Search Results (25)

Proton spin–lattice and spin–spin NMR relaxation studies were conducted on lung tissue samples from 10 patients. For each case, relaxation properties of tumor tissue were compared with those of the corresponding reference tissue. The spin–lattice relaxation measurements were performed over a wide frequency range, from 10 kHz to 10 MHz, spanning three orders of magnitude. These were complemented by both spin–lattice and spin–spin relaxation data acquired at 18.7 MHz. Notably, the spin–spin relaxation process exhibited a bi-exponential character. This relaxation behavior was quantitatively analyzed using dedicated models to achieve two main goals: to evaluate the diagnostic potential of low-field NMR relaxometry, and to gain insights into the dynamics of water and macromolecules in tissue, in comparison with aqueous solutions of proteins and polymers. The frequency dependence of the spin–lattice relaxation rates was well described by a power-law function, with an exponent of approximately 0.3 closely matching the theoretical prediction for reptation dynamics in polymer systems, associated with the intermolecular relaxation contribution. The combined analysis of spin–lattice and spin–spin relaxation data revealed specific parameters (such as ratios between the relaxation rates or between the amplitudes of individual relaxation components) that can be considered as potential markers of pathological changes affecting molecular dynamics in tissues. Full article

This study conducts a detailed viscoelastic simulation of the side-by-side PA6/PA66 bicomponent melt spinning process to investigate the mechanisms behind reduced fiber elasticity. A two-dimensional (2D) axisymmetric finite element model was developed using ANSYS Polyflow, incorporating the Phan–Thien–Tanner (PTT) constitutive equation and a non-isothermal crystallization model. Simulation outcomes were validated with experimental and published data, showing close agreement in fiber radius, velocity, and temperature profiles (within 8% deviation). Results indicate that the dominance of the higher-viscosity PA66 phase induces uneven stress distributions and localized crystallization, leading to decreased elastic recovery. Higher winding speeds amplify this effect. This work offers a predictive framework for optimizing industrial melt spinning conditions to improve elasticity in bicomponent fibers. Key results indicate that the dominance of the PA66 component—due to its higher melt viscosity—leads to uneven stress distribution, elevated tensile stress, and localized crystallinity peaks along the spin line. These factors collectively contribute to reduced elastic recovery in the fiber. Moreover, increased winding speeds amplify axial stress and crystallinity disparities, further exacerbating the stiffness of the final product. In contrast, better elasticity was associated with lower pressure drop, balanced crystallinity, and minimized axial velocity differences between the two polymer phases. The findings offer valuable insights into optimizing industrial melt spinning processes to enhance fiber elasticity. This research not only improves fundamental understanding of viscoelastic flow behavior in bicomponent spinning but also provides a predictive framework for tailoring mechanical properties of fibers through process and material parameter adjustments. Full article

In environmental chemistry, photocatalysts for eliminating organic contaminants in water have gained significant interest. Our study introduces a unique heterostructure combining MIL-101(Cr) and bismuth oxyiodide (Bi₅O₇I). We evaluated this nanostructure’s efficiency in adsorbing and degrading tetracycline (TC) under visible light. The Bi₅O₇I@MIL-101(Cr) composite, with a surface area of 637 m²/g, prevents self-aggregation seen in its components, enhancing visible light absorption. Its photocatalytic efficiency surpassed Bi₅O₇I and MIL-101(Cr) by 33.4 and 9.2 times, respectively. Comprehensive analyses, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirmed the successful formation of the heterostructure with defined morphological characteristics. BET analysis demonstrated its high surface area, while X-ray diffraction (XRD) confirmed its crystallinity. Electron spin resonance (ESR) tests showed significant generation of reactive oxygen species (ROS) like h⁺ and·•O₂⁻ under light, crucial for TC degradation. The material maintained exceptional durability over five cycles. Density functional theory (DFT) simulations and empirical investigations revealed a type I heterojunction between Bi₅O₇I and MIL-101(Cr), facilitating efficient electron–hole pair separation. This study underscores the superior photocatalytic activity and stability of Bi₅O₇I@MIL-101(Cr), offering insights into designing innovative photocatalysts for water purification. Full article

¹H fast field-cycling and time-domain nuclear magnetic resonance relaxometry studies have been performed for 15 samples of sugar of different kinds and origins (brown, white, cane, beet sugar). The extensive data set, including results for crystal sugar and sugar/water mixtures, has been thoroughly analyzed, with a focus on identifying relaxation contributions associated with the solid and liquid fractions of the systems and non-exponentiality of the relaxation processes. It has been observed that ¹H spin–lattice relaxation rates for crystal sugar (solid) vary between 0.45 s⁻¹ and 0.59 s⁻¹, and the relaxation process shows only small deviations from exponentiality (a quantitative measure of the exponentiality has been provided). The ¹H spin–lattice relaxation process for sugar/water mixtures has turned out to be bi-exponential, with the relaxation rates varying between about 13 s⁻¹–17 s⁻¹ (for the faster component) and about 2.1 s⁻¹–3.5 s⁻¹ (for the slower component), with the ratio between the amplitudes of the relaxation contributions ranging between 2.8 and 4.2. The narrow ranges in which the parameters vary make them a promising marker of the quality and authenticity of sugar. Full article

With the megatrend of digitalization, the demand for sensors in previously difficult-to-access scenarios is increasing. Filament-shaped sensors (FSS) are ideal for this demand, especially in applications in which the monitoring of textile structures is the focus. Electrically conductive bicomponent filaments based on thermoplastic polyurethane (TPU) and doped with carbon nanotubes (CNTs) offer great potential due to their flexible mechanical properties. Through the core-conducting, bicomponent structure, the sensing material is protected from environmental factors such as surrounding conductive materials and external moisture. The insulating material, however, simultaneously complicates the contacting method in order to measure sensing changes in the conductive core. In this work, laser cutting is employed as a technology in order to expose the conductive core of the filaments. The filament is then coated with silver and mechanically crimped, providing both a conductive interface for the data acquisition device as well as a protective layer. Laser parameters (power 20–100 W and speed 5–50 mm/s) are investigated to identify the parameters with the best cutting properties for which the filaments are analyzed visually and electrically. This work provides a robust and reproducible method for contacting core-conducting TPU filaments for strain-sensing applications. This study shows that while the choice of laser parameter influences the morphology of the cut surface, its impact on the resulting linear resistivity is negligible. Full article

In this study, textile fiber prototypes based on polyester and different Cu nanoparticles (CuNP) content were produced using melt-spinning to obtain bi-component multifilament fibers and melt-blowing to obtain non-woven fabrics. The prototypes were tested against pathogenic microorganisms such as S. aureus, E. coli, and C. albicans. It was shown that bi-component fibers offer excellent protection against pathogens, with up to 99% growth inhibition with 0.5% w/w for S. aureus and E. coli; meanwhile, non-woven fabric only shows activity against E. coli from 0.1% w/w of CuNP. Using different analytical techniques, it was possible to identify that the CuNP were confined exclusively in the outer cover of the bi-component fibers which may be associated with increased antimicrobial activity compared to the fibers in the non-woven fabric. The use of polymeric nanocomposites based on polyester/copper offers an alternative of great interest due to the versatility of the raw material and the high efficiency of copper nanoparticles as an antimicrobial additive. Full article

The miniaturization of quantum sensors is a popular trend for the development of quantum technology. One of the key components of these sensors is a coil which is used for spin modulation and manipulation. The bi-planar coils have the advantage of producing three-dimensional magnetic fields with only two planes of current confinement, whereas the traditional Helmholtz coils require three-dimensional current distribution. Thus, the bi-planar coils are compatible with the current micro-fabrication process and are quite suitable for the compact design of the chip-scale atomic devices that require stable or modulated magnetic fields. This paper presents a design of a miniature bi-planar coil. Both the magnetic fields produced by the coils and their inhomogeneities were designed theoretically. The magnetic field gradient is a crucial parameter for the coils, especially for generating magnetic fields in very small areas. We used a NMR (Nuclear Magnetic Resonance) method based on the relaxation of ${}^{131}Xe$ nuclear spins to measure the magnetic field gradient in situ. This is the first time that the field inhomogeneities of the field of such small bi-planar coils have been measured. Our results indicate that the designed gradient caused error is 0.08 for the $B_y$ and the $B_x$ coils, and the measured gradient caused error using the nuclear spin relaxation method is $0.09\pm 0.02$, suggesting that our method is suitable for measuring gradients. Due to the poor sensitivity of our magnetometer under a large $B_z$ bias field, we could not measure the $B_z$ magnetic field gradient. Our method also helps to improve the gradients of the miniature bi-planar coil design, which is critical for chip-scale atomic devices. Full article

Carbon fibers (CF) and their composites (CC) are one of the world’s most promising and avant-garde high-performance materials, as they combine excellent mechanical characteristics with high weight reduction potential. Polyethylene (PE) is the perfect alternative precursor for CF as it combines widespread availability, low cost, high carbon content, and, most importantly, precursor fibers that can be produced via melt-spinning. PE-based CF production involves a challenging and time-consuming diffusion-limited chemical stabilization step. The work presented in this article tackles the challenge of reducing the chemical stabilization process time by converting a bicomponent island-in-the-sea fiber, consisting of PA6 as sea matrix and HDPE as island material, into an ultra-thin PE-precursor fiber. The produced precursor fiber is then successfully converted into an ultra-thin PE-based CF through sulfonation and subsequent carbonization in a continuous set-up. The resulting CF has a smooth surface with no observable surface defects and a filament diameter of around 3 µm. The successful conversion to ultra-thin CF is shown in both batch and continuous processes. Additionally, a reduction in sulfonation reaction time from 4 h to 3 h is achieved. Full article

Protective clothing in gas and oil industries requires high-performance characteristics, with superior anti-static and ultraviolet (UV) protection and good thermal wear comfort in cold weather regions. This study examined the manufacturing and properties of various ceramic-embedded composite fabrics made from a new scheme (not a coating method) for protective clothing in the gas and oil industries. Therefore, sheath–core yarn specimens embedded with various ceramics, such as aluminum oxide (Al₂O₃)–graphite, zinc oxide–zirconium (ZnO–ZrC), and zinc oxide–antimony tin oxide (ZnO–ATO) were produced using a bi-component melt spinning machine, which is a novel method that was not tried before. Fabric specimens were also made from these ceramic-embedded sheath–core yarn specimens. UV-protection and anti-static properties of the ceramic-embedded composite specimen were compared with the thermal radiation and far-infrared (FIR) characteristics. The UV-protection factor (UPF) was measured according to the AS/NZ 4399 (1996) standard. ATLAS measuring equipment was used to analyze five duplicate specimens (4 × 8 cm). An anti-static assessment was also conducted using the JIS L 1094 standard method. A light heat emission apparatus was used to assess thermal radiation. A 10 × 10 cm specimen was prepared, and five duplicate assessments were conducted. Statistical analysis (F-test) was performed to verify the statistical significance of the experimental data with a 99% confidence limit. The ZnO–ATO-embedded composite fabric exhibited greater UV protection than the Al₂O₃–graphite-embedded and regular (control) specimen, indicating the excellent UV-protection property of the ZnO. In addition, the ZnO–ATO-embedded composite specimen exhibited excellent anti-static properties with lower rub-static voltage than the control fabric, which was attributed to the better electrical conductivity of ATO particles. In particular, the ZnO–ZrC-embedded composite specimen showed superior thermal radiation with excellent UPF and relatively good anti-static characteristics. Based on the high-performance characteristics of protective clothing worn in gas and oil industries, ZnO–ATO-embedded composite fabric has practical use for fabricating workwear protective clothing. In addition, considering protective clothing suitable for cold weather, ZnO–ZrC-embedded composite fabric is useful for protective clothing in cold weather regions. Full article

Solution blow spinning was used to prepare nonwoven bicomponent fibers constituted by poly (ethylene oxide)-Polysulfone (PEO-PSF). As a new material, deep characterization was carried out to have a database to understand final performance regarding its multiple functions as a potential material for biomedical applications. The morphology was studied by field emission scanning electron and transmission electron microscopy and optical profilometry. Structural characterization was carried out by Fourier transform infrared spectroscopy and thermal degradation by thermogravimetric analysis. Additionally, wettability and mechanical behavior were studied by contact angle measurements and tensile tests, respectively. The bicomponent material was constituted of fibers with a structure mainly described by a core-shell structure, where the PSF phase is located at the center of the fibers, and the PEO phase is mainly located at the outer parts of the fibers, leading to a kind of shell wall. The study of possible interactions between different phases revealed them to be lacking, pointing to the presence of an interface core/shell more than an interphase. The morphology and roughness of the bicomponent material improved its wettability when glycerol was tested. Indeed, its mechanical properties were enhanced due to the PSF core provided as reinforcement material. Full article

In this study, side-by-side bicomponent fibers were prepared by melt spinning using bio-based thermoplastic polyurethane (TPU) and TPU/polylactic acid (PLA) blends. The morphology, thermal and mechanical properties of the fibers were investigated. To this end, the synthesis of TPU using biomass-based polyols and the preparation of TPU/PLA blends were preceded. Their morphological and structural characteristics were investigated. The synthesis of TPU was confirmed through Fourier transform infrared analysis, and as a result of gel permeation chromatograph analysis, a compound having a weight average molecular weight of 196,107 was synthesized. The TPU/PLA blends were blended in the ratio of 80/20, 60/40, 40/60, and 20/80 through a melt extruder. They formed a sea–island structure as a result of scanning electron microscope analysis, and an increase in the PLA content in the TPU matrix caused a decrease in the melt flow index. Finally, TPU/(TPU/PLA) side-by-side bicomponent fibers were prepared by utilizing the above two materials. These fibers exhibited tensile strengths of up to 3624 MPa, with improved biocarbon content of up to 71.5%. These results demonstrate the potential of TPU/(TPU/PLA) side-by-side bicomponent fibers for various applications. Full article

Thermoresponsive self-crimping polybutylene terephtlate (PBT)-based bicomponent fibers were fabricated by melt-spinning to serve as primary constituents for textiles, such as nonwoven battings, for an adaptive single insulting layer. Due to the intrinsically mismatching modulus and coefficient of thermal expansion (CTE), the fibers curl or straighten with temperature, similar to the concept of Timoshenko’s bimetallic strip. Maximizing the curvature is driven by an optimum of fiber diameter, overall CTE, and fiber moduli, which are all affected by drawing ratio and, consequently, fiber’s microstructure. A draw ratio of 2.33 yielded the best combination of mechanical and thermal properties; it was observed that increasing the draw ratio does not necessarily increase the self-crimping behavior. Tests performed on non-woven battings of these fibers exhibited comparable thermoreponsive behaviors to polypropylene-based thermoresponsive fibers from previous studies in the −20 °C to 20 °C temperature range, which has potential for wearable insulations for both commercial and defense sectors alike. Full article

Electronic band-gap is a key factor in applying two-dimensional (2D) topological insulators into room-temperature quantum spin Hall effect (QSH) spintronic devices. Employing pseudopotential plane-wave first-principles calculations, we investigate spin-orbit coupling (SOC) electronic structures of the novel 2D topological insulator series of antimony (Sb) and bismuth (Bi) monolayers (isolated double atomic layers) functionalized by organic-groups (methyl, amino and hydroxyl). Cohesive energies and phonon frequency dispersion spectra indicate that these organic-group decorated Sb and Bi monolayers possess structural stability in both energetic statics and lattice dynamics. The giant electronic band-gaps adequate for room-temperature applications are attributed to the effective SOC enhancement of group functionalization. The nontrivial topology of these novel 2D monolayer materials is verified by the Z₂ invariant derived from wave-function parity and edge-states of their nanoribbons, which is prospective for QSH spintronic devices. The chemical functional group changes the p-orbital component of Fermi level electrons, leading to strong intra-layer spin-orbit coupling, opening a large band-gap of approaching 1.4 eV at Dirac-cone point and resulting in a global indirect band-gap of 0.75 eV, which, even underestimated, is adequate for room-temperature operations. Sb and Bi monolayers functionalized by organic groups are also predicted to maintain stable nontrivial topology under in-layer biaxial strain, which is suitable for epitaxy technology to realize QSH spintronic devices. Full article

High thermostability of phase change materials is the critical factor for producing phase change thermoregulated fiber (PCTF) by melt spinning. To achieve the production of PCTF from melt spinning, a composite phase change material with high thermostability was developed, and a sheath-core structure of PCTF was also developed from bicomponent melt spinning. The sheath layer was polyamide 6, and the core layer was made from a composite of polyethylene and paraffin. The PCTF was characterized by scanning electron microscopy (SEM), thermal analysis (TG), Fourier Transform Infra-Red (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and fiber strength tester. The results showed that the core material had a very high thermostability at a volatilization temperature of 235 °C, the PCTF had an endothermic and exothermic process in the temperature range of 20–30 °C, and the maximum latent heat of the PCTF reached 20.11 J/g. The tenacity of the PCTF gradually decreased and then reached a stable state with the increase of temperature from −25 °C to 80 °C. The PCTF had a tenacity of 343.59 MPa at 0 °C, and of 254.63 MPa at 25 °C, which fully meets the application requirements of fiber in textiles. Full article

The increasing interest in luminescent waveguides, applied as light concentrators, sensing elements, or decorative illuminating systems, is fostering efforts to further expand their functionality. Yarns and textiles based on a combination of distinct melt-spun polymer optical fibers (POFs), doped with individual luminescent dyes, can be beneficial for such applications since they enable easy tuning of the color of emitted light. Based on the energy transfer occurring between differently dyed filaments within a yarn or textile, the collective emission properties of such assemblies are adjustable over a wide range. The presented study demonstrates this effect using multicolor, meltspun, and photoluminescent POFs to measure their superimposed photoluminescent emission spectra. By varying the concentration of luminophores in yarn and fabric composition, the overall color of the resulting photoluminescent textiles can be tailored by the recapturing of light escaping from individual POFs. The ensuing color space is a mean to address the needs of specific applications, such as decorative elements and textile illumination by UV down-conversion. Full article