bluuebunny/crossref_metadata_2025_split huggingface dataset:
Segment‐averaged LET concept and analytical calculation from microdosimetric quantities in proton radiation therapy
Authors: Bertolet A. , Baratto‐Roldán A. , Cortés‐Giraldo M. A. , Carabe‐Fernandez A. 
Published: June 2019

PurposeThis work introduces the concept of segment‐averaged linear energy transfer (LET) as a new approach to average distributions of LET of proton beams based on a revisiting of microdosimetry theory. The concept of segment‐averaged LET is then used to generate an analytical model from Monte Carlo simulations data to perform fast and accurate calculations of LET distributions for proton beams.Methods and materialThe distribution of energy imparted by a proton beam into a representative biological structure or site is influenced by the distributions of (a) LET, (b) segment length, which is the section of the proton track in the site, and (c) energy straggling of the proton beam. The distribution of LET is thus generated by the LET of each component of the beam in the site. However, the situation when the LET of each single proton varies appreciably along its path in the site is not defined. Therefore, a new distribution can be obtained if the particle track segment is decomposed into smaller portions in which LET is roughly constant. We have called “segment distribution” of LET the one generated by the contribution of each portion. The average of that distribution is called segment‐averaged LET. This quantity is obtained in the microdosimetry theory from the average and standard deviation of the distributions of energy imparted to the site, segment length, and energy imparted per collision. All this information is calculated for protons of clinically relevant energies by means of Geant4‐DNA microdosimetric simulations. Finally, a set of analytical functions is proposed for each one of the previous quantities. The presented model functions are fitted to data from Geant4‐DNA simulations for monoenergetic beams from 100 keV to 100 MeV and for spherical sites of 1, 5, and 10 μm in diameter.ResultsThe average differences along the considered energy range between calculations based on our analytical models and MC for segment‐averaged dose‐averaged restricted LET are −0.2 ± 0.7 keV/μm for the 1 μm case, 0.0 ± 0.9 keV/μm for the 5 μm case, and −0.3 ± 1.1 keV/μm for the 10 μm case, respectively. All average differences are below the average standard deviation (1σ) of the MC calculations.ConclusionsA new way of averaging LET for a proton beam is performed to incorporate the effects produced by the variation of stopping power of each individual proton along microscopic biological structures. An analytical model based on MC simulations allows for fast and accurate calculations of segment‐averaged dose‐averaged restricted LET for proton beams, which otherwise would need to be calculated from exhaustive MC simulations of clinical plans.
Automated 4π radiotherapy treatment planning with evolving knowledge‐base
Authors: Landers Angelia , O’Connor Daniel , Ruan Dan , Sheng Ke 
Published: June 2019

PurposeNon‐coplanar 4π radiotherapy generalizes intensity modulated radiation therapy (IMRT) to automate beam geometry selection but requires complicated hyperparameter tuning to attain superior plan quality, which can be tedious and inconsistent. In this study, a fully automated 4π treatment planning was developed using evolving knowledge‐base (EKB) planning guided by dose prediction.MethodsTwenty 4π lung and twenty 4π head and neck (HN) cases were included. A statistical voxel dose learning model was initially trained on low‐quality plans created using generic hyperparameter templates without manual tuning. To improve the automated plan quality without being limited by the training data quality, a new 4π optimization problem was formulated to include a one‐sided penalty on the organ‐at‐risk (OAR) dose deviation from the predicted dose. This directional OAR penalty encourages superior OAR sparing. The fast iterative shrinkage‐thresholding algorithm (FISTA) was used to solve the large‐scale beam orientation optimization problem. With the improved plans, new predictions were created to guide the next loop of EKB planning for a total of 10 loops. Plan quality was evaluated using a plan quality metric (PQM) points system based on clinical dose constraints and compared with automated planning approaches guided by manual high‐quality plans using all non‐coplanar beams, automated plans using individually evolved targeted dose, and manually created 4π plans.ResultsFor the lung cases, the final EKB plans had significantly higher PQM than manually created 4π (+2.60%). The improvements plateaued after the third loop. The final HN EKB plans and manually created 4π plans had comparable PQMs, but had lower PQM compared to automated plans using a high‐quality training set (−3.00% and −4.44%, respectively). The PQM consistently increased up to the sixth loop. Individually evolved plans were able to improve the plan quality from initial condition due to the one‐sided cost function but the 60% of them were trapped in undesired local minima that were substantially worse than their corresponding EKB plans.ConclusionEvolving knowledge‐base planning is a novel automated planning technique guided by the predicted three‐dimensional dose distribution, which can evolve from low‐quality plans. EKB allows new beams to be used in the automated planning workflow for superior plan quality.
A variational method for analysis of laminates with parallel arrays of intralaminar cracks
Authors: Vinogradov Vladimir 
Published: June 2019

SummaryThis paper presents a robust variational method for prediction of the effective thermoelastic properties of laminates with parallel, but not necessarily coplanar intralaminar cracks. Arbitrary laminate layup, crack patterns, and any in‐plane forces and bending moments, and temperature change can be treated simultaneously. The method is based on the principle of minimum complementary energy. The admissible in‐plane stress components are assumed to be linear through the ply thickness. Simple matrix expressions are derived for the effective compliance matrix, thermal expansions and curvatures, and specific heat of a cracked laminate. Predictions for the Young's modulus, Poisson's ratio, shear modulus, flexural rigidity, and thermal expansion as functions of crack density for various laminates of symmetric and nonsymmetric layups demonstrated excellent agreement with experimental results of seven independently published studies. Accuracy and robustness of the method are complemented by the fact that no experimentally fitted parameters are required. It is shown that the same formalism can be applied to analysis of closed intralaminar cracks, as well as nonuniform and nonsymmetrical distributions of cracks.
Predictive value of C‐reactive protein and the Pediatric Risk of Mortality III Score for occurrence of postoperative ventilator‐associated pneumonia in pediatric patients with congenital heart disease
Authors: Sun Yuelin , Zhao Tianxin , Li Dong , Huo Junming , Hu Lan , Xu Feng 
Published: June 2019

AbstractImportanceVentilator‐associated pneumonia (VAP) is one of the most common complications after cardiac surgery in children with congenital heart disease (CHD). Early prediction of the incidence of VAP is important for clinical prevention and treatment.ObjectiveTo determine the value of serum C‐reactive protein (CRP) levels and the Pediatric Risk of Mortality III (PRISM III) score in predicting the risk of postoperative VAP in pediatric patients with CHD.MethodsWe performed a retrospective review of clinical data of 481 pediatric patients with CHD who were admitted to our pediatric intensive care unit. These patients received mechanical ventilation for 48 hours or longer after corrective surgery. On the basis of their clinical manifestations and laboratory results, patients were separated into two groups of those with VAP and those without VAP. CRP levels were measured and PRISM III scores were collected within 12 hours of admission to the pediatric intensive care unit. The Pearson correlation coefficient was used to evaluate the association of CRP levels and the PRISM score with the occurrence of postoperative VAP. A linear regression model was constructed to obtain a joint function and receiver operating curves were used to assess the predictive value.ResultsCRP levels and the PRISM III score in the VAP group were significantly higher than those in the non‐VAP group (P < 0.05). Receiver operating curves suggested that using CRP + the PRISM III score to predict the incidence of VAP after congenial heart surgery was more accurate than using either of them alone (CRP + the PRISM III score: sensitivity: 53.2%, specificity: 85.7%). When CRP + the PRISM III score was greater than 45.460, patients were more likely to have VAP.InterpretationAlthough using CRP levels plus the PRISM III score to predict the incidence of VAP after congenial heart surgery is more accurate than using either of them alone, its predictive value is still limited.
Comparison of magnetic resonance imaging and computed tomography to measure preoperative parameters of children with pectus excavatum
Authors: Sun Jihang , Chen Chenghao , Peng Yun , Zhang Yue , Tian Hongwei , Yu Jie , Cao Jun , Zeng Qi 
Published: June 2019

AbstractImportancePectus excavatum (PE) is the most common thoracic wall deformity in children, we need a method which could be used to evaluate pulmonary functions and effects on development.ObjectiveTo evaluate the use of 3D T1‐weighted (3DT1) and mDIXON magnetic resonance imaging (MRI) sequences for measuring the thoracic parameters and morphology of children with PE, comparing the measurements with those made on computed tomography (CT).MethodsThis is a retrospective study of children with thoracic deformities who were hospitalized at the Department of Thoracic Surgery of the Heart Center, Beijing Children's Hospital, between June 2014 and June 2015. Chest CT was performed first, with the MRI scanning then being performed 0–3 days later. The mDIXON sequences were obtained in inspiratory and expiratory phases and the 3DT1 sequences were obtained during free breathing. Thoracic volume was measured using the acquired images.ResultsThe lung volumes measured on mDIXON MRI and CT were highly correlated, with the Haller index not being significantly different between the two methods. Bland‐Altman analyses showed that lung, cardiac, and retrosternal parameters were similar between the two methods. Pulmonary parameters were higher with the end‐inspiratory phase mDIXON images than with the end‐expiratory phase images, as expected, while cardiac parameters were unaffected by the respiratory phase.InterpretationThoracic volumes measured on mDIXON MRI in combination with held respiration could reflect lung volume functions and help in observing the movement functions of the lungs and heart. The method could be used instead of CT, avoiding subjecting the patient to potentially harmful radiation.
Structural characterization of β‐ketoacyl ACP synthase I bound to platencin and fragment screening molecules at two substrate binding sites
Authors: Patterson Edward I. , Nanson Jeffrey D. , Abendroth Jan , Bryan Cassie , Sankaran Banumathi , Myler Peter J. , Forwood Jade K. 
Published: June 2019

AbstractThe bacterial fatty acid pathway is essential for membrane synthesis and a range of other metabolic and cellular functions. The β‐ketoacyl‐ACP synthases carry out the initial elongation reaction of this pathway, utilizing acetyl‐CoA as a primer to elongate malonyl‐ACP by two carbons, and subsequent elongation of the fatty acyl‐ACP substrate by two carbons. Here we describe the structures of the β‐ketoacyl‐ACP synthase I from Brucella melitensis in complex with platencin, 7‐hydroxycoumarin, and (5‐thiophen‐2‐ylisoxazol‐3‐yl)methanol. The enzyme is a dimer and based on structural and sequence conservation, harbors the same active site configuration as other β‐ketoacyl‐ACP synthases. The platencin binding site overlaps with the fatty acyl compound supplied by ACP, while 7‐hydroxyl‐coumarin and (5‐thiophen‐2‐ylisoxazol‐3‐yl)methanol bind at the secondary fatty acyl binding site. These high‐resolution structures, ranging between 1.25 and 1.70 å resolution, provide a basis for in silico inhibitor screening and optimization, and can aid in rational drug design by revealing the high‐resolution binding interfaces of molecules at the malonyl‐ACP and acyl‐ACP active sites.
Rational Design of Sterically Hindered and Unsymmetrical NpyNimOph Pincer‐Type Ligands and Their Palladium(II) Complexes: Catalytic Applications in Suzuki–Miyaura Reaction and Allylation of Aldehydes
Authors: Maji Ankur , Singh Ovender , Rathi Sweety , Singh U. P. , Ghosh Kaushik 
Published: June 2019

AbstractPalladium(II) complexes 1–4 [Pd(L1 to L4)Cl] derived from pincer‐type tridentate ligands having NpyNimOph donors were synthesized from ligands L1H to L4H (where L1H=(2‐phenyl‐2‐(pyridin‐2‐ylmethyl)hydrazono)methyl)phenol, L2H =[2‐((2‐phenyl‐2‐(pyridinyl‐2‐ylmethyl) hydrazono) methyl) phenol], L3H=[2‐((2‐benzyl‐2‐phenylhydrazono) methyl)‐4,6‐di‐tert‐butylphenol], and L4H=[2‐((2‐benzyl‐2‐phenylhydrazono)methyl)‐6‐(tert‐butyl)‐4‐methoxy phenol where H stands for dissociable proton)in quantitative yields. Synthesized ligands L1H to L4H and corresponding palladium(II) complexes 1–4 were characterized by NMR, IR and HR‐MS spectroscopic studies. Molecular structures of ligand L4H and complexes 1 and 3 were determined by X‐ray crystallography. Complexes 1–4 were utilized as catalysts to investigate Suzuki–Miyaura cross‐coupling reaction upon catalyst loading 0.01 mol%. These catalysts also catalysed allylation of aldehydes upto 95% yield upon catalyst loading 0.5 mol% with broad substrate scopes. Theoretical and experimental investigation was performed to speculate reaction pathway of Suzuki–Miyaura cross‐coupling reaction. A reaction model has also proposed for allylation of aldehydes the presence of allyltributylstannane.
Experimental study on seismic performance of T‐shaped partly precast reinforced concrete shear wall with grouting sleeves
Authors: Li Jianbao , Fan Qiaoqiao , Lu Zheng , Wang Yan 
Published: June 2019

SummaryPrefabricated structure has prominent advantages such as easy control of construction quality, saving fabricating time and natural resources, and reducing environmental pollution and construction noise. The mostly used structural system in high‐rise buildings is reinforced concrete shear wall structure, which has high load capacity and lateral stiffness. Focusing on the connection of reinforcements, three T‐shaped partly prefabricated reinforced concrete shear walls and one cast‐in situ specimen in same dimensions as a control group are tested under low‐frequency cyclic loading to analyze their seismic performances in this paper. During the experiment, the axial compression ratio of specimens is fixed at 0.3, 0.4, and 0.5. Through the observation of phenomena and data analysis, hysteretic curve, skeleton curve, stiffness degradation, ductility, and load bearing capacity are compared and analyzed. The results show that partly prefabricated reinforced concrete shear wall has similar load bearing capacity with the cast in situ specimen, and it also has excellent ductility, stiffness, and energy‐dissipating capacity. The experimental results and analysis indicate that partly prefabricated reinforced concrete shear wall has outstanding seismic performances; under effective and reliable design, it can be used in building structures to play the same role as cast in situ components.
Simulating subhourly variability of wind power output
Authors: Fertig Emily 
Published: June 2019

AbstractAs installed wind power capacity grows, subhourly variability in wind power output becomes increasingly important for determining the system flexibility needs, operating reserve requirements, and cost associated with wind integration. This paper presents a new methodology for simulating subhourly wind power output based on hourly average time series, which are often produced for system planning analyses, for both existing wind plants and expanded, hypothetical portfolios of wind plants. The subhourly model has an AR(p)‐ARCH(q) structure with exogenous input in the heteroskedasticity term. Model coefficients may be fit directly to high‐pass filtered historical data if it exists; for sets of wind plants containing hypothetical plants for which there are no historical data, this paper presents a method to determine model coefficients based on wind plant capacities, capacity factors, and pairwise distances. Unlike predecessors, the model presented in this paper is independent of wind speed data, captures explicitly the high variability associated with intermediate levels of power output, and captures distance‐dependent correlation between the power output of wind plants across subhourly frequencies. The model is parameterized with 1‐minute 2014 plant‐level wind power data from Electric Reliability Council of Texas (ERCOT) and validated out‐of‐sample against analogous 2015 data. The expanded‐capacity model, fit to 2014 data, produces accurate subhourly time series for the 2015 wind fleet (a 49% capacity expansion) based only on the 2015 system's wind plant capacities, capacity factors, and pairwise distances. This supports its use in simulating subhourly fleet aggregate wind power variability for future high‐wind scenarios.
Removal of COD from synthetic wastewater in vertical flow constructed wetland
Authors: Xu Qiaoling , Cui Lihua 
Published: June 2019

AbstractThree vertical flow constructed wetlands, that is, system A (planted with Pennisetum sinese Roxb), system B (planted with Pennisetum purpureum Schum.), and system C (without plants as the control) were constructed to estimate the contribution of substrates, plants, and microorganisms to organic matter removal. The organic compounds accumulated in the substrate in systems A, B, and C were 12.03%, 11.91%, and 9.4%, respectively. Synergistic utilization of organic compounds by microorganisms and plants in systems A, B, and C were 80.95%, 81.58%, and 80.11%, respectively. Substrate interception and adsorption of organic compounds in plant systems A and B were more extensive than in the nonplant control system C. The total accumulative and absorptive capacity of systems A, B, and C was as follows: B (2,713 g) > A (2,698 g) > C (2,076 g). The amounts of insoluble organic accumulated on the upper substrates of the three systems showed the order C > A > B. No constructed wetland clogging occurred for A and B systems during the experiment, while system C suffered clogging in early September. Therefore, substrate blockage may be related to the type of organic compound accumulated. Accumulation of insoluble organic matter is the direct cause of system blockage.Practitioner points

Substrate interception and adsorption of organic compounds in plant systems were more extensive than those in the nonplant control system.

Distribution characteristics of the surface layer were significantly higher than those of the middle and bottom layers.

Substrate blockage is related to the type of organic compound accumulated.

Accumulation of insoluble organic compounds may be the direct cause of system blockage.

The upper substrate is the main site for organic compound removal.
Fischer-Tropsch products from biomass-derived syngas and renewable hydrogen
Authors: Gruber Hannes , Groß Peter , Rauch Reinhard , Reichhold Alexander , Zweiler Richard , Aichernig Christian , Müller Stefan , Ataimisch Nabeel , Hofbauer Hermann 
Published: June 2019

AbstractGlobal climate change will make it necessary to transform transportation and mobility away from what we know now towards a sustainable, flexible, and dynamic sector. A severe reduction of fossil-based CO2 emissions in all energy-consuming sectors will be necessary to keep global warming below 2 °C above preindustrial levels. Thus, long-distance transportation will have to increase the share of renewable fuel consumed until alternative powertrains are ready to step in. Additionally, it is predicted that the share of renewables in the power generation sector grows worldwide. Thus, the need to store the excess electricity produced by fluctuating renewable sources is going to grow alike. The “Winddiesel” technology enables the integrative use of excess electricity combined with biomass-based fuel production. Surplus electricity can be converted to H2 via electrolysis in a first step. The fluctuating H2 source is combined with biomass-derived CO-rich syngas from gasification of lignocellulosic feedstock. Fischer-Tropsch synthesis converts the syngas to renewable hydrocarbons. This research article summarizes the experiments performed and presents new insights regarding the effects of load changes on the Fischer-Tropsch synthesis. Long-term campaigns were carried out, and performance-indicating parameters such as per-pass CO conversion, product distribution, and productivity were evaluated. The experiments showed that integrating renewable H2 into a biomass-to-liquid Fischer-Tropsch concept could increase the productivity while product distribution remains almost the same. Furthermore, the economic assessment performed indicates good preconditions towards commercialization of the proposed system.
Spark channel dynamics in railgun switches in unipolar and oscillatory discharges
Authors: Kharlov A.V. 
Published: June 2019

AbstractSpark gaps are often used to commute energy in the discharge of a capacitive storage to a load. In some applications, a unipolar pulse is not feasible, and an oscillatory (underdamped sinusoidal) regime must be realized for the discharge of the capacitor bank. Spark gaps, which were developed for unipolar discharge, cannot be directly employed in an under-damped (oscillatory) regime since at the transition of the current through zero, the spark channel could stop motion and ignite in the following half period. This work has two main objectives: (i) To develop and test a simulation model of spark channel motion in linear rail geometry, which must be valid for both the oscillatory and unipolar regimes of capacitor bank discharge; and (ii) to investigate arc motion and electrode heating, depending on the current and charge transfer, over a wide range of operation. A self-consistent treatment of plasma motion and electrode heating (taking into account the radiation of a plasma channel) is applied in the present paper, and it is shown that radiation can significantly impact on the temperature of the electrodes. Electrode ablation and the temperature dependence of the main thermal parameters are also taken into account. Stainless steel (Cr/Ni/Ti 18/10/0.6÷0.8), copper (Cu), chromium (Cr), tungsten (W), and molybdenum (Mo) are used here as electrode materials since these materials are widely used for the manufacture of electrodes. The results of numerical calculations are compared with experimental results, and conditions are defined for reduced electrode erosion.
Speeding and Speed Modification of Older Drivers: Does Vehicle Type Make a Difference?
Authors: Cull Andrew W. , Porter Michelle M. , Nakagawa Satoru , Smith Glenys A. , Rapoport Mark J. , Marshall Shawn C. , Bédard Michel , Tuokko Holly , Vrkljan Brenda , Naglie Gary , Myers Anita M. , Mazer Barbara 
Published: June 2019

ABSTRACTThe purpose of this study was to examine whether vehicle type based on size (car vs. other = truck/van/SUV) had an impact on the speeding, acceleration, and braking patterns of older male and female drivers (70 years and older) from a Canadian longitudinal study. The primary hypothesis was that older adults driving larger vehicles (e.g., trucks, SUVs, or vans) would be more likely to speed than those driving cars. Participants (n = 493) had a device installed in their vehicles that recorded their everyday driving. The findings suggest that the type of vehicle driven had little or no impact on per cent of time speeding or on the braking and accelerating patterns of older drivers. Given that the propensity for exceeding the speed limit was high among these older drivers, regardless of vehicle type, future research should examine what effect this behaviour has on older-driver road safety.