the accumulated high-order dispersion in subsequent amplification stages.This strategic approach results in a significant reduction in the final output pulse duration for the coherently combined laser beam,reducing it from 488 to 260 fs after the gratings compressor,while concurrently enhancing the energy of the primary peak from 65%to 92%.

Modeling of contact temperatures and their influence on the tribological performance of PEEK and PTFE in a dual-pin-ondisk tribometer

The direct blending of polyether ether ketone(PEEK)with a solid lubricant such as polytetrafluoroethylene(PTFE)improves its tribological performance,but compromises its outstanding mechanical properties and processability.While these negative effects might be circumvented via the hybrid wear method,the influence of the contact temperature between multiple sliding components acting together is not fully understood.Herein,an analytical temperature model considering the influence of both micro-and macro-thermal behavior is extended to predict the contact temperature of a dual-pin-on-disk hybrid wear system.The interactions between several heat sources are investigated and experimentally verified.The analytical results show that the nominal temperature rise of the shared wear track is determined by the combined effect of the heat generated by both pin components,while the rise in flash temperature at the region in contact with each pin component is dependent upon its individual characteristics and working conditions.Hence,while different temperature peaks can coexist in the shared wear track,the maximum value dominates the performance of the system.For the experimentally investigated PEEK–PTFE–steel hybrid wear system,the formation of tribofilms is blocked,and the hybrid wear system fails,when the peak temperature exceeds the glass transition temperature of both pins due to an increase in applied load.

推进监狱工作现代化初探

建设现代监狱,进一步完善监狱的形态和质态,是监狱当代的现实使命。树立矫正为本的理念,全力提升矫正的有效性,把矫正融入罪犯行刑的全过程,实施矫正社会化战略,社会要素有效参与到矫正过程,从而最大限度降低重新犯罪率,实现监狱改造人的目标任务。

论矫正时代

新时代对监狱在社会发展过程中担负的使命和社会角色定位提出了更高要求,监狱由此进入新的矫正时代,改造质量成为评价监狱的目标指向。梳理现代监狱的发展和变革,围绕实现矫正效能,研究有效干预罪犯犯因性需求的路径方法,归纳总结矫正时代的工作思路、理念、方法和手段,对于提高罪犯的干预效果,降低重新犯罪率,促进罪犯回归后更好地融入社会且成为社会的建设者具有重要价值。

Resolving and weighing the quantum orbits in strong-field tunneling ionization

Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits.Identifying the contributions of these orbits is crucial for exploring the application of tunneling and for understanding various tunneling-triggered strong-field phenomena.We perform a combined experimental and theoretical study to identify the relative contributions of the quantum orbits corresponding to the electrons tunneling ionized during the adjacent rising and falling quarter cycles of the electric field of the laser pulse.In our scheme,a perturbative second-harmonic field is added to the fundamental driving field.By analyzing the relative phase dependence of the signal in the photoelectron momentum distribution,the relative contributions of these two orbits are unambiguously determined.Our results show that their relative contributions sensitively depend on the longitudinal momentum and modulate with the transverse momentum of the photoelectron,which is attributed to the interference of the electron wave packets of the long orbit.The relative contributions of these orbits resolved here are important for the application of strong-field tunneling ionization as a photoelectron spectroscopy for attosecond time-resolved measurements.

Chondroinductive/chondroconductive peptides and their-functionalized biomaterials for cartilage tissue engineering

The repair of articular cartilage defects is still challenging in the fields of orthopedics and maxillofacial surgery due to the avascular structure of articular cartilage and the limited regenerative capacity of mature chondrocytes.To provide viable treatment options,tremendous efforts have been made to develop various chondrogenically-functionalized biomaterials for cartilage tissue engineering.Peptides that are derived from and mimic the functions of chondroconductive cartilage extracellular matrix and chondroinductive growth factors,represent a unique group of bioactive agents for chondrogenic functionalization.Since they can be chemically synthesized,peptides bear better reproducibility,more stable efficacy,higher modifiability and yielding efficiency in comparison with naturally derived biomaterials and recombinant growth factors.In this review,we summarize the current knowledge in the designs of the chondroinductive/chondroconductive peptides,the underlying molecular mechanisms and their-functionalized biomaterials for cartilage tissue engineering.We also systematically compare their in-vitro and in-vivo efficacies in inducing chondrogenesis.Our vision is to stimulate the development of novel peptides and their-functionalized biomaterials for cartilage tissue engineering.

Dicalcium silicate-induced mitochondrial dysfunction and autophagy-mediated macrophagic inflammation promotes osteogenic differentiation of BMSCs

Dicalcium silicate(Ca_(2)SiO_(4),C_(2)S)has osteogenic potential but induces macrophagic inflammation.Mitochondrial function plays a vital role in macrophage polarization and macrophagic inflammation.The mitochondrial function of C_(2)S-treated macrophages is still unclear.This study hypothesized:(i)the C_(2)S modulates mitochondrial function and autophagy in macrophages to regulate macro-phagic inflammation,and(ii)C_(2)S-induced macrophagic inflammation regulates osteogenesis.We used RAW264.7 cells as a model of macrophage.The C_(2)S(75–150μg/ml)extract was used to analyze the macrophagic mitochondrial function and macrophagemediated effect on osteogenic differentiation of mouse bone marrow-derived mesenchymal stem cells(BMSCs).The results showed that C_(2)S extract(150μg/ml)induced TNF-α,IL-1βand IL-6 production in macrophages.C_(2)S extract(150μg/ml)enhanced reactive oxygen species level and intracellular calcium level but reduced mitochondrial membrane potential and ATP production.TEM images showed reduced mitochondrial abundance and altered the mitochondrial morphology in C_(2)S(150μg/ml)-treated macrophages.Protein level expression of PINK1,Parkin,Beclin1 and LC3 was upregulated but TOMM20 was downregulated.mRNA sequencing and KEGG analysis showed that C_(2)S-induced differentially expressed mRNAs in macrophages were mainly distributed in the essential signaling pathways involved in mitochondrial function and autophagy.The conditioned medium from C_(2)S-treated macrophage robustly promoted osteogenic differentiation in BMSCs.In conclusion,our results indicate mitochondrial dysfunction and autophagy as the possible mechanism of C_(2)S-induced macrophagic inflammation.The promotion of osteogenic differentiation of BMSCs by the C_(2)S-induced macrophagic inflammation suggests the potential application of C_(2)S in developing immunomodulatory bone grafts.

Full experimental determination of tunneling time with attosecond-scale streaking method

Tunneling is one of the most fundamental and ubiquitous processes in the quantum world.The question of how long a particle takes to tunnel through a potential barrier has sparked a long-standing debate since the early days of quantum mechanics.Here,we propose and demonstrate a novel scheme to accurately determine the tunneling time of an electron.In this scheme,a weak laser field is used to streak the tunneling current produced by a strong elliptically polarized laser field in an attoclock configuration,allowing us to retrieve the tunneling ionization time relative to the field maximum with a precision of a few attoseconds.This overcomes the difficulties in previous attoclock measurements wherein the Coulomb effect on the photoelectron momentum distribution has to be removed with theoretical models and it requires accurate information of the driving laser fields.We demonstrate that the tunneling time of an electron from an atom is close to zero within our experimental accuracy.Our study represents a straightforward approach toward attosecond time-resolved imaging of electron motion in atoms and molecules.