697 research outputs found
Large Scale Image Segmentation with Structured Loss based Deep Learning for Connectome Reconstruction
We present a method combining affinity prediction with region agglomeration,
which improves significantly upon the state of the art of neuron segmentation
from electron microscopy (EM) in accuracy and scalability. Our method consists
of a 3D U-NET, trained to predict affinities between voxels, followed by
iterative region agglomeration. We train using a structured loss based on
MALIS, encouraging topologically correct segmentations obtained from affinity
thresholding. Our extension consists of two parts: First, we present a
quasi-linear method to compute the loss gradient, improving over the original
quadratic algorithm. Second, we compute the gradient in two separate passes to
avoid spurious gradient contributions in early training stages. Our predictions
are accurate enough that simple learning-free percentile-based agglomeration
outperforms more involved methods used earlier on inferior predictions. We
present results on three diverse EM datasets, achieving relative improvements
over previous results of 27%, 15%, and 250%. Our findings suggest that a single
method can be applied to both nearly isotropic block-face EM data and
anisotropic serial sectioned EM data. The runtime of our method scales linearly
with the size of the volume and achieves a throughput of about 2.6 seconds per
megavoxel, qualifying our method for the processing of very large datasets
National study of NAFLD management identifies variation in delivery of care in the UK between 2019 to 2022
Background & Aims: Non-alcoholic fatty liver disease (NAFLD) is associated with liver and cardiovascular morbidity and mortality. Recently published NAFLD Quality Standards include 11 key performance indicators (KPIs) of good clinical care. This national study, endorsed by British Association for the Study of the Liver (BASL) and British Society of Gastroenterology (BSG), aimed to benchmark NAFLD care in UK hospitals against these KPIs. Methods: This study included all new patients with NAFLD reviewed in the outpatient clinic in the months of March 2019 and March 2022. Participating UK hospitals self-registered for the study through BASL/BSG. KPI outcomes were compared using Fisher's exact or Chi-square tests. Results: Data from 776 patients with NAFLD attending 34 hospitals (England [25], Scotland [four], Wales [three], Northern Ireland [two]) were collected. A total of 85.3% of hospitals reported established local liver disease assessment pathways, yet only 27.9% of patients with suspected NAFLD had non-invasive fibrosis assessment documented at the point of referral to secondary care. In secondary care, 79.1% of patients had fibrosis assessment. Assessment of cardiometabolic risk factors including obesity, type 2 diabetes, hypertension, and smoking were conducted in 73.2%, 33.0%, 19.3%, and 54.9% of all patients, respectively. There was limited documentation of diet (35.7%) and exercise advice (55.1%). Excluding those on statins, only 9.1% of patients with NAFLD at increased cardiovascular risk (T2DM and/or QRISK-3 >10%) had documented discussion of statin treatment. Significant KPI improvements from 2019 to 2022 were evident in use of non-invasive fibrosis assessment before secondary care referral, statin recommendations, and diet and exercise recommendations. Conclusions: This national study identified substantial variation in NAFLD management in the UK with clear areas for improvement, particularly fibrosis risk assessment before secondary care referral and management of associated cardiometabolic risk factors. Impact and implications: This study identified significant variation in the management of NAFLD in the UK. Only 27.9% of patients with suspected NAFLD had non-invasive fibrosis assessment performed to identify those at greater risk of advanced liver disease before specialist referral. Greater emphasis is needed on the management of associated cardiometabolic risk factors in individuals with NAFLD. Hospitals with multidisciplinary NAFLD service provision had higher rates of fibrosis evaluation and assessment and management of cardiometabolic risk than hospitals without multidisciplinary services. Further work is needed to align guideline recommendations and real-world practice in NAFLD care.</p
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BOD and toxicity of log leachates
A series of log storage experiments were conducted to determine
whether leachates derived from water storage of logs are acutely
toxic to fish. Log segments approximately 18 inches long and 16 inches
in diameter were stored in tanks and held submerged for a period of
7 days. The holding water containing leached materials was made
toxic with mercury to retard biological decomposition of the leached
substances. Mercury was selectively removed from leachate samples
by chelation prior to biochemical oxygen demand (BOD) and bioassay
testing.
Trout and salmon fry were subjected to the leachate water in
short term acute bioassay tests. Results are reported as a median
tolerance limit, (TLm), i. e., the concentration of leachate at which
50 percent of the test fish died for any given exposure time. Leachates
were also tested for BODâ‚…, BOD k-rate, chemical oxygen demand
(COD), wood sugar and Pearl Benson Index (PBI).
Test results show that leachates from Douglas fir stored in fresh
water exert a slight acute toxicity to fish. A TLm₉₆ of 20 percent
leachate by volume, for a 50 year old Douglas fir log, was the most
toxic leachate observed. Leachates from ponderosa pine, hemlock
and an older fir log stored under identical conditions produced no
measurable acute toxicity. Leachates contained a significant quantity
of BOD and PBI exerting substances. The highest BOD₅, (1.36 g/ft²
of submerged surface area) was exerted by leachate from a ponderosa
pine log segment stored with bark removed. The highest PBI valve
(12.5 g/ft²), was observed for leachate from a young Douglas fir log
segment. BOD:COD ratios and BOD k-rate ranged widely for the
various leachates, but were relatively low which indicated a significant
fraction of non-biodegradable substances. Hoffbuhr (9) also observed
a high non-biodegradable fraction in samples taken from log storage
ponds. Wood sugars were found to account for a large part of the degradable
portion of leachates. Leachate from ponderosa pine log with
bark intact exerted a high BOD and also contained the highest concentration
of wood sugar observed, 0.84 g/ft²
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