Order in de Broglie - Bohm quantum mechanics

A usual assumption in the so-called {\it de Broglie - Bohm} approach to quantum dynamics is that the quantum trajectories subject to typical `guiding' wavefunctions turn to be quite irregular, i.e. {\it chaotic} (in the dynamical systems' sense). In the present paper, we consider mainly cases in which the quantum trajectories are {\it ordered}, i.e. they have zero Lyapunov characteristic numbers. We use perturbative methods to establish the existence of such trajectories from a theoretical point of view, while we analyze their properties via numerical experiments. Using a 2D harmonic oscillator system, we first establish conditions under which a trajectory can be shown to avoid close encounters with a moving nodal point, thus avoiding the source of chaos in this system. We then consider series expansions for trajectories both in the interior and the exterior of the domain covered by nodal lines, probing the domain of convergence as well as how successful the series are in comparison with numerical computations or regular trajectories. We then examine a H\'{e}non - Heiles system possessing regular trajectories, thus generalizing previous results. Finally, we explore a key issue of physical interest in the context of the de Broglie - Bohm formalism, namely the influence of order in the so-called {\it quantum relaxation} effect. We show that the existence of regular trajectories poses restrictions to the quantum relaxation process, and we give examples in which the relaxation is suppressed even when we consider initial ensembles of only chaotic trajectories, provided, however, that the system as a whole is characterized by a certain degree of order.Comment: 25 pages, 12 figure

Validation of the Finnish version of the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) and evaluation of the applicability of the Multiple Sclerosis Neuropsychological Questionnaire (MSNQ) and the Fatigue Scale for Motor and Cognitive Functions (FSMC)

Objectives Cognitive impairment is frequent in multiple sclerosis (MS) as approximately half of the patients manifest some degree of cognitive impairment. The Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) has been designed for brief cognitive evaluation. The purpose of the study was to validate the BICAMS along with the Finnish versions of one self-rating questionnaire each for cognition and fatigue. Methods A total of 65 MS patients and 45 healthy controls (HC) were assessed with the BICAMS, the Multiple Sclerosis Neuropsychological Questionnaire (MSNQ), and the Fatigue Scale for Motor and Cognitive Functions (FSMC) twice, approximately within nine days. Results MS patients scored markedly lower than the HCs on each of the three tests of the BICAMS. Of the patients, 60% scored at least 1.5 SD below the mean of the HCs on at least one test; 49% on the SDMT, 26% on the CVLT-II, and 28% on the BVMT-R. Correlation coefficients for the repeated measurement were between 0.75 and 0.89 for the three tests in the whole study sample. MS patients reported more cognitive symptoms and more fatigue than the HCs. Cronbach's alpha was 0.94 for the MSNQ and 0.98 for the FSMC. Correlation coefficient for the repeated measurement was 0.91 for the MSNQ and between 0.92 and 0.94 for the FSMC scores for the whole study sample. Conclusions The present study supports the validity of the Finnish version of the BICAMS. The SDMT was the most sensitive of the three BICAMS tests and showed cognitive impairment in half of the patients. The Finnish versions of the MSNQ and the FSMC proved useful tools in approaching concerns related to cognition and fatigue.Peer reviewe

Non-invasive management of peripheral arterial disease.

BACKGROUND: Peripheral arterial disease (PAD) is common and symptoms can be debilitating and lethal. Risk management, exercise, radiological and surgical intervention are all valuable therapies, but morbidity and mortality rates from this disease are increasing. Circulatory enhancement can be achieved using simple medical electronic devices, with claims of minimal adverse side effects. The evidence for these is variable, prompting a review of the available literature. METHODS: Embase and Medline were interrogated for full text articles in humans and written in English. Any external medical devices used in the management of peripheral arterial disease were included if they had objective outcome data. RESULTS: Thirty-one papers met inclusion criteria, but protocols were heterogenous. The medical devices reported were intermittent pneumatic compression (IPC), electronic nerve (NMES) or muscle stimulators (EMS), and galvanic electrical dressings. In patients with intermittent claudication, IPC devices increase popliteal artery velocity (49-70 %) and flow (49-84 %). Gastrocnemius EMS increased superficial femoral artery flow by 140 %. Over 4.5-6 months IPC increased intermittent claudication distance (ICD) (97-150 %) and absolute walking distance (AWD) (84-112 %), with an associated increase in quality of life. NMES of the calf increased ICD and AWD by 82 % and 61-150 % at 4 weeks, and 26 % and 34 % at 8 weeks. In patients with critical limb ischaemia IPC reduced rest pain in 40-100 % and was associated with ulcer healing rates of 26 %. IPC had an early limb salvage rate of 58-83 % at 1-3 months, and 58-94 % at 1.5-3.5 years. No studies have reported the use of EMS or NMES in the management of CLI. CONCLUSION: There is evidence to support the use of IPC in the management of claudication and CLI. There is a building body of literature to support the use of electrical stimulators in PAD, but this is low level to date. Devices may be of special benefit to those with limited exercise capacity, and in non-reconstructable critical limb ischaemia. Galvanic stimulation is not recommended

The effect of age on recollection is not moderated by differential estimation methods

Episodic memory performance declines with increasing age. It has sometimes been reported that this decline is more marked when episodic recollection is estimated by “objective” measures such as source memory performance than when it is estimated by “subjective” measures such as the “Remember/Know” procedure. Here, our main goal was to directly contrast recollection estimates derived from these procedures in the same samples of young and older participants (24 adults per age group, within-subjects manipulation of test procedure). Following identical study phases in which words were paired with either faces or scenes, participants’ memories were assessed in separate test blocks using either Remember/Know or source memory procedures. Contrary to several prior reports, the deleterious effects of age on recollection estimates did not differ according to test type. Thus, we found no evidence that age differentially impacts subjective and objective recollection estimates. Additionally, and consistent with prior findings, effects of age on estimates of familiarity-driven recognition were small and non-significant

Executive functioning, motor difficulties and developmental coordination disorder

The current study assessed a comprehensive range of executive functions (EFs) in children with poor motor skills, comparing profiles of children with a diagnosis of developmental coordination disorder (DCD) and those identified with motor difficulties (MD). Children in both groups performed more poorly than typically-developing controls on nonverbal measures of working memory, inhibition, planning and fluency, but not on tests of switching. The similar patterns of strengths and weaknesses in children with MD and DCD have important implications for parents, teachers and clinicians, as children with MD may struggle with EF tasks even though their motor difficulties are not identified

Congregational bonding social capital and psychological type : an empirical enquiry among Australian churchgoers

This study explores the variation in levels of bonding social capital experienced by individual churchgoers, drawing on data generated by the Australian National Church Life Survey, and employing a five-item measure of church-related bonding social capital. Data provided by 2065 Australian churchgoers are used to test the thesis that individual differences in bonding social capital are related to a psychological model of psychological types (employing the Jungian distinctions). The data demonstrated that higher levels of bonding social capital were found among extraverts (compared with introverts), among intuitive types (compared with sensing types) and among feeling types (compared with thinking types), but no significant differences were found between judging types and perceiving types

The UCLA Study of Children with Moderate-to-Severe Traumatic Brain Injury: Event-Related Potential Measure of Interhemispheric Transfer Time

Traumatic brain injury (TBI) frequently results in diffuse axonal injury and other white matter damage. The corpus callosum (CC) is particularly vulnerable to injury following TBI. Damage to this white matter tract has been associated with impaired neurocognitive functioning in children with TBI. Event-related potentials can identify stimulus-locked neural activity with high temporal resolution. They were used in this study to measure interhemispheric transfer time (IHTT) as an indicator of CC integrity in 44 children with moderate/severe TBI at 3-5 months post-injury, compared with 39 healthy control children. Neurocognitive performance also was examined in these groups. Nearly half of the children with TBI had IHTTs that were outside the range of the healthy control group children. This subgroup of TBI children with slow IHTT also had significantly poorer neurocognitive functioning than healthy controls-even after correction for premorbid intellectual functioning. We discuss alternative models for the relationship between IHTT and neurocognitive functioning following TBI. Slow IHTT may be a biomarker that identifies children at risk for poor cognitive functioning following moderate/severe TBI

Age-related Differences in Prestimulus Subsequent Memory Effects Assessed with Event-related Potentials

Prestimulus subsequent memory effects (preSMEs)—differences in neural activity elicited by a task cue at encoding that are predictive of later memory performance—are thought to reflect differential engagement of preparatory processes that benefit episodic memory encoding. We investigated age differences in preSMEs indexed by differences in ERP amplitude just before the onset of a study item. Young and older adults incidentally encoded words for a subsequent memory test. Each study word was preceded by a task cue that signaled a judgment to perform on the word. Words were presented for either a short (300 msec) or long (1000 msec) duration with the aim of placing differential benefits on engaging preparatory processes initiated by the task cue. ERPs associated with subsequent successful and unsuccessful recollection, operationalized here by source memory accuracy, were estimated time-locked to the onset of the task cue. In a late time window (1000–2000 msec after onset of the cue), young adults demonstrated frontally distributed preSMEs for both the short and long study durations, albeit with opposite polarities in the two conditions. This finding suggests that preSMEs in young adults are sensitive to perceived task demands. Although older adults showed no evidence of preSMEs in the same late time window, significant preSMEs were observed in an earlier time window (500–1000 msec) that was invariant with study duration. These results are broadly consistent with the proposal that older adults differ from their younger counterparts in how they engage preparatory processes during memory encoding