Parasitic Signals Research Articles

Dynamic range limitations of non-coherent continous-wave THz photomixing systems with broadband detectors.

The dynamic range of non-coherent continuous-wave (CW) THz photomixing (PM) systems with broadband detectors can be significantly limited by various parasitic effects. Specifically, we examine the generation of parasitic (i) THz and (ii) IR radiation, and (iii) higher harmonics in CW THz PM emitters. (i) The parasitic broadband THz radiation, spanning from 100 to 250 GHz with a total output power of 20 nW, results from not perfectly clean laser spectra. As a result, for a frequency-flat Golay cell detector, the PM-system dynamic range is limited to 32.8 dB at 500 GHz, 26.7 dB at 1 THz, and 8.5 dB at 2.3 THz. In the case of detectors with a frequency-declining responsivity, the dynamic range can drop by ∼10 dB more. (ii) The IR radiation leaking from a PM emitter (≈20 μW) is sensitive to the PM emitter bias, which results in its modulation with an amplitude of about 1.3 μW, when a standard PM-emitter bias modulation is applied. The detected IR radiation could be confused for the THz signal. (iii) Parasitic generation of higher harmonics in PM systems can also limit the system's dynamic range or create spectral artifacts. However, we show that the harmonics are low at least at ∼1 THz and above. Specifically, they are less than 400 pW for fundamental frequencies above 750 GHz, which is more than 43 dB below the power of the fundamental harmonic. The above-stated values were obtained for a commonly-used PIN-diode photomixer mounted on a Si lens and 1.5 μm distributed-feedback lasers. In general, suppression of these parasitic signals is crucial for non-coherent CW THz PM systems.

About the rational choice of the damper shape for an ultrasonic piezoelectric transducer

The results of the study on the influence of the geometric shape of the damper on its effectiveness and the overall efficiency of the radiation-reception system are presented. One of the possible forms of the damper is considered, where it is shaped like a truncated cone, and its generatrix has an inclination angle relative to the plane of the piezoplate. A criterion for evaluating the efficiency of the damper’s operation is proposed. The study includes the results of computational-theoretical (using the finite element method) and experimental research on the influence of the incline angle of the damper’s generatrix on the signal reflected from its rear part. The inclination angle of the generatrix, at which the minimum of parasitic signals is achieved, is determined. The radiation-reception system is investigated under water loading, and a satisfactory agreement between the theoretical and experimental results is noted.

Analysis of Transient Current and Heat Flow during Voltage Holds: For Relaxed and Unrelaxed G/NMC811 Cells

This study investigates the transient heat flow during voltage holds for multi-layer pouch G/NMC811 lithium-ion cells. When applying a voltage hold to estimate the amount of parasitic side reactions, there is first a transient phase followed by a steady state. According to the literature, reversible processes mainly influence the transient phase, while the steady state presents the side reaction current. This work investigates the contributions to the transient behavior, evaluating the thermal and electrical signals and deconvoluting the different parasitic side reactions. In addition, a comparison between relaxed and unrelaxed states is performed, analyzing different temperatures and voltages. The results show that the relaxed graphite cells quickly reached a constant parasitic heat flow value with minimal transient effects. In contrast, the unrelaxed cells presented increased transient effects in the parasitic heat flow signal that can last more than 300 h. The electric transient originates mainly from anode overhang effects and SEI regrowth, while the thermal transient consists predominantly of SEI regrowth. Overall, the thermal signals stabilize faster than the electrical signals, giving calorimetry an advantage for faster estimation of parasitic side reactions.

Parasitic mixing in photomixers as continuous wave terahertz sources

We present observations of parasitic frequency components in the emission spectrum of typical photomixer sources for continuous wave (CW) terahertz generation. Broadband tunable photomixer systems are often used in combination with direct power detectors, e.g., for source and/or detector characterization. Here, spectral components besides the intended terahertz emission at the difference frequency of the two excitation lasers can significantly distort the measurement results. In this work, the appearance of parasitic mixing signals is observed in broadband measurements with a broadband antenna-coupled field-effect transistor as terahertz detector (TeraFET). The measurements reveal weaker spectral absorption features than expected and also a signal plateau towards higher frequencies, both strongly indicating a background in the detection signals. The photomixer emission is investigated in detail with a terahertz Fourier-transform infrared spectrometer (FTIR). We relate the observed parasitic frequency components with good quantitative agreement with the mode spectra of the semiconductor lasers. We also present one possible approach to overcome some of the issues, and we emphasize the importance of our findings to avoid distorted measurement results. To our knowledge, the essential aspect of parasitic mixing has so far been largely ignored in the literature where terahertz CW photomixer emitters are widely used for spectrally resolved measurements.

Achieving shot noise limit imaging with a polarization-modulated optical loop in a laser frequency-shifted feedback system

This paper introduces a novel approach to attain the shot-noise limit in laser frequency-shift feedback (LFSF) imaging systems by employing a polarization-modulated optical loop. Compared to the traditional LFSF imaging system, the proposed system effectively eliminates detrimental parasitic feedback signals, enhancing both the signal-to-noise ratio and the response range of the LFSF imaging system. Specifically, in the polarization-modulated optical loop, only the measurement light propagating through the loop undergoes efficient modulation, while the parasitic feedback light experiences high-frequency modulation beyond the bandwidth of the photodetector. Experimental findings demonstrate the superiority of our proposed system over traditional LFSF imaging systems in the insensitivity of parasitic feedback, showcasing a higher signal-to-noise ratio and response range. Moreover, the proposed system achieved a distinctive polarization imaging technique, which exhibits the capability to discern and analyze the distinct specular reflection and depolarized scattering components in the measurement light, thus providing more comprehensive target information.

EPR dosimetry of biohydroxyapatite below liquid nitrogen temperature

Hydroxyapatite, major component of all organic solid tissues, can be used as a sensitive biodosimeter based on the electron paramagnetic resonance (EPR) spectroscopy. However, the dosimetric signal of biohydroxyapatite overlaps with the so-called parasitic signals due to the close g factor values and broadening of the resonance line at room temperature. Moreover, the unsaturated parasitic signals possess the intensity comparable to the dosimetric resonance. All of these significantly complicates the dose determination and limits applicability mainly to the cases of relatively large accumulated dose. The negligibly saturated dosimteric spectrum can be at least partially separated at the liquid nitrogen temperatures (LNT) due to the strong saturation and suppression of the parasitic resonance lines and the linewidth shortening as shown in the present work. Moreover, the advances in the modern EPR equipment in the last two decades resulted in high sensitivity and stability of the signals measured. These are the key parameters along with the computer simulations for the precise dosimetric spectrum separation and processing. This could lead to the higher accuracy of the LNT EPR method proposed in the present work. To test the approach, the stepwise dose calibration of biohydroxyapatite over the range 0.5 - 20 Gy was made. The corresponding dosimetric signal measured at 70 K exhibited the linear dose response. The results suggest the applicability of the LNT EPR method in the retrospective dosimetry.

Early Leishmania infectivity depends on miR-372/373/520d family-mediated reprogramming of polyamines metabolism in THP-1-derived macrophages

Leishmania amazonensis is a protozoan that primarily causes cutaneous leishmaniasis in humans. The parasite relies on the amino acid arginine to survive within macrophages and establish infection, since it is a precursor for producing polyamines. On the other hand, arginine can be metabolized via nitric oxide synthase 2 (NOS2) to produce the microbicidal molecule nitric oxide (NO), although this mechanism does not apply to human macrophages since they lack NOS2 activity. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at posttranscriptional levels. Our previous work showed that mmu-miR-294 targets Nos2 favoring Leishmania survival in murine macrophages. Here, we demonstrate that human macrophages upregulate the hsa-miR-372, hsa-miR-373, and hsa-miR-520d, which present the same seed sequence as the murine mmu-miR-294. Inhibition of the miR-372 impaired Leishmania survival in THP-1 macrophages and the effect was further enhanced with combinatorial inhibition of the miR-372/373/520d family, pointing to a cooperative mechanism. However, this reduction in survival is not caused by miRNA-targeting of NOS2, since the seed-binding motif found in mice is not conserved in the human 3′UTR. Instead, we showed the miR-372/373/520d family targeting the macrophage’s main arginine transporter SLC7A2/CAT2 during infection. Arginine-related metabolism was markedly altered in response to infection and miRNA inhibition, as measured by Mass Spectrometry-based metabolomics. We found that Leishmania infection upregulates polyamines production in macrophages, as opposed to simultaneous inhibition of miR-372/373/520d, which decreased putrescine and spermine levels compared to the negative control. Overall, our study demonstrates miRNA-dependent modulation of polyamines production, establishing permissive conditions for intracellular parasite survival. Although the effector mechanisms causing host cell immunometabolic adaptations involve various parasite and host-derived signals, our findings suggest that the miR-372/373/520d family may represent a potential target for the development of new therapeutic strategies against cutaneous leishmaniasis.

ВИБІР НЕЙРОМЕРЕЖЕВОГО КЛАСИФІКАТОРА ДЛЯ ВИРІШЕННЯ ЗАВДАННЯ АНАЛІЗУ СИГНАЛІВ РЕБ ТА ШТУЧНИХ ЗАВАД

At present, the task of ensuring high-quality control of unmanned aerial vehicles and the transmission of reliable information in a complex interference environment is relevant. This task becomes especially important when intentional interference is used in the form of countermeasures. Various methods are used to detect and localize powerful sources of parasitic signals, including: time domain methods: signal spectrum analysis, correlation function analysis, phase shift analysis; frequency domain methods: signal amplitude response analysis, signal phase response analysis, power spectral density analysis; spatial domain methods: antenna directivity analysis, signal strength analysis at different points in space. Analyzing signals affected by EW and artificial interference is a challenging task. Traditional signal analysis methods are often ineffective for this task because they cannot take into account the complex characteristics of EW and artificial interference. Neural network classifiers are a promising tool for analyzing signals with EW and artificial interference. Neural networks can learn from large datasets and detect complex patterns that cannot be detected by traditional methods. This article describes the process of selecting a neural network classifier for analyzing EW and artificial interference signals. Various factors that should be considered when choosing a neural network architecture, training algorithm, and network parameters are discussed). The paper presents an analytical review of neural network classifiers, their varieties and features, and selects the optimal one for solving the task.

IDENTIFICATION OF DEFECTS IN A COATING WEDGE BASED ON ULTRASONIC NON-DESTRUCTIVE TESTING METHODS AND CONVOLUTIONAL NEURAL NETWORKS

The paper deals with the identification of a crack-like defect in a coated wedge based on ultrasonic nondestructive testing. The authors propose an approach of defect identification followed by determination of its geometrical parameters. The approach is based on a shadowed ultrasonic nondestructive testing method combined with deep machine learning technologies. A wedge-shaped area is inspected for the presence of an internal defect. On one edge of the wedge there is a source of ultrasonic vibrations, on the opposite edge there is a receiver. Passing through the coating and body of the wedge, part of the signal is reflected from inhomogeneities and defects that may be present in it. The signal reaching the opposite edge of the wedge is read by the receiver. The received data is processed by a neural network model, which predicts the presence or absence of an internal defect and, if present, determines geometric parameters such as size and position. A finite element model of ultrasonic wave propagation inside the wedge is constructed. Special damping layers are used, due to which the influence of parasitic signal reflections and its further propagation into the wedge body is significantly reduced. Based on the built model, the shadow method of ultrasonic scanning is implemented. This method implies that on one side of the wedge are installed excitation devices, and on the opposite side – receiving devices. Several numerical experiments for various combinations of geometric parameters of the wedge and the defect have been performed using a distributed computing system. Based on the obtained data, a neural network model was built and trained, capable of identifying the defect and determining its characteristics. The input of the model is spectrograms of the readout signal, and the output is values characterizing the defect.

Protein kinase PfPK2 mediated signalling is critical for host erythrocyte invasion by malaria parasite.

Signalling pathways in malaria parasite remain poorly defined and major reason for this is the lack of understanding of the function of majority of parasite protein kinases and phosphatases in parasite signalling and its biology. In the present study, we have elucidated the function of Protein Kinase 2 (PfPK2), which is known to be indispensable for the survival of human malaria parasite Plasmodium falciparum. We demonstrate that it is involved in the invasion of host erythrocytes, which is critical for establishing infection. In addition, PfPK2 may also be involved in the maturation of the parasite post-invasion. PfPK2 regulates the release of microneme proteins like Apical Membrane Antigen 1 (AMA1), which facilitates the formation of Tight Junction between the merozoite and host erythrocyte- a key step in the process of invasion. Comparative phosphoproteomics studies revealed that PfPK2 may be involved in regulation of several key proteins involved in invasion and signalling. Furthermore, PfPK2 regulates the generation of cGMP and the release of calcium in the parasite, which are key second messengers for the process of invasion. These and other studies have shed light on a novel signalling pathway in which PfPK2 acts as an upstream regulator of important cGMP-calcium signalling, which plays an important role in parasite invasion.

Second sound resonators and tweezers as vorticity or velocity probes: Fabrication, model, and method.

An analytical model of open-cavity second sound resonators is presented and validated against simulations and experiments in superfluid helium using a new resonator design that achieves unprecedented resolution. The model incorporates diffraction, geometrical misalignments, and flow through the cavity and is validated using cavities operated up to their 20th resonance in superfluid helium. An important finding is that resonators can be optimized to selectively sense either the quantum vortex density carried by the throughflow-as typically done in the literature-or the mean velocity of the throughflow. We propose two velocity probing methods: one that takes advantage of misalignments between the tweezers' plates and other that drives the resonator non-linearly, beyond a threshold that results in the self-sustainment of a vortex tangle within the cavity. A new mathematical treatment of the resonant signal is proposed to adequately filter out parasitic signals, such as temperature and pressure drift, and accurately separate the quantum vorticity signal. This elliptic method consists in a geometrical projection of the resonance in the inverse complex plane. Its effectiveness is demonstrated over a wide range of operating conditions. The resonator model and elliptic method are being utilized to characterize a new design of resonators with high resolution, thanks to miniaturization and design optimization. These second-sound tweezers are capable of providing time-space resolved information similar to classical local probes in turbulence, down to sub-millimeter and sub-millisecond scales. The principle, design, and microfabrication of second sound tweezers are being presented, along with their potential for exploring quantum turbulence.

Background-Free Near-Infrared Biphoton Emission from Single GaAs Nanowires.

The generation of photon pairs from nanoscale structures with high rates is still a challenge for the integration of quantum devices, as it suffers from parasitic signals from the substrate. In this work, we report type-0 spontaneous parametric down-conversion at 1550 nm from individual bottom-up grown zinc-blende GaAs nanowires with lengths of up to 5 μm and diameters of up to 450 nm. The nanowires were deposited on a transparent ITO substrate, and we measured a background-free coincidence rate of 0.05 Hz in a Hanbury-Brown-Twiss setup. Taking into account transmission losses, the pump fluence, and the nanowire volume, we achieved a biphoton generation of 60 GHz/Wm, which is at least 3 times higher than that of previously reported single nonlinear micro- and nanostructures. We also studied the correlations between the second-harmonic generation and the spontaneous parametric down-conversion intensities with respect to the pump polarization and in different individual nanowires.

Substrate Signal Inhibition in Raman Analysis of Microplastic Particles.

In Raman analysis, the substrate material serves very often for signal enhancement, especially when metallic surfaces are involved; however, in other cases, the substrate has an opposite effect as it is the source of a parasitic signal preventing the observation of the sample material of interest. This is particularly true with the advent of microfluidic devices involving either silicon or polymer surfaces. On the other hand, in a vast majority of Raman experiments, the analysis is made on a horizontal support holding the sample of interest. In our paper, we report that a simple tilting of the supporting substrate, in this case, silicon, can drastically decrease and eventually inhibit the Raman signal of the substrate material, leading to an easier observation of the target analyte of the sample, in this case, microplastic particles. This effect is very pronounced especially when looking for tiny particles. Explanation of this trend is provided thanks to a supporting experiment and further numerical simulations that suggest that the lensing effect of the particles plays an important role. These findings may be useful for Raman analysis of other microscale particles having curved shapes, including biological cells.

The correlation between Trichomonas vaginalis infection and reproductive system cancer: a systematic review and meta-analysis

BackgroundTrichomonas vaginalis (T. vaginalis) is a microaerophilic protozoan parasite which is responsible for trichomoniasis, the most common non-viral sexually transmitted infection in the world. The infection greatly damages the reproductive system. However, whether T. vaginalis infection can cause reproductive system cancer remains controversial.MethodsThis study systematically searched PubMed, EMBASE, Ovid and Google scholar, and 144 relevant articles were retrieved and classified into three categories: epidemiological investigations (68), reviews (30) and research articles (46). These three types of articles were verified according to their respective inclusion and exclusion criteria. Stata 16 was used to conduct a meta-analysis on the articles of epidemiological investigations for analysing the correlation between T. vaginalis infection and reproductive system cancer.ResultsThe result of meta-analysis indicated that the rate of T. vaginalis infection in the cancer group was significantly higher than that in the non-cancer group (OR = 1.87, 95% CI 1.29–2.71, I2 = 52%). Moreover, the cancer rate of the population infected with T. vaginalis was significantly higher than that of the population without T. vaginalis infection (OR = 2.77, 95% CI 2.37–3.25, I2 = 31%). The review articles and most research articles stated that the infection of T. vaginalis could lead to cancer and the pathogenic mechanisms were as follows: T. vaginalis promoting inflammatory response, T. vaginalis infection changing the internal environment around parasitic sites and signal transduction pathway, the metabolites secreted by T. vaginalis inducing carcinogenesis and T. vaginalis increasing other pathogenic microbial infection to promote the occurrence of cancer.ConclusionsOur study confirmed that there was a correlation between the infection of T. vaginalis and reproductive system cancer, and provided some possible research directions for clarifying the carcinogenic mechanisms caused by T. vaginalis infection.

Voltage and frequency controlled Ge/SeO2 thin film transistors designed as rectifiers, negative capacitance and negative conductance sources

Herein voltage and frequency controlled thin film transistors fabricated by depositing SeO2 onto germanium thin crystals are reported. For these devices measurements of the current-voltage characteristics revealed a biasing dependent rectification ratios. The devices showed metal-oxide-semiconductor character under reverse biasing conditions. In addition, the biasing dependent capacitance and conductance spectral studies in the frequency domain of 20M-1000MHz has shown the possibility of switching the capacitance and negative conductance from negative mode to positive mode. The features of the Ge/SeO2 devices make them attractive for use in electronic circuits as parasitic capacitive circuit elements, noise reducers, signal amplifiers and microwave oscillators.

New frontiers in host-parasite interactions, from cell to organism.

New frontiers in host-parasite interactions, from cell to organism.

Measurement System for Short-Pulsed Magnetic Fields.

A measurement system based on the colossal magnetoresistance CMR-B-scalar sensor was developed for the measurement of short-duration high-amplitude magnetic fields. The system consists of a magnetic field sensor made from thin nanostructured manganite film with minimized memory effect, and a magnetic field recording module. The memory effect of the La1-xSrx(Mn1-yCoy)zO3 manganite films doped with different amounts of Co and Mn was investigated by measuring the magnetoresistance (MR) and resistance relaxation in pulsed magnetic fields up to 20 T in the temperature range of 80-365 K. It was found that for low-temperature applications, films doped with Co (LSMCO) are preferable due to the minimized magnetic memory effect at these temperatures, compared with LSMO films without Co. For applications at temperatures higher than room temperature, nanostructured manganite LSMO films with increased Mn content above the stoichiometric level have to be used. These films do not exhibit magnetic memory effects and have higher MR values. To avoid parasitic signal due to electromotive forces appearing in the transmission line of the sensor during measurement of short-pulsed magnetic fields, a bipolar-pulsed voltage supply for the sensor was used. For signal recording, a measurement module consisting of a pulsed voltage generator with a frequency up to 12.5 MHz, a 16-bit ADC with a sampling rate of 25 MHz, and a microprocessor was proposed. The circuit of the measurement module was shielded against low- and high-frequency electromagnetic noise, and the recorded signal was transmitted to a personal computer using a fiber optic link. The system was tested using magnetic field generators, generating magnetic fields with pulse durations ranging from 3 to 20 μs. The developed magnetic field measurement system can be used for the measurement of high-pulsed magnetic fields with pulse durations in the order of microseconds in different fields of science and industry.

Базовые конструкции СВЧ балансных фильтров на оттекающих поверхностных акустических волнах

Ladder filters on leaky surface acoustic waves (LSAW) with electrical connection of resonators provide the lowest insertion loss IL=0.6-1.2 dB as compared with other types of LSAW filters, such as longitudinally coupled resonator filters. A drawback of ordinary nonsymmetrical ladder filters on LSAW is their limited selectivity (or minimal attenuation in the stop band) about UR=40-45 dB. In addition some problems arise when matching nonsymmetrical ladder filters to balanced or differential microcircuits. The present paper describes basic symmetric П-type and Т-type sections as well as various structures of ladder filters that allow to achieve a high selectivity thanks of parasitic electromagnetic signal (EMS) suppression. An extra advantage of balanced LSAW filters is their possibility to work with high impedance symmetric loads. The results of our study have been illustrated by few examples of balanced filters constructions on frequency 1217 MHz with selectivity UR=55-7- dB and low insertion loss IL=1,5-2,0 dB. Filters exhibiting high selectivity UR=55-70 dB and small insertion loss IL=1,2-4,0 dB. The described constructions may be used as basic for application on TV tuners, receivers of communication and navigation systems in frequency range 600-2000 MHz.

Calibration of a Stationary Multichannel GPR Monitoring System Using Internal Reflection Measurements

Advanced and extensive processing of ground-penetrating radar (GPR) data, for example, needed for full-waveform inversion approaches, requires a reliable temporal calibration of the system. Usually, the calibration of GPR systems is performed with a known medium between the transmitting and receiving antennas. Thereby, the observed time difference between the expected and measured signal arrival times, termed as time-zero, can be accounted for as a system-specific time delay. For measurement configurations where the antennas are permanently positioned around an object for monitoring purposes, time-consuming additional measurements where parts of the system need to be deinstalled would be required. This is not feasible for the proposed system. Therefore, novel calibration methods for such stationary monitoring systems are required to capture the temporal drift of time-zero. In this article, we present a novel calibration approach that uses internal signal reflections in the measurement system to derive the system-specific time delay without the necessity of knowing the medium between the antennas. We demonstrate that parasitic reflection and coupling signals can be used for accurate in situ calibrations. The presented approach is capable of identifying and correcting for the differences in hardware fabrication, while also correcting the temporal changes in time-zero during experiments. The presented approach is able to reduce the error in time-zero to below 25 ps, enabling high-resolution soil research. The presented approach is characterized by requiring no additional calibration setups or measurements since all the necessary data can be acquired during the original soil measurement.

Abstract 2701: Motility and More: the trypanosome flagellum as a platform for parasite signaling and motility.

Abstract 2701: Motility and More: the trypanosome flagellum as a platform for parasite signaling and motility.