Concentric Zone Theory

2019 ◽  
pp. 1-6
Author(s):  
Reza Banai
Keyword(s):  
Concentric Zone

Suburban Neighborhood Poverty in U.S. Metropolitan Areas in 2000

2009 ◽  
Vol 8 (2) ◽  
pp. 155-176 ◽  
Author(s):  
Amy L. Holliday ◽  
Rachel E. Dwyer
Keyword(s):  
Central City ◽  
The United States ◽  
Zone Model ◽  
Neighborhood Poverty ◽  
Suburban Areas ◽  
Racial Profile ◽  
Suburban Poverty ◽  
Census 2000 ◽  
Concentric Zone ◽  
Place Stratification

Suburban areas have become more diverse and stratified in the United States, with a particularly striking increase in poverty, challenging theories that conceptualize poverty predominantly as a central city phenomenon. Little scholarly work has examined suburban poverty, however, and the small existing literature focuses primarily on inner–ring suburbs in the Northeast and Midwest and relies too much on the concentric zone model of metropolitan development. We use Census 2000 summary data to examine the prevalence and form, characteristics, and determinants of suburban poverty at the neighborhood and metropolitan levels across the entire country. We draw on more sophisticated ecological and place stratification perspectives and argue that suburban poverty manifests in more varied forms than the typical model and diverges in crucial respects from central city poverty. Our results identify a particularly distinctive racial profile for suburban poverty, associated especially with Hispanic residential location, with implications for trends in racial segregation as well.

scholarly journals Membrane Specializations in the Form of Regular Membrane-to-Membrane Attachment Sites in Paramecium. A Correlated Freeze-Etching and Ultrathin-Sectioning Analysis

1973 ◽  
Vol 13 (3) ◽  
pp. 687-719
Author(s):  
H. PLATTNER ◽  
F. MILLER ◽  
L. BACHMANN
Keyword(s):  
Membrane Complex ◽  
Type D ◽  
Attachment Sites ◽  
Morphometric Analyses ◽  
Concentric Zone ◽  
Membrane Attachment ◽  
Ciliary Necklaces ◽  
Freeze Etching ◽  
Membrane Bound ◽  
Membrane Type

The outer membrane complex of Paramecium was investigated by ultrathin-sectioning techniques and by freeze-etching of unfixed cells without cryoprotectants. Granules were found in the freeze-etched cortical membrane complex in a highly ordered arrangement; morphometric analyses and partial disruption of this membrane complex showed that some of these granular membrane specializations (which we call types a, b, e, f, g) represent membrane-to-membrane attachment sites. Type a: granules arranged in rings (single or double), 300 nm in diameter, connect plasmalemma and alveolar membranes around trichocysts. Type b: within these a-type rings, a concentric zone (180 nm diameter) of granules connects plasma membrane and trichocyst membrane. Type c: the trichocyst membrane further contains a central ring or patch, 80 nm in diameter, of rather large granules where it is in contact with the crystalline trichocyst matrix. Type d: ‘ciliary necklaces’ are formed by groups of triple rows of 3-6, most frequently 5 granules, with 21-nm periodicity. Rows of granules also connect the alveolar membranes to the apical portion of the trichocyst membrane (type e) and the alveolar membrane to the plasmalemma around cilia (type f). Type g: the inner alveolar membrane displays an intense granularity and contains double rows of granules along alveolar septa at attachment sites between 2 alveolar membranes. Upon experimental discharge of the majority of trichocysts only the innermost concentric circles of membrane-bound granules of this region (b- and c-type) disappeared from the plasmalemma, while the outermost a-type rings of granules persisted for a longer time. Among other possible functions, these regular membrane-to-membrane attachments are likely to maintain the specific cellular shape.

scholarly journals Distribution of Microbes Producing Antimicrobial ε-Poly-l-Lysine Polymers in Soil Microflora Determined by a Novel Method

2002 ◽  
Vol 68 (7) ◽  
pp. 3575-3581 ◽  
Author(s):  
Masanobu Nishikawa ◽  
Ken'ichi Ogawa
Keyword(s):  
Screening Method ◽  
Agar Plate ◽  
Soil Microflora ◽  
Phylogenetic Position ◽  
Structural Variations ◽  
Modified Polymer ◽  
Concentric Zone ◽  
Molecular Masses ◽  
Novel Method ◽  
Horizontal Transfers

ABSTRACT We developed a simple and sensitive screening method to investigate the distribution of microbes producing an antimicrobial poly(amino acid), ε-poly-l-lysine (ε-PL), in microflora. An acidic dye, Poly R-478, incorporated in an agar plate detected ε-PL producers by electrostatic interaction with the secreted basic polymers. All ε-PL producers, isolated after careful and sufficient screening of soil microflora, belonged exclusively to two groups of bacteria of the family Streptomycetaceae and ergot fungi. They were characterized based on the density and diameter of the concentric zone formed by the secreted polymers. The density depended on each isolate. The increase in the diameter of the concentric zone per unit of time varied among isolates and was negatively correlated with the molecular weight. Although the distribution of ε-PL producers was extremely limited, their products were structurally varied. The molecular masses of the secreted polymers among the isolates ranged from 0.8 to 2.0 kDa. There were also isolates producing unknown polymers inconsistent with the correlation or producing a mixture of polymers with original and modified structures. A chemically modified polymer was an ε-PL derivative, as determined by mass spectrometry. Since the structural variations had no relation to the phylogenetic position of the isolates, it is possible that enzymes involved in the synthesis diversified after putative horizontal transfers of relevant genes.

Intracellular distribution of succinate dehydrogenase activity in skeletal muscle fibers of geese

1984 ◽  
Vol 62 (2) ◽  
pp. 235-240 ◽  
Author(s):  
H. J. Swatland
Keyword(s):  
Skeletal Muscle ◽  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Adenosine Triphosphatase ◽  
Muscle Fibers ◽  
Fiber Types ◽  
Succinate Dehydrogenase Activity ◽  
Individual Muscle ◽  
Concentric Zone ◽  
Pectoralis Muscles

Samples of iliotibialis anterior and pectoralis muscles were taken from five ganders (Anser domesticus). Serial transverse sections were reacted for succinate dehydrogenase (SDH) and alkali-stable adenosine triphosphatase (ATPase). The distribution of SDH activity within individual muscle fibers was measured with a scanning photometer. In many individual fibers, SDH activity was stronger in the periphery than in the axis. This gradient was steepest (−0.034 ± 0.019 absorbance units per concentric zone of 2 μm diameter measurements) in pectoralis fibers with strong SDH activity. In the pectoralis, radial gradients were correlated with fiber area so that the smallest fibers tended to have the steepest gradients of SDH activity. However, this relationship was reversed in fibers with strong ATPase and weak SDH activity in the iliotibialis anterior, and the largest fibers tended to have the steepest gradients. In all fiber types of both muscles, fibers with greater mean SDH activity tended to have steeper gradients.

Petrogenesis of plagioclase phenocrysts of Mount Etna, Sicily, with particular reference to the 1983 eruption: contribution from cathodoluminescence petrography

1999 ◽  
Vol 63 (2) ◽  
pp. 189-198 ◽  
Author(s):  
D. Stirling ◽  
A. M. Duncan ◽  
J. E. Guest ◽  
A. A. Finch
Keyword(s):  
Trace Element ◽  
Heterogeneous Nucleation ◽  
Outer Zone ◽  
Basic Magma ◽  
Mount Etna ◽  
Concentric Zone ◽  
Trace Element Contents ◽  
Element Contents ◽  
Two Phases ◽  
The Relationship

AbstractThe cathodoluminescence (CL) characteristics of plagioclase phenocrysts in water-quenched lavas from the 1983 eruption of Etna have been investigated to examine the application of plagioclase CL to the study of magmatic processes. The phenocrysts have a green luminescent inner zone that is sharply bounded by a blue luminescent outer zone, with the boundary often coinciding with a concentric zone of glass inclusions.Strong compositional differences between the green (An70–An75) and blue (An50–An60) luminescent areas are interpreted as the result of two phases of growth under differing conditions. The green luminescent cores are considered to be anorthite-rich cumulate crystals from a basic magma which have been disrupted by the injection of a more evolved melt, resulting in heterogeneous nucleation and crystallization of the outer blue luminescent zone. The relationship between the CL and the trace element contents of the plagioclase crystals is discussed.

A New Look at Gentrification: 1. Gentrification and Domestic Technologies

1997 ◽  
Vol 29 (7) ◽  
pp. 1275-1296 ◽  
Author(s):  
P A Redfern
Keyword(s):  
Urban Development ◽  
Zone Model ◽  
Supply Side ◽  
Demand Side ◽  
Concentric Zone ◽  
New Look

In this paper I take issue with what I identify as a basic consensus in gentrification studies. I argue that gentrification studies have been conducted within a context framed by two basic models of urban development, namely the Burgess concentric-zone model and the Alonso bid-rent model. These two models lie at the heart of what are more usually seen as the parameters of the gentrification debate, namely the ‘supply-side’ rent-gap account of gentrification offered by Neil Smith and his followers and the ‘demand-side’ consumption-oriented explanations offered by David Ley and his followers. Both sets of explanations are, however, fatally compromised by seeking to answer the question ‘why does gentrification occur?’ before answering the question ‘how does gentrification occur?’. Starting with the question ‘how?’, rather than ‘why?’, draws attention to the hitherto almost completely neglected role of domestic technologies in permitting gentrification to occur, thereby helping break the theoretical logjam in which the gentrification debate currently finds itself.

Chemostratigraphic division of the Blake River Group, Rouyn–Noranda area, Abitibi, Quebec

1984 ◽  
Vol 21 (2) ◽  
pp. 220-231 ◽  
Author(s):  
Léopold Gélinas ◽  
Pierre Trudel ◽  
Claude Hubert
Keyword(s):  
Earth Element ◽  
Basaltic Magma ◽  
Volcanic Belt ◽  
Progressive Increase ◽  
Calc Alkaline ◽  
Significant Modification ◽  
Rhyolitic Magma ◽  
Tholeiitic Magma ◽  
Concentric Zone ◽  
Mafic Magmas

The effusive rocks of the Blake River Group in the Abitibi volcanic belt, Rouyn–Noranda region, belong to a bimodal sequence in which andesites and rhyolites clearly dominate. The identification of calc-alkaline and tholeiitic affinities is made upon examination of the major, trace, and rare earth element (REE) content. Thus, the andesites (58% normalized SiO2 value without volatiles) of the calc-alkaline units have average K (4800 ppm), Ba (160 ppm), and Rb (13 ppm) values that are greater than the average K (1800 ppm), Ba (130 ppm), and Rb (3 ppm) values for andésites (57% SiO2) that belong to associated tholeiitic units. Furthermore, tholeiitic andesites have distinctive average values of Ti (9600 ppm) and Y (40 ppm) that are higher than the average values of Ti (6700 ppm) and Y (25 ppm) of calc-alkaline andesites. An effective discrimination between the calc-alkaline and tholeiitic affinities is obtained using the Zr/Y and Ti/Zr ratios, which are, respectively, less than 4 and greater than 70 in andesites of the tholeiitic units.REE profiles of tholeiitic andesites are flat when compared with those of calc-alkaline andesites, which show an enrichment in light rare earths.The tholeiitic units of the Blake River Group are found in the proximity of the Porcupine-Destor and Larder Lake – Cadillac faults, the major faults of the region, and at the periphery of an ensemble of calc-alkaline units. Four of the five tholeiitic units are differentiated, showing an enrichment of iron passing from basalt to andesite. These units possess felsic variole-bearing flows, the result of an unmixing, which was probably responsible for the formation of minor associated quantities of porphyries and rhyolitic volcaniclastites.A progressive increase in the concentration of hygromagmatophile elements (REE, Zr, Nb) is observed in the tholeiitic units from the Pelletier unit beginning at the base and passing through the Trémoy, Destor, and Dufresnoy units, at the top of the Blake River Group. The calc-alkaline units are characterized by an alternation of rhyolitic complexes and calc-alkaline andesites. This cyclic repetition occurs without significant modification of the calc-alkaline andesite composition.It is proposed that the volcanism responsible for the formation of the Blake River Group was restricted to a concentric zone centring on a continental environment. Mafic magmas nourished the central reservoir where melting of the sialic crust took place. The rhyolitic magma occupying the upper part of this reservoir mixed with the basaltic magma, producing calc-alkaline andesites. Successive mantle melt products were also emplaced into subsidiary reservoirs peripheral to the central chamber. Injections of tholeiitic magma in the peripheral reservoirs underwent differentiation and unmixing during emplacement of a part of the magma at the surface.

Impact of distance on migration in Turkey

2015 ◽  
Vol 13 (2) ◽  
pp. 269-294 ◽  
Author(s):  
Turgay Kerem Koramaz ◽  
Vedia Dökmeci
Keyword(s):  
Economic Development ◽  
Metropolitan Areas ◽  
Concentric Zone ◽  
The Relationship

In Turkey, a large gap in economic development has encouraged migration from less developed to more developed provinces. The aim of this study is to study in detail the relationship between migrants and the concentric zones surrounding them from 2007 until 2012. According to the results of the study, the highest amount of migration is shown to be between the origin province and a 400km concentric zone, beyond which they gradually decrease. This pattern is often repeated, but in less populated provinces, which are further from large metropolitan areas, it becomes more homogenous, with unique peaks in the more distant concentric zones.

Possible ways of drawing a magnetic product into the concentric zone of a semicounterflow or counterflow separator

1975 ◽  
Vol 11 (4) ◽  
pp. 406-410
Author(s):  
A. N. Maryuta ◽  
I. K. Mladetskii ◽  
P. A. Novitskii
Keyword(s):  
Concentric Zone ◽  
Magnetic Product
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