Search Results (374)

We briefly review the early development of the mean-field dynamics for cooperatively interacting quantum many-body systems, mapped to pseudo-spin (Ising-like) systems. We start with (Anderson, 1958) pseudo-spin mapping the BCS (1957) Hamiltonian of superconductivity, reducing it to a mean-field Hamiltonian of the XY (or effectively Ising) model in a transverse field. Then, we obtain the mean-field estimate for the equilibrium gap in the ground-state energy at different temperatures (gap disappearing at the transition temperature), which fits Landau’s (1949) phenomenological theory of superfluidity. We then present in detail a general dynamical extension (for non-equilibrium cases) of the mean-field theory of quantum Ising systems (in a transverse field), following de Gennes’ (1963) decomposition of the mean field into the orthogonal classical cooperative (longitudinal) component and the quantum (transverse) component, with each of the component following Suzuki–Kubo (1968) mean-field dynamics. Next, we discuss its applications to quantum hysteresis in Ising magnets (in the presence of an oscillating transverse field), to quantum heat engines (employing the transverse Ising model as a working fluid), and to the quantum annealing of the Sherrington–Kirkpatrick (1975) spin glass by tuning down (to zero) the transverse field, which provides us with a very fast computational algorithm, leading to ground-state energy values converging to the best-known analytic estimate for the model. Finally, we summarize the main results obtained and draw conclusions about the effectiveness of the de Gennes–Suzuki–Kubo mean-field equations for the study of various dynamical aspects of quantum condensed matter systems. Full article

This study presents the development and characterization of Grätzel cells (DSSCs), part of third-generation photovoltaic technologies, fabricated with and without the addition of graphene nanoparticles. A TiO₂ paste was prepared by combining colloidal solutions of Polyethylene Glycol (PEG) and Titanium Tetrachloride (TiCl₄), and then deposited on FTO (Fluorine-doped Tin Oxide) glass substrates via spin coating and sensitized with N719 dye. Each cell was assembled using two FTO electrodes, a photoanode (TiO₂/N719) and a platinum-coated counter electrode, separated by a liquid iodide/triiodide-based electrolyte to complete the redox cycle. The core objective was to optimize the graphene nanoparticle concentration within the TiO₂ matrix to improve photovoltaic performance. Samples with 0.1%, 0.2%, and 0.5% graphene were tested under simulated illumination (AM 1.5G), evaluating photocurrent, efficiency, and Fill Factor (FF). Optical analysis included desorption of N719 using NaOH to quantify intrinsic light absorption. Graphene’s high transparency and charge transport properties positively affected light harvesting. Results showed that graphene dosage is critical; 0.1% yielded the best efficiency, while excess concentrations diminished electronic and optical behavior. Controlled integration of graphene nanoparticles enhances DSSC performance and supports the development of more efficient and sustainable solar cells. Full article

The local segmental mobility of polymer chains in polydimethylsiloxane (PDMS) plays a critical role in determining the material’s behaviour. Incorporation of zeolite particles can modify these local dynamics, which is crucial as they affect the overall performance of the resulting composite material with potential for various industrial applications. The aim of this study was to investigate the influence of zeolite addition on the local dynamic behaviour of PDMS chain segments in PDMS–zeolite composites. To investigate the effect of zeolite morphology and loading on the segmental dynamics and phase behaviour of PDMS, Zeolite A (with cubic and spherical morphologies) and Zeolite X were incorporated into the PDMS matrix at 20, 30, and 40 wt%. The electron spin resonance (ESR)-spin probe method was used to study molecular dynamics, while the thermal behaviour was analysed using differential scanning calorimetry (DSC). ESR results revealed that the presence of zeolites increases the isothermal crystallisation rate affecting segmental mobility in the amorphous phase below the crystallisation temperature. This effect was found to depend more strongly on zeolite morphology than on filler content. DSC measurements showed no change in glass transition temperature with the addition of zeolite; however, shifts in cold crystallisation and melting behaviour were observed, indicating changes in crystal structure and its degree of perfection. These findings suggest that zeolites act as heterogeneous nucleation agents, with their structural properties playing a critical role in the crystallisation behaviour of PDMS. Full article

Size is a surface coating applied to glass fibres during manufacture, and it is arguably the most important component in a glass-reinforced composite. Research and development on sizings and composite interfaces are severely limited, because conventional laboratory- scale glass fibre sizing analysis commonly involves sample preparation by dip coating, resulting in a size layer up to two orders of magnitude thicker than industrially produced glass fibre products. This makes it difficult to make useful comparisons between industrial and lab-scale-prepared samples when investigating size performance. This paper presents a novel, but simple, use of laboratory spin coating to apply a size layer to glass fibres that are similar to industrial-sized fibres. Thermogravimetric analysis and electron microscopy were used to investigate the size layers of glass fibres spin-coated with two chemically different sizing formulations, under a range of conditions. The average size layer thickness on spin-coated glass fibres could be easily and simply controlled in a range from 0.05 to 0.6 µm, compared to 0.4–1.3 µm on samples dip coated with the same size formulation and 0.06–0.10 µm on industrial reference samples. This novel application of the spin coating method offers the potential of improved research sample preparation, as it eliminates the need to alter the concentration of the sizing formulations to unacceptably low levels to obtain normal size layer thicknesses. Full article

Background: Platelet-rich fibrin (PRF) is an autologous platelet concentrate (APC) produced through blood centrifugation. Despite the development of various centrifugation systems, protocol variability continues to pose challenges in selecting the optimal method. This study investigated the effects of three different centrifuges and collection tubes on the fibrin characteristics and growth factor release in leukocyte- and platelet-rich fibrin (L-PRF) and advanced platelet-rich fibrin plus (A-PRF+). Methods: Blood samples from six healthy female volunteers were processed using three centrifuges (Duo, IntraSpin, and LMC-3000) and three collection tubes (Pyrex, A-P, and silica-coated plastic) under high- (~700× g for 12 min) and low-speed (~200× g for 8 min) protocols. Fibrin clot weight and length were assessed. Growth factor release of platelet-derived growth factor-BB (PDGF-BB) and vascular endothelial growth factor (VEGF) was quantified using ELISA. Fibrin architecture was examined via scanning electron microscopy (SEM). Results: High-speed protocols tended to produce larger clots, whereas low-speed protocols generated smaller but more biologically active matrices. The IntraSpin and Duo centrifuges yielded greater clot dimensions and higher growth factor release than the LMC-3000. While tube type had no significant effect on growth factor levels, silica-coated tubes tended to produce the largest clots. The Pyrex tubes demonstrated comparable or superior growth factor release. Conclusions: PRF quality is influenced by centrifuge design, g-force, and tube material. Low-speed protocols with certified centrifuges are recommended, and FDA-approved glass tubes may provide a reliable alternative to reduce silica-related risks. Standardization and appropriate material selection are essential for consistent, safe, and effective regenerative outcomes. Full article

Bioactive coatings are of great interest for orthopedic applications, as they combine mechanical stability with biological functionality. In this study, stainless steel discs were coated with 45S5 bioactive glass doped with 1.0 wt% samarium by spin coating, followed by surface functionalization with benfotiamine through spraying. This strategy integrates three components: a metallic substrate as a stable and inexpensive support, a bioactive glass layer with well-known osteogenic potential, and a superficial organic layer of benfotiamine, a lipid-soluble analog of vitamin B1 with higher bioavailability. Samarium doping was selected based on previously reported antimicrobial potential against clinically relevant staphylococci, while the rationale for benfotiamine functionalization derives from literature describing vitamin B1 derivatives with anti-resorptive and osteogenic activity. The coatings were characterized by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) microscopy. Bioactivity was assessed by immersion in simulated body fluid (SBF), where phosphate bands indicated the formation of calcium phosphate phases (CaPs). Wettability tests showed a reduced contact angle after benfotiamine functionalization. Cytocompatibility was evaluated by LDH and MTT assays with MC3T3-E1 cells, suggesting overall biocompatibility and enhanced cell viability after 7 days for the benfotiamine-functionalized coatings. The present findings support a simple and cost-effective route to multifunctional coatings with potential relevance for future orthopedic applications. Full article

Geometrically frustrated magnets exhibit exotic excitations due to competing interactions between spins. The spinel compound MgCr₂O₄, a three-dimensional Heisenberg antiferromagnet, hosts both spin-wave and spin-resonance modes, but the origin of its resonant excitations remains debated. Suppressing magnetic order via non-magnetic doping can help isolate these modes in neutron scattering studies. We synthesized Ga³⁺ and Cd²⁺-doped MgCr₂O₄ via solid-state reaction and analyzed their structure and magnetism. Ga³⁺ doping (0–20%) causes anomalous lattice shrinkage due to site disorder from Ga³⁺ occupying both Mg²⁺ and Cr³⁺ sites. Magnetically, Ga³⁺ doping drives the system from the antiferromagnetic order to a spin-glass state, fully suppressing magnetic ordering at 20% doping. In contrast, Cd²⁺ replaces only Mg²⁺, expanding the lattice and meantime inducing strong spin-glass behavior. At 10% Cd²⁺, long-range antiferromagnetic order is entirely suppressed. Thus, 10% Cd-doped MgCr₂O₄ offers an ideal platform to study the resonant magnetic excitations without any spin-wave interference. Full article

In this work, a sol–gel spin coating method was applied to obtain ZnO and ZnO:Ga thin films on a glass and ITO-coated glass substrate. Their structural, optical, and electrical properties were investigated with respect to their dependence on the different substrates, the number of layers (two and four), and the annealing temperature (300 and 400 °C). X-ray diffraction (XRD) patterns showed a hexagonal structure corresponding to the wurtzite phase for ZnO and ZnO:Ga films. ZnO films, deposited on a glass substrate, reveal greater crystallite sizes compared with ZnO films obtained from an ITO substrate. A Ga dopant worsened film crystallization. X-Ray photoelectron spectroscopy (XPS) proves the presence of Ga in a ZnO structure. ZnO films show lower transparency and haze values up to 44.12 (glass substrate) and 33.73 (ITO substrate) at a wavelength of 550 nm. The significant enhancement of ZnO film transparency is observed with Ga doping (with average transmittance in the visible spectral range above 85%, independent of the substrate used). Sheet resistance values are lower for ZnO:Ga films, and the figure of merit values are better compared with those of undoped ZnO films. Work function is studied for ZnO and ZnO:Ga films, deposited on Si, ITO, and glass substrates. Full article

Analysis of the EPR of dilute transition-ion complexes and metalloproteins in random phases, such as frozen solutions, powders, glasses, and gels, requires a model for the spectral ‘powder’ shape. Such a model comprises a description of the line shape and the linewidth of individual molecules as well as a notion of their physical origin. Spectral features sharpen up with decreasing temperature until the limit of constant linewidth of inhomogeneous broadening. At and below this temperature limit, each molecule has a linewidth that slightly differs from those of its congeners, and which is not related in a simple way to lifetime broadening. Choice of the model not only affects precise assignment of g-values, but also concentration determination (‘spin counting’), and therefore, calculation of stoichiometries in multi-center complexes. Forty years ago, the theoretically and experimentally well-founded statistical theory of g-strain was developed as a prime model for EPR powder patterns. In the intervening years until today, this model was universally ignored in favor of models that are incompatible with physical reality, resulting in many mistakes in EPR spectral interpretation. The purpose of this review is to outline the differences between the models, to reveal where analyses went astray, and thus to turn a very long standstill in EPR powder shape understanding into a new start towards proper methodology. Full article

Nitrogen vacancy (NV) diamonds are promising room temperature quantum sensors. As the technology moves towards application, efficient use of energy and cost become critical for miniaturization. This work focuses on microwave-based spin control using the short-circuited end of a slot line, analyzed by finite element method (FEM) for magnetic field amplitude and uniformity. A microstrip-to-slot-line converter with a $-10$ dB bandwidth of $3.2$ GHz was implemented. Rabi oscillation measurements with an NV microdiamond on a glass fiber show uniform excitation over $1.5$ MHz across the slot, allowing spin manipulation within the coherence time of the NV center. Full article

Hydrogel films receive significant attention among researchers because they combine increased stimuli responsiveness and faster responses to the already excellent properties of their component materials. However, their preparation is complex and requires that many difficulties are overcome. The present work presents a new study regarding the preparation of pure and nanoparticle-loaded alginate-based films by spin-coating. Two-microliter solutions of sodium alginate and calcium chloride with different concentrations were deposited on a glass substrate and subjected to rapid rotations of between 100 and 1000 RPM. Film formation can be achieved by optimizing the ratio between the viscosity of the solutions, depending on their concentrations and the rotation speed. When these conditions are in the right range, a homogeneous film is obtained, showing good adherence to the substrate and uniform thickness. Films containing silver nanoparticles were prepared, exploiting the reaction between sodium borohydride and silver nitrate. The two reagents were added to the sodium alginate and calcium nitrate solution, respectively. Their concentration is the driving force for the formation of a uniform film: particles of about 50 nm that are well-dispersed throughout the film are obtained using AgNO₃ at 4 mM and NaBH₄ at 2 or 0.2 mM; meanwhile, at higher concentrations, one can also obtain the precipitation of inorganic crystals. Full article

In this study, the influence of annealing on the phase evolution and mechanical properties of the Fe₆₂Ni₁₈P₁₃C₇ (at.%) alloy was investigated. Ribbons produced via melt-spinning were annealed at various temperatures, and their structural transformations and hardness were evaluated. The alloy exhibited a narrow supercooled liquid region (ΔT_x ≈ 22 °C), confirming its low glass-forming ability (GFA). Primary crystallization began at approximately 380 °C with the formation of α-(Fe,Ni) and Fe₂NiP, followed by the emergence of γ-(Fe,Ni) phase at higher temperatures. A significant increase in hardness was observed after annealing up to 415 °C, primarily due to nanocrystallization and phosphide precipitation. Further heating resulted in a hardness plateau, followed by a noticeable decline. Additionally, samples were produced via selective laser melting (SLM). The microstructure of the SLM-processed material revealed extensive cracking and the coexistence of phosphorus-rich regions corresponding to Fe₂NiP and iron-rich regions associated with γ-(Fe,Ni). Full article

Tungsten-doped vanadium dioxide (W-VO₂) shows semiconductor-to-metal phase transition properties at room temperature, which is an ideal thermo-chromic smart window material. However, low visual transmittance and solar modulation limit its application in building energy saving. In this paper, a W-VO_2−x@AA core-shell nanoparticle is proposed to improve the thermo-chromic performance of W-VO₂. Oxygen vacancies were used to promote the connection of W-VO_2−x nanoparticles with L-ascorbic acid (AA) molecules. Oxygen vacancies were tuned in W-VO₂ nanoparticles by thermal annealing temperatures in vacuum, and W-VO_2−x@AA nanoparticles were synthesized by the hydrothermal method. A smart window was formed by dispersing W-VO_2−x@AA core-shell nanoparticles into PVP evenly and spin-coating them on the surface of glass. The visual transmittance of this smart window reaches up to 67%, and the solar modulation reaches up to 12.1%. This enhanced thermo-chromic performance is related to the electron density enhanced by the AA surface molecular coordination effect through W dopant and oxygen vacancies. This work provides a new strategy to enhance the thermo-chromic performance of W-VO₂ and its application in the building energy-saving field. Full article

Thermosensitive Poly(N-isopropylacrylamide) (PNIPAm) films were synthesized via atmospheric pressure dielectric barrier discharge (APDBD) plasma polymerization. In order to control the thickness of the films, a spin coating technique was used during the deposition of N-isopropylacrylamide (NIPAM) monomer solution onto several glass substrates. We used the coefficient of determination (R-square value) in linear regression to investigate the significance and optimize spin coating parameters during the fabrication of NIPAM coatings before exposure to APDBD plasma to ensure reproducible and uniform film properties. The spin coating parameters investigated in this study include spin speed, spin time, and NIPAM solution concentration with R-square values of 0.978, 0.946, and 0.944, respectively. Also, as a result of the thermosensitive nature of NIPAM, the spin coating operating conditions of temperature and humidity were maintained at 39.0 °C and 15%, respectively. During the APDBD plasma polymerization, argon was used as the discharge gas, and the distance between the two parallel electrodes and plasma frequency were maintained at 5.0 mm and 17 kHz, respectively. The plasma exposure time required for polymerization of PNIPAm coatings was optimized to 60 s. Also, the results showed that a coating with minimal defects had an optimal thickness of 5.18 μm, fabricated under conditions of 90 wt.% NIPAM concentration, spin speed of 4000 rpm, and total spin time of 7 s. Full article

Polarized Small-Angle Neutron Scattering is a versatile low-energy neutron scattering technique that allows for the access of magnetic information on nanosize objects of size 2–100 nm, from individual properties like the magnetization distribution inside the object to the collective behaviors, e.g., spin-glass effects or long-range magnetic ordering. The multi-scale possibilities of this technique is particularly relevant to encompass simultaneously the individual and collective many-body phenomena. In this article, we report the direct measurement of the magnetic form factor of “Prussian Blue Analog” molecular-based Ferromagnetic nanoparticles ${\mathrm{Cs}}_{\mathrm{x}}^{\mathrm{I}}{\mathrm{Ni}}^{\mathrm{II}}\left[{\mathrm{Cr}}^{\mathrm{III}}{\left(\mathrm{CN}\right)}_6\right]$ embedded in a polymer matrix with use of Polarized Small-Angle Neutron Scattering. We show that PSANS is particularly adapted to evaluate the internal magnetization distribution in nanoparticles and determine their magnetic morphology. Full article