Isolating quantum coherences in structural imaging using intermolecular double-quantum coherence MRI

Intermolecular multiple-quantum coherence (iMQC) MR imaging provides a fundamentally different contrast mechanism. It allows probing tissue microstructure by tuning the direction and strength of the correlation gradient. However, iMQC images of a specific quantum-coherence can easily be contaminated by leakage signals from undesired quantum coherences (zero, single, and triple quantum coherence in this work). Using a modified double-quantum CRAZED imaging sequence, we show that signals originating from various coherence orders (M=0, 1, 2, 3) can be predicted in k-space and effectively isolated by means of a four-step phase cycling scheme and judicious choice of flip angles. Finally, preliminary data suggest the method to be able to provide information on trabecular bone architecture such as regional mean trabecular plate separation.     

Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images in vivo

Until recently, NMR imaging with intermolecular multiple-quantum coherences (iMQCs) has been based on the acquisition of a single echo. In vivo studies of iMQC image contrast would greatly benefit from a method that could acquire several orders of quantum coherence during the same acquisition. This would enable comparison of the image contrast for various orders and eliminate image coregistration problems between scans. It has previously been demonstrated that multiple orders of iMQC images can be simultaneously acquired of a simple phantom. Here, we examine the technique and its effect on biological tissue, both in vivo and in vitro. First, we establish the effectiveness of the iMQC sequence in vivo using earthworms as specimens. We then further show that the multi-CRAZED sequence enhances detection of next generation (nanoparticle) contrast agents on excised tumor tissue.     

Ionic Partition Diagram of the Zwitterionic Antihistamine Cetirizine

A recent analysis of the lipophilicity profile of cetirizine in the octanol/water and dodecane/water systems revealed a partial intramolecular charge neutralization that can partly explain why cetirizine has pharmacokinetic properties differing from those of first‐generation antihistamines such as hydroxyzine. As conformational changes are the principal driving force for this intramolecular effect, the present study deals with the partitioning of cetirizine and hydroxyzine in an apolar medium well‐suited to reveal intramolecular interactions, namely the 1,2‐dichloroethane/water system. The lipophilicity of the different electrical forms of cetirizine and hydroxyzine was studied by two‐phase titrimetry and cyclic voltammetry. The differences in lipophilicity between the dicationic, monocationic, zwitterionic, and anionic species of cetirizine indicated intramolecular interactions via folded conformations, which render the molecule markedly more lipophilic than expected at physiological pH. Folded conformations were also found to predominate in monocationic and neutral hydroxyzine. The ionic partition diagram of cetirizine indicates that it acts as a proton transporter across interfaces under certain conditions of pH and Galvani potential difference. This study underlines the importance of conformational effects on the partition properties of cetirizine and hydroxyzine, as well as the complexity of its interfacial mechanisms of transfer. In particular, cetirizine can facilitate proton transfer, a property of potential biological relevance.     

Asymmetric flow field flow fractionation of aqueous C60 nanoparticles with size determination by dynamic light scattering and quantification by liquid chromatography atmospheric pressure photo-ionization mass spectrometry

A size separation method was developed for aqueous C₆₀ fullerene aggregates (aqu/C₆₀) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may alter suspension characteristics. Aqu/C₆₀ aggregates generated by sonication in deionized water ranged in size from 80 to 260 nm in hydrodynamic diameter (D_h) as determined by DLS in flow through mode, which was corroborated by analysis of fractions by DLS in batch mode and by TEM. The mass of C₆₀ in each fraction was determined by LC–APPI–MS. Only 5.2 ± 6.7% of the total aqu/C₆₀ mass had D_h less than 80 nm, while 58 ± 32% of the total aqu/C₆₀ mass had D_h between 80 and 150 nm and 14 ± 9.2% of the total aqu/C₆₀ were between 150 and 260 nm in D_h. With the optimal fractionation parameters, 77 ± 5.8% of the aqu/C₆₀ mass eluted from the AF4 channel, indicating deposition on the AF4 membrane had occurred during fractionation; use of alternative membranes did not reduce deposition. Channel flow splitting increased detector response although channel split ratios greater than 80% of the channel flow led to decreased detector response. This is the first report on the use of AF4 for fractionating a colloidal suspension of aqu/C₆₀.     

Remodeling the B-Model

We propose a complete, new formalism to compute unambiguously B-model open and closed amplitudes in local Calabi–Yau geometries, including the mirrors of toric manifolds. The formalism is based on the recursive solution of matrix models recently proposed by Eynard and Orantin. The resulting amplitudes are non-perturbative in both the closed and the open moduli. The formalism can then be used to study stringy phase transitions in the open/closed moduli space. At large radius, this formalism may be seen as a mirror formalism to the topological vertex, but it is also valid in other phases in the moduli space. We develop the formalism in general and provide an extensive number of checks, including a test at the orbifold point of A _p fibrations, where the amplitudes compute the ’t Hooft expansion of vevs of Wilson loops in Chern-Simons theory on lens spaces. We also use our formalism to predict the disk amplitude for the orbifold .     

Special Issue: Optimization and Stochastic Control in Finance,Journal of Optimization Theory and Applications

In this paper, we study the near-optimal control for systems governed by forward–backward stochastic differential equations via dynamic programming principle. Since the nonsmoothness is inherent in this field, the viscosity solution approach is employed to investigate the relationships among the value function, the adjoint equations along near-optimal trajectories. Unlike the classical case, the definition of viscosity solution contains a perturbation factor, through which the illusory differentiability conditions on the value function are dispensed properly. Moreover, we establish new relationships between variational equations and adjoint equations. As an application, a kind of stochastic recursive near-optimal control problem is given to illustrate our theoretical results.     

Evaluation of Raman and SERS analytical protocols in the analysis of Cape Jasmine dye (Gardenia augusta L.)

The identification of organic colorants in works of art (such as dyes on textiles or organic pigments) by Raman spectroscopy is generally limited by the presence of a strong fluorescence background. In this paper, the effectiveness of minimizing fluorescence in the analysis of Cape Jasmine (Gardenia augusta L.) by dispersive Raman spectroscopy at three different excitation wavelengths (633, 785 and 1064 nm) and by surface‐enhanced Raman spectroscopy (SERS) with and without acid hydrolysis is evaluated and compared. It is shown that these vibrational techniques offer an alternative analytical approach, when, as is particularly the case of Cape Jasmine, sample preparation procedures that are routinely applied for natural organic dyes and pigments cause alterations that lead to low sensitivity in the more classical high‐performance liquid chromatography‐photodiode array (HPLC‐PDA) analytical protocols. Samples of the yellow dye G. augusta L. in the following forms were analyzed: dyed on alum mordanted wool, dyed on nonmordanted and alum mordanted silk, pigment precipitated on hydrated aluminum oxide, extract mixed with a protein binder and painted on glass, and as a water‐based glaze applied on a mock‐up of a typical Chinese wall‐painting. Raman bands at 1537, 1209 and 1165 cm⁻¹ are identified as discriminating markers for the carotenoid colorant components crocetin and crocin. Copyright © 2009 John Wiley & Sons, Ltd.     

Phenol photodegradation on platinized-TiO2 photocatalysts related to charge-carrier dynamics

Three commercial TiO2 compounds (Degussa P25, Sachtleben UV100, and Millenium PC50) and their platinized forms have been studied by the time-resolved microwave conductivity (TRMC) method to follow their charge-carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge-carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidenced.