| 1. |
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| 2. |
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| 3. |
- Andréasson, Frida, et al.
(författare)
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Bioavailability of DOC in leachates, soil matrix solutions and soil water extracts from beech forest floors
- 2009
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 41:8, s. 1652-1658
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Tidskriftsartikel (refereegranskat)abstract
- The biodegradability of dissolved organic carbon (DOC) in different fractions from the forest floor was studied. Soil leachate (SI, the soil solution in macropores which is freely drained from forest floor after rainfall), the soil matrix solution (SMS, the soil solution in meso-/micropores of the soil matrix), and soil water extracts (SWE) from two different beech forest floors were compared. Zero-tension and tension lysimeters were used to collect SL and SMS, respectively. Loss of DOC (during 21 days) and respiration of CO2-C (during 7 days) were used as conventional measures of the availability of DOC. Bacterial production, measured using the leucine incorporation technique, and bacterial growth efficiency were also estimated. All methods were used to study differences in biodegradability between plots with and without ground flora (Deschampsia flexuosa or Anemone nemorosa) and different type of forest floor (with an organic (O) horizon or a mull (A) horizon). There were no differences in bioavailability of DOC from soil solutions extracted from plots with and without ground flora. The bioavailability of DOC in the different collected soil solutions varied, however. DOC in SWE was the most available, with a mean of 39% of DOC-loss in 21 days, and 18% of DOC being respired in 7 days. DOC in soil matrix solution was the least available of the soil solutions (7% respired), significantly less than DOC in soil leachate (11% respired). The methods measuring biodegradation of DOC, DOC-loss and CO2-C respiration gave similar results and were comparable to bacterial production and bacterial growth efficiency, with the exception of SWE from the O-horizon at the a flexuosa site, which had low bacterial production and bacterial growth efficiency, indicating a limitation of the bacterial growth. This study is one of the first to use bacterial production and bacterial growth efficiency for measuring bioavailability in terrestrial environments, giving an extra dimension for the process of biodegradation of DOC. (C) 2009 Elsevier Ltd. All rights reserved.
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| 4. |
- Andréasson, Frida, et al.
(författare)
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Differences in soil organic matter, extractable nutrients, and acidity in European beech (Fagus sylvatica L.) forest soils related to the presence of ground flora
- 2012
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Ingår i: Journal of Forest Research. - : Informa UK Limited. - 1341-6979 .- 1610-7403. ; 17:4, s. 333-342
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Tidskriftsartikel (refereegranskat)abstract
- Differences in soil organic matter (SOM) content, soil acidity, and soil exchangeable nutrients (NH4-N, NO3-N, Ca, K, Na, Mg) related to the presence of ground flora were studied. The study was carried out for a growing season in two different Fagus sylvatica L. forests in southern Sweden, and the differences in soil characteristics below naturally occurring patches of Deschampsia flexuosa (L.) Trin. or Anemone nemorosa L. were compared with those with no ground flora. Patches of D. flexuosa led to higher soil pH, but lower SOM, water content, base saturation, and NH4-N concentration compared with adjacent zones without D. flexuosa. The lower SOM content suggested an increased rate of decomposition which caused soil pH to increase because of release of basic cations. In the presence of A. nemorosa, pH was higher and the exchangeable acidity lower than for patches without the herb. In early spring, when A. nemorosa emerged and flowered, the NH4-N concentration was somewhat lower in the presence of the herb than when it was absent. For the evergreen grass D. flexuosa NH4-N concentrations were lower in patches with the grass later in the summer season (July). This work indicates the presence of spatial and temporal differences in nutrient circulation and decomposition on the small ground flora scale, which should be considered when studying nutrient and carbon cycles of temperate forests.
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| 5. |
- Andreasson, Joakim, 1973, et al.
(författare)
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All-photonic molecular half-adder
- 2006
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 128:50, s. 16259-16265
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Tidskriftsartikel (refereegranskat)abstract
- One molecule acts as both an AND and an XOR Boolean logic gate that share the same two photonic inputs. The molecule comprises a half-adder, adding two binary digits with only light as inputs and outputs, and consists of three covalently linked photochromic moieties, a spiropyran and two quinolinederived dihydroindolizines. The AND function is based on the absorption properties of the molecule, whereas the XOR function is based on an off-on-off response of the fluorescence to the inputs that results from interchromophore excited-state quenching interactions. The half-adder is simple to operate and can be cycled many times.
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| 6. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Efficient non-radiative deactivation and conformational flexibility of meso-diaryloctaalkylporphyrins in the excited triplet state
- 2000
-
Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 104:41, s. 9307-9314
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Tidskriftsartikel (refereegranskat)abstract
- The excited triplet state deactivation of zinc(II) meso-diaryloctaalkylporphyrins (ZnDAOAP) has been studied over a wide temperature range using transient triplet-triplet absorption spectroscopy together with steady-state and time-resolved phosphorescence techniques, The results from transient absorption measurements show that the depopulation of the initially formed triplet state (T-1A state) is unusually fast at temperatures above 150 K. The efficiency of the deactivation originates from a spin allowed transition to a second tripler state (T-1B state), The transformation process T-1A-->T-1B is therefore the dominating deactivation channel of the T-1A state in this temperature range, and direct intersystem crossing T-1A-->S-0 makes negligible contribution. The subsequent ground-state recovery T-1B-->S-0 is also very efficient in comparison to many other porphyrins. Due to the substantial activation energy found for the transformation process, it most likely involves a conformational distortion of the porphyrin macrocycle. At low temperature, however, the relaxation of the T-1A State occurs by direct intersystem crossing to the ground state.
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| 7. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Molecular AND logic gate based on electric dichroism of a photochromic dihydroindolizine
- 2005
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 44:46, s. 7591-7594
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Tidskriftsartikel (refereegranskat)abstract
- (Chemical Equation Presented) Very ANDy: A photochromic molecular switch has been found to act as an AND Boolean logic gate. The switch takes as input both UV light, which causes photo-isomerization of a dihydroindolizine to an open, dipolar form, and an electric field, which aligns this isomer in solution (see scheme). The output of the gate is read as the electric linear dichroism response of the open isomer. The gate can be reset with visible light. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
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| 8. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Photoinduced hole transfer from the triplet state in a porphyrin-based donor-bridge-acceptor system
- 2003
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 107:42, s. 8825-8833
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Tidskriftsartikel (refereegranskat)abstract
- The triplet excited-state deactivation of a gold porphyrin (AuP) in porphyrin-based donor-bridge-acceptor (D-B-A) systems has been studied. The results from room temperature and 80 K measurements are presented. The primary objectives have been to investigate whether electrons/electron holes or excitation energy could be transferred from (AuP)-Au-3 to the appended zinc porphyrin (ZnP) in the dimers. As the bridging chromophores in our D-B-A systems separate the ZnP and AuP moieties by 19 A edge-to-edge, we do not expect a significant contribution to either electron or energy transfer from a direct (through space) exchange mechanism. This gives us the opportunity to scrutinize how the bridging chromophores influence the transfer reactions. The results show that quenching of (AuP)-Au-3 occurs with high efficiency in the dimers that are connected by fully conjugated bridging chromophores, whereas no quenching is observed when the conjugation of the bridge is broken. We also observed that the decay of (AuP)-Au-3 is complex at temperatures below 110 K. In addition to the two previously published lifetimes on the order of some 10-100 mus, we have found a third lifetime on the nanosecond time scale.
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| 9. |
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| 10. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Temperature and viscosity dependence of the triplet energy transfer process in porphyrin dimers
- 2002
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Ingår i: Photochemical & Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-905X .- 1474-9092. ; 1:2, s. 111-119
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Tidskriftsartikel (refereegranskat)abstract
- The temperature and viscosity dependence of the triplet energy transfer (TET) process in porphyrin dimers has been studied. A zinc porphyrin (donor) and a free base porphyrin (acceptor) are covalently linked together by rigid bridging chromophores at a center-center distance of 25 Angstrom. Due to the large donor-acceptor distance and the weakness of the spin forbidden transitions involved, neither direct (through space) electron exchange nor Coulombic mechanisms are expected to contribute to the observed TET process. The results from transient absorption measurements at temperatures between room temperature and 80 K show that TET occurs with unexpectedly high efficiency in the systems connected by fully conjugated bridges and a pronounced temperature dependence of the process is observed. Comparison of the TET efficiencies in dimers connected by different bridging chromophores correlates well with a transfer reaction governed by a through bond exchange (superexchange) interaction. However, in high viscosity media the TET process is dramatically slowed down. This is attributed to a conformational gating of the TET process where the electronic coupling varies strongly with the relative orientation of the donor and the bridging chromophore. Further, the zinc porphyrin donor offers two distinct donor species, T-1A and T-1B. At room temperature, the TET rate constant of the T-1A Species is about two orders of magnitude larger than for the T-1B species. The dimers studied are well suited model systems for materials where the rate of the transfer reactions can be changed by external stimuli.
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| 11. |
- Andreasson, Joakim, 1973, et al.
(författare)
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The gold porphyrin first excited singlet state
- 2002
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Ingår i: Photochemistry and Photobiology. - 0031-8655 .- 1751-1097. ; 76:1, s. 47-50
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Tidskriftsartikel (refereegranskat)abstract
- Gold porphyrins are often used as electron-accepting chromophores in artificial photosynthetic constructs. Because of the heavy atom effect, the gold porphyrin first-excited singlet state undergoes rapid intersystem crossing to form the triplet state. The lowest triplet state can undergo a reduction by electron donation from a nearby porphyrin or another moiety. In addition, it can be involved in triplet-triplet energy transfer interactions with other chromophores. In contrast, little has been known about the short-lived singlet excited state. In this work, ultrafast time-resolved absorption spectroscopy has been used to investigate the singlet excited state of Au(III) 5,15-bis(3,5-di-t-butylphenyl)-2,8,12,18,-tetraethyl-3,7,13,17-tetrameth ylporphyrin in ethanol solution. The excited singlet state is found to form with the laser pulse and decay with a time constant of 240 fs to give the triplet state. The triplet returns to the ground state with a lifetime of 400 ps. The lifetime of the singlet state is comparable with the time constants for energy and photoinduced electron transfer in some model and natural photosynthetic systems. Thus, it is kinetically competent to take part in such processes in suitably designed supermolecular systems.
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| 12. |
- Andreasson, Joakim, 1973, et al.
(författare)
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The photophysical properties of the adenine chromophore
- 1999
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Ingår i: Journal of Physical Chemistry B. ; 103:44, s. 9782-9789
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Tidskriftsartikel (refereegranskat)abstract
- The efficient nonradiative deactivation process of the excited adenine chromophore is studied in this paper. By comparing the photophysical properties and temperature dependence of several alkylated adenine derivatives, a mechanism for the thermally activated internal conversion process is suggested, Several alkylamino derivatives of adenine show dual fluorescence, and the solvent dependence of the excited states is investigated. It is concluded that the long wavelength emission originates from a CT state involving the alkylamino group and purine chromophore as donor and acceptor, respectively. The experimental observations are supported by quantum mechanical calculations, and the results are summarized into a model for the photophysical properties of the adenine chromophore. In this model, the two excited states associated with the dual emission from the alkylamino derivatives are populated from a common Franck-Condon state followed by independent decay to the ground state.
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| 13. |
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| 14. |
- Andréasson, Sara Näslund, et al.
(författare)
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Peritonectomy with high voltage electrocautery generates higher levels of ultrafine smoke particles
- 2008
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Ingår i: European Journal of Surgical Oncology. - : Elsevier BV. - 0748-7983 .- 1532-2157. ; 35:7, s. 780-784
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: To adequately perform peritonectomy, the use of an electrocautery device at a high voltage is recommended. The aim of this study was to analyse the amount of airborne and ultrafine particles (UFP) generated during peritonectomy and to compare this with standard colon and rectal cancer surgery (CRC). METHOD: UFP was measured approximately 2-3cm from the breathing area of the surgeon (personal sampling) and 3m from where the electrocautery smoke was generated (stationary sampling) from 14 consecutive peritonectomy procedures and 11 standard CRC resections. The sampling was by P-Trak UFP counter that has the capacity to detect particle size ranging from 0.02 to 1mum. RESULTS: The cumulative level of UFP of personal sampling in the peritonectomy group was higher (9.3x10(6)particle/ml/h (pt/ml/h)) than in the control group (4.8x10(5)pt/ml/h). A higher cumulative level of UFP in stationary sampling was observed in the PC group (2.6x10(6) pt/ml/h) than in the control group (3.9x10(4)pt/ml/h). CONCLUSION: Peritonectomy procedure with high voltage electrocautery generates elevated levels of UFP than standard CRC surgery does. The level of UFP produced by a peritonectomy is comparable to cigarette smoking. More efficient smoke evacuator systems are needed in order to reduce the levels of UFP generated during electrocautery surgery.
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| 15. |
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| 16. |
- Cederlund, Martin, et al.
(författare)
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Vitreous levels of oxidative stress biomarkers and the radical-scavenger α(1)-microglobulin/A1M in human rhegmatogenous retinal detachment.
- 2013
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Ingår i: Graefe's Archive for Clinical and Experimental Ophthalmology. - : Springer Science and Business Media LLC. - 1435-702X .- 0721-832X. ; 251:3, s. 725-732
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To explore oxidative stress and the radical scavenger α(1)-microglobulin (A1M) in the vitreous body of human eyes with primary rhegmatogenous retinal detachment (RRD). METHODS: Levels of carbonyl groups, a marker of oxidative stress, and A1M were measured by ELISA and RIA in 14 vitreous samples derived from patients suffering from RRD, and compared with 14 samples from macula hole (MH) patients. Carbonyl group and A1M levels in RRD samples were statistically related to detachment characteristics. Analysis of total protein level, SDS-PAGE, and Western blotting of A1M was also performed. In a separate experiment, mRNA expression of A1M was measured by RT-PCR in rat retina explants. RESULTS: Levels of carbonyl groups and A1M varied widely in RRD vitreous samples, but were significantly higher in samples derived from eyes with large detachment area and macula-off status, while the presence of vitreous hemorrhage did not show any significant correlation. Compared with MH samples, RRD samples displayed significantly higher levels of A1M, whereas changes in total protein levels and carbonyl groups were not significant. Novel forms of A1M, not previously seen in plasma, were found in the vitreous body by Western blotting. Furthermore, A1M expression was seen in rat retina explants and was upregulated after 24 h of culturing. CONCLUSION: Oxidative stress is a prominent feature of human eyes with primary RRD, and is directly related to detachment severity. Affected eyes can launch a protective response in the form of the radical scavenger A1M possibly derived from the retina. The results thus indicate potential therapeutic cell loss prevention in RRD by employing the endogeneous radical scavenger A1M.
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| 17. |
- Chang, Bo, et al.
(författare)
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A homologous genetic basis of the murine cpfl1 mutant and human achromatopsia linked to mutations in the PDE6C gene
- 2009
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:46, s. 19581-19586
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Tidskriftsartikel (refereegranskat)abstract
- Retinal cone photoreceptors mediate fine visual acuity, daylight vision, and color vision. Congenital hereditary conditions in which there is a lack of cone function in humans cause achromatopsia, an autosomal recessive trait, characterized by low vision, photophobia, and lack of color discrimination. Herein we report the identification of mutations in the PDE6C gene encoding the catalytic subunit of the cone photoreceptor phosphodiesterase as a cause of autosomal recessive achromatopsia. Moreover, we show that the spontaneous mouse mutant cpfl1 that features a lack of cone function and rapid degeneration of the cone photoreceptors represents a homologous mouse model for PDE6C associated achromatopsia.
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| 18. |
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| 19. |
- Eng, Mattias P, 1977, et al.
(författare)
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Triplet photophysics of gold(III) porphyrins
- 2005
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 109:9, s. 1776-1784
-
Tidskriftsartikel (refereegranskat)abstract
- Gold porphyrins are often used as electron-accepting chromophores in donor-acceptor complexes for the study of photoinduced electron transfer, and they can also be involved in triplet-triplet energy-transfer interactions with other chromophores. Since the lowest excited singlet state is very short-lived (240 fs), the triplet state is usually the starting point for the transfer reactions, and it is therefore crucial to understand its photophysics. The triplet state of various gold porphyrins has been reported to have a lifetime of around 1.5 ns at room temperature and to have a biexponential decay both in emission and in transient absorption with decay times of around 10 and 100,us at 80 K. In this paper, the triplet photophysics of two gold porphyrins (Au-III 5,15-bis(3,5-di-tert-butylphenyl)-2,8,12,18-tetraethyl-3,7,13,17-tetrame thylporphyrin and Au-III 5,10,15,20-tetra(3,5-di-tert-butylphenyl)porphyrin) are studied by steady-state and time-resolved absorption and emission spectroscopy over a wide temperature range (4-300 K). The study reveals the existence of a dark state with an approximate lifetime of 50 ns, which was not previously observed. This state acts as an intermediate between the short-lived singlet and the triplet state manifold. In addition, we present DFT calculations, in which the core electrons of the central metal were replaced by a pseudopotential to account for the relativistic effects, which suggest that the lowest excited singlet state is an optically forbidden ligand-to-metal charge-transfer (LMCT) state. This LMCT state is an obvious candidate for the experimentally observed dark state, and it is shown to dictate the photophysical properties of gold porphyrins by acting as a gate for triplet state formation versus direct return to the ground state.
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| 20. |
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| 21. |
- Friedman, James S., et al.
(författare)
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Premature truncation of a novel protein, RD3, exhibiting subnuclear localization is associated with retinal degeneration
- 2006
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Ingår i: American Journal of Human Genetics. - 0002-9297. ; 79:6, s. 1059-1070
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Tidskriftsartikel (refereegranskat)abstract
- The rd3 mouse is one of the oldest identified models of early-onset retinal degeneration. Using the positional candidate approach, we have identified a C -> T substitution in a novel gene, Rd3, that encodes an evolutionarily conserved protein of 195 amino acids. The rd3 mutation results in a predicted stop codon after residue 106. This change is observed in four rd3 lines derived from the original collected mice but not in the nine wild-type mouse strains that were examined. Rd3 is preferentially expressed in the retina and exhibits increasing expression through early postnatal development. In transiently transfected COS-1 cells, the RD3-fusion protein shows subnuclear localization adjacent to promyelocytic leukemia-gene-product bodies. The truncated mutant RD3 protein is detectable in COS-1 cells but appears to get degraded rapidly. To explore potential association of the human RD3 gene at chromosome 1q32 with retinopathies, we performed a mutation screen of 881 probands from North America, India, and Europe. In addition to several alterations of uncertain significance, we identified a homozygous alteration in the invariant G nucleotide of the RD3 exon 2 donor splice site in two siblings with Leber congenital amaurosis. This mutation is predicted to result in premature truncation of the RD3 protein, segregates with the disease, and is not detected in 121 ethnically matched control individuals. We suggest that the retinopathy-associated RD3 protein is part of subnuclear protein complexes involved in diverse processes, such as transcription and splicing.
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| 22. |
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| 23. |
- From, Malin, et al.
(författare)
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Tuning the properties of regenerated cellulose : Effects of polarity and water solubility of the coagulation medium
- 2020
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 236
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of different alcohols and esters as a coagulation medium in the regeneration of cellulose dissolved in an aqueous LiOH-urea-based solvent was thoroughly investigated using various methods such as solid state NMR, X-ray diffraction, water contact angle, oxygen gas permeability, mechanical testing, and scanning electron microscopy. It was observed that several material properties of the regenerated cellulose films follow trends that correlate to the degree of cellulose II crystallinity, which is determined to be set by the miscibility of the coagulant medium (nonsolvent) and the aqueous alkali cellulose solvent rather than the nonsolvents’ polarity. This article provides an insight, thus creating a possibility to carefully tune and control the cellulose material properties when tailor-made for different applications.
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| 24. |
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| 25. |
- Gärdlund, Linda, et al.
(författare)
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Influence of polyelectrolyte complexes on strength properties of papers made from unbleached kraft pulps with different yields
- 2005
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 20:1, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- The properties of the materials combined in corrugated board are set to give the board its strength, flexibility and protection towards impact and pressure. The raw material is of course the single fibre but additives that enhance e.g. the wet and dry paper strength are also added. As the strength enhancing additives used today are most efficient between pH 4 and pH 7 there is a need for new types of additives that can be used under alkaline conditions. In the present report polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were investigated as strength enhancing additives. The components can be used under alkaline conditions and results showed that PAH alone or incorporated into a PEC gave different effects regarding strength properties of sheets from kraft pulps of different yields. The results showed that by treating the fibres with PEC´s of PAH and PAA it was possible to considerably increase the tensile properties, the Z-strength and the compression strength of papers made from the treated fibres. The results showed an increase of as much as 54 % to 180 % in dry Z-strength and 14 % to 53 % in compression strength, when using the PEC as an additive, indicating an increase in inter-fibre joint strength. It was also found that a heat treatment of the non-treated papers and of the papers from the PAH treated fibres gave a large improvement in tensile properties as well as Z-strength properties for the different pulps. For the PEC treated fibres it was not necessary to heat-treat the paper to achieve a higher dry strength. The molecular mechanism behind the large improvements is not identified in the present work but the problem is currently being investigated in the lab of the authors.
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| 26. |
- Gärdlund, Linda, et al.
(författare)
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Influence of polyelectrolyte complexes on the strength properties of papers from unbleached kraft pulps with different yields
- 2005
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 20:1, s. 36-42
-
Tidskriftsartikel (refereegranskat)abstract
- The properties of the materials combined in corrugated board are set to give the board its strength, flexibility and protection towards impact and pressure. The raw material is of course the single fibre but additives that enhance e.g. the wet and dry paper strength are also added. As the strength enhancing additives used today are most efficient between pH 4 and pH 7 there is a need for new types of additives that can be used under alkaline conditions. In the present report polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were investigated as strength enhancing additives. The components can be used under alkaline conditions and results showed that PAH alone or incorporated into a PEC gave different effects regarding strength properties of sheets from kraft pulps of different yields. The results showed that by treating the fibres with PEC's of PAH and PAA it was possible to considerably increase the tensile properties, the Z-strength and the compression strength of papers made from the treated fibres. The results showed an increase of as much as 54 % to 180 % in dry Z-strength and 14 % to 53 % in compression strength, when using the PEC as an additive, indicating an increase in inter-fibre joint strength. It was also found that a heat treatment of the non-treated papers and of the papers from the PAH treated fibres gave a large improvement in tensile properties as well as Z-strength properties for the different pulps. For the PLC treated fibres it was not necessary to heat-treat the paper to achieve a higher dry strength. The molecular mechanism behind the large improvements is not identified in the present work but the problem is currently being investigated in the lab of the authors.
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| 27. |
- Hou, Lili, 1984, et al.
(författare)
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A general approach for all-visible-light switching of diarylethenes through triplet sensitization using semiconducting nanocrystals
- 2022
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 10:42, s. 15833-15842
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Tidskriftsartikel (refereegranskat)abstract
- Coupling semiconducting nanocrystals (NCs) with organic molecules provides an efficient route to generate and transfer triplet excitons. These excitons can be used to power photochemical transformations such as photoisomerization reactions using low energy radiation. Thus, it is desirable to develop a general approach that can efficiently be used to control photoswitches using all-visible-light aiming at future applications in life- and materials sciences. Here, we demonstrate a simple 'cocktail' strategy that can achieve all-visible-light switchable diarylethenes (DAEs) through triplet energy transfer from the hybrid of CdS NCs and phenanthrene-3-carboxylic acid, with high photoisomerization efficiency and improved fatigue resistance. The size-tunable excitation energies of CdS NCs make it possible to precisely match the clear spectral window of the relevant DAE photoswitch. We demonstrate reversible all-visible-light photoisomerization of a series of DAE derivatives both in the liquid and solid state, even in the presence of oxygen. Our general strategy is promising for fabrication of all-visible-light activated optoelectronic devices as well as memories, and should in principle be adaptable to photopharmacology.
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| 28. |
- Hou, Lili, 1984, et al.
(författare)
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Optically Switchable NIR Photoluminescence of PbS Semiconducting Nanocrystals using Diarylethene Photoswitches
- 2022
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 144:39, s. 17758-17762
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Tidskriftsartikel (refereegranskat)abstract
- Precisely modulated photoluminescence (PL) with external control is highly demanded in material and biological sciences. However, it is challenging to switch the PL on and off in the NIR region with a high modulation contrast. Here, we demonstrate that reversible on and off switching of the PL in the NIR region can be achieved in a bicomponent system comprised of PbS semiconducting nanocrystals (NCs) and diarylethene (DAE) photoswitches. Photoisomerization of DAE to the ring-closed form upon UV light irradiation causes substantial quenching of the NIR PL of PbS NCs due to efficient triplet energy transfer. The NIR PL fully recovers to an on state upon reversing the photoisomerization of DAE to the ring-open form with green light irradiation. Importantly, fully reversible switching occurs without obvious fatigue, and the high PL on/off ratio (>100) outperforms all previously reported assemblies of NCs and photoswitches.
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| 29. |
- Kyrychenko, Alexander, et al.
(författare)
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Sterically induced conformational relaxation and structure of meso-diaryloctaalkyl porphyrins in the excited triplet state: Experimental and DFT studies
- 2002
-
Ingår i: Journal of Physical Chemistry B Materials. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 106:48, s. 12613-12622
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Tidskriftsartikel (refereegranskat)abstract
- The excited triplet state conformations of zinc and free base 5,15-diaryloctaalkylporhyrins are studied by experimental and computational (density functional theory, DFT) methods. From the observations of an unusual triplet state dynamics, i.e., fast nonradiative and biexponential decay, it has been suggested that these porphyrins exist in two distinguishable conformers in the lowest excited triplet state. X-ray crystallography and,DFT (B3LYP/6-31G(d)) optimization of the ground state show that the porphyrins are planar prior to excitation. However, in the excited triplet state, the planar structure relaxes to an out-of-plane distorted saddle-shaped conformer. This distorted conformer and the lowest triplet potential energy surface are characterized by DFT calculations. It is suggested that the conformational relaxation explains the unusual triplet dynamics of this class of porphyrins.
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| 30. |
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| 31. |
- Kärnbratt, Joakim, 1982, et al.
(författare)
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Photochromic Supramolecular Memory With Nondestructive Readout
- 2010
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 49:10, s. 1854-1857
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Tidskriftsartikel (refereegranskat)abstract
- Looking without touching: The light-controlled isomerization of a complex containing a pyridine-appended dithienylethene (DTE; green) and a porphyrin dimer induces dramatic structural and spectral changes (see picture). These changes are monitored in a region outside the photochromically active absorption bands of DTE, therefore allowing a nondestructive readout so that the process functions as a molecular optically controlled memory.
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| 32. |
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| 33. |
- Larsson, Wera, 1992, et al.
(författare)
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Diarylethene Isomerization by Using Triplet–Triplet Annihilation Photon Upconversion
- 2023
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Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 29:13
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Tidskriftsartikel (refereegranskat)abstract
- Green-to-blue triplet–triplet annihilation photon upconversion with the well-studied upconversion pair 9,10-diphenylanthracene (DPA)/platinum octaethylporphyrin (PtOEP) was used to reversibly drive the photoisomerization of diarylethene (DAE) photoswitches by using visible light. By carefully selecting the kinetic and spectral properties of the molecular system as well as the experimental geometry, a single green light source can be used to selectively trigger both the ring-opening and the ring-closing reactions, whilst also inducing fluorescence from the colored closed isomer that can be used as a readout to monitor the isomerization process in situ. The upconversion solution and the DAE solution are kept physically separated, allowing them to be characterized both concomitantly and individually without further separation processes. The ring-closing reaction using upconverted photons was quantified and compared to the efficiency of direct isomerization with ultraviolet light.
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| 34. |
- Mystek, Katarzyna, et al.
(författare)
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The preparation of cellulose acetate capsules using emulsification techniques: High-shear bulk mixing and microfluidics
- 2023
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 38:4, s. 593-605
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Tidskriftsartikel (refereegranskat)abstract
- This work describes an emulsification-solvent-evaporation method for the preparation of liquid-filled capsules made from cellulose acetate. Two different emulsification techniques were applied: bulk emulsification by high-shear mixing, and droplet generation using microfluidics. The bulk emulsification method resulted in the formation of oil-in-water emulsions composed of an organic mixture of isooctane and cellulose acetate in methyl acetate, and an aqueous phase of high-molecular-weight polyvinyl alcohol (PVA). Upon the solvent evaporation, the emulsion droplets evolved into isooctane-filled cellulose acetate capsules. In contrast, microfluidics led to the formation of monodisperse droplets composed of the aqueous PVA solution dispersed in the organic phase. Upon the solvent evaporation, the emulsion droplets evolved into water-filled cellulose acetate capsules. Owing to the thermoplastic properties of the cellulose acetate, the capsules formed with the bulk mixing demonstrated a significant expansion when exposed to an increased temperature. Such expanded capsules hold great promise as building blocks in lightweight materials.
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| 35. |
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| 36. |
- Naren, Gaowa, 1990, et al.
(författare)
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Rapid amplitude-modulation of a diarylethene photoswitch: en route to contrast-enhanced fluorescence imaging
- 2021
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6539 .- 2041-6520. ; 12:20, s. 7073-7078
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Tidskriftsartikel (refereegranskat)abstract
- A water soluble diarylethene (DAE) derivative that displays exceptionally intense fluorescence from the colorless open form has been synthesized and characterized using UV/vis spectroscopy and fluorescence microscopy. We show that the bright emission from the open form can be rapidly switched using amplitude modulated red light, that is, by light at wavelengths longer than those absorbed by the fluorescent species. This is highly appealing in any context where undesired background fluorescence disturbs the measurement, e.g., the autofluorescence commonly observed in fluorescence microscopy. We show that this scheme is conveniently applicable using lock-in detection, and that robust amplitude modulation of the probe fluorescence is indeed possible also in cell studies using fluorescence microscopy.
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| 37. |
- Nejström, Malin, et al.
(författare)
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On Structural and Molecular Order in Cellulose Acetate Butyrate Films
- 2023
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 15:9
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose acetate butyrate (CAB) is a possible candidate, being a raw material derived from renewable resources, to replace fossil-based materials. This is due to its thermoplastic properties and the relative ease with which it could be implemented within the existing industry. With a significant amount of variation in CAB on the market today, a knowledge gap has been identified regarding the understanding of the polymer structural arrangement in films. This relates to the underlying mechanisms that regulate CAB film material properties, insights that are important in product development. In this study, commercially available CAB was investigated with XRD, SEM, AFM, and TOPEM DSC in order to obtain physicochemical information related to its micro-structural features in solvent-cast films. The film-forming ability relates mostly to the number of hydroxyl groups, and the semi-crystallinity of the films depends on the type and position of the side groups along the cellulose backbone. The appearance of signs of possible cholesteric ordering in the films could be connected to higher amounts of hydroxyl groups along the backbone that disturb the helix arrangement, while the overall order was primarily related to the butyrate substitution and secondarily related to the molecular weight of the particular CAB studied. Cold crystallization was also observed in one CAB sample.
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| 38. |
- Nejström, Malin
(författare)
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Structural impact on some physical properties of cellulose-based films
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose is a natural material that can be used both in its original form and as a building block for creating new types of materials. This work focused on regenerated cellulose (RC) and cellulose acetate butyrate (CAB) in which the hydroxyls on the cellulose backbone were substituted with ester groups. In this work both RC and CAB were formed as free-standing films via initial dissolution and characterized with respect to their structural and morphological aspects, as well as some other material properties. Cellulose pulp was dissolved in cold aqueous alkali urea solution and regenerated in either alcohols or esters to form RC films. Variations of commercially available CAB were dissolved in acetone and solvent cast to form CAB films.This work strove to understand the structural relations of cellulose-based films, the fundamental principles of these materials and how they affect the material properties. This work examined the effect of the polarity of the regeneration liquid on the crystallinity and on other material properties of dried RC films (Papers I and III). This work also investigated the variation in degree of substitution of butyrate and the variation in molecular weight of commercially available CAB and how those could affect the microstructural order of a solvent cast film to the degree that a measurable change in material properties could be observed (Paper II). This was done via structural analysisusing solid-state nuclear magnetic resonance (ss-NMR), x-ray diffraction (XRD), and temperature-modulated differential scanning calorimetry (TOPEM DSC), on RC and CAB films. The qualitative concept of “film formability” was used in this work to determine the practical film properties (related to the ease of handling a film) based on subjective observations.Both the RC films and the CAB films were transparent, with some variations. The CAB films were more fragile than the RC films, even when theCAB films were almost triple the RC films’ thickness. The RC films could be bent considerably, even sharply folded, whereas the CAB films were only slightly bendable before they snapped.The crystallinity of the RC films varied with the regeneration liquid used,and an increase in crystallinity was observed in the following order: EtOH
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| 39. |
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| 40. |
- Sjödin, Åke, et al.
(författare)
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Mätningar av bilavgaser i Tingstadstunneln med FTIR och konventionell mätteknik
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kontinuerliga mätningar (bestämningar av 10-minutersmedelvärden) av halter av N2O (dikväveoxid, lustgas), CO2, CO och HCHO (formaldehyd) har utförts i Tingstadstunneln i Göteborg under en treveckors period i november och december 1994 med ett fjärranalysinstriment (FTIR). Parallellt har kontinuerliga mätningar av CO, totalkolväten och kväveoxider i tunneln utförts med konventionella instrument. Under hela vinterhalvåret 1994/95 bestämdes dessutom veckomedelvärden av sju trafikrelaterade VOC-komponenter på samma plats med s k diffusionsprovtagare. Under mätkampanjen registrerades komtinuerligt även trafikflödet, trafikens sammansättning och hastighet samt vindhastigheten genom tunneln. Ur mätningarna har härletts genomsnittliga utsläppsfaktorer för tunneltrafiken per fkm för CO på 6 g, THC 0.8 g, NOx 1 g, formaldehyd 20 mg, bensen 50 mg, toluen 120 mg. m+p-xylen 65 mg, o-xylen 25 mg etylbensen 20 mg, oktan 2 mg samt nonan 1 mg.
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| 41. |
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| 42. |
- Warnoff, Carin, et al.
(författare)
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Is poor self-rated health associated with low-grade inflammation in 43 110 late adolescent men of the general population? A cross-sectional study
- 2016
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Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Self-rated health is a powerful predictor of long-term health and mortality, hence the importance of a better understanding of its biological determinants. Previous studies have shown that low-grade inflammation is associated with poor self-rated health in clinical and healthy populations, but the evidence is sparse in men and completely lacking for men in late adolescence. The aim of this study was to investigate the association between low-grade inflammation and self-rated health among conscripts. It was hypothesised that high levels of inflammatory factors would be associated with poor self-rated health.DESIGN: Data from 49 321 men (18-21 years) conscripted for military service in 1969 and 1970 were used. Inflammation had been measured through erythrocyte sedimentation rate (ESR). Self-rated health had been assessed on a five-point scale, and was dichotomised into Good ('Very good'/'Good'/'Fair') versus Poor ('Poor'/'Very poor'). Data from 43 110 conscripts with normal levels of ESR, and who reported self-rated health remained after exclusion of those with ESR <1 and >11 mm/h. Associations were calculated using logistic regression analyses. Adjustments were made for body mass index, socioeconomic position, inflammatory disease, emotion regulation, smoking, risky use of alcohol and physical activity.RESULTS: High levels of ESR were associated with higher odds for poor self-rated health (OR: 1.077 for each unit mm/h increase in ESR, 95% CI 1.049 to 1.105).CONCLUSIONS: The present study shows for the first time a significant association between a marker of inflammation and self-rated health in late adolescent men, adding to evidence of an association between low-grade inflammation and subjective health perception also in men, as previously demonstrated in women. Further support for inflammation as part of a general psychobiological process that underpins subjective health perception is hereby provided.
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| 43. |
- Zylberstein, Dimitri, 1951, et al.
(författare)
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Homocysteine levels and lacunar brain infarcts in elderly women: the prospective population study of women in Gothenburg.
- 2008
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Ingår i: Journal of the American Geriatrics Society. - : Wiley. - 1532-5415 .- 0002-8614. ; 56:6, s. 1087-91
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To examine whether total serum homocysteine (tHcy) in a population-based sample of middle-aged women is an independent risk factor for presence of lacunar infarcts (LIs) 24 years later. DESIGN: Prospective population study, follow-up time 24 years. SETTING: Gothenburg, an urban area in western Sweden. PARTICIPANTS: Five hundred twenty-six women, 89.6% of the original study sample of the Population Study of Women in Gothenburg, aged 46 to 60 at baseline in 1968/69 and re-examined at age 70 to 84. MEASUREMENTS: After 24 years of follow-up, all subjects underwent a psychiatric examination, and 277 computerized tomography (CT) scans of the brain were performed. Two radiologists assessed LIs and white matter lesions (WMLs). Baseline serum tHcy was analyzed from frozen stored serum samples. Logistic regression analyses were performed controlling for potential confounders such as age and selected cardiovascular risk factors. RESULTS: Thirty-four subjects had LIs in 1992 (12.3%). In the full multivariate-adjusted stepwise model, LIs were associated with elevated tHcy (odds ratio (OR)=1.09, 95% confidence interval (CI)=1.01-1.17 per micromol/L of tHcy increment). Women with tHcy values in the highest tertile were almost three times as likely to have LIs (OR=2.82, 95% CI=1.34-5.93) as were those in the lowest tertile. tHcy was not related to WMLs. Subjects who did not undergo a CT scan did not differ from those who did regarding tHcy or any of the covariates studied. CONCLUSION: tHcy in middle-aged women is an independent risk factor for LIs, but not WMLs, as observed using CT later in life.
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