5,829 research outputs found
Fast Ridge Regression with Randomized Principal Component Analysis and Gradient Descent
We propose a new two stage algorithm LING for large scale regression
problems. LING has the same risk as the well known Ridge Regression under the
fixed design setting and can be computed much faster. Our experiments have
shown that LING performs well in terms of both prediction accuracy and
computational efficiency compared with other large scale regression algorithms
like Gradient Descent, Stochastic Gradient Descent and Principal Component
Regression on both simulated and real datasets
Breaking and restoration of rotational symmetry for irreducible tensor operators on the lattice
We study the breaking of rotational symmetry on the lattice for irreducible
tensor operators and practical methods for suppressing this breaking. We
illustrate the features of the general problem using an cluster model
for Be. We focus on the lowest states with non-zero angular momentum and
examine the matrix elements of multipole moment operators. We show that the
physical reduced matrix element is well reproduced by averaging over all
possible orientations of the quantum state, and this is expressed as a sum of
matrix elements weighted by the corresponding Clebsch-Gordan coefficients. For
our cluster model we find that the effects of rotational symmetry
breaking can be largely eliminated for lattice spacings of fm, and
we expect similar improvement for actual lattice Monte Carlo calculations.Comment: 8 pages, 4 figure
Precise determination of lattice phase shifts and mixing angles
We introduce a general and accurate method for determining lattice phase
shifts and mixing angles, which is applicable to arbitrary, non-cubic lattices.
Our method combines angular momentum projection, spherical wall boundaries and
an adjustable auxiliary potential. This allows us to construct radial lattice
wave functions and to determine phase shifts at arbitrary energies. For coupled
partial waves, we use a complex-valued auxiliary potential that breaks
time-reversal invariance. We benchmark our method using a system of two
spin-1/2 particles interacting through a finite-range potential with a strong
tensor component. We are able to extract phase shifts and mixing angles for all
angular momenta and energies, with precision greater than that of extant
methods. We discuss a wide range of applications from nuclear lattice
simulations to optical lattice experiments.Comment: 7 pp, 4 figs, 1 tabl
Recommended from our members
Striatal dopamine D1-type receptor availability: no difference from control but association with cortical thickness in methamphetamine users.
Chronic methamphetamine use poses potentially devastating consequences for directly affected individuals and for society. Lower dopamine D2-type receptor availability has been observed in striata of methamphetamine users as compared with controls, but an analogous comparison of D1-type receptors has been conducted only on post-mortem material, with no differences in methamphetamine users from controls in the caudate nucleus and putamen and higher D1-receptor density in the nucleus accumbens. Released from neurons when methamphetamine is self-administered, dopamine binds to both D1- and D2-type receptors in the striatum, with downstream effects on cortical activity. Thus, both receptor subtypes may contribute to methamphetamine-induced alterations in cortical morphology and behavior. In this study, 21 methamphetamine-dependent subjects and 23 healthy controls participated in positron emission tomography and structural magnetic resonance imaging for assessment of striatal D1- and D2-type receptor availability and cortical gray-matter thickness, respectively. Although D2-type receptor availability (BPnd) was lower in the methamphetamine group, as shown previously, the groups did not differ in D1-type BPnd. In the methamphetamine group, mean cortical gray-matter thickness was negatively associated with cumulative methamphetamine use and craving for the drug. Striatal D1-type but not D2-type BPnd was negatively associated with global mean cortical gray-matter thickness in the methamphetamine group, but no association was found between gray-matter thickness and BPnd for either dopamine receptor subtype in the control group. These results suggest a role of striatal D1-type receptors in cortical adaptation to chronic methamphetamine use
Time fractals and discrete scale invariance with trapped ions
We show that a one-dimensional chain of trapped ions can be engineered to
produce a quantum mechanical system with discrete scale invariance and
fractal-like time dependence. By discrete scale invariance we mean a system
that replicates itself under a rescaling of distance for some scale factor, and
a time fractal is a signal that is invariant under the rescaling of time. These
features are reminiscent of the Efimov effect, which has been predicted and
observed in bound states of three-body systems. We demonstrate that discrete
scale invariance in the trapped ion system can be controlled with two
independently tunable parameters. We also discuss the extension to n-body
states where the discrete scaling symmetry has an exotic heterogeneous
structure. The results we present can be realized using currently available
technologies developed for trapped ion quantum systems.Comment: 4 + 5 pages (main + supplemental materials), 2 + 3 figures (main +
supplemental materials), version to appear in Physical Review A Rapid
Communication
Business confidence in government regulators: cooperative goals and confirmation of face in China
Purpose – This study aims to examine the conditions that help businesses develop confidence in their government regulators. Businesses are dependent upon governments and subject to their regulations. This study proposes that businesses and governments that confirm each other’s social face have the relationship that helps businesses become confident in their government regulators. It also uses the theory of cooperation and competition to identify when they confirm social face.
Design/methodology/approach – Data were collected in Shanghai, China, from government bodies and business organizations from diverse industries. One hundred forty-six pairs of government officials and business managers provided us data for our analysis.
Findings – Structural equation analysis suggests that cooperative, but not competitive or independent, goals provide the foundation for mutual confirmation of social face that in turn results in business confidence that the government is competent, caring and regulates effectively.
Practical implications – These findings were interpreted as reaffirming the value of relationships for collaboration between business and government and the usefulness of the concepts of social face and goal interdependence for understanding how to develop high-quality business–government relationships in China.
Originality/value – This study directly investigates social face among Chinese people and explores its impact on inter-organizational government–business relationships. This study uses social face and goal interdependence to understand when business and regulators develop relationships that promote effective regulation
Pharmaceutical approaches for COVID-19: An update on current therapeutic opportunities
SARS-CoV-2, a newly discovered coronavirus, has been linked to the COVID-19 pandemic and is currently an important public health issue. Despite all the work done to date around the world, there is still no viable treatment for COVID-19. This study examined the most recent evidence on the efficacy and safety of several therapeutic options available including natural substances, synthetic drugs and vaccines in the treatment of COVID-19. Various natural compounds such as sarsapogenin, lycorine, biscoclaurine, vitamin B12, glycyrrhizic acid, riboflavin, resveratrol and kaempferol, various vaccines and drugs such as AZD1222, mRNA-1273, BNT162b2, Sputnik V, and remdesivir, lopinavir, favipiravir, darunavir, oseltamivir, and umifenovir, resp., have been discussed comprehensively. We attempted to provide exhaustive information regarding the various prospective therapeutic approaches available in order to assist researchers and physicians in treating COVID-19 patients
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