The effect of reactive plasticizer on viscoelastic and mechanical properties of solid rocket propellants based on different types of HTPB resin

Conventional plasticizers deteriorate mechanical and viscoelastic properties of the propellants due to their migration upon aging and long-term storage,which affects reliability and safety properties during exploitation.To address this issue,conventional plasticizer,dioctyl adipate(DOA),is replaced by reactive one,castor oil(CO).In addition,three different types of HTPB were used to obtain propellants with designed viscoelastic and mechanical properties.The CO increased propellants viscosity,without a significant impact on the propellant processability,regardless to the type of prepolymer.Conversely,mechanical properties were different depending on the type of resin,which were further analyzed by gel permeation chromatography(GPC).Addition of CO formed a denser polymer network and shifted T_(g) to higher values,compared to the compositions with DOA.The tensile strength of CO-containing propellants was lower at +20℃ and +50℃ compared to the reference compositions,while the strain at maximum load and strain at break were significantly increased with pronounced plastic deformation,especially for samples at -30℃.The inclusion of CO in the propellants composition gives more room for adjusting a wide range of mechanical properties.

凝胶渗透色谱和气相色谱-质谱法测定动物食品中27种有机氯和15种拟除虫菊酯类农药残留量

A GC-MS method for the determination of 27 organochlorine pesticides and 15 Pyrethroid pesticides in animal food is established.The method was based on Gel Permeation chromatography combined with solid-phase extraction for sample preparation.Rapid qualitative and quantitative analyses was carried out by gas chromatography-mass spectrometry under the selective-ion monitoring mode.The experimental results showed that the correlation coefficients were better than 0.99,the recoveries for spiked standards were 70%-104%,the relative standard deviations were 2.1%-15.9%.

Recombinant human bone morphogenetic protein-7 expressed from CHO cells possessing the activity of bone-induced in vitro

Objective To express the recombinant human bone morphogenetic protein-7 (rhBMP-7) in Chinese hamster ovary (CHO) cells and to establish the in vitro biological activity assay of rhBMP-7. Methods Human BMP-7 cDNA was subcloned into pcDNA3.1 mammalian expression vector and transfected to CHO cells by using the lipofectin transfection method. BMP-7 expression cell culture supernatants were harvested and purified for target protein. To analyze the bioactivity of the secreted rhBMP-7, a novel in vitro assay was established by measuring its alkaline phosphatase (ALP) stimulating of osteoblast cell line, W-20-17. Results BMP-7 stably expressing cell clone was selected, which secreted mature disulfide-linked homodimer form of hBMP-7 and had an apparent molecular weight of 36kDa. rhBMP-7 with >95% purity was obtained using 3 step chromatography method. Bioactivity assay showed that the purified protein specifically stimulated W-20-17 cell producing ALP, with a 4-fold increase of ALP activity at 100ng/ml or more, and the EC50 of 15.6ng/ml. Conclusion Purified rhBMP-7 from this CHO expression system has significant biological activity in induction of osteoblast phenotype, which demonstrates potential bone regeneration activity.

Discrimination of Car Headlight Plastic by Gel Permeation Chromatography

Car headlight plastic as a kind of evidence often can be seen in traffic accidents and some other cases.We tested 20 brands of car headlight plastic using gel chromatography.The data were processed using the Statistical Package for the Social Sciences(SPSS)one‑way analysis of variance(ANOVA)and the discrimination rate was 97.14%.This indicated that we could discriminate between different headlights by the molecular weight of their headlight plastic.Gel permeation chromatography is an effective method of discriminating between headlights,particularly in the case of a traffic accident.

Fractionation of edible bird’s nest glycoprotein hydrolysates:characterisation and antioxidative activities of the fractions

E dible bird’s nest(EBN)hydrolysates have been proven to exhibit enhanced bioactivities.However,being a macromolecule,fractions with different molecular weights would have different properties and bioactivities.Hence,this research was aimed to determine the chemical properties and antioxidant activities of freezedried(EBN_(FD))and spray-dried EBN(EBN_(SD))hydrolysates fractionated using gel permeation chromatography(GPC).Overall,two well-separated fractions were identified(EBN_(fFD1),EBN_(fFD2),EBN_(fSD1) and EBN_(fSD2)).EBNFD demonstrated significantly higher(P≤0.05)peptide(3.6%),total carbohydrate(27.7%)and sialic acid(18.2%)contents than that of EBNSD.Similar trend was observed in low molecular weight fractionates(EBN_(fFD2) and EBN_(fSD2)).Meanwhile,the first fractionates(EBN_(fFD1) and EBN_(fSD1))exhibited significantly higher(P≤0.05)hydroxyl radical(·OH)scavenging activity.Fourier transform infrared(FTIR)spectroscopy demonstrated that all EBN fractionates have similar spectrum,except in the region of N—H(amideⅡ)and C—H alkyl group.In conclusion,EBN fractionates with different molecular weights showed different chemical properties and antioxidant activities.

SUPPORTED ZIEGLER-NATTA CATALYSTS FOR ETHYLENE SLURRY POLYMERIZATION AND CONTROL OF MOLECULAR WEIGHT DISTRIBUTION OF POLYETHYLENE

The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidati...

Operational Laboratory Methods for GDGTs Groups Separation

Glycerol dialkyl glycerol tetraethers(GDGTs), specific membrane lipids synthesized mainly by bacteria and archaea, can be divided into isoprenoids and methyl branched alkyl GDGTs(i GDGTs and brGDGTs, respectively). Three GDGTs groups(i GDGTs, brGDGTs, and other membrane lipids) in a peat sample were separated and collected in this study using semi-preparative high-performance liquid chromatography(HPLC) and silica gel column chromatography. The obtained recoveries for the whole analytical procedure were 85% – 55% using semi-preparative HPLC and 70% – 20% using gel column chromatography. In addition, in each method, the recoveries of brGDGTs and iGDGTs were similar, regardless of the huge difference in their contents. High purity was found in the fractionated groups, determined based on ether cleavage and reduction. Moreover, the semi-preparative HPLC method could realize a better separation efficiency than the silica gel method, but it was time-consuming and required expensive equipment, while the silica gel chromatography method featured merits of time saving and convenient operation at the cost of a slight reduction in separation efficiency. The advantages of the silica gel method make it an operational laboratory method for batch experiments and isotopic studies.

Bulk growth and separation of single-walled carbon nanotubes from rhenium catalyst

Bulk synthesis of single-walled carbon nanotubes(SWNTs)using solid catalyst has been challenging,despite of recent breakthrough in the chirality-specific growth on the flat substrate surface.In this work,we propose a porous magnesia support rhenium catalyst for bulk synthesis of SWNTs.It is found that the well-dispersed catalyst with a high melting point and the optimal chemical vapor deposition reaction conditions account for the growth of SWNTs.Detailed characterizations reveal the produced SWNTs are dominant in(n,n−1)and(n,n−2)species.Furthermore,by using a multicolumn chromatography post-growth separation method,SWNTs with three defined diameter ranges were obtained.This work guides the design of porous oxide supported catalyst for bulk synthesis and diameter-dependent sorting of SWNTs,which will ultimately help harness the extraordinary properties of SWNTs.

Preparation and Characterization of the Phenolated Wood Using Sulfuric Acid as a Catalyst Ⅱ. FT-IR and GPC Characterization

By means of gel permeation chromatography analysis, the molecular weight of liquefied wood under different reaction conditions was investigated to trace the change in the structural characteristics of the liquefied wood. The insoluble residues were analyzed by Fourier transform infrared to investigate the liquefaction order of three main wood components. The results indicate that both reaction temperature and reaction time could affect the molecular characteristics of the liquefied wood obtained. The mo...

Influence of microwave on chromium complex composition in tanning liquor

Since microwave irradiation could promote hydrolysis and olation of chromium tanning liquor,but the influence of microwave on chromium complex component in the liquor was still unknown.Chromium sulphate solution(0%basicity)and 33%basicity chromium tanning liquor were subjected microwave(MW)and water bath(WB)heating,and the samples without any warming were regarded as control.Ion exchange chromatography(IEC)and gel filtration chromatography(GFC)were used to measure the charge composition and molecular size of chromium complexes in each sample.FT-IR was used to characterize the structure of chromium complexes in each composition separated by IEC.Moreover,the chromium tanning liquor after warming was used in hide powder tanning trials to illustrate whether microwave would affect its tanning ability.The results show there are more high positive charge and large molecular size complexes in chromium tanning liquor after warming but the phenomena are more significant in MW samples compared with WB due to non-thermal effect of microwave.In addition,microwave has more powerful effect on 33%basicity chromium tanning liquor hydrolysis and olation to generate larger molecular size complexes.In FT-IR results,the combination pattern between chromium and ligands are changed after warming but there is no difference between WB and MW.The chromium exhaustion and thermal stability of hide powder tanned with chromium tanning liquor after microwave irradiation are both higher.It could conclude that both thermal and non-thermal effects of microwave promote the process together,and the nonthermal effect leads to more high positive charge and large molecular size complexes and has stronger influence on high polarity system.In short,this work would provide theoretical basis for applying microwave in tanning agent modification and chrome tanning process further.

Extraction and purification of deguelin from Derris trifoliata Lour root

This article deals with extraction and purification of deguelin,which is a main rotenoid occurred in the root of Derris trifoliate Lour.Deguelin has gained much attention of scientists because of its potential ability to inhibit cancer cell proliferation.The dried root powder was extracted with ethanol by ultrasonic-assisted extraction for 30 min,and then filtrated and concentrated to give pasty concentrate.The concentrate was loaded onto silica gel column chromatography subsequently;and the chemical was eluted using a binary solvent mixture of petroleum ether(60-90ºC)-ethyl acetate(4:1,v/v).All tentative identification was carried out by high performance liquid chromatography(HPLC).Most crystal of deguelin was obtained after the fractions mainly containing deguelin were pooled and placed in the dark at 4ºC for three days.With recrystallization from carbon tetrachloride for three times,the purity of deguelin crystal was 99.15%and the yield was 0.55%of the dried weight of D.trifoliate Lour root.

Antibacterial and antioxidant effects from seaweed,Sargassum wightii(Greville,1848)against marine ornamental fish pathogens

Objective:To screen seaweed Sargassum wightii(S.wightii)for bioactive natural substance against marine ornamental fish bacterial pathogens,and also study the antioxidant properties,brine shrimp toxicity effect.Methods:Crude extract was made using three solvents(acetone,ethanol and methanol)and screened for antibacterial activity and purified by column chromatography,purified fractions obtained were tested for the activity.The 1st fraction of acetone extract showed maximum activity,this was again subjected for purification and obtained three sub-fractions also tested for the activity.Total phenols and flavonoid contents,reducing power,free radical scavenging activities(DPPH and H_(2)O_(2))and brine shrimp toxicity were also studied using purified acetone extract followed by standard methods.Results:The purified acetone extract showed maximum activity against eight pathogens among ten.GC-MS results revealed two major compounds such as 24-methylene cholesterol(79.9%)and methyl oleate(30.3%)which presented in higher percentage in purified extract and had highest phenols and flavonoid contents,reducing power,free radical scavenging activities,and also showed less toxicity effect.In he present study,the purified extract of S.wightii had potential antibacterial activity against Aeromonas hydrophila[(22.25±0.35)mm]and minimum activity against Streptococcus sp.[(10.00±0.00)mm].The purified extract of S.wightii also had potential total antioxidant activity of(3.87±0.04)μg at 100μg/mL concentration and the lowest activity was exhibited(1.52±0.01)μg at 25μg/mL.Conclusions:The present study concluded that the brown seaweed,S.wightii has potential antimicrobial and antioxidant activities,which can be used in aquaculture industry for treated bacterial diseases in infected fishes.