A Control Process for Active Solar-Tracking Systems for Photovoltaic Technology and the Circuit Layout Necessary for the Implementation of the Method.

What basically determines how much energy is generated by a photovoltaic (PV) system is the amount of solar irradiation that is absorbed by its PV modules. One of the technical solutions to boost this quantity, and thusly also maximize the return on PV investments, is solar tracking, which makes the following of the sun on its daily and annual journey in the sky possible and also takes changes in cloud conditions into consideration. The solar-tracking solutions that PV systems are most frequently equipped with deploy active sensor technologies, while passive ones are less common in present-day practice. However, even the popular solutions of today have their limitations. Their active sensor-tracking algorithms leave room for improvement for at least three major reasons, as they do not prevent the unnecessary operation of the motors in cloudy weather, they do not make the modules assume an appropriate position after nightfall, and they do not make sure that the structure and the electronics of the PV systems are protected from rain and the strong winds in the event of storms. This paper introduces a new active sensor-tracking algorithm, which has not only been tested but it is also in the process of patenting (patent ID: p2100209). By their contribution, the authors endeavor to propose a solution that can solve all three of the issues mentioned above. The concept is based on two fundamental findings. According to the first one, periodic movement can not only considerably decrease motor movement but also increase system lifetime, while the second one simply suggests that moving the modules into an almost horizontal position facing the equator at low light levels is conducive to the prevention of damages caused by storms and fast reaction to the increase in the amount of light at daybreak. A positive feature of the new system for PV power plant operators is that it performs the tracking of the sun practically without any decrease in power compared to the focal point position, since it works with an average inaccuracy of 1.9°.

An Economic Analysis of the Shading Effects of Transmission Lines on Photovoltaic Power Plant Investment Decisions: A Case Study.

In today's photovoltaic (PV) power plants, traditional crystalline PV modules are the prevalent technology, which is highly susceptible to partial shading due to the risk of irreversible damage. Therefore, it is advisable to explore potential construction sites for objects that might cause shading, including high-voltage transmission towers, whose shading effects can be significant due to their height. By means of innovative simulation, using a model, validated with actual data, this study endeavored to deliver novel information related to the problems of shading by high-voltage transmission lines. In the context of Hungary, it examined the risk factors, technical and economic aspects, and possible solutions important for PV projects. It provides new insight, much needed also at the international level, considering the fact that the extent of the shadows cast by conductors on the surface at low Sun elevations is not known at present and neither are the shading characteristics of conductors between two transmission towers, depending on their height, in winter, when the Sun is low. An added practical benefit of the study is that its technical and economic approaches and the software solutions are all based on the practice of PV system design and construction. Related to the investigated issues, this can facilitate the formulation of the technical and economic aspects of suitable PV power plant building strategies in Hungary.

Impaired myelination of the human hippocampal formation in Down syndrome.

Myelination is considered as one of the last steps of neuronal development and is essential to the physiologically matured function of afferent and efferent pathways. In the present study, myelin formation was examined in the human fetal, postnatal and adult hippocampal formation in Down syndrome and in age-matched controls with immunohistochemistry detecting a protein component of the myelin sheath, the myelin basic protein synthesized by oligodendroglial cells. Myelination is mainly a postnatal event in the hippocampal formation of both healthy controls and in patients with Down syndrome. In patients with Down syndrome the sequence of myelination of the hippocampal formation followed a similar developmental pattern to that in controls. However, myelin formation was generally delayed in Down syndrome compared to age-matched controls. In addition, in the hilus of the dentate gyrus a decreased density of myelinated axons was detected from the start of myelination until adulthood. The majority of local axons (mossy fibers) are not myelinated in the hilar region and myelinated fibers arriving in the hilus come mainly from the subcortical septal nuclei. Since intact septo-hippocampal connections are necessary for memory formation, we hypothesize that decreased myelination in the hilus may contribute to the mental retardation of Down syndrome patients.

Role of endogenous pituitary adenylate cyclase activating polypeptide (PACAP) in myelination of the rodent brain: lessons from PACAP-deficient mice.

Pituitary adenylate-cyclase activator polypeptide (PACAP), as a consequence of its effect on the elevation of intracellular cAMP level, strongly influences brain development including myelination. While proliferation of oligodendroglial progenitors is stimulated by PACAP applied in vitro, their differentiation is inhibited. However, the in vivo role of PACAP on myelination has never been examined. In the present study the role of endogenous PACAP in myelination was examined in PACAP-deficient mice, in several areas of the brain with a special attention to the cerebral cortex. In young postnatal and adult mice myelination was studied with immunohistochemistry detecting a protein present in the myelin sheath, the myelin basic protein, with Luxol Fast Blue staining and with electron microscopy. Results obtained in PACAP-deficient mice were compared to age-matched wild type controls. We found that the sequence of myelination in the PACAP-deficient animals was similar to that observed in controls. According to this, in both PACAP-deficient and wild type mice, the somatosensory cortex was myelinated before motor areas that preceded the myelination of associational cortical areas. Archicortical associational areas such as the cingulate cortex were myelinated before neocortical areas. Myelination in the corpus callosum followed the known rostro-caudal direction in both PACAP-deficient and wild type animals, and the ventrolateral part of the corpus callosum was myelinated earlier than the dorsomedial part in both groups. In contrast to the similarity in its sequence, striking difference was found in the onset of myelination that started earlier in PACAP-deficient mice than in wild type controls in all of the examined brain regions, including cerebral archi- and neocortex. The first myelinated axons in each of the examined brain regions were observed earlier in the PACAP-deficient mice than in controls. When age-matched animals of the two groups were compared, density of myelinated fibers in the PACAP-deficient mice was higher than in controls in all of the examined areas. We propose that endogenous PACAP exerts an inhibitory role on myelination in vivo. Since myelin sheath of the central nervous system contains several factors blocking neurite outgrowth, inhibition of myelination by PACAP gives time for axonal development and synapse formation, and therefore, strengthens neuronal plasticity.

Myelination in the human hippocampal formation from midgestation to adulthood.

Myelination, one of the last steps of neuronal development, was examined in the human fetal and postnatal hippocampal formation using immunohistochemistry to detect a protein component of the myelin sheath, the myelin basic protein synthesized by oligodendroglial cells. Myelin basic protein-immunoreactive oligodendroglial cells were first seen at the 20th gestational week in the fimbria fornicis and in the alveus. Between the 21st and 35th weeks, myelinated axons also appeared in the fimbria fornicis. At the age of 39 gestational weeks, short and thin myelinated fibers were present in the fimbria, in the alveus, and less so in the stratum oriens of the hippocampus, while the first oligodendroglial cells appeared in the stratum lacunosum-moleculare and in the hilus. By the 2nd postnatal week myelinated fibers appeared in the stratum lacunosum-moleculare of Ammon's horn. At the 3rd month, myelination was strong in the alveus, moderate in the strata oriens, lacunosum-moleculare and radiatum of Ammon's horn, while only a small number of myelinated fibers were detected in the hilus. By the 5th month, the first oligodendroglial cells were detected in the molecular layer of the dentate gyrus. Myelination continued in the following years, particularly in the dentate gyrus, where even at the age of 11 years the density of myelinated fibers did not reach the adult level. It appears that the first myelinated axons belong to the long-projecting large hippocampal pyramidal cells and/or to their subcortical and cortical afferents. The sequence of myelination follows the known developmental pattern of hippocampal afferent and efferent pathways, and the prolonged myelination might be a factor in the prolonged functional maturation of hippocampal circuitry.

Clinicopathological variability in neurodegeneration with brain iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) is a rare, progressive neurodegenerative disorder with extrapyramidal and cognitive clinical symptoms characterized by iron accumulation predominantly in the globus pallidus, cs well as extensive axonal spheroids in various regions of the brain. Recent studies indicate multiple genetic causes, however the illness can occur without obvious genetic background. The most frequent genetic form is the pantothene kinase associated neurodegeneration (PKAN) with mutation in the pantothenate kinase 2 (PANK2) gene. Further forms include phosphoslipase A2 (PLA2G6) gene mutation, neuroferritinopathy, and aceruloplasminaemia. To demonstrate the phenotypic variability associated with NBIA we present two patients. In the first patient iron deposition in the globus pallidus and axonal spheroids throughout the whole brain confirmed the neuropathological diagnosis of NBIA. Based on the long duration (27 years), the relatively late onset (at age of 13) of the disease, and the symmetrical hypointensity in the globus pallidus, without the eye-of-the-tiger sign in cranial MRI, this case most likely represented an idiopathic form of NBIA but atypical PKAN may be also considered. In our second patient, who is still alive after duration of 9 years, MRI revealed the typical eye-of-the-tiger phenomenon that supported the clinical diagnosis of NBIA and wcs highly suggestive of PKAN. Since NBIA shows similarities with other neurodegenerative disorders, genetic examination may be essential in the diagnosis of this disease, however, cranial MRI together with the clinical picture may be highly indicative of NBIA.

A correlative light and electron microscopic study of postnatal myelination in the murine corpus callosum.

Oligodendroglial cells differ in their ultrastructural appearance depending on their myelin producing and maintaining activity. To better understand the relationship between light and electron microscopic features of myelination, myelin formation in the corpus callosum was studied in young postnatal mice. Immunostaining for myelin basic protein (MBP), which has an important role in myelin compaction, was compared with conventional Luxol Fast Blue myelin staining and with electron microscopic images of unlabeled tissue. MBP-immunostaining labeled a few oligodendroglial cells at postnatal day (P)3, and a few axons at P7 in the corpus callosum, below the fronto-parietal somatosensory cortex. By P10 there were more myelinated axons below the somatosensory cortex and the first MBP-immunoreaction appeared in the cingulum: labeling appeared even later in the remaining areas of corpus callosum. Electron microscopy revealed numerous medium oligodendroglial cells at P7 in the corpus callosum, below the somatosensory cortex with the first sign of myelination at P10. By P14, there were numerous myelin sheaths with loosely built structure, and the number of myelin sheaths increased continuously thereafter. However, even as late as P28, the presence of both thick, compact and thin, loosely structured myelin sheaths in the same section suggested ongoing myelination. With Luxol Fast Blue myelin staining was first observed in the corpus callosum relatively late, at P14. Areal differences in myelination of the corpus callosum, seen with MBP-immunohistochemistry, indicate that myelin formation follows cortical maturation rather than the rostro-caudal developmental growth of the corpus callosum. Myelination of the afferent and efferent fibers within the cortical areas seems to follow the inside-out maturational pattern of cortical neurons, with the first myelinated axons always appearing in layers V-VI. In addition to the known neuronal and astroglial factors that regulate myelin formation by oligodendroglial cells, we suggest that these cells and their myelin covering may also influence axonal maturation. Light microscopic data obtained with MBP-immunohistochemistry correlates well with electron microscopic observations but not with Luxol Fast Blue staining which reveals myelinated axons only relatively late in development. Therefore, both MBP-immunostaining and electron microscopy are useful, alone or in combination, for the detection of myelination, demyelination as well as remyelination processes in animal models and also in humans.