Effect of Sensory Feedback from the Proximal Upper Limb on Voluntary Isometric Finger Flexion and Extension in Hemiparetic Stroke Subjects

This study investigated the potential influence of proximal sensory feedback on voluntary distal motor activity in the paretic upper limb of hemiparetic stroke survivors and the potential effect of voluntary distal motor activity on proximal muscle activity. Ten stroke subjects and 10 neurologically intact control subjects performed maximum voluntary isometric flexion and extension, respectively, at the metacarpophalangeal (MCP) joints of the fingers in two static arm postures and under three conditions of electrical stimulation of the arm. The tasks were quantified in terms of maximum MCP torque [MCP flexion (MCPflex) or MCP extension (MCPext)] and activity of targeted (flexor digitorum superficialis or extensor digitorum communis) and nontargeted upper limb muscles. From a previous study on the MCP stretch reflex poststroke, we expected stroke subjects to exhibit a modulation of voluntary MCP torque production by arm posture and electrical stimulation and increased nontargeted muscle activity. Posture 1 (flexed elbow, neutral shoulder) led to greater MCPflex in stroke subjects than posture 2 (extended elbow, flexed shoulder). Electrical stimulation did not influence MCPflex or MCPext in either subject group. In stroke subjects, posture 1 led to greater nontargeted upper limb flexor activity during MCPflex and to greater elbow flexor and extensor activity during MCPext. Stroke subjects exhibited greater elbow flexor activity during MCPflex and greater elbow flexor and extensor activity during MCPext than control subjects. The results suggest that static arm posture can modulate voluntary distal motor activity and accompanying muscle activity in the paretic upper limb poststroke

Modulation of Stretch Reflexes of the Finger Flexors by Sensory Feedback from the Proximal Upper Limb Poststroke

Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, namely static arm posture (3 different shoulder/elbow postures) and electrical stimulation (surface stimulation of biceps brachii or triceps brachii, or none). Fast (300°/s) imposed stretch elicited stretch reflex flexion torque at the MCP joints and reflex electromyographic (EMG) activity in flexor digitorum superficialis. Both measures were greatest in an arm posture of 90° of elbow flexion and neutral shoulder position. Biceps stimulation resulted in greater MCP stretch reflex flexion torque. Fast imposed stretch also elicited reflex EMG activity in nonstretched heteronymous upper limb muscles, both proximal and distal. These results suggest that in the spastic hemiparetic upper limb poststroke, sensorimotor coupling of proximal and distal upper limb segments is involved in both the increased stretch reflex response of the finger flexors and an increased reflex coupling of heteronymous muscles. Both phenomena may be mediated through changes poststroke in the spinal reflex circuits and/or in the descending influence of supraspinal pathways

Desarrollo de un guante ortótico para proveer asistencia en la extensión de los dedos a pacientes que han sufrido derrame cerebral

An externally actuated glove, controlled by a microprocessor, is being developed to assist fi nger extension in stroke survivors. The goal of this device is to allow repeated practice of specifi c tasks for hand therapy in the home environment. The device allows the user three control modes: voice recognition, electromyography or manual. These modes can be used either independently or combined according to the needs of the user. Both position and force feedback are available for control and safety. Initial testing of the prototype has shown promising performance.Se presenta el desarrollo de un guante activado externamente y controlado por un microprocesador para asistir la extensión de los dedos en pacientes con derrame cerebral. La meta del dispositivo es permitir la repetición de tareas específi cas para realizar terapia de la mano en un ambiente casero. El usuario puede controlar el dispositivo por tres medios diferentes: reconocimiento de voz, electromiografía o manualmente. Estos medios pueden ser usados tanto independientemente como en combinación según las necesidades del paciente. Para el control y la seguridad, se tiene retroalimentación de posición y de fuerza. Las pruebas iniciales del prototipo han demostrado un desempeño prometedo

Superconduction thin films

Superconduction thin films, and properties and applications of Josephson effect at radio frequencie

Are the orthostatic fluid shifts to the calves augmented in autonomic failure?

In autonomic failure (AF), blood pressure (BP) falls upon standing which is commonly ascribed to defective vasoconstriction and excessive pooling. Observations on the amount of pooling in AF are contradictory. We evaluated pooling using strain-gauge plethysmography (SGP) during head-up tilt (HUT) with a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs and thus to maximise pooling. 23 healthy subjects and 12 patients with AF were tilted for 5 min. BP and calf volume changes, as measured by SGP, were measured continuously. Multiple regression analysis was used to examine the effect of AF on orthostatic fluid shifts after adjustment for potential confounders. Patients did not differ from controls with respect to the increase of calf volume after 5 min HUT. The acute (0-1 min) and the prolonged (1-5 min) phases of calf volume responses to HUT were also similar between patients and controls. No correlation was found between the degree of orthostatic hypotension and the orthostatic calf volume change in AF. In one patient an additional measurement was made before rising from bed in the early morning demonstrating a greater albeit small increase of calf volume upon HUT. Orthostatic fluid shifts at the level of the calf in AF are not augmented during the course of the day despite marked hypotension. However, a small increase of pooling may be expected when the patient first gets out of bed in the morning probably due to the absence of oedema.Paroxysmal Cerebral Disorder

The career orientation of final year teacher training students

The research was prompted by the assumption that the many problems in South African education (e.g. continuous curiculum changes, insufficient in-service training and support, classroom overcrowding, discipline problems,administrative paperwork, low teacher morale, high teacher attrition rate, low societal status of the teaching profession) must have an adverse effect on the career orientation of teacher training students. Our research was embedded in the theoretical framework of eco-systemic theory (Bronfenbrenner 1990), through which we indicated how the teacher is surrounded and influenced by various societal systems in four levels of proximity: the micro, meso, exo and macro levels. From these systems we established the conceptual framework, in which we discussed negative forces on the teacher as these are eminent in societal expectations about the teacher, the professional identity of the teacher and the retention rate in the teaching profession. The discussion of these negative forces and their impact affirmed our initial assumption and led to our research question: To what extent are teaching training students positively inclined towards a career in teaching? This question implied attention to a) the career motivation, and b) the moral values of the modern South African teaching training student. The empirical study was conceptualised as a pilot project. We involved the full number of final year teaching training students at one of the largest education faculties in South Africa, namely at the University of Pretoria. The students (n = 403) were asked to complete a questionnaire which focused inter alia on respondents’ exposure to daily news, reasons for choosing the education career path, attitudes towards the teaching profession and medium to long term prospects in the profession. Moral inclinations were also probed, e.g. with items on religion, discipline, language of instruction, multicultural teaching and being a role model. The questionnaire findings were verified in a focus group interview with five purposively selected respondents in the questionnaire survey. Our findings nullified our initial assumptions. Not only were the students strongly committed to their chosen career, notwithstanding the questionable societal status of the teaching profession and the formidable teaching challenges (of which they were apparently keenly aware), but they also conveyed a strong message about moral values and the teacher’s role in modelling those in and beyond the school. Our findings are prospective and certainly need verification on a broader scale. We are also planning a follow-up study with the same respondents, once they have completed two years of full time teaching. The findings could serve as impetus for education management measures to ensure that aspiring teachers’ level of commitment is sustainable. One of these measures could be an online advice and counselling service for beginner teachers.Die navorsing het ontstaan uit die aanname dat die onderwysproblematiek in Suid-Afrika (voortdurende kurrikulumwysigings, gebrekkige indiensopleiding, dissiplineprobleme, lae beroepsmotivering onder onderwysers en gebrekkige aansien van die onderwysberoep) ’n negatiewe uitwerking op die beroepsinstelling van onderwysstudente het. Vanuit die teoretiese raamwerk wat gebruik is, naamlik Bronfenbrenner (1990) se ekosistemiese samelewingsmodel, is die negatiewe kragte wat op die onderwys inwerk, nader toegelig. In die lig van die intensiteit van hierdie kragte het die volgende as navorsingsvraag gedien: In welke mate het die huidige onderwysstudent ’n positiewe beroepsingesteldheid? In ’n vraelysopname onder 403 finalejaar onderwysstudente, is die aanvanklike aanname verkeerd bewys. Die vraelysrespondente was nie alleen positief ingestel teenoor hul toekomstige loopbaan in die onderwys nie, maar hulle was ook uitgesproke oor hul taak daarin as morele rolmodelle. Die positiewe aard van ons voorlopige bevindings onderstreep alreeds die absolute noodsaaklikheid van onderwysbestuursmaatreëls om die volhoubaarheid van beginneronderwysers se positiewe beroepsingesteldheid te verseker. ’n Elektroniese advies- en motiveringsdiens vir beginneronderwysers kan heel moontlik as eerste en uitvoerbare projek hiertoe dien.http://www.journals.co.za/ej/ejour_akgees.htmlgv201

Polaris B, an optical companion of Polaris (alpha UMi) system: atmospheric parameters, chemical composition, distance and mass

We present an analysis of high-resolution spectroscopic observations of Polaris B, the optical companion of the Polaris Ab system. The star has a radial velocity V_r of -16.6km/s to -18.9km/s, and a projected rotational velocity vsini=110 km/s. The derived atmospheric parameters are: Teff=6900K; logg=4.3; V_t=2.5km/s. Polaris B has elemental abundances generally similar to those of the Cepheid Polaris A (Usenko et al. 2005a), although carbon, sodium and magnesium are close to the solar values. At a spectral type of F3V Polaris B has a luminosity of 3.868L_sun, an absolute magnitude of +3.30mag, and a distance of 109.5pc. The mass of the star is estimated to be 1.39M_sun, close to a mass of 1.38+/-0.61M_sun for the recently-resolved orbital periods companion Polaris Ab observed by Evans et al. (2007).Comment: 6 pages, 3 figures, 1 tabl

Polaris the Cepheid returns: 4.5 years of monitoring from ground and space

We present the analysis of 4.5 years of nearly continuous observations of the classical Cepheid Polaris, which comprise the most precise data available for this star. We have made spectroscopic measurements from ground and photometric measurements from the WIRE star tracker and the SMEI instrument on the Coriolis satellite. Measurements of the amplitude of the dominant oscillation (P = 4 days), that go back more than a century, show a decrease from 120 mmag to 30 mmag (V magnitude) around the turn of the millennium. It has been speculated that the reason for the decrease in amplitude is the evolution of Polaris towards the edge of the instability strip. However, our new data reveal an increase in the amplitude by about 30% from 2003-2006. It now appears that the amplitude change is cyclic rather than monotonic, and most likely the result of a pulsation phenomenon. In addition, previous radial velocity campaigns have claimed the detection of long-period variation in Polaris (P > 40 days). Our radial velocity data are more precise than previous datasets, and we find no evidence for additional variation for periods in the range 3-50 days with an upper limit of 100 m/s. However, in the WIRE data we find evidence of variation on time-scales of 2-6 days, which we interpret as being due to granulation.Comment: Accepted by ApJ. 8 pages. Quality of figures 1+3+7 degrade

Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope

Polaris, the nearest and brightest classical Cepheid, is a single-lined spectroscopic binary with an orbital period of 30 years. Using the High Resolution Channel of the Advanced Camera for Surveys onboard the Hubble Space Telescope (HST) at a wavelength of ~2255\AA, we have directly detected the faint companion at a separation of 0\farcs17. A second HST observation 1.04 yr later confirms orbital motion in a retrograde direction. By combining our two measures with the spectroscopic orbit of Kamper and an analysis of the Hipparcos and FK5 proper motions by Wielen et al., we find a mass for Polaris Aa of 4.5^{+2.2}_{-1.4} M_\odot--the first purely dynamical mass determined for any Cepheid. For the faint companion Polaris Ab we find a dynamical mass of 1.26^{+0.14}_{-0.07} M_\odot, consistent with an inferred spectral type of F6 V and with the flux difference of 5.4 mag observed at 2255\AA. The magnitude difference at the V band is estimated to be 7.2 mag. Continued HST observations will significantly reduce the mass errors, which are presently still too large to provide critical constraints on the roles of convective overshoot, mass loss, rotation, and opacities in the evolution of intermediate-mass stars. Our astrometry, combined with two centuries of archival measurements, also confirms that the well-known, more distant (18") visual companion, Polaris B, has a nearly common proper motion with that of the Aa,Ab pair. This is consistent with orbital motion in a long-period bound system. The ultraviolet brightness of Polaris B is in accordance with its known F3 V spectral type if it has the same distance as Polaris Aa,Ab.Comment: 31 pages, 12 figures, 6 tables; accepted for publication in the Astronomical Journa

Mg II h + k emission lines as stellar activity indicators of main sequence F-K stars

The main purpose of this study is to use the IUE spectra in the analysis of magnetic activity of main sequence F-K stars. Combining IUE observations of MgII and optical spectroscopy of Ca II, the registry of ctivity of stars can be extended in time. We retrieved all the high-resolution spectra of F, G, and K main sequence stars observed by IUE (i.e. 1623 spectra of 259 F to K dwarf stars). We obtained the continuum surface flux near the Mg II h+k lines near 2800 \AA and the MgII line-core surface flux from the IUE spectra. We obtained a relation between the mean continuum flux near the MgII lines with the colour $B-V$ of the star. For a set of 117 nearly simultaneous observations of Mg II and Ca II fluxes of 21 F5 to K3 main sequence stars, we obtained a colour dependent relation between the Mount Wilson CaII S-index and the MgII emission line-core flux. As an application of this calibration, we computed the Mount Wilson index for all the dF to dK stars which have high resolution IUE spectra. For some of the most frequently observed main sequence stars, we analysed the Mount Wilson index S from the IUE spectra, together with the ones derived from visible spectra. We confirm the cyclic chromospheric activity of epsilon Eri (HD 22049) and beta Hydri (HD 2151), and we find a magnetic cycle in alpha Cen B (HD 128621). Complete abstract in the paper.Comment: 10 pages, accepted for publication in Astronomy and Astrophysic