Dinâmica sazonal do metilmercúrio em ecossistemas fluviais amazônicos.

Amazonian rivers are characterized by high natural diversity of water quality among subbasins. Extensive areas of floodplain associated with these rivers are inundated seasonally leading to thermal stratification, which combined with large inputs of allocthonous organic matter results in anoxic conditions especially conducive to mercury (Hg) methylation. The large seasonal and spatial variation of limnological conditions and the relatively undisturbed nature of most drainage basins make Amazonian rivers interesting sites for studying the natural dynamics of methylmercury (MeHg). The huge discharge of Amazonian rivers also makes them important sites for hydroelectric impoundments. In Brazil, a large percentage of electric energy comes from hydroelectric dams, with many of them planned or already constructed on Amazonian rivers. Damming a river can have a major impact on MeHg dynamics in a river system, both above and below the dam. Studies have shown that rivers downstream from a dam can be more contaminated by Hg than in the reservoir itself. However, it is not clear how far downstream this contamination occurs and how it varies seasonally. This study aimed to investigate the influence of the seasonal flood pulse and associated variations in limnological parameters on the dynamics of MeHg in the principal Brazilian tributaries of the Amazon river. It also aimed to investigate the effects of impoundment on MeHg dynamics and bioaccumulation both above and below a dam. Water samples were collected in the Amazon main stem and its main Brazilian tributaries (n = 38) during two distinct phases of the flood-pulse cycle (high and low-water seasons). Water, plankton and fish were collected for one year in Balbina reservoir and in different sites between 0.5 and 250 km downstream from the dam. Limnological conditions were measured at the same time of water collection at each site. The MeHg concentrations in river waters varied between 0.02 and 0.76 ng.L-1. These concentrations increased with water level (r2 = 0.528%; p < 0.0001) and decreased with dissolved oxygen concentrations (multiple regression: F = 11.5; r2 = 0.443; p < 0.001). Due to higher MeHg concentrations and water discharge, MeHg transport was much higher in all rivers at high water, demonstrating a dominant influence of the flood pulse on MeHg dynamics in river systems. The MeHg concentrations in water from Balbina reservoir were substantially higher in the anoxic hypolimnion when compared with the epilimnion. The high MeHg concentrations in hypolimnetic water exported from the reservoir to the river declined gradually to background levels 200 km downstream from the dam. Uniform depth distributions of MeHg and oxygen were encountered in the reservoir only during the rainy season, when vertical mixing was greatest and coincided with uniform MeHg concentrations along the river downstream from the dam. MeHg in plankton and total Hg concentrations in fish from downstream sites were higher than reservoir values, suggesting that MeHg exported from the dam was accumulated by biota. MeHg concentrations in both natural and impounded river systems were influenced by seasonality, with dissolved oxygen being the main predictor of variation. In tributaries of the Amazon river, changes in water level influence in the floodplain and in the limnological parameters, specially dissolved oxygen, and MeHg dynamics. In the Balbina reservoir, where the water level is manually controlled, the rainy and dry seasons control the limnology of reservoir, and, consequently, MeHg dynamics. The influence of the dam on MeHg concentrations decreases downstream, while the influence of the natural flood cycle increases.Rios amazônicos são caracterizados pela alta diversidade natural de qualidade da água entre as sub-bacias. Áreas alagáveis extensas associadas a estes rios são inundadas sazonalmente levando à estratificação termal, que combinada com o grande aporte de matéria orgânica alóctone resulta em condições anóxicas especialmente propícias à metilação do mercúrio (Hg). A grande variação sazonal e espacial das condições limnológicas e a natureza relativamente preservada da maioria das bacias de drenagem tornam os rios amazônicos locais interessantes para o estudo da dinâmica natural do metilmercúrio (MeHg). A enorme vazão dos rios amazônicos também faz deles locais interessantes para os represamentos hidrelétricos. No Brasil, um grande percentual da energia elétrica vem de hidroelétricas, e muitas delas têm sido planejadas ou construídas nos rios amazônicos. Barramentos podem ter um grande impacto na dinâmica do MeHg do rio, acima e abaixo da barragem. Estudos tem demonstrado que os rios à jusante de uma barragem podem ser mais contaminados por Hg do que o próprio reservatório. Entretanto, não é claro até que distância esta contaminação ocorre à jusante e como ela varia sazonalmente. Este estudo objetivou investigar a influência do pulso de inundação sazonal e as variações associadas aos parâmetros limnológicos sobre a dinâmica do MeHg nos principais tributários brasileiros do rio Amazonas. Este também objetivou investigar os efeitos do represamento na dinâmica e bioacumulação do MeHg acima e abaixo da barragem do reservatório de Balbina. Amostras de água foram coletadas ao longo do rio Amazonas e nos seus principais tributários brasileiros (n = 38) durante duas fases distintas do ciclo do pulso de inundação (estações cheia e seca). Água, plâncton e peixes foram coletados ao longo de um ano no reservatório de Balbina e em diferentes locais entre 0,5 e 250 km à jusante da barragem. Condições limnológicas foram medidas paralelamente à coleta de água em cada local. A concentração de MeHg na água dos rios variou entre 0,02 e 0,76 ng.L-1. Estas concentrações aumentaram com a cota dos rios (r2 = 0,528%; p < 0,0001) e diminuíram com as concentrações de oxigênio dissolvido (regressão múltipla: F = 11,5; r2 = 0,443; p < 0,001). O transporte de MeHg foi muito maior em todos os rios na cheia, devido às maiores concentrações de MeHg e de vazão da água, demonstrando a influência dominante do pulso de inundação do rio sobre a dinâmica do MeHg no sistema fluvial. As concentrações de MeHg na água do reservatório de Balbina foram substancialmente maiores no hipolímnio anóxico quando comparado com o epilímnio. As altas concentrações de MeHg na água do hipolímnio exportado do reservatório para o rio diminuíram gradualmente para concentrações base a 200 km à jusante da barragem. Uma distribuição uniforme do MeHg e do oxigênio foram encontradas ao longo das diferentes profundidades do reservatório somente durante a estação chuvosa quando a mistura vertical foi grande e coincidiu com concentrações de MeHg uniformes ao longo do rio à jusante da barragem. Concentrações de MeHg no plâncton e de Hg total nos peixes dos locais à jusante foram maiores do que os valores do reservatório, sugerindo que o MeHg exportado da barragem foi acumulado pela biota. As concentrações de MeHg em ambos sistemas, rios naturais e represado, foram influenciadas pela sazonalidade e o oxigênio dissolvido foi o principal preditor da variação. Nos tributários do rio Amazonas, o nível da água dos rios influencia na disponibilidade de áreas alagáveis, que altera os parâmetros limnológicos, especialmente o oxigênio dissolvido, e a dinâmica do MeHg. No reservatório de Balbina, onde o nível da água é controlado manualmente, as épocas de chuva e seca influenciam a limnologia do reservatório, e, consequentemente, a dinâmica do MeHg. A influência da hidrelétrica nas concentrações de MeHg diminui ao longo do rio à jusante, enquanto que aumenta a influência da inundação das áreas alagáveis naturais

Generalized Multi-Output Gaussian Process Censored Regression

When modelling censored observations, a typical approach in current regression methods is to use a censored-Gaussian (i.e. Tobit) model to describe the conditional output distribution. In this paper, as in the case of missing data, we argue that exploiting correlations between multiple outputs can enable models to better address the bias introduced by censored data. To do so, we introduce a heteroscedastic multi-output Gaussian process model which combines the non-parametric flexibility of GPs with the ability to leverage information from correlated outputs under input-dependent noise conditions. To address the resulting inference intractability, we further devise a variational bound to the marginal log-likelihood suitable for stochastic optimization. We empirically evaluate our model against other generative models for censored data on both synthetic and real world tasks and further show how it can be generalized to deal with arbitrary likelihood functions. Results show how the added flexibility allows our model to better estimate the underlying non-censored (i.e. true) process under potentially complex censoring dynamics.Comment: 7 pages, 3 figures, 3 table

Orbital angular momentum states enabling fiber-based high-dimensional quantum communication

Quantum networks are the ultimate target in quantum communication, where many connected users can share information carried by quantum systems. The keystones of such structures are the reliable generation, transmission and manipulation of quantum states. Two-dimensional quantum states, qubits, are steadily adopted as information units. However, high-dimensional quantum states, qudits, constitute a richer resource for future quantum networks, exceeding the limitations imposed by the ubiquitous qubits. The generation and manipulation of such $D$-level systems have been improved over the last ten years, but their reliable transmission between remote locations remains the main challenge. Here, we show how a recent air-core fiber supporting orbital angular momentum (OAM) modes can be exploited to faithfully transmit $D$-dimensional states. Four OAM quantum states and their superpositions are created, propagated in a 1.2 km long fiber and detected with high fidelities. In addition, three quantum key distribution (QKD) protocols are implemented as concrete applications to assert the practicality of our results. This experiment enhances the distribution of high-dimensional quantum states, attesting the orbital angular momentum as vessel for the future quantum network

MERCURY ON FISH -- SOURCES AND CONTAMINATION.

O mercúrio ocorre naturalmente no meio ambiente, entretanto, devido aos diversos usos que se faz do metal, suas concentrações vêm aumentando no meio e consequentemente na biota. Este metal pode ocorrer como mercúrio metálico ou como diferentes espécies químicas orgânicas ou inorgânicas, sendo a espécie química deste metal importante para a compreensão da sua toxicologia. A forma do Hg mais tóxica é o metilmercúrio, e as condições e sítios propícios para a metilação do metal vem sendo estudados. Além da concentração e forma do metal no meio, para o entendimento das concentrações na biota também é importante a avaliação de fatores como idade, tamanho, hábito alimentar, sexo entre outros. Os fatores físico-químicos do ambiente também devem ser considerados por influenciar na metilação do Hg e na absorção deste metal pela biota. O estudo com peixes é importante quando se trata de ecossistema aquático porque estes organismos apresentam diferentes hábitos alimentares e de vida e ocupam diferentes nichos. Além disto, quando se trata de contaminação humana, peixes são o alimento mais contaminado por mercúrio que os homens consomem. Estudos sobre peixes cultivados em piscicultura vêm demonstrando que estes são menos contaminados do que os provenientes de ambientes naturais. No entanto, a ração fornecida a esses peixes pode representar uma importante fonte de contaminação e, portanto, deve ter um rígido controle.Mercury occurs naturally in the environment, however, due to the diverse array of its use, the concentrations have been increase in the environment and, consequently, in the biota. This metal can occur as metallic mercury or as different organic or inorganic chemical species, being these chemical classifications important criteria to the understanding of its toxicology. The most toxic mercury species is the methylmercury, and suitable conditions and sites for methylation have been studied. Besides the environmental concentrations and the chemical species, to understand the biota concentrations a wide range of factors are important to be assessed, as age, size, food habit, sex and others. The physic-chemic environmental factors must be considered because of their effects on the Hg methylation and biota absorption. Fish study is important if to deal with aquatic ecosystem because this organism presents different food and life habits and is engaged in different niches. Moreover, when deal with human contaminations, there are the most mercury contaminated food consumed. Studies on farmed fishes have showed these fishes less contaminated than those proceeding from natural environments. However, the supplied ration to those fishes can represent an important contamination source and, because of that, should have a strict control

“Gap hunting” to characterize clustered probe signals in Illumina methylation array data

Additional file 6: Figures S26–S31. All remaining SBE site scenarios. Each additional scenario of a SBE site-mapping SNP delimited in Fig. 4 not including the scenario shown in Fig. 5. Each of these figures contains 4 plots, showing every combination of CpG site interrogations on the forward and reverse strand as well as which nucleotide is the reference nucleotide

Nearby Threats: Reversing, Analyzing, and Attacking Google’s 'Nearby Connections' on Android

Google’s Nearby Connections API enables any An-droid (and Android Things) application to provide proximity-based services to its users, regardless of their network connectivity.The API uses Bluetooth BR/EDR, Bluetooth LE and Wi-Fi to let“nearby” clients (discoverers) and servers (advertisers) connectand exchange different types of payloads. The implementation ofthe API is proprietary, closed-source and obfuscated. The updatesof the API are automatically installed by Google across differentversions of Android, without user interaction. Little is knownpublicly about the security guarantees offered by the API, eventhough it presents a significant attack surface.In this work we present the first security analysis of theGoogle’s Nearby Connections API, based on reverse-engineeringof its Android implementation. We discover and implement sev-eral attacks grouped into two families: connection manipulation(CMA) and range extension attacks (REA). CMA-attacks allow anattacker to insert himself as a man-in-the-middle and manipulateconnections (even unrelated to nearby), and to tamper withthe victim’s interface and network configuration. REA-attacksallow an attacker to tunnel any nearby connection to remotelocations, even between two honest devices. Our attacks areenabled by REArby, a toolkit we developed while reversingthe API implementation. REArby includes a dynamic binaryinstrumenter, a packet dissector, and the implementations ofcustom Nearby Connections client and server. We plan to open-source REArby after a responsible disclosure period

Blurtooth: Exploiting cross-transport key derivation in Bluetooth classic and Bluetooth low energy

Bluetooth is a pervasive wireless technology specified in an open standard. The standard defines Bluetooth Classic (BT) for high- throughput wireless services and Bluetooth Low Energy (BLE) very low-power ones. The standard also specifies security mechanisms, such as pairing, session establishment, and cross-transport key derivation (CTKD). CTKD enables devices to establish BT and BLE security keys by pairing just once. CTKD was introduced in 2014 with Bluetooth 4.2 to improve usability. However, the security im- plications of CTKD were not studied carefully. This work demonstrates that CTKD is a valuable and novel Blue- tooth attack surface. It enables, among others, to exploit BT and BLE just by targeting one of the two (i.e., Bluetooth cross-transport ex- ploitation). We present the design of the first cross-transport attacks on Bluetooth. Our attacks exploit issues that we identified in the specification of CTKD. For example, we find that CTKD enables an adversary to overwrite pairing keys across transports. We leverage these vulnerabilities to impersonate, machine-in-the-middle, and establish unintended sessions with any Bluetooth device support- ing CTKD. Since the presented attacks blur the security boundary between BT and BLE, we name them BLUR attacks. We provide a low-cost implementation of the attacks and test it on a broad set of devices. In particular, we successfully attack 16 devices with 14 unique Bluetooth chips from popular vendors (e.g., Cypress, Intel, Qualcomm, CSR, Google, and Samsung), with Bluetooth standard versions of up to 5.2. We discuss why the countermeasures in the Bluetooth are not effective against our attacks, and we develop and evaluate practical and effective alternatives

Worth the Weight? Post Weigh-In Rapid Weight Gain is Not Related to Winning or Losing in Professional Mixed Martial Arts.

Body mass (BM) manipulation via rapid weight loss (RWL) and rapid weight gain (RWG) is a common practice among mixed martial art (MMA) athletes to ensure qualification for the division in which the athlete wishes to compete. Professional MMA competitors in California are required to weigh in twice: 24 hr prior to competition and immediately prior to the bout after they have typically engaged in RWG. In analyzing data from five MMA events sanctioned by the Californian State Athletic Commission, the authors used Bayesian analyses to compare bout winners (n = 31) and losers (n = 31) in terms of in-competition BM (in kilograms) and the amount of BM regained between the two weigh-ins (in kilograms). These data do not support the hypothesis that differences in in-competition BM (Bayes factor [BF10] = 0.667, d = 0.23) or the amount of BM regained between the two weigh-ins (BF10 = 0.821, d = 0.23) determine winning or losing. In addition, there was no statistical difference between bouts ending via strikes, submission, or decision for either in-competition BM (BF10 = 0.686, ω2 < 0.01) or the amount of BM regained between the two weigh-ins (BF10 = 0.732, ω2 = 0.054). In conclusion, the authors report for the first time that the magnitude of RWG does not predict winning or losing in a professional cohort of MMA athletes. In addition, they also report that MMA athletes typically compete at a BM that is at least 1-2 divisions higher than the division in which they officially weighed-in. These analyses may provide impetus for governing bodies and coaches to enact changes at both professional and amateur levels to reduce negative health consequences associated with extreme RWL and RWG