Heterogeneous multicore fiber-based microwave frequency measurement.

A novel microwave frequency measurement scheme using a heterogeneous multicore fiber (MCF) is experimentally demonstrated. The inherently different relative group delays among the cores of a heterogeneous 7-core MCF are used to realize two individual 2-tap microwave filters with different free spectral ranges (FSRs). The ratio of the frequency response traces of these two filters is used to establish an amplitude comparison function (ACF). Furthermore, by varying the operational wavelength, the relative group delays between the cores and consequently the FSRs of the filters are tuned and different ACF curves are obtained. The complementary information provided by these different ACFs allows us to estimate the unknown frequency with an improved accuracy, over a broad measurement range. In our experiments, a measurement error of ±71 MHz is achieved over a frequency range of 0.5-40 GHz. The proposed scheme offers flexibility and compactness, thanks to the parallelism provided by the MCF.

Experimental demonstration of dispersion-diversity multicore fiber optical beamforming.

Phased array antenna (PAA) beam-steering in high radiofrequency bands will be key for upcoming 5G & Beyond wireless communications systems. As a compact and efficient solution to provide tunable beam steering simultaneously to parallel antenna distribution and connectivity, we experimentally demonstrate, for the first time to our knowledge, tunable optical beamforming implemented on a dispersion-diversity multicore optical fiber. The uniqueness of this fiber lies in the fact that each one of its seven step-index trench-assisted cores has been tailored to provide the required chromatic dispersion to enable tunable optical true-time delay line operation. Continuous 1D beam-steering was demonstrated by measuring the radiating pattern of an in-house fabricated 8-element PAA in an anechoic chamber at the radiofrequency of 26 GHz, sweeping the beam-pointing angle from -43° up to 40° by varying the operating optical wavelength from 1542.50 up to 1548.28 nm. Next-generation fiber-wireless communications systems will benefit from the demonstrated dispersion-diversity MCF optical beamforming in terms of flexibility, versatility, capacity, and connectivity along with reduced size, weight, and power consumption.

Changes of organochlorine compound concentrations in maternal serum during pregnancy and comparison to serum cord blood composition.

The concentrations of organochlorine compounds (OCs), including pentachlorobenzene, hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, ß-, γ- and δ-HCH), polychlorobiphenyls (PCBs 28, 52, 101, 118, 138, 153 and 180), DDT and metabolites, were measured in maternal serum samples collected at the first trimester of pregnancy, at delivery and in umbilical cord from a cohort of mother-newborn pairs from Tarragona (Spain) (n = 50), representing general population of a Mediterranean area from Southern Europe. The observed concentrations were generally low in comparison with previous studies in other world areas. Higher OC concentrations were observed in the maternal serum collected at delivery than in the first trimester and the cord blood concentrations were lower than the maternal levels. These results show for the first time a small but statistically significant increase in maternal venous concentration of OCs between the first trimester and delivery when measured in ng/ml. HCB, ß-HCH and the PCB congeners in cord blood were significantly correlated with the concentrations of these compounds in maternal venous blood and the coefficients were stronger for the samples collected at delivery which was consistent with OC transfer from mother to foetus. In the case of DDT compounds, only 4,4'-DDT showed maternal-cord blood correlation which documented the low metabolic capacity of newborns for OC transformation, e.g. DDT into DDE. Maternal age was the most significant driver of the observed maternal venous OC concentrations in both periods, older ages involving higher concentrations. Higher body mass index was only significantly correlated with higher 4,4'-DDE concentrations in maternal venous blood and cord blood. In some cases, social class and education level were significantly correlated with OC concentrations, e.g. 4,4'-DDE in maternal venous blood from the first trimester and cord blood and PCB153 in maternal venous blood at delivery. In these cases, highest concentrations were found in the women with highest education level and most affluent social class. Comparison of the maternal OC concentrations of this cohort with those observed in 2002 in population of the same geographic area and age range shows decreases between two and ten times over this fourteen-year period.

Bending and twisting effects on multicore fiber differential group delay.

In this paper we provide the theoretical and experimental evaluation of fiber bending and twisting effects on the group delay performance of a homogeneous 7-core fiber. We have experimentally evaluated the differential group delay between the central and outer cores for different curvature radii and twisting conditions, demonstrating that fiber twisting counteracts the degradation introduced by the curvature itself. These findings are generally applicable to time-sensitive application areas such as radio-over-fiber distribution and microwave photonics signal processing in fiber-wireless access networks, as well as high-capacity long-haul digital communications where digital multiple-input multiple-output processing may be required.

Ring-core few-mode fiber for tunable true time delay line operation.

We propose, for the first time to our knowledge, tunable true time delay line operation for radiofrequency signals on a few-mode fiber link. In particular, the custom design of a 7-LP-mode ring-core few-mode fiber together with a set of 5 broadband long period gratings inscribed at the proper positions along the fiber allows 4-sample true time delay line tunability over a 20-nm optical wavelength range. We study the performance of the designed true time delay line in the context of reconfigurable microwave photonics signal processing by theoretically evaluating microwave signal filtering and optical beamforming networks for phased array antennas.

Sampled true time delay line operation by inscription of long period gratings in few-mode fibers.

We propose and experimentally demonstrate distributed microwave photonics signal processing over a few-mode fiber link by implementing 4-sample true time delay line operation. The inscription of a set of long period gratings at specific locations along the few-mode fiber allows the excitation of the higher-order modes while adjusting the individual sample group delays and amplitudes that are required for sampled true time delay line behavior. Since solely the injection of the fundamental mode at the few-mode fiber input is required, we render this signal processing system independent of any preceding fiber link that may be required in addition to distribute the signal. We experimentally validate the performance of the implemented true time delay line when applied to radiofrequency signal filtering.

Few-mode fiber true time delay lines for distributed radiofrequency signal processing.

We report, for the first time to our knowledge, distributed radiofrequency signal processing built upon true time delay operation on a step-index few-mode fiber. Two 3-sample configurations with different time delay properties are implemented over the same 60-meter 4-LP-mode fiber link. The inscription of a long period grating at a specific fiber position converts part of the LP01 mode into the LP02, permitting sample time delay engineering. Delay line performance is experimentally demonstrated when applied to radiofrequency signal filtering, example of fiber-distributed processing functionality exhibiting one order or magnitude gain in terms of compactness.

Experimental demonstration of multi-cavity optoelectronic oscillation over a multicore fiber.

We report, for the first time to our knowledge, the experimental demonstration of multi-cavity optoelectronic oscillators where the cavities are provided by the different cores of a multicore fiber. We implemented two multi-cavity architectures over a 20-m-long 7-core fiber link: unbalanced dual-cavity oscillation (the cavity lengths are a multiple of a reference value) and multi-cavity Vernier oscillation (the cavity lengths are slightly different). Since all the cavities are hosted under a single fiber cladding and are subject to the same environmental and mechanical conditions, optoelectronic oscillators built upon multicore fibers benefit from improved performance stability as compared to independent singlemode fiber cavities.

Dispersion-engineered multicore fibers for distributed radiofrequency signal processing.

We report a trench-assisted heterogeneous multicore fiber optimized in terms of higher-order dispersion and crosstalk for radiofrequency true time delay operation. The analysis of the influence of the core refractive index profile on the dispersion slope and effective index reveals a tradeoff between the behavior of the crosstalk against fiber curvatures and the linearity of the propagation group delay. We investigate the optimization of the multicore fiber in the framework of this tradeoff and present a design that features a group delay relative error below 5% for an optical wavelength range up to 100 nm and a crosstalk level below -80 dB for bending radii larger than 103 mm. The performance of the true time delay line is validated in the context of microwave signal filtering and optical beamforming for phased array antennas. This work opens the way towards the development of compact fiber-integrated solutions that enable the implementation of a variety of distributed signal processing functionalities that will be key in future fiber-wireless communications networks and systems.

Multi-cavity optoelectronic oscillators using multicore fibers.

We propose the use of both homogeneous and heterogeneous multicore fibers to implement multi-cavity optoelectronic oscillators. We present design equations and examples that show the potential for unique performance in terms of spectral selectivity, tunability and high-frequency operation.

Design of heterogeneous multicore fibers as sampled true-time delay lines.

We present a novel procedure for designing a sampled discrete true-time delay line (TTDL) for Microwave Photonics applications based on a heterogeneous MCF. Both simple step-index (SI) and trench-assisted SI profiles are numerically evaluated in terms of physical dimensions and material dopant concentrations in order to individually tailor the group delay and chromatic dispersion of each core. The proposed TTDL features unique properties beyond the current state of the art in terms of record bandwidth, compactness, flexibility, and versatility.

Intentional thought dynamics during exercise performed until volitional exhaustion.

Using a non-linear approach, intentional dynamics of thoughts were examined during constant cycling performed until volitional exhaustion. Participants (n = 12) completed two sessions at 80% Wmax. Their (1) intrinsic thought dynamics (i.e., no-imposed thoughts condition) and (2) intentional thought dynamics (i.e., imposed task-unrelated thoughts condition; TUT) were recorded and then classified into four categories: internal and external TUT (TUT-I, TUT-E) and external and internal task-related thoughts (TRT-E, TRT-I). The probability estimates for maintaining each thought category stable, the rate of switching from one category to another, and the entropy dynamics along the testing procedure were assessed and compared through time phase. Friedman ANOVA tests revealed a significant effect of effort increase on thought contents only in the imposed TUT test. While TUT-I probabilities decreased significantly (P < .001) as effort increased, TRT-I probabilities increased (P < .05). Moreover, the entropy to the entire thought dynamics increased at the outset of task performance and decreased upon approaching volitional exhaustion (P < .001). As time spent in constant effort increased, and volitional exhaustion approached, task relatedness (TUT, TRT), direction (internal, external), and entropy of thought contents changed unintentionally providing further evidence for a nonlinear dynamics of attention focus.

Predicting COVID-19 pandemic waves including vaccination data with deep learning.

Introduction: During the recent COVID-19 pandemics, many models were developed to predict the number of new infections. After almost a year, models had also the challenge to include information about the waning effect of vaccines and by infection, and also how this effect start to disappear. Methods: We present a deep learning-based approach to predict the number of daily COVID-19 cases in 30 countries, considering the non-pharmaceutical interventions (NPIs) applied in those countries and including vaccination data of the most used vaccines. Results: We empirically validate the proposed approach for 4 months between January and April 2021, once vaccination was available and applied to the population and the COVID-19 variants were closer to the one considered for developing the vaccines. With the predictions of new cases, we can prescribe NPIs plans that present the best trade-off between the expected number of COVID-19 cases and the social and economic cost of applying such interventions. Discussion: Whereas, mathematical models which include the effect of vaccines in the spread of the SARS-COV-2 pandemic are available, to the best of our knowledge we are the first to propose a data driven method based on recurrent neural networks that considers the waning effect of the immunization acquired either by vaccine administration or by recovering from the illness. This work contributes with an accurate, scalable, data-driven approach to modeling the pandemic curves of cases when vaccination data is available.

Dispersion-Diversity Multicore Fiber Signal Processing.

Beyond playing a primary role in high-capacity communication networks, multicore optical fibers can bring many advantages to optical and microwave signal processing, as not only space but also chromatic dispersion are introduced as new degrees of freedom. The key lies in developing radically new multicore fibers where the refractive index profile of each individual core is tailored properly to provide parallel dispersion-diversity signal processing with application in a variety of scenarios such as parallel channel equalization, analogue-to-digital conversion, optical computing, pulse generation and shaping, multiparameter fiber sensing, medical imaging, optical coherence tomography, broadband measurement instrumentation, and next-generation fiber-wireless communications. Here, we experimentally prove, for the first time to our knowledge, reconfigurable two-dimensional dispersion-managed signal processing performed by a novel dispersion-diversity heterogeneous multicore fiber. The fiber comprises seven different trench-assisted cores featuring a different refractive index profile in terms of both radial geometry and core dopant concentration. As a representative application case, we demonstrate reconfigurable microwave signal filtering with increased compactness as well as performance flexibility and versatility as compared to previous technologies.

Changes of agonist and synergist muscles activity during a sustained submaximal brake-pulling gesture.

We analyzed the time course of changes in muscle activity of the prime mover and synergist muscles during a sustained brake-pulling action and investigated the relationship between muscle activity and braking force fluctuation (FF). Thirty-two participants performed a continuous fatiguing protocol (CFP) at 30% of maximal voluntary contraction (MVC) until failure. Surface electromyography was used to analyze root mean square (RMS) values in the flexor digitorum superficialis (FD), flexor carpi radialis (FC), extensor digitorum communis (ED), extensor carpi radialis (EC), brachioradialis (BR), biceps brachii (BB), and triceps brachii (TB). The FF and RMS in all muscles increased progressively (P<0.01) during the CFP, with sharp increments at time limit particularly in FD and FC (P<0.001). The RMS of the FD and FC were comparable to the baseline MVC values at time limit, in comparison to the other muscles that did not reach such levels of activity (P<0.003). The three flexor/extensor ratios used to measure coactivation levels decreased significantly (P<0.001). In contrast to RMS, MVC was still depressed at the minute 10 of recovery. The results suggest that the time limit was mainly constrained by fatigue-related mechanisms of the FD and FC but not by those of other synergist and antagonist muscles.

Cucumis metuliferus reduces Meloidogyne incognita virulence against the Mi1.2 resistance gene in a tomato-melon rotation sequence.

BACKGROUND: Susceptible tomato cv. Durinta, ungrafted or grafted onto cv. Aligator resistant rootstock, both followed by the susceptible melon cv. Paloma, ungrafted or grafted onto Cucumis metuliferus BGV11135, and in the reverse order, were cultivated from 2015 to 2017 in the same plots in a plastic greenhouse, infested or not with Meloidogyne incognita. For each crop, soil nematode densities, galling index, number of eggs per plant and crop yield were determined. Virulence selection was evaluated in pot experiments. RESULTS: In the tomato-melon rotation, nematode densities increased progressively for the grafted tomato, being higher than for ungrafted plants at the end of the study; this was not the case in the melon-tomato rotation. Grafted crops yielded more than ungrafted crops in the infested plots. Virulence against the Mi1.2 gene was detected, but not against C. metuliferus. Reproduction of M. incognita on the resistant tomato was ∼ 120% that on the susceptible cultivar after the first grafted tomato crop, but this decreased to just 25% at the end of the experiment. CONCLUSION: Alternating different resistant plant species suppresses nematode population growth rate and yield losses. Although this strategy does not prevent virulence selection, the level was reduced. © 2018 Society of Chemical Industry.

Entrainment from the para-Hisian region for differentiating atrioventricular node reentrant tachycardia from orthodromic atrioventricular reentrant tachycardia.

AIMS: The difference between the stimulus-atrial and ventriculo-atrial intervals (SA-VA) and between the post-pacing interval and the tachycardia cycle length (PPI-TCL) during entrainment from the right ventricular apex distinguishes atrioventricular node reentrant (AVNRT) from orthodromic atrioventricular reentrant tachycardia (AVRT). We hypothesized that these features still apply when entrainment is performed from the para-Hisian region. METHODS AND RESULTS: Forty-seven supraventricular tachycardias (34 AVNRT/13 AVRT) were included. The SA-VA and PPI-TCL were obtained in all patients by using two right-sided diagnostic catheters. In 24 of them, these measurements were also performed upon His-bundle capture during entrainment. A paced QRS widening of >or=40 ms during entrainment, when compared with the tachycardia QRS width, identified absence of His-bundle capture, P < 0.001. A SA-VA >75 ms distinguished AVNRT from AVRT, P < 0.001 (sensitivity/specificity 97%/100%). A PPI-TCL >100 ms was diagnostic of AVNRT, P < 0.001 (sensitivity/specificity 97%/92%). Upon His-bundle capture, the SA-VA and PPI-TCL shortened in AVNRT (121 +/- 23 to 66 +/- 24 ms; 139 +/- 30 to 85 +/- 31 ms, respectively, P < 0.001) and no longer differentiated AVNRT from AVRT. CONCLUSION: Para-Hisian entrainment without His-bundle capture distinguishes AVNRT from AVRT with the advantage of using only two diagnostic catheters.

[Evaluation of patient satisfaction after stroke rehabilitation program. Validation study for the Spanish version of the Satisfaction Pound Scale]. / Evaluación de la satisfacción con el programa de rehabilitación tras el ictus: validación de la versión española de la Pound Satisfaction Scale.

BACKGROUND AND OBJECTIVE: The Satisfaction Pound Scale is a specific questionnaire to evaluate satisfaction with the rehabilitation program after a stroke. The aim of this study was to adapt this scale to Spanish and to evaluate its metric characteristics. METHOD: The adaptation included translation and back-translation methods. Metric characteristics were evaluated in 74 patients, all of whom were administered the Satisfaction Pound Scale and the Short Form 36 (SF-36). The statistical model was tested by confirmatory factor analysis (CFA). Reliability was determined through Cronbach alpha coefficient and a test-retest procedure. Construct validity was assessed by means of correlations between the satisfaction scale and the SF-36. RESULTS: Adjustment indicators in the CFA were very good. Reproducibility test showed correlations higher than 0.85, and all correlations between SF-36 dimensions and the satisfaction scale were lower than 0.2, in accordance with the hypotheses raised. CONCLUSIONS: The Spanish version of the Satisfaction Pounds Scale is reliable and valid, therefore it is a useful tool to assess satisfaction with the post-stroke rehabilitation program in our area.

Dynamics of Perceived Exertion in Constant-Power Cycling: Time- and Workload-Dependent Thresholds.

PURPOSE: The purpose of this study was to test the dynamics of perceived exertion shifts (PES) as a function of time and workload during constant-power cycling. METHOD: Fifty-two participants assigned to 4 groups performed a cycling task at 4 different constant workloads corresponding to their individual rates of perceived exertion (RPEs = 13, 15, 17, and 19, respectively). PES ("increased"/"decreased" perceptions) without magnitude were reported when they occurred. PES "increased" percentages in different nonoverlapping temporal windows and for each workload were calculated to study the time- and workload-dependent relations, respectively. RESULTS: A fluctuating PES dynamic characterized the cycling at RPE-13 and RPE-15. In contrast, a nonfluctuating PES dynamic characterized the cycling at RPE-17 and RPE-19. A time-dependent PES threshold, manifested as a switch from PES fluctuating to nonfluctuating dynamics, emerged in the RPE-15 condition near volitional exhaustion. A workload-dependent PES threshold occurred from RPE-15 to RPE-17. CONCLUSIONS: Time- and workload-dependent thresholds were revealed studying the PES dynamics in constant cycling. Monitoring PES can complement or provide an alternative to the use of physiological measures for an accurate control of training workloads.