4,761 research outputs found
On Efficiency and Validity of Previous Homeplug MAC Performance Analysis
The Medium Access Control protocol of Power Line Communication networks
(defined in Homeplug and IEEE 1901 standards) has received relatively modest
attention from the research community. As a consequence, there is only one
analytic model that complies with the standardised MAC procedures and considers
unsaturated conditions. We identify two important limitations of the existing
analytic model: high computational expense and predicted results just prior to
the predicted saturation point do not correspond to long-term network
performance. In this work, we present a simplification of the previously
defined analytic model of Homeplug MAC able to substantially reduce its
complexity and demonstrate that the previous performance results just before
predicted saturation correspond to a transitory phase. We determine that the
causes of previous misprediction are common analytical assumptions and the
potential occurrence of a transitory phase, that we show to be of extremely
long duration under certain circumstances. We also provide techniques, both
analytical and experimental, to correctly predict long-term behaviour and
analyse the effect of specific Homeplug/IEEE 1901 features on the magnitude of
misprediction errors
Modeling, Analysis and Impact of a Long Transitory Phase in Random Access Protocols
In random access protocols, the service rate depends on the number of
stations with a packet buffered for transmission. We demonstrate via numerical
analysis that this state-dependent rate along with the consideration of Poisson
traffic and infinite (or large enough to be considered infinite) buffer size
may cause a high-throughput and extremely long (in the order of hours)
transitory phase when traffic arrivals are right above the stability limit. We
also perform an experimental evaluation to provide further insight into the
characterisation of this transitory phase of the network by analysing
statistical properties of its duration. The identification of the presence as
well as the characterisation of this behaviour is crucial to avoid
misprediction, which has a significant potential impact on network performance
and optimisation. Furthermore, we discuss practical implications of this
finding and propose a distributed and low-complexity mechanism to keep the
network operating in the high-throughput phase.Comment: 13 pages, 10 figures, Submitted to IEEE/ACM Transactions on
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A role for von Hippel-Lindau protein in pancreatic beta-cell function.
ObjectiveThe Vhlh gene codes for the von Hippel-Lindau protein (VHL), a tumor suppressor that is a key player in the cellular response to oxygen sensing. In humans, a germline mutation in the VHL gene leads to the von Hippel-Lindau disease, a familial syndrome characterized by benign and malignant tumors of the kidney, central nervous system, and pancreas.Research design and methodsWe use Cre-lox recombination to eliminate Vhlh in adult mouse pancreatic beta-cells. Morphology of mutant islets is assessed by immunofluorescence analysis. To determine the functional state of Vhlh(-/-) islets, insulin secretion is measured in vivo and in vitro, and quantitative PCR is used to identify changes in gene expression.ResultsLoss of VHL in beta-cells leads to a severe glucose-intolerant phenotype in adult animals. Although VHL is not required for beta-cell specification and development, it is critical for beta-cell function. Insulin production is normal in beta-cells lacking VHL; however, insulin secretion in the presence of high concentrations of glucose is impaired. Furthermore, the loss of VHL leads to dysregulation of glycolytic enzymes, pointing to a perturbation of the intracellular energy homeostasis.ConclusionsWe show that loss of VHL in beta-cells leads to defects in glucose homeostasis, indicating an important and previously unappreciated role for VHL in beta-cell function. We believe that the beta-cell-specific Vhlh-deficient mice might be a useful tool as a "genetic hypoxia" model, to unravel the possible link between hypoxia signaling and impairment of beta-cell function
Multi-domain ferroelectricity as a limiting factor for voltage amplification in ferroelectric field-effect transistors
We revise the possibility of having an amplified surface potential in
ferroelectric field-effect transistors pointed out by [S. Salahuddin and S.
Datta, Nano Lett. 8, 405 (2008)]. We show that the negative-capacitance regime
that allows for such an amplification is actually bounded by the appearance of
multi-domain ferroelectricity. This imposes a severe limit to the maximum
step-up of the surface potential obtainable in the device. We indicate new
device design rules taking into account this scenario.Comment: 4 pages, 3 figure
El coleccionismo de fotografía en España y la colección Castellano
La primera parte de este artículo repasa varias de las principales colecciones de fotografía en España de los siglos XIX y XX, centrándose en su proceso de institucionalización, mediante el cual el archivo personal de un fotógrafo se transforma en una colección. La segunda parte estudia una gran excepción dentro de este panorama, una colección privada de fotografía, la reunida por el pintor madrileño Manuel Castellano entre los años 1850 y 1875 aproximadamente. Un análisis de su contenido y de las anotaciones escritas sobre las fotografías sugiere algunos posibles criterios seguidos en la formación de la colección, en su presentación y sobre la forma en la que fue contemplada.The first part of this paper presents an overview of several of the principal photographic collections in Spain from the 19th and 20th centuries, focusing on their process of institutionalisation by which a photographer's personal archive is transformed into a collection. The second part studies a notable exception within this panorama: a private photographic collection assembled by the Madrid painter Manuel Castellano between 1850-1870, approximately. An analysis of its content and the written annotations about these photos suggests certain possible criteria followed in its presentation and regarding the way in which it was contemplated
Prevalencia de patógenos zoonósicos (virus de Influenza Aviar, flavivirus del Complejo Antigénico de la Encefalitis Japonesa y Salmonella spp.) y resultados preliminares de parasitofauna hemática en paloma doméstica (Columba livia doméstica) y animales de la colección del Parque zoológico Municipal de Córdoba
Premio extraordinario de Trabajo Fin de Máster curso 2013-2014. Medicina,Sanidad y Mejora Animal.Durante el periodo 2013-2014 se realizó un estudio transversal para determinar la
prevalencia de patógenos zoonósicos y hemoparásitos en 154 palomas domésticas (Columba
livia var. domestica) capturadas en el Parque Zoológico Municipal de Córdoba (PZMC) y en
93 muestras de animales de la colección del Parque.
Las muestras de suero se analizaron para detectar anticuerpos frente a virus de la
Influenza Aviar (VIA) y flavivirus del Complejo Antigénico de la Encefalitis Japonesa
(CAEJ). Así mismo, se analizaron muestras de contenidos digestivos y heces para el
aislamiento de Salmonella spp. Paralelamente, se determinó la frecuencia de infección de
hemoparásitos en 60 palomas.
No se detectaron anticuerpos frente a VIA en ninguna de las 148 (0,0%; IC95%:0,0-
1,9) palomas analizadas mediante bELISA, mientras que se confirmó seropositividad en 5 de
28 (18,5%; IC95%:6,0-31,0) aves de la colección. Once de 142 (8,5%; IC95%:4,0-12,9) sueros
de palomas presentaron anticuerpos frente a flavivirus del CAEJ mediante bELISA. Además,
4 de los 49 (8,2%; IC95%:1,9-14,5) ejemplares de la colección analizados resultaron
seropositivos frente a flavivirus. El cultivo para el aislamiento de Salmonella spp. determinó
ausencia de infección en las 152 muestras de contenido digestivo de paloma (0,0%;
IC95%:0,0-1,9), mientras que 4 de 44 (9,1%; IC95%:1,0-17,2) muestras de heces de los
animales de la colección resultaron positivas. Haemoproteus sub. Haemoproteus spp. fue
detectado en 52 de las 60 (86,7%; IC95%:78,3-95,0) palomas analizadas.
Los resultados obtenidos indican circulación de flavivirus del CAEJ en la población
de palomas y animales del PZMC. Estas especies podrían ser usadas como centinelas para la
monitorización de flavivirus en zonas urbanas. La ausencia de positividad frente a VIA y
Salmonella spp., sugieren que las palomas no tienen un papel relevante en la epidemiología
de estos patógenos. Los resultados determinan una elevada diseminación de Haemoproteus
(H.) en las poblaciones de palomas del PZMC, lo cual podría tener implicación para la
conservación de algunas especies de aves.A cross-sectional study was carried out to determine the prevalence of different
pathogenic zoonotic agents and hemoparasites in 154 domestic pigeon (Columba livia var.
domestica) and 93 samples of animals from the Córdoba Municipal Zoo Park (CMZP)
between 2013 and 2014.
Serum samples were tested to determine the presence of antibodies against Avian
Influenza virus (AIV) and flaviviruses of the Japanese Encephalitis Antigenic Complex
(JEAC). Moreover, samples of digestive content were analyzed for Salmonella spp. isolation.
Seropositivity to AIV was not found in any of the 148 pigeons samples tested, while 5
out of 28 (18.5%; IC95%:6.0-31.0) zoo birds showed positive results using bELISA. A total of
11 out of 142 (8.5%; IC95%:4.0-12.9) pigeons analyzed presented antibodies to JEAC by
bELISA. Thus, 4 out of 49 (8.2%; IC95%:1.9-14.5) zoo animals were seropositive against
flaviviruses. Salmonella spp. was not isolated in any of the 152 intestine samples of pigeon
(0.0%; IC95%:0.0-1.9), but 4 out of 44 samples (9.1%; IC95%:1.0-17.2) from zoo animals were
positive. Finally, 52 out of 60 (86.7%; IC95%:78.3-95.0) were infected by Haemoproteus sub.
Haemoproteus spp.
The results obtained in the present study indicate circulation of flaviviruses of the
JEAC in domestic pigeons and animals from the CMZP. The absence of seropositivity
against AIV and the negative cultures to Salmonella spp. in the pigeons tested, suggest a
limited role of this species in the epidemiology of both diseases. Parasitological results
suggest a widespread of Haemoproteus (H.) in the pigeon population, which could has
implications for the conservation of bird species
AIP and MEN1 mutations and AIP immunohistochemistry in pituitary adenomas in a tertiary referral center.
Background: Pituitary adenomas have a high disease burden due to tumor growth/
invasion and disordered hormonal secretion. Germline mutations in genes such as MEN1
and AIP are associated with early onset of aggressive pituitary adenomas that can be
resistant to medical therapy.
Aims: We performed a retrospective screening study using published risk criteria to
assess the frequency of AIP and MEN1 mutations in pituitary adenoma patients in a
tertiary referral center.
Methods: Pituitary adenoma patients with pediatric/adolescent onset, macroadenomas
occurring ≤30 years of age, familial isolated pituitary adenoma (FIPA) kindreds and
acromegaly or prolactinoma cases that were uncontrolled by medical therapy were
studied genetically. We also assessed whether immunohistochemical staining for
AIP (AIP-IHC) in somatotropinomas was associated with somatostatin analogs (SSA)
response.
Results: Fifty-five patients met the study criteria and underwent genetic screening for
AIP/MEN1 mutations. No mutations were identified and large deletions/duplications were
ruled out using MLPA. In a cohort of sporadic somatotropinomas, low AIP-IHC tumors
were significantly larger (P = 0.002) and were more frequently sparsely granulated
(P = 0.046) than high AIP-IHC tumors. No significant relationship between AIP-IHC and
SSA responses was seen.
Conclusions: Germline mutations in AIP/MEN1 in pituitary adenoma patients are rare and
the use of general risk criteria did not identify cases in a large tertiary-referral setting.
In acromegaly, low AIP-IHC was related to larger tumor size and more frequent sparsely
granulated subtype but no relationship with SSA responsiveness was seen. The genetics
of pituitary adenomas remains largely unexplained and AIP screening criteria could be
significantly refined to focus on large, aggressive tumors in young patients
On the use of logistic functions for coastal flood assessment
Coastal flooding results as the combination of wave conditions, mean water level and
terrain characteristics. The associated damage can be expressed as a function of the
flooding water column and it will rarely remain stationary in a sea level scenario. The
objective of the study is to determine the importance of the dynamic (waves) and
hydrostatic (sea level) component as a function of a damage level and to determine what
combinations of hydrodynamic drivers may lead to unacceptable damage levels.
The analysis has been performed through the use of logistic functions in the beach of
Sant Pere Pescador (Girona province), covering an extension of 6,3 kilometres with an
average width of 90m. The approach of the research consists of the creation of two
multinomial regression models to be analyzed for 6 hydrodynamic scenarios derived from
a coupled hydromorphodynamic model, one made in a node-by-node basis and the other
one through polygons. The results show that a node-by-node model has nearly 10% of
information loss due to the small variability and the small number of measurements.
However, both models successfully predict similar expected prediction and probability to
reach a flood categories for the proposed scenarios.
Results from the multinomial regression clearly reveals sea level rise as the main
contribution to flood increase, with the wave return period being less significant. The
model also suggests that a drastic increase in the flooding water column, approximately
between 0,6 and 1 m will occur for sea level rise bigger than 0,25m. According the IPCC
predictions for the sea level rise in the Mediterranean Coast, this is expected to occur
between a time range of 2040-2070 (for the RCP 8.5, the most dramatic climate scenario)
or starting in 2045 (for RCP 2.6 and RCP 4.5, less severe scenarios).
For what concerns the spatial extension of the flooding, the expected categories of
flooding shows that the northern region of the Sant Pere Pescador beach is likely to suffer
more severe flooding than the central and southern regions, both in intensity and spatial
extent, reaching water depths larger than 0,6 - 1m for scenarios with sea level rise larger
than 0,25m.Las inundaciones de costas son fenómenos causados por la combinación del oleaje, el nivel
medio del mar y las características del terreno. El daño asociado puede ser expresado en
función de la columna de agua de inundación, tomando diferentes valores para distintas
situaciones de subida del nivel del mar. El objetivo del presente estudio es determinar la
importancia de la componente dinámica (olas) e hidrostática (nivel del mar) como
componentes de predicción del nivel de daño para poder determinar qué combinaciones
de parámetros hidrodinámicos lleva a niveles de daño inaceptables.
El análisis se ha llevado a cabo a través del uso de modelos logísticos en la zona de playa
de Sant Pere Pescador (Provincia de Girona), cubriendo una extensión de 6,3 Km de
largo con un ancho medio de 90m. Para su desarrollo, se han elaborados dos modelos
multinomiales de regresión analizando 6 escenarios hidrodinámicos. Uno de los modelos
se ha centrado en el estudio nodo a nodo y el otro mediante el análisis de polígonos. Los
resultados muestran que, para el modelo nodo a nodo, hay una pérdida de cerca del 10%
de la información inicial debido a la escasa variabilidad en la muestra y debido al reducido
número de datos disponibles. No obstante, ambos modelos consiguen predecir de manera
similar la probabilidad y la predicción de llegar a ciertas categorías de inundación para
los distintos escenarios.
Los resultados del modelo de regresión logística muestran la subida del nivel del mar
como principal contribuyente al incremento de la cota de inundación, mientras que el
período de retorno de la ola es menos significativo. El modelo también indica que para
niveles de incremento del nivel del mar mayores que 0,25m, gran parte de la costa se va
a ver seriamente afectada con inundaciones entre 0,6 y 1 metro de agua. Según las
predicciones del IPCC, para incrementos del nivel del mar en la costa del Mediterráneo,
se espera que una subida del nivel del mar alcance los 0,25m entre el 2040 y el 2070 (para
el RCP 8.5, el escenario climático más severo) o 2045 (para escenarios climáticos menos
graves como el RCP 2.6 y RCP 4.5).
En cuanto a la extensión de la inundación, se prevé que en la zona norte de la Playa de
Sant Pere Pescador se obtengan mayores categorías de inundación, en comparación con
la zona centro y sur, debido a la elevación y la configuración de las dunas. Concretamente,
se esperan valores de inundación entre 0,6m y 1m en la zona norte para escenarios de
subida del nivel del mar mayor que 0,25m.Les inundacions de costes son fenòmens causats per la combinació de l’onatge, el nivell
mig del mar i les característiques del terreny. Els danys associats poden ser expressats en
funció de la columna d’aigua d’inundació, prenent valors variables en funció dels diferents
escenaris d’augment del nivell. del mar. L’objectiu d’aquest treball és determinar la
importància de la component dinàmica (onades) i hidrostàtica (nivell del mar) en la
predicció del nivell de dany per tal de determinar quines combinacions dels paràmetres
hidrodinàmics duen a nivells de dany inacceptables.
L’anàlisi s’ha dut a terme a través de l’ús de models logístics en la zona de platja de Sant
Pere Pescador (Província de Girona), cobrint una extensió de 6,3 Km de llarg i un ample
mitjà de 90m. S’han analitzat 6 escenaris hidrodinàmics mitjançant l’elaboració de dos
models multinomials, un centrat en l’estudi node a node i l’altre mitjançant polígons. Els
resultats mostren que, per el model node a node, hi ha una pèrdua aproximada d’un 10%
de la informació inicial, degut a l’escassa variabilitat en la mostra i al reduït nombre de
dades mesurades. No obstant, ambdós models aconsegueixen predir de manera molt
similar la probabilitat i les prediccions d’arribar a certes categories d’inundació per a
diferents escenaris.
Els resultats del model de regressió logístic mostra la pujada del nivell del mar com a
principal contribuïdor a l’increment del nivell d’inundació, mentre que el període de
retorn resulta menys significatiu. El model també indica que, per a nivells d’increment
del mar majors de 0,25m, gran part de la costa es veurà greument afectada amb
inundacions d’entre 0,6 i 1m d’aigua. Segons les prediccions del IPCC, s’espera que en la
costa Mediterrània el nivell del mar pugi fins els 0,25m entre el 2040 i el 2070 (per el
RCP 8.5, que és l’escenari climàtic més advers) o al 2045 (per a prediccions climàtiques
menys greus, com el RCP 2.6 i 4.5)
Pel que fa l’extensió de la inundació, es preveu que a la zona nord de la Platja de Sant
Pere Pescador s’hi obtinguin majors cotes d’inundació que en les zones centre i sud, degut
a l’elevació i la configuració de les dunes. Concretament, s’esperen valors d’inundació
entre 0,6 i 1m per a escenaris on la pujada del nivell del mar sobrepassi els 0,25m
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