4,630 research outputs found
Adaptive Transmission Techniques for Mobile Satellite Links
Adapting the transmission rate in an LMS channel is a challenging task
because of the relatively fast time variations, of the long delays involved,
and of the difficulty in mapping the parameters of a time-varying channel into
communication performance. In this paper, we propose two strategies for dealing
with these impairments, namely, multi-layer coding (MLC) in the forward link,
and open-loop adaptation in the return link. Both strategies rely on
physical-layer abstraction tools for predicting the link performance. We will
show that, in both cases, it is possible to increase the average spectral
efficiency while at the same time keeping the outage probability under a given
threshold. To do so, the forward link strategy will rely on introducing some
latency in the data stream by using retransmissions. The return link, on the
other hand, will rely on a statistical characterization of a physical-layer
abstraction measure.Comment: Presented at the 30th AIAA International Communications Satellite
Systems Conference (ICSSC), Ottawa, Canada, 2012. Best Professional Paper
Awar
Geographic Variation in Specific Gravity Among Japanese Larch From Different Provenances
Genetic variation in wood specific gravity is reported for Japanese larch from twenty seed sources at age 17 years from planting in central New Brunswick, Canada. Information on native tamarack and European larch is also presented. Differences in mean specific gravity among provenances of Japanese larch (range 0.385 to 0.417) are highly significant. Specific gravity is not correlated with 12-year height, specific gravity of trees of the same provenances growing in Michigan, or with latitude, or elevation of the provenances. There is a weak but significant negative correlation between specific gravity and tree diameter at 1.3 m. Provenance x environment interaction in respect to specific gravity is high, making it difficult to identify provenances that will be superior over a wide area
Processing of strong flux trapping high T(subc) oxide superconductors: Center director's discretionary fund
Magnetic suspension effect was first observed in samples of YBa2Cu3O7/AgO(Y-123/AgO) composites. Magnetization measurements of these samples show a much larger hysteresis which corresponds to a large critical current density. In addition to the Y-123AgO composites, recently similar suspension effects in other RE-123/AgO, where RE stands for rare-Earth elements, were also observed. Some samples exhibit even stronger flux pinning than that of the Y-123/AgO sample. An interesting observation was that in order to form the composite which exhibits strong flux trapping effect the sintering temperature depends on the particular RE-123 compound used. The paper presents the detailed processing conditions for the formation of these RE-123/AgO composites, as well as the magnetization and critical field data
Inclusive Practice: researching the relationships between dyslexia, personality, and art students’ drawing ability.
This paper addresses the conference theme of inclusivity
from two standpoints. Firstly, involving collaboration
between researchers from fields including psychology,
educational study support and studio drawing practice,
which has revealed insights into students’ learning
difficulties in drawing, which are not easily accessible
through mono-disciplinary research practice. Secondly it
involves a proposal outlining a strategy for the teaching
of drawing which attempts to include students of varying
abilities in drawing, and to empower their practice
equally. The paper demonstrates the effectiveness of
an inclusive, cross-disciplinary approach to exploring
the relations between personality factors, perceptual
problems, visual memory and drawing skills in art
students who report difficulties producing accurate drawn
representations of their observational experiences. Results
indicate that whilst in general drawing ability seems not
to relate to dyslexia, higher drawing ability does appear
related to the personality measure of conscientiousness,
and also both to sex (in the biological sense, males
drawing better than females) and to gender (those who
perceive themselves as more masculine drawing better,
whether they are male or female). Poor drawers are less
good at accurately copying angles and proportions, and
their visual memory is less good. These findings inform a
proposed inclusive group teaching strategy for drawing
which attempts to address these weaknesses without hindering the progress of the more able student
Concave Plasmonic Particles: Broad-Band Geometrical Tunability in the Near Infra-Red
Optical resonances spanning the Near and Short Infra-Red spectral regime were
exhibited experimentally by arrays of plasmonic nano-particles with concave
cross-section. The concavity of the particle was shown to be the key ingredient
for enabling the broad band tunability of the resonance frequency, even for
particles with dimensional aspect ratios of order unity. The atypical
flexibility of setting the resonance wavelength is shown to stem from a unique
interplay of local geometry with surface charge distributions
RIPK3 restricts viral pathogenesis via cell death-independent neuroinflammation
Receptor-interacting protein kinase-3 (RIPK3) is an activator of necroptotic cell death, but recent work has implicated additional roles for RIPK3 in inflammatory signaling independent of cell death. However, while necroptosis has been shown to contribute to antiviral immunity, death-independent roles for RIPK3 in host defense have not been demonstrated. Using a mouse model of West Nile virus (WNV) encephalitis, we show that RIPK3 restricts WNV pathogenesis independently of cell death. Ripk3(-/-) mice exhibited enhanced mortality compared to wild-type (WT) controls, while mice lacking the necroptotic effector MLKL, or both MLKL and caspase-8, were unaffected. The enhanced susceptibility of Ripk3(-/-) mice arose from suppressed neuronal chemokine expression and decreased central nervous system (CNS) recruitment of T lymphocytes and inflammatory myeloid cells, while peripheral immunity remained intact. These data identify pleiotropic functions for RIPK3 in the restriction of viral pathogenesis and implicate RIPK3 as a key coordinator of immune responses within the CNS
Technisch werkdocument HBO-Monitor 1995: De arbeidsmarktpositie van afgestudeerden van het hoger beroepsonderwijs uit het studiejaar 1993/1994
Rigorous Real-Time Feynman Path Integral for Vector Potentials
we will show the existence and uniqueness of a real-time, time-sliced Feynman
path integral for quantum systems with vector potential. Our formulation of the
path integral will be derived on the transition probability amplitude via
improper Riemann integrals. Our formulation will hold for vector potential
Hamiltonian for which its potential and vector potential each carries at most a
finite number of singularities and discontinuities
Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A in Syntrophus aciditrophicus, a New Twist on ATP Formation.
UnlabelledSyntrophus aciditrophicus is a model syntrophic bacterium that degrades key intermediates in anaerobic decomposition, such as benzoate, cyclohexane-1-carboxylate, and certain fatty acids, to acetate when grown with hydrogen-/formate-consuming microorganisms. ATP formation coupled to acetate production is the main source for energy conservation by S. aciditrophicus However, the absence of homologs for phosphate acetyltransferase and acetate kinase in the genome of S. aciditrophicus leaves it unclear as to how ATP is formed, as most fermentative bacteria rely on these two enzymes to synthesize ATP from acetyl coenzyme A (CoA) and phosphate. Here, we combine transcriptomic, proteomic, metabolite, and enzymatic approaches to show that S. aciditrophicus uses AMP-forming, acetyl-CoA synthetase (Acs1) for ATP synthesis from acetyl-CoA. acs1 mRNA and Acs1 were abundant in transcriptomes and proteomes, respectively, of S. aciditrophicus grown in pure culture and coculture. Cell extracts of S. aciditrophicus had low or undetectable acetate kinase and phosphate acetyltransferase activities but had high acetyl-CoA synthetase activity under all growth conditions tested. Both Acs1 purified from S. aciditrophicus and recombinantly produced Acs1 catalyzed ATP and acetate formation from acetyl-CoA, AMP, and pyrophosphate. High pyrophosphate levels and a high AMP-to-ATP ratio (5.9 ± 1.4) in S. aciditrophicus cells support the operation of Acs1 in the acetate-forming direction. Thus, S. aciditrophicus has a unique approach to conserve energy involving pyrophosphate, AMP, acetyl-CoA, and an AMP-forming, acetyl-CoA synthetase.ImportanceBacteria use two enzymes, phosphate acetyltransferase and acetate kinase, to make ATP from acetyl-CoA, while acetate-forming archaea use a single enzyme, an ADP-forming, acetyl-CoA synthetase, to synthesize ATP and acetate from acetyl-CoA. Syntrophus aciditrophicus apparently relies on a different approach to conserve energy during acetyl-CoA metabolism, as its genome does not have homologs to the genes for phosphate acetyltransferase and acetate kinase. Here, we show that S. aciditrophicus uses an alternative approach, an AMP-forming, acetyl-CoA synthetase, to make ATP from acetyl-CoA. AMP-forming, acetyl-CoA synthetases were previously thought to function only in the activation of acetate to acetyl-CoA
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