A hybrid optical-wireless network for decimetre-level terrestrial positioning

Global navigation satellite systems (GNSS) are widely used for navigation and time distribution, features indispensable for critical infrastructure such as mobile communication networks, as well as emerging technologies like automated driving and sustainable energy grids. While GNSS can provide centimetre-level precision, GNSS receivers are prone to many-metre errors due to multipath propagation and obstructed view of the sky, which occur especially in urban areas where accurate positioning is needed most. Moreover, the vulnerabilities of GNSS, combined with the lack of a back-up system, pose a severe risk to GNSS-dependent technologies. Here, we demonstrate a terrestrial positioning system which is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronised at the sub-nanosecond level through a fibre-optic Ethernet network. Employing optical and wireless transmission schemes similar to those encountered in mobile communication networks, and exploiting spectrally efficient virtual wideband signals, the detrimental effects of multipath propagation are mitigated, thus enabling robust decimetre-level positioning and sub-nanosecond timing in a multipath-prone outdoor environment. This work provides a glimpse of a future in which telecommunication networks provide not only connectivity, but also GNSS-independent timing and positioning services with unprecedented accuracy and reliability.Comment: 38 pages, 9 figures, 3 table

NEAT-FT: the European fiber link collaboration

The development of clocks based on optical transitions during the past three decades culminates in the availability of optical clocks with unprecedented stability and uncertainty . Simultaneously, increasing requirements for accurate time and frequency signals, e.g. for tests of fundamental physics or novel applications in relativistic geodesy, put forward new challenges. Typically, such applications rely on the comparison of two remote clocks. Thus, major challenges are how to synchronize these clocks over long distances or how to get the time or frequency signal of a clock to the location where it is required. It is generally agreed that optical fiber links are an excellent alternative to established satellite based distant clock comparison and synchronization techniques. A European joint research project called Network for European Accurate Time and Frequency Transfer (NEAT-FT) has been initiated in 2011 to lay the foundations for a novel approach to disseminate high-precision timing and ultrastable frequency signals by using existing fiber infrastructure. Since Europe has a large number of modern ultra-precise clocks, special emphasis is put on the development of new techniques for time transfer and phase-coherent comparison of remotely located optical clocks and the feasibility of a European fibre network connecting optical clocks in Europe. This talk highlights recent achievements and discusses some applications and prospects

Salmonella enterica serotype Virchow associated with human infections in Switzerland: 2004-2009

BACKGROUND: Salmonellosis is one of the most important foodborne diseases and a major threat to public health. Salmonella serotype Virchow ranks among the top five serovars in Europe. METHOD: A total of 153 strains isolated from different patients from 2004 through 2009 in Switzerland were further characterized by (i) assessing phenotypic antibiotic resistance profiles using the disk diffusion method and (ii) by genotyping using pulsed-field gel electrophoresis (PFGE) after macrorestriction with XbaI in order to evaluate strain relationship. RESULTS: The relative frequency of S. Virchow among other Salmonella serovars varied between 4th to 8th rank. The annual incidence ranged from 0.45/100'000 in 2004 to 0.40/100'000 in 2009. A total of 48 strains (32%) were resistant to one to 3 antimicrobials, 54 strains (36%) displayed resistance patterns to more than three antibiotics. No trend was identifiable over the years 2004 to 2009. We found a high prevalence (62%) of nalidixic acid resistant strains, suggesting an equally high rate of decreased fluoroqionolone susceptibility, whereas intermediate resistance to ciprofloxacin was negligible. Two strains were extended spectrum β-lactamase (ESBL) producers. Analysis of PFGE patterns uncovered a predominant cluster (similarity coefficient above 80%) consisting of 104 of the 153 strains. CONCLUSION: The worldwide increase of antibiotic resistances in Salmonella is an emerging public health problem. For Switzerland, no clear trend is identifiable over the years 2004 to 2009 for S. Virchow. Antimicrobial susceptibility and resistance profiles varied considerably within this period. Nevertheless, the situation in Switzerland coincided with findings in other European countries. Genotyping results of this strain collection revealed no evidence for an undetected outbreak within this time period

Dissemination of Cephalosporin Resistance Genes between Escherichia coli Strains from Farm Animals and Humans by Specific Plasmid Lineages

Third-generation cephalosporins are a class of β-lactam antibiotics that are often used for the treatment of human infections caused by Gram-negative bacteria, especially Escherichia coli. Worryingly, the incidence of human infections caused by third-generation cephalosporin-resistant E. coli is increasing worldwide. Recent studies have suggested that these E. coli strains, and their antibiotic resistance genes, can spread from food-producing animals, via the food-chain, to humans. However, these studies used traditional typing methods, which may not have provided sufficient resolution to reliably assess the relatedness of these strains. We therefore used whole-genome sequencing (WGS) to study the relatedness of cephalosporin-resistant E. coli from humans, chicken meat, poultry and pigs. One strain collection included pairs of human and poultry-associated strains that had previously been considered to be identical based on Multi-Locus Sequence Typing, plasmid typing and antibiotic resistance gene sequencing. The second collection included isolates from farmers and their pigs. WGS analysis revealed considerable heterogeneity between human and poultry-associated isolates. The most closely related pairs of strains from both sources carried 1263 Single-Nucleotide Polymorphisms (SNPs) per Mbp core genome. In contrast, epidemiologically linked strains from humans and pigs differed by only 1.8 SNPs per Mbp core genome. WGS-based plasmid reconstructions revealed three distinct plasmid lineages (IncI1- and IncK-type) that carried cephalosporin resistance genes of the Extended-Spectrum Beta-Lactamase (ESBL)- and AmpC-types. The plasmid backbones within each lineage were virtually identical and were shared by genetically unrelated human and animal isolates. Plasmid reconstructions from short-read sequencing data were validated by long-read DNA sequencing for two strains. Our findings failed to demonstrate evidence for recent clonal transmission of cephalosporin-resistant E. coli strains from poultry to humans, as has been suggested based on traditional, low-resolution typing methods. Instead, our data suggest that cephalosporin resistance genes are mainly disseminated in animals and humans via distinct plasmids

CPE and colistin resistance

Tegen bepaalde type bacteriën werken antibiotica niet meer. Ze zijn daar resistent tegen geworden. Voorbeelden zijn colistine-resistente bacteriën. Deze bacteriën kunnen in de ontlasting van mensen, vee, en huisdieren zitten en in vlees. Het RIVM heeft voor het eerst onderzocht hoe vaak deze resistente bacteriën voorkomen bij de Nederlandse bevolking. Van 661 mensen is de ontlasting onderzocht. Colistineresistente bacteriën kwamen bij 36 mensen voor. De gegevens zijn als controle gebruikt voor de AREND-studie. Daarin is onder andere onderzocht of colistine-resistente bacteriën even vaak bij dierenartsen en hun assistenten voorkomen dan bij de bevolking. Dat blijkt het geval te zijn. Antibioticaresistente bacteriën kunnen in de darmen zitten van gezonde personen of dieren zonder dat zij daar last van hebben. Maar ze kunnen ook infecties veroorzaken. Infecties door deze bacteriën zijn moeilijker te behandelen met antibiotica. De bacteriën worden onder andere via de ontlasting of via besmet voedsel verspreid. Een goede hygiëne is dan ook belangrijk om besmetting te voorkomen.Antibiotics no longer work against certain types of bacteria. They have become resistant. Examples are colistin resistant bacteria. These bacteria can be found in the faeces of humans, livestock, pets and in meat. For the first time, RIVM has investigated how often these resistant bacteria occur in the Dutch population. The stools of 661 people were examined. Colistin resistant bacteria were found in 36 people. This data was used as a control for the AREND study. This study investigated whether colistin-resistant bacteria occur just as often in veterinarians and their assistants as in the population at large. This appeared to be the case. Antibiotic-resistant bacteria can be present in the intestines of healthy people or animals without causing any health problems, but they can also cause infections. Infections with these bacteria are more difficult to treat with antibiotics. The bacteria are spread for example through faeces or contaminated food. Good hygiene is therefore important to prevent contamination.Ministerie van VW

CPE en colistine resistentie

Tegen bepaalde type bacteriën werken antibiotica niet meer. Ze zijn daar resistent tegen geworden. Voorbeelden zijn colistine-resistente bacteriën. Deze bacteriën kunnen in de ontlasting van mensen, vee, en huisdieren zitten en in vlees. Het RIVM heeft voor het eerst onderzocht hoe vaak deze resistente bacteriën voorkomen bij de Nederlandse bevolking. Van 661 mensen is de ontlasting onderzocht. Colistineresistente bacteriën kwamen bij 36 mensen voor. De gegevens zijn als controle gebruikt voor de AREND-studie. Daarin is onder andere onderzocht of colistine-resistente bacteriën even vaak bij dierenartsen en hun assistenten voorkomen dan bij de bevolking. Dat blijkt het geval te zijn. Antibioticaresistente bacteriën kunnen in de darmen zitten van gezonde personen of dieren zonder dat zij daar last van hebben. Maar ze kunnen ook infecties veroorzaken. Infecties door deze bacteriën zijn moeilijker te behandelen met antibiotica. De bacteriën worden onder andere via de ontlasting of via besmet voedsel verspreid. Een goede hygiëne is dan ook belangrijk om besmetting te voorkomen