Classroom composition, classroom quality and German skills of very young dual language learners and German-only learners

This study examined associations between the classroom percentage of dual language learners (DLLs), observed classroom quality, and children's German majority language skills. The cross-sectional sample of 2.5 years olds (n = 93 immigrant DLLs and n = 363 monolingual German-only learners) was clustered within n = 197 classrooms. Classrooms with higher percentages of DLLs demonstrated slightly lower levels of overall classroom process quality. DLLs scored about 1 SD below monolingual children on German language skills when adjusting for family and classroom covariates. Moderation analyses revealed that this difference did not depend on the percentage of DLLs in a classroom. In fact, the classroom percentage of DLLs was related to children's German skills only when omitting the child level language status (DLL vs. monolingual) from the analyses. However, classroom quality moderated the difference between DLLs’ and monolingual children's German skills. This difference was estimated as about only 0.5 SD for DLLs and monolingual children experiencing higher classroom quality, but as about 1.5 SD for those experiencing lower quality. We conclude that high quality classrooms may promote the majority language skills of DLLs

Retention of gait stability improvements over 1.5 years in older adults:effects of perturbation exposure and triceps surae neuromuscular exercise

The plantarflexors play a crucial role in recovery from sudden disturbances to gait. The objective of this study was to investigate whether medium (months)- or long(years)-term exercise-induced enhancement of triceps surae (TS) neuromuscular capacities affects older adults' ability to retain improvements in reactive gait stability during perturbed walking acquired from perturbation training sessions. Thirty-four adult women (65 +/- 7 yr) were recruited to a perturbation training group (n = 13) or a group that additionally completed 14 wk of TS neuromuscular exercise (n = 21), 12 of whom continued with the exercise for 1.5 yr. The margin of stability (MoS) was analyzed at touchdown of the perturbed step and the first recovery step following eight separate unexpected trip perturbations during treadmill walking. TS muscle-tendon unit mechanical properties and motor skill performance were assessed with ultrasonography and dynamometry. Two perturbation training sessions (baseline and after 14 wk) caused an improvement in the reactive gait stability to the perturbations (increased MoS) in both groups. The perturbation training group retained the reactive gait stability improvements acquired over 14 wk and over 1.5 yr. with a minor decay over time. Despite the improvements in TS capacities in the additional exercise group. no benefits for the reactive gait stability following perturbations were identified. Therefore, older adults' neuromotor system shows rapid plasticity to repeated unexpected perturbations and an ability to retain these adaptations in reactive gait stability over a long time period, but an additional exercise-related enhancement of TS capacities seems not to further improve these effects. NEW & NOTEWORTHY Older adults' neuromotor system shows rapid plasticity to repeated exposure to unexpected perturbations to gait and an ability to retain the majority of these adaptations in reactive recovery responses over a prolonged time period of 1.5 yr. However, an additional exercise-related enhancement of TS neuromuscular capacities is not necessarily transferred to the recovery behavior during unexpected perturbations to gait in older adults

Differential Geometry applied to Acoustics : Non Linear Propagation in Reissner Beams

Although acoustics is one of the disciplines of mechanics, its "geometrization" is still limited to a few areas. As shown in the work on nonlinear propagation in Reissner beams, it seems that an interpretation of the theories of acoustics through the concepts of differential geometry can help to address the non-linear phenomena in their intrinsic qualities. This results in a field of research aimed at establishing and solving dynamic models purged of any artificial nonlinearity by taking advantage of symmetry properties underlying the use of Lie groups. The geometric constructions needed for reduction are presented in the context of the "covariant" approach.Comment: Submitted to GSI2013 - Geometric Science of Informatio

Effect Of Triceps Surae Muscle-Tendon Unit Mechanical Properties On Gait Stability And Adaptability In Older Female Adults

INTRODUCTION Ageing induces a gradual degradation in the human neuro-motor system resulting in decreased mobility and locomotor performance (Beijersbergen et al., 2013). Moreover, inadequate recovery responses following tripping have been associated with age-related deteriorations in ankle plantar flexion moment output (magnitude and rate) in the push-off phase (Pijnappels et al., 2004). Therefore, the objective of this study was (1) to examine if gait stability and adaptability during perturbed walking is associated with TS muscle strength and Achilles tendon (AT) stiffness in older female adults, and (2) to determine whether elderly with different TS muscle strength capacities show an altered dynamic stability control during perturbed walking, and (3) whether gait plasticity is preserved in old age. METHODS Thirty-four older female adults (65±7yrs) experienced unexpected trip perturbations to the swing phase of the right leg while walking on a treadmill (Süptitz et al., 2013). Using a motion capture system (VICON; Oxford, UK) the margin of stability (MoS) and base of support (BoS) were assessed at touchdown (TD) of the perturbed leg and at each following six recovery steps. In order to examine the reactive adaptation potential, the MoS at TD of the perturbed leg was examined in eight unexpected perturbation trials. In an additional session, TS muscle strength and AT stiffness were determined using simultaneous ultrasonography and dynamometry. Pearson correlations were used to inspect the relationship between TS MTU mechanical properties and dynamic stability parameters (both MoS and BoS) of the recovery steps in first perturbation trial. A median split was implemented to classify the subjects into two groups based on their TS muscle strength (strong: n = 16; weak: n = 18). RESULTS The strong group had about 42% higher voluntary isometric plantarflexion moments and 33% higher AT stiffness than the weak group (138±22Nm vs. 97±10Nm; 588±156Nmm-1 vs. 441±129Nmm-1; p<0.01). The gait perturbation reduced the MoS at TD of the perturbed leg (-0.10±0.08m) compared to baseline unperturbed walking, indicating instability. The strong group needed three recovery steps to return to MoS baseline and the weak group was unable to return to baseline level within the analysed six recovery steps. Significant correlations between both TS muscle strength and AT stiffness, and MoS and BoS at TD of the first recovery step were found (0.41<r<0.68; p<0.05). After eight gait perturbations, both groups were able to adapt their reactive response to the perturbation (increasing MoS at TD), with no between-group differences. DISCUSSION The current data suggest that TS muscle strength and AT stiffness partly limit dynamic gait stability control after an unexpected perturbation during walking in older female adults. Recovery stepping behaviour seems to be less effective in weaker older adults, which is explained mainly by the reduced ability to effectively increase the BoS after perturbations. However, independent of TS MTU mechanical properties, older adults seem to be able to improve their reactive response. CONCLUSION TS MTU mechanical properties partly limit dynamic stability during perturbed walking in older adults, but they preserve their gait plasticity independent of their TS muscle strength. Thus, in order to reduce falls risk, older adults may benefit from interventions increasing TS muscle strength and tendon stiffness, and by improving reactive recovery responses via repeated gait perturbations. REFERENCES Beijersbergen et al., (2013). Ageing Res Rev. 12, 618-27. doi:10.1016/j.arr.2013.03.001 Pijnappels et al., (2004). J Biomech. 37, 1811-18. doi:10.1016/j.jbiomech.2004.02.038 Süptitz et al., (2013). Hum Mov Sci 32, 1404-14. doi:10.1016/j.humov.2013.07.00

Quantification of magnetic force microscopy images using combined electrostatic and magnetostatic imaging

A method for calibrating the force gradients and probe magnetic moment in phase-contrast magnetic force microscopy ~MFM! is introduced. It is based upon the combined electrostatic force microscopy EFM and MFM images of a conducting non magnetic metal strip. The behavior of the phase contrast in EFM is analyzed and modeled as a finite area capacitor. This model is used in conjunction with the imaging data to derive the proportionality constant between the phase and the force gradient. This calibration is further used to relate the measured MFM images with the field gradient from the same conducting strip to derive the effective magnetic moment of the probe. The knowledge of the phase-force gradient proportionality constant and the probe’s effective moment is essential to directly quantify field derivatives in MFM images

Is adenomyosis the neglected phenotype of an endomyometrial dysfunction syndrome?

Since the dissociation between adenomyoma and endometriosis in the 1920s and the laparoscopic progress in the diagnosis and surgery of endometriosis, the literature has been greatly focused on the disease endometriosis. The study of adenomyosis, on the other hand, has been neglected as the diagnosis remained based on hysterectomy specimens. However, since the introduction of magnetic resonance and sonographic imaging techniques in the 1980s, the myometrial junctional zone has been identified as a third uterine zone and interest in adenomyosis was renewed. This has also been the start for the interest in the role of the myometrial junctional zone dysfunction and adenomyosis in reproductive and obstetrical disorders