Some aspects of rock mechanics applicable to underground coal mining

Three aspects of rock mechanics, namely, in-situ stress estimation by acoustic emission (AB) method, strength of rock mass and role of chemicals to reduce the strength are covered. It i:s possible to detect the previously applied maximum stress by stressing a rock specimen to the point where there is a substantial increase in AB activity .This is known as Kaiser effect. From the AB signatures in the second and subsequent loading.s, AB take-off point was identified more easily than in the fIrst loading. In determining the compressive strength of rock mass, two factors have to be considered, namely, the size effect on the compressive strength of intact rock and the effect of dis,continuities on the compressive strength of rock mass. Although a modified Bieniawski criterion gives best agreement \u27 .ith the triaxial test data, modifications have been suggested to Hoek-Brown criterion due to its popularity. It is po~;sible to reduce the tensile strength of sandstone by saturating it with weak chemical solutions made with dodecyltrimethyl ammonium bromide, polyethylene oxide and aluminium chloride by up to 30%. In the case of compressive strength, there is no appreciable effect. The possible explanation is that the chemical solutions produce an effect on the strength of sandstone only when the failure mechanism is dominated by tensile mode

Environmental engineering in mines

The total environment in which mining takes place is the result of many physical, regional and circumstantial conditions. This is a 1986 text which deals with the assessment and control of these conditions, providing a source of ready reference for engineers and advanced students studying the mining environment. With the need for greater economy in the extraction of minerals, the search for deposits of minerals, increasing mining legislation and pressure from environmental groups, the study of mining engineering is becoming increasingly important. This book relates the mining environment to both the efficiency and safety of the production process, and to the physiological and psychological effects on personnel and the public. Each element of the environment - gas, dust, radiation, heat, water and noise - is considered in relation to its accompanying hazards, its sources, detection, and control measures, resulting in a detailed text for the study of the design, operation and maintenance of mines

Amphiphilic homopolymer as a reaction medium in water: Product selectivity within polymeric nanopockets

A styrene-based water-soluble polymer has been explored for its use as a host for lipophilic substrates in aqueous medium. Unimolecular reactions, namely, photo-Fries rearrangement of naphthyl esters, α-cleavage reaction of 1-phenyl-3-p-tolyl-propan-2-one, and Norrish type I and type II reactions of benzoin alkyl ethers were examined. We find that the hydrophobic domains generated by the polymer not only restrict the mobility of the radicals but also modestly incarcerate the substrate, intermediates, and products during the time scale of the reactions. Comparative studies of the same photoreactions in micelles formed from small molecule surfactants and an amphiphilic diblock copolymer demonstrate that the styrene-based water-soluble polymer aggregates in aqueous medium offer better selectivity

A styrene based water soluble polymer as a reaction medium for photodimerization of aromatic hydrocarbons in water

A styrene based water soluble polymer (polymer-A) has been explored as a host for solubilizing otherwise insoluble aromatic hydrocarbons in water. The increased local concentration of encapsulated aromatic hydrocarbons within the hydrophobic pockets of polymer-A was utilized for performing efficient photodimerization of acenaphthylene (1) and six 9-substituted anthracenes [AnCOOH, AnCHO, AnCH2OH, AnCH3, AnBr and AnCN] in water. Photodimerization of these aromatic hydrocarbons were more efficient than in water and yielded dimers even at low concentrations (∼10−4 M). At the same concentration of anthracenes in organic solvents such as benzene and methanol, no dimers were formed even after 48 h of irradiation. Although the polymer-A was able to increase the local concentration of the reactant aromatics it was unable to orient them towards a single dimer

A styrene based water soluble polymer as a reaction medium for photodimerization of aromatic hydrocarbons in water

A styrene based water soluble polymer (polymer-A) has been explored as a host for solubilizing otherwise insoluble aromatic hydrocarbons in water. The increased local concentration of encapsulated aromatic hydrocarbons within the hydrophobic pockets of polymer-A was utilized for performing efficient photodimerization of acenaphthylene (1) and six 9-substituted anthracenes [AnCOOH, AnCHO, AnCH<SUB>2</SUB>OH, AnCH<SUB>3</SUB>, AnBr and AnCN] in water. Photodimerization of these aromatic hydrocarbons were more efficient than in water and yielded dimers even at low concentrations (∼ 10<SUP>-4</SUP> M). At the same concentration of anthracenes in organic solvents such as benzene and methanol, no dimers were formed even after 48 h of irradiation. Although the polymer-A was able to increase the local concentration of the reactant aromatics it was unable to orient them towards a single dimer

Self-organization of the bacterial cell-division protein FtsZ in confined environments

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Not AvailableTwo major bacterial blight (BB) resistance genes (Xa21 and xa13) and a major gene for blast resistance (Pi54) were introgressed into an Indian rice variety MTU1010 through marker-assisted backcross breeding. Improved Samba Mahsuri (possessing Xa21 and xa13) and NLR145 (possessing Pi54) were used as donor parents. Marker-assisted backcrossing was continued till BC2 generation wherein PCR based functional markers specific for the resistance genes were used for foreground selection and a set of parental polymorphic microsatellite markers were used for background selection at each stage of backcrossing. Selected BC2F1 plants from both crosses, having the highest recoveries of MTU1010 genome (90% and 92%, respectively), were intercrossed to obtain intercross F1 (ICF1) plants, which were then selfed to generate 880 ICF2 plants possessing different combinations of the BB and blast resistance genes. Among the ICF2 plants, seven triple homozygous plants (xa13xa13Xa21Xa21Pi54Pi54) with recurrent parent genome recovery ranging from 82% to 92% were identified. All the seven ICF2 plants showed high resistance against the bacterial blight disease with a lesion lengths of only 0.53–2.28 cm, 1%–5% disease leaf areas and disease scoring values of ‘1’ or ‘3’. The seven ICF2 plants were selfed to generate ICF3, which were then screened for blast resistance, and all were observed to be highly resistant to the diseases. Several ICF3 lines possessing high level of resistance against BB and blast, coupled with yield, grain quality and plant type on par with MTU1010 were identified and advanced for further selection and evaluation.Department of Biotechnology (DBT), Government of India (Grant No. BT/PR11705/AGR/02/646/2008)

Controlling Anthropogenic and Natural Seismicity: Insights From Active Stabilization of the Spring‐Slider Model

International audienceWe present a theoretical study focusing on exploring the possibility of controlling anthropogenic and natural seismicity. We actively control the pressure of injected fluids using a negative-feedback control system. Our analysis is based on the spring-slider model for modeling the earthquake instability. We use a general Coulomb-type rheology for describing the frictional behavior of a fault system. This model leads to a nonautonomous system, whose steady state and stability are studied using a double-scale asymptotic analysis. This approach renders the dominant order of the system time invariant. Established tools from the classical mathematical theory of control are used for designing a proper stabilizing controller. We show that the system is stabilizable by controlling fluid pressure. This is a central result for industrial operations. A stabilizing controller is then designed and tested. The controller regulates in real time the applied pressure in order to assure stability, avoid unwanted seismicity, and drive the system from unstable states of high potential energy, to stable ones of low energy. The controller performs well even in the absence of complete knowledge of the frictional properties of the system. Finally, we present two numerical examples (scenarios) and illustrate how anthropogenic and natural earthquakes could be, in theory, prevented

Marker-Assisted Pyramiding of Genes Conferring Resistance Against Bacterial Blight and Blast Diseases into Indian Rice Variety MTU1010

Two major bacterial blight (BB) resistance genes (Xa21 and xa13) and a major gene for blast resistance (Pi54) were introgressed into an Indian rice variety MTU1010 through marker-assisted backcross breeding. Improved Samba Mahsuri (possessing Xa21 and xa13) and NLR145 (possessing Pi54) were used as donor parents. Marker-assisted backcrossing was continued till BC2 generation wherein PCR based functional markers specific for the resistance genes were used for foreground selection and a set of parental polymorphic microsatellite markers were used for background selection at each stage of backcrossing. Selected BC2F1 plants from both crosses, having the highest recoveries of MTU1010 genome (90% and 92%, respectively), were intercrossed to obtain intercross F1 (ICF1) plants, which were then selfed to generate 880 ICF2 plants possessing different combinations of the BB and blast resistance genes. Among the ICF2 plants, seven triple homozygous plants (xa13xa13Xa21Xa21Pi54Pi54) with recurrent parent genome recovery ranging from 82% to 92% were identified. All the seven ICF2 plants showed high resistance against the bacterial blight disease with a lesion lengths of only 0.53–2.28 cm, 1%–5% disease leaf areas and disease scoring values of ‘1’ or ‘3’. The seven ICF2 plants were selfed to generate ICF3, which were then screened for blast resistance, and all were observed to be highly resistant to the diseases. Several ICF3 lines possessing high level of resistance against BB and blast, coupled with yield, grain quality and plant type on par with MTU1010 were identified and advanced for further selection and evaluation