A Comparison of the Seasonality and Interannual Variability of Phytoplankton Biomass and Production in the Western and Eastern Gyres of the Subarctic Pacific Using Multi-Sensor Satellite Data

This study documents the results of a multi-sensor satellite investigation aimed at comparing the seasonality and interannual variability of phytoplankton biomass and primary productivity (PP) in the western and eastern gyres of the subarctic Pacific. Satellite data helped discern several features, most importantly the existence of significant east-west gradients in the supply of nitrate in winter, in the consumption of nitrate by phytoplankton and in phytoplankton production and biomass accumulation over the growth season. In the western subarctic gyre many of these features appear to be regulated by the strength of sea surface winds through increased iron and nitrate inputs. Multiple regression analysis of data extracted from 12 boxes spanning different hydrographic regimes in the subarctic Pacific, showed that over 65% of the variations in PP in the subarctic Pacific could be explained solely on the basis of changes in the strength of sea surface winds and the intensity of incident irradiance (PAR). The dependence of PP on sea surface wind stress was far greater in the western subarctic Pacific Gyre (WSG), than in the Alaskan Gyre (ALG) due to diminishing impact of surface winds towards the east. Spring accumulation of phytoplankton biomass was greater in the WSG than in the ALG despite the higher rates of PP in the latter. This study assumes particular significance because it helps ascertain the existence of several sub-regions within the two broader domains of the WSG and the ALG. In addition, large interannual variations in phytoplankton biomass and PP were observed in the subarctic Pacific following the onset of the El-Niño event of 1997 and the transition to La-Niña conditions in 1999. These variations were largely the result of differences in meteorological and oceanographic conditions across the subarctic Pacific following the development of the El-Niño.     

A comparative approach towards ethnic segregation patterns in Belgian cities using multiscalar individualized neighborhoods

Levels of spatial segregation in Western European cities are persistent over space and time. To demonstrate the degree or appearance of spatial segregation, most studies on urban residential patterns still rely on fixed spatial units, aspatial measures and single scales. However, a spatial or temporal comparison of patterns and levels of segregation based on such units or metrics is not without problems. To that end, this paper takes an explicit geographic approach and considers individualized neighborhoods using EquiPop-software, allowing various scales. Using the k-nearest neighbors for all individuals increases international comparability and facilitates interpretation, so far often hampered in segregation research. This multiscalar, multigroup comparative approach on ethnic urban geographies – using Belgium as a case study – provides an empirical illustration of a valuable method and tool applicable in segregation research, thereby furthering the comprehension of the increasingly diverse urban geographies and building on emerging work in the US, Europe and beyond.     

Advanced Marginality as a comparative research strategy in praxis: the Danish “Grey Belt” in conversation with the French “Red Belt”

Urban Outcast and advanced marginality belongs to a theory culture rarely engaged in comparative urban studies. Here the potential of advanced marginality as a comparative research strategy is explored paying special attention to the concepts of epistemic reflexivity, analogical reasoning and homology. These concepts are applied as the foundation of a comparative research design comprising three necessary and interconnected analytical moments linking reflexivity, theory and empirical analysis. Empirically this strategy and design is confronted in the case of four Danish “Grey belt” housing estates. The empirical confrontation demonstrates that both strategy and design are relevant and productive. Nevertheless, there is a need to question, adapt and extent the six original properties of advanced marginality. Secondly the empirical confrontation demonstrates that both strategy and design can contribute to the current conversations on the comparative in urban studies empirically and conceptually, underscoring the curiosity of its eclipse in these conversations.     

Terrestrial Kr-Kr ages of Antarctic meteorites

The production rate of ³⁸Ar in meteorites—P(38)—has been determined, as a function of the sample's chemical composition, from ⁸¹Kr-Kr exposure ages of four eucrite falls. The cosmogenic ⁷⁸Kr/⁸³Kr ratio is used to estimate the shielding dependence of P(38).

From the “true” ³⁸Ar exposure ages and the apparent ⁸¹Kr-Kr exposure ages of nine Antarctic eucrite finds, terrestrial ages are calculated. They range from about 3 × 10⁵ a (Pecora Escarpment 82502) to very recent falls (Thiel Mountains 82502). Polymict eucrites from the Allan Hills (A78132, A79017 and A81009) have within the limits of error the same exposure age (15.2 × 10⁶ a) and the same terrestrial age (1.1 × 10⁵ a). This is taken as strong evidence that these meteorites are fragments of the same fall. A similar case are the Elephant Moraine polymict eucrites A79005, A79006 and 82600 with an exposure age of 26 × 10⁶ a and a terrestrial age of 1.8 × 10⁵ a. EETA79004 may be different from this group because its exposure age and terrestrial age are 21 × 10⁶ a and 2.5 × 10⁵ a, respectively.

The distribution of terrestrial ages of Allan Hills meteorites is discussed. Meteorites from this blue ice field have two sources: Directly deposited falls and meteorites transported to the Allan Hills inside the moving Antarctic ice sheet. During the surface residence time meteorites decompose due to weathering processes. The weathering “half-life” is about 1.6 × 10⁵ a. From the different age distributions of Allan Hills and Yamato meteorites, it is concluded that meteorite concentrations of different Antarctic ice fields need different explanations.     

Zusammenhang zwischen Fehlordnungsgrad und Bildungstemperatur bei synthetischen Cristobaliten

By hydrothermal hydrolysis of silicium nitride cristobalite with different degrees of disorder was formed metastably in the stability range of quartz. The synthesis conditions were 2 kbars \(P_{{\text{H}}_{\text{2}} {\text{O}}}\) , temperatures between 200 and 610° C, and run durations of two days. Differential thermal analysis was applied to investigate order-disorder phenomena in the newly formed phases, since it turned out to be most sensitive to disorder effects; the results have been corroborated by infraredspectroscopic, electron optical, and X-ray investigations as well. In the DTA curve the degree of disorder of cristobalite can be recognized by four characteristic features: 1. the temperature of inversion (t _i) from tetragonal (low-) to cubic (high-) cristobalite, 2. the width of the inversion temperature interval, 3. the shape of the inversion peak, and 4. the hysteresis between (t _i) measured during heating and subsequent cooling. With increasing order, (t _i) and the sharpness of the peak increase, whereas the inversion temperature interval decreases. The heating-cooling hysteresis, which is negative in poorly ordered crystals, becomes increasingly positive with improving degree of order. All the different methods of investigation have shown that the degree of order increases with increasing synthesis temperature if all other conditions are kept constant. The relatively low temperatures of formation can be understood as a consequence of high SiO₂ supersaturations due to the rapid decay of Si₃N₄ under hydrous conditions. Substitution of NH ₄ ⁺ ions in cristobalite which might behave like alkali ions has not been observed.     

Zur Charakterisierung suspendierter Wasserinhaltsstoffe. Teil 1: Analytische Methoden

Über Möglichkeiten zur Charakterisierung von suspendierten Inhaltstoffen in Oberflächenwässern wird berichtet. Die Kenntnis der Rohwnsserbeschaffenheit, die neben der Konzentrationsangabe Aussagen über Art und Eigenschaften der Partikel einschließt, ist eine Voraussetzung für die Verbesserung der Bemessungsgrundlagen und den optimalen Betrieb von Wasseraufbereitungsanlagen. Es werden Analysenmethoden zur Erfassung des Feststoffgehaltes ausgewählt, die regelmäßig im Betriebslaboratorium durchführbar sind (z. B. Trübung, Zentrifugationswert). Geeignete Möglichkeiten zur Untersuchung der Partikeleigenschaften wie granulometrische, mikroskopische, röntgen- und differentialthermoanalytische Methoden werden diskutiert.