52,884 research outputs found
Controllable Gaussian-qubit interface for extremal quantum state engineering
We study state engineering through bilinear interactions between two remote
qubits and two-mode Gaussian light fields. The attainable two-qubit states span
the entire physically allowed region in the entanglement-versus-global-purity
plane. Two-mode Gaussian states with maximal entanglement at fixed global and
marginal entropies produce maximally entangled two-qubit states in the
corresponding entropic diagram. We show that a small set of parameters
characterizing extremally entangled two-mode Gaussian states is sufficient to
control the engineering of extremally entangled two-qubit states, which can be
realized in realistic matter-light scenarios.Comment: 4+3 pages, 6 figures, RevTeX4. Close to published version with
appendi
Kinetics of viral self-assembly: the role of ss RNA antenna
A big class of viruses self-assemble from a large number of identical capsid
proteins with long flexible N-terminal tails and ss RNA. We study the role of
the strong Coulomb interaction of positive N-terminal tails with ss RNA in the
kinetics of the in vitro virus self-assembly. Capsid proteins stick to
unassembled chain of ss RNA (which we call "antenna") and slide on it towards
the assembly site. We show that at excess of capsid proteins such
one-dimensional diffusion accelerates self-assembly more than ten times. On the
other hand at excess of ss RNA, antenna slows self-assembly down. Several
experiments are proposed to verify the role of ss RNA antenna.Comment: 4 pages, 3 figures, several experiments are proposed, a new idea of
experiment is adde
An NPZ Model with State-Dependent Delay due to Size-Structure in Juvenile Zooplankton
The study of planktonic ecosystems is important as they make up the bottom
trophic levels of aquatic food webs. We study a closed
Nutrient-Phytoplankton-Zooplankton (NPZ) model that includes size structure in
the juvenile zooplankton. The closed nature of the system allows the
formulation of a conservation law of biomass that governs the system. The model
consists of a system of nonlinear ordinary differential equation coupled to a
partial differential equation. We are able to transform this system into a
system of delay differential equations where the delay is of threshold type and
is state-dependent. The system of delay differential equations can be further
transformed into one with fixed delay. Using the different forms of the model
we perform a qualitative analysis of the solutions, which includes studying
existence and uniqueness, positivity and boundedness, local and global
stability, and conditions for extinction. Key parameters that are explored are
the total biomass in the system and the maturity level at which the juvenile
zooplankton reach maturity. Numerical simulations are also performed to verify
our analytical results
Production of a Z boson and two jets with one heavy-quark tag
We present a next-to-leading-order calculation of the production of a Z boson
with two jets, one or more of which contains a heavy quark (Q=c,b). We show
that the cross section with only one heavy-quark jet is larger than that with
two heavy-quark jets at both the Fermilab Tevatron and the CERN LHC. These
processes are the dominant irreducible backgrounds to a Higgs boson produced in
association with a Z boson, followed by h->bb. Our calculation makes use of a
heavy-quark distribution function, which resums collinear logarithms and makes
the next-to-leading-order calculation tractable.Comment: 11 pages, 5 figures. Erratum adde
Assessment of Neuropsychological Trajectories in Longitudinal Population-Based Studies of Children
This paper provides a strategy for the assessment of brain function in longitudinal cohort studies of children. The proposed strategy invokes both domain-specific and omnibus intelligence test approaches. In order to minimise testing burden and practice effects, the cohort is divided into four groups with one-quarter tested at 6-monthly intervals in the 0–2-year age range (at ages 6 months, 1.0, 1.5 and 2.0 years) and at annual intervals from ages 3–20 (one-quarter of the children at age 3, another at age 4, etc). This strategy allows investigation of cognitive development and of the relationship between environmental influences and development at each age. It also allows introduction of new domains of function when age-appropriate. As far as possible, tests are used that will provide a rich source of both longitudinal and cross-sectional data. The testing strategy allows the introduction of novel tests and new domains as well as piloting of tests when the test burden is relatively light. In addition to the recommended tests for each age and domain, alternative tests are described. Assessment methodology and knowledge about child cognitive development will change over the next 20 years, and strategies are suggested for altering the proposed test schedule as appropriate
b-Initiated processes at the LHC: a reappraisal
Several key processes at the LHC in the standard model and beyond that
involve quarks, such as single-top, Higgs, and weak vector boson associated
production, can be described in QCD either in a 4-flavor or 5-flavor scheme. In
the former, quarks appear only in the final state and are typically
considered massive. In 5-flavor schemes, calculations include quarks in the
initial state, are simpler and allow the resummation of possibly large initial
state logarithms of the type into the
parton distribution function (PDF), being the typical scale of the
hard process. In this work we critically reconsider the rationale for using
5-flavor improved schemes at the LHC. Our motivation stems from the observation
that the effects of initial state logs are rarely very large in hadron
collisions: 4-flavor computations are pertubatively well behaved and a
substantial agreement between predictions in the two schemes is found. We
identify two distinct reasons that explain this behaviour, i.e., the
resummation of the initial state logarithms into the -PDF is relevant only
at large Bjorken and the possibly large ratios 's are
always accompanied by universal phase space suppression factors. Our study
paves the way to using both schemes for the same process so to exploit their
complementary advantages for different observables, such as employing a
5-flavor scheme to accurately predict the total cross section at NNLO and the
corresponding 4-flavor computation at NLO for fully exclusive studies.Comment: Fixed typo in Eq. (A.10) and few typos in Eq. (C.2) and (C.3
A Low Cost Remote Sensing System Using PC and Stereo Equipment
A system using a personal computer, speaker, and a microphone is used to
detect objects, and make crude measurements using a carrier modulated by a
pseudorandom noise (PN) code. This system can be constructed using a personal
computer and audio equipment commonly found in the laboratory or at home, or
more sophisticated equipment that can be purchased at reasonable cost. We
demonstrate its value as an instructional tool for teaching concepts of remote
sensing and digital signal processing.Comment: Accepted for publication in American Journal of Physic
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