959 resultados para Voltage reference circuits


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Poster at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

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This master’s thesis was done for a small company, Vipetec Oy, which offers specialized technological services for companies mainly in forest industry. The study was initiated partly because the company wants to expand its customer base to a new industry. There were two goals connected to each other. First was to find out how much and what kind of value current customers have realized from ATA Process Event Library, one of the products that the company offers. Second was to determine the best way to present this value and its implications for future value potential to both current and potential customers. ATA helps to make grade and product changes, starting after machine downtime, and recovery from production break faster for customers. All three events sometimes occur in production line. The faster operation results to savings in time and material. In addition to ATA Vipetec also offers other services related to development of automation and optimization of controls. Theoretical part concentrates on the concept of value, how it can be delivered to customers, and what kind of risk customer faces in industrial purchasing. Also the function of reference marketing towards customers is discussed. In the empirical part the realized value for existing customers is evaluated based on both numerical data and interviews. There’s also a brief case study about one customer. After that the value-based reference marketing for a target industry is examined through interviews of these potential customers. Finally answers to the research questions are stated and compared also to the theoretical knowledge about the subject. Results show that those customers’ machines which use the full service concept of ATA usually are able to save more time and material than the machines which use only some features of the product. Interviews indicated that sales arguments which focus on improved competitive status are not as effective as current arguments which focus on numerical improvements. In the case of potential customers in the new industry, current sales arguments likely work best for those whose irregular production situations are caused mainly by fault situations. When the actions of Vipetec were compared to ten key elements of creating customer references, it was seen that many of them the company has either already included in its strategy or has good chances to include them with the help of the results of this study.

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Background: The function of the autonomic nervous system (ANS) can be evaluated with heart rate variability (HRV). Decreased HRV is associated with aging, the male sex, increased heart rate, and overall increased cardiometabolic risk. It has been hypothesized that early atherosclerotic vascular changes and ANS function are related. Aims: The aims were to assess reference values on HRV in young adults, and examine associations with HRV and cardiometabolic risk factors and metabolic syndrome (MetS) and to study relations between HRV and ultrasonographically measured vascular properties. Participants and methods: The present thesis is part of the Cardiovascular Risk in Young Finns Study. The thesis is based on the follow-up study in 2001, when the study individuals were 24-39 years of age. HRV data were available on 1 956 individuals. Results: HRV was inversely associated with age and heart rate (for all p<0.001). Highfrequency HRV (HF) was higher, and low-frequency HRV (LF) lower in women than men (p<0.0001 for both). MetS was associated with 11% decreased HF and 12% increased LF/HF-ratio in women, and 8% decreased HF and 4% increased LF/HF-ratio in men. Carotid artery distensibility was independently associated with HF and total HRV (for both p<0.05). Conclusions: The reference values in young adults were generated. Decreased HRV was associated with age, the male sex and increased heart rate. Women had higher HF and lower LF variability than men. MetS was related to decrease in HRV. The observed associations between carotid elasticity and HRV, supports the hypothesis that reduction in carotid elasticity may lead to decrease in autonomic cardiac control.

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The influence of voltage on the conductance of toad skin was studied to identify the time course of the activation/deactivation dynamics of voltage-dependent Cl- channels located in the apical membrane of mitochondrion-rich cells in this tissue. Positive apical voltage induced an important conductance inhibition which took a few seconds to fully develop and was instantaneously released by pulse inversion to negative voltage, indicating a short-duration memory of the inhibiting factors. Sinusoidal stimulation at 23.4 mM [Cl-] showed hysteresis in the current versus voltage curves, even at very low frequency, suggesting that the rate of voltage application was also relevant for the inhibition/releasing effect to develop. We conclude that the voltage modulation of apical Cl- permeability is essentially a fast process and the apparent slow components of activation/deactivation obtained in the whole skin are a consequence of a gradual voltage build-up across the apical membrane due to voltage sharing between apical and basolateral membranes

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Reactive arthritis (ReA) is an inflammatory joint disease, which belongs to the group of Spondyloarthritis (SpA). It may occur after infections with certain gram-negative bacteria such as Salmonella and Yersinia. SpAs are strongly associated with the human leucocyte antigen (HLA)-B27. Despite active research, the mechanism by which HLA-B27 causes disease susceptibility is still unknown. However, HLA-B27 has a tendency to misfold during assembly. It is possible that the misfolding of HLA-B27 could alter signaling pathways and/or molecules involved in inflammatory response in cells. We have earlier discovered that in HLA-B27-positive cells the interaction between the host and causative bacteria is disturbed. Our recent studies indicate that the expression of HLA-B27 may alter certain signaling molecules by disturbing their activation. The aim of this study was to investigate whether the expression of HLA-B27 disturbs the signaling molecules, especially the phosphorylation of transcription factor STAT1. STAT1 is an important mediator of inflammatory responses. Our results show that the phosphorylation of the STAT1 is significantly altered in HLA-B27-expressing U937 monocytic cells compared with control cells. STAT1 tyrosine 701 is more strongly phosphorylated in HLAB27- expressing cells; whereas the phosphorylation of STAT1 serine 727 is prolonged. Phosphorylation of STAT1 was discovered to be dependent on protein kinase PKR. Furthermore, we found out that the expression of posttranscriptional gene regulator HuR was altered in HLA-B27-expressing cells. We also detected that HLA-B27-positive cells secrete more interleukin 6, which is an important mediator of inflammation. These results help to understand how HLA-B27 may confer susceptibility to SpAs.

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Static lung volume (LV) measurements have a number of clinical and research applications; however, no previous studies have provided reference values for such tests using a healthy sample of the adult Brazilian population. With this as our main purpose, we prospectively evaluated 100 non-smoking subjects (50 males and 50 females), 20 to 80 years old, randomly selected from more than 8,000 individuals. Gender-specific linear prediction equations were developed by multiple regression analysis with total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), RV/TLC ratio and inspiratory capacity (IC) as dependent variables, and with age, height, weight, lean body mass and indexes of physical fitness as independent ones. Simpler demographic and anthropometric variables were as useful as more complex measurements in predicting LV values, independent of gender and age (R2 values ranging from 0.49 to 0.78, P<0.001). Interestingly, prediction equations from North American and European studies overestimated the LV at low volumes and underestimated them at high volumes (P<0.05). Our results, therefore, provide a more appropriate frame of reference to evaluate the normalcy of static lung volume values in Brazilian males and females aged 20 to 80 years.

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The strength of the respiratory muscles can be evaluated from static measurements (maximal inspiratory and expiratory pressures, MIP and MEP) or inferred from dynamic maneuvers (maximal voluntary ventilation, MVV). Although these data could be suitable for a number of clinical and research applications, no previous studies have provided reference values for such tests using a healthy, randomly selected sample of the adult Brazilian population. With this main purpose, we prospectively evaluated 100 non-smoking subjects (50 males and 50 females), 20 to 80 years old, selected from more than 8,000 individuals. Gender-specific linear prediction equations for MIP, MEP and MVV were developed by multiple regression analysis: age and, secondarily, anthropometric measurements explained up to 56% of the variability of the dependent variables. The most cited previous studies using either Caucasian or non-Caucasian samples systematically underestimated the observed values of MIP (P<0.05). Interestingly, the self-reported level of regular physical activity and maximum aerobic power correlates strongly with both respiratory and peripheral muscular strength (knee extensor peak torque) (P<0.01). Our results, therefore, provide a new frame of reference to evaluate the normalcy of some useful indexes of respiratory muscle strength in Brazilian males and females aged 20 to 80.

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Carbon monoxide diffusing capacity (DLCO) or transfer factor (TLCO) is a particularly useful test of the appropriateness of gas exchange across the lung alveolocapillary membrane. With the purpose of establishing predictive equations for DLCO using a non-smoking sample of the adult Brazilian population, we prospectively evaluated 100 subjects (50 males and 50 females aged 20 to 80 years), randomly selected from more than 8,000 individuals. Gender-specific linear prediction equations were developed by multiple regression analysis with single breath (SB) absolute and volume-corrected (VA) DLCO values as dependent variables. In the prediction equations, age (years) and height (cm) had opposite effects on DLCOSB (ml min-1 mmHg-1), independent of gender (-0.13 (age) + 0.32 (height) - 13.07 in males and -0.075 (age) + 0.18 (height) + 0.20 in females). On the other hand, height had a positive effect on DLCOSB but a negative one on DLCOSB/VA (P<0.01). We found that the predictive values from the most cited studies using predominantly Caucasian samples were significantly different from the actually measured values (P<0.05). Furthermore, oxygen uptake at maximal exercise (VO2max) correlated highly to DLCOSB (R = 0.71, P<0.001); this variable, however, did not maintain an independent role to explain the VO2max variability in the multiple regression analysis (P>0.05). Our results therefore provide an original frame of reference for either DLCOSB or DLCOSB/VA in Brazilian males and females aged 20 to 80 years, obtained from the standardized single-breath technique.

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Recent technological developments have created new devices that could improve and simplify the construction of stimulus isolators. HEXFET transistors can switch large currents and hundreds of volts in nanoseconds. The newer opto-isolators can give a pulse rise time of a few nanoseconds, with output compatible with MOSFET devices, in which delays are reduced to nanoseconds. Integrated DC/DC converters are now available. Using these new resources we developed a new electrical stimulus isolator circuit with selectable constant-current and constant-voltage modes, which are precise and easy to construct. The circuit works like a regulated power supply in both modes with output switched to zero or to free mode through an opto-isolator device. The isolator analyses showed good practical performance. The output to ground resistance was 1011 ohms and capacitance 35 picofarads. The rise time and fall time were identical (5 µs) and constant. The selectable voltage or current output mode made it very convenient to use. The current mode, with higher output resistance values in low current ranges, permits intracellular stimulation even with tip resistances close to 100 megaohms. The high compliance of 200 V guarantees the value of the current stimulus. The very low output resistance in the voltage mode made the device highly suitable for extracellular stimulation with low impedance electrodes. Most importantly, these characteristics were achieved with a circuit that was easy to build and modify and assembled with components available in Brazil.

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Breast cancer is a highly heterogenous malignancy, which despite of the similar histological type shows different clinical behaviour and response to therapy. Prognostic factors are used to estimate the risk for recurrence and the likelihood of treatment effectiveness. Because breast cancer is one of the most common causes of cancer death in women worldwide, identification of new prognostic markers are needed to develop more specific and targeted therapies. Cancer is caused by uncontrolled cell proliferation. The cell cycle is controlled by specific proteins, which are known as cyclins. They function at important checkpoints by activating cyclin-dependent kinase enzymes. Overexpression of different cyclins has been linked to several cancer types and altered expression of cyclins A, B1, D1 and E has been associated with poor survival. Little is known about the combined expression of cyclins in relation to the tumour grade, breast cancer subtype and other known prognostic factors. In this study cyclins A, B1 and E were shown to correlate with histological grade, Ki-67 and HER2 expression. Overexpression of cyclin D1 correlated with receptor status and non-basal breast cancer suggesting that cyclin D1 might be a marker of good prognosis. Proteolysis in the surrounding tumour stroma is increased during cancer development. Matrix metalloproteinases (MMPs) are proteolytic enzymes that are capable of degrading extracellular matrix proteins. Increased expression and activation of several MMPs have been found in many cancers and MMPs appear to be important regulators of invasion and metastasis. In this study MMP-1 expression was analysed in breast cancer epithelial cells and in cancer associated stromal cells. MMP-1 expression by breast cancer epithelial cells was found to carry an independent prognostic value as did Ki-67 and bcl-2. The results suggest that in addition to stromal cells MMP-1 expression in tumour cells control breast cancer progression. Decorin is a small proteoglycan and an important component of the extracellular matrix. Decorin has been shown to inhibit growth of tumour cells and reduced decorin expression is associated with a poor prognosis in several cancer types. There has been some suspicion wheather different cancer cells express decorin. In this study decorin expression was shown to localize only in the cells of the original stroma, while breast cancer epithelial cells were negative for decorin expression. However, transduction of decorin in decorin-negative human breast cancer cells markedly modulated the growth pattern of these cells. This study provides evidence that targeted decorin transduction to breast cancer cells could be used as a novel adjuvant therapy in breast malignancies.

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The effect of the skin secretion of the amphibian Siphonops paulensis was investigated by monitoring the changes in conductance of an artificial planar lipid bilayer. Skin secretion was obtained by exposure of the animals to ether-saturated air, and then rinsing the animals with distilled water. Artificial lipid bilayers were obtained by spreading a solution of azolectin over an aperture of a Delrin cup inserted into a cut-away polyvinyl chloride block. In 9 of 12 experiments, the addition of the skin secretion to lipid bilayers displayed voltage-dependent channels with average unitary conductance of 258 ± 41.67 pS, rather than nonspecific changes in bilayer conductance. These channels were not sensitive to 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid or tetraethylammonium ion, but the experimental protocol used does not permit us to specify their characteristics.

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Non-metallic implants made of bioresorbable or biostable synthetic polymers are attractive options in many surgical procedures, ranging from bioresorbable suture anchors of arthroscopic surgery to reconstructive skull implants made of biostable fiber-reinforced composites. Among other benefits, non-metallic implants produce less interference in imaging. Bioresorbable polymer implants may be true multifunctional, serving as osteoconductive scaffolds and as matrices for simultaneous delivery of bone enhancement agents. As a major advantage for loading conditions, mechanical properties of biostable fiber-reinforced composites can be matched with those of the bone. Unsolved problems of these biomaterials are related to the risk of staphylococcal biofilm infections and to the low osteoconductivity of contemporary bioresorbable composite implants. This thesis was focused on the research and development of a multifunctional implant model with enhanced osteoconductivity and low susceptibility to infection. In addition, the experimental models for assessment, diagnostics and prophylaxis of biomaterial-related infections were established. The first experiment (Study I) established an in vitro method for simultaneous evaluation of calcium phosphate and biofilm formation on bisphenol-Aglycidyldimethacrylate and triethylenglycoldimethacrylate (BisGMA-TEGDMA) thermosets with different content of bioactive glass 45S5. The second experiment (Study II) showed no significant difference in osteointegration of nanostructured and microsized polylactide-co-glycolide/β-tricalcium phosphate (PLGA /β-TCP) composites in a minipig model. The third experiment (Study III) demonstrated that positron emission tomography (PET) imaging with the novel 68Ga labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) CD33 related sialic-acid immunoglobulin like lectins (Siglec-9) tracer was able to detect inflammatory response to S. epidermidis and S. aureus peri-implant infections in an intraosseous polytetrafluoroethylene catheter model. In the fourth experiment (Study IV), BisGMATEGDMA thermosets coated with lactose-modified chitosan (Chitlac) and silver nanoparticles exhibited antibacterial activity against S. aureus and P. aeruginosa strains in an in vitro biofilm model and showed in vivo biocompatibility in a minipig model. In the last experiment (Study V), a selective androgen modulator (SARM) released from a poly(lactide)-co-ε-caprolactone (PLCL) polymer matrix failed to produce a dose-dependent enhancement of peri-implant osteogenesis in a bone marrow ablation model.

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Mycobacterium avium is an important pathogen among immunodeficient patients, especially patients with AIDS. The natural history of this disease is unclear. Several environmental sources have been implicated as the origin of this infection. Polyclonal infection with this species is observed, challenging the understanding of its pathogenesis and treatment. In the present study 45 M. avium strains were recovered from 39 patients admitted to a reference hospital between 1996 and 1998. Species identification was performed using a species-specific nucleic acid hybridization test (AccuProbe®) from Gen-Probe®. Strains were genotyped using IS1245 restriction fragment length polymorphism typing. Blood was the main source of the organism. In one patient with disseminated disease, M. avium could be recovered more than once from potentially sterile sites. Strains isolated from this patient had different genotypes, indicating that the infection was polyclonal. Four patient clones were characterized in this population, the largest clone being detected in eight patients. This finding points to a common-source transmission of the organism.

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A recent study from our laboratory has provided evidence for the generation of slow potentials occurring in anticipation to task-performance feedback stimuli, in multiple association cortical areas, consistently including two prefrontal areas. In the present study, we intended to determine whether these slow potentials would indicate some abnormality (topographic) in schizophrenic patients, and thus serve as an indication of abnormal association cortex activity. We recorded slow potentials while subjects performed a paired-associates memory task. A 123-channel EEG montage and common average reference were used for 20 unmedicated schizophrenic (mean duration of illness: 11.3 ± 9.2 years; mean number of previous hospitalizations: 1.2 ± 1.9) and 22 healthy control subjects during a visual paired-associates matching task. For the topographic analysis, we used a simple index of individual topographic deviation from normality, corrected for absolute potential intensities. Slow potentials were observed in all subjects. Control subjects showed a simple spatial pattern of voltage extrema (left central positive and right prefrontal negative), whereas schizophrenic patients presented a more complex, fragmented pattern. Topographic deviation was significantly different between groups (P < 0.001). The increased topographic complexity in schizophrenics could be visualized in grand averages computed across subjects. Increased topographic complexity could also be seen when grand averages were computed for subgroups of patients assembled either according to task-performance (high versus low) or by their scores on psychopathological scales. There was no significant correlation between topographic deviation and psychopathology scores. We conclude that the slow potential topographic abnormalities of schizophrenia indicate an abnormality in the configuration of large-scale electrical activity in association cortices.