Latitudinal variation in a photoperiod response gene in European barley: insight into the dynamics of agricultural spread from ‘historic’ specimens

Between ca. 6000 BC and ca. 500 BC, barley cultivation spread across the continent of Europe from the extreme south to the extreme north. Carbon-dating would suggest that this spread, and indeed the spread of crop cultivation generally, varied in its pace, with ‘delays’ at certain points along its route. Such delays in the spread of agriculture have been explained as resulting from the slow assimilation of agricultural practices by existing indigenous human populations or as the time taken for the crops to adapt to novel climatic conditions, such as altered temperature regimes and day-lengths. A mutant form of the photoperiod response gene, Ppd-H1, causes barley to be non-responsive to long days, while the wild-type responsive form allows plants to flower in response to long days. We sequenced this gene in 65 ‘historic’ barley accessions, from the late 19th and early 20th centuries, in order to explore the potential role of environmental adaptation in the spread of agriculture. We chose to use ‘historic’ material, to complement the richer patterns in extant genetic lines, by spreading the data range in both time and space. Our ‘historic’ barley data shows a latitudinal divide in the Ppd-H1 gene similar to that found in extant lines, but with clearer geographical resolution, and extending northwards into the Arctic Circle. We discuss the implications of our results in relation to the dynamics of agricultural spread across Europe.     

台湾现阶段大力扶持海外侨教的措施与借鉴

针对近年来祖国大陆海外华文教育快速发展带来的挑战 ,台湾当局在延续其历年经验性做法的基础上 ,以满足海外侨教现实需要为目标 ,注重以创新思维拓展侨教工作 ,采取各种更加灵活和有力的措施 ,多方面多渠道地扶持海外侨教工作。本文分析了台湾现阶段扶持海外侨教的主要措施 ,论述了其可资借鉴与参考之处。     

SEISMIC SOIL-STRUCTURE INTERACTION: BENEFICIAL OR DETRIMENTAL?

The role of soil-structure interaction (SSI) in the seismic response of structures is reex-plored using recorded motions and theoretical considerations. Firstly, the way current seismic provisions treat SSI effects is briefly discussed. The idealised design spectra of the codes along with the increased fundamental period and effective damping due to SSI lead invariably to reduced forces in the structure. Reality, however, often differs from this view. It is shown that, in certain seismic and soil environments, an increase in the fundamental natural period of a moderately flexible structure due to SSI may have a detrimental effect on the imposed seismic demand. Secondly, a widely used structural model for assessing SSI effects on inelastic bridge piers is examined. Using theoretical arguments and rigorous numerical analyses it is shown that indiscriminate use of ductility concepts and geometric relations may lead to erroneous conclusions in the assessment of seismic performance. Numerical examples are presented which highlight critical issues of the problem.     

SOME DESIGN PRINCIPLES RELEVANT TO TORSIONAL PHENOMENA IN DUCTILE BUILDINGS

Recent studies provided opportunities to review some of the principles, which have been used in the formulations of internationally accepted code-recommendations relevant to the seismic design of ductile buildings also subjected to torsional phenomena. With the progress of this study, features emerged which are considered to have contributed to a better understanding of structural behaviour. Moreover, the identification of deeply embedded fallacies, relevant to ductile response, suggested the introduction of some changes in seismic design strategies, yet not widely known or appreciated. Reasons for necessary re-interpretations of traditional structural properties, together with illustrative examples, demonstrating applications, rather than set code-type rules, are offered.     

A PROCEDURE FOR COMBINING VERTICAL AND HORIZONTAL SEISMIC ACTION EFFECTS

The vertical component of earthquake ground motion has generally been neglected in the earthquake-resistant design of structures. This is gradually changing due to the increase in near-source records obtained recently, coupled with field observations confirming the possible destructive effect of high vertical vibrations.

In this paper, simple procedures are suggested for assessing the significance of vertical ground motion, indicating when it should be included in the determination of seismic actions on buildings. Proposals are made for the calculation of elastic and inelastic vertical periods of vibration incorporating the effects of vertical and horizontal motion amplitude and the cross-coupling between the two vibration periods. Simplified analysis may then be used to evaluate realistic vertical forces by employing the vertical period of vibration with pertinent spectra without resorting to inelastic dynamic analysis.

Finally, a procedure is suggested for combining vertical and horizontal seismic action effects which accounts for the likelihood of coincidence, or otherwise, of peak response in the two directions.     

FRAGILITY OF STANDARD INDUSTRIAL STRUCTURES BY A RESPONSE SURFACE BASED METHOD

National and international regulatory standards require industrial risk assessment, taking into account natural hazards including earthquakes, in the framework of Quantitative Risk Analysis (QRA). Seismic fragility analysis of industrial components may be carried out similarly as what has been done for buildings, even though some peculiar aspects require the development of specific tools. In the present paper a contribution to the definition of a rational procedure for seismic vulnerability assessment of standardised industrial constructions in a probabilistic framework is given. The method covers a range of components of the same structural type. Seismic reliability formulation for structures is used. Both seismic capacity and demand are considered probabilistic with the latter assessed by dynamic analyses. The application example refers to shell elephant foot buckling of unanchored sliding tanks. A regression-based method is applied to relate fragility curves to parameters varying in the domain of variables for structural design.     

SEGMENTAL CROSS-SPECTRUM AS A NEW TECHNIQUE IN SITE RESPONSE ESTIMATION USING SPECTRAL RATIO ANALYSIS

Different aspects of spectral analysis for site response evaluation are investigated in this study. The segmental cross-spectrum is proposed in spectral analysis of earthquake ground motions. The performance of segmental cross-spectrum in contrast with the conventional methods is investigated through the mathematical modelling, numerical analysis and application to earthquake data recorded at Chiba and Shinfuji downhole arrays in Japan. In analysis of earthquake data, the soil amplification function is identified using both uphole/downhole (U/D) and H/V spectral ratios. The advantage of seg-mental cross-spectrum is assessed by comparing identified amplification functions using different spectral methods and theoretical soil response. The reliability of site response estimations obtained by H/V spectral ratio using segmental cross- and Fourier spectra is also examined by means of cross-validation with the U/D spectral ratio of earthquake motion and theoretical soil response. Furthermore, the application of segmental cross-spectrum in nonlinear soil response is examined by comparing the amplification function of weak and strong motions for both methods. The results validate the advantage of segmental cross-spectrum in both linear and nonlinear soil response, particularly, when it used with H/V technique.     

ANALYTICAL MODELS FOR BRICK MASONRY INFILLED R/C FRAMES UNDER LATERAL LOADING

Proposed in this paper are two analytical models for predicting the inelastic response of unreinforced brick masonry infills in reinforced concrete frames subjected to mono-tonic and reversed cyclic loading. The first model is based on the traditional diagonal strut concept, while the second one is a simple isoparametric element with shear deformation only. All the essential characteristics of the hysteretic behaviour of the panel, including strength and stiffness degradation, pinching and slippage, are explicitly taken into account. The models are implemented in a general-purpose program for the inelastic time-history analysis of structures, and are used for studying the seismic behaviour of typical multistorey frames with various arrangements of infill panels, including structures with an open ground storey. The results of the analysis are in agreement with both experimentally observed behaviour and with experience regarding seismically damaged buildings.     

对费正清中国史观的理性考察

美国的中国学研究始于费正清。在半个多世纪里,他以自己独特的视角审视、考察中国。20世纪50年代,他提出了著名的“冲击－反应”模式,用来作为其解释中西文明冲突的工具。多年来,史学界对此多有争论,对他的中国史观也褒贬不一。对费正清的中国史观以及他提出的“冲击－反应”模式的背景及其实质进行一些理性探讨,有利于更好地了解我们的历史。     

科技手段与书画鉴定

在当今的器物学鉴定工作中,不少高科技的鉴定技术已经成功地应用于文物年代的分期断代和真伪鉴别上。但在古代书画鉴定工作中,由于其特殊性和复杂性,目前仍停留在传统的鉴定方法上。本文就运用一些必要的科学手段来证实鉴定结果进行了深入的探讨