Strong photo-absorption by a single quantum wire in waveguide-transmission spectroscopy

We measured the absorption spectrum of a single T-shaped, 14x6 nm lateral-sized quantum wire embedded in an optical waveguide using waveguide-transmission spectroscopy at 5 K. In spite of its small volume, the one-dimensional-exciton ground state shows a large absorption coefficient of 80 /cm, or a 98 % absorption probability for a single pass of the 500-um-long waveguide.Comment: 4 pages, 3 figure

Room-temperature excitonic absorption in quantum wires

We measured absorption spectra of T-shaped quantum wires at room temperature using waveguide-transmission spectroscopy. Strong and narrow room-temperature one-dimensional-exciton absorption peak was observed, which shows peak modal absorption coefficient of 160 cm$^{-1}$ per 20 wires with $\Gamma$-factor of $4.3\times10^{-3}$, width of 7.2 meV, and strong polarization anisotropy.Comment: 3pages, 3figure, 1tabl

Imaging of emission patterns in a T-shaped quantum wire laser

Spatially and spectrally resolved microscopic images of spontaneous and stimulated emissions are imaged at the mirror facets of a GaAs T-shaped quantum wire laser with high uniformity. Laser emission from the one-dimensional ground state reveals a circular image located at the core of a T-shaped optical waveguide but significantly smaller in area than the low power spontaneous emission from the same waveguide. These images unambiguously allow assignment of all spontaneous and laser emissions to the wire ground state and respective intersecting wells in the structure.Comment: 4 pages, 3 figure

Zn-induced wipeout effect on Cu NQR spectra in La2−x_{2-x}Srx_xCu1−y_{1-y}Zny_yO4_4

We report a systematic study of Zn-substitution effect on Cu NQR spectrum for high $T_c$ superconductors La$_{2-x}$Sr$_x$Cu$_{1-y}$Zn$_y$O$_4$ from carrier-underdoped to -overdoped regimes (polycrystalline samples, $x$ =0.10, 0.15, and 0.20). We observed no appreciable wipeout effect for the overdoped samples, a gradual and partial wipeout effect below about 80 K for the optimally doped ones, and very abrupt and full wipeout effect below about 40 K for the underdoped ones. The wipeout effect indicates a highly enhanced spectral weight of Cu spin fluctuations at a low frequency. We associate the wipeout effect with a Zn-induced local magnetism far above 40 K and with a localization effect below 40 K.Comment: 2 pages, 3 figures, accepted for publication in Physica C (LT23, Hiroshima 2002

Flow of a falling liquid curtain onto a moving substrate

In this study, we investigate a low-Weber-number flow of a liquid curtain bridged between two vertical edge guides and the upper surface of a moving substrate. Surface waves are observed on the liquid curtain, which are generated due to a large pressure difference between the inner and outer region of the meniscus on the substrate, and propagate upstream. They are categorized as varicose waves that propagate upstream on the curtain and become stationary because of the downstream flow. The Kistler\u27s equation, which governs the flow in thin liquid curtains, is solved under the downstream boundary conditions, and the numerical solutions are studied carefully. The solutions are categorized into three cases depending on the boundary conditions. The stability of the varicose waves is also discussed as wavelets were observed on these waves. The two types of modes staggered and peak-valley patterns are considered in the present study, and they depend on the Reynolds number, the Weber number, and the amplitude of the surface waves. The former is observed in our experiment, while the latter is predicted by our calculation. Both the types of modes can be derived using the equations with periodic coefficients that originated from the periodic base flow due to the varicose waves. The stability analysis of the waves shows that the appearance of the peak-valley pattern requires a significantly greater amplitude of the waves, and a significantly higher Weber number and Reynolds number compared to the condition in which the staggered pattern is observed

Identifying Suspicious Regions of Covid-19 by Abnormality-Sensitive Activation Mapping

This paper presents a fully-automated method for the identification of suspicious regions of a coronavirus disease (COVID-19) on chest CT volumes. One major role of chest CT scanning in COVID-19 diagnoses is identification of an inflammation particular to the disease. This task is generally performed by radiologists through an interpretation of the CT volumes, however, because of the heavy workload, an automatic analysis method using a computer is desired. Most computer-aided diagnosis studies have addressed only a portion of the elements necessary for the identification. In this work, we realize the identification method through a classification task by using a 2.5-dimensional CNN with three-dimensional attention mechanisms. We visualize the suspicious regions by applying a backpropagation based on positive gradients to attention-weighted features. We perform experiments on an in-house dataset and two public datasets to reveal the generalization ability of the proposed method. The proposed architecture achieved AUCs of over 0.900 for all the datasets, and mean sensitivity $0.853 \pm 0.036$ and specificity $0.870 \pm 0.040$. The method can also identify notable lesions pointed out in the radiology report as suspicious regions.Comment: 10 pages, 3 figure

Discotic liquid crystals of transition metal complexes 48: Synthesis of novel phthalocyanine-fullerene dyads and effect of a methoxy group on their clearing points

In our previous work, we could successfully synthesize the 1:1 phthalocyanine-fullerene (Pc-C-60) dyads, (OFbaC(60))PcCu(OCH3) 2, in very high yields (81 similar to 96%) by using Prato reaction. In this study, we have prepared novel Pc-C-60 dyads, (OFbaC(60)) PcM (M = Co (a), Ni (b), Cu (c), metal free (d)) 3a-3d without the methoxy group. The target Pc-C-60 dyads 3a-3d could be successfully synthesized in good yields also by Prato reaction. It is surprising for us that removal of a very small methoxy group from the big (OFbaC(60))PcCu(OCH3) molecule (2) significantly lowers the cp of (OFbaC(60))PcCu (3c) by about 70 degrees C in comparison with that of 2 having the methoxy group. Very interestingly, each of the novel dyads 3a-3d synthesized here shows perfect homeotropic alignment in the tetragonal columnar phase (Col(tet)). Moreover, it is noteworthy that 3c and 3d show only one Col(tet.o) mesophase having ordered stacking distance with perfect homeotropic alignment. Such simple phase transition can contribute to maintain stable performance in wide temperature range, when they will be applied to organic thin film solar cells.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 17(4):264-282 (2013)journal articl