Dislocation strain as the mechanism of phonon scattering at grain boundaries

Thermal conductivities of polycrystalline thermoelectric materials are satisfactorily calculated by replacing the commonly used Casimir model (freqeuncy-independent) with grain boundary dislocation strain model (frequency-dependent) of Klemens. It is demonstrated that the grain boundaries are better described as a collection of dislocations rather than perfectly scattering interfaces

Multi-modal curriculum learning for semi-supervised image classification

Semi-supervised image classification aims to classify a large quantity of unlabeled images by typically harnessing scarce labeled images. Existing semi-supervised methods often suffer from inadequate classification accuracy when encountering difficult yet critical images, such as outliers, because they treat all unlabeled images equally and conduct classifications in an imperfectly ordered sequence. In this paper, we employ the curriculum learning methodology by investigating the difficulty of classifying every unlabeled image. The reliability and the discriminability of these unlabeled images are particularly investigated for evaluating their difficulty. As a result, an optimized image sequence is generated during the iterative propagations, and the unlabeled images are logically classified from simple to difficult. Furthermore, since images are usually characterized by multiple visual feature descriptors, we associate each kind of features with a teacher, and design a multi-modal curriculum learning (MMCL) strategy to integrate the information from different feature modalities. In each propagation, each teacher analyzes the difficulties of the currently unlabeled images from its own modality viewpoint. A consensus is subsequently reached among all the teachers, determining the currently simplest images (i.e., a curriculum), which are to be reliably classified by the multi-modal learner. This well-organized propagation process leveraging multiple teachers and one learner enables our MMCL to outperform five state-of-the-art methods on eight popular image data sets

Nucleotide Sequences within the U5 Region of the Viral RNA Genome Are the Major Determinants for an Human Immunodeficiency Virus Type 1 to Maintain a Primer Binding Site Complementary to tRNAHis

AbstractThe initiation of reverse transcription of the human immunodeficiency virus type 1 (HIV-1) genome requires cellular tRNALys,3as a primer and occurs at a site in the viral RNA genome, designated as the primer binding site (PBS), which is complementary to the 3′-terminal 18 nucleotides of tRNALys,3. We previously described an HIV-1 virus [designated as HXB2(His-AC)], which contained a sequence within the U5 region complementary to the anticodon region of tRNAHisin addition to a PBS complementary to the 3′-terminal 18 nucleotides of the tRNAHis. That virus maintained a PBS complementary to tRNAHisafter extendedin vitroculture (Wakefieldet al., J. Virol.70, 966–975, 1996). In the present study, we report that subcloning a 200-base-pair DNA fragment encompassing the U5 and PBS regions from an integrated provirus of HXB2(His-AC) back into the wild-type genome (pHXB2) resulted in an infectious virus, designated as HXB2(His-AC-gac), which again stably maintained a PBS complementary to tRNAHis. DNA sequence analysis of the 200-base-pair region revealed only three nucleotide changes from HXB2(His-AC): a T-to-G change at nucleotide 174, a G-to-A change at nucleotide 181, and a T-to-C change at nucleotide 200. The new mutant virus replicated in CD4+Sup T1 cells similarly to the wild-type virus. Comparison of the nucleotide sequence of nucleocapsid gene of the wild-type and HXB2 (His-AC-gac) virus revealed no differences. Although we found numerous mutations in the reverse transcriptase gene in proviral clones derived from HXB2 (His-AC-gac), no common mutations were found among the 13 clones examined. Comparison of the virion-associated tRNAs of HXB2(His-AC-gac) with those of the wild type revealed that both viruses incorporated a similar subset of cellular tRNAs, with tRNALys,3being the predominant tRNA found within virions. There was no selective enrichment for tRNAHiswithin virions of HXB2(His-AC-gac) virus which selectively use tRNAHisto initiate reverse transcription. The results of these studies suggest that the U5 and PBS regions in the viral RNA genome are important determinants for HXB2(His-AC) viruses in the selective use of tRNAHisto initiate reverse transcription

Patterns of weight change in a commercial weight loss program

Objectives: In this study, we examined compliance and progress factors associated with weight loss and maintenance, individual patterns of weight trends following weight loss, and impact of early weight loss on longer-term weight change. Methods: We conducted secondary analysis of pre-post data. Participants were 8769 persons (mean age = 47.63 ± 13.78 years; 77.74% women; mean weight = 97.20 ± 22.82 kilograms; BMI = 34.09 ± 6.84) in a commercial weight management program. We carried out multiple regression analyses on weight change and percentage, and used ANOVA and the Pearson chi-square test to examine participant characteristics, weight change patterns, and early weight loss success. Results: Participants were active in the program for 222 ± 158 days, completed 15 ± 13 appointments, achieving -8.53 ± 7.87 kilograms lost (-8.61% ± 7.64%). Greater weight loss was associated with appointment frequency (β = -0.46) and total spending (β = -2.89) (p \u3c .01). We identified 5 weight change patterns (F = 37.56, p \u3c .001) (total weight loss for each group was: Stable = -10.4% [N=2036]; Minimal Regain = -10.5% [N=3766]; Modest Regain = -8.8% [N=1476]; Large Regain = -7.3% [N=753]; No Loss/Gain = +3.7% [N=737]; all p \u3c .05). Over 5000 participants achieved early weight loss (losing \u3e 5%) within the first 2 months resulting in significantly greater final weight loss (-8.43% to -14.56% vs -1.18% to -3.15%). Conclusions: We identified several weight patterns; increased health coaching attendance was associated with greater weight loss

Multi-Task Imitation Learning for Linear Dynamical Systems

We study representation learning for efficient imitation learning over linear systems. In particular, we consider a setting where learning is split into two phases: (a) a pre-training step where a shared $k$-dimensional representation is learned from $H$ source policies, and (b) a target policy fine-tuning step where the learned representation is used to parameterize the policy class. We find that the imitation gap over trajectories generated by the learned target policy is bounded by $\tilde{O}\left( \frac{k n_x}{HN_{\mathrm{shared}}} + \frac{k n_u}{N_{\mathrm{target}}}\right)$, where $n_x > k$ is the state dimension, $n_u$ is the input dimension, $N_{\mathrm{shared}}$ denotes the total amount of data collected for each policy during representation learning, and $N_{\mathrm{target}}$ is the amount of target task data. This result formalizes the intuition that aggregating data across related tasks to learn a representation can significantly improve the sample efficiency of learning a target task. The trends suggested by this bound are corroborated in simulation.Comment: Appeared in L4DC 2023. V3: corrected typo in assumption

High thermoelectric performance in (Bi_(0.25)Sb_(0.75)_2 Te_3 due to band convergence and improved by carrier concentration control

Bi_2Te_3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by optimizing the converging valence bands of Bi_2Te_3 and Sb_2Te_3 in the (Bi_(1−x)Sb_x)_2Te_3 system when x = 0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi0.25Sb0.75)2Te3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT = 1.05 (at 300 K) without nanostructuring

Psychometric properties of the 26-item eating attitudes test (EAT-26): an application of rasch analysis

Background: The 26-item Eating Attitudes Test (EAT-26) is a commonly used tool to assess eating disorder risk. The purpose of this study was to examine the psychometric properties of the EAT-26 with a combined sample: (1) of adults with overweight and obesity enrolled in a behavioral weight loss program and (2) general adult sample (n = 469; age = 36.17 ± 17.83 years; female = 72.5%; white = 66.3%; obese BMI category = 58%). Methods: Rasch modeling was used to assess model-data fit, create an item-person map to evaluate relative distribution items and persons, item difficulty, and person’s eating disorder (ED) risk level of the EAT-26. Differential item functioning (DIF) and rating scale functioning of the EAT-26 were also evaluated using Rasch analysis. Results: A total of 7 misfit items were removed from the final analysis due to unacceptable Infit and Outfit mean square residual values. The item-person map showed that the items were biased toward participants with moderate to high levels of ED risk and did not cover those who had low risk for having an ED (\u3c − 1 logits). The DIF analyses results showed that none of the items functioned differently across sex, but 5 items were flagged based on obesity status. The six-category Likert-type rating scale did not function well indicating a different response format may be needed. Conclusion: Several concerns were identified with the psychometric evaluation of the EAT-26 that may question its utility in assessing ED risk in individuals at low risk for ED, within samples of people who have overweight and obesity seeking weight loss treatment. Plain English Summary: The 26-item Eating Attitudes Test is a self-rated measure of eating attitudes that measures symptoms and concerns of eating disorders (ED). Very little is known about how this instrument performs differently based on individual factors like body mass index (BMI) and sex (male/female). We used an advanced measurement theory (i.e., Rasch analysis) to determine if the EAT-26 is an adequate measure to detect disordered eating in men and women of different BMIs. Results indicated that the EAT-26 was biased toward participants with moderate to high levels of disordered eating risk and did not adequately detect individuals at low risk for disordered eating. The EAT-26 did not function differently based on sex (male/female). However, five questions did function differently based on obesity status (those without obesity/ those with obesity). Finally, we observed the six-category rating scale did not function appropriately and that a new response format may be warranted. In sum, there were several issues (e.g., poor rating scale and different item functioning) with the EAT-26 and future work should develop screening tools that detect low risk of disordered eating as well as function well in adults with overweight and obesity

Electron-Spin Excitation Coupling in an Electron Doped Copper Oxide Superconductor

High-temperature (high-Tc) superconductivity in the copper oxides arises from electron or hole doping of their antiferromagnetic (AF) insulating parent compounds. The evolution of the AF phase with doping and its spatial coexistence with superconductivity are governed by the nature of charge and spin correlations and provide clues to the mechanism of high-Tc superconductivity. Here we use a combined neutron scattering and scanning tunneling spectroscopy (STS) to study the Tc evolution of electron-doped superconducting Pr0.88LaCe0.12CuO4-delta obtained through the oxygen annealing process. We find that spin excitations detected by neutron scattering have two distinct modes that evolve with Tc in a remarkably similar fashion to the electron tunneling modes in STS. These results demonstrate that antiferromagnetism and superconductivity compete locally and coexist spatially on nanometer length scales, and the dominant electron-boson coupling at low energies originates from the electron-spin excitations.Comment: 30 pages, 12 figures, supplementary information include

Dislocation strain as the mechanism of phonon scattering at grain boundaries

Thermal conductivities of polycrystalline thermoelectric materials are satisfactorily calculated by replacing the commonly used Casimir model (freqeuncy-independent) with grain boundary dislocation strain model (frequency-dependent) of Klemens. It is demonstrated that the grain boundaries are better described as a collection of dislocations rather than perfectly scattering interfaces

Brief Report: Estimating Differences and Ratios in Median Times to Event

Time differences and time ratios are often more interpretable estimates of effect than hazard ratios for time-to-event data, especially for common outcomes. We developed a SAS macro for estimating time differences and time ratios between baseline-fixed binary exposure groups based on inverse probability weighted Kaplan-Meier curves. The macro uses pooled logistic regression to calculate inverse probability of censoring and exposure weights, draws Kaplan-Meier curves based on the weighted data, and estimates the time difference and time ratio at a user-defined survival proportion. The macro also calculates the risk difference and risk ratio at a user-specified time. Confidence intervals are constructed by bootstrap. We provide an example assessing the effect of exclusive breastfeeding during diarrhea on the incidence of subsequent diarrhea in children followed from birth to 3 years in Vellore, India. The SAS macro provided here should facilitate the wider reporting of time differences and time ratios