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Search Results: 1 - 10 of 297493 matches for " J Schouten "
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Are Mutations in Genetically Modified Plants Dangerous?
Henk J. Schouten,Evert Jacobsen
Journal of Biomedicine and Biotechnology , 2007, DOI: 10.1155/2007/82612
Abstract:
Utilising polyphenylene oxide for high exposure solar UVA dosimetry
D. J. Turnbull,P. W. Schouten
Atmospheric Chemistry and Physics Discussions , 2008,
Abstract: Researchers at the University of Southern Queensland have developed a personal UV dosimeter that can quantitatively assess high exposure solar UVA exposures. The chemical polyphenylene oxide has been previously reported on its ability to measure high UVB exposures. This current research has found that polyphenylene oxide, cast in thin film form, is responsive to both the UVA and UVB parts of the solar spectrum. Further to this, the UVB wavelengths were filtered out with the use of mylar. This combined system responded to the UVA wavelengths only and underwent a change in optical absorbance as a result of UVA exposure. Preliminary results indicate that this UVA dosimeter saturates steadily when exposed to sunlight and can measure exposures of more than 20 MJ/m2 of solar UVA radiation with an uncertainty level of no more than ±5%.
Utilising polyphenylene oxide for high exposure solar UVA dosimetry
D. J. Turnbull,P. W. Schouten
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: A personal UV dosimeter that can quantitatively assess high exposure solar UVA exposures has been developed. The chemical polyphenylene oxide has been previously reported on its ability to measure high UVB exposures. This current research has found that polyphenylene oxide, cast in thin film form, is responsive to both the UVA and UVB parts of the solar spectrum. Further to this, the UVB wavelengths were filtered out with the use of mylar. This combined system responded to the UVA wavelengths only and underwent a change in optical absorbance as a result of UVA exposure. Preliminary results indicate that this UVA dosimeter saturates steadily when exposed to sunlight and can measure exposures of more than 20 MJ/m2 of solar UVA radiation with an uncertainty level of no more than ±5%.
Warm Middle Jurassic–Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean
H. C. Jenkyns, L. Schouten-Huibers, S. Schouten,J. S. Sinninghe Damsté
Climate of the Past (CP) & Discussions (CPD) , 2012,
Abstract: Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (~160 Ma) to the Early Cretaceous (~115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian–Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (~26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O data, assuming an isotopic composition of waters inhabited by these fossils of 1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic–Lower Cretaceous interval that are consistently lower by ~14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.
Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean
H. C. Jenkyns,L. Schouten-Huibers,S. Schouten,J. S. Sinninghe Damsté
Climate of the Past Discussions , 2011, DOI: 10.5194/cpd-7-1339-2011
Abstract: Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (~160 Ma) to the Early Cretaceous (~115 Ma) in the Southern Ocean. The Jurassic and Cretaceous "cold snaps" represent falls of only a few degrees. Belemnite δ18O data give palaeotemperatures that are consistently lower by ~14 °C than does TEX86 and these molluscs likely record conditions below the thermocline. Such long-term warm climatic conditions would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.
Prevalence and determinants of unemployment among ageing HIV-1-infected and HIV-uninfected individuals
I Stolte,J Kuiper,J Schouten,F Wit
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18130
Abstract: Purpose of the study: People living with HIV (PLWH) appear to be at increased risk for earlier onset of age-associated non-communicable co-morbidity (AANCC) and declines in physical and mental capacities, compared to the general population [1]. This earlier onset of AANCC in the setting of HIV infection is likely to negatively affect work participation and quality of life. Present study investigates prevalence and determinants of unemployment among older HIV-1-infected and HIV-uninfected participants of the AGEhIV Cohort Study. Methods: Data were collected (Oct. 2010–Jan. 2012) within the ongoing prospective AGEhIV Cohort Study, recruiting HIV-1-infected patients >45 years from a tertiary care HIV outpatient clinic, and HIV-uninfected Public Health Service attendants, comparable regarding age, gender and ethnicity. Data on socio-demographics, lifestyle, quality of life, AANCC and unemployment were collected, using a self-administered questionnaire and through medical examination. Current analysis was restricted to participants in the working age (45–65 years). Logistic regression analysis was used to study determinants of unemployment. Summary of results: The majority from the first enrolled 277 HIV-1-infected and 251 HIV-uninfected subjects was male (88%), Dutch (76%) and homosexual (74%). About 50% was highly educated and the median age was 52 [IQR: 48–57]. Almost all (94%) HIV-1-infected individuals were on cART, median time since first ART was 11 years [IQR: 4–15], median time since HIV-diagnosis was 12 years [IQR: 7–18] and they had been diagnosed with more AANCC than HIV-uninfected individuals (p<0.01). Unemployment was higher among HIV-1-infected (36.5%) compared to HIV-uninfected participants (21.9%) (p<0.01). In multivariate analysis, being HIV-infected (ORadj 2.0 [95% CI: 1.3–3.3]), experiencing >2 AANCC (ORadj 3.1 [95% CI: 1.4–6.8]), lower physical health status (ORadj 2.0 [95% CI: 1.6–2.6]), being unmarried (ORadj 2.1 [95% CI: 1.3–3.2]) and older age (ORadj 60-65 yrs: 9.1 [95% CI: 4.5–18]) were independently associated with higher levels of unemployment. Conclusions: Unemployment among HIV-1-infected individuals is higher compared to HIV-uninfected individuals, independent of socio-demographic characteristics, lifestyle, quality of life or number of concomitantly diagnosed AANCC. This suggests that, apart from these factors, specific HIV-related determinants, such as stage of HIV disease, but also experienced stigma, work related conditions, influence unemployment.
Nitrification and growth of autotrophic nitrifying bacteria and Thaumarchaeota in the coastal North Sea
B. Veuger,A. Pitcher,S. Schouten,J. S. Sinninghe Damsté
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-16877-2012
Abstract: Nitrification and the associated growth of autotrophic nitrifiers, as well as the contributions of bacteria and Thaumarchaeota to total autotrophic C-fixation by nitrifiers were investigated in the Dutch coastal North Sea from October 2007 to March 2008. Rates of nitrification were determined by incubation of water samples with 15N-ammonium and growth of autotrophic nitrifiers was measured by incubation with 13C-DIC in the presence and absence of nitrification inhibitors (nitrapyrin and chlorate) in combination with compound-specific stable isotope (13C) analysis of bacterial- and Thaumarchaeotal lipid biomarkers. Net nitrification during the sampling period was evident from the concentration dynamics of ammonium, nitrite and nitrate. Measured nitrification rates were high (41–221 nmol N l 1h 1). Ammonium assimilation was always substantially lower than nitrification with nitrification on average contributing 89% (range 73–97%) to total ammonium consumption. 13C-DIC fixation into bacterial and Thaumarchaeotal lipids was strongly reduced by the nitrification inhibitors (27–95%). The inhibitor-sensitive 13C-PLFA pool was dominated by the common PLFAs 16:0, 16:1ω7c and 18:1ω7c throughout the whole sampling period and occasionally also included the polyunsaturated fatty acids 18:2ω6c and 18:3ω3. Cell-specific 13C-DIC fixation activity of the nitrifying bacteria was much higher than that of the nitrifying Thaumarchaeota throughout the whole sampling period, even during the peak in Thaumarchaeotal abundance and activity. This suggests that the contribution of autotrophic Thaumarchaeota to nitrification during winter in the coastal North Sea may have been smaller than expected from their gene abundance. These results emphasize the importance of direct measurements of the actual activity of bacteria and Thaumarchaeota, rather than abundance measurements only, in order to elucidate their biogeochemical importance. The ratio between rates of nitrification versus DIC fixation by nitrifiers was higher or even much higher than typical values for autotrophic nitrifiers, indicating that little DIC was fixed relative to the amount of energy that was generated by nitrification.
The effect of temperature and salinity on the stable hydrogen isotopic composition of long chain alkenones produced by Emiliania huxleyi and Gephyrocapsa oceanica
S. Schouten,J. Ossebaar,K. Schreiber,M. V. M. Kienhuis
Biogeosciences Discussions , 2005,
Abstract: Two haptophyte algae, Emiliania huxleyi and Gephyrocapsa oceanica, were cultured at different temperatures and salinities to investigate the impact of these factors on the hydrogen isotopic composition of long chain alkenones synthesized by these algae. Results showed that alkenones synthesized by G. oceanica were on average depleted in D by 30 per mil compared to those of E. huxleyi when grown under similar conditions. The fractionation factor, αalkenones-H2O, ranged from 0.760 to 0.815 for E. huxleyi and from 0.741 to 0.788 for G. oceanica. There was no significant correlation of αalkenones-H2O with temperature but a positive linear correlation was observed between αalkenones-H2O and salinity with ~3 per mil change in fractionation per salinity unit. This suggests that salinity can have a substantial impact on the stable hydrogen isotopic composition of long chain alkenones in natural environments and, vice versa, that δD can possibly be used as a proxy to estimate paleosalinity.
HIV-associated idiopathic non-cirrhotic portal hypertension is an underdiagnosed disorder: results of a large cohort study
T Ko?ter,H Rossing,J Schouten,P Taimr
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18314
Abstract: Purpose of the study Idiopathic non-cirrhotic portal hypertension (INCPH) has been reported increasingly in patients with chronic HIV infection. However, several aspects of this disorder remain to be elucidated. The aim of our study was to evaluate the prevalence and risk factors of HIV associated INCPH. Methods All adult HIV patients attending the outpatient clinic between February and September 2011 underwent sonographical spleen size determination and assessment of portosystemic collaterals. Patients with splenomegaly underwent an extensive ultrasound examination. Gastroscopy was performed when additional signs of portal hypertension or collaterals were observed. All children with HIV infection underwent extensive ultrasound examination. INCPH was diagnosed according to the general definition. Differences between INCPH cases (group 1) and HIV patients treated with didanosine (ddI) without portal hypertension (group 2) were assessed at HIV diagnosis, start of ddI and INCPH diagnosis. Summary of results Four out of 1010 screened adult HIV patients were diagnosed with INCPH (prevalence of 4‰). Hundred of the 1010 screened patients were treated with ddI. All INCPH patients were treated with ddI, representing an INCPH prevalence of 4% in patients exposed to ddI. In The Netherlands, 7000 patients were treated with ddI and only 17 are diagnosed with INCPH, suggesting underdiagnosis in 260 patients. No differences in clinical characteristics predictive for the development of INCPH could be demonstrated between group 1 and group 2 at HIV infection or start of ddI treatment. INCPH patients were treated longer with ddI [86 vs. 51 months, p<0.01] and concomitant treatment with ddI and stavudine [21 vs. 4 months, p<0.01]. Corrected for age and duration of follow-up of HIV, active protein c [0.64 vs. 1.13, p<0.01] and active protein s [0.67 vs. 1.01, p<0.01] levels were lower in the INCPH group. None of the 38 children with HIV infection were diagnosed with INCPH. None of these children were ever treated with ddI. Conclusions In our study HIV-associated INCPH only occurred in patients exposed to ddI. Awareness for this disorder is warranted considering the suggested underdiagnosis based on these study results. Risk factors are long term treatment with ddI and concomitant treatment with stavudine and screening for signs of portal hypertension in this subgroup may be recommended. A possible pathophysiological role for thrombophilia remains to be elucidated.
Un acto más de la agricultura: Nostalgia y crítica del pasado franquista en Tranvía a la Malvarrosa de Manuel Vicent
Schouten,Fiona;
Olivar , 2008,
Abstract: the novel tranvía a la malvarrosa (1994) by manuel vicent evokes a nostalgic image of the past: the smells, colours, and sounds of 1950s valencia make the sentimental, professional and moral education of the protagonist appear highly attractive. however, while the novel's narrator remembers those days nostalgically, he simultaneously criticises the francoist regime that formed their background. the combination of a critical sentiment with a nostalgic one seems slightly paradoxical, but it can be supposed that criticism of the past contains and controls the emotional force of nostalgia. nonetheless, in this case it turns out that nostalgia ends up undermining the critical tone. in fact, the emphasis the narrator places on the dark sides of the past heightens his nostalgia, since it suggests a decadence that is attractive and intriguing.
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