다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

Fiber grating sensors

The PASCAL Visual Object Classes Challenge

The determination of contact area is pivotal to understand how biomaterials properties influence cell adhesion. In particular, the influence of surface charges is well-known but still controversial, especially when new functional materials and methods are introduced. Here, we use for the first time Holographic Total Internal Reflection Microscopy (HoloTIRM) to study the influence of the spontaneous polarization of ferroelectric lithium niobate (LN) on the adhesion properties of fibroblast cells. The selective illumination of a very thin region directly above the substrate, achieved by Total Internal Reflection, provides high-contrast images of the contact regions. Holographic recording, on the other hand, allows for label-free quantitative phase imaging of the contact areas between cells and LN. Phase signal is more sensitive in the first 100nm and, thus more reliable in order to locate focal contacts. This work shows that cells adhering on negatively polarized LN present a significant increase of the contact area in comparison with cells adhering on the positively polarized LN substrate, as well as an intensification of contact vicinity. This confirms the potential of LN as a platform for investigating the role of charges on cellular processes. The similarity of cell adhesion behavior on negatively polarized LN and glass control also confirms the possibility to use LN as an active substrate without impairing cell behavior.

Label-free investigation of the effects of lithium niobate polarization on cell adhesion

Optical methods in Earth Sciences

We present a new method for numerically reconstructing digital holograms on tilted planes. The method is based on the angular spectrum of plane waves. Fast Fourier transform algorithm is used twice and coordinate rotation in the Fourier domain enables to reconstruct the object field on the tilted planes. Correction of the anamorphism resulting from the coordinate transformation is performed by suitable interpolation of the spectral data. Experimental results are presented to demonstrate the method for a single-axis rotation. The algorithm is especially useful for tomographic image reconstruction.

Reconstruction of digital holograms on tilted planes

Optical waveguide writing with femtosecond laser pulses represents a good alternative to traditional fabrication 
methods thanks to its simplicity, flexibility and possibility to realize 3D structures. The direct use of a laser oscillator 
allows a simpler setup, without amplification stages, greater processing speed, up to 1 cm/s, and intrinsically symmetric 
waveguide cross-sections due to isotropic heat diffusion. 
In this work we report on the fabrication and optical characterization of waveguides at telecom wavelengths by a 
stretched-cavity (26 MHz repetition rate) Ti:Sapphire oscillator. The best results have been obtained on Corning 0211 
and the previously unexplored Schott IOG10. Operation at 1.55-micron is demonstrated and a comparison between 
optical properties of the waveguides on the two glasses is made. The refractive index profiles have been measured with 
two different techniques: the innovative Digital Holography Microscopy (DHM), applied for the first time to optical 
waveguides, and near-field refractive index profilometry (RNF). The shape of the refractive index profile was found to 
depend strongly on the glass type. 
We demonstrate passive photonic devices at 1.55-micron, exploiting the unique 3D capabilities of the technique. These 
devices include: (i) a 1x2 splitter, obtained by writing two straight waveguides at an angle and separated by a depth 
displacement; (ii) a 1x4 splitter, realized by combining 1x2 splitters on different planes in the depth; (iii) a WDM 
coupler, with a good rejection of the 980-nm signal with respect to the 1550-nm one. Perspectives of the technique will 
also be addressed.

Pietro Ferraro

Papers

Label-free investigation of the effects of lithium niobate polarization on cell adhesion

Optical methods in Earth Sciences

Reconstruction of digital holograms on tilted planes

3D photonic devices at telecom wavelengths fabricated by a femtosecond oscillator

Quaternary on Optics in Italy, Part III: Optical Methods in Testing and Characterization of Materials