2,565 research outputs found
Specific selection of antigen-reactive lymphocytes into antigenically stimulated lymph nodes in sheep
The physical limits of communication
It has been well-known since the pioneering work of Claude Shannon in the
1940s that a message transmitted with optimal efficiency over a channel of
limited bandwidth is indistinguishable from random noise to a receiver who is
unfamiliar with the language in which the message is written. In this letter we
demonstrate an equivalent result about electromagnetic transmissions. We show
that when electromagnetic radiation is used as the transmission medium, the
most information-efficient format for a given message is indistinguishable from
black-body radiation to a receiver who is unfamiliar with that format. The
characteristic temperature of the radiation is set by the amount of energy used
to make the transmission. If information is not encoded in the direction of the
radiation, but only its timing, energy or polarization, then the most efficient
format has the form of a one-dimensional black-body spectrum which is easily
distinguished from the three-dimensional case.Comment: 9 pages, 1 postscript figure, typeset in LaTeX using the RevTeX macro
packag
The systemic autoinflammatory disorders for dermatologists. Part 1: overview
The systemic autoinflammatory disorders (SAIDs) or periodic fever syndromes are disorders of innate immunity, which can be inherited or acquired. They are almost all very rare and easily overlooked; typically, patients will have seen multiple specialities prior to diagnosis, so a high level of clinical suspicion is key. It is important to note that these are âhighâvalueâ diagnoses as the majority of these syndromes can be very effectively controlled, dramatically improving quality of life and providing protection against the development of irreversible complications such as AA amyloidosis. In this article, we take an overview of SAIDs and look at the common features; in Part 2, we take a more inâdepth look at the better recognized or more dermatologically relevant conditions
The systemic autoinflammatory disorders for dermatologists. Part 2: disease examples
The systemic autoinflammatory disorders (SAIDS) or periodic fever syndromes are disorders of innate immunity, which can be inherited or acquired. They are almost all very rare and easily overlooked; typically, patients will have seen multiple specialities prior to diagnosis, so a high level of clinical suspicion is key. It is important to note that these are âhigh-valueâ diagnoses as the majority of these syndromes can be very effectively controlled, dramatically improving quality of life and providing protection against the development of irreversible complications such as AA amyloidosis. In Part 1 of this review, we took an overview of SAIDS and described the common features; in this article, we take a more in-depth look at the better recognized or more dermatologically relevant conditions
How cities prepare for climate change: Comparing Hamburg and Rotterdam
This paper compares the different ways in which the cities of Hamburg and Rotterdam are taking preemptive action to adapt to climate change. Literature, interviews, secondary data, official statistics, project reports and policy briefs were used to identify institutional arrangements used by the city governments to encourage innovations in climate adaptation strategies and involve the private sector in climate change policy implementation. We focus on cases that create positive opportunities; exploring how innovations are facilitated within the theoretical frameworks of the Porter hypothesis and eco-innovation. We examine two possible pathways of climate change governance, firstly strict regulation and formal enforcement, and secondly institutional eco-innovation and voluntary measures. We found that different emphasis is placed on the preferred pathway in each of the case studies. Hamburg focuses on formal enforcements while the Rotterdam city government encourages institutional eco-innovation by acting as a platform and also providing incentives. Our findings suggest that a well-designed institutional framework can enhance innovation and increase environmental and business performance. The framework could vary in instruments and patterns, using both formal constraints and incentives to increase voluntary actions to shape policy. The formal rules could be stringent or incentivising to shape the climate change measures. The research aims to contribute to both practice and science by providing examples that might motivate and inspire other cities to design appropriate institutions for climate change policy implementation
Developments in the scientific and clinical understanding of autoinflammatory disorders
The autoinflammatory diseases, also known as periodic fever syndromes, are disorders of innate immunity which can be inherited or acquired and which cause recurrent, self-limiting, seemingly spontaneous episodes of systemic inflammation and fever in the absence of autoantibody production or infection. There has been much recent progress in elucidating their aetiologies and treatment. With the exception of familial Mediterranean fever, which is common in certain populations, autoinflammatory diseases are mostly rare but should not be overlooked in the differential diagnosis of recurrent fevers since DNA diagnosis and effective therapies are available for many of them
Quasispecies Made Simple
Quasispecies are clouds of genotypes that appear in a population at mutationâselection balance. This concept has recently attracted the attention of virologists, because many RNA viruses appear to generate high levels of genetic variation that may enhance the evolution of drug resistance and immune escape. The literature on these important evolutionary processes is, however, quite challenging. Here we use simple models to link mutationâselection balance theory to the most novel property of quasispecies: the error thresholdâa mutation rate below which populations equilibrate in a traditional mutationâselection balance and above which the population experiences an error catastrophe, that is, the loss of the favored genotype through frequent deleterious mutations. These models show that a single fitness landscape may contain multiple, hierarchically organized error thresholds and that an error threshold is affected by the extent of back mutation and redundancy in the genotype-to-phenotype map. Importantly, an error threshold is distinct from an extinction threshold, which is the complete loss of the population through lethal mutations. Based on this framework, we argue that the lethal mutagenesis of a viral infection by mutation-inducing drugs is not a true error catastophe, but is an extinction catastrophe
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