Simple cubic packing of gold nanoparticles through rational design of their dendrimeric corona

The first simple-cubic liquid crystal was obtained by coating monodisperse Au nanoparticles (NPs) with a thick corona of amino-substituted organic dendrons. This unusual structure was determined by grazing-incidence diffraction and electron density reconstruction and explained by analyzing the radial density profile of the corona. Another novel structure is proposed for the phase preceding the cubic one: a hexagonal superlattice composed of alternating dense and sparse strings of Au NPs.     

Self-organization of bent rod molecules into hexagonally ordered vesicular columns

Bent-shaped rigid-core molecules with flexible chiral dendrons grafted to the outer side of the bend were synthesized and characterized by circular dichroism, differential scanning calorimetry, X-ray scatterings, and transmission electron microscopy in solution and the solid state. The bent aromatic rods based on hepta- and nonaphenylene with nitrile groups at both ends self-assemble into well-ordered hollow tubular structures in aqueous solution, while the bent rod based on heptaphenylene without nitrile groups showed no apparent aggregations in aqueous solution. In the solid state, the rigid-flexible molecules based on heptaphenylene rod without the nitrile group self-assemble into a 2D oblique columnar structure with the columnar cross-section containing two interlocked molecules. Remarkably, the rigid flexible molecules based on hepta-, nona-, and undecaphenylene with nitrile groups self-assemble into a hexagonal columnar structure with weak 3D order. A model of vesicular channel structure is proposed based on small- and wide-angle X-ray diffraction on oriented fibers, density measurement, reconstruction and simulation of electron density maps, and molecular dynamics simulation. In contrast to the hollow tubular structure found in solution, in the solid both the outside and the interior of the columns are filled by the pendant aliphatic coils. Filling of the interior of these vesicular channels is made possible by some bent rod molecules turning their obtuse apex inward. One in 7, 2 in 8, and 4 in 10 molecules are thus inverted in a column slice in compounds with hepta-, nona-, and undecaphenylene cores, respectively. These are new examples of vesicular double-segregated columnar structures recently discovered in some dendrons.     

A new microcontroller-based RADFET dosimeter reader

A new reader for radiation dose measurements using RADFET (pMOSFET) dosemeters has been developed. The threshold voltage (V_T) of the pMOSFETs is measured using a “one-point” method that determines V_T as the gate voltage for a given drain current. Using V_T, the absorbed dose, which is directly proportional to the threshold voltage shift, is calculated. The reader is based on a low cost 8-bit PIC 18F4520 microcontroller (MCU), and works independently of a personal computer, uses a touch screen and stores the data in microcontroller memory. Good agreement in threshold voltage values, obtained using a high-quality source-measure unit and the reader, was obtained. In addition, the reader can be used for threshold voltage measurement with other types of MOSFETs, especially in long duration experiments, as well as for the real-time measurements in radiotherapy, either as an autonomous system or integrated in a larger monitoring configuration.     

Novel goniofufurone and 7-epi-goniofufurone mimics from an unexpected titanium-mediated displacement process

Treatment of 7-O-benzoyl-5-O-benzyl derivatives of (+)-goniofufurone or 7-epi-(+)-goniofufurone with titanium(IV) chloride or titanium(IV) bromide gave 7-chloro and 7-bromo-7-deoxy-goniofufurone mimics as the main reaction products along with minor amounts of the corresponding C-7 epimers. An unexpected cyclized product, benzoxepane 8 was isolated in some cases.     

IR spectroelectrochemical studies of Fe2V4O13, FeVO4 and InVO4 thin films obtained via sol-gel synthesis

In this paper we generalize the IR spectroscopic properties of M³⁺VO₄ (M=Fe, In) orthovanadate and Fe₂V₄O₁₃ films. The films were prepared using the sol-gel synthesis route from M³⁺ nitrates and vanadium oxoisopropoxide. The vibrational bands in the IR absorbance spectra of the films are classified in terms of terminal V-O stretching (1050–880 cm^–1), bridging V-O^...Fe and V^...O^...Fe stretching (880–550 cm^–1), mixed V-O-V deformations and Fe-O stretching (<550 cm^–1) modes. Ex situ IR spectra of films were measured after consecutive charging/discharging to various intercalation coefficients x and correlated to the current peaks in the cyclic voltammetry curves measured in 1 M LiClO₄/propylene carbonate electrolyte. We classified the ex situ IR spectra of charged/discharged films according to their vibrational band changes. The results reveal that, for small values of the intercalation coefficient, crystalline FeVO₄, InVO₄ and Fe₂V₄O₁₃ films exhibit a simultaneous decrease in the intensity of all IR bands while the band frequencies remain unaffected. For the higher intercalation levels, IR mode frequencies are shifted, signaling the presence of reduced vanadium. Further charging leads to an amorphization of the film structure, which was established from the similarity of the IR spectra of charged films with those of amorphous films prepared at lower annealing temperatures. The results confirm that ex situ IR spectroelectrochemical measurement is an effective way to assess the structural changes in films with different levels of intercalation. Electronic Publication     

Arbitrage conditions for electricity markets with production and storage

Computational Management Science - This work analyzes the notion of arbitrage for market models with electricity production from fuel. Several generators, fuel storage, and the related fuel and...     

Chirality Induction through Nano-Phase Separation: Alternating Network Gyroid Phase by Thermotropic Self-Assembly of X-Shaped Bolapolyphiles

The single gyroid phase as well as the alternating double network gyroid, composed of two alternating single gyroid networks, hold a significant place in ordered nanoscale morphologies for their potential applications as photonic crystals, metamaterials and templates for porous ceramics and metals. Here, we report the first alternating network cubic liquid crystals. They form through self-assembly of X-shaped polyphiles, where glycerol-capped terphenyl rods lie on the gyroid surface while semiperfluorinated and aliphatic side-chains fill their respective separate channel networks. This new self-assembly mode can be considered as a two-color symmetry-broken double gyroid morphology, providing a tailored way to fabricate novel chiral structures with sub-10 nm periodicities using achiral compounds.     

On primitive elements of algebraic function fields and models of $$X_0(N)$$ X 0 ( N )

The Ramanujan Journal - This paper is a continuation of our previous works where we study maps from $$X_0(N)$$ , $$N\ge 1$$ , into $${\mathbb {P}}^2$$ constructed via modular forms of the same...     

A novel bis-phenanthridine triamine with pH controlled binding to nucleotides and nucleic acids

The new bis-phenanthridine triamine is characterised by three pK(a) values: 3.65; 6.0 and >7.5. A significant difference in the protonation state of at pH = 5 (four positive charges) and at pH = 7 (less than two positive charges) accounts for the strong dependence of -nucleotide binding constants on nucleotide charge under acidic conditions, whereas at neutral pH all -nucleotide complexes are of comparable stability. All experimental data point at intercalation as the dominant binding mode of to polynucleotides. However, there is no indication of bis-intercalation of the two phenanthridine subunits in binding to double stranded polynucleotides, the respective complexes being most likely mono-intercalative. Thermal stabilisation of calf thymus DNA (ct-DNA) and poly A-poly U duplexes upon addition of is significantly higher at pH = 5 than at neutral conditions. This is not the case with poly dA-poly dT, indicating that the specific secondary structure of the latter, most likely the shape of the minor groove, plays a key role in complex stability. At pH = 5 acts as a fluorimetric probe for poly G (emission quenching) as opposed to other ss-polynucleotides (emission increase), while at neutral conditions this specificity is lost. One order of magnitude higher cytotoxicity of compared to its "monomer" can be accounted for by cooperative action of two phenanthridinium units and the charged triamine linker. The results presented here are of interest to the development of e.g. sequence-selective cytostatic drugs, and in particular for the possibility to control the drug activity properties over binding to DNA and/or RNA by variation of the pH of its surrounding.