Correlation between topographic progression of geographic atrophy and visual acuity changes

Background: To analyze topographic progression of geographic atrophy with different concentric circles centered on the fovea in correlation with decrease of visual acuity. Methods: We retrospectively analysed 36 eyes of 26 patients diagnosed with geographic atrophy and followed at least 1 year. 1mm circular area at the foveal center were defined as Zone 1, and doughnut shape areas from between 1 and 2 mm to between 5 and 6 mm were defined as Zone 2 to Zone 6. Then, changes of geographic atrophy area in each zone were measured with semi-automatic software. Correlation analysis and regression analysis were performed to determine the relationship between changes in visual acuity and atrophic area in each zone. Result: Mean age was 76.9 years and follow-up period were 3.38 years. The mean atrophic area increased from 8.09 to 16.34 mm2 and visual acuity decreased from 0.39 to 0.69 on logMAR. Mean change of total geographic atrophy area was not significantly correlated with visual acuity decrease. While geographic atrophy progression within Zone 1, Zone 2 and Zone 3 showed significant causal relationship with decrease of visual acuity (all p<0.05). Conclusion: In contrast to the total geographic atrophy area, progression of geographic atrophy in parafoveal area was significantly correlated with decrease of visual acuity.

Shape, Size and Distribution of Metal Particles Embedded in a Ceramic Matrix

The presented paper is a review of own work done on two systems of composites, Al2O3‑Ni and Al2O3-Fe. The previous own results of research into shape, size and distribution of the metal particles and spinel phase embedded in a ceramic matrix are referred to and new ones are presented. Metal particles as well as spinel can be distributed uniformly in a ceramic matrix or can form graded structures. Most often there are agglomerates of metal or spinel particles rather than separated particles embedded in ceramic grains. In composites the growing spinel forms a thick oval layer around a metal particle, however, separate spinel areas embedded in a ceramic matrix are noticed, too. Also, the characteristic “doughnut” shape of spinel is found. Since the metal and spinel phase influence the mechanical properties, the required properties of ceramic-metal composites can be tailored by changing the size, shape and distribution of the phases.

Single-crystal guest exchange and phase transformations in a porous metallocycle

One of the target architectures for porous crystals investigated by our group is the "doughnut-shaped" metallocycle. The "doughnut" shape of the metallocycles prevents them from packing efficiently and results in the formation of crevices, cavities or channels in the packing arrangement. Naturally, owing to close-packing requirements the occurrence of empty space in the crystal structure is energetically unfavourable and therefore the available "space" is usually occupied by solvent molecules. Ideally, the porous phase can be obtained by removing the solvent molecules from the channels without disrupting the host framework. In this regard we have conducted a further investigation of the porous metallocycle previously reported by Barbour et al.[1] Single crystals of a previously reported porous metallocycle [Ag2L2](BF4)2·2CH3CN (1) were grown from acetonitrile and immersed in different organic solvents. The crystals thus treated were subjected to single-crystal X-ray diffraction analysis, which revealed that the acetonitrile guest molecules had been replaced by the solvent that the compound was exposed to, yielding five different solvates: [Ag2L2](BF4)2·2(CH3)2CO (2), [Ag2L2](BF4)2·2CHCl3 (3), [Ag2L2](BF4)2·C6H6 (4), [Ag2L2](BF4)2·C6H4F2 (5), [Ag2L2](BF4)2·C7H8 (6). Thermogravimetric analysis supports these findings.

Deformation, Vibration, Buckling of Continuum Nanotorus

A nanotorus is theoretically described as carbon nanotube bent into a torus (doughnut shape). Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than previously expected for certain specific radii. Its properties vary widely depending on radius of the torus and radius of the tube. Here, we developed a continuum model of nanotorus and obtained a closed form solutions for nanotorus deformation, vibration, and buckling and embedded in an elastic medium. The nanotorus is considered as a continuum model.

A Doughnut-shaped Vessel from Kaminaljuyú, with a Distributional Analysis of This Unusual Form

A rare ceramic form commonly called the doughnut-shape is reported for Kaminaljuyú, Guatemala, Miraflores phase. This specimen provides another example of the stucco technique on Pre-Classic pottery. A trial distribution of doughnut-shaped vessels is plotted for the Americas. Although this chart is based upon only a few published illustrations, certain deductions can be made as to the value of this form as a horizon marker. The horizontal variety of doughnut vessel may be a good marker for the Late Pre-Classic horizon in Mesoamerica.