Atomic structure of Cs layer grown on Si(0 0 1)(2 × 1) surface at room temperature

The atomic structure of Cs atoms adsorbed on the Si(0 0 1)(2 × 1) surface has been investigated by coaxial impact collision ion scattering spectroscopy. When 0.5 ML of Cs atoms are adsorbed on Si(0 0 1) at room temperature, it is found that Cs atoms occupy a single absorption site on T3 with a height of 3.18 ± 0.05 Å from the second layer of Si(0 0 1)(2 × 1) surface, and the bond length between Cs and the nearest Si atoms is 3.71 ± 0.05 Å.     

Fuzzy selection and existence of fuzzy fixed point

In this paper, we shall prove a new fuzzy continuous selection theorem in a compact convex set and next a fixed point theorem for fuzzy mappings is established.     

Atomic structure of Cs grown on Si(0 0 1)(2×1) surface by coaxial impact collision ion scattering spectroscopy

The atomic structure and the saturation coverage of Cs on the Si(0 0 1)(2×1) surface at room temperature have been studied by coaxial impact collision ion scattering spectroscopy (CAICISS). For the atomic structure of saturated Cs/Si(0 0 1)(2×1) surface, it is found that Cs atoms occupy a single adsorption site at T3 on the Si(0 0 1) surface. The height of Cs atoms adsorbed at T3 site is 3.18±0.05 Å from the second layer of Si(0 0 1)(2×1) surface. The saturation coverage estimated from the measured CAICISS intensity ratio and the proposed atomic structure is found to be 0.46±0.06 ML.     

Gamma-ray pulse height spectrum of241Am-Be source by ‘Li-BC501 (n-γ) spectrometer system

Neutrons from a source are moderated by means of hydrogenous materials such as polyethylene (PE) or water to reduce the energy of fast neutrons and to increase the fluence rate of moderated neutrons. The rise-time and -ray pulse height spectrum from a PE moderated²⁴¹Am-Be neutron-gamma (n-) mixed source were measured by using⁶Li-BC501 scintillation detector and pulse shape discriminator (PSD) system. The difference in rise-time between and neutron signals tumed out to be 18.5 ns for the⁶Li-BC501 (n-) spectrometer system. The figure of merit (FOM) for this separation was estimated to be 1.52, and this was compared with the published results. From this comparison, the⁶Li-BC501 system has much superior characteristics in (n-) separation to other detector systems. Two Compton edges at around 1.87 and 3.99 MeV which are produced by H(n,)D reaction and by the first excited state of¹²C^* from Be(, n)¹²C^* reaction were also investigated.     

Neutron activation analysis with PE moderated252Cf neutron source

The 1.369 MeV -rays emitted from²⁴Na²⁴Mg+^–+ after²³Na(n,)²⁴Na reaction were counted by high purity germanium (HPGe) detector and the half-life of²⁴Na was derived. This process was simulated by Monte Carlo Neutron and Photon Transport Code (MCNP-4A).²⁵²Cf neutron source was moderated by a polyethylene (PE) cylinder to increase the cross section of neutron absorption reaction and to decrease the biological hazard. NaCl powder of 20 cm³ and 40 cm³ volume in cylindrical polypropylene capsules were irradiated by the neutrons passed through the moderator. MCNP-4A was used to determine the optimum size of PE moderator, to assume the realistic geometry of the HPGe detector, and to assume the absolute efficiencies of the detector. The count rates for 1.369 MeV -rays in the HPGe detector were calculated by MCNP-4A for 20 cm³ and 40 cm³ NaCl. The accumulated counts calculated tumed out to be higher than those actually measured by 31% with a relative error of 3%. The half-life of²⁴Na measured within 4% and 1% for 20 cm³ and 40cm³ NaCl agrees with that of the reference. So, we can say that the result of MCNP-4A has about 30% of accuracy and 3% of precision in simulating the neutron activation analysis.     

Modular posets and semigroups

Posets and poset homomorphisms (preserving both order and parallelism) have been shown to form a category which is equivalent to the category of pogroupoids and their homomorphisms. Among the posets those posets whose associated pogroupoids are semigroups are identified as being precisely those posets which are (C ₂+1)-free. In the case of lattices this condition means that the lattice is alsoN ₅-free and hence modular. Using the standard connection: semigroup to poset to pogroupoid, it is observed that in many cases the image pogroupoid obtained is a semigroup even if quite different from the original one. The nature of this mapping appears intriguing in the poset setting and may well be so seen from the semigroup theory viewpoint.     

On L-fuzzy Ideals in Semirings I

In this paper we extend the concept of an L-fuzzy (characteristic) left (resp. right) ideal of a ring to a semiring R, and we show that each level left (resp. right) ideal of an .L-fuzzy left (resp. right) ideal of R is characteristic iff is L-fuzzy characteristic.     

Competitive reaction pathways in the nucleophilic substitution reactions of aryl benzenesulfonates with benzylamines in acetonitrile

The reactions of aryl benzenesulfonates (YC6H4SO2OC6H4Z) with benzylamines (XC6H4CH2NH2) in acetonitrile at 65.0 degrees C have been studied. The reactions proceed competitively by S-O (kS-O) and C-O (kC-O) bond scission, but the former provides the major reaction pathway. On the basis of analyses of the Hammett and Br?nsted coefficients together with the cross-interaction constants rho(XY), rho(YZ), and rho(XZ), stepwise mechanisms are proposed in which the S-O bond cleavage proceeds by rate-limiting formation of a trigonal-bipyramidal pentacoordinate (TBP-5C) intermediate, whereas the C-O bond scission takes place by rate-limiting expulsion of the sulfonate anion (YC6H4SO3-) from a Meisenheimer-type complex.