Crystallization Behaviors of amino-terminated polyurethane (ATPU)-grafted polypropylene

Summary A melt-grafting approach was employed to prepare a novel functional polypropylene(FPP)—amino-terminated polyurethane grafted polypropylene (PP-g-ATPU). The crystallization behaviors of PP and PP/FPP blends were characterized using differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and polarized optical microscopy (POM). The effects of FPP composition on crystallization behavior, crystal transformation, and morphology of PP/FPP crystalline were investigated. The results showed that at a low dosage (<2.0 wt%) ATPU acted as a heterogeneous nucleation agent during the crystallization of PP/FPP blends. However, when the content of ATPU reached 2.0 wt% or higher, ATPU deteriorated the crystallization of PP or PP/FPP blends. The crystallite size decreased and the number of crystallites increased as the ATPU content increased. The Avrami analysis was adopted to describe the isothermal crystallization process. The difference in the exponent n between PP and PP/FPP suggested that the isothermal crystallization kinetics of PP/FPP blends followed a three-dimensional growth via heterogeneous nucleation. In terms of the half-time of the crystallization, t_1/2, the crystallization rate of functional PP blends was faster than that of PP homopolymer at a given crystallization temperature.     

认知无线电多址接入系统的研究

针对认知无线电(Cognitive Radio)频谱不连续,随机性和变化性大,以及TDMA,FDMA,CDMA不适用的问题,提出了一个基于变换域通信(Transform Domain Communication System)平台的认知无线电多址接入系统.该系统发射机通过将非空闲的频谱幅度置0,实现对授权用户的躲避;采用m状态序列产生的伪随机相位矢量,生成近似正交的调制基函数实现用户的多址接入;接收端通过本地基函数与接收信号相关估计出原始数据,并理论分析了系统的误码率.仿真表明,系统的检测概率,多址接入的用户数以及收发两端基函数的不一致会影响系统的性能.该系统能利用非连续频谱,并且基函数能够自适应变化,适合认知无线电。     

Engineering of functional supramacromolecular complexes of proteins (enzymes) using reversed micelles as matrix microreactors

The size of the inner water cavity of reversed micelles formedin a triple system ‘water-surfactant-organic solvent’can be widely varied by changing the degree of surfactant hydration.This gives grounds to use reversed micelles as matrix microreactorsfor the design of supramolecular complexes of proteins. Usingultracentrifugation analysis, it has been demonstrated thatthe oligomeric composition of various enzymes (ketoglutaratedehydrogenase, alkaline phosphatase, lactic dehydrogenase, glyceraldehyde-3-phosphatedehydrogenase) solubilized in reversed micelles of Aerosol OT[sodium bis(2-ethylehexyl)sulfosuccinate] in octane changesupon variation of the degree of hydration. An oligomeric complexforms under conditions when the radius of the micelle innercavity is big enough to incorporate this complex as a whole.At lower degrees of hydration the micelles ‘uncouple’such complexes to their components. The catalytic propertiesof various oligomeric complexes have been studied. Possibilitiesof using reversed micelles for the separation of subunits ofoligomeric enzymes under non-denaturating conditions have beendemonstrated. In particular, the isolated subunits of alkalinephosphatase, lactic dehydrogenase and glyceralde-hyde-3-phosphatedehydrogenase have been found to be active in Aerosol OT reversedmicelles. The dependences of the catalytic activity of oligomericenzymes represent saw-like curves. The maxima of the catalyticactivity observed at these curves relate to the functioningof various oligomeric forms of an enzyme. The radii of the micelleinner cavity under conditions when these maxima are observedcorrelate with the linear dimensions of the enzyme oligomericforms. Correlation of the position of a maximum with the shapeof an oligomeric complex is discussed.     

Selective separation of yttrium from rare earth elements by ion interaction chromatography. Analytical and larger scale applications

ABSTRACT

New ion interaction chromatographic (IIC) method employing Kromasil 100 C₁₈ column and tetra-n-butylammonium hydroxide (TBAOH) as an ion interaction reagent (IIR) is able to separate yttrium from Rare Earth Elements (REE) as anionic complexes with nitrilotriacetic acid (NTA). New method for the chromatographic determination of Y in REE mixture was devised and validated by the analysis of the certified reference material (CRM). Potential possibilities of the new chromatographic system for larger scale applications including macro-micro events were demonstrated.     

In vivo and in vitro lipid accumulation inBorago officinalis L.

Seeds of 13 accessions of borage (Borago officinalis) varied in total fatty acid content from 28.6 to 35.1% seed weight, with linoleic, γ-linolenic, oleic and palmitic as the predominant fatty acids, averaging 38.1%, 22.8%, 16.3% and 11.3% of total fatty acids, respectively. There was an inverse relation between γ-linolenic acid (25.0 to 17.6%) and oleic acid (14.5 to 21.3%). Fatty acid content of leaf tissues was 9.1% dry weight, with α-linolenic acid 55.2% and γ-linolenic acid 4.4% of total fatty acids. Cotyledons were the major source of fatty acids in seeds. Seed fatty acid content increased from <1 mg at six days postanthesis to about seven mg at maturity (22 to 24 days). Individual fatty acid content of seed was relatively constant after day 8. When immature embryos from 6 to 16 days postanthesis were cultured in a liquid or semisolid basal medium, fatty acid composition was similar to that of in vivo-grown seeds. Growth of cultured embryos decreased as sucrose concentration was increased from 3 to 20% in the basal medium, and most embryos did not survive 30% sucrose; fatty acid as a percentage of dry weight was maximal at 6% sucrose.     

Polyesters containing sulfur. I. Products of melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with some diols

Several new polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with ethanediol, 1,3-propane diol, 1,4-butanediol, 1,5-pentenediol, 1,6-hexanediol, 1,2-propanediol, and 2,2′-oxydiethanol. The structure of all polyesters was determined from elemental analysis and infrared (IR) spectra. Yield, reduced viscosity, molecular weight, and softening temperature for reaction products have been found. Initial decomposition and initial intensive decomposition temperature were defined from the curves of thermogravimetric analysis.     

Cold sintering of diatomaceous earth

Diatomite, a natural silicate-based sedimentary rock, was densified by cold sintering at room temperature and 150°C under various pressures (100, 200, and 300 MPa) and using different NaOH water solutions (0–3 M). The relative density of cold sintered diatomite can be as high as 90%, a condition that can be achieved by conventional firing only at 1200–1300°C. The cold sintered materials maintain the same mineralogical composition of the starting powder (quartz, glass, and illite) and are constituted by well-deformed and flattened grains oriented orthogonally to the applied pressure. Conversely, an evident phase evolution takes place upon conventional firing with the formation of cristobalite and mullite. The bending strength of cold sintered artifacts can exceed 40 MPa and increases to ≈80 MPa after post-annealing at 800°C, such mechanical strength is much larger than that of conventionally pressed samples sintered at 800°C, which is only ≈1 MPa.     

Terahertz time domain spectroscopy of graphene and MXene polymer composites

The rising demand for faster and more efficient electronic devices forces electronics industry to shift toward terahertz frequencies. Therefore there is a growing need for efficient, lightweight, and easy to produce absorbing materials in the terahertz range for electromagnetic interference (EMI) shielding and related applications. This study presents a study on basic optical properties of two types polymer-based composites loaded with two-dimensional structures—graphene and MXene phases (Ti₂C). In said range, total EMI shielding efficiency (SE) and its components, the absorption coefficient (α ), refractive index, and complex dielectric function are investigated. The ratio of SE absorption component to reflection component (SE_ABS :SE_R ) of fabricated composites is equal or higher than 30:1 in over 80% of studied range. The fabricated composites exhibit low (<0.1) loss tangent in studied range. The addition of 1 wt% of graphene increases the composite α over 10-fold in respect to pure polymer–up to 60 cm⁻¹ for frequency higher than 2 THz.     

CR composites with improved processing safety crosslinked via Heck's reaction

The aim of this study was to optimize the composition of the chloroprene rubber (CR) composites crosslinked via the Heck-type reaction to ensure their safe processing at elevated temperature. The developed curing system consisting of iron (III) acetylacetonate (Fe(acac)) and triethanolamine (TEOA) demonstrates high activity and more eco-friendly composition in comparison with metal oxide system, commercially used for CR crosslinking. However, the high activity of Fe(acac)/TEOA system results in a short scorch time, which is the greatest disadvantage regarding the safe processing of CR rubber and thus, must be improved. Therefore, CR compounds with Fe(acac) in the presence of different additives were studied. The longest scorch times (t₀₂) were observed for rubber compounds with urotropine (U), N-cyclohexyl-2-benzothiazole sulfenamide (CBS) or salicylic acid. Moreover, vulcanizates containing these additives exhibited higher tensile strengths and elongation at breaks compared to CR crosslinked with Fe(acac)/TEOA system.