Performance of a prototype microwave frequency standard based on laser-detected,trapped171Yb+ ions

A microwave frequency standard based on buffer gas-cooled¹⁷¹Yb⁺ ions confined in a linear Paul trap has been demonstrated in prototype form. The standard exhibits a fractional frequency instability characterised by an Allan deviation of (_y() = 2.9 × 10^–13–1/2 for < 2 × 10⁴ s. Factors affecting the stability of the standard have been systematically investigated.     

Indentation deformation/fracture of normal and anomalous glasses

Vickers deformation/fracture indentations have been investigated in six silicate glasses. The characteristic damage patterns fall into two distinct groups, according to whether the glass shows “normal” or “anomalous” mechanical behaviour. Observations of the damage morphology during and after contact, of the scales of the deformation and fracture zones, and of the residual stress intensity about the impressions, all point to a basic difference in the local stress/strain micromechanics. This difference is discussed in relation to the factors which control the brittleness of glass.     

Laser cooling of 171Yb+ ions in a linear paul trap

We report laser cooling of trapped ¹⁷¹Yb⁺ ions. The ions are confined in a linear Paul trap. Temperatures below 1 K have been achieved, and evidence of a phase transition to a crystal-like state has been observed. The metastable ² D _3/2 level is drained using a transition at 609.1 nm not previously used for this purpose. Laser cooling of ¹⁷¹Yb⁺ may be of importance to the development of new microwave frequency standards.     

Decompositions of para-complex vector bundles and para-complex affine immersions

In this work we study decompositions of para-complex and para-holomorphic vector-bundles endowed with a connection ? over a para-complex manifold. First we obtain results on the connections induced on the subbundles, their second fundamental forms and their curvature tensors. In particular we analyze para-holomorphic decompositions. Then we introduce the notion of para-complex affine immersions and apply the above results to obtain existence and uniqueness theorems for para-complex affine immersions. This is a generalization of the results obtained by Abe and Kurosu [AK] to para-complex geometry. Further we prove that any connection with vanishing (0, 2)-curvature, with respect to the grading defined by the para-complex structure, induces a unique para-holomorphic structure.     

Spinorial representation of surfaces into 4-dimensional space forms

In this paper we give a geometrically invariant spinorial representation of surfaces in four-dimensional space forms. In the Euclidean space, we obtain a representation formula which generalizes the Weierstrass representation formula of minimal surfaces. We also obtain as particular cases the spinorial characterizations of surfaces in $\mathbb R ^3$ and in $S^3$ given by Friedrich and by Morel.     

Enhancement of antibacterial effect of quaternary ammonium with inorganic nanosheets against <Emphasis Type="Italic">Enterobacter cloacae</Emphasis>

To suppress nosocomial infections, numerous studies of quaternary ammonium cations (R₄N⁺) to improve the antibiotic properties have been investigated. However, most of them reported developments of novel organic or polymeric materials with R₄N⁺. To pioneer antibacterial inorganic materials hybridized with R₄N⁺, a colloidal solution of metal oxide nanosheets, which have a small particle size (typically less than 10 nm), is considered to be a suitable option because oxide nanosheets with a negative surface charge strongly interact R₄N⁺. Herein, we demonstrate for the first time that the high antibacterial/bactericidal effects of titanate nanosheets (TNS) adsorbing tetramethylammonium (TMA-TNS) or tetrabultylammonium ions (TBA-TNS). Their antibacterial effects against Enterobacter cloacae were evaluated using a colony forming unit (CFU) counting method. The results showed that the synthesized TNS composites had superior antibacterial and bactericidal effects to those of free R₄N⁺ and TBA-TNS exhibited the strongest effect (69% CFU reduction compared with that of free TBA⁺ and 98% CFU reduction compared with the control) among the samples examined. Dark incubation was employed to ensure that photocatalytic reaction of semiconducting TNS did not contribute to the process. Compared with TiO₂ spherical particles, such high bactericidal effect would be induced by a synergistic function of TBA⁺ and TNS, which physically damages bacteria due to long hydrophobic alkyl chains and an anisotropic nanocrystalline structure with sharp edges, respectively.