6,381 research outputs found
The equation of state for scalar-tensor gravity
We show that the field equation of Brans-Dicke gravity and scalar-tensor
gravity can be derived as the equation of state of Rindler spacetime, where the
local thermodynamic equilibrium is maintained. Our derivation implies that the
effective energy can not feel the heat flow across the Rindler horizon.Comment: 6 pages, to be published in Prog. Theor. Phy
Building quantum neural networks based on swap test
Artificial neural network, consisting of many neurons in different layers, is
an important method to simulate humain brain. Usually, one neuron has two
operations: one is linear, the other is nonlinear. The linear operation is
inner product and the nonlinear operation is represented by an activation
function. In this work, we introduce a kind of quantum neuron whose inputs and
outputs are quantum states. The inner product and activation operator of the
quantum neurons can be realized by quantum circuits. Based on the quantum
neuron, we propose a model of quantum neural network in which the weights
between neurons are all quantum states. We also construct a quantum circuit to
realize this quantum neural network model. A learning algorithm is proposed
meanwhile. We show the validity of learning algorithm theoretically and
demonstrate the potential of the quantum neural network numerically.Comment: 10 pages, 13 figure
Premedication with dexmedetomidine in pediatric patients: a systematic review and meta-analysis
Premedication is important in pediatric anesthesia. This meta-analysis aimed to investigate the role of dexmedetomidine as a premedicant for pediatric patients. A systematic literature search was conducted to identify randomized controlled trials comparing dexmedetomidine premedication with midazolam or ketamine premedication or placebo in children. Two reviewers independently performed the study selection, quality assessment and data extraction. The original data were pooled for the meta-analysis with Review Manager 5. The main parameters investigated included satisfactory separation from parents, satisfactory mask induction, postoperative rescue analgesia, emergence agitation and postoperative nausea and vomiting. Thirteen randomized controlled trials involving 1190 patients were included. When compared with midazolam, premedication with dexmedetomidine resulted in an increase in satisfactory separation from parents (RD = 0.18, 95% CI: 0.06 to 0.30, p = 0.003) and a decrease in the use of postoperative rescue analgesia (RD = -0.19, 95% CI: -0.29 to -0.09, p = 0.0003). Children treated with dexmedetomidine had a lower heart rate before induction. The incidence of satisfactory mask induction, emergence agitation and PONV did not differ between the groups. Dexmedetomidine was superior in providing satisfactory intravenous cannulation compared to placebo. This meta-analysis suggests that dexmedetomidine is superior to midazolam premedication because it resulted in enhanced preoperative sedation and decreased postoperative pain. Additional studies are needed to evaluate the dosing schemes and long-term outcomes of dexmedetomidine premedication in pediatric anesthesia
An Approach to the Production of Soluble Protein from a Fungal Gene Encoding an Aggregation-Prone Xylanase in Escherichia coli
The development of new procedures and protocols that allow researchers to obtain
recombinant proteins is of fundamental importance in the biotechnology field. A
strategy was explored to overcome inclusion-body formation observed when
expressing an aggregation-prone fungal xylanase in Escherichia
coli. pHsh is an expression plasmid that uses a synthetic
heat-shock (Hsh) promoter, in which gene expression is regulated by an
alternative sigma factor (σ32). A derivative of pHsh was
constructed by fusing a signal peptide to xynA2 gene to
facilitate export of the recombinant protein to the periplasm. The xylanase was
produced in a soluble form. Three factors were essential to achieving such
soluble expression of the xylanase: 1) the target gene was under the control of
the Hsh promoter, 2) the gene product was exported into the periplasm, and 3)
gene expression was induced by a temperature upshift. For the first time we
report the expression of periplasmic proteins under the control of an Hsh
promoter regulated by σ32. One unique feature of this approach
was that over 200 copies of the Hsh promoter in an E. coli cell
significantly increased the concentration of σ32. The growth
inhibition of the recombinant cells corresponded to an increase in the levels of
soluble periplasmic protein. Therefore, an alternative protocol was designed to
induce gene expression from pHsh-ex to obtain high levels of active soluble
enzymes
A path to precision cosmology: synergy between four promising late-universe cosmological probes
In the next decades, it is necessary to forge new late-universe cosmological
probes to precisely constrain the Hubble constant and the equation of state of
dark energy simultaneously. In this work, we show that the four typical
late-universe cosmological probes, the 21 cm intensity mapping (IM), fast radio
burst (FRB), gravitational wave (GW) standard siren, and strong gravitational
lensing (SGL), are expected to be forged into useful tools in solving the
Hubble tension and exploring dark energy. We propose that the synergy of them
is rather important in cosmology. We simulate the 21 cm IM, FRB, GW, and SGL
data based on the hypothetical observations of the Hydrogen Intensity and
Real-time Analysis eXperiment (HIRAX), the Square Kilometre Array (SKA), the
Einstein Telescope (ET), and the Large Synoptic Survey Telescope (LSST),
respectively. We find that the four probes show obviously different parameter
degeneracy orientations in cosmological constraints, so any combination of them
can break the parameter degeneracies and thus significantly improve the
constraint precision. The joint 21 cm IM+FRB+GW+SGL data can provide the
constraint errors of and in the CDM model, which meet the standard of
precision cosmology, i.e., the constraint precision of parameters is better
than 1%. In addition, the joint data give in the CDM
model, and and in the CDM model,
which are all better than the constraints obtained by the CMB+BAO+SN data. We
show that the synergy between the four late-universe cosmological probes has
magnificent prospects.Comment: 28 pages, 9 figures; accepted for publication in JCA
- …