Potential Application of the Modulated Scatterer Technique to Multilayered Material Evaluation and Health Monitoring

Modulated scatterer technique (MST) is based on illuminating a small antenna, usually a dipole, loaded with a PIN diode, with an electromagnetic wave. The scattered (or reflected) wave from the probe may then be used to determine dielectric properties of the material in which the probe is located or embedded. The PIN diode is turned on and off which not only changes the impedance of the probe, but also modulates (with the same rate) the reflection from the probe. A major challenge associated with MST is detecting and distinguishing the desired probe response in the ever-present reflections from surrounding structures and materials. This challenge can be overcome by incorporating a swept-frequency method into the measurements. A swept-frequency technique allows the use of the Fourier Transform method which results in separate detection of the reflection from the probe (similar to pulsed methods). Having the ability to discriminate the probe response renders the MST technique useful for multilayer structure applications as well. The probe can be placed in a given layer of a material, and the properties of that layer can be monitored (regardless of the presence of other layers). Additionally, the probe can be placed at an interface and changes in that interface (such as disbonding) can be detected. The ratio of the reflection from a probe, between the on and off states, has been shown to be a unique technique for evaluating properties of materials. This paper presents the basis and some results of applying swept-frequency MST for inspecting layered materials

Concurrent anodal transcranial direct-current stimulation and motor task to influence sensorimotor cortex activation

Functional targeting with anodal high-definition transcranial direct current stimulation (HD-atDCS) of involved brain areas during performance of a motor task (online) may facilitate sensorimotor cortex neuroplasticity compared to performing the motor task after HD-atDCS (offline). The aim of this study was to employ functional near-infrared spectroscopy to compare the time course of motor task-related changes in sensorimotor cortex activation between online and offline HD-atDCS. We hypothesized that online HD-atDCS would have a greater effect on task-related sensorimotor cortex activation than offline HD-atDCS. In a within-subject sham controlled and randomized study design, 9 healthy participants underwent 3 HD-atDCS sessions (online, offline and sham) targeting the left sensorimotor cortex separated by 1 week. Functional near-infrared spectroscopy hemodynamic changes were measured from the left sensorimotor cortex during a simple finger opposition motor task before (Pre), immediately (T1) and 30 min after (T2) each session. The movement rates were not different between (online, offline, sham) or within (Pre, T1, T2) sessions. At T2, online HD-atDCS was associated with a significant increase (large effect size) in sensorimotor cortex activation (Hedges g = 1.01, p<0.001) when compared to sham; there was a nonsignificant trend to increase activation between offline and sham (Hedges g = 0.52, p=0.05) and between online and offline (Hedges g = 0.53, p=0.06). Concurrent application of HD-atDCS during a motor task may produce larger sensorimotor cortex activation than sequential application

Whole blood coagulation and platelet activation in the athlete: A comparison of marathon, triathlon and long distance cycling

<p>Abstract</p> <p>Introduction</p> <p>Serious thrombembolic events occur in otherwise healthy marathon athletes during competition. We tested the hypothesis that during heavy endurance sports coagulation and platelets are activated depending on the type of endurance sport with respect to its running fraction.</p> <p>Materials and Methods</p> <p>68 healthy athletes participating in marathon (MAR, running 42 km, n = 24), triathlon (TRI, swimming 2.5 km + cycling 90 km + running 21 km, n = 22), and long distance cycling (CYC, 151 km, n = 22) were included in the study. Blood samples were taken before and immediately after completion of competition to perform rotational thrombelastometry. We assessed coagulation time (CT), maximum clot firmness (MCF) after intrinsically activation and fibrin polymerization (FIBTEM). Furthermore, platelet aggregation was tested after activation with ADP and thrombin activating peptide 6 (TRAP) by using multiple platelet function analyzer.</p> <p>Results</p> <p>Complete data sets were obtained in 58 athletes (MAR: n = 20, TRI: n = 19, CYC: n = 19). CT significantly decreased in all groups (MAR -9.9%, TRI -8.3%, CYC -7.4%) without differences between groups. In parallel, MCF (MAR +7.4%, TRI +6.1%, CYC +8.3%) and fibrin polymerization (MAR +14.7%, TRI +6.1%, CYC +8.3%) were significantly increased in all groups. However, platelets were only activated during MAR and TRI as indicated by increased AUC during TRAP-activation (MAR +15.8%) and increased AUC during ADP-activation in MAR (+50.3%) and TRI (+57.5%).</p> <p>Discussion</p> <p>While coagulation is activated during physical activity irrespective of type we observed significant platelet activation only during marathon and to a lesser extent during triathlon. We speculate that prolonged running may increase platelet activity, possibly, due to mechanical alteration. Thus, particularly prolonged running may increase the risk of thrombembolic incidents in running athletes.</p

Work in Progress -- Instrumentation on a Truss Adapted for Pre-College Outreach

Engineering content is a valuable addition to pre-college instruction in science, technology, engineering, and mathematics (STEM) since it applies scientific concepts, illustrates scientific relevance and technology, and provides measurement opportunities. Also, complex systems and interactions can be shown. This work describes outreach resources using a seven-member instrumented truss apparatus. This aluminum bench-top model is scaled to support up to fifty pounds. Electrical resistance gauges are installed on several members for strain measurement. The resource set includes the truss apparatus, instrumentation, a PowerPoint presentation, and a background document. The pre-college objective is a set of demonstration resources for middle or high school classrooms. Effective outreach design is modeled by tailoring to accommodate curriculum standards, level-appropriate concept terms, and grade continuity. The resources were developed by students in an interdisciplinary college class on sensors and structures. The development activities involved testing the models and measurements and refining the construction. Selected resources were implemented and evaluated in a local middle school classroom. The interdisciplinary content includes structural, force analysis, sensing, and measurement components

Performance of the EUDET-type beam telescopes

Test beam measurements at the test beam facilities of DESY have been conducted to characterise the performance of the EUDET-type beam telescopes originally developed within the EUDET project. The beam telescopes are equipped with six sensor planes using MIMOSA26 monolithic active pixel devices. A programmable Trigger Logic Unit provides trigger logic and time stamp information on particle passage. Both data acquisition framework and offline reconstruction software packages are available. User devices are easily integrable into the data acquisition framework via predefined interfaces. The biased residual distribution is studied as a function of the beam energy, plane spacing and sensor threshold. Its standard deviation at the two centre pixel planes using all six planes for tracking in a 6\,GeV electron/positron-beam is measured to be (2.88\,\pm\,0.08)\,\upmu\meter.Iterative track fits using the formalism of General Broken Lines are performed to estimate the intrinsic resolution of the individual pixel planes. The mean intrinsic resolution over the six sensors used is found to be (3.24\,\pm\,0.09)\,\upmu\meter.With a 5\,GeV electron/positron beam, the track resolution halfway between the two inner pixel planes using an equidistant plane spacing of 20\,mm is estimated to (1.83\,\pm\,0.03)\,\upmu\meter assuming the measured intrinsic resolution. Towards lower beam energies the track resolution deteriorates due to increasing multiple scattering. Threshold studies show an optimal working point of the MIMOSA26 sensors at a sensor threshold of between five and six times their RMS noise. Measurements at different plane spacings are used to calibrate the amount of multiple scattering in the material traversed and allow for corrections to the predicted angular scattering for electron beams

Ipsilateral M1 transcranial direct current stimulation increases excitability of the contralateral M1 during an active motor task: Implications for stroke rehabilitation

IntroductionAnodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits an increase in cortical excitability that outlasts the period of stimulation. However, little is known about effects of a-tDCS on the contralateral M1 during and after ipsilateral M1 stimulation. Therefore, we investigated the changes in corticospinal excitability and inhibition of the left M1 during and after 20min of a-tDCS to the right M1.Material and methodsEight healthy participants received real (2mA) and SHAM a-tDCS to the right M1 randomized across 2 testing sessions. Single- and paired-pulse transcranial magnetic stimulation (TMS) was applied to the left M1 to measure changes motor-evoked potential (MEP) amplitude from the right extensor carpi radialis (ECR) at 130% of resting and active motor threshold, cortical silent period (CSP) and short-interval cortical inhibition (SICI). Active motor threshold was measured during a wrist extension contraction that was less than 5% of maximal electromyographic activation of the ECR. TMS measurements were recorded at baseline, every 5min for 20min during and 10min after a-tDCS.ResultsThe results showed a significant (P<0.05) increase in left M1 MEP amplitude and reduction in CSP duration during (10 and 15min) and after (immediately and 10min post) a-tDCS to the right M1, only during the active motor task. A significant reduction (P<0.05) in SICI during the active task was also found immediately and 10min post a-tDCS. No significant changes in MEP amplitude, CSP and SICI were observed in the resting or active task during SHAM tDCS.DiscussionThe increase in left M1 MEP amplitude and reduction in CSP and SICI during and after 20min of right M1 a-tDCS is most likely to be attributed to a reduction in interhemispheric inhibition that is modulated by a-tDCS during the performance of an active task. Our findings may have significant implications for stroke rehabilitation whereby the application of a-tDCS on the contralesional M1 during neurorehabilitation of the paretic limb may be beneficial for inducing neuroplasticity of the ipsilesional M1 to improve motor function

Effects of ON and OFF subthalamic nucleus-DBS on prefrontal cortex activation during a cognitive task: an fNIRS study

Subthalamic nucleus (STN) deep brain stimulation (DBS) therapy is an effective treatment for the appendicular motor symptoms of Parkinson’s disease (PD). The STN contains multiple segregated circuits subserving motor, cognitive and mood functions through distinct connectivity to cortical regions. Therefore, we examined prefrontal cortical (PFC) effects of “ON” and “OFF” STN-DBS on executive function (Go/NoGo) using functional near-infrared spectroscopy (fNIRS). Methods Out of 8 PD STN-DBS patients, we present here preliminary analysis of a male (62y) PD patient with bilateral STN-DBS (unipolar, 180Hz, 3.5V). The patient was tested after 12h withdrawal of dopamine medications in both an “OFF” and “ON” DBS session separated by 30min. The subject performed a computerised GoNoGo task with 3 alternating Go/NoGo blocks of 30s duration (20 trials/block) interspersed with 30s rest. Reaction time (RT) and accuracy (omission-Om and commission-Cm errors) results were the average of the 3 Go/NoGo blocks. During performance of the Go/NoGo blocks, changes in oxygenated (O2Hb) and deoxygenated (HHb) haemoglobin concentrations were measured by a fNIRS system (Oxymon MkIII, Artinis Medical Systems) covering the bilateral PFC regions. Results/Discussion Clinical motor performance (UPDRSIII) improved from OFF (31) to ON (20). RT during Go and NoGo was ∼40ms faster in OFF (460 and 364ms) than ON (516 and 407ms). Furthermore, the NoGo condition increased misses (Om) in ON (7%) than OFF (0%); while false alarms (Cm) were similarly increased in ON (27%) and OFF (30%). The Go and NoGo conditions increased bilateral PFC activation (i.e., increase in O2Hb and decrease in HHb). However, there was a general decrease in PFC activation in OFF relative to ON, and this was more obvious in Go than NoGo (see Fig. 1) Conclusion These preliminary results indicate that STN-DBS modulates neurovascular responses in the bilateral PFC that are associated with response inhibition

Focal Hemodynamic Responses in the Stimulated Hemisphere During High-Definition Transcranial Direct Current Stimulation

OBJECTIVE: High-definition transcranial direct current stimulation (HD-tDCS) using a 4 × 1 electrode montage has been previously shown using modeling and physiological studies to constrain the electric field within the spatial extent of the electrodes. The aim of this proof-of-concept study was to determine if functional near-infrared spectroscopy (fNIRS) neuroimaging can be used to determine a hemodynamic correlate of this 4 × 1 HD-tDCS electric field on the brain. MATERIALS AND METHODS: In a three session cross-over study design, 13 healthy males received one sham (2 mA, 30 sec) and two real (HD-tDCS-1 and HD-tDCS-2, 2 mA, 10 min) anodal HD-tDCS targeting the left M1 via a 4 × 1 electrode montage (anode on C3 and 4 return electrodes 3.5 cm from anode). The two real HD-tDCS sessions afforded a within-subject replication of the findings. fNIRS was used to measure changes in brain hemodynamics (oxygenated hemoglobin integral-O2 Hbint ) during each 10 min session from two regions of interest (ROIs) in the stimulated left hemisphere that corresponded to "within" (Lin ) and "outside" (Lout ) the spatial extent of the 4 × 1 electrode montage, and two corresponding ROIs (Rin and Rout ) in the right hemisphere. RESULTS: The ANOVA showed that both real anodal HD-tDCS compared to sham induced a significantly greater O2 Hbint in the Lin than Lout ROIs of the stimulated left hemisphere; while there were no significant differences between the real and sham sessions for the right hemisphere ROIs. Intra-class correlation coefficients showed "fair-to-good" reproducibility for the left stimulated hemisphere ROIs. CONCLUSIONS: The greater O2 Hbint "within" than "outside" the spatial extent of the 4 × 1 electrode montage represents a hemodynamic correlate of the electrical field distribution, and thus provides a prospective reliable method to determine the dose of stimulation that is necessary to optimize HD-tDCS parameters in various applications