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Bromodomain-containing protein 7 (BRD7), a member of the bromodomain-containing protein family, plays important roles in chromatin modification and transcriptional regulation. A recent model of Brd7-knockout mice presented azoospermia and male infertility, implying the potential role of BRD7 in spermatogenic failure in humans. This case-control study aimed to explore the association of the BRD7 gene with spermatogenic efficiency and the risk of spermatogenic defects in humans.A total of six heterozygous variants were detected in the coding and splicing regions of the BRD7 gene in patients with azoospermia. For each of four rare variants predicted to potentially damage BRD7 function, we further identified these four variants in oligozoospermia and normozoospermia as well. However, no difference in the allele and genotype frequencies of rare variants were observed between cases with spermatogenic failure and controls with normozoospermia; the sperm products of variant carriers were similar to those of noncarriers. Moreover, similar distribution of the alleles, genotypes and haplotypes of seven tag single nucleotide polymorphisms (tagSNPs) was observed between the cases with azoospermia and oligozoospermia and controls with normozoospermia; associations of tagSNP-distinguished BRD7 alleles with sperm products were not identified.The lack of an association of BRD7-linked rare and common variants with spermatogenic failure implied a limited contribution of the BRD7 gene to spermatogenic efficiency and susceptibility to male infertility in humans.RéSUMé: CONTEXTE: Le bromodomaine contenant la protéine 7 (BRD7), un membre de la famille du bromodomaine contenant des protéines, joue des rôles importants dans la modification de la chromatine et la régulation transcriptionnelle. Un modèle récent de souris Brd7-knockout présentait une azoospermie et une infertilité mâle, ce qui implique un rôle potentiel de BRD7 dans l’altération de la spermatogenèse chez l’homme. Cette étude cas-témoins visait à explorer l’association du gène BRD7 avec l’efficacité de la spermatogenèse et le risque d’altérations spermatogéniques chez l’homme. RéSULTATS: Un total de six variants hétérozygotes ont été détectés dans les régions de codage et d’épissage du gène BRD7 chez les patients présentant une azoospermie. Pour chacun des quatre variants rares prédits pour potentiellement endommager la fonction BRD7, nous avons en outre identifié ces quatre variants dans l’oligozoospermie et la normozoospermie. Cependant, nous n’avons observé aucune différence dans les fréquences d’allèle et de génotype des variants rares entre les cas avec altérations de la spermatogenèse et les témoins avec normozoospermie ; les produits du sperme des porteurs de variants étaient semblables à ceux des non-porteurs. Par ailleurs, on a observé une distribution semblable des allèles, des génotypes et des haplotypes de sept polymorphismes simples de nucléotide de balise (tagSNPs) entre les cas avec azoospermie ou oligozoospermie et les témoins normozoospermiques; aucune association n’a pas été identifiée entre les allèles BRD7 tagSNP-distingués et des produits du sperme. CONCLUSION: L’absence d’association des variants rares liés à BRD7 et des variants communs liés à BRD7 avec les altérations de la spermatogenèse implique une contribution limitée du gène BRD7 à l’efficacité spermatogénique et à la susceptibilité à l’infertilité masculine chez l’homme.

To quantitatively assess the risks of pedestrian evacuation through staircases with different slopes when a flood intrudes into the underground space, a numerical model was designed to simulate flood flow patterns on staircase and escalator under different slope conditions (26.6°, 28.2°, 29.1°, 30°, and 35°). A safety index (F (v2, y)) was employed to assess the risks of pedestrian evacuation through the staircase under different slopes. When the water depth at the staircase entrance (under slopes ranging from 26.6° to 28.2°) was 0.3 m and the unit width discharge was 0.28 m2/s, pedestrians safely evacuated the underground space. However, when the staircase slope was beyond 28.2°, the safety index value was higher than the critical value and the flood caused serious threats to them. Therefore, it is suggested that when the underground space becomes flooded, pedestrians should avoid steep slopes and choose a gentle staircase as a safer escape route. The obtained results provide a theoretical guideline for pedestrian evacuation from a flooded staircase.

Background: The role of CXCL8 and LSECtin in colon cancer liver metastasis and immune checkpoint inhibitors (ICIs) treatment effect were widely recognized. However, the regulatory role of CXCL8 on LSECtin is still unclear. Methods: The expression of CXCL8 or LSECtin was analyzed by TCGA database, and verified by GES110225 and clinical samples. The relationship between the expression of CXCL8 or LSECtin and immune cells infiltration, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, Gene Ontology (GO) items, stromal score, Estimation of STromal and Immune cells in MAlignant Tumours (ESTIMAT) immune score, tumor mutation burden (TMB), mismatch repair gene and immune checkpoints expression were analyzed by Spearman. The effects of CXCL8 on LSECtin expression, proliferation, and invasion ability were clarified by recombinant CXCL8 or CXCL8 interfering RNA. Results: In colon cancer, the expression of CXCL8 was higher, but LSECtin was lower than that in normal mucosa. The expression of CXCL8 or LSECtin was significantly positively correlated with immune cells infiltration, stromal score, ESTIMATE immune score, TMB, and immune checkpoints expression. The expression of LSECtin was closely related to the cytokine-cytokine receptor interaction pathway and response of chemokine function, such as CXCL8/CXCR1/2 pathway. There was a significant positive correlation between the expression of CXCL8 and LSECtin in colon cancer. CXCL8 up-regulated LSECtin through AKT signal and promoted the proliferation and invasion ability of colon cancer. Conclusions: CXCL8 up-regulated LSECtin by activating AKT signal and correlated with the immune microenvironment modulation in colon cancer.

Through cryogenic treatment and electrolytic passivation treatment of M2 high-speed steel(HSS), the effect of electrolytic passivation process parameters on the life of M2 HSS taps and the combined effect of cryogenic treatment and electrolytic passivation treatment on the wear resistance of the M2 HSS were investigated by using a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the life of M2 HSS tap after electrolytic passivation treatment increases most significantly under the theoretical edge radius, the functional relationship between the charge consumption (y) and the tap edge radius (x) is as follows: y = 8.135x-48.842. The wear resistance of the sample after cryogenic and electrolytic passivation treatment is the highest, which is 1.52 times higher than those of the traditional heat treatment sample. This is due to the increase of the number of carbides on the surface of the specimens after cryogenic treatment, the distribution and size of carbides are relatively uniform, the average size of carbides is reduced by 60.4%. There is a carbon layer on the surface of the sample after passivation, which can effectively improve the wear condition. The size and number of carbides in the surface layer of the sample remain unchanged after passivation treatment, indicating that cryogenic treatment plays a key role in the performance of the material.

Joubert syndrome (JBTS), a rare genetic disorder resulted from primary cilium defects or basal-body dysfunction, is characterized by agenesis of cerebellar vermis and abnormal brain stem. Both genotypes and phenotypes of JBTS are highly heterogeneous. The identification of pathogenic gene variation is essential for making a definite diagnosis on JBTS. Here, we found that hypoplasia of cerebellar vermis occurred in three male members in a Chinese family. Then, we performed whole exome sequencing to identify a novel missense mutation c.599T > C (p. L200P) in the OFD1 gene which is the candidate gene of X-linked JBTS (JBST10). The following analysis showed that the variant was absent in the 1000 Genomes, ExAC and the 200 female controls; the position 200 Leucine residue was highly conserved across species; the missense variant was predicted to be deleterious using PolyPhen-2, PROVEAN, SIFT and Mutation Taster. The OFD1 expression was heavily lower in the proband and an induced male fetus compared with a healthy male with a wild-type OFD1 gene. The in vitro expression analysis of transiently transfecting c.599T or c.599C plasmids into HEK-293T cells confirmed that the missense mutation caused OFD1 reduction at the protein level. And further the mutated OFD1 decreased the level of Gli1 protein, a read-out of Sonic hedgehog (SHH) signaling essential for development of central neural system. A known pathogenic variant c.515T > C (p. L172P) showed the similar results. All of these observations suggested that the missense mutation causes the loss function of OFD1, resulting in SHH signaling impairs and brain development abnormality. In addition, the three patients have Dandy-Walker malformation, macrogyria and tetralogy of Fallot, respectively, the latter two of which are firstly found in JBTS10 patients. In conclusion, our findings expand the context of genotype and phenotype in the JBTS10 patients.

Accurate and rapid simulation and monitoring of urban inundation play important roles in urban flood prediction and warning. This paper presents a case study of campus-scale rainfall-flood ...

The generation and development of coherent structure in 7-rod bundle lattice are researched by Unsteady Reynolds-Averaged Navier-Stokes (URANS) method with the Reynolds Stress Model (RSM). The influence of the coherent structure on the flow resistance and heat transfer coefficient is also analyzed. It is revealed that the coherent structure is helpful to improve the performance of lattice. Decreasing the pitch-to-diameter (P/D) or properly changing the shape of rod can contribute to the generation of coherent structure. The flow redistribution caused by corner channel has great influence to the coherent structure.

The development of sequencing techniques identified numerous genetic variants, and accurate evaluation of the clinical significance of these variants facilitates the diagnosis of Mendelian diseases. In the present study, 549 rare single- nucleotide variants of uncertain significance were extracted from the ADPKD and ClinVar databases. MaxEntScan scoresplice is an in silico splicing prediction tool that was used to analyze rare PKD1 and PKD2 variants of unknown significance. An in vitro minigene splicing assay was used to verify 37 splicing-altering candidates that were located within seven residues of the splice donor sequence excluding canonical GT dinucleotides or within 21 residues of the acceptor sequence excluding canonical AG dinucleotides of PKD1 and PKD2. We demonstrated that eight PKD1 variants alter RNA splicing and were predicted to be pathogenic.

Background and objective Stroke is a major contributor to the global burden of disease. Although numerous modifiable risk factors (RF) for stroke have been identified, some remain unexplained. Increasing studies have investigated stroke risk in arthritis, but their results are inconsistent. We aimed to synthesize, quantify, and compare the risk of stroke for the major types of arthritis in cohort studies by using a systematic review and meta-analysis approach. Methods We searched Chinese and English databases to identify relevant studies from inception to April 30, 2020. Only studies adjusting at least for age and sex were included. We calculated pooled effect estimates for relative risk (RR) and 95% confidence interval (CI) and identified potential sources of heterogeneity and publication bias. Results A total of 1,348 articles were retrieved, and after an preliminary screening of titles and abstracts, 69 were reviewed for full text, and finally, 32 met the criteria for meta-analysis. Stroke risk in arthritis was significantly increased in studies adjusting for age and sex (RR = 1.36, 95% CI: 1.27–1.46) and for at least one traditional risk factor (RR = 1.40, 95% CI: 1.28–1.54). The results of studies stratified by stroke subtype were consistent with the main finding (ischemic stroke: RR = 1.53, 95% CI: 1.32–1.78; hemorrhagic stroke: RR = 1.45, 95% CI: 1.15–1.84). In subgroup analysis by arthritis type, stroke risk was significantly increased in rheumatoid arthritis (RR = 1.38, 95% CI: 1.29–1.48), ankylosing spondylitis (RR = 1.49, 95% CI: 1.25–1.77), psoriatic arthritis (RR = 1.33, 95% CI: 1.22–1.45), and gout (RR = 1.40, 95% CI: 1.13–1.73) but not osteoarthritis (RR = 1.03, 95% CI: 0.91–1.16). Age and sex subgroup analyses indicated that stroke risk was similar by sex (women: RR = 1.47, 95% CI: 1.31–1.66; men: RR = 1.44, 95% CI: 1.28–1.61); risk was higher with younger age ( Conclusions Stroke risk was increased in multiple arthritis and similar between ischemic and hemorrhagic stroke. Young patients with arthritis had the highest risk.

Water levels are essential components for the observation and management of water resources. However, the existing water level monitoring methods either require manpower, which is inefficient, or are restricted to a certain environment. This paper proposes a novel approach that can automatically monitor, recognize and calculate the water level based on deep learning. First, a series of experiments were performed in a physical pool to obtain images from real scenes. Then, the original Single Shot MultiBox Detector (SSD) preprocessing model was trained and optimized. Subsequently, a trained and verified staff gauge detection model was obtained, which was applied to extract the staff gauge information from images. Finally, a 24-hour time series of water level changes was simulated and analyzed using photographic images principle, and the NSE and R2 were 0.98 and 0.99, respectively. These results indicate that the proposed method is more accurate in practice and can provide a relatively accurate and reliable measurement technique.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics and quantum computing devices. The mechanical exfoliation technique of micro-size TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large area and high quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature above 6 K, 2 times higher than that of mechanical exfoliated NbSe2 flakes. Simultaneously, the transport measurements at high magnetic fields reveal that the parallel characteristic field Bc// is at least 4.5 times higher than the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe2 film shows the signature of quantum Griffiths singularity when approaching the zero-temperature quantum critical point.

BACKGROUND Numerous studies have been performed to investigate the association between the primary AZFc duplication and male infertility risk; however, the sample sizes have been small and the results have been controversial. A meta-analysis was performed to assess these associations. METHODS A systematic search was conducted to identify all relevant studies from the PubMed, Web of Science, Medline, CNKI, and Wanfang databases up to October 22, 2019. The odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of associations. All of the statistical analyses were conducted by using RevMan 5.3. RESULTS Eleven studies were identified that involved 3140 infertile men and 2280 fertile men. Overall, there was a statistically significant association between the primary AZFc duplication and male infertility (OR = 1.66, 95% CI = 1.29-2.14, P

In order to investigate the effects of the terrain slopes and rainfall intensity on the steady infiltration rate of permeable pavement, an experiment with the combinations of three types of permeability, three kinds of rainfall intensity, different cross slope and longitudinal slope are undertaken. Through analyzing the experimental data, it is indicated that: (1) the relation between the steady infiltration rate and the cross and longitudinal slopes can be described by power functions, i.e. as the slopes increase, the steady infiltration rate decreases. The steady infiltration rate can be reduced by 23.3%–72.2% and 12.6%–22.2% for the slopes ranging from 0° to 5° and from 5° to 10°, respectively, illustrating the infiltration is more sensitive to the 0°–5° slope; (2) Under the same conditions, the effect of the cross slope on the steady infiltration rate is about 1.1–1.4 times as high as that of the longitudinal slope, i.e. the cross slope varying could lead to more obvious infiltration change, comparing to the longitudinal slope; (3) The relation between the rainfall intensity and the infiltration rate can be reflected by power function as well. The higher the rainfall intensity, the more the steady infiltration rate increases; (4) The comprehensive effect of the cross slope, longitudinal slope and rainfall intensity on steady infiltration rate can be expressed by quadratic polynomial functions. The main purpose of the manuscript is to determine how the slopes and the rainfall intensities affect the infiltration process and guide the plan and design of the permeable pavement in practical engineering.

Land use has significant impact on the hydrologic and hydraulic processes in a catchment. This work applies a hydrodynamic based numerical model to quantitatively investigate the land use effect on the flood patterns under various rainfall and terrain conditions in an ideal V-shaped catchment and a realistic catchment, indicating the land use could considerably affect the rainfall-flood process and such effect varies with the catchment terrain, land use scenario and the rainfall events. The rainfall-flood process is less sensitive for the side slope than the channel slope. For a channel slope lower than the critical value determined as 0.035-0.040 in this work, the forest located in the middle of the catchment slope could most effectively attenuate the flood peak. When the channel slope is higher than the critical one, forest located in the downstream of the catchment could most significantly mitigate the peak discharge. Moreover, the attenuation effect becomes more obvious as the rainfall becomes heavier. The research can help more reasonably guide the land use plan related to flood risk.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics, and quantum computing devices. The mechanical exfoliation technique of microsize TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large-area and high-quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe

The search for nontrivial superconductivity in novel quantum materials is currently a most attractive topic in condensed matter physics and material science. The experimental studies have progressed quickly over the past couple of years. In this article, we report systematic studies of superconductivity in Au2Pb single crystals. The bulk superconductivity (onset transition temperature, Tconset=1.3 K) of Au2Pb is characterised by both transport and diamagnetic measurements, where the upper critical field Hc2 shows unusual quasi-linear temperature dependence. The superconducting gap is revealed by point-contact measurement with gold tip. However, when using tungsten (W) tip, which is much harder, the superconducting gap probed is largely enhanced as demonstrated by the increases of both Tconset and upper critical field (Hc2). This can be interpreted as a result of increase in density of states under external anisotropic stress imposed by the tip, as revealed by first-principles calculations. Furthermore, novel phase winding of the pseudospin texture along k-space loops around the Fermi energy is uncovered from the calculations, indicating that the observed superconductivity in Au2Pb may have nontrivial topology. Researchers in China have uncovered evidence for a new type of superconductivity in an old alloy. Jian Wang from Peking University and co-workers measured the superconducting properties of gold-lead (Au2Pb) and observed what could be an unusual effect known as topological superconductivity–superconductivity that arises due to a particular electronic structure. The researchers measured the low temperature resistivity of a single crystal of Au2Pb and confirmed that it is a superconductor. Simulations indicated that its superconductivity arises from its electronic structure, which has a nontrivial topological arrangement. Superconducting materials enable ultrasensitive sensors of magnetic fields and powerful magnets, but they usually exhibit their unusual properties only at low temperatures. Materials that exhibit superconductivity in new and unusual ways are of interest because they may open the door for ways to circumvent these limitations.

Porous single-crystalline hematite (α-Fe2O3) nanorod array has been synthesized on large-area Ti foil via a facile hydrothermal method followed by a simple annealing treatment in Ar gas at 450 °C. The nanorods attained from 6 h hydrothermal reaction are average 30 nm in diameter and 450 nm in length. When used directly as additive-free anode for lithium ion batteries (LIBs), the α-Fe2O3 nanorod array demonstrates excellent cycling performance up to 50 times (∼562 mAh g−1 retained at C/5) and good rate capability, in distinct contrast to α-Fe2O3 nanorod powder-based electrode. The improved electrochemical performance could be ascribed to the enhanced electron transport and Li+ diffusion that result from the well-defined array architecture and the porous nature of the single-crystalline nanorods. Fe3O4 and C/α-Fe2O3 nanorod arrays are further prepared to improve the lithium storage property. Our work represents a successful example of fabricating iron oxide 1D nanostructure arrays directly on nonreactive cu...

Increasing nitrogen oxides (NOx) emissions over the fast developing regions have been of great concern due to their critical associations with the aggravated haze and climate change. However, little geographically specific data exists for estimating spatio-temporal trends of NOx emissions. In order to quantify the spatial and temporal variations of NOx emissions, a spatially explicit approach based on the continuous satellite observations of artificial nighttime stable lights (NSLs) from the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) was developed to estimate NOx emissions from the largest emission source of fossil fuel combustion. The NSL based model was established with three types of data including satellite data of nighttime stable lights, geographical data of administrative boundaries, and provincial energy consumptions in China, where a significant growth of NOx emission has experienced during three policy stages corresponding to the 9th-11th)Five-Year Plan (FYP, 1995-2010). The estimated national NOx emissions increased by 8.2% per year during the study period, and the total annual NOx emissions in China estimated by the NSL-based model were approximately 4.1%-13.8% higher than the previous estimates. The spatio-temporal variations of NOx emissions at city scale were then evaluated by the Moran's I indices. The global Moran's I indices for measuring spatial agglomerations of China's NOx emission increased by 50.7% during 1995-2010. Although the inland cities have shown larger contribution to the emission growth than the more developed coastal cities since 2005, the High-High clusters of NOx emission located in Beijing-Tianjin-Hebei regions, the Yangtze River Delta, and the Pearl River Delta should still be the major focus of NOx mitigation. Our results indicate that the readily available DMSP/OLS nighttime stable lights based model could be an easily accessible and effective tool for achieving strategic decision making toward NOx reduction.

The flow and heat transfer in rod bundles are of vital importance in the reactor design. Studies on the turbulent flow in tight lattice have presented the quasi periodic large scale vortex structure is highly accounted for the local flow and heat transfer and turbulent mixing in rod bundles. In this work, the Unsteady Reynolds Averaged Navier–Stokes (URANS) simulation with the Reynolds Stress Model (RSM) is adopted to simulate the flow and vortex structure in rod bundles. The vortex structure in sparse lattice with nonuniform wall roughness is also investigated and compared with that in tight lattice. The results indicate that the quasi periodic large scale vortex structure and flow pulsation are available in both tight lattice and the sparse lattice with non-uniform wall roughness. Due to the existence of the vortex structure, the heat transfer in spare lattice is enhanced.

Quasi periodic large scale vortex structure is an important phenomenon in rod-bundle-like lattice, which also plays an important role in the local flow and heat transfer around bundles. In this work, the heat transfer and vortex structure in sparse lattice with non-uniform wall roughness are investigated with the unsteady Reynolds-Averaged Navier-Stokes (URANS) simulation with a Reynolds Stress Model (RSM) in FLUENT 6.3. The pitch to diameter ratio (P/D) of the sparse lattice is 1.12. It is found that the transverse flow mixing, heat transfer and the vortex structure are enhanced with the wall roughness increasing.

We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.

The discovery of graphene has ignited intensive investigation on two dimensional (2D) materials. Among them, transition metal dichalcogenide (TMDC), a typical representative, attracts much attention due to the excellent performance in field effect transistor (FET) related measurements and applications. Particularly, when TMDC eventually reaches few-layer dimension, a wide range of electronic and optical properties, in striking contrast to bulk samples, are detected. In this Letter, we synthesized single crystalline WS2 nanoflakes by physical vapor deposition (PVD) method and carried out a series of transport measurements of contact resistance and magnetoresistance. Focused ion beam (FIB) technology was applied to deposit Pt electrodes on WS2 flakes. Different from the electron beam lithography (EBL) fabricated electrodes, FIB-deposited leads exhibited ohmic contact, resolving the dilemma of Schottky barrier. Furthermore, a temperature-modulated negative-to-positive transition of magnetoresistance (MR) associated with a crossover of carrier type at similar temperature was demonstrated. Our work offers a pathway to optimize the contact for TMDC and reveals the magnetoresistance characteristics of WS2 flakes, which may stimulate further studies on TMDC and corresponding potential electronic and optoelectronic applications.

Bismuth oxyhalides, such as bismuth oxychlorides (BiOCl), are layered materials with [Bisub2/subOsub2/sub]sup2+/suplayers sandwiched between two sheets of Cl ions. Much work has focused on the potential for bismuth oxyhalides to be a photocatalyst, but their nonlinear optical properties are rarely studied. In this work, the nonlinear refractive index of BiOCl nanosheets has been characterized with Z-scan measurement under 800 nm femtosecond pulsed laser excitation. A shift from saturable absorption to reverse saturable absorption was observed at higher input pump intensities in the experiments. The transition process was analyzed using a phenomenological model based on saturable absorption and two-photon absorption.

Transition metal dichalcogenides (TMDCs), such as tungsten disulfide (WS(2)), are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Recent advances in nanoscale materials characterization and few layer TMDCs' unique optical properties make them a research hot-spot in nonlinear optics. In this work, the nonlinear refractive index of monolayer WS(2) has been characterized with Z-scan measurement under 800nm femtosecond pulsed laser excitation, and a value of n2 ≃ (8.1 ± 0.41) × 10(-13)m(2)/W is obtained. A shift from saturable absorption to reverse saturable absorption was observed at higher input pump intensities in the experiments. The transition process was analyzed using a phenomenological model based on two photon absorption, and the two photon absorption coefficient was estimated about (3.7±0.28)×10(-6)m/W.

Dr. M. Lanza, M. Reguant, G. Zou, P. Lv, Prof. H. Duan State Key Laboratory for Turbulence and Complex System Department of Mechanics and Engineering Science, CAPT College of Engineering, Peking University Beijing 100871 , China E-mail: hlduan@pku.edu.cn H. Li, D. Yu Department of Physics State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 , China R. Chin Stanford Nanocharacterization Laboratory McCullough 225, 476 Lomita Mall Stanford University California 94305-4045 , United States of America H. Liang Department of Modern Mechanics University of Science and Technology of China Hefei , Anhui 230027 , China Y. Zhang, Z. Liu Center for Nanochemistry (CNC) Beijing National Laboratory for Molecular Sciences State Key Laboratory for Structural Chemistry of Unstable and Stable Species College of Chemistry and Molecular Engineering Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 , China