18420 research outputs found
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Atmosphere Control by Chemoresistive Polymer Composites
No full textThis work reports about polymer-nanostructured carbon composite (PNCC) and it possible application for relative humidity registration and volatile organic compound (VOC) detection in the air. PNCC have been produced using high structured carbon black (HSCB) nanoparticles and polyisoprene (PI), ethylene-vinylacetate (EVA) copolymer, polyvinylacetate (PVAc), polyethylene glycol (PEG) and polyvinylalcohol (PVA). Matrix material for composite production has been selected with respect to desired analyte to bee tested. Composites show selective response to particular species of analytes vapour. It has been found that humidity sensing mechanism changes from proton conductivity to electron tunnelling by addition of HSCB to PVA matrix. Plasticizer effect on PVAc-NCC ethanol vapour sensitivity has been evaluated.
Methods of Acoustic Emission Diagnostics of Pre-Destruction State
No full textIn this paper discusses ways of measuring equipment and, in particular, to a method for monitoring and diagnosis based on the use acoustic emission (AE).
Offered by methods can be applied:
1.During cyclic fatigue test different constructions in order to assess their technical condition;
2.During test on the residual strength constructions, as well as in monitoring and diagnosis of technical condition of machines and heavy-duty construction for which the functioning is limited to the damage or unacceptable.
3.To estimate process of destruction of composite structures consisting of a matrix and unidirectional reinforcing elements (fibers
Thermal Performance Analysis of Solar Collectors Installed for Combisystem in the Apartment Building
No full textThe paper focuses on the application of wood pellet and solar combisystem for space heating and hot water preparation at apartment buildings under the climate of Northern Europe. The pilot project has been implemented in the city of Sigulda (N 57° 09.410 E 024° 52.194), Latvia. The system was designed and optimised using TRNSYS − a dynamic simulation tool. The pilot project was continuously monitored. To the analysis the heat transfer fluid flow rate and the influence of the inlet temperature on the performance of solar collectors were subjected. The thermal performance of a solar collector loop was studied using a direct method. A multiple regression analysis was carried out using STATGRAPHICS Centurion 16.1.15 with an aim to identify the operational and weather parameters of the system which cause the strongest influence on the collector’s performance. The parameters to be used for the system's optimization have been evaluated
Time-Dependent Cytokine Expression in Bone of Experimental Animals after Hydroxyapatite (HAp) Implantation
No full textProinflammatory cytokines mediate bone loss around the implants in patients with peri-implant disease. However, there is no complete data about the expression of cytokines into the bone around the implants. The aim of this work was to investigate the distribution and appearance of inflammatory cytokines and anti-inflammatory proteins in the bone of jaw of experimental rabbits in different time periods after HAp implantation. Material was obtained from 8 rabbits in lower jaw 6 and 8 months after HAp implants were placed. Tissues were processed for immunohistochemical detection of tumor necrosis factor alfa (TNFα), Interleukin 1, 6, 8, 10 (IL-1, IL-6, IL-8, IL-10) and defensin 2. Results demonstrated practically unchanged expression of IL-6 and IL-10 between both – experimental and control side 6 months after implantation, while IL-1 and IL-8 notably increased in control side. IL-1 and IL-10 expression did not change in either the experimental side nor the controle side after 8 months HAP implantation, but IL-6 and IL-8 demonstrated a decrease in the control sites. Only IL-8 was elevated with time in experimental sites, while IL-10 showed individual variations in 2 cases
Passive Wireless Sensor Network Analyzing at Medium Access Level
No full textA wireless packet sniffer focused on wireless sensor network analysis, using medium access control protocol packets, has been proposed. Proposed infrastructure and its parts are described . The main goal of this research is to develop simple network infrastructure and program for wireless sensor network analysis which is presented in the following chapters. In this research two main assumptions are made – first, network sniffing is used, which does not disturb network operation, and second, offline data analyzing is used, which means that the data is analyzed when all of it is collected and saved on a computer, but data still is analyzed in real time
Anthropogenic Influence on the Dynamics of the River Lamprey Lampetra fluviatilis Landings in the River Daugava Basin
No full textThe construction of the Daugava hydro power station (HPS) cascade has significantly transformed Latvia’s largest river the Daugava, reducing its importance in the natural reproduction of anadromous fish species. Currently in Latvia, as well as in other Baltic Sea countries, the river lamprey catch is decreasing, whereas the landings in the river Daugava have tended to increase. The dynamics of the river lamprey landings show the possible redistribution of lamprey stocks between the rivers Gauja and the Daugava. Possibly, this is a result of anthropogenic influence and changes in the river lamprey resource management may be necessary in the future
Reconstruction of Anthropogenic Impact Intensity Changes during Last 300 Years in Lake Engure Using Analysis of Sedimentary Records
No full textEnvironmental pollution with trace elements is considered as one of the most important environmental problems. Analysis of trace element accumulation in sedimentary phases of lakes may reflect the overall regional pollution level, but analysis of trace element accumulation patterns in sediment profiles can help to reconstruct the history of anthropogenic impacts. The aim of this study was to analyse trace element concentrations in the sediments of Lake Engure in Latvia and analyze factors influencing their availability. The metal concentrations in sediments of Lake Engure are at background levels, especially in comparison to metal concentrations in West European countries. However, analysis of element concentration changes in sedimentary profiles gives information about trends of recent accumulation (within the last 300 years) and the balance between natural and human induced accumulation processes
Sacred Forests and Trees in Latvia and in the Latvian Mind
No full textWhat influence has the common natural environment had for the different cultures in the Baltics? How have the connections between nation and nature been understood, and can we speak about "transnational environments"? In the present volume different descriptive, philosophical, theoretical and methodological approaches towards Umwelt and landscape in the Baltics and beyond are employed and combined under the umbrella of the newly emerging field of environmental humanities. The book thus aims to bring different discourses on nature and culture into discussion. It wants to reflect on the uniting and separating moments in the history and literature of the Baltics, to combine Baltic studies with global concerns, and to trigger further national and international cooperation in humanities on the Baltic environmental history. Authors of this collections are from Estonia (Jaan Undusk, Liina Lukas, Kadri Tüür, Ulrike Plath et al.), Germany (Gert von Pistohlkors, Christa Grewe-Volpp et al.), Latvia (Kaspars Klavinš), and Lithuania (Audronė Raškauskienė, Irena Ragaišienė)