mgm: Estimating Time-Varying Mixed Graphical Models in High-Dimensional Data

We present the R-package mgm for the estimation of k-order Mixed Graphical Models (MGMs) and mixed Vector Autoregressive (mVAR) models in high-dimensional data. These are a useful extensions of graphical models for only one variable type, since data sets consisting of mixed types of variables (continuous, count, categorical) are ubiquitous. In addition, we allow to relax the stationarity assumption of both models by introducing time-varying versions MGMs and mVAR models based on a kernel weighting approach. Time-varying models offer a rich description of temporally evolving systems and allow to identify external influences on the model structure such as the impact of interventions. We provide the background of all implemented methods and provide fully reproducible examples that illustrate how to use the package

Shot noise and photon-induced correlations in 500 GHz SIS detectors

Photon-induced current correlations in SIS detectors can result in an output noise that is greater or less than shot noise. Evidence of these correlations had been observed for 100 GHz rf by accurate noise measurements as reported in our previous work. We now present a detailed analysis of these current correlations for frequencies between 100 and 500 GHz. We also report new measurements of photon-induced noise in a 490 GHz SIS mixer, and discuss the Gaussian beam techniques used to eliminate the thermal background radiation. For small 490 GHz rf power, the output noise is equal to shot noise. The results of the 100 and 490 GHz photon noise measurement are summarized in context to shot noise and the effect of the current correlations predicted by the theoretical model

On Morals, Markets, and Climate Change: Exploring Pope Francis’ Challenge

The relation between Culture and Business has caught researchers’ attention long ago; itis not hard to find studies relating to these topics. According to Hofstede et al. (2010, p.18), Hampden-Turner and Trompenaars (2012, p. 8), and Erez and Gati (2004, p. 5),culture can be defined in many levels, for example, organizational culture, and national culture. The field of Business also contains several disciplines, for example, International Business Management, Project Management, and Project Governance. However, not somany studies can be found studying the relation between National Culture and Project Governance; therefore, this study is focused on this relation.This study is designed following a qualitative approach in order to clarify the relation between National Culture and Project Governance Principles. Case studies are used targeting the IT industry of three countries, Spain, Sweden, and Taiwan. These cases also contain the classical theory of cultural dimensions from Hofstede. Hofstede’s dimensionsare Power Distance (PDI), Individualism vs. Collectivism (IDV), Uncertainty Avoidance(UAI), Masculinity vs. Femininity (MAS), Long-term Orientation (LTO), and Indulgencevs. Restraint (IDU). They are applied in this study for distinguishing the differences between countries. This study is also based on the definition of Project GovernancePrinciples from Garland (2009), Klakegg (2008), and Müller et al. (2013). ProjectGovernance Principles are split into two categories as well, hard/ structural principles andsoft/ behaviour principles.In order to clarify the link between National Culture and Project Governance Principles,this thesis’ authors interviewed 19 people, including 10 project managers and 9 experts.All of them have a long experience dealing with Project Management in the three selected countries. Their answers are based on the knowledge and experience of Project Management and Project Governance, as well as their opinions about their own national culture. After analysing the interviews, the authors consider that differences between these three countries in Project Governance and Project Governance Principles do exist. On the other hand, there are also some similar parts, for example, the influence ofcustomers’ orientation and preference. Moreover, respondents, Project Managers and Experts, all mentioned it is also necessary to be aware of the globalized environment, inother words, there is no influence of a single national culture in one country anymore.However, they all admit the importance of their own national culture as well. All these findings from this study encourage further and deeper study in the future

A Tutorial on Estimating Time-Varying Vector Autoregressive Models

Time series of individual subjects have become a common data type in psychological research. These data allow one to estimate models of within-subject dynamics, and thereby avoid the notorious problem of making within-subjects inferences from between-subjects data, and naturally address heterogeneity between subjects. A popular model for these data is the Vector Autoregressive (VAR) model, in which each variable is predicted as a linear function of all variables at previous time points. A key assumption of this model is that its parameters are constant (or stationary) across time. However, in many areas of psychological research time-varying parameters are plausible or even the subject of study. In this tutorial paper, we introduce methods to estimate time-varying VAR models based on splines and kernel-smoothing with/without regularization. We use simulations to evaluate the relative performance of all methods in scenarios typical in applied research, and discuss their strengths and weaknesses. Finally, we provide a step-by-step tutorial showing how to apply the discussed methods to an openly available time series of mood-related measurements

ARE ALTERNATIVE TREATMENTS EFFECTIVE? ISSUES & METHODS INVOLVED IN MEASURING EFFECTIVENESS OF ALTERNATIVE TREATMENTS

This paper reviews common research methods which have been used in alternative medicine. We focus on a case series method called the before-after treatment experimental design. How this method can be used by practitioners to measure the effectiveness of their treatments is explored in depth. We address what variables should be measured before, during and after treatment. References to commonly used measurement instruments for physical, emotional and spiritually based variables are included

Intermodulation electrostatic force microscopy for imaging surface photo-voltage

We demonstrate an alternative to Kelvin Probe Force Microscopy for imaging surface potential. The open-loop, single-pass technique applies a low-frequency AC voltage to the atomic force microscopy tip while driving the cantilever near its resonance frequency. Frequency mixing due to the nonlinear capacitance gives intermodulation products of the two drive frequencies near the cantilever resonance, where they are measured with high signal to noise ratio. Analysis of this intermodulation response allows for quantitative reconstruction of the contact potential difference. We derive the theory of the method, validate it with numerical simulation and a control experiment, and we demonstrate its utility for fast imaging of the surface photo-voltage on an organic photo-voltaic material.Comment: 4 pages, 3 figures, peer-reviewed, preprin

Travelling to exotic places with cavity QED systems

Recent theoretical schemes for utilizing cavity QED models as quantum simulators are reviewed. By considering a quadrature representation for the fields, it is shown how Jahn-Teller models, effective Abelian or non-Abelian gauge potentials, transverse Hall currents, and relativistic effects naturally arise in these systems. Some of the analytical predictions are verified numerically using realistic experimental parameters taking into account for system losses. Thereby demonstrating their feasibility with current experimental setups.Comment: 5 pages, 3 figure

Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3

TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature T_N < 41K is accompanied by ferroelectric order for T < 28K. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally-modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks spatial inversion symmetry and can account for magnetoelectricity in TbMnO3.Comment: 4 pages revtex, accepted by Phys. Rev. Lett. on June 21, 200