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Polymers Apr 2023This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness...
This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness on its mechanical behavior and energy absorption properties under static crushing loadings. Hence, a series of compression tests were carried out on EPP foams with different densities and thicknesses. For foam with a density of 60 kg/m, the mean crushing strength, energy absorption (E, energy absorption efficiency (E), specific energy absorption (SEA), and energy absorption per unit volume (w) increased by 245.3%, 187.2%, 42.3%, 54.3%, and 242.8%, respectively, compared to foam with a density of 20 kg/m. Meanwhile, compared to foam with a thickness of 30 mm, the mean crushing strength, energy absorption (), energy absorption efficiency (), SEA, and energy absorption per unit volume () for foam with a thickness of 75 mm increased by 53.3%, 25.2%, -10.8%, -4.7%, and -10.6%, respectively. The results show that foam density has a significantly greater influence on static compressive performance than foam thickness. The microstructures of the EPP foam before and after static compression were compared by observing with a scanning electron microscope (SEM), and the failure mechanism was analyzed. Results showed that the load and energy as well as the deformation and instability processes of its cells were transferred layer by layer. The influence of density on the degree of destruction of the internal cells was obvious. Due to its larger mass and larger internal damping, thicker foams were less damaged, and less deformation was produced. Additionally, the EPP foam exhibited a considerable ability to recover after compression.
PubMed: 37177205
DOI: 10.3390/polym15092059 -
Plastic and Reconstructive Surgery.... Dec 2021Foot soft tissue coverage represents a challenge to reconstructive surgeons due to a lack of donor sites for this specialized skin. This glabrous tethered thick skin is...
BACKGROUND
Foot soft tissue coverage represents a challenge to reconstructive surgeons due to a lack of donor sites for this specialized skin. This glabrous tethered thick skin is designed to withstand weight bearing stress and is hard to replace. The limited arch of rotation of foot local flaps contributes to further difficulties. In this study, we share our experience in foot soft tissue loss coverage using techniques tailored to each wound presentation.
METHODS
This case series presents eight patients with wounds of the plantar and dorsal surfaces of the foot, heel, and ankle. Closure techniques were selected and planned based on wound presentation and comorbidity status.
RESULTS
Patients' mean age at surgery was 61 years. Etiologies of wounds include trauma, frostbite, diabetic ulceration, malignancy, pressure ulcer with osteomyelitis, and necrotizing infection. Coverage techniques included split and full-thickness skin graft, medial plantar arch pinch graft, cultured epithelial autograft, Hyalomatrix wound device, EpiFix tissue matrix, pedicle flap, and free rectus flap. Complete soft tissue coverage was achieved in each case within reasonable postoperative periods, and ambulation was preserved and/or restored.
CONCLUSIONS
Foot soft tissue reconstruction is challenging and should be planned carefully due to the required specialized skin replacement. Primary closure should be considered first and attempted if possible. Technique escalation in accordance with the reconstructive ladder should be undertaken based on wound etiology, presentation, amount and nature of tissue loss, available resources, and surgeon experience.
PubMed: 34966631
DOI: 10.1097/GOX.0000000000003989 -
Retina (Philadelphia, Pa.) Apr 2022To investigate the prevalence of ciliochoroidal effusion (CE) in central serous chorioretinopathy (CSC) using anterior-segment optical coherence tomography and its...
PURPOSE
To investigate the prevalence of ciliochoroidal effusion (CE) in central serous chorioretinopathy (CSC) using anterior-segment optical coherence tomography and its association with the clinical features of CSC.
METHODS
Overall, 164 eyes of 164 patients with CSC and 51 eyes of 51 age- and sex-matched normal control participants were retrospectively examined. Anterior-segment optical coherence tomography was used to assess patients with CSC and control subjects for CE and scleral thickness. Central serous chorioretinopathy eyes were divided into two groups: eyes with CE (CE group) and eyes without CE (non-CE group). Scleral thickness was measured at the point that was 6 mm posterior to the scleral spur in four directions.
RESULTS
Among the 164 eyes with CSC, 32 eyes (19.5%) displayed CE, and this proportion was significantly higher than that in control subjects (2.0%) (P = 0.001). Scleral thickness was significantly greater in the CE group compared with the non-CE group at all four directions (P < 0.05 for all). Multivariable analysis revealed that the mean scleral thickness (odds ratio: 1.01; 95% confidence interval: 1.00-1.02; P = 0.007) was significantly associated with the incidence of CE.
CONCLUSION
Central serous chorioretinopathy may accompany fluid accumulation in the anterior segment more frequently than previously expected in association with thick sclera.
Topics: Central Serous Chorioretinopathy; Choroid; Choroidal Effusions; Fluorescein Angiography; Humans; Retrospective Studies; Tomography, Optical Coherence
PubMed: 34907128
DOI: 10.1097/IAE.0000000000003376 -
Therapeutic Advances in Ophthalmology 2022The distance between the optic disc center and the fovea is a biometric parameter; however, it is unclear whether DFD (disc-fovea distance) affects the choroidal...
BACKGROUND
The distance between the optic disc center and the fovea is a biometric parameter; however, it is unclear whether DFD (disc-fovea distance) affects the choroidal thickness.
OBJECTIVE
The aim of this study is to investigate the association between DFD and choroidal thickness.
DESIGN
This is a prospective, and cross-sectional study.
METHODS
Two hundred fifty eyes of 250 healthy participants were examined in terms of DFD, age, axial length, spherical equivalent, and choroidal thickness. Inclusion criteria included aged between 20-40 years, no posterior segment disorders, and participants with best-corrected visual acuity (10/10 according to Snellen's chart). Participants with high hypermetropia (>4 diopter) or myopia (>6 diopter) or any systemic disease likely to affect choroidal thickness were excluded. Choroidal thickness measurements were performed at subfoveal, 1.0 mm temporal, and 1.0 mm nasal using the enhanced-depth imaging optical coherence tomography.
RESULTS
The mean age of all the participants was 26.21 ± 5.73 years, mean DFD was 4634.29 ± 274.70 µm, mean axial length was 23.62 ± 0.83 mm, and mean spherical equivalent was -0.61 ± 1.06 diopter. The mean subfoveal, nasal, and temporal choroidal thicknesses were 388.73 ± 90.15 µm, 351.26 ± 88.09 µm, and 366.50 ± 79.56 µm, respectively. A negative correlation was found between subfoveal, nasal, and temporal choroidal thicknesses and axial length ( = -0.157, = 0.013; = -0.168, = 0.008; = -0.174, = 0.006, respectively). Insignificant correlation was found between choroidal thicknesses and spherical equivalent ( > 0.05). There was not a statistically significant correlation between DFD and subfoveal, nasal, and temporal choroidal thicknesses ( = -0.028, = 0.655; = 0.030, = 0.641; = -0.025, = 0.699, respectively). In addition, there was not a statistically significant correlation between age and choroidal thickness.
CONCLUSION
This study shows that DFD and spherical equivalent do not affect choroidal thickness; axial length negatively affects choroidal thickness. In addition, age does not affect choroidal thickness between 20 and 40 years.
PubMed: 35602660
DOI: 10.1177/25158414221096062 -
Experimental Eye Research Nov 2021To assess age-related changes in the rhesus macaque eye and evaluate them to corresponding human age-related eye disease.
PURPOSE
To assess age-related changes in the rhesus macaque eye and evaluate them to corresponding human age-related eye disease.
METHODS
Data from eye exams and imaging tests including intraocular pressure (IOP), lens thickness, axial length, and retinal optical coherence tomography (OCT) images were evaluated from 142 individuals and statistically analyzed for age-related changes. Quantitative autofluorescence (qAF) was measured as was the presence of macular lesions as related to age.
RESULTS
Ages of the 142 rhesus macaques ranged from 0.7 to 29 years (mean = 16.4 years, stdev = 7.5 years). Anterior segment measurements such as IOP, lens thickness, and axial length were acquired. Advanced retinal imaging in the form of optical coherence tomography and qAF were obtained. Quantitative assessments were made and variations by age groups were analyzed to compare with established age-related changes in human eyes. Quantitative analysis of data revealed age-related increase in intraocular pressure (0.165 mm Hg per increase in year of age), ocular biometry (lens thickness 7.2 μm per increase in year of age; and axial length 52.8 μm per increase in year of age), and presence of macular lesions. Age-related changes in thicknesses of retinal layers on OCT were observed and quantified, showing decreased thickness of the retinal ganglion cell layer and inner nuclear layer, and increased thickness of photoreceptor outer segment and choroidal layers. Age was correlated with increased qAF by 1.021 autofluorescence units per increase in year of age.
CONCLUSIONS
The rhesus macaque has age-related ocular changes similar to humans. IOP increases with age while retinal ganglion cell layer thickness decreases. Macular lesions develop in some aged animals. Our findings support the concept that rhesus macaques may be useful for the study of important age-related diseases such as glaucoma, macular diseases, and cone disorders, and for development of therapies for these diseases.
Topics: Aging; Animals; Biometry; Disease Models, Animal; Eye Diseases; Macaca mulatta; Retinal Ganglion Cells; Tomography, Optical Coherence
PubMed: 34506802
DOI: 10.1016/j.exer.2021.108754 -
Proceedings of the National Academy of... Dec 2021The relationship between sample thickness and quality of data obtained is investigated by microcrystal electron diffraction (MicroED). Several electron microscopy (EM)...
The relationship between sample thickness and quality of data obtained is investigated by microcrystal electron diffraction (MicroED). Several electron microscopy (EM) grids containing proteinase K microcrystals of similar sizes from the same crystallization batch were prepared. Each grid was transferred into a focused ion beam and a scanning electron microscope in which the crystals were then systematically thinned into lamellae between 95- and 1,650-nm thick. MicroED data were collected at either 120-, 200-, or 300-kV accelerating voltages. Lamellae thicknesses were expressed in multiples of the corresponding inelastic mean free path to allow the results from different acceleration voltages to be compared. The quality of the data and subsequently determined structures were assessed using standard crystallographic measures. Structures were reliably determined with similar quality from crystalline lamellae up to twice the inelastic mean free path. Lower resolution diffraction was observed at three times the mean free path for all three accelerating voltages, but the data quality was insufficient to yield structures. Finally, no coherent diffraction was observed from lamellae thicker than four times the calculated inelastic mean free path. This study benchmarks the ideal specimen thickness with implications for all cryo-EM methods.
Topics: Animals; Benchmarking; Cryoelectron Microscopy; Crystallization; Crystallography; Electrons; Humans; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Models, Molecular; Specimen Handling
PubMed: 34873060
DOI: 10.1073/pnas.2108884118 -
Journal of Ophthalmology 2021To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with...
OBJECTIVE
To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes.
METHODS
30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT.
RESULTS
The central and minimum ET obtained with both devices were correlated: central ET, = 0.86, < 0.05; minimum ET, = 0.72, < 0.05. Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 m on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, = 0.994, < 0.05; minimum CT, = 0.995, < 0.05. SS-OCT tended to overestimate these figures by 11 and 14 m on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT.
CONCLUSION
SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.
PubMed: 34650817
DOI: 10.1155/2021/3444083 -
Advanced Science (Weinheim,... Jul 2023Nanosized perovskite ferroelectrics are widely employed in several electromechanical, photonics, and thermoelectric applications. Scaling of ferroelectric materials...
Nanosized perovskite ferroelectrics are widely employed in several electromechanical, photonics, and thermoelectric applications. Scaling of ferroelectric materials entails a severe reduction in the lattice (phonon) thermal conductivity, particularly at sub-100 nm length scales. Such thermal conductivity reduction can be accurately predicted using the information of phonon mean free path (MFP) distribution. The current understanding of phonon MFP distribution in perovskite ferroelectrics is still inconclusive despite the critical thermal management implications. Here, high-quality single-crystalline barium titanate (BTO) thin films, a representative perovskite ferroelectric material, are grown at several thicknesses. Using experimental thermal conductivity measurements and first-principles based modeling (including four-phonon scattering), the phonon MFP distribution is determined in BTO. The simulation results agree with the measured thickness-dependent thermal conductivity. The results show that the phonons with sub-100 nm MFP dominate the thermal transport in BTO, and phonons with MFP exceeding 10 nm contribute ≈35% to the total thermal conductivity, in significant contrast to previously published experimental results. The experimentally validated phonon MFP distribution is consistent with the theoretical predictions of other complex crystals with strong anharmonicity. This work paves the way for thermal management in nanostructured and ferroelectric-domain-engineered systems for oxide perovskite-based functional materials.
PubMed: 37092575
DOI: 10.1002/advs.202301273 -
Clinical and Experimental Dental... Dec 2020Creating a tooth-like appearance by use of dental ceramics is still a challenge. Opalescence is a unique property of dental enamel, attempted to be mimicked by dental...
OBJECTIVES
Creating a tooth-like appearance by use of dental ceramics is still a challenge. Opalescence is a unique property of dental enamel, attempted to be mimicked by dental restorative materials. This study aimed to assess the effect of ceramic thickness on opalescence.
MATERIALS AND METHODS
Twenty-four discs were fabricated of feldspathic ceramic, IPS e.max, zirconia and Enamic ceramics with 10 mm diameter and 0.5 and 1 mm thicknesses (n = 12). The opalescence of ceramic specimens was calculated by measuring the difference in yellow-blue axis (CIE ∆b*) and red-green axis (CIE ∆a*) between the transmitted and reflected spectra. One-way ANOVA was applied to compare the opalescence of different ceramic specimens with variable thicknesses at .05 level of significance.
RESULTS
The opalescence of feldspathic, IPS e.max, zirconia and Enamic ceramic specimens with 0.5 mm thickness was 1.06 ± 0.15, 3.39 ± 0.15, 1.98 ± 0.15 and 1.44 ± 0.15, respectively. By increasing the thickness to 1 mm, the opalescence of feldspathic, IPS e.max, zirconia and Enamic ceramics changed to 1.12 ± 0.15, 1.47 ± 0.15, 3.85 ± 0.15 and 2.00 ± 0.15, respectively. In all groups except for IPS e.max, the mean opalescence of 1-mm-thick specimens was higher than that of 0.5-mm-thick specimens.
CONCLUSION
Type and thickness of ceramic affect its opalescence. The opalescence of all ceramic specimens tested in this study with 0.5 and 1 mm thicknesses was lower than that of the enamel.
Topics: Ceramics; Dental Enamel; Dental Porcelain; Dental Restoration, Permanent; Humans; Iridescence; Materials Testing; Surface Properties; Zirconium
PubMed: 32902165
DOI: 10.1002/cre2.325 -
Journal of Ophthalmic & Vision Research 2020To investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of Saudi participants. (Review)
Review
PURPOSE
To investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of Saudi participants.
METHODS
Thirty-six randomly selected adults aged 27.0 5.7 years who attended a Riyadh hospital from 2016 to 2017 were categorized into three groups: non-myopic (spherical equivalent refraction [SER], +1.00 to -0.50 diopters [D]), low myopic (SER, -0.75 to -3.00D), and moderate to high myopic (SER -3.25D). Full, inner, and outer retinal thicknesses were measured at nine locations by spectral-domain stratus optical coherence tomography (Optovue Inc., Fremont, CA, USA) and were compared according to refractive group and sex.
RESULTS
The mean SERs for the non-myopia, low myopia, and moderate to high myopia groups were 0.2 0.6, -1.5 0.5, and -7.5 1.9 D, respectively. Refractive error, but not sex, had significant effects on the retinal layer thickness measurements at different locations ( 0.05). The parafoveal and outer retinal layers were significantly thicker than the perifoveal and inner retina layers in all groups ( 0.05). The full foveal thickness was higher and the full parafoveal and perifoveal regions were thinner in moderate to high myopic eyes than in the non-myopic eyes ( 0.05), but were similar to those in the low myopic eyes ( 0.05). The foveal thicknesses measured in the inner and outer layers of the retina were higher but the thicknesses measured at the inner and outer layers of the parafoveal and perifoveal regions were lower in moderate to high myopic eyes.
CONCLUSION
There were regional differences in the retinal layer thicknesses of healthy Saudi eyes, which was dependent on the central refractions. This is important when interpreting retinal nerve fiber layer thicknesses in myopia and disease management in Saudi participants.
PubMed: 32308952
DOI: 10.18502/jovr.v15i2.6735