25,762 research outputs found
Heavy Meson Masses in the \epsilon-Regime of HM\chi PT
The pseudoscalar and vector heavy meson masses are calculated in the
\epsilon-regime of Heavy Meson Chiral Perturbation Theory to order \epsilon^4.
The results of this calculation will allow the determination of low-energy
coefficients (LECs) directly from Lattice QCD calculations of the heavy mesons
masses for lattices that satisfy the \epsilon-regime criteria. In particular,
the LECs that parametrize the NLO volume dependance of the heavy meson masses
are necessary for evaluating the light pseudoscalar meson (\pi, K, \eta) and
heavy meson ({D^0, D^+, D^+_s}, {B^-,\bar{B}^0,\bar{B}^0_s}) scattering phase
shifts.Comment: 16 pages, 6 figure
A simple method for estimation of coagulation efficiency in mixed aerosols
Aerosols of KBr and AgNO3 were mixed, exposed to light in a glass tube and collected in the dark. About 15% of the collected material was reduced to silver upon development. Thus, two aerosols of particles that react to form a photo-reducible compound can be used to measure coagulation efficiency
Stability of Magneto-optical Traps with Large Field Gradients: Limits on the Tight Confinement of Single Atoms
We report measurements of the stability of magneto-optical traps (MOTs) for neutral atoms in the limit of tight confinement of a single atom. For quadrupole magnetic field gradients at the trap center greater than ∼1 kG/cm, we find that stochastic diffusion of atoms out of the trapping volume becomes the dominant particle loss mechanism, ultimately limiting the MOT size to greater than ∼5 μm. We measured and modeled the diffusive loss rate as a function of laser power, detuning, and field gradient for trapped cesium atoms. In addition, for as few as two atoms, the collisional loss rates become very high for tightly confined traps, allowing the direct observation of isolated two-body atomic collisions in a MOT
Robust Quantum Error Correction via Convex Optimization
We present a semidefinite program optimization approach to quantum error
correction that yields codes and recovery procedures that are robust against
significant variations in the noise channel. Our approach allows us to optimize
the encoding, recovery, or both, and is amenable to approximations that
significantly improve computational cost while retaining fidelity. We
illustrate our theory numerically for optimized 5-qubit codes, using the
standard [5,1,3] code as a benchmark. Our optimized encoding and recovery
yields fidelities that are uniformly higher by 1-2 orders of magnitude against
random unitary weight-2 errors compared to the [5,1,3] code with standard
recovery. We observe similar improvement for a 4-qubit decoherence-free
subspace code.Comment: 4 pages, including 3 figures. v2: new example
Religious leaders\u27 perceptions of advance care planning: a secondary analysis of interviews with Buddhist, Christian, Hindu, Islamic, Jewish, Sikh and Bahai leaders
Background: International guidance for advance care planning (ACP) supports the integration of spiritual and religious aspects of care within the planning process. Religious leaders’ perspectives could improve how ACP programs respect patients’ faith backgrounds. This study aimed to examine: (i) how religious leaders understand and consider ACP and its implications, including (ii) how religion affects followers’ approaches to end-of-life care and ACP, and (iii) their implications for healthcare.
Methods: Interview transcripts from a primary qualitative study conducted with religious leaders to inform an ACP website, ACPTalk, were used as data in this study. ACPTalk aims to assist health professionals conduct sensitive conversations with people from different religious backgrounds. A qualitative secondary analysis conducted on the interview transcripts focussed on religious leaders’ statements related to this study’s aims. Interview transcripts were thematically analysed using an inductive, comparative, and cyclical procedure informed by grounded theory.
Results: Thirty-five religious leaders (26 male; mean 58.6-years-old), from eight Christian and six non-Christian (Jewish, Buddhist, Islamic, Hindu, Sikh, Bahá’í) backgrounds were included. Three themes emerged which focussed on: religious leaders’ ACP understanding and experiences; explanations for religious followers’ approaches towards end-of-life care; and health professionals’ need to enquire about how religion matters. Most leaders had some understanding of ACP and, once fully comprehended, most held ACP in positive regard. Religious followers’ preferences for end-of-life care reflected family and geographical origins, cultural traditions, personal attitudes, and religiosity and faith interpretations. Implications for healthcare included the importance of avoiding generalisations and openness to individualised and/ or standardised religious expressions of one’s religion.
Conclusions: Knowledge of religious beliefs and values around death and dying could be useful in preparing health professionals for ACP with patients from different religions but equally important is avoidance of assumptions. Community-based initiatives, programs and faith settin
Improving Loss Estimation for Woodframe Buildings. Volume 2: Appendices
This report documents Tasks 4.1 and 4.5 of the CUREE-Caltech Woodframe Project. It presents a theoretical and empirical methodology for creating probabilistic relationships between seismic shaking severity and physical damage and loss for buildings in general, and for woodframe buildings in particular. The methodology, called assembly-based vulnerability (ABV), is illustrated for 19 specific woodframe buildings of varying ages, sizes, configuration, quality of construction, and retrofit and redesign conditions. The study employs variations on four basic floorplans, called index buildings. These include a small house and a large house, a townhouse and an apartment building. The resulting seismic vulnerability functions give the probability distribution of repair cost as a function of instrumental ground-motion severity. These vulnerability functions are useful by themselves, and are also transformed to seismic fragility functions compatible with the HAZUS software.
The methods and data employed here use well-accepted structural engineering techniques, laboratory test data and computer programs produced by Element 1 of the CUREE-Caltech Woodframe Project, other recently published research, and standard construction cost-estimating methods. While based on such well established principles, this report represents a substantially new contribution to the field of earthquake loss estimation. Its methodology is notable in that it calculates detailed structural response using nonlinear time-history structural analysis as opposed to the simplifying assumptions required by nonlinear pushover methods. It models physical damage at the level of individual building assemblies such as individual windows, segments of wall, etc., for which detailed laboratory testing is available, as opposed to two or three broad component categories that cannot be directly tested. And it explicitly models uncertainty in ground motion, structural response, component damageability, and contractor costs. Consequently, a very detailed, verifiable, probabilistic picture of physical performance and repair cost is produced, capable of informing a variety of decisions regarding seismic retrofit, code development, code enforcement, performance-based design for above-code applications, and insurance practices
Efficient Optimal Minimum Error Discrimination of Symmetric Quantum States
This paper deals with the quantum optimal discrimination among mixed quantum
states enjoying geometrical uniform symmetry with respect to a reference
density operator . It is well-known that the minimal error probability
is given by the positive operator-valued measure (POVM) obtained as a solution
of a convex optimization problem, namely a set of operators satisfying
geometrical symmetry, with respect to a reference operator , and
maximizing . In this paper, by resolving the dual
problem, we show that the same result is obtained by minimizing the trace of a
semidefinite positive operator commuting with the symmetry operator and
such that . The new formulation gives a deeper insight into the
optimization problem and allows to obtain closed-form analytical solutions, as
shown by a simple but not trivial explanatory example. Besides the theoretical
interest, the result leads to semidefinite programming solutions of reduced
complexity, allowing to extend the numerical performance evaluation to quantum
communication systems modeled in Hilbert spaces of large dimension.Comment: 5 pages, 1 Table, no figure
Mixed perturbative expansion: the validity of a model for the cascading
A new type of perturbative expansion is built in order to give a rigorous
derivation and to clarify the range of validity of some commonly used model
equations.
This model describes the evolution of the modulation of two short and
localized pulses, fundamental and second harmonic, propagating together in a
bulk uniaxial crystal with non-vanishing second order susceptibility
and interacting through the nonlinear effect known as ``cascading'' in
nonlinear optics.
The perturbative method mixes a multi-scale expansion with a power series
expansion of the susceptibility, and must be carefully adapted to the physical
situation. It allows the determination of the physical conditions under which
the model is valid: the order of magnitude of the walk-off, phase-mismatch,and
anisotropy must have determined values.Comment: arxiv version is already officia
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