Load-Deformation Behavior of Nitinol Stents

The rate of fracture of Nitinol stents in the superficial femoral artery (SFA) is higher than desirable. Development of more fracture-resistant stents requires a better understanding of in-vivo loads, how stents deform under these loads, and the influence of the artery on stent deformation. In the work reported here, testing devices were designed and constructed to measure loads in stents undergoing tensile, bending, and torsional deformations. Tests to measure mechanical stiffnesses were performed on stents, mock arteries, and stents emplaced in mock arteries. Significant stent/artery interaction was observed under tension and bending; little interaction occurred under torsion loads. The results are explained by changes in stent geometry under load. The deformation, load, and stent/artery interaction information will be useful in validating finite element codes for designing and analyzing stents.     

Production decisions under joint price and production uncertainty

While production decisions in the presence of price uncertainty have been extensively studied, this is not so for the case in which the level of production is itself uncertain. In this paper,we provide a decision analysis under multiplicative production uncertainty, both with and without price uncertainty. We depict equilibrium and obtain comparative statics results with the aid of a diagram based on the difference between expected price and marginal cost. Comparative statics results are obtained for the model with production uncertainty alone and also for simultaneous price and production uncertainty (including two special cases). We first derive results based on the Arrow–Pratt coefficients of risk aversion, and then supplement these with the Ross measure of relative risk aversion, since this proves useful in the presence of multiple sources of uncertainty. We find that increases in risk (both price and production) or input prices reduce expected output. However, expected output supply is an increasing function of (expected) price only for “low” levels of risk aversion, and in general the relationship is ambiguous.     

An EPR investigation of room temperature radiation damage and molecular motion in the ferroelectric phosphates

Several types of paramagnetic centers have been detected in the room temperature irradiated KH₂PO₄, KD₂PO₄, KH₂PO₄KH₂AsO₄, KD₂PO₄KD₂AsO₄ and in the newly discovered ferroelectric NaTh₂(PO₄)₃. Comparative studies of temperature dependence in the EPR spectra show that as in KH₂PO₄-type crystals, the ferroelectric phase transition in NaTh₂(PO₄)₃ crystals also seems to be related to the motion of the PO₄ units. The results help to clarify some earlier observed anomalies on the effects of γ-irradiation on dielectric properties of KH₂PO₄ and in particular, show that the extent of the damage can be controlled by changing the impurity content of the unirradiated samples.     

Separation of C19 and C21 dihydroxysteroids by open-hole tubular glass columns and lipophilic gel chromatography.

The combination of lipophilic gel chromatography and high-resolution glass capillary chromatography has been shown to be an important means of identification and quantification of steroid urinary metabolites. Some problems in the use of capillary columns, such as coating with polar and apolar stationary phases, column performance, thermal stability and injection systems have been investigated and this type of chromatography has been used in the analysis of 33 dihydroxysteroids. Gel chromatography is a method complementary to high-efficiency gas chromatography. The steroids are eluted according to the number of hydroxyl groups in the molecules.     

Observation of symmetry lowering and electron localization in the doublet-states of a spin-frustrated equilateral triangular lattice: Cu3(O2C16H23) x 1.2C6H12

Cu3(O2C16H23)6.1.2C6H12, containing a Cu36+ core in an equilateral triangle geometry, has been found to be a versatile model system for investigating the spin-frustration phenomenon in a triangular lattice. It affords well-resolved EPR spectra from both of the two possible (Stotal = 1/2 and 3/2) spin states of the Cu36+ core. From 295 to 100 K, the spectra consist of a triplet, but with the central line overlapped by an additional, sharp peak, which replaces the triplet at 30 K and below. The triplet was thus assigned to the excited state with Stotal = 3/2, located at 324 +/- 5 K ( approximately 225 cm-1), with the zero-field parameters D = -535 G, E = 0, g parallel = 2.209 and g perpendicular = 2.057. The singlet was attributed to the Stotal = 1/2 state, with gxx = 2.005, gyy = 2.050, gzz = 2.282, and, surprisingly, a hyperfine splitting arising from a single Cu2+ nucleus, with Azz = 157 G. The detailed magnetic measurements on a three-electron, equilateral triangular system, and the observation of symmetry lowering in the doublet ground state, should be of broad theoretical and experimental interest in molecular magnetism.     

Infinite average lifetime of an unstable bright state in the green fluorescent protein

The time evolution of the fluorescence intensity emitted by well-defined ensembles of green fluorescent proteins has been studied by using a standard confocal microscope. In contrast with previous results obtained in single-molecule experiments, the photobleaching of the ensemble is well described by a model based on Lévy statistics. By assuming the presence of thermally activated barriers, this simple model allows us to obtain information about their height distribution.     

Thin-Layer Chromatographic Enantioseparation of (RS)-Etodolac Using Indirect Approach

JPC – Journal of Planar Chromatography – Modern TLC - Enantioseparation of (RS)-etodolac was achieved by an indirect approach. Extraction of the drug (RS)-etodolac (Etd) was done from...     

Solid-Supported Synthesis of Bio-active Carvacrol Compounds Using Microwaves

The most abundant and potent natural products having a broad spectrum of biological activity against various pests are terpenoids, especially monoterpenoids. The chemical modification of natural monoterpenoids has been reported to result in modified biological activity. The present work emphasizes the structural modification of carvacrol, a phenolic monoterpenoid, through the synthesis of different ether and ester derivatives that are useful for structure–activity relationship studies to exploit the potent molecules. The carvacrol was reacted with alkyl halides and acid chlorides under microwaves using solid supports such as silica gel, alumina, and fly ash to give ethers and esters, respectively. The synthesis of dimeric ether and ester compounds using dihalides and acid dichlorides was conducted with novel reactions. Additional features of the methodology include very fast reactions, higher yields and purities of the products, and an ecofriendly approach.