2,410 research outputs found
Fundamentals of Heterogeneous Cellular Networks with Energy Harvesting
We develop a new tractable model for K-tier heterogeneous cellular networks
(HetNets), where each base station (BS) is powered solely by a self-contained
energy harvesting module. The BSs across tiers differ in terms of the energy
harvesting rate, energy storage capacity, transmit power and deployment
density. Since a BS may not always have enough energy, it may need to be kept
OFF and allowed to recharge while nearby users are served by neighboring BSs
that are ON. We show that the fraction of time a k^{th} tier BS can be kept ON,
termed availability \rho_k, is a fundamental metric of interest. Using tools
from random walk theory, fixed point analysis and stochastic geometry, we
characterize the set of K-tuples (\rho_1, \rho_2, ... \rho_K), termed the
availability region, that is achievable by general uncoordinated operational
strategies, where the decision to toggle the current ON/OFF state of a BS is
taken independently of the other BSs. If the availability vector corresponding
to the optimal system performance, e.g., in terms of rate, lies in this
availability region, there is no performance loss due to the presence of
unreliable energy sources. As a part of our analysis, we model the temporal
dynamics of the energy level at each BS as a birth-death process, derive the
energy utilization rate, and use hitting/stopping time analysis to prove that
there exists a fundamental limit on \rho_k that cannot be surpassed by any
uncoordinated strategy.Comment: submitted to IEEE Transactions on Wireless Communications, July 201
Cetacean strandings and museum collections: A focus on Sicily island crossroads for mediterranean species
The study examined the extent of the cetacean strandings in Italy, with a particular focus on Sicily Island. The paper aimed to contribute to the description of a pattern that contemplates the “regular and rare” cetacean species passage along the Sicilian coast. The estimate of marine cetacean strandings was extrapolated from the National Strandings Data Bank (BDS—Banca Dati Spiaggiamenti) and evaluated according to a subdivision in three coastal subregions: the Tyrrhenian sub-basin (northern Sicilian coast), the Ionian sub-basin (eastern Sicilian coast), and the Channel of Sicily (southern Sicilian coast). Along the Italian coast, more than 4880 stranding events have been counted in the period 1990–2019. Most of these were recorded in five Italian regions: Apulia, Sicily, Sardinia, Tuscany, and Calabria. Approximately 15% of the recorded strandings in Italy occurred on the Sicilian coast. In Sicily Island, 725 stranded cetaceans were recorded in 709 stranding events, resulting in approximately 20 carcasses every year; the total number of specimens identified to species level was 539. The distribution along the Sicilian coast was the following: 312 recorded in the Tyrrhenian sub-basin, 193 in the Ionian sub-basin, and 220 in the Channel of Sicily. Stenella coeruleoalba was the species that can be considered as the stable record along the time-lapse investigated, and some rare species have been recorded as well. The role of Sicily Island as a sentinel territory of the cetacean distribution for the central Mediterranean Sea and as a region receiving a marine resource suitable for the scientific research and cetological museum collections is discussed herein
Griffiths phase-like behaviour and spin-phonon coupling in double perovskite TbNiMnO
The Griffiths phase-like features and the spin-phonon coupling effects
observed in TbNiMnO are reported. The double perovskite compound
crystallizes in monoclinic space group and exhibits a magnetic phase
transition at 111 K as an abrupt change in magnetization. A negative
deviation from ideal Curie-Weiss law exhibited by 1/ curves and
less-than-unity susceptibility exponents from the power-law analysis of inverse
susceptibility are reminiscent of Griffiths phase-like features. Arrott plots
derived from magnetization isotherms support the inhomogeneous nature of
magnetism in this material. The observed effects originate from
antiferromagnetic interactions which arise from inherent disorder in the
system. Raman scattering experiments display no magnetic-order-induced phonon
renormalization below in TbNiMnO which is different from the
results observed in other double perovskites and is correlated to the smaller
size of the rare earth. The temperature evolution of full-width-at-half-maximum
for the {\it stretching} mode at 645 cm presents an anomaly which
coincides with the magnetic transition temperature and signals a close
connection between magnetism and lattice in this material.Comment: 17 pages, 8 figures; accepted in J. Appl. Phy
The MIR Flickr Retrieval Evaluation Proposal Based on User Tags and Textual Passwords
In most well known image retrieval test sets, the imagery typically cannot be freely distributed or is not representative of a large community of users. In this paper we present a collection for the MIR community comprising 69,000 images from the Flickr website which are redistributable for research purposes and represent a real community of users both in the image content and image tags. We have extracted the tags and EXIF image meta data, and also make all of these publicly available. In addition we discuss several challenges for benchmarking retrieval and classification methods and applications
Investigations of the Morphology of Dust Shells of Comet C/2001 Q4 (NEAT)
The morphology of the dust fans and shells in the images of comet C/2001 Q4 (NEAT) showed significant changes between 2004 April and June due to rapid changes in the Earth viewing and solar illumination geometry. We model the trajectories of dust grains ejected from distributed sources on the comet to explain the observed dust morphology in the images obtained on 2004 April 16, May 12, 16, and 21, and June 3. From the fit to the observations we derive the direction of the rotation pole of the nucleus as αp = 270° ± 10° and δp = 15° ± 10°. The derived latitudes of the sources vary between -85° and +80°. Six of the sources are found to lie on a single meridian within ±25°. Using theoretical production rates of water from these sources, reported water production rates, and the archived visual light curve of the comet, we estimate the total active area on the comet to be 38.7 ± 5.8 km2 near perihelion. The fractional active area on the comet is 12% ± 2% or 25% ± 4% at perihelion, corresponding to a nuclear radius of 5 or 3.5 km, respectively. The large outgassing areas estimated in the present work can be attributed to the fact that comet 2001Q4 is a comet from the Oort Cloud visiting the inner solar system for the first time
Differential genotypical expression of a NEDD9 in normal and tumor tissues: a possible pharmacological target
Background: Neural precursor cell expressed developmentally down regulated-9 (NEDD9) is a scaffolding metastatic marker protein in multiple cancer types. Generally, the expression occurs during the embryonic development and depletes in adults. Expression of NEDD9 in adults leads to the progression of tumor which is sufficient for the cellular invasion. Elevated behavior of the gene mediates metastatic movement which includes protease dependent neovessel formation, invasion and migration of tumor cells from the site of origin to the distant tissues.Methods: The current study involves the screening and elucidation of differential expression of NEDD9 in normal and tumor subtypes with various tissues of mice by immunohistochemistry.Results: The validating approaches in the study, low expression of NEDD9 was observed in the normal tissues and predominance in the tumor subsets.Conclusions: The experimental analysis proven that NEDD9 expression is merely associated with tumor progression and the molecular mechanism of NEDD9 is restricted in the establishment of metastatic cascade. NEDD9 association in tumor prognosis which helps in the emergence of diagnostic and therapeutic approaches
Acoustic complexity indices reveal the acoustic communities of the old-growth Mediterranean forest of Sasso Fratino Integral Natural Reserve (Central Italy)
The Sasso Fratino Integral Natural Reserve (Central Italy), a rare example of climax Mediterranean forest, provides an extraordinary opportunity to create an important soundscape reference of old-growth forest. In this study, we describe the soundscape of three localities (Lama, Sasso 950, Sasso 1400) representative of a gradient of variety and complexity of habitats, recorded during the period 10 May to 9 June 2017. Our results reveal temporal partitioning into acoustically homogeneous periods across 24 h suggesting that soniferous species (mainly birds) adopt ecological routines in which their acoustic activity is organized according to specific transient physiological needs. We processed multi-temporal aggregates of 1, 5, 10, and 15 s recordings and calculated the Acoustic Signature (AS) with four new indices: Ecoacoustic Events (EE), Acoustic Signature Dissimilarity (ASD), and their fractal dimensions (DEE and DASD), derived from the Acoustic Complexity Index (ACI). The use of the EE and ASD greatly improved the AS interpretation, adding further details such as the emergence of a clear sequence of patterns consistent with the daily evolution of the overall soundscape. DEE and DASD confirm the patterns observed using the AS, but provide more clarity and detail about the great acoustic complexity that exists across temporal scales in this old-growth forest. The temporal turnover of different acoustic communities occurs as a result of a gradual shift of different homogenous acoustic properties. We conclude that soniferous species use distinct, species-specific temporal resolutions according to their physiological and ecological needs and that the fractal approach used here provides a novel tool to overcome the difficulties associated with describing multi-temporal acoustic patterns
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