High-Strength Organic-Inorganic Composites with Superior Thermal Insulation and Acoustic Attenuation.

We demonstrate facile fabrication of highly filled, lightweight organic-inorganic composites comprising polyurethanes covalently linked with naturally occurring clinoptilolite microparticles. These polyurethane/clinoptilolite (PUC) composites are shown to mitigate particle aggregation usually observed in composites with high particle loadings and possess enhanced thermal insulation and acoustic attenuation compared with conventionally employed materials (e.g., drywall and gypsum). In addition to these functional properties, the PUC composites also possess flexural strengths and strain capacities comparable to and higher than ordinary Portland cement (OPC), respectively, while being ∼1.5× lighter than OPC. The porosity, density, and mechanical and functional properties of these composites are tuned by systematically varying their composition (diisocyanate, polyurethane, and inorganic contents) and the nature of the organic (reactivity and source of polyol) components. The fabrication process involves mild curing conditions and uses commonly available reagents (naturally occurring aluminosilicate particles, polyols, and diisocyanate), thereby making the process scalable. Finally, the composite properties are shown to be independent of the polyol source (virgin or recycled), underlining the generality of this approach for the scalable utilization of recycled polyols.

Critical Examination of Distance-Gain-Size (DGS) Diagrams of Ultrasonic NDE with Sound Field Calculations.

Ultrasonic non-destructive evaluation, which has been used widely, can detect and size critical flaws in structures. Advances in sound field calculations can further improve its effectiveness. Two calculation methods were used to characterize the relevant sound fields of an ultrasonic transducer and the results were applied to construct and evaluate Distance-Gain-Size (DGS) diagrams, which are useful in flaw sizing. Two published DGS diagrams were found to be deficient because the backward diffraction path was overly simplified and the third one included an arbitrary procedure. Newly constructed DGS diagrams exhibited transducer size dependence, revealing another deficiency in the existing DGS diagrams. However, the extent of the present calculations must be expanded to provide a catalog of DGS diagrams to cover a wide range of practical needs. Details of the new construction method are presented, incorporating two-way diffraction procedures.

Transmission Sensitivities of Contact Ultrasonic Transducers and Their Applications.

In all ultrasonic material evaluation methods, transducers and sensors play a key role of mechanoelectrical conversion. Their transduction characteristics must be known quantitatively in designing and implementing successful structural health monitoring (SHM) systems. Yet, their calibration and verification have lagged behind most other aspects of SHM system development. This study aims to extend recent advances in quantifying the transmission and receiving sensitivities to normally incident longitudinal waves of ultrasonic transducers and acoustic emission sensors. This paper covers extending the range of detection to lower frequencies, expanding to areal and multiple sensing methods and examining transducer loading effects. Using the refined transmission characteristics, the receiving sensitivities of transducers and sensors were reexamined under the conditions representing their actual usage. Results confirm that the interfacial wave transmission is governed by wave propagation theory and that the receiving sensitivity of resonant acoustic emission sensors peaks at antiresonance.

Rayleigh Wave Calibration of Acoustic Emission Sensors and Ultrasonic Transducers.

Acoustic emission (AE) sensors and ultrasonic transducers were characterized for the detection of Rayleigh waves (RW). Small aperture reference sensors were characterized first using the fracture of glass capillary tubes in combination with a theoretical displacement calculation, which utilized finite element method (FEM) and was verified by laser interferometer. For the calibration of 18 commercial sensors and two piezoceramic disks, a 90° angle beam transducer was used to generate RW pulses on an aluminum transfer block. By a substitution method, RW receiving sensitivity of a sensor under test was determined over the range of frequency from 22 kHz to 2 MHz. Results were compared to the sensitivities to normally incident waves (NW) and to other guided waves (GW). It was found that (1) NW sensitivities are always higher than RW sensitivities, (2) differences between NW and RW receiving sensitivities are dependent on frequency and sensor size, (3) most sensors show comparable RW and GW receiving sensitivities, especially those of commonly used AE sensors, and (4) the receiving sensitivities of small aperture (1 mm diameter) sensors behave differently from larger sensors.

Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors.

Receiving displacement sensitivities (Rx) of ultrasonic transducers and acoustic emission (AE) sensors are evaluated using sinewave packet excitation method and compared to the corresponding data from pulse excitation method with a particular emphasis on low frequency behavior below 20 kHz, down to 10 Hz. Both methods rely on the determination of transmitter displacement characteristics using a laser interferometric method. Results obtained by two calibration methods are in good agreement, with average spectral differences below 1 dB, indicating that the two calibration methods yield identical receiving sensitivities. At low test frequencies, effects of attenuation increase substantially due to increasing sensor impedance and Rx requires correction in order to evaluate the inherent sensitivity of a sensor, or open-circuit sensitivity. This can differ by more than 20 dB from results that used common preamplifiers with ~10 kΩ input impedance, leading to apparent velocity response below 100 kHz for typical AE sensors. Damped broadband sensors and ultrasonic transducers exhibit inherent velocity response (Type 1) below their main resonance frequency. In sensors with under-damped resonance, a steep sensitivity decrease occurs showing frequency dependence of f²~f5 (Type 2), while mass-loaded sensors exhibit flat displacement response (Type 0). Such behaviors originate from sensor characteristics that can best be described by the damped harmonic oscillator model. This model accounts for the three typical behaviors. At low frequencies, typically below 1 kHz, receiving sensitivity exhibits another Type 0 behavior of frequency independent Rx. Seven of 12 sensors showed this flat region, while three more appear to approach the Type 0 region. This appears to originate from the quasi-static piezoelectric response of a sensing element. In using impulse method, a minimum pulse duration is necessary to obtain spectral fidelity at low frequencies and an approximate rule is given. Various factors for sensitivity improvement are also discussed.

On the Piezoelectric Detection of Guided Ultrasonic Waves.

In order to quantify the wave motion of guided ultrasonic waves, the characteristics of piezoelectric detectors, or ultrasonic transducers and acoustic emission sensors, have been evaluated systematically. Such guided waves are widely used in structural health monitoring and nondestructive evaluation, but methods of calibrating piezoelectric detectors have been inadequate. This study relied on laser interferometry for the base displacement measurement of bar waves, from which eight different guided wave test set-ups are developed with known wave motion using piezoelectric transmitters. Both plates and bars of 12.7 and 6.4 mm thickness were used as wave propagation media. The upper frequency limit was 2 MHz. Output of guided wave detectors were obtained on the test set-ups and their receiving sensitivities were characterized and averaged. While each sensitivity spectrum was noisy for a detector, the averaged spectrum showed a good convergence to a unique receiving sensitivity. Twelve detectors were evaluated and their sensitivity spectra determined in absolute units. Generally, these showed rapidly dropping sensitivity with increasing frequency due to waveform cancellation on their sensing areas. This effect contributed to vastly different sensitivities to guided wave and to normally incident wave for each one of the 12 detectors tested. Various other effects are discussed and recommendations on methods of implementing the approach developed are provided.

Calibration Methods of Acoustic Emission Sensors.

This study examined outstanding issues of sensitivity calibration methods for ultrasonic and acoustic emission transducers and provides workable solutions based on physically measureable quantities, laser-based displacement measurement in particular. This leads to mutually consistent determination of transmitting and receiving sensitivities of sensors and transducers. Methods of circumventing problems of extraneous vibrations on free transmitters are used, giving the foundation for face-to-face calibration methods. Working on many ultrasonic and acoustic emission transducers, their receiving and transmitting sensitivities are found to be always different, while their ratios exhibit unexpected similarity. This behavior is attributed to monopolar pulse generation and bipolar received signals due to electrical charge transfer during elastic wave motion and reflection on the back face. This is verified through a quantitative piezoelectric sensing experiment. Displacement vs. velocity calibration terminology is clarified, redefining the "V/µbar" reference for contact sensor calibration. With demonstrated differences in the transmitting and receiving sensitivities of transducers, the requirement of the Hill-Adams equation invalidates the basic premise of the currently formulated reciprocity calibration methods for acoustic emission transducers. In addition, the measured reciprocity parameter for the case of through-transmission significantly deviates from the approximate theoretical prediction. It is demonstrated that three methods provide reliable sensor calibration results that are complimentary among them.

Correction: Ono, K. Calibration Methods of Acoustic Emission Sensors. Materials 2016, 9, 508.

The author wishes to make the following corrections to this paper [1].[...].

ent-Kaurane-type diterpenoids from a cell suspension culture of the liverwort Jungermannia subulata.

A cell suspension culture of the liverwort Jungermannia subulata was established from callus tissue induced by culturing spores. From the suspension culture, three new ent-kaurane-type diterpenoids were isolated together with three previously reported ent-kaurane-type diterpenoids. Five ent-kaurane-type diterpenoids were isolated from the intact J. subulata, two of which were new compounds. Their structures were determined by spectroscopic methods, chemical reaction, and X-ray crystallographic analysis.

Stable genetic transformation of Larix gmelinii L. by particle bombardment of zygotic embryos.

We report a new protocol for the stable transformation of Larix gmelinii. Thirty mature zygotic embryos precultured for 3 days on solid medium supplemented with benzyladenine were bombarded with plasmids pUC-GHG (GUS, HPT, and GFP genes) or pBI221-HPT (HPT and GUS genes). After a 2-month culture on selection medium, hygromycin-resistant calli appeared on the surfaces of the necrotic embryos. The frequencies of embryos with resistant calli were 18.4% and 17.4% in the transformations with pUC-GHG and pBI221-HPT DNA, respectively. More than 20 adventitious shoots formed from each of the transgenic calli. Of 17 elongated shoots selected for culturing on a rooting medium, five shoots rooted after 2 months. Expression of the GFP and GUS genes was detected in the resistant tissues by microscopic observations and by a histological GUS activity assay, respectively. PCR and Southern analysis confirmed the stable insertion of the introduced DNA into the genome.

Efficient plant regeneration from suspension cells of Allium cepa L.

Plant regeneration from calli of three cultivars of Allium cepa (Senshuki, O.Pki and Shojovaka) was investigated. Callus was induced on four variations of BDS medium containing different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzyladenine (BAP). The regeneration frequency of calli of cvs. Senshuki and O.Pki subcultured on solid MS medium supplemented with BAP ranged from 50% to 80%; this frequency decreased to less than 30% after subculture in the dark in liquid BDS medium. By repeating the dark/light transitions of the culture protocol and by selecting for green cell clusters, we were able to increase the regeneration frequency to more than 80% in all three cultivars. These cell clusters maintained a high regeneration capacity in subsequent subcultures in the absence of light for 2 months. Most (97%) of the regenerated plantlets had a normal diploid karyotype (2 n=16) that was identical to that of the mother plants, although 3% of the regenerated plants of cv. Shojovaka had a tetraploid karyotype.

Copper deficiency induced expression of Fe-superoxide dismutase gene in Matteuccia struthiopteris.

Iron-superoxide dismutase (Fe-SOD) activity was not detected in extracts from the leaves of ferns, Equisetum arvense and Matteuccia struthiopteris. To know why ferns lack Fe-SOD activity, the Fe-SOD like gene (MsFeSOD1) was isolated from M. struthiopteris and its expression was investigated with a focus on the metals Fe and Cu using the prothalli of the fern. The expression of MsFeSOD1 mRNA was induced by a deficiency of Cu, but Fe-SOD activity was not detected. The recombinant protein of MsFeSOD1 produced in E. coli showed Fe-SOD activity. These findings suggest that the fern Fe-SOD like gene was transcriptionally regulated by Cu but an additional mechanism is involved in the formation of an active enzyme.

Chalcone synthase-like gene in the liverwort, Marchantia paleacea var. diptera.

A chalcone synthase (CHS)-like gene, MpCHSLK1, was isolated from liverwort, Marchantia paleacea var. diptera. Phylogenetic analysis revealed that MpCHSLK1 is closely related to stilbene synthase of the whisk fern, Psilotum nudum. Southern blot analysis using an MpCHSLK1 probe revealed that the gene belongs to a small gene family. Northern blot analysis indicated that CHS-like genes were expressed in either the mother plants or photoautotrophic cells. In photoautotrophic cells, the CHS-like genes were expressed light-dependently, and this expression was completely inhibited by the photosynthetic electron transport inhibitor, DCMU.

Photosynthetic electron transport differentially regulates the expression of superoxide dismutase genes in liverwort, Marchantia paleacea var. diptera.

Liverwort, Marchantia paleacea var. diptera, contains Mn-superoxide dismutase (Mn-SOD) in mitochondria, Fe-SOD in chloroplast and CuZn-SOD in cytosol. An Mn-SOD gene (MpMnSOD) was isolated from the liverwort. Using this clone together with the liverwort Fe-SOD and CuZn-SOD genes as probes, the expression of three SOD genes was investigated. Under heterotrophic conditions, the transcript of three SOD genes was accumulated light independently. On the other hand, under photoautotrophic conditions, the transcript levels of Fe-SOD and Mn-SOD increased in the light while that of CuZn-SOD decreased. The reverse occurred in the dark. In contrast to the transcript level, the activity of the three SODs was barely affected by light. The transcription inhibitor, cordycepin, inhibited either the light-promoted accumulation of Fe-SOD and Mn-SOD transcript or the light-induced reduction of the CuZn-SOD transcript. Photosynthetic electron transport inhibitors, DCMU and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, inhibited the photo-response in three SOD genes. These results suggest that the transcript abundance of three SOD genes in liverwort is regulated by photosynthetic electron transport but the mechanism regulating the transcript abundance of the CuZn-SOD gene is different from that of the Fe-SOD and Mn-SOD genes.

Effects of antibiotics that inhibit the bacterial peptidoglycan synthesis pathway on moss chloroplast division.

Moss chloroplasts should prove useful for studying the cyanobacteria-derived system in chloroplasts. To determine the effects of antibiotics that inhibit bacterial peptidoglycan synthesis, the numbers of chloroplasts in treated Physcomitrella patens cells were counted. Ampicillin and D-cycloserine caused a rapid decrease in the number of chloroplasts per cell. Fosfomycin affected half of the cells, while vancomycin affected a few cells. Conversely, bacitracin had no effect. With the decrease in chloroplast number, macrochloroplasts appeared in antibiotic-treated cells. Removal of the antibiotics resulted in the recovery of chloroplast number, suggesting that the decrease in number was directly dependent on the antibiotic treatment. Microscopic observations showed that the decrease in the number of chloroplasts resulted from cell division without chloroplast division. These results suggest that enzymes derived from the bacterial peptidoglycan synthesis pathway are related to moss chloroplast division.

Inhibition of plastid division by ampicillin in the pteridophyte Selaginella nipponica Fr. et Sav.

We investigated the effect of the beta-lactam antibiotic, ampicillin, on plastid division in the pteridophyte Selaginella nipponica. Guard cells of plantlets treated with 1 mM ampicillin only often had one plastid, whereas guard cells of untreated plantlets had two to four plastids. We generated a S. nipponica cell culture system and used it to investigate the effects of ampicillin. Treatment with 1 mM ampicillin had no effect on cell division in culture. We classified cultured cells into four types based on the number of plastids they contained: one (Type I), two (Type II), three or four (Type III) and more than five (Type IV). After 3 d in culture, the percentage of each cell type (I-IV) was 29.5, 46.7, 20.9, and 1.9%, respectively. Subsequently, the percentage of Types III and IV increased gradually, reaching 61.9 and 11.4%, respectively, after 15 d in culture in the absence of ampicillin. When 1 mM ampicillin was added, there was a minimal increase in the number of Type III and IV cells, with high percentages of Type I and II cells (32.4 and 45.7%, respectively) after 15 d. These results suggest that ampicillin inhibits plastid division in S. nipponica.

Photosynthetic electron transport regulates the stability of the transcript for the protochlorophyllide oxidoreductase gene in the liverwort, Marchantia paleacea var. diptera.

The transfer of Marchantia paleacea var. diptera cells to darkness caused a reversible repression in the accumulation of transcript for a gene, por, encoding the NADPH: protochlorophyllide oxidoreductase (EC 1.3.1.33). The photosynthetic inhibitor DCMU and DBMIB repressed the accumulation in light. In the presence of transcription inhibitor cordycepin, not only incubation in the dark but also addition of DCMU or DBMIB in light stimulated the degradation of the por transcript. These findings suggest that photosynthetic electron transport is involved in regulating the stability of the por transcript.

A thermally re-mendable cross-linked polymeric material.

We have developed a transparent organic polymeric material that can repeatedly mend or "re-mend" itself under mild conditions. The material is a tough solid at room temperature and below with mechanical properties equaling those of commercial epoxy resins. At temperatures above 120 degrees C, approximately 30% (as determined by solid-state nuclear magnetic resonance spectroscopy) of "intermonomer" linkages disconnect but then reconnect upon cooling, This process is fully reversible and can be used to restore a fractured part of the polymer multiple times, and it does not require additional ingredients such as a catalyst, additional monomer, or special surface treatment of the fractured interface.