Rough Morphology Research Articles

Cultural landscape transformations in the "Prosecco hills of Conegliano and Valdobbiadene" UNESCO World Heritage Site in the context of terrain morphology

The "Prosecco Hills of Conegliano and Valdobbiadene" has been inscribed in the UNESCO World Heritage List since 2019 under the category “cultural landscapes”. The study analysed land use and landscape changes in the last six decades through spatial analyses and landscape metrics, identifying main changes and comparing similarities and differences between the Core and the Buffer Zone. The main aims were to identify the main drivers that contributed to the preservation of the traditional cultural landscape and to provide data and indications for landscape planning and conservation, with particular attention to the opportunities/threats due to the expected increase of tourism resulting from the recent UNESCO recognition. The study was conducted in the framework of the UNESCO site Management Plan.Results demonstrated that the Core Zone traditional landscape has a higher level of integrity compared to the Buffer Zone, due to the different terrain morphology that represents the main driver. The rough morphology of the Core Zone contributed to the preservation of traditional vineyards interspersed with small woods, linear tree formations and forest patches, as it was not possible to introduce mechanisation in viticulture due to steep slopes that oblige farmers to cultivate vines on ciglioni (earth terraces). Core Zone's main change was due to forestation (21% of the surface) on steeper slopes and higher altitudes, caused by the abandonment of pastures that occurred in the last decades. The main transformations in the Buffer Zone were agricultural intensification (29% of the surface) due to the replacement of traditional mixed crops, meadows, and arable land with modern and mechanised vineyards, and urban sprawl (average rate of 10 ha/year). The study highlighted that despite land use changes the Buffer Zone still contributes to the conservation of the overall UNESCO site landscape quality. Buffer Zone can also have a potential key-role in mitigating the increasing tourist flows, but additional urban sprawl or the spread of other modern vineyards should be avoided. The main long-term objective should be the preservation of the cultural landscape and the peaceful coexistence of farmers, local population and tourists, with mutual benefits, by applying a participatory approach.

Tailoring Optical Performance of Polyvinyl Alcohol/Crystal Violet Band-Pass Filters via Solvent Features

Optical filters are essential components for a variety of applicative fields, such as communications, chemical analysis and optical signal processing. This article describes the preparation and characterization of a new optical filter made of polyvinyl alcohol and incremental amounts of crystal violet. By using distinct solvents (H2O, dimethyl sulfoxide (DMSO) and H2O2) to obtain the dyed polymer films, new insights were gained into the pathway that underlies the possibility of tailoring the material’s optical performance. The effect of the dye content on the sample’s main properties was inspected via UV–VIS spectroscopy analysis combined with colorimetry, refractometry and atomic force microscopy experiments. The results revealed that the colorimetric parameters are affected by the dye amount and are dramatically changed when the solvent used for film preparation is different. The rise in the refractive index upon polymer dyeing was due to the synergistic effect of the larger polarizability of the dye and the occurrence of hydrogen bonds among the system components. Spectral data evidenced that samples prepared in H2O and DMSO preserve the absorption characteristics of the added dye, whereas H2O2 acts as an oxidizing agent and enhances transparency. Also, for the first two solvents, multiple absorption edges were noted as a result of dye incorporation, which was responsible for the occurrence of new exciton-like states, hence the band gap reduction. The films processed in H2O were able to block radiations in the 506–633 nm range while allowing other wavelengths to pass with a transmittance above 90%. The samples attained in DMSO presented similar properties, with the difference that the domain of light attenuation was shifted towards higher wavelengths. Atomic force microscopy showed the dye’s effect on the level of surface roughness uniformity and morphology isotropy. The dyed polymer foils in non-oxidizing agents have suitable features for use as band-pass filters.

Magnetic hydrogel scaffold based on hyaluronic acid/chitosan and gelatin natural polymers

Owing to their native extracellular matrix-like features, magnetic hydrogels have been proven to be promising biomaterials as tissue engineering templates In the present work, magnetic hydrogels scaffold based on chitosan, gelatin, hyaluronic acid, containing Fe3O4 as magnetic nanoparticles (IONPs) were prepared. The prepared hydrogels were loaded with ciprofloxacin hydrochloride as a model drug. The magnetic hydrogel was prepared using different volumes of chitosan, 1%, gelatin, 10%, and hyaluronic acid, 1% in glutaraldehyde as the crosslinking agent and Fe3O4 as magnetic nanoparticles. The hydrogel scaffold and magnetic scaffold hydrogel samples were characterized by scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and Fourier-transform infrared spectroscopy (FTIR). The porosity, mechanical properties, swelling degree, and antibacterial activity of the hydrogel scaffold were also determined as well as the drug release profiles of the hydrogels. SEM imaging revealed that the magnetic hydrogel scaffold showed a relatively rough morphology with an irregular surface. The data obtained indicated that the hydrogel surface has three-dimensional porous microstructures and the porosity varied depending on the hydrogel formulation. The breaking load of the hydrogel scaffold increased from 1.361 Kgf to 4.98 Kgf by increasing the glutaraldehyde concentration from 0.2 mL to 0.8 mL. Swelling degree values in water were from 250 to 2000% after 24 h. The antibacterial activity of the hydrogel scaffold ranged from 54% to about 97% for Gram-positive bacteria (S. aureus) and from about 26–92% for Gram-negative bacteria (E. coli). The ciprofloxacin hydrochloride loaded hydrogel has a sustained release of ciprofloxacin hydrochloride over 10 h. The presence of IONPs gave a faster release of ciprofloxacin hydrochloride.

Nanofoamed Polyamide Membranes: Mechanisms, Developments, and Environmental Implications.

Thin film composite (TFC) polyamide membranes have been widely applied for environmental applications, such as desalination and water reuse. The separation performance of TFC polyamide membranes strongly depends on their nanovoid-containing roughness morphology. These nanovoids not only influence the effective filtration area of the polyamide film but also regulate the water transport pathways through the film. Although there have been ongoing debates on the formation mechanisms of nanovoids, a nanofoaming theory─stipulating the shaping of polyamide roughness morphology by nanobubbles of degassed CO2 and the vapor of volatile solvents─has gained much attention in recent years. In this review, we provide a comprehensive summary of the nanofoaming mechanism, including related fundamental principles and strategies to tailor nanovoid formation for improved membrane separation performance. The effects of nanovoids on the fouling behaviors of TFC membranes are also discussed. In addition, numerical models on the role of nanovoids in regulating the water transport pathways toward improved water permeance and antifouling ability are highlighted. The comprehensive summary on the nanofoaming mechanism in this review provides insightful guidelines for the future design and optimization of TFC polyamide membranes toward various environmental applications.

Investigation of the Anticorrosive Activity of Piper divaricatum Essential Oil on Steel in 1 M HCl.

Piper divaricatum essential oil (PDEO), extracted from plants of the Brazilian Amazon, was investigated for the first time as a novel green or eco-friendly inhibitor for steel corrosion in 1 M HCl at 25 °C. Our electrochemical studies demonstrate that for different PDEO concentrations, lower E corr and i corr values were obtained. The influence of the oil concentration on corrosion inhibition, 0.5-4 g/L, was determined for 1 and 7 days of immersion. The corrosion rate (CR) and inhibition efficiency (IE) were determined by mass loss. The steel surface in the presence and absence of oil was investigated by scanning electron microscopy (SEM). The main PDEO compounds, determined by gas chromatography-mass spectrometry (GC-MS), were methyleugenol (20.68%) and eugenol (15.42%). The CR and IE for 2 g/L PDEO exhibited an optimal value of 4.31 mm/year and 98.3% for 7 days of immersion, respectively. The surface with 2 g/L oil for 7 days exhibited a less rough morphology, which was attributed to the corrosion inhibitory effect of PDEO. In addition, the PDEO adsorption process on the steel surface obeyed the Langmuir isotherm model. Negative values found for free standard energy ( < 0 kJ·mol-1) were attributed as a favorable process, i.e., an indicative of physisorption and chemisorption between the PDEO components and the steel surface. Our results reveal that the PDEO has a promising character for anticorrosive steel applications and metal coating in industries.

Evolution of tool wear and machining quality during dry milling of AlCoCrFeNi2.1 eutectic high entropy alloy

AlCoCrFeNi2.1, a new class of eutectic high entropy alloy (EHEA) has drawn significant interest owing to the lamellar structure of alternating face-centered cubic (FCC) and B2 phases. Properties such as high strength and high plasticity render the machining of this alloy challenging. Addressing this issue, the milling experiments were conducted under dry conditions to investigate the machining quality of AlCoCrFeNi2.1 EHEA as well as the tool wear. The cutting temperature and cutting force were measured to explain the changes in tool wear and machining quality. The tool wear mechanisms and evolution modes were clarified. Finally, the change of surface roughness and surface morphology under different parameters were analyzed and the characterization method of plastic flow marked by B2 phase was proposed. Results showed that both the cutting temperature and cutting force increase as the milling parameters become larger. The width of flank wear increases with the increase of the cutting speed and the feed rate when the volume of material removal volume is constant. The tool wear modes evolved differently with different cutting parameters, for instance, abrasive wear dominated while the cutting speed was less than 80 m/min, but for higher speeds up to 110 m/min, adhesive wear and coating peeling occurred. As the cutting speed increases further, crater wear on the rake face starts to arise in addition to the flank wear. Abrasive wear and adhesive wear with increasing feed rate were dominant until a certain threshold (0.10 mm/tooth) beyond which the coating peels off the tool. Furthermore, chipping occurred for a higher feed rate of 0.14 mm/tooth. In particular, the formation of tool adhesive wear is mainly caused by the FCC phase adheres. In terms of machining quality, larger cutting parameters will worsen the surface roughness and morphology as well as lead to deeper subsurface plastic flow. The research will be conducive to promoting the applications of AlCoCrFeNi2.1 HEA.

High-speed turning of AISI 4340 alloy steel using carbide tools in a sustainable minimum quantity lubrication environment

Purpose This study aims to investigate the machining performance of CVD-coated carbide tools by considering most crucial machinability aspects: cutting force, tool life, surface roughness and chip morphology in high-speed hard turning of AISI 4340 alloy steel under a sustainable minimum quantity lubrication (MQL) environment. Design/methodology/approach The purpose of this study is to analyze the performance of coated carbide tools under MQL environment therefore, machining tests were performed in accordance with the Taguchi L9 orthogonal array, accommodating the three crucial machining parameters such as cutting speed (V = 300–400 m/min), feed rate (F = 0.1–0.2 mm/rev) and depth of cut (DOC = 0.2–0.4 mm). The measured or calculated values obtained in each experimental run were validated for normality assumptions before drawing any statistical inferences. Taguchi signal-to-noise (S/N) ratio and analysis of variance methodologies were used to examine the effect of machining variables on the performance outcomes. Findings The quantitative analysis revealed that the depth of cut exerted the most significant influence on cutting force, with a contributing rate of 60.72%. Cutting speed was identified as the primary variable affecting the tool life, exhibiting a 47.58% contribution, while feed rate had the most dominating impact on surface roughness, with an overall contributing rate of 89.95%. The lowest cutting force (184.55 N) and the longest tool life (7.10 min) were achieved with low machining parameters at V = 300 m/min, F = 0.1 mm/rev, DOC = 0.2 mm. Conversely, the lowest surface roughness (496 nm) was achieved with high cutting speed, low feed rate and moderate depth of cut at V = 400 m/min, F = 0.1 mm/rev and DOC = 0.3 mm. Moreover, the microscopic examination of the chips revealed a serrated shape formation under all machining conditions. However, the degree of serration increased with an incremental raise with cutting speed and feed rate. Research limitations/implications The study is limited to study the effect of machining parameters within the stated range of cutting speed, feed rate and depth of cut as well as other parameters. Practical implications Practitioners may consider to adopt this machining technique to create more sustainable working environment as well as eliminate the disposal cost of the used metal cutting fluid. Social implications By applying this machining technique, diseases caused by metal cutting fluid to the mechanist will be significantly reduced, therefore creating better lifestyles. Originality/value Hard turning is commonly carried out with advanced cutting tools such as ceramics, cubic boron nitride and polycrystalline cubic boron nitride to attain exceptional surface finish. However, the high cost of these tools necessitates exploration of alternative approaches. Therefore, this study investigates the potential of using cost-effective, multilayer-coated carbide tools under MQL conditions to achieve comparable surface quality. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0013/

Reusable SERS Platform of Femtosecond Laser Processed Substrate for Detection of Malachite Green.

This study presents the development of highly efficient Surface-Enhanced Raman Scattering (SERS) substrates through femtosecond (fs) laser processing of crystalline silicon (Si), resulting in mountain-like microstructures. These microstructures, when decorated with gold nanoparticles (Au NPs), exhibit remarkable SERS performance due to the creation of concentrated hotspots. The enhanced Raman signals originate from the excitation of localized surface plasmon resonance (LSPR) of the Au NPs and the multi-scale rough morphology of the Si substrates. Finite-element method simulations confirm the electromagnetic field enhancement in narrow gaps, supporting the experimental observations. The fabricated substrates show high uniformity, oxidation resistance, long-term stability, and exceptional reproducibility, making them ideal for molecular detection, especially in food safety applications. A remarkable enhancement factor (EF) of 1010 is attained in the detection of Malachite Green (MG), boasting a limit of detection (LoD) as low as 10-14 M. This underscores the immense potential of this technique for achieving highly sensitive and dependable SERS-based sensing capabilities.

The Effects of Alloy Composition and Surface Integrity on the Machinability of Austenitic Stainless Steels 304 and 304L

Austenitic stainless steels, such as 304 and 304L, are extensively utilized in diverse industries due to their favorable properties, including biocompatibility, high durability, ductility, toughness at cryogenic temperatures, and excellent corrosion resistance. Additionally, these steels exhibit notable resistance to fatigue and oxidation. Despite these advantages, they are challenging to machine due to characteristics such as high work hardening, built-up edge formation, and low heat conductivity. The material 304L distinguishes itself from material 304 through its lower carbon content, making it more resistance to corrosion. 304L is experiencing a consistent rise in industrial demand. It is anticipated that this advanced material will progressively supersede 304 in various applications. The variability in alloy compositions and surface integrity of blanks can influence the tool wear and may even lead to abrupt tool breakage, necessitating supervision during machining operations. This study delves into the correlation between the alloy compositions, micro structure, surface integrity, and machinability of these special steels, focusing on turning processes. Various blanks of 304 and 304L in the form of bars, sourced from different manufacturers, were utilized in the study. These blanks exhibited slight variations in alloy composition (albeit within the standard range) and differed in the state of surface integrity characterized by variations in microstructure, grain size, microhardness, and residual stress. All blanks (across this array of materials) were subjected to turning using the same tool specifications and sets of machining parameters for comparative analysis. Various machinability indicators, including cutting forces, surface roughness, burr formation, tool wear, and chip morphology, were thoroughly examined. The findings highlight that the key factors influencing machinability include the microhardness of the surface and the residual stress state in the subsurface of the bars before the turning process. In contrast, changing the alloy composition within the standard range has hardly any effect on the machinability of these steels. The machinability of the examined specimens was adversely affected when the hardness exceeded 350 HV from the surface up to 2 mm below the surface and simultaneously the surface compressive residual stress exceeded −130 MPa.

Dynamic mechanical behavior and failure characteristics of jointed rock-like specimen under impact load

Understanding the mechanical response and failure characteristics of jointed rock masses under multiple dynamic disturbances is crucial for the stability and safety of rock engineering projects. In this study, multi-stage impact loading tests and numerical simulations were conducted on jointed rock-like specimens with sawtooth joints to investigate the effect of joint roughness and joint morphology on dynamic properties and failure characteristics of jointed rock. The results indicate that the dynamic strength, average Young’s modulus, and total impact numbers decreased with the increase of the Joint roughness coefficient (JRC). The triangular tooth-shaped joints with smaller joint heights had higher bearing capacities. The failure modes and damage evolution characteristics of jointed specimens under impacts were also investigated from the energy perspective. The results show that the dynamic failure modes of jointed rock-like specimens mainly include two types: abrasive failure and tensile cracking failure, and tensile cracking failure can be further divided into tensile splitting failure and oblique tensile failure. The total energy and energy density of the specimens with different JRC were investigated. The results show that the total deformation energy and energy density decreased with the increase of JRC under impact loading. The higher the roughness of the specimens, the faster the increase in the damage variable. The asperity height had a significant impact on the damage evolution under impact load. The higher the triangle joint asperity height, the fewer the number of impacts required to reach the same level of damage under the same swing angle. These findings contribute to a deeper understanding of the complex failure mechanisms in jointed rock masses, providing valuable insights for designing safer and more resilient rock engineering structures.

Impacts of Material and Machine on the Variation of Additively Manufactured Cooling Channels

Abstract While additive manufacturing (AM) can reduce component development time and create unique internal cooling designs, the AM process also introduces several sources of variability, such as the selection of machine, material, and print parameters. Because of these sources, wide variations in a part's geometrical accuracy and surface roughness levels can occur, especially for small internal cooling features that are difficult to post-process. This study investigates how the selection of machine and material in the AM process influences variations in surface quality and deviations from the design intent. Two microscale cooling geometries were tested: wavy channels and diamond-shaped pin fins. Test coupons were fabricated with five different additive machines and four materials using process parameters recommended by the manufacturers. The as-built geometry was measured non-destructively with computed tomography scans. To evaluate surface roughness, the coupons were cut open and examined using a laser microscope. Three distinct roughness profiles on the coupon surfaces were captured including upskin, downskin, and channel walls built at 90 deg to the build plate. Results indicated that both material and machine contribute to producing different roughness levels and very different surface morphologies. The roughness levels on the downskin surfaces are significantly greater than on the upskin or sidewall surfaces. Geometric analysis revealed that while the hydraulic diameter of all coupons was well captured, the pin cross section varied considerably. Along with characterizing the coupon surfaces, cooling performance was investigated by experimentally measuring friction factor and heat transfer. The variations in surface morphology as a function of material and machine resulted in heat transfer fluctuating by up to 50% between coupons featuring wavy channels and 26% for coupons with pin fin arrays. Increased arithmetic mean surface roughness led to increased heat transfer and pressure drop; however, a secondary driver in the performance of the wavy channels was found to be the roughness morphology, which could be described using the surface skewness and kurtosis.

Green Synthesis of Electroactive Magnesium Ferrite Nanoparticles for the Selective Determination of Mefenamic Acid in Blood, Pharmaceutical Products, and Wastewater

Mefenamic acid (MNA) treats sports injuries, rheumatoid arthritis, and osteoarthritis. However, improper use/disposal of MNA results in the accumulation of toxic metabolites that may serious disease. The purpose of this study is to fabricate a nano ferrite-based electrochemical sensor for robust, and sensitive determination of MNA. Magnesium ferrite nanoparticles (MgFe4O7-NPs) were synthesized using a green approach using a Mentha leaf extract. The analytical characterization of MgFe4O7-NPs displayed a hexagonal structure and a particle size of less than 21 nm with rough and porous morphology. The synthesized MgFe4O7-NPs were used to fabricate an electrochemical sensor by modifying a glassy carbon electrode (MgFe4O7-NPs/GCE). The cyclic voltammetry (CV) characterization of the electrode confirms excellent redox and diffusion control for electroactive species. Thus, the MgFe4O7-NPs/GCE was used to determine MNA by differential pulse voltammetry (DPV). The results showed a linear relationship between oxidation peak current and concentration of MNA from 10 × 10−9 to 2.30 × 10−4 M (R 2 = 0.9918) with a detection limit of 1.12 × 10−9 M. The analytical performance of the fabricated sensor has been evaluated for MNA in blood samples, pharmaceutical tablets, and water samples with satisfactory results.

Acoustic Emission Measurements During a Four-Point Bending Test on a Reinforced Concrete Specimen

Acoustic emission (AE) measurements were carried out during a four-point bending test to in-vestigate the influence of the shear load-bearing capacity of reinforced concrete beams (so-called Leonhardt beam) with shear reinforcement. The results of AE measurements show that the AE activity begins immediately after starting loading. During the test approximately 3.500 AE events could be automatically located using longitudinal and transverse wave arrival times. Most AE events are in the central region of the specimen within the sensor network. Therefore, only the flexural tensile cracks are represented through AE locations. The transverse shear crack that occurred during the ultimate failure of the specimen is outside the sensor arrangement and has not been detected. Due to the localization error, the AE events are distributed in a cloud-like manner, and as a result, they do not sharply depict the macroscopic flexural tensile cracks. Ra-ther, acoustic emission indicates that a crack network of many small microscopic cracks formed in the tensile area, resulting in a very rough and fragmented crack morphology. Additional to the conventional source location, we applied the so-called collapsing method to highlight structures already inherent within the unfocused AE events clouds.

Thiolated dextrin nanoparticles for curcumin delivery: Stability, in vitro release, and binding mechanism

To achieve the effective loading and delivery of curcumin, novel disulfide-crosslinked nanoparticles based on modified dextrin were developed for the encapsulation of curcumin. Thiolated dextrin (Dt-SH) was obtained via sodium periodate oxidation and cysteamine grafting. The Dt-SH exhibited a rough, flake-like morphology, was classified as an amorphous material and demonstrated enhanced enzyme resistance. Subsequently, spherical nanoparticles with sizes ranging from 92.52 to 157.12 nm and zeta potentials between +23.59 and + 29.90 mV were self-assembled in an aqueous solution. Thiol modification promoted interconnection and aggregation of the nanoparticles. These nanoparticles exhibited pH-dependent size variations. Taking curcumin as a hydrophobic model, nanoparticles showed intestinal targeted release in vitro. Fluorescence spectroscopy and thermodynamic analysis indicated that curcumin bound to Dt-SH nanoparticles primarily through hydrogen bonding and van der Waals forces, with hydrophobic interactions contributing. These findings supported the potential of thiolated dextrin nanoparticles in the effective delivery of hydrophobic compounds.

Performance evaluation of cold plasma and h-BN nano-lubricant multi-field coupling assisted micro-milling of aluminum alloy 6061-T651

Micro-milling has been employed in various fields due to its efficiency, flexibility, material, and structural versatility in the machining of small and high-quality parts. However, when micro-milling highly plastic aluminum alloys, it is difficult to produce a smooth surface due to the easy sticking of tools. To solve this problem, a multi-energy field coupling method of adding nano-lubricant to the micro-milling area by minimum quantity lubrication (MQL) and modifying the aluminum alloy by cold plasma (CP) was introduced. In this paper, the experiments of CP and h-BN nano-lubricant minimum quantity lubrication (NMQL) multi-field coupling assisted (CPNMQL) micro-milling of aluminum alloy 6061-T65 were carried out to analyze 3D surface roughness (Sa), tool texture, milling forces (Fx and Fy), and surface morphology. The results revealed that the CP could increase the surface microhardness and improve material removal rate; Cottonseed oil with h-BN nanoparticles exhibited superior lubricating properties; The milling forces Fx and Fy were significantly reduced; Sa (0.029 µm) under CPNMQL condition decreased by 60 %, 72.1 %, 27.5 %, and 53.2 % comparing to dry (0.104 µm), NMQL (0.04 µm), and CP (0.062 µm) conditions. In addition, the smallest and most uniform tool mark texture height and depth of 0.038 µm was obtained under CPNMQL condition, a 76.3 % reduction over dry condition.

Evaluation of Enamel Surface Properties Submitted to Bleaching With 35% Hydrogen Peroxide Associated With Titanium Tetrafluoride (TiF4).

This study evaluated the color change, surface roughness, mineral content and morphology of enamel bleached with 35% hydrogen peroxide (HP) combined with an experimental gel containing 1% titanium tetrafluoride (TiF4). Bovine enamel blocks were treated with (n = 12): (TiF) experimental gel containing 1% TiF4, (HP) 35% HP, (HPT) 35% HP + 1% TiF4and (CT) control. Bleaching with HP was performed in 3 sessions (3 × 15 min/applications). pH, colorimetric parameters, surface roughness, mineral content and enamel morphology were determined. The pH was evaluated for 45 min. The color parameters were determined before bleaching (T0), and 14 days elapsed from the last bleaching session (T4). Surface roughness was analyzed at T0 and immediately after last bleaching session (T3). Enamel mineral content and morphology were verified at T4. Data were statistically analyzed by one-way, two-way ANOVA and Kruskal-Wallis (α = 0.05). TiF increased surface roughness, and no differences between HP and HPT in terms of color and - mineral content. Ti was detected only on TiF, and slight surface morphology changes were observed in bleached enamel. The combination of TiF4 and 35% HP did not interfere with the enamel bleaching effect, controlled surface roughness, and kept mineral content but promoted a minor surface morphology alteration. Due to the adverse effects of bleaching, titanium tetrafluoride (TiF4) has gained attention for its therapeutic properties, including the ability to reverse mineral loss and neutralize remineralization of mineral structures. Therefore, TiF4's remineralizing capacitymay be a good alternative for incorporation into hydrogen peroxide bleaching agents.

Finite element analysis and experimental study on the cutting mechanism of SiCp/Al composite in laser ultrasonic elliptic vibration turning

SiCp/Al composites have excellent material properties and are increasingly being used in the aerospace, military, and electronic packaging industries. However, the inhomogeneity and non-conductivity of conventional turning (CT) results in poor material surface quality and high cutting forces, which seriously hinder the application of particlereinforced metal matrix composites. The thermal softening property of laser-assisted turning (LAT) and the intermittent cutting property of two-dimensional (2D) ultrasonic elliptical vibratory turning (UEVT) offer unique advantages in improving material surface quality. Therefore, a novel laser ultrasonic elliptical vibratory turning (LUEVT) machining technique is proposed to improve the machining of SiCp/Al composites with two different volume fractions. The effect of highfrequency intermittent machining on material processing was further investigated by adjusting the pulsed laser power. Finite element modelling was used to predict the machining state, surface roughness, and chip morphology between the workpiece and the PCD tool. The effects of varying the machining parameters during the experiment on the two composites were analysed. The results showed that the LUEVT of 25 % and 45 % SiCp/Al composites were reduced by 39.3 % and 30.7 % respectively compared to the CT cutting forces. The experiments verified the consistency of the surface roughness and chip morphology with the finite element simulation results. The stability of the cutting force during the cutting process is also improved, as the material removal process mainly takes the form of small particle fragmentation and matrix encapsulation.

Evolution toward extremely high imipenem resistance in Mycobacterium abscessus outbreak strains.

Treatment of Mycobacterium abscessus pulmonary disease requires multiple antibiotics including intravenous β-lactams (e.g., imipenem). M. abscessus produces a β-lactamase (BlaMab) that inactivates β-lactam drugs but less efficiently carbapenems. Due to intrinsic and acquired resistance in M. abscessus and poor clinical outcomes, it is critical to understand the development of antibiotic resistance both within the host and in the setting of outbreaks. We compared serial longitudinally collected M. abscessus subsp. massiliense isolates from the index case of a cystic fibrosis center outbreak and four outbreak-related strains. We found strikingly high imipenem resistance in the later patient isolates, including the outbreak strain (MIC > 512 µg/mL). The phenomenon was recapitulated upon exposure of intracellular bacteria to imipenem. Addition of the β-lactamase inhibitor avibactam abrogated the resistant phenotype. Imipenem resistance was caused by an increase in β-lactamase activity and increased blaMab mRNA level. Concurrent increase in transcription of the preceding ppiA gene indicated upregulation of the entire operon in the resistant strains. Deletion of the porin mspA coincided with the first increase in MIC (from 8 to 32 µg/mL). A frameshift mutation in msp2 responsible for the rough colony morphology and a SNP in ATP-dependent helicase hrpA cooccurred with the second increase in MIC (from 32 to 256 µg/mL). Increased BlaMab expression and enzymatic activity may have been due to altered regulation of the ppiA-blaMab operon by the mutated HrpA alone or in combination with other genes described above. This work supports using carbapenem/β-lactamase inhibitor combinations for treating M. abscessus, particularly imipenem-resistant strains.

Insights into the Mechanisms of Single-Photon and Two-Photon Excited Surface Enhanced Fluorescence by Submicrometer Silver Particles.

Surface enhanced fluorescence (SEF) based on noble metal nanoparticles is an effective means to achieve high sensitivity in fluorescence detection. Currently, the physical mechanism behind enhanced fluorescence is not fully understood. This paper measures the fluorescence signals of Dihydroporphyrin f methyl ether (CPD4) under both single-photon and two-photon excitation based on submicrometer silver particles with rough morphologies, achieving enhancement factors of 34 and 45 times, respectively. On this basis, by combining the radiative field characteristics produced by the silver particles, a stimulated radiation model of molecules is established to elucidate the changes in the molecular photophysical process when influenced by silver particles. Moreover, the fluorescence lifetime of the molecules was measured, showing that the presence of silver particles induces an increase in the molecular radiative decay rate, causing the fluorescence lifetime to decay from 3.8 ns to 3 ns. The results indicate that the fluorescence enhancement primarily originates from the submicrometer silver particles' enhancement effect on the excitation light. Additionally, the fluorescence signal emitted by the molecules couples with the silver particles, causing the local surface plasmon resonances generated by the silver particles to also emit light signals of the same frequency. Under the combined effect, the fluorescence of the molecules is significantly enhanced. The findings provide a theoretical foundation for understanding the fluorescence enhancement mechanism of silver particles, adjusting the enhancement effect, and developing enhanced fluorescence detection devices based on submicrometer silver particles, holding significant practical importance.

Impact of deposition pressure on the structural, nanomechanical, and tribological properties of δ-TaN coatings deposited via magnetron sputtering on Ti6Al7Nb alloy

In the present study, δ-TaN thin films were deposited by reactive magnetron sputtering (physical vapour deposition) on Ti6Al7Nb alloy by varying the deposition pressure (0.8–0.2 Pa). Their crystalline structure, chemical composition, surface roughness, and surface morphology were investigated by using grazing incidence X-ray diffraction, energy dispersive spectroscopy, scanning probe microscope, and field emission scanning electron microscopy (FESEM), respectively. Structural analysis results confirmed the deposition of cubic δ-TaN thin films along the (111) basal plane; moreover, spherical dome-like surface morphology was observed by FESEM. Further, to analyze the nanomechanical properties of the deposited δ-TaN coatings, such as hardness (H) and modulus (E), scratch tests were performed utilizing the nanomechanical system. Moreover, friction and wear properties of the coating and bare sample (substrate) were investigated on nano-tribometer equipment using a rotary ball-on-disk type configuration. The stainless steel (SS-316) and silicon nitride (Si3N4) balls were used as the counter materials for the tribological tests. The observations of nanomechanical tests revealed that H (GPa), E (GPa), and H/E ratio values increased from 11.83 to 28.30 GPa, 176.02 to 248.45 GPa, and 0.06 to 0.11, respectively, with the decrease of the deposition pressure. In the scratch test, the highest critical load (cohesion failure) was found for δ-TaN coating deposited at the lowest deposition pressure (0.2 Pa). Tribological results of δ-TaN coatings demonstrated average coefficient of friction (COF) value ranges between 0.066–0.092 and 0.072–0.029 against steel and Si3N4 balls, respectively. The wear rate values were observed to vary from 8.15 × 10−5 to 7.56 × 10−6 and from 1.77 × 10−3 to 8.99 × 10−6 against steel and Si3N4 balls, respectively. Generally, the average COF and wear rate decreased against 316 SS and Si3N4 balls as the deposition pressure of coatings decreased. However, the coating deposited at 0.8 and 0.6 Pa against Si3N4 ball showed early delamination of the coating, resulting in the sudden fluctuation in COF plots and higher wear rate in the range of 10−3 mm3/N.m.