Isolation and Identification of 2-Chloro-10-(3-dimethylaminopropyl)-phenothiazine from Mumiyo

2-Chloro-10-(3-dimethylaminopropyl)-phenothiazine (aminazine) was isolated from the organic extract of mumiyo by distribution chromatography. Its quantitative content was determined by titration.     

基于量子化学计算方法的天然气水合物稳定性研究进展

天然气水合物以资源丰富、优质、洁净等特点,被视为21世纪新能源。天然气水合物稳定性的研究对天然气水合物资源勘探开发具有重要意义。本文简述了微观、介观、宏观、矿藏四个尺度天然气水合物稳定性的研究,重点从微观量子尺度介绍了量子化学计算方法对水合物晶体结构及其稳定性以及水合物宏观物理特性微观表征的计算研究。应用量子化学计算方法可以对天然气水合物的晶体结构、电子轨道分布、振动光谱、成键特性及主客体相互作用进行计算研究,其结果能够为天然气水合物在油气储运、水合物成藏、开采及其综合利用等方面的研究提供理论支持。目前,量子化学计算方法的优化与分子动力学模拟、分子力学模拟等方法的结合将有助于水合物形成和分解微观机理研究的发展,提升计算精度和扩大研究体系,为矿场尺度的天然气水合物资源开采利用提供理论支持。     

自然键轨道方法研究分子的芳香性

用自然键轨道方法研究了环状共轭分子的芳香性,提出了用自然键轨道的准离域能作为量度分子芳香性的标准,用INDO方法和DV-Xα方法计算了20多个环状有机或无机分子的自然键轨道的准离域能。根据准离域能标准判断的分子芳香性大小顺序与文献的结果基本一致,表明本文提出的芳香性量度标准的有效性和可用性。     

The compatibility of (natural) polyols with heavy metal- and zinc-free poly(vinyl chloride): Their effect on rheology and implications for plate-out

This paper describes the rheological effects observed after addition of (natural) polyols to several different types of heavy metal-free PVC formulations. It is found that addition of natural polyols, such as sorbitol, leads to changes in the rheology of the system comparable to the addition of external lubricants. Hence as suggested previously, addition of (natural) polyols may lead to the occurrence of undesirable plate-out phenomena. The magnitude of the effect on the rheology depends on the number of hydroxyl groups in the polyol and its propensity to undergo intramolecular cyclodehydration reactions. It is established that the undesirable rheological effects, which coincide with plate-out phenomena, can be suppressed by the addition of various types of inorganic as well as organic substances, most of which are known PVC additives. This will allow for the use of (natural) polyols as efficient and benign co-stabilisers in next generation stabiliser systems.     

Defining the electroanalytically measured species in a natural water sample

The possible definition, using electroanalytical techniques, of the chemical species disolved in natural waters is discussed. Emphasis is place on the formulation of concepts rather than completely rigorous mathematical solutions. The time of measurement is identified as the critical parameter for determining which species in solution will be measured when using transient techniques. When measurements are made in stirred solutions, as is the case in anodic stripping voltammetry and conventional polarography the effective diffusion layer thickness becomes the critical parameter. It may be regarded as being analogous to the time of mesurement and for most experimental systems it is simple to measure. It is recommended that whenever polarographic or voltammetric measurements are made on complex natural systems either the effective diffusion layer thickness or the time of measurement should be reported. Evidence in the literature suggests that a better appreciation of exactly what species are measured would greatly increase our understanding of natural systems.     

The role of natural gas as a primary fuel in the near future, including comparisons of acquisition, transmission and waste handling costs of as with competitive alternatives

Natural gas comprises about a quarter of the United States' energy use. It is more environmentally friendly than oil and coal due to lower carbon dioxide (CO2) emissions per unit, less costly per unit of energy and more readily available domestically in abundant supply. However, due to a number of barriers in the political, infrastructural, pricing and other arenas, the use of natural gas as a significant energy source in the United States has been limited. In our paper, we highlight the favorable qualities of natural gas and its benefits for the consumer, producer, and environment, having compared the costs of the various components of the natural gas business such as drilling and transport to that of coal and oil. Moreover, we touch upon the major issues that have prevented a more prevalent use of the gas, such as the fact that the infrastructure of natural gas is more costly since it is transported though pipelines whereas other energy sources such as oil and coal have flexible systems that use trains, trucks and ships. In addition, the powerful lobbies of the coal and oil businesses, along with the inertia in the congress to pass a national climate change bill further dampens incentives for these industries to invest in natural gas, despite its various attractive qualities. We also include discussions of policy proposals to incentive greater use of natural gas in the future.     

Relationship between the decrease of degree of polymerisation of cellulose and the loss of groundwood pulp paper mechanical properties during accelerated ageing

During natural ageing, paper undergoes colour changes and becomes brittle. It is mainly due to the degradation of cellulose, the main component of paper fibres. From the viewpoint of conservation/protection of paper-based information carriers, as well as of the utilisation of secondary fibres, knowledge of the impact of a decrease of the degree of polymerisation (DP) of cellulose on mechanical properties of paper becomes of key importance. In this paper, correlations between the decrease of DP of cellulose and the loss of paper folding endurance (FE) using three model samples (pure cellulose, groundwood pulp paper, and degraded groundwood pulp paper) at accelerated ageing were investigated. The existence of such correlations between DP and FE is supported by experimental results; the correlations are linear for pure cellulose and groundwood pulp paper ageing, while exponential correlation was observed in case of degraded groundwood pulp paper. The results indicate that the rate of paper degradation can be evaluated by means of the rate of glycosidic bonds breaking in cellulosic polymer chains both for cellulose and groundwood pulp paper.     

Harnessing the mechanism of glutathione reductase for synthesis of active site bound metallic nanoparticles and electrical connection to electrodes

It is demonstrated herein that the FAD-dependent enzyme glutathione reductase (GR) catalyzes the NADPH-dependent reduction of AuCl4-, forming gold nanoparticles at the active site that are tightly bound through the catalytic cysteines. The nanoparticles can be removed from the GR active site with thiol reagents such as 2-mercaptoethanol. The deep enzyme active site cavity stabilizes very small metallic clusters and prevents them from aggregating in the absence of capping ligands. The behavior of the GR-nanoparticle complexes in solution, and their electrochemical properties when immobilized on graphite paper electrodes are presented. It is shown that the borohydride ion, a known reducing agent for GR, is catalytically oxidized by larger GR-nanoparticle (>or=150 gold atoms) complexes generating catalytic currents, whereas NADPH (the natural reducing agent for GR) is not. It is proposed that the surface of the Toray graphite paper electrode employed here interferes with NADPH binding to the GR-nanoparticle complex. The catalytic currents with borohydride begin at the potential of GR-bound FAD, showing that there is essentially zero resistance to electron transfer (i.e., zero overpotential) from GR-bound FAD through the gold nanoparticle to the electrode.     

心血管病患者饮用天然矿泉水的探讨

天然矿泉水是来自地下深处的泉水，水质清纯无污染，含有人体必需的微量元素。分析测定了来自不同地区的矿泉水样，对矿泉水中硅元素（硅酸含量）与钾、钠元素含量进行相关性研究，并从医学角度为心血管病患者饮用天然矿泉水提供依据。     

Turn‐On Fluorogenic Probes for the Selective and Quantitative Detection of the Cyanide Anion from Natural Sources

We report new indene derivatives that are good fluorogenic probes for the cyanide anion, one of which is a highly selective and sensitive fluorogenic probe for the fluorescent detection—as well as reliable quantification—of the cyanide anion in water or buffer, with a 10³‐fold increase of fluorescence and low detection limit. It is therefore useful for the quantification of natural cyanide from aqueous extracts of green almond seeds, thus proving that the system is suitable for fast detection and quantification of cyanide from natural sources.     

How to find a saddle point

This paper explains a method for finding saddle points on a multidimensional surface and shows how it may be used to define saddle-point seeking curves that have properties similar to well-known orthogonal trajectories. It is shown that a gradient extremal is a special case of one of these curves, and its chemical significance as the path, defined by local criteria, which starts from a stable structure and leads to a transition state, is discussed briefly in relation to the intrinsic reaction coordinate. It is emphasized that this theory gives a natural method for locating points that have Hessians of similar structure to those of transition states.     

On the SCF calculation of excited states: Singlet states in the two-electron problem

The problem of determining SCF wave functions for excited electronic states is examined for singlet states of two-electron systems using a Lowdin natural orbital transformation of the full CI wave function. This analysis facilitates the comparison of various SCF methods with one another. The distribution of the full CI states among the natural orbital MCSCF states is obtained for the S states of helium using a modest Gaussian basis set. For SCF methods that are not equivalent to the full CI wave functions, it is shown that the Hartree-Fock plus all single excitation wave functions are equivalent to that of Hartree-Fock plus one single excitation. It is further shown that these wave functions are equivalent to the perfect pair or TCSCF wave functions in which the CI expansion coefficients are restricted to have opposite signs. The case of the natural orbital MCSCF wave function for two orbitals is examined in greater detail. It is shown that the first excited state must always be found on the lower natural orbital MCSCF CI root, thus precluding the use of the Hylleras-Undeim-MacDonald (HUM) theorem in locating this state. It is finally demonstrated that the solution obtained by applying the HUM theorem (minimizing the upper MCSCF CI root with respect to orbital mixing parameters) is an artifact of the MCSCF method and does not correspond to any of the full CI states.     

Radiation effects in the transient hot-wire technique

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity and thermal diffusivity of fluids. It is well established that fluid radiation effects significantly influence these measurements, especially those for the thermal diffusivity. Corrections for radiation effects are based on the models developed and deviations of the measured data from the ideal line source model. In this paper, the effect of fluid radiation on the measurements of the thermal conductivity of n-pentane is presented. For comparison, the influence of thermal radiation effect on measurement of transparent fluids, such as argon is also shown. The difference between the influence of natural convection and thermal radiation is also demonstrated.     

13C and 18O isotopic analysis to determine the origin of L-tartaric acid

Due to the ever-increasing amount of attention paid to the 'naturalness' of ingredients in food and beverages by both consumers and controlling authorities, the search for suitable methods for the characterisation of origin is of primary importance. Within the European Community the wine production industry is often faced with the problem of origin control of tartaric acid. This has led to the decision that only L-tartaric acid extracted from grapes (therefore natural) should be used. In order to implement these regulations, a screening of different techniques has been carried out to assess the methodology that best identifies the origin of the tartaric acid. It has already been indicated in previous scientific literature that isotope ratio mass spectrometry is an ideal technique for this type of identification. In this paper we present the results obtained for the measurement of the isotope ratios of carbon-13 and oxygen-18 of natural and synthetic samples of L-tartaric acid considering also natural samples of different geographical origin and years of production.     

Ecotoxicity of the Adipate Plasticizers: Influence of the Structure of the Alcohol Substituent

A significant increase in the production of plastic materials and the expansion of their areas of application contributed to the accumulation of a large amount of waste of polymeric materials. Most of the polymer composition is made up of plasticizers. Phthalate plasticizers have been recognized as potentially hazardous to humans and the environment due to the long period of their biodegradation and the formation of persistent toxic metabolites. It is known that the industrial plasticizer dioctyl adipate is characterized by reduced toxicity and a short biodegradation period. The paper describes the synthesis of a number of new asymmetric esters based on adipic acid and ethoxylated butanol by azeotropic esterification. The receipt of the products was confirmed by IR spectra. The physicochemical properties of the synthesized compounds were investigated. The glass transition temperatures of PVC composites plasticized with alkyl butoxyethyl adipates were determined using DSC analysis. The ecological safety of esters was assessed by the phytotesting method. Samples of adipates were tested for fungal resistance, and the process of their biodegradation in soil was also studied. It is shown that the synthesized esters have good plasticizing properties and are environmentally safe. When utilized under natural conditions, they can serve as a potential source of carbon for soil microorganisms and do not form stable toxic metabolites; therefore, they are not able to accumulate in nature; when the plasticizers under study are disposed of in the soil, toxic substances do not enter.     

Surface and bulk aspects of the natural and artificial photo-ageing of Bisphenol A polycarbonate as revealed by ESCA and difference UV spectroscopy

ESCA and difference uv spectroscopy have been used to monitor the changes in surface and bulk chemistry, respectively, of Bisphenol A polycarbonate during natural and artificial weathering. It is shown that photo-oxidation, and not a photo-Fries rearrangement mechanism, is the predominant process in the surface regions for both types of exposure. For a close correlation with natural weathering the use of a black lamp as an artificial uv source is advocated. Difference uv spectra obtained for natural and black lamp exposures reveal that changes in bulk chemistry cannot be interpreted in terms of a photo-Fries reaction.     

Environmental accounting for the lagoon of Venice and the case of fishing

This paper presents the application of the eMergy evaluation, introduced by H.T. Odum as an efficient methodology of environmental accounting. The results of this analysis are a part of a wider sustainability assessment for the Province of Venice realized in 2003. Within a territorial sustainability analysis, it is necessary to implement an environmental accounting method, which is able: to precisely consider the boundaries of the investigated system (spatial scale); to arbitrarily separate the life of the investigated system into periods (temporal scale); to account for both economic and natural support to a given territorial system in order to implement a sustainable management of resources; to assess all the items supporting the system on the basis of a physical unit that is objective (while the traditional economic evaluation method is based on individual preferences, hence it is subjective). The Province of Venice is a very complex system due, on one hand, to the heavy and consolidated presence of industrial activity since the beginning of the 20th century and, on the other hand, to the principal natural ecosystem which characterizes it: the lagoon, the largest wetland in the Mediterranean Sea. The role of the lagoon, as a provider of resources and services is represented by the analysis of two aspects: the lagoon as an ecosystem on the basis of the evaluation of all flows that cyclically support its biotic activity and the lagoon as a productive system on the basis of the contribution of both natural and "economic" inputs that support human activity. In particular, the case of clam fishing will be presented to put on evidence the importance of natural inputs that are systematically neglected by the traditional accounting methodologies.     

壳聚糖接枝共聚改性最新研究进展

壳聚糖是一种天然高分子,也是迄今为止唯一发现的阳离子碱性多糖。壳聚糖分子链中富含羟基和氨基等反应性官能团,具有生物相容性、生物可降解性、抗菌性、无细胞毒性等优良性能,在生化、医药、环保、农业等领域有广泛的应用前景。然而,由于其大分子具有较好的立构规整性和较强的氢键作用,除稀盐酸、稀醋酸外,壳聚糖不溶于水和其它有机溶剂,因而限制了它的应用范围。为了扩大其应用领域,常通过接枝共聚反应来改善壳聚糖的性能。本文介绍了壳聚糖接枝共聚改性的最新研究进展,包括自由基引发接枝法、偶联接枝法以及催化接枝法。     

Modern Trends in the In Vitro Production and Use of Callus,Suspension Cells and Root Cultures of Medicinal Plants

This paper studies modern methods of producing and using callus, suspension cells and root cultures of medicinal plants in vitro. A new solution for natural product production is the use of an alternative source of renewable, environmentally friendly raw materials: callus, suspension and root cultures of higher plants in vitro. The possibility of using hairy root cultures as producers of various biologically active substances is studied. It is proven that the application of the genetic engineering achievements that combine in vitro tissue culture and molecular biology methods was groundbreaking in terms of the intensification of the extraction process of compounds significant for the medical industry. It is established that of all the callus processing methods, suspension and root cultures in vitro, the Agrobacterium method is the most widely used in practice. The use of agrobacteria has advantages over the biolistic method since it increases the proportion of stable transformation events, can deliver large DNA segments and does not require special ballistic devices. As a result of the research, the most effective strains of agrobacteria are identified.