| 51. |
- Schyman, Patric, et al.
(författare)
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Hydrogen Abstraction from Deoxyribose by a Neighbouring Uracil-5-yl Radical
- 2007
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 9, s. 5975-5979
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen abstraction from the C1 and C2 positions of deoxyadenosine by a neighbouring uracil-5-yl radical in the 5-AU-3 DNA sequence is explored using DFT. This hydrogen abstraction is the first step in a sequence leading to single or double strand break in DNA. The uracil-5-yl radical can be the result of photolysis or low-energy electron (LEE) attachment. If the radical is produced by photolysis the neighbouring adenine will become a cation radical and if it is produced by LEE the adenine will remain neutral. The hydrogen abstraction reactions for both cases were investigated. It is concluded that it is possible for the uracil-5-yl to abstract hydrogen from C1 and C2. When adenine is neutral there is a preference for the C1 site and when the adenine is a radical cation the C2 site is the preferred. If adenine is positively charged, the rate-limiting step when abstracting hydrogen from C1 is the formation of an intermediate crosslink between uracil and adenine. This crosslink might be avoided in dsDNA, making C1 the preferred site for abstraction.
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| 52. |
- Wojas, Natalia
(författare)
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The dynamic surface nature of calcite and its role in determining the adsorptive stability toward hydrophobizing carboxylic fatty acids
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Calcium carbonate has attracted a lot of interest over the centuries. Nowadays, mainly as mineral pigment and filler, it has a wide use in technological applications ranging from paper, construction, polymers, and environmental solutions to consumer goods. Amongst these uses, the filler pigment is required to display either hydrophilicity (for applications in aqueous colloidal systems, including, for example, in paper and emulsion paints), or, in contrast, oleophilicity (for applications in contact with oil-based systems, such as plastics and volatile solvent-containing sealants). To achieve oleophilicity, and resulting hydrophobicity, the filler is surface treated, typically using carboxylic fatty acids. In this thesis, effects of humidity and fatty carboxylic acids vapor on CaCO3 surface wettability and nanomechanical properties were studied, with the aim to gain knowledge on layer packing density and order, as well as resistance to water exposure and mechanical wear. A better understanding of the dynamic nature of the calcite surface presented in this work allows the industry to increase sustainable control over materials production and storage. First, a setup combining an atomic force microscope (AFM) with a humidifier was used to map nanomechanical properties of growing surface domains (hydrated form of CaCO3) formed by ion dissolution, diffusion, and redeposition, a process that is not reversible upon drying. Secondly, AFM and contact angle goniometer measurements showed that the stability of the calcite surface improves with increasing carboxylic acid chain length (C2 to C18). Meanwhile, X-ray photoelectron spectroscopy and vibrational sum frequency spectroscopy techniques demonstrated that a coherent layer with maximum packing density of carboxylate and carboxylic acid species was achieved with the use of stearic acid (C18) with high enough vapor pressure and exposure time. The AFM images successfully visualized that a complete C18 monolayer is capable of countering nano-wear of the calcite surface despite the humidity (under the range of loads investigated in this work) and the layer has self-healing properties, while calcite displayed high abrasive wear. Further, when calcite coated by a highly packed monolayer of C18 was covered with a water droplet, a large contact angle hysteresis resulted in a coffee ring effect (CRE). That is leading to formation of hillocks at the contact line consisting of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules transported from the bare calcite region that also is created next to the droplet edge. Interestingly, C18 coated calcite remained considerably more stable in the case where a water droplet saturated with octanoic acid was used instead of water; thus, it was concluded that the CRE can be contained via reduction of the liquid surface tension and contact angle hysteresis.
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| 53. |
- Buckland, Philip I., 1973-
(författare)
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The Bugs Coleopteran Ecology Package (BugsCEP) database : 1000 sites and half a million fossils later
- 2014
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Ingår i: Quaternary International. - : Elsevier. - 1040-6182 .- 1873-4553. ; 341, s. 272-282
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Tidskriftsartikel (refereegranskat)abstract
- The Bugs database project started in the late 1980s as what would now be considered a relatively simple system, albeit advanced for its time, linking fossil beetle species lists to modern habitat and distribution information. Since then, Bugs has grown into a complex database of fossils records, habitat and distribution data, dating and climate reference data wrapped into an advanced software analysis package. At the time of writing, the database contains raw data and metadata for 1124 sites, and Russell Coope directly contributed to the analysis of over 154 (14%) of them, some 98790 identifications published in 231 publications. Such quantifications are infeasible without databases, and the analytical power of combining a database of modern and fossil insects with analysis tools is potentially immense for numerous areas of science ranging from conservation to Quaternary geology.BugsCEP, The Bugs Coleopteran Ecology Package, is the latest incarnation of the Bugs database project. Released in 2007, the database is continually added too and is available for free download from http://www.bugscep.com. The software tools include quantitative habitat reconstruction and visualisation, correlation matrices, MCR climate reconstruction, searching by habitat and retrieving, among other things, a list of taxa known from the selected habitat types. It also provides a system for entering, storing and managing palaeoentomological data as well as a number of expert system like reporting facilities.Work is underway to create an online version of BugsCEP, implemented through the Strategic Environmental Archaeology Database (SEAD) project (http://www.sead.se). The aim is to provide more direct access to the latest data, a community orientated updating system, and integration with other proxy data. Eventually, the tools available in the offline BugsCEP will be duplicated and Bugs will be entirely in the web.This paper summarises aspects of the current scope, capabilities and applications of the BugsCEP database and software, with special reference to and quantifications of the contributions of Russell Coope to the field of palaeoentomology as represented in the database. The paper also serves to illustrate the potential for the use of BugsCEP in biographical studies, and discusses some of the issues relating to the use of large scale sources of quantitative data.All datasets used in this article are available through the current version of BugsCEP available at http://www.bugscep.com.
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| 54. |
- Munthe, Christian, 1962
(författare)
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Mellan genialitet och galenskap: Recension av Benjamin Labatuts roman "MANIAC"
- 2023
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Ingår i: Tidskriften Alba. - 1403-5448.
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- John von Neumann var ett för de allra flesta okänt ungerskt underbarn av judisk härkomst som sedermera flydde undan nazisterna till USA, där han dog 1957. Han var ett matematiskt universalgeni som gav viktiga, för att inte säga avgörande, bidrag till fysikens, biologins, data- och samhällsvetenskapens och meteorologins (och därmed klimatvetenskapens) utveckling under 1900-talet. Vid sidan av den mer allmänt kände Alan Turing föranstaltade han det som vi idag lär känna som A.I. och teoretiserade tidigt om hur man kunde tänka på maskiner som livsformer analogt med biologiska – en idé som idag ingår både i evolutionsbiologiska verktygslådor liksom i visioner och mardrömsscenarier om en teknologisk singularitet bortom vilken generella A.I. dominerar och, i värsta fall, tränger ut människoarten. Det är denne märkliga och skrämmande person Benjamín Labatuts välskrivna roman sätter i centrum för en berättelse om gränslandet mellan genialitet och galenskap, vetenskap och teknik från förra sekelskiftet till nu, logikseminariernas tankelekar och konkret global politisk utveckling på liv och död. Romanen är pärlande klart översatt av Anna Petronella Foultier. Man behöver nog ha ett visst intresse för vetenskap, teknik och/eller global politik för att uppskatta den fullt ut, men mycket sådant förklaras under hand på ett skenbart enkelt vis, så jättestora kunskaper behövs inte.
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| 55. |
- Antonsen, Simen, et al.
(författare)
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Atmospheric Chemistry of tert-butylamine and AMP
- 2017
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Ingår i: Energy Procedia. Volume 114, 2017, Pages 1026-103213th International Conference on Greenhouse Gas Control Technologies, GHGT 2016; Lausanne; Switzerland; 14 November 2016 through 18 November 2016. - : Elsevier BV. - 1876-6102.
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Konferensbidrag (refereegranskat)abstract
- © 2017 The Authors. The atmospheric chemistry of (CH 3 ) 3 CNH 2 (tert-butylamine, tBA) and (CH 3 ) 2 (CH 2 OH)CNH 2 (2-amino-2-methyl-1-propanol, AMP) has been studied by quantum chemistry methods and in photo-oxidation experiments in the EUPHORE chamber in Valencia (Spain). Aerosol formation and composition has been quantified. Yields of nitramines and other products in the photo-oxidations have been determined and complete photo-oxidation schemes including branching between the major reaction routes have been obtained. Published by Elsevier Ltd.
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| 56. |
- Lutz, Anna, 1986, et al.
(författare)
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Gas to Particle Partitioning of Organic Acids in the Boreal Atmosphere
- 2019
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Ingår i: Acs Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:7, s. 1279-1287
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Tidskriftsartikel (refereegranskat)abstract
- Gas to particle partitioning of carboxylic acids was investigated using a high-resolution chemical ionization time-of-flight mass spectrometer (HR-CI-ToF-MS) with the filter inlet for gases and aerosol (FIGAERO). Specifically, the partitioning coefficients of 640 components with unique molecular composition were calculated from an assumed linear relationship between [particle]/[gas] versus the mass of the organic fraction (M-org) according to Raoult's law, i.e., equilibrium phase partitioning. We demonstrate that, using the full data set, most of the compounds do not follow a linear relationship. This is especially the case for low- and high-molecular-weight species. Using a subset of the data, with concurrent low sulfate ambient observations ([SO42- < 0.4 mu g m(-3)), the relationship improved significantly and K-i could be derived from the slope of a linear regression to the data. The 100 species with the highest R-2 (>= 0.7) of this regression are presented. The restrictions during high sulfate conditions can be explained by changes in either the equilibrium conditions (e.g., the activity coeffient, gamma(i)) or uptake kinetics (mass transfer limitation). This study demonstrates that partitioning of compounds in the complex ambient atmosphere follows ideal Raoult's law for some limited conditions and stresses the need for studies also in more polluted environments.
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| 57. |
- Meng, X. X. Y., et al.
(författare)
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Humidity-Dependent Phase State of Gasoline Vehicle Emission-Related Aerosols
- 2021
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:2, s. 832-841
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Tidskriftsartikel (refereegranskat)abstract
- The phase states of primarily emitted and secondarily formed aerosols from gasoline vehicle exhausts were investigated by quantifying the particle rebound fraction (f). The rebound behaviors of gasoline vehicle emission-related aerosols varied with engines, fuel types, and photochemical aging time, showing distinguished differences from biogenic secondary organic aerosols. The nonliquid-to-liquid phase transition of primary aerosols emitted from port fuel injection (PFI) and gasoline direct injection (GDI) vehicles started at a relative humidity (RH) = 50 and 60%, and liquefaction was accomplished at 60 and 70%, respectively. The RH at which f declined to 0.5 decreased from 70 to 65% for the PFI case with 92# fuel, corresponding to the photochemical aging time from 0.37 to 4.62 days. For the GDI case, such RH enhanced from 60 to 65%. Our results can be used to imply the phase state of traffic-related aerosols and further understand their roles in urban atmospheric chemistry. Taking Beijing, China, as an example, traffic-related aerosols were mainly nonliquid during winter with the majority ambient RH below 50%, whereas they were mostly liquid during the morning rush hour of summer, and traffic-related secondary aerosols fluctuated between nonliquid and liquid during the daytime and tended to be liquid at night with increased ambient RH.
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| 58. |
- Zhao, D. F., et al.
(författare)
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Size-dependent hygroscopicity parameter (κ) and chemical composition of secondary organic cloud condensation nuclei
- 2015
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Ingår i: Geophysical Research Letters. - 1944-8007. ; 42:24
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Tidskriftsartikel (refereegranskat)abstract
- Secondary organic aerosol components (SOA) contribute significantly to the activation of cloud condensation nuclei (CCN) in the atmosphere. The CCN activity of internally mixed submicron SOA particles is often parameterized assuming a size-independent single-hygroscopicity parameter κ. In the experiments done in a large atmospheric reactor (SAPHIR, Simulation of Atmospheric PHotochemistry In a large Reaction chamber, Jülich), we consistently observed size-dependent κ and particle composition for SOA from different precursors in the size range of 50nm–200nm. Smaller particles had higher κ and a higher degree of oxidation, although all particles were formed from the same reaction mixture. Since decreasing volatility and increasing hygroscopicity often covary with the degree of oxidation, the size dependence of composition and hence of CCN activity can be understood by enrichment of higher oxygenated, low-volatility hygroscopic compounds in smaller particles. Neglecting the size dependence of κ can lead to significant bias in the prediction of the activated fraction of particles during cloud formation.
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| 59. |
- Grönbeck, Henrik, 1966, et al.
(författare)
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Ab initio molecular dynamics calculations of H2O on BaO(001)
- 2008
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 77:24, s. 245419-
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations are used to explore water adsorption on BaO(001). The stable configuration is found to be a novel hydroxide pair. A detailed analysis demonstrates that the electrostatic repulsion between the OH− species is screened by Ba2+ cations and that the net interaction is provided by hydrogen bonding. Ab initio molecular dynamics at low coverage reveals that the pair is stable at elevated temperatures. The large structural flexibility of the hydoxylated surface may, however, lead to pair dissociation at high coverage. Simulations of a mixed (H2O+OH) overlayer uncover proton transfer between H2O and OH groups.
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| 60. |
- Mårtensson-Pendrill, Ann-Marie, 1952
(författare)
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The Manhattan Project - a part of physics history
- 2006
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Ingår i: Physics Education. - 0031-9120. ; 41:6, s. 493-501
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Tidskriftsartikel (refereegranskat)abstract
- Current physics textbooks tend to exclude military applications, but it is explained here how a study of the Manhattan project—the devastatingly successful attempt to develop an atomic bomb—can show students how the lives and work of physicists are shaped by events in society. Much of the original source material is available in books and on the internet (and referenced here), which allows students to discover the views of the scientists for themselves.
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