25,526 research outputs found
Approximate theoretical performance evaluation for a diverging rocket
A simplified combustion model, which is motivated by available performance studies on the diverging rocket reactor, has been used as basis for an engine performance
evaluation. Comparison with conventional rocket configurations shows that an upper performance limit for the diverging reactor is comparable with performance
estimates for engines using an adiabatic work cycle. Development of the diverging reactor for engine applications may, however, offer some advantages for very hot, high-energy, propellant systems
Short SULF1/SULF2 splice variants predominate in mammary tumours with a potential to facilitate receptor tyrosine kinase-mediated cell signalling
The relative roles of SULF1 and SULF2 enzymes in tumour growth are controversial, but short SULF1/SULF2 splice variants predominate in human mammary tumours despite their non-detectable levels in normal mammary tissue. Compared with the normal, the level of receptor tyrosine kinase (RTK) activity was markedly increased in triple-positive mammary tumours during later stages of tumour progression showing increased p-EGFR, p-FGFR1 and p-cMet activity in triple-positive but not in triple-negative tumours. The abundance of catalytically inactive short SULF1/SULF2 variants permits high levels of HS sulphation and thus growth driving RTK cell signalling in primary mammary tumours. Also observed in this study, however, was increased N-sulphation detected by antibody 10E4 indicating that not only 6-O sulphation but also N-sulphation may contribute to increased RTK cell signalling in mammary tumours. The levels of such increases in not only SULF1/SULF2 but also in pEGFR, pFGFR1, p-cMet and Smad1/5/8 signalling were further enhanced following lymph node metastasis. The over-expression of Sulf1 and Sulf2 variants in mammary tumour-derived MDA-MB231 and MCF7 cell lines by transfection further confirms Sulf1-/Sulf2-mediated differential modulation of growth. The short variants of both Sulf1 and Sulf2 promoted FGF2-induced MDA-MB231 and MCF7 in vitro growth while full-length Sulf1 inhibited growth supporting in vivo mammary tumour cell signalling patterns of growth. Since a number of mammary tumours become drug resistant to hormonal therapy, Sulf1/Sulf2 inhibition could be an alternative therapeutic approach to target such tumours by down-regulating RTK-mediated cell signalling
Flow and acoustic characteristics of subsonic and supersonic jets from convergent nozzle
Acoustic and flow characteristics of subsonic and supersonic jets from convergent nozzle
Damping of bulk excitations over an elongated BEC - the role of radial modes
We report the measurement of Beliaev damping of bulk excitations in cigar
shaped Bose Einstein condensates of atomic vapor. By using post selection,
excitation line shapes of the total population are compared with those of the
undamped excitations. We find that the damping depends on the initial
excitation energy of the decaying quasi particle, as well as on the excitation
momentum. We model the condensate as an infinite cylinder and calculate the
damping rates of the different radial modes. The derived damping rates are in
good agreement with the experimentally measured ones. The damping rates
strongly depend on the destructive interference between pathways for damping,
due to the quantum many-body nature of both excitation and damping products.Comment: 5 pages, 4 figure
Hybrid Superconductor-Quantum Point Contact Devices using InSb Nanowires
Proposals for studying topological superconductivity and Majorana bound
states in nanowires proximity coupled to superconductors require that transport
in the nanowire is ballistic. Previous work on hybrid nanowire-superconductor
systems has shown evidence for Majorana bound states, but these experiments
were also marked by disorder, which disrupts ballistic transport. In this
letter, we demonstrate ballistic transport in InSb nanowires interfaced
directly with superconducting Al by observing quantized conductance at
zero-magnetic field. Additionally, we demonstrate that the nanowire is
proximity coupled to the superconducting contacts by observing Andreev
reflection. These results are important steps for robustly establishing
topological superconductivity in InSb nanowires
Unique Mass Texture for Quarks and Leptons
Texture specific quark mass matrices which are hermitian and hierarchical are
examined in detail . In the case of texture 6 zeros matrices, out of sixteen
possibilities examined by us, none is able to fit the low energy data (LED),
for example, , ,
, lies in the range (PDG). Similarly none of the 32 texture 5 zeros mass matrices considered
is able to reproduce LED. In particular, the latest data from LEP regarding
rules out all of them. In the texture 4
zeros case, we find that there is a unique texture structure for and
mass matrices which is able to fit the data.Comment: 12 pages, LaTeX,some changes in the references,minor changes in the
text,to appear in Phys Rev D(Rapid communications
Causal Quantum Theory and the Collapse Locality Loophole
Causal quantum theory is an umbrella term for ordinary quantum theory
modified by two hypotheses: state vector reduction is a well-defined process,
and strict local causality applies. The first of these holds in some versions
of Copenhagen quantum theory and need not necessarily imply practically
testable deviations from ordinary quantum theory. The second implies that
measurement events which are spacelike separated have no non-local
correlations. To test this prediction, which sharply differs from standard
quantum theory, requires a precise theory of state vector reduction.
Formally speaking, any precise version of causal quantum theory defines a
local hidden variable theory. However, causal quantum theory is most naturally
seen as a variant of standard quantum theory. For that reason it seems a more
serious rival to standard quantum theory than local hidden variable models
relying on the locality or detector efficiency loopholes.
Some plausible versions of causal quantum theory are not refuted by any Bell
experiments to date, nor is it obvious that they are inconsistent with other
experiments. They evade refutation via a neglected loophole in Bell experiments
-- the {\it collapse locality loophole} -- which exists because of the possible
time lag between a particle entering a measuring device and a collapse taking
place. Fairly definitive tests of causal versus standard quantum theory could
be made by observing entangled particles separated by light
seconds.Comment: Discussion expanded; typos corrected; references adde
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