Signal Transfer Research Articles

Adaptive Multi-Channel Event Segmentation and Feature Extraction for Monitoring Health Outcomes.

To develop a multi-channel device event segmentation and feature extraction algorithm that is robust to changes in data distribution. We introduce an adaptive transfer learning algorithm to classify and segment events from non-stationary multi-channel temporal data. Using a multivariate hidden Markov model (HMM) and Fisher's linear discriminant analysis (FLDA) the algorithm adaptively adjusts to shifts in distribution over time. The proposed algorithm is unsupervised and learns to label events without requiring a priori information about true event states. The procedure is illustrated on experimental data collected from a cohort in a human viral challenge (HVC) study, where certain subjects have disrupted wake and sleep patterns after exposure to an H1N1 influenza pathogen. Simulations establish that the proposed adaptive algorithm significantly outperforms other event classification methods. When applied to early time points in the HVC data, the algorithm extracts sleep/wake features that are predictive of both infection and infection onset time. The proposed transfer learning event segmentation method is robust to temporal shifts in data distribution and can be used to produce highly discriminative event-labeled features for health monitoring. Our integrated multisensor signal processing and transfer learning method is applicable to many ambulatory monitoring applications.

Speed of phototransduction in the microvillus regulates the accuracy and bandwidth of the rhabdomeric photoreceptor.

Phototransduction reactions in the rhabdomeric photoreceptor are profoundly stochastic due to the small number of participating molecules and small reaction space. The resulting quantum bumps (QBs) vary in their timing (latency), amplitudes and durations, and these variabilities within each cell are not correlated. Using modeling and electrophysiological recordings, we investigated how the QB properties depend on the cascade speed and how they influence signal transfer. Parametric analysis in the model supported by experimental data revealed that faster cascades elicit larger and narrower QBs with faster onsets and smaller variabilities than slower cascades. Latency dispersion was stronger affected by modification of upstream than downstream activation parameters. The variability caused by downstream modifications closely matched the experimental variability. Frequency response modeling showed that corner frequency is a reciprocal function of the characteristic duration of the multiphoton response, which, in turn, is a non-linear function of QB duration and latency dispersion. All QB variabilities contributed noise but only latency dispersion slowed and spread multiphoton responses, lowering the corner frequency. Using the discovered QB correlations, we evaluated transduction noise for dissimilar species and two extreme adaptation states, and compared it to photon noise. The noise emitted by the cascade was non-additive and depended non-linearly on the interaction between the QB duration and the three QB variabilities. Increased QB duration strongly suppressed both noise and corner frequency. This trade-off might be acceptable for nocturnal but not diurnal species because corner frequency is the principal determinant of information capacity. To offset the increase in noise accompanying the QB narrowing during light adaptation and the response-expanding effect of latency dispersion, the cascade accelerates. This explains the widespread evolutionary tendency of diurnal fliers to have fast phototransduction, especially after light adaptation, which thus appears to be a common adaptation to contain stochasticity, improve SNR and expand the bandwidth.

Visual Stimulus Content in V4 Is Conveyed by Gamma-Rhythmic Information Packages.

Selective visual attention allows the brain to focus on behaviorally relevant information while ignoring irrelevant signals. As a possible mechanism, routing-by-synchronization was proposed: neural populations receiving attended signals align their gamma-rhythmic activity to that of the sending populations, such that incoming spikes arrive at excitability peaks of receiving populations, enhancing signal transfer. Conversely, non-attended signals arrive unaligned to the receiver's oscillation, reducing signal transfer. Therefore, visual signals should be transferred through gamma-rhythmic bursts of information, resulting in a modulation of the stimulus content within the receiving population's activity by its gamma phase and amplitude. To test this prediction, we quantified gamma-phase-dependent stimulus content within neural activity from area V4 of two male macaques performing a visual attention task. For the attended stimulus, we find highest stimulus information content near excitability peaks, an effect that increases with oscillation amplitude, establishing a functional link between selective processing and gamma-activity.SIGNIFICANCE STATEMENT The ability to focus on the behaviorally relevant signals is essential for the brain to cope with the continuous, high-dimensional stream of sensory information it receives. What are the neural mechanisms which allow such selective processing in the visual system? We analyzed data from area V4 and found that the amount of visual signal information content is tightly linked to the phase of local gamma-rhythmic activity, with maximal signal content occurring near peaks of neural excitability. Our investigations provide direct evidence that selective attention relies on rhythmic temporal coordination between visual areas, and establish novel methods for pinpointing pulsed transmission schemes in neural data.

Connexin Signaling in the Juxtaglomerular Apparatus (JGA) of Developing, Postnatal Healthy and Nephrotic Human Kidneys.

Our study analyzed the expression pattern of different connexins (Cxs) and renin positive cells in the juxtaglomerular apparatus (JGA) of developing, postnatal healthy human kidneys and in nephrotic syndrome of the Finnish type (CNF), by using double immunofluorescence, electron microscopy and statistical measuring. The JGA contained several cell types connected by Cxs, and consisting of macula densa, extraglomerular mesangium (EM) and juxtaglomerular cells (JC), which release renin involved in renin-angiotensin- aldosteron system (RAS) of arterial blood pressure control. During JGA development, strong Cx40 expression gradually decreased, while expression of Cx37, Cx43 and Cx45 increased, postnatally showing more equalized expression patterning. In parallel, initially dispersed renin cells localized to JGA, and greatly increased expression in postnatal kidneys. In CNF kidneys, increased levels of Cx43, Cx37 and Cx45 co-localized with accumulations of renin cells in JGA. Additionally, they reappeared in extraglomerular mesangial cells, indicating association between return to embryonic Cxs patterning and pathologically changed kidney tissue. Based on the described Cxs and renin expression patterning, we suggest involvement of Cx40 primarily in the formation of JGA in developing kidneys, while Cx37, Cx43 and Cx45 might participate in JGA signal transfer important for postnatal maintenance of kidney function and blood pressure control.

Visualization of blurring process due to analog components in a digital radiography system using a simple method.

To obtain useful medical X-ray images for diagnosis, it is necessary to accurately evaluate the characteristics and fully understand the features of the system to determine the imaging target and conditions. This study describes the performance of a digital radiography (DR) system in detail and proposes a method for characterizing the blurring process due to the presence of analog components in an imaging system. Our method does not involve any specialized technique, such as a simulation that requires long computing time on a high-performance computer. The method is based on the concept of the modulation transfer function (MTF). The functions that corresponded to the MTF of the analog components of the system when the Fourier transform was performed were examined. Indirect conversion type flat-panel detectors (FPD) in the general radiography energy range and direct conversion type FPD in the mammography were used for verification. A Gaussian function and Lorentz function were synthesized for modelling the blurring process of the indirect type FPDs. The spreads and shapes of the modeled functions depended on the systems. For the direct conversion type FPD, a combination of a Lorentz function with a narrow width and an impulse function characterized the results. Furthermore, based on the structure of each detector and the signal transfer process, the visualized results were considered reliable. The results of these experiments will aid in the detailed understanding of the image quality characteristics of the DR system by the feasible approach.

The characteristics of Co40Fe40W10B10 thin films on glass and Si(100) substrates

In this study, the Co40Fe40W10B10 film was sputtered onto a substrate of glass and Si(100) with thicknesses from 10 nm to 100 nm, by using the sputtering technique. As shown in the X-ray Diffraction (XRD) patterns, the structure was amorphous when B was refined by the grain size. Under the effect of the thickness, the values of the low-frequency alternating current magnetic susceptibility (χac) increased gradually. When the optimal resonance frequency (fres) was 500 Hz, the maximum value of χac with glass/Co40Fe40W10B10 was 0.35, at a thickness at 100 nm; at 100 Hz, the maximum χac of Si(100)/Co40Fe40W10B10 was 0.15, at a thickness of 100 nm. The highest χac indicates that the spin sensitivity was maximized at an fres. Moreover, the high surface energy is resulted from high adhesive characteristics. The glass/Co40Fe40W10B10 film of 37.8 mJ/mm2 exhibited the highest surface energy, at a thickness of 40 nm, while the highest surface energy of Si(100)/Co40Fe40W10B10 was 53.1 mJ/mm2 at a thickness of 100 nm. The transmittance percentage (%) of glass/Co40Fe40W10B10 film was 30.5 %, at a thickness of 10 nm. As indicated by the results, the transmittance percentage decreased with an increasing thickness, because the thickness and interface effects inhibited the transfer of photon signals through the film, causing the optical transmittance characteristics to be affected.

Enzyme-free dual-DNA walker based on catalytic hairpin assembled DNAzyme for sensing telomerase activity

Telomerase is a potential tumor biomarker. Herein, an enzyme-free and isothermal fluorescence strategy, dual-3D DNA walker based on catalytic hairpin assembled DNAzyme (CHA-DNAzyme), for ultrasensitive detection of telomerase activity is described. Upon incubation with telomerase, the telomerase primer is elongated to form telomeric repeat sequences (TR). The elongated TR stochastically moves along the predesign track by continuous strand displacement reaction to assemble the intact DNAzyme (CHA walker). Then, the activated DNAzyme autonomously moves along the other track by cleaving DNA hairpins to release fluorescent-labeled DNA fragments from AuNPs (DNAzyme walker). As a result, a large amount of fluorescence is recovered to analyze telomerase activity. The use of CHA walker and DNAzyme walker endows the sensing strategy with high sensitivity and signal transfer efficiency. The strategy exhibits a wide analytical range from 10 to 1000 HeLa cells mL−¹ with a limit of detection of 7 cells mL−¹. The strategy not only can detect telomerase activity in different tumor cells, but also quantifies telomerase activity of cancer cells from accumulated normal cells. In addition, the practicability of the strategy is validated by detecting telomerase activity in human serum.

Asymmetric Scattering and Reciprocity in a Plasmonic Dimer

We study the scattering of polarized light by two equal corner stacked Au nanorods that exhibit strong electromagnetic coupling. In the far field, this plasmonic dimer manifests very prominent asymmetric scattering in the transverse direction. Calculations based on a system of two coupled oscillators, as well as simulations based on the boundary element method, show that, while in one configuration both vertical and horizontal polarization states are scattered to the detector, when we interchange the source and the detector, the scattered intensity of the horizontal polarization drops to zero. Following Perrin’s criterion, it can be shown that this system, as well as any other linear system not involving magneto-optical effects, obeys the optical reciprocity principle. We show that the optical response of the plasmonic dimer, while preserving electromagnetic reciprocity, can be used for the non-reciprocal transfer of signals at a subwavelength scale.

Design, Fabrication, and Performance Evaluation of Portable and Large-Area Blackbody System.

In this study, a portable and large-area blackbody system was developed following a series of processes including design, computational analysis, fabrication, and experimental analysis and evaluation. The blackbody system was designed to be lightweight (5 kg), and its temperature could exceed the ambient temperature by up to 15 °C under operation. A carbon-fiber-based heat source was used to achieve a uniform temperature distribution. A heat shield fabricated from an insulation material was embedded at the opposite side of the heating element to minimize heat loss. A prototype of the blackbody system was fabricated based on the design and transient coupled electro-thermal simulation results. The operation performance of this system, such as the thermal response, signal transfer function, and noise equivalent temperature difference, was evaluated by employing an infrared imaging system. In addition, emissivity was measured during operation. The results of this study show that the developed portable and large-area blackbody system can be expected to serve as a reliable reference source for the calibration of aerial infrared images for the application of aerial infrared techniques to remote sensing.

Improved Ion Transport in Hydrogel-Based Nanofluidics for Osmotic Energy Conversion.

In nature, ultrafast signal transfer based on ion transport, which is the foundation of biological processes, commonly works in a hydrogel–water mixed mechanism. Inspired by organisms’ hydrogel-based system, we introduce hydrogel into nanofluidics to prepare a hydrogel hybrid membrane. The introduction of a space charged hydrogel improves the ion selectivity evidently. Also, a power generator based on the hydrogel hybrid membrane shows an excellent energy conversion property; a maximum power density up to 11.72 W/m2 is achieved at a 500-fold salinity gradient. Furthermore, the membrane shows excellent mechanical properties. These values are achievable, which indicates our membrane’s huge potential applications in osmotic energy conversion.

Noise immunity of wireless personal area networks under digital production conditions

Subject of Research. The paper considers the effect of working-environment factors on wireless personal networks. A classification of such factors is given and the noise immunity of wireless personal networks is determined on a real production example. Method. A method for noise immunity evaluation was proposed based on a received signal strength indicator (RSSI). RSSI values can be obtained natively from almost any receiver and transmitter, that makes this method affordable compared to application of network analyzers and other specialized equipment. In the carried out experiment the receiver and transmitter were located at a distance ranging from 0.5 to 25 m. The act of signal transfer was carried out alternately under the impact of each working-environment factor. Then the measured RSSI values were analyzed and converted into the maximum permissible distance between the receiver and the transmitter in accordance with the proposed method. Main Results. Data on the working-environment effect on the noise immunity of wireless personal networks is obtained. The most significant factors are: girded thick-walled steel obstacles, welding machines and similar frequency range networks. Nevertheless, it is concluded that the effect is not significant enough to decide against the application of wireless personal networks, since the exposure of many factors can be offset by the use of mesh topology and dense arrangement of receivers and transmitters. Practical Relevance. The results are of particular interest in the context of production digitization, where the wireless method of data transmission from the field level sensors becomes preferable to the wired one due to the requirement for flexibility and mobility of a production process.

Reliable Nickel-Free Surface Finish Solution for High-Frequency, HDI PCB Applications

Abstract The evolution of Internet-enabled mobile devices has driven innovation in the manufacturing and design of technology capable of high-frequency electronic signal transfer. Among the primary factors affecting the integrity of high-frequency signals is the surface finish applied on printed circuit board copper pads—a need commonly met through the electroless nickel immersion gold process (ENIG). However, there are well-documented limitations of ENIG due to the presence of nickel, the properties of which result in an overall reduced performance in the high-frequency data transfer rate for ENIG-applied electronics, compared with bare copper. An innovation over traditional ENIG is a nickel-less approach involving a special nano-engineered barrier designed to coat copper contacts, finished with an outermost gold layer. In this study, assemblies involving this nickel-less novel surface finish have been subjected to extended thermal exposure, then intermetallics analyses, contact resistance comparison after every reflow cycle (up to six reflow cycles) to assess the prevention of copper atom diffusion into the gold layer, solder ball pull and shear tests to evaluate the aging and long-term reliability of solder joints, and insertion loss testing to gauge whether this surface finish can be used for high-frequency, high-density interconnect applications.

A ratiometric electrochemiluminescence resonance energy transfer platform based on novel dye BODIPY derivatives for sensitive detection of lactoferrin

A ratiometric electrochemiluminescence resonance energy transfer (ECL-RET) platform depended on novel dye BODIPY derivatives was proposed for rapid detection of lactoferrin. This ECL-RET platform is composed of aptamer decorated BODIPY composites and C60@BSA, in which BODIPY derivative is the ECL probe and can generate significant resonance energy transfer with K2S2O8. BODIPY derivative and K2S2O8 are used as built-in reference signal and calibration signal respectively to eliminate background signal and abnormal change signal by double signal self-calibration process. At the same time, C60, as the accelerator of K2S2O8, can effectively increase the ECL signal and further transfer as much energy as possible to BODIPY derivative. Under optimal conditions, the constructed ECL-RET platform exhibited sensitive detection of lactoferrin in the wide linear range of 10-4- 850 ng/mL with a LOD of 42 fg/mL. Meanwhile, the proposed ECL-RET aptasensor demonstrated superior stability, specificity and reproducibility, displaying favorable application value in practical diagnosis of this method.

All-optical flexible 5G signal generation and transmission for spectrum resource optimization

As available spectrum gets congested by different applications, spectral efficiency can be enhanced through spectrum sharing and coexistence. In this paper, we demonstrate the idea of spectrum sharing and coexistence by using optical heterodyning as a flex-spectrum photonic RF transmitter. Flexibility was achieved by tuning the RF carrier frequency from 1–5 GHz, frequencies around two spectra from a commercial telecom antenna and from a radio astronomy observatory area. We compared the spectrum of our adopted flex-spectrum photonic RF transmitter with these two practical spectra. This allowed us to demonstrate the feasibility of our adopted photonic RF transmitter to coexist with these distinct spectra. Results indicated that it is feasible to use these adopted photonic transmitters in different application environments for coexistence and spectrum sharing. Error-free 26 km fiber transmission was achieved at 2.1 Gbps and 8.5 Gbps. This further showed the feasibility of these photonic RF transmitters for controlled transfer of different data signals relating to different applications using the same RF channel.

Molecular Platform for Frequency Upconversion at the Single-Photon Level

Direct detection of single photons at wavelengths beyond 2 microns under ambient conditions remains an outstanding technological challenge. One promising approach is frequency upconversion into the visible (VIS) or near-infrared (NIR) domain, where single photon detectors are readily available. Here, we propose a nanoscale solution based on a molecular optomechanical platform to up-convert photons from the far and mid-infrared (covering part of the THz gap) into the VIS-NIR domain. We perform a detailed analysis of its outgoing noise spectral density and conversion efficiency with a full quantum model. Our platform consists in doubly resonant nanoantennas focusing both the incoming long-wavelength radiation and the short-wavelength pump laser field into the same active region. There, infrared active vibrational modes are resonantly excited and couple through their Raman polarizability to the pump field. This optomechanical interaction is enhanced by the antenna and leads to the coherent transfer of the incoming low-frequency signal onto the anti-Stokes sideband of the pump laser. Our calculations demonstrate that our scheme is realizable with current technology and that optimized platforms can reach single photon sensitivity in a spectral region where this capability remains unavailable to date.

Computation of intermolecular forces that carry sound across vacuum gaps

A recently understood ability of sound to cross narrow vacuum gaps between material bodies has numerous implications in modern technology, where it opens additional channels for the transfer of heat and acoustic signals between narrowly separated objects. Acoustic vibrations in a body are characterized by perturbations of its surface and of its material density, which affect molecules of another body via intermolecular forces. Methods of continuum mechanics allow the description of the acoustic waves initiated by external body forces, including van der Waals forces. The expressions for such forces have been known for many years, but their applications to configurations relevant to sound transmission are often based on restrictive approximations and asymptotic expansions, which are rarely satisfied in practical situations, where amplitudes of molecular displacements may be in a picometer range. This paper develops a method of accurate computations of van der Waals forces caused by such perturbations with scales comparable with intermolecular distances in a material. The accuracy of the developed approach is limited only by calculation errors, and the scope of its applications is not only limited to acoustic perturbations but also includes the description of van der Waals forces caused by arbitrary molecular density perturbations, by corrugated surfaces, contaminated materials, etc.

Development of Magnetic Torque Stimulation (MTS) Utilizing Rotating Uniform Magnetic Field for Mechanical Activation of Cardiac Cells

Regulation of cell signaling through physical stimulation is an emerging topic in biomedicine. Background: While recent advances in biophysical technologies show capabilities for spatiotemporal stimulation, interfacing those tools with biological systems for intact signal transfer and noncontact stimulation remains challenging. Here, we describe the use of a magnetic torque stimulation (MTS) system combined with engineered magnetic particles to apply forces on the surface of individual cells. MTS utilizes an externally rotating magnetic field to induce a spin on magnetic particles and generate torsional force to stimulate mechanotransduction pathways in two types of human heart cells—cardiomyocytes and cardiac fibroblasts. Methods: The MTS system operates in a noncontact mode with two magnets separated (60 mm) from each other and generates a torque of up to 15 pN µm across the entire area of a 35-mm cell culture dish. The MTS system can mechanically stimulate both types of human heart cells, inducing maturation and hypertrophy. Results: Our findings show that application of the MTS system under hypoxic conditions induces not only nuclear localization of mechanoresponsive YAP proteins in human heart cells but also overexpression of hypertrophy markers, including β-myosin heavy chain (βMHC), cardiotrophin-1 (CT-1), microRNA-21 (miR-21), and transforming growth factor beta-1 (TGFβ-1). Conclusions: These results have important implications for the applicability of the MTS system to diverse in vitro studies that require remote and noninvasive mechanical regulation.

Residue interaction dynamics in Vaucheria aureochrome1 light-oxygen-voltage: Bridging theory and experiments.

Allosteric communication is the basis of signaling and information transfer. Collective interactions between amino acid residues, which are spatially distributed in the three dimensional structure of a protein molecule, form the basis of allosteric network. While the construction of residue interaction graphs (RIG) is based on static crystal structures of proteins, it is important to extract information on protein dynamics to understand allostery. Therefore, quantitative analysis of RIG based on the framework of differential network (DN), is immensely helpful in identifying key amino acid residue interactions within such communication pathways. While the simultaneous availability of protein structures from two different states is essential for DN, there are additional challenges. Crystallographic artifacts like nonbiological dimeric arrangements within the crystal lattice automatically influence the construction and eventually the interpretation of RIG. Therefore, experimental validation of predictions from the analyses of RIG is naturally scarce in the literature. Herein, we study the photo sensor domain of the signaling photoreceptor transcription factor, aureochrome1, to understand light-driven signaling. We perform direct experiments to verify the predictions from RIG using the machinery of DN. However, the agreement leaves scope for improvement. We then discuss the notion of quaternary structure alignment to obtain a biologically meaningful dimer. Thence, we reconstruct the RIG and reanalyze the modified structure. Results of these reanalyses render far superior agreement with experiments. Therefore, this notion of addressing crystallographic biases provides a fresh yet general approach for reconciliation of theory and experiments. It is applicable beyond the present case to all signaling proteins in general.

Transient Close-Range Electromagnetic Field Coupling Between Loop Antennas at the Interface of Dissipative Half-Spaces

The problem of electromagnetic (EM) field short-range coupling between coplanar loop antennas located at the interface of two half-spaces with dielectric and conductive properties is solved analytically in the time domain (TD) via the Cagniard-DeHoop (CdH) technique under the diffusive approximation. It is demonstrated that the thus obtained closed-form TD analytical expressions can be applied to evaluate the close-range EM-field signal transfer between two loops lying on the surface of a dissipative half-space.

Signal transfer via smart conductive networks for high temperature performing wearable electronics

High temperature performing textile conductive networks for wearable electronic applications are demonstrated. Different types of conductive yarns, namely steel, copper, and silver-coated were used as signal transmission tracks in order to configure the smart conductive network architecture. Conductive networks were formed between the layers of high temperature-resistant fabric substrates which of the following substrates most likely consist of reactively sputtered aluminum particles, polybenzimidazoles (PBI), aramid, and glass fibers. The specimens were constructed using welding and conventional sewing techniques and their operating characteristics in terms of high temperature resistance (limited flame spread, convective heat transfer, radiant heat) and electrical properties (conductivity and signal quality in data transfer) were determined. As a result of thermal tests, the excellent performances among conductive networks are attributed to steel and copper threads used as signal transmission line hidden in the interface among aluminum, 100 % aramid (nonwoven), and epoxy layer used as a substrate. The efficient exploitation of smart conductive networks will boost the viability of data transfer quality among wearable electronic components performing at high temperatures.