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1.
  • Le Breton, Michael, 1986-, et al. (författare)
  • Chlorine oxidation of VOCs at a semi-rural site in Beijing: significant chlorine liberation from ClNO2 and subsequent gas- and particle-phase Cl-VOC production
  • 2018
  • Ingår i: Atmospheric Chemistry and Physics. - 1680-7316. ; 18:17, s. 13013-13030
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitryl chloride (ClNO2) accumulation at night acts as a significant reservoir for active chlorine and impacts the following day's photochemistry when the chlorine atom is liberated at sunrise. Here, we report simultaneous measurements of N2O5and a suite of inorganic halogens including ClNO2and reactions of chloride with volatile organic compounds (Cl-VOCs) in the gas and particle phases utilising the Filter Inlet for Gas and AEROsols time-of-flight chemical ionisation mass spectrometer (FIGAERO-ToF-CIMS) during an intensive measurement campaign 40km northwest of Beijing in May and June 2016. A maximum mixing ratio of 2900ppt of ClNO2was observed with a mean campaign nighttime mixing ratio of 487ppt, appearing to have an anthropogenic source supported by correlation with SO2, CO and benzene, which often persisted at high levels after sunrise until midday. This was attributed to such high mixing ratios persisting after numerous e-folding times of the photolytic lifetime enabling the chlorine atom production to reach 2.3 × 105moleculescm-3from ClNO2alone, peaking at 09:30LT and up to 8.4 × 105moleculescm-3when including the supporting inorganic halogen measurements. Cl-VOCs were observed in the particle and gas phases for the first time at high time resolution and illustrate how the iodide ToF-CIMS can detect unique markers of chlorine atom chemistry in ambient air from both biogenic and anthropogenic sources. Their presence and abundance can be explained via time series of their measured and steady-state calculated precursors, enabling the assessment of competing OH and chlorine atom oxidation via measurements of products from both of these mechanisms and their relative contribution to secondary organic aerosol (SOA) formation.
2.
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3.
  • Hassellöv, Martin, 1970-, et al. (författare)
  • REACH missar nano!
  • 2009
  • Ingår i: Miljöforskning. ; 3/4
  • Tidskriftsartikel (övrigt vetenskapligt)
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4.
  • Farewell, Anne, 1961- (författare)
  • Rising to the Top: Promoting Deeper Learning in the Laboratory
  • 2018
  • Ingår i: National Center for Case Study Teaching in Science.
  • Bokkapitel (refereegranskat)abstract
    • Inquiry-based labs differ from cookbook labs in that inquiry-based labs contain an element of experimentation. A cookbook lab can be performed by a student without understanding any of the theory connected with the exercise whereas inquiry-based labs require a degree of conceptual knowledge for a student to perform the lab. Inquiry-based labs also strengthen and deepen students understanding of topics discussed in lectures or reading assignments. There are many variations and degrees of inquiry in these labs ranging from a lab that is entirely designed by the students to those that include small questions requiring that the students predict the outcomes of a lab or fill in missing information (guided inquiry). A simple specific example of a cookbook lab would be instructing students to measure volume changes between ice and liquid water. The students would be given step by step instructions to follow and would not need to apply any conceptual knowledge. An inquiry based lab on the same topic would allow the students to design their own experiment to discover how the volume of liquid water differs from that of ice. One goal of this activity is to introduce inquiry-based lab design. Beyond lab design, lab supervision is crucial to encouraging students to use their conceptual knowledge when doing a practical lab. Lab assistants or teachers who are involved in the lab can use student questions to encourage deeper understanding. This case study includes a role-play exercise for this skill. This case study has been designed to be used in science education courses for both graduate student laboratory assistants and lecturers or professors in natural sciences at the university or college level. It includes discussion and role-play of a hypothetical laboratory. No specific knowledge of biology or chemistry is needed beyond high school level to complete this task, though knowledge of the existence of microorganisms (yeast) and proteins is assumed. In addition, this activity is suitable for participants with little or no pedagogics training.
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5.
  • Wang, Y. J., et al. (författare)
  • The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing, China
  • 2019
  • Ingår i: Atmospheric Chemistry and Physics. - 1680-7316. ; 19:11, s. 7649-7665
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NO(x)and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ng m(-3), higher than those reported in other summertime studies (0.14-6.44 ng m(-3)). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low- to high-NOx regimes coincided with a shift from organic- to inorganic-dominated oxidation products. The transition thresholds were NO2 similar to 20 ppb for daytime and NO2 similar to 25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO3 concentrations and (NO3-)/NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while the NO3- concentrations and (NO3-)/NACs ratios showed increasing trends, signaling a shift from organic- to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NC+4M5NC) / 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH > 30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as important factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols.
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6.
  • Charpentier Ljungqvist, Fredrik, 1982- (författare)
  • Global nedkylning : klimatet och människan under 10 000 år
  • 2009
  • Bok (populärvet., debatt m.m.)abstract
    • <p>Klimatet har förändrats både regionalt och globalt sedan senaste istiden tog slut, ofta med dramatiska konsekvenser för naturen och människan. Fastän det talas så mycket om klimatförändringar idag är det få som vet särskilt mycket om hur klimatet har varierat förr.</p><p>Det är först under de senaste åren som forskningen börjat kunna beskriva vad som faktiskt hänt med klimatet under olika tider, på olika platser. Historikern Fredrik Charpentier Ljungqvist har tagit ett samlat grepp på den senaste forskningen och resultatet är en resa i vått och torrt, i hetta och kyla, jorden runt under 10 000 år. Vi får stifta bekantskap med många olika folk och kulturer – babylonier, romare, mayaindianer och vikingar – som alla under historiens gång varit utsatta för klimatförändringar.</p>
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7.
  • van der Spoel, David, et al. (författare)
  • Structural studies of melting on the picosecond time scale
  • 2008
  • Ingår i: Physical Chemistry, Chemical Physics - PCCP. - 1463-9076 .- 1463-9084. ; 10:42, s. 6344-6349
  • Forskningsöversikt (refereegranskat)abstract
    • <p>Ultrafast structural studies of laser-induced melting have demonstrated that the solid-liquid phase transition can take place on a picosecond time scale in a variety of materials. Experimental studies using ångström wavelength X-rays from the sub-picosecond pulse source at Stanford (now retired) on non-thermal melting of semi-conductors, such as indium antimonide, employed the decay of a single Bragg-peak to measure the time component of the phase transition. These materials were found to start melting within one picosecond after the laser pulse. Recent computer simulations have described the thermal melting of ice induced by an infrared laser pulse. Here it was shown that melting can happen within a few picoseconds, somewhat slower than non-thermal melting in semi-conductors. These computer simulations are compatible with spectroscopy experiments on ice-melting, demonstrating that simulations form a very powerful complement to experiments targeting the process of phase-transitions. Here we present an overview of recent experimental and theoretical studies of melting, as well as new simulations of ice-melting where the effect of the size of the crystal on scattering is studied. Based on simulations of a near-macroscopic crystal, we predict the decay of the most intense Bragg peaks of ice following heating by laser pulse, by modeling the scattering from the melting sample in the simulations.</p>
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8.
  • Schyman, Patric, et al. (författare)
  • Hydrogen Abstraction from Deoxyribose by a Neighbouring Uracil-5-yl Radical
  • 2007
  • Ingår i: Physical Chemistry, Chemical Physics - PCCP. - Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 9, s. 5975-5979
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Hydrogen abstraction from the C1<img src="http://www.rsc.org/images/entities/char_2032.gif" /> and C2<img src="http://www.rsc.org/images/entities/char_2032.gif" /> positions of deoxyadenosine by a neighbouring uracil-5-yl radical in the 5<img src="http://www.rsc.org/images/entities/char_2032.gif" />-AU<img src="http://www.rsc.org/images/entities/char_02d9.gif" />-3<img src="http://www.rsc.org/images/entities/char_2032.gif" /> 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<img src="http://www.rsc.org/images/entities/char_2032.gif" /> and C2<img src="http://www.rsc.org/images/entities/char_2032.gif" />. When adenine is neutral there is a preference for the C1<img src="http://www.rsc.org/images/entities/char_2032.gif" /> site and when the adenine is a radical cation the C2<img src="http://www.rsc.org/images/entities/char_2032.gif" /> site is the preferred. If adenine is positively charged, the rate-limiting step when abstracting hydrogen from C1<img src="http://www.rsc.org/images/entities/char_2032.gif" /> is the formation of an intermediate crosslink between uracil and adenine. This crosslink might be avoided in dsDNA, making C1<img src="http://www.rsc.org/images/entities/char_2032.gif" /> the preferred site for abstraction.</p>
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9.
  • Buckland, Philip I., 1973- (författare)
  • The Bugs Coleopteran Ecology Package (BugsCEP) : the development and implementation of software for palaeoenvironmental and palaeoclimatological research
  • 2009
  • Ingår i: Bugs. - Mauritius : VDM Verlag Dr. Muller Aktiengesellschaft & Co. KG. - 363913530X - 978-3639135305
  • Bok (övrigt vetenskapligt)abstract
    • <p>This book describes the development and practical application of a unique database orientated software package, BugsCEP, for environmental, climatic and biodiversity reconstruction from beetle assemblages. BugsCEP consists of a database of ecology and distribution data for over 9400 insect taxa, and includes temperature tolerance data for 436 species. It contains abundance and summary data for over 770 sites, most of the known European Quaternary fossil coleopteran record, supported by a bibliography of over 3700 sources. Built in statistics, including a specially developed habitat classification system, provide semi-quantitative environmental reconstructions to aid in the interpretation of sites. BugsCEP's querying and reporting functions also increase the efficiency with which analyses can be undertaken, including the facility to explore the fossil record of species by searching ecology and distribution data. The Mutual Climatic Range (MCR) reconstruction method is implemented and improved upon, including predictive modelling and the graphical output of reconstructions and climate space maps. BugsCEP is available from www.bugscep.com.</p>
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10.
  • Vitalis Pemunta, Ngambouk, 1973-, et al. (författare)
  • Modern State Law: Regulating Tradition or Protecting the Environment in the Mankon Kingdom of Northwest Cameroon?
  • 2019
  • Ingår i: Endemic Species. Eusebio Cano Carmona (red.). - London, United Kingdom : Intechopen. - 978-1-83962-354-7 ; s. 181-
  • Bokkapitel (refereegranskat)abstract
    • Most African countries including Cameroon find themselves in a situation of legal pluralism and at crossroads with implications for the sustainable management of natural resources. Traditional institutions and knowledge systems have been hailed as invaluable mechanisms for the conservation of flora and fauna. This chapter examines the conflict between traditional institutions and State law in the hierarchically stratified Mankon Kingdom of the Grassfield region of Northwest Cameroon where the latter prohibits the harvesting of culturally valuable plant and animal species for myriad ritual ceremonies and for therapeutic purposes. It demonstrates that the lack of cultural sensitivity can be antithetical to conservation initiatives. In other words, there is the need to align current legislative regulations for the management of natural species with the traditional use of territory, gender roles as well as to raise the cultural and educational level of the population through sensitization on the need to conserve the natural environment on which their culture depends for its survival.
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