| 1. |
- Di Francesco, Davide, et al.
(författare)
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Debottlenecking a Pulp Mill by Producing Biofuels from Black Liquor in Three Steps
- 2021
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 14:11, s. 2414-2425
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Tidskriftsartikel (refereegranskat)abstract
- By extracting lignin, pulp production can be increased without heavy investments in a new recovery boiler, the typical bottleneck of a pulp mill. The extraction is performed by using 0.20 and 0.15 weight equivalents of CO2 and H2SO4 respectively. Herein, we describe lignin esterification with fatty acids using benign reagents to generate a lignin ester mixable with gas oils. The esterification is accomplished by activating the fatty acid and lignin with acetic anhydride which can be regenerated from the acetic acid recycled in this reaction. The resulting mass balance ratio is fatty acid/lignin/acetic acid (2 : 1 : 0.1). This lignin ester can be hydroprocessed to generate hydrocarbons in gasoline, aviation, and diesel range. A 300-hour continuous production of fuel was accomplished. By recirculating reagents from both the esterification step and applying a water gas shift reaction on off-gases from the hydroprocessing, a favorable overall mass balance is realized.
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| 2. |
- Argyropoulos, Dimitris D. S., et al.
(författare)
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Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges
- 2023
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Ingår i: ChemSusChem. - : John Wiley and Sons Inc. - 1864-5631 .- 1864-564X. ; 16:23
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Forskningsöversikt (refereegranskat)abstract
- Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.
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| 3. |
- Dahlstrand, Christian, et al.
(författare)
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Exploration of the π-Electronic Structure of Singlet, Triplet, and Quintet States of Fulvenes and Fulvalenes Using the Electron Localization Function
- 2012
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 116:20, s. 5008-5017
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Tidskriftsartikel (refereegranskat)abstract
- The singlet ground states and lowest triplet states of penta- and heptafulvene, their benzannulated derivatives, as well as the lowest quintet states of pentaheptafulvalenes, either the parent compound or compounds in which the two rings are intercepted by either an alkynyl or a phenyl segment, were investigated at the (U)OLYP/6-311G(d,p) density functional theory level. The influence of (anti)-aromaticity was analyzed by the structure-based aromaticity index HOMA, the harmonic oscillator model of aromaticity. The extent of (anti)aromatic character was also evaluated in terms of the pi-electron (de)localization as measured by the pi component of the electron localization function (ELF pi). The natural atomic orbital (NAO) occupancies were calculated in order to evaluate the degree of pi-electron shift caused by the opposing electron-counting rules for aromaticity in the electronic ground state (S-0; Hiickel's rule) and the first pi pi* excited triplet state (T-1; Baird's rule). Pentaheptafulvalene (5) shows a shift of 0.5 pi electrons from the 5-ring to the 7-ring when going from the S-0 state to the lowest quintet state (Qu(1)). The pentaheptafulvalene 5 and [5.6.7]quinarene 7 were also investigated in their 90 degrees twisted conformations. From our study it is apparent that excitation localization in fulvalenes, but not in fulvenes, to a substantial degree is determined by aromaticity localization to triplet biradical 4n pi-electron cycles. Isolated benzene rings in these compounds tend to remain as closed-shell 6 pi-electron cycles.
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| 4. |
- Dahlstrand, Christian
(författare)
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Ground and Excited State Aromaticity : Design Tools for π-Conjugated Functional Molecules and Materials
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is on the aromaticity of the ground state and electronically excited states of π-conjugated molecules and polymers, as well as how aromaticity is connected to their properties.The electronic structures of polybenzenoid hydrocarbons (PBHs) were explored through density functional theory (DFT) calculations and the π-component of the electron localization function (ELFπ). The study revealed how the π-electronic structure is influenced by the fusion of double bonds or benzene rings to the PBHs. We also demonstrated that the π-electrons of benzene extend to accommodate as much aromaticity as possible when bond length distorted. The aromatic chameleon property displayed by fulvenes, isobenzofulvenes, fulvalenes, bis(fulvene)s, and polyfulvenes were investigated using DFT calculations. The tria-, penta-, and heptafulvenes were shown to possess ionization energies and electron affinities which can be tuned extensively by substitution, some of which even outperform TTF and TCNQ, the prototypical electron donor and acceptor, respectively. The singlet-triplet energy gap of pentafulvenes can be tuned extensively by substitution to the point that the triplet state is lower than the singlet state and thus becomes the ground state. The ELFπ of isobenzofulvene shows that the benzene ring in an electronically excited state can be more aromatic than the corresponding ring in the ground state. We have shown that the 6-ring of [5.6.7]quinarene is influenced by a Hückel aromatic resonance structure with 4n+2 π-electrons in the excited quintet state. The bis(fulvene)s which are composed of a donor type heptafulvene and an acceptor type pentafulvene, retain the basic donor-acceptor properties of the two fragments and could function as compact donor-acceptor dyads. A few of the designed polyfulvenes were found to have band gaps below 1 eV at the PBC-B3LYP/6-31G(d) level.Various 2,7-disubstituted fluorenones and dibenzofulvenes were synthesized and their excited state properties were investigated by absorption spectroscopy and time-dependent DFT calculations. It was found that the 1A → 1B transition of ππ* character can be tuned by substitution in the 2,7-positions. The 2,7-bis(N,N-dimethyl) derivatives of fluorenone and dibenzofulvene displayed low energy transitions at 2.18 and 1.61 eV, respectively, in toluene.
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| 5. |
- Dahlstrand, Christian, et al.
(författare)
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Polyfulvenes : Polymers with "Handles" That Enable Extensive Electronic Structure Tuning
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:46, s. 25726-25737
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental electronic structure properties of substituted poly(penta)fulvenes and pentafulvene-based polymers are analyzed through qualitative molecular orbital (MO) theory combined with calculations at the B3LYP and HSE06 hybrid density functional theory (DFT) levels. We argue that the pentafulvene monomer unit has a unique character because electron density in the exocyclic C=C double bond can be polarized into and out of the five-membered ring, a feature that is not available to other more commonly used monomers. It is investigated how the energy gaps between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively), as approximate band gaps, are influenced by exocyclic substitution, introduction of linker groups, benzannulation, and ring substitution. In particular, the exocyclic positions of the fulvene act as handles by which the electronic structure of the polymer can be tuned between the quinoid and fulvenoid valence bond isomers; electron-withdrawing exocyclic substituents lead to polyfulvenes in the quinoid form while those with electron-donating substituents prefer the fulvenoid. Taken together, the HOMO-LUMO gaps of polyfulvenes can be tuned extensively, varying in ranges 0.77-2.44 eV (B3LYP) and 0.35-2.00 eV (HSE06) suggesting that they are a class of polymers with highly interesting, yet nearly unexplored, properties.
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| 6. |
- Dahlstrand, Christian, et al.
(författare)
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Substituent Effects on the Electron Affinities and Ionization Energies of Tria-, Penta-, and Heptafulvenes : A Computational Investigation
- 2010
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 75:23, s. 8060-8068
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Tidskriftsartikel (refereegranskat)abstract
- The extent of substituent influence on the vertical electron affinities (EAs) and ionization energies (IEs) of 43 substituted tria-, penta-, and heptafulvenes was examined computationally at the OVGF/6-311G(d)//B3LYP/6-311G(d) level of theory and compared with those of tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (TTF) as representing strong electron-acceptor and -donor compounds, respectively. The substituents X at the exocyclic positions of the fulvenes were either NH2, H, or CN, while the substituents Y at the ring positions were H, CI, F, CN, or NH2. The variations of the EAs and lEs were rationalized by qualitative arguments based on frontier orbital symmetries for the different fulvene classes with either X or Y being constant. The minimum and maximum values found for the calculated EAs of the tria-, penta-, and heptafulvenes were 0.51-2.05, 0.24-3.63, and 0.53-3.14 eV, respectively, and for the IEs 5.27-9.96, 7.07-10.31, and 6.35-10.59 eV, respectively. Two of the investigated fulvenes outperform TCNQ (calcd EA = 2.63 eV) and one outperforms TTF (calcd IE = 6.25 eV) with regard to acceptor and donor abilities, respectively. We also evaluated the properties of bis(fulvene)s, i.e., compounds composed of a donor-type heptafulvene fused with an acceptor-type pentafulvene, and it was revealed that these bis(fulvene)s can be designed so that the IE and EA of the two separate fulvene segments are retained, potentially allowing for the design of compact donor-acceptor dyads.
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| 7. |
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| 8. |
- Dahlstrand, Henrik, et al.
(författare)
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Comparison of metal ion concentrations and implant survival after total hip arthroplasty with metal-on-metal versus metal-on-polyethylene articulations : a 16-year follow-up of a prospective randomized study
- 2017
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3674 .- 1745-3682. ; 88:5, s. 490-495
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose - Large metal-on-metal (MoM) articulations are associated with metal wear and corrosion, leading to increased metal ion concentrations and unacceptable revision rates. There are few comparative studies of 28-mm MoM articulations with conventional metal-on-polyethylene (MoP) couplings. We present a long-term follow-up of a randomized controlled trial comparing MoM versus MoP 28-mm articulations, focused on metal ions and implant survival. Patients and methods - 85 patients with a mean age of 65 years at surgery were randomized to a MoM (Metasul) or a MoP (Protasul) bearing. After 16 years, 38 patients had died and 4 had undergone revision surgery. 13 patients were unavailable for clinical follow-up, leaving 30 patients (n = 14 MoM and n = 16 MoP) for analysis of metal ion concentrations and clinical outcome. Results - 15-year implant survival was similar in both groups (MoM 96% [95% CI 88-100] versus MoP 97% [95% CI 91-100]). The mean serum cobalt concentration was 4-fold higher in the MoM (1.5 mu g/L) compared with the MoP cohort (0.4 mu g/L, p < 0.001) and the mean chromium concentration was double in the MoM (2.2 mu g/L) compared with the MoP cohort (1.0 mu g/L, p = 0.05). Mean creatinine levels were similar in both groups (MoM 93 mu mol/L versus MoP 92 mu mol/L). Harris hip scores differed only marginally between the MoM and MoP cohorts. Interpretation - This is the longest follow-up of a randomized trial on 28-mm MoM articulations, and although implant survival in the 2 groups was similar, metal ion concentrations remained elevated in the MoM cohort even in the long term.
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| 9. |
- Dahlstrand, Henrik, et al.
(författare)
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Elevated serum concentrations of cobalt, chromium, nickel, and manganese after metal-on-metal alloarthroplasty of the hip : a prospective randomized study
- 2009
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Ingår i: The Journal of Arthroplasty. - : Elsevier BV. - 0883-5403 .- 1532-8406. ; 24:6, s. 837-845
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Tidskriftsartikel (refereegranskat)abstract
- In this prospective randomized study, we investigate metal ion concentrations and clinical outcome 2 years after metal-on-metal (28 patients) or metal-on-polyethylene (26 patients) hip arthroplasty with 28-mm modular heads. Metal ion concentrations in patient serum were analyzed by high-resolution plasma mass spectrometry. The clinical outcome was almost identical in both groups with respect to the Harris hip score and the Medical Outcome Study Short Form-36; and on plain radiography, no signs of loosening occurred in any group. In the metal-on-metal group, concentrations of all investigated ions increased significantly when compared with preoperative values: cobalt, 15.3-fold (95% confidence interval [CI], 9.4-21.2); chromium, 5.2-fold (CI, 3.5-7.0); nickel, 2.1-fold (CI, 1.2-3.0); and manganese, 1.6-fold (CI, 1.3-2.0). In the metal-on-polyethylene group, a smaller but significant increase in the concentrations of cobalt and nickel occurred, whereas concentrations of the other ions did not change significantly.
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| 10. |
- Dahlstrand, Henrik
(författare)
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Evaluation of a metal-on-metal total hip arthroplasty
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: After the introduction of the Metasul system by Weber in 1988, total hip arthroplasty (THA) with metal-on-metal (MoM) bearings became increasingly popular in the 1990s. MoM bearings aimed to reduce the problem of aseptic loosening associated with polyethylene wear particles from conventional polyethylene cups. The following introduction of hip resurfacing added positive factors as bone sparing and large caliber heads, reducing the risk of dislocations. After almost two decades of increasing use of MoM prostheses, reports of implant failure and adverse reactions to metal became numerous. Starting in 2009, a dramatic decrease in the use of MoM bearings has been seen. Patients and methods: Paper I was an experimental in vitro study measuring the amount of metal worn off from a MoM prosthesis with a 28-mm diameter head, using a hip simulator. Papers II-IV were all based on a prospective, randomized, controlled clinical trial including 85 patients allocated into two groups. One group was operated with a MoM prosthesis while the other group received a similar prosthesis with a conventional metal-on-polyethylene (MoP) bearing. All components were cemented and 28-mm heads were used. Clinical outcome and serum metal ion concentrations were evaluated at short-term (three, six, 12 and 24 months, paper II), medium-term (7 years, paper III) and long-term (16 years, paper IV) follow-up. Overall longterm survival of the implants was estimated after a mean of 16 years (paper IV). Results: A so-called run-in phase with higher initial wear from MoM implants was seen in the joint simulator testing within the equivalent of the first year of use. As expected, patients with MoM bearings showed higher cobalt (Co) and chromium (Cr) ion concentrations compared to patients in the MoP group at all time-points from 3 months to 16 years postoperatively. The percentage of circulating HLA DR+ CD8+ T-cells was higher in the MoM compared to MoP group (10.6 vs. 6.7 %; p = 0.03) and was positively correlated to systemic concentrations of Co and Cr. At the last follow-up 16 years after the index surgery, radiographic result and clinical performance was similar in both groups (Harris hip score: MoM=91, MoP=95, p=0.28) and no difference between groups was seen regarding implant survival (MoM: 93 % [95% CI: 83-100%]; MoP: 95 % [95% CI: 87-100%], p=0.99). Conclusions: This thesis evaluated a 28-mm head THA, comparing a MoM bearing with a conventional MoP articulation. Both articulations performed equally well in regard to long-term implant survival and clinical outcome. Due to the absence of clinical superiority of the MoM bearing and concerns about biological effects of the MoM articulation, the use of MoP articulations is recommended.
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| 11. |
- Dahlstrand, Karl, et al.
(författare)
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Ersättning för kränkning ur ett rättssociologiskt perspektiv. "En särskild typ av omtanke och kärlek".
- 2011
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Ingår i: Brottsoffret och kriminalpolitiken. - 9789139206002 ; , s. 359-380
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Bokkapitel (refereegranskat)abstract
- I artikeln kommer brottsoffrens kränkningsersättning att analyseras ur ett rättssociologiskt perspektiv. Ersättningen kommer att relateras till den svenska kriminalpolitiska utvecklingen, till olika samhälls- och rättsvetenskapliga teorier och begrepp vilka kan vara användbara för en fördjupad förståelse av ersättningen utifrån skadeståndsrättsligt, viktimologiskt och kriminalpolitiskt perspektiv. Sedan Aristoteles (384–322 f.Kr.) införde distinktionen mellan den distributiva och korrektiva (av Thomas av Aquino även kallad för den kompensatoriska och som jag använder här) formen av rättvisa, har dessa olika kategorier av rättvisa uppfattats som två i grunden separata företeelser. Distributiv rättvisa gäller, förenklat sett, hur resurser skall fördelas, och den förutsätter normalt intressekonflikter mellan individer och grupper gentemot kollektivets nyttigheter, ofta i form av staten. Den kompensatoriska rättvisan avser hur ersättning för ett visst handlande skall bestämmas och rör i princip enbart relationen mellan två parter. I det mellanmänskliga umgänget kan någon begå orättvisa gärningar eller skada någon annan, och den som ofrivilligt blivit föremål för sådan orättvisa eller skada skall enligt den kompensatoriska rättvisan ersättas och kompenseras för detta, samtidigt som den som begått handlingen skall straffas. I praktiken, har det hävdats, föregås den kompensatoriska rättvisan av den distributiva, eftersom en strukturell orättvisa påverkar hur de mellanmänskliga handlingarna värderas och eventuellt korrigeras utifrån rättvisehänsyn.1 Grundläggande för den kompensatoriska och korrektiva rättvisan är dess djupa korrelativa i meningen växelvisa dimension, skadevållarens skyldigheter går inte att skilja från den skadelidandes rättigheter och vice versa. Det finns en överhängande risk med att det sammantagna ersättningssystemet framstår som alltför komplext ur den enskildes synvinkel. Detta är olyckligt eftersom ersättningens symboliska funktion av att konkretisera rättens normativa grund hotas. Avslutningsvis skulle jag därför vilja lyfta fram behovet av ökad kunskap om hur ersättningssystemet upplevs utifrån brottsoffrens perspektiv. Att skaffa sådan kunskap är dock ingen enkel uppgift, eftersom skilda kunskapsnivåer hos respondenterna rörande samspelet mellan försäkringar, skadestånd och straff spelar stor roll för utfallet. För att knyta an till min inledning vill jag därför åter betona värdet av förenkling och överblickbarhet i fråga om samhällets reaktioner på brottsliga gärningar. Detta är inte minst viktigt för att på sikt stödet skall kunna bevaras för en human kriminalpolitik grundad på kunskap: när rättens kommunikation inte når mottagaren ökar bara fixeringen vid det oförlösta, och detta medför i praktiken krav på vedergällning och upprättelse.
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| 12. |
- Dahlstrand, Karl, et al.
(författare)
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Rättens transcendens. Om skälighet inom avtalsrätten och relevansen av Rawls rättviseteori
- 2014
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Ingår i: Vetenskapssocieteten i Lund. Årsbok 2014. - 0349-053X. - 9789198055122 ; , s. 39-64
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Bokkapitel (refereegranskat)abstract
- Följande kapitel kommer att behandla avtalsrättens centrala generalklausul som gör det möjligt att jämka eller ogiltigförklara oskäliga avtalsvillkor. Paragrafen är omstridd och har tilldragit sig intresse då den öppnar upp för rättstillämparens skönsmässiga avgöranden – det inte finns några riktlinjer för vad som kan betecknas som oskäligt utöver den domstolspraxis som utvecklats. Det kan därmed vara svårt att förutse effekterna av ett avtal och generalklausulen har även tillämpats analogt inom andra rättsområden än avtalsrätten. Generalklausulen är därtill intressant ur flera moralfilosofiska, samhällsvetenskapliga och rättsvetenskapliga perspektiv. I den följande framställningen kommer särskilt den analytiska filosofin och John Rawls rättviseteori att lyftas fram och diskuteras utifrån denna generalklausul.
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| 13. |
- Finke, Aaron D., et al.
(författare)
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The 6,6-Dicyanopentafulvene Core : A Template for the Design of Electron-Acceptor Compounds
- 2015
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 21:22, s. 8168-8176
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Tidskriftsartikel (refereegranskat)abstract
- The electron-accepting ability of 6,6-dicyanopentafulvenes (DCFs) can be varied extensively through substitution on the five-membered ring. The reduction potentials for a set of 2,3,4,5-tetraphenyl-substituted DCFs, with varying substituents at the para-position of the phenyl rings, strongly correlate with their Hammett sigma(p)-parameters. By combining cyclic voltammetry with DFT calculations ((U)B3LYP/6-311+G(d)), using the conductor-like polarizable continuum model (CPCM) for implicit solvation, the absolute reduction potentials of a set of twenty DCFs were reproduced with a mean absolute deviation of 0.10eV and a maximum deviation of 0.19eV. Our experimentally investigated DCFs have reduction potentials within 3.67-4.41eV, however, the computations reveal that DCFs with experimental reduction potentials as high as 5.3eV could be achieved, higher than that of F-4-TCNQ (5.02eV). Thus, the DCF core is a template that allows variation in the reduction potentials by about 1.6eV.
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| 14. |
- Hailer, Nils P., et al.
(författare)
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Elevation of circulating HLA DR+ CD8+ T-cells and correlation with chromium and cobalt concentrations 6 years after metal-on-metal hip arthroplasty : a randomized trial
- 2011
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3674 .- 1745-3682. ; 82:1, s. 6-12
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose Following metal-on-metal hip arthroplasty (THA), immunological reactions including changes in lymphocyte populations, aseptic loosening, and lymphocytic pseudotumors occur. We hypothesized that changes in lymphocyte subpopulations would be associated with elevated metal ion concentrations. Methods A randomized trial involving 85 patients matched for age and sex and randomized to receiving metal-on-metal (n = 41) or metal-on-polyethylene total hip arthroplasty (n = 44) was conducted. 36 patients were eligible for follow-up after mean 7 (6-8) years. Concentrations of chromium and cobalt were analyzed by high-resolution inductively coupled plasma mass spectrometry. Leukocyte subpopulations and immunoglobulins in patient blood were measured using standard laboratory methods. Results Patients with a metal-on-metal hip had higher serum concentrations of chromium (1.05 vs. 0.36 μg/L; p < 0.001) and cobalt (0.86 vs. 0.24 μg/L; p < 0.001) than those with metal-on-polyethylene. The percentage of HLA DR(+) CD8(+) T-cells was higher in the metal-on-metal group (10.6 vs. 6.7%; p = 0.03) and correlated positively with chromium and cobalt concentrations in patient blood (Pearson's correlation coefficient: 0.39, p = 0.02; 0.36, p = 0.03, respectively). The percentage of B-cells was lower in the metal-on-metal group (p = 0.01). The two groups were similar with respect to immunoglobulin concentrations and Harris hip scores, and there were no radiographic signs of loosening. Interpretation We conclude that immunological alterations appear to be associated with increased cobalt and chromium concentrations. It is tempting to speculate that HLA DR(+) CD8(+) T-cells are involved in the pathogenesis of allergic reactions, implant loosening, and lymphocytic pseudotumors.
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| 15. |
- Jorner, Kjell, et al.
(författare)
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Impact of Ground- and Excited-State Aromaticity on Cyclopentadiene and Silole Excitation Energies and Excited-State Polarities
- 2014
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 20:30, s. 9295-9303
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Tidskriftsartikel (refereegranskat)abstract
- A new qualitative model for estimating the properties of substituted cyclopentadienes and siloles in their lowest pi pi* excited states is introduced and confirmed through quantum chemical calculations, and then applied to explain earlier reported experimental excitation energies. According to our model, which is based on excited-state aromaticity and antiaromaticity, siloles and cyclopentadienes are cross-hyperconjugated "aromatic chameleons" that adapt their electronic structures to conform to the various aromaticity rules in different electronic states (Huckel's rule in the pi(2) electronic ground state (S-0) and Baird's rule in the lowest pi pi* excited singlet and triplet states (S-1 and T-1)). By using pen-and-paper arguments, one can explain polarity changes upon excitation of substituted cyclopentadienes and siloles, and one can tune their lowest excitation energies by combined considerations of ground-and excited-state aromaticity/antiaromaticity effects. Finally, the "aromatic chameleon" model can be extended to other monocyclic compound classes of potential use in organic electronics, thereby providing a unified view of the S-0, T-1, and S-1 states of a range of different cyclic cross-pi-conjugated and cross-hyperconjugated compound classes.
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| 16. |
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| 17. |
- Micke, Patrick, et al.
(författare)
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The prognostic impact of the tumour stroma fraction : A machine learning-based analysis in 16 human solid tumour types
- 2021
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Ingår i: EBioMedicine. - : Elsevier. - 2352-3964. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- Background: The development of a reactive tumour stroma is a hallmark of tumour progression and pronounced tumour stroma is generally considered to be associated with clinical aggressiveness. The variability between tumour types regarding stroma fraction, and its prognosis associations, have not been systematically analysed.Methods: Using an objective machine-learning method we quantified the tumour stroma in 16 solid cancer types from 2732 patients, representing retrospective tissue collections of surgically resected primary tumours. Image analysis performed tissue segmentation into stromal and epithelial compartment based on pan-cytokeratin staining and autofluorescence patterns.Findings: The stroma fraction was highly variable within and across the tumour types, with kidney cancer showing the lowest and pancreato-biliary type periampullary cancer showing the highest stroma proportion (median 19% and 73% respectively). Adjusted Cox regression models revealed both positive (pancreato-biliary type periampullary cancer and oestrogen negative breast cancer, HR(95%CI)=0.56(0.34-0.92) and HR (95%CI)=0.41(0.17-0.98) respectively) and negative (intestinal type periampullary cancer, HR(95%CI)=3.59 (1.49-8.62)) associations of the tumour stroma fraction with survival.Interpretation: Our study provides an objective quantification of the tumour stroma fraction across major types of solid cancer. Findings strongly argue against the commonly promoted view of a general associations between high stroma abundance and poor prognosis. The results also suggest that full exploitation of the prognostic potential of tumour stroma requires analyses that go beyond determination of stroma abundance.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Yadav, Sangeeta, et al.
(författare)
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Exploiting the Aromatic Chameleon Character of Fulvenes for Computational Design of Baird-Aromatic Triplet Ground State Compounds
- 2019
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Ingår i: Chemistry - An Asian Journal. - : Wiley-VCH Verlagsgesellschaft. - 1861-4728 .- 1861-471X. ; 14:10, s. 1870-1878
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Tidskriftsartikel (refereegranskat)abstract
- Due to the reversal in electron counts for aromaticity and antiaromaticity in the closed-shell singlet state (normally ground state, S-0) and lowest * triplet state (T-1 or T-0), as given by Huckel's and Baird's rules, respectively, fulvenes are influenced by their substituents in the opposite manner in the T-1 and S-0 states. This effect is caused by a reversal in the dipole moment when going from S-0 to T-1 as fulvenes adapt to the difference in electron counts for aromaticity in various states; they are aromatic chameleons. Thus, a substituent pattern that enhances (reduces) fulvene aromaticity in S-0 reduces (enhances) aromaticity in T-1, allowing for rationalizations of the triplet state energies (E-T) of substituted fulvenes. Through quantum chemical calculations, we now assess which substituents and which positions on the pentafulvene core are the most powerful for designing compounds with low or inverted E-T. As a means to increase the -electron withdrawing capacity of cyano groups, we found that protonation at the cyano N atoms of 6,6-dicyanopentafulvenes can be a route to on-demand formation of a fulvenium dication with a triplet ground state (T-0). The five-membered ring of this species is markedly Baird-aromatic, although less than the cyclopentadienyl cation known to have a Baird-aromatic T-0 state.
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- Zhu, Jun, et al.
(författare)
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On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the n-Contribution to the Electron Localization Function
- 2010
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Ingår i: Symmetry. - Basel : MDPI. - 2073-8994. ; 2:3, s. 1653-1682
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Tidskriftsartikel (refereegranskat)abstract
- The degree of p-electron (de)localization and aromaticity of a series of polybenzenoid hydrocarbons (PBHs) has been analyzed through the π-contribution to the electron localization function (ELFπ), calculated at the B3LYP/6-311G(d,p) hybrid density functional theory level. The extent of p-electron delocalization in the various hexagons of a PBH was determined through analysis of the bifurcation values of the ELFp basins (BV(ELFp)), the spans in the bifurcation values in each hexagon (ΔBV(ELFπ)), and the ring-closure bifurcation values of the ELFπ (RCBV(ELFπ)). These computed results were compared to the qualitative description of local aromaticities of the different hexagons in terms of Clar structures with p-sextets. Benzene, [18]annulene, and thirty two PBHs were analyzed at their equilibrium geometries, and benzene and triphenylene were also analyzed at bond length distorted structures. In general, the description of PBHs in terms of Clar valence structures is supported by the ELFp properties, although there are exceptions. For PBHs at their equilibrium geometries there is a clear sigmoidal relationship between the CC bond lengths and the amount of p-electron (de)localization at these bonds, however, this relationship is lost for bond distorted geometries. In the latter cases, we specifically examined benzene in D3h symmetric “1,3,5-cyclohexatriene” structures and triphenylene in eight different structures. From the distorted benzenes and triphenylenes it becomes clear that there is a distinct tendency for the p-electron network to retain delocalization (aromaticity). The ELFp analysis thus reveals an antidistortive rather than a distortive behavior of the p-electrons in these investigated compounds.
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