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Search Results: 1 - 10 of 326256 matches for " Anja S. Euser "
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Determinants of Physiological and Perceived Physiological Stress Reactivity in Children and Adolescents
Brittany E. Evans, Kirstin Greaves-Lord, Anja S. Euser, Joke H. M. Tulen, Ingmar H. A. Franken, Anja C. Huizink
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061724
Abstract: Aims Abnormal physiological stress reactivity is increasingly investigated as a vulnerability marker for various physical and psychological health problems. However, studies are inconsistent in taking into account potential covariates that may influence the developing stress system. We systematically tested determinants (individual, developmental, environmental and substance use-related) of physiological and perceived physiological stress reactivity. We also examined the relation between physiological and perceived physiological stress reactivity. Method In a stratified sample of 363 children (7–12 years) and 344 adolescents (13–20 years) from the general population, we examined cortisol, heart rate, respiratory sinus arrhythmia and perceived physiological stress reactivity to a psychosocial stress procedure. Results Using multivariate linear regression models, we found that individual, developmental, environmental and substance use-related factors were related to each of the stress response indices. These determinant factors were different for each of the stress reactivity indices, and different in children versus adolescents. Perceived physiological stress reactivity predicted cortisol reactivity in adolescents only. All other relations between perceived physiological and physiological stress reactivity were not significant. Conclusions As physiological stress variables are often examined as vulnerability markers for the development of health problems, we maintain that it is essential that future studies take into consideration factors that may account for found relations. Our study provides an overview and indication of which variables should be considered in the investigation of the relation between physiological stress indices and illness.
Multifactorial Determinants of Target and Novelty-Evoked P300 Amplitudes in Children of Addicted Parents
Anja S. Euser, Brittany E. Evans, Kirstin Greaves-Lord, Ben J. M. van de Wetering, Anja C. Huizink, Ingmar H. A. Franken
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080087
Abstract: Background Although P300 amplitude reductions constitute a persistent finding in children of addicted parents, relatively little is known about the specificity of this finding. The major aim of this study was to investigate the association between parental rearing, adverse life events, stress-reactivity, substance use and psychopathology on the one hand, and P300 amplitude in response to both target and novel distracter stimuli on the other hand. Moreover, we assessed whether risk group status (i.e., having a parental history of Substance Use Disorders [SUD]) uniquely contributed to P300 amplitude variation above and beyond these other variables. Methods Event-related potentials were recorded in high-risk adolescents with a parental history of SUD (HR;n=80) and normal-risk controls (NR;n=100) while performing a visual Novelty Oddball paradigm. Stress-evoked cortisol levels were assessed and parenting, life adversities, substance use and psychopathology were examined by using self-reports. Results HR adolescents displayed smaller P300 amplitudes in response to novel- and to target stimuli than NR controls, while the latter only approached significance. Interestingly, the effect of having a parental history of SUD on target-P300 disappeared when all other variables were taken into account. Externalizing problem behavior was a powerful predictor of target-P300. In contrast, risk group status uniquely predicted novelty-P300 amplitude reductions above and beyond all other factors. Conclusion Overall, the present findings suggest that the P300 amplitude reduction to novel stimuli might be a more specific endophenotype for SUD than the target-P300 amplitude. This pattern of results underscores the importance of conducting multifactorial assessments when examining important cognitive processes in at-risk adolescents.
Incentives in Web Studies: Methodological Issues and a Review
Anja S. G?ritz
International Journal of Internet Science , 2006,
Abstract: Two meta-analyses review the effectiveness of incentives in Web studies. The first analysis summarizes 32 experiments on the impact of material incentives on response. It is based on a sample of 212,810 people. A significant effect (odds ratio = 1.19; 95% confidence interval: 1.13—1.25) is revealed, indicating that incentives motivate people to start a Web survey. The second analysis comprises 26 experiments on the impact of incentives on retention and is based on a sample of 7,073 people. It yields a significant effect (odds ratio = 1.27; 95% confidence interval: 1.12—1.44), indicating that once people have accessed a survey for whatever reasons, they are more likely to finish if an incentive is offered. The established incentive effects are stable across various study characteristics. Conclusions did not appear to be due to publication bias.
Source Rock evaluation, Modelling, Maturation, and Reservoir characterization of the Block 18 oilfields, Sab’atayn Basin, Yemen
A.S. Alaug,D. Leyth?euser,B. Bruns,A.F. Ahmed
Iranian Journal of Earth Sciences , 2011,
Abstract: A total of 183 core and cutting samples from seven exploratory wells were selected to be analyzed by Rock-Eval pyrolysis. These cores have been drilled through the Lam and Meem Members of the Madbi Formation and contain the major source rocks of Yemen′s sedimentary basins. Contents of total organic carbon were measured and Rock-Eval pyrolysis was performed to evaluate the hydrocarbon potential of Block 18 oilfields in central Yemen. Most of the studied samples have fair to excellent petroleum generation potential as shown by the results of PP, PI, HI and TOC. They have also sufficient TOC values with an average value of 1.48 wt% and a maximum value of 12.34 wt% with a good petroleum potential averaging 4.54 kg HC/ton of rock and a maximum value of 44.78kg HC/ton of rock. HI values of the Madbi Formation in its full thickness range from 16 mg to 1114 mg HC/g TOC with an average value of 273 mg HC/g TOC. Kerogen types II and III, and a small amount of type I can be observed. These kerogens are thermally mature and mostly within the hydrocarbon generation zone. In a numerical simulation approach the thermal and burial history of the Alif-1 well, which is representative for this area was modelled. Using vitrinite reflectance data, as means of calibration, the modelling results were subjected to a sensitivity analysis concerning paleo-heat flow, radiogenic heat production, basement thickness and eroded overburden or maximum burial, respectively. The calculated temperature during deepest burial of the source rock layers of the Madbi Formation reached 158 °C for the Lam Member and 182 °C for the Meem Member. Compliance with the measured R0 values, used as calibration parameter, could be achieved by assuming an erosion of 1100 m of the Upper Tawilah Group. The heat flow is maximized at the onset of basin rifting in Late Jurassic to 90 mW/m2 having a base level of 60 mW/m2. Thus, the Lam Member has reached the main oil to wet gas window at its deepest burial whereas the Meem Member has undergone the wet gas window in its full thickness. The isopach map of the Alif Member, as the main reservoir in the studied area, indicates thickening of the sandstone unit towards the eastern and western parts of Block 18 around the Dostour Al-Wahdah gasfield in the east and at the Alif oilfields in the west.
Precise Balancing of Viscous and Radiation Forces on a Particle in Liquid-Filled Photonic Bandgap Fiber
T. G. Euser,M. K. Garbos,J. S. Y. Chen,P. St. J. Russell
Physics , 2009, DOI: 10.1364/OL.34.003674
Abstract: It is shown that, in the liquid-filled hollow core of a single-mode photonic crystal fiber, a micron-sized particle can be held stably against a fluidic counter-flow using radiation pressure, and moved to and fro (over 10s of cm) by ramping the laser power up and down. The results represent a major advance over previous work on particle transport in optically multimode liquid-filled fibers, in which the fluctuating transverse field pattern renders the radiation and trapping forces unpredictable. The counter-flowing liquid can be loaded with sequences of chemicals in precisely controlled concentrations and doses, making possible studies of single particles, vesicles or cells.
Cryptographic Protocols Based on Nielsen Transformations  [PDF]
Benjamin Fine, Anja I. S. Moldenhauer, Gerhard Rosenberger
Journal of Computer and Communications (JCC) , 2016, DOI: 10.4236/jcc.2016.412004
Abstract: We introduce in this paper cryptographic protocols which use combinatorial group theory. Based on a combinatorial distribution of shares we present secret sharing schemes and cryptosystems using Nielsen transformations. Nielsen transformations are a linear technique to study free groups and general infinite groups. In addition the group of all automorphisms of a free group F, denoted by AUT (F), is generated by a regular Nielsen transformation between two basis of F, and each regular Nielsen transformation between two basis of F defines an automorphism of F.
Quantitative broadband chemical sensing in air-suspended solid-core fibers
T. G. Euser,J. S. Y. Chen,N. J. Farrer,M. Scharrer,P. J. Sadler,P. St. J. Russell
Physics , 2007, DOI: 10.1063/1.2924408
Abstract: We demonstrate a quantitative broadband fiber sensor, based on evanescent field sensing in the cladding holes of an air-suspended solid-core photonic crystal fiber. We discuss the fabrication process, together with the structural- and optical characterization of a range of different fibers. Measured mode profiles are in good agreement with finite element method calculations made without free parameters. The fraction of the light in the hollow cladding can be tuned via the core diameter of the fiber. Dispersion measurements are in excellent agreement with theory and demonstrate tuning of the zero dispersion wavelength via the core diameter. Optimum design parameters for absorption sensors are discussed using a general parameter diagram. From our analysis, we estimate that a sensitivity increase of three orders of magnitude is feasible compared to standard cuvette measurements. Our study applies to both liquid and gas fiber sensors. We demonstrate the applicability of our results to liquid chemical sensing by measuring the broad absorption peak of an aqueous nickel chloride solution. We find striking agreement with the reference spectrum measured in a standard cuvette, even though the sample volume has decreased by three orders of magnitude. Our results demonstrate that air-suspended solid-core PCFs can be used in quantitative broadband chemical sensing measurements.
Rydberg atoms in hollow-core photonic crystal fibres
G. Epple,K. S. Kleinbach,T. G. Euser,N. Y. Joly,T. Pfau,P. St. J. Russell,R. L?w
Physics , 2014, DOI: 10.1038/ncomms5132
Abstract: The exceptionally large polarisability of highly excited Rydberg atoms (six orders of magnitude higher than ground-state atoms) makes them of great interest in fields such as quantum optics, quantum computing, quantum simulation and metrology. If however they are to be used routinely in applications, a major requirement is their integration into technically feasible, miniaturised devices. Here we show that a Rydberg medium based on room temperature caesium vapour can be confined in broadband-guiding kagome-style hollow-core photonic crystal fibres. Three-photon spectroscopy performed on a caesium-filled fibre detects Rydberg states up to a principal quantum number of n = 40. Besides small energy level shifts we observe narrow lines confirming the coherence of the Rydberg excitation. Using different Rydberg states and core diameters we study the influence of confinement within the fibre core after different exposure times. Understanding these effects is essential for the successful future development of novel applications based on integrated room temperature Rydberg systems.
The relationship between transformational leadership, integrity and an ethical climate in organisations
Anja S. van Aswegen,Amos S. Engelbrecht
South African Journal of Human Resource Management , 2009, DOI: 10.4102/sajhrm.v7i1.175
Abstract: By effectively utilising the transformational leadership process, an organisation’s culture can be transformed into one that encourages ethical behaviour. The aim of this study was to validate a theoretical model to explain the relationships between leadership, integrity and an ethical climate. A non-probability sample of employees (n = 203) from medium to large companies was used. Data were analysed by item, factor and multiple regression analyses. The results revealed that transformational leadership has a positive effect on the dimensions of an ethical climate. No convincing support was found for the proposition that integrity moderates the relationship between transformational leadership and the dimensions of an ethical climate. How to cite this article: Van Aswegen, A.S., & Engelbrecht, A.S. (2009). The relationship between transformational leadership, integrity and an ethical climate in organisations. SA Journal of Human Resource Management/SA Tydskrif vir Menslikehulpbronbestuur 7(1), Art. #175, 9 pages. DOI: 10.4102/sajhrm.v7i1.175
Real-Time Particle Mass Spectrometry Based on Resonant Micro Strings
Silvan Schmid,S?ren Dohn,Anja Boisen
Sensors , 2010, DOI: 10.3390/s100908092
Abstract: Micro- and nanomechanical resonators are widely being used as mass sensors due to their unprecedented mass sensitivity. We present a simple closed-form expression which allows a fast and quantitative calculation of the position and mass of individual particles placed on a micro or nano string by measuring the resonant frequency shifts ofthe first two bending modes. The method has been tested by detecting the mass spectrum of micro particles placed on a micro string. This method enables real-time mass spectrometry necessary for applications such as personal monitoring devices for the assessment of theexposure dose of airborne nanoparticles.
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