642 research outputs found
The craft settings in Kainua-Marzabotto: places and archaeological issues
Excavations in the Etruscan city of Marzabotto, the ancient Kainua, have brought to light a well-developed production structure over time which, especially for the Etruscan world, makes Marzabotto an especially favourable, paradigmatic context for the study of this particular aspect. Thanks to the contributions from the most recent investigations, together with the revision of older excavation data, this theme has in recent years benefitted from a series of updated considerations. The quality and variety of the data collected permits analyses from multiple points of view, not only on an architectural and urban planning level, but also on social, economic and political-institutional levels
A negative mass theorem for surfaces of positive genus
We define the "sum of squares of the wavelengths" of a Riemannian surface
(M,g) to be the regularized trace of the inverse of the Laplacian. We normalize
by scaling and adding a constant, to obtain a "mass", which is scale invariant
and vanishes at the round sphere. This is an anlaog for closed surfaces of the
ADM mass from general relativity. We show that if M has positive genus then on
each conformal class, the mass attains a negative minimum. For the minimizing
metric, there is a sharp logarithmic Hardy-Littlewood-Sobolev inequality and a
Moser-Trudinger-Onofri type inequality.Comment: 8 page
Controlled Fabrication of Metallic Electrodes with Atomic Separation
We report a new technique for fabricating metallic electrodes on insulating
substrates with separations on the 1 nm scale. The fabrication technique, which
combines lithographic and electrochemical methods, provides atomic resolution
without requiring sophisticated instrumentation. The process is simple,
controllable, reversible, and robust, allowing rapid fabrication of electrode
pairs with high yield. We expect the method to prove useful in interfacing
molecular-scale structures to macroscopic probes and electronic devices
Anti-Kaon Induced Reactions on the Nucleon
Using a previously established effective Lagrangian model we describe
anti-kaon induced reactions on the nucleon. The dominantly contributing
channels in the cm-energy region from threshold up to 1.72 GeV are included (K
N, \pi \Sigma, \pi \Lambda). We solve the Bethe-Salpeter equation in an unitary
-matrix approximation.Comment: 21 pages, 13 figures, minor typos corrected, accepted for publication
in Phys. Rev.
Situated Learning with Bebras Tasklets
A Bebras short task, a tasklet, is designed to provide a source for exploring a computational thinking concept: at the end of the contest it could be used as a starting point to delve deeper into a computing topic. In this paper we report an experience which aims at taking full advantage of the potential of Bebras tasklets. A math teacher asked her pupils to act as Bebras \u201ctrainers\u201d for younger mates. The pupils, in pairs, were assigned to design and prepare a tangible game inspired by a Bebras tasklet, devised for the younger pupils to practice. They also had to explain the game to the younger pupils, make them play and support them in solving it. In carrying out this assignment the pupils acting as trainers had to deeply explore the Bebras tasklet and face its computational thinking challenge, and also practiced soft skills as collaborating with peers towards a common goal, adapting language and communicative style to engage with younger mates, devising and designing a tangible object, and planning its creation. The experience proved that using Bebras tasklets as the social and cultural context for situated learning of computational thinking competencies is indeed quite productive
Inferring biochemical reaction pathways: the case of the gemcitabine pharmacokinetics.
Background
The representation of a biochemical system as a network is the precursor of any mathematical model of the processes driving the dynamics of that system. Pharmacokinetics uses mathematical models to describe the interactions between drug, and drug metabolites and targets and through the simulation of these models predicts drug levels and/or dynamic behaviors of drug entities in the body. Therefore, the development of computational techniques for inferring the interaction network of the drug entities and its kinetic parameters from observational data is raising great interest in the scientic community of pharmacologists. In fact, the network inference is a set of mathematical procedures deducing the structure of a model from the experimental data associated to the nodes of the network of interactions. In this paper, we deal with the inference of a pharmacokinetic network from the concentrations of the drug and its metabolites observed at discrete time points.
Results
The method of network inference presented in this paper is inspired by the theory of time-lagged correlation inference with regard to the deduction of the interaction network, and on a maximum likelihood approach with regard to the estimation of the kinetic parameters of the network. Both network inference and parameter estimation have been designed specically to identify systems of biotransformations, at the biochemical level, from noisy time-resolved experimental data. We use our inference method to deduce the metabolic pathway of the gemcitabine. The inputs to our inference algorithm are the experimental time series of the concentration of gemcitabine and its metabolites. The output is the set of reactions of the metabolic network of the gemcitabine.
Conclusions
Time-lagged correlation based inference pairs up to a probabilistic model of parameter inference from metabolites time series allows the identication of the microscopic pharmacokinetics and pharmacodynamics of a drug with a minimal a priori knowledge. In fact, the inference model presented in this paper is completely unsupervised. It takes as input the time series of the concetrations of the parent drug and its metabolites. The method, applied to the case study of the gemcitabine pharmacokinetics, shows good accuracy and sensitivit
Genotoxic activity of 2-amino-N-hydroxylaminopurine (AHA) in Aspergillus nidulans
In Aspergillus nidulans, as well as in other eukaryotic cells, not all base analogs are mutagenic. For example, 2-aminopurine (2-AP) is non-mutagenic or weakly mutagenic for eukaryotes while it is mutagenic for bacteria. Because of their potential use in genetical research, an effort has been made to find base analogs mutagenic for eukaryotic cells. Work in this field has been successful: in fact, 6- hydroxylamino-purine (HAP) and 2-amino-N-hydroxylaminopurine (AHA) have been found mutagenic for yeast as well as for other eukaryotic cells. (Pavlov et al. 1991, Mut. Res. 253:33-46). In particular, Brockman et al. (Mut. Res. 177:61-75, 1987) tested the mutagenic activity of HAP and AHA in Neurospora crassa and found that AHA is about equally mutagenic as HAP at low doses but more mutagenic at high doses. In this paper we report the genotoxic activity of AHA in A. nidulans. In this mold, we have tested AHA-induced lethality and mutagenic and recombinogenic effect
Aharonov-Bohm effect and broken valley-degeneracy in graphene rings
We analyze theoretically the electronic properties of Aharonov-Bohm rings
made of graphene. We show that the combined effect of the ring confinement and
applied magnetic flux offers a controllable way to lift the orbital degeneracy
originating from the two valleys, even in the absence of intervalley
scattering. The phenomenon has observable consequences on the persistent
current circulating around the closed graphene ring, as well as on the ring
conductance. We explicitly confirm this prediction analytically for a circular
ring with a smooth boundary modelled by a space-dependent mass term in the
Dirac equation. This model describes rings with zero or weak intervalley
scattering so that the valley isospin is a good quantum number. The tunable
breaking of the valley degeneracy by the flux allows for the controlled
manipulation of valley isospins. We compare our analytical model to another
type of ring with strong intervalley scattering. For the latter case, we study
a ring of hexagonal form with lattice-terminated zigzag edges numerically. We
find for the hexagonal ring that the orbital degeneracy can still be controlled
via the flux, similar to the ring with the mass confinement.Comment: 7 pages, 7 figures, replaced with considerably extended new versio
Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces
We report on a study of magnetotransport in LaAlO3/SrTiO3 interfaces
characterized by mobilities of the order of several thousands cm/Vs. We
observe Shubnikov-de Haas oscillations that indicate a two-dimensional
character of the Fermi surface. The frequency of the oscillations signals a
multiple sub-bands occupation in the quantum well or a multiple valley
configuration. From the temperature dependence of the oscillation amplitude we
extract an effective carrier mass \,. An electric field
applied in the back-gate geometry increases the mobility, the carrier density
and the oscillation frequency.Comment: 4 pages, 4 figure
A Single-centre, Before-After Study of the Short- and Long-term Efficacy of NariventÂź in the Treatment of Nasal Congestion
Objective:Nasal congestion is a common symptom in allergic and nonallergic rhinitis, rhinosinusitis and nasal polyposis. The present study evaluated the clinical effectiveness of NariventÂź, an osmo..
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