Brownian non-Gaussian polymer diffusion and queing theory in the mean-field limit

We link the Brownian non-Gaussian diffusion of a polymer center of mass to a microscopic cause: the polymerization/depolymerization phenomenon occurring when the polymer is in contact with a monomer chemostat. The anomalous behavior is triggered by the polymer critical point, separating the dilute and the dense phase in the grand canonical ensemble. In the mean-field limit we establish contact with queuing theory and show that the kurtosis of the polymer center of mass diverges alike a response function when the system becomes critical, a result which holds for general polymer dynamics (Zimm, Rouse, reptation). Both the equilibrium and nonequilibrium behaviors are solved exactly as a reference study for novel stochastic modeling and experimental setup.

Energy Inflow into the Magnetosphere and Its Distribution During Magnetic Storm

The energy inflow from the solar wind into the magnetosphere and its dissipation in the circular current and auroral ionosphere during maximums of magnetic storm intensity are considered. All magnetic storms with Dst intensities from –18 nT to –422 nT for the period from 1996 to 2014 were divided into groups. For each group, the mean contribution of energy from the solar wind to the magnetosphere and subsequent characteristics of the energy dissipation in the auroral ionosphere and circular current were determined by the superposed epoch analysis method. The nonlinearity of the dependence of the intensity of magnetic storms on the energy coming from the solar wind into the magnetosphere was revealed. Anomalous behavior of magnetic storms with intensity |Dst| > 200 nT was detected. A discussion of the results is given.

Residual Magnetic Moment Influences the Features of Fe3s XPS Spectrum: A Case Study

Background: Fe 3sXPS spectrumexhibits doublet peak instead of predicted singlet peak based on spin-orbit coupling theory. This anomalous behavior is considered to be magnetic origin. However, the effect of residual magnetic moment to the features of Fe3s doublet peakis not understood fully. Objective: This study aims to verify the effect of residual magnetic moment on the spectral features of Fe3s XPS spectrum of magnetic material. Method: As a case study, we have carried out a high temperature XPS study of the Fe 3s spectrum of magnetic domain aligned (MDA) sample with composition composed of SrFe10.8Al1.2O19. In addition, the XPS data have been compared with the data acquired at different temperatures of magnetic domain non-aligned (MDNA) sample. Results: The results show that the majority peak intensity and minority peak width of Fe 3s spectrum of MDA are smaller than those of the MDNA sample, and they increase systematically with increasing temperature. However, it is noted that the features of Fe3s spectrum of both MDA and MDNA samples are completely overlapped near and above the Curie temperature, Tc ~ 670K. Conclusion: The analysis of XPS data suggests that the residual magnetic moment influences the spectral features of Fe3s spectrum. These results provide evidences that it is important to consider the contribution of residual magnetic moment while deriving information from Fe 3s XPS spectrum of MDA sample.

Anomalous behavior induced by water insertion in Molybdenum disulfide nanoflowers

The coexistence of negative photoconductivity and metallic-like behavior in conventional semiconductors is very uncommon. In this work, we report the existence of such unconventional physical properties in Molybdenum disulfide nanoflowers (MoS2-NF). This is achieved by making the surface of MoS2 hygroscopic by alcohol treatment and creating a transport channel that favors protonic over electronic conduction. On cooling the MoS2-NF in a heat sink, the excess water that condenses on the surface forms a proton (H3O+) wire which exhibits pinched hysteresis characteristics. The conductivity of MoS2 increased by two orders of magnitude in the proton-dominated conduction regime with an exceptionally high positive temperature coefficient of 1.3×104 Ω/K. Interestingly, MoS2-NF also exhibits strong negative photoresponse (NPC) at room temperature when illuminated with UV and infra-red radiation. This interesting behavior observed in MoS2 NF can be useful for energy harvesting applications and the realization of fast thermal memories and optical switches.

Liquid-Liquid Phase Transition in Supercooled H2O and D2O: A Path-Integral Computer Simulation Study

We perform path-integral molecular dynamics (PIMD) and classical MD simulations of H2O and D2O using the q-TIP4P/F water model over a wide range of temperatures and pressures. The density ρ(T), isothermal compressibility κT(T), and self-diffusion coefficients D(T) of H2O and D2O are in excellent agreement with available experimental data; the isobaric heat capacity CP(T) obtained from PIMD and MD simulations agree qualitatively well with the experiments. Some of these thermodynamic properties exhibit anomalous maxima upon isobaric cooling, consistent with recent experiments and with the possibility that H2O and D2O exhibit a liquid-liquid critical point (LLCP) at low temperatures and positive pressures. The data from PIMD/MD for H2O and D2O can be fitted remarkably well using the Two-State-Equation-of-State (TSEOS). Using the TSEOS, we estimate that the LLCP for q-TIP4P/F H2O, from PIMD simulations, is located at Pc = 167±9 MPa, Tc = 159±6 K, and ρc = 1.02±0.01 g/cm3. Isotope substitution effects are important; the LLCP location in q-TIP4P/F D2O is estimated to be Pc = 176 ± 4 MPa, Tc = 177 ± 2 K, and ρc = 1.13±0.01 g/cm3. Interestingly, for the water model studied, differences in the LLCP location from PIMD and MD simulations suggest that nuclear quantum effects (i.e., atoms delocalization) play an important role in the thermodynamics of water around the LLCP (from the MD simulations of q-TIP4P/F water, Pc = 203 ± 4 MPa, Tc = 175 ± 2 K, and ρc = 1.03 ± 0.01 g/cm3). Overall, our results strongly support the LLPT scenario to explain water anomalous behavior, independently of the fundamental differences between classical MD and PIMD techniques. The reported values of Tc for D2O and, particularly, H2O suggest that improved water models are needed for the study of supercooled water.

The low temperature heat capacity of Li2Mo0.05W0.95O4

The heat capacity of a lithium tungstate single crystal doped by 5% molybdenum Li2Mo0.05W0.95O4 in the range of 78.5–302.8 K was measured by the adiabatic method. No anomalous behavior of heat capacity was found. The heat capacity function was obtained in the range of 0–303 K by extrapolating to zero temperature and fitting experimental points. Thermodynamic functions of entropy, enthalpy increment and Gibbs free energy at 298.15 K were calculated using the obtained data.

Application of Benford’s Law on Cryptocurrencies

Blockchain-based currencies or cryptocurrencies have become a global phenomenon known to most people as a disruptive technology, and a new investment vehicle. However, due to their decentralized nature, regulating these markets has presented regulators with difficulties in finding a balance between nurturing innovation, and protecting consumers. The growing concerns about illicit activity have forced regulators to seek new ways of detecting, analyzing, and ultimately policing public blockchain transactions. Extensive research on machine learning, and transaction graph analysis algorithms has been done to track suspicious behaviour. However, having a macro view of a public ledger is equally important before pursuing a more fine-grained analysis. Benford’s law, the law of first digit, has been extensively used as a tool to discover accountant frauds (many other use cases exist). The basic motivation that drove our research presented in this paper was to test he applicability of the well established method to a new domain, in this case the identification of anomalous behavior using Benford’s law conformity test to the cryptocurrency domain. The research focused on transaction values in all major cryptocurrencies. A suitable time-period was identified that was long enough to sport sufficiently large number of observations for Benford’s law conformity tests and was also situated long enough in the past so that the anomalies were identified and well documented. The results show that most of the cryptocurrencies that did not conform to Benford’s law had well documented anomalous incidents, the first digits of aggregated transaction values of all well known cryptocurrency projects were conforming to Benford’s law. Thus the proposed method is applicable to the new domain.