Feasibility of post-gadolinium three-dimensional gradient-echo sequence to evaluate the pulmonary arterial vasculature

Purpose

To determine the feasibility of post-gadolinium three-dimensional gradient-echo (3D-GE) sequence for the evaluation of the pulmonary arterial vasculature in patients with suspected pulmonary embolism (PE) and in patients with a variety of other disease processes.

Materials and Methods

Twenty-six consecutive patients (18 females, 8 males; mean age±S.D., 46.6±21.1 years) who underwent chest magnetic resonance imaging (MRI) including post-gadolinium 3D-GE sequence for the evaluation of PE (Group A, n=13) and a variety of other disease processes (Group B, n=13) were included in the study. Post-gadolinium 3D-GE MR sequences were retrospectively, independently and blindly evaluated by two reviewers for the image quality of pulmonary arterial vasculature, and findings of PE and other disease processes. Clinical and imaging follow-up data for all patients were obtained. Interobserver agreement was calculated by kappa statistics.

Results

All central and lobar pulmonary arteries, 71.4–89.6% of segmental arteries and 46.7–52.7% of subsegmental arterial units in both groups were visualized with sufficient diagnostic image quality on post-gadolinium 3D-GE sequences. PE involving lobar and segmental arteries was diagnosed in two patients in each group. Other disease processes including pneumonia, lung nodules, superior vena cava stenosis, lung metastases, chronic lymphocytic leukemia and aortic aneurysm were detected in 10 of 26 patients. There was good to excellent interobserver agreement (0.73 to 1.00) for all findings.

Conclusion

Post-gadolinium 3D-GE sequence may be an alternative technique for the visualization of central, lobar and segmental arteries, and may diagnose PE and other pathologies involving the chest in different patient populations.     

A confirmation of agreement of different approaches for?scalar?gauge-invariant metric perturbations during inflation

We revisit an extension of the well-known formalism for gauge-invariant scalar metric fluctuations to study the spectra for both the inflaton and gauge-invariant (scalar) metric fluctuations in the framework of a single-field inflationary model, in which the quasi-exponential expansion is driven by an inflaton which is minimally coupled to gravity. The proposal here examined is valid also for fluctuations with large amplitudes, but for cosmological scales, where vector and tensor perturbations can be neglected and the fluid is irrotacional.     

Spirolactone syntheses through a rhodium-catalyzed intramolecular C-H insertion reaction: model studies towards the synthesis of syringolides

Model studies towards the total synthesis of syringolides using a rhodium-catalyzed intramolecular C-H insertion reaction as the key step are described. A highly stereospecific synthesis of spirolactones is achieved employing this methodology.     

Chromium(III) complexes with terdentate 2,6-bis(azolylmethyl)pyridine ligands: Synthesis, structures and ethylene polymerization behavior

Reactions of 2,6-bis(bromomethyl)pyridine with 3,5-dimethylpyrazole and 1H-indazole yield the terdentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (5) and 2,6-bis(indazol-2-ylmethyl)pyridine (6). The molecular structure of the new compound 6 was determined by single-crystal X-ray diffraction. These ligands react with the CrCl₃(THF)₃ complex in THF to form neutral complexes of general formula [CrCl₃{2,6-bis(azolylmethyl)pyridine-N,N,N}] (7, 8) which are isolated in high yields as stable green solids and characterized by means of elemental analysis, magnetic moments, IR, and mass spectroscopy. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active in the polymerization of ethylene.     

Characterization of O2 (1Δg)-derived oxidation products of tryptophan: A combination of tandem mass spectrometry analyses and isotopic labeling studies

The fragmentation mechanisms of singlet oxygen [O(2) ((1)Delta(g))]-derived oxidation products of tryptophan (W) were analyzed using collision-induced dissociation coupled with (18)O-isotopic labeling experiments and accurate mass measurements. The five identified oxidized products, namely two isomeric alcohols (trans and cis WOH), two isomeric hydroperoxides (trans and cis WOOH), and N-formylkynurenine (FMK), were shown to share some common fragment ions and losses of small neutral molecules. Conversely, each oxidation product has its own fragmentation mechanism and intermediates, which were confirmed by (18)O-labeling studies. Isomeric WOH lost mainly H(2)O + CO, while WOOH showed preferential elimination of C(2)H(5)NO(3) by two distinct mechanisms. Differences in the spatial arrangement of the two isomeric WOHs led to differences in the intensities of the fragment ions. The same behavior was also found for trans and cis WOOH. FMK was shown to dissociate by a diverse range of mechanisms, with the loss of ammonia the most favored route. MS/MS analyses, (18)O-labeling, and H(2)(18)O experiments demonstrated the ability of FMK to exchange its oxygen atoms with water. Moreover, this approach also revealed that the carbonyl group has more pronounced oxygen exchange ability compared with the formyl group. The understanding of fragmentation mechanisms involved in O(2) ((1)Delta(g))-mediated oxidation of W provides a useful step toward the structural characterization of oxidized peptides and proteins.     

A relax-and-cut algorithm for the prize-collecting Steiner problem in graphs

Given an undirected graph G with penalties associated with its vertices and costs associated with its edges, a Prize Collecting Steiner (PCS) tree is either an isolated vertex of G or else any tree of G, be it spanning or not. The weight of a PCS tree equals the sum of the costs for its edges plus the sum of the penalties for the vertices of G not spanned by the PCS tree. Accordingly, the Prize Collecting Steiner Problem in Graphs (PCSPG) is to find a PCS tree with the lowest weight. In this paper, after reformulating and re-interpreting a given PCSPG formulation, we use a Lagrangian Non Delayed Relax and Cut (NDRC) algorithm to generate primal and dual bounds to the problem. The algorithm is capable of adequately dealing with the exponentially many candidate inequalities to dualize. It incorporates ingredients such as a new PCSPG reduction test, an effective Lagrangian heuristic and a modification in the NDRC framework that allows duality gaps to be further reduced. The Lagrangian heuristic suggested here dominates their PCSPG counterparts in the literature. The NDRC PCSPG lower bounds, most of the time, nearly matched the corresponding Linear Programming relaxation bounds.     

GRASP with hybrid heuristic-subproblem optimization for the multi-level capacitated minimum spanning tree problem

We propose a GRASP using an hybrid heuristic-subproblem optimization approach for the Multi-Level Capacitated Minimum Spanning Tree (MLCMST) problem. The motivation behind such approach is that to evaluate moves rearranging the configuration of a subset of nodes may require to solve a smaller-sized MLCMST instance. We thus use heuristic rules to define, in both the construction and the local search phases, subproblems which are in turn solved exactly by employing an integer programming model. We report numerical results obtained on benchmark instances from the literature, showing the approach to be competitive in terms of solution quality. The proposed GRASP have in fact improved the best known upper bounds for almost all of the considered instances.     

Interfacial charge-transfer switch: ruthenium-dppz compounds anchored to nanocrystalline TiO2

The compound Ru(bpy)2(dppz-R)(PF6)2, where bpy is 2,2'-bipyridine and dppz-R is 11-(diethoxyphosphorylmethyl)dipyrido[3,2-a:2',3'-c]phenazine, was prepared and anchored to mesoporous nanocrystalline (anatase) TiO2 thin films as a probe of the effects of interfacial water on excited-state charge transfer processes at semiconductor interfaces. In nitrogen-saturated fluid acetonitrile, the Ru(bpy)2(dppz-R)(PF6)2 compound was found to be highly photoluminescent. Water was found to quench the excited state by a mechanism adequately described by the Perrin model, from which the radius of quenching was abstracted, 75 +/- 2 A. The Ru(bpy)2(dppz-R)(PF6)2 compounds were found to bind to the TiO2 thin films in high surface coverages, 5 x 10(-8) mol cm(-2). When these films were immersed in acetonitrile, long-lived excited states (tau = 825 ns) that were quenched by the addition of water were observed. About 30% of the excited states could not be quenched by water. Efficient electron injection, phi(inj) = 0.8, was observed after light excitation of Ru(bpy)2(dppz-R)/TiO2 in a 0.1 M LiClO4/acetonitrile solution. The addition of large concentrations of water, >0.5 M, was found to decrease the injection yield to phi(inj) = 0.3.     

Synthetic studies of complex immunostimulants from Quillaja saponaria: synthesis of the potent clinical immunoadjuvant QS-21Aapi

QS-21 is one of the most promising new adjuvants for immune response potentiation and dose-sparing in vaccine therapy given its exceedingly high level of potency and its favorable toxicity profile. Melanoma, breast cancer, small cell lung cancer, prostate cancer, HIV-1, and malaria are among the numerous maladies targeted in more than 80 recent and ongoing vaccine therapy clinical trials involving QS-21 as a critical adjuvant component for immune response augmentation. QS-21 is a natural product immunostimulatory adjuvant, eliciting both T-cell- and antibody-mediated immune responses with microgram doses. Herein is reported the synthesis of QS-21A(api) in a highly modular strategy, applying novel glycosylation methodologies to a convergent construction of the potent saponin immunostimulant. The chemical synthesis of QS-21 offers unique opportunities to probe its mode of biological action through the preparation of otherwise unattainable nonnatural saponin analogues.