A framework for distributed interaction in intelligent environments

Ubiquitous computing is extending its applications to an increasing number of domains. "Monolithic" approaches use centralised systems, controlling devices and users' requests. A different solution can be found in works proposing "distributed" intelligent devices that communicate, without a central reasoner, creating little communities to support the user. If the former approach uses all the available sensors being more easily context-aware, the latter is scalable and naturally supports multiple users. In this work we introduce a model for a distributed network of entities in Intelligent Environments. Each node satisfies users' requests through Natural User Interfaces. If a node cannot produce the expected output, it communicates with others in the network, generating paths where the final target is undetermined and intermediate nodes do not understand the request; this is the focus of our work. The system learns parameters and connections in the initial topology. We tested the system in two scenarios. Our approach finds paths close to the optimum with reasonable connections

Attosecond pulse shaping around a Cooper minimum

High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straight-forward interpretation as an emission time, in contrast to the usual attochirp group delay. Instead, the rapid RDM phase variation caused by the CM reshapes the attosecond bursts.Comment: 5 pages, 5 figure

SIMULATING STRONG FIELD RESCATTERING USING ATTOSECOND LIGHT

An atom or molecule interacting with an intense, ultrafast laser pulse is a fundamental problem in modern physics. At intensities that are approximately one-tenth an atomic unit of field (50 V/A) the physics is well described by a semi-classical 3-step model where an electron tunnel ionizes, driven by the strong-field and then rescatters with its parent core. The consequence of this physics has opened the areas of attosecond science and spatial-temporal molecular imaging. However in a strong field experiment, the exponential rate of tunnel ionization fixes the release phase of the electron wave packet (EWP) at the extreme of the laser field. In this talk, we will describe a method that allows for more precise studies of the strong field process. The approach simulates the 3-step model by replacing the tunneling step with single-photon ionization by an attosecond XUV pulse. A phase-locked intense low-frequency field drives the EWP mimicking steps (2) and (3) but with little or no ionization. We will present both experimental and theoretical results demonstrating the viability of this approach

Classical Effects of Laser Pulse Duration on Strong-field Double Ionization

We use classical electron ensembles and the aligned-electron approximation to examine the effect of laser pulse duration on the dynamics of strong-field double ionization. We cover the range of intensities $10^{14}-10^{16} W/cm^2$ for the laser wavelength 780 nm. The classical scenario suggests that the highest rate of recollision occurs early in the pulse and promotes double ionization production in few-cycle pulses. In addition, the purely classical ensemble calculation predicts an exponentially decreasing recollision rate with each subsequent half cycle. We confirm the exponential behavior by trajectory back-analysis

Inelastic scattering of broadband electron wave packets driven by an intense mid-infrared laser field

Intense, 100 fs laser pulses at 3.2 and 3.6 um are used to generate, by multi-photon ionization, broadband wave packets with up to 400 eV of kinetic energy and charge states up to Xe+6. The multiple ionization pathways are well described by a white electron wave packet and field-free inelastic cross sections, averaged over the intensity-dependent energy distribution for (e,ne) electron impact ionization. The analysis also suggests a contribution from a 4d core excitation in xenon

Attosecond Synchronization of High-Order Harmonics from Midinfrared Drivers

The group delay dispersion, also known as the attochirp, of high-order harmonics generated in gases has been identified as the main intrinsic limitation to the duration of Fourier-synthesized attosecond pulses. Theory implies that the attochirp, which is inversely proportional to the laser wavelength, can be decreased at longer wavelength. Here we report the first measurement of the wavelength dependence of the attochirp using an all-optical, in situ method [N. Dudovich et al., Nature Phys. 2, 781 (2006)]. We show that a 2 μm driving wavelength reduces the attochirp with respect to 0.8 μm at comparable intensities

Characteristics of Hoarding in Older Adults

Objective: This study determined the clinical characteristics of late-life hoarding disorder (HD). Methods: Older adults (age 60 and older) with HD (n = 55) and without psychiatric diagnoses (n = 39) were compared on psychiatric, functional, cognitive, and health-related measures. Associations between age and clinical characteristics in a large sample of mixed age (n = 210; age range: 20-78) participants with HD were also determined. Results: Individuals with late-life HD were characterized by substantial impairments in psychiatric, functional, cognitive, and medical status. Health risks (e.g., risks of falls and fire) were also common. However, older age was generally not associated with increased severity of hoarding or other clinical correlates (with the exception of one global clinician-rated measure of severity). Conclusions: Late-life HD is characterized by considerable morbidity and health risks, and these characteristics may be consistent across the lifespan in cross-sectional mixed-age samples of individuals with HD

Scaling of Wave-Packet Dynamics in an Intense Midinfrared Field

A theoretical investigation is presented that examines the wavelength scaling from near-visible (0.8 µm) to midinfrared (2 µm) of the photoelectron distribution and high harmonics generated by a "single" atom in an intense electromagnetic field. The calculations use a numerical solution of the time-dependent Schrödinger equation (TDSE) in argon and the strong-field approximation in helium. The scaling of electron energies (λ^2), harmonic cutoff (λ^2), and attochirp (λ^-1) agree with classical mechanics, but it is found that, surprisingly, the harmonic yield follows a λ^-(5-6) scaling at constant intensity. In addition, the TDSE results reveal an unexpected contribution from higher-order returns of the rescattering electron wave packet