The development of a passive, wireless sensor system

This thesis describes the development of a prototype passive, wireless sensor system based on magnetoelastic sensor technology. The application of the sensor system is aimed at the measurement of humidity levels in sealed containers and structures, in particular the detection of moisture ingress in building structures. The system uses magnetoelastic sensor elements as is commonly used in commercial electronic article surveillance (EAS) systems for the prevention of shoplifting. Magnetoelastic Metglas® 2826MB material is evaluated and it is shown that the application of a magnetic bias field of the appropriate magnitude is critical for optimum sensor performance. The sensors can be activated for the detection of water vapour by the application of an appropriate chemical interface layer. A polyvinyl alcohol (PVA) layer was found to produce a resonant frequency response of approximately 50 Hz/RH(%). The design and construction of a portable electronic sensor reader is described and it is shown that the reader can successfully interrogate the sensor inside sealed spaces at practical distances. The construction of a practical humidity sensor using a PVA coating and the humidity response of the sensor system is then calibrated using a commercial humidity sensor. The system showed good response over the 0-100 % relative humidity range, with some non-linearity observed at high humidity levels. The completed sensor system was then evaluated for practical applications including measurements inside a sealed food container as well as inside a wall cavity. The results indicated that the constructed system was capable of measuring humidity with reasonable accuracy in such applications

Disorder-Enhanced Dimensionless Thermoelectric Figure of Merit zT of Non-stoichiometric Organic Conductor (TTT)2I3+δ (δ ≤ 0.1)

Sample dependence of dimensionless thermoelectric figure of merit (zT) and power factor (PF) were determined for the non-stoichiometric organic conductor (TTT)2I3+δ (TTT = tetrathiatetracene, δ ≤ 0.1) with the simultaneous measurement of the electrical resistivity (ρ), thermopower (S) and thermal conductivity on small single crystals. Both the zT and PF show large sample dependence between 10 and 310 K, even though all the samples have nearly stoichiometric composition of TTT : I3- ~ 2 : 1 (δ ∼ 0). It was found that both the electrical conductivity (σ = 1/ρ) and S increase at room temperature as disorder — that is phase mismatch among the iodine chains — becomes more pronounced. This behavior contrasts the usual tendency that the S decreases as the σ increases in conventional conductors; and suggests a new strategy to improve the zT and PF by introducing an appropriate type of disorder

Detailed insights into pan-European population structure and inbreeding in wild and hatchery Pacific oysters (Crassostrea gigas) revealed by genome-wide SNP data.

Cultivated bivalves are important not only because of their economic value, but also due to their impacts on natural ecosystems. The Pacific oyster (Crassostrea gigas) is the world's most heavily cultivated shellfish species and has been introduced to all continents except Antarctica for aquaculture. We therefore used a medium-density single nucleotide polymorphism (SNP) array to investigate the genetic structure of this species in Europe, where it was introduced during the 1960s and has since become a prolific invader of coastal ecosystems across the continent. We analyzed 21,499 polymorphic SNPs in 232 individuals from 23 localities spanning a latitudinal cline from Portugal to Norway and including the source populations of Japan and Canada. We confirmed the results of previous studies by finding clear support for a southern and a northern group, with the former being indistinguishable from the source populations indicating the absence of a pronounced founder effect. We furthermore conducted a large-scale comparison of oysters sampled from the wild and from hatcheries to reveal substantial genetic differences including significantly higher levels of inbreeding in some but not all of the sampled hatchery cohorts. These findings were confirmed by a smaller but representative SNP dataset generated using restriction site-associated DNA sequencing. We therefore conclude that genomic approaches can generate increasingly detailed insights into the genetics of wild and hatchery produced Pacific oysters

Controlling factors of large-scale harmful algal blooms with Karenia selliformis after record-breaking marine heatwaves

Unprecedented, large-scale harmful algal blooms (HABs) dominated by Karenia selliformis occurred off the southeastern coast of Hokkaido, Japan, from late September to early November 2021, about a month after intense and extensive marine heatwaves (MHWs) had subsided. The aims of the present study were to understand the mechanism of development, maintenance, and decay of the HABs as well as to investigate the effect of the MHWs on the HABs. We developed a one-dimensional, lower trophic-level ecosystem model (NEMURO+) to simulate the HABs. The model successfully simulated the 2021 HABs and indicated that their development, maintenance, and decay were controlled primarily by changes of water temperature. Nitrate supply from subsurface layers by seasonal vertical diffusion in autumn also helped to maintain the HABs. Vertical diffusion following MHWs in 2021 contributed to the long duration of the preferred temperature for K. selliformis and the occurrence of pre-bloom of K. selliformis, resulting in preconditioning and accelerating the HABs. However, simulations for normal years (i.e., the climatological mean during 2003–2018) showed that HABs could have occurred, even in the absence of MHWs. The simulations indicated that massive blooms of other phytoplankton species (e.g., diatoms) would not have occurred in 2021, even in the absence of a K. selliformis bloom. The implication was that the HABs in 2021 were the species-specific responses of K. selliformis. The proposed mechanism of the HABs was peculiar to our study area and differed from that previously reported for other K. selliformis blooms. Specifically, the preferred temperature for the HABs of K. selliformis was clearly lower than the previously reported preferred temperature of K. selliformis; thus, the physiological characteristics of the K. selliformis that bloomed in our study area differed from those of other K. selliformis strains. These discoveries provide the first evidence to explain how MHWs affect HABs, and to understand how inter-regional dissimilarities of K. selliformis can lead to large-scale, devastating outbreaks under different oceanographic conditions

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4

The development of a passive, wireless sensor system

This thesis describes the development of a prototype passive, wireless sensor system based on magnetoelastic sensor technology. The application of the sensor system is aimed at the measurement of humidity levels in sealed containers and structures, in particular the detection of moisture ingress in building structures. The system uses magnetoelastic sensor elements as is commonly used in commercial electronic article surveillance (EAS) systems for the prevention of shoplifting. Magnetoelastic Metglas® 2826MB material is evaluated and it is shown that the application of a magnetic bias field of the appropriate magnitude is critical for optimum sensor performance. The sensors can be activated for the detection of water vapour by the application of an appropriate chemical interface layer. A polyvinyl alcohol (PVA) layer was found to produce a resonant frequency response of approximately 50 Hz/RH(%). The design and construction of a portable electronic sensor reader is described and it is shown that the reader can successfully interrogate the sensor inside sealed spaces at practical distances. The construction of a practical humidity sensor using a PVA coating and the humidity response of the sensor system is then calibrated using a commercial humidity sensor. The system showed good response over the 0-100 % relative humidity range, with some non-linearity observed at high humidity levels. The completed sensor system was then evaluated for practical applications including measurements inside a sealed food container as well as inside a wall cavity. The results indicated that the constructed system was capable of measuring humidity with reasonable accuracy in such applications.</p

The development of a passive, wireless sensor system

This thesis describes the development of a prototype passive, wireless sensor system based on magnetoelastic sensor technology. The application of the sensor system is aimed at the measurement of humidity levels in sealed containers and structures, in particular the detection of moisture ingress in building structures. The system uses magnetoelastic sensor elements as is commonly used in commercial electronic article surveillance (EAS) systems for the prevention of shoplifting. Magnetoelastic Metglas® 2826MB material is evaluated and it is shown that the application of a magnetic bias field of the appropriate magnitude is critical for optimum sensor performance. The sensors can be activated for the detection of water vapour by the application of an appropriate chemical interface layer. A polyvinyl alcohol (PVA) layer was found to produce a resonant frequency response of approximately 50 Hz/RH(%). The design and construction of a portable electronic sensor reader is described and it is shown that the reader can successfully interrogate the sensor inside sealed spaces at practical distances. The construction of a practical humidity sensor using a PVA coating and the humidity response of the sensor system is then calibrated using a commercial humidity sensor. The system showed good response over the 0-100 % relative humidity range, with some non-linearity observed at high humidity levels. The completed sensor system was then evaluated for practical applications including measurements inside a sealed food container as well as inside a wall cavity. The results indicated that the constructed system was capable of measuring humidity with reasonable accuracy in such applications