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101.
102.
We study the non-linear interaction of high-power far-infrared radiation on both the passive and activep-Ge laser material. Effects of dynamical spectral hole burning and cross-saturation are observed. Transiently increased gain is seen early in thep-Ge laser pulse. We present a detailed analysis, in a model of inhomogeneouslybroadened two-level systems, together with results obtained earlier at mid-infrared frequency. 相似文献
103.
Erhard Bieber Till v. Egidy Otto W. B. Schult 《Zeitschrift für Physik A Hadrons and Nuclei》1962,170(5):465-474
The internal conversion electrons and the gamma-rays emitted by Samarium after neutron capture were measured by means of a betaspectrometer and a bent-crystal spectrometer at the research reactor at Garching near Munich. Lines corresponding to 50 transitions between 59 keV and 1·7 MeV were found with the betaspectrometer. The measurement with the crystal spectrometer showed 11 lines between 250 keV and 740 keV. The multipolarity of a few lines was determined. A level scheme containing most of the measured lines is suggested. 相似文献
104.
Till?R?hrich Bassam Abu?Thaher Hans-Hartwig?OttoEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(1):55-68
Summary. 1,2-Thiazetidine-3-acetic acid 1,1-dioxide was N-alkylated using bromoacetates, and N-acylated using either acyl chlorides, protected amino acid fluorides, or N-protected amino acid NCA, which seemed to be the most universal method. Most of the obtained -sultam peptides were sensitive against humidity, they hydrolyzed forming sulfonic acids, and reactions with amines resulted in sulfonamides. Reactions of N-acylated products showed that the sulfonyl group was faster attacked than the imide structure. 相似文献
105.
Braunschweig T Chung JY Hewitt SM 《Combinatorial chemistry & high throughput screening》2004,7(6):575-585
Tissue microarrays (TMAs) are means of combining tens to hundreds of specimens of tissue onto a single slide for analysis at one time. TMAs are most frequently constructed from paraffin embedded tissue; however, they can be constructed from frozen tissue. The construction of TMAs is flexible, meeting the focused needs of the investigator. A TMA slide can be processed like an ordinary tissue section, and used for histochemical, immunohistochemical staining or in situ hybridization. Combined with automated new image analysis systems, TMAs are a powerful molecular profiling tool. By confirming the findings of microarray experiments or protein arrays, TMAs can be applied systematically to global cellular network analysis within tissue cell. TMAs are commonly used to confirm the results of expression microarrays as well as in the development of diagnostic and prognostics markers for clinical applications. This review will cover recent advancements in technology for the construction and use of TMAs. Because TMAs can be constructed from archival paraffin embedded tissue, they open up the vast archive of patient samples and make them accessible for medical research. TMAs play an ever increasing role in translational medicine, bridging the chasm of discovery at the research bench to the demonstration of clinical utility prior to implementation in patient care. 相似文献
106.
G. Várhegyi T. Székely F. Till E. Jakab P. Szabó 《Journal of Thermal Analysis and Calorimetry》1988,33(1):87-95
It has been known from the very beginning of the thermal analysis that the transport processes can significantly influence the thermoanalytical results. In this paper, three characteristic examples are given to show that this problem is more complex and arises more frequently than it is generally believed. The studied reactions are the carbon monoxide evolution from calcium oxalate, the thermal degradation of polytetrafluoroethylene, and the thermal decomposition of azodicarbonamide. TG and DSC experiments were carried out with sample masses varying between 0.05 and 8 mg. The necessity of the development of new kinetic models is concluded.
Zusammenfassung Seit den Anfängen der Thermoanalyse ist bekannt, dass Transportprozesse die thermoanalytischen Ergebnisse weitgehend beeinflussen können. Es werden hier drei Beispiele beschrieben, die zeigen, dass dieses Problem weitauf komplizierter ist und häufiger auftritt als allgemein angenommen wird. Die untersuchten Reaktionen sind die Kohlenmonoxidabspaltung aus Calziumoxalat, die thermische Zersetzung von Polytetrafluoräthylen und der thermische Zerfall von Azodicarbonamid. Die TG- und DSC- Untersuchungen wurden mit Probenmassen zwischen 0.05 und 8 mg durchgeführt. Es wird auf die Notwendigkeit der Entwicklung neuer kinetischer Modelle geschlossen.
, . , , . , . , 0,05 8 . .相似文献
107.
The reaction of 2-carboxybenzaldehyde with primary amines in the presence of cyanide leads to the formation of 2-substituted amino(3-oxo-2,3-dihydro-1H-isoindol-1-ylidene)acetonitriles. These compounds originate from the condensation of 2-carboxybenzaldehyde with the amine and two molecules of hydrogen cyanide and represent a novel class of isoindolinones. 相似文献
108.
Luis I. Domenianni Markus Bauer Till Schmidt-Räntsch Jörg Lindner Sven Schneider Peter Vöhringer 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309618
Transition-metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen-atom-transfer reactivity. They are typically prepared in situ upon optically induced N2 elimination from azido precursors. A full exploitation of their catalytic potential, however, requires in-depth knowledge of the primary photo-induced processes and the structural/electronic factors mediating the N2 loss with birth of the terminal metal-nitrogen core. Using femtosecond infrared spectroscopy, we elucidate here the primary molecular-level mechanisms responsible for the formation of a unique platinum(II) nitrene with a triplet ground state from a closed-shell platinum(II) azide precursor. The spectroscopic data in combination with quantum-chemical calculations provide compelling evidence that product formation requires the initial occupation of a singlet excited state with an anionic azide diradical ligand that is bound to a low-spin d8-configured PtII ion. Subsequent intersystem crossing generates the Pt-bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N2-releasing state possessing azide ππ* character as a design principle for accessing efficient N-atom-transfer catalysts. 相似文献
109.
Till MS Essigke T Becker T Ullmann GM 《The journal of physical chemistry. B》2008,112(42):13401-13410
The large interest in long-range proton transfer in biomolecules is triggered by its importance for many biochemical processes such as biological energy transduction and drug detoxification. Since long-range proton transfer occurs on a microsecond time scale, simulating this process on a molecular level is still a challenging task and not possible with standard simulation methods. In general, the dynamics of a reactive system can be described by a master equation. A natural way to describe long-range charge transfer in biomolecules is to decompose the process into elementary steps which are transitions between microstates. Each microstate has a defined protonation pattern. Although such a master equation can in principle be solved analytically, it is often too demanding to solve this equation because of the large number of microstates. In this paper, we describe a new method which solves the master equation by a sequential dynamical Monte Carlo algorithm. Starting from one microstate, the evolution of the system is simulated as a stochastic process. The energetic parameters required for these simulations are determined by continuum electrostatic calculations. We apply this method to simulate the proton transfer through gramicidin A, a transmembrane proton channel, in dependence on the applied membrane potential and the pH value of the solution. As elementary steps in our reaction, we consider proton uptake and release, proton transfer along a hydrogen bond, and rotations of water molecules that constitute a proton wire through the channel. A simulation of 8 mus length took about 5 min on an Intel Pentium 4 CPU with 3.2 GHz. We obtained good agreement with experimental data for the proton flux through gramicidin A over a wide range of pH values and membrane potentials. We find that proton desolvation as well as water rotations are equally important for the proton transfer through gramicidin A at physiological membrane potentials. Our method allows to simulate long-range charge transfer in biological systems at time scales, which are not accessible by other methods. 相似文献
110.
1,2,3,4-Tetrahydroisoquinoline-1-carbonitriles can serve as starting materials for the one-pot synthesis of 5,6-dihydropyrrolo[2,1 a]isoquinolines and 1-benzyl-3,4-dihydroisoquinolines. The latter compounds were transformed to lamellarin G trimethyl ether and lamellarin U in short reaction sequences. This method allows the introduction of acid-sensitive protecting groups for the phenolic hydroxy functions which would be cleaved under the harsh conditions of the classical Bischler-Napieralski reaction. 相似文献