Photon Counting OTDR : Advantages and Limitations

We give detailed insight into photon counting OTDR (nu-OTDR) operation, ranging from Geiger mode operation of avalanche photodiodes (APD), analysis of different APD bias schemes, to the discussion of OTDR perspectives. Our results demonstrate that an InGaAs/InP APD based nu-OTDR has the potential of outperforming the dynamic range of a conventional state-of-the-art OTDR by 10 dB as well as the 2-point resolution by a factor of 20. Considering the trace acquisition speed of nu-OTDRs, we find that a combination of rapid gating for high photon flux and free running mode for low photon flux is the most efficient solution. Concerning dead zones, our results are less promising. Without additional measures, e.g. an optical shutter, the photon counting approach is not competitive.Comment: 12 pages, 13 figures, accepted for publication by IEEE Journal of Lightwave Technolog

Larynx Preservation: Advantages and Limitations

For a long time standard treatment approach for resectable squamous cell carcinoma of larynx was surgery with or without subsequent radiotherapy. Surgery, particulary total laryngectomy, has been associated with serious impairment of quallity of life. Between nonsurgical approaches, concurrent cisplatin based chemoradiotherapy has become a very promising treatment modality for larynx preservation. However, concurrent chemotherapy has been associated with serious toxicity. The most recent treatment approach in larynx preservation is related to taxan based induction chemotherapy

3D Analysis of chromosome architecture: advantages and limitations with SEM

Three-dimensional mitotic plant chromosome architecture can be investigated with the highest resolution with scanning electron microscopy compared to other microscopic techniques at present. Specific chromatin staining techniques making use of simultaneous detection of back-scattered electrons and secondary electrons have provided conclusive information on the distribution of DNA and protein in barley chromosomes through mitosis. Applied to investigate the structural effects of different preparative procedures, these techniques were the groundwork for the ``dynamic matrix model{''} for chromosome condensation, which postulates an energy-dependent process of looping and bunching of chromatin coupled with attachment to a dynamic matrix of associated protein fibers. Data from SEM analysis shows basic higher order chromatin structures: chromomeres and matrix fibers. Visualization of nanogold-labeled phosphorylated histone H3 (ser10) with high resolution on chromomeres shows that functional modifications of chromatin can be located on structural elements in a 3D context. Copyright (C) 2005 S. Karger AG, Basel

Advantages and Limitations of Commercially Available Electrocuting Grids for Studying Mosquito Behaviour.

Mosquito feeding behaviour plays a major role in determining malaria transmission intensity and the impact of specific prevention measures. Human Landing Catch (HLC) is currently the only method that can directly and consistently measure the biting rates of anthropophagic mosquitoes, both indoors and outdoors. However, this method exposes the participant to mosquito-borne pathogens, therefore new exposure-free methods are needed to replace it. Commercially available electrocuting grids (EGs) were evaluated as an alternative to HLC using a Latin Square experimental design in Dar es Salaam, Tanzania. Both HLC and EGs were used to estimate the proportion of human exposure to mosquitoes occurring indoors (πi), as well as its two underlying parameters: the proportion of mosquitoes caught indoors (Pi) and the proportion of mosquitoes caught between the first and last hour when most people are indoors (Pfl). HLC and EGs methods accounted for 69% and 31% of the total number of female mosquitoes caught respectively and both methods caught more mosquitoes outdoors than indoors. Results from the gold standard HLC suggest that An. gambiae s.s. in Dar es Salaam is neither exophagic nor endophagic (Pi ≈ 0.5), whereas An. arabiensis is exophagic (Pi < < 0.5). Both species prefer to feed after 10 pm when most people are indoors (Pfl > >0.5). EGs yielded estimates of Pi for An. gambiae s.s., An. arabiensis and An. coustani, that were approximately equivalent to those with HLC but significantly underestimated Pfl for An. gambiae s.s. and An. coustani. The relative sampling sensitivity of EGs declined over the course of the night (p ≤ 0.001) for all mosquito taxa except An. arabiensis. Commercial EGs sample human-seeking mosquitoes with high sensitivity both indoors and outdoors and accurately measure the propensity of Anopheles malaria vectors to bite indoors rather than outdoors. However, further modifications are needed to stabilize sampling sensitivity over a full nocturnal cycle so that they can be used to survey patterns of human exposure to mosquitoes

Landslides and geophysical investigations: advantages and limitations

This special issue is dedicated to the geophysical methods applied to investigate, characterize, and monitor landslides. Over the years, both the advantages and limitations of these techniques have been highlighted, and some drawbacks are still open. Some papers were submitted to this special issue, and, after a thorough peer review process, only five articles were selected to be included in this special issue. This relatively small number is probably caused by the difficulty in applying geophysical techniques on slope movements given hard-operating conditions (e.g., high slopes, distance from access roads, and lack of security for the technical operator) and not because the methods limitations are greater than the advantages

ARGUMENTS TO JUSTIFY EURO - ADVANTAGES AND LIMITATIONS

Euro single currency was often used as an excuse to justify the worsening economic situation in some member countries, the European Central Bank being attacked several times; but we must not forget that for over 8/9 years euro gained against the dollar struggle, being the most used banknote in the world

Open source and accessibility: advantages and limitations

In this paper we discuss the open source process as it relates to accessibility software. Open source is a development model that has shown considerable benefits in a number of application areas. However the nature of accessibility tools and the intended users of such software products raise issues that must be addressed by the developer before users encounter the tools in real world contexts. In this paper we discuss the nature of the open source process, how it functions, and the motivations with regards to participation that developers self-report. We then explain the impact of these elements of the open source process as they relate to adaptive accessibility software. We use some specific examples of issues raised from the adoption of open source via a discussion of the ACCESS Framework, an accessibility engine designed to provide cross-platform accessibility support through plug-ins