Variation in Polymerization Degree of C-A-S-H Gels and Its Role in Strength Development of Alkali-activated Slag Binders

To investigate the variation in the degree of polymerization calcium aluminium silicate hydrate(C-A-S-H)gel and its role in the evolution of the strength of waterglass slag binders,the compressive strength,hydration products,degree of hydration of the slag,and the degree of polymerization of C-A-S-H gels of binders were examined.The experimental results indicate that the pH of the pore solution increased with an increase in the Na_(2)O concentration.However,mortar with an optimum compressive strength value of 81.0 MPa at 28 d was obtained when water glass modulus was 1.5.The main hydration product is a C-A-S-H gel for which the quantity and the degree of polymerization depend strongly on the Na_(2)O concentration;for a given range,both increase with increasing Na_(2)O concentration,thus yielding an enhanced strength.A further increase in the Na_(2)O concentration continuously increases the quantity of C-A-S-H gels while drastically reducing the degree of polymerization.The positive effect of the former is counteracted by the adverse effect of the latter,ultimately,leading to a decreased strength.Furthermore,we reveal that the degree of polymerization for C-A-S-H gels may be affected by pH,through a series of complex chemical reactions.

Studies on Single Chain Structure of Konjac Glucomannan

The simulation is carried out by employing the method of molecular dynamics with the single chain of konjac glucomannan （KGM） in vacuum as the structural model to discuss the factors that affect the single chain structure, the dynamic structure of the chain and the acting forces that maintain the chain structure. The results show that the shape and stability of the chain are affected by the degree of polymerization. As for the KGM with high degree of polymerization, its chain presents random coiling state and its stability declines. Both before and after deacetylation in the process of dynamic motion, the chain of KGM presents random coiling state with periodic variation of extension and coil and demonstrates favorable flexibility, indicating acetyl is not the main factor that affects the shape of chain, whereas dihedral angle and static actions are respectively the key bonding and nonbonding acting forces that influence the single chain conformations in vacuum.

Analysis of Hydration Mechanism and Microstructure of Composite Cementitious Materials for Filling Mining

To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum（CS）. The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.

Simultaneous Quantification of κ-Carrageenan Oligosaccharides of DP 3, 5 and 7 by LC-MS/MS: Application to an in vitro Absorption Study

Carrageenans are widely utilized in many commercial applications such as the food and pharmaceutical industry, due to their excellent functional properties. In this study, a sensitive LC-MS/MS method was developed to determine κ-3, κ-5, and κ-7 carrageenan oligosaccharides simultaneously. Optimum MRM transitions for κ-3, κ-5, and κ-7 carrageenan oligosaccharides were(645.079→565.111, [M-H]-),(515.137→474.946, [M-2H]^2-), and(471.484→445, [M-3H]^3-), respectively. Chromatographic separation was performed on an Amide column coupled with a guard column operated at 60℃ under stepwise gradient elution. The linearity of the LC-MS/MS method for κ-3, κ-5, and κ-7 carrageenan oligosaccharides, evaluated over the concentration range of 0.10- 20.0 μmol L^-1, was excellent. The precisions of the method for κ-3, κ-5, and κ-7 carrageenan oligosaccharides were from 0.91% to 9.66%, and the inter-day precisions were from 0.92% to 10.5%. Validation of the LC-MS/MS method indicated that the method was precise and in line with the CFDA guidance. This method has been successfully applied to an in vitro absorption study.

Chiral Separation Abilities of Homogeneously Synthesized Cellulose 3,5-Dimethylphenylcarbamates: Influences of Degree of Substitution and Molecular Weight

A series of cellulose 3,5-dimethylphenylcarbamates （CDMPCs） with different degrees of substitution （DS） and degrees of polymerization （DP） were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride （AmimC1）. Then, the CDMPCs were coated on silica gel and used as chiral stationary phases （CSPs）, and their chiral recognition abilities for seven racemates were evaluated by high performance liquid chromatography. The results showed that DS and DP of CDMPCs had a great influence on chiral recognition abilities of the CSPs. The CSPs with the DS ~ 1 gives a low chiral recognition to most racemates. On the contrast, the CSPs with the DS _〉 2 exhibited high chiral separation abilities. For example, six racemates could be separated on the CSP with CDMPC of DS ~ 2 （CSP-2）. Especially, for the enantioseparation of 1-（2-naphthyl） ethanol and Tr6ger＇s base, CSP-2 gave the highest separation ability in all of CSPs. On the other hand, when the DP of cellulose was in a range from 39 to 220, the chiral separation abilities of CDMPCs increased as the DP increased. This work demonstrates that the structure of cellulose esters such as DS and DP has important effect on their chiral separation ability, and therefore provides a practical method to design and prepare desirable CSPs for different racemates.

Regulation on polymerization degree and surface feature in graphitic carbon nitride towards efficient photocatalytic H2 evolution under visible-light irradiation

A kind of graphitic carbon nitride(TSC-550) with high polymerization degree and improved surface property was prepared by a new precursor of thiosemicarbazide. The sulfur motif and high nitrogen content in thiosemicarbazide promoted the polymerization of thiosemicarbazide to form graphitic carbon nitride framework with high degree of polymerization, which significantly influenced the electronic structure and surface chemical properties. TSC-550 possessed a narrow bandgap of 2.19 eV that facilitated the utilization of visible light, and possessed a less positive charge, acidic surface that resulted in enhanced hydrogen adsorption ability in water solution, which promoted the H;evolution kinetics. In addition, the extended π-conjugated electronic system promoted the separation and migration of photogenerated charge carries in plane of TSC-550 framework, as well as the increasing interlayer C–N interactions in TSC-550 created conductive paths across the layers to tunnel interlayers for rapid electron transportation. As a result, TSC-550 nanosheets showed excellent photocatalytic H;production activity,the AQY achieved 36.4% at 425 nm.

Influence of cellulose crystal plane on cellulose hydrolysis

Cellulose polymerization degree and crystal plane changing are both considered to affect acid hydrolysis,however,it is uncertain to identify which one is more important.In this study,the filter paper was treated with dilute hydrochloric acid to investigate the cellulose polymerization degree changing,and cotton linter was treated with NaOH for the purpose of changing its crystal plane.Both the treated and untreated samples were hydrolyzed under the condition of 1.0 wt%dilute hydrochloric acid with solid-liquid ratio 1:40 at 140℃for 30 min to compare the hydrolysis effects.It was found that the glucose yield increased from 9.5%to 19.7%when treated with 15%NaOH at 50℃for 30 min,and new crystal planes(1-10)(1-20)appeared after alkali treatment.According to the experimental results,it is concluded that crystal plane plays a vital role in cellulose acid hydrolysis.

Lifetime Evaluation of Medium and Small Size Power Transformers—— Part 1 : Theory

A new methodology that combines analytical and experimental methods is proposed for evaluating transformer lifetime. This first part of a two part series focuses on aging and lifetime evaluation of oil sealed transformers. The second part focuses on an experimental study of the various elements of transformers. A new computational formula based on the degree of polymerization (DP) of the insulation paper is proposed for lifetime evaluation of transformers.