Acoustic spectrometer: Resonant sensing platform for measuring volumetric properties of liquid samples

A sensing platform for measuring volumetric properties of liquid samples using phononic crystals is presented in this paper. The proposed sensor concept is based on the transmission of elastic and acoustic waves through solids and liquids respectively to gather relevant information about the properties of the liquid under test. A major difference between this concept and the majority of current resonant sensors, like the well-known quartz crystal microbalance, is that the acoustic spectrometer proposed measures bulk properties and not interfacial properties of the liquid. The sensing platform uses a disposable analyte container to facilitate the measurement of hazardous substances and enable its use in biomedical applications. An electronic characterization system based on the acquisition of three mixed signals was developed to obtain the frequency response of the designed sensor. Finally, experimental and theoretical realizations were performed, using different analytes and showing characteristic transmission features that can be used as measures to determine the physical value speed of sound

Liquefaction Evaluations at the Savannah River Site. A Case History

Over the past decade, liquefaction assessments have been performed for many existing and planned critical facilities at the Department of Energy’s Savannah River Site (SRS). The assessments incorporated site-specific Cyclic Resistance Ratio (CRR) and Ks with the use of the cone penetration test (CPT). The SRS-specific CRR and Ks were developed from laboratory testing of carefully collected samples. Test results show SRS soils have increased liquefaction resistance of two to three times when compared to standard literature for Holocene-age deposits. This increase in strength can be attributed to many factors such as aging and overconsolidation. The purpose of this paper is to discuss liquefaction methodologies used at the SRS. Specifically, 1) use of the CPT and correlations of CPT-derived results with that of high-quality undisturbed samples; 2) aging; and 3) Ks vertical confining stress factor

Fully-disposable multilayered phononic crystal liquid sensor with symmetry reduction and a resonant cavity

Phononic crystals are artificial structures with unique capabilities to control the transmission of acoustic waves. These novel periodic composite structures bring new possibilities for developing a fundamentally new sensor principle that combines features of both ultrasonic and resonant sensors. This paper reports the design, fabrication and evaluation of a phononic crystal sensor for biomedical applications, especially for its implementation in point of care testing technologies. The key feature of the sensor system is a fully-disposable multi-layered phononic crystal liquid sensor element with symmetry reduction and a resonant cavity. The phononic crystal structure consists of eleven layers with high acoustic impedance mismatch. A defect mode was utilized in order to generate a well-defined transmission peak inside the bandgap that can be used as a measure. The design of the structures has been optimized with simulations using a transmission line model. Experimental realizations were performed to evaluate the frequency response of the designed sensor using different liquid analytes. The frequency of the characteristic transmission peaks showed to be dependent on the properties of the analytes used in the experiments. Multi-layered phononic crystal sensors can be used in applications, like point of care testing, where the on-line measurement of small liquid samples is required

Cavity Resonance Sensor with Disposable Analyte Container for Point of Care Testing

The use of phononic crystals and resonant structures as sensing platforms paves the way to the development of new biomedical technologies. An acoustic sensor with a resonant cavity and a disposable element was investigated in this paper. The sensor consists of seven layers with high acoustic impedance mismatch. The disposable element used was a glass spectrophotometry cuvette and, during the experimentation, it was filled with different liquid analytes showing characteristic transmission features that could be used as measures to differentiate and identify them. Experimental transmission curves were obtained using an electronic characterization system that uses a double sideband modulation technique to acquire valuable information about the structure being analyzed. Simulations using the 1-D transmission line method were performed to support the experimental realizations. The frequency of maximum transmission has been found to be strongly dependent on the speed of sound of the analyte under test

High temperature ferromagnetism of Li-doped vanadium oxide nanotubes

The nature of a puzzling high temperature ferromagnetism of doped mixed-valent vanadium oxide nanotubes reported earlier by Krusin-Elbaum et al., Nature 431 (2004) 672, has been addressed by static magnetization, muon spin relaxation, nuclear magnetic and electron spin resonance spectroscopy techniques. A precise control of the charge doping was achieved by electrochemical Li intercalation. We find that it provides excess electrons, thereby increasing the number of interacting magnetic vanadium sites, and, at a certain doping level, yields a ferromagnetic-like response persisting up to room temperature. Thus we confirm the surprising previous results on the samples prepared by a completely different intercalation method. Moreover our spectroscopic data provide first ample evidence for the bulk nature of the effect. In particular, they enable a conclusion that the Li nucleates superparamagnetic nanosize spin clusters around the intercalation site which are responsible for the unusual high temperature ferromagnetism of vanadium oxide nanotubes.Comment: with some amendments published in Europhysics Letters (EPL) 88 (2009) 57002; http://epljournal.edpsciences.or

Liquefaction Resistance of Gravelly Soils

Liquefaction assessments of gravels and soils that contain a large gravel fraction are difficult. Undisturbed (intact) sampling of these soils is problematic and laboratory testing carried out on reconstituted samples or on frozen samples obtained from the field is time consuming, expensive, and interpretation of the results requires considerable judgment. Because of these and other issues, for a remote site in British Columbia, Canada (aka “Study Site”), it was decided to carry out the liquefaction potential assessment using existing published relationships and case history data on similar soils. This case history describes the approach utilized, including material mechanical properties, measured shear wave velocities and insitu density data obtained from shallow test pits excavated across the study site. Comparisons to published data on similar soils are discussed. To assess the liquefaction potential of the gravels, normalized shear wave velocity data were related to void ratio. The void ratio was then related to the CRR using published relationships on a similar gravelly soil tested in the laboratory. The liquefaction potential was assessed in the conventional manner comparing the cyclic resistance ratio (after appropriate consideration of correction factors used in laboratory cyclic testing) to the seismic demand (CSR). The approach described in the case history generalizes the methodology for application to other gravel deposits at other sites

Use of Transient Time Response as a Measure to Characterize Phononic Crystal Sensors

Phononic crystals are periodic composite structures with specific resonant features that are gaining popularity in the field as liquid sensors. The introduction of a structural defect in an otherwise periodic regular arrangement can generate a resonant mode, also called defect mode, inside the characteristic band gaps of phononic crystals. The morphology, as well as the frequency in which these defect modes appear, can give useful information on the composition and properties of an analyte. Currently, only gain and frequency measurements are performed using phononic crystal sensors. Other measurements like the transient response have been implemented in resonant sensors such as quartz microbalances showing great results and proving to be a great complimentary measure to the gain and frequency measurements. In the present paper, a study of the feasibility of using the transient response as a measure to acquire additional information about the analyte is presented. Theoretical studies using the transmission line model were realized to show the impact of variations in the concentration of an analyte, in this case, lithium carbonate solutions, in the transient time of the system. Experimental realizations were also performed showing that the proposed measurement scheme presents significant changes in the resulting data, indicating the potential use of this measure in phononic crystal sensors. This proposed measure could be implemented as a stand-alone measure or as a compliment to current sensing modalities

Metacognition as Evidence for Evidentialism

Metacognition is the monitoring and controlling of cognitive processes. I examine the role of metacognition in ‘ordinary retrieval cases’, cases in which it is intuitive that via recollection the subject has a justified belief. Drawing on psychological research on metacognition, I argue that evidentialism has a unique, accurate prediction in each ordinary retrieval case: the subject has evidence for the proposition she justifiedly believes. But, I argue, process reliabilism has no unique, accurate predictions in these cases. I conclude that ordinary retrieval cases better support evidentialism than process reliabilism. This conclusion challenges several common assumptions. One is that non-evidentialism alone allows for a naturalized epistemology, i.e., an epistemology that is fully in accordance with scientific research and methodology. Another is that process reliabilism fares much better than evidentialism in the epistemology of memory