2,453 research outputs found
Phase diffusion and locking in single-qubit lasers
Motivated by recent experiments, which demonstrated lasing and cooling of the
electromagnetic field in an electrical resonator coupled to a superconducting
qubit, we study the phase coherence and diffusion of the system in the lasing
state. We also discuss phase locking and synchronization induced by an
additional {\sl ac} driving of the resonator. We extend earlier work to account
for the strong qubit-resonator coupling and to include the effects of
low-frequency qubit's noise. We show that the strong coupling may lead to a
double peak structure of the spectrum, while the shape and width are determined
to the low-frequency noise.Comment: Revised version with a new section about the validity of the model
when applied to describe experiment
Combined analysis of neutrino decoherence at reactor experiments
Reactor experiments are well suited to probe the possible loss of coherence
of neutrino oscillations due to wave-packets separation. We combine data from
the short-baseline experiments Daya Bay and the Reactor Experiment for Neutrino
Oscillation (RENO) and from the long baseline reactor experiment KamLAND to
obtain the best current limit on the reactor antineutrino wave-packet width,
nm at 90% CL. We also find that the determination
of standard oscillation parameters is robust, i.e., it is mostly insensitive to
the presence of hypothetical decoherence effects once one combines the results
of the different reactor neutrino experiments.Comment: 8 pages, 4 figures. Version matches the one published in JHE
Paragons of character - Character strengths and well-being of moral, creative, and religious exemplars
Objective
Which traits best describe individuals who are recognized as exemplary in different domains? And can self-rated positively valued personality traits distinguish such individuals from the general population?
Background
The study of exemplary individuals’ personality traits traditionally focused on general and broad traits. Using character strengths, which are narrower and designed to describe desirable behavior, could provide new insights.
Method
In this study, we examined 204 outstanding individuals—exemplars who received or were nominated for a public award recognizing their exemplary behavior (e.g., a Carnegie Rescuers Award; n = 119), individuals holding a patent (n = 62), and individuals living in a religious order (n = 23). We compared these exemplars to comparison samples matched based on demographic variables. All participants completed self-report questionnaires assessing character strengths and well-being (e.g., satisfaction with life).
Results
Results showed that the three groups of exemplars differed meaningfully in their character strengths and well-being from the matched comparison groups. Compared with matched counterparts, moral exemplars scored higher on the strengths related to the virtues of courage, humanity, and justice as well as the character strength of humility, creative exemplars scored higher on the character strengths of creativity and honesty, and religious exemplars scored higher on gratitude and spirituality.
Conclusion
Overall, our findings suggest that character strengths are a useful framework for studying exemplary behavior
Few-Qubit lasing in circuit QED
Motivated by recent experiments, which demonstrated lasing and cooling of the
electromagnetic modes in a resonator coupled to a superconducting qubit, we
describe the specific mechanisms creating the population inversion, and we
study the spectral properties of these systems in the lasing state. Different
levels of the theoretical description, i.e., the semi-classical and the
semi-quantum approximation, as well as an analysis based on the full Liouville
equation are compared. We extend the usual quantum optics description to
account for strong qubit-resonator coupling and include the effects of
low-frequency noise. Beyond the lasing transition we find for a single- or
few-qubit system the phase diffusion strength to grow with the coupling
strength, which in turn deteriorates the lasing state.Comment: Prepared for the proceedings of the Nobel Symposium 2009, Qubits for
future quantum computers, May 2009 in Goeteborg, Sweden. Published versio
Calibration of building energy simulation models based on optimization: A case study
This study applies an optimization-based approach for calibrating building energy models using monitored data. The calibration was carried out on a test building coupling the EnergyPlus energy simulation tool with the GenOpt optimization tool. The objective function was set to minimize the difference between simulated and monitored energy consumption. For evaluating the model accuracy, the Mean Bias Error (MBE) and the Coefficient of Variation of the \RMSE\ (Cv (RMSE)) were calculated and found consistent with \ASHRAE\ guideline 14 limits for a model to be considered calibrated
Probing DNA-stabilized fluorescent silver nanocluster spectral heterogeneity by time-correlated single photon counting
Single-qubit lasing in the strong-coupling regime
Motivated by recent ``circuit QED'' experiments we study the lasing
transition and spectral properties of single-qubit lasers. In the strong
coupling, low-temperature regime quantum fluctuations dominate over thermal
noise and strongly influence the linewidth of the laser. When the qubit and the
resonator are detuned, amplitude and phase fluctuations of the radiation field
are coupled, and the phase diffusion model, commonly used to describe
conventional lasers, fails. We predict pronounced effects near the lasing
transition, with an enhanced linewidth and non-exponential decay of the
correlation functions. We cover a wide range of parameters by using two
complementary approaches, one based on the Liouville equation in a Fock state
basis, covering arbitrarily strong coupling but limited to low photon numbers,
the other based on the coherent-state representation, covering large photon
numbers but restricted to weak or intermediate coupling.Comment: 11 pages, 11 figure
Protumoral role of monocytes in human B-cell precursor acute lymphoblastic leukemia: involvement of the chemokine CXCL10
Abstract
Myelomonocytic cells play a key role in the progression of many solid tumors. However, very little is known about their contribution to the progression of hematopoietic cancers. We investigated the role of monocytes in the progression of human B-cell precursor acute lymphoblastic leukemia (BCP-ALL). We demonstrated that coculturing human monocytes in vitro with CD19+ BCP-ALL blasts from patients "conditioned" them to an inflammatory phenotype characterized by significant up-regulation of the chemokine, CXCL10. This phenotype was also observable ex vivo in monocytes isolated from BCP-ALL patients, which show elevated CXCL10 production compared with monocytes from healthy donors. Functionally, the "conditioned" monocytes promoted migration and invasive capacity of BCP-ALL cells. Increased invasion was mediated by matrix metalloproteinase 9 expression and activity in the BCP-ALL cells induced by the monocyte-derived CXCL10. However, neither the "conditioned" monocytes nor the CXCL10 produced by these cells had any effect on the proliferation/viability of BCP-ALL cells and angiogenesis. Collectively, our results strongly suggest a protumoral role for human monocytes in BCP-ALL, orchestrated by CXCL10 and its effect on tumor cell migration and invasion. These observations highlight the importance of the CXCL10/CXCR3 chemokine circuit in BCP-ALL progression
- …