Rational Surfaces Research Articles

Rational surface charge engineering of haloalkane dehalogenase for boosting the enzymatic performance in organic solvent solutions

Biocatalysis in organic solvents (OSs) has numerous important applications, but native enzymes in OSs often exhibit limited catalytic performance. Herein, we proposed a computation-aided surface charge engineering strategy to improve the catalytic performance of haloalkane dehalogenase DhaA in OSs based on the energetic analysis of substrate binding to the DhaA surface. Several variants with enhanced OS resistance were obtained by replacing negative charged residues on the surface with positive charged residue (Arg). Particularly, a four-substitution variant E16R/E93R/E121R/E257R exhibited the best catalytic performance (five-fold improvement in OS resistance and seven-fold half-life increase in 40% (vol) dimethylsulfoxide). As a result, the overall catalytic performance of the variant could be at least 26 times higher than the wild-type DhaA. Fluorescence spectroscopy and molecular dynamics simulation studies revealed that the residue substitution mainly enhanced OS resistance from four aspects: (a) improved the overall structural stability, (b) increased the hydrophobicity of the local microenvironment around the catalytic triad, (c) enriched the hydrophobic substrate around the enzyme molecule, and (d) lowered the contact frequency between OS molecules and the catalytic triad. Our findings validate that computation-aided surface charge engineering is an effective and ingenious rational strategy for tailoring enzyme performance in OSs.

Efficient computation of moving planes for rational parametric surfaces with base points using Dixon resultants

Moving planes have been widely recognized as a potent algebraic tool in various fundamental problems of geometric modeling, including implicitization, intersection computation, singularity calculation, and point inversion of parametric surfaces. For instance, a matrix representation that inherits the key properties of a parametric surface is constructed from a set of moving planes. In this paper, we present an efficient approach to computing such a set of moving planes that follow the given rational parametric surface. Our method is based on the calculation of Dixon resultant matrices, which allows for the computation of moving planes with simpler coefficients, improved efficiency and superior numerical stability when compared to the direct way of solving a linear system of equations for the same purpose. We also demonstrate the performance of our algorithm through experimental examples when applied to implicitization, surface intersection, singularity computation as well as inversion formula computation.

Numerical calculation for instability criterion of tearing modes influenced by energetic ions

The instability criterion of tearing modes, including the effects of circulating energetic ions (CEIs), is numerically solved through an iterative method and fast Fourier transform algorithm. The influence of beta (the ratio of pressure to the magnetic pressure) profile of CEIs and magnetic shear on instability criterion of the tearing modes are investigated systematically. CEIs impact the tearing modes through altering the total perturbed parallel current density, and the gradient of their beta profile at the rational surface (the location of tearing mode) plays an important role. The effect of CEIs on tearing modes depends on the deposition position and the toroidal circulating direction of CEIs. Specifically, the on-axis peaked co-CEIs have a stabilizing effect on tearing modes. For off-axis peaked co-CEIs, in order to stabilize the tearing modes, the deposition position of co-CEIs should be located between the magnetic axis and rational surface, and there is an optimal peak width and deposition location where the stabilizing effect is strongest. For counter-CEIs, they would destabilize the tearing modes when the deposition position is located between the magnetic axis and rational surface. However, if the deposition position is located near the outside rational surface, counter-CEIs have a stabilizing effect on tearing modes. Furthermore, there exists a critical deposition position for CEIs. Whether CEIs plays a stable role or an unstable role depends on the deposition position within or outside the critical deposition position. The critical deposition position is related to the orbital width of CEIs. Finally, the magnetic shear can stabilize the tearing modes, but the effect of co-CEIs on tearing modes is weakened as the magnetic shear increases.

Fano's last Fano

In 1949, Fano published his last paper on 3 -folds with canonical sectional curves. There, he constructed and described a 3 -fold of degree 22 in a projective space of dimension 13 with canonical curve section, which we like to call Fano's last Fano . We report on Fano's construction and we provide various (in our opinion missing) proofs in modern language. Moreover, we try to use results and techniques available at that time. After that we construct Fano's last Fano with modern tools, in particular, via the Hilbert scheme of zero cycles on a rational surface; as a consequence we easily point out the corresponding example in the Mori–Mukai classification.

Real forms on rational surfaces

Real forms on rational surfaces

Hollow Plasmonic P-Metal-N S-Scheme Heterojunction Photoreactor with Spatially Separated Dual Cocatalysts toward Artificial Photosynthesis.

Semiconductor-based step-scheme (S-scheme) heterojunctions possess many merits toward mimicking natural photosynthesis. However, their applications for solar-to-chemical energy conversion are hindered by inefficient charge utilization and unsatisfactory surface reactivity. Herein, two synergistic protocols are demonstrated to overcome these limitations based on the construction of a hollow plasmonic p-metal-n S-scheme heterojunction photoreactor with spatially separated dual noble-metal-free cocatalysts. On one side, plasmonic Au, inserted into the heterointerfaces of CuS@ZnIn2 S4 core-shell nanoboxes, not only accelerates the transfer and recombination of useless charges, enabling a more thorough separation of useful ones for CO2 reduction and H2 O oxidation but also generates hot electrons and holes, respectively injects them into ZnIn2 S4 and CuS, further increasing the number of active carriers participating in redox reactions. On the other side, Fe(OH)x and Ti3 C2 cocatalysts, separately located on the CuS and ZnIn2 S4 surface, enrich the redox sites, adjust the reduction potential and pathway for selective CO2 -to-CH4 transformation, and balance the transfer and consumption of photocarriers. As expected, significantly enhanced activity and selectivity in CH4 production are achieved by the smart design along with nearly stoichiometric ratios of reduction and oxidation products. This study paves the way for optimizing artificial photosynthetic systems via rational interfacial channel introduction and surface cocatalyst modification.

Designing anti(-bio)fouling membranes with synergistic grafting of quaternized and zwitterionic polymers through surface initiated atom transfer radical polymerization

Membrane-based filtration technologies have significant potential to address the global problem of freshwater scarcity. However, fouling, caused by nonspecific adsorption of foulants and microbiological growth during filtration, remains a considerable concern. To address this, a rational surface design method comprising bifunctional coating with both defensive and attacking techniques has been devised, which can successfully decrease fouling and biofouling. To generate a bifunctional membrane, a single-step surface-initiated atom-transfer radical polymerization (SI-ATRP) of monomers with zwitterionic and quaternized imidazolium moieties was done on a polydopamine (PDA) primed polyvinylidene fluoride (PVDF) membrane. The PDA layer’s catechol functionalities provided abundant anchoring sites, allowing the grafting of a dense polymer layer on the membrane. The addition of active zwitterionic and quaternized imidazolium moieties in the grafted polymer chains resulted in very low fouling and microbiological species death. Extensive antifouling studies revealed that the functionalized membranes have excellent flux recovery (>93%), low irreversible fouling (<8.5%), and long-term filtration stability. This surface functionalization strategy based on a bifunctional unit represents a significant advancement in fouling mitigation by minimizing membrane-foulant interactions and killing adhered bacteria, with the potential to significantly broaden the range of membrane-based filtration applications and contribute to more efficient and sustainable water purification processes.

Glucose Oxidase Loading in Ordered Porous Aluminosilicates: Exploring the Potential of Surface Modification for Electrochemical Glucose Sensing.

Enzymatic electrochemical sensors have become the leading glucose detection technology due to their rapid response, affordability, portability, selectivity, and sensitivity. However, the performance of these sensors is highly dependent on the surface properties of the electrode material used to store glucose oxidase and its ability to retain enzymatic activity under variable environmental conditions. Mesoporous thin films have recently attracted considerable attention as promising candidates for enzyme storage and activity preservation due to their well-defined nanoarchitecture and tunable surface properties. Herein, we systematically compare pathways for the immobilization of glucose oxidase (GOx) and their effectiveness in electrochemical glucose sensing, following modification protocols that lead to the electrostatic attraction (amino functionalization), covalent bonding (aldehyde functionalization), and electrostatic repulsion (oxygen plasma treatment) of the ordered porous aluminosilicate-coated electrodes. By direct comparison using a quartz crystal microbalance, we demonstrate that glucose oxidase can be loaded in a nanoarchitecture with a pore size of ∼50 nm and pore interconnections of ∼35 nm using the native aluminosilicate surface, as well as after amino or aldehyde surface modification, while oxygen plasma exposure of the native surface inhibits glucose oxidase loading. Despite a variety of routes for enzyme loading, quantitative electrochemical glucose sensing between 0 and 20 mM was only possible when the porous surface was functionalized with amino groups, which we relate to the role of surface chemistry in accessing the underlying substrate. Our results highlight the impact of rational surface modification on electrochemical biosensing performance and demonstrate the potential of tailoring porous nanoarchitecture surfaces for biosensing applications.

Error-field penetration thresholds in ohmically heated ITER and SPARC plasmas

The critical n = 1, n = 2, and n = 3 error-field amplitudes needed to trigger error-field penetration in ITER and SPARC, steady-state, ohmically heated plasmas are calculated using a standard asymptotic matching approach. The calculation incorporates plasma impurities, trapped particles, the bootstrap current, and neoclassical poloidal flow-damping. The energy confinement time is specified by the neo-Alcator scaling law in the low-density linear Ohmic confinement (LOC) regime and by the ITER-89P L-mode scaling law in the high-density saturated Ohmic confinement (SOC) regime. The response of the plasma in the inner region is calculated using a linearized version of the four-field model. At the normal operating electron number density, diamagnetic levels of rotation are found to be sufficient to protect ITER and SPARC ohmically heated plasmas from m=2/n=1 error-field penetration. On the other hand, SPARC, and especially ITER, ohmically heated plasmas may be vulnerable to n &amp;gt; 1 error-field penetration. ITER and SPARC ohmically heated plasmas are also slightly more susceptible to error-field penetration when the electron fluid at the rational surface rotates in the ion diamagnetic direction, rather than the electron diamagnetic direction. At electron number densities that are sufficiently low that the plasma lies in the LOC confinement regime, the error-field penetration threshold increases with increasing density. However, as soon as the electron number density becomes large enough that the plasma enters the SOC regime, the increase in the error-field penetration threshold with increasing density levels off.

The effect of pellet injection on turbulent transport in TJ-II

An improvement in confinement associated with the injection of pellets has been observed in TJ-II and other devices. By means of a simple model, we study here the modification of turbulent transport by the injection of pellets in TJ-II and how this modification affects the particle confinement time. The analysis of the results shows the relationship of the confinement improvement with the evolution of the shear flow due to turbulence, especially near low order rational surfaces. This work is based on pellet injections into the neutral beam injection heated phase of TJ-II plasmas. For this, single, double, or triple hydrogen pellet injection are considered and the post-injection evolution of selected plasma parameters are analyzed and compared.

The influence of electron cyclotron resonance heating on ion-driven fishbone instability

The effect of electron cyclotron resonance heating (ECRH) on fishbone instability is studied based on the generalized energy principle. Off-axis ECRH plays a stabilizing role in fishbone instability, while on-axis ECRH does not distinctly change the growth rate. The frequency of fishbone instability increases (decreases) for off-axis (on-axis) ECRH. The effect of ECRH is greatest when power is deposited near the rational surface. More concentrated power deposition has a better stabilizing effect. Furthermore, the non-resonance effect of trapped energetic electrons is the main factor behind the stabilization effect in the off-axis case, while it has a weak effect in the on-axis case. The frequency of fishbone instability is changed mainly by the Shafranov shift effect on trapped energetic ions since it can change the precessional drift frequency. The Shafranov shift effect can also affect the growth rate because the onset threshold of energetic ion beta is related to the frequency. The effects of magnetic Reynolds number and slowing-down critical energy are weak and can be neglected. This provides the possibility of using off-axis ECRH targeted to the rational surface to control fishbone instability.

Rainbow-Colored Carbon Nanotubes via Rational Surface Engineering for Smart Visualized Sensors.

Surface engineering is effective for developing materials with novel properties, multifunctionality, and smart features that can enable their use in emerging applications. However, surface engineering of carbon nanotubes (CNTs) to add color properties and functionalities has not been well established. Herein, a new surface engineering strategy is developed to achieve rainbow-colored CNTs with high chroma, high brightness, and strong color travel for visual hydrogen sensing. This approach involved constructing a bilayer structure of W and WO3 on CNTs (CNT/W/WO3 ) and a trilayer structure of W, WO3 , and Pd on CNTs (CNT/W/WO3 /Pd) with tunable thicknesses. The resulting CNT/W/WO3 composite film exhibits a wide range of visible colors, including yellow, orange, magenta, violet, blue, cyan, and green, owing to strong thin-film interference. This coloring method outperforms other structural coloring methods in both brightness and chroma. The smart CNT/W/WO3 /Pd films with porous characteristics quickly and precisely detectthe hydrogen leakage site. Furthermore, the smart CNT/W/WO3 /Pd films allow a concentration as low as 0.6% H2 /air to be detected by the naked eye in 58 s, offering a very practical and safe approach for the detection and localization of leaks in onboard hydrogen tanks.

Mechanochemically synthesized Mn3O4@β-cyclodextrin mediates efficient electron transfer process for peroxymonosulfate activation

The rational surface engineering of heterogeneous catalysts is of great significance in advanced oxidation processes (AOPs) for eliminating refractory contaminants but remains challenging. In this study, β-cyclodextrin modified Mn3O4 (Mn3O4@β-CD) was prepared through a mechanochemical approach for peroxymonosulfate (PMS) activation, which achieved efficient bisphenol A (BPA) removal via electron transfer process (ETP). The reactive PMS* complex with elevated potential was identified to dominate the ETP by withdrawing electrons from BPA with Mn3O4@β-CD working as electron shuttle, as evidenced by spectroscopy and electrochemical techniques. Experimental results and density functional theory (DFT) calculations showed that the β-CD modification enhanced the interfacial accumulation of pollutants and shortened the migration distance between pollutants (electron donor) and catalysts (electron shuttle) to mediate electron transfer more effectively. Benefitting from the improved ETP, the Mn3O4@β-CD/PMS system showed efficient PMS utilization and practical adaptability in actual waterbodies. This study provides a rational approach for modulating the surface structure of heterogeneous catalysts in PMS-based AOPs for environmental remediation.

Extension of ELM suppression window using RMPs in EAST

The q 95 window for Type-I edge localized modes (ELMs) suppression using n = 4 even parity resonant magnetic perturbations (RMPs) has been significantly expanded to the ranges [3.9, 4.1] and [4.2, 4.8] in EAST while maintaining good confinement, which is demonstrated to be reliable and repeatable over the last two years. This window is significantly wider than the previous one achieved using n = 4 odd parity RMPs, which is around . Here, n represents the toroidal mode number of the applied RMPs and q 95 is the safety factor at of the normalized poloidal magnetic flux. During ELM suppression, there is only a slight drop in the plasma stored energy and density (). The comparison of changes in the pedestal profiles suggests that ELM suppression is achieved when the pedestal gradient is kept lower than a threshold. This wide q 95 window for ELM suppression is consistent with the prediction made by MARS-F modeling prior to the experiment, which located it at one of the resonant q 95 windows for plasma response. The Chirikov parameter taking into account plasma response near the pedestal top, which measures plasma edge stochasticity, significantly increases when q 95 exceeds 4, mainly due to the denser neighboring rational surfaces. The modeling of plasma response reveals a strong coupling between resonant and non-resonant components across the pedestal region, which is a characteristic of the kink-peeling like response observed during RMP-ELM suppression in previous studies on EAST. These promising results demonstrate the reliability of ELM suppression using the n = 4 RMPs in EAST and expand the physical understanding on ELM suppression mechanism.

Direct preemptive stabilization of m,n=2,1 neoclassical tearing modes by electron cyclotron current drive in the DIII-D low-torque ITER baseline scenario

We report the first preemptive direct stabilization of m,n=2,1 neoclassical tearing modes (NTMs) in DIII-D low-torque ITER baseline scenario plasmas by electron cyclotron waves. These experiments strongly support that the observed stabilization is achieved by replacing the missing bootstrap current in the island by electron cyclotron current drive (ECCD). These plasmas (with and without ECCD) are stable to 2,1 NTMs when the differential rotation between the q = 1 and q = 2 surfaces ( Δf1,2 ) is sustained above a critical value ( ΔfCRIT≈1 kHz), but those evolving to low differential rotation ( Δf1,2<ΔfCRIT ) routinely develop a disruptive 2,1 island at the time and frequency of a sawtooth precursor. Preemptive, local and direct stabilization by ECCD is tested by scanning the current drive amplitude and location inside and outside of the q = 2 rational surface shot by shot. Analysis of only low differential rotation time windows, i.e. when stabilization from Δf1,2 is absent, shows focused ECCD at q = 2 prevents the onset of 2,1 NTMs. These results are important, as they give the first demonstration of disruptive NTM control by ECCD in the plasma scenario planned for ITER.

Effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes in tokamak plasmas with reversed magnetic shear

Effects of plasma radiation on the nonlinear evolution of neo-classical double tearing modes (NDTMs) in tokamak plasmas with reversed magnetic shear are numerically investigated based on a set of reduced magnetohydrodynamics (MHD) equations. Cases with different separations Δ rs = |r s2–r s1| between the two same rational surfaces are considered. In the small Δ rs cases, the plasma radiation destabilizes the NDTMs and makes the kinetic energy still grow gradually in the late nonlinear phase. Moreover, the NDTM harmonics with high mode numbers reach a high level in the presence of plasma radiation, forming a broad spectrum of MHD perturbations that induces a radially broadened region of MHD turbulence. As a result, the profiles of safety factors also enter a nonlinear oscillation phase. In the intermediate Δ rs case, the plasma radiation can advance the explosive burst of kinetic energy that results from the fast driven reconnection between the two rational surfaces, because it can further promote the destabilizing effects of bootstrap current perturbation on the magnetic island near the outer rational surfaces. In the large Δ rs case, through destabilizing the outer islands significantly, the plasma radiation can even induce the explosive burst in the reversed magnetic shear configuration where the burst cannot be induced in the absence of plasma radiation.

Reduction of the external resonant magnetic perturbation threshold for 2/1 locked mode excitation by the pre-excited mode on J-TEXT

A significant reduction of the external resonant magnetic perturbation (RMP) required for exciting the locked mode (LM) has been observed experimentally due to the presence of an existing LM on J-TEXT. In a plasma with edge safety factor q a slightly smaller than 3, 3/1 and 2/1 modes are observed to be destabilized successively by a rotating RMP field. The 3/1 mode is excited first and identified as an external kink mode, whose excitation threshold decreases with the operating q a increasing from 2.67 to 2.8 with the absence of a 3/1 rational surface. Shortly after excitation of the 3/1 external kink mode, 2/1 field penetration occurs and the 2/1 mode is excited, as identified by the phase between the 2/1 magnetic response and the RMP field jumping by π. The 2/1 mode is excited with a dominant kink structure and then converts into tearing mode for a duration of several milliseconds. During the excitation of the 2/1 mode, the phase difference between the 2/1 and 3/1 modes evolves from π to around 0 and the 2/1 mode amplitude grows to a saturation value comparable with that of the 3/1 mode. The presence of the 3/1 mode leads to a remarkable reduction of the external RMP current required for the 2/1 mode excitation, which can be explained by the contribution of a 2/1 resonant field from the 3/1 mode via the toroidal coupling effect. The larger 3/1 mode amplitude can lead to a greater reduction. This work reveals that the mode can be excited more easily with a reduced amplitude of RMP or error field due to the impact of the pre-existing mode and this might be a new consideration for error field correlation predictions and active magnetohydrodynamics control actuator designs.

Engineering the surface of Nbn+1CnTx MXenes to versatile bio-activity towards microorganisms

Two-dimensional (2D) transition metal carbides/nitrides (MXenes) are potential antibacterial agents. However, their activity against microorganisms is not fully understood. It could relate to MXenes' surface which further influences their biocidal action. Herein, we report no continuous biocidal activity for delaminated 2D niobium-based MXenes (Nbn+1XnTx) such as Nb2CTx and Nb4C3Tx prepared with HF/TMAOH protocol. Biocidal activity towards Bacillus subtilis and Staphylococcus aureus microorganisms was achieved by surface-functionalization with lysozyme macromolecule. MXenes' engineering with lysozyme changed MXene's surface charge from negative into positive thus enabling the elimination of bacteria cells during 48 h of incubation. In contrast, Nb4C3Tx functionalized with collagen stimulated the growth of Bacillus subtilis by 225 %, showing MXene's biocompatibility towards this particular strain. Altogether, our results show that MXenes are incredibly bio-tunable. Opposing bio-effects such as antimicrobial or growth-stimulating can be achieved towards various microorganisms with rational surface engineering.

Surface treatment of inorganic modifier for improving carbonation resistance of geopolymers

Geopolymer (GP) is a low-carbon binder with the potential to replace Portland cement in reinforced concrete, however, the risk of corrosion to reinforced steel bars due to its low carbonation resistance must be addressed. This study proposed the use of an inorganic surface modifier, sodium aluminate solution (AN), to improve the carbonation resistance of GP. The effects of AN surface treatment on carbonation depths were investigated for GP mortars using fly ash (FA), ground granulated blast furnace slag (BFS), or their blend as active fillers. Rational AN surface treatment conditions and microstructural changes of treated GPs were also discussed. The obtained results show that AN surface treatment can significantly reduce carbonation rates of FA/BFS blend-based GP, and largely delay the onset of neutralization of heat-cured GP through the reduction of cracks and the formation of Na-gmelinite and gismondine, which refine the surface layer of GP. The surface modification using 40 wt%-AN solution reduced carbonation rate coefficient by about 70% for the FA/BFS blend-based GP cured at 80 ℃, and by above 30% for that cured at 20℃. The larger the FA blending ratio or the smaller the liquid-active filler ratio, the greater the improvement in carbonation resistance of FA/BFS blend-based GPs, caused by the AN surface modification. For the ambient-cured GP, repeated surface treatment is preferred, while for the heat-cured GP, once treatment is enough, and seal curing after the AN surface treatment is recommended regardless of the curing method.

Siegel disks on rational surfaces

We show the existence of a rational surface automorphism of positive entropy with a given number of Siegel disks. Moreover, among automorphisms obtained from quadratic birational maps on the projective plane fixing irreducible cubic curves, we find out an automorphism of positive entropy with multiple Siegel disks.