Search Results (8)

Deep-sea hydraulic collection is a key technology for seabed mineral resource extraction, offering higher efficiency and environmental protection compared to other collection methods. However, due to their complex characteristics, the suction properties and influencing factors of polyhedral particles in hydraulic suction collection remain elusive. This study utilized dimensionless methods and conducted experiments to analyze the flow characteristics in cone-shaped collection hoods and the distribution of suction force on polyhedral particles, and researched the effect of various parameters, such as Φ, H/R, R/S, and H/d_p (referring to the nomenclature given in the last part of this paper), on the suction force coefficients of polyhedral particles based on the suction force coefficients of spheres by acquiring the suction coefficient ratio (k_c). The results indicate the following: (1) the presence of suction and coherent vortices in the horizontal positions of 0.1R to 0.2R within the central region, which move with changes in pump suction or cove height, benefiting particle collection; (2) the particle suction force (F_d) decreases with increasing sphericity (Φ), with a more pronounced decline in high-speed flow fields, exhibiting two peaks and one trough in the F_d curve within the hood’s flow field; (3) the k_c generally increases with decreasing Φ at the same collection position, showing increasingly stable fluctuations, and k_c is sensitive to surrounding flow velocities with a rapid growth trend at higher speed, revealing that the suction coefficient (C_d) of polyhedral particles is significantly larger than that of spherical particles with increasing flow speed in high-speed flow fields; (4) F_d decreases with increasing H/d_p, with a noticeable slowdown when H/d_p exceeds 3.5. This study reveals the force characteristics and influencing factors of non-spherical coarse particles in hydraulic suction collection flow fields, providing insights for the development of collection technologies and equipment for deep-sea solid mineral resources, particularly irregular coarse particles. Full article

Background/Objectives: Keratoconus (KC) is a bilateral eye disease characterized by corneal thinning and cone-like deformation, leading to visual impairment. This study evaluated the radial peripapillary capillaries (RPCs) in keratoconus patients with and without penetrating keratoplasty (PKP) using OCT and angio-OCT, comparing the results to a control group. Methods: This retrospective study included 149 eyes, 97 from patients who underwent PKP between January 2018 and February 2023 and 52 from patients who did not undergo PKP. The control group comprised 72 patients (144 eyes) who were healthy volunteers. Measurements included the best corrected visual acuity (BCVA), the intraocular pressure (IOP), slit-lamp biomicroscopy, a fundus examination, and corneal topography, as well as OCT and angio-OCT assessments of the RPCs, retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and central retinal thickness (CRT). Statistical analyses were performed using Student’s t-test and Pearson’s correlation coefficient. Results: The RNFL was significantly thinner in KC eyes after PKP compared to control eyes (p < 0.001), and the CRT was significantly thicker in KC eyes after PKP compared to control eyes (p = 0.003). However, the GCC was similar across the groups (p = 0.0885). Additionally, RPCs inside the disc were significantly reduced in KC eyes after PKP compared to control eyes (p < 0.0001). A significant positive correlation was found between RPC whole vessel density and RNFL thickness as measured via angio-OCT (r = 0.308, p < 0.0001). Conclusions: This study found that the RPC density inside the disc is significantly reduced in keratoconus patients after penetrating keratoplasty, highlighting RPCs inside the disc as a potential diagnostic tool for further assessment of keratoconus. Full article

Purpose: To investigate corneal densitometry artefacts found in Pentacam Scheimpflug scans and their potential effect on assessing keratoconic (KC) corneas compared to normal (N) corneas. Methods: The current study utilises Pentacam data of 458 N eyes, aged 35.6 ± 15.8 (range 10–87), referred to as the “N group”, and 314 KC eyes, aged 31.6 ± 10.8 (range 10–72), referred to as the “KC group”, where densitometry data were extracted and analysed via a custom-built MATLAB code. Radial summations of the densitometry were calculated at diameters ranging from 0.5 mm to 5.0 mm. The minimum normalised radial summation of densitometry (NRSD) value and angle were determined at each diameter and then linked. KC cone locations and areas of pathology were determined, and a comparison between N and KC groups was carried out both within the averaged area of pathology and over the corneal surface. Results: Joining minimum NRSD trajectory points marked a clear distortion line pointing to the nasal-superior direction at 65° from the nasal meridian. The findings were found to be independent of eye laterality or ocular condition. Consistency was detected in the right and left eyes among both the N and KC groups. The location of the KC cone centre and the area of pathology were determined, and the densitometry output was compared both within the area of pathology and over the whole cornea. When the average densitometry was compared between N and KC eyes within the KC area of pathology, the N group recorded a 16.37 ± 3.15 normalised grey-scale unit (NGSU), and the KC group recorded 17.74 ± 3.4 NGSU (p = 0.0001). However, when the whole cornea was considered, the N group recorded 16.71 ± 5.5 NGSU, and the KC group recorded 15.72 ± 3.98 NGSU (p = 0.0467). A weak correlation was found between the Bad D index and NGSU when the whole measured cornea was considered (R = −0.01); however, a better correlation was recorded within the KC area of pathology (R = 0.21). Conclusions: Nasal-superior artefacts are observed in the densitometry Pentacam maps, and analysis shows no significant differences in their appearance between N or KC corneas. When analysing KC corneas, it was found that the cone positions are mostly on the temporal-inferior side of the cornea, opposite to the densitometry artefact NRSD trajectory. The analysis suggests that the corneal densitometry artefacts do not interfere with the KC area of pathology as it reaches its extreme in the opposite direction; therefore, weighting the densitometry map to increase the contribution of the inferior-temporal cornea and decreasing that of the superior-nasal area would improve the classification or identification of KC if densitometry is to be used as a KC metric. Full article

Background: The aim of this study was to analyse the concentration of the nerve growth factor (NGF-β) in patients with keratoconus (KC) who are undergoing collagen fibre cross-linking (CXL) surgery in order to better understand the pathogenesis of this disease and observe the molecular changes occurring after the procedure. Among many cytokines, β-NGF seems to play an important role in the healing processes of corneal damage. Therefore, its role in the regenerative process after CXL treatment may affect the course of treatment and its final results. Tear samples from 52 patients were collected in this prospective study. Additionally, the patients also had a number of tests performed, including corneal topography using optical coherence tomography. Flat (K 1), steep (K 2), cylindrical (CYL), and central corneal thickness (CCT) keratometry were assessed. The tear samples were collected, and other tests were performed before the CXL procedure and afterwards, during the 12-month follow-up period. The NGF concentration was measured using the Bio-Plex Magnetic Luminex Assay. Lower levels of NGF-β were detected in the KC patients than in the control group (p < 0.001). The day after the procedure, the NGF-β level was significantly lower (on average by 2.3 pg/mL) (p = 0.037) than before the procedure, after which, the level of the reagent increases, but only in the group with the advanced cone, one month after CXL it was significantly higher (p = 0.047). Regarding the correlation of NGF with topographic measurements, the following were found: NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K1 before the CXL procedure; NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K1 one month after CXL; NGF-β correlates significantly (p < 0.05) and positively (r > 0) with CYL nine months after CXL; and, after twelve months, NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K2 and K1. Corneal sensitivity did not statistically and significantly correlate with the level of NGF-β secretion. Our study suggests that NGF may be crucial in the development and progression of KC as well as in the repair mechanisms after CXL surgery. Further research is needed on the role of NGF and other inflammatory biomarkers for rapid diagnosis and selection of targeted therapy in patients with keratoconus. Full article

Keratoconus (KC) is characterized by localized, central thinning and cone-like protrusion of the cornea. Its precise etiology remains undetermined, although both genetic and environmental factors are known to contribute to disease susceptibility. Due to KC’s complex nature, there is currently no ideal animal model to represent both the corneal phenotype and underlying pathophysiology. Attempts to establish a KC model have involved mice, rats, and rabbits, with some additional novel animals suggested. Genetic animal models have only been attempted in mice. Similarly, spontaneously occurring animal models for KC have only been discovered in mice. Models generated using chemical or environmental treatments have been attempted in mice, rats, and rabbits. Among several methods used to induce KC in animals, ultraviolet radiation exposure and treatment with collagenase are some of the most prevalent. There is a clear need for an experimental model animal to elucidate the underlying mechanisms behind the development and progression of keratoconus. An appropriate animal model could also aid in the development of treatments to slow or arrest the disorder. Full article

Keratoconus (KC) is one of the most significant corneal disorders worldwide, characterized by the progressive thinning and cone-shaped protrusion of the cornea, which can lead to severe visual impairment. The prevalence of KC varies greatly by ethnic groups and geographic regions and has been observed to be higher in recent years. Although studies reveal a possible link between KC and genetics, hormonal disturbances, environmental factors, and specific comorbidities such as Down Syndrome (DS), the exact cause of KC remains unknown. The incidence of KC ranges from 0% to 71% in DS patients, implying that as the worldwide population of DS patients grows, the number of KC patients may continue to rise significantly. As a result, this review aims to shed more light on the underlying relationship between KC and DS by examining the genetics relating to the cornea, central corneal thickness (CCT), and mechanical forces on the cornea, such as vigorous eye rubbing. Furthermore, this review discusses KC diagnostic and treatment strategies that may help detect KC in DS patients, as well as the available DS mouse models that could be used in modeling KC in DS patients. In summary, this review will provide improved clinical knowledge of KC in DS patients and promote additional KC-related research in these patients to enhance their eyesight and provide suitable treatment targets. Full article

A k-carrageenan–iron complex (KC–Fe) was synthesized by complexation between degraded KC and FeCl₃. Furthermore, KC–Fe and ammonium polyphosphate (APP) were simultaneously added into waterborne epoxy (EP) to improve its flame retardancy and smoke suppression performance. The structure and properties of KC–Fe were assessed using Fourier transform infrared spectroscopy (FTIR), ultraviolet (UV) spectroscopy, thermo gravimetric analysis (TGA), and X-ray powder diffraction analysis (XRD). The analysis showed that KC–Fe was successfully synthesized and exhibited good thermal properties with a 49% char residue at 800 °C. The enhanced flame retardancy and smoke suppression performance of waterborne epoxy were evaluated using a limiting oxygen index (LOI) and UL-94. Moreover, the flame retardancy of waterborne epoxy coated on a steel plate was also investigated using cone calorimetry. The results showed that the flame-retardant waterborne epoxy blend exhibited the best flame retardancy when the mass ratio of APP and KC–Fe was 2:1. The total heat release (THR) and total smoke production (TSP) was decreased by 44% and 45%, respectively, which indicated good fire safety performance and smoke suppression properties. Analysis of the residual char using FTIR, SEM, and elemental analysis (EDS) indicated that the action of KC–Fe was promoted by the presence of APP. The formation of a dense thermal stable char layer from an intumescent coating was essential to protect the underlying materials. Full article

In this paper, phosphated K-carrageenan (P-KC) was obtained by reacting POCl₃ with the renewable source K-carrageenan (KC). P-KC and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were added into waterborne epoxy (EP) to improve its flame retardancy. The structure of P-KC was studied comprehensively using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), showing the successful synthesis of P-KC. The flame retardancy of the EP was evaluated by the cone calorimeter test. The results showed that different mass ratios of DOPO and P-KC affected the flame retardancy of EP. When the mass ratio of DOPO and P-KC was 2:1, total heat release (THR) and total smoke production (TSP) decreased by 48.7% and 37.4%, respectively. The microstructures of residue char were observed by FTIR and scanning electron microscopy (SEM), indicating that the flame-retardant waterborne epoxy (FR-EP) system held a more cohesive and denser char structure. The char inhibited the diffusion of heat and oxygen, which played a key role in the flame retardancy. Full article