Periodic Folded Gold Nanostructures with a Sub-10 nm Nanogap for Surface-Enhanced Raman Spectroscopy.

Surface-enhanced Raman spectroscopy has emerged as a powerful spectroscopy technique for detection with its capacity for label-free, nondestructive analysis, and ultrasensitive characterization. High-performance surface-enhanced Raman scattering (SERS) substrates with homogeneity and low cost are the key factors in chemical and biomedical analysis. In this study, we propose the technique of atomic force microscopy (AFM) scratching and nanoskiving to prepare periodic folded gold (Au) nanostructures as SERS substrates. Initially, folded Au nanostructures with tunable nanogaps and periodic structures are created through the scratching of Au films by AFM, the deposition of Ag/Au films, and the cutting of epoxy resin, reducing fabrication cost and operational complexity. Periodic folded Au nanostructures show the three-dimensional nanofocusing effect, hotspot effect, and standing wave effect to generate an extremely high electromagnetic field. As a typical molecule to be tested, p-aminothiophenol has the lowest detection limit of up to 10-9 M, owing to the balance between the electromagnetic field energy concentration and the transmission loss in periodic folded Au nanostructures. Finally, by precisely controlling the periods and nanogap widths of the folded Au nanostructures, the synergistic effect of surface plasmon resonance is optimized and shows good SERS properties, providing a new strategy for the preparation of plasmonic nanostructures.

Exploring the structural color of micro-nano composite gratings with FDTD simulation and experimental validation.

The significance of micro-nano composite gratings (MNCGs) resides in their applications, including optical devices, sensors, and diffractive elements, which drive research interest in their diffraction characteristics. This study investigates both the diffraction characteristics of MNCGs and the factors that influence them by employing both Finite-Difference Time-Domain (FDTD) methods and experimental validation. The initial focus lies in deciphering the differences in diffraction characteristics between micro-gratings (MGs) and MNCGs by analyzing the coupling effects, diffraction order, color distribution, and intensity variation. Additionally, this research emphatically investigates five aspects to discover the influencing factors of MNCG's diffraction characteristics, such as the height, groove angle of MGs and the period, blaze angle, and height of nano-gratings (NGs). Results show that the structural coloration and saturation of MNCG surpass that of MG. NG plays the actual spectral role, and a reduction in the period of NG leads to enhanced splitting light capability of the white light. The optical detection tests validated the simulation results. The present study reveals the diffractive properties of MNCGs, providing technical insights for the design and processing of optically variable devices.

Examining the linkage between economic policy uncertainty, coal price, and carbon pricing in China: Evidence from pilot carbon markets.

Economic policies affect companies' production decisions. And the energy consumption volume is an intuitive reflection of the enterprise's production decisions. In China, coal is the main source of carbon emissions and the most important energy source. Therefore, the coal market and the uncertainty of economic policies are both directly tied to the carbon market. This study explores both the direct impact of economic policy uncertainty and coal price on carbon prices as well as the indirect impact of economic policy uncertainty on carbon prices through coal prices by utilizing the DCC-GARCH model and the NARDL model. The findings indicate that the dynamic correlations between coal prices and the CEPU are always negative and that those between the price of carbon and the CEPU vary by area. Meanwhile, the dynamic correlations between coal and carbon prices are only positive in Shenzhen and Beijing. Both coal prices and economic policy uncertainty produce asymmetrical impacts on carbon prices. Some policy implications are provided for developing the carbon markets in light of the results drawn from the study.

Fabrication and testing of a multifunctional SiO2@ZnO core-shell nanospheres incorporated polymer coating for sustainable marine transport.

We report the development of a coating system relying on the incorporation of SiO2@ZnO core-shell nanospheres in polyurethane media as a novel approach to achieve longevity and sustainability in marine transport. This polymeric coating showed significant improvement in surface abrasion resistance, the transition from a hydrophilic state to a hydrophobic state (~ 125.2° ± 2°), improved antifungal, antibacterial and antialgae effects which make the proposed coating ideal to protect steel surfaces against biofouling. To substantiate our claims, we performed X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, scanning acoustic microscopy, Thermogravimetric analysis (TGA), contact angle measurements, antimicrobial (antialgal, antibacterial, antifungal) tests and Taber abrasion tests (ASTM D1044 and D4060) to highlight the mechanical and biological functionality as well as the bonding configuration of this coating. The wear analysis of the Taber abraded coating using SEM and optical microscopy showed significant improvement in the adhesion and shear resistance achieved by the SiO2@ZnO core-shell nanospheres incorporated PU coating which was a contrasting feature compared to using PU alone. The overall investigations we performed led us to find out that the addition of 4% (wt.) SiO2@ZnO core-shell nanoparticles to the PU media deposited on the low carbon steel surface demonstrated remarkable antimicrobial performance with almost no bacterial growth, significant reductions in growth for algae to about 90% and fungus to about 95%.

A probe-based nanometric morphology measurement system using intermittent-contact mode.

In the present study, a homemade probe-based nanometric morphology measurement system is proposed, which can be easily integrated with other probes, such as a diamond probe and an electrochemical electrode. In this system, an intermittent-contact mode is adopted, which is based on a set of micro-force servo modules. The micro-force serve module is mainly composed of a piezoelectric ceramic transducer, a capacitive displacement sensor, an excitation piezoelectric ceramic ring, and a four-beam spring. The four-beam spring integrated with a diamond probe is driven by the excitation piezoelectric ceramic ring. The mechanical structure and the control system of the measurement system are also designed. The vibration amplitude and the resolution of a normal load are calibrated during the engagement process under open-loop control. Moreover, the optimal values for parameters P, I, and D are obtained for the closed-loop measurement. The performance of the developed system is verified by measuring a standard sample. The measured depths agree well with the results obtained by commercial atomic force microscopy. The developed system can be used to measure nanostructures with high precision.

Fatigue-free artificial ionic skin toughened by self-healable elastic nanomesh.

Robust ionic sensing materials that are both fatigue-resistant and self-healable like human skin are essential for soft electronics and robotics with extended service life. However, most existing self-healable artificial ionic skins produced on the basis of network reconfiguration suffer from a low fatigue threshold due to the easy fracture of low-energy amorphous polymer chains with susceptible crack propagation. Here we engineer a fatigue-free yet fully healable hybrid ionic skin toughened by a high-energy, self-healable elastic nanomesh, resembling the repairable nanofibrous interwoven structure of human skin. Such a design affords a superhigh fatigue threshold of 2950 J m-2 while maintaining skin-like compliance, stretchability, and strain-adaptive stiffening response. Moreover, nanofiber tension-induced moisture breathing of ionic matrix leads to a record-high strain-sensing gauge factor of 66.8, far exceeding previous intrinsically stretchable ionic conductors. This concept creates opportunities for designing durable ion-conducting materials that replicate the unparalleled combinatory properties of natural skins more precisely.

Comparison of the Indentation Processes Using the Single Indenter and Indenter Array: A Molecular Dynamics Study.

Fabrication of periodic nanostructures has drawn increasing interest owing to their applications of such functional structures in optics, biomedical and power generation devices. Nano-indentation technique has been proven as a method to fabricate periodic nanostructures. In this study, the molecular dynamic simulation approach is employed to investigate the nano-indentation process for fabricating periodic nano-pit arrays using a single indenter and an indenter array. The morphologies of indentations that machined using these two kinds of indenters are compared. The indentation force and the defect evolution during the nano-indentation process are further studied. Results show that indentation morphologies obtained by single indenter are mainly depended on the spacing of indenters, and a nano-pit array with a better shape and consistency can be obtained easier using the indenter array compared with using a single indenter. The stacking faults and dislocations induced by indentation are depended on the spacing of the indenters. Our findings are significant for understanding the differences of indentation processes using a single indenter and an indenter array and machining a high-quality periodic nano-pit array with high machining efficiency.

Enhanced spreading, migration and osteodifferentiation of HBMSCs on macroporous CS-Ta - A biocompatible macroporous coating for hard tissue repair.

Macroporous tantalum (Ta) coating was produced on titanium alloy implant for bone repair by cold spray (CS) technology, which is a promising technology for oxygen sensitive materials. The surface characteristics as well as in vitro cytocompatibility were systematically evaluated. The results showed that a rough and macroporous CS-Ta coating was formed on the Ti6Al4V (TC4) alloy surfaces. The surface roughness showed a significant enhancement from 17.06 µm (CS-Ta-S), 27.48 µm (CS-Ta-M) to 39.21 µm (CS-Ta-L) with the increase of the average pore diameter of CS-Ta coatings from 138.25 µm, 198.25 µm to 355.56 µm. In vitro results showed that macroporous CS-Ta structure with tantalum pentoxide (Ta2O5) was more favorable to induce human bone marrow derived mesenchymal stem cells (HBMSCs) spreading, migration and osteodifferentiation than TC4. Compared with the micro-scaled structure outside the macropores, the surface micro-nano structure inside the macropores was more favorable to promote osteodifferentiation with enhanced alkaline phosphatase (ALP) activity and extracellular matrix (ECM) mineralization. In particular, CS-Ta-L with the largest pore size showed significantly enhanced integrin-α5 expression, cell migration, ALP activity, ECM mineralization as well as osteogenic-related genes including ALP, osteopontin (OPN) and osteocalcin (OCN) expression. Our results indicated that macroporous Ta coatings by CS, especially CS-Ta-L, may be promising for hard tissue repairs.

[Market survey of Caryophylli Flos specifications].

The present study aimed to regulate the market circulation of Caryophylli Flos and formulate standards for commodity specifications and grades of Caryophylli Flos. Market survey was carried out in four major medicinal material markets with 48 samples of Caryophylli Flos collected. The property, 100-seed weight, impurity percentage, moisture, and eugenol content in Caryophylli Flos of different specifications from different producing areas were determined and analyzed. The results showed that 27.1% of the samples surveyed on the markets did not meet the requirements of Chinese Pharmacopoeia(2020 edition). The 100-seed weight and the property are important factors for the classification of Caryophylli Flos specifications. There were significant differences in the property, 100-seed weight, impurity percentage, and eugenol content in Caryophylli Flos samples of different specifications from different producing areas, and also differences in the proportions of different specifications in Caryophylli Flos samples from different producing areas. The African-originated Xiaohong(medium grade) and Guangxi-originated Xiaohong(medium grade) accounted for 70% and 66.7% respectively, the Indonesian-originated Dahong(top grade) for 56.2%. In conclusion, there are many problems in the circulation of Caryophylli Flos at present, mainly including the loss of origin information, no standards for specifications, non-implementation of grade standards, excessive impurities, and no evidence for authenticity identification. According to the classification of Caryophylli Flos specifications in this study, the average eugenol content of Xiaohong is significantly higher than the Dahong by 4.74%.

Molecular Dynamics Study on Tip-Based Nanomachining: A Review.

Tip-based nanomachining (TBN) approaches has proven to be a powerful and feasible technique for fabrication of microstructures. The molecular dynamics (MD) simulation has been widely applied in TBN approach to explore the mechanism which could not be fully revealed by experiments. This paper reviews the recent scientific progress in MD simulation of TBN approach. The establishing methods of the simulation model for various materials are first presented. Then, the analysis of the machining mechanism for TBN approach is discussed, including cutting force analysis, the analysis of material removal, and the defects analysis in subsurface. Finally, current shortcomings and future prospects of the TBN method in MD simulations are given. It is hopeful that this review can provide certain reference for the follow-up research.

An Endowment Effect Study in the European Union Emission Trading Market based on Trading Price and Price Fluctuation.

This paper pioneers to investigate the endowment effect in the European Union mission Trading Scheme (EU ETS) as well as the impacts of trading experience and compliance pressure on the endowment effect. This study is based on the complete transaction records of the market. In the data set, the records of two consecutive reverse transactions from a same emitting company are selected. The lowest price that the buyer is willing to pay (WTP) and the maximum price the seller is willing to accept (WTA) are evaluated by excluding their risk cost that is used to avoid short-term fluctuations in the price. By distinguishing the difference between WTA and WTP, and long-term fluctuations in the prices during the two transactions, the trader's endowment effect can be quantitively assessed. The results show that the degree of endowment effect of traders follows the trading experience. In addition, since the EU ETS is a cap-and-trade market, the traders face different levels of compliance pressure; when the pressure of the emission companies increases, the degree of endowment effect will also decrease.

Mechanical properties of gold nanowires prepared by nanoskiving approach.

The nanoskiving method based on nanocutting process is a new, low cost and easy way to machine nanowires. In this study, this technique is used to machine Au nanowires with different cutting directions and depths. Young's modulus and the yield strength of nanowires are then measured by an atomic force microscope-based three-point bending test. Results show that the Young's modulus of nanowires is independent of size and is not affected by cutting directions. However, the yield strength of nanowires machined by parallel cutting (NWs-b) is 42-64% higher than that machined by perpendicular cutting (NWs-a).

Restricted control of complex systems with prevention of instability propagation.

One of the challenges for complex systems is the issue of limited number of sensors and actuators for controlling relatively abundant number of agents. The infeasibility of large distribution of sensors and actuators prevents many advanced algorithms from exercising their power. Pinning control provides a remarkable resolution to this difficult problem albeit suboptimal solutions are often sought. In this paper, however, a restricted control approach is proposed particularly targeting the problem of controlling complex networks using only one sensor and one actuator at only one node. Performance achievability for both discrete frequencies and over frequency bands are investigated; the important problem of broad band stability is analyzed, and important results are obtained with easy-to-verified conditions; prevention of instability propagation is also delineated using the concept of bounding the controlled agent's norm. Numerical examples are provided for verification of the theoretical results.

Fabrication of polydimethylsiloxane nanofluidic chips under AFM tip-based nanomilling process.

In current research realm, polydimethylsiloxane (PDMS)-based nanofluidic devices are widely used in medical, chemical, and biological applications. In the present paper, a novel nanomilling technique (consisting of an AFM system and a piezoelectric actuator) was proposed to fabricate nanochannels (with controllable sizes) on PDMS chips, and nanochannel size was controlled by the driving voltage and frequency inputted to the piezoelectric actuator. Moreover, microchannel and nanochannel molds were respectively fabricated by UV lithography and AFM tip-based nanomilling, and finally, PDMS slabs with micro/nanochannels were obtained by transfer process. The influences of PDMS weight ratio on nanochannel size were also investigated. The bonding process of microchannel and nanochannel slabs was conducted on a homemade alignment system consisted of an optical monocular microscope and precision stages. Furthermore, the effects of nanochannel size on electrical characteristics of KCl solution (concentration of 1 mM) were analyzed. Therefore, it can be concluded that PDMS nanofluidic devices with multiple nanochannels of sub-100-nm depth can be efficiently and economically fabricated by the proposed method.

Mechanical characteristics of medical grade UHMWPE under dynamic compression.

The mechanical properties of medical grade ultrahigh molecular weight polyethylene (UHMWPE) are critical for the safety and integrity of UHMWPE implantation. Accordingly, the mechanical features of UHMWPE are tested under repeated stress-controlled and strain-controlled compression at room temperature. Some important effect factors, such as stress rate, mean stress, stress amplitude, strain rate, mean strain, strain range and multiple load steps are further considered in detail. Results indicate that the lower stress rate causes the greater accumulated plastic strain and the accumulated plastic strain rate becomes increasingly lower with increasing number of cycles. The strain range and accumulated plastic strain rate decrease rapidly in the first stage, and then become almost steady during the second stage. Especially, the accumulated plastic strain rate per cycle for each case is less than 0.01 %/cycle after the initial 100 cycles. This means that the plastic strain accumulates very slowly and the shakedown behavior always occurs. Moreover, obvious cyclic softening and stress relaxation behaviors can be observed under cyclic strain-controlled compression during the first 50 cycles. This indicates that the accumulated plastic stain in the initial 100 cycles and the cyclic stress relaxation during the first 50 cycles should be assessed for the functionality of UHMWPE implantation.

Dynamic patterns of H3K4me3, H3K27me3, and Nanog during rabbit embryo development.

Epigenetic modification and expression of key pluripotent factors are critical for development, cell fate determination, and differentiation in early embryos. In this study, we systematically examined the dynamic patterns of histone modifications (H3K4me3 and H3K27me3) and Nanog expression during the development of preimplantation rabbit embryos. Rabbit oocytes, 1-, 2-, 4-, 8-, and 16-cell embryos, morulae, and blastocysts were collected at specific time points following superovulation and assessed for nuclear H3K4me3, H3K27me3, and Nanog expression by immunofluorescence microscopy. The frequency of H3K4me3-positive nuclear staining was highest in oocytes through 4-cell embryos (100%), decreased in 8-cell (97.2%) and 16-cell (94.4%) embryos (P > 0.05), declined dramatically in morulae (86.7%) (1- through 8-cell embryos vs morulae, P < 0.05), and was the lowest in blastocysts (76.2%) (P < 0.05). Nuclear staining of H3K27me3 was negative in oocytes and embryos through the 16-cell stage but was positive in 25.9% of morulae and 34.2% of blastocyst (P < 0.05). Similarly, rabbit oocytes and embryos through the 16-cell stage did not express Nanog, but Nanog was expressed in 24.9% of morulae and 36.5% of blastocysts (P < 0.05). The observed decrease in H3K4me3 and increase in H3K27me3 as development progressed in preimplantation rabbit embryos, together with late Nanog expression, indicates a correlation of these factors with early embryonic cell fate determination and differentiation. Our study provides a specific and dynamic profile of histone modifications and gene expression that will be important for the derivation of rabbit embryonic stem cells and improving rabbit cloning by somatic cell nuclear transfer.

Nanofluidic devices prepared by an atomic force microscopy-based single-scratch approach.

Nanofluidic chips with different numbers of nanochannels were fabricated based on a commercial AFM system using a single-scratch approach. The electrical characterization and enzymatic reactions at the nanoscale were demonstrated using the obtained chips. The effects of the number of nanochannels and the solution concentration on the measured electric current were investigated. The influence of the hydrodynamic convection generated from the induced inflow at the end of the nanochannel on the ion transport through the nanochannel was also studied. Moreover, the enzymatic reactions for trypsin towards poly-l-lysine (PLL) or thrombin were conducted with a nanofluidic chip to investigate the reaction specificity between trypsin and PLL. Results show that the electric current change during the experimental process could be used as a label-free indicator to detect the enzymatic activity.

Combined treatment with cysteamine and leukemia inhibitory factor promotes guinea pig oocyte meiosis in vitro.

The guinea pig is an excellent but underused animal model due to its reproductive biology, which poses difficulties in inducing superovulation, embryo manipulation in vitro, and embryo transfer. We examined the effects of cysteamine (Cys), leukemia inhibitory factor (LIF), and Y27632 on guinea pig oocyte in vitro maturation (IVM). Cumulus-oocyte complexes were collected from antral follicles and classified into three different types before IVM. Among type I oocytes, maturation rates to metaphase II (MII) were similar in basal maturation medium and medium supplemented with Cys or LIF (39.5-40.9%), but combined Cys and LIF treatment increased the MII rate to 61.8%. Supplementation with Y27632 alone or in combination with Cys and LIF dramatically reduced the MII rate (27.7-29.7%). Similar trends were observed for type II oocytes, although their overall MII rate was lower than that of type I oocytes. The MII rate was higher among oocytes collected from 2-month-old guinea pigs compared with those from 4-month-old guinea pigs (56.5 vs. 44.8%). The optimal IVM duration was 24 h (52.5%), as 36 or 48 h of IVM reduced the MII rate (32.8-42.5%). Furthermore, Y27632 reduced the presence of microfilaments in oocytes. These findings indicate that combined supplementation of maturation medium with Cys and LIF, but not Y27632, improves the maturation efficiency of guinea pig oocytes. This study provides an important scientific basis for further efforts toward guinea pig in vitro fertilization, cloning, and gene editing by establishing an animal model for human reproduction and related diseases.

Genome-wide association study identifies two risk loci for tuberculosis in Han Chinese.

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb), and remains a leading public health problem. Previous studies have identified host genetic factors that contribute to Mtb infection outcomes. However, much of the heritability in TB remains unaccounted for and additional susceptibility loci most likely exist. We perform a multistage genome-wide association study on 2949 pulmonary TB patients and 5090 healthy controls (833 cases and 1220 controls were genome-wide genotyped) from Han Chinese population. We discover two risk loci: 14q24.3 (rs12437118, Pcombined = 1.72 × 10-11, OR = 1.277, ESRRB) and 20p13 (rs6114027, Pcombined = 2.37 × 10-11, OR = 1.339, TGM6). Moreover, we determine that the rs6114027 risk allele is related to decreased TGM6 transcripts in PBMCs from pulmonary TB patients and severer pulmonary TB disease. Furthermore, we find that tgm6-deficient mice are more susceptible to Mtb infection. Our results provide new insights into the genetic etiology of TB.

ROCK inhibitor Y-27632 maintains the propagation and characteristics of hair follicle stem cells.

Hair follicle stem cells (HFSCs) are an important source for skin tissue engineering studies and clinical applications. Here, we describe a differential enrichment approach to derive HFSCs from hair follicles of vibrissae and ear skin using the Rho-associated protein kinase (ROCK) inhibitor Y-27632. In the presence of Y-27632, primary cultured hair follicle cells grew in clustered colonies surrounded by keratinocyte-like cells and simultaneously expressed three HFSC markers: CD34, K15, and ITGB1. HFSCs cultured in medium containing Y-27632 were presented at a stable ratio of 30.7%, 34.1%, and 32.9% after passages 5, 10, and 15, respectively. By contrast, in medium containing epidermal growth factor, clustered HFSC colonies disappeared after 6 passages and lacked HFSC marker expression. After withdrawal of Y-27632 from the medium, HFSCs rapidly differentiated into keratinocyte-like cells. Furthermore, HFSCs derived with Y-27632 formed spherical clusters in collagen matrix in vitro, differentiated into keratinocytes and adipose cells under in vitro induction conditions, and cooperated with fetal dermal cells to regenerate hair follicles in vivo 6 weeks after their intracutaneous injection into immune-deficient mice. These findings suggest that Y-27632 maintains the self-renewal and stemness characteristics of HFSCs during primary skin tissue culture followed by enrichment passaging and that HFSCs derived with Y-27632 possess the differentiation potentials important for tissue engineering and other clinical applications.