1,149 research outputs found
Bilateral and unilateral arm training improve motor function through differing neuroplastic mechanisms: a single-blinded randomized controlled trial
No full textBACKGROUND AND PURPOSE:
This randomized controlled trial tests the efficacy of bilateral arm training with rhythmic auditory cueing (BATRAC) versus dose-matched therapeutic exercises (DMTEs) on upper-extremity (UE) function in stroke survivors and uses functional magnetic resonance imaging (fMRI) to examine effects on cortical reorganization.
METHODS:
A total of 111 adults with chronic UE paresis were randomized to 6 weeks (3×/week) of BATRAC or DMTE. Primary end points of UE assessments of Fugl-Meyer UE Test (FM) and modified Wolf Motor Function Test Time (WT) were performed 6 weeks prior to and at baseline, after training, and 4 months later. Pretraining and posttraining, fMRI for UE movement was evaluated in 17 BATRAC and 21 DMTE participants.
RESULTS:
The improvements in UE function (BATRAC: FM Δ = 1.1 + 0.5, P = .03; WT Δ = -2.6 + 0.8, P < .00; DMTE: FM Δ = 1.9 + 0.4, P < .00; WT Δ = -1.6 + 0.7; P = .04) were comparable between groups and retained after 4 months. Satisfaction was higher after BATRAC than DMTE (P = .003). BATRAC led to significantly higher increase in activation in ipsilesional precentral, anterior cingulate and postcentral gyri, and supplementary motor area and contralesional superior frontal gyrus (P < .05). Activation change in the latter was correlated with improvement in the WMFT (P = .01).
CONCLUSIONS:
BATRAC is not superior to DMTE, but both rehabilitation programs durably improve motor function for individuals with chronic UE hemiparesis and with varied deficit severity. Adaptations in brain activation are greater after BATRAC than DMTE, suggesting that given similar benefits to motor function, these therapies operate through different mechanisms
Characterization of branched ultrahigh molar mass polymers by asymmetrical flow field-flow fractionation and size exclusion chromatography
No full textThe molar mass distribution (MMD) of synthetic polymers is frequently analyzed by size exclusion chromatography (SEC) coupled to multi angle light scattering (MALS) detection. For ultrahigh molar mass (UHM) or branched polymers this method is not sufficient, because shear degradation and abnormal elution effects falsify the calculated molar mass distribution and information on branching. High temperatures above 130 degrees C have to be applied for dissolution and separation of semi-crystalline materials like polyolefins which requires special hardware setups. Asymmetrical flow field-flow fractionation (AF4) offers the possibility to overcome some of the main problems of SEC due to the absence of an obstructing porous stationary phase. The SEC-separation mainly depends on the pore size distribution of the used column set. The analyte molecules can enter the pores of the stationary phase in dependence on their hydrodynamic volume. The archived separation is a result of the retention time of the analyte species inside SEC-column which depends on the accessibility of the pores, the residence time inside the pores and the diffusion ability of the analyte molecules. The elution order in SEC is typically from low to high hydrodynamic volume. On the contrary AF4 separates according to the diffusion coefficient of the analyte molecules as long as the chosen conditions support the normal FFF-separation mechanism. The separation takes place in an empty channel and is caused by a cross-flow field perpendicular to the solvent flow. The analyte molecules will arrange in different channel heights depending on the diffusion coefficients. The parabolic-shaped flow profile inside the channel leads to different elution velocities. The species with low hydrodynamic volume will elute first while the species with high hydrodynamic volume elute later. The AF4 can be performed at ambient or high temperature (AT-/HT-AF4). We have analyzed one low molar mass polyethylene sample and a number of narrow distributed polystyrene standards as reference materials with known structure by AT/HT-SEC and AT/HT-AF4. Low density polyethylenes as well as polypropylene and polybutadiene, containing high degrees of branching and high molar masses, have been analyzed with both methods. As in SEC the relationship between the radius of gyration (R(g)) or the molar mass and the elution volume is curved up towards high elution volumes, a correct calculation of the MMD and the molar mass average or branching ratio is not possible using the data from the SEC measurements. In contrast to SEC. AF4 allows the precise determination of the MMD, the molar mass averages as well as the degree of branching because the molar mass vs. elution volume curve and the conformation plot is not falsified in this technique. In addition, higher molar masses can be detected using HT-AF4 due to the absence of significant shear degradation in the channel. As a result the average molar masses obtained from AF4 are higher compared to SEC. The analysis time in AF4 is comparable to that of SEC but the adjustable cross-flow program allows the user to influence the separation efficiency which is not possible in SEC without a costly change of the whole column combination. (C) 2011 Elsevier B.V. All rights reserved.BMBF [03X2006]; Basell Polyolefins (Frankfurt, Germany
Exploration of the effect of 2,6-(t-Bu)2-4-Me-C6H2OH (BHT) in chain shuttling polymerization
No full textThe interactions of a sterically hindered phenol [2,¿6-¿(t-¿Bu)¿2-¿4-¿Me-¿C6H2OH] (BHT) with the scavenger MAO (AlR3) and ZnR2 during Hf¿/Zr-¿based chain shuttling polymn. in a semi-¿batch reactor have been investigated. NMR model studies indicated preferential binding of BHT to aluminum under these conditions. Subsequently, reproducible polymn. runs gave rise to copolymers that were thoroughly characterized by HT-¿SEC, HT-¿HPLC, DSC, thermal fractionation (SSA)¿, 13C NMR, d. measurements, CRYSTAF and optical microscopy to unravel their complex microstructures. The obtained materials differ from a simple soln. blend of materials, sep. produced by single catalysts, but also from multi-¿block copolymers as obtained by DOW's continuous process, although a blocky structure can be rationalized
THE FANTASIO SET-UP (II): HIGH RESOLUTION OVERTONE SPECTROSCOPY OF ACETYLENE CONTAINING VAN DER WAALS DIMERS
No full textC. Lauzin, K. Didriche, P. Macko, J. Demaison, J. Lievin, and M. Herman, J. Phys. Chem. A, in press (2009).C. Lauzin, K. Didriche, J. Lievin, M. Herman, and A. Perrin, J. Chem. Phys, submitted (2009).K. Didriche, C. Lauzin, P. Macko, M. Herman, and W.J. Lafferty, Chem. Phys. Letters, doi:10.1016/j.cplett.2008.12.037 (2008).Author Institution: Service de Chimie quantique et Photophysique CP160/09, Faculte des Sciences, Universite; Libre de Bruxelles (U.L.B.), Av. Roosevelt, 50, B-1050, Bruxelles, Belgium; Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA) CNRS-UMR 7583 Universite; Paris Est et Paris 7, Faculte des Sciences et Technologie, 61, avenue du General de Gaulle; 94010 Creteil Cedex, France; Optical Technology Division, National; Institute for Standards and Technology, Gaithersburg, MD 20899-8441, USAWe have used the CW-CRDS facility in the FANTASIO set-up described in the previous presentation to investigate acetylene-containing dimers formed in a supersonic expansion, in the 1.5 microns range. Ab initio calculations were also performed in some cases. The acetylene partners so far include argon, carbon dioxide and nitrous oxide. The results will be illustrated
Synthesis and characterization of iPP-sPP stereoblock produced by a binary metallocene system
No full textStereoblock polypropylenes comprising of iPP and sPP segments are synthesized by polymerization of the following binary system of metallocenes: the Cs-symmetric [2,7-t-Bu2(Flu)2Ph2C(Cp)ZrCl2] and the C2-symmetric rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2. Blends of samples made either by each catalyst individually (solution blend) with materials obtained with the mixed catalyst system (reactor blend) are compared. The simultaneous presence of MAO and DEZ, enhancing fast and reversible transfer of the growing chains between the two active centers, leads to the formation of a stereoblock microstructure. In this case, low molecular weight polymers are obtained. The junction between the blocks is qualitatively observed in 13C NMR. When made in toluene, the stereoblock material consists of a majority of syndiotactic sequences, whereas the ratio is more equilibrated when the polymerization was conducted in the more polar chlorobenzene. This is confirmed by the results obtained with 13C NMR, CRYSTAF, HT HPLC, DSC, SSA, WAXD, and optical microscopy
Psychic Transformation: One Woman\u27s Journey
No full textThe author discusses the role of the unconscious in the production of her artwork
The block structure spaces of real projective spaces and orthogonal calculus of functors
No full textImproved hemiparetic muscle activation in treadmill versus overground walking
No full textObjective: treadmill training is a promising tool for retraining gait after stroke. The treadmill induces an immediate shift toward symmetry and longer paretic stance times due to altered muscle activation (active) or the motorized belt (passive). The authors investigated vastus lateralis and medial hamstrings activation differences between treadmill and overground walking in participants with stroke.Methods: vastus lateralis and medial hamstrings surface electromyography was recorded during velocity-matched overground and treadmill walking in 19 chronically hemiparetic subjects. Variables from ensemble averages of electromyography included burst onset and offset times (% cycle), duration (% cycle), integrated amplitude (mV.% cycle), and onset relative to foot strike (% cycle). Conditions were compared using paired t-tests (alpha = 0.05).Results: paretic vastus lateralis onset occurred earlier in the treadmill condition (overground: 47.1%, treadmill: 41.9%, P = 0.01). For nonparetic vastus lateralis in the treadmill condition, onset occurred later (overground: 85.2%, treadmill: 87.6%, P = 0.09), offset occurred earlier (overground: 54.7%, treadmill: 47.8%, P = 0.03), duration was shorter (overground: 69.1%, treadmill: 61.2%, P = 0.01), and integrated amplitude was lower (overground: 14.1, treadmill: 10.6, P = 0.05). Within limbs, paretic vastus lateralis onset occurred earlier relative to paretic foot strike. Nonparetic vastus lateralis onset occurred later relative to nonparetic foot strike.Conclusions: treadmill walking induces immediate changes in vastus lateralis, but not medial ham-strings, activation patterns. These alterations (earlier paretic vastus lateralis onset and later nonparetic vastus lateralis onset) during treadmill versus overground walking parallel the increased symmetry in gait patternin
Fibrinolytic responses to acute physical activity in older hypertensive men
No full textDeSouza, Christopher A., Donald R. Dengel, Marc A. Rogers, Kim Cox, and Richard F. Macko. Fibrinolytic responses to acute physical activity in older hypertensive men. J. Appl. Physiol. 82(6): 1765–1770, 1997.—We tested the hypothesis that the fibrinolytic response to acute physical activity is impaired in sedentary older hypertensive men, which may contribute to the risk of exertion-triggered acute myocardial infarction in this population. Tissue-type plasminogen activator (t-PA) antigen and activity and plasminogen activator inhibitor-1 (PAI-1) antigen and activity were measured in 12 hypertensive (69 ± 1 yr) and 11 normotensive (64 ± 1 yr) men before and after an acute bout of submaximal exercise. Contrary to our hypothesis, there were no differences between the two groups in the fibrinolytic response to exercise. t-PA antigen and activity were significantly elevated in both the hypertensive (38 and 172%, respectively) and normotensive (45 and 130%, respectively) groups immediately after exercise but they returned to resting levels within 30 min. There was no change in PAI-1 antigen levels immediately after exercise in either group; however, PAI-1 antigen was significantly lower at 30 and 60 min postexercise in both the hypertensive (31 and 16%, respectively) and normotensive (35 and 20%, respectively) groups. PAI-1 activity was significantly lower immediately after exercise in both the hypertensive (25%) and normotensive (22%) groups and remained lower than preexercise levels at 30 min (23 and 26%, respectively) and 60 min (16 and 12%, respectively) postexercise in both groups. The results of this study demonstrate that the fibrinolytic response to an acute bout of moderate physical activity is not impaired in sedentary older hypertensive men.</jats:p
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