Effective visualization of complex vascular structures using a non-parametric vessel detection method

The effective visualization of vascular structures is critical for diagnosis, surgical planning as well as treatment evaluation. In recent work, we have developed an algorithm for vessel detection that examines the intensity profile around each voxel in an angiographic image and determines the likelihood that any given voxel belongs to a vessel; we term this the "vesselness coefficient" of the voxel. Our results show that our algorithm works particularly well for visualizing branch points in vessels. Compared to standard Hessian based techniques, which are fine-tuned to identify long cylindrical structures, our technique identifies branches and connections with other vessels. Using our computed vesselness coefficient, we explore a set of techniques for visualizing vasculature. Visualizing vessels is particularly challenging because not only is their position in space important for clinicians but it is also important to be able to resolve their spatial relationship. We applied visualization techniques that provide shape cues as well as depth cues to allow the viewer to differentiate between vessels that are closer from those that are farther. We use our computed vesselness coefficient to effectively visualize vasculature in both clinical neurovascular x-ray computed tomography based angiography images, as well as images from three different animal studies. We conducted a formal user evaluation of our visualization techniques with the help of radiologists, surgeons, and other expert users. Results indicate that experts preferred distance color blending and tone shading for conveying depth over standard visualization techniques.     

Keggin type inorganic–organic hybrid material containing Mn(II) monosubstituted phosphotungstate and S-(+)-sec-butyl amine: Synthesis and characterization

A new inorganic–organic POM-based hybrid material comprising Keggin type mono manganese substituted phosphotungstate and enantiopure S-(+)-sec-butyl amine was synthesized in an aqueous media by simple ligand substitution method. The synthesized hybrid material was systematically characterized in solid as well as solution by various physicochemical techniques such as elemental analysis, TGA, UV–vis, FT-IR, ESR and multinuclear solution NMR (³¹P, ¹H, ¹³C). The presence of chirality in the synthesized material was confirmed by CD spectroscopy and polarimeter. The above study reveals the attachment of S-(+)-sec-butyl amine to Keggin type mono manganese substituted phosphotungstate through N → Mn bond. It also indicates the retainment of Keggin unit and presence of chirality in the synthesized material. An attempt was made to use the synthesized material as a heterogeneous catalyst for carrying out aerobic asymmetric oxidation of styrene using molecular oxygen. The catalyst shows the potential of being used as a stable recyclable catalytic material after simple regeneration without significant loss in conversion.     

Association of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) with age of puberty among children living near a chemical plant

Animal studies suggest that perfluorocarbons (PFCs) may alter sexual maturation. Relationships of human PFC exposure with puberty are not clear. We conducted a cross-sectional study to investigate whether perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were associated with indicators of sexual maturation in a 2005-2006 survey of residents with PFOA water contamination from the Mid-Ohio Valley. Participants were 3076 boys and 2931 girls aged 8-18 years. They were classified as having reached puberty based on either hormone levels (total >50 ng/dL and free >5 pg/mL testosterone in boys and estradiol >20 pg/mL in girls) or onset of menarche. We estimated the odds of having reached puberty classified by these criteria and the fitted median age of reaching puberty in relation to serum PFOA and PFOS concentrations measured when puberty status was assigned. For boys, there was a relationship of reduced odds of reached puberty (raised testosterone) with increasing PFOS (delay of 190 days between the highest and lowest quartile). For girls, higher concentrations of PFOA or PFOS were associated with reduced odds of postmenarche (130 and 138 days of delay, respectively). In conclusion, our study showed a later age of puberty in this population correlated with PFC concentrations.     

Effect of Δ9-tetrahydrocannabinol and merthiolate on acyltransferase activities in guinea pig liver microsomesand merthiolate on acyltransferase activities in guinea pig liver microsomes

Δ⁹-tetrahydrocannabinol (THC) and merthiolate have been utilized as lysophospholipid acyltransferase inhibitors in metabolic studies. However, their effects on acyltransferases other than lysophosphatidylcholine:acyl-CoA acyltransferase (LPCAT) are not known. We have therefore investigated the effectiveness of THC and merthiolate in inhibiting the acylation of lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylserine, lysophosphatidylinositol (LPI) and lysophosphatidic acid (LPA) in guinea pig liver microsomes using oleoyl-CoA and arachidonoyl-CoA as acyl donors. THC inhibited LPCAT and lysophosphatidylethanolamine: acyl-CoA acyltransferase (LPEAT) by 40–50%, but had no effect or only slightly increased the activities of the other acyltransferases when assayed with oleoyl-CoA as the acyl donor. The results obtained with arachidonoyl-CoA were similar to those with oleoyl-CoA, with the exception of a 40% inhibition of lysophosphatidylserine:acyl-CoA acyltransferase (LPSAT) at concentrations of 50 μM or higher. At similar concentrations, merthiolate was more effective than THC in inhibiting the acyltransferases examined. Selective effects on the acyltransferases were observed at low concentrations of merthiolate (20 μM or less). Thus, LPCAT was most susceptible, followed by LPI acyltransferases, LPSAT, LPEAT and lysophosphatidic acid:acyl-CoA acyltransferases (LPAAT). The presence of LPA did not affect the inhibition of LPCAT by merthiolate. Thus the resilience of LPAAT to merthiolate inhibition was not due to chelation of the compound by the acidic lysolipid. Thiol reagents includingN-ethylmaleiamide, 5,5′-dithio-bis-nitrobenzoic acid, iodoacetate, β-mercaptoethanol and dithiothreitol had little or no effect on the acyltransferases relative to equimolar concentrations of merthiolate. The above results indicate that merthiolate is a much more effective inhibitor of lysophospholipid:acyl-CoA acyltransferases than is THC, and that the selectivity exhibited by merthiolate may be due to direct and specific interaction with the acyltransferases.     

Novel electrohydrodynamic preparation of porous chitosan particles for drug delivery

Uniform spherical chitosan particles of size <10 μm in diameter are important in drug delivery applications due to their excellent biocompability and biodegradability. A high concentration of chitosan in the particles can help to control the release of drugs and methods for processing high viscosity chitosan solutions are therefore required. In principle, any type of polymer, whether hydrophobic or hydrophilic, can be electrosprayed to obtain monodisperse particles of diameter <10 μm. In practice, however, electrospraying of biopolymers having viscosities of >100 mPa s results in particles >10 μm diameter. In this study, by reducing surface tension of a high viscosity chitosan suspension, it was found that smaller diameter particles could be prepared. Chitosan solutions were electrosprayed in the stable cone-jet mode to systematically study the relationship between particle diameter, viscosity and surface tension. Increasing viscosity resulted in larger diameter particles with a broad size distribution, but decreasing surface tension had the opposite effect. Results show that a chitosan solution having a viscosity of ~80 mPa s can be used to prepare chitosan particles of diameter ~2.5 μm which on drying reduced to particles of 500 nm.     

Influence of hydroxyvalerate composition of polyhydroxy butyrate valerate (PHBV) copolymer on bone cell viability and in vitro degradation

The objective of this study was to elucidate the role of hydroxyvalerate (HV) composition in polyhydroxy butyrate valerate (PHBV) copolymer film on the degradation of copolymer and osteoblastic cell activity. Degradation was studied by monitoring time‐dependent changes in mass and chemical composition of the macroporous films. The mass loss of PHBV film upon 19 weeks of exposure to pH 7.4 phosphate buffer medium was found to range from 2.8% to 9.2% with a strong dependence on the original composition of the copolyester film and morphology. Tapping mode atomic force microscopy (TMAFM) was used to examine the roughness change of polyester films due to exposure to buffer medium. Chemical analysis of the degraded film was carried out using NMR to aid in the interpretation of the mass loss and TMAFM data. The NMR results showed a significant decrease in the mol % of HV content in the degraded PHBV film. Additionally, we established that UMR‐106 cell proliferation on macroporous PHBV matrix is minimally enhanced by the HV content of PHBV copolymer. Information provided by this study can be used in the selection of appropriate PHBV copolymer for clinical use where the biopolymer needs to remain physically intact and chemically unchanged during the intended period of biomedical application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Increasing the nonlinear character of microbubble oscillations at low acoustic pressures

The nonlinear response of gas bubbles to acoustic excitation is an important phenomenon in both the biomedical and engineering sciences. In medical ultrasound imaging, for example, microbubbles are used as contrast agents on account of their ability to scatter ultrasound nonlinearly. Increasing the degree of nonlinearity, however, normally requires an increase in the amplitude of excitation, which may also result in violent behaviour such as inertial cavitation and bubble fragmentation. These effects may be highly undesirable, particularly in biomedical applications, and the aim of this work was to investigate alternative means of enhancing nonlinear behaviour. In this preliminary report, it is shown through theoretical simulation and experimental verification that depositing nanoparticles on the surface of a bubble increases the nonlinear character of its response significantly at low excitation amplitudes. This is due to the fact that close packing of the nanoparticles restricts bubble compression.     

Analysis‐preserving video microscopy compression via correlation and mathematical morphology

The large amount video data produced by multi‐channel, high‐resolution microscopy system drives the need for a new high‐performance domain‐specific video compression technique. We describe a novel compression method for video microscopy data. The method is based on Pearson's correlation and mathematical morphology. The method makes use of the point‐spread function (PSF) in the microscopy video acquisition phase. We compare our method to other lossless compression methods and to lossy JPEG, JPEG2000, and H.264 compression for various kinds of video microscopy data including fluorescence video and brightfield video. We find that for certain data sets, the new method compresses much better than lossless compression with no impact on analysis results. It achieved a best compressed size of 0.77% of the original size, 25× smaller than the best lossless technique (which yields 20% for the same video). The compressed size scales with the video's scientific data content. Further testing showed that existing lossy algorithms greatly impacted data analysis at similar compression sizes. Microsc. Res. Tech. 78:1055–1061, 2015. © 2015 Wiley Periodicals, Inc.     

Use of Sb spray for improved performance of InAs/GaAs quantum dots for novel photovoltaic structures

Photoluminescence output from InAs/GaAs quantum dots has been improved by a Sb treatment immediately prior to capping with GaAs. Spectra taken at 300 and 80 K show a significant increase in output intensity when the quantum dots are exposed for 15 s under a Sb flux of approximately 0.1 monolayers per second, but this improvement is lost when the Sb exposure is extended to 30 s. There is no significant shift in the emission energies between samples indicating strain relief due to the cap layer is not responsible for the improvement. Analysis of temperature dependent photoluminescence taken between 80 and 300 K show increased activation energies at lower temperatures when an Sb spray is used, suggesting passivation of deep defect levels. For the higher temperature activation energy, corresponding to carrier escape from the QD to the barrier, whilst a 15 s Sb spray gives a substantial increase, the longer 30 s Sb spray sees the activation energy decrease, a result deduced to be due to Sb segregation providing shallow defect levels. A band structure including a very thin GaAsSb layer adjacent to the quantum dots is used to explain these results, with the 30 s Sb spray leading to shallow Sb segregation related defects and a lower activation energy. Depth dependent X-ray photoelectron spectroscopy data support the band structure proposed to explain the photoluminescence results and also reveals the highest concentration of Sb at the sample surface suggesting a ‘floating layer’ of Sb during growth of the GaAs cap. Some of the implications of these results, for growth of quantum dot samples and for two novel solar cell proposals, the intermediate band and hot carrier solar cells, are discussed.     

Ultrafine-grained steel fabricated using warm multiaxial forging: Microstructure and mechanical properties

Grain refinement of bulk metals using severe plastic deformation (SPD) is a popular approach to improve both strength and toughness. In this paper, grain refinement of steel processed by warm multiaxial forging (MAF) and its mechanical behavior has been investigated. Coarse-grained, plain low carbon steel was deformed using MAF at 500 °C. Microstructural evolution is characterized using electron backscattered diffraction and mechanical behavior has been studied. Fraction of low angle grain boundaries (LAB) is observed to increase with strain up to total engineering strain of 1.3 thereafter it starts decreasing whereas, high angle grain boundaries showed just the opposite trend. It appears that initially grain subdivision takes place with imposition of strain thereby increasing the fraction of LAB. After a critical strain these LAB transforms into the high angle boundaries (HAB). The initial coarser grains of average 30 μm size subdivided into grains of the size finer than 0.5 μm. This has been confirmed by TEM micrographs. Improved tensile strengths and hardness values are obtained after warm MAF.