Synthetic magnetism for photon fluids

We develop a theory of artificial gauge fields in photon fluids for the cases of both second-order and third-order optical nonlinearities. This applies to weak excitations in the presence of pump fields carrying orbital angular momentum, and is thus a type of Bogoliubov theory. The resulting artificial gauge fields experienced by the weak excitations are an interesting generalization of previous cases and reflect the PT-symmetry properties of the underlying non-Hermitian Hamiltonian. We illustrate the observable consequences of the resulting synthetic magnetic fields for examples involving both second-order and third-order nonlinearities

An 80 Mbit/s radiation-tolerant optical receiver for the CMS digital optical link

The CMS tracker slow control system will use approximately 1000 digital optical links for the transmission of timing, trigger and control signals. In this system, the 80 Mbit/s optical receiver at the detector end of each optical link has to be radiation hard since it will operate in the severe radiation environment of the CMS tracker (10 Mrad in 10 years). We have developed a prototype circuit in a 0.25 mu m commercial CMOS process using radiation tolerant layout practices to achieve the required radiation tolerance. This effective technique consists in the systematic use of enclosed (edgeless) NMOS transistors and guardrings, and relies in the natural total dose hardness of the thin gate oxide of deep submicron processes. The circuit features an automatic gain control loop allowing detection of wide dynamic range input signals (-20 to -3 d Bm) with minimum noise, compatible with the maximum expected radiation-induced drop in quantum efficiency of the PIN photodiode. A second feedback loop compensates a photodiode leakage current up to 100 mu A, and the circuit outputs an LVDS signal. Four receiver channels were integrated in a 2*2 mm/sup 2/ chip, out of which two were simultaneously bonded to two PIN photodiodes, and their BER performance was measured before and after an irradiation with 10 keV X-rays up to 20 Mrad (SiO/sub 2/). (11 refs)

A Radiation Tolerant 4.8 Gb/s Serializer for the Giga-Bit Transceiver

This paper describes the design of a full-custom 120:1 data serializer for the GigaBit Transceiver (GBT) which has been under development for the LHC upgrade (SLHC). The circuit operates at 4.8 Gb=s and is implemented in a commercial 130 nm CMOS technology. The serializer occupies an area of 0.6 mm2 and its power consumption is 300 mW. The paper focuses on the techniques used to achieve radiation tolerance and on the simulation method used to estimate the sensitivity to single event transient

Extreme Events in Resonant Radiation from Three-dimensional Light Bullets

We report measurements that show extreme events in the statistics of resonant radiation emitted from spatiotemporal light bullets. We trace the origin of these extreme events back to instabilities leading to steep gradients in the temporal profile of the intense light bullet that occur during the initial collapse dynamics. Numerical simulations reproduce the extreme valued statistics of the resonant radiation which are found to be intrinsically linked to the simultaneous occurrence of both temporal and spatial self-focusing dynamics. Small fluctuations in both the input energy and in the spatial phase curvature explain the observed extreme behaviour.Comment: 5 pages, 5 figures, submitte

Tackling Prejudice and Discrimination Towards Families with Same-Sex Parents: An Exploratory Study in Italy

Though studies have shown that the sexual orientation of parents does not influence their parenting skills or the well-being of their children, prejudice against same-sex families is still very widespread. Research has not sufficiently explored the ways in which parents tackle this prejudice. Using qualitative methodologies, in particular textual analyses, this study has analysed the discourse used by same-sex families to handle the prejudices that they face. The results highlighted that conflicts, which may even be ideological in nature, are sometimes created between traditional families and “atypical” families. These often result in estrangement and isolation from their own family and the communities to which they belong, in turn damaging the growth of the children involved. Furthermore, means for moving beyond conflict, sharing experiences and effectively tackling prejudices are also discussed

Filamentation in Kerr media from pulsed Bessel beams

In contrast with filamentation of ultrashort laser pulses with standard Gaussian beams in Kerr media, three different types of Bessel filaments are obtained in air or in water by focusing ultrashort laser pulses with an axicon. We thoroughly investigate the different regimes and show that the beam reshapes as a nonlinear Bessel beam which establishes a conical energy flux from the low intensity tails toward the high intensity peak. This flux efficiently sustains a high contrast long-distance propagation and easily generates a continuous plasma channel in air

Emission of correlated photon pairs from superluminal perturbations in dispersive media

We develop a perturbative theory that describes a superluminal refractive perturbation propagating in a dispersive medium and the subsequent excitation of the quantum vacuum zero-point fluctuations. We find a process similar to the anomalous Doppler effect: photons are emitted in correlated pairs and mainly within a Cerenkov-like cone, one on the forward and the other in backward directions. The number of photon pairs emitted from the perturbation increases strongly with the degree of superluminality and under realizable experimental conditions, it can reach up to ~0.01 photons per pulse. Moreover, it is in principle possible to engineer the host medium so as to modify the effective group refractive index. In the presence of "fast light" media, e.g. a with group index smaller than unity, a further ~10x enhancement may be achieved and the photon emission spectrum is characterized by two sharp peaks that, in future experiments would clearly identify the correlated emission of photon pairs.Comment: 9 pages, 7 figure

Effect of Species Horizontal Distribution on Defoliation of Ryegrass-Clover Swards Grazed by Sheep

Defoliation events on labelled white clover (Trifolium repens) growing points or ryegrass (Lolium perenne) tillers were measured during grazing tests by sheep with swards consisting of mixed ryegrass-clover (MIX) or alternate strips of clover and ryegrass (STRIP). Sward surface height was maintained at 6.4 cm by lawnmower cuts in order to obtain a similar surface height for both species. On average, during 13 grazing tests in STRIP and 11 in MIX swards, clover was the more defoliated species : 23.3% of the growing points in STRIP and 26.5% in MIX swards were defoliated compared to 16.2% and 12.5% of the tillers. No difference of clover defoliation probability occurred between STRIP and MIX swards, nor between clover growing points in different neighbourhoods in STRIP sward, indicating that the horizontal distribution of clover does not affect its pattern of defoliation by sheep