Automated reference-free detection of motion artifacts in magnetic resonance images

Objectives

Our objectives were to provide an automated method for spatially resolved detection and quantification of motion artifacts in MR images of the head and abdomen as well as a quality control of the trained architecture.

Materials and methods

T1-weighted MR images of the head and the upper abdomen were acquired in 16 healthy volunteers under rest and under motion. Images were divided into overlapping patches of different sizes achieving spatial separation. Using these patches as input data, a convolutional neural network (CNN) was trained to derive probability maps for the presence of motion artifacts. A deep visualization offers a human-interpretable quality control of the trained CNN. Results were visually assessed on probability maps and as classification accuracy on a per-patch, per-slice and per-volunteer basis.

Results

On visual assessment, a clear difference of probability maps was observed between data sets with and without motion. The overall accuracy of motion detection on a per-patch/per-volunteer basis reached 97%/100% in the head and 75%/100% in the abdomen, respectively.

Conclusion

Automated detection of motion artifacts in MRI is feasible with good accuracy in the head and abdomen. The proposed method provides quantification and localization of artifacts as well as a visualization of the learned content. It may be extended to other anatomic areas and used for quality assurance of MR images.

     

Rural networks and planned communities: Doxiadis Associates’ plans for rural settlements in post-independence Zambia

The paper focusses on the planning of rural settlements by the Athens-based firm Doxiadis Associates (DA), a key, even if unrealised, project for Zambia's nation-building and development efforts in the mid-1960s. In line with post-war discourses of modernisation, DA employed Christaller's 1933-Central Place Theory and its abstract hexagonal geometrical model to organise different-sized settlements within a single spatial system. By introducing a hierarchical rural network over Zambia, the firm aimed to standardise rural settlement patterns and to formulate a strategy to alleviate rural-urban migration. DA's top-down, large-scale approach even exceeded the State's aspirations and the firm's visions eventually faced two challenges: First, DA's modernist planning was questioned by the social/ecological considerations as formulated by George Kay's counterproposal on resettlement policy. Secondly, DA's ‘urbanising’ visions for rural areas were forestalled by some of the country's realities, which remained out of the planners’ field of control, and eventually called for more cautious responses to the realities on the ground. By exposing the challenges DA's rural proposal faced, the paper ultimately contemplates the multiple, and even conflicting reactions towards Zambia's rural settlement projects, and also adds nuances to the wider histories of rural development in Africa.     

Effect on exhaust emissions by the use of methylcyclopentadienyl manganese tricarbonyl (MMT) fuel additive and other lead replacement gasolines

This paper examines the potential effects on car exhaust emissions of a range of alternative lead replacement gasolines in the context of south European countries such as Greece. The main objective of this study was to assess the effects on emissions from non-catalyst passenger vehicles by the substitution of leaded ('super') gasoline with Euro95 unleaded enriched with the additive MMT or other alternative to leaded gasoline fuels. Regulated emissions, two non-regulated pollutants and vehicle performance were measured on two catalyst-equipped and two conventional, non-catalyst vehicles. It was found that there was no measurable effect on regulated emissions (CO, HC and NO(x)) and on fuel consumption by the introduction of the lead replacement fuels for both catalyst and non-catalyst cars. In the case of the non-catalyst car, the shift from leaded to unleaded gasoline was associated with an increase in benzene and formaldehyde emissions, a trend probably attributable to the increased aromatics content of the lead replacement fuels.     

A contribution to the study of some greek marbles

The use of marble in Architecture began on the 7th century B.C. and continued to be used without stop untill today. Greece and especially the East Macedonia region is an extremely privileged area on marble deposits both in quantities and qualities and colours. In the present work the main physical and engineering properties of some varieties of greek marbles are given and a comparison with the international standards is made. The experimental material (marbles) was from East Macedonia, Argolida-Arcadia and Magnessia, three of the biggest marble deposit areas in Greece. From the results obtained, it is concluded that the marbles examined satisfy all the international standard codes and thus they can be used as building stones and decoration materials.     

Investigation of sewage sludge stabilization potential by the addition of fly ash and lime

The aim of this work was the examination of stabilization potential of sewage sludge by the addition of fly ash and/or lime and the investigation of the effect of stabilization time on the properties of produced mixtures. Five samples were prepared by mixing fly ash, sewage sludge and lime in various ratios and the mixtures were stabilized for a period of 35 d. The addition of alkaline agents resulted in the increase of sample pH up to 12, the increase of total solids content to about 50% and the reduction of the organic fraction of the solids. The produced samples presented inhibition effects to seed germination and root length growth of three higher plants (one monocotyl and two dicotyls); however, samples with high sludge content resulted in negligible seed germination inhibition at prolonged stabilization times. The standard TCLP leaching procedure was applied in all the produced samples in order to evaluate the extraction potential of certain metallic elements; the content of metals in the eluates was varied, depending upon their speciation and form. Eluates presented significant inhibition to the marine photobacterium Vibrio fischeri bioluminescence, while the lowest inhibition was detected for the samples containing higher sludge content. These samples potentially could be applied as soil amendment, offering an efficient method for the combined utilization of two different solid wastes; however, low dosages of fly ash should be used for the production of a stabilized material presenting negligible effects with respect to its phytotoxic and ecotoxic properties.     

SAR distribution in human beings when using body-worn RF transmitters

This study analyzes the exposure of the human torso to electromagnetic fields caused by wireless body-mounted or handheld devices. Because of the frequency and distance ranges from 30-5800 MHz and 10 to 200 mm, respectively, both near-field and far-field effects are considered. A generic body model and simulations of anatomical models are used to evaluate the worst case tissue composition with respect to the absorption of electromagnetic energy. Both standing wave effects and enhanced coupling of reactive near-field components can lead to a specific absorption rate (SAR) increase in comparison to homogeneous tissue. In addition, the exposure and temperature increase of different inner organs is assessed. With respect to compliance testing, the observed SAR enhancement may require the introduction of a multiplication factor for the spatial peak SAR measured in the liquid-filled phantom in order to obtain a conservative exposure assessment. The observed tissue heating at the body surface under adiabatic conditions can be significant, whereas the temperature increase in the inner organs turned out to be negligible for the cases investigated.     

In vivo imaging of hydrogen peroxide with chemiluminescent nanoparticles

The overproduction of hydrogen peroxide is implicated in the development of numerous diseases and there is currently great interest in developing contrast agents that can image hydrogen peroxide in vivo. In this report, we demonstrate that nanoparticles formulated from peroxalate esters and fluorescent dyes can image hydrogen peroxide in vivo with high specificity and sensitivity. The peroxalate nanoparticles image hydrogen peroxide by undergoing a three-component chemiluminescent reaction between hydrogen peroxide, peroxalate esters and fluorescent dyes. The peroxalate nanoparticles have several attractive properties for in vivo imaging, such as tunable wavelength emission (460-630 nm), nanomolar sensitivity for hydrogen peroxide and excellent specificity for hydrogen peroxide over other reactive oxygen species. The peroxalate nanoparticles were capable of imaging hydrogen peroxide in the peritoneal cavity of mice during a lipopolysaccharide-induced inflammatory response. We anticipate numerous applications of peroxalate nanoparticles for in vivo imaging of hydrogen peroxide, given their high specificity and sensitivity and deep-tissue-imaging capability.     

Steady state behaviour of three phase air lift bioreactors – an integrated model and experimental verification

Beneckea natriegens growing both in suspension and immobilised on diatomaceous earth (silica) support particles, in a 3 dm three phase air lift bioreactor (TPALB), was employed to demonstrate the relationship between substrate loading rate and immobilised biomass loading at steady state. Sterile conditions were maintained during the experiments, while the hydraulic conditions and the inlet flowrate remained constant. The experiment ran for 12 days, whilst the inlet substrate (n‐propanol) concentration was varied both upwards and downwards between 250 and 750 mg dm⁻³. The bulk liquid substrate concentration and the immobilised biomass loading were found to vary between 6–120 mg dm⁻³ and 71–159 mg(dry biomass) g⁻¹ (silica), respectively. The experimental results demonstrated that there is a positive relationship between substrate loading and immobilised biomass loading. A mathematical model is proposed to calculate biofilm thickness and bulk liquid substrate concentration (for steady state) using the inlet flowrate and the inlet substrate concentration as input parameters. The model was able to predict both biofilm thickness and immobilised biomass loading for the lower substrate loading rates applied. © 1999 Society of Chemical Industry     

Differential Expression of the Host Lipid Regulators ANGPTL-3 and ANGPTL-4 in HCV Infection and Treatment

Host lipid metabolism reprogramming is essential for hepatitis C virus (HCV) infection and progression to severe liver disease. Direct-acting antivirals (DAAs) achieve a sustained virological response (SVR) in most patients, but virus eradication does not always protect against hepatocellular carcinoma (HCC). Angiopoietin-like protein-3 (ANGPTL-3) and angiopoietin-like protein-4 (ANGPTL-4) regulate the clearance of plasma lipids by inhibiting cellular lipase activity and possess emerging roles in tumourigenesis. We used ELISA and RT-qPCR to investigate ANGPTL-3 and ANGPTL-4 expression in HCV patients with characterised fibrosis throughout the natural history of hepatitis C and in long-term HCV infection in vitro, before and after DAA treatment. ANGPTL-3 was decreased in patients with advanced fibrosis compared to other disease stages, while ANGPTL-4 was progressively increased from acute infection to cirrhosis and HCC, peaking at the advanced fibrosis stage. Only ANGPTL-3 mRNA was down-regulated during early infection in vitro, although both ANGPTLs were increased later. DAA treatment did not alter ANGPTL-3 levels in advanced fibrosis/cirrhosis and in HCV infection in vitro, in contrast to ANGPTL-4. The association between ANGPTLs and fibrosis in HCV infection was underlined by an inverse correlation between the levels of ANGPTLs and serum transforming growth factor- β (TGF-β). Collectively, we demonstrate the pivotal role of advanced fibrosis in defining the expression fate of ANGPTLs in HCV infection and after treatment and propose a role for ANGPTL-3 as a contributor to post-treatment deregulation of lipid metabolism that could predispose certain individuals to HCC development.     

Ambient particulate matter exhibits direct inhibitory effects on oxidative stress enzymes

A primary mechanistic hypothesis by which ambient air particles have a significant negative impact on human health is via the induction of pulmonary inflammatory responses mediated through the generation of reactive oxygen species (ROS). Development of a biosensor for the assessment of particulate ROS activity would be a significant advance in air pollution monitoring. The objective of this study was to evaluate whether air particulates interact directly with protective enzymes involved in oxidative stress responses. We performed enzyme activity assays on four enzymes involved in oxidative stress responses (Cu/Zn superoxide dismutase, Mn superoxide dismutase, glutathione peroxidase, and glutathione reductase) in the presence of particles of varying toxicities and found distinctive inhibition patterns. On the basis of these findings, we suggest a strategy for an enzyme bioassay that could be used to assess the potential of particles to generate ROS-induced responses.