Investigating the effect of clustering of the urban field on sustainable population growth of centrally located and peripheral towns

In a previous study (Portnov and Erell, 1998a), an Index of Clustering was defined, which allowed an analysis of the combined effect of spatial isolation and remoteness of peripheral towns on the long-term patterns of their population growth. In the present paper, the analysis of the effect of clustering of the urban field on the patterns of population growth is extended to centrally located urban places, and the validity of this index is tested in two unevenly populated countries--Israel and Norway. In both countries, the effect of clustering of the urban field on the patterns of urban growth is twofold. In sparsely populated areas, the presence of neighboring towns appears to increase their chances of attracting potential migrants due to inter-urban exchanges, while in more densely populated areas, increasing clustering tends to reduce migration influx to a given locality due to inter-town competition. Following this conclusion, a strategy of "redirecting priorities" leading to the formation of urban clusters is proposed, which may enhance the potential of urban growth in geographical areas where this is desirable.     

Natural Gas Resource in Jurassic,Y Faulted Subbasin of Songliao Basin

IntroductionY faulted depression is a secondary depressionlocated in the northwest of the Southeast UPlift,Songliao basin. It crosses four secondary structuralbelt, such as Qingshankou anticline belts, Binxian Wangfu Depression, Changchunling anticline be…     

Wellsite Evaluation Method of Undercompacted Formation

IntroductionAny of the drilling operation is risky. The riskwould be higher especially when entering the unknown over - pressure Formation. So, we have todetect and evaluate the FOrmation pressure by allmeans (Table 1) in order to have the safe drillingop…     

欧州资料对华南历史地震活动性资料的补充--以香港出版的报纸为例

世界大部分地区有关地震危险性作的历史地震研究,系由早期未受过史学方法训练的地震学者所作,因而其中不免有欠妥之处。按历史方法论的观点（此点不能过份强调）是对资料进行恰当的组合与鉴定,对欧洲以外的世界其它许多的地区而言,殖民地的记录是主要的资料来源－例如,对西印度群岛而言,主要资料不是在西印度群岛本身找到,而是在对西印度群岛的从事贸易的港口的档案中找到的。     

中层重力波运动学特性的VHF雷达观测

利用ＳＯＵＳＹＶＨＦ雷达１９８７年６月在挪威的观测数据,分析了一个典型的内重力波事件的运动学特征．结果表明,该重力波的等相面明显下传,垂直波长随高度的增加而增大,背景风随高度增加而减弱,可以推断波顺风传播,与内重力波色散方程的预言是一致的;利用重力波色散方程导出的重力波运动学参量量值与其他探测手段得到的结果一致．     

A study on the mixing proportion in groundwater samples by using Piper diagram and Phreeqc model

Piper (1944) diagram has been the basis for several important interpretations of the hydrogeochemical data. As seen in this diagram, most natural waters contain relatively few dissolved constituents, with cations (metals or bases) and anions (acid radicles) in chemical equilibrium with one another. Apart from the facies representation, the composition of the mixed sample can be identified in terms of the composition of the parental solution. To bring out this advantage of the Piper diagram, a study was conducted in the Kalpakkam region of Tamilnadu, South India. By taking the geology and water table into consideration, two sample locations were selected as parent solution and third one as the mixture sample. All three samples were analyzed for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl), sulphate (SO4) and phosphate (PO4) by Ion Chromatograph (Metrohm IC 861). HCO3 was determined by volumetric titration. The Piper diagram shows that parent solutions clustered towards Na-Mg-Ca-HCO3-Cl and Na-HCO3 facies, and the mixing sample belongs to Na-Mg-HCO3 facies. Phreeqc interac-tive (Ver 2.8) along with the original composition of the mixture sample was used to correlate the mixing proportion identified by the Piper diagram.     

Choice of conodont Idiognathodus simulator （sensu stricto） as the event marker for the base of the global Gzhelian Stage （Upper Pennsylvanian Series,Carboniferous System）

We propose that the level at which the conodont species Idiognathodus simulator （Ellison 1941） （sensu stricto） first appears be selected to mark the base of the Gzhelian Stage, because we believe that this is the optimal level by which this boundary can be correlated. This taxon has a short range and a wide distribution, as shown by correlation of glacial-eustatic cyclothems across the Kasimovian-Gzhelian boundary interval among Midcontinent North America and the Moscow and Donets basins of eastern Europe, based on scale of the cyclothems along with several aspects of biostrati- graphy. Outside of these areas, I. simulator （sensu stricto） is known also from other parts of the U.S., and is reported from the southern Urals and south-central China in its expected position between other widespread taxa. Its first appearance is consistent with the current ammonoid placement of the boundary （first appearance of Shumardites cuyleri）, and it is also compatible with certain aspects of the distribution of Eurasian fusulinid faunas （e.g., lectotype ofRauserites rossicus）.     

Reobserving the Extreme-Ultraviolet Emission from Abell 2199: In Situ Measurement of Background Distribution by Offset Pointing

The EUV excess emission from the clusters A2199 and A1795 remains an unexplained astrophysical phenomenon. There has been many unsuccessful attempts to "trivialize" the findings. In this Letter, we present direct evidence proving that the most recent of such attempts, which attributes the detected signals to a background nonuniformity effect, is likewise excluded. We address the issue by a reobservation of A2199 that features a new filter orientation, usage of a more sensitive part of the detector, and, most crucially, the inclusion of a background pointing at approximately 2 degrees offset-the first in situ measurement of its kind. We first demonstrate quantitatively two facts: (1) the offset pointing provides an accurate background template for the cluster observation, while (2) data from other blank fields do not. We then performed a point-to-point subtraction of the in situ background from the cluster field, with an appropriate propagation of errors. The resulting cluster radial profile is consistent with that obtained by our original method of subtracting a flat asymptotic background. The emission now extends to a radius of 20&arcmin;; it confirms the rising prominence of EUV excess beyond approximately 5&arcmin; as previously reported.     

PCBs and PAHs in sea-surface microlayer and sub-surface water samples of the Venice Lagoon (Italy)

Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) are two classes of micropollutants intensively monitored and regulated due to their toxicity, persistency and wide diffusion. Their concentrations have been investigated in sea-microlayer (SML) and sub-surface water (SSW) samples collected at two sites of the Venice Lagoon, a fragile ecosystem highly influenced by industrial and anthropogenic emissions. The total sigmaPCB concentration varies from 0.45 ng/l to 2.1 ng/l in SSW while a clear enrichment is observed in the SML, where it ranges from 1.2 ng/l to 10.5 ng/l. The total sigmaPAH concentration shows marked differences between the two stations and varies from 12.4 ng/l to 266.8 ng/l in SSW; in SML it is more uniform and ranges from 19.6 ng/l to 178.9 ng/l. The enrichment factors are not larger than 1 for both pollutants in the 'dissolved' phase, while they are most significant for the 'particulate' phase (sigmaPCB: 5-9; sigmaPAH: 4-14).     

Political unification and regional consequences of German East-West migration

"The purpose of this paper is to evaluate the impact of the post-unification East to West transfer of the German population on levels of spatial concentration and deconcentration in Eastern and Western Germany. Using 1991 internal migration data, it was found that German East-to-West migration served to deconcentrate regional population in the West, but concentrate population in the East. Regional variations in German East-to-West migration during 1991 can be explained by the availability of employment and housing, a distance-minimisation effect, and the location of relatives and friends."