Theoretical analysis and numerical simulation of acoustic waves in gas hydrate-bearing sediments

Based on Carcione-Leclaire model,the time-splitting high-order staggered-grid finite-difference algorithm is proposed and constructed for understanding wave propagation mechanisms in gas hydrate-bearing sediments.Three compressional waves and two shear waves,as well as their energy distributions are investigated in detail.In particular,the influences of the friction coefficient between solid grains and gas hydrate and the viscosity of pore fluid on wave propagation are analyzed.The results show that our proposed numerical simulation algorithm proposed in this paper can effectively solve the problem of stiffness in the velocity-stress equations and suppress the grid dispersion,resulting in higher accuracy compared with the result of the Fourier pseudospectral method used by Carcione.The excitation mechanisms of the five wave modes are clearly revealed by the results of simulations.Besides,it is pointed that,the wave diffusion of the second kind of compressional and shear waves is influenced by the friction coefficient between solid grains and gas hydrate,while the diffusion of the third compressional wave is controlled by the fluid viscosity.Finally,two fluid-solid(gas-hydrate formation)models are constructed to study the mode conversion of various waves.The results show that the reflection,transmission,and transformation of various waves occur on the interface,forming a very complicated wave field,and the energy distribution of various converted waves in different phases is different.It is demonstrated from our studies that,the unconventional waves,such as the second and third kinds of compressional waves may be converted into conventional waves on an interface.These propagation mechanisms provide a concrete wave attenuation explanation in inhomogeneous media.

Optimizing surgical outcomes for elderly gallstone patients with a high body mass index using enhanced recovery after surgery protocol

BACKGROUND Rehabilitation of elderly patients with a high body mass index(BMI)after cholecystectomy carries risks and requires the adoption of effective perioperative management strategies.The enhanced recovery after surgery(ERAS)protocol is a comprehensive treatment approach that facilitates early patient recovery and reduces postoperative complications.AIM To compare the effectiveness of traditional perioperative management methods with the ERAS protocol in elderly patients with gallbladder stones and a high BMI.METHODS This retrospective cohort study examined data from 198 elderly patients with a high BMI who underwent cholecystectomy at the Shanghai Fourth People's Hospital from August 2019 to August 2022.Among them,99 patients were managed using the traditional perioperative care approach(non-ERAS protocol),while the remaining 99 patients were managed using the ERAS protocol.Relevant indicator data were collected for patients preoperatively,intraoperatively,and postoperatively,and surgical outcomes were compared between the two groups.RESULTS The comparison results between the two groups of patients in terms of age,sex,BMI,underlying diseases,surgical type,and preoperative hospital stay showed no statistically significant differences.However,the ERAS group had a significantly shorter preoperative fasting time than the non-ERAS group(4.0±0.9 h vs 7.6±0.9 h).Regarding intraoperative indicators,there were no significant differences between the two groups of patients.However,in terms of postoperative recovery,the ERAS protocol group exhibited significant advantages over the non-ERAS group,including a shorter hospital stay,lower postoperative pain scores and postoperative hunger scores,and higher satisfaction levels.The readmission rate was lower in the ERAS protocol group than in the non-ERAS group(3.0%vs 8.1%),although the difference was not significant.Furthermore,there were significant differences between the two groups in terms of postoperative nausea and vomiting severity,postoperative abdominal distention at 24 h,and daily life ability scores.CONCLUSION The findings of this study demonstrate that the ERAS protocol confers significant advantages in postoperative outcomes following cholecystectomy,including reduced readmission rates,decreased postoperative nausea and vomiting,alleviated abdominal distension,and enhanced functional capacity.While the protocol may not exhibit significant improvement in early postoperative symptoms,it does exhibit advantages in long-term postoperative symptoms and recovery.These findings underscore the importance of implementing the ERAS protocol in the postoperative management of cholecystectomy patients,as it contributes to improving patients'recovery and quality of life while reducing health care resource utilization.

The fabrication of hydroxyapatite mineralized hydrogels for bone tissue engineering

Bone is a complex but orderly mineralized tissue with hydroxyapatite(HA)as the inorganic phase and collagen as the organic phase.Inspired by natural bone tissues,HA-mineralized hydrogels have been widely designed and used in bone tissue engineering.HA is majorly utilized for the treatment of bone defects because of its excellent osteoconduction and bone inductivity.Hydrogel is a three-dimensional hydrophilic network structure with similar properties to the extracellular matrix(ECM).The combination of HA and hydrogels produces a new hybrid material that could effectively promote osteointegration and accelerate the healing of bone defects.In this review,the structure and growth of bone and the common strategies used to prepare HA were briefly introduced.Importantly,we discussed the fabrication of HA mineralized hydrogels from simple blending to in situ mineralization.We hope this review can provide a reference for the development of bone repair hydrogels.

分级多孔金-铜薄膜对苯甲醇的催化氧化

采用合金/去合金法,在金-铜合金线表面制备了分级多孔金-铜薄膜结构(Hierarchically porous Au-Cu thin films,HPAFs)。该分级多孔结构是由微米级的大尺寸孔道-系带和纳米级小尺寸系带-孔道构成。通过对电沉积、退火处理及腐蚀条件的控制可以调控表面多孔薄膜层的厚度、结构以及组成。研究结果表明,脱合金处理残留的铜在富金的系带上形成了金主导的AuCu合金-CuOx异质结构,其可以有效地促进分子氧的活化,而分级多孔结构有利于反应物分子在孔内的扩散传质,从而赋予HPAFs催化剂对苯甲醇分子氧氧化反应高催化活性。

Hot deformation behavior and microstructure evolution of TiC–Al_2O_3/Al composites

Hot compression behavior of TiC–Al2O3/Al composites was studied using the Gleeble-1500 system at a temperature range of 300–550 °C and at strain rate range of 0.01–10.00 s-1. The associated structural changes were studied by TEM observations. The results show that stress level decreases with deformation temperature increasing and strain rate decreasing, which can be represented by a Zener–Hollomon parameter in an exponent-type equation with hot deformation activation energy Q of 172.56 kJ·mol-1.Dynamic recovery occurs easily when strain rates are less than 10.00 s-1. Dynamic recrystallization can occur at strain rate of 10.00 s-1.