Resonances in a spring-pendulum: algorithms for equivariant singularity theory

A spring-pendulum in resonance is a time-independent Hamiltonian model system for formal reduction to one degree of freedom, where some symmetry (reversibility) is maintained. The reduction is handled by equivariant singularity theory with a distinguished parameter, yielding an integrable approximation of the Poincaré map. This makes a concise description of certain bifurcations possible. The computation of reparametrizations from normal form to the actual system is performed by Gröbner basis techniques.

Thermodynamic formalism for systems with Markov dynamics

The thermodynamic formalism allows one to access the chaotic properties of equilibrium and out-of-equilibrium systems, by deriving those from a dynamical partition function. The definition that has been given for this partition function within the framework of discrete time Markov chains was not suitable for continuous time Markov dynamics. Here we propose another interpretation of the definition that allows us to apply the thermodynamic formalism to continuous time. We also generalize the formalism --a dynamical Gibbs ensemble construction-- to a whole family of observables and their associated large deviation functions. This allows us to make the connection between the thermodynamic formalism and the observable involved in the much-studied fluctuation theorem. We illustrate our approach on various physical systems: random walks, exclusion processes, an Ising model and the contact process. In the latter cases, we identify a signature of the occurrence of dynamical phase transitions. We show that this signature can already be unravelled using the simplest dynamical ensemble one could define, based on the number of configuration changes a system has undergone over an asymptotically large time window.Comment: 64 pages, LaTeX; version accepted for publication in Journal of Statistical Physic

An Intersecting Loop Model as a Solvable Super Spin Chain

In this paper we investigate an integrable loop model and its connection with a supersymmetric spin chain. The Bethe Ansatz solution allows us to study some properties of the ground state. When the loop fugacity $q$ lies in the physical regime, we conjecture that the central charge is $c=q-1$ for $q$ integer $< 2$. Low-lying excitations are examined, supporting a superdiffusive behavior for $q=1$. We argue that these systems are interesting examples of integrable lattice models realizing $c \leq 0$ conformal field theories.Comment: latex file, 7 page

Metastable states in glassy systems

Truly stable metastable states are an artifact of the mean-field approximation or the zero temperature limit. If such appealing concepts in glass theory as configurational entropy are to have a meaning beyond these approximations, one needs to cast them in a form involving states with finite lifetimes. Starting from elementary examples and using results of Gaveau and Schulman, we propose a simple expression for the configurational entropy and revisit the question of taking flat averages over metastable states. The construction is applicable to finite dimensional systems, and we explicitly show that for simple mean-field glass models it recovers, justifies and generalises the known results. The calculation emphasises the appearance of new dynamical order parameters.Comment: 4 fig., 20 pages, revtex; added references and minor change

Excited Charmed Mesons: Observations, Analyses and Puzzles

We review the status of recently observed positive parity charmed resonances, both in the non-strange and in the strange sector. We describe the experimental findings, the main theoretical analyses and the open problems deserving further investigations.Comment: LaTeX, 25 pages, 5 figures. Invited revie

The socio-economic value of natural riverbanks in the Netherlands

Abstract Ecologists and economists both use a different approach to determine the value of nature. Its ecological value can be measured using criteria like rarity and diversity of species in an ecosystem. The economic value can be determined using non-market valuation techniques. This paper focuses on an empirical application of the Contingent Valuation Method (CVM) to find out whether this valuation method is a suitable method to estimate the economic value of natural riverbanks in the Netherlands. Natural riverbanks will provide habitat for species that particularly depend on the land water transit area. Since common riverbanks do not provide this habitat, natural river banks increase biodiversity in the Netherlands. On the basis of technical and ecological characteristics nine different types of natural riverbanks were distinguished. For each type a laymen description was made. This description served as a basis for economic valuation by means of CVM. The results of the CVM study shows that the average willingness to pay for non-use of a natural riverbank varied between 16 and 25 Dutch guilders per household year. The willingness to pay for recreational use ranged from 1,07 to 2,50 guilders per visit. The generated outcomes proved to be consistent with results from other studies. At first sight, the economic value of natural riverbanks seemed to be higher than their construction and maintenance cost

Benchmarking pharmaceutical quality and manufacturing costs of 3D printing against conventional compounding methods for personalization of medicine

Background: Modification of commercially available medicine, e.g. splitting or dissolving of tablets or pharmacy compounding, is current clinical practice when desired oral dosage forms are unavailable. These practices are defined as conventional pharmacy compounding techniques and are used to produce medicines that are not commercially available. 3D printing is an automated compounding technique that allows pharmacists to personalize oral dosage forms. This study aimed to compare the quality of 3D printing hydrocortisone tablets with conventional pharmacy compounded formulations. Secondary and tertiary aims were to assess manufacturing costs of 3D printed tablets and to explore whether modifying the hydrocortisone drug release profile is possible using 3D printing. Methods: Semi-solid extrusion (SSE) 3D printing was used to produce immediate release and sustained release hydrocortisone tablets. Conventional compounded hydrocortisone formulations were used as comparators, including pharmacy compounded capsules, split tablets, and commercially available tablets dissolved in syringes. Results: Immediate and sustained release hydrocortisone tablets were printed successfully. The acceptance values (AVs) of 3D printed tablets, tablet dissolved-in-syringe and one batch of pharmacy compounded capsules were ≤ 15. The AVs of the other 2 pharmacy compounded capsules and split tablets were &gt; 15 and did not comply with content uniformity requirements. Personalization of 3D printed tablets was possible with a dose range of 0.5 – 10.0 mg. Costs of 3D printed tablets were &lt;€ 3.00 per tablet for both release profiles. Conclusion: SSE 3D printing leads to higher quality hydrocortisone tablets compared to conventional pharmacy compounding methods at acceptable manufacturing costs. 3D printing further allows for modification of hydrocortisone release profiles, which is not possible using conventional manufacturing methods. The low dose minitablets are especially suitable for pediatric indications requiring a personalized hydrocortisone dose.</p

Life is in the air: An expedition into the Amazonian atmosphere

Biological particles suspended in the atmosphere have a crucial role in the dynamics of the biosphere underneath. Although much attention is paid for the chemical and physical properties of these particles, their biological taxonomic identity, which is relevant for ecological research, remains little studied. We took air samples at 300 meters above the forest in central Amazonia, in seven periods of 7 days, and used high-throughput DNA sequencing techniques to taxonomically identify airborne fungal and plant material. The use of a molecular identification technique improved taxonomic resolution when compared to morphological identification. This first appraisal of airborne diversity showed that fungal composition was strikingly different from what has been recorded in anthropogenic regions. For instance, basidiospores reached 30% of the OTUs instead of 3–5% as found in the literature; and the orders Capnodiales and Eurotiales—to which many allergenic fungi and crop pathogens belong—were much less frequently recorded than Pleosporales, Polyporales, and Agaricales. Plant OTUs corresponded mainly to Amazonian taxa frequently present in pollen records such as the genera Helicostilys and Cecropia and/or very abundant in the region such as Pourouma and Pouteria. The origin of extra-Amazonian plant material is unknown, but they belong to genera of predominantly wind-pollinated angiosperm families such as Poaceae and Betulaceae. Finally, the detection of two bryophyte genera feeds the debate about the role of long distance dispersal in the distribution of these plants