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  • Grün, A.
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Year
  • 1
    Language: English
    In: The journal of physical chemistry. A, 07 November 2013, Vol.117(44), pp.11233-45
    Description: The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC.
    Keywords: Sorption ; Absorption Spectroscopy ; Absorption (Physics) ; Fluorescence ; Anions ; Sensors ; Analytical Techniques ; Solvation ; Solvents ; Anions ; Fluorescence ; Sensors ; Kinetics ; Solvents ; Organic Solvents ; Absorption ; Hydrogen Ion Concentration ; Spectroscopy ; Anions ; Fluorescence ; Sensors ; Kinetics ; Solvents ; Organic Solvents ; Absorption ; Hydrogen Ion Concentration ; Spectroscopy ; Characteristics, Behavior and Fate ; Network Design ; Sewage;
    ISSN: 10895639
    E-ISSN: 1520-5215
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  • 2
    Language: English
    In: Tetrahedron Letters, 2011, Vol.52(21), pp.2744-2746
    Description: To clarify the inconsistent patent literature, the synthesis of Zoledronic and Risedronic acids involving a heterocyclic acetic acid (HAA), phosphorous acid (PA) and phosphorus trichloride (PC) as the reagents, and methanesulfonic acid as the solvent was studied in detail. It was found that the best synthesis can be accomplished at 80 °C using HAA and PC in a 1:3.1 molar ratio without any PA.
    Keywords: Rational Synthesis ; Optimization ; Dronic Acids ; Mechanism ; Chemistry
    ISSN: 0040-4039
    E-ISSN: 1873-3581
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  • 3
    In: Chemical Communications, 2010, Vol.46(4), pp.607-609
    Description: We report on the synthesis and trace analytical application of ionophore–gold nanoparticle conjugates as a basis of a new concept in confining ionophores to ion-selective membranes using inert nanoparticle carriers.
    Keywords: Confining ; Conjugates ; Inert ; Mathematical Analysis ; Nanocomposites ; Nanomaterials ; Nanostructure ; Synthesis ; Miscellaneous Sciences (So) ; Components and Materials (General) (Ea);
    ISSN: 1359-7345
    E-ISSN: 1364-548X
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  • 4
    Language: English
    In: Tetrahedron Letters, 04 May 2016, Vol.57(18), pp.1953-1957
    Description: A novel and efficient one-pot method has been developed for the synthesis of 1-substituted-3,4-dihydro-β-carbolines from tryptamine and a wide variety of carboxylic acids. The reaction was successfully applied to the synthesis of an important alkaloid harmalan as well as dihydro-eudistomin-U. This represents the first case in which 1-propanephosphonic acid cyclic anhydride (T3P®) has been used in the Bischler–Napieralski reaction. Unexpectedly it was observed that less than two equivalents of the T3P® reagent were sufficient for the two consecutive reactions.
    Keywords: Β-Carbolines ; Bischler–Napieralski Reaction ; Ring Closure ; One-Pot Synthesis ; T3p® ; Chemistry
    ISSN: 0040-4039
    E-ISSN: 1873-3581
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  • 5
    Language: English
    In: Optics letters, 15 October 2015, Vol.40(20), pp.4679-82
    Description: Nonlinear pulse compression mediated by three-wave mixing is demonstrated for ultrashort Ti:sapphire pulses in a type II phase-matched β-barium borate (BBO) crystal using noncollinear geometry. 170 μJ pulses at 800 nm with a pulse duration of 74 fs are compressed at their sum frequency to 32 fs with 55 μJ of pulse energy. Experiments and computer simulations demonstrate the potential of sum-frequency pulse compression to match the group velocities of the interacting waves to crystals that were initially not considered in the context of nonlinear pulse compression.
    Keywords: Energy Use ; Three-Wave Mixing ; Pulse Compression ; Femtosecond Pulses ; Nonlinearity ; Borates ; Crystals ; Compressing ; Lasers, Optics, and Electronics (So) ; Optics (Ea) ; Optics (Ah);
    ISSN: 01469592
    E-ISSN: 1539-4794
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  • 6
    In: Synthesis, 2017, Vol.49(14)
    In: Synthesis, 2017, Vol.49(14), pp.3069-3083
    Keywords: Organophosphorus chemistry ; Microwave irradiation ; Phosphinates ; Kabachnik–fields reaction ; Alkylation, deoxygenation ; Hirao reaction
    ISSN: 0039-7881
    E-ISSN: 1437-210X
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  • 7
    Language: English
    In: Synlett, 2015, Vol.26(13)
    In: Synlett, 2015, Vol.26(13), pp.1847-1851
    Keywords: Phase-transfer catalysis ; Sugar-based crown ethers ; Asymmetric michael reactions ; Asymmetric cyclopropanations ; Enantioselectivity
    ISSN: 0936-5214
    E-ISSN: 1437-2096
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  • 8
    Language: English
    In: Optics letters, 01 August 2011, Vol.36(15), pp.2803-5
    Description: An acousto-optic pulse shaper has been used to characterize few-cycle pulses generated in a hollow-core fiber. A grism pair precompensates for the dispersion of the acousto-optic crystal, allowing the full pulse-shaping window to be used for replica generation rather than self-compensation. A 9.4 fs pulse was measured, the shortest ever measured with an acousto-optic pulse shaper, to our knowledge.
    ISSN: 01469592
    E-ISSN: 1539-4794
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  • 9
    In: Synthesis, 2018, Vol.50(03)
    In: Synthesis, 2017, Vol.50(03), pp.625-643
    Keywords: Alkaloids-dihydronarciclasine analogues ; Phenanthridone scaffold ; Stereoselective synthesis ; Organocatalysis
    ISSN: 0039-7881
    E-ISSN: 1437-210X
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  • 10
    Language: English
    In: International Journal of Radiation Oncology, Biology, Physics, 01 February 2012, Vol.82(2), pp.e137-e143
    Description: To demonstrate the feasibility and safety of the simultaneous integrated boost technique for dose escalation in combination with helical tomotherapy in patients with cervical cancer. Forty patients (International Federation of Gynecology and Obstetrics Stage IB1 pN1–IVA) underwent primary chemoradiation with helical tomotherapy. Before therapy, 29/40 patients underwent laparoscopic pelvic and para-aortic lymphadenectomy. In 21%, 31%, and 3% of the patients, pelvic, pelvic and para-aortic, and skip metastases in the para-aortic region could be confirmed. All patients underwent radiation with 1.8–50.4 Gy to the tumor region and the pelvic (para-aortic) lymph node region (planning target volume-A), and a simultaneous boost with 2.12–59.36 Gy to the boost region (planning target volume-B). The boost region was defined using titan clips during laparoscopic staging. In all other patients, standardized borders for the planning target volume-B were defined. High-dose-rate brachytherapy was performed in 39/40 patients. The mean biologic effective dose to the macroscopic tumor ranged from 87.5 to 97.5 Gy. Chemotherapy consisted of weekly cisplatin 40 mg/m . Dose–volume histograms and acute gastrointestinal, genitourinary, and hematologic toxicity were evaluated. The mean treatment time was 45 days. The mean doses to the small bowel, rectum, and bladder were 28.5 ± 6.1 Gy, 47.9 ± 3.8 Gy, and 48 ± 3 Gy, respectively. Hematologic toxicity Grade 3 occurred in 20% of patients, diarrhea Grade 2 in 5%, and diarrhea Grade 3 in 2.5%. There was no Grade 3 genitourinary toxicity. All patients underwent curettage 3 months after chemoradiation, which confirmed complete pathologic response in 38/40 patients. The concept of simultaneous integrated boost for dose escalation in patients with cervical cancer is feasible, with a low rate of acute gastrointestinal and genitourinary toxicity. Whether dose escalation can be translated into improved outcome will be assessed after a longer follow-up time.
    Keywords: Chemoradiation ; Helical Tomotherapy ; Cervical Cancer ; Toxicity ; Simultaneous Boost ; Medicine
    ISSN: 0360-3016
    E-ISSN: 1879-355X
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