Undesired Structures Research Articles

Regulating mechanisms of ultrasonic vibration on the bulge formation in laser polishing

As a burgeoning surface finishing process, laser polishing (LP) introduces some undesired surface structures, limiting access to better laser-polished surfaces. Considering this, the paper proposes a novel hybrid processing method, ultrasonic vibration-assisted laser polishing (UVLP). Horizontal ultrasonic vibration, perpendicular to the laser scanning direction, is imposed on the workpiece, which promotes homogenized melt distribution in the melting pool, contributing to the polished surface flatness. Bulge, a typical surface structure formed in LP, serves as the verification vehicle for the effect of ultrasonic vibration here. In this investigation, comparative experiments were performed on 304 stainless steels to demonstrate the regulation phenomenon of ultrasonic vibration on the bulge formation. Subsequently, the corresponding numerical model was developed to explore the acting mechanisms of ultrasound from the thermal and hydrodynamic fields. The model also optimized the coupling method of volume expansion to better capture the change in melting pool volume during the polishing process, especially during the cooling phase. The results indicated that the forced melt oscillations are the dominant mechanism to uniformize the metallic materials distribution, regulating the bulge formed along the polished track. The degraded melt flow pattern, a simple harmonic oscillation, reached similar results. Furthermore, the developed model verified its effectiveness through surface flatness, melting pool dimensions, and microhardness.

Challenges in Measuring Transport Parameters of Carbonate‐Based Electrolytes

AbstractNumerical simulations are a powerful tool for the development and improvement of Li‐ion batteries. Modeling the mass transport of the involved electrolytic solutions requires precise determination of the corresponding electrolyte parameters. In this work, we attempt to measure the conductivity, the diffusion coefficient, the transference number and the thermodynamic factor for a system of 0.5 M LiPF6 dissolved in a blend of ethylene carbonate and ethyl methyl carbonate (EC : EMC, 3 : 7 weight) at 20 °C and 50 °C. Applying galvanostatic polarization experiments to symmetrical Li metal | electrolyte+separator | Li metal cells reveals, however, a potential response qualitatively deviating from theoretical expectations. Impeded diffusion processes indicate the presence of additional, undesired porous structures on the Li electrodes, preventing a reliable evaluation of the electrolyte parameters. To spectrally resolve the diffusive processes, we conduct very‐low‐frequency impedance spectroscopy. The impedance in fact exhibits multiple interfering diffusive features. In our measurements, an explicit identification of the impedance for the sole diffusion through the separator is however not feasible. Therefore, the authors doubt that polarizing experiments using Li metal electrodes yield accurate parameters for electrolytes.

Morphological study of depth-controlled high quality holes and lines fabricated on a metal substrate with a thin metal film by picosecond laser pulses

Laser micromachining is a convenient technique to structure and/or functionalize the surfaces of various materials. The use of ultrashort laser pulses has an obvious advantage to minimize the heat effect, which results in the formation of a hole without rims. Nevertheless, it is still difficult to fabricate a line without rims even with ultrashort laser pulses, because multiple irradiation of ultrashort laser pulses with a sufficient spatial overlap promotes the formation of rims and undesired structures. In this work we employ a metal substrate with a thin metal film, and demonstrate the fabrication of depth-controlled high quality lines, not to mention holes, through the selective removal of the film by picosecond laser pulses without forming rims and undesired structures. Morphological study of the target surface reveals that the fabricated structures have unprecedentedly flat bottoms with nearly vertical sidewalls to the surface.

Toward efficient and industrially compatible fully textured perovskite silicon tandem solar cells: Controlled process parameters for reliable perovskite formation

AbstractCapitalizing on the existing silicon industry, fully textured perovskite‐silicon tandem solar cells have a great potential to penetrate the electricity market. While the use of textured silicon with large pyramid size (> 1 μm) enhances the power conversion efficiency (PCE), it also presents process complications. To achieve high performance, meticulous control of deposition parameters on textured silicon is required. This study provides a guideline for the use of the hybrid evaporation/spin‐coating route to form high‐quality perovskite absorbers. Using various characterization techniques, we highlight intrinsic differences between perovskite growth on flat versus textured substrates. Furthermore, we provide pathways to ensure a high perovskite phase purity, reveal mitigation strategies to avoid the formation of undesired dendritic perovskite structures, give guidelines to ensure photostability, and discuss the “misleading” effect of residual PbI2 on the perovskite photoluminescence response. A good understanding of the perovskite growth on textured silicon enables the fabrication of a tandem device with a PCE > 26% (without employing additives or surface treatments) and a good operational stability. The comprehensive guidelines in this study provide a better understanding of perovskite formation on textured silicon and can be transferred when upscaling the hybrid route perovskite deposition.

Multiple Diffusion Processes in Lithium-Ion Battery Electrolytes

Numerical simulations are a powerful tool for the development and improvement of Li-ion batteries[1]. Modelling the mass transport of the involved electrolytic solutions requires precise determination of the corresponding electrolyte parameter. However, the determination methods are still controversially discussed.In this work, we attempt to measure the complete set of electrolyte parameter for a system of 0.5 M LiPF6 dissolved in a blend of ethylene carbonate and ethyl methyl carbonate (EC:EMC, 3:7 weight) at 20°C and 50°C. In order to determine the conductivity, the diffusion coefficient, the transference number and the thermodynamic factor we conduct a combination of concentration cell measurements, galvanostatic polarization experiments and electrochemical impedance spectroscopy[2].While the conductivity and concentration cell measurements show comparable results to the literature, we find the potential response in the polarization experiments deviating from theoretical expectations. Applying galvanostatic polarization experiments to symmetrical metal Li | electrolyte + separator | Li metal cells result in slower, impeded diffusion processes. This indicates the presence of additional, undesired porous structures on the Li electrodes, preventing a reliable evaluation of the electrolyte parameters[3]. To spectrally resolve the diffusive processes, we conduct very low frequency impedance spectroscopy in an attempt to identify the impedance for the sole diffusion through the separator[4].1. Max Schammer et al 2021 J. Electrochem. Soc. 168 0265112. Johannes Landesfeind and Hubert A. Gasteiger 2019 J. Electrochem. Soc. 166 A30793. Talian et al. The Journal of Physical Chemistry C 2019 123 (46), 27997-280074. F. Wohde et al 2016 J. Electrochem. Soc. 163 A714Figure 1: VLF-IS measurements with amplitudes of 60µA, 500µA and 10µA together wit the corresponding equivalent circuits, fits and Kramers-Kronig transformations at 20° C and 50°C respectively Figure 1

Enhancing supercapacitor performance through graphene flame synthesis on nickel current collectors and active carbon material from plant biomass

This study introduces a novel approach utilizing flame-synthesized few-layer graphene on a metal current collector for energy storage devices. The graphene was synthesized through a scalable, one-step method involving a flame generated by pre-mixed propane/oxygen/argon gases. To ensure purity and eliminate undesired amorphous structures, ultrasonication was employed. The method successfully produced 5 to 10 layers of graphene on a nickel substrate with rapid growth rates (30–60 s) facilitated by a steady supply of precursors at a stable temperature. The resulting current collector was utilized in the assembly of a supercapacitor, where activated carbon derived from barley straw served as the active electrode material. The cycling stability test reveals that all electrodes maintain approximately 98 % of their initial specific capacitance over 5000 charge-discharge cycles, except for the Ni/Flame-based graphene current collector, which experiences a substantial decrease in capacitance. This study presents a scalable and straightforward concept for incorporating thin layers of graphene onto a metal current collector to enhance the electrochemical characteristics of the electrode. The continuous processing capability and high growth rate of graphene contribute to the method's effectiveness. The study demonstrates the potential of flame-synthesized few-layer graphene for improving the electrochemical properties of supercapacitor electrodes, and its suitability for large-scale production, making it a promising avenue for future energy storage advancements.

Synthesis and Characterization of Magnetite/Gold Core Shell Nanoparticles Stabilized with a β-Cyclodextrin Nanosponge to Develop a Magneto-Plasmonic System

Magnetite/gold core-shell nanoparticles (magnetite/gold NPs) have important optical and magnetic properties that provide potential for applications, especially biomedical ones. However, their preparation is not exempt from difficulties that might lead to unexpected or undesired structures. This work reports the synthesis and characterization of magnetite/gold NPs using tetramethylammonium hydroxide (TMAH) to promote the formation of a continuous interface between the magnetite core and the thin gold shell. The synthesized magnetite/gold NPs were characterized using transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), field emission scanning electron microscope (FE-SEM), ζ-potential, vibrating sample magnetometer (VSM), selected area electron diffraction (SAED), UV-Visible spectroscopy, and dynamic light scattering (DLS), confirming the core-shell structure of the NPs with narrow size distribution while evidencing its plasmonic and superparamagnetic properties as well. Further, the magnetite/gold NPs were associated and stabilized with a β-cyclodextrin nanosponge (β-CDNSs), obtaining a versatile magneto-plasmonic system for potential applications in the encapsulation and controlled release of drugs.

Impact of mutual coupling between SKALA4.1 antennas to the spectral smoothness response

One of the advantages of arrays with aperiodic distributed elements is their ability to mitigate the detrimental mutual coupling effects on the radiation pattern. However, we show that the mutual coupling inside a random array can still generate undesired structures in the frequency response although the single antenna features a spectral smooth response. For small subsets (a couple of SKALA4.1 antennas and a 16-element array) of a low-frequency instrument station of the Square Kilometre Array, the combination of large mutual coupling and antenna geometry creates systematic distortions in the element frequency responses. This phenomenon compromises the station spectral smoothness response versus frequency. However, we demonstrate that it is possible to partially mitigate these frequency structures by reconfiguring the antenna distribution based on exclusion zones.

Interfacial Molecular Doping at Donor and Acceptor Interface in Bilayer Organic Solar Cells

Molecular doping is an effective means to tune the optoelectronic properties of organic semiconductors. Despite its versatility, its application in bulk heterojunction (BHJ) organic solar cells (OSCs) is still limited, especially blend‐cast doping. Difficulties in desolving molecular dopants in weakly polar solvents have led to the formation of undesired structures, with relatively high concentrations of dopants affecting the bicontinuous BHJ morphology. Bilayer OSCs are stacked structures with sequential deposition of donor and acceptor films, which make important contributions to the fine tuning of morphology and balanced charge transport. The sequential deposition of thin films in bilayer devices organically facilitates the sequential doping of pure donor polymers by dopants. The sequential doping of the dopant at the interface between the donor and the acceptor can efficiently improve the carrier mobility and the charge transfer between the donor and the acceptor without damaging the quality of the film, thus improving the device performance efficiently. With three different dopants F4TCNQ, F6TCNNQ, and BCF, sequential interfacial doping in bilayer devices is found to be a versatile and effective method to improve device performance. Making this simple doping strategy promising for high‐performance bilayer OSCs, it is evaluated as a promising alternative to BHJ OSCs.

Driving DNA Origami Assembly with a Terahertz Wave.

Terahertz (THz) waves show nontrivial interactions with living systems, but the underlying molecular mechanisms have yet to be explored. Here, we employ DNA origami as a model system to study the interactions between THz waves and DNA structures. We find that a 3-min THz illumination (35.2 THz) can drive the unwinding of DNA duplexes at ∼10 °C below their melting point. Computational study reveals that the THz wave can resonate with the vibration of DNA bases, provoking the hydrogen bond breaking. The cooperation of thermal and nonthermal effects allows the unfolding of undesired secondary structures and the THz illumination can generate diverse DNA origami assemblies with the yield (>80%) ∼ 4-fold higher than that by the contact heating at similar temperatures. We also demonstrate the in situ assembly of DNA origami in cell lysate. This method enables remotely controllable assembly of intact biomacromolecules, providing new insight into the bioeffects of THz waves.

Computer Aided System for Malignant Melanoma Detection

Melanoma is one of the skin cancers that attacks the cells of melanocytes that produce skin-forming pigments. In this project a new intelligent method of classifying melanoma lesions is implemented. The system consists of four stages; image pre-processing, image segmentation, feature extraction, and image classification. As the first step of the image analysis, pre-processing techniques are implemented to remove noise and undesired structures from the images using techniques such as median filtering and contrast enhancement. In the second step, a simple thresholding method is used to segment and localize the lesion, a boundary tracing algorithm is also implemented to validate the segmentation. Then, a wavelet approach is used to extract the features, more specifically Wavelet Packet Transform (WPT).Finally, the dimensionality of the selected features is reduced with Principal Component Analysis(PCA) and later supplied to an Artificial Neural Network and Support Vector Machine classifiers for classification. Incident rates of melanoma skin cancer have been rising since last two decades. So, early, fast and effective detection of skin cancer is paramount importance. If detected at an early stage. Skin has one of the highest cure rates, and the most cases, the treatment is quite simple and involves excision of the lesion. Moreover, at an early stage, skin cancer is very economical to treat, while at a late stage, cancerous lesions usually result in near fatal consequences and extremely high cost associated with the necessary treatments.

Facilitating Pt−WOx Species Interaction for Efficient Glycerol Hydrogenolysis to 1,3‐Propanediol

AbstractDesigning efficient catalysts for glycerol hydrogenolysis to 1,3‐propanediol (1,3‐PDO), which involves the selective cleavage of the secondary C−O bond, is a challenging task. Current Pt−WOx‐based catalysts often provide low atom efficiency of W and Pt toward 1,3‐PDO production due to undesired catalyst structures. Herein, we fabricate the highly‐dispersed substantially uniform WOx species on inert α‐Al2O3 support by simple high‐temperature heat‐treatment, and the amount of Pt−WOx interface active sites could be adjusted by Pt loading, showing an excellent catalytic performance in glycerol hydrogenolysis at high concentration of glycerol, especially the unprecedented W efficiency (76 g1,3‐PDOgW−1 h−1) toward 1,3‐PDO. The high catalytic efficiency is attributed to the strong interaction between the isolated WO4 species and platinum, which could in‐situ generate the Brønsted acid sites during the reaction as evidenced by IR analysis with NH3 adsorption.

Interactions of microorganisms and synthetic polymers in cultural heritage conservation

Since the 1960s, synthetic polymers (at the time assumed to be resistant to microbial colonization) have been employed to mitigate the ongoing deterioration of cultural heritage. Since then, the use of synthetic materials in heritage conservation attracted much interest. This paper reviews the last two decades of advances in the relationship microorganisms - synthetic polymers in the cultural heritage conservation field. Three topics are considered: (1) biodeterioration of traditional synthetic polymers, (2) biosusceptibility of novel composites based on synthetic polymers, and (3) biocleaning to remove undesired synthetic polymers. It is know that, if the undesired polymer chemical structures are not fully known, they are particularly difficult to remove. Therefore, the future employment of synthetic polymers definitely requires a more critical holistic conservation assessment.

Lead-DBS: an additional tool for stereotactic surgery.

Use Lead-DBS software to analyze stereotactical surgical outcome of an operated population and demonstrate that small target deviations do not compromise the stimulation of desired structures, even with small amperages. Image exams of patients submitted to deep brain stimulation for movement disorders treatment were processed in Lead-DBS software. Electrode stereotactic coordinates were subtracted from the planned target and those deviations, compared among different anatomical targets and sides operated firstly and secondly. We also quantified the frequency of relation between the activated tissue volume and the planned target through computer simulations. None of the 16 electrodes were exactly implanted at the planned coordinates. A stimulation of 3 mA reached 62.5% of the times the planned coordinates, rising to 68.75% with a 3,5 mA. No statistical significance was demonstrated in any comparison of laterality and anatomical sites. The simulation of small amperage fields could reach the intended target even when electrode placement is suboptimal. Furthermore, such a goal can be achieved without overlapping the volume of activated tissue with undesired structures. Software Lead-DBS proved to be a valuable complementary asset for surgical stereotactical result assessment.

New Four-fold Technique to Spread the Self-Gripping Mesh in Open Inguinal Hernia Surgery

Self-gripping mesh can be difficult to handle during spread to the inguinal floor because it can stick or adhere to the undesired structures because of micro-grips available on its underneath surface. This article aims to describe a new technique; we named it a four-fold technique to spread the self-gripping mesh to avoid this problem. The present study was a prospective comparative study between self-gripping mesh (polyester mesh with polylactic acid grips) and sutured mesh (polypropylene) in open inguinal hernioplasty under spinal anesthesia. This study was conducted from 1 November 2018 to 31 March 2020 in ABVIMS & Dr. R.M.L. Hospital, New Delhi. The potential candidates for the study were patients of 18 years age and above, presenting with a unilateral uncomplicated inguinal hernia that underwent open inguinal hernioplasty under spinal anesthesia. Sixty patients were alternatively allotted to group A (30 patients) and group B (30 patients) for comparison between self-gripping and sutured mesh. We used a 14 × 9-cm-size self-gripping mesh, which has semi-resorbable surface on one side and resorbable micro-grips on the other side to provide immediate fixation. Mesh was folded four times in a specific sequence before placing it, thus hiding the majority of the absorbable micro-grips. In this way, only the lower medial half of the mesh has the micro-grips exposed, and the mesh can now be fixed to the inguinal ligament without fixation to unintended tissues and structures underneath. Once the mesh is placed over the pubic tubercle and medial part of the inguinal ligament, it can be unfolded in the reverse order. The four-fold technique is an excellent method to spread the self-gripping mesh in inguinal hernia surgery to avoid sticking with undesired tissues.

Off-target glycans encountered along the synthetic biology route toward humanized N-glycans in Pichia pastoris.

The glycosylation pathways of several eukaryotic protein expression hosts are being engineered to enable the production of therapeutic glycoproteins with humanized application-customized glycan structures. In several expression hosts, this has been quite successful, but one caveat is that the new N-glycan structures inadvertently might be substrates for one or more of the multitude of endogenous glycosyltransferases in such heterologous background. This then results in the formation of novel, undesired glycan structures, which often remain insufficiently characterized. When expressing mouse interleukin-22 in a Pichia pastoris (syn. Komagataella phaffii) GlycoSwitchM5 strain, which had been optimized to produce Man5 GlcNAc2 N-glycans, glycan profiling revealed two major species: Man5 GlcNAc2 and an unexpected, partially α-mannosidase-resistant structure. A detailed structural analysis using exoglycosidase sequencing, mass spectrometry, linkage analysis, and nuclear magnetic resonance revealed that this novel glycan was Man5 GlcNAc2 modified with a Glcα-1,2-Manβ-1,2-Manβ-1,3-Glcα-1,3-R tetrasaccharide. Expression of a Golgi-targeted GlcNAc transferase-I strongly inhibited the formation of this novel modification, resulting in more homogeneous modification with the targeted GlcNAcMan5 GlcNAc2 structure. Our findings reinforce accumulating evidence that robustly customizing the N-glycosylation pathway in P. pastoris to produce particular human-type structures is still an incompletely solved synthetic biology challenge, which will require further innovation to enable safe glycoprotein pharmaceutical production.

Numerical study on the effect of viscosity on a multistage pump running in reverse mode

Utilization of pump as turbine (PAT) systems is known as an economically beneficial method to harvest hydropower energy, especially in a remote area. Despite the extensive investigations on the operation and parametric study of the PAT components, the turbine mode of multistage PATs in case of a viscous working fluid is found as a literature gap. In this paper, a numerical simulation method is employed as a predicting tool to investigate the consequences of changing the fluid viscosity affecting the flow patterns within the multistage PATs. The commercial solver ANSYS CFX 16 was used for simulation. Validation of numerical solution was done for the single-stage pump considering water and 48 cSt viscous fluid. The numerical results in the single-stage PAT showed that increasing the viscosity causes an efficiency drop mainly at the part-load condition and translates the maximum efficiency point to higher flow rates, where the vortices at impeller passage and draft tube are weaker. Increasing the viscosity up to 48 cSt, results in 12.5% reduction of efficiency at the best efficiency point (BEP) in two stage PAT. Based on the two-stage PAT results, the total hydraulic efficiency at the BEP has been increased by 1% and 1.5% for water and the 48 cSt viscous fluid, respectively, in comparison with the single-stage PAT. According to the post-processed streamlines at different stages of the two-stage PAT, the undesired vortical structures were caused by the diffuser and the return channel, which were mainly designed for the pump mode. The hydraulic analysis of two-stage PAT shows that using multistage pumps in reverse mode is reasonable for power generation in high head and flow rate sites.

Highly concentrated carbonate electrolyte for Li-ion batteries with lithium metal and graphite anodes

Highly concentrated lithium bis(fluorosulfonyl)imide (LiFSI) salt dissolved in carbonate solvent is employed as a high-performance and robust organic electrolyte for Li-ion batteries. The influences of Li salt type, concentration, and solvent type (such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethylene carbonate (EC)) on the electrochemical properties of Li metal and graphite anodes are systematically assessed. A superior electrolyte composition of 5.5 M LiFSI-DMC/EC is achieved, enhancing the anti-flammability, coulombic efficiency, and high rate capability. The optimal efficiency values of Li electrodeposition/stripping utilizing 5.5 M LiFSI-DMC/EC are 97.0% and 94.5% at 0.4 and 6 mA cm−2, respectively. Such an enhanced performance is due to the formation of a three-dimensional ion network, composed of contact ion pairs (CIPs) and ion aggregates (AGGs) in the highly concentrated LiFSI electrolyte, which effectively decreases the number of free solvent molecules and inhibits the formation of undesired dendritic Li structures. Raman spectroscopy is employed to confirm the formation of CIP and AGG compounds within the electrolyte. The electrochemical data of the 5.5 M LiFSI-DMC/EC electrolyte cell demonstrates a remarkable improvement in the specific capacity and rate capability of a graphite anode.

Lattice Expansion and Contraction in Metal-Organic Frameworks by Sequential Linker Reinstallation

Summary Isoreticular expansion of metal-organic frameworks (MOFs) by linker elongation often leads to interpenetration or other undesired structures. Here we report a sequential linker labilization and reinstallation method to expand the unit cell dimensions of MOFs while manipulating the framework structure and interpenetration. A stable Zr-based MOF was initially synthesized as a template. Subsequently, labile linkers with imine bonds were post-synthetically introduced into the structure to destabilize the Zr-MOF. Eventually, gradual dissociation of the imine-based linkers and reinstallation of longer linkers into the defective spaces lead to the formation of non-interpenetrated isoreticular Zr-MOFs with progressively increased pore sizes. Similarly, lattice contraction can also be realized by incorporating shorter linkers. In addition to providing a powerful tool that yields control over the structures and functions of MOFs, this work also highlights new opportunities by combining the dynamic covalent chemistry with coordination chemistry in MOFs.

Is UV-Induced Electron-Driven Proton Transfer Active in a Chemically Modified A·T DNA Base Pair?

Transient electronic and vibrational absorption spectroscopies have been used to investigate whether UV-induced electron-driven proton transfer (EDPT) mechanisms are active in a chemically modified adenine-thymine (A·T) DNA base pair. To enhance the fraction of biologically relevant Watson-Crick (WC) hydrogen-bonding motifs and eliminate undesired Hoogsteen structures, a chemically modified derivative of A was synthesized, 8-(tert-butyl)-9-ethyladenine (8tBA). Equimolar solutions of 8tBA and silyl-protected T nucleosides in chloroform yield a mixture of WC pairs, reverse WC pairs, and residual monomers. Unlike previous transient absorption studies of WC guanine-cytosine (G·C) pairs, no clear spectroscopic or kinetic evidence was identified for the participation of EDPT in the excited-state relaxation dynamics of 8tBA·T pairs, although ultrafast (sub-100 fs) EDPT cannot be discounted. Monomer-like dynamics are proposed to dominate in 8tBA·T.