5,448 research outputs found
Atmospheric transport of trace elements and nutrients to the oceans
This paper reviews atmospheric inputs of trace elements and nutrients to the oceans in the context of the GEOTRACES programme and provides new data from two Atlantic GEOTRACES cruises. We consider the deposition of nitrogen to the oceans, which is now dominated by anthropogenic emissions, the deposition of mineral dust and related trace elements, and the deposition of other trace elements which have a mixture of anthropogenic and dust sources. We then consider the solubility (as a surrogate for bioavailability) of the various elements. We consider briefly the sources, atmospheric transport and transformations of these elements and how this results in strong spatial deposition gradients. Solubility of the trace elements also varies systematically between elements, reflecting their sources and cycling, and for some trace elements there are also systematic gradients in solubility related to dust loading. Together these effects create strong spatial gradients in inputs of bioavailable trace elements to the oceans, and we are only just beginning to understand how these affect ocean biogeochemistry
Neural markers of suppression in impaired binocular vision
Even after conventional patching treatment, individuals with a history of amblyopia typically lack good stereo vision. This is often attributed to atypical suppression between the eyes, yet the specific mechanism is still unclear. Guided by computational models of binocular vision, we tested explicit predictions about how neural responses to contrast might differ in individuals with impaired binocular vision. Participants with a history of amblyopia (N = 25), and control participants with typical visual development (N = 19) took part in the study. Neural responses to different combinations of contrast in the left and right eyes, were measured using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Stimuli were sinusoidal gratings with a spatial frequency of 3c/deg, flickering at 4 Hz. In the fMRI experiment, we also ran population receptive field and retinotopic mapping sequences, and a phase-encoded localiser stimulus, to identify voxels in primary visual cortex (V1) sensitive to the main stimulus. Neural responses in both modalities increased monotonically with stimulus contrast. When measured with EEG, responses were attenuated in the weaker eye, consistent with a fixed tonic suppression of that eye. When measured with fMRI, a low contrast stimulus in the weaker eye substantially reduced the response to a high contrast stimulus in the stronger eye. This effect was stronger than when the stimulus-eye pairings were reversed, consistent with unbalanced dynamic suppression between the eyes. Measuring neural responses using different methods leads to different conclusions about visual differences in individuals with impaired binocular vision. Both of the atypical suppression effects may relate to binocular perceptual deficits, e.g. in stereopsis, and we anticipate that these measures could be informative for monitoring the progress of treatments aimed at recovering binocular vision
Concerns about how to use established minimal residual disease monitoring in the treatment of NPM1-mutant acute myeloid leukaemia (AML) following reduced intensity chemotherapy protocols for AML given as a result of the COVID-19 pandemic
Classification of Ultrasonic Weld Inspection Data Using Principal Component Analysis
Recent inservice inspection experience, round robin tests of ultrasonic inspection reliability [1] and calculations of flaw detection reliability necessary for specific nuclear power plant applications have consistently shown the need to improve the reliability of ultrasonic inspection. The need to improve ultrasonic inspection reliability is further emphasized when one reviews the pass rates for performance demonstrations specified by ASME Section XI Appendix VIII
Brain Tumor and Glioma Grade Classification Using Gaussian Convolutional Neural Network
Understanding brain diseases such as categorizing Brain-Tumor (BT) is critical to assess the tumors and facilitate the patient with proper cure as per their categorizations. Numerous imaging schemes exist for BT detection, such as Magnetic Resonance Imaging (MRI), generally utilized because of the better quality of images and the reality of depending on non-ionizing radiation. This paper proposes an approach
to detect distinctive BT types using Gaussian Convolutional Neural Network (GCNN) on two datasets. One of the datasets is used to classify tumors into pituitary, glioma, and meningioma. The other one separates the three grades of glioma, i.e., Grade-two, Grade-three, and Grade-four. These datasets have ’233’ and ’73’ victims with a total of ’3064’ and ’516’ images on T1-weighted complexity improved pictures for the first and second datasets, separately. The proposed approach achieves an accuracy of 99.8% and 97.14% for the
two datasets. The experimental results highlight the efficiency of the proposed approach for BT multi-class
categorization
Interpreting high-temperature magnetic susceptibility data of natural systems
High-temperature susceptibility (HT-χ) data are routinely measured in Earth, planetary, and environmental sciences to rapidly identify the magnetic mineralogy of natural systems. The interpretation of such data can be complicated. Whilst some minerals are relatively unaltered by heating and are easy to identify through their Curie or Néel temperature, other common magnetic phases, e.g., iron sulphides, are very unstable to heating. This makes HT-χ interpretation challenging, especially in multi-mineralogical samples. Here, we report a review of the HT-χ data measured primarily at Imperial College London of common magnetic minerals found in natural samples. We show examples of “near pure” natural samples, in addition to examples of interpretation of multi-phase HT-χ data. We hope that this paper will act be the first reference paper for HT-χ data interpretation
Active Region Modulation of Coronal Hole Solar Wind
Active regions (ARs) are a candidate source of the slow solar wind (SW), the origins of which are a topic of ongoing research. We present a case study that examines the processes by which SW is modulated in the presence of an AR in the vicinity of the SW source. We compare properties of SW associated with a coronal hole (CH)–quiet Sun boundary to SW associated with the same CH but one Carrington rotation later, when this region bordered the newly emerged NOAA AR 12532. Differences found in a range of in situ parameters are compared between these rotations in the context of source region mapping and remote sensing observations. Marked changes exist in the structure and composition of the SW, which we attribute to the influence of the AR on SW production from the CH boundary. These unique observations suggest that the features that emerge in the AR-associated wind are consistent with an increased occurrence of interchange reconnection during SW production, compared with the initial quiet Sun case
Effect of age on the hemodynamic and sympathetic responses at the onset of isometric handgrip exercise.
Cardiac and peripheral vasomotor factors contribute to the rapid pressor response at the onset of isometric handgrip exercise. We tested the hypothesis that age enhances the sympathetic and vasoconstrictor response at the onset of isometric handgrip exercise so that the pressor response is maintained, despite a diminished cardiac function. Twelve young and twelve older (24 ± 3 and 63 ± 8 yr) individuals performed 20-s isometric handgrip exercise at 30, 40, or 50% of maximal voluntary contraction force. Muscle sympathetic nerve activity (MSNA) was measured using microneurography. Mean arterial pressure (MAP) and cardiac output (Q) were assessed continuously by finger plethysmography and total peripheral resistance was calculated. MAP increased with the onset of handgrip; this increase was associated with handgrip intensity and was similar in both groups. Heart rate and Q increased with increasing handgrip intensity in both groups, but increases were greater in young vs. older individuals (age × handgrip intensity interaction, P \u3c 0.05). MSNA burst frequency increased (P \u3c 0.01), while MSNA burst incidence tended to increase (P = 0.06) with increasing handgrip intensity in both groups. The change in MSNA between baseline and handgrip, for both frequency and incidence, increased with increasing handgrip intensity for both groups. There was no effect of handgrip intensity or age on total peripheral resistance. The smaller heart rate and Q response during the first 20 s of handgrip exercise in older individuals was not accompanied by a greater sympathetic activation or vasoconstrictor response. However, increases in MAP were similar between groups, indicating that the pressor response at the onset of handgrip exercise is preserved with aging
In situ study of sigma phase formation in Cr-Co-Ni ternary alloys at 800°C using the long duration experiment facility at Diamond Light Source.
The new long duration experiment facility on beamline I11 at Diamond Light Source has been used to study the kinetics of sigma phase formation in three Cr-Co-Ni alloys. Diffraction data acquired during in situ exposure at 800°C for 50 d showed progressive increases in the sigma fraction. This was accompanied by changes in the proportions of the other phases, which differed markedly between the alloys studied. These results demonstrate the capabilities of the long duration facility for the study of metallurgical phenomena over periods of months to years, a capability not previously available at a synchrotron source
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