Defect Zone Research Articles

Defect quantification evaluation of a rolling element bearing based on physical modelling and instantaneous vibration energy investigation

The estimation of defect size of rolling element bearing (REB) is expected to remain a significant and challenging task in vibration-based condition monitoring of rotating machinery. The conventional approaches focus on extracting the time spacing of the double impulse signal to estimate the defect size of the REB which is subsequently found to be inaccurate and arbitrary. In this paper, a novel model is developed to estimate the defect size of the REB based on the theories of physics and kinematics, in which the multi-event excitations, i.e. the entry, destressing and collision generated by the rolling element-defect interaction, are considered and investigated. The kinematic and geometric contact mechanism, which is mapped onto the rolling element-defect interaction as the rolling element passes over the defect zone, are analyzed and modelled as a function of the time information. In view of the fact that the variation of the vibration energy contained in the multi-impact vibration response is deeply mapped to the time information, a novel idea is proposed to extract the time information by analyzing the instantaneous energy variation of the defect-induced impulse using the scheme of the autoregressive model and the smooth pseudo Wigner-Ville distribution. The proposed model and idea are validated by experiments under different defect size and rotational speed scenarios. The results calculated by the proposed model show good agreement with the real defect size. Experimental and modelling comparisons show that the proposed model has reliable effectiveness and good performance and confidence in quantifying the size of the defect area localized on the outer raceway of the REB, and can provide some theoretical guidance for damage detection and remaining useful life prediction of the REB.

ОСОБЕННОСТИ СТРУКТУРЫ СОЕДИНЕНИЯ В ЗОНЕ РЕМОНТА СВАРКОЙ ВЗРЫВОМ ДЕФЕКТОВ СПЛОШНОСТИ БИМЕТАЛЛИЧЕСКИХ ПЛИТ СТАЛЬ-ТИТАН

The paper studies microstructures in a welded joint of a titanium cladding layer. This joint was obtained by repeated cladding by explosion welding of defects that arose during the manufacturing of bimetallic plates "steel + titanium" by explosion welding. When removing titanium from the defect zone in the cladding layer, the transition zone was ground at an angle to the steel surface. It is shown that the structure of the welded joint is determined by the impact angle at the bevel section and the direction of the outflow of shock-compressed gas from the welding gap. The revealed structural features help to select the bevel angle to obtain a high-quality connection when repairing defects by explosion welding. The bevel angle on the edges should be ground so as to obtain a theoretical impact angle greater than the minimum and less than the maximum welding angle (however, the minimum possible welding angle at the beginning of the explosion welding process).

Treatment of chronic ruptures and defects of the Achilles tendon

Achilles tendon ruptures that are older than 4-6weeks or developed over amore extended period are chronic. Two challenges characterize the treatment. First, defect zones over alength of several centimeters must frequently be bridged. Second, aprolonged loss of function of the muscles leads to an irreversible fatty degeneration of the tissue. So that even if the tendon is restored, significant functional deficits remain. If there are doubts about the ability of the calf muscles to regenerate, regardless of the size of the defect, tendon transfers are recommended to use the power of an additional muscle to support the plantar flexion of the ankle. Established concepts are the transposition of the flexor hallucis longus or the peroneus brevis muscle. If the muscle is intact, defects of up to 2 cm can be treated with adirect suture. Defects between 2and 5 cm can be bridged using aVY-plasty or aturndown flap. For larger defects, free tendon transplants can be considered. The technical alternative for larger defects is atendon transfer of the flexor hallucis longus or the peroneus brevis muscle. Besides bridging the defect, another advantage of tendon transfer is that vital muscle tissue is placed in the bed of the Achilles tendon. Both tendons are covered with muscle tissue over nearly the full length, which offers advantages, especially in patients with critical soft tissue or after infection. Follow-up treatment is analogous to an acute Achilles tendon rupture. However, permanent impairments are possible; 75-80% of athletes regain their original performance level.

Bone-cartilage transfer for osteochondritis dissecans of the humeral capitellum

Treatment of focal cartilage defects of the humeral capitellum with autologous bone-cartilage cylinders to prevent development of arthritis of the elbow joint. High-grade, unstable lesions (> 50% of the capitellum, gradeIII-IV according to Dipaola), including those involving the lateral edge of the capitellum and with adepth of up to 15 mm. Stable lesions and generalized osteochondritis of the capitellum (including Panner's disease), as well as arelative contraindication for lesions > 10 mm, as the largest punch has amaximum diameter of 10 mm. Arthroscopy of the elbow joint, transition to open surgery. First, the size of the cartilage defect in the capitellum is determined. Then, one (or several) osteochondral cylinders (OATS Arthex) are removed, which as far as possible completely encompass the defect zone. Corresponding intact bone-cartilage cylinders are obtained from the ipsilateral proximal lateral femoral condyle, each with a0.3 mm larger diameter via an additive miniarthrotomy. The "healthy" cylinders are then inserted into the defect zone in a"press fit" technique. An upper arm cast in neutral position of the hand for 10-14days, simultaneously beginning physiotherapy (active-assisted movements) and lymphatic drainage. As soon as painless range of motion (ROM) is restored (goal: by week6), isometric training can be started. Resistance training starts from week12. Competitive sports are only recommended after 6(-8) months. The current state of research on the surgical treatment of OCD of the humeral capitellum using autologous osteochondral grafts shows mostly promising results. Arecent meta-analysis of 24studies reports asignificantly higher (p < 0.01) rate of return to sports (94%) compared to fragment fixation (64%) or microfracture and debridement (71%) [41]. However, the increased donor-site morbidity must be taken into account (ca. 7.8%).

Effects of electrical stimulation with alternating fields on the osseointegration of titanium implants in the rabbit tibia - a pilot study.

Introduction: Electrical stimulation has been used as a promising approach in bone repair for several decades. However, the therapeutic use is hampered by inconsistent results due to a lack of standardized application protocols. Recently, electrical stimulation has been considered for the improvement of the osseointegration of dental and endoprosthetic implants. Methods: In a pilot study, the suitability of a specifically developed device for electrical stimulation in situ was assessed. Here, the impact of alternating electric fields on implant osseointegration was tested in a gap model using New Zealand White Rabbits. Stimulation parameters were transmitted to the device via a radio transceiver, thus allowing for real-time monitoring and, if required, variations of stimulation parameters. The effect of electrical stimulation on implant osseointegration was quantified by the bone-implant contact (BIC) assessed by histomorphometric (2D) and µCT (3D) analysis. Results: Direct stimulation with an alternating electric potential of 150mV and 20Hz for three times a day (45min per unit) resulted in improved osseointegration of the triangular titanium implants in the tibiae of the rabbits. The ratio of bone area in histomorphometry (2D analysis) and bone volume (3D analysis) around the implant were significantly increased after stimulation compared to the untreated controls at sacrifice 84days after implantation. Conclusion: The developed experimental design of an electrical stimulation system, which was directly located in the defect zone of rabbit tibiae, provided feedback regarding the integrity of the stimulation device throughout an experiment and would allow variations in the stimulation parameters in future studies. Within this study, electrical stimulation resulted in enhanced implant osseointegration. However, direct electrical stimulation of bone tissue requires the definition of dose-response curves and optimal duration of treatment, which should be the subject of subsequent studies.

Computer Vision Method for Automatic Detection of Microstructure Defects of Concrete.

The search for structural and microstructural defects using simple human vision is associated with significant errors in determining voids, large pores, and violations of the integrity and compactness of particle packing in the micro- and macrostructure of concrete. Computer vision methods, in particular convolutional neural networks, have proven to be reliable tools for the automatic detection of defects during visual inspection of building structures. The study's objective is to create and compare computer vision algorithms that use convolutional neural networks to identify and analyze damaged sections in concrete samples from different structures. Networks of the following architectures were selected for operation: U-Net, LinkNet, and PSPNet. The analyzed images are photos of concrete samples obtained by laboratory tests to assess the quality in terms of the defection of the integrity and compactness of the structure. During the implementation process, changes in quality metrics such as macro-averaged precision, recall, and F1-score, as well as IoU (Jaccard coefficient) and accuracy, were monitored. The best metrics were demonstrated by the U-Net model, supplemented by the cellular automaton algorithm: precision = 0.91, recall = 0.90, F1 = 0.91, IoU = 0.84, and accuracy = 0.90. The developed segmentation algorithms are universal and show a high quality in highlighting areas of interest under any shooting conditions and different volumes of defective zones, regardless of their localization. The automatization of the process of calculating the damage area and a recommendation in the "critical/uncritical" format can be used to assess the condition of concrete of various types of structures, adjust the formulation, and change the technological parameters of production.

Advantages of cone beam computed tomography for evaluation of subchondral insufficiency fractures of the knee compared to MRI

To determine the diagnostic yield of cone beam computed tomography (CBCT) compared with 3 T magnetic resonance imaging (MRI) for the evaluation of subchondral insufficiency fractures of the knee. Consecutive patients with subchondral insufficiency fractures of the knee examined by 3 T MRI and CBCT of the femoral condyles were reviewed. Two experienced raters graded the lesion severity on 3 T MRI and CBCT images: grade 1: no signs of a subchondral bone lesion; grade 2: subchondral trabecular fracture or cystic changes, but without infraction of the subchondral bone plate; grade 3: collapse of the subchondral bone plate. Ratings were repeated after six weeks to determine reliability. In addition, the bone lesion size was measured as elliptical area (mm2) and compared between CBCT and T1-weighted MRI sequences. Among 30 patients included (43.3% women; mean age: 60.9 ± 12.8 years; body mass index (BMI) 29.0 ± 12.8 kg/m2), the medial femoral condyle was affected in 21/30 patients (70%). The grading of subchondral lesions between MRI and CBCT did not match in 12 cases (40%). Based on MRI images, an underestimation (i.e., undergrading) compared with CBCT was observed in nine cases (30%), whereas overgrading occurred in three cases (10%). Compared to CBCT, routine T1-weighted 3 T sequences significantly overestimated osseus defect zones in sagittal (84.7 ± 68.9 mm2 vs. 35.9 ± 38.2 mm2, p < 0.01, Cohen’s d = 1.14) and coronal orientation (53.1 ± 24.0 mm2 vs. 22.0 ± 15.2 mm2, p < 0.01, Cohen’s d = 1.23). The reproducibility of the grading determined by intra- and inter-rater agreement was very high in MRI (intra-class correlation coefficient (ICC) 0.78 and 0.90, respectively) and CBCT (ICC 0.96 and 0.96, respectively). In patients with subchondral insufficiency fractures of the knee, the use of CBCT revealed discrepancies in lesion grading compared with MRI. These findings are clinically relevant, as precise determination of subchondral bone plate integrity may influence the decision about conservative or surgical treatment. CBCT represents our imaging modality of choice for grading the lesion and assessing subchondral bone plate integrity. MRI remains the gold standard modality to detect especially early stages.

The influence of the conditions of applying sealing polymer materials on the deformation resistance of the sealanter to sclofibro concrete

The article deals with the features of the treatment of solid surfaces with a primer before using sealing materials. The adhesive strength of the sealant to the area of adhesion is the basis for sealing the joints. Lack of adhesion leads to the ingress of water, dirt, precipitation and other climatic effects, which eventually lead to the destruction of the seams. Therefore, it is extremely important to observe the seam treatment technology before applying the sealant. Proper treatment of seams with a primer, observing the time of application to the base, before using sealing materials will increase the durability and service lifespan of the sealed joint. To improve the adhesive strength between the adhesive and the substrate, as a rule, the hard surface (substrate) is pre-treated with a primer based on polyurethane foam or epoxy resins. These primers are used because when exposed to a hard surface, a polymer matrix is formed, which, upon further contact with the sealant, increases the adhesion strength in the contact zone. In surface defect zones with moisture content, a new surface layer is also formed due to the participation of polymer groups in forming intramolecular hydrogen bonds. The formation of a polymer layer on a solid surface containing defective zones requires a certain time. Tests were carried out to determine the resistance to deformations of a combination of sealant/primer sealing materials in combination with glass fiber reinforced concrete samples and to establish the influence of the conditions for applying a primer/sealant to the surface of a glass fiber reinforced concrete composition on resistance to a series of character cycles of equal loads and temperature changes, with a deformation of the sealing material of 25% . It has been established that the time of treatment of a solid surface with a primer should be at least 5 minutes. If this condition is not observed when sealing materials are applied to glass fiber reinforced concrete, it may cause the sealant to separate from the base.

Flash thermography to detect and evaluate impacts in polycarbonate parts produced by additive manufacturing

In this work, active thermography has been evaluated for detecting impacts on polycarbonate parts produced by additive manufacturing with different fillers and under various impact energies. Polycarbonate is a material with very good impact resistance, very useful in sectors where security is critical (e.g., aeronautics, vehicle engineering, ballistics, defense, etc.). The impacts were specifically generated on the back face (non-visible) of the part, using a standardized test under controlled energy conditions. Specifically, flash thermography was used, and different processing techniques was applied. The most favorable results were obtained by principal component analysis (PCA). From a qualitative perspective, the proposed method allows to detect and evaluate the impact from the back side of the part (non-impacted side) taking into account the different material fillings. From a quantitative point of view, by using parametric and non-parametric tests, it can be shown that there are statistically significant differences between the image levels in the defect zone and the non-defect zone, and it is even possible to establish a correlation between the medians of the detected levels and the impact energy.

Pump and probe wave mixing for imaging nonlinear features embedded into a massive concrete block

Abstract Nonlinear ultrasonic parameters are known to be highly sensitive to the presence of damage in materials, and numerous methods have already been reported. This study proposes a way to image a nonlinear defect embedded into a nonlinear medium. The nonlinear defect is mimicked by a Berea sandstone sphere (high nonlinearity). It is placed into a large concrete block (average nonlinearity) during casting. The proposed pump and probe propagating wave interaction method allows imaging the presence of the highly nonlinear region. The image contrast is magnified by a factor 8 in the defective zone. The results are validated using a model and the individual mechanical properties of both concrete and Berea Sandstone. These findings open perspectives for application to civil engineering concrete structures such as the assessment of durability distresses involving internal swelling.

Two-phase Hybrid Thermal Interface Alkali-treated E-Glass Fiber/MWCNT/Graphene/Copper Oxide Nanocomposites for Electronic Gadgets.

Two-phase hybrid mode thermal interface materials were created and characterized for mechanical properties, thermal conductivity, and wear behaviour. Therefore, the ultimate goal of this current research was to use alkali-treated glass fibre and other allotropes to produce high-performance two-phase thermal interface materials. Three different polymer composites were prepared to contain 20 vol.% alkalies [NaOH] treated e-glass fibre [E] and epoxy as a matrix with varying proportions of multi-walled carbon nanotube [MWCNT], graphene [G], copper oxide [C]. The one-phase material contained epoxy+20%e-glass+1%MWCNT [EMGC1], the two-phase hybrid composite contained epoxy+20%e-glass+1%MWCNT+1%graphene+1%CuO [EMGC2], and two-phase material contained epoxy+20%e-glass+1%graphene+1%CuO [EMGC3]. Vacuum bagging method was used for fabricating the composites. The higher thermal conductivity observed was 0.3466 W/mK for EMGC2, the alkali-treated glass fibre/hybrid mode nanofillers epoxy matrix composite was mechanically tougher than the other two composites [EMGC1 & EMGC3]. Scanning electron microscopy analysis revealed the fine filler dispersion and homogenous interaction with the glass fibre/epoxy resin composite of the upper and lower zone, which also revealed the defective zone, fibre elongation, fibre/filler breakages, and filler leached surfaces. Finally, it was concluded that the hybrid mode two-phased structure EMGC2 epoxy matrix composite replicated the maximum thermal conductivity, mechanical properties, and wear properties of the other two specimens.

Synchrotron X-ray microtomography and finite element modelling to uncover flax fibre defect’s role in tensile performances

Flax fibres offer performance capabilities comparable to glass fibres, thereby enhancing their potential in the biobased composites industry. However, these fibres have morphological defects affecting their mechanical features. In the present work, flax elementary fibres geometries with defects assessed by synchrotron X-ray microtomography were meshed to simulate a tensile test using finite element analysis. For the first time, the distribution of stresses in the vicinity of defects is revealed. The geometrical irregularities at the surface of the fibre and the delamination of cellulose layers within fibre cell wall turned out to concentrate stress up to 7.5 times compared to defect-free regions. These results demonstrate why flax fibres cannot reach their full potential in comparison to what could be expected from a structure mainly constituted from crystalline cellulose microfibrils, and why fracture in a composite is likely to initiate in those defect zones.

Enhancing shear strength of RC beams through externally bonded reinforcement with stainless-steel strips and FRCM jacket to mitigate the failure risk

This study aims to assess the efficacy of innovative and sustainable methods in improving the shear performance of Reinforced Concrete (RC) beams lacking shear stirrups. Eleven specimens, including two control specimens and nine strengthened ones, underwent monotonic loading through three-point testing. Various strengthening configurations were investigated, involving the application of Stainless-Steel Strips (SSSs) affixed to the beam surface in the defective zone, along with a Fiber-Reinforced Cementitious Matrix (FRCM) jacket. In the first set of beams, SSSs were vertically applied, while the second set featured beams with SSSs inclined at 60°, and the third set had SSSs inclined at 45°. Each set comprised three beams, allowing for the examination of the impact of SSS thicknesses, set at 1 mm, 1.25 mm, and 1.50 mm. After the installation of SSSs, all strengthened beams received an FRCM jacket, including a 5 mm Engineered Cementitious Composites (ECC) layer with embedded Glass Fiber Reinforced Polymer (GFRP) textile. The study concludes that incorporating SSS strips with an FRCM jacket delays the initiation of the first crack in defective beams. Increasing SSSs thickness contributes to a more favorable crack distribution. The 60° inclined SSSs proves to be the most effective, rectifying the deficiency from the absence of shear stirrups and surpassing the original beam's performance. Additionally, finite element analysis was conducted, and the results supported the accurateness of the developed model in simulating responses and crack patterns throughout all loading stages.

The process of reparative regeneration of the damaged stomach in rabbits

This research is relevant due to the increasing incidence of pathological conditions in the rabbit stomach requiring surgical intervention for treatment. In order to improve and expedite the recovery process post-surgery, the research team decided to thoroughly investigate the reparative and regenerative processes in the rabbit stomach wall at various stages of healing. To achieve this, studies were conducted on the first, third, seventh, tenth, fourteenth, and twenty-first days post-operative intervention, comparing them with histological analysis of the stomach wall in rabbits that did not undergo surgery. Histological investigations revealed an interesting phenomenon within the first 24 hours after stomach injury in rabbits: the muscular layer underwent contraction, leading to closure of the defect, albeit with simultaneous formation of folds in the wound area. Additionally, small fragments of the muscular layer were observed on the outer surface of the stomach, partially degraded. By the third day, active fibroblast proliferation was evident in the damaged submucosal layer, a crucial stage in the regeneration process. By the seventh day, initial restoration of the submucosal layer was observed, although the defect was not yet completely resolved. By the tenth day, all components of the stomach wall, including the muscular layer, submucosal layer, and muscular lamina of the mucous membrane, were fully restored, albeit with the muscular lamina in the defect zone remaining hypertrophic. By the fourteenth day, the muscular lamina of the mucous membrane exhibited uneven thickening, and the newly formed mucous membrane contained cavities and necrotic tissue. By the twenty-first day, the stomach wall was completely restored, with properly formed structures.

Analysis of the Influence of Shell Sand Content on the Performance of Ceramisite Lightweight Aggregate Concrete

This study investigates the impact of varying shell sand replacement rates (0%, 5%, 10%, 15%, 20%, 25%) on the properties of clay ceramsite lightweight aggregate concrete (CLC) through six experimental groups. Results indicate that a 5% replacement rate of shell sand yields optimal mechanical properties and working performance in CLC. Examination of specimen failure diagrams, electron microscopy and theoretical analysis reveals that shell sand predominantly influences CLC’s overall performance by influencing internal pore development and the formation of a “bonding defect zone” between shell sand and cementitious material. This also elucidates why specimen failure predominantly arises from internal ceramic particle fracture.

Production and characterization of activated carbon foams with various activation agents for electrochemical double layer capacitors (EDLCs) applications

Sucrose-based activated carbons were obtained by carbon foams with sugar and cobalt (II) nitrate as precursors, followed by using different chemical activation agents. The effect of Co(NO3)2 concentration, the carbonization temperature and the activation agent on the surface chemistry, porosity were investigated. Textural characterization and electrochemical tests were performed on the activated carbon samples (CF). The results showed that the activated carbon produced by H2SO4 and KOH at 800°C had a surface area of 691 m2/g and 1125 m2/g, 89% and 80% of the sample pore structure was microporous, and specific capacitance of 8.4 F/g and 162.2 F/g at a constant current density of 250 mA/g, respectively. K2CO3-activated carbon had 918 m2/g surface area and 63% of the sample pore structure with microporous and 1.4 F/g specific capacitance, H3PO4-activated carbon and ZnCl2-activated carbon had 1833 m2/g and 1597 m2/g surface area, 53% mesoporous and 50% mesoporous, 222.4 F/g and 149.9 F/g specific capacitance respectively. The most promosing result was observed in the electrochemical storage behavior of the carbon materials with hierarchical pore structure activated with H3PO4 is associated with increasing defect zones at the edges of micro- and mesoporous morphology, resulting in a higher surface area and increased conductivity of the material.

Synthesis and characterization of poly (methyl methacrylate)/ silver-doped hydroxyapatite dip coating on Ti6Al4V

This study intends to analyze the properties and potential applications of a novel composite coating composed of poly (methyl methacrylate) (PMMA) and silver-doped hydroxyapatite (HAPAg) produced from waste eggshells, which was dip-coated onto Ti6Al4V substrates. Medical implants frequently made of the titanium alloy Ti6Al4V can benefit greatly from surface coatings in terms of biocompatibility and performance. In order to add antibacterial and osteoconductive characteristics, silver-doped hydroxyapatite nanoparticles were dispersed within a PMMA matrix to create the PMMA/HAPAg composite coating. The coated samples report an average contact angle (CA) between 70 and 750 and total surface free energy (SFE) between 35 and 50 mJ/m2, which signifies its improved wettability. The 7.03% change in hydrophilicity was observed between PMMA/H0 (75.270 ± 1.690) and PMMA/H20 (700 ± 1.440) coated samples. The increase in adhesion strength and coating thickness with the increase in HAPAg reinforcement was observed. The surface morphology of the defective zones was examined using scanning electron microscopy (SEM), and information on the elemental composition of synthesized was obtained using Inductively Coupled Plasma Mass Spectroscopy (ICPMS), Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffractogram (XRD). Atomic force microscopy (AFM) reveals the surface roughness; root mean square roughness, roughness profile, skewness and kurtosis of the coated samples. The contact angle reports the hydrophilicity and SFE. Finally, the results conclude that the composite coating had a consistent distribution of HAPAg nanoparticles incorporated within the PMMA matrix. The minimal presence of Ag ions on the surface indicates the coating's potential antibacterial properties, and it is highly recommended for dental applications.

3D Anisotropic Magnetoresistance sensor for steel health monitoring

Electromagnetic sensors are widely used for safety and maintenance inspection purposes of ferromagnetic materials used in aerospace, construction and transport industry. In this paper, a portable device based on an Anisotropic Magnetoresistance (AMR) sensor for steel health monitoring is presented. The principle of operation of this device is the detection of magnetic anomalies of ferromagnetic materials, such as steel, due to stresses, corrosion, or other kind of defections. For this purpose, a cost-effective, low-consumption and high-sensitivity device has been developed, consisting of a sensor, a magnetic yoke and a microcontroller. The AMR sensor, is placed above the material under test, giving the ability of contactless measurement of the magnetic flux density on 3 axes. Additionally, a yoke, consisting of two iron poles and a permanent magnet between them, is used in this implementation, in order to create a closed magnetic circuit with the steel sample, enhancing the measurements. Then, a microcontroller with the appropriate electronic components receives the acquired data, enabling their real-time analysis and visualization of the measurements through a personal computer, smartphone, etc. Moreover, a 3D-printed enclosure has been designed and constructed, which both protects the sensor and maintains the desired position and alignment with the samples. The device can be portable due to an integrated Li-Po battery and its Wi-Fi capabilities. It can be used to determine the location of the defective spots or zones of the material under inspection, facilitating its treatment through rehabilitation methods that can be applied on the affected area. Both single-point and scanning mode monitoring are possible, making it suitable for many testing scenarios. Furthermore, its ease of use and portability render it accessible to a wide range of users, and appropriate for on-site measurements. The initial measurements using the device on test samples, demonstrate its reliability and accuracy in steel health monitoring.

Langerhans cell histiocytosis involving the temporal bone with destruction and subsequent reossification of the bony labyrinth boundaries.

With an incidence between 1-9/100 000 per year, Langerhans cell histiocytosis (LCH) is a rather rare disease from the hemato-oncologic disease spectrum (Hayes et al. 2009). The tumorlike disease with proliferation of histiocytic cells may manifest as localized to one organ or disseminated with infiltration of a wide variety of organs. Approximately 25-30 % of these cases show involvement of the temporal bone (Ni et al. 2017). With vertigo persisting for three years, chronic mastoiditis, and acute progressive hearing loss bilaterally (r > l) for three weeks, a 41-year-old woman presented at an emergency department. The DVT showed extensive bony destruction of large parts of the temporal bone on both sides, involving the vestibular organ, the cochlea, and the internal auditory canal. To confirm the suspicion of a systemic inflammatory process, a PE was performed from the mastoid with bioptic confirmation of an LCH. Systemic therapy was initiated. Post-therapeutic imaging showed almost complete remission with reossification of the preexisting defect zones and the internal auditory canal and labyrinth structures again showed bony margins. Clinically, there was an improvement of the vegetative symptoms with remaining bilateral sensorineural hearing loss. LCH of the temporal bone is a rare and often misdiagnosed disease due to its nonspecific clinical presentation. Awareness of temporal bone LCH and its occurrence in adults is essential for accurate and consistent diagnosis. · LCH is a rather rare disease from the hemato-oncological spectrum. · Affection of the temporal bone, especially such an extensive one (as in this case report), is rather atypical in adulthood. · Use of systemic therapy resulted in remission. · There was complete reossification of the osseous structures post-therapy. · A cochlear implant was able to be implanted to compensate for hearing loss.

BONE TISSUE REGENERATION INDUCED BY LOCAL DELIVERY OF BONE MORPHOGENETIC PROTEIN 2 FROM PRO-ANGIOGENIC NEAR-INFRARED-RESPONSIVE HYDROGELS

In this work, we combined tissue engineering and gene therapy technologies to develop a therapeutic platform for bone regeneration. We have developed photothermal fibrin-based hydrogels that incorporate degradable CuS nanoparticles (CuSNP) which transduce incident near-infrared (NIR) light into heat. A heat-activated and rapamycin-dependent transgene expression system was incorporated into mesenchymal stem cells to conditionally control the production of bone morphogenetic protein 2 (BMP-2). Genetically engineered cells were entrapped in the photothermal hydrogels. In the presence of rapamycin, photoinduced mild hyperthermia induced the release of BMP-2 from the NIR responsive cell constructs. Transcriptome analysis of BMP-2 expressing cells showed a signature of induced genes related to stem cell proliferation and angiogenesis. We next generated 4 mm diameter calvarial defects in the left parietal bone of immunocompetent mice. The defects were filled with NIR-responsive hydrogels entrapping cells that expressed BMP-2 under the control of the gene circuit. After one and eight days, rapamycin was administered intraperitoneally followed by irradiation with an NIR laser. Ten weeks after implantation, the animals were euthanized and samples from the bone defect zone were processed for histological analysis using Masson's trichrome staining and for immunohistochemistry analyses using specific CD31 and CD105 antibodies. Samples from mice that were only administered rapamycin or vehicle or that were only NIR-irradiated showed the persistence of fibrous tissue bridging the defect. In animals that were treated with rapamycin, NIR irradiation of implants resulted in the formation of new mineralized tissue with a high degree of vascularization, thus indicating the therapeutic potential of the approach.Acknowledgements: This research was supported by grants RTI2018-095159-B-I00 and PID2021-126325OB-I00 (MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”), by grant P2022/BMD- 7406 (Regional Government of Madrid). M.A.L-J. is the recipient of predoctoral fellowship PRE2019-090430 (MCIN/AEI/10.13039/501100011033).