Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of 27 December 2004 with the AMANDA-II detector

On 27 December 2004, a giant gamma flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: 0.05(0.5) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the gamma flux and 0.4(6.1) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the high-energy neutrino flux.     

Cucurbituril binding of trans-[{PtCl(NH3)2}2(micro-NH2(CH2)8NH2)]2+ and the effect on the reaction with cysteine

The effect of encapsulation by cucurbiturils Q[7] and Q[8] on the rate of reaction of the anti-cancer dinuclear platinum complex trans-[{PtCl(NH3)2}2(micro-NH2(CH2)8NH2)]2+ with the model biological nucleophiles glutathione and cysteine has been examined by NMR spectroscopy. It was expected that the octamethylene linking chain would fold inside the cucurbituril host and hence position the reactive platinum centres close to the cucurbituril portals, and thereby, confer resistance to degradation by biological nucleophiles. The upfield shifts of the resonances from the methylene protons in the linking ligand observed in 1H NMR spectra of the platinum complex upon addition of either Q[7] or Q[8] indicate that the cucurbituril is positioned over the linking ligand, with the Pt(II) centres projecting out of the portal. Furthermore, the relative changes in chemical shift of the methylene resonances suggest that the octamethylene linking chain folds within the cucurbituril cavity, particularly in Q[8]. Simple molecular models, based on the observed relative changes in chemical shift, could be constructed that were consistent with the proposed folding of the linking ligand within the cucurbituril cavity. Encapsulation by Q[7] was found to reduce the rate of reaction of the platinum complex with glutathione. Encapsulation by Q[7] and Q[8] was also found to reduce the rate of reaction of the platinum complex with cysteine, with Q[8] slowing the reaction to a greater extent than Q[7], consistent with the inferred encapsulation geometries. Encapsulation of dinuclear platinum complexes within the cucurbituril cavity may provide a novel way of reducing the reactivity and degradation of these promising chemotherapeutic agents with blood plasma proteins.     

Convex Komlós sets in Banach function spaces

In 1967 Komlós proved that for any sequence n{fn} in L₁(μ), with ‖fn‖?M<∞ (where μ is a probability measure), there exists a subsequence n{gn} of n{fn} and a function g∈L₁(μ) such that for any further subsequence n{hn} of n{gn},

     

Modulation versus Templating: Fine‐Tuning of Hierarchally Porous PCN‐250 Using Fatty Acids To Engineer Guest Adsorption

Modulation and templating are two synthetic techniques that have garnered significant attention over the last several years for the preparation of hierarchically porous metal–organic frameworks (HP‐MOFs). In this study, by using fatty acids with different lengths and concentrations as dual‐functional modulators/templates, we were able to obtain HP‐MOFs with tunable mesopores that exhibit different pore diameters and locations. We found that the length and concentration of the fatty acids can determine if micelle formation occurs, which in turn dictates the porosity of the resulting HP‐MOFs. The HP‐MOFs with different mesopores differed in their performance in gas uptake and dye adsorption, and the structure–performance relationships were ascribed to the pore diameters and locations. This approach could provide a potentially universal method to efficiently introduce hierarchal mesopores into existing microporous MOF adsorbents with tunable properties.     

In‐situ Electrochemical X‐ray Diffraction: A Rigorous Method to Navigate within Phase Diagrams Reveals β‐Fe1+xSe as Superconductor for All x

We report the precise postsynthetic control of the composition of β‐Fe_1+xSe by electrochemistry with simultaneous tracking of the associated structural changes via in situ synchrotron X‐ray diffraction. We access the full phase width of 0.01<x<0.04 and identify the superconducting state below 8 K, which in contrast to earlier reports is independent of the composition. However, in a second set of in situ X‐ray diffraction experiments, we demonstrate that β‐Fe_1+xSe forms a new phase in the presence of oxygen above a 100 °C which has the same anti‐PbO type structure but is not superconducting down to 1.8 K. The latter process can be reversed electrochemically to reinstate the superconducting state. These observations exploit the exquisite control afforded by electrochemistry in contrast with classical approaches of chemical synthesis.     

Deployment of the encapsulation-dehydration protocol to cryopreserve polar microalgae held at the Czech Republic Academy of Sciences Institute of Botany

Polar isolates of four chlorococcal microalgae originating from the Arctic and Antarctica withstand cryopreservation using encapsulation-dehydration. Viability assessments, which initially used chloroplhyll fluorescence (Kautsky) induction kinetics, revealed that all strains suffered photosynthetic impairment during early post-cryopreservation recovery. This cryoinjury was reversible, as indicated by cell regrowth in three of the four strains. Lack of growth in the fourth isolate was due to contaminating bacteria rather than cryogenic factors.     

Deployment of the encapsulation-dehydration protocol to cryopreserve microalgae held at the Sammlung von Algenkulturen, Universitat Gottingen, Germany

Encapsulation-dehydration was applied to cryopreserve 14 diverse algal strains, representing eukaryotic terrestrial microalgae; of these 12 survived to form cell colonies after recovery from cryostorage. Surviving algae had varying degrees of tolerance to osmotic dehydration and desiccation in this vitrification-based cryoprotective strategy. The extent of algal regrowth was affected by the mode of desiccation (silica gel or air-flow), the duration of evaporative desiccation and exposure to light during early recovery phase. This paper: (i) demonstrates the versatility of the encapsulation/dehydration method to cryopreserve diverse microalgae; (ii) confirms the successful transfer of this cryostorage technology to the Culture Collection of Algae at Gottingen University (SAG); and (iii) recommends encapsulation/dehydration as a feasible alternative to controlled rate cooling for preserving algae held in international culture collections.     

Bioactive borate glass scaffold for bone tissue engineering

Borate glass particles and microspheres with size distributions in the range of approximately 100–400 μm, were loosely compacted and sintered for 10 min at 600 °C to form a porous, three-dimensional construct (porosity 25–40%). Conversion of the borate glass to hydroxyapatite was investigated by soaking the constructs in a solution of K₂HPO₄ (0.25 M) at 37 °C and with a pH value of 9.0, and measuring the weight loss of the constructs as a function of time. Almost full conversion of the borate glass to hydroxyapatite was achieved in less than 6 days. X-ray diffraction revealed an initially amorphous product that subsequently crystallized to hydroxyapatite. The biocompatibility of the porous constructs was investigated by in vitro cell culture with human mesenchymal stem cells derived from bone marrow (bMSC) and human mesenchymal stem cell derived osteoblasts (MSC-Ob). The cells adhered to the scaffolds and the MSC-Obs produced alkaline phosphatase which is an indication of osteogenic differentiation. The data suggest strong bioactive characteristics for the borate glass constructs and the potential use of the constructs as scaffolds for tissue engineering of bone.