Galaxy groups in the 2dF Galaxy Redshift Survey: effects of environment on star formation

We estimate the fraction of star-forming galaxies in a catalogue of groups, constructed from the 2dF Galaxy Redshift Survey by Merchán & Zandivarez. We use the η spectral type parameter of galaxies and subdivide the sample of galaxies in groups into four types depending on the values of the η parameter following Madgwick et al. We obtain a strong correlation between the relative fraction of galaxies with high star formation and the parent group virial mass. We find that even in the environment of groups with low virial mass   M ∼10¹³ M_⊙  the star formation of their member galaxies is significantly suppressed. The relation between the fraction of early-type galaxies and the group virial mass obeys a simple power law spanning over three orders of magnitude in virial mass. Our results show quantitatively the way that the presence of galaxies with high star formation rates is inhibited in massive galaxy systems.     

A Catalog of Luminous Infrared Galaxies in the IRAS Survey and Second Data Release of SDSS

We selected a sample of luminous infrared galaxies by cross-identification of the Faint Source Catalogue (FSC) and Point Source Catalogue (PSC) of the IRAS Survey with the Second Data Release of the SDSS. The size of our sample is 1267 for FSC and 427 for PSC by using the 2σ significance level cross-section. The "likelihood ratio" method is used to estimate the individual's reliability and for defining two more reliable subsamples (908 for FSC and 356 for PSC). A catalog of infrared, optical and radio data is compiled and will be used in further work. Some statistical results show that luminous infrared galaxies are quite different from ultra-luminous infrared galaxies. The AGN fractions of galaxies at different infrared luminosities and the radio-infrared correlations are consistent with the previous studies.     

中国古代太阳中天观测及二至点测算精度

研究了元代《授时历议))所保存的天象观测和推步资料，得出：(1)在AD1277—1280年问所作的98次太阳中天观测的时刻及地平高度的绝对值平均误差分别为2．64min和6．78′．(2)6部古历——《大衍历》、《宣明历》、《纪元历》、《统天历》、《重修大明历》和《授时历》推步BC522年前的3个冬至时刻的误差范围为0．97—3．51d；而AD435—1280年间的45个冬至时刻的绝对值平均误差则分别为9．35、10．42、5．54、2．97、5．68、3．36h．(3)古代确定的AD442—1280年间的16个二至时刻的绝对值平均误差为199．59min，其中元代的误差为27．89min．     

A conceptually based stochastic point process model for daily stream‐flow generation

Based on the stochastic and phenomenological aspects of hydrological processes, a conceptually based stochastic point process (SPP) model for daily stream‐flow generation is proposed in this paper. In which, storms are defined by a stochastic point process with marked values. All the random variables defining the process are assumed to be mutually independent, which constitutes a compound Poisson point process. The direct surface runoff is regarded as occurring from storage in a cascade of surface linear reservoirs and is responsible for the short‐term variation of the daily stream flows. The baseflow component is considered as coming from subsurface/groundwater storage and is responsible for the long‐term persistence of the storm time‐series. This type of model is proposed as a more realistic model of daily stream flow than models based on pure stochastic processes. Studies on the instantaneous unit hydrograph and the mechanism of baseflow could thereby provide some parameters for this model. Copyright © 2002 John Wiley & Sons, Ltd.     

Short time-scale variability in the Faint Sky Variability Survey

We present the V -band variability analysis of the point sources in the Faint Sky Variability Survey on time-scales from 24 min to tens of days. We find that about one per cent of the point sources down to   V = 24  are variables. We discuss the variability-detection probabilities for each field depending on field sampling, amplitude and time-scale of the variability. The combination of colour and variability information allows us to explore the fraction of variable sources for different spectral types. We find that about 50 per cent of the variables show variability time-scales shorter than 6 h. The total number of variables is dominated by main-sequence sources. The distribution of variables with spectral type is fairly constant along the main sequence, with 1 per cent of the sources being variable, except at the blue end of the main sequence, between spectral types F0 and F5, where the fraction of variable sources increases to about 2 per cent. For bluer sources, above the main sequence, this percentage increases to about 3.5. We find that the combination of the sampling and the number of observations allows us to determine the variability time-scales and amplitudes for a maximum of 40 per cent of the variables found. About a third of the total number of short time-scale variables found in the survey were not detected in either B or/and I band. These show a similar variability time-scale distribution to that found for the variables detected in all three bands.     

Detecting subtle hydrochemical anomalies with multivariate statistics: an example from ‘homogeneous’ groundwaters in the Great Artesian Basin,Australia

The major ion composition of Great Artesian Basin groundwater in the lower Namoi River valley is relatively homogeneous in chemical composition. Traditional graphical techniques have been combined with multivariate statistical methods to determine whether subtle differences in the chemical composition of these waters can be delineated. Hierarchical cluster analysis and principal components analysis were successful in delineating minor variations within the groundwaters of the study area that were not visually identified in the graphical techniques applied. Hydrochemical interpretation allowed geochemical processes to be identified in each statistically defined water type and illustrated how these groundwaters differ from one another. Three main geochemical processes were identified in the groundwaters: ion exchange, precipitation, and mixing between waters from different sources. Both statistical methods delineated an anomalous sample suspected of being influenced by magmatic CO₂ input. The use of statistical methods to complement traditional graphical techniques for waters appearing homogeneous is emphasized for all investigations of this type. Copyright © 2006 John Wiley & Sons, Ltd.     

BOOK REVIEWS

Books reviewed in this article: Aerial Photography and Remote Sensing Aerial photography and image interpretation for Resource Management . DAVID P. PAINE . Analytical Models and Techniques Spatial Processes Models and Applications A. D. CLIFF AND J. K. ORD Quantitative and Statistical Approaches to Geography: A Practical Manual JOHN A. MATTHEWS . Cartography and Maps Map Data Processing . HERBERT FREEMAN AND GOFFREDO G. PIERONI , eds. Computer-assisted Cartography: Principles and Prospects, 1982 . MARK S. MONMONIER . Cultural Navajo Architecture: Forms, History, Distributions . STEPHEN C. JETT AND VIRGINIA E . SPENCER . Rational Landscapes and Humanistic Geography . EDWARD RELPH . Economic The Structure and Control of a State Economy . W. L. L'ESPERANCE . Economic Geography . JAMES O. WHEELER AND PETER O. MULLER . The Myth of the Family Farm: Agribusiness Dominance of U.S. Agriculture . INGOLF VOCELER . Libya: The Experience of Oil . J. A. ALLEN . Geography of Public Finance, Welfare Under Fiscal Federalism and local Government Finance . ROBERT BENNETT . Environmental Management, Resources, and Systems Mountains and Man . LARRY W. PRICE . Environmental Geology . DONALD R. COATES . An Introduction to Environmental Systems . G. H. DURY . The Environment: Chinese and American Views . Edited by LAURENCE J. C. MA AND ALLEN G. NOBLE . Land Use in America . RICHARD H. JACKSON . Medical Conceptual and Methodological Issues in Medical Geography . MELINDA S. MEADE (ed.). Philosophy and Geographic Thought Birds in Egg/Eggs in Bird . GUNNAR OLSSON . PhysicaI Climatology: Selected Applications . J. E. OLIVER . Geomorphological Techniques . ANDREW GOUDIE (ed.). Political Politics, Geography and Behaviour . RICHARD MUIR AND RONAN PADDISON . The State of the World Atlas . MICHAEL KIDRON AND RONALD SECAL . Population The Population of the South . DUDLEY L. POSTON , JR . AND ROBERT H. WELLER , eds. Regional Latin America: Economic Development and Regional Differentiation . ARTHUR MORRIS . Developing the Amazon . EMILIO F. MORAN . Western Europe: A Systematic Human Geography . BRIAN W. ILBERY . Settlement Systems in Sparsely Settled Regions: The United States and Australia . RICHARD E. LONSDALEAND JOHN H. HOLMES , eds. African Perspectives: The Economic Geography of Nine African States . HARM DE BUJ AND ESMOND MARTIN , eds. Rural Nonmetropolitan America in Transition . AMOS H. HAWLEY AND SARA MILLS MAZIE , eds. Social Crime and Environment . R. NORMAN DAVIDSON . The Ghetto: Readings with Interpretations . JOE T. DARDEN , ed. Urban Urban Problems and Planning in the Developed World . MICHAEL PACIONE (ed.) Problems and Planning in Third World Cities . Edited by MICHAEL PACIONE . The City in West Europe . D. BURTENSHAW , M. BATEMAN , AND C. J. ASHWORTH .     

Use of multivariate statistical methods in data-base maintenance

Multivariate statistical methods may be used to enhance large data bases by predicting missing information and verifying unchecked data vectors. In addition, new techniques may be used for exploratory purposes to investigate the interrelationships between variables. The techniques are being applied successfully in coal mining.     

REVIEWS OF GEOGRAPHIC SOFTWARE

Geographic Software Reviewed in this article: LIFE TABLES and the LESLIE MATRIX. CONDUIT MENTMAP2 . Lawrence W. Carstensen Jr . PC-MATLAB , Version 1.0. The Math Works, Inc. QUICKMAP , version 1.0. Sammamish Data Systems, Inc. SYSTAT: THE SYSTEM FOR STATISTICS , Version 2.1, Systat Inc. USA DISPLAY . Instant Tecall     

Some consequences of applying lognormal theory to pseudolognormal distributions

A logarithmic transformation may be used to improve the efficiency of estimates of the mean when observations follow the lognormal distribution. But if this transformation is applied to observations that follow another distribution, bias may be introduced. We consider some consequences of erroneously applying lognormal estimation theory and demonstrate that biased estimates may be obtained for certain classes of distributions. Illustrations of bias obtained in gold sampling are given.