Iterative regularization algorithms for constrained image deblurring on graphics processors

The ability of the modern graphics processors to operate on large matrices in parallel can be exploited for solving constrained image deblurring problems in a short time. In particular, in this paper we propose the parallel implementation of two iterative regularization methods: the well known expectation maximization algorithm and a recent scaled gradient projection method. The main differences between the considered approaches and their impact on the parallel implementations are discussed. The effectiveness of the parallel schemes and the speedups over standard CPU implementations are evaluated on test problems arising from astronomical images.     

Notes on a paper of Mess

These notes are a companion to the preceding paper by Geoffrey Mess, “Lorentz spacetimes of constant curvature”. Mess’ paper was written nearly 20 years ago and so we hope these notes will be useful as a guide to the literature that has appeared in the intervening years. Lars Andersson was supported in part by the NSF, contract no. DMS 0407732 and Thierry Barbot was supported by CNRS, ACI “Structures géométriques et Trous Noirs”.     

Principal parts bundles on projective spaces and quiver representations

We study the principal parts bundles \(\mathcal {P}^{k}\mathcal {O}_{\mathbb {P}^{n}}(d)\) as homogeneous bundles and we describe their associated quiver representations. With this technique we show that if n≥2 and 0≤d<k then there exists an invariant decomposition \(\mathcal {P}^{k}\mathcal {O}_{\mathbb {P}^{n}}(d)=Q_{k,d}\oplus(S^{d}V\otimes \mathcal {O}_{\mathbb {P}^{n}})\) with Q _k,d a stable homogeneous vector bundle. The decomposition properties of such bundles were previously known only for n=1 or k≤d or d<0. Moreover we show that the Taylor truncation maps \(H^{0}\mathcal {P}^{k}\mathcal {O}_{\mathbb {P}^{n}}(d)\to H^{0}\mathcal {P}^{h}\mathcal {O}_{\mathbb {P}^{n}}(d)\), defined for any h≤k and any d, have maximal rank.     

Inhibition of cell proliferation by a resveratrol analog in human pancreatic and breast cancer cells

Resveratrol has been reported to possess cancer preventive properties. In this study, we analyzed anti-tumor activity of a newly synthesized resveratrol analog, cis-3,4'',5-trimethoxy-3''-hydroxystilbene (hereafter called 11b) towards breast and pancreatic cancer cell lines. 11b treatments reduced the proliferation of human pancreatic and breast cancer cells, arrested cells in the G2/M phase, and increased the percentage of cells in the subG1/G0 fraction. The 11b treatments also increased the total levels of mitotic checkpoint proteins such as BubR1, Aurora B, Cyclin B, and phosphorylated histone H3. Mechanistically, 11b blocks microtubule polymerization in vitro and it disturbed microtubule networks in both pancreatic and breast cancer cell lines. Computational modeling of the 11b-tubulin interaction indicates that the dimethoxyphenyl group of 11b can bind to the colchicine binding site of tubulin. Our studies show that the 11b treatment effects occur at lower concentrations than similar effects associated with resveratrol treatments and that microtubules may be the primary target for the observed effects of 11b. These studies suggest that 11b should be further examined as a potentially potent clinical chemotherapeutic agent for treating pancreatic and breast cancer patients.     

The Formation of Large‐Area Conducting Graphene‐Like Platelets

The treatment of a suspension of graphite oxide (GO) with sodium azide leads to a material that, after reduction, features amino groups at the top and bottom of the sheets. These groups react through microcontact printing with an isothiocyanate monolayer on a silicon oxide substrate to form covalent bonds that strongly attach to the particles on the surface. With ultrasonication it is possible to obtain exfoliation of the sheets that are not covalently bound to the surface leaving single‐layer platelets attached to the substrate. The azido derivative can be also used to functionalize the graphene oxide with long alkylic chains through a click chemistry approach. This functionalization results in the exfoliation of this material in dimethylformamide. The novel materials were fully characterized by different techniques including IR spectroscopy, thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM and TEM), X‐Ray photoelectron spectroscopy (XPS), and solid state NMR spectroscopy. The material with amino groups, after the reduction step, is conductive with a resistivity only approximately seven times larger than that of unprocessed graphite. This implies that after reduction of the GO, the conjugated sp² network is largely restored. We consider this to be an important step towards a chemical approach for forming conducting large‐area platelet films of single‐layer graphene.     

A theoretical study of the solvent effect on Diels-Alder reaction in room temperature ionic liquids using a supermolecular approach

The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) in different room temperature ionic liquids containing imidazolium-based cations ([HBIM]⁺, [BMIM]⁺ and [BM₂IM]⁺) has been studied at the DFT level using a supermolecular approach. An analysis of the theoretical results shows that the ionic liquid cation coordination affects the equilibrium geometries and electronic structures of the reacting species throughout the reaction pathway leading to changes in reactivity and selectivity. They also indicate that the strong asynchronicity of the Diels-Alder reactions in ionic liquids is due to the polarisation effect of the cation.     

Magnetic–Fluorescent Colloidal Nanobeads: Preparation and Exploitation in Cell Separation Experiments

Nanostructures displaying fluorescence and magnetic properties at the same time are potentially useful for achieving simultaneous bio‐separation and bio‐sensing (e.g., magnetic separation coupled with multiplexing optical detection of different tumour cell populations). Spherical nanobeads that display both fluorescent and magnetic features are reported; they are fabricated by grafting fluorescent oligothiophene molecules to an amphiphilic polymer that is then used to enwrap iron oxide nanoparticles, which acts as the magnetic domain. By tuning experimental conditions, control over the number of magnetic nanoparticles per bead and over the bead diameter (30–400 nm) was achieved. A cell separation efficiency of the level required for cell sorting applications is also reported.

     

HPLC-CHIP coupled to a triple quadrupole mass spectrometer for carbonic anhydrase II quantification in human serum

A method for carbonic anhydrase II (CA II) absolute quantification in human serum is presented. This method is based on high-performance liquid chromatography (HPLC)-Chip microfluidic device incorporating a nanoelectrospray source interfaced to a triple quadrupole mass spectrometer. The fraction containing CA II was isolated by preparative reversed-phase HPLC, and peptides obtained from the tryptic digest of the protein mixture were separated by the HPLC-Chip system. The multiple-reaction monitoring acquisition mode of a selected suitable CA II peptide and peptide internal standard allowed the selective and sensitive determination of a CA II. Absolute recovery of the method was 52 ± 12%, while analytical recovery was 81 ± 10%. For the eight samples analyzed, the matrix effect was found to be only −14 ± 6%. A comparison among three regression lines type which were obtained by external calibration, matrix-matched calibration, and standard addition method, respectively, demonstrated that the first one is adequate in obtaining good accuracy and precision. Method quantification limit for CA II in serum was estimated to be 2 fmol/mL. CA II mean concentration in sera from eight healthy subjects was found to be 56 pmol/mL (relative standard deviation 24%).     

Numerical transformation methods: Blasius problem and its variants

Blasius problem is the simplest nonlinear boundary-layer problem. We hope that any approach developed for this epitome can be extended to more difficult hydrodynamics problems. With this motivation we review the so called Töpfer transformation, which allows us to find a non-iterative numerical solution of the Blasius problem by solving a related initial value problem and applying a scaling transformation. The applicability of a non-iterative transformation method to the Blasius problem is a consequence of its partial invariance with respect to a scaling group. Several problems in boundary-layer theory lack this kind of invariance and cannot be solved by non-iterative transformation methods. To overcome this drawback, we can modify the problem under study by introducing a numerical parameter, and require the invariance of the modified problem with respect to an extended scaling group involving this parameter. Then we apply initial value methods to the most recent developments involving variants and extensions of the Blasius problem.