排序方式: 共有156条查询结果,搜索用时 31 毫秒
91.
Dr. Michael Capron Dr. Sergio Díaz‐Tendero Sylvain Maclot Dr. Alicja Domaracka Elie Lattouf Dr. Arkadiusz Ławicki Dr. Rémi Maisonny Prof. Jean‐Yves Chesnel Dr. Alain Méry Dr. Jean‐Christophe Poully Dr. Jimmy Rangama Prof. Lamri Adoui Prof. Fernando Martín Prof. Manuel Alcamí Dr. Patrick Rousseau Prof. Bernd A. Huber 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9321-9332
Fragmentation of the γ‐aminobutyric acid molecule (GABA, NH2(CH2)3COOH) following collisions with slow O6+ ions (v≈0.3 a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH2CH2+, HCNH+, CH2CH2+, and COOH+ fragments. State‐of‐the‐art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential‐energy surface. For example, the weak contribution at [M?18]+, where M is the mass of the parent ion, can be interpreted as resulting from H2O loss that follows molecular folding of the long carbon chain of the amino acid. 相似文献
92.
Andrzej Krupa Anatol Jaworek Arkadiusz T. Sobczyk Artur Marchewicz Michał Szudyga Teresa Antes 《Journal of Electrostatics》2013,71(3):260-264
The paper presents results of experimental investigation of properties of charged sprays generated by two types of pressure atomizers with charging by induction. Among other possible methods of charged spray generation, the induction charging has been considered due to its most practical importance. The goal of this research is to optimise the charging process with respect to obtain droplets of required size and charge for their application for exhaust gas cleaning from submicron particles in electrostatic scrubber used for the removal of PM from Diesel engine exhausts. Electrostatic scrubbers use electrostatic forces in order to deposit fine charged particles onto oppositely charged droplets. 相似文献
93.
Capron M Díaz-Tendero S Maclot S Domaracka A Lattouf E Ławicki A Maisonny R Chesnel JY Méry A Poully JC Rangama J Adoui L Martín F Alcamí M Rousseau P Huber BA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9321-9332
Fragmentation of the γ-aminobutyric acid molecule (GABA, NH(2)(CH(2))(3)COOH) following collisions with slow O(6+) ions (v≈0.3?a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH(2)CH(2)(+), HCNH(+), CH(2)CH(2)(+), and COOH(+) fragments. State-of-the-art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential-energy surface. For example, the weak contribution at [M-18](+), where M is the mass of the parent ion, can be interpreted as resulting from H(2)O loss that follows molecular folding of the long carbon chain of the amino acid. 相似文献
94.
Sylvain Maclot Michael Capron Rémi Maisonny Arkadiusz Ławicki Dr. Alain Méry Dr. Jimmy Rangama Prof. Dr. Jean‐Yves Chesnel Sadia Bari Prof. Dr. Ronnie Hoekstra Dr. Thomas Schlathölter Prof. Dr. Bruno Manil Prof. Dr. Lamri Adoui Dr. Patrick Rousseau Prof. Dr. Bernd A. Huber 《Chemphyschem》2011,12(5):930-936
In general, radiation‐induced fragmentation of small amino acids is governed by the cleavage of the C? Cα bond. We present results obtained with 300 keV Xe20+ ions that allow molecules (glycine and valine) to be ionised at large distances without appreciable energy transfer. Also in the present case, the C? Cα bond turns out to be the weakest link and hence its scission is the dominant fragmentation channel. Intact ionised molecules are observed with very low intensities. When the molecules are embedded in a cluster of amino acids, a protective effect of the environment is observed. The fragmentation pattern changes: the C? Cα bond becomes more protected and stable amino acid cations are observed as fragments of the molecular clusters. Evidently, the molecular cluster acts as a “buffer” for the excess energy, capable of rapidly redistributing excess energy and charge. 相似文献
95.
Dobrowolski MA Ciesielski A Cyrański MK 《Physical chemistry chemical physics : PCCP》2011,13(46):20557-20563
The application of set of homodesmotic reactions allowed us to estimate the aromatic stabilization energy (ASE) of corannulene and coronene. Appropriate reactions have been applied to balance syn/anti mismatches in di-, tetra- and hexamethylene substituted derivatives. Based on many different polycyclic reference structures that compensate the effect of strain in the corannulene moiety the value of ASE comes to 44.5 kcal mol(-1). Planar corannulene is more stabilized by cyclic π-electron delocalization by ca. 10.7 kcal mol(-1), as compared with a bowl-shaped system. A similar approach for coronene leads to an ASE equal to 58.4 kcal mol(-1). 相似文献
96.
Pawel Sajkiewicz Arkadiusz Gradys Beata Misztal-Faraj 《European Polymer Journal》2010,46(10):2051-2062
The kinetics of isothermal crystallization of various polymers was investigated by light depolarization technique (LDT) using the new setup with direct registration of depolarization ratio. Experimental data were analyzed using new method proposed by Ziabicki who shown that degree of crystallinity is a non-linear function of degree of depolarization, crystal thickness, and its birefringence. Other experimental methods were involved providing supplementary information on crystal thickness (SAXS) and allowing comparison of crystallization kinetics (WAXS, DSC). The advantage of LDT relies on high sampling rate allowing on-line measurements and lack of inertia effects that exist in other methods like calorimetry. The limitations of the applicability of the method are discussed. The method needs supplementary information not only on crystal thickness but also on variable optical birefringence of real crystals. Our results show that LDT can be used in a simple way for investigation of crystallization kinetics at relatively high temperatures, providing large and perfect crystals. In such a case it is sufficient to use crystal intrinsic birefringence and final crystal thickness typical at particular temperature of crystallization. On the other hand, depolarization ratio combined with measurements by other methods (crystallinity and crystal thickness) can be used for estimation of crystal birefringence. 相似文献
97.
Oligomeric complexes of some heteroaromatic ligands and aromatic diamines with rhodium and molybdenum tetracarboxylates: 13C and 15N CPMAS NMR and density functional theory studies 下载免费PDF全文
Arkadiusz Leniak Bohdan Kamieński Jarosław Jaźwiński 《Magnetic resonance in chemistry : MRC》2015,53(5):344-352
Seven new oligomeric complexes of 4,4′‐bipyridine; 3,3′‐bipyridine; benzene‐1,4‐diamine; benzene‐1,3‐diamine; benzene‐1,2‐diamine; and benzidine with rhodium tetraacetate, as well as 4,4′‐bipyridine with molybdenum tetraacetate, have been obtained and investigated by elemental analysis and solid‐state nuclear magnetic resonance spectroscopy, 13C and 15N CPMAS NMR. The known complexes of pyrazine with rhodium tetrabenzoate, benzoquinone with rhodium tetrapivalate, 4,4′‐bipyridine with molybdenum tetrakistrifluoroacetate and the 1 : 1 complex of 2,2′‐bipyridine with rhodium tetraacetate exhibiting axial–equatorial ligation mode have been obtained as well for comparison purposes. Elemental analysis revealed 1 : 1 complex stoichiometry of all complexes. The 15N CPMAS NMR spectra of all new complexes consist of one narrow signal, indicating regular uniform structures. Benzidine forms a heterogeneous material, probably containing linear oligomers and products of further reactions. The complexes were characterized by the parameter complexation shift Δδ (Δδ = δcomplex ? δligand). This parameter ranged from around ?40 to ?90 ppm in the case of heteroaromatic ligands, from around ?12 to ?22 ppm for diamines and from ?16 to ?31 ppm for the complexes of molybdenum tetracarboxylates with 4,4′‐bipyridine. The experimental results have been supported by a density functional theory computation of 15N NMR chemical shifts and complexation shifts at the non‐relativistic Becke, three‐parameter, Perdew‐Wang 91/[6‐311++G(2d,p), Stuttgart] and GGA–PBE/QZ4P levels of theory and at the relativistic scalar and spin‐orbit zeroth order regular approximation/GGA–PBE/QZ4P level of theory. Nucleus‐independent chemical shifts have been calculated for the selected compounds. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Barbara Marczewska Pawe? Bilski Ewa Mandowska Arkadiusz Mandowski 《Central European Journal of Physics》2012,10(4):1009-1012
Lithium fluoride (LiF), one of the most pervasive alkali halides in optical device research, is routinely used in optical data storage and radiation protection. LiF crystals may contain different aggregate defects produced by several types of ionizing radiation, with the number of defects being proportional to the cumulative radiation dose. Stimulation of irradiated LiF detectors by heating or with blue light causes thermoluminescence (TL) or photoluminescence (PL), respectively. We developed a new PL reader equipped with a blue light-emitting diode for stimulation and a Hamamatsu photomultiplier for registering green emissions, dedicated to examining LiF detectors as well as more broadly investigating TL/PL emission from standard LiF detectors irradiated with gamma rays, 60 MeV protons and alpha particles. The results confirmed very high efficiency PL signal from alpha-irradiated LiF detectors corresponding to their low efficiency after gamma irradiation, and vice versa for TL readout. Combining the TL and PL readouts permits us to discriminate between how different kinds of radiation affect efficiency in LiF detectors. 相似文献
100.