Unsupervised sequence-to-sequence learning for automatic signal quality assessment in multi-channel electrical impedance-based hemodynamic monitoring.

BACKGROUND AND OBJECTIVE: This study proposes an unsupervised sequence-to-sequence learning approach that automatically assesses the motion-induced reliability degradation of the cardiac volume signal (CVS) in multi-channel electrical impedance-based hemodynamic monitoring. The proposed method attempts to tackle shortcomings in existing learning-based assessment approaches, such as the requirement of manual annotation for motion influence and the lack of explicit mechanisms for realizing motion-induced abnormalities under contextual variations in CVS over time. METHOD: By utilizing long-short term memory and variational auto-encoder structures, an encoder-decoder model is trained not only to self-reproduce an input sequence of the CVS but also to extrapolate the future in a parallel fashion. By doing so, the model can capture contextual knowledge lying in a temporal CVS sequence while being regularized to explore a general relationship over the entire time-series. A motion-influenced CVS of low-quality is detected, based on the residual between the input sequence and its neural representation with a cut-off value determined from the two-sigma rule of thumb over the training set. RESULT: Our experimental observations validated two claims: (i) in the learning environment of label-absence, assessment performance is achievable at a competitive level to the supervised setting, and (ii) the contextual information across a time series of CVS is advantageous for effectively realizing motion-induced unrealistic distortions in signal amplitude and morphology. We also investigated the capability as a pseudo-labeling tool to minimize human-craft annotation by preemptively providing strong candidates for motion-induced anomalies. Empirical evidence has shown that machine-guided annotation can reduce inevitable human-errors during manual assessment while minimizing cumbersome and time-consuming processes. CONCLUSION: The proposed method has a particular significance in the industrial field, where it is unavoidable to gather and utilize a large amount of CVS data to achieve high accuracy and robustness in real-world applications.

Connection between the time distribution and length scale of dynamic heterogeneity explored by probe reorientations of different sizes.

The rotational dynamics of fluorescent probes of different sizes in glass-forming materials were examined to correlate the time distribution and length scale of the dynamic heterogeneity (ξhet). As the size of the probe increased, the temperature dependence of the rotation correlation time (τc) shifted to longer times, and from this shift, the length scale associated with the glass transition (ξα) was estimated through the Debye-Stokes-Einstein (DSE) relationship and the length scale of the probe (ξsDFT) estimated from quantum mechanical calculations. The estimated ξα values roughly matched with ξhet obtained from calorimetric analysis but were considerably smaller than those deduced from 4D NMR, boson peak, and four-point dynamic susceptibility measurements but with a similar trend of decrease in the length scale upon the increase in the stretching exponent (ß) of the system. Because ß of the glass formers represents the time distribution of the system, and τc is related to the weighted average of the distribution, the length-scale distribution of the glass transition can be deduced by adopting the DSE relationship and assuming ξα is the weighted average of this distribution at the glass transition temperature. In such a case, the upper bound of the length scale and trend matches the experimentally obtained ξhet from 4D NMR, boson peak, and four-point dynamic susceptibility measurements. Furthermore, at a given temperature, as the probe size increased, the ß value reported by the probe increased, whereas the temperature dependence of ß, which strongly correlates with the fragility of the system, was independent of the probe size.

Optical scanning holography for a three-dimensional equal scale display.

We propose an optical scanning holography (OSH) for optical reconstruction with equal scale magnification or demagnification ratio along the transverse and longitudinal directions when the magnification or demagnification ratio of the hologram is priori known. First, we review the principles of OSH. Second, we propose an equal scale OSH that encodes a 3D distribution of a 3D scene with a scanning beam pattern that is formed by the superposition of two spherical waves with the same curvature direction. The hologram recorded by the equal scale OSH reconstructs the 3D scene with equal scale magnification or demagnification along the transverse and longitudinal directions. Finally, we provide simulation and experiment results to illustrate and clarify the proposed idea.

Coaxial scanning holography.

Optical scanning holography requires interference optics, which separates a laser beam into two paths and recombines the two path beams after being modulated spatially and temporarily. This requires high accuracy and stability of the apparatus with a highly coherent light source. In this Letter, we propose a coaxial scanning holography (CSH) capable of realizing scanning holography with high stability and low complexity by forming a scanning beam in a single optical path using a geometrical phase shift. An experimental verification of the CSH by optical acquisition and subsequent reconstruction of the hologram is reported.

Imaging properties of optical scanning holography and an aberration compensation filter.

We propose a numerical technique that analyses the imaging properties of optical scanning holography (OSH) constructed using real optical components in a real optical alignment situation. Using the proposing technique, we analyze the aberrations and the vulnerability of the OSH about the optical alignment. After that, we propose a digital filter that compensates the aberrations of the OSH. Finally, we show that the digital filter removes the aberrations of an experimentally recorded OSH.

Selective Synthesis of Molecular Borromean Rings: Engineering of Supramolecular Topology via Coordination-Driven Self-Assembly.

Molecular Borromean rings (BRs) is one of the rare topology among interlocked molecules. Template-free synthesis of BRs via coordination-driven self-assembly of tetracene-based Ru(II) acceptor and ditopic pyridyl donors is reported. NMR and single-crystal XRD analysis observed sequential transformation of a fully characterized monomeric rectangle to molecular BRs and vice versa. Crystal structure of BRs revealed that the particular topology was enforced by the appropriate geometry of the metallacycle and multiple parallel-displaced π-π interactions between the donor and tetracene moiety of the acceptor. Computational studies based on density functional theory also supported the formation of BRs through dispersive intermolecular interactions in solution.

Full-color optical scanning holography with common red, green, and blue channels [Invited].

We propose color optical scanning holography (OSH) that records red, green, and blue (RGB) holograms of real objects by single scanning. The proposed color OSH composes a RGB multiplexing unit, color time-dependent Fresnel zone plate generation unit, scanning unit, space-integrating photodetection unit, and demultiplexing unit. In the proposed color OSH, RGB beams follow a common path from the multiplexing unit to a photodetector, generating an electric current containing the object's complex RGB hologram information. In the demultiplexing unit, the complex RGB holograms are extracted and arranged as a complex color hologram. In experiments, we record the complex color hologram of a three-dimensional object composed of RGB transparencies using the color OSH. Numerical reconstruction shows that the recorded hologram contains information about the object's color as well as the diffracted field from the object.

Investigation of the biological and anti-cancer properties of ellagic acid-encapsulated nano-sized metalla-cages.

Three new large hexanuclear metalla-prisms 9-11 incorporating 1,3, 5-tris(pyridin-4-ylethynyl)benzene (tpeb) 4 and one of the dinuclear arene ruthenium clips [Ru2(p-iPrC6H4Me)2(OO∩OO)][CF3SO3]2 (OO∩OO =2,5-dioxydo-1,4-benzoquinonato [dobq] 1, 5,8-dihydroxy-1,4-naphthaquinonato (donq) 2, and 6,11-dihydroxy-5,12-naphthacenedionato [dotq] 3), which encapsulate the guest molecule ellagic acid (2,3,7,8-tetrahydroxy-chromeno[5,4,3-cde]chromene-5,10-dione, 5) were prepared. All complexes were isolated as triflate salts in good yields and were fully characterized by (1)H NMR spectroscopy and electrospray ionization mass spectrometry. The photophysical properties of these metalla-prisms were also investigated. Compounds 9 and 10 showed potent antioxidant activity, but 10 had the superior ORACPE value (1.30 ± 0.020). Ellagic acid (5) and compound 11 showed weaker activity than that of Trolox. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the metalla-prism compounds exhibit anticancer properties in vitro. Compound 10 inhibited the growth of all cancer cell lines at micromolar concentrations, with the highest cytotoxicity observed against A549 human lung cancer cells (IC50 =25.9 µM). However, these compounds had a lower anti-cancer activity than that of doxorubicin. In a tumoricidal assay, ellagic acid (5) and compound 10 induced cytotoxicity in tumor cells, while doxorubicin did not. While free ellagic acid had no effect on the granulocyte-colony stimulating factor and regulated on activation normal T cell expressed and secreted protein, the encapsulated metalla-prism 10 stimulated granulocyte-colony stimulating factor and reduced regulated on activation normal T cell expressed and secreted protein expression in the RAW264.7 macrophage line. Our results show that ellagic acid encapsulated in metalla-prisms inhibited cancer cells via the modulation of mRNA induction and protein expression levels of the granulocyte-colony stimulating factor and regulated on activation normal T cell expressed and secreted protein in macrophages.

Converting optical scanning holograms of real objects to binary Fourier holograms using an iterative direct binary search algorithm.

In this paper, we present a three-dimensional holographic imaging system. The proposed approach records a complex hologram of a real object using optical scanning holography, converts the complex form to binary data, and then reconstructs the recorded hologram using a spatial light modulator (SLM). The conversion from the recorded hologram to a binary hologram is achieved using a direct binary search algorithm. We present experimental results that verify the efficacy of our approach. To the best of our knowledge, this is the first time that a hologram of a real object has been reconstructed using a binary SLM.

Speckle-free digital holographic recording of a diffusely reflecting object.

We demonstrate holographic recording without speckle noise using the digital holographic technique called optical scanning holography (OSH). First, we record a complex hologram of a diffusely reflecting (DR) object using OSH. The incoherent mode of OSH makes it possible to record the complex hologram without speckle noise. Second, we convert the complex hologram to an off-axis real hologram digitally and finally we reconstruct the real hologram using an amplitude-only spatial light modulator (SLM) without twin-image noise and speckle noise. To the best of our knowledge, this is the first time demonstrating digital holographic recording of a DR object without speckle noise.

Solving inverse problems for optical scanning holography using an adaptively iterative shrinkage-thresholding algorithm.

Optical scanning holography (OSH) records a three-dimensional object into a two-dimensional hologram through two-dimensional optical scanning. The recovery of sectional images from the hologram, termed as an inverse problem, has been previously implemented by conventional methods as well as the use of l2 norm. However, conventional methods require time consuming processing of section by section without eliminating the defocus noise and the l2 norm method often suffers from the drawback of over-smoothing. Moreover, these methods require the whole hologram data (real and imaginary parts) to eliminate the twin image noise, whose computation complexity and the sophisticated post-processing are far from desirable. To handle these difficulties, an adaptively iterative shrinkage-thresholding (AIST) algorithm, characterized by fast computation and adaptive iteration, is proposed in this paper. Using only a half hologram data, the proposed method obtained satisfied on-axis reconstruction free of twin image noise. The experiments of multi-planar reconstruction and improvement of depth of focus further validate the feasibility and flexibility of our proposed AIST algorithm.

Multiple-image encryption by compressive holography.

We present multiple-image encryption (MIE) based on compressive holography. In the encryption, a holographic technique is employed to record multiple images simultaneously to form a hologram. The two-dimensional Fourier data of the hologram are then compressed by nonuniform sampling, which gives rise to compressive encryption. Decryption of individual images is cast into a minimization problem. The minimization retains the sparsity of recovered images in the wavelet basis. Meanwhile, total variation regularization is used to preserve edges in the reconstruction. Experiments have been conducted using holograms acquired by optical scanning holography as an example. Computer simulations of multiple images are subsequently demonstrated to illustrate the feasibility of the MIE scheme.

Dendroaspis natriuretic peptide regulates the cardiac L-type Ca2+ channel activity by the phosphorylation of α1c proteins.

Dendroaspis natriuretic peptide (DNP), a new member of the natriuretic peptide family, is structurally similar to atrial, brain, and C-type natriuretic peptides. However, the effects of DNP on the cardiac function are poorly defined. In the present study, we examined the effect of DNP on the cardiac L-type Ca(2+) channels in rabbit ventricular myocytes. DNP inhibited the L-type Ca(2+) current (I(Ca,L)) in a concentration dependent manner with a IC(50) of 25.5 nM, which was blocked by an inhibitor of protein kinase G (PKG), KT5823 (1 µM). DNP did not affect the voltage dependence of activation and inactivation of I(Ca,L). The α(1c) subunit of cardiac L-type Ca(2+) channel proteins was phosphorylated by the treatment of DNP (1 µM), which was completely blocked by KT5823 (1 µM). Finally, DNP also caused the shortening of action potential duration in rabbit ventricular tissue by 22.3 ± 4.2% of the control (n = 6), which was completely blocked by KT5823 (1 µM). These results clearly indicate that DNP inhibits the L-type Ca(2+) channel activity by phosphorylating the Ca(2+) channel protein via PKG activation.

Fabrication of nanometer-scale carbon nanotube field-effect transistors on flexible and transparent substrate.

We have successfully fabricated nanometer-scale carbon nanotube field effect transistors (CNT FETs) on a flexible and transparent substrate by electron-beam lithography. The measured current-voltage data show good hole conduction FET characteristics, and the on/off ratio of the current is more than 10(2). The conductance (as well as current) systematically decreases with the increase of the strain, suggesting that the bending of the substrate still affects the deformation condition of the short channel CNT FETs.

Three-dimensional display of a horizontal-parallax-only hologram.

We propose a three-dimensional (3D) holographic display by converting an optically recorded complex full-parallax (FP) hologram to an off-axis horizontal-parallax-only (HPO) hologram. First, we record the complex FP hologram of an object using optical scanning holography. We then convert the complex FP hologram to an off-axis HPO hologram through fringe-matched Gaussian low-pass filtering and with the introduction of an off-axis reference. Finally, we reconstruct the off-axis HPO hologram optically using an amplitude-only spatial light modulator. Until now, only computer-generated HPO holograms have been displayed optically. To the best of our knowledge, this is the first demonstration of a 3D display of an optically recorded HPO hologram.

Autofocusing in optical scanning holography.

We present autofocusing in optical scanning holography (OSH) with experimental results. We first record the complex hologram of an object using OSH and then create the Fresnel zone plate (FZP) that codes the object constant within the depth range of the object using Gaussian low-pass filtering. We subsequently synthesize a real-only spectrum hologram in which its phase term contains information about a distance parameter. Finally, we extract the distance parameter from the real-only spectrum hologram using fringe-adjusted filtering and the Wigner distribution. Using the extracted distance parameter, we reconstruct a three-dimensional image of the object from the complex hologram using digital convolution, which bypasses the conventional blind convolution to reconstruct a hologram. To the best of our knowledge, this is the first report with experimental results that autofocusing in OSH is possible without any searching algorithm or tracking process.

Blind sectional image reconstruction for optical scanning holography.

Optical scanning holography is a powerful holographic recording technique in which only a single two-dimensional scan is needed to record three-dimensional information. As in standard digital holography, for the reconstruction of a sectional image, the resulting data must then be postprocessed to obtain sectional content. We propose a blind sectional image reconstruction technique to automate the data processing. This reconstruction uses edge information to determine the appropriate Fresnel zone plates automatically and applies inverse imaging to recover the sectional images with significant suppression of the defocus noise. The experimental data used to verify the algorithm are measured from a physical implementation of the optical scanning holography system.

Algorithm for converting full-parallax holograms to horizontal-parallax-only holograms.

We propose an algorithm that converts a full-parallax hologram to a horizontal-parallax-only (HPO) hologram for 3D display. We first record a full-parallax hologram of an object. Subsequently, we filter the hologram with a Gaussian low-pass filter and a fringe-matched filter along the vertical direction. The final filtered output becomes an HPO hologram. To the best of our knowledge, this is the first algorithm proposed for converting full-parallax holographic information to HPO-holographic information.

Optical sectioning by optical scanning holography and a Wiener filter.

I propose a novel digital technique that reduces defocus noise in the reconstruction of the sectional images from the complex hologram of a thick object. In three-dimensional microscopy applications of holography, reducing the defocused light scattered from outside the focused plane is an important issue. In this technique I first extract a complex hologram of a thick object by using optical scanning holography. After that, I separate the power spectra of the focused and defocused planes from the complex hologram. Finally, I construct a Wiener filter by use of the power spectra. The Wiener filter reduces the defocus noise in the reconstruction of the sectional image of the focused plane. Computer simulations show that the proposed Wiener filter reduces the defocus noise and provides the sectional images.