An L-Shaped Three-Level and Single Common Element Sparse Sensor Array for 2-D DOA Estimation.

The degree of freedom (DOF) is an important performance metric for evaluating the design of a sparse array structure. Designing novel sparse arrays with higher degrees of freedom, while ensuring that the array structure can be mathematically represented, is a crucial research direction in the field of direction of arrival (DOA) estimation. In this paper, we propose a novel L-shaped sparse sensor array by adjusting the physical placement of the sensors in the sparse array. The proposed L-shaped sparse array consists of two sets of three-level and single-element sparse arrays (TSESAs), which estimate the azimuth and elevation angles, respectively, through one-dimensional (1-D) spatial spectrum search. Each TSESA is composed of a uniform linear subarray and two sparse subarrays, with one single common element in the two sparse subarrays. Compared to existing L-shaped sparse arrays, the proposed array achieves higher degrees of freedom, up to 4Q1Q2+8Q1-5, when estimating DOA using the received signal covariance. To facilitate the correct matching of azimuth and elevation angles, the cross-covariance between the two TSESA arrays is utilized for estimation. By comparing and analyzing performance parameters with commonly used L-shaped and other sparse arrays, it is found that the proposed L-shaped TSESA has higher degrees of freedom and array aperture, leading to improved two-dimensional (2-D) DOA estimation results. Finally, simulation experiments validate the excellent performance of the L-shaped TSESA in 2-D DOA estimation.

Engineered jadomycin analogues with altered sugar moieties revealing JadS as a substrate flexible O-glycosyltransferase.

Glycosyltransferases (GTs)-mediated glycodiversification studies have drawn significant attention recently, with the goal of generating bioactive compounds with improved pharmacological properties by diversifying the appended sugars. The key to achieving glycodiversification is to identify natural and/or engineered flexible GTs capable of acting upon a broad range of substrates. Here, we report the use of a combinatorial biosynthetic approach to probe the substrate flexibility of JadS, the GT in jadomycin biosynthesis, towards different non-native NDP-sugar substrates, enabling us to identify six jadomycin B analogues with different sugar moieties. Further structural engineering by precursor-directed biosynthesis allowed us to obtain 11 new jadomycin analogues. Our results for the first time show that JadS is a flexible O-GT that can utilize both L- and D- sugars as donor substrates, and tolerate structural changes at the C2, C4 and C6 positions of the sugar moiety. JadS may be further exploited to generate novel glycosylated jadomycin molecules in future glycodiversification studies.

A novel CO sensor based on the point contact between Pd decorated TiO2 nanotubes array.

To obtain a high sensitive CO sensor, a new nanostructure based on the point contact between Pd decorated TiO2 nanotubes was proposed in this paper. TiO2 nanotubes array was fabricated on titanium wire by electrochemical anodic oxidation, and Pd catalytic nanoparticles were modified by the micro-emulsion electrochemical deposition. The surface morphology was characterized by field emission scanning electron microscopy (FE-SEM), and CO sensitivity of the point contact between TiO2 nanotubes was investigated through the current-voltage (I-V) characteristic measurement. It was found that Pd epitaxially grew along the tube walls, and they were distributed on the surface of the nanotubes. The point contact based sensor between Pd decorated TiO2 nanotubes exhibited a strong temperature dependent sensitivity towards CO. From the I-V curves, we found the Schottky barrier was formed on the contact and the barrier height was also calculated.

H2 sensing properties of pd modified WO3-Fe2O3 nanostructured composite films prepared by amorphous W-Fe dealloying.

Tungsten trioxide nanopetal with Fe2O3 composite films were synthesized by dealloying the W-Fe alloy film in HCl aqueous solution; nano-Pd particles were directly electrochemical deposited on the surface of dealloying films in a micro-emulsion system and following thermal oxidation in air. The structure, morphology, chemical composition and quality of the prepared WO3 nanopetal with Fe2O3 composite films were characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The results showed that the thickness of the WO3 nanopetals were less than 50 nm, which were monoclinic phase after controlled thermal oxidation process, and the nano-Pd particles were evenly dispersed on the WO3 film surface with controlled diameters ranging from 20 to 40 nm. The sensors were tested for 25-2000 ppm H2 at temperatures from 50 to 200 degrees C; and the H2 sensing properties of Pd loading (1.54 at.%) WO3-Fe2O3 composited films exibited the best response at the low working temperature of 125 degrees C.

Zn(II), Pb(II), and Cd(II) adsorption from aqueous solution by magnetic silica gel: preparation, characterization, and adsorption.

A novel magnetic silica gel adsorbent (Fe3O4-Si-COOH) was successfully prepared by introducing carboxyl group in situ to improve the performance for Pb(II), Zn(II), and Cd(II) adsorption. Infrared spectroscopy (IR), scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analyzer (TGA), the Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) characterizations suggested that Fe3O4-Si-COOH has been successfully prepared. The adsorption performance was evaluated by batch experiments with different initial concentrations, ionic strength, contact time, and pH. The adsorption kinetics data followed pseudo-second-order model and exhibited a three-stage intraparticle diffusion mode. Isothermal adsorption equilibrium data were best fitted by the Freundlich model and the adsorption capacity were 155, 110, and 93 mg/g (initial concentration 210 mg/L) for Pb(II), Zn(II), and Cd(II), respectively. The result of X-ray photoelectron spectroscopy (XPS) survey spectrum suggested that the main adsorption mechanism is that the H+ of carboxyl groups exchanged with heavy metal ions in the adsorption processes. In addition, the adsorbed Fe3O4-Si-COOH could be regenerated and the adsorption capacity of reused Fe3O4-Si-COOH could maintain 80.3% after five cycles. Hence, the Fe3O4-Si-COOH could be a kind of potential material for removing Pb(II), Zn(II), and Cd(II) from wastewater. Graphical abstract.

Identification of JadG as the B ring opening oxygenase catalyzing the oxidative C-C bond cleavage reaction in jadomycin biosynthesis.

Jadomycin B is a member of atypical angucycline antibiotics whose biosynthesis involves a unique ring opening C-C bond cleavage reaction. Here, we firmly identified JadG as the enzyme responsible for the B ring opening reaction in jadomycin biosynthesis. In vitro analysis of the JadG catalyzed reaction revealed that it requires FMNH(2) or FADH(2) as cofactors in the conversion of dehydrorabelomycin to jadomycin A. The cofactors could be supplied by either a cluster-situated flavin reductase JadY or the Escherichia coli Fre. JadY was characterized as a NAD(P)H-dependent FMN/FAD reductase, with FMN as the preferred substrate. Disruption mutant of jadY still produced jadomycin, indicating that the function of JadY could be substituted by other enzymes in the host. JadG represents the biochemically verified member of an enzyme class catalyzing an unprecedented C-C bond cleavage reaction.