STUDIES ON CRITICAL CONCENTRATION OF LIQUID CRYSTALLINE ETHYLCELLULOSE

Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming Liquid crystal phase decreased with increasing solubility parameter delta of solvent until approaching the delta of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of delta. The experiments of using mixed solvents which showed good linear relation between C-crit and delta also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature T-crit of EC, and a T-C phase diagram could be drawn.

INFLUENCE OF MOLECULAR WEIGHT OF CHITIN AND ITS THREE DERIVATIVES ON CRITICAL CONCENTRATION OF LYOTROPIC LIQUID CRYSTALLINE PHASE TRANSITION

The critical concentration of lyotropic liquid crystalline phase transition for chitin derivatives was determined using a polarization microscope. The influence of molecular weight on critical concentration of liquid crystalline solution for chitin, chitosan, cyanoethyl chitosan and propionyl chitin successively increases as the chain rigidity decreases. Therefore it can be used as an indicator of the chain rigidity.

CRITICAL CONCENTRATIONS OF α(1→3)-D-GLUCAN FROM LENTINUS EDODES IN NaOH AQUEOUS SOLUTION

Critical concentrations of α-(1→3)-D-glucan L-FV-Ⅱ from Lentinus edodes were studied by viscometry andfluorescence probe techniques. The dependence of the reduced viscosity on concentration of the glucan in 0.5 mol/L NaOHaqueous solutions with or without urea showed two turning points corresponding to the dynamic contact concentration c_s andthe overlap concentration c~* of the polymer. The values of c_s and c~* were found to be 1×10^(-3) g cm^(-3) and 1.1×10^(-2) g cm^(-3),respectively, for L-FV-Ⅱ in 0.5 mol/L NaOH aqueous solutions. The two critical concentrations of L-FV-Ⅱ in 0.5 mol/LNaOH aqueous solutions were also found to be 1.2×10^(-3) g cm^(-3) fbr c_s and 9.2×10^(-3) g cm^(-3) for c~* from the concentrationdependence of phenanthrene fluorescence intensities. The overlap concentration c~* of L-FV-Ⅱ in 0.5 mol/L NaOH aqueoussolutions was lower than that of polystyrene with same molecular weight in benzene, owing to the fact that polysaccharidetends to undergo aggregation caused by intermolecular hydrogen bonding. A normal viscosity behavior of L-FV-Ⅱ in 0.5 mol/L urea/0.5 mol/L NaOH aqueous solutions can still be observed in an extremely low concentration range at 25℃.

Combining the critical nitrogen concentration and machine learning algorithms to estimate nitrogen deficiency in rice from UAV hyperspectral data

Rapid and large area acquisition of nitrogen(N)deficiency status is important for achieving the optimal fertilization of rice.Most existing studies,however,focus on the use of unmanned aerial vehicle(UAV)remote sensing to diagnose N nutrition in rice,while there are fewer studies on the quantitative description of the degree of N deficiency in rice,and the effects of the critical N concentration on the spectral changes in rice have rarely been explored.Therefore,based on the canopy spectral data obtained by remotely-sensed UAV hyperspectral images,the N content in rice was obtained through field sampling.The construction method of the rice curve for the northeastern critical N concentration was studied,and on this basis,N deficiency was determined.Taking the spectrum of the critical N concentration state as the standard spectrum,the spectral reflectivity data were transformed by the ratios and differences,and the feature extraction of the spectral data was carried out by the successive projections algorithm(SPA).Finally,by taking the characteristic band as the input variable and N deficiency as the output variable,a set of multivariate linear regression(MLR),long short-term memory(LSTM)inversion models based on extreme learning machine(ELM),and the nondominated sorting genetic algorithmⅢextreme learning machine(NSGA-Ⅲ-ELM)were constructed.The results showed two key aspects of this system:1)The correlation between the N deficiency data and original spectrum was poor,but the correlation between the N deficiency data and N deficiency could be improved by a difference change and ratio transformation;2)The inversion results based on the ratio spectrum and NSGA-Ⅲ-ELM algorithm were the best,as the R2values of the training set and validation set were 0.852 and 0.810,and the root mean square error(RMSE)values were 0.291 and 0.308,respectively.From the perspective of the spectral data,the inversion accuracy of the ratio spectrum was better than the accuracy of the original spectrum or difference spectrum.At the algorithm level,the model inversion results based on LSTM algorithms showed a serious overfitting phenomenon and poor inversion effect.The inversion accuracy based on the NSGA-Ⅲ-ELM algorithm was better than the accuracy of the MLR algorithm or the ELM algorithm.Therefore,the inversion model based on the ratio spectrum and NSGA-Ⅲ-ELM algorithm could effectively invert the N deficiency in rice and provide critical technical support for accurate topdressing based on the N status in the rice.

Effect of polyoxypropylene chain length on the critical micelle concentration of propylene oxide-ethylene oxide block copolymers

In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (Γ), surface area demand per molecule (A), surface tension at CMC (γCMC). A linear decrease of ln[CMC] vs number of oxypropylene units in copolymer molecule was observed. The change in the work of cohesion per oxypropylene group when passing from molecular into micellar state, calculated from the Shinoda equation, was 0.43kT for the studied compounds.

Relationship between Critical Hydrogen Concentration and Applied Stress for Hydrogen Induced Cracking in 0.2 wt—%C Annealed Plain Steel

1.IntroductionSo far there are few people who studythe relationship between the criticalhydrogen concentration and the stress forhvdrogen induced cracking (CCHIC)quantitatively.Several researchers have cal-culated the CCHIC of steels under no stressby means of H permeation method,but no

Critical phosphorus concentrations in winter wheat genotypes with various phosphorus efficiencies

Under greenhouse conditions, a pot experiment was conducted to seek critical phosphorus concentrations of wheat genotypes with high and low phosphorus use efficiency. Results indicated that low efficient genotype was much more sensitive to phosphorus deficiency, with low or without phosphorus application, seed yield and dry matter of biomass were much lower. The yield of all the genotypes gradually got higher as application rate increased, but high efficient genotype——Lofflin produced relatively higher yields of seeds and biomass with low or without phosphorus input. Highly tolerate to low availability of soil phosphorus and efficient activation and absorption for soil unavailable phosphorus had been displayed. As application rates increased, yields of both genotypes were increased but high efficient genotype maintained stable while low efficient one showed continuously increase with remuneration decrease progressively. Critical phosphorus concentrations in high efficient genotypes of winter wheat were lower than that in low efficient ones and changed with various development stages, for example, at seedling state, the concentrations of high efficient genotype were 4.50—4.60 g/kg while low efficient one was 5.0 g/kg. They were 2.25—2.30 g/kg and 2.52 g/kg at flower stage, 1.96—2.05 g/kg and 2.15 g/kg at maturity respectively. But the values in seeds were reversal, higher in high efficient genotype(4.05—4.10 g/kg) than that in low efficient(3.90 g/kg). Therefore, phosphorus high efficient genotypes belong to the phosphorus resource saving type.

Correlation of Critical Micelle Concentration of Sodium Alkyl Benzenesulfonates with MolecularDescriptors

The hydrophobic-hydrophilic segment geometries of 36 sodium alkyl benzenesulfonates were fully optimized and calculated by abinitio RHF/6-31G（d）, quantum chemical data such as the charge density, the energy of molecular orbital and the dipole moment were obtained. Based on two topological descriptors and one quantum chemical descriptor, a significant quantitative structure-property relationship （QSPR） model for the critical micelle concentration （Cmc） of sodium alkyl benzenesulfonate surfactants was obtained by using the multiple linear regression technique. The good correlation coefficient of Re （0. 980） and cross-validation correlation coefficient Rcv^2 （0. 974） indicate the excellent capability and stability of the regression equation developed. In addition, linear relationships between logarithm of Cmc and the dipole moment of surfaetant hydrophobic hydrophilic segments for each homologous series have also been established with high correlation coefficient.

A Method for Determination of Critical Micellar Concentration of Surfactant

Measure the chemiluminescence value of acridine compound as luminescent agent in the surfactant solution with a series of concentrations,according to the value of the obtained luminescent value and the value of the corresponding surfactant concentration in the surfactant solution,linear fitting is carried out to obtain several fitting lines,and the minimum value of the surfactant concentration corresponding to the intersection of the two adjacent fitting lines is the critical micelle concentration of the surfactant.According to the results,the critical micelle concentration of Dodecyl trimethyl ammonium chloride is 11.5 mmol/L,Hexadecyl trimethyl ammonium Bromide is 0.357 mmol/L,Sodium dodecyl sulfate is 7.64 mmol/L,sodium N-lauroylsarcosinate is 0.890 mmol/L,Triton X-100 is 0.309 mmol/L,3-((3-Cholamidopropyl)dimethylammonium)-1-propanesulfonate is 9.53 mmol/L,3-(N,N-dimethyldodecylammonio)propanesulfonate is 1.73 mmol/L.The results were similar to those obtained by traditional methods,the method can be used in the study of critical micelle concentration of surfactants.

The Significance of Flotation Frothers Chemical Structure and Fundamental Properties: A Review

Froth flotation is a separation process widely used in the mineral processing industry that depends on differences in particle surface properties to separate valuable materials from undesired gangue. In froth flotation, an addition of a surfactant, acting as frother is usually needed. The basic function of the frother is to produce a swarm of air bubbles, which remain sufficiently stable for the hydrophobic mineral particles to be captured by them. This Paper presents a combination method of a foaming agent-surfactant composition with desirable selectivity and foaming properties. Wherein 1-butanol (C4H10O) is a main flotation foaming agent, which decides bubble sizes in a collecting area;and tetraethylene glycol (C8H18O5) is an auxiliary foaming agent, which affects a rising velocity of the bubbles in the collecting area and a foaming capability in a selected area. Set concentrations of the two components are respectively 60 ppm for the 1-butanol and 120 ppm for the tetraethylene glycol. An addition sequence is the 1-butanol followed by the tetraethylene glycol. The dual advantages of the selectivity and foaming properties of the foaming agent-surfactant composition in the present disclosure are verified through a series of tests, and desirable yields can be obtained in practice.

Determining nitrogen status and quantifying nitrogen fertilizer requirement using a critical nitrogen dilution curve for hybrid indica rice under mechanical pot-seedling transplanting pattern

Field experiments of nitrogen(N)treatment at five different application rates(0,75,150,225,and 300 kg ha^(-1))were conducted under pot-seedling mechanical transplanting(PMT)in 2018 and 2019.Two high-quality and high-yielding hybrids of indica rice,Huiliangyou 898 and Y Liangyou 900,were used in this study.The N nutrition index(NNI)and accumulated N deficit(N_(and)),used to assess the N nutrition status in real-time,were calculated for the indica cultivars under PMT with a critical nitrogen concentration(N_(c))dilution model based on shoot dry matter(DM)during the whole rice growth stage.The relationships between NNI and N_(and) with relative yield(RY)were determined,and accurate N application schemes were developed for hybrids indica rice under PMT.The results indicated that high application rate of N-fertilizer significantly increased the concentrations of shoot DM and N in aboveground organs during the observed stages in the two cultivars for two years(P<0.05).The N_(c) dilution model of hybrid indica cultivars was N_(c)=4.02 DM^(-0.42)(R^(2)=0.97)combining the two cultivars under PMT.Root-mean-square error and normalized root-mean-square error of the curve verification were 0.23 and 10.61%,respectively.The NNI and Nand ranged from 0.58 to 1.31 and 109 to–55 kg ha^(-1),respectively,in the two cultivars for all N treatments.NNI showed a linear relationship with Nand during the entire growth stage(0.53<R^(2)<0.99,P<0.01).In addition,NNI showed a linear-plateau relationship with RY(0.73<R<0.92,P<0.01)throughout the observed stages.These results suggest that the models can accurately diagnose the N-nutrition status and support effective N-fertilizer management in real-time for hybrid indica rice under PMT.

Research on the Critical Conditions for Clay Particle Release During Saline Aquifer Freshening Process

Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.

Long-lasting chemiluminescence by aggregation-induced emission surfactant with ultralow critical micelle concentration

The development of green and simple chemiluminescence(CL)systems with intensive and long-lasting emission is highly desirable in lighting and extension of their applications.In this study,it is found that the involvement of aggregation-induced emission(AIE)surfactant could greatly enhance the CL of luminol–H2O2–Co2+system.The inserted hydrophobic tetraphenylethylene fluorophore in AIE is able to increase the hydrophobicity of alkyl chain and decrease the critical micelle concentration(CMC)of surfactant.The synergistic effect of micelle-improved enrichment and CL resonance energy transfer endows luminol–H2O2–Co2+system intensive and long-lasting emission under neutral pH conditions(pH 7.4).The visible emission is still observed even after 60 min.Our study has opened a new avenue for exploring green and simple effective CL systems through AIE surfactant with unltralow CMC toward various applications in lighting,optical sensing,and photocatalysis,etc.

Physico-chemical parameters for the assembly of moxifloxacin hydrochloride and cetyltrimethylammonium chloride mixture in aqueous and alcoholic media

The aggregation behavior of the mixture of cetyltrimethylammonium chloride(CTAC), a cationic surfactant, and moxifloxacin hydrochloride(MFH), a fourth-generation fluoroquinolone antibiotic drug, has been studied using the conductivity technique in aqueous and alcoholic(EtOH, 1-PrOH, and 2-BuOH)media. The study was performed at several temperatures between 298.15 and 323.15 K at 5 K intervals.The assembly has been characterized by evaluating the micellar parameters, such as the critical micelle concentration(CMC) and the counter ion binding(β), of the CTAC + MFH mixture. The values of the CMC for the assembly of the CTAC + MFH mixture were reliant on the composition of alcohols in the mixed solvents and the temperature. The CMC values of the CTAC + MFH mixture increased with increasing temperature;that is, assembly was delayed by increased temperature. The micellization of the CTAC + MFH mixed system was delayed in alcoholic media. The observed-ΔG0mvalues for the association of the CTAC + MFH mixed system demonstrated a spontaneous aggregation process under all study conditions.Based on the-ΔH^(0)_(m) and +ΔS^(0)_(m) values, the association of the CTAC + MFH mixture is exothermic and the interaction forces acting between the CTAC and MFH species are hydrophobic, ion–dipole, and electrostatic interactions. The transfer properties and enthalpy–entropy compensation were also assessed and described comprehensively.

Adsorption of Natural Surfactant on Sandstone in Enhanced Oil Recovery: Isotherms and Kinetics Studies

In chemical enhanced oil recovery, surfactants are injected into the reservoir with the intention to lower interfacial tension (IFT) between the water and oil phases, and thereby bring about efficient displacement of oil. However, the adsorption of the surfactants to reservoir rock surfaces leads to the loss and reduction in concentration of the surfactants, which in turn reduces the overall efficiency of the oil recovery process, with attendant financial losses. In this work, the adsorption of Quillaja Saponaria (QS), a novel, natural, non-ionic surfactant, on crushed sandstone reservoir rock is investigated. X-ray diffraction (XRD) study of clean sandstone particles has been undertaken to determine the main components present in the sand particles. The conductivity method was used to measure CMC and the surfactant concentrations in aqueous solutions. Batch adsorption experiments were used to determine the amount of QS adsorbed on rock surface. Equilibrium conditions were reached after almost 5 days. From the results of the study, the Langmuir isotherm model is more suited for predicting the adsorption behaviour of QS on sandstone. The kinetic adsorption of QS obeys the pseudo-second order model. This study is particularly relevant in surfactant selection for chemical EOR processes.

Effect of chloride ion on bacterial pre-oxidation of arsenic-containing gold concentrate

The bacterial pre-oxidation process of arsenic-containing gold concentrates and the bacterial activity under different chloride ion concentrations were studied by using a mixture of thermophilic strains TCJ domesticated in production.The experimental result shows that with different samples and leaching systems,the adaptability and Cl- tolerance of bacteria are different,and that appropriate chloride ion concentration is conductive to bacterial oxidation,while higher chloride ion concentration will inhibit the bacterial activity and affect the pre-oxidation performance.Under the present production conditions,TCJ can adapt to the changes of water quality in the source of water and its critical chloride ion tolerance value is 2.7 g/L.

Entanglement of Polymer Chains in Concentrated Region by Fluorescence Probe Technique

The fluorescence of polystyrene labeled with pyrenyl groups has been investigated in concentrated solutions. The ratio of excimer to monomer intensities (I-c/I-m) of pyrenyl labels is found to vary with increasing polymer concentration (C) and display fractional dependence on the C. A critical concentration, C-m at about 0.32g/ml, is first manifested. The results are interpreted by interchain interaction and entanglement of polymer chains.

Intrachain and Interchain Interactions in Polystyrene: Dilute andSemidilutc Solutions

Excimer formation in pyrenyl labeled polystyrene has been investigated in dilutesolution region. The change of the intensity ratio of excimer to monomer (Ie/Im) with increasingconcentration (C), is interpreted by intrachain and interchain interactions. The double logarithmicPlot of Ie/Im vs C displays two critical points, Cs at about 2.5×10-3g/ml and C+ at about 3.2×10-2g/ml. In dilute region C<Cs, excimer formation may be controlled by intrachain interaction.

INTERMOLECULAR AND INTRAMOLECULAR INTERACTIONS OF POLYMER GUAR GUM IN SOLUTIONS

The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c^＊, presented by de-Gennes, is determined successfully.

The Influence of Ce(NO_3)_3·6H_2O on the Inhibitive Effect of Ca(NO_2)_2 in Simulated Concrete Pore Solution

The effects of cerium nitrite on corrosion behaviors of carbon steel in simulated concrete pore solutions were studied with the methods of linear polarization, electrochemical impedance spectroscopy and surface analysis. In pore solutions in the presence of Ce（NO3）3？6H2O, the corrosion potential, polarization resistance and impedance of carbon steel obviously increased in contrast to the situation in the absence of cerium salts. The pore solution with [NO2-] / [Cl-] = 0.3 and 0.1% Ce（NO3）3？6H2O, carbon steel shows better corrosion resistance than that in the pore solution with [NO2-] / [Cl-] = 0.6, which indicates that a small amount of Ce（NO3）3？6H2O in pore solutions can effectively promote passivation of the steel and reduce the threshold [NO2-] / [Cl-] ratio for corrosion control. The surface layer formed in cerium salt containing pore solutions is more compact and smooth and 1.36%Ce is examined on the sample surface. The addition of 0.1% Ce（NO3）3？6H2O in pore solutions can decrease the corrosion rate of steel in pore solutions and has little influence on pH change of the solutions. However, more cerium nitrate addition above 0.1% may result in pH decrease of the solution.