Strong generators of the subregular $$\mathcal {W}$$W-algebra $$\mathcal {W}^{K-N}(\mathfrak {sl}_N,f_{sub})$$WK-N(slN,fsub) and combinatorial description at critical level

Letters in Mathematical Physics - We construct explicitly strong generators of the affine $$\mathcal {W}$$-algebra $$\mathcal {W}^{K_0-N}(\mathfrak {sl}_N, f_{sub})$$ of subregular type A....     

An approach to normalization of coarticulation effects for vowels in connected speech

A method is proposed to reduce the ambiguity of vowels in connected speech by normalizing the coarticulation effects. The method is applied to vowels in phonetic environments where great ambiguity would be likely to occur, taking as their features the first and second formant trajectories. The separability between vowel clusters is found to be greatly improved for the vowel samples. In addition, distribution of the vowels on a feature plane characterized by this method seems to reflect their perceptual nature when presented to listeners without isolation from their phonetic environments. The results suggest that the method proposed here is useful for automatic speech recognition and help infer some possible mechanisms underlying dynamic aspects of human speech recognition.     

New fabrication method for anisotropic gratings formed in photocrosslinkable polymer liquid crystals

We present a new fabrication method, called two-step ultraviolet exposure, to prepare anisotropic gratings in photocrosslinkable polymer liquid crystal films. Using the controllability of the reorientation direction of mesogenic molecules, anisotropic phase gratings, in which the mesogenic molecules were periodically modulated in orthogonal directions, were prepared by the use of one grating photomask. The resultant gratings diffract the light and convert the polarization states at the same time, and have applications as diffraction optical devices. PACS 42.65.Hw; 42.70.Df; 42.70.Nq; 78.20.-e; 78.40.Me     

Reliability of mean transit time obtained using perfusion-weighted MR imaging; comparison with positron emission tomography

The purpose of this project was to assess the reliability of the cerebral mean transit time (MTT) obtained using perfusion-weighted MR imaging by comparing it with the MTT obtained when performing positron emission tomography (PET). Ten patients with chronic occlusive cerebrovascular disease were investigated. They had either unilateral internal carotid artery occlusion or middle cerebral artery occlusion. The regions-of-interest were placed in non-infarcted areas within the territory of the middle cerebral artery on the affected side. Control regions-of-interest were placed in mirrored regions of the contralateral side. Linear regression analyses were performed using the parameters of the MTT obtained with perfusion-weighted MR imaging and the MTT, cerebral blood flow, vascular reactivity, and oxygen extraction fraction obtained with PET. The respective MTTs of the affected and non-affected sides obtained with perfusion-weighted MR imaging versus those with PET were 7.3 +/- 2.2 s and 6.0 +/- 1.2 s versus 8.2 +/- 3.0 s and 6.4 +/- 1.7 s. The MTT obtained using perfusion-weighted MR imaging and PET demonstrated statistically significant correlation (r = 0.87, p < 0.0001). The MTT obtained with perfusion-weighted MR imaging correlated statistically with cerebral blood flow (r = -0.74, p < 0.001), vascular reactivity (r = -0.73, p < 0.001) and oxygen extraction fraction (r = 0.61, p < 0.01). Similarly, the MTT obtained using PET statistically correlated with cerebral blood flow (r = -0.78, p < 0.0001), vascular reactivity (r = -0.51, p < 0.05) and oxygen extraction fraction (r = 0.68, p < 0.01). The reliability of the MTT obtained using perfusion-weighted MR imaging appears to be approximately equal to that obtained with positron emission tomography.     

Fabrication and optical reflection behavior of a two-dimensional barium titanate ceramic photonic crystal

We demonstrate a method for fabricating a two-dimensional hexagonal array of nanoscale barium titanate ceramic pillars. A precursor array was prepared by introducing a sol solution into an electron-beam resist mold with air holes and subsequently dry etching the unnecessary gel layer formed on the mold. A ceramic array, consisting of barium titanate ceramic pillars with a radius of 85 nm, a lattice constant of 450 nm, and a height of 500 nm, was fabricated by sintering the precursor array at 1073 K. The reflection spectra for the ceramic array in the visible range revealed the underlying photonic band gaps, which were in good agreement with results calculated using a plane-wave method. PACS 77.84.-s; 42.70.-a; 42.70.Qs     

Experimental evaluation and constitutive modeling of non-proportional deformation for asymmetric steels

Recently non-proportional deformation has received increased attention from researchers working in the area of experimental and computational modeling of metal deformation. However, most of them are numerical in nature with limited experimental data available, making it further difficult to model non-proportional deformation. In the present work, two-stage uniaxial tests, along with uniaxial cyclic and biaxial tests for different stress ratios, have been performed to evaluate deformation behavior of ultra-low carbon high strength automotive steel. Behaviors like cross-effect and hardening stagnation, which are attributed to the evolution of complex dislocation structures, were observed in this steel. It was also noticed that this steel exhibits tension-compression asymmetry. As for constitutive modeling, a modified asymmetric yield function is proposed to be used with a combined isotropic-kinematic hardening model. Also methods to account for the hardening stagnation during reverse loading and the cross-effect during two-stage deformation are proposed. The resulting constitutive model showed reasonably good agreement with experimental results.     

Stress-optical studies of VI B transition metal dichalcogenides

The effect of a uniaxial stress on the excitonic optical spectra are studied for MoS₂, WS₂, MoSe₂ and WSe₂. Stress dichroism appears in the A′, B′ excitons in diselenides, while it is absent in the A, B excitons in the four compounds. The A′, B′ excitons shift oppositely to the A, B excitons, indicating that A, B and A′, B′ are not pair excitons split by interlayer interaction.     

Identification of low chlorinated biphenyls in human milk by gas chromatography--mass spectrometry.

Trichlorobiphenyl and tetrachlorobiphenyls in human milk were analysed by gas chromatography--mass spectrometry and mass fragmentography using silicone OV-1 and Apiezon L grease as stationary phases. Low-chlorinated biphenyls had been considered to be excreted rapidly from the body, but in this work quantities of tri- and tetrachlorobiphenyls amounting to approximately 30% of the total of polychlorinated biphenyls (PCBs) accumulated in the milk were identified. This result is important in relation to the quantification of PCBs and in studies of the mechanism of biological degradation.