40,175 research outputs found
Synchronizing Sequencing Software to a Live Drummer
Copyright 2013 Massachusetts Institute of Technology. MIT allows authors to archive published versions of their articles after an embargo period. The article is available at
Investigation of Mechanical Properties of Cryogenically Treated Music Wire
It has been reported that treating music wire (high carbon steel wire) by
cooling to cryogenic temperatures can enhance its mechanical properties with
particular reference to those properties important for musical performance. We
use such wire for suspending many of the optics in Advanced LIGO, the upgrade
to LIGO - the Laser Interferometric Gravitational-Wave Observatory. Two
properties that particularly interest us are mechanical loss and breaking
strength. A decrease in mechanical loss would directly reduce the thermal noise
associated with the suspension, thus enhancing the noise performance of mirror
suspensions within the detector. An increase in strength could allow thinner
wire to be safely used, which would enhance the dilution factor of the
suspension, again leading to lower suspension thermal noise. In this article we
describe the results of an investigation into some of the mechanical properties
of music wire, comparing untreated wire with the same wire which has been
cryogenically treated. For the samples we studied we conclude that there is no
significant difference in the properties of interest for application in
gravitational wave detectors
A mathematical model of tumor-immune interactions
A mathematical model of the interactions between a growing tumor and the immune system is presented. The equations and parameters of the model are based on experimental and clinical results from published studies. The model includes the primary cell populations involved in effector T cell mediated tumor killing: regulatory T cells, helper T cells, and dendritic cells. A key feature is the inclusion of multiple mechanisms of immunosuppression through the main cytokines and growth factors mediating the interactions between the cell populations. Decreased access of effector cells to the tumor interior with increasing tumor size is accounted for. The model is applied to tumors with different growth rates and antigenicities to gauge the relative importance of various immunosuppressive mechanisms. The most important factors leading to tumor escape are TGF-induced immunosuppression, conversion of helper T cells into regulatory T cells, and the limitation of immune cell access to the full tumor at large tumor sizes. The results suggest that for a given tumor growth rate, there is an optimal antigenicity maximizing the response of the immune system. Further increases in antigenicity result in increased immunosuppression, and therefore a decrease in tumor killing rate
Low temperature coefficient of resistance and high gage factor in beryllium-doped silicon
The gage factor and resistivity of p-type silicon doped with beryllium was studied as a function of temperature, crystal orientation, and beryllium doping concentration. It was shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gage factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, whereas the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon
A Platform Independent Architecture for Virtual Characters and Avatars
We have developed a Platform Independent Architecture for Virtual Characters and Avatars (PIAVCA), a character animation system that aims to be independent of any underlying graphics framework and so be easily portable. PIAVCA supports body animation based on a skeletal representation and facial animation based on morph targets
Fire extinguishment in oxygen enriched atmospheres
Current state-of-the-art of fire suppression and extinguishment techniques in oxygen enriched atmosphere is reviewed. Four classes of extinguishment action are considered: cooling, separation of reactants, dilution or removal of fuel, and use of chemically reactive agents. Current practice seems to show preference for very fast acting water spray applications to all interior surfaces of earth-based chambers. In space, reliance has been placed on fire prevention methods through the removal of ignition sources and use of nonflammable materials. Recommendations are made for further work related to fire suppression and extinguishment in oxygen enriched atmospheres, and an extensive bibliography is appended
Bigger Bursts From Merging Neutron Stars
GRB 990123 may have radiated more than one solar mass equivalent in just its
gamma emissions. Though this may be within the upper limit of the binding
energy available from neutron stars in the Schwarzschild metric, it is
difficult to imagine a process with the required efficiency of conversion to
gamma rays. Neutron stars of ~10 solar mass are permitted in the Yilmaz metric.
A merger of two neutron stars of maximum mass could release approximately 10
solar mass equivalent binding energy.Comment: 5 pages, 1 figure, submitted to ApJ Letter
On circulant states with positive partial transpose
We construct a large class of quantum "d x d" states which are positive under
partial transposition (so called PPT states). The construction is based on
certain direct sum decomposition of the total Hilbert space displaying
characteristic circular structure - that is way we call them circulant states.
It turns out that partial transposition maps any such decomposition into
another one and hence both original density matrix and its partially transposed
partner share similar cyclic properties. This class contains many well known
examples of PPT states from the literature and gives rise to a huge family of
completely new states.Comment: 15 pages; minor correction
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