Magnetisation process in the rare earth tetraborides, NdB4 and HoB4.

A field-induced magnetisation process in the frustrated antiferromagnets is often much richer compared to the materials without competing interactions. The applied field tends to stabilise unusual spin configurations which frequently results in the appearance of magnetisation plateaux. Here we report a study into the field-induced magnetisation of the two frustrated rare earth tetraborides, HoB4 and NdB4. NdB4 shows a fractional magnetisation plateau occurring at M/M sat ≈ [Formula: see text] before saturating in a field of 33 kOe. On cooling down to 0.5 K the temperature dependent susceptibility of NdB4 shows an unconventional transition where the system returns to the zero field antiferromagnetic state from a higher-temperature ferrimagnetic state. We are able to reconstruct the magnetic phase diagram of NdB4 from the magnetisation, susceptibility and resistivity measurements for both H [Formula: see text] c and H ⊥ c. For HoB4, the most interesting behaviour is found at the lowest temperature of 0.5 K, where the field dependent magnetisation demonstrates a new fractional [Formula: see text]-magnetisation plateau. Further insight into the relations between the exchange interactions and single ion effects is gained through high-field magnetisation measurements in both HoB4 and NdB4.

Validation of the Verbal and Social Interaction questionnaire: carers' focus in the carer-resident relationship in supported housing facilities for persons with psychiatric disabilities (VSI-SH).

A questionnaire to measure the verbal and social interactions between carers and residents in supported housing facilities for persons with psychiatric disabilities has been developed. It is an adaptation of a questionnaire originally used in a forensic psychiatric setting. The aim of the present study was thus to investigate the construct validity and the reliability of this new version of the Verbal and Social Interactions questionnaire for use in supported housing facilities (VSI-SH). Two hundred and twenty-three carers from municipal and privately run housing facilities completed the questionnaire. A factor analysis was performed, which resulted in six factors. The number of items was reduced from the original 47 to 30 in order to minimize factorial complexity and multiple loadings. The reliability was tested with Cronbach's alpha and good internal consistency for the questionnaire and five of the six factors was found. The resulting six factors and the items were compared to the conceptual model and four of the six factors corresponded well with the categories in this original theoretical model. The questionnaire can be a useful contribution to the study of interactions between carers and residents in supported housing facilities for persons with psychiatric disabilities.

The prevalence and workplace costs of adult attention deficit hyperactivity disorder in a large manufacturing firm.

BACKGROUND: Little is known about the effects of adult attention deficit hyperactivity disorder (ADHD) on work performance or accidents-injuries.MethodA survey was administered in 2005 and 2006 to employees of a large manufacturing firm to assess the prevalence and correlates of adult ADHD. Respondents (4,140 in 2005, 4,423 in 2006, including 2,656 in both surveys) represented 35-38% of the workforce. ADHD was assessed with the World Health Organization (WHO) Adult ADHD Self-Report Scale (ASRS), a validated screening scale for DSM-IV adult ADHD. Sickness absence, work performance and workplace accidents-injuries were assessed with the WHO Health and Work Performance Questionnaire (HPQ). RESULTS: The estimated current prevalence (standard error) of DSM-IV ADHD was 1.9% (0.4). ADHD was associated with a 4-5% reduction in work performance (chi12=9.1, p=0.001), a 2.1 relative-odds of sickness absence (chi12=6.2, p=0.013), and a 2.0 relative-odds of workplace accidents-injuries (chi12=5.1, p=0.024). The human capital value (standard error) of the lost work performance associated with ADHD totaled USD 4,336 (676) per worker with ADHD in the year before interview. No data were available to monetize other workplace costs of accidents-injuries (e.g. destruction of equipment). Only a small minority of workers with ADHD were in treatment. CONCLUSIONS: Adult ADHD is a significantly impairing condition among workers. Given the low rate of treatment and high human capital costs, in conjunction with evidence from controlled trials that treatment can reduce ADHD-related impairments, ADHD would seem to be a good candidate for workplace trials that evaluate treatment cost-effectiveness from the employer's perspective.

Validation of the verbal and social interaction questionnaire: nurses' focus in the nurse-patient relationship in forensic nursing care.

There is a need to develop a questionnaire that measures nurses' verbal and social interactions (VSI) with their patients from the nurses' perspective as well as from the patients' perspective in the psychiatric and especially in the forensic psychiatric field. The major aim of the present study was to determine the construct validity and the internal consistency reliability of the VSI questionnaire. The study had a methodological and developmental design and was carried out in four steps: construction of the items, face validity, data collection and data analysis. The number of items was reduced from 50 to 21. The factor analysis of the final 21 items resulted in three quite distinct factors, namely, 'inviting the patient to establish a relationship', 'showing interest in the patients' feelings, experiences and behaviour' and 'helping the patients to establish structure and routines in their everyday life'. The results showed satisfactory psychometric properties in terms of content validity, construct validity and the internal consistency reliability of the questionnaire.

Comparison of user assessed needs for care between psychiatric inpatients and supported community residents.

The aim of the present study was to compare user assessed needs for care for psychiatric patients in inpatient settings with that of residents in supported community residences. The Camberwell Assessment of Need was administered to 75 patients and residents in different housing settings. Residents in supported community settings had more needs for care (8.1), than patients in inpatient settings (5.8), partly because of differences in duration of illness. A greater proportion of those living in supported community residences reported needs in the areas of psychotic symptoms, accommodation, food, daytime activities, sexual expression and looking after the home. There were no differences in numbers of unmet needs. Relatives and friends provided emotional and social support predominantly in the areas of company and psychological distress. In conclusion, living in supported community residences does not imply more unmet needs, or less adequate response to needs from services, despite a greater number of needs being reported. In some areas of need, relatives and friends play an important role in the provision of support.

Improvements in diabetes management and outcomes in a Medicaid managed care system.

OBJECTIVE: To determine the impact of managed care on effectiveness of diabetes management in Tennessee, where a statewide Medicaid program (TennCare) delivers services through capitated managed care organizations (MCOs). RESEARCH DESIGN AND METHODS: This retrospective cohort study documented the health care utilization experiences and clinical outcomes of a convenience sample of Tennessee Medicaid enrollees with chronic diabetes before and after the initiation of TennCare. Exposures to recommended diabetic services and outcomes were compared before and after TennCare for 171 enrollees with diabetes in the state's largest academic MCO who met age, continuous enrollment, insurance, and diagnostic criteria for two years before (1992 and 1993) and two years after TennCare (1995 and 1996). Claims data were used to assess baseline characteristics and chart review data were used to assess health services utilization for 71% of cohort members (n = 121) for whom complete medical records were available. The paired t-test was used to compare exposures and outcomes before and after TennCare. RESULTS: Participants had an average of 6.4 outpatient clinic visits per year before TennCare vs. 8.2 visits per year after TennCare (P = .0009), 0.6 vs. 1.0 diabetic eye examinations (P = .0042), 0.2 vs. 0.5 foot examinations (P = .0358), 0.4 vs. 0.6 cholesterol assessments (P < .0001), and 0.5 vs. 1.0 glycosylated hemoglobin assessments annually (P < .0001). Average glycosylated hemoglobin decreased from 10.3 to 8.2 (P < .0001). Although hospitalizations and hospital days increased overall, there was no increase in emergency visits, preventable emergency visits, or preventable hospitalizations. CONCLUSIONS: Enrollees with diabetes experienced increases in utilization of recommended health services and improved glucose control following the initiation of Medicaid managed care. These improvements may reflect improved chronic disease care in a primary care gatekeeper system.

Modulations of soleus H-reflex excitability during gait initiation: central versus peripheral influences.

Soleus and tibialis anterior electromyogram (EMG) and soleus H-reflexes were recorded from the stance limb of an individual who suffered a traumatic peroneal nerve injury and of four nonimpaired individuals during gait initiation. The control subjects also initiated walking after swaying forward (sway-gait initiation), which eliminated the initial tibialis anterior activation. During the initial period of gait initiation, H-reflexes were depressed to 43% of standing values during normal-gait initiation and 86% during sway-gait initiation in the nonimpaired subjects. H-reflexes of the nerve-injured subject were depressed to 37%, even though no tibialis anterior EMG was observed. The findings support the view that reciprocal inhibition of the soleus during a task, which normally involves tibialis anterior activation, is due to a centrally mediated process.

The influence of stimulus cue on the initiation of stepping in young and older adults.

OBJECTIVES: To investigate the influence of different reaction stimulus cues on the characteristics of ground reaction forces during the initiation of rapid forward stepping, and to determine whether age-related differences in step initiation are influenced by the type of stimulus cue used to trigger stepping. DESIGN: Case-control study. SETTING: University-based research laboratory. PARTICIPANTS: Fifteen healthy younger adults and 35 community-dwelling older adult volunteers. MAIN OUTCOME MEASURES: Subjects performed forward step initiation in response to 3 different reaction stimulus cues (light, sound, electrocutaneous) during simple reaction-time conditions. Ground reaction force data were collected and used to characterize the timing and magnitude features of the postural (weight-transfer) and step components. RESULTS: In comparison with the light and sound stimuli, the nonnoxious electrocutaneous trigger cue was associated with an increase in the magnitude of the initial displacement of the center of pressure (COP) in the mediolateral direction. Overall, older subjects were slower to initiate the postural and step components, and displayed a reduction in the initial posterior displacement of the COP. CONCLUSIONS: The postural component for lateral weight transfer was augmented by the electrocutaneous trigger cue, suggesting its potential to enhance step initiation among clinical populations. Age-related changes in stepping were unaffected by the type of stimulus cue, but the older group had a slower response initiation time and less forward propulsion. The abilities of many older persons may be compromised in situations where rapid adjustments in the base of support through stepping are triggered by environmental stimuli.

Facilitation of quadriceps activation following a concentrically controlled knee flexion movement: the influence of transition rate.

STUDY DESIGN: Single group repeated measures design. OBJECTIVE: To determine if the rate of transition between knee flexion and extension influences the subsequent concentric activation of the quadriceps and knee extension torque during reciprocal movements. BACKGROUND: Preloading a muscle by stretching, a prior isometric or eccentric muscle action, or a prior movement controlled concentrically by the antagonist muscle group increases the maximal torque-generating capability of the agonist. We hypothesized that the rate of transition from the prior movement may be the critical factor that influences the degree of muscle facilitation and torque potentiation. Rapid reversal of antagonistic movements has been postulated as a potential facilitatory mechanism. METHODS: Knee extension torque and electromyographic (EMG) amplitude (dependent variables) from 2 of the vasti muscles were recorded while subjects (N = 20; 12 men, 8 women, mean age, 28.5+/-2.68 years) maximally activated their quadriceps at 3 constant angular velocities, 100 degrees/s, 200 degrees/s, and 300 degrees/s, and 2 preload conditions, SLOW and RAPID (independent variables). In the SLOW transition condition, subjects actively flexed their knee to 110 degrees from an extended position, paused in this position for 3 seconds, and then extended to 0 degrees. In the RAPID transition condition, the same movement from knee flexion to extension was performed without a pause. RESULTS: Peak torque, the root-mean-square (RMS) average, peak (peak rectified and smoothed), and initial (100 milliseconds prior to torque onset) EMG amplitudes were all significantly greater during the RAPID transition condition. Peak torque decreased with increasing movement velocity. There were no interactions between the preload conditions and angular velocity on peak torque or the EMG amplitude variables. There was also no influence of velocity on the EMG amplitude variables. CONCLUSIONS: The effect of preloading the quadriceps by prior concentric activation of the hamstrings is dependent on the rate of transition between the flexion and extension movements and is due primarily to neural facilitation.

Control strategies for initiation of human gait are influenced by accuracy constraints.

The accuracy of placement of swing limb heel-strike was used to determine strategies of motor control of the stance limb during gait initiation (GI). Subjects initiated gait as fast as possible with the swing limb heel-strike landing on either a small or large target. Stance limb ground reaction forces, electromyogram duration and temporal data for GI were measured. It was hypothesized that accuracy would affect movement speed and the rate of rise, or the slope, of the ground reaction forces that control GI. The slopes of the stance limb forces that coincide with swing limb toe-off remained invariant. However, the slopes of forces and peak forces related to swing limb heel-strike were significantly less for the small target. These initial data suggest that principles of upper extremity motor control may be generalized to the initiation of movement from upright stance.

Modulation of triceps surae H-reflexes as a function of the reflex activation history during standing and stepping.

The facilitatory effectiveness of spindle afferent feedback is controlled by modulation of segmental reflex excitability such that the level of muscle activation is appropriate for the task. Phase-dependent modes of reflex modulation have been well-characterized. We hypothesized that segmental reflex excitability of the triceps surae was also modulated in a manner associated with the activation history of the spindle afferents and the segmental reflex pathway during isometric contractions, standing and stepping. In the first experiment. pairs of soleus (S) H-reflexes were evoked 80 ms apart with equal strength stimuli at rest and while subjects isometrically contracted their S against loads of 10%. 20%. and 50% of their maximum voluntary efforts. The percent depression of the second H-reflex relative to the first was used as a measure of the effect of reflex activation history. At rest, the second H-reflexes were depressed an average of 73% relative to the first. The degree of depression was progressively reduced as the plantarflexion torque increased. In the second experiment, paired H-reflexes were obtained from the S and medial (MG) and lateral gastrocnemii (LG) muscles while subjects were standing and during the stance phase of step initiation. The degree of depression of the second H-reflex during standing ( > 78%) was similar in magnitude to that produced at rest in Experiment I. At the end of the stance phase of stepping. depression of the second H-reflex of all three muscles was reduced to less than 25%. We conclude that the segmental reflex excitability is modulated as a function of the reflex activation history during these tasks.

Principles underlying the organization of movement initiation from quiet stance.

The purpose of this study was to determine common principles underlying the programming of movement initiation from quiet stance. Subjects were asked to initiate gait, step over a ruler, or to step over a 10 cm high obstacle at a self-paced speed and as fast as possible. The independent variables were initiation condition (gait initiation, stepping over a ruler or obstacle) and initiation speed (self-paced and as fast as possible). The dependent measures for the stance limb only were the latency between postural soleus (S(1)) EMG inhibition and tibialis anterior (TA) EMG onset, the duration of both TA and soleus (S(2)) activity following TA, duration and slope, impulse, and peak forces of the anterior-posterior (Fx) ground reaction force. Selected timing events were also monitored. Analysis of variance was used to determine main and interaction effects. The following results were obtained. (1) The interval from the inhibition of S(1) postural activity to the onset of TA remained invariant between all conditions. (2) The duration of TA increased and S(2) decreased with an increase in speed of initiation. There was no difference in TA and S(2) duration between the initiation conditions. (3) Time to heel-off remained invariant for all conditions. (4) Prior to heel-off all force variables increased with initiation speed but were similar between initiation conditions. After heel-off force variables were different between speeds and conditions being greater for fast speed and stepping over the obstacle. Two conclusions may be drawn from this study. First, the results indicate that gait initiation consists of two, highly coordinated motor programs. Heel-off of the stance limb is the division between these two programs. Second, our findings also suggest that gait initiation and stepping are governed by the same motor programs.

Academic managed care organizations and adverse selection under Medicaid managed care in Tennessee.

CONTEXT: Health plans competing in a managed care system may face serious financial consequences if they are disproportionately selected by enrollees with expensive health conditions. Academic medical centers (AMCs) have traditionally provided medical care for the sickest patients and may be at particularly high risk for adverse selection, but whether this occurs is not known. OBJECTIVE: To determine whether managed care organizations (MCOs) representing AMCs are adversely selected by Medicaid managed care (MMC) enrollees with expensive chronic health conditions. DESIGN AND SETTING: Observational study using state Medicaid claims data from all of 1994 and January to August 1995 for Tennessee's statewide MMC program (TennCare). PARTICIPANTS: All 12 capitated MCOs in Tennessee, which collectively provided services for 1.2 million Medicaid enrollees from January 1994 through August 1995 following the initiation of TennCare. MAIN OUTCOME MEASURES: Prevalence of 6 state-specified high-cost chronic conditions-acquired immunodeficiency syndrome (AIDS), coagulation defects, cystic fibrosis, pregnancy, prematurity, and organ transplantation-and 27 additional high-cost conditions compared by academic, statewide, and regional MCOs. RESULTS: The prevalence of state-specified high-cost chronic conditions was generally higher for academic MCOs compared with other MCOs. Specifically, prevalence of AIDS was 14.1 times higher in academic MCOs than in statewide MCOs; coagulation defects, 6.4 times higher; transplantations, 4.4; pregnancy, 3.3; cystic fibrosis, 2.4; and prevalence of prematurity was equivalent. Prevalence was higher for academic than for statewide MCOs for 22 of the additional 27 high-cost conditions considered and similar for the remaining 5 conditions. CONCLUSIONS: Our results suggest that academic MCOs in an MMC system are selected by a large percentage of the sickest patients. Adverse selection may present serious financial risks for AMCs participating in managed care.

Internet-based patient information systems: what are they, why are they here, how will they be used, and will they work?

Web-based patient information systems are an emerging tool in the drive towards improving efficiency and effectiveness of health care. Providers and health plans may be able to achieve three key objectives with these systems: improve the health status of patients, improve marketing programs, and reduce costs. To discover what we know about these systems, we examine how they perform today, review the trends that are shaping their development, present a case study of a large East Coast HMO, and postulate future trends.

Limits of the dual-strategy hypothesis in an isometric plantar flexion contraction.

Movements have been described as being governed by a speed-sensitive (SS) or speed-insensitive (SI) strategy. The SS strategy is used when the subject controls, either explicitly or implicitly, movement speed or time. In contrast, the SI strategy is utilized when there is no intention or requirement to control movement speed. The different strategies demonstrate a specific relationship between torque trajectories and muscle activity. The purpose of this study was to determine the effect of accuracy and force level on strategy selection. Ten healthy adults were instructed to generate isometric pulse contractions of the right soleus at 20%, 40%, and 60% of maximum voluntary contraction (MVC) to reach five target sizes of percentage MVC (4%, 8%, 12%, 16%, 20%). The following results were observed: (1) there was no difference in time to peak force, peak dF/dt, slope of force, and electromyographic (EMG) measures between the 12%, 16%, and 20% target sizes; (2) differences were noted, however, between the 12%, 16%, and 20% targets and the smaller targets; (3) for the dependent measures there were significant differences between each force level. No difference between the larger targets implies that subjects do not need to implement a strategy and suggests an upper limit to the dual-strategy hypothesis. The difference between the smaller and larger targets and the difference between the force levels is indicative of an SS strategy. When asked to use different force levels, subjects controlled the rate of rise of force and regulated time to peak force. Between target sizes, force and time were modulated equally.

Intensity pattern of snoring sounds as a predictor for sleep-disordered breathing.

The relationship between a new operational definition of sleep sounds and apnea was examined in a population of 69 patients referred for overnight evaluations in a sleep disorders center. The sample contained 18 women (mean age 53.6 years) and 51 men (mean age 48.4 years). Subjects underwent polysomnography (PSG) with concurrent graphical recording of sleep sound intensities throughout the night. An acoustical signature event (ASE) was defined as a loud sound preceded by at least 10 but no more than 90 seconds of silence. Multiple regression was performed using known correlates of apnea and ASE to predict PSG levels of respiratory disturbance. Of the commonly known correlates, only self-reported estimate of snoring and apnea severity explained significant variance to the respiratory disturbance index (RDI; R2 = 0.24, p < 0.0001). ASE was entered into the equation as the last step, significantly improving explained variance (R2delta = 0.54, p < 0.0001). The final equation R2 was 78% (p < 0.0001). An alternative analysis compared ASE findings to polysomnographic findings in each matched 30-second interval (60,231 observations) in an analysis of receiver's operating characteristics. This analysis resulted in d' = 2.67, indicating acceptable accuracy for screening.

Relationship between motoneuron pool excitability and parameters of timing and force in an isometric ankle-extension movement.

The changes in peak facilitation and slope of facilitation of the H-reflex were compared to the parameters of an isometric plantarflexion task. The amplitude of the reflex was significantly greater for reflexes elicited within 50 msec. of the onset of soleus muscle activity. Neither peak amplitude of the reflex nor slope correlated with rate of rise of isometric force; however, they did show a modest relationship between premotor time and reaction time.

The relation between limb loading and control parameters of gait initiation in persons with stroke.

OBJECTIVE: This study investigated the relation between limb loading and selected characteristics of gait initiation in patients after stroke. SUBJECTS AND SETTING: Thirteen patients attending a rehabilitation clinic volunteered for the study. DESIGN: For the description of clinical features, patients were divided into two groups dependent on the amount of body weight shared by the involved limb during stance before gait initiation. MAIN OUTCOME MEASURES: Patients performed six trials of gait initiation with either their involved or noninvolved limb on a force platform. Peak ground reaction forces and bilateral tibialis anterior and gastrocnemius electromyographic (EMG) activity were used for group comparison. RESULTS: All patients showed the correct loading and unloading characteristics in the vertical and medial-lateral direction during gait initiation. Strong correlations were noted between initial limb loading and ground reaction forces during gait initiation (r = .79 to .95). Changes in ground reaction forces were significantly less (p < .001) for those patients who demonstrated decreased weight bearing on their involved limb before gait initiation. These patients were also unable to generate forward momentum, as evidenced by the fore-aft ground reaction force, with the involved limb. For all patients, increased gastrocnemius activity was noted in the stance (noninvolved) limb. The data are further discussed in regard to the relationship of the interaction of bilateral EMG activity and ground reaction forces. CONCLUSION: This study suggests that there is a correlation between symmetrical weight bearing and the ability to provide those forces that generate forward momentum in the initiation of gait.