Improvements of detection accuracy and its confidence of defective areas by YOLOv2 using a data set augmentation method

Artificial Life and Robotics - Recently, CNN (Convolutional Neural Network) and Grad-CAM (Gradient-weighted Class Activation Map) are being applied to various kinds of defect detection and position...     

Noncontact pulse wave detection by two-band infrared video-based measurement on face without visible lighting

In this paper, we propose a novel noncontact pulse wave monitoring method that is robust to fluctuations in illumination through use of two-band infrared video signals. Because the proposed method uses infrared light for illumination, the method can be used to detect a pulse wave on a human face without visible lighting. The corresponding two-band pixel values in the video signals can be separated into hemoglobin and shading components by application of a separation matrix in logarithmic space for the two pixel values. Because the shading component has been separated, the extracted hemoglobin component is then robust to fluctuations in the illumination. The pixel values in the region of interest were spatially averaged over all the pixels of each frame. These averaged values were then used to form the raw trace signal. Finally, the pulse wave and the corresponding pulse rate were obtained from the raw trace signal through several signal processing stages, including detrending, use of an adaptive bandpass filter, and peak detection. We evaluated the absolute error rate for the pulse rate between the estimated value and the ground truth obtained using an electrocardiogram. In the experiments, we found that the performance of the proposed method was greatly improved compared with that of conventional methods using single-band infrared video.     

An improved approximation lower bound for finding almost stable maximum matchings

In the stable marriage problem that allows incomplete preference lists, all stable matchings for a given instance have the same size. However, if we ignore the stability, there can be larger matchings. Biró et al. defined the problem of finding a maximum cardinality matching that contains minimum number of blocking pairs. They proved that this problem is not approximable within some constant δ>1 unless P=NP, even when all preference lists are of length at most 3. In this paper, we improve this constant δ to n1−ε for any ε>0, where n is the number of men in an input.     

Giant spin Hall effect in perpendicularly spin-polarized FePt/Au devices

Conversion of charge current into pure spin current and vice versa in non-magnetic semiconductors or metals, which are called the direct and inverse spin Hall effects (SHEs), provide a new functionality of materials for future spin-electronic architectures. Thus, the realization of a large SHE in a device with a simple and practical geometry is a crucial issue for its applications. Here, we present a multi-terminal device with a Au Hall cross and an FePt perpendicular spin injector to detect giant direct and inverse SHEs at room temperature. Perpendicularly magnetized FePt injects or detects perpendicularly polarized spin current without magnetic field, enabling the unambiguous identification of SHEs. The unprecedentedly large spin Hall resistance of up to 2.9 mOmega is attributed to the large spin Hall angle in Au through the skew scattering mechanism and the highly efficient spin injection due to the well-matched spin resistances of the chosen materials.     

Metamaterial Demonstrates Both a High Refractive Index and Extremely Low Reflection in the 0.3-THz Band

Communication and imaging in the terahertz waveband have advanced rapidly in offering industrial applications. However, optical elements such as collimated lenses in the terahertz waveband are bulky compared with the wavelength due to the lack of naturally occurring substances with a high refractive index and low loss. It is essential to miniaturize optical elements in the terahertz waveband for industrial application. Metamaterials consisting of subwavelength structures can arbitrarily control permittivity and permeability and provide a range of refractive indices. Here, we demonstrate a metamaterial with both a high refractive index and extremely low reflection consisting of symmetrically aligned paired cut metal wires with 18,800 units on the front and back surfaces of a dielectric substrate. Measurements by terahertz time-domain spectroscopy (THz-TDS) confirm a high effective refractive index of 6.66 + j0.123, extremely low reflection power of 1.16%, and the unprecedented high figure of merit (FOM = |n _real/n _imag|) of above 300 in the 0.3-THz band. Components with such specifications would enable miniature, high-performance optical elements in the terahertz waveband such as ultrathin flat antennas with high directivity. Further, the concept of the metamaterial with both a high refractive index and extremely low reflection potentially offers a wide range of attractive applications such as solid immersion lenses and cloaking devices.     

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Airborne Monoterpenes Emitted from a <Emphasis Type="Italic">Cupressus lusitanica</Emphasis> Cell Culture Induce a Signaling Cascade that Produces β-Thujaplicin

A cell culture of Cupressus lusitanica was used to investigate the reaction of a plant to certain airborne chemicals. Compared with laboratory and field methods using intact plants or tissues, a cell culture is advantageous because it is not affected by environmental factors, and the experiments are easier to reproduce. When exposed to an elicitor, our cell line produces 10 monoterpenes and β-thujaplicin, which is a strong phytoalexin. These monoterpenes are emitted into the vapor phase and are expected to play a role in airborne signaling. In the present study, the cells were exposed to monoterpene vapors, and the volatiles present in the culture flasks were monitored. When the culture cells were exposed to low doses of sabinene, we detected γ-terpinene and p-cymene. After exposure to γ-terpinene, we found p-cymene and terpinolene, whereas p-cymene exposure resulted in terpinolene emission. By contrast, the other seven monoterpenes we investigated did not induce any emissions of other monoterpenes. These results strongly suggest that in C. lusitanica a signaling cascade exists that starts with the emission of sabinene and moves to γ-terpinene, p-cymene, and finally to terpinolene, which accelerates the production of the phytoalexin β-thujaplicin.     

Shear Thinning of Nanometer-Thick Liquid Lubricant Films Measured at High Shear Rates

Viscosities of liquid films that were confined and sheared in a nanometer-scale gap were higher than those in the bulk state, and decreased with increasing shear rate, which is called shear thinning. However, the previous findings were based on the experimental results obtained at shear rates of 10^?1–10⁶ s^?1 by using a surface force apparatus (SFA). In this study, we succeeded in measuring shear rate dependence of viscous friction at the high shear rates of 10⁵–10⁸ s^?1. To measure the viscous friction at high shear rates, we used a fiber wobbling method that is a highly sensitive shear force measurement method we developed. The confined polymer lubricant (PFPE Z03) showed shear thinning behavior even at high shear rates up to 10⁸ s^?1, and the relationship between effective viscosity η and shear rate $\dot{\gamma }$ was well expressed by the equation that was $\log_{10} \eta = C - n\log_{10} \dot{\gamma }$ where C ≈ 4.6 ± 0.6 and n ≈ 1.1 ± 0.1. This equation agreed well with the universal curve of shear thinning determined based on the SFA measurements conducted at shear rates of 10^?1–10⁶ s^?1. This result indicates the measured shear thinning behavior was consistent at wide range of shear rates from 10^?1–10⁸ s^?1.     

Parylene Mobile Microplates Integrated with an Enzymatic Release for Handling of Single Adherent Cells

An approach for manipulating single adherent cells is developed that is integrated with an enzymatic batch release. This strategy uses an array of releasable microfabricated mobile substrates, termed microplates, formed from a biocompatible polymer, parylene. A parylene microplate array of 10–70 μm in diameter can be formed on an alginate hydrogel sacrificial layer by using a standard photolithographic process. The parylene surfaces are modified with fibronectin to enhance cell attachment, growth, and stretching. To load single cells onto these microplates, cells are initially placed in suspension at an optimized seeding density and are allowed to settle, stretch, and grow on individual microplates. The sacrificial layer underneath the microplate array can be dissolved on a time‐scale of several seconds without cytotoxicity. This system allows the inspection of selected single adherent cells. The ability to assess single cells while maintaining their adhesive properties will broaden the examination of a variety of attributes, such as cell shape and cytoskeletal properties.