Hamiltonians separable in cartesian coordinates and third-order integrals of motion

We present in this article all Hamiltonian systems in E(2) that are separable in cartesian coordinates and that admit a third-order integral, both in quantum and in classical mechanics. Many of these superintegrable systems are new, and it is seen that there exists a relation between quantum superintegrable potentials, invariant solutions of the Korteweg-De Vries equation and the Painlev\'e transcendents.Comment: 19 pages, Will be published in J. Math. Phy

Singularity confinement and algebraic integrability

Two important notions of integrability for discrete mappings are algebraic integrability and singularity confinement, have been used for discrete mappings. Algebraic integrability is related to the existence of sufficiently many conserved quantities whereas singularity confinement is associated with the local analysis of singularities. In this paper, the relationship between these two notions is explored for birational autonomous mappings. Two types of results are obtained: first, algebraically integrable mappings are shown to have the singularity confinement property. Second, a proof of the non-existence of algebraic conserved quantities of discrete systems based on the lack of confinement property is given.Comment: 18 pages, no figur

Fundamental limitations on "warp drive" spacetimes

"Warp drive" spacetimes are useful as "gedanken-experiments" that force us to confront the foundations of general relativity, and among other things, to precisely formulate the notion of "superluminal" communication. We verify the non-perturbative violation of the classical energy conditions of the Alcubierre and Natario warp drive spacetimes and apply linearized gravity to the weak-field warp drive, testing the energy conditions to first and second order of the non-relativistic warp-bubble velocity. We are primarily interested in a secondary feature of the warp drive that has not previously been remarked upon, if it could be built, the warp drive would be an example of a "reaction-less drive". For both the Alcubierre and Natario warp drives we find that the occurrence of significant energy condition violations is not just a high-speed effect, but that the violations persist even at arbitrarily low speeds. An interesting feature of this construction is that it is now meaningful to place a finite mass spaceship at the center of the warp bubble, and compare the warp field energy with the mass-energy of the spaceship. There is no hope of doing this in Alcubierre's original version of the warp-field, since by definition the point in the center of the warp bubble moves on a geodesic and is "massless". That is, in Alcubierre's original formalism and in the Natario formalism the spaceship is always treated as a test particle, while in the linearized theory we can treat the spaceship as a finite mass object. For both the Alcubierre and Natario warp drives we find that even at low speeds the net (negative) energy stored in the warp fields must be a significant fraction of the mass of the spaceship.Comment: 18 pages, Revtex4. V2: one reference added, some clarifying comments and discussion, no physics changes, accepted for publication in Classical and Quantum Gravit

A common framework for identifying linkage rules across different types of interactions

Species interactions, ranging from antagonisms to mutualisms, form the architecture of biodiversity and determine ecosystem functioning. Understanding the rules responsible for who interacts with whom, as well as the functional consequences of these interspecific interactions, is central to predict community dynamics and stability. Species traits sensu lato may affect different ecological processes by determining species interactions through a two-step process. First, ecological and life-history traits govern species distributions and abundance, and hence determine species co-occurrence and the potential for species to interact. Secondly, morphological or physiological traits between co-occurring potential interaction partners should match for the realization of an interaction. Here, we review recent advances on predicting interactions from species co-occurrence and develop a probabilistic model for inferring trait matching. The models proposed here integrate both neutral and trait-matching constraints, while using only information about known interactions, thereby overcoming problems originating from undersampling of rare interactions (i.e. missing links). They can easily accommodate qualitative or quantitative data and can incorporate trait variation within species, such as values that vary along developmental stages or environmental gradients. We use three case studies to show that the proposed models can detect strong trait matching (e.g. predator‿prey system), relaxed trait matching (e.g. herbivore‿plant system) and barrier trait matching (e.g. plant‿pollinator systems). Only by elucidating which species traits are important in each process (i.e. in determining interaction establishment and frequency), we can advance in explaining how species interact and the consequences of these interactions for ecosystem functioning. A lay summary is available for this articlePeer Reviewe

Do Queensland cattle possess rumen bacteria capable of degrading Leucaena toxins?

Leucaena leucocephala is a leguminous fodder tree used by northern Australian producers to provide protein and boost the weight gains of extensively grazing cattle. There is a range of commercial Leucaena cultivars available which all contain a toxic non-protein amino acid, mimosine. Many rumen bacteria can degrade mimosine to 3,4-dihydroxypyridine (3,4-DHP), which is also toxic to cattle. To enable cattle to safely gain the full benefits of Leucaena, a bacterium, Synergistes jonesii, was isolated that could degrade the toxic metabolites 3,4 DHP and 2,3-hydroxypyridine (2,3-DHP) (Allison et al. 1992). A fermenter-grown mixed bacterial inoculum, containing S. jonesii, has been produced by DAF for over 20 years as an oral drench for cattle to prevent Leucaena toxicity and maximise weight gains (Klieve et al. 2002)

Development of a mixed microbial drench for detoxification of three Leucaena cultivars

The adoption of Leucaena leucocephala in Queensland, as a high protein, leguminous fodder shrub, has been hindered by insect infestation, with psyllids thriving on Leucaena planted in high humidity regions. A psyllid-resistant cultivar of Leucaena has therefore been developed (Redlands). Nonetheless, all Leucaena cultivars contain the non-protein amino acid, mimosine, which in the rumen of cattle can be degraded by many different bacteria to the toxic metabolite 3hydroxy-4-(1H)-pyridone (3,4-DHP). For over 20 years, a mixed microbial drench containing Synergistes jonesii has been produced by DAF to degrade mimosine, 3, 4-DHP and its degradation product 2,3-dihydroxypyridine (2,3-DHP), to reduce any toxic side-effects of feeding Leucaena to cattle (Klieve et al. 2002). This drench is produced in an in-vitro fermentation system supplied with leaf material from the Leucaena cultivar, Cunningham. Previous research found replacing the Cunningham leaf with either psyllid-resistant Redlands or psyllid-tolerant Wondergraze leaf, negatively impacted the mixed bacterial populations’ ability to degrade 3,4-DHP (Ouwerkerk et al. 2019). This study aimed to test how supplying leaf material from a combination of three cultivars, Cunningham, Redlands and Wondergraze of Leucaena (TriMix) to the fermentation system, would affect S. jonesii populations, the ability of the mixed microbial populations to degrade mimosine, 3,4-DHP and 2,3 DHP and if these microbial populations would grow and retain activity, in fermentations supplied leaf from each single Leucaena cultivar

Sapling age structure and growth series reveal a shift in recruitment dynamics of sugar maple and American beech over the last 40 years

Northern hardwoods have undergone a marked change in their dynamics, with American beech (Fagus grandifolia Ehrh.) increasing in abundance relative to sugar maple (Acer saccharum Marsh.). This study aims to better understand this sudden shift in recruitment dynamics. We performed an extensive analysis of the age structure, radial growth pattern, and release history on >700 saplings from 34 mature maple–beech stands of southern Quebec. We found (i) that the sapling age structures showed a progressive decrease in the establishment of maple relative to beech starting about 40 years ago, (ii) a change in the species growth hierarchy that started in the 1980s due to increasing radial growth of beech, (iii) that this growth trend is negligible for both maple and beech when we account for size and suppression status, and finally (iv) that the growth trend appears to be independent of present soil conditions. These results contrast with previous studies conducted at the adult stage that reported a growth decline for maple. We conclude that this change in recruitment dynamics is not related to growth, and consequently, further studies investigating this phenomenon should concentrate on establishment and survival

Shunt dysfunction patterns after transjugular intrahepatic portosystemic shunt creation using a combination of a generic stent-graft and bare-stents.

Even though transjugular intrahepatic portosystemic shunt (TIPS) using Fluency Stent-grafts provides good shunt patency rates, shunt dysfunction is a great concern after TIPS creation, occurring in up to 20% of cases within one year. The objective of this study was to describe shunt dysfunction patterns after TIPS creation using a combination of generic stent-grafts/bare-stents. Single-center retrospective study of all TIPS revisions between January 2005 and December 2020. TIPS revision angiograms were analyzed for stents' positions, stenoses' diameters, and stenoses' locations. Out of 99 TIPS, a total of 33 TIPS revisions were included. The median time to TIPS revision was 10.4 months. Angiograms showed four patterns of TIPS dysfunction-associated features (DAF), defined as follows: Type 1 was defined as stenosis located after the stent end in the hepatic vein (HV), type 2 as intra-stent stenosis located in the hepatic vein, type 3 as intra-stent stenosis or a kink in the parenchymal tract or the portal vein end of the TIPS, and type 4 as a complete TIPS occlusion. Types 1, 2, 3, and 4 were seen in 23 (69.7%), 5 (15.2%), 2 (6.1%), and 3 (9.1%) TIPS respectively. TIPS revision was successful in 30 (90.1%) patients with median pre- and post-TIPS revision PSG of 18.5 mmHg and 8 mmHg respectively (p < .001). Our results illustrate the four angiographic patterns of TIPS DAF after TIPS creation using a combination of generic stent-grafts/bare-stents and emphasize the need for appropriate stent length extending to the HV/inferior vena cava junction

Changes in mixed microbial inoculums to prevent the toxic side-effects in cattle grazing new varieties of Leucaena.

Leucaena leucocephala is a legume fodder crop that grows in tropical and subtropical environments. Leucaena provides a high quality feed for cattle boosting liveweight gain both per animal and per hectare, improving profitability for steer turnover by 121% compared with the base scenario of grazing buffel grass (Bowen and Chudleigh, 2018). A number of commercial leucaena cultivars, Cunningham, Peru, Taramba, El Salvadore, and Wondergraze, are used in Queensland. Leucaena contains a toxic amino acid, mimosine, which many rumen bacteria can degrade to a toxic metabolite 3-hydroxy-4-(1H)-pyridone (DHP). Productivity from leucaena-pasture can be reduced by DHP-induced depressions in intake. A DHP degrading bacterium, Synergistes jonesii was isolated from a mixed bacterial population isolated from a goat from Hawaii (Allison et al., 1992). For over twenty years DAF has provided a mixed bacterial rumen inoculum, containing S. jonesii, for cattle grazing Leucaenapastures, produced in an in vitro fermentation system with Cunningham cultivar as the feed source. All of the commercial cultivars are susceptible to attack by psyllid insects, limiting their use in higher rainfall areas - to address this limitation, a commercial psyllid-resistant cultivar, Redlands, was released in 2019. To assess if the leucaena inoculum is impacted by Redland’s anti-psyllid, chemical characteristics a series of 30 day in vitro anaerobic fermentations were undertaken feeding either Redlands, Cunningham or Wondergraze cultivars. The fermentations were conducted following the method of Klieve et al. (2002). Fermentations were started with either cryopreserved leuceana inoculum from a single day of a production fermentation; or day 30 of a Wondergraze or Redlands fermentation. Daily samples were taken and assays set up on days 10, 15, 20, 25 and 30 to monitor the fermentation’s ability to break down mimosine, 3,4 DHP and 2,3 DHP. Genomic DNA extracted from daily samples was used in a S. jonesii quantitative PCR and for barcoded amplicon sequencing of the 16S rRNA gene V3 –V4 region using the Illumina MiSeq platform