Dilution Theory Research Articles

One-Shot Coherence Dilution

Manipulation and quantification of quantum resources are fundamental problems in quantum physics. In the asymptotic limit, coherence distillation and dilution have been proposed by manipulating infinite identical copies of states. In the nonasymptotic setting, finite data-size effects emerge, and the practically relevant problem of coherence manipulation using finite resources has been left open. This Letter establishes the one-shot theory of coherence dilution, which involves converting maximally coherent states into an arbitrary quantum state using maximally incoherent operations, dephasing-covariant incoherent operations, incoherent operations, or strictly incoherent operations. We introduce several coherence monotones with concrete operational interpretations that estimate the one-shot coherence cost-the minimum amount of maximally coherent states needed for faithful coherence dilution. Furthermore, we derive the asymptotic coherence dilution results with maximally incoherent operations, incoherent operations, and strictly incoherent operations as special cases. Our result can be applied in the analyses of quantum information processing tasks that exploit coherence as resources, such as quantum key distribution and random number generation.

The Roles of Blending and of Molecular Weight Distribution on Craze Initiation

Craze initiation stress was measured in three-point bending isochronal creep tests on a series of entangled bimodal blends of polystyrenes of narrow dispersity, on three polystyrenes of broad dispersity, and on four blends of polystyrenes of broad dispersity. Crazing stress was found to increase rapidly with small additions of the higher molar mass component, quickly reaching a plateau. A simple model based on the weighted addition of the crazing stress contributions of the individual weight fractions obtained from an established piecewise linear crazing law was able to predict the crazing stress accurately in the bimodal blends using a power law exponent of 2.59 (90% CI [1.75–17.34]). In broad dispersity systems, in particular where short unentangled chains dilute the polymer, it was found necessary to modify the model using dynamic tube dilution theory. Dilution leads to a change in the entanglement length and hence in the molar mass at which transitions to disentanglement and chain scission crazing occur. With the improved model, crazing stress could be predicted even for the broad dispersity polymers with wide and bimodal distributions. This represents an opportunity for the molecular design of polymers by blending to achieve improved resistance to craze initiation.

Social Structure Imbalance of Chinese Population: Theoretical Mechanism and Empirical Analysis

With constant reduction in fertility rate, China is not only faced with the plight of population growth, but also has a serious imbalance in the social structure of population. Based on educational resource dilution theory, this paper theoretically and empirically analyzes the interaction mechanism between education and fertility rate & the law of population development, and finally demonstrates the imbalance of social structure of population and its forming mechanism. It comes to the conclusions as follows:firstly, on the one hand, the interaction mechanism between education and fertility rate can lead to the gradual rise in fertility rate and thereby make population development enter into a high fertility trap; on the other hand, it may cause fertility rate continue to decline and fall into the trap of low fertility, finally forming the Z pattern of population development, namely at middle education level education is significantly negatively related with fertility rate, but at higher or lower education levels there is no significant correlation between education and fertility; secondly, owing to obvious urban-rural, regional and ethnic differences in education development, affected by the Z law of population development, all residents are bound to gradually be divided into two categories, the fertility rate of residents will differentiate high and low ends, and this development of population will lead to the imbalance of the population of urban and rural structure, regional structure, national structure and quality structure. Furthermore, based on nationwide census county-level data, this paper uses instrumental variables method and Hausman-Taylor estimation method to examine the Z law of population development and resulting imbalance of population social structure. It not only enriches current population structure research, but also has important implications for the reform of population and education in China.

PLAČIAI ŽINOMŲ PREKIŲ ŽENKLŲ APSAUGĄ PAGRINDŽIANČIŲ TEORIJŲ ANALIZĖ

Straipsnyje analizuojamos teorijos, pagrindžiančios plačiai žinomų prekių ženklų apsaugą, įtvirtintą Sutarties dėl intelektinės nuosavybės teisių aspektų, susijusių su prekyba (TRIPS), 16 straipsnio 3 dalyje. Straipsniu siekiama atskleisti pagrindines remiantis TRIPS 16 straipsnio 3 dalimi saugomas prekių ženklų funkcijas ir jų ribas bei nustatyti galbūt tinkamiausią šios apsaugos doktrininį pagrindimą.

Modeling of Performance Loss and pH Gradients in Hydroxide Exchange Membrane Fuel Cells Exposed to Carbon Dioxide

Hydroxide exchange membrane fuel cells (HEMFCs) have been attracting significant interest due to recent advancements in membrane stability and performance, as well as cost advantages of materials enabled by the alkaline environment1. A critical challenge for HEMFCs is mitigating performance loss upon exposure to carbon dioxide, which is caused by carbonate and bicarbonate formation in the polymer electrolyte. The presence of carbonate and bicarbonate reduces conductivity of the membrane and induces concentration overpotential through pH gradients. Therefore, transport of carbonate and bicarbonate in alkaline polymer electrolytes is a critically important issue for the future of HEMFCs. Modeling can provide crucial insight into the magnitude of the carbon dioxide poisoning effect and possibilities for performance improvement. As an initial investigation, we have created a 1-D model of carbonate transport through the thickness of the membrane electrode assembly (MEA) based on dilute solution theory. The model considers the kinetics of CO2 hydration and dehydration by both the carbonic acid and alkaline reactions2, CO2 + H2O ↔ H2CO3 [1a]H2CO3 + OH- ↔ H2O + HCO3 - [1b]CO2 + OH- ↔ HCO3 - [2] Additionally, the acid-base equilibrium between carbonate, bicarbonate, and hydroxide, HCO3 - + OH- ↔ CO3 2- + H2O [3] is considered. The model is used to predict the pH profile through the MEA and quantify the effects of temperatures, flow rates, and CO2concentration on HEMFC performance. Figure 1 shows the pH profile in the anode, membrane, and cathode for the case of O2 with 400 ppm CO2 as the oxidant. At open circuit, the pH is lower at the cathode than at the anode due to the difference in CO2 partial pressure, although the gradient is small. Once current is applied, the ionic potential gradient drives bicarbonate and carbonate towards the anode, and the pH gradient reverses. At moderate and high current densities, nearly all CO2is removed from the cathode gas stream and electrochemically pumped into the anode gas stream. The electrochemical pumping of carbonate and bicarbonate towards the anode lowers the anode pH until the rate of CO2 dehydration balances the flux of CO2 through the membrane. Carbonate and bicarbonate carry both CO2 and charge simultaneously. When the CO2flux through the membrane is small relative to the current density, the current is carried either by hydroxide ions or by counterbalanced fluxes of carbonate and bicarbonate. A large pH gradient is required to drive the counterbalancing diffusion of bicarbonate from anode to cathode. At high pH, charge transport shifts from the carbonate-bicarbonate shuttle to hydroxide ions, and the pH gradient flattens. In Figure 1, these dynamics are illustrated by the steep pH gradient from ca. 10-12, and the much flatter gradient above a pH of 12. Figure 2 shows the effect of 400 ppm carbon dioxide on MEA performance for varying reactant flowrates. Increasing the cathode flowrate increases the amount of CO2 electrochemically pumped into the anode gas stream. Reducing the anode flowrate provides less dilution for the pumped CO2, increasing the anode partial pressure of CO2. Both of these factors force the anode pH lower to accelerate CO2 dehydration, leading to larger pH gradients and reduced performance. Even at the high operating temperature of 95 °C, the introduction of 400 ppm CO2into the cathode gas stream can cause roughly 0.2 V of performance loss.

When Bigger Is Better: Household Size, Abuse Injuries, Neglect, and Family Response in Novosibirsk, Russia.

Although previous research has demonstrated larger households to be at higher risk of physical abuse and neglect of children, we argue that unilateral conceptualization of larger households as a risk factor is inappropriate. Application of resource dilution theory must capture the possibility that larger families may have more members with both the agency and will to intervene against child maltreatment. We hypothesized a negative interaction between household size and protective informal social control by family members in predicting abuse injuries and neglect. A three-stage probability proportional to size cluster sample representative of Novosibirsk, Russia, was collected from 306 cohabiting couples. One parent in each household was interviewed. A focal child was selected using most recent birthday. When responses limited to families with minor children (below age 18) were selected, 172 families remained in the data. Physical abuse and neglect were measured using the Conflict Tactics Scales (CTS). Protective informal social control by family members was measured using the Informal Social Control of Child Maltreatment (ISC_CM) Scale. Models were tested using random effects regression and logistic regression. Nearly 7% of focal children were injured in the last year, 10% were neglected. Consistent with previous research, protective informal social control was associated with lower odds of injury and fewer instances of neglect. The significant negative interaction between household size and protective control is consistent with the idea that larger households may be protective when adult family members intervene against maltreatment to protect children. Replication and further investigation of protective ISC_CM in Western populations is much needed. Future research should not conceptualize or measure household size as a unilateral risk factor.

Evaluating Transport Properties and Ionic Dissociation of LiPF6 in Concentrated Electrolyte

The presence of lithium hexafluorophosphate (LiPF6) ion pairs in carbonate-based electrolyte solutions is widely accepted in the field of battery electrolyte research and is expected to affect solution transport properties. No existing techniques are capable of directly quantifying salt dissociation in these solutions. Previous publications by others have provided estimates of dissociation degrees using dilute solution theory and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG-NMR) measurements of self-diffusivity. However, the behavior of a concentrated electrolyte solution can deviate significantly from dilute solution theory predictions. This work, for the first time, instead uses Onsager–Stefan–Maxwell concentrated solution theory and the generalized Darken relation with PFG-NMR measurements to quantify the degrees of dissociation in electrolyte solutions (LiPF6 in ethylene carbonate/diethyl carbonate, 1:1 by weight). At LiPF6 concentrations ranging from 0.1 M to 1.5 M, the salt dissociation degree is found to range from 61% to 37%. Transport properties are then calculated through concentrated solution theory with corrections for these significant levels of ion pairing.

Method of Measuring Salt Transference Numbers in Ion-Selective Membranes

A technique to measure the cation-transference number of salts in fully hydrated ion-selective membranes has been developed and demonstrated on Nafion 117 for LiCl and Li2SO4. Dilute solution theory is used to identify experimental conditions that reduce the propagation of uncertainties in membrane properties to transference number estimates. This technique has advantages over commonly used methods, including the elimination of the need for the analysis of electrode potentials in approaches that exploit electroanalytical methods or the need for additional information required to reconcile NMR-based methods with the bulk transport property. It additionally allows for numerous measurements per day and offers the possibility to relate trace measurements of either cations or anions to values of transference number. For LiCl both modes of the technique were employed; the anion-tracer method is more precise and gives t+ = 0.936 ± 0.010. The experimental procedure was repeated using the cation-tracer method for Li2SO4, and t+ = 0.95 ± 0.06 was estimated.

First-Principles Study of Ion Diffusions in CH3NH3PbI3 and (NH2)2CHPbI3 for Perovskite Solar Cells

Perovskite solar cells (PSCs), which photo-absorbing layer consists of organometal halide perovskites, have gotten much attention because of their rapidly increasing power conversion efficiencies (3.8% in 2009, but nowadays over 22% cell has appeared). [1, 2] Especially, lead halide perovskites such as CH3NH3PbI3 (MAPbI3) and (NH2)2CHPbI3 (FAPbI3) show remarkable properties for solar cell applications, e.g. high optical absorption coefficients and long diffusion lengths of both charge carriers. However, the current−voltage (J−V) curve of PSCs often depends on voltage sweep rates and sweep directions, [3, 4] which make the evaluation of conversion efficiency difficult. Recently, the rate-dependent J−V hysteresis, which is due to a slow process continued about seconds, was attributed to ionic diffusions in MAPbI3. [5] In this study, we calculated activation barriers of ion diffusions in tetragonal MAPbI3 and trigonal FAPbI3 by first-principles calculations. The vacancy migrations of I− anions in both perovskites show low barriers of 0.3 to 0.45 eV, which values indicate that MAPbI3 and FAPbI3 are ion conductors. Furthermore, MA+ and FA+ cations have rather low barriers c.a. 0.6 eV. The results strongly suggest that the not only anions but also molecular cations can migrate in the perovskites when a bias voltage is applied. Based on the dilute diffusion theory, we can expect that small vacancy concentrations suppress these ion conductions. In addition, we suggest that replacement of MA molecule with larger one is also able to reduce MA migrations and to prevent the degradation of PSC photo absorbers. [6] [1] A. Kojima, K. Teshima, Y. Shirai, and T. Miyasaka, J. Am. Chem. Soc., 131, 6050 (2009). [2] Best Research-Cell Efficiencies, National Renewable Energy Laboratory. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg [3] A. Dualeh, T. Moehl, N. Tétreault, J. Teuscher, P. Gao, M. K. Nazeeruddin, M. Grätzel, ACS Nano, 8, 362 (2014). [4] H. J. Snaith, A. Abate, J. M. Ball, G. E. Eperon, T. Leijtens, N. K. Noel, S. D. Stranks, J. T.-W. Wang, K. Wojciechowski, W. Zhang, J. Phys. Chem. Lett., 5, 1511 (2014). [5] W. Tress, N. Marinova, T. Moehl, S. M. Zakeeruddin, M. K. Nazeeruddin, M. Grätzel, Energy Environ. Sci., 8, 995 (2015). [6] J. Haruyama, K. Sodeyama, L. Han, and Y. Tateyama, J. Am. Chem. Soc., 137, 10048 (2015).

Sibship Size and Gendered Resource Dilution in Different Societal Contexts.

Resource dilution theory hypothesizes that children’s educational attainment suffers from being raised with many siblings, as the parental resources have to be shared with more children. Based on economic and cultural theories, we hypothesize that resource dilution is gendered: especially a larger number of brothers is harmful to a person’s educational attainment. Using the Survey of Health, Ageing and Retirement in Europe, covering 18 European countries, we show that the number of brothers is more negatively related with the odds of obtaining a college degree than the number of sisters. This holds particularly for women. However, this pattern is weaker in countries that are known to have a more gender-egalitarian climate.

Active microrheology of colloidal suspensions: Simulation and microstructural theory

Discrete particle simulations by accelerated Stokesian dynamics (ASD) and a microstructural theory are applied to study the structure and viscosity of hard-sphere Brownian suspensions in active microrheology (MR). The work considers moderate to dense suspensions, from near to far from equilibrium conditions. The microscopic theory explicitly considers many-body hydrodynamic interactions in active MR and is compared with the results of ASD simulations, which include detailed near- and far-field hydrodynamic interactions. We consider probe and bath particles which are spherical and of the same radius a. Two conditions of moving the probe sphere are considered: These apply constant force (CF) and constant velocity (CV), which approximately model magnetic bead and optical tweezer experiments, respectively. The structure is quantified using the probability distribution of colloidal particles around the probe, Pb|p(r)=ng(r), giving the probability of finding a bath particle centered at a vector position r relative to a moving probe particle instantaneously centered at the origin; n is the bath particles number density, and is related to the suspension solid volume fraction, ϕ, by n=3ϕ/4πa3. The pair distribution function for the bath particles relative to the probe, g(r), is computed as a solution to the pair Smoluchowski equation (SE) for 0.2≤ϕ≤0.50, and a range of Péclet numbers, describing the ratio of external force on the probe to thermal forces and defined as Pef=Fexta/(kbT) and PeU=6πηUexta2/(kbT) for CF and CV conditions, respectively. Results of simulation and theory demonstrate that a wake zone depleted of bath particles behind the moving probe forms at large Péclet numbers, while a boundary-layer accumulation develops upstream and near the probe. The wake length saturates at Pef≫1 for CF, while it continuously grows with PeU in CV. This contrast in behavior is related to the dispersion in the motion of the probe under CF conditions, while CV motion has no dispersion; the dispersion is a direct result of many-body nonthermal interactions. This effect is incorporated in the theory as a force-induced diffusion flux in pair SE. We also demonstrate that, despite this difference of structure in the two methods of moving the probe, the probability distribution of particles near the probe is primarily set by the Péclet number, for both CF and CV conditions, in agreement with dilute theories; as a consequence, similar values for apparent viscosity are found for the CF and CV conditions. Using the microscopic theory, the structural anisotropy and Brownian viscosity near equilibrium are shown to be quantitatively similar in both CF and CV motions, which is in contrast with the dilute theory which predicts larger distortions and Brownian viscosities in CV, by a factor of two relative to CF MR. This difference relative to dilute theory arises due to the determining role of many-body interactions associated with the underlying equilibrium structure in the semidilute to concentrated regime.

Pulmonary transit time measurement by contrast-enhanced ultrasound in left ventricular dyssynchrony.

BackgroundPulmonary transit time (PTT) is an indirect measure of preload and left ventricular function, which can be estimated using the indicator dilution theory by contrast-enhanced ultrasound (CEUS). In this study, we first assessed the accuracy of PTT-CEUS by comparing it with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Secondly, we tested the hypothesis that PTT-CEUS correlates with the severity of heart failure, assessed by MRI and N-terminal pro-B-type natriuretic peptide (NT-proBNP).Methods and resultsTwenty patients referred to our hospital for cardiac resynchronization therapy (CRT) were enrolled. DCE-MRI, CEUS, and NT-proBNP measurements were performed within an hour. Mean transit time (MTT) was obtained by estimating the time evolution of indicator concentration within regions of interest drawn in the right and left ventricles in video loops of DCE-MRI and CEUS. PTT was estimated as the difference of the left and right ventricular MTT. Normalized PTT (nPTT) was obtained by multiplication of PTT with the heart rate. Mean PTT-CEUS was 10.5±2.4s and PTT-DCE-MRI was 10.4±2.0s (P=0.88). The correlations of PTT and nPTT by CEUS and DCE-MRI were strong; r=0.75 (P=0.0001) and r=0.76 (P=0.0001), respectively. Bland–Altman analysis revealed a bias of 0.1s for PTT. nPTT-CEUS correlated moderately with left ventricle volumes. The correlations for PTT-CEUS and nPTT-CEUS were moderate to strong with NT-proBNP; r=0.54 (P=0.022) and r=0.68 (P=0.002), respectively.Conclusions(n)PTT-CEUS showed strong agreement with that by DCE-MRI. Given the good correlation with NT-proBNP level, (n)PTT-CEUS may provide a novel, clinically feasible measure to quantify the severity of heart failure.Clinical Trial Registry: NCT01735838

Brewing Bokashi: Strengthening Student Skills in Dilution Theory through Fermentation Analysis.

One of the basic microbiological techniques that students should master is that of using dilution theory to calculate the levels of bacteria in a fluid. This tip reports on using a rice water-milk fermentation mixture termed Bokashi as an easily implemented exercise in the basic microbiological lab to give students multiple opportunities to use dilution theory. Due to the shifts in bacterial community composition over time, a variety of microbes can be cultured using selective and nonselective media. Microscopic observation and the use of GEN III microplates to determine the collective phenotypic pattern of the mixture both give additional opportunities for students to hone their skills in bacterial analysis. Due to the decrease in the pH of the mixture over time, the notion of acid tolerance in bacteria can be explored and assessed using the microplate. By performing multiple rounds of serial dilutions and spread plating, students can practice their skill at using dilution theory several times over the course of the exercise.

The power of the kashrut: older but shorter. The impact of religious nutritional and hygienic rules on stature and life expectancy of Jewish conscripts in the early 19th century.

We test the impact of several demographic, economic and social factors on stature in an early nineteenth century environment. We use a database of conscripts from the period 1818-1860 of a rural province in The Netherlands (Drenthe). This area had a rather high biological standard of living. This database of 413 conscripts contains information about family structure, family rank order, height, tax income, occupation and age of death. Conscripts came from two communities: one from a particular village (Oosterhesselen) and the other was Jewish conscripts that came from the countryside of the province. Our statistical analysis shows a positive significant relationship between family size and height, which confirms the resource dilution theory. Remarkably, the sign of the relation between family size and life expectancy is inverse. Other factors such as the potato crisis and income had the expected effect on conscript heights. The community effect was strong. Jewish conscripts were much shorter than their counterparts. Access to nutrition, the specific food laws and other factors can explain this difference. An increasing sibship size had a negative impact on body height but positive effects on life expectancy when adulthood was reached. Specifically for the Jewish community was the positive effect of the death of the father on conscript height. The mechanisms behind this phenomenon are unclear and open for further research.

Interfacial polarization of disseminated conductive minerals in absence of redox-active species — Part 1: Mechanistic model and validation

Electrically conductive mineral inclusions are commonly present in organic-rich mudrock and source-rock formations such as veins, laminations, rods, grains, flakes, and beds. Laboratory and subsurface electromagnetic (EM) measurements performed on geomaterials containing electrically conductive inclusions generally exhibit frequency dispersion due to interfacial polarization phenomena at host-inclusion interfaces. In the absence of redox-active species, surfaces of electrically conductive mineral inclusions are impermeable to the transport of charge carriers, inhibit the exchange of charges and behave as perfectly polarized (PP) interfaces under the influence of an externally applied EM field. Interfacial polarization phenomena involving charge separation, migration, accumulation/depletion, and relaxation around PP interfaces is referred to as PP interfacial polarization; it influences the magnitude and direction of the electric field and charge carrier migration in the geomaterial. We have developed a mechanistic model to quantify the complex-valued electrical conductivity response of geomaterials containing electrically conductive mineral inclusions, such as pyrite and magnetite, uniformly distributed in a fluid-filled, porous matrix made of nonconductive grains possessing surface conductance, such as silica and clay grains. The model first uses a linear approximation of the Poisson-Nernst-Planck equations of dilute solution theory to determine the induced dipole moment of a single isolated conductive inclusion and that of a single isolated nonconductive grain surrounded by an electrolyte. A consistent effective-medium formulation was then implemented to determine the effective complex-valued electrical conductivity of the geomaterial. Model predictions were in good agreement with laboratory measurements of multifrequency complex-valued electrical conductivity, relaxation time, and chargeability of mixtures containing electrically conductive inclusions.

Controlling Hydrogen Activation, Spillover, and Desorption with Pd-Au Single-Atom Alloys.

Key descriptors in hydrogenation catalysis are the nature of the active sites for H2 activation and the adsorption strength of H atoms to the surface. Using atomically resolved model systems of dilute Pd-Au surface alloys and density functional theory calculations, we determine key aspects of H2 activation, diffusion, and desorption. Pd monomers in a Au(111) surface catalyze the dissociative adsorption of H2 at temperatures as low as 85 K, a process previously expected to require contiguous Pd sites. H atoms preside at the Pd sites and desorb at temperatures significantly lower than those from pure Pd (175 versus 310 K). This facile H2 activation and weak adsorption of H atom intermediates are key requirements for active and selective hydrogenations. We also demonstrate weak adsorption of CO, a common catalyst poison, which is sufficient to force H atoms to spill over from Pd to Au sites, as evidenced by low-temperature H2 desorption.

Interfacial tension and a three-phase generalized self-consistent theory of non-dilute soft composite solids.

In the dilute limit Eshelby's inclusion theory captures the behavior of a wide range of systems and properties. However, because Eshelby's approach neglects interfacial stress, it breaks down in soft materials as the inclusion size approaches the elastocapillarity length L≡γ/E. Here, we use a three-phase generalized self-consistent method to calculate the elastic moduli of composites comprised of an isotropic, linear-elastic compliant solid hosting a spatially random monodisperse distribution of spherical liquid droplets. As opposed to similar approaches, we explicitly capture the liquid-solid interfacial stress when it is treated as an isotropic, strain-independent surface tension. Within this framework, the composite stiffness depends solely on the ratio of the elastocapillarity length L to the inclusion radius R. Independent of inclusion volume fraction, we find that the composite is stiffened by the inclusions whenever R < 3L/2. Over the same range of parameters, we compare our results with alternative approaches (dilute and Mori-Tanaka theories that include surface tension). Our framework can be easily extended to calculate the composite properties of more general soft materials where surface tension plays a role.

Family Resource Allocation after Firstborns Leave Home: Implications for Secondborns' Academic Functioning.

This study assessed secondborn adolescents' perceptions of changes in the allocation of family resources following their firstborn siblings' departure from home after high school, and whether perceived changes were related to changes over 1year in secondborns' academic functioning. Participants were secondborn siblings (mean age=16.58, SD=0.91) from 115 families in which the older sibling had left the family home in the previous year. Allocation of resources was measured via coded qualitative interviews. Most (77%) secondborns reported increases in at least one type of family resource (i.e., parental companionship, attention, material goods), and many reported an increase in multiple types of resources in the year following their older sibling's departure. Consistent with resource dilution theory, perceptions of increases in fathers' companionship, fathers' attention, and mothers' companionship were related to improvements over time in secondborns' academic functioning.

Automatic extraction of forward stroke volume using dynamic PET/CT: a dual-tracer and dual-scanner validation in patients with heart valve disease.

BackgroundThe aim of this study was to develop and validate an automated method for extracting forward stroke volume (FSV) using indicator dilution theory directly from dynamic positron emission tomography (PET) studies for two different tracers and scanners.Methods35 subjects underwent a dynamic 11C-acetate PET scan on a Siemens Biograph TruePoint-64 PET/CT (scanner I). In addition, 10 subjects underwent both dynamic 15O-water PET and 11C-acetate PET scans on a GE Discovery-ST PET/CT (scanner II). The left ventricular (LV)-aortic time-activity curve (TAC) was extracted automatically from PET data using cluster analysis. The first-pass peak was isolated by automatic extrapolation of the downslope of the TAC. FSV was calculated as the injected dose divided by the product of heart rate and the area under the curve of the first-pass peak. Gold standard FSV was measured using phase-contrast cardiovascular magnetic resonance (CMR).ResultsFSVPET correlated highly with FSVCMR (r = 0.87, slope = 0.90 for scanner I, r = 0.87, slope = 1.65, and r = 0.85, slope = 1.69 for scanner II for 15O-water and 11C-acetate, respectively) although a systematic bias was observed for both scanners (p < 0.001 for all). FSV based on 11C-acetate and 15O-water correlated highly (r = 0.99, slope = 1.03) with no significant difference between FSV estimates (p = 0.14).ConclusionsFSV can be obtained automatically using dynamic PET/CT and cluster analysis. Results are almost identical for 11C-acetate and 15O-water. A scanner-dependent bias was observed, and a scanner calibration factor is required for multi-scanner studies. Generalization of the method to other tracers and scanners requires further validation.

First-Principles Study of Ion Diffusion in Perovskite Solar Cell Sensitizers.

Hysteresis in current-voltage curves has been an important issue for conversion efficiency evaluation and development of perovskite solar cells (PSCs). In this study, we explored the ion diffusion effects in tetragonal CH3NH3PbI3 (MAPbI3) and trigonal (NH2)2CHPbI3 (FAPbI3) by first-principles calculations. The calculated activation energies of the anionic and cationic vacancy migrations clearly show that I(-) anions in both MAPbI3 and FAPbI3 can easily diffuse with low barriers of ca. 0.45 eV, comparable to that observed in ion-conducting materials. More interestingly, typical MA(+) cations and larger FA(+) cations both have rather low barriers as well, indicating that the cation molecules can migrate in the perovskite sensitizers when a bias voltage is applied. These results can explain the ion displacement scenario recently proposed by experiments. With the dilute diffusion theory, we discuss that smaller vacancy concentrations (higher crystallinity) and replacement of MA(+) with larger cation molecules will be essential for suppressing hysteresis as well as preventing aging behavior of PSC photosensitizers.