内镜结扎术治疗食管静脉曲张急性出血

采用内镜结扎术(EVL)治疗食管静脉曲张急性出血78例。首次EVL的实施距出血发作时间:8h以内10例,9～48h 26例,49～72h 37例,超过72h 5例。急性出血被控制后,每隔2周重复EVL直至静脉曲张被根除或缩小至Ⅰ°以下。经该法治疗,近期止血率达93.6％;63例生存病人经平均4次(2～7次)EVL,55例(87％)食管静脉曲张被根除或缩小至Ⅰ°以下;未发现与EVL有关的严重并发症。平均随访25月(8～48月),有11例病人复发出血(17％),这些再出血大多发生在曲张静脉根除之前,且容易被重复EVL控制出血。该组结果显示:EVL止血效果确切,安全易行,并发症少;对食管静脉曲张急性出血,尤其伴有肝功能不良者,EVL可作为首选的有效治疗方法。

输精管结扎与前列腺癌

输精管结扎与前列腺癌之间的关系尚未得出最终结论,近2年世界卫生组织和美国国立卫生研究院组织专家讨论,对现有问题作评价,认为需作进一步研究,但对计划生育政策和输精管结扎的应用并未提出新的意见。

用于聚氨酯发泡轮胎的微孔泡沫的合成研究

采用低不饱和度、高相对分子质量聚醚多元醇和纯二苯基甲烷二异氰酸酯(MDI),合成了聚醚型聚氨酯微孔弹性体材料。该聚醚型微孔弹性体泡沫材料具有优异的力学性能,可用于自结皮微孔弹性体轮胎的制备。

公路下磷矿开采采场结构参数的数值计算优选

贵州开磷集团用沙坝矿的部分矿体位于金阳公路下面,压矿量达2 262万t。在对矿岩进行了力学参数测试与分析的基础上,选择了房柱式中深孔落矿嗣后胶结充填采矿法,同时利用数值计算方法优选出采场结构参数,实现了公路下磷矿体的安全开采。

In-situ building of multiscale porous NiFeZn/NiZn-Ni heterojunction for superior overall water splitting

The development of efficient nonprecious bifunctional electrocatalysts for water electrolysis is crucial to enhance the sluggish kinetics of the oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).A self-supporting,multiscale porous NiFeZn/NiZn-Ni catalyst with a triple interface heterojunction on nickel foam(NF)(NiFeZn/NiZn-Ni/NF)was in-situ fabricated using an electroplating-annealing-etching strategy.The unique multiinterface engineering and three-dimensional porous scaffold significantly modify the mass transport and electron interaction,resulting in superior bifunctional electrocatalytic performance for water splitting.The NiFeZn/NiZn-Ni/NF catalyst demonstrates low overpotentials of 187 m V for HER and 320 mV for OER at a current density of 600 mA/cm^(2),along with high durability over 150 h in alkaline solution.Furthermore,an electrolytic cell assembled with NiFeZn/NiZn-Ni/NF as both the cathode and anode achieves the current densities of 600 and 1000 m A/cm^(2) at cell voltages of 1.796 and 1.901 V,respectively,maintaining the high stability at 50 mA/cm^(2) for over 100 h.These findings highlight the potential of NiFeZn/NiZn-Ni/NF as a cost-effective and highly efficient bifunctional electrocatalyst for overall water splitting.

Preparation and electrochemical lithium storage performance of porous silicon microsphere composite with metal modification and carbon coating

This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃spheres as a precursor.pSi/Sb⁃Sn@C had a 3D structure with bimetallic(Sb⁃Sn)modified porous silicon micro⁃spheres(pSi/Sb⁃Sn)as the core and carbon coating as the shell.Carbon shells can improve the electronic conductivi⁃ty and mechanical stability of porous silicon microspheres,which is beneficial for obtaining a stable solid electrolyte interface(SEI)film.The 3D porous core promotes the diffusion of lithium ions,increases the intercalation/delithia⁃tion active sites,and buffers the volume expansion during the intercalation process.The introduction of active met⁃als(Sb⁃Sn)can improve the conductivity of the composite and contribute to a certain amount of lithium storage ca⁃pacity.Due to its unique composition and microstructure,pSi/Sb⁃Sn@C showed a reversible capacity of 1247.4 mAh·g^(-1) after 300 charge/discharge cycles at a current density of 1.0 A·g^(-1),demonstrating excellent rate lithium storage performance and enhanced electrochemical cycling stability.

Research progress on carbon-based zinc-ion capacitors

Zinc-ion capacitors(ZICs),which consist of a capacitor-type electrode and a battery-type electrode,not only possess the high power density of supercapacitors and the high energy density of batteries,but also have other advantages such as abundant resources,high safety and environmental friendliness.However,they still face problems such as insufficient specific capacitance,a short cycling life,and narrow operating voltage and temperature ranges,which are hindering their practical use.We provide a comprehensive overview of the fundamental theory of carbon-based ZICs and summarize recent research progress from three perspectives:the carbon cathode,electrolyte and zinc anode.The influence of the structure and surface chemical properties of the carbon materials on the capacitive performance of ZICs is considered together with theoretical guidance for advancing their development and practical use.

Design and fabrication of sintered wick for miniature cylindrical heat pipe

Miniature cylindrical metal powder sintered wick heat pipe （sintered heat pipe） is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process for sintered wick is important for its quality. The sintering process was optimally designed based on the equation of the heat transfer limit of sintered heat pipe. Four-step sintering process was proposed to fabricate sintered wick. The sintering parameters including sintering temperature, sintering time, sintering atmosphere and sintering position were discussed. The experimental results showed that the proper sintering temperature was 950 ℃ for Cu powder of 159μm and 900 ℃ for Cu powders of 81 and 38 μm, respectively, while the wick thickness was 0.45 mm and sintering time was 3 h. The optimized sintering time was 3 h for 0.45 and 0.6 mm wick thickness and 1 h for 0.75 mm wick thickness, respectively, when copper powder diameter was 159μm and sintering temperature was 950 ℃. Redox reduction reaction between H2 and CuO during sintering could produce segmentation cracks in Cu powders as a second structure. Sintering at vertical position can effectively avoid the generation of gap between wick and the inner wall of pipe.

Synthesis of three-dimensional ordered mesoporous MnO_2 and its catalytic performance in formaldehyde oxidation

Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry（ia3d）.It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4＋ ions on the（110）crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4＋ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.

Effect of pore structures on corrosion resistance of porous Ni_3Al intermetallics

Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH solution using electrochemical methods and immersion test. Effect of porous structures on the corrosion behavior of the porous Ni3Al intermetallics was studied. The results indicate that the porous Ni3Al intermetallics with higher porosities suffer more serious corrosion than the ones with lower porosities because the complicated interconnected porous structures and the large true surface areas exist in the samples with a higher porosity. But the corrosion rates of the porous Ni3Al intermetallics are not proportional to the true surface areas. The reason is that the pore size, pore size distribution and pore shape of the porous Ni3Al intermetallics change with the increasing porosity. All the porous Ni3Al intermetallics with different porosities exhibit excellent corrosion resistance in a strong alkali solution.

Preparation of Al-doped ZnO sputter target by hot pressing

Al-doped ZnO （AZO） target was prepared by hot pressing using ZnO and Al2O3 powder in mass ratio of 98：2.The effects of hot pressing conditions including temperature,pressure and preserving time on relative density were investigated.Pore evolution and phase structure change during densification process were studied.The results show that AZO target with super high relative density of 99% was prepared by two-stage hot pressing method under pressure of 35MPa,temperature of 1 050℃ and 1 150℃ with preserving time of 1 h,respectively.At temperature around 1 050℃,the number of isolated pore wasminimum.At temperature lower than 900℃,there existed Al2O3 phase.At temperature higher than 1 000℃,ZnAl2O4 phase was generated and its content was increased with temperature increasing.Hot pressing method had the advantage over pressureless sintering that the content of ZnAl2O4 was lower and sintering temperature could be also lower.With increasing the hot pressing temperature and preserving time,the electric resistivity of AZO target decreased greatly.A low resistivity of 3 10-3 cm was achieved under the temperature of 1 100℃,pressure of 35MPa and preserving time of 10 h.

Effect of secondary pore distribution on adsorption diffusion performance of n-hexane on 5A zeolite pellets

Adsorption rates of n-hexane on the 5A zeolite at 100 to 300 ℃ and 0.01 to 10 kPa are determined by an intelligent gravimetric analyzer （IGA-100）, and the adsorption diffusion performance of n-hexane on 5A zeolite pellets with different secondary pore distributions is analyzed. The results indicate that 5A-1 and 5A-6 zeolites have similar micropore and mesopore size distribution, while the 5A-6 zeolite has a larger secondary pore volume when the pore diameter is between 0.1 and 1 μm and more secondary pores when the pore diameter is less than 0.01 μm. The effective diffusion coefficient of nhexane on the 5A-6 zeolite pellet is 10 ^-6 to 10 4 cm^2/s, about 2 to 5 times higher than that on the 5A-1 zeolite. The effective diffusion coefficient of n-hexane on the 5A-1 zeolite pellet improves from 5 × 10^-7 to 2 × 10 6cm^2/s when the temperature increases from 100 to 300 ~C. However, the effective diffusion coefficient of n-hexane on the 5A-6 zeolite remains almost unchanged at different temperatures. The molecular average free path of n-hexane decreases from 627.15-963.28 to 0.63-0, 96 Ixm with the adsorption pressure increasing from 0.01 to 10 kPa. Such a flee path is close to the secondary pore diameter, resulting in significant Knudsen diffusion in the secondary pores. Thus, the effective diffusion coefficient of n-hexane on the 5A zeolite pellets increases before 1 kPa and decreases after 1 kPa.

Finite element analysis of stress at implant-bone interface of dental implants with different structures

The effect of structure,elastic modulus and thickness of lower modulus layer in porous titanium implants on the stress distribution at the implant-bone interface was investigated.Three-dimensional finite element models of different titanium implants were constructed.The structures of the implants included the whole lower modulus style （No.1）,bio-mimetic style （No.2）,the whole lower modulus style in cancellous bone （No.3） and the whole dense style No.4.The stress distributions at bone-implant interface under static loading were analyzed using Ansys Workbench 10.0 software.The results indicated that the distribution of interface stress is strongly depended on the structure of the implants.The maximum stresses in cancellous bone and root region of implant No.2 are lower than those in the other three implants.A decrease in the modulus of the low modulus layer facilitates the interface stress transferring.Increasing the thickness of the low modulus layer can reduce the stress and induce a more uniform stress distribution at the interface.Among the four implants,biomimetic style implant No.2 is superior in transferring implant-bone interface stress to surrounding bones.

Mechanical properties and pore structure deformation behaviour of biomedical porous titanium

Porous titanium has been shown to exhibit desirable properties as biomedical materials. In view of the load-bearing situation, the mechanical properties and pore structure deformation behaviour of porous titanium were studied. Porous titanium with porosities varying from 36%-66% and average pore size of 230 μm was fabricated by powder sintering. Microstructural features were characterized using scanning electron microscopy. Uniaxial compression tests were used to probe the mechanical response in terms of elastic modulus and compressive strength. The mechanical properties of porous titanium were found to be close to the those of human bone, with stiffness values ranging from 1.86 to 14.7 GPa and compressive strength values of 85.16-461.94 MPa. The relationships between mechanical properties and relative densities were established, and the increase in relative density showed significant effects on mechanical properties and deformations of porous titanium. In a lower relative density, the microscopic deformation mechanism of porous titanium was yielding, bending and buckling of cell walls, while the deformation of yielding and bending of cell walls was observed in the porous titanium with higher relative density.

我国海岸带胶结壳有孔虫分布的控制因素

有孔虫化石在我国近年来海平面变迁和海区演变历史的研究中起着重要的作用。按壳壁成分,有孔虫可分为钙质和胶结壳两类,具胶结壳的有孔虫除了深海和高纬度海区外,主要在海滨沼泽、河口、泻湖等海陆过渡相环境中出现。一般认为,“滨海(有孔虫)生物群的特点在于其胶结壳性质”,“河口、港湾、泻湖低盐水体的沿岸沉积通常以胶结壳有孔虫占优势”。

Effect of pore structure on seismic rock-physics characteristics of dense carbonates

The Ordovician carbonate rocks of the Yingshan formation in the Tarim Basin have a complex pore structure owing to diagenetic and secondary structures. Seismic elastic parameters（e.g., wave velocity） depend on porosity and pore structure. We estimated the average specific surface, average pore-throat radius, pore roundness, and average aspect ratio of carbonate rocks from the Tazhong area. High P-wave velocity samples have small average specific surface, small average pore-throat radius, and large average aspect ratio. Differences in the pore structure of dense carbonate samples lead to fluid-related velocity variability. However, the relation between velocity dispersion and average specific surface, or the average aspect ratio, is not linear. For large or small average specific surface, the pore structure of the rock samples becomes uniform, which weakens squirt fl ow and minimizes the residuals of ultrasonic data and predictions with the Gassmann equation. When rigid dissolved（casting mold） pores coexist with less rigid microcracks, there are significant P-wave velocity differences between measurements and predictions.

Solid-phase sintering process and forced convective heat transfer performance of porous-structured micro-channels

A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was studied and optimized to obtain porous-structured micro-channels with high porosity. The flow resistance and heat transfer performance in the composite micro-channels were investigated. The composite micro-channels show acceptable flow resistance, significant enhancement of heat transfer and dramatic improvement of flow boiling stability, which indicates a promising prospect for the application in forced convective heat transfer.

Manufacture, characterization and application of porous metal-fiber sintered felt used as mass-transfer-controlling medium for direct methanol fuel cells

Fabrication, characterization and performance of a porous metal-fiber sintered felt （PMFSF） based on multi-tooth cutting and solid-phase sintering were studied. The PMFSF was used as the anodic methanol barrier in a passive air-breathing direct methanol fuel cell to mitigate the effects of methanol crossover. Compared with the commercial SUS316L felt made of bundle-drawn fibers, this self-made PMFSF has larger pore diameter, polarized pore distribution, irregular fiber shape, rougher surface, lower mass flow resistance and evident hydrophobicity. The results reveal that the use of a PMFSF significantly enhances the cell performance since it helps to maintain a balance between the reactant and product management while depressing methanol crossover. The PMFSF with a porosity of 70% yields the highest cell performance at a methanol concentration of 4 mol/L.

A novel model for assessing the pore structure of tight sands and its application

Pore-structure poses great influence on the permeability and electrical property of tight sand reservoirs and is critical to the petrophysical research of such reservoirs.The uncertainty of permeability for tight sands is very common and the relationship between pore- structure and electrical property is often unclear.We propose a new parameterδ,integrating porosity,maximum radius of connected pore-throats,and sorting degree,for investigating the permeability and electrical properties of tight sands.Core data and wireline log analyses show that this newδcan be used to accurately predict the tight sands permeability and has a close relation with electrical parameters,allowing the estimation of formation factor F and cementation exponent m.The normalization of the resistivity difference caused by the pore- structure is used to highlight the influence of fluid type on Rt,enhancing the coincidence rate in the Pickett crossplot significantly.