Wave Amplitude Research Articles

Experimental study of the vertical structure of internal solitary waves in the continuous pycnocline

In order to reveal the complex structural characteristics of internal solitary waves (ISWs) in the actual ocean, an experimental study of the vertical structure of ISWs in the continuous pycnocline (a transition layer with sharp density changes) was conducted in a stratified fluid flume. The gravity collapse method was used to generate ISWs, and their wave-flow fields were measured using a coupled wave-flow measurement technique. The vertical structure of wave-flow fields was investigated as was the applicability of the Dubreil–Jacotin–Long (DJL) equation. The results show that the waveform of ISWs contains multiple isodensity lines that varied with fluid depth. The wave amplitude and wavelength of ISWs exhibited depth-dependent changes, which were negatively correlated. The vertical structure of the flow fields exhibited an approximate circular wave packet, with stronger horizontal flow than vertical flow. The larger the characteristic amplitude, the stronger the intensity of the flow field, and the faster the intensity of the vertical flow field increased. The applicability of the DJL equation was closely related to the stratified environment, with better agreement when the upper layer fluid constituted a larger ratio of the total fluid thickness.

The Distribution of Pc5 Ultralow-frequency Waves at Geostationary Orbit

Using GOES magnetometer data spanning over 30 yr, we study the distribution of Pc5 ultralow-frequency waves at geosynchronous orbit. The CLEAN algorithm was applied to detect narrowband Pc5 waves. This method was first used in astronomical radio interferometry, but has since been applied to many other areas. The algorithm allows for identification of multiple individual peaks within the same power spectral density. We found close to 30,000 events in each magnetic field component in field-aligned coordinates. With some exceptions, results were in agreement with previous studies. Wave occurrence along magnetic local time (MLT) was higher in the 18–23 MLT sector. However, the largest accumulated wave amplitudes were observed on the dayside, peaking close to local noon. As expected, wave amplitudes were larger during more active solar wind conditions. For the radial and parallel components, amplitudes were maximum at the interplanetary magnetic field clock angle of −30° to −45°. The resultant database of Pc5 ultralow-frequency wave events can be used to constrain radiation belt models, while the CLEAN method provides a unique technique to automatically detect narrowband plasma waves in the magnetosphere and beyond.

A Randomized Controlled Clinical Trial of Xingnao Kaiqiao Acupuncture Combined With Modern Rehabilitation Therapy in the Treatment of Cognitive Dysfunction After Acute Ischemic Stroke

Objective: To investigate the therapeutic effect of Xingnao Kaiqiao acupuncture combined with modern rehabilitation therapy on cognitive dysfunction after acute ischemic stroke (AIS). Methods: Totally 140 patients with cognitive impairment after AIS admitted to Sichuan Provincial Rehabilitation Hospital from September 2016 to May 2021 were included in this prospective randomized controlled trial. After admission, patients were randomly divided into the trial group and the control group based on a computer-generated random number table. Patients in the trial group were treated with Xingnao Kaiqiao acupuncture combined with modern rehabilitation therapy, and those in the control group were treated with modern rehabilitation therapy alone. Before and after treatment, Mini-Mental State Examination (MMSE) and Barthel index (BI) were used to evaluate the cognitive function and daily living activities, and event-related potentials (ERP) were also measured in both groups. Statistical analyses were performed to compare the results between the two groups. Results: Finally 135 patients were included, 67 in the trial group and 68 in the control group. After treatment, the MMSE score and BI were significantly improved in both groups as compared with those before treatment (both P < .001). In the trial group, the BI and the MMSE subscores in the domains of orientation, registration, recall, and language were significantly higher than those in the control group (all P < 0.05). The global MMSE score of the trial group was higher than that of the control group both after 2 and 4 weeks of treatment, and the differences were statistically significant (P = 0.000/0.001). In the analysis of time effect alone, time had significant effects on the MMSE score in both groups (P < 0.001). After treatment, the latencies of P3 waves were significantly shorter and the amplitudes of P3 waves were significantly higher in the trial group as compared with the control group (both P < 0.05). Conclusion: Xingnao Kaiqiao acupuncture combined with modern rehabilitation therapy may be associated with a better efficacy in treating cognitive dysfunction after AIS. The effect of Xingnao Kaiqiao acupuncture on ERP may play a role in the mechanism underlying such a therapeutic effect.

Strain waves on additively manufactured plates for an on-orbit impact detector concept

Orbital debris impacts on spacecraft are an emerging threat to space missions due to the exponential increase in the number of satellites orbiting the Earth. Debris characteristics (size, material, velocity, etc.) are not well known for the size range of 10 mm or less that is undetectable using Earth telescopes or radar observation. The objective of this research was to determine wether a concept designed to detect impact of particles in the ∼1 to 5 mm range, find the location of the impact, and characterize the impacting projectile (velocity, size, angle, density), is feasible.The paper describes the design, fabrication, and tests performed on “witness plates” (the concept) made of two parallel layers of additively manufactured aluminum and instrumented with sixteen gages, eight on each layer. Laboratory experiments have shown that the waves can be recorded and properly interpreted to find location of impact, sound speed in the plate, and to estimate impact velocity. It was shown analytically that the amplitude of the first strain wave that propagates from the impact point is expected to decay as 1/r. This was observed as well in the signals recorded in the experiments. CTH computations were performed during the pre-test design phase and the post-test analysis phase. In fact, the numerical simulations have been key and pervasive in this research effort as they provided invaluable insight for the initial design and the correct interpretation of signal anomalies seen during the tests. Additionally, the computations confirmed the 1/r law derived analytically, i.e. that the assumptions for the derivation were justified. The main conclusions of the research are that, for a normal impact, the 1/r law for front gages can be easily used to determine the diameter of the impactor. It is possible that the back gages could be used to determine the density of the impactor as well. Finally, it was shown that oblique impacts generate an expected assymetry in the signals recorded. Though this aspect should be investigated further, the assymetry is probably uniquely related to the impact angle, which could provide the angle information.

Longitudinal changes in retinal ganglion cell function in optic pathway glioma evaluated by photopic negative response

Photopic negative response (PhNR), an index of retinal ganglion cell (RGC) function, is impaired in patients with optic pathway gliomas (OPGs). The aim of this longitudinal study was to evaluate whether PhNR deteriorates over time in OPG patients. Fourteen pediatric patients affected by OPG (4 males and 10 females, mean age 12.4 ± 5.7 years, 8 with neurofibromatosis type 1 [NF1]) with ≥ 12 months of follow-up and ≥ 2 evaluations, were included in this retrospective study. All patients received chemotherapy and/or OPG surgical resection, at least 5 years prior to the study. At baseline, all patients underwent a complete ophthalmological examination. Follow-up included clinical examination and PhNR measurements as well as brain MRI (according to pediatric oncologist indications) every 6 or 12 months. Mean follow-up duration was 16.7 ± 7.5 months (range 12-36 months). Photopic electroretinograms were elicited by 2.0 cd/m2 Ganzfeld white flashes presented on a steady 20 cd/m2 white background. The PhNR amplitude was measured as the difference between baseline and the maximal negative amplitude (minimum) of the negative wave, following the photopic b-wave. Compared to baseline, mean PhNR amplitude was significantly decreased at the end of follow-up (p =0.008). NF1-related OPGs exhibited a decline in PhNR amplitude (p =0.005) and an increase in PhNR peak-time during the follow-up (p =0.013), whereas sporadic OPGs showed no significant changes. Tumor size remained stable in all patients on MRI. PhNR amplitude decreased over the observation period, suggesting progressive RGC dysfunction in NF1-related pediatric OPGs, despite stable size on MRI imaging. PhNR could serve as a non-invasive objective tool for assessing longitudinal changes in RGC function in the clinical management of childhood OPG.

The feasibility of atrial Fibrillatory wave amplitude in predicting ablation outcomes in persistent atrial fibrillation

BackgroundAtrial fibrosis has a significant impact on the success rate of catheter ablation (CA) treatment of atrial fibrillation (AF). The fibrotic tissues could be reflected by the amplitude of the fibrillatory wave (F-wave). Methods and Results704 patients with persistent AF and at least 1-year follow-up after CA were included as the internal group. 101 patients from another hospital were used as the external validation cohort. A 12‑lead ECG was performed before CA and the maximum FWA in three ECG leads (aVL, aVF, V1) were measured. The FWA score (0 to 6 points according to the amplitude range of the three leads) of each patients was calculated. Five models including clinical features, FWA score, CHA2DS2-VASc score, APPLE score and the fusion of clinical features and FWA score were built. The FWA score was superior to the model constructed by clinical variables, CHA2DS2-VASc score and APPLE score. It not only had good predictive performance for AF recurrence, with an AUC value of 0.812 (95% CI 0.724–0.900), but also showed a significant predictive value for the recurrence rate according to F-wave amplitude. In the external validation cohort, the FWA score showed similar results (AUC 0.768, 95% CI 0.672–0.865). ConclusionsThe present study reveals the significant predictive value of the FWA score for persistent AF ablation recurrence.

Numerical investigation of rock-breaking mechanisms and influencing factors of different PDC cutters during rotary percussion drilling

While drilling deep or ultra-deep wells in hard rock formations, there are significant problems such as easy wear of drilling cutters and a low rate of penetration (ROP), and rotary percussion drilling technology is one of the essential techniques for improving drilling efficiency. However, there is currently limited research on the compatibility of rotary percussion drilling tools, polycrystalline diamond compact (PDC) cutters, and hard rock formations. Considering the motion mechanism of rotary percussion drilling tools, a three-dimensional rock-breaking numerical model was established for different cutters (planar, axe-shaped, and triple-ridged) under impact loads. Penetration depths, cutting widths, and rock-breaking volumes of different cutters under static and dynamic load coupling were analyzed. Changes in tensile, compressive, and shear stresses during the cutter rock-breaking process were compared, revealing the different cutter rock-breaking mechanisms under impact loads. The cutter rock-breaking laws under different impact amplitudes and frequencies were analyzed quantitatively, and the differences in rock-breaking effects of different cutters under various geological conditions were assessed. The results indicated that cutter penetration depth during rotary percussion drilling could be increased by 16.04% compared to that during conventional drilling. Under the same impact load, the rock-breaking effects of different cutters on hard and soft rocks exhibited similar variation patterns. The penetration depth followed the order axe-shaped > triple-ridged > planar cutters, with an average tangential order of triple-ridged < axe-shaped < planar cutters. When drilling through hard rock, the average penetration depths of planar, axe-shaped, and triple-ridged cutters were 5.57, 6.06, and 3.91 mm, respectively. The average tangential forces were 670.57, 541.76, and 347.89 N, respectively. During the transition from soft to hard rock during drilling, the tangential forces of the planar, axe-shaped, and triple-ridged cutters increased by 8.41%, 3.21%, and 2.64%, respectively. The planar cutter experienced the most significant instantaneous tangential-force change and was more prone to impact damage. Increasing the amplitude of the axial stress waves helps enhance the penetration depth of the drill bit, whereas increasing the frequency of the stress waves can reduce the intensity of fluctuations during drill-bit penetration and increase drill-bit stability. The research results provide insights into optimizing drilling cutters and engineering parameters during rotary percussion drilling.

Two-phase analysis of heat transfer of nanofluid flow in a wavy channel heat exchanger: A numerical approach

The heat transfer improvement by using CuO/water nanofluid (NF) in a wavy channel is evaluated numerically using the turbulent two-phase mixture and the κ - ε models. The numerical work is a 2-dimensional model created and analyzed in Gambit and Ansys Fluent software, respectively. The flow Reynolds (Re) numbers of 8000 to 40,000, wavelength ranging from 0 to 0.4 m, and solid volume fraction (SVF) of 0 % to 4 % are investigated. In all cases, a constant heat flux of q′′=5000 W/m2 is applied on the outer surface of the heat exchanger. The heat transfer and fluid flow were analyzed by the flow visualization method and heat transfer evaluation indexes. The results show that by increasing the Re number, the vortices increase and more turbulence are generated in the vicinity of the waves near the channel inlet. As the amplitude of the channel waves increased, the velocity at the top of the wave increased, and the resulting pressure gradient behind the wave is intensified and the reverse flow is generated. The improving effect of using NF is more prominent where the effect of other enhancing factors is weak. For wall amplitude of 0.1m, by increasing the SVF from 1 to 4% the average Nu number (Nuavg) increased by 35% and 22% in Re = 8,000 and 40,000, respectively.

Fluctuating pressure gradients and corrugated surfaces effects on wind turbines power output

This paper investigates the effect of corrugated surfaces on the wind turbines power output for both laminar and turbulent flows. Conservation principles including continuity and momentum equations, wind turbine power equations, and the corrugated surface equation have been implemented to build up a theoretical model then which has been solved using MATLAB. This model simulates wind turbines power output and analyzes several case studies implementing different parameters such as air pressure wave amplitude (Po), air wave fluctuation frequency (n), and wind layer turbulence (b). Also, different complex terrains in two main scenarios representing two different positions (X) of the wind turbine are analyzed. This analysis indicates the importance of wind turbines micro siting. In addition, it is found that increasing the pressure ratio increased wind turbine power output, while increasing the frequency decreased the power ratio of the wind turbines for both laminar and turbulent flow conditions. Increasing turbulence for the turbulent model increased the power ratio.

Freak wave generation modulated by high wind and linear shear flow in finite water depth

In finite water depths, the effects of high winds and linear shear flow (LSF), encompassing both uniform flow and constant vorticity shear flow on freak wave generation are explored. A nonlinear Schrödinger equation, adjusted for high wind and LSF conditions, is derived using potential flow theory and the multiscale method. This equation accounts for the modulational instability (MI) of water waves and the evolution of freak wave amplitudes. MI analysis reveals that for waves to maintain MI, high tail winds (moving in the same direction as the wave) require less vorticity and deeper water, while adverse winds (moving in the opposite direction) necessitate more vorticity and shallower water depths compared to conditions without wind. Uniform up-flows (down-flows), positive (negative) vorticity, and high tail (adverse) winds, which inhibit (promote) wave propagation, increase (decrease) the MI growth rate and amplify (diminish) freak wave heights. It is through this MI that the generation of freak waves is either promoted or inhibited.

Association of Aortic Stiffness and Pressure Pulsatility With Noninvasive Estimates of Hepatic Steatosis and Fibrosis: The Framingham Heart Study.

Arterial stiffening may contribute to the pathogenesis of metabolic dysfunction-associated steatotic liver disease. We aimed to assess relations of vascular hemodynamic measures with measures of hepatic steatosis and fibrosis in the community. Our sample was drawn from the Framingham Offspring, New Offspring Spouse, Third Generation, Omni-1, and Omni-2 cohorts (N=3875; mean age, 56 years; 54% women). We used vibration-controlled transient elastography to assess controlled attenuation parameter and liver stiffness measurements as measures of liver steatosis and liver fibrosis, respectively. We assessed noninvasive vascular hemodynamics using arterial tonometry. We assessed cross-sectional relations of vascular hemodynamic measures with continuous and dichotomous measures of hepatic steatosis and fibrosis using multivariable linear and logistic regression. In multivariable models adjusting for cardiometabolic risk factors, higher carotid-femoral pulse wave velocity (estimated β per SD, 0.05 [95% CI, 0.01-0.09]; P=0.003), but not forward pressure wave amplitude and central pulse pressure, was associated with more liver steatosis (higher controlled attenuation parameter). Additionally, higher carotid-femoral pulse wave velocity (β=0.11 [95% CI, 0.07-0.15]; P<0.001), forward pressure wave amplitude (β=0.05 [95% CI, 0.01-0.09]; P=0.01), and central pulse pressure (β=0.05 [95% CI, 0.01-0.09]; P=0.01) were associated with more hepatic fibrosis (higher liver stiffness measurement). Associations were more prominent among men and among participants with obesity, diabetes, and metabolic syndrome (interaction P values, <0.001-0.04). Higher carotid-femoral pulse wave velocity, but not forward pressure wave amplitude and central pulse pressure, was associated with higher odds of hepatic steatosis (odds ratio, 1.16 [95% CI, 1.02-1.31]; P=0.02) and fibrosis (odds ratio, 1.40 [95% CI, 1.19-1.64]; P<0.001). Elevated aortic stiffness and pressure pulsatility may contribute to hepatic steatosis and fibrosis.

Primary somatosensory cortex CB1 and 5‑HT1A receptors interaction in the penicillin model of epilepsy.

Cannabinoid and serotonin systems regulate many biological processes. The aim of the present study was to investigate the functional interaction between the cannabinoid and serotonergic systems of the primary somatosensory region (S1) of the brain in epileptiform activity caused by penicillin. The ACEA (an agonist of CB1 receptor), AM‑251 (an antagonist of CB1 receptor), 8‑OH‑DPAT (an agonist of 5‑HT1A receptor) and WAY‑100635 (an antagonist of 5‑HT1A receptor) were administered into the S1 after the same site administration of penicillin in urethane‑anesthetized rats. Electrocorticographic recording was done for a 90‑min period. The spike waves number and amplitude were recorded in 15‑min intervals. Areas under the curve (AUC) of the above‑mentioned spike alterations was calculated in 90 min. Spike waves with frequency of 30/min and amplitude of 1.3 mV were appeared after penicillin microinjection. The ACEA (50 ng), 8‑OH‑DPAT (500 ng) and ACEA (10 ng) plus 8‑OH‑DPAT (100 ng) reduced epileptiform activity. The AM‑251 (50 ng) and WAY‑100365 (500 ng) prevented the reducing effects of ACEA (50 ng) and 8‑OH‑DPAT (500 ng). The AM‑251 alone increased spike waves frequency. The AUC results supported the effects of the above‑mentioned treatments. The results showed that activating CB1 and 5‑HT1A receptors in the S1 may reduce the epileptiform activity caused by penicillin. Therefore, alone and together activation of central CB1 and 5‑HT1A receptors might be considered in the management of epilepsy treatment.

State of the art and future directions for measuring event-related potentials during cycling exercise: a systematic review

Intro Electroencephalography (EEG) is a technique for measuring brain activity that is widely used in neuroscience research. Event-related potentials (ERPs) in the EEG make it possible to study sensory and cognitive processes in the brain. Previous reports have shown that aerobic exercise can have an impact on components of ERPs such as amplitude and latency. However, they focused on the measurement of ERPs after exercise. Objectives The aim of this systematic review was to investigate the feasibility of measuring ERPs during cycling, and to assess the impact of cycling on ERPs during cycling. Methods We followed the PRISMA guidelines for new systematic reviews. To be eligible, studies had to include healthy adults and measure ERPs during cycling. All articles were found using Google Scholar and by searching references. Data extracted from the studies included: objectives of ERP studies, ERP paradigm, EEG system, study population data, exercise characteristics (duration, intensity, pedaling cadence), and ERP and behavioral outcomes. The Cochrane Risk of Bias 2 tool was used to assess study bias. Results Twenty studies were selected. The effect of cycling on ERPs was mainly based on a comparison of P3 wave amplitude between cycling and resting states, using an attentional task. The ERP paradigm most often used was the auditory oddball task. Exercise characteristics and study methods varied considerably. Discussion It is possible to measure ERPs during cycling under conditions that are likely to introduce more artifacts, including a 3-h athletic exercise session and cycling outdoors. Secondly, no assessment of the effect of cycling on ERPs was possible, because the methods differed too widely between studies. In addition, the theories proposed to explain the results sometimes seemed to contradict each other. Although most studies reported significant results, the direction of the effects was inconsistent. Finally, we suggest some areas for improvement for future studies on the subject.

Interaction between visual working memory and upright postural control in young adults: an event-related potential study based on the n-back paradigm.

As a part of the overall information-processing system of the brain, postural control is related to the cognitive processes of working memory. Previous studies have suggested that cognitive tasks and postural control processes can compete for resources in common brain areas, although there is an "inverted U" relationship between arousal level and behavioral control - the arousal level of individuals changes when performing cognitive tasks. However, the exact neural connections between the two are unclear. This may be related to the nature of cognitive tasks. Some studies believe that posture occupies not only spatial information processing resources but also visual non-spatial information processing resources. Other studies believe that posture control only occupies spatial information processing resources in the central system, but does not occupy non-spatial information processing resources. Previous studies used different cognitive task materials and reached different conclusions. In this study, we used the same visuospatial and non-spatial materials, the n-back visual working memory paradigm, the event-related potential technique to investigate the effects of visuospatial and non-spatial working memory tasks on adolescents' postural control under different cognitive loads. The results of this study showed that in both visuospatial and non-spatial conditions, the N1 effect of the parieto-occipital lobe was larger during upright posture than in the sitting position (160-180 ms), the P300 effect of the central parieto-occipital region (280-460 ms) was induced by working memory in different postures, and the P300 wave amplitude was higher in the sitting position than in the upright position. We demonstrated that upright postural control enhances early selective attention but interferes with central memory encoding, thus confirming that postural control and visuospatial and non-spatial working memory share brain regions and compete with each other.

Decoupling the complex amplitudes of partial waves in two-photon ionization

Decoupling the complex amplitudes of partial waves in two-photon ionization

Real-Time Method and Implementation of Head-Wave Extraction for Ultrasonic Imaging While Drilling

Extracting head waves and subsequently uploading their results from the downhole to the surface system in real time could improve the real-time guidance of ultrasonic imaging logging while drilling (UILWD) for drilling operations. To realize the downhole real-time extraction of head waves in this logging, three aspects were explored in this study. First, an improved energy ratio head-wave arrival extraction algorithm based on the weighting coefficients and characteristic functions, along with an amplitude detection method relying on peak-to-peak values, was proposed. Second, an echo reception pre-processing analog circuit and a digital signal processing circuit based on FPGA were designed. A pipeline algorithm was developed in FPGA to extract the arrival time and amplitude of the head wave. Finally, software simulations, laboratory tests, and field experiments related to this method were conducted. Our results showed that the real-time head-wave extraction method demonstrated a strong anti-noise ability in real time. The maximum relative error of the arrival time was less than 5%. The relative error of the amplitude was acceptable, and 90% of this value was within 5%. Through the measurement, the time of processing a single-channel waveform by a downhole algorithm was less than 15 ms, thus meeting the requirements for the real-time processing of downholes.

Battery parameter identification for unmanned aerial vehicles with hybrid power system

Unmanned aerial vehicles (UAVs) nowadays are getting soaring importance in many aspects like agricultural and military fields. A hybrid power system is a promising solution toward high energy density and power density demands for UAVs as it integrates power sources like internal combustion engine (ICE), fuel cell (FC) and lowcapacity lithium-polymer (LIPO) batteries. For robust energy management, accurate state-of-charge (SOC) estimation is indispensable, which necessitates open circuit voltage (OCV) determination and parameter identification of battery. The presented research demonstrates the feasibility of carrying out incremental OCV test and even dynamic stress test (DST) by making use of the hybrid powered UAV system itself. Based on battery relaxation terminal voltage as well as current wave excitation, novel methods for OCV determination and parameter identification are proposed. Results of SOC estimation against DST through adaptive unscented Kalman filter (AUKF) algorithm show that parameters and OCV identified with longer relaxation time don’t yield better SOC estimation accuracy. Besides, it also discloses that OCV played the vital role in affecting SOC estimation accuracy. A detailed analysis is presented showing that mean discharging rate and current wave amplitude are the major factors which affect the quality of OCV identified related to SOC estimation accuracy.

Influence of atmospheric wind on the propagation of radio waves

Background. It is necessary to study the influence of the physical characteristics of the atmosphere, in particular, wind on atmospheric turbulence and, consequently, on the characteristics of the radio signal it is shown. Aim. The dependence of the time-spectral function of the radio signal energy flux on the wind speed in the troposphere in the antenna plane is found. Methods. A method of transition from the Cartesian coordinate system in the antenna plane to the polar coordinate system of wave numbers has been developed. Based on this method the relationship between the Fourier spectral function of the correlation moment and the representation of the Bessel function is found. For the Fourier spectral function of the correlation moment, the previously obtained solution of the differential equation for the fluctuations of the eikonal amplitude of electromagnetic wave in a turbulent atmosphere at the front of the electromagnetic wave at the coordinate of the receiving antenna is used. Using the inverse Fourier transform the relationship between the time-spectral function of the radio signal energy flux and the time-correlation function of this flux is found. Results. Based on the study of the time-correlation function of the radio signal energy flow its relationship with the two-point correlation moment characterizing the fluctuations of the eikonal amplitude of the radio signal is found. To analyze the effect of wind, a turbulence model was used, reflecting the inertial turbulence interval, in which the energy flow from larger turbulent vortices to smaller vortices is determined by the viscous dissipation of the smallest vortices. Conclusion. Numerical calculations have shown that such a wind in the antenna plane blows away turbulent vortices in this plane, bettering the quality of the received radio signal.

High strength induced wide band gap formations in additively manufactured cubic metamaterial

Strength and band gap are the two basic physical features of the cubic metamaterial. How to design band gap characteristics with high strength of structure is the key for the further industrial application in vibration control of the cubic metamaterial. Here a cubic metamaterial is designed by optimal selection of crystal orientation angle to obtain wide band gaps with high strength. The prototype samples were fabricated using advanced additive manufacturing technology to tensile-pressure experiments and sine frequency sweep experiment, thereby demonstrating the validity of the obtained results. Results indicated that the normalized bandwidth of simple cubic (SC) metamaterials is 0.47 and the ultimate strength is 25.99 MPa. The normalized bandwidth is increased by 3.1 times and 47 times higher than that of the metamaterials of face-centered cubic (FCC) and body-centered cubic (BCC). Its ultimate strength is increased by 3.5 times and 6.7 times. The static simulation results revealed that the maximum mises stress values of SC, FCC, and BCC metamaterials were 1.71, 10.49, and 31.40 MPa respectively. The attenuation amplitude of the elastic wave measured by experiment is 80 dB, which is consistent with the simulation results. The bandwidths of cubic metamaterials exhibit a positive correlation with their strength. The variation in crystal orientation angles plays a crucial role in elucidating the underlying mechanism behind the positive correlation between the strength and the band gap. The further buckling analysis of SC metamaterial with high strength and wide bandgap characteristics reveals that the negative Poisson’s ratio structure experiences a reduction in bandwidth and strength as buckling deformation intensifies.

Arterial function in response to a 50km ultramarathon in recreational athletes.

This study was performed to determine whether prolonged endurance running results in acute endothelial dysfunction and wave-reflection, as endothelial dysfunction and arterial stiffness are cardiovascular risk factors. Vascular function (conduit artery/macrovascular and resistance artery/microvascular) was assessed in 11 experienced runners (8 males, 3 females) before, during and after a 50km ultramarathon. Blood pressure (BP), heart rate (HR), wave reflection, augmentation index (AIx) and AIx corrected for HR (AIx75) were taken at all time points-Baseline (BL), following 10, 20, 30 and 40km, 1h post-completion (1HP) and 24h post-completion (24HP). Flow-mediated dilatation (FMD) and inflammatory biomarkers were examined at BL, 1HP and 24HP. Reactive hyperaemia area under the curve (AUC) and shear rate AUC to peak dilatation were lower (∼75%) at 1HP compared with BL (P<0.001 for both) and reactive hyperaemia was higher at 24HP (∼27%) compared with BL (P=0.018). Compared to BL, both mean central systolicBP and mean central diastolic BP were 7% and 10% higher, respectively, following 10km and 6% and 9% higher, respectively, following 20km, and then decreased by 5% and 8%, respectively, at 24HP (P<0.05 for all). AIx (%) decreased following 20km and following 40km compared with BL (P<0.05 for both) but increased following 40km when corrected for HR (AIx75) compared with BL (P=0.02). Forward wave amplitude significantly increased at 10km (15%) compared with BL (P=0.049), whereas backward wave reflection and reflected magnitude were similar at all time points. FMD and baseline diameter remained similar. These data indicate preservation of macrovascular (endothelial) function, but not microvascular function resulting from the 50km ultramarathon.