A study on optical absorption and constants of doped poly(ethylene oxide)

Thin films of polymer electrolyte based on poly(ethylene oxide) doped with sodium iodide (NaI) were prepared using the solution cast method. The films obtained have average thickness of 70 μm and different NaI concentrations. Absorption and reflectance spectra of UV-radiation were studied in the wavelength range 300-800 nm. The optical results were analyzed in terms of absorption formula for non-crystalline materials.The optical energy gap and the basic optical constants, refractive index, and dielectric constants of the prepared films have been investigated and showed a clear dependence on the NaI concentration. The interpreted absorption mechanism is a direct electron transition.The observed optical energy gap for neat poly(ethylene oxide) is about 2.6 eV, and decreases to a value 2.36 eV for the film of 15 wt% NaI content. It was found that the calculated refractive index and the dielectric constants of the polymer electrolyte thin films increase with NaI content. Models were used to describe the dependences of the dielectric constant on the NaI concentration, and the refractive index on the incident photon energy.     

脲系磷化合物的研究(Ⅲ)—O,O-二异丙基-N''-对氯苯甲酰基磷酰脲的晶体结构

标题化合物的晶体结构已被测定。该化合物的组成为[(i一PrO)_2P(O)NHCONHCO《》一c1]其晶体属三斜晶系,pi空间群,晶胞参数为:a=9.0216(9)A.b=9.9652(48)A.c=11.9518(43)A,a=64.746(28)。,β=69.266(17)。,r=71.718(23)。,v=891.9 A_3.z=2.D_0=1.407g/cm3。2419个大于3(?)(I)反射点参加结构的最小二乘修正.最终R因子为O.076。结构分析结果表明.该化合物中的脲基为酮式不存在烯醇变体.同时证明,在晶体状态下.脲化合物分子不具有任何对称性,分子内部有六员环的内氢键结构,p原子与相邻原子为四面体配位。     

Positive solutions of a logistic equation on unbounded intervals

In this paper, we study the existence of positive solutions of a one-parameter family of logistic equations on or on . These equations are stationary versions of the Fisher equations and the KPP equations. We also study the blow-up region of a sequence of the solutions when the parameter approaches a critical value and the non-existence of positive solutions beyond the critical value. We use the direct method and the sub and super solution method.

     

成本管理在工程项目建造过程中的应用

目前我国施工企业在工程施工中普遍存在着成本支出大,效益低下等问题.加强成本管理是各施工企业迫在眉睫的任务.在施工准备阶段:应强化成本核算、细化成本指标,树立正确的承包思想;在施工阶段:应尽量降低项目的成本,多为项目增收;在竣工决算阶段:要利用施工索赔实施成本控制.     

对针式万用表直流电压档灵敏度的改进

在分析实验室现有万用表情况的基础上论述了对指针式万用表直流电压档测量灵敏度改进的原理及方法，并进行验证，阐述了这一改进对于提高此类万用表灵敏度的重要作用。     

带模糊约束的最小费用流问题

本文首次提出了带模糊约束的最小费用流问题,建立了相应的数学模型并给出了求解这一模型的有关算法。最后,给出了一个具体实例。     

Direct injection of biological fluids: Application of HPLC-analysis with precolumn enrichment to the pharmacokinetic studies of lonazolac

Summary Lonazolac and its p-hydroxylated metabolite M1 are determined in serum by high performance liquid chromatography using direct injection of comparatively large volumes with precolumn enrichment. No sample workup is required prior to analysis. Reproducibility, calibration plots, recoveries and detection limits are presented, together with various applications of the method. Data from direct injection of serum are also compared to results from a conventional extraction work-up.Presented at the 14th International Symposium on Chromagraphy London, September, 1982     

Optimization of the irradiation power in chemical exchange dependent saturation transfer experiments

In chemical exchange dependent saturation transfer imaging experiments, exchangeable solute protons are saturated and the transfer of saturation to water is subsequently detected. When the applied irradiation power is comparable to the resonance frequency difference between the water protons and saturated solute protons, the proton transfer (PT) efficiency is reduced due to concomitant direct saturation effects. In this study, the PT process is modeled using a two-pool system. An empirical general proton transfer ratio (PTR) equation for arbitrary RF irradiation power is derived, and its optimal power to maximize the PTR is analyzed. The results are confirmed experimentally on 4.7 T using a poly-L-lysine solution. The theory provides a useful tool for optimizing the irradiation power of the PT sequences in the presence of direct saturation effects.     

Direct EPR detection of transient and continuous wave signals at 2.5 GHz

Direct detection of free induction decays and electron spin echoes, and the recording of echo-detected EPR spectra and electron spin echo envelope modulation patterns at a microwave frequency of 2.5 GHz is demonstrated. This corresponds to the measurement of the transverse magnetization in the laboratory frame, rather than in the rotating frame as usually done by down-converting the signal (homodyne detection). An oscilloscope with a 6-GHz analog bandwidth, a sampling rate of 20 GigaSamples per second, and a trigger frequency of 5 GHz for the edge trigger and 750 MHz for the advanced trigger, is used in these experiments. For signal averaging a 3-GHz microwave clock divider has been developed to synchronize the oscilloscope with the frequency of the EPR signal. Moreover, direct detection of continuous wave EPR signals at 2.5 GHz is described.     

Initial attempts at directly detecting alpha wave activity in the brain using MRI

The “direct detection” of neuronal activity by MRI could offer improved spatial and temporal resolution compared to the blood oxygenation level-dependent (BOLD) effect. Here we describe initial attempts to use MRI to detect directly the neuronal currents resulting from spontaneous alpha wave activity, which have previously been shown to generate the largest extracranial magnetic fields. Experiments were successfully carried out on four subjects at 3 T. A single slice was imaged at a rate of 25 images per second under two conditions. The first (in darkness with eyes-closed) was chosen to promote alpha wave activity, while the second (eyes-open viewing a visual stimulus) was chosen to suppress it. The fluctuations of the phase and magnitude of the resulting MR image data were frequency analysed, and tested for the signature of both alpha wave activity and neuronal activity evoked by the visual stimulus.

Regions were found that consistently showed elevated power in fluctuations of the phase of the MR signal, in the frequency range of alpha waves, during the eyes-closed condition. It was conservatively assumed that if oscillations occurred at the same frequency in the magnitude signal from the same region or at the same frequency in the phase or magnitude signal from other regions overlying large vessels or cerebrospinal fluid (CSF), then the phase changes were not due to neuronal activity related to alpha waves. Using these criteria the data obtained were consistent with direct detection of alpha wave activity in three of the four volunteers. No significant MR signal fluctuations due to evoked activity were identified.