Absolute frequency measurement of the 87Sr optical lattice clock at NTSC using International Atomic Time

We report the absolute frequency measurement of the 5s2 1S0-5s5p 3P0 transition in 87Sr optical lattice clock (Sr1) at National Time Service Center (NTSC). Its systematic frequency shifts are evaluated carefully with a total relative uncertainty of 5.1E10-17. The measured absolute frequency is 429 228 004 229 872.91(18) Hz with a relative uncertainty of 4.13E10-16, with reference to the ensemble of primary and secondary frequency standards published in the Circular T bulletin by BIPM through a global navigation satellite system (GNSS) link

Retroperitoneal neuroglial heterotopia: a case report and literature review

BackgroundNeuroglial heterotopia is a rare lesion composed of differentiated neuroectodermal cells that manifest in extracranial locations, with the majority of cases predominantly occurring in the head and neck region. Retroperitoneal neuroglial heterotopia is exceptionally rare, with isolated cases published in the scientific literature.Case reportHere, we present the case of a 3-year-old girl who was admitted without clinical signs but presented with a palpable abdominal mass. Ultrasonography and computed tomography scans revealed a sizable cystic lesion within the retroperitoneal space. Subsequently, laparoscopic resection was performed. Histological examination unveiled neuroglial cell-lined cysts encompassing fibrous connective tissue, ganglia, glial tissue, and nerve bundles. Notably, distinct areas and cell types exhibited expression of S100, glial fibrillary acidic protein, and neuron-specific enolase. Follow-up assessments revealed no relapses or late complications.ConclusionIn cases of retroperitoneal neuroglial heterotopia, most children may remain asymptomatic without any congenital anomalies. Despite their detectability through imaging, accurate preoperative diagnosis is seldom achieved. Generally, a favorable prognosis follows complete surgical resection, although further cases are required to confirm its long-term efficacy, necessitating extended follow-up for verification

Attention-deficit/hyperactivity disorder is characterized by a delay in subcortical maturation

Although previous studies have found that ADHD is characterized by a delay in cortical maturation, it is not clear whether this phenomenon was secondary to developmental trajectories in subcortical regions (caudate, putamen, pallidum, thalamus, hippocampus and amygdala). Using the ADHD-200 dataset, we estimated subcortical volumes in 339 individuals with ADHD and 568 typically developing controls. We defined the growth trajectory of each subcortical structure, delineating a phase of childhood increase followed by an adolescent decrease in subcortical volumes using a quadratic growth model. From these trajectories, the age of attaining peak subcortical volumes was derived and used as an index of subcortical maturation. We found that subcortical structures (caudate, putamen, pallidum, thalamus, hippocampus and amygdala) followed curvilinear trajectories similar to those reported in previous studies. The volumes of these subcortical structures in ADHD were also delayed in the developmental trajectory, which suggested that ADHD may be characterized by a delay in subcortical maturation. This delay may lead to a shift in which individuals with ADHD go through the process of pruning the nerve connections that is part of the normal maturation process during adolescence. Further, we also found that the asymmetric development of subcortical structures was abnormal in ADHD, which resulted from the imbalance of the maturation delay of bilateral subcortical structures. The subcortical maturation delay may play an important role in the pathophysiology of ADHD. Our findings provide new potential targets to investigate the pathophysiology of ADHD

Demonstration of a time scale with the 87Sr optical lattice clock at NTSC

Optical clocks have been applied to the generation of time scales since they provide superb uncertainty and instability in recent years. This paper presents the simulations about the impact of the optical clock’s operational strategies on the performance of the generated time scale through two distinct steering algorithms. By post-processing the measured frequency difference between the 87Sr optical lattice clock and the hydrogen maser at the National Time Service Center, we realized an “optically steered” time scale TS(Sr), and the variation of the time difference TT(BIPM22)-TS(Sr) is 0.1 ns during the modified Julian date 59794–59819

Efficient Carrier Separation and Band Structure Tuning of Two-Dimensional C₂N/GaTe van der Waals Heterostructure

Efficient carrier separation and suitable band structure are critical for developing better nanoscale optoelectronic devices. However, so far, researchers have not developed a single material system that can satisfy these requirements. Here we design a novel C₂N/GaTe van der Waals heterostructure based on the density functional theory. Our results suggest that this heterostructure is an indirect band gap semiconductor (1.39 eV) with intrinsic type-II band alignment, facilitating the separation of photogenerated carriers. Meanwhile, this heterostructure exhibits improved visible optical absorption compared with that of the isolate C₂N and GaTe monolayers. More fascinatingly, we find that an intriguing indirect-to-direct band gap semiconductor transition can be induced at the compressive strain of 3%. Simultaneously, the band gaps and carrier effective masses can also be significantly reduced by the biaxial strain. Furthermore, the band edge positions of C₂N/GaTe heterostructure can be effectively tuned to straddle the redox potentials of water splitting by isoelectronic anion S and Se substitution at the Te site, and the enhanced optical absorptions are also observed in the doped heterostructures, indicating that S (Se)-doped C₂N/GaTe heterostructures are potential photocatalysts for water splitting. In addition, effective spatial separation of photogenerated carriers is expected to occur for all of the above cases. These findings suggest that the C₂N/GaTe heterostructure is a promising candidate for application in future nanoelectronics and optoelectronics devices and also provides some valuable information for future experimental research

Discussion on Mode of Key Link in Increase and Decrease Connection of Urban and Rural Construction Land

With the methods of qualitative analysis, induction and deduction, modes of key links in increase and decrease connection of urban and rural construction land are proposed in view of the involved three key links, namely reclamation of rural construction land, fund raising and management of connection turnover index, based on the comprehensive analysis of political connotation in increase and decrease of urban and rural construction land. The modes include “village relocation and combination”, “hollow village” reconstruction, high-rise stereo, village relocation in the mountain and related capital raising and turnover index management and the applicable regions of various modes are analyzed and studied. The research result provides reference for the reasonable operation of increase and decrease link of urban and rural construction land

Single-layer ZnMN2 (M = Si, Ge, Sn) zinc nitrides as promising photocatalysts

Searching for two-dimensional semiconductor materials that are suitable for visible-light photocatalytic water splitting provides a sustainable solution to deal with the future energy crisis and environmental problems. Herein, based on first-principles calculations, single-layer ZnMN2 (M = Si, Ge, Sn) zinc nitrides are proposed as efficient photocatalysts for water splitting. Stability analyses show that the single-layer ZnMN2 zinc nitrides exhibit energetic and dynamical stability. The electronic properties reveal that all of the single-layer ZnMN2 zinc nitrides are semiconductors. Interestingly, single-layer ZnSnN2 is a direct band gap semiconductor with a desirable band gap (1.74 eV), and the optical adsorption spectrum confirms its optical absorption in the visible light region. The hydrogen evolution reaction (HER) calculations show that the catalytic activity for single-layer ZnMN2 (M = Ge, Sn) is better than that of single-layer ZnSiN2. Furthermore, the band gaps and band edge positions for the single-layer ZnMN2 zinc nitrides can be effectively tuned by biaxial strain. Especially, single-layer ZnGeN2 can be effectively tuned to match better with the redox potentials of water and enhance the light absorption in the visible light region at a tensile strain of 5%, which is confirmed by the corresponding optical absorption spectrum. Our results provide guidance for experimental synthesis efforts and future searches for single-layer materials suitable for photocatalytic water splitting