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Search Results: 1 - 10 of 251392 matches for " Cecilia Br?nnmark "
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Growth and Structure of ZnO Nanorods on a Sub-Micrometer Glass Pipette and Their Application as Intracellular Potentiometric Selective Ion Sensors
Muhammad H. Asif,Omer Nur,Magnus Willander,Peter Str?lfors,Cecilia Brnnmark,Fredrik Elinder,Ulrika H. Englund,Jun Lu,Lars Hultman
Materials , 2010, DOI: 10.3390/ma3094657
Abstract: This paper presents the growth and structure of ZnO nanorods on a sub-micrometer glass pipette and their application as an intracellular selective ion sensor. Highly oriented, vertical and aligned ZnO nanorods were grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) by the low temperature aqueous chemical growth (ACG) technique. The relatively large surface-to-volume ratio of ZnO nanorods makes them attractive for electrochemical sensing. Transmission electron microscopy studies show that ZnO nanorods are single crystals and grow along the crystal’s c-axis. The ZnO nanorods were functionalized with a polymeric membrane for selective intracellular measurements of Na +. The membrane-coated ZnO nanorods exhibited a Na +-dependent electrochemical potential difference versus an Ag/AgCl reference micro-electrode within a wide concentration range from 0.5 mM to 100 mM. The fabrication of functionalized ZnO nanorods paves the way to sense a wide range of biochemical species at the intracellular level.
Researching Lean: Methodological Implications of Loose Definitions
Mikael Brnnmark,Jostein Langstrand,Stina Johansson,Agneta Halvarsson
Quality Innovation Prosperity , 2012,
Abstract: Recently, Lean Production (Lean) has become a prevailing management concept in Sweden. However, previous research seems to show that the Lean concept and the impact of Lean vary considerably between organizations. This paper illustrates some key methodological issues that need to be considered when researching loosely defined management concepts such as Lean. The paper is based on a review of the literature and five comparative Swedish cases studies. Our study indicates that Lean has changed over time and that operationalization and interpretations of the concept vary considerably. This study concludes that future Lean studies should include a thorough assessment of the Lean interventions, study settings, and in particular non-Lean factors mediating the outcomes of Lean-inspired change programs.
A linear auroral current-voltage relation in fluid theory
J. Vedin ,K. R nnmark
Annales Geophysicae (ANGEO) , 2004,
Abstract: Progress in our understanding of auroral currents and auroral electron acceleration has for decades been hampered by an apparent incompatibility between kinetic and fluid models of the physics involved. A well established kinetic model predicts that steady upward field-aligned currents should be linearly related to the potential drop along the field line, but collisionless fluid models that reproduce this linear current-voltage relation have not been found. Using temperatures calculated from the kinetic model in the presence of an upward auroral current, we construct here approximants for the parallel and perpendicular temperatures. Although our model is rather simplified, we find that the fluid equations predict a realistic large-scale parallel electric field and a linear current-voltage relation when these approximants are employed as nonlocal equations of state. This suggests that the concepts we introduce can be applied to the development of accurate equations of state for fluid simulations of auroral flux tubes. Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions) – Space plasma physics (kinetic and MHD theory)
Generation mechanism for VLF chorus emissions observed at a low-latitude ground station
A. K. Singh ,K. R nnmark
Annales Geophysicae (ANGEO) , 2004,
Abstract: A detailed spectral analysis of VLF chorus emissions observed at the low-latitude ground station Gulmarg (geomag. lat., 24° 26' N, geomag. long., 147° 9' E, L=1.28) during the strong magnetic activity on 7-8 March 1986 have been carried out, which shows that each chorus element originates from the upper edge of the underlying hiss band. To explain various temporal and spectral features of these emissions, a possible generation mechanism has been presented based on the backward wave oscillator regime of the magnetospheric cyclotron maser. On the basis of this model, we have computed various chorus parameters as well as some magnetospheric parameters affecting the generation process. A comparison of the observed chorus characteristics with the proposed generation mechanism shows a good agreement.
The importance of solar illumination for discrete and diffuse aurora
M. Hamrin, P. Norqvist, K. R nnmark,D. Fellg rd
Annales Geophysicae (ANGEO) , 2005,
Abstract: We present a comprehensive overview of the occurrence of discrete and diffuse aurora in the nightside Northern Hemisphere at invariant latitudes 55°-75°. Twenty-one months of Freja observations (1 January 1993 to 30 September 1994) from the Northern Hemisphere, obtained at altitude, are included in this investigation. We investigate the importance of seasonal effects, solar illumination and geomagnetic activity for the auroral precipitation. The seasonal variations in the occurrence of discrete aurora are separated from the dependence on solar illumination of the ionosphere. When the effects of sunlight are eliminated, aurora is found to be more common during the summer. The occurrence of diffuse, as well as discrete aurora, is suppressed by solar illumination of the ionosphere. This dependence of diffuse auroral precipitation on ionospheric conditions is not predicted by theories that attribute diffuse aurora to equatorial pitch-angle diffusion of hot magnetospheric electrons.
Article: Heating of beam ions by ion acoustic waves
A. Vaivads,K. R?nnmark,T. Oscarsson,M. André
Annales Geophysicae (ANGEO) , 2003,
Abstract: Satellite measurements show that ion beams above the auroral acceleration region are heated to hundreds of eV in a direction perpendicular to the magnetic field. We show that ion acoustic waves may be responsible for much of this heating. Even in the absence of a positive slope in the velocity distribution of the beam ions, ion acoustic waves can be generated by a fan instability. We present analytical estimates of the wave growth rate and ion beam heating rate. These estimates, which are confirmed by particle simulations, indicate that the perpendicular temperature of the beam ions will increase by 30 eV/s, or by 1 eV in 20–25 km. From the simulations we also conclude that the heating saturates at a perpendicular temperature around 200 eV, which is consistent with observations. Key words. Ionosphere (wave-particle interactions) · Magnetospheric Physics (plasma waves and instabilities) · Space plasma physics (wave-particle interactions).
Statistical Downscaling Based on Dynamically Downscaled Predictors: Application to Monthly Precipitation in Sweden
Statistical Downscaling Based on Dynamically DownscaledPredictors: Application to Monthly Precipitation in Sweden

Cecilia HELLSTR?M,Deliang CHEN,<br>Cecilia HELLSTR?M,Deliang CHEN
大气科学进展 , 2003,
Abstract: A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.
GALS – Gradient Analysis by Least Squares
M. Hamrin, K. R nnmark, N. B rlin, J. Vedin,A. Vaivads
Annales Geophysicae (ANGEO) , 2008,
Abstract: We present a method, GALS (Gradient Analysis by Least Squares) for estimating the gradient of a physical field from multi-spacecraft observations. To obtain the best possible spatial resolution, the gradient is estimated in the frame of reference where structures in the field are essentially locally stationary. The estimates are refined iteratively by a least squares method. We show that GALS is not very sensitive to the spacecraft configuration and resolves structures much smaller than the characteristic size of the spacecraft distribution. Furthermore, GALS requires little user input. GALS has been tested on synthetic magnetic field data and data from the Cluster FGM instrument. GALS will also be useful for other types of data. The results indicate that GALS is robust and superior to the curlometer method for estimating the current from magnetic field measurements.
Sub-keV ring current ions as the tracer of substorm injection
A. Reiniusson, G. Stenberg, P. Norqvist, A. I. Eriksson,K. R nnmark
Annales Geophysicae (ANGEO) , 2006,
Abstract: We use Freja satellite data to investigate irregular small-scale density variations. The observations are made in the auroral region at about 1000-1700 km. The density variations are a few percent, and the structures are found to be spatial down to a scale length of a few ion gyroradii. Irregular density variations are often found in an environment of whistler mode/lower hybrid waves and we show that at the density gradients both the electric and magnetic wave fields are enhanced.
On the Detection of Visual Features from Digital Curves Using a Metaheuristic Approach  [PDF]
Cecilia Di Ruberto
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.331241
Abstract: In computational shape analysis a crucial step consists in extracting meaningful features from digital curves. Dominant points are those points with curvature extreme on the curve that can suitably describe the curve both for visual perception and for recognition. Many approaches have been developed for detecting dominant points. In this paper we present a novel method that combines the dominant point detection and the ant colony optimization search. The method is inspired by the ant colony search (ACS) suggested by Yin in [1] but it results in a much more efficient and effective approximation algorithm. The excellent results have been compared both to works using an optimal search approach and to works based on exact approximation strategy.
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