Quantum Zeno effect for exponentially decaying systems

The quantum Zeno effect--suppression of decay by frequent measurements--was believed to occur only when the response of the detector is so quick that the initial tiny deviation from the exponential decay law is detectable. However, we show that it can occur even for exactly exponentially decaying systems, for which this condition is never satisfied, by considering a realistic case where the detector has a finite energy band of detection. The conventional theories correspond to the limit of an infinite bandwidth. This implies that the Zeno effect occurs more widely than expected thus far.     

Total synthesis of (+)-batzelladine A and (-)-batzelladine D, and identification of their target protein

Asymmetric total synthesis of batzelladine A (1) and batzelladine D (2) has been achieved. Our synthesis of batzelladines features 1) stereoselective construction of the cyclic guanidine system by means of successive 1,3-dipolar cycloaddition reaction and subsequent cyclization, 2) direct esterification of the bicyclic carboxylic acid 35 with the guanidine alcohol 8 or 59 to construct the whole carbon skeleton of batzelladines, and 3) one-step formation of the alpha,beta-unsaturated aldehyde 53 from the primary alcohol 47 with tetra-n-propylammoniumperruthenate (TPAP), providing an efficient route to the left-hand bicyclic guanidine alcohol of batzelladine A (1). With the synthetic compounds 1 and 2 in hand, their target protein was examined by using immobilized CD4 and gp120 affinity gels. The results indicated that batzelladines A (1) and D (2) bind specifically to CD4.     

Electronic structures and optical absorption of multilayer graphenes

We study the electronic structures and the optical absorption spectra of the multilayer graphenes in the effective mass approximation. We decompose the Hamiltonian of graphene with an arbitrary thickness into smaller subsystems effectively identical to monolayer or bilayer graphene, and express the optical spectrum as a summation over the subsystems. We include the full band parameters which compose the bulk graphite, and closely study their effects on the band structure. We found that the particular band parameters destroying the electron–hole symmetry can affect the optical spectrum through shift of the absorption edge.     

Transmission electron microscopy imaging of individual functional groups of fullerene derivatives

Mobility and reactivity of the functionalized fullerenes with pyrrolidine (C60-C3NH7) incorporated in single-wall carbon nanotubes were examined by high-resolution transmission electron microscopy. An individual functional group attached to each fullerene cage is unambiguously visualized. This provides a direct evidence for the functionalized structure on a single-molecular basis. A rotational motion of the incorporated molecules tends to occur during the observation and, consequently, each fullerene molecule is likely to stand facing its functionalized group towards the nanotube wall. A fine structure analysis of electron energy-loss spectra for the nitrogen K(1s) edge shows a considerable change in the nitrogen chemical state and suggests a strong tube-fullerene interaction.     

Highly luminescent glycocluster: silole-core carbosilane dendrimer having peripheral globotriaose

A novel glycocluster periphery functionalized by globotriaose (Galα1-4Galβ1-4Glcβ1-) possessing a silole moiety as a luminophor was synthesized. The photoluminescence spectrum of the glycocluster in pure water showed extremely strong emission at 475 nm. Analogous intense emission of the silole dendrimer was also observed in a lower water fraction of water/acetone mixture. The water fraction of the silole dendrimer solution strongly affected the emission intensity; however, these luminescences were constantly detected at around 475 nm.     

Radiation damage analysis of 7,7,8,8,-tetracyanoquinodimethane (TCNQ) and 2,3,5,6,-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (F4TCNQ) by electron diffraction and electron energy loss spectroscopy

The electron irradiation sensitivity is compared between TCNQ and F(4)TCNQ. The characteristic doses, D(1/e), determined by the attenuation of the diffraction intensities are 0.08-0.11Ccm(-2) for TCNQ, and 0.04-0.06Ccm(-2) for F(4)TCNQ, respectively. It is found that F(4)TCNQ is more sensitive to radiation damage than TCNQ in spite of the substitution of hydrogen with fluorine. From electron energy-loss spectroscopy (EELS), it is found that the damaging process for the two materials begins in a similar way, as seen from mass loss and spectrum changes observed for doses which exceed the characteristic dose. Although sensitive to the sample orientation, the carbon K-edge fine structures of TCNQ are almost preserved below the critical dose. Theoretical calculation predicts that the scission of hydrogen contributes to the spectrum shape very little compared to nitrogen scission. Beyond the characteristic dose, fluorine loss from F(4)TCNQ occurs faster than nitrogen loss but little loss of carbon is observed. In a similar way, nitrogen loss from TCNQ occurs beyond the characteristic dose, while carbon appears constant. From detailed analysis of the carbon and nitrogen K-edge fine structures of TCNQ and F(4)TCNQ, it is found that the pi* peak of nitrogen in TCNQ decreases below the characteristic dose, while pi* loss of nitrogen in F(4)TCNQ, and pi* loss and sigma* increase of carbon in both materials are observed beyond the characteristic dose. The changes in the fine structures are believed to be due to the chemical alteration such as cross-linking, in which the pi-bonding system of nitrogen or carbon turns into sigma-bonding. The difference in characteristic dose between TCNQ and F(4)TCNQ is explained by considering "effective molecular occupancy", where F(4)TCNQ has a larger intermolecular empty space than TCNQ.     

Hofstadter butterfly and integer quantum hall effect in three dimensions

For a three-dimensional (3D) lattice in magnetic fields we have shown that the hopping along the third direction, which normally smears out the Landau quantization gaps, can rather give rise to a Hofstadter's butterfly specific to 3D when a criterion is fulfilled by anisotropic (quasi-one-dimensional) systems. In 3D the angle of the magnetic field plays the role of the field intensity in 2D, so that the butterfly can occur in much smaller fields. We have also calculated the Hall conductivity in terms of the topological invariant in the Kohmoto-Halperin-Wu formula, and each of sigma(xy),sigma(zx) is found to be quantized.