AIM:To evaluate the main factors associated with mortality in patients undergoing surgery for perforated peptic ulcer referred to an academic department of general surgery in a large southern Italian city. METHODS:One...AIM:To evaluate the main factors associated with mortality in patients undergoing surgery for perforated peptic ulcer referred to an academic department of general surgery in a large southern Italian city. METHODS:One hundred and forty-nine consecutive patients (M:F ratio=110:39,mean age 52 yrs,range 16-95) with peptic ulcer disease were investigated for clinical history (including age,sex,previous history of peptic ulcer,associated diseases,delayed abdominal surgery,ulcer site,operation type,shock on admission,postoperative general complications, and intra-abdominal and/or wound infections),serum analyses and radiological findings. RESULTS:The overall mortality rate was 4.0%.Among all factors,an age above 65 years,one or more associated diseases,delayed abdominal surgery,shock on admission, postoperative abdominal complications and/or wound infections,were significantly associated (x^2) with increased mortality in patients undergoing surgery (0.0001<P<0.03). CONCLUSION:Factors such as concomitant diseases,shock on admission,delayed surgery,and postoperative abdominal and wound infections are significantly associated with fatal outcomes and need careful evaluation within the general workup of patients admitted for perforated peptic ulcer.展开更多
Micrometer-scale macroporous aluminosilicate catalyst was prepared via the sol-gel process. Results of catalytic cracking of 1, 3, 5-triisopropylbenzene showed that the synthesized aluminosilicate catalyst exhibited m...Micrometer-scale macroporous aluminosilicate catalyst was prepared via the sol-gel process. Results of catalytic cracking of 1, 3, 5-triisopropylbenzene showed that the synthesized aluminosilicate catalyst exhibited much higher activity than traditional ZSM-5 zeolite under the same condition. It is worth mentioning that the polymer product selectivity of aluminosilicate was much lower than that of ZSM-5, which might be useful for implementing the catalytic cracking process. The unique structure of macroporous aluminosilicate with interconnected-macropores and continuous skeletons was believed to be responsible for its excellent catalytic activity and low polymer product selectivity. Detailed discussion on the reaction pathway was also conducted.展开更多
Porous g-C3N4samples were obtained by simply calcining bulk g-C3N4in static air in a muffle oven.The photocatalytic performance of these samples was evaluated through the removal of aqueous organic dyes（methylene blu...Porous g-C3N4samples were obtained by simply calcining bulk g-C3N4in static air in a muffle oven.The photocatalytic performance of these samples was evaluated through the removal of aqueous organic dyes（methylene blue and methyl orange）and tetracycline hydrochloride under visible-light irradiation（λ〉420 nm）.Compared to bulk g-C3N4,porous g-C3N4exhibited much better capability for removing these contaminants,especially under visible-light irradiation,due to the enlarged specific surface area and more efficient separation of photogenerated charge carries.In particular,porous g-C3N4obtained by calcining bulk g-C3N4in air at 525℃ showed the highest visible-light-driven catalytic activity among these samples.Superoxide radical anions（·O2^-）were found to be the primary active species responsible for photodegradation.展开更多
Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental resu...Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size;along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.展开更多
Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures w...Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures were coldcompacted into dense cylindrical precursors for foaming at specific temperatures under air atmosphere.The effects of severalparameters including precursor compaction pressure,foaming agent content as well as temperature and time of the foaming processon the cell microstructure,linear expansion,relative density and compressive properties were investigated.A uniform distribution ofcells with sizes less than100μm,which form semi open-cell structures with relative densities in the range of55.4%-84.4%,wasobtained.The elevation of compaction pressure between127-318MPa and blowing agent up to15%(mass fraction)led to anincrease in the linear expansion,compressive strength and densification strain.By varying the foaming temperature from800to1000°C,all of the investigated parameters increased except compressive strength and relative density.The results indicated theoptimal foaming temperature and time as900°C and10-25min,respectively.展开更多
Difficulties with soft coal seams having a high gas content and high stress levels can be addressed by a technology of pressure relief and permeability increase.Slotting the seam by auxiliary drilling with a water jet...Difficulties with soft coal seams having a high gas content and high stress levels can be addressed by a technology of pressure relief and permeability increase.Slotting the seam by auxiliary drilling with a water jet that breaks the coal and slots the coal seam during the process of retreat drilling achieves pressure relief and permeability increase.Improved efficiency of gas extraction from a field test,high gas coal seam was observed.Investigating the theory of pressure relief and permeability increase required analyzing the characteristics of the double power slotting process and the effects of coal pressure relief and permeability increase.The influence of confining pressure on coal physical properties was examined by using FLAC3D software code to simulate changes of coal stress within the tool destruction area.The double power joint drilling method was modeled.Field experiments were performed and the effects are analyzed.This research shows that there is an ''islanding effect'' in front of the joint double power drill and slotting equipment.The failure strength of the coal seam is substantially reduced within the tool destruction area.Drilling depths are increased by 72% and the diameter of the borehole is increased by 30%.The amount of powdered coal extracted from the drill head increases by 17 times when using the new method.A 30 day total flow measurement from the double power drilled and slotted bores showed that gas extraction increased by 1.3 times compared to the standard drilled bores.Gas concentrations increased from 30% to 60% and were more stable so the overall extraction efficiency increased by a factor of two times.展开更多
The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the anal...The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.展开更多
In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure ...In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.展开更多
This paper report the synthesis and properties of a series of composite polymer electrolytes formed by dispersion of a non-ionic organic plastic material SN （succinonitrile） into poly（vinyl alcohol） complexed with...This paper report the synthesis and properties of a series of composite polymer electrolytes formed by dispersion of a non-ionic organic plastic material SN （succinonitrile） into poly（vinyl alcohol） complexed with magnesium acid salt. SEM （scanning electron microscope） images of different SN concentrations of films revealed that large open pore structure were also frequently present, when SN content increase up to 7.5 wt%. The addition of SN greatly enhances ionic conductivities of the electrolytes which is due to the high polarity and diffusivity of SN. The Mg2~ （magnesium ion） ion conduction is confirmed from impedance spectroscopy and transport number measurements. The highest conducting sample in the plasticized system was used to fabricate Mg （magnesium） battery with configuration Mg/SPE/TiO2. The discharge capacity of the fabricated battery was 17.5 mAh/gm.展开更多
In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixi...In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixing of the coolant. The communication of the outer strap affects the hydraulic force exerted by the spacer grid of the fuel assembly which could induce fuel assembly bow. In present study, in order to understand the influencing factors of hydraulic force exerted by the spacer grid, outer straps with various flow opening design features, different location and size are investigated by a commercially CFD （computational fluid dynamics） code, ANSYS CFX 12.1. Three dimensional rod bundles including the outer strap without and with different openings are modelled for simulation. The analysis results show that the openings on the spacer grid outer strap can reduce the lateral hydraulic loadings perpendicular to the centerline of the fuel rods exerted by the spacer grids obviously because of the pressures inside and outside the spacer grids being balanced. Besides, influences of the opening design features on the hydraulic force, resistance characteristics and lateral flow factor are investigated in details.展开更多
Amavadin is a natural vanadium compound that accumulates to high level in poisonous Amanita mushrooms. Recently, amavadin was found to have potential therapeutic effect in cancer treatment. However, its toxicity and t...Amavadin is a natural vanadium compound that accumulates to high level in poisonous Amanita mushrooms. Recently, amavadin was found to have potential therapeutic effect in cancer treatment. However, its toxicity and the possible mechanism of actions are still not clear. In this study, we investigated the toxic effects of amavadin on rat kidney mitochondria and the possible mechanism. We found that amavadin induced significantly permeability transition pore （PTP） opening in the mitochondria. Amavadin y inhibited the generation of reactive oxygen species （ROS） in succinate buffer, and at high concentration of 200 gM it increased the ROS generation in malate buffer. With the addition of rotenone, the ROS generation in malate buffer was strongly enhanced than that induced by amavadin alone, but remained unchanged in succinate buffer. Results from the present study suggest that amavadin act upon electron transport chain downstream of rotenone, and the ubiquinone binding site in complex I is the most possible binding site.展开更多
文摘AIM:To evaluate the main factors associated with mortality in patients undergoing surgery for perforated peptic ulcer referred to an academic department of general surgery in a large southern Italian city. METHODS:One hundred and forty-nine consecutive patients (M:F ratio=110:39,mean age 52 yrs,range 16-95) with peptic ulcer disease were investigated for clinical history (including age,sex,previous history of peptic ulcer,associated diseases,delayed abdominal surgery,ulcer site,operation type,shock on admission,postoperative general complications, and intra-abdominal and/or wound infections),serum analyses and radiological findings. RESULTS:The overall mortality rate was 4.0%.Among all factors,an age above 65 years,one or more associated diseases,delayed abdominal surgery,shock on admission, postoperative abdominal complications and/or wound infections,were significantly associated (x^2) with increased mortality in patients undergoing surgery (0.0001<P<0.03). CONCLUSION:Factors such as concomitant diseases,shock on admission,delayed surgery,and postoperative abdominal and wound infections are significantly associated with fatal outcomes and need careful evaluation within the general workup of patients admitted for perforated peptic ulcer.
基金Financial supports from the National Natural Science Foundation of China(No.20973022)
文摘Micrometer-scale macroporous aluminosilicate catalyst was prepared via the sol-gel process. Results of catalytic cracking of 1, 3, 5-triisopropylbenzene showed that the synthesized aluminosilicate catalyst exhibited much higher activity than traditional ZSM-5 zeolite under the same condition. It is worth mentioning that the polymer product selectivity of aluminosilicate was much lower than that of ZSM-5, which might be useful for implementing the catalytic cracking process. The unique structure of macroporous aluminosilicate with interconnected-macropores and continuous skeletons was believed to be responsible for its excellent catalytic activity and low polymer product selectivity. Detailed discussion on the reaction pathway was also conducted.
基金Supported by the National Natural Science Foundation of China(Grant No.21477022)
文摘Porous g-C3N4samples were obtained by simply calcining bulk g-C3N4in static air in a muffle oven.The photocatalytic performance of these samples was evaluated through the removal of aqueous organic dyes（methylene blue and methyl orange）and tetracycline hydrochloride under visible-light irradiation（λ〉420 nm）.Compared to bulk g-C3N4,porous g-C3N4exhibited much better capability for removing these contaminants,especially under visible-light irradiation,due to the enlarged specific surface area and more efficient separation of photogenerated charge carries.In particular,porous g-C3N4obtained by calcining bulk g-C3N4in air at 525℃ showed the highest visible-light-driven catalytic activity among these samples.Superoxide radical anions（·O2^-）were found to be the primary active species responsible for photodegradation.
基金Project(51304254) supported by the National Natural Science Foundation of ChinaProject(2013GK4064) supported by the Strategic Emerging Industry Program of the Ministry of Science and Technology of Hunan Province,China
文摘Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size;along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.
文摘Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3foamingagent and applying the powder compact melting process.To this end,the aluminum and CaCO3powder mixtures were coldcompacted into dense cylindrical precursors for foaming at specific temperatures under air atmosphere.The effects of severalparameters including precursor compaction pressure,foaming agent content as well as temperature and time of the foaming processon the cell microstructure,linear expansion,relative density and compressive properties were investigated.A uniform distribution ofcells with sizes less than100μm,which form semi open-cell structures with relative densities in the range of55.4%-84.4%,wasobtained.The elevation of compaction pressure between127-318MPa and blowing agent up to15%(mass fraction)led to anincrease in the linear expansion,compressive strength and densification strain.By varying the foaming temperature from800to1000°C,all of the investigated parameters increased except compressive strength and relative density.The results indicated theoptimal foaming temperature and time as900°C and10-25min,respectively.
基金supports provided by the National Key Basic Research and Development Program of China (No. 2011CB201205)the National Natural Science Foundation of China (No. 51074161)the Independent research of State Key Laboratory of Coal Resources and Mine Safety of China University of Mining & Technology (No. SKLCRSM08X03)
文摘Difficulties with soft coal seams having a high gas content and high stress levels can be addressed by a technology of pressure relief and permeability increase.Slotting the seam by auxiliary drilling with a water jet that breaks the coal and slots the coal seam during the process of retreat drilling achieves pressure relief and permeability increase.Improved efficiency of gas extraction from a field test,high gas coal seam was observed.Investigating the theory of pressure relief and permeability increase required analyzing the characteristics of the double power slotting process and the effects of coal pressure relief and permeability increase.The influence of confining pressure on coal physical properties was examined by using FLAC3D software code to simulate changes of coal stress within the tool destruction area.The double power joint drilling method was modeled.Field experiments were performed and the effects are analyzed.This research shows that there is an ''islanding effect'' in front of the joint double power drill and slotting equipment.The failure strength of the coal seam is substantially reduced within the tool destruction area.Drilling depths are increased by 72% and the diameter of the borehole is increased by 30%.The amount of powdered coal extracted from the drill head increases by 17 times when using the new method.A 30 day total flow measurement from the double power drilled and slotted bores showed that gas extraction increased by 1.3 times compared to the standard drilled bores.Gas concentrations increased from 30% to 60% and were more stable so the overall extraction efficiency increased by a factor of two times.
基金Project(2013CB036004)supported by National Basic Research Program of ChinaProjects(51178468,51378510)supported by National Natural Science Foundation of ChinaProject(CX2013B077)supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.
文摘In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.
文摘This paper report the synthesis and properties of a series of composite polymer electrolytes formed by dispersion of a non-ionic organic plastic material SN （succinonitrile） into poly（vinyl alcohol） complexed with magnesium acid salt. SEM （scanning electron microscope） images of different SN concentrations of films revealed that large open pore structure were also frequently present, when SN content increase up to 7.5 wt%. The addition of SN greatly enhances ionic conductivities of the electrolytes which is due to the high polarity and diffusivity of SN. The Mg2~ （magnesium ion） ion conduction is confirmed from impedance spectroscopy and transport number measurements. The highest conducting sample in the plasticized system was used to fabricate Mg （magnesium） battery with configuration Mg/SPE/TiO2. The discharge capacity of the fabricated battery was 17.5 mAh/gm.
文摘In advanced nuclear fuel design, the outer strap of a spacer grid plays an important role on fuel assembly mechanical and thermal-hydraulic performance, e.g., precluding the risk of hang-up and improvement on the mixing of the coolant. The communication of the outer strap affects the hydraulic force exerted by the spacer grid of the fuel assembly which could induce fuel assembly bow. In present study, in order to understand the influencing factors of hydraulic force exerted by the spacer grid, outer straps with various flow opening design features, different location and size are investigated by a commercially CFD （computational fluid dynamics） code, ANSYS CFX 12.1. Three dimensional rod bundles including the outer strap without and with different openings are modelled for simulation. The analysis results show that the openings on the spacer grid outer strap can reduce the lateral hydraulic loadings perpendicular to the centerline of the fuel rods exerted by the spacer grids obviously because of the pressures inside and outside the spacer grids being balanced. Besides, influences of the opening design features on the hydraulic force, resistance characteristics and lateral flow factor are investigated in details.
基金supported by the Innovative Experiment Project of Peking University Health Science Center, 2012
文摘Amavadin is a natural vanadium compound that accumulates to high level in poisonous Amanita mushrooms. Recently, amavadin was found to have potential therapeutic effect in cancer treatment. However, its toxicity and the possible mechanism of actions are still not clear. In this study, we investigated the toxic effects of amavadin on rat kidney mitochondria and the possible mechanism. We found that amavadin induced significantly permeability transition pore （PTP） opening in the mitochondria. Amavadin y inhibited the generation of reactive oxygen species （ROS） in succinate buffer, and at high concentration of 200 gM it increased the ROS generation in malate buffer. With the addition of rotenone, the ROS generation in malate buffer was strongly enhanced than that induced by amavadin alone, but remained unchanged in succinate buffer. Results from the present study suggest that amavadin act upon electron transport chain downstream of rotenone, and the ubiquinone binding site in complex I is the most possible binding site.
