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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Neural computing & applications 7 (1998), S. 334-342 
    ISSN: 1433-3058
    Keywords: Benchmarks ; Learning criteria ; Multilayer perceptron networks ; Pattern classification ; Radial basis function networks ; Training methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper presents a study of two learning criteria and two approaches to using them for training neural network classifiers, specifically a Multi-Layer Perceptron (MLP) and Radial Basis Function (RBF) networks. The first approach, which is a traditional one, relies on the use of two popular learning criteria, i.e. learning via minimising a Mean Squared Error (MSE) function or a Cross Entropy (CE) function. It is shown that the two criteria have different charcteristics in learning speed and outlier effects, and that this approach does not necessarily result in a minimal classification error. To be suitable for classification tasks, in our second approach an empirical classification criterion is introduced for the testing process while using the MSE or CE function for the training. Experimental results on several benchmarks indicate that the second approach, compared with the first, leads to an improved generalisation performance, and that the use of the CE function, compared with the MSE function, gives a faster training speed and improved or equal generalisation performance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 0-0 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The heavier halide molecules form layered crystals indicative of the presence of a specific directed intermolecular interaction. It is shown that this interaction within the crystal can be defined and characterized using the topology of the electron density within the theory of atoms in crystals. It is also shown that its presence in the crystal and the resulting geometry of the layered structure can be predicted in terms of the topology of the Laplacian distribution of an isolated Cl2 molecule, as it relates to the definition of Lewis acid and base sites within the valence shell of an atom. The generality of the definition of both primary and secondary interactions in terms of the topology of the electron density is demonstrated for all types of crystal. The electron density of solid molecular chlorine was determined by fitting the experimental X-ray structure factors and by theoretical calculation and its topology determined. Each Cl atom is found to be linked by bond paths, lines of maximum electron density, to twelve other atoms in the crystal: to four atoms in the same layer parallel to the bc plane, one of which defines the intramolecular bond of the Cl2 group, to six atoms in the four neighbouring molecules lying in the same stack parallel to the b axis and to two atoms in molecules situated in a neighbouring stack.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1351
    Keywords: Cobalt staining ; Gas chromatography-mass spectrometry ; Immunohistochemistry ; Insect ; Neuromodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The two Protocerebral-Medulla 4 neurons (PM4a and b) in the locust brain have adjacent cell bodies in the medial deutocerebrum. They project through the posterior protocerebrum, forming limited arborisations en route, and enter the lobula and medulla of the ipsilateral optic lobe, where they form extensive, overlapping arborisations. The PM4a and b neurons are octopamine immunoreactive. Their octopamine content (approximately 25 pg per cell) is confirmed by gas chromatography-mass spectrometry; each cell contains approximately 25 pg p-octopamine. Simultaneous intracellular recording from exposed PM4a and b cell bodies reveals that the two cells are physiologically indistinguishable. They receive multimodal sensory inputs. Tactile/mechanosensory stimuli to much of the animal's body and head, acoustic stimuli, and simple visual stimuli all give rise to e.p.s.p.s and action potentials in the PM4 cell body. Simultaneous recording from the cell body in the deutocerebrum and the axon in the lobula demonstrates that action potentials are predominantly initiated in the deutocerebrum and propagate centrifugally, towards the optic lobe. Occasionally, bright light flashes will initiate an action potential in the axon in the optic stalk, which probably propagates bidirectionally: centripetally to the cell body, and centrifugally into the optic lobe. The extensive arborisations in the lobula and medulla are therefore likely to be sites of octopamine release. Because PM4 neurons are octopaminergic, project to the optic lobe, and receive modalities of sensory input known to dishabituate the Descending Contralateral Movement Detector (DCMD) visual interneuron, it is proposed that PM4 neurons are neuromodulatory — mediating dishabituation or arousal of the visual system.
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  • 5
    ISSN: 1432-1424
    Keywords: Key words: Apoptosis — 4-Aminopyridine — High K+ concentration — Gene expression — Membrane potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Mcl-1, a member of the Bcl-2 family, has been identified as an inhibitor of apoptosis induced by anticancer agents and radiation in myeloblastic leukemia cells. The molecular mechanism underlying this phenomenon, however, is not yet understood. In the present study, we report that hyperpolarization of the membrane potential is required for prevention of mcl-1 mediated cell death in murine myeloblastic FDC-P1 cells. In cells transfected with mcl-1, the membrane potential, measured by the whole-cell patch clamp, was hyperpolarized more than −30 mV compared with control cells. The membrane potential was repolarized by increased extracellular K+ concentration (56 mV per 10-fold change in K+ concentration). Using the cell-attached patch-clamp technique, K+ channel activity was 1.7 times higher in mcl-1 transfected cells (NP o = 22.7 ± 3.3%) than control cells (NP o = 13.2 ± 1.9%). Viabilities of control and mcl-1 transfected cells after treatment with the cytotoxin etoposide (20 μg/ml), were 37.9 ± 3.9% and 78.2 ± 2.0%, respectively. Suppression of K+ channel activity by 4-aminopyridine (4-AP) before etoposide treatment significantly reduced the viability of mcl-1 transfected cells to 49.0 ± 4.6%. These results indicate that as part of the prevention of cell death, mcl-1 causes a hyperpolarization of membrane potential through activation of K+ channel activity.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The energy balances of most African countries suggest that biofuels (woodfuel, crop and wood residues, and dung) constitute the largest share of total energy consumption (up to 97% in some sub-Saharan Africa countries). There is, however, an increasing scarcity of woodfuel (fuelwood and charcoal), the major biofuel, and a feared increase in greenhouse gas (GHG) emissions associated with biofuel combustion. The extent of GHG emissions is estimated from biofuel consumption levels that are in turn based on methodologies that might be inaccurate. A questionnaire, supplemented by informal interviews, are used to collect data, yielding information regarding end-uses, technologies used, scale of consumption, determinants of fuel consumption, and interfuel substitution (among other parameters). The survey revealed that cooking is the major end-use, with other common uses, such as space and water heating. Improved stoves that provide better combustion efficiency and, thus, reduce woodfuel consumption have not been widely disseminated and are associated with higher methane emissions than open fires. More than 90% of the households in Africa use open fires. Consumption is presented as per capita for households and as products and quantity of fuel in the small scale industries, commercial, and public sectors. Among the determinants for biofuel consumption are affordability, availability of the fuel, and interfuel substitutions. Flaws in estimating biofuel consumption yield large uncertainties in GHG emissions, with implications for the development of policies on energy planning and environmental protection. However, the application of scenarios can guide policy formulation.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 1996-01-01
    Print ISSN: 0273-1177
    Electronic ISSN: 1879-1948
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Elsevier
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