Intelligent Roundabout Insertion using Deep Reinforcement Learning

An important topic in the autonomous driving research is the development of maneuver planning systems. Vehicles have to interact and negotiate with each other so that optimal choices, in terms of time and safety, are taken. For this purpose, we present a maneuver planning module able to negotiate the entering in busy roundabouts. The proposed module is based on a neural network trained to predict when and how entering the roundabout throughout the whole duration of the maneuver. Our model is trained with a novel implementation of A3C, which we will call Delayed A3C (D-A3C), in a synthetic environment where vehicles move in a realistic manner with interaction capabilities. In addition, the system is trained such that agents feature a unique tunable behavior, emulating real world scenarios where drivers have their own driving styles. Similarly, the maneuver can be performed using different aggressiveness levels, which is particularly useful to manage busy scenarios where conservative rule-based policies would result in undefined waits

Electronic and magnetic states in core multishell nanowires: Edge localization, Landau levels and Aharonov-Bohm oscillations

We study the electronic states of hexagonal core multishell semiconductor nanowires, including the effect of magnetic fields. We find that the two dimensional electron states formed at the interface between different layers are mostly localized at the six edges of the hexagonal prism, and behave as a set of quasi-1D quantum channels. They can be manipulated by magnetic fields either parallel or perpendicular to the wire axis. These results can be rationalized in terms of Aharonov-Bohm oscillations or Landau level formation. We also show that inter-channel coupling and magnetic behavior is influenced by the geometric details of the nanowires. © 2009 IOP Publishing Ltd

Magnetic states in prismatic core multishell nanowires

We study the electronic states of core multi-shell semiconductor nanowires, including the effect of strong magnetic fields. We show that the multi-shell overgrowth of a free-standing nanowire, together with the prismatic symmetry of the substrate, may induce quantum confinement of carriers in a set of quasi-1D quantum channels corresponding to the nanowire edges. Localization and inter-channel tunnel coupling are controlled by the curvature at the edges and the diameter of the underlying nanowire. We also show that a magnetic field may induce either Aharonov-Bohm oscillations of the energy levels in the axial configuration, or a dimensional transition of the quantum states from quasi-1D to Landau levels for fields normal to the axis. Explicit predictions are given for nanostructures based on GaAs, InAs, and InGaN with different symmetries.Comment: 13 pages, 4 figures, To be published in Nano Letter

Microstratigraphic Records as Tools for the Detection of Climatic Changes in Tana di Badalucco Cave (Liguria, NW Italy)

Tana di Badalucco cave is located in Imperia (Liguria, Italy), not far from the French border. This site is scarcely known and it has never been studied accurately, even though dierent archaeological excavations have returned really important elements, both in the archaeological and the paleoenvironmental aspects. Its stratigraphy ranges from Middle Paleolithic to Metal Ages, thus it has registered important climate and environmental variations specific to the Upper Pleistocene and Holocene. From 2012, the Soprintendenza Archeologia della Liguria, the Museo di Archeologia Ligure, and DiSTAV (University of Genova) have been collaborating in order to finally study this promising and complex stratigraphy, trying to reconstruct the paleoenvironmental context of the region. In this work, we present what we were able to assess thanks to the use of micromorphology, the study of undisturbed thin soil sections. This technique has proven useful in recognizing the alternating of cold and warmer conditions during the Quaternary, as well as in identifying primitive signs of human and animal occupation

Cylindrical Two-Dimensional Electron Gas in a Transverse Magnetic Field

We compute the single-particle states of a two-dimensional electron gas confined to the surface of a cylinder immersed in a magnetic field. The envelope-function equation has been solved exactly for both an homogeneous and a periodically modulated magnetic field perpendicular to the cylinder axis. The nature and energy dispersion of the quantum states reflects the interplay between different lengthscales, namely, the cylinder diameter, the magnetic length, and, possibly, the wavelength of the field modulation. We show that a transverse homogeneous magnetic field drives carrier states from a quasi-2D (cylindrical) regime to a quasi-1D regime where carriers form channels along the cylinder surface. Furthermore, a magnetic field which is periodically modulated along the cylinder axis may confine the carriers to tunnel-coupled stripes, rings or dots on the cylinder surface, depending on the ratio between the the field periodicity and the cylinder radius. Results in different regimes are traced to either incipient Landau levels formation or Aharonov-Bohm behaviour.Comment: 23 pages, 14 figure

Weight Loss Expectations in Obese Patients and Treatment Attrition: An Observational Multicenter Study

Objective: To investigate the influence of weight loss expectations (expected 1-year BMI loss, dream and maximum acceptable BMI) on attrition in obese patients seeking treatment. Research Methods and Procedures: Obese subjects (1785; 1393 women; median age, 46 years; median BMI, 36.7 kg/m2) seeking treatment in 23 medical Italian centers were evaluated. Baseline diet and weight history, weight loss expectations, and primary motivation for seeking treatment (health or improving appearance) were systematically recorded. Psychiatric distress, binge eating, and body image dissatisfaction were tested at baseline by self-administered questionnaires (Symptom Check List-90, Binge Eating Scale, and Body Uneasiness Test). Attrition and BMI change at 12 months were prospectively recorded. Results: At 12 months, 923 of 1785 patients (51.7%) had discontinued treatment. Compared with continuers, dropouts had a significantly lower age, a lower age at first dieting, lower dream BMI, a higher expected 1-year BMI loss, and a higher weight phobia. At logistic regression analysis, the strongest predictors of attrition at 12 months were lower age and higher expected 1-year BMI loss. The risk of drop-out increased systematically for unit increase in expected BMI loss at 12 months (hazard ratio, 1.12; 95% confidence interval, 1.04 to 1.20; p 0.0018). The risk was particularly elevated in the first 6 months. Discussion: Baseline weight loss expectations are independent cognitive predictors of attrition in obese patients entering a weight-losing program; the higher the expectations, the higher attrition at 12 months. Unrealistic weight goals should be tackled at the very beginning of treatment

Coherent ultrafast charge transfer in an organic photovoltaic blend

Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system

Interaction of Vault Particles with Estrogen Receptor in the MCF-7 Breast Cancer Cell

A 104-kD protein was coimmunoprecipitated with the estrogen receptor from the flowtrough of a phosphocellulose chromatography of MCF-7 cell nuclear extract. mAbs to this protein identified several cDNA clones coding for the human 104-kD major vault protein. Vaults are large ribonucleoprotein particles of unknown function present in all eukaryotic cells. They have a complex morphology, including several small molecules of RNA, but a single protein species, the major vault protein, accounts for >70% of their mass. Their shape is reminiscent of the nucleopore central plug, but no proteins of known function have been described to interact with them. Western blot analysis of vaults purified on sucrose gradient showed the presence of estrogen receptor co-migrating with the vault peak. The AER317 antibody to estrogen receptor coimmunoprecipitated the major vault protein and the vault RNA also in the 20,000 g supernatant fraction. Reconstitution experiments of estrogen receptor fragments with the major vault protein mapped the site of the interaction between amino acids 241 and 280 of human estrogen receptor, where the nuclear localization signal sequences are located. Estradiol treatment of cells increased the amount of major vault protein present in the nuclear extract and coimmunoprecipitated with estrogen receptor, whereas the anti-estrogen ICI182,780 had no effect. The hormone-dependent interaction of vaults with estrogen receptor was reproducible in vitro and was prevented by sodium molybdate. Antibodies to progesterone and glucocorticoid receptors were able to coimmunoprecipitate the major vault protein. The association of nuclear receptors with vaults could be related to their intracellular traffic

Tracking the coherent generation of polaron pairs in conjugated polymers

The optical excitation of organic semiconductors not only generates charge-neutral electron-hole pairs (excitons), but also charge-separated polaron pairs with high yield. The microscopic mechanisms underlying this charge separation have been debated for many years. Here we use ultrafast two-dimensional electronic spectroscopy to study the dynamics of polaron pair formation in a prototypical polymer thin film on a sub-20-fs time scale. We observe multi-period peak oscillations persisting for up to about 1 ps as distinct signatures of vibronic quantum coherence at room temperature. The measured two-dimensional spectra show pronounced peak splittings revealing that the elementary optical excitations of this polymer are hybridized exciton-polaron-pairs, strongly coupled to a dominant underdamped vibrational mode. Coherent vibronic coupling induces ultrafast polaron pair formation, accelerates the charge separation dynamics and makes it insensitive to disorder. These findings open up new perspectives for tailoring light-to-current conversion in organic materials