Using a virtual cortical module implementing a neural field model to modulate brain rhythms in Parkinson’s disease

We propose a new method for selective modulation of cortical rhythms based on neural field theory, in which the activity of a cortical area is extensively monitored using a two-dimensional microelectrode array. The example of Parkinson’s disease illustrates the proposed method, in which a neural field model is assumed to accurately describe experimentally recorded activity. In addition, we propose a new closed-loop stimulation signal that is both space- and time- dependent. This method is especially designed to specifically modulate a targeted brain rhythm, without interfering with other rhythms. A new class of neuroprosthetic devices is also proposed, in which the multielectrode array is seen as an artificial neural network interacting with biological tissue. Such a bio-inspired approach may provide a solution to optimize interactions between the stimulation device and the cortex aiming to attenuate or augment specific cortical rhythms. The next step will be to validate this new approach experimentally in patients with Parkinson’s disease

The impact of organic livestock standards on animal welfare – a questionnaire survey of advisors, inspectors and veterinarians

This report was presented at the UK Organic Research 2002 Conference. A questionnaire survey of organic sector body inspectors, organic advisors and farm animal veterinarians was conducted to examine the respondents’ perceptions of the ability of the organic standards to deliver positive impacts on welfare of organic livestock. A total of 44 separate standards concerning livestock production were extracted from the United Kingdom Register of Organic Food Production livestock production standards. The respondents were asked to consider the potential impact of each standard on animal welfare in comparison to the routine practices used on conventional farms, using a five-point scale (improve significantly, improve slightly, no impact, deteriorate slightly and deteriorate significantly). A simple scoring system was used to rank the different standards in terms of their perceived positive impact on animal welfare. The significance of differences between respondent groups and livestock species were examined. Preliminary findings of the survey are summarised and the usefulness of the approach to evaluate livestock production standards is discussed

A model for generating circadian rhythm by coupling ultradian oscillators

BACKGROUND: Organisms ranging from humans to cyanobacteria undergo circadian rhythm, that is, variations in behavior that cycle over a period about 24 hours in length. A fundamental property of circadian rhythm is that it is free-running, and continues with a period close to 24 hours in the absence of light cycles or other external cues. Regulatory networks involving feedback inhibition and feedforward stimulation of mRNA transcription and translation are thought to be critical for many circadian mechanisms, and genes coding for essential components of circadian rhythm have been identified in several organisms. However, it is not clear how such components are organized to generate a circadian oscillation. RESULTS: We propose a model in which two independent transcriptional-translational oscillators with periods much shorter than 24 hours are coupled to drive a forced oscillator that has a circadian period, using mechanisms and parameters of conventional molecular biology. Furthermore, the resulting circadian oscillator can be entrained by an external light-dark cycle through known mechanisms. We rationalize the mathematical basis for the observed behavior of the model, and show that the behavior is not dependent on the details of the component ultradian oscillators but occurs even if quite generalized basic oscillators are used. CONCLUSION: We conclude that coupled, independent, transcriptional-translational oscillators with relatively short periods can be the basis for circadian oscillators. The resulting circadian oscillator can be entrained by 24-hour light-dark cycles, and the model suggests a mechanism for its evolution

Nonuniqueness phenomena in discontinuous dynamical systems and their regularizations

In a recent paper by Guglielmi and Hairer (SIADS 2015), an analysis in the $\varepsilon\to 0$ limit was proposed of regularized discontinuous ODEs in codimension-2 switching domains; this was obtained by studying a certain 2-dimensional system describing the so-called hidden dynamics. In particular, the existence of a unique limit solution was not proved in all cases, a few of which were labeled as ambiguous, and it was not clear whether or not the ambiguity could be resolved. In this paper, we show that it cannot be resolved in general. A first contribution of this paper is an illustration of the dependence of the limit solution on the form of the switching function. Considering the parameter dependence in the ambiguous class of discontinuous systems, a second contribution is a bifurcation analysis, revealing a range of possible behaviors. Finally, we investigate the sensitivity of solutions in the transition from codimension-2 domains to codimension-3 when there is a limit cycle in the hidden dynamics.Comment: 32 pages, 5 figure

Histocompatibility Antigens and Spondylitis

This is a transcript of a discussion about HL-A antigens and spondylitis at Medical Grand Rounds by the Department of Medicine, Surgery, and Ophthalmology on January 29, 1974, at the Medical College of Virginia, Richmond

Chaos in a ring circuit

A ring-shaped logic circuit is proposed here as a robust design for a True Random Number Generator (TRNG). Most existing TRNGs rely on physical noise as a source of randomness, where the underlying idealized deterministic system is simply oscillatory. The design proposed here is based on chaotic dynamics and therefore intrinsically displays random behavior, even in the ideal noise-free situation. The paper presents several mathematical models for the circuit having different levels of detail. They take the form of differential equations using steep sigmoid terms for the transfer functions of logic gates. A large part of the analysis is concerned with the hard step-function limit, leading to a model known in mathematical biology as a Glass network. In this framework, an underlying discrete structure (a state space diagram) is used to describe the likely structure of the global attractor for this system. The latter takes the form of intertwined periodic paths, along which trajectories alternate unpredictably. It is also invariant under the action of the cyclic group. A combination of analytical results and numerical investigations confirms the occurrence of symmetric chaos in this system, which when implemented in (noisy) hardware, should therefore serve as a robust TRNG

Biological invasions in agricultural settings: insights from evolutionary biology and population genetics

Invasion biology and agriculture are intimately related for several reasons and in particular because many agricultural pest species are recent invaders. In this article we suggest that the reconstruction of invasion routes with population genetics-based methods can address fundamental questions in ecology and practical aspects of the management of biological invasions in agricultural settings. We provide a brief description of the methods used to reconstruct invasion routes and describe their main characteristics. In particular, we focus on a scenario - the bridgehead invasion scenario -, which had been overlooked until recently. We show that this scenario, in which an invasive population is the source of other invasive populations, is evolutionarily parsimonious and may have played a crucial role in shaping the distribution of many recent agricultural pests

Characterising risk of non-steroidal-anti-inflammatory drug related acute kidney injury: a retrospective cohort study

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed for pain and inflammation. NSAID complications include acute kidney injury (AKI), causing burden to patients and health services through increased morbidity, mortality, and hospital admissions. AIM: To measure the extent of NSAID prescribing in an adult population, the degree to which patients with potential higher risk of AKI were exposed to NSAIDs, and to quantify their risk of AKI. DESIGN & SETTING: Retrospective 2-year closed-cohort study. METHOD: A retrospective cohort of adults was identified from a pseudonymised electronic primary care database in Hampshire, UK. The cohort had clinical information, prescribing data, and complete GP- and hospital-ordered biochemistry data. NSAID exposure (minimum one prescription in a 2-month period) was categorised as never, intermittent, and continuous, and first AKI using the national AKI e-alert algorithm. Descriptive statistics and logistic regression were used to explore NSAID prescribing patterns and AKI risk. RESULTS: The baseline population was 702 265. NSAID prescription fell from 19 364 (2.8%) to 16 251 (2.4%) over 2 years. NSAID prescribing was positively associated with older age, female sex, greater socioeconomic deprivation, and certain comorbidities (diabetes, hypertension, osteoarthritis, and rheumatoid arthritis) and negatively with cardiovascular disease (CVD) and heart failure. Among those prescribed NSAIDs, AKI was associated with older age, greater deprivation, chronic kidney disease (CKD), CVD, heart failure, diabetes, and hypertension. CONCLUSION: Despite generally good prescribing practice, NSAID prescribing was identified in some people at higher risk of AKI (for example, patients with CKD and older) for whom medication review and NSAID deprescribing should be considered