Superhydrophobic Array Devices for the Enhanced Formation of 3D Cancer Models.

During the metastatic cascade, cancer cells travel through the bloodstream as circulating tumor cells (CTCs) to a secondary site. Clustered CTCs have greater shear stress and treatment resistance, yet their biology remains poorly understood. We therefore engineered a tunable superhydrophobic array device (SHArD). The SHArD-C was applied to culture a clinically relevant model of CTC clusters. Using our device, we cultured a model of cancer cell aggregates of various sizes with immortalized cancer cell lines. These exhibited higher E-cadherin expression and are significantly more capable of surviving high fluid shear stress-related forces compared to single cells and model clusters grown using the control method, helping to explain why clustering may provide a metastatic advantage. Additionally, the SHArD-S, when compared with the AggreWell 800 method, provides a more consistent spheroid-forming device culturing reproducible sizes of spheroids for multiple cancer cell lines. Overall, we designed, fabricated, and validated an easily tunable engineered device which grows physiologically relevant three-dimensional (3D) cancer models containing tens to thousands of cells.

CDK4/6 Inhibitors Impede Chemoresistance and Inhibit Tumor Growth of Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is characterized by rapid development of chemoresistance and poor outcomes. Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) are widely used in breast cancer and other cancer types. However, the molecular mechanisms of CDK4/6 in SCLC chemoresistance remain poorly understood. Here, Rb1flox/flox, Trp53flox/flox, Ptenflox/flox (RTP) and Rb1flox/flox, Trp53flox/flox, MycLSL/LSL (RPM) spontaneous SCLC mouse models, SCLC cell line-derived xenograft (CDX) models, and SCLC patient-derived xenograft (PDX) models are established to reveal the potential effects of CDK4/6is on SCLC chemoresistance. In this study, it is found that CDK4/6is palbociclib (PD) or ribociclib (LEE) combined with chemotherapeutic drugs significantly inhibit SCLC tumor growth. Mechanistically, CDK4/6is do not function through the classic Retionblastoma1 (RB) dependent axis in SCLC. CDK4/6is induce impair autophagy through the AMBRA1-lysosome signaling pathway. The upregulated AMBRA1 protein expression leads to CDK6 degradation via autophagy,  and the following TFEB and TFE3 nuclear translocation inhibition leading to the lysosome-related genes levels downregulation. Moreover, it is found that the expression of CDK6 is higher in SCLC tumors than in normal tissue and it is associated with the survival and prognosis of SCLC patients. Finally, these findings demonstrate that combining CDK4/6is with chemotherapy treatment may serve as a potential therapeutic option for SCLC patients.

Targeting Hippo/YAP in intrahepatic cholangiocarcinoma: Promising molecules in cancer therapy.

The tumorigenesis of intrahepatic cholangiocarcinoma (ICC) has been identified to be exceptionally involved in dysregulated Hippo/Yes-associated protein (YAP) signaling pathway (Hippo/YAP). Hippo/YAP functions as a master regulator engaged in a plethora of physiological and oncogenic processes as well. Therefore, the aberrant Hippo/YAP could serve as an Achilles' heel regarding the molecular therapeutic avenues for ICC patients. Herein, we comprehensively review the recent studies about the underlying mechanism of disrupted Hippo/YAP in ICC, how diagnostic values could be utilized upon the critical genes in this pathway, and what opportunities could be given upon this target pathway.

Humoral and cellular immune responses following Omicron BA.2.2 breakthrough infection and Omicron BA.5 reinfection.

The emergence of novel Omicron subvariants has raised concerns regarding the efficacy of immunity induced by prior Omicron subvariants breakthrough infection (BTI) or reinfection against current circulating Omicron subvariants. Here, we prospectively investigated the durability of antibody and T cell responses in individuals post Omicron BA.2.2 BTI, with or without subsequent Omicron BA.5 reinfection. Our findings reveal that the emerging Omicron subvariants, including CH.1.1, XBB, and JN.1, exhibit extensive immune evasion induced by previous infections. Notably, the level of IgG and neutralizing antibodies were found to correlate with subsequent Omicron BA.5 reinfection. Fortunately, T cell responses recognizing both Omicron BA.2 and CH.1.1 peptides were observed. Furthermore, Omicron BA.5 reinfection may alleviate immune imprinting induced by WT-vaccination, bolster virus-specific ICS+ T cell responses, and promote the phenotypic differentiation of virus-specific memory CD8+ T cells. Antigen-updated or T cell-conserved vaccines are needed to control the transmission of diverse emerging SARS-CoV-2 variants.

Molecular epidemiology of Acinetobacter baumannii during COVID-19 at a hospital in northern China.

BACKGROUND: The wide spread of carbapenem-resistance clones of Acinetobacter baumannii has made it a global public problem. Some studies have shown that the prevalence of Acinetobacter baumannii clones can change over time. However, few studies with respect to the change of epidemiological clones in Acinetobacter baumannii during Corona Virus Disease 2019 (COVID-19) were reported. This study aims to investigate the molecular epidemiology and resistance mechanisms of Acinetobacter baumannii during COVID-19. RESULTS: A total of 95 non-replicated Acinetobacter baumannii isolates were enrolled in this study, of which 60.0% (n = 57) were identified as carbapenem-resistant Acinetobacter baumannii (CRAB). The positive rate of the blaOXA-23 gene in CRAB isolates was 100%. A total of 28 Oxford sequence types (STs) were identified, of which the most prevalent STs were ST540 (n = 13, 13.7%), ST469 (n = 13, 13.7%), ST373 (n = 8, 8.4%), ST938 (n = 7, 7.4%) and ST208 (n = 6, 6.3%). Differently, the most widespread clone of Acinetobacter baumannii in China during COVID-19 was ST208 (22.1%). Further study of multidrug-resistant ST540 showed that all of them were carrying blaOXA-23, blaOXA-66, blaADC-25 and blaTEM-1D, simultaneously, and first detected Tn2009 in ST540. The blaOXA-23 gene was located on transposons Tn2006 or Tn2009. In addition, the ST540 strain also contains a drug-resistant plasmid with msr(E), armA, sul1 and mph(E) genes. CONCLUSION: The prevalent clones of Acinetobacter baumannii in our organization have changed during COVID-19, which was different from that of China. ST540 strains which carried multiple drug-resistant mobile elements was spreading, indicating that it is essential to strengthen the molecular epidemiology of Acinetobacter baumannii.

New HCC Subtypes Based on CD8 Tex-Related lncRNA Signature Could Predict Prognosis, Immunological and Drug Sensitivity Characteristics of Hepatocellular Carcinoma.

Purpose: Hepatocellular carcinoma has become one of the severe diseases threatening human health. T cell exhaustion is deemed as a reason for immunotherapy resistance. However, little is known about the roles of CD8 Tex-related lncRNAs in HCC. Materials and Methods: We processed single-cell RNA sequencing to identify CD8 Tex-related genes. CD8 Tex-related lncRNAs were identified based on their correlations with mRNAs. Unsupervised clustering approach was used to identify molecular clusters of CD8 Tex-related lncRNAs. Differences in prognosis and immune infiltration between the clusters were explored. Machine learning algorithms were used to construct a prognostic signature. Samples were classified as low- and high-risk groups based on their risk scores. We identified prognosis-related lncRNAs and constructed a ceRNA network. In vitro experiments were conducted to investigate the impacts of CD8 Tex-related lncRNAs on proliferation and apoptosis of HCC cells. Results: We clarified cell types within two HCC single-cell datasets. We identified specific markers of CD8 Tex cells and analyzed their potential functions. Twenty-eight lncRNAs were identified as CD8 Tex-related. Based on CD8 Tex-related lncRNAs, samples were categorized into two distinct clusters, which exhibited significant differences in survival rates and immune infiltration. Ninety-six algorithm combinations were employed to establish a prognostic signature. RSF emerged as the one with the highest C-index. Patients in high- and low-risk groups exhibited marked differences in prognosis, enriched pathways, mutations and drug sensitivities. MCM3AP-AS1, MAPKAPK5-AS1 and PART1 were regarded as prognosis-related lncRNAs. A ceRNA network was constructed based on CD8 Tex-related lncRNAs and mRNAs. Experiments on cell lines and organoids indicated that downregulation of MCM3AP-AS1, MAPKAPK5-AS1 and PART1 suppressed cell proliferation and induced apoptosis. Conclusion: CD8 Tex-related lncRNAs played crucial roles in HCC progression. Our findings provided new insights into the regulatory mechanisms of CD8 Tex-related lncRNAs in HCC.

A novel basement membrane-related gene signature predicts prognosis and immunotherapy response in hepatocellular carcinoma.

Background: Basement membranes (BMs) have recently emerged as significant players in cancer progression and metastasis, rendering them promising targets for potential anti-cancer therapies. Here, we aimed to develop a novel signature of basement membrane-related genes (BMRGs) for the prediction of clinical prognosis and tumor microenvironment in hepatocellular carcinoma (HCC). Methods: The differentially expressed BMRGs were subjected to univariate Cox regression analysis to identify BMRGs with prognostic significance. A six-BMRGs risk score model was constructed using Least Absolute Shrinkage Selection Operator (LASSO) Cox regression. Furthermore, a nomogram incorporating the BMRGs score and other clinicopathological features was developed for accurate prediction of survival rate in patients with HCC. Results: A total of 121 differentially expressed BMRGs were screened from the TCGA HCC cohort. The functions of these BMRGs were significantly enriched in the extracellular matrix structure and signal transduction. The six-BMRGs risk score, comprising CD151, CTSA, MMP1, ROBO3, ADAMTS5 and MEP1A, was established for the prediction of clinical prognosis, tumor microenvironment characteristics, and immunotherapy response in HCC. Kaplan-Meier analysis revealed that the BMRGs score-high group showed a significantly shorter overall survival than BMRGs score-low group. A nomogram showed that the BMRGs score could be used as a new effective clinical predictor and can be combined with other clinical variables to improve the prognosis of patients with HCC. Furthermore, the high BMRGs score subgroup exhibited an immunosuppressive state characterized by infiltration of macrophages and T-regulatory cells, elevated tumor immune dysfunction and exclusion (TIDE) score, as well as enhanced expression of immune checkpoints including PD-1, PD-L1, CTLA4, PD-L2, HAVCR2, and TIGIT. Finally, a multi-step analysis was conducted to identify two pivotal hub genes, PKM and ITGA3, in the high-scoring group of BMRGs, which exhibited significant associations with an unfavorable prognosis in HCC. Conclusion: Our study suggests that the BMRGs score can serve as a robust biomarker for predicting clinical outcomes and evaluating the tumor microenvironment in patients with HCC, thereby facilitating more effective clinical implementation of immunotherapy.

Experimental verification about treatment of Bu-Shen-Yi-Jing-Fang in Alzheimer's disease by the analysis of the feasible signaling pathway of network pharmacology.

CONTEXT: Bu-shen-yi-jing-fang (BSYJF) has been reported to reduce amyloid-ß (Aß)1-42 deposition in the brain of APP/PS1 mice and ameliorate cognitive function. However, its neuroprotective mechanism remains unclear. OBJECTIVE: This study aims to investigate whether BSYJF exerts a protective effect on Aß1-42-induced oxidative stress injury and explore its possible mechanism. MATERIALS AND METHODS: The platform databases TCMSP, Swiss, TTD, DrugBank, and GeneCards were used to mine the targets of Alzheimer's disease (AD) and BSYJF. The platform databases STRING and Metascape were used to build the interaction network of the target protein, and Cytoscape software was used to analyze this network and screen out the key pathways. Aß1-42-treated SKNMC cells were established to verify the mechanism of BSYJF and the key proteins. The downstream proteins and antioxidants as well as apoptosis and ferroptosis of the PI3K/AKT/Nrf2 signaling pathway were validated using an in vitro SKNMC cell model experiment. The expression levels of related proteins were detected using Western blotting. Flow cytometry and immunofluorescence staining were used to analyze apoptosis and ferroptosis. RESULTS: Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis considered the key signal pathways, mainly involving the PI3K/AKT signaling pathway. Experimental validation demonstrated that BSYJF treatment markedly increased the activity of the PI3K/AKT pathway, which could exert anti-AD effects. CONCLUSIONS: Our data provided compelling evidence that the protective effects of BSYJF might be associated with their regulation of the PI3K/AKT/Nrf2 signaling pathway. These studies offered a potential therapy for natural herbal medicine treatment of AD.

Modification of the electrokinetic motion of microalgae through light illumination for viability assessment.

The viability detection of microalgae with the electrokinetic (EK) technique shows vast applications in the biology and maritime industry. However, due to the slight variations in the EK properties between alive and dead microalgae cells, the accuracy and practicability of this technique is limited. In this paper, the light illumination pretreatment was conducted to modify the EK velocity of microalgae for enhancing the EK difference. The effects of the illumination time and light color on the EK velocities of Chlorella vulgaris and Isochrysis galbana were systematically measured, and the EK differences between alive and dead cells were calculated and compared. The results indicate that under light illumination, the photosynthesis of the alive cells leads to the amplification of the zeta potential, leading toward increase in the EK difference along with the illumination time. By using light with different color spectra to treat the microalgae, it was found that the EK difference changes with the light color according to the following order: white light > red light > blue light > green light. The difference in EK potential with exposure to white light treatment surpasses over 10-fold in comparison to those without such treatment. The light pretreatment technique, as illustrated in this study, offers an advantageous strategy to enhance the EK difference between living and dead cells, proving beneficial in the field of microalgae biotechnology.

Suppressed thermal transport in silicon nanoribbons by inhomogeneous strain.

Nanoscale structures can produce extreme strain that enables unprecedented material properties, such as tailored electronic bandgap1-5, elevated superconducting temperature6,7 and enhanced electrocatalytic activity8,9. While uniform strains are known to elicit limited effects on heat flow10-15, the impact of inhomogeneous strains has remained elusive owing to the coexistence of interfaces16-20 and defects21-23. Here we address this gap by introducing inhomogeneous strain through bending individual silicon nanoribbons on a custom-fabricated microdevice and measuring its effect on thermal transport while characterizing the strain-dependent vibrational spectra with sub-nanometre resolution. Our results show that a strain gradient of 0.112% per nanometre could lead to a drastic thermal conductivity reduction of 34 ± 5%, in clear contrast to the nearly constant values measured under uniform strains10,12,14,15. We further map the local lattice vibrational spectra using electron energy-loss spectroscopy, which reveals phonon peak shifts of several millielectron-volts along the strain gradient. This unique phonon spectra broadening effect intensifies phonon scattering and substantially impedes thermal transport, as evidenced by first-principles calculations. Our work uncovers a crucial piece of the long-standing puzzle of lattice dynamics under inhomogeneous strain, which is absent under uniform strain and eludes conventional understanding.

Near-unity quantum yield and long-term emission stability in halide perovskite nanocrystal glass composite.

Metal halide perovskites are promising optoelectronic materials due to their outstanding luminescent properties. However, the instability of perovskites has long been the bottleneck to their practical applications. Here Cs4PbBr6 nanocrystals based glass composite (Cs4PbBr6 NCs@glass) are successfully prepared, which displays green emission color (520 nm), narrow bandwidth (23 nm) and a near-unity photoluminescence quantum yield (PLQY). The H2O molecules permeating in the lattice of Cs4PbBr6 were found to be a crucial role in the subband energy emission. The Cs4PbBr6 NCs@glass has excellent emission stability; maintains 93 % of initial PL intensity after ultraviolet light irradiation for over 5000 h. In addition, by adjusting the halogen content, we have achieved tunable emission color from blue (450 nm) to green (520 nm) and red (670 nm) on Cs4PbX6 NCs@glass (X = Cl, Br, I), which covers up to 127 % of the National Television Systems Board (NTSC) standard system. Our finding indicates the commercial applications of perovskite materials in lighting and display.

Stable Interstrand Cross-Links Generated from the Repair of 1,N6-Ethenoadenine in DNA by α-Ketoglutarate/Fe(II)-Dependent Dioxygenase ALKBH2.

DNA cross-links severely challenge replication and transcription in cells, promoting senescence and cell death. In this paper, we report a novel type of DNA interstrand cross-link (ICL) produced as a side product during the attempted repair of 1,N6-ethenoadenine (εA) by human α-ketoglutarate/Fe(II)-dependent enzyme ALKBH2. This stable/nonreversible ICL was characterized by denaturing polyacrylamide gel electrophoresis analysis and quantified by high-resolution LC-MS in well-matched and mismatched DNA duplexes, yielding 5.7% as the highest level for cross-link formation. The binary lesion is proposed to be generated through covalent bond formation between the epoxide intermediate of εA repair and the exocyclic N6-amino group of adenine or the N4-amino group of cytosine residues in the complementary strand under physiological conditions. The cross-links occur in diverse sequence contexts, and molecular dynamics simulations rationalize the context specificity of cross-link formation. In addition, the cross-link generated from attempted εA repair was detected in cells by highly sensitive LC-MS techniques, giving biological relevance to the cross-link adducts. Overall, a combination of biochemical, computational, and mass spectrometric methods was used to discover and characterize this new type of stable cross-link both in vitro and in human cells, thereby uniquely demonstrating the existence of a potentially harmful ICL during DNA repair by human ALKBH2.

Surgical treatment improves overall survival of hepatocellular carcinoma with extrahepatic metastases after conversion therapy: a multicenter retrospective study.

Systemic therapy is typically the primary treatment choice for hepatocellular carcinoma (HCC) patients with extrahepatic metastases. Some patients may achieve partial response (PR) or complete response (CR) with systemic treatment, leading to the possibility of their primary tumor becoming resectable. This study aimed to investigate whether these patients could achieve longer survival through surgical resection of their primary tumor. We retrospectively collected data from 150 HCC patients with extrahepatic metastases treated at 15 different centers from January 1st, 2015, to November 30th, 2022. We evaluated their overall survival (OS) and progress-free survival (PFS) and analyzed risk factors impacting both OS and PFS were analyzed. Patients who received surgical treatment had longer OS compared to those who did not (median OS 16.5 months vs. 11.3 months). However, there was no significant difference in progression-free survival between the two groups. Portal vein invasion (P = 0.025) was identified as a risk factor for poor prognosis in patients, while effective first-line treatment (P = 0.039) and surgical treatment (P = 0.005) were protective factors. No factors showed statistical significance in the analysis of PFS. Effective first-line treatment (P = 0.027) and surgical treatment (P = 0.006) were both independent protective factors for prolonging patient prognosis, while portal vein invasion was an independent risk factor (P = 0.044). HCC patients with extrahepatic metastases who achieve PR/CR with conversion therapy may experience longer OS through surgical treatment. This study is the first to analyze the clinical outcomes of patients receiving surgical treatment for HCC with extrahepatic metastases.

A murine model of DC-SIGN humanization exhibits increased susceptibility against SARS-CoV-2.

To generate a new murine model for virus, DC-SIGN gene in murine was humanized. In this study, we successfully generated a humanized C57BL/6N mouse model expressing human DC-SIGN (hDC-SIGN) using CRISPR/Cas9 technology, and evaluated its characters and susceptibility to virus. The humanized mice could survival as usual, and with normal physiological index just like the wild-type mice. Whereas, we found significant differences in the intestinal flora and metabolic profiles between wild-type mice and humanized mice. Following intranasal infection with SARS-CoV-2, hDC-SIGN mice exhibited significantly increased viral loads in the lungs and nasal turbinates, along with more severe lung damage. This phenomenon may be associated with differential lipid metabolism and Fcγ receptor-mediated phagocytosis in two mouse models. This study provides a useful tool for investigating the mechanisms of coronavirus infection and potential drug therapies against novel coronavirus.

An immune-related adverse event of Behcet's-like syndrome following pembrolizumab treatment.

BACKGROUND: In recent years, the emergence of immunotherapy has renewed therapeutic modality. Different from traditional anti-tumor therapy, immune-related adverse events of skin, gastrointestinal tract, liver, lung, endocrine glands commonly occurred. At present, only one case of immune-related adverse event of Behcet's-like syndrome following pembrolizumab treatment was reported in USA, and no one is reported in China. CASE PRESENTATION: Here, we report a rare case of Behcet's-like symptom following pembrolizumab treatment. A 43-year-old female was diagnosed as lymph node and bone metastasis of adenocarcinoma with unknown primary lesion, probably being of pulmonary origin. She was treated with pembrolizumab 200 mg every three weeks in combination with chemotherapy for 6 cycles, followed by pembrolizumab monotherapy maintenance. However, she developed Behcet's-like syndrome with oral ulcer, genital uler, phlebitis, and vision loss after 9 cycles of pembrolizumab treatment. She was treated with prednisone 5 mg orally three times a day. Two weeks later, dose of glucocorticoid gaven to the patient gradually decreased with improved symptoms. After a treatment-free withdrawal period, the patient requested to continue pembrolizumab treatment. Unfortunately, the above symptoms recurred on the second day following pembrolizumab treatment, and glucocorticoid was taken once again. The symptoms improved and the condition was under control. CONCLUSIONS: In view of the exponential growth of immunocheckpoint inhibitors (ICIs) in a variety of tumors, we should be alert to related adverse events, especially the rare rheumatic manifestations.

Three-way decisions in generalized intuitionistic fuzzy environments: survey and challenges.

Enhancing decision-making under risks is crucial in various fields, and three-way decision (3WD) methods have been extensively utilized and proven to be effective in numerous scenarios. However, traditional methods may not be sufficient when addressing intricate decision-making scenarios characterized by uncertain and ambiguous information. In response to this challenge, the generalized intuitionistic fuzzy set (IFS) theory extends the conventional fuzzy set theory by introducing two pivotal concepts, i.e., membership degrees and non-membership degrees. These concepts offer a more comprehensive means of portraying the relationship between elements and fuzzy concepts, thereby boosting the ability to model complex problems. The generalized IFS theory brings about heightened flexibility and precision in problem-solving, allowing for a more thorough and accurate description of intricate phenomena. Consequently, the generalized IFS theory emerges as a more refined tool for articulating fuzzy phenomena. The paper offers a thorough review of the research advancements made in 3WD methods within the context of generalized intuitionistic fuzzy (IF) environments. First, the paper summarizes fundamental aspects of 3WD methods and the IFS theory. Second, the paper discusses the latest development trends, including the application of these methods in new fields and the development of new hybrid methods. Furthermore, the paper analyzes the strengths and weaknesses of research methods employed in recent years. While these methods have yielded impressive outcomes in decision-making, there are still some limitations and challenges that need to be addressed. Finally, the paper proposes key challenges and future research directions. Overall, the paper offers a comprehensive and insightful review of the latest research progress on 3WD methods in generalized IF environments, which can provide guidance for scholars and engineers in the intelligent decision-making field with situations characterized by various uncertainties.

Impact of antifibrotic therapy on disease progression, all-cause mortality, and risk of acute exacerbation in non-IPF fibrosing interstitial lung diseases: evidence from a meta-analysis of randomized controlled trials and prospective controlled studies.

BACKGROUND: Nintedanib and pirfenidone are preferred pharmacological therapies for patients with idiopathic pulmonary fibrosis (IPF). However, evidence favoring antifibrotic therapy in patients with non-IPF fibrosing interstitial lung diseases (ILD) is limited. OBJECTIVE: To investigate the effects of antifibrotic therapy on disease progression, all-cause mortality, and acute exacerbation (AE) risk in patients with non-IPF fibrosing ILDs. DESIGN: Meta-analysis. DATA SOURCES AND METHODS: Electronic databases were searched for articles published before 28 February 2023. Studies that evaluated the efficacy of antifibrotic agents in patients with fibrosing ILDs were selected. The primary outcome was the disease progression risk, and the secondary outcomes included all-cause mortality and AE risk. The GRADE criteria were used for the certainty of evidence assessment. RESULTS: Nine studies with 1990 participants were included. Antifibrotic therapy reduced the rate of patients with disease progression (five trials with 1741 subjects; relative risk (RR), 0.56; 95% CI, 0.42-0.75; p < 0.0001; I2 = 0; high-certainty evidence). Antifibrotic therapy did not significantly decrease all-cause mortality (nine trials with 1990 subjects; RR, 0.76; 95% CI, 0.55-1.03; p = 0.08; I2 = 0; low-certainty evidence). However, in patients with progressive fibrosing ILDs (PF-ILD), antifibrotic therapy decreased all-cause mortality (four trials with 1100 subjects; RR, 0.69; 95% CI, 0.48-0.98; p = 0.04; I2 = 0; low-certainty evidence). CONCLUSION: Our study supports the use of antifibrotic agents in patients with PF-ILDs, which could slow disease progression and decrease all-cause mortality. TRIAL REGISTRATION: This study protocol was registered with PROSPERO (registration number: CRD42023411272).

Reexamination of Damping in Sliding Friction.

Friction is responsible for about one-third of the primary energy consumption in the world. So far, a thorough atomistic understanding of the frictional energy dissipation mechanisms is still lacking. The Amontons' law states that kinetic friction is independent of the sliding velocity while the Prandtl-Tomlinson model suggests that damping is proportional to the relative sliding velocity between two contacting objects. Through careful analysis of the energy dissipation process in atomic force microscopy measurements, here we propose that damping force is proportional to the tip oscillation speed induced by friction. It is shown that a physically well-founded damping term can better reproduce the multiple peaks in the velocity-dependent friction force observed in both experiments and molecular dynamics simulations. Importantly, the analysis gives a clear physical picture of the dynamics of energy dissipation in different friction phases, which provides insight into long-standing puzzles in sliding friction, such as velocity weakening and spring-stiffness-dependent friction.

Direct observation of carbon slurry flow behavior and its effect on electrochemical performance in a microfluidic electrochemical flow capacitor.

Carbon slurries have been used as "flowable electrodes" in various electrochemical systems, and the slurry flow characteristics play an important role in the system electrochemical performance. For example, in an electrochemical flow capacitor (EFC), activated carbon particles must pass electrical charge from a stationary electrode to surrounding particles via particle-electrode and particle-particle interactions to store energy in the electric double layer. So far, particle behaviors under a continuous flow condition have not been observed due to the slurry's opacity, and studies of the device's performance thus have been mainly on a bulk level. To understand the relation between the hydrodynamic behavior and the electrochemical performance of carbon slurries, we have constructed a microfluidic EFC (µ-EFC) using transparent materials. The µ-EFC allows for direct observation of particle interactions in flowing carbon slurries using high-speed camera recording, and concurrent measurements of the electrochemical performance via chronoamperometry. The results indicate an interesting dependence of the particle cluster interaction on the flowrate, and its effect on the slurry charging/discharging behavior. It is found that an optimal flowrate could exist for better electrochemical performance.