3,725 research outputs found
Early perceptions of an epidemic
This article surveys some descriptions of the Fore people made on early contact in the 1950s by patrol officers, social anthropologists and medical doctors. Sorcery accusations and cannibalism initially impressed these outside observers, though gradually they came to realize that a strange and fatal condition called kuru was a major affliction of the Fore, especially women and children. Fore attributed kuru to sorcery, anthropologists speculated on psychosomatic causes and medical officers began to wonder if it was a mysterious encephalitis
Thermal spray processing
Thermal spray processing has been used for a number of years to cost-effecticely apply TBC's for a wide range of heat engine applications. In particular, bond coats are applied by plasma spray and HVOF techniques and partially-stabilized zirconia top coats are applied by plasma spray methods. Thermal spray involves melting and rapid transport of the molten particles to the substrate, where high-rate solidification and coating build-up occur. It is the very nature of this melt processing that leads to the unique layered microstructure, as well as the apparent imperfections, so readily identified with thermal spray. Modeling the process, process-induced residual stresses, and thermal conductivity will be discussed in light of a new understanding of porosity and its anisotropy. Microcracking can be understood using new approaches, allowing a fuller view of the processing-performance connection. Detailed electron microscopic, novel neutron diffraction and fracture analysis of the deposits can lead to a better understanding of how overall microstructure can be controlled to influence critical properties of the deposited TBC system
Block circulant matrices with circulant blocks, weil sums and mutually unbiased bases, II. The prime power case
In our previous paper \cite{co1} we have shown that the theory of circulant
matrices allows to recover the result that there exists Mutually Unbiased
Bases in dimension , being an arbitrary prime number. Two orthonormal
bases of are said mutually unbiased if
one has that ( hermitian scalar product in ). In this paper we show that the theory of block-circulant matrices with
circulant blocks allows to show very simply the known result that if
( a prime number, any integer) there exists mutually Unbiased
Bases in . Our result relies heavily on an idea of Klimov, Munoz,
Romero \cite{klimuro}. As a subproduct we recover properties of quadratic Weil
sums for , which generalizes the fact that in the prime case the
quadratic Gauss sums properties follow from our results
First Results from Pb+Pb collisions at the LHC
At the end of 2010, the CERN Large Hadron Collider started operation with
heavy ion beams, colliding lead nuclei at a centre-of-mass energy of 2.76
TeV/nucleon and opening a new era in ultra-relativistic heavy ion physics at
energies exceeding previous accelerators by more than an order of magnitude.
This review summarizes the results from the first year of heavy ion physics at
LHC obtained by the three experiments participating in the heavy ion program,
ALICE, ATLAS, and CMS.Comment: To appear in Annual Review of Nuclear and Particle Scienc
Roots of the derivative of the Riemann zeta function and of characteristic polynomials
We investigate the horizontal distribution of zeros of the derivative of the
Riemann zeta function and compare this to the radial distribution of zeros of
the derivative of the characteristic polynomial of a random unitary matrix.
Both cases show a surprising bimodal distribution which has yet to be
explained. We show by example that the bimodality is a general phenomenon. For
the unitary matrix case we prove a conjecture of Mezzadri concerning the
leading order behavior, and we show that the same follows from the random
matrix conjectures for the zeros of the zeta function.Comment: 24 pages, 6 figure
Vacuum Polarization and the Electric Charge of the Positron
We show that higher-order vacuum polarization would contribute a measureable
net charge to atoms, if the charges of electrons and positrons do not balance
precisely. We obtain the limit for the sum of
the charges of electron and positron. This also constitutes a new bound on
certain violations of PCT invariance.Comment: 9 pages, 1 figure attached as PostScript file, DUKE-TH-92-38. Revised
versio
More Discriminants with the Brezing-Weng Method
The Brezing-Weng method is a general framework to generate families of
pairing-friendly elliptic curves. Here, we introduce an improvement which can
be used to generate more curves with larger discriminants. Apart from the
number of curves this yields, it provides an easy way to avoid endomorphism
rings with small class number
SIC-POVMs and the Extended Clifford Group
We describe the structure of the extended Clifford Group (defined to be the
group consisting of all operators, unitary and anti-unitary, which normalize
the generalized Pauli group (or Weyl-Heisenberg group as it is often called)).
We also obtain a number of results concerning the structure of the Clifford
Group proper (i.e. the group consisting just of the unitary operators which
normalize the generalized Pauli group). We then investigate the action of the
extended Clifford group operators on symmetric informationally complete POVMs
(or SIC-POVMs) covariant relative to the action of the generalized Pauli group.
We show that each of the fiducial vectors which has been constructed so far
(including all the vectors constructed numerically by Renes et al) is an
eigenvector of one of a special class of order 3 Clifford unitaries. This
suggests a strengthening of a conjuecture of Zauner's. We give a complete
characterization of the orbits and stability groups in dimensions 2-7. Finally,
we show that the problem of constructing fiducial vectors may be expected to
simplify in the infinite sequence of dimensions 7, 13, 19, 21, 31,... . We
illustrate this point by constructing exact expressions for fiducial vectors in
dimensions 7 and 19.Comment: 27 pages. Version 2 contains some additional discussion of Zauner's
original conjecture, and an alternative, possibly stronger version of the
conjecture in version 1 of this paper; also a few other minor improvement
Maturation of mammalian H/ACA box snoRNAs: PAPD5-dependent adenylation and PARN-dependent trimming
Small nucleolar and small Cajal body RNAs (snoRNAs and scaRNAs) of the H/ACA box and C/D box type are generated by exonucleolytic shortening of longer precursors. Removal of the last few nucleotides at the 3' end is known to be a distinct step. We report that, in human cells, knock-down of the poly(A) specific ribonuclease (PARN), previously implicated only in mRNA metabolism, causes the accumulation of oligoadenylated processing intermediates of H/ACA box but not C/D box RNAs. In agreement with a role of PARN in snoRNA and scaRNA processing, the enzyme is concentrated in nucleoli and Cajal bodies. Oligo(A) tails are attached to a short stub of intron sequence remaining beyond the mature 3' end of the snoRNAs. The noncanonical poly(A) polymerase PAPD5 is responsible for addition of the oligo(A) tails. We suggest that deadenylation is coupled to clean 3' end trimming, which might serve to enhance snoRNA stability
- …