The compositions and contents of phenolic components during the three periods(alcoholic fermentation,malolactic fermentation and aging process)of wine making by Cabernet Sauvignon were analyzed by high performance liq...The compositions and contents of phenolic components during the three periods(alcoholic fermentation,malolactic fermentation and aging process)of wine making by Cabernet Sauvignon were analyzed by high performance liquid chromatography.The color parameters of the wine were also determined by CIELab method.Correlation analysis and principal component analysis were adopted to analyze the correlation between phenolic content and color parameters.In fermentation and aging periods,anthocyanins and other phenolic components in wine increased at first,and before the end of malolactic fermentation,the contents reached the highest,and later experienced a downward trend,then contents change showed a stable trend in the later stage of storage.During the whole wine-making,anthocyanins had significant correlation with CIELab parameter a*and anthocyanin malvidin-3-O-glucoside was mainly observed to present a large impact on a*in aging period,causing the red color change of wine.Other phenolic components affected the CIELab parameters a*,b*and L*differently.Statistical analysis about the color parameters and 15 phenolic components revealed correlations between the color properties and detectable phenolic contents.展开更多
Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacia...Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacial structures consisting of carbon nanotubes with different morphologies at the fiber/matrix interface is conducive to the further modulation of the mechanical,tribological,electromagnetic interference(EMI)shielding and thermal conductivity properties of carbon fiber/phenolic resin composites.Specially,array carbon nanotubes can deep into the resin matrix,effectively hindering crack extension,and constructing an electrically and thermally conductive network.Compared with the carbon fiber/phenolic composites,the tensile strength and modulus of elasticity(163.86±9.60 MPa,5.06±0.25 GPa)of the array carbon nanotubes reinforced carbon fiber/phenolic composites were enhanced by 57.09%and 22.22%.The average friction coefficient and wear rate(0.20±0.02,1.11×10^(-13)±0.13×10^(-13)m^(3)N^(−1)m^(−1))were reduced by 39.39%and 74.31%.EMI shielding effectiveness up to 40 dB in the X-band at 0.4 mm sample thickness,diffusion coefficient(0.39±0.003 mm^(2)/s)and thermal conductivity(0.54±0.004 W/(m K))were enhanced by up to 14.37%and 50.42%.This study reveals the beneficial effects of morphological changes of carbon nanotubes on the design of interfacial structure,proposes the reinforcement mechanism of array carbon nanotubes,and opens up the prospect of carbon fiber/phenolic composites for electronic applications.展开更多
In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in ...In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in high-temperature environments.This paper introduces a machine learning(ML)framework to forecast the surface roughness of carbon-phenolic composites under various thermal conditions by employing an ML algorithm derived from historical experimental datasets.Firstly,ablation experiments and collection of surface roughness height data of C/Ph composites under different thermal environments were conducted in an electric arc wind tunnel.Then,an ML model based on Ridge regression is developed for surface roughness prediction.The model involves incorporating feature engineering to choose the most concise and pertinent features,as well as developing an ML model.The ML model considers thermal environment parameters and feature screened by feature engineering as inputs,and predicts the surface height as the output.The results demonstrate that the suggested ML framework effectively anticipates the surface shape and associated surface roughness parameters in various heat flow conditions.Compared with the conventional 3D confocal microscope scanning,the method can obtain the surface topography information of the same area in a much shorter time,thus significantly saving time and cost.展开更多
The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results sho...The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results showed that the mica improved the thermal properties of the composites,the thermal expansion coefficient decreased,and the liquid phase formation caused the composites to shrink and increase the density.The flexural strength of mica surface modified composites not only increased to 78.64MPa after thermal treatment at 800-1200℃,but reached 83.02 MPa after high temperature treatment at1400℃.The improvement of the mechanical properties of the residual product benefits from the formation of high temperature ceramic phases such as Mo_(2)C and MoB,and the improvement of the shear strength of the composites by the mica.The shear strength of MBm5-2 at room temperature reached 33.08 MPa,indicating that the improvement of the interlayer properties of the composites further improved its mechanical properties.展开更多
A Ti_(3)SiC_(2)-modified high-silica oxygen/phenolic aerogel composite with excellent oxidation resistance and high-temperature performance was prepared.The experimental results show that the obtained composite has si...A Ti_(3)SiC_(2)-modified high-silica oxygen/phenolic aerogel composite with excellent oxidation resistance and high-temperature performance was prepared.The experimental results show that the obtained composite has significantly improved oxidation resistance.When the addition amount of Ti_(3)SiC_(2)is 75%,the carbonization volume shrinkage rate of the composite after aerobic static combustion is only 5.95%.At the same time,the LAR and MAR after 30 seconds of oxyacetylene ablation under a heat flux density of 1.5 MW/m2 are 0.0307 mm/s and 0.0149 g/s,respectively.The compressive strength after aerobic static combustion at 1000℃is up to 20.43%of that before aerobic static combustion,which is 1.99 times that of the unfilled material,significantly improving the high-temperature mechanical properties of the composite.展开更多
Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and h...Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and high-molecular-weight(LMW and HMW)fractions via Sephadex LH-20 column chromatography;afterwards,they were characterized by RP-HPLC-ESI-MS.The LMW fraction consisted primarily of flavan-3-ols and ellagic acid derivatives and following digestion there was an overall loss in phenolics from 16%to 100%.In the HMW fraction,procyanidins with degrees of polymerization ranging from dimers to hexamers were present.Following digestion,a loss in higher oligomeric procyanidins was observed,along with a significant increase in quantity of dimers.This increase was attributed to the dimerization of(+)-catechin/(-)-epicatechin and the scission of larger procyanidins,mainly tetramers to hexamers.The loss of phenolics following digestion,as seen by HPLC characterization,was reflected in reduced total phenolics content and antioxidant capacity,as determined by selected in vitro antioxidant assays.展开更多
Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al_2O_3-SiO_2/boron phenol formaldehyde resin（MAS/BPF） compos...Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al_2O_3-SiO_2/boron phenol formaldehyde resin（MAS/BPF） composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS/BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS/BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS/BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.展开更多
The characteristics of two different kinds of lignocellulosic materials(vegetable fillers)with two morphologies as Argania nut-shells(ANS)particles and Coir Fibers(CF)were used as reinforcement for phenolic resin(Bake...The characteristics of two different kinds of lignocellulosic materials(vegetable fillers)with two morphologies as Argania nut-shells(ANS)particles and Coir Fibers(CF)were used as reinforcement for phenolic resin(Bakelite)in this work,and the composite are studied as a function of filler types,shape,content(10,20,and 30%wt.percent)and manufacturing loading force(1500 and 3000 LBs).Compression molding was used to create the composites,which were then evaluated using Scanning electronic microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),bending,dynamic-mechanical-thermal and rheological studies.The morphology of broken samples demonstrates that both fillers are well dispersed and distributed.When fillers are added to the matrix,the flexural characteristics improve,and the optimal values are attained in the case of Argania nut-shells.The results showed that the kind and shape of the fillers had a direct influence on the dynamic mechanical characteristics of the composites due to the reinforcement's modulus augmentation.It was noticed that,the increment of manufacturing loading force decreased the mechanical and dynamical properties of composites.The optimum properties obtained indicate that the composites can only be manufactured at low manufacturing loading force(1500 LBs).展开更多
Phenol composition of two carnation （Dianthus caryophyllus） cvs ＂Gloriana＂ and ＂Roland＂, partially and highly resistant to F. oxysporum f. sp. dianthi, respectively, has been investigated with the aim of assessi...Phenol composition of two carnation （Dianthus caryophyllus） cvs ＂Gloriana＂ and ＂Roland＂, partially and highly resistant to F. oxysporum f. sp. dianthi, respectively, has been investigated with the aim of assessing the possible role of phenolic constituents both as biochemical markers of resistance and antifungal molecules. Analyses were performed through chromatography, NMR and MS methods. The results indicate that protocatechuic and vanillic acids are present in healthy and infected tissues of both cvs; the flavonol glycoside peltatoside. 2,6-Dimethoxybenzoic acid was detected in small amounts only in infected ＂Gloriana＂ cv while the highly resistant ＂Roland＂ cv contained the flavone datiscetin. This latter compound, due to its noticeable antifungal activity evidenced in in vitro trials, could be conceived both as a biochemical marker of resistance towards this pathogen and as a phytoanticipin.展开更多
The genus of Astragalus provides a significant source of pollen and nectar for honeybees.In this study,37 Astragalus honey samples in 8 different regions from Turkey were investigated for the phenolic compositions and...The genus of Astragalus provides a significant source of pollen and nectar for honeybees.In this study,37 Astragalus honey samples in 8 different regions from Turkey were investigated for the phenolic compositions and antioxidant,antimicrobial,anti-quorum sensing,anti-inflammatory and enzyme inhibitory(urease,tyrosinase,butyrylcholinesterase(BChE),and acetylcholinesterase(AChE))activities with chemometric approaches.Seventeen phenolic compounds and organic acids were detected using HPLC-DAD and levulinic,gallic,p-hydroxy benzoic,vanilic and p-coumaric acids were found to be common compounds in all studied Astragalus honey samples.The ET coded Astragalus honey sample from Erzurum showed the best antioxidant activity in DPPH^(•)(IC_(50):12.54±0.25 mg/mL),ABTS^(•+)(IC_(50):4.20±0.12 mg/mL)andβ-carotene linoleic acid(IC_(50):3.85±0.11 mg/mL)assays.Astragalus honey samples studied displayed moderate antimicrobial activity against Candida species,gram-negative and gram-positive bacteria while they showed high quorum sensing inhibition effects.The NB coded Astragalus honey sample from Ni˘gde exhibited the highest anti-inflammatory activity against COX-1(76.11±0.80%)and COX-2(55.98±0.93%)enzymes.The studied Astragalus honey samples showed mild enzyme inhibitory activities against AChE,BChE,urease and tyrosinase.The chemometric characterization based on the botanical origin of Astragalus honey samples was determined using principal component analysis(PCA)and hierarchical cluster analysis(HCA).展开更多
A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient...A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient for the Nomex fabric/phenolic composite in the study occurred in the following order:dry sliding condition>distilled water‐bathed sliding condition>sea water‐bathed sliding condition.The fabric composite’s wear rate from high to low was as follows:distilled water‐bathed sliding condition>sea water‐bathed sliding condition>dry sliding condition.Under water‐bathed sliding conditions,penetration of water into the cracks accelerated the composite’s invalidation process,resulting in a higher wear rate.We also found that the extent of corrosion and transfer film formed on the counterpart pin significantly influenced the wear rate of the Nomex fabric composite.Discussion of the Nomex fabric composite’s wear mechanisms under the sliding conditions investigated is provided on the basis of the characterization results.展开更多
基金This work was supported by Scientific Research Foundation for the Returned Overseas Scholars of Shenyang Pharmaceutical University(GGJJ2016102).
文摘The compositions and contents of phenolic components during the three periods(alcoholic fermentation,malolactic fermentation and aging process)of wine making by Cabernet Sauvignon were analyzed by high performance liquid chromatography.The color parameters of the wine were also determined by CIELab method.Correlation analysis and principal component analysis were adopted to analyze the correlation between phenolic content and color parameters.In fermentation and aging periods,anthocyanins and other phenolic components in wine increased at first,and before the end of malolactic fermentation,the contents reached the highest,and later experienced a downward trend,then contents change showed a stable trend in the later stage of storage.During the whole wine-making,anthocyanins had significant correlation with CIELab parameter a*and anthocyanin malvidin-3-O-glucoside was mainly observed to present a large impact on a*in aging period,causing the red color change of wine.Other phenolic components affected the CIELab parameters a*,b*and L*differently.Statistical analysis about the color parameters and 15 phenolic components revealed correlations between the color properties and detectable phenolic contents.
基金supported by the National Natural Science Foundation of China(No.51872232)the Key Scientific and Technological Innovation Research Team of Shaanxi Province(No.2022TD-31)the Key R&D Program of Shaanxi Province(No.2021ZDLGY14-04).
文摘Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacial structures consisting of carbon nanotubes with different morphologies at the fiber/matrix interface is conducive to the further modulation of the mechanical,tribological,electromagnetic interference(EMI)shielding and thermal conductivity properties of carbon fiber/phenolic resin composites.Specially,array carbon nanotubes can deep into the resin matrix,effectively hindering crack extension,and constructing an electrically and thermally conductive network.Compared with the carbon fiber/phenolic composites,the tensile strength and modulus of elasticity(163.86±9.60 MPa,5.06±0.25 GPa)of the array carbon nanotubes reinforced carbon fiber/phenolic composites were enhanced by 57.09%and 22.22%.The average friction coefficient and wear rate(0.20±0.02,1.11×10^(-13)±0.13×10^(-13)m^(3)N^(−1)m^(−1))were reduced by 39.39%and 74.31%.EMI shielding effectiveness up to 40 dB in the X-band at 0.4 mm sample thickness,diffusion coefficient(0.39±0.003 mm^(2)/s)and thermal conductivity(0.54±0.004 W/(m K))were enhanced by up to 14.37%and 50.42%.This study reveals the beneficial effects of morphological changes of carbon nanotubes on the design of interfacial structure,proposes the reinforcement mechanism of array carbon nanotubes,and opens up the prospect of carbon fiber/phenolic composites for electronic applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2241240,12172045,and 12221002).
文摘In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in high-temperature environments.This paper introduces a machine learning(ML)framework to forecast the surface roughness of carbon-phenolic composites under various thermal conditions by employing an ML algorithm derived from historical experimental datasets.Firstly,ablation experiments and collection of surface roughness height data of C/Ph composites under different thermal environments were conducted in an electric arc wind tunnel.Then,an ML model based on Ridge regression is developed for surface roughness prediction.The model involves incorporating feature engineering to choose the most concise and pertinent features,as well as developing an ML model.The ML model considers thermal environment parameters and feature screened by feature engineering as inputs,and predicts the surface height as the output.The results demonstrate that the suggested ML framework effectively anticipates the surface shape and associated surface roughness parameters in various heat flow conditions.Compared with the conventional 3D confocal microscope scanning,the method can obtain the surface topography information of the same area in a much shorter time,thus significantly saving time and cost.
基金Funded by the National Natural Science Foundation of China(Nos.52171045,52162013,and 51932006)。
文摘The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results showed that the mica improved the thermal properties of the composites,the thermal expansion coefficient decreased,and the liquid phase formation caused the composites to shrink and increase the density.The flexural strength of mica surface modified composites not only increased to 78.64MPa after thermal treatment at 800-1200℃,but reached 83.02 MPa after high temperature treatment at1400℃.The improvement of the mechanical properties of the residual product benefits from the formation of high temperature ceramic phases such as Mo_(2)C and MoB,and the improvement of the shear strength of the composites by the mica.The shear strength of MBm5-2 at room temperature reached 33.08 MPa,indicating that the improvement of the interlayer properties of the composites further improved its mechanical properties.
基金Funded by by the Wuhan Science and Technology Project(No.2024010702030141)。
文摘A Ti_(3)SiC_(2)-modified high-silica oxygen/phenolic aerogel composite with excellent oxidation resistance and high-temperature performance was prepared.The experimental results show that the obtained composite has significantly improved oxidation resistance.When the addition amount of Ti_(3)SiC_(2)is 75%,the carbonization volume shrinkage rate of the composite after aerobic static combustion is only 5.95%.At the same time,the LAR and MAR after 30 seconds of oxyacetylene ablation under a heat flux density of 1.5 MW/m2 are 0.0307 mm/s and 0.0149 g/s,respectively.The compressive strength after aerobic static combustion at 1000℃is up to 20.43%of that before aerobic static combustion,which is 1.99 times that of the unfilled material,significantly improving the high-temperature mechanical properties of the composite.
文摘Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and high-molecular-weight(LMW and HMW)fractions via Sephadex LH-20 column chromatography;afterwards,they were characterized by RP-HPLC-ESI-MS.The LMW fraction consisted primarily of flavan-3-ols and ellagic acid derivatives and following digestion there was an overall loss in phenolics from 16%to 100%.In the HMW fraction,procyanidins with degrees of polymerization ranging from dimers to hexamers were present.Following digestion,a loss in higher oligomeric procyanidins was observed,along with a significant increase in quantity of dimers.This increase was attributed to the dimerization of(+)-catechin/(-)-epicatechin and the scission of larger procyanidins,mainly tetramers to hexamers.The loss of phenolics following digestion,as seen by HPLC characterization,was reflected in reduced total phenolics content and antioxidant capacity,as determined by selected in vitro antioxidant assays.
文摘Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al_2O_3-SiO_2/boron phenol formaldehyde resin（MAS/BPF） composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS/BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS/BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS/BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.
文摘The characteristics of two different kinds of lignocellulosic materials(vegetable fillers)with two morphologies as Argania nut-shells(ANS)particles and Coir Fibers(CF)were used as reinforcement for phenolic resin(Bakelite)in this work,and the composite are studied as a function of filler types,shape,content(10,20,and 30%wt.percent)and manufacturing loading force(1500 and 3000 LBs).Compression molding was used to create the composites,which were then evaluated using Scanning electronic microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),bending,dynamic-mechanical-thermal and rheological studies.The morphology of broken samples demonstrates that both fillers are well dispersed and distributed.When fillers are added to the matrix,the flexural characteristics improve,and the optimal values are attained in the case of Argania nut-shells.The results showed that the kind and shape of the fillers had a direct influence on the dynamic mechanical characteristics of the composites due to the reinforcement's modulus augmentation.It was noticed that,the increment of manufacturing loading force decreased the mechanical and dynamical properties of composites.The optimum properties obtained indicate that the composites can only be manufactured at low manufacturing loading force(1500 LBs).
文摘Phenol composition of two carnation （Dianthus caryophyllus） cvs ＂Gloriana＂ and ＂Roland＂, partially and highly resistant to F. oxysporum f. sp. dianthi, respectively, has been investigated with the aim of assessing the possible role of phenolic constituents both as biochemical markers of resistance and antifungal molecules. Analyses were performed through chromatography, NMR and MS methods. The results indicate that protocatechuic and vanillic acids are present in healthy and infected tissues of both cvs; the flavonol glycoside peltatoside. 2,6-Dimethoxybenzoic acid was detected in small amounts only in infected ＂Gloriana＂ cv while the highly resistant ＂Roland＂ cv contained the flavone datiscetin. This latter compound, due to its noticeable antifungal activity evidenced in in vitro trials, could be conceived both as a biochemical marker of resistance towards this pathogen and as a phytoanticipin.
基金supported by grants from Ministry of Agriculture and Forestry,Turkey and General Directorate of Agricultural Research and Policies(TAGEM 17/AR-GE/13).
文摘The genus of Astragalus provides a significant source of pollen and nectar for honeybees.In this study,37 Astragalus honey samples in 8 different regions from Turkey were investigated for the phenolic compositions and antioxidant,antimicrobial,anti-quorum sensing,anti-inflammatory and enzyme inhibitory(urease,tyrosinase,butyrylcholinesterase(BChE),and acetylcholinesterase(AChE))activities with chemometric approaches.Seventeen phenolic compounds and organic acids were detected using HPLC-DAD and levulinic,gallic,p-hydroxy benzoic,vanilic and p-coumaric acids were found to be common compounds in all studied Astragalus honey samples.The ET coded Astragalus honey sample from Erzurum showed the best antioxidant activity in DPPH^(•)(IC_(50):12.54±0.25 mg/mL),ABTS^(•+)(IC_(50):4.20±0.12 mg/mL)andβ-carotene linoleic acid(IC_(50):3.85±0.11 mg/mL)assays.Astragalus honey samples studied displayed moderate antimicrobial activity against Candida species,gram-negative and gram-positive bacteria while they showed high quorum sensing inhibition effects.The NB coded Astragalus honey sample from Ni˘gde exhibited the highest anti-inflammatory activity against COX-1(76.11±0.80%)and COX-2(55.98±0.93%)enzymes.The studied Astragalus honey samples showed mild enzyme inhibitory activities against AChE,BChE,urease and tyrosinase.The chemometric characterization based on the botanical origin of Astragalus honey samples was determined using principal component analysis(PCA)and hierarchical cluster analysis(HCA).
基金The authors acknowledge the financial support of the National Science Foundation of China grant Nos.51375472 and 51305429.
文摘A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient for the Nomex fabric/phenolic composite in the study occurred in the following order:dry sliding condition>distilled water‐bathed sliding condition>sea water‐bathed sliding condition.The fabric composite’s wear rate from high to low was as follows:distilled water‐bathed sliding condition>sea water‐bathed sliding condition>dry sliding condition.Under water‐bathed sliding conditions,penetration of water into the cracks accelerated the composite’s invalidation process,resulting in a higher wear rate.We also found that the extent of corrosion and transfer film formed on the counterpart pin significantly influenced the wear rate of the Nomex fabric composite.Discussion of the Nomex fabric composite’s wear mechanisms under the sliding conditions investigated is provided on the basis of the characterization results.
