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Ning Wang,1,2 Zhenjiang Guo,3 Xiaowei Gong,1 Shiwei Kang,1 Zhaobo Cui,2 Yadong Yuan1 1Department of Respiratory and Critical Care Medicine, The Second Hospital of Hebei Medical University, Shijiazhuang, People’s Republic of China; 2Department of Respiratory and Critical Care Medicine, Hengshui People’s Hospital, Hengshui, People’s Republic of China; 3Department of Gastrointestinal Surgery, Hengshui People’s Hospital, Hengshui, People’s Republic of ChinaCorrespondence: Yadong Yuan, Department of Respiratory and Critical Care Medicine, The Second Hospital of Hebei Medical University, No. 215 Heping West Road, Shijiazhuang, Hebei, 050000, People’s Republic of China, Tel/Fax +86-311-66003989, Email yuanyd1108@163.comBackground: Pulmonary hypertension (PH) is a life-threatening complication of chronic obstructive pulmonary disease (COPD). Timely diagnosis of PH in COPD patients is vital to achieve proper treatment; however, there is no algorithm to identify those at high risk. We aimed to develop a predictive model for PH in patients with COPD that provides individualized risk estimates.Methods: A total of 527 patients with COPD who were admitted to our hospital between May 2019 and December 2020 were retrospectively enrolled in this study. Using echocardiographic results as a standard, patients were stratified into a moderate- or high-PH probability group and a low-PH probability group. They were randomly grouped into either the training set (n = 368 patients) or validation set (n = 159 patients) in a ratio of 7:3. We utilized the least absolute shrinkage and selection operator (LASSO) regression model to select the feature variables. The characteristic variables selected in the LASSO regression were analyzed using multivariable logistic regression to construct the predictive model. The predictive model was displayed using a nomogram. We used the receiver operating characteristic curve, calibration curve, and clinical decision curve analysis (DCA) to evaluate model performance, and internal validation was assessed.Results: The predictive factors included in the prediction model were Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage, emphysema, PaCO2, NT-pro-BNP, red blood cell (RBC) distribution width-standard deviation (RDW-SD), and neutrophil/lymphocyte ratio (NLR). The predictive model yielded an area under the curve (AUC) of 0.770 (95% confidence interval [CI], 0.719– 0.820); in the internal validation, the AUC was 0.741 (95% CI, 0.659– 0.823). The predictive model was well calibrated, and the DCA showed that the proposed nomogram had strong clinical applicability.Conclusion: This study showed that a simple nomogram could be used to calculate the risk of PH in patients with COPD which can be useful for the individualized clinical management of COPD patients who may be occur with PH. Further studies need to be confirmed by larger sample sizes and validated in the stable COPD population.Keywords: chronic obstructive pulmonary disease, pulmonary hypertension, nomogram, LASSO regression

The gas-containing nanobubbles have attracted extensive attention due to their remarkable properties and extensive application potential. However, a number of fundamental aspects of nanobubbles, including thermodynamic states for the confined gas, remain still unclear. Here we theoretically demonstrate that the van der Waals (vdW) gases confined in nanobubbles exhibit a unique thermodynamic state of remarkably deviating from the bulk gas phase, and the state transition behavior due to the size-dependent Laplace pressure. In general, the vdW gas inside nanobubbles present multiple stable or transient states, where 0–2 states are for supercritical gas and 0–4 for subcritical gas. Our further analysis based on Rayleigh–Plesset equation and free energy determination indicates that the gas states in nanobubbles exhibits different levels of stability, from which the coexistence of multiple bubble states and microphase equilibrium between droplets and bubbles are predicted. This work provides insight to understand the thermodynamic states appeared for gas in nanobubbles.

Artificially added or undesired organic and inorganic contaminants in solution that are interfacially active always tend to be adsorbed at the gas-liquid interface of micro- and nano-bubbles, affecting the stability of the tiny bubbles. In this work, by using molecular dynamics simulations we study how the adsorbed surfactant-like molecules, with their amphiphilic character, affect the dissolution of the existing bulk nanobubbles under low gas supersaturation environments. We find that, depending on the concentration of the dissolved gas and the molecular structure of surfactants, two fates of bulk nanobubbles whose interfaces are saturated by surfactants are found: either remaining stable or being completely dissolved. With gas dissolution, the bubble shrinks and the insoluble surfactants form a monolayer with an increasing areal density until an extremely low (close to 0) surface tension is reached. In the limit of vanishing surface tension, the chemical structure of surfactants crucially affects the bubble stability by changing the monolayer elastic energy. Two basic conditions for stable nanobubbles at low gas saturation are identified: vanishing surface tension due to bubble dissolution and positive spontaneous curvature of the surfactant monolayer. Based on this observation, we discuss the similarity in the stability mechanism of bulk nanobubbles and that of microemulsions.

In the nanoscale regime, flow behaviors for liquids show qualitative deviations from bulk expectations. In this work, we reveal by molecular dynamics simulations that plug flow down to nanoscale induces molecular friction that leads to a new flow structure due to the molecular clogging of the encaged liquid. This plug-like nanoscale liquid flow shows several features differ from the macroscopic plug flow and Poiseuille flow: It leads to enhanced liquid/solid friction, producing a friction of several order of magnitude larger than that of Couette flow; the friction enhancement is sensitively dependent of the liquid column length and the wettability of the solid substrates; it leads to the local compaction of liquid molecules that may induce solidification phenomenon for a long liquid column. Graphical abstract

Analogous to other porous solids, pinned nanobubbles serve as a zero-dimensional stable nanoscale chamber with controllable thermodynamic parameters, whereas they can respond to state change of guest molecule. Here we analyzed peculiarities of phase transitions in pinned nanobubbles, which were experimentally proved to be superstable. By combining molecular dynamics simulation and thermodynamic analysis, we reveal that guest molecules encapsulated inside a nanobubble exhibit distinct state behaviors: a state in vapor phase, a reversible two-state oscillation, and a stable nanodroplet@nanobubble state, depending on the number of guest molecules and the external pressure. The free-energy landscape shows how state metastability gradually develops with external stimuli and leads to the specific bistable state of two-state oscillation. The existence of strong coupling between nanobubble breathing and two-state oscillation is identified. Our simulation results demonstrate that the flexibility of pinned nanobubbles plays at least the same important role as space confinement in determining the states of guest molecules. Our findings indicate that pinned nanobubbles, serving as soft porous media that possess high stability and reversible transformability, show a wealth of properties that are not found in bulk solutions and in porous solids.

Numerous experiments have shown that bulk nanobubble suspensions are often characterized by a high magnitude of zeta potential. However, the underlying physical mechanism of how the bulk nanobubbles can stably exist has remained unclear so far. In this paper, based on theoretical analysis, we report a stability mechanism for charged bulk nanobubbles. The strong affinity of negative charges for the nanobubble interface causes charge enrichment, and the resulting electric field energy gives rise to a local minimum for the free energy cost of bubble formation, leading to thermodynamic metastability of the charged nanobubbles. The excess surface charges mechanically generate a size-dependent force, which balances the Laplace pressure and acts as a restoring force when a nanobubble is thermodynamically perturbed away from its equilibrium state. With this negative feedback mechanism, we discuss the nanobubble stability as a function of surface charge and gas supersaturation. We also compare our theoretical prediction with recent experimental observations, and a good agreement is found. This mechanism provides new fundamental insights into the origin of the unexplained stability of bulk nanobubbles.

To analyze the risk factors of central venous catheter-related thrombosis (CRT) in critically ill patients and develop the model of a nomogram.A prospective investigation study was conducted on 385 critically ill patients who received central venous catheters during hospitalization in Hengshui People's Hospital from May 2018 to March 2021. Color Doppler ultrasonography was performed daily after catheterization. Patients were divided into thrombosis group and non-thrombosis group according to whether CRT was formed. The patient's gender, age, body mass index (BMI), acute physiology and chronic health evaluation II (APACHE II) score, complications, existing tumor, D-dimer level on the 3rd day after catheterization, maximum velocity of right internal jugular vein on the 3rd day after catheterization, mechanical ventilation time, and catheter indwelling time were recorded, and the differences of above indexes between the two groups were compared. Multivariate Logistic regression was performed on the influencing factors with statistical differences between the two groups to establish the nomogram prediction. The receiver operator characteristic curve (ROC curve) and calibration curve were used to evaluate the predictive power of the model.The incidence of central venous CRT in critically ill patients was 16.1% (62/385). Compared with non-thrombosis patients, the thrombosis group patients had higher APACHE II score, the proportion of existing tumor, and D-dimer level on the 3rd day after catheterization [APACHE II score: 17 (15, 19) vs. 15 (12, 18), the proportion of existing tumor: 51.6% (32/62) vs. 35.3% (114/323), D-dimer (mg/L): 0.84 (0.64, 0.94) vs. 0.57 (0.44, 0.76), all P0.05], the maximum flow rate of right internal jugular vein was slower on the 3rd day after catheterization [cm/s: 14 (13, 15) vs. 16 (14, 18), P0.05]. Univariate analysis showed that high APACHE II score, critical patients with existing tumor, high D-dimer level on the 3rd day after catheterization, and slow maximum flow rate of right internal jugular vein on the 3rd day after catheterization were more likely to develop central venous CRT. Further multivariate Logistic regression analysis showed that high APACHE II score, existing tumor, high D-dimer level on the 3rd day after catheterization and slow maximum flow rate of right internal jugular vein on the 3rd day after catheterization were independent risk factors for central venous CRT in critical patients [odds ratio (OR) and 95% confidence interval (95%CI) were 0.876 (0.801-0.957), 0.482 (0.259-0.895), 0.039 (0.011-0.139), 1.401 (1.218-1.611), and P values were 0.003, 0.021,0.001,0.001, respectively]. According to the results of multivariate analysis, the prediction model of the nomogram was constructed. The area under ROC curve (AUC) was 0.820, 95%CI was 0.767-0.872, P0.001. The calibration curve showed that the prediction probability of central venous CRT nomogram model in critically ill patients had good consistency with the actual occurrence probability.Existing tumor, high APACHE II score, elevated D-dimer on the 3rd day after catheterization, and decreased maximum velocity of right internal jugular vein on the 3rd day after catheterization are independent risk factors for central venous CRT in critical patients. The prediction model based on the proposed model has good clinical efficacy.

According to surface chemistry and topography of different high-modulus carbon fiber (HMCF), interfacial properties of various HMCF composite were evaluated, and nanoscale wetting analysis of HMCF were studied using experimental methods and molecular dynamics simulation. Hierarchical amount of active functional groups and nanoscale grooves were detected on the surface of pristine HMCF (p-HMCF), anodic oxidized HMCF (a-HMCF) and sized HMCF (s-HMCF). Remarkable enhancements in interfacial properties of a-HMCF and s-HMCF composites were obtained, which was ascribed to free-void interface from improved surface energy and wettability. Poor interfacial bonding of p-HMCF composites was due to generation of many nanobubbles with pinned contact lines during the wetting of the surface microgrooves with high aspect ratio and chemical inertness. Schematic of interfacial compatibility mechanisms was proposed to illustrate the correlation between surface features of carbon surface and interfacial properties of their composites.

Surface nanobubbles have been presumed to lead to the experimental observation that liquid boiling often occurs at a much lower supersaturation than expected, yet no qualitative theory exists to explain how they participate in the process. Here, we report through a simple theoretical analysis on how the metastable nanobubbles nucleate the liquid-to-vapor transition by serving as an intermediate phase. The appearance of metastable nanobubbles inhibits the shrink of the bubble nucleus and changes bubble nucleation into a multistep process. We show three possible mechanisms for heterogeneous nucleation starting from metastable surface nanobubbles: nucleation from pinned nanobubbles, nucleation via nanobubble depinning, and nucleation through nanobubble coalescence, each predicting a significant reduction in a nucleation barrier. The occurrence of a specific nucleation pathway of bubble nucleation depends on the detailed geometry of local substrate roughness. These results give insight into how the appearance of surface nanobubbles changes the nucleation mechanisms of liquid boiling.

Gas bubbles are ubiquitous in electrochemical processes, particularly in water electrolysis. Due to the development of gas-evolving electrocatalysis and energy conversion technology, a deep understanding of gas bubble behaviors at the electrode surface is highly desirable. In this work, by combining theoretical analysis and molecular simulations, we study the behaviors of a single nanobubble electrogenerated at a nanoelectrode. With the dynamic equilibrium model, the stability criteria for stationary surface nanobubbles are established. We show theoretically that a slight change in either the gas solubility or solute concentration results in various nanobubble dynamic states at a nanoelectrode: contact line pinning in aqueous and ethylene glycol solutions, oscillation of pinning states in dimethyl sulfoxide, and mobile nanobubbles in methanol. The above complex nanobubble behavior at the electrode/electrolyte interface is explained by the competition between gas influx into the nanobubble and outflux from the nanobubble.

By employing molecular dynamics simulations we investigate the fluctuation of surface nanobubbles immersed in liquid phase. Our simulation results indicate that in comparison with the surrounding liquid and nanobubble interior, the vapor-liquid or gas-liquid interface of nanobubbles always exhibits the largest compressibility, demonstrating the enhanced fluctuation for nanobubble interfaces. We also find that vapor surface nanobubbles and gas surface nanobubbles exhibit different fluctuation behaviors. For vapor nanobubbles that appear in overheated pure liquid, both density fluctuation and interface fluctuation are independent on the external pressure since the internal pressure remains constant at a given temperature. For gas nanobubbles that appear in gas supersaturated solution, the density fluctuation monotonously decreases with the increase of gas concentration, while the interface fluctuation shows a nonmonotonic variation. Departure from the intermediate gas concentration with the minimal interface fluctuation would enhance the fluctuation, which may finally lead to nanobubble destabilization. Finally, our simulation results indicate that the complicated interface fluctuation of surface nanobubbles comprises two different modes: interface deformation and interface oscillation, both of which display similar trends as that of the combined interface fluctuation.

The pump-assisted separate heat pipe (PASHP) has a broad application prospect in the field of saving energy. Two-phase flow boiling in PASHP is a multifarious physical process and the study of the characteristic of the flow boiling in PASHP is significant. The experimental investigation of two-phase flow boiling of R134a in PASHP was conducted. The results indicate that the flow patterns agree with the Wojtan-Ursenbacher-Thome map. The pressure drop has been compared with Muller-Steinhagen-Heck correlation, and the compared results indicate that the experimental data are inside the 10% confidence interval predictions. The heat transfer coefficients were compared with correlation given by Mohseni. It indicates that all the experimental data are inside the 10% confidence interval predictions at x > 0.1. However, part of error is beyond 30% at x ≤ 0.1. A new heat transfer coefficient correlation was developed, and most of the estimated values are within an error band of ±10% of the experimental data.

The solvent exchange procedure has become the most-used protocol to produce surface nanobubbles, while the molecular mechanisms behind the solvent exchange are far from being fully understood. In this paper, we build a simple model and use molecular dynamics simulations to investigate the dynamic characteristics of solvent exchange for producing nanobubbles. We find that at the first stage of solvent exchange, there exists an interface between interchanging solvents of different gas solubility. This interface moves toward the substrate gradually as the exchange process proceeds. Our simulations reveal directed diffusion of gas molecules against the gas concentration gradient, driven by the solubility gradient of the liquid composition across the moving solvent-solvent interface. It is this directed diffusion that causes gas retention and produces a local gas oversaturation much higher near the substrate than far from it. At the second stage of solvent exchange, the high local gas oversaturation leads to bubble nucleation either on the solid surface or in the bulk solution, which is found to depend on the substrate hydrophobicity and the degree of local gas oversaturation. Our findings suggest that solvent exchange could be developed into a standard procedure to produce oversaturation and used to a variety of nucleation applications other than generating nanobubbles.

Although the stability of most surface nanobubbles observed can be well interpreted by contact line pinning and supersaturation theory, there is increasing evidence that at least for certain situations, contact line pinning is not required for nanobubble stability. This raises a significant question of what is the stability mechanism for those sessile nanobubbles. Through theoretical analysis and molecular dynamics simulations, in this work, we report two mechanisms for stabilizing surface nanobubbles on flat and homogeneous substrates. One is attributed to constant adsorption of trace impurities on the nanobubble gas?liquid interface, through which nanobubble growing or shrinking causes the increase and decrease of interfacial tension, acting as a restoring force to bring the nanobubble to its equilibrium size. The other is attributed to the deformation of a soft substrate induced by the formed nanobubble, which in turn stabilizes the nanobubble via impeding the contact line motion, similar to self-pinning of microdroplets on soft substrates. Both mechanisms can interpret, depending on the specified conditions, how surface nanobubbles can remain stable in the absence of contact line pinning.

The precise determination of the line tension of sessile droplets still represents a major challenge. At present, the estimates of the line tension from contact angle measurements can differ by 4–5 orders of magnitude. Here we show that the pinning effect of the droplet contact line caused by the substrate inhomogeneities influences the apparent contact angle of the droplet, affecting the determination of the line tension via the corrected Young’s equation. We introduce the contribution of pinning effects into the Gibbs free energy differential and derive a modified version of the Young’s equation. Using classical density functional theory, we isolate the line tension and the pinning force contributions for substrates with different heterogeneity. The pinning effect leads to metastability of wetting states and influences the contact angle, hence introducing errors in the estimation of line tensions using the traditional analysis of contact angles, based on the modified Young’s equation.

The gripper of home service robot is required to be lightweight, appropriately-sized and compliant to grasp everyday objects. To meet the demand, an underactuated robot hand with suction cups is proposed which is capable of grasping objects of various shapes, sizes and materials. Using one actuator with tendon-driven mechanism, the inherent compliant hand can realize three grasping modes to adapt to different object shapes. Additionally, soft material applied on fingers makes the hand more flexible and controllable. Kinematic and mechanical analysis offer a theory evidence for design optimization and configuring proper grasping modes. Furthermore, in the experiment, robot hand is validated to have satisfactory grasping effect with three grasping modes.

The process of homogeneous bubble nucleation is almost impossible to probe experimentally, except near the critical point or for liquids under large negative tension. Elsewhere in the phase diagram, the bubble nucleation barrier is so high as to be effectively insurmountable. Consequently, there is a severe lack of experimental studies of homogenous bubble nucleation under conditions of practical importance (e.g., cavitation). Here we use a simple geometric relation to show that we can obtain information about the homogeneous nucleation process from Molecular Dynamics studies of bubble formation in solvophobic nanopores on a solid surface. The free energy of pinned nanobubbles has two extrema as a function of volume: one state corresponds to a free-energy maximum ("the critical nucleus"), the other corresponds to a free-energy minimum (the metastable, pinned nanobubble). Provided that the surface tension does not depend on nanobubble curvature, the radius of the curvature of the metastable surface nanobubble is independent of the radius of the pore and is equal to the radius of the critical nucleus in homogenous bubble nucleation. This observation opens the way to probe the parameters that determine homogeneous bubble nucleation under experimentally accessible conditions, e.g. with AFM studies of metastable nanobubbles. Our theoretical analysis also indicates that a surface with pores of different sizes can be used to determine the curvature corrections to the surface tension. Our conclusions are not limited to bubble nucleation but suggest that a similar approach could be used to probe the structure of critical nuclei in crystal nucleation.

Here, we propose theoretically the existence of a new type of nanobubble in undersaturated liquids. These nanobubbles have a concave vapor–liquid interface featured with a negative curvature rather than a positive curvature for nanobubbles in supersaturated liquids, so that they often hide inside of the substrate textures and it might not be easy to characterize them through atomic force microscopy (AFM) measurements. However, these hidden nanobubbles are still stabilized by the contact line pinning effect and stay at the thermodynamically metastable state. We further demonstrate that similar to the nanobubbles in supersaturated liquids the contact angle of the hidden nanobubbles is more sensitive to the nanobubble size rather than the substrate chemistry, and their curvature radius is dependent on the chemical potential but independent of the base radius. Finally, we show several potential situations for the appearance of the hidden nanobubbles.

The present study aimed to detect the mutation characteristics of mitochondrial DNA (mtDNA) in Eca109 of Ec9706 cells, and to investigate their association with the nuclear genome (nDNA), thus providing a basis for gene targeting therapies for esophageal squamous cell carcinoma (ESCC). In vitro‑cultured Ec9706 and Eca109 cells were analyzed the changes of single‑nucleotide polymorphisms (SNPs), insertions/deletions (INDELs), copy number varia-tion, and structure variation (SV) of their genome by high‑throughput sequencing. The loci with SV on chromosome 1‑12 of the two ESCC cell lines were ≥5% of the mtDNA, but SV on chromosome 13‑22, X and Y was ≤3%; >40% of loci exhibited gain or loss; intergenic loci with INDEL changes and SNP features accounted for the majority of mutations. The affected genes encoded proteins including nDNA‑encoding intra‑mitochondrial‑transporting proteins, ATP energy generation‑associated proteins and mitochondrial electron respiratory chain proteins, and these proteins were all nucleus‑encoded mitochondrial proteins. The transcription, duplication, and translation of the abnormally expressed mtDNA in Ec9706 and Eca109 cells were closely associated with disorders of nuclear DNA products.

Although the morphology of surface nanobubbles has been studied widely with different AFM modes, AFM images may not reflect the real shapes of the nanobubbles due to AFM tip-nanobubble interactions. In addition, the interplay between surface nanobubble deformation and induced capillary force has not been well understood in this context. In our work we used constraint lattice density functional theory to investigate the interaction between AFM tips and pinned surface nanobubbles systematically, especially concentrating on the effects of tip hydrophilicity and shape. For a hydrophilic tip contacting a nanobubble, its hydrophilic nature facilitates its departure from the bubble surface, displaying a weak and intermediate-range attraction. However, when the tip squeezes the nanobubble during the approach process, the nanobubble shows an elastic effect that prevents the tip from penetrating the bubble, leading to a strong nanobubble deformation and repulsive interactions. On the contrary, a hydrophobic tip can easily pierce the vapor-liquid interface of the nanobubble during the approach process, leading to the disappearance of the repulsive force. In the retraction process, however, the adhesion between the tip and the nanobubble leads to a much stronger lengthening effect on nanobubble deformation and a strong long-range attractive force. The trends of force evolution from our simulations agree qualitatively well with recent experimental AFM observations. This favorable agreement demonstrates that our model catches the main intergradient of tip-nanobubble interactions for pinned surface nanobubbles and may therefore provide important insight into how to design minimally invasive AFM experiments.

In contrast to stability theories of nanobubbles, the molecular mechanism of how nanobubbles lose stability is far from being understood. In this work, we try to interpret recent experimental observations that the addition of surfactants destabilizes nanobubbles with an unclear mechanism. Using molecular dynamics simulations, we identify two surfactant-induced molecular mechanisms for nanobubbles losing stability, either through depinning of a contact line or reducing vapor-liquid surface tension. One corresponds to the case with significant adsorption of surfactants on the substrates, which causes depinning of the nanobubble contact line and thus leads to nanobubble instability. The other stresses surfactant adsorption on the vapor-liquid interface of nanobubbles, especially for insoluble surfactants, which reduces the surface tension of the interface and leads to an irreversible liquid-to-vapor phase transition. Our finding can help improve our understanding in nanobubble stability, and the insight pres...

We numerically study different forms of nanoscale gaseous domains on a model for rough surfaces. Our calculations based on the constrained lattice density functional theory show that the inter-connectivity of pores surrounded by neighboring nanoposts, which model the surface roughness, leads to the formation of stable microscopic Cassie states. We investigate the dependence of the stability of the micro-Cassie states on substrate roughness, fluid-solid interaction, and chemical potential and then address the differences between the origin of the micro-Cassie states and that of surface nanobubbles within similar models. Finally, we show that the micro-Cassie states share some features with experimentally observed micropancakes at solid-water interfaces.