217 research outputs found

    Hydrogen Spectroscopy with a Lamb-shift Polarimeter - An Alternative Approach Towards Anti-Hydrogen Spectroscopy Experiments

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    A Lamb-shift polarimeter, which has been built for a fast determination of the polarization of protons and deuterons of an atomic-beam source and which is frequently used in the ANKE experiment at COSY-J\"ulich, is shown to be an excellent device for atomic-spectroscopy measurements of metastable hydrogen isotopes. It is demonstrated that magnetic and electric dipole transitions in hydrogen can be measured as a function of the external magnetic field, giving access to the full Breit-Rabi diagram for the 22S1/22^2S_{1/2} and the 22P1/22^2P_{1/2} states. This will allow the study of hyperfine structure, gg factors and the classical Lamb shift. Although the data are not yet competitive with state-of-the-art measurements, the potential of the method is enormous, including a possible application to anti-hydrogen spectroscopy.Comment: 6 pages, 7 figures, accepted by European Physical Journal

    The Polarized H and D Atomic Beam Source for ANKE at COSY-J\"ulich

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    A polarized atomic beam source was developed for the polarized internal storage-cell gas target at the magnet spectrometer ANKE of COSY-J\"ulich. The intensities of the beams injected into the storage cell, measured with a compression tube, are 7.5⋅10167.5\cdot 10^{16} hydrogen atoms/s (two hyperfine states) and 3.9⋅10163.9\cdot 10^{16} deuterium atoms/s (three hyperfine states). For the hydrogen beam the achieved vector polarizations are pz≈±0.92p_{\rm z}\approx\pm0.92. For the deuterium beam, the obtained combinations of vector and tensor (pzzp_{\rm zz}) polarizations are pz≈±0.90p_{\rm z}\approx\pm 0.90 (with a constant pzz≈+0.86p_{\rm zz}\approx +0.86), and pzz=+0.90p_{\rm zz}=+0.90 or pzz=−1.71p_{\rm zz}=-1.71 (both with vanishing pzp_{\rm z}). The paper includes a detailed technical description of the apparatus and of the investigations performed during the development.Comment: 18 pages, 26 figures, 4 table

    Function of sesquiterpenes from Schizophyllum commune in interspecific interactions

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    11-keto-alpha-boswellic acid, a novel triterpenoid from Boswellia spp. with chemotaxonomic potential and antitumor activity against triple-negative breast cancer cells

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    Boswellic acids, and particularly 11-keto-boswellic acids, triterpenoids derived from the genus Boswellia (Burseraceae), are known for their anti-inflammatory and potential antitumor efficacy. Although boswellic acids generally occur as α-isomers (oleanane type) and β-isomers (ursane type), 11-keto-boswellic acid (KBA) was found only as the β-isomer, β-KBA. Here, the existence and natural occurrence of the respective α-isomer, 11-keto-α-boswellic acid (α-KBA), is demonstrated for the first time. Initially, α-KBA was synthesized and characterized by high-resolution mass spectrometry (HR-MS) and nuclear magnetic resonance (NMR) spectroscopy, and a highly selective, sensitive, and accurate high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method was developed by Design of Experiments (DoE) using a pentafluorophenyl stationary phase. This method allowed the selective quantification of individual 11-keto-boswellic acids and provided evidence for α-KBA in Boswellia spp. oleogum resins. The contents of α-KBA as well as further boswellic acids and the composition of essential oils were used to chemotaxonomically classify 41 Boswellia oleogum resins from 9 different species. Moreover, α-KBA exhibited cytotoxicity against three treatment-resistant triple-negative breast cancer (TNBC) cell lines in vitro and also induced apoptosis in MDA-MB-231 xenografts in vivo. The respective β-isomer and the acetylated form demonstrate higher cytotoxic efficacies against TNBC cells. This provides further insights into the structure-activity relationship of boswellic acids and could support future developments of potential anti-inflammatory and antitumor drugs
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