Study on stability of formation for gravity field exploration subjected to disturbance based on prescribed performance control

Double satellite formation for gravity field exploration is a complex space virtual instrument system with high-precision, whose normal manner is threatened by the space debris environment. The normal manner of the formation based on control with prescribed performance is studied. Based on the random impact of space debris, nonlinear dynamical equations with 20 variables are established considering the relative attitude of the double satellite. The interferential characteristics and expected stability under certain disturbance conditions by the space debris in low Earth orbit are analyzed. To simplify the relative motion of the formation and the motion of the test mass (TM) relative to the cage, a prescribed performance function is introduced to constrain the relative attitude errors of transient and steady states. An adaptive attitude control design method based on a prescribed performance function is proposed. Finally, the analysis is carried out. The results show that the probability of normal manner of the formation is about 78.45% in the first year and about 45.59% in the first three years. The normal manner of the double satellite formation for gravity field exploration can be effectively simulated and analyzed based on the prescribed performance control methods.

[Data standard and data sharing in clinical cohort studies]

Data standard plays an important role in the process of data collection, Integration and sharing in clinical cohort studies, and more attention have been paid to it. This paper summarizes the 5 international proven data standard model, analyze their characteristics and development status, and match their data modules with the general data set of the clinical cohorts to evaluate the international data standard models' applicability and provide reference for the development and improvement of the data standard model for clinical cohort studies in China.

[Quality assessment of global lung cancer screening guidelines and consensus]

Objective: To understand the research progress and quality of lung cancer screening guidelines and consensus in China and abroad, and to provide reference for the formulation of high-quality lung cancer screening guidelines in China. Methods: Databases including PubMed, Medline, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, SinoMed, VIP and Wanfang Data were searched, websites and important references were also searched by hand retrieval. The Appraisal of Guidelines for Research & Evaluation Ⅱ(AGREE Ⅱ) and Reporting Items for Practice Guidelines in Healthcare (RIGHT) were used to assess the quality of newly published or updated guidelines and consensus. Results: A total of 9 guidelines and consensus published between 2015 and 2020 were included in this study, with countries including the United States, China, Canada, Saudi Arabia and South Africa. The field of scope and purpose and clarity of presentation scored relatively high but the rigor of development and applicability scored low. Five guidelines were judged to be A-level, all of which were published abroad, and the remaining four were B-level, including three guidelines and consensus issued by China and 1 guideline issued by South Africa. The report rate of RIGHT were higher in basic information and background, lower in review and quality assurance, funding and declaration and management of interests. There were 5 guidelines with a good level and 4 guidelines and consensus with a moderate level. The best overall quality guidelines were those published by the American College of Chest Physicians in 2018 and by the Canadian Task Force on Preventive Health Care in 2016. Conclusions: The number of countries and institutions that issue lung cancer screening guidelines and consensus had been increasing gradually, but the quality in China remained low. It is necessary to develop high-quality lung cancer screening guidelines suitable for China's national conditions in combination with evidence-based methods to guide practice.

High fructose causes cardiac hypertrophy via mitochondrial signaling pathway

High fructose diet can cause cardiac hypertrophy and oxidative stress is a key mediator for myocardial hypertrophy. Disruption of cystic fibrosis transmembrane conductance regulator (CFTR) leads to oxidative stress. This study aims to reveal mitochondrial oxidative stress-related signaling pathway in high fructose-induced cardiac hypertrophy. Mice were fed high fructose to develop cardiac hypertrophy. Fructose and H₂O₂ were used to induce cardiomyocyte hypertrophy in vitro. Mitochondria-targeted antioxidant SkQ1 was applied to investigate the possible role of mitochondrial reactive oxygen species (ROS). CFTR silence was performed to detect the role of CFTR in high fructose-induced myocardial hypertrophy. ROS, glutathione (GSH), mitochondrial function and hypertrophic markers were measured. We confirmed that long-term high fructose diet caused cardiac hypertrophy and diastolic dysfunction and elevated mitochondrial ROS. However, SkQ1 administration prevented heart hypertrophy and mitochondrial oxidative stress. Cadiomyocytes incubated with fructose or H₂O₂ exhibited significantly increased cell areas but SkQ1 treatment ameliorated cardiomyocyte hypertrophy induced by high fructose or H₂O₂ in vitro. Those results revealed that the underlying mechanism for high fructose-induced heart hypertrophy was attributed to mitochondrial oxidative stress. Moreover, CFTR expression was decreased by high fructose intervention and CFTR silence resulted in an increase in mitochondrial ROS, which suggested high fructose diet affected mitochondrial oxidative stress by regulating CFTR expression. Electron transport chain impairment might be related to mitochondrial oxidative damage. In conclusion, our findings indicated that mitochondrial oxidative stress plays a central role in pathogenesis of high fructose-induced cardiac hypertrophy. High fructose decreases CFTR expression to regulate mitochondrial oxidative stress.

Elevated expression of connective tissue growth factor, osteopontin and increased collagen content in human ascending thoracic aortic aneurysms

Little is known about the molecular mechanisms of ascending thoracic aortic aneurysms (ATAAs). Abnormal extracellular matrix changes and variations of vascular smooth muscle cells (VSMCs) have been implicated in abdominal aortic aneurysm formation. Our objective was to investigate the alterations of collagen, stimulators of collagen synthesis and synthetic VSMCs in patients with ATAA. Surgical samples from ATAA were taken from 20 patients, and 18 control aortas were obtained during coronary artery bypass surgery. All aortic wall specimens were fixed for histology and immunohistochemistry for collagen, connective tissue growth factor (CTGF) and osteopontin. Realtime polymerase chain reaction was used to determine their mRNA expression. Histology and semi-quantitative analysis demonstrated that protein levels of collagen, CTGF and osteopontin significantly increased by 1.9-, 1.4- and 2.2-fold, respectively ( P < 0.01 for all) in the ATAA group than in the control group. Similar results were shown in mRNA levels of type Iα1and IIIα1 collagen, CTGF and osteopontin. The protein levels of CTGF and osteopontin were positively correlated with aortic diameter ( r = 0.67, r = 0.73; P < 0.01 for both). In conclusion, overexpression of aortic CTGF and synthetic VSMCs marker (osteopontin), which is likely to be responsible for elevated aortic collagen content, may provide a potential mechanism for aneurysmal enlargement.

Detection of hepatitis B virus markers using a biosensor based on imaging ellipsometry

A biosensor based on imaging ellipsometry (BIE) has been developed and validated in 169 patients for detecting five markers of hepatitis B virus (HBV) infection. The methodology has been established to pave the way for clinical diagnosis, including ligand screening, determination of the sensitivity, set-up of cut-off values (CoVs) and comparison with other clinical methods. A matrix assay method was established for ligand screening. The CoVs of HBV markers were derived with the help of receiver operating characteristic curves. Enzyme-linked immunosorbent assay (ELISA) was the reference method. Ligands with high bioactivity were selected and sensitivities of 1 ng/mL and 1 IU/mL for hepatitis B surface antigen (HBsAg) and surface antibody (anti-HBs) were obtained respectively. The CoVs of HBsAg, anti-HBs, hepatitis B e antigen, hepatitis B e antibody and core antibody were as follows: 15%, 18%, 15%, 20% and 15%, respectively, which were the percentages over the values of corresponding ligand controls. BIE can simultaneously detect up to five markers within 1 h with results in acceptable agreement with ELISA, and thus shows a potential for diagnosing hepatitis B with high throughput.

Fabrication and characterization of needle-like nano-HA and HA/MWNT composites

Hydroxyapatite (HA) ceramic has been used in tissue engineering and orthopedics for its good biocompatibility and osteoconductivity. However, its clinical applications are usually limited by the low strength and brittleness. The objective of this research was to develop a new kind of HA composites in which multi-wall carbon nanotubes (MWNTs) were introduced to the HA ceramic matrix to improve the mechanical properties of the resulting composites. A simple chemical wet method was applied to synthesize the HA ceramic particles with the aid of surfactant and ultrasonication technique at normal atmospheric pressure. The morphology and microstructure of the synthesized HA were characterized by XRD and TEM as a function of treatment time. The results showed that the synthesized HA particles are needle-like with a length of 80-160 nm along the (211) direction and an aspect ratio of 5-15. MWNTs were treated with a mixture of nitric acid and sulfuric acid. The HA/MWNT composites were prepared by solution blending. The composites were sintered using a hot-press method. The mechanical properties of the HA/MWNT composites with different volume percentages of MWNTs were examined. The fracture toughness and flexural strength were improved by 50% and 28% separately when the volume percentage of MWNTs reached 7%.

An essential role for mitogen-activated protein kinases, ERKs, in preventing heat-induced cell death

Stimulation of mitogen-activated protein kinases (MAPKs) or extracellular signal regulated protein kinases (ERKs) after exposure of mammalian cells to ultraviolet (UV) and X-irradiation occurs through activation of receptor tyrosine kinases via Ras/Raf/Mek/ERKs cascade. This activation of MAPKs is proposed to play a role in the replacement of damaged proteins during these stresses. Heat shock also activates MAPKs; however, the signaling cascade and the biochemical and physiological links between activation by heat and downstream effects are unknown. In this report we demonstrate that, unlike irradiation, heat induces MAPKs through ceramide metabolism to sphingosine with stimulation of Raf-1 protein kinase. The activation of MAPKs by heat does not occur in all cell types, because the step(s) downstream of ceramide to activation of Raf-1 protein kinase is missing in myeloid leukemic cells such as HL-60, U937, and K562, while it is present in NIH3T3 fibroblasts. Heat-induced MAPK activation may enhance the ability of cells to survive a severe heat shock. Blocking 60-70% of the activity of MAPK (ERK1) by stable overexpression of the dominant negative allele ERK1-KR renders NIH3T3 and K562 cells up to 100-fold more sensitive to cytotoxic effects of heat. Conversely, NIH3T3 and K562 cells stably overexpressing the wild-type ERK1 develop resistance to killing by heat. These results suggest that increased thermal sensitivity of leukemic cells to thermal stress or other cancer therapy regimens could be attributable to lack of pertinent activation of the MAPK pathway by such stresses.

Glycogen synthase kinase 3beta and extracellular signal-regulated kinase inactivate heat shock transcription factor 1 by facilitating the disappearance of transcriptionally active granules after heat shock

Heat shock transcription factor 1 (HSF-1) activates the transcription of heat shock genes in eukaryotes. Under normal physiological growth conditions, HSF-1 is a monomer. Its transcriptional activity is repressed by constitutive phosphorylation. Upon activation, HSF-1 forms trimers, acquires DNA binding activity, increases transcriptional activity, and appears as punctate granules in the nucleus. In this study, using bromouridine incorporation and confocal laser microscopy, we demonstrated that newly synthesized pre-mRNAs colocalize to the HSF-1 punctate granules after heat shock, suggesting that these granules are sites of transcription. We further present evidence that glycogen synthase kinase 3beta (GSK-3beta) and extracellular signal-regulated kinase mitogen-activated protein kinase (ERK MAPK) participate in the down regulation of HSF-1 transcriptional activity. Transient increases in the expression of GSK-3beta facilitate the disappearance of HSF-1 punctate granules and reduce hsp-70 transcription after heat shock. We have also shown that ERK is the priming kinase for GSK-3beta. Taken together, these results indicate that GSK-3beta and ERK MAPK facilitate the inactivation of activated HSF-1 after heat shock by dispersing HSF-1 from the sites of transcription.

Analysis of the phosphorylation of human heat shock transcription factor-1 by MAP kinase family members

The activation of heat shock transcription factor-1 (HSF-1) after treatment of mammalian cells with stresses such as heat shock, heavy metals, or ethanol induces the synthesis of heat shock proteins. HSF-1 is phosphorylated at normal growth temperature and is hyperphosphorylated upon stress. We recently presented evidence that HSF-1 can be phosphorylated by the mitogen activated protein kinase, ERK1, and that such phosphorylation appears to negatively regulate the activity of HSF-1. In this report, we have tested the ability of ERK1 to phosphorylate various HSF-1 deletion mutants. Our results show that ERK1 phosphorylation is dependent on a region of HSF-1 extending from amino acids 280 to 308. This region contains three serine residues that are potential ERK1 phosphorylation sites. The region falls within a previously defined regulatory domain of HSF-1. The possibility of protein kinases other than ERK1 phosphorylating HSF-1 was also examined using in-gel kinase assays. The results show that HSF-1 can be phosphorylated in a ras-dependent manner by other members of the MAP kinase family such as JNK and p38 protein kinases and possibly others.

Stellettin A, a new triterpenoid pigment from the marine sponge Stelletta tenuis

A new isomalabaricane triterpenoid, stellettin A [1], was isolated from the sponge Stelletta tenuis collected off Hainan Island, People's Republic of China. Its structure and stereochemistry were established by analysis of its spectral data and reference to related compounds.