Advanced MRI Technologies (United States)

Biological nitrogen fixation (BNF) is the largest natural source of new nitrogen (N) that supports terrestrial productivity1,2, yet estimates of global terrestrial BNF remain highly uncertain3,4. Here we show that this uncertainty is partly because of sampling bias, asfield BNF measurements in natural terrestrial ecosystems occur where N fixers are 17 times more prevalent than their mean abundances worldwide. To correct this bias, we develop new estimates of global terrestrial BNF by upscaling field BNF measurements using spatially explicit abundances of all major biogeochemical N-fixing niches. We find that natural biomes sustain lower BNF, 65 (52-77) Tg N yr-1, than previous empirical bottom-up estimates3,4, with most BNF occurring in tropical forests and drylands. We also find high agricultural BNF in croplands and cultivated pastures, 56 (54-58) Tg N yr-1. Agricultural BNF has increased terrestrial BNF by 64% and total terrestrial N inputs from all sources by 60% over pre-industrial levels. Our results indicate that BNF may impose stronger constraints on the carbon sink in natural terrestrial biomes and represent a larger source of agricultural N than is generally considered in analyses of the global N cycle5,6, with implications for proposed safe operating limits for N use7,8.

To facilitate high spatial-temporal resolution fMRI (≦1mm3) at more broadly available field strengths (3T) and to better understand the neural underpinnings of joy, we used SE-based generalized Slice Dithered Enhanced Resolution (gSLIDER). This sequence increases SNR efficiency utilizing sub-voxel shifts along the slice direction. To improve the effective temporal resolution of gSLIDER, we utilized the temporal information within individual gSLIDER RF encodings to develop gSLIDER with Sliding Window Accelerated Temporal resolution (gSLIDER-SWAT). We first validated gSLIDER-SWAT using a classic hemifield checkerboard paradigm, demonstrating robust activation in primary visual cortex even with stimulus frequency increased to the Nyquist frequency of gSLIDER (i.e., TR = block duration). gSLIDER provided ~2× gain in tSNR over traditional SE-EPI. GLM and ICA results suggest improved signal detection with gSLIDER-SWAT's nominal 5-fold higher temporal resolution that was not seen with simple temporal interpolation. Next, we applied gSLIDER-SWAT to investigate the neural networks underlying joy using naturalistic video stimuli. Regions significantly activated during joy included the left amygdala, specifically the basolateral subnuclei, and rostral anterior cingulate, both part of the salience network; the hippocampus, involved in memory; the striatum, part of the reward circuit; prefrontal cortex, part of the executive network and involved in emotion processing and regulation [bilateral mPFC/BA10/11, left MFG (BA46)]; and throughout visual cortex. This proof of concept study demonstrates the feasibility of measuring the networks underlying joy at high resolutions at 3T with gSLIDER-SWAT, and highlights the importance of continued innovation of imaging techniques beyond the limits of standard GE fMRI.

Peter Anthony D'Amato, the inimitable pioneer of carnivorous plants, founder of California Carnivores, and author of The Savage Garden, passed away from cancer on the afternoon of 26 June 2024. He leaves behind his brother, Dino D'Amato, his niece Tara Page, his nephew Anthony D'Amato, and of course his California Carnivores tribe that loved him and called him family.

PurposePeripheral nerve stimulation (PNS) remains a physiologic limitation to boosting spatiotemporal resolution with more powerful gradients. We investigate discrepancies in previous measurements and model predictions from PNS experienced by volunteers scanned with the investigational “Impulse” gradient coil on the NexGen 7T scanner.MethodsTwenty‐nine volunteers (18 males, mean ± standard deviation age 52.2 ± 17.1 years) underwent PNS characterizations in the scanner. The process was repeated after the subject positions were moved by 2 and 4 cm toward the feet, away from isocenter. These new data were compared with prior experimental data acquired at the factory (32 volunteers, 16 males, mean ± standard deviation age 58.3 ± 13.5 years) and to modeling results initially used to guide the gradient winding pattern.ResultsThe PNS threshold for the x‐axis (left–right) was significantly below the threshold level predicted by the model used to optimize the wiring pattern and thresholds measured in the factory, whereas there was closer agreement for the y‐axis (anterior–posterior) and z‐axis (superior–inferior). The x‐axis threshold increased as the subject was moved in the Z‐direction toward the foot end of the magnet, at the expense of gradient nonlinearity distortions. Sensitivity of the threshold for the x‐axis was measured as 20 mT/m per centimeter Z‐offset.ConclusionThe PNS threshold of the x‐axis measured in the scanner was much lower than predicted by the optimization model and as measured at the factory. Our measurements verified that PNS thresholds of asymmetric head gradient coils were sensitive to head position, subject variability, and age. The discrepancy of the PNS prediction model remains to be elucidated.

Purpose:High resolution fMRI is a rapidly growing research field focused on capturing functional signal changes across cortical layers. However, the data acquisition is limited by low spatial frequency EPI artifacts; termed here as Fuzzy Ripples. These artifacts limit the practical applicability of acquisition protocols with higher spatial resolution, faster acquisition speed, and they challenge imaging in lower brain areas.Methods:We characterize Fuzzy Ripple artifacts across commonly used sequences and distinguish them from conventional EPI Nyquist ghosts, off-resonance effects, and GRAPPA artifacts. To investigate their origin, we employ dual polarity readouts.Results:Our findings indicate that Fuzzy Ripples are primarily caused by readout-specific imperfections in k-space trajectories, which can be exacerbated by inductive coupling between third-order shims and readout gradients. We also find that these artifacts can be mitigated through complex-valued averaging of dual polarity EPI or by disconnecting the third-order shim coils.Conclusion:The proposed mitigation strategies allow overcoming current limitations in layer-fMRI protocols:(1)Achieving resolutions beyond 0.8mm is feasible, and even at 3T, we achieved 0.53mm voxel functional connectivity mapping.(2)Sub-millimeter sampling acceleration can be increased to allow sub-second TRs and laminar whole brain protocols with up to GRAPPA 8.(3)Sub-millimeter fMRI is achievable in lower brain areas, including the cerebellum.

ABSTRACT Mobile or cellular phones are now an integral part of modern telecommunications, the use of phones is not limited to phone calls only but people are getting various information’s and using them for political, civic, health and many more purposes. In many countries, over half the population uses mobile phones. In 2014, there is an estimated 6.9 billion subscriptions globally and this number is going to rise sharply in coming years. In some parts of the world, mobile phones are the most reliable or the only phones available. Due to presence of the large number of mobile phone users, it is important to investigate, understand and monitor any potential public health impact.

This paper compares 4 different multipliers and the one with the least area and power is applied in 1D-DWT.The multipliers are implemented using booth algorithms as well as Wallace tree structures.The advantage of using Modified Booth algorithm is that the number of partial products is reduced by half.The Wallace tree structure is used for partial product reduction.1D-DWT is implemented using modified Wallace tree structures alone as it has the least area and power.The 1D-DWT is mainly used for image compression.