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BackgroundWe aimed to investigate corneal densitometry and correlations with corneal morphological parameters in bilateral keratoconus (KCN) patients with unilateral Vogt's striae.MethodsOne hundred and-twelve patients (224 eyes) with bilateral KCN and unilateral Vogt's striae were enrolled in this cross-sectional contralateral eye study. Corneal densitometry and morphological parameters were measured using Pentacam HR.ResultsOur study revealed that corneal densitometry values of the anterior 0–2 mm and 2–6 mm, intermediate 0–2 mm and 2–6 mm, posterior 2–6 mm, and total cornea 2–6 mm in eyes with Vogt’s striae were significantly higher than those in eyes without Vogt's striae (P P P P P

Graphene is an excellent piezoresistive material. The gauge factor of graphene mirrors the sensitivity of electromechanical devices. This paper mainly studies the gauge factors of different layers of graphene under different deformation conditions. Specifically, a theoretical model was combined with linearized Boltzmann transport equation, and the density function theory (DFT) to explore how the layer number of graphene affects sensitivity. The results show that monolayer graphene is slightly more sensitive than two-layer graphene, and significantly more sensitive than three-layer graphene and four- layer graphene. In particular, monolayer graphene remains highly sensitive under large deformation conditions, which gives monolayer graphene a significant advantage over other layers of graphene. Furthermore, a microelectromechanical system (MEMS) pressure sensor was proposed with monolayer graphene, and compared with previous similar sensors with multilayer graphene in terms of sensitivity.

To investigate the changes in posterior corneal elevations (PCEs) in the circular areas and local points after corneal collagen cross-linking (CXL) for the treatment of keratoconus.Method 1 divided the cornea into 0-2, 2-4, 4-6, and 6-8 mm regions centering on the apex. Method 2 obtained other 34 PCE values of local point that were identified on the nasal, supra-nasal, sub-nasal, superior, inferior, temporal, supra-temporal, and sub-temporal sides of the circle with diameters of 2, 4, 6, and 8 mm, and the apex and thinnest point.Method 1 showed a forward displacement of PCE at 1 month after CXL and then a backward displacement at 3 months. In Method 2, the points on the temporal side of 2 mm and 4 mm showed the same trend. The backward displacements of PCE on the temporal side of 2 mm at 6 months and on the temporal side of 4 mm at 12 months after CXL were both statistically different than those at 1 month after CXL (P 0.05). No significant forward displacement of PCE was found in all local points in different quadrants at 1 year after CXL.The PCEs in circular areas and characteristic points of different diameters in keratoconic eyes after CXL change with time. Local point assessment of the PCE is more clinically significant. In points selected in different quadrants of the cornea, the change in temporal points was more significant after CXL.

Purpose: To investigate the changes in corneal optic density (COD) in patients with type II diabetes and explore the possible influencing factors. Methods: Central corneal thickness (CCT) and corneal optic density (COD) were measured in 52 patients (104 eyes) with type II diabetes mellitus (DM) and 23 age-matched healthy controls (46 eyes). COD values of the anterior, middle, and posterior layers and four annulus regions (0–2, 2–6, 6–10, and 10–12 mm) were collected. Patients with DM were divided into the non-diabetic retinopathy (NDR) and diabetic retinopathy (DR) groups. Results: Patients with DM had higher COD values than the controls; the differences were significant in the total (P=0.011), anterior layer (P=0.002), middle layer (P=0.019), and 0–6 mm central region (0–2 mm, P=0.008; 2–6 mm, P=0.007). The 0–6 mm central region COD was higher in the NDR group and highest in the DR group compared with controls; the 6–12 mm peripheral COD value was highest in the NDR group. The correlation between age and COD values was lower in patients with DM than in controls. CCT was positively correlated with the total COD value (r=0.26, P=0.008) in the DM group. Conclusion: The corneal clarity of patients with DM decreased in general and altered before the appearance of DR. COD values increased in early diabetes without DR. As DR emerged, the central and peripheral COD changed differently. In addition toretinal condition, age and CCT may also affect corneal transparency of patients with DM.

This study aimed to investigate the diagnostic value of corneal anterior, posterior, and total higher-order aberrations in keratoconic eyes.We enrolled 94 patients (152 eyes) with mild keratoconus (Group 1), 64 patients (101 eyes) with moderate keratoconus (Group 2), and 32 patients (52 eyes) with advanced keratoconus (Group 3) according to the Amsler-Krumeich classification system; 99 healthy controls (197 normal eyes) were likewise enrolled. Anterior, posterior, and total corneal higher-order aberrations were assessed using a rotating Scheimpflug camera. The 3rd-order and 4th-order root-mean-square values were calculated for higher-order aberrations, including coma, spherical, and trefoil aberrations. Differences between keratoconic and normal eyes were analyzed using Kruskal-Wallis tests. Receiver operating characteristic curves were evaluated for the keratoconus and control groups.The differences in coma 90, coma, trefoil, and spherical aberrations, as well as 3rd-order and 4th-order root-mean-square values, were statistically significant between the keratoconus and control groups for all anterior, posterior, and corneal aberrations. The absolute values of these higher-order aberrations were higher in the keratoconus groups than in the control group and increased with keratoconus severity in Groups 1-3. Coma and 3rd-order RMS values showed excellent sensitivity and specificity for discriminating between normal and keratoconus eyes for all anterior, posterior, and corneal aberrations.Coma aberrations and 3rd-order root-mean-square values may be valuable for diagnosing keratoconus. Combining these data with topography information may enable the effective and efficient detection of keratoconus in the future.

Y-doping can effectively improve the performance of HfO x -based resistive random-access memory (RRAM) devices, but the underlying physical mechanism of Y-doping affecting the performance of HfO x -based memristors is still missing and unclear. Although impedance spectroscopy (IS) has been widely used to investigate impedance characteristics and switching mechanisms of RRAM devices, there is less IS analysis on Y-doped HfO x -based RRAM devices as well as devices at different temperatures. Here, the effect of Y-doping on the switching mechanism of HfO x -based RRAM devices with a Ti/HfO x /Pt structure were reported using current–voltage characteristics and IS. The results indicated that doping Y into HfO x films could decrease the forming/operate voltage and improve the RS uniform. Both doped and undoped HfO x -based RRAM devices obeyed the oxygen vacancies (V O) conductive filament model along the grain boundary (GB). Additionally, the GB resistive activation energy of the Y-doped device was inferior to that of the undoped device. It exhibited a shift of the V O trap level towards the conduction band bottom after Y-doping in the HfO x film, which was the main reason for the improved RS performance.

Purpose: To assess the corneal high-order aberration(HOA) and its correlation with corneal morphological parameters in patients with bilateral keratoconus (KCN) and unilateral Vogt’s striae.Methods: A total of 168 eyes of 84 patients with KCN, whose corneas had definite signs of unilateral Vogt’s striae were enrolled. Corneal HOA and morphological parameters were measured using Pentacam HR.Results: The corneal morphological parameters between KCN eyes with and without Vogt’s striae were evidently different (P < 0.001). The 3rd coma 90°, 4th spherical aberration, 5th coma 90°, RMS (total), and RMS (HOA) in the front, back surfaces and total cornea in KCN eyes with Vogt’s striae were significantly higher than those in KCN eyes without Vogt’s striae (P < 0.001). In KCN eyes with Vogt’s striae, the 3rd coma 90° and 4th spherical aberration in the front surface and total cornea were negatively correlated with K1, K2, Km, Kmax, ACE, and PCE (P < 0.05). The 3rd coma 90° , 4th spherical aberration in back surface and RMS (total), RMS (HOA) in the front, back surfaces, total cornea were positively correlated with K1, K2, Km, Kmax, ACE, and PCE (P < 0.05).Conclusions: Corneal HOA especially vertical coma and spherical aberration may increase when Vogt’s striae appeared in KCN eyes. The scale of increase was significantly related with changes in corneal shapes.

Purpose: To investigate the changes in posterior corneal elevations (PCEs) in the circular areas and local points after corneal collagen cross-linking (CXL) for the treatment of keratoconus.Methods: Method 1 divided the cornea into 0–2, 2–4, 4–6, and 6–8 mm regions centering on the apex. Method 2 obtained other 34 PCE values of local point that were identified on the nasal, supra-nasal, sub-nasal, superior, inferior, temporal, supra-temporal, and sub-temporal sides of the circle with diameters of 2, 4, 6, and 8 mm, and the apex and thinnest point.Results: Method 1 showed a forward displacement of PCE at 1 month after CXL and then a backward displacement at 3 months. In Method 2, the points on the temporal side of 2 mm and 4 mm showed the same trend. The backward displacements of PCE on the temporal side of 2 mm at 6 months and on the temporal side of 4 mm at 12 months after CXL were both statistically different than those at 1 month after CXL (P < 0.05). The PCE of the thinnest point was correlated with other corneal points, except the points on the nasal and sub-nasal sides of 4 mm.Conclusion: The PCEs in circular areas and characteristic points of different diameters in keratoconic eyes after CXL change with time. Local point assessment of the PCE is more clinically significant. In points selected in different quadrants of the cornea, the change in temporal points was more significant after CXL.

The preparation of perovskite-polymer composites is one of the most effective ways to improve the stability and expand the application of inorganic perovskite quantum dots (QDs). The current study adopts a convenient and rapid ultraviolet polymerization method to prepare perovskites-polymer (CsPbX3, X = mixed Cl/Br, Br, mixed Br/I, and I) composites using inexpensive commercial epoxy resin (EP). The photoluminescence (PL) spectrum and photoluminescence quantum yield (PLQY) show that the composites can well retain the luminescent colors of the original solutions. The emission spectra of these composites can be tuned in the range of 420 nm-680 nm, which are almost consistent with the emission spectrum of perovskites QDs. Moreover, perovskite-EP composites demonstrate excellent stability in air and water without changing the PLQY for more than 30 days in air and maintaining the PL intensity above 85% for 10 days in water. These new perovskite-EP composites exhibit tensile and flexural properties due to the incorporation of flexible epoxy resin, which can be well applied to the fields of flexible luminescent devices and optical functional materials.

Constructing junctions can efficiently improve the photocatalytic performance by suppressing the recombination of photogenerated electron–hole pairs and prolonging the lifetime of carriers. In this...

Lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) present the distinctive ability to utilize short-wave infrared light, good ambient stability, and convenient solution-based fabrication processes and thus attract much attention in the photovoltaic research field. The performance of CQDSCs has been improved by constructing the ZnO/PbS heterojunction, due to suitable band levels and electron mobility of ZnO electron transfer layer (ETL). However, the huge number of defects in low-temperature processed ZnO cause an unbalanced carrier-related processes, which restrict further performance enhancement and flexible production of CQDSCs. Here, we described a facile method to passivate defects in low-temperature sol–gel ZnO by introducing polyethylenimine (PEI) into the precursor solution. Versus the original ZnO film, the composite ZnO:PEI films exhibit better crystallization because of the Zn–N interaction. A series of electronic analyses have shown that the addition of PEI reduces the work function ...

We have predicted four squaraine (SQ) structures with different heterocyclic anchoring groups (HAGs), including hydantoin moiety (HY), rhodanine (RD), 2-(1,1-dicyanomethylene) (DCRD) and barbituric acid (BA), to simultaneously enhance the lower open-circuit photovoltage (Voc) and adsorption stability of the gold-standard SQ dye with widely used carboxylic acid anchoring group (CA) without sacrificing its extremely large short-circuit current (Jsc). For the first time, these HAGs are put together to discuss their impacts on the relative adsorption stability and the intrinsic reasons affecting the Voc, including adsorption modes, conduction band energy shift (ΔECB), electron injection, charge recombination, and the dye aggregation effects. Especially, charge decomposition analysis has been performed to explain the origin of different extent of ΔECB, and the reduced density gradient analysis offers a pictorial representation of the weak interactions between the two monomers. The results show that the adsorption stability order is BA ≈ HY > RD ≈ CA > DCRD. And the Voc order is BA > HY > RD > CA > DCRD. In addition, we find these SQ dyes show comparable maximum photocurrent density (about 22 mA/cm2). Thus, SQ dyes with BA, HY, and RD are promising candidates for the experimental synthesis of high-performance dye sensitized solar cells.

Background We aimed to compare the intraocular pressure (IOP) measurements by a dynamic Scheimpflug analyzer (Corvis ST), a non-contact tonometer, and an ocular response analyzer after hyperopic small-incision lenticule extraction (SMILE). Methods Thirteen patients who underwent hyperopic SMILE in one eye were enrolled prospectively. IOP and corneal biomechanical parameters were measured preoperatively and at 1 week, 1 month, and 3 months postoperatively with a non-contact tonometer (IOPNCT), Corvis ST (biomechanical corrected IOP [bIOP]), and ocular response analyzer (Goldmann-correlated intraocular pressure [IOPg] and cornea compensated IOP [IOPcc]). A linear mixed model was used to compare the IOPs and biomechanical values among methods at each time point. Results IOPNCT, IOPg, and IOPcc dropped significantly after surgery, with the amplitude being 3.15 ± 0.48 mmHg, 5.49 ± 0.94 mmHg, and 4.34 ± 0.97 mmHg, respectively, at the last follow-up visit. IOPNCT decreased by 0.11 ± 0.06 mmHg per μm of excised central corneal thickness. bIOP did not change significantly after surgery. Preoperatively, no difference was found among the four measurements (P > 0.05). Postoperatively, IOPNCT and bIOP were higher than IOPg and IOPcc. bIOP was independent of cornea thickness at last follow-up visit, whereas it correlated significantly with corneal biomechanics similar to the other three IOP values. Conclusion bIOP is a relative accurate measure of IOP after hyperopic SMILE.

The physical mechanism of the effect of Si dopant on the formation of oxygen vacancy (VO) and the uniformity of conductive filaments (CFs) are explored in Ta2O5-based resistive random access memory (Ta2O5-RRAM). On the basis of first-principle calculations, we investigated the effect of Si dopant on the electronic structure of Ta2O5, including the formation energy of VO, Bader charge, density of states (DOS), and interaction of Si dopant with VO. Results of formation energy and Bader charge reveal that Si dopant is favorable to the formation of VO. Results of DOS reveal that Si dopant can improve the conductivity of Ta2O5. The interaction of Si dopant with VO can enhance the uniformity of CFs. Si dopant is favorable in reducing the formation energy of VO and improving the switching uniformity of Ta2O5-RRAM devices.

To evaluate and investigate the distribution of corneal density and its Correlation with stray-light value in adult and healthy eyes.A prospective study. Human corneal specimens ranging in age between 20 and 49 years, 116 patients (232 eyes) in total, divided into three groups: 20-29, 30-39, 40-49. Pentacam was used to evaluate total corneal average density and corneal thickness at different diameter around the corneal apex, for corneal density were ≤ 2 mm,2 mm and ≤ 6 mm,6 mm and ≤ 10 mm, for corneal thickness were 2 mm, 6 mm and 10 mm, C-quant was used for the stray-light value. Software SPSS 17.0 was used for statistical analysis. Independent samples t testing method was applied to compare the corneal densitometry in different gender and between left eyes and right ones, One-way ANOVA was applied to analyze the differences of corneal density in different age groups and diameters. Pearson correlation analysis was applied to assess the correlation in corneal densitometry values of different diameters, between corneal density of different diameters and age, corneal density of different diameters and corneal thickness of different diameters, corneal density of different diameters and stray-light values.Corneal density for ≤ 2 mm,2 mm and ≤ 6 mm,6 mm and ≤ 10 mm diameter are 10.1 ± 1.5(8.2-16.7), 9.3 ± 1.3(7.9-14.2), 9.6 ± 1.7(7.3-16.2). Corneal density of6 mm and ≤ 10 mm diameter in different age groups were 8.9 ± 1.1, 9.3 ± 1.2, 10.7 ± 2.1, there was a statistical difference in these values (F = 28.939, P = 0.000), and there was a positive correlation between corneal density of6 mm and ≤ 10 mm diameter and age (r = 0.417, P = 0.000), There were no statistical differences in corneal density values of ≤ 2 mm and2 mm and ≤ 6 mm in different age groups (F = 1.575, 1.436; P0.05), and they had no correlation with age (r = 0.002, 0.048; P0.05). There was no statistical difference in corneal density in different gender (t = 1.744, 1.647, -1.181; P0.05). Corneal density values of left eyes and right ones had positive relationships at the same diameter (r = 0.977, P = 0.000; r = 0.992, P = 0.000; r = 0.933, P = 0.000), and there were no statistical differences (t = 0.124, 0.199, -0.020;P0.05). Between corneal density values of different diameter, there are also some positive relationships,6 mm and ≤ 10 mm and ≤ 2 mm (r = 0.710, P = 0.000),6 mm and ≤ 10 mm and2 mm and ≤ 6 mm (r = 0.748, P = 0.000), ≤ 2 mm and2 mm and ≤ 6 mm (r = 0.973, P = 0.000), relationship between ≤ 2 mm and2 mm and ≤ 6 mm,2 mm and ≤ 6 mm and6 mm and ≤ 10 mm was obvious, and there was statistical difference in them (F = 17.057, P = 0.000) . The ocular stray light value was 0.95 ± 0.19(0.48-1.38), Corneal density values of ≤ 2 mm,2 mm and ≤ 6 mm and6 mm and ≤ 10 mm diameter had positive relationships with the stray light value (r = 0.134,0.146,0.159, P = 0.042,0.026,0.016).Corneal density can be influenced by age, the influence from age infected the corneal density of peripheral more. There was no correlation between corneal density and corneal thickness. There were some influences of corneal density of healthy eyes to the ocular stray light.