(ProQuest: ... denotes formulae and/or non-USASCII text omitted) We perform a next-to-next-to-leading order (NNLO) analysis of nuclear parton distribution functions (nPDFs) using neutral current ...charged-lepton (scriptl super(+ or -)+nucleus) deeply inelastic scattering (DIS) data and Drell-Yan (DY) cross-section ratios ... for several nuclear targets. We study in detail the parametrizations and the atomic mass (A) dependence of the nuclear PDFs at this order. The present nuclear PDFs global analysis provides us a complete set of nuclear PDFs, ..., with a full functional dependence on x, A, Q super(2). The uncertainties of the obtained nuclear modification factors for each parton flavour are estimated using the well-known Hessian method. The nuclear charm quark distributions are also added into the analysis. We compare the parametrization results with the available data and the results of other nuclear PDFs groups. We found our nuclear PDFs to be in reasonably good agreement with them. The estimates of errors provided by our global analysis are rather smaller than those of other groups. In general, a very good agreement is achieved. We also briefly review the recent heavy-ion collisions data including the first experimental data from the LHC proton+lead and lead+lead run which can be used in the global fits of nuclear PDFs. We highlight different aspects of the high luminosity Pb-Pb and p-Pb data which have been recorded by the CMS Collaboration.
We extract polarized parton distribution functions (PPDFs), referred to as “KTA17,” together with the highly correlated strong coupling αs from recent and up-to-date g1 and g2 polarized structure ...functions world data at next-to-next-to-leading order in perturbative QCD. The stability and reliability of the results are ensured by including nonperturbative target mass corrections as well as higher-twist terms which are particularly important at the large-x region at low Q2. Their role in extracting the PPDFs in the nucleon is studied. Sum rules are discussed and compared with other results from the literature. This analysis is made by means of the Jacobi polynomials expansion technique to the DGLAP evolution. The uncertainties on the observables and on the PPDFs throughout this paper are computed using standard Hessian error propagation which served to provide a more realistic estimate of the PPDFs uncertainties.
In this article we obtain a new set of nuclear parton distribution functions (nuclear PDFs) at next-to-leading order and next-to-next-to-leading order accuracy in perturbative QCD. The common nuclear ...deep-inelastic scattering (DIS) data analyzed in our study are complemented by the available charged-current neutrino DIS data with nuclear targets and data from Drell-Yan cross section measurements for several nuclear targets. In addition, the most recent DIS data from the Jefferson Lab CLAS and Hall C experiments are also added to our data sample. For these specific datasets, we consider the impact of target mass corrections and higher twist effects which are expected to be important in the region of large x and intermediate-to-low Q2. Our analysis is based on a publicly available open-source tool, APFEL, which has been modified to be applicable for our analysis of nuclear PDFs. Heavy-quark contributions to nuclear DIS are considered within the framework of the FONLL general-mass variable-flavor-number scheme. The most recent CT18 PDFs are used as baseline proton PDFs. The uncertainties of nuclear PDFs are determined using the standard Hessian approach. The results of our global QCD analysis are compared with existing nuclear PDF sets and with the fitted cross sections, for which our set of nuclear PDFs provides a very good description.
Describe characteristics of small strokes causing acute vestibular syndrome (AVS).
Ambispective cross-sectional study of patients with AVS (acute vertigo or dizziness, nystagmus, nausea/vomiting, ...head-motion intolerance, unsteady gait) with at least one stroke risk factor from 1999 to 2011 at a single stroke referral center. Patients underwent nonquantitative HINTS "plus" examination (head impulse, nystagmus, test-of-skew plus hearing), neuroimaging to confirm diagnoses (97% by MRI), and repeat MRI in those with initially normal imaging but clinical signs of a central lesion. We identified patients with diffusion-weighted imaging (DWI) strokes ≤10 mm in axial diameter.
Of 190 high-risk AVS presentations (105 strokes), we found small strokes in 15 patients (median age 64 years, range 41-85). The most common vestibular structure infarcted was the inferior cerebellar peduncle (73%); the most common stroke location was the lateral medulla (60%). Focal neurologic signs were present in only 27%. The HINTS "plus" battery identified small strokes with greater sensitivity than early MRI-DWI (100% vs 47%, p < 0.001). False-negative initial MRIs (6-48 hours) were more common with small strokes than large strokes (53% n = 8/15 vs 7.8% n = 7/90, p < 0.001). Nonlacunar stroke mechanisms were responsible in 47%, including 6 vertebral artery occlusions or dissections.
Small strokes affecting central vestibular projections can present with isolated AVS. The HINTS "plus" hearing battery identifies these patients with greater accuracy than early MRI-DWI, which is falsely negative in half, up to 48 hours after onset. We found nonlacunar mechanisms in half, suggesting greater risk than might otherwise be assumed for patients with such small infarctions.
•A new conical Latent Heat Thermal Energy Storage (LHTES) system was proposed.•Thermal behavior and performance of the conical and cylindrical systems was compared.•The conic design showed a superior ...thermal performance during charging.•Solidification behavior was not affected by the shape of the vertical LHTES design.•Natural convection effect could be utilized for optimizing the LHTES design.
The shell-and-tube latent heat thermal energy storage (LHTES) system has been widely studied. In this paper, the effect of geometric design on vertical shell and tube LHTES systems is investigated. Accordingly, cylindrical and conically shaped experimental tests are developed for this purpose. The thermal performance of the conical and cylindrical systems is compared experimentally and theoretically. The temporal variation of the experimental temperature is used to validate the mathematical model and demonstrate the effects of natural convection on heat transfer in the phase change material (PCM) during the charging and discharging processes of both systems. The melting/solidification time, liquid fraction, and stored/released energy are used to evaluate the performance of the two systems. The results show that the conical system can store thermal energy much faster than the cylindrical system at the same operating condition at a specific charging time before the system is fully charged. This is enabled since the conical design allows natural convection to dominate in a large volume of PCM at top of the container. However, there is no significant difference during the discharging process. The results indicate that the natural convection effect can be advantageously utilized by optimization of the design of the shell-and-tube LHTES system.
•The power generation potential of storage units should be used as the performance metric.•The discharging cut-off temperature affects the viability of dual-media storage systems.•The shell-and-tube ...system have 20% lower power generation capacity than a 2-tank system.•The NCOTES was introduced as a techno-economic metric for comparison of TES systems.•Dual-media thermocline system had 55% lower NCOTES than a 2-tank system.
The present study conducts a comprehensive comparative techno-economic analysis of some near-term sensible thermal energy storage (TES) alternatives to the ‘standard’ two-tank molten salt system for concentrated solar power (CSP) plants. As such, we conducted detailed, relative annual transient simulations for single-medium thermocline (SMT), dual-media thermocline (DMT), and shell-and-tube (ST) systems. To be consistent with recent literature, the DMT and ST systems use concrete with a porosity of 0.2 (e.g. where concrete occupies 80% of the system) as their low cost filler material. The systems were integrated into a validated 19.9MWe Gemasolar CSP model, which has a solar multiple of 2.5. For a relative analysis, the storage capacity of each TES alternative was fixed at 722MWhth (15 h storage) for all TES alternatives. Based on this capacity, a geometric optimization was performed on DMT and ST systems to maximize the discharged power and minimize the pressure drop. Using the optimum designs, it was found that a CSP plant with a two-tank molten salt system enables the highest amount of electricity generation in a year followed by the SMT and DMT systems, which resulted in 7% and 9% less electricity generation, respectively. As the worst performer, a CSP plant integrated with a ST system generates 20% less electricity over a year. This implies that despite having the same theoretical capacity, the real performance is not same for the alternatives. While these losses may seem egregious at first, large TES cost reductions are made possible in these alternatives due to the fact that a single tank or concrete can be used (noting that concrete is <1/20th the price per kg of molten salt). We propose herein that the true techno-economic advantage (or lack thereof) of choosing alternative TES systems should be judged by a ‘normalized cost of thermal energy storage (NCOTES)’ which normalizes the cost of storage systems with regards to their annual electricity generation capacity. According to our analysis, optimized DMT and ST systems without embedded pipes (e.g. bored or formed concrete) can achieve 55% and 46% reductions relative to the NCOTES of the two-tank system, respectively (with 650K as cut-off discharge temperature), while the SMT system has an 13% lower NCOTES than the two-tank system. With embedded pipes, however, the ST design has a higher NCOTES (+1% to +100%, depending on the discharge cut-off temperature), indicating that embedded piping is the biggest cost driver and that the elimination of piping should be a priority in ST systems. Overall, this study provides a methodology for the relative comparison of various sensible TES alternatives, and it gives insight into the most promising alternatives for moving beyond two-tank molten salt systems.
We present a first QCD analysis of next-to-next-leading-order (NNLO) contributions of the spin-dependent parton distribution functions (PPDFs) in the nucleon and their uncertainties using the Jacobi ...polynomial approach. Having the NNLO contributions of the quark-quark and gluon-quark splitting functions in perturbative QCD Nucl. Phys. B889, 351 (2014), one can obtain the evolution of longitudinally polarized parton densities of hadrons up to NNLO accuracy of QCD. Very large sets of recent and up-to-date experimental data of spin structure functions of the proton (ProQuest: Formulae and/or non-USASCII text omitted), neutron (ProQuest: Formulae and/or non-USASCII text omitted), and deuteron gd1 have been used in this analysis. The predictions for the NNLO calculations of the polarized parton distribution functions as well as the proton, neutron and deuteron polarized structure functions are compared with the corresponding results of the NLO approximation. We form a mutually consistent set of polarized PDFs due to the inclusion of the most available experimental data including the recently high-precision measurements from COMPASS16 experiments Phys. Lett. B 753, 18 (2016). We have performed a careful estimation of the uncertainties using the most common and practical method, the Hessian method, for the polarized PDFs originating from the experimental errors. The proton, neutron and deuteron structure functions and also their first moments, Gammap,n,d, are in good agreement with the experimental data at small and large momentum fractions of x. We will discuss how our knowledge of spin-dependence structure functions can improve at small and large values of x by the recent COMPASS16 measurements at CERN, the PHENIX and STAR measurements at RHIC, and at the future proposed colliders such as the Electron-Ion Collider.
Objectives
Dizziness and vertigo account for roughly 4% of chief symptoms in the emergency department (ED). Little is known about the aggregate costs of ED evaluations for these patients. The authors ...sought to estimate the annual national costs associated with ED visits for dizziness.
Methods
This cost study of adult U.S. ED visits presenting with dizziness or vertigo combined public‐use ED visit data (1995 to 2009) from the National Hospital Ambulatory Medical Care Survey (NHAMCS) and cost data (2003 to 2008) from the Medical Expenditure Panel Survey (MEPS). We calculated total visits, test utilization, and ED diagnoses from NHAMCS. Diagnosis groups were defined using the Healthcare Cost and Utilization Project's Clinical Classifications Software (HCUP‐CCS). Total visits and the proportion undergoing neuroimaging for future years were extrapolated using an autoregressive forecasting model. The average ED visit cost‐per‐diagnosis‐group from MEPS were calculated, adjusting to 2011 dollars using the Hospital Personal Health Care Expenditures price index. An overall weighted mean across the diagnostic groups was used to estimate total national costs. Year 2011 data are reported in 2011 dollars.
Results
The estimated number of 2011 US ED visits for dizziness or vertigo was 3.9 million (95% confidence interval CI = 3.6 to 4.2 million). The proportion undergoing diagnostic imaging by computed tomography (CT), magnetic resonance imaging (MRI), or both in 2011 was estimated to be 39.9% (39.4% CT, 2.3% MRI). The mean per‐ED‐dizziness‐visit cost was $1,004 in 2011 dollars. The total extrapolated 2011 national costs were $3.9 billion. HCUP‐CCS key diagnostic groups for those presenting with dizziness and vertigo included the following (fraction of dizziness visits, cost‐per‐ED‐visit, attributable annual national costs): otologic/vestibular (25.7%; $768; $757 million), cardiovascular (16.5%, $1,489; $941 million), and cerebrovascular (3.1%; $1059; $127 million). Neuroimaging was estimated to account for about 12% of the total costs for dizziness visits in 2011 (CT scans $360 million, MRI scans $110 million).
Conclusions
Total U.S. national costs for patients presenting with dizziness to the ED are substantial and are estimated to now exceed $4 billion per year (about 4% of total ED costs). Rising costs over time appear to reflect the rising prevalence of ED visits for dizziness and increased rates of imaging use. Future economic studies should focus on the specific breakdown of total costs, emphasizing areas of high cost and use that might be safely reduced.
Resumen
Incremento Anual de los Costes de las Atenciones por Mareo en los Servicios de Urgencias de Estados Unidos
Objectivos
El mareo y el vértigo suman aproximadamente el 4% de los motivos de consulta en el servicio de urgencias (SU). Se conoce poco sobre los costes globales de las evaluaciones del SU en estos pacientes. Se buscó estimar los costes anuales nacionales asociados con las visitas al SU por mareo.
Metodología
Este estudio de costes de visitas al SU de adultos norteamericanos que acudieron con mareo o vértigo combinó los datos públicos de las visitas a los SU (1995 a 2009) recogidos por el National Hospital Ambulatory Medical Care Survey (NHAMCS) y los costes (2003 a 2008) recogidos por el Medical Expenditure Panel Survey (MEPS). Se calcularon el total de visitas, el uso de pruebas diagnósticas y los diagnósticos del SU del NHAMCS. Los grupos diagnósticos se definieron según el Healthcare Cost and Utilization Project's Clinical Classifications Software (HCUP‐CCS). Los datos del año 2011 se documentaron en dólares de 2011. El total de visitas y la proporción de neuroimagen llevada a cabo en los futuros años se extrapoló usando un modelo predictivo autorregresivo. La media del coste por visita al SU por grupo diagnóstico del MEPS se calculó, ajustándose a dólares de 2011, mediante el índice de precios de los Hospital Personal Health Care Expenditures. Se utilizó una media ponderada global entre los grupos diagnósticos para estimar los costes totales nacionales.
Resultados
El número de visitas al SU en Estados Unidos en 2011 por mareo o vértigo fue de 3,9 millones (IC 95% = 3,6 a 4,2 millones). El porcentaje de pruebas diagnósticas de imagen llevadas a cabo por tomografía computarizada (TC), resonancia magnética (RM) o ambas en 2011 se estimó en un 39,9% (39,4% TC, 2,3% RM). La media de coste por visita al SU por mareo fue de 1.004 dólares de 2011. Los costes totales, extrapolados para todo el país, fueron de 3.900 millones de dólares. Los grupos diagnósticos HCUP‐CCS para aquéllos que presentaron mareo o vértigo incluyeron los siguientes (proporción de visitas por mareo; coste por visita al SU; costes anuales nacionales atribuibles): otológico/vestibular (25,7%; 768 dólares; 757 millones de dólares), cardiovascular (16,5%, 1.489 dólares; 941 millones de dólares) y cerebrovascular (3,1%; 1.059 dólares; 127 millones de dólares). Se estimó una suma en la neuroimagen del 12% del total de costes para las visitas por mareo en 2011 (360 millones de dólares para la TC y 110 millones de dólares para la RM).
Conclusiones
Los costes totales en Estados Unidos para los pacientes que acuden por mareo al SU son sustanciales, y se estima que sobrepasan en estos momentos los 4.000 millones de dólares por año (aproximadamente un 4% de los costes totales del SU). El incremento de los costes con el paso del tiempo parece reflejar el crecimiento de la prevalencia de las visitas al SU por mareo y el aumento de porcentajes de utilización de la neuroimagen. Futuros estudios económicos deberían centrarse en el desglose de los costes totales, y hacer énfasis en las áreas de alto uso y coste que pueden ser reducidas sin riesgo.
•Often neglected, the relative influence of natural convection was found to depend on geometric parameters and PCM properties.•The error of ignoring natural convection in modelling depends on the ...effectiveness ratio and melting/solidification process.•The error value depends on the following non-dimensional groups: roL,Ra,Bi,Ste.•A critical specific geometry, S, was proposed as a check for when natural convection can be neglected: S=R2-ro22roL<0.005.•A critical Rayleigh number was also found to predict when natural convection is negligible: Racritical=8×105.
There is little understanding of the relative importance of natural convection when designing latent heat thermal energy storage (LHTES) systems based on geometric parameters and/or phase change material (PCM) properties. For high temperature shell-and-tube LHTES systems, this study aims: (i) to determine the error of ignoring natural convection, and (ii) to quantify this error for different geometric parameters and PCM properties. In particular, the study defines the circumstances under which natural convection is important and the error of choosing a ‘conduction-only modelling approach’. To do so, the performance of LHTES systems with nine geometric aspect ratios and three commercial PCMs (of different melting points) were analyzed by means of a validated CFD model.
The results showed that the error is a function of the process under analysis (melting or solidification) and the ratio of stored/delivered energy divided by the maximum capacity of PCM (i.e. its effectiveness). Geometry also plays a critical role in the relative importance of natural convection. The study demonstrates that a specific system geometry (i.e. a dimensionless number defined based on the inner and outer radius as well as the length of shell-and-tube geometry: S=R2-ro22roL) can be used to determine the relevance of natural convection. It was found that regardless of PCM type, the error is of neglecting natural congestion is small if S<0.005. For S>0.005, the error depends on the following non-dimensional groups: roL,Ra,Ste,andBi. As might be expected, the Rayleigh number was found to be the most influential group. Notably, a critical Rayleigh number value (8 × 105) was found, below which the error of neglecting natural convection is <1%. Finally, two correlations were developed in order to quantify the error achieved – one for melting and another for solidification.
The polarized nucleon structure function in the nonsinglet case is investigated here by a new insight rather than conventional perturbative QCD (pQCD). For this purpose, we note that the solution of ...the evolution equations in moment space involves noninteger powers of the coupling constant. Therefore, it is possible to employ a new approach which is called the fractional analytical perturbation theory. Consequently, it is possible to remove the Landau singularities of the renormalized coupling, i.e., at the scales Q∼Λ, using this approach. This provides an opportunity to continue the desired calculations toward small values of energy scales even less than the Λ scale. To modify the analytical perturbation theory, a newer approach is introduced, called 2δanQCD, in which the spectral function of the holomorphic coupling is parameterized in the low-energy region by two delta functions. This model gives us more reliable results for the considered QCD observables, even in the deep infrared region. We calculate the nonsinglet part of the polarized nucleon structure function, using the 2δanQCD model, and compare it with the result from the underlying pQCD where both are in a new defined scheme, called the Lambert scheme. For this purpose, we employ the anQCD package in the Mathematica environment to establish the analytic (holomorphic) coupling constant. The results at various energy scales are also compared with the available experimental data, and it turns out that there is a good consistency between them. The results show that the obtained nucleon structure function at small energy scales has smoother behavior when using the 2δanQCD model than the underlying pQCD. In fact, the coupling constant in analytic QCD behaves moderately, and it makes the result approach the available data in a better way. We also consider the Q2 dependence of the Bjorken sum rule (BSR), using the 2δanQCD model. There is a good agreement between the available experimental data for the BSR and the results from the utilized model, especially at low-energy scales.
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