Decorrelation-based blood flow velocity estimation: effect of spread of flow velocity,linear flow velocity gradients,and parabolic flow

In recent years, a new method to measure transverse blood flow, based on the decorrelation of the radio frequency (RF) signals has been developed. In this paper, we investigated the influence of nonuniform flow on the velocity estimation. The decorrelation characteristics of transverse blood flow using an intravascular ultrasound (IVUS) array catheter are studied by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers; moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals were measured. The correlation coefficient method was used to present the results. Three velocity profiles were simulated: random spread of blood-flow velocity, linear blood-flow velocity gradient, and parabolic blood-flow. Radio frequency and envelope signals were used to calculate the decorrelation pattern. The results were compared to the mean decorrelation pattern for plug blood-flow. The RF signals decorrelation patterns were in good agreement with those obtained for plug blood flow. Envelope decorrelation patterns show a close agreement with the one for plug blood flow. For axial blood flow, there is a discrepancy between decorrelation patterns. The results presented here suggest that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow probably will not be affected by different transverse blood-flow conditions     

Fast processing of black and white films used in the EM lab

Kodak black and while film emulsions 4489, 4162, 2415, TMAX-100, TMAX-400, MPD-4 and RPC-651 can be developed in less than 10 minutes on a film processor, quickly printed on resin coated paper and dried with auto-processor and dryer. Adjustments to the ASA (ISO) to compensate for increased contrast with auto-processing are described.     

Highly linear micropower class AB current mirrors using Quasi-Floating Gate transistors

A design approach to achieve low-voltage micropower class AB CMOS cascode current mirrors is presented. Both class AB operation and dynamic cascode biasing are based on the use of Quasi-Floating Gate transistors. They allow high linearity for large signal currents and accurately set quiescent currents without requiring extra power consumption or supply voltage requirements. Measurement results show that dynamic cascode biasing allows a wider input range and a linearity improvement of more than 23 dB with respect to the use of conventional biasing. A THD value better than −35 dB is measured for input amplitudes up to 100 times the bias currents. Two class AB current mirror topologies are proposed, with slightly different ways to achieve class AB operation and dynamic biasing. The proposed current mirrors, fabricated in a 0.5 µm CMOS technology, are able to operate with a supply voltage of 1.2 V and a quiescent power consumption of only 36 µW, using a silicon area <0.025 mm².     

Slow virus disease: deciphering conflicting data on the transmissible spongiform encephalopathies (TSE) also called prion diseases

The transmissible spongiform encephalopathies (TSE) that manifest as Creutzfeldt-Jakob disease in humans, as scrapie in sheep and goats, mad cow disease in cattle, or chronic wasting disease in cervids (deer) represent a serious human health crisis and a significant economical problem. Despite much research, the nature of the elusive pathogen directly involved with TSE is currently unresolved. This article reviews current pathogen-cell plasma membrane properties, showing that the primary biochemical marker of the prion disease is used as a receptor by the intracellular bacterium Brucella abortus. Such observation makes plausible the role for the prion in the pathogenesis of TSE, and supports the concept that Spiroplasma, a wall-less bacterium, may be a transmissible agent of TSE. Over the past three decades, we have published convincing evidence that Spiroplasma infection is associated with TSE. The bacterial-prion-receptor concept by other laboratories support a model for TSE wherein a Spiroplasma bacterium can bind to prion receptors (alone or with anchors) on the cell surface lipid raft, allowing entry of the microbe into the cell to initiate infection. The relevance of this new concept is that it offers a new window for future research involving a bacterium in the pathogenesis of TSE. Data from the bacterial-prion-receptor model will aid in the development diagnostic tests and/or treatment protocols for TSE.     

Influence of shear thinning and material flow on robotic dispensing of poly(ethylene glycol) diacrylate/poloxamer 407 hydrogels

Robotic dispensing of hydrogels offers a direct way for generating complex hydrogel shapes. For this, there is a general need for hydrogel formulations with suitable rheological properties. In this contribution, hydrogel formulations containing poly(ethylene glycol) diacrylate (PEG‐DA) and Poloxamer 407 are characterized regarding their flow behavior during robotic dispensing. Formulations contain between 15% and 20% PEG‐DA and 22.5% and 25% Poloxamer 407. All formulations show shear thinning which can be described using a power law with a power law index between 0.10 and 0.11 and calculated shear rates at the wall of the dispensing needle of 379 s^?1 with a dispensing speed of 8 mm s^?1 and a dispensing needle inner diameter of 0.51 mm. Thus, facilitating the generation of smooth hydrogel strands, three‐dimensional hydrogel objects can be prepared without flow after robotic dispensing and can be cured afterward to elastic hydrogels, retaining the shape of the dispensed object. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45083.     

Hydrogen storage in hybrid nanostructured carbon/palladium materials: Influence of particle size and surface chemistry

Hydrogen adsorption on porous materials is one of the possible methods proposed for hydrogen storage for transport applications. One way for increasing adsorption at room temperature is the inclusion of metal nanoparticles to increase hydrogen–surface interactions. In this study, ordered mesoporous carbon materials were synthesized by replication of nanostructured mesoporous SBA-15 silica. The combination of different carbon precursors allowed to tailor the textural, structural and chemical properties of the materials. These carbons were used for the synthesis of hybrid nanostructured carbon/palladium materials with different sizes of metal nanoparticles. The hydrogen sorption isotherms were measured at 77 K and 298 K between 0.1 and 8 MPa. Hydrogen storage capacities strongly correlate with the textural properties of the carbon at 77 K. At room temperature, Pd nanoparticles enhance hydrogen storage capacity by reversible formation of hydride PdH_x and through the spillover mechanism. The hydrogen uptake depends on the combined influences of metal particle size and of carbon chemical properties. Carbons obtained from sucrose precursors lead to the hybrid materials with the highest storage capacities since they exhibits a large microporous volume and a high density of oxygenated surface groups.     

Update on the development of virus-resistant papaya: virus-resistant transgenic papaya for people in rural communities of Thailand

Papaya (Carica papaya L.) is one of the most important and preferred crops in rural communities in Thailand. Papaya ringspot virus (PRSV) is a serious disease of papaya throughout Thailand. Efforts to control the virus by various methods either have not been successful or have not resulted in sustainable control. In 1995, collaborative research by the Department of Agriculture of Thailand and Cornell University to develop transgenic papaya resistant to PRSV was initiated. Two local Thai cultivars were transformed by microprojectile bombardment with the use of a nontranslatable coat protein gene of PRSV from Khon Kaen. Numerous kanamycin-resistantplants were regenerated and were inoculated with the PRSV Khon Kaen isolate for selection of resistant lines. Since 1997, promising RO transgenic lines have been transferred to the research station at Thapra for subsequent screenhouse tests and selection of the most PRSV-resistant lines. In selection set 1, three R3 lines initially derived from Khaknuan papaya showed excellent resistance to PRSV (97% to 100%) and had a yield of fruit 70 times higher than nontransgenic Khaknuan papaya. In selection set 2, one R3 line initially derived from Khakdam papaya showed 100% resistance. Safety assessments of these transgenic papayas have so far found no impact on the surrounding ecology. No natural crossing between transgenic and nonmodified papaya was observed beyond a distance of 10 m from the test plots. Analysis of the nutritional composition found no differences in nutrient levels in comparison with the nonmodified counterparts. Molecular characterization by Southern blotting revealed three copies of the transgene presented; however, no coat protein product was expressed. Data on additional topics, such as the effects offeeding the transgenic papaya to rats and the stability of the gene inserts, are currently being gathered.     

Effects of Si addition on the microstructure and the hydrogen storage properties of Ti26.5V45Fe8.5Cr20Ce0.5 BCC solid solution alloys

The microstructure and the hydrogen storage properties of Ti_26.5(V_0.45Fe_0.085)_100−xCr₂₀Ce_0.5Si_x (x = 0 and 1) have been investigated by EPMA, XRD, in situ temperature XRD, neutron diffraction and P-C isotherm. Si addition results in the precipitation of a TiFe₂-type Laves phase and produces chemical heterogeneity in the BCC phase. As a consequence, Si-added alloy exhibits a lower hydrogen capacity and both a higher plateau pressure and slope factor as compared to Si-free alloy. Si enters in both Laves and BCC phases with a higher preference for the former phase. For both alloys, all metal atoms (Ti, V, Fe and Cr) are supposed to be randomly distributed in the 2a sites of the BCC phase and deuterium atoms occupy the 8c sites on fully charged deuterides. Si has no significant influence on the hydrogen occupation. Two hydrides are observed during the desorption process for Ti_26.5(V_0.45Fe_0.085)₁₀₀Cr₂₀Ce_0.5 alloy, a hydrogen rich one with distorted FCC structure (space group: P4/mmm) and a hydrogen poor one with BCT structure (space group: I4/mmm).     

Region growing with pulse-coupled neural networks: an alternative to seeded region growing.

The seeded region growing (SRG) algorithm is a fast robust parameter-free method for segmenting intensity images given initial seed locations for each region. The requirement of predetermined seeds means that the model cannot operate fully autonomously. In this paper, we demonstrate a novel region growing variant of the pulse-coupled neural network (PCNN), which offers comparable performance to the SRG and is able to generate seed locations internally, opening the way to fully autonomous operation.