66,219 research outputs found
The Madagascar Bloom – a serendipitous study
No full textThe late austral summer (February-April) phytoplankton bloom that occurs east of Madagascar exhibits significant interannual variability and at its largest extent covers ~1% of the world’s ocean surface area. The bloom raises many intriguing questions about how it begins, is sustained, propagates to the east, exports carbon and ends. It has been observed and studied using satellite ocean color observations, but the lack of in situ data makes it difficult to address these questions. Here we describe observations that were made serendipitously on a cruise in February 2005. These show clearly for the first time the simultaneous existence of a deep chlorophyll maximum at ~70-110 m depths (seen in SeaSoar fluorimeter data) and a surface chlorophyll signature (seen in SeaWiFS satellite ocean color data). The observations also show the modulation of biological signature at the surface by the eddy field, but not of the deep chlorophyll maximum. Trichodesmium dominates the bloom nearer to Madagascar, while the diatom Rhizosolenia clevei (and its symbiont Richelia intracellularis) dominates further from the island. The surface bloom seen in the SeaWiFS data is confined to the shallow (~30 m) mixed layer. It is hypothesized that the interannual variability in bloom intensity may be due to variations in coastal upwelling and thus the supply of iron, which is a micronutrient that can limit diazotroph growth
Fully pipelined bloom filter architecture
No full textRecently, we proposed a two-stage pipelined Bloom filter architecture to save power for network security applications. In this letter, we generalize the pipelined Bloom filter architecture to k-stage and show that significant power savings can be achieved by employing one hash function per stage. We analytically show that the expected power consumption and latency of the fully pipelined Bloom filter architecture will not be greater than that of the two hash functions and two clock cycles, respectively, however large the number of hash functions is. Furthermore, we discuss the worst-case performance of the proposed architecture.Recently, we proposed a two-stage pipelined Bloom filter architecture to save power for network security applications. In this letter, we generalize the pipelined Bloom filter architecture to k-stage and show that significant power savings can be achieved by employing one hash function per stage. We analytically show that the expected power consumption and latency of the fully pipelined Bloom filter architecture will not be greater than that of the two hash functions and two clock cycles, respectively, however large the number of hash functions is. Furthermore, we discuss the worst-case performance of the proposed architectur
Low-power bloom filter architecture for deep packet inspection
No full textBloom filters are frequently used to identify malicious content like viruses in high speed networks. However, architectures proposed to implement bloom filters are not power efficient. In this letter, we propose a new bloom filter architecture that exploits the well-known pipelining technique. Through power analysis we show that pipelining can reduce the power consumption of bloom filters up to 90%, which leads to the energy-efficient implementation of intrusion detection systems
Energy-efficient pipelined bloom filters for network intrusion detection
No full textSoftware-based detection techniques are commonly used to identify the predefined signatures in network streams. However, the software-based techniques can not keep up with the speeds that network bandwidth increases. Hence, hardware-based systems have started to emerge. Bloom filters are frequently used to identify malicious content like viruses in high speed networks. However, architectures proposed to implement Bloom filters are not power efficient. We propose a new Bloom filter architecture that exploits the well-known pipelining technique. Through extensive power analysis we show that pipelining can reduce the power consumption of Bloom filters up to 90%, which leads to the energy-efficient implementation of network intrusion detection system
Physical controls and mesoscale variability in the Labrador Sea spring phytoplankton bloom observed by Seaglider
No full textWe investigated the 2005 spring phytoplankton bloom in the Labrador Sea using Seaglider, an autonomous underwater vehicle equipped with hydrographic, bio-optical and oxygen sensors. The Labrador Sea blooms in distinct phases, two of which were observed by Seaglider: the north bloom and the central Labrador Sea bloom. The dominant north bloom and subsequent zooplankton growth are enabled by the advection of low-salinity water from West Greenland in the strong and eddy-rich separation of the boundary current. The glider observed high fluorescence and oxygen supersaturation within haline-stratified eddy-like features; higher fluorescence was observed at the edges than centers of the eddies. In the central Labrador Sea, the bloom occurred in thermally stratified water. Two regions with elevated subsurface chlorophyll were also observed: a 5 m thin-layer in the southwest Labrador Current, and in the Labrador shelf-break front. The thin layer observations were consistent with vertical shearing of an initially thicker chlorophyll patch. Observations at the front showed high fluorescence down to 100 m depth and aligned with the isopycnals defining the front. The high-resolution Seaglider sampling across the entire Labrador Sea provides first estimates of the scale dependence of coincident biological and physical variables
Increasing the power efficiency of Bloom filters for network string matching
No full textAlthough software based techniques are widely accepted in computer security systems, there is a growing interest to utilize hardware opportunities in order to compensate for the network bandwidth increases. Recently, hardware based virus protection systems have started to emerge. This type of hardware systems work by identifying the malicious content and removing it from the network streams. In principle, they make use of string matching. Bit by bit, they compare the virus signatures with the bit strings in the network. The bloom filters are ideal data structures for string matching. Nonetheless, they consume large power when many of them used in parallel to match different virus signatures. In this paper, we propose a new type of Bloom filter architecture which exploits well-known pipelining techniqu
CCN forwarding engine based on Bloom filters
No full textThe lack of scalable routing algorithms is one of the main obstacles that slow down a large deployment of Content Centric Networking on an Internet-scale. From one side, content based networking promises to solve the current problems of the Internet. On the other hand, instead, it requires routers to account for a very huge amount of content names. Bloom Filters are widely recognized as a possible solution to this limitation. At the same time, their adoption requires careful tuning rules and novel design methodologies. In this perspective, the present contribution proposes a Bloom Filter-based routing scheme for Content Centric Networking (CCN) and shows several preliminary observations about Bloom Filters size and signaling overhead
Let the Tree Bloom: Scalable Opportunistic Routing with ORPL
No full textRouting in battery-operated wireless networks is challenging, posing a tradeoff between energy and latency. Previous work has shown that opportunistic routing can achieve low-latency data collection in duty-cycled networks. However, applications are now considered where nodes are not only periodic data sources, but rather addressable end points generating traffic with arbitrary patterns.
We present ORPL, an opportunistic routing protocol that supports any-to-any, on-demand traffic. ORPL builds upon RPL, the standard protocol for low-power IPv6 networks. By combining RPL's tree-like topology with opportunistic routing, ORPL forwards data to any destination based on the mere knowledge of the nodes' sub-tree. We use bitmaps and Bloom filters to represent and propagate this information in a space-efficient way, making ORPL scale to large networks of addressable nodes. Our results in a 135-node testbed show that ORPL outperforms a number of state-of-the-art solutions including RPL and CTP, conciliating a sub-second latency and a sub-percent duty cycle. ORPL also increases robustness and scalability, addressing the whole network reliably through a 64-byte Bloom filter, where RPL needs kilobytes of routing tables for the same task
Effect of 1-methylcyclopropene on upland cotton
No full textEthylene plays a key role in square and boll abscission in cotton (Gossypium
hirsutum L.). When subjected to stress, cotton plants synthesize higher rates of ethylene
which can result in the loss of immature fruit. The ethylene action inhibitor 1-
methylcyclopropene (1-MCP) is used in many fruit, vegetable, and floriculture crops to
counter the effects of ethylene. Protecting a cotton crop from ethylene through its early
reproductive stages may boost yields by increasing fruit retention. A two-year field study
was conducted in 2005 and 2006 at the Texas Agricultural Experiment Station in
Burleson County, Texas to evaluate the effects of 1-MCP concentration and timing on
cotton growth and yield components.
The study was designed as a randomized complete block with 4 replications.
Three rates of 1-MCP (250, 500, and 1250 g ha-1 of actual product) were applied as a
foliar spray at a delivery rate of 93.50 L -1 ha. Each rate was applied at pinhead-square
and fourteen days after pinhead-square; pinhead-square, fourteen days after pinheadsquare,
and early bloom; early bloom and fourteen days after early bloom; early bloom,
fourteen days after early bloom, and twenty-eight days after early bloom. Plant heights,
total number of nodes per plant, percent square abscission, nodes above white flower (NAWF), relative chlorophyll content, fruit number, fruit size, and fruit distribution were
not affected by 1-MCP. In 2006, electrolytic leakage was significantly increased by two,
250 g ha-1, 1-MCP treatments. In 2005, yield was significantly increased by six of the 1-
MCP treatments and suggests an increase in boll retention, boll size, seed number, or
seed size. The analysis of yield components conducted through box-mapping, however,
failed to explain the observed yield response. In 2006, 1-MCP did not significantly
influence yield
Habitat effects on Ostreopsis cf. ovata bloom dynamics
No full textIn the last few decades, Ostreopsis spp., toxic benthic dinolagellates of tropical origin, generated large interest in the Mediterranean Sea, where several bloom events have been observed. Ecology and proliferation dynamics of O. cf. ovata are driven by complex interactions among biotic and abiotic drivers, and understanding mechanisms triggering bloom events is still far from being complete. The aim of the present study is to highlight the role of di erent habitat conditions, elucidating the e ects of i) exposure to hydrodynamic conditions, ii) macroalgal community and iii) urbanisation level, in driving O. cf. ovata bloom dynamics. A signi cant e ect of hydro- dynamics was observed only for cells in seawater, with higher abundances in sheltered zones, irrespective of the urbanisation level. Similarly, a signi cant e ect of the dominant macroalgal community, with higher abun- dances in Corallinales and turf dominated communities, and lower ones in Cystoseira amentacea canopies, has been recorded, consistently in the di erently urbanised sites. Additionally, stretches of the coast su ering from a more intense anthropic exploitation are in general more prone to the proliferation of potentially toxic benthic microalgae. All these results imply a larger risk exposure to toxic e ects for humans in urban beaches and sheltered areas, usually more attended by swimmers and bathers. These ndings underline the need to preserve, and eventually restore, canopy dominated assemblages, which presently are under regression because of human threats, providing a straightforward example that restoration of relevant habitats implies a cascading im- provement of human welfare
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