Synthesis of (E)- and (Z)-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors

(E)- and (Z)-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors were synthesized. A Wadsworth-Horner-Emmons reaction, followed by amide formation and reduction of the amide were used for the construction of the α-fluoro-α,β-unsaturated amine functionality.     

The non-linear dielectric effect in liquid xenon

The non-linear dielectric effect (NLDE), that is the increase in the dielectric constant divided by the square of the applied field, is measured for a number of non-polar molecular liquids and for liquid xenon. The values of the NLDE are compared with results in the literature and with values predicted by theory. The agreement with other experiments is quite good, but with theory is very poor, the only exception being Liquid xenon, where agreement is good. A possible explanation is given. The prediction that the NLDE should increase strongly near the critical point due to the divergence of the isothermal compressibility could not be established by experiment. The conclusion is drawn that this failure is due to the reduction by the theory of second-order effects to first-order thermodynamic and molecular properties.     

Upper bounds on the independence and the clique covering number

New upper bounds for the independence number and for the clique covering number of a graph are given in terms of the rank, respectively the eigenvalues, of the adjacency matrix. We formulate a conjecture concerning an upper bound of the clique covering number. This upper bound is related to an old conjecture of Alan J. Hoffman which is shown to be false. Key words: adjacency matrix, eigenvalues, independence number, clique covering number. AMS classification: 05C.     

Reply to comment on “A local realist model for correlations of the singlet state" by M.P. Seevinck and J.-Å. Larsson

The general conclusion of Seevinck and Larsson is that our model exploits the so-called coincidence-time loophole and produces sinusoidal (quantum-like) correlations but does not model the singlet state because it does not violate the relevant Bell inequality derived by Larsson and Gill, since in order to obtain the sinusoidal correlations the probability of coincidences in our model goes to zero. In this reply, we refute their arguments that lead to this conclusion and demonstrate that our model can reproduce results of photon and ion-trap experiments with frequencies of coincidences that are not in conflict with the observations.     

Looped structure of flowerlike micelles revealed by 1H NMR relaxometry and light scattering

We present experimental proof that so-called "flowerlike micelles" exist and that they have some distinctly different properties compared to their "starlike" counterparts. Amphiphilic AB diblock and BAB triblock copolymers consisting of poly(ethylene glycol) (PEG) as hydrophilic A block and thermosensitive poly(N-isopropylacrylamide) (pNIPAm) B block(s) were synthesized via atom transfer radical polymerization (ATRP). In aqueous solutions, both block copolymer types form micelles above the cloud point of pNIPAm. Static and dynamic light scattering measurements in combination with NMR relaxation experiments proved the existence of flowerlike micelles based on pNIPAm(16kDa)-PEG(4kDa)-pNIPAm(16kDa) which had a smaller radius and lower mass and aggregation number than starlike micelles based on mPEG(2kDa)-pNIPAm(16kDa). Furthermore, the PEG surface density was much lower for the flowerlike micelles, which we attribute to the looped configuration of the hydrophilic PEG block. (1)H NMR relaxation measurements showed biphasic T(2) relaxation for PEG, indicating rigid PEG segments close to the micelle core and more flexible distal segments. Even the flexible distal segments were shown to have a lower mobility in the flowerlike micelles compared to the starlike micelles, indicating strain due to loop formation. Taken together, it is demonstrated that self-assemblies of BAB triblock copolymers have their hydrophilic block in a looped conformation and thus indeed adopt a flowerlike conformation.     

Porphyrin‐based,light‐activated antimicrobial materials

New light‐activated antimicrobial materials with a potentially wide range of possible uses in civilian settings were synthesized by the grafting of protoporphyrin IX and zinc protoporphyrin IX to nylon fibers. These fibers were shown to be active against Staphylococcus aureus at light exposures of 10,000 lux and greater and against Escherichia coli at 60,000 lux. They were ineffective against both strains in the absence of light. At 40,000 lux, these fibers showed increased antimicrobial activity against S. aureus with increasing exposure time. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2297–2303, 2003     

Ferroelectric liquid crystal gels Network stabilized ferroelectric display

Liquid crystal (LC) mixtures of a reactive diacrylate and a commercial ferroelectric liquid crystal (FLC) mixture were produced. The mixtures were brought into cells provided with orientation layers in which various orientations such as uniaxial and twisted orientations, could be induced. When the desired orientation had been obtained, the polymerization of the reactive molecules was induced creating a three-dimensional anisotropic network containing the FLC molecules which were not chemically attached to the network (ferroelectric gels). The presence of the anisotropic network was found to have a large effect on various properties of the FLC molecules. For example, complex orientations (for example, 180° twisted) obtained by polymerization (formation of the gel) in the nematic phase remained unchanged when the gel was cooled to the FLC phase. Likewise uniaxial orientation, which cannot be realised in thick cells containing the pure FLC, could be realised when ferroelectric gels were used. For this reason the ferroelectric gels will be referred to as an anisotropic network-stabilized FLC. Optical properties such as effective birefringence and tilt angle were also influenced by the network. When use was made of a network with a lower birefringence than the FLC, a reduced effective birefringence in gels was observed. This is important for technologies involving thicker cells. The switching covered a range of voltages in the case of the gels, instead of showing a well-defined threshold voltage as in the bulk. The possibility of using this effect to obtain grey scales in cells during passive addressing has also been demonstrated.     

Quantum theory as a description of robust experiments: Derivation of the Pauli equation

It is shown that the Pauli equation and the concept of spin naturally emerge from logical inference applied to experiments on a charged particle under the conditions that (i) space is homogeneous (ii) the observed events are logically independent, and (iii) the observed frequency distributions are robust with respect to small changes in the conditions under which the experiment is carried out. The derivation does not take recourse to concepts of quantum theory and is based on the same principles which have already been shown to lead to e.g. the Schrödinger equation and the probability distributions of pairs of particles in the singlet or triplet state. Application to Stern–Gerlach experiments with chargeless, magnetic particles, provides additional support for the thesis that quantum theory follows from logical inference applied to a well-defined class of experiments.     

Lipid length and iso-branching of trehalose diesters influences Mincle agonist activity

We report on the efficient synthesis of linear trehalose diesters (TDEs) and iso-branched TDEs (maradolipids or iso-TDEs) and their ability to activate bone marrow-derived macrophages (BMDMs) as determined by cytokine (IL-1β, IL-12, IL-6, IL-10) and chemokine (MIP-2) production. Both classes of TDEs were found to activate BMDMs in a Mincle-dependent manner, with longer-chain (≥C18) lipids leading to a robust inflammatory response. On the whole, the iso-branched TDEs led to greater cytokine production and a faster immune response when compared to their linear counterparts. Moreover, C12-TDE and iso-C12-TDE elicited the production of MIP-2 by BMDMs, thereby providing the first example of TDEs with a chain length of ≤ C12 leading to a Mincle-dependent immune response and one that is less inflammatory in nature.     

Design of a superhydrophobic surface using woven structures

The relationship between surface tension and roughness is reviewed. The Cassie-Baxter model is restated in its original form, which better describes the most general cases of surface roughness. Using mechanical and chemical surface modification of nylon 6,6 woven fabric, an artificial superhydrophobic surface was prepared. A plain woven fabric mimicking the Lotus leaf was created by further grafting 1H,1H-perfluorooctylamine or octadecylamine to poly(acrylic acid) chains which had previously been grafted onto a nylon 6,6 woven fabric surface. Water contact angles as high as 168 degrees were achieved. Good agreement between the predictions based on the original Cassie-Baxter model and experiments was obtained. The version of the Cassie-Baxter model in current use could not be applied to this problem since the surface area fractions in this form is valid only when the liquid is in contact with a flat, porous surface. The angle at which a water droplet rolls off the surface has also been used to define a superhydrophobic surface. It is shown that the roll-off angle is highly dependent on droplet size. The roll-off angles of these superhydrophobic surfaces were less than 5 degrees when a 0.5 mL water droplet was applied.