Graded-index fiber lens proposed for ultrasmall probes used in biomedical imaging

The quality and parameters of probing optical beams are extremely important in biomedical imaging systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, penetration depth, and signal-to-noise ratio of the image in optical coherence tomography. We present a beam profile characterization of different variations of graded-index (GRIN) fiber lenses, which were recently proposed for biomedical imaging probes. Those GRIN lens modules are made of a single mode fiber and a GRIN fiber lens with or without a fiber spacer between them. We discuss theoretical analysis methods, fabrication techniques, and measured performance compared with theory.     

Laterally organized carbon nanotube arrays based on hot-filament chemical vapor deposition

Lateral porous anodic alumina (PAA) templates were used to organize carbon nanotubes (CNTs) grown by a hot-filament assisted chemical vapor deposition (HFCVD) process. For the CNT growth, we used a modified “home-made” HFCVD system with two independently powered filaments which are fitted respectively on the methane (CH₄) gas line, which serves as a carbon precursor and on the hydrogen (H₂) gas line, which acts as an etching agent for the parasitic amorphous carbon. Various activation powers of the hot filaments were used to directly or indirectly decompose the gas mixtures at relatively low substrate temperatures. A parametric study of the HFCVD process has been carried out for optimizing the confined CNTs growth inside the lateral PAA templates.     

Evaluation of polyphenolic fingerprints and antioxidant profiles of wild fruits

High‐performance thin‐layer chromatography and UV–vis spectrometry, coupled with multivariate exploratory techniques, have been investigated to fingerprint some local wild fruit extracts. The study was conducted using extracts of sea buckthorn (Hippophae rhamnoides), bilberry (Vaccinium myrtillus), cranberry (Vaccinium oxycoccos), rose hip (Cynosbati fructus), blackberry (Rubus fruticosus), raspberry (Rubus idaeus) and less‐known berries such as cornelian cherry (Cornus mas) and blackthorn (Prunus spinosa), all acquired from local markets. The extracts were firstly subjected to chromatographic separation coupled with digital image analysis and secondly to spectrophotometric analysis. Also, the DPPH˙ scavenging profiles were investigated through the UV–vis spectrum (200–700 nm), and RSA%–time profiles were determined for the first time using these samples, at different concentrations.