The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,sa...The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,saline aquifers,depleted oil or gas reservoirs,and unmineable coal seams.Furthermore,carbon capture,utilization,and storage(CCUS)methods are an acceptable and sustainable technology to meet the goals of the Paris Agreement,in which Kazakhstan is expected to reduce greenhouse gas emissions by 25%compared with the 1990 level.Unmineable coal seams are an attractive option among all geostorage solutions,as CO_(2)sequestration in coal comes with an income stream via enhanced coalbed methane(ECBM)recovery.This paper identifies four carboniferous coal formations,namely Karagandy,Teniz-Korzhinkol,Ekibustuz,and Chu coal basins of Kazakhstan,as CO_(2)geostorage solutions for their unmineable coal seams.The ideal depth of CO_(2)storage is identified as 800 m to ensure the supercritical state of CO_(2).However,the Ekibustuz coal basin fails to meet the required depth of 800 m in its unmineable coal seams.The conventional formula for calculating CO_(2)storage in coal basins has been modified,and a new formula has been proposed for assessing the CO_(2)storage potential in a coal seam.The CO_(2)storage capacities of unmineable coal seam of these coal basins are 24.60 Bt,0.61 Bt,14.02 Bt,and 5.42 Bt,respectively.The Langmuir volume of the coal fields was calculated using the proximate analysis of coalfields and found to vary between 36.42 and 98.90 m3/ton.This paper is the first to outline CO_(2)storage potential in Kazakhstani coal basins,albeit with limited data,along with a detailed geological and paleographic review of the carboniferous coalfields of Kazakhstan.A short overview of the CO_(2)-ECBM process was also included in the paper.Instead of any experimental work for CO_(2)storage,this paper attempts to present the CO_(2)storage capacity of carboniferous coal formation using the modified version of previously determined formulas for CO_(2)storage.展开更多
Herbicide resistance in crops has extended the scope of herbicide applications to control weeds. The introduction of herbicide resistant crops resulted in a major shift in the way that herbicides are used in many crop...Herbicide resistance in crops has extended the scope of herbicide applications to control weeds. The introduction of herbicide resistant crops resulted in a major shift in the way that herbicides are used in many crops, but not necessarily increased the prevalence of herbicide use, especially in wheat. Wheat is one of the most widely grown crops in the world and currently only two major herbicide-resistant wheat groups have been commercialized to manage weeds in a cost-effective manner. However, sustainable wheat production is threatened by the expanding occurrence of herbicide-resistant weed populations with limited efforts to discover new herbicide molecules. Selective control of certain problematic weeds in wheat was impossible until development and introduction of the technologies, Clearfield and Co AXium Production Systems. However, the current limitations of reliance on specific herbicides and evolution of resistant weeds mandate precautions and considerations when using these systems to prevent the loss of existing herbicide resources and continue sustainable wheat production. The focus of this review is to provide an overview of natural pre-existing herbicide resistance and development of herbicide-resistant technologies in wheat. The mechanisms of resistance to herbicides in wheat as well as the weed populations in wheat cropping systems, and implications for weed management are discussed.展开更多
Adsorption isotherm relates the gas storage capacity as a function of pressure at constant temperature.In this paper,adsorption isotherm of two dry borehole samples was constructed in the laboratory using the manometr...Adsorption isotherm relates the gas storage capacity as a function of pressure at constant temperature.In this paper,adsorption isotherm of two dry borehole samples was constructed in the laboratory using the manometric method.Isotherm was measured for two gases,i.e.,CH4 and CO2 to pressure up to 8.4 MPa.Before the construction of sorption isotherm,coal was characterized by proximate,ultimate and petrographic analysis.Coalbed gas content of these two samples was found 2.29 m3/t and 2.75 m3/t.SEM images were obtained for the pore size distribution of coal using pore image analysis.Prediction of coalbed methane recovery from CH4 adsorption isotherm showed that these coalbeds are under saturated.CO2 isotherm was constructed to estimate enhanced coalbed methane(ECBM)recovery.Volume wise CO2/CH4 sorption ratio was found 2.09 times to 2.75 times respectively.This paper presents the interpretation of isotherm data to find the recovery factor of methane production from Jharia coalfield.展开更多
Tuberculosis(TB) is a leading cause of morbidity and mortality in more than one-third of the world population. Its impact on global health is a result of decades of neglect for such an important infectious disease, la...Tuberculosis(TB) is a leading cause of morbidity and mortality in more than one-third of the world population. Its impact on global health is a result of decades of neglect for such an important infectious disease, lack of resources for national TB control programs, poor case detection, and inadequate/inappropriate therapy in high-burden countries. The worldwide dissemination of multidrug(MDR) and extensively drug resistant(XDR) Mycobacterium tuberculosis poses a serious threat to human health due to inadequacy of long and cumbersome tuberculosis(TB) therapy. Treatment regimens consist of at least four drugs with different mechanisms of action. Several new molecules in clinical development hasencouraged the scientific community to discover new drug targets and new drug candidates. Therefore, new drugs are urgently needed to shorten and improve the treatment course in drug resistant TB, and to minimize the occurrence of new infections and death. Nowadays, various new investigational drugs, such as bedaquine(TMC207), nitroimidazoles(PA-824, OPC-67683), diamines(SQ109), oxazolidinones(Linezolid, PNU-100480(Sutezolid), ADZ5847), pyrroles(LL3858) and fluoroquinolones(moxifloxacin and gatifloxacin), have entered clinical trials and are in progress to be developed for the treatment of MDR-TB. In this perspectivearticle, an overview of the new anti-TB drugs with different structures that are either being clinically used or in advanced stages clinical stages as well as of preclinical development are presented. This review provides snapshots of the efforts that are being made in the development of new drugs as lead anti-TB agents. Finally, it is crucial to improve the connection between research and development institutes, industries, drug contro l authorities, and international policy-making bodies to deliver efficacious therapies for patients who are suffering from TB.展开更多
Food-borne diseases are the main public health problem throughout the world. Milk is important component of human diet including fats, proteins, vitamins and minerals. It is a best source of calcium and phosphorus. Di...Food-borne diseases are the main public health problem throughout the world. Milk is important component of human diet including fats, proteins, vitamins and minerals. It is a best source of calcium and phosphorus. Different types of pathogenic bacteria like S. aureus and Salmonella enter in milk and then multiply, after multiplication they become active in causing diseases. These bacteria create serious problems for human health. This study aimed to isolate and identify pathogenic bacteria Staphylococcus aureus and Salmonella from raw milk samples of different cities of Pakistan. Primary screening of raw milk samples was done on the basis of morphological, cultural and biochemical techniques. The final identification was made using 16SrRNA sequence analysis. A total of 200 raw milk samples were collected from different cities of Pakistan. Selective medium xylose lysine deoxycholate agar (XLD) and Mannitol salt agar were used for the identification of Salmonella sp. and S. aureus. Staphylococcus aureus produced yellow colonies with yellow zones on Mannitol salt agar. Staphylococcus aureus exhibited gram-positive character with purple coloration and it was detected as cocci-shaped. Biochemically 91 (45%) samples enhibited Catalase, Coagulase, DNase, Urease, Citrate, fermentation tests positive and indole, oxidase and H2S tests negative with nonmotile character, indicating the presence of Staphylococcus aureus. Salmonella sp. was detected as gram negative rods with pink coloration on gram staining. Biochemically 87 (43%) samples revealed catalase, citrate, H2S and fermentation tests positive while oxidase, DNase, Indole and urease tests negative, indicating the presence of Salmonella sp. in these samples. Of the 200 samples tested, 43% were positive for Salmonella, while 45% samples were contaminated with S. aureus. The 16SrRNA sequence analysis confirmed the results of biochemical and cultural characterization by depicting 99% identity of samples with S. aureus and 98% identity with Salmonella spp. The occurrence of high percentage of these pathogenic bacteria in raw milk may be linked to its contamination at the time of collection, processing, strorage and distribution. This quantitative data could be utilized to better establish the appropriate levels of protection for raw milk, dairy products and processing technologies.展开更多
The present study reports and discusses the genesis of zincian chromite in the ultramafic xenoliths from the Dongripali area,Bastar craton,Central India.The zincian chromite is in the ultramafic xenoliths of Bengpal s...The present study reports and discusses the genesis of zincian chromite in the ultramafic xenoliths from the Dongripali area,Bastar craton,Central India.The zincian chromite is in the ultramafic xenoliths of Bengpal supracrustal rock hosted by Neoarchaean Bundeli gneisses.Compositionally zincian chromite shows a range of Cr_(2)O_(3)(39.69 to 51.66 wt%),Al_(2)O_(3)(05.30 wt%to 08.71 wt%),FeO(21.74 wt%to 27.51 wt%),Fe_(2)O_(3)(10.19 wt%to 19.36wt%)with higher ZnO content ranging from 1.73 wt%to 4.08 wt%.Accordingly,their Cr#[Cr/(Cr+Al)]varies in a narrow range from 0.83 to 0.85.Its calculated melt composition supports metamorphic or post-magmatic nature rather than common occurrences such as inclusion in diamonds,meteorites,and association with any sulfide-rich mineralised belt.This reveals that the post-magmatic processes play a vital role in transforming chromite to zincian chromite.The empirical thermometric calculation from chromite,amphibole,and pyroxene support their metamorphic origin and formed during low-P and high-T amphibolite grade facies of metamorphism(~700℃).The Neoarchaean granitic magmatism has a significant role in generating and transferring the heat during contact metamorphism with hydration of ultramafic xenoliths and further alteration,i.e.,serpentinisation.The olivine is a major repository for Mn,Zn,and Co in peridotite/ultramafic;these elements get mobilised during the metamorphism and serpentinisation.This is a possible reason for the mobilisation of zinc and incorporation in the chromite within altered ultramafic.As a result,chromiterich ultramafic xenolith subjected to metamorphic process gets enrichment of Zn and Fe due to elemental exchange.It converts common chromite into zincian chromite,as reported in altered ultramafics elsewhere.展开更多
Many studies have been performed on the pyridazine(1,2-diazine) derivatives in the past decade. This heterocyclic nucleus possesses almost all types of pharmacological activities. This small and simple pyridazine nucl...Many studies have been performed on the pyridazine(1,2-diazine) derivatives in the past decade. This heterocyclic nucleus possesses almost all types of pharmacological activities. This small and simple pyridazine nucleus is present in various compounds that are involved in the research aiming to evaluate new compounds with interesting biological activities, including anti-bacterial, anti-fungal, anti-viral, analgesic, anti-inflammatory, anti-platelets, anti-ulcer, anti-secretory, anti-depressants, anxiolytics, sedative-hypnotics, anti-convulsant, anti-tumor, anti-thrombotics, cardiotonics, vasodilatators, anti-arrhythmics, anti-diabetic, anti-tubercular agents and so on. This review focuses on the pyridazine derivatives with potential activities that have been developed. Pyridazine compounds draw attention of scientists and researchers because of their diverse biological activities as well as simple chemical and easy functionalization at various ring positions, making them attractive synthetic building blocks for designing and development of novel pyridazinone-based therapeutic agents.展开更多
A new P/M route based hot powder pre-form forging process has been evolved to develop high density brake materials for heavy duty applications. Number of iron based MMC’s so developed offer better characteristics for...A new P/M route based hot powder pre-form forging process has been evolved to develop high density brake materials for heavy duty applications. Number of iron based MMC’s so developed offer better characteristics for braking applications in comparison to the materials developed through conventional P/M route based on high pressure compaction and pressure sintering. The process so developed in the present investigations is much simpler and easy to adopt by existing P/M industries. Hot powder pre-form forging technique for making heavy duty brake pads offers better opportunity for pore free material with better bonding between various metallic and non-metallic constituents. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested for high energy (32,933kgfm) on Sub-scale dynamometer under Rejected Take Off conditions. The results have also been compared with respect to brake pads employed in heavy duty Military aircraft tested under identical laboratory conditions. The present work indicates that the newly developed materials compare better than the one being currently employed in heavy duty aircraft. The reasons for better performance are improved processing technique and resulting higher levels of density and improved binding of the product.展开更多
A promising friction material, Iron -based friction material, was prepared by powder metallurgy (PM) processing utilizing hot powder preform forging (near net-shape).The preparation of the product and its characteriza...A promising friction material, Iron -based friction material, was prepared by powder metallurgy (PM) processing utilizing hot powder preform forging (near net-shape).The preparation of the product and its characterization are presented in this paper. These products are useful in heavy duty Military Aircraft applications such as AN-32. In order to eliminate costly environmental control systems to protect products during their high temperature processing (as is conventionally practiced employing hydrogen gas), the present investigation relies on carbon (mixed in the brake pad formulation) as reducing agent and high temperature oxidation resistant glassy coating (separately developed) applied over the product’s surface after cold compacting. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested in sub-scale dynamometer under Rejected Take Off conditions. It was observed that the obtained density in the present investigation is higher than the reported density obtained by sintering route, and wear is on the lower side of the range as per the Aeronautical Standards. Optical metallography was used to investigate the microstructure of friction, interface and backing layer. It was observed that the distribution of ingredients in matrix was homogeneous. The results also indicate that the coefficient of friction is more stable, and wear is lower with respect to temperature rise. .展开更多
Employing well-established mixing rules for mean properties, appropriate expressions are derived for predicting minimum fluidization velocities of multi-component solid mixtures in terms of mono- component values for ...Employing well-established mixing rules for mean properties, appropriate expressions are derived for predicting minimum fluidization velocities of multi-component solid mixtures in terms of mono- component values for the velocity and the bed voidage at incipient fluidization. Based on flow regime and the mixing level of constituent species, it is found that these relationships differ significantly from each other, whether related to size-different or density-different mixtures. For mixed beds of size-different mixtures, the effect of volume contraction is accounted for by the mean voidage term, which is absent for segregated beds. Incorporating the volume-change of mixing leads to values of the mixture minimum fluidization velocities even lower than corresponding values for segregated bed, thus conforming to the trend reported in the literature. Size-different mixtures exhibit flow regime dependence irrespective of whether the bed is mixed or segregated. On the other hand, the mixing of constituent species does not affect the minimum fiuidization velocity of density-different mixtures, as the difference in the expres- sions for a segregated and a mixed system is rather inconsequential. Comparison with experimental data available in the literature is made to test the efficacy of the minimum fluidization velocity expressions derived here.展开更多
Towards the development of a predictive model for computing the minimum fluidization velocity, the volume-contraction phenomenon arising from the mixing of unequal solid species is accounted for in the prediction of t...Towards the development of a predictive model for computing the minimum fluidization velocity, the volume-contraction phenomenon arising from the mixing of unequal solid species is accounted for in the prediction of the bed void fraction of binary-solid mixtures at the incipient fluidization conditions. Com- parison with experimental data obtained from the literature clearly shows that significantly improved predictions are obtained except for cases where the stratification pattern whether arising from the slow defluidization or the difference in the densities of the two species affects the mixing of the constituent species.展开更多
文摘The increasing atmospheric CO_(2)concentration linked to human activity results in global warming by the greenhouse effect.This anthropogenic CO_(2)may be sequestrated into geological formations,e.g.,porous basalts,saline aquifers,depleted oil or gas reservoirs,and unmineable coal seams.Furthermore,carbon capture,utilization,and storage(CCUS)methods are an acceptable and sustainable technology to meet the goals of the Paris Agreement,in which Kazakhstan is expected to reduce greenhouse gas emissions by 25%compared with the 1990 level.Unmineable coal seams are an attractive option among all geostorage solutions,as CO_(2)sequestration in coal comes with an income stream via enhanced coalbed methane(ECBM)recovery.This paper identifies four carboniferous coal formations,namely Karagandy,Teniz-Korzhinkol,Ekibustuz,and Chu coal basins of Kazakhstan,as CO_(2)geostorage solutions for their unmineable coal seams.The ideal depth of CO_(2)storage is identified as 800 m to ensure the supercritical state of CO_(2).However,the Ekibustuz coal basin fails to meet the required depth of 800 m in its unmineable coal seams.The conventional formula for calculating CO_(2)storage in coal basins has been modified,and a new formula has been proposed for assessing the CO_(2)storage potential in a coal seam.The CO_(2)storage capacities of unmineable coal seam of these coal basins are 24.60 Bt,0.61 Bt,14.02 Bt,and 5.42 Bt,respectively.The Langmuir volume of the coal fields was calculated using the proximate analysis of coalfields and found to vary between 36.42 and 98.90 m3/ton.This paper is the first to outline CO_(2)storage potential in Kazakhstani coal basins,albeit with limited data,along with a detailed geological and paleographic review of the carboniferous coalfields of Kazakhstan.A short overview of the CO_(2)-ECBM process was also included in the paper.Instead of any experimental work for CO_(2)storage,this paper attempts to present the CO_(2)storage capacity of carboniferous coal formation using the modified version of previously determined formulas for CO_(2)storage.
基金supported by Heartland Plant Innovations, Inc., Manhattan, Kansas
文摘Herbicide resistance in crops has extended the scope of herbicide applications to control weeds. The introduction of herbicide resistant crops resulted in a major shift in the way that herbicides are used in many crops, but not necessarily increased the prevalence of herbicide use, especially in wheat. Wheat is one of the most widely grown crops in the world and currently only two major herbicide-resistant wheat groups have been commercialized to manage weeds in a cost-effective manner. However, sustainable wheat production is threatened by the expanding occurrence of herbicide-resistant weed populations with limited efforts to discover new herbicide molecules. Selective control of certain problematic weeds in wheat was impossible until development and introduction of the technologies, Clearfield and Co AXium Production Systems. However, the current limitations of reliance on specific herbicides and evolution of resistant weeds mandate precautions and considerations when using these systems to prevent the loss of existing herbicide resources and continue sustainable wheat production. The focus of this review is to provide an overview of natural pre-existing herbicide resistance and development of herbicide-resistant technologies in wheat. The mechanisms of resistance to herbicides in wheat as well as the weed populations in wheat cropping systems, and implications for weed management are discussed.
文摘Adsorption isotherm relates the gas storage capacity as a function of pressure at constant temperature.In this paper,adsorption isotherm of two dry borehole samples was constructed in the laboratory using the manometric method.Isotherm was measured for two gases,i.e.,CH4 and CO2 to pressure up to 8.4 MPa.Before the construction of sorption isotherm,coal was characterized by proximate,ultimate and petrographic analysis.Coalbed gas content of these two samples was found 2.29 m3/t and 2.75 m3/t.SEM images were obtained for the pore size distribution of coal using pore image analysis.Prediction of coalbed methane recovery from CH4 adsorption isotherm showed that these coalbeds are under saturated.CO2 isotherm was constructed to estimate enhanced coalbed methane(ECBM)recovery.Volume wise CO2/CH4 sorption ratio was found 2.09 times to 2.75 times respectively.This paper presents the interpretation of isotherm data to find the recovery factor of methane production from Jharia coalfield.
文摘Tuberculosis(TB) is a leading cause of morbidity and mortality in more than one-third of the world population. Its impact on global health is a result of decades of neglect for such an important infectious disease, lack of resources for national TB control programs, poor case detection, and inadequate/inappropriate therapy in high-burden countries. The worldwide dissemination of multidrug(MDR) and extensively drug resistant(XDR) Mycobacterium tuberculosis poses a serious threat to human health due to inadequacy of long and cumbersome tuberculosis(TB) therapy. Treatment regimens consist of at least four drugs with different mechanisms of action. Several new molecules in clinical development hasencouraged the scientific community to discover new drug targets and new drug candidates. Therefore, new drugs are urgently needed to shorten and improve the treatment course in drug resistant TB, and to minimize the occurrence of new infections and death. Nowadays, various new investigational drugs, such as bedaquine(TMC207), nitroimidazoles(PA-824, OPC-67683), diamines(SQ109), oxazolidinones(Linezolid, PNU-100480(Sutezolid), ADZ5847), pyrroles(LL3858) and fluoroquinolones(moxifloxacin and gatifloxacin), have entered clinical trials and are in progress to be developed for the treatment of MDR-TB. In this perspectivearticle, an overview of the new anti-TB drugs with different structures that are either being clinically used or in advanced stages clinical stages as well as of preclinical development are presented. This review provides snapshots of the efforts that are being made in the development of new drugs as lead anti-TB agents. Finally, it is crucial to improve the connection between research and development institutes, industries, drug contro l authorities, and international policy-making bodies to deliver efficacious therapies for patients who are suffering from TB.
文摘Food-borne diseases are the main public health problem throughout the world. Milk is important component of human diet including fats, proteins, vitamins and minerals. It is a best source of calcium and phosphorus. Different types of pathogenic bacteria like S. aureus and Salmonella enter in milk and then multiply, after multiplication they become active in causing diseases. These bacteria create serious problems for human health. This study aimed to isolate and identify pathogenic bacteria Staphylococcus aureus and Salmonella from raw milk samples of different cities of Pakistan. Primary screening of raw milk samples was done on the basis of morphological, cultural and biochemical techniques. The final identification was made using 16SrRNA sequence analysis. A total of 200 raw milk samples were collected from different cities of Pakistan. Selective medium xylose lysine deoxycholate agar (XLD) and Mannitol salt agar were used for the identification of Salmonella sp. and S. aureus. Staphylococcus aureus produced yellow colonies with yellow zones on Mannitol salt agar. Staphylococcus aureus exhibited gram-positive character with purple coloration and it was detected as cocci-shaped. Biochemically 91 (45%) samples enhibited Catalase, Coagulase, DNase, Urease, Citrate, fermentation tests positive and indole, oxidase and H2S tests negative with nonmotile character, indicating the presence of Staphylococcus aureus. Salmonella sp. was detected as gram negative rods with pink coloration on gram staining. Biochemically 87 (43%) samples revealed catalase, citrate, H2S and fermentation tests positive while oxidase, DNase, Indole and urease tests negative, indicating the presence of Salmonella sp. in these samples. Of the 200 samples tested, 43% were positive for Salmonella, while 45% samples were contaminated with S. aureus. The 16SrRNA sequence analysis confirmed the results of biochemical and cultural characterization by depicting 99% identity of samples with S. aureus and 98% identity with Salmonella spp. The occurrence of high percentage of these pathogenic bacteria in raw milk may be linked to its contamination at the time of collection, processing, strorage and distribution. This quantitative data could be utilized to better establish the appropriate levels of protection for raw milk, dairy products and processing technologies.
基金Geological Survey of India,Ministry of Mines,Government of India for funding the opportunity to work in this projects。
文摘The present study reports and discusses the genesis of zincian chromite in the ultramafic xenoliths from the Dongripali area,Bastar craton,Central India.The zincian chromite is in the ultramafic xenoliths of Bengpal supracrustal rock hosted by Neoarchaean Bundeli gneisses.Compositionally zincian chromite shows a range of Cr_(2)O_(3)(39.69 to 51.66 wt%),Al_(2)O_(3)(05.30 wt%to 08.71 wt%),FeO(21.74 wt%to 27.51 wt%),Fe_(2)O_(3)(10.19 wt%to 19.36wt%)with higher ZnO content ranging from 1.73 wt%to 4.08 wt%.Accordingly,their Cr#[Cr/(Cr+Al)]varies in a narrow range from 0.83 to 0.85.Its calculated melt composition supports metamorphic or post-magmatic nature rather than common occurrences such as inclusion in diamonds,meteorites,and association with any sulfide-rich mineralised belt.This reveals that the post-magmatic processes play a vital role in transforming chromite to zincian chromite.The empirical thermometric calculation from chromite,amphibole,and pyroxene support their metamorphic origin and formed during low-P and high-T amphibolite grade facies of metamorphism(~700℃).The Neoarchaean granitic magmatism has a significant role in generating and transferring the heat during contact metamorphism with hydration of ultramafic xenoliths and further alteration,i.e.,serpentinisation.The olivine is a major repository for Mn,Zn,and Co in peridotite/ultramafic;these elements get mobilised during the metamorphism and serpentinisation.This is a possible reason for the mobilisation of zinc and incorporation in the chromite within altered ultramafic.As a result,chromiterich ultramafic xenolith subjected to metamorphic process gets enrichment of Zn and Fe due to elemental exchange.It converts common chromite into zincian chromite,as reported in altered ultramafics elsewhere.
文摘Many studies have been performed on the pyridazine(1,2-diazine) derivatives in the past decade. This heterocyclic nucleus possesses almost all types of pharmacological activities. This small and simple pyridazine nucleus is present in various compounds that are involved in the research aiming to evaluate new compounds with interesting biological activities, including anti-bacterial, anti-fungal, anti-viral, analgesic, anti-inflammatory, anti-platelets, anti-ulcer, anti-secretory, anti-depressants, anxiolytics, sedative-hypnotics, anti-convulsant, anti-tumor, anti-thrombotics, cardiotonics, vasodilatators, anti-arrhythmics, anti-diabetic, anti-tubercular agents and so on. This review focuses on the pyridazine derivatives with potential activities that have been developed. Pyridazine compounds draw attention of scientists and researchers because of their diverse biological activities as well as simple chemical and easy functionalization at various ring positions, making them attractive synthetic building blocks for designing and development of novel pyridazinone-based therapeutic agents.
文摘A new P/M route based hot powder pre-form forging process has been evolved to develop high density brake materials for heavy duty applications. Number of iron based MMC’s so developed offer better characteristics for braking applications in comparison to the materials developed through conventional P/M route based on high pressure compaction and pressure sintering. The process so developed in the present investigations is much simpler and easy to adopt by existing P/M industries. Hot powder pre-form forging technique for making heavy duty brake pads offers better opportunity for pore free material with better bonding between various metallic and non-metallic constituents. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested for high energy (32,933kgfm) on Sub-scale dynamometer under Rejected Take Off conditions. The results have also been compared with respect to brake pads employed in heavy duty Military aircraft tested under identical laboratory conditions. The present work indicates that the newly developed materials compare better than the one being currently employed in heavy duty aircraft. The reasons for better performance are improved processing technique and resulting higher levels of density and improved binding of the product.
文摘A promising friction material, Iron -based friction material, was prepared by powder metallurgy (PM) processing utilizing hot powder preform forging (near net-shape).The preparation of the product and its characterization are presented in this paper. These products are useful in heavy duty Military Aircraft applications such as AN-32. In order to eliminate costly environmental control systems to protect products during their high temperature processing (as is conventionally practiced employing hydrogen gas), the present investigation relies on carbon (mixed in the brake pad formulation) as reducing agent and high temperature oxidation resistant glassy coating (separately developed) applied over the product’s surface after cold compacting. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested in sub-scale dynamometer under Rejected Take Off conditions. It was observed that the obtained density in the present investigation is higher than the reported density obtained by sintering route, and wear is on the lower side of the range as per the Aeronautical Standards. Optical metallography was used to investigate the microstructure of friction, interface and backing layer. It was observed that the distribution of ingredients in matrix was homogeneous. The results also indicate that the coefficient of friction is more stable, and wear is lower with respect to temperature rise. .
基金the Deanship of Scientific Research at King Saud University for funding this work through the Research Group Project Number RGP-VPP-188
文摘Employing well-established mixing rules for mean properties, appropriate expressions are derived for predicting minimum fluidization velocities of multi-component solid mixtures in terms of mono- component values for the velocity and the bed voidage at incipient fluidization. Based on flow regime and the mixing level of constituent species, it is found that these relationships differ significantly from each other, whether related to size-different or density-different mixtures. For mixed beds of size-different mixtures, the effect of volume contraction is accounted for by the mean voidage term, which is absent for segregated beds. Incorporating the volume-change of mixing leads to values of the mixture minimum fluidization velocities even lower than corresponding values for segregated bed, thus conforming to the trend reported in the literature. Size-different mixtures exhibit flow regime dependence irrespective of whether the bed is mixed or segregated. On the other hand, the mixing of constituent species does not affect the minimum fiuidization velocity of density-different mixtures, as the difference in the expres- sions for a segregated and a mixed system is rather inconsequential. Comparison with experimental data available in the literature is made to test the efficacy of the minimum fluidization velocity expressions derived here.
基金supported by the SABIC grant (Project ENG-3034),King Saud University,Riyadh
文摘Towards the development of a predictive model for computing the minimum fluidization velocity, the volume-contraction phenomenon arising from the mixing of unequal solid species is accounted for in the prediction of the bed void fraction of binary-solid mixtures at the incipient fluidization conditions. Com- parison with experimental data obtained from the literature clearly shows that significantly improved predictions are obtained except for cases where the stratification pattern whether arising from the slow defluidization or the difference in the densities of the two species affects the mixing of the constituent species.
