Microwave photonics doppler speed measurement based on sagnac loops and four-wave mixing effect in a highly nonlinear fiber.

Photonic radars are increasingly being developed and offer a promising replacement for traditional RF radars. They feature higher precision, and smaller size compared to the current microwave radars. One important part of a moving target indicating (MTI) radar is the Doppler shift measurement used to measure the radial velocity of a moving target. Therefore, for any photonic radar operating at MTI mode, it is necessary to have a Doppler measurement subsystem. In this paper, a microwave photonic Doppler frequency measurement system is conceived and implemented for this purpose specifically. The operation is based on making a Doppler shift-dependent yet low-frequency voltage component. It is all-optical and hence has the potential to be integrated into many electronic warfare systems. This feature not only makes the system independent of any sophisticated electrical device but also makes the measurement time lower than that of the electrical counterparts. The specific design presented here provides a much better stability compared to the recent works. An error as low as 0.012 Hz at a 10 GHz radar frequency was obtained, and the system performance was demonstrated up to 40 GHz, at which a 4.75 Hz error was recorded.

Platelets regulate ischemia-induced revascularization and angiogenesis by secretion of growth factor-modulating factors.

In ischemic tissue, platelets can modulate angiogenesis. The specific factors influencing this function, however, are poorly understood. Here, we characterized the complement anaphylatoxin C5a-mediated activation of C5a receptor 1 (C5aR1) expressed on platelets as a potent regulator of ischemia-driven revascularization. We assessed the relevance of the anaphylatoxin receptor C5aR1 on platelets in patients with coronary artery disease as well as those with peripheral artery disease and used genetic mouse models to characterize its significance for ischemia and growth factor-driven revascularization. The presence of C5aR1-expressing platelets was increased in the hindlimb ischemia model. Ischemia-driven angiogenesis was significantly improved in C5aR1-/- mice but not in C5-/- mice, suggesting a specific role of C5aR1. Experiments using the supernatant of C5a-stimulated platelets suggested a paracrine mechanism of angiogenesis inhibition by platelets by means of antiangiogenic CXC chemokine ligand 4 (CXCL4, PF4). Lineage-specific C5aR1 deletion verified that the secretion of CXCL4 depends on C5aR1 ligation on platelets. Using C5aR1-/-CXCL4-/- mice, we observed no additional effect in the revascularization response, underscoring a strong dependence of CXCL4 secretion on the C5a-C5aR1-axis. We identified a novel mechanism for inhibition of neovascularization via platelet C5aR1, which was mediated by the release of antiangiogenic CXCL4.

Comparison of Accuracy Between Pulp/Tooth Ratio and Tooth Coronal Index Methods for Dental Age Estimation Using Digital Panoramic Radiographs

ABSTRACT Objective: To evaluate the reliability and the accuracy of Tooth Coronal Index (TCI) and Pulp/Tooth Ratio (PTR) methods in dental age estimation using digital panoramic radiography. Material and Methods: In this cross-sectional study, 237 dental panoramic images were collected. The two methods (TCI and PTR) were applied to all left mandibular first and second molars based on inclusion and exclusion criteria. In order to analyze the acquired data, statistical methods were used. The estimated ages derived by exclusive formula were compared to the chronological age, and the error ranges for each indicator were measured to determine their accuracy. Results: There were negative correlations between PTR in the first molar (r=-0.89) and in the second molar (r=-0.788), as well as TCI in the first molar (r=-0.587) and in the second molar (r=-.242). In this study, we found that the Pulp/Tooth Ratio (PTR) accuracy rate for mandibular first and second molar teeth was 79.21% and 62.09 %, respectively, although the Tooth Coronal Index (TCI) value for these teeth was 34.45% and 5.85%. Conclusion: Pulp/Tooth Ratio and Tooth Coronal Index are potential age estimation indices. Although PTR was the more accurate one in our study. The results also demonstrated that indices related to the first molar tooth could be used to estimate age with greater accuracy and validity.

Transcriptomic analysis of poco1, a mitochondrial pentatricopeptide repeat protein mutant in Arabidopsis thaliana.

BACKGROUND: Flowering is a crucial stage during plant development. Plants may respond to unfavorable conditions by accelerating reproductive processes like flowering. In a recent study, we showed that PRECOCIOUS1 (POCO1) is a mitochondrial pentatricopeptide repeat (PPR) protein involved in flowering time and abscisic acid (ABA) signaling in Arabidopsis thaliana. Here, we use RNA-seq data to investigate global gene expression alteration in the poco1 mutant. RESULTS: RNA-seq analysis was performed during different developmental stages for wild-type and poco1 plants. The most profound differences in gene expression were found when wild-type and poco1 plants of the same developmental stage were compared. Coverage analysis confirmed the T-DNA insertion in POCO1, which was concomitant with truncated transcripts. Many biological processes were found to be enriched. Several flowering-related genes such as FLOWERING LOCUS T (FT), which may be involved in the early-flowering phenotype of poco1, were differentially regulated. Numerous ABA-associated genes, including the core components of ABA signaling such as ABA receptors, protein phosphatases, protein kinases, and ABA-responsive element (ABRE) binding proteins (AREBs)/ABRE-binding factors (ABFs) as well as important genes for stomatal function, were mostly down-regulated in poco1. Drought and oxidative stress-related genes, including ABA-induced stress genes, were differentially regulated. RNA-seq analysis also uncovered differentially regulated genes encoding various classes of transcription factors and genes involved in cellular signaling. Furthermore, the expression of stress-associated nuclear genes encoding mitochondrial proteins (NGEMPs) was found to be altered in poco1. Redox-related genes were affected, suggesting that the redox state in poco1 might be altered. CONCLUSION: The identification of various enriched biological processes indicates that complex regulatory mechanisms underlie poco1 development. Differentially regulated genes associated with flowering may contribute to the early-flowering phenotype of poco1. Our data suggest the involvement of POCO1 in the early ABA signaling process. The down-regulation of many ABA-related genes suggests an association of poco1 mutation with the ABA signaling deficiency. This condition further affects the expression of many stress-related, especially drought-associated genes in poco1, consistent with the drought sensitivity of poco1. poco1 mutation also affects the expression of genes associated with the cellular regulation, redox, and mitochondrial perturbation.

PRECOCIOUS1 (POCO1), a mitochondrial pentatricopeptide repeat protein affects flowering time in Arabidopsis thaliana.

Flowering is a vital developmental shift in plants from vegetative to reproductive phase. The timing of this shift is regulated by various linked genetic pathways including environmental cues and internal regulation. Here we report a role for an Arabidopsis gene, AT1G15480, which encodes a P-class pentatricopeptide repeat (PPR) protein, affecting flowering time. We show that AT1G15480 is localized to mitochondria. An AT1G15480 T-DNA insertion line exhibits an early-flowering phenotype, which is quite a rare phenotype among PPR mutants. The early-flowering phenotype was observed under both long and short days compared with wild type plants. Genetic complementation confirmed the observed phenotype. We therefore named the PPR protein PRECOCIOUS1 (POCO1). poco1 plants showed lower respiration, ATP content and higher accumulation of superoxide. Importantly, the quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed that the expression of FLOWERING LOCUS C (FLC), which is a key floral repressor, was strongly downregulated in the poco1. Likewise, the expression level of the FLC positive regulator ABSCISIC ACID-INSENSITIVE 5 (ABI5) was reduced in the poco1. Consistent with the qRT-PCR results, poco1 plants showed reduced sensitivity to abscisic acid compared with wild type with respect to primary root growth and days to flowering. Furthermore, the poco1 mutation enhances the sensitivity to drought stress. Further analysis showed that POCO1 affects mitochondrial RNA editing. Taken together, our data demonstrate a remarkable function of POCO1 in flowering time and the abscisic acid signalling pathway.

Microwave photonics instantaneous frequency measurement receiver based on a Sagnac Loop: publisher's note.

This publisher's note amends the author listing in Opt. Lett.43, 2233 (2018).OPLEDP0146-959210.1364/OL.43.002233.

Microwave photonics instantaneous frequency measurement receiver based on a Sagnac loop.

A microwave photonics instantaneous frequency measurement receiver was conceived and practically demonstrated. The system is based on phase modulation inside a Sagnac loop and therefore needs no bias voltage, resulting in no DC bias drifts. The system provides a DC output whose amplitude is a function of input signal frequency, and thus no high-frequency photo-detector is required. Furthermore, the system exhibits a very good sensitivity without the aid of any sort of electrical noise cancellation techniques, such as lock-in amplification. This makes the system response faster, which would be another benefit for electronic warfare applications. Less than 6% measurement error was achieved over a 0.01-40 GHz frequency range for -30 dBm RF level. Also, a 10% error was achieved at -51 dBm RF power level.

Reconfigurable microwave photonic in-phase and quadrature detector for frequency agile radar.

A microwave photonic in-phase and quadrature detector is conceived and practically demonstrated. The detector has the ability to become electronically reconfigured to operate at any frequency over a wide range. This makes it an excellent candidate for frequency agile radars and other electronic warfare systems based on frequency hopping. The detector exhibits a very low amplitude and phase imbalance, which removes the need for any imbalance compensation technique. The system is designed based on the transversal filtering concept and reconfigurability is achieved via wavelength control in a dispersive fiber. The system operation was demonstrated over a frequency range of 3.5-35 GHz, with a maximum of -32 dB amplitude imbalance.

Broadband all-optical microwave photonics phase detector.

A microwave photonics phase detector is conceived and practically demonstrated. The phase-detector system employs a semiconductor optical amplifier as a four-wave mixer to enable phase detection over a broad frequency range. The system behavior is first mathematically modeled and then demonstrated practically. Phase measurement over a frequency range of 1-18 GHz is achieved. This phase detector is an excellent candidate for wideband applications such as frequency-agile radar.

Photonic simultaneous frequency identification of radio-frequency signals with multiple tones.

A photonic approach to instantaneously identify frequency components of microwave signals with multiple tones is conceived and practically demonstrated. A mathematical model was first developed to predict the behavior of the system. Then the system operation was tested in practice. The system employs a double mixing technique that enables high-frequency measurement without the need for any high-frequency RF component or broadband photodetector. The system operation was demonstrated over a frequency range of 0.1-40 GHz. Frequency measurement of two simultaneous RF tones is demonstrated; however, the system has the potential to be expanded to measure a larger number of simultaneous RF tones. It also has the potential to operate over a wider frequency range.

Reconfigurable photonic radar warning receiver based on cascaded grating.

A photonic radar warning receiver was conceived and practically demonstrated. The system was very flexible in terms of frequency measurement range and resolution. This was achieved using a cascaded grating which provided different time delays for different wavelengths. The system was thus able to become reconfigured to operate at both broadband, low resolution and narrow band, high resolution modes.

Instantaneous frequency measurement system using optical mixing in highly nonlinear fiber.

A broadband photonic instantaneous frequency measurement system utilizing four-wave mixing in highly nonlinear fiber is demonstrated. This new approach is highly stable and does not require any high-speed electronics or photodetectors. A first principles model accurately predicts the system response. Frequency measurement responses from 1 to 40 GHz are demonstrated and simple reconfiguration allows the system to operate over multiple bands.

Wideband RF photonic in-phase and quadrature-phase generation.

A photonic implementation of a practical broadband RF Hilbert transformer is demonstrated by using a four-tap transversal system. An almost ideal 90 degrees phase shift with less than 3 dB of amplitude ripple has been achieved from 2.4 to 17.6 GHz. An efficient method to realize both transformed (quadrature-phase) and reference (in-phase) signal has been achieved by using a coarse wavelength division multiplexing coupler. Extension of the transformer bandwidth and further improvements of its implementation are discussed.