In this study,the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined.Chloroform extraction of the oil ...In this study,the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined.Chloroform extraction of the oil shale increases the intensity of the peaks in the X-ray diffractograms.Infrared spectra and X-ray diffractograms reveal the presence of mineral,calcite,quartz,kaolinite,and pyrite in the mineral matrix of the oil shale.Hydrochloric and hydrofluoric acids dissolution do not alter the organic matter.The nonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by first-order reaction.A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433K and 873K.Furthermore,the results indicate that the removal of mineral matter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.展开更多
This paper demonstrates the thermal pyrolysis of olive residue,low density polyethylene(LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis(TGA).Measurements were carried...This paper demonstrates the thermal pyrolysis of olive residue,low density polyethylene(LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis(TGA).Measurements were carried out in the temperature range 300K^973K at heating rates of 2K/min,10K/min,20K/min and 50K/min.Based on the results obtained,three temperature regimes were selected for studying the non-isothermal kinetics of olive residue/LDPE mixture.The first two were dominated by the olive residue pyrolysis,while the third was linked to the LDPE pyrolysis,which occurred at much higher temperatures.Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis.The maximum degradation temperatures of each component in the mixture were higher than those the individual components;thus an increase in thermal stability was expected.The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.展开更多
Cupressus atlantica Gaussen （Cupressaceae） is an endemic and endangered coniferous tree geographically restricted to the N＇Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dorman...Cupressus atlantica Gaussen （Cupressaceae） is an endemic and endangered coniferous tree geographically restricted to the N＇Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dormancy which delays and reduces germination. To improve seed germination, different pre-treatments were conducted on C. atlantica seeds after storage for different periods （one, two and five years） including： scarification with sandy paper; soaking seeds in hot distilled water at 60℃ and 80℃ for 15 min and soaking seeds for 48 h in a gibberellic acid （GA3） at 1,000 and 2,000 mg·L-1. Results showed that scarification with sandy paper increased the germination rate of Atlas cypress by up to 67%, indicating that the species possess essentially an exogenous dormancy （physical dormancy） due to the hard seed coat （hardseededness）. Exogenous application of gibberellic acid （GA3） at 1,000 mg.L-1 was also effective in breaking seed dormancy and germination induction. These two treatments induced faster speed germination expressed by low number of days to first germination （8-10 days） and low values of mean germination times （MGT）. However, germination rate, under any treatment, is greatly dependent on the year of seed collection. Seeds collected in year 2004 gave the highest value, suggesting that even after five years of storage, the germination capacity of C. atlantica seeds could remain high. This observation is very interesting in the ex-situ conservation of such endemic and endangered species where the production of seeds is irregular over the years.展开更多
The aim of this study was to test the impact of Rhizophagus irregularis, an arbuscular mycorrhizal fungus (AMF), on durum wheat growth and soil microbial functionalities in a field inoculation trial conducted in Moroc...The aim of this study was to test the impact of Rhizophagus irregularis, an arbuscular mycorrhizal fungus (AMF), on durum wheat growth and soil microbial functionalities in a field inoculation trial conducted in Morocco. The results showed that i) the R. irregularis inoculum effectively improved wheat growth, ii) wheat growth promotion depended on the soil mycorrhizal infectivity and iii) functional abilities of soil microflora depended on AMF inoculation. This study confirms that field AMF inoculation can be proposed as an effective agronomic practice in wheat production and as a sustainable cultural practice to manage soil biofunctioning. To fully promote inoculation practices, a better knowledge of AMF ecology has to be acquired to better adapt AMF inoculation to environmental conditions, and thus warrant better yields and agricultural sustainability.展开更多
We give sufficient conditions ensuring the existence and uniqueness of an Eberlein-weakly almost periodic solution to the following linear equation dx/dt(t) = A(t)x(t) + f(t) in a Banach space X, where (A(t)) t ∈□ i...We give sufficient conditions ensuring the existence and uniqueness of an Eberlein-weakly almost periodic solution to the following linear equation dx/dt(t) = A(t)x(t) + f(t) in a Banach space X, where (A(t)) t ∈□ is a family of infinitesimal generators such that for all t ∈□, A(t + T) = A(t) for some T > 0, for which the homogeneuous linear equation dx/dt(t) = A(t)x(t) is well posed, stable and has an exponential dichotomy, and f:□ →X is Eberlein-weakly amost periodic.展开更多
In irrigation schemes under rotational water supply in semiarid region, the water allocation and irrigation scheduling are often based on a fixed-area proportionate water depth with every irrigation cycle irrespective...In irrigation schemes under rotational water supply in semiarid region, the water allocation and irrigation scheduling are often based on a fixed-area proportionate water depth with every irrigation cycle irrespective of crops and their growth stages, for an equitable water supply. An experiment was conducted during the 2004- 2005 season in Haouz irrigated area in Morocco, which objective was i) to evaluate the effects of the surface irrigation scheduling method (existing rule) adopted by the irrigation agency on winter wheat production compared to a full irrigation method and ii) to evaluate drip irrigation versus surface irrigation impacts on water saving and yield of winter wheat. The methodology was based on the FAO-56 dual approach for the surface irrigation scheduling. Ground measurements of the Normalized Difference Vegetation Index (NDVI) were used to derive the basal crop coefficient and the vegetation fraction cover. The simple FAO-56 approach was used for drip irrigation scheduling. For surface irrigation, the existing rule approach resulted in yield and WUE reductions of 22% and 15%, respectively, compared with the optimized irrigation scheduling proposed by the FAO-56 for full irrigation treatment. This revealed the negative effects of the irrigation schedules adopted in irrigation schemes under rotational water supply on crops productivity. It was also demon-strated that drip irrigation applied to wheat was more efficient with 20% of water saving in comparison with surface irrigation (full irrigation treatment). Drip irrigation gives also higher wheat yield compared to surface irrigation (+28% and +52% for full irrigation and existing rule treatments respectively). The same improvement was observed for water use efficiency (+24 and +59% respectively).展开更多
The aim of this work is to study the existence of a periodic solution for some neutral partial functional differential equations. Our approach is based on the R-boundedness of linear operators Lp-multipliers and UMD-s...The aim of this work is to study the existence of a periodic solution for some neutral partial functional differential equations. Our approach is based on the R-boundedness of linear operators Lp-multipliers and UMD-spaces.展开更多
This work is devoted to the synthesis and characterization of yttrium-doped SrBi_2Nb_2O_9 ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple characterizations, speci...This work is devoted to the synthesis and characterization of yttrium-doped SrBi_2Nb_2O_9 ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple characterizations, specifically scanning electron microscopy(SEM), X-ray powder diffraction(XRD), and Fourier transform infrared spectroscopy(FTIR), were used to validate the structural feature. The crystallite size was estimated by Scherrer's formula and the Williamson–Hall plot. The effect of the process on the band intensities of the FTIR spectra was investigated. The crystallite size and microstructure of ceramics prepared from different synthesis processes were strongly influenced by the sinterability. SEM images revealed nanograin ceramics for materials prepared by co-precipitation and hydrothermal methods and micrograin ceramics prepared by the solid state method. The synthesized compounds underwent phase transitions at 480–465°C. The dielectric and electrical properties of these Y-doped SrBi_2Nb_2O_9 ceramics appear to be dependent on the grain size.展开更多
Atlantic forest natural soil flora was tested on two leguminous pioneer species Acacia gummifera and Retama monosperma to be used in rehabilitation programs of the coastal sand dunes forest of the Essaouira region.The...Atlantic forest natural soil flora was tested on two leguminous pioneer species Acacia gummifera and Retama monosperma to be used in rehabilitation programs of the coastal sand dunes forest of the Essaouira region.The rhizospheric soil of two endemic plant species:R.nonosperma and Juniperus phoenicea was sampled and split into two categories,one from native rhizospheric soil,the other of the sterilized rhizospheric soil.Investigation was focused on mycorrhizal formations,but other forms of beneficial symbiosis such as rhizobia and viable soil microflora were also studied.Growth and nutrition variables assessed included lengths of roots and shoots,number of branches,ratio of root to shoot dry mass and water,nitrogen and phosphorus levels.Results showed important mycorrhizal associations in roots of both plants,presence of nodules and abundance of viable soil microflora.J.phoenicea had a 100%frequency of mycorrhizal formation and an intensity of 80%compared to a frequency of 80%and intensity of 54%for R.monosperma.Nodules had the same density of CFU regardless of the origin.Abundance of viable microflora in rhisospheric soil of R.monosperma,J.phoenicea and the control differed significantly.Among the studied variables for A.gummifera and R.monosperma,nitrogen and phosphorus uptakes significantly wit the use of the nonsterilized rhizospheric soil.Both species doubled their phosphorus uptake when colonized by mycorrhizal species,R.monosperma doubled its nitrogen uptake and A.gummifera increased it by seven times compared with the control.No significant difference was noted for the other variables.展开更多
This Ce-doped strontium bismuth tantalate SrBi<sub>1.8</sub>Ce<sub>0.2</sub>Ta<sub>2</sub>O<sub>9</sub> was prepared by solid-state reaction. X-ray diffraction was used ...This Ce-doped strontium bismuth tantalate SrBi<sub>1.8</sub>Ce<sub>0.2</sub>Ta<sub>2</sub>O<sub>9</sub> was prepared by solid-state reaction. X-ray diffraction was used to determine the crystal structure of the powders. The Raman spectrum of SrBi<sub>1.8</sub>Ce<sub>0.2</sub>Ta<sub>2</sub>O<sub>9</sub> sample was measured to confirm X-ray diffraction result. The microstructure of ceramic was observed by Scanning Electron Microscope (SEM). The Temperature dependence of the dielectric properties of ceramic was investigated from the room temperature to 400°C.展开更多
The Gabon geology offered favorable and natural environments for the formation of various types of mineralization. The Etéké gold district, aim of this study, is located in the Ngounié province (souther...The Gabon geology offered favorable and natural environments for the formation of various types of mineralization. The Etéké gold district, aim of this study, is located in the Ngounié province (southern Gabon) on the western edge of the Chaillu massif. Geologically, the gold mineralization is associated with the Eburnean orogeny and hosted in the Archean greenstone belts. Also, this deposit is covered by a significant vegetation cover and a very extensive lateritic weathering profile, which hinders the most accurate study. Through this paper, we aim to propose a genesis pattern of this mineralization via a multidisciplinary approach. To do this, a petrographic, metallogenic, and geochemical characterization has been established in the different sectors of the Etéké deposit. The studied deposits display varied facies which are encased in granitoid. They are essentially formed of abundant granitoid, and amphibolite compared to the volcano-sedimentary formations. These rocks display magmatic textures, affected by metamorphism, and not sufficiently preserved. Based on our multidisciplinary approach, the studied samples collected from the core’s boreholes allowed us to decipher a volcanogenic and metamorphosed origin of the gold genesis.展开更多
Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-r...Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, Fourier transform infrared （FTIR） and Raman spectroscopies. SEM morphological analysis reveals the presence of sub spherical and prismatic micro crystalline aggregates, while EDS semi-quantitative analysis confirms the nominal Lu/Ca compo- sition. The unit cell and the space group were determined by X-ray powder diffraction data showing that the compound crystallizes in the rhombohedral R3c wfiitlockite-type structure, with unit cell constants a - b 1.04164（1） nm, c 3.7302（1） nm and cell volume V 3.5051（1） nm^3. The investigation was completed with the structural refinement by the Rietveld method, and discussion of the distribution of Lu within cationic sites according to the results of the Rietveld refinement. The FIIR and Raman spectra, correlated to isostructural rare earth phosphates from literature, show slight band shifts of the phosphate modes correlated to the evolving size of the rare earth elements.展开更多
Over the past few years, Cu-based materials have been intensively studied focusing on their structural and thermoelectric properties. In this work, copper sulphide powders were synthesized by the sol-gel method. The c...Over the past few years, Cu-based materials have been intensively studied focusing on their structural and thermoelectric properties. In this work, copper sulphide powders were synthesized by the sol-gel method. The chemical composition and the morphological properties of the obtained samples were analyzed by X-ray diffraction, differential thermal analysis, and scanning electron microscopy. It is shown that the decomposition from one phase to another can be obtained by annealing. The electrical resistivity and the crystallite size were found to be strongly affected by the phase transition. Thermoelectric analyses showed that the digenite phase exhibits the highest power factor at room temperature. The Seebeck coefficient of the compound Cu1.8S shows a pronounced peak at the γ-β transition temperature. This behavior was statistically explained in terms of a dramatic increase in the disorder in the atoms-carriers ensemble.展开更多
From a mixture of α-,β-and y-himachalenes extracted from waste wood of Atlas cedar(Cedrus atlantica),cadalene(1,6-dimethyl-4-isopropylnaphthalene)and iso-cadalene(1,6-dimethyl-3-isopropylnaphthalene)were produced in...From a mixture of α-,β-and y-himachalenes extracted from waste wood of Atlas cedar(Cedrus atlantica),cadalene(1,6-dimethyl-4-isopropylnaphthalene)and iso-cadalene(1,6-dimethyl-3-isopropylnaphthalene)were produced in two steps with up to 71%±5%yield through the ar-himachalene intermediate using I2 and/or AlCl3 as reagents.The selectivity is shown to sharply depend on the operating conditions:while I2/AlCl3 in dichloromethane promotes the formation of cadalene,the formation of iso-cadalene is favored in the presence of AlCl3 in cyclohexane.The bicyclic aromatic compounds were thus obtained through unique rearrangements involving sequential C—C bond cleavage/fo rmation and hydride transfer processes.In the absence of AlCl3 or I2,dihydrocurcumene was also found to be formed with up to 70%selectivity.A tentative mechanism is proposed and discussed.展开更多
In this work,we are concerned with a general class of abstract semilinear autonomous functional differential equations with a non-dense domain on a Banach space.Our objective is to study,using the Crandall-Liggett app...In this work,we are concerned with a general class of abstract semilinear autonomous functional differential equations with a non-dense domain on a Banach space.Our objective is to study,using the Crandall-Liggett approach,the solutions as a semigroup of non-linear operators.展开更多
This paper reported the synthesis of Ho-doped SBN(SrBi_(2-x)Ho_xNb_2O_9:x = 0 and 0.4) by a co-precipitation method and investigated the synthesized material with X-ray diffraction analyses,infrared spectroscopy,and e...This paper reported the synthesis of Ho-doped SBN(SrBi_(2-x)Ho_xNb_2O_9:x = 0 and 0.4) by a co-precipitation method and investigated the synthesized material with X-ray diffraction analyses,infrared spectroscopy,and electrical measurements.The results show that the Ho-doped SBN has low loss values at higher frequencies and the flattening of dielectric constant which are very desirable in nonvolatile ferroelectric random access memory applications.展开更多
文摘In this study,the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined.Chloroform extraction of the oil shale increases the intensity of the peaks in the X-ray diffractograms.Infrared spectra and X-ray diffractograms reveal the presence of mineral,calcite,quartz,kaolinite,and pyrite in the mineral matrix of the oil shale.Hydrochloric and hydrofluoric acids dissolution do not alter the organic matter.The nonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by first-order reaction.A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433K and 873K.Furthermore,the results indicate that the removal of mineral matter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.
文摘This paper demonstrates the thermal pyrolysis of olive residue,low density polyethylene(LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis(TGA).Measurements were carried out in the temperature range 300K^973K at heating rates of 2K/min,10K/min,20K/min and 50K/min.Based on the results obtained,three temperature regimes were selected for studying the non-isothermal kinetics of olive residue/LDPE mixture.The first two were dominated by the olive residue pyrolysis,while the third was linked to the LDPE pyrolysis,which occurred at much higher temperatures.Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis.The maximum degradation temperatures of each component in the mixture were higher than those the individual components;thus an increase in thermal stability was expected.The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.
文摘Cupressus atlantica Gaussen （Cupressaceae） is an endemic and endangered coniferous tree geographically restricted to the N＇Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dormancy which delays and reduces germination. To improve seed germination, different pre-treatments were conducted on C. atlantica seeds after storage for different periods （one, two and five years） including： scarification with sandy paper; soaking seeds in hot distilled water at 60℃ and 80℃ for 15 min and soaking seeds for 48 h in a gibberellic acid （GA3） at 1,000 and 2,000 mg·L-1. Results showed that scarification with sandy paper increased the germination rate of Atlas cypress by up to 67%, indicating that the species possess essentially an exogenous dormancy （physical dormancy） due to the hard seed coat （hardseededness）. Exogenous application of gibberellic acid （GA3） at 1,000 mg.L-1 was also effective in breaking seed dormancy and germination induction. These two treatments induced faster speed germination expressed by low number of days to first germination （8-10 days） and low values of mean germination times （MGT）. However, germination rate, under any treatment, is greatly dependent on the year of seed collection. Seeds collected in year 2004 gave the highest value, suggesting that even after five years of storage, the germination capacity of C. atlantica seeds could remain high. This observation is very interesting in the ex-situ conservation of such endemic and endangered species where the production of seeds is irregular over the years.
文摘The aim of this study was to test the impact of Rhizophagus irregularis, an arbuscular mycorrhizal fungus (AMF), on durum wheat growth and soil microbial functionalities in a field inoculation trial conducted in Morocco. The results showed that i) the R. irregularis inoculum effectively improved wheat growth, ii) wheat growth promotion depended on the soil mycorrhizal infectivity and iii) functional abilities of soil microflora depended on AMF inoculation. This study confirms that field AMF inoculation can be proposed as an effective agronomic practice in wheat production and as a sustainable cultural practice to manage soil biofunctioning. To fully promote inoculation practices, a better knowledge of AMF ecology has to be acquired to better adapt AMF inoculation to environmental conditions, and thus warrant better yields and agricultural sustainability.
文摘We give sufficient conditions ensuring the existence and uniqueness of an Eberlein-weakly almost periodic solution to the following linear equation dx/dt(t) = A(t)x(t) + f(t) in a Banach space X, where (A(t)) t ∈□ is a family of infinitesimal generators such that for all t ∈□, A(t + T) = A(t) for some T > 0, for which the homogeneuous linear equation dx/dt(t) = A(t)x(t) is well posed, stable and has an exponential dichotomy, and f:□ →X is Eberlein-weakly amost periodic.
文摘In irrigation schemes under rotational water supply in semiarid region, the water allocation and irrigation scheduling are often based on a fixed-area proportionate water depth with every irrigation cycle irrespective of crops and their growth stages, for an equitable water supply. An experiment was conducted during the 2004- 2005 season in Haouz irrigated area in Morocco, which objective was i) to evaluate the effects of the surface irrigation scheduling method (existing rule) adopted by the irrigation agency on winter wheat production compared to a full irrigation method and ii) to evaluate drip irrigation versus surface irrigation impacts on water saving and yield of winter wheat. The methodology was based on the FAO-56 dual approach for the surface irrigation scheduling. Ground measurements of the Normalized Difference Vegetation Index (NDVI) were used to derive the basal crop coefficient and the vegetation fraction cover. The simple FAO-56 approach was used for drip irrigation scheduling. For surface irrigation, the existing rule approach resulted in yield and WUE reductions of 22% and 15%, respectively, compared with the optimized irrigation scheduling proposed by the FAO-56 for full irrigation treatment. This revealed the negative effects of the irrigation schedules adopted in irrigation schemes under rotational water supply on crops productivity. It was also demon-strated that drip irrigation applied to wheat was more efficient with 20% of water saving in comparison with surface irrigation (full irrigation treatment). Drip irrigation gives also higher wheat yield compared to surface irrigation (+28% and +52% for full irrigation and existing rule treatments respectively). The same improvement was observed for water use efficiency (+24 and +59% respectively).
文摘The aim of this work is to study the existence of a periodic solution for some neutral partial functional differential equations. Our approach is based on the R-boundedness of linear operators Lp-multipliers and UMD-spaces.
文摘This work is devoted to the synthesis and characterization of yttrium-doped SrBi_2Nb_2O_9 ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple characterizations, specifically scanning electron microscopy(SEM), X-ray powder diffraction(XRD), and Fourier transform infrared spectroscopy(FTIR), were used to validate the structural feature. The crystallite size was estimated by Scherrer's formula and the Williamson–Hall plot. The effect of the process on the band intensities of the FTIR spectra was investigated. The crystallite size and microstructure of ceramics prepared from different synthesis processes were strongly influenced by the sinterability. SEM images revealed nanograin ceramics for materials prepared by co-precipitation and hydrothermal methods and micrograin ceramics prepared by the solid state method. The synthesized compounds underwent phase transitions at 480–465°C. The dielectric and electrical properties of these Y-doped SrBi_2Nb_2O_9 ceramics appear to be dependent on the grain size.
基金This work was supported by the Cadi Ayyad University and"Laboratoire Ecologie et Environnement(L2E)"an associated unit to the "Centre National de la Recherche Scientifique et Technologique(CNRST)"URAC32.
文摘Atlantic forest natural soil flora was tested on two leguminous pioneer species Acacia gummifera and Retama monosperma to be used in rehabilitation programs of the coastal sand dunes forest of the Essaouira region.The rhizospheric soil of two endemic plant species:R.nonosperma and Juniperus phoenicea was sampled and split into two categories,one from native rhizospheric soil,the other of the sterilized rhizospheric soil.Investigation was focused on mycorrhizal formations,but other forms of beneficial symbiosis such as rhizobia and viable soil microflora were also studied.Growth and nutrition variables assessed included lengths of roots and shoots,number of branches,ratio of root to shoot dry mass and water,nitrogen and phosphorus levels.Results showed important mycorrhizal associations in roots of both plants,presence of nodules and abundance of viable soil microflora.J.phoenicea had a 100%frequency of mycorrhizal formation and an intensity of 80%compared to a frequency of 80%and intensity of 54%for R.monosperma.Nodules had the same density of CFU regardless of the origin.Abundance of viable microflora in rhisospheric soil of R.monosperma,J.phoenicea and the control differed significantly.Among the studied variables for A.gummifera and R.monosperma,nitrogen and phosphorus uptakes significantly wit the use of the nonsterilized rhizospheric soil.Both species doubled their phosphorus uptake when colonized by mycorrhizal species,R.monosperma doubled its nitrogen uptake and A.gummifera increased it by seven times compared with the control.No significant difference was noted for the other variables.
文摘This Ce-doped strontium bismuth tantalate SrBi<sub>1.8</sub>Ce<sub>0.2</sub>Ta<sub>2</sub>O<sub>9</sub> was prepared by solid-state reaction. X-ray diffraction was used to determine the crystal structure of the powders. The Raman spectrum of SrBi<sub>1.8</sub>Ce<sub>0.2</sub>Ta<sub>2</sub>O<sub>9</sub> sample was measured to confirm X-ray diffraction result. The microstructure of ceramic was observed by Scanning Electron Microscope (SEM). The Temperature dependence of the dielectric properties of ceramic was investigated from the room temperature to 400°C.
文摘The Gabon geology offered favorable and natural environments for the formation of various types of mineralization. The Etéké gold district, aim of this study, is located in the Ngounié province (southern Gabon) on the western edge of the Chaillu massif. Geologically, the gold mineralization is associated with the Eburnean orogeny and hosted in the Archean greenstone belts. Also, this deposit is covered by a significant vegetation cover and a very extensive lateritic weathering profile, which hinders the most accurate study. Through this paper, we aim to propose a genesis pattern of this mineralization via a multidisciplinary approach. To do this, a petrographic, metallogenic, and geochemical characterization has been established in the different sectors of the Etéké deposit. The studied deposits display varied facies which are encased in granitoid. They are essentially formed of abundant granitoid, and amphibolite compared to the volcano-sedimentary formations. These rocks display magmatic textures, affected by metamorphism, and not sufficiently preserved. Based on our multidisciplinary approach, the studied samples collected from the core’s boreholes allowed us to decipher a volcanogenic and metamorphosed origin of the gold genesis.
基金Project partially supported by CNR(Italy)-CNRST(Morocco) Bilateral Project "Novel Ca_9RE(PO_4)_7 biomaterials:synthesis and multi-methodological characterization via X-ray techniques" reference CNR 1588/16
文摘Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, Fourier transform infrared （FTIR） and Raman spectroscopies. SEM morphological analysis reveals the presence of sub spherical and prismatic micro crystalline aggregates, while EDS semi-quantitative analysis confirms the nominal Lu/Ca compo- sition. The unit cell and the space group were determined by X-ray powder diffraction data showing that the compound crystallizes in the rhombohedral R3c wfiitlockite-type structure, with unit cell constants a - b 1.04164（1） nm, c 3.7302（1） nm and cell volume V 3.5051（1） nm^3. The investigation was completed with the structural refinement by the Rietveld method, and discussion of the distribution of Lu within cationic sites according to the results of the Rietveld refinement. The FIIR and Raman spectra, correlated to isostructural rare earth phosphates from literature, show slight band shifts of the phosphate modes correlated to the evolving size of the rare earth elements.
文摘Over the past few years, Cu-based materials have been intensively studied focusing on their structural and thermoelectric properties. In this work, copper sulphide powders were synthesized by the sol-gel method. The chemical composition and the morphological properties of the obtained samples were analyzed by X-ray diffraction, differential thermal analysis, and scanning electron microscopy. It is shown that the decomposition from one phase to another can be obtained by annealing. The electrical resistivity and the crystallite size were found to be strongly affected by the phase transition. Thermoelectric analyses showed that the digenite phase exhibits the highest power factor at room temperature. The Seebeck coefficient of the compound Cu1.8S shows a pronounced peak at the γ-β transition temperature. This behavior was statistically explained in terms of a dramatic increase in the disorder in the atoms-carriers ensemble.
文摘From a mixture of α-,β-and y-himachalenes extracted from waste wood of Atlas cedar(Cedrus atlantica),cadalene(1,6-dimethyl-4-isopropylnaphthalene)and iso-cadalene(1,6-dimethyl-3-isopropylnaphthalene)were produced in two steps with up to 71%±5%yield through the ar-himachalene intermediate using I2 and/or AlCl3 as reagents.The selectivity is shown to sharply depend on the operating conditions:while I2/AlCl3 in dichloromethane promotes the formation of cadalene,the formation of iso-cadalene is favored in the presence of AlCl3 in cyclohexane.The bicyclic aromatic compounds were thus obtained through unique rearrangements involving sequential C—C bond cleavage/fo rmation and hydride transfer processes.In the absence of AlCl3 or I2,dihydrocurcumene was also found to be formed with up to 70%selectivity.A tentative mechanism is proposed and discussed.
文摘In this work,we are concerned with a general class of abstract semilinear autonomous functional differential equations with a non-dense domain on a Banach space.Our objective is to study,using the Crandall-Liggett approach,the solutions as a semigroup of non-linear operators.
文摘This paper reported the synthesis of Ho-doped SBN(SrBi_(2-x)Ho_xNb_2O_9:x = 0 and 0.4) by a co-precipitation method and investigated the synthesized material with X-ray diffraction analyses,infrared spectroscopy,and electrical measurements.The results show that the Ho-doped SBN has low loss values at higher frequencies and the flattening of dielectric constant which are very desirable in nonvolatile ferroelectric random access memory applications.
