Glycine Betaine Monooxygenase, an Unusual Rieske-Type Oxygenase System, Catalyzes the Oxidative N-Demethylation of Glycine Betaine in Chromohalobacter salexigens DSM 3043.

Although some bacteria, including Chromohalobacter salexigens DSM 3043, can use glycine betaine (GB) as a sole source of carbon and energy, little information is available about the genes and their encoded proteins involved in the initial step of the GB degradation pathway. In the present study, the results of conserved domain analysis, construction of in-frame deletion mutants, and an in vivo functional complementation assay suggested that the open reading frames Csal_1004 and Csal_1005, designated bmoA and bmoB, respectively, may act as the terminal oxygenase and the ferredoxin reductase genes in a novel Rieske-type oxygenase system to convert GB to dimethylglycine in C. salexigens DSM 3043. To further verify their function, BmoA and BmoB were heterologously overexpressed in Escherichia coli, and 13C nuclear magnetic resonance analysis revealed that dimethylglycine was accumulated in E. coli BL21(DE3) expressing BmoAB or BmoA. In addition, His-tagged BmoA and BmoB were individually purified to electrophoretic homogeneity and estimated to be a homotrimer and a monomer, respectively. In vitro biochemical analysis indicated that BmoB is an NADH-dependent flavin reductase with one noncovalently bound flavin adenine dinucleotide (FAD) as its prosthetic group. In the presence of BmoB, NADH, and flavin, BmoA could aerobically degrade GB to dimethylglycine with the concomitant production of formaldehyde. BmoA exhibited strict substrate specificity for GB, and its demethylation activity was stimulated by Fe2+ Phylogenetic analysis showed that BmoA belongs to group V of the Rieske nonheme iron oxygenase (RO) family, and all the members in this group were able to use quaternary ammonium compounds as substrates.IMPORTANCE GB is widely distributed in nature. In addition to being accumulated intracellularly as a compatible solute to deal with osmotic stress, it can be utilized by many bacteria as a source of carbon and energy. However, very limited knowledge is presently available about the molecular and biochemical mechanisms for the initial step of the aerobic GB degradation pathway in bacteria. Here, we report the molecular and biochemical characterization of a novel two-component Rieske-type monooxygenase system, GB monooxygenase (BMO), which is responsible for oxidative demethylation of GB to dimethylglycine in C. salexigens DSM 3043. The results gained in this study extend our knowledge on the catalytic reaction of microbial GB degradation to dimethylglycine.

Establishment of a markerless gene deletion system in Chromohalobacter salexigens DSM 3043.

Chromohalobacter salexigens DSM 3043 can grow over a wide range of salinity, which makes it as an excellent model organism for understanding the mechanism of prokaryotic osmoregulation. Functional analysis of C. salexigens genes is an essential way to reveal their roles in cellular osmoregulation. However, the lack of an effective markerless gene deletion system has prevented construction of multiple gene deletion mutants for the members in the genus. Here, we report the development of a markerless gene deletion system in C. salexigens using allelic exchange method. In this system, the in vitro mutant allele of target gene was inserted into a pK18mobsacB-based integrative vector pMDC21, which contained a chloramphenicol resistance cassette as the positive selection marker and a sacB gene from Bacillus subtilis as the counterselectable marker. To validate this system, two single-gene deletion mutants and a double-gene deletion mutant were constructed. In addition, our results showed that growth of the merodiploids and sucrose screening at 25 °C were more effective to decrease the occurrence of spontaneous sucrose resistance colonies than at higher temperature (30 or 37 °C), and growth of the merodiploids in mineral salt medium instead of the complex medium was critical to increase the recovery rate of deletion mutants.

A Transparent Antipeep Piezoelectric Nanogenerator to Harvest Tapping Energy on Screen.

Aligning PbZr(0.52)Ti(0.48)O3 (PZT) nanowires in polydimethylsiloxane introduces dielectrophoresis, improving the electromechanical properties of nanogenerators, and the light transmittance of composite films. A novel transparent and antipeep piezoelectric nanogenerator is developed that can be used for harvesting the energy from the light tapping of a finger on a cell phone, with an output current of 0.8 nA.

Flexible fiber nanogenerator with 209 V output voltage directly powers a light-emitting diode.

On the basis of a vertically aligned ultralong Pb(Zr(0.52)Ti(0.48))O(3) (PZT) nanowire array fabricated using electrospinning nanofibers, we developed a new type of integrated nanogenerator (NG) with ultrahigh output voltage of 209 V and current density of 23.5 µA/cm(2), which are 3.6 times and 2.9 times of the previous record values, respectively. The output electricity can be directly used to stimulate the frog's sciatic nerve and to induce a contraction of a frog's gastrocnemius. The NG can instantaneously power a commercial light-emitting diode (LED) without the energy storage process.

Magnetic force driven nanogenerators as a noncontact energy harvester and sensor.

Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source. The CLNG can harvest the mechanical movement energy in a noncontact mode to generate electricity. Their output voltage and current can be as large as 3.2 V and 50 nA, respectively, which is large enough to power up a liquid crystal display. We also demonstrate a means by which a magnetic sensor can be built.

Gridding Triboelectric Nanogenerator for Raindrop Energy Harvesting.

Triboelectric nanogenerator (TENG) has the great potential to harvest the electrostatic energy and mechanical energy of raindrops. However, raindrops are small and scattered, and it is difficult to harvest their mechanical energy effectively. In this paper, a gridding triboelectric nanogenerator (G-TENG) with an area of 81 cm2 is designed and developed to effectively harvest the mechanical energy of raindrops on a large scale. Its peak output power density is 8.56 mW/m2, which is 245 times the value of 35 µW/m2 of a general TENG without gridding. Each unit of the G-TENG can work independently, which can effectively decrease the mutual counteraction of elastic deformation among the adjacent positions of the raindrop impacting layer and avoid the accumulation of raindrops. Under the impact of simulated raindrops from a shower at a flow rate of 0.137 mL/(cm2·s), the open-circuit voltage (Voc) and the short-circuit current density (Jsc) of the G-TENG reach 400 V and 2.5 mA/m2, respectively. The peak output power density reaches 110 mW/m2, which is 42 times the reported maximum value of 2.6 mW/m2 of raindrop energy harvesting TENGs with the size larger than 10 cm2. Moreover, the G-TENG can harvest the mechanical energy of raindrops at a wide range of raindrop flow rates from 0.055 to 0.219 mL/(cm2·s). This work contributes to the raindrop mechanical energy harvesting on a large scale.

Enhancing the filtration efficiency and wearing time of disposable surgical masks using TENG technology.

The COVID-19 pandemic has caused an unprecedented human and health crisis. And the shortage of protective equipment, especially the personal protective disposable surgical masks, has been a great challenge. Here, we developed an effective and simple scheme to prolong the lifetime of disposable surgical masks without changing their current structure, which is beneficial to solve the shortage of personal masks. After electrifying the meltblown PP filter by the new-developed single-electrode-based sliding triboelectric nanogenerator (TENG) charge replenishment (NGCR) technology, the processed filter is bipolar charged and has a filtration efficiency beyond 95% for the particulate matter (PM) ranging from PM0.3 to PM10.0. Further, we demonstrate the 80 °C dry heating is an effective decontamination method. This method is compatible with single-electrode-based sliding TENG charge replenishment technology. The 80 °C dry heating and the NGCR technology can make up an effective regeneration procedure for the mask. Even after ten cycles of simulated 4 h wearing process and such regeneration procedure, the filtration efficiency of the disposable surgical masks PM0.3 is still higher than 95%.

High performance temperature difference triboelectric nanogenerator.

Usually, high temperature decreases the output performance of triboelectric nanogenerator because of the dissipation of triboelectric charges through the thermionic emission. Here, a temperature difference triboelectric nanogenerator is designed and fabricated to enhance the electrical output performance in high temperature environment. As the hotter friction layer's temperature of nanogenerator is 0 K to 145 K higher than the cooler part's temperature, the output voltage, current, surface charge density and output power are increased 2.7, 2.2, 3.0 and 2.9 times, respectively (from 315 V, 9.1 µA, 19.6 µC m-2, 69 µW to 858 V, 20 µA, 58.8 µC m-2, 206.7 µW). With the further increase of temperature difference from 145 K to 219 K, the surface charge density and output performance gradually decrease. At the optimal temperature difference (145 K), the largest output current density is 443 µA cm-2, which is 26.6% larger than the reported record value (350 µA cm-2).

Enhancing the Performance of a Self-Standing Si/PCNF Anode by Optimizing the Porous Structure.

Embedding silicon nanoparticles into carbon nanofibers is one of the effective methods to fabricate a self-standing and binder-free Si-based anode material for lithium-ion batteries. However, the sluggish Li-ion transport limits the electrochemical performance in the regular strategies, especially under high rate conditions. Herein, a kind of silicon nanoparticle in porous carbon nanofiber structures (Si/PCNFs) has been fabricated through a facile electrospinning and subsequent thermal treatment. By adjusting the mass ratio to 0.4:1, a Si/PCNF anode material with an effective Li+-migration pathway and excellent structural stability can be obtained, resulting in an optimal electrochemical performance. Although increasing the mass ratio of PEG to PAN further can lead to a larger pore size and can be beneficial to Li+ migration, thus being profitable for the rate capacity, the structural stability will get worse at the same time as more defects will form and lead to a weaker C-C binding, thus decrease the cycling stability. Remarkably, the rate capacity reaches 1033.4 mA h g-1 at the current density of 5 A g-1, and the cycling capacity is 933.2 mA h g-1 at 0.5 A g-1 after 200 cycles, maintaining a retention rate of 80.9% with an initial coulombic efficiency of 83.37%.

Ultrasensitive Fiber-Based ZnO Nanowire Network Ultraviolet Photodetector Enabled by the Synergism between Interface and Surface Gating Effects.

A flexible UV photodetector with a high on/off ratio is extremely important for environmental sensing, optical communication, and flexible optoelectronic devices. In this work, a flexible fiber-based UV photodetector with an ultrahigh on/off ratio is developed by utilizing the synergism between interface and surface gating effects on a ZnO nanowire network structure. The synergism between two gating effects is realized by the interplay between surface band bending and the Fermi level through the nanowire network structure, which is proved through the control experiments between the ZnO micro/nanowire photodetector and micro/nanowire junction photodetector, and the corresponding Kelvin probe force microscopy (KPFM) measurements. The on/off ratio of the fiber-based ZnO nanowire network UV photodetector reaches 1.98 × 108 when illuminated by 1.0 mW cm-2 UV light, which is 20 times larger than the largest reported result under the same UV illumination. This new UV sensor also has a high resolution to UV light intensity change in the nW cm-2 range. Furthermore, when the fiber-based photodetector is curved, it still shows excellent performance as above. This work gives a new effective route for the development of a high-performance UV photodetector or other optoelectronic detection devices.

[Determination of five kinds of trace elements in Mongolian medicines by microwave digestion-ICP-AES].

With the combination of the microwave digestion and ICP-AES, and by optimizing the instrument conditions, the micro digestion-ICP-AES method for the determination of eight metal elements, Zn, Fe, Ca, Mn, K, Mg, Sr and Na, in Mongolian medicines has been established. This method works by determining one solution sample with many kinds of elements at one time. The average recovery of the method is between 92.2% and 113.3% and the RSD is between 0.4% and 3.2%. The accuracy and precision of the method was tested by comparing the values of GBW070602. The determination results were found to be basically consistent with the reference values, which means the test result is reliable.

Core-Shell Fiber-Based 2D Woven Triboelectric Nanogenerator for Effective Motion Energy Harvesting.

Personal electronic devices have a general development trend of miniaturization, functionality, and wearability. Their wireless, sustainable, and independent operation is critically important, which requests new power technologies that can harvest the ambient environmental energy. Here, we report a new kind of 2D woven wearable triboelectric nanogenerator (2DW-WTNG) composed of core-shell fibers via the twisting process and weaving process in the textile manufacture. The 2DW-WTNG can convert the body motion energy into electricity with an output current of 575 nA and an output voltage of 6.35 V. At an external load of 50 MΩ, it generated a maximum power density of 2.33 mW/m2. Electricity can be produced from the 2DW-WTNG driven in arbitrary in-plane directions. A tiny displacement of 0.4 mm can drive the 2DW-WTNG, which verified its capability to harvest energy from small human movement. The robust 2DW-WTNG can work continuously for 12 h without obvious performance degradation.

Flexible Self-Powered ZnO Film UV Sensor with a High Response.

Response (on/off ratio) is one of the key parameters of ultraviolet (UV) sensors. In this paper, a kind of highly sensitive ZnO UV sensor with highly increased on/off current ratio was designed and developed. Under a weak UV intensity of 0.1 mW/cm2, this ultrathin ZnO film-based UV sensor has an on/off current ratio of 1.3 × 106 which is 3 times higher than the record value for ZnO-based UV sensors. In addition, it shows good flexibility and stable UV detection property during the bending process. When bending the sensor to a radius of curvature of about 18.5 mm, the sensor also shows high UV detection performance.

Piezoelectric nanofiber/polymer composite membrane for noise harvesting and active acoustic wave detection.

Being one of the most common forms of energy existing in the ambient environment, acoustic waves have a great potential to be an energy source. However, the effective energy conversion of an acoustic wave is a great challenge due to its low energy density and broad bandwidth. In this work, we developed a new piezoelectric nanogenerator (PENG), which is mainly composed of a piece of piezoelectric nanofiber/polymer composite membrane. As an energy harvester, the PENG can effectively scavenge a broad low-frequency (from 50 Hz to 400 Hz) acoustic energy from the ambient environment, and it can even scavenge a very weak acoustic energy with a minimum pressure of only 0.18 Pa. When a drum was used as an excitation source, the maximum open-circuit voltage and short-circuit current density of the PENG reached 1.8 V and 1.67 mA m-2, respectively. In addition, the PENG had a good stability and its output frequency and amplitude were closely related to the driving sound wave, which made the PENG capable of detecting acoustic signals in the living environment and have the potential to be applied as a self-powered active acoustic detector.

Epidemiological survey of hepatitis B and analysis of hepatitis B vaccine coverage rate among children aged 1-14 years in Lhasa in 2006, 2014 and 2020 / 中华预防医学杂志

In 2006, 2014 and 2020, the positive rates of HBsAg in 560, 384 and 402 children aged 1 to 14 years were 4.5%, 2.6% and 2.5%, respectively, with no statistically significant differences (P>0.05). The positive rate of anti-HBs was highest in 2014 (57.8%) and lowest in 2006 (34.1%) (P<0.05). The positive rate of anti-HBc was highest in 2006 (15.7%), and decreased in 2014 (7.8%) and 2020 (5.7%) (P<0.001). The timely rate of the first dose of hepatitis B vaccine for children in Lhasa in 2006, 2014 and 2020 was 7.7% (43/560), 50.3% (193/384) and 94.8% (381/402), respectively. The overall vaccination rates were 15.4% (86/560), 35.2% (135/384) and 96.0% (386/402), respectively, showing a trend of gradual increases (χtrend values were 718.63 and 589.59, both P values<0.001).

[Sodium ion transportation system and its possible mechanisms in bacteria].

Sodium ion with high concentration is toxic to living cells, and microorganisms adapt to the environment containing high concentration of salt by the strategies of salt-in-cytoplasm and compatible solutes. The Na+ extrusion system plays important roles in maintaining cytoplasmic Na+ homeostasis and pH level in microbial cells. Two possible mechanisms of Na+ circulation across the cytoplasmic membrane have been proposed, namely primary Na+ pump and secondary Na+/H+ antiporter. Primary sodium pumps coupled the extrusion of Na+ to respiration, and the activity of which was insensitive to uncoupler CCCP ( carbonyl-cyanide m-chlorophenylhydrazone). There were two types of secondary Na+/H+ antiporters-encoding genes designated single gene and multiple subunits, respectively. The types of transportation systems for Na+, possible mechanisms of Na+ extrusion, and projects for further study in bacteria are reviewed.

[Study progress on compatible solutes in moderately halophilic bacteria].

Moderately halophilic bacteria which grow best in media with 3% to 15% salt constitute a heterogenous group of microorganisms which belong to different genera. These bacteria can inhabit the salt or soda lakes, coastal lagoons or man-made salterns. Moderately halophilc bacteria living in higher saline environments can not only cope with high osmotic stress but also adapt osmotic shock in short time. To adapt to these environments, all the species make a osmoprotection by the accumulation a restricted range of low molecular mass molecules, small, organic compatible solutes, such as sugars, amino acids, betaines and ectoines. Therefore, the osmoadaptation of moderately halophilc bacteria is regulated by the so-called "compatible solute" strategy. Compatible solutes are operationally defined as organic osmolytes that can be amassed by the cell in exceedingly high concentrations without disturbing vital cellular functions and the correct folding of proteins. As a result, compatible solutes can make important contributions to the restoration of the turgor under conditions of low water activity by counteracting the efflux of water from the cell. In addition, they have a stabilizing, both in vivo and vitro, on the native structure of proteins and cell components. This mechanism has a minimal requirement for genetic change and a high degree of flexibility in allowing moderate halophiles to adapt to saline environment. In this review, the adaptation to saline environments, the variety and characteristic of compatible solutes, and the functional mechanism of moderately halophilic bacteria are reviewed and discussed.

Theoretical Study of the BaTiO3 Powder's Volume Ratio's Influence on the Output of Composite Piezoelectric Nanogenerator.

The combination of the piezoelectric materials and polymer is an effective way to make the piezoelectric nanogenerator (PENG) possess both the polymer's good flexibility and ferroelectric material's high piezoelectric coefficient. The volume ratio of ferroelectric material in the composite is an important factor that determines the PENG's output performance. In this paper, the BaTiO3/polydimethylsiloxane (PDMS) composite PENG was demonstrated as having an optimal volume ratio (46%) at which the PENG can output its highest voltage, and this phenomenon can be ascribed to the trade-off between the composite PENG's top electrode charge and its capacitance. These results are of practical importance for the composite PENG's performance optimization.

Ultrasensitive 2D ZnO Piezotronic Transistor Array for High Resolution Tactile Imaging.

In this paper, a new kind of 2D piezotronic transistor (PT) with the highest sensitivity till date has been designed and demonstrated, and the 2DPT array with ultrahigh spatial resolution has been developed through assembling ZnO nanoplatelets into ordered nanoplatelet array. As active sensors by directly converting applied mechanical actuations into electrical control signals without applying gate voltage, the ZnO 2DPT array has a great advantage as a fundamental component of piezotronics. The 2DPT array paves the way for a large-scale and integrated production of two terminal vertical transistors, which will contribute to its application in many fields such as human-machine interfacing, smart sensor, and processor systems.

Ultrasensitive Vertical Piezotronic Transistor Based on ZnO Twin Nanoplatelet.

High sensitivity of pressure/strain sensors is the key to accurately evaluating external mechanical stimuli and could become more important in future generations of human-machine interfaces and artificial skin. Here we report the study of a two-terminal piezotronic transistor based on ZnO twin nanoplatelets (TNPT). Owing to the mirror symmetrical structure of ZnO twin nanplatelet, compressive pressure-induced positive piezoelectric polarization charges created at both metal-semiconductor interfaces can simultaneously lower both Schottky barrier heights and thus significantly modulate the carrier transport. Our device exhibits the highest pressure sensitivity of 1448.08-1677.53 meV/MPa, which is more than ∼20 times larger than the highest value reported previously, and a fast response time of <5 ms. In addition, it can be used as a photodector with an ultrahigh external photoresponsivity of ∼1.45 × 104 AW-1, which is ∼105 times larger in magnitude than that of commercial UV photodetectors. The coupling between the mirror symmetrical structure and strong piezotronic effect in ZnO twin nanoplatelets may enable the development of ultrasensitive pressure/strain sensors for various applications such as artificial skin, health monitoring, and adaptive biomedical probes.