QuaSI: Quantile Sparse Image Prior for Spatio-Temporal Denoising of Retinal OCT Data

Optical coherence tomography (OCT) enables high-resolution and non-invasive 3D imaging of the human retina but is inherently impaired by speckle noise. This paper introduces a spatio-temporal denoising algorithm for OCT data on a B-scan level using a novel quantile sparse image (QuaSI) prior. To remove speckle noise while preserving image structures of diagnostic relevance, we implement our QuaSI prior via median filter regularization coupled with a Huber data fidelity model in a variational approach. For efficient energy minimization, we develop an alternating direction method of multipliers (ADMM) scheme using a linearization of median filtering. Our spatio-temporal method can handle both, denoising of single B-scans and temporally consecutive B-scans, to gain volumetric OCT data with enhanced signal-to-noise ratio. Our algorithm based on 4 B-scans only achieved comparable performance to averaging 13 B-scans and outperformed other current denoising methods.Comment: submitted to MICCAI'1

Effect of Axial Agitator Configuration (Up-Pumping, Down-Pumping, Reverse Rotation) on Flow Patterns Generated in Stirred Vessels

Single phase turbulent flow in a tank stirred with two different axial impellers - a pitched blade turbine (PBT) and a Mixel TT (MTT)- has been studied using Laser Doppler Velocimetry. The effect of the agitator configuration, i.e. up-pumping, down-pumping and reverse rotation, on the turbulent flow field, as well as power, circulation and pumping numbers has been investigated. An agitation index for each configuration was also determined. In the down-pumping mode, the impellers induced one circulation loop and the upper part of the tank was poorly mixed. When up-pumping, two circulation loops are formed, the second in the upper vessel. The PBT pumping upwards was observed to have a lower flow number and to consume more power than when down-pumping, however the agitation index and circulation efficiencies were notably higher. The MTT has been shown to circulate liquid more efficiently in the up-pumping configuration than in the other two modes. Only small effects of the MTT configuration on the power number, flow number and pumping effectiveness have been observed

Lensless high-resolution on-chip optofluidic microscopes for Caenorhabditis elegans and cell imaging

Low-cost and high-resolution on-chip microscopes are vital for reducing cost and improving efficiency for modern biomedicine and bioscience. Despite the needs, the conventional microscope design has proven difficult to miniaturize. Here, we report the implementation and application of two high-resolution (≈0.9 μm for the first and ≈0.8 μm for the second), lensless, and fully on-chip microscopes based on the optofluidic microscopy (OFM) method. These systems abandon the conventional microscope design, which requires expensive lenses and large space to magnify images, and instead utilizes microfluidic flow to deliver specimens across array(s) of micrometer-size apertures defined on a metal-coated CMOS sensor to generate direct projection images. The first system utilizes a gravity-driven microfluidic flow for sample scanning and is suited for imaging elongate objects, such as Caenorhabditis elegans; and the second system employs an electrokinetic drive for flow control and is suited for imaging cells and other spherical/ellipsoidal objects. As a demonstration of the OFM for bioscience research, we show that the prototypes can be used to perform automated phenotype characterization of different Caenorhabditis elegans mutant strains, and to image spores and single cellular entities. The optofluidic microscope design, readily fabricable with existing semiconductor and microfluidic technologies, offers low-cost and highly compact imaging solutions. More functionalities, such as on-chip phase and fluorescence imaging, can also be readily adapted into OFM systems. We anticipate that the OFM can significantly address a range of biomedical and bioscience needs, and engender new microscope applications

METU interoperable database system

and Sevgi Foundation, Turkey) is a multidatabase system based on OMG's (OMG is a registered trademark, and CORBA, ORB, OMG IDL, Object Request Broker are trademarks of OMG) distributed object management architecture. It is implemented on top of a CORBA compliant ORB, namely, DEC's ObjectBroker (ObjectBroker is a registered trademark of DEC Corp.) [DDO96]. In MIND all local databases are encapsulated in generic Database Object. The interface of the generic Database Object is de ned in CORBA IDL and multiple implementations of this interface, one for each component DBMSs, namely, Oracle7 (Oracle7 is a trademark of Oracle Corp.), Sybase (Sybase is a trademark of Sybase Corp.), Adabas D (Adabas D is a trademark of Software AG Corp.) and MOOD [Dog94] are provided. MIND provides its users a common data model and a single global query language based on SQL. The main functionalities of MIND are global query processing, global transaction management and schema integration. The basic component classes in the system are

The fit of tapered posts in root canals luted with zinc phosphate cement:A histological study

Objectives. Stress transmission to the root through passive fitting dental posts is partly influenced by the thickness of the cement layer between the post and the prepared root canal surface as well as the fit of the post in the root canal. The objective of this study was to compare the cement gap between the post surfaces and the root canals using five prefabricated, tapered, unthreaded titanium posts of different manufacturers, without and with cement. Methods. Following the endodontic treatment with hand instruments of 100 intact anterior teeth, post spaces were prepared using opening drills of the corresponding size of post. Fifty posts were cemented with zinc phosphate cement into the roots for each system while another 50 posts were inserted into the canal without using the cement. After histological sectioning, the cement gap was measured at six sites for three times at the coronal, middle and apical regions between the root canal wall and the post surface under a light microscope before and after cementation. Results. Before cementation, the highest overall cement gap was observed with the Dr Mooser post system (R) (46 mu m) and the lowest with the Velva post system (R) and Cylindro-Conical system (R) (30 mu m). Significantly less (P <0.05) mean cement gap was observed with respect to the Erlangen post system (R) (41 mu m), the Dr Mooser post system (R) (48 mu m), the MP Pirec post system (R) (34 mu m) and Velva post system (R) (33 pm) when compared with the Cylindro-Conical system (R) (62 tm). The Cylindro-Conical system (R) (79, 61 gm) and MP Pirec post system (R) (25, 24 tm) demonstrated no significant difference (P > 0.001) compared with Velva-Post (R) (38, 20 mu m) at the coronal and middle part, respectively (Mann-Whitney U-test, Boneferroni correction). Significant differences (P <0.001) were observed between the cement gap at the coronal and apical part for the Cylindro-Conical system (R) (79, 46 mu m), Dr Mooser post system (R) (45, 56 mu m) and MP Pirec post system (R) (25, 52 mu m). After cementation, the highest cement gap at the coronal part was obtained with the Cylindro-Conical system (R) (79 +/- 21 mu m) and the lowest with the MP Pirec post system (R) (25 +/- 9 mu m). However, at the apical end, the MP Pirec post system (R) (52 +/- 89 gm) and Dr Mooser post system (R) (56 +/- 16 gm) revealed the highest gap. Significance. Form-congruence between the preparation drill and the post systems exhibited differences. The most consistent cement gap either at the coronal, middle or apical parts of the root canals was obtained with the Erlangen post system (R). (c) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All. rights reserve

Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers

The systematic trends in structural and electronic properties of perylene diimide (PDI) derived dye molecules have been investigated by DFT calculations based on projector augmented wave (PAW) method including gradient corrected exchange-correlation effects. TDDFT calculations have been performed to study the visible absorbance activity of these complexes. The effect of different ligands and halogen atoms attached to PDI were studied to characterize the light harvesting properties. The atomic size and electronegativity of the halogen were observed to alter the relaxed molecular geometries which in turn influenced the electronic behavior of the dye molecules. Ground state molecular structure of isolated dye molecules studied in this work depends on both the halogen atom and the carboxylic acid groups. DFT calculations revealed that the carboxylic acid ligands did not play an important role in changing the HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI and substrate titania surface of the solar cell or photocatalyst. A commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also studied for electronic and structural properties in order to make a comparison with PDI derivatives for light harvesting properties. Results of this work suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds can be useful as sensitizers in solar cells and in artificial photosynthesis.Comment: Single pdf file, 14 pages with 7 figures and 4 table

Influence of various surface-conditioning methods on the bond strength of metal brackets to ceramic surfaces

With the increase in adult orthodontic treatment comes the need to find a reliable method for bonding orthodontic brackets onto metal or ceramic crowns and fixed partial dentures. In this study, shear bond strength and surface roughness tests were used to examine the effect of 4 different surface conditioning methods: fine diamond bur, sandblasting, 5% hydrofluoric acid, and silica coating for bonding metal brackets to ceramic surfaces of feldspathic porcelain. Sandblasting and hydrofluoric acid were further tested after silane application. A total of 120 ceramic disc samples were produced, and 50 were used for surface roughness measurements. The glazed ceramic surfaces were used as controls. Metal brackets were bonded to the ceramic substrates with a self-curing composite. The samples were stored in 0.9% NaCl solution for 24 hours and then thermocycled (5000 times, 5degreesC to 55degreesC, 30 seconds). Shear bond tests were performed with a universal testing device, and the results were statistically analyzed. Chemical surface conditioning with either hydrofluoric acid (4.3 mum) or silicatization (4.4 mum) resulted in significantly lower surface roughness than mechanical conditioning (9.3 mum, diamond bur; 9.7 mum, sandblasting) (P <.001). The surface roughness values reflect the mean peak-and-valley distances. The bond strengths of the brackets bonded to the ceramic surfaces treated by hydrofluoric acid with and without silane (12.2 and 14.7 MPa, respectively), silicatization (14.9 MPa), and sandblasting with silane (15.8 MPa) were significantly higher (P <.001) than those treated by mechanical roughening with fine diamond burs (1.6 MPa) or sandblasting (2.8 MPa). The highest bond strength values were obtained with sandblasting and silicatization with silane or hydrofluoric acid without silane; these fulfilled the required threshold. The use of silane after hydrofluoric acid etching did not increase the bond strength. Diamond roughening and sandblasting showed the highest surface roughness; they can damage the ceramic surface. Acid etching gave acceptable results for clinical use, but the health risks should be considered. The silicatization technique has the potential to replace the other methods; yet cohesive failures were observed in the ceramic during removal of the brackets