Full-Service MAC Protocol for Metro-Reach GPONs

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”An advanced medium access control protocol is presented demonstrating dynamic bandwidth allocation for long-reach gigabit-capable passive optical networks (GPONs). The protocol enables the optical line terminal to overlap the idle time slots in each packet transmission cycle with a virtual polling cycle to increase the effective transmission bandwidth. Contrasting the new scheme with developed algorithms, network modeling has exhibited significant improvement in channel throughput, mean packet delay, and packet loss rate in the presence of class-of-service and service-level differentiation. In particular, the displayed 34% increase in the overall channel throughput and 30 times reduction in mean packet delay for service-level 1 and service-level 2 optical network units (ONUs) at accustomed 50% ONU load constitutes the highest extended-reach GPON performance reported up to date.Peer reviewe

Isotopic liftings of Clifford algebras and applications in elementary particle mass matrices

Isotopic liftings of algebraic structures are investigated in the context of Clifford algebras, where it is defined a new product involving an arbitrary, but fixed, element of the Clifford algebra. This element acts as the unit with respect to the introduced product, and is called isounit. We construct isotopies in both associative and non-associative arbitrary algebras, and examples of these constructions are exhibited using Clifford algebras, which although associative, can generate the octonionic, non-associative, algebra. The whole formalism is developed in a Clifford algebraic arena, giving also the necessary pre-requisites to introduce isotopies of the exterior algebra. The flavor hadronic symmetry of the six u,d,s,c,b,t quarks is shown to be exact, when the generators of the isotopic Lie algebra su(6) are constructed, and the unit of the isotopic Clifford algebra is shown to be a function of the six quark masses. The limits constraining the parameters, that are entries of the representation of the isounit in the isotopic group SU(6), are based on the most recent limits imposed on quark masses.Comment: 19 page

Influence of shower fluctuations and primary composition on studies of the shower longitudinal development

We study the influence of shower fluctuations, and the possible presence of different nuclear species in the primary cosmic ray spectrum, on the experimental determination of both shower energy and the proton air inelastic cross section from studies of the longitudinal development of atmospheric showers in fluorescence experiments. We investigate the potential of track length integral and shower size at maximum as estimators of shower energy. We find that at very high energy (~10^19-10^20 eV) the error of the total energy assignment is dominated by the dependence on the hadronic interaction model, and is of the order of 5%. At lower energy (~10^17-10^18 eV), the uncertainty of the energy determination due to the limited knowledge of the primary cosmic ray composition is more important. The distribution of depth of shower maximum is discussed as a measure of the proton-air cross section. Uncertainties in a possible experimental measurement of this cross section introduced by intrinsic shower fluctuations, the model of hadronic interactions, and the unknown mixture of primary nuclei in the cosmic radiation are numerically evaluated.Comment: 12 pages, 11 figures, 4 table

Long-Term Safety of Tedizolid in a Patient With Spondilodiscitis After Switch From Linezolid Due to Toxicity

The patient is a 57-year-old man with liver cirrhosis, Bricker anastomosis after a radical cystoprostatectomy and, a history of bacteremias caused by extended-spectrum -lactamase-positive Escherichia coli, Enterococcus faecium, and Candida albicans. He presented with persistent low back pain and was diagnosed with vertebral osteomyelitis, for which he received ertapenem-linezolid treatment. However, after 20 days, linezolid had to be discontinued because of myelotoxicity and metabolic acidosis. The patient was switched to tedizolid, which, in combination with ertapenem, was successfully given for 114 days until biopsy showed no growth of gram-positive cocci. We conclude that tedizolid can be an alternative to linezolid in case of toxicity, especially in long-term treatments

Tratamiento de fracturas toracolumbares: nuestra experiencia en el periodo 2000-2003. Protocolo de actuación

Presentamos una revisión de los resultados obtenidos en pacientes intervenidos de fracturas tóraco-lumbares durante los años 2000 a 2003, en ambos inclusive, por el servicio de Traumatología y Cirugía Ortopédica del Hospital Universitario Virgen de las Nieves de Granada; así como el protocolo seguido en el manejo diagnóstico-terapéutico de este tipo de pacientes. Las fracturas más frecuentes fueron en L1 y del tipo A3 de la clasificación AO. La vía de abordaje más utilizada fue la posterior (138 casos). En 132 casos se instrumentó la vértebra fracturada y en 39 casos fue necesaria la descompresión. El índice sagital medio preoperatorio fue de 17,5º y el postoperatorio de 3,5º. La pérdida de altura vertebral preoperatoria fue del 52% y del 14% al final del tratamiento. En 39 pacientes con déficit neurológico se realizó descompresión. En el 79% de los casos los resultados fueron excelentes y en el resto regulares o malos.We present the results of surgical treatment in patients with thoraco-lumbar fractures operated on between the years 2000 and 2003 at the Orthopedic and Traumatology Department of the hospital Virgen de las Nieves Hospital of Granada, Spain. The diagnosis and therapeutic protocol of this type of patients is also evaluated. A3 type from AO classification fracture of L1, was the most frequent injury. Posterior surgical approach of the spine was mainly used (138 cases), in 132 cases the fracture was stabilized by means of internal fixation and 39 cases required decompression of the lumbar canal. The average sagital index was 17,5º preoperative and 3,5º after surgery. The average loss of height was 52% preoperative and 14% at the end of treatment. In 39 surgical decompression was indicated for neurological impairment. Excellent results were obtained in 79% of the cases, the rest were fair and poor

νd→μ−Δ++n\nu d \to \mu^- \Delta^{++} n Reaction and Axial Vector N−ΔN-\Delta Coupling

The reaction $\nu d \to \mu^- \Delta^{++} n$ is studied in the region of low $q^2$ to investigate the effect of deuteron structure and width of the $\Delta$ resonance on the differential cross section. The results are used to extract the axial vector $N-\Delta$ coupling $C^{A}_5$ from the experimental data on this reaction. The possibility to determine this coupling from electroweak interaction experiments with high intensity electron accelerators is discussed.Comment: 14 pages, REVTEX, 5 figure

Importancia de la embolización preoperatoria en el tratamiento del quiste óseo aneurismático: Presentación de un caso clínico

Se describe el tratamiento de un quiste óseo aneurismático localizado en el raquis dorsal, en un niño de 8 años de edad. El quiste óseo aneurismático es una lesión benigna y a menudo extremadamente vascular. En la columna puede causar extensa destrucción ósea y compromiso de las estructuras neurales. Se demuestra el valor de la embolización preoperatoria reduciendo la vascularización y permitiendo su extirpación quirúrgica total.I n this report, th e managemen t o f a n aneurysma l bon e cyst i n th e thoraci c spin e o f an 8 year s ol d bo y is described . Aneurysma l bon e is a histologicall y benig n lesio n tha t is ofte n extremel y vascular . I n th e spine , it ca n caus e extensiv e bon e destructio n an d compress neura l structures. Th e valu e o f preoperativ e embo - lizatio n t o reduc e vascularity , allowin g tota l excisio n is demonstrated

On the energy determination of extensive air showers through the fluorescence technique

The determination of the shower development in air using fluorescence yield is subject to corrections due to the angular spread of the particles in the shower. This could introduce systematic errors in the energy determination of an extensive air shower through the fluorescence technique.Comment: 4 pages, 2 figure

Microscopic description of d-wave superconductivity by Van Hove nesting in the Hubbard model

We devise a computational approach to the Hubbard model that captures the strong coupling dynamics arising when the Fermi level is at a Van Hove singularity in the density of states. We rely on an approximate degeneracy among the many-body states accounting for the main instabilities of the system (antiferromagnetism, d-wave superconductivity). The Fermi line turns out to be deformed in a manner consistent with the pinning of the Fermi level to the Van Hove singularity. For a doping rate $\delta \sim 0.2$, the ground state is characterized by d-wave symmetry, quasiparticles gapped only at the saddle-points of the band, and a large peak at zero momentum in the d-wave pairing correlations.Comment: 4 pages, 2 Postscript figure

Stress tensor fluctuations in de Sitter spacetime

The two-point function of the stress tensor operator of a quantum field in de Sitter spacetime is calculated for an arbitrary number of dimensions. We assume the field to be in the Bunch-Davies vacuum, and formulate our calculation in terms of de Sitter-invariant bitensors. Explicit results for free minimally coupled scalar fields with arbitrary mass are provided. We find long-range stress tensor correlations for sufficiently light fields (with mass m much smaller than the Hubble scale H), namely, the two-point function decays at large separations like an inverse power of the physical distance with an exponent proportional to m^2/H^2. In contrast, we show that for the massless case it decays at large separations like the fourth power of the physical distance. There is thus a discontinuity in the massless limit. As a byproduct of our work, we present a novel and simple geometric interpretation of de Sitter-invariant bitensors for pairs of points which cannot be connected by geodesics.Comment: 35 pages, 4 figure