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The appetite of honeybees for food is crucial to their survival and reproduction, as they sustain their entire colony by collecting pollen and nectar for nutrients. Dopamine, an important neurotransmitter, regulates appetite and satiety. However, how dopamine regulates honeybee foraging behavior remains unexplored. In this study, we investigated dopamine expression in 23-day-old Apis mellifera under different food-wanting conditions and identified differentially expressed genes (DEGs) in the brains of honeybees using RNA sequencing technology. We showed that dopamine levels in honeybees starved for 2 h were higher than those sated after 2 h of starvation. RNA-seq results revealed there were differences in the expression of cytochrome P450-dependent monooxygenase (CYP9Q1) in honeybees, which regulated the sucrose sensitivity of honeybees under different intake states. Furthermore, CYP9Q1 targeted the expression of the insulin receptor substrate (IRS) to promote dopamine synthesis. Our findings emphasize the relationship between dopamine and honeybees' desire for food at the molecular level, providing a reference for further exploring the mechanism of food wanting. [ABSTRACT FROM AUTHOR]

Skin inflammation and immune regulation have been suggested to be associated with allergic contact dermatitis (ACD) progression, but whether the system's immune regulation is a cause or a potential mechanism is still unknown. This study aims to assess the upstream and downstream of systemic immune factors on ACD within a bidirectional Mendelian-randomization design. A bidirectional two-sample MR analysis was employed to implement the results from genome-wide association studies for 52 system immune factors and ACD. Genetic associations with systemic immune factors and ACD were obtained from the IEU Open GWAS project database. The inverse-variance weighted (IVW) method was adopted as the primary MR analysis, MR-Egger, weighted median, MR-pleiotropy residual sum, and outlier (MR-PRESSO) was also used as the sensitivity analyses. Only Tumor necrosis factor ligand superfamily member 11 (TNFS11) from among 52 systemic immune factors was associated with a protective effect of ACD. However, ACD was associated with a decrease in Interleukin-9 (IL9) and an increase in C-X-C motif chemokine 1 (GROα), Tumor necrosis factor ligand superfamily member 10 (TRAIL), C4, and complement factor B of the assessed systemic immune factors. This study identified TNFS11 as the upstream regulator and IL9, GROα, TRAIL, C4, and complement factor B as the downstream regulator of ACD, providing opportunities for new therapeutic exploitation of ACD. Nonetheless, these associations of systemic immune factors need to be verified in vivo. [ABSTRACT FROM AUTHOR]

TiO2-Al2O3 supports with different incorporation methods of titania were synthesized via three methods: impregnation (TA-I), co-precipitation (TA-CP), and co-precipitation–hydrothermal treatment (TA-HT). And the NiMoP catalysts prepared on the corresponding supports were evaluated for hydrodesulfurization (HDS) reactions. The results demonstrated that the Ti atoms in TA-I are attached to alumina through hydroxyl groups, while the Ti atoms in TA-CP and TA-HT can be dispersed in the alumina skeleton. Variations in the incorporation modes of TiO2 affect the support properties, consequently influencing the nature of the active metal on the supports. The Ti atoms dispersed in the Al2O3 skeleton allow an increase in the basic hydroxyl groups. Meanwhile, TiO2 in TA-CP and TA-HT can absorb hydrogen molecules and be partially reduced. Furthermore, metal species supported on the TA-CP and TA-HT are more easily reduced and better dispersed. For the NiMoP catalysts prepared with TA-CP and TA-HT, the Ti element promotes the sulfidation degree of Mo, besides shortening the average (Ni)MoS2 slab. The catalysts prepared with TA-CP exhibited superior activity for 4,6-DMDBT hydrodesulfurization. This can be ascribed not only to the relatively high sulfidation degree of Mo and proportion of the NiMoS active phase but also to the well-dispersed (Ni)MoS2 slabs. Moreover, the Ti4+ ions dispersed in the Al2O3 skeleton can be partially reduced to act as electron donors, enhancing the metallic character of the S layers in MoS2, which facilitates the improvement of the hydrogenation desulfurization activity. [ABSTRACT FROM AUTHOR]

As an advanced design technology for large wide-body airliners, the three-dimensional (3D) dual-sidestay (DSS) landing gear retraction mechanism can share the ground loads transferred by the landing gear, reducing the load on the wings. However, the addition of a strut system may significantly impact the synchronous locking performance of the landing gear with extremely high sensitivity. To study this impact pattern, both a rigid–flexible-coupling dynamic model of DSS landing gear considering joint clearance and node deviation and a synchronous locking test platform are established in this paper, and the simulation model is validated through the experimental results. Based on the simulation model, this paper conducts a detailed study on the influence of different node deviations and joint clearance on the synchronous locking dynamic characteristics of the DSS landing gear. The results show that, as the node deviation increases, the locking of the lock link gradually lags until one side cannot be fully locked; the structural clearance has a smaller impact on the synchronous locking of the landing gear. The feasible region of parameters satisfying the synchronous locking condition is given, which provides a basis and support for the parameter design of dual-sidestay retraction mechanisms. [ABSTRACT FROM AUTHOR]

During the landing and taxiing process of aircraft, the frame-type landing gear (FTLG) usually generates large pitch vibrations under external excitation. Excessive vibration increases localized loads on the landing gear, which may lead to localized failure of the structure. To minimize this undesirable vibration, a passive oil–pneumatic pitch-stabilizing buffer (PSB) is designed in this paper to provide pitch damping. This paper applies the basic principles of dynamics to establish a dynamic model of FTLG considering the influence of PSB. And based on the design of experiments (DOE) method, by changing the filling parameters and structural parameters of PSB, the results of the changes of the frame vibration angle, angular velocity, and landing gear load are obtained, so as to analyze the effects of different parameters on the dynamic performance of the landing gear in the landing and taxiing process. The results demonstrate that increasing the oil damping coefficient of PSB and decreasing the installation angle of PSB on the main strut during the landing period resulted in less frame vibration and lower wheelset load ratios, but increased the landing overloads of landing gears. In the taxiing phase, increasing the PSB air spring stiffness can effectively reduce the frame vibration caused by the uneven road surface. The PSB structural parameters have little effect on the dynamic performance of FTLG. [ABSTRACT FROM AUTHOR]

The tail-sitter VTOL UAV boasts not only high-speed cruising and air hovering capabilities, but also its unique tail-sitting vertical takeoff and landing and hovering attitude enable aerial operations with an exceptionally small cross-sectional area. This feature effectively broadens the scope of application for the UAV in intelligent agriculture, encompassing tasks such as agricultural inspection, production monitoring, and topographic mapping. Given the necessity for frequent modal transitions, this paper is grounded in a thorough examination of the typical structural characteristics of the tail-sitter VTOL UAV. A comprehensive technical solution for tail-sitter VTOL UAVs, based on the free-tail configuration, is proposed in this paper. The free-tail structure is utilized to address the limitations of traditional tailless layout and fixed landing gear in terms of flight stability and takeoff/landing performance of tail-sitter VTOL UAVs. However, the implementation of this solution necessitates the addition of a new maneuvering unit. Consequently, this paper delves into the aerodynamic coupling characteristics and laws between the layout parameters such as tail number, tail length, and tail area and the tail-sitter VTOL UAV fuselage. To optimize the free-tail configuration, a multi-objective optimization is performed by integrating the overall UAV dynamics, landing dynamics, and modal transition trajectory constraints. The results of stability modeling simulations and flight tests demonstrate that the tail-sitter VTOL UAV equipped with this technical solution exhibits enhanced maneuverability and flight efficiency compared to the conventional tailless layout. [ABSTRACT FROM AUTHOR]

A dynamic model is established to investigate the shimmy instability of a landing gear system, considering the influence of nonlinear damping. The stability criterion is utilized to determine the critical speed at which the landing gear system becomes unstable. The central manifold theorem and canonical method are employed to simplify the dynamic model of the landing gear. The first Lyapunov coefficient of the system is theoretically derived and verified using numerical simulation. Further investigation on the Hopf bifurcation characteristics and stability of the shimmy in the landing gear system is conducted. The results indicate that above a certain threshold speed, with a tire stability distance greater than half the tire length in contact with the ground plus the slack length, the aircraft remains stable during taxiing. At critical speeds, a shimmy system with higher-order nonlinear damping will undergo supercritical Hopf bifurcation. Quantitative analysis suggests an increase in the linear damping coefficient within a range that ensures a stability margin to mitigate undesired oscillation, while the nonlinear damping coefficient should be designed within a reasonable range to decrease the amplitude of the limit cycle. [ABSTRACT FROM AUTHOR]

Arresting gear systems play a vital role in carrier-based aircraft landing. In order to accurately understand the process of arresting hook and cable, this study introduces a parameter inversion method to model the arresting cable and applies it to the transient dynamics model of the arresting hook and cable. The feasibility of the arresting cable model and its application to the transient dynamics model of the arresting hook and cable are validated through arresting hook and cable impact tests. The study compares three different models of arresting cables for simulation results and concludes that assuming the arresting cable to be a beam with metal elastic parameters during the modeling process cannot ignore the influence of the cable's torsional and bending stiffness on the modeling. The study also investigates the dynamic response of the arresting hook during the aircraft arrestment and hooking process and concludes that the stress peak of the hook arm is much lower throughout the entire arrestment process than at the moment of hooking the cable. The study further identifies factors that affect the stress on the arresting hook arm, such as the aircraft's yaw angle, deck angle, cruising speed, and the initial position of the arresting hook and cable before engagement. The research results have significant implications for improving the design optimization of the structural strength of the functional components of the naval aircraft arresting system and provide theoretical guidance and technical reserves for subsequent related studies. [ABSTRACT FROM AUTHOR]

The torsion spring of a carrier-based aircraft landing gear is a key component, which is normally manufactured out of AerMet100 ultra-high-strength steel. The takeoff and landing performance is greatly influenced by its bearing capacity and structural durability. To carry out the structure anti-fatigue design, it is necessary to investigate the influence of the spring structure features on its fatigue life, based on which the strain fatigue analysis and parameter optimization design of the torsion spring are executed. Through the finite element analysis conducted with ABAQUS, it was determined that there exists serious stress concentration in the relief groove. Based on the theory of strain fatigue, the fatigue life of the torsion spring was obtained, and the fracture position and lifecycle were consistent with the test results. A structure optimization platform based on a parametric method was established. Samples were selected through the DOE (design of experiment), and a surrogate model was established based on RBF (radial basis functions), followed by optimization using MIGA (multi-island genetic algorithms). With the parameter optimization of the relief groove, the structure was reconstituted and reanalyzed. From the simulation results, the peak strain was reduced by 30.7%, while the fatigue life was increased by 86.2% under the same loads and constraints. Moreover, laboratory tests were performed on the torsion spring after reconstruction, which showed that the fatigue life increases by 85.6% after optimization. The method presented in this paper can provide theoretical support and technical guidance for the application and structural optimization of ultra-high-strength steel structures. [ABSTRACT FROM AUTHOR]

During aircraft braking, the change of ground adhesion forces can cause forward and backward vibration of the landing gear, and the performance of the brake disc may exacerbate this vibration. In order to solve this problem, a rigid–flexible coupling dynamic model of a two-wheel strut landing gear considering the friction characters of brake discs with different materials and a hydraulic brake system model is established in this paper. The brake disc friction characteristics effect on the low-frequency brake-induced vibration of the landing gear given different brake disc materials and ambient temperatures is studied. It is shown that the C/SiC brake disc has a "negative slope" phenomenon between the friction coefficient of the brake disc and the wheel speed, and this variable friction characteristic has a great effect on the low-frequency braking-induced vibration of the landing gear. In addition, the variable friction characteristics of the C/SiC brake disc are easily affected by ambient temperature, while the friction coefficient of the C/C brake disc changes stably. [ABSTRACT FROM AUTHOR]

Rotorcraft Unmanned Aerial Vehicles (UAVs) often need to take off and land under complex working conditions. The rugged terrains may cause the UAV to tilt during takeoff and landing and even cause rollover and other accidents in severe cases. In this paper, a new four-legged landing gear of multirotor UAVs with a passive cushioning structure is designed, aiming at the landing stability requirement of rotorcraft UAVs in complex terrains. The mathematical model of the landing gear dynamics is established in MATLAB/Simulink, and the drop test simulation is carried out under different landing terrain conditions. By comparing the simulation results of the drop test multibody dynamic model in Simcenter3D dynamics software, the adaptive landing and cushioning capacity of the landing gear and the accuracy of the mathematical model are verified. Combined with the landing stability criterion and control strategy of adaptive landing gear adjustment, the landing stability of adaptive landing gear under different slope angles of landing surface and horizontal velocities is studied. The landing stability boundary under different combinations of these two parameters is found. [ABSTRACT FROM AUTHOR]

The release load of holdback bar will affect the safety of catapult-assisted takeoff of carrier-based aircraft, and the accurate control of releasing the load will ensure success. The magnitude and the control accuracy of release load are important parameters which impact the takeoff performance, therefore unstable release load and insufficient release precision are the main factors affecting the takeoff safety. In this paper, mechanical models of the carrier-based aircraft in the catapult-assisted takeoff tensioning state and gliding state after release are established based on multi-body dynamics, contact mechanics and tribological theory, and the influence of the release load of the holdback bar on the catapult-assisted takeoff performance is analyzed. Furthermore, a kinetic model of the holdback bar device is established, and the kinetic characteristics of the release process of the holdback bar are studied. Based on the kinetic model and friction model of the holdback bar, the influencing factors of the sensitivity of the holdback bar release load are analyzed and the structural parameters are optimized. The results show that the released load decreases slowly with the increase of the contact surface angle of the holdback bar structure and increases rapidly when that angle reaches the critical value; besides, the release load increases slowly with the increase of the friction coefficient of the contact surface and increases faster when the critical friction coefficient is reached. [ABSTRACT FROM AUTHOR]

The catapult process of a carrier-based aircraft includes multiple links such as catapult tensioning, separation of the holding rod, dragging and running, separation of the catapult and drag shuttle, and free running. The connection relationships between the front landing gear of the carrier-based aircraft and other related components in each link are different, therefore, it is necessary to adjust the topological relationships of the dynamic model in real time, when solving the catapult dynamics of a carrier-based aircraft. In this paper, a dynamic model of the multibody system of the catapult take-off is established, and a variable topology solution is carried out for the dynamic model by adjusting dynamic augmentation equations; in addition, a dynamic analysis of a carrier-based aircraft catapult and take-off process is carried out. A catapult dynamics model and variable topology solution method were established, which solved the changes at the moment of the restraining rod separation, catapult rod separation, and catapult tackle during the aircraft catapult take-off. After the restraining rod was separated from the front landing gear, the catapult force was transmitted to the rear strut, which instantly increased the load of the rear strut by 238.5 kN. In addition, after the carrier-based aircraft reached the end of the catapult's stroke, the catapult rod was separated from the catapult tow shuttle then unloaded, and the load of the rear strut was reduced from 486.2 kN to −20.3 kN. Under the protruding effect of the nose gear, the pitch angle of the carrier-based aircraft increased rapidly from −0.93° and reached 0.54° when the carrier-based aircraft rushed out of the deck. [ABSTRACT FROM AUTHOR]

The test of arresting hook bounce is one of the most essential technologies in the design and research of arresting hook. In order to research the dynamic performance of the hook after touchdown and impacting with the deck when the aircraft is arrested, an approach for a certain type of aircraft arresting hook bounce test is proposed in this paper. Solutions to critical technique issues arising in the test process such as aircraft sinking velocity control, aircraft horizontal velocity simulation, and simulation of the performance of the damper are derived and verified by the bounce test of the arresting hook. The bounce height, bounce distance, stroke length of the arresting hook damper after the hook is impacted are measured by the test. The test method proposed can be used for researching the bounce of arresting hook and providing reliable test data for the design of carrier-based aircraft and arresting hook. [ABSTRACT FROM AUTHOR]

Featured Application: Tolerance design is an essential process for a landing gear retraction mechanism. The results of the tolerance design would affect joint clearances, as well as the kinematic accuracy and robustness of the mechanism. The work presented here can be applied in the tolerance design of landing gear retraction mechanisms. It can also be used to analyze the kinematic accuracy and robustness of complicated mechanisms. Joint clearances inevitably affect the kinematic accuracy and robustness of landing gear retraction mechanisms. However, the complexity and uncertainty of the clearances lead to difficulty in establishing mathematic models and analyzing effects. In the interest of assessing the clearance effects on the kinematic accuracy of landing gears, an integrated tolerance theory is proposed in this paper. In the theory proposed, Jacobian–Torsor model is combined with robust analysis to establish the kinematic accuracy model and predict the influences of clearances. The overall steps to apply the theory presented in practice are given. A typical landing gear retraction mechanism is chosen for the case study and the results show that the tendencies of clearances can be observed. Through the process of tolerance design, robust study, and tolerance redesign, the kinematic accuracy is significantly improved. The integrated tolerance theory proposed and the study conducted will provide designers new insights for the clearance analysis of landing gear mechanisms. [ABSTRACT FROM AUTHOR]

In order to research the safety characteristics of carrier-based aircraft in yaw arrest, a complete dynamic model of the arresting system of a certain type of aircraft was developed to understand more about its dynamic properties. Based on the discrete kink-wave model, a simulation of centering arrest was conducted. The simulation results were compared with experimental data from the United States (US) military standards, demonstrating that the basic changing laws are almost the same. On the basis of centering arrest, a simulation of yaw arrest was carried out. The results show that in yaw state, the difference in the lengths of the arresting cables on either side of the hook is smaller in the early stage after the hook hangs on the rope, which leads to little influence on load fluctuation produced by the kink-wave. With the increase in arresting distance, the difference in the lengths of the arresting cables on either side becomes larger, resulting in a situation in which the cable tension on the departure side will gradually become greater than that on the opposite side. In this situation, yaw landing has a negative impact on the characteristics of arresting safety, and the excessive yaw angle causes the aircraft to rush out of the safe landing area. [ABSTRACT FROM AUTHOR]

To design and analyze a hook lock mechanism for a certain type of aircraft landing gear, numerical continuation and bifurcation theory are employed to study the performance of the lock mechanism in this paper. First, dynamic and static models of the hook lock mechanism are created separately, and by analyzing the locking and unlocking processes of the lock mechanism, the dynamic results are compared with the static numerical continuation results. According to the results, the static numerical continuation results agree excellently with the dynamic model results at the position of the stable equilibrium solution. Although the dynamic results can hardly explain the jump phenomenon of the lock mechanism at the moment of locking or unlocking, the bifurcation point of the static results suggests the occurrence of a stability change in the lock mechanism at the moment of jumping, thereby explaining the jumping mechanism of the lock mechanism. Therefore, the influences of the landing gear overload, lock spring parameters and attachment position on the performance of the lock mechanism are investigated. Furthermore, the critical installation position of the limit stop is defined, and the critical unlocking force of the lock mechanism is designed optimally based on the multi-island genetic algorithm. [ABSTRACT FROM AUTHOR]

Transepithelial fluid and salt re-absorption in epithelial tissues play an important role in fluid and salt homeostasis. In absorptive epithelium, fluid and salt flux is controlled by machinery mainly composed of epithelial sodium channels (ENaC), cystic fibrosis transmembrane conductance regulator (CFTR), Na+/H+ exchanger (NHE), aquaporin, and sodium potassium adenosine triphosphatase (Na+/K+-ATPase). Dysregulation of fluid and salt transport across epithelium contributes to the pathogenesis of many diseases, such as pulmonary edema and cystic fibrosis. Intracellular and extracellular signals, i.e., hormones and protein kinases, regulate fluid and salt turnover and resolution. Increasing evidence demonstrates that transepithelial fluid transport is regulated by cyclic guanosine monophosphate-dependent protein kinase (cGK) signals. cGK2 was originally identified and cloned from intestinal specimens, the presence of which has also been confirmed in the kidney and the lung. cGK2 regulates fluid and salt through ENaC, CFTR and NHE. Deficient cGK2 regulation of transepithelial ion transport was seen in acute lung injury, and cGK2 could be a novel druggable target to restore edematous disorder in epithelial tissues. [ABSTRACT FROM AUTHOR]

With the rapid development of the aerospace field, traditional energy absorption materials are becoming more and more inadequate and cannot meet the requirements of having a light weight, high energy absorption efficiency, and high energy absorption density. Since existing studies have shown that carbon nanotube (CNT) buckypaper is a promising candidate for energy absorption, owing to its extremely high energy absorption efficiency and remarkable mass density of energy absorption, this study explores the application of buckypaper as the landing buffer material in a manned lunar lander. Firstly, coarse-grained molecular dynamics simulations were implemented to investigate the compression stress-strain relationships of buckypapers with different densities and the effect of the compression rate within the range of the landing velocity. Then, based on a self-designed manned lunar lander, buckypapers of appropriate densities were selected to be the energy absorption materials within the landing mechanisms of the lander. For comparison, suitable aluminum honeycomb materials, the most common energy absorption materials in lunar landers, were determined for the same landing mechanisms. Afterwards, the two soft-landing multibody dynamic models are established, respectively, and their soft-landing performances under three severe landing cases are analyzed, respectively. The results depicted that the landers, respectively, adopting the two energy absorption materials well, satisfy the soft-landing performance requirements in all the cases. It is worth mentioning that the lander employing the buckypaper is proved to demonstrate a better soft-landing performance, mainly reflected in reducing the mass of the energy absorption element by 8.14 kg and lowing the maximum center-of-mass overload of the lander by 0.54 g. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a complex systemic autoimmune disorder that primarily involves joints, further affects the life quality of patients, and has increased mortality. The pathogenesis of RA involves multiple pathways, resulting in some patients showing resistance to the existing drugs. Salubrinal is a small molecule compound that has recently been shown to exert multiple beneficial effects on bone tissue. However, the effect of Salubrinal in RA has not been clearly confirmed. Hence, we induced collagen-induced arthritis (CIA) in DBA/1J mice and found that Salubrinal treatment decreased the clinical score of CIA mice, inhibiting joint damage and bone destruction. Furthermore, Salubrinal treatment downregulated osteoclast number in knee joint of CIA in mice, and suppressed bone marrow-derived osteoclast formation and function, downregulated osteoclast-related gene expression. Moreover, Salubrinal treatment inhibited RANKL-induced NF-κB signaling pathway, and promoted P65 degradation through the ubiquitin-proteasome system, further restrained RANKL-induced osteoclastogenesis. This study explains the mechanism by which Salubrinal ameliorates arthritis of CIA in mice, indicating that Salubrinal may be a potential drug for RA, and expands the potential uses of Salubrinal in the treatment of bone destruction-related diseases. [ABSTRACT FROM AUTHOR]

Shield segments of subway tunnels are often exposed to the combined actions of several hygrothermal factors that could lead to accidents such as water seepage and tunnel collapse. Further, they often break and deform owing to formation pressure. In addition, uncertainties related to the stress relaxation characteristics and bonding performance of carbon-fiber-reinforced plastics (CFRPs) under a hygrothermal environment make their application in subway systems difficult. This study analyzes the effects of the slip-on-bending strength of CFRP-strengthened shield segments in a hygrothermal environment. In the study, the shield segments are damaged at ambient pressure under a combination of humidity (0%, 5%, and 10%) and temperature (20 °C, 25 °C, 30 °C, and 40 °C). An experimental procedure is designed to evaluate a CFRP-reinforced concrete arch. The method predicts the load–slip relationship and maximum shearing stress and strain. Moreover, confined compression tests are conducted on a tunnel segment lining strengthened with CFRP to evaluate the bearing capacity of the CFRP-strengthened shield segments. An equation for the latter's ultimate bearing capacity is developed based on the elastic layer system theory, stress boundary condition, and bending stress characteristics of axisymmetric elements. It was found that the results from the developed model are compared with the experimental values of CFRP-strengthened shield segments under different humidity values (0%, 5%, and 10%) and a constant temperature. The ultimate strength—the debonding deflection of the CFRP-strengthened shield segment—can be predicted using the proposed ultimate bearing capacity equation with sufficient accuracy. [ABSTRACT FROM AUTHOR]

In this paper, an impedance control algorithm based on velocity for capturing two low impact docking mechanisms (LIDMs) is presented. The main idea of this algorithm is to track desired forces when the position errors of two LIDMs are random by designing the relationship between the velocity and contact forces measured by a load sensing ring to achieve low impact docking. In this paper, the governing equation of an impedance controller between the deviation of forces and velocity is derived, and simulations are designed to verify how impedance parameters affect the control characteristics. The performance of the presented control algorithm is validated by using the MATLAB and ADAMS software for capturing simulations. The results of capturing simulations demonstrate that the impedance control algorithm can respond fast and has excellent robustness when the environmental errors are random, and the contact forces and torques satisfy the low impact requirements.