Topology of music recommendation networks

We study the topology of several music recommendation networks, which arise from relationships between artist, co-occurrence of songs in play lists or experts' recommendation. The analysis uncovers the emergence of complex network phenomena in these kinds of recommendation networks, built considering artists as nodes and their resemblance as links. We observe structural properties that provide some hints on navigation and possible optimizations on the design of music recommendation systems. Finally, the analysis derived from existing music knowledge sources provides a deeper understanding of the human music similarity perception.     

Frequency decay for Navier–Stokes stationary solutions

We consider stationary Navier–Stokes equations in ${\mathbb{R}}^3$ with a regular external force and we prove the exponential frequency decay of the solutions. Moreover, if the external force is small enough, we give a pointwise exponential frequency decay for such solutions. If a damping term is added to the equation, a pointwise decay is obtained without the smallness condition over the force.     

Two adaptive scaled gradient projection methods for Stiefel manifold constrained optimization

Numerical Algorithms - This article is concerned with the problem of minimizing a smooth function over the Stiefel manifold. In order to address this problem, we introduce two adaptive scaled...     

Some considerations about NS5 and LST Hawking radiation

We have studied the Hawking radiation corresponding to the NS5 and Little String Theory (LST) black hole models using two semi-classical methods: the complex path method and a gravitational anomaly. After summarizing some known concepts about the thermodynamics of these theories, we have computed the emission rates for the two black hole models. The temperature calculated from, e.g. the well-known surface gravity expression, is shown to be identical to that obtained from both the computation of the gravitational anomaly and the complex path method. Moreover, the two semi-classical methods show that NS5 exhibits non-thermal behavior that contrasts with the thermal behavior of LST. We remark that energy conservation is the key factor leading to a non-thermal profile for NS5. In contrast, LST keeps a thermal profile even when energy conservation is considered because temperature in this model does not depend on energy.     

Electrical Behaviour of Heterobimetallic [MM′(EtCS2)4] (MM′=NiPd,NiPt, PdPt) and MM′X‐Chain Polymers [PtM(EtCS2)4I] (M=Ni,Pd)

Herein, we report the isolation of new heterobimetallic complexes [Ni_0.6Pd_1.4(EtCS₂)₄] ( 1 ), [NiPt(EtCS₂)₄] ( 2 ) and [Pd_0.4Pt_1.6(EtCS₂)₄] ( 3 ), which were constructed by using transmetallation procedures. Subsequent oxidation with iodine furnished the MM′X monodimensional chains [Ni_0.6Pt_1.4(EtCS₂)₄I] ( 4 ) and [Ni_0.1Pd_0.3Pt_1.6(EtCS₂)₄I] ( 5 ). The physical properties of these systems were investigated and the chain structures 4 and 5 were found to be reminiscent of the parent [Pt₂(EtCS₂)₄I] species. However, they were more sensitively dependent on the localised nature of the charge on the Ni ion, which caused spontaneous breaking of the conduction bands.     

Orienting Tetramolecular G‐Quadruplex Formation: The Quest for the Elusive RNA Antiparallel Quadruplex

DNA and RNA G‐quadruplexes (G4) are unusual nucleic acid structures involved in a number of key biological processes. RNA G‐quadruplexes are less studied although recent evidence demonstrates that they are biologically relevant. Compared to DNA quadruplexes, RNA G4 are generally more stable and less polymorphic. Duplexes and quadruplexes may be combined to obtain pure tetrameric species. Here, we investigated whether classical antiparallel duplexes can drive the formation of antiparallel tetramolecular quadruplexes. This concept was first successfully applied to DNA G4. In contrast, RNA G4 were found to be much more unwilling to adopt the forced antiparallel orientation, highlighting that the reason RNA adopts a different structure must not be sought in the loops but in the G‐stem structure itself. RNA antiparallel G4 formation is likely to be restricted to a very small set of peculiar sequences, in which other structural features overcome the formidable intrinsic barrier preventing its formation.