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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The structures of the blend membrane of regenerated silk fibroin and glucose oxidase were investigated by means of FT-IR spectra, electronic absorption spectra and SEM. The structures of the membranes were partly transferred from silk I to silk II after the membrane had been treated with ethanol. It was found that the glucose oxidase in the membrane existed in molecular aggregates and the blend membrane had an islands sea structure. p-Benzoquinone in solution was employed to speed up the electron transfer between glucose oxidase in a regenerated silk fibroin membrane and a glassy carbon electrode. The effects of pH, temperature, concentration of p-benzoquinone and applied potential on the sensor were examined. The major advantage of water dispersed regenerated silk fibroin is its ability to immobilize the enzyme without any significant loss of enzymatic activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3853-3855 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High performance magnetic field gradient coils have always been desirable in today's ultrafast magnetic resonance imaging (MRI) applications, such as single-shot echo-planar imaging and fast spin echo imaging, as well as MR diffusion imaging and microscopy. We present a Lagrange multiplier technique of a minimum inductance gradient coil with spherical geometry. Based on this minimization approach, we construct a functional F in terms of the stored magnetic energy, the magnetic field and a set of field constraint points which are chosen over the desired imaging volume. Minimizing F, we obtain the continuous current density distribution for the spherical gradient coil. Applying the stream function technique to the continuous current distribution, the discrete current pattern can then be generated. Employing the Biot–Savart law to the discrete current loops, the gradient magnetic field has been re-evaluated in order to validate the theory. Using this approach, we have been able to design a spherical z-gradient coil which is capable of generating a gradient field of 176 mT/m with slew rate of 3422 T/m/s over a 30-cm-diam spherical volume if driven by a 350 V–220 A current amplifier. A prototype of the spherical z-gradient coil has been built. The agreement between the analytical and experimental results is excellent. Initial imaging experiments have been conducted. The results indicate the potential use of such a coil for in vivo and in vitro fast NMR applications. © 1997 American Institute of Physics.
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  • 3
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The IR spectra, the electronic absorption bands, and scanning electron microscopy (SEM) of the blend membranes of regenerated silk fibroin and glucose oxidase were reported for the first time and the second generation of glucose sensor based on glucose oxidase immobilized in the regenerated silk fibroin membrane was first constructed. The IR absorption spectra of the pure regenerated silk fibroin membrane were ascribed to its structural characteristics by which the part transition from silk I to silk II was recognized in ethanol immersion. Those spectra of the blend membrane of regenerated silk fibroin and glucose oxidase were identified as a composite of the absorption bands characteristic of both macromolecules. The electronic absorption bands showed that the glucose oxidase in the membrane exists in aggregates. A sea islands' structure was observed by SEM. These findings suggest that the regenerated silk fibroin and glucose oxidase are incompatible and their molecular interactions are very weak. A tetrathiafulvalene-mediating glucose sensor, employing immobilization of glucose oxidase by regenerated silk fibroin, was fabricated. The influences of temperature, applied potential, and pH on steady-state electrocatalytic oxidation of glucose at the sensor were evaluated. The response of the sensor to glucose under N2 saturation reached 95% steady-state current within 40 s. The sensor could be used repeatedly for 1.5 months without deterioration of the response. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Before or after the blend membrane of regenerated silk fibroin (RSF), poly(vinyl alcohol) (PVA), and peroxidase is treated with ethanol, RSF, PVA, and peroxidase maintain their own structures. The conformational transition of RSF in the blend membrane is accomplished from the silk I structure to the silk II structure by ethanol treatment, which is used to immobilize peroxidase. A ferrocene-mediating sensor for H2O2 is made, which is based on the immobilization of peroxidase in the blend membrane of RSF and PVA. Performance and characteristics of the sensor were evaluated with respect to response time, detection limit, selectivity, and dependencies on temperature and pH as well as on operating and storage stability. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 1040-0397
    Keywords: Regenerated silk fibroin ; PVA ; Sensor ; Glucose oxidase ; Glucose ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure, water absorbability and mechanical properties of the blend membranes of regenerated silk fibroin and poly(vinyl alcohol) were investigated. IR spectra showed regenerated silk fibroin in the blend membranes exists chiefly in the silk I structure after ethanol treatment. An amperometric biosensor for glucose was constructed by coupling glucose oxidase in the blend membrane of regenerated silk fibroin and PVA with platinum electrode. Its experimental parameters such as pH, temperature and applied potential were optimized. It determined glucose in less than 25 s with good reproducibility and exhibited high storage and operational stability.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two enzmyes, glucose oxidase and peroxidase, were for the first time simultaneously immobilized in regenerated silk fibroin membrane. The structure and morphology of the regenerated silk fibroin membrane containing both glucose oxidase and peroxidase were investigated with IR spectra and SEM. The bienzymes do not change the structures of the regenerated silk fibroin in the membrane, which has an islands-sea structure. For the first time, an amperometric methylene green mediating sensor for glucose based on co-immobilization of both glucose oxidase and peroxidase in regenerated silk fibroin was constructed. Cyclic voltammetry and amperometry were used to test the suitability of methylene green shuttling electrons between peroxidase and the glassy carbon electrode. The bienzyme-based system offers fast response and high sensitivity of the sensor to glucose. The effects of pH, temperature, and the concentration of the mediator on the response current were evaluated, and the dependence of the Michaelis-Menten constant Km app on the concentration of the mediator was investigated.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6849-6851 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A better understanding of the appearance of a biopsy needle and its image artifacts as well as its interaction with various sequence parameters in magnetic resonance (MR) imaging is beneficial for its application in MR image guided surgical procedures. A standard analytical solution to an infinite long cylindrically shaped object immersed in a uniform magnetic field has been used to predict MR image artifacts. In a more practical setting, we investigated the characteristics of MR image artifacts associated with a finite length metallic needle, specifically at the tip of a biopsy needle when it is approximately parallel to the main magnetic field. The origin of the needle tip artifact, which is exhibited as a blooming ball, was studied using MR imaging techniques and numerical simulation employing finite element method. Satisfactory agreement between theory and experiment has been achieved. Results showed that the image artifacts associated with biopsy needle are present and dependent on MR imaging parameters, but the artifacts can be reduced if optimal imaging parameters were used. © 1998 American Institute of Physics.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interleaved echo-planar imaging (EPI) is a fast clinical magnetic resonance imaging (MRI) scheme that obtains multiple echoes with a proper phase encoding (PE) strategy to generate multiple k-space PE lines. Since these PE data lines are from different echoes that may carry different phase and amplitude errors originating from the static magnetic field inhomogeneity and nuclear spin relaxation, to form an image free of artifacts, both phase and amplitude errors need to be compensated properly. To address this issue, we have developed a general image reconstruction technique which is capable of accomplishing two-dimensional (2D) phase correction for image reconstruction of interleaved EPI data. In this technique we formulated the reconstruction as a problem of finding an optimal solution to a set of linear algebraic equations corresponding to an imaging measurement. The phase errors, as well as other constraints, can be incorporated into these equations. The final solution can be obtained by inverting the coefficient matrix of the equation via a complex singular value decomposition (SVD) procedure, free of k-space data gridding. 2D phase corrected images have been successfully reconstructed using a set of imaging data acquired on a clinical MRI scanner. The significance of the work is that it has demonstrated that the 2D spatial phase correction can be accomplished for a set of interleaved EPI acquisition. Also, this is a flexible image reconstruction method for further improving the resulting image quality. © 1998 American Institute of Physics.
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  • 9
    Publication Date: 2016-08-03
    Description: Article Many species of nematodes use pheromones called ascarosides to coordinate their behaviour and development. Here, Zhao et al . demonstrate that the beetle vector of the pinewood nematode ( Bursaphelenchus xylophilus ) also uses and responds to ascarosides in its interactions with the nematodes. Nature Communications doi: 10.1038/ncomms12341 Authors: Lilin Zhao, Xinxing Zhang, Yanan Wei, Jiao Zhou, Wei Zhang, Peijun Qin, Satya Chinta, Xiangbo Kong, Yunpeng Liu, Haiying Yu, Songnian Hu, Zhen Zou, Rebecca A. Butcher, Jianghua Sun
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 10
    Publication Date: 2017-06-11
    Description: Large-scale coastal reclamation has caused significant changes in Spartina alterniflora (S. alterniflora) distribution in coastal regions of China. However, few studies have focused on estimation of the wetland vegetation biomass, especially of S. alterniflora, in coastal regions using LiDAR and hyperspectral data. In this study, the applicability of LiDAR and hypersectral data for estimating S. alterniflora biomass and mapping its distribution in coastal regions of China was explored to attempt problems of wetland vegetation biomass estimation caused by different vegetation types and different canopy height. Results showed that the highest correlation coefficient with S. alterniflora biomass was vegetation canopy height (0.817), followed by Normalized Difference Vegetation Index (NDVI) (0.635), Atmospherically Resistant Vegetation Index (ARVI) (0.631), Visible Atmospherically Resistant Index (VARI) (0.599), and Ratio Vegetation Index (RVI) (0.520). A multivariate linear estimation model of S. alterniflora biomass using a variable backward elimination method was developed with R squared coefficient of 0.902 and the residual predictive deviation (RPD) of 2.62. The model accuracy of S. alterniflora biomass was higher than that of wetland vegetation for mixed vegetation types because it improved the estimation accuracy caused by differences in spectral features and canopy heights of different kinds of wetland vegetation. The result indicated that estimated S. alterniflora biomass was in agreement with the field survey result. Owing to its basis in the fusion of LiDAR data and hyperspectral data, the proposed method provides an advantage for S. alterniflora mapping. The integration of high spatial resolution hyperspectral imagery and LiDAR data derived canopy height had significantly improved the accuracy of mapping S. alterniflora biomass.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI Publishing
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