Density-controlled, solution-based growth of ZnO nanorod arrays via layer-by-layer polymer thin films for enhanced field emission Density-controlled, solution-based growth of ZnO nanorod arrays via layer-by-layer polymer thin films for enhanced field emis

Abstract A simple, scalable, and cost-effective technique for controlling the growth density of ZnO nanorod arrays based on a layer-by-layer polyelectrolyte polymer film is demonstrated. The ZnO nanorods were synthesized using a low temperature (T = 90 • C), solution-based method. The density-control technique utilizes a polymer thin film pre-coated on the substrate to control the mass transport of the reactant to the substrate. The density-controlled arrays were investigated as potential field emission candidates. The field emission results revealed that an emitter density of 7 nanorods μm −2 and a tapered nanorod morphology generated a high field enhancement factor of 5884. This novel technique shows promise for applications in flat panel display technology

be estimated? Bayesian view

How accurately can the parameters from a model of anisotropic 3 He gas diffusion in lung acinar airway

Whole-brain background-suppressed pCASL MRI with 1D-accelerated 3D RARE Stack-Of-Spirals readout

<div><p>Arterial Spin Labeled (ASL) perfusion MRI enables non-invasive, quantitative measurements of tissue perfusion, and has a broad range of applications including brain functional imaging. However, ASL suffers from low signal-to-noise ratio (SNR), limiting image resolution. Acquisitions using 3D readouts are optimal for background-suppression of static signals, but can be SAR intensive and typically suffer from through-plane blurring. In this study, we investigated the use of accelerated 3D readouts to obtain whole-brain, high-SNR ASL perfusion maps and reduce SAR deposition. Parallel imaging was implemented along the partition-encoding direction in a pseudo-continuous ASL sequence with background-suppression and 3D RARE Stack-Of-Spirals readout, and its performance was evaluated in three small cohorts. First, both non-accelerated and two-fold accelerated single-shot versions of the sequence were evaluated in healthy volunteers during a motor-photic task, and the performance was compared in terms of temporal SNR, GM-WM contrast, and statistical significance of the detected activation. Secondly, single-shot 1D-accelerated imaging was compared to a two-shot accelerated version to assess benefits of SNR and spatial resolution for applications in which temporal resolution is not paramount. Third, the efficacy of this approach in clinical populations was assessed by applying the single-shot 1D-accelerated version to a larger cohort of elderly volunteers. Accelerated data demonstrated the ability to detect functional activation at the subject level, including cerebellar activity, without loss in the perfusion signal temporal stability and the statistical power of the activations. The use of acceleration also resulted in increased GM-WM contrast, likely due to reduced through-plane partial volume effects, that were further attenuated with the use of two-shot readouts. In a clinical cohort, image quality remained excellent, and expected effects of age and sex on cerebral blood flow could be detected. The sequence is freely available upon request for academic use and could benefit a broad range of cognitive and clinical neuroscience research.</p></div

Role of collateral paths in long-range diffusion in lungs

The long-range apparent diffusion coefficient (LRADC) of 3He gas in lungs, measured over times of several seconds and distances of 1–3 cm, probes the connections between the airways. Previous work has shown the LRADC to be small in health and substantially elevated in emphy-sema, reflecting tissue destruction, which is known to create collateral pathways. To better understand what controls LRADC, we report com-puter simulations and measurements of 3He gas diffusion in healthy lungs. The lung is generated with a random algorithm using well-defined rules, yielding a three-dimensional set of nodes or junctions, each con-nected by airways to one parent node and two daughters; airway dimen-sions are taken from published values. Spin magnetization in the simu-lated lung is modulated sinusoidally, and the diffusion equation is solved to 1,000 s. The modulated magnetization decays with a time constant corresponding to an LRADC of 0.001 cm2/s, which is smaller by a factor of 20 than the values in healthy lungs measured here an

Mean CBF maps obtained in Study 1 without and with acceleration from a representative subject, in ml/min/100g, alongside the corresponding anatomical dataset.

<p>Note the reduced through-plane blurring and increase in GM—WM tissue contrast with acceleration in the coronal and sagittal views.</p

Results of the functional activation data analysis in Study 1.

<p>Panels (A) and (B) show the task>rest activation clusters for two representative subjects, obtained with the non-accelerated and the 1D-accelerated data in both visual (left) and motor (right) areas. Panel (C) shows the group activation maps obtained with each readout type. Panel (D) shows the differences in activity across readouts. Non-accelerated data only presented higher activity than accelerated data in the white matter region below the left motor cortex cluster and above the primary visual cortex cluster, likely reflecting the effects of image blurring, while 1D-accelerated data presented higher differential activation within both clusters.</p

(A) Modulation transfer function (MTF) and (B) normalized point spread function (PSF) of the non-accelerated (blue) and 1D-accelerated (1-shot = red, 2-shot = green) readouts.

<p>The width of the PSF decreased from 2.86 to 1.54 (1-shot) and 1.30 (2-shot) with the use of acceleration, increasing the effective voxel resolution.</p