1,487 research outputs found
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
New simple Lie algebras over fields of characteristic 2
New simple Lie algebras over fields of characteristic
On simple Lie algebras of dimension seven over
On simple Lie algebras of dimension seven overelds of characteristic
RELOAD/CoAP architecture with resource aggregation/disaggregation service
M2M communication is expected to occur at a global level and for this reason federations of device networks are also expected. In such large scale environments, a critical issue is how to discover the available resources in a scalable manner. For this purpose CoAP Usage for RELOAD, a generic self-organizing P2P overlay network service, has been proposed to be used as a lookup service, to store available resources and as a cache for sensor data. However, such approach alone does not allow building an aggregate resource hierarchy, a very relevant issue for an efficient organization of data in future IoT applications. Here we address this issue and propose an architecture incorporating a resource aggregation/disaggregation service
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
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
Stage III Kienböck's Disease Treated with Hyperbaric Oxygen: the Role of an Unusual Approach to a Rare Condition
Kienböck's disease is a rare condition characterised by avascular necrosis of the lunate bone. Its natural history and aetiopathogenesis have not yet been clarified, nor are its triggering factors identified. We present a case of a 17-year-old male gymnast, without relevant medical/family history, with stage IIIA Kienböck's disease diagnosed in 2016. Initially, submitted to conservative treatment that proved to be insufficient. Consequently, surgical treatment was proposed, but refused. The patient instead underwent experimental treatment with hyperbaric oxygen (120 sessions, 100% oxygen at 2.5 atm, for 70 min periods, once daily, five times per week). In April 2018, a favourable clinical and radiological evolution was observed, with an improvement in the patterns of pain, motion and strength and an almost complete involution of the process of aseptic necrosis of the semilunar. To the best of our knowledge, this is the first report of Kienböck's disease treated with hyperbaric oxygen.info:eu-repo/semantics/publishedVersio
Multilingual simultaneous sentence end and punctuation prediction
This paper describes the model and its corresponding setup, proposed by the Unbabel & INESC-ID team for the 1st Shared Task on Sentence End and Punctuation Prediction in NLG Text (SEPP-NLG 2021). The shared task covers 4 languages (English, German, French and Italian) and includes two subtasks: Subtask 1 - detecting the end of a sentence, and subtask 2 - predicting a range of punctuation marks. Our team proposes a single multilingual and multitask model that is able to produce suitable results for all the languages and subtasks involved. The results show that it is possible to achieve state-of-the-art results using one single multilingual model for both tasks and multiple languages. Using a single multilingual model to solve the task for multiple languages is of particular importance, since training a different model for each language is a cumbersome and time-consuming process.info:eu-repo/semantics/publishedVersio
Melhor Suporte Nutricional — «Melhor» Composição Corporal? Uma Análise em Recém-Nascidos de Baixo Peso
Objectivo: Avaliar o impacto de diferentes estratégias de suporte nutricional na composição corporal de recém-nascidos de baixo peso (RNBP), por intermédio não só do peso, mas também das áreas muscular braquial (AMB) e adiposa braquial (AAB).
Indivíduos e métodos: Comparou-se a média do dia de recuperação do peso, da AMB e da AAB entre dois grupos de RNBP assistidos em períodos distintos, com suportes nutricionais diferentes — grupo I (n=10): 1991 versus grupo II (n=24): 1995/96. Os
recém-nascidos foram incluidos de modo consecutivo e avaliados prospectivamente sob o ponto de vista antropométrico.
Resultados: Não houve diferenças significativas da média das idades gestacionais e dos pesos de nascimento entre os dois grupos. Os recém-nascidos do grupo II, comparativamente com os do grupo I, receberam provisões mais precoces de energia, lípidos e proteínas através da alimentação parentérica. Não se observaram diferenças significativas no dia de recuperação do peso e da AMB entre
os grupos. No entanto, os RN do grupo II recuperaram mais precocemente a AAB (dia 6,9 ± 2,5 vs dia 12,6 ± 5,1) (p<0,01), após um período inicial de declínio dos respectivos valores.
Conclusões: O atraso na adequada provisão de energia e proteínas pode ter um impacto negativo na reserva lipídica, não detectada pela observação isolada da evolução ponderai. A medição das áreas braquiais representa um método simples e não invasivo de avaliação indirecta da composição corporal dos RNBP
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