12,895 research outputs found
Even circuits of prescribed clockwise parity
We show that a graph has an orientation under which every circuit of even
length is clockwise odd if and only if the graph contains no subgraph which is,
after the contraction of at most one circuit of odd length, an even subdivision
of K_{2,3}. In fact we give a more general characterisation of graphs that have
an orientation under which every even circuit has a prescribed clockwise
parity. This problem was motivated by the study of Pfaffian graphs, which are
the graphs that have an orientation under which every alternating circuit is
clockwise odd. Their significance is that they are precisely the graphs to
which Kasteleyn's powerful method for enumerating perfect matchings may be
applied
The role of dietary polyphenols in the moderation of the inflammatory response in early stage colorectal cancer
Current focus in colorectal cancer management is on reducing overall mortality by increasing the number of early stage cancers diagnosed and treated with curative intent. Despite the success of screening programmes in down-staging colorectal cancer, interval cancer rates are substantial and other strategies are desirable. Sporadic colorectal cancer is largely associated with lifestyle factors including diet. Polyphenols are phytochemicals ingested as part of a normal diet which are abundant in plant foods including fruits/berries and vegetables. These may exert their anti-carcinogenic effects via the modulation of inflammatory pathways. Key signal transduction pathways are fundamental to the association of inflammation and disease progression including those mediated by NF-κB and STAT, PI3K and COX. Our aim was to examine the evidence for the effect of dietary polyphenols intake on tumour and host inflammatory responses to determine if polyphenols may be effective as part of a dietary intervention. There is good epidemiological evidence of a reduction in colorectal cancer risk from case-control and cohort studies assessing polyphenol intake. It would be premature to suggest a major public health intervention to promote their consumption however, dietary change is safe and feasible, emphasising the need for further investigation of polyphenols and colorectal cancer risk
Propfan Test Assessment (PTA)
The objectives of the Propfan Test Assessment (PTA) Program were to validate in flight the structural integrity of large-scale propfan blades and to measure noise characteristics of the propfan in both near and far fields. All program objectives were met or exceeded, on schedule and under budget. A Gulfstream Aerospace Corporation GII aircraft was modified to provide a testbed for the 2.74m (9 ft) diameter Hamilton Standard SR-7 propfan which was driven by a 4475 kw (600 shp) turboshaft engine mounted on the left-hand wing of the aircraft. Flight research tests were performed for 20 combinations of speed and altitude within a flight envelope that extended to Mach numbers of 0.85 and altitudes of 12,192m (40,000 ft). Propfan blade stress, near-field noise on aircraft surfaces, and cabin noise were recorded. Primary variables were propfan power and tip speed, and the nacelle tilt angle. Extensive low altitude far-field noise tests were made to measure flyover and sideline noise and the lateral attenuation of noise. In coopertion with the FAA, tests were also made of flyover noise for the aircraft at 6100m (20,000 ft) and 10,668m (35,000 ft). A final series of tests were flown to evaluate an advanced cabin wall noise treatment that was produced under a separate program by NASA-Langley Research Center
Shifting the Quantum-Classical Boundary: Theory and Experiment for Statistically Classical Optical Fields
The growing recognition that entanglement is not exclusively a quantum
property, and does not even originate with Schr\"odinger's famous remark about
it [Proc. Camb. Phil. Soc. 31, 555 (1935)], prompts examination of its role in
marking the quantum-classical boundary. We have done this by subjecting
correlations of classical optical fields to new Bell-analysis experiments, and
report here values of the Bell parameter greater than . This
is many standard deviations outside the limit established by the
Clauser-Horne-Shimony-Holt (CHSH) Bell inequality [Phys. Rev. Lett. 23, 880
(1969)], in agreement with our theoretical classical prediction, and not far
from the Tsirelson limit . These results cast a new light
on the standard quantum-classical boundary description, and suggest a
reinterpretation of it.Comment: Comments and Remarks are warmly welcome! arXiv admin note: text
overlap with arXiv:1406.333
Propfan Test Assessment (PTA): Flight test report
The Propfan Test Assessment (PTA) aircraft was flown to obtain glade stress and noise data for a 2.74m (9 ft.) diameter single rotation propfan. Tests were performed at Mach numbers to 0.85 and altitudes to 12,192m (40,000 ft.). The propfan was well-behaved structurally over the entire flight envelope, demonstrating that the blade design technology was completely adequate. Noise data were characterized by strong signals at blade passage frequency and up to 10 harmonics. Cabin noise was not so high as to preclude attainment of comfortable levels with suitable wall treatment. Community noise was not excessive
Propfan test assessment testbed aircraft stability and control/performance 1/9-scale wind tunnel tests
One-ninth scale wind tunnel model tests of the Propfan Test Assessment (PTA) aircraft were performed in three different NASA facilities. Wing and propfan nacelle static pressures, model forces and moments, and flow field at the propfan plane were measured in these tests. Tests started in June 1985 and were completed in January 1987. These data were needed to assure PTA safety of flight, predict PTA performance, and validate analytical codes that will be used to predict flow fields in which the propfan will operate
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