Steerable filters generated with the hypercomplex dual-tree wavelet transform

The use of wavelets in the image processing domain is still in its infancy, and largely associated with image compression. With the advent of the dual-tree hypercomplex wavelet transform (DHWT) and its improved shift invariance and directional selectivity, applications in other areas of image processing are more conceivable. This paper discusses the problems and solutions in developing the DHWT and its inverse. It also offers a practical implementation of the algorithms involved. The aim of this work is to apply the DHWT in machine vision. Tentative work on a possible new way of feature extraction is presented. The paper shows that 2-D hypercomplex basis wavelets can be used to generate steerable filters which allow rotation as well as translation.</p

Demographic and genetic consequences of disturbed sex determination.

During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination. The resulting genotype-phenotype mismatches can have long-lasting effects on population demography and genetics. I review the theoretical and empirical work in this context and explore in a simple population model the role of the fitness vyy of chromosomally aberrant YY genotypes that are a consequence of environmentally induced feminization. Low vyy is mostly beneficial for population growth. During feminization, low vyy reduces the proportion of genetic males and hence accelerates population growth, especially at low rates of feminization and at high fitness costs of the feminization itself (i.e. when feminization would otherwise not affect population dynamics much). When sex reversal ceases, low vyy mitigates the negative effects of feminization and can even prevent population extinction. Little is known about vyy in natural populations. The available models now need to be parametrized in order to better predict the long-term consequences of disturbed sex determination.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'

Size-dependent discrimination of mating partners in the simultaneous hermaphroditic cestode Schistocephalus solidus

The cestode Schistocephalus solidus is a simultaneous hermaphrodite that reproduces in the gut of birds, or for this study in an in vitro system that simulates the gut of the bird. Like many other helminth parasites, S. solidus can reproduce by self- and cross-fertilization. Hermaphrodites are expected to mate not primarily to get their own eggs fertilized, but rather to get the opportunity to fertilize a partner's eggs. Because S. solidus has a size-dependent sex allocation (i.e., larger worms are more biased toward female allocation and produce more egg mass), we expect larger individuals to be attractive mating partners for smaller ones. However, this may be a one-directional preference, as smaller individuals may not be attractive to larger ones. We tested this experimentally by studying the reaction of focal worms of different sizes to a compartment containing a potential mating partner that was either smaller or larger than the focal worm. The focal worms were, on average, closer to the compartment containing the stimulus than to an empty control compartment. Moreover, they indeed showed a preference for larger stimulus worms than for smaller ones. They even tended to avoid being close to stimulus worms of very small size compared to themselves. This may reveal a general preference for cross-fertilization over selfing, but it also indicates that all the genetic benefits from outcrossing do not necessarily outweigh the costs of mating with a relatively small individual and that the worms may take this into account in their reproductive decision

Fütterungsversuche zur Erzeugung von Bioforellen

Vergleichsgruppen von Regenbogenforellen wurden mit einem Öko-Trockenfuttermittel und einem vergleichbaren konventionellen Produkt aufgezogen. Das tägliche Wachstum der Ökofuttermittel-Gruppe war geringer, die Futterverwertung und Merkmale der Produktqualität waren nicht unterscheidbar. Tendenziell wurden die konventionellen Forellen geräuchert, die Öko-Forellen bei Ofengarung sensorisch besser bewertet. Im Vergleich von fünf verschiedenen Brutfuttermitteln, waren die Bio-Brutfuttermittel bezüglich Futterquotient und Wirtschaftlichkeit schlechter zu bewerten. Erst bei einem 20 % höheren Verkaufspreis für biologisch erzeugte Setzlinge würden mit dem Bio-Extrudat im Vergleich zum konventionellem Extrudat bessere wirtschaftliche Ergebnisse erreicht. In Freilandversuchen eingesetzte moderne extrudierte Biofuttermittel wurden sehr gut verwertet. Aufgrund der deutlich höheren Futtermittelpreise lagen die Zuwachskosten dennoch um 20 –30 % über der konventionellen Produktion. Um eine vergleichbare Marktleistung zu erzielen, müsste bei der Produktion von Bioforellen ein Biozuschlag von 9 % erzielt werden, für eine vergleichbare Arbeitsentlohnung bereits 19 % und um den Faktor Zulaufwasser gleich zu verwerten sogar 50 %. Die Fleischqualitätsmerkmale unterschieden sich auch in diesem Versuch nur gering. In einem weiteren Versuch wurden Regenbogenforellen mit extrudierten Futtermitteln aufgezogen, zwei Öko- und ein konventionelles Futter. Aufgrund der in diesem Versuch erzielten Ergebnisse wurde festgestellt, dass die hier verwendeten modernen Ökofuttermittel hinsichtlich der Leistungsfähigkeit und der Umweltverträglichkeit auf dem gleichen Niveau wie das konventionelle Futter liegen. Die Zuwachskosten pro Kilogramm Fisch unterschieden sich allerdings aufgrund des deutlich höheren Preises für Ökofuttermittel enorm (+ 23 – 36 %). Die Bioforelle stellt eine Erweiterung der Produktpalette in der ökologischen Landwirtschaft dar und bezieht eine weitere Produzenten- und Käufergruppe mit ein. Die Erzeugung befindet sich in einer Pilotphase. Teurere Forellenfuttermittel, geringere Bestandsdichten und hohe Zertifizierungskosten machen die Bioforellenproduktion im Vergleich zur konventionellen Erzeugung deutlich kostspieliger. Die zertifizierte Forellenzucht kann als Alternative zur konventionellen Produktion erst lukrativ sein, wenn beim Absatz ein deutlicher Biozuschlag unterstellt wird

Optimization of crystal nucleation close to a metastable fluid-fluid phase transition

The presence of a metastable fluid-fluid critical point is thought to dramatically influence the crystallization pathway, increasing the nucleation rate by many orders of magnitude over the predictions of classical nucleation theory. We use molecular dynamics simulations to study the kinetics of crystallization in the vicinity of this metastable critical point and throughout the metastable fluid-fluid phase diagram. To quantitatively understand how the fluid-fluid phase separation affects the crystal nucleation, we evaluate accurately the kinetics and reconstruct the thermodynamic free-energy landscape of crystal formation. Contrary to expectations, we find no special advantage of the proximity of the metastable critical point on the crystallization rates. However, we find that the ultrafast formation of a dense liquid phase causes the crystallization to accelerate both near the metastable critical point and almost everywhere below the fluid-fluid spinodal line. These results unveil three different scenarios for crystallization that could guide the optimization of the process in experimentsThis work has been supported by the MINECO of the Spanish government through Grants No. FIS2012-31025 and FIS2011-22603. LX thanks the financial support from MOST 973 of China (Grants No. 2015CB856800 and 2012CB921404) and National Science Foundation of China (Grants No. 11174006 and 11290162). HES thanks the NSF Chemistry Division for support (grants CHE 0911389, CHE 0908218, and CHE 1213217). SVB thanks the Office of the Academic Affairs of Yeshiva University for funding the Yeshiva University high-performance computer cluster and acknowledges the partial support of this research through Dr. Bernard W. Gamson computational Science Center at Yeshiva College. (FIS2012-31025 - MINECO of the Spanish government; FIS2011-22603 - MINECO of the Spanish government; 2015CB856800 - MOST 973 of China; 2012CB921404 - MOST 973 of China; 11174006 - National Science Foundation of China; 11290162 - National Science Foundation of China; CHE 0911389 - NSF Chemistry Division; CHE 0908218 - NSF Chemistry Division; CHE 1213217 - NSF Chemistry Division; Office of the Academic Affairs of Yeshiva University; Dr. Bernard W. Gamson computational Science Center at Yeshiva College)Published versio