Analysis of heat balance of piston hydraulic damper system installed on thrust bearing

[Objectives] This paper aims to analyze the thermal equilibrium performance of a piston hydraulic damper in a stable working state so as to solve the problem in which the oil circuit of the hydraulic damping system of a longitudinal vibration-reduction thrust bearing is closed and the external disturbance input is unknown. [Methods] To this end,a micro-mechanism for the heat production calculation of piston friction loss and hydraulic fluid loss is applied to the thermal analysis of the hydraulic damping system in order to deduce the formula of the power loss calculation of the piston vibration and the reciprocating flow of the hydraulic oil. Meanwhile,the piston friction loss and head loss of the model are calculated,and the heat production variation of the hydraulic damping system with dynamic frequency and piston stroke is analyzed. In addition,the input power of the external disturbance is ascertained and the thermal finite element model of the bearing part established,allowing the steady temperature rise and heat flow distribution of the structure to be calculated.[Results] The calculation results show that the input power of the external disturbance is roughly equal to the sum of the thermal power of each part,the steady temperature rise of the system is fairly low and the heat flow division is reasonable.[Conclusions] The results show that the heat production calculation method described in this paper is quite feasible. Furthermore, the calculated temperature rise of the system is within the permissible range, and corresponding effective measures can be taken to reduce local temperature rise at intensive heat flow parts according to the heat flow division diagram of the system

Piezoelectric Nanomaterial‐Mediated Physical Signals Regulate Cell Differentiation for Regenerative Medicine

Tissue damage often causes considerable suffering to patients due to slow recovery and poor prognosis. The use of electroactive materials to deliver biophysical signals plays a key role in regulating tissue regeneration processes. Among these materials, piezoelectric materials have unique electromechanical conversion capabilities, making them suitable for use as cell scaffolds. They can deform and emit electrical signals in response to external stimuli, thereby regulating cell proliferation and differentiation. In this review, recent advances are presented in piezoelectric materials as physical signaling mediators that regulate cell differentiation. The basic mechanisms, classification of these materials, and their different applications in tissue regeneration are described. Finally, a comprehensive discussion of current challenges and prospects in the field is provided. Together, existing experimental results basically show that piezoelectric materials can improve the process and effect of tissue repair, providing new technical options for the development of tissue engineering in the future

Rice Flag Leaf Physiology, Organ and Canopy Temperature in Response to Water Stress

Using two rice cultivars, the effect of severe, mild and no water stress, W3, W2 and W1, respectively, on flag leaf physiology, the ecological characteristics of canopy and organ temperatures were studied in 2008 and 2009. The grain yield was reduced under W3 due to decreased seed setting rate and 1000 grain weight but not under W2. Water stress had a significant effect on the flag leaf physiological characteristics along with the soluble sugar and amino proline content. Catalase and peroxidase activities, photosynthetic and transpiration rates, and stomatal conductance in W2 were significantly higher than in W3 and similar to those in W1. The organ and canopy temperatures were significantly higher in W3 than in either W1 or W2, and there was no significant difference between W1 and W2. This study clearly showed that water stress had a significant effect on leaf physiology, temperature of organs and canopy. Mild water stress (soil water potential maintained at -15- -20 kPa) could construct a population that is water-saving and resistant to heat stress. This facilitates access to a high yield as well

Analysis of Bone Mineral Density/Content of Paratroopers and Hoopsters

The different mechanical stimulus affects the bone mass and bone strength. The aim of this study was to investigate the effect of landing posture of the hoopster and paratrooper on the bone mass. In this study, 39 male participants were recruited including 13 paratroopers, 13 hoopsters, and 13 common students (control groups). Bone area (BA), BMD and BMC of calcaneus, and 1–5th of the metatarsus, hip, and lumbar spine (L1–L4) were measured by the dual-energy X-ray absorptiometry. Also, the vertical ground reaction forces (GRFs) of hoopsters and paratroopers were measured by the landing of 1.2 m 3D force platform. BA of hoopsters at the calcaneus, lumbar spine, and hip were significantly higher than the control group. The lumbar spine, hip, calcaneus, the 1st and 2nd metatarsals, BMC of paratroopers, and control groups were significantly lower than hoopsters. BMD of the lumbar spine, hip, and right and left femoral necks in hoopsters were significantly higher than the other participants. BMC and BMD of lower limber showed no significant difference between paratroopers and the control group. Besides, peak GRFs of paratroopers (11.06 times of BW) were significantly higher than hoopsters (6.49 times of BW). The higher GRF in the landing train is not always in accordance with higher BMD and BMC. Variable loads in hoopsters can improve bone remodeling and play an important role in bone expansions for trabecular bones. This will be considered by the method of training to prevent bone loss

Synthesis and Structure–Activity Relationship of Palmatine Derivatives as a Novel Class of Antibacterial Agents against Helicobacter pylori

Taking palmatine (PMT) as the lead, 20 new PMT derivatives were synthesized and examined for their antibacterial activities against six tested metronidazole (MTZ)-resistant Helicobacter pylori (H. pylori) strains. The structure–activity relationship (SAR) indicated that the introduction of a suitable secondary amine substituent at the 9-position might be beneficial for potency. Among them, compound 1c exhibited the most potent activities against MTZ-resistant strains, with minimum inhibitory concentration (MIC) values of 4–16 μg/mL, better than that of the lead. It also exhibited a good safety profile with a half-lethal dose (LD50) of over 1000 mg/kg. Meanwhile, 1c might exert its antimicrobial activity through targeting H. pylori urease. These results suggested that PMT derivatives might be a new family of anti-H. pylori components

Synthesis, Biological Evaluation, and Autophagy Mechanism of 12<i>N</i>‑Substituted Sophoridinamines as Novel Anticancer Agents

A series of 12<i>N</i>-substituted sophoridinamine derivatives were synthesized and evaluated for their cytotoxic activities in human HepG2 hepatoma cells. Structure–activity relationship revealed that introduction of a suitable arylidene or arylethyl at the <i>N</i>′-end could greatly enhance antiproliferation potency. Among them, compound <b>6b</b> possessing a <i>N</i>′-trimethoxyphenyl methylene exhibited potent antiproliferation effect against three human tumor cell lines including HepG2, leukemia (K562), and breast cancer (HMLE), with IC₅₀ between 0.55 and 1.7 μM. The underlying mechanism of <b>6b</b> against tumor cells is to block autophagic flux, mainly through neutralizing lysosomal acidity. Our results indicated that compound <b>6b</b> is a potent lysosomal deacidification agent and is accordingly able to block autophagic flux and inhibit tumor cell growth