Synthesis and non‐isothermal crystallization kinetics of poly(ethylene terephthalate)‐co‐poly(propylene glycol) copolymers

Poly(ethylene terephthalate)‐co‐poly(propylene glycol) (PET‐co‐PPG) copolymers with PPG ratio ranging from 0 to 0.90 mol% were synthesized by the melt copolycondensation. The intrinsic viscosity, structure, non‐isothermal crystallization behavior, nucleation and spherulitic growth of the copolymers were investigated by Ubbelohde viscometer, Proton Nuclear Magnetic Resonance (¹H‐NMR), differential scanning calorimetry, and polarized optical microscopy, respectively. The non‐isothermal crystallization process of the copolymers was analyzed by Avrami, Ozawa, Mo's, Kissinger, and Dobreva methods, respectively. The results showed that the crystallizability of PET was apparently enhanced with incorporating a small amount of PPG, which first rose and then reduced with increasing amount of PPG in the copolymers at a given cooling rate. The crystallization mechanism was a three‐dimensional growth with both instantaneous and sporadic nucleation. Particularly, PET‐co‐PPG containing 0.60 mol% PPG exhibited the highest crystallizability among all the copolymers. Copyright © 2015 John Wiley & Sons, Ltd.     

红敏光致聚合物全息记录材料噪声研究

本文从几个不同的方面研究了明胶全息记录材料体系(PPG)产生噪声的原因,并研究了单体丙烯酰胺(Am)与交联剂亚甲基双丙烯酰胺(B.Am)浓度比值、三乙醇胺(TEA)浓度、曝光量、后处理条件等对噪声的影响.结果表明:单体/交联剂比例为30:1时,体系噪声有所降低.三乙醇胺浓度对体系噪声影响较大,适宜浓度为1%.后处理工艺中,水洗温度对噪声有直接影响,最佳温度为28℃.     

基于PPG的心率和呼吸频率的测量研究

利用光电容积脉搏波描记法(PhotoPlethysmoGraphy,PPG)测量人体生理参数具有操作简单、性能稳定和适应性强等优点.采用反射式光电测量法获得桡动脉PPG信号,对PPG信号做快速傅里叶变换,分析频域实现人体心率和呼吸频率的检测.实验结果表明利用快速傅里叶变换获得的心率和呼吸频率与监护仪获得的相应数据之间有...     

Preparation and characterization of a polyimide nanofoam through grafting of labile poly(propylene glycol) oligomer

Preparation of a polyimide nanofoam (PI‐F) for microelectronic applications was carried out using a polyimide precursor synthesized from poly[(amic acid)‐co‐(amic ester)] and grafted with a labile poly(propylene glycol) (PPG) oligomer. Polyimide precursor was synthesized by partial esterification of poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). The precursor was then grafted with bromide‐terminated poly(propylene glycol) in the presence of K₂CO₃ in hexamethylphosphoramide and N‐methylpyrrolidone, imidized at 200°C in nitrogen and the product was subsequently decomposed in air at 300°C to eliminate the labile PPG oligomer to produce PMDA/ODA polyimide nanofoam. Nuclear magnetic resonance spectroscopy (¹H‐NMR) and Fourier transform infrared spectroscopy (FT‐IR) techniques were used to characterize the formation of polyimide precursor and extent of grafting of PPG with polyimide. The results of thermogravimetric analysis (TGA) showed three step decomposition of nanofoam with the removal of PPG at 350°C and decomposition of polyimide at around 600°C. The polyimide nanofoams were also characterized by small angle X‐ray scattering (SAXS), field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). The morphology showed nanophase‐separated structures with uniformly distributed and non‐interconnected pores of 20–40 nm in size. Dynamic mechanical analysis (DMA) indicated higher storage modulus for the foamed structure compared to the pure PI with reduction in loss tangent for the former system. Copyright © 2004 John Wiley & Sons, Ltd.     

How stable is a collagen triple helix? An ab initio study on various collagen and β‐sheet forming sequences

Collagen forms the well characterized triple helical secondary structure, stabilized by interchain H-bonds. Here we have investigated the stability of fully optimized collagen triple helices and beta-pleated sheets by using first principles (ab initio and DFT) calculations so as to determine the secondary structure preference depending on the amino acid composition. Models composed of a total of 18 amino acid residues were studied at six different amino acid compositions: (i) L-alanine only, (ii) glycine only, (iii) L-alanines and glycine, (iv) L-alanines and D-alanine, (v) L-prolines with glycine, (vi) L-proline, L-hydroxyproline, and glycine. The last two, v and vi, were designed to mimic the core part of collagen. Furthermore, ii, iii, and iv model the binding and/or recognition sites of collagen. Finally, i models the G-->A replacement, rare in collagen. All calculated structures show great resemblance to those determined by X-ray crystallography. Calculated triple helix formation affinities correlate well with experimentally determined stabilities derived from melting point (T(m)) data of different collagen models. The stabilization energy of a collagen triple helical structure over that of a beta-pleated sheet is 2.1 kcal mol(-1) per triplet for the [(-Pro-Hyp-Gly-)(2)](3) collagen peptide. This changes to 4.8 kcal mol(-1) per triplet of destabilization energy for the [(-Ala-Ala-Gly-)(2)](3) sequence, known to be disfavored in collagen. The present study proves that by using first principles methods for calculating stabilities of supramolecular complexes, such as collagen and beta-pleated sheets, one can obtain stability data in full agreement with experimental observations, which envisage the applicability of QM in molecular design.     

基于最小二乘法的动态光谱补偿拟合提取

高信噪比的动态光谱(dynamic spectrum, DS)提取是实现高精度动态光谱血液成分无创检测的一个关键。为了进一步提高提取的精度和速度,从原理上分析了各单波长光电容积脉搏波(photoelectric plethysmography,PPG)的线性相似性,并基于此性质提出了补偿拟合法：首先按照PPG单周期采样点数进行滑动平均得到漂移基线进行补偿,除去基线漂移;其次用各波长对数PPG与全波长叠加平均模板PPG进行最小二乘拟合,提取一次项系数构成DS。利用拟合提取法对近红外和可见光波段各25组PPG数据样本进行DS提取实验验证,并将结果与单沿提取法进行平滑性指标的对比,结果表明：近红外和可见光波段补偿拟合法获取DS的平均方差分别为单沿提取法的77.9%和59.5%,稳定提高了DS的平滑性;近红外和可见光波段补偿拟合法处理时间分别可以达到单沿提取法的10%和20%,处理速度得到显著改善。补偿拟合法在单沿提取法的基础上稳定提高了DS的信噪比,改善了DS提取质量,缩减了提取时间,并简化了处理步骤,有望推动DS无创血液成分检测的发展。     

Modeling of thermodynamic behavior of PVT properties and cloud point temperatures of polymer blends and polymer blend + carbon dioxide systems using non-cubic equations of state

In recent years, many factors influencing phase behavior of polymer blends have been studied because of their widely technological importance, as a simple method of formulating new materials with tailored properties which make them suitable for a variety of applications. This work has three main goals which were reached by using the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) and the Sanchez–Lacombe (SL) non-cubic equations of state (EoS), which in previous works have shown their ability to handle long chain and associating interactions. First, both equations of state were tested with the correlation of the specific volumes of pure blends (PBD/PS, PPO/PS, PVME/PS, PEO/PES) and the prediction of the specific volumes for blends; second, the modeling of blend miscibilities in the liquid–liquid equilibria (LLE) of PBD/PS, PPG/PEGE, PVME/PS, PEO/PES, and PnPMA/PS blends; third, the modeling of the phase behavior of PS/PVME blends at various compositions in the presence of CO₂. PC-SAFT and SL pure-component parameters were regressed by fitting pure-component data of real substances (liquid pressure–volume–temperature, PVT, data for polymers and vapor pressure and saturated liquid molar volume for CO₂) and the fluid phase behavior of blend systems were simulated fitting one binary interaction parameter (k_ij) by regression of experimental data using the modified likelihood maximum method. Results were compared with experimental data obtained from literature and an excellent agreement was obtained with both EoS, which were also capable of predicting the fluid phase behavior corresponding to the critical solution temperatures (LCST: lower critical solution temperature, UCST: upper critical solution temperature) of blends.     

Monitoring heart and respiratory rates at radial artery based on PPG

To develop an apparatus for simultaneous monitoring of heart and respiratory rates using photoplethysmography (PPG) and Fast Fourier Transform algorithm (FFT), the PPG waveform was measured at the radial artery with an original based on diffuse reflectance mode photoplethysmographic device. An FFT algorithm was used to extract heart and respiratory information from the PPG waveform. The results good agree with conventional method. The correlation coefficient of heart rate and respiratory rate obtained using PPG waveform and conventional method is 0.988 and 0.976, respectively. The PPG waveform and FFT algorithm can contribute to quicker and more accurate measurement of human heart rate and respiration rate. A portable watch-like device can be made via this method and be utilized to monitor heart and respiratory rates in hospitals or daily life care.     

Determination of plutonium and other transuranic elements by inductively coupled plasma mass spectrometry: A historical perspective and new frontiers in the environmental sciences

Inductively coupled plasma mass spectrometry (ICPMS), particularly with sector field mass analyzers (SF-ICPMS), has emerged in the past several years as an excellent analytical technique for rapid, highly sensitive determination of transuranic elements (TRU) in environmental samples. SF-ICPMS has advantages of simplicity of sample preparation, high sample throughput, widespread availability in laboratories worldwide, and relatively straightforward operation when compared to other competing mass spectrometric techniques. Arguably, SF-ICPMS is the preferred technique for routine, high-throughput determination of ²³⁷Np and the Pu isotopes, excepting ²³⁸Pu, at fg-pg levels in environmental samples. Many research groups have now demonstrated the SF-ICPMS determination of ^239 + 240Pu activities, ²⁴⁰Pu/²³⁹Pu and other Pu atom ratios in several different application areas. Many studies have examined the relative contribution of global fallout vs. local/regional Pu sources in the environment through measurement of ²⁴⁰Pu/²³⁹Pu and, in some cases, ²⁴¹Pu/²³⁹Pu and ²⁴²Pu/²³⁹Pu. “Stratospheric fallout”, which was deposited from thermonuclear tests, conducted largely during the 1952–1964 time period, is characterized by a well-defined ²⁴⁰Pu/²³⁹Pu of ~ 0.18, while most other sources have different ratios. Examples of local/regional Pu sources are the Nevada Test Site, the Chernobyl plume, and accidents at Palomares, Spain and Thule, Greenland. The determination of Pu activities and atom ratios has stimulated much interest in the use of Pu as a marine tracer; several studies have shown that Pu is transported over long distances by ocean currents. ²⁴⁰Pu/²³⁹Pu ratios > 0.20 in sediments and seawater of the North Pacific are ascribed to ocean current transport of fallout from the Pacific Proving Ground. In nuclear forensics, much effort is focused on detection and fingerprinting of small amounts of TRU in environmental samples consisting of bulk material or individual isolated particles. Activity measurements of ^239 + 240Pu, determined by SF-ICPMS, have the potential to supplement and/or replace ¹³⁷Cs as a tracer of erosion, deposition, and sedimentation. Undoubtedly, the application of SF-ICPMS in TRU analysis will continue to expand, witness new developments, and generate interesting unforeseen applications in upcoming years.