Continuous Absorption Research Articles

Deep-subwavelength broadband sound absorbing metasurface based on the update finger coiling-up method

The bulky structure of traditional sound-absorbing materials limits its application to control low-frequency noise, and new deep-subwavelength low-frequency broadband acoustic materials have an urgent need. This paper proposes an update finger coiling-up method, which can improve the sound absorption coefficient and working bandwidth of the unit without increasing the thickness. In addition, the complexity of the structure can be simplified to facilitate manufacturing. The influence of the typical parameters of the unit on the sound absorption performance and the coupling performance of the unit are also studied. Finally, by combining 16 finger coiled-up units, a metasurface with continuous broadband sound absorption in the range of 375 Hz to 855 Hz is obtained, and the average sound absorption coefficient is above 0.85. In particular, the thickness of the metasurface is only 38 mm, which is 1/24 of the corresponding operating wavelength at 375 Hz. The proposed update finger coiling-up method provides a new idea for reducing the thickness of sound-absorbing materials, which will have good application prospects in noise control field.

Mechanism and Kinetic Study of Cyclodextrin Use to Facilitate NO2 Absorption in Sulfite Solutions.

An innovative strategy to control nitrogen oxide emission from flue gas was developed using the wet flue gas denitrification technology. The use of cyclodextrin (CD) as an additive facilitated NO2 absorption by the sulfite absorbent. Compared with absorption by a sulfite solution (59.12%), the instantaneous absorption efficiencies employing CD improved to 94.57%. Moreover, 48 h of continuous absorption indicated cyclic utilization of CD. The favorable role of CD was ascribed to facilitating the limiting step for the entire NO2 absorption-dissolution process which included both water solubility and gas-liquid mass transfer. Furthermore, we propose a potential mechanism of CD/sulfite mixed solution absorbing NO2, among which the favorable role of the additive is related to its amphiphilic behavior toward gas and liquid phases. Additionally, a kinetic model describing the rates of gas-liquid transfer and macro absorption was established based on various operating conditions. This model explains the absorption improvement in the kinetic aspect and provides theoretical guidance for practical applications.

Ultra-broadband perfect terahertz absorber with periodic-conductivity graphene metasurface

We present an interesting scheme of ultra-broadband perfect terahertz (THz) absorber with periodic-conductivity graphene metasurface, instead of the common metasurfaces of geometrically patterned graphene with uniform conductivity. By exploiting periodic modulation of graphene conductivity, the graphene metasurface absorber produces a sequence of dense high-order resonance modes with near-perfect absorption peaks. The density of resonant modes can be largely enhanced to perform an ultra-broadband even continuum absorption in THz regime with suppression of the modulation minimum of graphene conductivity. Under the resistive loss effect of graphene on the modes broadening, the THz perfect absorber can perform a record ultra-broadband of 3.71 THz, which covers more than one-third of the whole THz region of 0.1–10 THz. Such scheme of periodic-conductivity graphene metasurface is of interest in pushing forward to broadband THz absorber, which has promising application prospects in THz stealth, imaging and communication fields.

Transformation of reduced graphene aerogel-supported atomically dispersed iridium into stable clusters approximated as Ir6 during ethylene hydrogenation catalysis

Transformation of atomically dispersed reduced graphene aerogel (rGA)-supported complexes, IrI(C2H4)2+, with an iridium loading of 9.9 wt%, to form low-nuclearity clusters was investigated during ethylene hydrogenation catalysis. Continuous-scan X-ray absorption spectra demonstrate the formation of clusters well approximated as Ir4 during reaction at 100 °C in flowing equimolar ethylene and H2. The Ir4 clusters transformed into clusters well approximated as Ir6 when the feed molar ratio was switched to H2:C2H4 = 2 and remained stable in pure H2 at 100 °C. Catalyst performance data show that hydrogenation activity increased with metal nuclearity in the order of atomically dispersed iridium/rGA≪ Ir4/rGA < Ir6/rGA. Continuous scan X-ray absorption data, complemented with aberration-corrected scanning transmission electron microscopy images, demonstrate that the supported clusters approximated as Ir6 are stable even in H2 at atmospheric pressure and 100 °C. These supported iridium clusters are among the ones having the highest metal loadings reported for a supported metal cluster catalyst.

MO671: Should We Undergo Peritoneal Dialysis in Malnourished Chronic Kidney Disease Patients?

Abstract BACKGROUND AND AIMS The implementation of peritoneal dialysis (PD) in end-stage renal disease has been associated with various long-term pathophysiologic changes, which result in adverse consequences, such as malnutrition, occurring in 30–50% of patients. Specific factors to PD might be associated with poor oral intake as continuous absorption of glucose from PD solutions and abdominal fullness induced by the dialysate can suppress appetite. There are several accepted strategies for stratifying malnutrition in PD, such as laboratory markers [serum albumin and normalized protein catabolic ratio (nPCR)] and the recent use of bioimpedance spectroscopy (BIS) (with low lean tissue index). We aimed to evaluate if PD patients with a poor nutritional status at the beginning of the technique had worse outcomes (peritonitis, PD failure, hospitalizations, and death). METHOD We studied a cohort of incident patients from a single PD unit between 1 July 2011 and 31 August 2021, who had one BIS measurement and a peritoneal equilibration test in the first 3 months after the start of PD. We also collect laboratory data within 6 months from the BIS evaluation (serum albumin). Besides demographic parameters, we evaluated established endpoints (peritonitis, PD failure, hospitalizations and death). RESULTS There were included 91 PD patients. The mean age of patients was 65.40 $ \pm $ 13.88 years with a median dialysis vintage of 24 (IQR 14–31.61) months; 59.3% were male and 28% had diabetes. During the follow-up period, 5.5% of the cohort died, 56% were hospitalized and 47.3% had at least one episode of peritonitis. Furthermore, the transfer to hemodialysis occurred in 18 cases (19.8%) and 15 (16.5%) received a renal transplant. There was no difference in nutritional markers median in patients that had clinical endpoints versus those who had not (Table 1). In a multivariable analysis, neither nPCR, nor albumin nor lean tissue index were predictors of peritonitis, PD failure or hospital admissions. CONCLUSION In this study, we found that malnourished patients, prevalent in PD, did not have worse clinical endpoints (higher rate of infections, hospital admissions and PD failure). Although adequate nutrition has been deemed vital to the success of PD, this modality of renal replacement therapy did not result in worse outcomes, despite the malnutrition markers at the beginning of PD. Further studies are warranted to evaluate the positive impact of PD in nutrition status.

A solar-heated antibacterial sodium alginate aerogel for highly efficient cleanup of viscous oil spills

Hypothesis. Major oil spills highlight the need for environmentally responsible and cost-effective recovery technologies. However, challenges remain for heavy oil spill recovery because of its high viscosity and low fluidity. To achieve this goal, an ecofriendly bio-based aerogel with efficient photothermal conversion ability was developed as a novel absorbent to achieve the fast removal of heavy oil spill by reducing the oil viscosity.Experiments. From the renewable and abundant raw material sodium alginate (SA), hydrophobic and antibacterial SA/graphene oxide/ZIF-8 aerogel (SAGZM) was successfully fabricated via freezing-drying and chemical vapor deposition (CVD) technique. A series of characterization and tests, including aerogel structure, selective wettability, photothermal conversion ability, crude oil removal capability, and antibacterial ability, have been investigated in detail. SAGZM aerogels have rich pore structure, high porosity, excellent mechanical properties, and better photothermal conversion efficiency.Findings. Under sunlight illumination, the recovery ability of SAGZM for heavy crude oil was investigated through infrared thermal imaging, oil permeability behavior analysis, and the continuous absorption for crude oil. In addition, these results are well supported by the theoretical liquid absorption coefficient. This study indicates that SAGZM is highly efficient in in situ regulating oil viscosity through its remarkably photothermal conversion capability. Importantly, SAGZM possesses an excellent antibacterial ability that is often neglected in the design of environmentally friendly materials in extending its service life. The findings of this work not only provide an eco-friendly bio-based aerogel material but also demonstrate that the photo-responsive SAGZM is efficient in heavy crude oil absorption. The proposed solar-heated SA-based aerogel provides a sustainable approach and material to solve the recovery problem of viscous crude oil spills.

Non-magnetic adsorbent functionalized magnetism and spin filtering in a two-dimensional GaN monolayer

Exotic properties provided by the adsorption of non-magnetic Si atoms on a two-dimensional–GaN (2D–GaN) monolayer have been predicted using a generalized gradient approximation within density functional theory. This includes the occurrence of spin filtering, high magnetism and the continuous emission of electromagnetic radiation. A comprehensive ab-initio study of the structural, electronic, magnetic and optical properties of a 2D–GaN monolayer possessing several Si atoms as adsorbents has been performed. The semiconducting pure GaN monolayer was converted into its metallic analogue in several Si-adsorbed GaN monolayer systems. Along with the main strong absorption lying in the deep ultraviolet region near 5.5 eV observed in all of the Si-adsorbed 2D-GaN monolayer systems, a strong continuous absorption from the far infrared to visible light region has been observed in some of the systems studied. These systems may be useful for the development of light-emitting devices, which will emit in the various regions of the electromagnetic spectrum, including the visible light region. The emission in the deep ultraviolet light region may be used for sterilization, water purification etc.

Methane as a reddish coating agent

Experiments in quartz ampoules that simulate the saltation of quartz grains in a methane atmosphere show that the solid phase acquires a reddish color, reminiscent of the color observed on Triton, Pluto, and Charon. Reflection spectroscopy of the coated grains show a wide, continuous absorption spectrum peaking at near-UV wavelengths, in line with the reddish color. X-ray photoelectron spectroscopy indicates the grains are coated with a substance containing CC and CO bonds, and estimates the average thickness of the surface layer to 2.3 Å. Solid state Raman measurements of the coating shows a transition at 1540 cm−1. A model is proposed to describe these measurements. The model is a polydiene, anchored to the quartz surface. Electron structure calculations show that a polydiene with around 8 CH units reproduces the measurements. AFM-IR experiments support this result. Our findings suggest a pathway for synthesis of complex molecules with CC bonds on planets and moons with a solid surface and a methane-containing atmosphere.

Computational optimal transport for molecular spectra: The semi-discrete case.

Comparing a discrete molecular spectrum to a continuous molecular spectrum in a quantitative manner is a challenging problem, for example, when attempting to fit a theoretical stick spectrum to a continuous spectrum. In this paper, the use of computational optimal transport is investigated for such a problem. In the optimal transport literature, the comparison of a discrete and a continuous spectrum is referred to as semi-discrete optimal transport and is a situation where a metric such as least-squares may be difficult to define except under special conditions. The merits of an optimal transport approach for this problem are investigated using the transport distance defined for the semi-discrete case. A tutorial on semi-discrete optimal transport for molecular spectra is included in this paper, and several well-chosen synthetic spectra are investigated to demonstrate the utility of computational optimal transport for the semi-discrete case. Among several types of investigations, we include calculations showing how the frequency resolution of the continuous spectrum affects the transport distance between a discrete and a continuous spectrum. We also use the transport distance to measure the distance between a continuous experimental electronic absorption spectrum of SO2 and a theoretical stick spectrum for the same system. The comparison of the theoretical and experimental SO2 spectra also allows us to suggest a theoretical value for the band origin that is closer to the observed band origin than previous theoretical values.

The Role of the Continuum Absorption Definition in the Case of H2O–N2 Absorption

The Role of the Continuum Absorption Definition in the Case of H2O–N2 Absorption

Continuum, cyclotron line, and absorption variability in the high-mass X-ray binary Vela X-1

Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability, and convenient physical parameters (close distance, high inclination, and small orbital separation), which facilitate the observation and analysis of the system, Vela X-1 is one of the key systems for understanding accretion processes in high-mass X-ray binaries on all scales. We revisit Vela X-1 with two new observations taken with NuSTAR at orbital phases ∼0.68–0.78 and ∼0.36–0.52, which show a plethora of variability and allow us to study the accretion geometry and stellar wind properties of the system. We follow the evolution of spectral parameters down to the pulse period timescale using a partially covered power law continuum with a Fermi-Dirac cutoff to model the continuum and local absorption. We are able to confirm anti-correlations between the photon index and the luminosity and, for low fluxes, between the folding energy and the luminosity, implying a change of properties in the Comptonising plasma. We were not able to confirm a previously seen correlation between the cyclotron line energy and the luminosity of the source in the overall observation, but we observed a drop in the cyclotron line energy following a strong flare. We see strong variability in absorption between the two observations and within one observation (for the ∼0.36–0.52 orbital phases) that can be explained by the presence of a large-scale structure, such as accretion and photoionisation wakes in the system, and our variable line of sight through this structure.

Non-magnetic Ge Functionalized Magnetism in 2D-GaN Monolayer

Exotic properties are predicted to be functionalized by the adsorption of non-magnetic Ge atom on the two-dimensional GaN (2D–GaN) monolayer. They include the existence of spin filtering, high magnetism and continuous emission of electromagnetic radiation. A comprehensive ab-initio study of structural, electronic, magnetic and optical properties of 2D–GaN monolayer possessing several Ge atoms as adsorbents has been performed. We employ the norm-conserving pseudopotentials for atoms and plane waves in a generalised gradient approximation within density functional theory (DFT). The semiconducting pure GaN monolayer is converted into a metallic one in far 2-Ge atoms adsorbed above Ga in 2D-GaN monolayer systems. The behaviour of magnetism is found to be site-independent. The binding energies per adatom of the Ge-atoms adsorbed above N are larger than those of the Ge-atoms adsorbed above Ga atoms. Along with the main strong absorption lying in the ultraviolet region in all the Ge-adsorbed GaN monolayers, strong continuous absorption from the far infrared region to the visible region has been seen in some systems. These systems may be useful for development of light-emitting devices that will emit in various regions of the energy spectrum including visible region. The emission in the deep ultraviolet region may also be used for sterilization, water purification, etc.

Predicting Impact of Food and Feeding Time on Oral Absorption of Drugs with a Novel Rat Continuous Intestinal Absorption Model.

Intricacies in intestinal physiology, drug properties, and food effects should be incorporated into models to predict complex oral drug absorption. A previously published human continuous intestinal absorption model based on the convection-diffusion equation was modified specifically for the male Sprague-Dawley rat in this report. Species-specific physiologic conditions along intestinal length - experimental velocity and pH under fasted and fed conditions, were measured and incorporated into the intestinal absorption model. Concentration-time (C-t) profiles were measured upon a single intravenous and peroral (PO) dose for three drugs: amlodipine (AML), digoxin (DIG), and glyburide (GLY). Absorption profiles were predicted and compared with experimentally collected data under three feeding conditions: 12-hour fasted rats were provided food at two specific times after oral drug dose (1 hour and 2 hours for AML and GLY; 0.5 hours and 1 hour for DIG), or they were provided food for the entire study. Intravenous versus PO C-t profiles suggested absorption even at later times and informed design of appropriate mathematical input functions based on experimental feeding times. With this model, AML, DIG, and GLY oral C-t profiles for all feeding groups were generally well predicted, with exposure overlap coefficients in the range of 0.80-0.97. Efflux transport for DIG and uptake and efflux transport for GLY were included, modeling uptake transporter inhibition in the presence of food. Results indicate that the continuous intestinal rat model incorporates complex physiologic processes and feeding times relative to drug dose into a simple framework to provide accurate prediction of oral absorption. SIGNIFICANCE STATEMENT: A novel rat continuous intestinal model predicts drug absorption with respect to time and intestinal length. Feeding time relative to dose was modeled as a key effect. Experimental fasted/fed intestinal pH and velocity, efflux and uptake transporter expression along intestinal length, and uptake transporter inhibition in the presence of food were modeled. The model uses the pharmacokinetic profiles of three model drugs and provides a novel framework to study food effects on absorption.

Solar-assisted high-efficient cleanup of viscous crude oil spill using an ink-modified plant fiber sponge

Rapid and efficient clean-up of viscous crude oil spills is still a global challenge due to its high viscous and poor flowability at room temperature. The hydrophobic/oleophilic absorbents with three-dimensional porous structure have been considered as a promising candidate to handle oil spills. However, they still have limited application in recovering the high viscous oil. Inspired by the viscosity of crude oil depended on the temperature, a solar-heated ink modified plant fiber sponge (PFS@GC) is fabricated via a simple and environmentally friendly physical foaming strategy combined with in-situ ink coating treatment. After wrapping by the polydimethylsiloxane (PDMS), the modified PFS@GC (PFS@GC@PDMS) exhibits excellent compressibility, high hydrophobic (141° in water contact angle), solar absorption (> 96.0%), and oil absorptive capacity (12.0–27.8 g/g). Benefiting from the favorable mechanical property and photothermal conversion capacity, PFS@GC@PDMS is demonstrated as a high-performance absorbent for crude oil clean-up and recovery. In addition, PFS@GC@PDMS can also be applied in a continuous absorption system for uninterrupted recovering of oil spills on the water surface. The proposed solar-heated absorbent design provides a new opportunity for exploring biomass in addressing large-scale oil spill disasters.

Multi synergistic coupling design for broadband sound absorption based on compact porous composite embedded with massless membrane resonator

Aiming at the poor absorption of metaporous below the quarter-wavelength resonance frequency, a novel metaporous featuring with continuous high absorption within low-frequency range was proposed based on multi synergistic coupling effects. On account of abundant adjustable parameters and coupling effects with porous domain, massless membrane resonator absorber (MMRA) was firstly designed as inclusion and embedded in polyurethane foam to form a metaporous absorber (MPA). Then, a developed metaporous absorber (DMPA) was designed step by step to achieve broadband absorption. The predicted and experimental results both indicate that an average absorption coefficient of 90% within 400–1500 Hz can be achieved, with the sample thickness of only 60 mm. Both weak and strong synergistic coupling between the porous materials and MMRA are found to form multi-wideband quasi-perfect absorption peaks. Broadband and low-frequency characteristics, as well as the flexible adjustability, make our design well promising in practical noise control engineering.

Mechanism study of water control and oil recovery improvement by polymer gels based on nuclear magnetic resonance

Polymer gels have been widely used to control excessive water production and improve oil recovery. NMR techniques have been gradually applied to analyze the remaining oil distributions in the core during gel treatment in recent years. However, studies about the NMR technique applied to analyze the gelation performance and microscopic water control mechanisms are still immature. In this paper, we first compared the gelation performance of polymer gels using both the Bottle Test method and core displacement method by monitoring the changes in the real-time tested relaxation time (T2) values. Then, the T2 changes of both oil- and water-phase permeabilities after gel treatment in cores were investigated separately. Finally, the disproportionate permeability reduction (DPR) mechanism of polymer gels was investigated by combining the NMR technique in the displacement experiment. Results show that the gelation time of polymer gel in both the tube and the cores can be measured- by the relationship curve between 1/T2 and reaction time. The reduction of single-phase permeability of oil after polymer gel treatment is much smaller than that tested by the water phase. T2 data also proves that the polymer gel has certain selective water plugging performance. In addition, when the oil and water coexist, polymer gel's disproportionate permeability reduction (DPR) mechanism is mainly reflected in the gradual increase of oil saturation after gel treatment. However, the flow resistance of water in the pore space gradually increases due to the continuous water absorption and swelling of gels. It can squeeze the crude oil channel during the chase water flooding period. Finally, gel injection in heterogeneous cores can plug the high-permeability layer. MRI results demonstrated that the chase water could divert and flood the low-permeability layer usually with high residual oils, thus improving oil recovery. In summary, this study's results will help further enhance the understanding of polymer gel cross-linking mechanisms in porous media and provide an experimental basis in the analysis of the DPR mechanism of polymer gels. It can also lay a theoretical foundation for the field application of polymer gels.

High-throughput identification of genes influencing the competitive ability to obtain nutrients and performance of biocontrol in Pseudomonas putida JBC17

Elucidating underlying mechanisms of biocontrol agents (BCAs) could aid in selecting potent BCAs and increasing their biocontrol efficacy. Nutrient competition is an important biocontrol mechanism; however, essential nutrient sources, and contributing genes for nutrient competition still remain to be explored. Pseudomonas putida JBC17 (JBC17WT) suppressed green mold in satsuma mandarins by inhibiting conidial germination of Penicillium digitatum via nutrient competition. To analyze genes essential for biocontrol performance of JBC17WT, we generated a transposon (Tn)-mediated mutant library and selected mutants with the ability to suppress conidial germination. Several mutants in the genes of flagella-formation, including fliR, fliH, and flgG, increased biocontrol performance and enhanced inhibition of conidial germination. They lost swimming motility, exhibited increased growth and rapid carbon and nitrogen utilization than the wild type under nutrient-poor conditions. The nutrient competition assay using polytetrafluoroethylene cylinders revealed that conidial germination was inhibited by nutrient absorption under nutrient-poor conditions. In addition, genes, including amidohydrolase (ytcJ), tonB-dependent receptor (cirA), argininosuccinate synthase (argG), D-3-phosphoglycerate dehydrogenase (serA), and chaperone protein (dnaJ), were involved in the inhibition of conidial germination. The results of this study indicate that rapid and continuous absorption of nutrients by JBC17WT restrict nutrient availability for conidial germination on nutrient-limited fruit surfaces, thereby decreasing the chances of fungal spores infecting fruits. The high-throughput analysis of Tn mutants of this study highlighted the importance of nutrient competition and the genes that influence biocontrol ability, which contributes to the development of biocontrol applications.

Extraction Induced by Emulsion Breaking for Ca, Fe, Mg, and Zn Determination in Edible Oils Using High-Resolution Continuous Source Flame Atomic Absorption Spectrometry

Extraction Induced by Emulsion Breaking for Ca, Fe, Mg, and Zn Determination in Edible Oils Using High-Resolution Continuous Source Flame Atomic Absorption Spectrometry

Ultra-broadband sound absorption performance of a multi-cavity composite structure filled with polyurethane

In order to improve the sound absorption performance of the resonator, porous materials are introduced, an acoustic metamaterial structure (P_TMCCR) composed of a tunable multi-cavity coupled resonator (TMCCR) and polyurethane-filled slits was established. Firstly, the TMCCR was designed by combining theoretical research with finite element simulation, which enables the continuous ultra-broadband sound absorption performance by adjusting the resonant frequencies of each component. Secondly, a simulation model of the P_TMCCR was established and its effectiveness verified through an impedance-tube test. Finally, sound absorption effects of polyurethane infill and the influences of various filling modes were investigated. The results demonstrate that the P_TMCCR (after filling) exhibited a significantly improved sound absorption bandwidth and coefficient, leading to more stable sound absorption effects. The double-layer P_TMCCR effectively absorbs sound within 375 to 4270 Hz and the average sound absorption coefficient exceeded 85% from 430 to 2370 Hz, filling the bottom with polyurethane and communicating with the incident surface can significantly improve sound absorption in the frequency band less than 250 Hz. The P_TMCCR is easy to prepare and its frequency band of sound absorption is adjustable on demand to realize continuous and stable sound absorption effects, suggesting potential for use in sound absorption and noise reduction applications.

O2–O2 CIA in the gas phase: Cross-section of weak bands, and continuum absorption between 297–500 nm

Oxygen–oxygen collision-induced absorption (O2–O2 CIA) of solar radiation heats the atmosphere, affects radiative transfer, and needs to be considered in spectroscopy applications in Earth’s atmosphere. The lack of O2–O2 CIA spectra in the gas phase below 335 nm wavelength is limiting remote sensing applications in this spectral range. This study reports measurements of the O2–O2 CIA cross-section in the gas phase at high signal-to-noise ratio and spectral resolution, sufficient to fully resolve spectral band shapes (0.31–0.42 nm FWHM, full width at half maximum) using Cavity Enhanced Extinction Spectroscopy at atmospheric pressure, and variable temperature (293, 263, and 223 Kelvin). Excellent agreement with literature spectra is observed for selected strong bands. Several heretofore unmeasured weak absorption bands are characterized for the first time in the gas phase under controlled laboratory conditions, i.e., the bands centered at 315 and 328 nm (b1Σg++b1Σg+←X3Σg−+X3Σg−, vibrational quanta change Δνtot=4,3), 420 nm (a1Δg+b1Σg+←X3Σg−+X3Σg−,Δνtot=2), and 495 nm (a1Δg+a1Δg←X3Σg−+X3Σg−,Δνtot=3). The band shape at 344 nm deviates from the available literature, in part owing to the overlap of neighboring bands that give rise to non-zero continuum absorption. The consistency of spectral band shapes of transitions with non-zero Δνtot is used to predict the absorption bands at 301 nm (b1Σg++b1Σg+←X3Σg−+X3Σg−, Δνtot=5), and 397 nm (a1Δg+b1Σg+←X3Σg−+X3Σg−,Δνtot=3). A complete O2–O2 CIA cross section spectrum is presented between 297–500 nm, that is optimized for use in hyperspectral (and other) remote sensing applications.