575 research outputs found
A geometrical sink-based cooperative coverage hole recovery strategy for WSNs
© 2015 IEEE. Unlike sporadic node failures, coverage holes emerging from multiple temporally-correlated node failures can severely affect quality of service in a network and put the integrity of entire wireless sensor networks at risk. Conventional topology control schemes addressing such undesirable topological changes have usually overlooked the status of participating nodes in the recovery process with respect to the deployed sink node(s) in the network. In this paper, a cooperative coverage hole recovery model is proposed which utilises the simple geometrical procedure of circle inversion. In this model, autonomous nodes consider their distances to the deployed sink node(s) in addition to their local status, while relocating towards the coverage holes. By defining suitable metrics, the performance of our proposed model performance is compared with a force-based approach
Boundary node selection algorithms in WSNs
Physical damage and/or node power exhaustion may lead to coverage holes in WSNs. Coverage holes can be directly detected by certain proximate nodes known as boundary nodes (B-nodes). Due to the sensor nodes' redundant deployment and autonomous fault detection, holes are surrounded by a margin of B-nodes (MB-nodes). If all B-nodes in the margin take part in the hole recovery processes, either by increasing their transmission power or by relocating towards region of interest (ROI), the probability of collision, interference, disconnection, and isolation may increase affecting the rest of the network's performance and QoS. Thus, distributed boundary node selection algorithms (BNS-Algorithms) are proposed to address these issues. BNS-algorithms allow B-nodes to self-select based on available 1-hop information extracted from nodes' simple geometrical and statistical features. Our results show that the performance of the proposed distributed BNS-algorithms approaches that of their centralized counterparts. © 2011 IEEE
Novel insights into transfer processes in the reaction 16O+208Pb at sub-barrier energies
The collision of the doubly-magic nuclei O+Pb is a benchmark
in nuclear reaction studies. Our new measurements of back-scattered
projectile-like fragments at sub-barrier energies show show that transfer of 2
protons () is much more probable than -particle transfer.
transfer probabilities are strongly enhanced compared to expectations for the
sequential transfer of two uncorrelated protons; at energies around the fusion
barrier absolute probabilities for two proton transfer are similar to those for
one proton transfer. This strong enhancement indicates strong pairing
correlations in O, and suggests evidence for the occurrence of a nuclear
supercurrent of two-proton Cooper pairs in this reaction, already at energies
well below the fusion barrier.Comment: 5 pages, 3 figure
Molecular Identification and Detection of Streptococcus Pneumoniae Serotypes Isolated from Selected Hospitals in Tehran Using Multiplex PCR Method
BACKGROUND AND OBJECTIVE: Streptococcus pneumoniae is one of the major pathogens responsible for invasive diseases such as pneumonia and meningitis. Epidemiological studies of these microorganisms are necessary to evaluate the effect of pneumococcal vaccine in any community. Therefore, the present study was conducted for molecular identification and detection of Streptococcus pneumoniae serotypes isolated from selected hospitals in Tehran using multiplex PCR method.
METHODS: This cross-sectional study was performed on 32 isolates of Streptococcus pneumoniae from clinical specimens of patients admitted to different hospitals in Tehran. The isolates were identified by phenotypic tests and PCR method. Multiplex PCR was used to determine the serotype.
FINDINGS: The number and percentage of Streptococcus pneumoniae isolates isolated from cerebrospinal fluid, sputum, blood, bronchoalveolar lavage, eyes, and nasal discharge were 12 (37.6%), 7 (21.8%), 6 (18.7%), 3 (9.5%), 2 (6.2%), and 2 (6.2%) isolates, respectively. In the present study, the identified serotypes were the serotypes 1, 4, 6A/B, 7F, 9V, 11A, 14, 15A, 19A, 19F, and 23F.
CONCLUSION: Based on the results of this study, more than 50% of the serotypes were not among the serotypes present in the vaccines that are commonly used in the community
Molecular identification and detection of streptococcus pneumoniae serotypes isolated from selected hospitals in tehran using multiplex PCR method
BACKGROUND AND OBJECTIVE: Streptococcus pneumoniae is one of the major pathogens responsible for invasive diseases such as pneumonia and meningitis. Epidemiological studies of these microorganisms are necessary to evaluate the effect of pneumococcal vaccine in any community. Therefore, the present study was conducted for molecular identification and detection of Streptococcus pneumoniae serotypes isolated from selected hospitals in Tehran using multiplex PCR method. METHODS: This cross-sectional study was performed on 32 isolates of Streptococcus pneumoniae from clinical specimens of patients admitted to different hospitals in Tehran. The isolates were identified by phenotypic tests and PCR method. Multiplex PCR was used to determine the serotype. FINDINGS: The number and percentage of Streptococcus pneumoniae isolates isolated from cerebrospinal fluid, sputum, blood, bronchoalveolar lavage, eyes, and nasal discharge were 12 (37.6), 7 (21.8), 6 (18.7), 3 (9.5), 2 (6.2), and 2 (6.2) isolates, respectively. In the present study, the identified serotypes were the serotypes 1, 4, 6A/B, 7F, 9V, 11A, 14, 15A, 19A, 19F, and 23F. CONCLUSION: Based on the results of this study, more than 50 of the serotypes were not among the serotypes present in the vaccines that are commonly used in the community. © 2019, Babol University of Medical Sciences. All rights reserved
Constructing living buildings: a review of relevant technologies for a novel application of biohybrid robotics
Biohybrid robotics takes an engineering approach to the expansion and exploitation of biological behaviours for application to automated tasks. Here, we identify the construction of living buildings and infrastructure as a high-potential application domain for biohybrid robotics, and review technological advances relevant to its future development. Construction, civil infrastructure maintenance and building occupancy in the last decades have comprised a major portion of economic production, energy consumption and carbon emissions. Integrating biological organisms into automated construction tasks and permanent building components therefore has high potential for impact. Live materials can provide several advantages over standard synthetic construction materials, including self-repair of damage, increase rather than degradation of structural performance over time, resilience to corrosive environments, support of biodiversity, and mitigation of urban heat islands. Here, we review relevant technologies, which are currently disparate. They span robotics, self-organizing systems, artificial life, construction automation, structural engineering, architecture, bioengineering, biomaterials, and molecular and cellular biology. In these disciplines, developments relevant to biohybrid construction and living buildings are in the early stages, and typically are not exchanged between disciplines. We, therefore, consider this review useful to the future development of biohybrid engineering for this highly interdisciplinary application.publishe
Expression of Arabidopsis WEE1 in Tobacco Induces Unexpected Morphological and Developmental Changes
WEE1 regulates the cell cycle by inactivating cyclin dependent protein kinases (CDKs) via phosphorylation. In yeast and animal cells, CDC25 phosphatase dephosphorylates the CDK releasing cells into mitosis, but in plants, its role is less clear. Expression of fission yeast CDC25 (Spcdc25) in tobacco results in small cell size, premature flowering and increased shoot morphogenetic capacity in culture. When Arath;WEE1 is over-expressed in Arabidopsis, root apical meristem cell size increases, and morphogenetic capacity of cultured hypocotyls is reduced. However expression of Arath;WEE1 in tobacco plants resulted in precocious flowering and increased shoot morphogenesis of stem explants, and in BY2 cultures cell size was reduced. This phenotype is similar to expression of Spcdc25 and is consistent with a dominant negative effect on WEE1 action. Consistent with this putative mechanism, WEE1 protein levels fell and CDKB levels rose prematurely, coinciding with early mitosis. The phenotype is not due to sense-mediated silencing of WEE1, as overall levels of WEE1 transcript were not reduced in BY2 lines expressing Arath;WEE1. However the pattern of native WEE1 transcript accumulation through the cell cycle was altered by Arath;WEE1 expression, suggesting feedback inhibition of native WEE1 transcription
Revealing the Dynamic Magneto-ionic Environments of Repeating Fast Radio Burst Sources through Multi-year Polarimetric Monitoring with CHIME/FRB
Fast radio bursts (FRBs) display a confounding variety of burst properties
and host galaxy associations. Repeating FRBs offer insight into the FRB
population by enabling spectral, temporal and polarimetric properties to be
tracked over time. Here, we report on the polarized observations of 12
repeating sources using multi-year monitoring with the Canadian Hydrogen
Intensity Mapping Experiment (CHIME) over 400-800 MHz. We observe significant
RM variations from many sources in our sample, including RM changes of several
hundred over month timescales from FRBs 20181119A,
20190303A and 20190417A, and more modest RM variability ( few tens rad m) from FRBs 20181030A, 20190208A, 20190213B and
20190117A over equivalent timescales. Several repeaters display a frequency
dependent degree of linear polarization that is consistent with depolarization
via scattering. Combining our measurements of RM variations with equivalent
constraints on DM variability, we estimate the average line-of-sight magnetic
field strength in the local environment of each repeater. In general, repeating
FRBs display RM variations that are more prevalent/extreme than those seen from
radio pulsars in the Milky Way and the Magellanic Clouds, suggesting repeating
FRBs and pulsars occupy distinct magneto-ionic environments
Recent experimental results in sub- and near-barrier heavy ion fusion reactions
Recent advances obtained in the field of near and sub-barrier heavy-ion
fusion reactions are reviewed. Emphasis is given to the results obtained in the
last decade, and focus will be mainly on the experimental work performed
concerning the influence of transfer channels on fusion cross sections and the
hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier
fusion taught us that cross sections may strongly depend on the low-energy
collective modes of the colliding nuclei, and, possibly, on couplings to
transfer channels. The coupled-channels (CC) model has been quite successful in
the interpretation of the experimental evidences. Fusion barrier distributions
often yield the fingerprint of the relevant coupled channels. Recent results
obtained by using radioactive beams are reported. At deep sub-barrier energies,
the slope of the excitation function in a semi-logarithmic plot keeps
increasing in many cases and standard CC calculations over-predict the cross
sections. This was named a hindrance phenomenon, and its physical origin is
still a matter of debate. Recent theoretical developments suggest that this
effect, at least partially, may be a consequence of the Pauli exclusion
principle. The hindrance may have far-reaching consequences in astrophysics
where fusion of light systems determines stellar evolution during the carbon
and oxygen burning stages, and yields important information for exotic
reactions that take place in the inner crust of accreting neutron stars.Comment: 40 pages, 63 figures, review paper accepted for EPJ
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