Probing and improving coherence in Free-electron lasers

Free electron lasers or FELs, have transformed the way science has been done in the last decades by providing coherent, highly brilliant radiation at wavelengths not achievable with conventional lasers. Their most important characteristic, along side brightness, is their coherence, which allows users to perform experiments that rely on precise phase characteristics of the probing radiation.The FEL generates intense radiation by transferring energy from a relativistic electron beam to the EM field. Both the electron beam properties and the FEL-process itself determine the final characteristics of the FEL radiation. Through specific numerical and experimental tools it is possible to probe the coherence properties of FELs and gain insight into the fundamental processes influencing them. By understanding these processes, we can improve the coherence of the resulting FEL radiation using optical lasers or magnetic elements to act on specific features of the electron beam.Investigations of transverse coherence by a Young-like experimental setup revealed differences between SASE and seeded FELs in the way that coherence is built up during the amplification process. Using the existing formalism, we used a double slit experiment to determine the transverse coherence of an FEL at various stages in the amplification process in both seeded and SASE operation. The results revealed significant differences in the way coherence is built up in the two FEL operation modes.Longitudinal coherence improvement by EEHG seeding requires a strong magnetic chicane, which can makes it vulnerable to collective instabilities in the electron beam. This work shows how one can mitigate the effect of these instabilities by a creating a wavelength dependence with time of the seed laser. The EEHG technique is also explored here as a seeding option for SXL, the soft X-ray FEL at MAX IV

MARKETING RESEARCH REGARDING FACULTY-CHOISE CRITERIA AND INFORMATION SOURCES UTILISED

Today, marketing is essential to any educational institution of higher education, so much as it is imperative that the needs of potential candidates to be identified and satisfied in a manner which will generate long-term effects (post-graduation), may paeducational marketing, institution of higher education, marketing research.

Electronic waste management in Romania: pathways for sustainable practices

This chapter aims to examine the current challenges in electronic waste (e-waste) management in a new EU Member State like Romania. The chapter analyses the route from unsound disposal practices (e.g. illegal dumping) towards sustainable practices of e-waste under EU targets and objectives. This e-waste stream is toxic for the environment and public health, thus, proper collection, treatment, and recycling facilities are required. The waste management infrastructure must be completed by a comprehensive e-waste statistic database, reliable monitoring, and law enforcement activities. The chapter reveals the current gaps in e-waste management activities in Romania while highlighting the best practices in this sector. The chapter identifies the specific pathways for sustainable practices associated with electronic waste management. The role of different actors involved in e-waste flows is examined such as public institutions, private sector, NGOs or local community. This emerging e-waste stream has a high recycling and recovery potential which could further support a circular economy in Romania

We are what we eat: how the diet of infants affects their gut microbiome

Simultaneous analysis of the gut microbiome and host gene expression in infants reveals the impact of diet (breastfeeding versus formula) on host-microbiome interactions.https://doi.org/10.1186/gb-2012-13-4-15

Assessing the benefits of using mate-pairs to resolve repeats in de novo short-read prokaryotic assemblies

<p>Abstract</p> <p>Background</p> <p>Next-generation sequencing technologies allow genomes to be sequenced more quickly and less expensively than ever before. However, as sequencing technology has improved, the difficulty of <it>de novo </it>genome assembly has increased, due in large part to the shorter reads generated by the new technologies. The use of mated sequences (referred to as mate-pairs) is a standard means of disambiguating assemblies to obtain a more complete picture of the genome without resorting to manual finishing. Here, we examine the effectiveness of mate-pair information in resolving repeated sequences in the DNA (a paramount issue to overcome). While it has been empirically accepted that mate-pairs improve assemblies, and a variety of assemblers use mate-pairs in the context of repeat resolution, the effectiveness of mate-pairs in this context has not been systematically evaluated in previous literature.</p> <p>Results</p> <p>We show that, in high-coverage prokaryotic assemblies, libraries of short mate-pairs (about 4-6 times the read-length) more effectively disambiguate repeat regions than the libraries that are commonly constructed in current genome projects. We also demonstrate that the best assemblies can be obtained by 'tuning' mate-pair libraries to accommodate the specific repeat structure of the genome being assembled - information that can be obtained through an initial assembly using unpaired reads. These results are shown across 360 simulations on 'ideal' prokaryotic data as well as assembly of 8 bacterial genomes using SOAPdenovo. The simulation results provide an upper-bound on the potential value of mate-pairs for resolving repeated sequences in real prokaryotic data sets. The assembly results show that our method of tuning mate-pairs exploits fundamental properties of these genomes, leading to better assemblies even when using an off -the-shelf assembler in the presence of base-call errors.</p> <p>Conclusions</p> <p>Our results demonstrate that dramatic improvements in prokaryotic genome assembly quality can be achieved by tuning mate-pair sizes to the actual repeat structure of a genome, suggesting the possible need to change the way sequencing projects are designed. We propose that a two-tiered approach - first generate an assembly of the genome with unpaired reads in order to evaluate the repeat structure of the genome; then generate the mate-pair libraries that provide most information towards the resolution of repeats in the genome being assembled - is not only possible, but likely also more cost-effective as it will significantly reduce downstream manual finishing costs. In future work we intend to address the question of whether this result can be extended to larger eukaryotic genomes, where repeat structure can be quite different.</p