Fe(0)-Dissimilatory Nitrate Reduction to Ammonium for Autotrophic Recovery of Reactive Nitrogen.

Bioreduction of nitrate to value-added ammonium is a potentially sustainable strategy to recycle nutrients from wastewater. Here, we have proven the feasibility of the reduction of autotrophic nitrate to ammonium with electrons extracted from Fe(0). Using a Geobacter-dominated anodic biofilm as an inoculum, we achieved nitrate-to-ammonium efficiency up to 90 ± 3% with a nitrate reduction rate of 35 ± 1.3 mg N/d/L. An electron acceptor instead of an inoculum greatly influenced the Fe(0)-dissimilatory nitrate reduction to ammonium (DNRA), where nitrite as the electron acceptor provided an effective selective pressure to enrich Geobacter from initial 5 to 56%. The DNRA repressing denitrification was demonstrated by the reverse tendencies of upregulated nrfA and downregulated nirS gene transcription. This finding provides a new route for autotrophic nitrate removal and recycling from water, which has a broader implication on biogeochemical nitrogen and iron cycling.

High-speed electro-optic modulator based on silicon nitride loaded lithium niobate on an insulator platform.

Electro-optic (EO) modulators, which convert signals from the electrical to optical domain plays a key role in modern optical communication systems. Lithium niobate on insulator (LNOI) technology has emerged as a competitive solution to realize high-performance integrated EO modulators. In this Letter, we design and experimentally demonstrate a Mach-Zehnder interferometer-based modulator on a silicon nitride loaded LNOI platform, which not only takes full advantage of the excellent EO effect of LiNbO3, but also avoids the direct etching of LiNbO3 thin film. The measured half-wave voltage length product of the fabricated modulator is 2.24 V·cm, and the extinction ratio is ∼20dB. Moreover, the 3 dB EO bandwidth is ∼30GHz, while the modulated data rate for on-off key signals can reach up to 80 Gbps.

Demonstration of various optical directed logic operations by using an integrated photonic circuit.

Optical directed logic is a novel logic operation scheme that employs electrical signals as operands to control the working states of optical switches to perform the logic operations. In this Letter, we propose and demonstrate an integrated photonic circuit which can implement five different optical logic operations by utilizing two optical modes. The proposed device is fabricated on a silicon-on-insulator substrate by using electron beam lithography and inductively coupled plasma etching processes. The static experimental results show that the fabricated device can implement five different operations correctly-XOR, XNOR, NOR, NOT, and AND-from which we can see that the signal-to-noise ratios are larger than 17.6 dB over the entire C band for all five logic functions. At last, all five logic operations with the speed of 10 Kbps are demonstrated. The proposed device with simple structure, large bandwidth, and versatility would be a promising candidate for information processing in optical mode division multiplexing networks.

Integrated non-blocking optical router harnessing wavelength- and mode-selective property for photonic networks-on-chip.

In this paper, we propose and demonstrate a 4×4 non-blocking optical router utilizing 8 mode (de)multiplexers and a 4×4 microring-based grid network, which can passively assign signals carried by optical wavelength and mode channels from an arbitrary input port to corresponding output ports without additional switch time, realizing the non-blocking property. The proposed device is fabricated on a silicon-on-insulator platform using the standard Complementary Metal-Oxide-Semiconductor (CMOS) fabrication processes. The insertion loss is lower than 5.7 dB including the loss of the auxiliary mode (de)multiplexers (AMUXs), while the crosstalk is lower than -15.6 dB for all routing states. Moreover, the transmission spectra from the input ports to the next cascading device are also measured to demonstrate the feasibility of further expanding via cascading multiple blocks, with the insertion loss and crosstalk lower than 7.1 dB (including the mode coupling loss of AMUXs) and -16.4 dB, respectively. The 12 Gbps dynamic transmission experiment is demonstrated with clear and open eye diagrams, illustrating the utility of the device. The device has high geometrical symmetry and good scalability, we exhibit all solutions to expand the 4×4 optical router to 8×8 and 16×16 optical routers with the advantages and deficiencies of each solution discussed.

Electron Flow Shifts from Anode Respiration to Nitrate Reduction During Electroactive Biofilm Thickening.

As electrons generated through substrate oxidation compete with electrodes, dissimilatory nitrate reduction to ammonium (DNRA), denitrification in bioelectrochemical systems in the presence of nitrate, and nitrate reduction through an electroactive biofilm (EAB) are unpredictable. We find that pathways of nitrate reduction are related to EAB thickness and that 76 ± 2 µm is the critical thickness of a biofilm at which both the inner and outer layers simultaneously include DNRA, leading to a maximum level of DNRA efficiency of 42%. Fractions of electrons flowing during nitrate reduction are relatively stable, but their distributions between DNRA and denitrification vary with biofilm thickness. Electrons prefer denitrification in an EAB that is 66 ± 2 µm, while DNRA reversely surpasses denitrification when the thickness increases in the range of 76 ± 2 to 210 ± 2 µm. Biofilm thickening enhances the DNRA of all biofilms close to solution, where nirK remains constant and nrfA is significantly upregulated. However, nrfA is downregulated in layers close to the electrode when the biofilm is thicker than 76 ± 2 µm. These findings reveal the spatially heterogeneous reduction of nitrate in thick EABs, highlighting the importance of biofilm thickness to the regulation of end products of nitrate reduction.

On-chip switchable and reconfigurable optical mode exchange device using cascaded three-waveguide-coupling switches.

Data exchange between different data channels can offer more flexible and advanced functions for many optical networks. In this paper, we propose a switchable and reconfigurable data exchange device for arbitrary two optical mode channels based on three-waveguide-coupling (TWC) switches in mode-division multiplexing (MDM) networks. The working principle of the TWC switches is numerically analyzed using the coupled supermode theory. As a proof of concept, switchable data exchange between arbitrary two mode channels among the first three-order quasi-transverse electric modes is experimentally demonstrated successfully. The insertion losses of the device are less than 5.6 dB, including the coupling loss of the multiplexer and demultiplexer, while the mode crosstalk is less than -13.0 dB for all functions. The proposed device is expected to offer more flexibility to on-chip MDM networks due to its low loss, low crosstalk and good scalability.

Single layer graphene electrodes for quantum dot-light emitting diodes.

Single layer graphene was employed as the electrode in quantum dot-light emitting diodes (QD-LEDs) to replace indium tin oxide (ITO). The graphene layer demonstrated low surface roughness, good hole injection ability, and proper work function matching with the poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) layer. Together with the hole transport layer and electron transport layer, the fabricated QD-LED showed good current efficiency and power efficiency, which were even higher than an ITO-based similar device under low current density. The result indicates that graphene can be used as anodes to replace ITO in QD-LEDs.

[The Effects of Complex of Benzoquinone on Fermi Resonance].

Fermi resonance phenomenon exists in simple compounds and it also widely exists in vibration spectra of complex. The complex can be formed by adding up simple compounds. As a result, the characteristic parameters of some parts of molecule will make changes, and the molecular spectra have a significant change along with it. Benzoquinone and proline in the solution form charge-transfer complex under certain conditions, but the spectra intensity is weak, our research uses Teflon liquid-core optical fiber technology to gain high quality resonance Raman spectra. We acquire Raman spectra of Benzoquinone and its complex in experiments, and analyze the characteristic parameters of Fermi resonance according to J. F. Bertran quantum theory. The results shows that, because of the formation of complex, Fermi resonance peak of C==0 bond shifts to high wavelength, the spectra intensity decreases, the frequency space increases, the coupling coefficient increases. The explanation is that, in the solution of complex, proline is donor, while benzoquinone is acceptor, the non-bonding electron of N atom which is belong to proline transfers to the pi anti-bonding orbital of benzoquinone, then n-pi* charge transfer complex is produced. That causes the change of molecular energy level, changes the Raman spectra. All these researches provide new idea and clue for spectral line certification and attribution of complex molecules, complexes and polymer.

[Study of Fermi resonance characteristic of CS2 in THF].

In the present paper, an innovative experiment was done. The authors measured the Raman spectra of CS2 mixed with THF at different volume fractions. According to the J. F. Bertran theory, we analyzed the changing regularity of v1-2v2 Fermi resonance along with the different concentration. It was shown that the characteristic parameters of Fermi resonance in solution, such as spectra intensity, frequency space, coupling coefficient and anharmonic constant, will make changes along with solution concentration variation. Because of the existing of solvent effects, the spectra intensity decreases gradually, and the coupling coefficient increases gradually. The explanation of such changes is that the vibration spectra are affected not only by scattering coefficient, but also by more weak hydrogen bond's formation. In addition, the asymmetric frequency shift of the Raman spectra was also found in the paper. The fundamental frequency v1 basically has no shifts, but the overtone frequency 2v2 moves towards the high wave number gradually, which is inconsistent with the theory of symmetrical movement. According to the study of molecular microcosmic action, the formation and mechanism of the weak hydrogen bond can preferably explain the above phenomenon. The research has a major influence on the further study of solvent effects in Fermi resonance. And the paper will also provide certain reference value for the study of molecule vibration spectra in solution.

A novel high level canonical piecewise linear model based on the simplicial partition and its application.

The piecewise linear (PWL) model has attracted more and more attention in recent research because it can handle complex nonlinearity while maintaining linearity in local regions. A large number of compact representations for PWL modeling have been introduced, such as hinging hyperplanes and its generalized version. However, the existing methods usually give rise to many and complex subregions, which is an issue known as "curse of partitions", and hampered practical applications of PWL models. In this paper, a novel high level canonical PWL model is presented to tackle the curse of partitions. In more detail, an improved simplicial partition strategy with alterable intervals is proposed to improve the model representation capability. The proposed PWL model guarantees an unchangeable topology during training and thus a limited number of subregions after training. Several numerical experiments, and a simulated chemical process, are used to demonstrate the effectiveness of the proposed model.

Colloidal PbSe quantum dot-solution-filled liquid-core optical fiber for 1.55 µm telecommunication wavelengths.

We have studied the optical properties of PbSe colloidal quantum dot-solution filled hollow core multimode silica waveguides as a function of quantum dot-solution concentration, waveguide length, optical pump power and choice of organic solvent in order to establish the conditions to maximize near infrared spontaneous emission intensities. The optical performance was compared and showed good agreement with a simple three level system model for the quantum dots confined in an optical waveguide. Near infrared absorption-free solvent of tetrachlorethylene was confirmed to be a good candidate for the waveguide medium due to the enhancement of output intensity from the liquid-core fiber compared to the performance in toluene-based fiber. This approach demonstrates a useful method for early characterization of quantum dot materials in a waveguide test-bed with minimal material processing on the colloidal nanoparticles.

[Effect of the change in fundamental Raman scattering coefficient with the concentration on Fermi resonance in binary solution].

The Raman scattering coefficients of the fundamental v1 (992 cm(-1)) of C6 H6 and the fundamental v1 (656 cm(-1) ) of CS2 changed dramatically with relative concentration of the binary solution of CS2 and C6 H6. The Raman spectra of the binary solution with different relative concentrations were measured. The results show that both the v1 fundamentals intensities changed dramatically with the relative concentration of the solution and the fundamental v1 of C6 H6 has little effect on the Fermi resonance v1 +v6-v8. On the contrary, the change in the v1 fundamental intensity of the CS2 changed which has more effect not only on the Fermi resonance v1 - 2v2 but also on the v2 fundamental. In this report, the experimental results were analyzed based on the J. F. Bertran theory and group theory.

[Analysis of spectral intensity of fermi resonance of molecules].

Raman spectra of liquid carbon disulfide (CS) and carbon tetrachloride (CCl4) were measured. And the spectral intensity was analyzed using the J. F. Bertran theory and the group theory. The rule about Fermi resonance was obtained from the Raman spectra of carbon disulfide (CS) and carbon tetrachloride (CCL4): (1) The energy can transfer between a fundamental and an overtone frequency about Fermi resonance; the two spectra have the same intensity. The spectral intensity of the two spectra was equal (R=1) about Fermi resonance, when the difference between fundamental of Fermi resonance and overtone of Fermi resonance was very small. (2) The intensity of overtone is stronger than that of fundamental's. (3) The spectrum of Fermi resonance was observed, but the fundamental frequency was not. This article has very good reference value for the assignments in the molecular structure and the research of contents.

[Investigation of hydrophobic effect on the hydrogen-bond formation of 1,1,3,3-tetramethylurea by Raman methods].

The binary systems of 1,1,3,3-tetramethylurea (TMU) with water, TMU with methanol, TMU with ethanol and N,N-dimethylformamide(DMF) with water were measured by Raman method. With the analysis of the frequency changes of stretching vibration of carboxyl with concentration the authors found that the frequency shift underwent two processes: first, the frequency of stretching vibration of carboxyl down shifts with the increase in hydrogen-bond acceptor concentration; secondly, when the concentration of binary system surpasses a critical value, the wave number remains almost constant, and only the rela tive intensity changes. Through this critical volume ratio, the authors found that the large self-associated water molecule was in volved in the TMU aqueous binary system; while the small self-associated molecule or dimer formation was present in other binary systems.

[Solvent effects on raman spectroscopy of 1, 1,3, 3-tetramethylurea in organic solvents].

Raman spectra of 1,1,3,3-tetramethylurea in 20 solvents were obtained to investigate the solute-solvent interactions and to correlate solvent properties such as the Kirkwood-Bauer-Magat (KBM)equation, the solvent acceptor number (AN)and the linear solvation energy relationships (LSER), respectively, with the Raman shifts of carbonyl group. There is little linear relation between dielectric constants and the Raman shift. These solvents were divided into two sections by the acceptor number. The two sections exhibit a good correlation with AN, respectively. These frequencies show a better correlation with LSER than the solvent AN. How the solvents interacts with the C==O can be obtained from the regression coefficients.

[Investigation of effect of solvents on C=O Fermi resonance with solvent variation method].

Fermi resonance is one of the general and important phenomena in vibration spectra. The method of solvent variation is one of the main methods to study Fermi resonance. In the present paper, FTIR spectroscopy was used to study the Fermi resonance of p-benzoquinone in thirteen solvents. The results show that there are some function relationships between the dielectric constant of solvent and the intensity ratio of Fermi resonance. And the empirical formula was obtained by curve fitting. The equation of Kirkwood-Bauer-Magat was applied to the study of Fermi resonance. And the authors obtained the relation between the intensity ratio R and the dielectric constant epsilon. This result is in accordance with the empirical formula. In order to confirm our result, the infrared data of R. A. Nyquist and J. K. Seehra were analyzed. These results are in accord with that of p-benzoquinone.

[CCD spectrum processing of automobile lamp testing with wavelet analysis].

According to the wavelet multi-resolution analysis, the optical spectrum signal received by CCD was processed and analyzed by using the wavelet transformation technique. The noise in the optical spectrum signal can be removed by using the wavelet multi-resolution analysis technique. The curve of spectral signal can be smoothed. The ratio of signal to noise was enhanced. The spectrum of Asource by CCD was smoothed with wavelet multi-resolution analysis. The processing results with different wavelets in different orders were discussed. An effective data processing method was used for spectrum analysis. The difficulty in the analysis and processing of real-time signal can be solved, which is significant in the color testing field.