A Study on the Preparation of a Vulcanizing Mixture and Its Application in Natural Rubber Latex.

The traditional preparation process of natural rubber latex requires tedious treatment of a variety of rubber additives. In this paper, a new process of wet mixed grinding was used to prepare a reinforced vulcanization mixture and a rapid vulcanization effect. The effect of different amounts of vulcanization mixtures on the mechanical properties of natural latex film was studied, and the pre-vulcanization process of latex and the vulcanization process of film were optimized. The results showed that with the increase in the amount of vulcanization mixture, the tensile strength increased from 5.96 MPa to 29.28 MPa, and the tear strength increased from 7.59 kN/m to 52.81 kN/m. When the vulcanization temperature of the latex film is heated from 80 °C to 100 °C, the vulcanization time is shortened by 5~6 times. The new vulcanization mixture prepared in this work has the characteristics of simple production and fast vulcanization speed, which provides a new solution for the development of the latex product industry.

A cellulosic multi-bands fluorescence probe for rapid detection of pH and glutathione.

The detection of pH and glutathione (GSH) is positively significant for the cell microenvironment imaging. Here, to assess the pH value and the concentration of GSH efficiently and visually, a cellulose-based multi-bands ratiometric fluorescence probe was designed by assembling MnO2-modified cellulose gold nanoclusters, fluorescein isothiocyanate-grafted cellulose nanocrystals (CNCs) and protoporphyrin IX-modified CNCs. The probe exhibits GSH-responsive, pH-sensitive and GSH/pH-independent fluorescent properties at 440 nm, 520 nm, and 633 nm, respectively. Furthermore, the probe identifies GSH within 4 s by degrading MnO2 into Mn2+ in response to GSH. Ingeniously, the green fluorescence of the probe at 520 nm was decreased with pH, and the red fluorescence at 633 nm remained stable. Therefore, the probe displayed distinguishing fluorescence colors from pink to blue and from green to blue for the synchronous detection of pH and GSH concentration within 4 s. The design strategy provides insights to construct multi-bands fluorescence probes for the rapid detection of multiple target analytes.

La(Ca)CrO3-Filled SiCN Precursor Thin Film Temperature Sensor Capable to Measure up to 1100 °C High Temperature.

Thin-film sensors are regarded as advanced technologies for in situ condition monitoring of components operating in harsh environments, such as aerospace engines. Nevertheless, these sensors encounter challenges due to the high-temperature oxidation of materials and intricate manufacturing processes. This paper presents a simple method to fabricate high temperature-resistant oxidized SiCN precursor and La(Ca)CrO3 composite thin film temperature sensors by screen printing and air annealing. The developed sensor demonstrates a broad temperature response ranging from 200 °C to 1100 °C with negative temperature coefficients (NTC). It exhibits exceptional resistance to high-temperature oxidation and maintains performance stability. Notably, the sensor's resistance changes by 3% after exposure to an 1100 °C air environment for 1 h. This oxidation resistance improvement surpasses the currently reported SiCN precursor thin-film sensors. Additionally, the sensor's temperature coefficient of resistance (TCR) can reach up to -7900 ppm/°C at 200 °C. This strategy is expected to be used for other high-temperature thin-film sensors such as strain gauges, heat flux sensors, and thermocouples. There is great potential for applications in high-temperature field monitoring.

Electrohydrodynamic Printed Ultra-Micro AgNPs Thin Film Temperature Sensors Array for High-Resolution Sensing.

Current methods for thin film sensors preparation include screen printing, inkjet printing, and MEMS (microelectromechanical systems) techniques. However, their limitations in achieving sub-10 µm line widths hinder high-density sensors array fabrication. Electrohydrodynamic (EHD) printing is a promising alternative due to its ability to print multiple materials and multilayer structures with patterned films less than 10 µm width. In this paper, we innovatively proposed a method using only EHD printing to prepare ultra-micro thin film temperature sensors array. The sensitive layer of the four sensors was compactly integrated within an area measuring 450 µm × 450 µm, featuring a line width of less than 10 µm, and a film thickness ranging from 150 nm to 230 nm. The conductive network of silver nanoparticles exhibited a porosity of 0.86%. After a 17 h temperature-resistance test, significant differences in the performance of the four sensors were observed. Sensor 3 showcased relatively superior performance, boasting a fitted linearity of 0.99994 and a TCR of 937.8 ppm/°C within the temperature range of 20 °C to 120 °C. Moreover, after the 17 h test, a resistance change rate of 0.17% was recorded at 20 °C.

Oxidation and Ablation Behavior of Particle-Filled SiCN Precursor Coatings for Thin-Film Sensors.

Polymer-derived ceramic (PDC) thin-film sensors have a very high potential for extreme environments. However, the erosion caused by high-temperature airflow at the hot-end poses a significant challenge to the stability of PDC thin-film sensors. Here, we fabricate a thin-film coating by PDC/TiB2/B composite ceramic material, which can be used to enhance the oxidation resistance and ablation resistance of the sensors. Due to the formation of a dense oxide layer on the surface of the thin-film coating in a high-temperature air environment, it effectively prevents the ingress of oxygen as a pivotal barrier. The coating exhibits an exceptionally thin oxide layer thickness of merely 8 µm, while its oxidation resistance was rigorously assessed under air exposure at 800 °C, proving its enduring protection for a minimum duration of 10 h. Additionally, during ablation testing using a flame gun that can generate temperatures of up to 1000 °C, the linear ablation rate of thin-film coating is merely 1.04 µm/min. Our analysis reveals that the volatilization of B2O3 occurs while new SiO2 is formed on the thin-film coating surface. This phenomenon leads to the absorption of heat, thereby enhancing the ablative resistance performance of the thin-film sensor. The results indicate that the thin-film sensor exhibits exceptional resistance to oxidation and ablation when protected by the coating, which has great potential for aerospace applications.

Abnormal Graphitization Behavior in Near-Surface/Interface Region of Polymer-Derived Ceramics.

The in situ free carbon generated in polymer-derived ceramics (PDCs) plays a crucial role in their unique microstructure and resultant properties. This study advances a new phenomenon of graphitization of PDCs. Specifically, whether in micro-/nanoscale films or millimeter-scale bulks, the surface/interface radically changes the fate of carbon and the evolution of PDC nanodomains, promotes the graphitization of carbon, and evolves a free carbon enriched layer in the near-surface/interface region. Affected by the enrichment behavior of free carbon in the near-surface/interface region, PDCs exhibit highly abnormal properties such as the skin behavior and edge effect of the current. The current intensity in the near-surface/interface region of PDCs is orders of magnitude higher than that in its interior. Ultrahigh conductivity of up to 14.47 S cm-1 is obtained under the action of the interface and surface, which is 5-8 orders of magnitude higher than that of the bulk prepared under the same conditions. Such surface/interface interactions are of interest for the regulation of free carbon and its resultant properties, which are the core of PDC applications. Finally, the first PDC thin-film strain gauge that can survive a butane flame with a high temperature of up to ≈1300 °C is fabricated.

Thin-Film Platinum Resistance Temperature Detector with a SiCN/Yttria-Stabilized Zirconia Protective Layer by Direct Ink Writing for High-Temperature Applications.

In situ temperature monitoring of curved high-temperature components in extreme environments is challenging for a variety of applications in fields such as aero engines and gas turbines. Recently, extrusion-based direct ink writing (DIW) has been utilized to fabricate platinum (Pt) resistance temperature detectors (RTDs). However, the current Pt RTD prepared by DIW technology suffers from a limited temperature range and poor high-temperature stability. Here, DIW technology and yttria-stabilized zirconia (YSZ)-modified precursor ceramic film packaging have been used to build a Pt RTD with high-temperature resistance, small disturbance, and high stability. The results indicate that the protective layer formed by the liquid phase anchors the Pt particles and reduces the agglomeration and volatilization of the Pt sensitive layer at high temperature. Attributed to the SiCN/YSZ protective layer, the temperature resistance curve of the Pt RTD in the range of 50-800 °C has little deviation from the fitting curve, and the fitting correlation coefficient is above 0.9999. Interestingly, the Pt RTD also has high repeatability and stability. The high temperature resistance drift rate is only 0.05%/h after 100 h of long-term testing at 800 °C and can withstand butane flame up to ∼1300 °C without damage. Moreover, the Pt RTD can be conformally deposited on the outer ring of aerospace bearings by DIW technology and then realize on-site, nondestructive, and real-time monitoring of bearing temperature. The fabricated Pt RTD shows great potential for high-temperature applications, and the novel technology proposed provides a feasible pathway for temperature monitoring of aeroengine internal curved hot-end components.

A SiCN Thin Film Thermistor Based on DVB Modified Polymer-Derived Ceramics.

Carbon-rich SiCN ceramics were prepared by divinylbenzene (DVB)-modified polysilazane (PSN2), and a high-conductivity SiCN thin film sensor suitable for medium-low temperature sensing was fabricated. The modified liquid precursors were patterned by direct ink writing to produce SiCN resistive grids with line widths of several hundreds of micrometers and thicknesses of several micrometers. The introduction of DVB not only increases the critical thickness of SiCN ceramics several times, but also significantly improves the conductivity of SiCN, making it meet the conductivity requirements of sensing applications in the mid-low temperature range. The electrical conductivity and microstructure of DVB-modified SiCN ceramics were studied in detail. In the temperature range of 30~400 °C, the temperature resistance performance of DVB modified SiCN resistance grid was measured. The SiCN ceramics with low DVB content not only have excellent electrical conductivity, but also have good oxidation resistance.

Al2O3-Modified Polymer-Derived Ceramic SiCN High-Temperature Anti-Oxidative Composite Coating Fabricated by Direct Writing.

A reliable protective layer is one of the main challenges in preventing oxidation of thin film sensors to achieve accurate, effective, and stable readings at high temperatures. In this work, an Al2O3-modified polymer-derived ceramic SiCN composite coating fabricated by a direct-writing technique is utilized as a protective layer for thin film sensors. The microstructure evolution of the Al2O3/SiCN films is examined herein. The protective layer exhibits excellent oxidation resistance and thermal stability at high temperatures up to 1000 °C, which contributes to improving the stability and lifetime of thin film sensors in extreme environments. The TiB2/SiCN thin film resistive grid with the Al2O3/SiCN composite film as a protective layer is fabricated and tested. The results indicate that the coating can protect the TiB2/SiCN thin film resistive grid at high temperatures up to 1000 °C, which is about 200 °C higher than that of the TiB2/SiCN thin film resistive grid without a protective layer. The resistance change rates of the TiB2/SiCN thin film resistive grid with a protective layer are 0.5%/h at 900 °C and 10.7%/h at 1000 °C.

In Situ Laser Fabrication of Polymer-Derived Ceramic Composite Thin-Film Sensors for Harsh Environments.

Polymer-derived ceramic (PDC) is considered an excellent sensing material for harsh environments such as aero-engines and nuclear reactors. However, there are many inherent limitations not only in pure PDC but also in its common fabrication method by furnace thermolysis. Therefore, this study proposes a novel method of rapid in situ fabrication of PDC composite thin-film sensors by laser pyrolysis. Using this method with different fillers, a sensitive PDC composite film layer with high-quality graphite can be obtained quickly, which is more flexible and efficient compared to the traditional furnace thermolysis. Furthermore, this study analyzes the reaction differences between laser pyrolysis and furnace thermolysis. The laser pyrolysis method principally produces ß-SiC and enhances the graphitization of amorphous carbon, while the degree of graphitization by furnace thermolysis is low. In addition, it is capable of rapidly preparing an insulating PDC composite film, which still has a resistance of 5 MΩ at 600 °C. As a proof of this method, the PDC composite thin-film strain sensors are fabricated in situ on nickel alloys and aluminum oxide substrates, respectively. The sensor fabricated on the nickel alloy with a high gauge factor of over 100 can be used in high-temperature environments below 350 °C without the protection of an oxidation-resistant coating. In this way, the approach pioneers the in situ laser fabrication of functional PDC films for sensors, and it has great potential for the in situ sensing of complex curved surfaces in harsh environments.

Procalcitonin kinetics to guide sequential invasive-noninvasive mechanical ventilation weaning in patients with acute exacerbation of chronic obstructive pulmonary disease and respiratory failure: procalcitonin's adjunct role.

How to identify the optimum switch point of sequential invasive and noninvasive ventilation is the focus of clinical attention on the patients suffering from acute exacerbation of chronic obstructive pulmonary disease (AECOPD) complicated by acute respiratory failure (ARF). This study aims to explore the clinical significance of taking the change rate of procalcitonin (PCT) as identifying the timing of weaning on the mechanical ventilation for the patients of AECOPD followed by ARF as a complication. There were altogether 140 patients of AECOPD complicated with ARF, who were randomly selected and divided into a study group and a control group respectively. A change rate of serum PCT level exceeding 50% was taken as the switch point selection of tracheal intubation removal for the patients of the study group, while the 'pulmonary infection control (PIC) window' was done for those in the control group. With CRP, IL-6, TNF-a, PaCO2, PaO2, and Lac having been detected before and after treatment to them all, clinical indexes were obtained and compared between these two groups. The CRP, TNF-a, and IL-6 levels of the patients in the study group after treatment (p < 0.05) were lower than those in the control group. There was no significant difference in PaCO2, PaO2, and Lac between these two groups before and after treatment (p > 0.05). Even so, some other indexes available for the study group of patients were found to be lower than those for the control group (p < 0.05) in the following aspects: duration of invasive ventilation support, total time of mechanical ventilation support, incidence rate of ventilator-associated pneumonia, 48-hour reintubation rate, incidence rate of upper gastrointestinal bleeding, hospitalization time of critical respiratory illness, total hospitalization time, RICU treatment cost, total treatment cost, and mortality. It is preferable to take the change rate of PCT level exceeding 50% as the switch point of weaning time in sequential mechanical ventilation rather than the PIC window. AbbreviationsAECOPD: acute exacerbation of chronic obstructive pulmonary disease; ARF: acute respiratory failure; PCT: procalcitonin; PaO2: the oxygen partial pressure; PaCO2: the partial pressure of carbon dioxide; TNF-a: serum tumor necrosis factor-a; IL-6: interleukin-6; CRP: serum C-reactive protein; PIC window: pulmonary infection control window; RICU: respiration and intensive care unit.

Spatial Distribution and Environmental Risk of Arsenic and Antimony in Soil Around an Antimony Smelter of Qinglong County.

The purpose of this study was to investigate the distribution of arsenic (As) and antimony (Sb) in soils around an antimony smelter at Qinglong together with the soil pollution levels and potential ecological risk. The results show that (1) total concentrations of As (23 ~ 539 mg/kg) and Sb (19.7 ~ 5681 mg kg-1) were higher than the Guizhou province-level background values (As, 20; Sb, 2.24), especially Sb. Their dominant geochemical speciation was the residual fraction which accounted for > 90% of the total concentrations. (2) The distribution of As and Sb in soils influenced mainly by land-use type, altitude, predominant wind direction, and distance from the pollution source. (3) The geo-accumulation index shows that the soil was highly contaminated with Sb and moderately with As. The potential ecological risk index shows that As posed a moderate risk and Sb a high risk. The general ecological risk was classified as high risk. However, the risk index coding method shows low environmental risk from As and Sb.

Ferromagnetic tip induced unconventional superconductivity in Weyl semimetal.

The metallic tip-induced superconductivity in normal Weyl semimetal offers a promising platform to study topological superconductivity, which is currently a research focus in condensed matter physics. Here we experimentally uncover that unconventional superconductivity can be induced by hard point contact (PC) method of ferromagnetic tips in TaAs single crystals. The magneto-transport measurements of the ferromagnetic tip-induced superconducting (FTISC) states exhibit the quantum oscillations, which reveal that the superconductivity is induced in the topologically nontrivial Fermi surface of the Weyl semimetal, and show compatibility of ferromagnetism and induced superconductivity. We further measure the point contact spectra (PCS) of tunneling transport for FTISC states which are potentially of nontrivial topology. Considering that the magnetic Weyl semimetal with novel superconductivity is hard to realize in experiment, our results show a new route to investigate the unconventional superconductivity by combining the topological semimetal with ferromagnetism through hard PC method.

Generic Theory for Majorana Zero Modes in 2D Superconductors.

It is well known that non-Abelian Majorana zero modes (MZM) are located at vortex cores in a p_{x}+𝒾p_{y} topological superconductor, which can be realized in a 2D spin-orbit coupled system with a single Fermi surface and by proximity coupling to an s-wave superconductor. Here we show that the existence of non-Abelian MZMs is unrelated to the bulk topology of a 2D superconductor, and propose that such exotic modes can result in a much broader range of superconductors, being topological or trivial. For a generic 2D system with multiple Fermi surfaces that is gapped out by superconducting pairings, we show that at least a single MZM survives if there are only an odd number of Fermi surfaces of which the corresponding superconducting orders have vortices; such a MZM is protected by an emergent Chern-Simons invariant, irrespective of the bulk topology of the superconductor. This result enriches new experimental schemes for realizing non-Abelian MZMs. In particular, we propose a minimal scheme to realize the MZMs in a 2D superconducting Dirac semimetal with trivial bulk topology, which can be well achieved based on recent cold-atom experiments.

Autonomous homing control of a powered parafoil with insufficient altitude.

In order to realize safe and accurate homing of a powered parafoil under the condition of insufficient initial altitude, a multiphase homing path is designed according to the flight characteristics of the vehicle. With consideration that the traditional control methods cannot ensure the quality of path following because of the nonlinear, large inertial and longtime delay existed in the system and strong disturbances in a complex environment, a homing controller, composed of the vertical and horizontal trajectory tracking controllers, is designed based on active disturbance rejection control (ADRC). Then autonomous homing simulation experiment of the powered parafoil with insufficient altitude is carried on in a windy environment. The simulation results show that the planned multiphase homing trajectory can fulfill the requirements of fixed-point homing and flare landing; the designed homing controller can overcome the influences of uncertain items of the internal and external disturbances, track the desired homing path more rapidly and steadily, and possesses better control performances than traditional PID controllers.

Origin of 3.45 eV Emission Line and Yellow Luminescence Band in GaN Nanowires: Surface Microwire and Defect.

The physical origin of the strong emission line at 3.45 eV and broadening yellow luminescence (YL) band centered at 2.2 eV in GaN nanowire (NW) has been debated for many years. Here, we solve these two notable issues by using state-of-the-art first-principles calculations based on many-body perturbation theory combined with polarization-resolved experiments. We demonstrate that the ubiquitous surface "microwires" with amazing characteristics, i.e., the outgrowth nanocrystal along the NW side wall, are vital and offer a new perspective to provide insight into some puzzles in epitaxy materials. Furthermore, inversion of the top valence bands, in the decreasing order of crystal-field split-off hole (CH) and heavy/light hole, results in the optical transition polarized along the NW axis due to quantum confinement. The optical emission from bound excitons localized around the surface microwire to CH band is responsible for the 3.45 eV line with E∥c polarization. Both gallium vacancy and carbon-related defects tend to assemble at the NW surface layer, determining the broadening YL band.