Development of a systems analysis approach for resolving the structure of biodegrading soil systems

An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption, and biodegradation of napththalene.     

Analysis of polynuclear aromatic hydrocarbons by glass capillary gas chromatography using simultaneous flame ionization and electron capture detection

The possibility of simultaneous application of an electron capture (ECD) and a flame ionization detector (FID) connected to a glass capillary column for analyzing polynuclear aromatic hydrocarbons (PNA) has been investigated. The ECD/FID ratio is determined for 46 PNA compounds. The ratios vary from 0.02 to 117 with relative standard deviations better than 20 percent determined from 10 replicate analyses. The results suggest that the method may be used for obtaining additional evidence in identifying PNA in environmental samples. Impurities and transformation products in the standard were identified by computerized glass capillary gas chromatography/mass spectrometry. Quinones and diones are responsible for the high EC-response determined in some trace components in the standard. An application of the method is shown for PNA from particulates in urban atmospheres.     

纳米稀土-介质薄膜光电发射光谱和能带结构

用真空蒸发沉积的方法制备了纳米稀土(La、Nd、Sm)粒子 BaO介质薄膜.研究表明薄膜的光电发射光谱响应阈值受纳米稀土粒子形状和大小的影响,球形纳米稀土(Sm)粒子 BaO介质薄膜的光谱响应阈值波长为720 nm,条状纳米稀土(La和Nd)粒子 BaO介质薄膜阈值波长分别为650 nm和660 nm.研究得到纳米稀土粒子 介质薄膜等效界面位垒高度在1.7～2.0 eV之间.由于纳米稀土粒子与BaO介质各自逸出功不同,当构成薄膜后使得纳米粒子周围的空间电荷分布发生变化,纳米粒子周围的能带发生弯曲.     

H2S-sensing properties of SnO2 produced by ball milling and different chemical reactions

In this work, the mechanochemical synthesis of a moderately agglomerated tin oxide (SnO₂) powders and the subsequent preparation of semiconductor gas sensors as prototypes, were studied. Tin (II) chloride (SnCl₂) powder was milled with calcium hydroxide (Ca(OH)₂) and potassium carbonate, (K₂CO₃) powder, respectively, in a ball mill at room temperature and in an air atmosphere. Heat treatment of milled mixtures at 400 °C resulted in the formation of a tetragonal phase, confirmed by X-ray diffraction (XRD). During milling in the presence of water, a high number of hydroxide (OH) groups are formed at the surface. When SnCl₂ was milled with K₂CO₃, no water was produced and the Fourier-transform infrared spectrum (FT-IR) of the powder has no surface hydroxyl deformations. On exposure to hydrogen sulfide (H₂S) gas, the particles, prepared from anhydrous powder, have higher sensitivity than these, prepared from hydrated powder. The SnO₂ thick film, prepared from anhydrous powder may be successfully applied to a H₂S gas sensor.     

A new dodecylsulfate-selective supported liquid membrane electrode based on its N-cetylpyridinium ion-pair

A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS⁻) ion are described. The active element is a membrane containing a dissolved ion association complex of DS⁻ with cetylpyridinium (CP⁺) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS⁻ anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10⁻³ to 1.0×10⁻⁶ mol dm⁻³ at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade⁻¹) at low concentrations (1.0×10⁻⁹ to 1.0×10⁻⁶ mol dm⁻³). Moreover, this electrode showed good selectivity and precision (R.S.D.?2.0%), and was usable within the pH range 4.0-6.8. The proposed electrode revealed a lower limit of detection of 6.3×10⁻⁷ mol dm⁻³ and improved selectivity in comparison with the some previously reported DS⁻ ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C⁻¹. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions.     

Investigation of the Interactions of β‐Peptides with DNA Duplexes by Circular Dichroism Spectroscopy

The interaction of β‐peptides with the DNA duplexes of dA₂₀dT₂₀ and a GCN4‐binding CRE sequence was examined. To gauge the factors that govern these interactions, two β‐pentadecapeptides, 1 and 2 , a β‐dodecapeptide, 3 , three β‐decapeptides, 4 – 6 , three β‐heptapeptides, 7 – 9 , and β‐octaarginine 10 were designed and synthesized. The β‐peptides were conceived to adopt a β‐peptide 3₁₄ helix, in which the side chains at position i and i + 3 are aligned vertically along one side of the helix. The side chains of Lys, Asn, and Arg were positioned such that potential H‐bonding sites were created for a helical conformation to interact with the base pairs of DNA. CD Analysis showed that β‐peptides 1, 2 , and 10 interacted with dA₂₀dT₂₀. In addition, β‐peptides 1 and 2 showed significant interaction with a DNA‐duplex 20mer containing the ATF/CREB recognition sequence for the regulatory protein GCN4. It is impossible, at this stage of the investigation, to make a safe proposal about the actual nature of the interaction of the structures(s) of the complexes, the formation of which is suggested by the CD spectra reported herein.     

Conformation of Tax-response elements in the human T-cell leukemia virus type I promoter

Background: HTLV I Tax is believed to activate viral gene expression by binding bZIP proteins (such as CRIB) and increasing their affinities for proviral THE target sites. Each 21 by THE target site contains an imperfect copy of the intrinsically bent CRE target site (the TRE core) surrounded by highly conserved flanking sequences. These flanking sequences are essential for maximal increases in DNA affinity and transactivation, but they are not, apparently, contacted by protein. Here we employ non-denaturing gel electrophoresis to evaluate TRE conformation in the presence and absence of bZIP proteins, and to explore the role of DNA conformation in viral transactivation.Results: Our results show that the TRE-1 flanking sequences modulate the structure and modestly increase the affinity of a CREB bZIP peptide for the TRE-1 core recognition sequence. These flanking sequences are also essential for a maximal increase in stability of the CREB-DNA complex in the presence of Tax.Conclusions: The CRE-like TRE core and the TRE flanking sequences are both essential for formation of stable CRIB-TRE-1 and Tax-CREB-TRE-1 complexes. These two DNA segments may have co-evolved into a unique structure capable of recognizing Tax and a bZIP protein.     

多个时间常数线性体系暂态响应方程参数的代数求解法

从线性条件出发,推导了含n个时间常数体系恒电位阶跃时暂态响应方程,并提出一套解析形为ΔI=ΔI_∞+sum from i=1 to n k_iexp(-t/τ_i)暂态方程各未知参数的代数解法。该方法可对未知体系时间常数个数进行判定,比起一般曲线拟合更加快速简便,且抗干扰能力较强。     

冲击压缩下玻璃等脆性材料中失效波的研究进展

失效波的研究始于Rasorenov和Kanel发现K1 9玻璃样品后自由表面速度时程曲线上有反常再压缩信号。失效波是二十世纪九十年代冲击动力学研究领域的一个重要发现 ,它是指在一维平面应变冲击压缩下 ,在玻璃等脆性材料中由冲击波引起的一种独特的失效或破坏现象。较为系统地回顾近年来对失效波的研究工作 ,评述了研究现状、最新结果、发展趋势、研究方法和实验手段 ,对尚存的问题进行了分析讨论 ,并介绍了玻璃材料的基本特性。最后简单汇报了作者在这方面的研究工作和取得的阶段性结果。     

Reflecting a single attosecond pulse by using periodic Mo/Si multilayer mirrors with different layers

The reflecting of a single attosecond pulse from a periodic Mo/Si multilayer was investigated. By changing the number of bi-layers, the periodic multilayer showed greatly different spectral and temporal responses of the attosecond pulse reflection, which has been discussed in detail in this paper. The capability of attosecond pulse reflection of the periodic multilayers with different bi-layer numbers has been evaluated using suitable temporal parameters. In addition, the condition for obtaining high-efficiency reflected pulses has been analyzed by comparing the pulse responses of the periodic multilayer with different layers. The transfer-matrix method together with the fast Fourier transform has been used in our simulation.