南海红树林内生真菌1356~#代谢产物的研究

从南海红树林内生真菌1356#分离出两种鞘胺醇(A,B)和三种环二肽(C,D,E)?它们的结构通过IR,MS,1D NMR和2D NMR谱推导出来?(3＇E,4E)-1-(-D-吡喃葡萄糖基-3-羟基-2-(2＇-羟基十八碳酰基)氨基-10-甲基-3＇,4,9-十八碳三烯(A)是一种新的鞘胺醇甙?     

丽江机场雷暴天气特征分析

本文基于丽江机场最近9年(2007~2015年)的观测资料,总结了丽江机场雷暴发生、变化的特征和规律。结果表明:丽江机场近年来年雷暴日数稳定在60d左右,多发生在6~9月,总概率密度达到了82.3%,峰值出现在8月。平均雷暴初终日在4月13日和10月20日,平均间隔190d。从日变化看,雷暴多发生在15~19时,总概率密度达到了48.7%,峰值出现在16时,持续时间在0~1h内的最多,占总数的58.7%。雷暴发生规律除日变化外与水汽(相对湿度)基本一致,雨季午后53%~57%的相对湿度对雷暴的发生有一定的指示意义。雷暴发生次数波动较大的时段为午后到深夜,打夜雷的情况有所增多,夜雷多为系统性雷暴,对丽江机场的航班影响较大。      

时空因素对我国赴泰旅游安全事件的影响

以2010年~2014年我国旅行社责任险出险案例为基础,遴选出568起我国游客赴泰旅游出险案例为研究样本,运用非线性典型相关分析法探究时空因素与我国赴泰旅游安全事件类型间的关联影响机制。研究表明:在时间变量上,旅游安全事件类型分布与时间因素间呈差异性关联特征,其发生频率与泰国旅游旺季有所差异,与旅游活动时段的相关性更高;在空间变量上,旅游安全事件呈高发场所集中分布特征;与旅游六要素空间既有差异性关联特征,又具有交叉性关联特征;与具体地点具有较强的单一关联特征。     

The selection of internal migration models for European regions

"A full multiregional projection model requires migration data that are simultaneously classified by age and gender and region of origin and region of destination. Except for a very small number of regions, these data requirements are so high that aggregation of the data (which is equivalent to simplification of the model) is called for. This paper investigates the extent to which the full internal migration matrix can be simplified without seriously affecting the performance of the resulting multiregional model. Using IPF (iterative proportional fitting) methods, a log-linear analysis of alternative model specifications is made, using data for Italy, the Netherlands and the UK....A reasonable balance between goodness-of-fit and parsimony is found for the model in which time interacts with the main effects only (i.e. with age/sex, with origin and with destination)."     

The transformation of housing and household structures in France and Great Britain

"In France and Great Britain, the last 30 years have seen considerable evolution in the housing stock...and in household structure....This article describes the dynamic interaction of processes influencing the evolution of both households and dwellings. In the two countries, the life course of individuals has become more and more complex. This translates into an ever greater variety of housing needs, not only at different stages in family life, but also in relation to growing job insecurity regardless of family situation. At the same time, policies encouraging home-ownership seem to have reached their limits, because of the new demand for rented accommodation. The answer to sociological and economic evolution cannot be found in a ?single' type of housing and tenure status, but rather in a wide range of dwellings and in the development of a more flexible housing market."     

Inorganic chemistry of O2 in a dense primitive atmosphere

A simple steady-state photochemical model is developed in order to determine typical molecular oxygen concentrations for a comprehensive range of primitive abiotic atmospheres. Carbon dioxide is assumed to be the dominant constituent in these atmospheres since CO2 photodissociation may potentially result in the enhancement of the O2 partial pressure. The respective effects of the H2O content, temperature, eddy diffusion coefficient and UV flux on the results are investigated. It is shown that for any pressure at the surface, the partial pressure of molecular oxygen does not exceed 10 mbar. The peculiar case of a runaway greenhouse which has possibly taken place on Venus is qualitatively envisaged. Although O2 is basically absent in the present Venus atmosphere, a transient presence in a primitive stage cannot be ruled out. Possible mechanisms for O2 removal in such an atmosphere are reviewed. At the present stage, we think that the detection of large O2 amounts would be at least a good clue for the presence of life on an extrasolar planet.     

Mass spectrometric study of three-body ion-molecule clustering reactions of CpHq+ ions with N2 or CH4 in N2-CH4 mixtures

Thermochemical data for several ion-molecule clustering of hydrocarbon ions with N2 or CH4 were obtained from clustering equilibria studies in gas mixtures irradiated by alpha-particles. High-pressure mass spectrometry was used to determine the enthalpy and entropy changes of clustering (delta H0 and delta S0, respectively) for the reactions X+(N2)n-1 + 2N2 <==> X(+)(N2)n + N2 with X = CH5, n = 1-2; X = C2H5, n = 1-4; and X = C3H7, n = 1. For X = CH5, the values (delta H0; delta S0) are found to be (-6.8 kcal mol-1; -19.7 cal mol-1 K-1) for n = 1, and (-5.3 kcal mol-1; -15.9 cal mol-1 K-1) for n = 2. For X = C2H5, (delta H0; delta S0) = (-6.9 kcal mol-1; -18.2 cal mol-1 K-1), for n = 1, and (-4.6 kcal mol-1; -20.8 cal mol-1 K-1) for n = 2. From the equilibrium measurements at 129 K, estimates of the thermochemical values could be obtained for n = 3-4. The results obtained for the free energy, delta G0, were -1.4 kcal mol-1 for n = 3, and -1.1 kcal mol-1 for n = 4. For X = C3H7 we found delta G0 = -0.7 kcal mol-1 at 213 K. The association reactions X+ + 2CH4 <==> X+(CH4) + CH4 with X = CH5, C2H5, C2H7, and C3H7 were also studied, resulting in free energy values at 206 K of -3.1, -1.9, -0.5 and -1.3 kcal mol-1, respectively. The results for CH5, C2H5 and C3H7 are compared with previously reported measurements.     

Two formation regions for Titan's hazes: indirect clues and possible synthesis mechanisms

It is suggested that aerosol particles forming the detached and main haze layers of Titan's atmosphere do not originate in the same atmospheric levels. Particles present above approximately 350 km could be formed of polyacetylenes synthetized in the 500-800 km altitude range through successive insertion reactions involving the C2H radical under the action of solar ultraviolet photons (Yung et al., Astrophys. J. Suppl. 55, 465, 1984). They might contain C-N oligomers in comparable amounts, as well as C-H-N oligomers synthetized at high altitude (900-1000 km) by the action of suprathermal Saturn plasma electrons. Physically, they are expected to consist of fluffy aggregates of density approximately 0.01-0.1 g cm-3. Their mass production rate is small (10(-15)-10(-14) kg m-2 s-1), that is typically 10% or less of the main haze production rate. Due to their low fall velocity, they are very sensitive to large scale horizontal motions and one substantial part of them may be swept away by meridional circulation at the detached haze level. The altitude range where these aerosols are created is well above the range proposed by Cabane et al. (Planet. Space Sci. 41, 257, 1993) for aerosols of the main haze layer, on the basis of a new fractal microphysical modeling of Titan's aggregates, that is approximately 350-400 km. A natural outcome of this apparent discrepancy is to suppose that there is a second formation region, below approximately 400 km altitude, giving rise to the main haze layer. The aim of the present paper is to review the different possible formation mechanisms of this main haze layer and assess their ability to account for the observed characteristics of the haze. Several conditions are established. The first one, called "condition A", concerns the formation altitude range imposed by fractal modeling. Possible chemical and energy sources are examined. Two additional constraints, relative to the minimum gas mass ("condition B") and input energy ("condition C") required for efficient conversion of gas into aerosols, are defined. By comparing the production rates of the haze, as derived from microphysical models, and of gaseous chemical species, as derived from photochemical models, five possible source constituents are identified: N2, CH4, C2H2, C2H6 and HCN. Polymerization of C2H2 into (C2H2)n through action of solar ultraviolet photons is shown to be rather improbable (condition A is hardly satisfied). From both our current knowledge of the gaseous phase photochemistry, through modeling and laboratory experiments, and existing models of the interaction between Saturn magnetosphere and Titan atmosphere, the formation of C-H-N polymers through action of Saturn magnetospheric energetic particles (E approximately 100 keV), is proposed as the basic polymerization mechanism in the lower formation region (conditions A,B and C are jointly satisfied).     

Population aging in South-East Asia and policies of old-age support

"The problem of ageing is generally perceived as being typical of developed countries, as these have in most cases reached the last stage of their demographic transition. On the other hand, a rapid decline of the fertility rate, knowingly associated [with] a quick improvement of socio-economic factors and, often, [with] successful birth-control policies, is causing a sharp increase of the relative amount of elderly people also in some developing countries. This has a dramatic impact on family structures that, in traditional societies, assist the elderly relatives, while the government is usually still unable to provide institutional support. The issue is analysed in the South East Asian context." (SUMMARY IN ENG AND FRE)     

Singapore in the 1990s. Can population policies reverse the demographic transition?

Singapore experienced an extraordinary demographic transition from a population growth of over 4% per year in the late 1950s to around 1.6% in the 1990s and below replacement fertility since 1986. In 1987 official government policy shifted to measures for increasing fertility. This paper explores whether Singapore's pronatalist policies can reverse the demographic transition. The present policies aim to selectively increase fertility among the well educated. By 1987 the slogan switched from "stop at two" to "have three, if you can afford it." The policy included tax relief for a third child and other measures to encourage a third child. The policies are expected to have a different influence on society according to one's education, income, and family size. The government target is to selectively increase population by 40% over 25 years. Singapore's transition may follow the theory that low fertility is attained in societies where kin relationships are less important than personal educational achievements. The three ethnic groups responded differently to educational and fertility policies. The Chinese acquired the best education and attained the lowest fertility. The Chinese, who comprised 76% of total population in 1986, continued to have low fertility, while increases occurred among the Malays and the Indians. Future trends are considered difficult to predict. A survey conducted in 1992 in Ang Mo Kio among 489 reproductive age respondents revealed that Malays had the earliest marriage and first births before the age of 25 years (75% of Malays and 50% of Indians). The Chinese had their first child at 25 years or older. Without controls for the age of the mother, a strong statistically significant association was found between ethnic group and age at marriage and age at first birth. The relationship was not supported for current fertility. A comparison of women married for 5 years or less and 5 years or more revealed that women in recent marriages showed a greater likelihood of postponing marriage and childbirth for all ethnic groups. Since 1987, third order births as a percentage of all births increased from 21.47% before 1987 to 23.11% during 1987-92, which only suggests the favorable impact of the pronatalist policy. Educational changes are likely to become more influential in affecting choice of family size.