We report the formation of a series of metal-containing hydrogenated silicon clusters using an ion trap. Mass analyses reveal that many types of transition metal ions M(+) ( M = Hf, Ta, W, Re, Ir, etc.) react with silane (SiH4) to form dehydrogenated MSi( +)(n) cluster ions ( n = 14, 13, 12, 11, 9, respectively) as an end product, indicating that the metal atom is endohedral and stabilizes the Si polyhedral cage. This finding is confirmed by our ab initio calculation that WSi12 is a W-encapsulating Si12 cage cluster, and is very stable owing to both the electronic and the geometrical shell closures.

Motor proteins are able to move protein filaments in vitro. However, useful work cannot be extracted from the existing in vitro systems because filament motions are in random directions on two-dimensional surfaces. We succeeded in restricting kinesin-driven movements of microtubules along linear tracks by using micrometer-scaled grooves lithographically fabricated on glass surfaces. We also accomplished the extraction of unidirectional movement from the bidirectional movements along the linear tracks by adding arrowhead patterns on the tracks. These "rectifiers" enabled us to construct microminiturized circulators in which populations of microtubules rotated in one direction, and to actively transport microtubules between two pools connected by arrowheaded tracks in the fields of micrometer scales.

We report on muon spin relaxation measurements of the 4f 2 -based heavy-fermion superconductor filled-skutterudite PrOs4Sb12. The results reveal the spontaneous appearance of static internal magnetic fields below the superconducting transition temperature, providing unambiguous evidence for the breaking of time-reversal symmetry in the superconducting state. A discussion is made on which of the spin or orbital component of Cooper pairs carries a nonzero momentum.PACS numbers: 74.70. Tx, 76.75.+i, 74.70.Dd, 74.25.Ha Many unconventional superconducting (SC) states, as in Ce-and U-based heavy-fermion (HF) compounds or high-T c cuprates, appear in close proximity to magnetic instabilities when a certain parameter (pressure, atomic doping, or oxygen content) is varied [1,2,3]. This fact strongly suggests that the attractive interactions binding electrons into Cooper pairs are mediated by magnetic moment fluctuations. As another possible pairing glue, fluctuations of quadrupole moments-distorted shapes of the electronic clouds of ions, are theoretically considered to be possible [4,5]. An interesting question to be addressed is what is the nature of superconductivity in such a system. For this study, Pr-based compounds with a 4f 2 configuration are likely candidates, since nonmagnetic but quadrupolar active low-energy levels can be realized due to the crystalline-electric-field (CEF) effect; in 5f systems, CEF levels are less clear due to the tendency to be itinerant.One promising candidate material for this study is the recently found superconductor PrOs 4 Sb 12 [6], which is to date the only known Pr-based HF superconductor, with a superconducting transition temperature of 1.82 K (hereafter referred to as T c1 ). The estimated electronic specific heat coefficient γ = 350 − 700 mJ/K 2 mol [6,7] and the enhanced cyclotron-effective masses [8] reflect the existence of strong electron correlations. Specific heat (C), magnetic susceptibility (χ), and inelastic neutron studies provide evidence that PrOs 4 Sb 12 has a nonmagnetic ground state and a magnetic triplet excited state separated by ∆E CEF /k B = 8 K [7,9], which is 5 times larger than T c1 . In the temperature-versus-magneticfield (T -vs-H) phase diagram, a field-induced ordered phase (µ 0 H 4 T) [9] appears close to the superconducting phase (the upper critical field µ 0 H c2 = 2.2 T). It was recently proven to be an antiferro-quadrupolar ordered phase by elastic neutron scattering measurements [10]. This fact strongly indicates that quantum quadrupole fluctuations of the Pr ions play an important role in realizing the HF superconductivity in PrOs 4 Sb 12 , considering that the T -vs-H phase diagram is analogous to those for the HF and cuprate systems, where a magnetically ordered phase exists close to the SC phase in the T -vs-pressure, -atomic-doping, or -oxygen-content phase diagram. This scenario is further supported by the enhanced T c1 compared to T c = 0.74 K for a 4f 0 reference compound LaOs 4 Sb 12 [8,11].The remarkable unconventional SC properties ...

On the basis of a topological discussion as well as an ab initio calculation, we show that it is possible to construct a fullerene-like Si cage by doping of a transition metal atom. The cage is a simple 3-polytope which maximizes the number of its inner diagonals close to the metal atom. Our topological argument also reveals how closely the structure of the fullerene-like Si cages studied is related to that of fullerenes themselves.

Electron beam (e-beam) irradiation has been found to reduce the dissolution rate of evaporated C60 films in organic solvents such as monochlorobenzene, which shows that this material acts as a negative e-beam resist with a sensitivity of 1×10-2 C/cm2. It has higher dry-etch durability than conventional novolac resists. Its applicability to nanofabrication has been demonstrated by fabricating Si pillars of 20–30 nm diameter using electron cyclotron resonance microwave plasma etching and dot patterns defined in the C60 film as etching masks.

The imaging of living specimens in water by x-ray microscopy can be greatly enhanced with the use of an intense flash x-ray source and sophisticated technologies for reading x-ray images. A subnanosecond [corrected] x-ray pulse from a laser-produced plasma was used to record the x-ray image of living sea urchin sperm in an x-ray resist. The resist relief was visualized at high resolution by atomic-force microscopy. Internal structure of the sperm head was evident, and the carbon density in a flagellum was estimated from the relief height.

The authors demonstrate the ability of scanning tunneling microscopy and spectroscopy to simultaneously measure the distributions of both the surface potential and the individual dopant atoms on the atomically flat hydrogen-terminated Si(111) surfaces prepared by an aqueous NH4F etching without disturbing the original dopant distribution. At the p-n junctions, the acceptor and donor atoms were detected distinctly, and the variation in the observed height reflected the surface potential under the biasing condition. Further, a strong correlation between the dopant fluctuations and the surface potential distributions was identified.

We have studied stable structures of hydrogenated Si clusters grown from silane gas in an ion trap developed for cluster growth. The grown clusters were extracted from the ion trap through two different pathways and were analyzed by mass spectrometers. The Si6Hx+ cations were stably grown, among them clusters with x=1, 7, and 13 were always observed, regardless of the growth conditions or the extraction pathways. The stable structures of these clusters were theoretically investigated. Clusters of x=1, 7, and 13 corresponded to the compact structure, the intermediate structure which has both compact and bulklike configurations, and the bulklike sp3 structure, respectively.