| 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
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; :30, s. 3638-3646
-
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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| 26. |
- Mattsson, A, et al.
(författare)
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MODEL STUDIES OF THE CHEMISORPTION OF HYDROGEN AND OXYGEN ON CU(100)
- 1987
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 36:14, s. 7389-7401
-
Tidskriftsartikel (refereegranskat)abstract
- Atomic chemisorption of hydrogen and oxygen on Cu(100) has been studied using up to 25 copper atoms as a model of the surface. The computational procedure used involves a reduction of the metal atoms to one-electron systems and extensive configuration-interaction calculations of the adsorbate and the cluster-adsorbate bonds. The calculations support the fourfold hollow site as the preferred chemisorption site for oxygen, with a barrier-to-surface migration of 25 kcal/mol. The calculated chemisorption energies for both hydrogen and oxygen, 51 and 90 kcal/mol, respectively, are in good agreement with experimental estimates (56 kcal/mol for hydrogen and 97 kcal/mol for oxygen). The effects of reducing the metal atoms to one-electron systems have been investigated through comparisons with all-electron calculations for Cu5H and Cu5O at the self-consistent-field level and by comparisons to previous calculations on Cu5Cl and Cu9Cl in which the 3d electrons were treated explicitly.
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| 27. |
- Maunsbach, Ulf, et al.
(författare)
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Gränslös varumärkesanvändning
- 2006
-
Ingår i: Festskrift till Peter Seipel. - 9139011402
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 28. |
- Mok, Bobo W., et al.
(författare)
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Default Pathway of var2csa Switching and Translational Repression in Plasmodium falciparum
- 2008
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 3:4, s. e1982-
-
Tidskriftsartikel (refereegranskat)abstract
- Antigenic variation is a subtle process of fundamental importance to the survival of a microbial pathogen. In Plasmodium falciparum malaria, PfEMP1 is the major variable antigen and adhesin expressed at the surface of the infected erythrocyte, which is encoded for by members of a family of 60 var-genes. Peri-nuclear repositioning and epigenetic mechanisms control their mono-allelic expression. The switching of PfEMP1 depends in part on variable transition rates and short-lived immune responses to shared minor epitopes. Here we show var-genes to switch to a common gene that is highly transcribed, but sparsely translated into PfEMP1 and not expressed at the erythrocyte surface. Highly clonal and adhesive P. falciparum, which expressed distinct var-genes and the corresponding PfEMP1s at onset, were propagated without enrichment or panning. The parasites successively and spontaneously switched to transcribe a shared var-gene (var2csa) matched by the loss of PfEMP1 surface expression and host cell-binding. The var2csa gene repositioned in the peri-nuclear area upon activation, away from the telomeric clusters and heterochromatin to transcribe spliced, full-length RNA. Despite abundant transcripts, the level of intracellular PfEMP1 was low suggesting post-transcriptional mechanisms to partake in protein expression. In vivo, off-switching and translational repression may constitute one pathway, among others, coordinating PfEMP1 expression.
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| 29. |
- Olsson, Karl-Gunnar, 1955, et al.
(författare)
-
Architecture and Engineering - education of Form and Force
- 2019
-
Ingår i: IASS Symposium 2019 - 60th Anniversary Symposium of the International Association for Shell and Spatial Structures; Structural Membranes 2019 - 9th International Conference on Textile Composites and Inflatable Structures, FORM and FORCE. - 9788412110104 ; , s. 145-152
-
Konferensbidrag (refereegranskat)abstract
- Inspired by the work and attitudes of architects and engineers like Jorg Schlaich, Renzo Piano, Piero Luigi Nervi, Sverre Fehn, Ted Happold, and environments like ILEK in Stuttgart and ETH in Zurich, a vision of a new kind of architects and engineers arose at Chalmers University of Technology in the early 2000. With support from the university and the branch, a double degree Architecture and Engineering programme was developed. Since the programme started in 2006 it has been a very popular programme, and among all Swedish MSc in Engineering and Master of Architecture programmes it has almost every year been the most difficult programme to get admitted to. The concept of the programme is a 180 ects (European Credit Transfer and Accumulation System) bachelor's degree, where the fundamentals from the engineering science: mathematics, mechanics, physics and materials, is combined with history of architecture and engineering, artistic explorative courses, and the fundamentals of the architectural design process. After three years the students can choose to continue for a Master of Science in Engineering with different possible directions, from mathematics and data science to industrial ecology, acoustics, management, structural engineering, and building technology, or to continue for a Master of Architecture. For the latter they need 150 etcs minimum in pure architectural design projects. In this paper the basic concepts of the programme, the culture developed around it and the strengths we can experience in the examined students will be discussed and reflected. Today students from the programme can be found at architecture and engineering companies all over the world and are appreciated for their ability to address complex architectural and engineering design issues with attitudes, insights and skills from the both professions.
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| 30. |
- Panas, Itai, 1959, et al.
(författare)
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MECHANISM FOR H-2 DISSOCIATION ON TRANSITION-METAL CLUSTERS AND SURFACES
- 1989
-
Ingår i: ACS Symposium Series. - 1947-5918 .- 0097-6156. ; 394, s. 125-139
-
Tidskriftsartikel (refereegranskat)abstract
- Basic rules are set up for the requirements on a cluster for dissociatively chemisorbing H2. These rules are built on previous experience from model calculations on transition metal complexes and surfaces. If these rules are combined with the knowledge of the atomic spectra of the transition metals, an understanding of both the low reactivity of the Co6-Co9 clusters compared to the corresponding nickel clusters and the similarly large reactivities of Co10 and Ni10 can be obtained. It is found that all the Co6-Co9 clusters have stable closed valence shell configurations. The present model for dissociating H2 does not involve the electron donation from the cluster to H2 that has been suggested previously. The correlation between ionization energies and reactivities of the clusters is shown to be a secondary consequence of the electronic structure of the clusters.
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| 31. |
- Panas, Itai, 1959, et al.
(författare)
-
MODEL STUDIES OF THE CHEMISORPTION OF HYDROGEN AND OXYGEN ON NICKEL SURFACES .1. THE DESIGN OF A ONE-ELECTRON EFFECTIVE CORE POTENTIAL WHICH INCLUDES 3D RELAXATION EFFECTS
- 1987
-
Ingår i: Chemical Physics. - 0301-0104. ; 112:3, s. 325-337
-
Tidskriftsartikel (refereegranskat)abstract
- The present article is the first in a series describing investigations of the chemisorption and dissociation of hydrogen and oxygen on nickel surfaces. This paper deals with methodological questions, mainly concerning the form and properties of the crucial one-electron effective core potential (ECP) on nickel, which is used to describe chemisorption situations with sufficiently large nickel—adsorbate distances. Atomic chemisorption in the fourfold position on the Ni(100) surface is chosen as the model problem for testing and designing the nickel ECP. All-electron calculations on Ni4 and Ni5 with and without adsorbed atoms have been performed to produce reference results. Particularly noteworthy of the all-electron results is the large effect of 3d relaxation. To mimic cluster 3d relaxation effects a diffuse attractive 3d projection operator was added to the original standard form of the ECP.
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| 32. |
- Panas, Itai, 1959, et al.
(författare)
-
MODEL STUDIES OF THE CHEMISORPTION OF HYDROGEN AND OXYGEN ON NICKEL SURFACES .2. ATOMIC CHEMISORPTION ON NI(100)
- 1988
-
Ingår i: Theoretica Chimica Acta. - 0040-5744. ; 74:3, s. 167-184
-
Tidskriftsartikel (refereegranskat)abstract
- Atomic chemisorption of hydrogen and oxygen on the Ni(100) surface has been studied using an Effective Core Potential (ECP) approach described in a previous paper. Clusters of up to 50 nickel atoms have been used to model the surface. The computed chemisorption energies are 62 kcal/mol (exp. 63 kcal/mol) for hydrogen and 106 kcal/mol (exp. 115–130 kcal/mol) for oxygen. Correlating the adsorbate and the cluster-adsorbate bonds is extremely important for obtaining accceptable results, particularly for oxygen. Reasonable convergence of chemisorption energies is obtained with 40–50 cluster atoms for both hydrogen and oxygen. For hydrogen the addition of a third cluster layer stabilizes the results considerably. Both hydrogen and oxygen are adsorbed at (or close to) the four-fold hollow site. The calculated barriers for surface migration are also in good agreement with the experimental estimates. The calculated equilibrium heights above the surface are on the other hand too high compared with experiments. This disagreement is believed to be due to core-valence correlation effects, which are not incorporated in the present ECP. The cluster convergence for the height above the surface is much slower than for the chemisorption energy.
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| 33. |
- Panas, Itai, 1959, et al.
(författare)
-
ON THE CLUSTER CONVERGENCE OF CHEMISORPTION ENERGIES
- 1988
-
Ingår i: Chemical Physics Letters. - 0009-2614. ; 149:3, s. 265-272
-
Tidskriftsartikel (refereegranskat)abstract
- A new rule is suggested for calculating chemisorption energies using the cluster model. This rule is built on the realization that relatively large clusters (50 atoms and more) often need to be prepared for bonding by making an excitation to a proper bonding state (such a state will always be easily accessible in an infinite cluster). For hydrogen chemisorption, this bonding state must have a singly occupied orbital of the same symmetry as the hydrogen 1 s orbital. The new rule is applied to hydrogen chemisorption in the hollow sites of Ni(100) and Ni(111). When a cluster is prepared in a bonding state, even quite small clusters (≈ 10 atoms) give chemisorption energies in reasonable agreement with experimental surface results.
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| 34. |
- Panas, Itai, 1959, et al.
(författare)
-
The mechanism for the O2 dissociation on Ni(100)
- 1989
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 90, s. 6791-6801
-
Tidskriftsartikel (refereegranskat)abstract
- The dissociation of O2 on Ni(100) has been studied using a cluster model approach. The three principally different reaction pathways, over an on‐top position, over a bridge position, and over a fourfold hollow position, were considered. The dissociation mechanisms were found to be very similar for these pathways. In the entrance channel a chemisorbed, peroxo‐form, of molecular O2 is first formed, which is strongly bound to the Ni(100) surface by two polar covalent bonds. The binding energy at the fourfold hollow site is found to be 78 kcal/mol, which is about 20 kcal/mol larger than for the other two sites, and much larger than the chemisorption energies for the experimentally observed O2 on Pt(111) and Ag(110). The reason for this difference is discussed. In a simplified valence‐bond picture the wave function of this molecularly bound O2 has a large component of a πu to πg excited state of O2. The dissociation of O2 then proceeds by two stepwise electron transfers from the surface over to the O2 3σu orbital, which completes the breaking of the O–O bond. In this latter process the energy passes over a local barrier, which is still far below the long distance asymptote, however. The local barrier height is much higher for the fourfold hollow dissociation, 35 kcal/mol over the local molecular minimum, than for the other two pathways, where the barrier height is only 6–8 kcal/mol. The 3d orbitals on nickel remain passive for all the three dissociation pathways, which is in line with the fact that also nontransition metals dissociate O2. This behavior is in contrast to the dissociation of H2 on Ni(100), where the 3d orbitals play a key role for the on‐top dissociation.
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| 35. |
- Perumal, Sathya Sai Ramakrishna Raj
(författare)
-
Spin-Orbit and Spin-Spin Coupling in the Triplet State
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The underlying theory of “Spin” of an electron and its associated inter-actions causing internal fields and spectral shift to bulk-magnetism iswell established now. Our understanding of spin properties is significant andmore useful than ever before. In recent years there seems to be an enormousinterest towards application oriented materials that harness those spin prop-erties. Theoretical simulations remain in a position to “assist or pilot” theexperimental discovery of new materials.In this work, we have outlined available methodologies for spin coupling inmulti-reference and DFT techniques. We have benchmarked multi-referencespin-Hamiltonian computation in isoelectronic diradicals - Trimethylenemethane(TMM) and Oxyallyl. Also with DFT, parameters are predicted with anewly discovered TMM-like stable diradicals, reported to have large positiveexchange interactions. Excellent agreement were obtained and our findingsemphasize that the dipole-dipole interactions alone can predict the splittingof triplet states and that DFT spin procedures hold well in organic species.We have extended our spin-studies to a highly application oriented ma-terial - nanographene. Using our novel spin-parameter arguments we haveexplained the magnetism of graphene. Our studies highlight a few signifi-cant aspects - first there seems to be a size dependency with respect to thespin-Hamiltonian; second, there is a negligible contribution of spin-orbit cou-pling in these systems; third, we give a theoretical account of spin restrictedand unrestricted schemes for the DFT method and their consequences forthe spin and spatial symmetry of the molecules; and, finally, we highlightthe importance of impurities and defects for magnetism in graphene. Wepredict triplet-singlet transitions through linear response TDDFT for thetris(8-hydroxyquinoline) aluminium complex, an organic molecule shown tohave spintronics applications in recent experiments. Our spin studies werein line with those observations and could help to understand the role of thespin-coupling phenomena.
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| 36. |
- Perumal, Sathya S R R, 1983-
(författare)
-
Spin-Spin and Spin-Orbit coupling studies of small species and magnetic system
- 2010
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The spin of an electron often misleadingly interpreted as the classical rotationof a particle. The quantum spin distinguishes itself from classicalrotation by possessing quantized states and can be detected by its magneticmoment. The properties of spin and its collective behavior with otherfundamental properties are fascinating in basic sciences. In many aspectsit offers scope for designing new materials by manipulating the ensemblesof spin. In recent years attention towards high density storage devices hasdriven the attention to the fundamental level were quantum physics rules.To understand better design of molecule based storage materials, studies onspin degrees of freedom and their coupling properties can not be neglected. To account for many body effect of two or more electrons consistent withrelativity, an approximation like the Breit Hamiltonian(BH) is used in modernquantum chemical calculations, which is successful in explaining the splitin the spectra and corresponding properties associated with it. Often differenttactics are involved for a specific level of computations. For example themulti-configurational practice is different from the functional based calculations,and it depends on the size of the system to choose between resourcesand accuracy. As the coupling terms offers extra burden of calculating theintegrals it is literally challenging. One can readily employ approximations as it suits best for the applicationoriented device computations. The possible methods available in the literatureare presented in chapter 2. The theoretical implementations of couplingfor the multi-reference and density functional method are discussed in detail.The multi-reference method precedes the density functional methodin terms of accuracy and generalizations, however it is inefficient in dealingvery large systems involving many transition elements, which is vital formolecule based magnets as they often possess open shell manifolds. On theother hand existing density functional method exercise perturbations techniqueswhich is extremely specialized for a specific system - highly coupledspins. The importance of spin-spin coupling(SSC) in organic radical-Oxyallyl(OXA)was systematically studied with different basis sets and compared with asimilar isoelectronic radical(TMM). The method of spin-spin coupling implementationsare also emphasized. Similar coupling studies were carriedivout for the species HCP and NCN along with spin-orbit coupling(SOC).The splitting of the triplet states are in good agreement with experiments
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| 37. |
- Privalov, Timofei, et al.
(författare)
-
Electron transfer in uranyl(VI)-uranyl(V) complexes in solution
- 2004
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126:31, s. 9801-9808
-
Tidskriftsartikel (refereegranskat)abstract
- The rates and mechanisms of the electron self-exchange between U(V) and U(VI) in solution have been studied with quantum chemical methods. Both outer-sphere and inner-sphere mechanisms have been investigated; the former for the aqua ions, the latter for binuclear complexes containing hydroxide, fluoride, and carbonate as bridging ligand. The calculated rate constant for the self-exchange reaction UO2+(aq) + UO22+(aq)UO22+(aq) + UO2+(aq), at 25 degreesC, is k = 26 M-1 s(-1). The lower limit of the rate of electron transfer in the inner-sphere complexes is estimated to be in the range 2 x 10(4) to 4 x 10(6) M-1 s(-1), indicating that the rate for the overall exchange reaction may be determined by the rate of formation and dissociation of the binuclear complex. The activation energy for the outer-sphere model calculated from the Marcus model is nearly the same as that obtained by a direct calculation of the precursor- and transition-state energy. A simple model with one water ligand is shown to recover 60% of the reorganization energy. This finding is important because it indicates the possibility to carry out theoretical studies of electron-transfer reactions involving M3+ and M4+ actinide species that have eight or nine water ligands in the first coordination sphere.
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| 38. |
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| 39. |
- Ramberg, Ulf, et al.
(författare)
-
Capturing progression of formal knowledge and employability skills by monitoring case discussions in class
- 2021
-
Ingår i: Teaching in Higher Education. - : Informa UK Limited. - 1356-2517 .- 1470-1294. ; 26:2, s. 246-264
-
Tidskriftsartikel (refereegranskat)abstract
- Capturing progression in students’ formal knowledge and employability skills is essential in higher education but evokes questions concerning how to assess and monitor progression. While methods for capturing students’ formal knowledge progression have traditionally been at the forefront, methods for capturing employability skills have been less researched within higher education. The aim of this study was to develop and evaluate a method to capture students’ progression of formal knowledge and employability skills in higher education. We developed a rubric to monitor case discussions in class and evaluated the rubric by using it while observing case discussions in six professional education programmes involving around 370 undergraduate and graduate students. We found that it was possible to capture similar changes in the progression of formal knowledge and skills in all professional programmes. One advantage of using this method is that students can be monitored while they participate in case discussions within their respective curricula.
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| 40. |
- Real, Florent, et al.
(författare)
-
Ab initio study of the mechanism for photoinduced yl-oxygen exchange in uranyl(VI) in acidic aqueous solution
- 2008
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 130:35, s. 11742-11751
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanism for the photochemically induced isotope-exchange reaction (UO22+)-O-17/18(aq) + (H2O)-O-16 reversible arrow (UO22+)-O-16 (aq) + (H2O)-O-17/18 has been studied using quantum-chemical methods. There is a dense manifold of states between 22 000 and 54 000 cm(-1) that results from excitations from the sigma(u) and pi(u) bonding orbitals in the (1)Sigma(+)(g) ground state to the nonbonding f(delta) and f(phi) orbitals localized on uranium. On the basis of investigations of the reaction profile in the (1)Sigma(+)(g) ground state and the excited states (3)Delta(g) (the lowest triplet state) and (3)Gamma(g) (one of the several higher triplet states), the latter two of which have the electron configurations sigma(u)f(delta) and pi(u)f(phi) respectively, we suggest that the isotope exchange takes place in one of the higher triplet states, of which the (3)Gamma(g) state was used as a representative. The geometries of the luminescent (3)Delta(g) state, the lowest in the sigma(u)f(delta,phi) manifold (the ""sigma"" states), and the (1)Sigma(+)(g) ground state are very similar, except that the bond distances are slightly longer in the former. This is presumably a result of transfer of a bonding electron to a nonbonding f orbital, which makes the excited state in some respects similar to uranyl(V). As is the case for all of the states of the pi(u)f(delta,phi) manifold (the ""pi"" states), the geometry of the (3)Gamma(g) state is very different from that of the (3)Delta(g) ""sigma"" state and has nonequivalent U-O-yl distances of 1.982 and 1.763 angstrom; in the (3)Gamma(g) state, the yl-exchange takes place by transfer of a proton or hydrogen from water to the more distant yl-oxygen. The activation barriers for proton/hydrogen transfer in the ground state and the (3)Delta(g) and (3)Gamma(g) states are 186, 219, and 84 kJ/mol, respectively. The relaxation energy for the (3)Gamma(g) state in the solvent after photoexcitation is -86 kJ/mol, indicating that the energy barrier can be overcome; the ""pi"" states are therefore the most probable route for proton/hydrogen transfer. They can be populated after UV irradiation but are too high in energy (similar to 36000-40000 cm(-1)) to be reached by a single-photon absorption at 436 nm (22 900 cm(-1)), where experimental data have demonstrated that exchange can take place. Okuyama et al. [Bull. Res. Lab. Nucl. React. (Tokyo Inst. Technol.) 1978, 3, 39-50] have demonstrated that an intermediate is formed when an acidic solution of UO22+ (aq) is flash-photolyzed in the UV range. The absorption spectrum of this short-lived intermediate (which has a maximum at 560 nm) indicates that this species arises from 436 nm excitation of the luminescent (3)Delta(g) state (which has a lifetime of similar to 2 x 10(-6) s); this is sufficient to reach the reactive ""pi"" states. It has been speculated that the primary reaction in acidic solutions of UO22+(aq) is the formation of a uranyl(V) species; our resuls indicate that the structure in the luminescent state has some similarity to that of UO2+ but that the reactive species in the states is a cation radical with a distinctly different structure.
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| 41. |
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| 42. |
- Real, Florent, et al.
(författare)
-
Theoretical investigation of the energies and geometries of photoexcited uranyl(VI) ion : A comparison between wave-function theory and density functional theory
- 2007
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:21, s. 214302-
-
Tidskriftsartikel (refereegranskat)abstract
- In order to assess the accuracy of wave-function and density functional theory (DFT) based methods for excited states of the uranyl(VI) UO22+ molecule excitation energies and geometries of states originating from excitation from the sigma(u), sigma(g), pi(u), and pi(g) orbitals to the nonbonding 5f(delta) and 5f(phi) have been calculated with different methods. The investigation included linear-response CCSD (LR-CCSD), multiconfigurational perturbation theory (CASSCF/CASPT2), size-extensivity corrected multireference configuration interaction (MRCI) and AQCC, and the DFT based methods time-dependent density functional theory (TD-DFT) with different functionals and the hybrid DFT/MRCI method. Excellent agreement between all nonperturbative wave-function based methods was obtained. CASPT2 does not give energies in agreement with the nonperturbative wave-function based methods, and neither does TD-DFT, in particular, for the higher excitations. The CAM-B3LYP functional, which has a corrected asymptotic behavior, improves the accuracy especially in the higher region of the electronic spectrum. The hybrid DFT/MRCI method performs better than TD-DFT, again compared to the nonperturbative wave-function based results. However, TD-DFT, with common functionals such as B3LYP, yields acceptable geometries and relaxation energies for all excited states compared to LR-CCSD. The structure of excited states corresponding to excitation out of the highest occupied sigma(u) orbital are symmetric while that arising from excitations out of the pi(u) orbitals have asymmetric structures. The distant oxygen atom acquires a radical character and likely becomes a strong proton acceptor. These electronic states may play an important role in photoinduced proton exchange with a water molecule of the aqueous environment.
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| 43. |
- Reuterswärd, Philippa, et al.
(författare)
-
Levels of human proteins in plasma as indicators for acute severe pediatric malaria
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundExisting low resource diagnostics for malaria infection suffer from sensitivity and specificity issues while lacking sufficient prognostic value. Identifying human host proteins could improve the possibilities to predict the risk of development of acute severe malaria. This will possible enable improved treatment and thereby lead to a decrease in mortality of malaria infected children. Furthermore, discovering host proteins with altered levels during active infection could generate leads to better understand host-parasite interaction.ResultsHere, we have analyzed a total of 541 pediatric plasma samples that were collected from community controls and individuals with mild or severe malaria in Rwanda. Protein profiles of these plasma samples were generated with an antibody-based suspension bead array containing 255 antibodies targeting 115 human proteins. We present 22 proteins with a strong discriminatory capacity (adjusted p-values below 10-19) for separating malaria cases from community controls. This panel of proteins contains among others acute phase proteins and proteins connected to cell adhesion and migration. Among these, three proteins showed lower plasma levels in the group of malaria-infected individuals compared to the control group. One of these proteins is the anti-adhesive secreted protein acidic and cysteine rich (SPARC) with possible connections to parasite cytoadhesion. A multi-protein panel of six proteins, including SPARC, could differentiate between controls and malaria cases with an AUC of 0.98. Furthermore, a panel of 37 proteins, including proteins associated to erythrocyte membranes, was identified as candidates for separation of mild and severe malaria patients (adjusted pvalues below 0.05).ConclusionThe herein identified set of human proteins has a significant discriminatory capacity between community controls and malaria cases. We also present proteins offering the possibility to enable stratification and risk prediction for the development of severe malaria. This constitutes an important set that could enable enhanced understanding and thereby also possibilities for better treatment of acute severe pediatric malaria.
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| 44. |
- Reuterswärd, Philippa, et al.
(författare)
-
Levels of human proteins in plasma associated with acute paediatric malaria
- 2018
-
Ingår i: Malaria Journal. - : BMC. - 1475-2875. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The intimate interaction between the pathophysiology of the human host and the biology of the Plasmodium falciparum parasite results in a wide spectrum of disease outcomes in malaria. Development of severe disease is associated with a progressively augmented imbalance in pro- and anti-inflammatory responses to high parasite loads and sequestration of parasitized erythrocytes. Although these phenomena collectively constitute common denominators for the wide variety of discrete severe malaria manifestations, the mechanistic rationales behind discrepancies in outcome are poorly understood. Exploration of the human pathophysiological response by variations in protein profiles in plasma presents an excellent opportunity to increase the understanding. This is ultimately required for better prediction, prevention and treatment of malaria, which is essential for ongoing elimination and eradication efforts. Results: An affinity proteomics approach was used to analyse 541 paediatric plasma samples collected from community controls and patients with mild or severe malaria in Rwanda. Protein profiles were generated with an antibody-based suspension bead array containing 255 antibodies targetting 115 human proteins. Here, 57 proteins were identified with significantly altered levels (adjusted p-values<0.001) in patients with malaria compared to controls. From these, the 27 most significant proteins (adjusted p-values<10(-14)) were selected for a stringent analysis approach. Here, 24 proteins showed elevated levels in malaria patients and included proteins involved in acute inflammatory response as well as cell adhesion. The remaining three proteins, also implicated in immune regulation and cellular adhesivity, displayed lower abundance in malaria patients. In addition, 37 proteins (adjusted p-values<0.05) were identified with increased levels in patients with severe compared to mild malaria. This set includes, proteins involved in tissue remodelling and erythrocyte membrane proteins. Collectively, this approach has been successfully used to identify proteins both with known and unknown association with different stages of malaria. Conclusion: In this study, a high-throughput affinity proteomics approach was used to find protein profiles in plasma linked to P. falciparum infection and malaria disease progression. The proteins presented herein are mainly involved in inflammatory response, cellular adhesion and as constituents of erythrocyte membrane. These findings have a great potential to provide increased conceptual understanding of host-parasite interaction and malaria pathogenesis.
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| 45. |
- Ribacke, Ulf, et al.
(författare)
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Genome wide gene amplifications and deletions in Plasmodium falciparum
- 2007
-
Ingår i: Molecular and biochemical parasitology (Print). - : Elsevier BV. - 0166-6851 .- 1872-9428. ; 155:1, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- The extent to which duplications and deletions occur in the Plasmodium falciparum genome, outside of the subtelomeres, and their contribution to the virulence of the malaria parasite is not known. Here we show the presence of multiple genome wide copy number polymorphisms (CNPs) covering 82 genes, the most extensive spanning a cumulative size of 110 kilobases. CNPs were identified in both laboratory strains and fresh clinical isolates using a 70-mer oligonucleotide microarray in conjunction with fluorescent in situ hybridizations and real-time quantitative PCR. The CNPs were found on all chromosomes except on chromosomes 6 and 8 and involved a total of 50 genes with increased copy numbers and 32 genes with decreased copy numbers relative to the 3D7 parasite. The genes, amplified in up to six copies, encode molecules involved in cell cycle regulation. cell division, drug resistance, erythrocyte invasion, sexual differentiation and unknown functions. These together with previous findings, suggest that the malaria parasite employs gene duplications and deletions as general strategies to enhance its survival and spread. Further analysis of the impact of discovered genetic differences and the underlying mechanisms is likely to generate a better understanding of the biology and the virulence of the malaria parasite.
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| 46. |
- Ribacke, Ulf, et al.
(författare)
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Improved in vitro culture of plasmodium falciparum permits establishment of clinical isolates with preserved multiplication, invasion and rosetting phenotypes
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- To be able to robustly propagate P. falciparum at optimal conditions in vitro is of fundamental importance for genotypic and phenotypic studies of both established and fresh clinical isolates. Cryo-preserved P. falciparum isolates from Ugandan children with severe or uncomplicated malaria were investigated for parasite phenotypes under different in vitro growth conditions or studied directly from the peripheral blood. The parasite cultures showed a minimal loss of parasite-mass and preserved percentage of multiple infected pRBCs to that in peripheral blood, maintained adhesive phenotypes and good outgrowth and multiplication rates when grown in suspension and supplemented with gas. In contrast, abnormal and greatly fluctuating levels of multiple infections were observed during static growth conditions and outgrowth and multiplication rates were inferior. Serum, as compared to Albumax, was found necessary for optimal presentation of PfEMP1 at the pRBC surface and/or for binding of serum proteins (immunoglobulins). Optimal in vitro growth conditions of P. falciparum therefore include orbital shaking (50 rev/min), human serum (10%) and a fixed gas composition (5% O2, 5% CO2, 90% N2). We subsequently established 100% of 76 frozen patient isolates and found rosetting with schizont pRBCs in every isolate (>26% schizont rosetting rate). Rosetting during schizogony was often followed by invasion of the bound RBC as seen by regular and time-lapse microscopy as well as transmission electron microscopy. The peripheral parasitemia, the level of rosetting and the rate of multiplication correlated positively to one another for individual isolates. Rosetting was also more frequent with trophozoite and schizont pRBCs of children with severe versus uncomplicated malaria (p<0.002; p<0.004). The associations suggest that rosetting enhances the ability of the parasite to multiply within the human host.
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| 47. |
- Ruipérez, Fernando, 1978-, et al.
(författare)
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An ab initio theoretical study of the electronic structure of UO2+ and [UO2(CO3)3]5-
- 2009
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society. - 1089-5639 .- 1520-5215. ; 113, s. 1420-1428
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Tidskriftsartikel (refereegranskat)abstract
- The electronic spectra up to 50000 cm-1 of uranyl(V) both as a bare ion, UO21, and coordinated with three carbonate ligands, [UO2(CO3)3]5-, are presented. Solvent effects were treated by a nonequilibrium continuum solvent model. The transition energies were obtained at the spin-orbit level using relativistic wave function based multiconfigurational methods such as the complete active space self-consistent field method (CASSCF) and the complete active space with second-order perturbation theory (CASPT2) followed by a calculation of the spin-orbit effects at the variation-perturbation level. Earlier relativistic intermediate Hamiltonian Fock space coupled-cluster calculations on the spectrum of the bare uranyl(V) ion were extended to investigate the influence of electron correlation effects on spacings between the electronic states. This study is an attempt to contribute to an enhanced understanding of the electronic structure of actinyl ions. Both spectra show transitions within nonbonding orbitals and between nonbonding and antibonding orbitals as well as charge transfers from the uranyl oxygens to uranium. The ground state in UO2+ is found to be 2Φ5/2u, corresponding to the σu2φu1 configuration, while in [UO2(CO3)3]5-, it is 2∆3/2u, arising from the σu2δu1 configuration. It is remarkable that the excited state corresponding to an excitation from the nonbonding δu to the uranyl antibonding 3πu* molecular orbital is significantly lower in energy in the carbonate complex, 6623 cm-1, than that in the bare ion, 17908 cm-1. The first ligand (carbonate) to metal charge-transfer excitation is estimated to occur above 50000 cm-1. The reported results compare favorably with experiment when available.
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| 48. |
- Ruiperez, Fernando, et al.
(författare)
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Charge Transfer in Uranyl(VI) Halides [UO2X4]2− (X = F, Cl, Br, and I). A Quantum Chemical Study of the Absorption Spectra
- 2010
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 114:10, s. 3615-3621
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Tidskriftsartikel (refereegranskat)abstract
- The electronic spectra of uranyl(VI) coordinated with four equatorial halide ligands, [UO2X4]2− (X = F, Cl, Br, and I), have been calculated at the all-electron level using the multiconfigurational CASPT2 method, with spin−orbit coupling included through the variational-perturbational method. The halide-to-uranyl charge-transfer states were taken into account in the calculation by including ligand orbitals in the active space. In order to do that, it is assumed that the charge transfer takes place from only one of the four ligands. Two models, which in principle can describe this, were investigated: the first one makes use of a localizing technique and the second one replaces three ligands by ab initio model potentials (AIMPs). The basis set dependence was investigated by using two different basis sets for the halides, of triple-ζ and quadruple-ζ quality. The localization procedure turned out to be strongly basis set dependent, and the most stable results were obtained with ab initio model potentials. The ground state is a closed shell singlet state, and the first excitation is from the bonding σu orbital on uranyl to the nonbonding δu orbitals, except for the [UO2I4]2− complex, where the first excited state has a mixed character of charge transfer from the I− and the σu1u1 configuration. In [UO2F4]2− there is no charge transfer excitation below 50000 cm−1, while in [UO2Cl4]2− it appears around 33000 cm−1 and in [UO2Br4]2− around 23000 cm−1. A blueshift of the spectra, from F− to I−, is observed. The calculations compare reasonably well with available experimental results.
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| 49. |
- Ruipérez, Fernando, 1978-, et al.
(författare)
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Charge transfer in uranyl(VI) halides [UO2X4]2- (X = F, Cl, Br and I). A quantum chemical study of the absorption spectra
-
Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215.
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic spectra of uranyl(VI) coordinated with four equatorial halide ligands, [UO2X4]2- (X = F, Cl, Br and I), have been calculated at the all-electron level using the multiconfigurational CASPT2 method, with spin-orbit coupling included through the variational-perturbational method. The halide-to-uranyl charge-transfer states were taken into account in the calculation by including ligand orbitals in the active space. In order to do that, it is assumed that the charge transfer takes place from only one of the four ligands. Two models which in principle can describe this were investigated: the first one makes use of a localizing technique and the second one replaces three ligands by ab initio model potentials (AIMPs). The basis set dependence was investigated by using two different basis sets for the halides, of triple-ζ and quadruple-ζ quality. The localization procedure turned out to be strongly basis set dependent, and the most stable results were obtained with ab initio model potentials. The ground state is a closed shell singlet state, and the first excitation is from the bonding σu orbital on uranyl to the nonbonding δu orbitals, except for the [UO2I4]2− complex, where the first excited state has a mixed character of charge transfer from the I− and the σu1φu1 configuration. In [UO2F4]2− there is no charge transfer excitation below 50000 cm−1 , while in [UO2Cl4]2− it appears around 33000 cm−1 and in [UO2Br4]2− around 23000 cm−1 . A blueshift of the spectra, from F− to I−, is observed. The calculations compare reasonably well with available experimental results.
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| 50. |
- Schüle, Josef, et al.
(författare)
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Ab initio investigation of methyl adsorption on Ni(111)
- 1988
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Ingår i: Journal of Molecular Structure: THEOCHEM. - 0166-1280. ; 47, s. 151-153
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Tidskriftsartikel (refereegranskat)abstract
- Single reference CI calculations have been performed to investigate the adsorption of methyl on Ni(111) using clusters as models for the surface. Methyl is adsorbed in the threefold hollow position. The calculated symmetric C-H stretching frequency is in reasonable agreement with experiment. The lowering of the C-H frequency is explained by the large charge transfer from the surface to methyl.
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