High efficiency coupling of photon pairs in practice

Multi-photon and quantum communication experiments such as loophole-free Bell tests and device independent quantum key distribution require entangled photon sources which display high coupling efficiency. In this paper we put forward a simple quantum theoretical model which allows the experimenter to design a source with high pair coupling efficiency. In particular we apply this approach to a situation where high coupling has not been previously obtained: we demonstrate a symmetric coupling efficiency of more than 80% in a highly frequency non-degenerate configuration. Furthermore, we demonstrate this technique in a broad range of configurations, i.e. in continuous wave and pulsed pump regimes, and for different nonlinear crystals

Coccolithophore fluxes in the open tropical North Atlantic: influence of thermocline depth, Amazon water, and Saharan dust

Coccolithophores are calcifying phytoplankton and major contributors to both the organic and inorganic oceanic carbon pumps. Their export fluxes, species composition, and seasonal patterns were determined in two sediment trap moorings (M4 at 12 degrees N, 49 degrees W and M2 at 14 degrees N, 37 degrees W) collecting settling particles synchronously from October 2012 to November 2013 at 1200 m of water depth in the open equatorial North Atlantic. The two trap locations showed a similar seasonal pattern in total coccolith export fluxes and a predominantly tropical coccolithophore settling assemblage. Species fluxes were dominated throughout the year by lower photic zone (LPZ) taxa (Florisphaera profunda, Gladiolithus flabellatus) but also included upper photic zone (UPZ) taxa (Umbellosphaera spp., Rhabdosphaera spp., Umbilicosphaera spp., Helicosphaera spp.). The LPZ flora was most abundant during fall 2012, whereas the UPZ flora was more important during summer. In spite of these similarities, the western part of the study area produced persistently higher fluxes, averaging 241 x 10(7) +/- 76 x 10(7) coccoliths m(-2) d(-1) at station M4 compared to only 66 x 10(7) +/- 31 x 10(7) coccoliths m(-2) d(-1) at station M2. Higher fluxes at M4 were mainly produced by the LPZ species, favoured by the westward deepening of the thermocline and nutricline. Still, most UPZ species also contributed to higher fluxes, reflecting enhanced productivity in the western equatorial North Atlantic. Such was the case of two marked flux peaks of the more opportunistic species Gephyrocapsa muellerae and Emiliania huxleyi in January and April 2013 at M4, indicating a fast response to the nutrient enrichment of the UPZ, probably by wind-forced mixing. Later, increased fluxes of G. oceanica and E. huxleyi in October-November 2013 coincided with the occurrence of Amazon-River-affected surface waters. Since the spring and fall events of 2013 were also accompanied by two dust flux peaks, we propose a scenario in which atmospheric dust also provided fertilizing nutrients to this area. Enhanced surface buoyancy associated with the river plume indicates that the Amazon acted not only as a nutrient source, but also as a surface density retainer for nutrients supplied from the atmosphere. Nevertheless, lower total coccolith fluxes during these events compared to the maxima recorded in November 2012 and July 2013 indicate that transient productivity by opportunistic species was less important than "background" tropical productivity in the equatorial North Atlantic. This study illustrates how two apparently similar sites in the tropical open ocean actually differ greatly in ecological and oceanographic terms. The results presented here provide valuable insights into the processes governing the ecological dynamics and the downward export of coccolithophores in the tropical North Atlantic.Netherlands Organization for Scientific Research (NWO) [822.01.008]; European Research Council (ERC) [311152]; University of Bremen; European Union [600411]info:eu-repo/semantics/publishedVersio

Dark matter from cosmic defects on galactic scales?

We discuss the possible dynamical role of extended cosmic defects on galactic scales, specifically focusing on the possibility that they may provide the dark matter suggested by the classical problem of galactic rotation curves. We emphasize that the more standard defects (such as Goto-Nambu strings) are unsuitable for this task, but show that more general models (such as transonic wiggly strings) could in principle have a better chance. In any case, we show that observational data severely restricts any such scenarios.Comment: Submitted to Phys. Rev. D (Brief Reports). v2: Reference added and some typos corrected, matches published versio

Peripartum Cardiomyopathy. Post Partum Cardiorespiratory Arrest Complicated by Placental Accretism

Peripartum cardiomiopathy is a rare and life-threatening cardiac disease that affects young women previously healthy, during the peripartum period. It is a form of dilated cardiomyopathy with left-sided systolic dysfunction, which may lead to symptoms and signs of congestive heart failure. The exclusion diagnosis is based essentially on clinical presentation and initial symptoms may mimic physiologic alterations of pregnancy. The authors present a case of a 34 week multiple gestation with a growth restriction of one of the fetus and with a suspicion of a mild pre-eclampsia, motive by which we decided labour induction. During placental expulsion, in which we noticed difficulty in finding placental cleavage, the patient presented an assistoly, recovering after cardiorespiratory reanimation. However, the profuse bleeding after labour leaded to a life saving hysterectomy. Histological examination revealed placenta accreta. The echocardiography performed post-operatively diagnosed a dilated cardiomyopathy

Nonlinear interaction between two heralded single photons

Harnessing nonlinearities strong enough to allow two single photons to interact with one another is not only a fascinating challenge but is central to numerous advanced applications in quantum information science. Currently, all known approaches are extremely challenging although a few have led to experimental realisations with attenuated classical laser light. This has included cross-phase modulation with weak classical light in atomic ensembles and optical fibres, converting incident laser light into a non-classical stream of photon or Rydberg blockades as well as all-optical switches with attenuated classical light in various atomic systems. Here we report the observation of a nonlinear parametric interaction between two true single photons. Single photons are initially generated by heralding one photon from each of two independent spontaneous parametric downconversion sources. The two heralded single photons are subsequently combined in a nonlinear waveguide where they are converted into a single photon with a higher energy. Our approach highlights the potential for quantum nonlinear optics with integrated devices, and as the photons are at telecom wavelengths, it is well adapted to applications in quantum communication.Comment: 4 pages, 4 figure

Variações morfológicas induzidas por uma tempestade na Praia de Carcavelos, Portugal: contribuição para a gestão costeira

Field data based information on the coastal sediment dynamics becomes even more relevant for coastal managers in the present context of climate changes. Due to the sea level rise and the increase of frequency and intensity of coastal storms, coastal managers need to implement effective and efficient solutions for increasing coastal resilience, namely through reprofiling the beach for restoring the sediment balance and providing space for the beach natural dynamics. The study characterises and quantifies the morphological changes in an Atlantic urban sandy beach under extreme wave energy and sea level conditions. The erosion of the foreshore and backshore of this particular beach was characterised as function of the intensity and duration of the hydrodynamic forcing parameters (waves and sea level). This 24-hour duration storm event, which delivered to the beach a total energy of 1.7x109 J, caused the seaward displacement by the undertow current of approximately 3x103 m3 of median well sorted sand from the beach foreshore and backshore.Informação sobre a dinâmica sedimentar costeira baseada em dados de campo torna-se ainda mais relevante para gestores costeiros no presente contexto de alterações climáticas. Devido à subida do nível do mar e ao aumento da frequência e intensidade de tempestades marítimas, os gestores costeiros necessitam de implementar soluções eficazes e eficientes para melhorar a resiliência costeira, nomeadamente através do reperfilamento da praia para restabelecer o balanço sedimentar e conceder espaço para a dinâmica natural da praia. O estudo caracteriza e quantifica as variações morfológicas numa praia arenosa, urbana e Atlântica sob ação de condições extremas de energia das ondas e nível do mar. A erosão da face e do topo da praia foi caracterizada em função da intensidade e duração dos parâmetros forçadores hidrodinâmicos (ondas e nível do mar). Este evento de tempestade com duração de 24 horas, que transmitiu à praia uma energia total de 1.7x109 J, causou a extração de aproximadamente 3x103 m3 de areia média da face e do topo da praia e o seu transporte pela corrente de retorno para maiores profundidades.info:eu-repo/semantics/publishedVersio

Self-reported variables as determinants of upper limb musculoskeletal symptoms in assembly line workers

Background: Assembly lines work is frequently associated to work-related upper limb musculoskeletal disorders. The related disability and absenteeism make it important to implement efficient health surveillance systems. The main objective of this study was to identify self-reported variables that can determine work-related upper limb musculoskeletal symptoms—discomfort/pain–during a 6-month follow-up. Methods: This was a prospective study with a 6-month follow-up period, performed in an assembly line. Upper limb musculoskeletal discomfort/pain was assessed through the presence of self-reported symptoms. Uni- and multivariate logistic regression analyses were used to evaluate which self-reported variables were associated to upper limb symptoms after 6 months at the present and to upper limbs symptoms in the past month. Results: Of the 200 workers at baseline, 145 replied to the survey after 6 months. For both outcomes, “having upper limb symptoms during the previous 6 months” and “education” were possible predictors. Conclusion: Our results suggest that having previous upper limb symptoms was related to its maintenance after 6 months, sustaining it as a specific determinant. It can be a hypothesis that this population had mainly workers with chronic symptoms, although our results give only limited support to self-reported indicators as determinants for upper limb symptoms. Nevertheless, the development of an efficient health surveillance system for high demanding jobs should implicate self-reported indicators, but also clinical and work conditions assessment should be accounted on the future.publishersversionpublishe

Análise configuracional da cidade de Sines: Contribuições para a sustentabilidade do planeamento urbano e território

A cidade de Sines, apesar do seu caracter histórico, caracteriza-se pelo seu crescimento fragmentado, caótico e disperso característico das cidades portuárias recentes. Neste paper procuramos dar conta dessas formas de crescimento diverso, por um lado, bem como encontrar as bases sólidas para a sustentabilidade do seu planeamento urbano e territorial futuro. Segundo Bill Hillier, as cidades tendem a crescer com um padrão específico: “Estrutura da roda deformada (deformed wheel)”. As cidades que seguem este padrão explicitamente, apresentam segundo o autor, um melhor desempenho social, económico e ambiental. No caso de Sines, embora essa estrutura esteja implícita, ela apresenta-se muito fragmentada. A reconstrução desse padrão espacial global requer várias intervenções locais, que por sua vez, terão reflexos a nível global. A identificação desse padrão espacial que tem reflexos a nível da sociedade é feita através da teoria da sintaxe espacial ou lógica social do espaço, criada por Bill Hillier e Julienne Hanson partir dos anos 70 na UCL. Com base na estrutura espacial da cidade enquanto sistema, a presente investigação procura assim compreender as tendências do crescimento urbano, através de análises quantitativas e descritivas que nos permitem ter uma leitura simples e direta do funcionamento do sistema espacial duma forma diacrónica e sincrónica. O método explora as diferentes técnicas que a sintaxe espacial nos oferece: Eixos axiais, espaços convexos e isovistas, que são as entidades espaciais definidas pela teoria. Trata-se de elaborar um conjunto de análises configuracionais, representadas por um conjunto de mapas e gráficos, com representação própria, baseadas na matemática dos grafos. O método permite encontrar diferentes valores sociais do espaço em função da sua posição e relação com o resto do sistema. Nestas análises são obtidas diversas medidas sintáticas que, por sua vez, representam certos padrões espaciais. Os resultados obtidos permitiram fazer uma proposta simples de alteração da estrutura global da cidade a partir de intervenções locais ao nível dos espaços públicos com vista ao melhoramento do ambiente urbano da cidade de Sines. As simulações de cenários futuros a partir dessas intervenções locais devolvem-nos claramente a imagem do padrão geral de crescimento de cidades sustentáveis segundo a estrutura da roda deformada.info:eu-repo/semantics/publishedVersio

The complexities in genotyping of congenital adrenal hyperplasia: 21-hydroxylase deficiency

The deficiency of 21-hydroxylase due to CYP21A2 pathogenic variants is a rather frequent disease with serious consequences, going from a real mortality risk to infertility and to milder symptoms, nevertheless important for affecting the patients’ self-esteem. In the most severe cases life-threatening adrenal salt wasting crises may occur. Significant morbidity including the possibility of mistaken gender determination, precocious puberty, infertility and growth arrest with consequent short stature may also affect these patients. In the less severe cases milder symptoms like hirsutism will likely affect the image of the self with strong psychological consequences. Its diagnosis is confirmed by 17OH-progesterone dosages exceeding the cut-off value of 10/15 ng/ml but genotyping is progressively assuming an essential role in the study of these patients particularly in confirming difficult cases, determining some aspects of the prognosis and allowing a correct genetic counseling. Genotyping is a difficult process due to the occurrence of both a gene and a highly homologous pseudo gene. However, new tools are opening new possibilities to this analysis and improving the chances of a correct diagnosis and better understanding of the underlying mechanisms of the disease. Beyond the 10 classic pathogenic variants usually searched for in most laboratories, a correct analysis of 21OH-deficiency cases implies completely sequencing of the entire gene and the determination of gene duplications. These are now recognized to occur frequently and can be responsible for some false positive cases. And finally, because gene conversions can include several pathogenic variants one cannot be certain of identifying that both alleles are affected without studying parental DNA samples. A complete genotype characterization should be considered essential in the preparation for pregnancy, even in the case of parents with milder forms of the disease, or even just carriers, since it has been reported that giving birth to progeny with the severe classic forms occurs with a much higher frequency than expected.The work was supported by the Foundation for Science and Technology (FCT) (PTDC/MEC-ONC/31384/2017). SG was funded through FCT grant SFRH/BPD/1117441/2015