Self-organization on social media: endo-exo bursts and baseline fluctuations

A salient dynamic property of social media is bursting behavior. In this paper, we study bursting behavior in terms of the temporal relation between a preceding baseline fluctuation and the successive burst response using a frequency time series of 3,000 keywords on Twitter. We found that there is a fluctuation threshold up to which the burst size increases as the fluctuation increases and that above the threshold, there appears a variety of burst sizes. We call this threshold the critical threshold. Investigating this threshold in relation to endogenous bursts and exogenous bursts based on peak ratio and burst size reveals that the bursts below this threshold are endogenously caused and above this threshold, exogenous bursts emerge. Analysis of the 3,000 keywords shows that all the nouns have both endogenous and exogenous origins of bursts and that each keyword has a critical threshold in the baseline fluctuation value to distinguish between the two. Having a threshold for an input value for activating the system implies that Twitter is an excitable medium. These findings are useful for characterizing how excitable a keyword is on Twitter and could be used, for example, to predict the response to particular information on social media.Comment: Presented at WebAL-1: Workshop on Artificial Life and the Web 2014 (arXiv:1406.2507

Optical Imaging of a Single Molecule with Subnanometer Resolution by Photoinduced Force Microscopy

Yamamoto T., Yamane H., Yokoshi N., et al. Optical Imaging of a Single Molecule with Subnanometer Resolution by Photoinduced Force Microscopy. ACS Nano 18, 1724 (2024); https://doi.org/10.1021/acsnano.3c10924.Visualizing the optical response of individual molecules is a long-standing goal in catalysis, molecular nanotechnology, and biotechnology. The molecular response is dominated not only by the electronic states in their isolated environment but also by neighboring molecules and the substrate. Information about the transfer of energy and charge in real environments is essential for the design of the desired molecular functions. However, visualizing these factors with spatial resolution beyond the molecular scale has been challenging. Here, by combining photoinduced force microscopy and Kelvin probe force microscopy, we have mapped the photoinduced force in a pentacene bilayer with a spatial resolution of 0.6 nm and observed its “multipole excitation”. We identified the excitation as the result of energy and charge transfer between the molecules and to the Ag substrate. These findings can be achieved only by combining microscopy techniques to simultaneously visualize the optical response of the molecules and the charge transfer between the neighboring environments. Our approach and findings provide insights into designing molecular functions by considering the optical response at each step of layering molecules

Attempt to Generate a Strong and Uniform Magnetic Field by Face-to-face HTS Bulk Elements in a Magnet System

AbstractA unique experimental attempt aiming to obtain a uniform magnetic field space as required for NMR has been carried out with use of HTS bulk magnets. The magnetic poles were activated as 1.8 T (North) and 1.4 T (South) at 30K by applyinga pulsed magnetic field up to 7 T, and positioned face-to-face with gaps less than 70mm. The uniformity of the magnetic field required for detecting the NMR signals isless than 1,500ppm at more than 0.3 T in the cross sectional plane of 2 x 2 mm2. After thepreliminary trials whichrevealed auniformity of 5,421ppm at 0.44 T in a70mm gap, we attached a ferromagnetic iron plate to a magnetic pole surface to change the magnetic field distribution to be concave. The best uniformity of 358ppm at 1.11 T was obtained at 9mm distance from the iron plate surface in a gap of 30mm. It is stated that the concave magnetic field distribution was compensated by the counter conical-shape field, resulting in the uniform field plane

Measurement of fatigue in knee flexor and extensor muscles.

In order to examine fatigue of the knee flexor and extensor muscles and to investigate the characteristics of muscular fatigue in different sports, a Cybex machine was used to measure muscle fatigue and recovery during isokinetic knee flexion and extension. Eighteen baseball players, 12 soccer players and 13 marathon runners were studied. Each subject was tested in the sitting position and made to perform 50 consecutive right knee bends and stretches at maximum strength. This was done 3 times with an interval of 10 min between each series. The peak torque to body weight ratio and the fatigue rate were determined in each case. In all subjects, the peak torque to body weight ratio was higher for extensors than flexors. Over the 3 trials, the fatigue rate of extensors showed little change, while that of flexors had a tendency to increase. In each subject, knee extensors showed a high fatigue rate but a quick recovery, while knee flexors showed a low fatigue rate but a slow recovery. As the marathon runners had the smallest fatigue rates for both flexors and extensors, we concluded that marathon runners had more stamina than baseball players and soccer players.</p

High-capacitance supercapacitors using nitrogen-decorated porous carbon derived from novolac resin containing peptide linkage

We fabricated nitrogen-decorated porous carbon exhibiting high capacitance per unit volume and unit weight via chemical activation of novolac resin containing peptide linkage. The porosity and the amount of nitrogen atoms were controlled by changing the molecular weight of novolac resin, the added amount of potassium hydroxide, or both. After chemical activation, positively charged nitrogen atoms (i.e., pyridine/pyrrole) at 400.3 eV in photoemission spectra contributed to both a shift in the point of zero charge toward negative potential and the generation of pseudocapacitance. Suitably developed pores and the positively charged nitrogen atoms make nitrogen-decorated novolac resin-derived porous carbon a promising material for electrodes in high-performance supercapacitors.ArticleELECTROCHIMICA ACTA. 55(20):5624-5628 (2010)journal articl