The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments u...The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.展开更多
The considerable post-harvest losses (5% to 40% depending on storage time) due to the high water content level of the onion varieties in Senegal are the main cause of the problem of access to local onion all year roun...The considerable post-harvest losses (5% to 40% depending on storage time) due to the high water content level of the onion varieties in Senegal are the main cause of the problem of access to local onion all year round. Therefore, drying is one of the techniques that can be used to solve the problem of onion perishability. This study deals with the characterization of naturally convective kinetics drying of four onion varieties in relation to their maturity level. The experiment was carried out using the gravimetric method. The Welch and Turkey statistical tests display a significant difference between the effective diffusivity coefficients depending on the maturity level within each variety and across the four varieties. The effective diffusivity coefficients of the Galmi Violet, Safari, Gandiol F1 and Orient F1varieties range from 2.18 × 10−11 ± 2.69 × 10−12 to 1.32 × 10−10 ± 1.17 × 10−11 m2⋅s−1 at a maturity level less than 80%. When the maturity level is greater than 85%, the effective diffusivity coefficients range from 1.30 × 10−11 ± 1.24 × 10−12 to 8.05 × 10−11 ± 8.94 × 10−13 m2⋅s−1. As far as the activation energy is concerned, the study only reveals a significant difference between the varieties whatever the maturity level is. The Galmi Violet variety stands out with an average activation energy of 66.71 ± 0.12 KJ⋅mol−1 K−1 for the maturity level below 80% and 58.74 ± 0.11 KJ⋅mol−1 for the maturity level above 85%. For the three remaining varieties, the average activation energy ranges from 58.15 ± 0.19 to 59.12 ± 0.13 KJ⋅mol−1 for a maturity level less than 80% whereas the rates go from 47.63 ± 0.28 to 49.96 ± 0.77 KJ⋅mol−1 when the maturity level is greater than 85%. In summary, the higher the maturity level is, the lower the effective diffusivity coefficients will be. The same tendency was observed with the activation energy. The Galmi Violet variety represents the limitative one in case of the drying of the four varieties mix together.展开更多
The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the au...The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the austral summer, totals remained below average. Higher temperatures during austral winter and spring 2023, which affected most of Central South America, then aggravated drought conditions. This coincided with an intense El Niño and abnormally warm tropical North Atlantic Ocean temperatures since mid-2023. Decreased rainfall across the Amazon basin, negative anomalies in evapotranspiration (derived from latent heat) and soil moisture indicators, as well as increased temperatures during the dry-to-wet transition season, September-October-November (SON) 2023, combined to delay the onset of the wet season in the hydrological year 2023-24 by nearly two months and caused it to be uncharacteristically weak. SON 2023 registered a precipitation deficit of the order of 50 to 100 mm/month, and temperatures +3˚C higher than usual in Amazonia, leading to reduced evapotranspiration and soil moisture indicators. These processes, in turn, determined an exceptionally late onset and a lengthening of the dry season, affecting the 2023-2024 hydrological year. These changes were aggravated by a heat wave from June to December 2023. Drought-heat compound events and their consequences are the most critical natural threats to society. River levels reached record lows, or dried up completely, affecting Amazonian ecosystems. Increased risk of wildfires is another concern exacerbated by these conditions.展开更多
Synthetic dry adhesives inspired by the nano-and micro-scale hairs found on the feet of geckos and some spiders have beendeveloped for almost a decade. Elastomeric single level micro-scale mushroom shaped fibres are c...Synthetic dry adhesives inspired by the nano-and micro-scale hairs found on the feet of geckos and some spiders have beendeveloped for almost a decade. Elastomeric single level micro-scale mushroom shaped fibres are currently able to function evenbetter than natural dry adhesives on smooth surfaces under normal loading. However, the adhesion of these single level syntheticdry adhesives on rough surfaces is still not optimal because of the reduced contact surface area. In nature, contact area ismaximized by hierarchically structuring different scales of fibres capable of conforming surface roughness. In this paper, weadapt the nature’s solution arid propose a novel dual-level hierarchical adhesive design using Polydimethylsiloxane (PDMS),which is tested under peel loading at different orientations. A negative macro-scale mold is manufactured by using a laser cutterto define holes in a Poly(methyl methacrylate) (PMMA) plate. After casting PDMS macro-scale fibres by using the obtainedPMMA mold, a previously prepared micro-fibre adhesive is bonded to the macro-scale fibre substrate. Once the bondingpolymer is cured, the micro-fibre adhesive is cut to form macro scale mushroom caps. Each macro-fibre of the resulting hierarchicaladhesive is able to conform to loads applied in different directions. The dual-level structure enhances the peel strengthon smooth surfaces compared to a single-level dry adhesive, but also weakens the shear strength of the adhesive for a given areain contact. The adhesive appears to be very performance sensitive to the specific size of the fibre tips, and experiments indicatethat designing hierarchical structures is not as simple as placing multiple scales of fibres on top of one another, but can requiresignificant design optimization to enhance the contact mechanics and adhesion strength.展开更多
Phosphorus （P） and zinc （Zn） deficiencies are the major problems that decrease crop productivity under rice-wheat cropping system. Field experiments were conducted to investigate impacts of P （0, 40, 80 and 120 k...Phosphorus （P） and zinc （Zn） deficiencies are the major problems that decrease crop productivity under rice-wheat cropping system. Field experiments were conducted to investigate impacts of P （0, 40, 80 and 120 kg/hm^2） and Zn levels （0, 5, 10 and 15 kg/hm^2） on dry matter （DM） accumulation and partitioning, and harvest index of three rice genotypes ＇fine （Bamati-385） vs. coarse （F-Malakand and Pukhraj）＇ at various growth stages （tiliering, heading and physiological maturity）. The experiments were conducted at farmers＇ field at Batkhela in Northwestern Pakistan for two years in summer 2011 and 2012. The two year pooled data reveled that there were no differences in percent of DM partitioning into leaves and culms with application of different P and Zn levels, and genotypes at tillering. The highest P level （120 kg/hm^2） partitioned more DM into panicles than leaves and culms at heading and physiological maturity stages. The highest Zn level （15 kg/hm^2） accumulated more DM and partitioned more DM into panicles than leaves and culms at heading and physiological maturity stages. The hybrid rice （Pukhraj） produced and partitioned more DM into panicles than F-Malakand and Bamati-385 at heading and physiological maturity stages. Higher DM accumulation and greater amounts of partitioning into panicles at heading and physiological maturity stages was noticed with increase in P and Zn levels, and the increase was significantly higher in the coarse rice genotypes than fine. We concluded that the growing hybrid rice with application of 120 kg/hm^2 P ＋ 15 kg/hm^2 Zn not only increases total DM accumulation and partitioned greater amounts into the reproductive plant parts （panicles） but also results in higher harvest index.展开更多
Thirty healthy Holstein dairy cows in the dry period were randomly divided into three groups and fed diets with different net energy for lactation (group A: 1.2 Mcal/kg DM, group B: 1.3 Mcal/kg DM, and group C: 1.4 Mc...Thirty healthy Holstein dairy cows in the dry period were randomly divided into three groups and fed diets with different net energy for lactation (group A: 1.2 Mcal/kg DM, group B: 1.3 Mcal/kg DM, and group C: 1.4 Mcal/kg DM) for 8 weeks prepartum. Thereafter, dairy cows were fed a diet of the same formulation (1.66 Mcal/kg DM) for 12 weeks postpartum. The effects of different dietary energy densities in the dry period on postpartum performance and metabolic parameters of dairy cows were observed. Milk yield was reduced by 14.5% in the low-energy diet group;however, there were no differences in milk composition between the three groups. Postpartum plasma β-hydroxybutyrate, non-esterified fatty acid, growth hormone, and glucagon levels were significantly decreased whereas leptin and neuropeptide levels were elevated in the low-energy diet group. Moreover, body fat mobilization was attenuated, and the decline in postpartum body condition was reduced in the low-energy diet group, thus effectively reducing the postpartum negative energy balance.展开更多
基金supported by the National Basic Research (973) Program of China (Grant No.2015CB452804)
文摘The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.
文摘The considerable post-harvest losses (5% to 40% depending on storage time) due to the high water content level of the onion varieties in Senegal are the main cause of the problem of access to local onion all year round. Therefore, drying is one of the techniques that can be used to solve the problem of onion perishability. This study deals with the characterization of naturally convective kinetics drying of four onion varieties in relation to their maturity level. The experiment was carried out using the gravimetric method. The Welch and Turkey statistical tests display a significant difference between the effective diffusivity coefficients depending on the maturity level within each variety and across the four varieties. The effective diffusivity coefficients of the Galmi Violet, Safari, Gandiol F1 and Orient F1varieties range from 2.18 × 10−11 ± 2.69 × 10−12 to 1.32 × 10−10 ± 1.17 × 10−11 m2⋅s−1 at a maturity level less than 80%. When the maturity level is greater than 85%, the effective diffusivity coefficients range from 1.30 × 10−11 ± 1.24 × 10−12 to 8.05 × 10−11 ± 8.94 × 10−13 m2⋅s−1. As far as the activation energy is concerned, the study only reveals a significant difference between the varieties whatever the maturity level is. The Galmi Violet variety stands out with an average activation energy of 66.71 ± 0.12 KJ⋅mol−1 K−1 for the maturity level below 80% and 58.74 ± 0.11 KJ⋅mol−1 for the maturity level above 85%. For the three remaining varieties, the average activation energy ranges from 58.15 ± 0.19 to 59.12 ± 0.13 KJ⋅mol−1 for a maturity level less than 80% whereas the rates go from 47.63 ± 0.28 to 49.96 ± 0.77 KJ⋅mol−1 when the maturity level is greater than 85%. In summary, the higher the maturity level is, the lower the effective diffusivity coefficients will be. The same tendency was observed with the activation energy. The Galmi Violet variety represents the limitative one in case of the drying of the four varieties mix together.
文摘The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the austral summer, totals remained below average. Higher temperatures during austral winter and spring 2023, which affected most of Central South America, then aggravated drought conditions. This coincided with an intense El Niño and abnormally warm tropical North Atlantic Ocean temperatures since mid-2023. Decreased rainfall across the Amazon basin, negative anomalies in evapotranspiration (derived from latent heat) and soil moisture indicators, as well as increased temperatures during the dry-to-wet transition season, September-October-November (SON) 2023, combined to delay the onset of the wet season in the hydrological year 2023-24 by nearly two months and caused it to be uncharacteristically weak. SON 2023 registered a precipitation deficit of the order of 50 to 100 mm/month, and temperatures +3˚C higher than usual in Amazonia, leading to reduced evapotranspiration and soil moisture indicators. These processes, in turn, determined an exceptionally late onset and a lengthening of the dry season, affecting the 2023-2024 hydrological year. These changes were aggravated by a heat wave from June to December 2023. Drought-heat compound events and their consequences are the most critical natural threats to society. River levels reached record lows, or dried up completely, affecting Amazonian ecosystems. Increased risk of wildfires is another concern exacerbated by these conditions.
基金Finallcial support was provided by the Natural Sciences and Engineering Research Council of Canada(NSERC)the European Space Agency(ESA)
文摘Synthetic dry adhesives inspired by the nano-and micro-scale hairs found on the feet of geckos and some spiders have beendeveloped for almost a decade. Elastomeric single level micro-scale mushroom shaped fibres are currently able to function evenbetter than natural dry adhesives on smooth surfaces under normal loading. However, the adhesion of these single level syntheticdry adhesives on rough surfaces is still not optimal because of the reduced contact surface area. In nature, contact area ismaximized by hierarchically structuring different scales of fibres capable of conforming surface roughness. In this paper, weadapt the nature’s solution arid propose a novel dual-level hierarchical adhesive design using Polydimethylsiloxane (PDMS),which is tested under peel loading at different orientations. A negative macro-scale mold is manufactured by using a laser cutterto define holes in a Poly(methyl methacrylate) (PMMA) plate. After casting PDMS macro-scale fibres by using the obtainedPMMA mold, a previously prepared micro-fibre adhesive is bonded to the macro-scale fibre substrate. Once the bondingpolymer is cured, the micro-fibre adhesive is cut to form macro scale mushroom caps. Each macro-fibre of the resulting hierarchicaladhesive is able to conform to loads applied in different directions. The dual-level structure enhances the peel strengthon smooth surfaces compared to a single-level dry adhesive, but also weakens the shear strength of the adhesive for a given areain contact. The adhesive appears to be very performance sensitive to the specific size of the fibre tips, and experiments indicatethat designing hierarchical structures is not as simple as placing multiple scales of fibres on top of one another, but can requiresignificant design optimization to enhance the contact mechanics and adhesion strength.
文摘Phosphorus （P） and zinc （Zn） deficiencies are the major problems that decrease crop productivity under rice-wheat cropping system. Field experiments were conducted to investigate impacts of P （0, 40, 80 and 120 kg/hm^2） and Zn levels （0, 5, 10 and 15 kg/hm^2） on dry matter （DM） accumulation and partitioning, and harvest index of three rice genotypes ＇fine （Bamati-385） vs. coarse （F-Malakand and Pukhraj）＇ at various growth stages （tiliering, heading and physiological maturity）. The experiments were conducted at farmers＇ field at Batkhela in Northwestern Pakistan for two years in summer 2011 and 2012. The two year pooled data reveled that there were no differences in percent of DM partitioning into leaves and culms with application of different P and Zn levels, and genotypes at tillering. The highest P level （120 kg/hm^2） partitioned more DM into panicles than leaves and culms at heading and physiological maturity stages. The highest Zn level （15 kg/hm^2） accumulated more DM and partitioned more DM into panicles than leaves and culms at heading and physiological maturity stages. The hybrid rice （Pukhraj） produced and partitioned more DM into panicles than F-Malakand and Bamati-385 at heading and physiological maturity stages. Higher DM accumulation and greater amounts of partitioning into panicles at heading and physiological maturity stages was noticed with increase in P and Zn levels, and the increase was significantly higher in the coarse rice genotypes than fine. We concluded that the growing hybrid rice with application of 120 kg/hm^2 P ＋ 15 kg/hm^2 Zn not only increases total DM accumulation and partitioned greater amounts into the reproductive plant parts （panicles） but also results in higher harvest index.
文摘Thirty healthy Holstein dairy cows in the dry period were randomly divided into three groups and fed diets with different net energy for lactation (group A: 1.2 Mcal/kg DM, group B: 1.3 Mcal/kg DM, and group C: 1.4 Mcal/kg DM) for 8 weeks prepartum. Thereafter, dairy cows were fed a diet of the same formulation (1.66 Mcal/kg DM) for 12 weeks postpartum. The effects of different dietary energy densities in the dry period on postpartum performance and metabolic parameters of dairy cows were observed. Milk yield was reduced by 14.5% in the low-energy diet group;however, there were no differences in milk composition between the three groups. Postpartum plasma β-hydroxybutyrate, non-esterified fatty acid, growth hormone, and glucagon levels were significantly decreased whereas leptin and neuropeptide levels were elevated in the low-energy diet group. Moreover, body fat mobilization was attenuated, and the decline in postpartum body condition was reduced in the low-energy diet group, thus effectively reducing the postpartum negative energy balance.
