Publikační záznamy NTC

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Showing 1 - 20 out of 185 results

Is the Finnish grip tight enough? A manometric study of two manual perineal protection techniques
(2025) Rusavy, Zdenek; Čechová, Hana; Dendorfer, Sebastian; Kalis, Vladimir; Ismail, Khaled M.
Several manual perineal protection techniques have been proposed, while some were proven to be harmful;1 others such as the “Finnish grip” were proven effective.2 In the Finnish technique (FMPP), the thumb and index fingers of the dominant hand are used to reduce tension on the posterior fourchette by squeezing the lateral perineal aspects toward the midline. The flexed middle finger in coordination with non-dominant hand facilitates slow and controlled head expulsion.3, 4 In contrast, in the Viennese technique (VMPP), the upward displacement of the fetal head is facilitated by ulnar part of the accoucheur's dominant hand, while the extended middle, ring and little fingers are used to support the index finger in reducing the perineal stretch.4 Proponents of VMPP argue that the grip with index finger and thumb alone is insufficient for proper midline strain reduction. In our experiment, we set out to measure and compare index finger and thumb forces exerted when performing these maneuvers
Rare-earth engineering of NaAlO3 perovskites unlocks unified optoelectronic, thermoelectric, and spintronic functionalities
(2025) Imran, Muhammad; Azam, Sikander; Rafiq, Qaiser; Ur Rahman, Amin
Perovskite oxides hold promise for energy and quantum technologies, but wide-gap hosts like NaAlO3 are limited by poor transport and deep-UV absorption. Using first-principles GGA + U + SOC calculations, we investigate Eu3+-, Gd3+-, and Tb3+-doped NaAlO3, analyzing electronic, optical, elastic, and thermoelectric properties. Rare-earth substitution is thermodynamically favorable (formation energies 1.2-1.6 eV) and induces strong f-p hybridization, reducing the pristine bandgap (similar to 6.2 eV) to similar to 3.1 eV (Tb). Spin-resolved band structures reveal Gd-driven half-metallicity, Eu-induced spin-selective metallicity, and Tb-stabilized p-type semiconducting behavior. Optical spectra show red-shifted absorption (similar to 2.0-2.2 eV), large dielectric constants (epsilon(1)(0) approximate to 95 for Eu), and plasmonic resonances near 4 eV, enabling visible-light harvesting. Elastic analysis indicates slight lattice softening with preserved ductility (B/G approximate to 1.56-1.57). Thermoelectric results show Seebeck coefficients >210 mu V/K (Eu, Tb) with ZT similar to 0.45 at 500 K, surpassing pristine NaAlO3. These findings position rare-earth-doped NaAlO3 as a multifunctional platform for photovoltaics, photocatalysis, thermoelectrics, and spintronics.
Programmable Hydrogels: Frontiers in Dynamic Closed-Loop Systems, Biomimetic Synergy, and Clinical Translation
(2025) Xiang, Guangli; Yin, Bohan; Shiroud Heidari, Behzad; Youssef, George; Gosecka, Monika; Gosecki, Mateusz; Torres, Fernando G.; Wong, Siu Hong Dexter; Dodda, Jagan Mohan
Programmable hydrogels are an emerging class of intelligent materials engineered to respond precisely to specific stimuli, offering tailored functionalities with significant potential for biomedical applications, including drug delivery, tissue engineering, and wound healing. This review comprehensively explores various programmable hydrogels responsive to diverse triggers, including temperature, gene expression, color, shape, and mechanical force. The design and fabrication methods underlying these systems are detailed, highlighting the roles of crosslinkers, adhesion groups, and photosensitive functional groups. Furthermore, the key physical, chemical, and biological properties that govern the performance and functionality of hydrogels are analyzed. The review further examines the mechanisms and recent advancements in self-executing hydrogels, such as self-activated, self-oxygenated, self-expandable, and self-powered systems, demonstrating how these innovative designs drive the development of next-generation programmable hydrogels. The main challenges in hydrogel design, including complexity, reproducibility, and clinical translation, are also addressed. Finally, a perspective on future research directions, highlighting the integration of the latest technologies to realize programmable hydrogels with dynamic closed-loop responsiveness, bionic synergy, and robust clinical applicability, is offered.
Ternary Transition Metal Oxides for Electrochemical Energy Storage: Synthesis, Advantages, Design Strategies, and Future Prospects
(2025) Sivakumar, Periyasamy; Subramanian, Palaniappan; Kannan, Palanisamy; Minár, Jan; Jung, Hyun
Ternary transition metal oxides (TTMOs) have emerged as a new class of electrode materials for high-performance energy storage systems, particularly supercapacitors (SCs) and hybrid battery-capacitor devices. This comprehensive review aims to comprehensively survey recent advances in the design, synthesis, and analysis of TTMOs-based nanostructures for SC electrodes. It begins by outlining the key concepts related to charge storage mechanisms in SC electrodes, electric double-layer (EDL) capacitance, pseudocapacitive (PC), and battery-type (BT) behavior, followed by a clarification of device configurations, including symmetric SC (SSC), asymmetric SC (ASC), and hybrid SC (HSC) devices. This review then examines the fabrication strategies for TTMOs, emphasizing the impact of synthetic approaches on material morphology, crystallinity, and electrochemical performance. Special attention is given to the structure-property relationships that govern ion transport and charge storage dynamics in these materials. The influence of morphological features, including dimensionality, porosity, and hierarchical architecture, on electrochemical behavior is critically analyzed. A comparative evaluation of electrochemical matrices across various TTMO electrodes is presented, highlighting key performance and challenges. Ultimately, the review highlights emerging trends, current limitations, and future research directions that are poised to accelerate the development of next-generation TTMO materials for advanced energy storage technologies.
Exploring the Rational Design and Strategy of Metal Ion-Integrated 3D Hierarchical Spinel Oxide Nano/Microarchitecture for Battery-Supercapacitor Hybrid Energy Storage System
(2025) Sivakumar, Periyasamy; Raj, C. Justin; Subramanian, Palaniappan; Savariraj, Antonysamy Dennyson; Manikandan, Ramu; Singh, Priti; Dixit, Mudit; Jung, Hyun
The synergistic interaction and strategic manipulation of electronic structures by incorporating metal ions into the host matrix have captivated research efforts for supercapacitors. This study presents an efficient strategy for synthesizing Cu-ion-incorporated NiCo2O4 (CNCO) nano/microarchitectures using a hydrothermal method followed by heat treatment. It establishes a clear link between variations in Cu content and their effects on material properties, which influence electrochemical performance. Optimizing the Cu content enhances ion transport and conductivity, while creating active sites for faster charge transfer. The porous framework boosts structural integrity and mass transport, reducing aggregation risks. Enhanced performance stems from synergistic interactions between Cu and the NCO matrix in the CNCO nano/microarchitecture. The experimental findings are further substantiated by computational analyses utilizing density functional theory (DFT) calculations. Impressively, the regulated CNCO electrode material exhibits a remarkable specific capacitance of 1301 F/g at 1 A/g and a rate capability of 81.3% at 20 A/g, significantly outperforming other CNCO variants. The optimized CNCO electrode material contributes to a high-performance battery-supercapacitor hybrid system, achieving an energy density of 61.36 Wh/kg at a power density of 1.18 kW/kg, with excellent cyclic stability. This system illuminates green and pink light-emitting diodes.
Quantitative Analysis of Flash-Pulse Thermographic Detection of Gunshot Residue
(Japanese Society for Non-Destructive Inspection and co-organized by Kobe University, 2025) Švantner, Michal; Moskovchenko, Alexey; Muzika, Lukáš; Skála, Jiří; Honner, Milan
This study addresses the detection of gunshot residue (GSR) around a bullet hole, which is one of the key forensic procedures for estimating the firing distance. GSR was inspected using flash-pulse thermography (FPT) with Kurtosis statistical processing. The result of such an inspection is a pattern composed of numerous small indications distributed around the hole, attributed to gunshot residue particles. The number and spatial distribution of these indications depend on the firing distance. Analyzing such results based on individual indications is impractical, as the pattern must be evaluated as a whole. Therefore, quantifying the overall result can significantly improve the analysis of the firing distance estimation. This study presents a quantification procedure based on threshold-based mass-marking of indications and evaluation of several statistical characteristics. The correlation between these characteristics and firing distance is then analyzed. A strong but distinctly nonlinear correlation was found between the firing distance and some simple quantitative characteristics, such as the total number of indications. However, the study shows that some derived characteristics, such as the contrast between marked areas and background, exhibit a near-linear correlation. These parameters are, therefore, promising for firing distance analysis based on FPT inspection of GSR on through-shot targets.
Crack angle estimation with induction thermography and machine learning
(Tanger s.r.o., 2025) Moskovchenko, Alexey; Švantner, Michal
Induction thermography is a well-established method for detecting and analysing cracks in metal products, such as rails. However, quantifying defects, particularly those with complex geometries, remains a challenging and intricate task. This paper addresses one critical aspect of defect quantification: the determination of crack inclination angles, which is essential for accurate depth estimation and hazard level assessment. We propose a novel approach that combines induction thermography data analysis with machine learning regression models to estimate crack angles. The regression model is trained on a dataset generated through numerical simulations, ensuring robust and reliable performance. The effectiveness of the proposed method is demonstrated through both numerical and experimental results, showcasing its potential for improving crack characterization in industrial applications. This work advances the field of non-destructive testing by providing a more precise and automated solution for crack inclination angle determination, contributing to enhanced structural integrity assessments
Flash-pulse thermography evaluation of cold spray 316L steel coatings
(Tanger s.r.o, 2025) Moskovchenko, Alexey; Švantner, Michal; Vostřák, Marek; Dlouhá, Žaneta; Houdková, Šárka
This study investigates the application of infrared (IR) thermography for evaluating thermal-sprayed coatings, focusing on distinguishing coatings subjected to different thermal treatments and varying porosity levels. Experimental thermographic analysis demonstrated the capability of IR thermography to differentiate between coating variants. The Fourier transform method and phase analysis at low frequencies proved remarkably effective. This approach enabled the visualization of areas with differing thicknesses in the thermographic images and facilitated detailed analysis through phase-frequency plots. The results highlight the potential of IR thermography as a powerful, non-destructive tool for characterizing thermal-sprayed coatings, offering insights into their structural and thermal properties. This method holds promise for quality control and optimization in industrial applications involving thermal spray processes
Improvement of morphology and electrical properties of boron-doped diamond films via seeding with HPHT nanodiamonds synthesized from 9-borabicyclononane
(2025) Stehlík, Štěpán; Potocky, Stepan; Aubrechtova Dragounova, Katerina; Bělský, Petr; Medlín, Rostislav; Vincze, Andrej; Ekimov, Evgeny A.; Kromka, Alexander
Boron-doped diamond (BDD) films are becoming increasingly popular as electrode materials due to their broad potential window and stability in harsh conditions and environments. Therefore, optimizing the crystal quality and minimizing defect density to maximize electronic properties (e.g. conductivity) of BDD is of great importance. This study investigates the influence of different hydrogenated nanodiamond (H-ND) seeding layers on the growth and properties of BDD films. Three types of seeding H-NDs were examined: detonation (H-DND) and topdown high-pressure high-temperature NDs (TD_HPHT H-ND), and boron-doped NDs (H-BND) newly synthesized at high-pressure high-temperature from an organic precursor. Purified and oxidized BND (O-BND) samples yielded clear, blue, and stable colloidal dispersions. Subsequent thermal hydrogenation reversed their zeta potential from - 32 mV to +44 mV and promoted the seeding of negatively charged surfaces. All three H-ND types formed dense seeding layers on SiO2 and Si/SiOx substrates, which enabled the growth of BDD films by chemical vapor deposition (CVD). Despite variations in initial surface coverage among the seeding layers (13-25 %), all NDs facilitated the growth of fully closed BDD films approximately 1 mu m thick. Significant differences in film morphology and electrical properties were observed. H-BND nucleation yielded the BDD films with the largest crystals (up to 1000 nm) and lowest sheet resistance (400 Omega/sq). This superior performance is attributed to the uniform particle shape and monocrystalline character of H-BND, as corroborated by FTIR, TEM, and SAXS measurements. These findings highlight the critical role of seeding layer properties in determining consequent diamond film evolution and establish H-BNDs as promising seeding material for the growth of high-quality BDD films suitable for electronic and electrochemical applications.
Transition in morphology and properties in bottom-up HPHT nanodiamonds synthesized from chloroadamantane
(2025) Stehlík, Štěpán; Bělský, Petr; Kovářík, Tomáš; Nemeckova, Zuzana; Henych, Jiri; Ukraintsev, Egor; Vlk, Ales; Ledinsky, Martin; Ekimov, Evgeny
Direct bottom-up high pressure high temperature (BU_HPHT) synthesis of nanodiamonds (NDs) from organic precursors excels in the ability to control the size of the resulting BU_HPHT NDs via the temperature of the synthesis. Here we investigated size-dependent thermal, colloidal, and structural properties of the BU_HPHT NDs and focused on the transition in morphology and properties occurring at around 900 degrees C (approximate to 2 nm). Using transmission electron microscopy, small angle X-ray scattering and atomic force microscopy we show that the sub-900 degrees C samples (<2 nm NDs) do not have nanoparticle character but 2D platelet morphology with sub-nm unit thickness. Correspondingly, sub-900 degrees C samples (<2 nm NDs) have a negative zeta potential and hydrophobic character and should be considered as a form of a molecular diamond. The above-900C (>2 nm NDs) samples have nanocrystalline character, positive zeta potential and are dispersible in water similarly to other types of hydrogenated NDs. By in situ Raman spectroscopy experiments, we show that the transition is also related to the structural instability of the oxidized sub-2 nm BU_HPHT NDs.
Evidence of spin and charge density waves in Chromium electronic bands
(2025) Bisti, Federico; Settembri, Paolo; Minár, Jan; Rogalev, Victor A.; Widmer, Roland; Gröning, Oliver; Shi, Ming; Schmitt, Thorsten; Profeta, Gianni; Strocov, Vladimir N.
The incommensurate spin density wave (SDW) of Chromium represents the classic example of itinerant antiferromagnetism induced by the nesting of the Fermi surface, which is further enriched by the co-presence of a charge density wave (CDW). Here, we explore its electronic band structure using soft-X-ray angle-resolved photoemission spectroscopy (ARPES) for a proper bulk-sensitive investigation. We find that the long-range magnetic order gives rise to a very rich ARPES signal, which can only be interpreted with a proper first-principles description of the SDW and CDW, combined with a band unfolding procedure, reaching a remarkable agreement with experiments. Additional features of the SDW order are obscured by superimposed effects related to the photoemission process, which, unexpectedly, are not predicted by the free-electron model for the final states. We demonstrate that, even for excitation photon energies up to 1 keV, a multiple scattering description of the photoemission final states is required.
Impact of hot isostatic pressing on the microstructure of AISI 316L austenitic steel processed by laser direct energy deposition
(2026) Bricín, David; Jansa, Zdeněk; Janová, Denisa; Špirit, Zbyněk; Beneš, Petr; Kubátová, Dana; Kotous, Jakub
This article deals with the microstructural analysis of austenitic steel AISI 316L processed by the direct energy deposition (L-DED) process and further processed by hot isostatic pressing (HIP). The samples for the experiment were made from atomized powder with an average spherical particle size of 55±30 μm. The powder was processed into blocks with dimensions of 33x33x18 mm, using a deposition layer thickness of 0.6 mm and a Zig-Zag deposition strategy. HIP processing was performed at a temperature of 1150 °C and a pressure of 100 MPa. The analysis of the samples consisted of X-ray phase diffraction analysis and scanning lectron microscopy analysis. X-ray phase analysis revealed that the HIP process causes coarsening of the crystallite structure and a change in the residual stresses acting in the (111) plane, where both tensile and compressive stresses were detected after additive manufacturing process, while only compressive stress was measured after HIP processing. From the point of view of microstructural analysis, recrystallization of the structure was observed, including the formation of a twin structure with an increased fraction of special Σ3 grain boundaries. This was accompanied by the coarsening of oxide inclusions.
Illuminating stability and spectral shifts: A DFT+U study of Eu-doped ZnWO4 for visible-light optoelectronics
(2025) Tayyab, Muhammad; Azam, Sikander; Rafiq, Qaiser; Tirth, Vineet; Algahtani, Ali; Rahman, Amin Ur; Ahmad, Syed Sheraz; Khan, M. Tahir
Tungstate-based oxides have attracted significant attention owing to their excellent structural stability, chemical robustness, and versatile optical properties, making them suitable for next-generation optoelectronic and phosphor applications. Among these, ZnWO4 has emerged as a promising host matrix; however, the role of europium (Eu) substitution in modulating its optoelectronic behavior remains underexplored. In this work, we employ spin-polarized density functional theory (DFT) within the GGA + U framework to investigate the structural, electronic, and optical properties of pristine ZnWO4 and Eu-doped ZnWO4 systems. Phonon dispersion analysis confirms dynamical stability for both pristine and doped structures. Eu doping reduces the bandgap, introduces new localized states near the Fermi level, and significantly alters the density of states, thereby enhancing electronic transitions. The optical response reveals a broadened dielectric function, red-shifted absorption edge, and intensified extinction coefficient, consistent with the presence of Eu 4f states. Additionally, reflectivity and energy-loss spectra indicate improved photon-phonon coupling and optical tunability upon doping. These findings highlight that Eu incorporation not only stabilizes the ZnWO4 lattice but also tailors its optoelectronic features, positioning Eu-doped ZnWO4 as a potential candidate for white-light-emitting diodes (wLEDs) and related optoelectronic technologies.
Chitosan nanoparticles in vaccine delivery systems
(Woodhead Publishing, 2024) Acharya, Biswajeet; Behera, Amulyaratna; Deshmukh, Kalim Abdul Rashid; Sagadevan, Suresh; Moharana, Srikanta
Recent advances in nanostructured boron nitride based flame retardant composites: A comprehensive review
(2026) Jayan, Deepthi K.; Deshmukh, Kalim Abdul Rashid
With formerly unattainable control over material properties at the nanoscale, nanotechnology has emerged as a paradigm shift in materials research. Given the increasing demand for fire-resistant materials in industries, the use of nanomaterials in flame-retardant composites has garnered significant attention among their many other uses. The nanostructured boron nitride (BN) is a potential candidate in this area since it possesses outstanding structural and chemical properties and its two-dimensional (2D) structure endows them with thermal stability, high surface area, and natural flame resistance making them extremely valuable for fire safety improvement in many materials. In recent years, progress in the synthesis, functionalization, and use of nanostructured BN in flame retardant composites cast new light on the fundamental processes that underlie their flame-retardant properties but also triggered the creation of new, high-performance flame-retardant materials. This review provides an integral overview of the most recent advancements in nanostructured BN-based flame-retardant composites, systematically exploring the synthesis routes, properties, characterization methods, and flame retardancy mechanisms. The review explores the underlying principles of the flame-resistant BN-based composites, emphasizing their versatile applications in different industries highlighting their vast potential as next-generation flame retardants. The future trends and challenges associated with the extensive utilization of the nanostructured BN in flame retardant applications are briefed. With a detailed description of the state-of-the-art in nanostructured BN with flame-retardant composites, the current review intends to promote research activities in this emerging area leading to the progress of next-generation sustainable flame-retardant materials with excellent performance.With formerly unattainable control over material properties at the nanoscale, nanotechnology has emerged as a paradigm shift in materials research. Given the increasing demand for fire-resistant materials in industries, the use of nanomaterials in flame-retardant composites has garnered significant attention among their many other uses. The nanostructured boron nitride (BN) is a potential candidate in this area since it possesses outstanding structural and chemical properties and its two-dimensional (2D) structure endows them with thermal stability, high surface area, and natural flame resistance making them extremely valuable for fire safety improvement in many materials. In recent years, progress in the synthesis, functionalization, and use of nanostructured BN in flame retardant composites cast new light on the fundamental processes that underlie their flame-retardant properties but also triggered the creation of new, high-performance flame-retardant materials. This review provides an integral overview of the most recent advancements in nanostructured BN-based flame-retardant composites, systematically exploring the synthesis routes, properties, characterization methods, and flame retardancy mechanisms. The review explores the underlying principles of the flame-resistant BN-based composites, emphasizing their versatile applications in different industries highlighting their vast potential as next-generation flame retardants. The future trends and challenges associated with the extensive utilization of the nanostructured BN in flame retardant applications are briefed. With a detailed description of the state-of-the-art in nanostructured BN with flame-retardant composites, the current review intends to promote research activities in this emerging area leading to the progress of next-generation sustainable flame-retardant materials with excellent performance.
Vanadium-Engineered Co2NiSe4 nanomaterial: coupled thermoelectric, piezoelectric, and electronic optimization via DFT+U for advanced energy applications
(2025) Riaz, Ayesha; Azam, Sikander; Rafiq, Qaiser; Khan, Muhammad Tahir; Rahman, Amin Ur; Ahkam, Qazi Muhammad; Hussain, Rafaqat; Khan, Rajwali
The multifunctional potential of quaternary chalcogenides can be dramatically expanded by targeted pointdefect engineering. In this work, we employ density functional theory (DFT) with on-site Coulomb correction (GGA + U) to explore the structural, electronic, optical, thermoelectric, and piezoelectric properties of pristine and dilute vanadium-doped Co2NiSe4 (<= 10 at.%). Our results reveal that V substitution in monoclinic Co2NiSe4 introduces a resonant V d3 impurity level, which simultaneously (i) narrows the electronic band gap from 0.52 eV to 0.30 eV, (ii) lncrease the total spin moment from 3.2 to 3.6 mu B per formula unit, and (iii) triples the density of states at the Fermi level (Ef). These modifications lead to a significant enhancement in electrical conductivity and phonon-defect scattering, collectively boosting the thermoelectric figure of merit (zT) up to approximate to 1.1 at 900 K for 5 at.% V. Concurrently, the dielectric onset red-shifts into the near-infrared, and the dielectric constant and absorption spectrum broaden, enabling broadband light harvesting and potential NIR optoelectronic applications. The piezoelectric modulus e33 also shows a notable 23 % increase, rising to 2.70 C/m2 at 10 % V doping, indicating strong electromechanical coupling driven by lattice distortion and local symmetry breaking. Simulated X-ray absorption spectra at the Co L2,3 edges further reveal redshifted and broadened absorption peaks upon V doping, confirming enhanced Co-V hybridization and an increased unoccupied 3d-state density, which supports improved conductivity and optical response. These mutually reinforcing electronic, vibrational, and electromechanical enhancements position V-doped Co2NiSe4 as a promising multifunctional material platform for integrated heat-to-power conversion, near-infrared photodetection, and spintronic or spin-filter applications. The study highlights how targeted substitutional doping in chalcogenides can unlock simultaneous improvements across energy, sensing, and actuation domains.
Revealing electronic correlations in YNi2B2C using photoemission spectroscopy
(2025) Pulkkinen, Aki Ismo Olavi; Kremer, Geoffroy; Strocov, Vladimir N.; Weber, Frank; Minár, Jan; Monney, Claude
The low-energy electronic structure of materials is crucial to understanding and modeling their physical properties. Angle-resolved photoemission spectroscopy (ARPES) is the best experimental technique to measure this electronic structure, but its interpretation can be delicate. Here we use a combination of density functional theory (DFT) and one-step model of photoemission to decipher the soft x-ray ARPES spectra of the quaternary borocarbide superconductor YNi2B2C. Our analysis reveals the presence of moderate electronic correlations beyond the semilocal DFT within the generalized gradient approximation. We show that DFT and the full potential Korringa-Kohn-Rostoker method combined with the dynamical mean field theory (DFT+DMFT) with average Coulomb interaction U = 3.0 eV and the exchange energy J = 0.9 eV applied to the Ni d-states are necessary for reproducing the experimentally observed SX-ARPES spectra.
Cleaved surfaces and homoepitaxial growth of InBi(001)
(2025) Rehaag, Thomas J.; Mayoh, Daniel A.; Bárta, Tomáš; Slaney-Parker, Freya; Elhoussieny, Ibrahim; Minár, Jan; Bell, Gavin R.
InBi is a semimetal with topologically non-trivial electronic surface states, which is also chemically and structurally compatible with conventional III-V semiconductors. Single crystal InBi has been grown and its (001) cleave surfaces studied. They do not conform to the single Bi-Bi cleave plane previously assumed in band structure studies of the material but instead expose both In- and Bi-terminated surface regions. Crystals cleaved in ultra-high vacuum have been used as substrates for ultra-low temperature homoepitaxy via periodic supply epitaxy (PSE) with alternate Bi and In fluxes. Homoepitaxial growth of good quality InBi was not achieved under these conditions. The 3D and 2D surface structures produced by PSE were studied by reflection high energy electron diffraction and atomic force microscopy. By studying InBi homoepitaxy for the first time, this work highlights the challenge of growing high quality InBi epilayers beyond the ultra-thin heteroepitaxial layers recently demonstrated [Molecules 2024, 29(12), 2825].
Improved prediction of ultrashort pulse laser ablation efficiency
(2025) Redka, David; Vela, Sergio; Spellauge, Maximilian; Minár, Jan; Morales, Miguel; Molpeceres, Carlos; Huber, Heinz Paul
Achieving maximum efficiency and precision in ultrafast laser ablation is crucial for micromachining applications, where advanced models are pivotal to predict and optimize laser-material interactions. Existing models for predicting laser ablation efficiency assume an equivalence between the threshold fluence determined by ablation depth and diameter. However, experimental measurements have shown this assumption does not hold. In this work, we present a new model for ablation efficiency by introducing a minimum ablation depth (d0) into the ablation depth equation, which accounts for the discrepancy between depth and diameter thresholds. We have designated this framework as the threshold-refined ablation model (TRM). Unlike the Furmanski model, which places the fluence corresponding to maximum ablation efficiency at e2 times the threshold fluence, the TRM predicts this maximum occurs at a lower range (three to five times the threshold fluence), aligning with experimental findings. The new model has been validated against single-pulse experiments for metals, glasses, and dielectrics. For most cases, the TRM demonstrates significantly better agreement with experiments, providing enhanced predictive accuracy for sub-ps and fs pulses.
Spin-orbital mixing in the topological ladder of the two-dimensional metal PtTe2
(2025) Qahosh, M.; Masilamani, M.; Boban, H.; Hou, Xiao; Bihlmayer, G.; Mokrousov, Y.; Karain, W.; Minár, Jan; Reinert, F.; Schusser, Jakub; Schneider, C.M.; Plucinski, L.
We visualize the topological ladder and band inversions in PtTe2 using spin-polarized photoemission spectroscopy augmented by three-dimensional momentum imaging. This approach enables the detection of spin polarization in dispersive bands and provides access to topological properties beyond the reach of conventional methods. Extensive mapping of spin-momentum space reveals distinct topological surface states, including a surface Dirac cone at a binding energy ??∼2.3eV and additional states at ??∼1.6eV, ??∼1.0eV, and near the Fermi level. The electronic structure analysis demonstrates strong hybridization between Pt and Te atomic orbitals, confirming the nontrivial topology of these surface states. Furthermore, by comparison to one-step model photoemission calculations, we identify a robust correlation between the initial-state and measured spin polarizations while revealing asymmetries in specific experimental spin textures. These asymmetries, absent in the initial states due to symmetry constraints, arise from the breaking of time-reversal symmetry during the photoemission process, emphasizing the crucial influence of symmetries on experimental signatures of topology. A phase analysis of ladder states in real space suggests a route to probe them using photoemission, paving the way towards spectroscopic access to the quantum geometric tensor.

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