Two-Channel System Dynamics of the Outer Weser Estuary—A Modeling Study

In this paper, we unravel the mechanisms responsible for the development of the two-channel system in the Outer Weser Estuary. A process-based morphodynamic model is built based on a flat-bed approach using simplified boundary conditions and accelerated morphological development. The results are analyzed in two steps: first, by checking for morphodynamic equilibrium in the simulations and second, by applying a newly developed method that interprets simulations based on categorization of the two-channel system and cross-sectional correlation analysis. All simulations reach a morphodynamic equilibrium and develop two channels that vary considerably over time and between the simulations. Variations can be found in the location and depth of the two channels, the development of the dominant channel over time and the alteration in the dominance pattern. The conclusions are that the development of the two-channel system is mainly caused by the tides and the basin geometry. Furthermore, it is shown that the alternation pattern and period are dependent on the dominance of the tides compared to the influence of river discharge.

Syllable Contact and Emergent Lenition in Bashkir

This study examines the syllable contact phonology of Bashkir (Kipchak, southern Urals, Russia), a language which exhibits a unique variation on general Turkic syllable contact phenomena, and proposes an Optimality Theoretic analysis, drawing on previous approaches to syllable contact in Turkic (Baertsch & Davis 2001, 2004, Gouskova 2001, 2004, Washington 2010). Bashkir desonorizes affix-initial coronal sonorants (/qullar/ --> [qul.dar]) to mandate compliance with the Syllable Contact Law (Davis, 1998). This occurs even at boundaries which would otherwise exhibit falling sonority, thereby maximizing sonority fall. Bashkir also exhibits a unique continuancy alternation pattern in desonorized affixes (taw-ðar, uram-dar, gaz-dar). This study adopts the Syllable Contact Hierarchy analysis proposed in Gouskova (2004), with ranking of relevant faithfulness constraints below all *DIST constraints mandating maximal sonority fall. It is proposed that continuancy alternations derived from a synchronically active lenition process, otherwise dominated by relevant faithfulness constraints, which emerges when unfaithfulness is forced to satisfy constraints on syllable contact.

Cross-reactive immunity drives global oscillation and opposed alternation patterns of seasonal influenza A viruses

Several human pathogens exhibit distinct patterns of seasonality and circulate as pairs of discrete strains. For instance, the activity of the two co-circulating influenza A virus subtypes oscillates and peaks during winter seasons of the world’s temperate climate zones. These periods of increased activity are usually caused by a single dominant subtype. Alternation of dominant strains in successive influenza seasons makes epidemic forecasting a major challenge. From the start of the 2009 influenza pandemic we enrolled influenza A virus infected patients (n = 2,980) in a global prospective clinical study. Complete hemagglutinin (HA) sequences were obtained from 1,078 A/H1N1 and 1,033 A/H3N2 viruses and were linked to patient data. We then used phylodynamics to construct high resolution spatio-temporal phylogenetic HA trees and estimated global influenza A effective reproductive numbers (R) over time (2009-2013). We demonstrate that R, a parameter to define host immunity, oscillates around R = 1 with a clear opposed alternation pattern between phases of the A/H1N1 and A/H3N2 subtypes. Moreover, we find a similar alternation pattern for the number of global virus migration events between the sampled geographical locations. Both observations suggest a between-strain competition for susceptible hosts on a global level. Extrinsic factors that affect person-to-person transmission are a major driver of influenza seasonality, which forces influenza epidemics to coincide with winter seasons. The data presented here indicate that also cross-reactive host immunity is a key intrinsic driver of global influenza seasonality, which determines the outcome of competition between influenza A virus strains at the onset of each epidemic season.Significance statementAnnual influenza epidemics coincide with winter seasons in many parts of the world. Environmental factors, such as air humidity variation or temperature change, are commonly believed to drive these seasonality patterns. Interestingly, three out of the four latest pandemics (1918, 1968 and 2009) did not spread in winter initially, but during summer. This questions to what extent other factors could also impact virus spread among humans. We demonstrate that cross-reactive host immunity is a key factor. It drives the well-known seasonal patterns of virus activity oscillation and alternation of the dominant influenza virus subtype in successive seasons. Furthermore, this factor may also explain the efficient spread of pandemic viruses during summer when cross-reactive host immunity is relatively low.

From linear to cyclic oligoparaphenylenes: electronic and molecular changes traced in the vibrational Raman spectra and reformulation of the bond length alternation pattern

Linear versus cyclic π-electron conjugation is discussed in oligoparaphenylenes.

Geometrical Structure of Carbon Nanotubes with Alternation Pattern

In this paper we consider the geometrical structure of carbon nanotubes with artificially inplanebond alternation. The quinoid and the Kekule structures of carbon nanotubes with two differentbond lengths are fully described for various symmetries, including chiral and achiral carbon nanotubes.Consideration of the geometrical structure or the atomic structure is the first step for studies of carbonnanotubes with dimerization structures.

Five more phases of the structural family [M(H2O)2(15-crown-5)](NO3)2

The structures of five more phases of the structural family of compounds [M(H2O)2(15-crown-5)](NO3)2 have been determined. All of these phases are stable at room temperature or above, but transform to other phases if cooled slowly. All five phase transitions take place without significant damage to the single crystal. The M = Co phase, which has a three-dimensional hydrogen-bonding pattern, is a disordered version of the structure known at room temperature; Z′ changes from 2 to ½. The other four structures have a two-dimensional hydrogen-bonding pattern, are all modulated variants of the same basic cell (or subcell) and are at least mostly ordered. For M = Mg and Zn the structure found somewhat above room temperature is the Z′ = 8 variant found previously for M = Fe. For M = Cu and Ni the Z′ = 2 phase found is the same as seen previously for one of the room-temperature polymorphs with M = Mn. There are now two phases and one transition known for each M studied that has a two-dimensional hydrogen-bonding pattern. The changes in the modulation patterns during these transitions are Z′ 3 ↔ 8 (Mg, Fe, Zn), Z′ 3 ↔ 2 (Mn, Ni) and Z′ 5 ↔ 2 (Cu). In all two-dimensional hydrogen-bonded crystals the alternation pattern of conformational enantiomers along the modulation direction becomes more perfect above the phase transition. All stable [M(H2O)2(15-crown-5)](NO3)2 phases whose existence at accessible temperatures is indicated by differential scanning calorimetry (DSC) have now been characterized.

Development of Spontaneous Alternation in Infancy

Spontaneous alternation is a reduced tendency to return to the same location on successive trials. It is measured in rats in a T maze and is thought to depend on an intact hippocampus. In human infants, we measured alternation in the tendency to reach toward one of two identical toys placed in locations to the left and right of midline. Infants at 6 months returned to the same side as frequently as they alternated, but 18--month-old infants showed a significant alternation pattern. At 6 months, infants show inhibition of return, but do not show alternation in motor behavior; at 18 months, infants show both, but they are negatively related. These data suggest that preference for novelty may rest on different internal mechanisms even in quite similar tasks, and suggest that whereas inhibition of return is related to control by the posterior attention network, spontaneous alternation may be related to inhibitory control by the anterior attention network.