LVDC power distribution system: computational modelling

In the doctoral dissertation, low-voltage direct current (LVDC) distribution system stability, supply security and power quality are evaluated by computational modelling and measurements on an LVDC research platform. Computational models for the LVDC network analysis are developed. Time-domain simulation models are implemented in the time-domain simulation environment PSCAD/EMTDC. The PSCAD/EMTDC models of the LVDC network are applied to the transient behaviour and power quality studies. The LVDC network power loss model is developed in a MATLAB environment and is capable of fast estimation of the network and component power losses. The model integrates analytical equations that describe the power loss mechanism of the network components with power flow calculations. For an LVDC network research platform, a monitoring and control software solution is developed. The solution is used to deliver measurement data for verification of the developed models and analysis of the modelling results. In the work, the power loss mechanism of the LVDC network components and its main dependencies are described. Energy loss distribution of the LVDC network components is presented. Power quality measurements and current spectra are provided and harmonic pollution on the DC network is analysed. The transient behaviour of the network is verified through time-domain simulations. DC capacitor guidelines for an LVDC power distribution network are introduced. The power loss analysis results show that one of the main optimisation targets for an LVDC power distribution network should be reduction of the no-load losses and efficiency improvement of converters at partial loads. Low-frequency spectra of the network voltages and currents are shown, and harmonic propagation is analysed. Power quality in the LVDC network point of common coupling (PCC) is discussed. Power quality standard requirements are shown to be met by the LVDC network. The network behaviour during transients is analysed by time-domain simulations. The network is shown to be transient stable during large-scale disturbances. Measurement results on the LVDC research platform proving this are presented in the work.

Distribution channel plan for wound care products: Case 3M Finland Ltd.

The aim of this master’s thesis was to make a qualitative marketing research and on the basis of this to develop a distribution plan for the case company Finnish 3M Ltd.’s wound care products. The literature review includes three important parts: distribution channel planning, the buying behavior of seniors, and special characteristics of health care products’ marketing. The empirical part of this thesis comprises two different parts. The first part is a marketing research, in which the buying behavior of wound care products is studied in Espoo. The research aim was to examine, in which distribution channels the wound care patients under home care would most preferably buy wound care products during the time period, when municipalities will not yet provide the products for free. The data was collected through semi-structured phone interviews and regular interviews, and was treated qualitatively and anonymously. The study revealed that the recommendations of nurses and doctors influenced most the buying behavior of wound care customers. In the second part of the thesis a distribution channel plan for wound care products was made for the case company 3M Finland Ltd. based on the results. 3M Finland Ltd. should focus on pharmacies, online-stores and municipal health centers as their main distributors.

Distribution of 131I-labeled Bothrops erythromelas venom in mice

Bothrops erythromelas is responsible for many snake bites in northeastern Brazil. In the present study we determined the in vivo distribution of the venom following its subcutaneous injection into mice. B. erythromelas venom and albumin were labeled individually with 131I by the chloramine T method, and separated in a Sephacryl® S-200 column. The efficiency of labeling was 68%. Male Swiss mice (40-45 g), which had been provided with drinking water containing 0.05% KI over a period of 10 days prior to the experiment, were inoculated dorsally (sc) with 0.3 ml (2.35 x 105 cpm/mouse) of 131I-venom (N = 42), 131I-albumin or 131I (controls, N = 28 each). Thirty minutes and 1, 3, 6, 12, 18 and 24 h after inoculation, the animals were perfused with 0.85% NaCl and skin and various organs were collected in order to determine radioactivity content. There was a high rate of venom absorption in the skin (51%) within the first 30 min compared to albumin (20.1%) and free iodine (8.2%). Up to the third hour after injection there was a tendency for venom and albumin to concentrate in the stomach (3rd h), small intestine (3rd h) and large intestine (6th h). Both control groups had more radioactivity in the digestive tract, especially in the stomach, but these levels decreased essentially to baseline by 12-18 h postinjection. In the kidneys, the distribution profiles of venom, albumin and iodine were similar. Counts at 30 min postinjection were low in all three groups (1.37, 1.86 and 0.77, respectively), and diminished to essentially 0% by 12-18 h. Albumin tended to concentrate in muscle until the 3rd h postinjection (1.98%). There was a low binding of labeled venom in the liver (<0.54%), thyroid (<0.11%) and lungs (<0.08%), and no iodinated venom was detected in brain, heart, diaphragm, spleen or bladder. The low venom binding observed in most internal organs, comparable to that of albumin, suggests that B. erythromelas venom does not specifically target most internal organs. That is, the systemic effects of envenomation are mainly due to an indirect action

Chemoreceptors and cardiovascular control in acute and chronic systemic hypoxia

This review describes the ways in which the primary bradycardia and peripheral vasoconstriction evoked by selective stimulation of peripheral chemoreceptors can be modified by the secondary effects of a chemoreceptor-induced increase in ventilation. The evidence that strong stimulation of peripheral chemoreceptors can evoke the behavioural and cardiovascular components of the alerting or defence response which is characteristically evoked by novel or noxious stimuli is considered. The functional significance of all these influences in systemic hypoxia is then discussed with emphasis on the fact that these reflex changes can be overcome by the local effects of hypoxia: central neural hypoxia depresses ventilation, hypoxia acting on the heart causes bradycardia and local hypoxia of skeletal muscle and brain induces vasodilatation. Further, it is proposed that these local influences can become interdependent, so generating a positive feedback loop that may explain sudden infant death syndrome (SIDS). It is also argued that a major contributor to these local influences is adenosine. The role of adenosine in determining the distribution of O2 in skeletal muscle microcirculation in hypoxia is discussed, together with its possible cellular mechanisms of action. Finally, evidence is presented that in chronic systemic hypoxia, the reflex vasoconstrictor influences of the sympathetic nervous system are reduced and/or the local dilator influences of hypoxia are enhanced. In vitro and in vivo findings suggest this is partly explained by upregulation of nitric oxide (NO) synthesis by the vascular endothelium which facilitates vasodilatation induced by adenosine and other NO-dependent dilators and attenuates noradrenaline-evoked vasoconstriction.

Collagen arrangement in hepatic granuloma in mice infected with Schistosoma mansoni: dependence on fiber radiation centers

The collagen structure of isolated and in situ liver granuloma from Swiss Webster mice infected with Schistosoma mansoni was sequentially and three-dimensionally analyzed during different times of infection (early acute, acute, transitional acute-chronic, and chronic phases) by laser scanning confocal microscopy and electron scanning variable vacuum microscopy. The initial granuloma structure is characterized by vascular collagen residues and by anchorage points (or fiber radiation centers), from where collagenous fibers are angularly shed and self-assembled. During the exudative-productive stage, the self-assembly of these fibers minimizes energy and mass through continuous tension and focal compression. The curvature or angles between collagen fibers probably depends on the fibroblastic or myofibroblastic organization of stress fibers. Gradually, the loose unstable lattice of the exudative-productive stage transforms into a highly packed and stable architecture as a result of progressive compactness. The three-dimensional architecture of granulomas provides increased tissue integrity, efficient distribution of soluble compounds and a haptotactic background to the cells.

Abnormal subcellular distribution of GLUT4 protein in obese and insulin-treated diabetic female dogs

The GLUT4 transporter plays a key role in insulin-induced glucose uptake, which is impaired in insulin resistance. The objective of the present study was to investigate the tissue content and the subcellular distribution of GLUT4 protein in 4- to 12-year-old control, obese and insulin-treated diabetic mongrel female dogs (4 animals per group). The parametrial white adipose tissue was sampled and processed to obtain both plasma membrane and microsome subcellular fractions for GLUT4 analysis by Western blotting. There was no significant difference in glycemia and insulinemia between control and obese animals. Diabetic dogs showed hyperglycemia (369.9 ± 89.9 mg/dl). Compared to control, the plasma membrane GLUT4, reported per g tissue, was reduced by 55% (P < 0.01) in obese dogs, and increased by 30% (P < 0.05) in diabetic dogs, and the microsomal GLUT4 was increased by ~45% (P < 0.001) in both obese and diabetic animals. Considering the sum of GLUT4 measured in plasma membrane and microsome as total cellular GLUT4, percent GLUT4 present in plasma membrane was reduced by ~65% (P < 0.001) in obese compared to control and diabetic animals. Since insulin stimulates GLUT4 translocation to the plasma membrane, percent GLUT4 in plasma membrane was divided by the insulinemia at the time of tissue removal and was found to be reduced by 75% (P < 0.01) in obese compared to control dogs. We conclude that the insulin-stimulated translocation of GLUT4 to the cell surface is reduced in obese female dogs. This probably contributes to insulin resistance, which plays an important role in glucose homeostasis in dogs.

Changes in cell shape and desmin intermediate filament distribution are associated with down-regulation of desmin expression in C2C12 myoblasts grown in the absence of extracellular Ca2+

Desmin is the main intermediate filament (IF) protein of muscle cells. In skeletal muscle, desmin IFs form a scaffold that interconnects the entire contractile apparatus with the subsarcolemmal cytoskeleton and cytoplasmic organelles. The interaction between desmin and the sarcolemma is mediated by a number of membrane proteins, many of which are Ca2+-sensitive. In the present study, we analyzed the effects of the Ca2+ chelator EGTA (1.75 mM) on the expression and distribution of desmin in C2C12 myoblasts grown in culture. We used indirect immunofluorescence microscopy and reverse transcription polymerase chain reaction (RT-PCR) to analyze desmin distribution and expression in C2C12 cells grown in the presence or absence of EGTA. Control C2C12 myoblasts showed a well-spread morphology after a few hours in culture and became bipolar when grown for 24 h in the presence of EGTA. Control C2C12 cells showed a dense network of desmin from the perinuclear region to the cell periphery, whereas EGTA-treated cells showed desmin aggregates in the cytoplasm. RT-PCR analysis revealed a down-regulation of desmin expression in EGTA-treated C2C12 cells compared to untreated cells. The present results suggest that extracellular Ca2+ availability plays a role in the regulation of desmin expression and in the spatial distribution of desmin IFs in myoblasts, and is involved in the generation and maintenance of myoblast cell shape.

Distribution of the human leukocyte antigen class II alleles in Brazilian patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is a global medical problem. The current standard of treatment consists of the combination of peginterferon plus ribavirin. This regimen eradicates HCV in 55% of cases. The immune response to HCV is an important determinant of disease evolution and can be influenced by various host factors. HLA class II may play an important role in immune response against HCV. The objective of the present study was to determine the distribution of HLA class II (DRB1 and DQB1) alleles, their association with chronic HCV infection and their response to interferon therapy. One hundred and two unrelated white Brazilian patients with chronic HCV infection, 52 responders (45 males and 7 females) and 50 non-responders (43 males and 7 females) to antiviral treatment, were included in the study. Healthy Brazilian bone marrow donors of Caucasian origin from the same geographic area constituted the control group (HLA-DRB1, N = 99 and HLA-DQB1, N = 222 individuals). HLA class II genotyping was performed using a low-resolution DRB1, DQB1 sequence-specific primer amplification. There were higher frequencies of HLA-DRB1*13 (26.5 vs 14.1%) and HLA-DQB1*02 (52.9 vs 38.7%) in patients compared with controls; however, these were not significantly different after P correction (Pc = 0.39 and Pc = 0.082, respectively). There was no significant difference between the phenotypic frequencies of HLA-DRB1 (17.3 vs 14.0%) and HLA-DQB1 alleles in responder and non-responder HCV patients. The HLA-DRB1*07 allele was significantly more common in HCV patients (33.3 vs 12.1%) than in controls (Pc = 0.0039), suggesting that the HLA-DRB1*07 allele is associated with chronic HCV infection.

NMDA receptor blockade alters the intracellular distribution of neuronal nitric oxide synthase in the superficial layers of the rat superior colliculus

Nitric oxide (NO) is a molecular messenger involved in several events of synaptic plasticity in the central nervous system. Ca2+ influx through the N-methyl-D-aspartate receptor (NMDAR) triggers the synthesis of NO by activating the enzyme neuronal nitric oxide synthase (nNOS) in postsynaptic densities. Therefore, NMDAR and nNOS are part of the intricate scenario of postsynaptic densities. In the present study, we hypothesized that the intracellular distribution of nNOS in the neurons of superior colliculus (SC) superficial layers is an NMDAR activity-dependent process. We used osmotic minipumps to promote chronic blockade of the receptors with the pharmacological agent MK-801 in the SC of 7 adult rats. The effective blockade of NMDAR was assessed by changes in the protein level of the immediate early gene NGFI-A, which is a well-known NMDAR activity-dependent expressing transcription factor. Upon chronic infusion of MK-801, a decrease of 47% in the number of cells expressing NGFI-A was observed in the SC of treated animals. Additionally, the filled dendritic extent by the histochemical product of nicotinamide adenine di-nucleotide phosphate diaphorase was reduced by 45% when compared to the contralateral SC of the same animals and by 64% when compared to the SC of control animals. We conclude that the proper intracellular localization of nNOS in the retinorecipient layers of SC depends on NMDAR activation. These results are consistent with the view that the participation of NO in the physiological and plastic events of the central nervous system might be closely related to an NMDAR activity-dependent function.

Mitochondrial control region haplotypes of the South American sea lion Otaria flavescens (Shaw, 1800)

The South American sea lion, Otaria flavescens, is widely distributed along the Pacific and Atlantic coasts of South America. However, along the Brazilian coast, there are only two nonbreeding sites for the species (Refúgio de Vida Silvestre da Ilha dos Lobos and Refúgio de Vida Silvestre do Molhe Leste da Barra do Rio Grande), both in Southern Brazil. In this region, the species is continuously under the effect of anthropic activities, mainly those related to environmental contamination with organic and inorganic chemicals and fishery interactions. This paper reports, for the first time, the genetic diversity of O. flavescens found along the Southern Brazilian coast. A 287-bp fragment of the mitochondrial DNA control region (D-loop) was analyzed. Seven novel haplotypes were found in 56 individuals (OFA1-OFA7), with OFA1 being the most frequent (47.54%). Nucleotide diversity was moderate (π = 0.62%) and haplotype diversity was relatively low (67%). Furthermore, the median joining network analysis indicated that Brazilian haplotypes formed a reciprocal monophyletic clade when compared to the haplotypes from the Peruvian population on the Pacific coast. These two populations do not share haplotypes and may have become isolated some time back. Further genetic studies covering the entire species distribution are necessary to better understand the biological implications of the results reported here for the management and conservation of South American sea lions.

Central chemoreceptors and neural mechanisms of cardiorespiratory control

The arterial partial pressure (P CO2) of carbon dioxide is virtually constant because of the close match between the metabolic production of this gas and its excretion via breathing. Blood gas homeostasis does not rely solely on changes in lung ventilation, but also to a considerable extent on circulatory adjustments that regulate the transport of CO2 from its sites of production to the lungs. The neural mechanisms that coordinate circulatory and ventilatory changes to achieve blood gas homeostasis are the subject of this review. Emphasis will be placed on the control of sympathetic outflow by central chemoreceptors. High levels of CO2 exert an excitatory effect on sympathetic outflow that is mediated by specialized chemoreceptors such as the neurons located in the retrotrapezoid region. In addition, high CO2 causes an aversive awareness in conscious animals, activating wake-promoting pathways such as the noradrenergic neurons. These neuronal groups, which may also be directly activated by brain acidification, have projections that contribute to the CO2-induced rise in breathing and sympathetic outflow. However, since the level of activity of the retrotrapezoid nucleus is regulated by converging inputs from wake-promoting systems, behavior-specific inputs from higher centers and by chemical drive, the main focus of the present manuscript is to review the contribution of central chemoreceptors to the control of autonomic and respiratory mechanisms.

Control of Bubbling Fluidized Bed Conditions

The objectives of this master’s thesis were to understand the importance of bubbling fluidized bed (BFB) conditions and to find out how digital image processing and acoustic emission technology can help in monitoring the bed quality. An acoustic emission (AE) measurement system and a bottom ash camera system were evaluated in acquiring information about the bed conditions. The theory part of the study describes the fundamentals of BFB boiler and evaluates the characteristics of bubbling bed. Causes and effects of bed material coarsening are explained. The ways and methods to monitor the behaviour of BFB are determined. The study introduces the operating principles of AE technology and digital image processing. The empirical part of the study describes an experimental arrangement and results of a case study at an industrial BFB boiler. Sand consumption of the boiler was reduced by optimization of bottom ash handling and sand feeding. Furthermore, data from the AE measurement system and the bottom ash camera system was collected. The feasibility of these two systems was evaluated. The particle size of bottom ash and the changes in particle size distribution were monitored during the test period. Neither of the systems evaluated was ready to serve in bed quality control accurately or fast enough. Particle size distributions according to the bottom ash camera did not correspond to the results of manual sieving. Comprehensive interpretation of the collected AE data requires much experience. Both technologies do have potential and with more research and development they may enable acquiring reliable and real-time information about the bed conditions. This information could help to maintain disturbance-free combustion process and to optimize bottom ash handling system.

Distribution of Smart Solutions for External Lighting in Switzerland - Case C2 Smartlight Ltd.

Establishing of export operations is the key to the competitiveness for all producing companies in high-tech industry. Distribution partnerships between exporting producer and local distributors of relevant foreign market are utilized by SMEs to gain cost-efficiency of operation. The purpose of this study was to investigate the Swiss market of outdoor lighting solutions and propose distribution channels for the case of company C2 SmartLight Ltd. The literature framework consists of three main parts: description of distribution channels for business products, the selection process of the distributor and management of the distributors. The empirical part of this study composed of the observation of Swiss lighting market, highlighting key customers, trends of energy efficiency and key industry players of the lighting market. The aim was to identify potential distribution channels, which reach the target customer groups and identify the market opportunity. Secondly, the data was collected through semi-structured phone interviews. The company, which operates in outdoor lighting business and has an established distributor in Switzerland, was interviewed and used as a benchmark. As a result of this research the market opportunity for distribution of C2 SmartLight products was identified based on potential customers and market need. C2 SmartLight Ltd. should establish a connection with wholesalers that distribute easy to handle and store electrical equipment. The results of this study can be used by other SME companies, operating in a similar field of economy, for selection of distributors.

Geographical and temporal distribution of human giardiasis in Ontario, Canada

Affiliation: Pascal Michel : Département de pathologie et microbiologie, Faculté de médecine vétérinaire, Université de Montréal

Plasticité intermodale chez le hamster énucléé à la naissance : Études de la distribution des interneurones CaBPir dans les cortex visuel et auditif primaires.

La période postnatale et l’expérience sensorielle sont critiques pour le développement du système visuel. Les interneurones inhibiteurs exprimant l’acide γ-aminobutyrique (GABA) jouent un rôle important dans le contrôle de l’activité neuronale, le raffinement et le traitement de l’information sensorielle qui parvient au cortex cérébral. Durant le développement, lorsque le cortex cérébral est très susceptible aux influences extrinsèques, le GABA agit dans la formation des périodes critiques de sensibilité ainsi que dans la plasticité dépendante de l’expérience. Ainsi, ce système inhibiteur servirait à ajuster le fonctionnement des aires sensorielles primaires selon les conditions spécifiques d’activité en provenance du milieu, des afférences corticales (thalamiques et autres) et de l’expérience sensorielle. Certaines études montrent que des différences dans la densité et la distribution de ces neurones inhibiteurs corticaux reflètent les caractéristiques fonctionnelles distinctes entre les différentes aires corticales. La Parvalbumine (PV), la Calretinine (CR) et la Calbindine (CB) sont des protéines chélatrices du calcium (calcium binding proteins ou CaBPs) localisées dans différentes sous-populations d’interneurones GABAergiques corticaux. Ces protéines tamponnent le calcium intracellulaire de sorte qu’elles peuvent moduler différemment plusieurs fonctions neuronales, notamment l’aspect temporel des potentiels d’action, la transmission synaptique et la potentialisation à long terme. Plusieurs études récentes montrent que les interneurones immunoréactifs (ir) aux CaBPs sont également très sensibles à l’expérience et à l’activité sensorielle durant le développement et chez l’adulte. Ainsi, ces neurones pourraient avoir un rôle crucial à jouer dans le phénomène de compensation ou de plasticité intermodale entre les cortex sensoriels primaires. Chez le hamster (Mesocricetus auratus), l’énucléation à la naissance fait en sorte que le cortex visuel primaire peut être recruté par les autres modalités sensorielles, telles que le toucher et l’audition. Suite à cette privation oculaire, il y a établissement de projections ectopiques permanentes entre les collicules inférieurs (CI) et le corps genouillé latéral (CGL). Ceci a pour effet d’acheminer l’information auditive vers le cortex visuel primaire (V1) durant le développement postnatal. À l’aide de ce modèle, l’objectif général de ce projet de thèse est d’étudier l’influence et le rôle de l’activité sensorielle sur la distribution et l’organisation des interneurones corticaux immunoréactifs aux CaBPs dans les aires sensorielles visuelle et auditive primaires du hamster adulte. Les changements dans l’expression des CaBPs ont été déterminés d’une manière quantitative en évaluant les profils de distribution laminaire de ces neurones révélés par immunohistochimie. Dans une première expérience, nous avons étudié la distribution laminaire des CaBPs dans les aires visuelle (V1) et auditive (A1) primaires chez le hamster normal adulte. Les neurones immunoréactifs à la PV et la CB, mais non à la CR, sont distribués différemment dans ces deux cortex primaires dédiés à une modalité sensorielle différente. Dans une deuxième étude, une comparaison a été effectuée entre des animaux contrôles et des hamsters énucléés à la naissance. Cette étude montre que le cortex visuel primaire de ces animaux adopte une chimioarchitecture en PV similaire à celle du cortex auditif. Nos recherches montrent donc qu’une suppression de l’activité visuelle à la naissance peut influencer l’expression des CaBPs dans l’aire V1 du hamster adulte. Ceci suggère également que le type d’activité des afférences en provenance d’autres modalités sensorielles peut moduler, en partie, une circuiterie corticale en CaBPs qui lui est propre dans le cortex hôte ou recruté. Ainsi, nos travaux appuient l’hypothèse selon laquelle il serait possible que certaines de ces sous-populations d’interneurones GABAergiques jouent un rôle crucial dans le phénomène de la plasticité intermodale.