The top 500 results for "Czech Republic" are:

A SiC Schottky diode and a Si surface barrier detector have been compared during Rutherford backscattering spectrometry (RBS) using 2–3 MeV proton beams. Both detectors are suited to detect high energetic ions with high-energy resolution for spectroscopic analysis. The correlations between the detector parameters and the surface passivating layers, ion energy and current dependence, ion penetration depth, detection efficiency and energy resolution, are outlined. Comparative RBS analysis performed using SiC and Si detectors has been investigated to highlight the advantages and disadvantages of the use of SiC with respect to the traditional Si junction detector. RBS spectrometry has been carried out using projectiles of proton incident on different targets to analyse their composition and thickness by the detection of the backscattered ions revealed by Si and SiC detectors.

A neural network for software compensation was developed for the highly granular CALICE Analogue Hadronic Calorimeter (AHCAL). The neural network uses spatial and temporal event information from the AHCAL and energy information, which is expected to improve sensitivity to shower development and the neutron fraction of the hadron shower. The neural network method produced a depth-dependent energy weighting and a time-dependent threshold for enhancing energy deposits consistent with the timescale of evaporation neutrons. Additionally, it was observed to learn an energy-weighting indicative of longitudinal leakage correction. In addition, the method produced a linear detector response and outperformed a published control method regarding resolution for every particle energy studied.

Bioinks play a crucial role in tissue engineering, influencing mechanical and chemical properties of the printed scaffold as well as the behavior of encapsulated cells. Recently, there has been a shift from animal origin materials to their synthetic alternatives. In this context, we present here bioinks based on fully synthetic and biodegradable poly(α,L-amino acids) (PolyAA) as an alternative to animal-based gelatin methacrylate (Gel-Ma) bioinks. Additionally, we first reported the possibility of the visible light photoinitiated incorporation of the bifunctional cell adhesive RGD peptide into the PolyAA hydrogel matrix. The obtained hydrogels are shown to be cytocompatible, and their mechanical properties closely resemble those of gelatin methacrylate-based scaffolds. Moreover, combining the unique properties of PolyAA-based bioinks, the photocrosslinking strategy, and the use of droplet-based printing allows the printing of constructs with high shape fidelity and structural integrity from low-viscosity bioinks without using any sacrificial components. Overall, presented PolyAA-based materials are a promising and versatile toolbox that extends the range of bioinks for droplet bioprinting.

A hydrophobic coating containing modified iron oxides was prepared for corrosion protection of aluminum alloy. The modified iron oxide particles were synthesized using the annealing method and the evaluation of the corrosion-resistant benefits of modified iron oxides as additive in the epoxy resin coating was conducted. The raw FeOOH phase can be transformed into the α-Fe₂O₃ phase by increasing the annealing temperature. The morphology, colors, and pore size of the modified iron oxide are controllably evolved via finely adjusting the annealing temperature, which is beneficial for the compatibility, dispersion, and stability with epoxy resin. Besides, modified α-Fe₂O₃ annealed at 700 °C exhibited elliptical morphology and good solubility in epoxy resin solvents to form a hydrophobic corrosion inhibition layer (TP700), which further improves the corrosion resistance. Findings of corrosion electrochemical measurements and salt spray test confirmed the existence of TP700 composite coating resulted in the best corrosion protective properties on aluminum alloy during the corrosion process with the minimum corrosion current of 7.75 × 10⁻¹⁰ A cm⁻² and the maximum |Z|_0.01Hz value of 1.80 × 10⁸ Ω cm², which both are about two orders of magnitude higher than the commercial Fe₂O₃. Our results suggest a new venue for preparing modified iron oxide pigment on the surface of aluminum alloy materials for enhanced anti-corrosion applications.

A rarefaction region (RR) occurs at the trailing edge of the fast solar wind stream. It comes from an area of small longitudinal extent on the solar surface and exhibits a fine and complex structure. In our study, we did a superposed epoch analysis of the proton and α parameters across the RR and observed their gradual evolution. We did not find any clear boundary between the fast and slow solar winds inside the RR because a majority of our observations show that most of the RR plasma corresponds to the fast solar wind; only the α–proton drift velocity decreases from the beginning of the RR. We investigate different ways of its reduction in interplanetary space and show that this feature is likely associated with the mirroring of the multicomponent solar wind. Nevertheless, considering the observed solar wind characteristics and taking into account the mutual relations between the proton and α parameters, we define the composition boundary where the α relative abundance and α–proton temperature ratio change abruptly from the values typical for the fast wind toward slow wind values. This boundary is the most probable candidate for the stream interface. Based on these findings, we speculate that the RR formation starts already near the Sun and formulate two possible scenarios.

Determining the number of propagating degrees of freedom in metric-affine theories of gravity requires the use of Hamiltonian constraint analysis, except in some subclasses of theories. We develop the technicalities necessary for such analyses and apply them to the Weyl-invariant and projective-invariant case of metric-affine-R² theory that is known to propagate just the graviton. This serves as a check of the formalism and a case study where we introduce appropriate ADM variables for the distortion 3-tensor tensor and its time derivatives, that will be useful when analyzing more general metric-affine theories where the physical spectrum is not known.

DANSS is a spectrometer for reactor antineutrinos based on plastic scintillator. The sensitive volume of the detector is made of 2500 polystyrene based scintillator plates with wavelength shifting (WLS) fiber readout (strips). We present a study of the light yield of strips during 6.5 years of DANSS continuous running. Overall ageing at the rate 0.55 ± 0.05 (syst.) % per year is observed that is considerably smaller than in other similar experiments. We also observe the WLS fiber attenuation length shortening at the rate 0.26 ± 0.04(stat.) % per year.

Debunking conspiracy theories is a never-ending battle. These theories often suggest that the condensation trails left by jet aircraft are, in fact, chemical or biological agents intentionally dispersed for various purposes. Although any discussion with supporters of conspiracy theories is pointless, this paper outlines several potential strategies for incorporating this theory into physics education. Specifically, the concept of 'chemtrails' can be leveraged to introduce basic principles of thermodynamics, facilitate the construction of atmospheric models, analyze readily available data, and, importantly, underscore the significance of critical and scientific thinking, which is so important for students these days.

The ¹¹B(p,α)2α reaction, generating three alpha particles, emerges as a promising alternative or complementary route for clean and efficient energy generation. A comprehensive understanding of reaction dynamics, energy distribution of emitted particles, and optimization of fusion efficiency requires precise diagnostic methods. CR39 detectors, being highly sensitive to ions and neutrons while remaining transparent to low fluxes of electrons and gammas, are extensively utilized as primary Solid State Nuclear Track Detector devices in laser-plasma environments. This study presents the CR-39 track detector calibration to low-energy protons and alpha particles. CR-39 irradiation took place at INFN-LNL (Istituto Nazionale di Fisica Nucleare — Laboratori Nazionali di Legnaro, Legnaro, Italy) across a range of energies (≥ 80 keV) up to a few MeV, employing various etching times with a NaOH solution. The observed discrepancy in particle diameters, related to a specific etching time, presents a promising avenue for distinguishing alpha particles from proton contributions. This finding holds potential for future practical applications in the study of ¹¹B(p,α)2α fusion reactions.

The reaction occurring between protons and ¹¹B isotope (p+¹¹B → 3α+8.7 MeV) has recently attracted attention as a possible candidate to overcome the generation of high-energy neutrons via the more studied Deuterium-Tritium fusion reaction. Since the early 2000s, several experiments have been carried out to investigate the viability of triggering this aneutronic reaction in laser-target interaction schemes. During these experiments, the total number of escaping α particles is measured to infer fusion reaction efficiency. However, the accurate detection of α particles in such experiments poses a real challenge. In this scenario, RadioChromic Films (RCFs) arranged in a stack configuration can be used for the fluence and energy spectra reconstruction of generated protons, being this mandatory information in both "pitcher-catcher" and "in plasma" p-¹¹B irradiation schemes. Nevertheless, RCF response exhibits a dependence on Linear Energy Transfer (LET), which leads to an underestimation of the response in high-LET conditions. This can result in dosimetric errors if not properly taken into account. In this work, an analytical procedure able to reconstruct the incident energy spectra in an RCF stack was developed and validated thanks to a calibration procedure that was established for high and low proton energy (4–60 MeV) beams to properly reconstruct the incident spectra in the "pitcher-catcher" irradiation scheme.

The ToASt ASIC is a 64-channel integrated circuit developed for the readout of the Silicon strip detector project designed to be placed in the Micro-Vertex Detector of the PANDA experiment. ToASt is implemented in a commercial 110 nm CMOS technology and can provide information on the position, time, and deposited energy of the particle passing through the detector. Its time resolution is given by its 160 MHz master clock. The ASIC has been developed in the framework of the European FAIRnet project. The chip has been characterized electrically both standalone and coupled with sensors, with focus on its noise performances. It has also been tested for radiation tolerance, both in terms of Total Ionizing Dose and Single Event Upset. In particular, this work aims to guarantee that the studied ASICs can sustain the levels of ionizing radiation expected in the PANDA experiment and to study the noise characteristics for the two polarities of the ASIC.

A collisional magnetized plasma sheath with two groups of electrons has been studied using a fluid model including the effects of the ionization source term and the collisional force between ions and neutral atoms. Two kinds of non-Maxwellian descriptions of electron velocity distribution, non-extensive distribution and truncated distribution, are applied in the model, and the ionization effects of both kinds are considered. By applying Sagdeev potential, the modified Bohm sheath criterion is derived. The effects of ionization, magnetic field, and high-temperature electron concentration ratio on plasma sheath density, potential, sheath thickness, and ion kinetic energy are studied. In cases with high background gas density, ion density accumulates at the sheath edge position, forming a peak and manifesting as a rapid drop in the potential profile. The distribution characteristics of electrons have a significant impact on the transport properties of ions. Oscillations and non-monotonic characteristics of net charge near the sheath edge occur as the magnetic field angle increases, leading to an increase in the sheath layer width. It can be seen that in the case of a collisional sheath structure with high-temperature electrons, it is essential to consider the sheath changes induced by the ionization and the collisional force. Compared to a symmetric electron velocity distribution, the actual thickness of the sheath layer in a truncated electron distribution assumption could be significantly reduced.

Transbronchial microwave ablation (MWA) with flexible antennas has gradually become an attractive alternative to percutaneous MWA for lung cancer due to its characteristic of non-invasiveness. However, flexible antennas for the precision ablation of lung tumors that are adjacent to critical bronchial structures are still not available. In this study, a non-invasive flexible directional (FD) antenna for early stage central lung tumors surrounding the bronchia was proposed. A comprehensive numerical MWA model with the FD antenna was developed in a real human-sized left lung model. The structure of the antenna and the treatment protocol were optimized by a generic algorithm for the precision ablation of two cases of early stage central lung cancer (i.e. spherical-like and ellipsoidal tumors). The electromagnetic efficiency of the optimized antenna was also improved by implementing an optimized $\pi$-matching network for impedance matching. The results indicate that the electromagnetic energy of MWA can be restricted to a particular area for precision ablation of specific lung tumors using the FD antenna. This study contributes to the field of lung cancer management with MWA.

The present research aims to study the dry turning machinability characteristics of in situ Al-4Mg/MgAl₂O₄ nanocomposite by High-Speed Steel tool. The influence of various machining process parameters, such as feed rate, depth of cut and cutting speed on the surface roughness and cutting force of the nanocomposites was measured while performing dry turning. From the turning operation results, it is noticed that up to 100 m min⁻¹, the cutting force increased and with further increases in cutting speed, the cutting force starts decreasing up to 150 m min⁻¹. The type of chips and built-up edge (BUE) development were studied using a scanning electron microscope. BUE formations were higher at low cutting speeds (50 m min⁻¹) and lower at high cutting speeds (150 m min⁻¹). At a given depth of cut and feed rate, with an increase in cutting speed, the length of the chip and chip curls increased. Further, higher 2 wt% of in situ MgAl₂O₄ addition changes long-curled chips to segmental-type chips. With a feed rate of 0.14 mm/rev, the Al-4Mg/1 wt% MgAl₂O₄ nanocomposite showed the lowest surface roughness value of 2.4 μm proving usage of high speed steel can provide a better surface finish while turning Al-4Mg/MgAl₂O₄ nanocomposite.

This paper analyses the efficiency of various frequency cepstral coefficients (FCC) in a non-speech application, specifically in classifying acoustic impulse events-gunshots. There are various methods for such event identification available. The majority of these methods are based on time or frequency domain algorithms. However, both of these domains have their limitations and disadvantages. In this article, an FCC, combining the advantages of both frequency and time domains, is presented and analyzed. These originally speech features showed potential not only in speech-related applications but also in other acoustic applications. The comparison of the classification efficiency based on features obtained using four different FCC, namely mel-FCC (MFCC), inverse mel-frequency cepstral coefficients (IMFCC), linear-frequency cepstral coefficients (LFCC), and gammatone-frequency cepstral coefficients (GTCC) is presented. An optimal frame length for an FCC calculation is also explored. Various gunshots from short guns and rifle guns of different calibers and multiple acoustic impulse events, similar to the gunshots, to represent false alarms are used. More than 600 acoustic events records have been acquired and used for training and validation of two designed classifiers, support vector machine, and neural network. Accuracy, recall and Matthew's correlation coefficient measure the classification success rate. The results reveal the superiority of GFCC to other analyzed methods.

Building on prior analysis of ASDEX Upgrade (AUG) experiments (Henderson et al 2023 Nucl. Fusion63 086024), this study compares simple analytical formula predictions for divertor detachment onset and reattachment timescales in JET experiments. Detachment onset primarily scales with divertor neutral pressure, impurity concentration, power directed to the targets, machine size, and integral perpendicular power decay length. JET experiments, focusing on seeding mixtures of Ne and Ar, align with the detachment onset predictions. Radiation efficiencies among the impurities show good agreement with the model predictions, contrasting with AUG observations which suggested higher efficiency for Ar and lower efficiency for Ne. The time taken to re-ionise the neutral volume in front of the outer target in fully detached divertor conditions was measured following both abrupt increases in injected neutral beam power and, separately, cutting of the impurity gas flow. Re-ionisation of the neutrals occurs within approximately 1 s on JET, which aligns with the simple model prediction derived from AUG data. While the AUG results are not new, their comparison with the JET results enhances understanding, reinforcing confidence in using simple models to predict future reactor scenarios.

Ultraviolet (UV) processing in the interstellar medium (ISM) induces the dehydrogenation of hydrocarbons. Aliphatics, including alkanes, are present in different interstellar environments, being prevalently formed in evolved stars; thus, the dehydrogenation by UV photoprocessing of alkanes plays an important role in the chemistry of the ISM, leading to the formation of unsaturated hydrocarbons and eventually to aromatics, the latter ubiquitously detected in the ISM. Here, through combined experimental results and ab initio calculations, we show that UV absorption (mainly at the Lyα emission line of hydrogen at 121.6 nm) promotes an alkane to an excited Rydberg state from where it evolves toward fragmentation, inducing the formation of olefinic C=C bonds, which are necessary precursors of aromatic hydrocarbons. We show that the photochemistry of aliphatics in the ISM does not primarily produce direct hydrogen elimination but preferential C–C photocleavage. Our results provide an efficient synthetic route for the formation of unsaturated aliphatics, including propene and dienes, and suggest that aromatics could be formed in dark clouds by a bottom-up mechanism involving molecular fragments produced by UV photoprocessing of aliphatics.

The electrical properties and activation energy of epoxy/graphite flakes (GFs) micro-composite with different content of GFs (0.0625–1 wt%) were studied for electrical properties using Novocontrol Alpha Analyser (10⁻² Hz—10⁷ Hz). GFs sizes ranged from (100 nm to 10 μm). The analysis was performed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), visible spectrum reflectance spectra (VIS) spectra, and Fourier Transform Infrared spectra (FTIR) spectroscopy. Increasing GFs content caused multiple changes in electrical characteristics. At 0.0625 wt%, all electrical properties noticeably increased. But at 0.125 to 0.25 wt%, immobilized nanolayers were formed leading to decreased permittivity, dielectric loss (tan(δ)), quality factor (Q-factor), capacitance, conductivity, and figure of merit (F-factor). At 0.25 wt%, the epoxy microcomposite had lower permittivity, tan(δ), conductivity, and capacitance compared with unfilled epoxy. With 0.5 wt% of GFs, signified the percolation threshold, initiating a rise in permittivity, conductivity, capacitance, and tan(δ), accompanied by the closer proximity of grain boundaries, facilitating the formation of conductive channels. At a concentration of 1 wt% of GFs, the establishment of continuous interfacial conductive pathways resulted in a remarkable augmentation of all dielectric properties. The Cole-Cole analysis has been employed to investigate variations in epoxy/GFs microcomposites based on concentration levels.

Rapid and accurate determination of rutin content in pharmaceuticals in an important issue. Here, a paper-based electrochemical sensor for in situ growth of chain ZIF-8 using multi-walled carbon nanotubes (MWCNTs) as a template was constructed by hydrothermal method. The results showed that the combination of ZIF-8 and MWCNTs not only promoted the dispersion of MWCNTs, but also made up for the conductivity of ZIF-8. Under optimum conditions, the Ipa was linearly related to the concentration of rutin in the range of 0.01–10 and 10–190 μM with a limit of detection (LOD) of 2.82 nM. Finally, the paper-based electrochemical sensor can be used for the electrochemical detection of rutin through the determination of rutin in pharmaceuticals.

Large terrestrial bodies in our solar system like the Earth, Mars, Mercury, and the Moon exhibit geologically complex surfaces with compositional heterogeneity. From past studies using large telescopes and spacecraft, it was shown that asteroids with diameters larger than 100 km also show surface heterogeneity at hemispheric scales, while on smaller objects, such features remain to be detected. Here, we investigate candidates for surface heterogeneity in a sample of 130 main-belt asteroids using multiepoch spectroscopic data from the MIT–Hawaii Near-Earth Object Spectroscopic Survey, which has been observing asteroids for about 20 yr using a self-consistent observation technique. Twelve conservative candidates with spectra more than 3σ apart from each other at 2.4 μm and 52 optimistic candidates for surface heterogeneity are detected. These candidates include eight objects already reported as being heterogeneous. Our study suggests that the size boundary between small homogeneous asteroids and larger heterogeneous objects, if it exists, is lower than 100 km. A-type asteroids have a higher proportion of heterogeneous candidates than other asteroids. This may be because olivine, which is the main surface constituent of these objects, reacts more efficiently to space weathering with respect to pyroxene, such that a similar range of surface ages will translate into a wider range of optical-to-near-infrared spectral slopes in the case of A-type bodies.