Step-like Transitions Research Articles

Achieving superior strength and ductility synergy in bulk ultrafine grained Al-Mg-Sc-Zr alloy via powder pre-aging

Introducing high density of nano-precipitates to recrystallized ultrafine grains is helpful to realize strength-ductility synergy but is a challenging task, because recrystallization and precipitate growth/coarsening usually concur. Here we develop a pre-aging powder metallurgy processing route to achieve such microstructure in Al-Mg-Sc-Zr alloy. During the pre-aging stage, atomic clusters including short-range order are formed within the grains, which provide new sites for the nucleation and enable the formation of fine Al3(Sc, Zr) precipitates. Subsequent high-temperature sintering and hot extrusion lead to grain recrystallization. The nano-precipitates not only further strengthen the ultrafine-grained alloy by Orowan mechanism, but also greatly enhance the strain-hardening rate by dislocation-precipitate interaction, resulting in excellent strength-ductility synergy. The utilization of digital image correlation (DIC) analysis allows for the observation of dynamic strain aging during the tensile process, whereby the strain demonstrates a distinctive step-like transition coinciding with the passage of the Portevin-Le Chatelier (PLC) band. This work provides a new path for improving the mechanical properties of the same type of metallic materials.

Integrated Optical Diagnostics Of Cyclopentane Sprays To Characterize Transcritical Phase Transitions

This research investigates spray phase transitions under subcritical and transcritical conditions relevant to high-pressure combustion systems. Using advanced optical diagnostic techniques, including shadowgraphy (SH), Mie scattering (MS), and infrared radiation (IR) measurements, the study focuses on cyclopentane sprays in a high-pressure, high-temperature chamber filled with gaseous nitrogen. Three cases are studied to understand spray behavior under varying injection conditions. SH and MS analyses reveal significant differences across the cases. As the chamber temperature increases, the liquid core length shortens, indicating enhanced vaporization. This is particularly evident in the MS images, where step-like transitions in the axial distribution highlight abrupt phase changes from liquid to gas in subcritical conditions. Such transitions are absent under supercritical conditions, suggesting a smoother phase transition process. IR measurements provide additional insights into the spray dynamics, especially under transcritical conditions. The IR images display complex downstream (at x/D > 125) signal patterns with bimodal distributions. The application of inverse Abel deconvolution highlights negative intensities near the spray axis downstream, indicative of regions near the pseudo-critical temperature. This phenomenon, characterized by blocked background radiation due to critical opalescence, offers indirect evidence of the pseudo-critical temperature and the associated phase transition dynamics. Dynamic Mode Decomposition (DMD) analysis identifies dominant frequencies around 4.5 kHz, corresponding to injection pressure fluctuations. This correlation suggests that injection pressure variations significantly influence spray fluctuations. Differences in mode shapes among the cases are also observed; lateral fluctuations near the injector nozzle exit are present in Cases 1 and 2 but not in Case 3. Axial fluctuations beyond a certain length are consistent in all cases. The lateral fluctuations are related to the chamber pressure and the potential large-scale vortex formation or cavitation in the nozzle. The combined use of SH, MS, and IR methodologies provides a comprehensive understanding of transcritical spray dynamics, emphasizing the effectiveness of combining multiple optical diagnostic techniques. These findings will improve numerical simulations and contribute to the development of more efficient high-pressure combustion systems. The research underscores the complexity of phase transitions in sprays and the critical role of precise diagnostics in the advancement of combustion technology.

(Benzimidazolium)2GeI4: A layered two-dimensional perovskite with dielectric switching and broadband near-infrared photoluminescence

Two-dimensional (2D) lead halide perovskites have attracted tremendous attention due to their outstanding physical properties. However, the presence of toxic lead is a major problem for large-scale applications. Here, we report the synthesis, phase transition, dielectric and photoluminescence (PL) properties of a lead-free 2D Ge-based perovskite (BIM)2GeI4 (BIM = benzimidazolium) which experiences a phase transition at 405 K accompanied by an order-disorder change of organic spacer. Moreover, the step-like dielectric transition near the phase transition temperature makes it suitable for dielectric switching. Meanwhile, (BIM)2GeI4 has a direct bandgap of 2.23 eV and broadband emission from 550 to 1000 nm, implying its unique optical property for potential near-infrared lighting and displaying. This work provides a fresh example for the development of lead-free 2D Ge-based perovskite with potential applications in the fields of optoelectronics and high temperature dielectric switching.

Response of the Verwey transition in magnetite to controlled point-like disorder induced by 2.5 MeV electron irradiation

Controlled point-like disorder induced by low temperature 2.5 MeV electron irradiation was used to probe the nature of the Verwey transition in magnetite, Fe3O4. Two large single crystals, one with optimal transition temperature, TV≈121 K, and another with TV≈109 K, as well as magnetite magnetosome nanocrystals harvested from the lysed cells of the marine magnetotactic vibrio Magnetovibrio blakemorei strain MV-1, TV≈110 K, were examined. Temperature-dependent resistivity is consistent with the semiconductor-to-semiconductor (insulator) sharp, step-like Verwey transition from a state with a small bandgap of around 60 meV to a state with a large bandgap of about 300 meV. The irradiation causes an up-shift of the resistivity curves above the transition without transition smearing or broadening. It also causes an apparent down-shift of the resistivity maximum at high temperatures. In the lower TV crystal, the electron irradiation drives the transition temperature into a “forbidden” interval of TV , believed to separate the first order from the second order phase transition. Contrary to this belief, the transition itself remains sharp and hysteretic without a significant change in the hysteresis width indicating the strong 1st order character of the Verwey transition for all TV values. The separate 2nd order - looking transition is likely due to sample inhomogeneities. We conclude that the sudden change of the bandgap accompanied (or driven) by the monoclinic distortion and the change of magnetic anisotropy is the reason for the Verwey transition in magnetite and the effect of additional disorder is mostly in the smearing of the sharp gap edges near the Fermi level.

Marine bird mass mortality events as an indicator of the impacts of ocean warming

The frequency and severity of marine heatwaves (MHWs), an emergent property of global warming, has led to large-scale disruptions to marine ecosystems. As upper trophic species, marine birds reflect shifts in trophic structure and stability; therefore, a sharp increase in marine bird mortality is a clear signal of ecosystem impact. In this study, we analyzed 29 yr (1993-2021) of beached bird monitoring data (~90000 surveys) to identify marine bird mortality events throughout the Northeast Pacific and Alaska, USA, and examined linkages to ocean-climate variability. Mortality events were documented throughout the study period, but massive events (>500 km in extent, >10 carcasses km-1) occurred infrequently (n = 5), with an unprecedented sequence from 2014-2019. Event characteristics, including encounter rate (carcasses km-1), duration, and spatial extent, were positively related to prior-year averaged sea surface temperature anomaly, with event magnitude (product of encounter rate, extent, and duration) displaying a step-like transition, increasing 5-fold between +0°C and +1°C above baseline (1981-2010) temperatures. Mortality events occurred more frequently following MHWs, and a common sequence of mortality events (at 1-6 and 10-16 mo after heatwave onset) was observed in the California Current large marine ecosystem following 3 prolonged MHW events. Following the second wave of mortality at 10-16 mo after MHW onset, a consistent 16 mo period of depressed carcass encounter rates ensued. Given continued global warming, our results point to more frequent large-scale mortality events and the potential for a new lower carrying capacity for marine birds in the Northeast Pacific.

Bi-stability and critical transitions in mental health care systems: a model-based analysis

BackgroundDelayed initiation and early discontinuation of treatment due to limited availability and accessibility of services may often result in people with mild or moderate mental disorders developing more severe disorders, leading to an increase in demand for specialised care that would be expected to further restrict service availability and accessibility (due to increased waiting times, higher out-of-pocket costs, etc.).MethodsWe developed a simple system dynamics model of the interaction of specialised services capacity and disease progression to examine the impact of service availability and accessibility on the effectiveness and efficiency of mental health care systems.ResultsModel analysis indicates that, under certain conditions, increasing services capacity can precipitate an abrupt, step-like transition from a state of persistently high unmet need for specialised services to an alternative, stable state in which people presenting for care receive immediate and effective treatment. This qualitative shift in services system functioning results from a ‘virtuous cycle’ in which increasing treatment-dependent recovery among patients with mild to moderate disorders reduces the number of severely ill patients requiring intensive and/or prolonged treatment, effectively ‘releasing’ services capacity that can be used to further reduce the disease progression rate. We present an empirical case study of tertiary-level child and adolescent mental health services in the Australian state of South Australia demonstrating that the conditions under which such critical transitions can occur apply in real-world services systems.ConclusionsPolicy and planning decisions aimed at increasing specialised services capacity have the potential to dramatically increase the effectiveness and efficiency of mental health care systems, promoting long-term sustainability and resilience in the face of future threats to population mental health (e.g., economic crises, natural disasters, global pandemics).

Modeling of Spin Crossover in Linear Trinuclear Complexes: Effects of External Pressure.

In the present study, a model is suggested to explain the course of spin transformation in crystals containing linear trinuclear iron(II) clusters as structural units. The energy spectrum of an isolated trimer is described with due allowance of the effects of the cubic crystal field formed by the nearest surrounding of each FeII ion as well as by consideration of intracluster interactions in the nearest neighbor approximation. The intercluster cooperative interaction promoting the spin transition is assumed to arise from the coupling of molecular modes with phonons, that is, a feature characteristic for molecular crystals containing as a structural element single spin-crossover ions or complexes formed by these ions. It is demonstrated that in dependence on the relative strengths of intra- and intercluster interactions, the trinuclear systems can exhibit a variety of different types of spin transitions and, namely, gradual, step-like transitions and those characterized by a hysteresis loop. The effects of external pressure on the spin transitions in crystals of trinuclear clusters are explored taking into account that pressure affects both the energy gap between the high-spin and low-spin states and the characteristic parameters of cooperative interaction. In the framework of the suggested model, the spin transformation in the Fe3(bntrz)6(tcnset)6 compound is comprehensively explained. The model also allows a qualitative and quantitative reproduction of the temperature and course of the spin transition in this compound under applied pressure.

An Exploration of an Early Gravity Transition in Light of Cosmological Tensions

We study a step-like transition in the value of the effective Planck mass (or effective gravitational constant) on cosmological scales prior to recombination. We employ cosmic microwave background, baryon acoustic oscillations, and Type Ia supernova data and find they are sufficient to strongly constrain our implementation of the effective field theory of dark energy and modified gravity, used to model the transition, to a limited parameter space. The data prefer a ∼5% shift in the value of the effective Planck mass (<10% at 2σ) prior to recombination. This Transitional Planck Mass (TPM) model is free to undergo its transition at any point over multiple decades of scale factor prior to recombination, (68% confidence level). This lowers the sound horizon at last scattering, which increases the Hubble constant to 71.09 ± 0.75 km s−1 Mpc−1 with a combination of local measurements as prior and to km s−1 Mpc−1 when the prior is excluded. The TPM model improves χ 2 with respect to ΛCDM by Δχ 2 = −23.72 with the H 0 prior and Δχ 2 = −4.8 without the prior. The model allows for both H 0 > 70 kms−1 Mpc−1 and S 8 < 0.80 simultaneously with lower values of S 8 due to a reduction in the matter density Ω m to offset the increase in H 0 relative to ΛCDM. While this is a particular modified gravity model, studying other variants of modified gravity may be a productive path for potentially resolving cosmological tensions while avoiding the need for a cosmological constant.

Optical system for the measurement of the surface topography of additively manufactured parts

Additive manufacturing (AM) is now regularly used for customised fabrication of parts with complex shapes and geometries. However, the large range of relevant scales, high slopes, step-like transitions, undercuts, alternation between dark and overly bright regions and other complex features present on the surfaces, in particular of metal additive parts, represent a significant challenge for current optical measurement technologies. Measuring surfaces with such complex features requires high numerical aperture (NA) optics, and state-of-the-art systems commonly include optics that can only reliably acquire surface topographies over a small field of view (FOV), typically tens or hundreds of micrometers. Such measurements are often insufficient for practical applications. Here, we present an optical system that features a large NA (0.3) and a wide FOV mm, capable of measuring AM parts in a single measurement, without the need for lateral stitching to increase the FOV. The proposed system exhibits optical properties that provide facility for large-field, high-resolution measurement of industrially-produced additively manufactured parts.

Reformed QoE-Based Approach in Bitrate-Adaptation for Dynamic Adaptive Streaming Systems

With the COVID-19 pandemic, the demand for popular streaming applications is expected to soar. Ensuring high user-perceived quality correlates with higher profits for content providers and delivery systems. Dynamic adaptive streaming over HTTP (DASH) is a widely adopted video streaming standard, utilized by service providers to provide competitive quality of experience (QoE). DASH is capable of providing seamless streaming even during uncertain network conditions by switching across different video qualities and their corresponding segment bitrates. This paper introduces a non-complex algorithm that allows smooth step-like transition in the streamed video quality. The proposed approach deploys an optimization model to manage key elements that affect the user-perceived experience such as video quality, re-buffering and quality switching events. The objective is to optimize the QoE metric, which is constrained by the network throughput, segment size and buffer occupancy to continuously select the optimum bitrate levels with low complexity.

Realistic neutron star models in f(T) gravity

We investigate the nonrotating neutron stars in f(T) gravity with f(T)=T+alpha {T}^2, where T is the torsion scalar in the teleparallel formalism of gravity. In particular, we utilize the SLy and BSk family of equations of state for perfect fluid to describe the neutron stellar matter and search for the effects of the f(T) modification on the models of neutron stars. For positive alpha , the modification results in a smaller stellar mass in comparison to general relativity, while the neutron stars will contain larger amount of matter for negative alpha . Moreover, there seems to be an upper limit for the central density of the neutron stars with alpha >0, beyond which the effective f(T) fluid would have a steplike phase transition in density and pressure profiles, collapsing the numerical system. We obtain the mass–radius relations of the realistic models of neutron stars and subject them to the joint constraints from the observed massive pulsars PSR J0030+0451, PSR J0740+6620, and PSR J2215+5135, and gravitational wave events GW170817 and GW190814. For the neutron star model in f(T) gravity to be able to accommodate all the mentioned data, the model parameter alpha needs to be smaller than -,4.295, -,6.476, -,4.4, and -,2.12 (in the unit of {G}^2M_odot ^2/c^4) for SLy, BSk19, BSk20, and BSk21 equations of state, respectively. If one considers the unknown compact object in the event GW190814 not to be a neutron star and hence excludes this dataset, the constraints can be loosened to alpha <-,0.594, -,3.5, 0.4 and 1.9 (in the unit of {G}^2M_odot ^2/c^4), respectively.

Hydrodynamic simulations of sedimenting dilute particle suspensions under repulsive DLVO interactions

We present guidelines to estimate the effect of electrostatic repulsion in sedimenting dilute particle suspensions. Our results are based on combined Langevin dynamics and lattice Boltzmann simulations for a range of particle radii, Debye lengths and particle concentrations. They show a simple relationship between the slope K of the concentration-dependent sedimentation velocity and the range χ of the electrostatic repulsion normalized by the average particle-particle distance. When χ → 0, the particles are too far away from each other to interact electrostatically and K = 6.55 as predicted by the theory of Batchelor. As χ increases, K likewise increases as if the particle radius increased in proportion to χ up to a maximum around χ = 0.4. Over the range χ = 0.4-1, K relaxes exponentially to a concentration-dependent constant consistent with known results for ordered particle distributions. Meanwhile the radial distribution function transitions from a disordered gas-like to a liquid-like form. Power law fits to the concentration-dependent sedimentation velocity similarly yield a simple master curve for the exponent as a function of χ, with a step-like transition from 1 to 1/3 centered around χ = 0.6.

Temperature-Dependent Structural Changes of Na2Mn3(P2O7)2 Phase in NaLiMnP2O7 Mixed Phase Compound

XRD measurements revealed that the investigated NaLiMnP2O7 compound consists of two phases: Na2Mn3(P2O7)2 and LiMnPO4. We found by XRD measurements that at 313 K Na2Mn3(P2O7)2 shows the triclinic symmetry of the compound (space group P-1), while LiMnPO4 phase showed the orthorhombic crystal symmetry (space group Pnma). The phase change between 773 K and 813 K was proved by thermal XRD, impedance spectroscopy and DTA analysis. No evident changes of peak intensities in thermal XRD were observed for LiMnPO4 phase. The impedance of NaLiMnP2O7 ceramics was measured at different temperatures and the total ionic conductivity of the compound was found to be of 5.3 × 10−9 S/m at 400 K on heating stage and only slightly higher on cooling stage. However, the conductivity value at 800 K was much higher – about 1.45 S/m on both stages. The step-like phase transition resulted in the conductivity increase of about 3 orders of magnitude in a narrow range of temperature. The ionic transference number was found to be 0.91 at room temperature. The XRD spectra and conductivity analysis of synthesised two separate phases showed that the phase transition takes place only in Na2Mn3(P2O7)2 ceramics.

Effect of Particle Size on Magnetic Phase Coexistence in Nanocrystalline La0.4Bi0.3Sr0.3MnO3

Magnetic phase coexistence in the substituted perovskite compound, La0.4Bi0.3Sr0.3MnO3, is attributed to the spontaneous moment and a step-like metamagnetic transition observed in the magnetization measurements in its magnetically order state. The magnetism of samples reduced to nanometer sizes by the “top down” approach exhibits interesting changes with respect to the bulk, thus giving a handle in influencing the physical properties by reducing the particle size. The bulk sample orders ferromagnetically at TC = 295 K, whereas in nano-sized samples with particle sizes in the range of 21–30 nm, even though TC does not change, the transitions are suppressed. The nano-sized powder samples show a broad hump in the plot of magnetic susceptibility, signifying the possible disordered antiferromagnetic state. A systematic decrease in the magnitude of magnetization in nano-sized samples shows that the reduction in magnetic interaction could be attributed to the formation of a magnetic dead layer around the magnetic core.

Swelling of Tendomer Gels

We propose a new type of polymer gels made of tendomers as elastic elements. Tendomers are a pair of rotaxanes with a specific nonlinear response and an almost step-like softening transition by increasing their extension. We consider the swelling equilibrium of tendomer gels in good solvents based on a Flory–Huggins type of approach. Using the exact solution for the single tendomer force–extension relation, we calculate the swelling equilibrium of the gels numerically. For the limiting cases of the linear and nonlinear elastic regimes of the tendomer strands, we derive analytic solutions for the equilibrium degree of swelling as a function of the system parameters. We show that the resulting tendomer networks can swell much more than conventional gels and that the preparation conditions can be tuned such that the gels swell predominantly in a linear or a nonlinear response regime. Tendomer gels are also a prototype of a super-soft and practically entanglement-free gel since at preparation state, the tendomers consist mainly of long elastically inactive tails that act as a reservoir of chain segments upon swelling or deformation. This results in a c*-like state at swelling equilibrium for appropriate preparation and swelling conditions. Besides swelling in a good solvent, we also consider the swelling equilibrium of charged tendomer gels. Specific preparation conditions are taken into account in terms of a prestrain coefficient of the network. Monte-Carlo simulations and numerical calculations are performed to test the theoretical predictions. Finally, we discuss a possible route for the synthesis of tendomer gels.

Disorder and epitaxial strain control of metamagnetic transition, large saturation magnetization, and magneto-terahertz properties of YMn0.5Cr0.5O3 polycrystals and thin films

The multiferroic YMn0.5Cr0.5O3 (YMCO) compound possesses magnetic phases that are debatable for their origin in intrinsic and extrinsic attributes. To extract the contribution of the polycrystalline disorder as well as determine the effect of structural modifications and epitaxial strain on the magnetic properties, we have formed YMCO bulk in polycrystalline pellet and powder forms, and epitaxial thin films with a wide range of compressive and tensile strains. The temperature and field dependent magnetization of polycrystals discards the possibility of magnetization reversal and unveils the presence of multidomain states with soft and hard characters in powder form. The epitaxial YMCO films possess an extraordinary structural control of their magnetic properties, as the tuning of compressive strain results in an increase of 4–5 factors of magnitude in the saturation magnetic moment. This strain engineering further allows a tuning of the magnetic property from spin frustration/short-range ordering to the long-range ordering, which also induces a rare phenomenon of sharp step-like metamagnetic transition. The implementation of magneto-terahertz time-domain spectroscopy on this system does not show the manifestation of any magnon/electromaganon resonance typical of a magnetoelectric phase, thus suggesting either a very weak or lack of coupling between magnetic and electric ordered parameters in polycrystalline YMCO. This study resolves some longstanding issues on the magnetic and magnetoelectric phases in addition to the epitaxial control of large magnetization and metamagnetic transition being potentially relevant in several aspects of spintronics applications.

FEATURES OF MANUFACTURE OF ADVANCED PROVISIONAL BRIDGE-BASED PROSTHESES

Abstract. The relevance of the topic is related to the need to improve methods of preparation of dentitions for orthopedic treatment, taking into account the defects of dentitions in patients with reduced occlusion height, taking into account the condition of the masticatory muscles and temporary use of plastic dentures, which provide gradual lifting of occlusion to normalize the masticatory group muscles and reorganization of myostatic reflexes.&#x0D; The aim of the research. Improving the effectiveness of preparation for orthopedic treatment of patients with partial tooth loss, with reduced occlusion height, by improving the design of a temporary bridge-based prosthesis.&#x0D; Materials and methods of research. We examined, treated and conducted clinical observation of 93 patients, who were divided into three groups according to the height of the reduction in occlusion, to achieve this goal and solve problems during the dissertation. Group 1 consisted of 32 patients with included dentition defects with reduced occlusion height up to 2 mm (n=32), group 2 - patients with included dentition defects with reduced occlusion height up to 2-4 mm (n=31), group 3 - these are patients with included dentition defects with reduced occlusion height up to 4-6 mm (n=30). All patients of the main groups belonged to the second and third age groups according to the WHO, aged 35-55 years. The control group (n=30) are young people who belonged to the 1st age group according to the WHO with intact dentition, without concomitant somatic and dental pathology, were admitted in one visit. Also, 123 fiberglass-reinforced plastic prostheses were made.&#x0D; Research results. When drawing up a plan for orthopedic treatment of patients with reduced occlusion height, we took into account possible complications, which are characterized by chipping of the facing material, pathological changes in the temporomandibular joint and masticatory muscle group. We have improved the method of manufacturing non-removable temporary plastic orthopedic constructions by reinforcing with fiberglass tapes and beams, to prevent them and gradually raise the bite.&#x0D; Expanded data on the dynamics of changes in myostatic reflexes and the effectiveness of the use of fixed orthopedic constructions, depending on the pathological process, the timing of adaptation of the masticatory muscle group to orthopedic constructions, according to the degree of reduction in occlusion height. The absence of complaints of breakage and other technical defects of the proposed temporary orthopedic constructions in 100% of cases, successfully allows to use it in the clinic of orthopedic dentistry.&#x0D; A new method of preparing patients for permanent orthopedic treatment by combined reinforcement of temporary non-removable bridge constructions with fiberglass tapes and beams is proposed, which differ in that after preliminary modeling of the frame of the bridge constructions, the technology of double reinforcement, model two support platforms with a step-like transition between them, in which fiberglass tapes and beams are fitted with dental tweezers, after which they are polymerized by the generally accepted method with a photopolymer lamp. Complete the modeling of the constructions and polymerize the prosthesis in the pneumopolymerizer with subsequent grinding and polymerize the prosthesis.&#x0D; Conclusion. The results of the research revealed the high efficiency of the improved method of manufacturing non-removable makeshift plastic of orthopedic constructions.

Field-induced phase transitions of tetramer-singlet states in synthetic SU(4) magnets

Phase transitions of quantum dimer magnets can be explained in terms of Bose-Einstein condensation of magnons. Here we consider a natural extension of the dimer magnets to SU(4)-symmetric tetramer systems, which could be created with four nuclear-spin components (named “u,” “d,” “c,” and “s”) of 173Yb atoms in optical superlattices. We apply the cluster mean-field approximation to the SU(4) Heisenberg model on a tetramerized square lattice, and study the phase transition phenomena in the presence of the field that creates a population imbalance between the two components u,d and the other two c,s. When the population of the four components is balanced, the ground state is approximately given by the direct product of local SU(4)-singlet states. When the field is applied, the population ratio of the components u and d is increased and the system eventually reaches a “saturated” state, which is a SU(2) system with only u and d. We show that in the saturation process, the system exhibits two successive step-like transitions, in contrast to the standard dimer magnets with continuous transition process associated with Bose-Einstein condensation of magnons. The intermediate phase in between the two step-like transitions is a nontrivial solid phase with alternating arrangement of the SU(4)-singlet and four-site resonating-valence-bond states.

Choice of surgical treatment for slipped capital femoral epiphysis with severe chronic displacement of the epiphysis

Background. The spatial relationship between the epiphysis and the acetabulum in slipped capital femoral epiphysis (SCFE) with severe chronic epiphysis displacement is restored by different corrective extra-articular femoral osteotomies and a standard Dunn procedure. Severe residual deformity of the femoral component of the joint with symptoms of femoroacetabular impingement and a large number of severe ischemic complications forced the surgeons to improve the technique of these surgical interventions. In particular, a modified Dunn procedure was proposed using a low traumatic surgical hip dislocation. However, the selection of surgical treatment in these patients remains a subject of discussion.&#x0D; Aim. This study aimed to improve the results of treatment in children with SCFE with severe chronic epiphysis displacement.&#x0D; Materials and methods. Data of preoperative and postoperative clinical and radiological studies of 40 patients (24 male and 16 female) aged 1215 years who were suffering from SCFE with severe chronic epiphysis displacement were analyzed. In all cases, on the lesion side, displacement was found in typical directions (posterior-downward or only posterior), and in the contralateral joint, the disease was still at its initial stage (pre-slip). In group 1 (n = 20 children), a corrective extra-articular femoral (anterior-rotational or rotational-valgus) osteotomy was performed according to the method we have proposed in 2011 [22], and in group 2 (n = 20 children), the modified Dunn procedure that strictly followed our technique was performed. The follow-up period after surgery in both groups ranged from 1 month to 2.5 years.&#x0D; Results. At 2.5 years after surgery, good anatomical and functional outcomes were observed only in 1 (12.5%) of 8 patients in group 1, while they were observed in 7 (87.5%) of 8 patients in group 2. Poor results were determined by residual epiphyseal displacement (from 22 to 28) and/or step-like transition of the anterior femoral neck surface to the head in 5 (62.5%) children in group 1 and by femoral head avascular necrosis (diagnosed in 6 months after surgery) in 1 (12.5%) child in group 2.&#x0D; Conclusion. The results allow us to make a preliminary conclusion about the high efficiency of the modified Dunn procedure and the low efficiency of the corrective extra-articular femoral osteotomy in SCFE with severe chronic displacement of the epiphysis. The modified Dunn procedure corrects the pronounced deformity of the femoral component of the affected joint and femoroacetabular impingement in the above-mentioned anatomical situations.

Development and characterization of multifunctional yttrium iron garnet/epoxy nanodielectrics

In the present work, a series of yttrium iron garnet/epoxy nanocomposite systems were fabricated, and the morphology of nanocomposites were tested by Scanning Electron Microscopy. The thermal stability of the developed systems was assessed by Thermogravimetric Analysis; their thermal properties were further investigated via Differential Scanning Calorimetry (DSC) and their viscoelastic response via Dynamic Mechanical Analysis (DMA). Finally, the dielectric characterization was carried out by means of Broadband Dielectric Spectroscopy. DSC curves revealed an endothermic step-like transition of all systems, attributed to the glass to rubber transition of the polymer matrix. All nanocomposites exhibit a two stages degradation profile. The presence of nanoinclusions enhances the thermal stability of the systems shifting the onset of the first degradation process to higher temperatures. Through the DSC and DMA techniques, the transition from glassy to rubbery state of the polymer matrix was observed and the characteristic Tg temperature was determined. The addition of the ceramic inclusions enhances the thermomechanical properties, as well as the dielectric response of the nanocomposites, as implied by the augmenting values of the real part of dielectric permittivity along with the storage modulus with the reinforcing phase loading. Three dielectric relaxation processes were identified: interfacial polarization, glass to rubber transition of the polymer matrix and reorientation of the small polar side groups of the polymer chain at low, intermediate and high frequencies, respectively. Furthermore, the ability of the systems to store energy was examined via the dielectric reinforcing function.