20,926 research outputs found
Mean rotor wake characteristics of an aerodynamically loaded 0.5 m diameter fan
Mean rotor wake properties at several downstream distances behind the rotor of a loaded 1.2 pressure ratio fan were measured with a cross film anemometer in an anechoic wind tunnel. Mean wake characteristics in the midspan and near tip region were determined utilizing an ensemble averaging technique. The upwash and streamwise components of the velocity behind the rotor indicate a complex structure superimposed on the major velocity defects at a down stream spacing of 0.5 rotor chords. Spectral analysis indicates high levels of the second and fourth harmonics of the blade passage frequency in the midspan region while the blade passage frequency and its second and third harmonic are predominant in the tip region
Dynamics of trusses having nonlinear joints
The transient analysis of trusses having nonlinear joints can be accomplished using the residual force technique. The technique was applied a two degree of freedom spring mass system, a four bay planar truss, and an actual ten bay deployable truss. Joints chosen for analysis were the nonlinear gap joints and the linear Voigt joints. Results from the nonlinear gap analyses generally indicate that coupling between the modes can display some interesting effects during free vibration. One particularly interesting effect was that the damping of the structure appeared to be higher than could be accounted for from modal damping alone. Energy transferral from the lower to the higher modes was found to exist as a result of the modal coupling. The apparently increased damping was due to the fact that the energy transferred to the higher modes is inherently dissipated more quickly. Another interesting phenomenon was that the lower modes could drive the higher modes even during free vibration and that these modes could display a rather large quasi-steady state behavior even when modal damping was present. Gaps were also found to increase the amplitude and period of the free vibration response as expected
Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics
Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites
Arabidopsis nucleolar protein database (AtNoPDB)
The Arabidopsis Nucleolar Protein Database (http://bioinf.scri.sari.ac.uk/cgi-bin/atnopdb/home) provides information on 217 proteins identified in a proteomic analysis of nucleoli isolated from Arabidopsis cell culture. The database is organized on the basis of the Arabidopsis gene identifier number. The information provided includes protein description, protein class, whether or not the plant protein has a homologue in the most recent human nucleolar proteome and the results of reciprocal BLAST analysis of the human proteome. In addition, for one-third of the 217 Arabidopsis nucleolar proteins, localization images are available from analysis of full-length cDNA–green fluorescent protein (GFP) fusions and the strength of signal in different parts of the cell—nucleolus, nucleolus-associated structures, nucleoplasm, nuclear bodies and extra-nuclear—is provided. For each protein, the most likely human and yeast orthologues, where identifiable through BLASTX analysis, are given with links to relevant information sources
A low-luminosity soft state in the short period black hole X-ray binary Swift J1753.5-0127
We present results from the spectral fitting of the candidate black hole
X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this
source. We fit the 0.7-78 keV spectrum with a number of models, however the
preferred model is one of a multi-temperature disk with an inner disk
temperature keV scattered into a steep
power-law with photon index and an additional
hard power law tail (). We report on the emergence of a
strong disk-dominated component in the X-ray spectrum and we conclude that the
source has entered the soft state for the first time in its ~10 year prolonged
outburst. Using reasonable estimates for the distance to the source ( kpc)
and black hole mass (), we find the unabsorbed luminosity (0.1-100
keV) to be % of the Eddington luminosity, making this one of the
lowest luminosity soft states recorded in X-ray binaries. We also find that the
accretion disk extended towards the compact object during its transition from
hard to soft, with the inner radius estimated to be
or ~, dependent on the boundary
condition chosen, assuming the above distance and mass, a spectral hardening
factor and a binary inclination .Comment: 10 pages, 5 figures, accepted for publication in MNRA
Events leading up to the June 2015 outburst of V404 Cyg
On 2015 June 15 the burst alert telescope (BAT) on board {\em Swift} detected
an X-ray outburst from the black hole transient V404 Cyg. We monitored V404 Cyg
for the last 10 years with the 2-m Faulkes Telescope North in three optical
bands (V, R, and i). We found that, one week prior to this outburst, the
optical flux was 0.1--0.3 mag brighter than the quiescent orbital modulation,
implying an optical precursor to the X-ray outburst. There is also a hint of a
gradual optical decay (years) followed by a rise lasting two months prior to
the outburst. We fortuitously obtained an optical spectrum of V404 Cyg 13 hours
before the BAT trigger. This too was brighter () than
quiescence, and showed spectral lines typical of an accretion disk, with
characteristic absorption features of the donor being much weaker. No He II
emission was detected, which would have been expected had the X-ray flux been
substantially brightening. This, combined with the presence of intense
H emission, about 7 times the quiescent level, suggests that the disk
entered the hot, outburst state before the X-ray outburst began. We propose
that the outburst is produced by a viscous-thermal instability triggered close
to the inner edge of a truncated disk. An X-ray delay of a week is consistent
with the time needed to refill the inner region and hence move the inner edge
of the disk inwards, allowing matter to reach the central BH, finally turning
on the X-ray emission.Comment: Accepted by ApJ Letter, 7 pages, 5 figure
Investigation of the feasibility of an external biosensor for continuous determination of blood oxygenation /and concomitant heart rate and respiratory rate/ based upon optical backscatter for use in spacecraft and aircraft Final report, 24 Jun. 1964 - 1 Nov. 1965
External biosensor using optical backscatter for continuous determination of blood oxygenation in humans and animal
Optical Spectroscopy of Bright Fermi LAT Blazars
We report on HET and Palomar 5 m spectroscopy of recently identified
-ray blazars in the {\it Fermi} LAT Bright Source List. These data
provide identifications for 10 newly discovered -ray flat spectrum
radio quasars (FSRQ) and six new BL Lacs plus improved spectroscopy for six
additional BL Lacs. We substantially improve the identification completeness of
the bright LAT blazars and give new redshifts and constraints, new
estimates of the black hole masses and new measurements of the optical SED.Comment: 8 pages, 5 figures, 2 tables. Accepted for publication in Ap
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Evolutionary bi-stability in pathogen transmission mode
Many pathogens transmit to new hosts by both infection (horizontal transmission) and transfer to the
infected host's offspring (vertical transmission). These two transmission modes require speci®c adap-
tations of the pathogen that can be mutually exclusive, resulting in a trade-off between horizontal and
vertical transmission. We show that in mathematical models such trade-offs can lead to the simultaneous
existence of two evolutionary stable states (evolutionary bi-stability) of allocation of resources to the two
modes of transmission. We also show that jumping between evolutionary stable states can be induced by
gradual environmental changes. Using quantitative PCR-based estimates of abundance in seed and vege-
tative parts, we show that the pathogen of wheat, Phaeosphaeria nodorum, has jumped between two
distinct states of transmission mode twice in the past 160 years, which, based on published evidence,
we interpret as adaptation to environmental change. The ®nding of evolutionary bi-stability has impli-
cations for human, animal and other plant diseases. An ill-judged change in a disease control
programme could cause the pathogen to evolve a new, and possibly more damaging, combination of
transmission modes. Similarly, environmental changes can shift the balance between transmission
modes, with adverse effects on human, animal and plant health
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