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Accurate sleep stage classification is crucial for diagnosing sleep disorders and evaluating sleep quality. While polysomnography (PSG) remains the gold standard, photoplethysmography (PPG) is more practical due to its affordability and widespread use in wearable devices. However, state-of-the-art sleep staging methods often require prolonged continuous signal acquisition, making them impractical for wearable devices due to high energy consumption. Shorter signal acquisitions are more feasible but less accurate. Our work proposes an adapted sleep staging model based on top-performing state-of-the-art methods and evaluates its performance with different PPG segment sizes. We concatenate 30-second PPG segments over 15-minute intervals to leverage longer segment contexts. This approach achieved an accuracy of 0.75, a Cohen's Kappa of 0.60, an F1-Weighted score of 0.74, and an F1-Macro score of 0.60. Although reducing segment size decreased sensitivity for deep and REM stages, our strategy outperformed single 30-second window methods, particularly for these stages., Comment: 11 pages, 5 figures, 1 table

The merging of two black holes is a notoriously difficult process to describe exactly. Nevertheless, the hindrances posed by gravity's nonlinearity can be circumvented by focusing on the strict extreme mass ratio limit, in which one of the black holes is infinitely larger than the other. Such an approach has been developed by Emparan and Mart\'inez and applied within General Relativity to investigate the time evolution of event horizons melding, using nothing but elementary concepts in gravitational physics and simple integrations of geodesics. We apply this strategy to study black hole mergers in higher derivative gravity, in order to assess how the defining characteristics of the fusion process change as the gravitational theory is modified. We adopt the case of Einsteinian cubic gravity for concreteness, and determine how the mergers' duration and the relative area increment change as the theory's single coupling parameter is varied., Comment: v2: 13 pages, 11 figures, minor modifications and an added subsection about entropy and area growth (including two new figures)

Hypertension, a leading contributor to cardiovascular morbidity, underscores the need for accurate and continuous blood pressure (BP) monitoring. Photoplethysmography (PPG) presents a promising approach to this end. However, the precision of BP estimates derived from PPG signals has been the subject of ongoing debate, necessitating a comprehensive evaluation of their effectiveness and constraints. We developed a calibration-based Siamese ResNet model for BP estimation, using a signal input paired with a reference BP reading. We compared the use of normalized PPG (N-PPG) against the normalized Invasive Arterial Blood Pressure (N-IABP) signals as input. The N-IABP signals do not directly present systolic and diastolic values but theoretically provide a more accurate BP measure than PPG signals since it is a direct pressure sensor inside the body. Our strategy establishes a critical benchmark for PPG performance, realistically calibrating expectations for PPG's BP estimation capabilities. Nonetheless, we compared the performance of our models using different signal-filtering conditions to evaluate the impact of filtering on the results. We evaluated our method using the AAMI and the BHS standards employing the VitalDB dataset. The N-IABP signals meet with AAMI standards for both Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP), with errors of 1.29+-6.33mmHg for systolic pressure and 1.17+-5.78mmHg for systolic and diastolic pressure respectively for the raw N-IABP signal. In contrast, N-PPG signals, in their best setup, exhibited inferior performance than N-IABP, presenting 1.49+-11.82mmHg and 0.89+-7.27mmHg for systolic and diastolic pressure respectively. Our findings highlight the potential and limitations of employing PPG for BP estimation, showing that these signals contain information correlated to BP but may not be sufficient for predicting it accurately., Comment: 17 pages, 7 figures, 3 tables

We study the $J/\psi \to \phi \pi^+ a_0(980)^- (a_0^- \to \pi^- \eta)$ decay, evaluating the double mass distribution in terms of the $\pi^- \eta$ and $\pi^+ a^-_0$ invariant masses. We show that the $\pi^- \eta$ mass distribution exhibits the typical cusp structure of the $a_0(980)$ seen in recent high statistics experiments, and the $\pi^+ a^-_0$ spectrum shows clearly a peak around $M_{\rm inv}(\pi^+ a^-_0)=1420 \,{\rm MeV}$, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of $10^{-5}$, which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the $\eta \pi^+\pi^-$ mass distribution in the $J/\psi \to \phi \eta \pi^+\pi^-$ decay and encourage further analysis to extract from there the $\phi \pi^+ a_0^-$ and $\phi \pi^- a_0^+$ decay modes., Comment: 8 pages, 3 figures; V2: discussion added, references added, version to appear in Phys. Rev. D

We study the $D^+ \to \bar K^0 \pi^+ \eta$ reaction where the $a_0(980)$ excitation plays a dominant role. We consider mechanisms of external and internal emission at the quark level, hadronize the $q \bar q$ components into two mesons and allow these mesons to undergo final state interaction where the $a_0(980)$ state is generated. While the $a_0(980)$ production is the dominant term, we also find other terms in the reaction that interfere with this production mode and, through interference with it, lead to a shape of the $a_0(980)$ significantly different from the one observed in other experiments, with an apparently much larger width., Comment: 8 pages, 12 figures

Sleep is a crucial aspect of our overall health and well-being. It plays a vital role in regulating our mental and physical health, impacting our mood, memory, and cognitive function to our physical resilience and immune system. The classification of sleep stages is a mandatory step to assess sleep quality, providing the metrics to estimate the quality of sleep and how well our body is functioning during this essential period of rest. Photoplethysmography (PPG) has been demonstrated to be an effective signal for sleep stage inference, meaning it can be used on its own or in a combination with others signals to determine sleep stage. This information is valuable in identifying potential sleep issues and developing strategies to improve sleep quality and overall health. In this work, we present a machine learning sleep-wake classification model based on the eXtreme Gradient Boosting (XGBoost) algorithm and features extracted from PPG signal and activity counts. The performance of our method was comparable to current state-of-the-art methods with a Sensitivity of 91.15 $\pm$ 1.16%, Specificity of 53.66 $\pm$ 1.12%, F1-score of 83.88 $\pm$ 0.56%, and Kappa of 48.0 $\pm$ 0.86%. Our method offers a significant improvement over other approaches as it uses a reduced number of features, making it suitable for implementation in wearable devices that have limited computational power., Comment: 8 pages, 3 figures

Diabetes is a prevalent chronic condition that compromises the health of millions of people worldwide. Minimally invasive methods are needed to prevent and control diabetes but most devices for measuring glucose levels are invasive and not amenable for continuous monitoring. Here, we present an alternative method to overcome these shortcomings based on non-invasive optical photoplethysmography (PPG) for detecting diabetes. We classify non-Diabetic and Diabetic patients using the PPG signal and metadata for training Logistic Regression (LR) and eXtreme Gradient Boosting (XGBoost) algorithms. We used PPG signals from a publicly available dataset. To prevent overfitting, we divided the data into five folds for cross-validation. By ensuring that patients in the training set are not in the testing set, the model's performance can be evaluated on unseen subjects' data, providing a more accurate assessment of its generalization. Our model achieved an F1-Score and AUC of $58.8\pm20.0\%$ and $79.2\pm15.0\%$ for LR and $51.7\pm16.5\%$ and $73.6\pm17.0\%$ for XGBoost, respectively. Feature analysis suggested that PPG morphological features contains diabetes-related information alongside metadata. Our findings are within the same range reported in the literature, indicating that machine learning methods are promising for developing remote, non-invasive, and continuous measurement devices for detecting and preventing diabetes., Comment: 11 pages, 6 figures

Photoplethysmography (PPG) is a non-invasive technology that measures changes in blood volume in the microvascular bed of tissue. It is commonly used in medical devices such as pulse oximeters and wrist worn heart rate monitors to monitor cardiovascular hemodynamics. PPG allows for the assessment of parameters (e.g., heart rate, pulse waveform, and peripheral perfusion) that can indicate conditions such as vasoconstriction or vasodilation, and provides information about microvascular blood flow, making it a valuable tool for monitoring cardiovascular health. However, PPG is subject to a number of sources of variations that can impact its accuracy and reliability, especially when using a wearable device for continuous monitoring, such as motion artifacts, skin pigmentation, and vasomotion. In this study, we extracted 27 statistical features from the PPG signal for training machine-learning models based on gradient boosting (XGBoost and CatBoost) and Random Forest (RF) algorithms to assess quality of PPG signals that were labeled as good or poor quality. We used the PPG time series from a publicly available dataset and evaluated the algorithm s performance using Sensitivity (Se), Positive Predicted Value (PPV), and F1-score (F1) metrics. Our model achieved Se, PPV, and F1-score of 94.4, 95.6, and 95.0 for XGBoost, 94.7, 95.9, and 95.3 for CatBoost, and 93.7, 91.3 and 92.5 for RF, respectively. Our findings are comparable to state-of-the-art reported in the literature but using a much simpler model, indicating that ML models are promising for developing remote, non-invasive, and continuous measurement devices., Comment: 9 pages

We use ray-tracing techniques to determine the evolution of the event horizon of a large black hole that ``gobbles'' a tiny, traversable wormhole. This calculation has physical meaning in the extreme mass ratio limit. Two setups are considered: a single-mouth wormhole connecting two otherwise independent universes, and a double-mouth zero-length wormhole within the same universe. In the first setting it turns out that, at early times, there exist two disconnected horizons, one in each universe, which then merge as the wormhole falls into the large black hole. In the second setup, we observe the appearance of an `island', a region of spacetime that is spatially disconnected from the exterior of the black hole, but in causal contact with future null infinity. The island shrinks as time evolves and eventually disappears after sufficient time has elapsed, as compared to the distance between the two mouths. This provides a communication channel with the interior of the large black hole for a certain time interval. We compute numerically the lifetime of the island and verify that it depends linearly on the inter-mouth distance. Extending the analysis to wormholes with finite length, we show that the achronal averaged null energy condition prevents the appearance of islands., Comment: 15 pages, 10 figures; v2: minor corrections, matches published version

The Super $\tau$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $\tau$-Charm factory -- the BEPCII, providing a unique platform for exploring the asymmetry of matter-antimatter (charge-parity violation), in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions, as well as searching for exotic hadrons and physics beyond the Standard Model. The STCF project in China is under development with an extensive R\&D program. This document presents the physics opportunities at the STCF, describes conceptual designs of the STCF detector system, and discusses future plans for detector R\&D and physics case studies.

It has been generally expected that the $X(3872)$ has a spin-2 partner, $X_2$, with quantum numbers $J^{PC}=2^{++}$. In the hadronic molecular model, its mass was predicted to be below the $D^*\bar D^*$ threshold, and the new structure reported in the $\gamma \psi(2S)$ invariant mass distribution by the Belle Collaboration with mass $M= (4014.3 \pm 4.0 \pm 1.5)$ MeV and decay width $\Gamma= (4 \pm 11 \pm 6)$ MeV, with a global significance of 2.8 $\sigma$, is a nice candidate for it. We consider the radiative decay widths for the $X_{2}\to \gamma\psi$ with $\psi=J/\psi, \psi(2S)$ treating the $X_2$ as a $D^*\bar{D}^*$ shallow bound state, and estimate the events of $X_2$ in two-photon collisions that can be collected in the $\gamma J/\psi\to\gamma\ell^+\ell^-$ ($\ell=e,\mu$) final states at Belle. Based on the upper limit for the ratio of decay widths of $X(3872)\to \gamma \psi(2S)$ and $X(3872)\to \gamma J/\psi$ measured by BESIII, we predict the similar ratio $\Gamma(X_2\to \gamma \psi(2S))/\Gamma(X_2\to \gamma J/\psi)$ to be smaller than $1.0$. We suggest searching for the $X_2$ signal in the $\gamma J/\psi$ invariant mass distribution via two-photon fusions. The results will lead to insights into both the $X(3872)$ and the new structure observed by Belle., Comment: 21 pages, 3 figures. Version to appear in PLB

In this work, we interpret the newly observed $\eta_1(1855)$ resonance with exotic $J^{PC}=1^{-+}$ quantum numbers in the $I=0$ sector, reported by the BESIII Collaboration, as a dynamically generated state from the interaction between the lightest pseudoscalar mesons and axial-vector mesons. The interaction is derived from the lowest order chiral Lagrangian from which the Weinberg-Tomozawa term is obtained, describing the transition amplitudes among the relevant channels, which are then unitarized using the Bethe-Salpeter equation, according to the chiral unitary approach. We evaluate the $\eta_1(1855)$ decays into the $\eta\eta^{\prime}$ and $K\bar{K}^*\pi$ channels and find that the latter has a larger branching fraction. We also investigate its SU(3) partners, and according to our findings, the $\pi_1(1400)$ and $\pi_1(1600)$ structures may correspond to dynamically generated states, with the former one coupled mostly to the $b_1\pi$ component and the latter one coupled to the $K_1(1270)\bar{K}$ channel. In particular, our result for the ratio $\Gamma(\pi_1(1600)\to f_1(1285)\pi)/ \Gamma(\pi_1(1600)\to \eta^{\prime}\pi)$ is consistent with the measured value, which supports our interpretation for the higher $\pi_1$ state. We also report two poles with a mass about 1.7~GeV in the $I=1/2$ sector, which may be responsible for the $K^*(1680)$. We suggest searching for two additional $\eta_1$ exotic mesons with masses around 1.4 and 1.7~GeV. In particular, the predicted $\eta_1(1700)$ is expected to have a width around 0.1~GeV and can decay easily into $K\bar K\pi\pi$., Comment: Accepted for publication in Universe with a DOI link https://doi.org/10.3390/universe9020109

Active perception and foveal vision are the foundations of the human visual system. While foveal vision reduces the amount of information to process during a gaze fixation, active perception will change the gaze direction to the most promising parts of the visual field. We propose a methodology to emulate how humans and robots with foveal cameras would explore a scene, identifying the objects present in their surroundings with in least number of gaze shifts. Our approach is based on three key methods. First, we take an off-the-shelf deep object detector, pre-trained on a large dataset of regular images, and calibrate the classification outputs to the case of foveated images. Second, a body-centered semantic map, encoding the objects classifications and corresponding uncertainties, is sequentially updated with the calibrated detections, considering several data fusion techniques. Third, the next best gaze fixation point is determined based on information-theoretic metrics that aim at minimizing the overall expected uncertainty of the semantic map. When compared to the random selection of next gaze shifts, the proposed method achieves an increase in detection F1-score of 2-3 percentage points for the same number of gaze shifts and reduces to one third the number of required gaze shifts to attain similar performance., Comment: 6 pages, 8 figures, ICDL 2022 (International Conference on Development and Learning, formerly ICDL-EpiRob)

This paper introduces a new multi-strain epidemic model with reinfection and cross-immunity to provide insights into the resurgence of the COVID-19 epidemic in an area with reportedly high seroprevalence due to a largely unmitigated outbreak: the state of Amazonas, Brazil. Although high seroprevalence could have been expected to trigger herd immunity and prevent further waves in the state, we have observed persistent levels of infection after the first wave and eventually the emergence of a second viral strain just before an augmented second wave. Our experiments suggest that the persistent levels of infection after the first wave may be due to reinfection, whereas the higher peak at the second wave can be explained by the emergence of the second variant and a low level of cross-immunity between the original and the second variant. Finally, the proposed model provides insights into the effect of reinfection and cross-immunity on the long-term spread of an unmitigated epidemic.

Hyperspectral imaging measures the amount of electromagnetic energy across the instantaneous field of view at a very high resolution in hundreds or thousands of spectral channels. This enables objects to be detected and the identification of materials that have subtle differences between them. However, the increase in spectral resolution often means that there is a decrease in the number of photons received in each channel, which means that the noise linked to the image formation process is greater. This degradation limits the quality of the extracted information and its potential applications. Thus, denoising is a fundamental problem in hyperspectral image (HSI) processing. As images of natural scenes with highly correlated spectral channels, HSIs are characterized by a high level of self-similarity and can be well approximated by low-rank representations. These characteristics underlie the state-of-the-art methods used in HSI denoising. However, where there are rarely occurring pixel types, the denoising performance of these methods is not optimal, and the subsequent detection of these pixels may be compromised. To address these hurdles, in this article, we introduce RhyDe (Robust hyperspectral Denoising), a powerful HSI denoiser, which implements explicit low-rank representation, promotes self-similarity, and, by using a form of collaborative sparsity, preserves rare pixels. The denoising and detection effectiveness of the proposed robust HSI denoiser is illustrated using semireal and real data.

This paper introduces two very fast and competitive hyperspectral image (HSI) restoration algorithms: fast hyperspectral denoising (FastHyDe), a denoising algorithm able to cope with Gaussian and Poissonian noise, and fast hyperspectral inpainting (FastHyIn), an inpainting algorithm to restore HSIs where some observations from known pixels in some known bands are missing. FastHyDe and FastHyIn fully exploit extremely compact and sparse HSI representations linked with their low-rank and self-similarity characteristics. In a series of experiments with simulated and real data, the newly introduced FastHyDe and FastHyIn compete with the state-of-the-art methods, with much lower computational complexity.

By looking at the pseudoscalar-vector meson spectra in the $\bar{B}\to J/\psi \rho\bar{K}$ and $\bar{B}\to J/\psi \bar{K}^*\pi$ weak decays, we theoretically investigate the double-pole structure of the $K_1(1270)$ resonance by using the Chiral Unitary approach to account for the final state interactions between the pseudoscalar and vector mesons. The $K_1(1270)$ resonance appears as dynamically generated through these interactions in coupled channels and influence the shape of the invariant mass distributions under consideration. We show how those shapes are affected by the $K_1(1270)$ double-pole structure to confront the results from our model with future experiments that might investigate the $PV$ spectra in these decays., Comment: 26 pages, 12 figures, and 2 Tables. Manuscript published in PRD

This work introduces a novel epidemiological model that simultaneously considers multiple viral strains, reinfections due to waning immunity response over time and an optimal control formulation. This enables us to derive optimal mitigation strategies over a prescribed time horizon under a more realistic framework that does not imply perennial immunity and a single strain, although these can also be derived as particular cases of our formulation. The model also allows estimation of the number of infections over time in the absence of mitigation strategies under any number of viral strains. We validate our approach in the light of the COVID-19 epidemic and present a number of experiments to shed light on the overall behaviour under one or two strains in the absence of sufficient mitigation measures. We also derive optimal control strategies for distinct mitigation costs and evaluate the effect of these costs on the optimal mitigation measures over a two-year horizon. The results show that relaxations in the mitigation measures cause a rapid increase in the number of cases, which then demand more restrictive measures in the future.

We present the results of a four-month, spectroscopic campaign of the Wolf-Rayet dust-making binary, WR137. We detect only small-amplitude, random variability in the CIII5696 emission line and its integrated quantities (radial velocity, equivalent width, skewness, kurtosis) that can be explained by stochastic clumps in the wind of the WC star. We find no evidence of large-scale, periodic variations often associated with Corotating Interaction Regions that could have explained the observed intrinsic continuum polarization of this star. Our moderately high-resolution and high signal-to-noise average Keck spectrum shows narrow double-peak emission profiles in the Halpha, Hbeta, Hgamma, HeII6678 and HeII5876 lines. These peaks have a stable blue-to-red intensity ratio with a mean of 0.997 and a root-mean-square of 0.004, commensurate with the noise level; no variability is found during the entire observing period. We suggest that these profiles arise in a decretion disk around the O9 companion, which is thus an O9e star. The characteristics of the profiles are compatible with those of other Be/Oe stars. The presence of this disk can explain the constant component of the continuum polarization of this system, for which the angle is perpendicular to the plane of the orbit, implying that the rotation axis of the O9e star is aligned with that of the orbit. It remains to be explained why the disk is so stable within the strong ultraviolet radiation field of the O star. We present a binary evolutionary scenario that is compatible with the current stellar and system parameters., Comment: 12 pages, 5 Figures

The World Health Organization (WHO) made the assessment that COVID-19 can be characterized as a pandemic on March 11, 2020. To the COVID-19 outbreak, there is no vaccination and no treatment. The only way to control the COVID-19 outbreak is sustained physical distancing. In this work, a simple control law was proposed to keep the infected individuals during the COVID-19 outbreak below the desired number. The proposed control law keeps the value of infected individuals controlled only adjusting the social distancing level. The stability analysis of the proposed control law is done and the uncertainties in the parameters were considered. A version of the proposed controller to daily update was developed. This is a very simple approach to the developed control law and can be calculated in a spreadsheet. In the end, numerical simulations were done to show the behavior of the number of infected individuals during an epidemic disease when the proposed control law is used to adjust the social distancing level., Comment: 11 pages, 3 figures

The current COVID-19 pandemic is affecting different countries in different ways. The assortment of reporting techniques alongside other issues, such as underreporting and budgetary constraints, makes predicting the spread and lethality of the virus a challenging task. This work attempts to gain a better understanding of how COVID-19 will affect one of the least studied countries, namely Brazil. Currently, several Brazilian states are in a state of lock-down. However, there is political pressure for this type of measures to be lifted. This work considers the impact that such a termination would have on how the virus evolves locally. This was done by extending the SEIR model with an on / off strategy. Given the simplicity of SEIR we also attempted to gain more insight by developing a neural regressor. We chose to employ features that current clinical studies have pinpointed has having a connection to the lethality of COVID-19. We discuss how this data can be processed in order to obtain a robust assessment.

Using the vector-exchange interaction in the local hidden gauge approach, which in the light quark sector generates the chiral Lagrangian, and has produced realistic results for $\Omega_c, \Xi_c, \Xi_b$ and the hidden charm pentaquark states, we study the meson-baryon interactions in the coupled channels that lead to the $\Xi_{bb}$ and $\Omega_{bbb}$ excited states of the molecular type. We obtain seven states of the $\Xi_{bb}$ type with energies between $10408$ and $10869$ MeV and one $\Omega_{bbb}$ state at $15212$ MeV., Comment: v1:17 pages, 19 tables; v2: 20 pages, 19 tables, discussion added, references added, version to appear in Chin. Phys. C

We have studied the meson-baryon interaction in coupled channels with the same quantum numbers of $\Xi_{bc}$. The interaction is attractive in some channels and of sufficient intensity to lead to bound states or resonances. We use a model describing the meson-baryon interaction based on an extrapolation of the local hidden gauge approach to the heavy sector, which has been successfully used in predicting $\Omega_c$ and hidden charm states. We obtain many states, some of them narrow or with zero width, as a consequence of the interaction, which qualify as molecular states in those channels. The success in related sectors of the picture used should encourage the experimental search for such states., Comment: 29 pages, 3 figures

We evaluate ratios of the $\chi_{c1}$ decay rates to $\eta$ ($\eta', K^-$) and one of the $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^{*}_2(1430)$ resonances, which in the local hidden gauge approach are dynamically generated from the vector-vector interaction. With the simple assumption that the $\chi_{c1}$ is a singlet of SU(3), and the input from the study of these resonances as vector-vector molecular states, we describe the experimental ratio $\mathcal{B}(\chi_{c1} \rightarrow \eta f_2(1270))/ \mathcal{B}(\chi_{c1} \rightarrow \eta' f_2'(1525))$ and make predictions for six more ratios that can be tested in future experiments., Comment: 12 pages, 2 figures, 1 table

We investigate the problems of 1-D and 2-D signal recovery from subsampled Hadamard measurements using Haar wavelet sparsity prior. These problems are of interest in, e.g., computational imaging applications relying on optical multiplexing or single-pixel imaging. However, the realization of such modalities is often hindered by the coherence between the Hadamard and Haar bases. The variable and multilevel density sampling strategies solve this issue by adjusting the subsampling process to the local and multilevel coherence, respectively, between the two bases; hence enabling successful signal recovery. In this work, we compute an explicit sample-complexity bound for Hadamard-Haar systems as well as uniform and non-uniform recovery guarantees; a seemingly missing result in the related literature. We explore the faithfulness of the numerical simulations to the theoretical results and show in a practically relevant instance, e.g., single-pixel camera, that the target signal can be obtained from a few Hadamard measurements., Comment: 36 pages, 11 figures