Method for Paraphrase Extraction from the News Text Corpus

The paper discusses the process of automatic extraction of paraphrases used in rewriting. The researchers propose the method for extracting paraphrases from English news text corpora. The method is based on both the developed syntactic rules to define phrases and synsets to identify synonymous words in the designed text corpus of BBC news. In order to implement the method, Natural Language Toolkit, Universal Dependencies parser and WordNet are used

Laser wakefield driven generation of isolated CEP-tunable intense sub-cycle pulses

Sources of intense, ultra-short electromagnetic pulses enable applications such as attosecond pulse generation, control of electron motion in solids and the observation of reaction dynamics at the electronic level. For such applications both high-intensity and carrier envelope phase~(CEP) tunability are beneficial, yet hard to obtain with current methods. In this work we present a new scheme for generation of isolated CEP-tunable intense sub-cycle pulses with central frequencies that range from the midinfrared to the ultraviolet. It utilizes an intense laser pulse which drives a wake in a plasma, co-propagating with a long-wavelength seed pulse. The moving electron density spike of the wake amplifies the seed and forms a sub-cycle pulse. Controlling the CEP of the seed pulse, or the delay between driver and seed leads to CEP-tunability, while frequency tunability can be achieved by adjusting the laser and plasma parameters. Our 2D and 3D Particle-In-Cell simulations predict laser-to-sub-cycle-pulse conversion efficiencies up to 1%, resulting in relativistically intense sub-cycle pulses.Comment: Replaced with updated versio