Structure of the ion-rich phase in DVB cross-linked graft-copolymer proton-exchange membranes

We report on correlations between the proton conductivity, the water swelling and the dry-state morphology of ETFE-g-poly(sulfonated styrene-co-DVB) proton-exchange membranes (PEMs). We focus on the influence of the systematically varied monomer composition. Especially, the impact of the DVB cross-linker on the ion-rich phase aggregated in the dry PEM is studied by small-angle X-ray scattering. A modified hard-sphere fluid model describing the ion-rich phase is applied to interpret the observed scattering function. We find hereby that the size and number density of the ion-rich domains decrease with increasing cross-link level. Consequently, the distance between the ion-rich domains is proportional to the cross-link level. The total volume fraction of water in the hydrated membrane is proportional to the overall volume fraction of the ion-rich phase, and the number of water molecules per ion-rich aggregate is inversely proportional to the level of cross-linking. We show that there is a clear correlation between the structure of the ion-rich phase formed in the dry state and the proton conductivity of the hydrated membrane: beyond a threshold, indicating the onset of percolation of the aqueous network, the conductivity is proportional to the hydration level and inversely proportional to the mean distance between the ion-rich domains.     

New calix[4]arenedimethacrylate derivatives for dental composites

Calix[4]arenes were double alkylated with various alkylhalogenides and the residual OH functions were subsequently dimethacrylated with methacryloyl chloride. The successful synthesis of polymerizable calixarenes was proved using ¹H NMR spectroscopy, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry and differential scanning calorimetry. The polymerization behaviour was confirmed by copolymerization with methacrylic acid methyl ester. Furthermore, the flexural strength, the flexural modulus of elasticity, the exothermic course of the photo‐curing reaction and the polymerization shrinkage of experimental dental filling composites containing the modified calixarenes were evaluated. Copyright © 2012 Society of Chemical Industry     

Methacrylated calix[4]arene phosphonic acids as functionalized crosslinker for radical polymerization

We describe the synthesis of 5,11,17,23‐tetra‐tert‐butyl‐25,27‐dioxypropylphosphonic acid‐26,28‐dimethacryloyloxy‐calix [4]arene and 5,11,17,23‐tetra‐tert‐butyl‐25‐oxypropylphosphonic acid‐27‐hydroxy‐26,28‐dimethacryloyloxy‐calix[4]arene starting from para‐tert‐butyl‐calix[4]arene. The complete reaction was proved by matrix‐assisted laser desorption ionization time of flight mass spectrometry and nuclear magnetic resonance spectroscopy. The influence of these compounds on the kinetics of the radical polymerization of methyl methacrylate was shown by dilatometry. Furthermore, the adhesive properties of dental adhesives containing these calix[4]arene derivatives were investigated. Copyright © 2012 Society of Chemical Industry     

An investigation of the synthesis and thermal stability of poly(dl-lactide)

Summary The synthesis and thermal degradability of poly (DL-lactide) were investigated. Key factors affecting the polymer molecular weight were found to be monomer recrystallization, initiator concentration and the vacuum level during drying/sealing of the polymerization reaction ampoule. It was found that poly (DL-lactide) is thermally unstable above its melting temperature. Monomer recrystallization, polymer precipitation and a low initiator content of the polymer significantly inhibited the rate and extent of thermal degradation.     

离子液体微波辅助萃取川芎中内酯类化合物

以离子液体1-丁基-3-甲基咪唑双三氟甲基磺酰亚胺鎓盐([Bmim]Tf2N)为萃取剂,采用微波辅助萃取法(MAE)对川芎中的洋川芎内酯I和H及藁本内酯的萃取进行了研究.考察了温度、时间、相比和原药粒径等因素对萃取效果的影响,比较了MAE和传统溶剂回流萃取法(SRE)的萃取率,并对萃取后的固体做了SEM研究.结果表明,萃取温度对萃取率影响显著,在180℃下对3种内酯类化合物均体现出良好的萃取效率;萃取在1min内达到平衡;固/液比为1/30～1/5g/mL和原药粒径0.096～0.25mm范围内对萃取效率没有显著影响;与SRE相比,MAE耗时短、效率高,对提高藁本内酯萃取效率尤为显著,提高达46%;由样品表面结构变化可见,MAE萃取的样品结构被破坏,有助于活性组分释放、提高萃取率.     

面粉厂的能量管理

全球能源价格的增长正在再一次使粮食加工工业对其增值工序的能耗问题变得敏感.由于能耗占面粉加工总成本高达6%,因而面粉和粗粒粉的加工厂关心探索降低能量需求的新的解决办法. 为了获得解决能量管理问题的办法,工序链内部能量需求的分析是重要的.目的是要证明用来削减能耗的投资在什么地方是会收到效果的,而在工厂哪些区段的能量消耗只属于边际重要性.     

DESIGN AND PERFORMANCE OF TWO ORTHOGONAL EXTRACTION TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETERS FOR FOCUSED ION BEAM INSTRUMENTS

The design and performance of two orthogonal extraction time-of-flight mass spectrometers are reported that were adapted to existing focused ion beam microscopes for secondary ion mass spectrometry. The performances of these designs were compared to that of a prototype previously described by our group. The differences include newly designed transfer ion optics and in the use of a larger microscope chamber. The two new prototypes allow a mass resolving power of either 600 Th/Th (compact design) or 3000 Th/Th (high resolution design) while simultaneously achieving a lateral spatial resolution of less than 50 nm. The spectrometers and their performance (effective ion yield, mass resolving power, lateral, and depth resolution) are described and compared. Additionally, example applications are presented with multivariate statistical methods to visualize the data sets. Both time-of-flight mass analyzers use orthogonal extraction which avoids the need to pulse the primary ion beam, and the of use monoisotopic gallium to preserve the mass resolution. The goal of the design was a cost-effective accessory to augment typical focused ion beam-scanning electron microscopy applications as an alternative to the cost of a dedicated secondary ion mass spectrometer. The modified instrument allows excellent non destructive imaging and easy sample access, and benefits from the presence of complementary non destructive analytical and imaging techniques that exploit the presence of an electron microscope.     

Controlling nanowear in a polymer by confining segmental relaxation

Molecular relaxation of a copolymer designed for nano-electromechanical systems was chemically confined by varying the spacing between cross-links, delta(c). A critical cross-link spacing of 1-3 nm marks a transition in the nano-mechanical properties evaluated by atomic force microscopy. The transition reveals an interplay between the cross-link spacing and the length scale for backbone relaxation, xi(alpha), in cooperatively rearranging regions. For delta(c) > xi(alpha), the natural backbone relaxation process is relatively unaffected by the cross-links and a ductile, low hardness behavior results. For delta(c) < xi(alpha), the cross-links directly interfere with backbone relaxation and confine segmental mobility, leading to a brittle, high hardness response.     

Length-dependent extraction of single-walled carbon nanotubes

A two-phase liquid-liquid extraction process is presented which is capable of extracting water-soluble single-walled carbon nanotubes into an organic phase. The extraction utilizes electrostatic interactions between a common phase transfer agent and the sidewall functional groups on the nanotubes. Large length-dependent van der Waals forces for nanotubes allow the ability to control the length of nanotubes extracted into the organic phase as demonstrated by atomic force microscopy.     

1997 American Urological Association Gallup survey: Changes in diagnosis and management of prostate cancer and benign prostatic hyperplasia, and other practice trends from 1994 to 1997

PURPOSE: The American Urological Association first commissioned the Gallup Organization to conduct a study to assess urologist practice patterns in 1992. We present the results of the 1997 survey, the sixth consecutive Gallup survey performed for the Association. MATERIALS AND METHODS: A random sample of 502 American urologists who had completed urological residency and practiced at least 20 hours weekly in 1996 was interviewed by telephone in February and March 1997. RESULTS: Emerging trends showed significant changes since 1994 in how urologists diagnosed and treated prostate cancer. The survey revealed a significant change in the tests routinely ordered to stage newly diagnosed prostate cancer and for diagnostic evaluation of patients with benign prostatic hyperplasia. CONCLUSIONS: Urologists are becoming more cost conscious and effective in ordering pretreatment testing. Urologists are becoming more oriented toward medical treatment for the management of benign prostatic hyperplasia, and less laser surgery is being performed.