Integrability of a conducting elastic rod in a magnetic field

We consider the equilibrium equations for a conducting elastic rod placed in a uniform magnetic field, motivated by the problem of electrodynamic space tethers. When expressed in body coordinates the equations are found to sit in a hierarchy of non-canonical Hamiltonian systems involving an increasing number of vector fields. These systems, which include the classical Euler and Kirchhoff rods, are shown to be completely integrable in the case of a transversely isotropic rod; they are in fact generated by a Lax pair. For the magnetic rod this gives a physical interpretation to a previously proposed abstract nine-dimensional integrable system. We use the conserved quantities to reduce the equations to a four-dimensional canonical Hamiltonian system, allowing the geometry of the phase space to be investigated through Poincar\'e sections. In the special case where the force in the rod is aligned with the magnetic field the system turns out to be superintegrable, meaning that the phase space breaks down completely into periodic orbits, corresponding to straight twisted rods.Comment: 19 pages, 1 figur

Design optimization of multibody systems by sequential approximation

Abstract. Design optimization of multibody systems is usually established by a direct coupling of multibody system analysis and mathematical programming algorithms. However, a direct coupling is hindered by the transient and computationally complex behavior of many multibody systems. In structural optimization often approximation concepts are used instead to interface numerical analysis and optimization. This paper shows that such an approach is valuable for the optimization of multibody systems as well. A design optimization tool has been developed for multibody systems that generates a sequence of approximate optimization problems. The approach is illustrated by three examples: an impact absorber, a slider-crank mechanism, and a stress-constrained four-bar mechanism. Furthermore, the consequences for an accurate and efficient accompanying design sensitivity analysis are discussed

Anticholinergic and Sedative Medications and Dynamic Gait Parameters in Older Patients

BACKGROUND: Anticholinergic and sedative medications are associated with poorer physical function in older age. Gait and physical function have traditionally been assessed with the time needed to execute objective function tests. Accelerometer-based gait parameters provide a precise capturing of gait dynamics and patterns and as such have added value. OBJECTIVES: This study examined the associations between cumulative exposure to anticholinergic and sedative medications and gait dimensions as assessed with accelerometer-based dynamic gait parameters. METHODS: Data were collected from outpatients of a diagnostic geriatric day clinic who underwent a comprehensive geriatric assessment (CGA). Cumulative exposure to anticholinergic and sedative medications was quantified with the Drug Burden Index (DBI), a linear additive pharmacological dose-response model. From a total of 22 dynamic gait parameters, the gait dimensions 'Regularity', 'Complexity', 'Stability', 'Pace', and 'Postural Control' were derived using factor analysis (and standardized total scores for these dimensions were calculated accordingly). Data were analyzed with multivariable linear regression analysis, in which adjustment was made for the covariates age, gender, body mass index (BMI), Mini Mental State Examination (MMSE) score, Charlson Comorbidity Index (CCI) including dementia, and number of medications not included in the DBI. RESULTS: A total of 184 patients participated, whose mean age was 79.8 years (± SD 5.8), of whom 110 (60%) were women and of whom 88 (48%) had polypharmacy (i.e., received treatment with ≥5 medications). Of the 893 medications that were prescribed in total, 157 medications (17.6%) had anticholinergic and/or sedative properties. Of the patients, 100 (54%) had no exposure (DBI = 0), 42 (23%) had moderate exposure (0 > DBI ≤ 1), while another 42 (23%) had high exposure (DBI >1) to anticholinergic and sedative medications. Findings showed that high cumulative exposure to anticholinergic and sedative medications was related with poorer function on the Regularity and Pace dimensions. Furthermore, moderate and high exposure were associated with poorer function on the Complexity dimension. CONCLUSIONS: These findings show that in older patients with comorbidities, cumulative anticholinergic and sedative exposure is associated with poorer function on multiple gait dimensions

The Cross-Cultural Dementia Screening (CCD):A new neuropsychological screening instrument for dementia in elderly immigrants

Objective: Currently, approximately 3.9% of the European population are non-EU citizens, and a large part of these people are from "non-Western" societies, such as Turkey and Morocco. For various reasons, the incidence of dementia in this group is expected to increase. However, cognitive testing is challenging due to language barriers and low education and/or illiteracy. The newly developed Cross-Cultural Dementia Screening (CCD) can be administered without an interpreter. It contains three subtests that assess memory, mental speed, and executive function. We hypothesized the CCD to be a culture-fair test that could discriminate between demented patients and cognitively healthy controls. Method: To test this hypothesis, 54 patients who had probable dementia were recruited via memory clinics. Controls (N = 1625) were recruited via their general practitioners. All patients and controls were aged 55 years and older and of six different self-defined ethnicities (Dutch, Turkish, Moroccan-Arabic, Moroccan-Berber, Surinamese-Creole, and Surinamese-Hindustani). Exclusion criteria included current or previous conditions that affect cognitive functioning. Results: There were performance differences between the ethnic groups, but these disappeared after correcting for age and education differences between the groups, which supports our central hypothesis that the CCD is a culture-fair test. Receiver-operating characteristic (ROC) and logistic regression analyses showed that the CCD has high predictive validity for dementia (sensitivity: 85%; specificity: 89%). Discussion: The CCD is a sensitive and culture-fair neuropsychological instrument for dementia screening in low-educated immigrant populations.</p

Dementiediagnostiek bij oudere migranten op de geheugenpolikliniek: obstakels en oplossingen

De komende tien jaar verdubbelt het aantal niet-westerse allochtone ouderen. Door specifieke risicofactoren (zoals hypertensie en diabetes) zal het aantal oudere migranten met dementie waarschijnlijk toenemen. Geheugenpoliklinieken zijn onvoldoende voorbereid op deze nieuwe patiëntenstroom, omdat zorgprofessionals onvoldoende kennis hebben van de obstakels die bij interculturele dementiediagnostiek een rol spelen. Zij dienen rekening te houden met taalbarrière, cultuurbarrière, het lage opleidingsniveau en analfabetisme van een aanzienlijk aantal patiënten, maar ook met onbekendheid met dementie, schaamte en bijzondere zorgverwachtingen van de patiënten en hun familie. Er worden aanbevelingen gedaan voor het verbeteren van communicatie, (neuropsychologische) testdiagnostiek en zorgadviezen in de klinische praktijk

Trajectories of long-term exposure to anticholinergic and sedative drugs: A latent class growth analysis

Introduction: A variety of drugs, which are frequently prescribed to older people, have anticholinergic and sedative effects whereby they may impair cognitive and physical function. Although substantial inter-individual variation in anticholinergic and sedative exposure has been documented, little is known about subpopulations with distinct trajectories of exposure. Methods: Data from the Longitudinal Aging Study Amsterdam (LASA), an ongoing Dutch population-based cohort study, collected over 20 years (1992-2012) at seven occasions, were analyzed. On each occasion, cumulative anticholinergic and sedative exposure was quantified with the Drug Burden Index, a linear additive pharmacological dose-response model. The most likely number of trajectories were empirically derived with Latent Class Growth Analysis using "Goodness of fit" statistics. Trajectories were then compared on physical and cognitive function. Results: A total of 763 participants completed all follow-ups (61% women; mean age 83, ±6). "Goodness of fit" statistics (Bayesian In-formation Criterion = 22916, Bootstrapped Likelihood Ratio Test of 3 vs. 2 classes = 514.12

Combined Chlorophyll Fluorescence and Transcriptomic Analysis Identifies the P3/P4 Transition as a Key stage in Rice Leaf Photosynthetic Development

Leaves are derived from heterotrophic meristem tissue that, at some point, must make the transition to autotrophy via the initiation of photosynthesis. However, the timing and spatial coordination of the molecular and cellular processes underpinning this switch are poorly characterized. Here, we report on the identification of a specific stage in rice (Oryza sativa) leaf development (P3/P4 transition) when photosynthetic competence is first established. Using a combined physiological and molecular approach, we show that elements of stomatal and vascular differentiation are coordinated with the onset of measurable light absorption for photosynthesis. Moreover, by exploring the response of the system to environmental perturbation, we show that the earliest stages of rice leaf development have significant plasticity with respect to elements of cellular differentiation of relevance for mature leaf photosynthetic performance. Finally, by performing an RNA sequencing analysis targeted at the early stages of rice leaf development, we uncover a palette of genes whose expression likely underpins the acquisition of photosynthetic capability. Our results identify the P3/P4 transition as a highly dynamic stage in rice leaf development when several processes for the initiation of photosynthetic competence are coordinated. As well as identifying gene targets for future manipulation of rice leaf structure/function, our data highlight a developmental window during which such manipulations are likely to be most effective

Simulating and delineating future land change trajectories across Europe

Explorations of future land use change are important to understand potential conflicts between competing land uses, trade-offs associated with particular land change trajectories, and the effectiveness of policies to steer land systems into desirable states. Most model-based explorations and scenario studies focused on conversions in broad land use classes, but disregarded changes in land management or focused on individual sectors only. Using the European Union (EU) as a case study, we developed an approach to identifying typical combinations of land cover and management changes by combining the results of multimodel simulations in the agriculture and forest sectors for four scenarios from 2000 to 2040. We visualized land change trajectories by mapping regional hotspots of change. Land change trajectories differed in extent and spatial pattern across the EU and among scenarios, indicating trajectory-specific option spaces for alternative land system outcomes. In spite of the large variation in the area of change, similar hotspots of land change were observed among the scenarios. All scenarios indicate a stronger polarization of land use in Europe, with a loss of multifunctional landscapes. We analyzed locations subject to change by comparing location characteristics associated with certain land change trajectories. Results indicate differences in the location conditions of different land change trajectories, with diverging impacts on ecosystem service provisioning. Policy and planning for future land use needs to account for the spatial variation of land change trajectories to achieve both overarching and location-specific targets