Refine
Year of publication
- 2010 (2775) (remove)
Document Type
- Article (969)
- Doctoral Thesis (378)
- Book (338)
- Part of Periodical (337)
- Part of a Book (212)
- Contribution to a Periodical (144)
- Review (141)
- Working Paper (84)
- Report (71)
- Conference Proceeding (31)
Language
- German (1691)
- English (841)
- mis (105)
- Portuguese (48)
- French (32)
- Croatian (29)
- Multiple languages (12)
- Italian (7)
- dut (3)
- Spanish (3)
Is part of the Bibliography
- no (2775) (remove)
Keywords
- Mosambik (114)
- Mozambique (114)
- Moçambique (113)
- Filmmusik (96)
- Deutsch (74)
- Christentum (65)
- Bibel (63)
- bible (63)
- christianity (63)
- Literatur (40)
Institute
- Extern (296)
- Medizin (292)
- Präsidium (235)
- Gesellschaftswissenschaften (99)
- Biowissenschaften (98)
- Biochemie und Chemie (97)
- Physik (87)
- Geschichtswissenschaften (68)
- Geowissenschaften (59)
- Wirtschaftswissenschaften (54)
During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1, and growth rates between 2 and 37 nm h -1. The corresponding H2O concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and htwosofour concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 °C)
Aging of biological systems ultimately leads to death of the individual. In humans, organ failure as the result of functional impairments after stroke, cardio-vascular disease, tumor development, neurodegeneration and other diseases are certainly crucial in bringing life to an end. But what happens in individuals with no obvious disease or disorders?
Plasticity resembling spike-timing dependent synaptic plasticity: the evidence in human cortex
(2010)
Spike-timing dependent plasticity (STDP) has been studied extensively in a variety of animal models during the past decade but whether it can be studied at the systems level of the human cortex has been a matter of debate. Only recently newly developed non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) have made it possible to induce and assess timing dependent plasticity in conscious human subjects. This review will present a critical synopsis of these experiments, which suggest that several of the principal characteristics and molecular mechanisms of TMS-induced plasticity correspond to those of STDP as studied at a cellular level. TMS combined with a second phasic stimulation modality can induce bidirectional long-lasting changes in the excitability of the stimulated cortex, whose polarity depends on the order of the associated stimulus-evoked events within a critical time window of tens of milliseconds. Pharmacological evidence suggests an NMDA receptor mediated form of synaptic plasticity. Studies in human motor cortex demonstrated that motor learning significantly modulates TMS-induced timing dependent plasticity, and, conversely, may be modulated bidirectionally by prior TMS-induced plasticity, providing circumstantial evidence that long-term potentiation-like mechanisms may be involved in motor learning. In summary, convergent evidence is being accumulated for the contention that it is now possible to induce STDP-like changes in the intact human central nervous system by means of TMS to study and interfere with synaptic plasticity in neural circuits in the context of behavior such as learning and memory. Keywords: spike-timing dependent plasticity, long-term potentiation, long-term depression, paired associative stimulation, transcranial magnetic stimulation, human, cortex, translational neuroscience
Potentiation of glycine-gated NR1/NR3A NMDA receptors relieves Ca2+-dependent outward rectification
(2010)
Glycine has diverse functions within the mammalian central nervous system. It inhibits postsynaptic neurons via strychnine-sensitive glycine receptors (GlyRs) and enhances neuronal excitation through co-activation of N-methyl-D-aspartate (NMDA) receptors. Classical Ca2+-permeable NMDA receptors are composed of glycine-binding NR1 and glutamate-binding NR2 subunits, and hence require both glutamate and glycine for efficient activation. In contrast, recombinant receptors composed of NR1 and the glycine binding NR3A and/or NR3B subunits lack glutamate binding sites and can be activated by glycine alone. Therefore these receptors are also named “excitatory glycine receptors”. Co-application of antagonists of the NR1 glycine-binding site or of the divalent cation Zn2+ markedly enhances the glycine responses of these receptors. To gain further insight into the properties of these glycine-gated NMDA receptors, we investigated their current-voltage (I–V) dependence. Whole-cell current-voltage relations of glycine currents recorded from NR1/NR3B and NR1/NR3A/NR3B expressing oocytes were found to be linear under our recording conditions. In contrast, NR1/NR3A receptors displayed a strong outwardly rectifying I–V relation. Interestingly, the voltage-dependent inward current block was abolished in the presence of NR1 antagonists, Zn2+ or a combination of both. Further analysis revealed that Ca2+ (1.8 mM) present in our recording solutions was responsible for the voltage-dependent inhibition of ion flux through NR1/NR3A receptors. Since physiological concentrations of the divalent cation Mg2+ did not affect the I–V dependence, our data suggest that relief of the voltage-dependent Ca2+ block of NR1/NR3A receptors by Zn2+ may be important for the regulation of excitatory glycinergic transmission, according to the Mg2+-block of conventional NR1/NR2 NMDA receptors. Keywords: NMDA receptor, excitatory glycine receptor, voltage block, NR3 subunit, supralinear potentiation, Zn2+, NR1 antagonist, ligand-binding domain
Although models based on independent component analysis (ICA) have been successful in explaining various properties of sensory coding in the cortex, it remains unclear how networks of spiking neurons using realistic plasticity rules can realize such computation. Here, we propose a biologically plausible mechanism for ICA-like learning with spiking neurons. Our model combines spike-timing dependent plasticity and synaptic scaling with an intrinsic plasticity rule that regulates neuronal excitability to maximize information transmission. We show that a stochastically spiking neuron learns one independent component for inputs encoded either as rates or using spike-spike correlations. Furthermore, different independent components can be recovered, when the activity of different neurons is decorrelated by adaptive lateral inhibition.
We examined whether positive transfer of cognitive training, which so far has been observed for individual tests only, also generalizes to cognitive abilities, thereby carrying greater promise for improving everyday intellectual competence in adulthood and old age. In the COGITO Study, 101 younger and 103 older adults practiced six tests of perceptual speed (PS), three tests of working memory (WM), and three tests of episodic memory (EM) for over 100 daily 1-h sessions. Transfer assessment included multiple tests of PS, WM, EM, and reasoning. In both age groups, reliable positive transfer was found not only for individual tests but also for cognitive abilities, represented as latent factors. Furthermore, the pattern of correlations between latent change factors of practiced and latent change factors of transfer tasks indicates systematic relations at the level of broad abilities, making the interpretation of effects as resulting from unspecific increases in motivation or self-concept less likely. Keywords: cognitive training, cognitive abilities, transfer, latent factors, working memory
Disruptive behaviour disorders are reflected by a great variety of symptoms ranging from impulsive-hot tempered quarrels to purposeful and goal directed acts of cruelty. A growing body of data indicates that there are neurobiological factors that increase the risk for developing disruptive behaviour disorders. In this review, we give a broad overview of recent studies investigating physiological, neural, genetic factors, and specific neurotransmitter systems. We also discuss the impact of psychosocial risk and consider the effects of gene-environment interactions. Due to the heterogeneity of disruptive behaviour disorders, it is concluded that specific subtypes of disruptive behaviour should be considered both in terms their biological basis and in regard to specific treatment needs.
Die Arbeit untersucht die Herstellung und ökonomische Umsetzung von "ethnischem Anderssein" in sog. Kultur-Kochkursen in Frankfurt am Main. In den beforschten Kultur-Kochkursen vermitteln ethnisch markierte KochkursleiterInnen "ihre Küche und Kultur" einem (multikulturalistisch) interessiertem Publikum. Die Arbeit fokussiert auf die performative Herstellung, Umsetzung und Repräsentation von (vermarktbarem) ethnischen Andersseins durch die KochkursleiterInnen in der Kochkurssituation und überprüft die Annahme, dass Ethnizität primär durch (Selbst-)Othering – die Betonung von unüberbrückbarer, essentieller kultureller Differenz – vermarktet wird. Die Befunde, welche auf Internetrecherchen, teilnehmenden Beobachtungen und narrativen Interviews basieren, zeigen, dass die organisierenden Institutionen die Kulturkochkurse zwar mit dem Verweis auf Authentizität, Tradition und Andersartigkeit bewerben, die Kultur-KochkursleiterInnen selbst in der Kochkurssituation allerdings kein kulturalistisches, exotisierendes und Differenz betonendes Ethnizitätskonzept perfomieren, sondern vielmehr Dynamik, Vielfalt und Vermischungen artikulieren, praktizieren und stark positiv konnotieren.
Leben bedeutet eine fortdauernde Anpassung an Umweltbedingungen durch ein hoch entwickeltes Informationsverarbeitungssystem. Diese Anpassung wird durch das neuroendokrine und autonome Nervensystem gewährleistet. Eine tages- und jahreszeitliche Organisation des neuroendokrinen und autonomen Systems findet durch das Photoneuroendokrine System (PNS) statt. Erst in jüngster Zeit konnte gezeigt werden, dass neben peptidergen Substanzen auch lipiderge Signalmoleküle des Endocannabinoidsystems eine essentielle Rolle bei der interzelluären Kommunikation spielen. Hierbei zählen Anandamid (AEA) und 2-Arachidonoylglycerol (2-AG) zu den umfassend erforschten Endocannabinoiden. ...