ABSTRACT
The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes. Here, we report a proof-of-principle experiment using plasma-accelerated beams to generate stable and reproducible FEL light seeded by an external laser. FEL radiation is emitted in the infrared range, showing the typical exponential growth of its energy over six consecutive undulators. Compared to SASE, the seeded FEL pulses have energies 2 orders of magnitude larger and stability that is 3 times higher.
ABSTRACT
Porcine circovirus type 3 (PCV3) was recently proposed as a new porcine circovirus. It has been described by researchers in the USA and China and associated with porcine dermatitis and nephropathy syndrome, reproductive failure and systemic inflammation disease. The study reports the occurrence of the new virus in Italy. PCV3 was detected in the tissues of foetuses and stillborn piglets coming from two farms located in the Po Valley. The genome sequences of the two Italian strains share 99.7% to 97.8% of nucleotide identity with those available in GenBank. Results strengthen the hypothesis of PCV3 as a new emerging porcine circovirus, widespread all over the world. It follows the urgency of investigating in depth epidemiology and pathogenicity associated with this new virus.
