The synergistic bactericidal effect of simultaneous 222 nm krypton-chlorine excilamp and 307 nm UVB light treatment on sliced cheese and its mechanisms.

In this study, we investigated the combined effect of 222 nm krypton-chlorine excilamp (EX) and 307 nm ultraviolet-B (UVB) light on the inactivation of Salmonella Typhimurium and Listeria monocytogenes on sliced cheese. The data confirmed that simultaneous exposure to EX and UVB irradiation for 80 s reduced S. Typhimurium and L. monocytogenes population by 3.50 and 3.20 log CFU/g, respectively, on sliced cheese. The synergistic cell count reductions in S. Typhimurium and L. monocytogenes in the combined treatment group were 0.88 and 0.59 log units, respectively. The inactivation mechanism underlying the EX and UVB combination treatment was evaluated using fluorescent staining. The combination of EX and UVB light induced the inactivation of reactive oxygen species (ROS) defense enzymes (superoxide dismutase) and synergistic ROS generation, resulting in synergistic lipid peroxidation and destruction of the cell membrane. There were no significant (P > 0.05) differences in the color, texture, or sensory attributes of sliced cheese between the combination treatment and control groups. These results demonstrate that combined treatment with EX and UVB light is a potential alternative strategy for inactivating foodborne pathogens in dairy products without affecting their quality.

Switchable Xe/Kr Selectivity in a Hofmann-Type Metal-Organic Framework via Temperature-Responsive Rotational Dynamics.

The development of adsorbents for Kr and Xe separation is essential to meet industrial demands and for energy conservation. Although a number of previous studies have focused on Xe-selective adsorbents, stimuli-responsive Xe/Kr-selective adsorbents still remain underdeveloped. Herein, a Hofmann-type framework Co(DABCO)[Ni(CN)4 ] (referred to as CoNi-DAB; DABCO = 1,4-diazabicyclo[2,2,2]octane) that provides a temperature-dependent switchable Xe/Kr separation performance is reported. CoNi-DAB showed high Kr/Xe (0.8/0.2) selectivity with significant Kr adsorption at 195 K as well as high Xe/Kr (0.2/0.8) selectivity with superior Xe adsorption at 298 K. Such adsorption features are associated with the temperature-dependent rotational configuration of the DABCO ligand, which affects the kinetic gate-opening temperature of Xe and Kr. The packing densities of Xe (2.886 g cm-3 at 298 K) and Kr (2.399 g  cm-3 at 195 K) inside the framework are remarkable and comparable with those of liquid Xe (3.057 g cm-3 ) and liquid Kr (2.413 g cm-3 ), respectively. Breakthrough experiments confirm the temperature-dependent reverse separation performance of CoNi-DAB at 298 K under dry and wet (88% relative humidity) conditions and at 195 K under dry conditions. The unique adsorption behavior is also verified through van der Waals (vdW)-corrected density functional theory (DFT) calculations and nudged elastic band (NEB) simulations.

A Microporous Hydrogen-Bonded Organic Framework Based on Hydrogen-Bonding Tetramers for Efficient Xe/Kr Separation.

Hydrogen-bonded organic frameworks (HOFs) have been emerging as a new type of very promising microporous materials for gas separation and purification, but few HOFs structures constructed through hydrogen-bonding tetramers have been explored in this field. Herein, we report the first microporous HOF (termed as HOF-FJU-46) afforded by hydrogen-bonding tetramers with 4-fold interpenetrated diamond networks, which shows excellent chemical and thermal stability. What's more, activated HOF-FJU-46 exhibits the highest xenon (Xe) uptake of 2.51 mmol g-1 and xenon/krypton (Kr) selectivity of 19.9 at the ambient condition among the reported HOFs up to date. Dynamic breakthrough tests confirmed the excellent Xe/Kr separation of HOF-FJU-46a, showing high Kr productivity (110 mL g-1 ) and Xe uptake (1.29 mmol g-1 ), as well as good recyclability. The single crystal X-ray diffraction and the molecular simulations revealed that the abundant accessible aromatic and pyrazole rings in the pore channels of HOF-FJU-46a can provide the multiple strong C-H⋅⋅⋅Xe interactions with Xe atoms.

Hydrogen-Bonding Assembly Meets Anion Coordination Chemistry: Framework Shaping and Polarity Tuning for Xenon/Krypton Separation.

Hybrid hydrogen-bonded (H-bonded) frameworks built from charged components or metallotectons offer diverse guest-framework interactions for target-specific separations. We present here a study to systematically explore the coordination chemistry of monovalent halide anions, i.e., F- , Cl- , Br- , and I- , with the aim to develop hybrid H-bond synthons that enable the controllable construction of microporous H-bonded frameworks exhibiting fine-tunable surface polarity within the adaptive cavities for realistic xenon/krypton (Xe/Kr) separation. The spherical halide anions, especially Cl- , Br- , and I- , are found to readily participate in the charge-assisted H-bonding assembly with well-defined coordination behaviors, resulting in robust frameworks bearing open halide anions within the distinctive 1D pore channels. The activated frameworks show preferential binding towards Xe (IAST Xe/Kr selectivity ca. 10.5) because of the enhanced polarizability and the pore confinement effect. Specifically, dynamic column Xe/Kr separation with a record-high separation factor (SF=7.0) among H-bonded frameworks was achieved, facilitating an efficient Xe/Kr separation in dilute, CO2 -containing gas streams exactly mimicking the off-gas of spent nuclear fuel (SNF) reprocessing.

Hydrogen-Bonded Metal-Nucleobase Frameworks for Efficient Separation of Xenon and Krypton.

Xe/Kr separation is an industrially important but challenging process owing to their inert properties and low concentrations in the air. Energy-effective adsorption-based separation is a promising technology. Herein, two isostructural hydrogen-bonded metal-nucleobase frameworks (HOF-ZJU-201 and HOF-ZJU-202) are capable of separating Xe/Kr under ambient conditions and strike an excellent balance between capacity and selectivity. The Xe capacity of HOF-ZJU-201a reaches 3.01 mmol g-1 at 298 K and 1.0 bar, while IAST selectivity and Henry's selectivity are 21.0 and 21.6, respectively. Direct breakthrough experiments confirmed the excellent separation performance, affording a Xe capacity of 25.8 mmol kg-1 from a Xe/Kr mixed-gas at dilute concentrations. Density functional theory calculations revealed that the selective binding arises from the enhanced polarization in the confined electric field produced by the electron-rich anions and the electron-deficient purine heterocyclic rings.

Self-Adjusting Metal-Organic Framework for Efficient Capture of Trace Xenon and Krypton.

The capture of the xenon and krypton from nuclear reprocessing off-gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high-performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off-gas conditions remains challenging. Herein, we report a self-adjusting metal-organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off-gas. The self-adjusting behavior of ATC-Cu and its mechanism have been visualized by the in-situ single-crystal X-ray diffraction studies and theoretical calculations. The self-adjusting behavior endows ATC-Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g-1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off-gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.

High-Silica CHA Zeolite Membrane with Ultra-High Selectivity and Irradiation Stability for Krypton/Xenon Separation.

Capture and storage of the long-lived 85 Kr is an efficient approach to mitigate the emission of volatile radionuclides from the spent nuclear fuel reprocessing facilities. However, it is challenging to separate krypton (Kr) from xenon (Xe) because of the chemical inertness and similar physical properties. Herein we prepared high-silica CHA zeolite membranes with ultra-high selectivity and irradiation stability for Kr/Xe separation. The suitable aperture size and rigid framework endures the membrane a strong size-exclusion effect. The ultrahigh selectivity of 51-152 together with the Kr permeance of 0.7-1.3×10-8  mol m-2 s-1 Pa-1 of high-silica CHA zeolite membranes far surpass the state-of-the-art polymeric membranes. The membrane is among the most stable polycrystalline membranes for separation of humid Kr/Xe mixtures. Together with the excellent irradiation stability, high-silica CHA zeolite membranes pave the way to separate radioactive Kr from Xe for a notable reduction of the volatile nuclear waste storage volume.

CoNi Alloy Nanoparticles Embedded in Metal-Organic Framework-Derived Carbon for the Highly Efficient Separation of Xenon and Krypton via a Charge-Transfer Effect.

Separation of Xe and Kr is one of the greatest challenges in the gas industries owing to their close molecular structure and similar properties. Energy-effective adsorption-based separation using chemically stable carbon adsorbents is a promising technology. We propose a strategy for Xe/Kr separation using MOF-derived metallic carbon adsorbents. M-Gallate (M=Ni, Co) were used as precursors to fabricate CoNi alloy nanoparticles embedded carbon adsorbents by one-step auto-reduction pyrolysis. The optimal NiCo@C-700 exhibits record-high IAST selectivity (24.1) and Henry's selectivity (20.1) of Xe/Kr among reported carbon adsorbents. DFT calculations, local density of states calculation, charge density difference, and Bader charge analysis reveal the great affinity with Xe benefits from the presence of Ni or CoNi nanoparticles as a result of more charge transfer from Xe than Kr to metal, thus providing higher binding energy. Breakthrough experiments further verify NiCo@C-700 a promising candidate for Xe/Kr separation.

Mixed Noble-Gas Compounds of Krypton(II) and Xenon(VI); [F5 Xe(FKrF)AsF6 ] and [F5 Xe(FKrF)2 AsF6 ].

The coordination chemistry of KrF2 has been limited in contrast with that of XeF2 , which exhibits a far richer coordination chemistry with main-group and transition-metal cations. In the present work, reactions of [XeF5 ][AsF6 ] with KrF2 in anhydrous HF solvent afforded [F5 Xe(FKrF)AsF6 ] and [F5 Xe(FKrF)2 AsF6 ], the first mixed krypton/xenon compounds. X-ray crystal structures and Raman spectra show the KrF2 ligands and [AsF6 ]- anions are F-coordinated to the xenon atoms of the [XeF5 ]+ cations. Quantum-chemical calculations are consistent with essentially noncovalent ligand-xenon bonds that may be described in terms of σ-hole bonding. These complexes significantly extend the XeF2 -KrF2 analogy and the limited chemistry of krypton by introducing a new class of coordination compound in which KrF2 functions as a ligand that coordinates to xenon(VI). The HF solvates, [F5 Xe(FH)AsF6 ] and [F5 Xe(FH)SbF6 ], are also characterized in this study and they provide rare examples of HF coordinated to xenon(VI).

Syntheses and Characterizations of the Mixed Noble-Gas Compounds, [FKrII FXeII F][AsF6 ]⋠0.5 KrII F2 ⋠2 HF, ([KrII 2 F3 ][AsF6 ])2 ⋠XeIV F4 , and XeIV F4 ⋠KrII F2.

Reaction of [XeF][AsF6 ] with excess KrF2 at -78 °C in anhydrous HF (aHF) solvent has yielded the first mixed KrII /XeII noble-gas compound, [FKrFXeF][AsF6 ] ⋅0.5 KrF2 ⋅2 HF, a salt of the [FKrFXeF]+ cation. The potent oxidative fluorinating properties of KrII fluoride species resulted in oxidation of XeII to XeIV in aHF at -60 °C to form the mixed KrII /XeIV cocrystals, ([Kr2 F3 ][AsF6 ])2 ⋅XeF4 and XeF4 ⋅KrF2 . Further decomposition at 22 °C resulted in oxidation of XeIV to XeVI to give the recently reported KrII /XeVI complexes, [F5 Xe(FKrF)n ][AsF6 ] (n=1, 2), [F5 Xe][AsF6 ], and a new KrII /XeVI complex, [(F5 Xe)2 (µ-FKrF)(AsF6 )2 ], which was characterized by low-temperature (LT) Raman spectroscopy. The [FKrFXeF][AsF6 ]⋅0.5 KrF2 ⋅2 HF, ([Kr2 F3 ][AsF6 ])2 ⋅XeF4 , and XeF4 ⋅KrF2 compounds were characterized by LT Raman spectroscopy and single-crystal X-ray diffraction. Quantum-chemical calculations were used to assess the bonding in [FKrFXeF]+ , [Kr2 F3 ]+ , and [Xe2 F3 ]+ and to aid in their vibrational assignments.

Label-free Proteomics for Discovering Biomarker Candidates for Controlling Krypton Misuse in Castrated Horses (Geldings).

Recent advances in label-free quantitative proteomics may support its application in identifying and monitoring biomarkers for the purpose of doping control in equine sports. In this study, we developed a workflow of label-free quantitative proteomics to propose plasma protein biomarkers in horses after administration with krypton (Kr), a potential erythropoiesis-stimulating agent. Plasma proteomes were profiled by using nanoliquid chromatography-high-resolution mass spectrometry. An in-house mass spectral library consisting of 1121 proteins was compiled using samples collected from geldings (castrated horses) in the administration trial and geldings in training. A data-independent acquisition method was used to quantify an array of plasma proteins across plasma samples from the administration trial. Statistical analyses proposed a profile of 83 biomarker candidates that successfully differentiated Kr-administered samples from control samples, with the ability to detect Kr exposure for up to 13 days (the last sample collected in the administration trial). The model also correctly classified 32 in-training geldings as untreated controls. This is significantly longer than the 1 h detection time of plasma Kr using headspace gas chromatography-tandem mass spectrometry. Bioinformatic analyses enriched biomarker candidates relevant to complement activation and iron metabolism. The upregulation of transferrin receptor protein 1, one of the candidates related to iron metabolism, in plasma after Kr administration was validated by selected reaction monitoring of corresponding peptides. These results have demonstrated label-free quantitative proteomics as a promising approach to propose plasma protein biomarkers to enhance doping control. Data are available via ProteomeXchange with identifier PXD017262.

Noble-Gas Chemistry More than Half a Century after the First Report of the Noble-Gas Compound.

Recent development in the synthesis and characterization of noble-gas compounds is reviewed, i.e., noble-gas chemistry reported in the last five years with emphasis on the publications issued after 2017. XeF2 is commercially available and has a wider practical application both in the laboratory use and in the industry. As a ligand it can coordinate to metal centers resulting in [M(XeF2)x]n+ salts. With strong Lewis acids, XeF2 acts as a fluoride ion donor forming [XeF]+ or [Xe2F3]+ salts. Latest examples are [Xe2F3][RuF6]·XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6]. Adducts NgF2·CrOF4 and NgF2·2CrOF4 (Ng = Xe, Kr) were synthesized and structurally characterized at low temperatures. The geometry of XeF6 was studied in solid argon and neon matrices. Xenon hexafluoride is a well-known fluoride ion donor forming various [XeF5]+ and [Xe2F11]+ salts. A large number of crystal structures of previously known or new [XeF5]+ and [Xe2F11]+ salts were reported, i.e., [Xe2F11][SbF6], [XeF5][SbF6], [XeF5][Sb2F11], [XeF5][BF4], [XeF5][TiF5], [XeF5]5[Ti10F45], [XeF5][Ti3F13], [XeF5]2[MnF6], [XeF5][MnF5], [XeF5]4[Mn8F36], [Xe2F11]2[SnF6], [Xe2F11]2[PbF6], [XeF5]4[Sn5F24], [XeF5][Xe2F11][CrVOF5]·2CrVIOF4, [XeF5]2[CrIVF6]·2CrVIOF4, [Xe2F11]2[CrIVF6], [XeF5]2[CrV2O2F8], [XeF5]2[CrV2O2F8]·2HF, [XeF5]2[CrV2O2F8]·2XeOF4, A[XeF5][SbF6]2 (A = Rb, Cs), Cs[XeF5][BixSb1-xF6]2 (x = ~0.37-0.39), NO2XeF5(SbF6)2, XeF5M(SbF6)3 (M = Ni, Mg, Zn, Co, Cu, Mn and Pd) and (XeF5)3[Hg(HF)]2(SbF6)7. Despite its extreme sensitivity, many new XeO3 adducts were synthesized, i.e., the 15-crown adduct of XeO3, adducts of XeO3 with triphenylphosphine oxide, dimethylsulfoxide and pyridine-N-oxide, and adducts between XeO3 and N-bases (pyridine and 4-dimethylaminopyridine). [Hg(KrF2)8][AsF6]2·2HF is a new example of a compound in which KrF2 serves as a ligand. Numerous new charged species of noble gases were reported (ArCH2+, ArOH+, [ArB3O4]+, [ArB3O5]+, [ArB4O6]+, [ArB5O7]+, [B12(CN)11Ne]-). Molecular ion HeH+ was finally detected in interstellar space. The discoveries of Na2He and ArNi at high pressure were reported. Bonding motifs in noble-gas compounds are briefly commented on in the last paragraph of this review.

Separation of Xe from Kr with Record Selectivity and Productivity in Anion-Pillared Ultramicroporous Materials by Inverse Size-Sieving.

The separation of xenon/krypton (Xe/Kr) mixture is of great importance to industry, but the available porous materials allow the adsorption of both, Xe and Kr only with limited selectivity. Herein we report an anion-pillared ultramicroporous material NbOFFIVE-2-Cu-i (ZU-62) with finely tuned pore aperture size and structure flexibility, which for the first time enables an inverse size-sieving effect in separation along with record Xe/Kr selectivity and ultrahigh Xe capacity. Evidenced by single-crystal X-ray diffraction, the rotation of anions and pyridine rings upon contact of larger-size Xe atoms adapts cavities to the shape/size of Xe and allows strong host-Xe interaction, while the smaller-size Kr is excluded. Breakthrough experiments confirmed that ZU-62 has a real practical potential for producing high-purity Kr and Xe from air-separation byproducts, showing record Kr productivity (206 mL g-1 ) and Xe productivity (42 mL g-1 , in desorption) as well as good recyclability.

Syntheses, Structures, and Bonding of NgF2 ⋠CrOF4 , NgF2 ⋠2CrOF4 (Ng=Kr, Xe), and (CrOF4 )∞.

The noble-gas difluoride adducts, NgF2 ⋅CrOF4 and NgF2 ⋅2CrOF4 (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single-crystal X-ray diffraction. The low fluoride ion affinity of CrOF4 renders it incapable of inducing fluoride ion transfer from NgF2 (Ng=Kr and Xe) to form ion-paired salts of the [NgF]+ cations having either the [CrOF5 ]- or [Cr2 O2 F9 ]- anions. The crystal structures show the NgF2 ⋅CrOF4 adducts are comprised of Ft -Ng-Fb - - -Cr(O)F4 structural units in which NgF2 is weakly coordinated to CrOF4 by means of a fluorine bridge, Fb , in which Ng-Fb is elongated relative to the terminal Ng-Ft bond. In contrast with XeF2 ⋅2MOF4 (M=Mo or W) and KrF2 ⋅2MoOF4 , in which the Lewis acidic, F4 (O)M- - -Fb - - -M(O)F3 moiety coordinates to Ng through a single M- - -Fb -Ng bridge, both fluorine ligands of NgF2 coordinate to CrOF4 molecules to form F4 (O)Cr- - -Fb -Ng-Fb - - -Cr(O)F4 adducts in which both Ng-Fb bonds are only marginally elongated relative to the Ng-F bonds of free NgF2 . Quantum-chemical calculations show that the Cr-Fb bonds of NgF2 ⋅CrOF4 and NgF2 ⋅2CrOF4 are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr- - -Fb -Ng bridge angles and staggered O-Cr- - -Fb -Ng-Ft dihedral angles. The crystal structures and Raman spectra of two CrOF4 polymorphs have also been obtained. Both are comprised of fluorine-bridged chains that are cis- and trans-fluorine-bridged with respect to oxygen.

Characteristics Comparison of Neon, Argon, and Krypton Ion Emissions from Gas Field Ionization Sources with a Single-Atom Tip.

A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. In this study, the characteristics of neon, argon, and krypton ion emissions from a single-atom tip are compared, specifically for faster fabrication by milling of a silicon sample. Although the boiling point of argon is about 87 K, our experiments on characterizing argon ion emission can be carried out at temperatures of about 50 K at an argon gas pressure lower than 0.1 Pa. Argon exhibits ion current characteristics, as a function of tip voltage, between those of neon and krypton. The value obtained by multiplying the ion emission current by the sputtering yield is suitable for a figure of merit (FOM) for faster fabrication. The FOM for argon is the highest among the three ion species. This value must be extensively evaluated from the viewpoint of practical nano-fabrication application. The instabilities of neon, argon, and krypton ion currents (3σ) become as low as 8% in 1 h, which is sufficient for fabrication applications. We conclude that an argon or krypton GFIS ion beam instrument will be a useful tool for nano-fabrication.

A Homoleptic KrF2 Complex, [Hg(KrF2 )8 ][AsF6 ]2 ⋠2 HF.

The reaction of Hg(AsF6 )2 with a large molar excess of KrF2 in anhydrous HF has afforded the first homoleptic KrF2 coordination complex of a metal cation, [Hg(KrF2 )8 ][AsF6 ]2 ⋅2 HF. The [Hg(KrF2 )8 ]2+ dication is well-isolated in the low-temperature crystal structure of its HF-solvated [AsF6 ]- salt, and consists of eight KrF2 molecules that are terminally coordinated to Hg2+ by means of Hg-F(KrF) bonds to form a slightly distorted, square-antiprismatic coordination sphere around mercury. The Raman spectrum of [Hg(KrF2 )8 ]2+ was assigned with the aid of calculated gas-phase vibrational frequencies. Computational studies indicate that both electrostatic and orbital interactions are important for metal-ligand bonding and provide insight into the geometry of the [Hg(KrF2 )8 ]2+ cation and the nature of noble-gas difluoride ligand bonding.

Coordination of KrF2 to a Naked Metal Cation, Mg2.

Examples of coordination compounds in which KrF2 functions as a ligand are very rare. In contrast, XeF2 provides a rich coordination chemistry with a variety of main-group and transition metal cations. The reactions of Mg(AsF6 )2 and KrF2 in HF or BrF5 solvent have afforded [Mg(KrF2 )4 (AsF6 )2 ] and [Mg(KrF2 )4 (AsF6 )2 ]⋅2 BrF5 , respectively, the first examples of a metal cation ligated by KrF2 . Their X-ray crystal structures and Raman spectra show that the KrF2 ligands and [AsF6 ]- anions are F-coordinated to a naked Mg2+ cation. Quantum-chemical calculations are consistent with essentially non-covalent ligand-metal bonding. These compounds significantly extend the XeF2 -KrF2 analogy and the limited chemistry of krypton by introducing a new class of coordination compound in which KrF2 functions as a ligand towards a naked metal cation.

Krypton Derivatization of an O2 -Tolerant Membrane-Bound [NiFe] Hydrogenase Reveals a Hydrophobic Tunnel Network for Gas Transport.

[NiFe] hydrogenases are metalloenzymes catalyzing the reversible heterolytic cleavage of hydrogen into protons and electrons. Gas tunnels make the deeply buried active site accessible to substrates and inhibitors. Understanding the architecture and function of the tunnels is pivotal to modulating the feature of O2 tolerance in a subgroup of these [NiFe] hydrogenases, as they are interesting for developments in renewable energy technologies. Here we describe the crystal structure of the O2 -tolerant membrane-bound [NiFe] hydrogenase of Ralstonia eutropha (ReMBH), using krypton-pressurized crystals. The positions of the krypton atoms allow a comprehensive description of the tunnel network within the enzyme. A detailed overview of tunnel sizes, lengths, and routes is presented from tunnel calculations. A comparison of the ReMBH tunnel characteristics with crystal structures of other O2 -tolerant and O2 -sensitive [NiFe] hydrogenases revealed considerable differences in tunnel size and quantity between the two groups, which might be related to the striking feature of O2 tolerance.

Krypton-enhanced ventilation CT with dual energy technique: experimental study for optimal krypton concentration.

PURPOSE/AIM OF THE STUDY: To assess the feasibility of krypton-enhanced ventilation CT using dual energy (DE) technique for various krypton concentrations and to determine the appropriate krypton concentration for DE ventilation CT through an animal study. MATERIALS AND METHODS: Baseline DECT was first performed on seven New Zealand white rabbits. The animals were then ventilated using 20%, 30%, 40%, 50%, 60%, to 70% krypton concentration, and DECT was performed for each concentration. Krypton extraction was performed through a workstation, and results were displayed on a color map. Overlay Hounsfield unit (HU) values were obtained by two observers in consensus readings. A linear mixed model was used to correlate overlay HU values and krypton concentrations. Visual assessments of the homogeneity of krypton maps were also performed. RESULTS: Mean overlay HU values according to krypton concentration were as follows; 20% krypton, 1.68 ± 5.15; 30% krypton, 3.73 ± 5.93; 40% krypton, 6.92 ± 5.51; 50% krypton, 10.88 ± 5.17; 60% krypton, 14.54 ± 4.23; and 70% krypton, 18.79 ± 3.63. We observed a significant correlation between overlay HU values on krypton maps and krypton concentrations (P < .001). For the krypton color maps, all observers determined universal enhancement on the 70% krypton map for all animals. CONCLUSION: It is feasible to evaluate lung ventilation function using DECT with a krypton concentration of at least 70%.