Direct evidence for the hydroxide extraction mechanism in the phase transfer catalyzed cyclopropanation of 4-halobutyronitrile in a solid-liquid system

The Hoffman degradation reaction is proposed as an unequivocal proof for the validity of the extraction mechanism in Phase Transfer Catalysis (PTC) in the presence of solid NaOH. 4-Chlorobutyronitrile is found to yield cyclopropyl cyanide via an extraction route while 4-bromobutyronitrile reacts to form the same product by the prevalent interfacial mechanism.     

Scaling of the Distribution of Shortest Paths in Percolation

We present a scaling hypothesis for the distribution function of the shortest paths connecting any two points on a percolating cluster which accounts for (i) the effect of the finite size of the system and (ii) the dependence of this distribution on the site occupancy probability p. We test the hypothesis for the case of two-dimensional percolation.     

Synthesis and characterization of hydroxy‐bisphosphonate micrometer‐sized particles by dispersion polymerization of a new styrylbisphosphonate monomer

Bisphosphonates (BPs) are nonhydrolyzable pyrophosphate (P‐O‐P) analogs possessing two phosphonate groups linked to a single carbon (P‐C‐P). The hydroxy‐bisphosphonates (hydroxyBPs) are obtained when the hydroxy group is also linked to this bridging carbon. Their ability to form bidentate or tridentate chelates with calcium ions results in a high affinity to hydroxyapatite (HAP) in dentin, enamel and bones. In this study, we designed and prepared crosslinked poly(styrylbisphosphonate) (PStBP) micrometer‐sized particles by dispersion polymerization of the styrylbisphosphonate (StBP) and ethylene glycol dimethacrylate (EDMA) monomers. The new StBP monomer was synthesized in an efficient one‐pot synthesis using tris(trimethylsilyl)phosphite as the phosphorus source followed by methanolysis. The StBP monomer was successfully isolated and characterized as tri‐sodium salt. Polymerization of the StBP monomer was carried out in two steps: in situ conversion of the tri‐sodium StBP monomer back to its acid form, followed by radical dispersion polymerization in the presence of the crosslinker EDMA monomer. The resulting crosslinked PStBP micrometer‐sized particles retained the unique high affinity of the hydroxy‐bisphosphonate side groups to calcium ions and exhibited good adhesive properties to HAP. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Engineering of new crosslinked near‐infrared fluorescent polyethylene glycol bisphosphonate nanoparticles for bone targeting

Bisphosphonates (BPs) are nonhydrolysable pyrophosphate analogs with high affinity to hydroxyapatite (HAP, bone mineral) and are mainly used for treatment of various bone diseases. In this study, we designed and prepared crosslinked BP nanoparticles by dispersion copolymerization of three monomers: methacrylate PEG bisphosphonate, N‐(3‐aminopropyl) methacrylamide, and tetra(ethylene glycol) diacrylate. The size and size distribution of these PEG‐BP nanoparticles were controlled by changing various polymerization parameters. These BP particles possess dual functionality: covalent attachment of a dye (e.g., near IR fluorescent dye) or drug to the nanoparticles through the primary amine groups belonging to the aminopropyl methacrylamide monomeric units and chelation to the bone mineral HAP through the BP groups belonging to the methacrylate PEG bisphosphonate monomeric units, for enhanced long term bone‐targeted imaging and therapy applications. Body distribution of the optimal crosslinked BP nanoparticles was tested on a chicken embryo model via intravenous administration. This study indicated that the fluorescence intensity of the all organs (e.g., blood, spleen, liver, kidney, and heart) except the bones decreased significantly within 48 h (p < 0.05) while that of the bones hardly changed over that time (p > 0.05). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4282–4291     

Duality,crossing and MacLane’s coherence

It is shown that MacLane’ rectangle, pentagon and hexagon identities in category theory, when applied in particle physics to duality diagrams or to rational conformal field theories in two dimensions, yield the necessary physical algebraic constraints. Supported in part by DOE grant no. DE-FG05-85ER40200 Supported by US-Israel BSF grant 87-00009/1.     

Formation and structural heat-stability of β-lactoglobulin/surfactant complexes

The binding of two model surfactants, sodium dodecyl sulfate and dodecyltrimethylammonium bromide to β-lactoglobulin was studied at room temperature and the thermal stability of the resulting complexes was evaluated by differential scanning calorimetry (DSC) measurements. Binding isotherms indicated both ionic and hydrophobic interactions depending on both the charge of the protein and surfactant at different pHs and on the binding molar ratios of surfactant to the globular protein. Zeta potential measurements indicated charge neutralisation of the protein, under suitable conditions, which also lead to aggregation and precipitation of the proteins. Surface tension measurements indicated similarity between the two types of oppositely charged protein-surfactant complexes and a difference between them when protein and surfactants are similarly charged. DSC measurements revealed different behavior in protein conformation in the presence of the two surfactants. The results obtained at room temperature and upon heating are discussed in terms of the nature of the surfactant/protein interactions involved in the complex formation.     

Balancing the Failure Modes in the Electronic Circuit of a Cardiac Pacemaker: A Decision Analysis

Cardiac pacemaker malfunctions are of continuous concern to the medical profession as well as to the electronics industry. Certain failures in cardiac pacemaker performance are critical and can result in patient deaths. Cardiac pacemakers are vulnerable to certain malfunctions in the electrode, batteries and the electronic circuit. This paper focuses on failures and reliability of the electronic circuit and how they affect its choice and design. The paper discusses the issues of balancing the various failure modes by considering both failure rates and failure outcomes. As the choice of an appropriate pacemaker is a decision problem under conditions of uncertainty, we employ decision analysis as the analytical and conceptual framework. Use of utility theory enables a systematic quantitative evaluation of such seeming intangibles as the various failure outcomes. Probabilities are assessed using specific engineering and reliability literature. The method is demonstrated on a choice problem between two specific electronic circuit designs. The methodology can be useful in designing the electronic circuit to meet certain reliability specifications, deciding whether or not to introduce redundancy, decisions affecting components and technology, and establishing minimal reliability standards, with regard not only to cardiac pacemakers but to other electronics as well.     

Clay-vesicle interactions: fluorescence measurements and structural implications for slow release formulations of herbicides

Clay-vesicle systems exhibit a potential for environmental applications, such as herbicide formulations for reduced leaching. Clay-vesicle interactions were addressed by combining adsorption and XRD measurements with fluorescence studies for didodecyldimethylammonium bromide (DDAB), dioctadecyldimethylammonium bromide (DDOB), and montmorillonite. XRD and adsorption data indicated that the adsorbing vesicles were transformed after 3 days into paraffinic and bilayer structures. Fluorescence studies revealed that adsorption was almost complete within 5 min for a loading below the cation exchange capacity (CEC). Aggregation and sedimentation of clay-surfactant particles occurred within several minutes. Fluorescent measurements of supernatants indicated decomposition of vesicles at a high clay/surfactant ratio due to rapidly adsorbing cationic monomers. The kinetics of energy transfer between vesicles labeled by NBD-PE (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl)) and montmorillonite labeled by rhodamine-B follows that of aggregation of surfactant-clay particles and structural changes of the vesicles at times of minutes to hours. Experiments following the reduction of NBD fluorescence by addition of dithionite indicate faster permeabilization of DDOB than DDAB vesicles, which was confirmed by leakage experiments. The faster permeabilization of DDOB vesicles in the presence of clay was correlated with their inferior suitability for the preparation of clay-based formulations of anionic herbicides for slow release.     

Low‐density polyethylene films doped with europium(III) complex: their properties and applications

Light‐converting polyethylene film containing europium(III) complex with phenanthroline was manufactured under an extrusion process. The film was characterized first by means of time‐of‐flight secondary‐ion‐mass spectrometry (TOF‐SIMS), ultraviolet‐visible‐infrared (UV‐vis‐IR) spectroscopy, then a study of excitation and luminescence spectra, quantum yield and lifetime of luminescence. The quantum yield of luminescence was measured as 5±2%, and the lifetime of luminescence was determined about 470 μsec. TOF‐SIMS surface mapping showed the uniform distribution of europium(III) over the film. Visualization of strong picosecond UV laser beams through the use of the developed film has been demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.