Reflection Magnitude Research Articles

Impact of sea surface waves and bubbles on water-leaving reflectance using Monte Carlo simulations

Bubbles formed in the upper layers of the sea surface due to wave breaking caused by strong winds significantly alter the radiative properties of seawater. These changes affect the water-leaving radiance recorded by a satellite or airborne sensor and lead to uncertainties in the retrieved water color measurements. This study focuses on how sea surface waves and different bubble-size populations affect the optical properties of seawater (particularly scattering) in upper ocean surface layers and how these changes impact the radiative transfer of solar energy within the sea. In this work, the spectral water-leaving reflectance caused by time-evolving sea surface waves and varying bubble sizes in the upper ocean surface layers is investigated using Monte Carlo simulations. For this study, the minimum bubble size in the distribution is assumed to be 1 µm, generated at a wind speed of 13 m s-1. The air-sea interface is modeled using the ECKV sea surface model. The in-situ inherent optical properties (IOPs) measured from Bay of Bengal (BoB) waters in the absence of bubbles were used to derive bubble population statistics from the Hall-Novarini (HN) model, while the scattering coefficients and scattering phase function resulting from bubbles in seawater were computed using Mie scattering theory and used for Monte Carlo simulations. The results demonstrate that changes in the time-evolving sea surface wave conditions significantly affect the spectral water-leaving reflectance, altering its magnitude by up to two-fold within a minute. Three distinct populations of bubble sizes were examined to calculate water-leaving reflectance. The findings indicate varying magnitudes of water-leaving reflectance among these populations. Specifically, the presence of smaller bubbles in the population results in higher water-leaving reflectance compared to larger bubbles. This increase in magnitude is primarily attributed to the number density and strong backscattering of these smaller bubbles. Additionally, the impact of the scattering phase function due to bubbles was investigated, revealing its significance in accurately calculating the water-leaving reflectance. In-situ measurements in coastal waters of the BoB using RAMSES TriOS radiometric sensors indicated that the magnitude of the water-leaving radiance spectrum changes due to the time-evolving sea surface conditions at a given wind speed. The theoretical outcome from Monte Carlo simulations was also consistent with the in-situ measurements. Additional measurements at different time intervals during wave breaks and bubble generation revealed that varying bubble sizes led to different magnitudes of water-leaving radiance, which also matched the simulation results, confirming the theoretical predictions. These results will significantly impact further studies investigating the spatial effects of waves and bubbles on water-leaving radiance. This will also contribute to enhancing the accuracy of watercolor products retrieved from satellite data.

Low-temperature transport and relaxation of photo-carriers in TiS2

The investigation of non-equilibrium carrier dynamics in two-dimensional semi-metallic materials, particularly at low temperatures, is crucial for elucidating their fundamental properties, including carrier–carrier interactions and electron–phonon scattering mechanisms. In this study, we examine the behavior of 1T-TiS2, utilizing scanning photocurrent microscopy, bias voltage-adjustable photoresponse measurements, and pump-probe techniques to explore the temperature-dependent transport and relaxation of photo-excited charge carriers. We observe a non-monotonic intrinsic photocurrent in the biased device, with a pronounced peak feature occurring at approximately 25 K, which is corroborated by pump-probe measurements that reveal a similar peak in the magnitude and relaxation time of the differential reflectance as a function of the temperature. Our results highlight the unique carrier dynamics in TiS2, offering valuable insights for the design of TiS2-based optoelectronic devices that can operate effectively across a wide temperature range.

Sex differences in the impact of ventricular-arterial coupling on left ventricular function in patients with hypertension.

Increased arterial stiffness elevates aortic load, which can have adverse impacts on left ventricular (LV) function and contribute to the onset of heart failure. This impact is known to be more pronounced in women. Optimal coordination between ventricular contraction and the arterial system is required to maintain efficient cardiac function. This study aimed to investigate sex differences in the impact of ventricular-arterial coupling (VAC) on LV function in patients with hypertension at rest and after handgrip exercise. Echocardiographic indexes of LV volumes, systolic function, and diastolic function were obtained in the usual way. Effective arterial elastance (EA) and index (EAI) were calculated from stroke volume measured using LV outflow waveform. Effective LV end-systolic elastance (ELV) and index (ELVI) were obtained using the single-beat method. Central aortic pressure waveform was recorded using the applanation tonometry. Characteristic impedance (Zc) of aortic root and reflection magnitude (RM) was calculated after Fourier transformation of both aortic pressure and flow waveforms. Sixty-four patients (31 women and 33 men) with hypertension were enrolled. Women showed higher ELVI (1.33±0.34 vs. 1.10±0.29 mmHg/ml∙m2, P = 0.004) and EAI (1.14±0.25 vs. 0.93±0.26 mmHg/ml∙m2, P = 0.001), but VAC was not different (women: 0.88±0.17 vs. men: 0.85±0.11, P = 0.431). Zc and RM were not different between women and men. After handgrip exercise, an increase in ELVI (P = 0.021) and a decrease in VAC (P = 0.035) were observed specifically in men, with no corresponding changes noted in women. In women, VAC was significantly associated with E' velocity (beta -0.344, P = 0.029) and left ventricular global longitudinal strain (beta 0.470, P = 0.012) after adjustment, but in men, no association was found. Hypertensive women demonstrated greater stiffness in both the left ventricle and arterial systems, along with impaired LV contractile reserve in response to handgrip exercise, as compared to men. The ventricular-arterial mismatch had a notable impact on LV diastolic and systolic dysfunction only in women, but not in men.

Sedimentation-controlled double BSRs and implications for paleo hydrate dissociation in the Shenhu area, south China sea

Double/multiple bottom-simulating reflectors (BSRs) have been discovered worldwide, but their preservation and formation mechanism remain unclear because most studies are based on seismic data, lacking direct evidence like well logging data. This study introduces a novel well log-based interpretation of double BSR, suggesting that the secondary BSR (BSR2) is the interface between little residual gas and the overlying water-saturated sediment, and the free gas is trapped by capillary seals. The BSR2's amplitude is influenced by the nearby porosity, with lower porosity resulting in stronger reflections. Seismic attributes reveal a dynamic process of hydrate cycle that hydrate dissociation occurs above BSR2, followed by gas migrate to form a new BSR1. The upshift of BSR2 is mainly controlled by sedimentation rate, which varies across different regions, leading to larger upshifts in areas with higher sedimentation rates. Moreover, BSR2's upshift is negatively related to the reflection magnitude of BSR2, because rapidly depositing sediments with higher porosity and lower percolation threshold allow lesser gas sealed beneath the BSR2. Our findings suggest that double BSRs are predominantly formed in muddy sediments under rapid geological events like rapid sedimentation. However, each BSR can be preserved as well as observed to indicate that the BSR has existed for an extended period of time during which the geologic environment has been relatively stable, e.g., low sedimentation rates. This detailed sedimentation-controlled BSR adjustment provides new insights for the interpretation of double BSR and the paleo hydrate dissociation.

Acute cardiovascular responses to the 100-mi Western States Endurance Run.

Ultramarathon participation is growing in popularity and exposes runners to unique stressors including extreme temperatures, high altitude, and exceedingly long exercise duration. However, the acute effects of ultramarathon participation on the cardiovascular system are not well understood. To determine the acute effects of trail ultramarathon participation on central artery stiffness and hemodynamics, 41 participants (9 F, 32 M) participating in the 2023 Western States Endurance Run underwent measures of carotid-femoral pulse wave velocity (cf-PWV) and pulse wave analysis pre- and <1 h post-race. Subendocardial viability ratio (SEVR) was calculated from central blood pressure (BP) waveforms. Serum was analyzed for creatine kinase (CK) activity as a measure of muscle damage. Normally distributed data are presented as means ± standard deviation (SD), and nonnormally distributed data are presented as median (interquartile range). Runners were middle-aged and generally lean [age = 44 ± 9 yr, body mass index (BMI) = 22.7 ± 1.8 kg·m-2]. There was no difference in cf-PWV from pre- to post-race (pre = 6.4 ± 1.0, post = 6.2 ± 0.85 m/s, P = 0.104), a finding that persisted after adjusting for mean arterial pressure (P = 0.563). Systolic and diastolic BPs were lower post-race (pre = 129/77 ± 9/7, post = 122/74 ± 10/8 mmHg, P < 0.001). Augmentation index (AIx; pre = 17.3 ± 12.2, post = 6.0 ± 13.7%, P < 0.001), AIx normalized to a heart rate of 75 beats/min (P = 0.043), reflection magnitude (pre = 55.5(49.0-60.8), post = 45.5(41.8-48.8)%, P < 0.001), and SEVR (pre = 173.0(158.0-190.0), post = 127.5(116.5-145.8)%, P < 0.001) were reduced post-race. CK increased markedly from pre- to post-race (pre = 111(85-162), post = 11,973(5,049-17,954) U/L, P < 0.001). Completing a 161-km trail ultramarathon does not affect central arterial stiffness and acutely reduces BP despite eliciting profound muscle damage. However, the reduced post-race SEVR suggests a short-term mismatch between myocardial work and coronary artery perfusion.NEW AND NOTEWORTHY Ultramarathon participation is growing dramatically. However, the acute cardiovascular effects of completing a 161-km trail ultramarathon remain unknown. We examined the acute effects of completing the 2023 Western States Endurance Run on arterial stiffness and central hemodynamics in a relatively large sample of males and females. We observed dramatic postexercise hypotension, reductions in reflected wave amplitude and reduced subendocardial viability ratio post-race. These findings suggest that ultramarathon participation has few negative effects on cardiovascular health.

A broad-beam reflective metasurface enhancing signal coverage for indoor wireless communication

ABSTRACT A broad-beam planar reflective metasurface design for indoor signal coverage is presented in this letter. The proposed metasurface unit is designed as a multi-resonant structure using an additional branch on the double ring, which achieves a reflection phase shift covering 360° and a reflection magnitude remaining above 0.8 by varying the length of the square ring. To simplify the array configuration, the unit incorporates 2-bit phase quantization. In order to broaden the reflection beam of metasurface, the phase distribution of the array is determined by the aperture field superposition method. The angles of the different electromagnetic (EM) waves within the single aperture are adjusted to be moderately distinct. The co-simulation and measurement of the horn antenna and the reflective metasurface are carried out. The results show that the metasurface can generate a broad beam at 4.8 GHz with a 3 dB beamwidth of 21°, achieving a beam gain of 18dBi. The broad beam can maintain a 3 dB beamwidth greater than 19° in the 4.2–5.6 GHz band. The reflective metasurface can be used as a passive repeater to optimize signal quality and enhance wireless communication coverage in indoor non-line-of-sight (NLOS) paths.

Gonadal status modulates large elastic artery stiffness in healthy middle-aged and older men.

Hypogonadism is a risk factor for cardiovascular disease (CVD) in men related, in part, to increased oxidative stress. Elevated large artery stiffness and central pulsatile hemodynamics (e.g., pulse pressure and wave reflection magnitude) are independent risk factors for CVD. However, whether large artery stiffness and central pulsatile hemodynamics are (1) elevated in hypogonadal men independent of traditional CVD risk factors and (2) related to increased oxidative stress is unknown. Young men (N = 23; 30 ± 4years) and middle-aged/older (MA/O) men with normal (> 400-1000ng/dL; n = 57; 59 ± 7years) or low testosterone (< 300ng/dL; n = 21; 59 ± 7years) underwent assessments of large artery stiffness (carotid ß-stiffness via ultrasonography) and central pulsatile hemodynamics (pulse wave analysis; SphygmoCor XCEL) following an infusion of saline or vitamin C to test the tonic suppression of vascular function by oxidative stress. Carotid stiffness differed by age (p < 0.001) and gonadal status within MA/O men (low testosterone vs. normal testosterone: 9.3 ± 0.7 vs. 8.0 ± 0.3U, p = 0.036). Central pulsatile hemodynamics did not differ by age or gonadal status (p > 0.119). Vitamin C did not alter carotid stiffness in any group (p > 0.171). There was a significant group × infusion interaction on aortic reflection magnitude (p = 0.015). Vitamin C treatment reduced aortic reflection magnitude in young and MA/O men with normal testosterone (both p < 0.001) but not MA/O men with low testosterone (p = 0.891). Collectively, hypogonadism may accelerate age-related large artery stiffening in MA/O men with low testosterone, independent of CVD risk factors; however, this is not related to increased reactive oxygen species sensitive to an acute vitamin C infusion.

Phase manipulation in reflective phase gradient photonic crystals.

Phase gradient photonic crystals (PGPCs) are proposed as promising candidates for phase manipulation and can enable arbitrary electromagnetic functions, such as deflection and focusing. In stark contrast to the proposed metasurfaces, the phase variation in PGPCs arises from simple edge-configuration rather than structure resonance. Moreover, the reflection magnitude maintains a constant of 1 for the reflective case in the Bragg gap, which affords significant convenience in design. Both theoretical and experimental results demonstrate that the deflector based on reflective PGPCs possesses strong angular stability and is applicable across a broadband frequency range. Our work provides a promising avenue for the implementation of phase manipulation on novel optical platforms, facilitating the development of innovative optical devices with distinctive features in the future.

Design and Implementation of Different Unit Cells for Reconfigurable Intelligent Surface

Recently, great attention has been given to the idea of a smart environment. It often involves the use of reconfigurable intelligent surfaces (RIS) for the management of electromagnetic wave reflections as the world awaits the emergence of 6G. Changeable intelligent surfaces may enhance the creation of wireless communication. The design and analysis of several unit cell reflections are presented in this work. The first design relies on the Switching Technique which involves switching on and off to acquire the phase as well as the coefficient of reflection to accommodate 6G standards. The unit cells design is configured to operate in the millimeter band and X band. In the second design, the radius of the circular patch was changed to adjustment of the phase and reflection coefficient. The use of Floquet technique is employed in investigating the scattering characteristics of a unit cell's constituent elements based on the assumption that every element consists of an extremely iterating periodic structure. To determine the optimal force reflection and the transformation phase, the return loss alongside reflection phase graphs of each resonant component were examined. The simulation results indicate that the first design exhibits a reflection phase shift range of -180 to 90 and a reflection magnitude over 0.93 at a frequency of 11GHz. In contrast, the second design demonstrates a reflection phase shift range of -135 to 135 and a reflection magnitude surpassing 0.9 at a frequency of 28GHz. The analysis and simulation of the design models were carried out using the CST model.

A wide-band high gain beamsteerable variable patch reflectarray antenna for THz applications

This article proposed a compact size, high gain, wideband reflectarray antenna for THz and 6 G applications. To enhance the aperture efficiency and gain, a single layer L-shape delay line-based unit cell with a size of 0.45λ0 is adopted. The λ0 is the free space wavelength at 1.35 THz. The SiO2 substrate is sandwiched between L- shape delay line and the ground plane of gold. The unit cell, equivalent parallel RLC circuit modelled with gap coupled capacitance is also presented which is validated through the Ansys-High Frequency Structure Simulator (HFSS) and Advanced Design System (ADS). The dimension of the RA is 3 mm having 610 elements. It is excited by the pyramidal horn antenna at an optimum distance (F/D =1.21). The optimum ratio (F/D) is calculated with the help of the cosq model at −10 dB edge taper. The operating bandwidth is obtained 46.15 % from 1 to 1.6 THz. The reflection phase and magnitude are 500° and 3.93 dB at 1.35 THz. It is adjusted by varying the length of the delay line. The maximum aperture efficiency and realized gain are 35 % and 28 dBi respectively. The Side lobe level is −15.5 dB and the Co-Cross polarization level is below −30 dB.

Arterial stiffness is associated with prehypertension in both non-hypertensives and treated hypertensives–A matched case control study

BackgroundPrehypertension (PHT) is a cardiovascular health risk defined by blood pressure (BP). Arterial stiffness (AS) provides beyond brachial BP inference on vascular ageing and pulse wave analysis (PWA) can measure it non-invasively.We compared association between AS and PHT using age and gender matched case-controls. MethodsThis is a sub analysis of previous PWA studies of hypertensives and non-hypertensives. Using oscillometric PWA by Mobil-o-Graph (IEM, Stolberg, Germany), parameters of AS (augmentation pressure and index, reflection magnitude, aortic pulse wave velocity, pulse pressure amplification), brachial hemodynamics (BH), and central hemodynamics (CH; aortic BP, cardiac output related parameters, stroke work) were derived. Age and gender matched case controls were compared as: 1) Nonhypertensives with BP at prehypertensive level (PHT) versus normotensives (NT) (n = 217 each), 2) Under treatment hypertensives with BP at prehypertensive level (PHT-T) versus untreated, nonhypertensives with BP at prehypertensive level (PHT-UT) (n = 74 each). ResultsPHTs had higher AS, BH and CH than NTs, with statistical significance for all but few parameters. PHT-T had comparable BH but higher AS, CH than PHT-UT with significance for few parameters. ConclusionPulse wave analysis derived arterial stiffness is associated with prehypertension compared to normal, after age and gender matching. In hypertensives, arterial stiffness is significantly higher despite being treated to prehypertension level as compared to control. It hints arterial stiffness to be better parameter than brachial BP to study prehypertension.

Wave Separation Analysis to Assess Cardiovascular Alterations Induced by Sepsis.

Sepsis induces a severe decompensation of arterial and cardiac functional properties, leading to important modifications of arterial blood pressure (ABP) waveform, not resolved by recommended therapy, as shown by previous works. The aim of this study is to quantify the changes in ABP waveform morphology and wave reflections during a long-term swine experiment of polymicrobial sepsis and resuscitation, to deepen the understanding of the cardiovascular response to standard resuscitation therapy. We analyzed 14 pigs: polymicrobial sepsis was induced in 9 pigs followed by standard resuscitation and 5 pigs were treated as sham controls. Septic animals were studied at baseline (T1), after sepsis development (T2), and after 24 h (T3) and 48 h (T4) of therapy administration, and sham controls at the same time points. ABP and arterial blood flow were measured in the left and right carotid artery, respectively. Pulse wave analysis and wave separation techniques were used to estimate arterial input impedance, carotid characteristic impedance, forward and backward waves, indices of wave reflections such as reflection magnitude and reflection index, and augmentation index. Sepsis led to an acute alteration of ABP waveform passing from type A to type B or C; consistently, the reflection phenomena were significantly reduced. The resuscitation was successful in reaching targeted hemodynamic stability, but it failed in restoring a physiological blood propagation and reflection. Septic pigs persistently showed altered reflected waves even after 48 hours of successful therapy according to guidelines, suggesting a persistent hidden cardiovascular disorder. The proposed indices may be useful to unravel the complex cardiovascular response to therapy administration in septic patients and could potentially be used for risk stratification of patient deterioration. Whether alterations of blood propagation and reflection contribute to persisting organ dysfunction after hemodynamic stabilization should be further investigated.

Mapping surface hoar from near-infrared texture in a laboratory

Abstract. Surface hoar crystals are snow grains that form when water vapor deposits on the snow surface. Once buried, surface hoar creates a weak layer in the snowpack that can later cause large avalanches to occur. The formation and persistence of surface hoar are highly spatiotemporally variable, making its detection difficult. Remote-sensing technology capable of detecting the presence and spatial distribution of surface hoar would be beneficial for avalanche forecasting, but this capability has yet to be developed. Here, we hypothesize that near-infrared (NIR) texture, defined as the spatial variability of reflectance magnitude, may produce an optical signature unique to surface hoar due to the distinct shape and orientation of the grains. We tested this hypothesis by performing reflectance experiments in a controlled cold laboratory environment to evaluate the potential and accuracy of surface hoar mapping from NIR texture using a near-infrared hyperspectral imager (NIR-HSI) and a lidar operating at 1064 nm. We analyzed 41 snow samples, three of which were surface hoar and 38 of which consisted of other grain morphologies. When using NIR-HSI under direct and diffuse illumination, we found that surface hoar displayed higher NIR texture relative to all other grain shapes across numerous spectral bands and a wide range of spatial resolutions (0.5–50 mm). Due to the large number of spectral- and spatial-resolution combinations, we conducted a detailed samplewise case study at 1324 nm spectral and 10 mm spatial resolution. The case study resulted in the median texture of surface hoar being 1.3 to 8.6 times greater than that of the 38 other samples under direct and diffuse illumination (p &lt; 0.05 in all cases). Using lidar, surface hoar also exhibited significantly increased NIR texture in 30 out of 38 samples, but only at select (5–25 mm) spatial resolutions. Leveraging these results, we propose a simple binary classification algorithm to map the extent of surface hoar on a pixelwise basis using both the NIR-HSI and lidar instruments. The NIR-HSI under direct and diffuse illumination performed best, with a median accuracy of 96.91 % and 97.37 %, respectively. Conversely, the median classification accuracy achieved with lidar was only 66.99 %. Further, to assess the repeatability of our method and demonstrate its mapping capacity, we ran the algorithm on a new sample with mixed microstructures, with an accuracy of 99.61 % and 96.15 % achieved using NIR-HSI under direct and diffuse illumination, respectively. As NIR-HSI detectors become increasingly available, our findings demonstrate the potential of a new tool for avalanche forecasters to remotely assess the spatiotemporal variability of surface hoar, which would improve avalanche forecasts and potentially save lives.

Generating terahertz multiple vortex beams using graphene metasurfaces

This paper investigates the generation of orbital angular momentum vortex beams using a graphene metasurface in the terahertz frequency band. The proposed design consists of 20 × 20 unit-cell elements to operate in 1.2 THz applications. Each element is a graphene ring patch printed on a silicon dioxide substrate backed with a polysilicon ground plane of size 75 × 75 × 25 µm3. The graphene reconfigurable surface conductivity is used to control the beam shape, direction, and directivity radiated from the metasurface, through the application of DC biasing voltages. A parametric study on the effect of graphene chemical potential, relaxation time and temperature on the unit-cell reflection properties is introduced. The reflection magnitude varies from − 2.1 dB to -0.8 dB with a 350-degree phase variation for µc ranging from 0.25 eV to 1.6 eV at \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au$$\\end{document} =5 ps, and T = 300 K. The effect of graphene relaxation time from 0.3 ps to 10 ps on the reflection coefficient at µc = 0.7 eV, and T = 300 K is investigated. The metasurface radiation characteristics are investigated under the illumination of two types of incidence sources, plane-wave, and focused-waves. A depiction of a single vortex beam in various orientations θ = 0, 30o, 50o, and 70o, φ = 90o for l = 1 is presented. The purity of the OAM single beam shows that 94% of the power is concentrated in the designed mode. A graphene metasurface can to convert linearly polarized input into multiple beams exhibiting orthogonal modes. Two/four vortex beams in different directions are demonstrated. The capacity for wireless communication in the terahertz band can be enhanced by utilizing a graphene metasurface.

GENDER DIFFERENCES IN THE IMPACT OF VENTRICULAR-ARTERIAL COUPLING ON LEFT VENTRICULAR FUNCTION IN PATIENTS WITH HYPERTENSION

Objective: Increased arterial stiffness elevates aortic load, which can have adverse impacts on left ventricular (LV) function and contribute to the onset of heart failure. This impact is known to be more pronounced in women. Optimal coordination between ventricular contraction and the arterial system is required to maintain efficient cardiac function. This study aimed to investigate gender differences in the impact of ventricular-arterial coupling (VAC) on LV function in patients with hypertension at rest and after handgrip exercise. Design and method: Echocardiographic indexes of LV volumes, systolic function, and diastolic function were obtained in the usual way. Effective arterial elastance (EA) and index (EAI) were calculated from stroke volume measured using LV outflow waveform. Effective LV end-systolic elastance (ELV) and index (ELVI) were obtained using the single-beat method. Central aortic pressure waveform was recorded using the applanation tonometry. Characteristic impedance (Zc) of aortic root and reflection magnitude (RM) was calculated after Fourier transformation of both aortic pressure and flow waveforms. Results: Sixty-four patients (31 women and 33 men) with hypertension were enrolled. Women showed higher ELVI (1.33±0.34 vs. 1.10±0.29 mmHg/ml/m2, P=0.004) and EAI (1.14±0.25 vs. 0.93±0.26 mmHg/ml/m2, P=0.001), but VAC was not different (women: 0.88±0.17 vs. men: 0.85±0.11, P=0.431). Zc and RM were not different between women and men. After handgrip exercise, an increase in ELVI (P=0.021) and a decrease in VAC (P=0.035) were observed specifically in men, with no corresponding changes noted in women. In women, VAC was significantly associated with E’ velocity (beta -0.344, P=0.029) and left ventricular global longitudinal strain (beta 0.470, P=0.012) after adjustment, but in men, no association was found. Conclusions: Hypertensive women demonstrated greater stiffness in both the left ventricle and arterial systems, along with impaired LV contractile reserve in response to handgrip exercise, as compared to men. The ventricular-arterial mismatch had a notable impact on LV diastolic and systolic dysfunction only in women, but not in men.

Objectively Measured Hot Flashes and Moderate-Vigorous Activity Predict Arterial Stiffness in Healthy Perimenopausal Women

Perimenopause is the period of transition when midlife women experience increases in cardiovascular disease (CVD) risk. Arterial stiffness (AS) is a preclinical CVD risk factor that precedes the manifestation of clinical CVD. Hot flashes (HF) are bothersome symptoms of menopause which are correlated with some subclinical CVD risk factors, but the exact relationship between HF and CVD risk factors remain equivocal. Habitual physical activity (PA) is effective in the prevention and treatment of CVD in many populations. However, the relationship between PA and CVD risk remains unclear for perimenopausal women. Therefore, the objective of our study was to determine the effects of HF and PA on AS in healthy perimenopausal women. We hypothesized that HFs would be associated with AS and PA would influence the association between HFs and AS. There were 61 participants (age 43-54) free from CVD risk factors included in this analysis. Arterial stiffness was measured via augmentation index (AIx), backwards wave (PB, mmHg), and reflection magnitude (RM, %). Hot flashes were measured objectively for 24 hours using ambulatory sternal skin conductance monitoring. Objective HF rate was calculated by normalizing HF count to wear time. Habitual PA activity was quantified objectively as average daily minutes of waking moderate-vigorous PA (MVPA) over 7-day using actigraphy and the R package GGIR. All statistical analyses were performed using R (version 4.2.3) and RStudio (2023.06.2+561). Pearson’s correlation and multiple regression were used to evaluate the associations between dependent and outcome variables. Age and body mass index (BMI) were controlled, and assumption testing was completed for all models. Objective HF rate was significantly positively correlated with PB, r(53) = 0.38, p &lt; 0.01, and RM, r(53) = 0.35, p &lt;0.01. Objective MVPA was significantly negatively associated with AIx, r(61) = -0.45, p &lt;0.001, PB, r(61) = -0.29, p &lt;0.05, and RM, r(61) = -0.34, p &lt; 0.01. Objective HF rate significantly predicted arterial stiffness variables, AIx (β = 14.58, p =0.05; adjR2 = 0.38), PB (β = 6.48, p&lt;0.01; adjR2 = 0.24), and RM (β = 17.79, p &lt;0.01; adjR2 = 0.39). Objective MVPA significantly predicted AIX (β = -0.12, p &lt;0.01; adjR2 = 0.41), and RM (β = -0.06, p = 0.05; adjR2 = 0.29). When HF and MVPA were added in the same model, HF and MVPA were both significant predictors of RM (βHF = 16.25, p &lt;0.01, βMVPA = -0.06, p &lt;0.05; adjR2 = 0.42), MVPA only was significant with AIx (βHF = 11.38, p = 0.10, βMVPA = -0.13, p &lt;0.01; adjR2 = 0.49), and HF only was significant with PB (βHF = 6.11, p &lt;0.01, βMVPA = -0.02, p = 0.212; adjR2 = 0.25). Adding the interaction between HF and MVPA did not help explain variation in any AS variable. In conclusion, our data showed that more objectively-measured HF were associated with negative AS outcomes and that greater MVPA may be worth considering in decreasing arterial stiffness in perimenopausal women. Contrary to our hypothesis, MVPA did not help to explain the effects of HF on AS. Future studies should focus on understanding the mechanisms behind the negative relationship between hot flashes and arterial stiffness in midlife women. NIH NHLBI R15 Grant 1R15HL145650-01A1 (Witkowski); Smith College McKinley Honors Fellowship (Tha Ra Wun). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effect of Aging and Hypertension on Ambulatory Blood Pressure, Arterial Stiffness, and Wave Reflection in Mid-life Adults

Introduction: Age-associated increases in blood pressure are partly due to increased arterial stiffness and wave reflection. How these vascular changes during aging contribute to daily fluctuations in blood pressure and hypertension remain to be elucidated. Therefore, the purpose of this study is to compare ambulatory blood pressure, arterial stiffness, and wave reflection between young healthy adults, mid-life adults without hypertension, and mid-life adults with hypertension. Methods: Twenty-five young (age: 26 ± 4 yr and body mass index [BMI]: 23.9 ± 2.5 kg/m2) and 31 mid-life adults (age: 57 ± 4 yr and BMI: 25.4 ± 2.6 kg/m2), free of obesity and major clinical diseases and non-smokers, were included. Hypertension was defined by the current use of anti-hypertension medications or offce seated blood pressure (BP) ≥ 130/80 mmHg. Young adults with hypertension were excluded. Twenty-four-hour ambulatory BP monitoring (Oscar 2™, SunTech Medical®) and assessment of aortic arterial stiffness and wave reflection (SphygmoCor XCEL, AtCor Medical) were performed in all participants. Results: Daytime, nighttime, and 24-hr systolic BP was similar between young adults (YA) and mid-life adults without hypertension (MA; n=12; P&gt;0.9 vs. YA), while mid-life adults with hypertension (MAHTN; n=19) had higher offce, 24-hr, daytime, and nighttime systolic and diastolic BP compared to YA and MA (p&lt;0.01 vs. YA and MA). Compared to YA, MA had higher nighttime diastolic BP (P=0.02). Aortic arterial stiffness, measured by carotid-to-femoral pulse wave velocity, was the highest in MAHTN (p&lt;0.001 vs. YA and P=0&lt;0.01 vs. MA), followed by MA (p&lt;0.01 vs. YA) and YA. Aortic wave reflection, measured by augmentation index and reflection magnitude, was higher in MA and MAHTN compared to YA but was similar between MA and MAHTN (p&lt;0.001 for MA vs. YA; p&lt;0.001 for MAHTN vs. YA; and P&gt;0.9 for MA vs. MAHTN). Conclusions: Our findings indicate that 1) mid-life adults with hypertension had higher ambulatory BP and arterial stiffness than mid-life adults without hypertension and young adults; 2) despite normal offce blood pressure, mid-life adults without hypertension had higher nighttime diastolic BP and arterial stiffness than young adults; and 3) regardless of hypertension, mid-life adults had higher wave reflection than young adults. These findings suggest that 1) vascular aging may present prior to the diagnosis of hypertension based on offce BP; 2) arterial stiffness, rather than wave reflection, may contribute to the development of hypertension during aging; and 3) compared to offce BP, ambulatory BP may be a more sensitive marker of age-associated increases in blood pressure. NIAAA K99/R00 AA028537 to CLH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Impact of cardiac rehabilitation on ventricular-arterial coupling and left ventricular function in patients with acute myocardial infarction.

To maintain efficient myocardial function, optimal coordination between ventricular contraction and the arterial system is required. Exercise-based cardiac rehabilitation (CR) has been demonstrated to improve left ventricular (LV) function. This study aimed to investigate the impact of CR on ventricular-arterial coupling (VAC) and its components, as well as their associations with changes in LV function in patients with acute myocardial infarction (AMI) and preserved or mildly reduced ejection fraction (EF). Effective arterial elastance (EA) and index (EAI) were calculated from the stroke volume and brachial systolic blood pressure. Effective LV end-systolic elastance (ELV) and index (ELVI) were obtained using the single-beat method. The characteristic impedance (Zc) of the aortic root was calculated after Fourier transformation of both aortic pressure and flow waveforms. Pulse wave separation analysis was performed to obtain the reflection magnitude (RM). An exercise-based, outpatient cardiac rehabilitation (CR) program was administered for up to 6 months. Twenty-nine patients were studied. However, eight patients declined to participate in the CR program and were subsequently classified as the non-CR group. At baseline, E' velocity showed significant associations with EAI (beta -0.393; P = 0.027) and VAC (beta -0.375; P = 0.037). There were also significant associations of LV global longitudinal strain (LV GLS) with EAI (beta 0.467; P = 0.011). Follow-up studies after a minimum of 6 months demonstrated a significant increase in E' velocity (P = 0.035), improved EF (P = 0.010), and LV GLS (P = 0.001), and a decreased EAI (P = 0.025) only in the CR group. Changes in E' velocity were significantly associated with changes in EAI (beta -0.424; P = 0.033). Increased aortic afterload and VA mismatch were associated with a negative impact on both LV diastolic and systolic function. The outpatient CR program effectively decreased aortic afterload and improved LV diastolic and systolic dysfunction in patients with AMI and preserved or mildly reduced EF.

Numerically Optimized Fourier Transform-Based Beamforming Accelerated by Neural Networks

Conventional beamforming methods for reconfigurable reflector antennas assume full control over the amplitude and phase of the reflected field. Here, we develop a novel beamforming methodology for reflecting Programmable Metasurfaces (PMS) with capacitive memory. Although utilizing such fully reactive PMS simplifies antenna design and reduces energy consumption, the PMS reflection magnitude is unity and thus a global optimization of the reflection phases over the PMS unit cells is required in each beamforming scenario. We propose an implementation of such an optimization method rooted in the traditional Fourier transform-based beamforming and evaluate its performance. Additionally, we show that a pair of trained feed-forward neural networks (FFNN) with one input, one hidden, and one output layer can replace time-consuming global optimizations in the case of a PMS comprising 3×10 unit cells. We train the FFNNs on a dataset obtained for typical single- and dual-beam beamforming scenarios. After training, the FFNNs perform requested beamforming tasks within a fraction of second and with about the same accuracy as the original optimization algorithm. The proposed methodology may find applications in future mobile telecommunication systems that require real-time beamforming on low-end hardware. The same beamforming methodology can be also employed in short-range wireless power transfer systems.

Design and Implementation of a Soiling Forecasting Tool for Parabolic Through Collector Mirrors

This study presents a new soiling forecasting algorithm that was designed to predict the deposition of dust on mirror of Parabolic Through Collector (PTC) plants. The PTC soiling model developed in this work is based on existing models for the dust dry deposition over geographic regions. The soiling forecast algorithm is characterized by specific mechanisms. The sedimentation mechanism, also known as “gravitational settling”, is proportional to the sun’s position. Brownian motion is defined as a diffusion process and depends on the air’s wind speed and temperature. Impaction mechanism depends on the wind speed and wind direction and occurs when particles do not follow the curved streamlines of their flow due to the inertia. All three mechanisms depend also on aerosol’s size. Two mechanisms contribute to the mirror’s cleaning, namely rebound and washout. Soiling rate (SR) is the daily rate of dust accumulation on the mirror’s surface and depends on deposition velocity, rebound, the number of particles and their size. The modelled reflectivity is a function of SR and the reflectivity of a cleaned mirror. The model was calibrated using reflectivity measurements which were acquired during a previous project campaign in the period July 2018 – May 2019. The validation of the model for June 2019 showed that it accurately captured the phasing and the magnitude of reflectivity. The results of this study can help the PTC’s operator to choose the optimal cleaning strategy to minimize the energy loss and to reduce O&amp;M cost.