Motion control of unmanned surface vehicles (USVs) is a crucial issue in sailing performance and navigation costs. The actuators of USVs currently available are mostly a combination of thrusters and rudders. The modeling for USVs with rudderless double thrusters is rarely studied. In this paper, the three degrees of freedom (DOFs) dynamic model and propeller thrust model of this kind of USV were derived and combined. The unknown parameters of the propeller thrust model were reduced from six to two. In the three-DOF model, the propulsion of the USV was completely provided by the resultant force generated by double thrusters and the rotational moment was related to the differential thrust. It combined the propeller thrust model to represent the thrust in more detail. We performed a series of tests for a 1.5 m long, 50 kg USV, in order to obtain the model parameters through system identification. Then, the accuracy of the modeling and identification results was verified by experimental testing. Finally, based on the established model and the proportional derivative+line of sight (PD+LOS) control algorithm, the path-following control of the USV was achieved through simulations and experiments. All these demonstrated the validity and practical value of the established model.
The present study describes a safe anchor path of antegrade lag screw fixation in the posterior column. Insertion of the lag screws of adequate length is possible in the posterior column along its functional axis.
Wear particle induced periprosthetic osteolysis is the main cause of aseptic
loosening of orthopedic implants. The aim of the present study is to determine
the protective effect of quercetin (QUE) against titanium (Ti) particle induced
endoplasmic reticulum stress (ERS) related apoptosis and osteolysis. In the
present study, RAW264.7 cells were pretreated with different concentrations (40,
80, and 160 μmol/l) of QUE for 30 min and then treated with Ti particle
(5 mg/ml) for 24 h. Cell viability and apoptosis were determined using MTT assay
and Annexin V-FITC Apoptosis Detection Kit, respectively. Protein and mRNA
expressions of ERS-related genes were examined by Western blot and real-time
PCR, respectively. The release of inflammatory cytokines was detected by ELISA.
Then, a mouse calvarial osteolysis model was established. Histological sections
of calvaria were stained with Hematoxylin-Eosin (H&E) or
tartrate-resistant acid phosphatase (TRAP). The results showed that Ti particle
reduced cell viability and induced apoptosis in RAW264.7 macrophages. The
cytotoxic effects of Ti particle were dramatically inhibited by QUE
pretreatment. Interestingly, we found that QUE also significantly reduced Ti
particle induced up-regulation of the expression levels of protein kinase
RNA-like ER kinase (PERK), inositol-requiring enzyme-1 (IRE1), glucose-regulated
protein (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP),
caspase-12, and caspase-3 and enhanced the down-regulation of Bcl-2. In
addition, QUE decreased Ti particle-induced inflammatory cytokines release from
RAW264.7 cells. Moreover, treatment with QUE markedly decreased osteoclast
number. In a mouse calvarial osteolysis model, QUE inhibited Ti particle induced
osteolysis in vivo by inhibiting osteoclast formation and
expressions of ERS-related genes. In conclusion, QUE can protect RAW264.7 cells
from Ti particle induced ERS-related apoptosis and suppress calvarial osteolysis
in vivo.
Osteonecrosis of the femoral head (ONFH) is a pathological process that initially occurs in the weight-bearing field of the femoral head. Due to the unknown pathogenesis, this study was for the investigation of the effect of microRNA-141 (miR-141) targeting transforming growth factor-β2 (TGF-β2) on regulating osteoblast activity and osteoclast activity in steroid-induced ONFH.Tissues of ONFH and normal femoral head were collected for detecting the expression of miR-141 and TGF-β2. A rat model of ONFH was constructed by injection of hormones, and transfected with miR-141 inhibitors and overexpressed TGF-β2. The apoptosis of bone cells was detected by TUNEL staining. The expression of osteoprotegerin (OPG), osteoprotegerin ligand (OPGL), Bcl-2, Bax, Runx2, BMP2 and RANK were detected.Highly expressed miR-141 and lowly expressed TGF-β2 existed in femoral head tissues in ONFH. Inhibited miR-141 resulted in elevated TGF-β2 in femoral head tissues in ONFH of rats. Depressed miR-141 or overexpressed TGF-β2 inhibited the apoptosis of bone cells of rats with ONFH and induced elevated OPG, Bcl-2, BMP2, Runx2 and declined OPGL, Bax and RANK expression in the femoral head tissues of rats with ONFH.Altogether, we find that down-regulated miR-141 promotes osteoblast activity and inhibits osteoclast activity to ameliorate ONFH via up-regulated TGF-β2 expression.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.