Biphenyl-Derived Phosphepines as Chiral Nucleophilic Catalysts: Enantioselective [4+1] Annulations To Form Functionalized Cyclopentenes

Because of the frequent occurrence of cyclopentane subunits in bioactive compounds, the development of efficient catalytic asymmetric methods for their synthesis is an important objective. Introduced herein is a new family of chiral nucleophilic catalysts, biphenyl-derived phosphepines, and we apply them to an enantioselective variant of a useful [4+1] annulation. A range of one-carbon coupling partners can be employed, thereby generating cyclopentenes which bear a fully substituted stereocenter [either all-carbon or heteroatom-substituted (sulfur and phosphorus)]. Stereocenters at the other four positions of the cyclopentane ring can also be introduced with good stereoselectivity. An initial mechanistic study indicates that phosphine addition to the electrophilic four-carbon coupling partner is not the turnover-limiting step of the catalytic cycle

Morpho-kinematic analysis of the point-symmetric, bipolar planetary nebulae Hb 5 and K 3-17, a pathway to poly-polarity

The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic information of Hb~5 is combined with {\it HST} imagery to construct a detailed 3D model of the nebula using the code SHAPE. The model shows that the large scale lobes are growing in a non-homologous way. The filamentary loops in the core are proven to actually be secondary lobes emerging from what appears to be a randomly punctured, dense, gaseous core and the material that forms the point symmetric structure flows within the lobes with a distinct kinematic pattern and its interaction with the lobes has had a shaping effect on them. Hb~5 and K~3-17 may represent a class of fast evolving planetary nebulae that will develop poly-polar characteristics once the nebular core evolves and expands.Comment: 19 pages, 8 figures. To appear in The Astrophysical Journa

Prevenção da epilepsia na infância: é posssível?

The evaluation of epilepsy has undergone a significant improvement recently due to new diagnostic procedures and results of clinical and experimental researches. Some years ago, the neuropediatric practice was much more involved with children with sequelae. Nowadays, especially in the pediatric field, there is an emphasis on the preventive aspects, including those of mental health, in which the pediatric neurologist has a strategic position. This article, according to the analysis of etiopathogenic factors, presents a discussion on the risk factors for epilepsy and the situations that can lower the seizure threshold. The epileptogenesis is reviewed based on publications with experimental models. Neuroprotective drugs are presented as well as the new forms of treatment, such as epilepsy surgery and vagal nerve stimulation, which can have a preventive action. Finally, future possible approaches are described, including herbal medicines, gene therapy and specific antiepileptic vaccine.Recentemente, a avaliação da epilepsia tem melhorado muito, devido aos novos procedimentos diagnósticos e também aos resultados das pesquisas na área clínica e experimental. Anos atrás, a prática neuropediátrica estava muito mais envolvida com as crianças seqüeladas. Atualmente, em especial no campo da pediatria, existe maior ênfase para os aspectos preventivos, incluindo os de saúde mental, nos quais o neuropediatra tem posição estratégica. Neste artigo, seguindo a cadeia fisiopatogênica, são inicialmente discutidos os fatores de risco para epilepsia, além das situações que possam diminuir o limiar para convulsões. A epileptogênese é revisada a partir das publicações com modelos experimentais; são apresentadas as drogas neuroprotetoras e as novas modalidades de tratamento, tais como cirurgia da epilepsia e estimulação  vagal, que podem ter ação preventiva. Finalmente, são descritas as futuras abordagens possíveis, que incluem medicações fitoterápicas, terapia gênica e vacinação antiepiléptica específica

Algal symbionts of the freshwater sponge Ephydatia muelleri

The freshwater sponge, Ephydatia muelleri, is an emerging model system for studying animal:microbe symbioses. Intracellular green microalgae are one of the more common symbionts that live in a facultative mutualism with E. muelleri. While these symbioses have long been known, the identity of the algal symbionts in E. muelleri cells has not been studied in detail. Here, we isolate and characterize endosymbiotic algae from E. muelleri collected from different geographic locations. We find that the algae can be transmitted through asexually produced gemmules and importantly that they can form symbioses with different, differentiated sponge cell types in the adult sponge. Our findings indicate that at least two algal lineages form endosymbioses with E. muelleri. One of the lineages includes species commonly found in samples from two locations in Canada and one in the United States (clade 1: closely related to Auxenochlorella pyrenoidosa). The other clade includes algae found in sponges from one site in Maine, USA, and Lewiniosphaera symbiontica, which is a strain isolated in 1956 from the freshwater sponge Spongilla. We compared microbiomes found in cultures of microalgae as well as the original sponge hosts, and found that very similar bacterial microbiomes associate with both clades (91 orders of Bacteria are shared among the samples we compared). The microbiomes found in the cultures resemble, with a high degree of overlap, the microbiome associated with the sponge host

Adaptable Security in Wireless Sensor Networks by Using Reconfigurable ECC Hardware Coprocessors

Specific features of Wireless Sensor Networks (WSNs) like the open accessibility to nodes, or the easy observability of radio communications, lead to severe security challenges. The application of traditional security schemes on sensor nodes is limited due to the restricted computation capability, low-power availability, and the inherent low data rate. In order to avoid dependencies on a compromised level of security, a WSN node with a microcontroller and a Field Programmable Gate Array (FPGA) is used along this work to implement a state-of-the art solution based on ECC (Elliptic Curve Cryptography). In this paper it is described how the reconfiguration possibilities of the system can be used to adapt ECC parameters in order to increase or reduce the security level depending on the application scenario or the energy budget. Two setups have been created to compare the software- and hardware-supported approaches. According to the results, the FPGA-based ECC implementation requires three orders of magnitude less energy, compared with a low power microcontroller implementation, even considering the power consumption overhead introduced by the hardware reconfiguratio

Adaptive probabilistic shaped modulation for high-capacity free-space optical links

Infrared free-space optics (FSO) provide an attractive solution for ultra-high-capacity wireless communications. However, the full potential of FSO is still being hindered by the apparent random fluctuations on the received optical power, which can be triggered by external factors such as atmospheric turbulence, weather instability, and pointing errors. Through the analysis of long-term experimental measurements, we identify the existence of significant time-domain memory in outdoor FSO links, which is found to be particularly strong under rainy weather conditions. Following this observation, we demonstrate that these memory effects can be effectively utilized to design accurate FSO channel estimation algorithms. Taking advantage of the arbitrary bit-rate granularity provided by probabilistic constellation shaping (PCS), and resorting to a simple moving average channel estimator, we demonstrate 400G+ transmission over a seamless fiber-FSO 55-m link with enhanced resilience towards adverse weather conditions. Comparing with unsupervised fixed modulation, we demonstrate a significant increase in average bit-rate (>35 Gbps) after continuous measurement over 3 hours, including raining periods