| 1. |
- Bouyoucef, S E, et al.
(författare)
-
Poster Session 2 : Monday 4 May 2015, 08
- 2015
-
Ingår i: European Heart Journal Cardiovascular Imaging. - : Oxford University Press (OUP). - 2047-2404 .- 2047-2412. ; 16 Suppl 1
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
|
|
| 3. |
- Elmendorf, Sarah C., et al.
(författare)
-
Global assessment of experimental climate warming on tundra vegetation : heterogeneity over space and time
- 2012
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 15:2, s. 164-175
-
Forskningsöversikt (refereegranskat)abstract
- Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation and associated ecosystem consequences have the potential to be much greater than we have observed to date.
|
|
| 4. |
- Faleye, A. C., et al.
(författare)
-
Concentration and reduction of antibiotic residues in selected wastewater treatment plants and receiving waterbodies in Durban, South Africa
- 2019
-
Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 678, s. 10-20
-
Tidskriftsartikel (refereegranskat)abstract
- In the province of KwaZulu-Natal, South Africa the incidence of resistant tuberculosis, upper respiratory tract diseases as well as diarrhoeal and parasitic infections is high. Treatment of these diseases with antibiotics is partly reflected by the excretion of the respective antibiotics and their subsequent occurrence in wastewater. Their quantitative reduction in wastewater treatment reflects their potential environmental as well as human impact, the latter due to the use of the recipient water for domestic purposes and for irrigation. Information of the occurrence and reduction of different classes of antibiotics in wastewater treatment is sparse, especially the particle bound fraction of these. Due to this, analyses of aqueous and particle bound antibiotics in untreated wastewater of four selected wastewater treatment plants (WWTPs) and their receiving water bodies was carried out in Durban, South Africa. The treatment step especially considered was the biological one, represented by activated sludge and trickling filters. The treatment further included secondary clarifiers and final chlorine disinfection. Composite samples were collected during the period February 2017 to May 2017 and analysed with online solid phase extraction - high performance liquid chromatography mass spectrometry (SPE-HPLC-MS). For the 13 assessed antibiotics, the limit of detection (LOD) and the limit of quantification (LOQ) ranged from 0.07 to 0.33 ng L-1 and 0.23 to 1.09 ng L-1 respectively, while the total percentage recovery was in the range of 51 to 111%. The percentage of individual antibiotics bound to the particulate fraction normally lost by sample (influent) filtration, if not analysed in parallel, was in the range of 2.6%-97.3% (n = 32). In this fraction (sludge from centrifuge sample), the concentration of bound antibiotics of all the target antibiotics were detected in the influent of all WWTP in concentration ranges between 1.3 ng L-1 (Azithromycin; AZI) to 81,748 ng(-1) (Ciprofloxacin; CIP). The antibiotics with the highest median concentrations in receiving water bodies of the respective WWTP were: Sulfamethoxazole; SUL (239 ng L-1) WWTP "K", Ciprofloxacin; CIP (708 ng L-1) WWTP "S" and Albendazole; ALB (325 ng L-1 and 683 ng L-1) WWTP "P" and "I" respectively.The overall percentage removal efficiency for the four WWTPs ranged from 21% to 100%. The biological treatment steps, activated sludge and trickling filters, were effective in removing antibiotics especially with the trickling filter and the impact of the sedimentation stage after activated sludge treatment. (C) 2019 Elsevier B.V. All rights reserved.
|
|
| 5. |
|
|
| 6. |
- Arft, M, et al.
(författare)
-
Responses of tundra plants to experimental warming : Meta-analysis of the international tundra experiment
- 1999
-
Ingår i: Ecological Monographs. - 0012-9615 .- 1557-7015. ; 69:4, s. 491-511
-
Tidskriftsartikel (refereegranskat)abstract
- The International Tundra Experiment (ITEX) is a collaborative, multisite experiment using a common temperature manipulation to examine variability in species response across climatic and geographic gradients of tundra ecosystems. ITEX was designed specifically to examine variability in arctic and alpine species response to increased temperature. We compiled from one to four years of experimental data from 13 different ITEX sites and used meta-analysis to analyze responses of plant phenology, growth, and reproduction to experimental warming. Results indicate that key phenological events such as leaf bud burst and flowering occurred earlier in warmed plots throughout the study period; however, there was little impact on growth cessation at the end of the season. Quantitative measures of vegetative growth were greatest in warmed plots in the early years of the experiment, whereas reproductive effort and success increased in later years. A shift away from vegetative growth and toward reproductive effort and success in the fourth treatment year suggests a shift from the initial response to a secondary response. The change in vegetative response may be due to depletion of stored plant reserves, whereas the lag in reproductive response may be due to the formation of flower buds one to several seasons prior to flowering. Both vegetative and reproductive responses varied among life-forms; herbaceous forms had stronger and more consistent vegetative growth responses than did woody forms. The greater responsiveness of the herbaceous forms may be attributed to their more flexible morphology and to their relatively greater proportion of stored plant reserves. Finally, warmer, low arctic sites produced the strongest growth responses, but colder sites produced a greater reproductive response. Greater resource investment in vegetative growth may be a conservative strategy in the Low Arctic, where there is more competition for light, nutrients, or water, and there may be little opportunity for successful germination or seedling development. In contrast, in the High Arctic, heavy investment in producing seed under a higher temperature scenario may provide an opportunity for species to colonize patches of unvegetated ground. The observed differential response to warming suggests that the primary forces driving the response vary across climatic zones, functional groups, and through time.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Habte, F, et al.
(författare)
-
A cylindrical SPECT camera with de-centralized readout scheme
- 2001
-
Ingår i: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT. - 0168-9002. ; 471:1-2, s. 80-84
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 10. |
|
|
| 11. |
- Apelqvist, Jan, et al.
(författare)
-
Prognostic value of systolic ankle and toe blood pressure levels in outcome of diabetic foot ulcer
- 1989
-
Ingår i: Diabetes Care. - : American Diabetes Association. - 1935-5548 .- 0149-5992. ; 12:6, s. 373-378
-
Tidskriftsartikel (refereegranskat)abstract
- The prognostic value of distal blood pressure measurements has been studied in 314 consecutive diabetic patients with foot ulcers. Systolic toe blood pressure was measured with a strain-gauge technique, and ankle pressure was measured with strain-gauge or Doppler techniques. Wound healing was defined as intact skin for at least 6 mo. One hundred ninety-seven patients healed primarily, 77 had amputations, and 40 died before healing had occurred. In 294 of 300 patients, it was possible to measure either ankle or toe pressure. Fourteen patients were not available for pressure measurements. Of these, 10 patients healed primarily, and 4 died before healing occurred. Both ankle and toe pressures were higher (P less than .001) among patients who healed without amputation compared with those who underwent amputation or died before healing. No differences were seen in ankle or toe pressure levels among those who had amputations or died. No patient healed primarily with an ankle pressure less than 40 mmHg. An upper limit above which amputation was not required could not be defined. Primary healing was achieved in 139 of 164 patients (85%) with a toe pressure level greater than 45 mmHg, whereas 43 of 117 patients (36%; P less than .001) healed without amputation when toe pressure was less than or equal to 45 mmHg. In conclusion, a combination of ankle and toe pressure measurements is a useful tool to predict primary healing in diabetic foot ulcers.
|
|
| 12. |
- Apelqvist, Jan, et al.
(författare)
-
Wound classification is more important than site of ulceration in the outcome of diabetic foot ulcers
- 1989
-
Ingår i: Diabetic Medicine. - 1464-5491. ; 6:6, s. 526-530
-
Tidskriftsartikel (refereegranskat)abstract
- The importance of wound classification and site of ulceration was evaluated in 314 consecutive diabetic patients with foot ulcers. The ulcers were classified as superficial (through the full thickness of the dermis; n = 150), deep (n = 50), osteomyelitis and/or abscess (n = 46), minor gangrene (n = 39) or major gangrene (n = 29). Wound healing was defined as intact skin for at least 6 months. In patients with superficial and deep ulcers, primary healing occurred in 88% and 78%, respectively, compared with 57% in those patient who developed an abscess and/or osteomyelitis. Only 2 out of 68 patients with gangrene healed (through mummification) without amputation. Patients with gangrene had lower ankle and toe blood pressure than patients with all other types of ulcers. There were only marginal differences in primary healing rate between different ulcer sites. The highest rate was seen in ulcers localized to the metatarsal heads (78%). Patients with multiple ulcers had the lowest primary healing rate (5%) compared with single ulcers at all sites. These differences were probably due to circulatory factors, since patients with multiple ulcers had lower distal perfusion pressures compared with all other groups.
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
- Engqvist, A, et al.
(författare)
-
Archipelago strait exchange processes - an overview
- 2004
-
Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 51:4-5, s. 371-392
-
Tidskriftsartikel (refereegranskat)abstract
- Archipelagos consist of a set of islands forming a collection of basins interconnected by straits, and are typically characterized by widely varying spatial and temporal scales regarding geometry and forcing conditions. Focusing on the strait exchange parameterization, we describe an archipelago water exchange model in which the archipelago is subdivided into a network of discrete basins and interconnecting straits and where the time integration assumes a series of quasi-steady states. We propose an algorithm that should be sufficiently flexible to provide reasonable strait exchange estimates under the variety of forcing conditions encountered in the Stockholm archipelago. We start from the functional formulation of two-layer hydraulic theory, which allows numerical schemes to be designed that, given the forcing conditions at the ends of a given strait, distinguish between maximal and sub-maximal flow cases and solve the flow accordingly. We relax the assumption of two homogeneous layers when necessary, using an approximate method based on a self-similarity assumption and with the sea-level difference over the strait as an explicit part of the problem. This method allows exchange flows with two groups of layers to be solved for the same set of geometries that the pure two-layer theory can handle, including sill-contraction combinations and non-rectangular cross-sections. We further show how aspiration of dense water from below the sill crest can be quantified with hydraulic theory, and be included in the method for stratified strait exchange. Rotational control in wide straits and in parallel straits connecting the same two basins is treated with a simple but robust scheme. We evaluate the calculations with data from the Oxdjupet strait in the Stockholm archipelago. Simulations with a three-dimensional, non-hydrostatic numerical model are performed to compensate for sparsity in data.
|
|
| 16. |
- Frost, R. J. W., et al.
(författare)
-
A compact accelerator driven neutron source at the Applied Nuclear Physics Laboratory, Lund University
- 2023
-
Ingår i: EPJ TECHNIQUES AND INSTRUMENTATION. - : Springer Nature. - 2195-7045. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Applied Nuclear Physics Group at Lund University has constructed a CANS (Compact Accelerator-driven Neutron Source). The CANS is based around a 3 MV, single-ended, Pelletron accelerator, which is used to impinge a 2.8 MeV deuterium beam into a beryllium target. The anticipated neutron production will be on the order of 10(10) n/s in 4 pi sr, with future upgrades expected to increase neutron production to 10(11) n/s. Neutron energy will be up to 9 MeV with peak emission at similar to 5 MeV. Shielding and moderation will be provided by a large water tank surrounding the target, with exit ports to allow moderated neutrons to be directed to experiments. The thermal-neutron flux at the exit of the extraction ports is anticipated to be up to 10(6) n/cm(2)/s. The CANS will be used to forward the activities of the group in the area of neutron-activation analysis, in addition to a broader range of neutron related applications.
|
|
| 17. |
|
|
| 18. |
- Khorram-Manesh, Amir, 1958, et al.
(författare)
-
Long-term outcome of a large series of patients surgically treated for pheochromocytoma
- 2005
-
Ingår i: Journal of internal medicine. - 0954-6820. ; 258:1, s. 55-66
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To analyse the morbidity, mortality and long-term outcome in a consecutive series of surgically treated patients with pheochromocytoma (PC), or paraganglioma (PG), from the western region of Sweden between 1950 and 1997. PATIENTS: All patients (n = 121) who had been hospitalized and treated for PC/PG over 47 years. DESIGN: Retrospective review of patients with PC/PG regarding presenting symptoms, tumour characteristics, clinical management and long-term outcome after treatment. SETTING: One referral centre for all patients from the western region of Sweden. RESULTS: During an observation of 15 +/- 6 years, 42 patients died vs. 23.6 expected in the general population (P < 0.001). There was no intra- or post-operative mortality. Four patients with sporadic disease died of malignant PC and six with hereditary disease of associated neuroectodermal tumours. Five patients died of other malignancies, 20 of cardiovascular disease and seven of other causes. Besides older age at primary surgery, elevated urinary excretion of methoxy-catecholamines was the only observed risk factor for death (P = 0.02). At diagnosis 85% of the patients were hypertensive; one year after surgery more than half were still hypertensive. However, pre- and post-operative hypertension did not influence the risk for death versus controls. CONCLUSION: Pheochromocytoma/PG can be safely treated by surgery. Death of malignant PC/PG was unusual, but the patients as a group had an increased risk of death. We recommend life-long follow-up of patients treated for PC/PG with screening for recurrent tumour in sporadic cases and for associated tumours in hereditary cases. This strategy would also be helpful in diagnosing cardiovascular disease at an early stage.
|
|
| 19. |
|
|
| 20. |
- Molin, Staffan, et al.
(författare)
-
Microbial risk assessment in heterogeneous aquifers : 2. Infection risk sensitivity
- 2010
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 46, s. W05519-
-
Tidskriftsartikel (refereegranskat)abstract
- The entire chain of events of human disease transmitted through contaminated water, from pathogen introduction into the source (E. coli, rotavirus, and Hepatitis A), pathogen migration through the aquifer pathway, to ingestion via a supply well, and finally, the potential infection in the human host, is investigated. The health risk calculations are based on a relevant hazardous event with safe setback distances estimated by considering the infection risk from peak exposure in compliance with an acceptable level defined by a regulatory agency. A site-specific hypothetical scenario is illustrated for an aquifer with similar characteristics as the Cape Cod site, Massachusetts (United States). Relatively large variation of safe distances for the three index pathogens is found; individually, none of the index pathogens could predict the safe distance under the wide range of conditions investigated. It is shown that colloid filtration theory (CFT) with spatially variable attachment-detachment rates yields significantly different results from the effective CFT model (i.e., assuming spatially constant parameters).
|
|
| 21. |
- Navarro, C. M., et al.
(författare)
-
Treatment of humerus fractures in the elderly: A systematic review covering effectiveness, safety, economic aspects and evolution of practice
- 2018
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 13:12
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives The objective of this Health Technology Assessment was to evaluate effectiveness, complications and cost-effectiveness of surgical or non-surgical treatment for proximal, diaphyseal or distal fractures of the humerus in elderly patients. Secondary objectives were to evaluate the intervention costs per treatment of proximal humerus fractures (PHF) and to investigate treatment traditions of PHF in Sweden. The assessment contains a systematic review of clinical and health economic studies comparing treatment options for humerus fractures in elderly patients. The results regarding the effectiveness of treatments are summarized in meta-analyses. The assessment also includes a cost analysis for treatment options and an analysis of registry data of PHF. For hemiarthroplasty (HA) and non-operative treatment, there was no clinically important difference for moderately displaced PHF at one-year follow-up regarding patient rated outcomes, (standardized mean difference [SMD]) -0.17 (95% CI: -0.56; 0.23). The intervention cost for HA was at least USD 5500 higher than non-surgical treatment. The trend in Sweden is that surgical treatment of PHF is increasing. When functional outcome of percutaneous fixation/plate fixation/prosthesis surgery and non-surgical treatment was compared for PHF there were no clinically relevant differences, SMD -0.05 (95% CI: -0.26; 0.15). There was not enough data for interpretation of quality of life or complications. Evidence was scarce regarding comparisons of different surgical options for humerus fracture treatment. The cost of plate fixation of a PHF was at least USD 3900 higher than non-surgical treatment, costs for complications excluded. In Sweden the incidence of plate fixation of PHF increased between 2005 and 2011. There is moderate/low certainty of evidence that surgical treatment of moderately displaced PHF in elderly patients has not been proven to be superior to less costly non-surgical treatment options. Further research of humerus fractures is likely to have an important impact.
|
|
| 22. |
- Navarro, C. M., et al.
(författare)
-
Treatment of radius or ulna fractures in the elderly: A systematic review covering effectiveness, safety, economic aspects and current practice
- 2019
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 14:3
-
Tidskriftsartikel (refereegranskat)abstract
- Background The objective of the present study was to evaluate effectiveness, complications and cost-effectiveness of any surgical or non-surgical treatment for radius or ulna fractures in elderly patients. Secondary objectives were to analyze present treatment traditions of distal radius fractures (DRF) in Sweden and to calculate resource usage for its treatment. The assessment contains a systematic review of clinical and health economic studies comparing treatment options for radius or ulna fractures. The results regarding the effectiveness of the treatments are summarized in meta-analyses. In addition, the assessment contains a cost analysis for different treatment options commonly used for DRF care, and an analysis of registry data on the incidence and treatment of DRF. In total 31 randomized controlled trials were included in meta-analyses. When comparing functional outcome for plate fixation versus non-surgical treatment for DRF, there were no clinically important differences at one-year follow-up (mean difference [MD], -3.29, 95% CI, -7.03; 0.44). Similar results were found when comparing plating and percutaneous methods with respect to functional outcome (standardized mean difference [SMD], -0.07, 95% CI, -0.21; 0.07) and grip strength (MD, -3.47, 95% CI, -11.21; 4.28). There were no differences for minor complications, (risk difference [RD], -0.01, 95% CI, -0.07; 0.05) whereas major complications were less common for the percutaneous group, (RD, 0.02, 95% CI, 0.02; 0.03). Given the low number of studies, the evidence above was rated as moderate certainty. The cost for plate fixation versus plaster cast was estimated to 1698 compared to 137 US dollars. For DRF, plate fixation increased in Sweden between 2005 and 2013, and was the most common surgical method in 2013. Surgical treatment of moderately displaced distal radius fractures in elderly patients offers no clear benefit compared to non-surgical treatment. Plating procedures have become more common during the second millennium and involve higher costs and higher risk of major complications than percutaneous options. BASZADEGAN H, 1990, ACTA ORTHOPAEDICA SCANDINAVICA, V61, P528
|
|
| 23. |
- SEILER, A, et al.
(författare)
-
BADGER ABUNDANCE AND ACTIVITY IN RELATION TO FRAGMENTATION OF FORAGING BIOTOPES
- 1995
-
Ingår i: ANNALES ZOOLOGICI FENNICI. - : FINNISH ZOOLOGICAL BOTANICAL PUBLISHING BOARD. - 0003-455X. ; 32:1, s. 37-45
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Eurasian badgers (Meles meles) living in the southern boreal forest of Sweden prefer to forage in patches of agricultural land (AL). In two adjacent areas with different proportion AL, capture-recapture studies from spring 1989 and 1991, and track-board s
|
|
| 24. |
- Stenstrom, A., et al.
(författare)
-
Genetic variation and clonal diversity in four clonal sedges (Carex) along the Arctic coast of Eurasia
- 2001
-
Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 10:2, s. 497-513
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the structure of genetic variation (at both ramet- and genet-level) and clonal diversity within and among populations in the four closely related arctic clonal sedges Carex bigelowii, C. ensifolia, C. lugens and C. stans by use of allozyme markers. Compared to other sedges and arctic plants, the studied taxa all had high levels of genetic variation, both within populations and taxa. These taxa contained most of the total gene diversity (HT) within populations and a small part of the diversity among populations (GST ranged 0.05-0.43). Carex bigelowii had genetic variation (HS = 0.173, mean for populations) at a comparable level to other outbreeding arctic plants and to other widespread, rhizomatous and mainly outbreeding Carex species. In contrast, C. ensifolia (HS = 0.335), C. lugens (HS = 0.339) and C. stans (HS = 0.294) had within-population variations that were higher than in most other studied Carex species and for arctic plants in general. Genetic variation was not related to any tested environmental variable, but it was lower in areas deglaciated only 10 000 years BP compared to areas deglaciated 60 000 years BP or not glaciated at all during the Weichselian. All the populations were multiclonal, except for two populations of C. stans that were monoclonal. In contrast to genetic variation, clonal diversity decreased with latitude and did not differ between areas with different times of deglaciation. In accordance with previous studies, C. bigelowii and C. lugens were found to be outbreeding, while C. ensifolia and C. stans had mixed mating systems.
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Stenstrom, P, et al.
(författare)
-
A new scalable modular data acquisition system for SPECT (PET)
- 1998
-
Ingår i: IEEE TRANSACTIONS ON NUCLEAR SCIENCE. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 45:3, s. 1117-1121
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 28. |
- Stenstrom, P, et al.
(författare)
-
Evaluation of a data acquisition system for SPECT (PET)
- 2000
-
Ingår i: IEEE TRANSACTIONS ON NUCLEAR SCIENCE. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 47:4, s. 1655-1659
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 29. |
|
|
| 30. |
- Tan, W., et al.
(författare)
-
Atmospheric Chemistry of 2-Amino-2-methyl-1-propanol: A Theoretical and Experimental Study of the OH-Initiated Degradation under Simulated Atmospheric Conditions
- 2021
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 125:34, s. 7502-7519
-
Tidskriftsartikel (refereegranskat)abstract
- The OH-initiated degradation of 2-amino-2-methyl-1-propanol [CH3C(NH2)(CH3)CH2OH, AMP] was investigated in a large atmospheric simulation chamber, employing time-resolved online high-resolution proton-transfer reaction-time-of-flight mass spectrometry (PTR-ToF-MS) and chemical analysis of aerosol online PTR-ToF-MS (CHARON-PTR-ToF-MS) instrumentation, and by theoretical calculations based on M06-2X/aug-cc-pVTZ quantum chemistry results and master equation modeling of the pivotal reaction steps. The quantum chemistry calculations reproduce the experimental rate coefficient of the AMP + OH reaction, aligning k(T) = 5.2 x 10(-12) x exp (505/T) cm(3) molecule(-1) s(-1) to the experimental value k(exp,300K) = 2.8 x 10(-11) cm(3) molecule(-1) s(-1). The theoretical calculations predict that the AMP + OH reaction proceeds via hydrogen abstraction from the -CH3 groups (5-10%), -CH2- group, (>70%) and -NH2 group (5-20%), whereas hydrogen abstraction from the -OH group can be disregarded under atmospheric conditions. A detailed mechanism for atmospheric AMP degradation was obtained as part of the theoretical study. The photo-oxidation experiments show 2-amino-2-methylpropanal [CH3C(NH2)(CH3)CHO] as the major gas-phase product and propan-2-imine [(CH3)(2)C=NH], 2-iminopropanol [(CH3)(CH2OH)C=NH], acetamide [CH3C(O)NH2], formaldehyde (CH2O), and nitramine 2-methyl-2-(nitroamino)-1-propanol [AMPNO(2), CH3C(CH3)(NHNO2)-CH2OH] as minor primary products; there is no experimental evidence of nitrosamine formation. The branching in the initial H abstraction by OH radicals was derived in analyses of the temporal gas-phase product profiles to be B-CH3/B-CH2/B-NH2 = 6:70:24. Secondary photo-oxidation products and products resulting from particle and surface processing of the primary gas-phase products were also observed and quantified. All the photo-oxidation experiments were accompanied by extensive particle formation that was initiated by the reaction of AMP with nitric acid and that mainly consisted of this salt. Minor amounts of the gas-phase photo-oxidation products, including AMPNO(2), were detected in the particles by CHARON-PTR-ToF-MS and GCxGC-NCD. Volatility measurements of laboratory-generated AMP nitrate nanoparticles gave Delta H-vap = 80 +/- 16 kJ mol(-1) and an estimated vapor pressure of (1.3 +/- 0.3) x 10(-5) Pa at 298 K. The atmospheric chemistry of AMP is evaluated and a validated chemistry model for implementation in dispersion models is presented.
|
|
| 31. |
|
|
