Solid-state low-temperature extrusion of P3HT ribbons

Ribbons of poly(3-hexylthiophene) (P3HT) 0.15 and 0.30 mm thickness were extruded at the temperatures of 200 and 250 °C, i.e., below and above the melting temperature of P3HT (～240 °C), using a small home-made extrusion device. The ribbons produced by this method are continuous and freestanding. WAXS results show that all the extruded samples are more crystalline than the original powder, and the different processing conditions cause different variations in the crystal unit cell dimensions of P3HT. In terms of the degree of orientation, the ribbons extruded in the solid state (T < T _m ) show significant degrees of anisotropy in opposition to the sample extruded in the molten state (T > T _m ), which is fully isotropic.     

Reactive Oxygen Species‐Responsive Protein Modification and Its Intracellular Delivery for Targeted Cancer Therapy

Herein we report a convenient chemical approach to reversibly modulate protein (RNase A) function and develop a protein that is responsive to reactive oxygen species (ROS) for targeted cancer therapy. The conjugation of RNase A with 4‐nitrophenyl 4‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl) benzyl carbonate (NBC) blocks protein lysine and temporarily deactivates the protein. However, the treatment of RNase A–NBC with hydrogen peroxide (one major intracellular ROS) efficiently cleaves the NBC conjugation and restores the RNase A activity. Thus, RNase A–NBC can be reactivated inside tumor cells by high levels of intracellular ROS, thereby restoring the cytotoxicity of RNase A for cancer therapy. Due to higher ROS levels inside tumor cells compared to healthy cells, and the resulting different levels of RNase A–NBC reactivation, RNase A–NBC shows a significant specific cytotoxicity against tumor cells.     

Chemical composition of ground pearl (Eurhizococcus colombianus) cysts

Ground pearl (Eurhizococcus colombianus) is a crop pest in Colombia, with special impact on fig, grass, rubus and tomato plants. The insect is resistant to external insecticide application because it produces a thick waxy shell that isolates it from the environment. The composition of this shell was determined by NMR and MS as a triglyceride, whose fatty acid is transformed into other products with the metamorphosis of the insect. Additionally, several enzymatic inhibitors were assayed to control the insect with negative results.     

Chemical equilibria in the uranyl(vi)-peroxide-carbonate system; identification of precursors for the formation of poly-peroxometallates

The focus of this study is on the identification of precursors in solution that might act as building blocks when solid uranyl(vi) poly-peroxometallate clusters containing peroxide and hydroxide bridges are formed. The precursors could be identified by using carbonate as an auxiliary ligand that prevented the formation of large clusters, such as the ones found in solids of fullerene type. Using data from potentiometric and NMR ((17)O and (13)C) experiments we identified the following complexes and determined their equilibrium constants: (UO(2))(2)(O(2))(CO(3))(4)(6-), UO(2)(O(2))CO(3)(2-), UO(2)(O(2))(CO(3))(2)(4-), (UO(2))(2)(O(2))(CO(3))(2)(2-), (UO(2))(2)(O(2))(2)(CO(3))(2-) and [UO(2)(O(2))(CO(3))](5)(10-). The NMR spectra of the pentamer show that all uranyl and carbonate sites are equivalent, which is only consistent with a ring structure built from uranyl units linked by peroxide bridges with the carbonate coordinated "outside" the ring; this proposed structure is very similar to [UO(2)(O(2))(oxalate)](5)(10-) identified by Burns et al. (J. Am. Chem. Soc., 2009, 131, 16648; Inorg. Chem., 2012, 51, 2403) in K(10)[UO(2)(O(2))(oxalate)](5)·(H(2)O)(13); similar ring structures where oxalate or carbonate has been replaced by hydroxide are important structure elements in solid poly-peroxometallate complexes. The equivalent uranyl sites in (UO(2))(2)(O(2))(2)(CO(3))(2-) suggest that the uranyl-units are linked by the carbonate ion and not by peroxide.     

Use of 1H and 31P HRMAS to evaluate the relationship between quantitative alterations in metabolite concentrations and tissue features in human brain tumour biopsies

Quantitative multinuclear high-resolution magic angle spinning was performed in order to determine the tissue pH values of and the absolute metabolite concentrations in 33 samples of human brain tumour tissue. Metabolite concentrations were quantified by 1D (1)H and (31)P HRMAS using the electronic reference to in vivo concentrations (ERETIC) synthetic signal. (1)H-(1)H homonuclear and (1)H-(31)P heteronuclear correlation experiments enabled the direct assessment of the (1)H-(31)P spin systems for signals that suffered from overlapping in the 1D (1)H spectra, and linked the information present in the 1D (1)H and (31)P spectra. Afterwards, the main histological features were determined, and high heterogeneity in the tumour content, necrotic content and nonaffected tissue content was observed. The metabolite profiles obtained by HRMAS showed characteristics typical of tumour tissues: rather low levels of energetic molecules and increased concentrations of protective metabolites. Nevertheless, these characteristics were more strongly correlated with the total amount of living tissue than with the tumour cell contents of the samples alone, which could indicate that the sampling conditions make a significant contribution aside from the effect of tumour development in vivo. The use of methylene diphosphonic acid as a chemical shift and concentration reference for the (31)P HRMAS spectra of tissues presented important drawbacks due to its interaction with the tissue. Moreover, the pH data obtained from (31)P HRMAS enabled us to establish a correlation between the pH and the distance between the N(CH(3))(3) signals of phosphocholine and choline in (1)H spectra of the tissue in these tumour samples.     

A short note on the monotonicity of the Erlang C formula in the Halfin–Whitt regime

We prove a monotonicity condition satisfied by the Erlang C formula when computed in the Halfin?CWhitt regime. This property was recently conjectured in (Janssen et al., Queueing Syst. Theory Appl. 68:361?C363, 2011).     

Hybridized globally divergence-free LDG methods. Part I: The Stokes problem

We devise and analyze a new local discontinuous Galerkin (LDG) method for the Stokes equations of incompressible fluid flow. This optimally convergent method is obtained by using an LDG method to discretize a vorticity-velocity formulation of the Stokes equations and by applying a new hybridization to the resulting discretization. One of the main features of the hybridized method is that it provides a globally divergence-free approximate velocity without having to construct globally divergence-free finite-dimensional spaces; only elementwise divergence-free basis functions are used. Another important feature is that it has significantly less degrees of freedom than all other LDG methods in the current literature; in particular, the approximation to the pressure is only defined on the faces of the elements. On the other hand, we show that, as expected, the condition number of the Schur-complement matrix for this approximate pressure is of order in the mesh size . Finally, we present numerical experiments that confirm the sharpness of our theoretical a priori error estimates.

     

Complexation behaviour and stability of Schiff bases in aqueous solution. The case of an acyclic diimino(amino) diphenol and its reduced triamine derivative

The copper(II), nickel(II), and zinc(II) complexes of the acyclic Schiff base H(2)L(A), obtained by [1 + 2] condensation of 1,2-ethanediamine,N-(2-aminoethyl)-N-methyl with 3-ethoxy-2-hydroxybenzaldehyde, and of H(2)L(B), the reduced derivative of H(2)L(A), were prepared and their properties studied by IR, NMR and SEM-EDS. In these complexes, the metal ion is always located in the coordination chamber of the ligand delimited by two phenol oxygens and nitrogen atoms (either aminic or iminic). The coordination behaviour of H(2)L(A) and H(2)L(B) towards H(+), Cu(2+), Ni(2+) and Zn(2+) in aqueous solution at 298 K and mu = 0.1 mol dm(-3) (Na)ClO(4) was also studied by potentiometric, NMR and UV-VIS measurements. In particular, potentiometric equilibrium studies indicate that H(2)L(A) is not stable enough to have a pH range in which it is the sole species in aqueous solution. In such a solution, the Schiff base forms over a limited pH range, between 6 and 10, with a maximum formation percentage at pH approximately 9. In addition, the involvement of imine nitrogens in the complexes markedly stabilises the azomethylene linkage, so that the metal complexes of H(2)L(A), particularly those of copper(II), are the species largely prevailing in solutions with pH >3.5. The stability constants of the complexes formed by metal ions with H(2)L(A) and H(2)L(B) follow the order Cu(2+) > Ni(2+) > Zn(2+); distribution plots show that copper(II) gives complexes more stable with H(2)L(A), whereas Ni(2+) and Zn(2+) prefer the reduced ligand, H(2)L(B).     

CsF-promoted acetyl dance at the narrow rim of p-tert-butyl[3.1.3.1]homooxacalixarene

In the acetylation of an oxygenated calix[4]arene homologue in the presence of CsF as a base, relaxation of the reaction system to the equilibrium composition takes place through several intra- and intermolecular steps that can be easily controlled to obtain the various acetyl derivatives. The effect of different bases is also discussed.