Persistence of Cultural Norms in Online Communities: The Curious Case of WikiLove

Tremendous progress in information and communication technologies in the last two decades has enabled the phenomenon of Internet-based groups and collectives, generally referred to as online communities. Many online communities have developed distinct cultures of their own, with accompanying norms. A particular research puzzle is the persistence and stability of such norms in online communities, even in the face of often exponential growth rates in uninitiated new users. We propose a network-theoretic approach to explain this persistence. Our approach consists of modelling the online community as a network of interactions, and representing cultural norms as transmissible ideas (or ‘memes’) propagating through this network. We argue that persistence of a norm over time depends, amongst other things, on the structure of the network through which it propagates. Using previous results from Network Science and Epidemiology, we show that certain structures are better than others to ensure persistence: namely, structures which have scale-free degree distributions and assortative mixing. We illustrate this theory using the case of the community of contributors at Wikipedia, a collaboratively generated online encyclopaedia

Computational Simulation of the Docking of Prochlorothrix Hollandica Plastocyanin to Photosystem I: Modeling the Electron Transfer Complex

We have used several docking algorithms (GRAMM, FTDOCK, DOT, AUTODOCK) to examine protein-protein interactions between plastocyanin (Pc)/photosystem I (PSI) in the electron transfer reaction. Because of the large size and complexity of this system, it is faster and easier to use computer simulations than conduct x-ray crystallography or nuclear magnetic resonance experiments. The main criterion for complex selection was the distance between the copper ion of Pc and the P700 chlorophyll special pair. Additionally, the unique tyrosine residue (Tyr(12)) of the hydrophobic docking surface of Prochlorothrix hollandica Pc yields a specific interaction with the lumenal surface of PSI, thus providing the second constraint for the complex. The structure that corresponded best to our criteria was obtained by the GRAMM algorithm. In this structure, the solvent-exposed histidine that coordinates copper in Pc is at the van der Waals distance from the pair of stacked tryptophans that separate the chlorophylls from the solvent, yielding the shortest possible metal-to-metal distance. The unique tyrosine on the surface of the Prochlorothrix Pc hydrophobic patch also participates in a hydrogen bond with the conserved Asn(633) of the PSI PsaB polypeptide (numbering from the Synechococcus elongatus crystal structure). Free energy calculations for complex formation with wild-type Pc, as well as the hydrophobic patch Tyr(12)Gly and Pro(14)Leu Pc mutants, were carried out using a molecular mechanics Poisson-Boltzman, surface area approach (MM/PBSA). The results are in reasonable agreement with our experimental studies, suggesting that the obtained structure can serve as an adequate model for P. hollandica Pc-PSI complex that can be extended for the study of other cyanobacterial Pc/PSI reaction pairs

The Small Worlds of Wikipedia: Implications for Growth, Quality and Sustainability of Collaborative Knowledge Networks

This work is a longitudinal network analysis of the interaction networks of Wikipedia, a free, user-led collaborativelygenerated online encyclopedia. Making a case for representing Wikipedia as a knowledge network, and using the lens of contemporary graph theory, we attempt to unravel its knowledge creation process and growth dynamics over time. Typical small-world characteristics of short path-length and high clustering have important theoretical implications for knowledge networks. We show Wikipedia’s small-world nature to be increasing over time, while also uncovering power laws and assortative mixing. Investigating the process by which an apparently un-coordinated, diversely motivated swarm of assorted contributors, create and maintain remarkably high quality content, we find an association between Quality and Structural Holes. We find that a few key high degree, cluster spanning nodes - ‘hubs’ - hold the growing network together, and discuss implications for the networks’ growth and emergent quality

Influence of the viscoelastic media properties on torsional wave propagation in pipe

Device and technique of modeled experiment of influence of the viscoelastic media properties on the torsional waves in pipe by echo-pulse method were proposed. The attenuation characteristics of torsional wave amplitude echo-pulses multiple reflected from pipe ends were investigated under loading on various media.Предложены прибор и техника модельного эксперимента влияния свойств контактных вязкоупругих сред на распространение крутильных волн в трубе эхо-импульсным методом. Исследованы зависимости ослабления амплитуд эхо-импульсов крутильных волн, переотражённых от торцов трубы, при нагружении на различные среды.Работа выполнена в рамках проекта № 15-19-00051 Российского научного фонда

Laws of the oxidation of carbon isotopes in plasma processes under magnetic field

From law of quantum mechanics it follows that spin precession phase of unpaired electron in external magnetic field cannot be determined. It uncertainty necessary take into account in different physical and chemical processes. The expression of the rate constant of a chemical reaction based on the number of discrete spin states was obtained. The equations of chemical kinetics of plasma oxidation of carbon isotopes in the magnetic field were given

Automation of the Monitoring System for Surface Contamination with α-Active Radionuclides

The paper presents research on radiation control at nuclear enterprises working with [alpha]-active radionuclides. The focus of the research is on the registration of 239Pu radionuclides on hands surface. The experimental results show the possibility to create a turnstile for automatic monitoring the presence of α-active radionuclides on hands. Such a device can be used with a minimum helium consumption of 66 liters per hour in a measuring chamber with an open bottom of 5.4 liters

Photo Processes On Self-associated Cationic Porphyrins And Plastocyanin Complexes 1. Ligation Of Plastocyanin Tyrosine 83 Onto Metalloporphyrins And Electron-transfer Fluorescence Quenching

The spectroscopic properties of the self-associated complexes formed between the anionic surface docking site of spinach plastocyanin and the cationic metalloporphyrins, in which the tyrosine 83 (Y83) moiety is placed just below the docking site, tetrakis(N-methyl-4-pyridyl)porphyrin (Pd(II)TMPyP4+ and Zn(II)TMPyP4+), have been studied and reported herein. The fluorescence quenching phenomenon of the self-assembled complex of Zn(II)TMPyP4+/plastocyanin has also been discovered. The observed red-shifting of the Soret and Q-bands of the UV-visible spectra, ca. 9 nm for Pd(II)TMPyP4+/plastocyanin and ca. 6 nm for the Zn(II)TMPyP4+/ plastocyanin complexes, was explained in terms of exciton theory coupled with the Gouterman model. Thus, the hydroxyphenyl terminus of the Y83 residue of the self-associated plastocyanin/cationic porphyrin complexes was implicated in the charge-transfer ligation with the central metal atoms of these metalloporphyrins. Moreover, ground-state spectrometric-binding studies between Pd(II)TMPyP4+ and the Y83 mutant plastocyanin (Y83F-PC) system proved that Y83 moiety of plastocyanin played a critical role in the formation of such ion-pair complexes. Difference absorption spectra and the Job\u27s plots showed that the electrostatic attractions between the cationic porphyrins and the anionic patch of plastocyanin, bearing the nearby Y83 residue, led to the predominant formation of a self-associated 1:1 complex in the ground-state with significantly high binding constants (K = (8.0 +/- 1.1) x 10(5) M-1 and (2.7 +/- 0.8) x 10(6) M-1 for Pd(II)TMPyP4+ and zinc variant, respectively) in low ionic strength buffer, 1 mM KCl and 1 mM phosphate buffer (pH 7.4). Molecular modeling calculations supported the formation of a 1: 1 self-associated complex between the porphyrin and plastocyanin with an average distance of ca. 9 A between the centers of mass of the porphyrin and Y83 positioned just behind the anionic surface docking site on the protein surface. The photoexcited singlet state of Zn(II)-TMPyP4+ was quenched by the Y83 residue of the self-associated plastocyanin in a static mechanism as evidenced by steady-state and time-resolved fluorescence experiments. Even when all the porphyrin was complexed (more than 97%), significant residual fluorescence from the complex was observed such that the amplitude of quenching of the singlet state of uncomplexed species was enormously obscured

Registration of a Laser Beam Scattered from an Aerosol Located in the Probe Beam Aperture

An experimental setup has been developed that allows recording the flux of probing radiation scattered from dispersed particles in the 0° direction. To suppress the beam passing through the swarm of dispersed particles a reference beam was used. The reference beam was formed from the probe beam and aligned in the registration plane with the beam passing through the swarm of particles. The Michelson interferometer was tested in an experimental setup to determine the sizes of dust particles of heterogeneous systems. It was shown that by placing a heterogeneous system in one of the arms of the interferometer, it was possible to register the scattered radiation at the angle 0°. This facilitates calculation of the sizes of particles with the same accuracy over the entire size range. To verify the method the iron powder particles sized 50-63 [mu]m were used

Mapping the single-cell transcriptomic response of murine diabetic kidney disease to therapies

Diabetic kidney disease (DKD) occurs in ∼40% of patients with diabetes and causes kidney failure, cardiovascular disease, and premature death. We analyzed the response of a murine DKD model to five treatment regimens using single-cell RNA sequencing (scRNA-seq). Our atlas of ∼1 million cells revealed a heterogeneous response of all kidney cell types both to DKD and its treatment. Both monotherapy and combination therapies targeted differing cell types and induced distinct and non-overlapping transcriptional changes. The early effects of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on the S1 segment of the proximal tubule suggest that this drug class induces fasting mimicry and hypoxia responses. Diabetes downregulated the spliceosome regulator serine/arginine-rich splicing factor 7 (Srsf7) in proximal tubule that was specifically rescued by SGLT2i. In vitro proximal tubule knockdown of Srsf7 induced a pro-inflammatory phenotype, implicating alternative splicing as a driver of DKD and suggesting SGLT2i regulation of proximal tubule alternative splicing as a potential mechanism of action for this drug class

Nanoparticle Formation in a Mixture of Fe, C, O[2] in Low-temperature Plasma in a Magnetic Field

The paper presents the results of researching a magnetic field influence on the formation of dispersed particles from the mixture of Fe+C+N[2]+Ar+O[2] at the temperature of more than 4000K. To optimize the composition of the plasmaforming gas, thermodynamic modeling was performed. The research establishes that an external magnetic field has a significant effect on the formation of a dispersed phase in the mixture of carbon and iron vapor. For example, in a powder obtained without a magnetic field, X-ray diffraction shows up to 95% C. In a powder obtained in the magnetic field of 15 mT, C (up to 50%), Fe[3]O[4] (up to 45%), Fe[2]O[3] (up to 15%), and FeO (less than 5%) are recorded. The observed results are explained by the coagulation of nanoparticles in the magnetic field