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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 -
European Journal of Dermatology : EJD Aug 2021The large-scale implementation of primary and secondary skin cancer prevention strategies in recent decades has led to an increase in the diagnosis of thin melanomas and...
The large-scale implementation of primary and secondary skin cancer prevention strategies in recent decades has led to an increase in the diagnosis of thin melanomas and a decrease in the mean thickness of tumours diagnosed. The number of newly diagnosed thick melanomas, however, has remained stable. To investigate associations between melanoma thickness, clinical presentation and demographic and phenotypic characteristics. The study is based on a cross-sectional study of 1,459 patients with melanoma from a dermatology department at a tertiary hospital in Spain between 2000 and 2017. We analysed associations between median Breslow thickness and demographic, phenotypic, and clinical characteristics, including the method of melanoma detection. Age ≥ 70 years (regression coefficient [RC] = 1.2, 95% CI: 1.1-1.3; p < 0.001), male sex (RC = 0.9, 95% CI: 0.8-0.9; p < 0.001), symptom-based detection (RC = 1.3, 95% CI: 1.1-1.4; p < 0.001), and a history of sunburn at the melanoma site (RC = 0.9, 95% CI: 0.8-0.9; p = 0.04) were all associated with thicker tumours. Melanomas on the lower extremities, by contrast, were significantly thinner (RC = 0.9, 95% CI: 0.8-0.9; p = 0.04). Thick melanomas occur preferentially in older men and show changes such as bleeding or an increase in volume or colour. This information should be incorporated into health training and education programs to design better prevention strategies and minimize diagnostic delays.
PubMed: 34463273
DOI: 10.1684/ejd.2021.4096 -
European Journal of Ophthalmology May 2022The aim of this study was to determine whether iris colour is related to the choroidal thickness of healthy individuals.
OBJECTIVE
The aim of this study was to determine whether iris colour is related to the choroidal thickness of healthy individuals.
METHODS
Healthy participants were divided into two groups. Group 1 had light-coloured eyes (blue and green), and group 2 had dark-coloured eyes (brown). The main outcome measures were iris thickness, subfoveal choroidal thickness and nasal and temporal choroidal thicknesses 500 µm away from the fovea.
RESULTS
Group 1 comprised 31 subjects with light-coloured eyes, and group 2 had 31 subjects with dark eyes. The mean ages of groups 1 and 2 were 26.7 ± 7.5 years and 24.1 ± 5.8 years, respectively ( = 0.14). The choroidal thicknesses of the subfoveal, nasal and temporal regions were 336.3 ± 52.1 µm, 321.9 ± 43.6 µm and 318.4 ± 49.2 µm, respectively, in group 1 and 396.5 ± 76.9 µm, 372 ± 79.3 µm and 379.6 ± 82.4 µm, respectively, in group 2. All the values in group 1 were statistically lower than those in group 2 ( = 0.001, = 0.001 and = 0.003, respectively). The iris thickness in group 1 (493.73 ± 95.44 µm) was thinner than in group 2 (524.61 ± 69.74 µm) but not statistically significant ( = 0.141).
CONCLUSION
The results showed that a thinner choroid can be seen in disease-free light-coloured eyes. The iris colour should be considered among the factors affecting the choroidal thickness, such as age, sex, race and refractive error.
Topics: Adult; Biometry; Choroid; Fovea Centralis; Humans; Refractive Errors; Tomography, Optical Coherence; Young Adult
PubMed: 34218695
DOI: 10.1177/11206721211029470 -
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 -
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 -
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 -
Eye & Contact Lens May 2022To examine the relationship between lens thickness and central corneal edema during short-term open-eye scleral lens wear, and to compare these empirical edema...
PURPOSE
To examine the relationship between lens thickness and central corneal edema during short-term open-eye scleral lens wear, and to compare these empirical edema measurements with theoretical modelling.
METHODS
Nine participants (mean age 30 years) with normal corneas wore scleral lenses {Dk 141×10-11 cm3 O2 [cm]/([sec] [cm2] [mm Hg])} under open-eye conditions on separate days with nominal center thicknesses of 150, 300, 600, and 1,200 μm. Epithelial, stromal, and total corneal edema were measured using high-resolution optical coherence tomography immediately after lens application and after 90 min of wear, before lens removal.
RESULTS
Central corneal edema was primarily stromal in nature and increased with increasing central lens thickness. The mean±standard error total corneal edema was 1.14±0.22%, 1.36±0.26%, 1.74±0.30%, and 2.13±0.24% for the 150, 300, 600, and 1,200 μm lenses, respectively. A significant difference in stromal and total corneal edema was observed between the 1,200 and 150 μm thickness lenses only (both P<0.05). Theoretical modelling overestimated the magnitude of central corneal edema and the influence of central lens thickness when the scleral lens Dk/t was less than 20.
CONCLUSION
Scleral lens-induced central corneal edema during short-term open-eye lens wear increases with increasing central lens thickness. Theoretical models overestimated the effect of increasing scleral lens thickness upon central corneal edema for higher lens thickness values (lens Dk/t<20) when controlling for initial central fluid reservoir thickness.
Topics: Adult; Contact Lenses; Cornea; Corneal Edema; Humans; Sclera; Tomography, Optical Coherence
PubMed: 35333796
DOI: 10.1097/ICL.0000000000000888 -
Journal of Ophthalmology 2021To evaluate the differences in macular choroidal thickness and volume between patients with primary open-angle glaucoma (POAG) and healthy controls to assess the...
PURPOSE
To evaluate the differences in macular choroidal thickness and volume between patients with primary open-angle glaucoma (POAG) and healthy controls to assess the correlation between macular choroidal thickness and visual field mean defect (MD).
METHODS
Case-control study. A total of 101 patients (101 eyes) with POAG who were hospitalized in our hospital and 102 healthy subjects (102 eyes) matched by age, sex, and axial length were consecutively selected as the POAG group and the control group, respectively. The macular choroidal thickness and volume in nine regions were measured in all subjects by enhanced-depth imaging optical coherence tomography (EDI-OCT).
RESULTS
The mean thicknesses of the choroid in the macular area in the POAG group and healthy group were 207.97 ± 62.83 m and 208.24 ± 47.97 m, and the mean volumes were 0.63 ± 0.19 m and 0.64 ± 0.14 m. There were no significant differences in macular choroidal thickness, volumes of various macular regions, or mean choroidal thickness or volume between the POAG and healthy groups (all > 0.05). The macular choroidal thickness of various macular regions was not correlated with visual field MD in the POAG group (all > 0.05).
CONCLUSION
The macular choroidal thicknesses and volumes in POAG patients were not significantly different from those in healthy individuals. The macular choroidal thickness was not correlated with MD in POAG patients. Therefore, macular choroidal thickness is not an appropriate parameter to evaluate damage caused by POAG, and the role of the macular choroid thickness in POAG needs to be further investigated.
PubMed: 34007481
DOI: 10.1155/2021/5574950 -
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 -
Journal of Musculoskeletal & Neuronal... Jun 2023To evaluate the relationship between cartilage loss and differences in muscle thickness and/or leg length in poliomyelitis sequelae (PMS). Our study is the first to...
OBJECTIVES
To evaluate the relationship between cartilage loss and differences in muscle thickness and/or leg length in poliomyelitis sequelae (PMS). Our study is the first to evaluate the relationship between cartilage loss and both muscle atrophy and leg length discrepancy in the same population.
METHODS
37 patients with PMS and 38 healthy controls were included. Talar and distal femoral cartilage thicknesses and gastrocnemius medialis and quadriceps femoris muscle thicknesses were measured via ultrasound. Leg length differences and manual muscle strength were also evaluated.
RESULTS
The mean muscle thicknesses and cartilage thicknesses were thinner in the more affected legs than in the less affected legs in the patient group. All of the ultrasonographic measurements were thinner in the less affected legs of the patient group than in the right legs of the control group, except for the knee cartilage thicknesses. While there was a correlation between the cartilage thickness difference and the muscle thickness difference between the less and more affected legs in the patient group, there was no correlation between the cartilage thickness difference and leg length differences.
CONCLUSIONS
Patients with PMS are predisposed to osteoarthritis. Talar and knee cartilage thicknesses may be more associated with the muscle thickness than the leg length discrepancy in PMS.
Topics: Humans; Leg; Cartilage; Quadriceps Muscle; Lower Extremity; Poliomyelitis; Ultrasonography
PubMed: 37259663
DOI: No ID Found