Residual Thickness Research Articles

Macular Alterations in a Cohort of Caucasian Patients Affected by Retinitis Pigmentosa

Objectives: Our objective was to investigate the prevalence of macular complications detected by spectral-domain optical coherence tomography (SD-OCT) in a large Caucasian cohort of RP patients, highlight the major alterations in chorioretinal structure, and compare the macular structural changes in eyes affected by retinal dystrophies with those in healthy controls. Methods: This was an observational, retrospective, and cross-sectional study. Three hundred and seven patients with RP were consecutively enrolled and underwent clinical assessment. In particular, SD-OCT images were used to ascertain the morphology of the posterior pole of patients with RP by evaluating the residual ellipsoid zone (EZ), the volume and thickness of the outer nuclear layer (ONLT), and subfoveal choroid thickness (SCT). At the same time, the pathological finding that the patients’ vision was reduced under treatment was analyzed. Results: A total of 436 eyes of 218 patients with RP were studied. Considering all of the eyes studied, 103 had cystoid macular edema (CME) (23.62%), 123 (28.21%) had vitreomacular traction (VMT), and 199 (45.75%) had epiretinal membranes (ERMs). There were also 12 (2.75%) cases of lamellar macular holes (LMHs), of which 3 (1.38% of all patients) cases were bilateral. Only 137 eyes (31.42%) did not have the above-mentioned alterations. SCT was significantly reduced compared to that of the control group (193.03 µm ± 67.90 SD vs. 295 µm ± 69.04 SD), while the foveal central macular thickness (FCMT) was greater (270.91 μm ± 74.04 SD vs. 221 µm ± 37.25 SD). Conclusions: This research highlights the high incidence of macular complications. The results of our study indicate the importance of regular monitoring of RP patients and early intervention to avoid further complications in this group of subjects with severe visual field impairment to avoid further central vision loss.

The Investigation of Overflow Water-Powered Projectile-Assisted Injection Molded Short-Glass-Fiber-Reinforced Polypropylene

Water-powered projectile-assisted injection molding (W-PAIM) is a novel injection molding technology that has been recently developed based on the ripe water-assisted injection molding (WAIM). Fiber orientation pattern and residual wall thickness (RWT) are two crucial factors determining the quality of W-PAIM parts composed of short fiber-reinforced thermoplastics (SFRTCs). However, limited work has been conducted on W-PAIM of SFRTC parts, which restricts its application process. In this work, an intensive investigation of W-PAIM parts composed of short fiber-reinforced polypropylene was conducted via a newly lab-developed W-PAIM platform. The results indicated that fibers were quite well oriented in the region extending from the core zone to the water channel, especially in the water channel zone, but randomly aligned in a small region near the mold wall. Nevertheless, fibers in the water channel zone of W-PAIM part were highly oriented, presenting an opposite alignment trend in fiber orientation compared to that in the water channel zone of the WAIM part as reported earlier. These disparities in fiber orientation between W-PAIM and WAIM parts were primarily attributed to the strong flow fields generated by projectile penetration. Additionally, the influence of three main processing parameters that significantly affected the projectile penetration on these two crucial factors was also investigated using the single-factor method. It was discovered that water injection delay time constituted the primary factor affecting the projectile penetration process, and reducing this time could greatly increase the relative thickness of the ordered area and the uniformity of RWT. More importantly, within the value range of the tested processing parameters, increased water pressure, elevated melt temperatures, and shorter water injection delay time could simultaneously improve fiber orientation and the uniformity of RWT in W-PAIM parts, which may improve the properties of W-PAIM parts and enlarge their application scope. This work provides a comprehensive guide for the fabrication of W-PAIM parts of SFRTCs.

Clinical safety and efficacy of elliptical thin-flap LASIK using a low-pulse energy femtosecond laser.

This study assessed the clinical safety and efficacy of elliptical thin-flap LASIK with a low-pulse energy femtosecond laser in 3 thickness subgroups (85, 90, and 100μm). A total of 80 patients who underwent bilateral LASIK surgery at Taiwan between April and September 2019 were retrospectively enrolled. Elliptical corneal flaps with wide temporal hinges and inverted-angled side cuts were created. Target flap thickness was calculated on the basis of residual stromal bed thickness and percent tissue altered. Before flap creation, an optical coherence tomography image for visualization of the precut flap position was obtained with the built-in camera. At postoperative month 1, the overall mean logMAR uncorrected distance visual acuity (UDVA) was - 0.04 ± 0.07 (20/18 Snellen), with 96% of eyes achieving UDVA of 20/20 or better. Postoperative mean manifest spherical equivalent was - 0.37 ± 0.42 D at 1 month. The visual and refractive outcomes in each of the 3 subgroups were similar. The achieved flap thicknesses were found to be highly predictable and consistent in the respective thickness subgroups. Optical coherence tomography-guided thin-flap LASIK performed with the low-pulse energy femtosecond laser was found to be safe with no intraoperative or postoperative complications.

Cesarean Scar niche: Comparison of Transvaginal Ultrasound Findings and Uterine Tissue Samples after Hysterectomy

BackgroundThe cesarean scar (CS) niche, a consequence of incomplete wound healing, can lead to gynecological complications and affect future pregnancies. While internal niches have been well-studied, external and bidirectional niches are also important. ObjectivesWe aimed to conduct a comparative analysis of the prevalence and measurements of different types of niches. Study DesignThis cross-sectional study examined 200 patients with prior cesarean delivery (CD) undergoing hysterectomy due to abnormal uterine bleeding. It evaluated internal, external, and bidirectional niche prevalence, measurements (height, residual myometrial thickness, and adjacent myometrial thickness), and classification in hysterectomy specimens compared to pre-hysterectomy TVS reports. The secondary outcome was to determine niche presence in uterine tissue samples based on the number of previous CDs. ResultsThe mean age of the study participants was 48.19 years, with 30% having undergone only one CD. Notably, 83.5% had niches detected via sonography, while 91% had niches identified in uterine tissue samples post-hysterectomy (p-value =0.008). Internal niches were common, with significant associations between niche presence and the number of previous CDs. 23.3% of patients with one CD had internal niches. Additionally, external niches were detected in 4% of hysterectomy samples but not observed in ultrasound reports. Key parameters such as RMT and AMT differed notably between ultrasound and tissue samples, highlighting discrepancies in niche detection methods. RMT ranged from 2.8-24 mm (7.68 ± 3.09 mm) in ultrasound reports versus 0-25 mm (4.28 ± 2.71 mm) in tissue samples (p < 0.001). AMT ranged from 6-29 mm (17.08 ± 4.53 mm) in ultrasound reports versus 7.5-30 mm (16 ± 5.03 mm) in tissue samples (p < 0.001). This study underscores the importance of accurate niche assessment in patients with prior CD. ConclusionsWe performed a comparative analysis of niche prevalence and measurements in gross specimens and TVS reports. The results highlight the importance of considering external and bidirectional niches, in addition to internal niches. These niches can reduce residual myometrial thickness and increase future pregnancy complications. Furthermore, we demonstrated that niche formation can occur after a single CD.

Inhomogeneous strain partitioning in the Cenozoic Bohai Bay Basin controlled by pre-existing crustal fabrics and oblique subduction: Insights from the Jizhong and Huanghua subbasins

The tectonic features and geodynamics of the Bohai Bay Basin (BBB) have been extensively studied over several decades. It is generally accepted that the Cenozoic BBB was subjected to a superimposed extensional and strike-slip stress field. However, the specific basin-forming mechanism remains ambiguous. Basin-scale studies with high spatial and temporal resolution reveal how strain migrates and localizes during multiphase rifting. Understanding these strain-related processes is crucial for deciphering the formation mechanisms and controlling factors of rift basins. This study investigates the rift-related evolution and strain partitioning in the Jizhong and Huanghua subbasins, the western half of the BBB. Using high-resolution 3D and 2D seismic datasets and well data, we present detailed geological sections, residual thickness maps, and fault systems, showing two distinct patterns of strain partitioning in the Cenozoic. In the Jizhong Subbasin, strain migrated inwards from the NE-trending boundary faults and finally became localized along the NE-trending rift axis; in the Huanghua Subbasin, strain migrated northeastwards from the southern part and then was largely localized along the near E–W-trending faults in the northeastern part. By integrating our results with previous studies of other subbasins, we identify two separate extensional domains within the Cenozoic BBB. The suborthogonal extensional domain in the Jizhong Subbasin is dominated by relatively stable NW–SE extension. In contrast, the extended areas to the east (i.e., the Huanghua, Bozhong, and Liaohe-Liaodongwan subbasins) comprise the oblique extensional domain, characterized by asymmetric transtensional pull-apart deformation and subjected to a clockwise-rotated extensional stress field from NW–SE to NNW–SSE. We suggest that the spatially inhomogeneous strain partitioning in the BBB has developed since the middle Eocene, and was controlled by the interaction of pre-existing crustal fabrics (e.g., the Tan-Lu Fault Zone) and the oblique subduction of the Pacific Plate. The boundary between the two domains may represent a transition zone where the margin-parallel residual velocity component of the oblique convergence decreased considerably landwards. Our study highlights the Cenozoic strain evolution and the associated geodynamics in the BBB, emphasizing the strain complexity within the back-arc rift basin under the oblique subduction background.

Comparing Cesarean Scar Defect Incidence After Locked and Unlocked Repair Methods Among Primiparous Patients: A Randomized Double-Blinded Trial.

To compare residual myometrial thickness (RMT) and cesarean scar defect (CSD) development after cesarean section using double-layer locked and unlocked closure techniques. We conducted a randomized double-blinded trial comparing double-layer locked and unlocked uterine closure techniques following cesarean section in primiparous women. The locked technique involved continuous suturing of the full myometrial thickness in the first layer, followed by back-and-forth needle maneuvering on both sides of the incision for the second layer. The unlocked method included running suturing of two-thirds of the myometrial thickness in the first layer, followed by suturing the upper half of the myometrial thickness in the second layer. Transvaginal ultrasonography was performed one year post-cesarean section, with RMT as the primary outcome and scar depth and width as secondary outcomes. Independent t-test and Chi-square test were utilized for statistical analysis. All 30 patients from the locked and 26 from the unlocked group in the follow-up were diagnosed with CSD (scar depth>2mm). The mean RMT for the unlocked and locked groups were 4.44±1.07mm and 4.12±0.48mm, respectively, showing no significant difference (p =0.14). There was also no significant difference in mean scar width between the locked and unlocked groups (3.68±1.44mm vs. 3.95±1.00mm, p =0.42). However, the mean scar depth was higher in the unlocked group (3.77±1.11 mm vs. 3.16±1.1mm, p =0.04). We have found no significant differences in the RMT and CSD prevalence between two-layered locked and unlocked uterine closure techniques, while the scar depth was greater in the unlocked group. Nonetheless, future randomized trials implementing larger sample sizes are required to precisely compare the outcomes of the double-layer locked and unlocked uterine suturing techniques.

Effect of Ni interlayer on microstructure and mechanical properties of Sn-based alloy/steel bimetallic materials via liquid-solid compound casting

Tin-based alloys have been widely used as an excellent bearing material. However, preparing of Tin/steel bimetallic materials with sound metallurgical interfaces has proven challenging. Importantly, a large number of brittle intermetallic compounds inevitably form at the interface, affecting the material's bonding properties. In this study, an electroplated Ni layer was used for the first time as an intermediate layer in Tin/steel bimetallic composites. It solves the problems of steel surface oxidation and poor wettability. Additionally, the introduction of the electroplated Ni layer impedes the formation of brittle phases, thereby improving interfacial bond strength. The results show that the Tin/steel interface of the Ni interlayer consists mainly of a large number of Ni3Sn4 phases rather than the commonly known FeSn2 phase. A thin layer of residual Ni plating also exists between the steel and the diffusion layer. Furthermore, the properties of Ni3Sn4 and FeSn2 phases were calculated using first-principles calculations. A Tin/steel bimetallic interface achieved a maximum shear strength of 58.63 MPa in the presence of the Ni intermediate layer. At that time, the residual thickness of the Ni layer was 1.5 μm, and the thickness of the diffusion layer was 4.8 μm.

The value of cesarean scar diverticulum in diagnosis of adverse events during dilatation and curettage in patient with cesarean scar pregnancy.

The aim of the present study was to explore the relationship between the size of cesarean scar diverticulum (CSD) measured on preoperative magnetic resonance imaging (MRI) and adverse events during dilatation and curettage (D&C) procedure in patients with cesarean scar pregnancy (CSP). The MRI of 197 CSP patients from October 2019 to August 2023 were retrospectively reviewed. The volume, area, and depth of CSD, residual myometrium thickness (RMT), and gestational sac diameter were recorded and tested for correlation with intraoperative estimated blood loss (EBL), and operation time and for any association with the intraoperative adverse events (intraoperative massive hemorrhage [39 cases] and D&C procedure failure [15 cases]). The Spearman test was used to characterize the correlation between the five MRI variables and both the EBL and operation time. The correlation between the five MRI variables and intraoperative adverse events was evaluated with student's t test and Mann-Whitney U test. Diagnostic power of the MRI variables was evaluated by the area under receiver operating characteristic curve (AUC). The volume, area, and depth of CSD and gestational sac diameter were positively correlated with both EBL and operation time, with the CSD volume having the highest correlation with them (r = 0.543 and 0.461, respectively). Conversely, the RMT displayed a negative correlation with the EBL and operation time. All five MRI variables were significantly associated with both intraoperative massive hemorrhage and D&C failure (all P < 0.001). The CSD volume demonstrated the highest AUC for diagnosing intraoperative massive hemorrhage and D&C failure at 0.893 (95% CI: 0.82-0.92) and 0.901 (95% CI: 0.85-0.94), respectively. The optimal cutoff values for CSD volume in predicting massive hemorrhage and D&C failure were determined to be 5.41 and 8.92 cm3, respectively, with corresponding sensitivities/specificities of 92.31/74.68 and 93.33/82.42, respectively. Quantifying the size of CSD based on preoperative MRI could aid in evaluating risk during D&C in CSP patients, with CSD volume possessing higher diagnostic efficacy than the other four MRI indicators.

Clinical Outcomes of Modified Manual Deep Anterior Lamellar Keratoplasty for Eyes with Previous Radial Keratotomy.

Background: The aim of this study was to evaluate the intraoperative complications and visual outcomes of manual deep anterior lamellar keratoplasty (mDALK) in patients who underwent previous radial keratotomy (RK) for myopia. Methods: The notes of patients who underwent mDALK after RK at three different hospitals-San Giovanni Addolorata Hospital (Rome, Italy), Mount Saint Joseph Hospital (Vancouver, Canada), and Tor Vergata University Hospital (Rome, Italy)-were retrospectively reviewed. We analyzed the manual dissection success rate and conversion to penetrating keratoplasty (PK), the residual recipient stromal thickness, the postoperative corrected distance visual acuity (CDVA), postoperative refraction, and topographic astigmatism. Results: Thirteen eyes of eleven patients were included in the analysis (male 7/11, 63.6%). Preoperatively, mean topographic astigmatism was 5.4 ± 3.5 D (range 1.6-14.8 D), and mean CDVA was 0.47 ± 0.2 logMAR (range 0.3-1.0 logMAR) [Snellen equivalent 20/50]. Manual dissection was performed in all cases. None of the examined eyes were converted to PK. An improvement in both topographic astigmatism (2.8 ± 0.9 D, p = 0.0135) and CDVA (0.23 ± 0.2 LogMAR, p = 0.0122) was recorded at 12-month follow-up. Conclusions: mDALK is a safe and effective surgical technique when applied to eyes previously treated with RK, with an observed improvement in CDVA and topographic astigmatism.

Nominal and achieved stromal ablation depth after myopic transepithelial photorefractive keratectomy: implications for residual stromal thickness calculation

BackgroundThe primary objective of this investigation was to compare the nominal central ablation depth with the achieved central corneal stromal ablation depth after StreamLight transepithelial photorefractive keratectomy (tPRK) for myopia with WaveLight® laser by Alcon Laboratories, TX, USA.MethodsThis ambispective study encompassed a retrospective analysis of 40 eyes who underwent treatment for myopia and astigmatism, followed by a prospective examination conducted 6–9 months postoperatively. Pre- and postoperative Avanti spectral-domain optical coherence tomography (SD-OCT; Optovue Inc., CA, USA) provided stromal and epithelial thickness maps. The difference between pre- and postoperative central stromal thicknesses at the corneal vertex was used to calculate the achieved stromal thickness ablation depth. This value was then compared with the corresponding central nominal depth on the laser ablation planning map.ResultsA total of 40 eyes (OD/OS:18/22) of 40 patients (31.4 ± 9.2 years) were available for evaluation. The mean treated spherical equivalent was − 2.98 ± 1.46 D. The mean nominal and achieved central stromal ablation depths were 51.22 µm and 59.67 μm, respectively, showing a mean stromal excessive ablation of 16.50%. The mean pre- and postoperative central epithelial thicknesses were 53.74 μm and 59.31 μm, respectively, showing a mean postoperative thickness increase of 10.46%. This increase in the epithelial thickness rendered the mean postoperative pachymetry reduction to 54.11 μm, only 2.33% greater than the mean nominal ablation depth.ConclusionsThe study revealed a central stromal ablation 16.50% greater than the nominal ablation depth. This excessive stromal removal was largely compensated for by the increase in epithelial thickness, resulting in a mean difference between the nominal ablation depth and the achieved central corneal pachymetry reduction of only 2.33%. This significant excessive central stromal ablation must be taken into consideration in the calculation of the residual stromal thickness.

Transvaginal uterine niche repair: surgical technique and outcome.

A uterine niche after caesarean section may play a role in secondary infertility. The transvaginal approach is a newly developed minimally invasive surgical technique for repairing a uterine isthmocele. To report on the feasibility, effectiveness, and safety of the transvaginal uterine niche repair. The technique is demonstrated in a live-surgery video. A retrospective chart review involving all patients with secondary infertility who underwent a transvaginal uterine niche repair in Ziekenhuis Oost-Limburg between August 2019 and July 2022 was conducted. We compared the pre- and postoperative residual myometrial thickness as a primary surgical outcome measurement. The pregnancy ratio and the peri- and postoperative complications were also reported. A total of 26 patients underwent a transvaginal uterine niche repair with an average operation time of 44 minutes. No major surgical complications were reported. 23 patients (88%) had good postoperative myometrial integrity, while 3 patients had a partial or complete postoperative recurrence of the uterine niche. The average pre- and postoperative myometrial thicknesses were 1.6 mm and 6.4 mm respectively. 64% of patients desiring pregnancy became pregnant after the transvaginal niche repair. There were no obstetric complications reported. A transvaginal approach is a safe and effective technique for uterine niche repair. It offers good results in re-establishing myometrial integrity and may favour fertility outcomes. It represents a valid minimal invasive procedure for patients with a very thin residual myometrial thickness and secondary infertility without leaving a visual scar.

Objective Analysis of Predictive Value of Ultrasound Quantitative Scoring System for Treatment Method Selection in Cesarean Scar Pregnancy.

This study aimed to explore the feasibility of using the ultrasound quantitative scoring system to guide the selection of surgical methods for a cesarean scar ectopic pregnancy (CSEP). A retrospective analysis was conducted of the medical records of 117 cases of patients with a CSEP. All patients underwent transvaginal ultrasound examination before treatment, and the ultrasound results were compared with the results of surgical exploration. The treatment methods that were delivered for the 2 patient groups with CSEP were analyzed, and agreement between the predicted and actual treatment protocols was tested using the kappa consistency test. Residual myometrial thickness at the scar site was mainly concentrated above 3 mm in the low-risk group, with 70 cases accounting for 76.9%, while in the high-risk group, this was primarily in the range of 1-3 mm with 18 cases accounting for 69.2%. The grading of nourishing blood supply to the gestational sac showed that 96.7% of patients in the low-risk group had Grade I and Grade II blood flow, while 84.6% of the high-risk group had Grade I and Grade II blood flow; Grade II blood flow was predominant in the high-risk group. The majority of patients in both the low- and high-risk groups experienced intraoperative blood loss of ≤50 mL (93.9% vs 80.6%, respectively). The consistency test between the actual and predicted treatment methods yielded a kappa coefficient of 0.644, indicating consistency between the two. For patients with CSEP in the low-risk group (score <4), the ultrasound quantitative scoring system could provide individualized assessment and offer clinically valuable treatment protocols.

Structured hysteroscopic examination of uterine niches: a modified Delphi procedure.

Uterine niches in the Caesarean section scar are seen in approximately half of women with a history of caesarean delivery. Whilst a structured ultrasound assessment of caesarean defects has been described, there is no consensus on a structured hysteroscopic evaluation. To propose a methodology for a structured hysteroscopic evaluation of uterine niches. We conducted a modified Delphi procedure, including two online rounds and two face-to-face meetings of the members of the ESGE Uterine Niches Working Group. The taskforce members have extensive experience in hysteroscopic niche evaluation. The consensus was predefined as a Rate of Agreement of at least 75%. Thirteen experts participated in this modified Delphi procedure. There was consensus on the need for a standardised methodology and the hysteroscopic definition of a niche as any indentation in the myometrium at the site of a previous CS. There was consensus that a hysteroscopic evaluation of a niche must be combined with ultrasound to measure the residual myometrial thickness. In addition, it was agreed that niches should be subclassified as 'simple', 'simple with one branch', or 'complex'. There was consensus that the following items should be described during a hysteroscopic niche evaluation: the number of niches, the size in relation to the size of cervical canal, the presence of polyps, crypts, cysts, fibrotic tissue, blood, mucus, placental remnants, a dynamic valve, the appearance of the endometrium, the number of blood vessels and bleeding from blood vessels within the defect. Using a modified Delphi procedure with international experts, consensus was achieved on the hysteroscopic evaluation and classification of niches in the uterine caesarean section scar. A structured registration form was developed to aid consistency in hysteroscopic niche reporting.

Comparison between 80-microns versus 100-microns flap femtosecond LASIK for correction of myopia and myopic astigmatism.

This study aimed to compare the safety, efficacy, and visual outcomes of 80-microns LASIK versus 100-microns LASIK in managing myopia and myopic astigmatism. The study was conducted at a tertiary care hospital in North India. This was a prospective contralateral eye study that included patients with myopia and myopic astigmatism seeking refractive correction. The eligibility criteria included normal corneal topography, an epithelial thickness less than 60 microns, a calculated percentage tissue ablation (with 100-microns flap) less than 40%, a calculated residual stromal bed thickness (with 100-microns flap) more than 300 microns, and willingness to participate and follow up. Patients with glaucoma, cataracts, other visually disabling ocular pathologies, and a history of past ocular surgery were excluded. All patients underwent LASIK with 80-microns LASIK in one eye and 100-microns LASIK in the other eye. The patients were followed up for 6 months, and the results were analyzed. The study included 216 eyes of 108 patients. The mean preoperative spherical equivalent in the 80-microns group and the 100-microns group was -3.53 ± 1.81 and -3.69 ± 1.32 diopters, respectively (P = 0.78). The mean 6 months decimal postoperative UCVA was 0.98 ± 0.13 in the 80-microns group and 0.97 ± 0.14 in the 100-microns group (P = 0.99). The postoperative change in the higher-order aberration profile was comparable in both groups (P = 0.78). The percentage tissue ablation was significantly lower in the 80-microns group (P = 0.002). The incidence of flap micro striae and OBL was higher in the 80-microns group, while neither of these had any visual implications. The study concluded that 80-microns LASIK is an efficacious and safe alternative to 100-micron LASIK, especially useful in patients with higher myopia.

Approximation of acoustic black holes with finite element mixed formulations and artificial neural network correction terms

Wave propagation in elastodynamic problems in solids often requires fine computational meshes. In this work we propose to combine stabilized finite element methods (FEM) with an artificial neural network (ANN) correction term to solve such problems on coarse meshes. Irreducible and mixed velocity–stress formulations for the linear elasticity problem in the frequency domain are first presented and discretized using a variational multiscale FEM. A non-linear ANN correction term is then designed to be added to the FEM algebraic matrix system and produce accurate solutions when solving elastodynamics on coarse meshes. As a case study we consider acoustic black holes (ABHs) on structural elements with high aspect ratios such as beams and plates. ABHs are traps for flexural waves based on reducing the structural thickness according to a power-law profile at the end of a beam, or within a two-dimensional circular indentation in a plate. For the ABH to function properly, the thickness at the termination/center must be very small, which demands very fine computational meshes. The proposed strategy combining the stabilized FEM with the ANN correction allows us to accurately simulate the response of ABHs on coarse meshes for values of the ABH order and residual thickness outside the training test, as well as for different excitation frequencies.

Behavior of randomly pitted Q690 high-strength steel H-section members under eccentric compression

Six Q690 high-strength steel H-section specimens with pits were tested under eccentric compression loads. The results showed that the pits changed the failure modes of the members under eccentric compression by inducing local buckling, which resulted in a significant reduction in the ultimate resistance, reaching 31.7 % when the volume loss ratio was 15 %. A numerical study was then conducted, which revealed that the ultimate resistance loss ratio varied with the volume loss ratio and the eccentricity ratio, but not with the slenderness ratio. Finally, the existing rules for determining the ultimate resistance were modified by using the equivalent residual thickness, and the applicability of the modification was assessed.

Outcomes of Photorefractive Keratectomy in Patients Who Underwent Keratoplasty

&amp;lt;i&amp;gt;Purpose&amp;lt;/i&amp;gt;: To assess the efficacy of photorefractive keratectomy (PRK) in patients who underwent corneal transplantation, and to determine the influencing factors. &amp;lt;i&amp;gt;Methods&amp;lt;/i&amp;gt;: The present study was a retrospective chart review research that was conducted at Dhahran Eye Specialist Hospital between 2014 and 2017. &amp;lt;i&amp;gt;Results&amp;lt;/i&amp;gt;: Seventy-nine eyes were included in the study. The mean BCVA showed an improvement of two lines post-PRK as compared to that before PRK (0.73 ± 0.1 and 0.54 ± 0.2, respectively). There was a statistically significant decrease in the cylindrical value postoperatively as compared to that preoperatively (−2.15 ± 1.4 and−3.25 ± 1.8, respectively; p &amp;lt; 0.001). However, there was no statistically significant difference in spherical equivalent and sphere. Three eyes (4%) developed postoperative complications. There was a medium positive correlation between residual stroma and achieved spherical equivalent (SE) (r = 0.305, p = 0.006), as well as between optical zone and postoperative uncorrected visual acuity (r = 0.350, p = 0.001), in addition to post SE (r = 0.307, p = 0.006). However, the depth of ablation showed a medium negative correlation with achieved SE (r = −0.375, p = 0.001). &amp;lt;i&amp;gt;Conclusion&amp;lt;/i&amp;gt;: PRK may be an option for correcting refractive errors in patients who underwent keratoplasty. The optical zone and residual stromal thickness have a positive correlation with the effects of the outcomes, whereas the depth of ablation has a negative correlation with the outcomes.

A study of asymmetric guided wave propagation mechanism in elbow and prediction of elbow erosion degree based on SAFE and GA-LSSVM methods

Aiming at the problems of complex sensor layout, low detection accuracy when using guided wave to detect the elbow’s erosion degree, this research presents a new approach based on asymmetric guided wave and Genetic Algorithm-Least Support Vector Machine (GA-LSSVM). The program for calculating elbow’s dispersion curve was compiled using the semi-analytical finite element (SAFE) method. Through numerical simulation, it is found that the bending mode in the guided wave signal at the outer arch back position of the receiving end decreases with the increase of the erosion degree, which leads to the decrease of the signal’s time domain energy. Finally, The GA-LSSVM model were used to predict various elbow specimens’ residual wall thickness, and the results shows the high prediction accuracy. The average accuracy of predicting the new elbows is 87.63%. This research provides a feasible scheme for detecting elbow’s erosion degrees in engineering.

The Risk Factors for Myopia Undercorrection in Second-Generation (Visumax 800) Keratorefractive Lenticule Extraction Surgery: A Retrospective Case-Control Study.

In this study, we aim to evaluate the risk factors of myopia undercorrection in recipients of second-generation keratorefractive lenticule extraction (KLEx) surgery. A retrospective case-control study was performed, and patients who received second-generation KLEx surgery were enrolled. The cases with myopia undercorrection were matched to non-myopia undercorrection cases with a 1:4 ratio according to age, and a total of 22 and 88 eyes were categorized into the undercorrection and control groups, respectively. Demographic, refractive, topographic, and surgical data were collected preoperatively. A generalized linear model was operated to evaluate the potential risk factors for myopia undercorrection. The uncorrected distance visual acuity (UDVA) at three months postoperation was significantly better in the control group (p = 0.006), and residual myopia and SE were significantly higher in the undercorrection group during the whole follow-up period (all p < 0.001). The UDVA value showed a trend of improvement in the control group (p < 0.001), and the changes to SE and residual myopia were significantly lower in the control group (both p < 0.001). Regarding the risk factors for myopia undercorrection in the whole population and the high-myopia population, a higher manifest sphere power, higher steep keratometry (K), higher topographic cylinder, lower central corneal thickness (CCT) at apex, higher CCT difference and lower residual stromal thickness (RST) correlated to myopia undercorrection (all p < 0.05). In the low-myopia population, only higher myopia and lower RST correlated to myopia undercorrection (both p < 0.05). In conclusion, a high-sphere power and irregular topographic pattern correlated to myopia undercorrection after the second KLEx surgery, especially for individuals with high myopia.

Effect of bottom critical dimension (CD) size on TiN residual

Abstract The relationship between bottom critical dimension (CD) size and TiN residual in semiconductor manufacturing was elucidated. As an excellent electrode material, TiN needs to be cut from the continuous TiN film during the capacitor preparation process to achieve parallel connection of capacitors and increase capacitance. However, TiN film may only partially be removed under different process conditions. To illustrate the reason for TiN residual and its relationship with bottom CD size, the TiN and oxide thin films were deposited by atomic layer deposition (ALD) and plasma enhanced chemical vapor deposition (PECVD), respectively. The results show that the amount of TiN residual and bottom CD size was strongly coupled when the bottom CD size larger than 140 nm TiN can be fully removed. However, if the trench bottom CD size is smaller than 85 nm, there are different degrees (residual TiN thickness within the various of 1.8-11 nm) of TiN remain. Therefore, the results of this paper are of much importance as a reference for process design.