Simultaneous Passage Research Articles

Daily impact of the simultaneous passage of binary typhoons on sea surface chlorophyll-a concentration dynamics in the Northwestern Pacific

Typhoons are recognized as one of the most destructive meteorological phenomena, exerting significant influences on marine ecosystems. Sea surface chlorophyll-a concentration (CHL)an essential indicator of phytoplankton biomass, can be utilized to characterize the disturbances of typhoons on the marine ecosystem. However, it is challenging to investigate this impact at a daily scale due to the missing CHL remote sensing data caused by cloud cover. Given that concurrent passing typhoons may interact with CHL, this study analyzes the effect of the simultaneous passage of binary typhoons Tembin and Bolaven on CHL by using daily CHL reconstruction data, and investigates the role of ocean environmental factors in driving the dynamics of CHL, including sea surface temperature (SST), mixed layer depth (MLD), and sea surface height anomaly (SSHA). The results show that typhoons Tembin and Bolaven increase CHL with the maximum increment of ∼3.2 mg∙m−3 during 4–6 days after typhoons passage. The maximum change areas of CHL are distributed near the intersection of typhoon track of (32°N, 125.2°E), corresponding to the regions of greater variation in SST and MLD. During 15 days before and after typhoons (i.e., from 15 August to 15 September 2012), SST is negatively correlated with CHL (the correlation coefficient of −0.85) and MLD is positively correlated with CHL (the correlation coefficient of −0.80). SST immediately declines after typhoons with a maximum cooling of 7.8 deg. C, showing the decreased SST from ∼28 deg. C to ∼23 deg. C can promote phytoplankton growth. MLD deepens from 10 m to >25 m caused by typhoon-induced strong winds, allowing more nutrients to be transported from the subsurface layer to the euphotic layer for phytoplankton blooms. Furthermore, oceanic eddies captured by SSHA change from cyclonic to anticyclonic eddies accompanied by the beginning of CHL increases, and the largest CHL increases correspond to the distribution of pre-existing cyclonic eddies. It suggests that Tembin and Boravin promote phytoplankton growth to increase CHL by enhancing vertical mixing and upwelling to transport nutrients to the sea surface. These findings inspire us to rethink the daily effects of typhoons on CHL, with critical importance for predicting and managing the ecological consequences of typhoons in the ocean.

Two-well linearization for solid-solid phase transitions

In this paper we consider nonlinearly elastic, frame-indifferent, and singularly perturbed two-well models for materials undergoing solid-solid phase transitions in any space dimensions, and we perform a simultaneous passage to sharp-interface and small-strain limits. Sequences of deformations with equibounded energies are decomposed via suitable Caccioppoli partitions into the sum of piecewise constant rigid movements and suitably rescaled displacements. These converge to limiting partitions, deformations, and displacements, respectively. Whereas limiting deformations are simple laminates whose gradients only attain two values, the limiting displacements belong to the class of special functions with bounded variation ( SBV ). The latter feature elastic contributions measuring the distance to simple laminates, as well as jumps associated to two consecutive phase transitions having vanishing distance, and thus undetected by the limiting deformations. By \Gamma - convergence we identify an effective limiting model given by the sum of a quadratic linearized elastic energy in terms of displacements along with two surface terms. The first one is proportional to the total length of interfaces created by jumps in the gradient of the limiting deformation. The second one is proportional to twice the total length of interfaces created by jumps in the limiting displacement, as well as by the boundaries of limiting partitions. A main tool of our analysis is a novel two-well rigidity estimate which has been derived in [Calc. Var. Partial Differential Equations 59, art. 44 (2020)] for a model with anisotropic second-order perturbation.

Assessment of vibrations caused by simultaneous passage of road and railway vehicles

Although subways are usually near the roads, very few studies have been carried out to assess the vibration caused by the simultaneous passage of road and railway vehicles. This study investigates the influences of effective parameters on railway and road induced vibrations. To this end, the force time histories of road and railway vehicles were obtained from vehicle/pavement and vehicle/railway track interaction models. The force time histories were imported to a three-dimensional finite element model to obtain the vibrations. A comprehensive field test was carried out to assess the validity of the results obtained from the model. A parametric study was performed to investigate the effects of different parameters such as soil properties, speed hump characteristics, depth of subway tunnel and vehicle speed on the railway/road vehicles induced-vibrations. Moreover, a comparison/distinction was made between the vibrations caused by rail and road vehicles.

Signal Separation from Thermal Neutrons in Electron–Neutron Detectors Using Convolutional Neural Nets in the ENDA Experiment

The electron–neutron detector array (ENDA) is being created in China within the large high-altitude air shower observatory (LHAASO) project. The concept of the array is to simultaneously record the electromagnetic and hadronic components of extensive air showers (EAS) with EN detectors. To estimate the number of hadrons in an EAS, the array detectors record secondary thermal neutrons delayed relative to the shower front. Some of the delayed pulses are created by the simultaneous passage of several charged particles through the scintillator (the signal from one particle lies below the detection threshold) and by the photomultiplier noise. We propose a neutron pulse separation method for EN detectors using convolutional neural networks and make a comparison with the baseline method being currently applied at the installation.

Ground vibrations induced by the passage of double-line trains in underground tunnels

Subway systems consist of double lines to transport passengers in the outbound and inbound directions. The existing prediction models for subway-induced vibrations ignored the superimposed effect caused by the successive passage of double-line trains. This study develops a computationally efficient method to simulate ground vibrations during the simultaneous passage of double-line trains in underground tunnels. An analytical model is applied to calculate the transfer function of a track-tunnel-ground system in a multi-layered half-space. Two alternative designs of tunnels in a double-line subway system are considered, which are a double-track tunnel and twin single-track tunnels. By introducing the relation between two different moving frames of reference, a fully coupled solution for the train-track-tunnel-ground system that considers the dynamic interaction between the double-line trains is proposed. The numerical results indicate that the simultaneous passage of double-line trains induces a significant superimposed effect of ground vibrations. The superimposed effect can increase the vertical velocity in the one-third octave spectrum by up to 5 dB, and the running RMS value by up to 40% under the same track roughness. The ground vibrations from one double-track tunnel are more than 30% higher than those from two single-track tunnels due to the passage of the single-line train and double-line trains.

Approach of the Hyades star cluster to the Solar system

ABSTRACT We present the results of calculations of the motion of the Hyades open cluster in the gravitational field of the Galaxy in the recent past. Our calculations show that the recent close passage of Hyades by the Solar system could cause a noticeable shift of the perihelion distances q of comets. The shift is negligible from q = 3 au to 2.6 au for the semimajor axes a = 14 210 au, but for a = 40 000 au, the perihelion could change from q = 35 au to 34 au, and much more for distant orbits. This could result in the detection of new comets, and drive the migration of comets from the outer region of the Solar system towards the orbit of Neptune. The effect can be enhanced by the simultaneous passage of several stars. For example, if several stars approached the Sun simultaneously in the time interval from −1.5 to −1.0 Myr, the effect may be amplified up to ten times.

Исследование взаимного аэродинамического влияния высокоскоростных пассажирских и грузовых поездов, следующих по смежным путям

The article considers the issues of impact of high-speed passenger traffic on the sections of JSC “Uzbekiston Temir Yillari” on removal of freight trains from the traffic schedule, the mutual aerodynamic influence of trains moving on adjacent tracks is investigated. In order to increase the tourist attractiveness of the republic and provide high-quality transport services to the population, it is planned to significantly increase the volume of passenger transportation by high-speed electric trains Afrosiyob. In the conditions of the projected increase in the size of freight traffic, this may lead to difficulties in passing trains through sections. In order to effectively use the capacity of the sections, in compliance with the conditions for ensuring the safety of train traffic, the possibility of simultaneous passage of freight trains of a passing or oncoming direction along the second main track when moving along the section of the Afrosiyob high-speed electric train is being considered.

Variation of Radar-Observed Precipitation Characteristics in Relation to the Simultaneous Passages of a Madden–Julian Oscillation Event and Convectively Coupled Equatorial Waves during the Years of the Maritime Continent Pilot Study

AbstractIn this study, we examined the variations of precipitation morphology and rainfall in relation to the simultaneous passages of a Madden–Julian oscillation (MJO) event and convectively coupled equatorial waves (CCEWs) observed during the Years of the Maritime Continent pilot study. We utilized globally merged infrared brightness temperature data and the radiosonde and radar data observed aboard the Research Vessel Mirai at 4°4′S, 101°54′E. As well as the observed MJO event, equatorial Rossby waves (ERWs), Kelvin waves (KWs), and mixed Rossby–gravity waves (MRGWs) were identified. The radar data exhibited high-frequency variation, mainly caused by KWs and MRGWs, and low-frequency variation, mainly caused by the MJO and ERWs. The MRGWs predominantly modulated convective echo areas and both convective and stratiform volumetric rainfall. In contrast, the MJO event had little influence on the variance of convective echoes. Moreover, stratiform echo areas and volumetric rainfall were more strongly modulated by the combined effects of the MJO, ERWs, KWs, and MRGWs than their convective counterparts. The intense development of stratiform echo areas and volumetric rainfall was coherent with the superimposition of the active phases of the MJO event and all the analyzed CCEWs. The strongest development and a significant reduction of convective echo-top heights before and after the peak MJO date, respectively, were coherent with the passages of ERWs and MRGWs, which were the dominant wave types in modulating echo-top heights. Thus, it appears that the superimposition of the CCEWs on the MJO event exerted complex modulations on the convective activities within the MJO event.

Structural and Dynamic Insights into the Conduction of Lithium-Ionic-Liquid Mixtures in Nanoporous Metal-Organic Frameworks as Solid-State Electrolytes.

Metal-organic framework (MOF)-based separators in Li-ion batteries (LIBs) have the potential to improve the battery performance. The mobility and conduction of lithium and organic ionic liquids (ILs) in these materials acting as (quasi) solid-state electrolytes are crucial for the battery power output. Here, we investigate the mobility of a Li-based IL in MOF nanopores and unveil the details of the conduction mechanism by molecular dynamics (MD) simulations. A complex conductivity depending on the Li-IL loading and on the IL composition is observed. Most importantly, the presence of Li prevents the collapse of the conductivity at high IL loadings. The fully atomistic MD simulations including guest-guest and guest-host interactions elucidate the competing mechanisms: Li follows a Grotthuss-like conduction mechanism with large mobility. While at small pore fillings, the Li conduction is limited by the large distance between the anions facilitating the Grotthuss-like conduction; the conduction at high pore fillings is governed by field-induced concentration inhomogeneities. Because of the small MOF pore windows, which hinders the simultaneous passage of the large IL cations and anions in opposite directions, the IL shows field-induced MOF pore blocking and ion bunching. The regions of low anion concentration and high cation concentration represent barriers for Li, decreasing its mobility. In comparison to Li-free IL, the IL bunching effect is attenuated by the formation of charge-neutral Li-anion complexes, resulting in a tremendously increased conductivity at maximum pore filling. The exploitation of this mechanism may enhance the development of advanced batteries based on IL and nanoporous separators.

Zone Recrystallization of Zirconium and Hafnium

The work studied the possibility of obtaining of the high-purity samples of zirconium and hafnium by the method of zone recrystallization of round rods with electron-beam heating in a vacuum of 1∙10-4 Pa. Some meltings were carried out in a constant electric field with the variability of its connection. It is shown that the simultaneous passage of several refining processes (evaporation of highly volatile metallic impurities, zone recrystallization with directional displacement of impurities to the end of the sample, electrotransport) made it possible to efficient refining of zirconium both from metallic impurities and from interstitial impurities. The best degree of purification was achieved when zone melting carrying out in an electric field directed opposite to the zone movement. In this case, the displacement of interstitial impurity ions coincided with the direction of movement of the liquid zone. Samples of zirconium with a purity of 99.89 wt. % were obtained (the concentration of aluminum was reduced by 5, iron - 11, copper - 45, chromium - 75, silicon - 10, titanium - 2.5, oxygen - 3.3, nitrogen - 3, carbon - 2 times). The hafnium samples refined by the zone recrystallization method were characterized by a purity of 99.85 wt. %. The concentrations of both all metal impurities and interstitial impurities were significantly reduced (concentration in wt% oxygen was 0.011, carbon - 0.0018, nitrogen - 5∙10-5). A study of gas evolution from samples of iodide hafnium and refined hafnium was carried out. It was found that the maximum gas release peak fell on the temperature range of 500 ... 550 °C. The use of an integrated approach, including high-temperature heating, stages of zone melting at different rates, and thermal cycling in the range of the polymorphic transformation temperature, made it possible to obtain single-crystal hafnium samples. According to X-ray diffraction data, the parameters of the hafnium crystal lattice were determined: а = (0.31950 ± 5·10-5) nm and с = (0.50542 ± 5·10-5) nm (at 298 K), which corresponds to the density ρ = 13.263 g/cm3 and axial ratio с/a = 1.5819.

Enhanced thermoelectric properties of screen-printed Bi–Sb–Te films on flexible substrate by electrical sintering process

Screen printing is a low-cost solution-based process for preparing thick-film thermoelements, which bridges the technology gap between bulk and thin-film thermoelectric devices. A screen-printed thermoelectric film on a polymer substrate may exhibit moderate flexibility but normally suffer low electrical conductivity due to the presence of porosity or organic residues. In this study, we present a current-assisted sintering process to consolidate screen-printed Bi–Sb–Te (BST) films on a polyimide substrate at the temperature below 350 °C with simultaneous passage of a pulse current of 2 × 103 A/cm2 in peak current density. The electrically sintered BST film shows greatly enhanced electrical conductivity, leading to a 45% higher thermoelectric power factor (20.2 μW/cm⋅K2) than the thermally sintered BST film (13.9 μW/cm⋅K2). The variations of crystal defect concentration, grain size and secondary precipitates in the BST films with increasing pulse current density and sintering temperature are investigated. The influences of grain boundaries and secondary precipitates on carrier scattering behavior and thermoelectric transport properties of the BST films are also discussed.

Experimental investigation on train-induced vibration of the ground railway embankment and under-crossing subway tunnels

This paper presents a field measurement of the train-induced vibration in the northwest Shanghai, where Shanghai Metro Line 11 crosses under Beijing-Shanghai Railway. Ground and tunnel accelerations are measured for the separate and simultaneous passages of the ground and subway trains. Vibration characteristics are subsequently analyzed in the time domain and in the frequency domain. Measurement results show that the ground vibration acceleration level (VAL) induced by the simultaneous operation of the ground and subway trains is 6 ~ 13 dB greater than that induced by the separate operation for the frequency range 20 ~ 160 Hz. Significant frequency components of the vibration induced by the simultaneous operation are shown to be redistributed to cover those induced by the separate operation. Measured data in this experimental test can also be used to validate future numerical models for predicting train induced vibration of similar embankment-tunnel systems.

Analysis of nonlinear frequency mixing in Timoshenko beams with a breathing crack using wavelet spectral finite element method

The nonlinear interaction of a dual-frequency Lamb wave with a breathing edge-crack leads to the generation of frequency sidebands in the response spectrum; a phenomenon referred to as the nonlinear frequency mixing. These sidebands appear at algebraic combinations of the two central interrogation frequencies and can serve as a reliable precursor to the existence of an incipient damage. In this paper, an iterative use of the wavelet spectral finite element method is presented for analyzing the phenomenon of nonlinear frequency mixing in a beam with a transverse edge-crack. The beam is modeled using the Timoshenko hypothesis while the local flexibility caused by the crack is modeled by introducing two springs corresponding to the bending and shear deformations, respectively. The intermittent contact between the two crack surfaces is simulated by switching between a defect-free beam configuration and the one containing an open-crack. The underlying steps involved in deriving the element level equations for healthy and damage spectral finite elements, together with an iterative procedure to solve the resulting set of nonlinear equations, are presented in detail. Using this numerical framework, it is exposited that relative strengths of the frequency sidebands are influenced strongly by the temporal overlap that the two constituent wave envelopes have when they propagate through the breathing crack. A modulation parameter is defined for quantifying this dependency. For a simultaneous passage (100% temporal overlap), the modulation parameter attains its maxima, while it reduces to zero when the two constituent waves propagate separately through the breathing crack with zero temporal overlap. Premised on this rationale, an operationally viable damage localization strategy, based on tuning the temporal overlap between the two constituent wave envelopes and further monitoring the modulation parameter, is proposed. The efficacy of the proposed strategy is demonstrated by considering an illustrative numerical example. The present investigation can be of potential use in the analyses concerning nonlinear wave-damage interactions and their effective use in localizing a damage.

Modulações hesitantes do olhar

Destacando alguns momentos do meio século de escrita dos Cahiers de Paul Valéry, será possível observar como um conceito estético oriundo da música – a modulação – é transformado pelo poeta francês, sendo empregado já nos manuscritos da Introdução ao Método de Leonardo da Vinci para refletir sobre o olhar, a figura e o desenho. Com efeito, ao ser deslocada do universo musical para a artes plásticas, a ideia de modulação deixará de ser pensada como uma transição sucessiva entre tons de diferentes partes de uma obra para ser concebida como passagem hesitante, sucessiva e simultânea, entre múltiplas camadas heterogêneas da experiência estética. Desse modo, o ato de modular abrirá um campo de reverberações entre as diferentes artes no interior do qual o conceito de forma, longe de ser definido pela purificação analítica dos componentes elementares de um meio, suporte ou área de competência estética, refina-se nas hesitações e intervalos entre diferentes práticas e materiais artísticos. Assim, o diálogo entre o conceito valeryano de modulação e a artes plásticas poderá também precisar aspectos importantes do formalismo poético atribuído a Valéry.

Claudin-15 forms a water channel through the tight junction with distinct function compared to claudin-2.

Claudin-15 is mainly expressed in the small intestine and indirectly involved in glucose absorption. Similar to claudin-2 and -10b, claudin-15 is known to form a paracellular channel for small cations. Claudin-2, but not claudin-10b, also forms water channels. Here we experimentally tested whether claudin-15 also mediates water transport and if yes, whether water transport is Na+ -coupled, as seen for claudin-2. MDCK C7 cells were stably transfected with claudin-15. Ion and water permeability were investigated in confluent monolayers of control and claudin-15-expressing cells. Water flux was induced by an osmotic or ionic gradient. Expression of claudin-15 in MDCK cells strongly increased cation permeability. The permeability ratios for monovalent cations indicated a passage of partially hydrated ions through the claudin-15 pore. Accordingly, its pore diameter was determined to be larger than that of claudin-2 and claudin-10b. Mannitol-induced water flux was elevated in claudin-15-expressing cells compared to control cells. In contrast to the Na+ -coupled water flux of claudin-2 channels, claudin-15-mediated water flux was inhibited by Na+ flux. Consequently, water flux was increased in Na+ -free solution. Likewise, Na+ flux was decreased after induction of water flux through claudin-15. Claudin-15, similar to claudin-2, forms a paracellular cation and water channel. In functional contrast to claudin-2, water and Na+ fluxes through claudin-15 inhibit each other. Claudin-15 allows Na+ to retain part of its hydration shell within the pore. This then reduces the simultaneous passage of additional water through the pore.

Aplicación del concepto de integral definida en problemas de ingeniería: Caso de estudio proyecto de ampliación del canal de Panamá

El presente trabajo consistió en la aplicación del concepto de integral definida en un caso práctico relacionado con procesos logísticos. Mediante la utilización de información y datos correspondientes al Proyecto de ampliación del Canal de Panamá en su primera fase, se realizó un análisis técnico del mismo para demostrar con fines didácticos, cómo se puede dar solución a un problema real de ingeniería de gran envergadura con base en fundamentos matemáticos de cálculo integral y principios físicos simples. El objetivo principal de este trabajo fue mostrar a la comunidad educativa, una forma de aplicar una estrategia de enseñanza de carácter investigativa y con sentido práctico de las matemáticas, con enfoque particular en el concepto geométrico de integral definida. Específicamente, se procedió a calcular las áreas de ampliación del Canal de Panamá que permitan el paso simultáneo de un barco Panamax y un Post-Panamax. La información base para el desarrollo del trabajo se la obtuvo de varias fuentes, como investigaciones y publicaciones acerca del Canal de Panamá y del proyecto de ampliación.

Influence of Aeration on the Composition of Biocenosis and Efficiency of Removal of Nitrogen-Containing Compounds on Rapid Filters for Drinking Water Treatment

Background . Nitrogen compounds are the most common components of groundwater in Ukraine. Nitrates for humans are not poisonous, but in the human body, they turn into nitrites, affecting the health of the whole organism. One of the possible ways to reduce the content of nitrogen compounds is the use of biotechnological treatment methods, which are not yet widely used in water treatment plants in Ukraine. Objective . The aim of the paper is to study the influence of oxygen on the biocenosis of rapid filters for the drinking water treatment and the efficiency of removing nitrogen-containing compounds. Methods . To assess the influence of aeration on the biocenosis of rapid filters for drinking water treatment, the total microbial number in the upper and lower parts of the filter was measured at different doses of oxygen that was fed to the filter. Results. The experiments show that depending on the different concentration of dissolved oxygen on rapid filters for drinking water treatment, the simultaneous passage of nitrification and denitrification is possible. It is established that with an increase in oxygen concentration up to 7 mg/dm 3 , the intensity of ammonium removal doesn’t increase, but the value of the CFU in the lower part of the filter decreases (up to 3000 CFU/cm 3 ). The concentration of oxygen in the aerator for ammonia removal is 7 mg/dm 3 (ammonium concentration in water after filtration is 0.11 mg/dm 3 ); nitrites – 7.5 mg/dm 3 (0.27 mg/dm 3 nitrites in water after filtration); nitrates – 5.5 mg/dm 3 (2.4 mg/dm 3 of nitrates in water after filtration). Conclusions. It is determined that under conditions of rapid filters, nitrification predominantly occurs in the upper part of the filter, and denitrification in the lower part. The optimum concentration of oxygen fed to the filter was established for the simultaneous passage of nitrification and denitrification, and the effective removal of nitrogen compounds in the preparation of drinking water. The concentration should be 5.5 mg/dm 3 .

Simultaneous passage of ultra-slim colonoscope and colonic stent catheter across left-sided colonic stent for placement of a hepatic flexure stent for malignant large-bowel obstruction.

Simultaneous passage of ultra-slim colonoscope and colonic stent catheter across left-sided colonic stent for placement of a hepatic flexure stent for malignant large-bowel obstruction.

Utility of Single‐Channel Electronic Resistivity Counters for Monitoring River Herring Populations

AbstractAutomated electronic counting systems are used to estimate river herring populations throughout New England. Measuring the accuracy of these counting systems is essential to understanding the limitations of counter‐derived estimates, which comprise a vital component of river herring stock assessments. Our objective was to conduct a direct visual–electronic comparison of passage to evaluate the accuracy and biases of using single‐channel electronic resistivity counting systems to monitor river herring. From 1999 to 2012, we conducted 1,189 direct comparisons. Of these, 555 occurred when river herring were actively migrating through the system. The counting system consistently underestimated passage, with 34–87% of seasonal observations recording fewer fish than were known to pass. Mixed‐effects logistic regression indicated that the probability of an inexact count increased with increasing passage rate, which we attribute to simultaneous passage. We explored two techniques to correct for the biases observed during our sampling period and produce corrected estimates of run size. Although our results have limitations, the consistency of observed bias provides evidence that single‐channel counters yield the resolution needed to infer population trend. Future monitoring should endeavor to correct the biases in single‐channel counters and to explore alternative technologies that provide greater accuracy.Received April 3, 2015; accepted August 10, 2015

Optimizing oxygenation and intubation conditions during awake fibre-optic intubation using a high-flow nasal oxygen-delivery system

Awake fibre-optic intubation is a widely practised technique for anticipated difficult airway management. Despite the administration of supplemental oxygen during the procedure, patients are still at risk of hypoxia because of the effects of sedation, local anaesthesia, procedural complications, and the presence of co-morbidities. Traditionally used oxygen-delivery devices are low flow, and most do not have a sufficient reservoir or allow adequate fresh gas flow to meet the patient's peak inspiratory flow rate, nor provide an adequate fractional inspired oxygen concentration to prevent desaturation should complications arise. A prospective observational study was conducted using a high-flow humidified transnasal oxygen-delivery system during awake fibre-optic intubation in 50 patients with anticipated difficult airways. There were no episodes of desaturation or hypercapnia using the high-flow system, and in all patients the oxygen saturation improved above baseline values, despite one instance of apnoea resulting from over-sedation. All patients reported a comfortable experience using the device. The high-flow nasal oxygen-delivery system improves oxygenation saturation, decreases the risk of desaturation during the procedure, and potentially, optimizes conditions for awake fibre-optic intubation. The soft nasal cannulae uniquely allow continuous oxygenation and simultaneous passage of the fibrescope and tracheal tube. The safety of the procedure may be increased, because any obstruction, hypoventilation, or periods of apnoea that may arise may be tolerated for longer, allowing more time to achieve ventilation in an optimally oxygenated patient.