Dynamics of pneumococcal nasopharyngeal carriage in healthy children attending a day care center in northern Spain. Influence of detection techniques on the results

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Cultural methods of detection for microorganisms: recent advances and successes

Most microbiological methods require culture to allow organisms to recover or to selectively increase, and target organisms are identified by growth on specific agar media. Many cultural methods take several days to complete and even then the results require confirmation. Alternative techniques include the use of chromogenic and fluorogenic substances to identify bacteria as they are growing, selective capture using antibodies after short periods of growth, molecular techniques, and direct staining with or without flow cytometry for enumeration and identification. Future microbiologists may not use culture but depend on the use of specific probes and sophisticated detection systems.

Dynamic modulation of detection window in conducting polymer based biosensors.

Here we demonstrate a novel application that employs the ion exchange properties of conducting polymers (CP) to modulate the detection window of a CP based biosensor under electrical stimuli. The detection window can be modulated by electrochemically controlling the degree of swelling of the CP associated with ion transport in and out of the polymer. We show that the modulation in the detection window of a caffeine imprinted polypyrrole biosensor, and by extension other CP based biosensors, can be achieved with this mechanism. Such dynamic modulation in the detection window has great potential for the development of smart biosensors, where the sensitivity of the sensor can be dynamically optimized for a specific test solution.

A surveillance strategy for invasive species of concern in deepwater habitats of the Northwestern Hawaiian Islands

This report describes a surveillance strategy to detect deepwater invasive species in the Northwestern Hawaiian Islands. A need for this strategy was identified in the Papahānaumokuākea Marine National Monument Management Plan and the Monument’s Draft Natural Resources Science Plan. This strategy focuses on detecting two species of concern, the octocoral Carijoa riisei and the red alga Hypnea musciformis. Most research on invasive species in the Hawaiian archipelago has focused on shallow water habitats within the limits of conventional SCUBA (0-30 m). Deeper habitats such as mesophotic reefs are much more difficult to access and consequently little is known about the distribution of deepwater invasive species or their impacts. Recent deepwater (>30 m) sightings of H. musciformis and C. riisei, in and near NWHI, respectively, have prompted a call for further research and surveillance of invasive species in deepwater habitats. This report compiles the most up to date information about these two species of concern in deepwater habitats. A literature search and conversations with subject matter experts was used to identify their current distribution, preferred habitat types, optimal detection methods and ways to efficiently sample the vast extent of NWHI. The proposed sampling strategy prioritizes survey effort where C. riisei and H. musciformis are most likely to be found. At coarse spatial scales (tens to hundreds of kilometers), opportunistic observations and distance from the Main Hawaiian Islands, a principal propagule source, are used to identify high-risk islands and banks. At fine spatial scales (meters to tens of kilometers) a habitat suitability model was developed to identify high-risk habitats. The habitat suitability model focused on habitat preferences of C. riisei, since the species is well studied and adequate data exists to map habitats. There was insufficient information to identify suitable habitat for H. muscifomis. Habitat preferences for the algae are poorly understood and there is a lack of data at relevant spatial scales to map those preferences which are known. The principal habitats identified by the habitat suitability model were ledges and the edges of rugose coral reefs, where the shade loving octocoral would likely be found. Habitat suitability maps were developed for seven atolls and banks to aid in survey site selection. The protocol relied on technical divers to conduct visual surveys of benthic habitats. It was developed to increase the efficiency of surveys, maximize the probability of detection, identify important information relevant to future surveys and standardize results. The strategy, model and protocol were tested during a field mission in 2009 at several atolls and islands in NWHI. The field mission did not detect any invasive species among deepwater habitats and much was learned to improve future surveys. Data gaps and improvements are discussed.

An investigation of survey technologies and modeling techniques for improving deepwater surveys of nonindigenous species in the Northwestern Hawaiian Islands

Nonindigenous species (NIS) are a major threat to marine ecosystems, with possible dramatic effects on biodiversity, biological productivity, habitat structure and fisheries. The Papahānaumokuākea Marine National Monument (PMNM) has taken active steps to mitigate the threats of NIS in Northwestern Hawaiian Islands (NWHI). Of particular concern are the 13 NIS already detected in NWHI and two invasive species found among the main Hawaiian Islands, snowflake coral (Carijoa riseii) and a red alga (Hypnea musciformis). Much of the information regarding NIS in NWHI has been collected or informed by surveys using conventional SCUBA or fishing gear. These technologies have significant drawbacks. SCUBA is generally constrained to depths shallower than 40 m and several NIS of concern have been detected well below this limit (e.g., L. kasmira – 256 m) and fishing gear is highly selective. Consequently, not all habitats or species can be properly represented. Effective management of NIS requires knowledge of their spatial distribution and abundance over their entire range. Surveys which provide this requisite information can be expensive, especially in the marine environment and even more so in deepwater. Technologies which minimize costs, increase the probability of detection and are capable of satisfying multiple objectives simultaneously are desired. This report examines survey technologies, with a focus on towed camera systems (TCSs), and modeling techniques which can increase NIS detection and sampling efficiency in deepwater habitats of NWHI; thus filling a critical data gap in present datasets. A pilot study conducted in 2008 at French Frigate Shoals and Brooks Banks was used to investigate the application of TCSs for surveying NIS in habitats deeper than 40 m. Cost and data quality were assessed. Over 100 hours of video was collected, in which 124 sightings of NIS were made among benthic habitats from 20 to 250 m. Most sightings were of a single cosmopolitan species, Lutjanus kasmira, but Cephalopholis argus, and Lutjanus fulvus, were also detected. The data expand the spatial distributions of observed NIS into deepwater habitats, identify algal plain as an important habitat and complement existing data collected using SCUBA and fishing gear. The technology’s principal drawback was its inability to identify organisms of particular concern, such as Carijoa riseii and Hypnea musciformis due to inadequate camera resolution and inability to thoroughly inspect sites. To solve this issue we recommend incorporating high-resolution cameras into TCSs, or using alternative technologies, such as technical SCUBA diving or remotely operated vehicles, in place of TCSs. We compared several different survey technologies by cost and their ability to detect NIS and these results are summarized in Table 3.

Capture probability of a survey trawl for red king crab (Paralithodes camtschaticus)

The relative abundance of Bristol Bay red king crab (Paralithodes camtschaticus) is estimated each year for stock assessment by using catch-per-swept-area data collected on the Alaska Fisheries Science Center’s annual eastern Bering Sea bottom trawl survey. To estimate survey trawl capture efficiency for red king crab, an experiment was conducted with an auxiliary net (fitted with its own heavy chain-link footrope) that was attached beneath the trawl to capture crabs escaping under the survey trawl footrope. Capture probability was then estimated by fitting a model to the proportion of crabs captured and crab size data. For males, mean capture probability was 72% at 95 mm (carapace length), the size at which full vulnerability to the survey trawl is assigned in the current management model; 84.1% at 135 mm, the legal size for the fishery; and 93% at 184 mm, the maximum size observed in this study. For females, mean capture probability was 70% at 90 mm, the size at which full vulnerability to the survey trawl is assigned in the current management model, and 77% at 162 mm, the maximum size observed in this study. The precision of our estimates for each sex decreased for juveniles under 60 mm and for the largest crab because of small sample sizes. In situ data collected from trawl-mounted video cameras were used to determine the importance of various factors associated with the capture of individual crabs. Capture probability was significantly higher when a crab was standing when struck by the footrope, rather than crouching, and higher when a crab was hit along its body axis, rather than from the side. Capture probability also increased as a function of increasing crab size but decreased with increasing footrope distance from the bottom and when artificial light was provided for the video camera.

Outage probability of the gaussian MIMO free-space optical channel with PPM

Atmospheric effects can significantly degrade the reliability of free-space optical communications. One such effect is scintillation, caused by atmospheric turbulence, refers to random fluctuations in the irradiance and phase of the received laser beam. In this paper we inv stigate the use of multiple lasers and multiple apertures to mitigate scintillation. Since the scintillation process is slow, we adopt a block fading channel model and study the outage probability under the assumptions of orthogonal pulse-position modulation and non-ideal photodetection. Assuming perfect receiver channel state information (CSI), we derive the signal-to-noise ratio (SNR) exponents for the cases when the scintillation is lognormal, exponential and gammagamma distributed, which cover a wide range of atmospheric turbulence conditions. Furthermore, when CSI is also available at the transmitter, we illustrate very large gains in SNR are possible (in some cases larger than 15 dB) by adapting the transmitted power. Under a long-term power constraint, we outline fundamental design criteria via a simple expression that relates the required number of lasers and apertures for a given code rate and number of codeword blocks to completely remove system outages. Copyright © 2009 IEEE.

Tuning of detection wavelength in a resonant-cavity-enhanced quantum-dot-embedded photodiode by changing detection angle

We have fabricated a resonant-cavity-enhanced photodiode (RCE-PD) with InGaAs quantum dots (QDs) as an active medium. This sort of QD-embedded RCE-PD is capable of a peak external quantum efficiency of 32% and responsivity of 0.27A/W at 1.058 mu m with a full width at half maximum (FWHM) of 5 nm. Angle-resolved photocurrent response eventually proves that with the detection angle changing from 0 degrees to 60 degrees, the peak-current wavelength shifts towards the short wavelength side by 37 nm, while the quantum efficiency remains larger than 15%.