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1.
The yet unknown intermetallic phase La5Al3Ni2 was obtained by partially crystallizing amorphous La50Al25Ni25 at 550 K (further heating above 600 K leads to irreversible disappearance of this phase), and its crystal structure was determined from X‐ray powder diffraction data. The crystal structure of the La5Al3Ni2 phase constitutes a new structure type (Cmcm, a = 14.231Å, b = 6.914Å, c = 10.460Å, oC40) and is built from [Al3Ni2] chains surrounded by La atoms. In the ternary system La‐Al‐Ni La5Al3Ni2 is located on the section La50Al50−nNin (0 ≤ n ≤ 50) with the binary compounds LaAl and LaNi as end members. Strikingly, also the crystal structures of the end members can be conceived as chain structures with Al and Ni chains surrounded by La, respectively. 相似文献
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3.
Edwin Haselbach Urs Klemm Rudolf Gschwind Thomas Bally Laurant Chassot Stephan Nitsche 《Helvetica chimica acta》1982,65(8):2464-2471
The radical cations of indeno [2, 1-a]indene ( 1 ), stilbene ( 2 ) and 3, 5, 3', 5'-tetramethylstilbene ( 3 ) were prepared by γ-irradiation of the neutral precursors in an electron-scavenging matrix at 77 K . Their electronic spectra were recorded and compared to the photoelectron spectra ( PE .) of the neutral precursors. The results show that either the fourth or the fifth excited doublet state of the cations is of «Non-Koopmans» type, with specific doublet energy (D) D (2Bg)=2.74 eV ( 1 +), =2.59 eV ( 2 +), =2.49 eV ( 3 +). Remarkably, 1 + possesses two electronic states in the 2.7-2.8 eV energy range: 2Au («Koopmans»-type) and 2Bg («Non -Koopmans»-type). The «SDT»-equation \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm D} = \sqrt {{\rm S} \cdot {\rm T}} $\end{document} approximately connecting excited singlet (S) and triplet (T) states of a neutral alternant system with the excited doublet (D) states of its radical cation - provided e-promotion occurs For all three excited states between the same (paired) orbitals-is satisfyingly exemplified by 1 : S1 = 3.92 eV and T1= 2.06 eV for 1 , D4 or 5=2.74 eV for 1 +. 相似文献
4.
H. Nitsche R. C. Gatti Sh. C. Lee 《Journal of Radioanalytical and Nuclear Chemistry》1992,161(2):401-411
We have developed an analytical method for detection of239Pu in aqueous samples at concentrations as low as 10–10M. This nuclear counting technique utilizes the uranium L X-rays, which follow the alpha-decay of plutonium. Because L X-rays are specific for the element and not for the individual isotope, the isotopic composition of the plutonium sample must be known. The counting efficiency in the 11–23 keV range is determined from a plutonium standard, and the concentration of the sample is then calculated from the L X-ray count and the isotopic composition. The total L X-ray count is corrected for possible contributions from other radionuclides present as impurities by measuring the low-energy gamma-spectrum for each contaminant to establish specific photon/X-ray ratios. The ratios are important when241Pu and242Pu are measured, because the respective decay chain members produce non-U L X-rays. This new method can replace the use of labor-intensive radiochemical separation techniques and elaborate activation methods for analysis of239Pu in aqueous samples. It is also applicable for assaying plutonium in liquid wastes that pose possible hazards to the environment. 相似文献
5.
Constrained peptides are promising next-generation therapeutics. Peptide stapling is a particularly attractive technique to generate constrained macrocycles with improved biological activity and metabolic stability. We introduce a biocompatible two-component stapling approach based on the reagent 2,6-dicyanopyridine and a pseudo-cysteine amino acid. Stapling can proceed either directly on-resin during solid-phase synthesis or following isolation of the linear peptide. The stapling reaction is orthogonal to natural amino acid side chains and completes in aqueous solution at physiological pH, enabling its direct use in biochemical assays. We performed a small screening campaign of short peptides targeting the Zika virus protease NS2B-NS3, allowing the direct comparison of linear with in situ stapled peptides. A stapled screening hit showed over 28-fold stronger inhibition than its linear analogue, demonstrating the successful identification of constrained peptide inhibitors.A synthetically straightforward and biocompatible peptide-stapling strategy that can be used directly in biochemical assays to identify constrained enzyme inhibitors. 相似文献
6.
Ingeborg Csöregh Thomas Brehmer Silke I. Nitsche Wilhelm Seichter Edwin Weber 《Journal of inclusion phenomena and macrocyclic chemistry》2003,47(3-4):113-121
X-ray crystal structures are reported of a free host compound 1, comprising two diphenylmethanol terminal groups attached to a central 9,10-ethynyl substituted anthracene unit, and of three inclusion compounds of a fluoren-9-ol substituted analogous host 2 with acetone, dimethyl sulphoxide (DMSO) and dimethylformamide (DMF) as guest, respectively. Despite the presence of two hydroxyl groups in 1, there is no O–H...O hydrogen bond between the molecules in the guest free crystal – only weaker C–H...O interactions and van der Waals' type connections. In the inclusion compounds of 2, H-bonded 1:2 host–guest associates are formed, where each of the host hydroxyl groups binds to a guest oxygen atom. The orientations of the host–guest connections in these complexes vary, being E for acetone and Z for both DMSO and DMF guests, relative to the host anthracene unit. The DMSO and DMF inclusion compounds of 2 proved to be isostructural. 相似文献
7.
W. Nitsche P. H. Heckmann E. Träbert H. v.Buttlar 《Zeitschrift für Physik A Hadrons and Nuclei》1981,299(4):301-306
Ratios of initial populations of foil-excited hydrogen-like ions of He, B, C, N and O have been measured. Combined with earlier results for H obtained by Tielert they show aZ-dependence of the population process and indicate a velocity dependence as well. For the population of thenp-levels (n=2–5) of He+ ann-dependence ∞n ?(3.6±0.4) has been observed. 相似文献
8.
W. Nitsche G. J. Wagner K. T. Knöpfle P. Grabmayr H. Riedesel 《Zeitschrift für Physik A Hadrons and Nuclei》1981,300(1):109-110
At 26 MeV/A, inelastic scattering of6Li ions from28Si proceeds predominantly via direct one-nucleon removal, while inelasticα scattering leads, in addition, to excitation of the target nucleus. 相似文献
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10.
Folden CM Gregorich KE Düllmann ChE Mahmud H Pang GK Schwantes JM Sudowe R Zielinski PM Nitsche H Hoffman DC 《Physical review letters》2004,93(21):212702
Seven 271Ds decay chains were identified in the bombardment of 208Pb targets with 311.5 and 314.3 MeV 64Ni projectiles using the Berkeley Gas-filled Separator. These data, combined with previous results, provide an excitation function for this reaction. From these results, an optimum energy of 321 MeV was estimated for the production of (272)111 in the new reaction 208Pb(65Cu,n). One decay chain was observed, resulting in a cross section of 1.7(+3.9)(-1.4) pb. This experiment confirms the discovery of element 111 by the Darmstadt Group who used the 209Bi(64Ni,n)(272)111 reaction. 相似文献