Forced vibrations of a finite length metabeam with periodically arranged internal hinges and external supports

The paper investigates a problem of forced vibrations of two finite length metabeams: one is with periodically arranged internal hinges and the second one with periodically arranged internal hinges and external supports. Based on the Euler–Bernoulli beam theory and the transfer matrix method, general solutions of the periodic beams are obtained. Applying the Bloch-Floquet theory, the explicit expressions are derived defining the metabeams band gap structures. The corresponding band gap dispersion curves are plotted and analysed. It is shown that when the frequency of forced vibrations coincides with the band gap frequencies a strong localization of flexible waves occurs at the interfaces of the periodic beams. The localization of flexible waves increases significantly with the number of hinges and supports

On the Sensing, Actuating and Energy Harvesting Properties of a Composite Plate with Piezoelectric Patches

The paper investigates how the energy input/output of a composite plate with piezoelectric patches, acting as a sensor, actuator, or energy harvester, can be regulated by changing the parameters of the piezoelectric patches, the external vibrating frequency and the boundary conditions imposed on the host plate-layer. It is shown that for any size of the piezoelectric patches there is always one location where the energy input/output reaches a maximum, whether the process is very low frequency or higher frequency. Furthermore, for a dynamic vibrational loading the energy input/output is highly sensitive whether the operating frequency is below or above the system’s resonance frequency. For the operating frequency close to but below the resonance frequency, the location for the maximum energy input/output is considerably different from the optimal location when the operating frequency is just above the systems resonance frequency. That is to say, a slight change in the operating frequency around the resonance frequency can make a considerable difference to the optimal locations for the piezoelectric patches for maximum energy input/output

Palaeoecological study of South Milton Ley, South Devon

1. Attend South Milton Ley and obtain 6 sediment cores from 3 different areas of the ley to investigate the impact of discharges from the sewage treatment works (STW). 2. From each of the 3 locations, extrude one master core at appropriate intervals and describe its stratigraphy. 3. From each of the 3 locations, measure the dry weight and organic matter content of selected levels of the master core. 4. Date the master core from each of the 3 locations to provide a chronology of the ley sediments using radiometric dating methods and/or spheroidal carbonaceous particles (SCPs). 5. Analyse the diatom assemblages in five to ten samples from selected depths of each master core. 6. Apply a diatom-phosphorus transfer function to the diatom assemblages of each master core to reconstruct total phosphorus concentrations and in turn determine the nutrient loading history of the ley. 7. Produce a summary report of the findings

Heavy metal pollution and co-selection for antibiotic resistance: A microbial palaeontology approach

This is the final version. Available on open access from Elsevier via the DOI in this recordFrequent and persistent heavy metal pollution has profound effects on the composition and activity of microbial communities. Heavy metals select for metal resistance but can also co-select for resistance to antibiotics, which is a global health concern. We here document metal concentration, metal resistance and antibiotic resistance along a sediment archive from a pond in the North West of the United Kingdom covering over a century of anthropogenic pollution. We specifically focus on zinc, as it is a ubiquitous and toxic metal contaminant known to co-select for antibiotic resistance, to assess the impact of temporal variation in heavy metal pollution on microbial community diversity and to quantify the selection effects of differential heavy metal exposure on antibiotic resistance. Zinc concentration and bioavailability was found to vary over the core, likely reflecting increased industrialisation around the middle of the 20th century. Zinc concentration had a significant effect on bacterial community composition, as revealed by a positive correlation between the level of zinc tolerance in culturable bacteria and zinc concentration. The proportion of zinc resistant isolates was also positively correlated with resistance to three clinically relevant antibiotics (oxacillin, cefotaxime and trimethoprim). The abundance of the class 1 integron-integrase gene, intI1, marker for anthropogenic pollutants correlated with the prevalence of zinc- and cefotaxime resistance but not with oxacillin and trimethoprim resistance. Our microbial palaeontology approach reveals that metal-contaminated sediments from depths that pre-date the use of antibiotics were enriched in antibiotic resistant bacteria, demonstrating the pervasive effects of metal-antibiotic co-selection in the environment.University of Exete

Организация деятельности педагога по совершенствованию умений диалогической речи у детей старшего дошкольного возраста.

В работе рассмотрены основы психического и речевого развития детей старшего дошкольного возраста, охарактеризованы лингво-методические основы развития диалогической речи у старшего дошкольного возраста, раскрыто содержание деятельности педагога по совершенствованию умений диалогической речи у детей старшего дошкольного возраста, разработан комплекс педагогических мероприятий по теме исследования

Use of sedimentary algal pigment analyses to infer past lake-water total phosphorus concentrations

AbstractWe tested the feasibility of using sedimentary algal pigment analyses by spectral deconvolution to infer past lake-water total phosphorus concentrations. We established equations that link lake-water nutrient concentrations and sediment pigment concentrations, using a combination of calibration in both space and time, with a training set of 31 Swedish lakes. The calibration dataset yielded a significant positive relationship between total carotenoid concentrations and lake-water total phosphorus concentrations. We also compared sediment-pigment-based nutrient inferences with time series of water column monitoring data to evaluate whether temporal changes in total phosphorus concentrations are well captured by analysis of sedimentary pigments. We found that changes in pigment preservation through time can alter the relationship between concentrations of lake-water nutrients and sedimentary pigments, thus limiting the reliability of historical ecological conditions inferred from pigments in the sediment. Our data suggested that ratios of Chlorophyll derivatives to total carotenoids (CD/TC ratio) and Chlorophyll a to Chlorophyll derivatives (CPI) can be used as proxies for pigment preservation. Using our approach, inferred temporal changes in water-column total phosphorus concentrations in lakes are promising, but require further development, specifically with respect to the influence of pigment degradation in both the water column and sediments, as well as the factors that control such degradation.</jats:p

Effects of climate change and industrialization on Lake Bolshoe Toko, eastern Siberia

AbstractIndustrialization in the Northern Hemisphere has led to warming and pollution of natural ecosystems. We used paleolimnological methods to explore whether recent climate change and/or pollution had affected a very remote lake ecosystem, i.e. one without nearby direct human influence. We compared sediment samples that date from before and after the onset of industrialization in the mid-nineteenth century, from four short cores taken at water depths between 12.1 and 68.3 m in Lake Bolshoe Toko, eastern Siberia. We analyzed diatom assemblage changes, including diversity estimates, in all four cores and geochemical changes (mercury, nitrogen, organic carbon) from one core taken at an intermediate water depth. Chronologies for two cores were established using 210Pb and 137Cs. Sedimentation rates were 0.018 and 0.033 cm year−1 at the shallow- and deep-water sites, respectively. We discovered an increase in light planktonic diatoms (Cyclotella) and a decrease in heavily silicified euplanktonic Aulacoseira through time at deep-water sites, related to more recent warmer air temperatures and shorter periods of lake-ice cover, which led to pronounced thermal stratification. Diatom beta diversity in shallow-water communities changed significantly because of the development of new habitats associated with macrophyte growth. Mercury concentrations increased by a factor of 1.6 since the mid-nineteenth century as a result of atmospheric fallout. Recent increases in the chrysophyte Mallomonas in all cores suggested an acidification trend. We conclude that even remote boreal lakes are susceptible to the effects of climate change and human-induced pollution.</jats:p

The effect of the location of piezoelectric patches on the sensing, actuating and energy harvesting properties of a composite plate

The paper investigates the effect of the location and size of piezoelectric patches in a composite multilayer plate on the energy input/output when the plate acts as a sensor, actuator, or an energy harvester. It is shown that whether the process is low frequency (static) or higher frequency, for any size of the piezoelectric patches there is always one location where the energy input/output reaches a maximum. In addition, it is shown that for a dynamic vibrational loading the energy input/output is extremely sensitive to the operating frequency. If the operating frequency is just below the systems resonant frequency (corresponding to the length and position of the patches) the best location for the maximum energy input/output is significantly different from the best location when the operating frequency is just above the systems resonant frequency. In other words, a very small change in the systems operating frequency in the vicinity of the resonance frequency can make a significant effect on the best locations for the patches for the energy input/output