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  • Author: Gang Zhang x
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Abstract

Hydrofoil is widely used in underwater vehicle for the excellent hydrodynamic characteristics. Currently, researches are mostly about the rigid hydrofoil while the flexible hydrofoil, like the caudal fin, has not been studied adequately. In this paper, the fish was regarded as the bionic object. Then the kinematics model to describe the fish swimming was put forward. A fin-peduncle propulsion mechanism was designed based on the kinematics model to achieve the similar sine curve swimming model. The propulsion mechanism was optimized by Matlab to reduce the deviation between the output curve of the fin-peduncle propulsion mechanism and the ideal motion trajectory. Moreover, the motion phase angles among flexible articulations are optimized to reduce fluid resistance and improve propulsive efficiency. Finally, the fish-like hydrofoil oscillation is simulated by fluid-solid coupling method based on the Fluent. It was shown that the optimized flexible fish-like oscillation could generate the motion that follows the similar law of sine. The propulsive efficiency of oscillating hydrofoil propeller is much higher than that of the screw propeller, and the flexible oscillation has higher propulsive efficiency than the rigid oscillation without obvious fluid resistance increase.

Abstract

Microstructure and dielectric properties of La2O3 doped Ti-rich barium strontium titanate ceramics, prepared by solid state method, were investigated with non-stoichiometric level and various La2O3 content, using XRD, SEM and LCR measuring system. With an increase of non-stoichiometric level, the unit cell volumes of perovskite lattices for the single phase Ti-rich barium strontium titanate ceramics increased due to the decreasing A site vacancy concentration V″A. The unit cell volume increased and then decreased slightly with the increasing La2O3 content. Relatively high non-stoichiometric level and high La2O3 content in Ti-rich barium strontium titanate ceramics contributed to the decreased average grain size as well as fine grain size distribution, which correspondingly improved the temperature stability of the relative dielectric constant. The relative dielectric constant єrRT, dielectric loss tanδRT and the maximum relative dielectric constant єrmax decreased and then increased with the increasing non-stoichiometric level. With the increase of La2O3 doping content, the relative dielectric constant єrRT increased initially and then decreased. The maximum relative dielectric constant єrmax can be increased by applying low doping content of La2O3 in Ti-rich barium strontium titanate ceramics due to the increased spontaneous polarization.

Abstract

Introduction: Ostrich characteristics include fast running, of which the probable enablers have been studied. Yet little research has taken place on one anatomical feature. It is mainly the special integuments on the ostrich foot which facilitate fast running on sand, because as point of direct sand contact they bear the whole weight and provide all the forward force. This study elucidates aspects of the integuments.

Material and Methods: A stereo microscope, scanning electron microscope (SEM), and confocal scanning laser microscope were used to observe these integuments. Their surface structure was shown accurately in photographs. An SEM equipped with energy dispersive spectroscopy was used to check element contents of the upper and bottom areas and those on the lateral area of the 3rd toe.

Results: The content of some chemical elements on the upper area (Mg 2.04%, Si 0.18%, P 1.97%, Ca 0.59%, and S 0.69%) was higher than that of the bottom area (Mg 0.14%, Si 0.09%, P 0.10%, Ca 0.28%, and S 0.90%). Zinc was the particular element on the upper area, while sodium, chlorine, and potassium were the specific elements on the bottom area. The parts which must withstand different frictions contained different chemical compounds.

Conclusion: The microscopic plane with layer-like structure and stripes may contribute to the wear-resistance of the papillae. The polygonal and prism structures are helpful to fix papillae in a firmer way.

Identification and Cementoblastic / Osteoblastic Differentiation of Postnatal Stem Cells from Human Periodontal Ligament

Background. Periodontal diseases that lead to the destruction of periodontal tissues, including periodontal ligament (PDL), cementum, and bone, are a major cause of tooth loss in adults and are a substantial public health burden worldwide. PDL is a specialized connective tissue that connects cementum and alveolar bone to maintain and support teeth in situ and preserve tissue homoeostasis. In this study we aimed to isolate, identify periodontal ligament stem cells and their osteoblastic/cementoblastic differentiation.

Methods. Periodontal ligament tissue was obtained from human impacted third molars (n=5) from different individuals from the oral surgery department, Department of Oral and Maxillofacial Surgery, Capital Medical University School of Stomatology (Beijing, China) following which a colony forming unit - fibroblast assay, identification of periodontal ligament stem cells (PDLSCs; STRO-1 + & CD146+) by using immunocytofluorescence and isolation of PDLSCs (STRO-1+) by using flow cytometry and cementoblastic/osteoblastic exvivo induction were performed.

Results. Mesenchymal stem cells were identified in the periodontal ligament derived by their capacity to form adherent clonogenic cell clusters. Ex-vivo expanded periodontal ligament stem cells were found to express the mesenchymal stem cell markers STRO-1 and CD146. Flow cytometric study showed that a total of 24.53% of periodontal ligament cell population stained positive for the STRO-1 antibody and of that population 1.14% were strongly positive.

Conclusions. The finding of this study indicated that some PDL cells possess crucial stem cells properties, such as self renewal and express the mesenchymal stem cell markers (STRO-1 and CD 146) on their cell surface and small round alizarin red-positive nodules formed in the PDLSC cultures after 4 weeks of induction, indicating calcium accumulation in vitro. Thus, PDL cells can be used for periodontal regenerative procedures.

Abstract

The precise chronology of the fluvial terraces of the Yellow River in China is essential to understand its geomorphological evolution history. More terrace ages are needed for the correlation of the terraces along the river and the construction of the longitudinal profile. In this study, seven terraces (T1–T7) in the Heiyukou area of the Jinshaan Canyon of the river were identified and were sampled for optical dating. The reliability of the ages was evaluated on the bases of bleachability, comparison of optical ages on fine and coarse grains, stratigraphic consistency of OSL ages, age distribution and geomorphological setting. The results show that the paired T2 terrace was formed at 72 ± 3 ka, and the T4, T5 strath terraces were dated to 108 ± 4 and >141 ± 4 ka, respectively. The ages for the samples from T6 and T7 were significantly underestimated, and the ‘infinitely old’ pre-Quaternary Red-Clay sample on the T7 terrace was dated to 134 ± 6 ka. The long-term river incision rates were calculated to be <0.36, 0.34 and 0.18 mm/a for at least the past 141, 108 and 72 ka, respectively, which also reflect the uplift rates of the Ordos plateau. The implication for dating terrace deposits is that terraces should be systemically sampled and dated using both fine and coarse grain fractions. The reliability of the ages obtained for high terraces should be evaluated using a relative chronology of dated samples on a case-by-case basis, if no independent numerical age controls are available.

Abstract

Background: Mandibular movements are reliable indicators of mandibular system disease and changes in movements can be useful to estimate treatment effect. Detection of mandibular movement is important.

Objectives: We evaluated four-dimensional (4D) visualization of mandibular and temporomandibular joint movement using 320-row computed tomography (CT).

Methods: A stepwise mouth gag was placed between mandibular and maxillary incisors to control mouth opening (0.5-cm increments) in healthy volunteers and one temporomandibular disorder (TMD) patient. A 320-row CT Joint-Move and Shot sequence was used for scanning with an image taken after each increment. 4D reconstruction was used to establish volume data.

Results: 4D visualization of joint and dentition in a rest state and in a state of mandibular movement from multiple angles and in different planes demonstrated differences between healthy subjects and the subject with TMD. The effective dose per scan was approximately 17% of the 16-slice spiral CT.

Conclusion: 4D visualization of mandibular movement can be achieved through 320-row volume CT, which may provide a diagnosis of temporomandibular joint disorder and assessment of treatment effects.

Abstract

Sparse coding is currently an active topic in signal processing and pattern recognition. Meta Face Learning (MFL) isatypical sparse coding method and exhibits promising performance for classification. Unfortunately, due to using the l1-norm minimization, MFLis expensive to compute and is not robust enough. To address these issues, this paper proposesafaster and more robust version of MFLwith the l2-norm regularization constraint on coding coefficients. The proposed method is used to learnaclass-specific dictionary for facial expression recognition. Extensive experiments on two popular facial expression databases, i.e., the JAFFEdatabase and the Cohn-Kanade database, demonstrate that our method shows promising computational efficiency and robustness on facial expression recognition tasks.

Abstract

In this paper, a floating-buoy wave energy converter using hydrostatic transmission system is studied. The entire work progress of wave energy power generation device is introduced, and the hydraulic transmission principles are emphasized through the simulation to verify the feasibility of design principle of hydraulic transmission system. The mathematical model of the accumulator is established and applied in the AMEsim simulation. The simulation results show that the accumulator plays an important role in the wave power hydraulic transmission system and that the correct configuration of accumulator parameters can improve the rapidity and stability of the system work. Experimental results are compared with the simulation results to validate the correctness of the simulation results. This would provide a valuable reference to the optimal design of wave power generation.

Abstract

The prevalence and microbial pattern reported for Community-acquired pneumonia (CAP) differ considerably and contemporary situation remains changing over time. We therefore searched both international and domestic databases for relevant references and pooled incidence of CAP and etiological distribution were estimated separately between children and adults groups. The results showed that CAP remained a major public health issue in China, with a relatively higher incidence than that reported in Western countries. Although pathogens were not detected in nearly half of patients, Mycoplasma pneumoniae remained to be the most frequently detected agent across age groups, the detection yield of which was lower than that reported from other countries. Notably, the incidence of influenza virus A in adults was almost four times higher than that in children while the prevalence of respiratory syncytial virus was much less common in adults than that in children. Despite some limitations, the value of this review, approaching to systematically review grey published data, is to sketch out the contemporary epidemiological and etiological situation of CAP in our country, which could be useful to help policymakers and clinicians make informed choices and to inspire future studies and surveillance.

Abstract

Introduction: To identify novel pathways involved in the pathogenesis of ketosis, an isobaric tag for relative and absolute quantitation/mass spectrometry was used to define differences in protein expression profiles between healthy dairy cows and those with clinical or subclinical ketosis.

Material and Methods: To define the novel pathways of ketosis in cattle, the differences in protein expression were analysed by bioinformatics. Go Ontology and Pathway analysis were carried out for enrich the role and pathway of the different expression proteins between healthy dairy cows and those with clinical or subclinical ketosis.

Results: Differences were identified in 19 proteins, 16 of which were relatively up-regulated while the remaining 3 were relatively down-regulated. Sorbitol dehydrogenase (SORD) and glyceraldehyde-3-phosphate dehydrogenase (G3PD) were up-regulated in cattle with ketosis. SORD and G3PD promoted glycolysis. These mechanisms lead to pyruvic acid production increase and ketone body accumulation.

Conclusion: The novel pathways of glycolysis provided new evidence for the research of ketosis.