Functional Limit Theorems for the Pólya Urn

Journal of Theoretical Probability - For the plain Pólya urn with two colors, black and white, we prove a functional central limit theorem for the number of white balls, assuming that the...     

A Closed Chemobrionic System as a Biochemical Delivery Platform

Inorganic cells bearing calcium silicate membranes were prepared and resembled closed chemical gardens. It was demonstrated that these inorganic cells can successfully be loaded with natural products, proteins and plasmid DNA, and their cargo can be released in a controlled manner. These cells demonstrated the ability of chemical gardens to act as platforms for the sustained delivery of biomolecules and are expected to introduce chemical gardens in the field of biosciences.     

Sliced AETG: a memory-efficient variant of the AETG covering array generation algorithm

Optimization Letters - The generation of covering arrays, which can be regarded as a generalization of orthogonal arrays, is an active research field. In this paper, we propose a memory efficient...     

Polymer packaging waste recycling: study of the pyrolysis of two blends via TGA

Journal of Thermal Analysis and Calorimetry - The aim of this work is the evaluation of thermal degradation temperatures of two polymeric blends constituted by polyethylene PE, polypropylene PP,...     

Investigation of the cytotoxicity of bioinspired coumarin analogues towards human breast cancer cells

Molecular Diversity - Coumarins possess a wide array of therapeutic capabilities, but often with unclear mechanism of action. We tested a small library of 18 coumarin derivatives against human...     

Effect of maleic anhydride content on the rheology and phase behavior of poly(styrene-co -maleic anhydride)/ poly(methyl methacrylate) blends

 We investigated the thermo- rheological behavior of high glass transition, high molecular weight and small dynamic asymmetry blends of poly(styrene-co-maleic anhydride) (SMA) and poly (methyl methacrylate) (PMMA) with varying amounts of maleic anhydride (MA) content, namely 8 wt%, 14 wt% and 32 wt%, in the SMA component. The phase separation (binodal) temperature of each blend was determined rheologically using a combination of dynamic frequency and temperature sweeps in parallel plate geometry; it was marked by a change in slope of the elastic modulus and the occurrence of a peak in tan δ in temperature sweeps. Failure of the time-temperature superposition principle and observation of two peaks in the Cole-Cole plots corroborated these findings. The blends displayed lower critical solution temperature (LCST) behavior with the critical temperatures exhibiting a non-monotonic dependence on the MA content. From rheological and thermal measurements it was concluded that SMA/PMMA blends containing 14% MA were more miscible than those containing 8% or 32% MA, a finding attributed to the compositional dependence of the interplay between SMA-SMA and SMA-PMMA interactions in the different samples. MA also influenced the dynamic asymmetry and pretransitional concentration fluctuations. The phase diagrams corresponding to each blend were modeled using a two-parameter temperature dependent interaction parameter, based on the concept of generalized Gibbs free energy of mixing. The fitted values of interaction parameter were in good agreement with values calculated explicitly using the Flory-Huggins theory. Received: 16 February 2001 Accepted: 11 July 2001     

A Mathematical Radiobiological Model (MRM) to Predict Complex DNA Damage and Cell Survival for Ionizing Particle Radiations of Varying Quality

Predicting radiobiological effects is important in different areas of basic or clinical applications using ionizing radiation (IR); for example, towards optimizing radiation protection or radiation therapy protocols. In this case, we utilized as a basis the ‘MultiScale Approach (MSA)’ model and developed an integrated mathematical radiobiological model (MRM) with several modifications and improvements. Based on this new adaptation of the MSA model, we have predicted cell-specific levels of initial complex DNA damage and cell survival for irradiation with ¹¹Β, ¹²C, ¹⁴Ν, ¹⁶Ο, ²⁰Νe, ⁴⁰Αr, ²⁸Si and ⁵⁶Fe ions by using only three input parameters (particle’s LET and two cell-specific parameters: the cross sectional area of each cell nucleus and its genome size). The model-predicted survival curves are in good agreement with the experimental ones. The particle Relative Biological Effectiveness (RBE) and Oxygen Enhancement Ratio (OER) are also calculated in a very satisfactory way. The proposed integrated MRM model (within current limitations) can be a useful tool for the assessment of radiation biological damage for ions used in hadron-beam radiation therapy or radiation protection purposes.     

A novel coordination mode of the 1-hydroxybenzotriazolate (btaO−) ligand: preparation,X-ray crystal structure and spectroscopic characterizationof the trinuclear complex [Ni3(btaO)6(NH3)6]

Reaction of Ni(NO₃)₂ · 6H₂O with 1-hydroxybenzotriazole (btaOH) in DMF/aqueous NH₃ and layering of the resulting solution with MeCN yields the complex [Ni₃(btaO)₆(NH₃)₆] · 0.47DMF · 0.75MeCN · 1.58H₂O, (ca. 80% yield), the structure of which has been determined by single-crystal X-ray crystallography. The asymmetric unit contains two, structurally similar, trinuclear molecules. The six-coordinate Ni^II atom is linked to each terminal Ni^II atom by three btaO^– ions; three NH₃ molecules complete the octahedral coordination at each terminal metal ion. The btaO^– ions behave as bidentate bridging ligands, binding through N(3) to the central Ni^II atom and through N(2) to the terminal Ni^II atoms, with the deprotonated oxygen atom remaining uncoordinated and participating in hydrogen bonding with the ammine ligand. The complex was also characterized by room-temperature effective magnetic moment and spectroscopic (i.r., ligand field) studies. The data are discussed in terms of the nature of bonding and other known structures.     

A New Iterative Approach for the Synthesis of Oligo(phenyleneethynediyl) Derivatives and Its Application for the Preparation of Fullerene?Oligo(phenyleneethynediyl) Conjugates as Active Photovoltaic Materials

Disymmetrically substituted oligo(phenyleneethynediyl) (OPE) derivatives were prepared from 2,5‐bis(octyloxy)‐4‐[(triisopropylsilyl)ethynyl]benzaldehyde ( 5 ) by an iterative approach using the following reaction sequence: i) Corey–Fuchs dibromoolefination, ii) treatment with an excess of lithium diisopropylamide, and iii) a metal‐catalyzed cross‐coupling reaction of the resulting terminal alkyne with 2,5‐diiodo‐1,4‐bis(octyloxy)benzene ( 3 ) (Schemes 2 and 3). Reaction of the OPE dimer 8 and trimer 13 thus obtained with N‐methylglycine and C₆₀ in refluxing toluene gave the corresponding C₆₀? OPE conjugates 16 and 17 , respectively (Scheme 4). On the other hand, treatment of the protected terminal alkynes 8 and 13 with Bu₄N followed by reaction of the resulting 9 and 14 with 4‐iodo‐N,N‐dibutylaniline under Sonogashira conditions yielded 10 and 15 , respectively (Schemes 2 and 3). Subsequent treatment with N‐methylglycine and C₆₀ in refluxing toluene furnished the C₆₀? OPE derivatives 18 and 19 (Scheme 4). Compound 9 was also subjected to a Pd‐catalyzed cross‐coupling reaction with 3 to give the centrosymmetrical OPE pentamer 20 (Scheme 5). Subsequent reduction followed by reaction of the resulting diol 21 with acid 22 under esterification conditions led to bis‐malonate 23 . Oxidative coupling of terminal alkyne 14 with the Hay catalyst gave bis‐aldehyde 24 (Scheme 6). Treatment with diisobutylaluminium hydride followed by dicylcohexylcarbodiimide‐mediated esterification with acid 22 gave bis‐malonate 26 . Finally, treatment of bis‐malonates 23 and 26 with C₆₀, I₂, and 1,8‐diazabicylco[5.4.0]undec‐7‐ene (DBU) in toluene afforded the bis[cyclopropafullerenes] 27 and 28 , respectively (Scheme 7). The C₆₀ derivatives 16 – 19, 27 , and 28 were tested as active materials in photovoltaic devices. Each C₆₀? OPE conjugate was sandwiched between poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)‐covered indium tin oxide and aluminium electrodes. Interestingly, the performances of the devices prepared from the N,N‐dialkylaniline‐terminated derivatives 18 and 19 are significantly improved when compared to those obtained with 16, 17, 27 , and 28 , thus showing that the efficiency of the devices can be significantly improved by increasing the donor ability of the OPE moiety.