Propulsion with a Rotating Elastic Nanorod

The dynamics of a rotating elastic filament is investigated using Stokesian simulations. The filament, straight and tilted with respect to its rotation axis for small driving torques, undergoes at a critical torque a strongly discontinuous shape bifurcation to a helical state. It induces a substantial forward propulsion whatever the sense of rotation: a nanomechanical force-rectification device is established.Comment: 4 pages, 3 figures, to be published in Physical Review Letter

Photo-excitation of a light-harvesting supra-molecular triad: a Time-Dependent DFT study

We present the first time-dependent density-functional theory (TDDFT) calculation on a light harvesting triad carotenoid-diaryl-porphyrin-C60. Besides the numerical challenge that the ab initio study of the electronic structure of such a large system presents, we show that TDDFT is able to provide an accurate description of the excited state properties of the system. In particular we calculate the photo-absorption spectrum of the supra-molecular assembly, and we provide an interpretation of the photo-excitation mechanism in terms of the properties of the component moieties. The spectrum is in good agreement with experimental data, and provides useful insight on the photo-induced charge transfer mechanism which characterizes the system.Comment: Accepted for publication on JPC, March 09th 200

First principle theory of correlated transport through nano-junctions

We report the inclusion of electron-electron correlation in the calculation of transport properties within an ab initio scheme. A key step is the reformulation of Landauer's approach in terms of an effective transmittance for the interacting electron system. We apply this framework to analyze the effect of short range interactions on Pt atomic wires and discuss the coherent and incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure

Hybrid applications over XML - integrating the declarative and navigational approaches

We discuss the design of a quasi-statically typed language for XML in which data may be associated with different structures and different algebras in different scopes, whilst preserving identity. In declarative scopes, data are trees and may be queried with the full flexibility associated with XML query algebras. In procedural scopes, data have more conventional structures, such as records and sets, and can be manipulated with the constructs normally found in mainstream languages. For its original form of structural polymorphism, the language offers integrated support for the development of hybrid applications over XML, where data change form to re flct programming expectations and enable their enforcement

SY29-2CONTRASTING THE CONCEPTS OF COMPLIANCE AND ENGAGEMENT

Compliance has been defined as "the degree of constancy and accuracy with which a patient follows a prescribed regimen, and engagement can be thought of as the "emotional involvement or commitment of a person. Compliance is related to algorithmic tasks with well-defined rules of conduct and with a priori acknowledged outcomes. They follow (a) a set of established instructions, (b) down a single pathway, (c) to one conclusion. Algorithmic tasks, which require compliance to be successful, are best suited to routine work. Engagement, on the other hand, is related to heuristic tasks, for which no algorithm exists, where one has to experiment with possibilities and devise new solutions. Therapy, and even more specifically, psychotherapy with addicted patients, has continuously to be developed between these two pole

Raman signatures of classical and quantum phases in coupled dots: A theoretical prediction

We study electron molecules in realistic vertically coupled quantum dots in a strong magnetic field. Computing the energy spectrum, pair correlation functions, and dynamical form factor as a function of inter-dot coupling via diagonalization of the many-body Hamiltonian, we identify structural transitions between different phases, some of which do not have a classical counterpart. The calculated Raman cross section shows how such phases can be experimentally singled out.Comment: 9 pages, 2 postscript figures, 1 colour postscript figure, Latex 2e, Europhysics Letters style and epsfig macros. Submitted to Europhysics Letter

Thermal denaturation of fluctuating finite DNA chains: the role of bending rigidity in bubble nucleation

Statistical DNA models available in the literature are often effective models where the base-pair state only (unbroken or broken) is considered. Because of a decrease by a factor of 30 of the effective bending rigidity of a sequence of broken bonds, or bubble, compared to the double stranded state, the inclusion of the molecular conformational degrees of freedom in a more general mesoscopic model is needed. In this paper we do so by presenting a 1D Ising model, which describes the internal base pair states, coupled to a discrete worm like chain model describing the chain configurations [J. Palmeri, M. Manghi, and N. Destainville, Phys. Rev. Lett. 99, 088103 (2007)]. This coupled model is exactly solved using a transfer matrix technique that presents an analogy with the path integral treatment of a quantum two-state diatomic molecule. When the chain fluctuations are integrated out, the denaturation transition temperature and width emerge naturally as an explicit function of the model parameters of a well defined Hamiltonian, revealing that the transition is driven by the difference in bending (entropy dominated) free energy between bubble and double-stranded segments. The calculated melting curve (fraction of open base pairs) is in good agreement with the experimental melting profile of polydA-polydT. The predicted variation of the mean-square-radius as a function of temperature leads to a coherent novel explanation for the experimentally observed thermal viscosity transition. Finally, the influence of the DNA strand length is studied in detail, underlining the importance of finite size effects, even for DNA made of several thousand base pairs.Comment: Latex, 28 pages pdf, 9 figure

Fluctuation induced interactions between domains in membranes

We study a model lipid bilayer composed of a mixture of two incompatible lipid types which have a natural tendency to segregate in the absence of membrane fluctuations. The membrane is mechanically characterized by a local bending rigidity $\kappa(\phi)$ which varies with the average local lipid composition $\phi$. We show, in the case where $\kappa$ varies weakly with $\phi$, that the effective interaction between lipids of the same type can either be everywhere attractive or can have a repulsive component at intermediate distances greater than the typical lipid size. When this interaction has a repulsive component, it can prevent macro-phase separation and lead to separation in mesophases with a finite domain size. This effect could be relevant to certain experimental and numerical observations of mesoscopic domains in such systems.Comment: 9 pages RevTex, 1 eps figur

Cadmium and other hazardous elements in phosphatic fertilizers in conformity to the new European Regulation 2019/1009

The current European Fertilizers Regulation EC n. 2003/2003 does not include any direction for the content in cadmium [1]. On 25 June 2019, the new EU Fertilizing Products and Amending Regulation (EU-FPR) 2019/1009 was promulgated by the European Parliament and the Council, fixing an initial and temporary limit for Cd content in inorganic macronutrient fertilizer to 60 mgCd ∙ kgP2O5-1 [2]. The new European limit for Cd would be the most stringent in the world and only 15% of the phosphorite deposits currently exploited exhibits a low cadmium content complying with the new standard once processed to fertilizer. Since there are no substitutes for phosphate rock in phosphatic fertilizer production [3,4], the outcome of the new standard application would make unsustainable the supply of phosphatic fertilizers. This will result in a short-term measure that goes beyond the long-term sustainability objective of the proposal. In addition, the new standard will inevitably and disproportionately penalise some producers, mainly from developing countries in North Africa. It is therefore important to investigate for Cd and other hazardous elements content in fertilizers used for food production. The present research has analysed a total of 41 samples of fertilizers both for hobby and professional use obtained from the Italian market. Producers of Western and Middle Eastern Europe use the same phosphorite deposits to obtain fertilizers, thus the results of this investigation can be extended to the whole area. Obtained samples were initially pulverized in a ball mill and subjected to acid digestion in a microwave oven. Different acid digestion methods (HNO3 - HF - aqua regia - H2O2) were developed and tested for processing phosphate rock, inorganic and organo-mineral fertilizers to optimize the dissolution of different matrices. Standard reference materials, NIST SRM-695 (NPK fertilizer) and BCR-032 (Morocco phosphate rock) were processed using the same methods. Elemental analyses were performed in ICP-OES (Na, Mg, Al, Si, P, S, K, Ca, Fe, Se, Hg) and ICP-MS (Li, Be, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Cd, Sn, Sb, Ba, Tl, Pb, Bi, U). The first results showed very low Cd concentrations in hobby products. This commercial sector is known to import low-cost phosphate rock from Russia or Cola Peninsula, with a lower nutrient quality, but also a lower Cd content in comparison with professional products. Uranium content was found in relatively high concentrations and a radioactivity study has been considered as a logical extension of this research. The next analysis of more samples collected in spring will account for different fertilizer types used in distinct agricultural phases. [1] European Union. Off. J. Eur. Union. 2003, EUR-Lex - 32003R2003. [2] European Union. Off. J. Eur. Union. 2019, EUR-Lex - 32019R1009. [3] Mar, S.S., Okazaki, M. Microchem. J. 2012, 104, 17–21. [4] Ulrich, A.E. Sci. Total Environ. 2019, 650(1), 541–545