69 research outputs found
Prenotification in web-based access panel surveys: the influence of mobile text messaging versus e-mail on response rates and sample composition
To compare the effectiveness of different prenotification and invitation procedures in a webbased three-wave access panel survey over 3 consecutive months, we experimentally varied the contact mode in a fully crossed two-factorial design with (a) three different prenotification conditions (mobile short messaging service [SMS], e-mail, no prenotice) and (b) two “invitation and reminder" conditions (SMS, e-mail). A group with nearly complete mobile phone coverage was randomly assigned to one of these six experimental conditions. As expected, SMS prenotifications outperformed e-mail prenotifications in terms of response rates across all three waves. Furthermore, e-mail invitation response rates outperformed those for SMS invitations. The combination of SMS prenotification and e-mail invitation performed best. The different experimental treatments did not have an effect on the sample composition of respondents between groups. (author's abstract
Number phase uncertainty relations: verification by homodyning
It is shown that fundamental uncertainty relations between photon number and
canonical phase of a single-mode optical field can be verified by means of
balanced homodyne measurement. All the relevant quantities can be sampled
directly from the measured phase-dependent quadrature distribution.Comment: 1 Ps figure (divided in 3 subfigures) using REVTE
Mol. Cell. Proteomics
In-depth MS-based proteomics has necessitated fractionation of either proteins or peptides or both, often requiring considerable analysis time. Here we employ long liquid chromatography runs with high resolution coupled to an instrument with fast sequencing speed to investigate how much of the proteome is directly accessible to liquid chromatography-tandem MS characterization without any prefractionation steps. Triplicate single-run analyses identified 2990 yeast proteins, 68% of the total measured in a comprehensive yeast proteome. Among them, we covered the enzymes of the glycolysis and gluconeogenesis pathway targeted in a recent multiple reaction monitoring study. In a mammalian cell line, we identified 5376 proteins in a triplicate run, including representatives of 173 out of 200 KEGG metabolic and signaling pathways. Remarkably, the majority of proteins could be detected in the samples at sub-femtomole amounts and many in the low attomole range, in agreement with absolute abundance estimation done in previous works (Picotti et al. Cell, 138, 795–806, 2009). Our results imply an unexpectedly large dynamic range of the MS signal and sensitivity for liquid chromatography-tandem MS alone. With further development, single-run analysis has the potential to radically simplify many proteomic studies while maintaining a systems-wide view of the proteome
Quantum versus classical descriptions of sub-Poissonian light generation in three-wave mixing
Sub-Poissonian light generation in the non-degenerate three-wave mixing is
studied numerically and analytically within quantum and classical approaches.
Husimi Q-functions and their classical trajectory simulations are analysed to
reveal a special regime corresponding to the time-stable sub-Poissonian
photocount statistics of the sum-frequency mode. Conditions for observation of
this regime are discussed. Theoretical predictions of the Fano factor and
explanation of the extraordinary stabilization of the sub-Poissonian photocount
behavior are obtained analytically by applying the classical trajectories.
Scaling laws for the maximum sub-Poissonian behavior are found. Noise
suppression levels in the non-degenerate vs degenerate three-wave mixing are
discussed on different time scales compared to the revival times. It is shown
that the non-degenerate conversion offers much better stabilization of the
suppressed noise in comparison to that of degenerate process.Comment: 9 pages, 12 figures, to be published in J. Optics
Generation of phase-coherent states
An interaction scheme involving nonlinear media is suggested for
the generation of phase-coherent states (PCS). The setup is based on parametric
amplification of vacuum followed by up-conversion of the resulting twin-beam.
The involved nonlinear interactions are studied by the exact numerical
diagonalization. An experimentally achievable working regime to approximate PCS
with high conversion rate is given, and the validity of parametric
approximation is discussed.Comment: To appear in PRA -- More info at http://enterprise.pv.infn.it
Phase Diffusion in Quantum Dissipative Systems
We study the dynamics of the quantum phase distribution associated with the
reduced density matrix of a system for a number of situations of practical
importance, as the system evolves under the influence of its environment,
interacting via a quantum nondemoliton type of coupling, such that there is
decoherence without dissipation, as well as when it interacts via a dissipative
interaction, resulting in decoherence as well as dissipation. The system is
taken to be either a two-level atom (or equivalently, a spin-1/2 system) or a
harmonic oscillator, and the environment is modeled as a bath of harmonic
oscillators, starting out in a squeezed thermal state. The impact of the
different environmental parameters on the dynamics of the quantum phase
distribution for the system starting out in various initial states, is
explicitly brought out. An interesting feature that emerges from our work is
that the relationship between squeezing and temperature effects depends on the
type of system-bath interaction. In the case of quantum nondemolition type of
interaction, squeezing and temperature work in tandem, producing a diffusive
effect on the phase distribution. In contrast, in case of a dissipative
interaction, the influence of temperature can be counteracted by squeezing,
which manifests as a resistence to randomization of phase. We make use of the
phase distributions to bring out a notion of complementarity in atomic systems.
We also study the dispersion of the phase using the phase distributions
conditioned on particular initial states of the system.Comment: Accepted for publication in Physical Review A; changes in section V;
20 pages, 12 figure
s-ordered phase-sum and phase-difference distribuitons of entangled coherent states
The -ordered phase-sum and phase-difference distributions are considered
for Bell-like superpositions of two-mode coherent states. The distributions are
sensitive, respectively, to the sum and difference of the phases of the
entangled coherent states. They show loss of information about the entangled
state and may take on negative values for some orderings .Comment: 8 pages, 2 figures, iopart. accepted for publication in J. Opt. B:
Quantum Semiclass Op
Large-scale analysis of Drosophila core promoter function using synthetic promoters
The core promoter plays a central role in setting metazoan gene expression levels, but how exactly it “computes” expression remains poorly understood. To dissect its function, we carried out a comprehensive structure–function analysis in Drosophila. First, we performed a genome-wide bioinformatic analysis, providing an improved picture of the sequence motifs architecture. We then measured synthetic promoters’ activities of ~3,000 mutational variants with and without an external stimulus (hormonal activation), at large scale and with high accuracy using robotics and a dual luciferase reporter assay. We observed a strong impact on activity of the different types of mutations, including knockout of individual sequence motifs and motif combinations, variations of motif strength, nucleosome positioning, and flanking sequences. A linear combination of the individual motif features largely accounts for the combinatorial effects on core promoter activity. These findings shed new light on the quantitative assessment of gene expression in metazoans
- …