Three Sequential Hydrolysis Products of the Ubiquitous Cu24 Isophthalate Metal-Organic Polyhedra.

Metal-organic polyhedra (MOPs) are increasingly studied as host-guest capsules, linked into networks, or incorporated into composite materials. As such, understanding the decomposition of MOP structures is of fundamental importance. The degradation of the ubiquitous copper(II) MOP Cu24[5-(hydroxy)isophthalate]24 (1) is studied in liquid water. At different intervals of water exposure, powder X-ray diffraction (PXRD) is performed and stepwise conversion of the MOP into three different coordination polymers is observed. First, the formation of a 2D coordination polymer, 2, is observed, which upon further exposure gives a 1D coordination polymer, 3, and finally a trinuclear copper(II) complex, 4. Compound 2 is characterized by PXRD owing to its transient nature, while 3 and 4 are characterized crystallographically. The final structure, 4, contains copper(II) trimers, and so its magnetic behavior is also investigated.

Mechanical Properties of a Metal-Organic Framework formed by Covalent Cross-Linking of Metal-Organic Polyhedra.

Overcoming the brittleness of metal-organic frameworks (MOFs) is a challenge for industrial applications. To increase the mechanical strength, MOFs have been blended with polymers to form composites. However, this also brings challenges, such as integration and integrity of MOF in the composite, which can hamper the selectivity of gas separations. In this report, an "all MOF" material with mechanical flexibility has been prepared by covalent cross-linking of metal-organic polyhedra (MOPs). The ubiquitous Cu24 isophthalate MOP has been decorated with a long alkyl chain having terminal alkene functionalities so that MOPs can be cross-linked via olefin metathesis using Grubbs second generation catalyst. Different degrees of cross-linked MOP materials have been obtained by varying the amount of catalyst in the reaction. Rheology of these structures with varying number of cross-links was performed to assess the cross-link density and its homogeneity throughout the sample. The mechanical properties were further investigated by the nanoindentation method, which showed increasing hardness with higher cross-link density. Thus, this strategy of cross-linking MOPs with covalent flexible units allows us to create MOFs of increasing mechanical strength while retaining the MOP cavities.

Amphiphile-like self assembly of metal organic polyhedra having both polar and non-polar groups.

Mixed linker metal-organic polyhedra (MOPs) with polar and non-polar groups on the same MOP have been synthesized. This yields two types of MOPs, one where the ligands are evenly and symmetrically distributed over each polyhedron, as confirmed crystallographically and the other where respective groups segregate. The segregation is confirmed by the amphiphile-like behavior of the latter MOP in different polarity solvents, as seen through transmission electron microscopy (TEM) even though the anchor points of the functional groups are ∼10 Šapart on the MOP surface.

Mechanically Flexible Organic Crystals Achieved by Introducing Weak Interactions in Structure: Supramolecular Shape Synthons.

Controlling mechanical properties of ordered organic materials remains a formidable challenge, despite their great potential for high performance mechanical actuators, transistors, solar cells, photonics, and bioelectronics. Here we demonstrate a crystal engineering approach to design mechanically reconfigurable, plastically flexible single crystals (of about 10) of three unrelated types of compounds by introducing active slip planes in structures via different noninterfering supramolecular weak interactions, namely van der Waals (vdW), π-stacking, and hydrogen bonding groups. Spherical hydrophobic groups, which assemble via shape complementarity (shape synthons), reliably form low energy slip planes, thus facilitating an impressive mechanical flexibility, which allowed molding the crystals into alphabetical characters to spell out "o r g a n i c c r y s t a l". The study, which reports the preparation of a series of exotic plastic crystals by design for the first time, demonstrates the potential of soft interactions for tuning the mechanical behavior of ordered molecular materials, including those from π-conjugated systems.

Interocular axial length difference in eyes with pediatric cataracts.

PURPOSE: We sought to report interocular axial length difference (IALD) between the operated eye and fellow eye at the time of pediatric cataract surgery. METHODS: A retrospective analysis of 171 cataractous (operated) eyes (mean patient age at surgery, 56.9 months; range, 0.2-230.0) was undertaken. Descriptive statistics, analysis of covariance, and regression analysis were used in statistical analysis. RESULTS: The mean IALD was 0.05 +/- 1.15 mm. If absolute values were used, mean IALD was 0.76 +/- 0.86. Nearly half of the subjects (48.0%) showed an IALD of >/=0.5 mm. Forty-one patients (24.0%) had operated (cataractous) eyes that were >/=0.5 mm shorter than the fellow eye, and 41 patients (24.0%) had operated eyes that were >/=0.5 mm longer than the fellow eye. The mean IALD in unilateral and bilateral cases was 0.10 +/- 1.33 and -0.03 +/- 0.76, respectively (P = 0.4). If absolute values were used, it was 0.98 +/- 0.90 and 0.40 +/- 0.65 in unilateral and bilateral cases, respectively (P < 0.001). IALD was more predictable in unilateral than in bilateral cases (P < 0.001). In unilateral cases, age at surgery (P = 0.04) and AL of the operated eye (P < 0.001) correlated with IALD. IALD did not correlate with gender, ethnicity, or type of cataract in either unilateral or bilateral cases. CONCLUSIONS: An IALD of >/=0.5 mm occurred in 48.0% of patients with pediatric cataracts and occurred more often with unilateral cataractous patients than with bilateral cases. In patients with unilateral cataract, age at surgery and AL of the operated eye could help predict the IALD.

Opacification of the visual axis after cataract surgery and single acrylic intraocular lens implantation in the first year of life.

PURPOSE: To report the incidence and risk factors for secondary surgical intervention to treat visual axis opacification (VAO) after cataract surgery and acrylic intraocular lens (IOL) implantation during the first year of life. METHODS: A retrospective review of 29 eyes of 20 patients receiving a hydrophobic acrylic (AcrySof; Alcon, Fort Worth, TX) IOL implantation was conducted. All eyes underwent primary posterior capsulectomy and anterior vitrectomy. Statistical analysis was performed using SPSS for Windows (SPSS, Chicago, IL). RESULTS: Average age at surgery was 4.8 +/- 3.7 months, and average follow-up was 33.4 +/- 16.1 months. Eleven of 29 (37.9%) eyes developed VAO requiring secondary surgical intervention at a median of 4.8 months (95% confidence interval 3.4 to 6.2). Average age at surgery for eyes that subsequently opacified was 3.8 +/- 3.0 months compared with 5.4 +/- 4.0 months for those whose visual axis remained clear (P = 0.26). The relative risk of subsequent VAO surgery was 2.7 for primary surgery performed at or before the first 6 months of life. Opacification was significantly related to eyes with associated ocular anomalies (eg, anterior segment dysgenesis, iris hypoplasia, or persistent fetal vasculature) with a relative risk of 8.6 (P < 0.001). Proliferation of cortex was the most common form of VAO, followed by mixed-type with predominantly fibrous, fibrous alone, or Elschnig pearls. When secondary surgery was required, it occurred primarily during the first 6 months (ie, 9 of 11 patients) after the initial cataract surgery. CONCLUSIONS: When cataract and IOL surgery was undertaken within the first year of life, a secondary surgical procedure was required in 37.9% of eyes to maintain a clear visual axis. Most secondary surgery for VAO occurred within the first 6 months after surgery. Postoperative opacification was most common in eyes with associated ocular anomalies.

Unilateral Lisch nodules in the absence of other features of neurofibromatosis 1.

PURPOSE: To report a 14-year-old boy with unilateral Lisch nodules without any other diagnostic features of neurofibromatosis type 1. DESIGN: Observational case report. METHODS: A complete ophthalmologic examination and medical genetics examination was performed. RESULTS: By clinical examination, multiple Lisch nodules were identified in the left eye. CONCLUSIONS: Lisch nodules, in the absence of other diagnostic features of neurofibromatosis type 1, are an atypical finding.

Postoperative stereoacuity following realignment for chronic acquired strabismus in adults.

BACKGROUND: There is controversy regarding whether or not visually mature individuals can permanently lose stereoacuity and under what conditions stereoacuity can be regained. Some have proposed a critical duration of misalignment in adults beyond which recovery of fine stereoacuity is not possible, despite successful surgical alignment. METHODS: Twenty-one adult patients (median age 59 years) with large-angle acquired strabismus and who were successfully surgically aligned after 7 to 501 months of misalignment were studied. Subjects had no evidence of motor or sensory fusion since the onset of strabismus, on preoperative exam, or by history. Stereoacuity was measured using 1 or more of the Frisby, Preschool Randot and Titmus tests, at 8 weeks and at 12 months. Data from tests with monocular clues were not used. RESULTS: At total of 67% of patients with chronic acquired strabismus and no preoperative fusion regained measurable stereoacuity and 44% regained fine stereoacuity of at least 60 seconds of arc. Of 10 patients with no or subnormal stereoacuity 8 weeks postoperatively, 6 (60%) showed improvement at the 12-month visit. Misalignment for up to 4 years did not preclude the development of postoperative stereoacuity. CONCLUSIONS: Although a minority of adult strabismus patients may permanently lose stereoacuity despite successful alignment for acquired strabismus, the majority do show recovery. Such recovery of stereoacuity may take several months to occur. In our adult series, duration of misalignment did not predict failure to recover stereoacuity.