Search results for "JUNCTION"
showing 10 items of 862 documents
Simultaneous determination of carrier lifetime and electron density-of-states in P3HT:PCBM organic solar cells under illumination by impedance spectr…
2010
We report new insights into recombination kinetics in poly(3-hexylthiophene):methanofullerene (P3HT:PCBM) bulk heterojunction (BHJ) solar cells, based on simultaneous determination of the density of states (DOS), internal recombination resistance, and carrier lifetime, at different steady states, by impedance spectroscopy. A set of measurements at open circuit under illumination was performed aiming to better understand the limitations to the photovoltage, which in this class of solar cells remains far below the theoretical limit which is the difference between the LUMO level of PCBM and the HOMO of P3HT (∼1.1 eV). Recombination kinetics follows a bimolecular law, being the recombination ti…
Residual strain effects on the two-dimensional electron gas concentration of AlGaN/GaN heterostructures
2001
Ga-face AlGaN/GaN heterostructures with different sheet carrier concentrations have been studied by photoluminescence and Raman spectroscopy. Compared to bulk GaN, an energy shift of the excitonic emission lines towards higher energies was observed, indicating the presence of residual compressive strain in the GaN layer. This strain was confirmed by the shift of the E2 Raman line, from which biaxial compressive stresses ranging between 0.34 and 1.7 GPa were deduced. The spontaneous and piezoelectric polarizations for each layer of the heterostructures have been also calculated. The analysis of these quantities clarified the influence of the residual stress on the sheet electron concentratio…
Two-Step Solution-Processed Two-Component Bilayer Phthalocyaninato Copper-Based Heterojunctions with Interesting Ambipolar Organic Transiting and Eth…
2016
International audience; The two-component phthalocyaninato copper-based heterojunctions fabricated from n-type CuPc(COOC8H17)(8) and p-type CuPc(OC8H17)(8) by a facile two-step solution-processing quasi-Langmuir-Shafer method with both n/p- and p/n-bilayer structures are revealed to exhibit typical ambipolar air-stable organic thin-film transistor (OTFT) performance. The p/n-bilayer devices constructed by depositing CuPc(COOC8H17)(8) film on CuPc(OC8H17)(8) sub-layer show superior OTFT performance with hole and electron mobility of 0.11 and 0.02 cm(2) V-1 s(-1), respectively, over the ones with n/p-bilayer heterojunction structure with the hole and electron mobility of 0.03 and 0.016 cm(2) …
Disruption of apical-basal polarity of human embryonic stem cells enhances hematoendothelial differentiation
2007
Abstract During murine development, the formation of tight junctions and acquisition of polarity are associated with allocation of the blastomeres on the outer surface of the embryo to the trophoblast lineage, whereas the absence of polarization directs cells to the inner cell mass. Here, we report the results of ultrastructural analyses that suggest a similar link between polarization and cell fate in human embryos. In contrast, the five human embryonic stem cell (hESC) lines displayed apical-basal, epithelial-type polarity with electron-dense tight junctions, apical microvilli, and asymmetric distribution of organelles. Consistent with these findings, molecules that are components of tigh…
Immunohistochemistry of cholinergic receptors.
1992
Acetylcholine and its receptors are involved in a variety of important signal transduction processes. As shown here paradigmatically for the human neuromuscular junction and the cerebral cortex, acetylcholine receptors can be visualized immunohistochemically at the cellular and subcellular level under physiological and pathological conditions. At normal motor endplates nicotinic cholinoceptors are localized at the surface of the postsynaptic junctional folds. In myasthenic syndromes investigation of muscle biopsies enables the diagnosis of receptor deficiencies at the ultrastructural level. In normal cerebral cortex pyramidal neurons are equipped with both nicotinic and muscarinic acetylcho…
Neuromuscular junction disassembly and muscle fatigue in mice lacking neurotrophin-4
2001
Neurotrophin-4 (NT-4) is produced by slow muscle fibers in an activity-dependent manner and promotes growth and remodeling of adult motorneuron innervation. However, both muscle fibers and motor neurons express NT-4 receptors, suggesting bidirectional NT-4 signaling at the neuromuscular junction. Mice lacking NT-4 displayed enlarged and fragmented neuromuscular junctions with disassembled postsynaptic acetylcholine receptor (AChR) clusters, reduced AChR binding, and acetylcholinesterase activity. Electromyographic responses, posttetanic potentiation, and action potential amplitude were also significantly reduced in muscle fibers from NT-4 knock-out mice. Slow-twitch soleus muscles from thes…
Lymphatic endothelial progenitors bud from the cardinal vein and intersomitic vessels in mammalian embryos.
2012
Abstract The lymphatic vasculature preserves tissue fluid balance by absorbing fluid and macromolecules and transporting them to the blood vessels for circulation. The stepwise process leading to the formation of the mammalian lymphatic vasculature starts by the expression of the gene Prox1 in a subpopulation of blood endothelial cells (BECs) on the cardinal vein (CV) at approximately E9.5. These Prox1-expressing lymphatic endothelial cells (LECs) will exit the CV to form lymph sacs, primitive structures from which the entire lymphatic network is derived. Until now, no conclusive information was available regarding the cellular processes by which these LEC progenitors exit the CV without co…
A Neurovascular Blood–Brain Barrier In Vitro Model
2014
The cerebral microvasculature possesses certain cellular features that constitute the blood-brain barrier (BBB) (Abbott et al., Neurobiol Dis 37:13-25, 2010). This dynamic barrier separates the brain parenchyma from peripheral blood flow and is of tremendous clinical importance: for example, BBB breakdown as in stroke is associated with the development of brain edema (Rosenberg and Yang, Neurosurg Focus 22:E4, 2007), inflammation (Kuhlmann et al., Neurosci Lett 449:168-172, 2009; Coisne and Engelhardt, Antioxid Redox Signal 15:1285-1303, 2011), and increased mortality. In vivo, the BBB consists of brain endothelial cells (BEC) that are embedded within a precisely regulated environment conta…
Wideband modeling of cascaded H-plane waveguide junctions using the generalised impedance matrix representation
2009
A strong interest in H-plane waveguide components composed of a large number of cascaded planar junctions is recently renewed. Therefore, the more efficient development of full-wave analysis tools of such devices is again receiving consideration, specially for its potential use within modern design tools. A novel technique for providing the wideband generalised impedance matrix representation of the inductive devices in the form of pole expansions, thus extracting the most expensive computations from the frequency loop is proposed. For such purpose, the whole device is first decomposed into simpler building blocks, i.e. planar junctions and uniform waveguides, which are modelled in terms of…
Logical and pseudo-logical optical fibre networks based on two-state (binary) optical fibre sensors for industrial monitoring and control systems
2005
The possibilities of development of logical and pseudo-logical optical fibre networks for monitoring and control of equipment and industrial sites are presented. Such networks composed of simple binary attenuation and optical fibre communication lines may also be used as fast and reliable systems developing a final command signal - logical and/or pseudo-logical, depending or the architecture of network and the type of located sensors. They realise the process similar to standard electronic logical sets but use the optical signal directly on the monitored or controlled device. The analysis of serial and parallel networks was carried out in the "dark" mode detection. The examples of networks …