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Analysis of the cardiovascular system represents a classical problem in which the solid and fluid phases interact intimately, and so is a rich field of application for state-of-the-art fluid-solid interaction (FSI) analyses. In this paper, we focus on the human aorta. Solution of the full FSI problem requires knowledge of the material properties of the wall and information on vessel support. We show that variation of distensibility along the aorta can be obtained from four-dimensional image data using image registration. If pressure data at one point in the vessel are available, these can be converted to absolute values. Alternatively, values of pulse wave velocity along the vessel can be obtained. The quality of the extracted data is improved by the incorporation into the registration of a regularisation term based on the one-dimensional wave equation. The method has been validated using simulated data. For idealised vessels, the accuracy with which the distensibility and wave velocity can be extracted is high (1%-2%). The method is applied to six clinical datasets from patients with mild coarctation, for which it is shown that wave velocity along the aorta is relatively constant.

A diverse range of reactivities is reported for Cu(II) incorporation into meso-tetrakis (Iƒ-alkylamidopheny)porphyrins in organized media (SDS micelles and AOT reversed micelles) as side-chain length and atropisomer structure are varied. Much more comparable reactivities are noted in homogeneous solution. The reactivity patterns in the organized assemblies are consistent with two separate, equilibrating interfacial orientations for the 4,0 atropisomer whose relative proportions vary with side chain length. The proposed orientations result in an inverted reactivity order for the short chain compounds in organized media (i.e. 4,0 3,1 > cis 2,2 > trans 2,2). A strong correlation between porphyrin core protonation constants and metalation anionic reactivities at the interfaces confirms the orientational hypothesis while catalytic metalation and elevated porphyrin basicities strongly support interfacial solubilization.

The reactivity of picket fence porphyrins (meso-tetrakis(o-(alkylcarbonyl)aminophenyl)phosphyrins) toward metalation with Cu 2+ or Zn 2+ shows an extremely wide rate range in aqueous anionic surfactant solutions (sodium dodecyl sulfate (SDS) micelles and Aerosol OT (AOT) reversed micelles, a factor of 35000) compared to homogeneous solution (N,N-dimethylformamide, range=156). The rates vary systematically as a function of the chain length of the N-alkyl substituent and, more significantly, the atropisomer configuration

Rate constants for the incorporation of Cu(II) and Zn(II) using the perchlorate salts were measured for the four atropisomers of C 2 and C 16 derivatives of meso-tetrakis(o-alkylamidophenyl)porphyrin, the «picket fence» porphyrins (PFPs) in N,N-dimethylformamide (DMF). A 156-fold variation in rate constants is noted for Cu(II) incorporation into the 25 PFPs studied in DMF which are 56.5-8800 times less reactive than meso-tetraphenylporphyrin (TPP)

The 4,0-atropisomer of intermediate (C{sub 6} or C{sub 7}) to long (C{sub 16}) chain length picket fence porphyrins (PFPs) exhibit red-shifted absorption and reduced singlet and triplet lifetimes in dilute aqueous surfactant solutions (i.e. below the critical micelle concentration). The spectral and photophysical behavior of these species is consistent with formation of premicellar aggregates containing two or more porphyrin chromophores lying in an offset, face-to-face arrangement ({lambda}{sub max} {approximately}426 nm, broad) or monomeric porphyrin in homogeneous or micellar solution ({lambda}{sub max} = 418-420 nm, sharp). The most characteristic behavior is noted at intermediate chain lengths for the free base or Pd(II) complex of 4,0-meso-tetrakis(2-hexanamidophenyl)porphyrin (4,0-THex) and for the free base of 4,0-THept, suggesting an optimal molecular hydrophobicity, side-chain length, and molecular topology for complex formation. The premicellar surfactant-porphyrin complexes are formed selectively from the 4,0-atropisomer and exhibit an SDS/porphyrin ratio of 3.2 for 4,0-THex. Acid-base titration behavior of the 4,0-THex J-aggregates suggests a structure in which the porphyrin core is isolated from the anionic surfactant head groups in a relatively hydrophobic microenvironment. Addition of alcohols or surfactant to disorganized aqueous aggregates of short- and long-chain 4,0-PFPs, respectively, apparently results in a modest reorganization of porphyrin chromophores ({lambda}{sub max} {approximately}436-438 nm)more » indicative of an inherent tendency toward J-aggregation for the 4,0-isomer. 102 refs., 6 figs., 10 tabs.« less

In this paper we propose a method for the nonrigid registration of contrast-enhanced dynamic sequences of magnetic resonance(MR) images. The algorithm has been developed with accuracy in mind, but also has a clinically viable execution time (i.e. a few minutes) as a goal. The algorithm is driven by multiresolution optical flow with the brightness consistency assumption relaxed, subject to a regularized best-fit within a family of transforms. The particular family of transforms we have employed uses a grid of control points and trilinear interpolation. We present validation results from a study simulating non-rigid deformation by a biomechanical model of the breast, with simulated uptake of a contrast agent. We further present results from applying the algorithm as part of a routine breast cancer screening protocol.

Gamma knife treatments are usually planned manually, requiring much expertise and time. We describe a new, fully automatic method of treatment planning. The treatment volume to be planned is first compared with a database of past treatments to find volumes closely matching in size and shape. The treatment parameters of the closest matches are used as starting points for the new treatment plan. Further optimization is performed with the Nelder-Mead simplex method: the coordinates and weight of the isocenters are allowed to vary until a maximally conformal plan specific to the new treatment volume is found. The method was tested on a randomly selected set of 10 acoustic neuromas and 10 meningiomas. Typically, matching a new volume took under 30 seconds. The time for simplex optimization, on a 3 GHz Xeon processor, ranged from under a minute for small volumes (1000 cubic mm, 2-3 isocenters), to several tens of hours for large volumes (30,000 cubic mm,20 isocenters). In 8/10 acoustic neuromas and 8/10 meningiomas, the automatic method found plans with conformation number equal or better than that of the manual plan. In 4/10 acoustic neuromas and 5/10 meningiomas, both overtreatment and undertreatment ratios were equal or better in automated plans. In conclusion, data-mining of past treatments can be used to derive starting parameters for treatment planning. These parameters can then be computer optimized to give good plans automatically.

— Previous studies from our laboratories and elsewhere have shown that amides between fatty acids and the synthetic α, α, α, α -tetra (o-aminophenyl)-porphyrins exhibit good surfactant properties which facilitate their incorporation into structured assemblies characterized by hydrophobic-hydrophilic compartmentalization. This paper will focus on a number of aspects of our studies of these porphyrins at different interfaces. The α, α, α, α (4,0) isomers are readily incorporated into Langmuir-Blodgett films as either free base or metal complexes. Studies of assemblies containing free base and palladium (II) complexes have been carried out in which the porphyrin is irradiated in the presence of oxygen and nonexcited but oxidizable substrates. Much of the reactivity observed can be attributed to 1O2* generation. These studies reveal the migration range and reactivity of activated oxygen in a structure related to biomem-branes. Several of these synthetic porphyrins have also been examined in cell suspensions and in synthetic reversed micelle solutions. Studies in the former have shown that the porphyrins can mediate the photoinactivation of several enzymes located inside and within the mitochondrial membrane in tumor cells extracted from rats. They are found to compare favorably to hematoporphyrin derivative in effectiveness. Studies of the same porphyrins in their reactivity towards copper ion incorporation in anionic reversed micelles indicate striking rate differences which can be interpreted in part to structural variations between the porphyrins as well as to their orientation at the hydrophobic-hydrophilic interface.

The purpose of this paper was to describe a mechanical system that can be used to accurately and objectively record muscle torque and its reliability. The system includes a Cybex II dynamometer and a simple microprocessor that digitalizes the analog signal from the Cybex II. Therefore, the system eliminates the subjectivity of reading the torque recording from the typical Cybex II paper recording. After digitalizing the analog signal from the Cybex II, the Cybex 11-Data Acquisition System determines the maximum torque in millivoltage and displays the maximum millivoltage recorded over a specified time period. Reliability of the system for dead weights was r = 0.99 (P/= 0.05). The data acquisition system in conjunction with the Cybex II dynamometer was confirmed as accurate instrumentation for the measurement of loads applied to the Cybex II. J Orthop Sports Phys Ther 1981;2(4):177-179.