The structure and properties of graphene on gold nanoparticles.

Graphene covered metal nanoparticles constitute a novel type of hybrid material, which provides a unique platform to study plasmonic effects, surface-enhanced Raman scattering (SERS), and metal-graphene interactions at the nanoscale. Such a hybrid material is fabricated by transferring graphene grown by chemical vapor deposition onto closely spaced gold nanoparticles produced on a silica wafer. The morphology and physical properties of nanoparticle-supported graphene are investigated by atomic force microscopy, optical reflectance spectroscopy, scanning tunneling microscopy and spectroscopy (STM/STS), and confocal Raman spectroscopy. This study shows that the graphene Raman peaks are enhanced by a factor which depends on the excitation wavelength, in accordance with the surface plasmon resonance of the gold nanoparticles, and also on the graphene-nanoparticle distance which is tuned by annealing at moderate temperatures. The observed SERS activity is correlated with the nanoscale corrugation of graphene. STM and STS measurements show that the local density of electronic states in graphene is modulated by the underlying gold nanoparticles.

Temperature and saturation dependence in the vapor sensing of butterfly wing scales.

The sensing of gasses/vapors in the ambient air is the focus of attention due to the need to monitor our everyday environment. Photonic crystals are sensing materials of the future because of their strong light-manipulating properties. Natural photonic structures are well-suited materials for testing detection principles because they are significantly cheaper than artificial photonic structures and are available in larger sizes. Additionally, natural photonic structures may provide new ideas for developing novel artificial photonic nanoarchitectures with improved properties. In the present paper, we discuss the effects arising from the sensor temperature and the vapor concentration in air during measurements with a photonic crystal-type optical gas sensor. Our results shed light on the sources of discrepancy between simulated and experimental sensing behaviors of photonic crystal-type structures. Through capillary condensation, the vapors will condensate to a liquid state inside the nanocavities. Due to the temperature and radius of curvature dependence of capillary condensation, the measured signals are affected by the sensor temperature as well as by the presence of a nanocavity size distribution. The sensing materials used are natural photonic nanoarchitectures present in the wing scales of blue butterflies.

Structure-color-species correlation in photonic nanoarchitectures occurring in blue lycaenid butterfly scales.

The blue colored males of nine Polyommatine butterfly species were investigated under the aspect of color-structure-species correlation. A large number of individuals from museum collections (in total more than 100) were used to obtain average reflectance spectra to reduce the effect of individual variations as much as possible. Structural characteristics were investigated by scanning electron microscopy and transmission electron microscopy. The relevant structural data were extracted using the Biophot Analyzer software. It was found that the position of the main reflectance peak is decided primarily by the nearest neighbor distance of holes in the perforated layers constituting the pepper-pot type structure. However, very different value of the 2D filling factor may have a large enough effect on the spectral position and the width and asymmetry of the peak to overrule the classification on taking into account only the nearest neighbor distance. The comparison of the structural and spectral data may indicate that the species Polyommatus amandus may constitute an evolutionary link between different groups of species. The examined pepper-pot type nanoarchitectures show that with the alteration of the structural parameters (first neighbor distance, 2D filling factor) the tuning of the reflectance of such nanoarchitectures may be achieved. These type of nanoarchitectures may be attractive for practical applications as their large scale manufacturing may require less strict conditions as compared with fully regular nanoarchitectures.

Bioinspired artificial photonic nanoarchitecture using the elytron of the beetle Trigonophorus rothschildi varians as a 'blueprint'.

An unusual, intercalated photonic nanoarchitecture was discovered in the elytra of Taiwanese Trigonophorus rothschildi varians beetles. It consists of a multilayer structure intercalated with a random distribution of cylindrical holes normal to the plane of the multilayer. The nanoarchitectures were characterized structurally by scanning electron microscopy and optically by normal incidence, integrated and goniometric reflectance measurements. They exhibit an unsaturated specular and saturated non-specular component of the reflected light. Bioinspired, artificial nanoarchitectures of similar structure and with similar properties were realized by drilling holes of submicron size in a multilayer structure, showing that such photonic nanoarchitectures of biological origin may constitute valuable blueprints for artificial photonic materials.

Comparison of divide and conquer and phaco-chop techniques during fluid-based phaco-emulsification.

PURPOSE: To determine whether, similar to ultrasound phaco-emulsification, applied energy and surgery time decrease using phaco-chop nucleus fragmentation method compared to divide and conquer technique using the fluid-based system. METHODS: This prospective, comparative, randomized clinical study included patients with cataract who were randomly assigned to use either standard divide and conquer technique (25 eyes of 25 patients, Group 1) or Nagahara phaco-chop maneuver (25 eyes of 25 patients, Group 2) during fluid-based phaco-emulsification. Surgical parameters were recorded and patients were examined 1 day, 10 days, and 1 month after surgery. Statistical analyses were performed using the paired test of Wilcoxon. RESULTS: Fluid-based time, mean fluid-based magnitude, effective fluid-based time, and the number of pulses were significantly less using phaco-chop technique compared to divide and conquer method (p<0.001). Surgery time was similar using the two nucleofractis techniques (p=0.97). Visual acuities showed no statistical differences between the two groups (p>0.05). CONCLUSIONS: Nuclear fragmentation can be performed with Nagahara phaco-chop technique using the fluid-based system as well. The applied fluid-based energy decreases compared to divide and conquer method. However, surgery time is not reduced due to the difficulties reaching the full occlusion necessary to hold the nucleus during the chop maneuver.

Corneal endothelial function after phacoemulsification using the fluid-based system compared to conventional ultrasound technique.

AIM: To quantitatively assess corneal endothelial changes after phacoemulsification with the fluid-based system compared to conventional ultrasound technique. METHODS: This prospective, randomized clinical study included patients with cataract who were randomly assigned either to have phacoemulsification with the fluid-based system (30 eyes of 30 patients--Group 1) or with traditional ultrasound (30 eyes of 30 patients--Group 2). Patients who were available at each follow-up visit (25 eyes in both groups) were enrolled in the statistical analysis. Endothelial function was evaluated by measuring central corneal thickness, central endothelial cell density (ECD), mean cell size, and coefficient of variation in cell size preoperatively, 10 days, 1 and 3 months, and 1 year after surgery. Statistical analyses were performed using two-way repeated measure ANOVA. RESULTS: An acute, reversible increase of central corneal thickness (CCT) was found 10 days after surgery, which was similar in both groups (P=0.35). ECD decreased, whereas mean cell size increased significantly immediately after surgery. However, the impairments were finished after 1 month. The alterations were similar in both groups (ECD: P=0.99; mean cell size: P=0.85). The coefficient of variation in cell size remained stable after surgery (P=0.08), and significant difference was not found between groups (P=0.99). The endothelial cell loss (ECL) was 6.5+/-8.4% in Group 1 and 6.5+/-11.7% in Group 2 (P=0.69). CONCLUSIONS: Corneal endothelial changes were similar using the fluid-based system compared to the traditional ultrasound technique. The fluid-based method proved to be as safe as conventional ultrasound in cataract surgery.

Wing scale microstructures and nanostructures in butterflies--natural photonic crystals.

The aim of our study was to investigate the correlation between structural colour and scale morphology in butterflies. Detailed correlations between blue colour and structure were investigated in three lycaenid subfamilies, which represent a monophylum in the butterfly family Lycaenidae (Lepidoptera): the Coppers (Lycaeninae), the Hairstreaks (Theclinae) and the Blues (Polyommatinae). Complex investigations such as spectral measurements and characterization by means of light microscopy, scanning electron microscopy and transmission electron microscopy enabled us to demonstrate that: (i) a wide array of nanostructures generate blue colours; (ii) monophyletic groups use qualitatively similar structures; and (iii) the hue of the blue colour is characteristic for the microstructure and nanostructure of the body of the scales.

[Initial experience with transpalpebral orbital lipectomy]. / Erfahrungen mit transpalpebraler orbitaler Lipektomie.

PURPOSE: The aim of this study was to evaluate the short-term effectiveness of transpalpebral orbital lipectomy. METHOD: Using a transpalpebral approach, 2.0-6.5 ml connective tissue was removed from 50 orbits of 33 patients with mild to severe Graves' orbitopathy (25 females, 8 males) over a 5-year period. Indications for surgery comprised cosmetic correction of exophthalmos (27/33 patients), corneal damage (5/33), and rapid bilateral deterioration of visual acuity in 1 patient. RESULTS: In 27 patients undergoing correction for aesthetic purposes no change in visual acuity ensued; in 4 of 5 keratopathy patients an improvement in visual acuity was detected. Diplopia ceased in 4 of 13 patients, diminished in 3 of 13 cases, and constantly increased in 2 of 13 cases. The high intraocular pressure returned to normal in 8 of 13 patients. The proptosis was reduced at 3.2+/-1.3 mm. CONCLUSION: Transpalpebral orbital lipectomy is a low-risk, highly effective technique for orbital decompression in both acute and chronic cases of Graves' orbitopathy.

Role of photonic-crystal-type structures in the thermal regulation of a Lycaenid butterfly sister species pair.

One of the possible functions of the photonic-crystal structure found on the wing scales of some butterflies is investigated. The optical and electron microscopic investigation of two male butterflies-blue (colored) and brown (discolored)-representing a sister species pair and originating from different altitudes, revealed that the blue color can be attributed unambiguously to the fine, spongelike medium, called "pepper-pot structure," present between the ridges and the cross ribs in the scales of the colored butterfly. Only traces of this structure can be found on the scales of the discolored butterfly. Other physical measurements, mainly optical reflectivity, transmission, and thermal measurements, are correlated with structural data and simulation results. The thermal measurements reveal that under identical illumination conditions the high-altitude butterfly reaches a temperature 1.3-1.5 times the temperature reached by the low-altitude butterfly. This is attributed to the photonic-crystal-like behavior of the pepper-pot structure, which significantly reduces the penetration of light with wavelength in the blue region of the spectrum into the body of the scales. This sheds some light on the adaptation that enhances the survival chance of the butterfly in a cold environment rich in blue and UV radiation.

1994 Up & Comers.

This year's Up & Comers are blazing a trail to the healthcare system of the year 2000 and beyond. Modern Healthcare profiles some rising stars, all 40 or under, in the new generation of healthcare executives who refuse to be bound by the past as they plan for the future.