Modulation of Relaxivity,Suspension Stability,and Biodistribution of Dendronized Iron Oxide Nanoparticles as a Function of the Organic Shell Design

Nanoparticles (NPs) with a mean diameter of 10 nm are functionalized with three dendrons: D1 a PEGylated PAMAM dendron of generation 0.5, D2 a hydrophilic oligoethyleneglycol‐derivatized dendron (D2) displaying a phosphonic acid at the focal point, and D2–2P the same dendron than D2 but with two phosphonic acid anchoring agents. Their grafting is confirmed by IR spectroscopy and elemental analysis. All dendronized NPs are stable over a long period of time in suspensions in water and in different physiological media and display a mean hydrodynamic diameter smaller than 50 nm whatever the molecule architecture. NMRD profiles and relaxivity measurements highlight the influence of the molecule architecture on the water diffusion close to the magnetic core thus influencing the relaxation properties at low magnetic field. The high hydrophilic architecture of the dendron D2 by contrast to dendron D1 allows maintaining the colloidal stability in different conditions while ensuring a very good accessibility of water molecule close to the magnetic core. Coupling of a fluorescent dye on dendrons have allowed investigating the biodistribution of dendronized NPs, which are found to be quickly eliminated through urinary and hepatobiliary pathways within 4 h. Furthermore, no enhanced permeation and retention effect in tumors can be observed.     

On coloring box graphs

We consider the chromatic number of a family of graphs we call box graphs, which arise from a box complex in n$n$-space. It is straightforward to show that any box graph in the plane has an admissible coloring with three colors, and that any box graph in n$n$-space has an admissible coloring with n+1$n+1$ colors. We show that for box graphs in n$n$-space, if the lengths of the boxes in the corresponding box complex take on no more than two values from the set {1,2,3}$\{1,2,3\}$, then the box graph is 3$3$-colorable, and for some graphs three colors are required. We also show that box graphs in 3-space which do not have cycles of length four (which we call “string complexes”) are 3$3$-colorable.     

Comparative analysis of automotive paints by laser induced breakdown spectroscopy and nonparametric permutation tests

Laser-induced breakdown spectroscopy (LIBS) has been investigated for the discrimination of automobile paint samples. Paint samples from automobiles of different makes, models, and years were collected and separated into sets based on the color, presence or absence of effect pigments and the number of paint layers. Twelve LIBS spectra were obtained for each paint sample, each an average of a five single shot “drill down” spectra from consecutive laser ablations in the same spot on the sample. Analyses by a nonparametric permutation test and a parametric Wald test were performed to determine the extent of discrimination within each set of paint samples. The discrimination power and Type I error were assessed for each data analysis method. Conversion of the spectral intensity to a log-scale (base 10) resulted in a higher overall discrimination power while observing the same significance level. Working on the log-scale, the nonparametric permutation tests gave an overall 89.83% discrimination power with a size of Type I error being 4.44% at the nominal significance level of 5%. White paint samples, as a group, were the most difficult to differentiate with the power being only 86.56% followed by 95.83% for black paint samples. Parametric analysis of the data set produced lower discrimination (85.17%) with 3.33% Type I errors, which is not recommended for both theoretical and practical considerations. The nonparametric testing method is applicable across many analytical comparisons, with the specific application described here being the pairwise comparison of automotive paint samples.     

Non‐parametric permutation test for the discrimination of float glass samples based on LIBS spectra

Laser‐induced breakdown spectroscopy (LIBS) coupled with non‐parametric permutation based hypothesis testing is demonstrated to have good performance in discriminating float glass samples. This type of pairwise sample comparison is important in manufacturing process quality control, forensic science and other applications where determination of a match probability between two samples is required. Analysis of the pairwise comparisons between multiple LIBS spectra from a single glass sample shows that some assumptions required by parametric methods may not hold in practice, motivating the adoption of a non‐parametric permutation test. Without rigid distributional assumptions, the permutation test exhibits excellent discriminating power while holding the actual size of Type I error at the nominal level. Copyright © 2010 John Wiley & Sons, Ltd.     

Diastereoselective access to trans-2-substituted cyclopentylamines

A highly diastereoselective synthesis of trans-2-substituted cyclopentylamines via a tandem hydrozirconation/Lewis acid-mediated cyclization sequence applied to butenyl oxazolidines is described. The method allows an easy preparation of diversely substituted cyclopentylamines which appear to be useful synthetic intermediates. This was further illustrated by the syntheses of (±)-Rodocaine, (±)-trans-pentacin, and enantiomerically enriched trans-cyclopentane-1,2-diamine.     

Groundstatable fermionic wavefunctions and their associated many-body Hamiltonians

In the vast majority of many-body problems, it is the kinetic energy part of the Hamiltonian that is best known microscopically, and it is the detailed form of the interactions between the particles, the potential energy term, that is harder to determine from first principles. An example is the case of high temperature superconductors: while a tight-binding model captures the kinetic term, it is not clear that there is superconductivity with only an onsite repulsion and, thus, that the problem is accurately described by the Hubbard model alone. Here we pose the question of whether, once the kinetic energy is fixed, a candidate ground state is groundstatable or not. The easiness to answer this question is strongly related to the presence or the absence of a sign problem in the system. When groundstatability is satisfied, it is simple to obtain the potential energy that will lead to such a ground state. As a concrete case study, we apply these ideas to different fermionic wavefunctions with superconductive or spin-density wave correlations and we also study the influence of Jastrow factors. The kinetic energy considered is a simple nearest neighbor hopping term.     

How to select a small set of diverse solutions to mixed integer programming problems

Given an oracle that generates a large number of solutions to mixed integer programs, we present exact and heuristic approaches to select a small subset of solutions that maximizes solution diversity. We obtain good results on binary variables, but report scaling problems when considering general integer and continuous variables.     

Room temperature Au(I)-catalyzed exo-selective cycloisomerization of acetylenic acids: an entry to functionalized gamma-lactones

A highly efficient gold-catalyzed cyclization reaction of various functionalized acetylenic acids is described. The cyclizations are conducted in the presence of Au(I) catalyst in acetonitrile at room temperature in a short reaction time. The reaction conditions are compatible with several functional groups, such as ester, alkene, alkyne, chloro, and free or protected alcohol, and lead to original gamma-lactones in good to excellent yields.