Corneal flattening following collagen crosslinking for keratoconus: Findings at 5-year follow-up

Purpose: To study the corneal flattening effect of cross-linking (CXL) overtime and to look for a potential association with preoperative topographic variables and the central depth of demarcation line (DDL). Methods: 201 eyes of 146 patients (mean age of 31.2 ± 7.3 years) with progressive keratoconus who underwent CXL between June 2007 and December 2012 were enrolled in this retrospective study. Follow-up visits were performed at different time intervals for at least 5 years. Preoperative parameters and depth of demarcation line were collected from LaserVision ophthalmology center in Lebanon. Corneal flattening was defined by a change in postoperative Kmax (ΔKmax) greater than 1.00 D. Results: ΔKmax increased from 50.25% to 61.69%, from first to last follow-up visits. The only factor significantly correlated to ΔKmax during all follow-up visits was preoperative maximum keratometry (Kmax) especially when greater than 50.00 D (OR, 1.92; 95% CI, 1.10–3.34). All eyes showed a corneal demarcation line (mean central depth (DDL): 217.11 ± 26.54 μm), with no statistically significant correlation between DDL and ΔKmax. Conclusion: CXL effect on cornea can be cumulative overtime and delayed flattening occurs in some cases. ΔKmax is positively correlated with preoperative Kmax and no association was found between ΔKmax and DDL. Therefore, DDL may not be a valid measure for the efficacy of CXL.

Variations in the Anatomic Morphology of the Lateral Distal Tibia: Surgical Implications for Distal Tibial Allograft Glenoid Reconstruction

Background: Distal tibial allograft glenoid augmentation has been introduced as a viable treatment approach for glenoid bone loss in conjunction with shoulder instability. No previous study, however, has assessed the morphologic variation of the distal tibia at the incisura as it relates to graft dimensions for glenoid augmentation. Increased concavity at the lateral distal tibia necessitates removal of the lateral cortex to obtain a flat surface, which may have implications for the strength of surgical fixation. Purpose: To assess the morphologic variation of the distal tibia at the incisura as it relates to graft dimensions for glenoid augmentation. Study Design: Descriptive laboratory study. Methods: Magnetic resonance images of the ankle were reviewed for morphology assessment of the appearance and depth of the distal tibia. A classification system was created reflecting the suitability for glenoid augmentation. Type A tibias contained a flat contour of the lateral tibia at the articular surface, indicative of an ideal graft. Type B tibias had slight concavity with a central depth <5 mm and were deemed acceptable grafts. Type C tibias had deep concavity with a central depth >5 mm and were deemed unacceptable. Statistical analysis was performed via univariate analyses to compare patient demographics against acceptable morphology for glenoid augmentation. Results: Eighty-five study patients met inclusion criteria (53 male, 32 female; mean age ± SD, 35.1 ± 10.3 years). Overall, 12 patients (14.1%) demonstrated type A morphology, with 61 patients (71.8%) having type B morphology for a total of 85.9% of acceptable grafts for glenoid augmentation. The interrater reliability was moderate to strong between observers (kappa value = 0.841). On univariate analysis, sex was the only variable significantly associated with an acceptable graft, with 100% of female patients having acceptable morphology, as compared with 77% of male patients ( P = .004). Conclusion: Variable morphology of the distal tibia at the incisura was found: 14.1% of patients demonstrated an ideal morphology for glenoid augmentation; an additional 71.8% were deemed suitable for graft usage; and 14.1% of tibias had unacceptable morphology. Sex was a significant factor for predicting acceptable grafts. Clinical Relevance: This information will assist surgeons in accepting or rejecting grafts based on the epidemiology of the distal tibial morphology as it relates to glenoid augmentation.

Surgical Implications of the Distal Tibia Morphology at the Incisura for Glenoid Augmentation

Objectives: Distal tibia allograft (DTA) glenoid augmentation has been introduced as a viable treatment approach for glenoid bone loss in conjunction with shoulder instability. An ideal graft has a flat or nearly flat lateral border of the tibia, allowing the surgeon to retain the lateral cortical bone for increased screw fixation (Figure 1A). DTA grafts with a deep concavity are difficult to prepare for fixation, as it is necessary to remove most of the cortical bone to create a flat contour of the graft (Figure 1B). Previous anatomic studies have sought to evaluate the morphology at the incisura as it pertains to syndesmosis fixation. No previous study has assessed the morphologic variation of the distal tibia at the incisura as it relates to graft dimensions for glenoid augmentation. Methods: Magnetic resonance images (MRI) of the ankle were reviewed over a 3 month period. Studies that met inclusionary criteria underwent morphology assessment to characterize the appearance and depth of the distal tibia at the incisura, both at the articular surface and the physeal scar, representing the typical depth of a DTA graft. Measurements were performed by two independent observers and inter-rater reliability was assessed. A three-part classification system was created reflecting the suitability of the distal tibial for glenoid augmentation. Type A grafts contained a flat contour of the lateral tibia, indicative of an ideal graft. Type B grafts had a slight concavity, with a central depth < 5 mm and were deemed acceptable grafts. Type C grafts had a deep concavity, with a central depth > 5 mm and were deemed unacceptable for glenoid augmentation. Statistical analysis was performed using univariate analyses to compare recorded patient demographics against acceptable morphology for glenoid augmentation. Results: 101 patients were identified with 16 excluded, leaving 85 patients for study inclusion (53 male, 32 female, average 35.1 years ±10.3 years). Overall, 12 patients (14.1%) demonstrated a type A morphology, with an additional 61 patients (71.8%) having a type B morphology for a total of 85.9% with an acceptable specimens for glenoid augmentation. The inter-rater reliability was moderate to strong between measuring observers (0.793). Only gender has found to effect the likelihood of an acceptable graft with 100% of female patients having an acceptable morphology, compared to 77% of male patients (p=0.004). Conclusion: The morphology of the distal tibia at the incisura, as it relates to glenoid augmentation was variable in this patient cohort. 14.1% of patients demonstrated an ideal morphology for glenoid augmentation, with an additional 71.8% were deemed suitable for graft usage with only minor contouring necessary. 14.1% of patients were found to have an unacceptable morphology. Gender was a significant factor for predicting acceptable grafts, with 100% of female patients having an acceptable morphology. This information will help surgeons accept or reject grafts based on the knowledge of the epidemiology of the distal tibia morphology as it relates to glenoid augmentation.

SPIN SYMMETRY IN THE RESONANT STATES OF NUCLEI

Spin breaking for the resonant states in 208 Pb is investigated by solving the Dirac equation with Woods–Saxon vector and scalar potentials in combination with an analytic continuation in the coupling constant method, where the stable and convergent energies and widths are obtained. Spin breaking are shown in correlation with the nuclear mean field shaped by the central depth Σ0, a radius (range) R and a diffusivity a, which play an important role in the splittings of energy and width. The energy-level crossings appear in several spin partners of resonant states, where the decay time is found to be different for the spin doublets even when their energies are fully degenerate.

Time series analysis of long term full disk observations of the Mn i 539.4 nm solar line

The equivalent width and central depth data of Mn 539.4 nm solar spectral line, observed in the period from 1979 to 1992 at Kitt Peak Observatory, was analyzed in pursuit for periodic changes. As the observations are highly unevenly sampled, test if the periods really exist in the observed data was needed. Two different methods for spectral analysis were applied to synthesized data sampled in the same way as observations. Comparation of these results with results obtained from the observed data showed that the parameters display at least three periodic changes with the periods of: 11years, quasi-biannual and 27 days. .

Sensitivity of the MnI 539.47 nm spectral line to solar activity

CCD observations of the MnI 539.47 nm spectral line in the solar flux made at the Astronomical Observatory in Belgrade between 1994 and 2003 have been reduced and certain line parameters, viz. the equivalent width, full width at half maximum and central depth have been derived. The variation of these parameters with the solar activity has been evaluated. The relative variation of the equivalent width from minimum to maximum of solar activity was found to be 1.4%, while the variation of the central depth is 2.3%. The full width at half maximum remains practically constant.

Doppler Mapping of CP-star Surfaces with Weak and Strong Magnetic Fields

A code for Doppler mapping of the distribution of chemical elements on stellar surfaces (Goncharskij et al., 1977, 1982) has been used during the past decade to make maps for several CP-stars. The code is based on Tikhonov’s method of solution of so-called ill-posed inverse problems and on an analytical expression of local line profiles in the form of the Milne-Eddington solution of the radiative transfer equation. This code takes into account the atmospheric model of the star through an assumed central depth of very strong and saturated lines, and through limb-darkening coefficients. As a solution one gets local line profiles and hence local equivalent widths.

Lower central depth in finitely generated soluble-by-finite groups

We say that a group G has finite lower central depth (or simply, finite depth) if the lower central series of G stabilises after a finite number of steps.In [1], we proved that if G is a finitely generated soluble group in which each two generator subgroup has finite depth then G is a finite-by-nilpotent group. Here, in answer to a question of R. Baer, we prove the following stronger version of this result.