Non-vacuum storage condition has a great impact on the explosion characteristics of aluminum powders. In this paper, vacuum-packed flake and globular aluminum powders stored in a dryer after opening the vacuum package...Non-vacuum storage condition has a great impact on the explosion characteristics of aluminum powders. In this paper, vacuum-packed flake and globular aluminum powders stored in a dryer after opening the vacuum package are selected as the experimental samples, and a 20 L spherical explosion device is chosen to test the minimum explosible concentration (MEC) values of aluminum dusts under different storage time. The results show that the MEC values of two types of unoxidized aluminum powders are 30 g/m^3. The MEC values of flake and globular aluminum powders firstly go up with the increase of storage time in the dryer and then reach the maximum values of 50 g/m^3 and 60 g/m^3 at respective storage time until finally they stabilize gradually. The main reason is that the oxidation rate is faster owing to the bigger specific surface area of globular aluminum powders. Hence, the storage time has more significant effect on the MEC of globular aluminum powder than that of flake aluminum powder. After a period of time, the outer surface is oxidized to generate a layer of film, which prevents the further oxidation of aluminum powder, resulting in the temporary stability of MEC.展开更多
In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation cou...In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.展开更多
To evaluate the effect of intrathecal administration of glycine on the minimum alveolar concentration （MAC） of isoflurane in rats. Methods Intrathecal catheters were implanted in 40 adult male rats anesthetized wit...To evaluate the effect of intrathecal administration of glycine on the minimum alveolar concentration （MAC） of isoflurane in rats. Methods Intrathecal catheters were implanted in 40 adult male rats anesthetized with isoflurane. Baseline MAC of isoflurane was measured during the infusion of artificial cerebrospinal fluid （CSF） alone. Subsequently, 10, 40, 80, 160, and 300 mmol/L of glycine dissolved in artificial CSF were infused for two hours at the same rate as under control conditions, and MAC for isoflurane was re-determined. Results Intrathecal administration of glycine produced a significant, dose-dependent decrease in MAC for isoflurane （up to -65.2% ± 16. 2% ）. Conclusions Intrathecal administration of glycine decreases anesthetic requirement. This result supports the idea that glycine receptors may be important to the immobilizing effect of anesthetics that enhance glycine receptor function such as isoflurane.展开更多
AIM： To investigate the increasing the susceptibility pylon） to metronidazole. mechanisms of aspirin of Helicobacter pylori （H METHODS： Hpylori reference strain 26695 and two metronidazole-resistant isolates of H ...AIM： To investigate the increasing the susceptibility pylon） to metronidazole. mechanisms of aspirin of Helicobacter pylori （H METHODS： Hpylori reference strain 26695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin （1 mmol/L）. The rdxA gene of Hpylori was amplified by PCR and sequenced. The permeability of Hpylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-^3H]-tetracycline. The outer membrane proteins （OMPs） of Hpylori 26695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins （hopA, hopB, hopC, hopD and hopE） and the putative RND efflux system （hefABC） of H pylori were analyzed using real-time quantitative PCR. RESULTS： The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin.The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and herA, hefB, hefC of H pylori did not change when treated with aspirin. CONCLUSION： Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of Hpylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression.展开更多
Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and ...Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and community-acquired infections ranging from relatively minor skin and soft tissue infections to life-threateningsystemic infections.The increasing incidence of methicillin-resistant strains has granted an increasing use of vancomycin causing a covert progressive increase of its minimum inhibitory concentration(MIC)(dubbed the MIC "creep").In this way,the emergence of vancomycinintermediate SA(VISA) strains and heteroresistantVISA has raised concern for the scarcity of alternative treatment options.Equally alarming,though fortunately less frequent,is the emergence of vancomycin-resistant SA.These strains show different mechanisms of resistance but have similar problems in terms of therapeutic approach.Ultimately,various debate issues have arisen regarding the emergence of SA strains with a minimum inhibitory concentration sitting on the superior limit of the sensitivity range(i.e.,MIC = 2 μg/mL).These strains have shown certain resilience to vancomycin and a different clinical behaviour regardless of vancomycin use,both in methicillin-resistant SA and in methicillin-sensitive SA.The aim of this text is to revise the clinical impact and consequences of the emergence of reduced vancomycin susceptibility SA strains,and the different optimal treatment options known.展开更多
文摘Non-vacuum storage condition has a great impact on the explosion characteristics of aluminum powders. In this paper, vacuum-packed flake and globular aluminum powders stored in a dryer after opening the vacuum package are selected as the experimental samples, and a 20 L spherical explosion device is chosen to test the minimum explosible concentration (MEC) values of aluminum dusts under different storage time. The results show that the MEC values of two types of unoxidized aluminum powders are 30 g/m^3. The MEC values of flake and globular aluminum powders firstly go up with the increase of storage time in the dryer and then reach the maximum values of 50 g/m^3 and 60 g/m^3 at respective storage time until finally they stabilize gradually. The main reason is that the oxidation rate is faster owing to the bigger specific surface area of globular aluminum powders. Hence, the storage time has more significant effect on the MEC of globular aluminum powder than that of flake aluminum powder. After a period of time, the outer surface is oxidized to generate a layer of film, which prevents the further oxidation of aluminum powder, resulting in the temporary stability of MEC.
基金This work was supported by the Sichuan Science and Technology Program(No.2020JDRC0108)the National Science Foundation of China(Nos.41774147 and 41774190).
文摘In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.
文摘To evaluate the effect of intrathecal administration of glycine on the minimum alveolar concentration （MAC） of isoflurane in rats. Methods Intrathecal catheters were implanted in 40 adult male rats anesthetized with isoflurane. Baseline MAC of isoflurane was measured during the infusion of artificial cerebrospinal fluid （CSF） alone. Subsequently, 10, 40, 80, 160, and 300 mmol/L of glycine dissolved in artificial CSF were infused for two hours at the same rate as under control conditions, and MAC for isoflurane was re-determined. Results Intrathecal administration of glycine produced a significant, dose-dependent decrease in MAC for isoflurane （up to -65.2% ± 16. 2% ）. Conclusions Intrathecal administration of glycine decreases anesthetic requirement. This result supports the idea that glycine receptors may be important to the immobilizing effect of anesthetics that enhance glycine receptor function such as isoflurane.
基金Supported by The National Natural Science Foundation of China, No. 30470777
文摘AIM： To investigate the increasing the susceptibility pylon） to metronidazole. mechanisms of aspirin of Helicobacter pylori （H METHODS： Hpylori reference strain 26695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin （1 mmol/L）. The rdxA gene of Hpylori was amplified by PCR and sequenced. The permeability of Hpylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-^3H]-tetracycline. The outer membrane proteins （OMPs） of Hpylori 26695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins （hopA, hopB, hopC, hopD and hopE） and the putative RND efflux system （hefABC） of H pylori were analyzed using real-time quantitative PCR. RESULTS： The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin.The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and herA, hefB, hefC of H pylori did not change when treated with aspirin. CONCLUSION： Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of Hpylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression.
文摘Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and community-acquired infections ranging from relatively minor skin and soft tissue infections to life-threateningsystemic infections.The increasing incidence of methicillin-resistant strains has granted an increasing use of vancomycin causing a covert progressive increase of its minimum inhibitory concentration(MIC)(dubbed the MIC "creep").In this way,the emergence of vancomycinintermediate SA(VISA) strains and heteroresistantVISA has raised concern for the scarcity of alternative treatment options.Equally alarming,though fortunately less frequent,is the emergence of vancomycin-resistant SA.These strains show different mechanisms of resistance but have similar problems in terms of therapeutic approach.Ultimately,various debate issues have arisen regarding the emergence of SA strains with a minimum inhibitory concentration sitting on the superior limit of the sensitivity range(i.e.,MIC = 2 μg/mL).These strains have shown certain resilience to vancomycin and a different clinical behaviour regardless of vancomycin use,both in methicillin-resistant SA and in methicillin-sensitive SA.The aim of this text is to revise the clinical impact and consequences of the emergence of reduced vancomycin susceptibility SA strains,and the different optimal treatment options known.
