Improved Upper Bounds to the Causal Quadratic Rate-Distortion Function for Gaussian Stationary Sources

We improve the existing achievable rate regions for causal and for zero-delay source coding of stationary Gaussian sources under an average mean squared error (MSE) distortion measure. To begin with, we find a closed-form expression for the information-theoretic causal rate-distortion function (RDF) under such distortion measure, denoted by $R_{c}^{it}(D)$, for first-order Gauss-Markov processes. Rc^{it}(D) is a lower bound to the optimal performance theoretically attainable (OPTA) by any causal source code, namely Rc^{op}(D). We show that, for Gaussian sources, the latter can also be upper bounded as Rc^{op}(D)\leq Rc^{it}(D) + 0.5 log_{2}(2\pi e) bits/sample. In order to analyze $R_{c}^{it}(D)$ for arbitrary zero-mean Gaussian stationary sources, we introduce \bar{Rc^{it}}(D), the information-theoretic causal RDF when the reconstruction error is jointly stationary with the source. Based upon \bar{Rc^{it}}(D), we derive three closed-form upper bounds to the additive rate loss defined as \bar{Rc^{it}}(D) - R(D), where R(D) denotes Shannon's RDF. Two of these bounds are strictly smaller than 0.5 bits/sample at all rates. These bounds differ from one another in their tightness and ease of evaluation; the tighter the bound, the more involved its evaluation. We then show that, for any source spectral density and any positive distortion D\leq \sigma_{x}^{2}, \bar{Rc^{it}}(D) can be realized by an AWGN channel surrounded by a unique set of causal pre-, post-, and feedback filters. We show that finding such filters constitutes a convex optimization problem. In order to solve the latter, we propose an iterative optimization procedure that yields the optimal filters and is guaranteed to converge to \bar{Rc^{it}}(D). Finally, by establishing a connection to feedback quantization we design a causal and a zero-delay coding scheme which, for Gaussian sources, achieves...Comment: 47 pages, revised version submitted to IEEE Trans. Information Theor

Analyticity of the density of electronic wavefunctions

We prove that the electronic densities of atomic and molecular eigenfunctions are real analytic in ${\mathbb R}^3$ away from the nuclei.Comment: 19 page

Development and Daily Management of an Explicit Strategy of Nonuse of Antimicrobial Drugs in Twelve Danish Organic Dairy Herds

Promotion of animal health and well-being at the individual animal and herd level is an important goal in organic farming. At the same time, chemical products affecting the natural balance among living organisms are prohibited in all areas of the organic farm. From an animal welfare point of view, however, no animal must suffer. Therefore, veterinary drugs are allowed under the European Union’s regulations for organic farming, despite the fact that they are powerful cell toxins affecting both pathogenic and necessary bacteria, and as such in organic terminology, are regarded as “chemical” or “artificial” products. In this article, we present and discuss interviews with 12 Danish organic dairy producers who claim that minimized use or nonuse of antimicrobial drugs is an explicit goal. The dairy producers were at different levels with regard to reduced antimicrobial treatment. An explicit strategy of no antimicrobial treatments is based primarily on a long-term effort to improve herd health, and secondarily, on finding alternative treatments for diseased animals. Improved hygiene, outdoor access, use of nursing cows, and blinding of chronic mastitis quarters were the main techniques in developing a strategy of not using antimicrobial treatments in the herd by dairy producers. Producers’ perception of disease changed from something unavoidable to a disturbing break in the daily rhythm that often could have been avoided. Change toward a nonantimicrobial strategy was gradual and stepwise. All dairy producers in this study desired to preserve the possibility of using antimicrobial drugs in emergencies

Danish Stable Schools for Experiential Common Learning in Groups of Organic Dairy Farmers

The farmer field school (FFS) is a concept for farmers’ learning, knowledge exchange, and empowerment that has been developed and used in developing countries. In Denmark, a research project focusing on explicit nonantibiotic strategies involves farmers who have actively expressed an interest in phasing out antibiotics from their herds through promotion of animal health. One way of reaching this goal was to form participatory focused farmer groups in an FFS approach, which was adapted to Danish conditions and named “stable schools.” Four stable schools were established and went through a 1-yr cycle with 2 visits at each of the 5 or 6 farms connected to each group. A facilitator was connected to each group whose role was to write the meeting agenda together with the host farmer, direct the meeting, and write the minutes to send to the group members ater the meeting. Through group focus interviews and individual semistructured qualitative interviews of all participants, the approach of the farmers’ goal-directed work toward a common goal was judged to be very valuable and fruitful and based on a common learning process. Complex farming situations were the focus of all groups and in this context, problems were identified and solutions proposed based on each farmer’s individual goals. In this article, we describe the experiences of 4 stable school groups (each comprising farmers and a facilitator), and the common process of building a concept that is suitable for Danish organic dairy farming

Comments on "A Framework for Control System Design Subject to Average Data-Rate Constraints"

Theorem~ 4.1 in the 2011 paper "A Framework for Control System Design Subject to Average Data-Rate Constraints" allows one to lower bound average operational data rates in feedback loops (including the situation in which encoder and decoder have side information). Unfortunately, its proof is invalid. In this note we first state the theorem and explain why its proof is flawed, and then provide a correct proof under weaker assumptions.Comment: Submitted to IEEE Transactions on Automatic Contro

Introduction to special issue. Distancing, disease and distress: The young and COVID-19: exploring young people’s experience of inequalities and their resourcefulness during the pandemic

The COVID-19 global pandemic has impacted everyone’s lives—young and old. When the World Health Organization declared the COVID-19 outbreak a pandemic on 11 March 2020 and one country after another went into lockdown, we as editors of YOUNG and youth researchers living in five different countries naturally started to think about and reflect on what impact the pandemic would have on young people’s everyday lives, their well-being and futures across different national settings. In response to this uncertainty and in the interest of capturing young people’s experiences, we as editors called for this special issue to focus on young people and COVID-19, exploring their changed everyday lives and how they adapted to the global pandemic. To accommodate the immense interest and the high quality of many of the submissions, this special issue of YOUNG is a double issue with 11 articles