There is a growing interest in quantitative analysis of large corpora among the international relations (IR) scholars, but many of them find it difficult to perform analysis consistently with ...existing theoretical frameworks using unsupervised machine learning models to further develop the field. To solve this problem, we created a set of techniques that utilize a semisupervised model that allows researchers to classify documents into predefined categories efficiently. We propose a dictionary making procedure to avoid inclusion of words that are likely to confuse the model and deteriorate the its classification performance classification accuracy using a new entropy-based diagnostic tool. In our experiments, we classify sentences of the United Nations General Assembly speeches into six predefined categories using the seeded Latent Dirichlet allocation and Newsmap, which were trained with a small “seed word dictionary” that we created following the procedure. The result shows that, while keyword dictionary can only classify 25% of sentences, Newsmap can classify over 60% of them accurately correctly and; its accuracy exceeds 70% when contextual information is taken into consideration by kernel smoothing of topic likelihoods. We argue that once seed word dictionaries are created by the international relations community, semisupervised models would become more useful than unsupervised models for theory-driven text analysis.
Purpose
The effects of the seat tube angle and crank arm length on metabolic responses, neuromuscular activation, and lower extremity joint kinematics were investigated during bicycling with a ...relatively lower seat height usually used for daily life.
Methods
Eleven young males performed bicycling on ergometer with various seat tube angles (60°, 65°, and 70°) and crank arm lengths (127, 140, 152, and 165 mm). Oxygen consumption was measured with electromyography of the knee extensor muscle, and hip, knee, and ankle joint angles. The seat height was set as the shorter than subject’s trochanter height, because this study simulates pedaling a bicycle in daily life on public roads.
Results
Significantly higher oxygen consumption was noted with a 70° of seat tube angle on comparison with a 65° of seat tube angle (
p
< 0.05). There were no significant effects of the crank arm length on oxygen consumption (
p
> 0.05).
Conclusions
From these results, the present study suggests that a shallower seat angle could help to decrease the physiological burden during bicycling with a relatively lower seat height.
In this work, we present a method for unsupervised domain adaptation. Many adversarial learning methods train domain classifier networks to distinguish the features as either a source or target and ...train a feature generator network to mimic the discriminator. Two problems exist with these methods. First, the domain classifier only tries to distinguish the features as a source or target and thus does not consider task-specific decision boundaries between classes. Therefore, a trained generator can generate ambiguous features near class boundaries. Second, these methods aim to completely match the feature distributions between different domains, which is difficult because of each domain's characteristics. To solve these problems, we introduce a new approach that attempts to align distributions of source and target by utilizing the task-specific decision boundaries. We propose to maximize the discrepancy between two classifiers' outputs to detect target samples that are far from the support of the source. A feature generator learns to generate target features near the support to minimize the discrepancy. Our method outperforms other methods on several datasets of image classification and semantic segmentation. The codes are available at https://github.com/mil-tokyo/MCD_DA
The present study investigated the effect of stretchable characteristics of elastic therapeutic tape and its elongation on surface electromyography (EMG) of knee extensor muscles during knee ...extension movements.
Nine healthy men performed knee extension movement with the application of normal elastic tape or highly stretchable tape and without the tapes (control). Tapes were applied on the anterior thigh to cross the knee joint with no elongation and elongation of 50 and 75% of the maximum stretchability. Surface EMG was recorded from the vastus lateralis (VL) muscle and proximal (RFp) and distal (RFd) sites of the rectus femoris muscle.
Under the no-elongation conditions, decreases in the surface EMG amplitude of the VL and RFd muscles were observed with normal tape during the isometric contraction phase and with highly stretchable tape during isometric and eccentric contraction phases, compared with the control (p < 0.05). There were no significant differences in surface EMG among the different elongation conditions in any muscles (p > 0.05).
These results suggest that the stretchable characteristics of tapes change the effect of elastic tape application on neuromuscular activation of the applied muscles and these effects are not dependent on the elongation of the tape.
The toe clearance strategy during leg swinging while walking is closely associated with the risk of tripping and/or falling and is influenced by aging and a fall history. However, it remains unclear ...how the toe clearance strategy is regulated by the neuromuscular system. The present study investigated the effect of aging and fall/tripping history in the older adults on the toe clearance strategy and neuromuscular regulation of the rectus femoris (RF) muscle, which plays an important role in leg swinging, during prolonged walking. Thirteen older adults (age: 71.3 ± 5.7 years) and nine young adults (age: 20.9 ± 0.8 years) men volunteered for the present study. The older adults were divided into those with (
= 6) and without (
= 7) a fall/tripping history. Subjects walked on a treadmill at their preferred gait speed for 20 min, and lower extremity kinematics and multi-channel surface electromyography along the RF muscle were recorded. Variability of the minimum toe clearance (MTC) and central locus activation (CLA) of the RF muscle in older adults was significantly greater than in the young adults (
< 0.05). MTC significantly decreased with time in the older adults (
< 0.05), but not in the young adults (
> 0.05). There were no significant correlations between any parameters of MTC and CLA in the older adults or young adults (
> 0.05). MTC and variability of CLA significantly decreased with time in the older adults without a fall/tripping history (
< 0.05), but not in the older adults with such a history (
> 0.05). These results suggest that aging and a fall/tripping history in the older adults alter the toe clearance strategy and regional neural regulation of the RF muscle during prolonged walking.
Quercetin is a polyphenolic flavonoid that has reported to block the binding of adenosine to A1 receptors at central nervous system and increase calcium release from the sarcoplasmic reticulum at ...skeletal muscle. The aim of the present study was to investigate the acute effect of quercetin ingestion on motor unit activation and muscle contractile properties. High-density surface electromyography during submaximal contractions and electrically elicited contraction torque in knee extensor muscles were measured before (PRE) and 60 min after (POST) quercetin glycosides or placebo ingestions in 13 young males. Individual motor units of the vastus lateralis muscle were identified from high-density surface electromyography by the Convolution Kernel Compensation technique. Firing rates of motor units recruited at 30–50% of the maximal voluntary contraction torque (MVC) were increased from PRE to POST only with quercetin (9.0 ± 2.3 to 10.5 ± 2.0 pps,
p
= 0.034). Twitch torque during doublet stimulation was decreased from PRE to POST with placebo (77.1 ± 17.1 to 73.9 ± 17.6 Nm,
p
= 0.005), but not with quercetin (
p
> 0.05). For motor units recruited at < 10% of MVC, normalized firing rate were decreased with quercetin (1.52 ± 0.33 to 1.58 ± 0.35%MVC/pps,
p
= 0.002) but increased with placebo (1.61 ± 0.32 to 1.57 ± 0.31%MVC/pps,
p
= 0.005). These results suggest that ingested quercetin has the functional roles to: mitigate reduction in the muscle contractile properties, enhance activations of relatively higher recruitment threshold motor units, and inhibit activation of relatively lower recruitment threshold motor units.
Abstract Few concepts figure more prominently in the study of international politics than threat. Yet scholars do not agree on how to identify and measure threats or systematically incorporate ...leaders’ perceptions of threat into their models. In this research note, we introduce a text-based strategy and method for identifying and measuring elite assessments of international threat from publicly available sources. Using semi-supervised machine learning models, we show how text sourced from newspaper articles can be parsed to discern arguments that distinguish threatening from non-threatening states, and to measure and track variation in the intensity of foreign threats over time. To demonstrate proof of concept, we use news summaries from The New York Times from 1861 to 2017 to create a geopolitical threat index (GTI) for the United States. We show that the index successfully matches periods in US history that historians identify as high and low threat and correctly identifies countries that have posed a threat to US security at different points in its history. We compare and contrast GTI with traditional indicators of international threat that rely on measures of material capability and interstate behavior.
Topic models have been widely used by researchers across disciplines to automatically analyze large textual data. However, they often fail to automate content analysis, because the algorithms cannot ...accurately classify individual sentences into pre-defined topics. Aiming to make topic classification more theoretically grounded and content analysis in general more topic-specific, we have developed Seeded Sequential Latent Dirichlet allocation (LDA), extending the existing LDA algorithm, and implementing it in a widely accessible open-source package. Taking a large corpus of speeches delivered by delegates at the United Nations General Assembly as an example, we explain how our algorithm differs from the original algorithm; why it can classify sentences more accurately; how it accepts pre-defined topics in deductive or semi-deductive analysis; how such ex-ante topic mapping differs from ex-post topic mapping; how it enables topic-specific framing analysis in applied research. We also offer practical guidance on how to determine the optimal number of topics and select seed words for the algorithm.
This study investigated the effect of home-based shallow and deep squat trainings on knee extension peak torque, muscle thickness, one-repetition maximum (1RM) leg press, and physical function in ...older individuals. Sixteen participants were randomly assigned to the shallow squat group (SS group; age, 71.0 ± 4.0 years) or deep squat group (DS group, age; 68.6 ± 3.6 years). Chairs of 40-cm height and chairs with a cushion of 20-cm height (60-cm in total) were used as the depth targets for squats, with participants instructed to sink until their hip touched the chair and cushion. Participants performed four sets of squats per day (35 repetitions per set), three days per week, for 12 weeks at their home. Knee extension peak torque, muscle thickness of quadriceps femoris (e.g., vastus lateralis, rectus femoris, and vastus intermedius), and physical function were measured at weeks 0 (baseline), 4, 8, and 12. Maximal isometric knee extension peak torque, muscle thickness, and walking speed did not change significantly over the 12-week training period in either group (P > 0.05). However, compared with the baseline, there was significant improvement in the results of 30-s sit-to-stand repetition tests after weeks 8 and 12 in both groups (P < 0.05). Additionally, 1RM leg press results were significantly improved after weeks 4 and 12 in the DS group, and weeks 4, 8, and 12 in the SS group (P < 0.05). Results indicate that home-based weight-bearing squat training improves lower limb function in older adults, as well as performance in physical functional tests related to activities of daily living. Moreover, such training benefits older adults regardless of whether squats are shallow or deep.
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