2,529 research outputs found
Mechanism for a Decaying Cosmological Constant
A mechanism is introduced to reduce a large cosmological constant to a
sufficiently small value consistent with observational upper limit. The basic
ingradient in this mechanism is a distinction which has been made between the
two unit systems used on cosmology and particle physics. We have used a
conformal invariant gravitational model to define a particular conformal frame
in terms of the large scale properties of the universe. It is then argued that
the contributions of mass scales in particle physics to the vacuum energy
density should be considered in a different conformal frame. In this manner a
cancellation mechanism is presented in which the conformal factor plays a key
role to relax the large effective cosmological constant.Comment: 6 pages, no figur
Hadamard States and Two-dimensional Gravity
We have used a two-dimensional analog of the Hadamard state-condition to
study the local constraints on the two-point function of a linear quantum field
conformally coupled to a two-dimensional gravitational background. We develop a
dynamical model in which the determination of the state of the quantum field is
essentially related to the determination of a conformal frame. A particular
conformal frame is then introduced in which a two-dimensional gravitational
equation is established.Comment: 7 pages, no figur
Mach's Principle and Model for a Broken Symmetric Theory of Gravity
We investigate spontaneous symmetry breaking in a conformally invariant
gravitational model. In particular, we use a conformally invariant scalar
tensor theory as the vacuum sector of a gravitational model to examine the idea
that gravitational coupling may be the result of a spontaneous symmetry
breaking. In this model matter is taken to be coupled with a metric which is
different but conformally related to the metric appearing explicitly in the
vacuum sector. We show that after the spontaneous symmetry breaking the
resulting theory is consistent with Mach's principle in the sense that inertial
masses of particles have variable configurations in a cosmological context.
Moreover, our analysis allows to construct a mechanism in which the resulting
large vacuum energy density relaxes during evolution of the universe.Comment: 9 pages, no figure
On Cosmological Implication of the Trace Anomaly
We establish a connection between the trace anomaly and a thermal radiation
in the context of the standard cosmology. This is done by solving the covariant
conservation equation of the stress tensor associated with a conformally
invariant quantum scalar field. The solution corresponds to a thermal radiation
with a temperature which is given in terms of a cut-off time excluding the
spacetime regions very close to the initial singularity. We discuss the
interrelation between this result and the result obtained in a two-dimensional
schwarzschild spacetime.Comment: 8 pages, no figure
A study on the ethical components of nursing practice (moral distress, ethical sensitivity, ethical decision)
This paper is an applied research in terms of objective and a descriptive research in terms of method. Having prepared the research plan, a questionnaire was designed based on goals and hypotheses of the research and was sent to the statistical universe. Also this paper is a field research in terms of data collection. As regards theoretical bases of the research, library data collection method has been applied. So, the required data has been gathered by referring to the related references, books, libraries and so on. To design a questionnaire and gather the opinions of the statistical universe members, field study method and researcher-made questionnaire have been used. The statistical universe comprises nurses and head of ICU and head nurses of Najmieh Hospital in Tehran. The respondents were selected by random sampling method. Also to estimate sample size, Morgan table was applied. The statistical universe consists of 65 members and according to the table, 56 questionnaires were determined for the research. So 60 questionnaires were sent and 58 ones were returned. Face and content validity of the research tool were approved by experts. The test reliability was estimated 0.777 by calculating Cronbach's alpha coefficient. In this paper, factor analysis based on partial least squares structural equations method has been applied to analyze more important factors and coefficients, estimate independent variables coefficients and even determine effectiveness of each independent variable on each other and determine appropriateness of the questions and their coefficients in explaining the related index. The main result of this paper presents a proper model for the relation of effective variables on nurse performance by using regression model. © IDOSI Publications, 2014
Factors affecting the policyholders' satisfaction <of> coldwater fish farmers of Mazandaran Province using agricultural insurance
The goal of this research was considering the reasons of policy holder satisfaction of breeding freshwater fish farms with agriculture insurance in Mazandaran province. The population of this research was the number of 63 freshwater fish breeders in Mazandaran province had assured their farms through Agricultural Insurance Fund during years 88 to 92 and they have utilized questionnaires for field data collection, its validity was approved by experts’ panel and its reliability was approved through utilization of Cronbach’s alpha coefficient (0.85). the variable " Agricultural Insurance Fund has considered on our complain on time" had more sound on satisfaction at the level of %30 followed by the variable " I am satisfied with specification and estimating damage of agricultural insurance" with the level of %28 and" the distance between damage and the time of compensation assessment by Insurance Fund is suitable " in level of %23 and" mangers and personnel attitude of Agricultural Insurance Fund is suitable" in level %20 are effective in measure of satisfaction. Obtained results from the research indicate that the main dissatisfaction of breeders had been about "becoming time-consuming between damage and compensation payment, being unsuitable and defective of specification and estimating compensation process, the way of considering on complain and demand of breeders and the way of managers and personnel of Agricultural Insurance Fund attitude and behavior
Improving the Segmentation of Anatomical Structures in Chest Radiographs using U-Net with an ImageNet Pre-trained Encoder
Accurate segmentation of anatomical structures in chest radiographs is
essential for many computer-aided diagnosis tasks. In this paper we investigate
the latest fully-convolutional architectures for the task of multi-class
segmentation of the lungs field, heart and clavicles in a chest radiograph. In
addition, we explore the influence of using different loss functions in the
training process of a neural network for semantic segmentation. We evaluate all
models on a common benchmark of 247 X-ray images from the JSRT database and
ground-truth segmentation masks from the SCR dataset. Our best performing
architecture, is a modified U-Net that benefits from pre-trained encoder
weights. This model outperformed the current state-of-the-art methods tested on
the same benchmark, with Jaccard overlap scores of 96.1% for lung fields, 90.6%
for heart and 85.5% for clavicles.Comment: Presented at the First International Workshop on Thoracic Image
Analysis (TIA), MICCAI 201
Quantum metamaterials: Electromagnetic waves in a Josephson qubit line
We consider the propagation of a classical electromagnetic wave through a
transmission line, formed by identical superconducting charge qubits inside a
superconducting resonator. Since the qubits can be in a coherent superposition
of quantum states, we show that such a system demonstrates interesting new
effects, such as a ``breathing'' photonic crystal with an oscillating bandgap,
and a ``quantum Archimedean screw'' that transports, at an arbitrary controlled
velocity, Josephson plasma waves through the transmission line. The key
ingredient of these effects is that the optical properties of the Josephson
transmission line are controlled by the quantum coherent state of the qubits.Comment: References adde
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