Influences of admixtures on the workability and strength of high performance concrete （HPC） are in- vestigated. The types of investigated admixtures include naphthalene series high range water reducing agent, polyca...Influences of admixtures on the workability and strength of high performance concrete （HPC） are in- vestigated. The types of investigated admixtures include naphthalene series high range water reducing agent, polycarboxlic series high range water reduce agent and sodium sulfate hardening accelerating agent. Two kinds of curing condition, namely steam curing condition and standard curing condition, are adopted. The result shows that HPC, added with polycarboxlic series of high performance water reducer, has high workability and strength, while sodium sulfate accelerating agent causes poor workability and low strength. Thus for vapor-cured HPC and its formulations, naphthalene series high range water reducing agent with less sodium sulfate should be given pri- ority. Therefore, the differences of curing conditions should be considered when selecting HPC admixtures.展开更多
The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse san...The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.展开更多
Objective: To study the changes between cerebral oxygen (O 2) delivery and uptake in dogs resuscitated under normotension or hypertension for 4 h. Methods: The model of ventricular fibrillation of 8 min in 12 dogs was...Objective: To study the changes between cerebral oxygen (O 2) delivery and uptake in dogs resuscitated under normotension or hypertension for 4 h. Methods: The model of ventricular fibrillation of 8 min in 12 dogs was made, followed by open cardiopulmonary resuscitation, reperfusion with normal or high mean arterial pressure (MAP), and controlled ventilation to 4 h. Animals were randomly assigned into Group NT (normotensive reperfusion, n=6) and Group HT (hypertensive reperfusion, n=6). Cerebral arteriovenous (sagittal sinus) O 2 content difference (Ca-ssO 2) and venous (sagittal sinus) PO 2 (PssO 2) were determined before cardiac arrest (CA) and 30, 60, 120, and 240 min after CA. Results: In Group NT, Ca-ssO 2 was lower at 30 min (P<0.05) but higher at 240 min (P<0.01) after CA than that before CA. In Group HT, Ca-ssO 2 was not significantly different from that in Group NT before CA but was lower than that in Group NT at 30 min after CA (P<0.01). Ca-ssO 2 was not significantly different in Group NT and HT thereafter. In both groups, PssO 2 was both higher at 30 min after reperfusion (P<0.01) and at 240 min after reperfusion lower (P<0.05) than those before CA .At 30 min after reperfusion, PssO 2 was higher (P<0.01) in Group HT than that in Group NT, with insignificant difference between two groups. Conclusion: Cerebral O 2 delivery and uptake are mismatched after CA and resuscitation. Hypertensive reperfusion improves oxygen delivery to the brain early after CA.展开更多
Objective To investigate the effect and significance of cardiomyocyte apoptosis and cardio-myocyte proliferation on cardiac hypertrophy by observing the dynamic changes of them during the development ofcardiac hypertr...Objective To investigate the effect and significance of cardiomyocyte apoptosis and cardio-myocyte proliferation on cardiac hypertrophy by observing the dynamic changes of them during the development ofcardiac hypertrophy in spontaneously hypertensive rats (SHR). Methods Hearts were excised from SHR andWistar-Kyoto rats(WKY) at different ages. Cardiac hypertrophic index (CHI) was calculated as the radio of heartweight to body weight; Cardiomyocyte apoptosis was identified by in situ TUT-mediated dUTP nick end labeling( TUNEL) ; Localization and expression of proliferating cell nuclear antigen (PCNA) were examined by immunohis-tochemistry. Results Compared with age-matched WKY, CHI in SHR was significantly increased at 12 weeksold and 24 weeks old (3.604 ±0.089 vs 2. 997 ±0.166, P <0. 01; 4. 156 ±0.385 vs 3. 119 ±0.208, P <0. 01) ,and CHI in SHR was increased little by little with the age increasing and attained platform since 20 weeks old. Incontrast with age-matched WKY, cardiomyocyte apoptotic index (APOI) in SHR at 12 weeks was not increased sig-nificantly (4. 248 ± 1. 592 vs 3. 678 ± 0. 856, P >0. 05) , but decreased markedly when their age were 24 weeks(3. 207 ± 1. 794 vs 5. 494 ± 1. 372, P<0.05); APOI in SHR at 12 weeks old, 16 weeks old, 20 weeks old and 24weeks old were 4. 248 ±1. 592, 5.707 ±1. 322, 7. 436 ± 1. 128, 3. 207 ± 1. 794, respectively. On the other hand,APOI in SHR from 12 weeks old to 20 weeks old increased gradually, and attained peak at 20 weeks old, but de-creased markedly after 20 weeks old (P <0. 01). Compared with age-matched WKY, the rate of cardiomyocyte PC-NA positive labeling (PCNAR) in SHR at 12 weeks old and 24 weeks old didn’ t have obvious difference. Conclu-sion Imbalance of cardiomyocyte apoptosis and cardiomyocyte proliferation existed during the development of car-diac hypertrophy in spontaneously hypertensive rats.展开更多
The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to gr...The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to grind these constituents. The program was arranged to determine the effect of cycles＇ number, superplasticizer type and dosage, silica fume dosage and condition, and gravel to sand ratio on properties of concrete. Naphthalene sulphonated formaldehyde （NSF） superplasticizers in the forms of liquid and powdered were used. Silica fume may be grinded with the other constituents （grinded）, or added to concrete mixer （normal）. The water/cement （w/c） ratio varied from 0.35 to 0.55 to achieve a constant slump （50-90 mm）. Slumps, bulk density and mechanical properties of concrete were measured. Scanning electron microscope （SEM） was also used to show the differences between traditional and superplasticized concrete. The results showed that grinding the mixture enhances fresh and hardened concrete properties. It is also observed that grinding the mixture for 500 cycles is more effective than other numbers of grinding. In addition, superplasticized concrete exhibits compressive strength higher than traditional one at varied ages. Moreover, using powdered superplasticizer has a remarkable effect on enhancing concrete properties rather than using it in a liquid form. A dosage of 1% by weight of cement gave the highest results of compressive strength. Silica fume has an essential role in improving concrete strength and durability since it acts as very efficient void filler and as a super pozzolana. SEM observations illustrate that grinding the mixture enhances transition zone （TZ） properties and makes it denser. On the other hand, grinded mixture can be packaged in bags and transported for use in crowded cities, and so, enhances quality control, since the only requirement to obtain superplasticized concrete is to add water and gravel. This technique has many benefits such as; saving cement, labor and noise, high quality control, and enhancing concrete permeability and durability. There are many fields of application of superplasticized concrete such as; in locations which are not easily accessible by ordinary concreting techniques, in repairing and strengthen, thin coating, and for small projects when ready mix supply is not feasible.展开更多
基金Supported by the National Basic Research Programe of China("973"Program)(2009CB623203)the Construction Department of Zhejiang Province Foundation(1006)+1 种基金the Education Department of Zhejiang Province Foundation(Y200909029)the Doctoral Innovation Foundation of Nanjing University of Aeronautics andAstronautics(BCXJ07-04)~~
文摘Influences of admixtures on the workability and strength of high performance concrete （HPC） are in- vestigated. The types of investigated admixtures include naphthalene series high range water reducing agent, polycarboxlic series high range water reduce agent and sodium sulfate hardening accelerating agent. Two kinds of curing condition, namely steam curing condition and standard curing condition, are adopted. The result shows that HPC, added with polycarboxlic series of high performance water reducer, has high workability and strength, while sodium sulfate accelerating agent causes poor workability and low strength. Thus for vapor-cured HPC and its formulations, naphthalene series high range water reducing agent with less sodium sulfate should be given pri- ority. Therefore, the differences of curing conditions should be considered when selecting HPC admixtures.
文摘The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.
文摘Objective: To study the changes between cerebral oxygen (O 2) delivery and uptake in dogs resuscitated under normotension or hypertension for 4 h. Methods: The model of ventricular fibrillation of 8 min in 12 dogs was made, followed by open cardiopulmonary resuscitation, reperfusion with normal or high mean arterial pressure (MAP), and controlled ventilation to 4 h. Animals were randomly assigned into Group NT (normotensive reperfusion, n=6) and Group HT (hypertensive reperfusion, n=6). Cerebral arteriovenous (sagittal sinus) O 2 content difference (Ca-ssO 2) and venous (sagittal sinus) PO 2 (PssO 2) were determined before cardiac arrest (CA) and 30, 60, 120, and 240 min after CA. Results: In Group NT, Ca-ssO 2 was lower at 30 min (P<0.05) but higher at 240 min (P<0.01) after CA than that before CA. In Group HT, Ca-ssO 2 was not significantly different from that in Group NT before CA but was lower than that in Group NT at 30 min after CA (P<0.01). Ca-ssO 2 was not significantly different in Group NT and HT thereafter. In both groups, PssO 2 was both higher at 30 min after reperfusion (P<0.01) and at 240 min after reperfusion lower (P<0.05) than those before CA .At 30 min after reperfusion, PssO 2 was higher (P<0.01) in Group HT than that in Group NT, with insignificant difference between two groups. Conclusion: Cerebral O 2 delivery and uptake are mismatched after CA and resuscitation. Hypertensive reperfusion improves oxygen delivery to the brain early after CA.
基金Supported by Shanghai Science and Technology Committee (024119018)
文摘Objective To investigate the effect and significance of cardiomyocyte apoptosis and cardio-myocyte proliferation on cardiac hypertrophy by observing the dynamic changes of them during the development ofcardiac hypertrophy in spontaneously hypertensive rats (SHR). Methods Hearts were excised from SHR andWistar-Kyoto rats(WKY) at different ages. Cardiac hypertrophic index (CHI) was calculated as the radio of heartweight to body weight; Cardiomyocyte apoptosis was identified by in situ TUT-mediated dUTP nick end labeling( TUNEL) ; Localization and expression of proliferating cell nuclear antigen (PCNA) were examined by immunohis-tochemistry. Results Compared with age-matched WKY, CHI in SHR was significantly increased at 12 weeksold and 24 weeks old (3.604 ±0.089 vs 2. 997 ±0.166, P <0. 01; 4. 156 ±0.385 vs 3. 119 ±0.208, P <0. 01) ,and CHI in SHR was increased little by little with the age increasing and attained platform since 20 weeks old. Incontrast with age-matched WKY, cardiomyocyte apoptotic index (APOI) in SHR at 12 weeks was not increased sig-nificantly (4. 248 ± 1. 592 vs 3. 678 ± 0. 856, P >0. 05) , but decreased markedly when their age were 24 weeks(3. 207 ± 1. 794 vs 5. 494 ± 1. 372, P<0.05); APOI in SHR at 12 weeks old, 16 weeks old, 20 weeks old and 24weeks old were 4. 248 ±1. 592, 5.707 ±1. 322, 7. 436 ± 1. 128, 3. 207 ± 1. 794, respectively. On the other hand,APOI in SHR from 12 weeks old to 20 weeks old increased gradually, and attained peak at 20 weeks old, but de-creased markedly after 20 weeks old (P <0. 01). Compared with age-matched WKY, the rate of cardiomyocyte PC-NA positive labeling (PCNAR) in SHR at 12 weeks old and 24 weeks old didn’ t have obvious difference. Conclu-sion Imbalance of cardiomyocyte apoptosis and cardiomyocyte proliferation existed during the development of car-diac hypertrophy in spontaneously hypertensive rats.
文摘The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to grind these constituents. The program was arranged to determine the effect of cycles＇ number, superplasticizer type and dosage, silica fume dosage and condition, and gravel to sand ratio on properties of concrete. Naphthalene sulphonated formaldehyde （NSF） superplasticizers in the forms of liquid and powdered were used. Silica fume may be grinded with the other constituents （grinded）, or added to concrete mixer （normal）. The water/cement （w/c） ratio varied from 0.35 to 0.55 to achieve a constant slump （50-90 mm）. Slumps, bulk density and mechanical properties of concrete were measured. Scanning electron microscope （SEM） was also used to show the differences between traditional and superplasticized concrete. The results showed that grinding the mixture enhances fresh and hardened concrete properties. It is also observed that grinding the mixture for 500 cycles is more effective than other numbers of grinding. In addition, superplasticized concrete exhibits compressive strength higher than traditional one at varied ages. Moreover, using powdered superplasticizer has a remarkable effect on enhancing concrete properties rather than using it in a liquid form. A dosage of 1% by weight of cement gave the highest results of compressive strength. Silica fume has an essential role in improving concrete strength and durability since it acts as very efficient void filler and as a super pozzolana. SEM observations illustrate that grinding the mixture enhances transition zone （TZ） properties and makes it denser. On the other hand, grinded mixture can be packaged in bags and transported for use in crowded cities, and so, enhances quality control, since the only requirement to obtain superplasticized concrete is to add water and gravel. This technique has many benefits such as; saving cement, labor and noise, high quality control, and enhancing concrete permeability and durability. There are many fields of application of superplasticized concrete such as; in locations which are not easily accessible by ordinary concreting techniques, in repairing and strengthen, thin coating, and for small projects when ready mix supply is not feasible.
