Inference on High-Dimensional Mean Vectors with Fewer Observations Than the Dimension

We focus on inference about high-dimensional mean vectors when the sample size is much fewer than the dimension. Such data situation occurs in many areas of modern science such as genetic microarrays, medical imaging, text recognition, finance, chemometrics, and so on. First, we give a given-radius confidence region for mean vectors. This inference can be utilized as a variable selection of high-dimensional data. Next, we give a given-width confidence interval for squared norm of mean vectors. This inference can be utilized in a classification procedure of high-dimensional data. In order to assure a prespecified coverage probability, we propose a two-stage estimation methodology and determine the required sample size for each inference. Finally, we demonstrate how the new methodologies perform by using a microarray data set.     

Oxygen distribution in nickel silicide films analyzed by time-of-flight secondary ion mass spectrometry

The oxygen distribution in Ni₂Si and NiSi films formed during a two-step silicidation process was analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS mass spectra revealed that both silicon and nickel reacted with oxygen at the Ni₂Si surface. In addition, silicon nitride was formed at the surface by the reaction of silicon with nitrogen in the TiN capping layer during the first silicidation annealing. The amount of nitrogen at the NiSi surface varied with silicidation annealing temperature and with the formation conditions of the TiN capping layer. We also showed that a small amount of oxygen was penetrated into the NiSi film and strongly affected the level of junction leakage current in n⁺–p junctions in n-channel MOSFETs. The oxygen concentration in the NiSi film decreased with an increase in the amount of nitrogen at the NiSi surface.     

High-throughput nitric oxide assay in biological fluids using microchip capillary electrophoresis

In order to develop a high-throughput screening method for the nitrogen monoxide metabolites, nitrite and nitrate, in biological fluids, we have investigated the simultaneous determination of these metabolites using microchip capillary electrophoresis (MCE). In this study, the control of applied voltage to obtain higher sensitivity by increasing the sample injection volume was investigated. Also, the improvement of reproducibility by correcting the injection volume using the internal standard was investigated. By increasing the sample volume, the limits of detection achieved for nitrite and nitrate were 24 and 12 microM, respectively. Because we used a 10-fold diluted sample when detecting nitrite and nitrate in human serum, it was necessary to increase the sensitivity by a factor of 10-50. The run-to-run and day-to-day relative standard deviations achieved were improved to less than 10% by using an internal standard to correct the injection volume. Moreover, we obtained successful separation of nitrite and nitrate in spiked human serum within 6.5 s under optimum analytical conditions. As a result, although it is necessary to obtain greater sensitivity, it was concluded that determination of the amount of NO metabolites in biological fluids using MCE is possible.     

Dissociation energetics of the phenol(+)⋯Ar(2) cluster ion: The role of π→H isomerization

The dissociation energetics in the phenol(+)?Ar(2)(2π) cluster ion have been investigated using photoionization efficiency and mass analyzed threshold ionization spectroscopy. The appearance energies for the loss of one and two Ar atoms are determined as ～210 and ～1115?cm(-1), respectively. The difference between the appearance energy for the first Ar ligand in phenol(+)?Ar(2)(2π) and the dissociation energy of the phenol(+)?Ar(π) dimer (535cm(-1)) is explained by the isomerization of one π-bound Ar ligand to the OH binding site (H-bond) upon ionization. The energy difference between phenol(+)?Ar(2)(2π) and phenol(+)?Ar(2)(H/π) could also be estimated to be around 325cm(-1), which corresponds roughly to the difference of the binding energy of a π-bound and H-bound Ar ligands. The binding energy of the H-bound Ar atom in phenol(+)?Ar(2)(H/π) is derived to be ～905cm(-1).     

Potentiality of IMAC as Sample Pretreatment Tool in Food Analysis for Veterinary Drugs

Immobilized metal ion affinity chromatography (IMAC) was evaluated as a sample pretreatment tool for residual veterinary drugs (VDs) in food. A test of six cations for the IMAC efficiency revealed that Cu²⁺ and Fe³⁺ were suitable in retaining tetracyclines, quinolones (QLs: fluoroquinolones, acid quinolones), macrolides, β-lactams, and aminoglycosides, but ineffective for sulfonamides and hormones. These results showed the IMAC had great potential for a multiclass multiresidual VDs analysis in a simple and selective way. This methodology was applied on milk analysis for eleven QLs, involving extraction with (1:1) acetonitrile/methanol and IMAC with Fe³⁺. Averaged recoveries ranged from 68 to 93% and limits of quantitation from 2 to 26 ng mL^?1. Ten commercial milk samples were found to be free from the QLs.     

Light-scattering study of polyelectrolyte complex formation between anionic and cationic nanogels in an aqueous salt-free system

We studied complex formation in an aqueous salt-free system (pH approximately 3 and at 25 degrees C) between nanogel particles having opposite charges. Anionic gel (AG) and cationic gel (CG) particles consist of lightly cross-linked N-isopropylacrylamide (NIPA) copolymers with 2-acrylamido-2-methylpropane sulfonic acid and with 1-vinylimidazole, respectively. The number of charges per particle was -4490 for AG and +20 300 for CG, as estimated from their molar masses (3.33 MD for AG and 11.7 MD for CG) by static light scattering (SLS) and their charge densities (1.35 mmol/g for AG and 1.74 mmol/g for CG) by potentiometric titration. The complexes were formed through the addition of AG to CG and vice versa using a turbidimetric titration technique. At the endpoint of the titration, the aggregate formed was a complex based upon stoichiometric charge neutralization: CG(n)()(+) + xAG(m)()(-) --> CG(n)()(+) (AG(m)()(-))(x)() where x = (n)()/(m)(). At different stages of the titration before the endpoint, the resulting complexes were examined in detail using dynamic light scattering, SLS, and electrophoretic light scattering (ELS). The main results are summarized as follows: (i) When AG with a hydrodynamic radius (R(h)) of 119 nm is added to CG (R(h) approximately 156 nm), the (R(h)) of the complex size decreases from 156 to 80 nm. (ii) In contrast to this (R(h)) change, the molar mass increases from 11.7 MD to 24 MD with increasing amounts of added AG. (iii) Upon addition of CG to AG, the complex formed has the same size ((R(h)) approximately 80 nm) and the same molar mass (55 +/- 2.5 MD) until 55 +/- 5% of AG has been consumed in the complexation. To understand these results, we used the following two models: the random model (RM), in which the added AG particles uniformly bind to all of the CG particles in the system via a strong electrostatic attraction, and the all-or-none model (AONM), in which part of the AG particles in the system preferably bind to the added CG particles to neutralize their electric charges but the other AG particles are uncomplexed and remain in the system. The complex formations upon addition of AG to CG and CG to AG were elucidated in terms of RM and AONM, respectively.     

Neutron diffraction data and molecular dynamics simulations of the molten mixture Ag(Br0.7I0.3)

The structure factors of the ionic liquid mixture Ag(Br(0.7)I(0.3)) at three temperatures, 723, 923, and 1023 K, as well as of the pure molten AgI at 923 K and the pure molten AgBr at 773 and 923 K, were studied experimentally and by means of molecular dynamics simulations. The experiments were carried out using the high intensity total scattering time-of-flight spectrometer, HIT-II, at the KENS spallation neutron source in Japan. The experimental data are very reliable, with the possible exception of the small momentum transfer region, whose accessibility is limited by neutron energy and detector positions. The simulations made use of the semiempirical rigid ion potentials of the Vashishta-Rahman [Phys. Rev. Lett. 40, 1337 (1978)] type using a new set of parameters appropriate for the mixture. Within the known constraints of the pairwise rigid ion potentials, the simulated structure factors are in fair agreement with experiment. The results for the pair distribution functions suggest that the molten mixture retains the superionic character found in previous calculations of both the AgI and AgBr melts. This suggestion is confirmed by the results for the self-diffusion coefficients. Values obtained for the ionic conductivities are also presented.     

Vibronic coupling in benzene cation and anion: vibronic coupling and frontier electron density in Jahn-Teller molecules

Vibronic coupling constants of Jahn-Teller molecules, benzene radical cation and anion, are computed as matrix elements of the electronic part of the vibronic coupling operator using the electronic wave functions calculated by generalized restricted Hartree-Fock and state-averaged complete active space self-consistent-field methods. The calculated vibronic coupling constants for benzene cation agree well with the experimental and theoretical values. Vibronic coupling density analysis, which illustrates the local properties of the coupling, is performed in order to explain the order of magnitude of the coupling constant from view of the electronic and vibrational structures. This analysis reveals that the couplings of the e2g2 and e2g3 modes in which the large displacements locate on C-C bonds are strong in the cation. On the other hand, they are greatly weakened in the anion because of the decrease of electron density in the region of the C-C bonds, which originates from the antibonding nature of the singly occupied molecular orbital of the anion. However, the difference of the electronic structure has a little influence on the vibronic coupling of the e2g4 mode. These results indicate that the vibronic coupling depends not only on the direction of the nuclear displacement but also on the frontier electron density.     

Degradation of protein in nanoplasma generated around gold nanoparticles in solution by laser irradiation

We developed a method of protein degradation in an aqueous solution containing gold nanoparticles by irradiation of a pulse laser. In the present study, lysozyme was used as an example. Lysozyme degradation proceeded most efficiently when a pH of the solution was adjusted so that it was at the isoelectric point. The scheme of the lysozyme degradation is as follows: (1) Lysozyme molecules in the solution are neutralized and adsorbed on the gold nanoparticles with its pH value adjusted at the isoelectric point, (2) nanoplasma is generated in the close vicinity of a gold nanoparticle which is excited by an intense 532-nm laser, (3) lysozyme molecules in the nanoplasma are degraded into small fragments. Lysozyme degradation does not proceed efficiently at a pH value deviated from the isoelectric point because the lysozyme molecules are dissolved uniformly so that only a small portion of the lysozyme molecules are located in the vicinity of gold nanoparticles which create the nanoplasma.     

Thick silica gel coatings on methylsilsesquioxane monoliths using anisotropic phase separation

Silica gel coatings on methyltrimethoxysilane (MTMS)-derived monoliths have been studied using wetting transition. Wetting transition is observed in a small confined space, where a coating solution phase-separates into a well-coarsened dimension, making all the phase-separating polymerizing silica phase dynamically flow onto the existing surface of a mold. Bulk coating experiments have shown reductions of both macropore volume and diameter due to the coated layer. Comparing HPLC efficiencies of the coated monolith with those of the non-coated MTMS monolith revealed that the retention factors drastically increased in both normal- and reversed-phase modes. This is attributed to the existence of considerable amounts of accessible micropores left inside the coated layer, where analyte molecules travel and adsorb for a considerable period of time.