| 1. |
- Blomberg, Margareta, et al.
(författare)
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Accurate Studies on the Structures and Reactivities of Transition Metal Complexes and Clusters
- 1986
-
Ingår i: NATO Science Series C. - 9789027722379 ; 176, s. 1-14
-
Konferensbidrag (refereegranskat)abstract
- Three different applications of CASSCF and Ci methods on transition metal systems are described. The first application is concerned with the accuracy of calculated binding energies. For NiH+ ad NiO+ comparison is made to molecular beam experiments. For NiCO+ and NiCO comparisons are made to measurements of appearance potential in fragmentation experiments. In the second application, comparisons are made to matrix isolation experiments for Ni(H2O), Cu(H2O), and Ni(C2H4)n with n=1,2. The final application is concerned with the modeling of chemical reactions of transition metal surfaces. A strategy for choosing a proper effective core potential for the metal atoms is outlined. Preliminary results for O2 dissociation on nickel clusters are presented.
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| 2. |
- Bozzola, Tiago, et al.
(författare)
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Sialic Acid Derivatives Inhibit SiaT Transporters and Delay Bacterial Growth
- 2022
-
Ingår i: Acs Chemical Biology. - : American Chemical Society (ACS). - 1554-8929 .- 1554-8937. ; 17:7, s. 1890-1900
-
Tidskriftsartikel (refereegranskat)abstract
- Antibiotic resistance is a major worldwide concern, and new drugs with mechanistically novel modes of action are urgently needed. Here, we report the structure-based drug design, synthesis, and evaluation in vitro and in cellular systems of sialic acid derivatives able to inhibit the bacterial sialic acid symporter SiaT. We designed and synthesized 21 sialic acid derivatives and screened their affinity for SiaT by a thermal shift assay and elucidated the inhibitory mechanism through binding thermodynamics, computational methods, and inhibitory kinetic studies. The most potent compounds, which have a 180-fold higher affinity compared to the natural substrate, were tested in bacterial growth assays and indicate bacterial growth delay in methicillin-resistant Staphylococcus aureus. This study represents the first example and a promising lead in developing sialic acid uptake inhibitors as novel antibacterial agents.
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| 3. |
- Panas, Itai, 1959, et al.
(författare)
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COMPARISON OF THE BINDING OF CARBON, NITROGEN, AND OXYGEN-ATOMS TO SINGLE NICKEL ATOMS AND TO NICKEL SURFACES
- 1988
-
Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 92:11, s. 3079-3086
-
Tidskriftsartikel (refereegranskat)abstract
- Multireference CCI calculations have been performed for the diatomic molecules NiC, NiN, and NiO, and for the cluster systems NiSC, NiSN, and Ni50. Of the diatomic molecules, NiN has by far the smallest dissociation energy, which we argue is primarily due to the small electron affinity of nitrogen. The bonding to nickel 3d, which is pronounced for the diatomic molecules, disappears almost entirely for the cluster systems. In the full geometry optimization of the NiSX systems, includingcluster relaxation, the final geometries are rather similar for the three adsorbates, all being adsorbed below the surface. The energy gain in penetrating the surface is much larger for carbon and nitrogen than it is for oxygen, however. This is in line with the experimentally determined surface geometries, where carbon and nitrogen adsorb close to the surface and reconstruct the surface, whereas oxygen stays further out and does not reconstruct the surface. For oxygen the restoring forces from neighboring atoms in the surface are larger than the driving force to reconstruct the surface. The origin of the difference between the adsorbates is that the 2p, orbital, which points toward the surface, is almost doubly occupied for oxygen, whereas this orbital is only partially occupied for carbon and nitrogen.
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| 4. |
- Andersson, Patrik, 1974, et al.
(författare)
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Framtidsbilder för samhällsbyggnad
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Framtidsbilder för samhällsbyggnad 2020De kommande 15 åren står institutionen för Bygg- och miljöteknik inför stora förändringar. Därför har institutionen initierat projektet Framtidsbilder 2020 där man engagerat en framtidspanel bestående av elva yngre disputerade forskare. Arbetet inleddes med ett breddgruppsmöte där 110 personer representerande institutionens personal och studenter deltog. Vid mötet identifierades ett antal trender och osäkra utvecklingar som påverkar framtiden inom samhällsbyggnadsområdet. Deltagarna bidrog också med idéer till en önskvärd utveckling, vilket har sammanställts och utgör grunden till en gemensam önskvärd framtid/vision för institutionen. Materialet från breddgruppsmötet har bearbetats av Framtidspanelen och resulterat i fyra scenarier som beskriver hur samhällsbyggnadsområdet kan se ut år 2020. Syftet med framtidsbilderna är att de ska vara vägledande för institutionens beslut och förhållningssätt under de kommande åren.Fyra scenarierTurning TorsoSamhället präglas av en ekonomi som är på uppgång, och av ett nytänkande och öppet samhälle. Materiell status och individualism är viktigt. Detta leder till en hög arbetsbelastning samt krav på exklusiva varor av hög kvali-tet. Det finns en stor medvetenhet om miljöpåverkan och klimatförändringar och lösningarna för att klara energiförsörjningen är innovativa.Eco-metropolenDet sveper en grön våg genom dagens samhälle. Under de senaste 15 åren har vi insett att jorden skall vara en bebolig plats även åt dem som kommer efter oss. Vi söker ständigt efter nya, mer förfinade metoder att tillvarata de resurser vi har. Samhället och individen är i balans. Ekonomin är god och vi är miljömedvetna, trygga och integrerade. Nytänkande premieras och icke- materialistiska värderingar står högt i kurs. Vi tänker individuellt, men agerar mer än gärna för kollektivets bästa. Utbildning är gratis TrädgårdsstadenEtt samhälle där vi lärt oss hantera stress, men känner oss otrygga och helst umgås i slutna sociala sammanhang. Vi bor enkelt inne i stan, eller gärna på landsbygden nära storstäderna. Minskade behov av högutbildade i samhället gör att vi har svårt att rekrytera studenter till teknikutbildningar. Det traditionella tankesättet leder till kulturkrockar med företag och personer från andra länder.Gated communitiesFörsämrad ekonomi och ökad egoism har lett fram till ett stressat, otryggt och segregerat samhälle. Accelererande klimatförändringar och ökad miljö-påverkan skrämmer oss, men trots det åtgärdar vi inte problemen, utan koncentrerar oss på konsekvenserna. Arbetslöshet i samhällsbyggnadssek-torn leder till sänkt status för samhällsbyggaren. Vi har därför svårt att rekrytera studenter, och även forskningen har låg status.
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| 5. |
- Beijer, Karin, et al.
(författare)
-
Översättning av experimentella data till reella förhållanden.
- 1982
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I rapporten görs en litteraturgenomgång där resultat av olika effekt och upptagsförsök på kadmium jämförs. Spridningen i publicerade försöksresultat är mycket stor. Försöksbetingelserna är ofta bristfälligt angivna, vilket försvårar tydningen av resultaten. Såväl upptag som effekt är mycket kraftigt beroende av yttre faktorer (pH, hårdhet, etc). Ca 2+ förefaller vara den viktigaste yttre faktorn.
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| 6. |
- Bengtsson, Roland, et al.
(författare)
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Stabilitet i ekosystem.
- 1980
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vid föreliggande genomgång av litteraturen inom området stabilitet-diversitet i ekosystem har några utvecklingstendenser inom forskningsområdet framträtt.
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| 7. |
- Bergström, Ulf, et al.
(författare)
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Polyphase (1.6–1.5 and 1.1–1.0 Ga) deformation and metamorphism of Proterozoic (1.7–1.1 Ga) continental crust, Idefjorden terrane, Sveconorwegian orogen
- 2020
-
Ingår i: Sweden. - : Geological Society of London. ; , s. 397-434
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Crust generated during an accretionary orogeny at 1.66–1.52 Ga (Gothian), and later during crustal extension at c. 1.51–1.49, c. 1.46, c. 1.34–1.30 Ga and after c. 1.33 Ga, dominate the Idefjorden terrane. Metamorphism under greenschist to, locally, high-pressure granulite facies, emplacement of syn-orogenic pegmatite and granite, and polyphase deformation followed at 1.05–1.02 Ga (Agder tectonothermal phase, Sveconorwegian orogeny). Sinistral transpressive deformation, including foreland-directed thrusting, preceded top-to-the-west movement and large-scale open folding along north–south axial trends during the younger orogeny. Crustal extension with emplacement of dolerite and lamprophyre dykes, norite–anorthosite, and a batholithic granite took place at c. 0.95–0.92 Ga (Dalane phase, Sveconorwegian orogeny). Ductile shear zones divide the Idefjorden terrane into segments distinguished by the character of the Gothian crustal component. Orthogneisses with c. 1.66 and c. 1.63–1.59 Ga protoliths occur in the Median segment; c. 1.59–1.52 Ga gneissic intrusive rocks and 1.6 Ga paragneisses with relicts of Gothian deformation and migmatization at c. 1.59 Ga and at c. 1.56–1.55 Ga occur in the Western segment. Mineral resources include stratabound Cu–Fe sulphides hosted by sandstone deposited after c. 1.33 Ga, and polymetallic quartz vein mineralization locally containing Au.
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| 8. |
- Biémont, E, et al.
(författare)
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Radiative lifetime and oscillator strength determinations in Sm III
- 2003
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 399:1, s. 343-349
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 6 levels belonging to the4f5(6Hdeg,6Fdeg)5d configuration of Sm III have beenmeasured for the first time using a time-resolved laser-inducedfluorescence technique. Experimental data have been compared withsemi-empirical calculations. The agreement is excellent for 4 levelswith 6Fdeg as a parent term. Larger discrepancies(53 and 37) are observed for 2 levels with 6Hdegand 6Fdeg, respectively, as a parent term and areexplainable by strong mixing and cancellation effects occurring in theline strength calculations which are responsible of instabilitiesoccurring in the lifetimes considered as a function of J value withinthe term. Branching ratios for the lines depopulating the levels ofinterest have been measured by Fourier transform spectroscopy. A firstset of oscillator strengths has been deduced for this ion.
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| 9. |
- Brolin, M, et al.
(författare)
-
Simultaneous transcription of duplicated var2csa gene copies in individual Plasmodium falciparum parasites
- 2009
-
Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 10:10, s. R117-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Single nucleotide polymorphisms are common in duplicated genes, causing functional preservation, alteration or silencing. The Plasmodium falciparum genes var2csa and Pf332 are duplicated in the haploid genome of the HB3 parasite line. Whereas the molecular function of Pf332 remains to be elucidated, VAR2CSA is known to be the main adhesin in placental parasite sequestration. Sequence variations introduced upon duplication of these genes provide discriminative possibilities to analyze allele-specific transcription with a bearing towards understanding gene dosage impact on parasite biology. Results: We demonstrate an approach combining real-time PCR allelic discrimination and discriminative RNA-FISH to distinguish between highly similar gene copies in P. falciparum parasites. The duplicated var2csa variants are simultaneously transcribed, both on a population level and intriguingly also in individual cells, with nuclear co-localization of the active genes and corresponding transcripts. This indicates transcriptional functionality of duplicated genes, challenges the dogma of mutually exclusive var gene transcription and suggests mechanisms behind antigenic variation, at least in respect to the duplicated and highly similar var2csa genes. Conclusions: Allelic discrimination assays have traditionally been applied to study zygosity in diploid genomes. The assays presented here are instead successfully applied to the identification and evaluation of transcriptional activity of duplicated genes in the haploid genome of the P. falciparum parasite. Allelic discrimination and gene or transcript localization by FISH not only provide insights into transcriptional regulation of genes such as the virulence associated var genes, but also suggest that this sensitive and precise approach could be used for further investigation of genome dynamics and gene regulation.
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| 10. |
- Danilo, Cecile, et al.
(författare)
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Effects of the first hydration sphere and the bulk solvent on the spectra of the f(2) isoelectronic actinide compounds : U4+, NpO2+, and PuO22
- 2010
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 12:5, s. 1116-1130
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic spectra of the 5f(2) isoelectronic actinide compounds U4+, NpO2+, and PuO22+ have been investigated theoretically both in gas phase and in solution. In the latter case the solvent was modelled by a saturated first hydration sphere, five water molecules for NpO2+, and PuO22+ and eight for U4+, and a continuum model describing the remaining solvent. The transition energies and oscillator strengths were obtained at the spin-orbit level using the relativistic wave function based multi-configuration methods CASPT2 (complete active space with second-order perturbation theory) and MRCI + DC (Davidson corrected multi-reference configuration interaction), followed by a spin-orbit CI based on a dressed effective spin-orbit Hamiltonian. This study is an attempt to contribute to an enhanced understanding of the electronic structure of tetravalent actinide ions and actinyl(V) and (VI) ions. The spin-orbit MRCI and spin-orbit CASPT2 transitions energies have been compared for the bare ions, leading us to the conclusion that the spin-orbit CASPT2 approach is reasonably accurate and can be used with confidence for the calculation of the hydrated species. The first hydration sphere and the bulk solvent lift degeneracies, but the effect on the transition energies is fairly small for the two actinyl ions, while it is larger, up to several thousands of wave numbers for U4+. The calculations allowed us to make assignments of the experimentally observed absorption spectra for all species. The computed transition energies and intensities compared favourably with experiment.
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| 11. |
- Danilo, Cecile, 1981-
(författare)
-
Modélisation théorique de la spectroscopie d'actinides des solvatés.
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The framework of this PhD is the interpretation of Nuclear Magnetic Relaxation Dispersion experiments performed on solvated U4+, NpO2+ and PuO22+, which all have an f2 configuration. Unexpectedly the two actinyl ions have a much higher relaxivity than U4+. One possible explanation is that the electronic relaxation rate is faster for Uranium(IV) than for the actinyl ions. We address this problem by exploring the electronic spectrum of the three compounds in solution. A preliminary step is the computation of the electronic spectra of these three ions in gas phase. A two-step SOCI method has been used to investigate the spectroscopy in gas phase and in solution. The influence of electron correlation (treated in the first step) and spin-orbit relaxation effects (considered in the second step) has been discussed thoroughly. The influence of the first hydration sphere and the bulk solvent effects has been investigated as well.Another issue that has been questioned is the accuracy of Density Functional Theory for the study of actinide species. This matter has been discussed by comparing its performance to wave-function based correlated methods. The chemical problem chosen was the water exchange in UO22+(H2O)5. This reaction can proceed via three pathways, the associative, the dissociative and the symmetric interchange. We looked at the two former ones using a model with one additional water in the second hydration sphere.The last part of the thesis dealt with the spectroscopy of coordinated Uranyl(V). Absorption spectrum of Uranyl(V) with various ligands has been recorded. The first sharp absorption band in the Near Infrared region were assigned to the Uranium centered 5f-5f transitions, but uncertainties remained for the assignment of transitions observed in the Visible region. We computed the spectra of naked UO2+ and [UO2(CO3)3]5- to elucidate the spectral changes induced by the carbonate ligands.
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| 12. |
- Danilo, Cecile, et al.
(författare)
-
Spin-orbit configuration interaction study of the electronic structure of the 5f(2) manifold of U4+ and the 5f manifold of U5
- 2008
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:15, s. 154310-
-
Tidskriftsartikel (refereegranskat)abstract
- The energy levels of the 5f configuration of U5+ and 5f(2) configuration of U4+ have been calculated in a dressed effective Hamiltonian relativistic spin-orbit configuration interaction framework. Electron correlation is treated in the scalar relativistic scheme with either the multistate multireference second-order multiconfigurational perturbation theory (MS-CASPT2) or with the multireference single and double configuration interaction (MRCI) and its size-extensive Davidson corrected variant. The CASPT2 method yields relative energies which are lower than those obtained with the MRCI method, the differences being the largest for the highest state S-1(0) of the 5f(2) manifold. Both valence correlation effects and spin-orbit polarization of the outer-core orbitals are shown to be important. The satisfactory agreement of the results with experiments and four-component correlated calculations illustrates the relevance of dressed spin-orbit configuration interaction methods for spectroscopy studies of heavy elements. (c) 2008 American Institute of Physics.
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| 13. |
- Dolk, Linus, et al.
(författare)
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The laboratory analysis of Bi II and its application to the Bi-rich HgMn star HR 7775
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 388:2, s. 692-703
-
Tidskriftsartikel (refereegranskat)abstract
- The bismuth spectrum emitted from a hollow cathode discharge has been recorded with a Fourier Transform Spectrometer (FTS). Accurate wavelengths have been determined for 104 lines, and several new energy levels have been found, while the accuracy of previously known level energies have been improved. The hyperfine structure of all observed lines has been analyzed, yielding hyperfine constants A and B for 56 levels. With the aid of the laboratory measurements the optical region spectrum of the HgMn star HR 7775 has been studied for all observable lines. The wavelengths and hfs constants established from the laboratory work have been combined with theoretical gf values to identify spectral lines and make an abundance estimation of bismuth. It has been established that bismuth is present in HR 7775 at an enhancement level of approximately 5 orders of magnitude relative to the meteoritic abundance, consistent with previous observations in the ultraviolet region of this star. Astrophysical gf values are presented for a number of lines.
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| 14. |
- Dolk, Linus, et al.
(författare)
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The presence of Nd and Pr in HgMn stars
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 385:1, s. 111-130
-
Tidskriftsartikel (refereegranskat)abstract
- Optical region spectra for a number of upper main sequence chemically peculiar (CP) stars have been observed to study singly and doubly ionized praseodymium and neodymium lines. In order to improve existing atomic data of these elements, laboratory measurements have been carried out with the Lund VUV Fourier Transform Spectrometer (FTS). From these measurements wavelengths and hyperfine structure (hfs) have been studied for selected , and lines of astrophysical interest. Radiative life times for some excited states of have been determined with the aid of laser spectroscopy at the Lund Laser Center (LLC) and have been combined with branching fractions measured in the laboratory to calculate gf values for some of the stronger optical lines of . With the aid of the derived gf values and laboratory measurements of the hfs, a praseodymium abundance was derived from selected lines in the spectrum of the Am star 32 Aqr. This abundance was used to derive astrophysical gf values for selected lines in 32 Aqr, and these gf values were used to get a praseodymium abundance for the HgMn star HR 7775. The praseodymium abundance in HR 7775 was then utilized to derive astrophysical gf values for all observable lines in this star. The neodymium abundance, derived from unblended lines of in HR 7775, has been utilized to establish astrophysical gf values for observed lines in the optical region of this star. Selected and lines have been identified and studied in a number of HgMn stars and three hot Am stars. The praseodymium and neodymium abundance change rapidly from an approximate 1-1.2 dex enhancement for the hot Am stars to 1.5-3 dex enhancement for the cool HgMn stars, indicating a well-defined boundary between the hot Am and HgMn stars in the vicinity of 10 500 K. The enhancement of praseodymium and neodymium in Am and HgMn stars may be explained by diffusive processes active in the stellar atmosphere, while the observed discontinuity might be explained by a thin hydrogen convection zone thought to be present for the Am stars, but absent in the HgMn stars. The absence of a convection zone would cause the diffused elements to gather higher in the atmosphere of HgMn stars compared to Am stars, and explain the observed increase in abundance.
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| 15. |
- Eriksson, Mattias, et al.
(författare)
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Spectral Data for Ta II with Application to the Tantalum Abundance in chi Lupi
- 2002
-
Ingår i: Physica Scripta. - 0031-8949. ; 65:6, s. 480-489
-
Tidskriftsartikel (refereegranskat)abstract
- Tantalum spectra, emitted from a hollow cathode, have been recorded with a Fourier transform spectrometer in the region 2000–5000 Ů The observed hyperfine patterns of Ta II have been analyzed, yielding center-of-gravity wavelengths for 199 lines and hyperfine constants for 38 even and 97 odd levels of Ta II. Improved energy level values have been derived. The laboratory data have been used for a study of the tantalum abundance of the CP star chi Lupi.
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| 16. |
- Fromager, Emmanuel, et al.
(författare)
-
On the universality of the long-/short-range separation in multiconfigurational density-functional theory. II. Investigating f0 actinide species
- 2009
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131
-
Tidskriftsartikel (refereegranskat)abstract
- In a previous paper [ Fromager et al., J. Chem. Phys. 126, 074111 (2007) ], some of the authors proposed a recipe for choosing the optimal value of the μ parameter that controls the long-range/short-range separation of the two-electron interaction in hybrid multiconfigurational self-consistent field short-range density-functional theory (MC-srDFT) methods. For general modeling with MC-srDFT methods, it is clearly desirable that the same universal value of μ can be used for any molecule. Their calculations on neutral light element compounds all yielded μopt = 0.4 a.u. In this work the authors investigate the universality of this value by considering “extreme” study cases, namely, neutral and charged isoelectronic f0 actinide compounds (ThO2, PaO2+, UO22+, UN2, CUO, and NpO23+). We find for these compounds that μopt = 0.3 a.u. but show that 0.4 a.u. is still acceptable. This is a promising result in the investigation of a universal range separation. The accuracy of the currently best MC-srDFT (μ = 0.3 a.u.) approach has also been tested for equilibrium geometries. Though it performs as well as wave function theory and DFT for static-correlation-free systems, it fails in describing the neptunyl (VII) ion NpO23+ where static correlation is significant; bending is preferred at the MC-srDFT (μ = 0.3 a.u.) level, whereas the molecule is known to be linear. This clearly shows the need for better short-range functionals, especially for the description of the short-range exchange. It also suggests that the bending tendencies observed in DFT for NpO23+ cannot be fully explained by the bad description of static correlation effects by standard functionals. A better description of the exchange seems to be essential too.
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| 17. |
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| 18. |
- Fromager, Emmanuel, 1979-
(författare)
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Traitement de l'interaction spin-orbite en chimie quantique et application à la réactivité des complexes d'actinides
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The recent methodological developments and the advent of faster computers enable nowadays to investigate theoretically the chemical reactivity of heavy element complexes. As an example we can mention actinide chemistry which is involved in the separation of nuclear wastes. In this case the relativistic effects induced by the heavy nuclei have to be calculated accurately. If the so-called scalar relativistic effects can be treated in electronic structure calculations with the same cost as non relativistic calculations, the treatment of spin-orbit coupling is however rather expensive. Pertinent approximations have then to be investigated. The present exchange program (Thèse en cotutelle) thesis, between Paul Sabatier University (Toulouse) and Stockholm University, focuses mainly on this problem.The first part is devoted to the development of one-component extraction procedures of relativistic pseudopotentials from reference all-electron four-component calculations. A new extraction procedure of the spin-orbit pseudopotential has been proposed and successfully tested on the halogens and the tellurium atom. Moreover, an uncontracted spin-orbit CI adapted version of the method has been formulated by means of the perturbation theory formalism. The atomic results on iodine demonstrate the validity of such an approach for an accurate computation of the spin-orbit coupling in a pseudopotential one-component scheme. The introduction of atomic core effects in "shape-consistent" pseudopotentials is finally discussed.The second part of this work is focused on applications as well as methodology. The electron transfer between actinyle complexes in solution, for which few experimental data are available, has been investigated by means of quantum chemical methods. Our results have shown similarities between uranium and neptunium complexes. From a methodological point of view, the tricky problem of solvent effects has been discussed. Moreover we have shown, using the EPCISO program implemented in Toulouse, that one-component approaches are well adapted to the calculation of spin-orbit coupling for early actinide complexes.
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| 19. |
- Gomes, Andre Severo Pereira, et al.
(författare)
-
Applied Computational Actinide Chemistry
- 2015
-
Ingår i: Computational Methods in Lanthanide and Actinide Chemistry. - Chichester : John Wiley & Sons. - 9781118688304 - 9781118688311 ; , s. 269-298
-
Bokkapitel (refereegranskat)abstract
- The theoretical modeling of lanthanide and actinide complexes in condensed media is challenging for theoretical chemistry, due in part to the intrinsic general challenge of devising a reliable model of the species in such environments and the necessity of ‘chemical’ accuracy. This chapter discusses the requirements, challenges, and pitfalls associated with attempting to theoretically model molecular properties for such systems that can be directly compared to experimental data, such as valence excitation spectra, core-excitation spectra, thermodynamics of chemical reactions, and redox properties. Spin-orbit effects are in general important to account for in excited-states calculations and in chemical reactions involving trans-uranium actinides and in many cases also uranium complexes. The most rigorous framework to include spin-orbit interaction is to treat it a priori in a four- or two-component relativistic framework. The Ultraviolet–visible (UV-Vis) spectroscopy of lanthanide and actinide elements directly reflects the electronic structure of the species involved.
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| 20. |
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| 21. |
- Jernelöv, Arne, et al.
(författare)
-
Stress in ecosystems.
- 1981
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A stress concept which relates to energy flows through eco-systems is suggested. The concept is introduced after discussion of observed phenomena, where the need of quantizations of responses to external pressure is printed out.
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| 22. |
- Johansson, S. G, et al.
(författare)
-
Comparison of New Experimental and Astrophysical F-values For Some Ru-ii Lines, Observed In Hst Spectra of Chi-lupi
- 1994
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 421:2, s. 809-815
-
Tidskriftsartikel (refereegranskat)abstract
- We report on experimental absolute oscillator strengths for 18 UV lines of Ru II, obtained by combining laser-induced fluorescence measurements of radiative lifetimes and branching fractions from line intensities in a calibrated Fourier-transform spectrum. HST/GHRS observations of the spectrum of the sharp-lined B star chi Lupi contain six of these lines, for which ''astrophysical'' relative f-values have been determined. The agreement is within 0.10 dex for a Ru abundance of log N(Ru)/N(H) = -7.90, which is 2.3 dex above the solar abundance.
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| 23. |
- Johansson, Sveneric, et al.
(författare)
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The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
- 2002
-
Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
-
Konferensbidrag (refereegranskat)abstract
- We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Šin detail.
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| 24. |
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| 25. |
- Macak, Peter, et al.
(författare)
-
A theoretical study of the fluoride exchange between UO2F+(aq) and UO22+(aq)
- 2006
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; :30, s. 3638-3646
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data on the thermodynamics and reaction mechanism of the inner-sphere. uoride exchange reaction (UO22+)-O-17 + UO2F+ reversible arrow (UO2F+)-O-17 + UO22+ have been compared with different intimate reaction mechanisms using quantum chemical methods. Two models have been tested that start from the outer sphere complexes, (H2O)[UAO2F(OH2)(4)(+)] center dot center dot center dot [UBO2(OH2)(5)(2+)] and [UAO2F(OH2)(4)(+)] center dot center dot center dot [UBO2(OH2)(5)(2+)]; the geometry and energies of the intermediates and transition states along possible reaction pathways have been calculated using different ab initio methods, SCF, B3LYP and MP2. Both the experimental data and the theoretical results suggest that the. uoride exchange takes place via the formation and breaking of a U - F - U bridge that is the rate determining step. The calculated activation enthalpy Delta H-not equal = 30.9 kJ mol(-1) is virtually identical to the experimental value 31 kJ mol(-1); however this agreement may be a coincidence as we do not expect a larger accuracy than 10 kJ mol(-1) with the methods used. The calculations show that the. uoride bridge is formed as an insertion of UAO2F(OH2)(4)(+) into UBO2(OH2)(5)(2+) followed by a subsequent transfer of water from the first to the second coordination sphere of U-B.
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