Reversible GANs for Memory-efficient Image-to-Image Translation

The Pix2pix and CycleGAN losses have vastly improved the qualitative and quantitative visual quality of results in image-to-image translation tasks. We extend this framework by exploring approximately invertible architectures which are well suited to these losses. These architectures are approximately invertible by design and thus partially satisfy cycle-consistency before training even begins. Furthermore, since invertible architectures have constant memory complexity in depth, these models can be built arbitrarily deep. We are able to demonstrate superior quantitative output on the Cityscapes and Maps datasets at near constant memory budget

Landscapes of facilitation:The effects of positive interactions on community structure

De biodiversiteit van onze wereld staat al lange tijd onder druk, in de meeste gevallen door toedoen van de mens. Het behouden van biodiversiteit vergt meer dan het beschermen van een natuurgebied. Het vereist kennis van en inzicht in de vele interacties die plaatsvinden tussen de verschillende soorten die aanwezig zijn. Gedurende een lange tijd richtte ecologisch onderzoek zich op negatieve interacties zoals competitie en predator-prooi relaties. In de afgelopen decennia ontstond er meer oog voor de rol van positieve interacties in het structureren van soortgemeenschappen. Wanneer verschillende soorten elkaar faciliteren, bijvoorbeeld door het bieden van schaduw, veiligheid of vaste ondergrond, kan er een domino-effect ontstaan. Bij zogenoemde facilitatie-cascades faciliteert een primaire habitatvormende soort een secondaire habitatvormer die op zijn beurt de biodiversiteit en soortenabundantie kan vergroten. Deze positieve interacties zijn gevoelig voor variatie in soorteigenschappen en functie van de habitatvormers. Zo blijken oesters en mosselen – op het eerste gezicht twee gelijke soorten – de ontwikkeling van verschillende macroalgen en geassocieerde soorten te faciliteren vanwege hun verschillende ecologische functies. Verder blijkt de morfologie van macroalgen effect te hebben op de soorten die gefaciliteerd worden. Eén primaire habitatvormer kan meerdere facilitatie-cascades genereren met positieve effecten op de biodiversiteit op zowel lange als korte afstanden. Hierdoor worden verschillende habitats sterk met elkaar in verbinding gebracht door een netwerk van positieve interacties. Deze complexe interactienetwerken onderstrepen het belang van cross-habitat managementinitiatieven die als doel hebben de biodiversiteit te vergroten door beheer en herstel van habitatvormende soorten en hun positieve interacties

Learning Layer-wise Equivariances Automatically using Gradients

Convolutions encode equivariance symmetries into neural networks leading to better generalisation performance. However, symmetries provide fixed hard constraints on the functions a network can represent, need to be specified in advance, and can not be adapted. Our goal is to allow flexible symmetry constraints that can automatically be learned from data using gradients. Learning symmetry and associated weight connectivity structures from scratch is difficult for two reasons. First, it requires efficient and flexible parameterisations of layer-wise equivariances. Secondly, symmetries act as constraints and are therefore not encouraged by training losses measuring data fit. To overcome these challenges, we improve parameterisations of soft equivariance and learn the amount of equivariance in layers by optimising the marginal likelihood, estimated using differentiable Laplace approximations. The objective balances data fit and model complexity enabling layer-wise symmetry discovery in deep networks. We demonstrate the ability to automatically learn layer-wise equivariances on image classification tasks, achieving equivalent or improved performance over baselines with hard-coded symmetry

A Pacific oyster invasion transforms shellfish reef structure by changing the development of associated seaweeds

Biological invasions are reshaping coastal ecosystems across the world. However, understanding the significance of such invasions is often hampered by the lack of process-based research, resulting in a limited mechanistic comprehension of novel ecological interactions and their consequences. The Pacific oyster (Crassostrea gigas) has invaded European coasts, resulting in an astonishing transformation of the intertidal shellfish reef communities in the Wadden Sea; from reefs constructed by blue mussels only (Mytilus edulis) to mixed reefs dominated by oysters. Shellfish reefs structure the marine vegetation on soft bottoms by accumulating seaweeds. Nevertheless, assessments of the consequences of the oyster take-over have almost exclusively focused on effects on associated fauna. By constructing small-scale reefs dominated by blue mussels or oysters and following the development of seaweeds over summer, we demonstrated that oysters promoted bloom-forming green algae communities with low primary biomass and low habitat complexity. In contrast, blue mussels promoted the development of meadow-like communities dominated by habitat forming brown seaweeds of the genus Fucus, with high primary biomass and high habitat complexity. An additional field survey showed that increasing numbers of Pacific oysters on a recently invaded natural blue mussel reef significantly decreased the development of the Fucus meadow in spring. Our results indicate that the invasion of oysters may have effects on the structure and function of intertidal reef-communities by changing energy flow and habitat-function

Bioengineering promotes habitat heterogeneity and biodiversity on mussel reefs

Loss of biodiversity is among the most pressing global problems. Yet, despite its pertinent nature, the biological processes involved in the maintenance of biodiversity are poorly understood. Habitat heterogeneity is widely regarded as a key factor underpinning the biodiversity of land- and sea-scapes. However, it remains unclear how species coexist in many of those ecosystems that lack conspicuous heterogeneity. We demonstrate how spatially self-organized mussel reefs create microhabitats/heterogeneity that facilitate diverse invertebrate communities. By comparing seawater filled pools with open inlets in a mussel reef, we found that natural reef pools, emerging due to the habitat engineering of the mussels, strongly increased variation in organic enrichment and promoted beta-diversity compared to the surrounding tidal flat. These findings significantly extend the scale of influence typically described for self-organized habitats and highlight the importance of bioengineering and its positive effects on habitat heterogeneity and community diversity

Protection of cyclooxygenase activity during heme-induced destabilization

Sheep vesicular gland cyclooxygenase is destroyed spontaneously when incubated with only substoichiometric amounts of heme. Peroxides may participate in this destruction, since glutathione peroxidase, catalase, and phenol, a cosubstrate for prostaglandin hydroperoxidase, all protect the cyclooxygenase activity. Stoichiometric or greater levels of heme also tend to protect the enzyme from inactivation. Therefore, to achieve optimal recoveries of enzyme activity during purification and storage, the addition of prostaglandin hydroperoxidase cosubstrate, such as phenol, in combination with high levels of heme is recommended. The current understanding of destabilization and protection of cyclooxygenase now allows an interpretation of the previously unexplained phenomenon of slow phenol activation of cyclooxygenase acetone powder preparations. Phenol appears to protect enzyme activity during the slow equilibration of apoenzyme with endogenous heme to form the active holoenzyme. In the absence of phenol, the progressive rise in activity is not seen as the enzyme is vulnerable to heme-induced destruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23259/1/0000192.pd

Perceived age as clinically useful biomarker of ageing: cohort study

Objective To determine whether perceived age correlates with survival and important age related phenotypes

Lipoprotein Particle Profiles Mark Familial and Sporadic Human Longevity

BACKGROUND: Genetic and biochemical studies have indicated an important role for lipid metabolism in human longevity. Ashkenazi Jewish centenarians and their offspring have large low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles as compared with control individuals. This profile also coincided with a lower prevalence of disease. Here, we investigate whether this observation can be confirmed for familial longevity in an outbred European population and whether it can be extended to sporadic longevity in the general population. METHODS AND FINDINGS: NMR-measured lipoprotein profiles were analyzed in 165 families from the Leiden Longevity Study, consisting of 340 long-lived siblings (females >91 y, males >89 y), 511 of their offspring, and 243 partners of the offspring. Offspring had larger (21.3 versus 21.1 nm; p = 0.020) and fewer (1,470 versus 1,561 nmol/l; p = 0.011) LDL particles than their same-aged partners. This effect was even more prominent in the long-lived siblings (p < 10(−3)) and could be pinpointed to a reduction specifically in the concentration of small LDL particles. No differences were observed for HDL particle phenotypes. The mean LDL particle sizes in 259 90-y-old singletons from a population-based study were similar to those in the long-lived siblings and thus significantly larger than in partners of the offspring, suggesting that the relevance of this phenotype extends beyond familial longevity. A low concentration of small LDL particles was associated with better overall health among both long-lived siblings (p = 0.003) and 90-y-old singletons (p = 0.007). CONCLUSIONS: Our study indicates that LDL particle profiles mark both familial and sporadic human longevity already in middle age

Structural Basis for Certain Naturally Occurring Bioflavonoids to Function as Reducing Co-Substrates of Cyclooxygenase I and II

Recent studies showed that some of the dietary bioflavonoids can strongly stimulate the catalytic activity of cyclooxygenase (COX) I and II in vitro and in vivo, presumably by facilitating enzyme re-activation. In this study, we sought to understand the structural basis of COX activation by these dietary compounds.A combination of molecular modeling studies, biochemical analysis and site-directed mutagenesis assay was used as research tools. Three-dimensional quantitative structure-activity relationship analysis (QSAR/CoMFA) predicted that the ability of bioflavonoids to activate COX I and II depends heavily on their B-ring structure, a moiety known to be associated with strong antioxidant ability. Using the homology modeling and docking approaches, we identified the peroxidase active site of COX I and II as the binding site for bioflavonoids. Upon binding to this site, bioflavonoid can directly interact with hematin of the COX enzyme and facilitate the electron transfer from bioflavonoid to hematin. The docking results were verified by biochemical analysis, which reveals that when the cyclooxygenase activity of COXs is inhibited by covalent modification, myricetin can still stimulate the conversion of PGG(2) to PGE(2), a reaction selectively catalyzed by the peroxidase activity. Using the site-directed mutagenesis analysis, we confirmed that Q189 at the peroxidase site of COX II is essential for bioflavonoids to bind and re-activate its catalytic activity.These findings provide the structural basis for bioflavonoids to function as high-affinity reducing co-substrates of COXs through binding to the peroxidase active site, facilitating electron transfer and enzyme re-activation