149 research outputs found
Measurements of Fluctuating Pressures on a 1/4-scale Model of the X-1 Airplane with a 10-percent-thick Wing in the Langley 16-foot Transonic Tunnel
Pressure distributions on the blade sections of the NACA 10-(0)(066)-03 propeller under operating conditions
The Effect of Blade-section Thickness Ratios on the Aerodynamic Characteristics of Related Full-scale Propellers at Mach Numbers up to 0.65
Effects of Leading-edge Slats on the Aerodynamic Characteristics of a 45 Degree Sweepback Wing-fuselage Configuration at Mach Numbers of 0.4 to 1.03
The Effect of Blade-Section Thickness Ratio on the Aerodynamic Characteristics of Related Full-Scale Propellers at Mach Numbers up to 0.65
The results of an investigation of two 10-foot-diameter, two-blade NACA propellers are presented for a range of blade angles from 20 degrees to 55 degrees at airspeeds up to 500 miles per hour. These results are compared with those from previous investigations of five related NACA propellers in order to evaluate the effects of blade-section thickness ratios on propeller aerodynamic characteristics
Is the five-flow conjecture almost false?
The number of nowhere zero Z_Q flows on a graph G can be shown to be a
polynomial in Q, defining the flow polynomial \Phi_G(Q). According to Tutte's
five-flow conjecture, \Phi_G(5) > 0 for any bridgeless G.A conjecture by Welsh
that \Phi_G(Q) has no real roots for Q \in (4,\infty) was recently disproved by
Haggard, Pearce and Royle. These authors conjectured the absence of roots for Q
\in [5,\infty). We study the real roots of \Phi_G(Q) for a family of non-planar
cubic graphs known as generalised Petersen graphs G(m,k). We show that the
modified conjecture on real flow roots is also false, by exhibiting infinitely
many real flow roots Q>5 within the class G(nk,k). In particular, we compute
explicitly the flow polynomial of G(119,7), showing that it has real roots at
Q\approx 5.0000197675 and Q\approx 5.1653424423. We moreover prove that the
graph families G(6n,6) and G(7n,7) possess real flow roots that accumulate at
Q=5 as n\to\infty (in the latter case from above and below); and that
Q_c(7)\approx 5.2352605291 is an accumulation point of real zeros of the flow
polynomials for G(7n,7) as n\to\infty.Comment: 44 pages (LaTeX2e). Includes tex file, three sty files, and a
mathematica script polyG119_7.m. Many improvements from version 3, in
particular Sections 3 and 4 have been mostly re-writen, and Sections 7 and 8
have been eliminated. (This material can now be found in arXiv:1303.5210.)
Final version published in J. Combin. Theory
Spatial compositional turnover varies with trophic level and body size in marine assemblages of micro- and macroorganisms
Abstract Aim Spatial compositional turnover varies considerably among co-occurring assemblages of organisms, presumably shaped by common processes related to species traits. We investigated patterns of spatial turnover in a diverse set of marine assemblages using zeta diversity, which extends traditional pairwise measures of turnover to capture the roles of both rare and common species in shaping assemblage turnover. We tested the generality of hypothesized patterns related to ecological traits and provide insights into mechanisms of biodiversity change. Location Temperate pelagic and benthic marine assemblages of micro- and macroorganisms along south-eastern Australia (30–36° S latitude). Time period 2008–2021. Major taxa studied Bacteria, phytoplankton, zooplankton, fish, and macrobenthic groups. Methods Six marine datasets spanning bacteria to fishes were collated for measures of “species” occurrence, with a 1° latitude grain. For each assemblage, ecological traits of body size, habitat and trophic level were analysed for the form and rate of decline in zeta diversity and for the species retention rate. Results Species at higher trophic levels showed two to three times the rate of zeta diversity decline compared with lower trophic levels, indicating an increase in turnover from phytoplankton to carnivorous fishes. Body size showed the hypothesized unimodal relationship with rates of turnover for macroorganisms. Patterns of bacterial turnover contrasted with those found for macroorganisms, with the highest levels of turnover in pelagic habitats compared with benthic (kelp-associated) habitats. The shape of retention rate curves showed the importance of both rare and common species in driving turnover; a finding that would not have been observable using pairwise (beta diversity) measures of turnover. Main conclusions Our results support theoretical predictions for phytoplankton and macroorganisms, showing an increase in turnover rate with trophic level, but these predictions did not hold for bacteria. Such deviations from theory need to be investigated further to identify underlying processes that govern microbial assemblage dynamics
A neurocomputational account of how inflammation enhances sensitivity to punishments versus rewards
BACKGROUND: Inflammation rapidly impairs mood and cognition and, when severe, can appear indistinguishable
from major depression. These sickness responses are characterized by an acute reorientation of motivational state;
pleasurable activities are avoided, and sensitivity to negative stimuli is enhanced. However, it remains unclear how
these rapid shifts in behavior are mediated within the brain.
METHODS: Here, we combined computational modeling of choice behavior, experimentally induced inflammation,
and functional brain imaging (functional magnetic resonance imaging) to describe these mechanisms. Using a
double-blind, randomized crossover study design, 24 healthy volunteers completed a probabilistic instrumental
learning task on two separate occasions, one 3 hours after typhoid vaccination and one 3 hours after saline (placebo)
injection. Participants learned to select high probability reward (win £1) and avoid high probability punishment (lose
£1) stimuli. An action-value learning algorithm was fit to the observed behavior, then used within functional magnetic
resonance imaging analyses to identify neural coding of prediction error signals driving motivational learning.
RESULTS: Inflammation acutely biased behavior, enhancing punishment compared with reward sensitivity, through
distinct actions on neural representations of reward and punishment prediction errors within the ventral striatum and
anterior insula. Consequently, choice options leading to potential rewards were less behaviorally attractive, and
those leading to punishments were more aversive.
CONCLUSIONS: Our findings demonstrate the neural mediation of a rapid, state-dependent reorientation of reward
versus punishment sensitivity during inflammation. This mechanism may aid the adaptive reallocation of metabolic
resources during acute sickness but might also account for
A horizon scan of priorities for coastal marine microbiome research
Research into the microbiomes of natural environments is changing the way ecologists and evolutionary biologists view the importance of microbes in ecosystem function. This is particularly relevant in ocean environments, where microbes constitute the majority of biomass and control most of the major biogeochemical cycles, including those that regulate the Earth's climate. Coastal marine environments provide goods and services that are imperative to human survival and well-being (e.g. fisheries, water purification), and emerging evidence indicates that these ecosystem services often depend on complex relationships between communities of microorganisms (the ‘microbiome’) and their hosts or environment – termed the ‘holobiont’. Understanding of coastal ecosystem function must therefore be framed under the holobiont concept, whereby macroorganisms and their associated microbiomes are considered as a synergistic ecological unit. Here we evaluated the current state of knowledge on coastal marine microbiome research and identified key questions within this growing research area. Although the list of questions is broad and ambitious, progress in the field is increasing exponentially, and the emergence of large, international collaborative networks and well-executed manipulative experiments are rapidly advancing the field of coastal marine microbiome research
Critical role of gap junction communication, calcium and nitric oxide signaling in bystander responses to focal photodynamic injury
Ionizing and nonionizing radiation affect not only directly targeted cells but also
surrounding “bystander” cells. The underlying mechanisms and therapeutic role of
bystander responses remain incompletely deined. Here we show that photosentizer
activation in a single cell triggers apoptosis in bystander cancer cells, which are
electrically coupled by gap junction channels and support the propagation of a Ca2+
wave initiated in the irradiated cell. The latter also acts as source of nitric oxide
(NO) that diffuses to bystander cells, in which NO levels are further increased by
a mechanism compatible with Ca2+-dependent enzymatic production. We detected
similar signals in tumors grown in dorsal skinfold chambers applied to live mice.
Pharmacological blockade of connexin channels signiicantly reduced the extent of
apoptosis in bystander cells, consistent with a critical role played by intercellular
communication, Ca2+ and NO in the bystander effects triggered by photodynamic
therapy
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