1,442 research outputs found
Silent Transitions in Automata with Storage
We consider the computational power of silent transitions in one-way automata
with storage. Specifically, we ask which storage mechanisms admit a
transformation of a given automaton into one that accepts the same language and
reads at least one input symbol in each step.
We study this question using the model of valence automata. Here, a finite
automaton is equipped with a storage mechanism that is given by a monoid.
This work presents generalizations of known results on silent transitions.
For two classes of monoids, it provides characterizations of those monoids that
allow the removal of \lambda-transitions. Both classes are defined by graph
products of copies of the bicyclic monoid and the group of integers. The first
class contains pushdown storages as well as the blind counters while the second
class contains the blind and the partially blind counters.Comment: 32 pages, submitte
Integrating Blood Collection Within Household Surveys: Lessons Learned From Nesting a Measles and Rubella Serological Survey Within a Post-Campaign Coverage Evaluation Survey in Southern Province, Zambia
Age-specific population immunity to many vaccine-preventable diseases can be measured using serological surveys. However, stand-alone serological surveys are infrequently conducted in low- and middle-income countries because of costs, operational challenges, and potential high refusal rates for blood collection. Nesting a serosurvey within a household cluster survey may overcome some of these challenges. We share lessons learned from nesting a serosurvey within a measles and rubella vaccination post-campaign coverage evaluation survey (PCES). In 15 of the 26 PCES clusters in Southern Province, Zambia, we collected dried blood spots from 581 participants aged 9 months and older. Household participation rates for the main PCES were higher in the serosurvey clusters (86%) than PCES-only clusters (71%), suggesting that a serosurvey can be successfully integrated without adversely affecting PCES participation. Among households that participated in the PCES, 80% also participated in the serosurvey and 86% of individuals available in the household provided a blood sample for the serosurvey. Substantial planning and coordination, additional staff training, and community mobilization were critical to the success of the serosurvey. Most challenges stemmed from using different data collecting tools and teams for the serosurvey and PCES. A more efficient design would be to fully integrate the serosurvey by adding blood collection and additional questions to the PCES
Effects of thin film Pd deposition on the hydrogen permeability of Pd60Cu40 wt% alloy membranes
Pd–Cu alloys have great potential as hydrogen separation membranes due to their relatively low cost and excellent durability compared to commercial dense metal membranes such as Pd and Pd–Ag alloys. At a composition of Pd60Cu40 wt% the body centred cubic (bcc) phase possesses the highest hydrogen permeability of the Pd–Cu alloy system. Furthermore, a Pd–Cu membrane containing a Pd-rich Pd–Cu fcc phase exhibits improved resistance to hydrogen sulphide (H2S) contamination.The basis of this study was to modify the surface composition of bcc Pd60Cu40 wt% membranes through deposition of a Pd thin film onto one side to produce a stable Pd-rich fcc layer and to investigate its effects on hydrogen permeability. The hydrogen permeability of two as-received Pd60Cu40 wt% membranes (Membranes 1 and 2) was measured in addition to two Pd coated Pd60Cu40 wt% membranes (Membranes 3 and 4) for comparison. A Pd-rich Pd–Cu fcc phase with an approximate composition of Pd70Cu30 wt% was formed as a result of Cu interdiffusion between the Pd–Cu bulk membrane and the Pd thin film during hydrogen permeability testing. This new phase was responsible for the reduction in hydrogen permeability shown in the Samples 3 and 4.Using variable temperature in-situ X-ray diffraction(XRD), it was observed that Cu interdiffusion occurred from the Pd–Cu bulk membrane and into the Pd thin film between 300 and 600 °C under 445 kPa of flowing helium. Under 445 kPa of flowing hydrogen the Pd thin film readily formed the β-palladium hydride (β-PdH) phase at room temperature and gradually formed the α-interstitial hydrogen solid solution (α-PdH) phase at around 200 °C with Cu interdiffusion also occurring between 300 and 600 °C
Necessity of Superposition of Macroscopically Distinct States for Quantum Computational Speedup
For quantum computation, we investigate the conjecture that the superposition
of macroscopically distinct states is necessary for a large quantum speedup.
Although this conjecture was supported for a circuit-based quantum computer
performing Shor's factoring algorithm [A. Ukena and A. Shimizu, Phys. Rev. A69
(2004) 022301], it needs to be generalized for it to be applicable to a large
class of algorithms and/or other models such as measurement-based quantum
computers. To treat such general cases, we first generalize the indices for the
superposition of macroscopically distinct states. We then generalize the
conjecture, using the generalized indices, in such a way that it is
unambiguously applicable to general models if a quantum algorithm achieves
exponential speedup. On the basis of this generalized conjecture, we further
extend the conjecture to Grover's quantum search algorithm, whose speedup is
large but quadratic. It is shown that this extended conjecture is also correct.
Since Grover's algorithm is a representative algorithm for unstructured
problems, the present result further supports the conjecture.Comment: 18 pages, 5 figures. Fixed typos throughout the manuscript. This
version has been publishe
Charged Particles in a 2+1 Curved Background
The coupling to a 2+1 background geometry of a quantized charged test
particle in a strong magnetic field is analyzed. Canonical operators adapting
to the fast and slow freedoms produce a natural expansion in the inverse square
root of the magnetic field strength. The fast freedom is solved to the second
order.
At any given time, space is parameterized by a couple of conjugate operators
and effectively behaves as the `phase space' of the slow freedom. The slow
Hamiltonian depends on the magnetic field norm, its covariant derivatives, the
scalar curvature and presents a peculiar coupling with the spin-connection.Comment: 22 page
Dirac's Observables for the Rest-Frame Instant Form of Tetrad Gravity in a Completely Fixed 3-Orthogonal Gauge
We define the {\it rest-frame instant form} of tetrad gravity restricted to
Christodoulou-Klainermann spacetimes. After a study of the Hamiltonian group of
gauge transformations generated by the 14 first class constraints of the
theory, we define and solve the multitemporal equations associated with the
rotation and space diffeomorphism constraints, finding how the cotriads and
their momenta depend on the corresponding gauge variables. This allows to find
quasi-Shanmugadhasan canonical transformation to the class of 3-orthogonal
gauges and to find the Dirac observables for superspace in these gauges.
The construction of the explicit form of the transformation and of the
solution of the rotation and supermomentum constraints is reduced to solve a
system of elliptic linear and quasi-linear partial differential equations. We
then show that the superhamiltonian constraint becomes the Lichnerowicz
equation for the conformal factor of the 3-metric and that the last gauge
variable is the momentum conjugated to the conformal factor. The gauge
transformations generated by the superhamiltonian constraint perform the
transitions among the allowed foliations of spacetime, so that the theory is
independent from its 3+1 splittings. In the special 3-orthogonal gauge defined
by the vanishing of the conformal factor momentum we determine the final Dirac
observables for the gravitational field even if we are not able to solve the
Lichnerowicz equation. The final Hamiltonian is the weak ADM energy restricted
to this completely fixed gauge.Comment: RevTeX file, 141 page
EDDY PROCESSES OF THE WESTERN ADRIATIC CURRENT NEAR CAPE GARGANO
Abstract Eddy processes of the Western Adriatic Current near Cape Gargano are highly modulated by the wind, growing during calm periods following strong wind events. Both single anticyclones and trains of multiple eddies with a regular spacing are observed. Suppression of a single anticyclone in the lee of the Cape was observed by profiling SEPTR moorings to occur when the horizontal gradient of the thermocline depth was increased by the wind. Eddies also form cyclonic filaments extending offshore. Such a filament was observed through the new technique of seismic oceanography to have downslope tilting isotherms and a long, thin, offshore extension in the bottom boundary layer. Recent measurements from two international collaborative research programs reveal new details of eddy activity and instability of the Western Adriatic Current (WAC) as it rounds Cape Gargano in the central Adriatic Sea. The "Dynamics of the Adriatic in Real-Time" (DART) program was focused on understanding the predictability of this system with observation and modelling from October 2005 through September 2006. These included, among other things, measurements from long-term current moorings, profiling SEPTR moorings, tow-yo CTD profiles, remote sensing, and high-resolution modelling using the U.S. Navy Coastal Ocean Model. Remote sensing and modelling, supported by in situ observations, revealed two distinct cases of WAC eddy activity Although Adriatic wind regimes and Cape topography provide the background setting for eddy formation, frontal instabilities and mixing processes determine many details of eddy structure and evolution. Acknowledgments: We thank the Italian CNR for providing R/V Urania ship time and CNR-ISMAR for coordinating the AdriaSeismic09 cruise
Effect of the reverse shock on the parameters of the observed X-Ray emission during the 1998 outburst of CI Cam
Based on the model of interaction between spherically symmetrical expanding
matter and the external medium, we have estimated the parameters of the matter
heated by the shock that was produced in the envelope ejected by the explosion
of a classical nova during its interaction with the stellar wind from the
optical companion. Using this model, we have shown that the matter ejected
during the outburst in the system CI Cam had no steep velocity gradients and
that the reverse shock could heat the ejected matter only to a temperature of
~0.1 keV. Therefore, this matter did not contribute to the mean temperature and
luminosity of the system observed in the energy range 3-20 keV.Comment: 7 pages, 5 figure
Phase-space dependence of particle-ratio fluctuations in Pb+Pb collisions from 20A to 158A GeV beam energy
A novel approach, the identity method, was used for particle identification
and the study of fluctuations of particle yield ratios in Pb+Pb collisions at
the CERN Super Proton Synchrotron (SPS). This procedure allows to unfold the
moments of the unknown multiplicity distributions of protons (p), kaons (K),
pions () and electrons (e). Using these moments the excitation function of
the fluctuation measure [A,B] was measured, with A and
B denoting different particle types. The obtained energy dependence of
agrees with previously published NA49 results on the related
measure . Moreover, was found to depend
on the phase space coverage for [K,p] and [K,] pairs. This feature most
likely explains the reported differences between measurements of NA49 and those
of STAR in central Au+Au collisions
Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
Substantial experimental and theoretical efforts worldwide are devoted to
explore the phase diagram of strongly interacting matter. At LHC and top RHIC
energies, QCD matter is studied at very high temperatures and nearly vanishing
net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was
created at experiments at RHIC and LHC. The transition from the QGP back to the
hadron gas is found to be a smooth cross over. For larger net-baryon densities
and lower temperatures, it is expected that the QCD phase diagram exhibits a
rich structure, such as a first-order phase transition between hadronic and
partonic matter which terminates in a critical point, or exotic phases like
quarkyonic matter. The discovery of these landmarks would be a breakthrough in
our understanding of the strong interaction and is therefore in the focus of
various high-energy heavy-ion research programs. The Compressed Baryonic Matter
(CBM) experiment at FAIR will play a unique role in the exploration of the QCD
phase diagram in the region of high net-baryon densities, because it is
designed to run at unprecedented interaction rates. High-rate operation is the
key prerequisite for high-precision measurements of multi-differential
observables and of rare diagnostic probes which are sensitive to the dense
phase of the nuclear fireball. The goal of the CBM experiment at SIS100
(sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD
matter: the phase structure at large baryon-chemical potentials (mu_B > 500
MeV), effects of chiral symmetry, and the equation-of-state at high density as
it is expected to occur in the core of neutron stars. In this article, we
review the motivation for and the physics programme of CBM, including
activities before the start of data taking in 2022, in the context of the
worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal
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