BACKGROUND Of 25%of randomised controlled trials(RCTs)on interventions for inflammatory bowel disease(IBD)have no power calculation.AIM To systematically review RCTs reporting interventions for the management of IBD a...BACKGROUND Of 25%of randomised controlled trials(RCTs)on interventions for inflammatory bowel disease(IBD)have no power calculation.AIM To systematically review RCTs reporting interventions for the management of IBD and to produce data for minimum sample sizes that would achieve appropriate power using the actual clinical data.METHODS We included RCTs retrieved from Cochrane IBD specialised Trial register and CENTRAL investigating any form of therapy for either induction or maintenance of remission against control,placebo,or no intervention of IBD in patients of any age.The relevant data was extracted,and the studies were grouped according to the intervention used.We recalculated sample size and the achieved difference,as well as minimum sample sizes needed in the future.RESULTS A total of 105 trials were included.There was a large discrepancy between the estimated figure for the minimal clinically important difference used for the calculations(15%group differences observed vs 30%used for calculation)explaining substantial actual sample size deficits.The minimum sample sizes indicated for future trials based on the 25 years of trial data were calculated and grouped by the intervention.CONCLUSION A third of intervention studies in IBD within the last 25 years are underpowered,with large variations in the calculation of sample sizes.The authors present a sample size estimate resource constructed on the published evidence base for future researchers and key stakeholders within the IBD trial field.展开更多
The effect of grain size of CaCO3 and SiO2 on the formation of C3S under various conditions, such as rapid heating rate（800 ℃/min）, normal heating rate（30 ℃/min） and in the presence or absence of ZnO, was studie...The effect of grain size of CaCO3 and SiO2 on the formation of C3S under various conditions, such as rapid heating rate（800 ℃/min）, normal heating rate（30 ℃/min） and in the presence or absence of ZnO, was studied. The results show that the decomposition temperature of CaCO3, the temperature of appearance of liquid phase and the f-CaO content descend when the grain size of CaCO3 and SiO2 becomes smaller, which attributes to the reactive activity enhancement of powders due to the decrease of the particle size. When the grain size of CaCO3 and SiO2 is below 1 μm, the rate of the formation of C3S is greatly raised. A rapid sintering rate and the presence of ZnO have an important effect on the formation of C3S and can lower the temperature of the formation of C3S by about 50 ℃.展开更多
The internal length scale(ILS)is a dominant parameter in strain gradient plasticity(SGP)theories,which helps to successfully explain the size effect of metals at the microscale.However,the ILS is usually introduced in...The internal length scale(ILS)is a dominant parameter in strain gradient plasticity(SGP)theories,which helps to successfully explain the size effect of metals at the microscale.However,the ILS is usually introduced into strain gradient frameworks for dimensional consistency and is model-dependent.Even now,its physical meaning,connection with the microstructure of the material,and dependence on the strain level have not been thoroughly elucidated.In the current work,Aifantis'SGP model is reformulated by incorporating a recently proposed power-law relation for strain-dependent ILS.A further extension of Aifantis'SGP model by including the grain size effect is conducted according to the Hall-Petch formulation,and then the predictions are compared with torsion experiments of thin wires.It is revealed that the ILS depends on the sample size and grain size simultaneously;these dependencies are dominated by the dislocation spacing and can be well described through the strain hardenmg exponent.Furthermore,both the original and generalized Aifantis models provide larger estimated values for the ILS than Fleck-Hutchinson's theory.展开更多
The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-f...The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-ferrous metals which offers great potential application in aerospace, biomedical and chemical industries, because of its low density （4.5 g/cm^3）, excellent corrosion resistance, high strength, attractive fracture behaviour and high melting point （1678℃）. The preferred welding process for titanium alloy is frequent GTA welding due to its comparatively easier applicability and better economy. In the case of single pass （GTA） welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. Many considerations come into the picture and one needs to carefully balance various pulse current parameters to reach an optimum combination. Four factors, five level, central composite, rotatable design matrix were used to optimize the required number of experimental conditions. Mathematical models were developed to predict the fusion zone grain size using analysis of variance （ANOVA） and regression analysis. The developed models were optimized using the traditional Hooke and Jeeve＇s algorithm. Experimental results were provided to illustrate the proposed approach.展开更多
Authigenic carbonate samples were collected from the northern Okinawa Trough.Based on their carbon and oxygen isotopes,these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation ...Authigenic carbonate samples were collected from the northern Okinawa Trough.Based on their carbon and oxygen isotopes,these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane(AOM).Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized.In order to trace the variation and diagenetic information of these framboidal pyrites,their diameters and geochemical components were studied using an electron probe.The results showed that their diameters varied from 4μm to 17μm(n=60;geometric mean of 9.9μm)and were of a normal distribution.The diameters of single pyrite that formed the framboidal pyrites varied from 1μm to 2μm.The framboidal pyrites with diameters of 6–14μm accounted for~80%of the total.The geometric mean of 9.9μm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment(weakly oxygenated bottom waters).The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67,and the pyrite content of single framboid varied between 0%and 86.4%.Therefore,numerous pyrites were oxygenated to iron oxides or oxyhydroxides,and were retained as pseudomorphism pyrites.The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment;however,acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.展开更多
Samples of chromium doped ZnO were synthesized using co-precipitation technique at room temperature. Structural and optical properties of Cr doped ZnO samples were investigated by X-ray diffraction technique (XRD and ...Samples of chromium doped ZnO were synthesized using co-precipitation technique at room temperature. Structural and optical properties of Cr doped ZnO samples were investigated by X-ray diffraction technique (XRD and UV-Visible spectroscopy (UV-Vis) respectively. X-ray diffraction (XRD) patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions go to the regular Zn sites in the ZnO crystal structure. The lattice constants were calculated using X-ray diffraction data and it is found that lattice parameters decrease with increasing Cr content. The average grain size was calculated using Scherrer’s formula for pure and Cr doped ZnO samples and it is observed that grain size is in the range 11 to17 nm. Band gap of Zn1–xCrxO samples has been evaluated using UV-Vis spectrometer. It is found that the band gap decreases as Cr increases;it is attributed to the s-d and p interactions and the smaller average grain size. It indicates that incorporation of Cr ions into the ZnO matrix. The chemical species of the grown crystals were identified by Fourier transform infrared spectroscopy (FTIR). From FTIR spectra it is observed that IR peaks corresponding to the Zn-O bands. Such results are presented in this paper quantitatively and qualitatively.展开更多
文摘BACKGROUND Of 25%of randomised controlled trials(RCTs)on interventions for inflammatory bowel disease(IBD)have no power calculation.AIM To systematically review RCTs reporting interventions for the management of IBD and to produce data for minimum sample sizes that would achieve appropriate power using the actual clinical data.METHODS We included RCTs retrieved from Cochrane IBD specialised Trial register and CENTRAL investigating any form of therapy for either induction or maintenance of remission against control,placebo,or no intervention of IBD in patients of any age.The relevant data was extracted,and the studies were grouped according to the intervention used.We recalculated sample size and the achieved difference,as well as minimum sample sizes needed in the future.RESULTS A total of 105 trials were included.There was a large discrepancy between the estimated figure for the minimal clinically important difference used for the calculations(15%group differences observed vs 30%used for calculation)explaining substantial actual sample size deficits.The minimum sample sizes indicated for future trials based on the 25 years of trial data were calculated and grouped by the intervention.CONCLUSION A third of intervention studies in IBD within the last 25 years are underpowered,with large variations in the calculation of sample sizes.The authors present a sample size estimate resource constructed on the published evidence base for future researchers and key stakeholders within the IBD trial field.
基金the Science Fund Project(No.04JY029-060-1)Key Subject Construction Project of Material Science of Sichuan Province of China and National Support Project(No.2006BAF02A24)
文摘The effect of grain size of CaCO3 and SiO2 on the formation of C3S under various conditions, such as rapid heating rate（800 ℃/min）, normal heating rate（30 ℃/min） and in the presence or absence of ZnO, was studied. The results show that the decomposition temperature of CaCO3, the temperature of appearance of liquid phase and the f-CaO content descend when the grain size of CaCO3 and SiO2 becomes smaller, which attributes to the reactive activity enhancement of powders due to the decrease of the particle size. When the grain size of CaCO3 and SiO2 is below 1 μm, the rate of the formation of C3S is greatly raised. A rapid sintering rate and the presence of ZnO have an important effect on the formation of C3S and can lower the temperature of the formation of C3S by about 50 ℃.
文摘The internal length scale(ILS)is a dominant parameter in strain gradient plasticity(SGP)theories,which helps to successfully explain the size effect of metals at the microscale.However,the ILS is usually introduced into strain gradient frameworks for dimensional consistency and is model-dependent.Even now,its physical meaning,connection with the microstructure of the material,and dependence on the strain level have not been thoroughly elucidated.In the current work,Aifantis'SGP model is reformulated by incorporating a recently proposed power-law relation for strain-dependent ILS.A further extension of Aifantis'SGP model by including the grain size effect is conducted according to the Hall-Petch formulation,and then the predictions are compared with torsion experiments of thin wires.It is revealed that the ILS depends on the sample size and grain size simultaneously;these dependencies are dominated by the dislocation spacing and can be well described through the strain hardenmg exponent.Furthermore,both the original and generalized Aifantis models provide larger estimated values for the ILS than Fleck-Hutchinson's theory.
文摘The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-ferrous metals which offers great potential application in aerospace, biomedical and chemical industries, because of its low density （4.5 g/cm^3）, excellent corrosion resistance, high strength, attractive fracture behaviour and high melting point （1678℃）. The preferred welding process for titanium alloy is frequent GTA welding due to its comparatively easier applicability and better economy. In the case of single pass （GTA） welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. Many considerations come into the picture and one needs to carefully balance various pulse current parameters to reach an optimum combination. Four factors, five level, central composite, rotatable design matrix were used to optimize the required number of experimental conditions. Mathematical models were developed to predict the fusion zone grain size using analysis of variance （ANOVA） and regression analysis. The developed models were optimized using the traditional Hooke and Jeeve＇s algorithm. Experimental results were provided to illustrate the proposed approach.
基金The National Natural Science Foundation of China under contract Nos 41476050,41106047,and 41506073
文摘Authigenic carbonate samples were collected from the northern Okinawa Trough.Based on their carbon and oxygen isotopes,these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane(AOM).Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized.In order to trace the variation and diagenetic information of these framboidal pyrites,their diameters and geochemical components were studied using an electron probe.The results showed that their diameters varied from 4μm to 17μm(n=60;geometric mean of 9.9μm)and were of a normal distribution.The diameters of single pyrite that formed the framboidal pyrites varied from 1μm to 2μm.The framboidal pyrites with diameters of 6–14μm accounted for~80%of the total.The geometric mean of 9.9μm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment(weakly oxygenated bottom waters).The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67,and the pyrite content of single framboid varied between 0%and 86.4%.Therefore,numerous pyrites were oxygenated to iron oxides or oxyhydroxides,and were retained as pseudomorphism pyrites.The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment;however,acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.
文摘Samples of chromium doped ZnO were synthesized using co-precipitation technique at room temperature. Structural and optical properties of Cr doped ZnO samples were investigated by X-ray diffraction technique (XRD and UV-Visible spectroscopy (UV-Vis) respectively. X-ray diffraction (XRD) patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions go to the regular Zn sites in the ZnO crystal structure. The lattice constants were calculated using X-ray diffraction data and it is found that lattice parameters decrease with increasing Cr content. The average grain size was calculated using Scherrer’s formula for pure and Cr doped ZnO samples and it is observed that grain size is in the range 11 to17 nm. Band gap of Zn1–xCrxO samples has been evaluated using UV-Vis spectrometer. It is found that the band gap decreases as Cr increases;it is attributed to the s-d and p interactions and the smaller average grain size. It indicates that incorporation of Cr ions into the ZnO matrix. The chemical species of the grown crystals were identified by Fourier transform infrared spectroscopy (FTIR). From FTIR spectra it is observed that IR peaks corresponding to the Zn-O bands. Such results are presented in this paper quantitatively and qualitatively.
