371 research outputs found
Assessing the Economic Gains from Telecom Competition
This paper develops and simulates a dynamic model of strategic telecom competition. The goal is to understand how regulatory policy, particularly relative to lease charges for local network elements, affects telecom competition, investment, retail prices, and consumer welfare. The model assumes two products, local voice service and data (broadband), and three types of players the regional Bell operating companies, referred to as incumbent local exchange carriers (ILECs), cable companies (Cables), and competitive local exchange carriers (CLECs). The game begins with a) ILECs established in each county with respect to the provision of local voice and data services and b) Cables established in roughly half of the counties with respect to the provision of data.There are one-time fixed costs of entering a county, product- and period-specific costs of operating in a county, and marginal costs of supplying each product. Economies of scope reduce the fixed entry and operating costs of supplying both products in a given county at a given point in time. Finally, in supplying telecom services in a given county, CLECs may enter by leasing ILEC infrastructure at specified access rates. The requirement that ILECs allow CLECs to lease their local network facilities was established in the Telecommunications Act of 1996 as part of a quid pro quo that promised ILECs entry into the long distance market. But the ILECs continue to contest the quid. The ILECs support their position by suggesting that leased access reduces telecom investment and output and raises telecom prices. Our model considers the entire range of options available to each of the players, but it reaches the opposite conclusion. Indeed, we find thatif UNE-P rates were set at the Supreme Court-approved total element long-run incremental cost (TELRIC) levels, telecom investment and employment outlays would increase by over one fifth in counties containing the majority of the U.S. population and by over 30 percent in counties containing almost a third of the population. The present value of telecom outlays over the next 5 and 20 years would rise by 155 billion, respectively. On average, the switch from actual to TELRIC UNE rates would lower local phone rates across the country's 3108 counties by 15 billion. Almost two fifths of the population would experience reductions in local phone rates of 20 percent or more. Over one fifth would experience rate reductions of 30 percent or more. These findings of price reductions are based on a fairly conservative parameterization of our model with respect to the specification of true ILEC and CLEC incremental long-run production costs.
Digital mammography, cancer screening: Factors important for image compression
The use of digital mammography for breast cancer screening poses several novel problems such as development of digital sensors, computer assisted diagnosis (CAD) methods for image noise suppression, enhancement, and pattern recognition, compression algorithms for image storage, transmission, and remote diagnosis. X-ray digital mammography using novel direct digital detection schemes or film digitizers results in large data sets and, therefore, image compression methods will play a significant role in the image processing and analysis by CAD techniques. In view of the extensive compression required, the relative merit of 'virtually lossless' versus lossy methods should be determined. A brief overview is presented here of the developments of digital sensors, CAD, and compression methods currently proposed and tested for mammography. The objective of the NCI/NASA Working Group on Digital Mammography is to stimulate the interest of the image processing and compression scientific community for this medical application and identify possible dual use technologies within the NASA centers
Normal and abnormal tissue identification system and method for medical images such as digital mammograms
A system and method for analyzing a medical image to determine whether an abnormality is present, for example, in digital mammograms, includes the application of a wavelet expansion to a raw image to obtain subspace images of varying resolution. At least one subspace image is selected that has a resolution commensurate with a desired predetermined detection resolution range. A functional form of a probability distribution function is determined for each selected subspace image, and an optimal statistical normal image region test is determined for each selected subspace image. A threshold level for the probability distribution function is established from the optimal statistical normal image region test for each selected subspace image. A region size comprising at least one sector is defined, and an output image is created that includes a combination of all regions for each selected subspace image. Each region has a first value when the region intensity level is above the threshold and a second value when the region intensity level is below the threshold. This permits the localization of a potential abnormality within the image
Morality and markets in the NHS
Since its establishment in 1948, the history of the National Health Service (NHS) has been characterized by
organisational turbulence and system reform. At the same time, progress in science, medicine and technology
throughout the western world have revolutionized the delivery of healthcare. The NHS has become a much loved, if
much critiqued, national treasure. It is against this backdrop that the role of this state-funded health service has been
brought into moral question. Certainly, the challenges facing healthcare policy-makers are numerous and complex,
but in the wake of the Health and Social Care Act (2012), no issue is more divisive than that of market-based reform.
Here we explore the turbulent history of the NHS, from its foundation to the birth of the healthcare marketplace.
We explore arguments for and against the healthcare market and resolve that, amid an evolving economic and moral
framework, the NHS must ensure that its original tenets of equity and autonomy remain at its core. We propose a
values-explicit, systems-based approach to renew focus on both the processes and the outcomes of care
Antarctic Krill Are Reservoirs for Distinct Southern Ocean Microbial Communities
Host-associated bacterial communities have received limited attention in polar habitats, but are likely to represent distinct nutrient-rich niches compared to the surrounding environment. Antarctic krill (Euphausia superba) are a super-abundant species with a circumpolar distribution, and the krill microbiome may make a substantial contribution to marine bacterial diversity in the Southern Ocean. We used high-throughput sequencing of the bacterial 16S ribosomal RNA gene to characterize bacterial diversity in seawater and krill tissue samples from four locations south of the Kerguelen Plateau, one of the most productive regions in the Indian Sector of the Southern Ocean. Krill-associated bacterial communities were distinct from those of the surrounding seawater, with different communities inhabiting the moults, digestive tract and faecal pellets, including several phyla not detected in the surrounding seawater. Digestive tissues from many individuals contained a potential gut symbiont (order: Mycoplasmoidales) shown to improve survival on a low quality diet in other crustaceans. Antarctic krill swarms thus influence Southern Ocean microbial communities not only through top-down grazing of eukaryotic cells and release of nutrients into the water column, but also by transporting distinct microbial assemblages horizontally via migration and vertically via sinking faecal pellets and moulted exuviae. Changes to Antarctic krill demographics or distribution through fishing pressure or climate-induced range shifts will also influence the composition and dispersal of Southern Ocean microbial communities
Complementary approaches to understanding the plant circadian clock
Circadian clocks are oscillatory genetic networks that help organisms adapt
to the 24-hour day/night cycle. The clock of the green alga Ostreococcus tauri
is the simplest plant clock discovered so far. Its many advantages as an
experimental system facilitate the testing of computational predictions.
We present a model of the Ostreococcus clock in the stochastic process
algebra Bio-PEPA and exploit its mapping to different analysis techniques, such
as ordinary differential equations, stochastic simulation algorithms and
model-checking. The small number of molecules reported for this system tests
the limits of the continuous approximation underlying differential equations.
We investigate the difference between continuous-deterministic and
discrete-stochastic approaches. Stochastic simulation and model-checking allow
us to formulate new hypotheses on the system behaviour, such as the presence of
self-sustained oscillations in single cells under constant light conditions.
We investigate how to model the timing of dawn and dusk in the context of
model-checking, which we use to compute how the probability distributions of
key biochemical species change over time. These show that the relative
variation in expression level is smallest at the time of peak expression,
making peak time an optimal experimental phase marker. Building on these
analyses, we use approaches from evolutionary systems biology to investigate
how changes in the rate of mRNA degradation impacts the phase of a key protein
likely to affect fitness. We explore how robust this circadian clock is towards
such potential mutational changes in its underlying biochemistry. Our work
shows that multiple approaches lead to a more complete understanding of the
clock
Efficient Parallel Statistical Model Checking of Biochemical Networks
We consider the problem of verifying stochastic models of biochemical
networks against behavioral properties expressed in temporal logic terms. Exact
probabilistic verification approaches such as, for example, CSL/PCTL model
checking, are undermined by a huge computational demand which rule them out for
most real case studies. Less demanding approaches, such as statistical model
checking, estimate the likelihood that a property is satisfied by sampling
executions out of the stochastic model. We propose a methodology for
efficiently estimating the likelihood that a LTL property P holds of a
stochastic model of a biochemical network. As with other statistical
verification techniques, the methodology we propose uses a stochastic
simulation algorithm for generating execution samples, however there are three
key aspects that improve the efficiency: first, the sample generation is driven
by on-the-fly verification of P which results in optimal overall simulation
time. Second, the confidence interval estimation for the probability of P to
hold is based on an efficient variant of the Wilson method which ensures a
faster convergence. Third, the whole methodology is designed according to a
parallel fashion and a prototype software tool has been implemented that
performs the sampling/verification process in parallel over an HPC
architecture
A viscoelastic deadly fluid in carnivorous pitcher plants
Background : The carnivorous plants of the genus Nepenthes, widely
distributed in the Asian tropics, rely mostly on nutrients derived from
arthropods trapped in their pitcher-shaped leaves and digested by their
enzymatic fluid. The genus exhibits a great diversity of prey and pitcher forms
and its mechanism of trapping has long intrigued scientists. The slippery inner
surfaces of the pitchers, which can be waxy or highly wettable, have so far
been considered as the key trapping devices. However, the occurrence of species
lacking such epidermal specializations but still effective at trapping insects
suggests the possible implication of other mechanisms. Methodology/Principal
Findings : Using a combination of insect bioassays, high-speed video and
rheological measurements, we show that the digestive fluid of Nepenthes
rafflesiana is highly viscoelastic and that this physical property is crucial
for the retention of insects in its traps. Trapping efficiency is shown to
remain strong even when the fluid is highly diluted by water, as long as the
elastic relaxation time of the fluid is higher than the typical time scale of
insect movements. Conclusions/Significance : This finding challenges the common
classification of Nepenthes pitchers as simple passive traps and is of great
adaptive significance for these tropical plants, which are often submitted to
high rainfalls and variations in fluid concentration. The viscoelastic trap
constitutes a cryptic but potentially widespread adaptation of Nepenthes
species and could be a homologous trait shared through common ancestry with the
sundew (Drosera) flypaper plants. Such large production of a highly
viscoelastic biopolymer fluid in permanent pools is nevertheless unique in the
plant kingdom and suggests novel applications for pest control
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