SPARC collaboration: new strategy for storage ring physics at FAIR

SPARC collaboration at FAIR pursues the worldwide unique research program by utilizing storage ring and trapping facilities for highly-charged heavy ions. The main focus is laid on the exploration of the physics at strong, ultra-short electromagnetic fields including the fundamental interactions between electrons and heavy nuclei as well as on the experiments at the border between nuclear and atomic physics. Very recently SPARC worked out a realization scheme for experiments with highly-charged heavy-ions at relativistic energies in the High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled to the present ESR. Both facilities provide unprecedented physics opportunities already at the very early stage of FAIR operation. The installation of CRYRING, dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much earlier realisation of the physics program of FLAIR with slow anti-protons.     

Nano‐antennae assisted emission of extreme ultraviolet radiation

High‐order harmonic generation in xenon with oscillator repetition rates is studied. The necessary intensity is reached via plasmonic field enhancement at nanostructured arrays of bow‐tie gold antennae. The theoretical analysis focuses on the thermal properties and the damage threshold of the bow‐tie antennae. On the experimental side the number of contributing atoms is determined and optimized. Extreme ultraviolet radiation is successfully observed with photon fluxes almost an order of magnitude larger than previously reported.     

Solid state polymerization of poly(lactic acid): Some fundamental parameters

Poly(lactic acid) (PLA) was submitted to solid state polymerization (SSP) in a fixed bed reactor under nitrogen flow, so as to examine technique efficiency for increasing the molecular weight and hence permitting the reduction of the melt polymerization residence times. In order to use a suitable starting material, SSP prepolymers of low and medium molecular weight were first prepared through solid state hydrolysis of commercial PLA grade under acidic and alkaline conditions. During these degradation runs, hydrolysis involved the random scission of ester groups in the polymer backbone, while the relevant kinetics and the resulting thermal properties were also examined. In a subsequent step, the prepolymers obtained were subjected to SSP at three temperatures, approximately 2.5–25.0 °C below their melting point. The process achieved an increase of up to 1.7 times the initial molecular weight, however, with different trends depending on the prepolymer characteristics, reaction temperature and time, as well as the pH of the hydrolysis medium. In addition to molecular weight build up, the effect of the SSP process on end product thermal properties was also investigated.     

Selective Reduction of Thiol Esters with Sodium Borohydride

A couple of years ago, Fujita and co-workers¹ reported the reduction of 2-thiazoline-2-thiol esters to alcohols with sodium borohydride in aqueous tetrahydrofuran. In connection with an ongoing synthetic project which requires the selective reduction of a stable acid derivative to the alcohol level in the presence of nitrile and ester groups, we examined the reaction of a variety of thiol esters with sodium borohydride. Our results show that the highly reactive (and thus unstable) 2-thiazoline-2-thiol ester derivatives are unnecessary and in fact various types of thiol esters are readily convertible to alcohols under mild conditions which do not effect the reduction of common acid derivatives such as nitrile, ester, and amide.     

Quantitative Raman spectroscopy in turbid matter: reflection or transmission mode?

Raman intensities from reflection (X _R ) and transmission (X _T ) setups are compared by calculations based on random walk and analytical approaches with respect to sample thickness, absorption, and scattering. Experiments incorporating strongly scattering organic polymer layers and powder tablets of pharmaceutical ingredients validate the theoretical findings. For nonabsorbing layers, the Raman reflection and transmission intensities rise steadily with the layer thickness, starting for very thin layers with the ratio X _T /X _R ?=?1 and approaching for thick layers, a lower limit of X _T /X _R ?=?0.5. This result is completely different from the primary irradiation where the ratio of transmittance/reflectance decays hyperbolically with the layer thickness to zero. In absorbing materials, X _R saturates at levels that depend strongly on the absorption and scattering coefficients. X _T passes through a maximum and decreases then exponentially with increasing layer thickness to zero. From the calculated radial intensity spreads, it follows that quantitative transmission Raman spectroscopy requires diameters of the detected sample areas be about six times larger than the sample thickness. In stratified systems, Raman transmission allows deep probing even of small quantities in buried layers. In double layers, the information is independent from the side of the measurements. In triple layers simulating coated tablets, the information of X _T originates mainly from the center of the bulk material whereas X _R highlights the irradiated boundary region. However, if the stratified sample is measured in a Raman reflection setup in front of a white diffusely reflecting surface, it is possible to monitor the whole depth of a multiple scattering sample with equal statistical weight. This may be a favorable approach for inline Raman spectroscopy in process analytical technology.

Rapid determination of 5-hydroxymethylfurfural by DART ionization with time-of-flight mass spectrometry

DART (direct analysis in real time), a novel technique with wide potential for rapid screening analysis, coupled with high-resolution time-of-flight mass spectrometry (TOF-MS) has been used for quantitative analysis of 5-hydroxymethylfurfural (5-HMF), a typical temperature marker of food. The DART/TOF-MS method was optimised and validated. Quantification of 5-HMF was achieved by use of a stable isotope-labelled 5-HMF standard prepared from glucose. Formation of 5-HMF from saccharides, a potential source of overestimation of results, was evaluated. Forty-four real samples (honey and caramelised condensed sweetened milk) and 50 model samples of heated honey were analysed. The possibility of using DART for analysis of heated samples of honey was confirmed. HPLC and DART/TOF-MS methods for determination of 5-HMF were compared. The correlation equation between these methods was DART?=?1.0287HPLC?+?0.21340, R ²?=?0.9557. The DART/TOF-MS method has been proved to enable efficient and rapid determination of 5-HMF in a variety of food matrices, for example honey and caramel.     

Aircraft noise: accounting for changes in air traffic with time of day

Aircraft noise contours are estimated using model calculations and, due to their impact on land use planning, they need to be highly accurate. During night time, not only the number and dominant types of aircraft may differ from daytime but also the flight paths flown may differ. To determine to which detail these variations in flight paths need to be considered, calculations were performed exemplarily for two airports using all available radar data over 1 year, taking into account their changes over the day. The results of this approach were compared with results of a simpler approach which does not consider such changes. While both calculations yielded similar results for the day and close to the airport, differences increased with distance as well as with the period of day (day相似文献   

Semisynthesis of fluorescent metabolite sensors on cell surfaces

Progress in understanding signal transduction and metabolic pathways is hampered by a shortage of suitable sensors for tracking metabolites, second messengers, and neurotransmitters in living cells. Here we introduce a class of rationally designed semisynthetic fluorescent sensor proteins, called Snifits, for measuring metabolite concentrations on the cell surface of mammalian cells. Functional Snifits are assembled on living cells through two selective chemical labeling reactions of a genetically encoded protein scaffold. Our best Snifit displayed fluorescence intensity ratio changes on living cells significantly higher than any previously reported cell-surface-targeted fluorescent sensor protein. This work establishes a generally applicable and rational strategy for the generation of cell-surface-targeted fluorescent sensor proteins for metabolites of interest.