Search results for "Ribbon"
showing 10 items of 105 documents
Enhancing single-parameter quantum charge pumping in carbon-based devices
2011
We present a theoretical study of quantum charge pumping with a single ac gate applied to graphene nanoribbons and carbon nanotubes operating with low resistance contacts. By combining Floquet theory with Green's function formalism, we show that the pumped current can be tuned and enhanced by up to two orders of magnitude by an appropriate choice of device length, gate voltage intensity and driving frequency and amplitude. These results offer a promising alternative for enhancing the pumped currents in these carbon-based devices.
Pineal 'synaptic' ribbon numbers and melatonin synthesis of rat are resistant to guanethidine sympathectomy.
1995
Chemical sympathectomy is widely used to study the impact of the noradrenergic system on neuronal and neuroendocrine circuits. We tested the effects of intraperitoneal injections of guanethidine, an adrenergic neuron blocking agent, on selected functional parameters of the rat pineal gland which are known to be under sympathetic influence. The reliability of the method was demonstrated by the clear enophthalmus developed by experimental animals. However, neither the numbers of 'synaptic' ribbons nor melatonin synthesis differed between treated and control rats, both parameters exhibiting the nocturnal increase seen in intact animals. These results are in striking contrast to those obtained …
Simulation of Fundamental Properties of CNT- and GNR-Metal Interconnects for Development of New Nanosensor Systems
2012
Cluster approach based on the multiple scattering theory formalism, realistic analytical and coherent potentials, as well as effective medium approximation (EMA-CPA), can be effectively used for nano-sized systems modeling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g., contacts of CNTs or (GNRs) with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems solving for resistance C-Me junctions with metal particles appear due to the influence of chirality effects …
Scattering Processes in Nanocarbon-Based Nanointerconnects
2017
Cluster approach based on the multiple scattering theory (MST) formalism, realistic analytical and coherent potentials as well as effective medium approximation (EMA–CPA) can be effectively used for nanosized systems modelling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g. contacts of CNTs or GNRs with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems connected with the resistance of C–Me junctions with metal particles appear due to the influence of chirali…
Synaptic ribbons, spheres and intermediate structures in the developing rat retina
1992
The present study was conducted to investigate the qualitative and quantitative development of synaptic bodies in retinae of Wistar rats during postnatal days 4-28. In addition, the effects of different light regimens and of eye pigmentation on SB numbers were studied. Synaptic bodies were counted and measured in the outer plexiform layer of retinal tissue fixed and processed by routine electron microscopical techniques. At postnatal days 4 and 5, retinae showed only few synaptic bodies. The main numerical development of synaptic bodies occurred between postnatal days 4 and 9, numbers remaining more or less constant thereafter. The intracellular location of synaptic ribbons changed from pre…
The response to isoproterenol of synaptic ribbon numbers in the rat pineal gland changes during postnatal development
1995
Abstract In the mammalian pineal gland synaptic ribbons (SRs) are dynamic organelles of pinealocytes undergoing a day/night rhythm, with small numbers during daytime and significantly higher numbers at night, similar to the formation of the pineal hormone melatonin. Whereas the day/night rhythm of melatonin synthesis is adrenergically regulated, data on the adrenergic regulation of SR numbers in the rat pineal gland are at variance. While some authors have demonstrated that isoproterenol (ISO) stimulates SR numbers, others could not find any effect. To clarify the issue, we carried out identical experiments in two age groups. It was found that in male Sprague-Dawley rats, administration of …
Effects of Presynaptic Mutations on a Postsynaptic Cacna1s Calcium Channel Colocalized with mGluR6 at Mouse Photoreceptor Ribbon Synapses
2008
Purpose Photoreceptor ribbon synapses translate light-dependent changes of membrane potential into graded transmitter release via L-type voltage-dependent calcium channel (VDCC) activity. Functional abnormalities (e.g., a reduced electroretinogram b-wave), arising from mutations of presynaptic proteins, such as Bassoon and the VDCCalpha1 subunit Cacna1f, have been shown to altered transmitter release. L-type VDCCalpha1 subtype expression in wild-type and mutant mice was examined, to investigate the underlying pathologic mechanism. Methods Two antisera against Cacna1f, and a Cacna1f mouse mutant (Cacna1fDeltaEx14-17) were generated. Immunocytochemistry for L-type VDCCalpha1 subunits and addi…
Inverse behaviour of "synaptic" ribbon and spherule numbers in the pineal gland of male guinea-pigs exposed to continuous illumination.
1986
There is increasing evidence that pineal “synaptic” ribbons are a heterogeneous population of organelles. In addition to “synaptic” ribbons (SR) sensu stricto, which consist of an electron-dense rod surrounded by electronlucent vesicles, “synaptic” spherules (SS) exist, the electrondense core of which is round and much wider than that of the SR. In the guinea-pig SR and SS numbers exhibit an inverse day/night rhythmicity. To gain more insight into the functional significance of SR and SS, guinea-pigs were exposed to continuous illumination for approximately 4 months (LL) and the respective structures in the pineal gland were quantitated under the electron microscope and compared with contro…
Ribbon synapses of the mammalian retina contain two types of synaptic bodies--ribbons and spheres.
1989
The present paper reports that the synaptic bodies of the retinal ribbon synapses in rat, guinea pig, golden hamster and mouse are a heterogeneous population of organelles. In addition to the well-known synaptic ribbons sensu stricto which consist of a platelike electron-dense central structure surrounded by electron-lucent synaptic vesicles, there are what is termed synaptic spheres, in which the core is not platelike, but round to oval. In rat retinae procured at day, ribbons outnumbered spheres by a factor of 4. At night spheres were not seen in photoreceptor cells. Spheres, like ribbons, may lie some distance from the synaptic site, perhaps indicating transit from their site of origin t…
Strain differences in the ratio of synaptic body types in photoreceptors of the rat retina.
1993
In the retinal outer plexiform layer of seven different rat strains, synaptic bodies (SB) were counted and, according to their morphology, characterized as synaptic ribbons (SR), synaptic spheres (SS) or intermediate structures. It was found that absolute SB numbers showed relatively small variations while SR/SS ratios differed considerably between the strains investigated. These results are discussed with respect to retinal pigmentation and to formation and degradation, respectively, of synaptic ribbons.