Mo2Ga2C: a new ternary nanolaminated carbide.

We report the discovery of a new hexagonal Mo2Ga2C phase, wherein two Ga layers ­ instead of one ­ are stacked in a simple hexagonal arrangement in between Mo2C layers. It is reasonable to assume this compound is the first of a larger family.

A family of oxide-carbide-carbon and oxide-nitride-carbon nanocomposites.

This paper describes a powerful and versatile approach that combines the benefits of sol-gel processing with controlled phase separation to yield oxide-carbide-carbon or oxide-nitride-carbon nanocomposites.

Effect of grain size on the electrical properties of samaria-doped ceria solid electrolyte.

Samaria-doped ceria (SDC) ceramic nanopowders have been synthesized by three different methods: co-precipitation, combustion, and hydrothermal. The Ce0.8Sm0.2O1.9 nanopowder with an average aggregate size of 47 nm and crystallite size of 7-11 nm prepared by the hydrothermal method has been used for further consolidation by pressureless (PLS) and spark plasma (SPS) consolidation methods at 1000-1400 degrees C to obtain dense ceramic samples with different grain sizes in the wide range of 80 to 1500 nm. The total electrical conductivities of 0.010-0.015 S/cm at 600 degrees C were obtained for the PLS-derived samples. The dense SDC nanostructured ceramics consolidated by SPS showed the very low activation energy of only 0.66 eV at temperatures of 300-400 degrees C, and the total electrical conductivity of 0.0056 S/cm. The enhancement of the grain-boundary framework quality by annealing of the nano-SDC electrolyte at 1000 degrees C for 20 hours almost doubled the average grain size. In addition the electrical conductivity was enhanced almost 40%, while keeping the activation energy unchanged.

Fabrication and characterization of TiN-Ag nano-dice.

TiN-Ag nanocomposite was synthesized by dc arc-plasma method. Microstructures of TiN-Ag nanocomposite were carefully characterized by powder X-ray diffraction method and transmission electron microscopy, and nano-morphologies by three-dimensional electron tomography. It was found that the surface of nanocrystalline TiN matrix was densely covered by finely dispersed Ag nanoparticles, and it was found that they were physically attached but not chemically bonded from their orientation relationships.

Nanoreactor engineering and spark plasma sintering of Gd20Ce80O1.90 nanopowders.

The concept of the in situ engineering of nanoreactors - morphologically homogeneous aggregates of synthesized complex intermediate metastable products has been realized. The nanoblast calcination technique was applied and the final composition was synthesized within the preliminary localized volumes of each single nanoreactor. Such technique provided the heredity of the final structure of nanosize product, and allowed the prevention of the uncontrolled agglomeration and production of Gd20Ce80O1.90 powder consisting of approximately 50 nm nano-aggregates of approximately 7 nm crystallites with a remarkably homogeneous composition and uniform morphology. Finally, the SPS consolidation of nanosized aggregates of Gd20Ce80O1.90 was analyzed. The CGO nanoceramics with average grain sizes of 32 nm and 16 nm were obtained by low-temperature SPS at 1050 degrees C and 970 degrees C, respectively under the pressures of 90-150 MPa.

A high-strain-rate superplastic ceramic.

High-strain-rate superplasticity describes the ability of a material to sustain large plastic deformation in tension at high strain rates of the order of 10-2 to 10-1 s-1 and is of great technological interest for the shape-forming of engineering materials. High-strain-rate superplasticity has been observed in aluminium-based and magnesium-based alloys. But for ceramic materials, superplastic deformation has been restricted to low strain rates of the order of 10-5 to 10-4 s-1 for most oxides and nitrides with the presence of intergranular cavities leading to premature failure. Here we show that a composite ceramic material consisting of tetragonal zirconium oxide, magnesium aluminate spinel and alpha-alumina phases exhibits superplasticity at strain rates up to 1 s-1. The composite also exhibits a large tensile elongation, exceeding 1,050 per cent for a strain rate of 0.4 s-1. The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase. We suggest that the present results hold promise for the application of shape-forming technologies to ceramic materials.

Prevalence of A-to-G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene in Japanese patients with diabetes mellitus and end stage renal disease.

The A-to-G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene (mt.3243A>G) is associated with both diabetes mellitus and myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Recently, this mutation was found in three diabetic subjects with progressive kidney disease, suggesting that it may be a contributing factor in the development of kidney disease in patients with diabetes. The aim of this study was to evaluate the contribution of this mutation to the development of end stage renal disease (ESRD) in patients with diabetes. The study group consisted of 135 patients with diabetes and ESRD. The control group consisted of 92 non-diabetic subjects with ESRD who were receiving hemodialysis. The mt.3243A>G mutation was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found the mt.3243A>G mutation in eight patients (8/135; 5.9%), all of whom were initially diagnosed with type II diabetes. Five of the eight patients were subsequently also diagnosed with MELAS. We did not find the mutation in any of the 92 nondiabetic subjects with ESRD. The prevalence of this mutation was 6.5-fold higher in patients with diabetes and ESRD than in those with diabetes alone (8/135 vs 5/550, respectively; chi2 = 13.704; P = 0.0002). The mt.3243A>G mutation may be a contributing genetic factor in the development of ESRD in Japanese patients with diabetes.

Electric double-sleeved vacuuming microtrephine for lens refilling.

An automated electric double-sleeved vacuuming microtrephine has been developed that consistently creates a 0.8 to 1.0 mm tear-free hole in the anterior lens capsule. This hole is required for lens refilling to retain accommodation after cataract removal. The trephine is double-sleeved. The stainless-steel outer sleeve vacuums the internal anterior capsule; the stainless steel rotating inner sleeve, which has a blade on the head, then slides forward and cuts the taut anterior capsule. All manipulations are controlled automatically by depressing a foot pedal. Using this instrument, a 0. 8 to 1.0 mm tear-free microhole in the anterior capsule was created successfully in 80% of excised pig (n = 30) and eye-bank (n = 10) eyes. This trephine will be useful for lens refilling in the future.

Accommodation in primate eyes after implantation of refilled endocapsular balloon.

PURPOSE: To restore accommodation after crystalline lens removal. METHODS: The crystalline lens of one eye of each of four primates was removed by phacoemulsification. Each operated-on eye underwent endocapsular silicone balloon implantation followed by filling with an organosilicone mixture. Seven months postoperatively, the anterior chamber depth and refractive power changes were measured before and after topical application of 4% pilocarpine. RESULTS: In the refilled eyes, the average anterior chamber depth reduction was 0.50 mm and the average maximal myopic change was 6.74 diopters. CONCLUSION: After lens removal, measurable accommodation was restored in the eyes with the endocapsular balloon filled with an organosilicone mixture.

[A case of multifocal choroiditis associated with progressive subretinal fibrosis].

Multifocal choroiditis associated with progressive subretinal fibrosis, which was reported by Cantrill and Folk in 1986, is characterized by acute multifocal choroiditis resulting in progressive subretinal fibrosis. All cases were young, healthy females. Our case was a 17-year-old female who complained of visual disturbance in her left eye. Ophalmoscopy showed multiple, small, yellowish-white hypopigmented, choroidial lesions in the posterior fundus of her left eye. These lesions showed hyperfluorescence in fluorescein angiography and hypofluorescence in indocyanine green (ICG) angiography. One month later the yellowish-white hypopigmented, choroidal lesions increased in number and subretinal fibrosis appeared in the macular area. Two months later subretinal fibrosis was also found in the area except for the macula. In her right eye, ophthalmoscopy and fluorescein angiography showed no abnormal findings, but ICG angiography revealed choroidal hypofluorescence areas. Two years later the subretinal fibrosis was increased and the yellowish-white lesions showed pigmentation.

Complications associated with endocapsular balloon implantation in rabbit eyes.

After phacoemulsifying the lens in six rabbit eyes through a 1.3 mm anterior capsule opening, we implanted a silicone balloon in the capsular bag and filled it with liquid silicone. The eyes were enucleated nine to 21 months postoperatively, embedded in paraffin, stained with toluidine blue, and examined by stereoscopic and light microscopy. We looked at the postoperative complications primarily. All balloons were securely fixated within the capsule. Surface wrinkles were observed in two balloons. The injected silicone remained transparent. None of the lens capsules was completely transparent, although all remained relatively clear. Retrocorneal membranes were produced in one eye in which the silicone leaked.

Refilling the lens with a inflatable endocapsular balloon: surgical procedure in animal eyes.

In this report we describe the surgical details involved in refilling the lenses of 13 rabbit and 3 primate eyes using an inflatable endocapsular balloon to restore accommodation. The procedure involves endocapsular phacoemulsification through a small "buttonhole" or "dumbbell" anterior capsulotomy or minicircular capsulotomy and the simultaneous preservation of capsular integrity, including the zonules and ciliary muscles. An inflatable balloon made of thin silicone membrane is then inserted into the empty capsular bag. A liquid silicone polymer is injected into the balloon through a delivery tube, and the empty capsular bag is refilled by the inflated balloon. The procedure was found to be reproducible, and an accommodation of 6 D was confirmed in one primate eye. Capsular opacification occurred, but the proliferation and migration of residual lens epithelial cells could be hindered by abundant refilling. This lens-refilling technique may provide restoration of accommodation in future cataract surgery.

Intercapsular cataract surgery with lens epithelial cell removal. Part IV: Capsular fibrosis induced by poly(methyl methacrylate).

Characteristic lens epithelial cell behavior in the pseudophakic eye was examined by comparing 30 eyes that had extracapsular cataract surgery by the intercapsular technique and posterior chamber intraocular lens (IOL) implantation with lens epithelial cell removal but without anterior capsule capsulectomy and nine aphakic eyes that had the same procedure but without posterior chamber lens implantation over a mean follow-up period of 30 and 23 months, respectively. Fibrous anterior capsule opacification was observed in 83% of the pseudophakic eyes in the area of contact with the IOL, while the region beyond the margin of the IOL remained transparent. Fibrous anterior capsular opacification was not noted in the aphakic eyes. This suggests that the IOL material, poly(methyl methacrylate), stimulates lens epithelial cells to undergo fibrous metaplasia and to produce collagen fibers. Various cytokines such as IL-1 and TGF-beta synthesized by lens epithelial cells may play a crucial role as mediators in the process. We recommend that this effect be considered as a parameter of biocompatibility in developing and evaluating new biomaterials.

Anterior capsule-supported intraocular lens. A new lens for small-incision surgery and for sealing the capsular opening.

A new intraocular lens made of PMMA and fixed in the anterior capsular opening is introduced. The lens diameter is 4 mm and the lens has no haptics in the conventional sense but is finely grooved around the circumference edge. The lens is inserted into the anterior capsule via a very small-diameter opening created by mini-circular capsulorhexis. The anterior capsular opening, with a round, smooth-edged margin, avoids stress concentration and, therefore, the capsule does not easily tear. This opening catches the lens and chokes it along the grooved edge. In animal experiments, firm fixation was obtained. This lens may be adequate for small-incision surgery, and in the future it may be used to prevent leakage of filling material during refilling of the lens, since it acts as a part of the anterior capsule and seals the capsular opening completely.

Histopathologic and immunohistochemical findings in gelatinous drop-like corneal dystrophy.

A cornea with gelatinous drop-like corneal dystrophy was examined by histochemical and immunohistochemical techniques. Pretreatment of the sections with potassium permanganate did not decrease the staining with Congo red dye. Immunohistochemically, amyloid deposits in the cornea with this disease almost did not stain with antibodies to amyloid protein AA and AA-3. However, the corneal epithelium reacted distinctly with antibodies to amyloid protein AA and AA-3. Cross-reactivity with antibodies to protein AA and serum precursor of protein AA has been reported and protein AA-3 is the synthesized peptide corresponding to the amino acid sequence 37-47 of the human amyloid protein AA molecule. The present study suggests at least that corneal epithelial cells with gelatinous drop-like corneal dystrophy may produce a precursor of amyloid related to protein AA-3.

Further development of experimental techniques for refilling the lens of animal eyes with a balloon.

Various techniques for experimental refilling of the lens of animal eyes are possible. We describe two new methods: Balloon insertion after endocapsular phacoemulsification and after phacoemulsification with circular capsulorhexis. The feasibility of these techniques was tested in both rabbit eyes and pig cadaver eyes. With organo-silicone gel as the balloon filling material, post-operative refractive changes of up to 4 diopters of residual hyperopia were achieved; accommodation changes were up to -1 diopter. The technique of refilling the lens with a balloon to avoid leakage of filling material warrants further study.