Residual Surface Research Articles

Surface charge characteristics in surface dielectric barrier discharge actuators with thin cylindrical exposed electrode

The influence of the cylindrical exposed electrode diameter on distribution and attenuation of the surface charge in surface dielectric barrier discharges is experimentally investigated using the Pockels effect of the Bi12SiO20 crystal. For the actuator with the smaller exposed electrode diameter, more positive charges accumulate closer to the exposed electrode after positive half periodic discharge, while the quantity of positive charges deposited on the surface in a discharge period at the same distance away from the exposed electrode is smaller. At the same time, the smaller the exposed electrode diameter is, the shorter decay time the positive charge filament needs. Combined with thrust generation of actuators, it can be indicated that a positive residual surface charge closer to the exposed electrode may play a more crucial role in the discharge and consequent thrust than one far away from the exposed electrode does. Also, the effect on the discharge of the positive residual surface charge may be greater than that of the negative residual surface charge. More explorations of the residual surface charge have been done by selectively enhancing the discharge of the actuator with a 10 μm exposed electrode using the pulse-AC dual power supply, drawing the same conclusions.

Cluster mean-field description of α emission

We show that the Hartree-Fock-Bogoliubov (HFB) method is able to describe experimental values of alpha decay widths by including a residual nucleon-nucleon Surface Gaussian Interaction (SGI) within the standard procedure used to calculate the nuclear mean field. We call this method the Cluster HFB (CHFB) approach. In this way we correct the deficient asymptotic behaviour of the corresponding single-particle (sp) wave functions generated by the standard mean field. The corrected mean field becomes a sum between the standard mean Woods-Saxon-like field and a cluster Gaussian component centered at the same radius as the SGI. Thus, we give a confirmation of the mean field plus cluster potential structure, which was assumed in our previous work on alpha-decay widths. Systematic calculations evidence the linear correlation between the SGI strength and fragmentation potential, allowing for reliable predictions concerning the half lives of superheavy emitters.

Phosphoinositides regulation of hyperpolarization-activated cyclic-nucleotide gated (HCN) channels.

Several ion channels are regulated by protein-lipid interactions. Hyperpolarization-activated cyclic-nucleotide gated (HCN) channels specifically, have been shown to be regulated by phosphoinositides (PIPs). PIPs enhance HCN activation via a rightward shift in voltage-dependency and has importance applications in neuronal and cardiac function. Using computational and electrophysiological approaches, we aim to examine putative sites for HCN-PIP interactions. Computational docking and coarse-grained simulations indicate that PIP binding to HCN1 and HCN4 channels are not well coordinated, but rather occurs over a broad surface of charged residues primarily in the HCN-domain, S2 and S3 helices that can be loosely organized in 2 or 3 overlapping clusters. Thus, HCN-PIP interactions are more resembling of electrostatic interactions that occur in myristoylated alanine-rich C kinase substrate (MARCKS) proteins, than the specifically coordinated interactions that occur in pleckstrin homology domains (PH domains) or ion channels such as inward rectifier potassium (Kir) channels. Our results also indicate that phosphatidylinositol (PI) interactions with HCN1 are even lower affinity, explaining why unphosphorylated PI have no effect on HCN1 activation unlike phosphorylated PIPs. Experimental validation of putative binding sites are addressed by electrophysiological approaches.

The Effect of Brushing on Residual Stress and Surface Roughness of EN AW-2024-T3 Aluminum Alloy Joints Welded Using the FSW Method

The Effect of Brushing on Residual Stress and Surface Roughness of EN AW-2024-T3 Aluminum Alloy Joints Welded Using the FSW Method

Microstructure and surface quality of SLM printed miniature helical gear in LSPwC

ABSTRACT The present work describes the influence of underwater laser shock peening without coating (LSPwC) on selective laser melting manufactured meso-size (outside diameter ≤ 10 mm) helical gears. Five experiments were conducted using energies in the 200 mJ up to 1 J, while the spot size and overlap were kept constant as 1 mm and 90 %, respectively. Responses were measured and compared in terms of surface residual stresses, surface roughness, and microstructure of LSPwC-treated samples. Results show the development of significant compressive residual stresses in the root of the LSPwC processed helical gear, where it changes the state from tensile +45 MPa to compressive −421 MPa. Surface roughness has shown improvement, while volumetric material peak confirms the reduction by over 50%. Microstructure study was performed at the surface and by cross-section using scanning electron microscopy and electron backscatter diffraction analysis. The grain refinement and change in misorientation were observed, confirming plastic deformation.

Impact of surface charges on energy deposition in surface dielectric barrier discharge: a modeling investigation

Surface charges have significant impact on the evolution of surface dielectric barrier discharge (SDBD). In this work, the role of residual surface charges on repetitively nanosecond pulsed SDBD in atmospheric air is investigated using a two-dimensional fluid model, based on the assumption of preserving the distribution of surface charges at the end of the previous high voltage (HV) pulse. In the bipolar mode when the polarity of residual surface charges is opposite to that of the current HV pulse, a lower breakdown voltage and more deposited energy can be observed, showing an obvious enhancement of SDBD. In the unipolar mode, residual surface charges suppress the development of discharges and energy deposition. It is found that more residual surface charges are accumulated during the negative pulsed discharge, which have a more pronounced effect on the subsequent positive pulsed one. This is explained by the fact that the negative surface streamers directly contact the dielectric and charge it, while the positive surface streamers float above the dielectric, forming a ion-rich region near the surface. The results in this work demonstrate the mechanism of how residual surface charges affect discharge dynamics, which can be utilized to regulate energy deposition in SDBDs.

Ensuring That Safety Glass Is Safe

In Australia, the building code prescribes where glass in buildings must adopt certified safety glass. However, this standard still permits the certification and installation of toughened glass with a residual surface stress that is insufficient to ensure fragmentation in a safe manner. Until the standard is amended to assure safe fragmentation, other precautions need to be taken to ensure that glass installed in buildings is not potentially lethal. This paper discusses safety glass testing, explaining why the current testing procedure does not assure safe fragmentation, and, in the absence of adequate statutory-backed guidance, how building surveyors should navigate the compliance pathway for toughened safety glass.

Optimizing the flatness of 4H-silicon carbide wafers by tuning the sequence of lapping

In this letter, we optimize the flatness of 4H silicon carbide (4H-SiC) wafers by tuning the sequence of single-sided lapping, enlightened by the different mechanical properties of the Si face and C face of 4H-SiC. After wire sawing, the coarse lapping and fine lapping are carried out to rapidly remove the surface damage and optimize the flatness of 4H-SiC wafers. From the point of view of controlling the values of the bow and warp of 4H-SiC wafers, the coarse-lapping sequence of the C-face lapping followed by Si-face lapping is beneficial, while the preferred fine-lapping sequence is Si-face lapping followed by C-face lapping. Nanoindentation tests indicate that the C face has higher hardness and lower fracture toughness than the Si face. This gives rise to thicker surface damage at the C face after the wire sawing. After removing the same amount of wire-sawing induced surface damage, the thickness of residual surface damage of the C face is higher than that of the Si face after the coarse lapping. The fine lapping basically removes all the surface damage and creates the near-perfect C face and Si face. The higher amount of surface damage of the C face after the coarse lapping and the higher fracture toughness of the near-perfect Si face after the fine lapping can tolerate more plastic deformations, which gives rise to the superior flatness of the C-face-followed-by-Si-face coarse lapped and the Si-face-followed-by-C-face fine lapped 4H-SiC wafers, respectively.

Combustion behavior of discrete magnesium diboride particles in the state of motion

Magnesium diboride (MgB2) is regarded as a potential substitute for the amorphous boron (B) due to its excellent energy-release characteristics. In this work, the motion track, flame, and reaction process of discrete MgB2 particles were investigated in the state of motion to reveal their combustion mechanism. The effect of different gaseous mediums on the sustained combustion time and the ingredients and microstructure characteristics of combustion residues were also analyzed. Furthermore, the size distribution of grains in the initial MgB2 particles, MgO cluster particles, and burnt grains in the combustion residues was obtained using graphic analysis. Based on the different motion tracks and flame features obtained, three different combustion modes can be identified; single-stage combustion, two-stage combustion, and micro-explosion combustion. Among them, the single-stage combustion and the two-stage combustion exhibit similar sustained combustion times (12.1 ms and 12.3 ms, respectively), whereas the micro-explosion combustion exhibits a significantly shorter sustained combustion time (5.6 ms) due to the disintegration of particles. Besides, the average sustained combustion time of MgB2 particles was prolonged in the oxygen but shortened in the water vapor. The obtained X-ray diffractometer patterns showed that the combustion residues were composed of MgB2, MgO, Mg, B2O3, and MgBx (indicating an incomplete oxidation during the combustion), and that the burn-off rate of discrete MgB2 particles could still be improved. The scanning electron microscopy images showed a coating layer of condensed B2O3 and clusters of MgO particles on the surface of the combustion residues. The average diameter of burnt MgBx grains and MgO particles were calculated as 1.04 μm and 0.18 μm, respectively. The burnt MgBx grains were products obtained after the coagulation of liquid B2O3 layer and initial MgB2 grains and were larger than the initial MgB2 grains (diameter of 0.24 μm). The MgO cluster particles were condensed from gas-phase reaction and agglomerated to produce a porous structure.

Regioselective protein oxidative cleavage enabled by enzyme-like recognition of an inorganic metal oxo cluster ligand

Oxidative modifications of proteins are key to many applications in biotechnology. Metal-catalyzed oxidation reactions efficiently oxidize proteins but with low selectivity, and are highly dependent on the protein surface residues to direct the reaction. Herein, we demonstrate that discrete inorganic ligands such as polyoxometalates enable an efficient and selective protein oxidative cleavage. In the presence of ascorbate (1 mM), the Cu-substituted polyoxometalate K8[Cu2+(H2O)(α2-P2W17O61)], (CuIIWD, 0.05 mM) selectively cleave hen egg white lysozyme under physiological conditions (pH =7.5, 37 °C) producing only four bands in the gel electropherogram (12.7, 11, 10, and 5 kDa). Liquid chromatography/mass spectrometry analysis reveals a regioselective cleavage in the vicinity of crystallographic CuIIWD/lysozyme interaction sites. Mechanistically, polyoxometalate is critical to position the Cu at the protein surface and limit the generation of oxidative species to the proximity of binding sites. Ultimately, this study outlines the potential of discrete, designable metal oxo clusters as catalysts for the selective modification of proteins through radical mechanisms under non-denaturing conditions.

The Relative Distance Prediction of Transmembrane Protein Surface Residue Based on Improved Residual Networks

(1) Background: Transmembrane proteins (TMPs) act as gateways connecting the intra- and extra-biomembrane environments, exchanging material and signals crossing the biofilm. Relevant evidence shows that corresponding interactions mostly happen on the TMPs’ surface. Therefore, knowledge of the relative distance among surface residues is critically helpful in discovering the potential local structural characters and setting the foundation for the protein’s interaction with other molecules. However, the prediction of fine-grained distances among residues with sequences remains challenging; (2) Methods: In this study, we proposed a deep-learning method called TMP-SurResD, which capitalized on the combination of the Residual Block (RB) and Squeeze-and-Excitation (SE) for simultaneously predicting the relative distance of functional surface residues based on sequences’ information; (3) Results: The comprehensive evaluation demonstrated that TMP-SurResD could successfully capture the relative distance between residues, with a Pearson Correlation Coefficient (PCC) of 0.7105 and 0.6999 on the validation and independent sets, respectively. In addition, TMP-SurResD outperformed other methods when applied to TMPs surface residue contact prediction, and the maximum Matthews Correlation Coefficient (MCC) reached 0.602 by setting a threshold to the predicted distance of 10; (4) Conclusions: TMP-SurResD can serve as a useful tool in supporting a sequence-based local structural feature construction and exploring the function and biological mechanisms of structure determination in TMPs, which can thus significantly facilitate the research direction of molecular drug action, target design, and disease treatment.

KINETICS OF ADSORPTION OF HEAVY METALS (IRON) FROM TEXTILE INDUSTRY WASTE USING CALCIUM CARBIDE RESIDUE AS ADSORBENT

This research was conducted to study the efficiency of residual calcium carbide as an adsorbent using a batch process to remove iron (II) from textile industrial waste. In this study, the iron (II) content in textile industrial waste was synthetically made using . The effluent was characterized using a standard method (atomic absorption spectrometry), while the functional groups responsible for the Adsorption of iron to the surface of the calcium carbide residue were observed using SEM and Fourier Transform Infra-red (FTIR). The SEM findings revealed a highly porous morphology. FTIR revealed the presence of various functional groups (OH, CH, C=C, and C-C). Factors affecting Adsorption, eg, contact time, adsorbent dose, pH, and iron concentration, were also studied. The maximum iron (II) ion adsorption was observed to occur at pH 6. Kinetic studies showed a good correlation and best suited the pseudo-second-order kinetic model. Langmuir and Freundlich's isotherm model was used to describe the Adsorption of iron (II) on calcium carbide residues. The data obtained from the adsorption process most closely matched the Langmuir model with a correlation value of R^2 = 0.9959 and q_e=1.697 mg/g. with a pseudo-second-order kinetic model with a correlation coefficient value (R2), which is 0.9962 for an adsorbent mass of 7.5 g. The Adsorption of iron ions from textile wastewater synthesis solution using calcium carbide residues shows a physisorption mechanism.

ProtRAP: Predicting Lipid Accessibility Together with Solvent Accessibility of Proteins in One Run

Solvent accessibility has been extensively used to characterize and predict the chemical properties of the surface residues of soluble proteins. However, there is not yet a widely accepted quantity of the same dimension for the study of lipid-accessible residues of membrane proteins. In this study, we propose that lipid accessibility, defined in a similar way to solvent accessibility, can be used to characterize the lipid-accessible residues of membrane proteins. Moreover, we developed a deep learning-based method, ProtRAP (Protein Relative Accessibility Predictor), to predict the relative lipid accessibility and relative solvent accessibility of residues from a given protein sequence, which can infer which residues are likely accessible to lipids, accessible to solvent, or buried in the protein interior in one run.

Innovative flotation separation considering pores blocking to facilitate residual carbon recovery from coal gasification fine slag

The conventional flotation of coal gasification fine slag has the dilemma of large collector dosage and low carbon recovery due to the developed porosity of the residual carbon. In this study, an innovative method to enhance the flotation recovery of residual carbon was proposed by pores blocking with pulverized coal. Flotation experiments were carried out to verify the effect of pore blocking on the recovery of residual carbon, and scanning electron microscope, X-ray photoelectron spectroscopy, and mercury intrusion porosimetry were used for mechanism analysis. The results showed that the addition of pulverized coal did play a role in pores blocking in the novel flotation, and its carbon recovery rate was improved by 14.11% (absolute value) compared to that of conventional flotation at the same ash content of the concentrates. On the one hand, the pulverized coal adheres on the pore openings on the residual carbon surface, thus preventing the collector adsorption into the pore channels; on the other hand, the adhesion of pulverized coal to the residual carbon surface increases the adsorption sites for collector. Therefore, pores blocking is beneficial for more adsorption of the collector on the outer surface of the residual carbon and thus improving its flotation recovery. This paper provides significant inspiration for efficient flotation of coal gasification fine slag.

Contributions from ClpS surface residues in modulating N-terminal peptide binding and their implications for NAAB development.

Numerous technologies are currently in development for use in next-generation protein sequencing platforms. A notable published approach employs fluorescently-tagged binding proteins to identity the N-terminus of immobilized peptides, in-between rounds of digestion. This approach makes use of N-terminal amino acid binder (NAAB) proteins, which would identify amino acids by chemical and shape complementarity. One source of NAABs is the ClpS protein family, which serve to recruit proteins to bacterial proteosomes based on the identity of the N-terminal amino acid. In this study, a Thermosynechococcus vestitus (also known as Thermosynechococcus elongatus) ClpS2 protein was used as the starting point for direct evolution of an NAAB with affinity and specificity for N-terminal leucine. Enriched variants were analyzed and shown to improve the interaction between the ClpS surface and the peptide chain, without increasing promiscuity. Interestingly, interactions were found that were unanticipated which favor different charged residues located at position 5 from the N-terminus of a target peptide.

Residual surface charge mediated near-field radiative energy transfer: A topological insulator analog

We study the modifications of near-field radiative energy transfer (NFRET) caused by residual surface charges, which are common in micro- and nano-systems like NEMS/MEMS. The host object with the residual surface charges and the inherent bulk state can be treated as an analog of the real three-dimensional topological insulator, which is inherent of also both surface states and bulk states and is promising to modulate NFRET. Through constructing such a topological insulator analog, we aim to modulate NFRET concerning only common trivial materials. Besides the well-known resonant modes (surface polariton and localized surface polariton) supported by the bulk state, the residual surface charges give rise to an additional temperature-dependent mode providing a new heat flux channel. For low temperatures we find a giant surface-charge-induced enhancement of the NFRET due to a good match between the surface-charge-induced resonance and the Planck window. However, for relative high temperatures where the Fröhlich resonance dominates the heat transfer rather the surface-charge-induced resonance, the residual charges result in a weakening of the NFRET. This work paves way for understanding and modulating the near-field radiative energy transfer for micro- and nano-systems.

Critical review of conformational B-cell epitope prediction methods.

Accurate in silico prediction of conformational B-cell epitopes would lead to major improvements in disease diagnostics, drug design and vaccine development. A variety of computational methods, mainly based on machine learning approaches, have been developed in the last decades to tackle this challenging problem. Here, we rigorously benchmarked nine state-of-the-art conformational B-cell epitope prediction webservers, including generic and antibody-specific methods, on a dataset of over 250 antibody-antigen structures. The results of our assessment and statistical analyses show that all the methods achieve very low performances, and some do not perform better than randomly generated patches of surface residues. In addition, we also found that commonly used consensus strategies that combine the results from multiple webservers are at best only marginally better than random. Finally, we applied all the predictors to the SARS-CoV-2 spike protein as an independent case study, and showed that they perform poorly in general, which largely recapitulates our benchmarking conclusions. We hope that these results will lead to greater caution when using these tools until the biases and issues that limit current methods have been addressed, promote the use of state-of-the-art evaluation methodologies in future publications and suggest new strategies to improve the performance of conformational B-cell epitope prediction methods.

Use of Conductivity as a Tool for On-site Residue Management and Definition of Smart Cleanroom Regimes

Surface residues that result from the use of cleaning and disinfection products are becoming an increasing focus of regulators in the Cleanroom industry. Driven largely by the update to EU GMP Annex 1 [1] and best practice recommendation from the PDA Journal of Pharmaceutical Science and Technology [2], it is now recognized that residues need to be managed to avoid any risks they could present to safety or product quality. Residue management can be successfully achieved by selection and use of low residue disinfectants, through the frequency and choice of rinsing agent for removal, the use of the most suitable tools for physical removal like cleanroom specific mops, or a combination of all these factors. Unlike product contact surfaces [3], there is no clear guidance as to what level of residue may be acceptable on small or large cleanroom surfaces, or how they can be quantified. For this reason, most people still rely on judging a surface to be ‘visibly clean’. To improve detection and to quantify the level of residue on a cleanroom surface, a pragmatic method has been developed to measure residue anywhere on-site: Quantification of disinfectant residues by the use of conductivity. The method of quantification of disinfectant residues using conductivity has been verified in studies by measuring the residues derived from different disinfectant types, at various scales (from bench scale upwards) and various locations, and from laboratory to representative pharmaceutical manufacturing areas. Compared to the current ‘gold standard’ that has long been used for the assessment of residues – an individual’s judgment of ‘visually clean’ - the data from conductivity measurements can eliminate this subjective human appraisal and replace it with scientific assessment. Comparison of the visual analysis rating versus conductivity data also revealed that the human eye does indeed underestimate the actual levels of disinfectant residues remaining on surfaces in a cleanroom, resulting in potential impacts of risk to safety, contamination, time, and cost.

Ultrasonic rolling strengthening effect on the bending fatigue behavior of 12Cr2Ni4A steel gears

An innovative method of ultrasonic rolling strengthening is proposed to process the tooth roots of spur cylindrical gears to improve their bending fatigue life. Variations in the residual stress, surface hardness, and depth of the hardened layer of the tooth root were studied. Subsequently, bending fatigue experiments of a single tooth were performed, and relationships linking residual surface stresses, surface hardness, hardened layer depth, and bending fatigue life were determined. The anti-fatigue mechanism of the ultrasonic rolling gear was clarified: it involves the conversion of tensile residual stresses in the gear tooth roots into residual compressive stresses. After ultrasonic rolling treatment, the bending fatigue strength of gears was increased twice, and their fatigue life was extended by 15 times.

Ultrasonic nitrogen jet-assisted femtosecond laser processing of quartz chips

Femtosecond (Fs) laser micromachining is the most effective and flexible method for edge-cutting or transforming the physical properties of various crystalline brittle materials. Fs-laser micro-machining produces slag on the residual surface of micro-structures that reduces the quality and processing efficiency of a machined residual surface. In order to overcome the challenges overlaid during the processing of brittle materials, Fs-laser assisted ultrasonic nitrogen jet micro-machining technique is proposed. The method was applied to quartz chips to investigate improvements in surface quality after laser processing. For conceptualizations, an ultrasonic nitrogen nozzle based on a piezoelectric transducer was designed and Finite Element Method (FEM) was employed to realize the transition of a flow field. An experiment was performed that differentiate the quality of micro-grooves into quartz chips, and the results promote the significance of Fs-laser-assisted ultrasonic nitrogen jet micromachining for the processing of brittle materials. Besides, the machining quality at residual surfaces of quartz chips after laser processing was substantially improved. The process provides an aid to break down the slag into further tiny nano-particles and prevent a recast layer, meanwhile, it enhances the surface quality and processing efficiency without implementing any extensive procedure.