Acceleration of nonylphenol and 4-tert-octylphenol degradation in sediment by Phragmites australis and associated rhizosphere bacteria

We investigated biodegradation of technical nonylphenol (tNP) in Phragmites australis rhizosphere sediment by conducting degradation experiments using sediments spiked with tNP. Accelerated tNP removal was observed in P. australis rhizosphere sediment, whereas tNP persisted in unvegetated sediment without plants and in autoclaved sediment with sterile plants, suggesting that the accelerated tNP removal resulted largely from tNP biodegradation by rhizosphere bacteria. Three bacterial strains, Stenotrophomonas sp. strain IT-1 and Sphingobium spp. strains IT-4 and IT-5, isolated from the rhizosphere were capable of utilizing tNP and 4-tert-octylphenol as a sole carbon source via type II ipso-substitution. Oxygen from P. australis roots, by creating highly oxygenated conditions in the sediment, stimulated cell growth and the tNP-degrading activity of the three strains. Moreover, organic compounds from P. australis roots functioned as carbon and energy sources for two strains, IT-4 and IT-5, supporting cell growth and tNP-degrading activity. Thus, P. australis roots elevated the cell growth and tNP-degrading activity of the three bacterial strains, leading to accelerated tNP removal. These results demonstrate that rhizoremediation of tNP-contaminated sediments using P. australis can be an effective strategy.     

Surface investigations using monolayer-resolvable high-resolution Rutherford backscattering spectroscopy

Energy spectra of scattered 0.5 MeV He ions from a clean (001) surface of SnTe are measured with a 90° sector magnetic spectrometer (ΔE/E 0.1%). The ions scattered from successive atomic layers can be resolved in the energy spectra. Inelastic energy losses and charge state distributions of 0.5 MeV He ions scattered from the topmost atomic layer of the SnTe(001) are measured. A position-dependent stopping power at the surface is proposed from the observed energy losses. The observed charge state distribution shows the importance of the charge-exchange processes with valence electrons in the tail of the electron distribution at the surface.     

Frequency-dependent conductance change of dielectrophoretic-trapped DNA-labeled microbeads and its application in DNA size determinations

DNA amplification is essential in several types of molecular biology approaches. A more rapid and easy analysis of amplicons is still required although many analysis methods have been developed. We have recently devised a new DNA detection method, where DNA amplicons are attached to dielectric microbead surfaces, so that their dielectrophoresis (DEP) force on the microbead reverses polarity, from negative to positive. The DNA-labeled microbeads are trapped on a microelectrode by positive DEP, enabling their rapid detection via DEP impedance measurement. In this paper, we report frequency-dependent conductance of DNA-labeled microbeads. To measure the impedance, sweep-frequency voltage was superimposed on fixed-frequency voltage, with the aim of inducing frequency-dependent conformational change of microbead-attached DNA, ultimately resulting in a change in the conductance of DNA-labeled microbeads. Microbeads labeled with DNA of various sizes (142-, 204-, 391-, and 796-bp) were examined. The normalized conductance sharply decreased at a specific frequency; the frequency was higher with larger DNA size, suggesting a potential application of this method in distinguishing DNA targets according to their size. By combining this method with previously devised DNA detection techniques, both the size and amount of target DNA can be determined within 20 min. This approach is easier and more rapid than conventional methods, such as a gel electrophoresis.     

Bacterial detection based on polymerase chain reaction and microbead dielectrophoresis characteristics

In this study, an electrical DNA detection method was applied to bacterial detection. DNA was extracted from bacteria and amplified by polymerase chain reaction. The microbeads were labelled with amplicons, altering their surface conductance and therefore their dielectrophoresis characteristics. Amplicon‐labelled microbeads could thus be trapped within a high‐strength electric field, where they formed a pearl chain between the electrodes, resulting in an increased conductance between the electrodes. This method reduces the amplicon detection time from 1–2 h to 15 min, compared with the conventional method. The presented method realised quantitative detection of specific bacteria at concentrations above 1 × 10⁵ and 2.4 × 10⁴ CFU/ml for bacterial solutions with and without other bacterial presence, respectively.Inspec keywords: microorganisms, enzymes, molecular biophysics, biochemistry, electrophoresis, bioelectric phenomena, DNA, biosensors, electrochemical electrodes, electrochemical sensors, microsensors, bioMEMS, surface conductivityOther keywords: bacterial detection, polymerase chain reaction, microbead dielectrophoresis characteristics, electrical DNA detection, surface conductance, amplicon‐labelled microbeads, high‐strength electric field, pearl chain, electrodes, amplicon detection time, quantitative detection, bacterial solutions, time 15 min to 2 h     

Proposal of Bow-Tie Antenna-Integrated Resonant Tunneling Diode Transmitter Utilizing Relaxation Oscillations and Its Application to Short-Distance Wireless Communications

We propose a resonant tunneling diode (RTD)-based relaxation oscillator and an oscillator-based terahertz (THz) wireless link that compensate for shortfalls in RF-oscillator emission power by adding several relaxation carrier wave harmonic modes. We believe that the proposed link can perform as well as or superior to large component-based wireless links that suppress power dissipation using collimating lenses and/or discrete antennas to add the power output of a relaxation oscillator. This hypothesis is investigated analytically using a physics-based equivalent circuit model of the proposed oscillator and a link budget analysis of the relaxation carrier wave. The model, which incorporates effects such as the non-linearity of the tunneling diode and the electromagnetic properties of the integrated bow-tie antenna on the oscillator, is used to quantitatively investigate the link characteristics in terms of the signal-to-noise ratio (SNR) and other parameters and to demonstrate that, by applying an appropriate device size and number of harmonic modes in the occupied bandwidth, link performance comparable to that of previously reported wireless links can be achieved. Based on these results, we discuss the potential for practical implementation of the proposed link configuration in mobile link applications for use in environments such as the Internet of Things (IoT).     

Control of pH by CO 2 Pressurization for Enzymatic Saccharification of Ca(OH) 2 -Pretreated Rice Straw in the Presence of CaCO 3

The aim of this study was to investigate the effect of pH control by CO ₂ pressurization on the enzymatic hydrolysis of herbaceous feedstock in the calcium capturing by carbonation (CaCCO) process for fermentable sugar production. The pH of the slurry of 5 % (w/w) Ca(OH) ₂ -pretreated/CO ₂ -neutralized rice straw could be controlled between 5.70 and 6.38 at 50 °C by changing the CO ₂ partial pressure ( p CO ₂ ) from 0.1 to 1.0 MPa. A mixture of fungal enzyme preparations, namely, Trichoderma reesei cellulases/hemicellulases and Aspergillus niger β-glucosidase, indicated that pH 5.5–6.0 is optimal for solubilizing sugars from Ca(OH) ₂ -pretreated rice straw. Enzymatic saccharification of pretreated rice straw under various p CO ₂ conditions revealed that the highest soluble sugar yields were obtained at p CO ₂ 0.4 MPa and over, which is consistent with the expected pH at the p CO ₂ without enzymes and demonstrates the effectiveness of pH control by CO ₂ pressurization.     

Effects of light intensity and water temperature on oxygen release from roots into water lettuce rhizosphere

The oxygen release rate into the rhizosphere by a floating aquatic plant-water lettuce-was determined under various light intensities (0.0-1.2x10(5)lx) and water temperatures (10-35 degrees C). The net specific oxygen release rate was expressed by a model equation comprising the gross oxygen release rate and the rhizosphere respiration terms. Experimental and simulated results show that the net specific oxygen release rate increased with light intensity up to the optimal value, but slight inhibition by higher light intensities was observed at 10-20 degrees C. With increased water temperature, the respiration rate became larger than the gross oxygen release rate. The maximum net specific oxygen release rate of 11.0-12.5mg-O(2)kg-wet(-1)h(-1) was obtained at the optimal condition of about 25 degrees C and 9.0x10(4)-1.1x10(5)lx. The net oxygen release rate was negligible at 35 degrees C at any light intensity because the respiration rate was much greater than the gross oxygen release rate into the rhizosphere.     

Characterization of microorganisms at different landfill depths using carbon-utilization patterns and 16S rRNA gene based T-RFLP

A borehole core from 20 m depth of a Japanese landfill was characterized chemically and microbially. The borehole core sample was typically divided into 5 waste layers; 2.4–4.0 m, 5.7–8.5 m, 9.25–9.6 m, 9.77–14.9 m, and 15.9–17.86 m depths. The waste layers' ages spanned about 14 years between the bottom and top. Archaeal 16S rRNA gene and eubacterial 16S rRNA gene in the waste samples at their respective levels were 9.8 × 10⁵–7.2 × 10⁷ and 1.2 × 10⁷–7.2 × 10⁹ copy/g-wet. Similar to populations of viable and culturable bacteria, those populations were high at 7.0 m and 17.5 m depth, but low at 3.0 m depth. The microorganisms' phenotypes and genotypes were evaluated, respectively, using carbon-utilization tests and by eubacterial 16S rRNA gene based T-RFLP. Low dominance of the VFA-utilizing bacteria in samples and low concentrations of VFAs in all waste layers suggest that the organic decomposition in this landfill site remained. Gamma-proteobacteria dominated the microbial community at 17.5 m depth. Clostridia were detected at 7.0, 11.5, and 17.5 m depths, suggesting strict anaerobic conditions in these deep layers. The Shannon–Weaver diversity index showed lower values at 3.0 m and 11.5 m depth with a T-RF pattern. The diversity index calculated from the carbon-utilization pattern increased slightly with depth at the landfill site. The landfill-site waste layers are expected to be mutually isolated and to form unique microbial communities depending on the buried wastes' composition, temperature, moisture content, and pressure inside the landfill.