Complications of the central nervous system in removal brain tumors lie in the differentiation between the neoplasm and healthy tissues. Tumor segmentation is a fundamental task in the detection and ...clinical treatment planning. In this work, two neural networks architectures based on the U-net network have been designed and trained to automatically segment different tumor substructures using the Multimodal Brain Tumor Segmentation Challenge (BraTS) 2020 training dataset. The first network was obtained by transferring all the operations and 2D layers of the U-net network to their 3D versions and replacing all its skip connections with concatenation blocks, the second architecture is similar to the first by adding a max pooling layer, a transposed convolution layer and a concatenation block. In both architectures the group normalization layer was used instead of batch normalization as a suggestion of the state-of-the-art. Our best model is capable of segmenting gliomas on the validation dataset with a Dice similarity coefficient of 0.85, 0.84 and 0.87 for the whole tumor, tumor core and enhancing tumor core respectively, therefore, the inference process takes 0.21 seconds per patient with a precision of 0.89. Different values of hyperparameters were tested, deeper architectures and different kernel numbers were implemented in the convolution and concatenation blocks, in no case was a significant improvement in our metrics obtained. Our models outperform most state-of-the-art methods in terms of Dice coefficient, sensitivity, specificity and precision.
Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining ...the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study, we focus on a challenging size range, i.e., particles that have grown to diameters of 10 and 15â¯nm following nucleation, and measure their water uptake. Water uptake is useful information for indirectly obtaining chemical composition of aerosol particles. We use a nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at subsaturated conditions (ca. 90â¯% relative humidity at 293â¯K) to measure the hygroscopicity of particles during the seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) campaign performed at CERN in 2012. In CLOUD7, the hygroscopicity of nucleated nanoparticles was measured in the presence of sulfuric acid, sulfuric acid-dimethylamine, and sulfuric acid-organics derived from α-pinene oxidation. The hygroscopicity parameter κ decreased with increasing particle size, indicating decreasing acidity of particles. No clear effect of the sulfuric acid concentration on the hygroscopicity of 10â¯nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15â¯nm particles sharply decreased with decreasing sulfuric acid concentrations. In particular, when the concentration of sulfuric acid was 5.1âÃâ10.sup.6 â¯moleculesâ¯cm.sup.-3 in the gas phase, and the dimethylamine mixing ratio was 11.8â¯ppt, the measured κ of 15â¯nm particles was 0.31â¯Â±â¯0.01: close to the value reported for dimethylaminium sulfate (DMAS) (κ.sub.DMAS ââ¼â0.28). Furthermore, the difference in κ between sulfuric acid and sulfuric acid-imethylamine experiments increased with increasing particle size. The κ values of particles in the presence of sulfuric acid and organics were much smaller than those of particles in the presence of sulfuric acid and dimethylamine. This suggests that the organics produced from α-pinene ozonolysis play a significant role in particle growth even at 10â¯nm sizes.
Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H.sub.2 SO.sub.4 -H.sub.2 O) system and the ternary system involving ammonia (H.sub.2 SO.sub.4 ...-H.sub.2 O-NH.sub.3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H.sub.2 SO.sub.4 ·NH.sub.3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H.sub.2 SO.sub.4 ·NH.sub.3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization-atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.
Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed ...from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre européen pour la recherche nucléaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovskii-Stokes-Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ~0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products.
A novel fibre-optic UV illumination system for sulphuric acid (H sub(2SO) sub(4)) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light ...(UV) power while causing practically no thermal effect on the aerosol chamber (temperature variation 0.005 degree C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H sub(2SO) sub(4) were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application.
A novel fibre-optic UV illumination system for sulphuric acid (H
2SO
4) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light (UV) power ...while causing practically no thermal effect on the aerosol chamber (temperature variation <0.005
°C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H
2SO
4 were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application.
► UV system provides sufficient UV power while causing practically no thermal effect. ► Precise concentrations of H
2SO
4 are generated by adjusting the UV light intensity. ► Spectrum in the UVB region is comparable to the atm. ground level actinic flux. ► The system allows for reasonably uniform illumination inside the aerosol chamber. ► Thermal inhomogeneities and warm spots on inner surface of the chamber are avoided.
We report comprehensive, demonstrably contaminant-free measurements of binary particle formation rates by sulfuric acid and water for neutral and ion-induced pathways conducted in the European ...Organization for Nuclear Research Cosmics Leaving Outdoor Droplets chamber. The recently developed Atmospheric Pressure interface-time of flight-mass spectrometer was used to detect contaminants in charged clusters and to identify runs free of any contaminants. Four parameters were varied to cover ambient conditions: sulfuric acid concentration (105 to 109 mol cm−3), relative humidity (11% to 58%), temperature (207 K to 299 K), and total ion concentration (0 to 6800 ions cm−3). Formation rates were directly measured with novel instruments at sizes close to the critical cluster size (mobility size of 1.3 nm to 3.2 nm). We compare our results with predictions from Classical Nucleation Theory normalized by Quantum Chemical calculation (QC-normalized CNT), which is described in a companion paper. The formation rates predicted by the QC-normalized CNT were extended from critical cluster sizes to measured sizes using the UHMA2 sectional particle microphysics model. Our results show, for the first time, good agreement between predicted and measured particle formation rates for the binary (neutral and ion-induced) sulfuric acid-water system. Formation rates increase with RH, sulfuric acid, and ion concentrations and decrease with temperature at fixed RH and sulfuric acid concentration. Under atmospheric conditions, neutral particle formation dominates at low temperatures, while ion-induced particle formation dominates at higher temperatures. The good agreement between the theory and our comprehensive data set gives confidence in using the QC-normalized CNT as a powerful tool to study neutral and ion-induced binary particle formation in atmospheric modeling.
Background and Purpose: Both aging and anterior cruciate ligament (ACL) reconstruction are associated with strength deficits, which can in turn influence performance of activities of daily living. ...Thus it is informative to understand mechanisms underlying strength deficits. Age-related declines in strength follow reductions in muscle fiber numbers and size, whereas strength deficits following ACL reconstruction may be caused by the loss of intraligamentous mechanoreceptors. A common link between these conditions is the gamma spindle system, or the gamma loop. Appropriately applied vibration can affect the gamma loop by causing disruption of afferent feedback to a muscle and result in decreased force capabilities. We investigated the effect of age and ACL reconstruction on gamma loop function. Methods: Maximal isometric strength (MVC) and electromyography (EMG) of the quadriceps were quantified before and after vibration stimulation of the infrapatellar tendon of 3 groups: young healthy (n=14; mean age=23.8 yrs), young ACL reconstructed (n=7; mean age=22.4 yrs), and older healthy (n=14; mean age=66.1 yrs) individuals. Results: The quadriceps MVC, vastus lateralis EMG, vastus medialis EMG, and rectus femoris EMG declined significantly in the young healthy group following vibration stimulation to the infrapatellar tendon, which indicated an intact gamma loop. There were no changes in these variables for the old healthy and ACL reconstructed groups. Conclusion: Gamma loop function was impaired in both the older and ACL reconstructed groups possibly due to either decreased muscle spindle sensitivity or the loss of mechanoreceptors. PUBLICATION ABSTRACT
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