Holography is a technique that is used to display objects or scenes in three dimensions. Such three-dimensional (3D) images, or holograms, can be seen with the unassisted eye and are very similar to ...how humans see the actual environment surrounding them. The concept of 3D telepresence, a real-time dynamic hologram depicting a scene occurring in a different location, has attracted considerable public interest since it was depicted in the original Star Wars film in 1977. However, the lack of sufficient computational power to produce realistic computer-generated holograms and the absence of large-area and dynamically updatable holographic recording media have prevented realization of the concept. Here we use a holographic stereographic technique and a photorefractive polymer material as the recording medium to demonstrate a holographic display that can refresh images every two seconds. A 50 Hz nanosecond pulsed laser is used to write the holographic pixels. Multicoloured holographic 3D images are produced by using angular multiplexing, and the full parallax display employs spatial multiplexing. 3D telepresence is demonstrated by taking multiple images from one location and transmitting the information via Ethernet to another location where the hologram is printed with the quasi-real-time dynamic 3D display. Further improvements could bring applications in telemedicine, prototyping, advertising, updatable 3D maps and entertainment.
: The finite element method was used to model the moisture movement and strain in the wood supports of panel paintings, in response to changing climate conditions – temperature and relative humidity ...(RH). The material properties of lime wood (Tilia sp.), determined experimentally, were used in the modelling. Critical amplitudes of cyclic sinusoidal RH fluctuations generating strain of 0.002 in the most responsive tangential direction of the unrestrained, single wood panel, which the pictorial layer was assumed to endure without damage, were derived for the mid‐RH region as a function of cycle duration, panel thickness and diffusion configuration. Panels do not respond significantly to diurnal fluctuations or shorter. The panels respond more and more significantly when the duration of the fluctuations increases until the panel fully responds to each cycle. These fluctuation periods are 14 and 90 days at 20 °C for a panel thickness of 10 and 40 mm, respectively, with two faces of a panel diffusively opened. Sinusoidal RH variations bringing about wood’s full response have the critical amplitude of ±6% RH, that is strain of 0.002 endangering the pictorial layer is produced at such amplitude in the tangential direction of the unrestrained panel.
: Numerical modelling was used to follow the moisture movement and strain in a composite system – an unrestrained, single wood panel coated with a layer of gesso, in response to cyclic sinusoidal ...variations in relative humidity (RH). The allowable magnitude of the variations, below which physical damage of the gesso layer on the wood does not occur over a selected time of exposure, was derived as a function of cycle duration, panel thickness and moisture diffusion configuration. The dimensional response of wood substrate becomes subject to restraint by the applied layer of gesso. The panels do not respond significantly to diurnal fluctuations or shorter irrespectively of the panel thickness. The panels respond more and more significantly when the duration of the fluctuations increases until a certain critical period at which the panel fully responds to each cycle. The analysis of the data obtained indicates that moderate RH variations within the approximate range 50 ± 15% are safe. This safe range was derived using the extremes of conservative criteria of the gesso’s fatigue fracture and assumption of worst‐case wooden substrate response. The reduction of allowable amplitude of RH cycles because of decrease in the gesso’s modulus of elasticity and thickness is discussed.
A search for the doubly charmed baryon Xi_cc^+ in the decay mode Xi_cc^+ -> Lambda_c^+ K^- pi^+ is performed with a data sample, corresponding to an integrated luminosity of 0.65/fb, of pp collisions ...recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV/c^2. Upper limits at the 95% confidence level on the ratio of the Xi_cc^+ production cross-section times branching fraction to that of the Lambda_c^+, R, are given as a function of the Xi_cc^+ mass and lifetime. The largest upper limits range from R < 1.4 x 10^-2 for a lifetime of 100 fs to R < 3.4 x 10^-4 for a lifetime of 400 fs.
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