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Juan Jesus Lopez Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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conformational preference of a chiral terpene vibrational circular dichroism vcd infrared and raman study of s limonene oxide
Physical Chemistry Chemical Physics, 2009Co-Authors: Juan Ramon Aviles Moreno, Francisco Partal Ureña, Juan Jesus Lopez GonzalezAbstract:S-(−)-Limonene oxide (4-isopropenyl-1-methyl-7-oxabicyclo[4.1.0]heptane) is a secondary metabolite and an Atmospheric Pollutant product of oxidation of other terpenes, such as limonene and α-pinene, among others. For the first time, a theoretical study of the molecular structure and a theoretical and experimental analysis of the infrared and Raman spectra of this chemical species are presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), with the six equatorial ones as the most stable (around 97%) on the basis of Boltzmann’s distribution law. In the current work, from a reliable assignment of the IR and Raman spectra and with the help from the study of the VCD spectrum of the title compound, five rotamers have been detected experimentally in the liquid phase. The present work reveals that IR, Raman and VCD are helpful complementary techniques to characterize flexible systems, as terpenes, which present several conformers.
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conformational flexibility in terpenes vibrational circular dichroism vcd infrared and raman study of s perillaldehyde
Journal of Physical Chemistry A, 2008Co-Authors: Francisco Partal Ureña, Juan Ramon Aviles Moreno, Juan Jesus Lopez GonzalezAbstract:S-(−)-Perillaldehyde (4-isopropenylcyclohex-1-ene-1-carbaldehyde) is a secondary metabolite and an Atmospheric Pollutant obtained from the oxidation of other terpenes, as limonene and α-pinene, among others. For the first time, a study of the molecular structure and the infrared and Raman spectra of this chemical is presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), being three of these equatorial rotamers the most stable (ca. 93%). A complete and reliable assignment of the IR and Raman spectra of the title compound is made, taking into account these three last rotamers, and the results are used to carry out a detailed interpretation, for the first time to our knowledge, of the VCD spectrum of this compound in the 1500−900 cm−1 region.
Enrico Traversa - One of the best experts on this subject based on the ideXlab platform.
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sol gel processed tio2 based nano sized powders for use in thick film gas sensors for Atmospheric Pollutant monitoring
Journal of Sol-Gel Science and Technology, 2001Co-Authors: Enrico Traversa, Maria Luisa Di Vona, Silvia Licoccia, M Sacerdoti, M C Carotta, Luigi Crema, G MartinelliAbstract:Sol-gel routes were used to prepare pure and 5 at% and 10 at% Ta- or Nb-dope TiO2 nano-sized powders. The thermal decomposition behaviour of the precursors was studied using simultaneous thermogravimetric and differential thermal analysis (TG/DTA). X-ray diffraction (XRD) analysis showed that the powders heated to 400°C were crystalline in the anatase TiO2 structure. The pure TiO2 powder heated to 850°C showed the rutile structure. The addition of Ta and Nb inhibited the anatase-to-rutile phase transformation up to 950–1050°C. Ta was soluble in the titania lattice up to the concentration of 10 at%, while the solubility of Nb was 5 at%. Thick films were fabricated with these powders by screen printing technology and then fired for 1 h at different temperatures in the 650–1050°C range. Scanning electron microscopy (SEM) observations showed that the anatase-to-rutile phase transformation induces a grain growth of about one order of magnitude for pure TiO2. The addition of Ta and Nb is effective to keep the TiO2 grain size at a nanometric level even at 950°C, though grain growth was observed with increasing temperature. The gas-sensitive electrical response of the thick films were tested in laboratory, in environments with CO in dry and wet air. Conductance measurements showed a good gas response only for the nanostructured titania-based films. For field tests, the prototype sensors were placed beside a conventional station for Atmospheric Pollutant monitoring. The electrical response of the thick films was compared with the results of the analytical instruments. The same trend was observed for both systems, demonstrating the use of gas sensors for this aim.
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Nanostructured thick-film gas sensors for Atmospheric Pollutant monitoring: quantitative analysis on field tests
Sensors and Actuators B-chemical, 2001Co-Authors: Maria Cristina Carotta, Luigi Crema, G Martinelli, M. Merli, Giovanna Ghiotti, Cesare Malagù, Enrico TraversaAbstract:Thick-film gas sensors were fabricated by screen-printing technology starting from different nanostructured semiconducting oxide powders both n-type and p-type; ultrafine and homogeneously sized ceramic powders were prepared using chemical methods such as sol–gel techniques and thermal decomposition of heteronuclear complexes. The temporal evolution of the conductivity changes in the various semiconducting oxide thick films were studied in comparison with the concentrations of CO, NO, NO2 and O3 in the atmosphere as measured by the analytical equipment. An air quality control experiment in an urban area through some arrays of nanostructured thick-film sensors without an in situ calibration is described. Through the calibration performed directly in the field, one of the monitoring units by means of the conventional equipment, it was possible to evaluate the Pollutants’ concentration in various points of the city. The good results obtained with this experiment allow us to consider the feasible use of the innovative station to measure the pollution due to the automotive traffic.
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Array of thick film sensors for Atmospheric Pollutant monitoring
Sensors and Actuators B-chemical, 2000Co-Authors: M C Carotta, Luigi Crema, G Martinelli, M. Gallana, M. Merli, Giovanna Ghiotti, Enrico TraversaAbstract:Abstract Chemical routes such as sol–gel techniques and thermal decomposition of heteronuclear complexes have been used to prepare nanosized powders of n-type (SnO2, TiO2 and In2O3) and p-type (LaFeO3) semiconducting oxides. Thick film gas sensors have been fabricated using these powders, printed on laser pre-cut 96% alumina substrates, each 2×2 mm element being provided with a heater, Au interdigitated contacts and a Pt-100 resistor for controlling the operating temperature. The films have been fired at different temperatures suitable to keep the grain size at the nanometer level. Electrical responses to some major polluting gases (CO, NO, NO2 and O3) obtained in the field have been compared with international standard analytical techniques.
Juan Ramon Aviles Moreno - One of the best experts on this subject based on the ideXlab platform.
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conformational preference of a chiral terpene vibrational circular dichroism vcd infrared and raman study of s limonene oxide
Physical Chemistry Chemical Physics, 2009Co-Authors: Juan Ramon Aviles Moreno, Francisco Partal Ureña, Juan Jesus Lopez GonzalezAbstract:S-(−)-Limonene oxide (4-isopropenyl-1-methyl-7-oxabicyclo[4.1.0]heptane) is a secondary metabolite and an Atmospheric Pollutant product of oxidation of other terpenes, such as limonene and α-pinene, among others. For the first time, a theoretical study of the molecular structure and a theoretical and experimental analysis of the infrared and Raman spectra of this chemical species are presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), with the six equatorial ones as the most stable (around 97%) on the basis of Boltzmann’s distribution law. In the current work, from a reliable assignment of the IR and Raman spectra and with the help from the study of the VCD spectrum of the title compound, five rotamers have been detected experimentally in the liquid phase. The present work reveals that IR, Raman and VCD are helpful complementary techniques to characterize flexible systems, as terpenes, which present several conformers.
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conformational flexibility in terpenes vibrational circular dichroism vcd infrared and raman study of s perillaldehyde
Journal of Physical Chemistry A, 2008Co-Authors: Francisco Partal Ureña, Juan Ramon Aviles Moreno, Juan Jesus Lopez GonzalezAbstract:S-(−)-Perillaldehyde (4-isopropenylcyclohex-1-ene-1-carbaldehyde) is a secondary metabolite and an Atmospheric Pollutant obtained from the oxidation of other terpenes, as limonene and α-pinene, among others. For the first time, a study of the molecular structure and the infrared and Raman spectra of this chemical is presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), being three of these equatorial rotamers the most stable (ca. 93%). A complete and reliable assignment of the IR and Raman spectra of the title compound is made, taking into account these three last rotamers, and the results are used to carry out a detailed interpretation, for the first time to our knowledge, of the VCD spectrum of this compound in the 1500−900 cm−1 region.
Francisco Partal Ureña - One of the best experts on this subject based on the ideXlab platform.
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conformational preference of a chiral terpene vibrational circular dichroism vcd infrared and raman study of s limonene oxide
Physical Chemistry Chemical Physics, 2009Co-Authors: Juan Ramon Aviles Moreno, Francisco Partal Ureña, Juan Jesus Lopez GonzalezAbstract:S-(−)-Limonene oxide (4-isopropenyl-1-methyl-7-oxabicyclo[4.1.0]heptane) is a secondary metabolite and an Atmospheric Pollutant product of oxidation of other terpenes, such as limonene and α-pinene, among others. For the first time, a theoretical study of the molecular structure and a theoretical and experimental analysis of the infrared and Raman spectra of this chemical species are presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), with the six equatorial ones as the most stable (around 97%) on the basis of Boltzmann’s distribution law. In the current work, from a reliable assignment of the IR and Raman spectra and with the help from the study of the VCD spectrum of the title compound, five rotamers have been detected experimentally in the liquid phase. The present work reveals that IR, Raman and VCD are helpful complementary techniques to characterize flexible systems, as terpenes, which present several conformers.
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conformational flexibility in terpenes vibrational circular dichroism vcd infrared and raman study of s perillaldehyde
Journal of Physical Chemistry A, 2008Co-Authors: Francisco Partal Ureña, Juan Ramon Aviles Moreno, Juan Jesus Lopez GonzalezAbstract:S-(−)-Perillaldehyde (4-isopropenylcyclohex-1-ene-1-carbaldehyde) is a secondary metabolite and an Atmospheric Pollutant obtained from the oxidation of other terpenes, as limonene and α-pinene, among others. For the first time, a study of the molecular structure and the infrared and Raman spectra of this chemical is presented. Theoretical calculations reveal the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and twelve rotamers (six equatorials and six axials), being three of these equatorial rotamers the most stable (ca. 93%). A complete and reliable assignment of the IR and Raman spectra of the title compound is made, taking into account these three last rotamers, and the results are used to carry out a detailed interpretation, for the first time to our knowledge, of the VCD spectrum of this compound in the 1500−900 cm−1 region.
Hongyu Zhang - One of the best experts on this subject based on the ideXlab platform.
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an adaptive decomposition and ensemble model for short term air Pollutant concentration forecast using iceemdan ica
Technological Forecasting and Social Change, 2021Co-Authors: Yujie Xiao, Xiaokang Wang, Jianqiang Wang, Hongyu ZhangAbstract:Abstract Precise short-term Atmospheric Pollutant concentration forecasting is significant for providing early warning information against harmful Pollutants. Many studies on Pollutant concentration prediction have proven the excellence of decomposition and ensemble models. However, in most of those studies, the training and test sets are divided based on the decomposition results rather than the original time series. In such decomposition and ensemble framework, future information is used for prediction, which is impractical. Furthermore, a significant boundary effect in the decomposition results is also a serious problem. Thus, this study develops an adaptive forecasting scheme aiming at ensuring the model practicality and adapting to the boundary effect. This study also introduces independent component analysis (ICA) to help extract the hidden information of the original series and improves the ability to screen influential variables. Finally, an adaptive decomposition and ensemble model combined with ICA is developed. Using data collected from Beijing Shunyi station, a case study and two comparative experiments are conducted, through which the contribution of the methods used in the proposed model and the superior performance of the model are demonstrated.
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a hybrid pso svm model based on clustering algorithm for short term Atmospheric Pollutant concentration forecasting
Technological Forecasting and Social Change, 2019Co-Authors: Shuixia Chen, Jianqiang Wang, Hongyu ZhangAbstract:Abstract Air pollution can lead to a wide range of hazards and can affect most organisms on Earth. Therefore, managing and controlling air pollution has become a top priority for many countries. An effective short-term Atmospheric Pollutant concentration forecasting (SAPCF) can mitigate the negative effects of Atmospheric pollution. In this paper, we propose a new hybrid forecasting model for SAPCF. Firstly, we analyse the influential factors of Pollutants to obtain the optimal combination of input variables. Secondly, we use a clustering algorithm to enhance the regularity of our modelling data. Thirdly, we build a particle swarm optimisation (PSO)–support vector machine (SVM) hybrid model called PSO–SVM and perform a case study in Temple of Heaven, Beijing to test its forecasting accuracy and validate its performance against three contrastive models. The first model inputs all possible variables in equal weight without influence factor analysis. The second model integrates the same input variables used in the proposed model without clustering. The third model inputs these same variables with genetic-algorithm optimised SVM parameters. The comparison amongst these models demonstrates the superior performance of our proposed hybrid model. We further verify the forecasting results of our hybrid model by conducting statistical tests.