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91.
Guillaume Watier 《Semigroup Forum》1996,53(1):194-207
LetM be a monoid presented by <Σ;u=v> whereu andv are words on the finite alphabet Σ./ Deciding the world problem forM is still an open question, though it seems decidable and partial results exist. The remaining cases to solve are presentations
of the form <a, b; bva=aua>,u, v∈{a, b}⋆ The word problem is then closely related to the left-divisibility problem, as shown by S.I. Adjan who introduced a procedure
that “almost” allows to decide the problem. The main contribution, due to Adjan and Oganesjan, states that ifbva is an unbordered factor ofaua then the word problem is deciable. We restrict Adjan's procedure to study the case whenbva is unbordered, which allows us to extend Adjan and Oganesjan's theorem. More specifically, we show (Proposition 4.24) that
the word problem is decidable for presentations <a, b; bva=aua> with the only following condition: Inbva, the leftmost train ofb is strictly longer than the others. The following corollary naturally holds: The word problem is decidable for presentations
of the form <a, b; b
m
a
n
=aua>,u∈{a, b}⋆,m, n>0 相似文献
92.
We report here the first experimental observation of the flourescence of a LO phonon replica from the An=2 excitonic level in cadmium sulfide. A very simple theoretical interpretation is given. We present also experimental data about phonon replicas in the case of forbidden transitions. 相似文献
93.
The use of 2.8 MeV neutrons produced by the D(d, n)3He reaction should be taken into consideration in some applications of radioactivation analysis. The low number of elements
activable by these neutrons makes possible to minimize the matrix interference and the background below the characteristic
photopeaks. The very low dead-time of the spectrometric measurements permits the use of the maximum neutron flux available
now and in the future. The purpose of this paper is to define experimentally the sensitivity of determination for the 16 main
elements activable with a 400 keV Van de Graaff accelerator at a 2.8 MeV neutron flux of 2·106 n·cm−2·sec−1 on the sample. 相似文献
94.
We analyze the general features of the formation and interaction of transverse traveling waves and the appearance of filamentation in broad area semiconductor lasers with current profiling. For small apertures, the emitted profile is symmetric consisting of two counterpropagating transverse traveling waves, both emanating from the center of the device. For larger apertures, the emission becomes asymmetric as one of the traveling waves expands to occupy an increased area while the other occupies the remaining, smaller spatial region. In both devices, the pattern becomes unstable at higher injection currents due to optical filamentation, although an intermediate state is present in the wider device whereby the dominant wave undergoes a Hopf bifurcation before filamentation occurs. 相似文献
95.
A remarkable analogy is established between the well-known spin Hall effect and the polarization dependence of Rayleigh scattering of light in microcavities. This dependence results from the strong spin effect in elastic scattering of exciton polaritons: if the initial polariton state has a zero spin and is characterized by some linear polarization, the scattered polaritons become strongly spin polarized. The polarization in the scattered state can be positive or negative dependent on the orientation of the linear polarization of the initial state and on the direction of scattering. Very surprisingly, spin polarizations of the polaritons scattered clockwise and anticlockwise have different signs. The optical spin Hall effect is possible due to strong longitudinal-transverse splitting and finite lifetime of exciton polaritons in microcavities. 相似文献
96.
Legros G Fuentes A Ben-Abdallah P Baillargeat J Joulain P Vantelon JP Torero JL 《Optics letters》2005,30(24):3311-3313
A remote scanning retrieval method was developed to investigate the soot layer produced by a laminar diffusion flame established over a flat plate burner in microgravity. Experiments were conducted during parabolic flights. This original application of an inverse problem leads to the three-dimensional recomposition by layers of the absorption field inside the flame. This technique provides a well-defined flame length that substitutes for other subjective definitions associated with emissions. 相似文献
97.
Madelin G Baril N Lewa CJ Franconi JM Canioni P Thiaudiére E de Certaines JD 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,161(1):108-111
A B(1) field gradient-based method previously described for the detection of mechanical vibrations has been applied to detect oscillatory motions in condensed matter originated from acoustic waves. A ladder-shaped coil generating a quasi-constant RF-field gradient was associated with a motion-encoding NMR sequence consisting in a repetitive binomial 13;31; RF pulse train (stroboscopic acquisition). The NMR response of a gel phantom subject to acoustic wave excitation in the 20-200 Hz range was investigated. Results showed a linear relationship between the NMR signal and the wave amplitude and a spectroscopic selectivity of the NMR sequence with respect to the input acoustic frequency. Spin displacements as short as a few tens of nanometers were able to be detected with this method. 相似文献
98.
Ismaili L Truong TT André C Thomassin M Mozer JL Robert JF Xicluna A Refouvelet B Millet J Nicod L Guillaume YC 《Journal of AOAC International》2003,86(2):222-228
The mechanism of the binding of D,L dansyl amino acids to teicoplanin was investigated. Na+ was used as an indicator of the interactions between the solutes and teicoplanin. The number (n) of sodium ions, Na+, excluded from the solute-teicoplanin interface when analyte transfer occurred was determined. A thermodynamic study and enthalpy-entropy compensation were performed to further explore the interaction mechanism. From these results, it was shown that teicoplanin was balanced between 2 conformational states characterized by distinct enantioselective properties. This approach indicates that liquid chromatography (LC) is a useful tool to extract physicochemical and molecular information from retention data. Thus, LC can be used as a complementary technique with the conventional techniques of molecular interaction analysis. 相似文献
99.
Guillaume Lafitte Audrey Beillard Sandrine Chambon Catherine Soulet Laurence Dumais Grégoire Mouis Jean-François Fournier Laurence Clary Claire Bouix-Peter Loic Tomas Craig S. Harris 《Tetrahedron letters》2018,59(3):256-259
During our search for novel CGRP antagonists, we had great difficulty in accessing one of our key motifs. Herein, we communicate how we solved the problem by an unprecedented Mitsunobu alkylation using unprotected amino alcohols. 相似文献
100.
Pacchioni M Cornia A Fabretti AC Zobbi L Bonacchi D Caneschi A Chastanet G Gatteschi D Sessoli R 《Chemical communications (Cambridge, England)》2004,(22):2604-2605
A novel single-molecule magnet of the Mn12 family, [Mn12O12(O2CC6H5)8(L)4(H2O)4].8CH2Cl2, has been synthesised by site-specific ligand exchange using a tailor-made dicarboxylate (L2-), which leads to selective occupation of axial binding sites. 相似文献