7,754 research outputs found
Variability of the Spectral Energy Distribution of the Blazar S5 0716+714
The emission from blazars is known to be variable at all wavelengths. The
flux variability is often accompanied by spectral changes. Spectral energy
distribution (SED) changes must be associated with changes in the spectra of
emitting electrons and/or the physical parameters of the jet. Meaningful
modeling of blazar broadband spectra is required to understand the extreme
conditions within the emission region. Not only is the broadband SED crucial,
but also information about its variability is needed to understand how the
highest states of emission occur and how they differ from the low states. This
may help in discriminating between models. Here we present the results of our
SED modeling of the blazar S5 0716+714 during various phases of its activity.
The SEDs are classified into different bins depending on the optical brightness
state of the source.Comment: 4 pages, 3 figures, contributed talk presented at the conference
Multifrequency Variability of Blazars, Guangzhou, China, September 22-24,
2010. To appear in Journal of Astrophysics and Astronomy (JAA
On Budget-Feasible Mechanism Design for Symmetric Submodular Objectives
We study a class of procurement auctions with a budget constraint, where an
auctioneer is interested in buying resources or services from a set of agents.
Ideally, the auctioneer would like to select a subset of the resources so as to
maximize his valuation function, without exceeding a given budget. As the
resources are owned by strategic agents however, our overall goal is to design
mechanisms that are truthful, budget-feasible, and obtain a good approximation
to the optimal value. Budget-feasibility creates additional challenges, making
several approaches inapplicable in this setting. Previous results on
budget-feasible mechanisms have considered mostly monotone valuation functions.
In this work, we mainly focus on symmetric submodular valuations, a prominent
class of non-monotone submodular functions that includes cut functions. We
begin first with a purely algorithmic result, obtaining a
-approximation for maximizing symmetric submodular functions
under a budget constraint. We view this as a standalone result of independent
interest, as it is the best known factor achieved by a deterministic algorithm.
We then proceed to propose truthful, budget feasible mechanisms (both
deterministic and randomized), paying particular attention on the Budgeted Max
Cut problem. Our results significantly improve the known approximation ratios
for these objectives, while establishing polynomial running time for cases
where only exponential mechanisms were known. At the heart of our approach lies
an appropriate combination of local search algorithms with results for monotone
submodular valuations, applied to the derived local optima.Comment: A conference version appears in WINE 201
The Methods to Improve Quality of Service by Accounting Secure Parameters
A solution to the problem of ensuring quality of service, providing a greater
number of services with higher efficiency taking into account network security
is proposed. In this paper, experiments were conducted to analyze the effect of
self-similarity and attacks on the quality of service parameters. Method of
buffering and control of channel capacity and calculating of routing cost
method in the network, which take into account the parameters of traffic
multifractality and the probability of detecting attacks in telecommunications
networks were proposed. The both proposed methods accounting the given
restrictions on the delay time and the number of lost packets for every type
quality of service traffic. During simulation the parameters of transmitted
traffic (self-similarity, intensity) and the parameters of network (current
channel load, node buffer size) were changed and the maximum allowable load of
network was determined. The results of analysis show that occurrence of
overload when transmitting traffic over a switched channel associated with
multifractal traffic characteristics and presence of attack. It was shown that
proposed methods can reduce the lost data and improve the efficiency of network
resources.Comment: 10 pages, 1 figure, 1 equation, 1 table. arXiv admin note: text
overlap with arXiv:1904.0520
Motor symptoms in Parkinson's disease: A unified framework
Parkinson’s disease (PD) is characterized by a range of motor symptoms. Besides the cardinal symptoms (akinesia and bradykinesia, tremor and rigidity), PD patients show additional motor deficits, including: gait disturbance, impaired handwriting, grip force and speech deficits, among others. Some of these motor symptoms (e.g., deficits of gait, speech, and handwriting) have similar clinical profiles, neural substrates, and respond similarly to dopaminergic medication and deep brain stimulation (DBS). Here, we provide an extensive review of the clinical characteristics and neural substrates of each of these motor symptoms, to highlight precisely how PD and its medical and surgical treatments impact motor symptoms. In conclusion, we offer a unified framework for understanding the range of motor symptoms in PD. We argue that various motor symptoms in PD reflect dysfunction of neural structures responsible for action selection, motor sequencing, and coordination and execution of movement
Pearls and Pitfalls in Diagnosing Pediatric Urinary Bladder Masses
Urinary bladder masses are rare in children, and the associated histologic features and prognoses in this population are different from those in adults. Most children with urinary bladder masses present with lower urinary tract symptoms, which may include hematuria, dysuria, frequent urination, and urgency to urinate. However, some of these masses may be identified incidentally or involve generic symptoms such as abdominal distention. In general, pediatric bladder tumors can be divided into those that originate from the bladder epithelium, known as urothelial neoplasms, and mesenchymal bladder neoplasms, which are more prevalent. The most common bladder malignancy in children is a rhabdomyosarcoma, whereas the most common benign bladder lesion in the pediatric population is a papillary urothelial neoplasm of low malignant potential (PUNLMP). The first-line imaging tool for assessing bladder lesions is ultrasonography, which may be followed by a cross-sectional imaging examination such as computed tomography or magnetic resonance imaging if the origin of the mass is unclear or if distant spread is suspected. Although imaging may enable the radiologist to suggest a differential diagnosis based on lesion location and patient age, tissue biopsy generally is required to identify the exact pathologic entity. This is usually performed at cystoscopy and may be curative in cases in which the lesion is small and has low recurrence potential. Knowledge of the clinical, histopathologic, and imaging features of common bladder neoplasms is essential, as it can aid in preventing imaging pitfalls. These may include the misinterpretation of either a pelvic mass as arising from the bladder or a bladder mass as arising from the pelvis, and interpreting an inflammatory mass or bladder detritus as a neoplasm
Phylogeography of the smooth-coated otter (Lutrogale perspicillata): distinct evolutionary lineages and hybridization with the Asian small clawed otter (Aonyx cinereus)
We investigated the phylogeography of the smooth-coated otter (Lutrogale perspicillata) to determine its spatial genetic structure for aiding an adaptive conservation management of the species. Fifty eight modern and 11 archival (dated 1882–1970) otters sampled from Iraq to Malaysian Borneo were genotyped (mtDNA Cytochrome-b, 10 microsatellite DNA loci). Moreover, 16 Aonyx cinereus (Asian
small-clawed otter) and seven Lutra lutra (Eurasian otter) were sequenced to increase information available for phylogenetic reconstructions. As reported in previous studies, we found that L. perspicillata, A. cinereus and A. capensis (African clawless otter) grouped in a clade sister to the genus Lutra, with L. perspicillata and A. cinereus being reciprocally monophyletic. Within L. perspicillata, we uncovered three Evolutionarily Significant Units and proved that L. p. maxwelli is not only endemic to Iraq but also the most recent subspecies. We suggest a revision of the distribution range limits of easternmost L. perspicillata subspecies. We show that smooth-coated otters in Singapore are L. perspicillata x A. cinereus hybrids with A. cinereus mtDNA, the first reported case of hybridization in the wild among otters. This result also provides evidence supporting the inclusion of L. perspicillata and
A. cinereus in the genus Amblonyx, thus avoiding the paraphyly of the genus Aonyx
Biofilter aquaponic system for nutrients removal from fresh market wastewater
Aquaponics is a significant wastewater treatment system which refers to the combination of conventional aquaculture (raising aquatic organism) with hydroponics (cultivating plants in water) in a symbiotic environment. This system has a high ability in removing nutrients compared to conventional methods because it is a natural and environmentally friendly system (aquaponics). The current chapter aimed to review the possible application of aquaponics system to treat fresh market wastewater with the intention to highlight the mechanism of phytoremediation occurs in aquaponic system. The literature revealed that aquaponic system was able to remove nutrients in terms of nitrogen and phosphorus
Fragment Flow and the Nuclear Equation of State
We use the Boltzmann-Uehling-Uhlenbeck model with a momentum-dependent
nuclear mean field to simulate the dynamical evolution of heavy ion collisions.
We re-examine the azimuthal anisotropy observable, proposed as sensitive to the
equation of state of nuclear matter. We obtain that this sensitivity is maximal
when the azimuthal anisotropy is calculated for nuclear composite fragments, in
agreement with some previous calculations. As a test case we concentrate on
semi-central collisions at 400 MeV.Comment: 12 pages, ReVTeX 3.0. 12 Postscript figures, uuencoded and appende
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