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A synthetic strategy for the controlled construction of plasmonic metal–semiconductor–plasmonic metal ternary heteronanocrystals with multiple plasmonic effects was developed.

A surface-enhanced Raman spectroscopy-based in situ analytical tool for the sensitive and rapid monitoring of hydrogen transport through graphene was developed.

We investigated the heat dissipation in heterostructure field-effect transistors (HFETs) using microRaman measurement of the temperature in active AIGaN/GaN. By varying the gate structure, the heat dissipation through the gate was clearly revealed. The temperature increased to 120 °C at the flat gate device although the inserted gate increased to only 37 °C. Our results showed that the inserted gate structure reduced the self-heating effect by three times compared to the flat gate structure. Temperature mapping using micro-Raman measurement confirmed that the temperature of the near gate area was lower than that of the near drain area. This indicated that the inserted gate electrode structure effectively prohibited self-heating effects.

This article reports GaN super-heterojunction Schottky barrier diodes (SHJ-SBDs) with substantially improved performance. Metal-2DEG sidewall n-ohmic contacts were deployed to achieve low contact resistance of $0.75~\Omega ~ \cdot ~mm$ , avoiding the risk of abnormally high contact resistance caused by inaccurate etch depth control. A pGaN notch formed near the cathode successfully eliminated excessive hole conduction caused by the sidewall n-ohmic contact. Isolation was improved by a high-energy Al implantation step. The resulting SHJ-SBD exhibited a breakdown voltage (BV) of ~12.5 kV and a specific resistance of 100.8 $\text{m}\Omega ~ \cdot ~cm^{2}$ .

We have developed a synthesis method of rhombic dodecahedral Pd@Pt core-shell nanocrystals bound exclusively by {110} facets with controlled numbers of Pt atomic layers to study the surface strain-catalytic activity relationship of Pt{110} facets. Through control over growth kinetics, the epitaxial and conformal overgrowth of Pt shells on the {110} facets of rhombic dodecahedral Pd nanocrystals could be achieved. Notably, the electrocatalytic activity of the Pd@Pt nanocrystals toward oxygen reduction reaction decreased as their Pt shells became thinner and thus more in-plane compressive surface strain was applied, which is in sharp contrast to previous reports on Pt-based catalysts. Density functional theory calculations revealed that the characteristic strain-activity relationship of Pt{110} facets is the result of the counteraction of out-of-plane surface strain against the applied in-plane surface strain, which can effectively impose a tensile environment on the surface atoms of the Pd@Pt nanocrystals under the compressive in-plane strain.

Background: To compare the sensory change and recovery of infraorbital area associated with zygomaticomaxillary and orbital floor fractures and their recoveries and investigate the factors that affect them.Methods: We retrospectively reviewed 652 patients diagnosed with zygomaticomaxillary (n= 430) or orbital floor (n= 222) fractures in a single center between January 2016 and January 2021. Patient data, including age, sex, medical history, injury mechanism, Knight and North classification (in zygomaticomaxillary fracture cases), injury indication for surgery (in orbital floor cases), combined injury, sensory change, and recovery period, were reviewed. The chi-square test was used for statistical analysis.Results: Orbital floor fractures occurred more frequently in younger patients than zygomaticomaxillary fractures (p< 0.001). High-energy injuries were more likely to be associated with zygomaticomaxillary fractures (p< 0.001), whereas low-energy injuries were more likely to be associated with orbital floor fractures (p< 0.001). The sensory changes associated with orbital floor and zygomaticomaxillary fractures were not significantly different (p= 0.773). Sensory recovery was more rapid and better after orbital floor than after zygomaticomaxillary fractures; however, the difference was not significantly different. Additionally, the low-energy group showed a higher incidence of sensory changes than the high-energy group, but the difference was not statistically significant (p= 0.512). Permanent sensory changes were more frequent in the high-energy group, the difference was statistically significant (p= 0.043).Conclusion: The study found no significant difference in the incidence of sensory changes associated with orbital floor and zygomaticomaxillary fractures. In case of orbital floor fractures and high-energy injuries, the risk of permanent sensory impairment should be considered.

Nanomaterials with core-shell architectures are prominent examples of strain-engineered materials. The lattice mismatch between the core and shell materials can cause strong interface strain, which affects the surface structures. Therefore, surface functional properties such as catalytic activities can be designed by fine-tuning the misfit strain at the interface. To precisely control the core-shell effect, it is essential to understand how the surface and interface strains are related at the atomic scale. Here, we elucidate the surface-interface strain relations by determining the full 3D atomic structure of Pd@Pt core-shell nanoparticles at the single-atom level via atomic electron tomography. Full 3D displacement fields and strain profiles of core-shell nanoparticles were obtained, which revealed a direct correlation between the surface and interface strain. The strain distributions show a strong shape-dependent anisotropy, whose nature was further corroborated by molecular statics simulations. From the observed surface strains, the surface oxygen reduction reaction activities were predicted. These findings give a deep understanding of structure-property relationships in strain-engineerable core-shell systems, which can lead to direct control over the resulting catalytic properties.

Odor is usually a complex mixture of various compounds. In many countries, odor complaints have been addressed using the air dilution olfactory method (ADOM) to reduce their malodor complaint. In this study, continuous monitoring of ammonia, hydrogen sulfide, and total volatile organic compounds (TVOC) using sensors was conducted in facilities for municipal and livestock wastewater treatment (LWT), and for food waste composting (FWC). Odor intensity was modeled by multivariate linear regression using sensor monitoring data with air dilution measured by the ADOM. In testing the performance of sensors in the lab, all three sensors showed acceptable values for linearity, accuracy, repeatability, lowest detection limit, and response time, so the sensors were acceptable for application in the field. In on-site real-time monitoring, the three sensors functioned well in the three environmental facilities during the testing period. Average ammonia and hydrogen sulfide concentrations were high in the LWT facility, while TVOC showed the highest concentration in the FWC facility. A longer sampling time is necessary for ammonia monitoring. Odor intensity from individual sensor data correlated well to complex odor measured by the ADOM. Finally, we suggest a protocol for field application of sensor monitoring and odor data reproduction.

The rational design and synthesis of multimetallic hollow nanostructures (HNSs) have been attracting great attention due to their structural and compositional advantages for application in electrocatalysis. Herein, the one-pot synthesis of Pd-Pt-Ag ternary alloy HNSs with controllable morphologies through a self-templating approach without any pre-synthesized templates is reported. Simultaneous reduction of multiple metal precursors by ascorbic acid in the presence of cetyltrimethylammonium chloride (CTAC) yielded initially metastable Pd-Ag nanocrystals, which can act as a self-template, and subsequent galvanic replacement and reduction led to the formation of final Pd-Pt-Ag HNSs. The size and hollowness (the ratio of inner cavity diameter to outer diameter) of the HNSs could be tuned through control over the concentration of CTAC. This can be attributed to the manipulated reduction kinetics of multiple metal precursors with the change in the CTAC concentration. The prepared Pd-Pt-Ag HNSs exhibited improved catalytic performance for ethanol electro-oxidation due to their large active surface areas and ternary alloy composition.

Aminotransferases (ATs) are pyridoxal 5'-phosphate-dependent enzymes that catalyze the transamination reactions between amino acid donor and keto acid acceptor substrates. Modern AT enzymes constitute ∼2% of all classified enzymatic activities, play central roles in nitrogen metabolism, and generate multitude of primary and secondary metabolites. ATs likely diverged into four distinct AT classes before the appearance of the last universal common ancestor and further expanded to a large and diverse enzyme family. Although the AT family underwent an extensive functional specialization, many AT enzymes retained considerable substrate promiscuity and multifunctionality because of their inherent mechanistic, structural, and functional constraints. This review summarizes the evolutionary history, diverse metabolic roles, reaction mechanisms, and structure-function relationships of the AT family enzymes, with a special emphasis on their substrate promiscuity and multifunctionality. Comprehensive characterization of AT substrate specificity is still needed to reveal their true metabolic functions in interconnecting various branches of the nitrogen metabolic network in different organisms.

Varistors are technologically important for their large energy handling capabilities and highly nonlinear electrical behavior when voltages above a characteristic switch field are applied. It is generally accepted that the prototypical ZnO–Bi2O3 varistor system forms electrostatic Schottky barriers at grain boundaries in response to residual Bi and other dopants left at grain surfaces during Bi2O3 segregation. While barrier heights can be modulated with formulation and defect chemistry, mechanisms by which dopant locations, defect compensation, and local phases determine varistor behavior are not completely understood. Bulk studies are challenging due to random grain boundary formation and difficulties studying individual boundaries. To circumvent these challenges in the ZnO–Bi2O3 varistor system, we use as-deposited and post-heat-treated thin film ZnO–Bi2O3 prototypes to simulate bulk varistor grain boundary phase formation and investigate resulting defect chemistry. Characterizing interactions between Bi2O3 films deposited on thin film and single-crystal ZnO by XRD and TEM-EDS revealed primarily Zn-out diffusion, resulting in two (Bi2O3)1−x(ZnO)x, or BZO, phases. Using these results, we present a saturated front model correlating changes in Bi2O3 thickness to phase evolution. We subsequently explore the influence of MnO doping leading to substantial changes in phase evolution for post-heat-treated (Mn:ZnO)–Bi2O3 stacks. Dopant-controlled Bi2O3 phase formations yield a 12 × difference, on average, between nonlinear coefficients for γ*- and β*-BZO.

Sophorolipids (SLs) from Candida batistae has a unique structure that contains ω-hydroxy fatty acids, which can be used as a building block in the polymer and fragrance industries. To improve the production of this industrially important SLs, we optimized the culture medium of C. batistae for the first time. Using an optimized culture medium composed of 50 g/L glucose, 50 g/L rapeseed oil, 5 g/L ammonium nitrate and 5 g/L yeast extract, SLs were produced at a concentration of 24.1 g/L in a flask culture. Sophorolipids production increased by about 19% (28.6 g/L) in a fed-batch fermentation using a 5 L fermentor. Sophorolipids production more increased by about 121% (53.2 g/L), compared with that in a flask culture, in a fed-batch fermentation using a 50 L fermentor, which was about 787% higher than that of the previously reported SLs production (6 g/L). These results indicate that a significant increase in C. batistae-derived SLs production can be achieved by optimization of the culture medium composition and fed-batch fermentation. Finally, we successfully separated and purified the SLs from the culture medium. The improved production of SLs from C. batistae in this study will help facilitate the successful development of applications for the SLs.

In this study, we investigate the effects of the purification of carbon nanotube (CNT) fibers on their mechanical and electrical properties and, more importantly on the efficiencies of various surface modifications. Even though the purification dominantly works on the surface of CNT fibers, the specific tensile strength and electrical conductivity of CNT fibers are enhanced from 0.50 N tex−1 and 932 S cm−1 to 0.91 N tex−1 and 5158 S cm−1 by the restoration of their defect structures and improvement of their alignment and density. Furthermore, the efficiencies of their surface modifications through both covalent and non-covalent approaches are greatly improved. Au nanoparticles are far more densely grown on the purified CNT fibers than as spun CNT fibers. The resulting Au/CNT nanocomposite fibers exhibit improved mechanical and physical properties, and possibility to be applied as a fibrous catalyst.

Biogenic amines are important messengers in neurotransmission, drawing attention to pharmaceutical applications. Here, we developed a novel biocatalytic process for the preparation of biogenic amines using aromatic l-amino acid decarboxylase (AADC) under an in situ product removal (ISPR) condition. The AADC from Bacillus atrophaeus (AADC-BA) showed broad substrate specificity for aromatic amino acids, affording > 90% conversions of 10 mM substrates to corresponding products: 2-phenylethylamine (2-PEA), tryptamine, serotonin, and dopamine. Owing to enzyme inhibitions by the reaction products, we implemented an ISPR strategy using a cation exchange resin and an open reactor system for removal of amine and CO2, respectively. Under the open-air conditions, the addition of Dowex 50WX8 afforded 81% conversion of 100 mM l-phenylalanine to 2-PEA within 1 h, whereas 56% conversion was obtained without the resin. The ISPR strategy enabled the preparative-scale production of serotonin from 5-hydroxy-l-tryptophan (405 mg), yielding > 99% conversion within 40 min.

Aromatic L-amino acid decarboxylases (AADCs) catalyze the conversion of aromatic L-amino acids into aromatic monoamines that play diverse physiological and biosynthetic roles in living organisms. For example, dopamine and serotonin serve as major neurotransmitters in animals, whereas tryptamine and tyramine are essential building blocks for synthesizing a myriad of secondary metabolites in plants. In contrast to the vital biological roles of AADCs in higher organisms, microbial AADCs are found in rather a limited range of microorganisms. For example, lactic acid bacteria are known to employ AADCs to achieve intracellular pH homeostasis and engender accumulation of tyramine, causing a toxic effect in fermented foods. Owing to the crucial pharmaceutical implications of aromatic monoamines and their derivatives, synthetic applications of AADCs have attracted growing attention. Besides, recent studies have uncovered that AADCs of human gut microbes influence host physiology and are involved in drug availability of Parkinson's disease medication. These findings bring the bacterial AADCs into a new arena of extensive research for biomedical applications. Here, we review catalytic features of AADCs and present microbial applications and challenges for biotechnological exploitation of AADCs. KEY POINTS: • Aromatic monoamines and their derivatives are increasingly important in the drug industry. • Aromatic L-amino acid decarboxylases are the only enzyme for synthesizing aromatic monoamines. • Microbial applications of aromatic L-amino acid decarboxylases have drawn growing attention.

Hollow, microrod-like Pt nanostructures are locally synthesized on a small, suspended microheater platform (9 μm × 110 μm) as the catalytic layer of a low-power hydrogen (H2) catalytic combustion s...

This letter reports an experimental demonstration of charge-balanced GaN super-heterojunction Schottky barrier diodes (SHJ-SBDs). Charge balance between the n-type delta-doping and the p-type doping was achieved by adjusting the thickness of the pGaN. This device structure enabled scaling of breakdown voltage to over 3 kV, and dynamic switching up to 2.8 kV without using any field-plate.

Advances in the DNA nanotechnology have enabled the fabrication of DNA-based hydrogels with precisely controlled structures and tunable mechanical and biological properties. Compared to DNA hydrogel, preparation of RNA-based hydrogel remains challenging due to the inherent instability of naked RNA. To overcome these limitations, we fabricated a DNA-RNA hybrid hydrogel via stepwise dual enzymatic polymerization. Multimeric short hairpin RNAs (shRNAs) were hybridized with functional DNA aptamers for targeting and mechanical properties of the hydrogel. The obtained DNA-RNA hybrid hydrogel was ultrasoft, robust, and injectable hence reconfigurable into any confined structures. As a model system, the hydrogel was able to mimic microtubule structures under physiological conditions and designed to release the functional small interfering RNA (siRNA)-aptamer complex (SAC) sequentially. In addition, we encoded restriction enzyme-responsive sites in DNA-RNA hybrid hydrogel to boost the release of SAC. This novel strategy provides an excellent platform for systematic RNA delivery through double-controlled release, SAC release from hydrogel, and subsequent release of siRNA from the SAC, which has promising potential in RNA therapy.

A potential method to tune reactivity In organic chemistry, reaction rates are often sensitive to substituents that either donate or withdraw electron density from a reactive carbon center. Heo et al. now report that when reactants are tethered to an electrode, the polarization effect of an applied potential can exert an analogous influence, essentially acting as a tunable functional group. The authors demonstrate rate modulations in ester hydrolysis and arene cross-coupling, as well as a two-step acid-to-amide conversion that benefits from inversion of the polarization midway through the reaction. Science , this issue p. 214

NAND flash-based storage devices (NFSDs) have been widely employed in various systems, including cloud servers as well as mobile devices. The core component of NFSDs is NAND flash memory (NFM) which has several advantages over the conventional hard disk drives (HDDs). An NFSD typically adopts a bunch of NFMs which are operated in parallel for maximizing the I/O throughput. However, optimizing for performance may not be desirable from the power budget (PB) perspective. In other words, concurrent operations of NFMs often drain inordinate current, which leads to the violation of the PB allocated for a storage device. In this article, we propose a novel power management scheme which maximizes concurrent operations of NFMs under the given power constraint. The proposed method quantizes the given power constraint of an NFSD. A quantum also called token is the basic unit of power management. The proposed power management scheme allocates tokens to NFMs and only the NFMs having enough tokens can perform their operations. We call this method multitoken-based power management (MTPM). The critical issue of MTPM is a deadlock which is resolved with the key allocation scheme. Furthermore, we enhance MTPM to improve performance. The extended method called keyless MTPM (KMTPM) improves the overall performance by relaxing the key acquisition requirement and allowing subatomic operations. In the experimental results, we confirm that the proposed methods always meet the given power constraint. The proposed KMTPM improves throughput by 22.85% compared to state of the art technique. In addition, KMTPM only incurs 3.8% of performance overhead and 0.015% of area overhead.

Toxin-antitoxin (TA) systems have been considered essential factors for bacterial survival. During our drug development program aimed against tuberculosis (TB), we discovered certain peptides that mimic the binding of the VapBC30 complex, leading to the arrest of bacterial cell growth and eventually cell death. Herein, we optimized these candidate peptides based on a hydrocarbon stapling strategy and performed biological in vitro evaluations. The V30-SP-8 peptide successfully penetrated Mycobacterium smegmatis cell membranes and exerted bactericidal activity at a minimum inhibitory concentration that inhibited 50% of the isolates (MIC50) < 6.25 μM. With the aid of structural and biochemical information for the VapBC30 TA system from M. tuberculosis, we suggest potential antimicrobial agents that could provide a platform to establish a novel antibacterial strategy. Reflecting the limited number of therapeutic agents targeting TA systems, we believe that this study not only provides chemical tools for exploring the biological events relevant to TA systems but also opens a new gateway toward TB drug discovery.

From simple 2-dimensional (2D) structures to highly complex 3-dimensional (3D) structures, DNA is widely used as a building block material. Despite this advancement, mass production of DNA nanostructures was a challenge due to the high cost that accompanies the preparation of diverse DNA strands. Rolling circle amplification (RCA) is one of the cost-effective methods for the mass production of repetitive DNA structures without using an expensive laboratory thermal cycler. Here, we report a DNA hydrogel containing various single-stranded DNA nanostructures (Y, X, Tetrahedron) in a one-pot system, prepared by RCA, and their selective separation with various restriction enzymes. Each DNA nanostructure in the DNA hydrogel contained distinctive restriction sites that were responsive to different kinds of restriction enzymes, achieving selective separation of Y-, X- and Tetrahedron-shaped DNA structures. This study has the potential to contribute towards DNA-based biomedical applications by employing mass production and precisely controlled release of DNA nanostructures.

Devising efficient routes to realize hybrid materials consisting of intimately coupled metal nanocatalysts and nonstoichiometric metal oxides with finely controlled configurations is highly desirable to develop advanced fuel cell catalysts. Here, we report a facile one-pot synthesis strategy for the formation of closely coupled metal (PtNi alloy)–metal oxide (CeOx, ceria) hybrid nanostructures. Heating an oleylamine/oleic acid solution of mixed metal (Pt, Ni, and Ce) precursors yielded well-defined PtNi/ceria hybrids, in which PtNi alloy nanodendrites with multiple branches are well dispersed on small-grained ceria nanosheets. Due to their small grain size, the ceria nanosheets in the hybrids contain abundant oxygen vacancies and have high conductivity. The prepared PtNi/ceria hybrids exhibited outstanding electrocatalytic activity and stability toward both methanol oxidation and oxygen reduction reactions in comparison to their carbon-supported counterparts and a commercial catalyst, which can be attributed to the synergistic effects of the Ni component and ceria on the enhancement of the electrocatalytic function. The current strategy will find use in the design of optimal multicomponent catalysts for target reactions.

We present a systematic study on the design of a novel GaN/AlGaN/GaN super-heterojunction Schottky diode. Through physics-based TCAD simulation, we discuss three important design aspects: 1) how to design a GaN/AlGaN/GaN structure to form a high-density 2-D electron gas and to scale it to multiple vertically stacked channels with less risk in reaching the critical thickness limited by the strain in epitaxy; 2) how to reach charge balance and how sensitive is the breakdown voltage with respect to the doping imbalance; and 3) how to ensure that the processes of depleting and accumulating electrons and holes in the structure are fast enough for practical power switching applications.