Minimum broadcast digraphs Liestman, Arthur L; Peters, Joseph G
Discrete Applied Mathematics,
07/1992, Letnik:
37
Journal Article
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Odprti dostop
Broadcasting is an information dissemination process in which a message is to be sent from a single originator to all members of a network by placing calls over the communication lines of the ...network. Numerous previous paper have investigated ways to construct sparse graphs (networks) in which this process can be completed in minimum time from any originator. In this paper, we consider the broadcasting problem in directed graphs. We show that several of the upper and lower bounds which have been produced for the undirected problem have analogs in the directed case. We describe several techniques to construct sparse digraphs on
n vertices in which broadcasting can be completed in minimum time from any originator. For several values of
n, these techniques produce the sparsest possible digraphs of this type (called minimum broadcast digraphs). For other values of
n, these techniques produce the sparsest known digraphs of this type.
Broadcasting in bounded degree graphs BERMOND, J.-C; HELL, P; LIESTMAN, A. L ...
SIAM journal on discrete mathematics,
02/1992, Letnik:
5, Številka:
1
Journal Article
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Odprti dostop
Broadcasting is an information dissemination process in which a message is to be sent from a single originator to all members of a network by placing calls over the communication lines of the ...network. Several previous papers have investigated methods to construct sparse graphs (networks) in which this process can be completed in minimum time from any originator. The graphs produced by these methods contain high degree vertices. Liestman and Peters, SIAM Journal on Discrete Mathematics, 1 (1988), pp. 531-540 and Bermond and Peyrat, Proceedings of the 19th SE Conference on Combinatorics, Graph Theory and Computing, Congressus Numerantium, 1988, pp. 283-292 began an investigation of graphs with fixed maximum degree in which broadcasting can be completed in near minimum time. This investigation is continued in this paper by giving lower bounds and constructing bounded degree graphs that allow rapid broadcasting. The constructions use ideas developed by Jerrum and Skyum IEEE Transactions on Computers, C-33(2), 1984, pp. 190-194, which allow passing from a graph with good average case behaviour to one with good worst case behaviour. In addition, de Bruijn digraphs de Bruijn, Koninkhjke Nederlandse Akademie Van Wetenschappen, Indagationes Mathematicae, Series A, 49 (1946), pp. 758-764, minimum broadcast graphs, and sparse broadcast graphs Bermond, Hell, Liestman, and Peters, Discrete Applied Mathematics, to appear are used. The resulting graphs yield the best broadcasting time known for bounded degree graphs. Also obtained are asymptotic upper and lower bounds for broadcasting time, as the maximum degree increases.
Substantial numbers of individuals in the world are short of both dietary energy and dietary protein. The effective use of proteins and the world food supply are the subject of papers of the NATO ...Advanced Study Institute (1972). The principal obj ectives of the meeting were to review existing knowledge of world protein sources in relation to human requirements, to discuss factors affecting protein utilization in the body, to assess critically the usefulness in human nutrition of methods used for the evaluation of protein quality, and to consider the role of the food scientist and technologist in the development and use of new protein foods
High quality Nb-based superconductor-insulator-superconductor (SIS) junctions with Al oxide (AlO\(_x\)) tunnel barriers grown from Al overlayers are widely reported in the literature. However, the ...thin barriers required for high critical current density (J\(_c\)) junctions exhibit defects that result in significant subgap leakage current that is detrimental for many applications. High quality, high-J\(_c\) junctions can be realized with AlN\(_x\) barriers, but control of J\(_c\) is more difficult than with AlO\(_x\). It is therefore of interest to study the growth of thin AlO\(_x\) barriers with the ultimate goal of achieving high quality, high-J\(_c\) AlO\(_x\) junctions. In this work, 100\%\ O\(_2\) and 2\%\ O\(_2\) in Ar gas mixtures are used both statically and dynamically to grow AlO\(_x\) tunnel barriers over a large range of oxygen exposures. In situ ellipsometry is used for the first time to extensively measure AlO\(_x\) tunnel barrier growth in real time, revealing a number of unexpected patterns. Finally, a set of test junction wafers was fabricated that exhibited the well-known dependence of J\(_c\) on oxygen exposure (E) in order to further validate the experimental setup.
To describe physicians' experiences in attempting to provide optimal care for families of children who suffer from sudden, acute life-threatening conditions (SALTC).
To generate descriptive data in ...this exploratory study, we used qualitative methods including focus groups and in-depth interviews. Transcripts of focus groups and interviews were analyzed for content using standard phenomenologic analysis methods, which resulted in a participant-generated conceptual model of optimal care for families of children with SALTC.
The intensive care unit of an urban pediatric teaching hospital.
Twenty-two pediatric intensive care unit physicians, including residents, fellows, and attendings.
None.
Each participating physician provided qualitative descriptions of experiences caring for families of children with SALTC.
Physicians identified 4 components of optimal care for families: (1) providing timely, accurate information about their child; (2) maintaining privacy for confidential discussions and personal grieving; (3) giving adequate emotional support; and (4) granting family members the right to hold and comfort their dying child. Physicians also described barriers to, and facilitators of this optimal care.
Descriptive information provided in this exploratory study offers a complex model of optimal family care. Issues that affect the quality of care to families include those related to the context of providing care in a large teaching hospital, as well as subtleties of communication between parents and staff. Physicians' beliefs about optimal care of families in the pediatric intensive care unit revealed implications for both practice and training in pediatrics.
Broadcast Networks of Bounded Degree Liestman, Arthur L.; Peters, Joseph G.
SIAM journal on discrete mathematics,
11/1988, Letnik:
1, Številka:
4
Journal Article
Recenzirano
Broadcasting is an information dissemination process in which a message is to be sent from a single originator to all members of a network by placing calls over the communication lines of the ...network. Several previous papers have investigated ways to construct sparse graphs (networks) in which this process can be completed in minimum time from any originator. The graphs produced by these methods contain high degree vertices. This paper describes graphs with fixed maximum degree in which broadcasting can be completed in near minimum time.
Type 1 diabetes (T1D) is an autoimmune disease that targets pancreatic islet beta cells and incorporates genetic and environmental factors
, including complex genetic elements
, patient exposures
and ...the gut microbiome
. Viral infections
and broader gut dysbioses
have been identified as potential causes or contributing factors; however, human studies have not yet identified microbial compositional or functional triggers that are predictive of islet autoimmunity or T1D. Here we analyse 10,913 metagenomes in stool samples from 783 mostly white, non-Hispanic children. The samples were collected monthly from three months of age until the clinical end point (islet autoimmunity or T1D) in the The Environmental Determinants of Diabetes in the Young (TEDDY) study, to characterize the natural history of the early gut microbiome in connection to islet autoimmunity, T1D diagnosis, and other common early life events such as antibiotic treatments and probiotics. The microbiomes of control children contained more genes that were related to fermentation and the biosynthesis of short-chain fatty acids, but these were not consistently associated with particular taxa across geographically diverse clinical centres, suggesting that microbial factors associated with T1D are taxonomically diffuse but functionally more coherent. When we investigated the broader establishment and development of the infant microbiome, both taxonomic and functional profiles were dynamic and highly individualized, and dominated in the first year of life by one of three largely exclusive Bifidobacterium species (B. bifidum, B. breve or B. longum) or by the phylum Proteobacteria. In particular, the strain-specific carriage of genes for the utilization of human milk oligosaccharide within a subset of B. longum was present specifically in breast-fed infants. These analyses of TEDDY gut metagenomes provide, to our knowledge, the largest and most detailed longitudinal functional profile of the developing gut microbiome in relation to islet autoimmunity, T1D and other early childhood events. Together with existing evidence from human cohorts
and a T1D mouse model
, these data support the protective effects of short-chain fatty acids in early-onset human T1D.
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