An Economic Model of Fair Use

The doctrine of fair use allows limited copying of creative works based on the rationale that copyright holders would consent to such uses if bargaining were possible. This paper develops a formal model of fair use in an effort to derive the efficient legal standard for applying the doctrine. The model interprets copies and originals as differentiated products and defines fair use as a threshold separating permissible copying from infringement. The analysis highlights the role of technology in shaping the efficient standard. Discussion of several key cases illustrates the applicability of the model.Fair use, Copyright law, Technological improvement

Dlgh1 coordinates actin polymerization, synaptic T cell receptor and lipid raft aggregation, and effector function in T cells.

Lipid raft membrane compartmentalization and membrane-associated guanylate kinase (MAGUK) family molecular scaffolds function in establishing cell polarity and organizing signal transducers within epithelial cell junctions and neuronal synapses. Here, we elucidate a role for the MAGUK protein, Dlgh1, in polarized T cell synapse assembly and T cell function. We find that Dlgh1 translocates to the immune synapse and lipid rafts in response to T cell receptor (TCR)/CD28 engagement and that LckSH3-mediated interactions with Dlgh1 control its membrane targeting. TCR/CD28 engagement induces the formation of endogenous Lck-Dlgh1-Zap70-Wiskott-Aldrich syndrome protein (WASp) complexes in which Dlgh1 acts to facilitate interactions of Lck with Zap70 and WASp. Using small interfering RNA and overexpression approaches, we show that Dlgh1 promotes antigen-induced actin polymerization, synaptic raft and TCR clustering, nuclear factor of activated T cell activity, and cytokine production. We propose that Dlgh1 coordinates TCR/CD28-induced actin-driven T cell synapse assembly, signal transduction, and effector function. These findings highlight common molecular strategies used to regulate cell polarity, synapse assembly, and transducer organization in diverse cellular systems

Detailed study of SNR G306.3-0.9 using XMM-Newton and Chandra observations

We used combined data from XMM-Newton and Chandra observatories to study the X-ray morphology of SNR G306.3-0.9. A spatially-resolved spectral analysis was used to obtain physical and geometrical parameters of different regions of the remnant. Spitzer infrared observations were also used to constrain the progenitor supernova and study the environment in which the SNR evolved. The X-ray morphology of the remnant displays a non-uniform structure of semi-circular appearance, with a bright southwest region and very weak or almost negligible X-ray emission in its northern part. These results indicate that the remnant is propagating in a non-uniform environment as the shock fronts are encountering a high-density medium, where enhanced infrared emission is detected. The X-ray spectral analysis of the selected regions shows distinct emission-line features of several metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by a combination of two absorbed thermal plasma models: one in equilibrium ionization with a mean temperature of ~0.19 keV, and another out of equilibrium ionization at a higher temperature of ~1.1 or 1.6-1.9 keV. For regions located in the northeast, central, and southwest part of the SNR, we found elevated abundances of Si, S, Ar, Ca, and Fe, typical of ejecta material. The outer regions located northwest and south show values of the abundances above solar but lower than to those found in the central regions. This suggests that the composition of the emitting outer parts of the SNR is a combination of ejecta and shocked material of the interstellar medium. The comparison between the S/Si, Ar/Si, and Ca/Si abundances ratios (1.75, 1.27, and 2.72 in the central region, respectively), favor a Type Ia progenitor for this SNR, a result that is also supported by an independent morphological analysis using X-ray and IR data.Comment: 8 pages, 7 figures. Accepted by Astronomy and Astrophysic

Seismic reliability analysis of isolated deck bridges using friction pendulum devices

In this study, the seismic reliability of multi-span continuous deck bridges equipped with isolation friction pendulum (FP) devices is investigated. The relevant aleatory uncertainties associated to the sliding friction coefficient of the FP isolators and to the seismic inputs are considered. A six-degree-of-freedom model is established to reproduce the elastic behavior of the reinforced concrete (RC) pier, the stiff response of the deck supported by the isolation devices and the non-linear response of the FPS bearings which depends on the sliding velocity. Moreover, the RC abutment is assumed as infinitely rigid. For what concerns the seismic inputs, a group of natural seismic records having various characteristics is adopted and properly scaled to increasing levels of intensity. The random variability of the friction coefficient is modelled by suitable probabilistic distribution. Then, considering several bridges and isolator configurations, the fragility curves of the RC pier and of the isolator devices (FP) are determined. Finally, in agreement with the hazard curve of the specific site, the convolution integral is adopted to determine the seismic reliability curves in the performance domain

Distribution of parallel vortices studied by spin-polarized neutron reflectivity and magnetization

We present the studies of non-uniformly distributed vortices in Nb/Al multilayers at applied field near parallel to film surface by using spin-polarized neutron reflectivity (SPNR) and DC magnetization measurements. We have observed peaks above the lower critical field, Hc1, in the M-H curves from the multilayers. Previous works with a model calculation of minimizing Gibbs free energy have suggested that the peaks could be ascribed to vortex line transitions for spatial commensuration in a thin film superconductor. In order to directly determine the distribution of vortices, we performed SPNR measurements on the multilayer and found that the distribution and density of vortices are different at ascending and descending fields. At ascending 2000 Oe which is just below the first peak in the M-H curve, SPNR shows that vortices are mostly localized near a middle line of the film meanwhile the vortices are distributed in broader region at the descending 2000 Oe. That is related to the observation of more vortices trapped at the descending field. As the applied field is sightly tilted (< 3.5degree), we observe another peak at a smaller field. The peak position is consistent with the parallel lower critical field (Hc1||). We discuss that the vortices run along the applied field below Hc1|| and rotate parallel to the surface at Hc1||.Comment: 17 pages, 9 figure

Nuclear quantum effects in ab initio dynamics: theory and experiments for lithium imide

Owing to their small mass, hydrogen atoms exhibit strong quantum behavior even at room temperature. Including these effects in first principles calculations is challenging, because of the huge computational effort required by conventional techniques. Here we present the first ab-initio application of a recently-developed stochastic scheme, which allows to approximate nuclear quantum effects inexpensively. The proton momentum distribution of lithium imide, a material of interest for hydrogen storage, was experimentally measured by inelastic neutron scattering experiments and compared with the outcome of quantum thermostatted ab initio dynamics. We obtain favorable agreement between theory and experiments for this purely quantum mechanical property, thereby demonstrating that it is possible to improve the modelling of complex hydrogen-containing materials without additional computational effort