Giant optical activity in quasi-two-dimensional planar nanostructures

We examine the spectral dependence in the visible frequency range of the polarization rotation of two-dimensional gratings consisting of chiral gold nanostructures with subwavelength features. The gratings, which do not diffract, are shown to exhibit giant specific rotation (approximately 10(4) degrees/mm) of polarization in direct transmission at normal incidence. The rotation is the same for light incident on the front and back sides of the sample. Such reciprocity indicates three dimensionality of the structure arising from the asymmetry of light-plasmon coupling at the air-metal and substrate-metal interfaces. The structures thus enable polarization control with quasi-two-dimensional planar objects. However, in contradiction with recently suggested interpretation of experiments on larger scale but otherwise similar structures, the observed polarization phenomena violate neither reciprocity nor time-reversal symmetry.     

Infrared-active vibrational modes of single-walled carbon nanotubes

The IR-active vibrational modes of single-walled carbon nanotubes have been observed by optical transmission through thin films of bundled nanotubes. Because IR-active chemical functional groups, e.g., -COOH, -OH, might be attached to the tube walls and contribute additional spectral features, we have also studied the effects of chemical purification and long-term high-temperature vacuum annealing on the IR spectrum. Through comparison with theory, we are able to assign much of the sharp structure observed in our IR spectra.     

A study on a micro mover driven by ultrasonic waves

In developing a mobile micro robot, it is important to realize an effective energy supply method. The existing general method is to supply energy from outside through a cable. However, supplying energy through a cable adds weight and restricts movement. Mounted energy sources, such as batteries, also add weight. We therefore propose a method of supplying energy to a robot externally without using a cable. Using the radiation of ultrasonic waves as a wave energy source, we devised a mover that can receive and use wave energy for propulsion. We investigated and clarified the movement this prototype mover through various experiments. Consequently, we proved the use of ultrasonic waves to be effective as a cable-free energy supply.     

Molecular dynamics and residual entropy in the soft crystal, SmE phase, of 4-butyl-4'-isothiocyano-1,1'-biphenyl

Molecular dynamics and resulting disorder in the soft crystal, smectic E (SmE) phase, were studied in detail for the title compound, 4-butyl-4'-isothiocyano-1,1'-biphenyl (4TCB), by (1)H NMR spectroscopy and adiabatic calorimetry. The ordered crystal phase of 4TCB was realized for the first time under ambient pressure after long two-step annealing and used as the reference state in the analysis of the experimental results. Four motional modes were identified in the SmE phase through the analysis of the (1)H NMR T(1). The residual entropy was determined as ca. 6 J K(-1) mol(-1). This magnitude implies that most of the disorder in the SmE phase at high temperatures is removed on cooling except for the head-to-tail disorder of the rod-shaped 4TCB molecule. Standard thermodynamic functions are tabulated below 375 K.     

Stereoselective photooxidation of enecarbamates: reactivity of ozone vs singlet oxygen

[reaction: see text]. Oxazolidinone-functionalized enecarbamates show contrasting behavior upon oxidation by singlet oxygen and by ozone. The observed stereoselectivity difference indicates that the oxidation with ozone is subject to classic steric effects, whereas the very high selectivity in the photooxidation with singlet oxygen is derived from vibrational deactivation.     

Alkyl group as entropy reservoir in an MMX chain complex, Pt2(n-PenCS2)4I

Heat capacity of halogen-bridged one-dimensional binuclear metal complex (so-called MMX chain) having four n-pentyl groups, Pt2(n-PenCS2)4I, was measured by adiabatic calorimetry. A first-order phase transition was observed at 207.4 K when measurement was made after cooling from room temperature. The enthalpy and entropy of transition were determined to be 10.19 kJ mol(-1) and 49.1 J K(-1) mol(-1), respectively. A monotropic phase transition was observed at 324 K on heating, and the entropy of transition was essentially null. The sample once heated above 324 K never returned to the initial phase at room temperature and underwent a higher-order phase transition at 173 K and a first-order phase transition at 220.5 K. The enthalpy and entropy of the first-order phase transition were estimated to be 11.6 kJ mol(-1) and 52.4 J K(-1) mol(-1), respectively. The magnitude of the entropy gain at the phase transition from the initial room-temperature phase to the high-temperature phase at 324 K shows that in Pt2(n-PenCS2)4I a large amount of entropy reserved in alkyl chain is transferred to dithiocarboxylato groups upon the phase transition, as in the cases of Pt2(n-PrCS2)4I and Pt2(n-BuCS2)4I.     

Analysis of activation in anterior cingulate cortex during cognitive process of selection following somatosensory stimuli: fMRI study with elaborate task paradigms

The anterior cingulate cortex (ACC) has been pointed out to play an important role in the cognitive process of selection underlying "early selection" of perceptually (visually or auditorily) and "late selection" of behaviorally relevant information. However, it is still unclear in cognitive process of selection that the ACC can be activated by somatosensory stimuli as perceptually relevant information. To determine whether the ACC is activated by "early selection" of somatosensory stimuli surely without effects of motor acts as behavior, eighteen normal subjects performed elaborately designed tasks of selection while receiving somatosensory stimuli on their toes of the right and left feet under three different conditions using functional magnetic resonance imaging (fMRI) at 1.5 T. ACC activation was observed to be 2.1+/-0.3% (mean +/- SE) in selection and finger movement as motor acts, and 1.3+/-0.3% in selection and counting (without motor acts), whereas there was no activation in non-selection. The present fMRI study demonstrates that the ACC is activated by "early selection" following somatosensory stimuli surely without subsequent motor acts.     

Convenient synthesis of alpha-trifluoromethylated acyloins from alpha-hydroxy or alpha-amino acids

Alpha-trifluoromethylated acyloins (2 and 6) have been prepared from alpha-hydroxy acids (1), N-acylprolines (5) or N-acyl-N-alkyl alpha-amino acids (8) by novel transformation reactions with trifluoroacetic anhydride (TFAA) in the presence of pyridine. The former reaction of 1 could proceed through mesoionic 1,3-dioxolium-4-olates, whereas the latter two reactions of alpha-amino acids (5 and 8) could involve mesoionic 1,3-oxazolium-5-olates. The reaction of 1 with TFAA shows more potential for practical applications because of the ready availability of the starting materials and ease of manipulation.     

Alexander numbering of knotted surface diagrams

A generic projection of a knotted oriented surface in 4-space divides -space into regions. The number of times (counted with sign) that a path from infinity to a given region intersects the projected surface is called the Alexander numbering of the region. The Alexander numbering is extended to branch and triple points of the projections. A formula that relates these indices is presented.