Thermal properties of hierarchical YSZ and LZO ceramic microspheres with multi-scaled voids investigated by using theoretical,experimental and simulation methods

Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ～ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity.     

BCLA CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia).However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation.In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.     

Clinical significance of contact lens related changes of ocular surface tissue observed on optical coherence images

PurposeTo investigate the relationship between the real contact lens imprint into the conjunctival tissue, observed by optical coherence tomography (OCT) and conjunctival staining and contact lens wearing comfort.Methods17 participants (mean age = 26.6 SD ± 3.6 years; 7 females) were fitted with three different contact lenses base curves of the same silicone hydrogel custom lens type (Visell 50; Hecht Contactlinsen, Au, Germany) in a randomised order. One lens was optimally fitted according to the manufacturer's recommendation, one fitted 0.4 mm flatter and one fitted 0.4 mm steeper. After 4 h of lens wear the contact lens edge in the area of the conjunctiva was imaged nasally and temporally using OCT (Optovue iVue SD-OCT). To correct the artefact due to optical distortion with OCT, the imprint of all worn lenses was measured on a glass plate afterwards. Conjunctival staining in the limbal region after 4 h of lens wear was classified using the CCLRU Grading Scale. Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent).ResultsThe mean conjunctival imprint of all contact lens edges was 32.0 ± 8.1 μm before and 7.3 ± 6.5 μm after distortion correction of the OCT images. The distortion corrected conjunctival imprint with the 0.4 mm steeper lens (11.5 ± 6.2 μm) was statistically significantly greater compared to the optimally fitted lens (6.5 ± 5.9 μm) (One-way ANOVA followed Tukey-test; p = 0.017) and greater compared to the 0.4 mm flatter lens (3.9 ± 5.3 μm) (p < 0.001). There was no statistically significant difference between the optimally fitted lens and the 0.4 mm flatter lens (p = 0.209). The nasally measured imprint (11.4 ± 9.0 μm) was significantly greater than the temporally measured (3.3 ± 7.6 μm) (p < 0.001). There was no statistically significant correlation between the amount of conjunctival imprint and the graded conjunctival staining (p = 0.346) or the wearer’s comfort (p = 0.735).ConclusionsContact lens edges imaged by OCT exhibited displacement artefacts. The observed conjunctival imprints are a combination of real conjunctival compression and artefacts. A deeper imprint of the contact lens into the conjunctiva caused by a steeper base curve was not related to clinically significant staining or changes in comfort after 4 h of lens wear. The observed differences between nasal and temporal imprint are likely to be caused by variations of conjunctival thickness and the shape of the underlying sclera.     

On the buckling properties of concentric carbon/boron-nitride multi-walled nanotubes: A finite element investigation

Finite element modeling approach is used here to investigate the behavior of concentric multi-walled boron-nitride and carbon nanotubes under the compressive loadings. Double-walled and triple-walled concentric boron-nitride and carbon nanotubes with different arrangements and geometries are considered. It is shown that multi-walled boron-nitride nanotubes lose their stabilities at larger compressive forces than other arrangements in which at least one carbon wall exists. Comparing the armchair and zig-zag multi-walled nanotubes, the latter one has larger buckling force than the former one. It is also shown that the nanotubes with smaller radii have larger critical compressive forces than those with larger radii.     

Effect of scleral lens use on conjunctival microbiota

AimThis study aimed to investigate the effect of scleral lens (SL) use on conjunctival microbiota.MethodA total of 26 eyes of 26 patients using an SL and 25 eyes of 25 healthy controls were included in the study. The samples were obtained from the lower fornices of the eyes using sterile swabs. For the bacteriological examination, a bacterial culture was obtained by inoculating the samples on chocolate agar, blood agar, MacConkey agar, and fluid thioglycollate medium. After 24–48 h of incubation at 37 ⁰C, the growth of different colonies of bacteria was identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (Bruker MALDI Biotyper).ResultsThe mean age of the study group was 41.6 ± 19.1 years (18–65); the mean age of the control group was 40 ± 6 (21–62) (p = 0.69). There were 10 male patients and 16 female patients in the study group and 9 male patients and 16 female patients in the control group (p = 0.86). The mean duration of SL use was 13.7 ± 13.4 months (1–42 months). No bacterial growth was observed in 17 (65.4 %) of the 26 eyes in the SL group and 5 (20 %) of the 25 eyes in the control group (p = 0.001). The most commonly observed microorganisms were Staphylococcus epidermidis (S.epidermidis) and Staphylococcus aureus (S.aureus) in both groups.ConclusionSL users were found to have a higher rate of culture negativity in comparison to the healthy controls, suggesting that SLs have a significant effect on conjunctival microbiota.     

Thermoelastic analysis of laminated composite and sandwich shells considering the effects of transverse shear and normal deformations

Abstract

In the present study, thermoelastic analysis of laminated composite and sandwich shells (cylindrical/spherical) is presented using fifth-order shear and normal deformation theory. The significant characteristic of the present theory is that it includes the effects of both transverse shear and normal deformations. The mathematical formulation uses the principle of virtual work to derive the variationally consistent governing equations and traction free boundary conditions. To obtain the static solution, these governing equations are solved by employing Navier’s solution technique. The shell is subjected to a mechanical/thermal load sinusoidally distributed over the top surface of the shell. The thermal load linearly varies across the thickness of the shell. The present results are compared with other higher-order models and 3D elasticity solution wherever possible. Thermal stresses presented in this study will act as a benchmark for the future work.     

Analysis of P. aeruginosa disinfectant sensitivity and microbial adhesions to worn cosmetic contact lenses

PurposeTo compare the sensitivity of two genotypes of P. aeruginosa to various disinfectant solutions and analyze the attached bacteria on worn cosmetic contact lenses (cosCLs).MethodsIn this prospective study, healthy volunteers wore etafilcon (brown), nelfilcon (gray), or hilafilcon (black) cosCLs and microbial adhesion analysis was performed. A rub-off test determined pigment dislodgement. Disinfectant sensitivity to Optifree Replenish (Alcon), Optifree Pure Moist (Alcon), Renu Fresh (Bausch & Lomb), and AoSept Plus (Ciba Vision) was tested at various disinfection times and compared between various genotypes and Type III secretion (T3S) system mutants.ResultsOf the 1152 cosCLs collected, 364 were culture positive (32%). The highest rate of culture-positive lens was hilafilcon (chi square, P = 0.0001). Hilafilcon also had a significantly greater number of isolates than etafilcon (P < 0.0001). Hilafilcon was the only lens to fail the rub-off test. Cytotoxic strains were significant more resistant to Renu Fresh than were invasive strains, even at 100% of recommended disinfection time (P = 0.0005). Of the tested disinfectants, Renu Fresh was significantly less effective in killing both genotypes of P. aeruginosa compared to AoSept Plus at all time points (25%, 50%, 75%, and 100% recommended disinfection time, P = 0.0001, 0.0001, 0.0005, and 0.0005, respectively). When the T3S system was dysfunctional, mutant strains were all susceptible to disinfectants (P = 0.0001 for both invasive and cytotoxic strains).ConclusionPseudomonas species is commonly found on cosCLs of asymptomatic individuals. Wearers of cosCLs that dislodge pigments may be predisposed to microbial contamination. Cytotoxic strains are more resistant to disinfectant solutions, especially to Renu Fresh. P. aeruginosa disinfectant resistance requires a functional T3S system.     

二甲醚球形扩散火焰的熄火机理研究

采用改进的PREMIX模型及"化学爆炸模式分析(CEMA)"方法,对二甲醚(DME)球形扩散火焰的熄火机理进行数值诊断,分析环境氧气摩尔分数(X_(O_2))及详细基元反应对熄火极限的影响,利用"爆炸因子"和"分岔因子"的概念,确定控制DME球形扩散火焰熄火的关键反应动力学因素。结果表明:DME冷焰具有比热焰更宽的可燃范围;冷焰对X_(O_2)的敏感性弱很多,热焰中具有正特征值的CEM首次出现在最高温度处;在熄火极限附近,CEM的特征值变为虚数,说明熄火伴随着振荡;热焰的熄火主要由小分子所参与的高温反应所控制,而冷焰熄火主要由大分子所参与的低温反应所控制。