Molybdenum disulfide has the characteristics of reducing friction and wear resistance and is often used as a solid lubricant in spacecraft. Due to the particularity of space missions, part of the ...rotating structure needs to perform reciprocating motion, which accelerates the wear of the molybdenum disulfide film. In this study, the molecular dynamics simulation method was used to study the reciprocating friction characteristics of molybdenum disulfide thin films. The effects of load and temperature on the friction and wear characteristics of molybdenum disulfide films during reciprocating friction were studied. The results show that the monolayer and bilayer molybdenum disulfide films have different damage thresholds. This study provides a new idea at the atomic level for the study of lubrication under the reciprocating motion of spacecraft.
Aiming at the reciprocating motion existing in the space rolling bearing, the wear characteristics of the reciprocating friction of MoS2 were studied. The friction simulation between Fe–Ni–Cr substrate and MoS2 is simulated by mixing multiple potential functions. and came to the following conclusions:•MoS2 films with different layers have different damage thresholds, and the higher the number of layers, the higher the damage threshold.•The number of layers of the MoS2 film will not affect the lubricating properties of the film, and the friction coefficient values of the films with different layers are similar.•At alternating space temperatures (0 K–500 K), the lubricating properties of MoS2 films do not change significantly.•The space alternating temperature (0 K–500 K) did not have a significant effect on the wear of the MoS2 film.
Knowledge regarding the health impacts of daily eating frequency (DEF) and nighttime fasting duration (NFD) on mortality is very limited.
This study aimed to examine whether DEF and NFD are ...associated with CVD and all-cause mortality.
This was a prospective cohort study of a nationally representative sample from the United States, including 30,464 adults who participated in the National Health and Nutrition Examination Survey 2003-2014. Using 24-h dietary recall, DEF was assessed by the number of eating episodes, and NFD was calculated by the first and last eating time across a day. Death information was obtained from the National Death Index up to 2019. Weighted Cox proportional hazards regression models were used to assess survival relationships of DEF and NFD with mortality.
During 307,686 person-years of follow-up, 4560 deaths occurred, including 1824 CVD cases. After adjustment for confounders, compared to DEF at 4-6 times, participants whose DEF was less than 3 times had greater CVD hazard-ratio (HR) = 1.33, 95% confidence-interval (CI): 1.06-1.67 and all-cause (HR = 1.16, 95% CI: 1.01-1.33) mortality risks. Furthermore, compared to NFD of 10 to 11 h, participants whose NFD was shorter than 10 h had HRs of 1.30 (95% CI: 1.08-1.55) for CVD mortality and 1.23 (95% CI: 1.08-1.39) for all-cause mortality. NFD longer than 14 h was also related to CVD mortality (HR = 1.37, 95% CI: 1.12-1.67) and all-cause mortality (HR = 1.36, 95% CI: 1.19-1.54). Similar results for the association of NFD and DEF with heart-specific and stroke-specific mortality were observed.
This study found that DEF less than 3 times and NFD shorter than 10 h or longer than 14 h were independently associated with greater cardiovascular and all-cause mortality.
Background
Thyroid cancer is the most common malignant tumor of the endocrine system. Most patients with thyroid cancer have a good prognosis, although a small proportion experience recurrence and ...metastasis and have a poor prognosis. Ferroptosis is a novel form of regulated cell death (RCD); previous studies have confirmed that ferroptosis was associated with thyroid cancer. The purpose of this study was to investigate the key ferroptosis-related genes in thyroid cancer and their relationship with prognosis and immune cell infiltration.
Methods
In this study, 497 thyroid cancer RNA expression datasets were downloaded from the cancer genome atlas (TCGA) cohort and a prognostic risk model for eight ferroptosis-related genes (FRGs) was constructed by Lasso-Cox regression. The prognostic value of the risk model and the correlation of prognostic features with immune scores and tumor immune cell infiltration were systematically analyzed.
Results
The prognostic risk model for eight FRGs (
DPP4
,
TYRO3
,
TIMP1
,
CDKN2A
,
SNCA
,
NR4A1
,
IL-6
and
FABP4
) were constructed and validated in training and testing cohorts. Kaplan-Meier curve and receiver operating characteristic (ROC) curve analysis confirmed that that the ferroptosis-related eight gene signature had good predictive value for the prognosis of thyroid cancer (THCA) patients. Multivariate regression analysis further showed that the risk score of the prognostic model could be used as an independent prognostic factor for THCA patients. Functional enrichment analysis showed that DEGs in high risk and low risk groups were involved in immune-related biological processes and that there were significant differences in immune cell infiltration between the two risk groups.
Conclusion
We identified eight key genes related to ferroptosis in THCA patients. Further studies are now needed to investigate the mechanisms involved; these genes may represent clinical diagnostic and prognostic biomarkers.
Immunogenic cell death (ICD) is a form of regulated cell death that elicits immune response. Common inducers of ICD include cancer chemotherapy and radiation therapy. A better understanding of ICD ...might contribute to modify the current regimens of anti-cancer therapy, especially immunotherapy. This study aimed to identify ICD-related prognostic gene signatures in breast cancer (BC). An ICD-based gene prognostic signature was developed using Lasso-cox regression and Kaplan-Meier survival analysis based on datasets acquired from the Cancer Genome Atlas and Gene Expression Omnibus. A nomogram model was developed to predict the prognosis of BC patients. Gene Set Enrichment Analysis (GESA) and Gene Set Variation Analysis (GSVA) were used to explore the differentially expressed signaling pathways in high and low-risk groups. CIBERSORT and ESTIMATE algorithms were performed to investigate the difference of immune status in tumor microenvironment of different risk groups. Six genes (
,
,
,
,
, and
) were selected for construction and validation of the prognosis model of BC based on public data. GSEA and GSVA analysis found that immune-related gene sets were enriched in low-risk group. Moreover, immune cell infiltration analysis showed that the immune features of the high-risk group were characterized by higher infiltration of tumor-associated macrophages and a lower proportion of CD8
T cells, suggesting an immune evasive tumor microenvironment. We constructed and validated an ICD-based gene signature for predicting prognosis of breast cancer patients. Our model provides a tool with good discrimination and calibration abilities to predict the prognosis of BC, especially triple-negative breast cancer (TNBC).
Background
Breast cancer (BC) is the most common malignancy affecting women. It is vital to explore sensitive biological markers to diagnose and treat BC patients. Recent studies have proved that ...long noncoding RNAs (lncRNAs) were involved in breast tumor progression. Nonetheless, whether lncRNA prostate cancer‐associated transcript 19 (PCAT19) impacts BC development remains unknown.
Methods
We performed various bioinformatic analyses, including machine learning models to identify critical regulatory lncRNAs affecting prognosis in BC. The in situ hybridization (ISH) assay was carried out to confirm the expression levels of lncRNA PCAT19 in tissue specimens. MTT assay, wound healing assay, and transwell assay were performed to investigate PCAT19's impact on proliferation, migration, and invasion of BC cells. Mouse xenografts were used to examine the proliferation‐inhibiting function of PCAT19 in vivo.
Results
Among the prognosis‐associated lncRNAs, PCAT19 predicted a favorable prognosis in BC. Patients with high expression levels of PCAT19 had a lower clinical stage and less lymph node metastasis. The PCAT19‐related genes were enriched in signaling pathways involved in tumor development, indicating PCAT19 was an essential regulator of BC. Using the ISH assay, we confirmed the expression level of lncRNA PCAT19 in human BC tissues was lower than normal breast tissues. Moreover, the knockdown of PCAT19 further confirmed its inhibiting ability in BC cell proliferation. Correspondingly, overexpressing PCAT19 reduced tumor size in mouse xenografts.
Conclusions
Our study demonstrated that lncRNA PCAT19 suppressed the development of BC. PCAT19 might be a promising prognostic biomarker, which provides new insights into risk stratification for BC patients.
This work demonstrated that lncRNA PCAT19 could curb breast cancer development by inhibiting proliferation. LncRNA PCAT19 is a potential biomarker of breast cancer and might help to improve precise patient stratification in the future.
Two NASA deep-space probes, Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) and New Horizons (NH), are moving towards the extremes of our solar system (Mercury and Pluto). ...The delivery of the science in these extreme environments is a challenge, and the missions require unique approaches. MESSENGER'S antenna system utilizes the first electronically scanned high-gain array for a deep-space telecommunication application. The array, which provides the high-data-rate downlink, is scanned in one dimension and is circularly polarized. Although a linearly polarized array would have satisfied the minimum mission science data rate requirements, MESSENGER'S circularly polarized array doubles it. To achieve this, the Johns Hopkins University/Applied Physics Laboratory (JHU/APL) developed an innovative technique to produce circular polarization from a narrow-wall slotted waveguide array. The new technique uses short parasitic monopoles mounted to the exterior of the waveguides. The result is a simple, lightweight, and all-metal circularly polarized array capable of operating at +300 O C, and a variety of measurement techniques were used to verify phased-array antenna system performance during qualification. The NH antenna system is a stack arrangement of a high-gain antenna (HGA), medium-gain antenna (MGA), and low-gain antenna (LGA). To minimize mission operating costs, the spacecraft is spin stabilized at all times except during encounters to maintain a fixed spacecraft attitude. This approach and application for a narrow beamwidth antenna is unique for a deep-space mission, resulting in new approaches to accurately measure the gain and radio-frequency (RF) boresight direction in a compact range facility. Because of the importance of the HGA function to overall mission success, testing of the HGA system at operational temperatures of -200 O C was also performed. Recent in-flight measurement of the NH HGA pattern verified ground alignments. The RF design of the NH antenna also forms the baseline RF design for a deployable antenna system JHU/APL is developing called the Hybrid Deployable Antenna (HDA). The HDA combines a fixed parabolic dish with a deployable/inflatable reflector annulus that greatly increases antenna area after launch. This concept provides a high-payoff deployable antenna system that is being developed to address the "all or nothing" risk by providing a viable backup capability. This paper discusses some of the challenges to advance this concept for a future deep-space mission.
This paper describes the design decisions taken and the mass properties tracking and testing flow chosen for the Van Allen Probes spacecraft and their deployable systems to achieve the coning angle ...requirements. Topics include a list of major requirements, a brief description of the error budget, a description of the tracking process of the spacecraft mass properties prior to test, a description of the spin balance and mass properties testing of the spacecraft core and deployable systems, and a presentation of the final mass properties and coning angle calculations of the fully deployed observatories. Launched August 30, 2012, the observed on-orbit, fully deployed configuration coning angles met the requirements, validating the spin balance and mass properties tracking, testing, and calculation methods chosen for the Van Allen Probes mission.
Aiming at the problem of the failure of bearing lubrication caused by the entry of fine dust into the spacecraft, a molecular dynamic simulation method was proposed to study the wear characteristics ...of the bearing lubricating film. Firstly, the atomic model of MoS2 thin film is established, and the motion state of dust particles on the surface of MoS2 thin film is divided (sliding abrasive and rotating abrasive). Secondly, the characteristics of sliding and rotating abrasive wear are studied by applying different loads to the abrasives. Finally, the surface structure of the substrate was changed to explore the adsorption and wear characteristics of the one-dimensional rough substrate. The following conclusions are obtained: (1) sliding abrasive and rotating abrasive have different wear mechanisms. The wear of sliding abrasive originates from the accumulation and release of tangential force. The main source of wear in rotating abrasive is the release of tangential force and the action of tangential force caused by rolling; (2) The relationship between sliding friction and rolling friction at the atomic scale is the same as that at the macroscopic scale. Rolling friction is much less friction than sliding friction. Rolling friction causes less damage to the film than sliding friction; (3) The one-dimensional rough substrate reduces the contact area between the film and the film, resulting in a decrease in the adsorption between the film and the substrate. The asperity structure of rough substrates reduces the lubricity of the film compared to smooth substrates.
•Lifetime phosphor thermometry was implemented in a rarefied tunnel at Ma = 10.•Strong radiation with random spatial and temporal distributions was corrected.•In situ calibration method showed best ...performance for heat flux calculation.•Global heat flux distribution reveals fine flow features on the model with tail-fin.
Lifetime-based phosphor thermometry using Mg4FGeO6:Mn is successfully implemented on a standard hypervelocity ballistic model 2 (HB-2 model) and an HB-2 model modified with tail fin in a hypersonic rarefied tunnel at a Mach number of 10. A novel Reynolds decomposition correction method is proposed to remove the heating device-induced strong background radiation, which is characterized by complex spatial and temporal distributions. Three methods are compared for heat flux calculation: an insitu calibration method, the Cook–Felderman method, and a double-layer numerical method. The in situ calibration method exhibits the least relative error (9.47 %), outperforming the other two methods. The global heat flux distribution at a high spatial resolution (0.25 mm/pixel) reveals the fine flow features of the models. Particularly, the modified HB-2 model exhibits a complex flow, related to the shock-boundary layer interaction, shock–shock interaction, and significant 3D effects. The presented measurement technique and data processing method can enable long-duration advanced aerothermal testing in hypersonic tunnels involving a large temperature rise.
Constrained sintering is a crucial issue for the development of laminated or composite ceramics. It had been suggested that flash sintering (FS) may eliminate the defects caused by constrained ...sintering. In this work, the interfacial tensile stresses of laminated ceramics during conventional sintering (CS), field assisted sintering technique (FAST) and FS were estimated and compared by combining a set of free sintering, bending creep and constrained sintering experiments with theoretical analysis. The interfacial tensile stress in constrained FS is significantly lower than those of both CS and FAST, and can only be explained by an extremely low uniaxial viscosity of the materials achieved during FS. The possible effects of temperature, density and microstructure on the uniaxial viscosity reduction have been carefully assessed to show that the electrical field itself is the key factor for the extremely low viscosity. Plausible mechanisms for the reduction in the uniaxial viscosity under different levels of electrical fields are also discussed.
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