bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non‐stationary model of oblique x‐ray incidence in amorphous selenium detectors: I. Point spread function
Authors: Acciavatti Raymond J. , Maidment Andrew D. A. 
Published: November 2018

PurposeIn previous work, a theoretical model of the point spread function (PSF) for oblique x‐ray incidence in amorphous selenium (a‐Se) detectors was proposed. The purpose of this paper is to develop a complementary model that includes two additional features. First, the incidence angle and the directionality of ray incidence are calculated at each position, assuming a divergent x‐ray beam geometry. This approach allows the non‐stationarity of the PSF to be modeled. Second, this paper develops a framework that is applicable to a digital system, unlike previous work which did not model the presence of a thin‐film transistor (TFT) array.MethodsAt each point on the detector, the incidence angle and the ray incidence direction are determined using ray tracing. Based on these calculations, an existing model for the PSF of the x‐ray converter (Med Phys. 1995;22:365‐374) is generalized to a non‐stationary model. The PSF is convolved with the product of two rectangle functions, which model the sampling of the TFT array. The rectangle functions match the detector element (del) size in two dimensions.ResultsIt is shown that the PSF can be calculated in closed form. This solution is used to simulate a digital mammography (DM) system at two x‐ray energies (20 and 40 keV). Based on the divergence of the x‐ray beam, the direction of ray incidence varies with position. Along this direction, the PSF is broader than the reference rect function matching the del size. The broadening is more pronounced with increasing obliquity. At high energy, the PSF deviates more strongly from the reference rect function, indicating that there is more blurring. In addition, the PSF is calculated along the polar angle perpendicular to the ray incidence direction. For this polar angle, the shape of the PSF is dependent upon whether the ray incidence direction is parallel with the sides of the detector. If the ray incidence direction is parallel with either dimension, the PSF is a perfect rectangle function, matching the del size. However, if the ray incidence direction is at an oblique angle relative to the sides of the detector, the PSF is not rectangular. These results illustrate the non‐stationarity of the PSF.ConclusionsThis paper demonstrates that an existing model of the PSF of a‐Se detectors can be generalized to include the effects of non‐stationarity and digitization. The PSF is determined in closed form. This solution offers the advantage of shorter computation time relative to approaches that use numerical methods. This model is a tool for simulating a‐Se detectors in future work, such as in virtual clinical trials with computational phantoms.
Multishot diffusion‐prepared magnitude‐stabilized balanced steady‐state free precession sequence for distortion‐free diffusion imaging
Authors: Gao Yu , Han Fei , Zhou Ziwu , Zhong Xiaodong , Bi Xiaoming , Neylon John , Santhanam Anand , Yang Yingli , Hu Peng 
Published: November 2018

PurposeTo develop and evaluate a multishot diffusion‐prepared (DP) magnitude‐stabilized balanced steady‐state free precession (bSSFP) diffusion imaging sequence with improved geometric fidelity.MethodsA signal spoiler (magnitude stabilizer; MS) was implemented in a DP‐bSSFP diffusion sequence. Effects of magnitude stabilizers with respect to phase errors were simulated using Bloch simulation. Phantom study was conducted to compare the apparent diffusion coefficient (ADC) accuracy and geometric reliability, quantified using target registration error (TRE), with diffusion‐weighted single‐shot echo‐planar imaging (DW‐ssEPI). Six volunteers were recruited. DW‐ssEPI, DP‐bSSFP with and without ECG triggering, and DP‐MS‐bSSFP with and without ECG triggering were acquired 10 times with b = 500 s/mm2 in a single‐shot manner to evaluate magnitude variability. Diffusion trace images and diffusion tensor images were acquired using a 4‐shot DP‐MS‐bSSFP.ResultsSimulation showed that the DP‐MS‐bSSFP approach is insensitive to phase errors. The DP‐MS‐bSSFP approach had satisfactory ADC accuracy on the phantom with <5% difference with DW‐ssEPI. The mean/max TRE for DW‐ssEPI was 2.31/4.29 mm and was 0.51/1.20 mm for DP‐MS‐bSSFP. In the repeated single‐shot study, DP‐bSSFP without ECG triggering had severe signal void artifacts and exhibited a nonrepeatable pattern, which can be partially mitigated by ECG triggering. Adding the MS provided stable signal magnitude across all repetitions. High‐quality ADC maps and color‐coded fractional anisotropy maps were generated using the 4‐shot DP‐MS‐bSSFP. The mean/max TRE was 2.89/10.80 mm for DW‐ssEPI and 0.59/1.69 mm for DP‐MS‐bSSFP. Good agreements of white matter ADC, cerebrospinal fluid ADC, and white matter fractional anisotropy value were observed between DP‐MS‐bSSFP and DW‐ssEPI.ConclusionThe proposed DP‐MS‐bSSFP approach provided high‐quality diffusion‐weighted and diffusion‐tensor images with minimal geometric distortion.
Collapse loads for rectangular foundations by three‐dimensional upper bound limit analysis using radial point interpolation method
Authors: Mohapatra Debasis , Kumar Jyant 
Published: November 2018

SummaryA three‐dimensional kinematic limit analysis approach based on the radial point interpolation method (RPIM) has been used to compute collapse loads for rectangular foundations. The analysis is based on the Mohr‐Coulomb yield criterion and the associated flow rule. It is understood that the internal plastic power dissipation function and flow rule constraints can be expressed entirely in terms of plastic strain rates without involving stresses. The optimization problem has been solved on basis of the semidefinite programming (SDP) by using highly efficient primal‐dual interior point solver MOSEK in MATLAB. The results have been presented in terms of the variation of the shape factors with changes in the aspect ratio (L/B) of the footing for different values of soil internal friction angle (ϕ). Computations have revealed that the shape factors, sc and sq, due to effects of cohesion and surcharge increase continuously with (1) decrease in L/B and (2) increase in ϕ. On the other hand, the shape factor sγ, due to the effect of soil unit weight, increases very marginally with an increase in L/B up to (1) ϕ = 25° for a rough footing and (2) ϕ = 35° for a smooth footing. Thereafter, for greater values of ϕ, the variation of sγ with L/B has been found to be quite similar to that of the factors sc and sq. The variations of (1) nodal velocity patterns, (2) plastic power dissipation, and (3) maximum plastic shear strain rates have also been examined to interpret the associated failure mechanism.
Longitudinal assessment of cerebral perfusion and vascular response to hypoventilation in a bigenic mouse model of Alzheimer's disease with amyloid and tau pathology
Authors: Govaerts Kristof , Lechat Benoit , Struys Tom , Kremer Anna , Borghgraef Peter , Van Leuven Fred , Himmelreich Uwe , Dresselaers Tom 
Published: November 2018

Alzheimer's disease is the most common neurodegenerative disease, and many patients also present with vascular dysfunction. In this study, we aimed to assess cerebral blood flow (CBF) and cerebrovascular response (CVR) as early, pre‐symptomatic (3 months of age), imaging markers in a bigenic model of Alzheimer's disease (APP.V717IxTau.P301L, biAT) and in the monogenic parental strains. We further developed our previously published combination of pulsed arterial spin labeling perfusion MRI and hypo‐ventilation paradigm, which allows weaning of the mice from the ventilator. Furthermore, the commonly used isoflurane anesthesia induces vasodilation and is thereby inherently a vascular challenge. We therefore assessed perfusion differences in the mouse models under free‐breathing isoflurane conditions. We report (i) that we can determine CBF and hypoventilation‐based CVR under ketamine/midazolam anesthesia and wean mice from the ventilator, making it a valuable tool for assessment of CBF and CVR in mice, (ii) that biAT mice exhibit lower cortical CBF than wild‐type mice at age 3 months, (iii) that CVR was increased in both biAT and APP.V717I mice but not in Tau.P301L mice, identifying the APP genotype as a strong influencer of brain CVR and (iv) that perfusion differences at baseline are masked by the widely used isoflurane anesthesia.
Medication administration in nursing homes: A qualitative study of the nurse role
Authors: Odberg Kristian Ringsby , Hansen Britt Sætre , Wangensteen Sigrid 
Published: November 2018

AbstractAimsThe objective of this study was to expand the knowledge of the nurse role during medication administration in the context of nursing homes. The following research question guided the study: How can the nurse role during medication administration in nursing homes be described?DesignA QUAL–qual mixed study design was applied.MethodsData were collected using partial participant observations and semi‐structured interviews of all staff members involved in medication administration. An inductive content analysis was performed.ResultsMedication administration is a pervasive process ingrained in the day‐to‐day activities of providing care to the patients. The nurse role is compensating, flexible and adaptable. There is a dynamic interaction between several contributory factors, those being shifting responsibility, a need for competence, invisible leadership, varying available competence, staff stability and vulnerable shifts.
In‐Cell NMR Spectroscopy of Intrinsically Disordered Proteins
Authors: Sciolino Nicholas , Burz David S. , Shekhtman Alexander 
Published: November 2018

AbstractThis review summarizes the results of in‐cell Nuclear Magnetic Resonance, NMR, spectroscopic investigations of the eukaryotic and prokaryotic intrinsically disordered proteins, IDPs: α‐synuclein, prokaryotic ubiquitin‐like protein, Pup, tubulin‐related neuronal protein, Tau, phenylalanyl‐glycyl‐repeat‐rich nucleoporins, FG Nups, and the negative regulator of flagellin synthesis, FlgM. The results show that the cellular behavior of IDPs may differ significantly from that observed in the test tube.
Basicity‐dependent properties of anion conducting membranes consisting of iminium cations for alkaline fuel cells
Authors: Ko Beom‐Seok , Yoshimura Kimio , Warapon Sinananwanich , Shishitani Hideyuki , Yamaguchi Susumu , Tanaka Hirohisa , Maekawa Yasunari 
Published: November 2018

ABSTRACTTo design novel anion‐conducting polymer electrolyte membranes (AEMs), this paper proposes a basicity index (BI) that is defined by the ion‐exchange ratios of AEMs from the OH− to Cl− forms in a neutral aqueous solution as a parameter for Arrhenius basicity (dissociation constant). Using a radiation‐induced graft polymerization technique, three iminium cations are introduced into fluorinated polymer films. The BI of the iminium‐containing AEMs is less than that of a conventional ammonium‐type AEM. The conductivity and water uptake correlate positively with the BI, whereas the thermal and chemical stabilities correlate negatively with the BI. The dependence on the BI stems from the stabilization of the iminium hydroxide in proportion to the basicity of the original diaza‐compounds, resulting in a decrease in conductivity and water uptake with keeping higher thermal and chemical stabilities. Notably, ion conductivity is sufficient and water uptake is less in AEMs with a medium BI. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 503–510
A comparison of biological activity of commercially available purified native botulinum neurotoxin serotypes A1 to F1 in vitro, ex vivo, and in vivo
Authors: Donald Sarah , Elliott Mark , Gray Bryony , Hornby Fraser , Lewandowska Agnieszka , Marlin Sandra , Favre‐Guilmard Christine , Périer Cindy , Cornet Sylvie , Kalinichev Mikhail , Krupp Johannes , Fonfria Elena 
Published: November 2018

AbstractBotulinum neurotoxin (BoNT) is a major therapeutic agent. Of seven native BoNT serotypes (A to G), only A and B are currently used in the clinic. Here we compared the potency of commercially available purified native serotypes A1 to F1 across in vitro, ex vivo, and in vivo assays. BoNT potency in vitro was assessed in rat primary cells (target protein cleavage and neurotransmitter release assays) in supraspinal, spinal, and sensory systems. BoNT potency ex vivo was measured in the mouse phrenic nerve hemidiaphragm (PNHD) assay, measuring muscle contractility. In vivo, BoNT‐induced muscle relaxation in mice and rats was assessed in the Digit Abduction Score (DAS) test, while effects on body weight (BW) gain were used to assess tolerability. In all assays, all BoNT serotypes were potent toxins, except serotype D1 in vivo which failed to produce significant muscle flaccidity in mice and rats. In rats, all serotypes were well‐tolerated, whereas in mice, reductions in BW were detected at high doses. Serotype A1 was the most potent serotype across in vitro, ex vivo, and in vivo assays. The rank order of potency of the serotypes revealed differences among assays. For example, species‐specificity was seen for serotype B1, and to a lesser extent for serotype C1. Serotypes F1 and C1, not currently in the clinic, showed preference for sensory over motor models and therefore could be considered for development in conditions involving the somatosensory system.
Where science, technology, engineering, and mathematics (STEM) graduates move: Human capital, employment patterns, and interstate migration in the United States
Authors: Wright Richard , Ellis Mark 
Published: November 2018

AbstractThis research investigates the interstate migration of workers in the United States who have earned an undergraduate STEM (science, technology, engineering, and mathematics) degree compared with those who have not. We build on previous studies that (a) classified “skilled” workers as having earned an undergraduate degree (b) used net migration gain or loss as a yardstick of relative destination attraction, and (c) advanced the idea that physical amenities play an outsized role in labour market preferences for skilled workers. We calibrate the attractivity of states for three levels of human capital and then evaluate these assessments of relative attractivity to show that workers with different types of human capital respond to different labour market signals in contradictory ways. Amenity, measured by heating degree days, has little to do with the state‐to‐state migration of workers who have a STEM degree, yet helps explain the migration patterns of workers with no undergraduate degree. Employment growth in a state influences migration for degreed workers in the recessionary years but not in the period of recovery. The opposite holds for workers without a degree. States with high percentages of any type of degreed workers attract both STEM and non‐STEM degreed migrants but not those without a degree. States with a large share of STEM degreed workers in their degreed workforce are especially attractive for STEM degreed migrants. The conclusions discuss what the findings imply about diverging access to labour market opportunity by human capital and state higher education policy.
How confident are predictability estimates of the winter North Atlantic Oscillation?
Authors: Weisheimer Antje , Decremer Damien , MacLeod David , O'Reilly Christopher , Stockdale Tim N. , Johnson Stephanie , Palmer Tim N. 
Published: November 2018

Atmospheric seasonal predictability in winter over the Euro‐Atlantic region is studied with an emphasis on the signal‐to‐noise paradox of the North Atlantic Oscillation. Seasonal hindcasts of the ECMWF model for the recent period 1981–2009 show, in agreement with other studies, that correlation skill over Greenland and parts of the Arctic is higher than the signal‐to‐noise ratio implies. This leads to the paradoxical situation where the real world appears more predictable than the models suggest, with the forecast ensembles being overly dispersive (or underconfident). However, it is demonstrated that these conclusions are not supported by the diagnosed relationship between ensemble mean root‐mean‐square error (RMSE) and ensemble spread which indicates a slight under‐dispersion (overconfidence). Furthermore, long atmospheric seasonal hindcasts suggest that over the 110‐year period from 1900 to 2009 the ensemble system is well calibrated (neither over‐ nor under‐dispersive). The observed skill changed drastically in the middle of the twentieth century and paradoxical regions during more recent hindcast periods were strongly under‐dispersive during mid‐century decades.Due to non‐stationarities of the climate system in the form of decadal variability, relatively short hindcasts are not sufficiently representative of longer‐term behaviour. In addition, small hindcast sample size can lead to skill estimates, in particular of correlation measures, that are not robust. It is shown that the relative uncertainty due to small hindcast sample size is often larger for correlation‐based than for RMSE‐based diagnostics. Correlation‐based measures like the RPC are shown to be highly sensitive to the strength of the predictable signal, implying that disentangling of physical deficiencies in the models on the one hand, and the effects of sampling uncertainty on the other hand, is difficult. Given the current lack of a causal physical mechanism to unravel the puzzle, our hypotheses of non‐stationarity and sampling uncertainty provide simple yet plausible explanations for the paradox.
Carbon and oxygen isotopic analyses of calcite in calcite–dolomite mixtures: Optimization of selective acid extraction
Authors: Liu Xi , Deng Wenfeng , Wei Gangjian 
Published: November 2018

RationaleCarbon and oxygen isotopic compositions of individual minerals in calcite–dolomite mixtures could be measured using a selective acid extraction technique based on the different reaction rates of calcite and dolomite with phosphoric acid. However, poor accuracies of calcite are usually obtained when mixtures of low calcite content are analyzed, which may result in incorrect conclusions. To overcome this shortcoming, improvements are needed in accuracy and precision when using the technique with mixtures of low calcite content.MethodsCalcite and dolomite were analyzed under different reaction conditions using a GV Isoprime™ II isotope ratio mass spectrometer equipped with a dual inlet (DI) and an automatic sampler, to study the relationships between isotopic compositions and CO2 yield, and reaction time and temperature. Artificial mixtures with varied calcite:dolomite ratios were prepared, and their calcite isotopic compositions were determined with the aim of optimizing analytical conditions.ResultsThe CO2 yields and isotopic compositions of calcite and dolomite were obtained on‐line under different experimental conditions using DI‐isotope ratio mass spectrometry (DI‐IRMS). Based on the analysis results of artificial mixtures, the reaction conditions for analyzing isotopic composition of calcite in mixtures were optimized as follows. Samples should have grain sizes of 75–80 μm; and samples with calcite contents of >50%, 30–50% and < 30% should be reacted with acid for 10–15 min at 50°C, 6 min at 50°C and 45 min at 25°C, respectively.ConclusionsOptimized analytical conditions are suggested for the determination of the isotopic compositions of calcite in mixtures with improved accuracy by an automatic selective acid extraction technique.
Concentration of stromal cell‐derived factor‐1 (SDF‐1/CXCL12) in the follicular fluid is associated with blastocyst development
Authors: Nishigaki Akemi , Tsuzuki‐Nakao Tomoko , Kido Takeharu , Kida Naoko , Kakita‐Kobayashi Maiko , Murata Hiromi , Okada Hidetaka 
Published: November 2018

AbstractPurposeTo study the association between stromal cell‐derived factor‐1 (SDF‐1/CXCL12) and vascular endothelial growth factor (VEGF) concentrations in individual human ovarian follicles and IVF outcomes.MethodsConcentrations of SDF‐1 and VEGF in 261 follicular fluid samples were measured with enzyme‐linked immunosorbent assay. IVF outcome parameters were included in fertilization rate, cleavage rate, embryo morphology on day 3, and blastocyst morphology on day 5.ResultsThe follicular concentration of SDF‐1 and VEGF was not significantly associated with fertilization and cleavage outcome, and embryo morphology. The rates of full blastocysts and good‐quality blastocysts were significantly higher in follicles with an SDF‐1 concentration of 275‐350 pg/mL than in the follicles with SDF‐1 concentrations of <200 and ≥350 pg/mL (P < 0.05). The follicular concentration of VEGF was not associated with the blastocyst morphology.ConclusionOur findings showed that follicular concentration of SDF‐1, and not VEGF, may be a valuable biochemical marker of blastocyst development.
Statistical methodology for constructing gestational age‐related charts using cross‐sectional and longitudinal data: The INTERGROWTH‐21stproject as a case study
Authors: Ohuma Eric O. , Altman Douglas G. ,   for the International Fetal and Newborn Growth Consortium for the 21 Century (INTERGROWTH‐21 Project)
Published: November 2018

Most studies aiming to construct reference or standard charts use a cross‐sectional design, collecting one measurement per participant. Reference or standard charts can also be constructed using a longitudinal design, collecting multiple measurements per participant. The choice of appropriate statistical methodology is important as inaccurate centiles resulting from inferior methods can lead to incorrect judgements about fetal or newborn size, resulting in suboptimal clinical care.Reference or standard centiles should ideally provide the best fit to the data, change smoothly with age (eg, gestational age), use as simple a statistical model as possible without compromising model fit, and allow the computation of Z‐scores from centiles to simplify assessment of individuals and enable comparison with different populations. Significance testing and goodness‐of‐fit statistics are usually used to discriminate between models. However, these methods tend not to be useful when examining large data sets as very small differences are statistically significant even if the models are indistinguishable on actual centile plots. Choosing the best model from amongst many is therefore not trivial. Model choice should not be based on statistical considerations (or tests) alone as sometimes the best model may not necessarily offer the best fit to the raw data across gestational age. In this paper, we describe the most commonly applied methodologies available for the construction of age‐specific reference or standard centiles for cross‐sectional and longitudinal data: Fractional polynomial regression, LMS, LMST, LMSP, and multilevel regression methods. For illustration, we used data from the INTERGROWTH‐21stProject, ie, newborn weight (cross‐sectional) and fetal head circumference (longitudinal) data as examples.