We present an in situ nanobeam grazing-incidence X-ray diffraction (nanoGIXD) study of real-sized organic field effect transistors (OFET) under applied voltage. The nano-sized beam allows for ...spatially resolved monitoring of the structural behavior across the poly(3-hexylthiophene) (P3HT) polymer channel and the interfacial regions of the source and drain gold electrodes before and after the operation cycle. We observe major alterations of the gold contacts, in particular diffusion of Au atoms into the polymer channel and a local reorientation of the recrystallized Au nanocrystallites quantified by Hermans' orientation factors. Therefore, the initially sharp electrode-polymer interfaces are significantly modified as a result of device operation. Our findings demonstrate that nanoGIXD has a high potential to probe functionality and reliability of working organic devices.
We present results of an x-ray study of structural properties of π-π conjugated networks in semicrystalline polymer thin films using nanofocused x-ray beam. We applied the x-ray cross-correlation ...analysis to x-ray scattering data from blends of poly(3-hexylthiophene) (P3HT) with gold nanoparticles. The Fourier spectra of the intensity cross-correlation functions for different films contain non-zero components of orders n = 2,4 and 6 revealing structural order in the system. The results suggest inhomogeneous structure of both samples, with preferential edge-on orientation of domains in one sample and mixed orientation in another sample.
Since modern synchrotrons with highly intense X-ray beams are in use to investigate organic materials, the stability of soft matter materials during beam exposure is a crucial issue. Grazing ...incidence X-ray diffraction and specular X-ray reflectivity measurements were performed on thin films of organic semiconducting materials, like poly(3-hexylthiophene) (P3HT), sexithiophene and pentacene. These films were irradiated with an average flux density between 1015 and 1016photons/(smm2) and evidenced a different stability in synchrotron X-ray radiation. The semi-crystalline P3HT showed a clear intensity decrease of the 100 Bragg peak and 020 Bragg peak compared to the rather stable diffraction features of the molecular crystals sexithiophene and pentacene. The difference in synchrotron X-ray radiation stability is explained by the interaction of the X-ray beam with the individual chemical components in the molecules as well as by the different crystallinities of the materials. Furthermore, the semi-crystalline P3HT film exhibited an increase of film thickness after irradiation and the surface roughness slightly decreased. To summarize, this study shows a strong influence of synchrotron X-ray radiation to specific organic thin films like e.g. P3HT, while others like pentacene and sexithiophene are observed as quite stable.
We present results of an x-ray study of structural properties of pi-pi conjugated networks in semicrystalline polymer thin films using nanofocused x-ray beam. We applied the x-ray cross-correlation ...analysis to x-ray scattering data from blends of poly(3-hexylthiophene) (P3HT) with gold nanoparticles. The Fourier spectra of the intensity cross-correlation functions for different films contain non-zero components of orders n = 2,4 and 6 revealing structural order in the system. The results suggest inhomogeneous structure of both samples, with preferential edge-on orientation of domains in one sample and mixed orientation in another sample.
J. Phys.: Conf. Series 499 012021 (2014) We present results of x-ray study of spatial properties of $\pi-\pi$
conjugated networks in polymer thin films. We applied the x-ray
cross-correlation ...analysis to x-ray scattering data from blends of
poly(3-hexylthiophene) (P3HT) and gold nanoparticles. The Fourier spectra of
the intensity cross-correlation functions for different films contain non-zero
components of orders $n=2,4$ and $6$ measuring the degree of structural order
in the system.
We present results of x-ray study of spatial properties of \(\pi-\pi\) conjugated networks in polymer thin films. We applied the x-ray cross-correlation analysis to x-ray scattering data from blends ...of poly(3-hexylthiophene) (P3HT) and gold nanoparticles. The Fourier spectra of the intensity cross-correlation functions for different films contain non-zero components of orders \(n=2,4\) and \(6\) measuring the degree of structural order in the system.
By definition, in-hospital patient data are restricted to the time between hospital admission and discharge (alive or dead). For hospitalised cases of COVID-19, a number of events during ...hospitalization are of interest regarding the influence of risk factors on the likelihood of experiencing these events. The same is true for predicting times from hospital admission of COVID-19 patients to intensive care or from start of ventilation (invasive or non-invasive) to extubation. This logical restriction of the data to the period of hospitalisation is associated with a substantial risk that inappropriate methods are used for analysis. Here, we briefly discuss the most common types of bias which can occur when analysing in-hospital COVID-19 data. Keywords: competing risk bias, immortal-time bias, competing events, time-dependent bias, time-varying exposure, time-to-event analysis
Objective: Comparison of functional magnetic resonance imaging (fMRI) representational maps, that were generated during voluntary thumb abduction, hand dorsiflexion and foot elevation to amplitude ...maps of motor-evoked potentials (MEPs) elicited by single transcranial magnetic stimulation (TMS) administered to cortical motor representation areas of the muscles of the thenar eminence, extensor carpi radialis and tibialis anterior muscles.
Methods: Stimulus locations that produced maximal motor-evoked potential amplitudes were compared to fMRI activation maxima in three-dimensional (3D)-space and in a 2D-projection using a novel technique that allowed fMRI activation sites to be projected onto the surface of the brain.
Results and conclusions: When analyzing pooled data from all target muscles, the location of projected fMRI and TMS activation maxima on the cortical surface differed by an average 13.9 mm. The differences in 3D distances were particularly large for representation areas of lower leg muscles. 3D distances between fMRI activation maxima and highest MEP site in TMS correlated significantly with higher TMS thresholds. These observations strongly suggest that higher TMS excitation thresholds and lower MEP amplitudes are largely due to the absolute distance between the stimulation site and the excitable cortical tissue targeting this muscle. After the projection 4 out of 5 representation sites as evaluated by TMS were located anterior to the fMRI activation maxima, an observation which may due to the orientation of the magnetic field induced by the current in the coil. The representation sites as evaluated with both methods were specific for the type of movement: distances between representation maxima of the same movements were significantly smaller than those within different movements. Nevertheless, fMRI and TMS provide complementary information, which is discussed on the basis of the functional map observed with both methods.
Early periventricular brain lesions can not only cause cerebral palsy, but can also induce a reorganization of language. Here, we asked whether these different functional consequences can be ...attributed to topographically distinct portions of the periventricular white matter damage. Eight patients with pre- and perinatally acquired left-sided periventricular brain lesions underwent focal transcranial magnetic stimulation to assess the integrity of cortico-spinal hand motor projections, and functional MRI to determine the hemispheric organization of language production. MRI lesion-symptom mapping revealed that two distinct portions of the periventricular lesions were critically involved in the disruption of cortico-spinal hand motor projections on the one hand and in the induction of language reorganization into the contra-lesional right hemisphere on the other hand. Both regions are located in a position compatible with the course of cortico-spinal/cortico-nuclear projections of the primary motor cortex in the periventricular white matter, as determined by the stereotaxic probabilistic cytoarchitectonic atlas developed by the Jülich group.
Objective. To determine if patients with traumatic brain injury (TBI) and motor deficits show differences in functional activation maps during repetitive hand movements relative to healthy controls. ...Are there predictors for motor outcome in the functional maps of these patients? Methods. In an exploratory cross-sectional study, functional magnetic resonance imaging (fMRI) was used to study the blood-oxygenation-level-dependent (BOLD) response in cortical motor areas of 34 patients suffering from moderate motor deficits after TBI as they performed unilateral fist-clenching motions. Twelve of these patients with unilateral motor deficits were studied 3 months after TBI and a 2nd time approximately 4 months later. Results. Compared to age-matched, healthy controls performing the same task, TBI patients showed diminished fMRI-signal change in the primary sensorimotor cortex contralateral to the moving hand (cSM1), the contralateral dorsal premotor cortex, and bilaterally in the supplementary motor areas (SMAs). Clinical impairment and the magnitude of the fMRI-signal change in cSM1 and SMA were negatively correlated. Patients with poor and good motor recovery showed comparable motor impairment at baseline. Only patients who evolved to “poor clinical outcome” had decreased fMRI-signal change in the cSM1 during baseline. Conclusions. These observations raise the hypothesis that the magnitude of the fMRI-signal change in the cSM1 region could have prognostic value in the evaluation of patients with TBI.
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