1,126 research outputs found
Impact Philanthropy to Improve Teaching Quality: Focus on High-Need Secondary Students
Offers models for improving teachers' skills, including through apprenticeships and in-school mentoring; for creating an environment for great teaching through better leadership and whole-school reform; and guidance for donors on the policy environment
Linear Scaling Calculations of Excitation Energies with Active-Space Particle-Particle Random Phase Approximation
We developed an efficient active-space particle-particle random phase
approximation (ppRPA) approach to calculate accurate charge-neutral excitation
energies of molecular systems. The active-space ppRPA approach constrains both
indexes in particle and hole pairs in the ppRPA matrix, which only selects
frontier orbitals with dominant contributions to low-lying excitation energies.
It employs the truncation in both orbital indexes in the particle-particle and
the hole-hole spaces. The resulting matrix, the eigenvalues of which are
excitation energies, has a dimension that is independent of the size of the
systems. The computational effort for the excitation energy calculation,
therefore, scales linearly with system size and is negligible compared with the
ground-state calculation of the (N-2)-electron system, where N is the electron
number of the molecule. With the active space consisting of 30 occupied and 30
virtual orbitals, the active-space ppRPA approach predicts excitation energies
of valence, charge-transfer, Rydberg, double and diradical excitations with the
mean absolute errors (MAEs) smaller than 0.03 eV compared with the full-space
ppRPA results. As a side product, we also applied the active-space ppRPA
approach in the renormalized singles (RS) T-matrix approach. Combining the
non-interacting pair approximation that approximates the contribution to the
self-energy outside the active space, the active-space
@PBE approach predicts accurate absolute and
relative core-level binding energies with the MAE around 1.58 eV and 0.3 eV,
respectively. The developed linear scaling calculation of excitation energies
is promising for applications to large and complex systems
Online Statistical Inference for Stochastic Optimization via Kiefer-Wolfowitz Methods
This paper investigates the problem of online statistical inference of model
parameters in stochastic optimization problems via the Kiefer-Wolfowitz
algorithm with random search directions. We first present the asymptotic
distribution for the Polyak-Ruppert-averaging type Kiefer-Wolfowitz (AKW)
estimators, whose asymptotic covariance matrices depend on the function-value
query complexity and the distribution of search directions. The distributional
result reflects the trade-off between statistical efficiency and function query
complexity. We further analyze the choices of random search directions to
minimize the asymptotic covariance matrix, and conclude that the optimal search
direction depends on the optimality criteria with respect to different summary
statistics of the Fisher information matrix. Based on the asymptotic
distribution result, we conduct online statistical inference by providing two
construction procedures of valid confidence intervals. We provide numerical
experiments verifying our theoretical results with the practical effectiveness
of the procedures
Precise tuning of polymeric fiber dimensions to enhance the mechanical properties of alginate hydrogel matrices
Hydrogels based on biopolymers, such as alginate, are commonly used as scaffolds in tissue engineering applications as they mimic the features of the native extracellular matrix (ECM). However, in their native state, they suffer from drawbacks including poor mechanical performance and a lack of biological functionalities. Herein, we have exploited a crystallization-driven self-assembly (CDSA) methodology to prepare well-defined one-dimensional micellar structures with controlled lengths to act as a mimic of fibrillar collagen in native ECM and improve the mechanical strength of alginate-based hydrogels. Poly(ε-caprolactone)-b-poly(methyl methacrylate)-b-poly(N, N-dimethyl acrylamide) triblock copolymers were self-assembled into 1D cylindrical micelles with precise lengths using CDSA epitaxial growth and subsequently combined with calcium alginate hydrogel networks to obtain nanocomposites. Rheological characterization determined that the inclusion of the cylindrical structures within the hydrogel network increased the strength of the hydrogel under shear. Furthermore, the strain at flow point of the alginate-based hydrogel was found to increase with nanoparticle content, reaching an improvement of 37% when loaded with 500 nm cylindrical micelles. Overall, this study has demonstrated that one-dimensional cylindrical nanoparticles with controlled lengths formed through CDSA are promising fibrillar collagen mimics to build ECM scaffold models, allowing exploration of the relationship between collagen fiber size and matrix mechanical properties
Pharmacokinetics of mequindox after intravenous and intramuscular administration to goat
Pharmacokinetics and bioavailability of mequindox were determined after single intravenous (i.v.) or intramuscular (i.m.) administrations of 7 mg/kg body weight (b.w.) to 10 healthy adult goats. Plasma mequindox concentrations were measured by high performance liquid chromatography. Pharmacokinetics were best described by a two-compartment open model and an one-compartment open model for i.v. and i.m. groups, respectively. The elimination half-life and volume of distribution after i.v. and i.m. administrations were statistically different (t1/2β, 1.8 to 1.5 h, P < 0.05 and Vd, 0.35 to 0.45 L·kg-1, P < 0.05, respectively). Mequindox was rapidly (t1/2a, 0.28 h) and almost completely absorbed (F, 99.8%) after i.m. administration. In conclusion, 2~3 times daily i.v. and i.m. administration of mequindox (7 mg/kg b.w.) in goats may be useful in treatment of infectious diseases caused by sensitive pathogens. The plasma disposition kinetics of mequindox in goats is reported for the first time.Key words: Mequindox, pharmacokinetics, high performance liquid chromatography (HPLC), goats
FedSoup: Improving Generalization and Personalization in Federated Learning via Selective Model Interpolation
Cross-silo federated learning (FL) enables the development of machine
learning models on datasets distributed across data centers such as hospitals
and clinical research laboratories. However, recent research has found that
current FL algorithms face a trade-off between local and global performance
when confronted with distribution shifts. Specifically, personalized FL methods
have a tendency to overfit to local data, leading to a sharp valley in the
local model and inhibiting its ability to generalize to out-of-distribution
data. In this paper, we propose a novel federated model soup method (i.e.,
selective interpolation of model parameters) to optimize the trade-off between
local and global performance. Specifically, during the federated training
phase, each client maintains its own global model pool by monitoring the
performance of the interpolated model between the local and global models. This
allows us to alleviate overfitting and seek flat minima, which can
significantly improve the model's generalization performance. We evaluate our
method on retinal and pathological image classification tasks, and our proposed
method achieves significant improvements for out-of-distribution
generalization. Our code is available at https://github.com/ubc-tea/FedSoup.Comment: Accepted by MICCAI202
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