Solar Thermal Energy Storage in a Photochromic Macrocycle

The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA–DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF–VHF). A stepwise energy release over two sequential ring‐closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long‐term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release.     

Unique description of chemical structures based on hierarchically ordered extended connectivities (HOC procedures). V. New topological indices,ordering of graphs,and recognition of graph similarity

The vertex numbering obtained by application of the HOC algorithm can be converted into two sequences of numbers: If each vertex starting with vertex 1 is only counted once, the sums of numberings of adjacent vertices form sequence S_i (i = 1?N), while the sums of S_i values form sequence M_i (i = 1?N). These two sequences can be used for (i) two new topological indices, ?? and ??, the latter being of extremely low degeneracy, and the former correlating with boiling points of alkanes; (ii) a criterion based on sequence S_i for ordering graphs which possess the same number N of vertices; and (iii) a quantitative measure, also based on sequence S_i, for appreciating the similarity or dissimilarity of pairs of graphs. Comparisons with other topological indices, ordering criteria, and similarity measures for graphs show that the newly devised procedures compare favorably with those known previously.     

Darstellung,Isolierung und Charakterisierung Gemischter Cyanothiocyanatoäthylendiamin-Chrom(III)-Komplexe

Preparation, Isolation and Characterisation of Mixed Cyanothiocyanato-ethylenediamine-Chromium(III) Complexes The complex salts K[Cr(CN)(NCS)₃(en)] and [Cr(CN)(NCS)(en)₂]SCN are prepared for the first time. After the preparative isolation by column chromatography on alumima, they are characterized by the chromium content and the spectra.     

Bioglass thin films for biomimetic implants

Pulsed laser deposition (PLD) method was used to obtain bioglass (BG) thin film coatings on titanium substrates. An UV excimer laser KrF* (λ = 248 nm, τ = 25 ns) was used for the multi-pulse irradiation of the BG targets with 57 or 61 wt.% SiO₂ content (and Na₂O-K₂O-CaO-MgO-P₂O₅ oxides). The depositions were performed in oxygen atmosphere at 13 Pa and for substrates temperature of 400 °C. The PLD films displayed typical BG of 2-5 μm particulates nucleated on the film surface or embedded in. The PLD films stoichiometry was found to be the same as the targets. XRD spectra have shown, the glass coatings obtained, had an amorphous structure. One set of samples, deposited in the same conditions, were dipped in simulated body fluids (SBFs) and subsequently extracted one by one after several time intervals 1, 3, 7, 14 and 21 days. After washing in deionized water and drying, the surface morphology of the samples and theirs composition were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), IR spectroscopy (FTIR) and energy dispersive X-ray analysis (EDX). After 3-7 days the Si content substantially decreases in the coatings and PO₄³⁻ maxima start to increase in FTIR spectra. The XRD spectra also confirm this evolution. After 14-21 days the XRD peaks show a crystallized fraction of the carbonated hydroxyapatite (HAP). The SEM micrographs show also significant changes of the films surface morphology. The coalescence of the BG droplets can be seen. The dissolution and growth processes could be assigned to the ionic exchange between BG and SBFs.     

Enhanced quantum well infrared photodetector focal plane arrays for space applications

A 30 months European Space Agency project started in March 2008, whose overall purpose is to expand and assess the performance of broadband (11–15 μm) quantum detectors for spectro-imaging applications: Dispersive Spectrometers and Fourier Transform Spectrometers. We present here the technical requirements, the development approach chosen as well as preliminary experimental results. Our approach is fully compatible with the final array format (1024 × 256, pitch 50–60 μm). We expect the requested uniformity, operability and SNR levels to be achieved at temperatures close to the goal values. The performance level will be demonstrated on 256 × 256, 50 μm pitch arrays. Also, operability and uniformity issues will be addressed on large mechanical 1024 × 256 hybrid arrays.     

Matrix-assisted refolding of autoprotease fusion proteins on an ion exchange column

Refolding of proteins must be performed under very dilute conditions to overcome the competing aggregation reaction, which has a high reaction order. Refolding on a chromatography column partially prevents formation of the intermediate form prone to aggregation. A chromatographic refolding procedure was developed using an autoprotease fusion protein with the mutant EDDIE from the N^pro autoprotease of pestivirus. Upon refolding, self-cleavage generates a target peptide with an authentic N-terminus. The refolding process was developed using the basic 1.8-kDa peptide sSNEVi-C fused to the autoprotease EDDIE or the acidic peptide pep6His, applying cation and anion exchange chromatography, respectively. Dissolved inclusion bodies were loaded on cation exchange chromatographic resins (Capto S, POROS HS, Fractogel EMD SO₃⁻, UNOsphere S, SP Sepharose FF, CM Sepharose FF, S Ceramic HyperD F, Toyopearl SP-650, and Toyopearl MegaCap II SP-550EC). A conditioning step was introduced in order to reduce the urea concentration prior to the refolding step. Refolding was initiated by applying an elution buffer containing a high concentration of Tris–HCl plus common refolding additives. The actual refolding process occurred concurrently with the elution step and was completed in the collected fraction. With Capto S, POROS HS, and Fractogel SO₃⁻, refolding could be performed at column loadings of 50 mg fusion protein/ml gel, resulting in a final eluate concentration of around 10–15 mg/ml, with refolding and cleavage step yields of around 75%. The overall yield of recovered peptide reached 50%. Similar yields were obtained using the anion exchange system and the pep6His fusion peptide. This chromatographic refolding process allows processing of fusion peptides at a concentration range 10- to 100-fold higher than that observed for common refolding systems.     

Semilinear Schrödinger flows on hyperbolic spaces: scattering in <Emphasis Type="Italic">H</Emphasis><Superscript>1</Superscript>

We prove global well-posedness and scattering in H ¹ for the defocusing nonlinear Schrödinger equations

$\left\{\begin{array}{ll}(i\partial_t+\Delta_g)u=u|u|^{2\sigma};\\u(0)=\phi,\end{array}\right.$

on the hyperbolic spaces \({\mathbb{H}^d}\), d ≥ 2, for exponents \({\sigma \in (0, 2/(d-2))}\). The main unexpected conclusion is scattering to linear solutions in the case of small exponents σ; for comparison, on Euclidean spaces scattering in H ¹ is not known for any exponent \({\sigma \in (1/d, 2/d]}\) and is known to fail for \({\sigma \in (0, 1/d]}\). Our main ingredients are certain noneuclidean global in time Strichartz estimates and noneuclidean Morawetz inequalities.

     

Numerical analyis of turbulent flow in a Coanda ejector

The task of this study is to investigate the influence of various geometric parameters and pressure ratios on the Coanda ejector performance. For numerically investigations we use an implicit formulation of the compressible Reynolds-average Navier-Stokes equations (RANS) for axisymmetric flow with a shear stress transport k − ω (SST model) turbulence model. The numerically results was obtained for a total pressure range 1-5 Bars, imposed at the reservoir inlet. The effect of various factors, such as, the pressure ratio, primary nozzle and ejector configurations on the system performance has been evaluated based on defined performance parameters. The numerical results have been compared with theoretical and experimental results for a given Coanda ejector configuration. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

DNA-assisted decoration of single-walled carbon nanotubes with gold nanoparticles for applications in surface-enhanced Raman scattering imaging of cells

Single-walled carbon nanotubes (SWNTs) are 1D nanostructures with distinct physical and chemical properties that have shown great promise for applications in many fields, including biomedicine. Since for biomedical application the water solubility is crucial and SWNTs have low solubility, various methods (including polymer and biopolymer wrapping, chemical modifications) have been developed to solubilize and disperse them in water. Due to their unique optical properties such as photoluminescence in the NIR and strong resonant Raman signatures, they can be used as nanoprobes in biomedical imaging and phototherapies. Furthermore, decoration of SWNTs with noble metal nanoparticles will induce an excellent surface-enhanced Raman scattering (SERS) effect of the nanoparticles-SWNTs composites, with applications in cell imaging. Herein, we present a new and facile strategy for the DNA-assisted decoration of SWNTs with gold nanoparticles (AuNPs) and their application in SERS imaging. By ultrasonication at room temperature of SWNTs with AuNPs functionalized with synthetic DNA, SWNT-AuNPs nanocomposites with enhanced Raman signal were obtained. Among the important advantages of the proposed method are the presence of the free DNA overhangs around the SWNT-AuNPs suitable for post-synthetic modification of nanocomposite through hybridization of complementary DNA strands containing molecules of interest attached by well-developed bio-conjugation chemistry.

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Graphical abstract ?

     

Stabilization of graphene sheets by a structured benzene/hexafluorobenzene mixed solvent

Applications requiring pristine graphene derived from graphite demand a solution stabilization method that utilizes an easily removable media. Using a combination of molecular dynamics simulations and experimental techniques, we investigate the solublization/suspension of pristine graphene sheets by an equimolar mixture of benzene and hexafluorobenzene (C(6)H(6)/C(6)F(6)) that is known to form an ordered structure solidifying at 23.7 °C. Our simulations show that the graphene surface templates the self-assembly of the mixture into periodic layers extending up to 30 ? from both sides of the graphene sheet. The solvent structuring is driven by quadrupolar interactions and consists of stacks of alternating C(6)H(6)/C(6)F(6) molecules rising from the surface of the graphene. These stacks result in density oscillations with a period of about 3.4 ?. The high affinity of the 1:1 C(6)H(6)/C(6)F(6) mixture with graphene is consistent with observed hysteresis in Wilhelmy plate measurements using highly ordered pyrolytic graphite (HOPG). AFM, SEM, and TEM techniques verify the state of the suspended material after sonication. As an example of the utility of this mixture, graphene suspensions are freeze-dried at room temperature to produce a sponge-like morphology that reflects the structure of the graphene sheets in solution.