Kirklandgreenwood7700

We report electron-beam activated motion of a catalytic nanoparticle along a graphene step edge and associated etching of the edge. The catalytic hydrogenation process was observed to be activated by a combination of elevated temperature and electron beam irradiation. Reduction of beam fluence on the particle was sufficient to stop the process, leading to the ability to switch on and off the etching. Baricitinib Such an approach enables the targeting of individual nanoparticles to induce motion and beam-controlled etching of matter through activated electrocatalytic processes. The applications of electron-beam control as a paradigm for molecular-scale robotics are discussed. © 2020 IOP Publishing Ltd.Measurement of the blood T1 time using conventional myocardial T1 mapping methods has gained clinical significance in the context of extracellular volume (ECV) mapping and synthetic hematocrit (Hct). However, its accuracy is potentially compromised by in-flow of non-inverted/non-saturated spins and in-flow of spins which are not partially saturated from previous imaging pulses. Bloch simulations were used to analyze various flow effects separately. T1 measurements of gadolinium doped water were performed using a flow phantom with adjustable flow velocities at 3T. Additionally, in vivo blood T1 measurements were performed in 6 healthy subjects. To study the T1 time as a function of the instantaneous flow velocity, T1 times were evaluated in an axial imaging slice of the descending aorta. Simulation results show more than 30% loss in accuracy for 10% non-prepared in-flowing spins. However, in- and out-flow to the imaging plane only demonstrated minor impact on the T1 time. Phantom T1 times were decreased by up to 200 ms in the flow phantom, due to in-flow of non-prepared spins. High flow velocities cause in-flow of spins that lack partial saturation from the imaging pulses but only lead to negligible T1 time deviation (less than 30 ms). In vivo measurements confirm a substantial variation of the T1 time depending on the flow velocity. The highest aortic T1 times are observed at the time point of minimal flow with increased flow velocity leading to reduction of the measured T1 time at peak velocity. In this work we attempt to dissect the effects of flow on T1 times, by using simulations, well-controlled, simplified phantom setup and the linear flow pattern in the descending aorta in vivo. Creative Commons Attribution license.Arterial Spin Labeling (ASL) is a non-contrast enhanced method for perfusion measurements. The obtained information is in general a snap-shot of the whole-brain perfusion. Image acquisition is performed after a certain delay time after the labeling of the arterial blood. Time-resolved information alongside flow territory mapping of individual arteries can become useful for the collection of important information such as arterial crossflow, and revascularization. Therefore, a method is presented that combines time-resolved flow territory mapping within a single scan based on encoding of the acquisition cycle using a ternary matrix approach. The super-selective tagging process is divided in individual blocks following a ternary matrix encoding scheme. In each block, the position of the labeling focus changes its position to each of the major brain feeding arteries. Contrary to conventional ASL approaches, no control condition is acquired and the individual flow territories are calculated by combining the label images only. The method was successfully evaluated in healthy volunteers. Each flow territory could be visualized over several post labeling delays within a single of approximately five minutes . Comparison of signal intensity (relative perfusion) did not show statistically significant differences between the methods. Encoding super-selective ASL using a ternary matrix allows for the vessel-selective and time-resolved acquisition of perfusion territories within a single scan. © 2020 Institute of Physics and Engineering in Medicine.Cellular senescence, triggered by sublethal damage, is characterized by indefinite growth arrest, altered gene expression patterns, and a senescence-associated secretory phenotype. While the accumulation of senescent cells during aging decreases tissue function and promotes many age-related diseases, at present there is no universal marker to detect senescent cells in tissues. Cyclin-dependent kinase inhibitors 2A (p16/CDKN2A) and 1A (p21/CDKN1A) can identify senescent cells, but few studies have examined the numbers of cells expressing these markers in different organs as a function of age. Here, we investigated systematically p16- and p21-positive cells in tissue arrays designed to include normal organs from persons across a broad spectrum of ages. Increased numbers of p21-positive and p16-positive cells with donor age were found in skin (epidermis), pancreas, and kidney, while p16-expressing cells increased in brain cortex, liver, spleen and intestine (colon), and p21-expressing cells increased in skin (dermis). The numbers of cells expressing p16 or p21 in lung did not change with age, and muscle did not appear to have p21- or p16-positive cells. In summary, different organs display different levels of the senescent proteins p16 and p21 as a function of age across the human life span.Using a cross sectional design, we aimed to identify the effect of aging on sensorimotor function and cortical motor representations of two intrinsic hand muscles, as well as the course and timing of those changes. Furthermore, the link between cortical motor representations, sensorimotor function, and intracortical inhibition and facilitation was investigated. Seventy-seven participants over the full adult lifespan were enrolled. For the first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscle, cortical motor representations, GABAA-mediated short-interval intracortical inhibition (SICI), and glutamate-mediated intracortical facilitation (ICF) were assessed using transcranial magnetic stimulation over the dominant primary motor cortex. Additionally, participants' dexterity and force were measured. Linear, polynomial, and piecewise linear regression analyses were conducted to identify the course and timing of age-related differences. Our results demonstrated variation in sensorimotor function over the lifespan, with a marked decline starting around the mid-thirties.