Mechanisms Generating Line Trajectories

In this work the problem of designing mechanisms to guide a line along a ruled surface is considered. This is motivated by the idea of illustrating, by means of a physical model, the set of lines in a general linear line complex. Cylindrical symmetry implies that the problem reduces of designing a mechanism to move a line along the regulus of a rectangular hyperbolic paraboloid. This leads to the study of several simple ruled surfaces and congruences of lines. In particular the paper studies the regulus of the elliptical hyperboloid, the cylindroid and linear line congruences. In each case relatively simple mechanisms are designed to constrain a line in the mechanism to a given space of lines

The slowing down of galaxy disks in dissipationless minor mergers

We have investigated the impact of dissipationless minor galaxy mergers on the angular momentum of the remnant. Our simulations cover a range of initial orbital characteristics and the system consists of a massive galaxy with a bulge and disk merging with a much less massive (one-tenth or one-twentieth) gasless companion which has a variety of morphologies (disk- or elliptical-like) and central baryonic mass concentrations. During the process of merging, the orbital angular momentum is redistributed into the internal angular momentum of the final system; the internal angular momentum of the primary galaxy can increase or decrease depending on the relative orientation of the orbital spin vectors (direct or retrograde), while the initially non-rotating dark matter halo always gains angular momentum. The specific angular momentum of the stellar component always decreases independent of the orbital parameters or morphology of the satellite, the decrease in the rotation velocity of the primary galaxy is accompanied by a change in the anisotropy of the orbits, and the ratio of rotation speed to velocity dispersion of the merger remnant is lower than the initial value, not only due to an increase in the dispersion but also to the slowing -down of the disk rotation. We briefly discuss several astrophysical implications of these results, suggesting that minor mergers do not cause a "random walk" process of the angular momentum of the stellar disk component of galaxies, but rather a steady decrease. Minor mergers may play a role in producing the large scatter observed in the Tully-Fisher relation for S0 galaxies, as well as in the increase of the velocity dispersion and the decrease in $v/\sigma$ at large radii as observed in S0 galaxies.Comment: 10 pages, 10 figures, accepted for publication in A&

Modeling the melting of multicomponent systems: the case of MgSiO3 perovskite under lower mantle conditions

Knowledge of the melting properties of materials, especially at extreme pressure conditions, represents a long-standing scientific challenge. For instance, there is currently considerable uncertainty over the melting temperatures of the high-pressure mantle mineral, bridgmanite (MgSiO3-perovskite), with current estimates of the melting T at the base of the mantle ranging from 4800 K to 8000 K. The difficulty with experimentally measuring high pressure melting temperatures has motivated the use of ab initio methods, however, melting is a complex multi-scale phenomenon and the timescale for melting can be prohibitively long. Here we show that a combination of empirical and ab-initio molecular dynamics calculations can be used to successfully predict the melting point of multicomponent systems, such as MgSiO3 perovskite. We predict the correct low-pressure melting T, and at high-pressure we show that the melting temperature is only 5000 K at 120 GPa, a value lower than nearly all previous estimates. In addition, we believe that this strategy is of general applicability and therefore suitable for any system under physical conditions where simpler models fail

Attitude towards drug therapy in a Community Mental Health Center evaluated by the Drug Attitude Inventory

Introduction: Negative attitude towards drug therapy can foster limited adherence to treatment, which remains one of the biggest obstacles for implementing effective treatments, especially long term. Purposes: The purposes of the study were 1) to evaluate the attitude towards drug therapy among a representative sample of patients treated in a community psychiatric service using 30-item Drug Attitude Inventory (DAI-30); 2) to evaluate the DAI-30 dimensions, applying factorial analysis; and 3) to highlight the socio-demographic and clinical variables correlated to DAI-30 score and factors. Methods: The DAI was administered, over a 7-month period, to all patients treated in our psychiatric outpatient services who agreed to participate in this study and provided their informed consent. Data were statistically analyzed. Results: With a response rate of 63.3%, 164 females and 136 males completed the DAI-30 with an average score of 14.24 (±10.46 SD), indicating moderately positive attitude towards drug therapy. The analysis of DAI-30 internal consistency confirmed its reliability (Cronbach’s alpha=0.84). Our factorial analysis highlighted three factors: Factor 1 (Cronbach’s alpha=0.81), composed of 7 items which indicate positive, trustful attitude; Factor 2 (Cronbach’s alpha=0.78), composed of 5 items indicating negative attitude of suspiciousness; and Factor 3 (Cronbach’s alpha=0.66), composed of 4 items suggesting defensive and control attitude towards drug therapy. Discussion: Among the selected variables, “monotherapy” and “total number of hospitalizations” were negatively correlated to the final score of DAI-30, whereas being “married” was positively correlated to it, in a statistically significant way, using the multiple linear regression model. These correlations suggest that positive attitude towards drug therapy could be reinforced by the condition of being married and reduced by relapses with hospitalization, as literature highlighted, and, paradoxically, by a monotherapy, which could suggest a sort of psychological dependence on therapy and, indirectly, on psychiatric service, potentially correlated to the long-term treatments of our patients

Stationary states in Langevin dynamics under asymmetric L\'evy noises

Properties of systems driven by white non-Gaussian noises can be very different from these systems driven by the white Gaussian noise. We investigate stationary probability densities for systems driven by $\alpha$-stable L\'evy type noises, which provide natural extension to the Gaussian noise having however a new property mainly a possibility of being asymmetric. Stationary probability densities are examined for a particle moving in parabolic, quartic and in generic double well potential models subjected to the action of $\alpha$-stable noises. Relevant solutions are constructed by methods of stochastic dynamics. In situations where analytical results are known they are compared with numerical results. Furthermore, the problem of estimation of the parameters of stationary densities is investigated.Comment: 9 pages, 9 figures, 3 table

Recent Advances on the Innate Immune Response to Coxiella burnetii.

Coxiella burnetii is an obligate intracellular Gram-negative bacterium and the causative agent of a worldwide zoonosis known as Q fever. The pathogen invades monocytes and macrophages, replicating within acidic phagolysosomes and evading host defenses through different immune evasion strategies that are mainly associated with the structure of its lipopolysaccharide. The main transmission routes are aerosols and ingestion of fomites from infected animals. The innate immune system provides the first host defense against the microorganism, and it is crucial to direct the infection towards a self-limiting respiratory disease or the chronic form. This review reports the advances in understanding the mechanisms of innate immunity acting during C. burnetii infection and the strategies that pathogen put in place to infect the host cells and to modify the expression of specific host cell genes in order to subvert cellular processes. The mechanisms through which different cell types with different genetic backgrounds are differently susceptible to C. burnetii intracellular growth are discussed. The subsets of cytokines induced following C. burnetii infection as well as the pathogen influence on an inflammasome-mediated response are also described. Finally, we discuss the use of animal experimental systems for studying the innate immune response against C. burnetii and discovering novel methods for prevention and treatment of disease in humans and livestock